Dissertations / Theses on the topic 'Optimization of biomass formation'

Master of Science
Department of Agricultural Economics
Jeffery Williams
Ethanol has become an important source of energy for transportation purposes in the U.S. The majority of the feedstock for this ethanol is corn grain. The use of crop residues and perennial grasses has been proposed as an alternative feedstock for ethanol production using cellulosic conversion processes. Commercial scale production of cellulosic ethanol is still on the horizon. In the meantime a wide variety of studies examining both the technical and economic feasibility of cellulosic ethanol production have been conducted. This is the first study that combines both county level cellulosic feedstock production and farmer participation rates to determine the feasibility of supplying it to cellulosic ethanol plants. This research determines the economic feasibility of supplying cellulosic feedstocks to seven potential add-on cellulosic ethanol plants of 25 million gallons per year at seven existing starch ethanol plants in Kansas. The feedstocks considered are corn stover, sorghum stalks, wheat straw, and perennial switchgrass. A mixed integer programing model determines the amount and mix of cellulosic feedstocks that can be delivered to these plants over a range of plant-gate feedstock prices given transportation costs and farm-gate production costs or breakeven prices. The variable costs of shipping are subtracted from the difference between plant-gate price and farm-gate price to find savings to the plant. The objective function of the model minimizes transportation costs which in turn maximizes savings to the plant. The role switchgrass may have as a feedstock given various switchgrass production subsidies is examined. The results indicate the minimum plant-gate price that must be paid to feedstock producers for all plants to have enough cellulosic feedstocks is $75 per dry ton. Switchgrass feedstocks were only a minor portion of biomass supplied and used without a production subsidy. A Biomass Crop Assistance Program payment increased the supply of switchgrass more than other production subsidies.

Achieving a sustainable process system is one of the main focuses in research and development throughout the world. Development in renewable resources is at the peak to replace and reduce the usage of fossil fuel in chemical and energy production. Bio-resources have shown great potential to accomplish a sustainable system, especially bio-waste which also known as biomass, to avoid interruption of food supplement within the supply chain network. However, worldwide implementation of biomass-based process technology is yet to be feasible due to high logistic cost, complexity of biomass properties, fluctuation of biomass availability, and relatively low conversion rate in biomass conversion technologies. Unique regional biomass system further creates research gaps as researches are conducted independently to only focus on specific biomass species available within the region. This raises issue of underutilisation of biomass where biomasses value are not used in the full potential, or ignorance of certain species of biomass (such as food waste, fruit shells and energy crop) in research development. This thesis specifically evaluated the current issues in biomass supply chain network management to enhance the feasibility of biomass industry implementation. The main objective of this thesis is to improve the biomass supply chain network management by integrating underutilised biomasses into existing biomass process plant (built) without major modification on the current process technologies such as equipment redesign or modifications. Underutilised biomasses are referring to those species that yet to have well-developed application (pilot plant scale) or potential biomasses that were ignored in a regional area due to issues such as low availability. This thesis discusses in detail on the relevant previous research works and supporting materials toward the introduction of novel philosophy, element targeting approach, which suggested selection of biomass feedstock via element characteristics instead of biomass species to consider underutilised biomasses into the system. Upon verification of the approach based on literature data and experimental work, element targeting approach is integrated into biomass supply chain optimisation model. The proposed mathematical models enable consideration of underutilised biomasses, and demonstration case studies results have shown promising improvement over the conventional approaches and its capability to handle fluctuation issues in biomass availability.

This study provides new insights into the formation mechanisms of various organic acids from hydrothermal decomposition of biomass under non-catalytic conditions. Firstly, the primary products from hydrothermal decomposition of mallee biomass and its main components are studied. Then, systematic research is undertaken to investigate the formation of various organic acids from hydrothermal decomposition of key intermediates including cellobiose, glucose, fructose and mannose. The reaction pathways of key organic acids from various sugar compounds are revealed.

To handle a great demand for biomass, alternative biomasses beyond stem wood are being introduced into the solid fuel combustion market, fuels with generally higher (>0,5 wt-%) ash content and different fuel ash compositions compared to stem wood, such as forest residue, bark, grass and straw. Unfortunately, combustion of these alternative fuels often causes more ash related problems such as fouling, slagging and higher particle emissions compared to combustion of stem wood. Many research studies have been conducted regarding ash melting and ash sintering in biomass combustion. However, literature discussing slagging of biomass ash is rather scarce, especially relating to fixed bed combustion. The majority of the biomass fuels available on the market today are phosphorus-poor and this thesis emanates from those. The overall objective was to obtain knowledge of slag formation in fixed-bed combustion of phosphorus-poor biomass, based on bench- and full-scale experiments, chemical analysis of produced ash fractions, chemical equilibrium calculations, viscosity estimations and statistical evaluations.   This thesis investigates slagging of [phosphorus-poor] biomass in fixed bed combustion. 85 fuels and 10 different burner/boiler technologies were utilized. The results in this thesis highlight the importance of the ash forming elements Si, Ca, K and Alin the slag formation process in fixed bed combustion of phosphorus-poor biomass. Increased Ca/Si ratios in the fuel reduce slag formation due to formation of more temperature stable phases, i.e. Ca/Mg-oxides and/or formation of carbonate melts with lower viscosity (not sticky) that are less prone to forming slag. A high Al/Si ratio increases the possibility of forming solid and thermally stable K−Al silicates that can reduce slag formation.   The fraction of ash melt, along with viscosity, are critical for slag formation and these parameters vary between different fuels. Four classes were defined according to their slagging potential; 1) No slag: fuel composition and the bottom ash contains low Si and K contents and higher Ca content. Fuel examples: non-contaminated stem- and pulpwood/energy wood, 2) Minor slagging tendency: fuel compositions show increased Si compared to non-slagging fuels and the bottom ash contains lower Ca, but increased Si content and approximately unchanged K content compared to the former category. Fuel examples: stem wood, bark and logging residue with increased Si-content due to light contamination. 3) Moderate slagging tendency: fuel composition contains further increased Si content. Increased share of formed silicate melt and higher viscosity (more sticky) compared to minor slagging fuels. Fuel examples: mostly contaminated woody fuels and grass and straws with relatively high amount of Ca. and 4) Major slagging tendency: Fuel composition contains high Si and K content. Sticky K-silicates causes major increase in slagging tendency. Fuel examples: different types of grass and straw fuels.   The burner/boiler technology can affect whether slagging will induce major problems in the burner or not. However, long residence times and high temperatures for the combustion residues in the hot part of the fuel bed are technical prerequisite for increased slag formation.   This thesis developed two qualitative fuel indices for predicting slagging in fixed bed combustion of phosphorus-poor biofuels – one index for fraction of fuel ash that forms slag and one index for sintering category of the formed slag. Both novel indices deliver acceptable results and are more reliable than previous indices found in the literature. Importantly, the fraction of fuel ash that forms slag index outperforms the sintering category for qualitative prediction of the problematic slagging potential of a certain fuel. Additional work is needed to further widen the compositional range as well as to fine tune the indices’ boundaries.

Mathematical modeling has been employed to improve the cost competitiveness of forest bioenergy supply chains. Most of the studies done in this area are at the strategic level, focus on one part of the supply chain and ignore uncertainties. The objective of this thesis is to optimize the value generated in a forest biomass power plant at the tactical level considering uncertainties. To achieve this, first the supply chain configuration of a power plant is presented and a nonlinear model is developed and solved to maximize its overall value. The model considers procurement, storage, production and ash management in an integrated framework and is applied to a real case study in Canada. The optimum solution forecasts $1.74M lower procurement cost compared to the actual cost of the power plant. Sensitivity analysis and Monte Carlo simulation are performed to identify important uncertain parameters and evaluate their impacts on the solution. The model is reformulated into a linear programming model to facilitate incorporating uncertainty in the decision making process. To include uncertainty in the biomass availability, biomass quality and both of them simultaneously, a two-stage stochastic programming model, a robust optimization model and a hybrid stochastic programming-robust optimization model are developed, respectively. The results show that including uncertainty in the optimization model provides a solution which is feasible for all realization of uncertain parameters within the defined scenario sets or uncertainty ranges, with a lower profit compared to the deterministic model. Including uncertainty in biomass availability using the stochastic model decreases the profit by $0.2M. In the robust optimization model, there is a trade-off between the profit and the selected range of biomass quality. Profit decreases by up to $3.67M when there are ±13% variation in moisture content and ±5% change in higher heating value. The hybrid model takes advantage of both modeling approaches and balances the profit and model tractability. With the cost of only $30,000, an implementable solution is provided by the hybrid model with unique first stage decision variables. These models could help managers of a biomass power plant to achieve higher profit by better managing their supply chains.

La biomasse peut jouer un rôle crucial comme source d'énergie renouvelable. La logistique représentant une part importante du coût, des chaînes d'approvisionnement efficaces doivent être conçues pour fournir aux bio-raffineries les quantités demandées, à des prix raisonnables et à des moments adéquats. Cette thèse porte sur la modélisation et l'optimisation de chaînes logistiques de biomasse pour plusieurs raffineries. Un modèle de données est élaboré pour structurer les informations nécessaires à une base de données alimentant les modèles mathématiques. Ensuite, un modèle linéaire multi-période à variables mixtes est proposé pour optimiser au niveau tactique et stratégique une chaîne logistique multi-biomasse. Les emplacements des raffineries peuvent être prédéfinis ou déterminés par le modèle. L'objectif est de minimiser un coût total incluant la production de biomasse, le stockage, la manutention, la création des raffineries et le transport, tout en satisfaisant les besoins des raffineries dans chaque période. Une version multi-objective est développée pour optimiser simultanément des critères économiques et environnementaux. Elle est résolue par une méthode de type ε-contrainte. Des grandes instances avec des données réelles pour deux régions de France (Picardie et Champagne Ardenne) sont préparées pour évaluer des modèles proposés. Enfin, des approches en deux phases sont appliquées pour résoudre les grands cas en un temps raisonnable, tout en évaluant l’écart à l’optimum fourni par la méthode exacte
Biomass can play a crucial role as one of the main sources of renewable energies. As logistics holds a significant share of biomass cost, efficient biomass supply chains must be designed to provide bio-refineries with adequate quantities of biomass at reasonable prices and appropriate times. This thesis focuses on modeling and optimization of multi-biomass supply chains for several bio-refineries. A data model is developed to list, analyze and structure the set of required data, in a logical way. The result is a set of tables that can be loaded into mathematical models for solving optimization problems. Then, a multi-period mixed integer linear programming model is proposed to optimize a multi-biomass supply chains for several bio-refineries, at the tactical and strategic level. Refineries can be already placed or located by the model. The aim is to minimize the total costs, including biomass production, storage, handling, refineries setup and transportation costs, while satisfying the demand of refineries in each period. Additionally, a multi-objective model is developed to optimize simultaneously the economic and environmental performance of biomass supply chains. The model is solved by using the ε-constraint method. Furthermore, large-scale tests on real data for two regions of France (Picardie & Champagne-Ardenne) are prepared to evaluate the proposed models. Finally, two-phase approaches are proposed to solve large-scale instances in reasonable running times, while evaluating the loss of optimality compared to the exact model

