KR20220093105A - How to dehumidify hydrogen chloride - Google Patents

Abstract

In a dehumidification method according to an embodiment of the present invention, a first dehumidification step of contacting hydrogen chloride gas 21 with concentrated sulfuric acid 13A, and hydrogen chloride gas 21A that has undergone the first dehumidification step, concentrated sulfuric acid 13B ) and a second dehumidification process. The concentration of concentrated sulfuric acid used in the second dehumidification step is higher than the concentration of concentrated sulfuric acid used in the first dehumidification step.

Description

How to dehumidify hydrogen chloride

The present invention relates to a method for dehumidifying hydrogen chloride gas.

As a method of removing water from hydrogen chloride gas, conventionally, an adsorption method, a cooling condensation method, a concentrated sulfuric acid method, and the like have been used. Among these methods, with respect to the concentrated sulfuric acid method, there is a trade-off relationship between the concentration of concentrated sulfuric acid used for dehumidification and the water concentration in hydrogen chloride after dehumidification. That is, in the case of processing hydrogen chloride gas having a high water concentration or in the case of a large processing amount, when the concentration of concentrated sulfuric acid decreases, the concentration of water contained in the obtained hydrogen chloride gas increases. Therefore, for example, Patent Document 1 describes a method of condensing moisture in hydrogen chloride gas by a cooling condensation method, and then dehumidifying the hydrogen chloride gas with reduced moisture concentration using a concentrated sulfuric acid drying tower. .

China Utility Model Registration Gazette 「No. 202265420 (Registered on June 6, 2012)」

When dehumidifying by the concentrated sulfuric acid method, in order to increase the certainty of dehumidification of the obtained hydrogen chloride gas, concentrated sulfuric acid of high concentration is used in large quantities in many cases. Therefore, improvement of the utilization efficiency of concentrated sulfuric acid is a very important subject from a viewpoint of cost and processing efficiency. However, Patent Document 1 does not disclose a configuration for increasing the utilization efficiency of concentrated sulfuric acid.

One aspect of this invention aims at improving the utilization efficiency of the concentrated sulfuric acid in the whole of a dehumidification process.

In order to solve the above problems, a dehumidification method according to an aspect of the present invention is a dehumidification method of hydrogen chloride gas in which hydrogen chloride gas is dehumidified by a multi-step process, comprising: a first dehumidification process of contacting hydrogen chloride gas with concentrated sulfuric acid; a second dehumidification step of contacting the hydrogen chloride gas that has passed through the first dehumidification step with concentrated sulfuric acid, wherein the concentration of concentrated sulfuric acid used in the second dehumidification step is the concentration of concentrated sulfuric acid used in the first dehumidification step It is characterized by a higher

ADVANTAGE OF THE INVENTION According to one aspect of this invention, the utilization efficiency of the concentrated sulfuric acid in the whole dehumidification process can be improved.

1 is a schematic diagram of a dehumidifying device according to a first embodiment;
Fig. 2 is a schematic diagram of a dehumidifying device according to a second embodiment.
Fig. 3 is a graph showing the relationship between the sulfuric acid concentration and the outlet water concentration of hydrogen chloride gas in the most downstream drying tower.
Fig. 4 is a schematic diagram of an apparatus used for deriving the relational expressions of the water removal rate of hydrogen chloride gas, the concentration of concentrated sulfuric acid, and the gas supply amount;

[Embodiment 1]

(Hydrogen chloride gas dehumidification device)

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of this invention is described in detail. First, an exemplary dehumidification apparatus 100 used in a method for dehumidifying hydrogen chloride gas according to an embodiment of the present invention will be described with reference to FIG. 1 .

1 is a schematic diagram showing the structure of a dehumidifying device 100 . The dehumidifying device 100 is a device that removes moisture in the hydrogen chloride gas through a multi-step process, that is, dehumidifies the hydrogen chloride gas. More specifically, the dehumidification apparatus 100 is an apparatus for dehumidifying hydrogen chloride gas using the dehydration action of concentrated sulfuric acid by bringing the hydrogen chloride gas into contact with concentrated sulfuric acid in a plurality of drying towers.

The dehumidification apparatus 100 includes a first drying tower 1A and a second drying tower 1B. The 1st drying tower 1A is a tower for performing the 1st dehumidification process of making the hydrogen chloride gas 21 and the 1st concentrated sulfuric acid 13A which is the 1st concentrated sulfuric acid for a 1st dehumidification process contact before dehumidification. The second drying tower 1B is a tower for performing a second dehumidification step in which the hydrogen chloride gas 21A that has undergone the first dehumidification step is brought into contact with the second concentrated sulfuric acid 13B, which is concentrated sulfuric acid for the second dehumidification step. . The hydrogen chloride gas 21A that has passed through the first dehumidification process is supplied from the first drying tower 1A to the second drying tower 1B through a pipe 41 . Unlike the embodiment described later, in the dehumidification apparatus 100, the concentrated sulfuric acid used in the second drying tower 1B is not reused in the first drying tower 1A.

The first drying tower 1A has a concentrated sulfuric acid supply tank 31A for supplying the concentrated sulfuric acid 11, a pump 2A, and a concentrated sulfuric acid 14A used in the first dehumidification process for recovering concentrated sulfuric acid 14A. A sulfuric acid recovery tank 32A is provided. The recovered concentrated sulfuric acid is stored as recovered concentrated sulfuric acid 12 in a concentrated sulfuric acid recovery tank 32A. In order to reuse concentrated sulfuric acid in the first drying tower 1A, the pump 2A pumps at least a portion of the concentrated sulfuric acid in the first drying tower 1A to an outlet (not shown) at the bottom of the first drying tower 1A. ) to the concentrated sulfuric acid supply port 6A formed in the upper part of the first drying tower 1A.

