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.     

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.     

Aspects of the smelting of high-vanadium pig iron

Conclusions The use of CVS in amounts up to 44 kg/ton made it possible to increase the vanadium content of the pig from 0.497 to 0.638% while keeping L_V at the usual level (80–82%). An increase in the percentage of CVS in the charge leads to a moderate increase in the manganese content of the pig. There is almost no change in the concentrations of the other elements, except for phosphorus. Converter slag introduces additional phosphorus into the blast furnace, resulting in an increase in the phosphorus content of the pig iron from 0.038 to 0.043%. The fact that the phosphorus content of the pig in isolated taps was greater than 0.05% can again be attributed to an increase in the amount of phosphorus introduced by the coke and pellets. The use of CVS makes it possible to moderately reduce the consumption of raw limestone in the blast-furnace charge. Chusovoi Metallurgical Plant, AMI Company, and the Institute of Metallurgy (in the Ural Division of the Russian Academy of Sciences) (Ekaterinburg). Translated from Metallurg, No. 7, pp. 18–20, July, 1999.     

高炉使用铁焦的㶲分析

 中国钢铁生产主要以高能耗和高排放的高炉-转炉长流程为主,节能减排压力较大。因此,积极研发高炉低碳炼铁技术,促进高炉工序CO₂减排尤为重要。铁焦是将含铁原料加入适宜的煤中,经焦化或炭化后成型的新型碳铁复合炉料,其高反应性可以显著降低热储备区温度、降低碳消耗,高炉使用适量的铁焦可实现一定程度的节能降碳。基于现场生产数据,采用㶲分析理论,建立高炉使用铁焦的㶲平衡模型,探索铁焦添加量对高炉物料消耗及能量利用效率的影响。结果表明,高炉使用铁焦后,炉内间接还原得到发展,碳利用率提高,炉内灰分量降低,冶炼单位生铁的碳素消耗和炉渣量均会降低,与未使用铁焦相比,高炉使用114 kg铁焦后,吨铁碳素消耗降低25.95 kg,渣量降低11.28 kg。此外,铁焦内部的金属铁仅需熔化,节省还原所需的㶲量,焦炭和鼓风带入㶲会显著降低,因此高炉冶炼吨铁消耗的总㶲量降低,同时,炉内传热也得到改善,内部㶲损失有效降低,与未使用铁焦相比,高炉使用114 kg/t铁焦后,目的㶲效率由46.14%提高至48.87%,热力学完善度由87.46%提高到88.02%。在此条件下,高炉吨铁的内部㶲损失降低192.63 MJ,实现节能6.57 kg(标煤)。     

Blast-furnace operation with coke fines

Conclusion Depending on the smelting conditions, the use of coke fines (36-25 mm) for up to 22% of the coke charged into a blast furnace having a standard bell-and-hopper charging appratus, led to a decrease in pig-iron output by 1.0–1.6% (or 0.2–0.4% for each 1% of coke fines), an increase in unit coke consumption by 0.8–1.0% (or by 1.0%-0.19-0.17%), and a deterioration in the drainage capacity of the hearth. The performance indices of the furnace equipped with a revolving distributor show that it is possible to force smelting while using up to 25% coke of the 36-25-mm fraction in the charge. If the coke in the charge consists of more than 30% fines, smelting rate decreases and hearth performance declines. These developments are accompanied by a 3.3–3.6% reduction in furnace productivity (0.12–0.13% for each 1.0% of the 36-25-mm fraction of coke) and a 0.85–0.90% increase in unit coke consumption (0.03–0.04% for each 1% of coke fines). West Siberian Metallurgical Combine. Translated from Metallurg, No. 1, pp. 38–39, January, 1999.     

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.     

Technological principles behind making the heating of steelmaking baths more efficient and reducing pollution

Improving the efficiency of the heating of the steelmaking bath through the use of oxygen while reducing pollution remains one of the most difficult but important problems in the science and practice of metallurgy. Of the different high-productivity steelmaking methods now used, the oxygen-converter method is the leading technology: the unit consumption of oxygen averages 65 m³/ton in oxygen-converter steelmaking, 30 m³/ton in electric steelmaking, 60 m³/ton in open-hearth practice, and 70 m³/ton in two-bath furnace steelmaking. Most of the oxygen is consumed in refining processes. The use of oxygen to improve thermal efficiency is limited. Oxygen-based steelmaking methods are characterized by low thermal efficiency, oxidation loss of metal in the charge, wear of refractories, and emissions of dust and products of incomplete combustion. An increase in the concentration of oxygen in the furnace chamber increases the rate of oxidative processes (combustion of carbon, iron, and other components of the melt) but reduces fuel consumption and increases the consumption of pig iron (heat-carrier prepared in the blast furnace). Attempts to use combustion air with an oxygen content higher than 25–30% in open-hearth steelmaking have shortened the life of the roof refractories and increased downtime for repairs. “TsNIIchermet” State Science Center. Translated from Metallurg, No. 9, pp. 25–28, September, 1996.     

New technological solutions to protect the lining of blast-furnace hearths

The use of schungite as a partial replacement for coke is practiced in Russia at a number of metallurgical plants, both in the production of foundry iron (its primary use) and in making conversion pig iron. The largest amount of coke is replaced when foundry iron is being made, the replacement coefficient in this case having a value within the range 0.8–1.3. Studies that included continuous monitoring of the temperature of the carbon blocks in blast furnaces with volumes of 1719, 3200, and 5580 m³ unambiguously demonstrate that the thickness of the slag crust in blast furnaces increases with the use of schungite. Protecting the lining of the hearth through the use of schungite is also accompanied by a decrease in coke consumption. __________ Translated from Metallurg, No. 8, pp. 53–57, August, 2007.     