In case of PF firing, solid fuels such as coal and biomass undergo various chemical and physical transformations (devolatilization, char oxidation, fragmentation and gas to particle conversion followed by nucleation, coagulation and condensation etc.) just in milliseconds after fuel enters to the furnace. These transformations depend on several operating parameters (temperature, pressure, heating rate etc.) along with several chemical and physical properties (ash, moisture content, density, porosity, mineral matter composition and their association in the fuel matrix, particle size, shape and density etc.). The resultant ash formed during combustion after such parallel transformations in relation with several physical and chemical transformations along with the operating parameters will have different particle sizes and mineralogical composition compare to the original fuel.The scope of this research work is to perform the experimental and modelling work to investigate the ash formation process in terms of particle sizes and their mineralogical composition after combustion. A vast experimental study was planned in the lab scale combustion simulator at ECN with six biomass and two coals (Bark, wood chips, waste wood, saw dust, olive residue, straw, UK and a Polish etc.) under typical PF-firing conditions. Ash release, conversion, size reduction and size distribution alongside with the change in inorganic chemical compositions, are derived at different char burn out levels in the reactor at 20, 90, 210 and 1300 milliseconds of residence times. Several of the past observations made in the literature review are reconfirmed with performed set of experiments. A qualitative predictive tool is also suggested to envisage the extent of first line physical transformations. Based on the extensive data pool at hand, a simple but reliable (R2 >0.95) set of linear correlations have been proposed to predict the elemental release of potassium, sodium, chlorine and sulfur.It is also concluded that such linear expressions can be particularly effective for the prediction of elemental release from the fuels of similar characteristics, such as woody biomass. Mathematical model is developed to predict the particle size after combustion by simplifying Dunn-rankin’s particle population balance model analytically and kinetically. Ash formation modelling has also been attempted. The developed understanding and models can be further used for the investigations of several ash related problems during combustion and co-firing such as slagging, fouling, corrosion and erosion etc.

The aim of the present study was to investigate a range of bioprocess strategies aimed at the achievement of maximum biomass yield in submerged cultivation of the Basidiomycete, Ganoderma lucidum. Although there had been previous studies into cultivation of G, lucidum, these had been almost exclusively centred round maximisation of the medically interesting polysaccharide, EPS. The present work is focused on the development of fermentation strategies to achieve this aim, which was a central interest of the sponsor. Additionally, to investigate the process physiology of these complex cultures to help improve the relatively poor, understanding of the bioprocessing of this Basidiomycete fungus and to understand the influence of process variables during submerged cultivation of G. lucidum on growth, polysaccharide production and substrate consumption.

Pressurised entrained‐flow gasification (PEFG) of sustainable woody biomass offers the opportunity for envi-ronmentally benign production of syngas that is suitable for synthesis of fuels and other chemicals. During the PEFG process, ash-forming matter in the fuel undergoes transformations. Slag formation is an important form of ash transformation that occurs inside a PEFG reactor. In most industrial-scale PEFG of coal, the ash-forming matter becomes predominately molten and flows down the side of the reactor wall to be continuously tapped and removed. The slagging behaviour of woody biomass fuels during PEFG is expected to be different to that of coal, due to significant differences in the amount, composition and reactivity of the ash-forming matter. The objective of this thesis study was to initiate the elucidation of slag formation during PEFG of woody biomass. This was carried out by obtaining and characterising ash deposits and slags from pilot-scale experimental cam-paigns. An oxygen-fired pilot-scale reactor (ETC Piteå, Sweden) was used for the study. A low reactor temperature (< 1200 °C) study was carried out with three different fuels fired in separate experimental campaigns: stem wood, bark and pulp mill debarking residue (PMDR). Deposits were taken from each of the campaigns from the reactor for chemical characterisation. The stem wood fuel resulted in very little deposit that exhibited only minor amounts of melt, or slag, formation with enrichment of Si. The bark and PMDR fuels resulted in larger amounts of deposits with greater amounts of melt formation that were also enriched in Si. It was found that silica-based fuel contaminants, e.g., quartz sand and feldspars, may have an important role in melt formation. Following on, high reactor temperature (> 1350 °C) experimental campaigns involving stem wood produced flowing slags that eventuated in blockages of the reactor outlet. These slags were also retrieved from the reactor and characterised. It was found that they likely comprised of products resulting from detrimental interactions between the fuel ash and the mullite-based refractory used for the reactor wall lining. Viscosity models and thermochemical equilibrium calculations (TECs) were utilised to offer an explanation for the behaviour of the slags. Additional TECs were carried out to investigate the propensity for melt formation between the main ash-forming elements of woody biomass, Ca, K and Si, under global reactor conditions with relevance to PEFG. The results showed that, in general, the conditions for melt formation are broadened with increasing pressure, increasing amounts of Si and increased concentrations of gaseous K species. Dissolution of Al₂O₃ from mullite (Al₆Si₂O₁₃) refractory due to ash deposits and the gasification atmosphere was also predicted by the calculations. A scheme of slag formation during PEFG of woody biomass in a reactor with mullite-based refractory lining was proposed in light of the experimental observations. Some practical suggestions to avoid ash-related problems during PEFG of woody biomass are also discussed. This work forms part of a broader study to elucidate the ash transformations that occur during PEFG of woody biomass, which is necessary in order to develop the process into commercial availability.
Godkänd; 2014; 20141102 (chamaf); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Charlie Ma Ämne: Energiteknik/Energy Engineering Uppsats: Slag Formation During Pilot-Scale Pressurised Entrained-Flow Gasification of Woody Biomass Examinator: Professor Marcus Öhman, Institutionen för teknikvetenskap och matematik, Luleå Tekniska universitet Diskutant: Universitetslektor Christoffer Boman, Umeå Universitet Tid: Fredag den 12 december 2014 kl 10.00 Plats: E246, Luleå tekniska universitet

Soot formation from complex solid fuels, such as coal or biomass, is an under-studied and little understood phenomena which has profound physical effects. Any time a solid fuel is combusted, from coal-burning power plants to wildland fires, soot formation within the flame can have a significant influence on combustion characteristics such as temperature, heat flux, and chemical profiles. If emitted from the flame, soot particles have long-last effects on human health and the environment. The work in this dissertation focuses on creating and implementing computational models to be used for predicting soot mechanisms in a combustion environment. Three models are discussed in this work; the first is a previously developed model designed to predict soot yield in coal systems. This model was implemented into a computational fluid dynamic software and results are presented. The second model is a detailed-physics based model developed here. Validation for this model is presented along with some results of its implementation into the same software. The third model is a simplified version of the detailed model and is presented with some comparison case studies implemented on a variety of platforms and scenarios. While the main focus of this work is the presentation of the three computational models and their implementations, a considerable bulk of this work will discuss some of the technical tools used to accomplish this work. Some of these tools include an introduction to Bayesian statistics used in parameter inference and the method of moments with methods to resolve the 'closure' problem.

2014 - 2015
A methodology to reduce the complexity of the process optimization was applied to multiproduct biorefinery fed by lignocellulosic biomass. A process superstructure was built to consider alternative process pathways to levulinic acid, succinic acid and ethanol. A Mixed Integer Non-Linear Problem was obtained and transformed in a Mixed Integer Linear Problem by means of a discretization procedure of the non-linear variables. Rigorous design methods accounting for complete kinetics schemes for hydrolysis and fermentation reactors for the production of levulinic acid, succinic acid and ethanol were included in a biorefinery superstructure optimization. A discretization method was applied to obtain a MILP approximation of the resulting MINLP master problem. The optimal flowsheet of a biorefinery with hardwood feedstock, obtained by maximizing the Net Present Value, yields comparable biomass allocation to levulinic acid and succinic acid (more than 40% each) and the its balance to ethanol. A sensitivity analysis highlighted that the optimal flowsheet and the relevant technical and economic performances are significantly dependent on the economic scenario (chemical products selling price, discount rate) and on the plant scale. Finally, process optimization achieved by maximizing two different economic objective functions, Net Present Value and Internal Rate of Return, provided different optimal flowsheets and biomass allocation to chemical products. The effect of the change of the biomass type and composition on the plant was also considered. Results highlight that the composition of the biomass feedstock in terms of cellulose, hemicellulose and lignin has a significant effect on the biomass allocation to the three product production processes and on the relevant optimal flowsheet. Case studies with a combined use of different seasonal biomass types during the year were also studied to provide a methodology to find the optimal biorefinery flowsheet in real scenarios. In the season based scenario studied, product yield distribution and overall productivity of the plant varies during the different periods provided a constant biomass feed rate. [edited by Author]
XIV n.s.

In this dissertation, we study the effects of emerging biomass markets on land use changes between alternatives of agricultural production, conventional timber production, and forest woody biomass production for energy use. Along with the uncertainty associated with woody biomass prices and rents, transaction costs incurred to land use play an important role in land allocation decisions and make this study distinct from other work. In Chapter 1, we introduce the background and objectives of our study. In Chapter 2, we analyze the behavior of a risk-neutral private landowner and social planner under uncertainty of woody biomass prices, assuming that there is a market emergence at some unknown time point in the future. Market emergence is characterized by a price jump and a certain timing of the price jump. Six different price jumps and five different timings of bioenergy market emergence are adopted to study their collective effects on land use change between agriculture and forestry. Chapter 3 studies this problem for a risk-averse private landowner. Two measures of relative risk aversion are used to examine how a landownerâ s preference may affect his or her land use decision. In Chapter 2, we find that, for three different quality categories of land, land rents from forestry increase significantly for higher price jumps and decreases in the length of time until bioenergy market emergence. One of the most important results is concerned with the presence of transaction costs. Here, we find that these costs may require unrealistic market emergence scenarios to lead to bioenergy adoption on any large scale. This result is even more likely with nonlinear transaction costs. Land allocation decisions in Chapter 3 are distinctly different from those in Chapter 2, due to the introduction of landowner risk aversion. In certain market emergence cases, some land units retain in agriculture entirely when the landowner is risk averse . The Chapter 4 studies a stochastic optimization problem of land use, assuming that woody biomass rents follow a stochastic diffusion called geometric Brownian motion that is later discretized by a binomial option pricing approach. The problems in Chapters 2 and 3 assume that the landowner must make all decisions at the beginning of his or her time horizon. This assumption is relaxed in Chapter 4. Now, the landowner is allowed to revise his or her land allocation decision among three alternatives over time as information about market emergence is collected. We observe that the different forms of transaction costs are not as significant as in Chapters 2 and 3. However, different values of volatility of forest biomass rents give rise to different land allocation decisions, especially for the land of high quality.
Ph. D.

