Research of boiler combustion regulation for reducing NOx emission and its effect on boiler efficiency

The effect of boiler combustion regulation on NO_x emission of two 1025t/h boilers has been studied.The re-searches show that NOx emission is influenced by coal species,operation conditions,etc,and can be reduced byregulating the combustion conditions.The effect of combustion regulation on boiler efficiency has also beenchecked.     

Mechanism analysis on the pulverized coal combustion flame stability and NOx emission in a swirl burner with deep air staging

Low NOx burner and air staged combustion are widely applied to control NOx emission in coal-fired power plants. The gas-solid two-phase flow, pulverized coal combustion and NOx emission characteristics of a single low NOx swirl burner in an existing coal-fired boiler was numerically simulated to analyze the mechanisms of flame stability and in-flame NOx reduction. And the detailed NOx formation and reduction model under fuel rich conditions was employed to optimize NOx emissions for the low NOx burner with air staged combustion of different burner stoichiometric ratios. The results show that the specially-designed swirl burner structures including the pulverized coal concentrator, flame stabilizing ring and baffle plate create an ignition region of high gas temperature, proper oxygen concentration and high pulverized coal concentration near the annular recirculation zone at the burner outlet for flame stability. At the same time, the annular recirculation zone is generated between the primary and secondary air jets to promote the rapid ignition and combustion of pulverized coal particles to consume oxygen, and then a reducing region is formed as fuel-rich environment to contribute to in-flame NO_X reduction. Moreover, the NOx concentration at the outlet of the combustion chamber is greatly reduced when the deep air staged combustion with the burner stoichiometric ratio of 0.75 is adopted, and the CO concentration at the outlet of the combustion chamber can be maintained simultaneously at a low level through the over-fired air injection of high velocity to enhance the mixing of the fresh air with the flue gas, which can provide the optimal solution for lower NOx emission in the existing coal-fired boilers.     

高温贫氧燃烧过程中NOx排放的特点

对高温贫氧燃烧过程中NOx的排放特点，以及燃烧过程中影响NOx生成的各主要因素，如预热空气中的含氧量，预热空气温度，预热空气和燃料的流动状态及混合方式以及燃料的化学成分等进行了研究和分析。并在此基础上提出了今后研究工作的方向和重点。图8表2参l0     

分级燃烧降低燃煤锅炉NOx排放的机理及影响因素分析

再燃燃料在还原性气氛下对主燃区煤粉燃烧生成的氮氧化物的还原反应中 ,再燃燃料中产生的中间产物氰基、氨基和烃根等起到分解氮氧化物的作用。同一再燃燃料中烃类物质在富燃料和贫燃料气氛中所起作用截然不同。实际应用中应使再燃区内各处处于弱还原性气氛下以保证再燃降低NOx 排放的效果 ,并尽量采用气体燃料作为再燃燃料 ,同时在获取所需NOx 排放水平前提下尽量选取较高的空气过量系数(化学当量比 ) ,以同时降低飞灰中的含碳量、减轻高温腐蚀的程度。     

天然气燃烧特性与NOx排放特性数学模拟

采用详细化学反应机理并运用良好搅拌反应器模型,通过化学反应动力学模型的数值计算,就典型的4种天然气组分进行了多种工况下的燃烧特性与NOx排放特性研究.计算结果表明：助燃剂中氧含量对着火时间非常敏感,氧含量较高,着火时间提前;低氧和富燃燃烧方式均可减少NOx排放.     

复合分级燃烧对四角切圆锅炉NOx排放特性的影响

采用复合分级燃烧技术对某一燃用褐煤的四角切圆600 MW锅炉进行了低氮燃烧改造。这种复合分级燃烧技术主要是将水平浓淡燃烧技术,燃尽风技术,偏置二次风技术等有机结合起来。改造后,对一次风量,辅助风的配风方式,燃尽风率,燃尽风配风方式,锅炉过量空气系数等对锅炉NOx排放特性的影响进行了研究。在改造和燃烧优化后,锅炉实现了在高效燃烧的同时NOx浓度大幅降低。     

