某300MW机组低氮燃烧器热态调整经验浅析

为全面掌握燃烧器改造后机组实际的NOx排放量与锅炉热效率,同时掌握锅炉运行特性,对某厂300MW机组,依次进行主燃烧器区域各二次风门、周界风门和各燃尽风风门、各角燃尽风风门上、下摆动,左、右摆动以及主燃烧器区域氧量的调整,提出二次风及燃烧器摆动,燃烬风及燃烬风摆动,二次风总风门,氧量方面的指导意见。     

对回转窑煤粉燃烧器合理配风的探讨

从当前的工程设计来看，回转窑煤粉燃烧器一次风的配风都过大，一般都要大20％-40％，个别大约50％～60％，其中有许多生产线煤风比实际需要的甚至大100％，压力的选择也过大。燃烧器的配风，实际上就是一次风的合理配用，本文对此进行探讨。     

对预分解窑煤粉燃烧用风命名之我见

目前,煤粉燃烧用风的命名混乱,这既影响技术交流,也给生产操作造成麻烦。对此,业内知名老专家——江旭昌先生对烧成系统中最复杂的用风问题进行了梳理。经他梳理后的概念清晰、独立且具有顾名思义的特征。即:通过窑头燃烧器喷入到窑内的常温风或冷风,即煤风和净风之和统称为"一次风";由冷却机产生的进窑高温风称为二次风;由冷却机产生的进炉高温风称为三次风;窑尾燃烧器所用的煤风称为"窑尾煤风",窑尾燃烧器所用的净风则称为"窑尾净风"。     

新型双通道煤粉燃烧器流场模拟

为了优化新型双通道煤粉燃烧器结构参数,采用计算流体动力学软件建立燃烧器-回转窑物理模型,使用κ-ε湍流模型和SIMPLE算法,对回转窑内流场进行冷态数值模拟。分析旋流角度和旋流风速变化对回流区的影响,结果表明:喷嘴附近二次风存在旋转现象;旋流风角度增大,回流区范围扩大,向靠近燃烧器方向移动,旋流风速增大,回流区范围增加幅度较小;低旋流角度,依赖轴向速度差卷吸二次风,高旋流角度加快旋流风径向扩散,不利于卷吸二次风。     

对窑外分解窑煤粉燃烧用风问题的看法

随着窑外分解窑的发展和生产的需要,为了降低窑用“一次风”量,增加对窑用“二次风”的使用和能够灵活调节火焰,提高窑头煤粉燃烧的热效率,自70年代以来,发达国家相继研制开发了三通道煤粉燃烧器。尽管各种燃烧器的组成结构不完全相同,但对所用风的要求基本上是一样的。即外风为轴流风,内风为旋流风,内、外风之间是煤风。1对一次风和一次风机的一般认识三通道煤粉燃烧器的“煤风”即是大家所熟悉的窑用“一次风”,产生“一次风”的风机即是“一次风机”。那么,这里的“轴流风”和“旋流风”应该称为什么风呢?产生它们的风机又应如何称呼呢?…     

水泥生产工艺方面的中庸之道(连载四)

<正>15好的燃烧器就一定有好的结果吗燃烧器对熟料煅烧的重要作用是不言而喻的,但由于每条窑的情况不同,而且就同一条窑来讲,原燃材料和工艺状况也在不断地变化着,所以,其使用的好坏还与对其适时合理的调整至关重要。如果调整不好,一台好的燃烧器就不一定能取得好的结果。只有合理调整燃烧器一次风的风量、风压,调整外风、内风、中心风的蝶阀开度,调整各风道的截面积、出口风速,调整燃烧器在几何上的三维定位、倾斜度,提高煤粉着火前段的煤粉浓度,强化各风道的回流混合,加强燃烧器对高温气体的卷席作用,才能达到好的燃烧效果和火焰形状。应该强调的是,对燃烧器的每一次调整,都要有专人做好认真仔细的记录,以备以后的调整和烧成工况的分析提供依据,切忌多人管理和记录,造成不应有的混乱局面。     

