LNG接收站BOG再冷凝系统优化研究
发布时间：2018-08-09 14:44
【摘要】：随着我国对天然气等清洁能源的需求逐渐增大,液化天然气(Liquefied Natural Gas,简称LNG)行业进入蓬勃发展期,LNG在能源消费中的比例不断增大,进口额逐年增加。在LNG储运过程中,LNG接收站处于进口转运的重要环节,我国LNG接收站建设发展进入黄金期。但随着接收站建设的加快和运营规模的扩大,接收站蒸发气(Boiling Off Gas,简称BOG)的处理和工艺控制的难度日益增加,出现了诸如BOG处理能耗大,控制系统稳定等问题。我国LNG接收站BOG处理大多采用再冷凝工艺,有必要对接收站BOG再冷凝工艺和控制系统进行优化研究。本文以某LNG接收站现场参数为依据,着重对该接收站BOG再冷凝工艺和控制方案进行研究,在合理分析的基础上提出可行的优化方案。主要内容如下:(1)建立接收站设备单元模型,计算BOG产生量;建立接收站静态模型,采用单因素变量法对再冷凝工艺中的关键参数进行变量研究,分析BOG再冷凝系统涉及的主要影响因素,得出接收站再冷凝系统运行的一般规律。(2)根据该接收站BOG处理工艺现状,提出用高压泵出口低温LNG对进入再冷凝器前BOG降温的预冷式再冷凝工艺,计算两种工艺安全平稳运行所需最小外输量。以接收站允许最小外输量为基础,对不同再冷凝工艺进行比较,采用预冷式再冷凝工艺,把BOG温度由-42.2℃预冷到-100℃后送入再冷凝器,在BOG处理量相同时,可使最小外输量降低15.02%,系统总能耗降低8.7%。通过流程优化得出预冷式再冷凝工艺操作参数选取的关键点。(3)依据接收站控制方案建立再冷凝系统动态模型,并添加实际生产中可能出现的不同扰动,观察系统的动态响应,发现当前再冷凝控制系统存在BOG处理量波动较大时,再冷凝系统压力、冷凝LNG流量,尤其是再冷凝器液位控制不稳定的问题。(4)分析当前控制系统存在的问题主要由再冷凝器压力采用串级比值控制方式引起。提出为再冷凝器添加一条直接用冷凝LNG流量调节再冷凝器压力的控制回路,当BOG处理量较平稳时,再冷凝器压力使用原有串级比值控制方式,当BOG处理量波动较大时,再冷凝器压力控制切换至增设的直接反馈控制方式。以此解决当前再冷凝器控制不稳定的问题。本文从工艺和控制系统两个角度对接收站BOG再冷凝系统进行了优化研究,研究成果能为接收站再冷凝系统的优化改进提供一定的参考和支持。
[Abstract]:With the increasing demand for clean energy such as natural gas in China, the proportion of LNG in energy consumption is increasing and the import amount is increasing year by year. In the process of LNG storage and transportation, the LNG receiving terminal is in the important link of import transshipment, and the construction and development of LNG receiving station in China has entered the golden period. However, with the acceleration of the construction of the receiving station and the expansion of the operation scale, the processing and process control of the evaporative gas (BOG) of the receiving station is becoming increasingly difficult, such as the large energy consumption of the BOG processing, the stability of the control system, and so on. The BOG treatment of LNG receiving station in China mostly adopts recondensation process. It is necessary to optimize the recondensation process and control system of BOG receiving station in China. Based on the field parameters of a certain LNG receiving station, this paper focuses on the study of the BOG recondensation process and control scheme of the receiving station, and puts forward a feasible optimization scheme on the basis of reasonable analysis. The main contents are as follows: (1) the equipment unit model of the receiving station is established to calculate the BOG output, the static model of the receiving station is established, and the key parameters in the recondensation process are studied by single factor variable method. The main influencing factors involved in the BOG recondensation system are analyzed, and the general rules of the operation of the recondensation system at the receiving station are obtained. (2) according to the status of the BOG treatment process at the receiving station, A precooled recondensation process for BOG cooling before entering the recondenser is proposed by using low temperature LNG at the outlet of the high pressure pump. The minimum external transport required for the safe and stable operation of the two processes is calculated. On the basis of the allowable minimum external transport at the receiving station, the different recondensation processes are compared. The BOG temperature is precooled from -42.2 鈩，
本文编号：2174414
[Abstract]:With the increasing demand for clean energy such as natural gas in China, the proportion of LNG in energy consumption is increasing and the import amount is increasing year by year. In the process of LNG storage and transportation, the LNG receiving terminal is in the important link of import transshipment, and the construction and development of LNG receiving station in China has entered the golden period. However, with the acceleration of the construction of the receiving station and the expansion of the operation scale, the processing and process control of the evaporative gas (BOG) of the receiving station is becoming increasingly difficult, such as the large energy consumption of the BOG processing, the stability of the control system, and so on. The BOG treatment of LNG receiving station in China mostly adopts recondensation process. It is necessary to optimize the recondensation process and control system of BOG receiving station in China. Based on the field parameters of a certain LNG receiving station, this paper focuses on the study of the BOG recondensation process and control scheme of the receiving station, and puts forward a feasible optimization scheme on the basis of reasonable analysis. The main contents are as follows: (1) the equipment unit model of the receiving station is established to calculate the BOG output, the static model of the receiving station is established, and the key parameters in the recondensation process are studied by single factor variable method. The main influencing factors involved in the BOG recondensation system are analyzed, and the general rules of the operation of the recondensation system at the receiving station are obtained. (2) according to the status of the BOG treatment process at the receiving station, A precooled recondensation process for BOG cooling before entering the recondenser is proposed by using low temperature LNG at the outlet of the high pressure pump. The minimum external transport required for the safe and stable operation of the two processes is calculated. On the basis of the allowable minimum external transport at the receiving station, the different recondensation processes are compared. The BOG temperature is precooled from -42.2 鈩，
本文编号：2174414
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