Large eddy simulation of a 660 MW utility boiler under variable load conditions

Large eddy simulation (LES) has become a promising tool for pulverized coal combustion with the development of computational fluid dynamics (CFD) technologies in recent years. LES can better capture the unsteady features and turbulent structures of coal jet flame than Reynolds averaged Navier Stokes (RANS). The coal-fired power plants in China are now required to be operated in a wide load range and quickly respond to the electric grid. The boiler performance of variable loads should be evaluated in terms of flow, heat transfer, and combustion processes. In this paper, LES was applied to simulate a 660 MW ultra-supercritical boiler under BMCR (boiler maximum continue rate), 75%THA-100, and 50%THA-100 conditions. The predicted gas velocities agree well with the thermal calculation and the temperature error is less than 130 K. The simulation results show that the operation load has significant effects on the boiler performance. It is also proved that LES can provide guidance for the design and operation of advanced coal-fired boilers.     

350MW级多炉型能源站的配置和运行优化

根据350MW级用户热负荷持续时间图,结合链条炉、煤粉炉、循环流化床锅炉的成本与容量、效率与负荷率的关系,建立以投资成本和运行成本为目标的数学模型,依据能量平衡、燃烧稳定性和锅炉调节特性形成约束条件,对该数学模型采用等微增率算法和序列二次规划算法分别进行最优化求解,对于配置优化,等微增率算法给出一台容量为51MW的链条炉,一台容量为187MW煤粉炉,一台容量为130MW的循环流化床锅炉;序列二次规划算法给出一台容量为38MW的链条炉,一台容量为214MW煤粉炉,一台容量为108MW的循环流化床锅炉,对比能源站规范设计三台180MW煤粉炉的配置,等微增率算法优化配置的投资成本减小17.6%,序列二次规划算法优化配置的投资成本减小21.2%。针对该用户侧连续14天共336个时间点的热负荷数据进行运行优化,相比于规范设计方法,等微增率法的运行成本降低10.4%,序列二次规划算法的运行成本降低15.7%。     

电站锅炉炉膛传热数值计算方法的研究_反应器网络综合模型

文中介绍一种适合于工程应用的电站锅炉炉膛三维传热值计算的反应器网络综合模型;编制了煤粉炉膛三维综合燃烧——传热过程计算程序;通过若干不同设计和运行工况的计算,显示和验证了模型的基本功能,并得到了一些有意义的结论。     

A numerical study of pulverized coal ignition by means of plasma torches in air–coal dust mixture ducts of utility boiler furnaces

Paper presents selected results of numerical simulation of processes in air–coal dust mixture duct of pulverized coal utility boiler furnace with plasma-system for pulverized coal ignition and combustion stabilization. Application of the system in utility boiler furnaces promises to achieve important savings compared with the use of heavy oil burners. Plasma torches are built in air–coal dust mixture ducts between coal mills and burners. Calculations have been performed for one of rectangular air–coal dust mixture ducts with two opposite plasma torches, used in 210 MW_e utility boiler firing pulverized Serbian lignite. The simulations are based on a three-dimensional mathematical model of mass, momentum and heat transfer in reacting turbulent gas-particle flow, specially developed for the purpose. Characteristics of processes in the duct are analyzed in the paper, with respect to the numerical results. The plasma-system thermal effect is discussed as well, regarding corresponding savings of liquid fuel. It has been emphasized that numerical simulation of the processes can be applied in optimization of pulverized coal ignition and combustion stabilization and enables efficient and cost-effective scaling-up procedure from laboratory to industrial scale.     

燃尽风对炉内流动和燃烧过程影响的数值模拟

燃尽风作为降低锅炉NOx排放浓度的一个措施已在我国得到逐步推广应用。应用数值模拟方法，对1台600MW对冲燃烧煤粉锅炉，在满负荷下燃尽风对炉内流动、燃烧和传热过程的影响开展了研究工作。应用混合分数／概率密度函数法模拟湍流燃烧，用P-1辐射模型开展辐射传热模拟，利用拉格朗日／欧拉法处理气固两相间的动量、质量和能量交换，对挥发份的析出采用单步反应模型，采用动力／扩散反应速率模型模拟煤粉颗粒的表面燃烧。研究发现：一方面，燃尽风的应用改善了炉内气流的充满情况，延迟了煤粉燃烧过程氧气的供应，加强了炉内的还原性气氛，降低了炉内最高火焰温度，有利于降低NOx排放浓度；但另一方面。燃尽风的应用将导致煤粉燃烧效率下降。     

