WO2012021956A1 - Method for obtaining lactic acid with a high degree of purity from fermentative liquor - Google Patents

Abstract

The present invention describes a process for obtaining lactic acid with a high degree of purity from a fermentative liquor (1) containing sodium lactate, with a view to the production of polylactic acid. The process comprises the unitary operations of centrifugation (101), centrifugal decantation (102), microfiltration (103), ultrafiltration (104), primary filtration in an activated charcoal bed (105), conventional electrodialysis (201), ion exchange columns in a chelating resin bed (202), bipolar electrodialysis (203), ion exchange columns (204), primary evaporation under vacuum (302), secondary filtration in an activated charcoal bed (304), liquid-liquid extraction from the aqueous phase to the organic phase (305), back extraction from the organic phase to the aqueous phase (306), and secondary, atmospheric evaporation (402).

Description

LIGHT ACID PROCEDURE WITH HIGH PURITY

 FROM FERMENTATIVE LIQUOR

FIELD OF INVENTION

 The present invention belongs to the field of processes for obtaining high purity lactic acid from a sodium lactate-containing fermentative liquor for the production of lactic polyacid.

 10 BACKGROUND OF THE INVENTION

 Lactic acid (2-hydroxypropanoic acid) has been increasingly used worldwide in the production of various biodegradable polymers motivated by modern medical applications (such as prosthetics).

15) and in the pharmaceutical area (such as controlled release medicinal products) and the strong ecological appeal of using lactic acid (lactic polyacid) biodegradable polymeric materials from

20 plastics of mineral origin. The successful use of a green route for the production of lactic polyacid requires a complex process that ensures the removal of all contaminants present in a natural raw material, the isolation of lactic acid and its concentration.

 The following are the main processes presented in the prior art for solving problems of regeneration, purification and concentration of lactic acid produced in fermentative media. How techniques differ significantly depending on the approach

30 adopted in each invention subsections are adopted depending on the technology used as the basis of each patent.

 In general, all of these technologies are found to focus on the isolated solution of regeneration, purification or concentration problems, which are separately ineffective in the production of high purity lactic acid from a fiber fermented liquor, peels and other impurities difficult to remove.

 Membrane Permeation Processes

 US 4,110,175 relates to an electrodialysis process using anionic and cationic membranes for the purpose of removing organic acids, including lactic acid, present in fruit juices and other aqueous solutions.

 EP 230021 describes a continuous fermentative process coupled with an electrodialysis process for continuous lactic acid withdrawal. However, as no preliminary separations and filtrations are made, various components of the fermentation liquor are adhered to the surface of the polymeric membranes, which implies a significant increase in electricity consumption.

Boyaval et al. (Biotechnology Letters, vol. 9, no. 5, pp. 207-212, 1987) presented a process composed of three unit operations: lactate production via fermentation, cell removal and cell debris through ultrafiltration, and concentration / purification of the lactic acid via electrodialysis. However, since no prefilters are made, the permeability of ultrafiltration membranes is drastically reduced over time, which requires frequent chemical cleaning of ultrafiltration modules. US 5,002,881 relates to a fermentation process wherein the fermentation product undergoes an ultrafiltration operation where the retentate returns to the fermentation vessel and the permeate, corresponding to an ammonium lactate solution, is concentrated through a reverse osmosis operation. The concentrated ammonium lactate is then fed to the electrodialysis operation for lactic acid recovery and purification. During electrodialysis, ammonium hydroxide is formed which can be returned to fermentation for pH correction. As a disadvantage, we can highlight the fact that the concentrated ammonium lactate solution also contains unconverted sugars, vitamins, proteins and other contaminants, contributing to the decrease of electrodialysis efficiency and resulting in a thermally unstable product.

 US 5,503,750 relates to a process having a sequence of membrane separation operations (ultrafiltration, nanofiltration and reverse osmosis) for concentration of an ammonium lactate solution and further conversion to lactic acid. A disadvantage of this process is the low recovery efficiency (approximately 54%), and the fact that the conversion of ammonium lactate to lactic acid uses ion exchange resins (which implies a large amount of resins, besides requiring successive regeneration operations).

US Patent 4,882,277 aims to simplify all steps used for lactic acid purification using only three unitary operations: microfiltration, ultrafiltration and electrodialysis performed continuously throughout the fermentation. The focus of this paper is on the arrangement of conventional electrodialysis operation on a laboratory scale.

 In addition to the previous document, US Patent 4,885,247 proposes a closer arrangement to industrial application, highlighting the possibility of residual lactate return to the fermenter in order to decrease the demand for alkaline solution to control the acidity of the medium and reduce the losses of the medium. process.

US 6,319,382 relates to a fermentation process (using ammonia for pH correction), purification and regeneration of lactic acid consisting of a fermentation step followed by microfiltration and ultrafiltration to remove cells, fragments of cells and macromolecules. The permeate passes through ion exchange resins (chelate resin) for the replacement of bivalent cations with monovalent cations (such as sodium), avoiding the formation of insoluble salts that could damage the membranes of the subsequent electrodialysis process. The bivalent cation-free permeate then undergoes a conventional electrodialysis process for acid regeneration and then bipolar electrodialysis for acid concentration. A disadvantage of this process can be highlighted by the fact that there is a high consumption of chemicals for the regeneration of ion exchange columns, the loss of product corresponding to the hold-up of ion exchange columns in each regeneration and the requirement proper monitoring of the contamination of regeneration solutions. In addition, these operations do not guarantee the removal of organic contaminants that generate color to the product and lead to instability. by the formation of Maillard compounds.

 US 2004033573A1 relates to a process using membrane separation steps including ultrafiltration, nanofiltration, reverse osmosis and electrodialysis. In this proposal, the fermentative liquor is ultrafiltered for the retention of high molecular weight substances. Then the permeate is acidified to a pH below 3.9. The acidified solution undergoes an isolation step via nanofiltration and / or reverse osmosis that promotes retention of bivalent ions, proteins, other nutrients and organic anions (such as lactate anion) and permeation of charge-free molecules (such as sodium lactate). Then, the use of bipolar electrodialysis for lactic acid solution concentration can be considered. The use of nanofiltration and / or reverse osmosis is an alternative to the conventional electrodialysis process.

