SLURRY BUBBLE COLUMN ARE USED FOR A WIDE RANGE OF CATALYTIC REACTIONS IN CHEMICAL INDUSTRY FOR NATURAL GAS CONVERSION TO USEFUL FUELS WITH FISCHER TROPSCH SYNTHESIS. IN SLURRY BUBBLE-COLUMN REACTORS ARE TWO PRINCIPAL FLOW REGIME: HOMOGENEOUS AND HETEROGENEOUS. GAS LIQUID MIXTURE HAVE DIFFERENT BEHAVIOR IN THE HOMOGENEOUS AND HETEROGENEOUS REGIME, SINCE THE RATE OF HEAT AND MASS TRANSFER DEPENDS ON THE HYDRODYNAMIC CONDITIONS.THE RELATION BETWEEN SUPERFICIAL GAS VELOCITY, CONCENTRATION OF SOLID SUSPENSION, LIQUID HEIGHT AND GAS SPARGER TYPE WITH GAS HOLD-UP ARE IMPORTANT DESIGNING PARAMETERS TO PREDICT THE HYDRODYNAMIC BEHAVIOR OF SLURRY BUBBLE-COLUMN REACTORS.ACCORDING TO DIFFERENT REPORTED CORRELATIONS, DISTINGUISHING THE BEST CORRELATION IS THE MOST IMPORTANT FACTOR FOR SCALING UP THE SLURRY BUBBLE-COLUMN REACTORS. OUR EXPERIMENTAL REACTOR IS A CYLINDRICAL BUBBLE-COLUMN MADE OF GLASS. WITH AN INSIDE DIAMETER OF 0.15(M) AND A HEIGHT OF 2.8(M). THE COLUMN ARE EQUIPPED TWO SPARGER, A POROUS PLAT AND A PERFORATED WITH THE SAME POROSITY GAS HOLD UP CAN BE DETERMINE WITH DIFFERENTIAL PRESSURE THEN TO ESTIMATE THE TRANSITION VELOCITY IN SLURRY BUBBLE COLUMN REACTORS. TO STUDY THE INFLUENCE OF PARTICLE CONCENTRATION ON THE HYDRODYNAMICS OF SLURRY BUBBLE COLUMN REACTORS, THE RESULTS SHOW THAT INCREASING THE SOLID CONCENTRATION (SILICA POWDER) DECREASE THE TOTAL GAS HOLD UP. ALSO THE DIAMETER OF BUBBLES ARE CHANGED WITH SPARGER TYPE AT CONSTANT POROSITY AND TO MAKE IMPORTANT EFFECT ON GAS HOLD UP.THE OTHER IMPORTANT PARAMETER ON GAS HOLD UP IN SLURRY BUBBLE COLUMN IS HEIGHT. THAT INCREASING THE LIQUID HEIGHT IN CREASE THE RESIDENT TIME IN THE REACTOR THERE FOR INCREASE THE GAS HOLD UP BUT THE ARE SOME LIMITATIONS FOR INCREASING COLUMN HEIGHT AND DETERMINING THE BEST HEIGHT IS IMPORTANT FACTOR FOR SCALING UP AND PREDICTING HYDRODYNAMIC BEHAVIOR.

