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1
PREZIUSO, MARCO. "Preservation of selected sourdough: comparison of freezing, freeze drying, drying and spray drying techniques." Doctoral thesis, Università degli studi del Molise, 2018. http://hdl.handle.net/11695/84477.
Testo completoAbstract (sommario):
La fermentazione con impasto acido è uno dei metodi più antichi utilizzati nell'industria dei prodotti lievitati da forno per la produzione di pane casereccio e di numerosi dolci tipici della tradizione italiana. L’impiego di “impasto acido” o “pasta madre” (impasto di tipo I) offre, rispetto all’uso del lievito di birra, numerosi vantaggi in termini di qualità sensoriale, nutrizionale e di shelf-life.
L’impasto acido di tipo I, infatti, è caratterizzato da un consorzio microbico eterogeneo, rappresentato principalmente da batteri lattici e da lieviti, la cui fermentazione conferisce al prodotto da forno caratteristiche quali gusto, consistenza e aroma migliorati, alta appetibilità, raffermamento ritardato e maggiore shelf-life. L’impasto deve essere costantemente rinfrescato per consentire ai microrganismi di rimanere in uno stato attivo e vitale. Il rinfresco viene realizzato utilizzando una quota della madre acida prelevata dalla precedente fermentazione, mescolandola con acqua e farina e lasciandola fermentare per almeno 6 ore a 30° C. Quindi, il mantenimento di una madre acida attiva richiede tempo e impegno maggiore al fine di garantirne la sua vitalità.
Per questi motivi, numerose panetterie industriali utilizzano la madre acida di tipo III che consiste in diverse preparazioni di madre acida essiccata o liofilizzata. Tali preparazioni, però, sono spesso caratterizzate da ridotta vitalità microbica e prevedono quasi sempre l'aggiunta di lievito di birra "Saccharomyces cerevisiae", che viene presentato come un "attivatore" ma che in realtà è responsabile solo per la lievitazione, causando spesso l'appiattimento delle caratteristiche aromatiche dei prodotti finiti.
Una corretta stabilizzazione della madre acida di tipo I nel tempo potrebbe rappresentare non solo un'importante pietra miliare in termini economici nell'industria della panificazione, ma anche un prerequisito per la protezione dei prodotti da forno tipici e tradizionali, senza l'uso di attivatori di lievito di birra.
Scopo della tesi di dottorato è stato, quindi, confrontare diverse tecniche di conservazione per identificare quella in grado di preservare meglio le caratteristiche microbiche della pasta madre di tipo I e quindi le caratteristiche sensoriali dei prodotti finiti.
A tal fine, una madre acida di tipo I, caratterizzata per pH, acidità titolabile totale (TTA), composizione dei composti organici volatili, cariche microbiche di batteri lattici e lieviti, è stata sottoposta a diverse modalità di conservazione: congelamento, essiccazione, liofilizzazione e spraizzazione. Dopo i trattamenti di conservazione, sono state valutate la vitalità microbica e le caratteristiche chimico-fisiche degli impasti. Quindi, la madre acida stabilizzata è stata utilizzata nella produzione di pani per valutare la capacità lievitante e fermentante degli impasti. I pani ottenuti sono stati sottoposti ad analisi sensoriale e ad analisi digitale dell’immagine. Risultati positivi e incoraggianti sono stati ottenuti principalmente con la pasta madre spraizzata.
Tra le diverse tecniche di conservazione testate, la spraizzazione ha consentito di registrare la maggior sopravvivenza sia dei lieviti sia dei batteri lattici. Inoltre, i risultati hanno messo in evidenza che la madre acida spraizzata, dopo opportuno rinfresco, consentiva di ottenere una buona lievitazione e di produrre pani con caratteristiche sensoriali paragonabili a quelle prodotte usando impasti acidi freschi.<br>Spontaneous sourdough fermentation is one of the oldest methods used in the bakery industry for the production of homemade, typical and traditional breads and various bakery typical product of the Italian tradition. The modern biotechnology of baked goods largely uses fresh sourdough (namely sourdough of type I) as a natural leavening agent because of the many advantages it offers over baker’s yeast resulting in a final product with high sensory quality. Type I sourdough has the largest application and resembles the traditional processes. It is fully known that sourdough is characterized by a heterogeneous microbial consortium, mainly represented by lactic acid bacteria and yeasts, whose fermentation confers to the bakery product its features such as improved taste, texture and aroma, high palatability, delayed staling and increased shelf-life. It is characterized by continuous (daily) propagation to keep the microorganisms in an active state. Furthermore, the ecosystem of sourdough type I can easily undergo modification due to factors affecting the management and preservation of the dough itself, such as modification of the ingredients used and the type of flour, the change in the storage temperature, the number of refreshments made, the hygienic conditions of the processing environment and the operator. Propagation of sourdough type I is achieved by daily back-slopping, using the mother sponge taken from the preceding fermentation, mixing it with water and flour, and allowing to ferment for at least 6 h at 30°C. So, the maintaining of a fresh sourdough starter requires a little extra time and effort because daily or weekly refreshments are necessary to guarantee its good vitality.
For these reasons, numerous industrial bakeries use sourdough of type III, that include the addition of "Saccharomyces cerevisiae" yeast, often causing flattening of the aromatic characteristics of the finished products.
A proper stabilization of the sourdough of type I over time could represent not only an important milestone in economic terms in the bakery industry but also a prerequisite for the protection of typical and traditional bakery products.
Aim of PhD thesis was, therefore, to compare different techniques in order to identify the one that could better preserve the microbial characteristics of the sourdough of type I and thus the finished baked products. For this purpose, a sourdough of type I has been subjected to different storage modes: freezing, drying, freeze-drying and spray drying. Sourdough was selected among numerous typical sourdoughs, previously characterized for lactic acid bacteria and yeast count, pH and Total Titratable Acidity (TTA) value and volatile organic composition. After the preservation treatments, microbial vitality and chemical-physical properties of the doughs were assessed. Then, the stabilized sourdough starter were used in breadmaking manufacture to assess the ability to leaven and ferment the doughs. The breads obtained were subjected to sensorial analysis and digital image analysis. Positive and encouraging results were obtained mainly with the sourdough spray-dried.
In fact, among the different storage techniques tested, spray drying showed the highest survival both of yeasts and lactic acid bacteria respect to the other techniques. Furthermore, the results suggested that spray-dried sourdough, opportunely refreshed, can be successfully used for breadmaking, leading to bread with sensorial characteristics comparable to those produced using fresh sourdoughs.
2
Tham, Thing Chai. "Improving drying efficiency and energy saving for crumb natural rubber drying with combined drying technologies." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52329/.