Doctor of Philosophy
Department of Biological and Agricultural Engineering
Yong Cheng Shi
Donghai Wang
Cellulosic ethanol made from low cost lignocellulosic biomass has been considered as new generation transportation fuel with economic and environmental advantages. Photoperiod-sensitive (PS) sorghum, because of its high biomass yield (2.6 kg dry mass/m2), about 18% of soluble sugar in dry mass, and drought tolerance, is a promising biomass for ethanol production. The overall goals of this study are to develop an efficient approach to convert PS sorghum to ethanol and to understand the structural characteristics of biomass. For increasing the efficiency of biomass conversion, an integrated method, using diluted sulfuric acid pretreatment, has been developed to utilize both the structural polysaccharide (cellulose) and the soluble sugar (sucrose, glucose, and fructose) for fermentation. Response surface methodology was employed to optimize the pretreatment condition for maximizing the cellulose-glucose conversion. Simultaneous enzymatic hydrolysis and yeast fermentation was used for ethanol production. The effects of the buffer concentration, the inoculation dosage and time, and the fermentation temperature were investigated for maximizing ethanol yield. A total conversion efficiency of 77.2% and an ethanol concentration of 2.3% (v/v) were obtained after 72 h fermentation. About 210 kg (~266 Liters) ethanol could be produced from one ton dry mass of PS sorghum under the optimized condition. The structural features of the PS sorghum were studied using techniques including scanning electron microscopy and X-ray diffraction/scattering. Biomass at different botanic locations was investigated. Wide-angle X-ray diffraction (WAXD) study showed that the PS sorghum rind had oriented crystal peaks and the highest degree of crystallinity, whereas the crystalline structures of the inner pith and leaf were less ordered. The results from WAXD suggested that crystalline cellulose was melted at 120 °C before its significant degradation. Both the cellulose crystallinity and the crystal size at the dimension lateral to fiber direction increased as the temperature increased from 120 to 160 °C. The efficiency of enzymatic hydrolysis increased because the protective structure was damaged and most hemicellulose was removed, resulting in the increase in accessible area as suggested by small-angle X-ray scattering result of the increased length of microvoids. The results from WAXD also suggested a simultaneous hydrolysis and crystallization of cellulose by acid.

The cost of pretreatment process for saccharification from biomass and the cost of dilute ethanol purification are significant components of the overall cost for fuel grade ethanol production through fermentation or other biological routes. This work focuses on developing optimal designs of dilute ethanol purification process and the new acid hydrolysis technology for the production of fermentable sugars from biomass where the overarching goal is to reduce the cost of ethanol production from biomass. In this thesis, the ethanol separation process with the reverse osmosis membrane pretreatment is developed to reduce separation cost and energy consumption especially when the feed is dilute. In addition, the new solid phase reactive separation system for biomass saccharification via acid hydrolysis is proposed. This new process is applied for both dilute and concentrated acid hydrolysis where the goal is to increase sugar yield and to reduce byproduct formation. The reaction kinetics of the concentrated acid hydrolysis is investigated through batch experiment. All of these use optimization approaches for seeking the best process designs and for parameter estimations.

In the last years the growing interest to use renewable energies instead of fossil fuels has been originated by the awareness to protect the environment and to behave in a sustainable way. Between the renewable energies, the wood energy plays an important role since it is widely and homogenously distributed in the world. The use of wood biomass has a positive impact on the rural activities, development and employment. Before starting any project of a new plant is necessary to survey the availability of resources at local level, their exploitation and supply chains involved. This is essential in order to avoid competition for resources and import from other regions or states. When planning the location of plants or storages it is necessary to consider the current land use, laws, social and economical aspects. Transportation operations are the most costly operation of the supply chain. Optimizing transportation means to fulfil the demand with minimum effort and available resources. Preferable sustainable and socio-economical friendly solutions minimize transport by prioritizing local fuels. Transport can be minimized by optimal utilization of vehicle payload and choosing the shortest travel paths. Studying the optimal supply both at small scale and large scale level is a valid decision support tool that helps decision makers to choose a good strategy to minimize costs and having supply efficiency. In this study a methodology that combines the use of linear programming and GIS has been developed. It considers different supply chains with all phases from stands to plants and relative costs. Surveys have been conducted with the purpose of knowing the location and demand of plants. A network analysis has been used to calculate transportation cost from sources (sawmills and stands) to destination. The linear programming considers the constraints of availability of wood fuel, supply costs and maximum capacities of supply phases. The optimization has been solved building a transportation model with the software LINGO and displaying results on GIS maps. The developed methodology has been applied to optimize the fuel supply of two plants located in Fiemme Valley (Trento province, in north-eastern Italy). The plants supply with forest residues and sawmill byproducts has been modeled for a period of ten years. The results show that chipping forest residues before being transported is cheaper than transportation of logging residues. Another transportation model has been formulated considering the seasonal fluctuation of fuel demand and supply and considering the possibility of storing fuel at terminal. The optimal location of a new terminal has been evaluated. Sensitivity analyses were done to study the effects of some parameters in the whole system and its possible improvement. Results of the test about the best terminal location show that terminal is used for only few volume of forest residues. As the formulation has been done, there are not significant differences in total costs comparing three terminal positions. This can be due also to the small scale area considered in the study. Observing results of sensitive analyses carried out during the study, the most useful is the one concerning the truck payload. A transportation model has been built for the supply of two plants in the Central Finland region with the aim to identify the optimal allocation of forest fuel. Additionally a comparison of different plant’s “paying ability” has been tested in order to see the effect on their supply areas. In the Finnish case study both plants are optimally supplied with logging residues. When there are constraints on paying ability for one plant, the other one has advantages. The wood energy plant supply analyzed in this study have been optimized using linear programming. The transportation model built in LINGO considers all cost factors along the supply chain, providing a global optimal solution. The decision variables are represented by fuel flows of different supply chains, while the objective function is to minimize costs of the whole system. Modeling produces more flexible solutions compared to manual planning, and allows easy testing of different strategies and scenarios. Using a GIS for modeling biomass supply allows to study the effect of variation of geographical factors on the supply and costs of biomass production.
In questi anni il crescente interesse all’utilizzo di fonti energetiche rinnovabili in sostituzione a fonti energetiche fossili è stato determinato dalla consapevolezza della necessità di salvaguardare l’ambiente e di comportarsi in maniera sostenibile. Tra le varie fonti energetiche rinnovabili, le biomasse legnose svolgono un ruolo importante, grazie alla loro locale ed omogenea distribuzione. L’utilizzo di biomasse legnose permette la riduzione delle emissioni di gas serra, l’utilizzo di risorse locali disponibili e sostenibili, la riduzione della dipendenza riguardo alle importazioni di energia, la maggior sicurezza dell’approvvigionamento di combustibili, il rispetto degli impegni assunti nel corso della Conferenza Internazionale di Kyoto. Inoltre l’utilizzo delle biomasse legnose forestali favorisce l’incremento delle attività, introiti ed occupazione nelle aree rurali. Per una corretta progettazione di un impianto è essenziale fare un’indagine sulla presenza di risorse disponibili sul territorio. La valutazione e la conoscenza della disponibilità di materia prima a livello locale e la logistica dell’approvvigionamento sono essenziali per evitare una competizione intrasettoriale e l’importazione di biocombustibili da altre regioni o stati. Quando si pianifica la posizione adatta per impianti o centri di stoccaggio è essenziale considerare l’uso attuale del territorio, la legislazione vigente e aspetti sociali ed economici. Nella catena di approvvigionamento di biomasse legnose le operazioni di trasporto sono quelle che, a parità di tipologia di materia prima, maggiormente determinano la differenza di costo. Ottimizzare i trasporti significa utilizzare il minor sforzo di trasporto possibile per soddisfare una domanda di combustibile con le risorse disponibili. I trasporti possono essere minimizzati utilizzando in maniera ottimale la capacità di carico dei mezzi di trasporto e scegliendo la strada più corta verso la destinazione finale. Le alternative di approvvigionamento che minimizzano i trasporti privilegiando le risorse di combustibile locali sono maggiormente sostenibili anche da un punto di vista socio-economico. Lo studio e l’ottimizzazione dell’approvvigionamento in piccole realtà locali, o anche a grande scala, può essere un valido strumento di supporto alle decisioni che il gestore di un impianto deve intraprendere per assicurare il funzionamento dell’impianto stesso e minimizzare i costi. All’interno di questo lavoro di ricerca è stata realizzata una metodologia che combina l’utilizzo della programmazione lineare con i sistemi informativi geografici. Nello studio sono state prese in considerazione diverse modalità di approvvigionamento per le differenti tipologie di materiale disponibile sul territorio. Per il cippato forestale sono stati considerate tutte le fasi e relativi costi di approvvigionamento da bordo strada all’impianto. Per conoscere offerta e domanda di combustibile, sono state raccolte informazioni sulle fonti e sulla destinazione del combustibile attraverso interviste e attingendo a banche dati. Attraverso una elaborazione di “network analysis” effettuata con gli strumenti GIS, sono stati individuati i costi di trasporto da ogni fonte di biomassa (bosco o segherie) fino alle potenziali destinazioni. Nella programmazione lineare sono stati presi in considerazione le limitazioni di disponibilità di combustibile, i costi di approvvigionamento e le capacità massime delle varie fasi delle catene di approvvigionamento per soddisfare la domanda di energia degli impianti. Il risultato dell’elaborazione eseguita con il software “LINGO” evidenzia le destinazioni ottimali del combustibile, che vengono poi visualizzate su mappe in GIS. La metodologia è stata applicata allo studio dell’ottimizzazione dell’approvvigionamento di due impianti termici a cippato situati in Val di Fiemme (Provincia di Trento). E’ stato simulato l’approvvigionamento di biomassa nel corso di un decennio con materiale proveniente da scarti di imprese di prima lavorazione del legno e da residui delle utilizzazioni forestali. Un’altra simulazione ha riguardato lo studio dell’approvvigionamento di cippato, nel corso di un anno e su scala bimestrale, in base alla domanda stagionale da parte degli impianti e alla disponibilità di residui nel corso dei periodi temporali considerati. In questo ultimo studio è stata considerata anche la possibilità di utilizzare un centro di stoccaggio del materiale. Sono state testate tre localizzazioni del centro di stoccaggio allo scopo di verificare la posizione più strategica, dal punto di vista economico. L’andamento dell’essicazione del materiale stoccato e dell’incremento della sua densità energetica è stato modellizzato dopo essere stato studiato con prove in campo. Alcune analisi di sensitività sono state realizzate allo scopo di verificare l’influenza dei diversi parametri considerati dal modello sul risultato finale. La metodologia applicata può essere utilizzata come strumento per decidere la localizzazione ottimale di impianti o centri di stoccaggio del materiale nel corso della loro progettazione. Una metodologia simile, per studiare l’approvvigionamento di materiale su grande scala, è stata applicata nella regione della Finlandia Centrale in particolare per rifornire una centrale e una bioraffineria. I due impianti presi in esame hanno una domanda elevata di combustibile e quindi con una forte competizione per le materie prime. L’ottimizzazione dell’utilizzo delle risorse evidenzia le aree di destinazione delle varie forme di biomassa disponibile. Ponendo dei limiti di disponibilità a pagare da parte di un impianto, si vuole studiare l’effetto sull’area di approvvigionamento. Nell’ottimizzazione dell’approvvigionamento nei dieci anni, la tipologia di approvvigionamento ottimale è la cippatura a bordo strada o in bosco ed il trasporto di materiale cippato all’impianto. Il cippato rimasto ad essiccare un anno è preferito, in quanto ha più elevato contenuto energetico. Per quanto riguarda lo studio dell’ottimale localizzazione di un centro di stoccaggio, tra le tre localizzazioni del terminal non si registrano differenze significative in termini di costo totale di approvvigionamento. Questo può essere dovuto alla piccola scala dell’area considerata. Inoltre ulteriori limitazioni sui volumi di trasporto dovrebbero essere prese in considerazione, magari adottando variabili binarie al posto di variabili continue. Per quanto riguarda le analisi di sensitività, la più utile anche dal punto di vista della logistica è quella del volume di trasporto di combustibile. Aumentando la capacità di trasporto dell’autocarro trasportante residui non cippati, questa modalità di approvvigionamento viene preferita. Diminuendo il contenuto idrico il cippato forestale è preferito a quello di segheria. Ne caso finlandese preso in esame, la modalità di approvvigionamento ottimale risulta essere per entrambi gli impianti l’utilizzo di residui forestali trasportati tal quali fino a una distanza di 60 km e imballati per distanze maggiori. Ponendo limitazioni sulla disponibilità a pagare da parte di un impianto, l’altro ne trae vantaggio in quanto si approvvigiona da un’area più vicina. Il modello matematico che è stato sviluppato, attraverso la programmazione lineare ed in particolare il “problema dei trasporti”, ricalca la problematica di approvvigionamento da risolvere. Un modello così sviluppato può fornire soluzioni più flessibili rispetto alla semplice pianificazione manuale e allo stesso tempo permette di testare diverse strategie e diversi possibile scenari. Grazie all’utilizzo del GIS è possibile visualizzare chiaramente da un punto di vista geografico le soluzioni ottenute, altrimenti consultabili leggendo una lista di numeri difficilmente comprensibile. L’utilizzo della programmazione lineare assieme ai sistemi informativi geografici sono un utile metodo per determinare la migliore localizzazione di strutture o l’approvvigionamento ottimale di materie prime. Le diverse analisi di sensitività permettono di capire i fattori che maggiormente influenzano la logistica dell’approvvigionamento.

