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EP-4102982-B1 - PROCESS TO IMPROVE PROTEIN RECOVERY IN STILLAGE PROCESSING STREAMS

EP4102982B1EP 4102982 B1EP4102982 B1EP 4102982B1EP-4102982-B1

Inventors

  • XIAO, Lan

Dates

Publication Date
20260506
Application Date
20210203

Claims (14)

  1. A method of recovering protein from stillage produced in an ethanol production process, the method comprising: treating stillage comprising oil, protein, and water upstream of a separation, concentration or evaporation step with a coagulant and at least one flocculant, to produce a treated stillage comprising solids which include at least a portion of the oil and protein, wherein the coagulant consists of one or more organic coagulants selected from the list consisting of poly(diallyldimethylammonium chloride) (polyDADMAC), epichlorohydrin-diethylamine, dimethylamine, polyamines, polyquaternary amines, and a combination thereof which means no inorganic coagulant is used; and subjecting the treated stillage to a solid/liquid separation process, to produce a clarified stillage comprising a clarified aqueous phase and a separated solids phase, wherein the separated solids phase comprises at least a portion of the protein from the stillage, wherein the stillage is whole stillage or thin stillage and the separated solids phase is in the form of a float layer; and separating at least a portion of the oil from the float layer to produce a de-oiled float layer by treating the float layer with an oil recovery agent comprising a blend of 75-95% castor oil ethoxylate, 5-15% hydrophobic precipitated silica, 10-30% vegetable oil, and ≤ 10% propylene glycol.
  2. The method of claim 1, wherein the stillage is thin stillage and the method comprises treating the thin stillage with the at least one organic coagulant and the at least one flocculant upstream of a concentration or evaporation step, to produce a treated thin stillage.
  3. The method of claim 1 or 2, further comprising drying the de-oiled float to produce distiller dry grain comprising the protein.
  4. The method of any one of claims 1-3, wherein the at least one organic coagulant comprises polydiallyldimethylammonium chloride (polyDADMAC), epichlorohydrin-dimethylamine, or a combination thereof.
  5. The method of any one of claims 1-4, wherein the at least one flocculant comprises an anionic flocculant.
  6. The method of claim 5, wherein the anionic flocculant is a polymer comprising a monomer unit derived from a monomer selected from 2-acrylamido-2-methylpropane sulfonic acid ("AMPS"), 2-acrylamido-2-methylbutane sulfonic acid ("AMBS"), [2-methyl-2-[(1-oxo-2-propenyl)amino]propyl]-phosphonic acid, methacrylic acid, acrylic acid, salts thereof, and combinations thereof, preferably wherein the anionic flocculant is a polymer comprising a monomer unit derived from acrylic acid.
  7. The method of any one of claims 1-6, wherein the separating at least a portion of the oil from the float layer comprises heating and mechanical processing.
  8. The method of claim 7, wherein the mechanical processing is performed with a decanter, a tricanter, a stacked disk centrifuge, or a combination thereof, more preferably wherein the mechanical processing is performed with a stacked disk centrifuge.
  9. The method of claim 8, wherein the heating produces a temperature of from about 65.5°C to about 104.4°C (about 150°F to about 220°F).
  10. The method of any one of claims 1-9, wherein the solid/liquid separation process comprises dissolved air flotation, induced air flotation, or a combination thereof.
  11. An ethanol production process comprising the method of any one of claims 1-10, wherein the ethanol production process is an ethanol biofuel process, a spirits distillery process, or a brewery process.
  12. The ethanol production process of claim 11, wherein the ethanol production process is an ethanol biofuel process.
  13. The ethanol production process of claim 12, wherein the ethanol biofuel production process is a wet milling process or a dry grind process.
  14. The ethanol production process of claim 13, wherein the ethanol biofuel production process is a dry grind process.

