Study of a blast-furnace smelting technology which involves the injection of pulverized-coal fuel, natural gas, and an oxygen-enriched blast into the hearth

Studies were made of features of a blast-furnace smelting technology that involves the injection of natural gas (NG), oxygen (O₂) and pulverized-coal fuel (PCF) into the hearth. The technology has been implemented in the compensation and overcompensation regimes, which has made it possible to maintain or improve the gasdynamics of the furnace, the conditions for the reduction of iron oxides, the heating of the charge, and PCF combustion in the tuyere zone as PCF consumption is increased and coke use is decreased. Under the given conditions, with the blast having an oxygen content of 25.64–25.7%, the hearth injection of 131–138 kg PCF and 65–69 m³ NG for each ton of pig iron has made it possible to reduce coke consumption by 171–185 kg/ton pig (30.2–32.7%), reduce the consumption of comparison fuel by 36–37 kg/ton (5.2–5.3%), and lower the production cost of the pig iron by 43–49 hryvnas/ton (3.7–6.4%). Here, furnace productivity has increased 3.8–6.5%, while the quality of the conversion pig iron remains the same as before. Measures are being implemented to further increase the level and efficiency of PCF use. __________ Translated from Metallurg, No. 5, pp. 41–44, May, 2006.     

Study of ways of reducing coke use at non-integrated metallurgical plants

To reduce the costs of blast-furnace smelting, the Svobodnyi Sokol plant has devised a comprehensive program of organizational-technical measures that include study of ways of reducing coke consumption. To do this, the plant began operating its blast furnaces with schungite when making foundry and conversion pig irons. Using schungite in the charge employed to make foundry iron makes it possible to save a significant (10–15%) amount of coke. The value of the coefficient that characterizes the replacement of coke by schungite varies broadly and can reach 1.0 or more, depending on the grade of iron being made and the furnace operating regime. The same coefficient has a value of 0.57 kg coke/kg schungite when 12–15 kg schungite/ton pig is used to make conversion pig iron. __________ Translated from Metallurg, No. 3, pp. 38–42, March, 2006.     

Briquets for washing blast furnaces

Periodic washing of the hearth of a blast furnace by charging hard-to-reduce iron-bearing materials helps form fluid iron-bearing slags whose iron is reduced mainly by coke fines in the coke column. Lump iron ore, specially prepared washing sinters, or welding slag are usually used for this purpose. The washing sinter contains up to 50% ferrous oxide. One alternative to the washing sinter might be briquets made from mill scale. Washing briquets made from mill scale with a cement binder (8–10% Portland cement M500) are made by vibrational compaction. These briquets have good cold strength, remain intact when heated in a reducing atmosphere to 1200°C at a rate of 500°C/h (which corresponds to the rate of heating of the blast-furnace charge), and have low reducibility. Inside the fusion zone, they form primary slags based on iron-calcium olivines with an FeO content on the order of 50%. __________ Translated from Metallurg, No. 5, pp. 46–50, May, 2007.     

Blast-furnace charging system

The blast furnace in the blast-furnace shop at the West Slovakian Metallurgical Combine is charged by means of a complex system that usually includes the following: an ore yard with a hopper gantry; a system to collect, weigh, and transport the charge materials to the top of the furnace; the charging apparatus of the furnace; a system that controls the charging operation. The use of continuous-acting mechanisms facilitates charging of the ore-bearing materials in the charge while minimizing the content of the −5-mm fraction of these components and the number of coke particles smaller than 25 mm. The productivity of the furnace could be increased further, which would allow the addition of an efficient aspiration system and make it easier to fully automate the furnace. __________ Translated from Metallurg, No. 7, pp. 45–46, July, 2006.     

The two-high blast furnace: A twenty-first-century system

In the twenty-first century, reduction in coke consumption during blast-furnace smelting to the theoretical minimum (160 kg/t of hot metal) is the key factor in improving the technology. One possibility is to include a cyclone reactor when using a 1: 1 mixture of coal-dust fuel and ore fines (concentrate) with an intense blast (1200°C, 30–40% O₂).     

