Patent Application
20080272001
The present invention relates to industrial processes for production of bulk chemicals, and to the treatment or processing of an aqueous stream containing organic material, such as a product stream comprising as a relevant component thereof, one or more complex salts or ionizable components, such as a salt of an organic acid. In particular it relates to treatment systems employing an electrodialysis (ED) treatment unit and/or a bipolar membrane-type electrodialysis (BPED) treatment unit, and to products produced thereby. It relates quite generally to processes for separation, treatment or refining of fermentation product streams, plant or animal extraction streams, enzymatically-produced product- or intermediate-bearing streams, streams of chemically modified material derived from one of the foregoing sources, or other bulk streams containing ionizable organic components. For simplicity of exposition, these shall be referred to herein as “fermentation product stream”. These streams will, as a rule, include a target organic material as a significant component, typically appearing in a mixture with other components that may also be addressed by the treatment process.
Many simple chemicals are produced on an industrial scale by processes of fermentation, microbial or chemical digestion or other mechanism, from material such as plant syrup or milling byproducts, milk, corn, soy or other agricultural matter that is available in great quantity, sometimes as the waste material from another harvesting or extraction process. Common examples of such chemicals include various carboxylic acids, such as tartaric, acetic, maleic, ascorbic acid, and other simple organic materials, as well as specialty chemicals or chimeric homovariants (like L-lactic acid), that may be present in or efficiently produced from the bulk matter using enzymes or special strains of industrially useful organisms. An end chemical may be produced directly in a fermentation process, or may result from reaction or processing of a ketone or other precursor that is produced from products of such fermentation. Typically, one or more stages of post-fermentation processing are required to extract, modify, concentrate or refine the desired product or intermediary from the fermentation stream. Such processing may include a filtration process such as ultrafiltration to remove high molecular weight (e.g., protein) and other potentially interfering material, an ion exchange process to remove divalent metals, decolorize, acidify or otherwise condition the stream; acid, base or chemical addition to condition the feed or to effect chemical modification, and other processes to change pH, remove or substitute minerals. A process may also include steps such as nanofiltration to concentrate the stream and/or separate unwanted species or components; processes to cleave or add portions of the molecular structure, and processes to precipitate or crystallize the product, and to clarify or otherwise modify the stream.
Typically, the relevant organic compound, for example, a form of a lactic, ascorbic or simple aliphatic acid, is present together with a certain residual amount of the starting material and nutrients, as well as metabolic products of the fermentation process, so that various sugars, alcohols, ketones or acids, and other compounds may be present in the stream. A target component or desired product is frequently present as, or is predominantly converted to, an ionizable salt at one stage of the processing. Recovery of product from the salt may be effected by separating ionizable components from solution using electrodialysis, i.e., electrically separating and driving relevant materials through ion-selective membranes into an output channel.
Some early systems of this type, as shown in U.S. Pat. No. 2,921,005 (1960) and U.S. Pat. No. 4,057,483 (1977) employed basic chamber constructions made of multiple cation exchange membranes, rather than the more common alteration of cation and anion exchange membranes generally used in electrodialysis “stacks”, and sometimes utilized multiple three- or four-chamber basic units to form stacks that provided suitable sources for protonation of the organic moiety or hydroxylation of the inorganic ion, while efficiently separating the soluble ionic parts of the salt.
The use of ion-selective membranes in these prior art constructions effected conversion of an organic acid salt to an acid and a base by providing separate cells or flow chambers in which protonation of the acid moiety could be effected. However, differences in transport number of the cationic and anionic components would generally impede complete separation with standard electrodialysis cell construction, and many arrangements were proposed with three- or four-chamber constructions, in which circulation (to increase concentration in or transfer of ions from), or dilute streams (to decrease back˜diffusion) could be run in various chambers to enhance overall effectiveness. With the development of commercial bipolar (“water splitting”) membranes, such electrodialysis units and treatment regimens could be modified to incorporate at least one bipolar (BP) membrane in their basic cell structure. This construction was intended to generate localized excesses of the hydronium and hydroxide ions needed for the respective anion- and cation-receiving sub-chambers, and to more effectively block entry of unwanted species. Effective architectures using BP membranes were able to obtain respectable yields in simple two- or three-chamber constructions, efficiently splitting water in the BP membrane at a chamber boundary. Concentration of the acid or base recovered by such bipolar electrodialysis units could be achieved by suitable control of the flow rates and recirculation of the streams in the chambers.
