Study On Performance Of Fluid Dynamics And Mass Transfer Of Rotating Bed In High-gravity

Rotating packed bed is a new high-gravity gas-liquid mass-transfer equipment developed in 1980. The centrifugal force .that is larger far than gravity makes gas-liquid contact turbulently in the rotating bed, which intensifies mass-transfer process and improves mass-transfer efficiency.The rotating packed bed has being studied in some companies and universities. The contents of the research mainly included improvement of packing, hydrodynamics, performance of mass-transfer etc. The Zhejiang University of Technology studied the pressure drop of the rotating packed bed. This paper advanced a new structure of the rotor, and studied the pressure drop and mass-transfer efficiency under the basis of previous work.The new rotor makes a sufficient gas-liquid contact and a proper residence time. The rotor is made of zigzag up-baffle and down-baffle. There is some space between the baffles. The up-baffle is static and the down-baffle turns with the rotor. Liquid is shattered equably in the rotor, enhancing the degree of the atomization. Gas and liquid flow zigzag along the baffles, which adds the residence time in the rotor.The paper studied the pressure drop and mass-transfer efficiency of the new rotating bed under the condition of 400-1200rpm and total reflux with the ethanol- water distillation system, 1 ami.. Data were collected on pressure drop, ethanol concentration of condenser and reboiler under different reflux rate and rotating speed in the test. The models were developed for mass-transfer and pressure drop.Furthermore, the structure of the rotor was properly changed, Firstly, enlarging the outer diameter of the rotor, the baffle numbers increased by 50%; secondly, making the up-baffle and down-baffle rotate together with the rotor; thirdly, filling the Raschig rings between the baffles. Under the condition of the same operation, the test was made.The experiments show that:HI1.The higher gas-liquid mass-transfer efficiency corresponds to the higher rotating speeds under the same reflux.2. Reflux effects on mass-transfer efficiency were found small in this work. The mass-transfer efficiency descends a little as the reflux increases and holds a fixed value in the end.3. The pressure drop increased as the reflux rate or rotational speeds increase.4. The number of theoretical trays can reach to 9.8 when the reflux rate is 25L/h and rotating speed is 1200 rpm, being equivalent to 49 theoretical trays per unit meter.5. The efficiency of mass-transfer of the rotating bed that is filled with Raschig rings between the baffles is lower far than the new rotating bed.The pictures of the moving liquid drops in the rotating bed were obtained by a digital camera. In the pictures, the shattered liquid can be observed. It indicates that the main body of mass-transfer between gas and liquid is liquid drops and mass-transfer between gas and liquid is carried out at the surface of atomized liquid.