Two staged toothed roller apparatus for increased recovery of oil from lemons and other citrus fruit using desporption

Abstract

A two stage system for extraction of oil from whole citrus fruit is provided. The first stage is known in the art and includes a first plurality of toothed rollers which convey citrus as the teeth penetrate and rupture oil glands. The oil passes into a first water pan. A novel second stage uses a second plurality of toothed rollers to continue the penetration and rupturing of oil glands. The second plurality of rollers are positioned in an isolated second pan to partially submerge the citrus. A middle phase liquor with extremely low oil concentration is transferred into said second pan to initiate desorption of oil from the citrus. The desorption technique in one embodiment increases yield by 4% or more. This technique is expected to increase yield even more as the recovery by the first stage is reduced.

Claims

1. A two stage apparatus for automatic extraction of oil from the peel of whole citrus fruit, comprising: a first stage in which a first plurality of parallel toothed rollers rotate around parallel axes of rotation, each of said first plurality of rollers having a plurality of teeth for penetrating oil glands of the peel of said citrus, first drive means for causing rotation of each of said first plurality of rollers in the same rotational direction to propel said citrus across said first plurality of rollers while penetrating said oil glands, a first water pan positioned below said first plurality of rollers to receive oil passing downwardly from said whole citrus to form an emulsion of water and citrus oil, a centrifuge or other separator for receiving said emulsion and separating oil from said emulsion, forming a middle phase liquor, a second stage in which a second plurality of toothed rollers rotate around parallel axes of rotation, each of said second plurality of rollers having a plurality of teeth for penetrating oil glands in the peel of said citrus, second drive means for causing rotation of each of said second plurality of rollers in the same rotational direction to propel said citrus across said second plurality of rollers while penetrating said oil glands, transfer means for transferring said citrus from said first plurality of rollers to second plurality of rollers, a second water pan positioned relative to said second plurality of rollers so that as citrus is propelled across said second plurality of rollers it is partially submerged in liquor in said water pan, pump means for transferring said middle phase liquor to said second water pan, whereby said citrus on said second plurality of rollers is at least partially submerged in said middle phase liquor to cause desorption of citrus oil into said middle phase liquor, and means for transferring said middle phase liquor with said desorbed citrus oil either into said first water pan, or into said centrifuge or other separator for recovery of oil.

2. The apparatus of claim 1 wherein said middle phase liquor has an oil concentration less than 0.55% by weight.

3. The apparatus of claim 1, wherein said middle phase liquor has an oil concentration less than 0.2% by weight.

4. The apparatus of claim 1, wherein said middle phase liquor flows through said second pan in a direction opposite from the direction of travel of said partially submerged citrus through said second pan.

5. The apparatus of claim 1 wherein the residence time of citrus on said first and second pluralities of rollers is increased by 30% or more, and the oil recovery is increased by at least 4% compared with the closest known prior art system.

6. The apparatus of claim 1 wherein the speed of said first and second pluralities of rollers is increased by 20% and achieves the same percentage of oil extraction compared with the closest known prior art system.

7. The apparatus of claim 1 wherein the residence time of citrus on said first and second pluralities of rollers is increased by less than 30% compared with the closest known prior art system, and wherein the speed of said first and second pluralities of rollers is increased by less than 20% compared with the closest known prior art system, and wherein the oil recovery is increased by less than 4% and throughput capacity is increased by less than 20%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic illustration of the preferred embodiment of the invention;

(2) FIG. 2 is a schematic illustration of the closest prior art known to applicants;

(3) FIG. 3 is a schematic illustration of a second embodiment of the invention; and

(4) FIG. 4 is a schematic illustration of a third embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) FIG. 1 illustrates the present invention, shown generally as 10. A first plurality of toothed rollers 20 is positioned above first pan 30. The rollers are horizontal, generally parallel and rotate about generally parallel axes 21. The toothed rollers are driven by means known in the art and have projections known in the art which penetrate the peel, and penetrate and rupture oil glands in the peel.

