The Study Of B/T Distillation Unit Of Aromatics Complex For Scale-up Revamping

Aromatics hydrocarbon is a very important material for organic chemical industry, whose productivity is only less than ethene and propylene. The market's requirement for benzene and xylene is so huge that it is hard to reach the number for the manufactures, meanwhile, toluene and heavy aromatics hydrocarbon are superfluous. Therefore, the large scale production of benzene and xylene is implemented by aromatics complex plant, transforming toluene and C9 alkylaromatic hydrocarbons into benzene and xylene, which named disproportionation and transalkylation process. In this process, the benzene and toluene separation unit is very important because it is both the feed providing unit and the products unit.There is a 10.522t/h stream would come into the B/T unit for distillation when the 450kt/a new PX plant come into operation of LiaoYang Petrochemical Company. It causes the benzene column need to handle 72kt/a feed more, and 15kt/a more for toluene column, but actually the columns haven't enough capacity to produce the eligible products after the feed increased so much. So it is necessary to take revamping for the benzene and toluene columns to increase their productivity and keep the products' purity.Process simulations of both produce status and revamping status have been completed by using ASPEN PLUS software. Some bottlenecks that limit the capacity of B/T distillation unit were analyzed, based on the powerful functions of sensitivity analysis, feedback control and optimization of ASPEN PLUS. The optimized values of product flowrates and reflux ratioes were figured out, and the relevant hydrodynamics checks were also calculated by FORTRAN codes. As result, B/T unit can scale-up successfully from 118kt/a to 190kt/a by applying those optimized parameters without changing the columns. The benzene and toluene products' purity can reach 99.947% and 99.803% respectively. It will bring much benefit for the company.