Study On The Mixing And Mass Transfer Characteristic Of A Novel External Loop Slurry Reactor

Airlift loop reactor is a kind of efficient gas-liquid or gas-liquid-solid multiphase reactor originating from bubble column,which combines the advantages of bubble column and stirred tank.The gas-liquid-solid multiphase reactor is also known as slurry reactor,and the liquid-solid separation performance is an important index to evaluate this kind of reactor.Filtration separation,hydrocyclone separation and membrane separation are commonly used in industrial production,which have their own advantages,disadvantages,and application limitations.Therefore,it is of great theoretical significance and application value to develop liquid-solid separation structure suitable for different liquid-solid separation requirements.This paper carried out experimental investigations on the new external airlift loop reactor with characteristic hydrocyclone as the liquid-solid separation structure,physical properties of solid particle,and the viscosity of liquid phase all have important effects on the hydrodynamic performances.The effects of solid particle properties and liquid viscosity on the hydrodynamic performances were also investigated.Then,in order to further optimize the mixing and separation performance of the external airlift loop reactor,a new external airlift loop reactor Ⅱ,which combines the jet inertial separation structure with the external airlift loop reactor,was proposed.And the hydrodynamic performances of the new external airlift loop reactor Ⅱ were also investigated.Firstly,aiming at the new external airlift loop reactor,the physical properties of solid particles such as brown corundum,FCC catalyst,quartz sand on the hydrodynamic performances of the reactor were investigated.The results show that the gas holdup,liquid circulating velocity,and volumetric mass transfer coefficient all increase with the increase of superficial gas velocity,no matter which solid particles are taken.With the superficial gas velocity constant,the gas holdup and liquid circulating velocity both decrease with the increase of solid mean diameter,density and sphericity,but increase with the increase of contact angle.The solid axial concentration decreases with the increase of axial height and increases with the increase of superficial gas velocity.The non-uniformity of solid axial concentration distribution will increase with the increase of particle size and density.Secondly,the effect of Glycerol-water solution at different mass concentration on hydrodynamic performances was investigated.When the liquid viscosity is 234.6 m Pa·s,22.94 m Pa·s and 2.501 m Pa·s respectively,the gas holdup and liquid circulating velocity both increase with the increase of superficial gas velocity.The gas holdup and liquid circulating velocity both decrease with the increase of liquid viscosity as the superficial gas velocity is constant.The high liquid viscosity has an obviously positive effect on the axial uniform distribution of solid concentration,while what is not obvious when the liquid viscosity is low enough.Finally,the liquid-solid separation ability and hydrodynamic performances were investigated in the external airlift loop reactor with an inertial separation structure,which is also named new external airlift loop reactor Ⅱ.It can be found that the minimum particle size of the solid staying in the reactor is 11.15 μm and the maximum throughput is 0.6 m3/h through the qualitative test of cycle performance of the new external airlift loop reactor Ⅱ.When the superficial gas velocity ranges from 0.043 m/s to 0.076 m/s,the gas holdup,liquid circulating velocity and volumetric mass transfer coefficient will all increase with the increase of superficial gas velocity,while decrease with the addition of solid particle.The solid axial concentration increases with the increase of superficial gas velocity,while the non-uniformity of solid axial concentration distribution decreases with the increase of superficial gas velocity.According to the experimental results under different experimental conditions,the empirical equations of gas holdup,liquid circulating velocity and volumetric mass transfer coefficient with superficial gas velocity are fitted respectively,which provide a basis for the development and design of external airlift slurry loop reactor.