Thermal treatment of powder

Claim 2

The method of claim 2 in which the particles of powder undergo an exothermic reaction while moving upwardly through a portion of the gravitating bed.

Claim 3

The method of claim 2 in which the particles of powder undergo both an endothermic reaction and an exothermic reaction while moving upwardly through various portions of the gravitating bed.

Claim 4

The method of claim 1 in which the particles of powder suspended in the entrance gas stream are hydrated aluminum disilicate particles, and particles of deexothermed kaolin powder are withdrawn, and in which the heat resulting from the kaolin exotherm is transferred to the gravitating balls, whereby the heat evolved by the exotherm provides a portion of the heat for the endothermic formation of meta kaolin from hydrated aluminum disilicate, and whereby the zone in which the exotherm occurs is maintained at such a precisely regulated narrow range of temperature that significant sintering of the deexothermed kaolin particles together to form aggregates is substantially prevented.

Claim 5

In a method of subjecting powder to a controlled increase of temperature, the improvement which includes the steps of: providing at least one confined bed of relatively large, substantially uniformly sized balls of heat transfer material which are subjected to a slight amount of slow movement, the diameter of said slightly moving balls being a uniform size within the range from about 1 to about 5 centimeters, the minimum cross section of said bed being at least several decimeters, whereby there are a plurality of zones of slightly moving balls in a reactor zone, there being a plurality of interstices among said uniformly sized balls in each zone; providing a system for relative movement between a hereinafter defined stream of gas containing suspended powder and said plurality of zones of saId slightly moving balls; heating said slightly moving balls in a ball heating zone to a heating zone temperature; establishing a reliable temperature gradient throughout a reactor zone consisting of a plurality of successive temperature zones, the temperature of said slightly moving balls being accurately regulated so that each temperature zone has a preselected range of temperature, a temperature zone at the gas entry to the reactor zone being at a preselected lower temperature and a temperature zone at the gas exit of the reactor zone being approximately at said heating zone temperature; directing an entry stream of gas into the reactor at said zone maintained at said preselected lower temperature; controlling the flow rate of said entry gas stream and the flow rate of the exit gas stream to suspend therein a preselected rate of powder flow, the amount of powder suspended in the entry gas stream being an amount adapted to provide said preselected flow rate of powder in said exit gas stream, and directing a gas stream containing said amount of suspended powder successively through a predetermined path of zones of said slightly moving balls, whereby the powder in the exit gas stream from the last-contacted zone has a temperature which is not remote from said heating zone temperature, any gas consumed or generated in said reactor zone being treated as a part of the gas stream; transferring heat between said slightly moving balls and the suspended powder, whereby the temperature of each particle of powder is controlled in a reliable manner, any exothermic reaction or endothermic reaction occurring within said reactor zone being instantly controlled by heat transfer involving said powder particle and said slightly moving balls; withdrawing an exit gas stream containing said suspended powder from a zone of the balls maintained at near said preselected elevated temperature; and separating heat-treated powder and heat-treated gas from said withdrawn exit gas stream.

Claim 6

The method of claim 6 in which balls, cooled by contact with said stream of gas containing suspended powder, are recirculated from the bottom of a gravitating bed to the top of a gravitating bed and in which various zones of the gravitating bed are maintained at different temperatures, including the preselected temperature of the heating zone, and in which the exit gas stream containing the suspended powder is withdrawn below said heating zone, and in which the gas stream containing suspended powder is injected into the gravitating bed at a zone near that at which the balls are withdrawn for recirculation.