Auswahl der wissenschaftlichen Literatur zum Thema „N2-free syngas“

Abstract Towards the goal of carbon neutrality, future chemical production could utilize captured CO2 as a carbon source instead of fossil carbon from petroleum or natural gas. However, the production of chemicals from CO2 is highly energy-intense. The required energy could be imported to Japan in the form of hydrogen. However, the long-distance transport of molecular hydrogen is challenging. NH3 has recently emerged as the most promising molecule for long-distance hydrogen transport and storage. The use of imported NH3 as an energy vector to realize carbon recycling in the Japanese chemical industry is promising. Syngas (H2+CO) is an important intermediate in the production of chemicals and fuels from CO2. Hydrogen is required not only as a constituent of syngas, but also as a reductant of CO2. If hydrogen is imported in the form of NH3, conventionally, NH3 would be cracked to H2 and N2, the product gases and unconverted NH3 separated, and CO/syngas then be produced through the reverse water gas shift reaction (RWGS). This conventional pathway is energy-intense and requires many unit operations. Here a novel process to produce nitrogen-free syngas directly, without producing molecular H2 first and without any dedicated gas separation steps is presented. This is realized by a using a metal oxide bed material that is active for catalytic cracking of NH3, as well as able to transport oxygen through a redox reaction in a newly designed process. This leads to an inherent separation of N2. This process, referred to herein as “NH3-RWGS” has the potential to decrease costs and increase efficiency of syngas production from CO2 and NH3.

This paper investigates novel IGCC plants that employ hydrogen separation membranes in order to capture carbon dioxide for long-term storage. The thermodynamic performance of these membrane-based plants are compared with similar IGCCs that capture CO2 using conventional (i.e., solvent absorption) technology. The basic plant configuration employs an entrained-flow, oxygen-blown coal gasifier with quench cooling, followed by an adiabatic water gas shift (WGS) reactor that converts most of CO contained in the syngas into CO2 and H2. The syngas then enters a WGS membrane reactor where the syngas undergoes further shifting; simultaneously, H2 in the syngas permeates through the hydrogen-selective, dense metal membrane into a counter-current nitrogen “sweep” flow. The permeated H2, diluted by N2, constitutes a decarbonized fuel for the combined cycle power plant whose exhaust is CO2 free. Exiting the membrane reactor is a hot, high pressure “raffinate” stream composed primarily of CO2 and steam, but also containing “fuel species” such as H2S, unconverted CO, and unpermeated H2. Two different schemes (oxygen catalytic combustion and cryogenic separation) have been investigated to both exploit the heating value of the fuel species and produce a CO2-rich stream for long term storage. Our calculations indicate that, when 85vol% of the H2+CO in the original syngas is extracted as H2 by the membrane reactor, the membrane-based IGCC systems are more efficient by ∼1.7 percentage points than the reference IGCC with CO2 capture based on commercially ready technology.

A multiparametric study was conducted on a hydrogen (H2) production rig designed to process 0.25 Nm3·h−1 of syngas. The rig consists of two Pd-Ag membrane permeator units and two Pd-Ag membrane reactor units for the water–gas shift (WGS) reaction, enabling a detailed and comprehensive analysis of its performance. The aim was to find the optimal conditions to maximize hydrogen production by WGS and its separation in a pure stream by varying the temperature, pressure, and steam-to-CO ratio (S/CO). Two syngas mixtures obtained from an updraft gasifier using different gasification agents (air–steam and oxy–steam) were used to investigate the effect of gas composition. The performance of the rig was investigated under nine combinations of temperature, pressure, and S/CO in the respective ranges of 300–350 °C, 2–8 bar, and 1.1–2 mol·mol−1, as planned with the help of design of experiment (DOE) software. The three parameters positively affected performance, both in terms of capacity to separate a pure stream of H2, reported as moles permeated per unit of surface area and time, and in producing new H2 from WGS, reported as moles of H2 produced per volume of catalyst unit and time. The highest yields were obtained using syngas from oxy–steam gasification, which had the highest H2 concentration and was free of N2.

