Abstract
In this study, a one-dimensional heterogeneous model with intraparticle diffusion limitation has been developed for methanol synthesis from syngas. The synthesis gas produced from the reformer is compressed at a pressure of 60-100 bar and then heated up to 200-250 degrees C in order to prepare it for the methanol production reaction. Syngas reacts on a copper oxide/zinc oxide/alumina catalyst. The annular multitubular (AMT) reactor proposed in this article has a design capability to efficiently remove the heat generated by the exothermic reaction in methanol synthesis and improve methanol production by at least 3% more than the conventional converter. In addition, the converter is operated under mild conditions, especially at the end of the tube, which makes the catalyst lasts for a longer period. This leads to process intensification and allows for the use of a compact distillation step. In addition, this new design has the advantage of preheating the feed gas in the reaction by having the inner tubes replace the feed gas preheater. Methanol production and temperature profile are the most important characteristics of methanol synthesis reactor. The predicted methanol concentration and temperature profile indicate that an increase in temperature is accompanied with a reduction in the methanol equilibrium concentration and hence limiting the profitability in the industrial plant. The use of an AMT reactor is shown to be able to overcome this limitation. The novelty lies in a process modification which employs an inner tube that is disposed in the reactor and then the catalyst is charged into a circular space surrounded by the reaction tube on one side and inner tube on the other side. Simulation studies show that this design allows the temperature to increase gradually and, hence, delays the equilibrium to be reached to the end of the reactor. In other words, more methanol is produced and less byproducts.