Study On Heat Transfer Performance For Reactor Of Hydrogen Production By Methanol

Alcohol-hydrogen fuel automobiles can utilize the residual heat of engine exhaust gas to produce hydrogen and carbon monoxide by the cracking reaction of methanol under the action of catalyst,and then mix methanol and its cracking gas into the engine cylinder to provide power for the engine,thereby reducing fuel consumption and emission pollution.The key to catalytic cracking of methanol is to make full use of the heat in the waste gas to make the reaction gas reach the catalytic reaction temperature.Therefore,it is very important to design,analyze and optimize the methanol cracking reactor for improving the catalytic performance of the methanol cracking reactor and realizing the optimization of the power performance,economy and emission performance of the methanol-fueled vehicle.Based on the theory of computational fluid dynamics and the kinetic model of methanol decomposition reaction,two kinds of methanol cracking reactors,spiral tube reactor and straight tube reactor,were designed by thermodynamic calculation.A three-dimensional porous media reactor model coupled with methanol cracking reaction was established using CFD software FLUENT.By adding solid-phase energy equation to UDF,the single-temperature model of porous media was modified to a gas-solid coupled heat transfer two-temperature model.Chemical reactions were added in the form of source terms of each component in methanol cracking reaction,and chemical reaction heat was added to the gas-solid energy equation to simulate the flow and heat transfer and chemical reaction of the model.According to the designed reactor calculation model,the process of methanol heating catalytic cracking in the reactor was simulated,and the simulation results were compared with the experimental results of methanol catalytic cracking.Then,the effects of reaction space velocity and heat waste gas velocity on methanol decomposition reaction were discussed by grouping simulation with different boundary conditions and control variables.Finally,according to the structural characteristics of the reactor,the model was optimized and improved.By reducing the diameter of heat transfer tube,increasing the length of the reactor shell,rationally utilizing the space to increase the effective heat transfer area and other methods,the reactor model was re-established,and the catalytic heat transfer performance of the improved reactor was significantly improved.