Building material production from fine synthetic gypsum powder

摘要

In the production of a building material mixture by mixing a fine synthetic calcium sulphate source powder, e.g. waste gypsum from flue gas desulphurisation, wet scrubbing or phosphoric acid manufacture, with an at least latent hydraulic binder, preferably flyash, the powder is also mixed with calcined gypsum, preferably hemihydrate, and is fired in its fine powder form in a rotary tube furnace. Also claimed is an apparatus for carrying out the above process, comprising a horizontal cylindrical firing furnace (1) with a central longitudinal burner (2) surrounded by different speed rotary tubes (3), each of which has a helical strip fixed to its inside.