Accepted Manuscripts

Guest Editorial  
Ashwani K. Gupta and Ronald Breault
J. Energy Resour. Technol   doi: 10.1115/1.4039654
The special issue contains selected papers presented at the 42nd International Clearwater Clean Energy Conference. The conference was held at the Sheraton Sand Keys Hotel, Clearwater, FL during June 11-15, 2017. The endorsing organizations for this conference included: American Institute of Chemical Engineers, American Public Power Association, CANMET Natural Resources, Canada, China Coal Research Institute, Ministry of Coal, People's Republic of China, Edison Electric Institute, Export Assistance Center, U.S. Commercial Service, International Energy Agency: Coal Research, Japan Coal Energy Center (JCOAL), National Mining Association, National Rural Electric Cooperative Association, Ohio Coal Development Office, U. S. Geological Survey
TOPICS: Sands, Mining, Engineers, Clean coal technology, Fuel systems, Coal, Natural resources, China, Renewable energy
Gang Wang, Qiqi Liu, Lulu Sun, Xiang Song, Wenzhou DU, Daocheng Yan and Yue Wang
J. Energy Resour. Technol   doi: 10.1115/1.4039659
In this report, the influence of pre-oxidation degree and ventilation flow on the parameters of spontaneous combustion of coal (temperature, gas concentration, exothermic intensity) was studied in six sets of programmed temperature experiments. The experimental results showed that the pre-oxidation exerted a positive effect on the spontaneous combustion parameters of coal in the early stage of coal-oxygen recombination reaction, but exerted an inhibitory effect in the later stage of coal-oxygen oxidation reaction. Air supply rate had a positive correlation with the initial oxidation of coal samples and 90 °C preoxidation spontaneous combustion parameters. Air supply rate had negative correlation with 140 °C preoxidation of coal samples. Meanwhile secondary oxidation significantly reduced the characteristic temperature of coal. The critical temperature of each coal sample was 83.7 °C (coal sample 1-Y), 68.3 °C (coal sample 1-L), 69.6 °C (coal sample 1-G), 82.1 °C (Coal sample 2-Y), 70.4 °C (coal sample 2-L), 70.0 °C (coal sample 2-G) and dry cracking temperature was 142.6 °C (coal sample 1-Y), 134.8 °C (coal sample 1-L), 136.2 °C (coal sample 1-G), 147.2 °C (coal sample 2-Y), 136.5 °C( coal sample 2-L), and 134.4 °C (coal sample 2-G). The curves of the characteristic parameters of primary and secondary oxidized coal showed exponential growth. And the oxidation process can be divided into three stages.
TOPICS: Temperature, Combustion, Coal, oxidation, Oxygen, Fracture (Process), Ventilation, Cracking (Materials), Flow (Dynamics)
Gabriele Cassetti, Maria Cristina Bellina and Emanuela Colombo
J. Energy Resour. Technol   doi: 10.1115/1.4039617
The core of the work is the investigation of the possible correlation between the thermodynamics and the hazards of a process. The objective is understanding the role of inefficiency in hazards consequences. To investigate such correlation a case study from oil and gas sector is developed, where exergy analysis is used to study the thermodynamics of the process and a simplified quantitative risk analysis (QRA) is performed to evaluate the consequences of identified hazards. The thermoeconomic approach is then used to correlate the two analyses. Through the analysis Authors want to identify those components where hazardous consequences may be affected by inefficiency, aiming to reduce the risk of fatalities in processes by operating on the process itself or suggesting possible alternative strategies. The purpose of the paper is also to propose for further investigation on the correlation between inefficiency and process hazards.
