Mathematical models and expert system for grate-kiln process of iron ore oxide pellet production.Part Ⅱ:Rotary kiln process control

Rotary kiln process for iron ore oxide pellet production is hard to detect and control.Construction of one-dimensional model of temperature field in rotary kiln was described.And the results lay a solid foundation for online control.Establishment of kiln process control expert system was presented,with maximum temperature of pellet and gas temperature at the feed end as control cores,and interval estimate as control strategy.Software was developed and put into application in a pellet plant.The results show that control guidance of this system is accurate and effective.After production application for nearly one year,the compressive strength and first grade rate of pellet are increased by 86 N and 2.54%,respectively,while FeO content is 0.05% lowered.This system can reveal detailed information of real time kiln process,and provide a powerful tool for online control of pellet production.

Mathematical Model for the Rotary Kiln Process and Its Application

A mathematical model to predict the operation behaviours of the rotary kiln process and to describe the axial distribution of process variables along the length of the reactor has been developed in present work.The model is established based on the principle of mass and heat balance in the system under a steady state with the consideration of kinetic characteristics of the processes.Four examples of the simulation processes in a pi- lot kiln and 3 commercial kilns by using the present mathematical model are given in this paper.The good agreement between the predicted results and the measured data has been obtained.

Mathematical models and expert system for grate-kiln process of iron ore oxide pellet production(Part Ⅰ):Mathematical models of grate process

Grate process is an important step in grate-kiln pellet production.However,as a relatively closed system,the process on grate is inaccessible to direct detection,therefore,it is hard to control.As a result,mathematical models of temperature distribution,moisture distribution and oxidation degree distribution in pellet bed,with good universality,computation speed and calculation accuracy,are presented based on analysis of heat transfer and physical-chemical reactions during grate process.And real-time visualization of temperature,moisture and oxidation degree distribution in pellet bed during grate process is realized.Model validation is displayed,and the similarity of 91% is proved.The results can reveal real time status on grate,and provide a solid foundation for the subsequent study of artificial intelligence control system of pellet production.

Modeling and optimization of rotary kiln treating EAF dust

Electric arc furnace （EAF） dust from steel industries is listed by the United Sates EPA as a hazardous waste under the regulations of the Resource Conservation and Recovery Act due to the presence of lead, cadmium and chlorine. The disposal of the approximately 650000 t of EAF dust per year in the U.S. and Canada is an expensive and unresolved problem for the majority of steel companies. The Waelz process has been considered as the best process for treating the EAF dust. A process model, combined thermodynamic modeling with heat transfer calculations, has been developed to simulate the chemical reactions, mass and heat trans- fer and heat balance in the kiln. The injection of air into the slag and the temperature profile along the kiln have been modeled. The effect of （CaO＋MgO）/SiO2 on the solidus temperature of slag has also been predicted and discussed. Some optimized results have been presented.

Mathematic simulation of heat transfer and operating optimization in alumina rotary kiln

Based on the analysis of material motion in the axial direction, heat transfer and mass transport processes in a rotary kiln, and combining with pulverized coal combustion, material pyrogenation, cooling of furnace wall finally, and heat transfer and mass transport equations, the combined heat transfer mathematical model for alumina rotary kiln was built up. According to the in-site real operation parameters, the heat transfer mathematical model was solved numerically for an alumina rotary kiln to predict the temperature profiles of gas and material in the axial direction. The results show that as the excess air coefficient reduces from 1.38 to 1.20, the temperature of the sintering zone increases and the length decreases. However, as the excess air coefficient reduces from 1.20 to 1.10, the temperature of the sintering zone decreases and the length increases. When the mixed coal amount at the end of kiln is reduced from 68.6 kg/t to 62.0 kg/t and the burned coal amount at the head of kiln correspondingly increases from 155.3 kg/t to 161.9 kg/t, the sintering zone temperature increases and the length reduces. The suitable excess air coefficient and mixed coal amount at the end of kiln are recommended for the rotary kiln operation optimization.

Simulation of water temperature distribution in Fenhe Reservoir

In order to evaluate the need of controlling the temperature of water discharged from the Fenhe Reservoir, the reservoir water temperature distribution was examined. A three-dimensional mathematical model was used to simulate the in-plane and vertical distribution of water temperature. The parameters of the model were calibrated with field data of the temperature distribution in the Fenhe Reservoir. The simulated temperature of discharged water is consistent with the measured data. The difference in temperature between the discharged water and the natural river channel is less than 3 ℃ under the current operating conditions. This will not significantly impact the environment of downstream areas.

