Gas flow and pressure balancing in modeling grate/kiln induration

The performance of iron-ore pellet induration plants, including their energy consumption, is critically dependent on the relative flowrates and conditions of gas streams involved in the process. Equations and procedures for gas flow and pressure balance calculations within a dynamic mathematical model of the complete grate/kiln induration process are presented. Detailed simulation results, including pellet temperature profiles, enthalpy balances, and heat losses for a particular operating plant are discussed. Energy consumption per tonne of product changes appreciably with production rate, and there is a rate at which the specific fuel usage is minimized. Fuel oil consumption is increased if part of the oil is burned in the grate furnace rather than in the kiln.     

工艺参数对转底炉冶炼能耗的影响

针对转底炉生产存在产品金属化率低、冶炼能耗高、烟气含尘量大、生产效率低等问题.通过建立转底炉冶炼数学模型,计算了不同工艺参数对转底炉冶炼能耗的影响规律.结果表明:转底炉产品金属化率与烟气对含碳球团的二次氧化有关,增大还原区煤气供应量,可以减少含碳球团二次氧化,提高产品金属化率;助燃风预热温度和富氧率对冶炼能耗影响显著,提高助燃风预热温度和富氧率可以降低燃烧消耗,提高冶炼效率.助燃风预热温度每提高100℃,煤气消耗可以减少75 m3;助燃风富氧率达到20％时,煤气消耗量减少50％,烟气量减少57％.     

Investigation of factors affecting pellet strength in straight grate induration machine

Abstract

During induration in a straight grate machine, the green pellets pass through four different thermal treatments, namely drying, preheating, heating and cooling. The pellet bed is fired with downdraught firing leading to thermal gradients through the bed. Corex sludge, which is used as fuel in the pellet mix, supplies the necessary energy for uniform heating of the pellet. The physicochemical conditions, e.g. the temperature and oxygen partial pressure mainly depend on the amount of fuel incorporated in the pellet mix. As a result the percentage and the distribution of various phases in the pellets vary, leading to deviation in quality. To study the distribution of phases and their impact on cold crushing strength at different carbon levels (1·20 and 1·35%), pellets from different layers of the induration bed in an industrial straight grate were characterised. It was observed that the strength of the pellets varied from 142 to 268 kg/pellet and 128 to 245 kg/pellet across bed, with carbon 1·20 and 1·35% respectively. It was found that middle layer pellets had higher strength compared to top and bottom layers. It was observed that amount of hematite, magnetite, porosity and the pore size plays a significant role on the pellet strength. Pellets with 1·20% carbon showed better physical and microstructural properties across the pellet bed compared to pellets with 1·35% carbon.     

降低轧钢加热工艺的燃耗与烧损

轧钢加热过程中，降低燃耗与烧损具有重要意义，分析了影响工业炉的燃耗与烧损的主要因素，得出结论：降低出炉温度，缩短在炉时间及控制了内气氛是关键，另外，加热工艺操作也很重要，最后提供了工业炉窑节能降耗的实践经验。     

球团竖炉的利用系数研究

利用过程集成的方法,对球团竖炉的干燥带进行了热量和质量衡算,根据球团竖炉利用系数的定义,考虑了影响球团竖炉利用系数的关键因素,建立了球团竖炉利用系数与竖炉结构及操作参数的定量关系式,得到球团竖炉利用系数与干燥床与焙烧带的面积比以及冷、热风与球团矿的热流比呈正比,导风墙与干燥床面积比与冷却风与球团矿的热流比之比至少为0．1624,球团矿的粉化是影响竖炉内气体流动的关键因素。     

强化链篦机-回转窑氧化球团生产的途径

本文通过对原料选择到成品球团矿产出各个工艺环节的分析，提出了强化链篦机-回转窑氧化球团生产的途径。特别强调了优化造球原料、造好球、布好料以及保证链篦机的运行和提高链篦机尾部温度提高入窑强度是强化生产的关键。     

带式焙烧机制备镁质熔剂性球团研究

为了提高高炉球团矿入炉比,从而降低钢铁生产能耗,缓解日益严峻的环保形势,基于氧化球团焙烧基础理论,结合相关学者研究成果,对镁质熔剂性球团特性进行分析和梳理,在此基础上对带式焙烧机球团工艺制备镁质熔剂性球团的热工参数进行了研究.结果表明,得益于镁质熔剂性球团的良好技术经济指标,可以实现高炉原料结构中球团矿比例的大幅提高....     

