U.S. patent application number 12/049994 was filed with the patent office on 2008-07-03 for process for the recovery of citric acid.
This patent application is currently assigned to A.E. STALEY MANUFACTURING COMPANY. Invention is credited to Avraham BANIEL, David Gonen, David Heidel, Asher Vitner.
Application Number | 20080161601 12/049994 |
Document ID | / |
Family ID | 32587527 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080161601 |
Kind Code |
A1 |
BANIEL; Avraham ; et
al. |
July 3, 2008 |
PROCESS FOR THE RECOVERY OF CITRIC ACID
Abstract
The invention provides a process for the recovery of citric acid
from an aqueous solution feed stream originating in germination of
carbohydrates and utilizing an amine solvent extraction step for
separation of impurities comprising: subjecting said aqueous
solution feed stream A to a treatment for partial recovery of
citric acid, wherein said treatment is other than amine solvent
extraction, to form a first portion of purified citric acid B and a
secondary feed stream F; subjecting at least a portion G of said
secondary feed stream F to a treatment consisting of amine solvent
extraction to form a second portion of purified citric acid
solution and to reject substantial of impurities initially present
in said portion of said secondary feed stream; subjecting said
second portion of purified citric acid solution to crystallization;
and recycling mother liquor from said crystallization.
Inventors: |
BANIEL; Avraham; (Jerusalem,
IL) ; Vitner; Asher; (Jerusalem, IL) ; Gonen;
David; (Herzeliya Pituach, IL) ; Heidel; David;
(Decatur, IL) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
A.E. STALEY MANUFACTURING
COMPANY
Decatur
IL
|
Family ID: |
32587527 |
Appl. No.: |
12/049994 |
Filed: |
March 17, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10548171 |
Apr 10, 2006 |
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PCT/IL04/00203 |
Mar 3, 2004 |
|
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12049994 |
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Current U.S.
Class: |
562/515 |
Current CPC
Class: |
C07C 51/48 20130101;
C07C 51/43 20130101; C07C 59/265 20130101; C07C 51/48 20130101;
C07C 51/43 20130101; C07C 59/265 20130101 |
Class at
Publication: |
562/515 |
International
Class: |
C07C 51/00 20060101
C07C051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2003 |
IL |
155161 |
Claims
1. A process for the recovery of citric acid from an aqueous
solution feed stream originating in fermentation of carbohydrates
and utilizing an amine solvent extraction step for separation of
impurities comprising: a) subjecting said aqueous solution feed
stream A to a treatment for partial recovery of citric acid,
wherein said treatment is other than amine solvent extraction, to
form a first portion of purified citric acid B and a secondary feed
stream F; b) subjecting at least a portion G of said secondary feed
stream F to a treatment consisting of amine solvent extraction to
form a second portion of purified citric acid solution and to
reject substantial of impurities initially present in said portion
of said secondary feed stream. c) subjecting said second portion of
purified citric acid solution to crystallization; and d) recycling
mother liquor from said crystallization to step a).
2. A process according to claim 1 wherein the treatment step a) is
a multi-step treatment.
3. A process according to claim 1 wherein the treatment step a) is
crystallization.
4. A process according to claim 2 wherein the multi-steps of said
multi-step treatment are crystallization and recrystallization.
5. A process according to claim 1 wherein the treatment step a) is
non-amine extraction.
6. A process according to claim 2 wherein the multi-steps of said
multi-step treatment are non-amine extraction followed by
crystallization.
7. A process according to claim 2 wherein the multi-steps of said
multi-step treatment are crystallization followed by non-amine
extraction.
8. A process according to claim 1 wherein the initial secondary
feed stream F formed in step a, prior to being sent to said
treatment of amine solvent extraction, is subjected to a second
step of partial citric acid recovery to form a partially purified
citric acid C and a tertiary feed stream G wherein said tertiary
feed stream is subjected to a treatment consisting of amine solvent
extraction according to step b and said partially purified citric
acid bypasses step b and is directly subjected to crystallization
treatment together with the purified citric acid solution b
produced in step b.
9. A process according to claim 1 wherein said aqueous solution
feed stream A contains citric acid at a concentration of between
about 16% and 75%.
10. A process according to claim 1 wherein said secondary feed
stream F contains citric acid at a concentration of about 5% to
30%.
11. A process according to claim 1 wherein said secondary feed
stream F contains citric acid at a concentration of about 16% to
75%.
Description
[0001] The present invention relates to the recovery of citric acid
from aqueous solutions originating in industrial fermentation of
carbohydrates. More particularly, the present invention relates to
an improved process for the recovery of citric acid from an aqueous
solution feed stream originating in fermentation of carbohydrates
and utilizing an amine solvent extraction step for separation of
impurities.
