US3607391A

US3607391A - Extraction

Info

Publication number: US3607391A
Application number: US806909A
Authority: US
Inventors: James Shann; David Vincent Bessant
Original assignee: Rose Downs and Thompson Ltd
Current assignee: Rose Downs and Thompson Ltd
Priority date: 1968-05-07
Filing date: 1969-03-13
Publication date: 1971-09-21
Anticipated expiration: 1988-09-21

Abstract

A method of, and apparatus for, extracting a soluble component of a soluble material, in which the material is introduced into a press and subjected to pressure and while that pressure is maintained on the material, a liquid solvent for the component is introduced into the press so as to pass through the material. In one variant of the invention the pressure on the material is increased after the liquid solvent has been added and in another variant the liquid solvent introduced into the press itself contains dissolved elements of the soluble component.

Description

United States Patent [72] Inventors James Shann Hull; David Vincent Beasant, South Cave, both of England [21] Appl. No. 806,909

[22] Filed Mar. 13, 1969 [45] Patented Sept. 21, 1971 [73] Assignee Rose, Downs & Thompson 'rnited Kingston-upon-l-lull, Yorkshire, England [32] Priority May 7, 1968, Aug. 2, 1968 [33] Great Britain [31 21526/68 and 36942/68 [54] EXTRACTION 5 Claims, 5 Drawing Figs.

[52] [1.8. CI 127/7, 23/270, 100/74, 127/6, 127/43, 127/44 [51] Int. Cl. C13d1/12, C13d1/10,C13d 1/04 [50] Field of Search 127/2-8,

[56] References Cited UNITED STATES PATENTS 1,015,371 1/1912 Wolfe 100/72 1,3 46,594 7/1920 Deerr 100/75 2,063,367 12/1936 De La Roza... 100/73 X 3,005,398 l0/l96l Sandler 23/270 X 3,037,445 6/1962 Burner et al. 100/72 X 3,111,080 11/1963 French etal 100/73 X 3,181,454 5/1965 Ginaven et al 100/74 Primary ExaminerMorris 0. Walk Assistant Examiner-D. G. Conlin Attorney-Holcombe, Wetherill & Brisebois ABSTRACT: A method of, and apparatus for. extracting a soluble component of a soluble material, in which the material is introduced into a press and subjected to pressure and while that pressure is maintained on the material, a liquid solvent for the component is introduced into the press so as to pass through the material. In one variant of the invention the pressure on the material is increased aft-er the liquid solvent has been added and in another variant the liquid solvent introduced into the press itself contains dissolved elements of the soluble component.

" PATENTE'U sEP21 1911 3,607; 391

SHEET 1 UP 2 l l l I 'l FIG. 4

INVENTOR ATTORNEY PATENTEU SEPZI I97! 350?, 391

SHEET 2 BF 2 INVENTOR ATTORNEY EXTRACTION This invention relates to the extraction of soluble components from solid materials and is particularly, but not exclusively, concerned with the extraction of sugar from sugarbearing materials, such as sugar cane and derivatives of sugar cane.

At present it is customary to pass sugar cane, possibly after the removal of the external fibers, through grinding rolls in order to rupture the sugar-containing cells and to extract part of the water and dissolved sugar. The remaining sugar is then removed by further rolling with the addition of water or weak sugar solution to the crushed cane between each rolling. The remaining sugar may also be removed from the crushed cane by treatment in a diffuser. It has been suggested that the cane should be treated in a series of screw presses and mixers, water being added to the cane material between successive pressings, i.e. while the material is subject to zero compression. It has also been proposed to inject water into a screw press at an intermediate point along the barrel, but, in that proposal, the press was specially designed by the provision of an expansion chamber to ensure that the pressure on the material was relieved at the point the water was injected.

The present invention is based on our discovery that, contrary to expectations, a higher extraction of soluble components from solid materials is achieved if the pressure on the material is maintained while the liquid solvent for the component is injected, than if the pressure is relieved.

In the case of sugar extraction, it has been found possible to achieve a 99 percent sugar extraction rate by pressing under increasing pressure and injecting water into the cane under pressure before each pressure increase.

One aspect of the present invention resides in a method of extracting a soluble component of a solid material, in which the material is subjected to pressure and, while that pressure is maintained on the material, a liquid solvent for the component is passed through the material. Preferably the pressure on the material is increased further, after the liquid solvent is added. The pressure may be progressively increased, and the liquid solvent applied to the material twice or more times at different intermediate pressure on the material. If desired the liquid solvent introduced into the material for extraction of the soluble component may itself contain dissolved elements of that component. Thus, the liquid solvent may be partly or wholly constituted by the liquid previously passed through the material.