 Ion Exchange Processes

 European patent document EP 0393818 complements US patent document US 4,885,247, including two ion exchange steps subsequent to the electrodialysis step. Strong acid ion exchange resins are used for removal of sodium cations that were not removed during conventional electrodialysis and weak basic ion exchange resins for removal of sulfate anions.

US 5,571,657 proposes the modification of strong acidic ion exchange resins by contact with ammonium and / or amine solutions to increase their selectivity to Na + cation, increasing thus the efficiency of the lactic acid regeneration process of sodium lactate solutions.

 Extractive Processes

 US 4,275,234 discloses a process for recovering aqueous organic acid solutions using an initial extraction with organic solvent followed by a second extraction with heated water. It is noteworthy that this application is restricted to solutions in which the organic acid is in its free form.

 Brazilian patent document BR 8906651 proposes a process for purification and recovery of lactic acid from solutions containing it by a sequence of liquid-liquid extractions. Initially, an aqueous lactate and lactic acid solution receives the addition of a complexing agent (composed of at least one macolytic octol) generating octol-lactic acid. This aqueous phase then undergoes liquid-liquid extraction with an organic solution of saturated halogenated cycloalkanes, alkylated and / or halogenated aromatic hydrocarbons and petroleum ether. The organic phase is separated and then goes through a liquid-liquid extraction with water or methanol. Disadvantages include the high reaction time for complex formation (about 8 h), the need for expensive complexing agents and the risks associated with the use of aromatic organic solvents which entail a number of operational difficulties.

Works such as B. Bar and JL Geiner (Biotechnology Progress, Vol. 3, No. ² 109, 1987), Malmary et al (J. Chem. Technol. Biotechnol., No. 75, pp. 1169-1173, 2000) , Hartl and Marr {Separation Science and Technology, n. 28, p. 805-819, 1993) and San-Marin and Cheryan (J. Chem. Technol. Biotechnol., No. 65, pp. 281-285, 1996) attested to the efficiency of separating lactic acid extraction from an aqueous solution by long chain, low basic trialkylamines which are capable of complexing with carboxylic acids even at low solute concentrations while maintaining high selectivity.

 US 4,444,881 discloses a process capable of purifying organic acids from a dilute fermentation solution. This solution is treated with a tertiary amine carbonate (e.g. tributylamine or tricyclohexylmethylamine), resulting in a calcium carbonate precipitate and an organic trialkyl ammonium salt. The organic salt solution is isolated, concentrated by solvent extraction, distilled and heated for the generation of lactic acid and tertiary amine. Disadvantages include the cost of specific chemicals, such as tertiary amines, and the absence of organic acid aftertreatments that ensure no impurities.

US 4,771,001 discloses a process for continuously withdrawing lactate throughout the cheese whey fermentation liquor. During fermentation, cells are separated and recirculated via microfiltration and ultrafiltration, where the permeate proceeds to the purification steps. The permeate is acidified and then undergoes a liquid-liquid extraction operation with a solution (water immiscible) of a 24-carbon tertiary trialkylamine and an organic solvent. The organic phase is then separated and undergoes a liquid-liquid extraction operation using a suspension of alkaline solids and alkaline earth solids in an aqueous ammonium hydroxide solution, which promotes the removal of lactic acid and lactate. This patent document does not address concentration steps or even isolation of lactic acid.

US 5,510,526 employs as extraction phase a solution of trialkylamine with strong attraction to lactic acid (for example, tri-n-octylamine and tri-n-dodecylamine) in a CO ₂ atmosphere extraction. Sodium bicarbonate crystals are formed and separated from the aqueous phase. Bicarbonate is converted to carbonate and returns to the fermentation process being used for pH neutralization. The type of alkylamine used should be chosen so that its attractive force is high enough to extract lactic acid from the lactate solution and weak enough to deliver the acid to water. Because they are viscous, these alkylamines should be added with kerosene and / or octanol. The lactic acid is removed from the organic phase by contact with water. If kerosene or octanol is used, a step prior to washing with water should be done to remove these solvents.

 US 6,478,965 discloses a route in the use of tertiary or secondary amines (e.g., TEA, DIA or DEMA) in extracting water from a lactic acid diluted stream (about 3%), thereby producing a concentrated stream. lactic acid 15%. A series of contactors is required to promote water extraction from the organic phase.

US 6,509,179 combines a set of unit operations for acid purification. It consists of acidification, salt removal, activated carbon filtration, primary extraction, secondary extraction, evaporation and vacuum distillation.

 US 7,026,145 proposes an improvement of the lactic acid extraction process using tertiary alkylamines through the use of sulfuric acid together with the amine solution, and a preliminary acidification step using the same acid.

 US 2004210088A1 describes various lactic acid production routes based on liquid-liquid extraction with specific amines and / or alcohols, with solvent removal through distillation columns in the top or bottom product ( depending on the route considered).

US 7,019,170 describes the recovery of lactic acid from a lactic acid and lactate solution by a sequence of liquid-liquid extraction operations. A first liquid-liquid extraction column promotes mass exchange between a lactic acid and lactate stream and a trialkylamine stream, generating a primary raffinate stream and a saturated trialkylamine stream. The saturated trialkylamine stream passes through a liquid-liquid extraction column with pure water, generating a pure lactic acid stream and a "living" trialkylamine stream. A third liquid-liquid extraction column promotes contact between the primary raffinate stream and the "live" trialkylamine stream, generating a secondary raffinate stream and a recovered trialkylamine stream (which may be returned to the first extraction operation). Evaporative Processes

 US 6,489,508 details the process of lactic acid concentration through evaporation highlighting the optimum operating conditions of both pressure (vacuum) and temperature, in order to minimize color change of the final product.

