Characteristics of black liquor sprays from gas-assisted atomizers in high-temperature environments

Black liquor droplets in an entrained-flow gasifier that are too large or too small can cause problems in the chemical recovery process. It is therefore important in gasifier design to understand the nature of the atomized gas spray. We used high-speed imaging to study black liquor sprays in cold and hot environments. Significant conclusions are that: 1. the droplet size distribution width is linked to the mean droplet size as for other sprays in the literature, necessitating a gasifier design that is tolerant of the distribution width associated with the target droplet size; 2. the shape of black liquor droplets is highly non-spherical, necessitating consideration of shape in addition to mass; 3. black liquor has exceptional ability to attach to the nozzle and thereby to form larger-than-desired fragments of liquor; and 4. the furnace environment has a measurable impact on droplet formation, making cold-spray-chamber test results difficult to apply to practical in-furnace spray performance. It had previously been assumed that the furnace environment does not affect the spray.