26/06/2018
Nagpur: Calcined clay is the most common material used as refractory material (lining of high temperature furnaces). As demand of calcined clay grows manifold, an alternative is needed. The city-based Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARDDC) has found a substitute to calcined clay that will reduce the material cost by at least five times. The centre is in the process of using the otherwise unutilized saprolite ore found at the bottom of a bauxite mines. “It is for the first time that saprolite is being used as a refractory material. Centre has already filed a national patent for it. Though the project is still in research stage, it has shown promise. We have tested the material in a furnace at MIDC Hingna over a period of last one year. The upscaling process, however, is yet to be tested,” said JNARDDC director Anupam Agnihotri. Generally pyrophyllite, high purity calcined clay, and silimanite are used as refractory materials. Saprolite was never looked upon as a refractory material in India. The principal investigator of the project Pravin Bhukte told TOI that JNARDDC initiated the research as an in-house project in the field. After getting promising results, it proposed a project to the ministry of mines, Government of India which has sponsored the project for Rs 41 lakh. By the end of project in 2017, JNARDDC hopes to convert these results to industrial process. Saprolite (major deposits Maharashtra, Chhattisgarh, Madhya Pradesh, west coast, and Gujarat) is high in silica and low in alumina. Refractory industry requires more than 40% alumina. But with the process developed by JNARDDC, the alumina percentage could be increased with thermal treatment or sintering from 37 to 45% thus improving the utility of the ore. A good refractory material also needs to have minimum iron content. Hence JNARDDC is trying to de-iron or reducing the iron content in the saprolite ore from existing 2.7 % to 2% to make it more suitable for the industry. Agnihotri said the product developed by JNARDDC could be used as refractory replacement in steel, cement, boiler, fertilizer and petrochemical industry. “The energy consumption in the process developed by the centre has been one tenth. Even after considering transportation and other costs, the total production cost of this new furnace material would be at least a fifth of conventional material,” he said. The process * Saprolite samples collected from western ghat bauxite deposits * Chemical and mineral properties studied * Material grinded and homegnized * The grinded material given heat treatment (sintering) at 1500+ degrees C * About 80-85% material could be recovered after sintering Advantages of the new material * It is equivalent in quality to existing refractory materials * It is using a non-utilized (waste) material * It helps utilize the entire content of a bauxite mine * Doesn’t require separate exploring for saprolite as it forms the bottom layer of every bauxite mine * The material cost can be reduced to a fifth by saving energy * It is a good alternative to calcined clay used as refractory material
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