The second drying tower 1B also includes a concentrated sulfuric acid supply tank 31B, a pump 2B, and a concentrated sulfuric acid recovery tank 32B for recovering the concentrated sulfuric acid 14B used in the second dehumidification step. . The recovered concentrated sulfuric acid is stored as recovered concentrated sulfuric acid 12 in a concentrated sulfuric acid recovery tank 32B. The pump 2B feeds the concentrated sulfuric acid into the second drying tower 1B through the concentrated sulfuric acid supply port 6B of the second drying tower 1B.

In the middle section of the first drying tower 1A, a packed layer 3A filled with a resin material is provided. By providing the filling layer 3A, the contact area between the hydrogen chloride gas 21 and the first concentrated sulfuric acid 13A before dehumidification increases, and the dehumidification of the hydrogen chloride gas 21 before dehumidification is efficiently performed.

Moreover, the storage part 4A for storing the concentrated sulfuric acid 14A used in the 1st dehumidification process is provided at the bottom of the 1st drying tower 1A. An overflow pipe for overflowing the concentrated sulfuric acid 14A stored in the storage 4A at a predetermined height from the bottom of the first drying tower 1A (vertically above the storage 4A) 8A) is provided. The overflow pipe 8A is connected to the concentrated sulfuric acid recovery tank 32A so as to be able to pass through it.

In order to supply the hydrogen chloride gas 21 before dehumidification, the hydrogen chloride gas supply port 5A is provided so that it may conduct|electrically_connect to the lower space of the filling layer 3A. The concentrated sulfuric acid supply port 6A is provided so that it may conduct|electrically_connect to the upper space of 3 A of packing layers, in order to supply the 1st concentrated sulfuric acid 13A. The concentrated sulfuric acid supply port 6A is connected to the scattering part 7A so that a liquid can pass therethrough. The dispersing part 7A is a member for dispersing the concentrated sulfuric acid solution to the packing material of the packing layer 3A.

The first drying tower 1A further includes a monitoring device 61A for monitoring the concentration of the concentrated sulfuric acid 14A used in the first dehumidification step, and a control device 60A. When receiving information on the concentration of the concentrated sulfuric acid 14A from the monitoring device 61A, the control device 60A controls the supply amount of the concentrated sulfuric acid 11 supplied from the concentrated sulfuric acid supply tank 31A according to the concentration. do.

Similarly for the second drying tower 1B, the packed bed 3B, the storage part 4B, the hydrogen chloride gas supply port 5B, the concentrated sulfuric acid supply port 6B, the scattering part 7B, and the overflow pipe 8B ) is provided. The roles of the monitoring device 61B and the control device 60B are also the same.

When the control device 60A and the control device 60B control the supply amount of the concentrated sulfuric acid 11, the concentration of the second concentrated sulfuric acid 13B used in the second dehumidification step is determined in the first dehumidification step. The supply amount of the concentrated sulfuric acid 11 is controlled so as to be higher than the concentration of the first concentrated sulfuric acid 13A. The control of the supply amount is realized, for example, when the control device 60A controls the control valve 62A and the control device 60B controls the control valve 62B. The control apparatus 60A and the control apparatus 60B are connected so that communication is possible, and control of such a supply_amount|feed_rate of the concentrated sulfuric acid 11 is attained.

In Fig. 1, ST means steam. LT and AT stand for level transmitter and analyzer transmitter, respectively.

(flow of hydrogen chloride gas)

The hydrogen chloride gas 21 before dehumidification is supplied into the first drying tower 1A from the hydrogen chloride gas supply port 5A. Thereafter, in the packed layer 3A, the hydrogen chloride gas 21 before dehumidification is in contact with the first concentrated sulfuric acid 13A to be dehumidified (first dehumidification step). The hydrogen chloride gas 21A that has passed through the first dehumidification step is discharged from the top of the first drying tower 1A, and is discharged from the hydrogen chloride gas supply port 5B of the second drying tower 1B to the second drying tower. (1B) is supplied inside. Thereafter, in the packed layer 3B, the hydrogen chloride gas 21A is in contact with the second concentrated sulfuric acid 13B to dehumidify (second dehumidification step). The hydrogen chloride gas 21B that has passed through the second dehumidification step is discharged from the top of the second drying tower 1B.

(flow of concentrated sulfuric acid)

The concentrated sulfuric acid 11 stored in the concentrated sulfuric acid supply tank 31A is usually about 98 wt% concentrated sulfuric acid. The concentrated sulfuric acid supply tank 31A is connected to the first drying tower 1A via a control valve 62A. Concentrated sulfuric acid 11 is supplied from the concentrated sulfuric acid supply tank 31A through the concentrated sulfuric acid supply port 6A of the first drying tower 1A, as part of the first concentrated sulfuric acid 13A, in the first drying tower ( 1A) is supplied. The supply amount of the concentrated sulfuric acid 11 supplied from the concentrated sulfuric acid supply tank 31A is controlled by the control device 60A as described above.

