Corex风口破损分析

Corex是一种使用非炼焦煤及纯氧代替焦炭和空气的熔融还原炼铁新工艺。与高炉工艺相比,Corex风口区域的温度更高,风口的使用寿命是一项重大挑战。在JSW公司,更换烧坏的风口所造成的休风几乎占工厂休风时间的15%。详细分析了风口破损及生产操作参数对破损的影响,以了解破损机理和根源。所有形式的风口破损不可能用一种普遍的原因来解释,但主要的原因集中在:入炉煤粉(6.3mm)过多、煤的平均粒度偏小、渣铁倒灌、关闭风口、结瘤脱落及滑料等。     

Raw materials for Corex and their influence on furnace performance

Abstract

The scarcity of good quality coking coal for the blast furnace (BF) has made steel makers look for an alternative iron-making process that requires little or no coke. The Corex process has been developed as an alternative to BF iron-making, which uses non-coking coal and a small amount of coke as fuel, and pellet/lump ore as iron-bearing feed. JSW Steel operates two Corex units each of 0?8 Mtpa, commissioned in 1998 and 2001 respectively. Iron oxides and non-coking coals have to meet certain physical, chemical and high temperature properties for stable operation and to attain high performance levels. Experience of the Corex operation with various coals and iron oxides over the years has helped in understanding the influence and sensitivity of raw materials on its performance and develop new raw material specifications. Statistical analysis of plant data showed that the significant parameters affecting fuel rate and production are moisture, volatile matter, char strength after reaction of coal, reduction disintegration index (RDI; %, –6?3 mm) of pellets and slag rate. This helped achieve the most efficient operating parameters, surpass rated capacity and utilise steel plant waste. The present paper brings out the impact of various raw material properties, and the modified specifications of coal and iron oxides for Corex.     

Recycling of steel plant mill scale via iron ore pelletisation process

Abstract

Mill scale is an iron oxide waste generated during steelmaking, casting and rolling. Total generation of mill scale at JSWSL is around 150 t/day and contains 60–70%FeO and 30–35%Fe₂O₃. To recover the iron, the mill scale must be smelted in a blast furnace or other reduction furnace; however, it is usually too fine to use without previous agglomeration such as via pellet or sinter mix. JSWSL operates a 4·2 Mtpa pellet plant to produce pellets for Corex and BF ironmaking units. The aim of this study is to determine the effect of mill scale on pellet properties. Detailed laboratory basket trials were conducted using up to 40% of mill scale in the pellet mix. The addition of mill scale up to 10% is considered to provide the optimum balance of chemical, physical and metallurgical properties of the pellet.     

流态化还原铁矿粉技术前景分析

从资源条件趋势的角度分析了中国需要流态化还原铁矿粉技术的必要性。中国巨大的钢铁需求和废钢严重不足,为流态化技术的推广提供了广阔空间,同时中国社会经济的发展和煤炭资源的相对优势,也为流态化技术的完善和真正实现工业化提供了条件和机会。     

Influence of operational parameters on silicon in hot metal from Corex

Abstract

Quality steel production at low cost demands superior quality of hot metal (HM) with low silicon (Si) and sulphur. High silicon is undesirable for its subsequent treatment during steelmaking, making the process costlier and less productive, hence there have been constant efforts to lower the silicon content in HM. Corex is the only commercially established and proven smelting reduction ironmaking technology alterative to conventional blast furnace (BF) ironmaking. While the mechanism of silicon transfer is largely understood in the BF, the Corex process still requires further operational guidance for its control. A statistical analysis of more than one year plant data has been carried out to understand the parameters influencing the silicon content and to provide directions for its prediction and control. Based on the understanding of the parameters affecting the silicon in HM, regression analysis was carried out and equations have been developed to predict the silicon in Corex HM. The present paper discusses the various parameters involved, the regression output for silicon prediction, its validation and its interrelation with operating parameters. The analysis indicates that high fuel rates due to high moisture, poor metallisation, high volatile matter, high slag volume, high coal fines and low production, along with high basicity and alumina in slag lead to high silicon in HM.     

