Treatment of residues of oil shale retorting for magnesium recovery

Claim 1

THE METHOD OF TREATING THE ASH RESIDUE OF OIL SHALE RETORTING WHICH COMPRISES FORMING A FINELY DIVIDED RESIDUE OF OIL SHALE RETORTING INTO AN AQUEOUS SLURRY CONTAINING MAGNESIUM HYDRATE AT A PH OF ABOUT 10, SAID SLURRY CONTAINING MOST OF THE MAGNESIUM AND CALCIUM CONTENT OF SAID RESIDUE AND A SUBSTANTIAL AMOUNT OF CLAYS AND OTHER INSOLUBLES IN FINER SIZES WITH COARSER SIZES OF QUARTZ, FELDPARS, UNREACTED CARBONATES AND CLAYS REMOVED, PASSING SAID SLURRY THROUGH A FIRST CARBONATION STAGE TO ESTABLISH A PH OF ABOUT 8, SEPARATING AT LEAST A PORTION OF EFFLUENT FROM THE SOLIDS OF THE DISCHARGE OF FIRST CARBONATION AND RECYCLING THE SEPARATED EFFLUENT TO THE SLURRY FORMATION STAGE, STABILIZING THE SEPARATED SOLIDS FROM FIRST CARBONATION CONTAINING THE MAGNESIUM HYDRATE AND FINE CLAYS WITH OVERFLOW SOLUTION FROM A THICKENING STAGE, SUBJECTING THE PULP SO FORMED TO A SECOND CARBONATION TREATMENT FOR PARTIAL REMOVAL OF SOLUBLE CALCIUM, NEUTRALIZING THE PULP FROM SECOND CARBONATION BY ACID ADDITION, INTRODUCING THE NEUTRALIZED PULP INTO THE THICKENER STAGE, DISCHARGING THE UNDERFLOW OF THICKENING CONTAINING CALCIUM CARBONATE AND FINE CLAY FROM THE TREATMENT, RETURNING A PORTION OF THE ACIDIFIED OVERFLOW OF THE THICKENING STAGE TO SAID STABILIZING STAGE, SEPARATING THE THICKENER UNDERFLOW AT A FILTRATION STAGE, RECYCLING THE SEPARATED FILTRATE TO THE THICKENING STAGE, EVAPORATING ANOTHER PORTION OF THE THICKENER OVERFLOW CONTAINING SUBSTANTIALLY NO SUSPENDED SOLIDS THEREBY INCREASING CONCENTRATION OF THE MAGNESIUM CHLORIDE CONTENT, INTRODUCING SULFURIC ACID INTO THE SOLUTION AT A SLOW RATE SO AS TO FORM THE CALCIUM CONTENT INTO SULFATE, FILTERING THE MATERIAL AFTER ACID ADDITION, DISCHARGING THE CAKE TO WASTE, AND SUBJECTING THE SEPARATED FILTRATE TO A TREATMENT TO CONVERT THE MAGNESIUM CHLORIDE CONTENT TO A HIGH GRADE MAGNESIUM PRODUCT AND TO EVOLVE CHLORINE IN VAPOR FORM AS A PRODUCT OF THE TREATMENT.

Claim 2

THE METHOD OF TREATING THE ASH RESIDUE OF OIL SHALE RETORTING WHICH COMPRISES FORMING A FINELY DIVIDED RESIDUE OF OIL SHALE RETORTING INTO AN AQUEOUS SLURRY CONTAINING MAGNESIUM HYDRATE AT A PH OF ABOUT 10, SAID SLURRY CONTAINING MOST OF THE MAGNESIUM AND CALCIUM CONTENT OF SAID RESIDUE AND A SUBSTANTIAL AMOUNT OF CLAYS AND OTHER INSOLUBLES IN FINER SIZES WITH COARSER SIZES OF QUARTZ, FELDPARS, UNREACTED CARBONATES AND CLAYS REMOVED, PASSING SAID SLURRY THROUGH A FIRST CARBONATION STAGE TO ESTABLISH A PH OF ABOUT 8, SEPARATING AT LEAST A PORTION OF EFFLUENT FROM THE SOLIDS OF THE DISCHARGE OF FIRST CARBONATION AND RECYCLING THE SEPARATED EFFLUENT TO THE SLURRY FORMATION STAGE, STABILIZING THE SEPARATED SOLIDS FROM FIRST CARBONATION CONTAINING THE MAGNESIUM HYDRATE AND FINE CLAYS WITH OVERFLOW SOLUTION FROM A THICKENING STAGE, SUBJECTING THE PULP SO FORMED TO A SECOND CARBONATION TREATMENT FOR PARTIAL REMOVAL OF SOLUBLE CALCIUM, NEUTRALIZING THE PULP FROM SECOND CARBONATION BY ACID ADDITION, INTRODUCING THE NEUTRALIZED PULP INTO THE THICKENER STAGE, DISCHARGING THE UNDERFLOW OF THICKENING CONTAINING CALCIUM CARBONATE AND FINE CLAY FROM THE TREATMENT, RETURNING A PORTION OF THE ACIDIFIED OVERFLOW OF THE THICKENING STAGE TO SAID STABILIZING STAGE, SEPARATING THE THICKENER UNDERFLOW AT A FILTRATION STAGE, RECYCLING THE SEPARATED FILTRATE TO THE THICKENING STAGE, EVAPORATING ANOTHER PORTION OF THE THICKENER OVERFLOW CONTAINING SUBSTANTIALLY NO SUSPENDED SOLIDS THEREBY INCREASING CONCENTRATION OF THE MAGNESIUM CHLORIDE CONTENT, INTRODUCING SULFURIC ACID INTO THE SOLUTION AT A SLOW RATE SO AS TO FORM THE CALCIUM CONTENT INTO SULFATE, FILTERING THE MATERIAL AFTER ACID ADDITION, DISCHARGING THE CAKE TO WASTE, AND SUBJECTING THE SEPARATED FILTRATE TO A TREATMENT TO CONVERT THE MAGNESIUM CHLORIDE CONTENT TO A HIGH GRADE MAGNESIUM PRODUCT AND TO EVOLVE CHLORINE IN VAPOR FORM AS A PRODUCT OF THE TREATMENT.