Optimization Of Ethylene Polymerization Heat Removal And Its Application

Polyethylene is one of the polymer resins with largest production capacity. With strongmechanical modeling properties and stability, it’s widely used in industry, agriculture anddaily life. Polyethylene plays a key role in plastics industry. Many polyethylene processtechnologies are available in the industry and keep development aiming at expandingproduction capacity or optimizing product properties.This paper focus on a capacity expansion project in a gas phase Polyethylene plant whichapplies Basell (Now Lyondellbasell) Lupotech G process. To balance new Ethylene balancefollowing site-wide Capacity expansion plan, Polyethylene plant had to increase its hourlyproduction from25t to30t~33t.This paper first introduced this Polyethylene plant’s process and pointed out several ways ofremoving polymerization heat from reactor. It was also pointed out that the bottleneckslimiting production capacity is the yield and the speed of removing polymerization heat. Toremove polymerization heat more rapidly, higher cycle gas flow, larger temp differencebetween cycle gas entering and leaving reactor or operating in condensate mode can be goodchoices.Based on the status of this polyethylene plant, a proposal was initiated in this paper to achievecapacity expansion with higher specific heat of cycle gas, by replacing components withlower specific heat with that with higher specific heat. Before the modification, ASPENPLUS was utilized to model the main process unit of the Polyethylene plant. The model wasthen validated with plant original design data for an assurance of its accuracy and reliability.The validated model was thereafter used to predict the new setup of reactor system to achievehigher production capacity. Minor modification was conducted in Ethylene purification unit toenable its capability of producing Ethane in Hydrogenation column. Test run in the unitshowed that it was feasible to achieve higher production throughput with higher cycle gasspecific heat by replacing Nitrogen in the cycle gas with Ethane.