燃煤电站掺烧污泥热力学与经济性分析

Thermodynamic and economic analysis of co-firing dried sludge in coal-fired power plants

我国污泥产量逐年增加,如何对其进行无害化、资源化处理成为亟待解决的问题,拟将燃煤电站与污泥干燥系统耦合,湿污泥干燥后进行掺烧。以某典型超临界660MW机组为研究对象,在THA工况下,通过对锅炉进行热力计算和对系统整体进行热力学分析及经济性分析,研究掺烧不同含水率(10%、20%、35%、50%、65%)不同掺烧量(2%、4%、6%、8%、10%)的干化污泥对排烟温度、锅炉效率、净发电效率、湿污泥发电折合净效率和干化污泥发电折合净效率等参数的影响。结果表明:当干化污泥含水率超过50%时会导致参数恶化且随掺烧量的增加变化趋势加剧;干化污泥的含水率应控制在50%及以下,若超过此值,掺烧量应小于4%;掺烧污泥导致系统的㶲效率降低,主要原因是锅炉和干燥设备的㶲损失增加;当掺烧含水率为20%,掺烧量为10%的干化污泥时,系统经济性最好,动态回收周期仅为4.02年。

The increasing volume of sewage sludge production in China has created an urgent need for its harmless and resourceful treatment.This paper aims to tackle this issue by adopting a novel strategy that integrates coal-fired power plants with a sewage sludge drying system,in this method,the sludge will be co-fired after being dried.By taking a typical supercritical 660 MW unit as the research object,the influences of moisture content(10%,20%,35%,50%,and 65%)and blending ratio(2%,4%,6%,8%,and 10%)of the dried sludge on parameters such as flue gas temperature,boiler efficiency,net power generation efficiency,equivalent net efficiency of sewage sludge power generation and equivalent net efficiency of dried sludge power generation are investigated through thermodynamic calculation of the boiler and comprehensive thermodynamic and economic analysis of the entire system under THA condition.The results indicate that,when the moisture content of the dried sludge exceeds 50%,it leads to parameter deterioration,and this trend intensifies with an increase in the blending ratio.Considering all factors,it is recommended to maintain the moisture content of the dried sludge at 50%or below,and if it exceeds this value,the blending ratio should be limited to less than 4%.Blending sludge leads to a reduction in the exergy efficiency of the system,which is mainly due to the increasing exergy losses in the boiler and drying equipment.Moreover,the study reveals that the optimal economic performance is achieved when blending the sludge with moisture content of 20%and blending ratio of 10%,in this case the dynamic payback period is only 4.02 years.