大型电站锅炉深度低氮燃烧耦合SNCR和SCR脱硝研究

分类号： TK224; TK227 单位代码： 10335 密 级： 学 号： 10408095

博士学位论文

中文论文题目中文论文题目：：

大型电站锅炉深度低氮燃烧耦合SNCR 和SCR 脱硝脱硝研究研究

英文论文题目英文论文题目：：Study on Low NO x Combustion Coupled with

SNCR and SCR to Control NO x emissions

申请人姓名： 胡 敏

指导教师： 岑可法 院士

合作导师：

专业名称： 工程热物理

研究方向： 电站锅炉NO x 控制技术

所在学院： 能源工程学系

论文提交日期 2012年

7

月

浙江大学博士学位论文 摘要

摘要

大气中的氮氧化合物主要来源于工业污染、生活污染和交通污染。在我国，有65%左右的NO x是由煤粉燃烧所产生的，煤粉锅炉产生的NO x又占煤粉燃烧排放总量的80%左右。从1998年到2007年，我国燃煤电厂NO x排放总量逐年增长，因此，降低燃煤锅炉的NO x排放是十分紧迫的环保任务。

本文以降低燃煤锅炉NO x的排放为主线，研究了低氮燃烧器改造，炉内空气分级以及烟气后处理技术等各种降低锅炉NO x排放的方法，采用实验和数值模拟的方法研究了各种低NO x方案的特点，脱硝效率，对锅炉蒸汽参数的影响等。

本文首先实验研究了300MW锅炉采用低NO x燃烧器和炉内空气分级对NO x 排放的影响。在炉膛的上部加设了三层SOFA风，将二次风风量的20%由SOFA 风喷口喷出，使得主燃烧器区域的处于缺氧状态，燃烧温度较低而且处于还原性气氛，使得NO x排放降低。本次改造可在不降低锅炉效率的情况下，显著的降低NO x排放，NO x排放从850mg/m3降低到425 mg/m3，脱硝效率达50%左右。

其次，研究了不同负荷下的SOFA风摆动对炉内温度、NO x排放和锅炉效率的影响：（1）SOFA的摆动对炉内的温度场影响不大；（2）在300MW负荷时，SOFA风的上摆可使烟气中NO的含量降低20ppm左右。在270MW和240MW 时，SOFA平摆时烟气中的NO含量最低。（3）300MW负荷条件下，锅炉效率在SOFA下摆时最大，平摆其次，上摆时最低。而在240MW负荷时，呈现相反的趋势，SOFA风下摆时锅炉效率最低，平摆时居中，上摆时最高。

然后，介绍了国内首次在300MW机组上安装以尿素为还原剂的SNCR脱硝系统，研究不同喷枪组合和安装位置对NO x排放的影响、不同负荷下的最佳投运喷枪及喷枪的位置、分析脱硝系统对锅炉蒸汽温度和减温水量的影响。根据以上的研究分析，300MW 负荷投运上层 2 支长枪和上层短枪的脱硝效果最好。采用CFD方法模拟计算了炉内的温度分布、各重要组分的分布、尿素的热解过程，重点研究了不同的氨氮比和不同的三次风带粉率对脱硝效率和氨逃逸的影响。（1）随着NSR的增加，NO x的脱除率也会增加，但与此同时也会造成氨逃逸的增加。因此在选择NSR时，并不能一味的只追求NO x脱除率的最大化，还

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浙江大学博士学位论文 摘要

应考虑将氨逃逸控制在一定的范围内。（2）当三次风带粉率低于10%，脱硝效率随着三次风带粉率的增加而降低；三次风带粉率超过10%时，脱硝效率又会有所增加。但是氨逃逸量总是随着三次风带粉率的增加而增加的。（3）尿素从喷射进入炉膛后很快就热解掉了，各工况下的尿素浓度分布都很相似。这主要是因为尿素热解需要的热量相对于烟气所带有的热量而言是很小的，所以尽管不同工况下的炉内温度有所差异，但都能够提供充足的能满足尿素热解所需要的热量。

最后，采用数值模拟的方法研究了600MW锅炉上SNCR+SCR混合脱硝系统的脱硝效果。SNCR脱硝效率为40.6%，SCR脱硝效率为43%，统合脱硝效率为66%，。经过SNCR + SCR 脱硝后，烟气中的NO为83.6 mg/m3，烟气的氨逃逸为3.2ppm，满足国家对燃煤电站锅炉的NO排放要求。

关键词氮氧化物; 燃煤锅炉; 炉内空气分级; SNCR; SCR

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浙江大学博士学位论文 Abstract

Abstract

Nitrogen oxides in the atmosphere primarily come from industrial pollution, domestic pollution and traffic pollution. In China, about 65% of NO x is produced by pulverized coal combustion, and the amount of NO x released from pulverized coal boilers accounts for about 80% of NO x produced by pulverized coal combustion. From 1998 to 2007, the total NO x emissions of coal-fired power plants in China is growing year by year, therefore, it is a very urgent task to reduce the NO x emissions of coal-fired boilers.

This article ,whose theme is to reduce the NO x emissions of coal-fired boilers, investigates the low-NO x reform of pulverized coal burner, the split-air arrangement in furnace and the flue gas treatment technology. Experimental and numerical methods are conducted to study the features these low NO x projects, denitrification efficiency and the impacets on steam parameters.

Fistly, experiments were conducted on a 300MW boiler to investigate the effects of using low NO x burners and the split-air technology on NO x emissions. Three layers of SOFA wind were arranged in the upper part of the furnace, and the amount of SOFA wind accounted for about 20% of the amount of secondary ai. As a result, the main combustion region in the furnace was in an oxygen lacking condition and the combustion temperature was lower, making the NO x was reduced. This transformation project could significantly reduce NO x emissions without reducing the boiler efficiency. NO x emissions were reduced from 850mg/m3 to 425 mg/m3,and the denitrification efficiency was up to 50%.

Secondly, the effects of the SOFA wind swing on the furnace temperature, NO x emissions and boiler efficiency were studied under different boiler loads: (1) the swing of the SOFA winds had little effect on the furnace temperature field. (2) when the boiler load was 300MW, the up swing of the SOFA winds could reduce the concentration of NO x in flue gas by 20ppm or so. Howerer when boiler load was

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浙江大学博士学位论文 Abstract

270MW or 240MW, the lowest NO content in the flue gas was detected when SOFA wind had no swing. (3) under the condition of 300MW, the boiler efficiency reached the top value when the SOFA wind swinged down, and the efficiency increased as the SOFA wind swinged up. On the contrary, the efficiency of 240MW increased as the SOFA wind swinged up.

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