锅炉燃烧及NOx生成特性的数值仿真

针对煤燃烧排放NOx污染物造成污染,为了能准确地预测NOx的生成及提出更有效的控制NOx排放的措施,提出建立了煤粉锅炉的三维物理模型,并将炉膛分区域进行合理的网格划分.应用涡团耗散概念(EDC)模型耦合对化学反应机理对炉膛内煤粉的流动、燃烧及NOx的生成特性进行研究,炉内各组分的浓度分布与NOx的生成分布存在很强的对应关系,采用EDC模型耦合反应动力学机理进行仿真.结果表明方法可以很好地反映NOx的生成特性.可以较为准确地模拟NOx的生成特性,可准确预测和有效控制NOx的排放,为优化设计提供了理论基础.     

煤粉炉进风量分配对NOx排放量的影响仿真研究

针对超超临界煤粉锅炉燃烧过程中NOx的排放问题,从煤粉炉内煤燃烧机理以及NOx的生成机理出发,充分考虑了煤粉在不同小室的燃尽情况,建立了适用于NOx排放量分析的超超临界锅炉的数学模型。采用小室法将炉膛分成12个小室,从而得到一系列常微分方程组。然后利用MATLAB对模型进行求解,并利用模型求解结果与锅炉出口氧气浓度及屏底烟气温度对比来验证模型的准确性。最后利用该数学模型研究了进风量分配对炉膛内温度、O_2浓度、NOx排放量的影响。结果表明,煤粉炉中NOx的生成主要来自于挥发分NOx和焦炭NOx。此外,若主燃烧器区域O_2浓度越高则NOx排放量越高。在主燃烧器区域进风量和总进风量不变时,减少燃烧器上部紧凑燃尽风(Close-coupled Over Fire Air,CCOFA)的比例,可以有效降低NOx的排放量。     

太阳能电池连续式烧结炉温度场分析

烧结炉炉膛温度的均匀性控制是确保高性能太阳能电池产品质量的关键技术。针对烧结炉炉膛内同时存在热传导、对流、辐射三种传热方式,且相互影响的复杂热流体状态,在分析烧结工艺的基础上,采用了新型环保节能的红外烧结方式,并从理论上分析炉内温度场传热方式和气氛流场气体流动状态,建立温度场对流传热和辐射传热的数学模型,通过对炉内流场与温度场的三维数值仿真结果分析,为优化炉膛的结构设计及控制炉膛内的气流以改善炉膛内温度分布的均匀性提供理论依据,为设备的成功制造提供了可靠的保障。     

电站锅炉系统仿真建模的研究

本文应用面向对象的方法对电站锅炉系统进行了建模研究,并用C＋＋语言建立了电站锅炉系统的仿真程序库。根据不同仿真目的需要及不同的锅炉系统使用该程序库可以方便建立满足使用要求的仿真模型。最后给出了一台210MW锅炉在负荷波动时的仿真曲线。     

基于Simulation CFD平台四角切圆燃烧锅炉冷态空气动力场的仿真研究

采用基于CAD的新型计算流体力学软件Simulation CFD,对350MW切圆燃烧锅炉炉内的冷态空气动力场进行了数值模拟研究,分析结果表明,该方法不仅可以方便直观地立体三维显示炉膛内气流的流动情况,而且相比其它传统的计算流体软件如Fluent,Simulation CFD对计算机的要求低,计算速度快,能在较短的时间内完成锅炉炉内流动状态数值模拟,有利于实现锅炉炉内流动问题的快速诊断,为开发基于Simulation CFD平台锅炉在线监测系统奠定了基础。     

鼓泡流化床流动特性的数值仿真和实验研究

研究鼓泡流化床传热效率优化问题,在不同的初始床层高度下,鼓泡流化床内气固两相流动特性和燃烧效率会发生明显的变化.为研究鼓泡流化床在不同的初始床层高度下的气固两相流动特性,为减少厂用电的消耗和炉膛内的磨损,提出建立脉动进口速度边界条件下的二维鼓泡流化床气固运动模型,对颗粒的流态化进行建模,采用Fluent仿真软件进行仿真.仿真结果和实验表明,随着初始床层高度的增加:气泡直径增大,气体泄漏率减小,床层压力分布基本不变,颗粒相速度增大,流动结构的非均匀性增强,炉膛内磨损增大.仿真结果为优化设计提供了依据.     

