Hydrodynamic modelling and blank running of a pilot‐scale internal loop airlift reactor for wastewater treatment

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Abstract
The pilot‐scale airlift internal‐loop reactor for wastewater treatment (AILRW) differs in hydraulic characteristics and parameter values from the other types due to a shrunk top cover and low gas supplement. A blank running performed in AILRW indicated that the gas holdup in the riser had an average value fit the model of α=2.47Vgs 0.97 . The local value was linear with the axis coordinate. The linear distribution coefficient kα was measured as a function of the average gas holdup. The top connecting gap size had a great effect on the circulation. A model based on frictional pressure drop at the bottom was shown to predict successfully the liquid circulation while other models failed due to the limited head space and the effects of high gas holdup in the connecting section at the top of reactor. A model to estimate the height of dispersion in the gas drain was proposed. The overall oxygen transfer coefficient which was measured for a low range of gas superficial velocity of 0.28 to 2.4(E‐2 ms‐1) varied from 3.4 to 9.35 (E‐3 s‐1).