WO2001066270A1

WO2001066270A1 - Method and apparatus for processing eggshells

Info

Publication number: WO2001066270A1
Application number: PCT/US2001/006720
Authority: WO
Inventors: Harlan Hemple
Original assignee: Ovogen, Llc
Priority date: 2000-03-03
Filing date: 2001-03-02
Publication date: 2001-09-13
Also published as: AU2001241931A1

Abstract

A method of processing eggshells (Figure 1) by contacting interrupted eggshells material with a current of gas, wherein at least a portion of the eggshell membranes float in the gas current, thereby separating the eggshell membranes from the eggshells. Also provided is an apparatus processing eggshells, which includes: means for contacting interrupted eggshell material with a current of gas, and means for collecting eggshell membranes separated from the interrupted eggshell material by a current of gas.

Description

Method and Apparatus for Processing Eggshells

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method and apparatus for processing eggshells.

Description of the Background

The broken eggshell waste produced during the preparation of processed egg products is an extremely valuable material. The waste contains, in addition to the eggshells themselves, eggshell membranes. Eggshell membranes contain collagen, which is extremely valuable in the fields of dermatology and cosmetology. Eggshells, after separation from the egg and eggshell membrane, consists essentially of calcium carbonate. Calcium carbonate is useful as, for example, an inorganic filler material in a variety of applications.

By processing eggshell waste, one can isolate the eggshell membranes, the eggshells, or both. Since the eggshell waste would otherwise be disposed of, processing the waste and selling isolated membranes and eggshells will dramatically improve the economics of producing processed egg products.

Methods of processing eggshell waste are known, but suffer from significant disadvantages. MacNeil et al. WO 98/41326 describe a process in which the interrupted eggshells are placed into a tank of water, where the lighter membranes float on the top of the water while the heavier eggshells remain at the bottom of the tank. However, this method suffers from the drawbacks that include:

(1) The need for multiple "refining tanks" to achieve a higher purity of calcium carbonate than is possible with just one separation tank. Such tanks would not only increase system size and cost considerably, they would also require the use of large amounts of water (liquid). This increase in effluent may not be cost effective for some companies.

(2) Production of "wet-only" membrane material. Because all membrane produced using the MacNeil et al method is wet, further processing would be required to dry a portion - or all - of this material for currently known applications.

Accordingly, there remains a need for methods of processing eggshell waste which overcomes these difficulties.

SUMMARY OF THE INVENTION The present invention is based on the discovery that eggshell membranes can be separated from eggshells by contacting interrupted eggshells, i.e., eggshell membranes and eggshells in which the binds of the eggshells that hold the membranes to the shells, with a gas current. Since the membranes are much lighter than the shells, as the gas contacts the interrupted eggshells the membranes float in the gas current while the shells do not. As a result, the membranes are separated from the shells.

Accordingly, the present invention provides a method of processing eggshells comprising: contacting interrupted eggshells with a current of gas, wherein at least a portion of the eggshell membranes float in the current of gas while the eggshells do not, thereby separating the eggshell membranes from the eggshells.

After contact with the current of gas, the separated eggshell membranes can be isolated and, if desired, further processed. In addition, the remaining eggshells can be further processed as well. A significa t advantage of the claimed a method is that both the separated membranes and the eggshells can be recovered and sold as is or further processed, with significant economic benefit.

The present invention also provides an apparatus for processing eggshells, comprising: means for contacting interrupted eggshell material with a current of gas, and means for collecting eggshell membranes separated from the interrupted eggshell material by a current of gas and/or means for collecting eggshells separated from eggshell membranes.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Figure 1: an embodiment of an apparatus for processing eggshells according to the present invention;

Figure 2: another embodiment of an apparatus for processing eggshells according to the present invention; and

Figure 3: detailed view of a portion of the apparatus shown in Figure 2.

Figure 4: a flow diagram a preferred embodiment of the present invention.

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method of processing eggshells. Throughout the present disclosure, the term "eggshells" refers to the material remaining after the shell of a whole egg has been broken and the contents inside, i.e., the egg yolk and egg whites, have been removed. Thus, one skilled in the art will readily appreciate that the methods described herein do not use whole, unbroken eggs as the substrate for contacting with the current of gas. Whole eggs are, of course, the ultimate starting material for the methods described herein, but the contents of the eggs will have been removed prior to contact with the current of gas.

A wide variety of eggshell starting materials may be used herein. The eggs may be unfertilized eggs or hatchery eggs. The eggs may produced by a variety of different animals, e.g., chickens, ducks, etc.

