Analysis of Reasons for Poor Drying Effect of Polypropylene Powder and Improvement Measures
A 400 000 t/a polypropylene plant of a company in Weinan,Shaanxi Province can produce homopolymers,random copolymers,and impact copolymers using Lyondell Basell's Spheripol Ⅱ polypropylene process.Since its commissioning in December 2014,the unit has been operating stably for over 9 years.During this period,the pre polymerization reaction system,drying system,and steam distillation system have been optimized and adjusted to achieve the goal of stable production,high yield,and long-term operation.The pre polymerization and polymerization reaction operating pressure of Spheripol Ⅱ polypropylene process is significantly increased,which can increase the hydrogen content in the loop reactor,expand the range of melt flow rate,improve product performance,and facilitate the control of morphology,isotropy,and molecular weight.Capable of producing the vast majority of products required by the market.After the mixture coming out of the loop reactor undergoes flash evaporation separation,steaming,and drying,the PP powder is sent to the extrusion granulation process through a nitrogen conveying system.The steam distillation process introduces a small amount of propylene,propane,and residual catalyst carried in the deactivated powder by low-pressure steam.The powder inevitably carries trace amounts of condensed water,which,if not removed in time,can cause operational fluctuations in the powder transportation and extrusion granulation processes,affecting product quality.Therefore,the drying effect of the powder is crucial.
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