克拉气田某处理厂干气烃露点问题的探讨

克拉气田某处理厂采用三甘醇脱水工艺对原料气进行脱水处理,脱水后的干气水露点合格,但烃露点较高。由于天然气具有反凝析现象,随着干气在输送过程中压力的降低,会有液态烃析出,从而对管道、设备、下游用户造成不同程度的危害。为了达到合格的烃露点,避免液态烃的析出,根据我国国家标准对烃露点的不同规定,提出了烃露点控制的改进流程及两种烃露点的控制方案。使用HYSYS软件进行模拟比较,确定采用GB 17820-2012《天然气》对天然气烃露点的控制要求,以保证处理厂至轮南首站的外输管线内无液态烃析出。同时,对气-气换热器和低温分离器进行初步选型,并提出了反凝析现象的控制措施。

Discussion on the problem of hydrocarbon dew point of dry gas of a processing plant in Kela Gas Field

The processing plant in Kela gas field uses triethylene glycol(TEG) dehydration process for the sweet gas dehydration. The water dew point of dry gas after TEG dehydration is up to standard but hydrocarbon dew point is higher. As the natural gas has retrograde condensation phenomenon, there will be liquid hydrocarbon precipitation with the decrease of dry gas pressure during the process of transportation, which will do harm to the pipeline, equipment and downstream users to some extent. In order to realize the qualified hydrocarbon dew point and avoid the precipitation of liquid hydrocarbon, the improved process of hydrocarbon dew point control and two kinds of control schemes about hydrocarbon dew point were proposed according to the different rules of Chinese national standards. For ensuring no liquid hydrocarbon in outer transmission pipeline of the processing plant to the initial station in Lunnan, the control requirement of natural gas hydrocarbon dew point was determined to adopt GB 17820-2012 Natural Gas by using HYSYS to simulation and comparison. Meanwhile, the model selection of gas-gas heat exchanger and low temperature separator were achieved, and the control measures of retrograde condensation phenomenon were put forward.