Gas suction and mass transfer in gas-liquid up-flow ejector loop reactors. Effect of nozzle and ejector geometry

Abstract

The aim is to develop a method for the design of up-flow ejector loop reactors for coalescent systems respecting the different energy dissipation and mechanism of interfacial mass transfer in the ejector and in the holding vessel. Measurements and correlations of gas entrainment rate (mG/mL) and of oxygen volumetric mass transfer coefficient (kLa) are reported describing their dependencies on operating conditions for various geometries of the ejector. The results show that the energy supplied into the ejector must be expressed as a two independent parts: one representing the energy of inner turbulence of the liquid jet leaving the nozzle and the one representing the kinetic energy of axial liquid flow entering the suction chamber. Turbulent transverse motion generated in the nozzle characterized by its pressure loss coefficient ς, produces a surface roughness of the jet and plays a dominant role in its ability to entrain the surrounding gas. The kinetic energy of the axial liquid flow characterized by liquid velocity in the nozzle vn, diminished for the energy spent on gas compression is utilized in the mixing shock for dispersing of the entrained gas into the liquid. The correlations formed for a prediction of mG/mL and of kLa in ejector based on the more of 700 individual ejector configurations have average deviation lower than 8%. Mass transfer and gas hold-up in the holding vessel were modeled using the previously verified slip velocity concept, characterizing the mutual flow of phases in homogeneous bubble beds. An example of the application of the correlations for evaluation of mass transfer performance of Ejector Loop Reactor is shown.