精对苯二甲酸装置除铁过滤器系统优化改造

Optimization and Transformation of the Iron Removal Filter System of the Purefined Terephthalic Acid Device

摘要: 精对苯二甲酸PTA装置氧化反应过程，为确保产品质量，对氧化循环母液按一定比例进行抽出，抽出比例约为8%~12%，抽出母液中富含醋酸、对苯二甲酸(TA)、间苯二甲酸(IPA)、苯甲酸(BA)、对羧基苯甲醛(4-CBA)、对甲基苯甲酸(PT酸)、钴、锰、铁等的残渣，残渣进入资源化处置装置，利用甲苯作为萃取剂萃取PTA生产装置所产生残渣中的副产物苯甲酸、PT酸，固相TA、IPA通过萃取过滤器分离后进入干燥机进行干燥，有机相即甲苯和苯甲酸溶液通过减压蒸馏塔将甲苯与苯甲酸分离，回收甲苯，生产副产品苯甲酸。萃取过滤器滤液进入下游倾析器用以分离水相和油相，水相进入钴锰催化剂回收系统去除铁铬等腐蚀金属，再回收钴锰催化剂。本文以一套220万吨/年PTA装置为例，除铁过滤器M-703运行过程中，遇到压差上升快，处理量较低情况，除铁效果差现象。通过现场调研，查阅文献分析，提出一系列改造方案，最终使除铁过滤器M-703处理能力满足设计要求。

Abstract: In the oxidation reaction process of a purified terephthalic acid (PTA) unit, the oxidized circulating mother liquor is withdrawn at a ratio of approximately 8%~12% to guarantee product quality. The withdrawn mother liquor contains residues enriched with acetic acid, terephthalic acid (TA), isophthalic acid (IPA), benzoic acid (BA), 4-carboxybenzaldehyde (4-CBA), p-toluic acid (PT acid), cobalt, manganese, iron and other components. The residues are sent to the resource recovery unit. Toluene is used as the extractant to recover the by-products benzoic acid and p-toluic acid from the residues generated in the PTA production process. Solid TA and IPA are separated by an extraction filter and then fed into a dryer for drying. The organic phase, namely the mixed solution of toluene and benzoic acid, is treated in a vacuum distillation column to realize the separation of toluene and benzoic acid. Toluene is recycled, and benzoic acid is obtained as a by-product. The filtrate from the extraction filter flows into the downstream decanter to separate the aqueous phase and oil phase. The aqueous phase enters the cobalt-manganese catalyst recovery system to remove corrosive metals such as iron and chromium, followed by the recovery of cobalt-manganese catalysts. Taking 2.2 million tons per annum PTA unit as the research object, the iron removal filter M-703 suffered from rapid differential pressure rise, low throughput and poor iron removal efficiency during operation. A series of retrofitting schemes were proposed based on field investigation and literature analysis. After implementation, the processing capacity of iron removal filter M-703 meets the design specifications.