Cotton gins have a readily available supply of biomass that is a by-product of cotton ginning. A 40 bph - cotton gin processing stripped cotton must manage 2,600 to 20,000 tonnes of cotton gin trash (CGT) annually. CGT contains approximately 16.3 MJ/kg (7000 Btu/lb.). CGT has the potential to serve as a renewable energy source. Gasification of biomasses such as CGT can offer processing facilities the opportunity to transform their waste biomass into electricity. The gasification of CGT yields 80% synthesis gas (syngas) and 20% biochar. The concentration of biochar in the syngas needs to be reduced prior to the direct fueling of an internal combustion engine driving a generator for electricity production. It was estimated that direct fueling of an internal combustion engine with syngas to drive the generator to produce electricity would cost $1M per megawatt (MW). In contrast, a 1MW system that consists of a boiler and steam turbine would cost $2M/MW. The current provisional patent for the TAMU fluidized bed gasification (FBG) unit uses a 1D2D and 1D3D cyclone for the removal of biochar. A cyclone test stand was designed and constructed to evaluate cyclone capture efficiencies of biochar. A statistical experiment design was used to evaluate cyclone performances for varying concentrations of biochar. A total of 24 tests for the 1D2D and 36 tests for the 1D3D cyclone were conducted at ambient conditions. Average collection efficiency for the 1D2D cyclone was 96.6% and 96.9% for the 1D3D cyclone. An analysis on the cyclone’s pressure drop was performed to compare the change in pressure drop from air only passing through the cyclone and when the cyclones are loaded with biochar. The average change in pressure drop for the 1D2D cyclone was a decrease of 74%, and the average change in pressure drop for the 1D3D cyclone was a decrease of 36%. An economic feasibility study was conducted to determine the price per kWh to produce electricity for a CGT fueled internal combustion engine power plant (ICPP) and a boiler and steam turbine power plant (SPP). The simulated cotton gin is a 40 bph rated facility operating for 2,000 hours a season (200% utilization) processing stripped cotton that yields approximately 180 kg/bale (400 lbs/bale) of CGT. Revenues consist of the electricity and natural gas expenses incurred during the ginning season, along with the extra electricity produced and sold back to the utility company at the whole price. Loan payments and operating costs include labor, maintenance, taxes, and insurance. Labor costs, the selling price of electricity and biochar are varied in the economic model. The ICPP has a NPV of $1,480,000, and the SPP has a NPV of -$160,000, under the base assumptions. The sensitivity analysis resulted in the selling price of electricity as having the largest change on the NPV for both of the power plants. The average predicted purchase price of electricity is $0.10/kWh for the twenty year simulation. The average price to produce electricity, with no source of revenue generation for the ICPP is $0.20/kWh and $0.26/kWh for the SPP.

Biomass, as a renewable energy resource, can be utilized to generate chemicals, heat, and electricity. Compared with biomass combustion, biomass gasification is more eco-friendly because it generates less amount of green gas (CO2) and other polluting gases (NOx and SO2). This research is focused on biomass gasification using a circulating fluidized bed. In the gasifier, fully fluidized biomass particles react with water vapor and air to generate syngas (CO and H2). A comprehensive model, consisting of three modules, hydrodynamics, mass transfer and energy transfer modules, is built to simulate this process using ANSYS Fluent software and C programming language. In the hydrodynamics module, the k-epsilon turbulence equations are coupled with the fluctuating energy equation to simulate gas-particle interaction in the turbulent flows occurring in the riser. In the mass transfer and energy transfer modules, heat transfer and mass transfer in turbulent flows are simulated to solve for the profiles of temperature and species concentration in the gasifier. The impacts of thermal radiation, water gas shift reaction (WGS), equivalence ratio (ER), and char combustion product distribution coefficient are also investigated to gain deeper understanding of biomass gasification process.

