Study On CFD Simulation Of Methanol Synthesis Process

It is known to all that methanol has been used widely in industry. It’s preparation has received much attention since its first industrialization in1923. At the same time, many types of methanol synthesis reactors were born, such as cold-shock, slurry-bed and tube-shell reactor. Among those, tube-shell reactor is used most widely and has gained most comprehensive study on both experiment and theoretical analysis. But the continuous field distribution of physical quantities in the reactor have yet not been reported at all. This paper is just aimed to get the field distribution of those physical quantities. Also CFD (Computational Fluid Dynamics) is introduced to methanol synthesis process, which can provide visual images to help people further understand the energy and mass transfer mechanisms in the tube-shell fixed-bed reactor.CFD commercial softwares have been used widely in aerospace, shipbuilding, machinery and other fields with their systematic transfer model equations, finite volume discretization method as main discrete method. Discreting the transfer equation, we can get values of variables at each discrete point, and images are used to reflect the change of different values. Of all the CFD commercial softwares, FLUENT, which has comprehensive functions has been used most widely and also has received much attention in chemical engineering field.This paper is set in the synthetic process of methanol which raw material is syngas. A2-D pseudo homogeneous steady-state model and a2-D temperature heterogeneous steady-state model have been established in fixed-bed reactor, based on Computational Fluid Dynamics and combined with kinetic models of the synthetic process of methanol. The software of FLUENT is used to solve corresponding control equations and User Defined Function (UDF) is used to add the sources of species transport equations and energy equation. The postprocessor is used to show the fields distribution of temperature and concentration.In the simulation, methanol synthesis process in the laboratory scale reaction tube of the fixed bed reactor is been simulated fist, and the results have been verified by the research results in the literature. On this basis, the heat exchange between the catalyst bed layer and cooling medium in the shell side is been considered and the reactor size is enlarged at the same time. Then methanol synthesis process in the tube-shell fixed-bed reactor with constant wall temperature or constant heat transfer coefficient boundary condition is been simulated. The visual fields of temperature and components concentration in the reaction system have been obtained. In addition, the effects of operating parameters such as temperature, flow rate and composition of raw material, reaction pressure and temperature of cooling medium on methanol concentration at the reactor outlet and temperature changes along axial direction of the reactor are investigated. And the appropriate operation conditions are obtained. The work of this paper can provide theoretical basis for further study of heat transfer mechanism and reaction performance in the fixed-bed methanol synthesis reactor.