轻烧镁球烧结降镁，效益更美 Light-burned magnesium balls sinter magnesium reduction, more beautiful

    近年来，钢铁行业形势严峻，铁前成本压力急剧增加，铁矿粉质量不断劣化。为了稳定烧结矿质量，同时进一步降低炼铁生产成本，首钢京唐公司经过一系列基础研究，最终实现了自然镁烧结，烧结矿品位、强度、粒度、冶金性能和熔滴性能得到改善，并创造了可观的经济效益。

　　轻烧镁球烧结降镁优势明显

　　作为亚太地区高炉的主要炉料，烧结矿一般占高炉结构的60%以上。通常在烧结配料中添加白云石、蛇纹石等含镁熔剂来提高高炉渣中的MgO含量，以改善炉渣的流动性和脱硫能力，适应炉渣中的高Al2O3质量分数。

　　烧结作为贡献高炉渣MgO的主要来源，其MgO含量受高炉渣需求和高炉操作习惯所限。日韩高炉渣中的MgO含量控制在3%~5%的水平，而国内大多在7%以上。受此影响，日本新日铁、韩国浦项光阳和现代制铁烧结矿的MgO含量在0.7%~1.2%的水平；而国内烧结矿的MgO含量大多在1.6%以上，高的甚至在3.0%以上。甚至有部分研究者认为，烧结中较高的MgO含量有利于烧结矿质量的提高。

　　近年来，大量国内轻烧镁球烧结研究者呼吁轻烧镁球烧结降镁，首钢京唐走在了实践的前列。项目组围绕首钢京唐开展了烧结过程热平衡测算、烧结基础特性测试和高温共聚焦原位观察、矿相研究、烧结杯试验、综合炉料熔滴性能测试的一系列烧结降MgO实验室研究。

　　研究发现：

　　降镁有助于提高烧结矿品位，有助于发展优质铁酸钙，提高烧结矿还原性。降低0.5%的MgO，可提高烧结矿TFe含量0.3%以上；在进口矿粉劣化的背景下，调镁更显出主动保烧结矿品位的价值。烧结矿品位的提高，有助于形成更多优质黏结相———针状铁酸钙，从而对烧结矿指标和还原性改善有利。

　　降镁有助于减少熔剂耗热，从而增加烧结有效热量。含镁熔剂在烧结过程中分解耗热，降低含镁熔剂配比有助于节能和改善烧结矿质量。烧结矿MgO含量降低0.5个百分点，含镁熔剂单耗降低14kg/t烧结矿，烧结过程分解耗热减少了约1%，相当于在烧结热损失一定的情况下，烧结过程的有效热量增加1%，从而有利于烧结矿粒度组成的改善。

　　降镁有助于改善烧结液相流动性，增强烧结黏结效果。烧结基础特性和高温共焦设备测试表明：烧结混匀料MgO含量从2.3%降低到0.3%后，液相流动性指数从0.7提高到1.9；与含MgO的方案相比，原位观察发现不含MgO的方案具有最高的液相流动速度。烧结液相流动性的改善，增强了黏结效果，有利于烧结矿粒度组成的改善。

　　烧结降镁搭配球团提镁，在保证高炉渣系稳定的基础上改善了综合炉料的熔滴性能。熔滴性能试验表明，综合炉料结构从烧结矿1.9%MgO+球团矿0.7%MgO转变为烧结矿1.5%MgO+球团矿1.7%MgO后，熔滴区间从64℃降低到59℃，最大压差从1910Pa降低到1590Pa，最终使综合炉料的S特性值从122.2kPa·℃降低到93.8kPa·℃。

　　工业实践创造效益

　　基础研究发现轻烧镁球烧结降镁的优势明显，而2012年11月首钢京唐球团生产镁质球团矿，为烧结降镁提供了条件。2013年2月开始研究人员在首钢京唐烧结开展了降MgO工业试验，取得了如下结果：烧结矿MgO含量从1.8%逐步降到1.5%水平，结合矿粉结构调整，烧结矿品位从55.95%提高到56.48%，2013年9月份后含镁熔剂在首钢京唐已基本停配。降镁后烧结指标改善明显：烧结矿<10mm比例从20.28%降低到17.85%，还原性从80.15%提高到84.7%，烧结矿熔滴性能显著改善，烧结矿的S特性值从262kPa·℃降低到87kPa·℃。近年来首钢京唐烧结矿主要指标如附表所示。

