CA2601596A1 - Method of oil extraction, such as corn oil - Google Patents

Abstract

A low energy and low cost method for extracting oil from crushed grains, seeds, nuts, and legumes using a halogenated solvent. Brominated solvents are preferred. In a preferred embodiment, n-PB is used to extract corn oil from crushed corn kernels. Very little energy is used, both to extract the oil from the seed, nut or legume and to separate the oil from the solvent.

Description

METHOD OF OIL EXTRACTION, SUCH AS CORN OIL
FIELD OF THE DISCLOSURE
The present disclosure is directed to methods for extracting oil from grains, seeds, nuts, and legumes using an extraction process. More particularly, the present disclosure is directed to methods for extracting oil using a halogenated solvent. A
preferred inethod extracts corn oil from corn using a broininated solvent.
BACKGROUND
Extraction of oil from edible iteins, such as grains, seeds, nuts, and legumes, is coinmon. Often, the item having the oil is ground, cracked, milled or otherwise processed to increase its surface area. Oil is then extracted from the solid material using various methods.
One common method for extracting corn oil from corn is by using ethanol.
Prior to contact with the ethanol, the corn kenlels are crushed, flaked, milled, or otherwise modified into smaller pieces than the whole kernel. Etllanol is passed over, through, and otherwise around the corn pieces, and the oil leaclies fi=om the corn into the ethanol, where it is carried away from the reinaining corn solids. The oil is then recovered from the ethanol by a separation process. This process, however, can be costly, due to the high amounts of energy needed to separate the oil from the ethanol and obtain a usable oil.
Other techniques for extracting oils from edible items, particularly from corn, are known. There exists, however, a desire for continued advancement and alternate designs for extraction of oils from materials, such as corn.

SUMMARY OF THE DISCLOSURE
The present disclosure is to a method for extracting oil from edible iteins, such as grains, seeds, nuts, and legumes, using a solvent. The process is a low cost inetlZod, as very little energy is used, both to extract the oil from the seed, nut or leguine, and to separate the oil from the solvent.
This oil extraction process can be designed and configured to be coinbined with a complementary downstream processes.

I

The solvent used to extract the oil or other material from the solid (e.g., corn), is a halogenated solvent, such as a brominated solvent. In a preferred embodiment, n-propyl bromide (n-PB) is used to extract corn oil from crushed corn kernels or kernel parts, such as the germ.
The process of this invention is complementary with downstream processes of corn cooking, fermentation and distillation processes. When n-PB solvent is used, it is beneficial to combine the process of this disclosure with a downstream process that also uses n-PB.
These and various other features which characterize the methods of this disclosure are pointed out with particularity in the attached claims. For a better understanding of the methods of the disclosure, their advantages, their use and objectives obtained by their use, reference should be made to the drawings and to the accompanying description, in whiclz there is illustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRYING
FIG. 1 is a schematic, generic flow chart of an oil extraction process according to the present invention and related processes.
FIG. 2 is schematic, detailed flow chart of an exainple embodiment of an oil extraction process according to the present invention and related processes.

DETAILED DESCRIPTION
As provided above, the present invention is directed to methods for extracting oil from edible items, such as grains, seeds, nuts, and legumes, using a solvent. The solvent is a halogenated solvent, and in some einbodiments, the solvent is a brominated solvent or a bromide.
The following discussion is specifically directed to the extraction of corn oil from corn, although it should be understood that the invention could be used to extract oil from any other seed, legume or nut. Additionally, in the following discussion, the solvent used is n-PB, (n-propyl bromide or 1-broino-propane), although it should be understood that the method could be used with other halogenated solvents. It has been found that n-PB, and all halogenated solvents, in general, solubilize oil very well.

The value of the process can be easily and quantitatively calculated. The value of the oil obtained should be higher than the cost of extraction, recovering the oil, and recovering or disposing of the solvent used. The present invention readily recovers the n-PB or other solvent for reuse, provides a clean crude corn oil for further processing, and provides clean corn flour for further processing, at a cost effective level. A generic process for extracting corn oil from corn particles and the related processes of separating out the corn oil and drying the corn solids are diagramed in FIG. 1.

