CFD Simulation And Mass Transfer Study Of A Novel Horizontal Twin-shaft Reactor

As the polymerization proceeds,the viscosity of polymer will become higher and higher.When the viscosity reaches hundreds of Pa s,the flow and mixing inside the reactor will become extremely difficult.The internal temperature distribution will be very uneven,which will cause local overheating and condensation,ultimately affecting the quality of the product.Therefore,it is necessary to research and develop a high-efficiency reactor for high-viscosity polymerization processes.The horizontal twin-shaft self-cleaning type reactor has high mixing efficiency and can effectively solve the problem that high-viscosity polymer adheres to the wall and the blade.In addition,it has a larger effective reaction space than the twin-screw extruder.A novel horizontal twin-shaft self-cleaning reactor has been designed and developed,which can effectively settle many problems in the high-viscosity polymerization process,and has a wide application prospect.In this paper,a novel horizontal twin-shaft self-cleaning reactor with double-layer kneading bars distributed in the radial direction is proposed.The flow,mixing,shearing and stretching properties inside the reactor are studied.The relationship between the mass transfer coefficient,rotational speed,material viscosity and liquid loading are investigated.The influence of the blade structure on the film formation characteristics under different viscosities is analyzed.The following research results has been achieved:A novel horizontal twin-shaft self-cleaning reactor with a double-layer kneading bars distributed in the radial direction is proposed.The motion process in the reactor is studied by MATLAB mathematical modeling and SOLIDWORKS 3D simulation,and the possibility of mechanical interference between two adjacent kneading bars is considered.When the reactor is running,the adjacent kneading bars are intermeshed with each other,which can achieve excellent self-cleaning effect.At the same time,due to the staggered arrangement of the kneading bars,the volume and mass of the two shafts are greatly reduced,the effective reaction space inside the reactor is increased,and the material cost is saved.So that the reactor can be applied to the polymerization process of the industrial scale reactor.The flow and mixing characteristics inside the reactor are systematically studied by means of computational fluid dynamics(CFD),and the mixing mechanism of the novel reactor is discussed.A flow pattern similar to a peanut shell is formed in the horizontal twin-shaft reactor.The differential rotation of the two shafts pushes the medium to form alternating cycle,forming chaotic mixing inside the reactor.As the mixing progresses,all material media experience the highest stretch and shear regions.Compared with the horizontal twin-shaft self-cleaning reactor with a single-layer kneading bars distributed in the radial direction,the novel horizontal twin-shaft self-cleaning reactor has a higher local shear rate where the adjacent kneading bars are mutually intermeshed,and a better overall stretching effect,higher mean instantaneous mixing efficiency and mean time-average mixing efficiency.The mass transfer efficiency of the reactor is investigated by CO2 mass transfer experiment.The mass transfer efficiency of the system increases with the increase of the rotational speed.Compared with the wheel with open window,the mass transfer performance between gas and liquid phase is improved more effectively by the kneading bars.It is found that the suspended film,stretch film,rupture film and"silkworm cocoon" film are formed under different viscosity conditions.The results show that the mass transfer efficiency varies with the thickness and area of the film.