AN ADVANCED SENSOR FOR MONITORING SLAGGING AND FOULING IN BLACK LIQUOR BOILERS

BLACK LIQUOR RECOVERY BOILERS EMPLOY BLACK LIQUOR AS A PRIMARY FUEL THAT CONTAINS LARGE AMOUNTS OF SODIUM CARBONATE, SODIUM SULFIDE, AND SMALL AMOUNTS OF SODIUM SULFATE. THE FUEL, AS INTRODUCED IN THE BOILER, CONTAINS APPROXIMATELY ONE-THIRD WATER, ONE-THIRD CHEMICALS, AND ONLYONE-THIRD COMBUSTIBLE MATERIALS. THE BLACK LIQUOR RECOVERY BOILER IS AN ESSENTIAL STEP OF THE KRAFT PULPING PROCESS FOR PRODUCTION OF PAPER. DOWN TIME, COSTLY REPAIRS, AND EVEN FATAL EXPLOSIONS HAVE BEEN ENCOUNTERED IN THE OPERATIONOF THESE LARGE RECOVERY BOILERS. BECAUSE OF THE BLACK LIQUOR CHARACTERISTICS, WITH LARGE AMOUNTS OF SODIUM BASED CHEMICALS, SLAGGING AND FOULING OF THE BOILER, AND IN SOME INSTANCES CORROSION DAMAGE, FREQUENTLY OCCUR UNLESS CAREFUL OPERATION IS MAINTAINED AT ALL TIMES. AN INNOVATIVE SLAGGING AND FOULING MONITORING SYSTEM FOR BLACK LIQUOR RECOVERY BOILERS IS BEING DEVELOPED TO PROVIDE TIMELY RATES AND LOCATIONS OF CORROSIVE DEPOSIT BUILDUP. THE SYSTEM WILL PROVIDE AN OPPORTUNITY FOR ON-LINE MONITORING OF SLAGGING CONDITIONS WITHIN A RECOVERY BOILER. THE INCIPIENTMONITORING TECHNIQUE WOULD PROVIDE A MEANS BOTH OF AVOIDING PROGRESSIVE SLAGGING AND OF ENABLING EFFECTIVE AND EARLY APPLICATION OF CLEANING TECHNIQUES, THEREBY REDUCING THE RISK OF A POSSIBLE CATASTROPHIC BOILER FAILURE ON EXPLOSION.