Preparation of the Corn Particles When corn is received by the processing facility, the corn is generally present as whole kernels. The corn kernels are screened to remove dirt, dust, mud and other foreign iteins, after which the kernels are washed with water to remove any remaining dirt, dust, and other materials stuck on the kernels. The majority of the water is drained or removed from the kernels, for example, by screening, decanting, filtering, or other known methods. After removal of the majority of the water, the kei7iels maybe further dried, such as by the application of heat, to remove the remaining water. Typically, however, any heating of the corn kernels is undesired witll the present invention, thus, any heating is preferably kept to a minimum or avoided. The washed corn typically has a moisture content of approximately 15%; it is not necessary to remove or reduce this moisture level.
Typically, corn has an oil content of about 1-4% in the washed or unwashed corn, although higher and lower levels of oil have been known for different varieties and hybrids of corn.
After washing and draining, the corn is reduced in size. The size reduction can be done by any of a number of methods, such as by using a hainmer mill, ball mill, ring crusher, rollers, and other known methods. A hammer mill is a preferred method of corn kernel size reduction. Ball mills are also suitable.
The resulting crushed particles (e.g., crushed corn kernels) have a range of sizes, typically between 100 microns and 1 mm, which are generally present in a bell curve distribution. Larger and smaller particulates will probably be present and are acceptable for the metliod of this invention. The crushed particles have a range of shapes, including blocky, jagged, irregular, flaky, and other possible shapes.

The size reduction of the corn not only decreases the size of the corn particles but also releases other components from the corn, components such as starcli, germ, and the husk. Although not needed, these various components could be removed from the corn kernel prior to subsequent processing. In the method of the present invention, it is preferred that all portions of the corn kernel remain together to obtain the highest possible oil yield.

Although not required, if not dried prior to size reduction, the crushed particles may now be dried, for example, by the application of heat.
Referring now to the figures, the crushed particles are passed into an extractor or an extraction process. See FIG. 1. Corn particles, also sometimes referred to as corn flour, flour feed, or the like, enter extractor 100 as stream 10, concurrently with solvent stream 20. It is in extractor 100 that corn particle streain 10 is combined with the halogenated solvent 20 and the oil present in the corn is extracted out from the corn solids and transferred to the solvent. Exiting extractor 100 is a solvent streain 30 that includes the extracted oil therein, and a corn solids stream 40 that may include some solvent wetting the solids. Solvent stream 30 may include some solid particles.

Entering extractor 100, as an example, is about 1,4001b/min (about 635 kg/min) of ground corn, which includes about 50-601bs (about 23-27 kg) of oil.

Oil Extraction Process The extraction process whicll occurs in extractor 100, to remove the corn oil from the corn solids, may be accomplished by various known extraction equipment and metlzods of using that equipment. Examples of suitable methods include percolation extraction and submersion or immersion extraction.
In percolation extraction, the particles are generally stationary on a screen, mesh or similar structure, and solvent is repeatedly passed through or over the particles. The solvent may be recycled over the solids or fresh solvent may be used.
An example of a suitable percolation extractor for use with the present invention is available from Crown Iron Works of Minneapolis, MN under the designation Mode15. A percolation extractor may include a single stage or may have multiple stage througll which the solids progress. The solvent may move either counter-current or concuiTent with the particles.

