循环流化床氮氧化物排放预测模型及优化控制研究

高明明1,于浩洋1,吕俊复2,于孝宏3,李文瑞4,李存怀4,魏 光4

(1.新能源电力系统国家重点实验室(华北电力大学),北京 102206;2.清华大学 电力系统及发电设备控制和仿真国家重点实验室,北京 100084;3.中国华电集团有限公司 天津分公司,天津 300203;4.华电国际电力股份有限公司 天津开发区分公司,天津 300270)

摘 要:随着环保要求的日益严格,为了降低CFB机组的NOx排放,需要对炉内生成的NOx浓度进行准确估计并应用到控制中,对此,建立精确实用的机理控制模型显得十分必要。同时,需要综合考虑降低炉内燃烧所生成的NOx与SNCR的优化控制,利用该模型对炉内外NOx综合控制进行优化。通过对NOx的生成机理进行分析,以CFB锅炉燃烧产生的燃料型NOx为主体,应用数学建模与仿真的方法,以给煤量、风量等作为模型输入,建立炉膛出口CO浓度预测模型,并以此模型为基础,与即燃碳模型为输入,建立可以用于控制的炉膛出口NOx浓度预测模型。利用上述方法建立了炉膛出口CO浓度预测模型和炉膛出口NOx浓度预测模型,并根据实际运行数据对模型进行参数求取及仿真,针对炉内燃烧控制与SNCR脱硝配合不佳,导致NOx排放水平较高的问题,根据所建立的炉膛出口NOx浓度预测模型,提出了炉内外NOx综合控制技术路线,设计了基于NOx浓度预测模型的一二次风量优化控制与SNCR优化控制思路。仿真证明了所建立的模型具有较好的精确度,满足实际控制系统的精度要求,并具有一定的预测效果。所设计的炉内外NOx综合控制技术路线与一、二次风量优化控制思路可以为今后循环流化床机组NOx低排放控制提供参考。

关键词:循环流化床;氮氧化物;NOx浓度预测模型;机理模型;优化控制

中图分类号:TK229.6X511

文献标志码:A

文章编号:1006-6772(2020)03-0046-06

收稿日期:2020-03-05;责任编辑:张晓宁

DOI:10.13226/j.issn.1006-6772.20030501

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基金项目:中国华电集团有限公司重大科技项目计划资助项目(CHDKJ19-01-88);国家重点研发计划资助项目(2016YFB0600205)

作者简介:高明明(1979—),男,山西吕梁人,副教授,博士,主要研究方向为大型循环流化床机组状态监测与控制。E-mail:gmm1@ncepu.edu.cn

引用格式:高明明,于浩洋,吕俊复,等.循环流化床氮氧化物排放预测模型及优化控制研究[J].洁净煤技术,2020,26(3):46-51.

GAO Mingming,YU Haoyang,LYU Junfu,et al.Study on prediction model and optimal control of nitrogen oxides emission of circulating fluidized bed[J].Clean Coal Technology,2020,26(3):46-51.

Study on prediction model and optimal control of nitroge xides emission of circulating fluidized bed

GAO Mingming1 ,YU Haoyang1,LYU Junfu2,YU Xiaohong3,LI Wenrui4,LI Cunhuai4,WEI Guang4

(1.State Key Lab of Alternate Electric Power System With Renewable Energy Sources(North China Electric Power University),Beijing 102206,China;2. State Key Laboratory of Power Systems,Tsinghua University,Beijing 100084,China;3.Tianjin Branch,China Huadian Group Go.,Ltd.,Tianjin 300203,China;4.Tianjin Development Area BranchHuadian Power International Co.,Ltd.,Tianjin 300270,China)

Abstract:With the increasingly strict requirements of environmental protection,in order to reduce the NOx emission of CFB units,it is necessary to accurately estimate the NOx concentration generated in the furnace and apply it to the control. For this,it is necessary to establish an accurate and practical mechanism control model. At the same time,it is necessary to comprehensively consider the optimization control to reduce nitrogen oxide and SNCR generated in the furnace combustion,and the comprehensive control of nitrogen oxide inside and outside the furnace should be optimized by using this model.Based on the analysis of the formation mechanism of nitrogen oxides,the CO concentration prediction model at the furnace outlet was established with fuel NOx produced by CFB boiler combustion as the main body,the method of mathematical modeling and simulation,and coal feed,air flow,etc. used as model inputs. Based on this model,the prediction model of the NOx concentration at the furnace outlet could be established by using the model as the input of the burning coal model.The above method was used to establish a prediction model of CO concentration at furnace outlet,and the parameters of the model were obtained and simulated based on the actual operating data,and the furnace combustion control was not well coordinated with SNCR denitration,which led to the problem of high levels of nitrogen oxide emissions. Based on the established prediction model of NOx concentration at furnace outlet,a comprehensive control technology route for nitrogen oxides inside and outside the furnace was proposed,and a primary and secondary air volume optimization and SNCR optimization control ideas were designed based on the NOx concentration prediction model.The simulation proves that the established model has good accuracy,meets the accuracy requirements of the actual control system,and has a certain predictive effect. The design of the integrated nitrogen oxide control technology route and optimized control ideas inside and outside the furnace can provide a reference for the low-emission control of nitrogen oxides in circulating fluidized bed units.

Key words:CFB;nitrogen oxides;NOx concentration prediction model;mechanism model;optimization control

0 引 言

近年来,循环流化床锅炉因具有污染物排放低等优势而得到迅速发展[1]。据统计,我国现有CFB锅炉总容量超过1亿kW,位居全世界第一,超过全世界其他国家总和[2]。流化床系统是蓄能量大的热源,能够为新加入的冷燃料提供足够的热量,使其迅速加热到着火温度,只要保证床层温度稳定,即可实现稳定运行。该技术对煤炭质量的要求较低,可以燃烧劣质煤甚至部分垃圾。与此同时,还可保持较高的燃烧效率,且床温较低,不易生成氮氧化物,具有低排放的优势[3]。随着我国对环保愈发重视,循环流化床电厂的污染物排放指标越发严格,环保部门要求新建