Testo completoAbstract (sommario):
Natural rubber (NR) or cis-1, 4-polyisoprene is obtained from the latex that is tapped from a tree known as Hevea Brasiliensis. It can be in the form of preserved latex concentrates or further processed into sheets, crepes, block rubber that associated with its unique characteristics such as great elongation strength, excellent building tack, low rolling resistance, low heat build-up and good low-temperature performance. These are essential characteristics in dynamic working environment and application especially for vehicle tyre and rubber thread. To produce good quality of technically specified rubber or block rubber from raw natural rubber, drying process plays a vital role in the raw rubber processing. To date, the level of technology involves rubber drying is still inefficient and primitive. Non-uniform drying and the occurrence of wet rubber in the final product are the major drawbacks when using the conventional type of trolley dryer. Also, fuel and electricity usage for a single drying operation is noticeably intense and costly. Indeed, the main limitation of conventional drying method is the drying time that is mainly dependent on temperature gradient inside the product and cannot be sustainably reduced because the product is heat sensitive; whereas drying at high temperature for prolong hours could result in quality deterioration too. The prime objective of this research was to investigate combined drying as a mean of crumb rubber processing to reduce the drying time, energy consumption and to produce the desirable dried product. In the present study, crumb rubbers were dried by alternative drying strategies whereby additional drying technologies such as hot air, vacuum, and microwave was integrated into the drying system. Both engineering properties (drying kinetics, effective moisture diffusivity and specific energy consumption) and physicochemical properties (colour, thermal oxidative level, rheological, textural and surface topography) of all dried products were measured and evaluated. The comparisons were made against samples from hot air drying. The finding shows the drying time of microwave-convective drying (MWHA) was found 89% and 50% shorter than convective hot air drying (HA) and microwave (MW) drying, respectively. In terms of drying rate performance, the maximum drying rate of MWHA was found 455% and 62.5% higher than HA and MW drying, respectively. On the other hand, effective diffusion coefficient (Deff) values of both MW drying and MWHA were ranging from 1.48 x 10-8 m2/s to 5.59 x 10-8 m2/s that is six times higher than HA which has lowest Deff recorded at 0.22 x 10-8 m2/s. It is noteworthy to mention that the energy consumption of MWHA is much lower than other drying strategies due to its excellent time saving and energy efficient features in the drying process. The average specific energy consumption (SEC) values of MWHA’s drying strategies were scored below 0.22 MJ/ gH2O whereby HA drying yields SEC values of 0.36-0.44 MJ/gH2O and highest was recorded in vacuum assisted drying which scored at 0.75 MJ/ gH2O. MWHA dried rubber has exhibits lightest colours, minimum total colour change and consistent colour appearance over the range of drying methods. The lesser colour change can be an indication of reduced oxidative reaction and hence better ageing properties of dried rubber. This is corresponding to the high value of activation energy obtained by MWHA’s dried rubber in the thermal degradation study by using the Coats-Redfern methods. Similarly, the rheological properties of MWHA dried rubber including PRI and Po were found in par and the volatile matter was 28.6% lower in comparison with SMR 20 block rubber. In terms of springiness indices, MWHA dried rubbers gave the highest at 72.23% showing marked performance in mechanical properties. In a nutshell, the potential of combined drying techniques in crumb rubber has been proven through this research and able to improve both engineering and physicochemical properties while the drying time is significantly reduced. Furthermore, these findings will supplement the knowledge on crumb rubber drying process which is beneficial to raw rubber processing industries in having economically feasible drying option to be applied to the existing plants.
3
Hashemi, Aghchehbody Seyed Jalaleddin. "Through drying of machine formed paper and drying nonuniformity." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37702.
Testo completoAbstract (sommario):
Transport phenomena characteristics were determined for the through air drying of machine-produced printing and heavier papers. The momentum transport is strongly affected by the specifications of machine-formed papers, but of the drying rate characteristics only the critical moisture content varied between the types of paper tested. To determine the impact of individual parameters of commercial papermaking these experiments with machine-formed paper were supplemented by the use of handsheets. The papermaking parameters of beating, wet pressing, formation and pulp blending all strongly affect the momentum transport through the paper but only the quality of sheet formation and composition of TMP-kraft pulp blends influences drying rates measurably.<br>The general phenomenon of nonuniformity in through drying was examined, including its association with nonuniformity of paper structure, with process conditions affecting drying nonuniformity, and implications for minimizing the cost of providing the flow of drying air through semi-permeable grades of paper. The development and decay of non-uniformity during drying was demonstrated through two techniques, one based on the measurement of local sheet moisture content, the other with continuous monitoring of the local air exhaust temperature from the sheet. Drying nonuniformity is quite sensitive to the quality of formation and to drying intensity, and is less severe at both the higher and lower end of the basis weight range. The biggest effect on drying nonuniformity is the improvement possible by reduction in the initial moisture content. In-plane moisture diffusivity was determined to be a very strong function of sheet moisture content, and is not fast enough to reduce the sheet moisture nonuniformity during drying.<br>The study provides guidance in the possible future use of through air drying for application to grades of paper heavier than those for which it is now used.
4
Bosch, Thomas. "Aggressive Freeze-Drying." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-177527.
Testo completo
5
Gil, Arnaud, and Alex Raffier. "Wallpaper drying solutions : Feasibility study of a low temperature drying process." Thesis, University of Gävle, Department of Technology and Built Environment, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-754.
Testo completoAbstract (sommario):
<p>The wallpaper company Duro Sweden AB, one of the most important Scandinavian</p><p>wallpaper manufacturers, wants to decrease its energy use and costs and make its</p><p>production more environmentally friendly. It implies changes in the key process energy</p><p>use whom consists mainly by drying process using heat production from oil.</p><p>The purpose of this project, studied by the consulting company Sweco Theorells AB,</p><p>is to determine the feasibility of a change in the energy utilisation implemented to the</p><p>most representative process to propose future solutions’ basis on the future energy</p><p>question.</p><p>The company use mainly two kind of energy, electricity with 1055MWh per year and</p><p>oil with 1985MWh per year. The oil power consumption and cost represent respectively</p><p>65% and 73% of the global part.</p><p>Several proposed changes with better energy efficiency are presented : use of district</p><p>heating as a heat source, Infrared Drying, combination, etc; but due to the important</p><p>rebate make by the Swedish government on the oil price, they are not currently viable to</p><p>achieve.</p><p>But the constant rise of the oil price could be sooner a strong incentive to make these</p><p>improvals, strongly environmentaly friendly and power consumption reducer,</p><p>economicaly viable in the long term.</p>
6
Yang, Xinbo. "SUITABILITY EVALUATION OF EMERGING DRYING TECHNOLOGIES FOR FINE CLEAN COAL DRYING." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1688.
Testo completoAbstract (sommario):
The selling price of coal product in the market depends on the heating value or BTU content of coal, which is a function of both ash and moisture content. Typically the ash content of fine coal and coarse coal reporting to the clean coal belt of a coal preparation plant are relatively similar from each other, however, the moisture content of fine coal is much higher, i.e., 2 to 3 times that of the coarse coal. In that case, although the fine coal proportion of the total clean coal tonnage produced from a plant is in the 10 to 15% range, as much as 33% of the total moisture content in the clean coal product is contributed by the fine coal fraction. A simple analysis indicates that if the moisture content of the fine coal fraction can be substantially reduced by 50% or more, the density-cut of the coarse coal cleaning circuit can be increased and higher overall plant yield can be obtained while satisfying the overall product heating value specification. To achieve this improvement, the use of a suitable drying technology for fine coal is required. The conventional thermal dryer using convective heating mechanism is an expensive option because of the inherent inefficiencies and safety issues in its operations. The major goal of this study was to evaluate two emerging coal drying technologies, the Nano Drying Technology (NDT) and the Parsepco Drying Technology (PDT), for further reducing moisture content of fine clean coal generating from coal preparation plants in Illinois. The Nano Drying Technology, developed by Nano Drying Technologies, LLC. in West Virginia, makes use of molecular sieves to extract residual moisture from mechanically dewatered coal. In this study, mechanically dewatered fine clean coal collected from Prairie Eagle coal preparation plant, IL and Kepler coal preparation plant, WV were used for the NDT system evaluation. The laboratory experimental results showed that the NDT is able to reduce the moisture content of Illinois fine clean coal from over 20% to less than 10%. Pilot-scale experiments were conducted at NDT LLC's pilot-scale facility in Beckley, WV to evaluate and optimize the system's performance. A parametric study conducted using the Box-Behnken experimental design showed that the mass ratio of molecular sieves to coal feed was the most significant factor for the NDT coal moisture reduction process. An optimal product moisture content of 7.3% was achieved for the IL No. 6 seam coal. The Parsepco Drying Technology is provided by Particle Separation System (PSS) Ltd. in South Africa, which utilizes medium wave infrared radiation to remove the moisture from dewatered fine clean coal. Pilot-scale tests were conducted in Illinois Coal Development Park with IL fine clean coal collected from Prairie Eagle coal preparation plant. Product moisture of 5.3% was achieved with production of 22.8 lb/hr. An optimization analysis on the preliminary tests results was then carried out using Historical Data Respond Surface Method in Design Expert software. The medium-wave infrared radiative (MIR) intensity at 60% of its full power was concluded to be the optimal condition for fine clean coal drying. Feed rate and retention time of drying controlled by coal depth and speed of belt were significant on production. The optimized condition predicted a coal product moisture of 9.5% with production of 57.7 lb/hr. An economic analysis of the plant yield improvement and the resulting revenue gain achievable in a coal preparation plant flow sheet was conducted for Prairie Eagle coal processing plant in Illinois which produces 88 tph mechanically dewatered fine clean coal with average moisture content of 19.66%. The increased coal production of the plant with introducing fine coal drying technology was estimated based on the feed washability data of Knight Hawk coal. Both NDT and PDT are able to reduce the fine coal product moisture to be less than 10%, however, the nanotechnology was proved to be more safety and economical for fine clean coal drying.