A second aspect of the invention resides in a process for extracting sugar from sugar-bearing material in which the material is introduced into a press adapted to permit escape of liquid pressed from the material, and subjected to progressively increasing compression, and in which a sugar solvent is injected into the material in the press on at least two occasions during the increase in pressure and without relaxation of the pressure. The sugar solvent may be either water or a part of the pressed miscella which is recirculated back and mixed with the water feed.

A third aspect of the invention resides in an apparatus for extracting a soluble component of a solid material, including a press adapted to permit escape of the component pressed from the material, means for introducing the material to the press, means for injecting a liquid solvent for the component into the interior of the press is that the pressure on the material is maintained and means for collecting the component pressed from the material.

The invention will be more readily understood by way ofexample from the following description of methods of extracting sugar from sugar cane, reference being made to the accompanying drawings, in which:

FIG. 11 illustrates diagrammatically a first method of treating sugar cane in a screw press,

FIG. 2 illustrates diagrammatically a second method,

FIG. 3 is an end view of part of the cage of the screw press of FIG. 1 or FIG. 2,

FIG. 4 is a side view of a liner bar, and FIG. 5 is a section on the line V-V ofFIG. 4.

The screw press indicated generally at il2 in FIG. I and FIG. 2 is a modified form of a known press used for pressing liquid from a liquid-bearing material. The known press comprises a screw rotating in a perforated cylindrical cage, the cross-sectional area between the screw and the cage reducing along the screw axis so that, as the material to be pressed is carried along the screw, it is progressively compressed and the con tained liquid is forced through the cage perforations. The cage is made up of a number of longitudinal sections, each made up of a series of axially extending lining bars arranged in the form of a cylinder and with spacers interposed between successive bars at their ends to form line perforations for the escape of liquid.

The press 12 shown in FIG. 1 has a cage formed in three sections, 13, M, 15, the diameter of each of which is less than that of the previous section, to obtain in steps the reduction in cross-sectional area between cage and screw. Defibered sugar cane is fed into the right-hand end of the press as viewed in FIG. 1, via a feed hopper, and the pressed cane is removed from the left-hand end.

While the sugar cane is within the press 12 and while it is subject to the high pressure developed within the press, it is washed with water which is introduced into the press at high pressure, which acts as a solvent for the contained sugar, and which leaves the press through the cage perforations. Thus, in FIG. 1, high-pressure water on line 16 is fed to the feed hopper and to points of the three

sections

13, 14, 15 of the cage, through the lines 17, l8, l9 and 20 respectively. Each of lines 17-20 has its own flow control valve 21 and flow and

pressure indicators

22, 23 respectively, to enable the water to be supplied at a pressure appropriate to the delivery location.

In order to obtain the injection of the water into the sections 13, M, 15, special liner bars 24 as shown. in FIGS. 4 and 5 are employed. Each such bar 24 has welded to its external surface a tubular socket 26, the central passage 27 of which is aligned with a passage 28 through the bar 2d.

One segment 30 of the discharge half of each

cage section

13, 14, 15 is modified by the removal of the spacers between the liner bars and by the replacement of one of those bars by an injector bar as shown in FIG. d and 5, the

appropriate line

18, 19 or 20 being connected to the socket 26 of the appropriate injector bar. FIG. 3 shows part of the modified segment, the lining bars 31 being located hard up against one another, without the interpolation of spacers, and being held in place by wedging strips 32 between the end lining bar 31 and the shoe frame bar 33 on which the lining bars are mounted. The absence of cage perforations adjacent the water injection ensures that the water penetrates the sugar cane within the press and does not emerge: until it has passed through the cane.

If desired the water supplied on line 1'6 may be replaced in whole or in part by miscella, or sugar'rich water obtained from a previous extraction.

FIG. 2 illustrates an alternative form of extraction process using a screw press, where the water is circulated a number of times through the sugar cane, increasing in sugar extraction each time. As in FIG. 1, the defibered sugar cane is introduced into the right-hand end of the press of FIG. I, the extracted cane being discharged at the left-hand end.