流化床-煤粉复合燃烧锅炉的炉膛传热计算方法

针对流化床－煤粉复合燃烧锅炉的特点,在综合考虑流化床、火焰和受热面之间换热的基础上,推导了流化床－煤粉复合燃烧锅炉炉膛传热计算的基本方程,得到了复合燃烧锅炉炉膛传热计算的零维模型半径验法。以某７５ｔ／ｈ树皮流化床－煤粉复合燃烧锅炉为例,进行了炉膛传热计算。图１表６参５     

旋流燃烧器掺烧燃气的设计与数值模拟

为了充分利用工业废气中有价值的热量,本文采用数值模拟计算和实验相结合的方法对旋流燃烧器加装燃气燃烧装置进行改造,提出了栅格型和旋流型两种改造方案,采用CFD方法选出最优的改造方案并用实验的方法去验证.结果表明:燃气经栅格型装置后流场稳定,燃气燃烧形成的高温烟气不影响煤粉燃烧,不会烧损燃烧器喷口,燃烧器整体运行状况良好....     

On-Line Performance Model of the Convection Passes of a Pulverized Coal Boiler

This article describes an on-line heat transfer simulation for the convection passes of a typical pulverized coal boiler (PCB) power plant that accounts for fouling. Performance analysis of heat exchanger assemblies employed in pulverized coal boilers was characterized using the effectiveness–number of transfer units (NTU) method. The model calculates instantaneous heat rates in different sections of the boiler so as to determine a local cleanliness factor. The effects of changing plant load are fully accounted for in the model. Generally, a close correlation between calculated cleanliness factors and normalized strain gage measurements of pendant section weight variations due to accumulated fouling was obtained. Furnace exit gas temperatures calculated by the model agreed reasonably well with measurements available in the literature for a similar design of PCB power plant.     

Modeling of NOx emissions from a W-shaped boiler furnace under different operating conditions

A numerical model for gas-particle flow dynamics has been combined with an NO_x chemistry post-processor to predict the formation of nitric oxide in a three-dimensional, W-shaped boiler furnace burning pulverized fuel. The model includes complex interactions in gas-particle turbulent flow, heat transfer, gaseous chemical reaction, coal combustion, and NO_x reaction chemistry. Because fuel nitrogen is released in proportion to burnout of pulverized coal particles, the particles are treated in a Lagrangian framework in order to track burning pulverized coal particles through the gas continuum. The results show capability of the model to describe NO_x emissions under different operating conditions for full and partial loads.     

膜法富氧局部助燃技术在煤粉锅炉上的应用

利用膜法富氧技术,在150 t/h煤粉锅炉上进行了局部增氧助燃技术的工业试验.实验表明:膜法富氧局部增氧助燃技术的应用,有效地解决了炉膛结焦和高温腐蚀问题;大渣及飞灰可燃物含量降低,提高了低负荷不投油稳燃能力;提高了锅炉热效率;降低了NOx排放量.     

A complete review based on various aspects of pulverized coal combustion

Coal is the most abundant energy source, and around 40% of the world's electricity is produced by coal combustion. The emission generated through it put a constraint on power production by coal combustion. There is a need to reduce the emissions generated through it to utilize the enormous energy of coal for power production. Detailed understanding of various aspects of coal combustion is required to reduce the emissions from coal‐fired furnaces. The aim of present paper is to review various aspects of pulverized coal combustion such as oxy‐fuel combustion, co‐combustion of coal and biomass, emissions from pulverized coal furnaces, ash formation and deposition, and carbon capture and sequestration (CCS) technologies to outline the progress made in these aspects. Both experimental and numerical aspects are included in this review. This review also discusses the thermodynamic aspects of the combustion process. Furthermore, the effect of various submodels such as devolatilization models, char combustion models, radiation models, and turbulent models on the process of pulverized coal combustion has been investigated in this paper.     