TOPICS: Exergy analysis, Hazards, Accounting, Thermodynamics, Risk analysis, Thermoeconomics, Risk
Juan Berrio, Nicolas Ratkovich and Eduardo Pereyra
J. Energy Resour. Technol   doi: 10.1115/1.4039609
The GLCC is a widely used alternative for gas-liquid conventional separation. Beside its maturity, the effect of some geometrical parameters over its performance are not fully understood. The main objective of this study is to use CFD modelling in order to evaluate the effect of geometrical modifications in the reduction of LCO and GCU. Simulations for two-phase flow were carried out under zero net liquid flow and the average liquid holdup was compared with Kanshio (2015) obtaining RMS errors around 13% between CFD and experimental data. An experimental setup, in which LCO data was acquired, was built in order to validate a CFD model that includes both phases entering to the GLCC. An average discrepancy below 6% was obtained by comparing simulations with experimental data. Once the model was validated, five geometrical variables were tested with CFD. The considered variables correspond to the inlet configuration (location and inclination angle), the effect of dual inlet and nozzle geometry (diameter and area reduction). Based on the results, the best configuration correspond to an angle of 27°, inlet location 10cm above the center, a dual inlet with 20cm of spacing between both legs, a nozzle of 3.5cm of diameter and a volute inlet of 15% of pipe area. The combination of these options in the same geometry reduced LCO in 98% with respect to the original case of the experimental setup. Finally, the swirling decaying was studied with CFD showing that liquid has a greater impact than the gas flowrate.
TOPICS: Computational fluid dynamics, Modeling, Nozzles, Engineering simulation, Geometry, Simulation, Swirling flow, Flow (Dynamics), Separation (Technology), Pipes, Two-phase flow, Errors
Tiankui Guo, Facheng Gong, Zhanqing Qu, Xuxin Tian and Binyan Liu
J. Energy Resour. Technol   doi: 10.1115/1.4039618
In order to generate a new fracture far away from the original fracture in refracturing and effectively enhance productivity, the technology of hydraulic refracturing guided by directional boreholes was presented. The effects of induced stress generated by the original hydraulic fracture, fracturing fluid percolation effect, wellbore internal pressure and in-situ stress on stress field distribution around wellbore were considered, a fracture initiation model of hydraulic refracturing guided by two directional boreholes was obtained. The variation of maximum principal stress (smax) under different conditions was investigated. The results show that, the directional boreholes result in a "sudden change region" of maximum principal stress around wellbore. Due to "sudden change region", the refracturing fracture tends to initiate around directional boreholes. Whether the new fracture initiates and propagates along directional boreholes depends on comprehensive effect of borehole azimuth, borehole diameter, borehole spacing, horizontal stress difference, height and net pressure of original fracture. The specific initiation position can be calculated using the theoretical model proposed in this paper. Sensitivity analysis with "Extended Fourier Amplitude Sensitivity Test" method shows that the initiation of new fracture is mostly influenced by parameters of directional boreholes and has little relation with in-situ stress and parameters of original fracture in hydraulic refracturing guided by directional boreholes. The study provides theoretical support for the technology of hydraulic refracturing guided by directional boreholes, which is helpful for the design of fracturing construction programs.
TOPICS: Fracture (Process), Stress, Pressure, Fluids, Construction, Percolation theory, Design, Sensitivity analysis
Tie Liu and Zhimin Yang
J. Energy Resour. Technol   doi: 10.1115/1.4039629
To evaluate the possibility of using the thermoelectric generator to enhance the performance of thermophotovoltaic converter, a model of a combined system in which the thermoelectric generator is attached on the backside of the thermophotovoltaic converter to harvest the heat produced in the thermophotovoltaic converter is established. The effect of the voltage output of the thermophotovoltaic cell, bang gap energy of the thermophotovoltaic cell, dimensionless current of the thermoelectric generator, and emitter temperature on the performance of the combined system is examined numerically. It is found that the performance of the thermophotovoltaic converter can be enhanced by using the thermoelectric generator. The improvement of the power output density is larger than that of the efficiency. There are optimally working regions of the cell voltage, dimensionless current, and band gap energy. The elevated emitter temperature results in an increase in the power output density but there is an optimal emitter temperature that yields the maximum efficiency of the combined system. Moreover, the thermoelectric generator is not suitable to harvest heat produced in the thermophotovoltaic converter when the emitter temperature is sufficiently high.
