| Coal-fired industrial boilers are one of the main sources of NOx emissions,the state has stricter requirements on its NOx emissions.The latest version of the"Boiler Air Pollutant Emission Standards"(GB 13271-2014)issued by the Ministry of Environmental Protection provides that the NOx emission limits for coal-fired industrial boilers in key regions is 200mg/m~3,so most of the coal-fired industrial boilers will face the dilemma of being eliminated due to excessive NOx emission.In this context,the high efficiency and low NOx pulverized coal industrial boilers is developed by the cooperation of the research team with a shanghai company.As the core equipment,the high efficiency and low NOx slag-tap pulverized coal burner also has the functions of rapid ignition with less oil,high heat load combustion and low NOx emissions,the pulverized coal burner adopts low NOx combustion technology to reduce the NOx emission,and finally achieves the excellent effect of NOx emission value below 150mg/m3.At the same time,some provinces and cities have put forward the ultra-low requirement that the NOx emission concentration of coal-fired industrial boilers is lower than 50mg/m~3.Based on this engineering background,this subject draws on the NOx ultra-low emission technology of power station boilers and applies selective non-catalytic reduction(SNCR)denitration technology to pulverized coal industrial boilers.Based on the high efficiency and low NOx pulverized coal industrial boiler,this paper builds an SNCR denitrification industrial test platform,conducts SNCR denitration test research in the furnace,and adopts the"low NOx combustion+SNCR denitration"technical scheme to realize the ultra-low emission of NOx less than 50 mg/m~3.Firstly,based on the theoretical analysis of the mechanism of NOx formation during pulverized coal combustion,the effect mechanism of high temperature and low oxygen combustion atmosphere on NOx formation and reduction is obtained.And the low NOx emission characteristics of high efficiency and low NOx pulverized coal industrial boiler are tested.The results show that:under the high temperature and low oxygen combustion atmosphere,the burner presents a strong reducing atmosphere,the pulverized coal is burned at a high temperature under a strong reducing atmosphere,which realizes the control of the amount of NOx produced.Secondly,the main factors that affect the SNCR denitration efficiency are analyzed,and the feasibility of SNCR denitration in the furnace of 8.4MW organic heat carrier pulverized coal industrial boiler system is studied.The results show that:after the proper injection position of reducing agent is selected,the furnace temperature in the injection zone can be maintained between 800?and 950?,and the residence time of the reducing agent in the furnace can reach 2.7s,the reaction temperature and residence time of the furnace in the injection area can meet the requirements of SNCR denitrification,the mixing degree of reducing agent and flue gas can be ensured by reasonable arrangement of spray gun,the furnace of the boiler has the conditions for SNCR denitrification.Then,based on the 8.4MW organic heat carrier high efficiency and low NOx pulverized coal industrial boiler,the SNCR denitration industrial test platform is built,and the SNCR denitration system is selected as reducing agent,material balance,system design and equipment selection.The urea solution is chosen as reducing agent,and the minimum amount of reducing agent is obtained through theoretical calculation.The SNCR denitration system consists of urea solution preparation module,urea solution storage module,urea solution metering and delivery module,and urea solution injection module.Finally,On the industrial test platform,the SNCR denitrification tests under different urea solution injection volume,different oxygen content,and different boiler loads are carried out at 20%,15%and 10%urea solutions.The results show that:with the increase of urea solution injection volume,NOx concentration decreased and denitrification efficiency increased;at 80%boiler load,the denitration efficiency of three concentrations of urea solution SNCR under different oxygen content can reach NOx lower than 50mg/m~3,and the denitration efficiency is above 80%;under different boiler load,the NOx emission concentration of SNCR denitration is lower than 50mg/m~3,and the denitration efficiency is greater than 80%.The SNCR denitration test preliminarily verified that the"low NOx combustion+SNCR denitration"technical scheme is feasible.On the basis of low NOx combustion,the SNCR denitration efficiency can reach more than 80%under different test conditions,and can fully achieve NOx in flue gas ultra-low emission requirements below50mg/m~3. |
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