 International publication WO 00 / 56693A1 describes a vacuum distillation process followed by crystallization, which allows the concentration of an 80% lactic acid solution to a concentration of 99%. The high energy consumption of the coupling of evaporation and crystallization operations is a significant disadvantage of this proposal.

 US 6,384,276 proposes the acidification of a solution of lactic acid and sodium lactate. Then an evaporative crystallization is made in which sodium lactate is crystallized and the lactic acid is kept in solution. However, it is observed that the success of this proposal depends on having a pure solution (free of sugars, proteins or vitamins) as load, otherwise there will be contamination of the final product and generation of a colored product.

 Alternative Processes

US 5,177,008 proposes the use of chromatographic separation operations for lactic acid separation for the reuse of this product from secondary streams of the ethanol industry. However, the high cost of this process, especially for large scale lactic acid production, significantly restricts the application of this technology. CN 101234960 proposes a concentration process which promotes the initial evaporation of lactic acid followed by rotary distillation (also called molecular distillation), generating a very high purity lactic acid stream.

 It would be useful if the technique had a process of obtaining lactic acid from fermentative broths that uses clarification, regeneration, purification and concentration of the liquor, the process operating under energy efficiency by process stream recycling, the final product being concentrated lactic acid of high purity.

 SUMMARY OF THE INVENTION

 Broadly, to produce a high purity lactic acid from fermentative broths while maintaining a high overall yield, a process consisting of a sequence of unit operations and various recycling streams has been developed in the present invention. reuse of by-products and intermediate streams.

 These operations involve:

 (a) clarification of the fermentative liquor containing sodium lactate by centrifugation, microfiltration, tangential ultrafiltration and final filtration on activated charcoal to obtain a clarified sodium lactate solution;

 b) regeneration of said solution obtained in step a) by submitting it to conventional electrodialysis (EDC) and bipolar electrodialysis;

c) subjecting the solution to ion exchange with resins, obtaining a current with 80 to 200 g / l of lactic acid and 10- 20% sodium lactate;

 d) purifying the lactic acid from step c) by evaporation, generating a lactic acid stream containing from 1-5% impurities. The concentrated lactic acid obtained is placed in contact with activated charcoal, obtaining colorless concentrated lactic acid, which must be extracted with organic alcohol or amine alcohol solution and, after extraction, washed with water to remove impurities. At the end of the step, purified lactic acid at 5-10 g / l containing from 0.01 to 3% impurities is obtained; and

 e) evaporating the purified lactic acid to obtain purified 80-90% concentrated lactic acid.

 Energy efficiency is guaranteed through reuse of thermal energy from intermediate currents.

 Thus the invention provides a process for obtaining high purity concentrated lactic acid through the clarification, regeneration, purification and concentration steps, the lactic acid being derived from a fermentative liquor containing sodium lactate and various contaminants present in the lactic acid. substrates of the fermentation process.

 Additionally, in the process of obtaining high purity concentrated lactic acid of the present invention, the proposed steps are combined synergistically.

 BRIEF DESCRIPTION OF THE FIGURES

The accompanying Figure 1 is a block diagram showing in a simplified manner the sequence of the main unit operations according to the process of the invention, showing only the main product streams and intermediate products.

 The accompanying Figure 2 shows a process flowchart of the invention which describes the unit operations and main streams of the process for producing concentrated high purity lactic acid containing some by-product recycling streams.

 The accompanying Figure 3 shows a process flowchart according to the invention which illustrates the unit operations and main process currents for producing concentrated high purity lactic acid considering energy integration.

 The accompanying Figure 4 shows a process flowchart according to the invention which illustrates the unit operations and main process currents for producing high purity concentrated lactic acid considering energy integration and mass integration (with recycle streams). by-products).

 DETAILED DESCRIPTION OF THE INVENTION

 The present invention describes a process for obtaining lactic acid from the steps of clarification, regeneration, purification and concentration of lactic acid from a fermentative liquor containing sodium lactate and various contaminants present in the fermentation process substrates.

 The proposed process is concerned with energy efficiency. For this reason, several energy reuse exchangers were considered and no crystallization and washing steps were used, as suggested in prior art documents.

Another concern of the inventors concerns the use of chemicals that are easily obtainable. on the market and are low cost, unlike previous documents that employ specific solvents.

 Lactic acid is produced by fermentation, typically the fermentation of a growth medium comprising a sugar solution and a protein, for example, milk protein in the form of milk protein permeate obtained from the milk protein concentrate. Fermentation is preferably effected by the addition of one or more protease enzymes to the fermenter to result in continuous production of hydrolyzed protein simultaneously with fermentation by means of a lactic acid-producing bacterial culture. Bacterial cultures producing lactic acid are cited, for example, in international publication WO 98/28433.

 The present invention combines several technologies which can be divided into four steps: clarification, regeneration, purification and concentration.

 The process of the invention is carried out continuously. Furthermore, the process of the invention further admits batch operation.

 The process of the invention provides an 80-90% aqueous lactic acid solution and 0.01 to 3% impurities.

 The process of the invention synergistically and successively combines the described steps to obtain an energy efficient, high purity concentrated product.

 Clarification Step

The process filler is derived from a fermentative liquor resulting from a milk fermentation process and consists of an aqueous solution containing 50 to 80 g / l sodium lactate (more specifically 60 to 70 g / l), 3 to 5 g / l cell mass (from microorganisms responsible for the fermentation process such as, for example, Lactobacillus casei) and fiber (from fermentation feedstock such as, for example, manioc fibers - Manihot esculenta), 10 to 50 g / l polysaccharides (more specifically 10 g / l to 30 g / l), 1 to 5 g / L protein and vitamins and 100 to 500 ppm of divalent cations (Mg ²⁺ , Ca ²⁺ and Sr ²⁺ ).

 The beginning of the process consists in the centrifugation of the fermentation broth, in order to promote the removal of fibers and other suspended solids, generating a pre-clarified fermentative liquor liquid stream and a wet slurry of fibers and cellular material. This operation is fundamental for the treatment of fermentative liquors that use as a substrate broths extracted from vegetables, specifically fibrous vegetables.

