Real Benefits of High Solids Firing, 1998 International Chemical Recovery Conference Proceedings

A considerable amount of information has been published and presented on the apparent benefits of high solids firing od black liquor. The purpose of this paper is to examine the claims made for high solids firing in the context of a major performance test and previously published test results. Recommendations on the factors that should be considered when selecting a design solids level for a retrofit of an existing liquor system on a new recovery boiler are then provided.

The performance test used as a basis for this paper was conducted on the SAPPI-Warren kraft recovery boiler located in Westbrook, Maine in early 1997. The conditions under which the data were collected, are unique to the author’s knowledge. Three widely varying percent solids levels were tested on four consecutive days (2 different loads per day and a repeat test). The solids levels tested were nominally 71%, 76% and 81%. This allows conclusions on the impact of solids concentration to be drawn independent of boiler design, operation and liquor properties.