7
Secmeler, Ozge. "Comparison Of Microwave Drying And Microwave Mixed-bed Drying Of Red Peppers." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1098979/index.pdf.
Testo completoAbstract (sommario):
The main objective of this work is to investigate whether the time required to dry red peppers in the diffusion controlled period can be reduced. For this purpose, the possibility of microwave drying in this period was studied. As comparison parameters the drying rates and color of the products were selected.
The conventional drying was conducted under constant external drying conditions with air at 60 0C and 3.5 % RH and 1.0 m/s velocity in a batch dryer. For the microwave drying a domestic microwave oven with three power levels, 286, 397 and 560 W was used.
Pre-experiments were done to obtain an insight on the possibility of moisture distribution within the structure of the red peppers and electrical field distribution inside the oven cavity. The non-uniformity due to the latter effect was tried to be overcome by designing and installing a six blade impeller into the bed having the symmetrical pair of blades fixed at three levels.
Samples for the microwave drying experiments were prepared by drying the peppers from approximately 90% of moisture to 20% in 7 hours in the conventional dryer at 600C and then cutting them into pieces about 1x1 cm. Thus prepared samples were dried further in the microwave oven to 14% moisture content without and with the agitator.
To compare the results, the effective diffusivity coefficients were calculated for all of the methods and parameters to enable the aimed comparison. These indicated that by using microwave drying, the drying time can be reduced by about 120 times. Further, by mixing the uniformity of drying and the drying rate could be improved. Considering color of the product, there was no significant difference with respect to the fresh samples after all operations.
8
Irawan, Anton. "Isothermal drying of pore networks : influence of pore structure on drying kinetics /." [S.l.] : [s.n.], 2006. http://diglib.uni-magdeburg.de/Dissertationen/2006/antirawan.htm.
Testo completo
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Brunzell, Lena. "Energy Efficient Textile Drying." Licentiate thesis, Karlstad University, Faculty of Technology and Science, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-729.
Testo completoAbstract (sommario):
<p>Traditionally, textiles were dried outdoors with the wind and the sun enhancing the drying process. Tumble dryers offer a fast and convenient way of drying textiles independent of weather conditions. Tumble dryers, however, consume large amounts of electrical energy. Over 4 million tumble dryers are sold each year in Europe and a considerable amount of energy is used for drying of clothes. Increasing energy costs and the awareness about environmental problems related to a large energy use has increased the demand for dryers with better energy efficiency. The aim with this thesis is to show how to improve the energy efficiency of domestic tumble dryers.</p><p>Two types of tumble dryers are available on the market today: the open cycle dryer and the closed cycle dryer. In the open cycle dryer room air is heated and led into the drying drum. The exhaust air leaves the dryer and is often evacuated outside the building. In the closed cycle dryer an internal airflow is recirculated inside the dryer. When the hot air has passed through the drying drum it is led through a heat exchanger where the water vapour is condensed before the air is heated again and led to the drum. The heat exchanger is cooled with room air.</p><p>Drying at low temperature has been shown to reduce the specific energy use for an open cycle tumble dryer. In Paper I a correlation between the specific energy use, the drying time and the heat supply was established for a specific load by using the exhaust air temperature. It was shown that the total drying time and specific energy use could be predicted from data during the first hour of the process. This result indicated a possibility to create a control system that makes it possible for the user to choose between low energy use or short drying time.</p><p>The focus of Paper II is to reduce the energy use for a closed cycle tumble dryer. Energy and mass balances were established in order to determine feasible improvements. Energy and mass flows in the dryer indicated that reducing leakage from the internal system of the dryer gave the largest reduction of specific energy use. Insulation of the back cover of the dryer and opening the internal system during the falling drying rate period also gave positive results on the energy use. In total a feasible reduction of the energy use of approximately 17% was calculated.</p>
10
Polat, Osman. "Through drying of paper." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75904.
Testo completoAbstract (sommario):
The first comprehensive set of measurements is obtained for rates of through drying paper with all drying conditions measured and controlled. Complete pressure drop-drying rate curves are determined for 235 handsheets of kraft paper of basis weights 25-150g/m$ sp{ rm 2}$ dried in air over a wide range of temperatures and throughflow rates.<br>The previous procedure of calculating permeability by Darcy's law is substantially in error at relevant throughflow rates. A new characteristic dimension for flow through both dry and moist paper is determined by application of fundamental momentum transport principles. During through drying the value of the d$ sb{ rm p}$ drops substantially from an upper to a lower asymptotic limit, shown to correspond to known water-fibre relations. A theoretically based Re-f-d$ sb{ rm p}$ treatment is shown to be a more powerful method than those used previously.<br>A comprehensive, tested correlation for through drying rates in the constant rate period is reported. Through drying is demonstrated to start with an increasing rate period during which, for industrial conditions, about half the water is removed. An original treatment, "drying period diagrams", shows the extent of the increasing, constant and falling rate periods as a function of drying conditions. The concept of an increasing-constant-falling rate triple point, X$ sb{ rm ICF}$, shows that typically there will be no constant rate period for industrial conditions of through drying light weight paper of low moisture content.<br>Sherwood number is calculated for the constant rate period of drying using the characteristic dimension and interfacial transfer area for moist paper determined by momentum transfer analysis. Sherwood number is related to drying conditions and to transport phenomena within the sheet.<br>Through drying rates are successfully predicted by a model which treats the process as three drying periods, i.e. increasing, constant and falling rate, with a variable specific surface of paper.
11
Some, D. K. A. "Ambient drying of maize." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370637.
Testo completo
12
Silayo, Valerian Cosmas Kanyengele. "Sun drying of grains." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262986.
Testo completo
13
Simate, Isaac Nyambe. "Mixed mode solar drying." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246686.
Testo completo
14
Klongpanich, Wiwat. "Longan drying in Thailand." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280651.
Testo completo
15
Gan, Kee Seng. "Solar drying of timber." Thesis, University of Strathclyde, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366956.
Testo completo
16
Bond, Jean-François. "Drying paper by impinging jets of superheated steam : drying rates and thermodynamic cycles." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41047.
