The indirect coal liquefaction route to produce transportation fuels, i.e., the Fischer-Tropsch synthesis, may favorably be carried out in the slurry phase. The paper reports on measurements of gas holdup and heat and mass transfer in bubble column slurry reactors of 4.1 and 10 cm diameter. The study was done under conditions prevailing In the Fischer-Tropsch slurry reactor (Rheinpreusen-Koppers process). The results enable, at least, an estimation of the majority of hydrodynamic properties involved in designing a slurry-phase reactor. Under the conditions of the Fischer-Tropsch synthesis the slurry reactor can be treated as a two-phase system which permits some conclusions concerning the favorable flow regimes and gas velocities.

Cocurrent and countercurrent absorption and desorption of CO2 in water was investigated in tall bubble columns (length 440 and 720 cm, diameter 15 and 20 cm, respectively). Operating conditions were applied which provided for high interphase mass transfer rates. Under these circumstances the relative gas holdup varies considerably with axial position whereas the mean bubble diameter measured at two points was found to be approximately constant. The measured data permit the calculation of local values of interfacial areas, superficial gas velocities, and frequency factors for bubble coalescence and break up. A dispersion model which takes into account the hydrostatic head and a variable gas velocity was applied to describe the measured concentration profiles in both phases. If increased mass transfer coefficients at the column bottom and measured local values of the hold up were used a striking agreement between experimental and predicted profiles could be obtained. The findings lead to a more sophisticated picture of the complex behaviour of gas‐liquid dispersions at high interphase mass transfer rates.

A plunging jet reactor (0.04-0.08 m 3) was used for the production of the exopolysaccharide xanthan with X a n t h o m o n a s campestris. The microorganism was not affected by the p u m p shear force. Similar specific growth rates and xanthan space-time yields to those in other reactor types were achieved at much lower specific power input. The better oxygen sorption efficiency in the jet reactor overcompensated for the effect of p o o r mixing in the wall region at high xanthan concentrations.

No abstract

No abstract