FLOW OF SUPERSATURATED SOLUTIONS IN PIPES. MODELING BULK PRECIPITATION AND SCALE FORMATION

Pipe flow of supersaturated solutions of sparingly soluble salts is simulated in this work. Models from the literature are selected to represent individual processes, which may occur simultaneously, such as nucleation, particle growth, coagulation, and particulate and ionic deposition on the pipe wall. As regards formulation, a fairly comprehensive population balance equation is employed for the sol:d phase combined with mass balance for the ionic species. A sufficiently accurate, yet computationally convenient, discretization scheme is used in the simulation algorithm. Arbitrary parameters are avoided with the exception of surface reaction parameters which are determined from experimental data since no theoretical values are available. The PbS-water system (previously studied experimentally in this laboratory) serves as a test case. The PbS effective surface energy is estimated from experimental data. Predictions are quite encouraging, reproducing statisfactorily the measured “beH”-shaped deposition versus pH curves. The predicted particle size distributions and their evolution are physically realistic, qualitatively and quantitatively. Despite necessary future improvements, the proposed simulation algorithm is already considered a useful tool for scale up in industrial and other applications.