 Practical experience shows that employing upstream centrifugation for other more restrictive filtration operations, such as membrane microfiltration, reduces the backwash frequency and increases permeate flow.

The wet sludge (containing from 5 to 25% fermentative liquor) generated in the centrifugation is still impregnated with fermentative liquor, which should be removed from this pulp in order to reduce sodium lactate losses in this clarification step. For this, a centrifugal decanter (decanter) is used which allows the formation of a dry pulp with 0.5 to 2.5% residual fermentative liquor. Dry pulp can be sold as a by-product. this process for use in fertilization or as animal feed, depending on a prior analysis of such viability.

 The pre-clarified liquor then undergoes a tangential microfiltration operation through 50 μιη, preferably 30 μιτι, pore diameter polymeric membranes, which promotes the separation of waste fibers and cells. The retained liquor stream in the microfiltration returns to the centrifuge inlet and the microfiltrated liquor stream then passes to the next filtration step.

 The microfiltrated liquor feeds the tangential ultrafiltration operation through 30 to 70 kDa porosity polymeric membranes, which promotes the separation of macromolecules and cell fragments. The ultrafiltration retained liquor stream returns to the centrifuge inlet and the ultrafiltrated liquor stream then moves to the next filtration step.

 Optionally, the ultrafiltrate liquor stream may be subjected to a nanofiltration step in order to reduce the concentration of bivalent cations present in the filtered medium. Several membranes may be used for such application, such as, for example, polymeric membranes with 1 to 30 kDa porosity.

The liquor resulting from ultrafiltration and / or nanofiltration (if this process is additionally used) feeds the activated carbon bed filtration operation, which allows the removal of organic compounds that impart coloration to the aqueous solution. When the coloring load increases considerably, powdered activated carbon can be used with agitation of 200 rpm and contact time of 10 to 60 minutes before bed. As a result, a clear, colorless aqueous sodium lactate solution is obtained.

 Regeneration Stage

The sodium lactate stream from the activated charcoal bed proceeds to the conventional electrodialysis (EDC) step, where sodium lactate is purified and concentrated. EDC is the application of a potential difference between pairs of positive (anionic membranes) and negatively (cationic membranes) charged membranes. The aqueous sodium lactate solution (50-80 g / l) is fed between a cationic and an anionic (cell) membrane alternately with a diluted 1 to 10 g / l sodium lactate solution. This solution receives the lactate anion that migrates through the anion membrane towards the anode and the sodium cation from the negatively charged side. At the end of the process, the aqueous sodium lactate solution is depleted and the non-ionizable polysaccharides, proteins and vitamins remain in this stream, which returns to the centrifugation and / or fermentation step. The yield of this step ranges from 70 to 90% recovery depending on operating conditions (flow, pressure, current, DDP, pH, concentration, etc.). The diluted sodium lactate solution can be concentrated up to 20 times with total residual impurities ranging from 1 to 10% and 50 to 200 ppm of divalent cations (Mg ²⁺ , Ca ²⁺ and Sr ²⁺ ).

Sodium lactate is converted to lactic acid by bipolar electrodialysis. The principle of operation of bipolar electrodialysis is similar to EDC, except for the addition of one bipolar membrane (positive and negative charges) in each cell (1 cationic membrane and 1 anionic membrane). Bipolar membranes are sensitive to polyvalent cations that deposit on their surface, thus decreasing the regeneration efficiency. Polyvalent cations are removed from the lactic acid solution to contents up to 10 ppm in chelating resin filters prior to bipolar electrodialysis. At the end of bipolar electrodialysis, a solution with concentrations between 80 and 200 g / l lactic acid, 1 to 5% total impurities and 10 to 20% sodium lactate is obtained. Final polishing for regeneration of all sodium lactate in lactic acid is performed on a column with strong ion exchange resins. The regenerated product is then directed to the purification step to remove the remaining impurities.

 Purification Step

The lactic acid solution with 1 to 5% impurities is sent to an evaporation column where it will be concentrated to 40 to 60% by mass. The evaporation step concentrates organic compounds that add color to the product, thus requiring a new activated carbon filtration step for complete color removal. This color-free (400 to 600 g / L) concentrated lactic acid stream is admitted to a first liquid-liquid extraction column where it will come in contact with an average molecular weight alcohol selected from linear C4-C12 alcohols and / or branched (eg, butanol, pentanol, octanol, decanol, dodecanol, etc.), high molecular weight tertiary amines or a mixture of these alcohols with tertiary amines (eg trioctyline amine). The lactic acid-rich alcoholic stream flows into a second column where it will be washed with demineralized water and will return in closed loop to the first column. At the end of the cycle, there is an aqueous stream with 5 to 20 g / l of lactic acid and an exhausted stream that is discarded or reused in the fermentation process. The 5 to 20 g / l aqueous solution of colorless lactic acid with 0.01 to 3% total impurities proceeds to the concentration step.

 Concentration Stage

 Concentration of the purified and regenerated aqueous lactic acid solution is carried out in a single evaporation step with the mass temperature between 100 and 150 degrees Celsius and top temperature at 100 degrees Celsius subjected to atmospheric pressure. 80-90% lactic acid in colorless water with a concentration of impurities between 0.01 and 3% is obtained at the end of evaporation.

 Another alternative that makes the evaporation step faster is the application of vacuum to the evaporation system.

 The passage of the final product on carbon block carbon filters can be performed for final polishing.

 In the following, the figures illustrating the different embodiments of the present process are described. It should be made clear to those skilled in the art, however, that various modifications and variations are possible for these figures within the scope of the present invention.

The accompanying figures correspond to process flowcharts where unit operations are numbered through the hundreds 100 (clarification step), 200 (regeneration step), 300 (purification step), 400 (concentration step) and 500 (fermentation step). ) with material chains represented by numerals 1 through 38. Full lines are used to describe liquid or solid and dashed lines to describe vapor streams.

