基于褐煤干燥技术的机炉热集成优化系统

Lignite Drying Technology-based Turbine-boiler Thermal Integrated System

在褐煤机组抽汽干燥系统的基础上,结合锅炉尾部烟气余热利用技术,提出了一种机炉热集成优化系统,利用褐煤干燥时蒸发的尾气预热空预器入口空气,同时在省煤器后的旁路烟道内加装两级烟水换热器,加热部分凝结水,节省汽轮机回热抽汽,从而进一步提高机组效率。结合某600MW超临界褐煤机组,分析对比了常规抽汽干燥系统和机炉热集成优化系统的热力学特性和综合节能效果,并初步探讨了优化系统的技术经济学性能。结果表明:案例机组在优化系统下可降低供电煤耗4.3 g/(k W·h),按年运行5 000 h计算,优化系统每年可减少标煤量1.29万t,年节约燃料费700余万元(按褐煤标煤560元/t计),静态投资回收期仅为3.3年,经济效益显著。

On the basis of the conventional steam extraction drying system for lignite-fired units,proposed was a type of turbine-boiler thermal integration and optimization system in combination with the flue gas waste heat utilization technology for use in the tail portions of boilers. The steam exhausted from the drying of the lignite was utilized to pre-heat the air at the inlet of the air preheater and at the same time,two stages of flue gas-water heat exchanger were additionally installed in the bypass flue gas duct after the economizer to heat a part of condensate water to save the amount of steam extracted from the steam turbine into the recuperator,thus further enhancing the efficiency of the unit. With a 600 MW supercritical lignite-fired unit serving as an example,through adopting the software Ebsilon Pro,the authors analyzed and contrasted the thermodynamic characteristics and comprehensive energy saving effectiveness of the conventional steam extraction drying system and turbine-boiler thermal integration and optimization system with their cost-effectiveness performance of the optimization system being preliminarily explored. It has been found that the exemplary unit can reduce the power supply coal consumption rate by 4. 3 g /( k W·h) if the optimization system is adopted when compared with the case if the conventional system is adopted. Therefore,the optimization system can cut down the standard coal consumption quantity of more than 12 900 tons each year as calculated according to the operation time duration in each year having 5 000 hours,thus annually saving the fuel expenses of more than RMB 7 million yuan( calculated as per the standard coal price of RMB 560 yuan / ton) and the static in-vestment payback period being only 3. 3 years,boasting outstanding economic benefits