Black liquor is a spent liquor of the pulp and paper industry. It is burned in kraft recovery boilers for chemical and energy recovery. The high dry solids content and viscosity of black liquor require a high spraying temperature this high spraying temperature changes the performance of the boiler. Kraft recovery boiler deposit formation, emissions and chemical recovery are strongly affected by the drop size, size distribution and velocity of the black liquor spray formed by a splashplate nozzle.
Black liquor droplet formation of a splashplate nozzle is the subject of this study. The sheet breakup mechanism was studied with a system based on a video and image-analysis. The drop size of mill-scale nozzles was also measured with an image-analysis-system. Measurements were carried out in a test chamber.
The sheet breakup mechanism and drop size tests were carried out both below and over the boiling point of black liquor. Special attention was paid to the effect of flashing on drop formation. Temperature increase normally decreases drop size. In the case when the wavy-sheet disintegration changes to perforated-sheet disintegration, the drop size increases. Spray velocity rises when the temperature is increased above the boiling point.