考虑炉气非灰特性的辐射全交换面积

考虑加热炉内炉气的非灰特性,区别了炉气对不同表面的发射率及其对不同表面有效辐射中各分量的吸收率,通过求解反射热流密度推导三元辐射体系(炉气-炉壁-钢坯表面)中辐射全交换面积的简化表达式。以某轧钢厂的一座步进梁式加热炉为例,对辐射全交换面积沿炉长方向的分布进行模拟计算,并研究了炉壁发射率对炉壁表面段与钢坯表面段间辐射全交换面积的影响。推导的辐射全交换面积表达式,耗费机时较少,可用于加热炉在线控制数学模型中钢坯表面辐射热流的准确计算。     

CSP辊底加热炉供煤气量随坯厚、坯温变化规律的模拟研究

研究了CSP辊底加热炉内的传热过程及其规律.采用数值模拟的方法,在进行合理简化后,建立总能量平衡基础上的炉内热过程数学模型,其中辐射传递方程的求解采用离散坐标法.自主开发了该炉型的通用热过程模拟软件,采集包钢CSP薄板坯连铸连轧厂的生产数据进行验证计算,计算所得钢坯温度与实际温度的相对误差小于1%,表明该模型假设合理,建模正确;该软件能够应用于该类型加热炉的设计、管理和研究等领域,为确定CSP生产线高拉速(提高入炉坯温)、多钢种的生产工艺参数创造了条件.     

Heat Transfer and Energy Analysis of a Pusher Type Reheating Furnace Using Oxygen Enhanced Air for Combustion

 Oxy-fuel firing is more energy efficient and environmental friendly than conventional air-fuel firing and its application for reheating furnaces has begun since 90s. In this study, a computational methodology is presented to predict the steady heat transfer to the billets and temperature distribution in a continuous Pusher type reheating furnace which combustion air is enhanced by oxygen. The furnace is modeled as 2D radiating medium and Weighted Sum of Gray Gases model is used for absorption coefficient. The billets are moved in constant speed through zones of furnace. Radiative heat flux calculated from the radiative heat exchange within the furnace is modeled using the FVM considering the effects of furnace walls and billets. Energy consumption per ton of steel, production rate and thermal efficiency of furnace, and trend of NOx emission in various levels of oxygen enrichment is investigated by comparison with baseline furnace (21% O2 in air).     

两种非灰气体辐射特性模型的研究

加热炉内的传热以非灰气体参与的辐射换热为主,准确求解炉气的辐射特性对于炉子热过程数学模型至关重要.本文考察了两种非灰气体辐射特性模型,即Edwards指数宽带模型和Leckner级数式,并应用这两种模型计算了二氧化碳和水蒸气的辐射特性.结果表明,在加热炉的工作温度和压力行程范围内,两种模型在总体上具有相当的精度,但是在实际生产过程中,却有必要根据模型的计算精度、采用的燃料不同和现场的硬件设备及其存储和耗时的要求,对二者的最优适用范围予以区分.     

加热炉内钢坯非稳态温度场模拟及“黑匣子”实验研究

采用数值模拟方法,以能量平衡和热传导方程为基础,通过分析加热炉内的传热过程,按照加热工艺要求,采用总括热吸收率法,建立了加热炉热工过程数学模型。并以普碳钢为实验钢种,合理设置测试点,完成了＂黑匣子＂实验,模拟结果与实验结果吻合较好。钢坯柱坐标下非稳态温度场的模拟是准确合理的,所建立的数学模型可以作为加热炉在线控制中钢坯温度场的动态实时跟踪计算和SCC决策的基础。     

Mathematical modeling of an aluminum casting furnace combustion chamber

A mathematical model has been developed for the combustion chambers of aluminum casting furnaces by combining the fluid flow code PHOENICS with a zone model for the radiative heat transfer analysis and a simplified flame model. It offers flexibility in specifying the size and the combustion and heat transfer characteristics of the furnace. Thus, the model can be used to study a combustion chamber under different operating conditions and for different design op-tions. This paper presents the model and describes the coupling mechanism between PHOENICS and the zone method. Various case studies have been carried out for a 72-ton melter-holder. Results are presented which show the negative effect of ambient air inleakage on furnace per-formance as an application example. T. BOURGEOIS, Formerly Graduate Student.     

