Simulation of Khangiran gas treating units for various cooling scenarios

Khangiran refinery sour gas feed has been acquired from Mozdouran reservoir in the past twenty eight years (1982-2010). In this period, the reservoir pressure has been dropped from 6600 psia to less than 5000 psia. It is anticipated that the pressure decrease will continue (even more rapidly due to higher production rates and sharper decrease in gas compressibility factor) in the near future. This considerable reduction in reservoir pressure has lead to appreciable increase in sour gas temperature entering the gas treating unit (GTU) due to Joule-Thompson effect. Such temperature increase had various adverse effects on the performance of the GTU process (e.g. higher contactors temperature peaks and larger antifoam consumptions). A variety of cooling scenarios have been considered in the present article. The required cooling facilities were designed for lowering the temperature of sour gas or lean solvent by air or water. The corresponding entire GTU processes were then simulated using both HYSYS and Aspen software's. The simulation results indicate that the sour gas cooling scenario is not sufficiently effective because of the temperature peak encountered in the absorption towers. Furthermore, although the solvent cooling strategy was more effective from both economical point of view and its impact on the contactor temperature profile, however it may lead to some operational difficulties resulting from heavy hydrocarbons condensation. To avoid such predicaments, both sour gas and lean solvent streams should be cooled simultaneously via air coolers. (C) 2010 Elsevier B.V. All rights reserved.