JPH0881215A - Production of granular ammonium sulfate - Google Patents

Abstract

PURPOSE: To make continuous liquid circulation between two steps of absorption and crystallization unnecessary by suppressing free sulfuric acid concentration in the mother liquor of ammonium sulfate in a method for producing ammonium sulfate from ammonium in gas of a coke oven. CONSTITUTION: Two spray type saturating towers 2 and 3 are provided in series in an adsorption step. A part of a coke oven gas reacted in the first saturating tower 2 is again reacted with a part of mother liquor of ammonium sulfate in the second saturating tower 3. When the concentration of free sulfuric acid in the mother liquor in a crystallization step becomes a prescribed concentration, production of granular ammonium sulfate in the crystallizing step is temporally stopped and whole crystals attached to the crystallizing apparatus are dissolved and the mother liquor of ammonium sulfate in the crystallization step is transferred to the first saturating tower 2 and exchanged for mother liquor of ammonium sulfate having low free sulfuric acid concentration and charged from the second saturating tower 3, and then, production of granular ammonium sulfate in the crystallization step is reopened. Consequently, continuous circulation of the mother liquor between two steps of the adsorption and crystallization is made unnecessary. Operational days can be extended to be 2-3 times longer than that o.f conventional method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing granular ammonium sulfate from ammonia in coke oven gas.

[0002]

2. Description of the Related Art A method for recovering ammonia contained in a coke oven gas and producing granular ammonium sulfate usually comprises two steps. The first step is an absorption step in which a coke oven gas is sprayed with a ammonium sulphate mother liquor containing sulfuric acid in a saturator to recover ammonia in the coke oven gas as ammonium sulfate. In the second step following this, the ammonium sulphate mother liquor that has absorbed the ammonia in the coke oven gas is heated and decompressed in an evaporator or a crystallizer to evaporate the water and concentrate the ammonium sulphate mother liquor to precipitate granular ammonium sulphate. It is a crystallization process.

FIG. 2 is a flow chart showing the production of ordinary granular ammonium sulfate. The first step, the absorption step, consists of a saturator 2 and a saturator circulation tank 4, while the second step, the crystallization step, consists of a heater 8, a decompression device 17, an evaporator 6 and a crystal can 7. ing.

In the absorption process, first, the coke oven gas is fed into the saturator 2 through the charging port 1. A mother liquor containing sulfuric acid is sprayed from the spray nozzle 21. Ammonia in the gas reacts with the mother liquor containing sulfuric acid to form liquid ammonium sulfate in the mother liquor. The gas that has completed the reaction is discharged through the gas outlet 31. The ammonium sulphate mother liquor is internally circulated in the absorption process so as to be returned from the lower outlet of the saturator to the saturator circulation tank 4 and returned to the saturator again to make a catalytic reaction with new gas. And then extracted to the crystallization process.

On the other hand, in the crystallization step, the ammonium sulphate liquor extracted through the pipe 24 is heated by the heater 8 and concentrated in the evaporator 6 which is decompressed by the decompressor 17 to form the crystal can 7. To precipitate crystalline ammonium sulfate.

The water vaporized in the crystallization process and discharged to the outside of the system and the sulfuric acid removed from the system as product ammonium sulfate are replenished to the saturator circulation tank 4 with working water 9 and sulfuric acid 10. Normally, the amount of industrial water added is 4 m ^{3 /} hour, and the amount of concentrated sulfuric acid added is 200 / hour.
It is L.

The ammonium sulfate mother liquor extracted from the absorption step to the crystallization step usually contains 2-3% (average 2.5%) of free sulfuric acid. This is the sulfuric acid remaining unreacted with the ammonia in the coke oven gas. This free sulfuric acid is concentrated similarly to ammonium sulfate in the crystallization process. When the concentration of free sulfuric acid in the mother liquor in the crystallization process reaches 6% or more, the quality of the product crystalline ammonium sulfate is deteriorated (increased amount of adhering sulfuric acid) and the corrosion of the crystallization device becomes remarkable.

Therefore, in order to suppress the concentration of free sulfuric acid in the mother liquor to 6% or less and to effectively utilize the unreacted sulfuric acid,
A method is used in which the partial ammonium sulfate mother liquor in the crystallization step and the partial ammonium sulfate mother liquor in the absorption step are constantly circulated via the pipe 28 and the pipe 24. The amount of ammonium sulfate mother liquor constantly circulated is usually 30 to 40 m ^{3 /} hour.