900MW超临界直流锅炉的数学模型与仿真研究

结合“上海外高桥电厂900MW锅炉机组”的具体特点,该文建立了一套整体式非线性固定边界的超临界直流锅炉蒸发器的仿真模型、炉膛的燃烧模型、启动分离器模型和过热蒸汽的仿真模型。分析了蒸发受热面传热系数的变化、燃烧器的结构对烟温的影响、炉膛辐射热量分配方案、以及分离器蒸汽干度、过热器蒸汽凝结的计算方法。通过实时仿真计算,以及对仿真模型的阶跃扰动测试,证实该模型的合理性,成功地解决了国内单机容量最大的火电机组900MW超临界直流锅炉的全工况实时仿真问题。     

电站锅炉过热器的集总参数动态建模与仿真

研究锅炉过热器优化控制问题,针对传统过热器模型无法对大扰动工况进行高精度仿真的问题,给出了一个电站锅炉过热器的集总参数动态模型。模型描述了过热器压力-流量及焓-温通道的动态过程,并且充分考虑了两个通道间的耦合效应;在焓-温通道建模时,采用了多段集总参数建模的方法,从而更好地反映了过热器温度的分布参数特性。以某600MW控制循环锅炉末级过热器为对象,对减温水流量、过热器入口蒸汽焓值和吸热量扰动下该模型的动态响应进行了仿真。仿真结果表明,模型动态响应合理、精度较高,可以满足控制系统优化性能的要求。     

炉内辐射能检测及燃烧补偿控制装置设计

本文简述电站锅炉炉膛火焰电视监测装置获得的信号进行炉内温度监测以及区域性燃烧辐射能计量的基本原理,分析辐射能在燃烧控制调节过程中所处的地位和影响,得出采取炉膛火焰辐射能信号进行燃烧补偿控制以提高燃烧效率和改善锅炉安全性能以及负荷动态特性的可行性和合理性。介绍基于上述技术原理的辐射能补偿控制装置的基本结构、硬件结构和实现形式。     

强化悬浮式RSP型分解炉石油焦燃烧特性实验及数值模拟研究

水泥生产中分解炉内主要化学物理过程是煤粉的燃烧.与煤粉相比,石油焦是一种经济的替代燃料.本文首先通过实验测试出石油焦燃烧的物理化学特性,根据这些特性建立了石油焦在强化悬浮式RSP型分解炉中燃烧的数值模拟模型.该模型结合气固二相流理论,采用快速反应的PDF模型,对分解炉内石油焦的燃烧过程进行了数值模拟,揭示了分解炉内石油焦的燃烧机理.研究结果表明RSP型分解炉的炉型适宜于石油焦的燃烧,并且数值模拟的结果能为石油焦在分解炉内优化燃烧提供了理论依据和有利的信息.     

Influence of combustion parameters on NOx production in an industrial boiler

NO_x formation during the combustion process occurs mainly through the oxidation of nitrogen in the combustion air (thermal NO_x) and through oxidation of nitrogen with the fuel (prompt NO_x). The present study aims to investigate numerically the problem of NO_x pollution using a model furnace of an industrial boiler utilizing fuel gas. The importance of this problem is mainly due to its relation to the pollutants produced by large boiler furnaces used widely in thermal industrial plants. Governing conservation equations of mass, momentum and energy, and equations representing the transport of species concentrations, turbulence, combustion and radiation modeling in addition to NO modeling equations were solved together to present temperature and NO distribution inside the radiation and convection sections of the boiler. The boiler under investigation is a 160 MW, water-tube boiler, gas fired with natural gas and having two vertically aligned burners.The simulation study provided the NO distribution in the combustion chamber and in the exhaust gas at various operating conditions of fuel to air ratio with varying either the fuel or air mass flow rate, inlet air temperature and combustion primary air swirl angle. In particular, the simulation provided more insight on the correlation between the maximum furnace temperature and furnace average temperatures and the thermal NO concentration. The results have shown that the furnace average temperature and NO concentration decrease as the excess air factor λ increases for a given air mass flow rate. When considering a fixed value of mass flow rate of fuel, the results show that increasing λ results in a maximum value of thermal NO concentration at the exit of the boiler at λ = 1.2. As the combustion air temperature increases, furnace temperature increases and the thermal NO concentration increases sharply. The results also show that NO concentration at exit of the boiler exhibits a minimum value at around swirl angle of 45°.     

