Browsing by Subject "Pyrolysis"
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Item A macro-particle, moving-boundary pyrolysis model(Texas Tech University, 1983-08) Lin, Ruey-jiaNot availableItem A mathematical simulation for a partial-oxidation-pyrolysis gasifier.(Texas Tech University, 1975-05) Albus, Clarence JohnNot availableItem Characteristics of radially propagating smoldering combustion in a sawdust bed(2015-12) Bush, Robert H., III; Ellzey, Janet L.In this thesis, experimental work on smoldering of sawdust beds is presented and discussed. Extensive study has been done on wood burning cook stoves with an emphasis on performance characterization and optimization. Few studies, however, have focused on the smoldering process with the goal of understanding the propagation of the front and the production of emissions. In this study, photographs, temperature and emission measurements on smoldering sawdust clearly showed the evolution of the combustion process: an initial conversion of the raw sawdust to char followed by the conversion of char to ash. In general, the char front propagated symmetrically in the radial direction while the ash front was not symmetric, and typically followed paths where oxygen was most readily available. Further analysis was accomplished by observing the characteristics of the sawdust bed before transition to flaming occurred. Contrary to expected results, flaming did not occur as the air flow was increased, but rather once it was decreased, suggesting that flaming is determined by a balance between generation of volatiles and dilution by incoming air. Experiments with vitiated air, in which the oxygen content of air is diluted by adding nitrogen, were conducted to determine a limit at which combustion was no longer self-sustaining. Experiments showed that vitiated air with 7% oxygen in the supply air did not support self-sustaining combustion. Finally, a comparison between poplar and walnut was conducted to show the effect of wood species. Comparison of temperature, hydrocarbon, and carbon monoxide outputs identified characteristic differences between the poplar and walnut species.Item Comparison of Biological and Thermal (Pyrolysis) Pathways for Conversion of Lignocellulose to Biofuels(2012-11-30) Imam, Tahmina 1983-Because of the limited supply of imported crude oil and environmental degradation, renewable energy is becoming commercially feasible and environmentally desirable. In this research, biological and thermal (pyrolysis) conversion pathways for biofuel production from lignocellulosic feedstocks were compared. For biological conversions of sorghum, ethanol yield was improved using M81-E variety (0.072 g/g juice) over Umbrella (0.065 g/g juice) for first-generation biomass (sorghum juice), and 0.042 g/g sorghum was obtained from the cellulosic portion of second-generation biomass. When ultrasonication was combined with hot water pretreatment, yields increased by 15% and 7% for cellulose to glucose, and hemicellulose to pentose, respectively. Ethanol yield was 10% higher when this pretreatment was combined with Accellerase 1500+XC for saccharification. Biological conversion yielded 1,600?2,300 L ethanol/ha for first-generation biomass, and 4,300?4,500 L ethanol/ha from lignocellulosic biomass. For thermal (pyrolysis) conversion of lignocellulosic switchgrass at 600 degrees C, product yield was 37% bio-oil, 26% syngas, and 25% bio-char. At 400 degrees C, product yield was 22% bio-oil, 8% syngas, and 56% bio-char. Bio-oil from pyrolysis was highly oxygenated (37 wt%). It required chemical transformation to increase its volatility and thermal stability, and to reduce its viscosity by removing objectionable oxygen, so the product could be used as transportation fuel (gasoline). As a consequence of upgrading bio-oil by catalytic hydrogenation, bio-oil oxygen decreased from 37?2 wt%, carbon increased from 50?83 wt%, hydrogen increased from 9?15 wt% and heating value increased from 36?46 MJ/kg, resulting in a fuel that was comparable to gasoline. The upgraded product passed the thermal stability test when kept under an oxygen-rich environment. The upgraded product consisted of 14.8% parrafins, 21.7% iso-parrafins, 3% napthene, 42.6% aromatics, 4.7% olefin, 4.7% DMF, 8% alcohol, and 0.6% ketone on a mass basis. Comparing the two pathways, biological conversion had 11 wt% ethanol yield from