The need for modern energy systems to embrace the requirements of energy security, sustainability and affordability in their designs has placed emphatic importance on exploitation of renewable resources, such as solar and wind energy, etc. However, these resources often lead to reduced reliability and dispatchability of energy systems; less-efficient conversion processes; high cost of power production; etc. One promising way to ameliorate these challenges is through hybridization of renewable energy resources, and by using organic Rankine cycle (ORC) for power generation. Thus, this PhD research project is aimed at conceptual design and techno-economic optimization of hybrid solar-biomass ORC power plants. The methodologies adopted are in four distinct phases: - First, novel hybrid concentrated solar power (CSP)-biomass scheme was conceived that could function as retrofit to existing CSP-ORC plants as well as in new hybrid plant designs. Thermodynamic models were developed for each plant sub-unit, and yearly techno-economic performance was assessed for the entire system. Specifically, the ORC was modelled based on characteristics of an existing CSP-ORC plant, which currently operates at Ottana, Italy. Off-design models of ORC components were integrated, and their performance was validated using experimental data obtained from the aforementioned real plant. - Second, detailed exergy and exergoeconomic analyses were performed on the proposed hybrid plant, in order to examine the system components with remarkable optimization potentials. The evaluation on optimization potentials considered intrinsic irreversibilities in the respective components, which are imposed by assumptions of systemic and economic constraints. This has been termed enhanced exergy and enhanced exergoeconomic analyses here. - Third, the techno-economic implications of using siloxane mixtures as ORC working fluid were investigated, with the aim of improving heat transfer processes in the ORC plant. The studied fluid pairs were actively selected to satisfy classical thermodynamic requirements, based on established criteria. - Fourth, the biomass retrofit system was optimized multi-objectively, to minimize biomass consumption rate (maximize exergetic efficiency) and to minimize exergy cost rate. Non-dominated Sorting Genetic Algorithm (NSGA-II) was adopted for multi-objective optimization. The conceptual scheme involves parallel hybridization of CSP and biomass systems, such that each is capable of feeding the ORC directly. Results showed that the proposed biomass hybridization concept would increase both thermodynamic efficiency and economic performance of CSP-ORC plants, thereby improving their market competitiveness. Total exergy destroyed and exergy efficiency were quantified for each component, and for the whole system. Overall system exergetic efficiency of about 7 % was obtained. Similarly, exergoeconomic factor was obtained for each system component, and their implications were analysed to identify system components with high potentials for optimization. Furthermore, it was observed that thermodynamic performance of the hybrid plant would be optimized by using siloxane mixtures as ORC working fluid. However, this would result in larger heat exchange surface area, with its attendant cost implications. Lastly, biomass combustion and furnace parameters were obtained, which would simultaneously optimize exergetic efficiency and exergy cost rate for the hybrid plant. In sum, a novel scheme has been developed for hybridizing solar and biomass energy for ORC plants, with huge potentials to improve techno-economic competitiveness of solar-ORC systems.

Atmospheric aerosols represent an important but uncertain component of the atmosphere, which are known to affect the Earth's radiative budget by scattering and absorbing solar and terrestrial radiation, and by influencing the optical properties and lifetime of clouds. Organic aerosols are a ubiquitous feature of atmospheric composition around the globe, yet also represent a significant source uncertainty with regard to the understanding of aerosol behaviour and their representation m regional and global models. Presented here are aircraft measurements of organic aerosols arising from biomass burning and biogenic production over West Africa; the predominant sources of submicron aerosols during the dry and wet seasons in a region which has received comparatively little study in the literature. Measurements were taken usuig an Aerodyne Quadrupole Aerosol Mass Spectrometer (Q-AMS) installed on the UK Facility for Atmospheric Measurements (FAAM) aircraft. The physical and chemical properties of biomass burning aerosols were investigated on a continental scale, with particular focus on the evolution of these characteristics as the aerosols aged during transport from the source region. Systematic evolution of the chemical composition of aerosols was observed and aerosols became increasingly oxygenated with increasing distance from source. Emission ratios were estimated for black carbon and organic carbon, which compare well with previous results though the estimates made here are on regional scales rather than from single fires. Evolution of the particle size distribution was dominated by coagulation rather than condensation, and negligible secondary organic aerosol (SOA) production was observed. The chemical evolution of biomass burning aerosols without an increase in mass from secondary production appears to be a consistent finding for biomass burning aerosols, when the same analysis was completed for biomass burning emissions from other regions.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 272-291).
The combustion of biomass is a major source of atmospheric trace gases and aerosols. Regional and global-scale models of atmospheric chemistry and climate take estimates for these emissions and arbitrarily "mix" them into grid boxes with horizontal scales of 10-200 km. This procedure ignores the complex non-linear chemical and physical transformations that take place in the highly concentrated environment of the young smoke plumes. In addition, the observations of the smoke plume from the Timbavati savannah fire [Hobbs et al., 2003] show much higher concentrations of ozone and secondary aerosol matter (nitrate, sulfate, and organic carbon [OC]) in the smoke plume than are predicted by current atmospheric chemistry models. To address these issues, we developed a new model of the gas- and aerosol-phase chemistry of biomass burning smoke plumes called ASP (Aerosol Simulation Program). Here we use ASP to simulate the gas-phase chemistry and particle dynamics of young biomass burning smoke plumes and to estimate the errors introduced by the artificial mixing of biomass burning emissions into large-scale grid boxes. This work is the first known attempt to simultaneously simulate the dynamics, gas-phase chemistry, aerosol-phase chemistry, and radiative transfer in a young biomass burning smoke plume. We simulated smoke plumes from three fires using ASP combined with a Lagrangian parcel model. We found that our model explained the formation of ozone in the Otavi and Alaska plumes fairly well but that our initial model simulation of the Timbavati smoke plume underestimated the formation of ozone and secondary aerosol matter. The initial model simulation for Timbavati appears to be missing a source of OH. Heterogeneous reactions of NO2 and SO2 could explain the high concentrations of OH and the rapid formation of ozone, nitrate and sulfate in the smoke plume if the uptake coefficients on smoke aerosols are large [O(10-3) and O(10-4), respectively]. Uncharacterized organic species in the smoke plume were likely responsible for the rapid formation of aerosol OC. The changes in the aerosol size distribution in our model simulations were dominated by plume dilution and condensational growth, with coagulation and nucleation having only a minor effect.
(cont.) We used ASP and a 3D Eulerian model to simulate the Timbavati smoke plume. We ran two test cases. In the reference chemistry case, the uncharacterized organic species were assumed to be unreactive and heterogeneous chemistry was not included. In the expanded chemistry case, the uncharacterized organic compounds were included, as were heterogeneous reactions of NO2 and SO2 with uptake coefficients of 10-3 and 2x10-4, respectively. The 3D Eulerian model matched the observed plume injection height, but required a large minimum horizontal diffusion coefficient to match the observed horizontal dispersion of the plume. Smoke aerosols reduced the modeled photolysis rates within and beneath the plume by 10%-20%. The expanded chemistry case provided a better match with observations of ozone, OH, and secondary aerosol matter than the reference chemistry case, but still underestimated the observed concentrations. We find that direct measurements of OH in the young smoke plumes would be the best way to determine if heterogeneous production of HONO from NO2 is taking place, and that these measurements should be a priority for future field campaigns. Using ASP within an Eulerian box model to evaluate the errors that can be caused by the automatic dilution of biomass burning emissions into global model grid boxes, we found that even if the chemical models for smoke plume chemistry are improved, the automatic dilution of smoke plume emissions in global models could result in large errors in predicted concentrations of O3, NOx and aerosol species downwind of biomass burning sources. The thesis discusses several potential approaches that could reduce these errors, such as the use of higher resolution grids over regions of intense biomass burning, the use of a plume-in-grid model, or the use of a computationally- efficient parameterization of a 3D Eulerian plume chemistry model.
by Matthew James Alvarado.
Ph.D.

