Continuous calcination of gypsum

Claim 1

APPARATUS FOR CONTINUOUSLY CALCINING GYPSUM AND THE LIKE, COMPRISING A REACTOR KETTLE, MEANS FOR FEEDING PULVERIZED GYPSUM INTO THE KETTLE, A SOURCE OF HEAT FOR CALCINING THE GYPSUM WITHIN THE KETTLE, A FLUE SYSTEM INCLUDING A WALL SURROUNDING THE KETTLE AND SPACED THEREFROM TO FORM AN ANNULAR HEATING CHAMBER FOR THE CIRCULATION OF HEATING GASES AROUND THE OUTSIDE OF THE KETTLE WALLS, THE GASES IN THE CHAMBER BEING AT A TEMPERATURE SUBSTANTIALLY HIGHER THAN THAT OF THE GYPSUM IN THE KETTLE, CONTROL MEANS FOR MAINTAINING THE GYPSUM WITHIN THE KETTLE AT CALCINING TEMPERATURE, A STANDPIPE HAVING AN INLET COMMUNICATING WITH THE KETTLE NEAR THE BOTTOM THEREOF AND HAVING A DISCHARGE PASSAGE EXTENDING VERTICALLY UPWARDLY PARALLEL TO THE KETTLE SIDE WALLS TO A DISCHARGE POINT NEAR THE TOP OF THE KETTLE, AN OUTWARDLY EXTENDING SPOUT CONNECTED TO SAID STANDPIPE AND COMMUNICATING WITH SAID DISCHARGE PASSAGE AT SAID DISCHARGE POINT, MEANS FOR HEATING THE DISCHARGE PASSAGE INCLUDING A FIRST STANDPIPE WALL IN HEAT EXCHANGE CONTACT WITH THE HEATING GASES IN THE HEATING CHAMBER THROUGHOUT AT LEAST THE MAJOR PORTION OF THE HEIGHT OF THE DISCHARGE PASSAGE AND A SECOND STANDPIPE WALL OUT OF HEAT EXCHANGE CONTACT WITH SAID HEATING GASES TO PROVIDE A TEMPERATURE WELL BELOW THAT OF THE HEATING GASES, SAID SECOND STANDPIPE WALL BEING IN HEAT EXCHANGE CONTACT WITH THE GYPSUM IN THE DISCHARGE PASSAGE THROUGHOUT THE HEIGHT OF THE DISCHARGE PASSAGE.