13A of 1st concentrated sulfuric acid is spread|dispersed toward the packing layer 3A through the dispersion|spreading part 7A. Concentrated sulfuric acid 14A (used in the first dehumidification step) in contact with hydrogen chloride gas 21 before dehumidification in packed bed 3A is stored in storage 4A for storing concentrated sulfuric acid 14A. .

At least a part of the concentrated sulfuric acid 14A stored in the storage 4A is transferred from the bottom of the first drying tower 1A to the concentrated sulfuric acid supply port 6A of the first drying tower 1A by the pump 2A. ) to be transferred. Concentrated sulfuric acid 14A is supplied to the first drying tower 1A as at least a portion of the first concentrated sulfuric acid 13A (as the case may be, integrated with the concentrated sulfuric acid 11 ).

The flow of concentrated sulfuric acid is the same also about the 2nd drying tower 1B. The 2nd concentrated sulfuric acid 13B supplied from the concentrated sulfuric acid supply port 6B is spread|dispersed toward the packing layer 3B through the dispersion|spreading part 7B. In the packed layer 3B, the concentrated sulfuric acid 14B contacted with the hydrogen chloride gas 21A that has undergone the first dehumidification step (used in the second dehumidification step) is stored in the storage 4B.

At least a part of the concentrated sulfuric acid 14B stored in the storage 4B is liquid fed from the bottom of the second drying tower 1B to the concentrated sulfuric acid supply port 6B by the pump 2B. Concentrated sulfuric acid 14B is supplied to the second drying tower 1B as at least a portion of the second concentrated sulfuric acid 13B (as the case may be, integrated with the concentrated sulfuric acid 11 ). The supply amount of the concentrated sulfuric acid 11 supplied from the concentrated sulfuric acid supply tank 31B is controlled by the control device 60B as described above.

In Embodiment 1, the concentration of the second concentrated sulfuric acid 13B (concentrated sulfuric acid used in the second dehumidification step) is higher than that of the first concentrated sulfuric acid 13A (concentrated sulfuric acid used in the first dehumidification step). As the second concentrated sulfuric acid 13B, for example, 96 wt% or more of concentrated sulfuric acid is used. As the first concentrated sulfuric acid 13A, 80 wt% or more and less than 95 wt%, preferably 85 wt% or more and less than 90 wt% of concentrated sulfuric acid is used.

Since the concentration of the first concentrated sulfuric acid 13A is sufficiently lower than 98 wt%, the concentrated sulfuric acid 11 in the concentrated sulfuric acid supply tank 31A does not need to be 98 wt% concentrated sulfuric acid.

Further, as described above, there is a concentration difference between the concentrated sulfuric acid used in the first dehumidification step and the concentrated sulfuric acid used in the second dehumidification step. For this reason, as the 1st concentrated sulfuric acid 13A, it is also possible to use the concentrated sulfuric acid 14B used in the 2nd dehumidification process and collect|recovered.

In the above, although the case where there are two drying towers was described with reference to FIG. 1, the drying tower is not limited to two, and three or more may be sufficient.

In addition, in the above, embodiment which performed a 1st dehumidification process in the 1st drying tower 1A and performed a 2nd dehumidification process in the 2nd drying tower 1B was demonstrated. However, the embodiment in which a plurality of dehumidification steps including the first dehumidification step and the second dehumidification step is performed within one drying tower may be used.

(Effect of Embodiment 1)

As described above, the dehumidification method of the first embodiment is a dehumidification method of hydrogen chloride gas in which hydrogen chloride gas is dehumidified by a multi-step process, and is performed using the dehumidification apparatus 100 . Further, in the dehumidification method of Embodiment 1, a first dehumidification step of bringing hydrogen chloride gas (hydrogen chloride gas 21 before dehumidification) and concentrated sulfuric acid (first concentrated sulfuric acid 13A) into contact with each other, and hydrogen chloride that has undergone the first dehumidification step and a second dehumidification step of bringing the gas (hydrogen chloride gas 21A) into contact with concentrated sulfuric acid (second concentrated sulfuric acid 13B). The concentration of concentrated sulfuric acid (second concentrated sulfuric acid 13B) used in the second dehumidification step is higher than the concentration of concentrated sulfuric acid (first concentrated sulfuric acid 13A) used in the first dehumidification step.

According to this dehumidification method, after the hydrogen chloride gas is dehumidified in the first dehumidification step, in the second dehumidification step, concentrated sulfuric acid having a higher concentration than the concentrated sulfuric acid used in the first dehumidification step is used to dehumidify. In the first dehumidification step, a relatively high dehumidification effect can be obtained even when a low concentration of concentrated sulfuric acid is used. Therefore, by effectively using the concentrated sulfuric acid at a low concentration in the first upstream dehumidification step, it is possible to increase the utilization efficiency of the concentrated sulfuric acid in the entire dehumidification step of a plurality of steps.

[Embodiment 2]

(Hydrogen chloride gas dehumidification device)

Another embodiment of the present invention will be described below. In addition, for convenience of description, about the member which has the same function as the member demonstrated in the said embodiment, the same code|symbol is attached|subjected, and the description is not repeated.