Biomass chemical looping gasification (BCLG) is a promising autothermic route for producing sustainable, N2-free, and carbon neutral syngas for producing liquid biofuels or high value hydrocarbons. However, different ash-related issues, such as high-temperature corrosion, fouling and slagging, bed agglomeration, or poisoning of the oxygen carrier might cause significant ecologic and economic challenges for reliable implementation of BCLG. In this work, lab-scale investigations under gasification-like conditions at 950 °C and thermodynamic modelling were combined for assessing the influence of composition, pre-treatment methods, such as torrefaction and water-leaching, and Ca-based additives on the release and fate of volatile inorganics, as well as on ash melting behavior. A deep characterization of both (non-)condensable gas species and ash composition behavior, joint with thermodynamic modelling has shown that different pre-treatment methods and/or Ca-additives can significantly counteract the above-mentioned problems. It can be concluded that torrefaction alone is not suitable to obtain the desired effects in terms of ash melting behavior or release of problematic volatile species. However, very promising results were achieved when torrefied or water-leached wheat straw was blended with 2 wt% CaCO3, since ash melting behavior was improved up to a similar level than woody biomass. Generally, both torrefaction and water-leaching reduced the amount of chlorine significantly.

The global net emissions of the Kyoto Protocol greenhouse gases (GHG), such as carbon dioxide (CO2), fluorinated gases, methane (CH4), and nitrous oxide (N2O), remain substantially high, despite concerted efforts to reduce them. Thermal treatment of solid waste contributes at least 2.8–4% of the GHG in part due to increased generation of municipal solid waste (MSW) and inefficient treatment processes, such as incineration and landfill. Thermal treatment processes, such as gasification and pyrolysis, are valuable ways to convert solid materials, such as wastes into syngas, liquids, and chars, for power generation, fuels, or for the bioremediation of soils. Subcoal™ is a commercial product based on paper and plastics from the source segregated waste that is not readily recyclable and that would otherwise potentially find its way in to landfills. This paper looks at the kinetic parameters associated with this product in pyrolysis, gasification, and combustion conditions for consideration as a fuel for power generation or as a reductant in the blast furnace ironmaking process. Thermogravimetric Analysis (TGA) in Nitrogen (N2), CO2, and in air, was used to measure and compare the reaction kinetics. The activation energy (Ea) and pre-exponential factor A were measured at different heating rates using non-isothermal Ozawa Flynn Wall and (OFW) and Kissinger-Akahira-Sonuse (KAS) model-free techniques. The TGA curves showed that the thermal degradation of Subcoal™ comprises three main processes: dehydration, devolatilization, and char and ash formation. In addition, the heating rate drifts the devolatilization temperature to a higher value. Likewise, the derivative thermogravimetry (DTG) results stated that Tm degradation increased as the heating rate increased. Substantial variance in Ea was noted between the four stages of thermal decomposition of Subcoal™ on both methods. The Ea for gasification reached 200.2 ± 33.6 kJ/mol by OFW and 179.0 ± 31.9 kJ/mol by KAS. Pyrolysis registered Ea values of 161.7 ± 24.7 kJ/mol by OFW and 142.6 ± 23.5 kJ/mol by KAS. Combustion returned the lowest Ea values for both OFW (76.74 ± 15.4 kJ/mol) and KAS (71.0 ± 4.4 kJ/mol). The low Ea values in combustion indicate shorter reaction time for Subcoal™ degradation compared to gasification and pyrolysis. Generally, TGA kinetics analysis using KAS and OFW methods show good consistency in evaluating Arrhenius constants.

The Fischer-Tropsch Synthesis (FTS) is a significant catalytic chemical reaction that produces ultra-clean fuels or chemicals with added value from a syngas mixture of CO and H2 obtained from biomass, coal, or natural gas. The presence of sulfur is not considered good for producing liquid fuels for(FTS). In this study, we reveal that the presence of sulfur in ferric sulfate Fe2(SO4)3 MOF provides the high amount, 52.50% of light hydrocarbons in the carbon chain distribution. The calcined ferric nitrate Fe(NO₃)₃ MOF reveals the highest 93.27% diesel production. Calcination is regarded as an essential factor in enhancing liquid fuel production. Here, we probed the calcination effect of Metal Organic Framework (MOF) on downstream application syngas to liquid fuels. The XRD results of MOF. N and P. MOF.N shows the formation of the active phase of iron carbide (Fe5C2), considered the most active phase of FTS. The scanning electron microscopy (SEM) images of iron sulfate MOF catalyst (P.MOF.S) reveals that the existence of sulfur creates pores inside the particles due to the reaction of free water molecules with the sulfur derivate. The surface functional groups of prepared MOFs and tested MOFS were analyzed by Fourier transforms infrared spectroscopy (FT-IR). The thermal stability of prepared MOFS was analyzed by Thermo gravimetric analysis (TGA). The surface areas and structural properties of the catalysts were measured by N2-Physiosorption technique.

