Gasification of sulphate soap for the lime kiln

Sulphate soap is a by-product of pulp mills utilized as a raw material for the chemical industry. However, this results in an increase in sulphur input of several kilograms SO₂ per ADt pulp into the mill. Another increasingly interesting alternative is to utilize soap in the lime kiln of the mill. This has a positive effect, in addition to sulphur problems, on the energy balance of the mill. The crucial problem is the high Na + K content of the soap, from 4 to 8%, which can result in plugging of the lime kiln. The operational problems can be avoided by gasifying the soap and by separating the inorganic materials from the product gas before the kiln. This paper describes research work on the gasification of crude sulphate soap carried out at VTT over the years 1991 and 1992. This work will be continued in 1993 by focusing on specified problems, after which commercial applications should be available. A detailed research report will be published after this second stage of research has been completed.