CA1220321A - Process for precipitating ammonium chloride - Google Patents
Process for precipitating ammonium chlorideInfo
- Publication number
- CA1220321A CA1220321A CA000452782A CA452782A CA1220321A CA 1220321 A CA1220321 A CA 1220321A CA 000452782 A CA000452782 A CA 000452782A CA 452782 A CA452782 A CA 452782A CA 1220321 A CA1220321 A CA 1220321A
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- CA
- Canada
- Prior art keywords
- ammonium chloride
- precipitation
- solid
- slurry
- solution
- Prior art date
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Abstract
ABSTRACT:
A process for precipitating ammonium chloride in ammonia-soda process wherein ammonium chloride and sodium bicarbonate are alternately precipitated by using sodium chloride, carbon dioxide gas and ammonia as raw materials, which comprises introducing a liquid cooling medium directly into an ammonium chloride precipitation solution in a precipitation tank to cool the solution by the heat of vaporization of the medium and thereby precipitate ammonium chloride to form a slurry containing solid ammonium chloride thus precipitated, wherein a part of the slurry is subjected to a solid concentrator and concentrated by the removal of a part of liquid therefrom, and the resulting concentrated slurry is returned to the precipitation solution to increase the solid ammonium chloride concentration in the precipitation solution and thus promote the grain growth of the solid ammonium chloride.
A process for precipitating ammonium chloride in ammonia-soda process wherein ammonium chloride and sodium bicarbonate are alternately precipitated by using sodium chloride, carbon dioxide gas and ammonia as raw materials, which comprises introducing a liquid cooling medium directly into an ammonium chloride precipitation solution in a precipitation tank to cool the solution by the heat of vaporization of the medium and thereby precipitate ammonium chloride to form a slurry containing solid ammonium chloride thus precipitated, wherein a part of the slurry is subjected to a solid concentrator and concentrated by the removal of a part of liquid therefrom, and the resulting concentrated slurry is returned to the precipitation solution to increase the solid ammonium chloride concentration in the precipitation solution and thus promote the grain growth of the solid ammonium chloride.
Description
1.~2~13~1 Our Ref.: A-342 PROCESS FOR PRECIPITATING AMMONIUM SALARIED
The present invention relates to a process for precipitating ammonium chloride in ammonia-soda process wherein ammonium chloride and sodium bicarbonate are S alternately precipitated. More particularly, the present invention relates to a process wherein a liquid cooling medium is brought in direct contact with an ammonium chloride precipitation solution to precipitate ammonium chloride efficiently and with a uniform particle size.
In the so-called ammonia-soda process wherein sodium bicarbonate is precipitated by introducing carbon dioxide gas into an ammonium chloride-separated mother liquor and ammonium chloride is precipitated by adding ammonia and sodium chloride to a sodium bicarbonate-separated mother liquor obtained by separating the precipitated sodium bicarbonate, the ammonium chloride precipitation step is conducted, for instance, by a process wherein ammonia is added to the sodium bicarbonate-separated mother liquor, the mother liquor is cooled to precipitate a part of .,
The present invention relates to a process for precipitating ammonium chloride in ammonia-soda process wherein ammonium chloride and sodium bicarbonate are S alternately precipitated. More particularly, the present invention relates to a process wherein a liquid cooling medium is brought in direct contact with an ammonium chloride precipitation solution to precipitate ammonium chloride efficiently and with a uniform particle size.
In the so-called ammonia-soda process wherein sodium bicarbonate is precipitated by introducing carbon dioxide gas into an ammonium chloride-separated mother liquor and ammonium chloride is precipitated by adding ammonia and sodium chloride to a sodium bicarbonate-separated mother liquor obtained by separating the precipitated sodium bicarbonate, the ammonium chloride precipitation step is conducted, for instance, by a process wherein ammonia is added to the sodium bicarbonate-separated mother liquor, the mother liquor is cooled to precipitate a part of .,
- 2 I
ammonium chloride, and after separating the precipitated ammonium chloride or without such separation, sodium chloride is then added to decrease the volubility of ammonium chloride and thereby further precipitate ammonium chloride, or a process wherein ammonia and sodium chloride are added to the above-mentioned sodium bicarbonate mother liquor, followed by cooling to precipitate ammonium chloride.