Pour répondre aux enjeux de la transition énergétique, il est communément admis qu'il est nécessaire de changer notre façon de produire de l'énergie. Parmi les sources renouvelables, la biomasse est la plus prometteuse de part sa grande disponibilité partout dans le monde, ainsi que ses usages multiples (production de chaleur, de biogaz et de bioproduits). La gazéification de biomasse est une voie de valorisation thermochimique qui permet de convertir les biomasses non fermentescibles en un gaz de synthèse appelé syngaz. Ce syngaz est majoritairement composé d'hydrogène, de monoxyde de carbone, de méthane, de dioxyde de carbone et d'eau. De nombreux gisements de biomasse sont de taille restreinte. Pour les valoriser, il est important de développer des technologies de petite échelle (production <1MW) qui restent énergétiquement intéressantes. Le procédé de gazéification à lit fixe autotherme est la technologie la plus pertinente pour répondre à ce besoin. En effet, l'autothermicité garantit le déroulement des réactions chimiques sans apport d'énergie extérieur. Pour assurer cette autothermicité, il est nécessaire d'apporter de l'oxygène dans le réacteur via l'agent gazéifiant. L'air est l'agent de gazéification principalement utilisé à ce jour. L'azote de l'air utilisé, inerte dans le procédé, devient alors l'espèce majoritaire du syngaz produit. Ceci rend la valorisation du syngaz en biocarburant particulièrement difficile. Pour pallier ce problème tout en conservant l'autothermicité, l'utilisation de nouveaux agents de gazéification peut être envisagée : mélange vapeur d'eau - oxygène, dioxyde de carbone - oxygène, air enrichi (> 21 %vol d'oxygène). Le but de cette thèse est d'anticiper les changements induits par l'utilisation de nouvelles atmosphères sur le procédé de gazéification de biomasse en lit-fixe co-courant. Pour cela, une étude numérique a été menée à l'aide de modèles thermodynamique et cinétique. Nous avons voulu comprendre plus en détail certains phénomènes du processus de gazéification à lit fixe co-courant. L'impact de l'atmosphère sur la vitesse de pyrolyse oxydante, avec ces nouvelles atmosphères, a été étudié expérimentalement par des études thermogravimétriques à l'échelle de la particule. Une seconde étude expérimentale s'est focalisée sur l'évolution de la taille de particules lors de leur gazéification en lit fixe co-courant et leur influence sur la perte de charge du lit dans le réacteur. Celle-ci permet en effet de piloter correctement le procédé et rend compte de son efficacité
It is well known that changing the way to produce energy is mandatory to meet the energetic transition needs. Among the renewable resources, biomass is the more promising thanks to its availability all around the world and its various uses (heat, biogas or bioproducts production). Biomass gasification is a thermochemical way to transform drought biomass into synthesis gas called syngas. Syngas is mainly composed of hydrogen, carbon monoxide, methane, carbon dioxide and water. Most of biomass deposits are small-size. To valorise them, small-scale technologies (< 1MW) must be developed. Autothermal downdraft fixed-bed gasification fits the best to meet this need. Indeed, autothermal behaviour enables kinetic reactions to take place without external sources of energy. Autothermal behaviour is ensured by feeding oxygen into the reactor via the gasifying agent. Nowadays, the most commonly used gasifying agent is air. Inert nitrogen from air then becomes the more abundant compound of the syngas. This makes syngas valorisation into biofuels particularly challenging. To fix this issue while keeping the autothermal behaviour, the use of new gasifying agents is considered: mixture of O2-H2O, mixture of O2-CO2 or enriched air (> 21 %vol O2). The aim of this thesis is to investigate and anticipate the changes induced by using these new atmospheres on the biomass downdraft gasification process. To reach this goal, a numerical study based on equilibrium and kinetic models has been led. More specific phenomena of the downdraft gasification process have also been investigated. Impact of these new atmospheres on the oxidative pyrolysis kinetic of a particle has been studied. It has been carried out thanks to a macro-thermogravimetric device. Another experimental study focused on the particles size evolution during downdraft gasification process and how they influence pressure drops though the bed in the reactor. Pressure drops enables to drive the process and is a relevant indicator of the process efficiency