 The basic sequence of unit operations, including main currents, is described in Figure 1. The unit operations correspond to centrifugation (101), centrifugal decanting (102), microfiltration (103), ultrafiltration (104), primary coal bed filtration. activated (105), conventional electrodialysis (201), chelating resin bed ion exchange columns (202), bipolar electrodialysis (203), ion exchange columns (204), primary vacuum evaporation (302), secondary bed filtration activated carbon (304), liquid-liquid extraction from the aqueous phase to the organic phase (305), back extraction from the organic phase to the aqueous phase (306) and secondary atmospheric evaporation (402).

 The fermentative liquor (1) is centrifuged at (101), generating a stream of supernatant liquid, called pre-clarified fermentative liquor (5), and a dense stream, called wet sludge (2), composed of fibers and cellular material. .

 The wet slurry (2) is then dehumidified in the centrifugal decanter (102), generating a dry pulp stream (3).

The pre-clarified fermentative liquor (5) undergoes a microfiltration operation (103), generating a microfiltration stream (7), which is fed to the ultrafiltration operation (104), generating an ultrafiltrate stream (9). . The ultrafiltrate liquor (9) then undergoes a activated carbon bed filtration process (105), yielding a clarified, colorless aqueous sodium lactate solution (10). Alternatively, the ultrafiltrate stream 9 is subjected to a step of nanofiltration (not shown) to reduce the concentration of bivalent cations present in the filtered medium.

 The aqueous sodium lactate solution (10) is fed to a conventional electrodialysis operation (201), generating a concentrated sodium lactate solution (12). The concentrated sodium lactate solution (12) then undergoes an ion exchange operation with chelating resins (202) to generate a concentrated stabilized sodium lactate solution (13) free of bivalent cations.

 The concentrated stabilized sodium lactate solution (13) feeds a bipolar electrodialysis operation (203), promoting lactic acid regeneration and generating a pre-regenerated lactic acid current (15). The pre-regenerated lactic acid stream (15) then undergoes a strong acid resin bed ion exchange operation (204), generating a regenerated lactic acid stream (16).

The regenerated lactic acid stream (16) is concentrated by a primary vacuum evaporation operation (302), generating a concentrated regenerated lactic acid stream (19). The concentrated regenerated lactic acid stream (19) then undergoes a activated carbon bed filtration process (304), generating a colorless lactic acid stream (22). The colorless lactic acid stream (22) passes through a sequence of liquid-liquid extractions, namely from the aqueous phase to the organic phase (305) and then from the organic phase to the aqueous phase (306) through contact. with a stream of demineralized water (24), generating a stream of impure lactic acid (23) and a dilute solution of lactic acid with high purity (28).

 The dilute high purity lactic acid solution (28) is concentrated by a secondary evaporation operation (402), generating a concentrated high purity lactic acid stream (30).

 Figure 2 further details the process streams, including by-products, intermediates and inputs.

 The streams of microfiltration concentrate (6), ultrafiltration concentrate (8) and centrifuge decanter supernatant (4) are returned to the centrifuge feed (101).

 The conventional electrodialysis operation (201) generates as a byproduct a dilute sodium lactate stream (11) ·

 The bipolar electrodialysis operation (203) generates a concentrated sodium hydroxide stream (14) which can be used as input for the process.

 Evaporation operations (302 and 402) generate water vapor streams (37 and 31) which can be used as process utilities.

 Activated charcoal filtration operations (105 and 304) intermittently generate tailings streams (21) during the activated charcoal bed regeneration periods.

 The liquid-liquid extraction operations (305 and 306) have internal recycling streams from the sodium lactate-rich organic phase (26) and from the sodium lactate-poor organic phase (27).

The secondary evaporation operation (402) may generate, depending on contamination, a precipitated sodium lactate stream (33) if it is not completely regenerated throughout the process.

 Figure 3 incorporates the possibility of energy reuse by the use of heat exchangers (301, 303, 401 and 403) to preheat the currents that feed the operations (302, 304 and 402). In addition to saving energy for evaporating water and concentrating currents (16) and (28), the heat exchanger (303) allows heating of the demineralized water stream (24), which guarantees an improvement in the performance of the water. counter-extraction operation (306).

 Figure 4 incorporates the possibility of integrating the regeneration, purification and lactic acid concentration process into the fermentation process.

 Said Figure 4 includes the fermentation operation (501), which may be performed in the form of successive batches or in continuous form.

 The current (35) corresponds to the feeding of cells, substrate and other nutrients to the fermentation (501).

 The stream (36) corresponds to the caustic soda solution continuously added for fermentation pH control (501).

 The wet sludge stream (2) is recirculated for the fermentation operation (501).

 The microfiltration and ultrafiltration tailings streams (6 and 8) are also recirculated for the fermentation operation (501).

 The caustic soda stream (11) generated in conventional electrodialysis is also recirculated for the fermentation operation (501) to promote lactic acid neutralization.

The diluted sodium lactate streams (14) generated as a byproduct of bipolar electrodialysis (203), dilute lactic acid (23) exhausted from liquid-liquid extraction (305) and precipitated sodium lactate (33) on secondary evaporation (402) are recirculated for the fermentation operation (501) .

 The invention will be illustrated below by a number of examples, which are not to be construed as limiting thereof.

 EXAMPLE 1

 This example illustrates sizing, testing, and mass balances for the clarification step.

 For a process designed to treat 250 kg / h of sodium lactate (70 g / L) in a fermentative liquor obtained through milk fermentation, two different scenarios were considered depending on the composition of the fermentative liquor. Scenario 1 refers to a liqueur composed of 5 g / l Lactobacillus casei cells and manioc fibers (Manihot esculenta), 5 g / l vitamins and proteins and 30 g / l unconsumed polysaccharides during the fermentation process. . Scenario 2 concerns a liqueur composed of 3 g / l Lactobacillus casei cells and manioc fibers (Manihot esculenta), 1 g / l vitamins and proteins and 10 g / l unconsumed polysaccharides during the fermentation process. .

