Gas hold-ups were measured in a 240mm dia. and 2400mm high three-columns-in-series reactor of the 2.4ton/day NKK direct coal liquefaction process. All measurements were carried out under high pressure in i) two-phase creosote oil/ hydrogen system at room temperature, ii) two-phase anthracene oil/hydrogen and iii) three-phase Illi-nois No.6 coal slurry/hydrogen systems at high temperature by the following three diffe-rent methods; “gas shut-down”, “neutron attenuation” and “gas purge” techniques.
For system i), the gas hold-up, εG, obtained by the three methods showed no signifi-cant difference and increased with the superficial gas velocity, UG. εG at a given UG in-creased with the pressure up to 12.8MPa and then leveled off with the further pressure in-crease. These variations of εG could possibly be attributed to those of the bubble size. The change of εG with UG for system ii) was found to be equivalent to that for system i), if changes in UG and the gas-liquid equilibrium composition due to evaporation of light anthracene oil fractions to the gas phase were appropriately evaluated. Furthermore, εGS for system iii) agreed reasonably well with those reported for coal liquefaction pilot plants and high pressure bouble column.
