Process optimization of a continuous airlift tower-loop reactor

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Abstract
Based on the experimental investigations with H. polymorpha and MethylomonasM 15 in bench‐scale airlift tower‐loop reactors, a general distributed parameter model was developed and used to simulate to cultivation process in a 40‐m‐high production reactor. This general model was simplified with regard to the gas phase and loop balances and was employed to optimize cell productivity and/or profit in a 20‐m‐high pilot‐plant airlift tower‐loop reactor. Maximum cell productivity always occurs in the oxygen‐transfer‐limited growth range. In case of a high “penalty factor” for nonconsumed substrate, maximum profit is attained at the boundary between substrate and oxygen‐transfer‐limited growth. Oxygen‐transfer limitation exists in the lower half of the tower, whereas in the upper half, substrate limitation prevails. The longitudinal dissolved oxygen concentration passes a minimum in this case as has been determined experimentally in the bench‐scale column. The simulation results agree fairly well with the data measured in the pilot plant.