In each case, the cooling is conducted in such a manner that a part of the ammonium chloride precipitation solution is cooled by a cooler to a super saturated state by taking advantage of such a nature that the saturated ammonium chloride solution can be brought to such a super saturated state, and the super saturated solution is returned to the precipitation tank where ammonium chloride in a super saturated state will be precipitated The cooler to be used in such a cooling step, is usually of an indirect cooling type with a cooling jacket provided at the cooling portion to cool the solution from outside. The structure is rather complicated, and the temperature control is rather delicate. Further, the precipitation of crystals takes place partially within the cooler thus frequently leading to a clogging problem.
In order to avoid such a problem, it is common to employ a plurality of coolers so that the operation will be switched from one golfer to another with a relatively ~L22~
short period of operation each time and they are cleaned frequently to avoid clogging. Thus, the conventional cooler is not necessarily satisfactory from the viewpoints of both operation and installation.
Whereas, the present applicant has previously proposed a process wherein a liquid cooling medium such as lion is introduced directly into the ammonium chloride precipitation solution to cool the solution by the heat of vaporization of the liquid cooling medium and thereby precipitate ammonium chloride (Japanese Examined Patent Publication No. 4284~/1979). This process has advantages such that it does not require a complicated structure or a cumbersome operation as used to be required by the conventional processes, and a smooth operation can be conducted under a stabilized condition for a long period of time with a minimum possibility of clogging which adversely affects the operation of the apparatus.
However, according to this process, the solid ammonium chloride concentration in the ammonium chloride precipitation solution is usually as low as from 3 to lo by weight. Accordingly, it is required to employ a considerably intensive cooling in order to precipitate ammonium chloride by cooling such a solution. Further, since it is usual to employ a perfect mixing type precipitation means the precipitated ammonium chloride tends to have a wine particle size, and has a drawback such that a substantial portion of the precipitated _ 4 I
ammonium chloride is likely to deposit on the inner wall of the precipitation tank to form a scale.
To prevent such a drawback, there have been proposed various considerations such as controlling or adjusting the amount or the manner of introducing the cooling medium, which are, however, dependent largely on experience or may vary largely depending upon individual types of the precipitation tanks For these reasons, the process has not yet been developed to a fully satisfactory extent.
As a means to cope with the above problem, it is conceivable to increase the ammonium chloride concentration in the precipitation tank. However, it is technically almost impossible to concentrate the solution by heating for evaporation. It is also technically extremely difficult to take out only liquid from the solution since the solution in the precipitation tank is in a perfect mixing state in which numerous ammonium chloride particles partially precipitated are uniformly dispersed.
Under these circumstances, the present inventors have conducted various researches and studies with an aim to obtain a means for precipitating ammonium chloride with a relatively large uniform particle size with a minimum possibility of deposition on the inner wall of the precipitation tank without requiring special considerations as mentioned above. As a result, it has I
been found that this object can be accomplished by increasing the solid ammonium chloride concentration in the precipitation solution.
Thus, the present invention provides a process for precipitating ammonium chloride in ammonia-soda process wherein ammonium chloride and sodium bicarbonate are alternately precipitated by using sodium chloride, carbon dioxide gas and ammonia as raw materials, which comprises introducing a liquid cooling medium directly into ammonium chloride precipitation solution to cool the solution by the heat of vaporization of the medium and thereby precipitate ammonium chloride to form a slurry containing solid ammonium chloride thus precipitated, wherein a part of the slurry is subjected to a solid concentrator and concentrated by the removal of a Hart of liquid therefrom, and the resulting concentrated slurry is returned to the precipitation solution to increase the solid ammonium chloride concentration in the precipitation solution and thus promote the grain growth of the solid ammonium chloride.
According to the process of the present invention, the slurry of solid ammonium chloride formed by the introduction of the liquid cooling medium into the ammonium chloride precipitation solution, is subjected to a solid concentrator, whereby the slurry is concentrated by the removal of a part ox liquid therefrom, and the concentrated slurry is returned to the precipitation solution. The concentrated slurry thus returned, serves to facilitate the crystal flow in the precipitation tank.
