JPS5879812A - Preparation of sodium carbonate monohydrate - Google Patents

Abstract

PURPOSE:To prepare high-purity sodium carbonate monohydrate in the state of crystal economically, by concentrating an aqueous solution of sodium carbonate containing sodium bicarbonate in the presence of a specific amount of sodium chloride. CONSTITUTION:Raw sodium bicarbonate obtained by ammonia soda process is decomposed with low-pressure steam, to give an aqueous solution of sodium carbonate containing preferably <=20mol% of sodium bicarbonate based on sodium carbonate, which is concentrated by spray type concentration and evaporation process, etc., the concentration of sodium chloride in the crystallizing solution is kept at 3-15wt% by the addition of salt, etc., and sodium carbonate monohydrate and sodium sesquicarbonate are crystallized. The crystal of sodium carbonate monohydrate obtained as above mentioned has mostly particle diameters of about 120-1,000mu, while the crystal of sodium sesquicarbonate has mostly particle diameters of <= about 120mu. Both can be easily separated and recovered by a cyclone, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for economically obtaining high purity sodium carbonate aqueous solution from an aqueous solution of sodium bicarbonate.

Conventionally, a method for obtaining a sodium carbonate water mass is to burn bicarbonate of soda obtained by the ammonia soda method to obtain so-called light ash, which has a low bulk specific gravity, and then add water to this to form a soda carbonate water mound. There is. However, the above method is complicated because it requires a step to obtain light ash.

On the other hand, a method has been studied in which a sodium bicarbonate aqueous solution obtained by the ammonia-soda method is thermally neutralized with caustic soda to form a sodium carbonate aqueous solution, and a sodium carbonate hydrate is directly obtained from the aqueous solution. However, in the above method, if the conversion rate of sodium bicarbonate to sulfur soda is not sufficient, the sodium bicarbonate is contained in the aqueous solution of sodium carbonate, so that when the sodium carbonate aqueous solution is precipitated, the sodium sesquicarbonate is It is difficult to obtain high-purity sodium monocarbonate hydrate through eutectic crystallization. Therefore, the above method has the problem that it requires a large amount of energy or caustic soda in order to increase the conversion rate of sodium carbonate to sodium carbonate, and is very uneconomical.

In view of the above, the present inventors have conducted extensive research on a method for obtaining iL of highly purified sodium carbonate hydrate from a sodium carbonate aqueous solution containing salt-rehydrated sodium acid. As a result, when the sodium leg acid aqueous solution is crystallized from the sodium carbonate aqueous solution, the particle size of the precipitated sodium carbonate hydrate crystals is increased by the presence of a specific amount of sodium chloride (hereinafter also referred to as di-salt). However, as the particle size of the sodium sesquicarbonate crystals becomes smaller, a difference occurs in the crystal size of each crystal, so it was discovered that sodium carbonate hydrate can be easily separated from the sodium sesquicarbonate, and the present invention was completed. reached.

In the present invention, when obtaining sodium carbonate hydrate from an aqueous sodium carbonate solution containing sodium bicarbonate, the sodium chloride concentration in the crystallizing solution is maintained at 3 to 15 ml to crystallize charcoal fil soda hydrate. This is a method for producing leg acid soda water, which is characterized by separation.

