Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DESCRIPTION
Title of Invention
METHOD FOR REDUCING CORROSIVE IONS IN AROMATIC
COMPOUND EXTRACTION SOLVENT
Technical Field
[0001]
The present invention relates to a method for reducing corrosive ions such
as chloride ions, sulfate ions, and sulfite ions in an aromatic compound
extraction
solvent, the method being capable of preventing corrosion in a system where a
solvent for extracting aromatic compounds such as benzene, toluene, and xylene
from a hydrocarbon stream circulates in petroleum refineries, coal chemical
plants, and the like.
Background Art
[0002]
In petroleum refining and in hydrocarbon refining at coal chemistry plants,
there is a perennial problem in that corrosive ions such as chloride ions,
sulfate
ions, and sulfite ions originating from various salts present in raw materials
cause equipment corrosion.
In this regard, a technique of adding an alkali to scavenge corrosive ions is
a possible solution. However, salts produced by adding an alkali can
adhere/precipitate and possibly cause serious troubles such as deposit buildup
and clogging in equipment.
[0003]
Patent Literature 1 discloses a method for preventing corrosion caused by
chloride in a condensation system of an oil refining process by using a
plurality of
amines such as monoethanolamine in combination. Patent Document 2
discloses that metal corrosion is prevented by introducing a quaternary
ammonium compound such as choline hydroxide (2-
hydroxyethyltrimethylammonium hydroxide) into a fluid that may come into
contact with the inside of petroleum refining equipment and the like to
prevent
generation of hydrogen chloride.
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,
Citation List
Patent Literature
[0004]
PTL1: JP 7-180073 A
PTL2: JP 2004-211195 A
Summary of Invention
Technical Problem
[0005]
However, with conventional methods, although chloride ions derived from
salts contained in petroleum and the like are reduced, it is difficult to
completely
remove them. Therefore, it is not uncommon that chlorides, chloride ions,
sulfate ions, and sulfite ions are present in hydrocarbon mixtures such as
naphtha obtained by refining petroleum and the like, and there is still the
problem of corrosion by corrosive ions in a system where such a hydrocarbon
mixture is used as a raw material.
[0006]
Meanwhile, a catalyst is used in a method for obtaining an aromatic
compound such as benzene, toluene, or xylene by reforming a hydrocarbon
mixture such as naphtha. The catalyst is either used continuously or
continuously recovered from the reaction product composition and regenerated,
but the catalytic activity deteriorates due to long-term use, and therefore a
catalyst regeneration treatment is carried out. Chlorine compounds are often
used in the catalyst regeneration treatment, and thus the reformed hydrocarbon
fed from the aromatic compound generator to the extractor may contain not only
chloride ions derived from the raw-material hydrocarbon mixture but also
chloride ions derived from the chlorine compound used in the catalyst
regeneration.
[0007]
Moreover, an aromatic hydrocarbon oil that is a reformed hydrocarbon and
the like are subjected to an aromatic compound extraction treatment involving
an
extraction solvent. In this extraction treatment, the aromatic hydrocarbon oil
is
dissolved in an extraction solvent, and the aromatic compound is extracted and
separated by distillation. Then, a feed stock aromatic hydrocarbon oil is
newly
supplied to the lean-extraction solvent, and distillation is performed again.
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Thus, the extraction solvent is recycled in the extractor from the viewpoint
of cost
reduction, prevention of environmental contamination, and the like.
As a result, corrosive ions contained in the successively fed raw-material
aromatic hydrocarbon oil build up in the recycled extraction solvent. In
conjunction
with a small amount of water present in the extraction solvent, an increased
concentration of corrosive ions in the extraction solvent causes rapid
corrosion of the
extractor. Even when an alkali is added to neutralize acid that produces
corrosive
ions in the extraction solvent as is known in the art, salts build up in the
circulation
system of the extraction solvent. Also, to date, there has been no technical
concept of
scavenging corrosive ions by adding an alkali.
[0008]
Thus, an increase of the corrosive ion concentration in the extraction solvent
is a problem specific to the extraction solvent of the circulation system, and
an
approach that provides a greater corrosion suppressing effect is required than
in a
system where the solvent is used only once and disposed of.