sorghum, and thermal conversion had 13 wt% gasoline yield from switchgrass. For process efficiency, thermal conversion had 35% energy loss versus 45% energy loss for biological conversions. For the biological pathway, ethanol cost was $2.5/gallon ($4/gallon, gasoline equivalent), whereas for the thermal pathway, switchgrass gasoline cost was $3.7/gallon, both with 15% before tax profit.Item Continuous refuse report: a feasibility investigation(Texas Tech University, 1972-08) Massie, John RichardNot availableItem Determination of pyrolysis kinetic parameters of San Miguel (Texas) lignite(Texas Tech University, 1982-08) Jih, Jefferson Shau-tungThe kinetics of San Miguel (Texas) lignite pyrolysis was investigated in range of 650 to 800°C at atmospheric pressure. An experimental system which facilitated the monitoring of the actual sample temperature, collection of gas and tar, and measurement of sample weight loss as a function of time was used. It is found that, in the range investigated, lignite decomposition into gas, tar, and char can be described by three parallel first order reactions. Examination of experimental data indicated that, in the range investigated, the rate of pyrolysis is controlled by intraparticle heat transfer. A simplified kinetic-transport model was used to estimate the individual reaction rate constants and the activation energies. The amount and composition of the pyrolysis gas products were also analyzed. The gas produced consisted mainly of carbon dioxide, carbon monoxide, hydrogen, and some low hydrocarbons. The hydrocarbon products consisted mainly of methane, ethane, ethylene, and trace amounts of C+3 compounds.Item Effect of Co-Firing Torrefied Woody Biomass with Coal in a 30 kWt Downfired Burner(2014-04-25) Thanapal, Siva SMesquite and juniper can be beneficially utilized for gasification and combustion applications. Torrefaction has been considered to be one of the thermal pretreatment options to improve the chemical (e.g. heat content) and physical (e.g. grindability) properties of raw biomass. A simple three component parallel reaction model (TCM) was formulated to study the effect of heating rate, temperature, residence time and type of biomass on torrefaction process. Typically inert environment (e.g. N_(2), He, Ar) is maintained to prevent oxidation of biomass during torrefaction. A novel method for utilization of carbon dioxide as the pretreatment medium for woody biomass has been investigated in the current study. Both raw and the torrefied biomass (TB) were pyrolyzed using TGA under N_(2). The TB fuels were also fired with coal in a 30 kWt downfired burner to study the NOx emission. In addition, tests were also done using raw biomass (RB) (mesquite and juniper) blended with coal and compared with results obtained from cofiring TB with coal. A zero dimensional model has been developed to predict the combustion performance of cofired fuels. The results are as follows. TGA studies yielded global kinetics based on maximum volatile release (MVR) method. TCM predicts higher loss of hemicellulose upon torrefaction when compared to the other components, cellulose and lignin resulting in improved heat values of TB. Comparable mass loss at lower temperatures, improved grindability, and improved fuel properties were observed upon using CO_(2) as the torrefaction medium. Co-firing 10% by mass of raw mesquite with coal reduced the NOx emission from 420 ppm to 280 ppm for an Equivalence ratio (ER) of 0.9. Further cofiring TB with coal reduced the NOx emission by 10% when compared to base case NOx emission from combustion of pure PRB coal. NOx emission decreased with increase in equivalence ratio. In addition, a term used in the biological literature, respiratory quotient (RQ), is applied to fossil and biomass fuels to rank the potential of fuels to produce carbon dioxide during oxidation process. Lesser the value of ?RQ? of a fuel, lower the global warming potential.Item Essays on Economic and Environmental Analysis of Taiwanese Bioenergy Production on Set-Aside Land(2012-02-14) Kung, Chih-ChunDomestic production of bioenergy by utilizing set-aside land in Taiwan can reduce Taiwan?s reliance on expensive and politically insecure foreign fossil fuels while also reducing the combustion of fossil fuels, which emit substantial amounts of greenhouse gases. After joining the World Trade Organization, Taiwan?s