GB2192403A - Continuous belt of sponge or foamed material for use in liquid/solid reactions - Google Patents

Abstract

A continuous web or belt of elastically compressible activated sponge material, e.g. activated regenerated porous cellulose or a foamed synthetic polymer, can be used for carrying out liquid/solid reactions, such as ion-exchange and chromatographic separations, in a continuous manner.

Description

SPECIFICATION Improvements to liquid/solid reactions The present invention relates to apparatus and a method for improving liquid-solid reactions by carrying them out in a continuous manner using a belt of Elastically Compressible and Flexible Sponge Material in the form of a continuous web, hereinafter referred to as a BECFASM.

The invention is particularly directed to - car- rying# out ion-exchange or chromatographic reactions in a continuous manner. Ion-exchange and chromatographic adsorbtions to isolate substances from their solution is already known. These reactions have previously been carried out in batch operations. For example, in a stirred tank reactor or in a fixed bed or column using Activated Granular Materials, hereinafter referred to as AGM's. Discs of activated materials have also been proposed.

Continuous adsorbtions onto AGM's has been proposed in British Patent No 1436547, by physically moving the AGM's from one vessel containing liquid to another by mechanical or physical means.

It has also been proposed to contain AGM's between webs of pervious inert materials, so that the assembly may-be contacted with liquids and effect adsorbtion.

The difficulty with these methods is the handling of the AGM's in a continuous manner, and to remove unwanted or unreacted fluids from them without physical damage or loss of the AGM's. Such loss is generally caused by attrition between the AGM's with subsequent escape of the fine particles produced. As the AGM's are thus reduced in size, so their physical characteristics such as bulk density change, which alters their hydrau iic properties for example.

The present invention provides a means of bringing into contact a solution of a substance which may have contaminarits present with a BECFASM in a continuous manner.

On contact, the solution is absorbed by the BECFASM and a substantial'amount of the desired substance adsorbed therein and thereon, in a continuous manner, by-drawing the web of the BECFASM through the solution by means of the apparatus provided in the invention.

A substantial part of any contaminants present in the solution are left therein. The web of the BECFASM together with the adsorbed substance and some of the depleted solution is then pass#ed through a squeezing device to displace or express a substantial amount of absorbed liquid present.

The web of the BECFASM together with the adsorbed substance may then be subjected to further treatment which may include washing to remove any solution and contaminants remaining in the BECFASM, desorbtion of the adsorbed substance or further washing of the web of the BECFASM as required. The operations may -be repeated in sequence, in a continuous manner.

In some cases, the adsorbed substance may be allowed to remain attached to the BECFASM to carry out reactions with other substances. This particularly applies if the adsorbed substance is an enzyme or an inorganic catalyst. The present invention is particularly useful for isolating polyelectrolytes from their solutions in a continuous manner, but is not limited to such. The BECFASM apparatus and method described in the invention may be used for the treatment of process water, boiler feed water or effluents. Also, the isolation of metals and other inorganic ma- terials and the removal of unwanted materials from their solutions.

The manufacture of elastically compressible sponge materials is already known. Examples include generally cellulosic materials usually made by incorporating crystals of a soluble material such as sodium sulphate decahydrate with a solution of cellulose in caustic soda together with insoluble fibres and other reinforcing materials.

The mixtures is the precipitated or regenerated in the form required by heat and/or acid, the crystals melting or dissolving to leave a porous cellulosic structure.

The cellulosic sponge so formed may have active groups incorporated or attached before or after regeneration, and may be cross-linked using known means before or after regeneration. See British Patents 1026706-, 1387265, 914421, 1226448, and others of a similar nature, or by known grafting techniques.

These patents are quoted by way of example and not limiting. Sponges of sulphopropyl cellulose, dimethylaminoethyl cellulose-and carboxymethyl cellulose are particularly preferred for use according to the present invention. Ligands such as dyes used for chromatographic separation may also be attached by suitable techniques.

