Heat processing of tar-bonded refractories

Conclusions

During the heat processing of tar-bonded refractories in a protective atmosphere at 250–400°C the tar at first passes through a stage of fusion and uniform distribution over the entire volume of the products, and then is subjected to pyrolysis, molecular association, and polymerization with an increase in the coking number; simultaneously some of the volatiles separated from the tar are subjected to additional cracking, and the separated pyrolytic carbon is deposited on the channels of the gas exit. As a result there is a substantial improvement in the basic properties of the tar dolomite and tar dolomite-magnesite refractories.

To achieve the maximum heat process effect in the tarred dolomite and tar dolomite-magnesite refractories, using hard tars, it should be carried out in a reducing atmosphere at 350–400°C, in vacuum (without continuous extraction) at 250–300°C, or in a neutral atmosphere (nitrogen current) at 350–400°C. Unfired refractories prepared with soft tars should be heat processed in the same media but at temperatures not exceeding the lower limit of the above-mentioned temperature ranges. The soaking time at maximum temperature for converter refractories of industrial standard dimensions with tar bond should be 8–12 h.

It would be desirable to set up the production of heat-processed converter refractories with a tar bond in tar dolomite workshops in order to increase the resistance of converter linings, reduce their heating time, and increase the permitted storage period and transportation times of the tar-bonded refractories.