By way of example, recovery of organic acids from corresponding salts or mixtures of material are described in the 1988 U.S. Pat. No. 4,781,809 of J. Falcone, Jr.. Several separation/conversion processes and some ED unit designs are described in that patent, as well as in the 1989 bipolar membrane patent, No. 4,851, I 00 of inventors Hodgdon and Alexander. A useful overview of water splitting membrane electrodialysis technology around that period is found in the article Electrodialysis water splitting technology by K. N. Mani, in J. Membrane Sci., 58 (1991) 117-138. In that article, the author discussed useful process and efficiency considerations, sketched a number of simple multi-chamber basic cells useful in bipolar electrodialysis stack construction utilizing different arrangements of ion exchange membranes, and also indicated a number of features and advantages relevant to integration of bipolar membrane-based electrodialysis treatment processes into a conventional product processing or treatment line, such as those previously employed in treating waste streams or processing fermentation products.
A number of factors in the 1990 time period when the Mani article appeared—such as a desire to reduce chemical consumption or diminish chemical waste streams (as compared to processing steps involving strong acid treatment and/or exchange beds with their concomitant chemical regeneration requirements)—appeared to weigh in favor of incorporating such BPED treatment units into a number of existing production line or treatment applications. In the intervening decade, however, relatively few large scale processing plants have been constructed with bipolar electrodialysis treatment units.
A number of factors appear to be responsible for the slow adoption of BPED treatment technology. Commercially available lines of bipolar membranes have remained rather expensive, and while electrical splitting efficiency and current capacity of these membranes appear good, economic considerations have limited the industrial acceptance of BPED processing systems to a few higher-value applications or to small experimental and/or environmental niches. Competing processes, such as filtration, ion exchange and precipitation are mature and proven technologies, and the bulk cost of acid and caustic for chemical treatment or ion exchange regeneration have remained low.
This has probably also slowed the adoption of bipolar electrodialysis technology by most bulk chemical commodity and separation industries to which BPED processes would otherwise appear technically well suited. The general nature of bulk fermentation and similar chemical production processes, which commonly involve many plant-specific details and carry the likely presence of potentially fouling or interfering biological components, has undoubtedly also been an obstacle, because these factors suggest that substantial investment of research, piloting and trouble-shooting might be required to bring any specific application into fully controlled production. Perhaps also, because many mills or chemical producers effectively constitute large private empires that maintain close control over all information relevant to their products and production processes, detailed process information, and the necessary experience and expertise have not been widely shared with or made available to equipment and membrane suppliers. Thus, many factors may be cited for the apparently limited adoption of bipolar treatment technology.
In this state of affairs, there remains a need to improve processes for producing and treating bulk or specialty chemicals.
In particular, there remains a need for processes wherein BPED is integrated in a process line to reduce chemical or energy consumption, lower capital requirements, enhance yield or quality of a product or by-product, or otherwise improve the overall production or treatment process.
One or more of these and other desirable ends are achieved according to the present invention, in a process and system wherein organic matter, such as that derived from a fermentation process, is treated as a batch or stream containing one or more organic components in a fluid medium. The medium, preferably filtered, e.g., by ultrafiltration or the like, is passed or circulated with the organic matter in salt form through a bipolar membrane electrodialysis unit to separate an ionizable organic acid stream and a co-ion stream. The organic acid stream is preferably concentrated (e.g., by recirculation, by dewatering or both), and the desired acid product is recovered from the concentrated stream, by a process such as crystallization. Advantageously, the ED treatment may produce several streams, and these may be integrated with the overall treatment system. Furthermore, the overall treatment may involve one or more chemical modification steps, with concentrated product flows of different organic salts at the different stages, any of which may be treated by electrodialysis. In one embodiment of a treatment line of the present invention, a bipolar electrodialysis assembly replaces the cation exchange media bed of a conventional process line design, and operates to produce an organic acid stream and an inorganic or weak organic base stream. The base stream (for example, caustic or ammonium hydroxide) is preferably applied elsewhere in the treatment system, for example to condition the medium or modify a component in a fermentation or product modification stage. The feed may be recirculated to extract a high yield of the target species, and the feed- or product-receiving chamber may include a filling of ion exchange beads to maintain a high operating current through the stack even as resistivity otherwise rises with the progressive depletion of the circulating fluid over time.
