镁铬耐火材料及高温装备绿色化应用研究进展

Research Progress of Magnesia Chrome Refractories and Their Application in Greenization for High Temperature Furnace

镁铬耐火材料是以方镁石和镁、铁尖晶石(Mg,Fe)(Cr,Al,Fe)2O 4为主晶相的碱性耐火材料,具有耐火度高、高温强度大、热震稳定性优良以及抗熔渣侵蚀性和经济性等优点,在钢铁、有色、水泥等高温工业装备领域有着广泛的应用,是诸多高温装备炉衬关键部位的主导材料。然而镁铬耐火材料在氧化性气氛或与碱性氧化物如K 2O、Na 2O、CaO等共存时,在一定温度下其Cr^3+会部分转化为Cr^6+,由此带来六价铬污染问题,与高温工业绿色、环保、高效的发展理念相违背。通过法规对镁铬耐火材料产业链进行规范引导、采取系列措施抑制镁铬耐火材料六价铬化合物的形成均无法从根本上消除Cr^6+带来的隐患,而最根本的办法是开展耐火材料无铬化研究与应用。针对高温工业装备应用镁铬耐火材料带来的污染问题,国内外耐火材料工作者相继开展了高温装备绿色化研究与应用工作。其中水泥回转窑、RH精炼炉用耐火材料取得的无铬化研究成果已经实现了产业实践,产生了积极的社会效益,特别是水泥回转窑烧成带用耐火材料率先实现了无铬化。目前在水泥回转窑烧成带取得较好使用效果的是镁钙锆质耐火材料及镁尖晶石质耐火材料,它们能够替代镁铬砖并满足服役要求,上述研究与应用成果极大促进了钢铁工业用RH精炼炉无铬化的研究与实践。当前RH精炼炉无铬化研究已经成功获得应用,并且有多种不含铬材料替代方案,其中以复合镁铝尖晶石砖的应用最为普遍,在国内外一些RH精炼炉用耐火材料已经相继实现无铬化,实现了绿色化发展理念。上述成功经验有以下两点:(1)依靠行业自主技术创新,实现企业的社会价值;(2)依赖于社会大众环保意识的提高以及政府相关环保产业政策的引导,两种合力共同推动了高温装备的绿色化应用与发展。在今后的一段时期内,镁铬耐火材料在有色等领域依然难以代替,仍然是一些炉衬关键部位的主导材料,开展有效的无铬化研究与应用任重道远,因此提高镁铬砖性能、延长服役寿命以及减少材料消耗仍是重要课题。为此需要做好以下两点:(1)提高材料抗FeO-SiO2渣侵蚀性能;(2)提高材料的抗铜硫渗透性能。随着高温工业新工艺的实施和新技术、新装备的涌现,镁铬耐火材料在一些新领域也有一定的应用前景,因此开展高温装备绿色化研究与应用仍然是一个持久和不断进步的过程。本文归纳了镁铬耐火材料的特性及其在高温工业装备中的应用与损毁机理,重点介绍了水泥回转窑、钢水精炼RH炉绿色化研究与应用取得的积极进展,分析了炼铜炉绿色化应用存在的主要难点以及研究方向,指出了在积极推行回转窑、RH炉绿色化的同时,提高镁铬砖性能并减少其在炼铜炉中的消耗仍然是重要课题。

Magnesia-chromium refractory is an alkaline refractory material with periclase and spinel(Mg,Fe)(Cr,Al,Fe)2O4 as the main crystalline phases.It has high refractoriness,high strength under high temperature,excellent thermal shock resistance,fine slag corrosion resistance and good economical efficiency,and has been widely used in iron and steel metallurgy,non-ferrous smelting,cement and other industries.Magnesium chromium refractories are the dominant materials in many key parts of high-temperature furnace.However,Cr^3+of Cr2O3 will be partly converted to Cr^6+at a certain temperature in oxidizing atmosphere or with alkaline oxides such as K2O,Na2O,CaO,etc.,resulting in hexavalent chromium pollution,which is not line with green,environmentally friendly and efficient for high temperature industry.It is impossible to eliminate the hidden danger caused by Cr^6+in magnesium chromium refractories by regulating the industrial chain and taking a series of measures to restrain the formation of hexavalent chromium compounds.However,the most consistent and permanent way is to carry out the research and application of chromium-free refractories.In view of the pollution caused by the application of magnesia-chromium refractories in high-temperature industrial furnace,refractory resear-chers all over the world have successively carried out green refractories research and application for high temperature furnace.A large number of chromium-free research results have been achieved for cement rotary kiln and RH refining furnace,and positive social benefits have been achieved along with the production practice,especially the chromium-free refractories used in burning zone in cement rotary kiln.At present,the magnesia-calcium-zirconium refractories and magnesia spinel refractories have achieved better application effect in burning zone of cement rotary kiln,which can replace magnesia chromium bricks very well.The application result above-mentioned has greatly promoted the research and practice of chromium-free for RH refining furnace in iron and steel metallurgy.At present,refractories of chromium-free for RH refining furnace have been successfully developed,and there are many alternative refractories of chromium-free,for example,composite magnesia alumina spinel bricks are most widely used.Refractories for some RH refining furnace have been chromium-free in many countries,and the development idea of greenization has been realized.There are two points by summarizing the above experience:(i)relying on industry independent technological innovation to realize the social value of enterprises;(ii)relying on the improvement of public awareness of environmental protection and the guiding role of government policies related to environmental protection industry.The joint forces of above two can promote application and development of greenization of high temperature furnaces At present and some time to come in the future,magnesia-chromium refractories are still difficult to be replaced in high temperature furnace of non-ferrous smelting and the dominant materials in many key parts of high-temperature furnace.It is a long way to carry out effective research and application of chromium-free bricks.Therefore,it is still an important subject to improve the properties of magnesia-chromium refractories,improve service life and reduce material consumption.Therefore,the following two points of work need to be done well:(i)improving the corrosion resis-tance of materials to FeO-SiO 2 slag,(ii)improving resistance to copper-sulfur penetration.While drawing on the successful experience of chro-mium-free practice in other fields,we should also see that with the implementation of new high temperature industrial processes and the emergence of new technologies and furnace,magnesium chromium refractories still have certain application prospects in some new fields.Therefore,the research and application in greenization for high temperature furnace is still a lasting and continuous progressive process.This paper summarizes the characteristics of magnesia-chromium refractory and its application and damage mechanism in high-temperature furnace.It emphatically introduces the positive progress in the research and application of greenization for cement rotary kiln and RH furnace,and analyses the main difficulties and research directions of greenization of copper furnace,to achieve less consumption of magnesia-chromium bricks in copper furnace while actively promoting greenization of rotary kiln and RH furnace.