Testo completoAbstract (sommario):
Drying of paper by impinging jets of superheated steam was studied in an apparatus which closely simulates conditions for a potential industrial impingement dryer.<br>Drying was found to consist in a constant rate period, followed by a falling rate period where the drying rate decreases linearly with moisture content. The relation found between the constant rate and Reynolds number and temperature of the jet is consistent with a previous correlation for air impingement heat transfer, suitably modified for conditions in a steam environment. For a given mass flux, steam drying is slower than air drying below an inversion temperature of 175$ sp circ$C and faster above. The specific blower power for steam drying is much lower than for air drying at temperatures in the industrial range.<br>Equilibrium moisture content measurements showed that complete drying can be obtained at steam temperatures only slightly above the boiling point. Expressions for the critical moisture content in impingement drying in steam and in air were obtained. In steam drying, the falling rate period was found to be determined more by internal transport resistance than by adsorption of water on the fibers.<br>A new arrangement for drying paper, in which the first half of the drying is done by a conventional dryer to which steam is supplied from a steam impingement dryer handling the second half, was analyzed. In regions with low electricity cost, recirculation of steam around the impingement dryer circuit by a mechanical fan is much more economical than by a thermocompressor. However, this advantage is only marginal where electricity cost is high. The overall performance is optimized by using the highest temperature and lowest jet velocity possible. The drying cycle proposed is a realistic and attractive means to increase drying capacity and reduce energy consumption.
17
Venkatachalapathy, Kamadenahally. "Combined osmotic and microwave drying of strawberries and blueberries." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0019/NQ44619.pdf.
Testo completo
18
Changrue, Viboon. "Hybrid (osmotic, microwave-vacuum) drying of strawberries and carrots." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102966.
Testo completoAbstract (sommario):
The main purpose of this study was to improve the performance of microwave assisted drying. The osmotic treatment was used as pretreatment due to its inherent low energy requirement attributes. The vacuum was applied to microwave drying system to capture low temperature vaporization concepts. The whole process might be called "osmotically dehydrated microwave vacuum drying". Carrots and strawberries were selected to study as a representative of vegetables and fruits, respectively.<br>The laboratory scale microwave vacuum dryer was setup and the preliminary tests were done with carrots and strawberries. The occurrence of condensation of vapor in vacuum container was found during the drying trials. The location of the open-ended valve which controls the vacuum level was found to have an influence on the condensation. The re-location of valve which allowed air passage to the vacuum container was able to decrease the condensation. The input power for the microwave vacuum drying could not be greater than 1.5 W/g. The continuous use of input power caused the high temperature in the process. The pulse mode (on/off) was recommended for further studies.<br>Water removal and solid gain of osmotic treatment were considered as factors that affect the dielectric properties dielectric constant (epsilon') and the loss factor (epsilon"). The experiment was set up to investigate the influence of osmotic conditions to dielectric properties. Two osmotic agents, sucrose and salt, were used for carrots; but only sucrose was used for strawberries. The effects of variations in sucrose and salt concentrations, solution temperatures, and length of immersion time on the dielectric properties were studied. The empirical models were generated from response surface methodology (RSM) to predict epsilon' and epsilon" for the various ranges of osmotic conditions considered in this thesis.<br>As a consideration of the osmotic pre-drying treatment, it was considered appropriate to maximize water loss (WL) and minimize solid gain (SG). The parameter appropriate to study this situation was WL/SG. The optimum conditions of osmotic process to acquire the maximum ratio of WL/SG were investigated. The results of the optimum conditions for carrots were found to be sucrose concentration 50%(w/w), salt concentration 5%(w/w), temperature 20°C and immersion time 3 hours 38 minutes. The optimum conditions for strawberries were found to be sucrose concentration 60%(w/w), temperature 20°C and immersion time 24 hours.<br>The microwave vacuum drying was then studied as a technique combined with the osmotic pretreatment. The studies were performed on carrots and strawberries. The input power levels 1 and 1.5 W/g with different power modes (continuous, 45s on/15s off and 30s on/30s off) were experimentally studied with a certain condition of osmotic treatment, which was acquired from the previous study. Osmotic treatment prior to microwave vacuum of carrots showed the advantage in most cases; fast drying time, less energy consumption and superior quality aspects except the taste which was affected from the salt. The study of strawberries did not show great advantage of osmotic pretreatment. The drying time and energy consumption of the process with and without osmotic pretreatment were the same but the process with osmotic pre-treatment resulted in better quality of dried strawberries.<br>The microwave vacuum drying of carrots and strawberries after osmotic pretreatment did not show constant rate period in drying rate curve while the processes without osmotic treatment of strawberries showed longer constant rate period than those observed for carrot drying. According to these phenomena, thin layer models of Lewis and Henderson & Pabis were fitted to the observed data which showed excellent fit for the process without constant rate period, but Page's model was a good fit for both constant rate and falling rate period of microwave vacuum drying.
19
Geidobler, Raimund. "Cyclodextrins as excipients in drying of proteins and controlled ice nucleation in freeze-drying." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-167191.
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20
Alvaredo, Alejandra Mónica. "Drying shrinkage and crack formation /." Zürich, 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10754.
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21
Luna, Fabio. "Drying of Multicomponent Liquid Films." Doctoral thesis, KTH, Chemical Engineering and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3778.
Testo completoAbstract (sommario):
<p>The convective drying of thin layers of multicomponentliquid mixtures into an inert gas, and the influence ofdifferent process controlling mechanisms on drying selectivityis studied. Drying experiments under gas-phase-controlledconditions are performed by low intensity evaporation, fromfree liquid surfaces, of ternary mixtures without non-volatilesolutes. Liquid-side-controlled experiments are carried out bydrying a multicomponent polymeric solution containing twovolatile components, one non-volatile polymer and an optionalnonvolatile softening substance.</p><p>Mathematical models to describe gas- andliquid-side-controlled drying based on interactive diffusion inboth liquid and gas phases as the main mechanisms for masstransfer are developed. For gas-phase-controlled drying, astability analysis of the ordinary differential equations thatdescribes the evaporation process is performed. Isothermal andnon-isothermal drying processes are considered in batch andcontinuous modes. The mathematical model to describe thecomposition profiles during batch drying of the polymeric film,considering liquid resistance, is solved numerically. Due tothe lack of experimental data, properties for this polymericsystem are estimated by using established methods. Ananalytical solution of the diffusion equation, by assuming anisothermal drying process and a constant matrix ofmulticomponent diffusion coefficients is developed. For thecontinuous case, liquid-side resistance is studied by modellingevaporation of a multicomponent falling liquid film into aninert gas including indirect heating.</p><p>The results of the gas-phase-controlled model are in goodagreement with experimental results. For the polymeric film,the agreement is only qualitative since the model does notaccount for a membrane that develops on the film surface. Thestability analysis permits the prediction of trajectories andfinal state of a liquid mixture in a gas-phase-controlleddrying process. For isothermal evaporation of ternary mixturesinto pure gas, the solutions are trajectories in the phaseplane represented by a triangular diagram of compositions. Thepredicted ternary dynamic azeotropic points are unstable orsaddle. On the other hand, binary azeotropes are stable whenthe combination of the selectivities of the correspondingcomponents is negative. In addition, pure component singularpoints are stable when they are contained within theirrespective isolated negative selectivity zones. Undernon-isothermal conditions, maximum temperature valuescharacterise stable azeotropes. Incremental loading of the gaswith one or more of the components leads to a node-saddlebifurcation, where a saddle azeotrope and a stable azeotropecoalesce and disappear. For continuous drying, the singularpoints are infinite and represent dynamic equilibrium pointswhose stability is mainly dependent on the ratio of inletgas-to-liquid flow rates. As long as the process isgas-phasecontrolled, these results also apply to a porous solidcontaining a liquid mixture.</p><p>In general, liquid-side control makes the drying processless selective but it is difficult to maintain this conditionduring the whole process. Under the influence of its owndynamics, a process starting as liquid-side-controlled tendstowards a gas-phase-controlled process. The presence ofnon-volatile components and indirect heating may delay thisdevelopment. Considering the evolution of the processcontrolling steps and its influence on selectivity, a modelaimed at describing the complete trajectory of a drying orevaporation process must include the coexistence of allrelevant mechanisms.</p><p><b>Keywords:</b>ternary mixture, falling film, diffusionequation, gas-phase control, liquid-phase control, selectivity,stability analysis, polymeric solution, evaporation, azeotrope,batch drying, continuous drying.</p>
22
Varikooty, Jalaiah. "Ocular Discomfort Upon Tear Drying." Thesis, University of Waterloo, 2003. http://hdl.handle.net/10012/1239.