Production of hydrogen is primarily achieved via catalytic steam reforming, partial oxidation,and auto-thermal reforming of natural gas. Although these processes are mature technologies, they are somewhat complex and CO is formed as a by-product, therefore requiring a separation process if a pure or hydrogen-rich stream is needed. As an alternative method, supported metal catalysts can be used to catalytically decompose hydrocarbons to produce hydrogen. The process is known as catalytic cracking of hydrocarbons. Methane, the hydrocarbon containing the highest percentage of hydrogen, can be used in such a process to produce a hydrogen-rich stream. The decomposition of methane occurs on the surface of the active metal to produce hydrogen and filamentous carbon. As a result, only hydrogen is produced as a gaseous product, which eliminates the need of further separation processes to separate CO2 or CO. Nickel is commonly used in research as a catalyst for methane cracking in the 500-700C temperature range. To conduct methane catalytic cracking in a continuous manner, regeneration of the deactivated catalyst is required and circulation of the catalysts between cracking and regeneration cycles must be achieved. Different reactor designs have been successfully used in cyclic operation, such as a set of parallel fixed-bed reactors alternating between cracking and regeneration, but catalyst agglomeration due to carbon deposition may lead to blockage of the reactor and elevated pressure drop through the fixed bed. Also poor heat transfer in the fixed bed may lead to elevated temperature during the regeneration step when carbon is burned in air, which may cause catalyst sintering. A fluidized bed reactor appears as a viable option for methane catalytic cracking, since it would permit cyclic operation by moving the catalyst between a cracker and a regenerator. In addition, there is the possibility of using fine catalyst particles, which improves catalyst effectiveness. The aims of this project were 1) to develop and characterize a suitable nickel-based catalyst and 2) to develop a model for thermal catalytic decomposition of methane in a fluidized bed.

This study is aimed to compare the fluidized bed and microwave drying with microwave assisted fluidized bed drying. For this purpose, macaroni beads (2.4&plusmn / 0.08 mm diameter) were dried from about 20% to 12% moisture content in a fluidized bed of 7.6 cm diameter, in a domestic microwave oven with a power of 609 W and in the fluidized bed placed in the microwave oven conditions. In the experiments with the fluidized bed three air temperatures / 50, 60 and 70&deg / C at an air velocity of 2.3 m/s and in those with the microwave oven two power levels / 50% and 100% were used. The drying curves indicated that the drying rate increased with the air temperature and microwave power in each drying method. Microwave assisted fluidized bed drying reduced the drying time by about 50% and 11% on the average compared with the fluidized bed and microwave drying, respectively. Therefore, it was concluded that the drying time was reduced more by the effect of microwave energy than the fluidization. The effective diffusivities in the fluidized bed and microwave assisted fluidized bed drying were found to be in the order of 4.125x10-11 and 8.772x10-11 m2/s on the average, respectively. The effective diffusivities for the fluidized bed drying were fitted to an Arrhenius type of equation and the magnitude of the activation energy was found to be in the order of 12595 kJ/kg mol.

No description available.

