Operation Optimization Of Gas Fractionation Unit Based On Process Simulation Technology

In oil refinery, gas separation unit focuses on the separation of liquefied petroleum gas(LPG), supplying fine propylene with purity of higher than 99.5%(mol) for the polypropylene unit(PP). Due to the high product quality specification, the process requires more distillation stages, bigger reflex ratio and high energy consumption. So, it is very important to reach a balance between the energy consumption and the product requirement, including purity and yield of propylene. Of course it is hardly realized only depending on the experience of site engineers, needing very much the supports of process simulation technology in the practical operation.In this study, an ASPEN process simulation model covering the whole gas separation unit, which belongs to Hainan subsidiary of SIONPEC and holds an annual processing capacity of 0.6 Mt, has been built firstly. Considering the feed and products are light hydrocarbon compounds, the Peng-Robinson thermodynamic state equation is selected as basic calculation method in the model. Secondly an emulation analysis is taken for the correspondence between the site parameters and calculated ones by ASPEN. As a result, the real plate efficiencies of depropanizing column, dethanizing column and fine propylene column as well as all reboilers and heat exchangers, very helpful for the following study. In turn, the running optimization with targeting the minimum energy consumption is developed, including the decision of optimal feed plate locations of the above three columns, and so on. In addition, a heat pump distillation is researched on the fine propylene column, two cases are suggested for the unit.