燃尽风及生物质气对燃煤锅炉燃烧过程及NO_x排放影响的数值模拟  

Numerical Simulation of the Effect of Over-Fire Air and Syngas on Combustion Process and NO_x Emission of Coal-Fired Boilers

作　　者：张小桃 黄勇 张川 赵伟 ZHANG Xiao-tao;HUANG Yong;ZHANG Chuan;ZHAO Wei(School of Electric Power,North China University of Water Resources and Electric Power,Zhengzhou,China,Post Code:450011)

机构地区：[1]华北水利水电大学电力学院,河南郑州450011

出　　处：《热能动力工程》2019年第2期39-46,共8页Journal of Engineering for Thermal Energy and Power

基　　金：国家自然科学基金(U1404521);河南省科技发展计划(112102210281)~~

摘　　要：为研究燃尽风以及掺烧生物质气对燃煤锅炉燃烧及NO_x排放的影响,对某电厂330 MW机组燃煤锅炉进行空气分级燃烧改造,在其主燃烧器上方5 m处增加3层分离式燃尽风(SOFA),基于FLUENT模拟软件,搭建了纯煤燃烧和煤粉掺烧生物质气模型,对锅炉无SOFA、有SOFA(15%和20%配风比)、有SOFA(15%和20%配风比)同时掺烧松木气等5种工况的炉内燃烧过程进行了数值模拟,分析不同工况下炉内速度场、温度场、组分场及污染物NOx排放特性。结果表明:在无SOFA和有15%SOFA工况下,一次风、二次风均能形成良好切圆,速度场稳定,在20%SOFA配比下,燃尽风切圆不太理想;与无SOFA纯煤燃烧工况相比,有SOFA工况下,主燃烧区中心温度均有所降低,分别降低了3. 31、27. 48、6. 78和40 K,而在SOFA区域温度有所上升,炉膛出口CO和O_2体积分数增大,CO2体积分数减小,与纯煤无SOFA工况相比,当SOFA配风比从15%增至20%时,NOx炉膛出口平均质量浓度在纯煤工况下分别降低了10. 76%和13. 28%,而在掺烧工况下分别降低了26%和28. 4%。In order to investigate the effect of over-fire air,co-firing syngas and other factors on combustion and NOxemission,a 330 MW coal-fired boiler was reformed to air staged combustion by setting 3 layers separated over fire air nozzles at distance of 5 m above the primary burner. The pulverized coal combustion model and the co-firing models were built using the Fluent software,and the combustion processes under different conditions were simulated. The velocity field,temperature field,flue gas components and the NOxemission were measured. The five cases were studied;pure coal fired without SOFA,pure coal fired with SOFA of 15% and 20% wind rates,and co-firing with pine syngas setting SOFA of 15% and20% wind rates. The results showed that,in cases without SOFA and with 15% SOFA,both the primary air( pine syngas under co-firing condition) and the secondary air can form good tangential circles,and the flow fields stay stable. In the case with 20% SOFA rate,however,SOFA tangential circles become worse.Compared with coal-fired cases without SOFA,the maximum temperature of the furnace in the SOFA cases decreases by 3. 31,27. 48,6. 78 and 40 K,respectively,but then it has a certain rise at the SOFA region.The O2 and CO volume fraction under co-firing conditions increase clearly than other cases,while the CO2 volume fraction decreases. At the outlet,compared with pure coal fired without SOFA case,the average NOxmass concentration decreases by 10. 76% and 13. 28% in coal-fired setting SOFA cases,as well as26% and 28. 4% in co-firing setting SOFA cases.

关 键 词：燃尽风 松木气 混合燃烧 NOX排放 数值模拟 

分 类 号：TK224[动力工程及工程热物理—动力机械及工程]