Effect of enriching the blast with oxygen on the production cost of pig iron

Conclusion By mathematically modeling the blast-furnace smelting of conversion pig iron with a change in the oxygen content of the blast from 21 to 30% and a change in blast temperature from 800 to 1400°C, it was possible to determine how blast temperature affects the increases that occur in furnace productivity, coke rate, and pig-iron cost when blast oxygen content is increased by 1% within the ranges from 21 to 25% and from 25 to 30%. Under the furnace operating conditions that were examined, the savings in coke realized when the blast is enriched with oxygen decrease as blast temperature increases. In fact, coke rate increases at blast temperatures above 1100°C when the blast is enriched with oxygen in the range 25–30%. The effect of oxygen enrichment on pig-iron cost within this concentration range is negative throughout the range of blast temperatures examined. Adding more oxygen to the blast reduces the production cost of the pig iron only when blast oxygen content is within the range 21–25% and blast temperature is no greater than 1000–1100°C. At higher temperatures, adding more oxygen to the blast is economically inexpedient even within the lower ranges of oxygen content. Moscow State Institute of Steel and Alloys. Translated from Metallurg, No. 5, pp. 43–44, May, 1999.     

Controlling the blast-furnace hearth

At OAO EVRAZ ZSMK, the operation of the blast-furnace hearth is regulated by means of special briquets with good granulometric composition, high iron content, and low impurity content. The briquet charge depends on the total iron-ore consumption, primarily in the intermediate region of the furnace. With steady briquet content (around 2.1% of the charge), the variation in the hearth obstruction is smooth and confined to a narrow range. When the briquets account for 1.0–2.5% of the total charge, the actual mean furnace productivity increases by 6.7%; the adjusted value increases by 3.5%. The actual coke consumption is reduced by 0.5%, and the adjusted value by 0.7%.     

The role of alkalis and conserving resources in blast-furnace smelting

In ferrous metallurgy, the potential for conserving resources is often determined by the behavior of the impurity elements in metals production. This behavior may be highly complex, and its features may be interpreted differently by different experts. For example, the presence of zinc and alkali metals in the blast-furnace charge is known to result in excessive coke consumption, a reduction in the productivity of the furnace, an increase in the yield of top dust, shortening of the campaign, and in some cases to complete destabilization of the smelting operation. In choosing a technology for blast-furnace smelting, accounting for the entry of alkali metals and zinc into the furnace is one of the most important factors that determines the expediency of controlling the heat “from the top” or “from the bottom” features of the slag formation process, the gasdynamics of the smelting operation, and other characteristics.     

Use of recycled materials in pig-iron production at a non-integrated metallurgical plant

Slags of the required basicity are obtained in blast furnaces at the Lipetsk Metallurgical Plant by adding raw fluxes (limestone and dolomite) to the charge in amounts of 200–300 kg/ton pig iron. Decomposition of the carbonates of calcium and magnesium in these fluxes requires a considerable amount of heat and increases coke consumption in the smelting operation by 45–65 kg/ton pig. To replace the limestone in the charge, the plant uses crushed rock obtained from converter slag. The rock is delivered by the Novolipetsk Metallurgical Combine and is of the 40–70 mm fraction. Most of the economic benefit from using converter slag stems from the replacement of a raw flux (limestone) by lime present in the slag in free form and in the form of compounds-mainly calcium silicates. An equally important factor that affects the cost-effectiveness of using converter slag in the blast-furnace charge is the slag’s 20% iron content. A substantial percentage of the iron in the slag is in the form of FeO and metallic inclusions. __________ Translated from Metallurg, No. 4, pp. 38–42, April, 2007.     