风速对骨料烘干煤粉燃烧器排放特性的影响

基于煤粉燃烧机理,结合骨料烘干工艺,建立了骨料烘干煤粉燃烧器内部场的控制模型,采用Fluent软件模拟煤粉燃烧器内部燃烧状况,考察了一、二、三次风的风速对煤粉燃烧器中心轴线处CO, CO2, NO和SO2浓度的影响。结果表明,在研究的风速范围内,一、二、三次风风速越大燃烧越充分,一、二、三次风风速越小,产生的NO越少;三次风风速为40 m/s时,SO2浓度最低;较合理的控制参数为一次风风速30~35 m/s,二次风风速45~50 m/s,三次风风速30~40 m/s。     

煤粉燃烧器及对熟料煅烧的影响

正煤粉燃烧器火焰的温度、长度、粗细、位置对熟料的烧成有重大影响,直接关系到产量、质量、耐火材料的使用寿命,以及回转窑内温度分布,特别是不规则的附窑皮粘附过渡带上容易引起筒体变形。1煤粉燃烧器的作用回转窑煤粉燃烧器的作用就是调节火焰(燃烧器也可称为射煤器),有力的火焰才是良好的火焰。下面以笔者的理解与实践分析燃烧器。1.1轴流风与旋流风的作用(1)轴流风。引射二次风及煤粉使之充分混合并具     

基于无烟煤为燃料的TJB燃烧器的使用效果及性能分析

我公司5000t/d水泥熟料生产线改用无烟煤后,原窑头燃烧器不太适应无烟煤。改用TJB燃烧器后,熟料质量明显改善,产量提高10%,热耗降低,一次风用量减少,点火容易升温较快。仔细观察发现,该燃烧器在用风、结构和尺寸上不同于原燃烧器。     

高速煤粉燃烧器内燃烧特性数值模拟及结构优化

高速煤粉燃烧器火焰喷射速度高达60~200 m/s,炉膛内火焰较长,对流换热比例提高,使得炉膛内温度分布均匀,没有传统低速煤粉燃烧器火焰短,炉膛内局部过热和结焦等缺点。笔者以14 MW高速煤粉燃烧器为研究对象,采用数值模拟的方法,研究旋流强度、二次风温度等关键参数对燃烧器内煤粉燃烧的影响,针对燃烧器内煤粉燃烧特点进行结构优化设计。对旋流强度研究结果表明,当旋流强度S=2.2、2.8、3.2及3.7时,燃烧器内回流区形状变化不大,从一次风喷口开始到旋流叶片位置结束,回流区环绕一次风管;最大回流量在一次风喷口附近,距离一次风喷口越远,回流量越小;旋流强度对一次风喷口附近最大回流量影响不大,喷口附近最大回流量均在0.45 kg/s左右,当距喷口超过一定距离(L/H<0.35)时,旋流强度对回流量的影响开始变得明显,表现为旋流强度越大,回流区末端回流量越大,回流区末端回流量最大为0.30 kg/s,最小为0.17 kg/s。研究燃烧器喷口处燃烧状态表明,喷口处火焰旋流强度为0.10~0.28,与入口旋流强度正相关,火焰喷射速度150 m/s,为中等旋流强度的高速旋流火焰;喷口中心区可燃性组分富集,缺氧,燃料和氧气分层分布。当旋流强度提高,喷口中心区可燃性组分浓度降低,CO浓度从11%降低到10%,H2浓度从1.65%降低到1.40%,焦炭浓度从0. 14%降低到0. 11%,喷口边缘O2浓度从13%降低到10%。旋流强度S=3.2和S=3.7时可燃组分和氧气浓度分布变化较小,说明旋流强度提高对燃烧的影响减弱。考察0、100和200℃下二次风温度对燃烧的影响,结果表明,当二次风温度提高,煤粉在燃烧器内的反应时间有所降低,从0.15 s降低到0.11 s,但燃烧器内的煤粉碳转化率提高20%,达到65%。对燃烧器结构进行优化,加入中心风,对比中心风直流和旋流与不加中心风3种状态,结果表明,加入旋流中心风和直流中心风后喷口中心区半径r≤75 mm范围内可燃组分浓度降低,采用直流时由于气流刚性较强,喷口中心区氧气浓度升高,采用旋流中心风对中心区氧浓度影响弱,对可燃组分浓度降低效果优于直流中心风。     

