新型液排渣燃烧器内燃烧特性的数值模拟

通过数值模拟的方式,研究了新型液排渣燃烧器在不同过量空气系数下的速度、温度以及组分浓度的分布情况.结果表明,在较小的过量空气系数(α=0.7,0.8)时,煤的燃尽情况较差;α≥1.0时,煤粉燃烧更完全,但却不利于氮氧化物的控制.采用分级燃烧的方式,控制燃烧器内为欠氧燃烧(取α=0.9)以降低局部氧浓度,既能达到液态排渣要求,又可抑制NOx的生成,并在高温烟气进入炉膛降温之后再补充燃尽风,使得可燃成分在炉膛内再次燃烧,提高燃尽率.通过模拟与实验相结合的方式,对燃烧器进行三种不同负荷下的热态实验研究,该燃烧器负荷适应性好,模拟结果与实验结果相吻合.     

微型燃烧器内甲烷预混催化燃烧的数值研究

微尺度燃烧存在热量损失大、易熄火、燃烧不完全、转化效率不高等问题,因此对微型燃烧器内甲烷的燃烧采取预混催化燃烧方式来提高燃烧的稳定性和转化效率,为微型发动机碳氢燃料燃烧技术奠定基础。采用连续介质层流有限速率模型和二阶离散方法对微型燃烧器微流道内的催化燃烧、流动和传热进行了三维数值模拟。结果表明,甲烷质量流量和过量空气系数对催化转化效率有一定影响,壁面温度是影响催化转化效率的主要因素。甲烷质量流量、壁面温度与最佳过量空气系数之间具有一定的变化关系。可根据催化温度选择富燃料或富氧燃烧方式来提高微尺度催化转化效率。恒壁温边界条件下,催化燃烧主要发生在燃烧腔的下壁面。     

300 MW四角切圆锅炉低负荷下燃烧特性数值模拟研究

随着环保标准提高,电站锅炉NO_x排放量控制日益严格。低氮改造可以有效降低NO_x生成,而对于改造后低负荷下炉内燃烧特性研究有限。对某电厂低氮改造后的一台300 MW四角切圆煤粉锅炉进行了低负荷下多工况燃烧特性的数值模拟,研究了过量空气系数、燃尽风量和一次风喷口给煤量对炉内速度场、温度场、组分浓度场的影响。通过改进网格系统,提高模拟结果的准确性。数值模拟结果和试验测量值偏差较小,说明其数值模拟结果可信。结果表明:随着过量空气系数的增加,炉内燃烧温度升高,还原性物质减少,NO_x排放量增加,当过量空气系数从1.20增加到1.30时,NO_x排放从221.12 mg/m~3增加到196.26 mg/m~3;随着燃尽风量增加,主燃区温度降低,燃尽区温度升高,主燃区温度的降低抑制了热力型NO_x的生成,NO_x排放量降低,当燃尽风量从20%增加到30%时,NO_x从231.21 mg/m~3降低到180.95 mg/m~3;一次风喷口给煤量变化对炉膛内温度场、组分浓度场和NO_x生成影响较小。     

运行参数变化对水煤浆流化燃烧过程的影响

为了深入了解水煤浆流化燃烧过程的规律,以"小室"为基础,结合流化床内气固两相流动及传热、水煤浆燃料的热解、挥发分及焦炭燃烧、污染物生成等子模型,建立了水煤浆在流化床锅炉中燃烧的综合数学模型。分析了当水煤浆流化燃烧装置锅炉负荷、过量空气系数及燃料中的挥发分份额等参数发生变化时炉内有关参数沿炉膛高度方向的变化规律。研究结果表明,与燃煤流化床锅炉相比,水煤浆燃烧锅炉炉膛底部的温度明显较低。另外,锅炉负荷越大,炉内温度越高,燃烧条件越好;过量空气系数对燃烧的影响并不是单调变化关系;煤种挥发分越高越有利于燃料的燃烧。     