Other examples include polyethers, polyurethanes, natural and synthetic rubbers, given for examples only and not exclusively. These are generally made by foaming, or by gas generating reactions within the mass. Active groups or ligands may be attached to or exposed on the walls of the alveoles thus formed. It is- important that a substantial number of the alveoles are interconnected.

No claims are made in the present invention for methods of manufacture for elastically compressible activated sponge.

Definitions The volumetric efficiency ratio here means the ratio of the volume of liquid expressed from an activated material of a particular total volume by a dewatering step and the volume of liquid before the dewatering step.

The present invention avoids the djsadvantages of AGM's fixed bed systems which have a tendency to form channels with consequent reduction in effectiveness.

It also avoids the disadvantage of stirred tank reactors which have large volumes of liquid held up in the system. It also avoids the disadvantages of previously proposed continuous systems using AGMS such as loss by attrition as previously described, also relatively large-volumes of liquid are trapped or entrained between and around the AGM's.

The amount of liquid re#maining with the AGM's is important when considering the volumetric efficiency of the reaction. This residual liquid is difficult- to remove by draining, and crushing or squeezing of the AGM's causes damage and loss by attrition even if contained within a pervious envelope or between layers of pervious material.# Regular distribution of the AGM's is difficult to achieve even when contained within pervious layers, causing by-passing and reduced contact between the liquid and the AGM's.

The method of contact according to the present invention has the advantage that the arrangement of the liquid flows and the BECFASM may be such that co-current or counter-current effects are achieved in a continuous manner. The volumetric efficiency of the BECFASM in the present invention is unexpectedly high when compared with systems using AGM's. The volume of the liquid in pro -cess is also unexpectedly low compared with previously proposed batch and continuous systems using AGM's.

This is particularly advantageous when dealing with valuable substances in dilute solu tions The space taken up by the apparatus proposed in the present invention is therefore much less than in previously proposed systems.

The times for the reaction$ to take place with a BECFASM is unexpectedly low compared with those for AGM's. This is probably because of the rapid absorbtion of liquid by the BECFASM especially when:elastically compressed and decompressed in the liquid concerned, and also because of the thinness of the- membrane walls between alveoles in the BECFASM compared with the #iameter of AGM's. This affects the times #of diffusion of the liquids i#nto the activated materials, if hydrophilic. The vast differences-in surface area between the-two, weight for weight is to the advantage of the BECFASM; in comparing speeds of reaction.

The fast reaction time with a BECFASM when used according to the irivention reduces the time that liquids are process and therefore reduces the risk of contamination or growth of micro-organisms whilst in process, as #well as the volumes of liquid in process.

Preferably the BECFASM is in the form of a continuous web moving through reaction zones so that after adsorbtion, and subsequent treatment, the process- steps concerned may be repeated in sequence in a continuous manner. Before being subjected to the adsorbtion step, the solution of the desired substance may advantageously be filtered, defatted, pasteurised, concentrated, and demineralised, or one or more of such pre-treatments, all by known means, and brought to the required temperature and pH for adsorbtion.

Contact between the BECFASM and the liquid may be made by spraying or raining the liquid onto the BECFASM or preferably by immersing the sponge in the liquid or by a sequential combination of both.

While immersed, the BECFASM is advantageously compressed and decompressed as previously described to displace liquid in and out of it. Baffles in suitable positions in the liquid assist in promoting co-current or counter-current contact, or to bring about closer contact between the BECFASM and the liquid.

Advantageously the BECFASM is moved in á continuous manner in and out of the reaction zones, but the movement may be carried out in an intermittent manner whilst maintaining the sequential operations required, and having the overall effect of continuous operation. Advantageously the web of BECFASM is squeezed or compressed in the direction of its thickness after its exit from the liquid concerned so that expressed liquid falls back into the vessel containing the liquid, or into a duct.