Testo completoAbstract (sommario):
<b>Purpose:</b> Assess the relationship between tear film drying and sensation between blinks. <b>Methods:</b> MATLAB sampled a slitlamp video camera, a potentiometer and a microphone while subjects kept one eye open for as long as possible. 23 subjects rated the intensity of the ocular sensation while video and voice data were collected simultaneously. The tear drying on the cornea was measured. <b>Results:</b> The sensation was triphasic. Two linear functions described the latter 2 parts of the data (r ≥ 0. 95). The correlation between TBUT and the elbow in the time-discomfort function was 0. 72. Extent of tear film drying was linearly correlated to time (median correlation = 0. 88). The correlation between the discomfort elbow and image elbow was 0. 93 with single data pair for each subject. Analysis of sensation characteristics showed significant differences between itching and burning for both intensity and time (p = 0. 03 and p = 0. 02 respectively). <b>Conclusions:</b> Simultaneous recording of ocular surface appearance, discomfort intensity and attributes of sensation provide novel information about the development of discomfort during ocular surface drying. The rapid increase in discomfort proceeding blinking has been quantified and the relationship between the time course of drying and discomfort is elucidated.
23
Holmes, D. M. "Lateral drying of ceramic suspensions." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604187.
Testo completoAbstract (sommario):
Many ceramic processing routes, such as tape casting, screen-printing and ink jet printing, involve deposition of a suspension of ceramic particles in a prescribed shape on a substrate. As the liquid evaporates from the suspension, the particles pack together and liquid leaves the pores. In water-based suspensions, these processes often occur at fronts that move from the edge to the centre of the drying layer. This is known as lateral drying. As drying proceeds, the body can change shape, residual stresses can develop and cracking can occur. However, existing models cannot predict either the shape changes that occur or adequately explain why the drying layer cracks. To study this, the drying behaviour of layers of alumina suspensions was investigated experimentally. Measurements were made of the movement of lateral fronts, the changes in local thickness and the activity at the surface of the layers, and the cracking behaviour and the dried thickness profiles were studied. By considering the redistribution of liquid at the first lateral front, where particles pack together, an expression for the thickness profile of the dried layers has been derived. Mass loss data, together with the local thickness measurements, suggest that the particles do not come into touching contact at this first front. Instead, a collapse event occurs when the repulsive layers between the particles are overcome. The development of stress in a drying layer is generally attributed to the build-up of capillary pressure at the surface of the body. However, this causes compression of the particle network, despite the constraint to shrinkage imposed by the substrate, and therefore cannot explain why cracking occurs. Here, it is proposed that the driving force for cracking actually arises from the collapse event. This predicts that cracking should occur while the space between the particles is still filled with liquid. This is consistent with the measurements of surface activity and local thickness, and the cracking behaviour observed.
24
Hassaballah, A. A. "Drying of alcohol by adsorption." Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376626.
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25
Ameobi, John Babatope. "Maize drying with ambient air." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386835.
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26
Phoungchandang, Singhanat. "The solar drying of bananas." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287810.
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27
Crisp, Jeremy. "The drying properties of rapeseed." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316063.
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Tseng, Kuo-Shu. "Volatile retention during drying process." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326958.
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29
Laklouk, Abdussalam M. "Survival of salmonella during drying." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278210.
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30
Revilla, Guillermo Osorio. "Spouted bed drying of liquids." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.256286.
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31
Ingham, Andrew James. "Technological enhancements in freeze drying." Thesis, University College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423019.
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32
Goodenough, Tim. "Electrohydrodynamically enhanced drying of foodstuffs." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289536.
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33
Marshall, Mark George. "A hybrid electroheat drying system." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310938.
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34
Chiu, Raymond Chi Hing. "Drying of granular ceramic films." Thesis, Ceramics Processing Research Laboratory, Massachusetts Institute of Technology, Materials Processing Center, 1991. http://hdl.handle.net/1721.1/13045.
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35
Hopkinson, Andrew Christopher Graham. "Cracking of drying ceramic dispersions." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608101.
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36
Patel, Suresh Dahyabhai. "Freeze-drying and solubility studies." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184399.
Testo completoAbstract (sommario):
The medium offering the greatest resistance to heat transfer from the freeze-drying shelf to the moving and subliming surface is the space between the flat shelf top and the concave vial bottom. The resistance to heat transfer can be greatly reduced by improving the thermal conductivity of the intervening space. Several heat transfer augmentation devices, including a multilayered corrugated aluminum quilt and a conformable fluid cushion device, which fill this gap are described. The devices are inexpensive and easy to use. Experimental data show that the resistance of the intervening space is reduced appreciably and the drying rate is greatly increased. The fluid cushion device is superior to the aluminum quilt as it reduces the consequences of spillage of solution and provides greater intervial uniformity among the same batch of vials. Drying times obtained in experiments with and without the fluid cushion device are compared here for different sizes and different types of vials. Product evaluation is conducted by measuring the reconstitution time and observing the product under a microscope. The solubilities of two univalent electrolytes, sodium chloride and potassium chloride, have been measured in eight cosolvent-water binary systems. The solubility of both the solutes has been found to be adequately described by the log-linear solubility equation, log S(m) = log S(w) + fσ. The rank order of the desolubilization slopes obtained for the electrolyte solutes is compared with the solubilization of nonelectrolyte solutes. These results indicate that a cosolvent which is most effective in solubilizing a nonelectrolyte is also most effective in desolubilizing an electrolyte. The solubility of oxacillin sodium in methanol-water mixtures has been determined at various temperatures ranging from +21 to -26 degrees centigrade. The data has been fitted to the log-linear relationship as proposed by Yalkowsky et. al. The heat of solution is determined using the van't Hoff equation and was found to be nearly constant at 1.2 Kcal/mole. There appears to be no dependency of the slope of the log S(m) vs. fraction cosolvent plot to the temperature. The data suggests that there is a polymorphic or amorphic transition of oxacillin at -14.5 degrees centigrade.
37
Tang, Yanfei. "Stratification in Drying Particle Suspensions." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/87435.
