300MW四角切圆锅炉低氮燃烧改造数值模拟

发布时间：2018-04-01 02:37

本文选题：切圆燃煤锅炉　切入点：NO_x排放　出处：《华北电力大学》2015年硕士论文

【摘要】：煤炭是我国最主要的一次能源,然而煤的燃烧对环境造成了极大的破坏,燃烧过程中产生的粉尘、硫氧化物和氮氧化物是我国大气污染主要来源。电站锅炉燃煤占我国总煤炭消耗的一半以上,为此,电站锅炉清洁高效燃烧就成为我国节能减排工作的重中之重。我国在“十五”期间基本解决了电站锅炉煤粉低负荷稳定燃烧问题;“十一五”期间集中解决烟气脱硫、点火启动节油问题;“十二五”期间将重点解决氮氧化物排放问题。目前已经有很多种电站锅炉降低NO_x排放的技术,包括低NO_x燃烧技术和催化还原脱硝技术等。从综合改造费用、脱硝效率和后期运行维护费用对比可以看出低NO_x燃烧技术在控制NO_x方面的优势,是电厂锅炉脱硝应该初步采用的措施。本文就是在这样的背景下,以某电厂300MW四角切圆贫煤锅炉为研究对象,运用Fluent数值计算软件对低氮燃烧改造前后炉内的流动、传热和燃烧进行预测,以期对电厂实际改造及改造后运行提供指导。首先,简单介绍了国内外低氮燃烧技术的发展,分析比较得出针对本台锅炉改造可能的方案。其次,介绍数值计算方法在本文改造应用中所用到的数学模型。然后,运用Fluent软件对锅炉改造前和和改造后100%负荷、80%负荷和60%负荷工况进行数值模拟计算,研究炉内流场、温度场和组分场的分布变化,验证改造方案的可行性,并通过初步验收试验结果与计算结果对比分析。研究结果表明:数值计算结果与初步性能试验结果基本吻合。低NO_x燃烧改造后,锅炉燃烧效率偏低、飞灰含碳量偏高及NO_x排放浓度高均得到极大改善。同时,改造后容易产生的过热汽温不稳和减温水量增加等负面影响不明显。最后,对改造后锅炉300MW负荷下不同运行工况进行数值计算,计算结果表明,不同磨煤机组合运行时,锅炉均能实现稳定运行,缩腰型配风方式是锅炉改造后运行较优的配风方式,过量空气系数为1.2,SOFA风率为18%时,锅炉运行较好。
[Abstract]:Coal is the most important primary energy in China. However, the combustion of coal has caused great damage to the environment. Dust, sulfur oxide and nitrogen oxide are the main sources of air pollution in China.The coal-burning of utility boilers accounts for more than half of the total coal consumption in China. Therefore, clean and efficient combustion of utility boilers has become the most important task of energy saving and emission reduction in China.China has basically solved the problem of low load and stable combustion of pulverized coal from utility boilers during the 10th Five-Year Plan period; it has concentrated on solving the problem of flue gas desulphurization and fuel saving by igniting fire during the 11th Five-Year Plan period; and it will focus on solving the problem of nitrogen oxide emission during the 12th Five-Year Plan period.At present, there are many technologies for reducing NO_x emission from utility boilers, including low NO_x combustion technology and catalytic reduction denitrification technology.From the comparison of comprehensive renovation cost, denitrification efficiency and later operation and maintenance cost, it can be seen that low NO_x combustion technology has advantages in controlling NO_x, which is a preliminary measure to be adopted in power plant boiler denitrification.In this paper, the flow, heat transfer and combustion in the boiler before and after the transformation of low nitrogen combustion are predicted by using the Fluent numerical calculation software, taking the 300MW tangential lean coal boiler of a power plant as the research object.The aim is to provide guidance for the actual retrofit and operation of the power plant after revamping.Firstly, the development of low nitrogen combustion technology at home and abroad is briefly introduced.Secondly, the mathematical model used in this paper is introduced.Then, using Fluent software to simulate the working conditions of 80% load and 60% load of 100% load before and after revamping, to study the distribution change of flow field, temperature field and component field in the furnace, and to verify the feasibility of the retrofit scheme.The results of preliminary acceptance test and calculation are compared and analyzed.The results show that the numerical results are in good agreement with the experimental results.After low NO_x combustion, the boiler combustion efficiency is low, the carbon content of fly ash is on the high side, and the high NO_x emission concentration is greatly improved.At the same time, the unsteady superheated steam temperature and the increase of cooling water are not obvious.Finally, the numerical calculation of the boiler under different operating conditions under 300MW load shows that the boiler can operate stably under the combined operation of different coal mills.The reduced waist type air distribution mode is the best way for boiler operation after retrofit. When the excess air coefficient is 1. 2 and the sofa air ratio is 18, the boiler runs better.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM621.2

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