2 is a schematic diagram showing the structure of the dehumidifying device 101 . The dehumidification device 101 is an example of a device used in the method for dehumidifying hydrogen chloride gas according to the second embodiment of the present invention. The dehumidification apparatus 101 contains the 1st drying tower 1A, the 2nd drying tower 1B, the 3rd drying tower 1C, and the mist separator 50. The 3rd drying tower 1C is a tower for performing the 3rd dehumidification process which makes the hydrogen chloride gas 21B which passed through the 2nd dehumidification process contact 3rd concentrated sulfuric acid 13C which is concentrated sulfuric acid for 3rd dehumidification process. The 3rd drying tower 1C is equipped with the pump 2C for liquid-feeding the concentrated sulfuric acid to the inside of the 3rd drying tower 1C through the concentrated sulfuric acid supply port 6C of the 3rd drying tower 1C. The concentrated sulfuric acid supply tank 31 is connected to the third drying tower 1C so as to be able to pass through it via a control valve 62 . The concentrated sulfuric acid recovery tank 32 is connected to the overflow pipe 8A of the first drying tower 1A so as to be able to flow therethrough.

The mist separator 50 is equipped with the glass filter 51 for capture|acquiring sulfuric acid mist, It is an apparatus for removing sulfuric acid mist from the hydrogen chloride gas 22 which passed through the multi-step process.

In the first drying tower 1A, a packed bed 3A, a storage unit 4A, a hydrogen chloride gas supply port 5A, a concentrated sulfuric acid supply port 6A, a scattering unit 7A, and an overflow pipe 8A is the same as in the first embodiment.

Similarly for the second drying tower 1B, the packed bed 3B, the storage part 4B, the hydrogen chloride gas supply port 5B, the concentrated sulfuric acid supply port 6B, the scattering part 7B, and the overflow pipe ( 8B) is provided. Similarly for the third drying tower (1C), the packed bed (3C), the storage part (4C), the hydrogen chloride gas supply port (5C), the concentrated sulfuric acid supply port (6C), the scattering part (7C), and the overflow pipe ( 8C) is provided.

(flow of hydrogen chloride gas)

The hydrogen chloride gas 21 before dehumidification is supplied into the first drying tower 1A from the hydrogen chloride gas supply port 5A. Thereafter, in the packed layer 3A, the hydrogen chloride gas 21 before dehumidification is in contact with the first concentrated sulfuric acid 13A to be dehumidified (first dehumidification step). The hydrogen chloride gas 21A that has undergone the first dehumidification process is discharged from the top of the first drying tower 1A, and is discharged from the hydrogen chloride gas supply port 5B of the second drying tower 1B through the pipe 41, 2 is supplied to the inside of the drying tower (1B). Thereafter, in the packed layer 3B, the hydrogen chloride gas 21A comes into contact with the second concentrated sulfuric acid 13B to dehumidify (second dehumidification step). The hydrogen chloride gas 21B that has undergone the second dehumidification process is discharged from the top of the second drying tower 1B, and is discharged from the hydrogen chloride gas supply port 5C of the third drying tower 1C through the pipe 42, 3 It is supplied to the inside of the drying tower (1C). Thereafter, in the packed layer 3C, the hydrogen chloride gas 21B comes into contact with the third concentrated sulfuric acid 13C, which is the concentrated sulfuric acid for the third dehumidification step, and dehumidifies (third dehumidification step). The hydrogen chloride gas 21C that has passed through the third dehumidification step is discharged from the top of the third drying tower 1C, and is supplied to the mist separator 50 through the pipe 43 .

When the hydrogen chloride gas 22 supplied to the mist separator 50 through all the dehumidification steps passes through the glass filter 51 in the mist separator 50, sulfuric acid mist contained in the hydrogen chloride gas 22 is captured. The hydrogen chloride gas that has passed through the glass filter 51 is discharged from the mist separator 50 as the hydrogen chloride gas 23 after treatment, and is supplied to a storage tank (not shown) or the like.

Concentrated sulfuric acid 11M recovered by the mist separator 50 can be reused as concentrated sulfuric acid or the like used for dehumidification in the drying tower.

(flow of concentrated sulfuric acid)

The concentrated sulfuric acid 11 stored in the concentrated sulfuric acid supply tank 31 is usually about 98 wt% concentrated sulfuric acid. Concentrated sulfuric acid 11 is supplied from the concentrated sulfuric acid supply tank 31 through the concentrated sulfuric acid supply port 6C of the third drying tower 1C, as at least a part of the third concentrated sulfuric acid 13C, in the third drying tower (1C) is supplied. The 3rd concentrated sulfuric acid 13C is spread|dispersed toward the packing layer 3C through the dispersion|spreading part 7C. In the packed bed 3C, the concentrated sulfuric acid 14C (used in the third dehumidification step) in contact with the hydrogen chloride gas 21C is stored in the storage 4C. The supply amount of the concentrated sulfuric acid 11 supplied from the concentrated sulfuric acid supply tank 31A is controlled by the control device 60 . The detail of the control method of the density|concentration by the control apparatus 60 is mentioned later.

At least a part of the concentrated sulfuric acid 14C used in the third dehumidification step stored in the storage 4C is removed from the bottom of the third drying tower 1C by the pump 2C to the third drying tower 1C. The liquid is fed to the concentrated sulfuric acid supply port (6C) of Concentrated sulfuric acid 14C is supplied to the third drying tower 1C as at least part of the third concentrated sulfuric acid 13C (as the case may be, integrated with the concentrated sulfuric acid 11).

When the concentrated sulfuric acid 14C stored in the storage 4C exceeds a predetermined amount, the concentrated sulfuric acid 14C in excess of the predetermined amount is transferred through the overflow pipe 8C to the third drying tower ( It is discharged from 1C), and is supplied into the storage part 4B of the 2nd drying tower 1B through the piping 44. That is, at least a part of the concentrated sulfuric acid 14C used in the third dehumidification step is reused as the second concentrated sulfuric acid 13B in the second dehumidification step.

