DMTO装置反应系统高温部位的腐蚀及选材研究

Corrosion of High-temperature Location in Reactor System of DMTO Unit and Material Selection

DMTO装置甲醇在高温酸性催化剂作用下的反应产物中有甲酸、乙酸等小分子有机酸,这些有机酸对设备都有强烈的腐蚀性。为此在含有乙酸的高温水蒸气容器中进行了腐蚀试验研究。试验表明:分别在乙酸浓度增高或乙酸温度升高时,20G和15Cr Mo腐蚀速率加快,S31603和S32168两种材料的腐蚀速率几乎不变;在530℃时,20G和15Cr Mo的腐蚀速率可达到0.75 mm/a;S32168或S31603耐腐蚀性能优异,在试验温度范围内腐蚀速率均小于0.002 5 mm/a。根据该试验,DMTO装置反应系统高温部位设备接触腐蚀性介质的内件选用S32168,设备外壳体选用常用的材料Q245R并适当增加腐蚀裕量,自第一套DMTO装置安全运行近五年来,证明DMTO装置反应系统等高温部位的选材,可完全满足DMTO装置运行要求。

The reaction products of methanol in DMTO unit at high temperature conditions and under the effect of acid catalyst are organic acid, acetic acid, etc, which are very corrosive to the equipment. The corrosion tests in the drum of high - temperature steam containing acetic acid demonstrate that, under the conditions of higher acetic acid concentration and higher acetic temperature, the corrosion rates of 20G and 15CrMo steels are accelerated and the corrosion rates of S3163 and $32168 steels remain unchanged. Under the temperature of 530 ℃ the corrosion rate of 20G and 15CrMo steels can be as high as 0.75 mm/a. Whereas, $32168 or $31603 has an excellent corrosion resistance, whose corrosion rate under the testing temperature is lower than 0.002 5 mm/a. Based upon the testing results, the $32168 steel is selected for the internals contacting the corrosion media in the high - temperature equipment in the DMTO unit. Q245R steel is selected for the equipment shells and higher corrosion allowance is considered. The 5 years＇ smooth safe operation of the DMTO unit has proven that the material selection for the high - temperature service of the reactor system of DMTO unit is very successful and has met all the requirements of operation of DMTO unit.