Desulfurization, Heat Exchanger, Methanol Synthesis Function Of The Coupling Reactor

Study on the performance of the fixed bed catalytic reactor operated under the reversal flow mode is a subject of the frontiers in chemical reaction engineering research in recent years. The fixed bed reactor under the reversal flow operation can make the reactant gas with near room temperature directly contact with the hot inert packing and catalyst, compared with the traditional reactor system with indirect heat transfer, this reactor gets not only bigger heat transfer coefficient, but also greater specific heat transfer area. Additionally, the reversal flow operation can create a bell type of axial temperature profile which is high in the middle and low in both ends of bed, and which is similar to the optimal temperature profile of the reversible exothermic reaction in favor of break chemical reaction equilibrium, and enhances one-way conversion. There for, the shortages of low heat transfer efficiency, complex processes and huge volume of reactor for the traditional fixed bed reactor of methanol synthesis can be made up by using the reversal flow operation.Two-thirds of methanol produced in China is synthesized in ammonia synthesis factories combining with methanol production where higher concentration of sulfur compound in syngas, unperfected sulfur removal and high spatial velocity result in very short life of the packed catalyst. Taking those into account, a reversal flow reactor with three different functions, catalytic reaction, sulfur removal and heat transfer is devised by packing desulfurizer in both ends of the reactor instead of the inert agent to extend the catalyst life and to reduce the production cost.This new reactor with three functions is studied systematically. The following parts are concerned with:1 .Investigation on the kinetics of H2S removal. The kinetics of H2S removal was investigated by using a fixed bed integral reactor packed with domestic desulfurizer T306, the experimental data were corrected to give a reaction rate equation.2.Experimental study on the performance of methanol synthesis reactor operated under the reversal flow. The influence of feed composition, flux and reversal flow period is inspected and analyzed in terms of:(1) The duration needed from the start-up of the reversal flow operation to a periodic steady state.(2) The factors influencing the velocity of heat wave propagation in reactor bed.(3) The factors influencing the temperature of the wave peak in the bed.(4) The factors influencing the CO and CO2 concentration at the exit of the reactor.3.Experimental study on the performance comparison between the reversal flow and the traditional steady-state operation. The steady-state methanol synthesis experiments under the similar conditions were carried out. The results obtained are analyzed in terms of:(1) Average bed temperature raised by the reaction.(2) Maximum bed temperature.(3) The conversions of CO and CO2.(4) Additional energy consumption under steady-state operation. 4.Experimental studies on the lowest concentration of COx in the feed gas whichcan sustain methanol synthesis reaction autothermally.5.Experimental study on temperature run-away phenomena. Temperature run-away under the reversal flow operation was probed by raising the initial bed temperature, increasing the catalyst load and the feed gas flux. Temperature run-away under the reversal flow operation is checked to be induced by:(1) Local temperature in catalyst bed is too high.(2) Initial temperature of catalyst bed is wholly too high.6.Study on the modeling of the new type reactor integrating three functions of desulfurization, heat transfer and methanol synthesis. The transient one-dimensional heterogerious model used to describe the methanol reactor under the reversal operation is established. Advanced difference mode is adapted to discrete the model differential equations. The model parameters are optimized by using complex optimization method, fitting the calculated concentrations of CO and CO2 at the exit of the reactor with those observed.