[0002] Amine Extractants are used industrially to recover citric
acid from solutions at low concentrations such that are typical of
fermentation broths and also at high concentrations obtained
generally by pre-concentration of such broths. Generally prior to
extraction the filtered fermentation broth is subjected to the
removal of cations in order to secure complete extraction of the
citric acid as well as other acids present as trace impurities. The
latter comprise acids that are stronger than citric acid both
mineral (HCl, H.sub.2SO.sub.4, H.sub.3PO.sub.4) and organic (e.g.
oxalic) as well as acids weaker than citric acid (e.g. acetic
acid). All contaminating acids are separated from citric acid as
part of the Amine Extractant recovery by playing on selectivities
of the extractant with respect to acid strength. The stronger acids
may alternately be removed by pretreatment of the decationised
broth by solid anion exchangers. The practice of the present
invention assumes as feed filtered decationised broth treated for
removal of contaminating acids. This feed is to be referred to as
"treated broth". As to the mode of removal of contaminating acids,
both of the described modes are compatible with the practice of the
present invention, the choice of anion exchange by a liquid or by a
solid exchanger is an optional choice for the practitioner of the
present invention.
[0003] An outstanding quality of Amine Extractants is the
efficiency and completeness of separating acids in an aqueous
solution from neutral molecules present in the same solution: the
acids report to the organic phase whereas the neutral solutes
report very weakly if at all. Fermentation broths contain an
enormous variety of essentially neutral solutes: residual feed
carbohydrates, their transformation products other than citric
acid, as well as obligate by-products of the activity of the
microorganism effecting the fermentation.
[0004] The efficiency of this separation is practically independent
of the ratio of impurities to citric acid. Crystallization, which
is the other major separation technology in use in citric acid
recovery, is very sensitive to this ratio and therefore limited in
its applicability. Thus, carefully filtered broths thoroughly
treated for maximum impurities removal by cation exchange and anion
exchange, when treated for direct recovery of citric acid by
crystallization, provide only for some 10% recovery at the required
food grade quality, beyond which the purity decreases with the
increase in impurities to citric acid ratio. The impurities are
mostly neutral solutes as explained above. These solutes in effect
block the direct use of crystallization which, when applicable, are
economically efficient.
[0005] Low molecular weight oxygenated solvents such as alkanols
(e.g. n-butanol) and esters (e.g. ethylacetate) can be used to
recover pure citric acid from concentrated aqueous solutions
separating it from impurities by simple low-cost liquid-liquid
extraction operations. This approach which has not been previously
proposed (GB874030) is described in detail further below. It is
more efficient in recovering pure citric acid from concentrated
fermentation broth than crystallization but the efficiency falls
with the extent of recovery and the concurrent increase in the
ratio of impurities to citric acid.
[0006] The present invention provides for novel systems of citric
acid recovery amenable to flexible design and having efficiencies
not attainable by existing technologies.
[0007] Thus according to the present invention there is now
provided a process for the recovery of citric acid from an aqueous
solution feed stream originating in fermentation of carbohydrates
and utilizing an amine solvent extraction step for separation of
impurities comprising: [0008] One) subjecting said aqueous solution
feed stream A to a treatment for partial recovery of citric acid,
wherein said treatment is other than amine solvent extraction, to
form a first portion of purified citric acid B and a secondary feed
stream F; [0009] Two) subjecting at least a portion G of said
secondary feed stream F to a treatment consisting of amine solvent
extraction to form a second portion of purified citric acid
solution and to reject substantially all of the impurities
initially present in said portion of said secondary feed stream.
[0010] Three) subjecting said second portion of purified citric
acid solution to crystallization; and [0011] Four) recycling mother
liquor from said crystallization.
[0012] In further preferred embodiments of the present invention
the treatment step of step a) is a multi-step treatment.
[0013] Thus, in a first preferred embodiment of the present
invention the initial secondary feed stream formed in a), prior to
being sent to amine solvent extraction, is subjected to a second
step of partial citric acid recovery and this second portion of
citric acid bypasses b) to join the purified citric acid solution
produced in b) that feeds crystallization c).
[0014] Thus in said preferred embodiments of the present invention
the initial secondary feed stream formed in step a, prior to being
sent to said treatment of amine solvent extraction, is subjected to
a second step of partial citric acid recovery to form a partially
purified citric acid and a tertiary feed stream wherein tertiary
feed stream is subjected to a treatment of amine solvent extraction
according to step b and said partially purified citric acid
bypasses step b and is directly subjected to crystallization
treatment together with the purified citric acid solution produced
in step b.
