集成乏气水回收的褐煤预干燥发电系统节能与节水协同机制研究

Lignite is one of the main fuels for thermal power generation in China. However, the high moisture content always results in low efficiencies of lignite-direct-fired power plants. Through the integration of lignite pre-drying and water recovery from drying exhaust gas, energy and water conservation can be realized simultaneously. To achieve this goal, theoretical analysis, simulation modeling, and experimental investigation will be carried out. Firstly, the energy coupling mechanism of lignite pre-drying, drying exhaust gas water recovery and power generation processes will be studied. Then simulation models of the thermal system for overall working conditions and water conservation analysis models for overall processes will be developed. By revealing the energy matching mechanisms in thermodynamic processes, energy and water saving potentials of various process structures, including different pre-drying integrations and heat sources, and water recovery schemes will be demonstrated. Moreover, the influences of complex external factors, including power loads, ambient conditions, and fuel types, on the energy and water saving potentials will be analyzed quantitatively. Optimization strategies for energy and water conservation will be provided through the system coupling of lignite pre-drying and drying exhaust gas water recovery. System configuration principles of water recovery system applicable to different fuel types and drying methods will thus be obtained. In addition, experiments will be conducted to explore the convection-condensation heat transfer characteristics of dusty vapor/air mixture. On this basis, efficient configurations of heat exchangers will be established. The aim of the project is to provide theoretical and technical fundamentals for the energy and water conservation in lignite pre-drying power systems. The research in this project will effectively improve the comprehensive benefits of lignite power generation, and enrich the theoretical framework of synergistic energy and water conservation in thermal systems.

褐煤是我国火力发电的重要燃料之一。褐煤中水分含量高导致直接燃褐煤发电效率普遍偏低，而通过集成褐煤预干燥和乏气水回收，有望实现褐煤发电系统节能节水的双重目标。为此，本课题拟采用理论分析、仿真模拟与实验研究相结合的方法，从褐煤预干燥、乏气水回收与燃煤发电过程的耦合机制出发，建立热力系统全工况仿真和全过程水平衡分析模型，通过优化各热力过程的能量匹配机制，研究采用不同干燥方式、热源和乏气水回收方式的节能节水特性，及其在负荷、环境、煤质等外部条件影响下的定量变化规律，获得通过褐煤预干燥和乏气水回收的系统耦合实现节能节水的协同策略，进而形成适应不同褐煤水分及干燥方式的乏气水回收系统构型；另外，通过实验研究查清含尘湿空气的对流-凝结换热特性，进而构建高效的乏气水回收换热系统结构。本项目旨在为实现褐煤发电系统的节能节水提供理论和技术基础，有效提高褐煤发电的综合效益，同时可以丰富热力系统节能节水的理论体系。

本项目以褐煤高效节水发电为研究背景，对集成乏气水回收的褐煤预干燥发电系统节能节水机理、全工况特性及含灰含湿乏气的对流-凝结换热和积灰特性开展了系统研究。提出了一种新型褐煤烟气预干燥-乏气深度水回收-乏气再循环系统，建立了系统的能量耦合和水平衡分析模型，定量研究了系统在不同设计参数下（乏气再循环率、乏气水回收率、煤中水分脱除率等）的节能和节水潜力，并提出了干燥提质因子揭示了系统节能原理；同时，对比分析了褐煤预干燥发电系统与锅炉烟气余热深度利用系统的㶲损分布和技术经济性，进一步揭示了系统的节能机理和技术可行性。同时，提出了不同类型的干燥乏气水回收和废水水回收系统，定量分析了不同集成构型的节能和节水潜力。在此基础上，建立了系统的能耗-环境影响分析模型，获得了集成乏气水回收的褐煤预干燥发电系统的节能、环保潜力。为分析褐煤预干燥发电系统的变工况能耗特性，建立了机炉耦合仿真模型，定量研究了外部运行条件（机组负荷、环境温度、原煤水分）及内部干燥过程参数（干燥程度、干燥机热效率、干燥乏气温度）变化对系统热力参数和节能潜力的影响规律。同时，建立了含灰含湿气体对流冷凝换热实验平台，实验研究了水平管束外含灰含湿气体对流冷凝换热的动态变化规律，获得了对流冷凝稳态换热特性，并据此提出了不同运行参数下的吹灰策略。本项目研究结果进一步丰富了热力系统和热力过程的能效评价机制、完善了能量梯级利用的设计及理论分析方法，为燃褐煤机组的优化设计提供了理论依据和技术基础。基于上述研究结果，在国内外期刊和会议上发表文章23篇，其中SCI检索论文10篇（含ESI热点论文、高被引论文2篇），参编英文专著章节1章，核心技术授权发明专利5项，协助培养博士和硕士研究生6名。