The use of a method as described in Patent Literature 1 to address the
problem in the circulation system requires a plurality of amines to be
optimally
combined for neutralization and precipitation and, moreover, the amines are
likely to
be discharged from the circulation system as volatile components due to
distillation,
thus deteriorating the corrosion suppressing effect. Depending on the
conditions,
commonly used alkanolamines and the like are likely to be discharged from the
circulation system as volatile components due to distillation and lack the
ability to
scavenge corrosive ions.
[0009]
The present invention has been made under such circumstances, and an object
of the present invention is to provide a method for reducing corrosive ions in
an
aromatic compound extraction solvent, by which the corrosive ions in the
aromatic
compound extraction solvent are conveniently and efficiently reduced, in order
to
suppress corrosion of an extractor caused by corrosive ions contained in an
aromatic
compound extraction solvent of a circulation system.
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[0009a]
The present specification discloses and claims a method for reducing corrosive
ions in an aromatic compound extraction solvent in a circulation system where
the
aromatic compound extraction solvent circulates, the corrosive ions being at
least one
kind selected from the group consisting of chloride ions, sulfate ions, and
sulfite ions,
the method comprising: a step of forming a non-volatile salt by adding a
corrosive ion
scavenger to react the corrosive ions with the corrosive ion scavenger, the
corrosive
ion scavenger being a quaternary ammonium compound represented by general
formula (1) below:
4-
RI -N -I-
I ¨
R2¨N¨ (CH2)11¨ OH . OH (1)
I
R3
._ ..,
wherein 111 to R3 are each independently a hydrocarbon group having 1 to 4
carbon atoms, and n is an integer from 1 to 10, and a step of removing the
salt
resulting from concentrating the solvent comprising the salt, wherein the
concentration is performed in a regenerator for the aromatic compound
extraction
solvent, and wherein a temperature of the extraction solvent circulation
system
including the regenerator is 180 C or lower.
[000913]
The present specification also discloses and claims a method for extracting
the
aromatic compound, using such a method for reducing corrosive ions in an
aromatic
compound extraction solvent, wherein the method comprises: mixing a desalted
aromatic hydrocarbon oil with the aromatic compound extraction solvent to
extract
the aromatic compound; distilling the solvent with the extracted aromatic
compounds
to separate the solvent and the aromatic compound; forming a non-volatile salt
by
adding the corrosive ion scavenger to react the corrosive ions with the
corrosive ion
scavenger; removing the salt resulting from concentrating the solvent
comprising the
salt; and feeding the desalted solvent to the circulation system.
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Solution to Problem
[00101
The present invention is based on the finding that by scavenging corrosive
ions in an aromatic compound extraction solvent in a circulation system as a
non-
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volatile salt and concentrating the extraction solvent containing this salt in
a
facility, the salt concentration in the system can be lowered and, moreover,
by
discharging the concentrated salt, the corrosive ions in the circulating
extraction
solvent can be conveniently and efficiently reduced.
[0011]
That is to say, the present invention provides [1] to [11] below.
[1] A method for reducing corrosive ions in an aromatic compound
extraction solvent in a circulation system where the aromatic compound
extraction solvent circulates,
the corrosive ions being at least one kind selected from the group consisting
of chloride ions, sulfate ions, and sulfite ions,
the method comprising:
a step of forming a non-volatile salt by adding a corrosive ion scavenger to
react the corrosive ions with the corrosive ion scavenger, and
a step of removing the salt resulting from concentrating the solvent
comprising the salt.
[2] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to [1], wherein the aromatic compound extraction
solvent is one or more selected from the group consisting of sulfolane,
diethylene
glycol, triethylene glycol, tetraethylene glycol, N-methylpyrrolidone,
dimethyl
sulfoxide, morpholine, N-formylmorpholine, methyl carbamate, diglycolamine,
furfural, and phenol.
[3] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to [1] or [2], wherein the corrosive ion
scavenger is a
quaternary ammonium compound represented by general formula (1) below:
[0012]
RI
R2¨N¨ (CH2),¨ OH = OH¨ (1)
R3
[0013]
wherein R1 to R3 are each independently a hydrocarbon group having 1 to 4
carbon atoms, and n is an integer of 1 to 10.
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[4] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to any one of [1] to [3], wherein one or more
selected
from the group consisting of ammonia and neutralizing amines are also used in
the circulation system.
[5] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to any one of [1] to [4], wherein the
concentration is
performed in a regenerator for the aromatic compound extraction solvent.