[0015] In especially preferred embodiments of the present invention
said aqueous solution feed stream A contains citric acid at a
concentration of between 16% and 75%.
[0016] In first preferred embodiments of the present invention said
secondary feed stream F contains citric acid at a concentration of
about 5% to 30% while in other preferred embodiments of the present
invention said secondary feed stream F contains citric acid at a
concentration of about 16% to 75%.
[0017] The technologies made possible by the present invention are
described in relation to citric acid fermentations fed by
carbohydrates low in impurities levels which results in
fermentation broths in which the impurities that accompany the
citric acid that is formed are mostly neutral and of minor amounts
compared to the citric acid content of the broth. Such broths are
amenable to recovery by Solvent Extraction (hereinafter referred to
as SX) applying amine extractants--as practiced on large industrial
scale. However the invention is not restricted to this particular
source of citric acid. Any primary citric acid aqueous solution
amenable to recovery by an Amine Extractant (hereinafter referred
to as an AE) can benefit by the present invention. Thus for
instance, a fermentation broth derived from impurities-rich
molasses can be treated by the traditional lime/sulfuric process to
obtain a citric acid solution amenable to AE-recovery and to the
benefits of the present invention.
[0018] While the invention will now be described in connection with
certain preferred embodiments in the following examples and with
reference to the accompanying figures, so that aspects thereof may
be more fully understood and appreciated, it is not intended to
limit the invention to these particular embodiments. On the
contrary, it is intended to cover all alternatives, modifications
and equivalents as may be included within the scope of the
invention as defined by the appended claims. Thus, the following
examples which include preferred embodiments will serve to
illustrate the practice of this invention, it being understood that
the particulars shown are by way of example and for purposes of
illustrative discussion of preferred embodiments of the present
invention only and are presented in the cause of providing what is
believed to the most useful and readily understood description of
the principles and conceptual aspects of the invention.
[0019] In the drawings:
[0020] FIG. 1 is a schematic flow sheet representation of the
concept of the present invention;
[0021] FIG. 1a represents in further detail a feature of FIG.
1;
[0022] FIG. 2 is a schematic flow sheet representation of a
preferred embodiment of the present invention;
[0023] FIG. 2a is a schematic flow sheet representation of a
comparable production by present art without the benefit of the
present invention.
[0024] FIG. 3 is a schematic flow sheet representation of a
preferred process as described in Example 1 hereinafter.
[0025] FIG. 4 is a schematic flow sheet representation of a
preferred process as described in Example 2 hereinafter.
[0026] FIG. 5 is a schematic flow sheet representation of a
preferred process as described in Example 3 hereinafter.
[0027] FIG. 6 is a schematic flow sheet representation of a
preferred process as described in Example 4 hereinafter; and.
[0028] FIG. 7 is a schematic flow sheet representation of a
preferred process as described in Example 5 hereinafter.
[0029] The concept underlying the invention is now explained in
conjunction with the diagram in FIG. 1. Letters in [ ] refer to
stream designations in FIG. 1 [0030] One) The core of each overall
recovery system consists of a unit of two sections: (1) a Solvent
Extraction (SX) by Amine Extractant section which recovers
practically fully all citric acid fed to it and rejects practically
all the impurities that accompany this citric acid as in present
art and (2) a crystallization section that accepts the purified
aqueous citric acid from the SX unit (as in present art) as well as
citric acid streams originating in treatments of the primary feed
preceding amine solvent recovery and that bypass amine extraction
to feed directly into the crystallization section. This core amine
recovery section of the overall recovery system is presented in
greater detail in FIG. 1a. [0031] Two) The primary feed to the
system (clarified and de-ionized fermentation broth) [A] is treated
in one or more recovery units that apply separation technologies
which do not involve Amine Extractants, for partial recovery of
citric acid [B], [C] without rejection of impurities. These remain
with the non-recovered citric acid [G] that is fed to the SX
section of the amine recovery as shown in FIG. 1a. [0032] Three)
Citric acid recovered prior to Amine Extraction SX may be of
commercial purity grade [B] [C], or of a purity grade that is
suitable for direct feeding to the crystallization section of the
core unit as illustrated by [b] or consist of streams of both of
these. [0033] Four) The aqueous waste stream from the Amine
Extractant SX section [Z] services the whole system. [0034] Five)
Residual impurities that report to the crystallization section of
the core unit collect in the mother liquor, which is recycled [a]
to recovery units preceding the core unit.