基于二维热传导方程的COB-LED散热器热模拟

针对COB-LED(Chip on Board-Light Emitting Diode)散热问题,文中基于二维热传导方程建立了一个可快速计算COB-LED散热器表面热分布的数学模型。为了便于模型求解,采用有限差分法求解该数学模型并选择交替方向隐格式作为其差分格式。根据模型中的边界条件和初始条件设计COB-LED常温点亮实验,并基于ANSYS有限元分析软件进行仿真分析。通过比较求解结果、仿真结果和实验结果验证该数学模型的合理性。结果表明,求解结果与实验结果中最高温度相对误差约23.57%,且两者的温度变化趋势一致。求解结果与仿真结果中最高温度相对误差约34.84%,且温度分布较为接近,证明了该数学模型的合理性与正确性。

基于正态曲线和有效积温的美国白蛾发生预测和除治效果评估机制研究

经拟合,美国白蛾成虫羽化符合正态分布。求算出成虫-成虫高峰日有效积温常数为877.6±84.3日度、当年成虫高峰日有效积温常数309.3±31.5日度,并给出了通过高峰日有效积温和成虫种群消长趋势指数进行当代和下一代成虫数量预测的方法。在全种群治理理念的指导下,提出了空间覆盖量和种群覆盖量的概念,并在此基础上制定了一套幼虫种群死亡量计算方法,其可靠性在对往年飞防除治实践中得到了验证。

Comprehensive model for a slag bath in electroslag remelting process with a current-conductive mould

A mathematical model was developed to describe the interaction of multiple physical fields in a slag bath during electroslag remelting （ESR） process with a current-conductive mould. The distributions of current density, magnetic induction intensity, electromagnetic force, Joule heating, fluid flow and temperature were simulated. The model was verified by temperature measurements during remelting 12CrMoVG steel with a slag of 50wt%-70wt% CaF2, 20wt%-30wt% CaO, 10wt%-20wt% A1203, and 〈10wt% SiO2 in a 600 mm diameter current-conductive mould. There is a good agreement between the calculated temperature results and the measured data in the slag bath. The calculated results show that the maximum values of current density, electromagnetic force and Joule heating are in the region between the comer electrodes and the conductivity element. The characteristics of current density distribution, magnetic induction intensity, electromagnetic force, Joule heating, velocity patterns and temperature profiles in the slag bath during ESR process with current-conductive mould were analyzed.

Work roll thermal contour prediction model of nonoriented electrical steel sheets in hot strip mills

The demands for profile and flatness of nonoriented electrical steels are becoming more and more severe. The temperature field and thermal contour of work rolls are the key factors that affect the profile and flatness control in the finishing trains of the hot rolling. A theoretic mathematical model was built by a two-dimensional finite difference to calculate the temperature field and thermal contour at any time within the entire rolling campaign in the hot rolling process. To improve the calculating speed and precision, some special solutions were introduced, including the development of this model, the simplification of boundary conditions, the computation of heat transfer coefficient, and the narrower mesh along the edge of the strip. The effects of rolling pace and work roll shifting on the temperature field and thermal contour of work rolls in the hot rolling process were demonstrated. The calculated results of the prediction model are in good agreement with the measured ones and can be applied to guiding profile and flatness control of nonoriented electrical steel sheets in hot strip mills.

Temperature Field Simulation Model for Rotary Kiln of Iron Ore Oxidized Pellet

Based on conduction,convection and radiation heat transfer among the flue gas,kiln wall,and the pellet bed material,and on the basis of the coal combustion and analysis of reaction heat of pellet induration in the rotary kiln,the temperature field model of rotary kiln was established.Using visual studio net,matlab and open source computer vision library as development tools,combining with the ActiveX data objects database technology,the temperature field simulation system for rotary kiln of iron ore oxidized pellet production was developed.Temperature distribution of pellet and flue gas in rotary kiln was dynamically displayed.

The monitoring of burden distribution uniformity and even sintering technology

After expanding the capacity by widening the trolley of the No. 3 sintering machine, severe uneven sintering occurred in the trolley＇ s lateral distribution, which affected the output and quality of sinter. In this study, the quantitative evaluation indices of the burden uniform distribution in the width direction of the sintering machine is introduced for the first time. By measuring the temperature of discharged gas, a plane temperature field is constructed. Through analyzing the temperature field and the burden layer＇ s differential thermal equilibrium, a mathematical model for evaluating the indices, which is an online reflection of the degree of uniform distribution, is built. Following the improvements in burden distribution equipment ,the optimization of the ignition system and the dynamic adjustment of the process ,the problem of uneven sintering in lateral distribution has been solved, and the quality and the yield of sinter have been improved.

汽车温差发电系统的多物理场建模分析与试验

为了得到沿尾气流动方向汽车温差发电系统各温差发电片之间的温度分布差异,建立了汽车温差发电系统的流热电多物理场数学模型,该模型充分考虑了尾气流动和热电材料的温度依变性.分析了尾气温度和流量对温度分布差异的影响,并进行了汽车温差发电系统台架试验.结果表明:尾气温度的增加会加剧尾气流动方向系统各区域温差发电片之间的温度分布差异,当尾气温度从450 K增加到600 K时,差异相对增加105%;尾气流量的增加有益于减小温度分布差异,相比之下尾气温度是影响温度分布差异的主要因素;该多物理场数学模型计算精度可达97%.

