Attack by alkali vapors and condensates, mainly potassium and sodium from fuels, raw materials and recycled dust, that penetrate alumina-silica refractories and form new minerals such as kalsilite and leucite with a large volume increase. The result is alkali bursting: cracking, swelling and spalling deep behind the hot face. It is common in cement preheaters and kiln inlets, blast furnace stacks, incinerators and glass regenerators, and is fought with dense, alkali-resistant castables and silicon carbide.
Riser duct castable is crumbling from alkali attack, the bypass has been closed too long.
Also heard as
- alkali bursting
- alkali spalling
Related terms
Spalling
Cracking off of pieces or layers from the hot face of a refractory lining.
Coating
Layer of clinker that sticks to the burning zone brick in a cement kiln and shields it from heat and wear.
Silicon carbide
Hard, highly conductive refractory used where abrasion, thermal shock and heat transfer all matter.
Checker
Brick laid in an open lattice inside a regenerator or hot blast stove to store and return heat.