[0035] One key advantage of the described multi-recovery systems,
as can be easily appreciated, resides in the fact that the
application of amine solvent extraction conserves fully its
advantages, namely, providing for recovery of citric acid and
rejection of neutral impurities--that are practically
complete--while processing only part of the citric acid of the
primary feed. An associated key advantage resides in that
recoveries by other separation processes that precede SX by Amine
Extractants can be selected for application in concentration ranges
where they are most efficient.
[0036] To illustrate the foregoing, a system is considered that
applies sequential crystallization to the primary feed [A] prior to
SX. Such a system is described in detail in Example 1 and is
considered in its essentials in FIG. 2 and FIG. 3. The fermentation
broth feed is subjected to evaporation and crystallization in two
successive stages. In the 1.sup.st of these about 20 (to 40) of the
100 citric acid in the primary feed are recovered at product purity
as stream [a]. These 20 CA represent 20% of the 100 CA fed to the
system but only 20 of the 120 CA (or about 17%) of the combined
primary feed that contains 100 CA and the mother liquor recycle [b]
that contains 20 CA. Normally only about 10% would be recoverable
by crystallization at the required level of purity from the feed as
such. However the recycle of mother liquor [b], which is formed
after rejection of impurities in the SX section, lowers the level
of impurities in the 1.sup.st crystallization and makes the higher
recovery of pure product possible.
[0037] The crop of the next crystallization [c], which does not
have the final level of purity, is still sufficiently pure to be
sent directly to the final crystallization, by-passing SX. Thus for
100 units of citric acid fed into the system and recovered at
product quality only about 60 go through SX.
[0038] FIG. 2a represents the equivalent production of 100 CA by
conventional amine solvent extraction technology as currently
practiced by industry (U.S. Pat. No. 4,275,234) in the same summary
fashion. While it obviously entails fewer operations, the SX
section required is nearly double in capacity requirements making
the whole system materially more expensive in investment and in
operating costs. It will be also obvious to a practitioner that the
novel system illustrated by FIG. 2 also provides for an efficient,
low-cost expansion of an existing plant by as much as 60%.
[0039] The concept underlying the invention teaches the provision
of one or two successive recovery operations in each of which a
fraction of the incoming citric acid is obtained at a high level of
purity while substantially all the incoming impurities remain in
the fraction that proceeds to the next operation, with amine
solvent extraction as the final recovery operation securing the
rejection of all impurities. It is a fact of all separation
processes that the costs of recovery of a component from a mixture
increase steeply at some point with the extent of recovery. Under
the invention, separation processes applied in each recovery,
having been selected for suitability, can be further optimized by
adjusting the extent of recovery and the number of steps
adopted--as extensively illustrated in Examples.
[0040] The invention does not mandate the choice of particular
separation technologies for the recovery or recoveries that precede
amine solvent extraction. The actual choice may be affected i.a. by
considerations particular to a plant or a location. The two
technologies chosen for the purpose of illustrating the practice of
the invention are crystallization (referred to herein as CRYS) and
extraction by alkanol. The latter (referred to herein as EXAL) is a
particular category of extraction by oxygenated solvents mentioned
above that is described in detail in Examples below. These
technologies provide for four reference modalities of practicing
the invention as tabulated below:
TABLE-US-00001 Modality 1 2 3 4 1.sup.st recovery CRYS EXAL CRYS
EXAL 2.sup.ND recovery None None EXAL CRYS
Each of these modalities admits variations that further provide for
efficiency.
[0041] As mentioned previously the invention provides for low-cost
expansion of an existing amine solvent recovery plant by adopting
it as the core operation in the present invention and adding to it
a recovery unit or two recovery units that apply selected
separation technologies. Expansion can be effected stage-wise
without restricting its eventual scope. As illustrated in FIG. 2
and in detail in the examples hereinafter), Modality 1 provides for
an expansion of about 80%. If Modality 3 is applied, with the 2nd
EXAL recovery decreasing further by half the citric acid feed to
amine recovery, an increase of capacity of well over 200% is
obtained.
[0042] Extraction of Citric Acid by a Non-Amine Solvent
[0043] Citric acid can be recovered by direct extraction with a
water-immiscible organic extractant followed by water stripping of
the resulting extract as described, for example, in U.S. Pat. No.
3,944,606,
[0044] According to U.S. Pat. No. 4,275,234 a citric acid
fermentation broth is extracted with a water-immiscible organic
extractant which comprises a solution of at least one secondary or
tertiary amine in which the aggregate number of carbon atoms is at
least 20 in admixture with hydrocarbon and alcoholathe resulting
extract is stripped with water at a temperature which is higher,
preferably by at least 20.degree.C. than the broth extraction
temperature.