This paper investigates novel IGCC plants that employ hydrogen separation membranes in order to capture carbon dioxide for long-term storage. The thermodynamic performance of these membrane-based plants are compared with similar IGCCs that capture CO2 using conventional (i.e. solvent absorption) technology. The basic plant configuration employs an entrained-flow, oxygen-blown coal gasifier with quench cooling, followed by an adiabatic water gas shift (WGS) reactor that converts most of CO contained in the syngas into CO2 and H2. The syngas then enters a WGS membrane reactor where the syngas undergoes further shifting; simultaneously, H2 in the syngas permeates through the hydrogen-selective, dense metal membrane into a counter-current nitrogen “sweep” flow. The permeated H2, diluted by N2, constitutes a decarbonized fuel for the combined cycle power plant whose exhaust is CO2-free. Exiting the membrane reactor is a hot, high pressure “raffinate” stream composed primarily of CO2 and steam, but also containing “fuel species” such as H2S, unconverted CO, and unpermeated H2. Two different schemes (oxygen catalytic combustion and cryogenic separation) have been investigated to both exploit the heating value of the fuel species and produce a CO2-rich stream for long term storage. Our calculations indicate that, when 85%vol of the H2+CO in the original syngas is extracted as H2 by the membrane reactor, the membrane-based IGCC systems are more efficient by ∼1.7 percentage points than the reference IGCC with CO2 capture based on commercially ready technology.

Wastes represent nowadays, one of the major concerns for modern societies and for the environment, either by the wastage of raw materials and also by the existence of poor management systems that can originate and contaminate the ground water and air, and therefore, change the environment irreversibly. Waste management policies enhance the basic principles of prevention, which are the reduction in origin, followed by its recovery through recycling or energy recovery, in order to reduce the environmental and health impacts of wastes. Refuse Derived Fuel (RDF) is a solid fuel made after basic processing steps or techniques that increase the calorific value of municipal solid waste (MSW), commercial or industrial waste materials. Therefore, energy production from RDF can provide economic and environmental benefits, as reduces the amount of wastes sent to landfill and allows the energy recovery from a renewable source. In this work, it was studied the gasification of RDF collected in a Portuguese company, using steam and air as gasifying agents. This study intended to evaluate the effect of temperature and different molar ratios of both agents in gas production, gas composition and mass conversion of RDF. Physical and chemical composition of RDF was determined according to EN 15359:2011. Results showed that RDF has high quality for thermal valorization being registered high values of Low Heating Value (LHV) (24330 kJ/kg), carbon content (56.2%) and volatile matter content (77.2%). Experiments of RDF gasification were performed in a laboratory scale fixed bed gasifier, under different conditions. The effect of reaction temperature was studied at 750°C and 850°C. Gasification experiments with steam were executed at S/B feeding molar ratios ranging from 0.5 to 1.5 and the ones performed with air ranging from ER 0.2 to 0.6. Results showed that, for the same operational conditions, the rise of gasification temperature improved gas production ratio (Nm3/kg RDF), gas LHV and mass conversion. Results also proved that steam gasification achieved higher LHV values compared with gasification using air in optimal conditions, 9.4 and 9.8 MJ/m3, respectively. The gasification of RDF using steam at S/B ratio of 1.0 enables the production of syngas with 51% of hydrogen (H2), 32% of carbon dioxide (CO2), 11% of carbon monoxide (CO) and 6% of methane (CH4) (in N2 free basis). The increasing of steam to RDF molar ratio, increased the contents of H2 and CO2, while the content of CO, CH4 and heating value decreased. Regarding to gas production ratio the utilization of air, especially at ER of 0.6, induced the formation of 1.5 m3 gas/kg RDF. Instead, steam gasification only allowed the production of 0.5 m3 gas/kg RDF. Mass conversion and carbon conversion achieved almost 100% in air gasification at highest molar ratio.