The hot air duct is a variety of tuyere devices that transport hot air from the hot air stove to the blast furnace.

The hot air pipe lining structure is usually composed of a refractory sprayed layer, refractory fiber, lightweight insulating refractory bricks and tough mullite bricks in working layer. The gas supply pipe is cast by castable. The mullite bricks in the pipeline generally adopt circular joints and have different masonry methods. The hot air in the hot air duct is distributed in the blast furnace, so the hot air duct plays an important role in the blast furnace.

The castable for hot air pipe is made of high-strength cement, mineral admixture, high-strength aggregate and anti-cracking agent through industrial production.

It has high wear resistance, high bonding strength with foundation concrete, strong impact resistance, high compressive strength , long service life and so on.