abstract: This dissertation presents a systematic study of the sorption mechanisms of hydrophobic silica aerogel (Cabot Nanogel®) granules for oil and volatile organic compounds (VOCs) in different phases. The performance of Nanogel for removing oil from laboratory synthetic oil-in-water emulsions and real oily wastewater, and VOCs from their aqueous solution, in both packed bed (PB) and inverse fluidized bed (IFB) modes was also investigated. The sorption mechanisms of VOCs in the vapor, pure liquid, and aqueous solution phases, free oil, emulsified oil, and oil from real wastewater on Nanogel were systematically studied via batch kinetics and equilibrium experiments. The VOC results show that the adsorption of vapor is very slow due to the extremely low thermal conductivity of Nanogel. The faster adsorption rates in the liquid and solution phases are controlled by the mass transport, either by capillary flow or by vapor diffusion/adsorption. The oil results show that Nanogel has a very high capacity for adsorption of pure oils. However, the rate for adsorption of oil from an oil-water emulsion on the Nanogel is 5-10 times slower than that for adsorption of pure oils or organics from their aqueous solutions. For an oil-water emulsion, the oil adsorption capacity decreases with an increasing proportion of the surfactant added. An even lower sorption capacity and a slower sorption rate were observed for a real oily wastewater sample due to the high stability and very small droplet size of the wastewater. The performance of Nanogel granules for removing emulsified oil, oil from real oily wastewater, and toluene at low concentrations in both PB and IFB modes was systematically investigated. The hydrodynamics characteristics of the Nanogel granules in an IFB were studied by measuring the pressure drop and bed expansion with superficial water velocity. The density of the Nanogel granules was calculated from the plateau pressure drop of the IFB. The oil/toluene removal efficiency and the capacity of the Nanogel granules in the PB or IFB were also measured experimentally and predicted by two models based on equilibrium and kinetic batch measurements of the Nanogel granules. / Dissertation/Thesis / Ph.D. Chemical Engineering 2011

This study investigates sources of steady state computational uncertainty in an effective heat transfer coefficient (HTC) within a non-reacting bubbling fluidized bed with immersed horizontal heat-conducting tubes. The methodical evaluation of this variation, or Uncertainty Quantification (UQ), is a critical step in the experimental analysis process, and is particularly important when the values of input physical parameters are unknown or experimental data is sparse. While the concept applies broadly to all studies, this application investigates a 2D unit cell analogue of a bubbling fluidized bed designed for large-scale carbon capture applications. Without adequate characterization of simulation uncertainties in the HTC, bed operating characteristics, including the thermal efficiency, carbon capture efficiency, and sorbent half-life cannot be well understood. We focus on three primary parameters, solid-solid coefficient of restitution, solid-wall coefficient of restitution, and turbulence model, and consider how their influences vary at different bed solid fractions. This is accomplished via sensitivity analysis and the Bayesian Spline Smoothing (BSS) Analysis of Variance (ANOVA) framework. Results indicate that uncertainties approach 20% at high gas fractions, with the turbulence model accounting for 80% of this variation and the solid-solid coefficient of restitution accounting for the additional 20%.

Climate change is becoming more severe than ever in human history and the emission of green house gas urgently needs to be reduced while global energy consumption remains booming. Large-scale application of clean fossil fuel combustion shall be considered as a priority for its economical advantages as well as reliability in meeting global energy needs. Oxygen-fired pressurized fluidized bed combustor technology with downstream carbon capture and sequestration is considered a key approach to clean coal combustion. In such technology, the fluidized bed combustor operates at elevated pressures and houses an in-bed heat exchanger tube bundle. It is essential to understand the rate of heat transfer between the immersed heat exchange surface and the fluidized bed as it is a key parameter in heat exchanger design. The goal of this work was to investigate the impact of pressure and presence of fine particles (i.e., surrogate for pulverized fuel) on the overall tube-to-bed heat transfer coefficient. Experiments were conducted in a pilot-scale fluidized bed with an inner diameter of 0.15 m under cold flow conditions. A tube bundle consisting of five horizontal staggered rows was completely submerged in the bed. One of the tubes was replaced by a heating cartridge housed in a hollowed copper rod. Five thermocouples distributed at 45º intervals along the copper rod circumference measured the surface temperature and ensured that local effects were included. The bed material was large glass beads of 1.0 mm in diameter while the fines were glass beads of 60 µm in diameter and thus susceptible to entrainment. The fine particles were continuously fed to the fluidized bed and then captured downstream by a filter system. Fluidization was conducted at 101, 600 and 1200 kPa with excess gas velocities (Ug - Umf) of 0.21, 0.29 and 0.51 m/s. Fine particle feed rates were 0, 9.5 and 14.4 kg/h. Two heating rod positions (2nd row and 4th row) were studies. Overall, the heat transfer coefficient approximately doubled when pressure was increased from 101 to 1200 kPa. At atmospheric conditions, where the slug flow regime occurred, the maximum heat transfer coefficient was at the bottom of the rod, while it moved to the side of the rod at high pressures where the bubbling regime occurred. As the heating rod moving from 2nd row to the 4th row, the averaged heat transfer coefficient increased by respectively 18%, 9% and 6% at 101, 600 and 1200 kPa. The addition of fine particles decreased the average heat transfer coefficient by 10 to 20 W/m2 K where the time – averaged heat transfer coefficient was approximately 220 and 450 W/m2K at 101 kPa and 1200 kPa respectively. There was no effect on the angular profile across the tube surface. The results showed that average heat transfer coefficients matched the correlation developed by Molerus et al. (1995) within a 5% difference across all conditions when fines were not present.

