Numerical Simulation Of Fuel Cells/Gas Turbine Hybrid Power System And Catalytic Combustion Experiment Study

Many researchers have begun the research on the molten carbonate fuel cell/micro-gas turbine (MCFC/MGT) since the end of last century. People found the MCFC/MGT hybrid system has the advantages different from traditional power system, in which the energy conversation rate and level of pollution emission all reached a satisfactory level according to the research on this new kind of hybrid system. Nowadays many countries have focused on the development of this new kind of energy technologies. In this paper, the simulation modeling of MCFC/MGT hybrid system has been built up firstly. And then the performance of MCFC and hybrid system on design and off-design conditions have been analyzed carefully using the mathematic modeling. There is some fuel in the exhaust of fuel cell with the characteristics of low heat value and higher flowing speed. These characteristics make the catalytic combustor is necessary to the hybrid system. The whole efficiency can be higher, the properties can be improved and the contamination outlet can be decreased when the catalytic combustion techinique is connected with the hybrid system. At the same time the catalytic combustor can provide the base for the use of different fuel. Based on the theoretical analysis in detail, a experimental platform has been built up for the the purpose of deeply understanding of the catalytic combustion. Some experiments have been performed on the experimental platform. The work performed in this paper can provided the necessary theoretical guide and experimental base for the development and use of MCFC/MGT hybrid system. Some developments have been achieved as follows.(1) Numerical model of fuel cellA one-dimensional mathematical model for molten carbonate fuel cell has been built. The mass, monument, energy, specifies mass balance equations and thermodynamic properties have been included, at the same time the different polarization loss, heat conversation ways and detailed gas characteristics have been considered in the modeling. During the building of modeling the thermodynamic and electrochemical characteristics have been considered, the coincidence between the current density field and temperature field were also included. The temperature, flux, compositions and related thermal characteristics will change along the flowing direction which should be considered. And the solution of coupling relation between temperature field, current density field and gas compositions is very important. The energy transfer methods considered include not only different heat transfer methods but the energy transfer connected with the mass transfer during the foundation of the thermodynamic mdel. The data for the polarization properties are from the experiment for the electrochemical model. The fuel cell model with so detailed parameters is rare for the study of hybrid system. The detailed fuel cell model can provide the detailed information about the fuel cell when the properties of the hybrid system changed. In the mathematic modeling there exists non-linear partial differential equations and the temperature and flow exits coupling relationship which cause the difficulties to solve the modeling quickly. Using the V-R (volume-resistance) modeling and distributed and lumped parameter method the partial differential equations for cell mass and momentum balance can be changed to ordinary differential equations which met the demand for real-time dynamic simulation. Steady state and dynamic characteristics of MCFC have been analyzed using the model. The results indicate that the V-R characteristic modeling method is valuable and viable in the MCFC system, and the model can be used for the simulation of MCFC.(2) Foundation of hybrid system and variable load performance analysisThe pressurized MCFC has been considered during the system design. The traditional design method based on MCFC has been broken through instead of using a more meaningful hybrid system design method based on a commercial available micro-gas turbine according to the MCFC working pressure requirement and modular design feature. Establishing the steady-state and dynamic model of the hybrid system, the thermal characteristic, regulation of controlled object and other characteristics have been studied for the hybrid system under wide range working condition changes. The mechanism and laws of hybrid system characteristics changes has been revealed. The non-design operation characteristics of hybrid system have been compared under different operation methods. The effects of different operation methods on the system characteristics were analyzed. The dynamic characteristics of hybrid system at starup, shutdown and load change have been studied. The problems and impact on the system occurred during the startup and shutdown have been analyzed according to the characteristics of the system. The corresponding solution strategies have also been mentioned. A series of auxiliary equipment have been added into the system for the system startup and shutdown, which can ensure the system security. The detailed steps for the system startup and shutdown have been presented for the studied system, and the system statup and shutdown characteristics have been calculated using the mathmatics model. This work can become a reference to the system control and management for the experimental system.(3) Research on the characteristics of catalytic combustion in the MCFC/MGT hybrid systemThe concept has ever been mentioned for the research of MCFC/MGT hybrid system, but the associated experiments have never been done. In this paper, a mathematical model of catalytic combustion chamber has been built. The mathematical model is a micro-channel model of one-dimensional distributed parameters based on a detailed chemical kinetic parameters. The accuracy of mathematic model was confirmed according to the comparison between the calculations and experimental results. The operations of catalytic combustion chamber including startup, design point and off-design point have been analyzed, at the same time the effects of different fuel compositions and operation parameters on the operations of catalutic combustion chamber have also been studied based on the model. The catalytic combustion experimental platform has been built for the experimental analysis to the catalytic combustion based on the results from calculations. The working characteristics of catalytic combustion burner of hybrid system under different working conditions have been analyzed on the experimental platform. The catalytic combustion reaction characteristics for the system starup and normal operation are studied experimentally for 7 different kinds of mental oxide catalysts. The effects of different operation parameters, such as inlet temperature, flow rate and so on, on the fuel conversion rate are analyzed; the reaction characteristics of different fuels and synthetic gas are studied when using different catalyst. The experimental results are important to the use of catalytic combustor and the foundation of the hybrid system.