A kier or keeve is a large circular boiler

Boiler

A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...

 or vat

Vat

Vat or VAT may refer to:* A type of container such as a barrel, storage tank, or tub, often constructed of welded sheet stainless steel, and used for holding, storing, and processing liquids such as milk, wine, and beer...

 used in bleaching or scouring cotton

Cotton

Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

 fabric. They were also used for processing paper pulp.

In use they were continuously rotated by an engine, steam being supplied through a rotating joint in the axle. They were usually spherical, sometimes cylindrical, and some were recycled from old boiler shells.