[0045] According to U.S. Pat. No. 4,344,095 a citric acid
fermentation broth is extracted with a mixture of a
water-immiscible amine and a water-immiscible organic acid
dissolved in a suitable water-immiscible solvent, and the resulting
extract is back-extracted with water.
[0046] Laboratory results concerning extraction of citric acid by
solvents, done in Tate and Lyle laboratories are presented in the
following tables and figures.
[0047] The distribution of citric acid between water and alkanols
is presented in Experiments 1-3.
EXAMPLE 1
The Distribution of Citric Acid Between Butanol and Aqueous
Solution
[0048] Citric acid, Butanol and water at various ratios were added
into vials. The vials were shaken at 30.degree. C. The composition
of the two resulting phases is presented in Table 1.
TABLE-US-00002 TABLE 1 The distribution of citric acid between
butanol and aqueous solution Butanolic phase Aqueous phase Citric
Citric gr Citric/ Citric Citric gr Citric/ Distribution eq/kg Wt %
gr solvent Eq/kg Wt % gr solvent coefficient 0.06 0.4 0.4 0.19 1.2
1.2 0.31 0.35 2.2 2.3 0.80 5.1 5.4 0.42 0.71 4.6 4.8 1.6 10.1 11
0.42 2.1 13.5 15.6 3.6 23.3 30 0.51
EXAMPLE 2
The Distribution of Citric Acid Between Pentanol and Aqueous
Solution
[0049] Citric acid, Pentanol and water at various ratios were added
into vials. The vials were shaken at 30.degree. C. The composition
of the two resulting phases is presented in Table 2.
TABLE-US-00003 TABLE 2 The distribution of citric acid between
pentanol and aqueous solution Pentanolic phase Aqueous phase Citric
Citric gr Citric/ Citric Citric gr Citric/ Distribution eq/kg Wt %
gr solvent eq/kg Wt % gr solvent coefficient 0.03 0.2 0.2 0.17 1.1
1.1 0.16 0.10 0.6 0.6 0.57 3.6 3.8 0.16 0.48 3.0 3.1 2.4 15.2 18
0.18 0.95 6.1 6.5 4.1 26.0 35 0.18 3.4 21.5 27 8.1 52.1 109
0.25
EXAMPLE 3
The Distribution of Citric Acid Between Hexanol and Aqueous
Solution
[0050] Citric acid, Hexanol and water at various ratios were added
into vials. The vials were shaken at 30.degree. C. The composition
of the two resulting phases is presented in Table 3.
TABLE-US-00004 TABLE 3 The distribution of citric acid between
Hexanol and aqueous solution Hexanolic phase Aqueous phase Citric
Citric gr Citric/ Citric Citric gr Citric/ Distribution eq/kg Wt %
gr solvent eq/kg Wt % gr solvent coefficient 0.05 0.4 0.4 0.58 3.7
3.8 0.09 0.07 0.4 0.4 0.68 4.4 4.6 0.10 0.17 1.1 1.1 1.6 10.2 11.4
0.10 0.62 4.0 4.1 4.5 28.6 40 0.10 2.1 13.5 15.7 8.5 54.1 118
0.13
[0051] In solutions containing both glucose and citric acid, citric
acid is selectively extracted into the NA solvent. The
citric/glucose selectivity decreases with the increase in the
distribution of citric into the solvent phase.
[0052] Although, non-amine solvents can efficiently extract citric
acid, the results indicate that the efficiency of the extraction is
reduced at lower citric acid concentrations thus, high extraction
yields require large number of extraction stages.
[0053] The distribution of citric acid by an amine extractant
follows a different pattern. The distribution coefficient at high
citric acid concentrations is much lower that at lower citric acid
concentration example of this phenomenon is presented in Experiment
4.
EXAMPLE 4
The Distribution of Citric Acid Between Amine Extractant and
Aqueous Solution
[0054] Citric acid, Amine extractant and water at various ratios
were added into vials. The vials were shaken at 30.degree. C. The
composition of the two resulting phases is presented in Table 4
TABLE-US-00005 TABLE 4 The distribution of citric acid between an
amine extractant and aqueous solution at 50.degree. C. Amine phase
Aqueous phase Citric Citric Gr Citric/ Citric Citric gr Citric/
Distribution eq/kg Wt % gr solvent eq/kg Wt % gr solvent
coefficient 0.09 0.6 0.6 0.08 0.5 0.5 1.21 0.15 0.9 1.0 0.14 0.9
0.9 1.05 0.46 3.0 3.1 0.41 2.6 2.7 1.15 0.87 5.6 5.9 0.74 4.7 5.0
1.19 1.43 9.2 10.1 1.64 10.5 11.7 0.86 1.84 11.8 13.3 3.71 23.7 31
0.43 1.96 12.5 14.3 4.75 30.4 44 0.33 2.1 13.3 15.4 6.4 41.0 70
0.22 2.3 14.7 17.3 8.2 52.3 110 0.16
[0055] The amine extractant is composed of alamine 47% A304, 3%
octanol in isopar.K. (Alamine 336 is a long chained tertiary amine,
IsoparK is a commercially diluent consisting of high boiling point
carbohydrate).