In submersion or immersion extraction, the corn particles are combined with a solvent in a tank, and the solids are allowed to settle. The liquid is decanted, filtered, centrifuged or otherwise removed from solids. A submersion or immersion extractor may include a single tank or may have multiple tanks through which the solids progress. The solvent may move either counter-current against or concurrent with the particles. An example of a suitable submersion or immersion extractor is available from Crown Iron Works under the designation Mode14.
A third suitable extraction method for extracting corn oil from corn solids using a solvent, such as n-PB, is by using sequential extraction screens to extract the oil from the corn, as illustrated in FIG. 2 and described in detailed below.
One suitable extraction system having multiple sequential extraction mechanisms, and methods of extracting, are described in PCT Publication WO 2004/057255, which has the Applicant as Karges-Faulconbridge, Inc and the inventor as Robert Wills.
The sequential screen extraction method described by this PCT publication uses multiple, generally vertically oriented curved screens for contacting the solids with solvent in a counter-current process. The entire disclosure of WO 2004/057255 is incorporated herein by reference.
Other extraction or separation methods and equipment could be used, such as cyclonic separators and other screens and filters.
Referring to FIG. 2, a multiple extractor configuration is illustrated; in this system, four extraction systems are sequentially configured. This process diagramined in FIG. 2 is merely an example of a possible process and possible equipment; it is not intended to be limiting the scope of the present disclosure in any way.
Corn particle streain 10 is fed to mixing unit 101, where it is mixed with recycled solvent streain 34 (described below). This mixture, as stream 22, is fed to mechanical separator 102, where it is split into solvent stream 30 and wet solids streain 12. Wet solids streain 12 is fed into mixing unit 103 where it is mixed with recycled solvent stream 36 (described later). This mixture, as stream 24, is fed to mechanical separator 104, where it is split into solvent streain 34 and wet solids streain 14. Wet solids stream 14 is fed into mixing unit 105 where it is mixed with recycled solvent stream 38. This inixture, as stream 26, is fed to mechanical separator 106, where it is split into solvent stream 36 and wet solids stream 16. Still further, wet solids stream 16 is fed into mixing unit 107 where it is mixed with fresh solvent stream 20. This mixture, as stream 28, is fed to mechanical separator 108, where it is split into solvent stream 38 and wet solids stream 40.
In this process, solvent streams 34, 36, 38 are recycled and reused in the process, Streain 34 is recycled from separator 104 and fed into unit 101, stream 36 is recycled from separator 106 and fed into unit 103, and stream 38 is recycled from separator 108 and fed into unit 105. Fresh solvent stream 20, in this embodiinent, is the only incoming source of solvent.
As in the general system of FIG. 1, it is in units 101, 103, 105, 107 that corn particle stream 10 is combined witll solvent 20 and in separators 102, 104, 106, 108 that oil present in the corn is extracted out from the corn solids and transferred to the solvent. Stream 30, from unit 101, is referred to as a"fu11 miscella". In the embodiment illustrated in FIG. 2, because there are four units, each stream is allotted a fourth (i.e., 1/4) designation. Stream 34, from unit 103, is referred to as a "3/4 miscella", stream 36, from unit 105, is referred to as a "1/2 miscella"
and streain 38, from unit 107, is referred to as a "1/4 miscella". As the process progresses up-streazn (i.e., counter-cur-rent to the corn particles), the concentration of oil in each solvent streain increases. Full miscella stream 30 has a lower solvent concentration and a higher oil concentration than 3/4 miscella streain 34, which has a lower solvent concentration and a higher oil concentration than 1/2 miscella stream 36, which has a lower solvent concentration and a higher oil concentration than miscella streain 38.
From the extraction unit, i.e., units 101, 103, 105, 107 and multiple separators 102, 104, 106, 108, the overall exiting streams are solvent stream 30, having the oil therein, and wet solids stream 40 having the corn particles wetted with solvent. Some amount of solid particles may be present in solvent streain 30.
During the extraction process, the moisture in the corn particles may be extracted from the corn and be present as free water.
The method of the present invention is generally suitable for extracting at least 90% of the oil present in corn when using n-PB, often at least 95% of the oil.
The exact ainount of oil extracted from the corn will be a function of the time of solvent/coni contact, temperature, and solvent:corn ratio. Other solvents may provide different levels of oil extraction. The size of the corn particles may also affect the amount of oil extracted. Generally, as the amount of solvent used in the extraction process increases the percentage of the oil extracted increases;
however the overall process efficiency decreases, due to the energy needed in recovering the solvent downstream.
The n-PB, or the other halogenated (e.g., brominated) solvent to be used, is selected based on various parameters, including the cost of the solvent, its flammability, its toxicity, reactivity, viscosity, vapor pressure, and latent heat of vaporization. Examples of other halogenated solvents that may be suitable include fluorinated and chlorinated solvents. n-propyl bromide (also referred to as 1-bromopropane) is a preferred solvent. In some embodiments, it may be beneficial to use a combination of solvents.
When using any of the extraction methods described above, e.g., percolation extraction, submersion or immersion extraction, cyclonic separators, etc., a solvent ratio (i.e., solvent to solids) of about 0.5:1 to 4:1 is typically used. A
preferred ratio, for n-PB to corn, is about 1:1 to 2:1, having more solvent present than corn.
It understood that wllen extracting oil from other materials, such as soy beans, other ratios maybe used; such as, 0.9:1 for solvent:soybeans.
Long chain molecules, often referred to as color bodies, will be extracted from the corn together with the oil. The n-PB will pull out most color bodies from the corn and extract thein with the oil. The amount of color bodies removed will depend on the nature of the color body and the properties of the n-PB (e.g., temperature of the n-PB).
To this point of the process, i.e., extraction the oil from the corn, no thermal energy has been added to the process. Some thermal energy may have been used to dry the corn either before or after crushing, but prior to the extraction process. It may be desired to increase the temperature of the solvent, for example, to just below its boiling point, during the extraction. For n-PB, the desired range would be approximately 120-140 F (about 49-60 C). It is theorized that as the teinperature increases, the viscosity of the oil extracted will decrease, thus allowing easier extraction from the corn solid.
From the extractor, two streams are obtained (see FIG. 1), wet solids stream which includes the conl solids saturated with solvent, and liquid stream 30 which has solvent and oil (including the color bodies) and may include some solids.
Any water present or extracted during the extraction step is typically present in solids stream 40.