agricultural sector idled about one-third of the national cropland, hereafter called ?set-aside land?. This potentially provides the land base for Taiwan to develop a bioenergy industry. This dissertation examines Taiwan?s potential for bioenergy production using feedstocks grown on set-aside land and discusses the consequent effects on Taiwan?s energy security plus benefits and greenhouse gas (GHG) emissions. The Taiwan Agricultural Sector Model (TASM) was used to simulate different agricultural policies related to bioenergy production. To do this simulation the TASM model was extended to include additional bioenergy production possibilities and GHG accounting. We find that Taiwan?s bioenergy production portfolio depends on prices of ethanol, electricity and GHG. When GHG prices go up, ethanol production decreases and electricity production increases because of the relatively stronger GHG offset power of biopower. Results from this pyrolysis study are then incorporated into the TASM model. Biochar from pyrolysis can be used in two ways: burn it or use it as a soil amendment. Considering both of these different uses of biochar, we examine bioenergy production and GHG offset to see to what extent Taiwan gets energy security benefits from the pyrolysis technology and how it contributes to climate change mitigation. Furthermore, by examining ethanol, electricity and pyrolysis together in the same framework, we are able to see how they affect each other under different GHG prices, coal prices and ethanol prices. Results show that ethanol is driven out by pyrolysis-based electricity when GHG price is high. We also find that when biochar is hauled back to the rice fields, GHG emission reduction is higher than that when biochar is burned for electricity; however, national electricity production is consequently higher when biochar is burned.Item Extraction of waste water from biomass gasification(Texas Tech University, 1980-08) Kao, Chih-hengA waste water mixture from the pyrolysis of cattle manure, wood residues and corn stover was examined. Some methods of waste water treatment were screened. Activated carbon adsorption and solvent (carbontetrachloride, methylene chloride, n-butyl alcohol and methyl ethyl ketone) extraction were the methods chosen to treat the waste water. The results showed that dual solvent extraction using methyl ethyl ketone as a polar solvent to extract the valuable pollutants from the waste water and nhexane as a volatile solvent to recover the dissolved, polar solvent from the extracted water is an effective method to treat the waste water. A computer program has been developed to aid in the design of a solvent extraction column.Item Fixed Bed Counter Current Gasification of Mesquite and Juniper Biomass Using Air-steam as Oxidizer(2012-11-27) Chen, Wei 1981-Thermal gasification of biomass is being considered as one of the most promising technologies for converting biomass into gaseous fuel. Here we present results of gasification, using an adiabatic bed gasifier with air, steam as gasification medium, of mesquite and juniper. From Thermo-gravimetric analyses the pre-exponential factor (B) and activation energy of fuels for pyrolysis were obtained using single reaction models (SRM) and parallel reaction model (PRM). The single reaction model including convention Arrhenius (SRM-CA) and maximum volatile release rate model (SRM-MVR). The parallel reaction model fits the experimental data very well, followed by MVR. The CA model the least accurate model. The activation energies obtained from PRM are around 161,000 kJ/kmol and 158,000 kJ/kmol for juniper and mesquite fuels, respectively. And, the activation energies obtained from MVR are around100,000 kJ/kmol and 85,000 kJ/kmol for juniper and mesquite fuels, respectively. The effects of equivalence ratio (ER), particle size, and moisture content on the temperature profile, gas composition, tar yield, and higher heating value (HHV) were investigated. For air gasification, when moisture increased from 6% to 12% and ER decreased from 4.2 to 2.7, the mole composition of the dry product gas for mesquite varied as follow: 18-30% CO, 2-5% H2, 1-1.5% CH4, 0.4-0.6% C2H6, 52-64% N2, and 10-12% CO2. The tar yield shows peak value (150 g/Nm^3) with change in moisture content between 6-24%. The tar collected from the gasification process included light tar and heavy tar. The main