【摘要】：隨著我國對天然氣等清潔能源的需求逐漸增大,液化天然氣(Liquefied Natural Gas,簡稱LNG)行業(yè)進(jìn)入蓬勃發(fā)展期,LNG在能源消費(fèi)中的比例不斷增大,進(jìn)口額逐年增加。在LNG儲(chǔ)運(yùn)過程中,LNG接收站處于進(jìn)口轉(zhuǎn)運(yùn)的重要環(huán)節(jié),我國LNG接收站建設(shè)發(fā)展進(jìn)入黃金期。但隨著接收站建設(shè)的加快和運(yùn)營規(guī)模的擴(kuò)大,接收站蒸發(fā)氣(Boiling Off Gas,簡稱BOG)的處理和工藝控制的難度日益增加,出現(xiàn)了諸如BOG處理能耗大,控制系統(tǒng)穩(wěn)定等問題。我國LNG接收站BOG處理大多采用再冷凝工藝,有必要對接收站BOG再冷凝工藝和控制系統(tǒng)進(jìn)行優(yōu)化研究。本文以某LNG接收站現(xiàn)場參數(shù)為依據(jù),著重對該接收站BOG再冷凝工藝和控制方案進(jìn)行研究,在合理分析的基礎(chǔ)上提出可行的優(yōu)化方案。主要內(nèi)容如下:(1)建立接收站設(shè)備單元模型,計(jì)算BOG產(chǎn)生量;建立接收站靜態(tài)模型,采用單因素變量法對再冷凝工藝中的關(guān)鍵參數(shù)進(jìn)行變量研究,分析BOG再冷凝系統(tǒng)涉及的主要影響因素,得出接收站再冷凝系統(tǒng)運(yùn)行的一般規(guī)律。(2)根據(jù)該接收站BOG處理工藝現(xiàn)狀,提出用高壓泵出口低溫LNG對進(jìn)入再冷凝器前BOG降溫的預(yù)冷式再冷凝工藝,計(jì)算兩種工藝安全平穩(wěn)運(yùn)行所需最小外輸量。以接收站允許最小外輸量為基礎(chǔ),對不同再冷凝工藝進(jìn)行比較,采用預(yù)冷式再冷凝工藝,把BOG溫度由-42.2℃預(yù)冷到-100℃后送入再冷凝器,在BOG處理量相同時(shí),可使最小外輸量降低15.02%,系統(tǒng)總能耗降低8.7%。通過流程優(yōu)化得出預(yù)冷式再冷凝工藝操作參數(shù)選取的關(guān)鍵點(diǎn)。(3)依據(jù)接收站控制方案建立再冷凝系統(tǒng)動(dòng)態(tài)模型,并添加實(shí)際生產(chǎn)中可能出現(xiàn)的不同擾動(dòng),觀察系統(tǒng)的動(dòng)態(tài)響應(yīng),發(fā)現(xiàn)當(dāng)前再冷凝控制系統(tǒng)存在BOG處理量波動(dòng)較大時(shí),再冷凝系統(tǒng)壓力、冷凝LNG流量,尤其是再冷凝器液位控制不穩(wěn)定的問題。(4)分析當(dāng)前控制系統(tǒng)存在的問題主要由再冷凝器壓力采用串級比值控制方式引起。提出為再冷凝器添加一條直接用冷凝LNG流量調(diào)節(jié)再冷凝器壓力的控制回路,當(dāng)BOG處理量較平穩(wěn)時(shí),再冷凝器壓力使用原有串級比值控制方式,當(dāng)BOG處理量波動(dòng)較大時(shí),再冷凝器壓力控制切換至增設(shè)的直接反饋控制方式。以此解決當(dāng)前再冷凝器控制不穩(wěn)定的問題。本文從工藝和控制系統(tǒng)兩個(gè)角度對接收站BOG再冷凝系統(tǒng)進(jìn)行了優(yōu)化研究,研究成果能為接收站再冷凝系統(tǒng)的優(yōu)化改進(jìn)提供一定的參考和支持。
[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，

本文編號：2174414