混煤燃烧过程未燃尽碳与NO_x排放协同优化研究

发布时间：2018-01-29 03:36

本文关键词： 混煤燃烧方式未燃尽碳 NOx 数值模拟协同优化　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：混煤燃烧技术作为电厂拓宽煤源的重要手段,已在我国电站锅炉中广泛运用。然而,混煤燃烧技术运用不合理则会造成燃烧效率低、污染物排放超标等问题。本文采用数值模拟、理论分析和试验验证相结合的手段,研究了不同混煤方式下的未燃尽碳量和NOx排放特性,以期获得混煤燃烧过程中未燃尽与NOx排放的协同优化策略。本文设计了2种用于混煤燃烧研究的试验炉,以试验炉为对象开展混煤燃烧的研究。研究结果表明:(1)对于未燃尽碳,采用炉内掺烧方式、针对低挥发分煤进行配风方式的优化、延长低挥发分煤在炉内的停留时间均能有效提高混煤的燃尽率,降低未燃尽碳;(2)对于NOx排放,采用炉内掺烧方式时,高挥发分煤析出的挥发分物质中包含大量中间产物HCN,其配合还原性气氛能将高挥发分煤在着火阶段生成的部分NOx还原。此外,试验炉的试验验证表明了数值模拟结果可以很好的反应试验炉中的趋势。以一台660MW四角切圆电站锅炉为对象,开展了电站锅炉的混煤燃烧研究。研究结果表明:(1)对于未燃尽碳,该电站锅炉混煤燃烧运行时包括混煤方式在内的多方面因素对混煤的未燃尽碳均有影响,但起决定性作用的是对低挥发分煤在炉内燃烧过程中的供O2状况。(2)对于NOx排放,将高挥发分煤由整个烟气流场的下游(上部燃烧器)喷入时能显著降低出口的NOx排放。同时满足上述优化条件的工况,即采用炉内掺烧方式配合合理的工况设置,相较采用炉外掺混方式的工况,能够在降低34%的飞灰含碳量的同时降低11%的出口NOx排放浓度,实现了未燃尽碳与NOx排放的协同优化。锅炉现场试验验证表明由本文的数值模拟研究得到的结论是可靠的,可以为实际工业应用提供理论指导。
[Abstract]:As an important means of widening coal source in power plant, mixed coal combustion technology has been widely used in power plant boilers in China. However, unreasonable use of mixed coal combustion technology will lead to low combustion efficiency. In this paper, numerical simulation, theoretical analysis and experimental verification are used to study the unburned carbon and NOx emission characteristics of different coal blending methods. In order to obtain the cooperative optimization strategy of unburned and NOx emissions in the combustion process of mixed coal, two kinds of test furnaces for the study of mixed coal combustion were designed in this paper. The study on the combustion of mixed coal is carried out in the test furnace. The results show that: 1) for the unburned carbon, the mixed combustion mode is adopted in the furnace, and the air distribution mode for the low volatile coal is optimized. Prolonging the residence time of low volatile coal in the furnace can effectively increase the burnout rate of mixed coal and reduce the unburned carbon. (2) for NOx emissions, the volatile matter precipitated from high volatile coal contains a large number of intermediate products, HCN, when the furnace is mixed. In addition, part of NOx produced by high volatile coal during ignition stage can be reduced with reductive atmosphere. The test results of the test furnace show that the numerical simulation results can be very good in the reaction test furnace. A 660MW tangential power plant boiler is taken as the object. The study on mixed coal combustion of utility boilers is carried out. The results show that: 1) for unburned carbon. Many factors, including coal mixing mode, have an effect on the unburned carbon of mixed coal in the boiler of this power station. However, the decisive effect is on the oxygen supply of low volatile coal during combustion in the furnace. 2) on the NOx emission. When the high volatile coal is injected from the downstream (upper burner) of the whole flue gas flow field, the NOx emission from the outlet can be significantly reduced. At the same time, the optimal conditions mentioned above can be satisfied. That is to say, compared with the outside mixing mode, the carbon content of 34% fly ash can be reduced and the export NOx emission concentration of 11% can be reduced by using the furnace mixing method with reasonable operating conditions. The co-optimization of unburned carbon and NOx emission is realized. The results of boiler field test show that the conclusions obtained from the numerical simulation in this paper are reliable and can provide theoretical guidance for practical industrial application.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773

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