基于液氮冷凝的VOCs深冷回收技术研究

Research on Cryogenic Recovery of VOCs Technology Based on Liquid Nitrogen Condensation

挥发性有机物(VOCs)是大气污染控制的重点控制污染物之一,是形成臭氧污染和PM_(2.5)的主要前体物。VOCs排放的控制治理对于人类健康、环境保护以及经济发展具有重要意义。冷凝法是一种可以直接实现废气资源化的回收方式,主要有机械冷凝法和液氮冷凝法。前者受限于制冷温度,难以达到-120℃以下。而液氮冷凝法的制冷温度可低达-180℃,能够满足日趋严格的排放标准。文章针对一种三级液氮冷凝的VOCs回收系统流程及装置开展了分析研究。计算结果表明,系统的经济效益比与处理气量呈弱相关性,而与废气浓度、废气类型密切相关。当浓度从3.8%增加至19.0%时,经济效益比从0.38增长至0.59,年碳减排量从1489 t增加至7484 t。进一步开展了罐区“甲醇+甲叔基丁基醚(MTBE)”、装车台“柴油+汽油+石脑油”以及罐区“柴油+汽油+石脑油”VOCs气体冷凝回收装置工程样机的研制,三者VOCs冷凝液年回收量分别达到69.88,135.41,692.69 m^(3);对应的年碳减排量分别为127,299,1534 t;后两者的年总液氮消耗量大约为2300 t,经济效益比在0.27左右。

Volatile organic compounds(VOCs)are one of the key pollutants in air pollution control,and are the main precursors for the formation of ozone pollution and PM_(2.5).The VOCs emission control is important to human health,environmental protection,and economic development.The condensation method is a recovery method that can directly realize waste gas recycling,mainly including the mechanical condensation method and liquid nitrogen condensation method.The cryogenic temperature of mechanical condensation method is difficult to reach-120℃.Meanwhile,the cryogenic temperature of the liquid nitrogen condensation method can be as low as-180℃,which can meet the increasingly stringent emission standards.In this study,an analysis and research on the process and device of a three-stage liquid nitrogen condensation VOCs recovery system were conducted.The calculation results shown that the economic benefit ratio of the system has a weak correlation with the amount of treated gas,but was tightly related to the concentration of exhaust gas and type of exhaust gas.When the concentration increased from^(3).8%to 19.0%,the economic benefit ratio increased from 0.38 to 0.59,and the annual carbon emission reduction increased from 1489 tons to 7484 tons.The development of VOCs gas condensation recovery device engineering prototypes for the“methanol+Methyl tert-butyl ether(MTBE)”in the tank area,the“diesel+gasoline+naphtha”in the loading platform,and the“diesel+gasoline+naphtha”in the tank area were carried out.The annual recycling volume of the three VOCs condensate reached 69.88 m^(3),135.41 m^(3),and 692.69 m^(3),respectively,corresponding to carbon emission reductions of 127 tons,299 tons,and 1534 tons,respectively.Besides,the total liquid nitrogen consumption of the latter two is about 2300 tons,and the corresponding economic benefit ratio is about 0.27.