General Requirements for Refractory Spraying Application

General Requirements for Refractory Spraying Application

Refractory spraying, also known as refractory patching material, is a type of monolithic refractory material used for lining furnaces, pipes, blast furnaces, and hot blast stoves.

Refractory spraying materials are composed of a specific particle size distribution (adhesion rate and bulk density must be properly controlled). The maximum particle size cannot exceed 5mm, as the nozzle diameter of the spray gun is 5mm; particles larger than 5mm will cause clogging of the spray gun nozzle.

The application of refractory spraying is done by spraying. The refractory spraying material achieves sufficient velocity within the spray gun pipe using compressed air or mechanical pressure. There are three spraying methods: wet method, semi-dry method, and flame method.

Applications of refractory spraying include blast furnaces, hot blast stoves and tapholes, converters and electric furnaces, ladles and secondary refining furnaces, heating furnaces, soaking pits, tubular heating furnaces, flues, and chimneys.

Refractory spray coatings must not experience blockages in the spraying machine's delivery hose; they must also possess strong adhesion, low rebound rate, and a uniform composition, preventing particle segregation and stratification. Furthermore, the coating should set and harden quickly with minimal drying shrinkage. For heavy-duty refractory spray coatings, the water content should be 10-16% when dry spraying.

During application, excessive water should be avoided, as it can cause the coating to run. Insufficient water will result in uneven wetting, low adhesion, and excessive rebound rate. The nozzle should be appropriately positioned 0.8-1mm from the surface, and air pressure should be used in conjunction with the spray. The general spray thickness is 50mm; for thicknesses greater than 50mm, multiple layers should be applied to prevent excessive thickness from causing peeling or collapse.