Prior to contacting the gas current, the binds that hold the eggshell membranes to the eggshells should be interrupted. Interrupting the binds facilitates the removal of the membranes from the shells by the gas current. Interrupting the binds may be accomplished by any of the apparatuses and procedures known in the art for this purpose. For example, a particularly preferred interrupting device is the COMITROL available from Urschel Laboratories, Inc. The head size used may vary depending on the consistency of the shell produced in a given facility. Generally accepted head sizes range from 100 to 350 thousandths of an inch.

In some instances, passing the broken eggshells through one treatment with the Urschel Comitrol as described above is not wholly effective at producing a food-grade calcium carbonate product. In a preferred embodiment, passing the material through two consecutive comitrol units provides significant improvement in the interruption of the shell and membrane. Optionally, the head sizes of the units can be varied to increase interruption. By way of example: the first comitrol may have a head size of 270 thousandths of an inch. The second comitrol may have a head size of 180 thousandths of an inch. This forces the material to pass through two heads, with contact likely in each particular head. Studies have revealed that the head sizes can be varied, but best results are gained by using either equal sized heads, or a larger head followed by a smaller head. Another preferred method uses a different Urschel Comitrol machine operating at higher RPMs (nearer to 10,000 RPM). This machine utilizes a microcut head which produces a smaller calcium particle size while retaining the membrane at a larger size. Such a machine produces a uniform calcium particle which is easier to separate from the membrane given the size and density differences. The machine requires higher operating speeds to prevent the cutting head from clogging with material.

If desired, the interrupted eggshell material may be treated to separate the membranes and shells on the basis of density. Since the shells have a much higher density, they tend to fall faster in liquid as compared to the membranes. This first stage separation may be accomplished by feeding the interrupted shells and membranes into a liquid separation tank. As will be readily appreciated, this density separation does not isolate all of the membranes from the shells. It does, however, provide a vehicle for washing any remaining egg material off of the shells and membranes. This egg material acts like a glue, and prevents effective separation. By removing this material with water, more effective later-stage separation is made possible. During this washing, it is preferable to agitate the interrupted eggshell material in the liquid separation tank in order to maximize contact between the washing liquid and the interrupted eggshell material. Such agitation may be provided by, for example, a boom at the bottom of the liquid separation tank. An example of a liquid treatment which may be used in the present invention is described by MacNeil et al. WO 98/41326, incorporated herein by reference.

The liquid used for this washing step is preferably water. The water may, if desired, contain appropriate buffer agents and/or other additives, such as any of the well-known defoaming agents used in processing eggshells and salt, which increases the buoyancy of the water so that the membranes float more effectively. Care must be taken to avoid harsh chemicals which may break down certain constituents in the membrane, if those constituents are to be recovered for certain applications. Additionally, treatment with certain chemicals will disallow labeling either the calcium carbonate shell or the protein membrane as "natural products." As such, care should be taken in the selection of chemicals.

The liquid (e.g., water) for washing the interrupted eggshell material may be used over a wide temperature range, such that the water is above the point of freezing and below the boiling point. Specific temperatures include 10, 25, 35, 50, 60, 70, 80, 90 and 95 °C.

The washing step may be conducted for any appropriate length of time. Suitable times periods include 1 second to 10 minutes. This range includes all specific values therebetween, such as 5, 10, and 30 seconds, 1, 2, and 8 minutes.

As described above, during this optional washing step, a portion of the membranes may become suspended in the washing liquid. If desired, this membrane portion may be isolated, for example, by filtering the washing solution. The isolated membrane may be dried, if desired. The filtered washing liquid may then be recycled to the liquid separation tank. The amount of membranes that remain associated with the eggshells and are then contacted with the gas current generally ranges from 30 to 80%. However, this value may vary from 1 to 99% depending on the conditions of the washing and/or the nature of the eggs that are processed. These ranges include all specific value and subranges therebetween, such as 2, 5, 10, 25, 35, 50, 65, 75, 80, 85, 90, 95, 97 and 98%. Accordingly, the portion of membranes present in the original interrupted material that remain after the liquid treatment may range from 99 to 1%, more preferable form 70 to 20%.

If desired, the interrupted eggshell material may be treated to separate the membranes and shells on the basis of density via vibration. Since the shells have a much higher bulk density, they tend to accumulate beneath the membranes when the interrupted eggshell material is subjected to vibration. A vibratory hopper is particularly preferred to accomplishing this separation. However, this vibratory treatment of the interrupted eggshell material is completely optional in the present invention.

