聚丙烯粉料干燥效果不佳原因分析及改进措施

Analysis of Reasons for Poor Drying Effect of Polypropylene Powder and Improvement Measures

陕西渭南某公司40万t/a聚丙烯装置采用Lyondell Basell公司Spheripol-Ⅱ代聚丙烯工艺可生产均聚物,无规共聚物和抗冲共聚物。自2014年12月投产以来,稳定运行9年多,期间对预聚合反应系统、干燥系统及汽蒸系统进行优化调整,使装置达到稳产高产长周期运行的目的。Spheripol-Ⅱ代聚丙烯工艺预聚合和聚合反应操作压力明显提高,可使环管反应器中的氢含量增高,扩大熔体流动速率的范围,产品的性能更好,有利于对形态、等规度和分子量的控制。能生产市场所需的绝大多数产品。从环管反应器出来的混合物经闪蒸分离、汽蒸、干燥后,PP粉料通过氮气输送系统送至挤压造粒工序。汽蒸工序通入低压蒸汽失活粉料中携带的少量丙烯、丙烷及残余催化剂,粉料不可避免地带入微量凝结水,这些水分若不及时除去,会造成粉料输送工序及挤压造粒工序的运行波动,影响产品质量,因此粉料干燥效果至关重要。

A 400000 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.