Study of turbulent mixing effects on barium sulfate precipitation in mixed suspension and mixed product removal and semibatch reactors.

摘要

The effects of turbulent mixing on reaction precipitation of barium sulfate in mixed suspension and mixed product removal (MSMPR) and semi-batch reactors were investigated experimentally and theoretically.;First, for the theoretical analysis of the precipitation, a simple, accurate and efficient numerical technique for solving the dynamic population balances associated with precipitation reactors was developed. The basis approach of this numerical technique was to determine the solute concentration dynamics first by using the method of moments and an efficient ordinary differential equation solver, and then to solve the dynamic population balance, a partial differential equation having coefficients which depend on the known solute concentration, by standard finite difference technique.;In chapters 3 and 4, the effects of non-ideal and nonhomogeneous turbulent mixing on barium sulfate precipitation in MSMPR and semi-batch reactors were observed experimentally and were analyzed theoretically. To generate the nonhomogeneous mixing in the reactors, joint feeding mode and plug flow reactor for MSMPR reactor were used, and double-jet separate feeding mode for the semi-batch reactor was applied. The nonhomogeneous mixing conditions resulted in significant reductions in particle size and increases in particle numbers.;To model the effects of nonhomogeneous mixing in the reactors a plug flow-stirred tank series reactor model for the MSMPR reactor and a plug flow-ideal semi-batch series reactor model for the semi-batch reactor were developed. The plug flow reactor represents the premixing region of the reactors in which turbulent micromixing is important, and stirred tank and ideal semi-batch reactors describe the homogeneous mixing region of the reactors where particle growth is important. The predictions of the model are in good agreement with experimental data.;The effects of high molecular weight additives (PVA and gelatin) on barium sulfate precipitation in an MSMPR reactor was investigated in chapter 5. As the additive concentration in the bulk solution was increased, the particle growth rate was decreased and the nucleation rate was increased. To explain the additive effect quantitatively a diffusion limitation model was developed. The model predictions were in good agreement with experimental data and were consistent with simple theories of polymer adsorption and diffusion in polymer solution.