In another or further process, the bipolar membrane electrodialysis unit is assembled with plural three-chamber repeating units, and is arranged to receive the feed stock in its second chambers. The second chambers may include ion exchange beads as described above, which may be of mixed or other type, as appropriate to the projected conditions. In operation, the unit transfers to and concentrates a desired component in the first chambers, providing an acid-enriched output stream, while passing undesired and non-ionized components straight through the second chambers as a depleted stream (e.g., depleted of the target product). The depleted stream may, for example, contain large molecules, alcohols, sugars and other non-ionized or poorly ionized material. Metal ions are transferred into the third chambers, the output of which (such as recovered caustic or trace nutrient species) may in certain cases be applied to other stages of the process line to enhance efficiency of the overall treatment and to effect certain cost savings.
Product may be recovered from the acid-enriched output stream of the first chambers, for example, by evaporation, crystallization or the like. Advantageously, the three-chamber bipolar ED in this embodiment, in addition to isolating and concentrating the target product in acid form, separates the product-carrying flow from many residual and impurity components retained in the depleted feed stream, and thus simultaneously operates as pre-filtration stage that advantageously provides different characteristics than those of a conventional filter-based or exchange-bed based treatment system in which physical pore size or binding affinities govern treatment. This is highly useful, because by diverting the large and the non-ionic components from the flow that passes to subsequent product treatment steps, the target material passed to downstream product treatment processes is a purer, or less contaminated product-bearing stream, and the downstream units therefore may achieve higher recovery, or a purer recovery, or produce smaller waste streams. Thus, for example, residual waste from a downstream product crystallization or other recovery step is advantageously reduced, and, in addition, all or a portion of the straight-through-depleted feed stream may be fed back to the underlying fermentation or other upstream process to maximize digestion of the included nutrients or other treatment of the raw stream, thereby increasing product yield. When depleted feed is returned to the fermentation or earlier stage, the returned portion may also be partially distilled or otherwise treated, if necessary, or a bleed may be set at an effective rate, to reduce the concentration of or to remove accumulated components such as metabolites or toxins in the feedback stream or fermentation vat below a level that might otherwise adversely affect the fermentation.
In yet another or further embodiment, an ED or BPED stage, or both, are placed to treat a waste stream remaining after a recovery step, such as the precipitation or crystallization of a product or intermediate, and the electrodialysis treatment operates to transfer remaining ionizable acid components into a recovery stream while passing non-ionized or opposite-charge components into one or more other streams such as a waste stream of lesser volume. In accordance with this aspect of the invention, the ED and/or BPED recovery process is applied at a downstream process end, and the recovery stream, which may be or may include recovered organic acid, base, or nutrient and trace mineral components, may be returned to an upstream process stage to increase yield.
These and other features of the invention will be understood from the description and claims herein, taken together with the drawings illustrating details and representative embodiments of the invention, wherein:
FIG. IA illustrates a prior art treatment process for production of bulk organic acid by refinement of fermentation product liquor;
FIG. IB schematically depicts a treatment or production process and processing line in accordance with the present invention;
The invention is best understood following a brief discussion of a prior art system, which serves to illustrate some characteristics of an organic process stream and relevant treatment modalities and process considerations.