As a method of avoiding the concentration of free sulfuric acid in the ammonium sulphate mother liquor during the crystallization step without constantly circulating the ammonium sulphate mother liquor between the absorption step and the crystallization step, the free sulfuric acid is neutralized. The method of extracting to the crystallization process is taken.

[0010]

As described above, the second
In the conventional method described in the figure, in order to suppress the concentration of free sulfuric acid in the ammonium sulfate mother liquor, a method of constantly circulating a part of the ammonium sulfate mother liquor between the absorption step and the crystallization step is adopted. But,
This constant circulation has the following problems.

The first problem is the precipitation of ammonium sulfate crystals in the saturator. The return solution from the crystallization process is a saturated solution of ammonium sulfate. When this is sprayed with a saturator, ammonium sulfate crystals are deposited at the liquid outlet and the upper gas outlet 31 at the bottom of the saturator. The precipitated crystals hinder the movement of liquid and gas. Therefore, it is necessary to add the working water 9 to the circulation tank 4 to dilute the mother liquor, to humidify by blowing the steam 30 into the gas, and to wash the working water from the pipe 32 above the saturator.
The equipment and energy costs were high.

The second problem is the adhesion of ammonium sulfate crystals to the crystal can. This occurs due to the influence of dilution and cleaning performed as a measure against the first problem. That is, since the concentration of the mother liquor charged to the crystallization step changes due to dilution and washing, the crystal precipitation is not stable and the crystal grain size becomes finer and adheres to each part of the crystal can. The adhered crystals need to be washed off with water (total dissolution), and thus the operation duration of the crystal can is limited to about 5 days.

A method of neutralizing free sulfuric acid and extracting it to the crystallization step without constantly circulating a part of the ammonium sulphate mother liquor between the absorption step and the crystallization step is the coloring of the mother liquor and the addition of a base (pyridine or the like). It is not preferable because it occurs. In addition to the neutralization step, a large number of new facilities and steps for decolorizing and debasing are required.

The method of the present invention was made in view of the above circumstances, and allows the free sulfuric acid concentration of the ammonium sulfate mother liquor in the crystallization step without constantly circulating the ammonium sulfate mother liquor between the absorption step and the crystallization step. It is intended to provide a method of suppressing the concentration below the value.

[0015]

The present invention is directed to the production of granular ammonium sulfate, which comprises an absorption step of absorbing ammonia in a coke oven gas into an ammonium sulfate mother liquor containing sulfuric acid and a crystallization step of crystallizing ammonium sulfate from the ammonium sulfate mother liquor. In the method, the first step is the absorption step.
The spray saturator and the second spray saturator are installed in series, and a part of the ammonium sulfate mother liquor reacted by the first spray saturator is sent to the second spray saturator to make the first spray saturator When the free sulfuric acid concentration in the mother liquor of the ammonium sulphate in the crystallization process reaches a predetermined concentration, the granular ammonium sulphate in the crystallization process reacts again with the coke oven gas that has finished the reaction in the saturator. The production of was temporarily suspended to effect total dissolution, and the ammonium sulphate mother liquor of this crystallization step was transferred to the first saturator and replaced with the ammonium sulphate mother liquor with a low concentration of free sulfuric acid charged from the second saturator, then, The method for producing granular ammonium sulfate is characterized by restarting the production of granular ammonium sulfate in the crystallization step.

[0016]

In the method of the present invention, the saturator, which was conventionally one tower, is made into two towers, which are connected in series. In the first saturator,
The introduced coke oven gas reacts with the mother liquor containing sulfuric acid,
Ammonia in the coke oven gas is absorbed. The reacted ammonium sulfate mother liquor is returned to the saturator through the saturator circulation tank and reacts with new coke oven gas to repeat internal circulation.
The sulfuric acid concentration in the ammonium sulphate mother liquor decreases as much as it reacts with ammonia, but by supplying sulfuric acid in the saturator circulation tank, it is always maintained at the prescribed sulfuric acid concentration necessary to absorb the ammonia in the coke oven gas. .