Tensile and fatigue properties of cold and warm compacted Alumix 431 alloy

Abstract

In this experimental study, tensile and fatigue properties of the Alumix 431 alloy (Al, Zn, Mg and Cu alloys) produced using the conventional press and sinter processes in different pressures and temperatures are investigated. The results clearly showed that the warm compacted specimens can reach the mechanical properties of the cold compacted ones under less pressure. In the fatigue tests it was observed that fracture started from large pores as shown in all scanning electron microscope (SEM) examinations and ductile fracture occurred. 85% of the 180 MPa/80°C and 77% of the 230 MPa/RT specimens fractured at the machined surface. Tensile and fatigue properties of warm compacted (180 MPa/80°C) and cold (230 MPa/RT) compacted specimens are almost equal at these same densities. This result indicates the economic benefit of warm compaction by the much lower applied compaction pressure.     

喷煤对COREX熔融气化炉风口前理论燃烧温度的影响

 风口前理论燃烧温度是衡量熔融气化炉风口前热平衡和预测炉缸热状态的重?问弧Ｒ谰菘悸荢iO2还原的理论燃烧温度计算公式,分析了在熔融气化炉喷煤对风口前理论燃烧温度的影响。计算了不同喷煤条件下,熔融气化炉风口前的理论燃烧温度。在此基础上讨论了喷煤比、挥发分及焦炭(半焦)进入燃烧区域的温度等参数的影响,为选择适合COREX熔融气化炉喷吹煤提供了必要的依据。     

南非撒旦那钢厂COREX与DR联合流程中的MIDREX生产工艺

COREX-DR-电炉流程是具有竞争力的紧凑型钢铁冶金流程。系统介绍了南非SALDANHA钢厂COREX-DR联合流程中的MIDREX直接还原生产工艺,以及采用COREX-DR联合工艺的污染物排放情况。分析了2004～2005年MIDREX直接还原竖炉的生产指标。指出南非SALADANHA钢厂COREX-DR联合流程中的MIDREX工艺在经济上有优势,采用COREX-DR-电炉的联合工艺可以提供生产优质钢的经济路线,并满足日益增长的环保要求。     

Water modelling study of fluid flow and mixing characteristics in bath during AOD process

Abstract

The fluid flow and mixing characteristics in the bath during the argon–oxygen decarburisation (AOD) process have been investigated on a water model of an 18 t AOD vessel blown through two annular tube type lances of constant cross-sectional area. The geometric similarity ratio between the model and its prototype (including the lances) was 1 : 3. Based on theoretical calculations of the parameters of the gas streams in the lances, the gas blowing rates used for the model were determined fairly precisely. Thus, sufficiently full kinematic similarity between the model and its prototype was ensured. The influence of the gas flowrate and the angle included between the two lances was examined. The results demonstrated that the liquid in the bath underwent vigorous circulatory motion during blowing, and there was no obvious dead zone in the bath, resulting in excellent mixing and a short mixing time. The gas flowrates, particularly that of the main lance, had a key influence on these characteristics. However, the gas jet of the sublance had a physical shielding effect on the gas jet of the main lance, and mixing efficiency could be improved by a suitable increase in the gas blowing rate of the sublance. The angular separation of the two lances also had a marked influence on the flow and mixing in the bath. An excessively large or small separation of the two lances would reduce the stability of blowing and would also be unfavourable to mixing. The optimum range of separation is 60–100° under the conditions of the present work. The relationships between the mixing time and the gas blowing rate, the stirring energy, the modified Froude numbers for the main lance and sublance, the lance arrangement, etc. have been obtained.     

Influence of magnesia on iron ore sinter properties and productivity

Abstract

Dolomite and other MgO bearing materials are being increasingly used as basic flux constituents for production of fluxed sinters. Addition of flux materials in sinter influences the resultant sinter microstructure and chemical properties. The physical and metallurgical properties of sinter mainly depend on mineralogy of the sinter. Dolomite is the source of double carbonate of calcium and magnesium. Recent studies reveal that, apart from the additional fuel needed, the addition of dolomite and MgO bearing material greatly influences the magnetite content and the properties of the sinter produced. The increasing use of MgO bearing fluxes in the blast furnace burden, and the trend to incorporate a major part of fluxes in the sinter mix led to an investigation of the influence of MgO on sinter properties and productivity. In this study, the systematic investigation has been made on the influence of MgO% (1·4 to 2·6) on sinter mineralogy and sinter properties with dolomite. Microstructural examination of dolomite sinter revealed that hematite and calcium ferrite phases decreased whereas magnetite phase increased with increase in MgO percentage in sinter. From the laboratory pot grate sintering results it was found that sinter reduction degradation index improved whereas tumbler index and reducibility decreased with increase in MgO%.     

