The recovery of alcohol and by-products from ethanol-water and methanol-water pulping liquors was studied. The recovery system proposed consists of three stages: black liquor flashing, lignin precipitation, and precipitation distillation of mother liquor. At the flash stage, 47 and 51% of the alcohol in the black liquor are recovered for ethanol and methanol processes, respectively. The lignin recovery yield at the precipitation stage is 67% for ethanol black liquor and 73% for methanol black liquor. The distillation of precipitation mother liquors enables recovery of 98% ethanol and 96% methanol from this stream as distillate, whereas the distillation residue contains significant amounts of sugars, furfural, and acetic acid that can be recovered. The study concludes with the overall mass balance for the recovery system proposed.
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BOTELLO et al. (1999) studied this question.
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