Recovery of solvent and by-products from organosolv black liquor

The recovery of alcohol and by-products from ethanol-water and methanol-wat er pulping liquors was studied. The recovery system proposed consists of th ree stages: black liquor flashing, lignin precipitation, and precipitation distillation of mother liquor. At the flash stage, 47 and 51% of the alcoho l in the black liquor are recovered for ethanol and methanol processes, res pectively. 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% metha nol from this stream as distillate, whereas the distillation residue contai ns significant amounts of sugars, furfural, and acetic acid that can be rec overed. The study concludes with the overall mass balance for the recovery system proposed.