(6) Whole citrus fruit such as lemons 40a-40p are fed onto toothed rollers 20 at first end 31 of pan 30 and conveyed by rollers 20 in the direction of arrow 41 across pan 30 to second end 32 of pan 30. It is to be understood that only a small number of citrus is shown in FIG. 1 for clarity. Normally, in operation, all rollers are covered with citrus. Toothed rollers 20 have projections (not shown in FIG. 1 for clarity) which penetrate and rupture the oil glands and the peel of the citrus fruit to cause oil to drain downwardly into and is collected in pan 30. Pan 30 is filled with centrifuged water 34 through water input line 33. Rollers 20 are preferably submerged in water to cause the citrus to be partially submerged in water 34. Water 34 is caused to move by displacement of incoming water 33 for example in a direction shown by arrow 35, which is counter to the direction 41 of citrus 40a-40k. The water 34 and oil shown by dots 36 form an emulsion of citrus oil and water which flows over a weir 37 at the first end of pan 30. The emulsion is transported to a paddle finisher 47, or other filtering or screening devices, to remove and discard any large fruit debris 47a. The emulsion then flows to a tank 48 and delivered by a pump 49 to a centrifuge 50, which separates the extracted citrus oil 51.

(7) It is significant to note that the first plurality of toothed rollers extracts approximately 87% to 91% of the original oil from the citrus fruit in the case of normal lemons. The citrus items 40j and 40k have approximately 9% to 13% of their original oil as they reach the second end 32 of pan 30. It is also significant to note that centrifuge 50 removes about 98-99% of the citrus oil in the primary extraction stage, and discharges a middle phase liquor 134 that is water with most preferably a 0.05-0.15% concentration of oil by weight; preferably less than 0.2% and less than 0.55% concentration of oil by weight.

(8) The above items 20-41 comprise the first stage, or primary oil extraction, and is known in the art.

(9) The novel aspect of the invention is the second stage, or secondary oil extraction stage shown generally as 100.

(10) The secondary oil extraction system 100 includes a second plurality of toothed rollers 120 similar to rollers 20. Rollers 120 are driven by means known in the art and are positioned in a second pan 130 which causes citrus items 40m, 40n and 40p to be partially submerged in middle phase liquor 134, which is transferred from centrifuge 50 through buffer tank 55, positive rotary pump 56 and flow meter 57 and enters the second end 132 of pan 130. The liquor 134 is caused to move from the second end 132 of pan 130 to first end 131 in a direction counter to the direction of motion of citrus 40m, 40n and 40p shown by arrow 141. The liquor 134 is caused to move by the displacement of incoming liquor 134. The citrus is transferred from the first plurality of rollers 20 to the second plurality of rollers 120 by means known in the art.

(11) As the citrus items 40m, 40n and 40p move across second pan 130, they are partially submerged in liquor 134. Since the liquor 134 has a preferred oil concentration of between 0.05 and 0.15% by weight, and the citrus (in the case of normal lemons) has about 9% to 13% of its original oil remaining, desorption of oil from the citrus into the liquor 134 is initiated. We have found that about one half (or 50%) of the remaining oil or 4.5% to 6.5% of the original oil remaining in the citrus is extracted by the desorption phenomenon, whereas only about 0.5% or less of the original oil remaining in the citrus is recovered by the dryer 300 portion of the closest known prior art (FIG. 2). The present invention in this embodiment accordingly extracts 4% or more oil than the closest known prior art.

(12) We have found that as the amount of oil extracted in the primary extraction decreases, the amount of oil extracted by the novel secondary extraction increases. Although the primary extraction with lemons achieves 87% to 91% extraction of lemon oil, we know from experience that primary extraction of oil from oranges and grapefruit is significantly lower, in the range of 65% to 80%. We expect that the novel secondary extraction system will recover 10% more of the original oil than the closest known prior art when the primary extraction drops to 70% oil recovery. This is a tremendous improvement over the dryer of the closest known prior art, which only recovers about 0.5% or less of original oil, regardless of the type of citrus and condition of the citrus.

(13) It is significant to note that the desorption occurring in pan 130 is “isolated” from the rest of the system. It is isolated in the sense that pan 130 and the second plurality of rollers 120 are isolated, and the middle phase liquor 134, with its extremely low concentration of oil is the only liquid that flows through pan 130 and contacts the citrus to initiate desorption. This “isolation” maximizes the desorption of oil into middle phase liquor 134.