In the second saturator, the coke oven gas that has passed through the first saturator is introduced, and the ammonia remaining in the gas reacts with the free sulfuric acid in the ammonium sulfate mother liquor. The ammonium sulfate mother liquor is internally circulated in the second saturator, and the concentration of free sulfuric acid in the ammonium sulphate mother liquor decreases as the internal circulation is repeated. Therefore, the free sulfuric acid concentration can be lowered by reducing the amount of ammonium sulfate mother liquor extracted in the next crystallization step and increasing the internal circulation amount. Further, the concentration of free sulfuric acid can be increased by increasing the amount of ammonium sulfate mother liquor extracted from the first saturator.

That is, according to the method of the present invention, the ammonia absorption step is divided into two steps to keep the concentration of free sulfuric acid in the mother liquor of the first saturator high, while releasing the free sulfuric acid in the mother liquor of the second saturator. The sulfuric acid concentration can be controlled low. Therefore, the concentration of free sulfuric acid in the mother liquor transferred to the crystallization step can be lowered while maintaining the absorption efficiency of ammonia.

In the method of the present invention, since the ammonia absorption step is divided into two steps, the amount of ammonia absorbed in one saturation unit may be smaller than that in the case where there is only one absorption step. The free sulfuric acid concentration in the mother liquor can be lower than in the prior art.

In the crystallization step, the ammonium sulphate mother liquor extracted from the second saturator is concentrated under reduced pressure to crystallize granular ammonium sulphate.
The supply amount of the ammonium sulphate mother liquor from the second saturator is adjusted so as to balance with the ammonium sulphate that crystallizes and the water that evaporates and is discharged to the outside of the system.

When the concentration of free sulfuric acid in the ammonium sulphate mother liquor in the crystallization process reaches a predetermined concentration due to the concentration of ammonium sulphate, the production of granular ammonium sulphate is temporarily stopped and the total dissolution is carried out, and the ammonium sulphate mother liquor in the crystallization process is Transfer to one saturator and replace with the ammonium sulfate mother liquor with low free sulfuric acid concentration charged from the second saturator. Here, the predetermined concentration is the upper limit of the permissible value of the free sulfuric acid concentration in the crystallization step, which is 6% (preferably 5%).

In the present invention, since the ammonium sulphate mother liquor is not constantly circulated between the crystallization step and the absorption step as in the prior art, total dissolution for washing away the adherence of fine ammonium sulfate crystals to the crystal can is unnecessary. However, total dissolution is necessary when the concentration of free sulfuric acid in the ammonium sulphate mother liquor in the crystallization step reaches the upper limit value of 5%. However, as compared with the conventional technique, the number of days in which the crystal can can continue to be operated until it is completely melted can be extended.

[0023]

【Example】

Example 1 FIG. 1 shows a manufacturing flow chart of this example. 1 is a coke oven gas charging port, 2 is a first spray saturator, 3
Is the second spray saturator, 4 is the first saturator circulation tank,
5 is a second saturator circulation tank, 6 is an evaporation can, 7 is a crystal can, 8
Is a heater, 9 is an industrial water addition port, 10 is a sulfuric acid addition port, 14 is an internal circulation liquid amount control valve of the second saturator, 16 is heating steam, 17 is a pressure reducing device, 18 is a storage tank for ammonium sulfate mother liquor, Reference numeral 21 is a spray nozzle of the first saturator, 22 is a gas pipe from the first saturator to the second saturator, 31 is a spray nozzle of the second saturator, and 32 is a gas outlet of the second saturator. , 41 is a circulating fluid pump of the first saturator, 51 is a circulating fluid pump of the second saturator, 71 is a working water addition port, 111 is an ammonia concentration meter in the inlet gas of the first saturator, 112 Is an ammonia concentration meter in the inlet gas of the second saturator, 113 is an ammonia concentration meter in the outlet gas of the second saturator, 121 is a sulfuric acid concentration meter of the liquid extracted from the first saturator, and 122 is a second concentration meter. Sulfuric acid concentration meter of the liquid extracted from the saturator, 123 is the internal liquid sulfuric acid concentration of the crystallization process 131 is an internal circulation liquid amount control valve of the first saturator, 132 is a withdrawal amount control valve from the first saturator to the second saturator, 151 is a liquid withdrawal amount control valve to the crystallization process, 152 Is a liquid transfer amount control valve to the absorption step, and F is a gas flow meter.

Evaporation can 6 and crystal can 7 used in this embodiment
The amount of liquid retained in the system is 150 tons.

