柴油机SCR系统NO_x催化还原反应的模拟研究

采用计算流体动力学与化学反应动力学结合的方法建立试验SCR催化器系统的三维模型,从时间的角度分析催化还原反应该过程。仿真研究表明了SCR系统在恒定工况条件下,一个喷射周期内反应物NO、NO2浓度分布随时间的推移而发生的物理、化学变化过程。     

A technical method to improve NOx/NH3 mixing ratio in SCR system and its engineering applications

A technical method for diagnosing the distribution of NO_x flux within the cross-section area in front of ammonia injection grid (AIG) was proposed for guiding the valve-tuning of AIG branch-pipes, in order to optimize the NO_x/NH₃ mixing ratio in the selective catalytic reduction (SCR) system of power plant. The weight coefficient of each branch-pipe in AIG system can be quantitatively determined with regard to the distribution of NO_x flux in the corresponding sub-zone of the cross-section area. The control strategy of the valves for different AIG branch-pipes can be achieved for guiding the NH₃ injection and improving the NO_x/NH₃ mixing ratio within the whole cross-section area in front of AIG. The technology has been applied on one side of the SCR system flue-gas tunnels (normally two tunnels for the SCR system called as A-side and B-side) of a 660 MW plant for more than one year. The ammonia consumption rate of the SCR system was reduced about 12.62% and the uniformity of outlet NO_x distribution was estimated to be greatly improved by about 79.01% with regard to the standard deviation. The rising rate of the flue gas resistance of the air preheater was slown down by 39.18% compared to that of the other flue-gas tunnel of SCR system. This implied that the formation of the sticky ammonium bisulfate (ABS) on air preheater was significantly inhibited through the application of this technology.     

基于互信息和PID神经网络的SCR脱硝扰动补偿控制

针对火电厂选择性催化还原(Selective Catalytic Reduction,SCR)烟气脱硝系统机理复杂,工况变化时呈现的不确定性、强扰动等特点,提出了一种基于互信息和PID神经网络的SCR烟气脱硝扰动补偿控制方法。利用PID前向神经网络的学习性能逼近被控对象的逆构成扰动观测器对系统进行反馈补偿,以达到超前消除系统扰动的目的。选取观测扰动和系统扰动的互信息为目标函数,采用改进的帝国竞争算法实现PID神经网络权值的优化调整。设计鲁棒PID控制器来进一步克服被控对象存在的不确定性。仿真实验表明,该方法具有突出的抗干扰能力和较好的鲁棒性,控制品质优于常规的PID控制。     

火电厂SCR烟气脱硝工艺系统设计

随着我国NOx排放标准的提高,仅仅依靠燃烧过程控制已不能满足要求,因此我国燃煤电厂今后将逐步建设烟气脱硝装置。主要介绍了火电厂烟气脱硝主流技术——选择性催化还原（SCR）烟气脱硝系统技术的原理及工艺系统的设计。     

F级燃机联合循环NOx排放控制措施经济性分析

以某F级燃机联合循环机组为例,考虑电价气价和年利用小时数等因素,研究燃机控制直接降NOx和使用SCR脱硝对于经济性的影响。     

An intelligent control of NH3 injection for optimizing the NOx/NH3 ratio in SCR system

The distribution of nitrogen oxides (NO_x) flux within the cross-section area in front of ammonia injection grid (AIG) under different operating conditions was obtained by computational fluid dynamics (CFD) method. Weight of NO_x flux in the sub-zone corresponding to each of the ammonia (NH₃) injection branch-pipes of AIG system was analyzed and the sensitivity of which against the plant power load was figured out. A number of “critical” ammonia injection branch-pipes were determined with regard to the weight sensitivity analysis. The selected “critical” branch-pipes were changed to be controlled by the automatic valves, and an intelligent tuning strategy was proposed. The NO_x/NH₃ mixing stoichiometry over the cross-section area in front of AIG system was significantly modified for the high utilization ratio of ammonia. A case work was launched on the selective catalytic reduction (SCR) system of a 660 MW plant. As a result, the ammonia consumption rate (ACR) was found to be reduced by 6.44% compared to that under previous control system, and was 9.31% lower than that of the unapplied system. The methodology for determining the “critical” branch-pipes and intelligent tuning strategy of ammonia injection notably saved the ammonia consumption of SCR system, and the formation of ammonium bisulfate (ABS) were greatly confined.     

船用柴油机选择性催化还原系统设计及试验验证

结合船用中速柴油机开展选择性催化还原(selective catalytic reduction,SCR)系统的设计和性能试验验证,着重关注还原剂均匀分布、排气均匀度、系统稳定可靠控制及催化剂布置等方面,形成适用于船用环境的SCR系统设计方案.基于6L21/31中速柴油机D2以及E3循环工况开展SCR系统配机试验,结果...     

煤层气发电高温NO_x烟气SCR处理技术及其应用

煤层气发电是煤层气利用的重要途径之一,但煤层气发电排放的高温尾气中含有大量的氮氧化物(NO_x),会对环境造成污染,需要对其进行脱硝处理,而高温烟气(约500℃)又不宜用V_2O_5/TiO_2蜂窝式催化剂进行直接脱硝处理。为此,在分析比较煤层气发电高温烟气与燃煤发电烟气差别的基础上,应用纳米组装和灌注法研制了GJ-HC-5型催化剂,并通过室内实验确定了脱除NO_x的最佳温度窗口(400~600℃)。之后,在某煤层气电厂进行中间试验,将发电机组高温烟气直接通入到SCR一体化装置进行脱硝处理,在SCR反应器进出口处连续监测,进口NO_x浓度约为620 mg/m~3,出口监测浓度约为20 mg/m~3,对烟气中的NO_x的脱除率始终保持在90%以上。试验结果表明,所研制的高温SCR催化剂符合实际烟气温度条件,且制备方法简单,是一种可行的煤层气发电高温烟气的脱硝方法。     

栅格型导流板对SCR反应器内流场影响特性分析

基于某水泥厂环保改造项目,对SCR反应器进行设计改造,应用计算流体力学软件对SCR反应器内流场进行数值模拟研究,前期获取大量实际运行数据,通过算法验证,本文使用的模拟方法具有可靠性,与实际较为吻合。随后,在比较分析不加装导流板反应器和原反应器（内置扇形导流板及多孔整流层）内流场的基础上,进一步研究了倒V型导流板+栅格整流层和栅格型导流板对SCR反应器内流场特性的影响,结果表明：栅格型导流板能有效改善流场均匀性,并且使得进入催化剂层的烟气速度偏差大大降低。