Advanced control of walking-beam reheating furnace

Rehearing furnace is an important device with complex dynamic characteristicsin steel plants. The temperature tracing control of reheating furnace has great importance both tothe quality of slabs and energy saving. A model-based control strategy, multivariable constrainedcontrol (MCC) for the reheating furnace control is used. With this control method, the furnace istreated as a six-input-six-output general model with loops coupled in nature. Compared with thetraditional control, the proposed control strategy gets better temperature tracing accuracy andexhibits some energy saving feature. The simulation results show that the performance of the furnaceis greatly improved.

Dynamic simulation on effect of flame arrangement on thermal process of regenerative reheating furnace

By analyzing the characteristics of combustion and billet heating process, a 3-D transient computer fluid dynamic simulation system based on commercial software CFX4.3 and some self-programmed codes were developed to simulate the thermal process in a continuous heating furnace using high temperature air combustion technology. The effects of different switching modes on injection entrancement of multi burners, combustion and billet heating process in furnace were analyzed numerically, and the computational results were compared with on-site measurement, which verified the practicability of this numerical simulation system. The results indicate that the flow pattern and distribution of temperature in regenerative reheating furnace with partial same-side-switching combustion mode are favorable to satisfy the high quality requirements of reheating, in which the terminal heating temperature of billets is more than 1 460 K and the temperature difference between two nodes is not more than 10 K. But since the surface average temperature of billets apart fi＇om heating zone is only about 1 350 K and continued heating is needed in soaking zone, the design and operation of current state are still needed to be optimized to improve the temperature schedule of billet heating. The distribution of velocity and temperature in regenerative reheating furnace with same-side-switching combustion mode cannot satisfy the even and fast heating process. The terminal heating temperature of billets is lower than that of the former case by 30 K. The distribution of flow and temperature can be improved by using cross-switching combustion mode, whose terminal temperature of billets is about 1 470 K with small temperature difference within 10 K.

Software sensor for slab reheating furnace

It has long been thought that a reheating furnace, with its inherent measurement difficulties and complex dynamics, posed almost insurmountable problems to engineers in steel plants. A novel software sensor is proposed to make more effective use of those measurements that are already available, which has great importance both to slab quality and energy saving. The proposed method is based on the mixtures of Gaussian processes (GP) with the expectation maximization (EM) algorithm employed for parameter esti- mation of the mixture of models. The mixture model can alleviate the computational complexity of GP and also accords with the changes of operating condition in practical processes. It is demonstrated by on-line estimation of the furnace gas temperature in 1580 reheating furnace in Baosteel Corporation (Group).

Numerical simulation of fluid flow in a reheating furnace with multi-swirling-burners

A general numerical simulating program for three-dimensional (3-D) andtime-dependent fluid flow for a reheating furnace with multi-swirling-burners has been developedbased upon an arbitrary Lagrangian-Eulerian scheme (ALE) with the finite volume method. Theparameters of fluid flow in a reheating furnace with multi-swirling-burners was calculated and the3-D velocity distributions were obtained. The design of the burners was optimized for forming betterswirling flow. The simulation shows that the fluid flow in the reheating furnace with the optimizedburners is reasonable.

Mathematical Model of Dynamic Operation and Optimum Control of Billet Reheating Furnace

This paper provides a mathematical model for the billet reheating process in furnace.A new optimum method is brought up that the objective function is the integral value of enthalpy increasing process of a billet.Different delays are simulated and calculated,some proper delay strategies are ob- tained.The on-line computer control model is de- veloped.The real production conditions simulated, the temperature deviation of drop out billet from the target temperature is kept within±15℃.

RESEARCH ON THE DYNAMIC MATHEMATICAL MODEL OF REHEATING FURNACE

This paper presented a dynamical mathematical model for reheating furnace based on energy balance, which consists of three submodels. With the inputting parameters, adopting the finite difference technique, not only the combustion gas temperature but also the temperature distribution of slabs in the furnace can be predicated. The dynamical mathematical model is the base for the further control and it also can be treated as a simulator of a reheating furnace, optimal and advanced controlling strategies can be applied based on the dynamical model.

Present development of rolling reheating furnace technology in Shougang

By analyzing recent development of reheating furnace in Shougang,the direction of rolling reheating furnace is large type,high efficiency,lower pollution and automation etc.Many advanced technologies are integrated in new rolling reheating furnace such as working beam,regenerative combustion,evaporation cooling and hot loading and hot feeding etc.It shows that reheating furnace technology is upgraded.During the process of product structure adjustment in Shougang,because product heating quality is improved,energy-saving of reheating furnace should pay attention to aspects such as energy-saving of heating variety steel,equality of heating steel,heating system,oxidation loss and so on.This will offer reference for energy-saving of domestic and overseas reheating furnace technology.

