Hydrodynamics and film formation characteristics in a horizontal self‐cleaning twin‐shaft kneader for polymer devolatilization

Abstract

A deep understanding of hydrodynamics and film formation characteristics is a prerequisite for the design of twin‐shaft kneaders. In this work, the hydrodynamics and film formation characteristics of a self‐cleaning twin‐shaft kneader are investigated using computational fluid dynamics method. Because of the intermeshing interaction and scratching action of the kneader rods, both bounded films and free films coexist in the kneader. Since both shafts rotate clockwise, more liquid is accumulated in the left cylinder. The liquid level of the left cylinder is higher which reduces the film formation rate of the left zone. The film formation rate in the right zone is 1.3–1.8 times that of the left zone and overlapping zone. The differences between the left and right cylinders would cause inconsistent devolatilization performances. To reduce the negative effects of asymmetric level, a static kneading rod is used to reduce the liquid level of the left zone and increase the film formation rate by 15%. We notice that adding a static kneading rod reduces the power consumption by 10%–30% compared with increasing the rotating speed to the same film formation rate. It could be an efficient method for polymer devolatilization.

Simulation study on mass transfer characteristics and disk structure optimization of a rotating disk reactor with high viscosity region

“…4,5 The polymer in the dynamic devolatilization equipment is driven by the rotating parts to form a film, which can improve the interface renewal rate between the polymer and the gas phase, enhance the mass transfer and heat transfer efficiency of the polymer, and strengthen the devolatilization process. Dynamic devolatilization equipment mainly includes rotating film devolatilization device, 6 horizontal disk reactor, 7 kneading reactor 8,9 and screw extruder. 10 The disk reactor is partially immersed in the liquid phase.…”