Drying of the Solids Solids stream 40, wet with n-PB or other solvent, and any water that might be present, is directed to a drying system 300. As described below, wet solids stream 40 may be combined with a second stream prior to drying. In drying system 300, the liquid remaining with the corn solids is vaporized or otherwise removed.
This drying may be done by various methods. Various preferred methods and equipment are described in PCT Publication WO 2004/057255. Example the suitable driers include continuous and batch driers, and include convection ovens, tube driers, tray driers, rotary driers, belt driers, and down-draft desolventizers. It is understood that other drying methods maybe used to remove the solvent from the corn solids at drying system 300.

Further, additional or alternate drying could be obtained by sparging the corn solids with an agent such as air, inert gasses, or steain (either dry steam or wet steain) to remove solvent from the corn solid surface. An example of preferred equipment for drying corn solids is a drier from Wyssmont of Fort Lee, NJ that uses a hot sparge agent.
The dried corn particles exit drying system 300 as corn flour streain 75. In one example, the corn solids 75 emerge from drying process 300 having about 1 to 2% moisture.

During the drying and any sparging process, it is desired to maintain the teinperature fairly low. By not heating the corn solids to too high a temperature, the protein in the corn reinains intact (i.e., it does not denature) and the sugars remain intact. Such solids are more desirable than those that have been denatured.
The dried solids emerge drying system 300 possibly without the saine shape and size as prior to the extraction processes. In soine embodiments, the corn particles may have to be reground. See, for example, FIG. 2 wherein the corn particles are ground at mi11350 to obtain corn flour streatn 75. Corn stream 75 is a suitable feed for many dowiistream processes, such as an ethanol ferinentation process.

The subsequent ethanol processing may be any known cooking, fermentation and distillation process. The cooking may be eitller a conventional "hot cook"
process or a newly developing "cold cook" process, which incorporates the use of enzymes.

The solvents reinoved from the solids at drying system 300, typically by heating the corn solids to above the boiling point of the solvent, e.g., n-PB.
The solvent boils off and the vapors are condensed, as stream 85. The solvent is reclaimed and can be reused in the extraction process.

Separation of Solvent from Oil In liquid streain 30 from the extraction process (see either FIG. 1 or FIG.
2), the oil and solvent, e.g., n-PB, are present generally as a solution; that is, the oil is at least partially dissolved in the n-PB. This stream 30 generally includes some amount of small corn material therein, typically in the order of about 200 microns less. This solid material is typically referred to as "fines". The n-PB and oil is generally present as a miscella with any fines suspended therein.
Preferably, prior to separating the oil from the solvent, the fines are removed in separator 200. Liquid streain 30 enters separator 200 and wet fines 50 and solvent/oil stream 60 exit separator 200. The separation of the fines from the liquid can be done by any suitable separation method, such as by membrane filtration, bag filtration, centrif-ugation, flash drier, ring drier, or by settling. A
hydroclone is a preferred method for removing fines from the solvent/oil miscella.
The wet fines 50 are combined with wet corn solids stream 40 from separator unit 108 to form wet corn solids stream 45. Solids stream 45, wet with solvent, enters drying system 300 where, as described above, the liquid reinaining with the corn solids is vaporized or otherwise reinoved.
After removal of the fines from liquid stream 30 at separator 200, the resulting miscella stream 60 is relatively free of solids. It has been found when an n-PB:corn ratio of approximately 1:1 - 2:1 is used, the miscella is approximately 1 to 2% oil. This miscella streain 60 is then fed to a liquid separator 250, such as a distillation coluinn, an evaporator, or other separator to separate the oil from the solvent. The evaporator could be a falling film evaporator or a rising film evaporator. The separation may be done at atmospheric conditions or under a vacuum.