At least a part of the concentrated sulfuric acid 15B stored in the storage 4B of the second drying tower is transferred from the bottom of the second drying tower 1B to the concentrated sulfuric acid of the second drying tower 1B by the pump 2B. The liquid is fed to the sulfuric acid supply port 6B. The concentrated sulfuric acid 15B is supplied to the second drying tower 1B as the second concentrated sulfuric acid 13B. The 2nd concentrated sulfuric acid 13B is spread|dispersed toward the packing layer 3B through the dispersion|spreading part 7B. In the packed layer 3B, the concentrated sulfuric acid 14B contacted with the hydrogen chloride gas 21A (used in the second dehumidification step) is stored in the storage 4B.

When the concentrated sulfuric acid 15B stored in the storage 4B exceeds a predetermined amount, the concentrated sulfuric acid 15B in excess of the predetermined amount is passed through the overflow pipe 8B to the second drying tower ( It is discharged from 1B), and is supplied into the storage part 4A of the 1st drying tower 1A through the piping 45. That is, at least a part of the concentrated sulfuric acid 14B used in the second dehumidification step is reused as the first concentrated sulfuric acid 13A in the first dehumidification step.

At least a part of the concentrated sulfuric acid 15A stored in the storage 4A of the first drying tower 1A is transferred from the bottom of the first drying tower 1A to the first drying tower 1A by the pump 2A. ) to the concentrated sulfuric acid supply port 6A. The concentrated sulfuric acid 15A is supplied to the first drying tower 1A as the first concentrated sulfuric acid 13A. 13A of 1st concentrated sulfuric acid is spread|dispersed toward the packing layer 3A through the dispersion|spreading part 7A. In the packed layer 3A, the concentrated sulfuric acid 14A (used in the first dehumidification step) contacted with the hydrogen chloride gas 21 before dehumidification is stored in the storage 4A.

When the concentrated sulfuric acid (concentrated sulfuric acid 15A) stored in the storage 4A exceeds a predetermined amount, the concentrated sulfuric acid 15A in excess of the predetermined amount is discharged through the overflow pipe 8A. 1 It is discharged|emitted from the drying tower 1A, and it collect|recovers in the concentrated sulfuric acid recovery tank 32. The recovered concentrated sulfuric acid is stored in a concentrated sulfuric acid recovery tank 32 as recovered concentrated sulfuric acid 12 .

As described above, by reusing the concentrated sulfuric acid used in the downstream dehumidification step in the upstream dehumidification step, the efficiency of using concentrated sulfuric acid in the entire multi-stage dehumidification step can be increased, and the amount of concentrated sulfuric acid waste can be further reduced. have.

In Embodiment 2, the concentration of concentrated sulfuric acid used in the dehumidification step (third dehumidification step) carried out at the most downstream is the highest concentration compared with the concentration of concentrated sulfuric acid used in other dehumidification steps. With this configuration, in the downstream dehumidification step, the reliability of the dehumidification of the hydrogen chloride gas can be improved.

In the method for dehumidifying hydrogen chloride gas by a multi-step process according to Embodiment 2, the multi-step process is performed after a first dehumidification step, a second dehumidification step performed after the first dehumidification step, and the second dehumidification step. consists of a third dehumidification process. After being used in the third dehumidification step, the concentration of concentrated sulfuric acid (concentrated sulfuric acid 14C) that is reused in the second dehumidification step is 96 wt% or more. Further, the concentration of concentrated sulfuric acid (concentration of concentrated sulfuric acid 15B) that is reused in the first dehumidification step after being used in the second dehumidification step is 85 wt% or more and less than 96 wt%. In addition, the concentration of concentrated sulfuric acid (concentration of concentrated sulfuric acid 15A) after being used in the first dehumidification step is 75 wt% or more and less than 85 wt%.

In Embodiment 2, although the case where there are three drying towers was demonstrated, the number of drying towers is not limited to three and may be two or more. When there are two drying towers, the multi-step process consists of the first dehumidification process and the second dehumidification process. The concentration of concentrated sulfuric acid (concentration of concentrated sulfuric acid 15B) that is reused in the first dehumidification step after being used in the second dehumidification step is 96 wt% or more. In addition, the concentration of concentrated sulfuric acid (concentration of concentrated sulfuric acid 15A) after being used in the first dehumidification step is 85 wt% or more and less than 90 wt%.

(Effect of Embodiment 2)

3 is a graph showing the relationship between the sulfuric acid concentration and the outlet water concentration of hydrogen chloride gas in the most downstream drying tower when hydrogen chloride gas having a water concentration of 200 ppm-mol is supplied at 5000 Nm 3 /H. Here, the sulfuric acid concentration in the most downstream drying column is the concentrated sulfuric acid concentration (wt%) in the storage part of the most downstream drying column. The outlet water concentration of the hydrogen chloride gas is the water concentration (ppm-mol) of the hydrogen chloride gas 22 that has undergone a multi-step process.

In Fig. 3, the line A shows the case where the drying tower is one tower (only the first dehumidification step). Line B shows the case of two-column operation (the multi-step process comprising the first dehumidification process and the second dehumidification process) according to the method of the second embodiment. Line C shows the case of three tower operation (the multi-step process comprising the first dehumidification process, the second dehumidification process, and the third dehumidification process) according to the method of the second embodiment.

