生物质CFB氮氧化物排放建模与优化控制

Modeling and Optimal Control for Nitrogen Oxide Emissions from Biomass Circulating Fluidized Bed

由于生物质循环流化床(CFB)燃烧不稳定,为实现负荷波动过程中机组NO_(x)的动态预测,从锅炉燃烧机理切入,建立了氧量模型与即燃碳模型;对炉内NO_(x)自生成与自还原机理进行分析,并结合数学建模的方法,建立了NO_(x)动态排放模型。进行给料量、二次风量开环阶跃试验;分析NO_(x)排放与氧量耦合情况,采用简化对角解耦与前馈补偿解耦法解除耦合。结合某130 t/h生物质CFB实际运行数据进行仿真试验。结果表明:模型拥有较好的预测效果,能反映氧量及NO_(x)排放过程的动态特性,可实现给料量控制NO_(x)排放质量浓度、二次风控制氧体积分数的单回路控制,所设计的NO_(x)排放质量浓度模型及解耦控制方法可以为今后生物质CFB机组适应动态运行以及智能控制策略设计提供参考。

Considering the combustion instability of the biomass circulating fluidized bed(CFB),the oxygen content model and the immediate combustion carbon model were established from the combustion mechanism of the boiler to realize the dynamic prediction of NO_(x) in the process of load fluctuation.The self-generation and self-reduction mechanism of NO_(x) in the furnace were analyzed,and the NO_(x) dynamic emission model was established by mathematical modeling methods.The open-loop step tests for the feed rate and the secondary air flow were carried out.The coupling between NO_(x) emission and oxygen content was analyzed,and the simplified diagonal decoupling and feedforward compensation decoupling method were used for decoupling.The simulation experiment was carried out using the actual operation data of a 130 t/h biomass CFB.Results show that the model has a good prediction effect.The dynamic characteristics of oxygen content and NO_(x) emission process can be reflected,and the single-loop control for NO_(x) emission by the feed rate and oxygen content by the secondary air flow can be realized.The designed NO_(x) emission concentration model and decoupling control methods can provide reference for the biomass CFB unit to adapt to dynamic operation and intelligent control strategy designs in the future.