超临界水中煤气化制氢热力发电系统的构建以及能量转化机理分析

发布时间：2018-03-02 08:27

本文关键词： 超临界水煤制氢火用效率图像火用分析　出处：《西安建筑科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：煤是当今火力发电最重要的燃料，但是煤在空气中直接燃烧生成NOx、SOx、CO2和PM2.5等污染物。超临界水中煤气化制氢技术是一种高效清洁的煤利用新技术，利用超临界水特有的性能，将煤转化为清洁高热值的H2和CO2，N、S等污染物作为固体残留直接排出反应器。本文构建了一种新型超临界水中煤气化制氢热力发电循环系统，采用能量分析和火用分析方法研究新系统的过程能耗，并基于能的品位概念，运用图像火用分析法，，进一步探究系统关键过程能量转化机理，以期达到煤的清洁利用以及节能减排的目的。首先，构建了一种新型超临界水中煤气化制氢热力发电循环系统，该系统使煤在超临界水中气化后的混合工质直接通入透平做功发电，充分利用反应器出口超临界水所携带的能量，并且使气化获得的气体直接发生氧化反应重新加热蒸汽，再次驱动透平做功发电，节省氢气分离提纯时的能耗，且将氢能直接转化为应用更广泛的电能。其次，对新系统进行能量分析和火用分析，以常规煤直接燃烧推动超临界机组再热循环系统为参照，对比发现新系统具有良好的能量效率和火用效率，指出影响系统能量效率和火用效率的关键过程为气化和燃烧两个化学反应过程。最后，基于能的品位概念，利用图像火用分析法，通过研究超临界水中煤气化制氢过程中化学能向物理能转化时能量品位的变化关系，揭示过程中火用损失产生的深层原因，阐明新系统火用损失减少和外部热源品位提升的机理。为超临界水中煤气化制氢热力发电循环系统的设计与优化提供理论依据。
[Abstract]:Coal is the most important fuel for thermal power generation today, but coal directly burns in the air to produce pollutants such as no _ XO _ XO _ 2 and PM2.5. Gasification of coal in supercritical water for hydrogen production is a new technology for efficient and clean coal utilization, which makes use of the unique properties of supercritical water. The coal is converted into clean and high calorific pollutants such as H2 and CO _ 2N _ 2N _ 2 as solid residue direct discharge reactor. In this paper, a new type of supercritical water gasification to produce hydrogen thermal power cycle system is constructed. Energy analysis and exergy analysis are used to study the process energy consumption of the new system. Based on the concept of energy grade and image exergy analysis, the mechanism of energy conversion in the key process of the system is further explored. In order to achieve clean use of coal and energy conservation and emission reduction purposes. Firstly, a new thermal power generation cycle system of coal gasification for hydrogen production in supercritical water is constructed, in which the mixed working fluid of coal gasified in supercritical water is directly pumped into the turbine for power generation. The energy carried by the supercritical water at the outlet of the reactor is fully utilized, and the gas obtained from the gasification is directly oxidized to reheat the steam, and the turbine is again driven for power generation, thus saving energy consumption in the process of hydrogen separation and purification. And the hydrogen energy is directly converted into more widely used electric energy. Secondly, the energy analysis and exergy analysis of the new system are carried out. The new system has good energy efficiency and exergy efficiency, compared with the conventional direct combustion supercritical unit reheat cycle system. It is pointed out that the key processes affecting system energy efficiency and exergy efficiency are gasification and combustion. Finally, based on the concept of grade of energy, by using image exergy analysis, the change of energy grade during the conversion of chemical energy to physical energy in the process of hydrogen production from coal gasification in supercritical water is studied, and the deep causes of exergy loss in the process are revealed. The mechanism of reducing exergy loss and increasing the grade of external heat source in the new system is expounded, which provides a theoretical basis for the design and optimization of the thermal power generation cycle system for the gasification of coal to produce hydrogen in supercritical water.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM611

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