Browsing by Subject "pretreatment"
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Item De-oiling and Pre-treatments for High-Quality Potato Chips(2012-02-14) Kim, Tae HoonA de-oiling step using a centrifuge ensures oil content reduction and improves the quality of fried snacks. A commercial deep-fat fryer with the basket loaded with potatoes and a sample holder was used to fry potato slices, non-pretreated, blanched in hot water (85?C/3.5min) and rinsed in 3 percent NaCl solution (25?C/5min). A de-oiling step (350 1 rpm and 457 1 rpm) for 1 min was conducted after the frying (145?, 165? and 185?C or 165?C) and cooling (0, 15, 30, 45 and 60 s or 0.60 and 120 s) steps. Lower frying temperature, higher centrifuge speed, and shorter cooling time resulted in the lowest oil uptake in potato chips. Pre-treatments (blanching and soaking) decreased (5 percent and by at least 10 percent), respectively, compared to the untreated chips. De-oiling led to increased hardness of the chips fried at 145? and 165?C (0 s cooling time), and the hardness decreased as cooling time. Pre-treatments (blanching and soaking) increased hardness (by 46 percent and 38 percent) and decreased work (by 20 percent and 27 percent), respectively, so that, during rupture, the pre-treated chips resulted in more crunchiness and firmness than the untreated chips. Potato chips showed less lightness and redness when fried at 145?C, and more lightness and redness when fried at 185?C; yellowness increased b* values as temperature increased. As cooling time increased, the lightness of the chips decreased, and the redness and the yellowness of the chips increased. Pre-treated samples resulted in increasing in lightness (L*) and yellowness (b*), whereas the redness (a*) values of the final products fluctuated. Higher frying temperature, centrifuge speed, and higher cooling time usually resulted in increasing shrinkage in thickness of potato chips; the chips fried at 165?C resulted in increasing in thickness. All the fried and de-oiled products resulted in a decrease in thickness, diameter, and volume except for the thickness of the chip soaked in NaCl, compared to raw slices. A consumer test showed that, blanching and de-oiling without cooling enhanced texture and overall quality of the chip, soaking and de-oiling improved the color, flavor, and the overall quality, and the two pre-treatments did not significantly influence the odor of the chip.Item Kinetic Modeling and Assessment of Lime Pretreatment of Poplar Wood(2012-02-14) Sierra Ramirez, RocioBecause of widespread availability, low cost, sustainability, and potential supply far greater than that of food crops, lignocellulosic biomass is one of the most promising feedstocks for producing biofuels through fermentation processes. Among lignocellulose choices, poplar wood is appealing because of high energy potential, above-average carbon mitigation potential, fast growth, and high yields. Lignocellulose structural features limit accessibility of enzymes or microorganisms. To overcome these limitations, pretreatment is required. Among several choices of pretreatment, lime pretreatment is preferred because lime is the cheapest alkali, safest to handle, easy to recover, and compatible with oxidants. The main effect of lime pretreatment is to degrade lignin, which occurs with good carbohydrate preservation and is enhanced with oxidants. Among several choices of oxidant, oxygen and air are preferred because of low cost and widespread availability. This study systematically assesses the effects of lime pretreatment on poplar wood using four different modes: long-term oxidative, long-term non-oxidative, short-term constant pressure, and short-term varying pressure. Long-term pretreatments use temperatures between 25 and 65? C, air if oxidant is used, and last several weeks. Short-term pretreatments use temperatures between 110 and 180? C, pressurized oxygen, and last several minutes to hours. Pretreatment was assessed on the basis of 3-day enzymatic digestibility using enzyme loadings of 15 FPU/g glucan in raw biomass. The results were used to recommend pretreatment conditions based on highest overall yield of glucan (after combined pretreatment and enzymatic hydrolysis) for each pretreatment mode. For each pretreatment mode, kinetic models for delignification and carbohydrates degradation were obtained and used to determine the conditions (temperature, pressure, and time) that maximize glucan preservation subjected to a target lignin yield. This study led to conclude that the most robust, and selective mode of lime pretreatment is varying pressure.Item Modeling and Optimization of a Bioethanol Production Facility(2011-10-21) Gabriel, Kerron JudeThe primary objective of this work is to identify the optimal bioethanol production plant capacity and configuration based on currently available technology for all the processing sections involved. To effect this study, a systematic method is utilized which involves the development of a superstructure for the overall technology selection, process simulation and model regression of each processing step as well as equipment costing and overall economic evaluation. The developed optimization model is also designed to incorporate various biomass feedstocks as well as realistic maximum equipment sizing thereby ensuring pragmatism of the work. For this study, the criterion for optimization is minimum ethanol price. The secondary and more interesting aim of this work was to develop a systematic method for evaluating the economics of biomass storage due to seasonal availabilities. In essence, a mathematical model was developed to link seasonal availabilities with plant capacity with subsequent integration into the original model developed. Similarly, the criterion for optimization is minimum ethanol price. The results of this work reveal that the optimal bioethanol production plant capacity is ~2800 MT biomass/day utilizing Ammonia Fiber Explosion pretreatment technology and corn stover as the preferred biomass feedstock. This configuration provides a minimum ethanol price of $1.96/gal. Results also show that this optimal pretreatment choice has a relatively high sensitivity to chemical cost thereby increasing the risk of implementation. Secondary to this optimal selection was lime pretreatment using switchgrass which showed a fairly stable sensitivity to market chemical cost. For the storage economics evaluation, results indicated that biomass storage is not economical beyond a plant capacity of ~98 MMgal/yr with an average biomass shortage period of 3 months. The study also showed that for storage to be economical at all plant capacities, the storage scheme employed should be general open air land use with a corresponding biomass loss rate as defined in the study of 0.5 percent per month.Item Selective Catalytic Reduction (SCR) of nitric oxide with ammonia using Cu-ZSM-5 and Va-based honeycomb monolith catalysts: effect of H2 pretreatment, NH3-to-NO ratio, O2, and space velocity(Texas A&M University, 2004-09-30) Gupta, SaurabhIn this work, the steady-state performance of zeolite-based (Cu-ZSM-5) and vanadium-based honeycomb monolith catalysts was investigated in the selective catalytic reduction process (SCR) for NO removal using NH3. The aim was to delineate the effect of various parameters including pretreatment of the catalyst sample with H2, NH3-to-NO ratio, inlet oxygen concentration, and space velocity. The concentrations of the species (e.g. NO, NH3, and others) were determined using a Fourier Transform Infrared (FTIR) spectrometer. The temperature was varied from ambient (25 C) to 500 C. The investigation showed that all of the above parameters (except pre-treatment with H2) significantly affected the peak NO reduction, the temperature at which peak NO reduction occurred, and residual ammonia left at higher temperatures (also known as 'NH3 slip'). Depending upon the particular values of the parameters, a peak NO reduction of around 90% was obtained for both the catalysts. However, an accompanied generation of N2O and NO2 species was observed as well, being much higher for the vanadium-based catalyst than for the Cu-ZSM-5 catalyst. For both catalysts, the peak NO reduction decreased with an increase in space velocity, and did not change significantly with an increase in oxygen concentration. The temperatures at which peak NO reduction and complete NH3 removal occurred increased with an increase in space velocity but decreased with an increase in oxygen concentration. The presence of more ammonia at the inlet (i.e. higher NH3-to-NO ratio) improved the peak NO reduction but simultaneously resulted in an increase in residual ammonia. Pretreatment of the catalyst sample with H2 (performed only for the Cu-ZSM-5 catalyst) did not produce any perceivable difference in any of the results for the conditions of these experiments.