Advances in airlift reactors: modified design and optimization of operation conditions

Abstract

AbstractAirlift reactor (ALR) is a promising multiphase reactor for industrial applications. Abundant reports about modifications of the conventional ALR and optimization of their operation conditions for the purpose of performance enhancement have been accumulated in literatures, demanding a review paper to summarize the reactor design modifications and operation condition optimization of the ALR. In this review, the published research findings and results have been summarized. The basic concepts including the ALRs’ conventional design, classification, principles of operation, and characteristic parameters have been analyzed and systematically organized. The updated advances in the ALR design modifications have been reported. In particular, the concepts of the “groveled ALR” solving the scaling up problem in wastewater treatment, large-scale application, and the ALR with the cross-shaped geometry modifier stabilizing and strengthening the reactor were considered. Also, new operation modes and optimal conditions for enhancing the performance of the ALR have also been summed up. Except for conventional gas-driven methods, new driven methods for the ALR, such as mixture emission of the gas and the liquid and gas-inducing impeller, have been introduced. Optimization of operation conditions for the ALR includes varying position of the gas spargers, utilizing elevated pressure reactor, and exploring the impact of operation parameters, such as superficial gas velocity, static liquid level, and fluid properties. Comparisons between conventional ALRs and the modified systems are carried out paying attention to analogies, similarities, and differences. Most of the documented research results are obtained for various reactor designs at a laboratory scale; studies at pilot and full scale are still insufficient, which indicates that universal scale up design rules permitting the ALR design with a high confidence are required.