Black liquor spray properties in-furnace conditions for swirl cone nozzles TAPPI Journal July 2026

 


Application: Spray characteristics of swirl cone nozzles were experimentally quantified under in-furnace conditions. Measured spray velocity, opening angle, and droplet size distributions provide a basis for selecting nozzle designs and optimizing operating practices to improve char-bed control and mitigate furnace fouling and emissions. In addition, these data support rigorous computational fluid dynamics (CFD) modeling.

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Author: Ari Kankkunen, Ari Ainsalo, Andy Jones, James Biggs, Jukka Röppänen, and Mika Järvinen
Black liquor spray properties in-furnace conditions for swir
ABSTRACT: Recovery boiler furnace operation is controlled for high chemical recovery, high steam production, and low emissions. Good control allows long runs with minimum cleaning without expensive shutdowns. An essential variable affecting boiler operation is black liquor spraying into the furnace. Poorly controlled black liquor spraying causes difficulties, e.g., in chemical recovery, fouling of heat transfer surfaces, and decreased energy production. A challenging measurement strategy with three different swirl cone nozzles . types A, C, and T . was carried out at a mill in the United States. Black liquor spray properties were measured under in-furnace conditions for flow rates of 2.0 L/s to 3.0 L/s. Three spraying temperatures of 119™‹C, 122™‹C, and 126™‹C, which were 2™‹C, 5™‹C, and 9™‹C above the boiling point (ƒ¢Te), were tested. These flow rates and temperatures are typical for industrial nozzle sizes with exit orifice sizes of 17 mm and 22 mm. An imaging method to measure droplet size in a highly challenging furnace environment was developed. Droplet volume median diameter (Dv50) for nozzles A, C, and T varied between 7 mm to 4 mm, 7 mm to 5 mm, and 8 mm to 6 mm, depending on the flow rate and temperature. The high number of droplets detected by the analysis program enabled data fitting into statistical correlations. The size and width parameters for the Rosin™]Rammer droplet size distribution function could be defined. The droplet size distribution was found to be surprisingly wide, probably because of swollen droplets. Spray velocity was measured in two locations, 5 cm from the nozzle and 1.8 m from the nozzle. Near the nozzle, the average velocity increased from 7.3 m/s to 13 m/s when the flow rate was increased from 2 L/s to 3 L/s. Increase of black liquor temperature increased spray velocity in most of the cases. At the distance of 1.8 m from the nozzle, average spray velocities varied between 4.0 m/s to 11 m/s, depending on nozzle geometry, flow rate, and temperature. The opening angles of the spray for nozzles A and C varied between 57™‹ to 78™‹. The opening angle of nozzle T with flow guide varied between 48™‹ to 56™‹. The highest penetration of the spray was estimated for nozzle T because of the narrow spray and large droplets.
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