composition of the light tar was moisture. The chemical properties of heavy tar were determined. For air-steam gasification, H2 rich mixture gas was produced. The HHV of the mesquite gas increased first when S: F ratio increased from 0.15 to 0.3 and when the S: F ratio increased to 0.45, HHV of the gas decreased. Mesquite was blended with the Wyoming Powder River Basin (PRB) coal with ratio of 90:10 and 80:20 in order to increase the Tpeak and HHV. It was found that the Tpeak increased with the increase of PRB coal weight percentage (0% to 20%).Item Fluidized bed gasification of agricultural residues(Texas Tech University, 1979-12) Hightower, James AlanNot availableItem Item Liquid-phase Processing of Fast Pyrolysis Bio-oil using Pt/HZSM-5 Catalyst(2013-05-01) Santos, Bjorn SanchezRecent developments in converting biomass to bio-chemicals and liquid fuels provide a promising sight to an emerging biofuels industry. Biomass can be converted to energy via thermochemical and biochemical pathways. Thermal degradation processes include liquefaction, gasification, and pyrolysis. Among these biomass technologies, pyrolysis (i.e. a thermochemical conversion process of any organic material in the absence of oxygen) has gained more attention because of its simplicity in design, construction and operation. This research study focuses on comparative assessment of two types of pyrolysis processes and catalytic upgrading of bio-oil for production of transportation fuel intermediates. Slow and fast pyrolysis processes were compared for their respective product yields and properties. Slow pyrolysis bio-oil displayed fossil fuel-like properties, although low yields limit the process making it uneconomically feasible. Fast pyrolysis, on the other hand, show high yields but produces relatively less quality bio-oil. Catalytic transformation of the high-boiling fraction (HBF) of the crude bio-oil from fast pyrolysis was therefore evaluated by performing liquid-phase reactions at moderate temperatures using Pt/HZSM-5 catalyst. High yields of upgraded bio-oils along with improved heating values and reduced oxygen contents were obtained at a reaction temperature of 200?C and ethanol/HBF ratio of 3:1. Better quality, however, was observed at 240 ?C even though reaction temperature has no significant effect on coke deposition. The addition of ethanol in the feed has greatly attenuated coke deposition in the catalyst. Major reactions observed are esterification, catalytic cracking, and reforming. Overall mass and energy balances in the conversion of energy sorghum biomass to produce a liquid fuel intermediate obtained sixteen percent (16 wt.%) of the biomass ending up as liquid fuel intermediate, while containing 26% of its initial energy.Item Mercury emission behavior during isolated coal particle combustion(2009-05-15) Puchakayala, Madhu BabuOf all the trace elements emitted during coal combustion, mercury is most problematic. Mercury from the atmosphere enters into oceanic and terrestrial waters. Part of the inorganic Hg in water is converted into organic Hg (CH3Hg), which is toxic and bioaccumulates in human and animal tissue. The largest source of human-caused mercury air emissions in the U.S is from combustion coal, a dominant fuel used for power generation. The Hg emitted from plants primarily occurs in two forms: elemental Hg and oxidized Hg (Hg2+). The coal chlorine content and ash composition, gas temperature, residence time and presence of different gases will decide the speciation of Hg into Hg0 and Hg2+. For Wyoming coal the concentrations of mercury and chlorine in coal are 120ppb and 140ppb. In order to understand the basic process of formulation of HgCl2 and Hg0 a numerical model is developed in the current work to simulate in the detail i) heating ii) transient pyrolysis of coal and evolution of mercury and chlorine, iii) gas phase oxidation iv) reaction chemistry of Hg and v) heterogeneous oxidation of carbon during isolated coal particle combustion. The model assumes that mercury and chlorine are released as a part of volatiles in the form of elemental mercury and HCl. Homogenous reaction are implemented for the oxidation of mercury. Heterogeneous Hg reactions are ignored. The model investigates the effect of different parameters on the extent of mercury oxidation; particle size, ambient temperature, volatile matter, blending coal with high