Testo completoAbstract (sommario):
This thesis is on molecular dynamics studies of drying suspensions of bidisperse nanoparticle mixtures. I first use an explicit solvent model to investigate how the structure of the dry film depends on the evaporation rate of the solvent and the initial volume fractions of the nanoparticles. My simulation results show that the particle mixtures stratify according to their sizes when the suspensions are quickly dried, consistent with the prediction of recent theories. I further show that stratification can be controlled using thermophoresis induced by a thermal gradient imposed on the drying suspension. To model larger systems on longer time scales, I explore implicit solvent models of drying particle suspensions in which the solvent is treated as a uniform viscous background and the liquid-vapor interface is replaced by a potential barrier that confines all the solutes in the solution. Drying is then modeled as a process in which the location of the confining potential is moved. In order to clarify the physical foundation of this moving interface method, I analyze the meniscus on the outside of a circular cylinder and apply the results to understand the capillary force experienced by a spherical particle at a liquid-vapor interface. My analyses show that the capillary force is approximately linear with the displacement of the particle from its equilibrium location at the interface. An analytical expression is derived for the corresponding spring constant that depends on the surface tension and lateral span of the interface and the particle radius. I further show that with a careful mapping, both explicit and implicit solvent models yield similar stratification behavior for drying suspensions of bidisperse particles. Finally, I apply the moving interface method based on an implicit solvent to study the drying of various soft matter solutions, including a solution film of a mixture of polymers and nanoparticles, a suspension droplet of bidisperse nanoparticles, a solution droplet of a polymer blend, and a solution droplet of diblock copolymers.<br>PHD<br>Drying is a ubiquitous phenomenon. In this thesis, I use molecular dynamics methods to simulate the drying of a suspension of a bidisperse mixture of nanoparticles that have two different radii. First, I use a model in which the solvent is included explicitly as point particles and the nanoparticles are modeled as spheres with finite radii. Their trajectories are generated by numerically solving the Newtonian equations of motion for all the particles in the system. My simulations show that the bidisperse nanoparticle mixtures stratify according to their sizes after drying. For example, a “small-on-top” stratified film can be produced in which the smaller nanoparticles are distributed on top of the larger particles in the drying film. I further use a similar model to demonstrate that stratification can be controlled by imposing a thermal gradient on the drying suspension. I then map an explicit solvent system to an implicit one in which the solvent is treated as a uniform viscous background and only the nanoparticles are kept. The physical foundation of this mapping is clarified. I compare simulations using the explicit and implicit solvent models and show that similar stratification behavior emerge in both models. Therefore, the implicit solvent model can be applied to study much larger systems on longer time scales. Finally, I apply the implicit solvent model to study the drying of various soft matter solutions, including a solution film of a mixture of polymers and nanoparticles, a droplet of a bidisperse nanoparticle suspension, a solution droplet of a polymer blend, and a droplet of a diblock copolymer solution.
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Du, Xi. "Membrane Drying of Ionic Liquid." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1353077367.
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Heredia, Salgado Mario Alejandro. "Sewage sludge drying and combustion." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13409.
Testo completoAbstract (sommario):
Mestrado em Sistemas Energéticos Sustentáveis<br>A brief review of the paper pulp production process in order to understand the origin of the sewage sludge was performed. Then a general revision of the current treatment options for this type of waste was addressed. The thermal treatment by combustion was focused and a review of the state of the art of this process was performed. The high moisture content of sludge was identified as a major concern. Thus a revision of the state of the art regarding thermal drying of sewage sludge was performed. The drying behavior of sewage sludge from
the pulp and paper industry was evaluated by experiment in a drying tunnel. Strong shrinkage, cracks and a weak crust phenomenon were identified. A drying kinetic model was developed by the use of Artificial Neural Networks achieving a high Pearson correlation coefficient in the validation tests. Additionally a theoretical assessment of the co-combustion process was performed having into account a 50 MWth combustion facility. The inclusion of different portions of sewage sludge in a fuel mixture and the influence of the sludge moisture content was studied. It was found that burning sewage sludge with more than 50 wt% moisture content is not possible. Furthermore the inclusion of sewage sludge in a biomass fuel mixture causes an increase in the fuel consumption, solids production and heat losses in the flue gas. Based on general thermodynamic considerations the thermal power of a sludge dryer was calculated. The use of waste heat to supply the energy needs of the drying process was addressed by the waste heat availability estimation as sensible heat and latent heat at the stack of the facility. A set of combustion experiments were done in a pilot scale bubbling fluidized bed combustor to assess the
combustion efficiency by monitoring the CO2, CO, H2O and O2 levels in conjunction with the temperature profile along the reactor height. Two different types of fuel samples were prepared. One composed by 100 wt% sewage sludge (fuel sample 1) and other composed by 50 wt% sewage sludge and 50 wt% residual forest biomass (particle size <1mm) (fuel sample 2). Low CO levels were onserved especially for the fuel sample 2 which indicates a very efficient combustion process. The CO emission level established by the Portuguese law for this type of reactor was never exceeded under typical operating conditions. The temperature profile along the reactor confirms that
the combustion of the fuel samples prepared occurs mainly in the freeboard zone. It was not observed agglomeration problems and the fluidization conditions were kept constant during all the experimental tests. After the combustion experiments a considerable ashes quantity were found and its particle size distribution was estimated.<br>Foi realizada uma revisão sucinta do processo de produção de pasta de papel, a fim de compreender a origem da lama biológica. Uma revisão geral das opções atuais de tratamento para este tipo de resíduo foi abordada. O tratamento térmico por combustão foi focalizado e uma avaliação do estado da arte deste processo foi realizada. Foi verificado que o elevado teor de humidade da lama representa uma grande preocupação. Por tanto, realizou-se uma revisão do estado da arte em relação à secagem térmica das lamas. O comportamento da lama secundaria da indústria de pasta e papel foi estudado experimentalmente em um túnel de secagem. Foram observados os fenómenos de encolhimento e rachaduras além do fenomeno de crosta, embora este último não seja muito pronunciado. Foi desenvolvido um modelo
de cinética de secagem com recurso ao uso de Redes Neurais Artificiais, sendo observado um elevado coeficiente de correlação nas experiências de validação. Foi realizada uma análise teórica ao processo de co-combustão de lama com biomassa florestal numa instalação de combustão de 50MWth. Estudou-se a inclusão de diferentes fracções de lama numa mistura de combustível contendo biomassa florestal, assim como também a influência do teor de humidade da lama. Verificou-se que a combustão de lamas biológicas com mais do que 50 wt% em teor de humidade não é possível. Além disso, a inclusão destas lamas na mistura de combustível provoca um aumento do consumo de combustível na instalação, da produção de sólidos e das perdas de calor no efluente gasoso da instalação. Com base em considerações
termodinâmicas foi determinada a potência térmica de um secador de lamas. A utilização do calor residual para suprir as necessidades energéticas do processo de secagem foi abordada a través da estimativa da disponibilidade de calor residual na forma de calor sensível e calor latente no efluente gasoso da instalação de combustão. Foi realizado um conjunto de experiências de combustão de lamas e sua mistura com biomassa florestal num reactor de leito fluidizado borbulhante á escala piloto para avaliar a eficiência de combustão
através da concentração de CO2, CO, O2 e H2O, em conjunto com o perfil de temperaturas ao longo do reactor. Foram utilizados dois tipos diferentes de amostras de combustível, uma composta por 100 wt% de lama biológica (combustível 1), e outra composta por 50 wt% de lama biológica e 50 wt% de biomassa florestal residual (tamanho de partícula <1mm) (combustível 2). Foram observados baixos níveis de CO no efluente gasoso, emparticular para a amostra de combustível 2, o qual indica um processo de combustão muito eficiente. Para condições de operação (temperatura e estequimetria) típicas, verificou-se que o limite de emissão de CO estabelecido pela lei Portuguesa
para este tipo de fornalhas não foi excedido. O perfil de temperatura ao longo do reactor confirma que a combustão das amostras de combustível preparadas ocorre principalmente na zona do freeboard. Não foram verificados problemas de aglomeração e as condições de fluidização foram mantidas constantes durante todos os ensaios experimentais. Após os ensaios de combustão foi observada uma quantidade considerável de cinzas na fornalha, tendo sido avaliada a sua distribuição granulométrica.
