VISUALIZATIONS OF GAS-ASSISTED ATOMIZATION OF BLACK LIQUOR AND SYRUP/WATER MIXTURES AT ELEVATED AMBIENT PRESSURES

Pressurized entrained flow high-temperature black liquor gasification (PEHT-BLG) is a novel technique to recover the inorganic chemicals and available energy in black liquor originating from kraft pulping. One of the key parts in the PEHT-BLG process is the spray atomizer where the viscous black liquor is disintegrated into a spray of fine droplets into the hot gasifier In this study a high-speed photography system was used in order to visualize the spray formation of black liquor and syruplwater mixtures at elevated ambient pressures based on a conventional coaxially convergent gas-assisted atomizer The main conclusion is that the breakup and atomization of black liquor by a gas-assisted atomizer is similar to that of a syruplwater mixture with similar physical properties. The observed difference in sphericity between black liquor and syruplwater may be explained by rapid cooling of the black liquor by the cool nitrogen gas at the nozzle exit, resulting in a sudden decrease in viscosity and possible skinning of the black liquor Furthermore, it was found that an increased ambient pressure appeared to contract the spray to a more dense cloud of droplets compared to the corresponding atmospheric case.