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。     

Use of liquid pig iron in electric-arc furnaces

Conclusions A technology for adding liquid pig iron to a DSP-10017 furnace has been developed, tested, and introduced commercially. The technology reduces the consumption of electric power by 44–55 kW·h/ton steel (to 406.3 kW·h/ton) and shortens the heat by an average of 10 min. The duration of the trial heats was 1 h, 51 min. Certain technological parameters of the steelmaking operation were determined. For example, it was established that the molten pig iron should be added only after complete melting of the scrap metal and that unit electric-power consumption during the addition should be within the range 230–320 kW·h/ton scrap. A total of 4–5 tons of iron ore (sinter) and 4–6 tons of lime should be added to the cold charge and the secondary scrap charge. The high SiO₂ content of the slag makes it necessary to carefully discharge the slag over the sill of the working door after the liquid pig iron has been added. Kuznetsk Metallurgical Combine. Translated from Metallurg, No. 6, p. 32, June, 2000.     

台车连续炉直接还原法

开发了一种在台车连续炉中实现铁矿直接还原的方法。台车连续炉的炉膛是直条形,炉底由若干个台车组成。含碳球团料层铺在台车上,通过炉膛时进行还原焙烧。为了得到高金属化率,在料层表面覆盖薄焦炭层保护。此方法已经成功地用于唐钢石人沟铁矿。生产线所用的炉子长70 m,宽2 8 m。炉底由26 个台车组成。用这种方法生产的海绵铁产品成分如下:金属化率大于92%,全铁约90%,硫小于0 08%。一座炉子的产量为5 t/h,总煤耗低于700 kg/t。和转底炉比较,台车连续炉的优点是:结构简单,供热点少,台车维修方便,主要缺点是台车运转速度不能太快,焙烧时间较长。     

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.     

Introduction of a System for Intensifying Steelmaking in a DSP 100 Arc Furnace at Ural Steel

Ural Steel has rebuilt its arc steelmaking furnace No. 1, equipping it with wall and door multi-lances that are moved into position by hydraulic manipulators. The changes have allowed the company to introduce a system that speeds up the steelmaking operation. Use of the system has shortened the average heat to 89 min. Unit electric-power consumption was previously 406 kWh/ton liquid steel and electrode consumption averaged 4.2 kg/ton. The replacement of 25 tons of solid pig iron by the same amount of liquid pig in each heat has made it possible to lower the average unit consumption of electric power to 382 kWh/ton and shortened the time of operation of the furnace under current to 50 min. The coefficient characterizing the use of oxygen in the blow is now within the range 0.86–0.92%.     

莱钢大高炉高渣比条件下低硅生产实践

通过改善炉缸活性、优化炉渣碱度的控制、开发炉缸液面控制技术。应用矿焦错档位布料矩阵和时间法精准控制布料技术,在渣比高达430 kg/t、入炉硅负荷135 kg/t的原料条件下,解决了低硅生产出现的渣铁排放不畅、煤气利用率不稳、炉温波动大等问题,月平均生铁硅含量由0.47%降低到0.37%,一类品率从43.67%提升到86.22%,取得了较好的技术经济指标。     

Technologies that improve the quality of steel and problems in choosing the composition of the charge

Conclusions The development, mastery, and gradual industrial adoption of modern methods for treating pig iron and steel outside the furnace at our factories will ultimately lead to the operation of converters on molten pig iron that has very low concentrations of all (except for carbon) impurities. This will in turn make it possible to improve the productivity of blast furnaces (while also conserving coke), reduce the consumption of fluxes in converter steelmaking, reduce the amount of iron lost with the slag, increase the percentage of coolants in the charge, prolong the life of the lining, and bring about other positive changes. Russian Academy of Natural Sciences. Translated from Metallurg, No. 10, pp. 17–19, October, 1998.     

济钢3200m~3高炉优化布料模式实践

济钢为进一步降低3200m3高炉燃料消耗,寻找适应自身原燃料条件、强化水平高的布料模式,进行了取消中心加焦的优化布料试验,整个试验过程炉况运行正常,最终形成了稳定的平台漏斗料面结构,煤气利用率提高2.78%,燃料比下降10～15kg/t,炉缸工作状态进一步得到改善。     

焦炭喷洒ZBS改质剂的改性机理及生产实践

 针对阳春新钢铁炼铁高炉所采购焦炭品种多、质量波动大,造成高炉炉况波动、成本偏高的问题,进行了焦炭提质增效的工业性试验研究。通过向焦炭立体喷洒ZBS焦炭改质剂,研究了ZBS改质剂与焦炭的相互作用行为,阐述了ZBS改性机理。研究发现,经过ZBS改性后的焦炭形成了碳的络合物和化合物,改变了碳的结构,提高了焦炭的石墨化度。经ZBS改质剂处理后,焦炭反应性(CRI)平均降低5.2%,反应后强度(CSR)平均提高7.83%。相较于基准期,高炉炉温波动小,硫含量合格, 生铁合格率达到100%。试验的1号高炉日产提高75 t,入炉焦比降低33.8 kg/t,综合燃料比降低11.63 kg/t。通过项目实施,达到了高炉稳产、增产、降低焦炭用量的目的,为高炉炼铁增产降耗提供了一种新方法。     

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.     

提高高炉煤比的实践

介绍了唐钢优化高炉配煤结构和喷煤系统操作、不断调整高炉操作制度的实践。在原燃料质量下降的情况下,努力协调好高炉护炉与提高煤比、提高生铁质量的关系,控制煤气流合理分布,使高炉煤比达到了180 kg/t以上,在节焦降耗方面取得了新的进展,有效地降低了生铁成本。     

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.