Studies On Fluid RTD And Miniemulsion Polymerization In Taylor Reactor

A Taylor reactor is constructed by two concentric cylinders and usually used as continuous reactor. The fluid in the gap is stirred by the relatively rotary cylinders (generally with stationary vessel and inner rotor), and the flow field is affected by Taylor vortex, Couette flow and Poiseuille flow because of the stirring overlying with the continuous fluid. The residence time distribution (RTD) can span from Plug Flow to perfectly mixing flow through increasing the inner cylinder speed. Also owing to its large heat transfer surface, relatively low shear force, less visco-wall problem and so on, the Taylor reactor has a bright application prospect in many fields such as bio-chemistry, enzyme catalysis chemical, medicine, photo-catalytic reaction, and polymerization etc.In this thesis, effects of the structural and operational parameters and the kinematic viscosity on the fluid RTD in the Taylor reactor were investigated by the tracer pulse-input method. It has been found that the flow mixing was enhanced with an increase in Taylor number (Ta) and a decrease in axial Reynolds number (Reax). Based on the tanks-in-series model, the relationship among number of equivalent CSTRs (N), rector structure parameters (r, L and b), Taylor number (Ta) and axial Reynolds number (Reax) was correlated by the expression: N=(-87.23r+126.8)(L/b)0.2Ta-0.6Reax0.5The equation has a broad applicability. The calculated results under the investigated conditions (Ta=280-3230, Reax=0.89～6.78) agreed with experimental data very well. The equation has a broad applicability.The conventional miniemulsion and RAFT (Reversible Addition-Fragmentation chain Transfer) miniemulsion polymerization in Taylor reactor were investigated also. The miniemulsion of styrene was input in the reactor to go through the stirring without polymerization. It was found that the seemingly steady latex was not any more steady in the reactor. The number of particle was greatly increased and the particle size distribution was broadened in a range of Ta. But when the Ta was exceeded, and the Taylor vortex changed to turbulent wavy vortex flow, the phenomenon would vanish. Then the miniemulsion polymerization of styrene was carried out under various conditions. It has been found that the monomer conversion of the Taylor reactor, in the same range of Ta as above, was higher than that of the Plug Flow Reactor (PFR), which was regarded as the maximum in all continuous reactors. All of these results could be explained by the increase of particle number. The results showed that the Taylor vortex offered process intensification to the miniemulsion polymerization, but also, led the molecular weight distribution broader. When Ta>1891, the increases both in particle number and polymerization rate would vanish.Many studies showed that the RAFT miniemulsion polymerization existed a rate retardation phenomenon, but there was still much debate about its mechanism. By using PEPDTA as RAFT agent, the RAFT miniemulsion polymerization of styrene was investigated also. However, the polymerization rate was not increased although the molecular weight distribution became broader. The analysis of rate retardation mechanism showed that the rate retardation of this system was mainly owed to the R radical group escaping from latex particles then the radical concentration decreasing.