Summary

In this process we develop and obtain heat-accumulating bricks from Red Mud.

Red Mud is the insoluble residue of the Bayer Process by which the Alumina is extracted from the Bauxite by dissolution in NaOH. This Mud is characterized by its content of oxides of Iron, Silica and Titanium, besides for its variable quantities of compounds such as Si, Ca, Na and some other elements. NaOH is responsible for its basic pH. 471,000 tons are produced in Galicia (NW Spain) each year. This residue is stored in lakes in open air and they represent an environmentally hazardous waste.

Among the electric heating systems, there are the thermal storage heaters.

Electric thermal storage heaters allows to store heat during periods when the electric power is at low off-peak rates and can subsequently release the stored heat on demand at the day light hours. The heat is stored in high-density refractory bricks with a similar composition to that of red mud.

This similarity prompted us to develop a process for production of heat-accumulating bricks from red mud, trying to provide a commercial outlet for this environmentally hazardous waste. After making a deep characterization, some thermal processing tests were carried out. Fired bricks consist mainly in solid solutions of Aluminum and Iron Titanates, Corundum and Hematite. Different conformation tests were done and the pressing was selected because of the outstanding results that were obtained.

Once we had developed and completed the production technique, some comparison tests were carried out, between the commercial and the lab bricks, obtaining satisfactory results. Also, some tests were done in ceramic industries and the product was homologated for its commercial use.

Once the patent, that covers this process, was negotiated, the private sector started to build a pilot plant for the initially production capacity of 10 tons/day which could be extended to 100 tons/day.

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