The aqueous sodium carbonate solution containing sodium bicarbonate used in the present invention is not particularly limited. For example, an aqueous solution of sodium carbonate containing sodium bicarbonate obtained by carbonating caustic soda, or an aqueous solution of sodium chloride containing sodium bicarbonate obtained after wet decomposition of crude sodium bicarbonate obtained by the ammonia soda method, etc. are generally used. In particular, in the present invention, the sodium bicarbonate in the sodium carbonate solution containing sodium bicarbonate is
It is desirable that the amount is 20 mol% or less of soda carbonate. That is, if the sodium bicarbonate in the sodium carbonate solution is present in an amount exceeding the above range, the crystals of sodium bicarbonate that are eutectic with the sodium carbonate hydrate will have many aggregated crystals, and the upper particle size will appear to be larger. Become. Therefore, separation of sodium carbonate hydrate and sodium sesquicarbonate, which will be described later, becomes difficult. Therefore, when the sodium bicarbonate content in the sodium bicarbonate-containing soda solution exceeds 20 mol% based on the soda carbonate,
It is preferable to apply the present invention after adjusting the content of sodium bicarbonate to 20 mol% or less. There are no particular limitations on the method for reducing the content of sodium carbonate in the sodium carbonate solution. For example, as described above, low-pressure steam is used to decarboxylate sodium bicarbonate to reduce the content of sodium bicarbonate, or in the case of a sodium bicarbonate/sodium carbonate aqueous system, 70% sodium carbonate and sodium carbonate hydrate are used. Utilizing the phenomenon that the ratio of sodium richate/sodium carbonate in a liquid at the eutectic point generally decreases as the temperature decreases, a sodium carbonate solution containing sodium bicarbonate is cooled and/or concentrated to make a sesquis A method of crystallization and separation such as sodium carbonate is preferably used.

In the present invention, when crystallizing sodium carbonate hydrate from an aqueous sodium carbonate solution containing sodium bicarbonate, it is extremely important to maintain the salt concentration in the sodium carbonate hydrate crystallization solution within the range of 3 to 15% by weight. . That is, as a result of various experiments, the present inventors have found that when performing crystallization of sodium carbonate hydrate from a sodium carbonate aqueous solution containing sodium bicarbonate, by keeping the salt concentration within the above range, the sodium carbonate water that generally precipitates can be reduced. Salt has a particle size of 120μ or less, approximately 5% by weight or less, and 1000μ
In this way, high-quality orthorhombic crystals with a uniform particle size of about 5 coulombic acid or less can be obtained, and the eutectic sodium carbonate is about 90%
The particle size of Kyoyoshi was less than 120μ, and it could be easily separated from the sodium carbonate water salt due to the difference in particle size. Incidentally, when the salt concentration in the above-mentioned sodium carbonate hydrate crystallization solution is lower than 3% by weight, the crystals of the sodium carbonate hydrate become plate-like, have a small bulk specific gravity, and have a small particle size. Since the particle size of the sesquicarbonate soda becomes slightly large, it becomes difficult to separate the sesqui[1 soda] from the sodium carbonate hydrate.

On the other hand, if the eclipse #X1iI in the crystallization liquid is higher than 11% or 15%, the crystals of carbonate soda Kiba become rod-shaped and have a small bulk specific gravity, and the particle size also becomes small.
Separation from the eutectic sodium sesquicarbonate becomes extremely difficult.

In the present invention, the 1n11 method for determining the salt concentration in the sodium carbonate hydrate crystallization solution is not limited in any way as long as the salt concentration in the crystallization solution is 3=1531 amount - at the time of crystallization of the sodium carbonate hydrate crystallization solution. . For example, a method of adding salt to a predetermined concentration before crystallizing the sodium carbonate water ring;
A common method is to add it directly during crystallization. The salt may be added in the form of solid, slurry, or aqueous solution. For example, it is a preferred embodiment to use the separated mother liquor of sodium carbonate water salt described below as the salt source. In addition, when the sodium carbonate aqueous solution contains salt by another process, if the salt concentration at the time of crystallization does not reach the above-mentioned level, add salt by the above method, and when the salt concentration exceeds the above range. Generally, a method is adopted in which a portion of the sodium carbonate hydrate crystallized solution is purged into another culm to prevent the salt from concentrating.

In the present invention, the apparatus and method for crystallizing the aqueous sodium carbonate solution are not particularly limited, and any known concentration method may be used without particular limitation. For example, a method in which the sodium carbonate aqueous solution is supplied by spray using a spray set concentration evaporator and brought into contact with high-temperature gas to crystallize the sodium leg acid hydrate;
A common method is to use a single- or multiple-effect evaporator to indirectly heat the aqueous sodium carbonate solution to evaporate and concentrate it to crystallize the sodium carbonate aqueous salt.

