An Approach for Simulation of Corex Process Smelter Gasifier for Prediction of Coal Rate and Silicon in Hot Metal

A thermodynamic model for the Corex process smelter gasifier focusing on coal pyrolysis as well as on the wustite reduction has been proposed. The compositions of hot metal, slag, and the export gas of the Corex process have been simulated satisfactorily for a given degree of metallization of directly reduced iron (DRI). The minimum coal rate is linked to the given degree of prereduction of DRI and the desired final silicon content in the hot metal.     

The Burden Structure and Its Consumption in the Melter Gasifier of the Corex Process

A major advancement in the Corex ironmaking process is the usage of lump coal considering the shortage of coking coal resources worldwide. However, the burden similar to that of the blast furnace is still essential for the enlarged melter gasifier. The notable difference is that the burden of the melter gasifier is composed of char formed from lump coal with a small amount of coke. The burden structure of the melter gasifier was investigated by the tuyere probing while the plant was shut down at different operating conditions. The specimens representing the different positions of lump zone, cohesive zone, and dripping zone were analyzed by means of coke/char size distribution and X-ray diffraction (XRD) for the degree of graphitization of coke. A chemical analysis of metal composition has also been performed to get a better understanding of the final reduction in the melter gasifier. The burden structure is supposed to be divided into three zones: active zone, outer of deadman, and deadman core, where coke/char was consumed differently. Based on these analyses, some technical advice to improve the Corex operation is given.     

Noninertial control of the blast furnace and the carburization of iron

Essentially, the reduction of iron in the blast furnace and the oxidative smelting of steel in the oxygen converter are opposing processes. In addressing the carburization of iron in the blast furnace and its decarburization in the converter, we consider noninertial control of the zonal blast-furnace processes. A functional relation is established between the parameters of the zonal processes and the parameters of the hot blast, the reducing gas, and the blast-furnace gas. On that basis, the batch and coke consumption and the yield of metal, slag, and gas in unit time may be strictly and continuously regulated. That, in turn, permits monitoring of the ore load on the coke. Noninertial control of the zonal blast-furnace processes by this means permits regulation of the slag’s oxidative potential, the ore load, and the consumption of injected dusty iron oxides and hence reduction of the carbon content in the hot metal to 2.0–2.5% or less. This approach leads ultimately to the creation of a single-stage process from ore to steel.     

Analysis of Material and Energy Consumption of Corex C3000

The first Corex C3000 unit has been built at Baoshan Iron and Steel Corporation, China, and some improvements compared with C2000 have been made. On the basis of material and heat balances, an analysis of material and energy consumption in the Corex C3000 smelting reduction process was conducted and the calculated consumption of lump ore and pellets, coal rate, oxygen consumption are compared with the target values of C3000. Regarding the heat balance calculation, the main factors affecting the energy consumption of C3000 are analysed, and the effective utilization of the sensible heat of top gas and molten slag, as well as the calorific heat of the export gas can be considered to realize lower energy consumption. In addition, the effects of metallization in the reduction shaft and oxidation degree of the gas produced in the melter‐gasifier on the Corex performance are discussed.     

Characteristics of coal required for superior performance of Corex ironmaking

Abstract

The Corex smelting reduction process was developed as an alternative to the blast furnace and consists of two reactors: the reduction shaft and the melter gasifier. Coal rather than coke is used for heat generation, production of reducing gases and to maintain adequate bed permeability; hence, coals have to meet certain physical, chemical and especially high temperature properties for stable process operation and high iron outputs. Statistical analysis was employed to investigate the influence of coal properties on Corex performance, and laboratory coal characterisation studies were correlated with plant performance. This paper details these coal characteristic studies and highlights the coal blend properties required for superior plant performance.     

Corex-3000 taphole maintenance technology and practice

Short taphole length is one of the most troublesome problems of Baosteel's Corex - 3000 after its startup.Owing to the melter gasifier process,the char bed floated up and down as the level of hot metal and slag in hearth changing.These cause a lot of problems such as the heavy erosion of taphole areas and hard cast house work.The high second tapping flow is a noticeable characteristic of Corex process.The reasons of short taphole is analysed,and countermeasures are put into practice,some improvements are...     

