What are environmentally friendly green refractory materials?

In recent years, the concept of developing environmentally friendly green refractory materials has been proposed, challenging traditional refractory materials. Some developed countries have stopped or restricted the production of products such as silica bricks, magnesia-chrome bricks, and refractory ceramic fibers, and have banned the use of raw materials such as tar, asphalt, and resins, actively seeking alternative refractory materials. China has also done a lot of work in this area and has achieved good results.

(1) Chromium-free. Magnesia-chrome bricks, which are widely used and have a large usage volume, easily produce hexavalent chromium, which is harmful to the human body, so substitutes must be found. Research has found that: white dolomite bricks can be used in cement rotary kiln sintering zones; aluminum-magnesium spinel bricks, magnesia-calcium-zirconium bricks; AOD furnaces are gradually being replaced by magnesia-calcium bricks; VOD furnaces use magnesia-dolomite bricks or dolomite bricks; RH furnaces use magnesium-aluminum spinel bricks and magnesia-zirconium castables; some non-ferrous metallurgical furnaces have also achieved success by changing from magnesia-chrome bricks to spinel refractory products. High-alumina bricks, widely used in coal-water slurry and coal-tar slurry gasifiers, may be replaced by calcium hexaaluminate castables.

(2) Harmlessness of refractory ceramic fibers. Traditional alumina silicate refractory fibers cannot be degraded after being inhaled by the human body, causing great harm, and their use is restricted in some developed countries. Henan Zhonggong New Refractory Materials Co., Ltd. has developed a castable mainly composed of lightweight calcium hexaaluminate aggregates. This aggregate is harmless to the human body and has better heat preservation performance at high temperatures than refractory fibers. Some researchers have also developed biodegradable fibers for human bodies.

(3) Elimination of the use of tar, asphalt, and other substances. Tar and asphalt are often used as binders for some refractory materials. When used at high temperatures, they emit yellow smoke and have a bad smell, which is harmful to health. After research, it was decided that all materials using tar, asphalt, and resin should be replaced with environmentally friendly binders. For example, the iron trough materials used in blast furnaces are replaced with sol, gel, cement, and Silon as binders; blast furnace gun mud is replaced with modified polymers, etc., which do not emit smoke and have good performance; the magnesia dry materials of the intermediate vessel are replaced with glucose and water glass binders, greatly reducing smoke, and their performance is the same as when using phenolic resin binders; steelmaking converters generally use magnesia sand, asphalt, and additives for hot-state direct current repair materials, which pollute the environment. By eliminating asphalt and using phosphoric acid and lignosulfonate as binders, not only is it environmentally friendly and pollution-free, but the sintering time is also shorter, and the service life is longer.

In summary, in the production and use of refractory materials, raw materials and products that pollute the environment and harm human health should be eliminated, and research should be conducted to produce green refractory materials to replace the above-mentioned products.