TOPICS: Optimization, Generators, Temperature, Density, Heat, Energy gap
Sreenivasa Rao Gubba, Ravichandra Jupudi, Shyam Sundar Pasunurthi, Sameera Wijeyakulasuriya, Roy Primus, Adam Klingbeil and Charles E.A. Finney
J. Energy Resour. Technol   doi: 10.1115/1.4039630
In an earlier publication [1] the authors compared numerical predictions of the mean cylinder pressure of diesel and dual-fuel combustion, to that of measured pressure data from a medium-speed, large-bore engine. In these earlier comparisons, measured data from a flush-mounted in-cylinder pressure transducer showed notable and repeatable pressure oscillations which were not evident in the mean cylinder pressure predictions from CFD. In this paper, the authors present a methodology for predicting and reporting the local cylinder pressure consistent with that of a measurement location. Such predictions for large-bore, medium-speed engine operation demonstrate pressure oscillations in accordance with those measured. The temporal occurrences of notable pressure oscillations were during the start of combustion and around the time of maximum cylinder pressure. With appropriate resolutions in time steps and mesh sizes, the local cell static pressure predicted for the transducer location showed oscillations in both diesel and dual-fuel combustion modes which agreed with those observed in the experimental data. Fast Fourier Transform (FFT) analysis on both experimental and calculated pressure traces revealed that the CFD predictions successfully captured both the amplitude and frequency range of the oscillations. Resolving propagating pressure waves with the smaller time steps and grid sizes necessary to achieve these results required a significant increase in computer resources.
TOPICS: Oscillations, Pressure, Computer simulation, Internal combustion engines, Cylinders, Combustion, Fuels, Diesel, Computational fluid dynamics, Transducers, Computers, Fast Fourier transforms, Large-bore engines, Engines, Pressure transducers, Waves
Technical Brief  
Xiaoyan Gao, Yaning Zhang, Bingxi Li, Gongnan Xie and Wenke Zhao
J. Energy Resour. Technol   doi: 10.1115/1.4039603
Biomass is a promissing alternative energy source for fossil fuel with the advantages of abundance, renewability, environmental friendliness, etc. This makes the development of biomass technology be of great potential and interesting. The experiments of biomass fast pyrolysis were performed in a micro quartz reactor for rice husk, corn stalk and birch wood, and scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and Raman microscope were then applied to analyze the collected chars. The average char yields of rice husk, corn stalk and birch wood pyrolyzed at 800 oC were 29.64%, 18.67% and 8.64%, respectively. The morphological structures of rice husk and corn stalk were mainly reserved in chars, while the raw surface textures of birch wood disappeared during the fast pyrolysis. The silicon concentrations in rice husk char and corn stalk char were much higher than birch wood char, and the graphitization degree of corn stalk char was the lowest among the three biomass chars.
TOPICS: Fuels, Biomass, Pyrolysis, Wood products, Fossil fuels, Quartz, Renewable energy, Silicon, Surface texture, Microscopes, Scanning electron microscopes
Oghare V Ogidiama and Tariq Shamim
J. Energy Resour. Technol   doi: 10.1115/1.4039606
The selective catalytic reduction (SCR) is a promising NOx (a mixture of NO and NO2) reduction technology for various applications. The SCR process entails the conversion of NOx by the use of a reducing agent such as ammonia and a suitable catalyst. Due to increasingly stricter NOx emission regulations, the SCR technology for NOx control needs continuous improvement. The improvement requires better understanding of complex processes occurring in the SCR system. The current study employs a mathematical model to elucidate the effect of key operating and geometric parameters on the performance of SCR systems. The model considers both standard and fast SCR reaction processes. The model was used to investigate the effects of NH3/NOx and NO2/NOx ratios in the exhaust on the SCR performance and the effect of using a dual layer SCR system. Furthermore, the effect of different operating parameters and the interdependence of parameters are analyzed by using a factorial approach. The results show that the SCR performance is very sensitive to NH3/NOx ratio. The SCR performance is also affected by the NO2/NOx ratio particularly at low temperatures. The optimal NOx conversion performance requires a combination of NH3/NOx ratio of 1.0, NO2/NOx ratio of 0.5, low space velocities and high inlet temperature. The results depict that adding a second catalyzed layer results in increased reaction activity especially when the concentration is still high after the first layer.
