GB1075377A - Improvements relating to the manufacture of refract ory material - Google Patents

Abstract

Refractory structural and lining materials are made by pre-heating normal coarse-grained quartzite at a temperature above 500 DEG C. and subsequently subjecting it to a hydrothermal treatment above 165 DEG C. For instance, lump form quartzite may be (1) heated to 1250 DEG C. and crushed; (2) heated to 1250 DEG C. and crushed to form a coarse and a fine grain fraction, the former being further heated to 1450 DEG C. prior to mixing with the latter fraction; or (3) crushed and separated into a fine grain and a coarse grain fraction, the latter then being heated to 1250 DEG to 1450 DEG C. and mixed with the former. The heating processes are carried out in conventional furnaces, e.g. shaft or fluidized bed furnaces. The powdered, pre-heated quartzite is subjected to treatment with saturated or super-heated steam at above 165 DEG C. for more than 65 "hours-atmospheres" (time in hours x atmospheres of pressure above atmospheric pressure) in an autoclave at, e.g. 10 to 20 atmospheres. Alternatively, the hydrothermal treatment is carried out at normal pressure and may be combined with the pre-heating of the quartzite by introducing steam into the pre-heating furnace. Lime milk may be added in a vacuum operation or the quartz may be saturated therewith in the autoclave. The treated quartzite, mixed if desired, with fine grain untreated quartzite, is processed in known ways to form, e.g. ramming masses, bricks and other shaped articles. In one method, pre-heated quartzite may be subjected to a preliminary hydrothermal treatment and/or mixed with lime milk, quartz powder, TiO2, spent sulphite liquor or molasses, prior to moulding, hydrothermal treatment and firing.