Total Heat Exchange Factor Based on Non-Gray Radiation Properties of Gas in Reheating Furnace

Modified mathematical models based on imaginary plane zone method in reheating furnace were developed in which non-gray radiation properties of gas were considered,and the Newton's method and the finite difference method were adopted.Effects of productivity,fuel consumption,fuel-air ratio,calorific value of fuel and inserting depth of thermocouple on total heat exchange factor along the length of reheating furnace were investigated.The resuits show that total heat exchange factor increases with productivity or inserting depth of thermocouple,and it decreases when fuel consumption,fuel-air ratio or calorific value of fuel increases.The results are valuable for dynamical compensation of total heat exchange factor for online control mathematical models in reheating furnace.     

专用炉模式下加热炉群混装一体化生产

分析了连铸-热轧区段混装一体化生产和加热炉群生产模式,并在此基础上建立了混装一体化生产下加热炉群调度模型.模型在满足加热炉生产工艺的基础上充分考虑了板坯进入加热炉前的等待时间和轧机空闲时间.采用禁忌搜索算法对模型进行了求解.最后,针对大批量少品种和小批量多品种两组板坯对某钢厂1580mm轧线非专用炉模式与专用炉模式分别进行了仿真.仿真结果表明连铸-热轧区段采用专用炉模式生产比传统的非专用炉模式生产能够明显提高加热炉热效率.      

环形加热炉无水冷大跨度新隔墙的实践

在研究了大型环形加热炉传统水冷式隔墙存在的、影响着炉子生产的问题之后,介绍了抚顺钢厂Ф11m环形加热炉利用1990年大修机会上去的一种不用水冷梁、下弦平直的由炉顶钢结构梁吊挂的大跨度隔墙。运行近两年表明:整体性强,坚固耐用;年节约工业用水可达55万t,减少的水冷热损失相当于年节约重油670t。     

订单生产对加热炉提出全新要求

对湘钢宽厚板厂加热炉进行了热平衡测试,其热效率为60．09％,可比单耗37．35kg／t,在国内同类型加热炉能耗比较中处于中上水平。分析了订单化生产对加热炉经济指标造成的影响,湘钢宽厚板厂加热炉比国内先进同类型加热炉氧化烧损率高0．8％-0．9％,而炉底强度低300-600kg／（m3·h）。针对订单化生产对加热炉操作提出全新要求,湘钢需要不断优化生产组织,提高板坯质量,实施热送热装,完善加热炉操作控制,     

基于炉气非灰辐射特性的钢坯表面热流研究

 基于加热炉内炉气的非灰辐射特性,指出三元辐射体系(炉气 炉壁 钢坯表面)中炉气存在2种发射率和6种吸收率。应用射线跟踪方法推导钢坯表面热流表达式,解除了Τимофеев公式中炉壁为零热流和炉气为灰体的限制。以某轧钢厂的一座步进梁式加热炉为例,对其钢坯表面热流进行了模拟计算。推导的钢坯表面热流表达式为加热炉在线控制数学模型中钢坯表面热流的简化算法提供了理论依据。此外,给出了炉气为非灰时的辐射全交换面积的一种计算方法,为准确求解加热炉炉膛内的辐射热交换创造了条件。     

绝热层结构等效有限元模型的研究及应用

为了简化绝热层的有限元计算模型,提出了等效换热系数的概念,将绝热层和热交换介质的传热过程简化成等效热交换,并由此给出了平壁和圆筒壁传热的等效换热系数计算公式。该方法不仅极大地简化了热力学中的有限元模型,而且顺利解决了一些由于模型过大导致的问题。仿真结果表明:该方法准确可信,将其应用于鼓风站管道的有限元计算中,取得了令人满意的结果。     

大型管道绝热层结构等效有限元模型的简化研究及应用

为了简化大型管道绝热层的有限元计算模型,本文给出了等效换热系数的概念,将绝热层和热交换介质的传热过程简化成等效热交换,并由此给出了平壁和圆筒壁传热的等效换热系数计算公式。该方法不仅极大地简化了热力学中的有限元模型,而且顺利解决了一些由于模型过大导致的问题。仿真结果表明:该方法准确可信, 将其应用于鼓风站管道的有限元计算中,取得了令人满意的结果。     