Development of process for thermomechanical treatment of ultrahigh strength steel prepared by electroslag refining

Abstract

Thermomechanical treatment (TMT) is the simultaneous use of work hardening, and grain refinement along with solid solution and precipitation strengthening. In this investigation, four alloys, with a base composition of 0·28%C, 1·0%Mn, 4·2%Cr, 1·0%Mo, 0·34%V, were prepared by electroslag refining (ESR) and by addition of small amounts of Ti and Nb and by increasing Cr and V to 4·8 and 0·48% respectively. In two of the alloys a yield strength in excess of 1550 MPa was obtained in the as cast quenched and tempered condition. Attempts were made to further increase the yield strength by thermomechanical treatment. The process parameters for thermomechanical treatment were optimised by adopting procedures such as calculation of stability of precipitates, hot compression test, determination of cooling rates in different coolants, and modelling of TTT and CCT diagrams. The process involved prerolling of the ESR ingot to a bar at 1200°C, followed by hot rolling in two passes starting from 950°C and finishing at 850°C with equal deformation of 25% in each pass to convert the bar into plates. These were immediately cooled in one of the cooling media: air, polymer–water solution (1 : 1·5) and oil. Yield strength in excess of 1750 MPa was obtained in oil cooled specimens of the alloy with titanium addition and that where Cr and V were increased. The niobium added specimen gave strengths, similar to that obtained for the base alloy, in spite of the fact that the as cast alloy had shown very high strengths, presumably because of the high soaking temperatures and grain growth. Air cooling gave the lowest strengths and oil cooling the highest.     

COREX工艺燃料消耗影响因素分析及优化方向

目前COREX工艺需要努力研究和改进的方向是提高产能和生产作业率、降低燃料比和生产成本。以物料平衡和热平衡计算为基础,从理论上分析了各种因素对COREX燃料消耗的影响,结合印度COREX-2000的生产实绩和宝钢COREX-3000生产实践情况,分析了降低燃料比的技术途径,并从工艺优化的角度提出了COREX工艺改进创新的方向。     

COREX竖炉炉料黏结的机理研究和影响因素分析

竖炉内炉料黏结是COREX炼铁工艺中的一个重大难题,国内外COREX生产操作都表明预还原竖炉内部的炉料容易黏结成块或黏结在竖炉的炉墙上,累积到一定程度后,会引起竖炉悬料,影响COREX还原煤气的利用和预还原竖炉的顺行,严重时甚至堵塞竖炉,使还原煤气难以接受或无法排料而被迫清空竖炉。在竖炉清空期间,对竖炉内黏结物进行了取样和分布情况调查,借助于化学成分检测、SEM和XRD等手段,分析了竖炉内黏结物形成的机理。在上述分析的基础上,通过实验室的试验研究考察了竖炉内炉料黏结的影响因素,结果表明,温度、金属化率、挤压时间、煤气成分等是黏结的主要影响因素。     

The life of a plant builder in the modern metals industry

Abstract

The 2007 SMEA Celebrity Lecture (Sheffield Metallurgical and Engineering Association) was given by Roy Tazzyman, the outgoing Managing Director of Siemens VAI–UK, on 4 July 2007 at the University of Sheffield, in conjunction with the Association's annual conference. Ken Ridal summarises the proceedings.     

