燃煤電站褐煤預干燥系統(tǒng)的集成優(yōu)化與性能分析
發(fā)布時間：2018-07-15 16:27
【摘要】：近年來,隨著中東部優(yōu)質動力煙煤、無煙煤儲量的日益減少以及開采難度的加大,越來越多的電廠開始燃用或摻燒褐煤,褐煤在電力工業(yè)的生產中開始扮演越來越重要的角色。對于直接燃用褐煤的電站而言,由于褐煤熱值低、含水量高、易風化等特點,一般需增設干燥裝置在褐煤送入鍋爐燃燒前對其進行干燥,以降低褐煤中的水分含量。本論文以如何實現褐煤干燥單元與整個熱力系統(tǒng)的高效集成耦合為核心,基于熱力學、傳熱學及技術經濟學等相關理論,對褐煤預干燥過程對入爐煤發(fā)熱量、鍋爐效率、廠用電率等機組熱力性能的影響進行理論分析,并建立了褐煤預干燥發(fā)電系統(tǒng)計算模型。基于該計算模型,本文從熱力學和經濟學角度對傳統(tǒng)褐煤煙氣干燥和蒸汽干燥系統(tǒng)進行了詳細的計算分析,結果表明:傳統(tǒng)褐煤干燥系統(tǒng)具有顯著的節(jié)能效果,對于案例機組,應用煙氣干燥系統(tǒng)和蒸汽干燥系統(tǒng)分別可使機組凈效率提高0.8個百分點和1.0個百分點,凈收益增加約2 000萬元和2 900萬元;但傳統(tǒng)褐煤干燥系統(tǒng)同樣存在很大的局限性,如:排煙余熱量有限、干燥程度較低(煙氣干燥系統(tǒng)),干燥所需的蒸汽量巨大、高品位能量降級利用(蒸汽干燥),這些問題就限制了褐煤干燥電站效率的進一步提高。針對傳統(tǒng)干燥系統(tǒng)的不足和局限性,本文基于能級匹配等原則,提出一種優(yōu)化的集成煙氣干燥與蒸汽干燥的兩級褐煤預干燥發(fā)電系統(tǒng),該系統(tǒng)通過布置兩級干燥單元并應用蒸汽引射器,可充分利用鍋爐排煙余熱和回熱系統(tǒng)低品位抽汽,從而降低干燥所需的蒸汽流量和品位,在保證入爐煤干燥程度的情況下,大幅降低由干燥抽汽帶來的汽輪機做功損失,相關計算結果表明:對于案例機組,應用兩級干燥系統(tǒng)后,機組凈效率可提高1.5個百分點,凈收益可增加約3 700萬元;與傳統(tǒng)煙氣干燥和蒸汽干燥系統(tǒng)相比,兩級干燥系統(tǒng)具有更好的熱力性能及經濟性能。本文的研究結果,為實現我國褐煤電站的優(yōu)化設計和高效運行奠定了科學理論基礎,為褐煤干燥單元與電站熱力系統(tǒng)的高效集成優(yōu)化指明了方向。
[Abstract]:In recent years, with the decrease of anthracite reserves and the increase of mining difficulty, more and more power plants begin to burn or mix lignite, and lignite plays an increasingly important role in the production of electric power industry. For the power station directly burning lignite, because of its low calorific value, high moisture content and easy weathering, it is generally necessary to add a drying device to dry lignite before it is put into the boiler to reduce the moisture content of lignite. Based on the relevant theories of thermodynamics, heat transfer and technical economics, this paper focuses on how to realize the efficient integration and coupling of lignite drying unit with the whole thermodynamic system, and gives rise to the calorific value of lignite pre-drying process and boiler efficiency. Based on the theoretical analysis of the thermal performance of the units such as the power consumption ratio, the calculation model of the lignite pre-drying power generation system is established. Based on the model, the traditional lignite flue gas drying system and steam drying system are calculated and analyzed in detail from the point of view of thermodynamics and economics. The results show that the traditional lignite drying system has remarkable energy saving effect. The application of flue gas drying system and steam drying system can increase the net efficiency of the unit by 0.8% and 1.0% respectively, and increase the net income by about 20 million yuan and 29 million yuan respectively, but the traditional lignite drying system also has great limitations. For example, the heat of exhaust smoke is limited, the drying degree is low (flue gas drying system), the amount of steam needed for drying is huge, and the high grade energy is degraded (steam drying). These problems limit the further improvement of efficiency of lignite drying power station. In view of the shortcomings and limitations of the traditional drying system, based on the principle of energy level matching, an optimized two-stage lignite pre-drying power generation system integrating flue gas drying and steam drying is proposed in this paper. Through the arrangement of two-stage drying units and the application of steam ejector, the system can make full use of the waste heat of boiler exhaust gas and the low-grade extraction of steam from the regenerative system, thus reducing the steam flow and grade required for drying, while ensuring the drying degree of coal into the furnace. The work loss of steam turbine caused by dry extraction is greatly reduced. The results show that: for the case unit, the net efficiency of the unit can be increased by 1.5 percentage points and the net income can be increased by about 37 million yuan after the application of the two-stage drying system; Compared with the traditional flue gas drying system and steam drying system, the two-stage drying system has better thermal and economic performance. The results of this paper lay a scientific theoretical foundation for the optimal design and efficient operation of lignite power stations in China, and point out the direction for the efficient integration and optimization of lignite drying units and thermal systems of power stations.
