METHOD AND SYSTEM FOR OBTAINING A CARBOXYLIC ACID WHICH IS PRODUCED IN A FERMENTATION PROCESS

Abstract

A plant and a process may be utilized to isolate a carboxylic acid from a fermentation broth. The process may involve separating a biomass from the fermentation broth containing a salt of the carboxylic acid to produce a low-biomass solution. The separation of the biomass may be performed in a first step by centrifugation, separation, precoat filtration, or microfiltration, and in a second step by ultrafiltration. The process may further involve concentrating the salt of the carboxylic acid in the low-biomass solution. The concentrated solution may then be acidified. Further, precipitation of the carboxylic acid may be obtained by acidification.

Claims

1.-16. (canceled)

17. A process for isolating a carboxylic acid from a fermentation broth, the process comprising: separating a biomass from the fermentation broth containing a salt of the carboxylic acid to produce a low-biomass solution; concentrating the salt of the carboxylic acid in the low-biomass solution to form a concentrated solution; acidifying the concentrated solution; and precipitating the carboxylic acid obtained by acidification.

18. The process of claim 17 wherein the separation of the biomass is performed in a first step by centrifugation, separation, precoat filtration, or microfiltration, and in a second step by ultrafiltration.

19. The process of claim 17 wherein prior to the acidification of the concentrated solution, the process comprises purifying the low-biomass solution or the concentrated solution by at least one of nanofiltration, cation exchange, anion exchange, or activated carbon purification.

20. The process of claim 17 wherein a concentration of the concentrated solution is above a solubility concentration of the carboxylic acid.

21. The process of claim 17 wherein the salt of the carboxylic acid is concentrated from 1%-10% by weight to 40%-50% by weight.

22. The process of claim 17 wherein the salt of the carboxylic acid is concentrated from 3%-7% by weight to 20%-25% by weight.

23. The process of claim 17 wherein concentrating the salt of the carboxylic acid in the low-biomass solution comprises a membrane process performed in one, two, or more stages.

24. The process of claim 23 wherein the membrane process is at least one of nanofiltration, reverse osmosis, high-pressure reverse osmosis, or membrane distillation.

25. The process of claim 17 wherein a pH of the concentrated solution after the concentration is between 5.0 and 8.0; or a pH in the concentrated solution after the acidification is between 1.8 and 3.0.

26. The process of claim 17 wherein the precipitation of the carboxylic acid is performed by way of a crystallization comprising cooling crystallization and isolation of the crystallized carboxylic acid.

27. The process of claim 26 wherein a mother liquor remaining after isolation of the crystallized carboxylic acid is, after a concentration of the carboxylic acid present therein has been increased, fed to the cooling crystallization.

28. The process of claim 17 wherein concentrating the salt of the carboxylic acid is performed with at least partial recovery of energy consumed by concentrating the salt of the carboxylic acid.

29. The process of claim 17 wherein prior to the acidification of the concentrated solution, the process comprises purifying the low-biomass solution or the concentrated solution, wherein the concentration or the purification is performed with at least partial recovery of energy consumed by the concentration or a fine purification step.

30. The process of claim 17 comprising feeding discharge streams obtained in the concentration to an upstream portion of the process or to an esterification.

31. The process of claim 17 wherein the carboxylic acid has a solubility at 20? C. of 5 to 110 g/l; the carboxylic acid is at least one of fumaric acid, succinic acid, adipic acid, itaconic acid, threonine, methionine, aspartic acid, glutamic acid, oxalic acid, asparagine, glutamine, histidine, isoleucine, leucine, phenylalanine, tryptophan, tyrosine, or valine; or the salt of the carboxylic acid in the concentrated solution has a two-fold or five-fold greater solubility than the carboxylic acid.

32. A plant for isolating a carboxylic acid from a fermentation broth containing salt of the carboxylic acid, the plant comprising: a separation unit for separating biomass from the fermentation broth; a concentration unit downstream of the separation unit for concentrating the salt of the carboxylic acid in a low-biomass fermentation broth to form a concentrated solution; and an acidification unit downstream of the concentration unit for acidifying the concentrated solution.

