How to Eliminate the Expansion of Phosphate Refractory Castables

For large-scale construction of phosphoric acid and phosphate refractory castables using vibration molding and other methods, trapping materials is an effective and economical method, so it is widely used. After weighing the trapped material, add coagulant and stir evenly, then add the remaining cement and continue stirring for 1 to 2 minutes before it can be used for molding. The material trapping time is mainly determined based on the chemical reaction speed between the cement and the metal contained in the refractory aggregate and powder, as well as environmental temperature and other conditions.

Phosphoric acid combined refractory castable samples were stored indoors, in the open air, and castable standard curing rooms. As the storage time increased, their normal temperature compressive strength increased, but indoor storage was better than outdoor storage. After 3 months of standard curing, the intensity tends to decrease slowly. When stored indoors, the compressive strength after burning is more than 10Mpa higher than that in the open air. The post-burning compressive strength stored in a standard curing room is also better than that in the open air. Samples stored in the open air may have lower performance than refractory castables due to changes in cold and heat and cycles of dryness and humidity.

1. Trapped material, that is, mix about 3/5 of the amount of refractory aggregate, powder, and cementing agent evenly, put it into the silo or trapped material site, and cover it with a plastic sheet to prevent the cementing agent from evaporating; at the same time, it must not come into contact with water. , the temperature should be greater than 15℃. Let it stand for some time to allow the cementing agent to fully react with the metal in the refractory aggregate and powder to release hydrogen.

2. Use a porcelain ball mill to grind or wash the powder with a strong acid (such as hydrochloric acid, etc.) and use magnetic separation and other methods to reduce the introduction or elimination of metal and other impurities.

3. Reduce the amount of cement, add inhibitors increase the molding pressure, etc.

It should be pointed out that although the storage environment has some influence on the room temperature performance of phosphoric acid and phosphate refractory castables, it has little effect on the high-temperature performance and does not affect its use. Therefore, after the phosphoric acid and phosphate refractory castables with coagulants are hardened, the requirements for the storage location are not very strict. Phosphoric acid and phosphate refractory castables without accelerators must be heat treated before they can be stored. It has no strength without heat treatment. The heat treatment temperature is low and it is easy to produce a “deliquescence” phenomenon. During the storage process or low-temperature use conditions of phosphoric acid and phosphate refractory castables, white crystals precipitate on the surface of the refractory castables. After chemical and X-ray analysis, the “white hair” is the crystallization of aluminum salt and calcium salt. Under high temperatures or long-term heating conditions, aluminum salts and calcium salts transform into insoluble salts, and the “white hair” disappears. This phenomenon generally has no impact on the performance of refractory castables. However, excessive precipitation will cause the internal structure of the castable to become loose, reduce its strength, and even collapse.