Effect of primary air flow types on particle distributions in the near swirl burner region

A three-component particle-dynamics anemometry is used to measure, in the near-burner region, the characteristics of gas-particle two phase flows with two swirl burners with different primary air flow types, on a gas-particle two phase test facility. One burner is the radial bias combustion swirl pulverized coal burner whose primary air is non-swirl, and the other is the swirl burner whose primary air is swirl. With the former one, particle volume fluxes, particle volume fractions and particle number concentrations are bigger near the edge of central recirculation zone, and the particle volume fractions and the particle number concentrations are also bigger in the central recirculation zone. With the latter one, the particle volume fluxes and particle number concentrations are less near the edge of the central recirculation zone, and they are bigger in the wall zone. The influence of gas-particle flow characteristics on combustion has been analyzed, and the theory of air-surrounding-coal combustion is given.     

Fractal and turbulence characteristics of aerodynamic fields of swirl burners

Turbulence intensities at the exit of a centrally fuel rich (CFR) burner were measured employing a probe with hot-film sensors. In addition, using glycol as a smog tracer, optical images of the highlighted primary airflow were taken with a CCD camera and contrast-enhanced by computer. Profiles of the interface between primary and secondary air were obtained from which fractal dimensions (FDs) of the primary air boundary were estimated. Results indicate that FDs of this air boundary are in the range of 1.10–1.30 depending on burner conditions. As the FD and mean turbulence intensities of the primary air boundary have uniform distributions, they can be used to analyze coal combustion and NO_x formation characteristics of the burner. When either decreasing the outer secondary air vane angle or increasing either the inner secondary air vane angle or total mass flow rate of the secondary air, the burner swirl number increases which subsequently shows up as an increase in the FD and mean turbulence intensities of the primary air boundary. Increasing the ratio of the mass flow rate of inner to outer secondary air decreases the burner swirl number, but increases the FD and mean turbulence intensities of primary air boundary.     

煤粉工业锅炉燃烧器研究进展

燃烧器作为煤粉燃烧技术核心关键设备,主要作用是将燃料与空气合理混合,使燃料稳定着火并形成某种流场以利于后续完全燃烧。实现安全节能环保燃烧,必须根据燃料的特性,选择合理的燃烧器类型及布置形式。因此,本文介绍了国内外几种典型的旋流燃烧器的分类及其特点,并总结了旋流燃烧器的发展趋势。     

Development of an oxycoal swirl burner operating at low O2 concentrations

This work is to clarify the underlying mechanisms of burning pulverised coal in a mixture of CO₂/O₂. The performance of two different burner designs, single central orifice-type (SCO) and single annular orifice-type (SAO), under oxycoal conditions was examined in a down-fired test facility. Based on detailed in-flame measurements, combined with numerical simulations, the main parameters influencing the stability of a CO₂/O₂ pulverised coal swirl flame were investigated. The oxycoal flame was stabilised at the burner quarl by: increasing the O₂ concentration above 34 vol% without changes to the air-firing burner design and by modifications of the burner geometry thus changing its aerodynamics. The modification of the burner allowed a decrease of the O₂ concentrations to 23 vol% for SCO burner and to less than 21 vol% for SAO burner. Comprehensive measurement data for axial and tangential velocity, flue gas temperature and oxygen concentration for stable oxy-firing at 21 vol% O₂ is presented. The results reported can be used as a guideline for a development of an industrial swirl burner capable of stable operation in both regimes, namely: air and oxycoal.     