This dewatering step may be carried out by compressing the activated sponge between platens or preferably between rotating members. The path of liquids in the system may be so arranged that they pass from one stage to another to assist in economy and efficiency of the overall operation. The volume of liquid required to desorb a given amount of adsorbed substance can be significantly less than the volume of the equivalent original solution of the substance. Thus the method according to the invention may be used to concentrate as well as isolate the desired substance. Also, probably because of the relatively small amount of solution of the desired substance in the process at any one time, and the relatively large amount in contact with the BECFASM, the excellence of contact, and the high volumetric efficiencies, the amount of the desired substance isolated is unexpectedly high. This may be even higher if multi-stage reactions are used as described later.

Elastic compression ratios of the BECFASM of between 1.2 to 1 and 20 to 1 are achievablue, with a preferred range of 4 to 1 and 16 to 1.

The BECFASM may be passed through the apparatus by means of driven rollers, and tensioned by spring loaded rollers or the equivalent. Several preferred embodiments of the invention will now be described with reference to the accompanying drawings.

Figure 1 shows a BECFASM and apparatus according to the invention arranged to adsorb a substance from its solution in a continuous manner.

Figure 2 shows a complete BECFASM and apparatus using the principle shown in Fig. 1.

for the adsorbtion of a substance from its solution followed by a washing step, a desorbtion step, a further washing step, and return of the web of BECFASM to the commencement of the sequence of the above steps in a continuous manner.

Figure 3 shows a modification of the apparatus in Figs. 1 & 2. for co-current or countercurrent reactions.

Figure 4 shows a modification of the apparatus shown-in Fig. 1. where a spray is used to impregnate the web of BECFASM with a liquid in a continuous manner.

Figure 5 shows a modification of the apparatus in Fig. 1. where a loop of the web of the BECFASM is moved through a liquid to provide a longer contact time, in a continuous manner.

Figure 6 shows a modification of the apparatus shown in Fig. 3. where multi-stage reactions between the web of BECFASM and liquids may be carried out in a continuous manner.

Figure 7 shows a modification to the apparatus shown in Fig. 1. where the path of the web of the BECFASM is arranged to provide greater contact area with compression rolls.

Fig. 1 is a vertical sectional view of a reaction vessel, used for an adsorbtion step. Referring to Fig. 1. a solution 1 of a substance together with any contaminants which may be present is fed into a vessel 2. A web of a BECFASM 3 is passed through the liquid 16 in a continuous manner. The liquid may be heated or- cooled by known means not shown. Reagents may be added at 9 or elsewhere to obtain the desired adsorbtion effect.

Stirring means (not shown), are advantageous.

The liquid 16 is first absorbed and some of the substance then adsorbed from the liquid 16 by- the web of BECFASM 3. Reaction takes place between the web 3 and the liquid 16.

The web 3 then passes under a roll 4 or fixed bar and by virtue of the tension in the web 3, the web 3 is reduced in thickness and liquid is expressed. Preferably a matching roll 5 is positioned and pressure applied to the rolls 4 & BR< 5 by appropriate means to provide a compressing effect on the web 3.

DuringXelastic decompression of the web 3 after the- rolls 4 and 5, liquid 16 is absorbed quickly into the web 3, and further reaction takes place. A substantial amount of the desired substance in solution is now adsorbed onto the web 3. The web 3 is then removed continuously from the liquid 16 in vessel 2, taking with it adsorbed substance and some of the liquid 16. Further reaction can then take place within the web 3. Squeeze rolls 6 & 7 displace liquid 16 now substantially depleted of the desired substance from the web 3 at 10 which in this embodiment, falls back into the vessel 2. Liquid depleted of the desired substance with a substantial part of any contaminants originally present are overflowed at 11.The dewatered and decompressed web 3 together with adsorbed substance and a small amount of residual liquid leaves the rolls 6 & BR< 7 in a continuous manner and is then available for further treatment. Inlets and outlets of liquids are advantageously submerged to assist in the prevention of unwanted foaming.

To produce a simple counter-current contact between solution 1 and the web 3, solution 1 is introduced at lx.

