集成低温热解的褐煤预干燥发电系统节能理论研究

Lignite is becoming a main fuel for power generation in China. However, direct lignite-fired power plant always faces some short comings including high investment and low thermal efficiency due to the high moisture content in lignite. It is an effective way to improve the thermal efficiency of lignite-fired power system to pre-dry lignite with the low grade energy in power system. The low temperature pyrolysis system is integrated in pre-dried lignite-fired power system in this project to produce high value-added products, i.e. tar and gas. Moreover, the waste heat released in the pyrolysis and drying process is recovered. Therefore, the heat, electricity, tar, gas, and water could be cogenerated in pre-dried lignite-fired power system integrated with low temperature pyrolysis system, and the comprehensive utilization efficiency of lignite could be increased. The energy coupling mechanism of lignite pre-drying, low temperature pyrolysis, power generation and waste heat recovery process will be studied. The aim is to reveal the energy matching mechanism in thermodynamic process. Then the process simulation model will be developed, based on which the thermal economic of power system with various process structures under complex external factors will be analyzed quantitatively. The thermal system of power generation process will be optimized and the system comprehensive evaluation method of energy efficiency will be obtained. The direct contacting with water is proposed to recover the waste heat and water in the dryer exhaust. The performance of this recovery system will be researched with theoretical and experimental methods. The heat transfer characteristics of dusty saturated moist air will be studied, and the efficient recovery system of waste heat and water will be optimized. The research in this project can enrich the theoretical system of the thermal system energy saving, and greatly improve the level of lignite utilization.

褐煤已逐渐成为我国火力发电行业的主要燃料之一，因其高含水率导致直接燃褐煤发电机组投资大、效率低。采用燃煤发电过程的低品位能量对褐煤进行预干燥，是提高褐煤利用效率的有效手段。在此基础上，进一步集成低温热解系统制取高附加值的焦油和煤气，同时回收预干燥和低温热解过程的废热及干燥乏气中的水分，实现热、电、焦油、煤气和水等的联产，有望进一步提高褐煤综合利用水平。本课题从褐煤预干燥、低温热解、发电与废热回收过程的能量耦合机制出发，揭示各热力过程能量的匹配机理，建立全系统流程仿真模型，得到多种系统流程结构在复杂外部因素条件下热经济性变化的定量规律，实现褐煤发电过程的节能优化，进而获得系统的综合能效评价方法；同时，提出采用与水直接接触的方式同时回收干燥乏气的热能和水分，研究获得回收过程中涉及的含尘饱和湿空气与水直接接触的凝结换热特性。该项目研究可丰富热力系统节能的理论体系，大幅度提高褐煤综合利用水平。

褐煤已逐渐成为我国火力发电行业的主要燃料之一，因其高含水率导致直接燃褐煤发电机组投资大、效率低。采用燃煤发电过程的低品位能量对褐煤进行预干燥，是提高褐煤利用效率的有效手段。在此基础上，进一步集成低温热解系统制取高附加值的焦油和煤气，有望进一步提高褐煤综合利用水平。本项目针对这一系统的关键基础问题展开研究：.首先，项目揭示了系统节能的机理为预干燥使褐煤燃烧过程的不可逆损失显著下降，进而建立了褐煤预干燥、低温热解等过程的计算分析模型，研究获得了不同褐煤干燥、低温热解热源种类及其能量供应系统对系统热经济性的定量影响规律。然后，研究获得了负荷、环境等参数变化对系统热经济性的定量影响规律，发现抽汽干燥的节能潜力随着负荷率的降低而降低，但烟气干燥的节能潜力基本不受负荷率的影响。最后，针对褐煤干燥乏气热能与水高效回收的问题展开了实验研究，得到干燥乏气成分、压力、流速，冷却水温度等对凝结换热特性的影响规律，建立了凝结换热模型和换热器设计理论模型。.基于以上研究成果，项目负责人获2017年国家科技进步二等奖（第4完成人）、2016年陕西省科学技术奖一等奖（第8完成人），发表SCI检索论文8篇、EI检索论文5篇，做国际、国内学术会议特邀报告各1次，发表其他国际、国内会议论文7篇，申请发明专利8项，授权4项。项目执行期间，项目组有1位博士研究生、3位硕士研究生毕业，项目负责人获评陕西省普通高校“青年杰出人才”。