Submitted by Jordan Amaro Gutierrez (lococl7@hotmail.com) on 2018-04-18T13:40:29Z No. of bitstreams: 1 Dissertação de mestrado_Jordan Amaro Gutierrez.pdf: 2106887 bytes, checksum: b7af38c2d830fedcbcf983350968a855 (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-04-18T14:14:12Z (GMT) No. of bitstreams: 1 amarogutierrez_j_me_guara.pdf: 2106887 bytes, checksum: b7af38c2d830fedcbcf983350968a855 (MD5) / Made available in DSpace on 2018-04-18T14:14:12Z (GMT). No. of bitstreams: 1 amarogutierrez_j_me_guara.pdf: 2106887 bytes, checksum: b7af38c2d830fedcbcf983350968a855 (MD5) Previous issue date: 2018-02-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho tem como objetivo desenvolver um modelo de equilíbrio químico modificado para determinar a composição do syngas (gás de síntese), obtida a partir da gaseificação da biomassa em gaseificadores de leito fluidizado. Para este estudo, foi aplicado um processo de otimização para determinar os fatores de correção (que modificam as constantes de equilíbrio químico), a eficiência de conversão de carbono e a entalpia da reação. Os agentes de gaseificação considerados foram ar, vapor, ar-vapor e ar-vapor-oxigênio. No método de otimização foram utilizados os multiplicadores de Kuhn–Tucker para obter pequenos erros RMS. Foram selecionadas 76 composições experimentais de syngas. Entre estas composições, 60 foram utilizadas para obter correlações para o fator de correção, a eficiência de conversão do carbono e a entalpia da reação. Em seguida, um modelo de equilíbrio químico modificado foi elaborado selecionando estas correlações. O modelo de equilíbrio químico modificado foi validado mostrando uma boa precisão para a determinação da composição do syngas, obtendo-se erros RMS entre 0,94 e 4,84. / This work aims to develop a modified chemical equilibrium model to accurately determine the syngas (synthesis gas) composition, as obtained from fluidized bed gasifiers. In order to do so, an optimization process was applied to determine the correction factors (which modify the chemical equilibrium constants), the carbon conversion efficiency and the enthalpy of the reaction. The gasification agents considered were air, steam, air–steam, and air–steam–oxygen. The optimization method were used the Kuhn–Tucker multipliers in order to obtain small RMS errors. A total of 76 experimental compositions of syngas were selected. Among these data, 60 were used to obtain correlations for the correction factor, the carbon conversion efficiency and the enthalpy of the reaction. Then, a modified chemical equilibrium model was developed by selecting these correlations. The modified chemical equilibrium model was validated showing very good accuracy for the determination of the syngas composition, the RMS error were found to be in the between 0.94 and 4.84.