Fig. 2. shows a vertical section through an apparatus for isolation of a desired- substance from its solution in a continuous manner, using a continuously moving web of BECFASM in accordance with the invention.

Referring to Fig. 2, Section 1 represents the adsorbtion step. Solution of the desired substance enters vessel 2 at 1, pre-conditioned as to any or all of the following pH, temperature, de-fatted, pasteurised, filtered, pre-con- centrated, demineralised. Reagents may be added at 9 or elsewhere into vessel 2. - An agitation device 15 is shown. A dewatered web of BECFASM 3 enters the liquid 16 and passes through optional compression rolls 12 & 13 to assist rapid absorbtion of the liquid 16. Roll 4 and optionally roll 5 compress the web of BECFASM 3 and on'elastic decompression more liquid 16 is absorbed.

Advantageously a baffle or baffles 14 may be placed to assist in directing the-flow of liquid 16 towards the web 3 and reduce any short circuiting of the liquid 1 to the overflow 11. A plate, duct or chute 26 directs-the fluid expressed at 10 back into vessel'2 or to an outlet not shown.

Section 2 represents the washing step.

Wash water 17 enters vessel 18 and is åb- sorbed by the dewatered web 3. The configuration of web 3 and parts of the apparatus may advantageously be similar to that shown for the adsorbtion step in Section 1. Any con taminants#which may have been present are here substantially removed, the web 3 retaining the adsorbed substance.

Section 3 represents the desorbtion step.

Desorbant fluid e.g. pH adjusted water or a strong electrolyte 19 enters vessel 20. Again the configuration of parts may advantageously be similar to that for the previous sections.

The desorbant alters the conditions within the web 3 so that the desired substance is desorbed. Water and further amounts of desorbant may be added to vessel 20. A solution of the desired substance leaves Section 3 at 21. This solution may then be concentrated.

and dried to form a powder, by known means.

If required, Section 4 represents a further optional washing stage similar to Section 2.

advantageously to reduce the amount of de sorbant left in the web at 3. The web 3 is guided back to Section 1. by means of rollers 22, 23, 24 & 25 or their equivalents. Advan tageously 24 is a device for providing tension to the- web of BECFASM 3 to take up any slack. One or more rollers or pairs of these rollers are driven to move the web 3 through the apparatus in a continuous manner.

Fig. 3 is a vertical section through another embodiment of the invention at the adsorbtion step where more than one compartment of Section 1 in Fig. 2. is used to provide a lon ger contact time and co-current contact of the liquid 16 with the web 3.

Fig. 4 is a vertical section through another embodiment of the invention to provide an evenly distributed spray of liquid over an area ~of web 3, the liquid travelling through-the web 3 by gravitational forces. The liquid 1 enters a tray 2a, which is perforated; The web 3 is taken by rollers 4 & 5 under the spray so produced, and leaves the section in a substan tially dewatered condition after dewatering compression rolls 6- & 7. The liquid 1 after contact with the web 3 leaves the vessel 2 at 28 either by pump or by overflow. Similar vessels and rolls may be added so that further sequential reactions may- be carried out in a continuous manner.

Another embodiment of the invention is shown in Fig. 5. The web of the BECFASM 3 passes into the reaction vessel 2 via optional compression rolls 4 & 5 and is allowed to fall into folds before removal by compression rolls 6 - & 7. Solutions 1 and reagents 9- enter the vessel 2 where required. Agitation means are optionally- installed in vessel 2. The desired substance in solution 1 reacts with the web 3. Sol. 1 then overflows at 11 or is otherwise ducted away. This embodiment is advan tageous when long reaction-times are desir able, and may also be used sequentially for washing and de#sorbtion steps in a continuous manner.

Another embodiment of the invention is shown in Fig. 6. Referring to Fig. 6., solution 1 of a substance which it is desired to adsorb or isolate together with any impurities that may be present enters vessel 2 via a spray pipe 31- or directly into vessel 2. The web of the BECFASM 3-may be suspended over or be guided beneath the- surface by rolls not shown, such rolls may also act as compres sion rolls.