乙烯裂解炉燃烧传热的CFD模拟

为了掌握乙烯炉炉膛内的热场分布规律,本文采用CFD方法对SL-Ⅱ型工业乙烯裂解炉辐射段内所发生的燃烧、辐射传热、烟气流动等过程进行了耦合模拟,并且详细地分析了炉膛内流场及温度场的分布情况。其中,裂解炉的几何模型按照工程图纸1:1的比例建立;网格划分在专业网格生成软件ICEM11.0中完成;计算采用标准k-ε双方程模型模拟湍流,漩涡耗散/有限速率燃烧反应模型(EDM/FRC)模拟侧壁烧嘴的预混燃烧和底部烧嘴的非预混燃烧,离散传递模型(DTM)模拟炉膛辐射传热,计算过程在CFX5.0中完成。计算得到了裂解炉炉膛内流场、温度场分布的详细信息,模拟结果与工业实测数据吻合较好。模拟结果表明,在底部烧嘴的射流核心区周围形成了大范围的回流,过渡段拐角处有小范围的回流现象;炉膛长度、宽度、高度方向都存在明显的温度梯度,说明传统的炉膛传热计算方法假定温度分布均匀是不准确的;炉膛的高温区主要集中在炉高4.5 m处;炉膛上部的热量,由于侧壁烧嘴的加入而得到了很好地补充,说明侧壁烧嘴的安装位置合理。研究结果表明CFD模拟是目前为止研究裂解炉内热场分布规律最为有效的手段之一,对于未来乙烯裂解炉的设计与优化作用很大。     

高炉煤气流分布过程的多算法融合预测模型

在高炉生产中,准确的预测高炉煤气流分布状况将有助于保证高炉的稳定顺行.针对传统高炉煤气流预测模型的缺陷,本文提出了一种将带遗传因子的自回归移动平均模型(FF-ARMAX)和基于限定记忆的正则化极限学习机(RFMLS-RELM)相结合的高炉煤气流多步预测模型.在数据预处理方面,建立FF-ARMAX模型消除原始数据中的测量误差,同时采用傅里叶变换法消除数据中叠加的环境噪声.最后采用RFMLS-RELM算法进行多步预测,对比试验表明,该算法在应用于煤气流预测时,预测精度更高,适用于对煤气流分布状况的多步预测.多步预测实验结果表明,该模型虽然仍旧无法完全解决预测误差随预测步数的增加而不断叠加的问题,但相较于其他传统预测模型能够实现更好的预测效果和更高的预测精度,为高炉操作人员分析炉况提供了有效的帮助和支持.     

基于数据驱动多输出ARMAX建模的高炉十字测温中心温度在线估计

高炉（Blast furnace,BF）炼铁中,十字测温作为炉顶温度和煤气流分布监测的最主要手段,对高炉的安全、稳定和高效运行起着重要作用.然而,由于高炉炉顶中心部位温度较高,造成十字测温装置中心位置传感器极易损坏,并且更换周期长,因而无法及时判断炉顶煤气流分布.针对这一实际工程问题,本文基于时间序列建模思想,集成采用多输出自回归移动平均（Multi-output autoregressive moving average,M-ARMAX）建模、因子分析、Pearson相关分析、基于赤池信息准则（Akaike information criterion,AIC）与模型拟合优度联合定阶等混合技术,提出一种模型结构简单、精度较高且易于工程实现的十字测温中心温度在线估计方法.首先,提出利用因子分析与Pearson相关分析相结合的稳健特征选择方法选取多输出建模输入变量.然后,采用样本均值消去法预处理采集的高炉样本数据,使其成为离散随机数.基于离散随机数,建立算法简单、易于工程实现的M-ARMAX温度模型:为了克服传统基于AIC阶数确定造成模型阶次高、结构复杂的问题,提出在AIC准则基础上进一步引入模型拟合优度来选取模型最小阶,可保证模型估计精度的同时降低模型阶次;同时,采用可快速收敛的递推最小二乘算法辨识M-ARMAX模型参数,并用残差分析方法检验模型.工业试验和比较分析表明:建立的M-ARMAX模型能够根据实时数据同时对十字测温装置多个中心温度点进行准确和稳定估计,且模型估计误差符合高斯白噪声特性.     

