内配煤球团直接还原铁生产对原料的选择

通过理论分析和实验室试验，研究了精矿粉和煤粉的化学成分对内配煤球团直接还原铁化学组成的影响，提出了用于内配煤球团直接还原铁生产的精矿粉和煤粉的质量要求。     

DIRECT REDUCTION OF MIXED MAGNETITE AND COAL PELLETS USING INDUCTION HEATING

A low-temperature process for iron-making, using mixed pellets of magnetite and domestic coal with an organic binder was investigated. Reduction tests performed in an induction furnace resulted in a product direct reduced iron (DRI) containing 75–80% metallic iron. The coal energy consumption of 23.71?GJ/ton DRI compares favorably with current DRI processes, although the total energy consumption of 33.65?GJ/ton is relatively high for iron-making. The use of low-grade coal as a reductant may improve the economics of the process as high-grade coking coal supplies dwindle worldwide.     

生物质合成气直接还原铁矿-生物质复合球团炼铁

为了使炼铁工业摆脱对化石能源的依赖及满足越来越严格的环境要求,将生物质能的开发利用与直接还原技术进行集成提出一种新型的绿色炼铁方法.把生物质、铁矿石粉与添加剂混合制取生球团,利用生物质催化气化制备的富氢合成气作为还原剂,生物质的高温燃烧为生球团的预热和预热球团的直接还原提供外加热源.对影响生物质直接还原炼铁的因素,如预热、还原温度及球团粒径进行了研究,发现减小球团粒径、增加预热和还原温度能够提高直接还原铁产品的全铁质量分数及金属化率.当采用品位65.21%的铁精矿为原料,在最优操作条件下(生球团粒径介于8~10 mm之间,900℃预热30 min,1000℃下还原60 min)可制得全铁TFe质量分数为86.1%,金属化率为94.9%的高质量直接还原铁产品.      

Mixed burden softening and melting phenomena in blast furnace operation Part 1 – X-ray observation of ferrous burden

Abstract

The cohesive zone in the blast furnace (BF) is largely affected by the high temperature properties of the ferrous burden. Lowering and minimising the width of this zone will increase the productivity and performance of the BF. Recently part of the BF ferrous burden has been replaced by direct reduced iron (DRI) and hot briquetted iron (HBI). The objective of the present work is to expand the current understanding of softening and melting (SM) mechanism of ferrous raw materials including DRI, HBI, pellets, lump ore and mixed burdens. A small scale 'deformation under load' experiment was designed to examine the interaction of ferrous burdens. The SM tests were conducted with ferrous burdens in different combinations and parameters such as bed contraction, pressure loss, reduction degree, etc. were measured. In addition, the process was visualised using X-ray fluoroscopy. There were microstructural differences between the ferrous materials which governed the initial compaction of bed. The softening of the single burdens of DRI and HBI occurs owing to softening of iron phase. In mixed burdens composed of DRI and pellets/lump ore, initial deformation is not affected by the presence of DRI; however the melting of the bed is dependent on the melting of DRI indicating its dominance over other burden components at later stages of deformation. The change in reduction degree between SM temperatures was found to be small.     

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。     

Influence of Direct Reduction Condition of Hematite Pellets with H2/CO on the Oxidation Behaviour of DRI in Air

Direct reduced iron (DRI) is the product of some commercial direct reduction (DR) of iron ore on base of natural gas. DRI tends to oxidize in air generally above 300 °C and then follows spontaneous combustion. To control the oxidation mechanism, several investigators have used different iron samples and methods. This paper gives the results of experimental work carried out for determination of DRI oxidation. The behaviour of DRI oxidation in air after isothermal reduction of hematite pellets with different size, temperature and H₂ / CO mixture is investigated.     

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。     

回转窑一步法直接还原铁生产的试验研究

以新疆磁铁精矿为原料,采用一步法直接还原,研究高强度、高还原性预热球团的制备及煤基直接还原的工艺.研究了实验室转鼓模拟回转窑装置中直接还原铁的生产工艺.讨论了配碳比、反应温度、反应时间等工艺参数对金属化率、脱硫率等回转窑直接还原铁的主要质量指标的影响,提出了本试验原料条件下,回转窑生产直接还原铁的最佳工艺参数.研究结果...     

