COMPREHENSIVE MODELING OF PRECIPITATION AND FOULING IN TURBULENT PIPE-FLOW

Supersaturation with respect to an active compound triggers several pr ecipitation-related processes that may proceed (essentially concurrent ly) along the flow path. The interaction between fluid dynamics and ph ysicochemical processes (i.e., nucleation, particle growth, and coagul ation) leads to an axial variation of bulk properties (species concent ration and particle size distribution) and of ionic and particulate de position rates at the pipe wall. To simulate this complicated system, very simple hydrodynamics (plug flow) is combined with rather comprehe nsive modeling of physicochemical phenomena. Considerable effort is de voted to the optimization of computational requirements, thus developi ng a numerical algorithm efficient and flexible enough to cope with ev en more demanding future tasks such as the inclusion of mixing. The pe rformance of the model is examined using, as a test case, the precipit ation of a sparingly soluble salt under conditions typical for geother mal installations. An extensive study of the effects of the initial sa turation ratio and of the tendency for particle coagulation on the dep osition rate and on the particle size distribution along the pipe is c arried out.