Further, very fine precipitates may be removed together with the liquid removed at the time of concentrating the slurry, and it is then possible to return a concentrated slurry having relatively large particles, to the precipitation solution, whereby the particles in the slurry serve as seed crystals and the precipitation of fine particles will thereby be prevented.
Now, the present invention will be described in detail with reference to the preferred embodiments.
In the accompanying drawing, Figure 1 is a flow sheet illustrating an embodiment of the process of the present invention.
I The cooling medium to be used in the present invention, should desirably be non-reactive with ammonium chloride since it is brought in direct contact with the ammonium chloride precipitation solution, and it should also be substantially non-reactive with other components in the precipitation solution.
As such a cooling medium, there may be mentioned a liquefiable cooling medium such as dichlorodifluoro-methane, trichlorotrifluoromethane, chlorodifluoro-methane, propane, n-butane and i-butane. However, those which require high pressure for their use or which have a possible danger of fire or explosion such as inflammability, are not desirable.
For this reason, among the above-mentioned cooling media, dichlorodifluoromethane and chlorodifluoromethane are particularly preferred as they have no such possible danger as mentioned above and they are capable of accomplishing the intended object without requiring a special high pressure.
The temperature to which the ammonium chloride precipitation solution is cooled by the contact with the cooling medium, may optionally be selected depending upon the amount of the precipitation of ammonium chloride and the desired particle size of ammonium chloride. For instance, in the case where dichlorodifluoromethane is used as the cooling medium, it is possible to precipitate ammonium chloride by cooling the precipitation solution to a temperature of from 0 to 25C when the internal pressure of the precipitation tank is about 3.1 kg/cm2G.
In the present invention, after the introduction of the liquid cooling medium, a part of the precipitation solution is subjected to a solid concentrator, whereby a part of liquid will be removed therefrom, and the remaining slurry containing ammonium chloride particles will be returned to the ammonium chloride precipitation tank so that the solid ammonium chloride concentration in the tank will be increased. The amount of the precipitation solution to be subjected to the solid concentrator, is within a range where the concentrated slurry after the removal of a necessary amount of liquid, ~2~2~ -is capable of being readily handled. It is preferably in such an amount whereby the flow of crystals in the precipitation tank can effectively be conducted.
Specifically, the amount is preferably from 2 to 10 times the amount of the precipitation solution supplied afresh.
If the amount is less than this range, the concentration of the concentrated slurry -tends to be too high, whereby the flyability will be poor and the flow of the precipitated crystals will be hindered. On the other hand, if the amount exceeds the above range, disintegration of the particles is likely to take place, or a larger installation will be required whereby a greater motive power will be required.
The concentrated slurry of ammonium chloride to be lo returned to the precipitation tank after the treatment by the solid concentrator, preferably has a solid concentra-lion of from 10 to 70~ by weight, more preferably from 20 to 70% by weight.
Accordingly, a part of liquid should be removed to bring the concentration within the above range. If the concentration is less than the above range, the crystal concentration in the precipitation tank tends to be too low. On the other hand, if the concentration exceeds the above range, the piping line is likely to be clogged, or disintegration of particles it likely to take place, such being undesirable ~32~
Within such a concentration range, it is particularly preferred to employ a range of from 30 to 60% by weight, whereby disintegration of the particles is minimum, the handling will be easy and the installation is not required to be excessively large. Further, it is preferred that at the time of removing a part of liquid by the solid concentrator, very fine particles contained in the slurry are also removed together with the liquid.
Such very fine particles are generally of a size having at most 150 em.
The 501 id concentrator may be provided at any location irrespective of whether the location is outside or inside the ammonium chloride precipitation tank.
However, it is preferred to provide it within the ammonium chloride precipitation tank so that the discharge outlet of the slurry to be returned, is open at the bottom of the precipitation tank and the liquid cooling medium is introduced from the bottom portion of the precipitation tank so that the slurry moves upward together with the rising of the cooling medium from the bottom upwardly, whereby the slurry contributes to the crystal growth of the ammonium chloride particles and the deposition of the crystals on the inner wall of the precipitation tank can be prevented.
As the solid concentrator to be used in the present invention, there may be mentioned various liquid cyclones or centrifugal concentrators.