TOPICS: Selective catalytic reduction, Nitrogen oxides, Temperature, Air pollution control, Low temperature, Catalysts, Exhaust systems
Yuan Ran, Yadong Deng, Tao Hu, Chuqi Su and Xun Liu
J. Energy Resour. Technol   doi: 10.1115/1.4039607
Thermoelectric technology applied in vehicle has become significantly essential due to the global energy crisis and the environmental protection issues. A novelty energy efficient technology called localized air-conditioning (LAC) powered by thermoelectric generator (TEG), i.e. TEG-powered LAC, is proposed in order to better utilize the generated power of TEG, only then will the fuel economy improvement be achieved. This system which has little impact on the original automotive electrical system is basically comprised of LAC, TEG, converter and battery. The TEG can directly convert thermal energy to electrical energy to power the novelty energy-efficient air conditioning system called LAC. The sub-models of LAC and TEG are built and integrated into a heavy-duty vehicle to quantitatively assess its performance by simulation analysis. The results indicate that the novelty TEG-powered LAC system can work normally with high efficiency and improve the fuel economy by 3.7%. Therefore, this system resolves the problem of proper use of the TEG's power and provides a fully new perspective to substitute the mechanical loads to engine with electrical loads powered by TEG to improve the fuel economy with much more practicality and rationality.
TOPICS: Air conditioning, Construction equipment, Generators, Corporate average fuel economy, Fuel efficiency, Stress, Vehicles, Simulation analysis, Thermal energy, Engines, Automotive electrical systems, Batteries
Pallavi Rastogi and Shripad P. Mahulikar
J. Energy Resour. Technol   doi: 10.1115/1.4039608
In this theoretical study, a fully-developed laminar convective water flow in a circular tube is "convectively overloaded" towards the micro-scale, by decreasing the tube diameter below 1 mm. The entropy generation rate is obtained (with and without the viscous dissipation term) for a given rate of heat removal using a fixed rate of coolant (water) flow. The uniform wall heat flux and mass flux in a tube increase towards the micro-scale, which is "thermal and flow overloading", respectively. The variations of - entropy generation rate due to fluid friction, fluid conduction heat transfer, and their sum-total, towards the micro-scale, are analyzed. Since, total entropy generation rate remains more or less the same towards the microscale, it is worth overloading a tube for miniaturization up to the laminar-flow limit.
TOPICS: Entropy, Microscale devices, Flow (Dynamics), Water, Heat flux, Coolants, Energy dissipation, Heat, Heat transfer, Fluids, Viscosity, Laminar flow, Heat conduction
Gerrit A. Schatte, Andreas Kohlhepp, Tobias Gschnaidtner, Christoph Wieland and Hartmut Spliethoff
J. Energy Resour. Technol   doi: 10.1115/1.4039610
Heat transfer to supercritical water in heated tubes and channels is relevant for steam generators in conventional power plants and future concepts for supercritical nuclear and solar-thermal power plants. Especially in the development of designs for future supercritical nuclear reactors and solar-thermal power plants requires an expanded understanding of supercritical heat transfer. A new experimental facility, the High Pressure Evaporation Rig HIPER, set up at the Institute for Energy Systems (Technische Universität München) aims to provide heat transfer data to fill the existing knowledge gaps at these conditions. The test rig consists of a closed loop high pressure cycle, in which de-ionized water is fed to an instrumented test section heated by the application of direct current. It is designed to withstand a maximum pressure of 380bar at 580°C in the test section. The maximum power rating of the system is 1MW. The test section is a vertical tube (material: AISI A213/P91) with a 7,000mm heated length, a 15.7mm internal diameter and a wall thickness of 5.6mm. It is equipped with 70 thermocouples distributed evenly along its length. It enables the determination of heat transfer coefficients in the supercritical region at various steady- state or transient conditions. In a first series of tests, experiments are conducted to investigate normal and deteriorated heat transfer under vertical upward flow conditions. The newly generated data and literature data are used to evaluate different correlations available for modeling heat transfer coefficients at supercritical pressures.