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Strachan, Scott. "Invertebrate Resistance to Wetland Drying." Thesis, Strachan, Scott (2016) Invertebrate Resistance to Wetland Drying. PhD thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/29962/.
Testo completoAbstract (sommario):
In regions with a drying climate, as waterbodies dry out more frequently or for longer, species traits interact with aquatic habitat influencing assemblage composition in wetlands. This thesis aimed to identify potential refuges from increased temperatures and altered water regimes for wetland invertebrates that resist drying using resting stages in the sediment. Using the literature on desiccation-responses by freshwater invertebrates, I reviewed relationships between life histories and the degree of desiccation to which individuals are exposed. Sediment microhabitats that retain moisture were sampled, showing that they could provide microrefuges for invertebrates during seasonal drying. Dry sediment was sampled from two habitats (open water (OW) and fringing trees (FT)) in eight wetlands, sediment properties were measured, and invertebrate emergence from inundated damp and artificially dried sediment were observed. FT sediment was cooler, had higher organic matter content, water saturation potential and different invertebrate assemblage composition. For most species the effect of drying depended on habitat; effects included mortality, reduced abundance and increased abundance. False starts occur when dry wetlands receive brief, unseasonable periods of inundation that trigger invertebrate hatching, but then dry out causing abortive hatching. OW and FT sediments were exposed to false starts in the laboratory. In OW, abortive hatching occurred and new assemblages emerged from egg banks during the next inundation. In FT, invertebrates emerged rapidly and survived drying, continuing to develop into assemblages that did not differ from permanently inundated controls. Overall, this research showed that shallow seasonal wetlands contain refuges from higher temperatures and prolonged drying, explaining the resistance of their fauna to drought. To sustain wetland biodiversity, FT vegetation should be protected and replanted (where necessary) and wetland sediment should be protected from degrading processes such as sedimentation and eutrophication, so that it retains microrefuges.
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CAPOZZI, LUIGI CARLO. "Continuous Freeze-Drying of Pharmaceuticals." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2749555.
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Scarborough, David Eugene. "The effect of resonant acoustic oscillations on the drying of poly(ethylene) terephthalate." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/18939.
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43
Anandharamakrishnan, C. "Experimental and computational fluid dynamics studies on spray-freeze-drying and spray-drying of proteins." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/8061.
Testo completoAbstract (sommario):
This thesis presents an experimental and computational fluid dynamics (CFD) study of spray-drying, spray-freezing and spray-freeze-drying of whey proteins. The effects of varying feed concentration (20 - 40% w/v) and outlet temperature (600 - 120 degrees Celcius) on whey protein denaturation (determined by DSC) and solubility at pH 4.6 (by Kjeldhal and RP-HPLC methods) have been investigated in a pilot-scale cocurrent spray dryer. The study confirms that low outlet gas temperatures (60 and 80 degrees Celcius) produce the lowest amount of denaturation, with almost complete denaturation observed at 120 degrees Celcius. Slightly more denaturation was found with a 40% feed concentration. A reversed phase HPLC technique has been applied to measure the loss of solubility of a-lactalbumin and P-lactoglobulin. Significantly higher losses in solubility were observed for P-lactoglobulin compared to alactalburnin. Increasing the feed concentratioq at higher outlet temperatures also caused noticeable increases in insolubility. The reversed phase HPLC results were consistent with those obtained from total protein nitrogen content (Kjeldhal) analyses. This comparative study suggests that the protein solubility can also be calculated from RP-HPLC technique. Spray-freeze drying is an alternative approach to spray drying, which is less likely to cause protein denaturation and loss of solubility. Conventional freeze-drying involves high capital and operating costs, due to the low temperatures, high vacuum and very long drying times. One solution to this problem is to reduce the dimensions of the material being dried. This is the basis of the spray-freeze-drying technique, involving atomisation of a liquid to form droplets, freezing the droplets and subliming off the ice at low temperature and atmospheric pressure in a fluidised bed. However, the quantities of gas required for atmospheric freeze-drying are prohibitively expensive. A pilot-scale spray-freeze-drying process was investigated, in which fluidisation was performed at sub-atmospheric pressures, allowing rapid freezedrying (in about one hour) but using much less gas. This was demonstrated using whey protein which yields a product with a highly porous structure, with little loss of protein solubility. This process has potential to produce high-value-added food and pharmaceutical products more quickly and cheaply than is currently possible by commercial vacuum freeze-drying processes. CFD simulations were developed for short and tall form spray-dryers to study the particle velocity, temperature and residence time during drying. These simulation results agreed well with the published experimental data. The tall-form spray dryer model predictions showed that more particles impact on the cylindrical wall position and this may affect the protein denaturation and solubility. This study suggests that a short form dryer with a bottom outlet is more suitable for drying of proteins. Similarly, a CFD simulation for the spray-freezing operation was developed to study the gas flow pattern and particle trajectories and histories. This CFD model also includes the latent heat effects during the phase change. The simulation predictions agreed reasonably well with the experimental results. A comparison of simulations for a solid and a hollow cone spray suggested that the latter yields lower particle temperatures with low particle collection efficiency. A modified chamber geometry was proposed and the simulation showed that the new design could achieve higher particle collection efficiencies.
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Siebert, Tim [Verfasser]. "Improving drying: Investigations on structure changes during single and serial combination drying processes / Tim Siebert." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219475254/34.
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45
Jay, Stephen. "Drying processess in the United Kingdom : assessment of industrial energy utilisation and efficiency of drying systems and the modelling of drying characters using neural networks." Thesis, Aston University, 1996. http://publications.aston.ac.uk/15330/.
Testo completoAbstract (sommario):
Drying is an important unit operation in process industry. Results have suggested that the energy used for drying has increased from 12% in 1978 to 18% of the total energy used in 1990. A literature survey of previous studies regarding overall drying energy consumption has demonstrated that there is little continuity of methods and energy trends could not be established. In the ceramics, timber and paper industrial sectors specific energy consumption and energy trends have been investigated by auditing drying equipment. Ceramic products examined have included tableware, tiles, sanitaryware, electrical ceramics, plasterboard, refractories, bricks and abrasives. Data from industry has shown that drying energy has not varied significantly in the ceramics sector over the last decade, representing about 31% of the total energy consumed. Information from the timber industry has established that radical changes have occurred over the last 20 years, both in terms of equipment and energy utilisation. The energy efficiency of hardwood drying has improved by 15% since the 1970s, although no significant savings have been realised for softwood. A survey estimating the energy efficiency and operating characteristics of 192 paper dryer sections has been conducted. Drying energy was found to increase to nearly 60% of the total energy used in the early 1980s, but has fallen over the last decade, representing 23% of the total in 1993. These results have demonstrated that effective energy saving measures, such as improved pressing and heat recovery, have been successfully implemented since the 1970s. Artificial neural networks have successfully been applied to model process characteristics of microwave and convective drying of paper coated gypsum cove. Parameters modelled have included product moisture loss, core gypsum temperature and quality factors relating to paper burning and bubbling defects. Evaluation of thermal and dielectric properties have highlighted gypsum's heat sensitive characteristics in convective and electromagnetic regimes. Modelling experimental data has shown that the networks were capable of simulating drying process characteristics to a high degree of accuracy. Product weight and temperature were predicted to within 0.5% and 5C of the target data respectively. Furthermore, it was demonstrated that the underlying properties of the data could be predicted through a high level of input noise.
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Hjort, Mikael. "Solar Powered Paper Drying in Bangladesh : A feasibility study on using a solar thermalenergy to dry handmade paper in Bangladesh." Thesis, Uppsala universitet, Fasta tillståndets fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-210903.
