Enhanced Separation of Corn Oil from the Ethanol Manufacturing Process

Abstract

An ethanol production process and system for recovering high value oil products. The invention includes adding a heated lipid (oil) stream to a thin stillage stream to break the water/oil emulsion and free bound oil then recovering the oil. The lipid stream may be heated by use of existing process steam or other process energy source, or may be heated by the introduction of energy from an external source. The process uses oil as the heat transfer mechanism to increase both the volume and quality of the oil recovered.

Claims

1. A process for the recovery of oil from an ethanol process comprising: processing a feedstock to create a process stream; fermenting the process stream to create a post-fermentation process stream; separating the post-fermentation process stream into an alcohol stream and a whole stillage stream; separating a thin stillage stream from the whole stillage stream, wherein the thin stillage stream includes bound oil; heating the lipid stream by means of indirect heat transfer; obtaining an oil product from the oil flow stream.

2. The process of claim 1 wherein the lipid stream is heated by use of heat exchangers.

3. The process of claim 1 wherein the lipid stream is heated by heating of the piping through which the lipid stream passes.

4. The process of claim 1 wherein the lipid stream is heated by heating a vessel in which the lipid stream resides.

5. The process of claim 1 wherein the lipid stream is obtained from the thin stillage stream.

6. A process for the recovery of oil from an ethanol process comprising: processing a feedstock to create a process stream; fermenting the process stream to create a post-fermentation process stream; separating the post-fermentation process stream into an alcohol stream and a whole stillage stream; separating a thin stillage stream from the whole stillage stream, wherein the thin stillage stream includes bound oil; heating the lipid stream by means of direct introduction of energy into the lipid stream; obtaining an oil product from the oil flow stream.

7. The process of claim 6 wherein the lipid stream is heated by the direct infusion of steam into the stream.

8. The process of claim 7 wherein the steam is at atmospheric pressure.

9. The process of claim 7 wherein the steam is at an elevated pressure immediately prior to the introduction into the lipid stream.

10. The process of claim 6 wherein the lipid stream is heated by use of electrical heaters.

11. The process of claim 6 wherein the lipid stream is heated by the introduction of microwave energy.

12. The process of claim 6 wherein the lipid stream is obtained from the thin stillage stream.

13. The process of claim 6 wherein the lipid stream is taken from the oil storage tank.

14. The process of claim 6 wherein lipids are recovered from a point in the ethanol process to create the lipid stream.

15. The process of claim 6 wherein the lipid stream is separated from the process stream prior to fermentation.

16. The process of claim 6 wherein the lipid stream is heated in a heat exchanger prior to being introduced to the thin stillage stream.

17. The process of claim 6 wherein the lipid is heated to a temperature of between about 190 degrees F. and 325 degrees F. before being introduced to the thin stillage stream.

18. The process of claim 6 wherein the lipid is heated to a temperature of between about 205 degrees F. and 215 degrees F. before being introduced to the thin stillage stream.

19. The process of claim 6 wherein the thin stillage stream is separated from the whole stillage stream using distillation.

20. The process of claim 6 wherein the oil product is separated from the oil flow stream using a centrifuge.

21. The process of claim 6 wherein upon introducing the heated lipid stream to the thin stillage stream, the heated lipid stream breaks emulsions in the thin stillage releasing bound oil.

22. The process of claim 6 wherein upon introducing the heated lipid stream to the thin stillage stream, the heated lipid stream decreases the viscosity of the thin stillage.

23. The process of claim 6 wherein upon introducing the heated lipid stream to the thin stillage stream, the heated lipid stream vaporizes water from the thin stillage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The advantages of the technology described may be better understood by referring to the descriptions below with the accompanying drawings. The drawings are not to scale and represent exemplary configurations that depict general principles of the technology which are not meant to limit the scope of the invention.

[0018] FIG. 1 is a flow chart showing an exemplary prior art ethanol production process.

[0019] FIG. 2 is a flow chart showing an embodiment of the process where the lipid stream is taken from oil recovered from the ethanol process.

[0020] FIG. 3 is a flow chart showing an embodiment of the process where the lipid stream is taken from an outside oil source.

[0021] FIG. 4 is a flow chart showing an embodiment of the process where the lipid stream is recovered from the front end of the process then introduced to the thin stillage stream at the back end of the process.

DETAILED DESCRIPTION

[0022] The processes of the present invention will now be described in detail by reference to various non-limiting embodiments, including the figures which are exemplary only.

[0023] Unless otherwise indicated, all numbers expressing dimensions, capacities, and so forth used in the specification and claims are to be understood as being modified in all instances by the term about. Without limiting the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0024] The present invention may be practiced by implementing process steps in different orders than as specifically set forth herein. All references to a step may include multiple steps (or substeps) within the meaning of a step. Likewise, all references to steps in plural form may also be construed as a single process step or various combinations of steps.

