Process for the production of powdered, surface-active, agglomeratable calcined material

Claim 1

A process for producing calcined lime from sludges containing organic material, comprising the steps of: a. so introducing an oxygen-containing gas into the bottom of a rotationally symmetrical reaction zone as to produce an upward flow of the gas in the outer region of the zone and a downward flow of the gas in a central region of the zone surrounded by said outer region; b. raising the temperature in said reaction zone to a calcining temperature by preheating the oxygen-containing gas and by introducing fuel into the downward flow of oxygen-containing gas at the upper end of the central region of the reaction zone and thereafter effecting the combustion of the fuel in said reaction zone; c. preheating a lime-bearing, raw material to a temperature high enough to insure that said material is dry and pneumatically conveyable; d. so introducing the preheated raw material into the upper end of the central region of the reaction zone that said preheated raw material will migrate downwardly through the central region of the reaction zone in admixture with the downwardly flowing gases therein and be deflected outwardly at the bottom of the reaction zone into the upwardly flowing gases in the outer region of the zone to thereby convert calcium compounds in said raw material to calcium oxide; e. increasing the temperature of the raw material at a mean rate of not less than 400° C. per second in said reaction zone to thereby disrupt the crystalline structure of and disintegrate the raw material into microcrystalline primary particles which have free surface valences and are therefore capable of agglomerating into larger, secondary particles in periods measured in fractions of a second; f. limiting the time of residence of the material in the reaction zone and the time that said material is in contact with the hot gases flowing therethrough to a period of not more than one second to thereby maintain the tendencies toward agglomeration possessed by said primary particles; g. removing those particles which are too large to be fully calcined in the time required for formation of the primary particles from the bottom of the reaction zone; h. removing calcined particles and the gas in which they are entrained from said reaction zone at the upper end thereof, said particles being agglomerated into larger, secondary particles as they are removed from the combustion zone; i. separating the secondary particles from the gases with which they are mixed at a temperature at or above said calcining temperature; and j. immediately thereafter surrounding the secondary particles with a gas which is inert with respect to said particles to inhibit unwanted reactions between the calcined material and compounds present in the environment of said material.