空分装置纯化器出口CO_2超标处理及对后系统的影响

Treatment of Excess CO_2 at the Outlet of Air Separation Unit Purifier and Its Influence on Post-system

纯化器是空气分离装置(空分装置)中对空气进行净化处理的关键设备,用来清除空气中水分、碳氢化合物、CO_2等杂质,解决空气在低温法分离过程中析出和冻结杂质的问题。低温法是利用空气中各组分沸点的不同,通过精馏来达到分离不同组分的方法。通过一系列的工艺过程,将空气液化,而气体分离过程需要在100K以下的低温环境下才能实现,而CO_2沸点为216.6K时,上述气体分离过程将会凝固。如果分子筛出口CO_2含量超标,被冻结的CO_2将沉积在板式换热器、透平膨胀机或精馏塔里,造成通道管路和阀门的冻堵问题,更严重的情况是将碳氢化合物带进精馏塔冷凝蒸发器的液氧中,碳氢化合物在冷凝蒸发器中积聚过多,会引起冷凝蒸发器爆炸,严重影响空分装置的安全与稳定运行。为了消除CO_2对空分装置安全运行的影响,维持空分设备长期安全可靠地运行,需要严格监控纯化器出口的CO_2含量。目前采取以下措施控制并清除:在空气入口安装阻挡装置,防止被污染的空气进入空分装置;在空气入口安装CO_2检测仪表,对空气中CO_2含量实时监控;降低纯化器入口空气温度,提高纯化器吸附效果;手动干预纯化系统顺控程序,缩短纯化器吸附时间;利用停车机会补充吸附剂,保证吸附剂床层厚度;对吸附剂进行高温活化,恢复吸附剂活性;对已老化或者达到吸附寿命的吸附剂进行更换等。

Purifier is the key equipment for purifying and treating the air in the air separation unit,which is used to clear the impurities such as water,hydrocarbons,CO2 and so on in the air,and to solve the problem of air precipitation and freezing in the process of separation at low temperature.The cryogenic method is a method to separate different components in rectification by using the different boiling points of each component in the air.Through a series of technological processes,the air is liquefied,but the gas separation process can only be realized at a low temperature below 100K,and the boiling point of CO2 is 216.6K,the above gas separation process will solidify.If the CO2 content at the outlet of the molecular sieve exceeds the standard,the frozen CO2 will be deposited in a plate heat exchanger,a turbine expander or a distillation column,resulting in the frozen blockage of channels and valves.The more serious situation is that the hydrocarbon is brought into the liquid oxygen of the condensing evaporator in the distillation tower,and if the hydrocarbon in the condenser accumulates too much,it will cause the explosion of condenser and seriously affect the safe and stable operation of the air separation unit.In order to eliminate the influence of CO2 on the safe operation of the air separation unit and maintain the safe and reliable operation of the air separation unit for a long time,it is necessary to strictly monitor the CO2 content at the outlet of the purifier.At present,the following measures are taken to control and clear the air:install a blocking device at the air entrance to prevent the polluted air from entering the air separation unit;install a CO2 detector at the air inlet,and monitor the CO2 content in the air in real time;reduce the inlet air temperature of the purifier,improve the adsorption effect of the purifier;manually intervene the purification system sequence control procedure,shorten the adsorption time of the purifier;utilize the stop opportunity to replenish the adsorbent to ensure the thickness of the adsorbent bed;the adsorbent was activated at high temperature to restore the activity of the adsorbent,and the adsorbent which had aged or reached the adsorption life was replaced.