[0025] The present invention may be practiced by implementing process units in different orders than as specifically set forth herein. All references to a unit may include multiple units (or subunits) within the meaning of a unit. Likewise, all references to units in plural form may also be construed as a single process unit or various combinations of units.

[0026] As used in this specification and the appended claims, the singular forms a, an, and the include plural referents unless the context clearly indicates otherwise.

[0027] Corn is used as an exemplary feedstock for the processes described herein. It should be noted, however, that other feedstocks such as sorghum may be used and the exemplary uses of the terms corn flow, corn oil, and other terms including the word corn should be read broad enough to include all suitable feedstocks.

[0028] One aspect of the invention includes a process for recovering high value co-products from an ethanol process. More specifically, the invention includes heating a lipid such as oil then introducing the heated lipid stream to a thin stillage stream to break emulsions and release bound oil from the thin stillage for recovery of the oil.

[0029] FIG. 2 shows one embodiment of the invention, which may include many of the traditional ethanol production steps discussed above and shown in FIG. 1. First, a feedstock such as corn or sorghum is introduced into a feedstock receiving vessel 10 to begin the feedstock flow stream (labeled CF in the figures). The feedstock is ground into flour with a hammer mill 12 then the flour is wet to create a mash 14. A fine grinding unit 16 may be used to further grind the mash which helps expose more surface area of the starch to enzymatic reactions and increases the yield. Other benefits associated with implementing the fine grinding operation in the front end of an ethanol process include the release of other useful components of the corn kernel including various lipids and other light density fractions. Next, enzymes are added in a liquefaction tank 18 to convert the starches in the corn mash to sugars 18. These sugars are thereafter converted into ethanol through fermentation 22.

[0030] Following fermentation 22, the product stream from the fermentation vessel 22 is delivered to a separation unit such as distillation units 24 where it is further heated with the alcohol removed from the fermentation product stream by vaporization, and is recaptured by condensation. As shown in FIG. 2, the distillation process 24 separates the corn flow stream into an ethanol flow stream (EF) comprising primarily alcohol and a DDGS flow stream (DF) comprising primarily fiber, protein, oil, and water. The ethanol flow stream is directed to further purification 26 and recovery 28, 30 processes, as is known in the art. The DDGS flow stream separated from the fermentation product stream is generally referred to as whole stillage. The whole stillage is sent to a separation unit such a de-watering centrifuge 32 where the whole stillage is separated into a primarily heavy solids stream referred to as wet cake, which may be directed to driers 36 for further dewatering in the production and recovery of DDGS 38.

[0031] The second stream separated from the whole stillage at separation step 32 is a primarily liquid stream which contains primarily dissolved solubles and, also, a small percentage of solids. This liquid stream is referred to as the thin stillage steam. The thin stillage may be sent to the evaporation step 34 where it is subjected to a series of dewatering processes by circulation through multiple evaporators 34. The thin stillage stream is then introduced to a heated lipid stream. As shown in FIG. 2, the lipid stream is introduced into the thin stillage stream at unit 46, which may be a blending tank (as shown) adapted to receive the two streams and allow them to mix. In an alternate embodiment the lipid stream is introduced into the pipe carrying the thin stillage (instead of into a blending tank) before introduction to the centrifuge 42. In this alternate embodiment the two streams mix within the pipes as the combined stream travels toward the next process unit.

[0032] In one embodiment, the lipid stream includes about between 98-100% oil. In another embodiment the lipids stream includes more than about 80% oil with the rest being primarily a mix of gums and other phosphatides. In another embodiment the lipid stream includes between about 70% and 90% lipids (oil) with the rest being primarily a mix of gums and other phosphatides. The pH may be between about 4.0 and about 5.5, with a preferred range tending more acidicabout 4.0 to 5.2. This chemical construct of the lipid stream (i.e., its high oil content) allows it to remain very stable under high heat conditions. This allows the heated lipid to facilitate the breaking of emulsions latter in the process (as described below). In order to effectively heat the lipid stream, however, it is preferred that its moisture content be not more than about 5%. Various additives are known and available that could be introduced into the lipid stream to increase stability when heated.