In the transition to a sustainable energy supply there is an increasing need to use biomass for replacement of fossil fuel. A key challenge is to utilize biomass conversion technologies in an environmentally sound manner. Important aspects are to minimize potential formation of persistent organic pollutants (POPs) such as dioxins and dioxin-like compounds. This thesis involves studies of formation characteristics of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and naphthalenes (PCNs) in microwave-assisted pyrolysis (MAP) and torrefaction using biomass as feedstock. The research focuses are on their levels, distributions, fingerprints (homologue profiles and isomer patterns) and the underlying formation pathways. The study also included efforts to optimize methods for extracting chlorinated aromatic compounds from thermally treated biomass. The overall objective was to contribute better understanding on the formation of dioxins and dioxin-like compounds in low temperature thermal processes. The main findings include the following: Pressurized liquid extraction (PLE) is applicable for simultaneous extraction of PCDDs, PCDFs, PCNs, polychlorinated phenols and benzenes from thermally treated wood. The choice of solvent for PLE is critical, and the extraction efficiency depends on the degrees of biomass carbonization. In MAP experiments PCDDs, PCDFs and PCNs were predominantly found in pyrolysis oils, while in torrefaction experiments they were mainly retained in solid chars with minor fractions in volatiles. In both cases, highly chlorinated congeners with low volatility tended to retain on particles whereas the less chlorinated congeners tended to volatize into the gas phase. Isomer patterns of PCDDs, PCDFs and PCNs generated in MAP were more selective than those reported in combustion processes. The presence of isomers with low thermodynamic stability suggests that the pathway of POPs formation in MAP may be governed not only by thermodynamic stabilities but also by kinetic factors. Formation of PCDDs, PCDFs and PCNs depends not only on the chlorine contents in biomass but also the presence of metal catalysts and organic/metal-based preservatives. Overall, the results provide information on the formation characteristics of PCDDs, PCDFs and PCNs in MAP and torrefaction. The obtained knowledge is useful regarding management and utilization of thermally treated biomass with minimum environmental impact.

Although more than a hundred papers dealing with the agglomeration problem in combustion and gasification of biomass can be found in the literature, very few studies focusing on the bed particle layer formation process in fluidized bed combustion (FBC) and fluidized bed gasification (FBG) can be found. With increased knowledge of the bed particle layer formation process — i.e. the main route behind bed agglomeration and bed material deposition in wood combustion/gasification — suitable combinations of fuel/bed material and/or bed material management measures can be suggested. This would not only aim to reduce the risk of ash related operational problems but also to enhance the catalytic activity of the bed material (e.g. for tar removal in gasification). The present investigation was therefore undertaken to determine the layer formation process on and within typical bed materials (i.e. quartz and olivine) and for a potentially interesting new bed material, K-feldspar. Bed material samples were collected from four different combustion and two different gasification appliances: two bubbling fluidized beds (BFB) (5 kWth/30 MWth), two full-scale circulating fluidized beds (CFB) (90/122 MWth), and two dual fluidized bed gasifiers (DFB) (8/15 MWth). Scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) were used to explore layer morphology and elemental composition and to gain information about crystalline phases of the layers. Phase diagrams and thermodynamic equilibrium calculations (TECs) were used to interpret the melting behavior of the layers and the melt fragments in deposits. In addition, a diffusion model was used to interpret the layer growth process. For quartz bed particles taken from BFB, the younger particles (< around 1 day) had only one thin layer, but for particles older than 3 days, the layer consisted of inner and outer layers. In addition to the inner and outer layers, a K-rich inner-inner layer was found for bed particles taken from CFB and DFB. No outer layers were found for quartz bed particles taken from DFB. The thin/absence of an outer layer could have resulted from the more significant attrition between particles in CFB and DFB. Reduced availability of Ca and a risk of layer breakage from the particle lead to the formation of the inner-inner layer. Similar elemental compositions of the layers upon the quartz bed particles taken from different fluidized bed techniques were found. The inner-inner layers are dominated by Si, K and Ca (excluding O), and the outer layers are rich in Ca, Si and Mg, which seem to resemble more closely the fuel ash composition. The inner layers, mainly consisted of Si and Ca, were found to have higher concentrations of Ca for older particles. The layer thickness increases with particle age, but the growth rate decreases. Melt was estimated to exist in the inner layer for younger particles (< around 1 day) and in the inner-inner layer. The existence of partially melted inner-inner layers, in particles from CFB and DFB, points towards higher risk of bed agglomeration in these techniques compared to BFB. Based on the experimental results, thermodynamic equilibrium calculations, and diffusion model analyses, a layer formation process on quartz bed particle was suggested: the layer formation is initiated by reaction of gaseous K compounds with quartz to form K-rich silicate melt, which prompts the diffusion of Ca2+. The gradual incorporation of Ca into the melt followed by the precipitation of Ca-silicates, e.g. Ca2SiO4, will result in the continuous inner layer growth. However, because of increasing concentration of Ca and release of K from the inner layer, the melt disappears in the inner layer and the layer formation process gradually becomes Ca diffusion controlled. The diffusion resistance increases with increasing thickness of a more Ca-rich layer, resulting in a decreasing layer growth rate. Crack layers with similar compositions dominated by Si, K and Ca were observed in relatively old quartz bed particles. A melt was predicted to exist in the crack layer according to thermodynamic equilibrium calculations. The crack layers found in quartz particles from BFB and CFB connect with the cracks in the inner layer, whereas for bed samples collected from DFB, the crack layers were found along existing cracks in the quartz particle. The different morphologies may indicate different routes of formation for crack layers in bed particles from different fluidized bed technologies. For quartz particles from BFB and CFB, crack formation through the inner layer down to the interface between the inner layer and the core of quartz bed particle initiates the cracks in the quartz bed particle. This allows for diffusion of gaseous alkali compounds to react with quartz in the bed particle core, thereby forming crack layers. The reaction is accelerated with bridge formation between crack layers. This may later lead to the breakdown of the bed particle into smaller alkali-silicate-rich fragments. For K-feldspar bed particles from BFB and CFB, only one layer was found for particles with an age of 1 day. For bed particles with ages older than 3 days, two layers including a homogenous inner layer containing cracks and a more particle-rich outer layer can be distinguished. Compared to bed particles from BFB with similar ages, the outer layer is thinner for bed particles from CFB. The inner layer is dominated by Ca, Si and Al (excluding O), whereas the outer layer is dominated by Ca, Si and Mg. The average concentration of Ca in the inner layer increases with bed particle age. Increasing layer thickness with decreasing growth rate was found, similar to that on quartz particles. For particles from DFB, the inner layer is also mainly consisted of Ca and Si, but cracks in the inner layer were not found. For all the particles, the Ca/Si molar ratio in the layer decreases towards the bed particle core and the change of concentration is more significant at the bed particle core/layer interface. The overall inner layer growth is resultant from the gradual incorporation of Ca into the layer. For olivine bed particles from DFB, the younger bed particles (< around 24 h) have only one layer, but after 24 h, an inner layer and an outer layer appear. Furthermore, for bed particles older than 180 h, the inner layer is separated into a distinguishable Ca-rich and Mg-rich zone. Two kinds of cracks in the inner layer either perpendicular or parallel to the particle surface were observed. Compared to the younger bed particles, the Ca concentration in the layer of older particles is much higher. A detailed mechanism for layer formation on olivine particles in fluidized bed gasification (most likely also applicable to combustion) based on the interaction between woody biomass ash and olivine has been proposed. The proposed mechanism is based on a solid-solid substitution reaction. However, a possible enabling step in the form of a Ca2+ transport via melts may occur. Ca2+ is incorporated into the crystal structure of olivine by replacing either Fe2+ or Mg2+. This substitution occurs via intermediate states where Ca-Mg silicates, such as CaMgSiO4, are formed. Mg2+ released from the crystal structure most likely forms MgO, which can be found in a distinguishable zone between the main particle layers. Due to a difference in the bond lengths between Mg/Fe and incorporated Ca2+ with their respective neighboring oxygen atoms, the crystal structure shifts, resulting in formation of cracks. The dominating elements in the inner layers are similar for each kind of bed material from BFB, CFB, and DFB, indicating limited effects of atmosphere on the inner layer formation. The initiation of layer formation differs depending on the bed material, but increasing Ca concentration in the inner layer with time for all bed materials indicates that the layer growth resulted from the incorporation of Ca into the layer. Compared to quartz, K-feldspar and olivine are more promising bed materials in wood combustion/gasification, especially in CFB and DFB techniques, from the perspective of mitigating bed agglomeration and bed material deposit build-up.

Thesis (M.S.)--West Virginia University, 2003.
Title from document title page. Document formatted into pages; contains vii, 137 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 71-76).

The global energy requirement is increasing at a rapid pace and fossil fuels have been one of the major players in meeting this growing energy demand. However, the resources for fossil fuels are finite. Therefore, it is essential to develop renewable energy sources like biofuels to help address growing energy needs. A key aspect in the production of biofuel is the biomass logistics chain that constitutes a complex collection of activities, which must be judiciously executed for a cost-effective operation. In this thesis, we introduce a two-phase optimization-simulation approach to determine tactical biomass logistics-related decisions cost effectively in view of the uncertainties encountered in real-life. These decisions include number of trucks to haul biomass from storage locations to a bio-refinery, the number of unloading equipment sets required at storage locations, and the number of satellite storage locations required to serve as collection points for the biomass secured from the fields. Later, an operational-level decision support tool is introduced to aid the "feedstock manager" at the bio-refinery by recommending which satellite storage facilities to unload, how much biomass to ship, how to allocate existing resources (trucks and unloading equipment sets) during each time period, and how to route unloading equipment sets between storage facilities. Another problem studied is the "Bale Collection Problem" associated with the farmgate operation. It is essentially a capacitated vehicle routing problem with unit demand (CVRP-UD), and its solution defines a cost-effective sequence for collecting bales from the field after harvest.
Master of Science

The US Department of Energy has set an ambitious goal of replacing 30% of current petroleum consumption with biomass and its products by the year 2030. To achieve this goal, various systems capable of handling biomass at this magnitude have to be designed and built. The transportation system for a cotton gin was studied and modeled with the current management policy (FIFO) used by the gin to gain understanding of a logistic system where the processing plant (gin) pays for the transportation of the feedstock. Alternate management policies for transporting cotton modules showed significant time savings of 24% in days-to-haul. To design a logistics system and management strategy that will minimize the cost of biomass delivery (round bales of switchgrass), a seven-county region in southern Piedmont region of Virginia was selected as the location for a 50 Mg/h bioprocessing plant which operates 24 h/day, 7 days/week. Some of the equipment are not be commercially available and need to be developed. The transport equipment (trucks, loaders and unloaders) was defined and the operational parameters estimated. One hundred and fifty-five secondary storage locations (SSLs) along with a 3.2-km procurement area for each SSL were determined for the region. The travel time from each SSL to the plant was calculated based on a network flow analysis. Seven different policies (strategies) for scheduling loaders were studied. The two key variables were maximum number of trucks required and the maximum at-plant inventory. Five policies were based on â Shortest Travel Time - Longest Travel Timeâ allocation and two policies were based on â Sector-basedâ allocation. Policies generating schedules with minimum truck requirement and at-plant storage were simulated. A discrete event simulation model for the logistic system was constructed and the productive operating times for system equipment and inventory was computed. Lowest delivered cost was $14.68/Mg with truck cost averaging $8.44/Mg and loader cost averaging $2.98/Mg. The at-plant inventory levels were held to a maximum of 390 loads. The loaders operated less than 9,500 hours and the unloaders operated for a total of 2,700 hours for both systems simulated.
Ph. D.

