褐煤抽气预干燥超临界二氧化碳循环发电系统性能分析

Performance Analysis of Supercritical CO_(2) Lignite-Fired Power Plant Integrated with Gas Extraction Pre-Drying System

为了提高褐煤发电系统能效,提出了一种基于抽气预干燥的褐煤超临界二氧化碳循环发电系统。首先以高温回热器热侧出口工质携带的高温热量为热源预热褐煤,使褐煤中的水分蒸发。其次预干燥褐煤抽气工质在干燥机中放热后,可以进入低温回热器加热冷侧低温工质,减少能量损失。基于热力学第一、第二定律,建立了新型超临界二氧化碳动力循环褐煤发电系统与褐煤预干燥系统高效耦合热力计算模型,并对直燃褐煤发电系统和褐煤抽气预干燥发电系统进行对比分析。以内蒙古锡林浩特胜利煤田原煤为例进行计算,结果表明:相比于直燃褐煤发电系统,褐煤抽气预干燥发电系统通过利用高温抽气干燥褐煤,可以使发电效率提高1.50%,发电标准煤耗率降低8.41 g·(kW·h)^(-1);进一步[火用]分析结果显示,系统能效的提高主要得益于锅炉燃烧[火用]损的降低,预干燥褐煤使得锅炉燃烧[火用]损降低4.47%,故系统[火用]效率提高1.34%;干燥机效率和褐煤干燥程度越高,褐煤抽气预干燥发电系统节能潜力越大。

To improve the energy efficiency of the lignite-fired power plant, a supercritical CO_(2)lignite-fired power plant integrated with gas extraction pre-drying system is proposed. Firstly, the high temperature heat carried by the working medium at the hot side outlet of the high temperature regenerator is used as the heat source to preheat the lignite to evaporate the water in the lignite. Secondly, the working fluid after releasing heat in the dryer enters the low temperature regenerator to heat the low temperature working fluid on the cold side to reduce energy loss. Based on the first and second laws of thermodynamics, the thermodynamic calculation model of a novel high-efficiency coupled system of supercritical CO_(2)lignite-fired power plant and gas extraction pre-drying system are established, and a comparative analysis is made between the direct-fired lignite power plant and the lignite-fired power plant integrated with gas extraction pre-drying system. Taking the lignite from the Shengli coalfield in Xilinhot, Inner Mongolia as an example, the calculation is carried out. Results show that the gas extraction pre-drying lignite can increase the power generation efficiency by 1.50% and reduce the standard coal consumption rate by 8.41 g·(kW·h)^(-1). Exergy analysis further shows that the gas extraction pre-drying lignite reduces the combustion exergy destruction of the boiler by 4.47%, which increases the exergy efficiency of the lignite-fired power plant by 1.34%. And the improvement of system exergy efficiency is mainly contributed to the reduction of the exergy destruction during the boiler combustion. The higher the dryer efficiency and the lignite drying degree, the greater the energy-saving potential of the lignite-fired power plant integrated with gas extraction pre-drying system.