What is tap hole clay?

What is tap hole clay?

Tap hole clay is an amorphous functional refractory material used in the process of sealing the iron outlet during the operation of iron-making blast furnaces. It can be divided into two main types: hydrated tap hole clay and dry tap hole clay. The former is used in small and medium-sized blast furnaces with lower top pressure and less intensified smelting, while the latter is employed in large and medium-sized blast furnaces with higher top pressure and more intensified smelting processes.

Functions of tap hole clay:

 Sealing the Iron Outlet: tap hole clay must possess good filling and sintering properties.

Stabilizing Iron Discharge: It should be easy to open the iron outlet and resistant to erosion and erosion.

Protecting the Furnace Bottom: The mud should not crack when rapidly heated and should have a high bonding strength between old and new mud.

Good Opening Performance: The boring head of the opening machine should be able to drill easily.

Moderate Plasticity: It should be convenient for mud gun operation and the formation of the iron outlet mud package.

Good Volume Stability: At high temperatures, the volume change should be minimal, preventing shrinkage and iron water leakage.

Types of tap hole clay:

Introduction to Hydrated tap hole clay:

Hydrated tap hole clay typically consists of materials such as clay, coke powder, vanadium-titanium slag, and tar asphalt, mixed with water as a binder. This type of mud was widely used in the early days due to its low cost. However, it has a relatively low bulk density and poor resistance to the erosion of molten iron and slag. Its use in large and medium-sized blast furnaces can lead to insufficient iron outlet depth, loss of coke during tapping, and other issues affecting normal furnace operation. Despite these drawbacks, hydrated tap hole clay is still being improved for use in many small and medium-sized blast furnaces (<2000m³) due to its low cost, with a consumption rate of over 1.2 kg·t⁻¹.

Introduction to anhydrous tap hole clay:

Anhydrous tap hole clay is generally made from materials such as corundum, high-alumina bauxite, clay, sericite, asphalt, silicon carbide, and coke powder, using tar and resins as binders. Corundum and high-alumina bauxite have a higher bulk density, providing a supportive framework for the mud and enhancing its resistance to erosion by molten iron and slag. Coke powder has good reducibility, protecting other carbon components and maintaining a reducing atmosphere at the furnace outlet. Silicon carbide has a low coefficient of thermal expansion, good thermal conductivity, and excellent resistance to thermal shock, improving the refractoriness, volume stability, high-temperature strength, and erosion resistance of the mud. Clay and asphalt enhance the plasticity of the mud, while sericite increases the sintering strength and plasticity. Dry tap hole clay has advantages such as no moisture inside the tapping channel, high strength, stable iron outlet depth, and minimal changes during the tapping process, avoiding large flows of iron.

The iron outlet is one of the most critical parts of a blast furnace, serving as the channel for the discharge of molten iron and slag. The number of iron outlets is usually set between 1 and 4. The smoothness of the outlet and the amount of iron passing through are important factors affecting the operation of the blast furnace. tap hole clay is a plastic refractory material used to seal the iron outlet and accounts for the largest proportion of the daily consumption of refractory materials in the steelmaking process, reaching 80% of the total cost. Therefore, research on tap hole clay is crucial and directly affects the lifespan of the blast furnace and the cost of iron and steel production.

Future Developments of tap hole clay:

tap hole clay is an essential consumable refractory material in the steel metallurgy industry, and its performance, environmental friendliness, and cost directly impact the development of the steel industry. Faced with the trends of greening, large-scale operations, and automation in modern steel enterprises, research on tap hole clay should also start from a new perspective and set new requirements to provide high-quality tap hole clay for the rapid development of the steel industry. Based on recent research progress on tap hole clay both domestically and internationally, the future development direction can be considered from the following aspects:

Modify the chemical composition or different proportions of the raw materials for tap hole clay, along with appropriate particle size and the lowest possible water content, while adjusting and developing in conjunction with the production environment and actual conditions to prepare superior tap hole clay products.

In response to the increasingly stringent national environmental control, develop environmentally friendly binders.

Introduce different functional fine powders and study the impact of different fine powder ratios on the properties of tap hole clay.

Improve and research the mud gunning system, mud gunning equipment, and mud gunning environment.