Kinetic Studies of Iron Ore–Coal Composite Pellet Reduction by TG–DTA

An attempt has been made to study the effect of coal quality on the reduction kinetics of iron ore–coal composite pellets under non-isothermal condition in inert atmosphere. During non-isothermal reduction of composite pellets, it is observed that (i) reduction rate of iron oxide increases with increasing temperature, (ii) reduction rate increases with increase in porosity of pellets and (iii) the computed values of activation energy (E) are lower during the initial stage of reduction (0.86–8.82 kJ mol⁻¹) than those in the later stages of reduction (12.37–38.32 kJ mol⁻¹). These values indicate that the initial stage reduction is controlled by gaseous diffusion mechanism and at final stage, mixed control reaction mechanism (i.e., both gaseous-diffusion and chemical reaction) is the rate controlling step. The present investigation aims at to assess the effect of Fe_tot/C_fix ratio in pellet, volatile matter in coal, and temperature on the reduction kinetics of iron ore–coal composite pellets using simultaneous thermogravimetric and differential thermal analyser (TG–DTA).     

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     

Reduction of Iron-Ore Pellets Using Different Gas Mixtures and Temperatures

Direct reduction of iron ore (DRI) is gaining an increased attention due to the growing need to decarbonize industrial processes. The current industrial DRI processes are performed using reformed natural gas, which results in CO₂ emission, although it is less than carbothermic reduction in the blast furnace. Carbon-free reduction may be realized through the utilization of green H₂ as a reducing agent, in place of natural gas. Herein, the effects of various gas mixtures and temperature on the reduction kinetics of the hematite iron-ore pellets are focused on in this work. Pellets are reduced at 700, 800, 850, and 900 °C in hydrogen and using various gas mixes at 850 °C. Morphology of the pellets is investigated with the help of scanning electron microscopy and mercury intrusion porosimetry. The effects of temperature and gas composition on the reduction kinetics and porosity of the pellets are discussed. A notable effect of reduction rate on the internal structure of the pellets is detected, slower reduction rate yielded bigger pores offsetting the gas composition. Higher temperature results in coarser pores and higher porosity. Increase of CO content in the gas mix also leads to bigger pore size.     

The Reaction Behavior of Direct Reduced Iron (DRI) in Steelmaking Slags: Effect of DRI Carbon and Preheating Temperature

An experimental study was conducted to quantify the rate of direct reduced iron (DRI) decarburization in a steelmaking slag using the constant volume pressure increase technique. Experiments were conducted by dropping DRI pellets into molten slag at temperatures from 1773 K to 1873 K (1500 °C to 1600 °C). Subsequent experiments were carried out in which the DRI pellets were preheated while the slag temperature remained constant. The effect of the initial carbon content and the preheating temperature of the DRI on the reaction rate was investigated. The decarburization of DRI seems to comprise two stages, a reaction between the FeO and DRI followed by decarburization through the iron oxide of slag. Carbon has a significant effect on the kinetics of both stages, whereas the preheating temperature mainly influences the rate of decarburization between FeO and carbon inside the pellet.     

混装铁焦对人造富矿还原行为的影响

 高炉炼铁是资源、能源的消耗大户,节能潜力巨大。铁焦是一种高反应性焦炭,将合适粒度和数量的铁焦与含铁炉料混装入炉,从理论上说具有降低焦比,取得节约稀缺炼焦煤资源和降低生产成本的潜力。对混合试样的还原机理进行了分析,并对铁焦与人造富矿的耦合反应进行了实验室研究,证明混入铁焦对烧结矿和球团矿的还原反应有明显的促进作用,提高温度和增加铁焦用量对提高铁矿石的还原度有利。     

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.     

Role of Heat Transfer in Early Stage Decarburization of DRI in Slag

The gas generation from reactions between direct reduced iron (DRI) pellets and steelmaking slags is known to take place in two stages; (1) the reaction of FeO and carbon within DRI, i.e., pellet internal reaction, followed by (2) the reduction of slag FeO with DRI carbon at the pellet?Cslag interface, if any carbon remains from the first step. To understand the controlling mechanism of the reaction between FeO and C inside DRI, the rate of the gas release and the temperature of pellets suspended in a slag-free atmosphere were quantified. The results were used to determine the apparent thermal conductivity of DRI that showed values of approximately 0.5 to 2 W.m^?1.K^?1 for a temperature range of 573?K to 1273?K (300?°C to 1000?°C). Furthermore, it was found that the experimental gas evolution rates are consistent with the values predicted by a heat?Ctransfer based model, confirming that the FeO-C reaction within pellet is controlled by the rate of heat transfer from the slag to the DRI pellet.     

