Ethanol from Sugarcane Bagasse (Hemicelluloses Extraction)

The process under analysis comprises three major sections: (1) Pretreatment and Hydrolysis; (2) Fermentation; and (3) Distillation.

Pretreatment and Hydrolysis. To extract hemicelluloses from sugarcane bagasse, a plug flow reactor is utilized with high temperature liquid hot water. The resulting mixture is then filtered and undissolved solids are directed to a cogeneration unit, in which they are combusted for steam and electricity generation. On the other hand, the filtered liquid stream is concentrated in multiple-effect evaporators prior to undergoing hydrolysis. Dilute sulfuric acid is then used to further hydrolyze the hemicelluloses, while lime is administered to adjust the pH. Following this, another concentration step is taken before the liquid is sent for fermentation. All vapors produced during the evaporation processes are condensed and disposed of.

Fermentation. The monomer sugars obtained from hydrolysis process are directed to the parallel batch fermenters, where the sugar will be fermented to produce Ethanol by adding yeast in a controlled temperature. The gases obtained in fermenters, mainly containing carbon dioxide, are sent to a scrubber to recover Ethanol.

Distillation. At the end of fermentation, the concentration of Ethanol in the wine is about 10 vol%. To achieve the desired 93 wt% Ethanol, the wine passes through a Concentration Column, where residual solids and most of water is removed from the bottom. After a separation step, solids are directed to the cogeneration unit, where they are burned. An Ethanol/water mixture is withdrawn as a side stream from the concentration column and conducted to a rectifying column where Hydrous Ethanol (93 wt%) is obtained as distillate.