The results of lines A to C shown in Fig. 3 are calculated values, respectively. The detail of the calculation method of the said calculated value is mentioned later.

In Fig. 3 , for example, when the outlet water concentration is 15 ppm-mol, the sulfuric acid concentration in the drying column is about 97 wt% in one column operation. On the other hand, it can be seen that in the case of two tower operation, about 94 wt%, and in the case of three tower operation, about 92.5 wt%. This means that concentrated sulfuric acid is effectively used for dehumidification by a plurality of drying towers (dehumidification by the method of Embodiment 2).

As described above, when the water concentration of the hydrogen chloride gas is reduced to a specific water concentration, concentrated sulfuric acid can be used more effectively in dehumidification by a plurality of towers (by a multi-step process), and the amount of concentrated sulfuric acid is reduced can be reduced This effect is more remarkable in the case of the three tower operation than in the case of the two tower operation.

(Relational expression of water removal rate of hydrogen chloride gas, concentration of concentrated sulfuric acid, and gas supply amount)

Here, the derivation of the relational expressions of the water removal rate of the hydrogen chloride gas, the concentration of concentrated sulfuric acid, and the gas supply amount will be described with reference to FIG. 4 . 4 is a schematic diagram of an apparatus used for deriving the relational expression. In general, when the flow rate of concentrated sulfuric acid circulating in the drying tower is made constant, it is empirically clear that the water removal rate of hydrogen chloride gas appears as a function of the concentration of concentrated sulfuric acid in the drying tower and the supply amount of hydrogen chloride gas.

Then, the inventors used the drying tower 1 shown in FIG. 4 and supplying hydrogen chloride gas at the predetermined supply amount F to the drying tower 1 in which concentrated sulfuric acid of predetermined sulfuric acid concentration C was circulated, the water removal rate in the case of K was measured. Here, the sulfuric acid concentration C is the concentration (wt%) of concentrated sulfuric acid circulating in the drying tower 1 . The hydrogen chloride gas supply amount F is the supply amount (Nm 3 /h) of the hydrogen chloride gas supplied to the drying tower 1 . The water removal rate K is represented by the following formula (1).

K = (α-β)/α ... (1)

In the formula (1), α and β mean the numerical values shown below.

α=(water concentration of hydrogen chloride gas supplied to drying tower 1 (C _HCl-in ))

β = (moisture concentration of hydrogen chloride gas discharged from drying tower 1 (C _HCl-out ))

Table 1 shows an example of the value of the water removal rate K when the hydrogen chloride gas supply amount F and the sulfuric acid concentration C are respectively set to predetermined values. In addition, the amount of circulating sulfuric acid per unit cross-sectional area of the drying tower 1 was 5 m 3 /m 2 /hr.

[Table 1]

From the results of Table 1 above, it was found that the relationship between the water removal rate K, the concentration of concentrated sulfuric acid C, and the hydrogen chloride gas supply amount F was expressed by the following formula (2).

K=0.024×ln(C)×ln(F) ...(2)

(Calculation method of hydrogen chloride gas water concentration and concentrated sulfuric acid concentration in each tower)

The hydrogen chloride gas water concentration and concentrated sulfuric acid concentration of each tower of Embodiment 2 can be calculated using Formula (2) derived as described above. The relationship between the water removal rate K, the concentrated sulfuric acid concentration C, and the hydrogen chloride gas supply amount F can be similarly applied to each tower.

In this case, the sulfuric acid concentration C is the concentration (wt%) of concentrated sulfuric acid in the storage sections 4A, 4B, and 4C of each tower. The hydrogen chloride gas supply amount F is the supply amount (Nm 3 /h) of the hydrogen chloride gas supplied to each tower. The water removal rate K of each drying tower is computable by using said Formula (1).

The above formulas (1) and (2) are stored in the storage device 64 communicatively connected to the control device 60, and the measured value (or target value) is used for the concentration of the dehumidification device 101 . The concentration control of sulfuric acid is performed by the control device 60 . The control method of the supply amount of concentrated sulfuric acid by the control device 60 is shown below.

(Control of the supply amount of concentrated sulfuric acid by the control device)

The control method of the supply amount of concentrated sulfuric acid by the control device 60 in the dehumidification device 101 includes a target value determination step and an operation control step.

<Target value determination process>

Control by the control device 60 maintains the first to third drying tower sulfuric acid concentrations in a predetermined range by adjusting the supply amount of concentrated sulfuric acid from the concentrated sulfuric acid supply tank 31, and the target moisture content of hydrogen chloride gas It aims to realize concentration. Therefore, in the target value determination step, the target value CA of the concentration _{C 3} of the concentrated sulfuric acid 14C used in the third dehumidification step, which is required for adjusting the supply amount of the concentrated sulfuric acid, is determined.

In the determination of the target value C _A by the following steps (A2) to (A9), the initial value is used at the start of operation. After starting the operation, the measured values are used. When the measured value is changed by the operation control process described later, the target value _CA is updated by repeating the following steps (A1) to (A8).

(A1) The control device 60 controls the moisture concentration C of the hydrogen chloride gas 21 before dehumidification supplied to the first drying tower 1A from the hydrogen chloride gas monitoring device 63 provided in the hydrogen chloride gas supply path 46 . Information indicating _HCl-in(1) ) and information indicating the hydrogen chloride gas supply amount F _HCl to the first drying tower 1A are received.