[6] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to any one of [1] to [5], wherein the corrosive
ion
scavenger is added in a frequency and a concentration determined based on a
corrosive ion concentration in the aromatic compound extraction solvent in
circulation.
[7] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to [6], wherein the corrosive ion scavenger is
added
so as to be 0.5 to 2 molar equivalents relative to the corrosive ion
concentration.
[8] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to any one of [1] to [5], wherein the corrosive
ion
scavenger is added in a frequency and a concentration determined based on a
metal ion concentration in the aromatic compound extraction solvent in
circulation.
[9] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to [8], wherein the metal ion is an iron ion.
[10] The method for reducing corrosive ions in an aromatic compound
extraction solvent according to any one of [1] to [9], wherein the aromatic
compound contains one or more selected from the group consisting of benzene,
toluene, and xylene.
[0014]
[11] A method for extracting an aromatic compound, using the method for
reducing corrosive ions in an aromatic compound extraction solvent according
to
any one of [1] to [10].
Advantageous Effects of Invention
[0015]
According to the present invention, corrosive ions in an aromatic compound
extraction solvent of a circulation system can be conveniently and efficiently
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reduced.
Accordingly, corrosion of an extractor caused by corrosive ions contained in
an aromatic compound extraction solvent of a circulation system can be
suppressed, enabling an aromatic compound to be efficiently extracted.
Brief Description of Drawing
[00161
[Fig. 1] Fig. 1 is a schematic system diagram of one example of an aromatic
compound extractor.
Description of Embodiments
[0017]
The method for reducing corrosive ions in an aromatic compound extraction
solvent of the present invention is a method applied to a circulation system
where the aromatic compound extraction solvent circulates, and chloride ions,
sulfate ions, and sulfite ions, i.e., corrosive ions, are reduced. The method
includes the step of forming a non-volatile salt by adding a corrosive ion
scavenger to react the corrosive ions with the corrosive ion scavenger, and
the
step of removing the salt by concentrating the solvent containing the salt.
Thus, by forming the corrosive ions in the aromatic compound extraction
solvent in the circulation system into a non-volatile salt and concentrating
the
extraction solvent containing the non-volatile salt, the corrosive ions in the
solvent that cause corrosion of an extractor can be conveniently and
efficiently
reduced.
[0018]
[Circulation system]
The method of the present invention is applied to a circulation system
where the aromatic compound extraction solvent contains at least one kind
selected from the group consisting of chloride ions, sulfate ions, and sulfite
ions
that are corrosive ions. An example is a system where a solvent is recycled in
the process of extracting an aromatic compound from an aromatic hydrocarbon
oil in the refining of a hydrocarbon oil such as petroleum.
The aromatic hydrocarbon oil is, for example, an oil that contains an
aromatic compound obtained by reformation, and specifically that contains
benzene, toluene or xylene as an aromatic compound, and a mixture of any of
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these.
[0019]
[Aromatic compound extraction solvent]
An aromatic compound extraction solvent commonly used in the refining of
a hydrocarbon oil can be used, and examples include sulfolane, diethylene
glycol,
triethylene glycol, tetraethylene glycol, N-methylpyrrolidone, dimethyl
sulfoxide,
morpholine, N-formylmorpholine, methyl carbamate, diglycolamine, furfural,
phenol, and the like. One of these solvents may be used singly, or two or more
may be used in combination. Among these, sulfolane is suitably used.
Sulfolane may gradually undergo thermal decomposition during use, and may
contain sulfuric acid as an impurity and possibly produce sulfate ions and
sulfite
ions, but sulfolane does not become problematic because the method of the
present invention is also capable of reducing sulfate ions and sulfite ions
derived
from sulfolane.
[0020]
[Corrosive ion scavenger]
The corrosive ion scavenger is a compound capable of forming a salt with
corrosive ions, and a corrosive ion scavenger not volatilizing in a
circulation
system to which the corrosive ion scavenger is added is used. Preferably, the
corrosive ion scavenger is strongly basic because the salt formed with
corrosive
ions is a neutral salt, and the corrosion of an extractor can be further
suppressed.