RDF在流化床中燃烧生成NOx的试验研究

对2种N元素含量不同的RDF物料在流化床中燃烧的排放物NOx的生成量进行了研究。试验表明：RDF在流化床中能完全燃烧，能满足燃烧系统运行要求；炉膛内NOx的生成量与炉膛温度分布基本相同；在相同工况下，含N元素多的RDF产生的烟气中NOx浓度大；过量空气系数、二次风加入都能改变NOx生成量，且含N元素多的RDF受这2个因素的影响大一些，而含N元素少的RDF基本不受影响。     

Numerical simulation on pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed

High temperature air combustion is a prospecting technology in energy saving and pollutants reduction. Numerical simulation on pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed was presented. The down-fired combustor, taken as the calculation domain, has the diameter of 220 mm and the height of 3000 mm. 2 cases with air staging combustion are simulated. Compared the simulation results with experimental data, there is a good agreement. It is found that the combustion model and NOx formation model are applicable to simulate the pulverized coal combustion and NOx emissions in high temperature air from circulating fluidized bed. The results show that there is a uniform temperature profile along the axis of the down-fired combustor. The NOx emissions are lower than those of ordinary pulverized coal combustion, and the NOx emissions are 390 mg/m3 and 352 mg/m3 in Case 1 and Case 2, respectively. At the range of 300-600 mm below the nozzle, the NO concentration decreases, mainly resulting from some homogeneous reactions and heterogeneous reaction. NO concentration has a little increase at the position of 800 mm below the nozzle as the tertiary air supplied to the combustor at the position of 600 mm below the nozzle.     

The Reduction of Thermal Nitrogen Oxides（NOx） Emission Using Staged Combustion in Furnace

The experimental study described in this paper is to investigated the control of thermal nitrogen oxides emissions from a 2.28 MW gas-fired test furnace.Tests,including changing axial or radial air flow rate.adding cooling water,and adding staged air,were performed to characterize and opimize the fuel-rich burning zone and the fuel-lean burnout zone independently.Detailed measurements of O2,CO2,CO,NOand NOx were made at the fuel-rich burning zone and furnace exit.The influence of forming CO,NO and NOx was examined.Results indicated that adding staged air in the fuel-rich burning zone(75cm from burner)will reduce the maximum NO and NOx emissions.Adding cooling water in a right position may further lower the NO and NOx emissions.In addition,the least formation of thermal nitrogen oxides in the first stage fuel-rich burning zone will occur at the stoichiometric ratio‘s inverse value ,(φ1)^-1,0.65 to 0.7.     

循环流化床锅炉低氧量燃烧对NOx排放的影响研究

叙述了NOx的生成机制及一次风率对NOx排放的影响,对循环流化床锅炉低氧量燃烧对NOx排放的影响进行了数据分析.     

锅炉燃烧调整对NOx排放和锅炉效率影响的试验研究

在2台典型的1025 t/h锅炉上进行了燃烧调整降低NOx排放浓度的试验研究,通过改变过量空气系数、辅助风配风方式、运行负荷和制粉系统运行方式等,测定了锅炉尾部烟道NOx排放浓度,分析了锅炉运行工况、运行方式对NOx排放的影响.结果表明:降低过量空气系数,烟煤锅炉NOx减排效果比贫煤锅炉好得多;降低负荷,烟煤锅炉的NOx排放量降低值较大;缩腰式配风的NOx排放浓度比均匀配风方式约降低10%,制粉系统的运行方式影响炉内燃料的燃烧状态和温度分布,也影响NOx的生成和排放.在不降低锅炉效率的前提下,调整燃烧工况,可降低锅炉排放NOx浓度1O%～20%.     

电站锅炉NOx排放控制的技术经济分析

根据近年来NOx排放控制技术的发展情况，总结了各种低NOx控制技术的特性以及其工程应用的技术经济性，可为电站锅炉的NOx排放控制技术改造提供参考，最后提出了低NOx技术可能的发展方向。     

SG-1 036/17.5-M871锅炉NOx排放特性的试验研究

通过采用燃烧优化技术进行南京华润热电有限公司4号炉NOx排放特性试验,大大降低了锅炉NOx的排放浓度,分析锅炉效率和NOx排放量与电站锅炉运行参数的关系,确定了锅炉低NOx运行方式,用于指导锅炉的高效低NOx的运行.     

