Emergency shutdown operation of recovery boilers

Claim 1

IN TH OPERATION OF A RECOVERY BOILER OF THE TYPE EMPLOYED IN THE SULPHATE PULP PROCESS, NORMAL OPERATION OF SAID BOILER COMPRISING FORMING A BURNING CHAR BED IN A VERTICALLY EXTENDING CLOSURE HAVING AIR ADMISSION PORTS, INCLUDING A DRAFT FLOWING UPWARDLY IN SAID ENCLOSURE TO DRAW GASES OUT OF AN UPPER PART THEREOF AND FEEDING BLACK LIQUOR ONTO SAID CHAR BED TO MAINTAIN THE SAME AT AN ELEVATED TEMPERATURE; A METHOD OF EFFECTING EMERGENCY SHUT-DOWN INCLUDING PERFORMING SUBSTANTIALLY SIMULTANEOULSY THE STEPS OF: (A) ELEVATING THE TEMPERATURE OF SUBSTANTIALLY THE WHOLE OF THE SURFACE OF SAID CHAR BED TO A TEMPERATURE SUBSTANTIALLY ABOVE SAID ELEVATED TEMPERATURE, (B) HALTING FEEDING OF THE BLACK LIQUOR TO ALLOW THE CHAR BED TO BE CONSUMED WITHOUT REPLACEMENT, (C) MAINTAINING AN OXYGEN-ENRICHED ATMOSPHERE IN THE VICINITY OF SAID CHAR BED TO ENCOURAGE THE FULL COMBUSTION THEREOF AND TO DISCOURAGE LIBERATION OF COMBUSTIBLE GASES, AND (D) MAINTAINING SAID UPWARDLY FLOWING DRAFT.