[0056] The above data indicate that amine extractant is very
efficient in the extraction at low citric acid concentrations while
the non amine extractant is more efficient at the higher citric
acid concentrations, thus suggesting that the combination of the
two extraction method will be efficient.
EXAMPLE 4
Pre Crystallization, Amine Extraction and Re Crystallization
[0057] The procedure was according to the following steps, which
should be read in conjunction with FIG. 3. [0058] One) 66 g of
treated broth, containing 27.6 g citric acid and 2 g impurities and
4.44 g mother liquor (obtained as a bleed from mother liquor from
crystallization of relatively pure citric acid solution in stage d)
were evaporated under vacuum at 70.degree. C. in a crystallizer.
11.44 g of 96.1 wt % citric acid wet solids and 17.25 g of mother
liquor were obtained. The mother liquor contained 10.12 g citric
acid and 1.96 g impurities. [0059] Two) 17.25 g mother liquor
solution obtained in a). was extracted at 40.degree. C. in five
counter-current stages (simulated by five separatory funnels) with
52.7 g of recycled extractant containing 47% w/w Alamine 336, 50%
w/w IsoparK (mixture of high boiling point hydrocarbons produced
by), 3% w/w of 1-n-octanol. [0060] Three) 62.75 g Extract
containing 16% w/w of citric acid was stripped at 100.degree. C. in
five simulated counter-current stages with 22.3 g of H.sub.2O to
yield 32.3 g of an aqueous back-extract containing 31% w/w citric
acid and less than 0.1% impurities. At the same time 52.7 g of
extractant phase practically free of CA was obtained which was
ready for recycle to a). after cooling. [0061] Four) 32.3 g of back
extract obtained in c) was evaporated under vacuum at 70.degree. C.
to form a solution containing 50% w/w of citric acid. 11.4 g of
citric acid crystals obtained in a) were dissolved in the
concentrated solution and the solution was crystallized to give
27.6 g of citric acid crystals (>99.8% w/w CA) and mother
liquor. The mother liquor is ready to be recycled to a).
EXAMPLE 5
Non Amine (Na) Solvent Extraction, Amine Extraction and Re
Crystallization
[0062] The procedure was according to the following steps that
should be read in conjunction with FIG. 4 appended hereto: [0063]
One) 46.2 g of 58% w/w citric acid treated broth was extracted at
40.degree. C. in four counter-current stages (simulated by four
separatory funnels) with 158.3 g of recycled extractant composed of
154.6 g hexanol and 3.7 g citric acid. The resulting phases were:
about 180 gr extractant containing 13.8% w/w citric acid and 0.148%
w/w of impurities and 26.6 g raffinate containing 24.8% w/w citric
acid and 6.5% w/w impurities. [0064] Two) 180 g extract containing
17.8% w/w of citric acid was stripped 40.degree. C. in four
simulated counter-current stages with 20.7 g of H.sub.2O to yield
42.5 g of an aqueous back-extract containing 50% w/w of citric
acid. The total solutes contain about 99% w/w of citric acid. At
the same time 158.3 g of extractant phase containing 3.7 g of
citric acid was obtained which was ready for recycle to Stage a).
[0065] Three) 42.5 g of a 50% w/w back extract obtained in b) were
evaporated under vacuum at 70.degree. C. 39.5 g Back extract
obtained in the amine extraction stages (Stages d) and the
concentrated solution obtained in the NA extraction were
crystallized to give 27.45 g of citric acid crystals (99.8% w/w CA)
and mother liquor. [0066] Four) 42 g solution were obtained by
mixing the mother liquor obtained in c) with the raffinate obtained
in b). The solution contained 32.9% w/w citric acid and 6.0% w/w
impurities. The solution was extracted at 40.degree. C. in five
counter-current stages (simulated by five separatory funnels) with
63.5 g of recycled extractant containing 47% w/w Alamine 336, 50%
w/w IsoparK, 3% w/w of 1-n-octanol. 47.5 g extract containing 18%
w/w of citric acid was stripped at 40.degree. C. in five simulated
counter-current stages with 18 g of H.sub.2O to yield 38.9 g of an
aqueous back-extract containing 36.6% w/w of 99% wt/wt citric acid.
