Yiwu Weng

Safety Analysis of a Solid Oxide Fuel Cell/Gas Turbine Hybrid System Fueled With Gasified Biomass

The effect of biomass gas on the safety performance of a solid oxide fuel cell (SOFC)/micro gas turbine (GT) hybrid system was studied with consideration of the fuel cell working temperature, fuel cell temperature gradient requirement, compressor surge zone, and turbine inlet temperature (TIT). The safety performance of the hybrid system on the design condition and off-design condition was also analyzed. Results show that the hybrid system is good adaptability to low concentrations of biomass gas. The electrical efficiency could reach 50% with different biomass gases and is higher than the other combined power systems that used biomass gas. The wood chip gas (WCG) would make the fuel cell or GT easier overheat than the other three gases. The cotton wood gas (CWG) and corn stalk gas (CSG) are easy to cause the TIT too low or the compressor surge. In the safety zone, considering the hybrid system load adjustment range, the effecting order (from large to small, following is same) is WCG, grape seed gas (GSG), CSG, and CWG. Considering the hybrid system electric efficiency, the effecting order is WCG, GSG, CWG, and CSG.

Numerical Investigations of the Influencing Factors on a Rotary Regenerator-Type Catalytic Combustion Reactor

Ultra-low calorific value gas (ULCVG) not only poses a problem for environmental pollution, but also createsa waste of energy resources if not utilized. A novel reactor, a rotary regenerator-type catalytic combustion reactor (RRCCR), which integrates the functions of a regenerator and combustor into one component, is proposed for the elimination and utilization of ULCVG. Compared to reversal-flow reactor, the operation of the RRCCR is achieved by incremental rotation rather than by valve control, and it has many outstanding characteristics, such as a compact structure, flexible application, and limited energy for circulation. Due to the effects of the variation of the gas flow and concentration on the performance of the reactor, different inlet velocities and concentrations are analyzed by numerical investigations. The results reveal that the two factors have a major impact on the performance of the reactor. The performance of the reactor is more sensitive to the increase of velocity and the decrease of methane concentration. When the inlet concentration (2%vol.) is reduced by 50%, to maintain the methane conversion over 90%, the inlet velocity can be reduced by more than three times. Finally, the highly-efficient and stable operating envelope of the reactor is drawn.

Effect of Steam on the Performance of an IT-SOFC/GT Hybrid System

The performance of an intermediate-temperature solid oxide fuel cell (IT-SOFC) and a gas turbine (GT) hybrid system fueled with gasified wood chips is analyzed. The effects of steam on the thermodynamic performances of reformer, fuel cell, gas turbine and hybrid system are studied. The results show that the system electrical efficiency can reach up to 59.24% at design condition, and it demonstrates excellent performance. As the steam increases, the reforming temperature decreases, which leads to CH4 reforming reaction equilibrium constant decreases, and the reaction will be suppressed. The water gas shift reaction equilibrium constant increases with the decrease of the temperature. But the total amount of H2 shows a decreasing trend. With the steam increases, the fuel cell electrode and ohmic polarization losses increase, Nernst potential decreases, the output power and electrical efficiency show a decreasing trend. And then the hybrid system output power and electrical efficiency decrease. The electrical efficiency decreases from 61% to 56.91%. In consideration of operation security of reformer, fuel cell stack and the hybrid system, maintaining a high value of the steam is very important.Copyright

Thermodynamic Analysis of Solid Oxide Fuel Cell and Gas Turbine Hybrid System Fueled With Gasified Biomass

In this work, the detailed model of a high temperature Solid Oxide Fuel Cell (SOFC) and Gas Turbine (GT) hybrid system was established by using MATLAB/Simulink platform, based on the equations of mass and energy balance and thermodynamic characteristics, with the consideration of various polarization losses and fuel cell heat loss. Influence of different biomass gases on the hybrid system performance was studied. Results show that the electrical efficiency could reach up to over 50% with four types of gasified biomass, higher than other hybrid power system using biomass gases. Biomass gases from different sources have different composition and calorific value, which significantly affect the hybrid system performance. The system output power and efficiency fueled with wood chip gas are higher than the system fueled with other three types of fuel. Restricted by compressor surge safety zone, the adjustable range of biomass gas fuel flow rate is small. The speed of the gas turbine has a significant impact on the hybrid system parameters such as output power and efficiency. When the rotational speed of the gas turbine is lower than the rated value, the hybrid system performance parameters change significantly, on the contrary, the hybrid system performance parameters change slightly.© 2014 ASME