Concept and present state of a coal-based smelting reduction process for iron ore fines

The concept of a two-stage smelting reduction process is presented. In the first stage highly metallized iron ore fines are produced in a circulating fluidized bed. In the second stage a hot metal is produced in a melter-gasifier where – together with metallized ore – coal and oxygen are injected to generate the required heat and the CO-rich reducing gas. The process was tested stepwise in pilot scale installations. Although only a reduction temperature of 830 °C instead of the required 880–900 °C could be realized in the pilot unit, test results make it very probable that a metallization of 90% can be reached with any fine ore without sticking problems, if the ore is covered with a carbon layer by CO decomposition in a pretreatment stage with the reduction offgas at 500–600 °C. The CO decomposition on the fresh ore leads to a high gas utilization which renders a CO₂ washing stage and gas recycling unnecessary. To prove the technical and economic feasibility of the combined process, the next development step should be the design and operation of a larger pilot plant with a capacity of at least 5 t hot metal/h for continuous and joint operation of both the melter/gasifier and the reduction stage.     

浦项FINEX熔融还原工艺技术研究

韩国浦项（POSCO）在COREX熔融还原工艺基础上，成功的开发了FINEX熔融还原炼铁工艺技术，并于2007年4月10日开工点火，设计产能150万妇，通过50天的验证，装置运行一切正常。FINEX工艺的基本原理是用四段流化床代替COREX装置的还原竖炉，流化床内还原气体和粉矿直接接触进行还原，还原后的热矿粉进入熔融气化炉。使用FINEX工艺，能够直接利用粒度小于8mm的粉矿，同时能够直接使用煤粉。COREX装置的熔融气化炉被用来对还原获得的海绵铁热压块进行最后还原和熔炼，也作为FINEX的煤气发生器，原来的还原竖炉用作为FINEX装置的贮料仓和加料仓。     

Mathematical model of COREX melter gasifier: Part I. Steady-state model

The COREX melter gasifier is a countercurrent reactor to produce liquid iron. Directly reduced iron (DRI), noncoking coal, and other additives are charged to the melter gasifier at their respective temperatures, and O₂ is blown through the tuyeres. Functionally, a melter gasifier is divided into three zones: a moving bed, fluidized bed, and free board. A model has been developed for the moving bed, where the tuyere region is two-dimensional (2-D) and the rest is one-dimensional (1-D). It is based on multiphase conservation of mass, momentum, and heat. The fluidized bed has been treated as 1-D. Partial equilibrium is calculated for the free board. The calculated temperature of the hot metal, the top gas, and the chemistry of the top gas agree with the reported plant data. The model has been used to study the effects of bed height, injection of impure O₂, coal chemistry, and reactivity on the process performance.     

HIsmelt熔融还原主反应器能质流转模型构建与验证

 HIsmelt熔融还原炼铁工艺以铁矿粉和煤粉作为原料,流程中不需要烧结、球团和焦化,与高炉炼铁流程相比具有降碳减排等优势。明晰能质流转过程对HIsmelt熔融还原炼铁实际生产具有指导意义。基于物料平衡、热平衡方程,对输入和输出HIsmelt主反应器物质和能量进行平衡计算,建立能质流转模型,并结合FactSage中Equilib模块计算的各元素在渣铁两相间的质量分配比及实际生产数据对其进行修正。该模型可以计算原料和燃料成分、矿煤质量比、二次燃烧率、热风氧含量等参数对铁水温度、炉渣成分、热风量、煤气量等主要冶炼指标的影响。其次依据该模型,进行了物料平衡、热平衡计算,依据实际生产数据对模型计算结果进行了验证,结果表明该模型与实际生产数据契合度较高。探究了矿煤质量比对冶炼的影响,矿煤质量比为1.39～1.45时,矿煤质量比降低0.1,会使二次燃烧率降低0.23%,进而造成煤气化学能的利用率降低,同时需要更多的热风使煤粉燃烧,热风量和煤气产生量增加,可以通过适当提高热风氧含量以提高二次燃烧率并使煤气量降低来改善;矿煤质量比降低0.001,会使铁水温度升高3.76 ℃,有利于铁水后续的加工处理,但铁水温度升高使铁元素在铁液与渣中的比值降低,使炉渣FeO质量分数升高0.026%,增加铁损,可通过降低富氧热风喷吹量来降低铁的氧化量,从而降低铁损。     