　　经过一年多工业实践，2014年首钢京唐烧结矿MgO含量已稳定在1.4%~1.5%的水平，在国内大型烧结厂中处于最低水平，2014年10月份更是进一步达到1.35%。

　　附图为首钢京唐烧结厂与国际上烧结厂MgO含量的比较。与部分国际先进厂矿相比，尽管首钢京唐烧结矿的MgO含量仍略高，但已属于不配加含镁熔剂的自然镁烧结矿。

　　据统计，首钢京唐烧结降镁的年效益达到812.5万元。2014年10月经过专家鉴定，首钢京唐烧结降镁研究及实践达到国内领先水平。

　　专家认为，首钢京唐烧结降镁成功实践在国内具有较大的应用前景。钢铁企业主要可以考虑如下两种应用方案：一是通过降低烧结矿MgO含量来适当降低高炉渣中MgO含量，为高炉精料做出贡献；二是降低烧结含镁熔剂配比，相应地在球团中添加适宜的含镁添加物———将烧结矿MgO含量转移到球团中，通过生产低镁烧结矿和高镁球团矿来改善综合炉料的冶金和熔滴性能，进而改善高炉技术经济指标。

In recent years, the situation of the iron and steel industry has been severe, the cost pressure before iron has increased sharply, and the quality of iron ore powder has continued to deteriorate. In order to stabilize the quality of the sintered ore and further reduce the cost of ironmaking, after a series of basic research, Shougang Jingtang Company has finally achieved natural magnesium sintering. The sintered ore grade, strength, particle size, metallurgical properties and droplet properties have been improved and created Considerable economic benefits.

优势 Light-burned magnesium sintering has obvious advantages in reducing magnesium

As the main charge of blast furnaces in the Asia-Pacific region, sinter ore generally accounts for more than 60% of the blast furnace structure. Usually dolomite, serpentine and other magnesium-containing fluxes are added to the sintering batch to increase the MgO content in the blast furnace slag to improve the fluidity and desulfurization ability of the slag and adapt to the high Al2O3 mass fraction in the slag.

Rhenium sintering is the main source of blast furnace slag MgO, and its MgO content is limited by blast furnace slag demand and blast furnace operating habits. The content of MgO in blast furnace slag from Japan and South Korea is controlled at the level of 3% to 5%, while most of them are above 7% in China. Affected by this, the MgO content of Japan's Nippon Steel, South Korea's Pohang Gwangyang, and Hyundai Iron Sinter is between 0.7% and 1.2%; while the MgO content of domestic sinters is mostly above 1.6%, which is even higher than 3.0. %the above. Some researchers even believe that the higher MgO content in sintering is conducive to improving the quality of sintered ore.

In recent years, a large number of domestic light-burned magnesium ball sintering researchers have called for light-burned magnesium ball sintering to reduce magnesium, and Shougang Jingtang has taken the lead in practice. The project team carried out a series of sintering MgO laboratory researches on sintering process thermal balance calculation, sintering basic characteristics test and high-temperature confocal in-situ observation, ore phase research, sintering cup test, comprehensive furnace melt droplet performance test around Shougang Jingtang.

  The study found:

Magnesium reduction helps to improve the grade of sinter ore, helps to develop high-quality calcium ferrite, and improves the reducibility of sinter ore. Reducing the MgO by 0.5% can increase the TFe content of the sintered ore by more than 0.3%. Against the background of the deterioration of imported ore powder, adjusting magnesium has more value in actively maintaining the sintering ore grade. Increasing the grade of sinter ore will help to form more high-quality binding phases-acicular calcium ferrite, which is beneficial to improving the sinter ore index and reducing property.