Evaluation of a New Process for Ironmaking: a Productivity Model for the Rotary Hearth Furnace

In order to address the key issues of capital costs and CO₂ emissions in ironmaking operations, a new process was proposed combining a Rotary Hearth Furnace (RHF) and a Bath Smelter. This paper describes the construction of a productivity model for the RHF based on previous studies concerning the reduction behaviour of pellets of carbon and iron oxides. The model was used to estimate changes in RHF productivity according to the type of carbon used in the RHF pellets, numbers of layers of pellets, final metallization degree of the direct reduced iron (DRI) produced, and initial sizes of the pellets. The results indicate that productivity gains between 33 and 46% can be achieved replacing coal with wood charcoal, a carbon source virtually free of net CO₂ emissions. Also, the productivity of the RHF can be doubled by reducing the charge only up to 70% metallization. The model allows the study of changes in overall energy consumption due to changes in the extent of primary oxidation of the gas at the pellet level showing that the use of wood charcoal increases the total amount of carbon consumed by less than five percent relative to operations with coal.     

Effects of Temperature and Atmosphere on Pellets Reduction Swelling Index

 After taking into account the conditions of the domestic iron resources and the non-coking coal resources, the process of coal gasification-shaft furnace is an effective way to develop direct reduction iron in China. The following tasks are very critical to choose suitable process of shaft furnace and gasification, including the production of oxidized pellets with excellent comprehensive properties as well as the study of the reaction behavior and mechanism of swelling. The results showed that the oxidized pellets of using domestic magnetic iron concentrate as raw materials have favorable comprehensive properties, including higher mechanical strength both before and after reduction, faster reduction rate and lower reduction swelling index (RSI). All of these properties can meet the shaft furnace yielding requirement. When the temperature was below 1223 K, the pellets′ RSI was lower than 20%. With increasing of the content of H2 in atmosphere, the pellets reaction rate accelerated, crushing strength enhanced and RSI decreased. The RSI dropped to 10.26% at 1323 K in 100% H2 atmosphere, and it is up to 39.88% in 100% CO atmosphere. The iron grains mainly presented in platelike when pellets were reduced by H2, however, in CO atmosphere the iron grains were precipitated in flocculent. The whisker shape of iron grains and heating effects of reduction reaction are the major factors leading to the poor pellets strength and increase of RSI. Appropriately controlling the temperature and increasing the ratio of H2 to CO in atmosphere are good for dropping the RSI.     

Analysis of Gas Thermodynamic Utilization and Reaction Kinetic Mechanism in Shaft Furnace

The technology of coal gasification in shaft furnace is an effective way to develop direct reduction iron in China.In order to clarify the process of the reduction of oxidized pellets in shaft furnace by carbon monoxide or hydrogen in two ways,i.e.thermodynamics and kinetics,the gas utilization and reaction mechanism were studied by theoretical computations and isothermal thermogravimetric experiment.The results showed that the gas utilization increased with the rise of temperature when xH 2 /xCO ≥1and with the increase of xCO /(xH 2 +xCO)when temperature is less than 1 073K.The water-gas shift reaction restrains efficient utilization of gas,particularly in high temperature and hydrogen-rich gas.The gas utilization dropped with increase of carburization quantity of direct reduction iron(DRI)and oxygen potential of atmosphere.With the increase of both temperature and content of H2 in inlet gas, the reaction rate increased.At 100% H2 atmosphere,the interfacial chemical reaction is the dominant reaction restricted step.For the H2-CO mixture atmosphere,the reduction process is controlled by both interfacial chemical reaction and internal diffusion.     

Development of Non‐coke Ironmaking Processes in China

Development of non‐coke ironmaking process in China is presented. It is concluded that coal‐based rotary kiln is still the main process for direct reduced iron (DRI) production in the near future in China. The most important problems of DRI production in China are small production scale and heavy environment pollution. Now the gas‐based shaft furnace process has become one of the significant processes of DRI production in China. The market demand for DRI production in China is continuously increasing. Due to the tense supply of coking coal and its heavy environmental load, more steel plants in China will use smelting reduction (SR) technology.     

直接还原铁生产技术的现状及展望

 分析了世界及中国直接还原铁的技术现状。直接还原工艺可以摆脱焦煤资源短缺的束缚,降低CO2排放,促进资源综合利用,且高品质的直接还原铁是生产洁净钢不可缺少的原材料,是钢铁工业发展不可缺少的组成部分。随着铁矿精选技术、煤制气技术的成熟,从及气基竖炉生产规模的不断增大,煤制气→竖炉将成为中国主要的直接还原生产工艺。高温高料层PSH工艺应当具有良好的应用前景。回转窑、隧道窑等工艺在特定地区可适当发展,但不会成为直接还原铁生产的主流。