During the separation process at separator 250, miscella stream 60 is typically heated to above the boiling point of the solvent, e.g., n-PB. The solvent boils off and the vapors are condensed, as stream 80. FIGS. I and 2 illustrate energy, such as heat, such as from steam, entering separator 250.
The separated solvent is reclaimed and can be reused in the extraction process. Stream 80, together with stream 85, provides that essentially all the solvent that is fed into the process, via stream 20, is reclaimed from the process.
Crude corn oil is also reclaimed from the liquid-liquid separation process as oil stream 70. For exainple, from an initial corn feed of 1,400 lb/min (about kg/min), which has about 50-601bs oil initially (about 23-27 kg), approximately 45-57 lbs (about 20-26 kg) of crude corn oil is obtained. The amount of oil obtained is dependent on the extraction efficiency, but typically the amount of oil obtained will be at least 80%, preferably at least 90%, and most preferably at least 95% of the oil initially present in the corn.

Summary One skilled in the art will realize, upon reading and understanding the discussion herein, that the process of the present invention is a low energy and low cost process for extraction of corn oil from corn, using a halogenated solvent such as n-PB. Very little energy is used, both to extract the oil from the corn and to separate the oil from the solvent.
This corn oil extraction process can be designed and configured to be combined with a complementary process downstream of the cooking, fermentation and distillation processes. Preferably, the solvent used for the oil extraction is the same as solvent used in a downstream process. For example, when n-PB is used, it would be beneficial to coinbine this process with a downstream process that also uses n-PB. The solids-drying process described in WO 2004/057255 is a preferred downstreain process with which to coinbine this described process. Those skilled in the art will understand that this process of the present disclosure can be coinbined with otlZer coinpleinentary processes.

The foregoing description, which has been disclosed by way of the above discussion and the drawings, addresses embodiments of the present disclosure encompassing the principles of the present invention. The methods maybe changed, modified and/or implemented using various types of equipment and arrangements.
Those skilled in the art will readily recognize various modifications and changes which maybe made to the described methods and equipment without strictly following the exemplary embodiments illustrated and described herein, and without departing from the scope of the present invention.

Claims (14)

1. A method of extracting oil from corn, the method comprising:
(a) providing corn particles;
(b) contacting the corn particles with halogenated solvent;
(c) extracting oil from the corn particles via the solvent;
(d) separating the corn particles from the solvent;
(e) drying the corn particles; and (f) separating the oil from the solvent.

2. The method of claim 1, wherein the step of providing corn particles comprises:
(a) providing corn particles by crushing corn kernels with hammer mill, ball mill, ring crusher, or rollers.

3. The method of any of the previous claims, wherein the step extracting oil from the corn particles comprises:
(a) extracting oil from the corn particles using percolation extraction or submersion or immersion extraction.

4. The method of claim 3, wherein the extraction is a multi-stage percolation extraction or submersion or immersion extraction.

5. The method of claim 4, wherein the multi-stage percolation extraction or submersion or immersion extraction has counter-current solvent flow.

6. The method of claims 1-2, wherein the step extracting oil from the corn particles comprises:
(a) extracting oil from the corn particles using at least one generally vertically curved screen.

7. The method of any of the previous claims, wherein the step of extracting oil from the corn particles via the solvent comprises:

(a) extracting oil and color bodies from the corn particles via the solvent.

8. The method of any of the previous claims, wherein the step of separating the corn particles from the solvent comprises:
(a) drying the corn particles to vaporize the solvent.

9. The method of claim 8, wherein after the step of drying the corn particles, de-oiled corn particles or flour is obtained.

10. The method of any of the previous claims, wherein the halogenated solvent is a brominated solvent.

11. The method of any of the previous claims, wherein the halogenated solvent is n-PB.

12. The method of any of the previous claims, having a final step of obtaining crude corn oil.

13. The method of any of the previous claims, wherein essentially all the solvent that is fed into the process is reclaimed from the process, and wherein the reclaimed solvent is recycled into the process.

14. The method of any of the previous claims, wherein the method is done upstream of any of ethanol cooking, fermentation and distillation processes.