In the present invention, as the apparatus and method for separating sodium carbonate hydrate and sodium sesquicarbonate, a separation method that utilizes the difference in particle size of the respective crystals may be adopted without particular limitation. For example, a method of separating sodium carbonate hydrate using a liquid cyclone or the like, or a method of separating and drying a mixture of sodium sesquicarbonate and sodium carbonate hydrate using a louver classifier, etc.
A method of separating the sodium carbonate aqueous salt by performing so-called wind classification or the like may be used alone or in combination.

The carbonate soda wood chips obtained by the above separation method have a particle size of 50
It is mainly orthorhombic with a bulk density of 1.1 or more and has excellent properties as a raw material for dense soda ash. In addition, if you want to directly obtain dense soda ash without drying the sodium carbonate hydrate, separate the sesquicarbonic soda and the sodium carbonate hydrate using a centrifuge, etc., and prepare the sodium carbonate hydrate using a steam tube dryer, fluidized fluid dryer, etc. After evaporating the crystallization water and making it into dense soda ash, the above-mentioned looper type classification &.

And/or by separating the particles of 120μ or more using a vibrating sieve or the like.-0 In order to make the present invention more specific, the present invention will be explained according to the attached directions. Although FIG. 1 shows a typical embodiment of the present invention, the present invention is not limited thereto.◎ The soda carbonate solution containing sodium bipod acid is added to the line 1. Adjusted in the supply liquid tank 100 by the raw materials supplied from
The sodium bicarbonate is then sent to the sodium bicarbonate decomposition device 200 via line 2, where it is heated with steam or the like supplied from line 3 to thermally decompose the sodium bicarbonate, that is, to remove the legs. When the sodium carbonate content of the sodium carbonate solution supplied to the decomposition device 200 is low, it can be directly transferred to the charcoal soda hydrate crystallizer 11600 or the sesquicarbonate soda crystallizer 3.
It may also be supplied to 00.

The soda carbonate solution that has been decarboxylated in the decomposition device 200 is sent through line 4 to the seven-stage soda removal device 300.

In addition, when decarboxylation is performed in the sodium bicarbonate decomposition device until the content of sodium bicarbonate reaches 20 mol% or less based on the sodium carbonate, the decarboxylation is carried out from the Yamabutsu decomposition device @200 to the sodium carbonate hydrate crystallization device 600. It may be liquid.

In the sesqui-crystallizer 300, the sesqui-sodium carbonate is crystallized by cooling or concentrating by evaporation under normal pressure or reduced pressure so that the amount of carbon-rich and ugly soda in the crystallization liquid is 20 mol% or less based on the charcoal soda. . The heat source necessary for the above concentration is sent to the heating device 400 through line 5, and the evaporated water is discharged through line 6.

The crystallized sodium sesquicarbonate is sent to the sodium sesquicarbonate separator @500 via line 7, and is separated into sodium sesquicarbonate and furnace liquid.

The sodium sesquicarbonate may be taken out as a product through line 8, or may be recycled and used again through line 9 as a raw material for sodium carbonate hydrate.

The furnace liquid of sodium sesquicarbonate having a sodium bicarbonate content of 20 mol % or less of the sodium carbonate is sent via line 10 to the sodium carbonate hydrate crystallizer 600 and concentrated. The heat source for concentration is connected to heating equipment f& from line 11 as needed.
700 and the evaporated water is discharged through line 12.

In the crystallization apparatus 600, the salt concentration in the sodium carbonate hydrate crystallization solution is maintained at 3 to 15% by weight and 11%.

The sodium carbonate hydrate and sesquisodium carbonate crystallized in the crystallization device 600 are sent to the sodium carbonate hydrate-sodium sesquicarbonate separation device 800 via line 14 .