33. The plant of claim 32 wherein the separation unit is configured for performing a centrifugation, a separation, a precoat filtration, a microfiltration, or an ultrafiltration; the concentration unit is configured for performing a nanofiltration, a reverse osmosis, a high-pressure reverse osmosis, or a membrane distillation; the acidification unit is a settling vessel having a conical bottom and a discharge device disposed in a tip of a cone of the settling vessel; or the plant comprises a purification unit disposed between the separation unit and the concentration unit for purifying the salt of the carboxylic acid in the low-biomass fermentation broth, wherein the purification unit is configured for performing a nanofiltration, a cation exchange, an anion exchange, or an activated carbon purification.

34. The plant of claim 32 comprising a cooling crystallizer disposed downstream of the acidification unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The invention is illustrated below with the aid of drawings. In detail, the drawings show:

[0068] FIG. 1 a preferred embodiment of the invention and

[0069] FIGS. 2 (2.1 and 2.2) a further preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0070] FIGS. 1 and 2 show inventive embodiments of the invention. To describe the figures, reference will be made in the following to the features of a plant equipped for carrying out the process of the invention.

[0071] According to FIG. 1, the plant 100 comprises a fermentation unit 1 in which a carboxylic acid is prepared by fermentation of carbohydrate-containing substrates by means of microorganisms. In particular, a fermentation broth which preferably contains a carboxylic acid salt and further impurities such as organic acids, by-products of the fermentation, microorganisms and constituents thereof and also residues of the substrates, e.g. sugar, is produced in the fermentation unit 1. The fermentation broth produced in the fermentation unit 1 is fed via a connecting piece 2 to a separator unit 3 and a preferably single-stage or multistage ultrafiltration unit 5 connected thereto via a connecting piece 4. In the separator unit, the biomass suspension 31 is separated from the fermentation broth so as to give a biomass-free fermentation broth. The biomass suspension 31 comprises essentially the microorganisms which have been separated off and remaining solids from the fermenter output. In the separator unit 3, the biomass 31 is precipitated by means of centrifugal force. The clear runnings from the separator are fed via the connecting piece 4 to the ultrafiltration unit 5. In the ultrafiltration unit 5, the fermentation broth coming from the separator unit 3 is purified in a second step. The membranes of the ultrafiltration unit 5 preferably have a separation limit of 0 kDa. The biomass-free fermentation broth is then fed via a connecting piece 6 to a purification unit 7. In the purification unit 7, the biomass-free fermentation broth is subjected to polishing by means of nanofiltration. Here, a nanofiltration membrane having a separation limit of from 100 to 400 Da is used. The process is carried out in such a way that the retentate 72 makes up not more than 2% of the total throughput. The retentate is discharged from the nanofiltration via the connecting piece 71. The permeate is subsequently fed via a connecting piece 8 to a concentration unit 9. Here, the content of the carboxylic acid salt in the biomass-free fermentation broth which has been purified by means of nanofiltration is concentrated to a value in the range from 7 to 50% by weight. Preference is given here to using a two-stage reverse osmosis configured as high-pressure reverse osmosis (pressure range up to 140 bar). The permeate 910 leaving the concentration unit 9 via the connecting piece 911 can be recirculated in the process. For example, it can be fed via connecting pieces 911, 912 as diafiltration water 913 to the purification unit 7 and/or via the connecting pieces 914 as make-up water for preparation of the media for the fermentation in the fermentation unit 1.

[0072] The concentrate from the concentration unit is fed via the connecting piece 10 directly to a further purification unit 11, so that no additional increase in pressure and no pump is necessary for this nanofiltration stage.

[0073] The nanofiltration arranged downstream of the reverse osmosis serves to concentrate the ammonium salt further when the osmotic pressure for the reverse osmosis becomes too high. Since part of the salt goes into the permeate in the nanofiltration, the solution can be concentrated still further. However, the permeate should then be recirculated upstream of the reverse osmosis.