Improving the energy efficiency of blast furnaces at PAO NLMK

Analysis of measures used to reduce energy expenditures shows that methods in which a single parameter is changed are ineffective. Coordinated adjustment of several parameters is required. Theoretical analysis reveals the combinations of parameters with the greatest effect. The influence of the granulometric composition of the sinter on the blast-furnace efficiency is considered in terms of the influence of the mean piece size on the reduction rate and the gas dynamics of the upper furnace region. When the reaction FeO + CO = Fe + CO₂ reaches equilibrium, the heat consumption in smelting is reduced by increasing the smelting rate. Analysis of specific approaches to reducing the heat consumption in blast furnaces for the example of PAO Novolipetskii Metallurgicheskii Kombinat (NLMK) indicates the basic measures that decrease heat consumption: optimization of the iron ore by reducing the proportion of the >45 mm fraction; increase in output of the blast furnaces to 75–90 t/day (per m² of hearth); operation with the highest permissible pressure (in terms of the charging-unit design); increase in hot strength of the coke to 60–62%; pulverized- coal injection at 140 kg/t of hot metal; and optimization of the ore distribution over the furnace radius. Between 2013 and 2016, those measures decreased coke consumption by more than 10 kg/t of hot metal. In addition, the total consumption of carbon fuel was reduced.     

熔融还原炼铁技术分析

分析了主要的熔融还原炼铁流程.COREX采用预还原竖炉+熔融气化炉的纯氧炼铁流程,已经工业化,但吨铁焦炭量维持在250 kg左右的水平,吨铁燃料比达到1 000 kg.FINEX采用多级流化床+热压块+熔融气化炉+煤气脱除CO:循环使用的纯氧炼铁流程,可直接处理粉矿,吨铁燃料比为800 ks左右,吨铁焦炭使用量在200kg左右,不过FINEX工艺复杂,效率低,仍在进行工业化试验.HISMELT试图采用一步法直接熔融还原粉矿,难度大,指标与预期相差较大,尚处在技术攻关阶段.可见,目前的熔融还原炼铁流程,离低能耗、低污染的炼铁目标相差甚远,最大的问题是预还原矿粉(球团)的低温还原性能差,提高铁矿的低温反应性能是熔融还原炼铁走向成功、高效、环保的关键所在.     

冶金焦的本质特性与现代高炉冶炼的对应关系

 在对鞍钢焦炭质量现状进行科学分析的基础上,研究了焦炭强度、热态性能、化学组成、粒度及质量波动等对高炉冶炼的影响规律,并通过对高炉风口焦炭的实际取样与研究加以验证,指导高炉操作实践;同时,系统地掌握焦炭质量、焦炭质量对高炉冶炼的影响、焦炭质量的评价方法等;尤其是利用“风口取样”,掌握焦炭在炉内的变化规律和炉缸工作状况,为高炉操作提供技术支持,同时为焦化厂低成本生产出符合高炉运行要求的焦炭提供了依据。     

新钢10号高炉6m湿熄焦冶炼生产实践

焦炭质量好坏对高炉生产顺行稳定、技术经济指标和高炉炉缸寿命等影响重大,通过制定一系列调整方案稳定炉况,最大程度改善技术经济指标。并通过具体措施对新钢10号高炉6 m湿熄焦冶炼生产实践进行了总结。     

Calculating the blast-furnace profile

A mathematical model is developed for calculating the height and outline of the working space in a blast furnace from the batch surface to the axis of the air tuyere, on the basis of data regarding the density, acceleration of the batch flux, and pressure difference of the gas. The optimal working height of blast furnaces in smelting titanomagnetite sinter and pellets is 10.1–21.8 m. For larger furnace height, relatively immobile refractory batch is formed in the bosh and periodically slips to the hearth, with impairment of the furnace’s thermal state. The calculated values obtained provide guidelines in the design and reconstruction of shaft furnaces.     

The use of siderites in blast furnaces operated on unfluxed pellets

Bakal siderites represent an important source of iron ore that can be used in the production of high-quality pig iron and steel. Their value in this regard stems from the stability of their chemical composition, low content of harmful impurities (sulfur, phosphorus), good reducibility, and good strength in the roasted state. These advantages, combined with the favorable composition of the country rock-which has a basicity (based on CaO + MgO/SiO₂) of up to 2.6-makes it possible to classify these siderites as iron-fluxes that can be used effectively in a blast furnace. Roasted siderite concentrate (RSC) can be used efficiently in the blast-furnace charge to make different grades of manganese-bearing foundry iron as long as unfluxed pellets are also employed. On the average, the addition of 10 kg of RSC to the charge per ton of pig iron reduces the consumption of dry skip coke by 0.6–1.5 kg/ton pig and increases furnace productivity by 0.9–2.0 tons/day by decreasing the amount of raw flux needed and increasing the iron content of the fluxed part of the charge. __________ Translated from Metallurg, No. 8, pp. 51–55, August, 2006.     