An example of such a corrosive ion scavenger is a quaternary ammonium
compound represented by general formula (1) below. Examples also include
extremely basic compounds such as 1,8-diazabicyclo[5.4.0]undecene-7 and
inorganic strong alkalis such as sodium hydroxide. Due to the concern of an
increased ash content in the solvent of the circulation system and from the
handleability viewpoint, the inorganic alkali to be added is preferably a
quaternary ammonium compound as referred to above.
[0021]
R1
R2 ¨ N ¨ (CH2)n¨OH - OH (1)
R3
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[0022]
In formula (1), R1 to R3 are each independently a hydrocarbon group
having 1 to 4 carbon atoms, and n is an integer of 1 to 10. Specific examples
of
10- to R3 include linear or branched alkyl groups and the like, such as a
methyl
group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group,
an
isobutyl group, a sec-butyl group, and a t-butyl group.
Specific examples of such quaternary ammonium compounds include
hydroxymethyltrimethylammonium hydroxide,
hydroxymethyltriethylammonium hydroxide, choline hydroxide, 2-
hydroxyethyltriethylammonium hydroxide, 3-hydroxypropyltrimethylammonium
hydroxide, and the like. One of these may be used singly, or two or more may
be
used in combination.
[0023]
Preferably, R1 to R3 are each independently a hydrocarbon group having 1
to 3 carbon atoms, and n is an integer of 1 to 4. When having such a low
molecular weight, the quaternary ammonium compound has excellent solubility
in water and exhibits a sufficient effect as a corrosive ion scavenger even in
a
small amount, and thus the extractor corrosion suppressing effect, which is
the
effect of the present invention, is further increased. Among these, choline
hydroxide (also referred to as choline), wherein Ri to R3 are all methyl
groups
and n is 2, is particularly preferable.
[0024]
In terms of handling, such a quaternary ammonium compound in general
is preferably used as an aqueous solution. The concentration thereof is not
particularly limited, and is preferably 5 to 50 mass%.
Since ammonia and other amines are weakly basic, salts formed by these
alkalis and corrosive ions are acidic salts, and even a small amount of water,
if
present, causes corrosion. On the other hand, since the quaternary ammonium
compound as described above is strongly basic, the salt formed by corrosive
ions
is a neutral salt and is unlikely to cause corrosion even in the presence of
water.
Moreover, the salt formed by the quaternary ammonium compound and
corrosive ions has deliquescent properties and fluidity, and is thus unlikely
to
adhere and is free from the risk of deposit buildup and clogging inside the
equipment of the circulation system.
[0025]
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The salt formed by the corrosive ion scavenger of the present invention and
corrosive ions has a high boiling point and is non-volatile in the circulation
system. Therefore, in the distillative refining process for the aromatic
hydrocarbon oil or the like, the salt is unlikely to evaporate and enter the
extracted aromatic compound, and the salt can be separated from the extraction
solvent by distillative concentration and can be removed as a distillation
residue.
[00261
The corrosive ion scavenger is preferably a quaternary ammonium
compound as described above. While a sufficient corrosive ion scavenging
effect
can be exerted solely by the corrosive ion scavenger, another agent such as
ammonia or a neutralizing amine may be used in combination in order to further
increase the corrosive ion scavenging effect.
Examples of the neutralizing amine include monoethanolamine,
cyclohexylamine, morpholine, diethylethanolamine, monoisopropanolamine, 3-
methoxypropylamine, 2-amino-2-methyl-1-propanol, and the like.
[0027]
Concerning the amount of the corrosive ion scavenger to be added, if the
corrosive ion concentration in the extraction solvent in the circulation
system can
be predicted or measured, the frequency and the concentration of the corrosive
ion scavenger to be added can be determined based on the corrosive ion
concentration. The corrosive ion concentration can be measured with an
absorptiometer, an ion chromatograph, a capillary electrophoresis analyzer, or
the like.
Concerning the concentration of the corrosive ion scavenger, from the
viewpoint of the effect of addition, preferably the corrosive ion scavenger is
added
so as to be 0.5 to 2 molar equivalents of the corrosive ion concentration, and
from
the viewpoint of obtaining a more stable corrosive ion scavenging effect, more
preferably 1 to 2 molar equivalents.
