污泥干燥及其与燃煤电站耦合的热力特性分析

Thermodynamic characteristic analysis of sewage sludge drying and its integration with coal-fired power plant

如何对污泥进行低成本的无害化处理及资源化利用已经成为亟待解决的问题。首先基于传热传质的原理建立了污泥干燥过程的热力模型;其次提出了污泥干燥过程的综合评价指标,从热力学第二定律的角度对干燥过程所耗热量和功量进行综合评价;最后对污泥干燥过程与燃煤电站耦合的系统进行热力学分析。结果显示:与发电系统耦合时,在满足换热温差的前提下,风泥比为3.32时的干燥综合能耗为最低;相比案例机组,耦合系统的供电量和供电效率有较大的提升;此外敏感性分析发现,干燥机压损比例的增加会使干燥综合能耗有不同程度的增加;考虑因掺烧污泥导致锅炉效率降低时的供电效率有一定的下降。

How to dispose the sewage sludge in a harmless way at low cost and utilize sewage sludge as resource has been an urgent problem to be solved. On the basis of the principle of heat and mass transfer, this paper firstly establishes the thermodynamic model of the sewage sludge drying process. Then, it proposes the comprehensive evaluation criterion of the sewage sludge drying process, which can assess the consumed heat and power in the drying process from the viewpoint of the second law of thermodynamics. Finally, the thermodynamic performance of the proposed system integrating sewage sludge drying process and coal-fired power plant is assessed. The results show that, when integrating with the coal-fired power plant and under the premise of the required heat transfer temperature difference is ensured, the comprehensive energy consumption reaches the lowest when the ratio of air to sewage sludge is 3.32. Compared with the reference case, the net power output and net thermal efficiency of the hybrid system are promoted. Furthermore, sensitivity analysis reveals that, the increase of pressure drop of the dryer will result in an increment of comprehensive energy consumption of drying process, and the system net thermal efficiency drops when considering the decrease of boiler efficiency owing to the co-incineration of coal and sewage sludge.