Modelling the behaviour of inorganic compounds in kraft recovery boilers

Models have been developed to describe the behaviour of inorganic compounds in the kraft recovery boiler. This boiler, which is fuelled by concentrated spent pulping liquor (black liquor), is the heart of the chemical recovery cycle of the kraft pulping process. The models predict the effects of boiler operating parameters and of black liquor composition on the formation of ash deposits on heat-transfer surfaces. Information about the compositions and growth-rates of the deposits can, in turn, be used to reduce fouling and corrosion problems in the boilers. The extensive work associated with the development of the models described in this article has been funded by the Technology Development Centre (Tekes), by Ahiström Machinery, by Kvaerner Pulping and by VTT.