[0033] In one embodiment, the lipid stream is heated at step 40 before it is introduced to the thin stillage stream at 46. The lipid stream is heated at step 40 to between about one hundred ninety (190) degrees F. to three hundred twenty-five (325) degrees F. In one embodiment the lipid stream is heated at step 40 to about between two hundred and five (205) degrees F. and two hundred and fifteen (215) degrees F. The heating step 40 can be done using any suitable device, including a plate and frame heat exchanger or in a tube and shell heat exchanger. The heating step 40 may include one or more separate heating steps or heat exchangers. The heating step 40 of the lipid stream may further be accomplished by the use of other heating mechanisms. In addition to the transfer of heat by passing the lipid stream though one or more heat exchangers, direct heating of the lipid stream may be employed. This direct heating may include electrical, steam or other methods of heating of the piping or of a vessel similar to a heat exchanger through which the lipid stream passes, or simply the introduction of steam, non-pressurized or pressurized, into the process stream immediately before separating or otherwise obtaining the free and freed oil from the process stream. Further, the lipid stream contains water and would be susceptible to selective heating or superheating by the introduction of microwave energy which would allow for a highly energy efficient method to heat the lipid stream immediately prior to introduction into the oil carrying process stream. After heating, the lipid stream is introduced into the process stream at step 46 (which is now primarily a thin stillage stream that has been separated from the whole stillage).

[0034] In one embodiment the thin stillage stream has a larger flow volume than the lipid stream which helps prevent degradation, which may otherwise occur if the thin stillage was subject to a continuous and prolonged temperature increase. The larger flow volume of the thin stillage stream allows it to experience a fleeting but sharp rise in temperature at the point of contact 46 with the lipid stream. As a result of process operations resulting in the agitation and churning of the process stream, pH, and the presence of small, insoluble solids in the process stream, a portion of the corn oil in the thin stillage is bound in an oil-in-water (O/W) emulsion which operates to impede the mechanical separation of the oil from the stream. The addition of the hot lipid stream to the thin stillage at step 46 results in a dynamic energy imbalance in the O/W emulsion which causes the water of the emulsion to vaporize or flash off. This operation frees the bound oil 44 in the thin stillage which is available to be removed in the back end centrifuges or other mechanical separators 42. The hot lipid also decreases the viscosity of the total flow and weakens any emulsion so that more thin stillage can be processed through the backend mechanical separators 42 to recover more oil 44.

[0035] In one embodiment, the corn oil flow (COF) stream exiting the blend tank 46 is directed to a holding tank 48 to allow for gravity separation before the stream is further directed to a mechanical separator 42 such as a centrifuge. The mechanical separator 42 separates the corn oil flow stream into a finished oil product stream and a thin stillage stream. The thin stillage stream is thereafter directed into evaporation 34 or drying 36 units where it is eventually recovered as DDGS 38. The finished oil product stream is recovered at step 44 and stored in an oil storage tank or directed to further purification processes.

[0036] In one embodiment shown in FIG. 2, the lipid stream is taken from the storage tank 44 holding the finished oil product which has already been recovered from thin stillage in the ethanol process. This oil can be safely heated up to the desired temperature as it is free of the solubles present in thin stillage. It is introduced to the thin stillage stream at step 46 in order to free bound oil and break the resident emulsion in that stream (as described above) for downstream recovery of the oil. In this embodiment, the lipid stream is taken from the back end of the process (finished oil tank 44) and recycled upstream to another part of the back end of the process.

[0037] Alternate embodiments include alternate sources of the lipid stream. FIG. 3 shows an alternate embodiment wherein the lipid stream is taken from an outside source (i.e., a source unrelated to the ethanol production process). As described above, the lipid stream is introduced to the thin stillage stream at step 46 in order to free bound oil and break the resident emulsion in that stream for downstream recovery of the oil.

[0038] In an alternate embodiment shown in FIG. 4, the lipids and other light density fractions are separated from the mash (referred to in FIG. 4 as the corn flow stream) at separation unit 20 prior to fermentation to form the lipid stream and a mash stream. The mash stream is directed to the fermentation tank 22 as described above. Separation step 20 removes one or more nonfermentable components (i.e., oil) from the corn flow stream which, in turn, results in the increase of alcohol yield per volume within the fermentation vessel 22. Additional benefits to the removal of the lipid stream from the mash/corn flow stream include the reduction or elimination of downstream fouling of equipment, particularly within the evaporation units 34 wherein deposits of the lipid material within the piping system requiring shutdown and cleaning operations on a periodic basis. After separation from the mash/corn flow stream, the lipid stream is directed downstream where it is reintroduced into the process stream at step 46 as shown in FIG. 2. In this embodiment, the lipid stream is taken from the front end of the ethanol production process and reintroduced to the back end of the process.

[0039] Having thus described the invention in connection with the preferred embodiments thereof, it will be evident to those skilled in the art that various revisions can be made to the preferred embodiments described herein without departing from the spirit and scope of the invention. It is my intention, however, that all such revisions and modifications that are evident to those skilled in the art will be included within the scope of the following claims.