新型低氮燃烧器在加热炉脱硝改造中的应用

抑制燃气燃烧装置产生的NO_x对保护大气环境是至关重要的一个方面。通过采用低NO_x的燃烧技术,改变燃烧条件抑制氮氧化物生成,从而降低NO_x的排放。影响燃烧过程中NO_x生成的主要因素是燃烧温度、烟气在高温区的停留时间、烟气中各种组分的浓度以及混合程度,对其进行了探讨。由于燃烧方法和燃烧条件对NO_x的生成有较大影响,因此可以通过改进燃烧技术来降低NO_x。选择新型低NO_x的燃烧器需考虑单台热负荷、燃料性质、空气供给量、温度、炉膛的高度,以及炉管与燃烧器的距离等影响因素,低氮燃烧器在加热炉脱硝改造中的应用取得了较好的效果。     

煤粉工业锅炉燃烧兰炭试验研究

为提高兰炭在煤粉工业锅炉上的燃烧效率,以陕西煤业化工集团生产的兰炭为原料,进行煤粉工业锅炉燃烧试验,分析了兰炭着火、稳燃、燃烬情况;针对兰炭燃烧过程中存在的问题提出解决方案。结果表明:高效煤粉工业锅炉双锥燃烧器的独特结构和浓相燃烧的方式,为兰炭的着火和稳燃提供了良好条件。在过量空气系数1.2,一、二、三次风比例分别为0.11、0.47、0.42,预热时间3 min,伴燃时间4 min的条件下,实现了兰炭粉的着火和自维持稳定燃烧,燃烧期间后部温度保持在550℃,炉膛中部温度大于800℃。针对兰炭燃烧存在燃烧器内燃点靠后、着火区域温度低和兰炭燃烧不完全等问题,提出可通过调整燃烧室的结构和尺寸,使燃烧器蓄热能力增强,延长煤粉预热时间,产生更多高温回流烟气,使兰炭在燃烧器中快速着火并稳定传播到炉膛,降低兰炭灰残炭率,提高燃烧效率。     

燃油燃气液槽换热系统在涂装前处理中的优化设计

本文介绍了通过优化加热器效率、热负荷比、对流放热系数、辐射放热系数设计方法，解决常见的火焰燃烧不充分、排烟温度高、喷淋液温度达不到工艺要求等问题。优化后的系统液槽内液体升温快，燃烧器可以较长小火燃烧时间停火，排烟温度低。     

模拟医疗垃圾组分的平衡分析

建立非化学当量平衡模型,根据物料守恒和G ibbs最小自由能原理对模拟医疗垃圾中的典型组分进行热力学平衡分析。考虑温度、压力和过量空气系数对产物的影响,从而预测完全燃烧后的可能产物及其所占百分比。结果表明,产物的生成和体积分数主要受温度和过量空气系数影响,压力的影响次之。要使得热解产物有高热值,应选择尽量小的过量空气系数,过量空气系数越大产物热值保持不变的温度越低。高的温度将促进污染物CO的产生,而加压有利于抑制CO的产生。     

褐煤燃烧过程的Aspen数值模拟研究

利用Aspen Plus软件对某褐煤的预干燥及燃烧过程进行模拟分析,研究干燥介质种类、干燥介质温度和干燥介质流量对干燥特性的影响,过量空气系数、空气预热温度和过氧系数对有害燃烧产物产率的影响。结果表明,提高干燥介质温度和增加干燥介质流量都利于褐煤的干燥,而干燥温度的影响更加明显。提高空气预热温度会使燃烧产物中的NO和NO_2产量增大;过量空气系数大于1时,过量空气系数增大会明显降低燃烧产物中NO和CO的产量;过氧系数大于1时,过氧系数增大会明显降低燃烧产物中CO的产量,而NO的产量会增加。褐煤燃烧过程有害燃烧产物的Aspen Plus数值模拟将对褐煤的高效清洁利用提供参考数据。     