Alternatively, interrupted eggshell material may be treated to separate the membranes and shells using a centrifuge separator or decanter. These units perform separation using centrification in a wet stream of material. The two solids (calcium carbonate shell and membrane) have different densities and are spun to separate the materials according to the densities. Centrifuges also separate the water from the solid elements, allowing the water to be recovered and reused. Potential suppliers of this device include Westfalia and Tetra Pak.

Alternatively, interrupted eggshell material may be treated to separate the membranes and shells using a jig separator. This device is used to separate different density particles in mining operations, uses water to create a stream. The water stream moves the materials according to their densities.

Alternatively, interrupted eggshell material may be treated to separate the membranes and shells using a hydrocyclone. Similar to a jig separator, the hydrocyclone achieves using water what an air classifier achieves using air. Instead of an air stream, a water stream separates the materials according to density. Shell from the comitrol unit is fed into the hydrocyclone. The heavier shell falls to the bottom, while the lighter membrane is pumped out of the top with the bulk of the water. The water is recycled. The shell exits from the bottom of the unit and proceeds to one or more finishing hydrocyclones, where the process can be repeated until a desirable amount of membrane has been removed. Potential supplier of this device include Krebs Engineers.

Next, the interrupted eggshell material is contacted with a current of gas. During the contacting at least a portion of the eggshell membranes are carried into the gas current, i.e., the membranes float in the gas current, while the eggshells do not, since the membranes are so much lighter as compared to the shells. Without being bound to any theory, the gas current appears to remove water from the eggshell material, permitting the lightweight membranes to float into the gas current. As a result, the eggshell membranes which are carried into the current of gas are physically separated from the eggshells.

The chemical composition of the gas is not particularly limited. For simplicity and cost, air is the preferred gas. However, other gases, such as nitrogen-air mixtures, could be used provided that components thereof do not adversely affect the eggshells or membranes.

The gas may be used at ambient temperature, i.e., without heating with an external heat source. Alternatively, the gas may be heated to a temperature that is above the ambient temperature in order to facilitate removing water from the eggshells. The temperature of the gas may vary over a wide range. For example, the gas may be used at a temperature of 100°C. This would aid in destroying harmful bacteria such as salmonella enteritis, while not discoloring the shell with too much heat. A preferred temperature range for the gas is 15 to 50°C. Thus, the gas may be used a temperature ranging from, for example, 10 to 120°C, inclusive of all specific values and subranges therebetween, such as 20, 25, 30, 50, 60, 75, 80, 90 and 95 °C. Preferably, the gas does not heat the eggshells above a temperature of 220 °F, although the gas may have a higher temperature. Above 220 °F, the eggshells may turn an undesirable brown color.

The eggshell material may be contacted with the current of gas in a variety of different ways. For example, the gas may be allowed to flow across the outer exposed surface of the eggshell material. In a more preferred embodiment, the eggshell material is placed on a holding device which allows the gas current to flow through the material. In other words, the current is applied to the bottom of the device and then the gas flows through the material. An example of such a device is a metal screen with openings through which the gas can flow.

The contacting with the current of gas may be conducted in a single step. Alternatively, multiple steps (stages) may be used. For example, in a first stage the eggshell material may be dried to a moisture level of 10-15%. Then, in a second stage, the material may be dried to an even lower moisture level, e.g., 1% or below moisture.

Since the membranes are much lighter than the eggshells, at least a portion of the membranes "float" into the gas current and are carried away from the remaining eggshell mass. In this way, the membranes are physically separated from the eggshells. The membrane which floats into the gas current may be collected in a containment device. The containment device may be a baghouse, a cyclone, a drum (e.g., 55 gallon type), bag, box, or any other device known to those skilled in the art.

After contact with the gas, the remaining eggshell material, which may still contain eggshell membranes, may be cooled in order to reduce the temperature of the material. This procedure reduces the amount of water condensation during further downstream processing.

Optionally, the remaining eggshell mass may be further processed in order to remove membranes which were not removed by the gas current. This processing step may be conducted in, for example, an air classifier. Membranes removed from the eggshells at this stage may be placed into the membrane containment device described above.

The remaining eggshells, which now contain little, if any, membranes, are now essentially pure calcium carbonate. The purity of the eggshells may be such that they are at least 95%, preferably at least 97%, more preferably at least 98% pure calcium carbonate . If the eggshells at this stage have not been dried to low moisture (e.g., 1% moisture) and/or pasteurized, they may be so treated at this stage. If desired, the shells may be ground to any desired size using methods well-known to those skilled in the art. An example of a suitable size range is 0.5 to 50 microns.