TOPICS: Heat transfer, Energy engineering, Water, Heat transfer coefficients, Solar thermal power, High pressure (Physics), Transients (Dynamics), Boilers, Energy / power systems, Evaporation, Modeling, Power stations, Cycles, Nuclear reactors, Thermocouples, Wall thickness, Pressure, Flow (Dynamics)
Joshua M. Hamel, Devin Allphin and Joshua Elroy
J. Energy Resour. Technol   doi: 10.1115/1.4039611
A system level computational model of a recently patented and prototyped novel steam engine technology was developed from first principles for the express purpose of performing design optimization studies for the engine's inventors. The developed system model consists of numerous sub-models including a flow model the intake process, a dynamic model of the intake valve response, a pressure model of the engine cylinder, a kinematic model of the engine piston, and an output model that determines engine performance parameters. A crank angle discretization strategy was employed to capture the performance of engine throughout a full cycle of operation, thus requiring all engine design sub-models to be evaluated at each crank angle of interest. To produce a system model with sufficient computational speed to be useful within optimization algorithms, which must exercise the system level model repeatedly, various simplifying assumptions and modeling approximations were utilized. The model was tested by performing a series of multi-objective design optimization case studies using the geometry and operating conditions of the prototype engine as a baseline. The results produced were determined to properly capture the fundamental behavior of the engine as observed in the operation of the prototype and demonstrated that the design of engine technology could be improved over the baseline using the developed computational model. Furthermore, the results of this study demonstrate the applicability of using a multi-objective optimization driven approach to conduct conceptual design efforts for various engine system technologies.
TOPICS: Pareto optimization, Model development, Steam engines, Engines, Engineering prototypes, Design, Optimization, Engine design, Geometry, Kinematics, Pressure, Flow (Dynamics), Pistons, Dynamic models, Conceptual design, Valves, Approximation, Cycles, Engine cylinders, Modeling, Optimization algorithms
Ge Hu, Shiyong Liao, Zhaohong Zuo, Kun Wang and Zhengbing Zhu
J. Energy Resour. Technol   doi: 10.1115/1.4039612
A numerical investigation was conducted to explore the kinetic effects of methanol addition on the formation and consumption of formaldehyde and benzene in premixed stoichiometric n-heptane/air flames at atmospheric pressure. The flame modeling was performed by solving the premixed flame model with a comprehensive kinetic scheme of hydrocarbon fuels. We studied the species distributions, formation temperatures, temperature sensitivities, reaction contributions, and the rates of production and consumption for formaldehyde and benzene. Results showed that formaldehyde and benzene were produced in two temperature zones and the accumulation effect in the low-temperature zone was the most important factor for the peak concentrations of them in flames. When methanol was added into n-heptane/air flames, cross-reactions were hardly found in the formation routes of formaldehyde and benzene. Both the increased peak concentration and the decreased formation temperature of formaldehyde were primarily attributed to the fact that CH3O (+M) <=>CH2O+H (+M) and CH2OH+O2<=>CH2O+HO2 were promoted in low-temperature zone. Methanol addition decreased the rates of production and consumption of benzene proportionally, and served as a diluent fuel in benzene formation and consumption. CH3, CH3O, CH2OH, C3H3, and A-C3H5 were the most important precursors for the formation of formaldehyde and benzene. The conversion rates of these species into formaldehyde and benzene were explored as well. Results showed that methanol addition suppressed the conversion of C3 species into benzene, but it hardly showed obvious effect on the conversion of CH3, CH3O, and CH2OH into formaldehyde
TOPICS: Flames, Benzene, Heptane, Methanol, Temperature, Fuels, Low temperature, Modeling, Atmospheric pressure, Diluents
Salaheldin Elkatatny
J. Energy Resour. Technol   doi: 10.1115/1.4039613
Static Poisson's ratio (?static) is a key factor in determine in-situ stresses in the reservoir section. ?static is used to calculate the minimum horizontal stress, which will affect the design of the optimum mud widow while drilling. In addition, it also affects the design of the casing setting depth. ?static is very important for field development and the incorrect estimation of it may lead to heavy investment decisions. ?static can be measured in the lab using a real reservoir cores. laboratory measurements of ?static will take long time and also will increase the overall cost. The goal of this study is to develop accurate models for predicting ?static for carbonate reservoirs based on log data using artificial intelligence (AI) techniques. More than 610 core and log data points from carbonate reservoirs were used to train and validate AI models. The more accurate AI model will be used to generate a new correlation for calculating ?static. The developed artificial neural network (ANN) model yielded more accurate results for estimating ?static based on log data; sonic times and bulk density compared to adaptive neuro fuzzy inference system (ANFIS) and support vector machine (SVM). The developed empirical equation for ?static gave a coefficient of determination (R2) of 0.97 and an average absolute percentage error (AAPE) of 1.13 %. The developed technique will help geomechanical engineers to estimate a complete trend of ?static without the need for coring and laboratory work and hence will reduce the overall cost of the well.
