GAS HOLD-UP, LIQUID CIRCULATION AND GAS-LIQUID MASS-TRANSFER IN SLURRY BUBBLE-COLUMNS

Hydrodynamic experiments have been performed with a small transparent piece of equipment. with and without an internal draft tube, operated at atmospheric pressure and room temperature. The effects of many parameters have been analysed separately: the role of the draft tube with various liquid phases (water, water-ethanol mixture and the reaction solvent) at various catalyst loadings. The overall gas hold-up is slightly reduced in the gas-lift operation, when compared to the simple bubble column. When varying the gas flow rate, the characteristic maximum of gas hold-up is only observed without the draft tube and for the ethanol-water mixture and the reaction solvent. The volumetric mass transfer coefficient has been determined in a very similar stainless steel reactor under pressure by two independent ways: a physical determination measuring dissolved hydrogen concentration variation with time and a chemical determination using a complete continuous reactor model including accurate reaction kinetics.