Chrome-free refractories

Various chrome-free refractory materials have been studied by dip testing of these refractories in ferrous silicate and calcium ferrite slags typical of those used in copper production furnaces. More recently, a rotating sample test procedure has been employed. 

Crites, M. D. and Schlesinger, M. E., Corrosion Testing of Chrome-Free Refractories for Copper Production Fiu-naces," Proceedings of Copper 99-Cobre 99 International Conference, Volume Vl-Smelting, Technology Department, Process Modeling and Fundamentals, The Minerals, Metals and Materials Society, 1999, pp. 187-194. 

Schlesinger ME, Karakus M, Crites MD, Somerville MA, Sun S. Chrome-free refractories for copper production frunaces. In Stett MA, ed. Advances in Refractories. Vol. m, Westerville, OH UNTTCER. Amer Ceram Soc, 1997 1703-1709. ANH Refractories Company Data Sheets, 2002. 

Martino M, Curletto L, Bonifacino V. Some correlations between composition and characteristics in the field of chrome-free refractories for steel degassing. No. 11 on CD-Rom. Proc. Unified Inti. Tech. Conf. on Refractories, Cancun, Mexico, 2001 13. 

The major application for magnesia is as a refractory lining in furnaces. In lesser quantities, it is made into a well-known milky solution and ingested. It is also used to manufacture other ceramics such as chrome-free spinels. Nonchrome spinel is not available in nature on an industrial scale. At Asahi Glass, spinel is produced by electrofusing magnesia with alumina. 

In the early 1960s, fired dolomite bricks had been developed for use in the burning zone of rotary cement kilns. Dolomite is chemically compatible with the cement-making process and readily acquires a protective coating with the clinker in the burning zone. The need for chrome-free linings in the cement-making process added impetus to penetration of dolomite refractories in this application. 

In the case of cement, one of the big advantages of doloma-based refractories is to provide chrome-free lining configurations. 

Kaneyasu A. Trends of basic refractories raw materials—magnesia aggregates for chrome-free bricks. Taikabutsu Overseas 2000 20(4) 245-248. 

MgO-spinel clinker is obtained by the same procedure, but with a substantial proportion of free MgO (75-85%). MgO-spinel is produced by sintering at temperatures of 1600-1800°C and a dense product is obtained. MgO-spinel refractory has better high temperature mechanical properties in arc furnace roof application compared to magnesia-chrome refractories, but it has lower strength than a high-alumina refractory. 

State, dense chrome oxide is the best refractory material for side walls. The refractory is backed by zircon blocks and another layer of clay blocks. The floor of the furnace is tilted to allow free flow of the glass to the exit channel. 

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