烟气循环燃烧减排NO_x的影响因素研究

烟气循环燃烧是一种新型燃烧方式,将燃烧烟气返回用于燃烧,形成循环燃烧过程,可以减少NOx的排放,富集回收CO2。通过正交方法设计燃烧实验,得到影响NOx排放的关键因素。实验表明烟气循环比是影响烟气中NOx含量的重要因素,烟气全部循环可以减少NOx排放24%。循环比与排出的CO2量成正比,利用烟气循环将空气燃烧产生的烟气与空气混合共同助燃,可以富集CO2。     

基于车载排放法商用车排放影响因素研究

为研究商用车实际道路排放试验的影响因素,基于便携式排放测量系统(portable emission measurement system,PEMS)测试技术,进行多组车载排放试验。通过试验数据定性分析试验工况、整车速比、整车载荷、试验海拔等对整车PEMS测试结果的影响。研究表明,整车变速箱、后桥配置存在最佳速比匹配区间,稳定的驾驶工况有利于整车排放,高海拔地区排放变差,且高负荷工况恶化严重,整车载荷、空气湿度与排放结果呈负相关。并从排放检测试验过程、整车配置、整车ECU数据等方面对试验数据进行分析,确定试验条件变化影响整车后处理转化效率和发动机燃烧性能,导致发动机排放性能变化。     

CFD study on influence of fuel temperature on NOx emission in a HiTAC furnace

The influence of the fuel temperature on NOx formation was investigated numerically. For this purpose CFD modeling of NOx emission in an experimental furnace equipped with high temperature air combustion (HiTAC) system was studied. The comparison between the predicted results and measured values have shown good agreement, which implies that the adopted combustion and NOx formation models are suitable for predicting the characteristics of the flow, combustion, heat transfer, and NOx emissions in the HiTAC chamber. Moreover the predicted results show that increase of the fuel temperature results in a higher fluid velocity, better fuel jet mixing with the combustion air, smaller flame and lower NOx emission.     

湍流燃烧模型在燃烧室数值计算中的对比分析

对比分析了不同燃烧模型对某型回流式燃气轮机燃烧室流场的影响,建立了描述燃烧室流场的控制方程组,采用Realizablek-ε湍流模型,湍流燃烧模型分别为涡耗散模型(ED)、涡耗散概念模型(EDC)、简单概率密度模型(PDF)和稳态小火焰模型(SFM).对比分析了不同燃烧模型下燃烧室的温度场、速度分布以及NOx排放量,并...     

预喷正时对柴油机燃烧与排放影响的试验研究

通过台架试验,分析对比柴油机各参数随预喷正时的变化,研究多次喷射预喷正时对柴油机燃烧和排放性能的影响。试验表明,预喷正时决定缸内燃烧的放热始点和放热率,影响缸内的燃烧温度、爆发压力、NOx排放和碳烟的生成,预喷正时为20°时,爆发压力最大;预喷正时为35°时,热效率最高,油耗率和烟度最低;预喷正时为45°时,NOx排放最小。综合分析选择预喷正时40°作为折中优化方案,降低发动机油耗和NOx、碳烟排放,同时提高发动机的热效率。     

氢内燃机NOx排放特性的试验研究

以一台2.0L氢内燃机为测试对象,对其排放及燃烧特性进行了试验研究,探讨了NOx随当量比Φ点火提前角的变化关系.试验结果表明:在Φ=0.88时,NOx生成量达到最大;在Φ<0.88时,NOx的生成量随Φ的增加而增加;在0.88<Φ<1.2时,NOx生成量随Φ的增加急剧减少;当混合气比较稀薄时,点火提前角对NOx的贡献率相对较小.研究结果可用于氢内燃机稀薄燃烧技术的开发,可有效降低氢内燃机NOx排放.     

柴油机富氧燃烧排放特性的试验研究

介绍了在S195柴油机上进行富氧燃烧的试验,对柴油机排放特性进行了比较与分析,目的是通过试验研究,找到在富氧条件下同时降低碳烟和NOx排放的方法。研究结果表明,增加进气氧的质量分数,碳烟排放大幅度下降,HC和CO也趋于下降,但NOx排放显增加;推迟供油提前角,可以使NOx排放降低,但碳烟有上升趋势,HC和CO排放增加。所以,采用富氧燃烧时必须同时推迟供油提前角,才能获得较低的排放量组合。