For clarification of the sodium lactate solution, a 40 m ³ / h feed and 4 m ³ / h concentrate centrifuge, a 0,5 m ³ / h feed and 0 0 centrifuge decanter are used. 05 m ³ / h concentrate, microfiltration and ultrafiltration systems with 4 m ³ / h processing capacities 3.5 m ³ / h microfiltration and ultrafiltrate respectively and a activated carbon bed filter for 3.5 m ³ / h filtration.

With respect to the microfiltration system, pilot scale tests indicated that this system should be operated using time-delayed backwash (at a frequency of 15 to 60 minutes) characterized by pumping in the opposite direction of the microfiltrate itself. Studies have indicated the following optimal design parameters for microfiltration modules: permeate flow rate to feed rate of about 0.15, permeability 1.0 x 10 ^{~ 4} L / (hm ² · Pa) (10 1.0 L / (h * m ² -bar)) and transmembrane pressure (difference between feed and permeate pressures) equal to 1.0 x 10 ⁵ Pa (1.0 bar). The membrane area required for this operation is about 400 m ² , which corresponds to the use of 8 50 m ² hollow fiber modules. The feed pump flow rate for this application is 35 m ³ / h.

Regarding the ultrafiltration system, pilot scale tests indicated the following optimal design parameters for ultrafiltration modules: permeate flow rate to feed rate of about 0.50, permeability 1.5 x 10 ^"4 L / (h · m ² · Pa) (15.0 L / (h · m · bar)) and transmembrane pressure (difference between feed and permeate pressures) of 1.5 x 10 ⁵ Pa (1.5 bar ) The membrane area required for this operation is about 150 m ² , which corresponds to the use of 6 dense 25 m ² flat membrane modules. The feed pump flow rate for this application is 8 m ³ / H.

Regarding the activated carbon bed filter, pilot scale tests indicated the following parameters design optimum: residence time of the coal-contact solution equal to 4 hours and a coal packing density of about 800 kg / m ³ . Thus, for processing 3.5 m ³ / h of aqueous sodium lactate solution, a 175-liter pot and a coal mass of 140 kg are used. Coal regeneration was also required every 3-6 hours of system operation using steam at 120-150 ° C.

 Pilot scale tests allowed the determination of mass balances for the clarification step for the two proposed scenarios, considering the 25% purge of ultrafiltration tailings (Tables 1 and 2 attached) and the 10% purge of ultrafiltration tailings (Tables 3 and 4 attached). It is noteworthy that, as it is a continuous operation and there is a concentration of contaminants due to the recirculation of the ultrafiltration tailings, it is necessary to purge part of this stream in order to avoid raising the concentration of these residues within the participating currents. this recycle.

 From the attached tables 1 to 4, the clarification step mass yield for sodium lactate can be determined to be about 80% for scenarios 1 and 2 for a purge of 25% and about 90% for scenarios 1 and 2 considering a 10% purge.

 EXAMPLE 2

 This example illustrates sizing, testing, and mass balances for the concentration step.

For a scaled process without energy reuse for a concentration of 250 kg / h sodium lactate from an aqueous lactic acid solution For a purified and regenerated lactic acid concentration of 15 g / l, the use of an atmospheric evaporator with a heat exchange capacity of about 12 W is required to remove 16,3 tonnes / hour of steam with a system for separating 17 kg / h from insoluble impurities as described in the attached Table 5 which lists the mass balance of the concentration step. From this table it is possible to estimate an energy consumption of about 172 MJ / kg of lactic acid.

 For a scaled process with energy reuse, a heat exchanger with heat exchange capacity of about 1.3 MW is included for preheating the purified and regenerated aqueous lactic acid solution from 25 ° C to 90 ° C, using as a hot fluid the water vapor generated in the atmospheric evaporator as described in the attached Table 6. From this table, it is possible to estimate an energy consumption of about 153 MJ / kg of lactic acid.

 EXAMPLE 3

 This example illustrates the sizing, testing, and mass balances for the primary evaporation of the purification step.

For a process without energy reuse at a concentration of 250 kg / h sodium lactate from a purified and regenerated aqueous lactic acid solution with a concentration of 125 g / l lactic acid, the use of an evaporator at vacuum (2.5 x 10 ⁴ Pa - 250 mbar) with a heat exchange capacity of about 1.0 MW for the removal of 0.6 tons / hour of water vapor as described in the attached Table 7 which lists the mass balance of the primary evaporation of the purification step. From this table is It is possible to estimate an energy consumption of about 15.2 MJ / kg lactic acid.

 For a scaled process with energy reuse, a heat exchanger with a heat exchange capacity of about 1.0 W is included for preheating and evaporation of the dilute regenerated lactic acid solution from 25 ° C to 80 ° C, using as a hot fluid water vapor at 120 ° C generated in the atmospheric evaporator as described in the attached Table 8.

 Thus, it is possible to promote primary evaporation using only the hot fluid generated in the concentration step.

 EXAMPLE 4

 This example illustrates the sizing, testing, and mass balances for the liquid-to-liquid extractions from the purification step.

For a process designed for the purification of 250 kg / h lactic acid from an aqueous concentrated lactic acid solution (500 g / l), a first conventional liquid-liquid extraction column is used to contact 500 l / h acid solution. concentrate with 1.0 m ³ / h octanol and a second conventional liquid-liquid counter-extraction column to contact 1.0 m ³ / h octanol with 1.0 m ³ / h demineralized water. As a result, an aqueous stream having a flow rate of 1.0 m ³ / h of diluted purified lactic acid solution at a concentration of 15 g / l is obtained.

Aqueous streams enter the bottom of the extraction columns and alcoholic streams at the top because the density of octanol (0.8 g / mL) is lower than that of water (1.0 g / mL). The first conventional column has 20 theoretical plates with 1.5 meters in diameter and has a decanter at the exit of the alcohol phase for retention of drag of the aqueous solution. Octanol from the first column is under pressure and overflows from the decanter to the bottom of the second column.

