4-17: Separation of acetic acid from pre-pulping extract for use in fermentation through counter current extraction using ethyl acetate

Liquid-liquid extraction (LLE) is a common separation method used to recover a solute from a solution and can be applied to the recovery of acetic acid from pre pulping extract prior to the fermentation process. Previous investigation has used a batch process for acetic acid removal from different levels of acetic acid present in pre pulping extract. In this study, the efficiency of counter-current extraction (CCE) process was investigated to recover acetic acid from a control solution system using ethyl acetate as a solvent. The CCE was carried out for acetic acid concentrations (10 g/L and 50 g/L) with equal volumes of the feed and solvent streams at the flow rates of 50 kg/hr, the natural pH (=2.3 and 2.0) of feed stream, and the column temperature (25 ^oC). The expected results from the physical runs were compared to output from a computer simulator, Aspen HYSYS.  The following values are from the Aspen HYSYS simulation (the expected outcome for the laboratory trials). In a one stage CCE at the natural pHs of 2.3 and 2.0, 51 % (10g/L) and 55 % (50 g/L) of the acetic acid could be extracted in the top product stream. The recovery of acetic acid through CCE process is not significantly influenced by the initial acetic acid concentration in the feed stream.