AbstractIn this paper, a single-/dual-stream foam separation device was constructed to simplify the conventional foam fractionation process (CFFP), by minimizing interactions between bubbles. This was expected to help reveal mechanisms in a ‘neat’ way. Results have shown negligible productivity of single-stream foam fractionation (SSFF) for the protein enrichment ratio (E) under conditions tested, whereas dual-stream foam fractionation (DSFF) was established as a reasonable basic unit of CFFP. The influence of DSFF operating conditions, such as the inlet protein concentration and gas velocity, were examined. Calculations of protein concentration and liquid volume were performed via foam thickness measurement, which is very difficult with CFFP. It was evident that the middle drainage channel played a key role in enrichment phenomena. The current DSFF system provides a control case for evaluating principles of foam fractionation. Furthermore, a simple mass-balance model has been proposed to represent the column-wide behavior of DSFF.