GB976085A - Method for producing a lime hydrate - Google Patents

Abstract

Dry powdery hydrated lime is produced by contacting a fast acting quicklime with watervapour and a carbon dioxide to form a dry film thereon, controlling the time and temperature of contact so that per square metre of surface area of said quicklime, having a hydration time of less than one minute, not more than 5 x 10-4 mols. of water and not more than 2 x 10-4 mols. of carbon dioxide combine, whereby the slaking time is increased by at least 100%, and thereafter hydrating said treated particles of quicklime with water essentially in the liquid state to form a substantially dry powdery lime hydrate. A preferred mixture is provided by flue gas containing carbon dioxide and water vapour, the quicklime undergoing treatment being at 250-450 DEG F., the flue gas between 212 DEG to 1000 DEG F. The hydration is preferably carried out under pressure with a small excess of water over the theoretical amount required and the slaked lime is preferably dried by dispersion in an atmosphere wherein the excess water is converted into the vapour phase. The dry powdery lime hydrate may be clustered by pounding between surfaces. The examples illustrate both the use of steam, and a mixture of steam and carbon dioxide resulting from a flue gas.