COREX煤气中H2含量的对比分析

宝钢2#COREX投产后各技术经济指标持续改善,竖炉金属化率稳定在85%以上,冷煤气中H2含量比1#COREX高出2个百分点,但竖炉炉顶煤气中H2含量相差很小。基于COREX工艺过程中H2含量变化的理论解析,分析了氢元素的守恒、海绵铁金属化率、拱顶温度和竖炉还原对H2含量的影响。研究结果表明,冷煤气中H2含量的增加主要由竖炉海绵铁金属化率的提高所致,且随着竖炉金属化率的提高,气化炉运行更稳定,料柱温度升高,气化炉用氧分配趋向合理等冶炼特征发生改变。     

COREX熔化气化炉风口回旋区的分形研究

以COREX熔化气化炉物理模型为基础,对高速摄影仪记录的回旋区颗粒运动情况进行分析得到模型观察面上回旋区的颗粒速度场,运用分形方法对回旋区内不规则边界的表面积进行研究。结果表明：不同条件下,回旋区内表面边界的分维数变化不大;回旋区内表面积随着风量的增大而增大,当吹气量由106 m3/h变为122 m3/h时,回旋区表面...     

Determination of thermal histories of coke in blast furnace through X-ray analysis

Abstract

A study has been undertaken to identify the source of coke fines sampled from the deadman area of the blast furnace. Using measurements of the coke crystallite dimension L _C, it was established that some of the fines found in the deadman area of a blast furnace were not simply the degradation products of the lump coke in this area. The L _C was measured using standard X-ray analysis techniques. The coke fines had a higher L _C than the coke lump and therefore have experienced a higher maximum temperature than the associated coke lump. This finding has been interpreted as at least some of the coke fines found in the deadman area (lower temperature region) have been blown there from the raceway by the high velocity hot blast.     

PM processing of elemental and prealloyed 6061 aluminium alloy with and without common lubricants and sintering aids

Abstract

A comparison has been made between compaction, sintering, microstructural and mechanical properties of the 6061 aluminium alloy prepared via premixed elemental (EL) and prealloyed (PA) powders (as received and degassed) with and without additions of sintering aids and various solid and/or liquid lubricants. Both EL and PA powders were cold pressed at different pressures, ranging from 250 to 770 MPa, and sintered under vacuum in the range 580–640^°C for 30–120 min. and then under pure nitrogen atmosphere for comparison. Vacuum degassing of the PA powder provided better compressibility and thus higher green densities than those for the as received PA or the premixed EL powder compacts pressed at compaction pressures ≥340 MPa. Near full sintered densities of , ～98%TD were obtained for both EL and PA 6061 Al alloys. Degassed PA Al with 0·6 wt-% paraffin wax (PW) or with only 0·12 wt-%Pb addition as sintering aid and no lubricant, and premixed EL with only 0·12 wt-%Pb addition and no lubricant gave the best optimum properties. It became apparent that additions of some solid lubricants such as lithium stearate (LS) and acrawax to both the premixed EL and PA powders provided reasonable green densities, but had deleterious effect on sintered densities and microstructures, particularly under vacuum sintering. Heating data curves during the sintering cycle, revealed formation of both transient and persistent liquid phases for the EL and mainly supersolidus liquid phase sintering (SLPS) mechanism for the PA. Tensile properties of the degassed, vacuum or nitrogen sintered PA Al alloy in T6 condition were higher than those of the equivalent alloy prepared by EL mixing with the former giving a tensile strength of 330 MPa and 6–8% elongation to failure, which are similar to those of the commercial (wrought) 6061 Al alloys.     

Investigation of coal properties to avoid lump coal fines generation in COREX process

Abstract

Cast productivity depends on casting speed. Since the early development of continuous casting, numerous attempts have been made at high speed casting. With regard to speed limitation by shell sticking, high temperature tensile strength properties of the solidifying shell in relation to mould friction are considered the governing factor. Hence, experimental work has been carried out to simulate shell loading under casting conditions, determining the shell strength for a wide range of carbon contents. Mould friction data have been derived from published plant measurements. As demonstrated, neither shell strength nor mould friction imposes significant limits on casting speed under regular casting conditions.     

八钢COREX主要工艺技术改进

文章介绍了八钢COREX项目在迁建过程中结合八钢的生产实际,所做的设计优化和工艺技术改进..分析了这些工艺技术改进措施,并提出了八钢COREX以后努力的方向.