常压塔塔顶冷凝系统铵盐腐蚀及控制

摘要

The overhead condensing systems of crude tower was taken as the research object. And the thermodynamic simula-tion of the oil and gas in the overhead was conducted using Aspen Plus,through which the deposition and deliquescence tem-peratures of NH4Cl salt were predicted,and the conditions of NH4Cl corrosion were determined. The vapor pressures of the saturated NH4Cl solution were calculated by Aspen Plus,and the calculated values were modified with the vapor pressure da-ta of NH4Cl solution derived from literatures,through which a relationship between the deliquesce relative humidity(fDRH) of NH4Cl and temperature (T)was obtained. It is found that there is a linear correlation between fDRHand T,which is fDRH=-0.200 07T+82.708. The calculated salt point,deliquesce point and water dew point in the overhead condensing systems of crude tower are 116 ℃,104 ℃ and 96 ℃,respectively. The sensitive area of NH4Cl deposition temperature is from 104 ℃to 116 ℃. The sensitive area of NH4Cl under-deposit corrosion is between 104 ℃ and 96 ℃. When the concentration of NH3is higher than 5 mg/L,the tower overhead system has NH4Cl salt deliquescence risk. The controlling of HCl and NH3 pressure reduces NH4Cl salts corrosion failures.%以常压塔顶冷凝系统为研究对象,利用Aspen Plus对塔顶系统油气进行热力学模拟,预测系统的NH4Cl结盐点和潮解点,判断NH4Cl腐蚀发生的条件.采用Aspen Plus计算NH4Cl饱和溶液的蒸汽压,通过文献数据对计算结果进行修正,推导 NH4Cl 的潮解相对湿度(fDRH)与温度(T)的关系.结果表明:fDRH与 T 呈线性关系,即 fDRH=-0.20007T+82.708;预测塔顶冷凝系统的关键温度点,盐点116 ℃,潮解点104 ℃,水露点96 ℃;塔顶系统116~104℃区域是铵盐沉积的敏感区域,104~96 ℃区域是发生铵盐垢下腐蚀的敏感区域;NH3的质量浓度高于5 mg/L时系统存在NH4Cl结盐潮解风险;控制系统的HCl和氨气分压能降低NH4Cl盐引起的事故率.