THE DEVELOPMENT OF AN ON-LINE BLACK-LIQUOR VISCOSITY METER METER AND CONTROLLER FOR KRAFT RECOVERY BOILERS.

BLACK LIQUOR IS A WASTE LIQUID FROM KRAFT WOOD PULPING. IT CONTAINS USED INORGANIC CHEMICALS AND ORGANIC WOOD RESIDUE. BLACK LIQUOR IS BURNED IN RECOVERY BOILERS TO RECOVER THE PULPING CHEMICALS FOR REUSE AND TO GENERATE STEAM FOR POWER GENERATION AND MILL CONSUMPTION. BECAUSE OF THIS DUAL FUNCTION THE OPERATION OF A RECOVERY BOILER IS PARTICULARLY DEMANDING. SUCCESSFUL COMBUSTION OF BLACK LIQUOR DEPENDS EXTENSIVELY ON THE CHARACTERISTICS OF THE DROPLETS FORMED ATTHE BOILER FIRING NOZZLE. DROPLET FORMATION AND SIZE, IN TURN, DEPEND ON THE VISCOSITY OF THE LIQUOR. EXISTING SENSORS AND INSTRUMENTATION DO NOT ALLOW ON-LINE MEASUREMENTOF LIQUOR VISCOSITY. THIS IS MOSTLY BECAUSE, AT HIGH CONCENTRATIONS, THIS LIQUID IS VERY VISCOUS, POTENTIALLY NON-NEWTONIAN, AND HIGHLY SCALE-FORMING. A CONSIDERABLE AMOUNT OF RESEARCH ON THE PROPERTIES AND BEHAVIOR OF KRAFT BLACK LIQUOR HAS BEEN SPONSORED BY DOE. THESE STUDIES HAVE REVEALED THE DEPENDENCE OF THE DRYING AND BURNING CHARACTERISTICS ON THE SIZE OF THE DROPLET, AND HENCE ON THEVISCOSITY OF THE LIQUOR. THE RESEARCH HAS ALSO PRODUCED IMPORTANT NEW KNOWLEDGE ON THE BASIC PHYSICAL PROPERTIES OF BLACK LIQUOR. THE DEVELOPMENT PLANNED HEREIN WILL BE BASED ON THIS WORK. A RELIABLE MEANS OF MEASURING BLACK LIQUOR VISCOSITY AT HIGH CONCENTRATION WILL PROVIDE A MAJOR MISSING ELEMENT FOR ACHIEVING DIRECT, ON-LINE CONTROL OF THE COMBUSTION PROCESS IN RECOVERY BOILERS. IT WILL FACILITATE THE USE OF HIGHER-THAN-PRESENT LIQUOR DRY SOLIDS CONTENTS IN THE FIRING OF RECOVERY BOILERS. BECAUSE OF THE HIGHER EFFICIENCY, A SAVING OF OTHER, PRIMARILY FOSSIL, FUELS WILL BE REALIZED. AN ADDITIONAL BENEFIT WILL BE IMPROVEMENTS IN THE OPERATING SAFETY OF THE BOILERS.