TOPICS: Artificial intelligence, Reservoirs, Design, Artificial neural networks, Stress, Support vector machines, Trains, Poisson ratio, Errors, Drilling, Density, Engineers
Ling Bai, Weidong Shi, Ling Zhou, Lingjie Zhang, Wei Li and Dr. Ramesh Agarwal
J. Energy Resour. Technol   doi: 10.1115/1.4039614
In industrial processes such as Chemical Looping Combustion (CLC), single-component spouted bed of monodisperse particles is very rarely used but the spouted beds of polydisperse particles have been widely used. The flow characteristics of polydisperse particles are much more complex than the single particle fraction in a fluidized bed. To investigate the gas-solid two-phase flow characteristics of the particles with different diameters in a spouted bed, the segregation and mixing characteristics, bubble morphology, minimum spouting velocity and pressure fluctuations of the particles with different sizes under different superficial gas velocities are studied by experiment. The results show that higher the initial bed height and larger the volume fraction of the bigger particles, higher is the minimum spouting velocity. Moreover, the magnitude of the minimum spouting velocity increases exponentially with increase in the volume fraction of the bigger particles. At low superficial gas velocity, there is a clear trend of segregation between the particles with different diameters. At moderate superficial gas velocity, the mixing trend among particles with different diameters is enhanced, and the pressure fluctuation in the bed presents certain regularity. At high superficial gas velocity, the particles with different diameters tend to separate again, and the pressure fluctuations become intense and the particle flow turns into a turbulent state. Also, when the bed is stable, the particles with different diameters distribute within the bed with regular stratification.
TOPICS: Pressure, Flow (Dynamics), Hydrodynamics, Combustion, Particulate matter, Turbulence, Fluctuations (Physics), Transients (Dynamics), Bubbles, Particle flow, Two-phase flow, Fluidized beds
Yan Tang, Xiaoxing Zhong, Guangyu Li and Xinhao Zhang
J. Energy Resour. Technol   doi: 10.1115/1.4039615
Coal fires exist in almost every coal-producing country and generate huge heat energy every year. The forced convective heat-extraction method is proposed in this paper to realize the wide-range heat exploitation in coal fire areas. The geological model of coal fire zones and combustion models of underground coal in O2-depleted air are established, and the boreholes arrangement, the injection rate of heat transfer medium (HTM) and the cooling effect on the environment are analyzed through a three-dimensional simulation software (Fluent). The results show that the boreholes arrangement of multi-hole press-in and oriented type proves to be suitable for coal fire zones. Besides, the temperature of the extracted HTM and the rate of heat extraction decrease as extraction time increases. Within the same period of extraction time, the temperature of extracted HTM can be increased by reducing the amount of HTM injected. The heat-extraction rate is more stable with relatively small HTM injection rate. Moreover, the temperature of coal fire zones can be reduced effectively by adopting the forced convective heat-extraction method, with the maximum temperature of coal fire zone, the average temperature of residue coal zone and the heat-extraction time in a cubic and quadratic function relationship respectively. This research provides a reference for the waste-energy exploitation in coal fire areas.