Testo completoAbstract (sommario):
Solar energy has a great potential to give cheap and abundant energy to rural areas of the world, but is the technology ready to be implemented today? This stydy looked at the possibilities to introduce more renewable energy into the local hand-made paper production in Bangladesh. Specifically the potential of solar heated vacuum tubes filled with water as a heat carrier. This type of solar thermal collectors are cheap to produce, relatively efficient at converting both direct and diffuse solar energy into usable energy, and have a very simple construction that do not require a lot of training to handle. The study showed that the collector could convert about 70 % of the energy from the sun into usable energy in the form of hot water circulated in the system. On average in Bangladesh the 5 m2 collector used is expected to have an output of about 25.6 MJ per day (yearly average) and about 4.8 MJ was needed to evaporate 1 kg of water from the drying papers (including the system losses). This can be compared with the old system that used about 8 MJ per kg water evaporated. Finally the study includes a step by step guide into how to build a system like this by locally available material. The only parts that were imported were some measurement equipment and parts of the collector that was not yet available through local distributors. The pump was also not produced in Bangladesh, but a similar pump could be bought by local companies that import this type of equipment.
47
Burton, Steven W. "An investigation of z-direction density profile development during impulse drying." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/5560.
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Shivhare, Uma Shanker. "Drying characteristics of corn in a microwave field with a surface-wave applicator." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70344.
Testo completoAbstract (sommario):
Microwave drying of corn was investigated at selected levels of initial moisture content, absorbed power by grain, and temperature and superficial velocity of air at inlet. A surface-wave applicator was used to couple microwaves with the corn.<br>The drying rate curves indicated that the microwave drying of corn took place in the falling rate period. It was hypothesized that diffusion is the controlling mechanism for moisture transfer from within the kernel in microwave drying of corn.<br>A mathematical model was developed to describe the change in moisture content at the surface as a function of the free moisture content of corn. The diffusion model employing varying surface conditions was used to describe the microwave drying process. An Arrhenius type equation was developed to describe the relationship between the diffusion coefficient and the outlet air temperature. The diffusion coefficient values varied from 0.0008 to 0.0082 cm$ sp2$/h when constant levels of microwave power were applied continuously for drying corn. Equilibrium moisture content was determined and regression equations were developed to describe the EMC with microwave power and air velocity.<br>The diffusion coefficient increased with the levels of absorbed power, decreased with increasing air velocity but remained insensitive to the inlet air temperature when microwaves were applied continuously for drying corn. The increased drying rates at higher power levels reduced the drying time considerably but at the cost of energy loss through the passing air and reduced germination and bulk density of dried corn. Application of absorbed microwave power at 0.25 W/g resulted in greater than 92% germination of dried corn. Deleterious effects on product quality was observed when the applied power exceeded 0.75 W/g.<br>Pulsed and variable microwave power effects were investigated in order to optimize the drying process. Time for drying corn increased but the effective duration for which microwaves were applied and the energy requirement in the pulsed mode was lower compared to both continuous and variable microwave operation.
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Cheng, Wei Min 1964. "Microwave power control strategies on the drying process." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81271.
Testo completoAbstract (sommario):
The current study was conducted for evaluating the effects of two different strategies viz., phase control and cycle control, on the microwave/air drying process. A phase-controlled electrical power regulator was developed and connected in series with the original cycle-controlled power regulator of an existing domestic microwave oven. The microwave oven was further modified such that combined microwave and convectional drying can be accommodated.<br>The system performance was evaluated. It was observed that phase-controlled power regulator could be successfully used for quasi-continuous (fast-switching) power regulation with the maximization of power efficiency. The degradation of output microwave power was recorded and the nonuniform distribution of microwave field in the cavity was also verified.<br>The effects of phase control and cycle control were evaluated through combined microwave and convective drying of potato samples. Results showed that different power control methods had different impacts on drying kinetics and product quality. In both drying modes, the drying time increased with the decrease of microwave power density and the increase of air velocity. The drying rates of cycle-controlled drying are significantly higher than those of phase-controlled drying. In terms of rehydration capacity the phase-controlled drying mode produced better results. The product colour and sensory attributes were independent of the power control methods.
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Li, Heping. "Microwave assisted osmotic dehydration of apple cylinders under continuous medium flow conditions for improving moisture transfer rate and product quality." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85933.
Testo completoAbstract (sommario):
Microwave assisted osmotic dehydration (MWOD) under continuous medium flow conditions is a new process with good potential for quality optimization. It combines microwave process with osmotic dehydration and improves the mass transfer rate of osmotic dehydration process and product quality. The thesis describes the design and development of this process.<br>Preliminary studies on osmotic dehydration were carried out in two parts. First, the effects of processing time, temperature and solution concentration on mass transfer under conventional osmotic dehydration process were investigated and suitable ranges of parameters: 40-60°C, 40-60°Brix and 3h, for further osmotic dehydration kinetics study were identified. Then, the osmotic dehydration efficiency under continuous flow condition process was evaluated. For this, a continuous flow osmotic contactor was developed and found to be an efficient process in terms of osmotic dehydration of apple cylinders. Solids diffusivity (Ds) was lower in continuous flow osmotic dehydration process compared with conventional osmotic dehydration correspondents (P<0.05). Being a separate operation unit, the dehydration process and solution management can be done in a more efficient way in this process.<br>Following the preliminary studies, the osmotic contactor was relocated under a microwave oven so that heating and mass transfer operations could be facilitated by continuous microwave treatment providing a microwave assisted osmotic dehydration (MWOD) process. Compared with conventional osmotic dehydration (COD), moisture loss (ML%), solids gain (SG%) and mass transport coefficients (km and ks) of MWOD were improved, the average k m was increased 80% and the average ks was decreased 20%, respectively. Moreover, product rehydration property and color profile were improved. Microwave heating had an important effect on water transfer during the osmotic dehydration. Application of microwave heating to osmotic dehydration process facilitated in increasing moisture loss from the sample and simultaneously restricted the product's solute gain. Higher moisture loss in mass transfers area helped to control and strongly counters the solids gain.<br>Modeling of the mass transfer phenomenon is necessary to optimize osmotic dehydration processes to have a high product quality at minimum energy costs. To explain the simultaneous mass-flow in an osmo-dehydration process, evaluation of equilibrium kinetics is important. Pseudo-equilibrium (practical equilibrium) and dynamic period data are necessary for estimating the time of osmotic process, and ultimate mass transport of the solutes and water, and hence these data were gathered.<br>The effect of osmotic dehydration treatment on sample subsequent air drying behavior and product quality parameters were investigated. Compared with control samples, osmostically treated samples moisture diffusivity during subsequent air drying process was reduced over same moisture content range: from 1.18*10-9m2/s to 0.77*10-9--1.07*10 -9 m2/s. Drying rates of MWOD pretreated samples varied depending on treatment conditions. MWOD pretreatment shifted product's color profile to those that can be achieved under freeze drying conditions.<br>Sorption isotherms induced by osmotic dehydration were studied, using a gravimetric-static method, and fitted to GAB model. Adsorption isotherms of products were affected by drying method and osmotic dehydration pretreatment conditions. Adsorption isotherms of osmo-air dried apple cylinders followed type II isotherms (Sigma shaped curve). Monolayer (Mm) values of the osmo-air dried products were reduced. Sorption isotherms of osmotically treated-air dried products were shifted from the control isotherms.<br>Overall, this work has demonstrated potential of microwave heating for improving moisture transfer during osmotic dehydration and microwave osmotic treatment on subsequent air drying and resulting product quality, as well as the importance of equilibrium kinetics study in process modeling.