Water is supplied through line 35 and is raised by a high pressure pump diagrammatically indicated at 36 to a pressure in excess of that obtaining within the press at the discharge end. The high pressure water is then injected into the cage adjacent the discharge end through line 37 and an injector lining bar as in FIGS. 4 and 5. After passing through the cane, the liquid leaves through the cage perforations and is collected in a first tank 38 as weak miscella containing a small proportion of dissolved sugar. From tank 38, the miscella is pumped by a medium pressure pump 40 through line M to an injection point located centrally of the press. The liquid passes through the cane at that part of the press and is collected in a second tank d2. Finally the miscella in tank 42 is pumped by the lowpressure pump 43 through line to an injection point at the input section of the press, and after passing again through the sugar-rich cane is collected in a third tank 45 from which it is discharged through line 46. The final concentrated sugar solution is then treated for sugar recovery.

In place of the screw presses previously described, a hydraulic ram press may be used having a perforated cage and a water passage through the ram to the interior of the press. The press is filled with the cane and the latter compressed to a first high pressure of, say, 300 lb/sq.in., sugar-rich moisture being expelled through the cage perforations. Without relaxing the pressure, water is injected into the material via the ram passage at a pressure sufficient to cause the water to pass through the material, say, 100 lb/sq.in The press pressure is then raised to say, 650 lb/sq.in., and a further quantity of water injected. Finally the press pressure is raised again to say, 800 lb/sq.in. Operating with the press and water pressures given, a sugar extraction rate of over 99 percent can be obtained and no subsequent diffusion treatment is needed. At the same time the moisture content of the extracted material is reduced to under 55 percent.

Efficient extraction can be obtained by using a single injection of water and without increasing the pressure afterwards. In this case, the higher the press pressure at which water injection, the better the extraction rate. In place of water, miscella from a pervious extraction may be used.

While reference has been made to the extraction of sugar from sugar cane, the process may be applied to increase the extraction rate in other solvent extractions, where the solvent may be other than water. An example is removal of oil from oil-rich vegetable matter.

We claim:

1. A process for extracting a soluble component of a solid material comprising the steps of subjecting said material to pressure to expel liquid from said material,

applying to said material in a first application fresh liquid solvent for said component while said material is subject to pressure, said solvent passing through said material and dissolving and removing some of said component,

collecting liquid solvent from said first application after having passed through said material,

applying, in a second application, some at least of said collected liquid solvent to said material so as to pass through said material, and

maintaining pressure of said material between said solvent applications.

2. A process according to claim 1 in which the material is fed along a prescribed path and is subjected to increasing pressure,

said first and second solvent applications are made at points spaced along said path,

fresh solvent is applied in the more downstream point along said path, and

at the more upstream point, the solvent applied is formed from liquid pressed from the material at the more downstream point.

3. Apparatus for extracting a soluble component from a solid material, comprising a screw press having a perforated cage and a screw mounted for rotation in said cage to feed material along the press while subjecting said material to an increasing pressure,

means for introducing said material to said press,

injection means for injecting liquid into said press at two points at least along its length, the pressure on the material being at least maintained between said points,

means for applying solvent for the component to each of said injection means at a pressure such that said solvent passes through said material,

a series of tanks for separately collecting liquid pressed from the material adjacent each of said points, and

means for applying liquid from each tank, except the first,

to an injection means upstream of that tank.

4. Apparatus as claimed in claim 3 in which there are means for supplying fresh solvent to the most downstream injection means. 5. Apparatus as claimed in claim 3 in which each said applying means is a pump arranged in the fluid path between each tank and injector.

Claims

2. A process according to claim 1 in which the material is fed along a prescribed path and is subjected to increasing pressure, said first and second solvent applications are made at points spaced along said path, fresh solvent is applied in the more downstream point along said path, and at the more upstream point, the solvent applied is formed from liquid pressed from the material at the more downstream point.
3. Apparatus for extracting a soluble component from a solid material, comprising a screw press having a perforated cage and a screw mounted for rotation in said cage to feed material along the press while subjecting said material to an increasing pressure, means for introducing said material to said press, injection means for injecting liquid into said press at two points at least along its length, the pressure on the material being at least maintained between said points, means for applying solvent for the component to each of said injection means at a pressure such that said solvent passes through said material, a series of tanks for separately collecting liquid pressed from the material adjacent each of said points, and means for applying liquid from each tank, except the first, to an injection means upstream of that tank.
4. Apparatus as claimed in claim 3 in which there are means for supplying fresh solvent to the most downstream injection means.
5. Apparatus as claimed in claim 3 in which each said applying means is a pump arranged in the fluid path between each tank and injector.