Factors influencing the ignition of flames from air-fired swirl pf burners retrofitted to oxy-fuel

Combustion tests were undertaken in a vertical pilot-scale furnace (1.2 MWt) at the IHI test facility in Aioi, Japan, to compare the performance of an air fired swirl burner retrofitted to oxy fired pf coal combustion with the oxy fired feed conditions established to match the furnace heat transfer for the air fired case. A turn down test at a reduced load was also conducted to study the impact on flame stability and furnace performance.Experimental results include gas temperature measurements using pyrometry to infer the ignition location of the flames, flue gas composition analysis, and residence time and carbon burnout. Theoretical computational fluid dynamics (CFD) modelling studies using the Fluent 6.2 code were made to infer mechanisms for flame ignition changes.Previous research has identified that differences in the gas compositions of air and oxy systems increase particle ignition times and reduce flame propagation velocity in laminar systems. The current study also suggests changes in jet aerodynamics, due to burner primary and secondary velocity differences (and hence the momentum flux ratio of the flows) also influence flame shape and type.For the oxy fuel retrofit considered, the higher momentum flux of the primary stream of the oxy-fuel burner causes the predicted ignition to be delayed and occur further distant from the burner nozzle, with the difference being accentuated at low load. However, the study was limited to experimental flames being all Type-0 (low swirl with no internal recirculation), and therefore future work consider higher swirl flames (with internal recirculation) more common in industry.     

Study on flow fields of centrally fuel rich swirl burner and its applications

Experiments on a single-phase test facility were done to optimize primary air outlet cones of a centrally fuel rich swirl coal combustion burner. On the basis of optimized results from the single-phase test, a three-component particle-dynamics anemometer was used to measure, in the near-burner region, the characteristics of gas/particle two-phase flows for the burner with two primary air outlet cones, on a gas/particle two-phase test facility. Velocities, RMS velocities and particle volume flux profiles were obtained. According to the results, the primary air outlet cone structure of the centrally fuel rich burner was matching a 670 ton per hour boiler. The performance of the burner on a 670 ton per hour boiler was studied.     

Study of the influence of vane angle on flow, gas species, temperature, and char burnout in a 200 MWe lignite-fired boiler

We measured various operational parameters of a 200-MW_e, wall-fired, lignite utility boiler under various outer secondary air vane angles. The parameters measured were gas temperature, gas species concentrations, char burnout, and component release rates (C, H and N). Cold air experiments of a single burner were conducted in the laboratory. A double swirl flow pulverized-coal burner has a single ring recirculation zone that forms in the secondary air region in the burner. By decreasing vane angles, maximum values of radial velocity, tangential velocity and turbulence intensity all increase. Moreover, swirl intensity of air flow and recirculation zone size increase. Concomitantly, in the central region of the burner, decreasing the vane angles of outer secondary air increases gas temperatures, CO concentrations, char burnout and component release rates of C, H, and N, while O₂ and NO_x concentrations decrease, and an early ignition of pulverized-coal occurs. Meanwhile, in the secondary air region of the burner, conditions are similar except that NO_x mean concentrations are reversed showing instead an increase. In the side wall region, gas temperatures increase, O₂ and NO_x concentrations decrease, but CO concentrations vary only slightly.     

Emissions and wall temperatures for lean prevaporized premixed gas turbine combustor

Experimental studies are carried out for investigating emission and wall temperature for traditional gas turbine combustor converted to lean premixed prevaporized (LPP) combustor. Vortex chamber, air preheating system, flat flame burner and inlet temperature control system are designed. Vortex chamber was maintained at the main air inlet port for controlling secondary air flow rate and wall temperature. Kerosene/air mixture temperature at exit from burner and entering combustion chamber was kept constant at 650 K for all runs. Special considerations were given for measuring NO_X, UHC, CO, local A/F ratio, flame temperature, exhaust gases temperature and wall temperature. For swirl and non swirl cases, secondary air ratio and primary zone air/fuel ratio were varied. The different operating parameters affecting flame temperature through it is affecting on local A/F ratio which is the main parameter for controlling flame temperature, emissions and walls temperatures. Flat flame burner and vortex chamber are useful tools for reducing emission and controlling walls temperatures. The inner liner wall temperatures are more affected by primary zone equivalence ratio while the outer liner wall temperatures are more affected by secondary air flow rate. Semi empirical correlations for NO_X, UHC and CO concentrations, exhaust gases temperature and maximum inner liner wall temperature are carried out. Good agreement between the measured and the calculated results are obtained. The present results are useful for further development of the traditional gas turbine combustor converted to LPP combustor.