【學位授予單位】：華北電力大學(北京)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM621
本文編號：2124684
[Abstract]:In recent years, with the decrease of anthracite reserves and the increase of mining difficulty, more and more power plants begin to burn or mix lignite, and lignite plays an increasingly important role in the production of electric power industry. For the power station directly burning lignite, because of its low calorific value, high moisture content and easy weathering, it is generally necessary to add a drying device to dry lignite before it is put into the boiler to reduce the moisture content of lignite. Based on the relevant theories of thermodynamics, heat transfer and technical economics, this paper focuses on how to realize the efficient integration and coupling of lignite drying unit with the whole thermodynamic system, and gives rise to the calorific value of lignite pre-drying process and boiler efficiency. Based on the theoretical analysis of the thermal performance of the units such as the power consumption ratio, the calculation model of the lignite pre-drying power generation system is established. Based on the model, the traditional lignite flue gas drying system and steam drying system are calculated and analyzed in detail from the point of view of thermodynamics and economics. The results show that the traditional lignite drying system has remarkable energy saving effect. The application of flue gas drying system and steam drying system can increase the net efficiency of the unit by 0.8% and 1.0% respectively, and increase the net income by about 20 million yuan and 29 million yuan respectively, but the traditional lignite drying system also has great limitations. For example, the heat of exhaust smoke is limited, the drying degree is low (flue gas drying system), the amount of steam needed for drying is huge, and the high grade energy is degraded (steam drying). These problems limit the further improvement of efficiency of lignite drying power station. In view of the shortcomings and limitations of the traditional drying system, based on the principle of energy level matching, an optimized two-stage lignite pre-drying power generation system integrating flue gas drying and steam drying is proposed in this paper. Through the arrangement of two-stage drying units and the application of steam ejector, the system can make full use of the waste heat of boiler exhaust gas and the low-grade extraction of steam from the regenerative system, thus reducing the steam flow and grade required for drying, while ensuring the drying degree of coal into the furnace. The work loss of steam turbine caused by dry extraction is greatly reduced. The results show that: for the case unit, the net efficiency of the unit can be increased by 1.5 percentage points and the net income can be increased by about 37 million yuan after the application of the two-stage drying system; Compared with the traditional flue gas drying system and steam drying system, the two-stage drying system has better thermal and economic performance. The results of this paper lay a scientific theoretical foundation for the optimal design and efficient operation of lignite power stations in China, and point out the direction for the efficient integration and optimization of lignite drying units and thermal systems of power stations.
【學位授予單位】：華北電力大學(北京)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM621
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