环冷机上球团冷却过程的仿真与优化

为了探索环冷机关键结构参数和操作参数对球团冷却效果及过程节能降耗的优化途径,运用双能量方程建立了某球团厂的环冷机球团料层内部气、固相非平衡传热模型,应用"未反应核模型"建立了料层内部的主要化学反应(磁铁矿氧化)的反应速率计算模型,基于Matlab平台实现了对不同操作条件下球团冷却过程的数值仿真。对多个设计工况的仿真结果表明:以球团产量、冷却效果不变为约束,当料层厚度达原厚度的2倍时,环冷机3段排气温度分别提高50、71、33℃,并可节约用风23.6%,即适当增加料层厚度有利于能量回收和节约用风。     

氧化铝回转窑熟料烧结过程影响参数研究

在对氧化铝熟料烧结过程进行分析的基础上,结合煤粉燃烧、物料热解、窑壁散热和窑内传热传质方程,建立了回转窑熟料烧结传热综合数学模型。在此基础上,利用现场实际参数,应用数值计算方法对模型进行计算求解,得到了氧化铝回转窑内气体和物料的轴向温度分布,并分析了熟料烧结过程中空气消耗系数和掺煤量等主要参数对窑内温度分布的影响,提出了相应的操作参数,为实现回转窑的操作优化和自动控制提供了可靠的依据,有利于实现回转窑生产的节能降耗。     

煤粉含碳球团炼铁半工业试验

作者提出一种以非焦煤和含煤球团为原料,用煤粉化铁炉连续生产铁水的方法。该工艺由煤粉,空气在前炉中旋转燃烧供热,燃烧产生的高温煤气经过火道进入竖炉,逆流预热预还原冷固结含煤球团,预还原后的球团在竖炉下部和火道中熔化,过热并进行终还原,最后流入前炉完成渣—铁分离。在已完成的半工业试验中,冶炼耗煤量为916 kg/t铁水,耗电量为80 kwh/t铁水,生产率为6 t铁水/(m~3·d)。本工艺可发展成一种只用非焦煤和铁精矿粉生产铁水的生产工艺。     

A dynamic mathematical model of the complete grate/kiln iron–ore pellet induration process

Induration (drying and hardening) of iron ore pellets is an energy-intensive feed preparation step for both the blast furnace and direct reduction routes to iron. It is commonly carried out by a ‘grate/kiln’ process. A mathematical model of the process is described, in which mechanistic models of the grate furnace, kiln, and cooler are linked to enable simulation of the entire process. The model includes equations for the gas stream pressure balances and process controller responses, and provides dynamic solutions. The validation of the model for an operating plant is discussed and steady-state solutions are compared with data from the plant.     

链箅机--回转窑氧化球团热工操作分析

论述了采用链苒机-回转窑工艺生产氧化球团热工系统的基本特点和基本热工制度、风流匹配；分析了生球的在链算机内进行干燥、预热及氧化的各段合理温度要求、调节温度故障的措施和有效预防破坏性高温停机的对策；探讨了干球在窑内不同部位的焙烧温度、火焰操作以及窑头出现止压的预防和控制办法。同时，对采用2段鼓风式环冷机冷却时，热球达到允分氧化与完全冷却的风温、风世的匹配进行了优化。     

Natural-gas heating of cupola furnaces for more energy-efficient iron production

Natural gas is employed to reduce coke consumption in cupola furnaces with an open or closed top. The usual approach here is combustion of the natural gas by means of burners in external chambers at the perimeter of the furnace housing. Depending on their design, the burners ensure partial or complete preliminary mixing of the gas and air, with an air excess of 1.2–1.5. Then the combustion products are sent directly to the batch bed. In this system, the coke consumption amounts to 8–9% of the metal charge, while the consumption of gaseous fuel is 30–40 m3/t of melt. In these conditions, the melt temperature rises slightly (by 10–20°C); the productivity is increased by 15–20%; and the harmful gas emissions (mainly CO) are reduced by 20–25%. The gas dynamics of the cupola furnace is periodically disrupted, with suspension of the batch bed, cooling of the melt produced, less complete chemical combustion, and damage to the furnace lining. When using this method, the gas–air mixture is supplied to the hot bed with an air excess no lower than 2.5–3.0. A high-temperature zone (1350–1380°C) of width 60–70 mm is formed and moves through the bed at a speed of 15–20 mm/min. This calls for uniform mixing of the gas and air, specific gas-dynamic conditions, and the creation of the required gas–air ratio, with an air excess of more than 2.5–3.0. If cold gas–air mixture is supplied to the furnace bed through a tuyere, the combustion zone divides the whole bed into two stages: the initial and final stages. The high temperature of the combustion zone ensures fast cooling of the material at ignition of the gas–air mixture. That prevents ignition in the space above the bed. The lack of direct contact between the high-temperature zone and the furnace’s working space improves the reliability and economic indices of this process (no heat losses). Bed combustion of natural gas in the heating of such cupola furnaces increases the productivity from 10 to 13.6 t/h (by 36%), with reduction in coke consumption by 80 kg/t (33.3%) and decrease in heat consumption by 25 kW (18.78%). The heat losses with the exhaust gases are reduced by 25.32 kW (16.2%). The total thermal efficiency of the system is increased from 35.58 to 42.26% (by 15.81%, rel.).     