The processes and operations designated 2 may include various direct chemical treatments or additions, for example to convert or transform the biomaterial by simple reaction such as esterification, conversion to a related salt or the like. The desired organic material from fermentation 2 appears in a stream 1a of process/product liquor, which, variously, may be withdrawn continuously or as a batch from the fermentation stage, and is treated by the processes 4. The stream 1a has one or more identified fermentation product components, in a suitable concentration such that the further treatments refine, produce or extract a more concentrated and relatively pure product from the stream.
The processes 4 may typically include filtration and/or ion exchange processes, a chemical modification process or a product separation process. By way of example, one process for the production of vitamin C is to transform and ferment simple sugars or alcohols to provide a gulonic acid or salt intermediate, such as 2-keto-L-gulonate which is acidified and subject to esterification to form ascorbate. The ascorbate may be the desired end product, or it may be further converted to an acid form, as required. Many other bulk and specialty chemicals are produced by treatment steps via a gluconate, lactate or other intermediate or product thereof that has been derived, in part, by fermentation.
As further shown in
The present invention will now be illustrated in the context of treatment processes as described generally above.
FIG. IB illustrates by way of example a system 100 that implements a product recovery process in accordance with one aspect of the present invention, configured with one or more bipolar membrane electrodialysis treatment units. As shown in
In accordance with one principal aspect of the invention, the medium 1a from process 2, preferably filtered or otherwise conditioned, e.g., by ultrafiltration, ion exchange or other steps, is passed or circulated with the organic matter in salt form through an electrodialysis system, that includes a bipolar membrane electrodialysis unit operated to separate an ionizable organic target into a stream of the target acid and a co-ion stream. The organic acid stream is preferably further concentrated (e.g., by recirculation, by subsequent dewatering or both), and a desired acid product is recovered from the concentrated stream, for example by crystallization, evaporation or other process, depending on the degree of purity desired and other factors. Economics of the concentration and recovery processes may have substantial impact on the overall treatment. Several aspects of the treatment according to the present invention provide benefits for this processing.
The ED unit may produce several streams, and these may be integrated with overall treatment. Thus inorganic ions removed from the ED feed may returned (as salts, acids or bases) to other steps, and non-ionic material in a depleted feed may be returned to an upstream utilization or downstream process.
In one embodiment of a treatment line of the present invention, a bipolar electrodialysis assembly, which may optionally be preceded by a conventional ED unit, replaces the cation exchange media bed of conventional process line designs (such as that of FIG. IA), and operates to produce an organic acid stream and an inorganic or weak organic base stream. The base stream (for example, caustic) is preferably applied elsewhere in the treatment system, for example to condition the medium or modify a component in one fermentation or product modification stage.
One embodiment of a system employing such a three-chamber bipolar electrodialysis assembly provides the feed stream (e.g., stream 1a) to the central chamber X, extracting 2KLG into chamber Y and the other salt ions (e.g., Na+ or NH4+) into chamber Z. The 2KLG is acidified by hydronium ions from water splitting in membrane 43b bounding chamber Y, while the metal ions combine with hydroxyl ions produced by the bipolar membrane bounding chamber Z. In this arrangement, the outflow 1Y from chamber Y is the desired product stream, while the outflow 1c of chamber X, namely the product-depleted portion of the feed stream 1a will contain certain sugars and material that is not ionized by the ED process. Thus, the unit 40 advantageously “filters out” such material from the treatment portion, stream 1Y, facilitating the downstream purification steps. For example, such impurities are not passed to crystallizer (18, FIG. IA) and need not be dealt with in the crystallizer waste (20,
In a further embodiment of this aspect of the invention, a conventional electrodialysis (ED or EDR) unit may be provided as a first stage ahead of the bipolar ED unit, to perform an initial treatment step. In this case, the first stage ED is preferably operated to remove the cationic and anionic portions of the targeted organic salt into the first stage concentrate stream, and the concentrate from the first stage serves as the input feed to the bipolar process described above.