A BUBBLE COLUMN REACTOR IS A MULTIPHASE FLOW REACTOR IN WHICH REACTANT GAS IS BUBBLED THROUGH A LIQUID SOLUTION. BUBBLE COLUMN REACTORS MAY BE OPERATED IN A BATCH OR CONTINUOUS MODE. THEY ARE KNOWN AS EXCELLENT REACTORS FOR PROCESSES, WHICH REQUIRE LARGE INTERFACIAL AREA FOR GAS-LIQUID MASS TRANSFER AND EFFICIENT MIXING FOR REACTING SPECIES FOR EXAMPLE IN BUBBLE COLUMN FERMENTORS. A BETTER KNOWLEDGE OF THE LOCAL HYDRODYNAMICS TO INCREASES THE PREDICTABILITY OF THE REACTOR DESIGN AND TO IMPROVE THE EFFICIENCY OF THE PROCESSES APPEARS CURRENTLY NECESSARY. THE USE OF NUMERICAL MODELING I.E. COMPUTATIONAL FLUID DYNAMICS (CFD) SHOULD BE ABLE TO IMPROVE THIS KNOWLEDGE BY PROVIDING A COMPLETE DESCRIPTION OF THE LOCAL HYDRODYNAMICS IF AN ADEQUATE MODEL IS USED. IN THIS RESEARCH, HYDRODYNAMIC BEHAVIOR OF BUBBLE COLUMN REACTOR WAS DETERMINED. IN PREVIOUS WORKS, THE PREDICTION OF GAS HOLDUP IS NOT ACCURATELY COVERED. FOR THAT REASON, THE TURBULENCY IN LIQUID PHASE IS MODELED BY STANDARD K-E MODEL. IN ADDITION, LOCAL AXIAL VELOCITY, VELOCITY DISTRIBUTION AND LOCAL GAS HOLD-UP WERE CALCULATED BY FLUENT 6.0.3, WHICH IS COMMERCIAL SOFTWARE. THE RESULTS HAVE BEEN COMPARED WITH EXPERIMENTAL DATA, WHICH SHOWS A QUITE GOOD AGREEMENT.

BUBBLE AND SLURRY BUBBLE COLUMN REACTORS USUALLY WORK UNDER PRESSURES OVER THE ATMOSPHERE IN THE INDUSTRIES. ALTHOUGH MANY STUDIES DID ABOUT BUBBLE AND SLURRY BUBBLE COLUMN REACTORS, THE NUMBERS OF EXPERIMENTAL STUDIES UNDER ELEVATED PRESSURE ARE VERY LIMITED. IN THIS ARTICLE WE THE EFFECTS OF PRESSURE AND SLURRY CONCENTRATION ON THE GAS HOLDUP HAVE BEEN MADE BY DIFFERENTIAL PRESSURE EXPERIMENTS.THE EXPERIMENTS IN THIS STUDY ARE MADE UNDER PRESSURES UP TO 18 BARS AND PARAFFIN AND SILICA WAS USED AS LIQUID AND SOLID CONTENTS. INCREASING THE OPERATION PRESSURE LEADS TO AN INCREASE IN GAS HOLDUP. IN THIS STUDY WE FOUND THAT THE EFFECT OF PRESSURE WILL BE VANISHED BY INCREASING THE SLURRY CONCENTRATION. THE EXPERIMENTS WERE COMMITTED IN A COLUMN WITH 16CM IN DIAMETER AND 2.8M IN HEIGHT. THE GASES USED IN THIS STUDY WERE NITROGEN AND AIR. FINALLY A NEW EXPERIMENTAL CORRELATION IN FUNCTION OF GAS DENSITY (RG), SUPERFICIAL VELOCITY OF GAS (U G), SLURRY DENSITY (RSL), SLURRY VISCOSITY (MSL) AND LIQUID SURFACE TENSION (SL) WAS DEVELOPED UNDER THE DATA EXTRACTED FROM THIS INVESTIGATION THAT IS IN GOOD AGREEMENT WITH EXPERIMENTAL POINTS.

THE INFLUENCE OF LIQUID RHEOLOGY ON THE GAS HOLDUP IN A SIMPLE BACH BUBBLE COLUMN WAS STUDIED. AQUEOUS SOLUTIONS OF CARBOXYMETHYL CELLULOSE (CMC) AT 17OC WERE USED AS A NON-NEWTONIAN FLUID. AIR WAS SPARGED TO A 0.11 M IN DIAMETER BUBBLE COLUMN VIA A SIEVE PLATE, HAVING 19 HOLE OF 1 MM IN DIAMETER. THE EXPERIMENTAL DATA SHOW THAT THE TOTAL GAS HOLDUP DECREASES BY INCREASING THE LIQUID APPARENT VISCOSITY. A CORRELATION FOR TOTAL GAS HOLDUP PREDICTION IN BUBBLE COLUMN WITH NON-NEWTONIAN LIQUID WAS PROPOSED. IT DOES REQUIRE VISCOSITY OF LIQUID EXPLICITY.