The coke oven gas is first charged into the first saturator 2 from the charging inlet 1, then charged into the second saturator 3 via the pipe 22, and discharged from the gas outlet 32. . The flow rate of the coke oven gas is measured by the gas flow meter F. The ammonia concentrations in the coke oven gas at the first saturator inlet, the second saturator inlet and the second saturator outlet are measured by ammonia concentration meters 111 and 113, respectively.

On the other hand, the ammonium sulfate mother liquor is pumped from the first saturator circulation tank 4 to the first spray saturator 2 by the pump 41,
After being sprayed by the spray nozzle 21 to absorb the ammonia in the coke oven gas, it returns to the first saturator circulation tank 4 and is internally circulated between the first saturator 2 and the first saturator circulation tank 4. The amount of the ammonium sulphate mother liquor circulated internally and the amount of the ammonium sulphate mother liquor withdrawn to the second saturator circulation tank 5 are controlled by the control valve 131.
And the opening of the control valve 132 are controlled. The free sulfuric acid concentration in the ammonium sulphate mother liquor at the outlet of the first saturator was measured by a sulfuric acid concentration meter 121, and the amount of sulfuric acid added from the pipe 10 and the internal circulation amount of the first saturator by the control valve 131 were adjusted. Control is performed so that a predetermined density is obtained. Further, industrial water is added from the pipe 9 for controlling the concentration of free sulfuric acid and ammonium sulfate and for controlling the flow rate. For example, a sulfuric acid concentration meter 121
The free sulfuric acid concentration at 1.0-1.5%,
Addition amount of sulfuric acid is 200L / h, addition amount of industrial water is 3m / h
^Set to ³ .

In the second saturator, as in the case of the first saturator, the ammonium sulfate mother liquor in the second saturator circulation tank 5 is pumped to the second spray saturator 3 by the pump 51 and the spray nozzle 31. Is absorbed in the coke oven gas that has passed through the first saturator to absorb residual ammonia. Thereafter, the ammonium sulfate mother liquor returns to the second saturator circulation tank 5 and is internally circulated between the second saturator 3 and the second saturator circulation tank 5. The amount of ammonium sulfate mother liquor circulated internally and the amount of ammonium sulfate mother liquor extracted to the crystallization step can be controlled by adjusting the opening degree of the control valve 14 and the control valve 151.

Further, the concentration of free sulfuric acid at the outlet of the second saturator is measured by the sulfuric acid concentration meter 122, and this value becomes equal to or lower than a predetermined concentration, and the concentration of ammonia at the outlet of the second saturator becomes equal to or lower than a predetermined concentration. As described above, the opening amounts of the control valve 132, the control valve 14, and the control valve 122 are adjusted so that the amount of ammonium sulfate mother liquor withdrawn from the first saturator circulation tank 4, the second saturator 3 and the second saturator circulation tank 5 The amount of ammonium sulphate mother liquor internally circulated between them and the amount of ammonium sulphate mother liquor withdrawn to the crystallization step are controlled. For example, sulfuric acid concentration meter 1
The concentration of free sulfuric acid at 22 was controlled to be 0.6 to 0.8%, and the amount of ammonium sulfate mother liquor extracted in the crystallization step was 3 m ^{3 /} h.
And The second saturator may be smaller than the first saturator in view of the ammonia concentration of the passing gas, but is preferably the same in scale. In this example, a second saturator of the same scale was used.

The ammonium sulphate mother liquor extracted from the second saturator is then sent to the crystallization process. At this time, it is more preferable to provide the ammonium sulfate mother liquor storage tank 18 as shown in FIG. 1 because the flow rate can be easily controlled when the ammonium sulfate mother liquor is replaced in the crystallization step described below.

In the crystallization process, the ammonium sulphate mother liquor pumped from the crystal can 7 is heated by the heater 8 and then evaporated.
Sent to. The evaporator 6 is decompressed by the decompression device 17, and the ammonium sulfate mother liquor is concentrated by removing water. The concentrated ammonium sulfate mother liquor descends along the downcomer into the crystal can 7,
The pump again circulates between the heater 8, the evaporator 6 and the crystal can 7 to proceed with concentration. From the concentrated ammonium sulphate mother liquor, ammonium sulphate was precipitated as crystals with seed crystals at the bottom of the crystal can 7 as nuclei.
It is extracted as granular ammonium sulfate from the bottom of the.