chlorine coal and feedlot biomass etc,. Mercury oxidation is increased when the coal is blended with feedlot biomass and high chlorine coal and Hg % conversion to HgCl2 increased from 10% to 90% when 20% FB is blended with coal. The ambient temperature has a negative effect on mercury oxidation, an increase in ambient temperature resulted in a decrease in the mercury oxidation. The percentage of oxidized mercury increases from 9% to 50% when the chlorine concentration is increased from 100ppm to 1000ppm. When the temperature is decreased from 1950 K to 950 K, the percentage of mercury oxidized increased from 3% to 27%.Item Mineral Nutrient Recovery from Pyrolysis Co-Products(2012-07-16) Wise, Jatara RobPyrolysis is the thermo-chemical degradation of biomass in an oxygen-free environment to product liquid, gaseous, and solid co-products. The liquid co-product, known as bio-oil, can be used as a transportation fuel. The gaseous co-product, known as synthesis gas, can be used to power the pyrolysis reactor or other machinery. The solid co-product, known as bio-char, has been studied as an amendment to enhance soil physical and chemical properties and nutrient status. Although previous publications have described the beneficial effects of pyrolysis bio-char on soil physical and chemical properties, relatively little has been published on the recovery of mineral nutrients from pyrolysis co-products. This work quantified the recovery of feedstock nutrients (P, K, Ca, and Mg) and micronutrients (Na, Zn, Fe, Cu, and Mn) from pyrolysis co-products from various feedstocks using three distinct pyrolysis reactor designs. The reactors comprised a laboratory-scale fixed-bed reactor and two fluidized-bed reactors located in College Station, TX and Wyndmoor, PA. Nutrient recoveries, on a feedstock basis, were calculated for a comparison of reactor efficiencies. In addition to nutrient recoveries, physical and chemical properties of input biomass and of bio-char generated by each reactor were characterized through ultimate and proximate analyses. For the fixed-bed reactor, results revealed variation among feedstocks for the recoveries of feedstock sources of macronutrients and Na, Fe, and Cu in pyrolysis co-products. Variation among species was also detected for the recoveries of feedstock sources of P, K, Ca, Mg, and Fe in pyrolysis co-products for samples pyrolyzed using the Wyndmoor reactor. For the College Station reactor, recoveries of feedstock sources of P, K, Ca, and Mg in pyrolysis co-products did not vary among species, but Zn did vary. Ultimate and proximate analyses of biomass and bio-chars generated by the three reactors revealed variation among species. Additionally, the results showed that the recovery of feedstock nutrients varied by reactor design. Statistical analysis revealed high correlations and linear relationships between the recovery of nutrients and reactor mass and energy efficiency and feedstock fiber properties.Item Modeling and simulation of linear thermoplastic thermal degradation(2012-05) Bruns, Morgan Chase; Ezekoye, Ofodike A.; Ganesan, Venkat; Howell, John R.; Koo, Joseph H.; Nyden, Marc R.; Ruoff, Rodney S.Thermal degradation of linear thermoplastics is modeled at several scales. High-density polyethylene (HDPE) is chosen as an example material. The relevant experimental data is surveyed. At the molecular scale, pyrolysis chemistry is studied with reactive molecular dynamics. Optimization is used to calibrate several pyrolysis mechanisms with thermogravimetric analysis (TGA) data. It is shown that molecular scale physics may be coupled to continuum scale transport equations through a population balance equation (PBE). A PBE solution method is presented and tested. This method has the advantage of preserving detailed information for the small species in the molecular weight distribution with minimal computational expense. The mass transport of these small species is modeled at the continuum scale with a bubble loss mechanism. This mechanism includes bubble nucleation, growth, and migration to the surface of the condensed phase. The bubble loss mechanism is combined with a random scission model of pyrolysis to predict TGA data for HDPE. The modeling techniques developed at these three scales are used to model two applications of engineering interest with a combined pyrolysis and devolatilization PBE. The model assumes