200W PEM Fuel Cell Stack with Online Model-Based Monitoring System

Although various designs have been introduced to improve the performance of a Proton Exchange Membrane Fuel Cell (PEMFC) stack system, fault conditions, such as drying or flooding, may still occur due to the complexity of the process. The development of a system which can detect these fault conditions is a key to operate PEMFC stack system effectively. In this study, a monitoring system for a 200W commercial PEMFC stack system has been developed by constructing models for determining the flooding and drying conditions inside the cell. Since the membrane resistance and pressure drop across the stack are important parameters for determining either drying or flooding conditions taking place inside the fuel cell, the online model-based monitoring system is developed by adopting existing algorithms. A number of instruments are installed to measure relevant data. The data acquisition system and mathematical models have been programmed under LabVIEWTM environment. To indicate the abnormally conditions inside the fuel cell stack, the model predictions is compared with the measured values and the size of the discrepancy will be the indicator

Carbon Dioxide Capture from Flue Gas Using a Potassium-Based Sorbent in a Circulating-Turbulent Fluidized Bed

This research aimed to study the carbon dioxide (CO2) capture process using a potassium-based solid sorbent in a circulating fluidized bed riser (CFBR). The solid sorbent in this study was potassium carbonate on gamma alumina supporter (K2CO3/g-Al2O3). The hydrodynamics under a circulating-turbulent fluidized bed (C-TFB) regime occurred when the gas velocity was 1.00 m/s and could promote a solid sorbent distribution, with transition and transport velocities of 0.82 and 2.22 m/s, respectively, giving a uniform solid volume fraction distribution of 0.15 along the CFBR for the CO2 capture process. The study started with finding the operating condition in the riser so that the particle flowed in the reactor in the C-TFB regime. In addition, the kinetic of the adsorption under C-TFB flow regime in the riser was studied and the kinetic parameters corresponding to C-TFB flow regime were determined using deactivation kinetic model

Two-Dimensional CFD Simulation of Reducing Operating Pressure Effect on the System Hydrodynamics in a Downer Reactor

The effect of the system hydrodynamics in a circulating fluidized bed downer (CFBD) reactor with a reducing operating pressure and solid mass flux on the hydrodynamics in a downer reactor were evaluated using a two-dimensional computational fluid dynamics simulation. Five low operating pressure conditions (0.90 to 0.99 atm) and four different solid mass fluxes (250 to 1,000 kg/m2 s) were explored. The simulation results demonstrated that the CFBD reactor had a higher mean free path when operated with a low solid mass flux than with a high solid mass flux. Moreover, a large difference between the operating and atmospheric pressures induced a high system turbulence or oscillation. The CFBD reactor with hydrodynamic fluctuation showed a good solid circulation between the gas and solid particles, as reflected by the solid volume fraction and velocities and granular temperature. These phenomena will be suitable for the chemical reaction systems. Therefore, a suitable solid mass flux was in the range of 500 to 750 kg/m2 s for all operating pressuresThe effect of the system hydrodynamics in a circulating fluidized bed downer (CFBD) reactor with a reducing operating pressure and solid mass flux on the hydrodynamics in a downer reactor were evaluated using a two-dimensional computational fluid dynamics simulation. Five low operating pressure conditions (0.90 to 0.99 atm) and four different solid mass fluxes (250 to 1,000 kg/m2 s) were explored. The simulation results demonstrated that the CFBD reactor had a higher mean free path when operated with a low solid mass flux than with a high solid mass flux. Moreover, a large difference between the operating and atmospheric pressures induced a high system turbulence or oscillation. The CFBD reactor with hydrodynamic fluctuation showed a good solid circulation between the gas and solid particles, as reflected by the solid volume fraction and velocities and granular temperature. These phenomena will be suitable for the chemical reaction systems. Therefore, a suitable solid mass flux was in the range of 500 to 750 kg/m2 s for all operating pressure

Simulation of Process Structure and Operating Parameters on the Efficiency of the Chemical Looping Combustion Combined with Humid Air Turbine Cycle Using Statistical Experimental Design

This study’s objective is to investigate the process structure and operating variables that affect the efficiency of the CLC combined with humid air turbine (HAT) unit to produce electricity. The investigation was carried out by using the Aspen Plus program with Peng-Robinson-Boston-Mathias (PR-BM) thermodynamics properties. In this study, the process structure and operating parameters were investigated. The process structure was related to process configuration, which reflected the number of compressor stages. The operating parameters were pressure, airflow rate, and compression methods. The four investigated responses consist of LHV efficiency, power production from the air reactor, work of air compressors, and air compressor discharge temperature. The 3k factorial experimental design was employed. After that, the result was analyzed by the analysis of variance (ANOVA). The result showed that the highest LHV efficiency was at 55.87 % when seven stages of compressors were used and the operating condition was at 15 atm of pressure in the air reactor, air compression using method 3, and 61,000 kmol/hr of airflow rate. The pressure and the method of compression highly affected LHV efficiency, as shown by their p-values. The pressure had the highest effect on LHV efficiency. The high pressure provided high power production. Method 3 provided the highest discharged temperature from the air compressor, which was the reason for the high power production in the air reactor. The compression ratio of the last compressor would be 65% of the pressure in the air reactor. Moreover, the efficiency could be improved to 57.67% by increasing the loading of Ni on the oxygen carrier from 25% to 40%. The benefit of the paper will be preliminary data for operation and investment decisions on a CLC power production because this result has not yet been demonstrated