[0028]
As means for indirectly detecting the corrosive ion concentration, the metal
ion concentration in the extraction solvent in the circulation system may be
measured. When corrosion of the extractor progresses with an increase in the
corrosive ion concentration in the circulating extraction solvent, the metal
ion
concentration in the circulation system increases. Accordingly, it is also
possible
to detect an increase of the corrosive ion concentration by way of an increase
of
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the metal ion concentration. The metal ion concentration can be measured with
an absorptiometer, an inductively coupled plasma atomic emission spectrometer
(ICP-AES), an inductively coupled plasma mass spectrometer (ICP-MS), or the
like.
In this case, it is preferable to find in advance a correlation between the
measurement-target metal ion concentration and the corrosive ion concentration
in the circulation system. Thus, the frequency and the concentration of the
corrosive ion scavenger to be added can be determined based on the metal ion
concentration of the circulation system.
Specifically, the measurement-target metal ion is preferably an iron ion
that is likely to be eluted due to equipment corrosion.
[0029]
By using the method of the present invention as described above as a
method for reducing corrosive ions in an extraction solvent when extracting an
aromatic compound in a circulation system, corrosion of an extractor caused by
corrosive ions contained in the extraction solvent of the circulation system
can be
effectively suppressed, thus enabling efficient extraction to be performed.
[0030]
Below, equipment and a treatment mechanism to which the method of the
present invention is applied will now be described by way of one example. Fig.
1
shows a schematic system diagram of one example of an aromatic compound
extractor to which the method of the present invention is applied.
In the system flow shown in Fig. 1, a raw-material aromatic hydrocarbon
oil that is continuously or intermittently fed from a feed 1 is subjected to a
desalting treatment in a chloride trap 2, then mixed with an aromatic compound
extraction solvent in an extraction column 3 to extract aromatic compounds
such
as benzene, toluene, and xylene. Components insoluble in the solvent are
withdrawn from the column top and washed in a washing column 4, and then a
raffinate 9 is separated.
On the other hand, the aromatic compounds extracted into the extraction
solvent are withdrawn from the bottom of the extraction column 3 together with
the extraction solvent. Thereafter, the aromatic compounds and the extraction
solvent are separated by distillation in a stripper column 5 and a recovery
column 6 to obtain the aromatic compounds.
[0031]
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Here, a corrosive ion scavenger is added as an aqueous solution from an
injection facility 10 provided elsewhere in the extraction solvent circulation
system, such as in the column top system of the stripper column 5.
The extraction solvent is distilled again for a regeneration treatment in the
recovery column 6, subjected to a dehydration treatment in a process water
stripper 8, returned to the extraction column 3, and recycled.
The recovered extraction solvent from the recovery column 6 contains a
non-volatile salt produced by reaction between the corrosive ion scavenger and
the corrosive ions in the extraction solvent. The recovered extraction solvent
containing such a salt is concentrated by distillation in a bypass regenerator
7.
By separating and removing a concentration residue and returning a volatilized
fraction back to the recovery column 6, a regenerated solvent with reduced
corrosive ions is fed to the circulation system.
[0032]
The corrosive ion scavenger may be added elsewhere in the circulation
system. For example, in the above apparatus, the corrosive ion scavenger can
be
added from the injection facility 10 provided in the column top system of the
stripper column 5 that is a subsequent stage relative to the aromatic compound
extraction column 3.
The temperature of the extraction solvent circulation system including the
regenerator 7 is preferably 180 C or lower from the viewpoint of preventing
volatilization of the corrosive ion scavenger and promoting the corrosive ion
scavenging effect thereof in the regenerator 7.
[0033]
As described above, the salt formed by the corrosive ion scavenger and the
corrosive ions is a salt that is non-volatile in the circulation system, and
is
therefore not discharged on the extract side by, for example, distillation
performed for extracting aromatic compounds and can be separated as a
distillation residue of solvent concentration in a specific place such as the
regenerator 7 provided in the circulation system for solvent regeneration.
Moreover, the salt may be removed out of the circulation system by providing a
means for discharging remaining residues containing the salt.
Examples
[0034]
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Below, the present invention will now be described in more detail, but the
present invention is not limited to the following Examples.
[0035]
[Test 1] Confirmatory test at laboratory level
(Test 1-1)
First, 100 mL of xylene, 96 mL of sulfolane, and 4 mL of pure water were
introduced into a 500 mL round-bottom flask. Hydrochloric acid and an aqueous
solution of choline hydroxide (choline) were added thereto to prepare a sample
solution having a chloride ion concentration of 100 mg/L and a choline
concentration of 340 mg/L.