Description

BACKGROUND OF THE INVENTION Stillage process streams typically involve milling/grinding, further processing, separation, and recovery/separation of solids and oils from the stillage. For example, in a dry milling process for the manufacture of ethanol, corn is ground up and processed to produce a "beer mash" which is fermented to form ethanol. Once the stream reaches the desired ethanol content, the material is then transferred to a stripper column. The stripper column facilitates recovery and removal of the ethanol and the remaining stream, known as whole stillage, is passed on for further processing. In ethanol production processes that involve dry milling of corn, for example, whole stillage contains non-fermentable components of the corn kernels including germ, protein, gluten, and fiber, as well as fats and oils and a small amount of starch, in addition to dead yeast cells. Whole stillage typically contains 9%-14% total solids of which 4% to 10% are suspended solids and 4% to 5% are dissolved solids. Many of the components of whole stillage; i.e., oil and protein solids, are useful, and considerable attention has been devoted in the industry to develop methods to separate and recover those components. Typically, various uses of heat and centrifuge pressures are applied to whole stillage, thin stillage, or syrup to recover at least some of these components. Typical prior art processes involve centrifuging away water from the whole stillage thereby forming a wet cake of concentrated solids and a thin stillage stream that is low in solids. The thin stillage then undergoes some form of drying or evaporation to form a viscous syrup. Part of the thin stillage stream may be reused in the process by recirculating to the front of the plant as backset and mixing it with new corn. The syrup is typically added to other solids recovered from the process to form a mass commonly known as Distiller Dry Grains and Solubles (DDGS), which can be used, for example, as an animal feed. U.S. Patent Nos. 9,051,538 and 9,516,891 disclose a multi-stage process for the separation of bio-components from a waste stream containing DDGS, in which the waste stream is separated into a stream containing predominantly protein, a stream containing predominantly oil, a stream containing predominantly water, and a stream that contains predominantly fibers, by using polymers and separation equipment including a plate separator, a press and a dissolved air floatation device. U.S. Patent No. 7,497,955 discloses a method of dewatering thin stillage process streams by adding to the process streams an anionic flocculating amount of an anionic copolymer comprising a monomer unit derived from acrylic acid. U.S. Patent No. 9,776,105 discloses a method of treating thin stillage upstream of a concentration or evaporation step with an inverse emulsion containing an anionic flocculant and an emulsifying agent. US Patent No. 9,516,891 discloses a multi-stage process for the separation of fibre material, protein and oil from whole stillage. There is a clear need and utility for improved methods, systems, and apparatus for improving clarification of ethanol stillage and generating DDGS product with enriched protein content, while maintaining or improving oil recovery from the stillage. BRIEF SUMMARY OF THE INVENTION The invention provides a method recovering protein from stillage produced in an ethanol production process, which method comprises: treating stillage comprising oil, protein, and water upstream of a separation, concentration or evaporation step with a coagulant and at least one flocculant, to produce a treated stillage comprising solids which include at least a portion of the oil and protein, wherein the coagulant consists of one or more organic coagulants selected from the list consisting of poly(diallyldimethylammonium chloride) (polyDADMAC), epichlorohydrin-diethylamine, dimethylamine, polyamines, polyquaternary amines, and a combination thereof which means no inorganic coagulant is used; andsubjecting the treated stillage to a solid/liquid separation process, to produce a clarified stillage comprising a clarified aqueous phase and a separated solids phase, wherein the separated solids phase comprises at least a portion of the protein from the stillage, wherein the stillage is whole stillage or thin stillage and the separated solids phase is in the form of a float layer; andseparating at least a portion of the oil from the float layer to produce a de-oiled float layer by treating the float layer with an oil recovery agent comprising a blend of 75-95% castor oil ethoxylate, 5-15% hydrophobic precipitated silica, 10-30% vegetable oil, and ≤ 10% propylene glycol. The float layer may be obtained in a process for producing ethanol from dry milled/dry ground corn. The method of the invention can be applied to any suitable stillage process for producing ethanol. For example, the method of the invention may be applied to stillage processes in which