(A2) The control device 60 receives, from the input device 65, information indicating the target concentration C _{1 ′} of the waste concentrated sulfuric acid input by the user into the input device 65 as an initial value at the start of operation. receive After the operation is started, information indicating the concentration C ₁ of the concentrated sulfuric acid 15A stored in the storage 4A of the first drying tower 1A is received from the monitoring device 61A.

(A3) control device 60, (i) F _HCl , (ii) C _HCl-in(1) received in step A1, and (iii) C _1′ (or C ₁ ) received in step A2 and (iv) the water concentration (C _HCl-out(1) ) of the hydrogen chloride gas 21A discharged from the first drying tower 1A is calculated using the formulas (1) and (2). Here, C _HCl-out(1) is the same as the water concentration (C _HCl-in(2) ) of the hydrogen chloride gas 21A supplied to the second drying tower 1B.

Specifically, the control device 60 performs the following calculation.

C _HCl-out(1) =C _HCl-in(1) {1-0.024×ln(C _1' )×ln(F _HCl )}

(A4) The control device 60 is the input device 65 as an initial value of information indicating the concentration C ₃ of the concentrated sulfuric acid 14C stored in the storage 4C of the third drying tower 1C. ), information indicating the concentration (C _feed ) of the concentrated sulfuric acid 11 is received from the input device 65 . The concentration (C _feed ) is usually 98 wt%.

(A5) The control device 60 receives, as an initial value, information indicating the target water concentration C _{HCl-out(3) ′} input to the input device 65 from the input device 65 . After the operation is started, information indicating the water concentration (C _{HCl-out( 3 )} ) of the hydrogen chloride gas 21C that has undergone the third dehumidification step is received from the hydrogen chloride gas monitoring device 66 .

(A6) The control device 60, (i) F _HCl , (ii) C _feed received in the A4 process, and C _HCl-out(3)' (or C _{HCl-out(3) received in the A5 process)} ) and (iii) using the formulas (1) and (2), the water concentration (C _HCl-in(3) ) of the hydrogen chloride gas 21B supplied to the third drying tower 1C is calculated. Here, C _HCl-in(3) is the same as the water concentration (C _HCl-out(2) ) of the hydrogen chloride gas 21A discharged from the second drying tower 1B.

Specifically, the control device 60 performs the following calculation.

C _HCl-in(3) =C _HCl-out(3) /{1-0.024×ln(C _feed )×ln(F _HCl )}

(A7) The control device 60 includes (i) F _HCl , (ii) C _{HCl-in (2)} calculated in step A3, (iii) C _{HCl-out (2)} calculated in step A6, and , (iv) The concentration (C ₂ ) of the concentrated sulfuric acid 15B in the second drying tower 1B is calculated using the formulas (1) and (2).

Specifically, the control device 60 performs the following calculation.

ln(C ₂ )=(C _HCl-in(2) -C _HCl-out(2) )/(C _HCl-in(2) × 0.024×ln(F _HCl ))

That is, C ₂ =e^{(C _HCl-in(2) -C _HCl-out(2) )/(C _HCl-in(2) ×0.024×ln(F _HCl ))}

(A8) The control device 60 includes (i) F _HCl , (ii) C _HCl-out(3) received in step A5, (iii) C _{HCl-in (3)} calculated in step A5, and , (iii) The target value _CA of the concentration of the concentrated sulfuric acid 14C in the third drying tower 1C is calculated using the formulas (1) and (2).

Specifically, the control device 60 performs the following calculation.

C _A =e^{(C _HCl-in(3) -C _HCl-out(3) )/(C _HCl-in(3) ×0.024×ln(F _HCl ))}

(A9) The control device 60 sets C _A calculated in step A8 as the target value C _A .

<Operation control process>

Following the target value determination process, an operation control process is executed. In the operation control process, the following processes B1 to B4 are executed by the control device 60 .

(B1) The control device 60 receives, from the monitoring device 61C, information indicating the concentration C ₃ of the concentrated sulfuric acid 14C used in the third dehumidification step.

(B2) The control device 60 compares the information on C ₃ acquired in the step B1 with the target value C _A .

(B3) When C ₃ is lower than the target value C _A , the control device 60 increases the opening degree of the control valve 62 from the concentrated sulfuric acid supply tank 31 to the third drying tower ( Increase the supply amount of concentrated sulfuric acid 11 supplied to 1C).

(B4) When C ₃ is higher than the target value C _A , the control device 60 lowers the opening degree of the control valve 62 , and supplies the concentrated sulfuric acid from the concentrated sulfuric acid supply tank 31 to the third drying tower 1C Reduce the supply amount of concentrated sulfuric acid (11).

(B5) When C ₃ is equal to the target value C _A , the control device 60 maintains the opening degree of the control valve 62 , and supplies the third drying tower 1C from the concentrated sulfuric acid supply tank 31 . The supply of concentrated sulfuric acid (11) is maintained.

(Example of driving)

Table 2 below shows the conditions and results of the dehumidification treatment by the dehumidification apparatus 101 of the second embodiment controlled by the concentration control method as described above.

