褐煤抽汽预干燥发电系统变负荷特性仿真研究

Simulation Study on the Part-Load Performance of Steam Pre-Dried Lignite-Fired Power System

燃褐煤发电机组投资大、效率低,采用汽轮机抽汽为热源对褐煤进行预干燥,是提高褐煤发电效率的有效手段。本文结合某600 MW机组,采用Aspen plus建立了系统变工况仿真模型,验证了模型的准确性,并基于此模型仿真研究了系统的变工况特性,结果表明:褐煤预干燥使得锅炉燃烧温度升高,烟气量降低,烟气酸露点下降;褐煤抽汽预干燥发电系统发电标准煤耗率随着机组负荷下降而增大,并且增大速度较直接燃褐煤发电机组快,在机组负荷下降至50%左右时,采用汽轮机抽汽对褐煤进行预干燥便不再节煤。

Conventional lignite-fired power plants,firing lignite directly,have many shortcomings,including low efficiency and high investment.The pre-drying of lignite,using steam extracted from steam turbines as heat source,is a potential way to increase the power generation efficiency.Based on a 600 MW reference case,the system simulation models were developed with Aspen Plus and validated in this paper.Then,the part-load performance of power systems was simulated and analyzed.Results show that the pre-drying could increase the combustion temperature of lignite,and decrease the acid dew point and flow rate of flue gas.The power generation efficiency of pre-dried lignite-fired power system decreases with the power load,and the descent rate of efficiency is bigger than that of conventional lignite-fired power system.As a result,the pre-drying of lignite is not energy saving when the power load ratio is smaller than 50%.