In the crystallization step, the ammonium sulfate mother liquor is concentrated to precipitate ammonium sulfate as described above, but at the same time, the free sulfuric acid in the ammonium sulfate mother liquor is also concentrated. Concentrated free sulfuric acid does not crystallize, but when the concentration of free sulfuric acid in the ammonium sulfate mother liquor reaches 6% or more, it adheres to the ammonium sulfate product and deteriorates the quality, as well as corrodes the crystallizer significantly. Therefore, when the free sulfuric acid concentration of the sulfuric acid concentration meter 123 installed in the internal liquid circulation line of the crystallization process reaches a predetermined concentration, a vacuum concentration operation in the evaporator is temporarily suspended to completely dissolve the solution. To do. Then, the ammonium sulfate mother liquor in the crystallization step is transferred to the first saturator circulation tank 4 and replaced with the ammonium sulphate mother liquor having a low free sulfuric acid concentration in the second saturator circulation tank 5 or the ammonium sulfate mother liquor storage tank 18.

For example, when the concentration of free sulfuric acid in the sulfuric acid concentration meter 123 reaches 5%, the operation of vacuum concentration in the evaporator is temporarily suspended to completely dissolve it. The number of continuously movable days of the crystallization process at this time is 12 to 9 days.

After that, the control valve 152 is fully opened, and the ammonium sulfate mother liquor in the crystallization process is transferred to the first saturator circulation tank 4 at about 30 m ^{3 /} h. After the transfer is completed, the control valve 151 is fully opened and the concentration of free sulfuric acid in the ammonium sulfate mother liquor storage tank 18 is 0.6 to
Accept 0.8% ammonium sulphate mother liquor at about 30 m ^{3 /} h.
During this time, the reaction between the coke oven gas and the ammonium sulfate mother liquor in the first saturator 2 and the second saturator 3 is continued. Further, the extraction of the ammonium sulfate mother liquor from the first saturator circulation tank 4 to the second saturator circulation tank 5 is also continued.

The amount of sulfuric acid added to the first saturator circulation tank 4 is reduced by an amount corresponding to the free sulfuric acid concentration in the ammonium sulfate mother liquor transferred from the crystallization step to the first saturator circulation tank 4. ,
The free sulfuric acid concentration in the sulfuric acid concentration meter 121 at the outlet of the first saturator 2 is maintained at 1.0 to 1.5%. For example, when 30 m ³ of ammonium sulphate per hour is received from the crystallization step, the addition amount of sulfuric acid of 200 L per hour is 50 L.

In this way, the ammonium sulphate mother liquor is exchanged between the crystallization step and the absorption step, and when the free sulfuric acid concentration of the sulfuric acid concentration meter 123 reaches a sufficiently low predetermined concentration, for example 0.6%. The vacuum concentration in the crystallization process is restarted.

The crystals obtained in this example had a 14-mesh over ratio of about 60% and were a product having a large crystal grain size.

In this example, since the ammonium sulfate saturated mother liquor in the crystallization process does not always return to the absorption process, there is no precipitation of ammonium sulfate crystals in the saturator, and therefore humidification steam in the coke oven gas is unnecessary. Met. Further, the steam required for the heater was 2.5 tons / hour, which is less than the conventional continuous heating because intermittent heating is required.

In the present embodiment, the operation of the control valve and the like was performed manually based on the measurement result of the sulfuric acid concentration meter or the like, but the control valve relating to the above operation is brought online and automatically controlled in conjunction with the measuring equipment. You can also

In the present invention, the saturator in the absorption step is two columns, but three or more saturators are connected in series, and the concentration of free sulfuric acid in the ammonium sulfate mother liquor internally circulated becomes lower as the latter stage saturator is lower. It is also possible to set as follows. In this case, it is desirable from the viewpoint of reducing the concentration of free sulfuric acid in the ammonium sulfate mother liquor extracted to the crystallization step, but on the other hand, since the reaction of ammonia and sulfuric acid is divided into three or more times, the efficiency of the reaction becomes lower in the latter-stage saturator. It is economically disadvantageous in view of the equipment cost of installing a saturator.