(14) The liquor 134 passes over weir 137 and is transferred through line 138 to a paddle finisher or other straining or filtering device 150 to remove fruit and other debris 151 prior to pump 139 transferring the liquor through line 33 into first pan 30. The oil desorbed into middle phase liquor 134 is ultimately returned through first pan 30 to centrifuge 50 to be separated and recovered. This minimizes the water used in the process.

(15) As shown in FIG. 3, an alternative to the series flow shown in FIG. 1 and described above is to split the flow of liquor 134 into two flowpaths 134a and 134b, which is referred to as parallel flow. Flowpath 134a enters second pan 130 and flowpath 134b enters first pan 30. In general series flow is preferred over parallel flow for the sake of reducing centrifuge capacity requirements.

(16) A final spray rinse is quickly applied by nozzle 160 as citrus 40p is discharged from rollers 120. Rinse water is collected and transferred to finisher or straining device 150 through line 161.

(17) It is significant to note that the embodiment shown in FIG. 1 utilizes twelve rollers in the second plurality of rollers 120. This number of rollers has a footprint equivalent to the prior art dryer 300 (FIG. 2) allowing this embodiment to be retrofitted to existing equipment. In the case where it is feasible to use a second plurality of rollers with a larger footprint, more than 12 rollers can be utilized.

(18) FIG. 2 represents the closest prior art system 210 known to applicants referred to herein and in the claims as the “closest known prior art.” A first plurality of toothed rollers 220 is positioned above pan 230 and transports citrus items 140a-140k in the direction of arrow 141 from the first end 231 to the second end 232 of pan 230. The toothed rollers penetrate the peels and oil glands of the citrus, causing oil to pass downwardly into pan 230. Water 234 from centrifuge 250 is transferred through line 233 into the second end 232 of pan 230. Water 234 is caused to move in the direction of arrow 235, which is counter to the direction 141 of citrus item 140a-140k. Water 234 forms an emulsion with oil extracted from the citrus. The emulsion passes over a weir 237 at the first end 231 of pan 230, and is then transferred through intermediary equipment including a paddle finisher 240 (which separates debris 245), buffer tank 241 and positive displacement or centrifugal pump 242 to centrifuge 250. Separated oil is transferred to oil storage 251. The centrifuged water emulsion is transferred to the second end 232 of pan 230 through buffer tank 255 and pump 256 and the process is repeated.

(19) As the citrus reaches the second end 232 of pan 230, a small amount of oil released from oil glands in the peel remains on the exterior surface of the citrus. This oil must be washed off the surface to avoid contaminating the citrus juice which is extracted later. The citrus is transferred by means known is the art from pan 230 to what is referred to in the art as a “dryer” 300. The purpose of dryer 300 is to essentially transfer oil from the outer surface of citrus to a second plurality of smooth rollers 320 by an overhead water spray 324, and then to wipe the oil off the surface of rollers 320 by wiper arms 360. The oil recovered forms an emulsion with water from overhead sprayer 320. That emulsion is transferred to centrifuge 250 and collected at oil storage 251. The dryer 300 does not submerge the citrus in a liquid bath and does not have toothed rollers which penetrate the oil glands in the peel of the citrus.

(20) FIG. 3 is a schematic illustration of a second embodiment of the invention. The only difference between this embodiment and that shown in FIG. 1 is that the middle phase liquor 134 is split into a first portion 134a which is transferred to second pan 130 and a second portion 134b which is transferred to first pan 30. This embodiment incorporates what we refer to as a “parallel” flow of middle liquor into both pans 30 and 130.

(21) FIG. 4 is a schematic illustration of a third embodiment of the invention. The only difference between this embodiment and that shown in FIG. 3 is that the water with desorbed oil 138 from second pan 130 is split into a first portion 138a which is transferred through separator 150 to first pan 30 and a second portion 138b which is transferred through separator 147 to centrifuge 50. This embodiment incorporated what we refer to as a “parallel” flow of not only the middle phase liquor 134, but also of the liquor 138 discharged from second pan 130 which includes the desorbed oil being split into a first portion 138a which is transferred to first pan 30 and a second portion 138b which is transferred to centrifuge 50.

(22) The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teaching. The embodiments were chosen and described to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best use the invention in various embodiments suited to the particular use contemplated.