33~
If gasified cooling medium is present in the precipitation solution to be concentrated, it is likely to impair the efficiency of the solid-liquid separation.
Therefore, it is desirable that the gas is preliminarily 6 removed by means of an apparatus such as a scrubber or other conventional means.
Now, the present invention will be described with reference to Examples. However, it should be understood that the present invention is by no means restricted by these specific Examples.
EXAMPLE 1:
Referring to Figure l, reference numeral l is a precipitation tank, and numeral 2 is a solid concentrator inserted into the tank from the top.
The concentrator has a discharge outlet 3 in the vicinity of the bottom within the precipitation tank.
Reference numeral 4 is a gas-liquid separation tank.
The ammonium chloride precipitation solution was introduced from line 5 into the tank 1 at a rate of 200 m3/hr. Further, liquid dichloro~ difluoromethane was introduced from line 6 directly into the tank 1 and vaporized within the tank to maintain the temperature in the tank at a level of 10C. The ammonium chloride concentration of the precipitation solution was adjusted to bring the ammonium chloride crystal concentration to about 5% by weight when cooled to 10C. The gasified dichlorodifluoromethane was withdrawn from line 7.
A slurry having an ammonium chloride solid concentration of about 50~ by weight was withdrawn at a rate of 1000 m3/hr from the precipitation tank 1, then led to the gas-liquid separation tank 4, and after the removal of the accompanying cooling gas, supplied by a pump 8 to a solid concentrator 2 composed of a liquid cyclone, whereby the slurry was concentrated to about 60%
by weight, and discharged from the outlet 3 to the bottom of the precipitation tank at a rate of about 830 m3/hr thereby to let the ammonium chloride crystals flow in the tank.
On the other hand, from line 9 of the solid concentrator 2, about 180 m3/hr of a liquid containing 0.05% by weight of ammonium chloride crystals having a particle size of about 50 em was withdrawn.
From a lower part 10 of the precipitation tank 1, a slurry containing about 50% by weight of crystals having an average particle size of 1200 em was withdrawn at a rate of 20 m3/hr. The crystal concentration in the precipitation tank was maintained at a level of about 50 by weight, and good quality crystals having a narrow particle size distribution were obtained under a stabilized condition for a long period of time with no substantial formation or deposition of scales on the inner wall of the precipitation tank.
EXAMPLES 2 to 6:
The precipitation of ammonium chloride was conducted in the same manner as in Example 1 except that the operation parameters were changed as shown in Table 1.
The results thereby obtained are also shown in Table 1.
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ammonium chloride, and after separating the precipitated ammonium chloride or without such separation, sodium chloride is then added to decrease the volubility of ammonium chloride and thereby further precipitate ammonium chloride, or a process wherein ammonia and sodium chloride are added to the above-mentioned sodium bicarbonate mother liquor, followed by cooling to precipitate ammonium chloride.
In each case, the cooling is conducted in such a manner that a part of the ammonium chloride precipitation solution is cooled by a cooler to a super saturated state by taking advantage of such a nature that the saturated ammonium chloride solution can be brought to such a super saturated state, and the super saturated solution is returned to the precipitation tank where ammonium chloride in a super saturated state will be precipitated The cooler to be used in such a cooling step, is usually of an indirect cooling type with a cooling jacket provided at the cooling portion to cool the solution from outside. The structure is rather complicated, and the temperature control is rather delicate. Further, the precipitation of crystals takes place partially within the cooler thus frequently leading to a clogging problem.
In order to avoid such a problem, it is common to employ a plurality of coolers so that the operation will be switched from one golfer to another with a relatively ~L22~
short period of operation each time and they are cleaned frequently to avoid clogging. Thus, the conventional cooler is not necessarily satisfactory from the viewpoints of both operation and installation.
Whereas, the present applicant has previously proposed a process wherein a liquid cooling medium such as lion is introduced directly into the ammonium chloride precipitation solution to cool the solution by the heat of vaporization of the liquid cooling medium and thereby precipitate ammonium chloride (Japanese Examined Patent Publication No. 4284~/1979). This process has advantages such that it does not require a complicated structure or a cumbersome operation as used to be required by the conventional processes, and a smooth operation can be conducted under a stabilized condition for a long period of time with a minimum possibility of clogging which adversely affects the operation of the apparatus.
