联合罐区氮封技术的应用与分析

Application and Analysis of Nitrogen Seal Technology in Joint Tank Farm

轻质油储罐在运行过程中存在两大隐患,一是储罐的呼吸损耗,不仅造成了油品挥发浪费,同时还在储罐内形成油气爆炸空间;二是如果油品中硫化氢浓度较高,在储存过程中硫化氢与储罐易形成硫化亚铁,在有氧环境下有"自燃"风险。对联合罐区的8台5000m^3重整原料和轻烃裂解料进行氮封改造,重点是对储罐的通气窗等进行封堵,增加氮气管线、氮气调节阀、呼吸阀、紧急泄压阀等设施,使储罐的油气空间保持正压的氮气封存状态,一般情况下气相空间的压力维持在300～500Pa左右。改造后,8台储罐基本消除了罐内的有氧环境,氧含量维持在0.1%～1.0%之间,杜绝了储罐自燃的风险。经过两年的监测,储罐运行过程中的挥发损耗明显降低,月均损失率由原来的0.18%下降至0.1%。氮封储罐在运行过程中存在氮气泄漏、质量波动等问题,解决这些问题需要对储罐的密封设施进行有效处理,正确开展储罐正负压实验,以及在储罐联通线上增加单向阀。

There are two hidden dangers in the operation of light oil storage tank.Firstly,the breathing loss of the storage tank not only causes the volatilization loss of oil products,but also forms fuel-air mixture explosion space in the tank.Secondly,if the concentration of hydrogen sulfide in oil is high,hydrogen sulfide easily reacts with the rust in tank to form ferrous sulfide during the storage,resulting in the risk of spontaneous combustion in the aerobic environment.Nitrogen seal modification was carried out on eight 5000-cubic-meter reforming raw material and light hydrocarbon cracking material tanks in the joint tank farm,focusing on blocking the vent of tank and installing nitrogen pipeline,nitrogen control valve,breathing valve,emergency relief valves and other facilities,so as to maintain a positive pressure nitrogen seal in the oil and gas space in storage tank.Usually the pressure in gas phase space is maintained at 300~500 Pa.After the modification,the aerobic environment in the eight storage tanks was eliminated,and the oxygen content was maintained between 0.1% and 1.0%,eliminating the risk of spontaneous combustion of the tanks.After two years of monitoring,the volatilization loss during the operation of tank was significantly reduced,and the monthly average loss rate decreased from 0.18% to 0.1%.Nitrogen leakage,mass fluctuation and other problems exist in the operation of nitrogen-sealed storage tank.To solve these problems,it is necessary to effectively deal with the sealing facilities of the tank,correctly carry out positive and negative pressure test on the tank and install one-way valve on the connection line of the tank.