海上天然气液化装置中酸性气体的脱除技术

海上油田伴生气是一种宝贵的能源,但其日产量小,不适合管道运输。为此,自主研发了一套建在自升式移动平台上的橇装天然气液化装置。根据海上油田伴生气的气质特点,探讨了天然气脱除酸性气体工艺的选择原则,确定了适合该装置的MDEA+MEA混合醇胺溶液脱酸性气体净化工艺,分析了CO2含量、醇胺循环量的变化对再沸器热负荷、富液温度的影响,并对填料塔的高度进行了优化分析。结果认为:定期分析原料气中CO2含量,适当调节MDEA胺液循环量,能够有效降低净化系统的运行成本,提高净化装置对海上油田伴生气不同组成的适应性;对于天然气处理量为11.6×104m3/d的脱碳工艺,天然气中CO2体积分数在0.45%～5.54%时,MDEA醇胺溶液循环量宜为200～500kmol/h,再沸器热负荷宜为200～600kW。该装置集天然气液化、LNG的储存与卸载于一身,简化了海上油田伴生气的开发过程,具有适应性强、投资小、建设周期短、现金回收快等优点。

Acid gas removing technology in an offshore skid-mount LNG plant

Associated gas in offshore oil fields is one of most valuable energy resources, but due to its tiny production, it is not cost effective for pipeline transportation. Therefore, a skid mounted LNG plant, which is set up on the offshore mobile platform, is independently developed. According to the characteristics of the associated gas in offshore oil fields, a criterion of determining the acid gas removing technology was discussed, then the mixed MDEA+MEA solutions were used in the CO2 removal process for this self developed plant. Moreover, an optimal analysis was made on the major parameters in this process such as the height of the packed column, the effect of the CO2 content and the influence of the circulating amount of the MDEA solution on the heat load of the reboiler and the rich fluid temperature of the absorption tower. Therefore, the following results are obtained: (1)The CO2 content in the feed gas should be regularly analyzed and the circulating amount of MDEA solution should be moderately adjusted, in this way, the operating cost of the plant will be effectively reduced and the adaptability of this plant will thus be improved for dealing with different composition associated gas in offshore oil fields. (2)As for the CO2 removal process with the capacity of 11.6×104m3/d, when the CO2 mole fraction is 0.45%~ 5.54% , the circulating amount of MDEA solution should be 500~200 kmol/h and the reboiler heat load should be 600~ 200 kW. (3)This above mentioned LNG plant, which can not only handle with the liquefied LNG process, but store and unload the LNG simultaneously, simplifies the development of the associated gas in offshore oil fields with many advantages like good adaptability, low investment, short construction circle, and quick return on capital.