However, according to this process, the solid ammonium chloride concentration in the ammonium chloride precipitation solution is usually as low as from 3 to lo by weight. Accordingly, it is required to employ a considerably intensive cooling in order to precipitate ammonium chloride by cooling such a solution. Further, since it is usual to employ a perfect mixing type precipitation means the precipitated ammonium chloride tends to have a wine particle size, and has a drawback such that a substantial portion of the precipitated _ 4 I
ammonium chloride is likely to deposit on the inner wall of the precipitation tank to form a scale.
To prevent such a drawback, there have been proposed various considerations such as controlling or adjusting the amount or the manner of introducing the cooling medium, which are, however, dependent largely on experience or may vary largely depending upon individual types of the precipitation tanks For these reasons, the process has not yet been developed to a fully satisfactory extent.
As a means to cope with the above problem, it is conceivable to increase the ammonium chloride concentration in the precipitation tank. However, it is technically almost impossible to concentrate the solution by heating for evaporation. It is also technically extremely difficult to take out only liquid from the solution since the solution in the precipitation tank is in a perfect mixing state in which numerous ammonium chloride particles partially precipitated are uniformly dispersed.
Under these circumstances, the present inventors have conducted various researches and studies with an aim to obtain a means for precipitating ammonium chloride with a relatively large uniform particle size with a minimum possibility of deposition on the inner wall of the precipitation tank without requiring special considerations as mentioned above. As a result, it has I
been found that this object can be accomplished by increasing the solid ammonium chloride concentration in the precipitation solution.
Thus, the present invention provides a process for precipitating ammonium chloride in ammonia-soda process wherein ammonium chloride and sodium bicarbonate are alternately precipitated by using sodium chloride, carbon dioxide gas and ammonia as raw materials, which comprises introducing a liquid cooling medium directly into ammonium chloride precipitation solution to cool the solution by the heat of vaporization of the medium and thereby precipitate ammonium chloride to form a slurry containing solid ammonium chloride thus precipitated, wherein a part of the slurry is subjected to a solid concentrator and concentrated by the removal of a Hart of liquid therefrom, and the resulting concentrated slurry is returned to the precipitation solution to increase the solid ammonium chloride concentration in the precipitation solution and thus promote the grain growth of the solid ammonium chloride.
According to the process of the present invention, the slurry of solid ammonium chloride formed by the introduction of the liquid cooling medium into the ammonium chloride precipitation solution, is subjected to a solid concentrator, whereby the slurry is concentrated by the removal of a part ox liquid therefrom, and the concentrated slurry is returned to the precipitation solution. The concentrated slurry thus returned, serves to facilitate the crystal flow in the precipitation tank.
Further, very fine precipitates may be removed together with the liquid removed at the time of concentrating the slurry, and it is then possible to return a concentrated slurry having relatively large particles, to the precipitation solution, whereby the particles in the slurry serve as seed crystals and the precipitation of fine particles will thereby be prevented.
Now, the present invention will be described in detail with reference to the preferred embodiments.
In the accompanying drawing, Figure 1 is a flow sheet illustrating an embodiment of the process of the present invention.
I The cooling medium to be used in the present invention, should desirably be non-reactive with ammonium chloride since it is brought in direct contact with the ammonium chloride precipitation solution, and it should also be substantially non-reactive with other components in the precipitation solution.
As such a cooling medium, there may be mentioned a liquefiable cooling medium such as dichlorodifluoro-methane, trichlorotrifluoromethane, chlorodifluoro-methane, propane, n-butane and i-butane. However, those which require high pressure for their use or which have a possible danger of fire or explosion such as inflammability, are not desirable.
For this reason, among the above-mentioned cooling media, dichlorodifluoromethane and chlorodifluoromethane are particularly preferred as they have no such possible danger as mentioned above and they are capable of accomplishing the intended object without requiring a special high pressure.
The temperature to which the ammonium chloride precipitation solution is cooled by the contact with the cooling medium, may optionally be selected depending upon the amount of the precipitation of ammonium chloride and the desired particle size of ammonium chloride. For instance, in the case where dichlorodifluoromethane is used as the cooling medium, it is possible to precipitate ammonium chloride by cooling the precipitation solution to a temperature of from 0 to 25C when the internal pressure of the precipitation tank is about 3.1 kg/cm2G.
