Method of recovering values from the pyrolysis of spent sodium sulfite liquor

Claim 1

A METHOD FOR RECOVERING SODA AND SULPHUR DIOXIDE FROM A SPENT SODIUM SULPHITE COOKING LIQUOR, COMPRISING PYROLYZING THE LIQUOR SO AS TO PRODUCE A HOT GAS CONTAINING HYDROGEN SULPHIDE AND FINE SODA PARTICLES, COOLING SAID GAS TO A TEMPERATURE BELOW 300*C., SUBJECTING THE GAS AT SAID TEMPERATURE TO A DRY CYCLONE SEPARATING PROCESS SO AS TO SEPARATE THE MAJOR PORTION OF THE SODA PARTICLES FROM THE GAS, SUBJECTING THE GAS TO A WET PURIFICATION PROCESS WITH AN AQUEOUS SOLUTION CONTAINING AT LEAST 100 GRAMS SODIUM BICARBONATE PER LITER AT A TEMPERATURE AT WHICH THERE IS NO SUBSTANTIAL CONDENSATION OF WATER VAPOR, BRINGING THE GAS IN CONTACT WITH A COLD SURFACE SO AS TO REMOVE THE MAJOR PORTION OF THE WATER VAPOUR BY CONDENSATION, AND COMBUSTING SAID COLD DRY GAS SO AS TO TRANSFORM ITS CONTENT OF HYDROGEN SULPHIDE INTO SULPHUR DIOXIDE.