Reaction occurs between the web 3 and the solution 1. The desired substance is partly ad sorbed onto the web 3 which is passed through dewratering compression rolls 6 and~7 in a continuous manner. Web 3 is then ready for- further treatment.

The- partially depleted solution 1c is taken back to vessel 2c by pump or by overflow.

Solution 1c enters vessel 2c at 31a or as previously described for solution 1 entering vessel 2 and similar reactions are carried out.

Further depleted solution is taken from 11 a to 31b in a manner similar to that previously described.

Even further depleted solution of the desired substance together with a substantial part of any impurities present in the original solution 1 is removed from vessel 2d either by pump or overflow for disposal or further treatment.

It will be seen that counter-current contact takes place between solutions and web 3.

This embodiment of the invention is particularly advantageous when the web of the BECFASM 3 is to be loaded to a greater extent with adsorbed substance, where the concentration of the desorbed substance is required to be higher, or where the total amount of substance to be adsorbed from the solution is required to be higher than would otherwise be achieved by a single stage in a continuous manner. This embodiment is used advantageously in sequential reactions of the web 3.

Referring to Fig. 7., the web of the BECFASM 3 passes through the roll 6 & 7 in a letter 'S' configuration, thus providing a greater area of contact, and greater traction if one or more of the rolls 6 & 7 are driven.

Also, the positions of the compression and decompression of the web of the BECFASM 3 are thus reverted.

In the embodiments of the invention previously described, the vessels through which the web of the BECFASM passes, may be advantageously profiled to reduce the volumes of liquids not in contact with the web of the BECFASM. Also, the apparatus shown many be housed advantageously in an airtight casing with appropriate re-sealable openings for access, so that the parts of the apparatus and liquids therein would otherwise be exposed may be kept in sanitary conditions.

Occasionally, depending on the quality of the sanitary- conditions required, one or more of the vessels shown in the drawings may be supplied advantageously with a sanitizing fluid and the web of the BECFASM passed through the apparatus in a continuous manner. One or more of the vessels shown in the drawings may advantageously be supplied with clean water after sanitizing, to remove any remaining sanitizing fluid left in the BECFASM or the apparatus.

The BECFASM may be made as a plain continuous web with an inner and outer surface as shown in the drawings or advantageously as a web where one end of the web may be turned through 180 degrees before joining to the other end of the web, to form a continuous web with special geometric properties.

The two sides of the web thus formed then have but one continuous surface. The two sides ~are thus presented alternately to sprays or rolls. This is advantageous in assisting the removal of any particles which may become embedded in the surface and making any wear of the web more even.

Advantageously the web of the BECFASM is reinforced with a pervious material such as a woven, inert material by attaching it to the web by stitching or bonding by suitable means, without significantly affecting its elastic compressibility. Advantageously the pervious reinforcement covers both sides of the full width of the web, so that mechanical wear of the surfaces is reduced and any pieces of sponge material which may become detached are retained within the sleeve or sandwich formed thus by the pervious material.

Example 1 Step 1. A regenerated cellulose sponge was manufactured according to British Patent No.

1387265 to produce an elastically compressible diethylaminoethyl cellulose. A BECFASM was then made by scarfing the edges of the sponge so formed to be joined and by stitching pieces of the sponge together to form a continuous loop or belt reinforced along its length with a strip of woven cotton attached by stitching. The BECFASM thus made had the following characteristics: Wet thickness 1.53 cms Compressed thickness 3mm when loaded between compression rolls 2.5 cms diameter for 1 second, with a load of 1 kg/cm.

Thickness 2 seconds after decompression 1.56 cm without permanent set Step 2. A solution having a protein concentration of 6 grams/litre was fed at a rate of 0.142 I/sec into a vessel 3.5 1 liquid capacity fitted with 2 slow speed stirrers.

