某LNG接收站再冷凝工藝優(yōu)化及控制方案設計
發(fā)布時間：2018-12-28 12:05
【摘要】：液化天然氣(Liquefied Natural Gas,即LNG)是當今世界發(fā)展最快的一種優(yōu)質(zhì)、清潔能源。作為液化天然氣產(chǎn)業(yè)鏈中較為重要的環(huán)節(jié)——LNG接收站,是LNG氣源與用戶管網(wǎng)的連接單元。近些年來,我國在大規(guī)模推動LNG接收站的建設,截至2014年底,我國在建LNG接收站24座,已投產(chǎn)10座。LNG接收站工藝系統(tǒng)卸料、壓縮機、泵等動設備運轉(zhuǎn)、外界熱量的導入、環(huán)境變化等因素將引起儲罐、設備及管線內(nèi)產(chǎn)生大量蒸發(fā)氣(Boil Off Gas,即BOG)。BOG氣體若處理不當,會影響裝置的運行,造成資源浪費和環(huán)境污染等問題。因此,接收站BOG處理單元的穩(wěn)定、安全、經(jīng)濟運行十分重要。 目前,LNG接收站BOG處理工藝普遍采用再冷凝工藝。 本論文利用Aspen HYSYS對某LNG接收站再冷凝工藝進行模擬分析及用能分析。結果表明：有效能損失最嚴重的單元為再氣化系統(tǒng),有效能損失占全流程的80%,其次是高壓泵和壓縮機,分別為17%,2.8%。 在對某LNG接收站再冷凝工藝進行模擬分析及用能分析的基礎上,對再冷凝工藝進行了參數(shù)優(yōu)化與流程改進。通過靈敏度分析選取LNG流量、LNG中CH4含量、LNG外輸壓力及BOG排出壓力為關鍵參數(shù),采用響應面法分析關鍵參數(shù)的交互程度并擬合得到這四個參數(shù)關于總能耗關系的方程,將此方程代入Matlab,以總能耗為目標函數(shù),求得最優(yōu)操作參數(shù),最終,總能耗降低15.06%。針對再冷凝工藝中外輸氣負荷低時運行困難及壓縮機能耗高等問題,對再冷凝工藝進行改進,在兩級壓縮機中間增加一臺再冷凝器,將部分BOG氣體冷凝液化為LNG,用LNG泵增壓,以達到緩解外輸負荷低時一個再冷凝器難以運行及降低壓縮機能耗的目的。經(jīng)計算,改進工藝的壓縮機能耗減少135.76kW,降低百分比約為45.56%,工藝總能耗降低13.98%,節(jié)能效果顯著。同時對改進工藝進行主要設備計算及裝置設備平面布置。 本論文對改進工藝進行了控制方案初步設計,并著重對整個LNG接收站自控系統(tǒng)的核心設備——BOG壓縮機及再冷凝器等的控制方案進行論述,以改善工藝的操作彈性,使裝置能更好適應接收站輸氣負荷的波動。
[Abstract]:Liquefied natural gas (Liquefied Natural Gas,) is the world's fastest growing quality, clean energy. As an important link in LNG industry chain, LNG receiving station is the connection unit between LNG gas source and user network. In recent years, China has been promoting the construction of LNG receiving stations on a large scale. By the end of 2014, 24 LNG receiving stations were under construction in our country, and 10 of them had been put into production. The process systems of LNG receiving stations, such as unloading materials, compressors, pumps, and so on, operated and imported heat from the outside. Factors such as environmental change will cause a large amount of evaporative gas (Boil Off Gas,) in storage tanks, equipments and pipelines. If the gas is not treated properly, it will affect the operation of the device and lead to the waste of resources and environmental pollution. Therefore, the receiving station BOG processing unit stability, security, economic operation is very important. At present, the BOG treatment process of LNG receiving station generally adopts recondensation process. In this paper, Aspen HYSYS is used to simulate and analyze the recondensation process of a LNG receiving station. The results show that the unit with the most serious effective loss is the regasification system, and the efficiency loss accounts for 80% of the whole process, followed by the high pressure pump and compressor, which are 172.8% respectively. Based on the simulation analysis and energy use analysis of the recondensation process at a LNG receiving station, the parameter optimization and process improvement of the recondensation process are carried out. LNG flow rate, CH4 content in LNG, LNG transport pressure and BOG discharge pressure are selected as key parameters by sensitivity analysis. The interaction degree of key parameters is analyzed by response surface method and the equation of total energy consumption is obtained by fitting the four parameters. Taking the total energy consumption as the objective function, the optimal operating parameters are obtained by using this equation in Matlab,. Finally, the total energy consumption is reduced by 15.06. Aiming at the problems of difficult operation and high energy consumption of recondensing process when the gas transmission load is low at home and abroad, the recondensing process is improved, a recondenser is added in the middle of the two-stage compressor, and part of BOG gas condensing and liquefaction is added to the LNG pump for LNG,. In order to reduce the energy consumption of compressor, it is difficult for a recondenser to operate when the load is low. The calculated results show that the energy consumption of the improved process is reduced by 135.76kW, and the reduction percentage is about 45.56kW, the total energy consumption of the process is reduced by 13.98kW, and the energy saving effect is remarkable. At the same time, the main equipment calculation and the layout of the equipment are carried out. In this paper, the control scheme of the improved technology is designed, and the control scheme of BOG compressor and recondenser, which is the core equipment of the automatic control system of the whole LNG receiving station, is discussed in order to improve the operation flexibility of the process. The device can better adapt to the fluctuation of the gas load at the receiving station.
