YANG Shi;

• 1:China Coal Research Institute Company of Energy Conservation
• 2:China
• 3:State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources
• 4:National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control

Abstract：

With increasingly strict monitoring of air pollutant emissions in China,Nitrogen oxide control technology has been widely used in various fields of industrial production.As a direct and simple nitrogen oxide emission control technology,oxygen-enriched air combustion technology has been used in gas-fired boilers and internal combustion engines.However,it is rarely used in coal-fired boilers.In order to verify the NO_xreduction effect of oxygen-enriched air combustion technology in pulverized coal industrial boilers,Shenfu bituminous coal was used as fuel,and the two-stage dropper tube furnace test system was used to simulate the actual situation of pulverized coal combustion in the boiler.The NO_xemission characteristics of oxygen enriched air staged combustion of bituminous coal were studied by using the hot test method,and the NO_xemission was compared with that of single-stage air supply and air staged combustion.The effect of key factors,such as temperature of main combustion zone,ratio of secondary air( expressed as excess oxygen coefficient in main combustion zone) and oxygen concentration of secondary air,on NO_xemission were investigated. The results show that,compared with single stage air and air-staged combustion,the NO_xremoval effect of oxygen enriched air staged combustion is much more significant.When the main combustion zone temperature is in the range of 1 200-1 500 ℃,The NO_xemission reduction ratio of oxygen-enriched air staged combustion is 6-12 percentage points higher than that of graded air combustion.Under the condition of oxygen enriched air staged combustion,and as the increase of the main combustion zone temperature,the coal combustion is more completed and the fuel nitrogen is decomposed into a large number of intermediate products such as NHi,HCN,etc,which makes the reducibility of the atmosphere in the main combustion zone enhanced and the proportion of NO_x reduced increased.Therefore,NO_xemission is reduced and the proportion of NO_xemission reduction is on the rise; the ratio of secondary air in oxygen enriched air staged combustion has a significant impact on NO_xemission.With the increase of excess oxygen coefficient in the main combustion zone,NO_xemission is reduced first and then increased.Therefore,there is an optimal ratio of secondary air to minimize NO_xemission concentration.When the temperature of the main combustion zone is 1 300 ℃,the optimum excess oxygen coefficient is about 0.58.When the temperature of the main combustion zone is 1 500 ℃,the optimum excess oxygen coefficient is about 0.55.At a certain excess air coefficient in the main combustion zone,increasing the concentration of secondary air oxygen can prolong the residence time of coal particles in the main combustion zone,and local oxygen-enriched environment is formed on the surface of the coal particles to promote the coal combustion,thereby enhancing the reducibility of the atmosphere in the main combustion zone and reducing the generation of NO_x.Therefore,when the secondary air oxygen concentration is the range of 21%-31%,NO_xemission decreases with the increase of the secondary air oxygen concentration. As the oxygen concentration of the secondary air gradually increases,the decreasing trend of NO_xemission gradually slows down.

Key Words： two-stage dropper tube furnace;oxygen enriched air staged combustion;bituminous;NOx emission characteristics

Abstract:

Keywords:

Foundation: 煤炭科学技术研究院科技发展基金项目技术创新项目(2018CX02)

Authors: YANG Shi;

DOI: 10.13226/j.issn.1006-6772.20022807

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