The BPED unit may also employ other cell constructions, with a single monotype exchange membrane (A or C) between two bipolar membranes to form a two-chamber bipolar cell architecture. Two such constructions are shown in
Electrode cells at each end may have different or independent fluid circulation (not specifically illustrated). In any of these embodiments, one or both streams may be recirculated to reach a desired removal or concentration endpoint. Furthermore, a filling of ion exchange beads or fabric may be placed in one or more chambers to assure a sufficient conductivity to maintain the desired level of current in the stack as a whole. For removal of the target organic moiety, an anion exchange bead filling is preferred in the central chamber, whereas either anion or mixed-type may be employed in the product-receiving chamber. Use of exchange beads helps to maintain conductivity and efficient transport when the solution conductivity is low, and allows the feed to be recirculated through the central chamber to extract a maximum amount of the target species into the adjacent product acid-receiving chamber. Thus one or several chambers may contain exchange resin. Suitable resins may include macroporous resins and those having fouling resistance for comparable feed streams, specialty decolorizing resins, and others. Flows may also be treated or maintained at a suitable pH to minimize fouling, and to assure that the desired organic product is ionizable in the treatment cells.
In operation, when a three chamber unit receives the feed in its second chambers and transfers the desired component in the first chambers, to provide an acid-enriched output stream, the undesired and non-ionized components may pass straight through the second chambers as a depleted stream. The depleted stream may, for example; contain large molecules, alcohols, sugars and other non-ionized or poorly ionized material. Metal ions or other cations are transferred into the third chambers, the output of which (such as recovered caustic, weak base, certain nutrient or trace elements) may in certain cases be applied to other stages of the process line to enhance efficiency of the overall treatment and effect certain enhancements or efficiencies. By recirculation of the feed and the product streams at appropriate flow rates, concentration of the target product in the acid enriched output stream of the first chambers may be increased, and further concentration, for example, by evaporation, crystallization or the like, using processes similar to those of the prior art examples described above provides enhanced recovery or recovery of a more pure product. Advantageously, the bipolar ED in this embodiment, in addition to isolating and concentrating the target product in acid form, separates the product-carrying flow from most residual and impurity components which remain present in the depleted feed stream. In this sense, the BPED (as well as the first-stage ED treatment described above, when that is employed), operates as pre-filtration stage that advantageously provides different characteristics than a conventional filter-based or exchange-bed based pretreatment, in which physical pore size or charge characteristics largely determine the final stream composition. The present invention, by diverting the large and the non-ionic components from the flow that passes to subsequent product treatment steps, provides a purer, or less contaminated product-bearing stream to the downstream product treatment processes, promoting higher recovery, or a purer recovery, and/or generating a smaller amount of downstream waste.
Thus, for example, residual waste from a downstream crystallization or other recovery will advantageously be reduced, and the crystallizer liquor may be subjected to a second crystallization stage without extensive preconditioning. As noted above, all or a portion of straight-through depleted feed stream 1c may be fed back to the underlying fermentation or upstream process to maximize digestion of the included nutrients or other treatment of the raw stream. When depleted feed is returned to the fermentation or earlier stage, the returned portion may also be partially distilled or otherwise treated, if necessary, or a bleed may be set at an effective rate, to recover a by-product, or to limit the concentration of or remove an accumulated component, metabolite or toxin in the feedback stream or fermentation vat below a level that would adversely affect the fermentation.
This filtration/recovery aspect of the BP treatment systems of the invention may also be applied downstream of the principal treatment, either in a system as described above, or by performing such ED on a fluid at the post-crystallization or post-recovery stage of a conventional production plant. In accordance with this aspect of the invention, an ED or BPED stage, or both, are provided to treat the waste liquor remaining after a recovery step, such as precipitation or crystallization of a product or intermediate. For example such electrodialysis may be performed on the waste output 20 of the process in
As is known, such crystallizer waste liquor may contain significant amounts of unrecovered product (e.g., 2KLG) as well as sugars, alcohols, etc. A BPED treatment may transfer remaining ionizable acid components into a secondary recovery stream while passing non-ionized or opposite-charge components into one or more other streams such as a waste stream of lesser volume, or a cleaner residual nutrient stream for return to the process, or a secondary byproduct such as a feed additive or fertilizer. Treatment of the waste 20 may involve preconditioning, such as dilution, filtration and/or pH adjustment, and may be done in stages, e.g., with ED followed by BPED, if the nature of the waste 20 does not admit of a single stage or direct treatment. In accordance with this aspect of the invention, the waste, which may for example include substantial amounts of unrecovered product, as well as undigested nutrients, trace minerals and co-products, is treated by the ED/BPED units to recover additional ionizable product. Electrical operation on the relatively high concentration crystallizer waste stream can be quite efficient, and by cleaning up product or precursor from the crystallizer waste, the overall yield may be significantly enhanced, which can improve economics of the overall production process.
