A One-Dimensional Flow Model of a Flashing Black Liquor Gun, 2010 TAPPI/PAPTAC International Chemical Recovery Conference

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This paper presents a new computational flow model for a flashing black liquor gun. The model is based on the numerical solution of one-dimensional conservation equations of mass, momentum, energy and steam mass fraction. Mass-momentum coupling is solved by the SIMPLE method. Scalar equations are solved by the fully implicit control volume method. As a first approximation for the vapor source term, the relaxation model is used by fitting its numerical constants for black liquor. For getting more information on the controlling processes, a simplified physical growth model of a single vapor bubble was developed and also implemented within the overall flow model. On the basis of pressure and velocity profiles obtained from the relaxation model, the growth of single vapor bubbles is predicted in the nozzle. The objective of this was the get more information of the mechanisms that control the flashing process. The overall flow model was also compared with water and black liquor experiments.