【學位授予單位】：西南石油大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TE83;TE974
[Abstract]:Liquefied natural gas (Liquefied Natural Gas,) is the world's fastest growing quality, clean energy. As an important link in LNG industry chain, LNG receiving station is the connection unit between LNG gas source and user network. In recent years, China has been promoting the construction of LNG receiving stations on a large scale. By the end of 2014, 24 LNG receiving stations were under construction in our country, and 10 of them had been put into production. The process systems of LNG receiving stations, such as unloading materials, compressors, pumps, and so on, operated and imported heat from the outside. Factors such as environmental change will cause a large amount of evaporative gas (Boil Off Gas,) in storage tanks, equipments and pipelines. If the gas is not treated properly, it will affect the operation of the device and lead to the waste of resources and environmental pollution. Therefore, the receiving station BOG processing unit stability, security, economic operation is very important. At present, the BOG treatment process of LNG receiving station generally adopts recondensation process. In this paper, Aspen HYSYS is used to simulate and analyze the recondensation process of a LNG receiving station. The results show that the unit with the most serious effective loss is the regasification system, and the efficiency loss accounts for 80% of the whole process, followed by the high pressure pump and compressor, which are 172.8% respectively. Based on the simulation analysis and energy use analysis of the recondensation process at a LNG receiving station, the parameter optimization and process improvement of the recondensation process are carried out. LNG flow rate, CH4 content in LNG, LNG transport pressure and BOG discharge pressure are selected as key parameters by sensitivity analysis. The interaction degree of key parameters is analyzed by response surface method and the equation of total energy consumption is obtained by fitting the four parameters. Taking the total energy consumption as the objective function, the optimal operating parameters are obtained by using this equation in Matlab,. Finally, the total energy consumption is reduced by 15.06. Aiming at the problems of difficult operation and high energy consumption of recondensing process when the gas transmission load is low at home and abroad, the recondensing process is improved, a recondenser is added in the middle of the two-stage compressor, and part of BOG gas condensing and liquefaction is added to the LNG pump for LNG,. In order to reduce the energy consumption of compressor, it is difficult for a recondenser to operate when the load is low. The calculated results show that the energy consumption of the improved process is reduced by 135.76kW, and the reduction percentage is about 45.56kW, the total energy consumption of the process is reduced by 13.98kW, and the energy saving effect is remarkable. At the same time, the main equipment calculation and the layout of the equipment are carried out. In this paper, the control scheme of the improved technology is designed, and the control scheme of BOG compressor and recondenser, which is the core equipment of the automatic control system of the whole LNG receiving station, is discussed in order to improve the operation flexibility of the process. The device can better adapt to the fluctuation of the gas load at the receiving station.
【學位授予單位】：西南石油大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TE83;TE974
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