链篦机—回转窑直接还原的适宜焙烧温度

在实验室进行了链篦机－回转窑直接还原的试验研究。结果表明：还原产品的铁收率得与入窑球团的抗压强度、抗磨能力正相关关系;球团抗压强度及抗磨能力取决于链篦机的焙烧温度。提高链篦机焙烧温度是提高链篦机－回转窑直接还原法铁假得率和杜绝结的重要途径。     

链篦机球团预热系统能耗分析及优化

链篦机作为“链篦机-回转窑”球团生产系统的关键设备,其运行状况直接影响生产系统的能耗、产品产量及质量.针对国内某厂链篦机球团预热系统,分别建立了各工艺段的热分析和(火用)分析模型,并根据实际生产中的热工测试数据,对其用能状况进行了计算分析.结果表明:该链篦机预热系统的整体热效率为51％～55％,(火用)效率为42％～46％,各工艺段的热效率均低于66％,(火用)效率均低于53％,废气排放能量损失是链篦机系统的主要能量损失.在此基础上,提出了链篦机球团预热系统的优化用能方法,即将抽风干燥段和预热—段排出的热风引入鼓风干燥段,用于球团干燥,可将系统的整体热效率提高到60％,(火用)效率提高到49.6％,从而有效地优化用能过程,提高用能水平,减少能源消耗.     

球团竖炉热工过程解析与模拟

在现场热工测试基础上,对导风墙一干燥床式球团竖炉的干燥、预热、焙烧与冷却过程进行解析,建立了导风墙一干燥床式球团竖炉热工过程的数学模型,并且对生产条件下的济钢2号球团竖炉进行了模拟,结果表明：计算值与模拟值基本相符,干燥床面积、焙烧风及冷却风与球团热流比、焙烧带氧含量是竖炉增产的关键因素,焙烧带氧含量须保证在5％以上。     

竖炉烘干气流分布优化

针对永通公司竖炉烘干气流分布不合理,由导风墙引入的冷却风流量不够,导致冷却风上行流入焙烧带,以及烘床梁篦条堵塞、变形等问题进行了分析,提出了相应的改进措施并予以实施。改造后,炉内气流分布得到优化,生球干燥速度加快,干燥效果好,球团矿产质量均得到提高。     

Fundamental Study on New Method of Reducing Iron Ore-Coal Pellet in Cocurrent Shaft Furnace

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高炉使用高比例球团的战略思考与球团生产的试验研究

 从战略发展角度分析了高炉使用高比例球团的优势和存在的问题,指出了高炉使用高比例球团的战略机遇。根据国内高硅铁精粉特点,开展了高硅酸性和熔剂性的镁质球团造球、干燥和焙烧等基础研究,分析了球团抗压强度、高温冶金性能、回转窑生产过程结圈形成机理等基础特性,提出了球团生产的基本操作参数设计特点,实现了链箅机回转窑生产高硅镁质酸性和熔剂性球团的稳定连续生产。完成了高比例球团矿高炉冶炼生产试验。实践证明,高比例球团矿冶炼的高炉生产稳定顺行,各项指标优于高比例烧结矿冶炼的高炉,操作思路可复制、冶炼结果可重现、操作经验可推广,并且环境效益巨大,SO₂、NO_x、PM和CO₂的排放远远优于高比例烧结矿生产的高炉。可以预见,优质冶金球团的制备和高炉高比例球团冶炼将是破解中国钢铁长流程降低污染物排放,实现低碳冶炼和可持续发展的最佳举措。     

链箅机-回转窑直接还原的适宜焙烧温度

在实验室进行的链箅机—回转窑直接还原法的试验研究表明,还原产品的铁收得率与入窑球团的抗压强度、抗磨能力呈正相关关系;球团抗压强度及抗磨能力取决于链箅机焙烧温度。提高链箅机焙烧温度是提高链箅机—回转窑直接还原法的铁收得率和杜绝结圈的重要途径