58 MW煤粉工业锅炉空气分级燃烧试验研究

加快推进燃煤工业锅炉环保改造,有效降低煤粉工业锅炉大气污染物排放量,特别是降低NOx排放迫在眉睫。空气分级燃烧技术是一种减排效果显著,改造成本较低的低氮燃烧技术,已在电站锅炉得到成功应用。为考察空气分级燃烧技术在煤粉工业锅炉上应用效果,以煤科院某58 MW煤粉工业锅炉空气分级改造项目为研究对象,通过在侧墙上布置6个火上风喷口,实现空气分级燃烧。通过工程试验,采用特制水冷取样枪以及耐高温烟气分析仪,测量了该锅炉原工况(不采用火上风)与分级燃烧(采用火上风)工况下,炉内3个不同截面(每个截面10个取样点)以及双锥燃烧器内6个测点处烟气温度及烟气组分。结果表明,分级燃烧工况下,双锥燃烧器内在x=0.3 m测点后形成了高温、强还原性气氛,有效抑制了燃烧初始阶段NOx的生成。这是因为分级工况下双锥燃烧器内氧气被迅速消耗,焦炭燃烧反应速率显著下降,焦炭气化反应明显增强,故形成了较强的还原性,有效遏制了NOx的生成。炉内不同截面烟气温度及组成变化规律表明,原工况烟气温度分布整体呈现燃烧器射流中心高、外侧低的趋势,氧含量分布与温度分布趋势相反,而分级工况受双锥燃烧强还原性高速火焰以及火上风喷射的影响,截面温度波动较大,中间截面呈现燃烧器射流中心偏低的现象。分级工况在炉内形成明显的还原区,且表现为燃烧器射流中心CO浓度高、外侧低的现象,有效降低了炉内NOx生成。58 MW煤粉工业锅炉火上风空气分级低氮改造,在双锥燃烧器及炉内创造了合理的贫氧还原区,具有良好的低氮效果。     

布朗流程合成氨装置一段转化炉故障原因分析与对策

某布朗流程合成氨一段转化炉能耗一直过高,掺烧瓦斯气以来出现了烧嘴箱外壁超温、天然气烧嘴被烧坏以及过热蒸汽盘管严重变形的故障。为找出一段炉故障的原因,对一段炉工艺的热负荷进行校核,计算发现:烧嘴超负荷、燃气轮机乏气分配不合理、燃料废气的可燃组分含量低和高压蒸汽产量过大是造成一段炉故障的主要原因。根据故障原因提出了一段炉改进方案。实施后,一段炉高效平稳运行3a。     

Catalytic oxidation of natural gas using flameless burners of a new design

Various aspects of operating burners traditionally used for oxidizing gaseous hydrocarbons and heat exchangers used for heat recovery are considered. A method developed by FAST ENGINEERING LTD. for the efficient burning of fuel with deep heat recovery of waste gases while maintaining a given adiabatic temperature is described. The method is based on using a flameless burner and heat exchangers of a new design. Burner operation is tested on an experimental stand with determination of the dependences for the aerodynamic drag of a granular layer and the content of unburned hydrocarbons, CO, and NO _x in combustion products on the consumption of the fuel-air mixture and the adiabatic temperature of fuel combustion. The described method for burning fuel is shown to provide the desired temperature of combustion products for a consumer of heat energy and to reduce the consumption of fuel by 5–20%. Burning fuel at an adiabatic combustion temperature of no more than 1200°C virtually eliminates the CO and NO _x content in the combustion products. Designed flameless burner, new generation of heat exchangers, and technology for the efficient burning of fuel can be applied to vapor and water-heating boilers, gas turbines, and catalytic reactors to produce synthesis gas from natural gas for processing into hydrogen, ammonia, methanol, synthetic liquid hydrocarbons, and so on.     