Effect of adding schungite to the blast-furnace charge on the smelting operation and the smelting products

Positive results obtained at several plants from the use of schungite in pig-iron smelting motivated the MMK to conduct trial heats on its blast furnaces. The use of schungite in short trial heats showed a decrease in coke rate and an increase in furnace productivity. __________ Translated from Metallurg, No. 1, pp. 38–40, January, 2007.     

Study of steel production with the use of hot-briquetted iron in the cold charge

The use of hot-briquetted iron in large furnaces makes their operation more efficient. The time of furnace operation under current is shortened by 4 min, while unit electric-power consumption is cut by 15 kWh/ton for the melting of the charge and by 8 kWh/ton for the completion of the heat as a whole. These results are obtained when the amount of hot-briquetted iron in the cold charge corresponds to 0.3–0.4 of the weight of the scrap and the ratio of the mass of the cold charge to the mass of the metallized pellets in the charge is within the range 1.0–1.1. __________ Translated from Metallurg, No. 3, pp. 50–51, March, 2007.     

济钢3200m~3高炉炉况变化分析

济钢3200 m3高炉实施强化冶炼技术以来,炉况的变化可分为两个阶段:第1阶段,高炉综合品位高,焦炭及烧结矿质量好,高炉风量、产量提升;第2阶段,受原料资源的限制,焦炭质量变差,烧结矿Al2O3含量高,渣比高,炉缸活性提升困难,风量低,产量下降。结合实际冶炼条件,提出了炉况调整思路,维持了高炉生产系统的稳定,实现了高炉长期稳定顺行。     

基于图像处理的高炉炉缸死铁层中焦粒信息分析

 高炉铁口水平线下(死铁层区)死料堆的位置、大小、孔隙度、更新速度等直接决定铁水及炉渣在炉缸内的流动方式,同时影响炉缸传热、耐材的侵蚀、铁水及渣的排出速度等。使用图像处理技术对莱钢1 880 m3高炉浸入死铁层中死料柱下部形状、孔隙度、焦粒尺寸、形貌分布等关键信息进行了提取。通过分析计算得到死料柱下部焦层二维孔隙度为56.73%。该区域焦粒平均粒度为15.3 mm,缩减了约70%。通过形貌分析发现炉缸死铁层中焦炭更接近椭球状,该现象说明自炉顶装入后焦炭各方向消耗速度不一致,具有明显的取向性。该高炉内渣铁通过炉缸该区域死料柱焦粒过程中,水平方向与竖直方向冲刷程度较深。有助于对高炉炉缸“黑箱”进行信息解析,进一步加深操作者对于高炉冶炼过程中死料柱下部及炉缸工作状态的认知。     

炉缸焦炭状态与炉况运行间关联性分析

为了研究炉缸内焦炭存在性状与炉况运行状态之间关系,采用炉内径向取样技术,通过对不同大型高炉炉缸区域所取焦炭的堆积程度、粒级存在状态、自身成分与结构以及热态性能等进行检测与分析,并统计出此阶段高炉运行指标,回归出炉缸焦炭存在状态与炉况运行指标间关联性规律。分析结果表明,炉缸内焦炭粒度每增加1 mm,约可提升喷煤量4.66 kg/t,降低燃料消耗4.77 kg/t,同时大型高炉要想获得较好的运行效果,死料柱内的渣、铁滞留量还应严格控制在45%以内。这也验证了良好高炉运行状态下,除应选用优质原燃料入炉,用以减轻炉内焦炭熔损程度,强化料柱功能外,还应在操作中贯彻以风量及风压为优先调剂举措,用于改善炉缸活跃程度。