In the present invention, after the introduction of the liquid cooling medium, a part of the precipitation solution is subjected to a solid concentrator, whereby a part of liquid will be removed therefrom, and the remaining slurry containing ammonium chloride particles will be returned to the ammonium chloride precipitation tank so that the solid ammonium chloride concentration in the tank will be increased. The amount of the precipitation solution to be subjected to the solid concentrator, is within a range where the concentrated slurry after the removal of a necessary amount of liquid, ~2~2~ -is capable of being readily handled. It is preferably in such an amount whereby the flow of crystals in the precipitation tank can effectively be conducted.
Specifically, the amount is preferably from 2 to 10 times the amount of the precipitation solution supplied afresh.
If the amount is less than this range, the concentration of the concentrated slurry -tends to be too high, whereby the flyability will be poor and the flow of the precipitated crystals will be hindered. On the other hand, if the amount exceeds the above range, disintegration of the particles is likely to take place, or a larger installation will be required whereby a greater motive power will be required.
The concentrated slurry of ammonium chloride to be lo returned to the precipitation tank after the treatment by the solid concentrator, preferably has a solid concentra-lion of from 10 to 70~ by weight, more preferably from 20 to 70% by weight.
Accordingly, a part of liquid should be removed to bring the concentration within the above range. If the concentration is less than the above range, the crystal concentration in the precipitation tank tends to be too low. On the other hand, if the concentration exceeds the above range, the piping line is likely to be clogged, or disintegration of particles it likely to take place, such being undesirable ~32~
Within such a concentration range, it is particularly preferred to employ a range of from 30 to 60% by weight, whereby disintegration of the particles is minimum, the handling will be easy and the installation is not required to be excessively large. Further, it is preferred that at the time of removing a part of liquid by the solid concentrator, very fine particles contained in the slurry are also removed together with the liquid.
Such very fine particles are generally of a size having at most 150 em.
The 501 id concentrator may be provided at any location irrespective of whether the location is outside or inside the ammonium chloride precipitation tank.
However, it is preferred to provide it within the ammonium chloride precipitation tank so that the discharge outlet of the slurry to be returned, is open at the bottom of the precipitation tank and the liquid cooling medium is introduced from the bottom portion of the precipitation tank so that the slurry moves upward together with the rising of the cooling medium from the bottom upwardly, whereby the slurry contributes to the crystal growth of the ammonium chloride particles and the deposition of the crystals on the inner wall of the precipitation tank can be prevented.
As the solid concentrator to be used in the present invention, there may be mentioned various liquid cyclones or centrifugal concentrators.
33~
If gasified cooling medium is present in the precipitation solution to be concentrated, it is likely to impair the efficiency of the solid-liquid separation.
Therefore, it is desirable that the gas is preliminarily 6 removed by means of an apparatus such as a scrubber or other conventional means.
Now, the present invention will be described with reference to Examples. However, it should be understood that the present invention is by no means restricted by these specific Examples.
EXAMPLE 1:
Referring to Figure l, reference numeral l is a precipitation tank, and numeral 2 is a solid concentrator inserted into the tank from the top.
The concentrator has a discharge outlet 3 in the vicinity of the bottom within the precipitation tank.
Reference numeral 4 is a gas-liquid separation tank.
The ammonium chloride precipitation solution was introduced from line 5 into the tank 1 at a rate of 200 m3/hr. Further, liquid dichloro~ difluoromethane was introduced from line 6 directly into the tank 1 and vaporized within the tank to maintain the temperature in the tank at a level of 10C. The ammonium chloride concentration of the precipitation solution was adjusted to bring the ammonium chloride crystal concentration to about 5% by weight when cooled to 10C. The gasified dichlorodifluoromethane was withdrawn from line 7.
A slurry having an ammonium chloride solid concentration of about 50~ by weight was withdrawn at a rate of 1000 m3/hr from the precipitation tank 1, then led to the gas-liquid separation tank 4, and after the removal of the accompanying cooling gas, supplied by a pump 8 to a solid concentrator 2 composed of a liquid cyclone, whereby the slurry was concentrated to about 60%
by weight, and discharged from the outlet 3 to the bottom of the precipitation tank at a rate of about 830 m3/hr thereby to let the ammonium chloride crystals flow in the tank.