TOPICS: Heat, Coal, Fire, High temperature, Temperature, Heat transfer, Cooling, Combustion, Simulation, Computer software
Review Article  
Yaning Zhang, Wenke Zhao, Bingxi Li and Gongnan Xie
J. Energy Resour. Technol   doi: 10.1115/1.4039604
As compared with the conventional electrical heating pyrolysis, microwave-assisted pyrolysis (MAP) is more rapid and efficient due to its unique heating mechanisms. However, bio-oil production from microwave-assisted pyrolysis of biomass is strongly dependent on the operation parameters. Based on the recent researches, this study reviews the effects of the main operation parameters including microwave power, pyrolysis temperature, and pyrolysis time on the bio-oil yield obtained from microwave-assisted pyrolysis of biomass. The results show that microwave power, pyrolysis temperature, and pyrolysis time usually increase the bi-oil yield initially and decrease the bi-oil yield finally. The reported optimal microwave powers, pyrolysis temperatures, and pyrolysis times were mainly in the ranges of 300-1500 W, 400-800 oC, and 6-25 min, respectively. The mechanisms for bio-oil produced from microwave-assisted pyrolysis of biomass as affected by the main operation parameters were also analyzed.
TOPICS: Microwaves, Biomass, Pyrolysis, Temperature, Heating
Maan Al-Zareer, Dr. Ibrahim Dincer and Marc A. Rosen
J. Energy Resour. Technol   doi: 10.1115/1.4039601
In this study, the syngas composition exiting a biomass gasifier is investigated to determine the effect of varying selected gasification parameters. The gasification parameters considered are the mass flow rate of steam, the gasification agent, the mass flow rate of oxygen, the gasification oxidant and the type of biomass. The syngas composition is represented by its hydrogen, carbon monoxide, carbon dioxide and water fractions. The oxygen fed to the gasifier is produced using a cryogenic air separation unit. The gasifier and the air separation unit are modeled and simulated with Aspen Plus, where the gasification reactions are carried out based on the Gibbs free energy minimization approach. Finally, the syngas composition for the different types of biomass as well as the different compositions of the three types of the biomass considered are compared in terms of chemical composition. It was found that for each type of biomass and at a specified steam flow rate there is an air to the air separation unit where the gasification of the biomass ends and biomass combustion starts and as the volatile matter in the biomass increases the further the shifting point occur, meaning at higher air flow rate. It was found for the three considered biomass types and their four mixtures that, as the volatile matter in the biomass increases, more hydrogen is observed in the syngas. An optimum biomass mixture can be achieved by determining the right amount of each type of biomass based on the reported sensitivity analysis.
TOPICS: Biomass, Syngas, Fuel gasification, Flow (Dynamics), Separation (Technology), Matter, Hydrogen, Oxygen, Steam, Water, Sensitivity analysis, Air flow, Gibbs' free energy, Combustion, Carbon dioxide, Carbon
Yang Yang, Meng Zhang and Donghai Wang
J. Energy Resour. Technol   doi: 10.1115/1.4039602
Biofuels derived from cellulosic biomass offer one of the best near- to mid-term alternatives to petroleum-based liquid transportation fuels. Biofuel conversion is mainly done through a biochemical pathway, on which size reduction, pelleting, pretreatment, enzymatic hydrolysis, and fermentation are main processes. Many studies reveal that biomass particle size dictates the energy consumption in the size reduction. Biomass particle size also influences sugar yield in enzymatic hydrolysis, and biofuel yield in fermentation is approximately proportional to the former enzymatic hydrolysis sugar yield. Most reported studies focus on the effects of biomass particle size on a specific process; as a result, in the current literature, there is no commonly accepted guidance to select the overall optimum particle size in order to minimize the energy consumption and maximize sugar yield. This study presents a comprehensive experimental investigation converting three types of biomass (big bluestem, wheat straw, and corn stover) into fermentable sugars and studies the effects of biomass particle size throughout the multistep bioconversion. Three particle sizes (4, 2 and 1 mm) were produced by knife milling and were pelletized with an ultrasonic pelleting system. Dilute acid method was applied to pretreat biomass before enzymatic hydrolysis. Results suggested 2 mm is the optimum particle size to minimize energy consumption in size reduction and pelleting and to maximize sugar yield among the three particle sizes for big bluestem and wheat straw biomass. Nevertheless, there is no significant difference in sugar yield for corn stover for the three particle sizes.
TOPICS: Biomass, Biofuel, Particle size, Energy consumption, Particulate matter, Size reduction (Materials), Bioconversion, Fuels, Milling, Transportation systems, Petroleum

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