DROP SIZE MODIFICATION IN BLACK LIQUOR SPRAYS FROM COMMERCIAL NOZZLES USING PULSED FLOW

Improved operation of kraft recovery boilers is expected to result from knowing how to obtain a controlled, well-defined droplet size distribution issuing from the black liquor spray nozzle. Black liquor drop size data were obtained from an environmentally acceptable spray facility capable of delivering liquor at normal firing temperatures using commercial nozzles. Image analysis techniques were developed from high-speed video images which gave good two-dimensional representations of black liquor sprays. Previous work showed that black liquor sprays have a characteristic size distribution which is determined by the fluid mechanical forces breaking up the liquid sheet issuing from the nozzle. This work has centered on applying flow pulsation as an independently controlled force on the sheet breakup process in an attempt to change the drop size distribution. Experiments are described which feature controlled frequency flow pulsations. Results are presented which show the dependence of median drop size on pulsation frequencies up to 450 Hz.