In the separation device 800, the sodium carbonate hydrate can be easily separated by utilizing the difference in particle size of each crystal. For example, in a separator*SOO, sodium sesquicarbonate and sodium carbonate hydrate crystals are simultaneously separated using a filter such as a centrifugal separator, which is then dried and classified using a louver classifier to separate carbonate sodium hydrate crystals. An operation of separating the carbonated sodium hydroxide salt into a slurry using a wet classifier such as a liquid cyclone is carried out. The slurry separated by the latter operation is dehydrated in a sodium carbonate hydrate crystal separator 900 and taken out through a line 16. −
Sodium bicarbonate aqueous salt-sesquicarbonate separator 800
The separated mother liquor etc. obtained in is recovered from line 13,
It is preferable to use a portion of the thick noodles as a source of salt through line 17 as it contains the base ring.

As understood from the above explanation, the method of the present invention completely removes the sodium bicarbonate contained in the aqueous solution of sodium carbonate.
11! #High purity sodium carbonate aqueous salt can be obtained without converting it to soda, and there is no need for heating or addition of caustic soda for conversion as in conventional methods, making it very economical. Furthermore, it is possible to obtain carbonate two-dumb hydrate crystals with excellent crystal morphology.

Examples will be shown to specifically explain the present invention.
The present invention is not limited to this.

Example 1 The experiment was carried out according to the flow sheet shown in FIG.

First, MaHOo, 0.3% (hereinafter referred to as wt%), Ha200.4.5 wt%, H2O9,i
990% sodium carbonate crystals at 50°C containing wt%
J9/Hr, NaHOO,o circulated from line 9,
4wt%Na, oo, 6.4wt%, MthO
l 1.3 wt%, If 2018.9 wt% at 50°C, 1633 kg/ar of sodium carbonate crystals and 1 Jaojo, 76 wt% saline solution 13
10&9/ilr is supplied to the supply liquid tank 100 and mixed,
This mixed solution was preheated by being brought into direct contact with 1020'/Hr of steam at 133° C. containing 37.0 Mao1% of OO□. After that, a multi-stage gas-liquid contact type sodium bicarbonate decomposition unit [200] was supplied from the upper part and thermally decomposed, M*HO0.3, Owt%,
Ha, 00.25.1 wt%.

138℃ decomposition solution containing 0.44vt% hog
Obtained at 74819/Hr. 1iaHOo, 1.3 wt%, N&, which is circulated into this decomposition liquid from line 17.
A 92°C solution containing 80.187wt and M&il 9.5at≦ was mixed at 2323.419/Hr,
Self-evaporating type seven carbonate soda crystallizer [300] and sesquicarbonate soda slurry solution to 4626.4 to 97
I took it out with HE. This slurry solution was treated with a decanter-type sesquicarbonate separator 500 containing 0.4 wt% of NaHOo.
pHa200. a4w t%t ”a'j 1.3
wt%.

H2O18,9w - containing 7-sukiyashi soda crystal 1
63.3 ky/Hr and NaHOO,i, 5 wt%
, Ha200°23.7wt%t”tLCl 5.
A separated mother liquor 4463, IJ9/Hr containing 2 wt% was obtained. This separated mother liquor is transferred to a sodium carbonate hydrate crystallizer 600.
The water was evaporated and condensed at 1 kg/Hr to obtain a slurry containing sodium sesquicarbonate crystals and sodium carbonate water mass crystals at 30901 kg/Hr for 97 Hr. still,
1jaHOo in the crystallization liquid in this crystallizer, concentration 1.4
wt%.

