RELATIONSHIP BETWEEN RISER AND DOWNCOMER GAS HOLD-UP IN INTERNAL-LOOPAIRLIFT REACTORS WITHOUT GAS-LIQUID SEPARATORS

An approach based on mechanistic principles was used to point out a re lationship between the gas holdups in the riser and downcomer of inter nal-loop airlift reactors without gas-liquid separators. The theoretic ally based relationship was shown to apply to experimental observation s in five reactors, including split-cylinder and concentric draft-tube types of reactor configurations, over a broader range of volumes (0.0 33-0.160 m3), heights (1.8-3.45 m) and riser-to-downcomer cross-sectio nal area ratios (1.8-7.7) than any of the previously published empiric al correlations. Unlike earlier equations, the proposed equation was c onsistent with the observation that, at low rates of gas input in the riser, there may be no gas in the downcomer.