Firing Very High Solids Black Liquor in Recovery Boilers, 2000 Engineering Conference Proceedings

Esa Vakkilainen, Ralf Holm--Going to very high black liquor dry solids interests recovery operators because of inherent benefits in reduced emissions, decreased fouling and increased steam generation. A co-operative research effort was started to study spraying, combustion and physical properties of kraft black liquors up to ‘air-dry’ solids.

Single droplet combustion tests with several black liquors were made at tube furnace. Increased dry solids cased only minor variations in combustion properties, except drying time which decreased significantly. 90 % black liquor was successfully fired at a mill. It was noticed, perhaps unexpectedly, that the liquor sheet formed from firing 90% black liquor looked quite similar to the corresponding sheet at firing 75% black liquor.

In light of the present experience from operation with 80 to 85% dry solids black liquor, no big difficulties are expected in the spraying and burning of black liquor with 90 % dry solids.