DHX轻烃回收工艺不同运行模式分析

Analysis on different operation modes of DHX light hydrocarbon recovery process

关键词:  轻烃回收  DHX工艺  运行模式  循环量  丙烷收率

Key words:  light hydrocarbon recovery  DHX process  operation mode  circulation rate  propane recovery

摘要:

DHX轻烃回收工艺常增设脱乙烷塔回流系统,以提高轻烃收率。以塔里木轻烃回收厂原料气组分、压力等实际参数为研究基础,在合理确定研究边界条件的基础上,应用HYSYS软件对DHX轻烃回收工艺可能存在的4种运行模式进行理论分析,通过对比分析可知:①J-T阀+回流泵的运行模式是不可行方案；②膨胀机制冷模式下,脱乙烷塔塔顶回流在显著提高丙烷收率的同时,可降低F线循环量43%,对于大型装置,可大幅度减小脱乙烷塔、DHX塔及屏蔽泵设计尺寸,减少设备投资与制造难度；③F线出冷箱温度对循环量的影响较大,在J-T阀制冷工况下,F线出冷箱温度应尽量控制在较高值,避免DHX塔底泵流量过小；在膨胀机制冷工况下,F线出冷箱温度不宜过高,避免DHX塔底泵超负荷运行；④在膨胀机制冷工况下,F线出冷箱温度过低时,DHX塔顶部回流量降至最小循环量以下,装置丙烷收率快速下降；⑤要使装置丙烷收率达到98%以上的先进水平,回流罐温度不宜高于-31 ℃。 

Abstract:

DHX light hydrocarbon recovery process often add deethanizer reflux system in order to improve the yield of light hydrocarbon. Based on the actual parameters such as gas components and pressure in light hydrocarbon recovery plant of Tarim, on the basis of reasonably determining the boundary conditions, the HYSYS software was used to analyze theoretically the four possible operating modes of DHX light hydrocarbon recovery process. It was concluded through the contrast analysis that (1) the scheme of J-T valve + reflux pump operation mode was infeasible; (2) Under the mode of expander refrigeration, the reflux at the top of the deethanizer could significantly increase the propane yield and reduce the circulation volume of the F line by 43%. For large equipment, the design size of the deethanizer, DHX tower and shielding pump could be significantly reduced to decrease the equipment investment and manufacturing difficulty; (3) The temperature of F line out of the cold box had a great influence on circulation rate. Under the refrigeration mode of J-T valve, the temperature of F line out of the cold box should be controlled as far as possible at a higher value to avoid low pump flow of DHX tower bottom; Under the mode of expander refrigeration, in order to avoid DHX bottom overload operation, the exorbitant temperature of F line out of the cold box was unsuitable; (4) Under the mode of expander refrigeration, when temperature of line F out of the cold box was too low, the circulating amount of absorbent at the top of DHX tower dropped below the minimum circulating amount, and the propane yield of the device dropped rapidly; (5) In order to make the propane yield of the device reaching the advanced level of above 98%, the temperature of the reflux tank should not be higher than -31 ℃.