Design Of Internals And Research On The Flow Characteristics In Bubbling-tower Reactor

Gas-liquid-solid recactors have been widely used in petrochemical,bio-chemical and energy-chemical fields.Compared to other gas-liquid-solid reactors,bubbling-tower reactors are simple in structure,good in leakproofness,no requirement of external mechanical stirring,and lesser in catalyst abrasion,and have been widely used in industry.However,bubbling-tower reactors have some shortcomings such as nonuniform of bubble size and gas holdup along axial and radial position,which affects the effect contact between gas,liquid and solid,and the effect of reaction,especially in large scale reactors.To sovle this problems,the measures including to optimize bubble distributor,to change the type of reactor and to add internal.Among them,adding internal is a feasible way to impove the flow of bas bubble and liquid.But the present internals have the shortcomings such as high pressure drop,no good contact between gas and liquid,et al.A new type internal was given and cold model experiments were made in the paper.1)According to the characteristics of flow of gas and liquid in bubbling-tower reactor,Jiaochi type internal was designed.A cold model bubbling-tower reactor experimental setup with the diameter of 1000 mm was erected,and air-water-alumina powder were employed as three phases of gas-liquid-solid.The characteristic dimensions of internal were optimized by measuring the changes of gas bubble size,gas holdup and liquid flow caused by the internals.2)There are three regions of local gas holdup along the axial direction: bubble distributor region,fully developed region and upper foam region.Local gas holdup decreased with the increase of r/R.Adding of internal resulted in the homogenization of gas holdup along radial direction.3)Bubble size increased with the height of axial direaction,and decreased with the increase of r/R.By adding internal,bubble size decreased to 1mm of diameter,and the bubble size was close to uniform along radial direction.There is no influence of fine solid powder adiding on the size of gas bubble.4)There is a circulation flow of gas and liquid in the bubbling-tower reactor.Gas and liquid upflowed in the centeral region of r/R<0.7 and downflowed in wall region of r/R>0.7.Axial liquid flow velocity increased with the increase of gas flow.Liquid flow velocity decreased from 0.8m/s to 0.4m/s with adding the internal when circular-tube distributor was used,and decreased from 1.5m/s to 1.12m/s when bubble-cap distributor was employed.The turning point of liquid flow did not change after adding the internals.