NMP萃取精馏系统防结焦技术的研究与应用

RESEARCH AND APPLICATION OF ANTI-COKING TECHNOLOGY IN NMP EXTRACTIVE DISTILLATION SYSTEM

针对NMP萃取精馏装置处理能力下降、再沸器进口管线堵塞、操作参数不易控制、产品质量不稳定等问题进行研究,发现使用过的N-甲基吡咯烷酮(NMP)的pH值为5.41,显酸性,与新萃取剂馏程段相比有8%以上发生了性质变化,且有黑色结焦物生成。将NMP进行通空气和氮气保护下的加热实验,发现在停工过程中负压操作时系统进入空气是导致NMP性质变化的主要原因。现场应用中,选用天然气作为停工时的系统保护气对NMP萃取精馏系统充压改造后,系统处理量提升近50%,产品质量稳定,说明停工阶段通入天然气保护的防结焦工艺技术方案可行。

In order to solve the problem existing in the N-methyl pyrrolidone（NMP）extraetive distillation system,such as reducing processing capacity, blocking of reboiler inlet tube, unstable operation and product quality,investigation on NMP extractant was carried out. It was found that compared with fresh NMP extractant the properties of used NMP extractant were changed including boiling range,pH value,color and some black coke-like deposits were formed. Tests of heating NMP extractant under air and pure nitrogen were carried out respectively, and the results showed that keeping NMP extraetant away from air was a good way to prevent its degradation. Therefore,an air leak into the vacuum operation system during unit shutdown was the main cause for the changing of NMP extractant. Field application was conducted using natural gas as a protective gas to prevent NMP extractant contact with air during unit shutdown,since then the processing capacity of the unit increased almost 50% and the product quality was stable,which indicated that this anti-coking technology,i, e. using natural gas as a protective gas during unit shutdown, is feasible.