The membranes may be removed from the containment device described above. The membranes may be packaged for shipment. Alternatively, the membranes may be further processed. Example of further membrane processing include fermentation, treatment with chemicals, homogenization, etc.

The present invention also provides an apparatus for processing eggshells according to the process described above. The apparatus includes means for contacting interrupted eggshell material with a current of gas, and means for collecting eggshell membranes separated from the interrupted eggshell material by a current of gas. In one embodiment, the apparatus also includes means for interrupting the binds of eggshells holding eggshell membranes to eggshells. In another embodiment, the apparatus includes means for collecting eggshells separated from eggshell membranes. In another embodiment, the apparatus contains means for liquid washing the interrupted eggshell material prior to contacting with the current of gas.

Referring to Figure 1, the process of the present invention may be more specifically illustrated by the apparatus pictured therein. Interrupted eggshells are stored in a product storage hopper and fed via a vibrating feeder to a fluid bed dryer/cooler. The dryer/cooler in equipped with an exhaust manifold into which membranes float in the direction indicated by the arrow. The gas current is supplied to the dryer/cooler via an air inlet manifold. After being contacted with the gas current, the remaining eggshells are transported in the direction shown by the arrow to an air classifier. Separated membranes from the exhaust manifold and the air classifier are collected in a baghouse. After passage through the air classifier the remaining eggshells are transported to a baghouse for packaging.

Figure 2 shows another embodiment of an apparatus that may be used to accomplish the present process. The apparatus shown in Figure 2 includes all of the components shown in Figure 1 and also includes a liquid separation tank. The liquid wash tank may be, for example, a standard hydrocyclone. The liquid wash tank may be equipped with a dewatering auger for removing the eggshells (e.g., SOM-A-PRESS auger). The dewatering auger may be equipped with a dewatering screw conveyor, which allows the moisture level to be reduced prior to entering the feeder and fluid bed dryer. A detailed view of the apparatus shown in Figure 2 is provided in Figure 3.

EXAMPLES Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.

1. Raw eggshell waste (consisting of calcium carbonate shell and attached protein membrane) is fed into a device which interrupts the binds holding the membrane to the calcium shell. Such a device is exemplified by the Urschel Comitrol.

2. Separated shells and membranes ("interrupted material") exit the interruption unit mingled together. Due to remaining moisture and egg albumen, the shells and membranes tend to cling together at this stage.

3. The interrupted material is fed by gravity or screw conveyor into a fluid-separation tank (ref. MacNeil et al) or separation device, which aids in separating the material due to contrasting densities of the shells and membranes. (The calcium shell has a much higher density than the membrane, and tends to fall faster than the membrane with introduced to a liquid.) The fluid separation tank contains an agitation device to aid in separating the membranes from the shells, providing a first stage separation by density.

4. The remaining interrupted material of the shell stream (that shell and membrane material which has not been collected during the fluid separation stage) is fed into a fluid bed dryer and subjected to heat sufficient to dry the material to between 10% and 15% moisture. (The material should be relatively dry to touch, with little or no surface water evident.) The fluid bed dryer consists of several chambers, with the operation of each outlined below: a) In the first chamber, the material is dried to the above-stated moisture levels. Hot air is fed through a horizontal screen over which the interrupted material passes, causing the material to "fluidize" (act like water in that it floats through the chamber). As the material dries, the lighter membrane material will float higher in the chamber and be pulled out with the air entering below. This material will be collected in a baghouse, cyclone, or other containment device, allowing the air to return to the first chamber of the fluid bed dryer. b) In the second chamber, the remaining interrupted material is subjected to higher heat levels that will reduce the moisture levels to below 1%. As in the first chamber, lighter membranes which are pulled out of the fluid bed dryer will be captured in a containment device. c) In the third chamber, cold air is placed in contact with the material to reduce the heat of the product(s). This will prevent condensation during packaging of the shell and/or membrane. Note that this stage can also be done in the subsequent conveying stage, in which the material is either subjected to cold air or is placed in contact with cold surface(s). As in the previous stage(s), any remaining membranes may be removed from the product stream and collected in the above-mentioned collection device(s).

5. Optionally, the remaining interrupted material will exit the fluid bed dryer and be conveyed (either pneumatically, by mechanical means, or using gravity) to an air classifier. The classifier will remove any remaining membrane from the shell using the dissimilar bulk densities of the materials to aid in classification. The membrane will be removed from the classifier and placed into the membrane containment device(s) mentioned above, and the shells will exit the classifier.

