关键词: 催化裂化装置, 分馏塔, 顶循环系统, 结盐, 气相分压, 铵盐, 露点温度, 腐蚀

Abstract:

Salt formation corrosion at the top circulation system of FCC fractionator threatens safe production and long-term operation of the unit. The quantitative analysis method can explain the conditions of salt formation more accurately, thus helping to take more effective measures to solve or alleviate the salt formation problem. The main component of salt is NH₄Cl, and the main sources include two aspects: one is vapor phase crystallization, the deposition temperature of NH₄Cl can be calculated by the partial pressure of NH₃ and HCl in the vapor phase, the higher the calculated deposition temperature, the greater the tendency of salt formation; another source is water phase dissolution, when there is water vapor condensation in the tower, NH₃ and HCl dissolution in the gas phase can produce NH₄Cl solution, the difference between the dew point temperature of water vapor in the tower and the top circulation return temperature can be used as the judgment index of salt formation tendency, the greater the temperature difference, the greater the salt formation tendency. According to the analysis results, the use of sulfur-containing wastewater at the top of the fractionator as a terminator will obviously increase the tendency of salt formation, whether from the perspective of gas phase crystallization or water phase dissolution. It should be used with caution for the unit with serious salt formation corrosion problems in the top circulation system of the fractionator.

Key words: FCC unit, fractionation column, top circulation system, salt formation, gas phase partial pressure, ammonium salt, dew point temperature, corrosion,