MTBE合成装置原料精制塔的波动原因分析

Reason Analysis on Feedstock Distillation Column Fluctuation in MTBE Production Plant

中国石油化工股份有限公司北京燕山分公司橡胶厂MTBE合成装置始建于1996年,其原料之一碳四组分主要有三个来源。一是丁二烯抽提和乙腈抽提两套装置的副产品碳四馏分;二是炼油厂气体分馏装置的副产品碳四馏分;三是丁基装置生产过程中未反应的异丁烯合成料。原料碳四中的异丁烯与甲醇反应,生产超高纯度的甲基叔丁基醚(简称MTBE)产品,供下游MTBE裂解装置制取高纯度的异丁烯,或者供炼厂作为高辛烷值组分调和高标号汽油使用。丁基装置生产过程中的未反应的异丁烯合成料进入MTBE合成装置反应器前,需经过一个碳四原料精制塔C-405。C-405主要进料为异丁烯和异戊二烯,塔底采出为异戊二烯,塔顶采出为异丁烯。但是在实际生产过程中,异丁烯回收效率偏低,塔底物流中异丁烯含量高而且含量波动大。同时在塔顶内部,出现未知聚合物附着。作者对原料精制塔物流进行取样分析,先后对该塔进料、塔顶出料以及塔底出料进行了色质联用分析、离子色谱分析和气相色谱定量分析,找出了原料精制塔波动的原因。

Synthetic Rubber Plant of Beijing Yanshan Petrochemical Co., Ltd., SINOPEC methyl tert-butyl ether（MTBE） production plant was established in 1996. One of the feedstock of this plant is C4 component, which come from 3 resources：（1）Byproduct C4 fractions from isobutylene extract unit and Acetonitrile（ACN） extract unit;（2）Byproduct C4 fractions from gas distillation unit in petroleum refinery;（3）un-reacted isobutylene in Isobutene Isoprene Rubber（ⅡR） plant. Isobutene in C4 feedstock react with methyl alcohol to produce super high purity MTBE, which is used to prepare high purity isobutylene in MTBE decomposition plant, or used as high-octane gasoline blending component. Un-reacted isobutylene in ⅡR plant pass through the C4 feedstock distillation column C-405 before feed into MTBE composition reactor. The main feeds of C-405 are isobutylene and isoprene. Isoprene flows from the bottom of the column and isobutylene rises from the top of the column. While, in the real production process, the isobutylene recovery rate is low as isobutylene content in the bottom stream is high and fluctuate frequently. Un-known polymerizations appear on the inner of the column top. The feedstock distillation column streams were sampling analyzed. Gas chromatograph-mass spectrometer（GC-MS）, Ion chromatography and Gas Chromatography were used to analyze the feedstock, the steam rising from the top and the stream coming from the bottom. The reason of feedstock distillation column fluctuation was revealed.