Modeling and simulation of a combined isomerization reactor/pressures swing adsorption/membrane unit.

摘要

In this work, a novel process for isomerizing and separating n-pentane and n-hexane to their branched isomers is proposed. Both reactor and separation units are combined in one vessel. The vessel is divided into two sections: a reactor section and a PSA separation section. The reactor section is packed with Pt/Y-zeolite catalyst. The PSA separation section is equipped with a 5A zeolite adsorbent. Also, to facilitate separation, the addition of hydrogen membrane to the adsorber section is studied in this work.; A dispersed plug flow mathematical model of the entire process is developed. The model links both reactor and separation sections. The model is used to investigate the dynamics of a PSAR and PSARM units. Different operating modes of both models are studied.; For a feed to a conventional PSAR unit, containing an equimolar fractions of 0.03 for each of n-C5, n-C6, i-C5 and i-C6, the molar fractions of i-C5 and i-C6 rise to values of 0.0439 and 0.045 after reaching equilibrium conversion at the end of the reactor section. The PSA section allows for complete separation of n-C5 and n-C6 from the reactor section effluent stream. The addition of a membrane to this section raises the concentration of i-C 5 and i-C6 in the product stream to 0.1 and 0.09, respectively. Recycling of waste streams back to the process allows for recovery of valuable hydrocarbon material. Eight models are developed to investigate the behavior of conventional PSAR and PSARM models in addition to models containing recycling of waste to feed and to the adsorber section. The study revealed that the system achieving the highest yield of isomers, for both PSAR and PSARM systems is the one that recycles the waste stream to the feed and utilizes part of the product stream as a purge stream.