Analysis of Efflorescence of Castables in Walking Beam Reheating Furnace

When the castable refractory linings are installed without drying out sufficiently and exposed to high humidity for a long time,white fibrous or powdery substance appears on the surface,which is called“efflorescence”.The main reason is the cement of castable refractory linings contacts with C02 and moisture in the atmosphere to form calcium carbonate(CaC03).In general,efflorescence takes place more readily in lightweight castable refractories.In the walking beam reheating furnace construction project,there are many white powdery substances in the walking beams,because the construction procedure causes poor ventilation in the surrounding area,and the internal moisture of castable refractory linings cannot be evaporated effectively.In future,the project programming should consider the environmental humidity and surrounding ventilation.

Numerical Simulation of a Batch-Type Reheating Furnace

A numerical analysis of a batch-type reheating furnace with and without thermal load was carried out using the Computational Fluid Dynamics technique. The furnace has two premixed burners and methane is used as fuel. Previous to the numerical experiments, a mesh convergence test was carried out and the average internal furnace temperature and the exhaust gases temperature were monitored as function of the number of cells in the discretized system. The influence of the Air/Fuel ratio, the position of the burners, and the thermal load on the average internal temperature, the exhaust gases temperature, and the molar fraction of methane and oxygen in the exhaust gases was numerically explored.

Application of the porous medium combustion technology in the chamber reheating furnaces at Baosteel

The design of the porous medium combustion （PMC） system which has been applied to chamber reheating furnaces is presented in this study and its main application effects are described in detail. Porous medium materials are mainly ceramic ball sucked granular bed porous media and foam ceramic porous media. This study investigates the foam ceramic porous medium and a schematic diagram of the combustion inside this porous medium. The PMC takes a solid medium as its main heat exchange way, thus greatly improving the heat transfer efficiency. Judging from the application effects,the following conclusions have been made： the PMC technology can save more than 25% of energy with remarkable effects; the furnace temperature uniformity can be significantly enhanced; the porous media combustion technology can make the heating furnace design in a more compact way, reduce the time for heating up the furnace, improve the heating rate and reduce energy consumption.

Castables for Steel Rolling Reheating Furnace

1 Scope This standard specifies the classification, technical requirements, test methods, quality appraisal procedures, packing, marking, transportation, storage and quality certificate of castables for steel rolling reheating furnace.

Optimal control for spatial-temporal distributed nonlinear autoregressive with exogenous inputs correlation model of steel rolling reheating furnace: a coordinated time-sharing control approach

Accurate control of slab temperature and heating rate is an important significance to improve product performance and reduce carbon emissions for steel rolling reheating furnace(SRRF).Firstly,a spatial temporal distributed-nonlinear autoregressive with exogenous inputs correlation model(STD-NARXCM)to spatial temporal distributed-autoregressive with exogenous inputs correlation model(STD-ARXCM)in working point is established.Secondly,a new coordinated time-sharing control architecture in different time periods is proposed,which is along the length of the SRRF to improve the control performance.Thirdly,a hybrid control algorithm of expert-fuzzy is proposed to improve the dynamic of the temperature and the heating rate during time period 0 to t_(1).A hybrid control algorithm of expert-fuzzy-PID is proposed to enhance the control accuracy and the heating rate during time period t_(1) to t_(2).A hybrid control algorithm of expert-active disturbance rejection control(ADRC)is proposed to boost the anti-interference and the heating rate during time period t_(2) to t_(3).Finally,the experimental results show that the coordinated time-sharing algorithm can meet the process requirements,the maximum deviation of temperature value is 8-13.5℃.

纳米隔热材料在板坯加热炉水梁中的应用研究

针对新型纳米绝热保温材料在高温板坯加热炉的应用,开展了传统水梁包扎方式与新型纳米隔热包扎方式的对比研究。通过数值仿真分析对不同方案隔热效果及温度分布进行了预测,并搭建水冷实验系统对采用不同包扎方式的水梁散热量进行测试分析。测试结果表明随着炉温逐步升高,纤维隔热材料的导热系数快速上升,常规纤维隔热水梁散热快速增加,而纳米隔热材料的导热系数增加较小,故此纳米隔热水梁的散热增加较为缓慢,两种方案散热量的差距随着炉温升高而逐渐增大。在此基础上开展了工程应用,应用效果与数值仿真及实验研究数据吻合良好。工程应用对比结果表明,纳米隔热水梁相对传统水梁包扎方案可实现水梁区域能耗降低25%,具有较好的经济和生态效益。