Ha2Go, concentration 18.6wt%, Mail concentration i
o wt%. The obtained slurry was divided into 100 pieces in a center-centered vessel with a 100-meter mesh screen [1 wash with water and
M acid soda containing Cl O, 4 wt%, H, 04, 9 wt% g Sodium sesquicarbonate crystals 11.6 wt%
A portion of the separated mother liquor was recycled through line 17. After drying the crystals at 100°C using a fluidized dryer, the crystals were further classified using a louver classifier.
Sodium carbonate hydrate crystals were obtained, and the sodium sesquicarbonate crystals in the crystals were reduced to 0.5 wt% or less. Further, the crystal form of the obtained next-order soda water salt was an orthorhombic crystal, and it was a powder having the particle size distribution shown in Table 1 and an apparent specific gravity of 1.19.

Table 1 Example 2 The experiment was carried out according to the flow sheet shown in FIG.

First, Ha200°43 obtained by the ammonia soda method
Weight @%, NH4HO0,3,8wt%, Nal'
1iaHOo, where 1000kg/Hr of rich soda crystals containing 1.0wt%* H2O20, Owt% are circulated from line 9, Q. 3wt%, Ha2Co36
．． 5 wt%, Mholl, 4wt%t H2O18,
Sodium sesquicarbonate crystals 1501 at 50°C containing 4wt%
1 sI/Hr and 712 kj/Hr of 60°C hot water are supplied to the supply liquid tank ioo and mixed, and this mixed liquid is
133 containing 6.5 MaOj% and 3.8 MaO1% of NH4
It was preheated by face-to-face contact with water vapor of 288 Nl'l/Er at °C. After that, it is supplied from the upper part of a multi-stage gas-liquid contact type sodium bicarbonate decomposition apparatus 2θ0 and thermally decomposed, NaHOo,
3.2 wt%, Ha200, 26.6 wt%e
13 containing Na0A'06wt%'
A decomposition solution at 8°C was obtained at 2020119/Hr. NILHGO3i, a circulated through line 17 to this decomposed liquid
wt%, Ha, 00318.6 wt%.

1745 t8 liquid at 92°C containing 19.4 wt% M&O
The mixture was mixed at a rate of 19/Hr and supplied to a self-evaporation type sodium sesquicarbonate crystallizer 300, and a sodium sesquicarbonate slurry solution was taken out at a rate of 343,649/Hr.

This slurry solution was passed through a decanter-type carbonic acid separator 500 using NaBOO, 0.3 at%, and Ha at 200°6.
5wt%, M turtle α/1.4wt%+”201 & 4
Seven ski carbonate soda crystals including wt Hata R50&p/Hr
and NaBOO,i, 41yt%t Ha x OOx
A separated mother liquor of 3286&p/Hr containing 24.3 wt% of Nap and 15.3 wt% of Nap was obtained.

This separated mother liquor is supplied to the sodium carbonate hydrate crystallization device 600, and the water is evaporated and concentrated at 105 Jlv/Hr to form a slurry containing 70% sodium carbonate crystals and 3090'90% sodium carbonate hydrate crystals. /Hr. Incidentally, the eclipse j [F1 degree] in the crystallization liquid in this crystallization apparatus was 10 wt%.

The obtained slurry was separated using a centrifugal separator with a 100 mesh screen and washed with water to obtain an H&OI of 0.3 w.
t%, H2O48wt%, sodium sesquicarbonate crystals9.
Sodium carbonate hydrate crystals containing 1wt% are 597&9/H
Obtained with r.

A portion of the separated mother liquor was recycled through line 17. The crystals were dried at 100°C using a fluidized dryer.[Later, as a result of being classified using a louver classifier, 510 k
g/nr of sodium carbonate water mass crystals were obtained, and the sodium sesquicarbonate crystals in the crystals were reduced to 0.5 wt% or less.

In addition, the crystal form of the obtained sodium carbonate hydrate was a lateral crystal form, and the particle size distribution was almost the same as that of Example 1.
It was a powder with fi 1.19.

Comparative example It was carried out according to the 7I:I-sheet shown in FIG.