At the same time 47.5 g of extractant phase practically free of CA
was obtained which was ready for recycle after cooling. The back
extract obtained in c) was evaporated under vacuum at 70.degree. C.
to form a solution containing 50% w/w of citric acid were ready to
be added to the crystallizer.
EXAMPLE 6
Non Amine (Na) Solvent Extraction, Amine Extraction and Re
Crystallization
[0067] Recycle of the Mother Liquor to the NA Solvent
Extraction
[0068] The procedure was according to the following steps that
should be read in conjunction with FIG. 5 appended hereto: [0069]
One) 46.2 g of 58% w/w citric acid treated broth and 3.1 g mother
liquor from the crystallizer were mixed and were extracted at
40.degree. C., in four counter-current stages (simulated by four
separatory funnels), with 177.7 g of recycled extractant composed
of 177.7 g hexanol and 3.75 g citric acid. The resulting phases
were: about 207 gr extractant containing 13.8% w/w citric acid and
0.16% w/w of impurities and 26 g raffinate containing 21.5% w/w
cacand 7.4% w/w impurities. [0070] Two) 206.5 g extract containing
113.8% w/w of citric acid was stripped at 40.degree. C. in four
simulated counter-current stages with 20.5 g of H.sub.2O to yield
50 g of an aqueous back-extract containing 50% w/w of citric acid.
The total solutes contain about 98.6% wt/wt of citric acid. At the
same time 181.9 of extractant phase containing 3.75 g of citric
acid was obtained which was ready for recycle to a). [0071] Three)
48 g of a 50% w/w back extract obtained in b) were evaporated under
vacuum at 70.degree. C. 30 g Back extract obtained in the amine
extraction stages (Stages d) and the concentrated solution obtained
in the NA extraction were crystallized to give 26.8 g of citric
acid crystals (99.8% w/w CA) and mother liquor. [0072] Four) The
raffinate from Stage a) was extracted at 40.degree. C. in five
counter-current stages (simulated by five separatory funnels) with
33.5 g of recycled extractant containing 47% w/w Alamine 336, 50%
w/w IsoparK., 3% w/w of 1-n-octanol. 38.8 g extract containing
14.2% w/w of citric acid was stripped at 100.degree. C. in five
simulated counter-current stages with 25 g of H.sub.2O to yield 25
g of an aqueous back-extract containing 18% w/w of 98.6% w/w citric
acid. At the same time 33.3 g of extractant phase practically free
of CA was obtained which was ready for recycle after cooling. The
back extract was evaporated under vacuum at 70.degree. C. to form a
solution containing 50% w/w of citric acid was ready to be added to
the crystallizer (c).
EXAMPLE 7
Solvent Extraction+Crystallization, Amine Extraction and
Recrystallization
[0073] Back Extraction with Water
[0074] The procedure was according to the following steps that
should be read in conjunction with FIG. 6 appended hereto: [0075]
One) 50 gr of 60% w/w citric acid treated broth were extracted at
40.degree. C. in four counter-current stages (simulated by four
separatory funnels) with 158.3 g of recycled extractant composed of
154.6 gr hexanol and 3.7 g citric acid. The resulting phases were:
about 180 gr extractant containing 13.8% w/w citric acid and 0.148%
w/w of impurities and 26.6 gr raffinate containing 24.8% w/w citric
acid and 6.5% w/wt impurities. [0076] Two) 180 gr extract
containing 17.8% w/w of citric acid was stripped at 40.degree. C.