COREX熔融气化炉内料柱的透液性指数及影响因素

休风时对COREX熔融气化炉进行风口取样,通过对风口试样的检测分析,用压差度的倒数表示炉内气相对料柱透液性的影响,用空隙度和温度强度的乘积表示炉内的渣铁液相对料柱透液性的影响,建立了表征熔融气化炉料柱透液性的公式.对两批风口试样的研究发现,熔融气化炉内不同位置风口试样的透液性指数与相应位置的滞留铁比呈现一致的对应关系.进一步分析了透液性指数的影响因素,发现在炉况不顺时,未反应完全的酸性脉石直接落入炉缸,导致沿风口径向部分位置的渣样熔化温度高于1500℃,影响了渣铁流动性.提出了增加料层厚度、采取合理的造渣制度、控制均匀的煤气流分布等技术措施,为改善熔融气化炉内料柱的透液性提供帮助.      

Influence of Coal Size on the Performance of Corex Process

The size distribution of coal used in the Corex process is of prime importance. It controls the permeability and stability of the char bed and thus the performance of the furnace. The particle size of the coal is monitored by its mean particle size (MPS) and the fraction of ‐6.3 mm in coal charge. A lower fraction of ‐6.3 mm in coal and higher coal MPS are desirable for improved performance. The variation in MPS and fraction ‐6.3mm of coal influences the fuel rates making the furnace unstable and thereby decreases the production. Theoretical calculations have been attempted using the actual plant data to know the impact of coal size on the permeability of the bed in the melter gasifier (MG). Statistical analysis was employed to investigate the influence of coal size on the performance of the Corex process. Attempts were made to establish the relationship between the coal size charged and performance indicators of the Corex process. It was found that a stable and improved performance of the Corex process requires MPS of coal in the range of 19‐22 mm and fraction ‐6.3 mm in coal less than 15 %. A regression equation for the fuel rate including coal size has been derived. The present paper discusses the influence of coal fines and MPS on the performance of the Corex process.     

煤制气直接还原铁两段串联流程估算

为了降低直接还原铁能耗,根据试验数据研究了煤制气直接还原铁两段串联流程。串联流程中第一段竖炉用煤制气粗煤气余热和含碳球团冶炼直接还原铁,含碳球团以焦粉、半焦粉或无烟煤粉为还原剂,铁精矿、无机黏结剂混合后加压制作,电炉熔化直接还原、脱硫和生产水渣。串联流程中第二段竖炉以第一段净化后的炉顶煤气为第二段直接还原铁还原气,以氧化球团为原料。结果表明,煤制气直接还原铁两段串联流程估算能耗为394.8kg/t;与铁水比可比能耗为487.8kg/t,比高炉低41.2kg/t,生产过程中产生的污染物和温室气体排放低于高炉,接近天然气直接还原铁。     

Mathematical Simulation of Burden Distribution in COREX Melter Gasifier by Discrete Element Method

 COREX process is one of the earliest industrialized smelting reduction ironmaking technology. A numerical simulation model based on discrete element method (DEM) has been developed to analyze the burden distribution in the melter gasifier of COREX process. The DEM considering the collisions between particles can directly reproduce the charging process. The burden trajectory, the location and the burden surface profile are analyzed in melter gasifier with a mixing charging of coal and direct reduction iron (DRI) at the same time. Considering the porosity of packed bed has an important effect on the gas flow distribution of melter gasifier, a method to calculate porosity has been proposed. The distribution of DRI and coal and the porosity in the radial direction are given under different charging patterns, which is necessary to judge the gas flow distribution and provide base data for further researching the melter gasifier for the next work in the future. The research results can be used to guide the operation of adjusting charging and provide important basis for optimizing the charging patterns in order to obtain the reasonable gas distribution.     

