基于风扇磨仓储式制粉系统的褐煤烟气预干燥发电系统分析及优化研究

Exergy Analysis and System Optimization of a Flue Gas Pre-dried Lignite-fired Power System Based on Fan Mill Dryer and Open Pulverizing System

基于风扇磨仓储式制粉系统的褐煤烟气预干燥发电系统建立了全厂分析模型,从热力学第二定律角度探究该系统的节能原理.以某600 MW超临界机组为例,对各级子系统及主要设备展开分析.结果表明:褐煤烟气预干燥发电系统的全厂效率相对常规褐煤发电系统可提高3.42%;采用仓储式制粉系统将干燥乏气与煤粉分离,杜绝了水分在炉内的循环,提高了燃烧温度,有效地降低了燃烧过程的损失,提高了锅炉效率;褐煤烟气预干燥系统的效率只有20.20%,不完善程度较大,通过优化低温炉烟抽取点至省煤器出口,可减小干燥介质混合过程的损失,从而使全厂效率提高0.33%.

An exergy analysis model was deve （FPLPS） based on fan mill dryer and open pu oped for the flue gas pre-dried lignite-fired power system verizing system, so as to explore its energy-saving mechanism from the perspective of the second law of thermodynamics, and to perform exergy analysis for the subsystems and main components of a 600 MW supercritical unit. Results indicate that the efficiency of the plant with FPLPS is relatively 3. 42% higher than that with conventional lignite-fired power system （CLPS）. The improvement of plant efficiency originates from the replacement of high-grade chemical ener- gy by lower-grade flue gas as the heat source for moisture evaporation, during which the exergy destruc- tion is reduced accordingly. Moreover, the dryer exhaust gas is separated from the coal powder in the open pulverizing system, which prevents the evaporated moisture from recycling in the furnace, thus raising the combustion temperature, reducing the inefficiency of the combustion process and increasing the boiler efficiency. However, the dryer exergy efficiency is only 20.20% due to high irreversibility. The retrofitting option by extracting cold flue gas from economizer outlet is estimated to increase the plant efficiency relatively by 0. 33%, benefiting from a reduction of the exergy destruction in the mixing of drying agents.