Utilization of forest-based biomass for bioenergy and biofuels production could generate additional revenue streams, reduce greenhouse gas (GHG) emissions and generate development opportunities for forest-dependent communities. Barriers such as the capital intensity of conversion technologies, complexity of biomass procurement logistics, and the need to establish sustainable supply chains must be overcome. Mathematical modeling has supported the optimal design of biomass supply chains for bioenergy or biofuels production separately, mostly from an economic perspective. Some studies incorporated environmental and/or social criteria in the optimal supply chain design. However, no study modeled forest-based biomass supply chains for the simultaneous bioenergy and biofuels production, considering economic, environmental and social benefits. The development of such model is the objective of this thesis. First, an optimization model is developed that determines the optimal network design and the optimal yearly flows of raw materials and products that maximize the net present value (NPV) of the supply chain. The model considers the flow of energy among co-located conversion technologies and is applied to a case study in Canada. Second, a life cycle environmental analysis is developed to analyze the environmental impacts of the supply chain alternatives in the case study. Third, the optimization model is reformulated as bi-objective with an environmental objective that maximizes the GHG emission savings associated with the supply chain. These savings are estimated by comparing the emissions of the forest-based biomass supply chain system, versus those of the baseline system where unused biomass is disposed with current methods and energy demands are satisfied with currently available sources. Finally, a multi-objective optimization model is generated that integrates a social objective. The social objective is quantified by a social benefit indicator that assigns different levels of impact of job creation based on the type and location of the jobs. The bi-objective and multi-objective optimization models are applied to the case study and solved using a Pareto-generating solution method. Results indicate a trade-off between the NPV of the supply chain and the other two objectives, and a positive correlation between the generation of high impact jobs in the region, and the overall GHG emission savings.
Forestry, Faculty of
Graduate

Thesis: S.M., Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 133-140).
The present work deals with the process of fluidized bed biomass gasification (FBBG), which is the thermochemical conversion of solid biomass into combustible synthetic gas using a fluidized bed. Fluidized bed gasifiers encounter high tar concentrations at the gasifier outlet necessitating expensive downstream cleaning equipment. Apart from the complex chemical pathways involved, tar production is also strongly dependent on the transport processes occurring inside the gasifier. Hence, the development of a detailed model to predict the variation of tar production under different operating conditions needs to include two important considerations: a comprehensive chemical kinetic sub-model and a detailed hydrodynamic sub-model. However, due to the huge computational expense associated with such a detailed simulation coupling the complex chemistry and hydrodynamics, there is a need to develop simplified models on both fronts. The first part of this work presents a detailed discussion on the chemistry models for biomass gasification: after introducing the existing state-of-the-art reaction mechanisms (both detailed and compact), two new global chemistry models, incorporating a global primary tar cracking reaction, for air-blown gasification and steam-blown gasification conditions are developed. The major gas species and total tar concentrations predicted using the global models in reactor network simulations of the gasifiers are compared with the corresponding predictions obtained using the detailed CRECK mechanism for biomass gasification, as well as with the available experimental observations. On the hydrodynamics front, an improved reactor network model based on the two-phase theory has been developed to better capture the mixing inhomogeneities in the bubbling fluidized bed, including mass transfer considerations between the bubble and emulsion phases. Finally, the predictions of various tar class concentrations and major gas species concentrations, obtained using the improved reactor network model in conjunction with the detailed CRECK kinetic reaction mechanism, for both air-blown gasification and steam gasification, are presented. Key words: Biomass gasification, Fluidized beds, Chemical reactor network modeling, chemical kinetics, chemistry mechanism reduction, Global chemistry model
by Rajesh Sridhar.
S.M.

There is a consensus worldwide that the share of renewable energy sources should be increased to mitigate climate change. The strive to increase the renewable energy fraction can partly be met by an increased utilization of different biomass feedstocks. Many of the "new" feedstocks puts stress on certain challenges such as air pollution emissions and operation stability of the combustion process. The overall objective was to investigate, evaluate, and explain the effects of fuel design and combustion control - fuel engineering - as primary measures for control of slag formation, deposit formation, and fine particle emissions during biomass combustion in small and medium scale fixed-bed appliances. The work in this thesis can be outlined as having two main focus areas, one more applied regarding fuel engineering measures and one more fundamental regarding the time-resolved release of ash forming elements, with particular focus on potassium. The overall conclusion related to the abatement of particle emissions and slag formation, is that the release of fine particle and deposit forming matter can be controlled simultaneously as the slag formation during fixed-bed biomass combustion. The methodology is in this perspective denoted “fuel engineering” and is based on a combined approach including both fuel design and process control measures. The studies on time-resolved potassium release showed that a Macro-TG reactor with single pellet experiments was a valuable tool for studying ash transformation along the fuel conversion. The combination of dedicated release determinations based on accurate mass balance considerations and ICP analysis, with phase composition characterization by XRD, is important for the understanding of potassium release in general and time-resolved data in particular. For wood, the results presented in this work supports the potassium release mechanism from "char-K" but questions the previously suggested release mechanism from decomposition of K-carbonates. For straw, the present data support the idea that the major part of the potassium release is attributed to volatilization of KCl. To further explore the detailed mechanisms, the novel approach developed and applied in this work should be complemented with other experimental and analytical techniques. The research in this thesis has explored some of the challenges related to the combined phenomena of fuel conversion and ash transformation during thermochemical conversion of biomass, and has contributed with novel methods and approaches that have gained new knowledge to be used for the development of more effective bioenergy systems.

Using biomass gasification to produce combustible gas is one of the promising sustainable energy optionsavailable for many countries. At present, a few small scale community based power generation systemsusing biomass gasifiers are in operation in Sri Lanka. However, due to the lack of proper knowledge, thesesystems are not being operated properly in full capacity. This stands as an obstacle for further expansionof the use of gasifier technology.The objective of this study was to identify the most influential parameters related to fuel wood gasificationwith a down draft gasifier in order to improve the gasification processes.A downdraft gasifier of 10kW electrical capacity was used to study the effect of equivalent ratio (Actual airfuel ratio to Stoicheometric air fuel ratio: ER) on the specific gas production, the heating value of gasproduced and the cold gas efficiency using three throat diameters (125mm, 150mm and 175mm). Six trialswere carried out for each throat diameter by varying the supply air flow to change the ER. The gassamples were tested for their compositions under steady state operating conditions. Using mass balancesfor C and N, the cold gas efficiencies, calorific values and the specific gas production rates weredetermined.The results showed that with all throat diameters the calorific value of gas reduced with the increase ofER. The cold gas efficiency reduced with ER in a similar trend for all three throat diameters. The specificgas production increased with ER under all throat diameters.Calorific value and specific gas production are changing inversely proportional manner. The ER to beoperated is depends on the type of application of the gas produced and engine characteristics. When alarge heat is required, low ER is to be used in which gas production is less. In the opposite way, when alarge amount of gas is needed, higher value of ER is recommended.

I studien har resurstillgången i form av biomassa inom Östergötland kartlagts för att undersöka om det finns en potentiell möjlighet för ett ökat tillvaratagande av skördad biomassa från skogsbruket. Det har även undersökts om ett tillvaratagande av biomassa för en ökad energiutvinning är ekonomiskt hållbart i förhållande till de rörliga transportkostnader som medförs. Utifrån den kartläggning som genomförts har därmed en matematisk modell skapats som ger förslag på hur biomassan skall fördelas från resurspunkter till värmeverk i Östergötlands 13 kommuner, för att därmed uppfylla den efterfrågan av fjärrvärme som finns i respektive kommun. Den matematiska modellen fördelar även ut de resurser som finns kvar efter att efterfrågan har uppfyllts, till ett antal optimalt placerade kondenskraftverk, där elektricitet skall utvinnas. Utifrån 4 framtagna scenarier tyder den matematiska modellens resultat på att ett ökat tillvaratagande av biomassa i form av grot och stubb kan genomföras med lönsamhet genom optimerad lokalisering av förbränningsstationer och fördelning av biomassa. Denna studie är en del av ett kommande forskningsprojekt och ger en första indikation på att det finns en potential för ett ökat tillvaratagande av biomassa från skogsbruket.

