Process for production of alumina from bauxite and other aluminous materials, by pyrogenic attack, in agglomeration plants, either under suction or pressure

Claim 1

A PROCESS OF EXTRACTING THE ALUNINUM CONTENT OF SILICEOUS BAUXITE SUBSTANTIALLY WITHOUT RECYCLE OF SINTERED MATERIAL FROM THE PROCESS, COMPRISING AGGLOMERATING INTO GRANULES A MIXTURE OF BAUXITE, SODIUM CARBONATE, AND A COMPOUND OF THE GROUP CONSISTING OF LIME AND CALCIUM HYDROXIDE, WITH TOTAL WATER PRESENT IN THE AGGLOMERATION, INCLUDING THAT COMBINED IN THE CALCIUM HYDROXIDE, SUBSTANTIALLY IN AN AMOUNT NECESSARY FOR BUT NOT SUBSTANTIALLY GREATER THAN THAT REQUIRED FOR THE HYDRATION OF THE SODIUM CARBONATE TO THE ONOHYDRAGE FORM, FROMATION OF TH EHIGHER HYDRATES BEING AVOIDED, THE AGGLOMERATING BEING AT A TEMPERATURE OF ABOUT 40 TO 65* C., THE GRANULES BEING ABOUT 1 TO 3 MM. IN THEIR LARGEST DIMENSION, THE CALCIUM OXIDE CONTENT TO THE GRANULES BEING THE REQUIRED TO BIND AT LEAST THE MAJOR PART, BY WEIGHT, OF THE SILICA CONTENT OF THE BAUXITE AS CALCIUM SILICO-ALUMINATE TO REDUCE LOSS OF THE SODIUM CARBONATE AS INSOLUBLE SODIUM SILICO-ALIMINATE AND BEING NOT SUBSTANTIALLY MORE THAN THAT STOICHIOMETRICALLY REQUIRED TO BIND ALL OF THE SAID SILICA CONTENT, BEING IN A MOLAR RATIO OF CAO TO SIO2 OF FROM ABOUT 1.6 TO ONE TO ABOUT TWO TO ONE, ADDING GRANULAR CARBONACEOUS FUEL AND SINTERING, THE SINTERING BEING CARRIED OUT BY HEAT DERIVED BY COMBUSION OF SAID FUEL, AND THEN LEACHING WITH WATER.