| 摘要 |
1,189,902. Pelletizing gypsum. CENTRAL GLASS CO. Ltd. 28 June, 1967 [15 Nov., 1966], No. 29880/67. Heading C1A. Gypsum pellets are made by breaking (e.g. grinding, crushing or pulverizing) crystals of wet process calcium sulphate hemihydrate in order to expose fresh active faces thereon, and thereafter pelletizing the broken crystals while adding water to them. The water content of the hemihydrate during pelletization may be maintained at 19-30% by weight, calculated on the weight of dry hemihydrate, by adjusting the initial water content or by subsequent addition of water to the pelletizing apparatus. Broken pellets of gypsum, i.e. dihydrate or partially hydrated hemihydrate may be added during pelletization to provide seed crystals. These pellets may be recycled from the pelletization apparatus. Various substances may be added to the hemihydrate during hydration and pelletization, e.g. acids, alkalis such as milk of lime, potassium chloride, Glauber's salt, sodium carbonate, sodium phosphate, glue or lignin sodium sulphonate. Rotary cylindrical, conical or dish pelletizers may be used. |