The iron and steel industry emitted 8 % of all CO2 emissions in Sweden, 2011. Investigating alternative energy carriers is the purpose of this thesis. By pyrolyzing biomass, an energetic solid, gaseous and liquid (bio oil) fraction is obtained. If pyrolyzing biomass in a fluidized-bed reactor, the highest value may be added to the combined products. Additional understanding of pyrolysis in fluidized beds is pursued, using Computational Fluid Dynamics (CFD) and comprehensive kinetic schemes. The obtained solid product is investigated as a bio-injectant in blast furnaces for ironmaking. A new approach of separately modeling, the primary and secondary pyrolysis, is developed in this thesis. A biomass particle devolatilizes during pyrolysis. Primary pyrolysis is the solid decomposition which results in the volatiles that can leave the particle. Secondary pyrolysis is the decompositions of these volatiles, primarily in the gas phase. The primary pyrolysis (35 species, 15 reactions) mainly occurs in the bed-zone and as such, the model needs to take into account the complex physical interaction of biomass-particles with the fluidizing media (sand) and the fluidizing agent (gas). This is accomplished by representing the components by Eulerian phases and implementing interaction terms, as well as using a Stiff Chemistry Solver for the implemented reactions.  The secondary pyrolysis (not considering heterogeneous reactions), mainly occurs outside the bed zone in one phase. The fluid flow is simpler but the chemistry is more complex, with a larger variety of molecules emerging. Carrying out the simulations time-effectively, for the secondary pyrolysis (134 species, 4169 reactions) is accomplished by using Dimension Reduction, Chemistry Agglomeration and In-situ Tabulation (ISAT); in a Probability Density Functional (PDF) framework. An analysis of the numerical results suggest that they can be matched adequately with experimental measurements, considering pressure profiles, temperature profiles and the overall yield of gas, solid and liquid products. Also, with some exceptions, the yield of major and minor gaseous species can be matched to some extent. Hence, the complex physics and chemistry of the integrated process can be considered fairly well-considered but improvements are possible. A parametric study of reaction atmospheres (or fluidizing agents), is pursued as means of understanding the process better. The models revealed significant effects of the atmosphere, both physically (during the primary and secondary pyrolysis) and chemically (during secondary pyrolysis). During primary pyrolysis, the physical influence of reaction atmospheres (N2, H2O) is investigated. When comparing steam to nitrogen, heat flux to the biomass particles, using steam, is better distributed on a bed level and on a particle level. During secondary pyrolysis, results suggest that turbulence interaction plays an important role in accelerating unwanted decomposition of the liquid-forming volatiles. Steam, which is one of the investigated atmospheres (N2, H2O, H2, CO, CO2), resulted in a lower extent of unwanted secondary pyrolysis. Altough, steam neither resulted in the shortest vapor residence time, nor the lowest peak temperature, nor the lowest peak radical concentration; all factors known to disfavor secondary pyrolysis. A repeated case, using a high degree of turbulence at the inlet, resulted in extensive decompositions. The attractiveness of the approach is apparent but more testing and development is required; also with regards to the kinetic schemes, which have been called for by several other researchers. The solid fraction after pyrolysis is known as charcoal. Regarding its use in blast furnaces; modelling results indicate that full substitution of fossil coal is possible. Substantial reductions in CO2 emissions are hence possible. Energy savings are furthermore possible due to the higher oxygen content of charcoal (and bio-injectants in general), which leads to larger volumes of blast furnace gas containing more latent energy (and less non-recoverable sensible energy). Energy savings are possible, even considering additional electricity consumption for oxygen enrichment and a higher injection-rate on energy basis. A survey of biomass availability and existing technology suppliers in Sweden, suggest that all injection into Blast furnace M3 in Luleå, can be covered by biomass. Based on statistics from 2008, replacement of coal-by-charcoal from pyrolysis could reduce the on-site carbon dioxide emissions by 28.1 % (or 17.3 % of the emissions from the whole industry). For reference, torrefied material and raw biomass can reduce the on-site emissions by 6.4 % and 5.7 % respectively.
Järn och stålindustrin stod för 8 % av alla koldioxidutsläpp i Sverige, 2011. Alternativa energibärare undersöks i denna avhandling. Genom pyrolys av biomassa, fås en energirik fast produkt, och samtidigt en gasformig och en vätskeformig produkt (bio-olja). Om en fluidbäddsreaktor används kan största möjliga mervärde tillföras de kombinerade produkterna. Djupare förståelse för pyrolys i fluidbäddar har eftersträvats med hjälp fluiddynamikberäkningar (CFD) och detaljerade kinetikscheman. Den fasta produkten har undersökts som bio-injektion i masugnar. En ny approach för modellering av primär och sekundär pyrolys separat, har utvecklats i denna avhandling. En biomassapartikel avflyktigas under pyrolys. Primär pyrolys är nedrytningen av den fasta biomassan till intermediärer (flyktiga ämnen) som kan lämna partikeln. Sekundärpyrolys är nedbrytning av dessa flyktiga ämnen, som primärt sker i gasfas. Primärpyrolysen (i detta arbete, 35 ämnen och 15 reaktioner) sker mestadels i bäddzonen och därmed behöver modellen ta hänsyn till den komplexa fysiska interaktionen av biomassapartiklarna med fluidbäddsmediet (sand) och fluidiseringsgasen. Detta åstadkoms med hjälp av Euleriska faser och interaktionstermer, samt en lösare för hantering av styva reaktionssystem. Sekundärpyrolysen sker huvudsakligen utanför bäddzonen. Fluiddynamiken är enklare men kemin är mer komplex, med fler ämnen närvarande. Att tidseffektivt köra beräkningarna, för sekundärpyrolysen (134 ämnen, 4169 reaktioner) åstadkoms med hjälp Dimensionsreducering, Kemiagglomerering och In-situtabulering (ISAT); som implementerats i en sannolikhetstäthetsfunktion (PDF). En analys av de numeriska beräkningarna antyder att de kan matchas med experimentella resultat, med avseende på tryckprofil, temperaturprofil, utbyte av gasformiga, fasta och vätskeformiga produkter. Dessutom, med några undantag, kan beräkningarna matchas ganska väl med de viktigaste gasformiga produkterna. Därmed kan de huvudsakliga fysiska och kemikaliska mekanismerna representeras av modellen men förbättringar är givetvis möjliga. En parameterstudie av reaktionsatmosfärer (dvs fluidiseringsgaser) genomfördes, för att förstå processen bättre. Modellen visade på betydande effekter av atmosfären, fysisk (både under primär och sekundärpyrolys), och kemiskt (under sekundärpyrolysen).   Under primärpyrolysen undersöktes den fysiska inverkan av reaktionsatmosfärer (N2, H2O). När ånga jämfördes med kvävgas, visade det sig att värmeflödet sker mer homogent på både bäddnivå och på partikelnivå, med ångatmosfär. Under sekundärpyrolysen, så antyder resultaten på att turbulensinteraktion spelar en viktig roll för accelererad oönskad sekundärpyrolys av de vätskebildande ämnena. Ånga som är en av de undersökta atmosfärerna (N2, H2O, H2, CO, CO2), resulterade i den lägsta omfattningen av sekundärpyrolys. Dock så ledde en ångatmosfär varken till den lägsta residenstiden, den lägsta peaktemperaturen eller den lägsta radikalkoncentrationen; som alla normalt motverkar sekundärpyrolysen. Ett repeterat case, med hög turbulens i inloppet, gav betydande sekundärpyrolys av de vätskebildande ämnena. Attraktiviteten av approachen är given men mer testning och utveckling behövs, som också påkallats av andra forskare. Den fasta produkten efter pyrolys kallas träkol. Angående dess applicering i masugnar, så visar modelleringsresultaten att full substitution av fossilt kol går att göra. Betydande minskningar i koldioxidutsläpp är därmed möjliga. Energibesparingar är dessutom möjligt, tack vare det höga syreinnehållet i träkol (och biobränslen generellt), vilket ger större volymer av masugnsgas med högre värmevärde (och mindre sensibel värme som inte är utvinnbar). Energibesparingar är möjliga även om hänsyn tas till högre eleffekt för syrgasanrikning i blästerluften och en högre injektionsåtgång på energibasis. En översikt över biomassatillgången och existerande teknikleverantörer i Sverige, indikerar att all injektion i Masugn 3 (i Luleå) kan ersättas med biomassa. Baserat på statistik från 2008, så kan ersatt kol med träkol, minska de platsspecifika koldioxidutsläppen med 28.1 % (eller 17.3 % av alla utsläpp från stålindustrin). Som jämförelse kan torrifierad biomassa and obehandlad biomassa reducera utsläppen med 6.4 % respektive 5.7 %.

QC 20150827

Nickel is a vital metal which occurs in two types of ore: laterites and sulfides. Historically sulfide ores have been the primary source of nickel however due to their limited resources and the vast occurrence of laterites, laterite processing has gained a great deal of attention. Nickel in laterite ores is accompanied by impurities such as magnesium and iron, due to their similarity in ionic radii and their capability in replacing one another in crystal lattices. Magnesium compounds are highly soluble, therefore, magnesium impurity in nickel processing leads to the production of non-recyclable process water which results in high water consumption and negative environmental impact due to the wastewater being discarded to the environment. An approach has been derived at the University of British Columbia which involves the removal of magnesium compounds from nickel plant wastewater streams as struvite. Struvite, MgNH₄PO₄·6H₂O, is a valuable fertilizer which provides three important nutrients of magnesium, phosphorus and nitrogen to plants. This study confirms the ability of the proposed flowsheet to successfully remove magnesium as struvite from nickel laterite plants from both aspects of the magnesium removal efficiency and the produced struvite purity; with the experiments conducted at the base conditions having magnesium removal efficiency of above 95 percent and the produced struvite purity being above 97 percent. This study focuses on the optimal conditions leading to the maximum magnesium removal and therefore struvite precipitation. Struvite precipitation is affected by many parameters. The most influential factors affecting struvite crystallization are mixing intensity, seeding and the seeding technique, pH, temperature, crystal retention time, magnesium to phosphate ratio, supersaturation level and the impurities present in the system. This study verifies that each of these parameters affect struvite precipitation differently. For instance, variations in supersaturation level and pH have greater effect on struvite precipitation then variations in temperature and mixing intensity. Additionally, this study confirms that the optimum condition for struvite precipitation is the same as the existing conditions of the effluent solution such as ambient temperature and pH; therefore, no further adjustment is required; however, solution seeding with struvite powder does improve the magnesium removal efficiency.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate

This research investigates the feasibility of exploiting local forest biomass for district heat generation in Williams Lake, BC. The objectives of this research are (1) to examine the economic viability of delivering forest biomass to the gate of a potential heating plant, and (2) to find a cost-optimized supply chain for delivering biomass to the plant. Considering the impact of biomass availability on the design of the supply chain and the required logistics in the system makes this study distinctive from the previous research. To achieve the first objective, the annual total delivery cost of biomass to the plant, namely the material, handling, processing, and transportation costs, was calculated for supply chain options with and without terminal storages. The results of the feasibility study showed that depending on the distance of source points to the plant, the delivery cost of woodchips to the plant ranged from $2.19 GJ⁻¹ to $2.87 GJ⁻¹. However, the gap between supply and demand in some months indicated that the direct flow of woodchips from source points to the plant would not be always possible. To meet the demand in months with biomass shortage, forest biomass should be stored in a terminal storage although this could increase the total annual cost to $6.59 GJ⁻¹. At the same time, transferring all the plant’s demand via terminal storage would not seem economical since in the months with more supply than demand and also with good accessibility to the collection areas, the direct flow is possible. Using a mix of direct and indirect flows might provide the opportunity to deliver forest biomass to the plant at a lower cost. A linear programming model was used to minimize the total annual cost and to determine the optimal flow of biomass to the heating plant. The optimization results revealed that the optimal flow of biomass would cost $2.62 GJ⁻¹, which is less expensive than the current delivery cost of natural gas to the plant ($6.39 GJ⁻¹). Therefore, the use of forest biomass for energy generation might be economical depending upon the capital and operating costs of the energy conversion facility.