First, NaHOO30.3% (hereinafter referred to as wt%), M&, 0.4.5 wt%, H2O9
, 99% sodium carbonate crystals at 50°C containing 1 wt%
0kg/Hr, Na circulated from line 9
HO01043wt%, Ma2ao37.2 It%r
N&CI 0.13 w t%tH2o 18.
Sesqui#soda crystals at 50°C containing 9 wt% 194
．． 8 kg/Hr and Na0j! 1353 kg/Hr of a saline solution containing 0.074 wt% is supplied to the supply liquid tank 100 and mixed, and this mixed liquid is aO.

104Mw of water vapor at 133°C containing 37.0maoj%,
The solution was preheated at 1/Hr. Thereafter, it was fed from the upper part of a multi-stage gas-liquid contact type sodium bicarbonate decomposition unit @200 and thermally decomposed to yield NaHOO, 3, Owt%.

Na, 00.25.1 wt%v”&O1O,O45
2816&s+/! 138℃ decomposition solution containing wt%!
Obtained from ir.

N a HOO is circulated through line 17 to this decomposition liquid.
sl, 9 wt % e Ha, a Os 26.
1 wt% e N a' l (197wt%
A 92°C solution containing
4626.4 kg of 7-sodium carbonate slurry solution was supplied to a self-evaporating type 7-sodium carbonate crystallization reactor 300.
I took it out with Hr. This slurry solution was processed into a decanter-type sesquicarbonate separator 500 using NaHOO, 0.43wt.
%, Na200.7.2 wt%IaOj 0.1
Sodium sesquicarbonate crystals containing 3 wt%, H, 018, 9 wt% 194.8 &9/Hr and NaHOO31
,7wt attack, M&, 00327.5wt%, Na01
A fraction containing 0.5 wt% G4375jI9/Hr was obtained. This separated mother liquor is transferred to a sodium carbonate hydrate crystallizer 600.
The water was evaporated and concentrated at a rate of 140,611 I/llr to obtain a slurry containing sodium sesquicarbonate crystals and sodium carbonate hydrate crystals at a rate of 296,919/hr. NaHOO8 concentration of 1.9wt%
, Na2CO3 concentration was 26.2wt%, and Na01t concentration was 0.97wt4. The obtained slurry is 100
After separation using a centrifugal separator with a messier screen, the mixture was washed with water to give Na010.03 wt% and H2O5.0 wt%.
, sodium carbonate hydrate crystals containing 9-J-wt% of sodium sesquicarbonate crystals were obtained at 787 kg/Hr. A portion of the separated mother liquor was recycled through line 17. After drying the crystals at 100°C using a fluidized dryer, the crystals were further classified using a louver classifier.
Sodium carbonate hydrate crystals were obtained, and the sodium sesquicarbonate crystals in the crystals were 5.2 wt %. However, the crystal form of the obtained sodium carbonate hydrate was an orthorhombic crystal, and it was a powder having the particle size distribution shown in Table 2 and an apparent specific gravity of 1.07.

Table 2

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an alternative embodiment of the present invention. In the figure, 100 is a supply liquid tank, 2
00 is a bicarbonate of soda decomposition equipment. 300 is a sesquicarbonate soda crystallization device, 400 is a heating device, and 500 is a sesquicarbonate soda separation device. 600 is a carbonate soda quartz crystal display Lroo is a heating device,
800 represents a sodium carbonate hydrate-sodium sesquicarbonate separation device, and 900 represents a sodium carbonate hydrate separation device. Patent applicant: Tokuyama Soda Co., Ltd.

Claims (1)

[Scope of Claims] 1. When obtaining sodium carbonate hydrate from an aqueous sodium carbonate solution containing sodium bicarbonate, the sodium chloride concentration in the crystallization solution is maintained at 3 to 15 bicarbonate to crystallize the sodium carbonate hydrate. , a method for producing sodium carbonate water salt, which is characterized by separating this. 2. The method according to claim 1, wherein the sodium bicarbonate in the aqueous sodium carbonate solution is 207 liters of soda carbonate or less.