Computer Simulation of the Slab Reheating Furnace

Abstract

The development of a mathematical model for predicting steady-state heat transfer within the push-type slab reheating furnace is described and preliminary model predictions presented. Radiative exchange within the furnace chambers is calculated using the zone method, while the thermal response of the slabs moving through the furnace is obtained using a finite difference approximation for transient two-dimensional conduction, neglecting axial effects. The model accounts for the presence of the skidrail structure and the furnace sidewalls, but in its current form requires knowledge of the temperature distribution within the furnace gas. In addition to longitudinal temperature and heat-flux profiles, contour plots of slab temperature in the transverse plane of the furnace are presented. At any longitudinal distance into the furnace, heat flux to the slab surface is shown to vary significantly across the slab, even for the case of uniform transverse gas temperature. In agreement with other studies, the primary cause of skidmark formation is found to be radiative shielding of the slab surface by the skidrail structure. The model indicates that skidmark severity can be expected to increase with furnace throughput, but this situation could be alleviated by reducing the size of the skidrail structure. The effectiveness of reflective coatings applied to the skidrail surfaces, in reducing skidmark effects, is found to depend upon the temperature of the surfaces relative to the local slab surface temperature.     

矿热炉炉衬结构的温度场分析

为进一步研究矿热炉炉衬中温度场的分布情况,采用ANSYS仿真软件对真实简化的炉衬模型进行仿真分析。通过改变炉内温度和对流换热系数的数值,得到炉壁处的温度数据,与实测数据进行对比,验证模拟数据的合理性。结果表明,炉衬中不同耐火材料的温度分布存在差异;炉壁温度会随着炉内温度的增大而逐渐升高,随着对流换热系数的增大而降低;炉壁温度随对流换热系数的变化曲线斜率从0.13降到0.06,当曲线斜率逼近于0时,对流换热系数不再影响炉壁温度的变化,得到最优化的对流换热系数;模拟数据占实测数据的百分比在3%~8%范围内时,模拟数据能合理反映炉壁温度值。这为炉体保温结构设计和耐火材料的选用提供依据。     

Simplified mathematical models of heat transfer in continuous fuel-fired furnaces

Introduction of the model based on the equations of radiative and convective heat transfer connected with equation of heat conduction in stock. Walking beam, roller-hearth and pusher furnaces. Radiative transport coefficients, mean beam lengths and configuration factors computation. Examples of furnace calculation. Use of the generalized temperature response charts.     

用段法分析高辐射率涂料强化传热的机理

用段法计算了灰体和非灰介质加热炉中的热交换，分析了炉壁热阻和炉壁内表面黑度对炉内辐射换热的影响，阐明在不同的介质中，炉壁特性对炉内辐射传热影响的机理是不同的，第一次得出在非灰介质加热炉中，炉壁温度会随炉壁黑度的增大而降低的结论。     

加热炉用耐火材料的进展

综述了加热炉用耐火材料的发展历程 ,介绍了各个时期加热炉用耐火材料的特点及应用情况 ,并重点阐述了正在迅速发展的蓄热式加热炉用耐火材料。还对加热炉用耐火材料的发展方向进行了探讨     

冶金工业中的计算传热问题和计算传热学的应用

简要介绍了冶金工业的范围、主要流程以及传热问题的分布情况。对于计算传热学研究和应用比较集中与活跃的工艺流程及设备，例如铸锭过程、连铸、炉子和电解槽等，介绍了应用实例和主要方法。以连续加热炉为背景，对照介绍了计算传热学与现代控制理论在这类问题中的某些本质联系。     

The Influence of Oxide Scale on Heat Transfer during Reheating of Steel

The present work presents methodology and development of a mathematical model for prediction of the influence of oxide scale on heat transfer during reheating of steel in an industrial furnace. In this developed model, temperatures inside the steel billet were measured and with thermocouples at selected places and were collected by a water cooled computer that was traveling inside the slab. CFD is used to calculate the flow field inside of a furnace. The mass‐transfer coefficient of the scale formation is obtained by solving the convection mass‐diffusion equation across a boundary layer to the surface of a flat plate. A model for inverse heat conduction is employed to calculate the local surface temperature and heat flux on top of the growing oxide scale layer on a slab moving through a walking beam reheating furnace. By using the inverse method, the transient temperature and heat flux was firstly determined on the surface of the steel. During subsequent computations, the growth of the scale was calculated and the surface temperature of the oxide scale was extracted by using the Cauchy data from the previous calculations. The sensibility of the model on steel physical parameters is studied, and suitable parameters were obtained for heating a low carbon steel plate in the reheating furnace. Results show that the oxide scale layer should not be neglected in reheating models.