This sample solution was distilled to remove water. The residual liquid
(sulfolane and xylene) remaining in the round-bottom flask was extracted twice
with 200 mL of pure water.
[0036]
(Test 1-2)
A sample solution was prepared that had the same chloride ion
concentration and choline concentration as the sample solution of Test 1-1 and
to
which monoethanolamine (MEA) was added so as to have a monoethanolamine
concentration of 172 mg/L and, otherwise, distillation and extraction were
performed in the same manner as in Test 1-1.
[0037]
(Test 1-3)
A sample solution having the same chloride ion concentration as the
sample solution of Test 1-1 to which no choline hydroxide (choline) was added
was prepared, and otherwise, distillation and extraction were performed in the
same manner as in Test 1-1.
[0038]
(Test 1-4)
A sample solution having the same chloride ion concentration and MEA
concentration as the sample solution of Test 1-2 to which no choline hydroxide
(choline) was added was prepared, and otherwise, distillation and extraction
were
performed in the same manner as in Test 1-2.
[0039]
Concerning the extracts of the first and second extractions in the above
tests, the chloride ion, choline hydroxide, and MEA concentrations were
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measured with a capillary electrophoresis analyzer. The measurement results
thereof are shown in Table 1.
[0040]
Table 1
Test No. 1-1 1-2 1-3 1-4
Amount added (mg/L)
Cl- 100 100 100 100
Choline 340 340
MEA 172 172
in extract (mg/L)
First 61 109 2.6 <1.0
Second 11.2 12.9 <1.0 3.7
Total 72.2 121.9 2.6 3.7
[00411
As can be understood from the results shown in Table 1, when choline
hydroxide was added (Test 1-1), the chloride ion concentration in the extract
was
20 times or higher than when no choline hydroxide was added (Test 1-3),
confirming an improved corrosive ion scavenging effect in the aromatic
compound
extraction solvent.
When choline hydroxide was added (Test 1-1), the chloride ion
concentration in the extract was at least 15 times higher than when only MEA
was added (Test 1-4), confirming that the corrosive ion scavenging effect in
the
aromatic compound extraction solvent was superior.
Moreover, when choline and MEA were added (Test 1-2), the chloride ion
concentration in the extract was high, and it can be said that the corrosive
ion
scavenging effect in the aromatic compound extraction solvent is further
improved.
[0042]
[Test 2] Test at actual equipment level
The following test was conducted in the equipment shown in Fig. 1 under a
condition where an aromatic hydrocarbon oil containing benzene, toluene, and
xylene and sulfolane (having a chloride ion concentration of 70 mg/L) were in
circulation.
An aqueous solution of choline hydroxide (choline) was added once a week
to a place near the column-top outlet of the stripper column 5. The amount of
choline hydroxide added was equimolar to the chloride ions in sulfolane. The
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concentration of chloride ions was measured by performing extraction with 50
mL of pure water twice, followed by ion chromatography.
After the equipment was operated for a predetermined number of days, 1 L
of sulfolane was recovered from the bottom of the recovery column 6, and the
chloride ion concentration in this sulfolane was measured. The measurement
results are shown in Table 2.
[0043[
Table 2
Days of operation (days) 1 7 14 20 30 35
Cumulative concentration of choline (mg/L) 267 533 800 1067 1333 1600
Cl in recovered sulfolane (mg/L) 101 88 71 62 52 46
[0044]
As can be understood from the results shown in Table 2, it was confirmed
that the chloride ion concentration in sulfolane recovered from the bottom of
the
recovery column 6 decreased as the cumulative concentration of choline
hydroxide increased. It was also confirmed that choline remained in the
recovered sulfolane.
The rate of chloride ion buildup in the bottom of the regenerator 7 was 60
mg/(L=day), i.e., increased about 3 times by adding choline hydroxide relative
to
23 mg/(L=day) attained when no choline hydroxide was added.
Accordingly, it can be said that a favorable corrosive ion scavenging effect
can be obtained due to choline hydroxide in actual equipment as well.
Reference Signs List
[0045]
1 Feed
2 Chloride trap
3 Extraction column
4 Washing column
Stripper column
6 Recovery column
7 Regenerator
8 Process water stripper
9 Raffinate
Injection facility (Place where corrosive ion scavenger is added)