Magnesium reduction helps to reduce the heat consumption of the flux, thereby increasing the effective heat of sintering. Magnesium-containing flux decomposes and consumes heat during the sintering process. Reducing the proportion of magnesium-containing flux helps to save energy and improve the quality of sintered ore. The sintered ore MgO content is reduced by 0.5 percentage points, the unit consumption of magnesium-containing flux is reduced by 14kg / t sintered ore, and the decomposition heat consumption during the sintering process is reduced by about 1%, which is equivalent to an increase in the effective heat of the sintering process with a certain sintering heat loss %, Which is conducive to the improvement of the particle size composition of the sinter.

Magnesium reduction helps to improve the liquidity of the sintering liquid phase and enhance the sintering bonding effect. The basic characteristics of sintering and high-temperature confocal equipment tests showed that: after reducing the MgO content of the sintered mix from 2.3% to 0.3%, the liquidity index increased from 0.7 to 1.9; compared with the solution containing MgO, in-situ observation found no The MgO-containing solution has the highest liquid flow rate. The improvement of the liquidity of the sintered liquid phase enhances the bonding effect and is beneficial to the improvement of the particle size composition of the sintered ore.

Sintering magnesium reduction and pelletizing magnesium extraction, on the basis of ensuring the stability of the blast furnace slag system, improved the melt droplet performance of the comprehensive charge. Droplet performance tests show that after the overall charge structure is changed from sintered ore 1.9% MgO + pellets 0.7% MgO to sintered ore 1.5% MgO + pellets 1.7% MgO, the droplet interval is reduced from 64 ° C to 59 ° C, the maximum pressure difference From 1910Pa to 1590Pa, the S characteristic value of the comprehensive charge is finally reduced from 122.2kPa · ° C to 93.8kPa · ° C.

Industrial practice creates benefits

Basic research found that the advantages of light-burned magnesium balls for sintering magnesium are obvious. In November 2012, Shougang Jingtang pellets produced magnesium pellets, which provided conditions for sintering magnesium reduction. In February 2013, researchers began an industrial test of reducing MgO at Shougang Jingtang Sintering, and achieved the following results: The sintered ore MgO content gradually decreased from 1.8% to 1.5%, combined with the ore powder structure adjustment, the sintered ore grade was 55.95% It increased to 56.48%. After September 2013, magnesium-containing flux had been basically stopped in Shougang Jingtang. After magnesium reduction, the sintering index improved significantly: the proportion of sintered ore <10mm decreased from 20.28% to 17.85%, the reducibility increased from 80.15% to 84.7%, the droplet properties of sintered ore improved significantly, and the S characteristic value of sintered ore decreased from 262kPa To 87kPa · ° C. The main indicators of Shougang Jingtang Sinter in recent years are shown in the attached table.

After more than one year of industrial practice, MgO content of Shougang Jingtang Sinter has stabilized at the level of 1.4% to 1.5% in 2014, the lowest level among large domestic sinter plants, and it reached 1.35% in October 2014.

The picture shows the comparison of MgO content between Shougang Jingtang Sintering Plant and international sintering plants. Compared with some international advanced factories and mines, although the MgO content of Shougang Jingtang sinter is still slightly higher, it is already a natural magnesium sinter with no magnesium-containing flux.

统计 According to statistics, Shougang Jingtang's annual sintering magnesium reduction reached 8.125 million yuan. In October 2014, after expert appraisal, Shougang Jingtang sintering magnesium reduction research and practice reached the domestic leading level.

Experts believe that the successful practice of Shougang Jingtang sintering magnesium reduction has great application prospects in China. Iron and steel enterprises can consider the following two application schemes: one is to reduce the MgO content of the sintered ore to appropriately reduce the MgO content in the blast furnace slag to contribute to the blast furnace concentrate; the second is to reduce the proportion of the sintered magnesium-containing flux, correspondingly in the ball Appropriate magnesium-containing additives are added to the pellets--the MgO content of the sintered ore is transferred to the pellets, and the metallurgical and molten droplet properties of the comprehensive charge are improved by producing low-magnesium sintered ore and high-magnesium pellets, thereby improving the technical and economic indicators of the blast furnace .