On the other hand, from line 9 of the solid concentrator 2, about 180 m3/hr of a liquid containing 0.05% by weight of ammonium chloride crystals having a particle size of about 50 em was withdrawn.
From a lower part 10 of the precipitation tank 1, a slurry containing about 50% by weight of crystals having an average particle size of 1200 em was withdrawn at a rate of 20 m3/hr. The crystal concentration in the precipitation tank was maintained at a level of about 50 by weight, and good quality crystals having a narrow particle size distribution were obtained under a stabilized condition for a long period of time with no substantial formation or deposition of scales on the inner wall of the precipitation tank.
EXAMPLES 2 to 6:
The precipitation of ammonium chloride was conducted in the same manner as in Example 1 except that the operation parameters were changed as shown in Table 1.
The results thereby obtained are also shown in Table 1.
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Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for precipitating ammonium chloride in ammonia-soda process wherein ammonium chloride and sodium bicarbonate are alternately precipitated by using sodium chloride, carbon dioxide gas and ammonia as raw materials, which comprises introducing a liquid cooling medium directly into an ammonium chloride precipitation solution in a precipitation tank to cool the solution by the heat of vaporization of the medium and thereby precipitate ammonium chloride to form a slurry containing solid ammonium chloride thus precipitated, wherein a part of the slurry is subjected to a solid concentrator and concentrated by the removal of a part of liquid therefrom, and the resulting concentrated slurry is returned to the precipitation solution to increase the solid ammonium chloride concentration in the precipitation solution and thus promote the grain growth of the solid ammonium chloride.
2. The process according to Claim 1, wherein the solid concentrator is a cyclone.
3. The process according to Claim 1, wherein the concentrated slurry to be returned to the precipitation solution has a solid concentration of from 20 to 70% by weight.
4. The process according to Claim 1, wherein the concentrated slurry is returned to the vicinity of the bottom of the precipitation tank.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7221183A JPS59199528A (en) | 1983-04-26 | 1983-04-26 | Method for depositing ammonium chloride |
| JP72211/1983 | 1983-04-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1220321A true CA1220321A (en) | 1987-04-14 |
Family
ID=13482675
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000452782A Expired CA1220321A (en) | 1983-04-26 | 1984-04-25 | Process for precipitating ammonium chloride |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS59199528A (en) |
| CA (1) | CA1220321A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109437238A (en) * | 2018-12-29 | 2019-03-08 | 广州市迈源科技有限公司 | A kind of ammonium chloride solution processing system and ammonium chloride solution processing method |
| CN110980765A (en) * | 2019-12-24 | 2020-04-10 | 武汉德泽环保科技有限公司 | Process for preparing ammonium chloride |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1056779C (en) * | 1996-08-08 | 2000-09-27 | 刘家栋 | Continuously self-cooling crystalizing technology |
| JP5008215B2 (en) * | 2000-09-29 | 2012-08-22 | 三菱瓦斯化学株式会社 | Crystallization method and apparatus |
| JP2011072998A (en) * | 2010-11-24 | 2011-04-14 | Mitsubishi Gas Chemical Co Inc | Crystallization method and apparatus |
| CN110026069A (en) * | 2019-04-11 | 2019-07-19 | 天津大学 | A kind of concentrated hydrochloric acid reactive distillation absorbs the technique and system of melamine tail gas |
-
1983
- 1983-04-26 JP JP7221183A patent/JPS59199528A/en active Granted
-
1984
- 1984-04-25 CA CA000452782A patent/CA1220321A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109437238A (en) * | 2018-12-29 | 2019-03-08 | 广州市迈源科技有限公司 | A kind of ammonium chloride solution processing system and ammonium chloride solution processing method |
| CN110980765A (en) * | 2019-12-24 | 2020-04-10 | 武汉德泽环保科技有限公司 | Process for preparing ammonium chloride |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0366250B2 (en) | 1991-10-16 |
| JPS59199528A (en) | 1984-11-12 |
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