燃用高碱煤1000MW超超临界一次再热锅炉炉膛特征参数的选取研究

研究了高碱煤锅炉炉膛特征参数的选取,对1000MW超超临界一次再热锅炉炉膛尺寸的选择进行了探究。

关键参数智能优化建模方法及其在铜板带加热炉智能燃烧系统中的应用

针对铜板带产品种类众多,数学模型参数调试难的问题,提出了基于智能优化的智能建模方法。该模型根据运行过程中采集的仪表数据和测试数据,通过智能优化算法优化出模型关键参数。结合加热炉一级控制程序的改进和二级数学模型的软件开发,智能燃烧系统在铜板带步进式加热炉上成功应用,改善了铸锭加热的一致性,并节省了吨铜的天然气消耗。

垃圾焚烧发电超高压机组系统配置方案研究

文章阐述了不同蒸汽参数机组的应用现状,分析了主蒸汽压力增加对锅炉、汽机等的影响,介绍了两种典型的垃圾焚烧发电超高压机组系统配置方案,分别是中温超高压机组的炉内再热、中温超高压机组的炉外再热方案。将两种方案进行了技术及经济性对比,同时以(2×750)t/d规模的炉排炉垃圾焚烧项目为例,与普通中温中压、中温次高压、中温超高压方案进行了对比。通过各种方案的技术经济对比分析,为垃圾焚烧电厂选择蒸汽参数及再热方案提供了参考。

加热炉水梁垫块结瘤研究及对策

在棒材生产中,偶有成品批量性出现固定位置轧疤、折叠缺陷的现象。由于缺陷处于轧件下部,在生产过程中不容易被发现,当在成品检查阶段发现时,经常导致批量产品判废,造成较大的成本损失和质量风险。每次问题均在加热炉检修之后消除,但经过一段时间会再次出现,成为生产中难以解决的瓶颈问题。在加热炉加热制度研究、烧嘴燃烧状态分析、垫块材质试验基础上,对加热炉水梁垫块结瘤问题进行系统性剖析,与现场实际情况结合,并多次进入加热炉内考察验证,总结出加热炉垫块结瘤问题的解决思路与预防措施。采取针对性措施后,结瘤问题得到明显改善,具有较高的推广价值。

莱钢厚板生产线加热炉提产能降燃耗技术分析

为了快速有效地降低加热炉能耗,针对莱钢厚板生产线能源消耗大户加热炉的燃料消耗影响因素进行分析,结合现场实际情况实施技术改造。装钢时序优化提高了装钢节奏,拓展热送热装坯型结构增加了板坯单重、提高了热送热装率;通过加热工艺优化、停轧降温制度、炉体节能技术等方面的措施,延长了加热炉维修周期和使用寿命。莱钢厚板线年产能提高到172.3万t,煤耗指标降低到1.424 GJ/t,达到了提高产能、降低能耗的预期效果。

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 to reheating furnaces has begun since 1990s. A computational method was presented to predict the steady heat transfer to the billets and temperature distribution in a continuous pusher type reheating furnace in which combustion air was enhanced by oxygen. Radiation heat flux calculated from the radiation heat exchange within the furnace was 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 were investigated by comparing with baseline furnace （21% of O2 in air）. The results showed that the best range of oxygen enrichments was between 21% and 45% by volume, as the higher slope of flame temperature and production increase occur in this range. The reduction of energy consumption can be obtained up to 18% per ton of steel for oxygen enrichment of 60 % by volume.

Thermal insulation constructal optimization for steel rolling reheating furnace wall based on entransy dissipation extremum principle

Analogizing with the heat conduction process, the entransy dissipation extremum principle for thermal insulation process can be described as: for a fixed boundary heat flux (heat loss) with certain constraints, the thermal insulation process is optimized when the entransy dissipation is maximized (maximum average temperature difference), while for a fixed boundary temperature, the thermal insulation process is optimized when the entransy dissipation is minimized (minimum average heat loss rate). Based on the constructal theory, the constructal optimizations of a single plane and cylindrical insulation layers as well as multi-layer insulation layers of the steel rolling reheating furnace walls are carried out for the fixed boundary temperatures and by taking the minimization of entransy dissipation rate as optimization objective. The optimal constructs of these three kinds of insulation structures with distributed thicknesses are obtained. The results show that compared with the insulation layers with uniform thicknesses and the optimal constructs of the insulation layers obtained by minimum heat loss rate, the optimal constructs of the insulation layers obtained by minimum entransy dissipation rate are obviously different from those of the former two insulation layers; the optimal constructs of the insulation layers obtained by minimum entransy dissipation rate can effectively reduce the average heat loss rates of the insulation layers, and can help to improve their global thermal insulation performances. The entransy dissipation extremum principle is applied to the constructal optimizations of insulation systems, which will help to extend the application range of the entransy dissipation extremum principle.