 The second conventional column has the same characteristics as the first one and the depleted octanol from the decanter is recovered in the first column, thus remaining in a closed loop.

 Pilot scale tests provided 70% lactic acid recovery on the first pass through the system. It is noteworthy that the remaining 30% lactic acid can be re-concentrated in the evaporation system and resubmitted for further liquid-liquid extraction, thus resulting in losses to the process.

 EXAMPLE 5

 This example illustrates sizing, testing, and mass balances for conventional electrodialysis of the regeneration step.

For a process designed for a concentration of 250 kg / h sodium lactate from a diluted 70 g / l sodium lactate solution a conventional electrodialysis (EDC) stack with a treatment capacity of 3, 6 m ³ / h. Considering a current density of 110 A / m ² with 80% current efficiency and a voltage of 155 V, 175 m ² of membrane area is required.

This process has a yield of about 80% from 6.5 m ³ / h of a 5 g / L sodium lactate solution and generates 6.5 m ³ / h of an aqueous solution as a byproduct. low in sodium lactate (14 g / L) containing polysaccharides, proteins and vitamins. Electrolytes consume 3 m ³ / h of a 2% sulfuric acid solution. The product stream corresponds to a 3.5 m ³ / h flow rate of a 125 g / l lactic acid solution.

 EXAMPLE 6

 This example illustrates the sizing, testing, and mass balances for bipolar electrodialysis of the regeneration step.

For a process sized for regeneration of 200 kg / h sodium lactate from a solution of 125 g / l sodium lactate, a bipolar electrodialysis (EDBM) stack with a capacity of 3.0 m ³ / h. Considering a current density of 600 A / m ² with 70% current efficiency, an average current of 2.5 A and a voltage of 165 V, 85 m ² of membrane area is required.

This process has a yield of about 90% lactic acid relative to the fed sodium lactate. The product stream corresponds to a flow rate of 3.0 m ³ / h of a lactic acid solution with a concentration of 112.5 g / l lactic acid and 12.5 g / l sodium lactate.

It should be made clear to those skilled in the art that while the present invention has been described with respect to lactic acid, many other carboxylic acids may also be subjected to a similar process, such as: formic acid, acetic acid, butyric acid, propionic acid, valeric acid, isovaleric acid, capronic acid, heptanoic acid, octanic acid, oxalic acid, maloic acid, glutaric acid, adipic acid, glycolic acid, glycolic acid, acid acrylic, tartaric acid, fumaric acid, benzoic acid, maleic acid, phthalic acid or salicylic acid.

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Microfiltered Liqueur

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Ultrafiltration Tailings Purge

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TABLE 6

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^ilt co ^p uro

l ^idlíái _S ^ãddd o ^ç uouaeco

^iléidt will co ^{p q} r indexes ecau- 28 29 ^{l O} or ^Sãddt oconcenarae 30 31 31 32

^Áidláit temperature coconut rou ^p

 (° C) 25 90 120 120 100 120

' ^{á V} a ^p or ^g au

 Mass Flow

(kg / hr) 16666 16666 333 16316 ^{of ya V} 1a ^p or ^g aa ^p su6316 17

Flow rate ^iitit rea ^p roveamenoener ^g co

 Volumetric

oh ^{i LddttS} action

(L / h) 16666 16666 277 - - 14 i ^idtp rec ^p to

Concentration

 (g / l)

 Lactate

 Sodium and

 Impurities 1.0 1.0 0.0 0.0 0.0 1000.0

Lactic Acid 15.0 15.0 900.0 0.0 0.0 0.0 20.0

Mass Flow

 (kg / h)

 Lactate

 Sodium and

 Impurities 16, 7 16, 7 0 0 0 16, 7

Lactic Acid 250 250 250 0 0 0.3 TABLE 7

indexes 16 19 37

Temperature (° C) 25 80 80

Mass Flow (kg / h) 2000 600 1400

Volumetric Flow Rate (L / h) 2 ^áidlt 0coco00 500 -

Concentration (g / l) ^d reagent

Sodium Lactate & Impurities 25 ^100,0 0.0 0.0

 Lactic Acid 125, 0 500, 0 0, 0 reareation

Mass Flow (kg / h)

' ^{á V} a ^p ro ^g ua

Sodium Lactate and Impurities 50 50 0

Lactic Acid 250 250 0

TABLE 8

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17 ^alidt core ^g generation

Indexes 18 19 37 32 38

Temperature (° C) 25 ^{iíáldlddi SAD} or ^O ouaeco 80 80 80100100

Mass Flow (kg / hr) 2000 200 ^áldéididt core ^g enerao ^p ra ^q ueca-0 600 1400 1603 1603

Volumetric Flow Rate (L / h) 2000 2000 ^{Láddid S ç} uoconcenraaeco 500 - - -

Concentration (g / l) ^alidt core ^g generation

Sodium Lactate and Impurities ^25,0 0 ^{25,0 100,0} 0 ^{'a V} a ^p or ^g au, 0 0,0 0,0

Lactic Acid 125,0 125 0 500 0 0 0 0 0,0 0,0

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 Mass Flow (kg / h)

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Sodium Lactate and Impurities 50,0 0 50 50 0 0 c ^dd onensation to ^p 0.0

Lactic Acid 250 250 250 0 0 0, ^ieittt rea ^p roe0vamenoener ^g co

Claims

 Process for obtaining high purity lactic acid from fermentative liqueur containing sodium lactate, vegetable fibers and polysaccharides comprising the steps of:

 (a) clarification comprising the following substeps:

 al) centrifuging (101) the fermentative liquor (1), generating a pre-clarified fermentative liquor supernatant stream (5) and a dense wet sludge stream (2) composed of fibers and cellular material containing from 5 to 25% of fermentative liquor, said wet sludge (2) being dehumidified in a centrifugal decanter (102), generating a stream of dry pulp (3) with 0.5 to 2.5% residual fermentative liquor;

