燃煤电站褐煤预干燥系统的集成优化与性能分析

发布时间：2018-07-15 16:27

【摘要】：近年来,随着中东部优质动力烟煤、无烟煤储量的日益减少以及开采难度的加大,越来越多的电厂开始燃用或掺烧褐煤,褐煤在电力工业的生产中开始扮演越来越重要的角色。对于直接燃用褐煤的电站而言,由于褐煤热值低、含水量高、易风化等特点,一般需增设干燥装置在褐煤送入锅炉燃烧前对其进行干燥,以降低褐煤中的水分含量。本论文以如何实现褐煤干燥单元与整个热力系统的高效集成耦合为核心,基于热力学、传热学及技术经济学等相关理论,对褐煤预干燥过程对入炉煤发热量、锅炉效率、厂用电率等机组热力性能的影响进行理论分析,并建立了褐煤预干燥发电系统计算模型。基于该计算模型,本文从热力学和经济学角度对传统褐煤烟气干燥和蒸汽干燥系统进行了详细的计算分析,结果表明:传统褐煤干燥系统具有显著的节能效果,对于案例机组,应用烟气干燥系统和蒸汽干燥系统分别可使机组净效率提高0.8个百分点和1.0个百分点,净收益增加约2 000万元和2 900万元;但传统褐煤干燥系统同样存在很大的局限性,如:排烟余热量有限、干燥程度较低(烟气干燥系统),干燥所需的蒸汽量巨大、高品位能量降级利用(蒸汽干燥),这些问题就限制了褐煤干燥电站效率的进一步提高。针对传统干燥系统的不足和局限性,本文基于能级匹配等原则,提出一种优化的集成烟气干燥与蒸汽干燥的两级褐煤预干燥发电系统,该系统通过布置两级干燥单元并应用蒸汽引射器,可充分利用锅炉排烟余热和回热系统低品位抽汽,从而降低干燥所需的蒸汽流量和品位,在保证入炉煤干燥程度的情况下,大幅降低由干燥抽汽带来的汽轮机做功损失,相关计算结果表明:对于案例机组,应用两级干燥系统后,机组净效率可提高1.5个百分点,净收益可增加约3 700万元;与传统烟气干燥和蒸汽干燥系统相比,两级干燥系统具有更好的热力性能及经济性能。本文的研究结果,为实现我国褐煤电站的优化设计和高效运行奠定了科学理论基础,为褐煤干燥单元与电站热力系统的高效集成优化指明了方向。
[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.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621

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