床温及SNCR脱硝对CFB锅炉NOx和N2O排放影响的试验研究

Experimental study on influence of bed temperature and SNCR denitrification on NOx and N2O emissions from CFB boiler

为了研究循环流化床(CFB)锅炉燃用无烟煤时床温及选择性非催化还原(SNCR)脱硝对于NO和N2O排放的影响,在1 MW CFB试验装置上开展了试验研究。结果表明:床温由880℃提高到970℃,NO排放质量浓度由119.5 mg/m^3上升到226.0 mg/m^3,N2O排放质量浓度由216.0 mg/m^3降低到102.2 mg/m^3;在氨氮摩尔比(NSR)为0~3.7之间,随着NSR的提高,脱硝效率从0上升到50.72%;进一步提高NSR到5.2,脱硝效率升至53.61%,增加较为缓慢;随着NSR从0提高到1.7,N2O排放质量浓度由84.3 mg/m^3上升至118.3 mg/m^3,增长较为缓慢;进一步提高NSR至2.0,N2O排放质量浓度上升至187.7 mg/m^3,增长速度提高;继续提高NSR至5.2,N2O排放质量浓度上升至381.4 mg/m^3;CFB锅炉采用以尿素为还原剂的SNCR脱硝工艺时,单纯通过加大NSR来提高脱硝效率不仅效果有限,过量喷入的还原剂会造成N2O排放量的显著提高。

In order to study the influence of bed temperature and selective noncatalytic reduction(SNCR)denitration on NO and N2O emission from CFB boilers burning anthracite,an experimental study was carried out on a 1 MW CFB test equipment.The results show that,when the bed temperature was increased from 880℃to 970℃,the NO emission mass concentration increased from 119.5 mg/m^3 to 226.0 mg/m^3,and the N2O emission mass concentration decreased from 216.0 mg/m3 to 102.2 mg/m^3.The denitrification efficiency increased from 0 to 50.72%when the ammonia to nitrogen molar ratio NSR was 0~3.7.When the NSR was further increased to 5.2,the denitrification efficiency rose to 53.61%,with a slow increase.With the increase of NSR from 0 to 1.7,the N2O emission mass concentration increased from 84.3 mg/m3 to 118.3 mg/m^3,with a slow growth rate.Further increasing the NSR to 2.0,the emission mass concentration of N2O increased to 187.7 mg/m^3,of which the growth rate increased.Contineously increasing the NSR to 5.2,the emission mass concentration of N2O increased to 381.4 mg/m^3.When the SNCR process with urea as reducing agent is adopted in CFB boiler,to enhance the denitrification efficiency,only increasing the NSR not only has limited effect,but also will significantly increase the N2O emission by excessive injection of reducing agent.