 (a) Microfiltration by tangential microfiltration into (103) the pre-clarified fermentative liquor (5) of substep (1), generating a stream of microfiltrated liquor (7);

 a3) feeding the stream (7) of substep a2) to a tangential ultrafiltration operation (104), generating an ultrafiltrate liquor stream (9);

 a4) filtering on activated carbon bed (105) the ultrafiltrate liquor (9) from substep a3), generating a clarified, colorless aqueous sodium lactate solution (10);

 (b) regeneration, comprising the following substeps: (bl) feeding said aqueous sodium lactate solution (10) from substep a4) to a conventional electrodialysis operation (201) generating a concentrated sodium lactate solution (12);

b2) subjecting said solution (12) of substep bl) to ion exchange with chelating resins (202), generating a concentrated solution of stabilized sodium lactate (13) free of bivalent cations;

 b3) feeding said solution (13) from substep b2) to a bipolar electrodialysis operation (203), promoting lactic acid regeneration and generating a pre-regenerated lactic acid stream (15) with a concentration of 80-200 g / L lactic acid and 10-20% sodium lactate;

 b4) subjecting said stream (15) from substep b3) to a strong acid resin bed ion exchange operation (204), generating a regenerated lactic acid stream (16);

 c) Purification, comprising the following substeps: cl) concentrating said stream (16) from substep b4) by primary vacuum evaporation (302), generating a concentrated regenerated lactic acid stream with 1-5% impurities (19);

 c2) filtering on activated carbon bed (304) said stream (19) of substep cl), generating a colorless lactic acid stream (22) with 0.1 to 3% impurities;

 c3) subjecting said stream (22) from substep c2) to a sequence of liquid-liquid extractions, the first extraction being from the aqueous phase to the organic phase (305) and the second extraction being from the organic phase to the aqueous phase (306). ) by contact with a demineralized water stream (24), generating respectively a crude lactic acid stream (23) and a dilute high purity lactic acid solution (28); and

d) Concentration, comprising concentrating the dilute high purity lactic acid solution (28) from substep c3) by secondary evaporation at (402), yielding a stream (30) of high purity lactic acid at a concentration of 80-90%.

 Process according to Claim 1, characterized in that the streams of microfiltration concentrate (6), ultrafiltration concentrate (8) and supernatant (4) of the centrifugal decanter (102) are fed back to the centrifugation feed (101). ).

 Process according to Claim 1 or 2, characterized in that it further performs a membrane nanofiltration operation between substeps a3) and a4).

 Process according to any one of claims 1 to 3, characterized in that the conventional electrodialysis operation (201) generates as a by-product a dilute sodium lactate stream (11).

 Process according to any one of claims 1 to 4, characterized in that the bipolar electrodialysis operation (203) generates as a byproduct a concentrated sodium hydroxide stream (14).

 Process according to Claim 5, characterized in that said concentrated sodium hydroxide stream (14) can be used as an input to the process.

 Process according to any one of Claims 1 to 6, characterized in that the activated carbon filtration operations (105, 304) intermittently generate tailings streams (21) during the regeneration periods. of the activated carbon bed.

Process according to any one of claims 1 to 7, characterized in that a liquid-liquid extraction substep c3) employs a moderate molecular weight alcohol selected from C _{4 to} C ₁₂ alcohols, a high molecular weight tertiary amine or a mixture in any proportion of said C ₄ -C ₁₂ alcohol and said amine.

 Process according to Claim 8, characterized in that the tertiary amine is trioctyline amine.

Process according to Claim 8, characterized in that the C ₄ -C ₁₂ alcohol is selected from the group comprised of butanol, pentanol, octanol, decanol, dodecanol or the like.

 Process according to any one of claims 1 to 10, characterized in that the water vapor streams (37, 31) generated respectively by evaporation operations (302, 402) are used as process utilities. .

 Process according to any one of Claims 1 to 11, characterized in that the liquid-liquid extraction operations (305, 306) generate internal recycle streams from an organic phase rich in sodium lactate (26). and an organic phase low in sodium lactate (27).

 Process according to any one of claims 1 to 12, characterized in that the secondary evaporation operation (402) can generate a precipitated sodium lactate stream (33).

Process according to any one of Claims 1 to 13, characterized in that it is carried out in an energy-efficient manner by the use of heat exchangers (301, 303, 401 and 403) used for preheating the supply currents. the operations (302,304,402).

 Process according to Claim 14, characterized in that the heat exchanger (303) heats the demineralized water stream (24) following the counter-extraction operation (306).

 Process according to any one of Claims 1 to 15, characterized in that it further includes batch fermentation (501), a feed stream (35) and a caustic soda stream (36) being added to the fermenter. .

 Process according to any one of Claims 1 to 15, characterized in that it additionally includes the continuous fermentation operation (501), a feed stream (35) and a caustic soda stream (36) being added to the fermenter. ).

 Process according to Claim 16 or 17, characterized in that the feed stream (35) consists of a fermentation broth obtained by milk fermentation containing 50 to 80 g / l sodium lactate, 3 to 5 g / l cell and fiber mass, 10 to 50 g / l polysaccharides, 1 to 5 g / l protein and vitamins and 100 to 500 ppm bivalent cations.

 Process according to Claim 18, characterized in that the sodium lactate concentration is preferably from 60 to 70 g / l.

 Process according to Claim 18, characterized in that the polysaccharide concentration is preferably from 10 to 30 g / l.

Process according to any one of claims 1 to 20, characterized in that the wet sludge stream (2), the tailings tailings stream and the microfiltration (6) and ultrafiltration (8), the caustic soda stream (11) generated in conventional electrodialysis, the dilute sodium lactate stream (14) generated as a byproduct of bipolar electrodialysis (203), the diluted lactic acid stream (23) exhausted from liquid-liquid extraction (305) and precipitated sodium lactate stream (33) on secondary evaporation (402) are recirculated to the fermentation operation (501).