[0074] The permeate from this second purification stage is recirculated to upstream of the reverse osmosis stage. The concentrated carboxylic acid salt solution is subsequently fed via a connecting piece 12 directly to an acidification unit 13 in which the carboxylic acid salt solution is admixed with a mineral acid, so that part of a carboxylic acid precipitates and a mixture of carboxylic acid solution and inorganic salt solution is obtained. The mineral acid is here fed from an acid unit 130 via a connecting piece 131 to the acidification unit 13. The introduction and discharge of cooling water into/from the integrated heat exchanger (not shown) on the acidification vessel occurs via the connecting pieces 251, 252. The acidification unit 13 is preferably configured as settling vessel having a conical bottom. The acidified carboxylic acid solution/salt solution mixture is fed via a connecting piece 14 to a cooling crystallization unit 15 in which the part of the carboxylic acid remaining in solution is isolated. The cooling crystallization unit 15 is preferably a multistage contact crystallizer. In the cooling crystallization unit 15, the cooling and crystallization of the carboxylic acid is effected by means of cooling brine 25 down to a crystallization temperature of from 0 to 10? C., with the cooling brine being fed and discharged into/from the crystallization unit 15 via connecting pieces 251, 252. A carboxylic acid crystal slurry can then be fed via a discharge device 161 and a connecting piece or a crystallizer 162 to a crystal purification 16. The discharge stream from the cooling crystallization (mother liquor) is fed via a connecting piece 17 to a work-up unit 18 in which this mother liquor is worked up, for example by means of a nanofiltration, so as to give a purified mother liquor stream and a carboxylic acid solution stream. The carboxylic acid solution stream 181 is fed back to the crystallization unit 15 via a connecting piece 182. The purified mother liquor stream, which now contains essentially only the inorganic salt solution, is fed via a connecting piece 19 to a thermal concentration unit 20, in which a multistage evaporation with vapor recirculation preferably takes place, and subsequently via a connecting piece 21 to a crystallization unit 22 in order to isolate the salt present in the purified mother liquor stream from the solution. A salt crystal slurry is then discharged via a connecting piece 23 to the salt crystallization 24.

[0075] According to FIG. 2, the feed stream 8 is fed into a reverse osmosis apparatus 9 which consists of two reverse osmosis stages 92, 96. The feed stream firstly goes into a circulation vessel 90 from where it is conveyed by means of a circulation pump 91 into the first stage of the reverse osmosis 92. The permeate from the first stage is conveyed via a connecting piece 93 into the circulation vessel 94 of the second stage 96. The concentrate stream is conveyed via a connecting piece 10 into the subsequent purification unit 11. This purification unit is a nanofiltration and is connected to the preceding reverse osmosis in such a way that no additional energy for increasing the pressure in the nanofiltration is necessary.

[0076] The permeate from the nanofiltration II is transferred via the connecting piece 12 into the acidification vessel 13.

[0077] The retentate 112 is removed from the plant 100, 100a via the connecting piece 111. It is proposed that the retentates from the two purification units be passed to utilization in terms of material in the form of an esterification by means of alcohol. In this way, there are no losses resulting from the two purification units.

[0078] The second stage of the reverse osmosis is operated using the process pump 95. While the permeate from the second stage goes via the connecting piece 97 to be used as make-up water for the fermentation 910, the concentrate goes via the connecting piece 98 to the circulation vessel 90.

[0079] In the acidification unit 13, acidification to the desired pH (in the example, succinic acid to pH 2.0) is effected by addition of acid 130 via the connecting piece 131. Cooling water is introduced and discharged via the connecting pieces 251 and 252. The acidified medium 14 is taken off via a discharge device 132 and fed into the first cooling crystallizer 150. The crystal slurry 161 is taken off via the discharge device 151 and passed to crystal work-up 16.

[0080] The solution 152 flowing out from the first cooling crystallizer 150 (mother liquor) is conveyed with the aid of the pump 153 via the heat exchanger 154 and via the connecting piece 155 into the second cooling crystallizer 156. In the heat exchanger 154, regenerative heat exchange between cold mother liquor 158 from the second crystallizer and the hotter feed stream 152 to the second crystallizer 156 via the connecting piece 155 takes place.

[0081] The second cooling crystallizer 156 is operated using cooling brine 253; 254. The crystal slurry 162 is taken off via a discharge device 159 and is likewise passed to the treatment of the carboxylic acid crystals 16.

[0082] The mother liquor 17 flowing out from the heat exchanger 154 is conveyed into the third purification unit 18 for further work-up. The residual carboxylic acid solution 182 present in the permeate is recirculated via the connecting piece 181 into the first crystallizer 150, while the concentrate goes via the connecting piece 19 to the multistage thermal concentration of the salt solution 20. The vapor 212 arising there is recirculated via the connecting piece 211 to thermal utilization and utilization in terms of material in the production plant. In one embodiment, it is proposed that this vapor be utilized thermally in the concentration unit 9 when this unit comprises a membrane distillation. For utilization of this vapor in terms of material, it can be used for flushing and cleaning purposes, in particular in the fermentation unit 1.