6. The shells, which have previously been dried (less than 1% moisture), pasteurized (utilizing heat from the drying process), and are protein-free, are now considered to be a purer form calcium carbonate. The process will have removed sufficient and other extraneous matter to render the shells 98% calcium carbonate. The shells are conveyed to a comminution mill to reduce the particle size to an appropriate level. A typical grinding mill would be an air-jet mill, a slow compression grinding mill, a wheel classifier mill, or any other device capable of rendering the product into smaller pieces. Typically, final particle sizes desired would be between 0.5 and 50 microns in size.

7. The powdered calcium carbonate will exit the grinding device and be conveyed (either pneumatically, by mechanical means, or using gravity) to an appropriate packaging device. Such a device might necessitate a baghouse or cyclone to store the powdered calcium carbonate.

8. Membrane may be recovered directly from its respective containment device for packaging or further processing.

The system as described above utilizes a three stage classification separation process: initial vibratory hopper to free up material, fluid bed dryer separation, and air classification.

Because eggshell quality and uniformity vary from egg processing plant to egg processing plant, the system may be modified as needed. Typical modifications might include: a) Use of fluid bed system only for separation. Smaller, more consistent membrane size will allow maximum separation to occur in the fluid bed dryer. b) Use of varying particle reduction systems. Classification mills, roller mills, hammermills, etc. all produce differing sizes of shell calcium carbonate. Desired reduction equipment may vary depending on the final application for the calcium carbonate. The system described in the attached drawings utilizes a READCO slow compression continuous mixer, which is one particular particle reduction alternative. c) Depending on the application of the membrane, the fluid bed dryer may consist of differing numbers of chambers ("stages" or "zones"). If the end-product membrane can be heat treated and still retain functionality, then a two zone fluid bed dryer will be effective (in which the first zone contains air heated sufficiently to pasteurize both the shell and membrane, and the second zone consists of cold air to reduce the output temperature of the product). If the end-product use for the membrane will dictate a heat- free process (i.e. if the heat were to denature certain sought-after proteins), then a three-stage fluid bed process would be needed (as described in 4 a-c, above). Note that a single heated zone fluid bed dryer may also perform the necessary function, as long as the product is later cooled prior to packaging or bulk storage (refer to 4c, above, for other means of cooling the product). d) An particularly preferred system would include:

1) Urschel comitrol to interrupt the binds of the shell and membrane

2) Two zone fluid bed dryer - zone 1 consisting of hot air to effect drying to less than 1% moisture and separate membrane, zone 2 consisting of cool air to reduce the output temperature of the product.

3) Air conveying system, which transports the membrane to its baghouse.

4) Air conveying system, which transports the calcium carbonate shell to a fine grinding/particle reduction device and then onward to a bulk storage device (silo, baghouse, etc).

5) An air classifier mill, to reduce the calcium carbonate shell down to a powder (preferably 1-20 microns in size).

6) A packaging system which would allow boxes, drums, bags, and/or bulk containers to be filled.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Claims

CLAIMS:

1. A method of processing eggshells, comprising: contacting an interrupted eggshell material with a current of gas, wherein at least a portion of the eggshell membranes float in the gas current, thereby separating the eggshell membranes from the eggshells.

2. The method of Claim 1, wherein the interrupted eggshell material is produced by interrupting the binds of eggshells holding the eggshell membranes to the eggshells.

3. The method of Claim 1, further comprising isolating the eggshell membranes separated from the eggshells.

4. The method of Claim 1, further comprising isolating the eggshells separated from the eggshell membranes.

5. The method of Claim 1, further comprising: isolating the eggshell membranes separated from the eggshells; and isolating the eggshells separated from the eggshell membranes.

6. The method of Claim 1, wherein the gas has a temperature of 10 to 100°C.

7. The method of Claim 1, wherein the gas has a temperature of 15 to 50°C.

8. The method of Claim 1, wherein the gas removes water from the interrupted eggshells.

9. The method of Claim 1, wherein prior to said contacting the interrupted eggshell material is washed with a liquid.

10. The method of Claim 9, wherein the liquid is water.

11. The method of Claim 9, wherein a portion of the membranes become suspended in the liquid.

12. The method of Claim 11, further comprising isolating the membranes suspended in the liquid.

13. An apparatus for processing eggshells, comprising: means for contacting interrupted eggshell material with a current of gas, and means for collecting eggshell membranes separated from the interrupted eggshell material by a current of gas.

14. The apparatus of Claim 13, further comprising means for interrupting the binds of eggshells holding eggshell membranes to eggshells.

15. The apparatus of Claim 13, further comprising means for collecting eggshells separated from eggshell membranes.

16. The apparatus of Claim 13, further comprising means for contacting interrupted eggshell material with a liquid.