切圆燃烧锅炉炉膛传热过程综合模型及模拟计算

本文针对大容量煤粉锅炉的特点,对炉内各过程的数值模拟提出切合实际简化模型,用假想面有效辐射分析法模型计算内辐射传热,应用理想反应器的串并联网络模拟炉内宏观流动－燃烧过程,从而建立了适合于任意形状炉膛的传热计算综合模型,通过对一台６７０Ｔ／Ｈ锅炉进行的实例计算,对模型的准确性和实用性进行了初步验证,得到了较满意的结果。     

BG-35/39-Y/3型锅炉燃烧器改造及燃烧调整优化

通过对BG—35／39—Y／3型锅炉进行节能技术改造，将煤粉燃烧器改为水平浓缩煤粉燃烧器后，锅炉燃用贫煤时，燃烧稳定，飞灰可燃物含量降低，热效率提高，锅炉可在60％额定负荷下断油稳燃。     

炉膛四角切向深度分级气固两相流的数值模拟

根据NOx的生成机理，利用FLUENT商用软件，通过利用CFD平台，对采用深度分级燃烧四角切圆的炉膛试验台内气固两相湍流流场进行冷态模拟。本文研究表明，采用合适的数学模型和计算方法，进行四角切圆燃煤锅炉炉内气固两相流的数值模拟是可行的。通过对不同一次风和二次风布置状况进行模拟，在实现炉膛中心处呈还原性气氛，炉膛四壁成氧化性气氛的水平分级的条件下，优化垂直分级，找出理想的气固两相流动状况下的一、二次风的布置工况，初步找出深度分级降低NOx生成的方法。     

锅炉烟道漏风对对流受热面传热的影响分析

在理论分析的基础上结合实例说明了烟道漏风对烟气温度、对流放热系数、辐射放热系数、对流传热系数、对流传热量的影响,为减轻锅炉漏风的危害提供了理论依据.具体数据通过对某台再热煤粉锅炉的热力计算得到.     

可调煤粉浓度燃烧技术在670t/h贫煤锅炉上的应用

河南省鹤壁万和发电有限责任公司２号炉是配２００ＭＷ机组的６７０ｔ／ｈ燃煤四角切圆燃烧锅炉,１９９８年３月应用浙江大学热能工程研究所开发的双稳可调浓淡煤粉燃烧器对原第二、第三层直流燃烧器进行改造。改造后连续运行至的实践表明,在４５－５０％负荷下调峰,可不投助燃烧油稳定燃烧。在同样工况下,改后的飞灰可燃物含量高负荷（２００ＭＷ）和低负荷（１００ＭＷ）时分别从１．８３％和１．３２％下降到１．１２％和１．     

410t/h煤粉炉乏气送粉改造降低NO_x排放的试验研究

针对某电厂410 t/h煤粉炉在300 t/h以上高负荷下运行时NOx排放无法达标的问题,提出了将原中储式温风送粉系统改造为乏气送粉系统,技术方案为排粉风机出来的乏气全部送入一次风管道,直接采用乏气作为送粉介质输送煤粉,避免乏气直接送入炉膛造成的局部富氧气氛,从而有效抑制乏气中的煤粉燃烧NOx生成量。试验及调试结果表明,采用乏气送粉改造后,锅炉燃烧稳定、热效率未受影响,NOx排放降低到100 mg/m3以下(折算到氧量6%)。     

某电厂220t/h锅炉煤粉燃烧器改造设计方案

为提高某电厂220t/h煤粉锅炉燃烧器低负荷稳燃能力，拟采用浓淡燃烧技术对该炉燃烧器进行改造；下层燃烧器采用水平浓淡燃烧器，上层燃烧器采用上下浓淡燃烧器；为保证低负荷时的主蒸汽温度，上层燃烧器为摆动式燃烧器。     

The heat transfer coefficients of the heating surface of 300 MWe CFB boiler

A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.     

确定燃煤锅炉卫燃带敷设面积的一种代数计算方法

沿用锅炉热力计算标准方法中的集总参数方法，建立了炉内火焰与水冷壁管及卫燃带间的换热方程，并据此建立了燃煤锅炉卫燃带敷设面积计算用的代数计算公式，并以一台400t／h煤粉锅炉为例，用该公式详细分析了煤质特性、卫燃带的热物理参数、锅炉的运行方式及不投油稳燃负荷对所需卫燃带面积的影响。图7参6