[0083] The salt concentrate comes into the evaporative crystallization 22 via a connecting piece 21. The finished salt crystals 24 (in the example, ammonium sulfate) are taken off via a connecting piece 23. The salt mother liquor 220 formed is recirculated partly to the evaporation 20, while another part thereof is discharged into the wastewater 222.

EXAMPLE

[0084] A fermentation broth containing ammonium succinate was prepurified by separation and ultrafiltration. A nanofiltration having a separation limit of 200 Da was subsequently carried out. The permeate from the nanofiltration had a succinate content of 68.5 g/l.

[0085] The concentration was increased to 212 g/l by means of high-pressure reverse osmosis. The concentration factor was 3.1.

[0086] 1 kg of this solution having a pH of 6.3 was acidified to a pH of 2.45 by means of concentrated sulfuric acid while cooling. The acid consumption was 102 ml of 96% strength sulfuric acid. The solution was subsequently cooled. A moist crystal slurry having a mass of 480 g was then separated off. The color of the crystal slurry was light, with a slightly yellowish color. The supernatant solution amounted to 708 g. At a temperature of 8? C., 20.5 g/l of succinic acid and 350 g/l of sulfate as ammonium sulfate were still present.

LIST OF REFERENCE NUMERALS

[0087] 1 Fermentation unit [0088] 2 Connecting piece [0089] 3 Separator unit [0090] 4 Connecting piece [0091] 5 Ultrafiltration unit [0092] 6 Connecting piece [0093] 7 Purification unit 1 [0094] 8 Connecting piece [0095] 9 Concentration unit or membrane process [0096] 10 Connecting piece [0097] 11 Purification unit 2 [0098] 12 Connecting piece [0099] 13 Acidification unit [0100] 14 Connecting piece [0101] 15 Cooling crystallization [0102] 16 Crystallization unit [0103] 17 Connecting piece [0104] 18 Purification unit 3 [0105] 19 Connecting piece [0106] 20 Thermal concentration unit [0107] 21 Connecting piece [0108] 22 Evaporative crystallization [0109] 23 Connecting piece [0110] 24 Salt crystallization [0111] 25 Cooling water/Cooling brine unit [0112] 31 Biomass suspension [0113] 51 Retentate from ultrafiltration [0114] 71 Connecting piece [0115] 72 Retentate from nanofiltration [0116] 90 Circulation vessel [0117] 91 Circulation pump [0118] 92 1st stage of reverse osmosis [0119] 93 Connecting piece [0120] 94 Circulation vessel, 2nd stage [0121] 95 Circulation pump [0122] 96 2nd stage of reverse osmosis [0123] 97 Permeate, 2nd stage [0124] 98 Concentrate, 2nd stage [0125] 100, 100a Plant [0126] 111 Connecting piece [0127] 112 Retentate from nanofiltration 2 [0128] 130 Acid unit [0129] 131 Connecting piece [0130] 132 Discharge device [0131] 150 Cooling crystallizer 1 or cooling crystallizer [0132] 151 Discharge device [0133] 152 Connecting piece [0134] 153 Pump [0135] 154 Heat exchanger [0136] 155 Connecting piece [0137] 156 Cooling crystallizer 2 or cooling crystallizer [0138] 157 Pump [0139] 158 Cold mother liquor [0140] 159 Discharge device [0141] 161 Crystal slurry from crystallizer 1 [0142] 162 Crystal slurry from crystallizer 2 [0143] 181 Connecting piece [0144] 182 Product recirculation [0145] 211 Connecting piece [0146] 212 Vapor [0147] 220 Connecting piece [0148] 221 Mother liquor recirculation [0149] 222 Wastewater [0150] 251 Cooling water, forward flow [0151] 252 Cooling water, backflow [0152] 253 Cooling brine, forward flow [0153] 254 Cooling brine, backflow [0154] 910 Permeate from reverse osmosis [0155] 911 Connecting piece [0156] 912 Connecting piece [0157] 913 Water for diafiltration [0158] 914 Make-up water for fermentation [0159] 915 Water for diafiltration