小浪底水库垂向二维水温数值模拟研究

采用垂向二维水动力水温数学模型,研究模拟小浪底水库水温分布结构及年内变化规律。结果表明:小浪底水库库尾水深小,水温呈等温分布;坝前水深较大,会出现水温分层情况,具体表现为:4—6月坝前水温呈稳定分层结构,7—11月坝前水温呈等温分布,12月—次年3月坝前水温处于逆温结构。

回转窑内传热及燃烧过程的数值模拟

运用流体模拟软件Fluent和Matlab分别对碳素煅烧回转窑内气体空间和物料料层内的传热过程进行了研究,预测了窑内烟气、窑内壁和料层的温度分布。结果表明,窑内的高温区域主要集中在挥发分大量燃烧的区段上;二、三次冷空气的引入均会使窑内烟气温度明显下降,但对料层温度影响不显著。将窑外壁的计算结果与其实际测试结果进行了比较,两者吻合较好,说明该模拟方法的适用性,从而为碳素回转窑的优化设计和经济运行提供了指导和依据。

环形加热炉传热数学模型的研究

建立了以在线优化控制为目的的环形加热炉炉内传热数学模型。管坯内部采用柱坐标形式的二维非稳态导热模型 ,炉膛传热过程采用分段零维模型 ,并提出了适用于在线控制的炉内辐射换热的新解法。实测验证了模型的合理性和准确程度 ,实现了管坯温度的在线跟踪。在此基础上 ,开发了环形加热炉在线优化控制系统。该系统投入运行后 ,管坯加热质量有明显改善 ,环形加热炉燃耗和管坯氧化烧损分别降低了 6%和8%。

回转窑内气体和物料温度分布的研究

为进一步探索回转窑的优化设计及经济运行情况,在已有的回转窑传热研究的基础上,将其内部的传质过程与对流、辐射、传导3种热交换方式相结合,建立了计算回转窑温度分布的综合数学模型,预测了窑内烟气、物料及窑内壁的温度分布,并对某厂回转窑进行数值计算。结果表明:在距窑头约14m处,气体温度达到最高值,约为1760℃,物料温度约为1465℃,随后气体和物料温度沿窑长逐渐下降,到达窑尾处时分别降至约1028℃和856℃。计算结果与实际运行结果吻合较好,说明该模拟方法具有一定适用性。

石油焦煅烧回转窑综合传热过程数值模拟

研究了石油焦煅烧回转窑内的物理和化学反应过程对回转窑内传热过程的影响,并在对回转窑内的物料输送过程、传质过程和传热过程具体分析的基础上,建立了石油焦煅烧回转窑的综合传热数学模型.应用数值计算方法对传热数学模型进行计算求解,预测了窑内气体、物料和窑壁内外表面的轴向温度分布.结果表明,窑内的高温区域主要集中在挥发分大量燃烧的区段上,三次风的注入会引起窑内气相温度的明显下降,但不会造成料床温度的明显变化;在物料与气体、窑内壁之间热交换过程中,物料与被覆盖的窑内壁表面之间的对流换热和气体与料床表面间的辐射换热为主要的传热机制.计算预测的结果与测量数据在规律上和数值上都能较好地符合,从而为石油焦煅烧回转窑的优化设计和经济运行提供了指导和依据.

高温岩体地热开发的块裂介质固流热耦合三维数值模拟

在深入论述高温岩体地热开发研究与发展现状的基础上,提出了高温岩体地热开发的块裂介质固流热耦合数学模型及其数值模拟方法,提出了该数学模型详细的求解策略与求解方法。对6 000 m深的高温岩体地热开发进行了详细的数值分析,揭示了:(1) 岩体温度随地热提取降低及其分布变化的规律;(2) 岩体中基质岩块内、裂缝内应力随地热提取的降低规律;(3) 裂缝宽度随地热提取变化的规律。对高温岩体地热开发决策、技术方案选择提供了理论基础及其方法。

电阻点焊温度场分布的数值模拟

为研究点焊时焊接规范对电极温度的影响 ,以及镀锌钢板点焊时焊接参数的选择 ,利用轴对称有限元程序模拟了电阻点焊的过程中电极与工件的温度场分布 ,模型中采用标定法来解决接触电阻产热的问题 ;运用生死单元技术解决镀锌钢板焊接时镀锌层熔化的模拟问题 .结果表明 ,有限元点焊模型可以得到与实际焊接十分吻合的模拟结果 .电阻点焊时 ,不同规范的焊接参数对电极的温度分布影响较大 ,采用标准规范时电极的温度最低 ,故选择焊接规范时应考虑到对电极的影响 .镀锌钢板焊接时 ,熔化的锌层对焊接过程以及电极温度分布有显著影响 ,若采用无锌钢板的焊接规范基本上不能形成熔核 ,而正常焊接时电极最高温度将比无锌钢板点焊时高出 2 0 % ,因此 ,如何降低电极温度是一个重要问题 .