GB923813A - Improvements in or relating to the calcining of limestone and like materials - Google Patents

Abstract

Limestone and material containing a major proportion of calcium carbonate, e.g. magnesianlimestone or chalk is calcined in a shaft kiln by introducing water into a hot combustible gas, produced by gasification of a mineral fuel oil or producer-gas from coal, so as to produce a mixture of combustible gas and superheated steam which is introduced into the calcining zone of the kiln for combustion with air also fed into that zone. The weight of water may be equal to that of hot combustible gas. Fig. 1 is a vertical section of a kiln, which may be circular in cross-section, and Fig. 2 is a horizontal section of Fig. 1. Water jets 7, which may be pressure nozzles and may be capable of individual manual withdrawal, discharge into duct 5, which may be external to the kiln, connected to oil gasifier 6 which may produce a gas from heavy fuel oil at e.g. 1250-1500 DEG C. The superheated steam/gas mixture formed, e.g. containing 21/H2O and at 680 DEG C., is fed to ports 4 and via 8 to ports 3. <PICT:0923813/III/1> <PICT:0923813/III/2> Combustion at, e.g. 1940 DEG C, occurs in air preheated chamber 2 into which the calcining zone 1 discharges. 9 and 10 are thermocouples. Fig. 3 (not shown) illustrates a kiln with a nozzle oil gasifier.