a chemically consistent form of the random scission pyrolysis mechanism and an average, parameterized form of the bubble loss mechanism. This model is used to predict the piloted ignition of HDPE. Predictions of the ignition times are reasonable but the model over predicts the ignition temperature. This discrepancy between model and data is attributed to surface oxidation reactions. The second application is the prediction of differential scanning calorimetry (DSC) data for HDPE. The model provides detailed information on the energy absorption of the thermally degrading sample, but the literature data is too variable to validate the model.Item Modeling of an experimental updraft countercurrent moving bed biomass gasifier(Texas Tech University, 1987-12) O'Hara, Michael LeeA steady-state model of a countercurrent, updraft, biomass gasifier was developed and verified against pilot-plant data. The gasifier was modeled in two parts: a combustion-fasification (CG) and a pyroiysis model. Development of the CG model demonstrated that the combustion reaction was mass transfer controlled, and the water-gas shift reaction was approximately at equilibrium. The CG model was studied for sensitivity to the particle diameter, air-to-steam ration, oxygen mass transfer coefficient, and the chemical reaction activation energies. THe pyroiysis model was based on the assumption that the pyroiysis process was heat transfer limited. The linearized results for a moving-boundary, phase-change model were used to develop the rate of the pyroiysis process.Item Reaction kinetics and thermophysical properties of feedlot waste during drying and pyrolysis.(Texas Tech University, 1974-08) Al-Haj-Ali, Najeh SalehNot availableItem Reactor internal gas composition profiles during gasification of cattle manure(Texas Tech University, 1982-05) Landeene, Brian CharlesNot availableItem Technical Feasibility Study on Biofuels Production from Pyrolysis of Nannochloropsis oculata and Algal Bio-oil Upgrading(2013-12-02) Maguyon, MonetIncreasing environmental concerns over greenhouse gas emissions, depleting petroleum reserves and rising oil prices has stimulated interest on biofuels production from biomass sources. This study explored on biofuels production from pyrolysis of Nannochloropsis oculata and subsequent bio-oil upgrading by fractional distillation and zeolite upgrading. The extent of producing biofuels from N. oculata was initially investigated at various pyrolysis temperatures (400, 500 and 600^(0)C) at 100 psig. The distribution of the products significantly varied with temperature. Maximum char and gas yields were achieved at 400^(0)C (52% wt) and 600^(0)C (15% wt), respectively. Liquid production (aqueous and bio-oil) peaked at 500^(0)C (35% wt). The effect of temperature was also tested against product compositions and properties. Mass and energy conversion efficiencies were also estimated to be about 76% and 68%, respectively. The operating condition for maximum bio-oil production from N. oculata pyrolysis was subsequently determined. Optimum yield was achieved at 5400C and 0 psig where liquid yield was about 43% wt (23% wt bio-oil, 20% wt aqueous) while char and gas yields were about 32 and 12% wt, respectively. The bio-oil obtained has high carbon (72% wt) and hydrogen (10% wt) contents and high energy content (36 MJ/kg). Char and gas also contain considerable energy contents of about 20 MJ/kg and 21MJ/m3, respectively. Separation of the bio-oil and aqueous liquid product (ALP) components by fractional distillation was then investigated. Heavy distillates has the highest yield (75% wt), followed by light distillates (19% wt). Significant reduction in moisture contents and increase in heating values were observed in the bio-oil distillates. The ALP distillate obtained at 150-1800C was found to contain considerable amounts of acids, esters, amides and lactams and has heating value of about 24 MJ/kg. Finally, HZSM-5 upgrading was done at various temperatures and reaction times. Reaction temperature greatly affected product yields and upgraded bio-oil composition. The best operating condition was found to be 285^(0)C for 3.5 h, which can produce treated bio-oil with higher hydrocarbons (86%), lower oxygenated (3%) and lower nitrogenous (11%) components. Higher heating value (40 MJ/kg), high carbon (80% wt), and low oxygen (3% wt) contents were also achieved.