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Membrane-based process for the recovery of lactic acid and glycerol from a "corn thin stillage" stream

  • US 5,250,182 A
  • Filed: 07/13/1992
  • Issued: 10/05/1993
  • Est. Priority Date: 07/13/1992
  • Status: Expired due to Fees
First Claim
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1. A two-step membrane recovery process for recovering lactic acid and glycerol, together, from thin stillage obtained from the distillation of beer produced in a fermentation zone, said process comprising,(1) in a first membrane recovery step,(a) flowing said thin stillage essentially free from insoluble suspended solids larger than about 10 μ

  • m, in cross-flow, to an ultrafiltration (UF) zone, at a temperature in the range from about 30°

    0 C.-100°

    C. and at a pressure in the range from 1 atm to 10 atm, said UF zone having at least one module containing a UF membrane having a pore size smaller than 0.1 μ

    m, sufficient to remove suspended solids >

    0.1 μ

    m and `heavies` in the range from 1000-200,000 Daltons; and

    ,(b) withdrawing an ultrafiltered permeate (UF permeate) and an ultrafiltered concentrate (UF concentrate) from said UF zone with recovery of UF permeate being at least 50% in said UF zone;

    said UF permeate containing essentially all `lights` consisting of soluble solids having a molecular weight <

    1000 Daltons, said solids being present in said thin stillage;

    said UF concentrate containing essentially all solid insoluble particulates >

    0.1 μ

    m and essentially all `heavies` consisting of soluble solids having a molecular weight >

    1000 Daltons; and

    ,(2) in a second membrane recovery step,(a) flowing said UF permeate at a temperature in the range from 30°

    0 C.-100°

    C. and at a pressure in the range from 5 atm to 40 atm, in cross-flow, to a nanofiltration (NF) zone having at least one module with a NF membrane permeable to non-ionized molecules having a molecular weight <

    200 Daltons; and

    ,(b) withdrawing a nanofiltered permeate (NF permeate) and a nanofiltered concentrate (NF concentrate) from said NF zone with recovery of NF permeate being at least 50% in said NF zone;

    said NF permeate containing a major proportion by weight of lactic acid and glycerol present in said UF permeate, said NF permeate being essentially free of dissolved solids having a molecular weight >

    200 Daltons;

    said NF concentrate containing essentially all soluble solids having a molecular weight >

    200 Daltons; and

    ,(3) recovering said UF concentrate and said NF concentrate;

    whereby no UF permeate or NF permeate is flowed to an evaporation zone, and the operation and maintenance of an evaporator for producing syrup from thin stillage is obviated.

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