天然气液化过程中重烃组分脱除工艺设计及应用

Design and application of heavy hydrocarbons removal in natural gas liquefaction process

天然气液化前需对原料气进行净化处理,脱除其中的CO_(2)、H_(2)O、H_(2)S和重烃(C_(5)及以上烃类,简写为“C_(5+)”)组分等,防止以上组分在液化段冻结形成固体,堵塞管道和设备。以西部某液化天然气(LNG)工厂为例,针对该厂管道原料天然气C_(5+)组分变化波动大、含量(物质的量分数,下同)高的情况,在对原料天然气组分检测分析的基础上,对原C_(5+)组分脱除工艺进行了改造设计,采用Aspen Hysys软件对设计的C_(5+)组分脱除新工艺进行了模拟计算并应用于生产,最后对生产中净化处理后的天然气组分进行了检测分析。结果表明,低温冷凝预分离+高性能活性炭吸附组合的C_(5+)组分脱除工艺理论上可行,在保证天然气C_(5+)组分满足液化过程要求的情况下,最大限度的保留了C_(2)~C_(4)组分不被脱除,提高了LNG的热值。模拟结果中脱除C_(5+)组分后的天然气中C_(5+)组分含量为0.007265%,与实际生产中净化处理后的天然气检测结果中的C_(5+)组分含量0.0076%相差不大,较为吻合。

Before natural gas liquefaction,the raw natural gas needs to be purified to remove CO_(2),H_(2)O,H_(2S) and heavy hydrocarbon(C_(5) and above hydrocarbons,abbreviated as“C_(5+)”) components in it,so as to prevent the above components from freezing and forming solid in the liquefaction section and blocking the pipeline and equipment.Taking a western liquefied natural gas(LNG) plant as an example,in view of the large variation and high content(mole fraction,the same as below) of C_(5+)components of raw natural gas in the pipeline of the plant,the original C_(5+)component removal process was reconstructed and designed based on the analysis and detection of raw natural gas components,and the designed C_(5+) component removal process was simulated and calculated with Aspen Hysys software and applied to production.Finally,the components of purified natural gas in production were detected and analyzed.The research shows that the C_(5+) component removal process combined with low temperature condensation pre-separation and high performance activated carbon adsorption is theoretically feasible.Under the condition that the C_(5+) components of natural gas meet the requirements of liquefaction process,the C_(2)~C_(4) components are retained to the maximum extent,and the heating value of LNG is improved.In the simulation results,the C_(5+) component content in the natural gas after C_(5+) component removal is 0.007265%,which is similar to 0.0076%of C_(5+) component content in the natural gas after purification in the actual production.