Wojciech Orciuch

Closure Problem for Precipitation

A closure procedure based on the probability density functions of the concentrations of chemically inert species has been proposed and applied to derive the mathematical forms of the local average values of the nonlinear reaction, nucleation and crystal growth terms. Applied to experimental results for BaSO 4 precipitation, satisfactory agreement between predicted and observed results was obtained for two tubular reactors. In experiments solutions of BaCl 2 and Na 2 SO 4 were contacted in tubular reactor equipped with an impingement mix-head.

Some hydrodynamic aspects of precipitation

Precipitation of sparingly soluble materials from two aqueous ionic solutions is considered. It is well known that the flow conditions in the system can affect particle size distribution and particle morphology. In the paper, three problems related to interactions between hydrodynamics (turbulent flow) and the precipitation process are considered, namely, effects of mixing on crystal size using computational fluid dynamics (CFD), relation between turbulent diffusion of fluids and solid particles, and the problem of aggregation kernel for small particles.

Shear Flow of Aggregated Nanosuspensions–Fundamentals and Model Formulation

Theoretical aspects of shear flows of aggregated nanosuspensions are presented and applied to formulate appropriate models. Technological context of this work is related to formulation of stable suspensions of nanoparticles of specific rheological properties by breaking‐up nanoparticle clusters in high shear devices. Accordingly the population balance modeling is applied with kinetics including effects of aggregation, breakage and restructuring of aggregates; effects of suspension rheology on the flow are included as well. Rheological model includes the effect of clustering of primary nanoparticles. Population balances are solved using QMOM that is linked to the CFD code. Results of numerical simulations are presented for laminar and turbulent flows. Part of the 1st International Conference on Industrial Processes for Nano and Micro Products, London, 2007.

Break‐Up of Nanoparticle Clusters—Process Modeling

A general model for suspension formulation that includes effects of particle breakage and clustering on suspension structure and resulting rheology is applied here to simulate agglomerate dispersion. The model employs the QMOM population balance to simulate variation of agglomerate size and structure in a system of complex geometry. As an example of such system a rotor–stator mixer is applied. Simulations are performed with the CFD code Fluent supplemented with UDFs for process kinetics, aggregate structure, and suspension rheology. A method of application of the population balance equation to describe evolution of fractal aggregates is presented and effects of application of either uniform or erosion daughter distribution are compared.