in four simulated counter-current stages with 24.8 g of H.sub.2O to
yield 42.5 g of an aqueous back-extract containing 50% w/w of
citric acid. The total solutes contain about 99% w/w of citric
acid. At the same time 158.3 g of extractant phase containing 3.7 g
of citric acid was obtained which was ready for recycle. [0077]
Three) 42.5 g of a 50% w/w back extract obtained in b) were
evaporated under vacuum at 70.degree. C. The concentrated solution
was crystallized to give 19 g of citric acid crystals (99.8% w/w
CA) and mother liquor. [0078] Four) 29.6 g solution obtained by
mixing the mother liquor obtained in c) with the raffinate obtained
in b). The solution contained 29.7% wt/wt CA and 6.6% w/w
impurities. The solution was extracted at 40.degree. C. in five
counter-current stages (simulated by five separatory funnels) with
51.4 g of recycled extractant containing 47% w/w Alamine 336, 50%
w/w IsoparK., 3% w/w of 1-n-octanol. 59.9 g extract containing
14.2% w/w of citric acid was stripped at 100.degree. C. in five
simulated counter-current stages with 30.3 g of H.sub.2O to yield
38.9 g of an aqueous back-extract containing 28% w/w of 99% w/w
citric acid. At the same time 51.4 g of extractant phase
practically free of CA was obtained which was ready for recycle
after cooling. [0079] Five) 38.9 g of back extract obtained in 4.4
were evaporated under vacuum at 70.degree. C. to form a solution
containing 45% w/w of citric acid. 19 g of citric acid crystals
obtained in c) were dissolved in the concentrated and the solution
was crystallized to give 22.9 g of citric acid crystals (>99.9%
w/w CA) and mother liquor.
EXAMPLE 8
Solvent Extraction+Crystallization, Amine Extraction and Re
Crystallization.
[0080] Back Extraction with Treated Broth
[0081] The procedure was according to the following steps that
should be read in conjunction with FIG. 7 appended hereto: [0082]
One) The procedure was similar to that in Example 4. [0083] Two)
180 g extract containing 17.8% w/w of citric acid was stripped at
40.degree. C. in four simulated counter-current stages with 24.8 g
of H.sub.2O to yield 42.5 g of an aqueous back-extract containing
50% w/w of citric acid. The total solutes contain about 99% wt/wt
of citric acid. At the same time 158.3 g of extractant phase
containing 3.7 g of citric acid was obtained which was ready for
recycle. [0084] Three) 42.5 g of a 50% w/w back extract obtained in
5.2 were evaporated under vacuum at 70.degree. C. The concentrated
solution was crystallized to give 19 g of citric acid crystals
(99.8% w/w CA) and mother liquor. [0085] Four) 29.6 g solution
obtained by mixing the mother liquor obtained in 5.3 with the
raffinate obtained in 5.2. The solution contained 29.7% w/w CA and
6.6% w/w impurities. The solution was extracted at 40.degree. C. in
five counter-current stages (simulated by five separatory funnels)
with 51.4 g of recycled extractant containing 47% w/w Alamine 336,
50% w/w IsoparK, 3% w/w of 1-n-octanol. 59.9 g extract containing
14.2% w/w of citric acid was stripped at 100.degree. C. in five
simulated counter-current stages with 30.3 g of H.sub.2O to yield
38.9 g of an aqueous back-extract containing 28% w/w of 99% w/w
citric acid. At the same time 51.4 g of extractant phase
practically free of CA was obtained which was ready for recycle
after cooling. [0086] Five) 38.9 g of back extract obtained in d)
were evaporated under vacuum at 70.degree. C. to form a solution
containing 45% w/w of citric acid. 19 g of citric acid crystals
obtained in c) were dissolved in the concentrated and the solution
was crystallized to give 22.9 g of citric acid crystals (>99.9%
w/w CA) and mother liquor. In all cases [0087] 1. Back extraction
for the extraction with amine extractant or with NA extractant can
be done with water, decationized beer or concentrated decationized
beer, mother liquor from any crystallizer or solutions obtained by
dissolution of citric acid crystals. [0088] 2. Mother liquor from
any crystallization stage could be recycled to another
crystallization stage (of lower purity or to any of the extraction
units used in the process. [0089] 3. Mother liquor from any
crystallization stage could be recycled to any extraction stage.
[0090] 4. The no-amine extraction product may by crystallized in a
separate crystallization unit or be added to the SX section
crystallization unit [0091] 5. Back extraction in SX or non-amine
extraction may be fed by water or/and citric acid solution from
various process stages. [0092] 6. Addition of the citric acid
solution can be done to the first extraction stage (extractant
exiting stage or to any intermediate extraction stage. The same can
be said for the solution used for back extraction. [0093] 7. The
fermentation broth can be subjected to any pre treatment stages
including ultra filtration, decationization, active carbon
treatment, pre extraction by solvent or resin to remove impurity
acids and any other treatment used in the field.
[0094] It will be evident to those skilled in the art that the
invention is not limited to the details of the foregoing
illustrative embodiments and that the present invention may be
embodied in other specific forms without departing from the spirit
or essential attributes thereof. The present embodiments are
therefore to be considered in all respects as illustrative and not
restrictive, the scope of the invention being indicated by the
appended claims rather than by the foregoing description, and all
changes which come within the meaning and range of equivalency of
the claims are therefore intended to be embraced therein.
* * * * *