CFD assisted modeling for control system design: A case study

This paper presents a novel modeling approach of coupling transient computational fluid dynamics (CFD) simulation with system identification for control system involving fluid flow and heat transfer. In order to illuminate the feasibility of this method, a fluid flow and heat transfer related process, i.e. a three dimension (3-D) spatio-temporal air temperature distribution and input (inlet air temperature) dependent process in the desert climate chamber, is considered. The distributed parameter models of the chamber temperature are identified using transient CFD simulation results and are then validated against the results obtained from the CFD simulations with high RT² (more than 0.97) and negative Young’s information criterion (YIC, less than ?11.8). The PI controllers embedded in CFD simulation are then developed based on the models. The performance of the closed-loop systems is also evaluated within the full-scale CFD model. The results show that CFD-based system identification is feasible to model fluid flow and heat transfer related processes.     

计算流体力学在烟气脱硫中的应用

为优化脱硫吸收塔内流场分布,提高脱硫效率,降低脱硫投资和运行成本,提出基于RANS方程和多相流模型的烟气脱硫数值模拟方法,基于FLUENT采用多相流模型针对吸收塔内烟气脱硫过程进行模拟.通过对吸收塔烟气和浆液区域进行建模及网格划分,并对内部和喷枪局部处流场进行数值模拟,分析得到浆液和烟气在吸收塔内的流动规律.模拟结果验...     

Numerical study of the optimum counter-flow mode of air jets in a large utility furnace

The SIMPLEC algorithm with the power-law scheme and the pseudo-time-step method were employed to numerically solve the governing equations for 3-D turbulent flow field in a 2023 t/h rated boiler furnace using two grid systems. The numerical diffusion was eliminated by adding a delayed correction term. The numerical results from two gridding systems agreed quantitatively and were compared with the other and also with the experiments. The grid independent simulation results are presented for two counter-flow modes of the air jets in an isothermal model of a tangentially fired furnace. The calculated velocity distribution qualitatively agreed with the experimental data. The results suggest that, unlike the concentrated counter-flow mode (identified as case CCF), the separated counter-flow mode (identified as case SCF) can efficiently prevent flow attachment to the furnace walls. The separated mode reduces the angular moment flow rate during flow attachment and SCF improves control of the heat imbalance in the horizontal flue.     

基于高炉炉况评价和反馈补偿的喷煤量决策优化

高炉炼铁过程操作者根据炉况设定喷煤量,针对在增减量的大小和时机上存在盲目性、粗糙性、滞后性难题,将高炉冶炼机理与专家经验、过程信息相结合,建立基于煤气流分布和炉缸热状态评价的喷煤反馈补偿模型.首先,分析提取表征高炉煤气流分布和炉缸热状态的重要参数,利用熵权法确定评价模型的输入参数权重,依据专家经验与数据统计分析相结合的方法划分参数等级,分别建立煤气流分布和基于炉温预测的炉缸热状态评价模型;其次,建立与炉缸热状态和煤气流分布相适应的喷煤量反馈补偿模型,消除喷煤设定值不确定性、滞后性影响,提高煤粉的燃烧效率,实时、准确地为现场操作人员提供喷煤设定值.     

Investigation into gas dynamics in an oxyfuel coal fired boiler during master fuel trip and blackout

In an oxygen fired power plant, a large amount of flue gas is recirculated, leading to an unavoidable interaction between the involved fans. The presented paper investigates the dynamics of the gas side at different safety related scenarios. A dynamic simulation model is therefore developed to study the flue gas behaviour in an oxyfuel pulverized coal fired boiler during a master fuel trip and a blackout of the plant. The generated numerical model contains the water/steam side of the boiler, starting from economiser inlet and ending at the hot reheat outlet, and the gas side, including all relevant fans, convective heat exchangers, gas–gas heat exchangers and flue gas cleaning devices. Furthermore, a set of additional models for coast down behaviour of axial fans has been implemented. For the master fuel trip case, different relevant parameters of process control measures regarding the gas dynamics have been analyzed and an optimized master fuel trip scenario is proposed. The blackout of an oxyfuel coal fired boiler at nominal load is detailed demonstrated. The numerical results show that the blackout scenario will not have any negative impact on investigated gas part of the boiler system since the observed lowest negative furnace pressure of −36 mbar can be handled with current state of the art technology.