Computational Fluid Dynamics Simulation of a Crude Oil Transport Pipeline: Effect of Crude Oil Properties

Transporting crude oil inside a pipeline is a common process in the petroleum industry. Crude oil from different sources has different properties due to terrains and climates which cause the transport profile to change during operations. In this study, the computational fluid dynamics model was developed using computer language code. The governing equations were employed to study the effect of crude oil properties such as crude oil density and viscosity on the transport profile using the 24 factorial experimental design. A good agreement between the developed numerical model and commercial software suggests that the proposed numerical scheme is suitable for simulating the transport profile of crude oil in a pipeline and predicting the phenomena affecting conditions. The result showed that the heat capacity and density of crude oil had statistical significance to the transport profile at 95% confidence level. The heat capacity had the most significant effect on wax appearance. Therefore, the physical properties of crude oil should be modified to prevent the occurrence of wax inside the crude oil pipeline

Computation of Biomass Combustion Characteristic and Kinetic Parameters by using Thermogravimetric Analysis

In this study, the response surface methodology and simplex-lattice design were applied to investigate the effect of biomass constituents on the kinetics of biomass combustion, important information for process design. The synthetic biomass made from pure cellulose, xylan and Organosolv lignin was used instead of real biomass for this purpose. The combustion process was employed using thermogravimetric analyzer. The results obtained from three different kinetic models including Kissinger-Akahira-Sunose, Ozawa-Flynn-Wall and Analytical Method were provided and compared. According to the analysis of variances (ANOVA), the higher cellulose and hemicellulose fraction provided greater activation energy and frequency factor. The proposed regression models with high R2 coefficient indicated that the predicted kinetic values and experimental data agreed very well. The contour plots generated from the proposed models were also provided in this study. They were used to observe the influence of biomass components on each kinetic parameter

Potassium Carbonate Supported on gamma-Alumina Sorbent Regeneration in Fluidized Bed Reactor for Carbon Dioxide Capture Technology

Nowadays, the world is facing severe climate change due to the rapid increase in the world population and the continuing growth of the economy and industry. These lead to substantial greenhouse gas emissions into the atmosphere, especially carbon dioxide, which causes global warming. Thus, carbon dioxide (CO2) capture becomes an essential technology for mitigating adverse effects on the atmosphere. The solid sorbent is an appropriate alternative for CO2 capture because it is cheap, environmentally benign, and recyclable. In this study, solid-sorbent regeneration using potassium carbonate supported on gamma-alumina in a fluidized bed reactor was investigated. The effects of operating variables of solid sorbent regeneration were studied by varying the temperatures of 100, 200, and 300 degrees Celsius and pressures in the range from 0 to 1 atmospheric pressure. The results showed that regeneration temperature had a positive effect and initial pressure had a negative effect on the sorbent regeneration, respectively. The sorbent regeneration can be enhanced by increasing the regeneration temperature and decreasing the initial pressure. The optimal condition for sorbent regeneration was at the temperature of 300 degrees Celsius and initial pressures of 0.35 bar. Kinetic studies of the sorbent regeneration were also conducted, and obtained a pseudo-second-order model to be the best-fit model

Effect of Inserting Baffles on the Solid Particle Segregation Behavior in Fluidized Bed Reactor: A Computational Study

In multi-solid, particle-size fluidized bed reactor systems, segregation is commonly observed. When segregation occurred, small solid particles were entrained to the top of the bed and escaped from the reactor. During the combustion process, the small solid particles that escaped from the boiler were burned and subjected to damage around the cyclone separator. This study then employed a computational fluid dynamics approach to investigate solid particle behavior in the reactor using three different sizes of solid particles. The effects of baffle insertion, baffle angle, stage number, and its arrangement were examined. The percentage of segregation was calculated to compare behavior among different reactor systems. The insertion of 45-degree baffles resulted in reduced segregation behavior compared to cases without baffles and with 90-degree baffles, attributed to solid hindering and collision phenomena. Additionally, a double-stage baffle with any arrangement could reduce segregation behavior. The best arrangement was “above-arrangement” due to particles hindering, swirling, and accumulating between the baffle stages. Therefore, to diminish segregation behavior and enhance combustion chemical reactions, the insertion of baffles in the reactor zone is recommended