Orientador: Roberto Testezlaf / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-17T14:05:19Z (GMT). No. of bitstreams: 1 SalcedoRamirez_JuanCamilo_M.pdf: 5267423 bytes, checksum: 8280ac47eb6e5c177b8a4533cedd1d53 (MD5) Previous issue date: 2010 / Resumo: O desempenho adequado de filtros de areia na irrigação localizada requer que os processos de filtração e retrolavagem sejam realizados de forma a reter as partículas em suspensão indesejadas e que a lavagem do meio filtrante retorne a operação do equipamento às suas condições originais de limpeza. A retrolavagem pode ser mais eficiente quando se atinge expansões homogêneas da camada com baixas perdas de pressão em função das características granulométricas da areia e da altura da camada filtrante. As faltas de experiência do produtor e de informações técnicas dos fabricantes determinam que a retrolavagem não seja realizada corretamente em campo, prejudicando a funcionalidade e eficiência dos filtros de areia. Neste contexto, o objetivo do presente trabalho foi desenvolver estudos sobre o comportamento das características hidrodinâmicas de pressão e vazão no processo da retrolavagem em filtros com variações nas características físicas da areia e nos componentes internos dos filtros. O trabalho foi dividido em três partes. Inicialmente, foi realizada, uma pesquisa de campo sobre os procedimentos e manejos utilizados pelos agricultores na execução da retrolavagem. Em uma segunda etapa, foi utilizada uma metodologia experimental para ensaios de laboratório em três filtros de areia convencionalmente usados no mercado brasileiro, para avaliar os efeitos de diferentes granulometrias da areia e diferentes alturas da camada filtrante sobre a perda de carga ao longo da camada e sobre o processo de fluidização do leito. Finalmente, na ultima parte, os resultados obtidos foram comparados com comportamento teóricos para estimativa da velocidade mínima de fluidização. Os procedimentos realizados pelos produtores demonstraram falta de conhecimento no processo da retrolavagem que é executado de forma empírica baseado em recomendações incorretas dos fornecedores. Experimentalmente, obteve-se que o processo de retrolavagem é afetado significativamente pela perda de pressão causada pelos componentes estruturais internos do filtro (crepina e difusor). As comparações dos resultados calculados a partir da equação de WEN & YU (1966) com os resultados experimentais, revelaram concordâncias explicitas para as granulometrias menores. A pesquisa permitiu concluir que a vazão da retrolavagem necessária para a expansão adequada do leito, aumenta proporcionalmente com as condições da altura da camada e da granulometria da areia / Abstract: The adequate sand filters performance in localized irrigation requires that filtration and backwash processes are capable to retain unwanted suspension particles and to wash properly the media depth, returning the equipment operation to its original condition of cleanliness. The backwash process can be more effective when it reaches bed uniform expansions with low head losses, which depends on the grain size and the depth of media bed. The lack of experience of farmers and technical information from the manufacturers determine that the backwash process has been performed incorrectly in the field, affecting adversely the functionality and efficiency of the sand filters. In this context, the objective of this study was to develop studies on the hydrodynamic behavior of the relationship of working pressure and flow rate in the backwash process of sand filters with variations in sand physical characteristics and the internal hydraulic components of the filters. This study was divided into three parts. Initially, a field survey on the farmers backwash procedures and management was performed. In a second step, an experimental methodology was developed to evaluate three commercial types of Brazilian sand filters to assess the effects of different grains diameters and media layer depths on the head losses and the process of layer fluidization. Finally, the experimental results of the minimum fluidization velocity were compared with estimated values using the theoretical behavior of the process. The results showed that the procedures performed by the producers showed a lack of knowledge in the backwash process, which is executed based on empirical basis, oriented by imprecise information of suppliers. The experimental part demonstrated that the backwash process is affected significantly by the head loss originated from the internal structural components of the filter (underdrain and diffuser). The mathematical comparisons of the experimental results with the values estimated by the equation & WEN YU (1966) showed explicit agreements for smaller particle size. The research allowed concluding that the values backwash flow rate required for an adequate expansion, increases proportionally with the depth and the particle size of sand layer / Mestrado / Agua e Solo / Mestre em Engenharia Agrícola