Among the other advantages achieved by the invention, it should also be observed that the production of a product stream and a re-usable co-stream allow great flexibility in addressing treatment economics. One or more savings in recovered nutrients, recovered acid, separation of a weak base or caustic stream, and reclaimed product waste may offset overall capital or maintenance expenses (e.g., for membranes, equipment and electricity), while the virtual filtration achieved by the various pass-through or interchamber transfer BPED configurations provides effective treatment and organic acid production with less capital investment, e.g., reducing the need for ultrafiltration or nanofiltration banks (12, 16 of
Several examples will serve to illustrate operating parameters and the general effectiveness of the described invention.
A bipolar electrodialysis 9″×10″ stack was assembled having eight three-chamber units and two two-chamber units with an electrode chamber at each end of the stack. The effective area of each membrane was about 232 cm2. The three-chamber unit included a bipolar membrane, a cation membrane (Ionics CR69EXMP) and an anion membrane arranged as described in
Approximately 1000 g of dry raw sodium ascorbate from fermentation with purity of 88.1% were dissolved in 5 liters of pure water to get about 20% solution of raw sodium ascorbate. The solution was fed into the feed tank of the ED system and circulated in the chamber X at flow rate about 0.8 liter/min as shown in the
The resulting ascorbic acid product solution was a very light yellow solution compared with the dark grey color of the feed solution. Yield was 88.0% based on ascorbate ion, and the current efficiency was 64%. When the product solution was concentrated and crystallized, product purity was 97.6% without sodium ion. It was believed that the 2.4% impurity might be largely oxidation products of ascorbic acid due to the drying process employed. Power consumption was about 1.1 kwh/kg ascorbic acid.
A bipolar electrodialysis 9″×10″ stack was assembled comprising five three-chamber units with an electrode chamber at each end of the stack. The effective area of each membrane was about 232 cm2, and the three-chamber units had a bipolar membrane, a cation membrane (Ionics CR69EXMP) and an anion membrane (Ionics AR103QDP) arranged as described in
The feed solution used in this process example was a synthetic solution containing 9.2% of sodium lactate with sugar and protein similar to a fermentation broth. Three liters of feed solution were placed in the feed tank of the ED system and circulated in the chamber X at flow rate about 0.5 liter/min as shown in the
Yield was about 94.3% with very little sugar and protein passing into the product, and the current efficiency was 88.8%. Power consumption was about 1.76 kwh/kg lactic acid.
The foregoing examples demonstrate efficient and effective organic acid separation, purification and conversion to acid form with desirable product characteristics.
The invention being thus disclosed and illustrative embodiments described, a number of variations and modifications thereof, as well as adaptations to other known treatment or production processes will occur to those of ordinary skill in the art. All such variations, modifications and adaptations are considered to be within the scope of the invention, and to be encompassed by the claims appended hereto.
All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.
This application is a Continuation of U.S. application Ser. No. 11/292,796, filed on Dec. 2, 2005, which is a Continuation under 35 U.S.C. 111(a) of PCT/US2005/009312, filed on Mar. 17, 2005, and published in English on Sep. 29, 2005, as WO 2005/089513, which claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application Ser. No. 60/553,753, filed Mar. 17, 2004, which applications and publication are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60553753 | Mar 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11292796 | Dec 2005 | US |
| Child | 12173908 | US | |
| Parent | PCT/US2005/009312 | Mar 2005 | US |
| Child | 11292796 | US |