For the purpose of sulphide removal in aquaculture ponds, three strains (name: TH21, QN71, QN51) were isolated and selected with the highest sulphide removal activity from Thanh Hoa and Quang Ninh coastal zones. These strains have identified and tested in a number of aquaculture ponds in different areas with good water quality results. With the objective of purple non sulfur bacteria biomass production containing 3 selected strains for wide application and suitable price for farmers, in this study, we study on optimum conditions of mixed purple non sulfur bacteria biomass production at pilot scale. The results showed that the sources of substrates were soybean meal (1g/l) and acetate (0.5g/l). These substrates are low cost, easy to find, convenient in large culture. The mixture of photosynthetic bacteria can be cultured in glass tanks, under micro aerobic and natural lighting conditions that produce highly concentrated photosynthetic bacteria and lowest rest media.
Nhằm mục tiêu xử lý sulphide trong môi trường nuôi trồng thủy sản, chúng tôi đã phân lập và lựa chọn được ba chủng vi khuẩn tía quang hợp có khả năng loại bỏ sulphide cao nhất ký hiệu TH21, QN71, QN52 từ các vùng ven biển Thanh Hóa và Quảng Ninh. Các chủng này đã được định loại và thử nghiệm tại một số ao nuôi thủy sản ở các vùng khác nhau thu được kết quả tốt về chất lượng nước. Để tạo chế phẩm vi khuẩn tía quang hợp từ 3 chủng lựa chọn được ứng dụng rộng rãi và có giá thành phù hợp cho nông hộ, trong nghiên cứu này, chúng tôi nghiên cứu tối ưu hóa các điều kiện sản xuất sinh khối hỗn hợp 3 chủng vi khuẩn tía quang hợp ở quy mô pilot. Kết quả cho thấy đã tìm kiếm được nguồn cơ chất là bột đậu tương (1g/l) và acetate (0.5g/l) là những chất có giá thành thấp, dễ tìm kiếm, thuận tiện trong nhân nuôi ở quy mô lớn. Hỗn hợp vi khuẩn tía quang hợp có thể nuôi trong các bể kính, ở điều kiện vi hiếu khí, có ánh sáng chiếu tự nhiên có thể sản xuất được chế phẩm vi khuẩn tía quang hợp có mật độ cao, cơ chất còn lại sau sản xuất là ít nhất.

Given the increasing demand for energy, climate change, and environmental concern of fossil fuels, it is becoming increasingly significant to find alternative renewable energy sources. Bioethanol as one sort of cellulosic biofuel produced from lignocellulosic biomass feedstocks has shown great potential as a renewable resource. Delivering a competitive, sustainable biofuel product requires comprehensive supply chain planning and design. Developing economically and environmentally optimal supply chain models is necessary in this context. Also, designing biomass bioethanol supply chain (BBSC) models addressing social issues requires using second-generation biomass which is not a source of food for humans. Currently, corn as a first-generation feedstock is the primary source of bioethanol in the United States which has given growth to new social issues such as the food versus fuel debate. Considering incentives for first-generation bioethanol producers to switch to second-generation biomass and associated production technologies will help to address such social issues. The scope of this study focuses on analyzing economic and environmental market incentives for second-generation bioethanol producers while considering different carbon policies as penalties and restrictions for emissions coming from BBSC activities. First, we develop an integrated life cycle emission and energy optimization model for analyzing an entire second-generation bioethanol supply chain using switchgrass as the source of biomass while finding the most appropriate potential locations for building new cellulosic biorefineries in North Dakota. Second, we propose a supply chain model by comparing a first-generation (corn) and a second-generation (corn stover) bioethanol supply chain to analyze how policymakers can incentivize first-generation bioethanol producers to switch their technology and biomass supply from first-generation to second-generation biomass. Third, we develop the model further by investigating the impact of four different carbon policies including the carbon tax, carbon cap, carbon cap-and-trade, and carbon offset on the supply chain strategic and operational decisions. This research will help to design robust BBSCs focused on sustainability in order to optimally utilize second-generation biomass resources in the future. The findings can be utilized by renewable energy policy decision makers, bioethanol producers, and investors to operate in a competitive market while protecting the environment.

This research has focussed on the impact of kaolin as additive on the agglomeration behaviours of willow, white wood, and miscanthus during their combustion processes in a laboratory-scale fixed bed whereby, Gooch ceramic crucible was used as the combustion chamber. It aimed at reducing agglomeration during the combustion of these selected problematic biomass fuels. Biomass fuels are CO2 neutral and very rich in alkali metals especially potassium, K and sodium, Na with potassium displaying the predominant roles in the agglomeration formation of these selected biomass fuels. During the combustion processes, agglomerates were formed in the combustion chamber at 750 0 C and 802 0 C under the atmospheric pressure. This was attributed to the formation of eutectic compounds in the form of alkali-silicates (K-silicates or Na- silicates). The eutectic compound has a lower melting temperature than the melting temperature of either the alkali metals or the silica from sand, which is the bed material. It therefore melts abruptly in the bed and formed lumps in form of agglomerates. Energy Dispersive X-ray spectroscopy (EDX) carried out on the agglomerates indicated that, the interior of the agglomerates was dominated with silicon, Si from the sand while the exterior or the peripheries were preponderated with alkali metals potassium K, and sodium Na from the biomass fuels ash. Other trace elements present in the agglomerates as confirmed by EDX analyses are; Aluminium Al, Calcium Ca, Chlorine Cl, Iron Fe, Phosphorus P, and Magnesium Mg. Meanwhile, with the addition of additive (kaolin) Al2 Si2 O5 (OH)4 to the bed materials and the combustion processes repeated under the same operating conditions, no agglomerate was formed at 750 0 C and 802 0 C. However, eutectic compound in the form of alumina-alkali-silicate was formed at a higher melting temperature than the alkali from the biomass fuels and the silica from bed materials, therefore no agglomerate was formed at these temperatures (750 0 C and 802 0 C). Factsage software was extensively utilized to predict the eutectic points (eutectic temperatures) on both the binary and the ternary phase diagrams. With the inclusion of additive (kaolin) in the bed materials, on the binary phase diagrams, agglomeration was predicted to occur in the combustion bed at 1200 0C if the biomass fuel is dominated by potassium, K. Consequently, if the biomass fuel is dominated by sodium, Na, agglomeration was predicted to occur at 1700 0 C in the combustion bed. However, on the ternary phase diagrams, with the addition of kaolin to the bed materials, initial agglomeration was predicted to occur at 1550 0 C if the biomass fuel is dominated by potassium, K but rose to 1700 0 C if the biomass fuel is dominated by sodium, Na. This justifies the affirmation that, Sodium, Na has a higher melting temperature than potassium, K. Elongation in the biomass particle size from < 1mm diameter before combustion to 7mm diameter in the agglomerates formed from the combustion of willow, and 10mm diameter in the agglomerates produced from the combustion of both the miscanthus and white wood is a clear manifestation that, agglomeration actually occurred in the bed. Post combustion analyses; Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM and EDX) carried out on the agglomerate samples also confirmed that, agglomeration took place in the bed. Huge agglomerates were formed at a lower melting temperature of 350 0C when potassium hydroxide, KOH and silica sand were heated directly (reality test). Harder and tougher agglomerates were produced at 502 0C. This confirmed that, agglomerates were produced from the formation of a low temperature alkali-silicate in the form of K-silicate. The results of this research have indicated that, Gooch ceramic crucible is a reliable combustion chamber for the combustion of biomass fuels experiments/tests in a laboratory –scale fixed bed. It accommodated more heat distribution into the combustion chamber than the conventional ceramic crucible. Moreover, kaolin was also confirmed as an additive capable of reducing agglomeration during the combustion of biomass fuels in a laboratory - scale fixed bed and other combustion beds.

The classic minimum induced drag spanload is not necessarily the best choice for an aircraft. For a single aircraft configuration, variations from the elliptic, minimum drag optimum load distribution can produce wing weight savings that result in airplane performance benefits. For a group of aircraft flying in formation, non-elliptic lift distributions can give high induced drag reductions both for the formation and for each airplane.

For single aircraft, a discrete vortex method which performs the calculations in the Trefftz plane has been used to calculate optimum spanloads for non-coplanar multi-surface configurations. The method includes constraints for lift coefficient, pitching moment coefficient and wing root bending moment. This wing structural constraint has been introduced such that wing geometry is not changed but the modified load distributions can be related to wing weight. Changes in wing induced drag and weight were converted to aircraft total gross weight and fuel weight benefits, so that optimum spanloads that give maximum take-off gross weight reductions can be found. Results show that a reduction in root bending moment from a lift distribution that gives minimum induced drag leads to more triangular spanloads, where the loads are shifted towards the root, reducing wing weight and increasing induced drag. A slight reduction in root bending moment is always beneficial, since the initial increase in induced drag is very small compared to the wing weight decrease. Total weight benefits were studied for a Boeing 777-200IGW type configuration, obtaining take-off gross weight improvements of about 1% for maximum range missions. When performing economical, reduced-range missions, improvements can almost double. A long range, more aerodynamically driven aircraft like the Boeing 777-200IGW will experience lower benefits as a result of increasing drag. Short to medium range aircraft will profit the most from more triangular lift distributions.

Formation flight configurations can also result in large induced drag reductions for load distributions that deviate from the elliptical one. Optimum spanloads for a group of aircraft flying in an arrow formation were studied using the same discrete vortex method, now under constraints in lift, pitching moment and rolling moment coefficients. It has been shown that large general improvements in induced drag can be obtained when the spanwise and vertical distances between aircraft are small. In certain cases, using our potential flow vortex model, this results in negative (thrust) induced drag on some airplanes in the configuration. The optimum load distributions necessary to achieve these benefits may, however, correspond to a geometry that will produce impractical lift distributions if the aircraft are flying alone. Optimum separation among airplanes in this type of formation is determined by such diverse factors as the ability to generate the required optimum load distributions or the need for collision avoidance.
Master of Science

This work focuses on high-temperature kraft black liquor gasification in the presence of H2O and CO2 in a laboratory-scale Laminar Entrained-Flow Reactor (LEFR). The effects of gasification conditions on hydroxide formation, carbon gasification rate, carbonate carbon and fixed carbon levels, alkali metal and sulfur species retention, and char yield were studied at atmospheric pressure and at 900-1000oC, and at residence times of 0.5-1.5 s. The results suggest that carbon gasification rates may be enhanced in the presence of H2O and CO2, with fixed carbon conversions of up to 95% at the earliest residence times at 1000oC. CO2 and H2O gasifying agents cause a significant increase in carbonate formation, with 22% of the initial carbon input forming carbonate as compared to 16% with one gasifying agent. Carbonate levels increase to a maximum level and then decrease at 900oC, but at 1000oC, carbonate decomposition processes are more dominant and cause lower levels of carbonate even at early residence times. The results show that alkali metal retention is high until vaporization occurs after 1.4 s at 900oC and at early residence times at 1000oC. Moreover, the results indicate that sulfur retention is an exothermic process, as sulfur capture increases with temperature. At 900oC, no hydroxide is produced until after 1.4 s, but at 1000oC, hydroxide appears to form readily even at the earliest residence times studied. The char product yields a maximum mole percent of 18-19% hydroxide, starting at intermediate residence times at 1000oC. Generally, hydroxide is not produced until fixed carbon conversions approach 95%. The results can be explained in terms of the interactions of phenolate and carboxylate catalytic moieties in the char product. The hydroxide formation results suggest that it may be possible to develop a gasification-causticization process that does not require external chemicals and would make the energy-efficient and environmentally friendly black liquor gasification technology an economic reality.