KRAFT BLACK LIQUOR RECOVERY IN A FLUIDIZED-BED - .1. A REVIEW

The Tomlinson recovery boiler has been the mainstay of the kraft pulping industry for over fifty years. It is clear, however, that the main drawbacks to this process are the large capital costs of new plant and the smelt-water explosion hazard. This paper examines some of the fundamental scientific information which supports the concept of fluid bed gasification as an alternative to the Tomlinson boiler. It is shown that a knowledge of thermodynamics is useful but insufficient to completely understand the behavior of the inorganic sulfur species during pyrolysis and gasification of kraft black liquor. Recent key experimental investigations at McGill have demonstrated that solid state reduction of sodium sulfate to sodium sulfide is feasible.