利用原有锅炉回收吹风气潜热的设计与实践

利用原有锅炉，设计与之匹配的卧式燃烧炉和燃烧器回收造气吹风气潜热。通过工程实践，总结了对燃烧炉设计、弛放气最小用量、安全运行、调节负荷等方面经验，为回收吹风气提供了新的技术路线。     

Premixed gas combustion stabilized in fiber felt and its application to a novel radiant burner

Premixed gas combustion stabilized in a unique ceramic fiber felt has been investigated. Our aim was to better understand the flame structure and flame stabilization mechanisms in the porous felt medium in order to develop a new radiant burner. A novel recuperative radiant burner was designed and constructed. A flame stabilizes near the downstream interface of the porous medium that is an excellent selective thermal emitter. The burner was developed for use as a gas-fired light source. The combustion performance of the burner at various operating conditions and the effect of heat recuperation are presented. Combustion modes on the fiber felt were examined carefully. An optimal flame structure for the premixed gas combustion is attained and the flame stabilizes in the porous fiber felt at radiant mode combustion over a wide range of firing rates. The burner emits desired spectral radiation and generates fairly intense light at the conditions of heat recuperation. The light radiant burner could be used as an alternative low-glare light source in an integrated heat and light system in which the light is distributed through light pipes.     

Pore-level numerical simulation of methane-air combustion in a simplified two-layer porous burner

A simplified two-dimensional model of two-layer porous burner based on pore level is developed.The heat transfer of solid phase in porous burner is seen as the synergistic effects of conduction through con-necting bridges and surface radiation between the solid particles in the model.A numerical simulation study on the characteristics of flow,combustion and heat transfer in the two-layer porous burner is car-ried out using the pore level model,and the effects of the control parameters such as the inlet velocity and solid thermal conductivity on thermal non-equilibrium are investigated.The results show that the flame structure is highly two-dimensional based on pore level.Obvious thermal non-equilibrium in the burner for the two phases and solid phase are observed,the largest temperature difference between the gas and solid phases is observed in combustion zone,while the temperature difference inside the solid particles is largest near the flame front.The results also reveal that thermal non-equilibrium of por-ous burner is much affected by the inlet velocity and solid thermal conductivity.     

Combustion Wave Structure of AP Composite Propellants

The combustion mechanism of ammonium perchlorate (AP) composite propellants were studied. The oxidizer-rich propellants tested were made with excess concentrations of AP particles. The pressure deflagration limit of propellant decreases with increasing the concentration of binder. The combustion wave consists of two reaction regions I and II: the region I is the zone of AP monopropellant flame and the region II is the zone of diffusion flame. The heat flux feedback from the gas phase to the burning surface increases as pressure increases, and the heat flux is responsible for the burning rate characteristics.     

Microwave plasma combustion of coal

Microwave plasma is studied as an alternative to oil or gas fuel for ignition and stabilisation of burning of lean coal. The study is performed on an experimental set-up, which includes a burner with a microwave plasma generator, coal and air supply systems, and measurement equipment. Power and thermochemical characteristics of the coal-plasma interaction have been measured and analysed. The obtained results indicate an essential intensification of ignition and combustion processes in the microwave burner compared to those in conventional burners. In particular, it has been demonstrated that the microwave energy consumption is only about 10% of the required expenditure of oil or gas, measured in heat equivalent. A design of an industrial microwave-plasma burner is proposed. Prospects of such burner for applications at industrial boilers of power plants are discussed.     

Regimes of gas combustion in a porous body of a cylindrical heat generator

A stationary model of filtration combustion of a gas with allowance for conditions at the entrance to the porous body and conditions of heat exchange with the gas phase surrounding the burner and with the heat exchanger is proposed and numerically analyzed. Ranges of parameters where the regime of gas combustion with a narrow reaction zone near the outer surface of the porous body are determined. Mechanical stresses arising in the porous body owing to high temperature gradients and gas pressure in the pores are estimated. The rate of gas combustion and the radiative heat flux from the burner surface are plotted as functions of process-dependent parameters. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 18–29, January–February, 2009.     

油烧辊道窑燃烧室结构的水力模型研究

本文以相似理论为基础,对油烧辊道窑燃烧室进行水力模型模拟研究,用萘颗粒作为示综剂进行流场及温度场的分析,以探讨辊道窑的最佳燃烧室结构及合理的烧咀布设。