The web of BECFASM made in #Step 1 was passed through the vessel at a speed of 3.26 cms/sec, between submerged idling compression rolls in a continuous manner. The web of the BECFASM was removed at the same speed- by a pair of driven, -dewatering compression rolls. The distance# between the point of entry of the BECFASM into the solution, and the dewatering rolls was 32cms. The contact time was 10 seconds. The concentration of protein in the liquid expressed by the dewatering rolls was 0.72 grams/litre.

The dewatered web of BECFASM was then passed in a continuous manner at 3.26 cms/sec into a similar vessel but containing a 5% solution of sodium chloride, between submerged compression. rolls. The solution was maintained in strength by continuous- addition of a solution of sodium chloride and the surplus ducted away.

The protein adsorbed by the BECFASM was thus isolated desorbed and ducted away in a continuous manner. The web of the BECFASM was removed continuously from the desorbtion vessel by dewatering compression rolls, and then passed at 3.26 cms/sec into a simiiar vessel containing clean water, between submerged compression rolls, water being added to the vessel continuously.

The web of the BECFASM was removed continuously from the-vessel by the dewatering compression rolls as before, and returned in a continuous manner to the first vessel for the adsorbtion stage to be repeated. The stages of adsorbtion, desorbtion, and washing were thus carried out in a continuous sequential manner.

The protein isolated was precipitated by adding hydrochloric acid to the isolated protein solution maintaining a temperature of 50 C, and the precipitated protein filtered off. The volume of liquid remaining after typical dewatering compression rolls was 0.2 cc's per cubic centimeter of decompressed sponge.

The volumetric efficiency ratio as defined was 80%. The ratio of compression at the compression rolls was typically 5/1. The adsorbtion ratio was 88%.

Example 2 Polyether sponge was processed in a similar manner, with the following characteristics: Thickness 9mm Thickness when compressed by a load of 1kg/cm of width by compression rolls 2.5cms diameter at 3.2 cms/sec was .61mm The thickness after compression was 9mm measured after 0.5 secs.

The volumetric efficiency was not less than 90%.

Claims (16)

1. A continuous belt of elastically compressible flexible activated sponge material (subsequently referred to as a BECFASM).

2. A BECFASM as claimed in claim 1 which is elastically compressible to between two thirds and one twentieth of its original thickness when wet.

3. A BECFASM as claimed in either of claims 1 or 2 where the material is an activated regenerated porous cellulose.

4. A BECFASM as claimed in either of claims 1 or 2 where the material is an activated foamed polymer including polyethers, polyurethanes, natural and synthethic rubbers.

5. A BECFASM as claimed in any of claims 1 to 4 reinforced to resist tension.

6. A BECFASM as claimed in any of claims 1 to 5 at least partly covered with a pervious flexible material including natural and synthetic woven materials.

7. A BECFASM as claimed in any of claims 1 to 6 in use to effect liquid/solid reactions.

8. A BECFASM as claimed in claim 7 in use to effect one or more liquid/solid reactions in a sequential and continuous manner.

9. A BECFASM as claimed in any of claims 1 to 8 in use in any apparatus shown in Figs.

1 to 7 and their accompanying descriptions.

10. A BECFASM as claimed in any of claims 1 to 9 in use to effect chromatographic separations.

11. A BECFASM as claimed in any of claims 1 to 9 in use to effect ion-exchange.

12. A BECFASM as claimed in either of -claims 10 or 11 where a substance is ad sorbed from its solution and remains attached to the BECFASM.

13-. A BECFASM as claimed in claim 12 where the substance is desorbed from the BECFASM.

14. A BECFASM as claimed in claim 12 in use to effect catalysis including enzymatic- re actions.

15. A BECFASM as.claimed in any of claims 1 to 11 and 13 in use to isolate a substance from its solution in a continuous manner.

16. Liquids or solids resulting from the use of a BECFASM as claimed in any of claims 1 to- 15-.