Investigation of Reduction and Smelting Mechanism in the Hi‐QIP Process

A new coal‐based reduction and smelting process for production of high quality iron pebbles in a rotary hearth furnace (Hi‐QIP Process) was developed. The reduction, carburization, smelting, and separating mechanism of the Hi‐QIP process were investigated. The experiments were carried out in a graphite heater furnace under rapidly heating up to 1773 K. A mixture of coal and ore produced molten metal and slag, which were held on the coal and did not come into contact with the refractory located under the coal layer. It is confirmed that the reduction of wettability between the iron and slag promotes the separation of them, when the content of FeO slag decreases. High productivity of the process is expected when using iron ore with small particle diameter and low gangue content. Favourable operating results were obtained in a pilot test using a rotary hearth furnace with a diameter of 7 m and a width of 1.5 m. This test demonstrated the possibility of continuous production of iron pebbles with high productivity (15t‐iron/d).     

熔融气化炉风口回旋区冶炼特征的数值模拟研究

相比于高炉风口喷吹富氧热风,熔融气化炉风口采用常温纯氧,使得炉内质量、动量、热量的传输以及煤气流分布等冶炼特征与高炉存在较大差异.通过建立熔融气化炉风口回旋区二维数学模型,系统考察熔融气化炉风口回旋区内速度分布、温度分布及气体组分分布的冶炼特征.结果表明:在气固相热交换及焦炭 (或块煤形成的半焦) 燃烧反应的综合作用下,熔融气化炉风口回旋区内气体温度迅速升高至3 500 K以上;此外,风口前端存在小规模的气体循环流动现象,故风口前端扩孔破损现象严重,进而导致非计划休风率较高;为减少此类休风现象,可适当额外喷吹富氢燃料性气体 (天然气、焦炉煤气),不仅能降低风口回旋区内气体温度,更可替代部分固体燃料,并充分发挥其中H₂的高温还原优势,提升熔融气化炉冶炼效率.      

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。     

Energy Consumption in Smelting Reduction

The concepts of theoretical gas utilization ratio, smelting heat of iron ore and effective calorific value of coal were introduced in this work. The practical gas utilization ratio and the gas consumption in the shaft of a reduction unit for smelting reduction were discussed. The Corex process was optimized and the energy consumption was minimized according to the relationship of gas production in the smelting unit and the degree of iron ore reduction in the reduction unit. It was proven that the most important factor for saving energy in smelting reduction process is to use coal with suitable effective calorific value for the smelting heat of iron ore.     

COREX熔化气化炉区域模型及其理论燃烧温度

把熔化气化炉划分为炉缸区、风口区、填充床、流化床和自由空间5个区域。在已开发的COREX工艺整体静态模型的基础上,对各区域分别建立了物料平衡热平衡模型并联立求解。根据各区域内的物理化学进程设定各区域间边界的条件,模型计算可给出熔化气化炉内各区域的能量分布和物料流状况。利用区域模型还可计算喷煤对理论燃烧温度、炉缸渣铁温度、煤气量等的影响。     

Control of redox processes in the blast furnace

Reductive blast-furnace smelting consists of multifactorial oxidative, heat-transfer, smelting, and reducing processes that involve solid carbon and are associated with carburization of the metal. Analysis yields functional relations of the zonal process with controllable parameters of the hot blast. The ore load on the coke, the batch and coke consumption, the reduction rate of iron, and the rate of slag formation may be regulated as a function of the blast flow rate. If the degree of reduction of iron declines from 0.998 to 0.96–0.98, the oxidation of the slag with respect to iron (the FeO content) may be increased to 2–10%, with slowing of the carburization of iron as the melt flows through the coke bed. Slag oxidation may be increased by the injection of powdered iron oxide into the hot blast through tuyeres. As a result, the carbon content in the metal will be 1.5–2.0%, which corresponds to the composition of austenitic steel.