[Table 2]

From Table 2, the trial calculated value trial-calculated using the conditions shown in Table 2, and the actual value of the sulfuric acid concentration measured by actually controlling by the control device 60 almost coincided. From this, it became clear that the sulfuric acid concentration of each tower in the dehumidification apparatus of Embodiment 2 was suitably controlled by the said control method, and the target water concentration in an outlet was achieved. More specifically, the following points were demonstrated about the control of sulfuric acid concentration. (i) The concentration of sulfuric acid in the third drying tower (concentration of concentrated sulfuric acid used in the third dehumidification process and then reused in the second dehumidification process) is 96 wt% or more. (ii) the second drying tower sulfuric acid concentration (concentration of concentrated sulfuric acid used in the second dehumidification step and then reused in the first dehumidification step) is within the range of 85 wt% or more and less than 96 wt%. (iii) The concentration of sulfuric acid in the first drying tower (concentration of concentrated sulfuric acid after being used in the first dehumidification step) is in the range of 75 wt% or more and less than 85 wt%.

(Application in trichlorosilane synthesis)

The hydrogen chloride gas whose water content was reduced by the dehumidification method of Embodiment 1 or Embodiment 2 can be used for the synthesis|combination of trichlorosilane. That is, it is possible to provide a method for producing trichlorosilane by reacting metal silicon with hydrogen chloride gas having a reduced water content by the dehumidification method described in the first or second embodiment.

The synthesis of trichlorosilane containing hydrogen chloride gas and metallic silicon as raw materials is performed in a synthesis tower. Moisture contained in the hydrogen chloride gas of the raw material may cause erosion of the dispersion plate in the synthesis tower. For this reason, it is preferable that the density|concentration of the water|moisture content contained in the hydrogen chloride gas used for reaction is lower.

By using the hydrogen chloride gas whose water content was reduced by the dehumidification method of Embodiment 1 or Embodiment 2, erosion in a trichlorosilane synthesis tower can be reduced. Thereby, the useful life of a dispersion plate can be improved.

The present invention is not limited to each of the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments, respectively, are also of the present invention. included in the technical scope.

1A, 1B, 1C: 1st drying tower, 2nd drying tower, 3rd drying tower
2A, 2B, 2C: Pump
3A, 3B, 3C: Filled layer
4A, 4B, 4C: Reservoir
5A, 5B, 5C: Hydrogen chloride gas supply port
6A, 6B, 6C : Concentrated sulfuric acid inlet
7A, 7B, 7C: scattering part
8A, 8B, 8C : overflow pipe
11, 11M: concentrated sulfuric acid
14A, 14B, 14C: Concentrated sulfuric acid used in the first, second, and third dehumidification processes
13A, 13B, 13C: 1, 2, 3 concentrated sulfuric acid (concentrated sulfuric acid used in the 1, 2, 3 dehumidification process)
21: hydrogen chloride gas before dehumidification
21A, 21B, 21C: Hydrogen chloride gas that has undergone the first, second, and third dehumidification processes
31, 31A, 31B: Concentrated sulfuric acid supply tank
32, 32A, 32B : Concentrated sulfuric acid recovery tank
50: mist separator
51: glass filter
60, 60A, 60B: control unit
61A, 61B, 61C: monitoring device
62, 62A, 62B: control valve
63: hydrogen chloride gas monitoring device
64: memory
65: input device
100, 101: dehumidification device

Claims (7)

A method for dehumidifying hydrogen chloride gas by dehumidifying the hydrogen chloride gas by a multi-step process, the method comprising:
A first dehumidification step of contacting hydrogen chloride gas with concentrated sulfuric acid;
a second dehumidification process of contacting the hydrogen chloride gas that has undergone the first dehumidification process with concentrated sulfuric acid;
A dehumidification method, characterized in that the concentration of concentrated sulfuric acid used in the second dehumidification step is higher than the concentration of the concentrated sulfuric acid used in the first dehumidification step. The method of claim 1,
A dehumidification method, characterized in that at least a part of concentrated sulfuric acid used in the second dehumidification step is reused in the first dehumidification step. 3. The method of claim 1 or 2,
The dehumidification method, characterized in that the concentration of concentrated sulfuric acid used in the dehumidification process carried out at the most downstream of the multi-step process is the highest compared to the concentration of concentrated sulfuric acid used in other dehumidification processes. 4. The method of claim 2 or 3,
The multi-step process consists of the first dehumidification process, the second dehumidification process, and a third dehumidification process performed after the second dehumidification process,
At least a part of concentrated sulfuric acid used in the third dehumidification process is reused in the second dehumidification process;
After being used in the third dehumidification process, the concentration of concentrated sulfuric acid reused in the second dehumidification process is 96 wt% or more,
After being used in the second dehumidification process, the concentration of concentrated sulfuric acid reused in the first dehumidification process is 85 wt% or more and less than 96 wt%,
The concentration of concentrated sulfuric acid after being used in the first dehumidification process is a dehumidification method, characterized in that 75 wt% or more and less than 85 wt%. 4. The method of claim 2 or 3,
The multi-step process consists of the first dehumidification process and the second dehumidification process,
After being used in the second dehumidification process, the concentration of concentrated sulfuric acid reused in the first dehumidification process is 96 wt% or more,
The concentration of concentrated sulfuric acid after being used in the first dehumidification step is 85 wt% or more and less than 90 wt%. 6. The method according to any one of claims 1 to 5,
The dehumidification method further comprising the step of removing sulfuric acid mist from the hydrogen chloride gas that has undergone the multi-step process by using a mist separator provided with a glass filter. A method for producing trichlorosilane by reacting hydrogen chloride gas having a reduced water content by the dehumidification method according to any one of claims 1 to 6 with metallic silicon.

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