Bio-Acrylic Acid Production from Raw Sugar (Single-Step Process)

The process under analysis comprises two major sections: (1) Fermentation; and (2) Extraction and Distillation.

Fermentation. The culture media used in the fermentation is prepared by diluting the raw sugar and nutrients in water. Such media is sterilized by direct steam injection, cooled and sent to fermentor. It is assumed that the fermentation is carried out in continuous mode with cell recycling, and under anaerobic process conditions in an agitated, jacketed fermentor. The pH control of the fermentation is made by addition of recycled sodium carbonate, in such a way that the pH of the fermentation broth is maintained at around 7. The temperature is controlled between 35 and 40 °C via circulation of cooling water in the fermentor jacket. The fermentation yield considered is about 70% and the acrylate concentration is about 50 g/l. After fermentation, biomass is separated from the broth and partially recycled to the fermentation.

Extraction and Distillation. The sodium acrylate solution exiting from the Cells Separation is pumped into a multi-stage countercurrent extraction unit. There, extractant separates the Acrylic Acid in the organic phase. The aqueous phase containing sodium bicarbonate is decomposed at high temperatures, producing dissolved sodium carbonate, that is recycled as neutralization component in the fermentation. The organic phase is initially decompressed in a flash unit, where the majority of the dissolved carbon dioxide is released. The liquid stream from the flash vessel is then fed to a distillation column, where under reduced pressure and elevated temperature conditions the water remained in the organic phase is removed. The acid is separated from extractant in a distillation column, and Glacial Acrylic Acid is obtained as distillate. The extractant is then back-extracted with water in a multi-stage extractor train and recycled.