Comparative Example Using the conventional apparatus for producing granular ammonium sulfate shown in FIG. 2,
A comparative test was conducted. Reference numeral 24 is a pipe for extracting the ammonium sulfate mother liquor from the absorption process to the crystallization process, 28 is a return pipe for the ammonium sulfate mother liquor from the crystallization process to the absorption process, 30 is a steam injection port, 3
1 is the gas outlet of the first saturator, 32 is the working water addition port, and the others are the same as in FIG.

The description of the absorption step and the crystallization step has already been given in the above section of the prior art. The ammonium sulphate mother liquor is constantly circulated between the absorption step and the crystallization step by the pipe 24 and the pipe 28 in order to avoid concentration of free sulfuric acid in the crystallization process. The concentration of free sulfuric acid in the circulating mother liquor in this comparative example is 2 to
It was 3% (average 2.5%). The ammonium sulfate crystal produced in this comparative example had a ratio of 14 mesh over of about 40%. In the crystallization process, if the operation cannot be continued due to crystal adhesion, total dissolution is performed. This is an operation in which the vacuum concentration operation in the crystallization process is temporarily stopped and working water is charged into the crystallization process to dissolve the attached crystals. The number of continuous working days from the total dissolution to the next total dissolution in this comparative example was 5 days.

The effects of Example 1 and Comparative Example described above are summarized in Table 1 below.

[0043]

[Table 1]

[0044]

As described above, according to the method of the present invention, it is not necessary to constantly circulate the ammonium sulfate mother liquor between the crystallization step and the absorption step. Further, the free sulfuric acid concentration of the ammonium sulfate mother liquor sent to the crystallization step can be controlled to be lower than a predetermined concentration, and the free sulfuric acid concentration in the ammonium sulfate mother liquor in the crystallization step can be suppressed to a predetermined concentration or lower. Therefore, the following effects are obtained.

First, the problem of ammonium sulphate precipitation in the saturator that occurs with the constant circulation of the ammonium sulphate mother liquor is solved. Therefore, pump power required for constant circulation of ammonium sulfate mother liquor, washing with industrial water in the saturator, and humidification of coke oven gas with steam are not required, and energy consumption can be greatly reduced.

As the above problem is solved, washing with industrial water in the saturator is eliminated, and the concentration of ammonium sulfate in the mother liquor, which has conventionally fluctuated due to the influence of dilution or the like, becomes stable. As a result, not only is it possible to obtain high-quality granular ammonium sulfate having a large grain size,
The problem of ammonium sulfate crystals adhering to the crystal can is also greatly improved.

Therefore, in the prior art, the deposition of ammonium sulfate crystals on the apparatus in the crystallization step is the rate-determining factor, and total dissolution is required every 5 days. However, in the method of the present invention, the total dissolution mainly occurs in the crystallization step. When the concentration of free sulfuric acid in the ammonium sulfate mother liquor reaches the upper limit, the rate becomes rate-determining, and it becomes possible to extend the period during which the crystallization process can be continuously operated about twice as long as the conventional one.

[Brief description of drawings]

FIG. 1 is a manufacturing flow chart of a first embodiment of the present invention.

FIG. 2 is a flow chart of the production of ordinary granular ammonium sulfate.

[Explanation of symbols]

1 Coke Oven Gas Charging Port 2 First Spray Saturator 3 Second Spray Saturator 4 First Saturator Circulation Tank 5 Second Saturator Circulation Tank 6 Evaporator 7 Crystal Can 8 Heater 10 Sulfuric Acid Addition Port 14 Internal circulation liquid amount control valve of second saturator 17 Pressure reducing device 111 Ammonia concentration meter in inlet gas of first saturator 112 112 Ammonia concentration meter in inlet gas of second saturator 113 Second saturator Ammonia concentration meter in outlet gas 121 Sulfuric acid concentration meter of liquid extracted from first saturator 122 Sulfuric acid concentration meter of liquid extracted from second saturator 123 Sulfuric acid concentration meter of internal liquid in crystallization process 131 First saturator Internal circulating liquid control valve 132 Controlling amount of extraction from the first saturator to second saturator 151 Controlling amount of liquid extraction to crystallization process 152 Controlling liquid transfer amount to absorption process F Gas flow meter

Claims (1)

[Claims] 1. A method for producing granular ammonium sulfate, comprising: an absorption step of absorbing ammonia in a coke oven gas into an ammonium sulfate mother liquor containing sulfuric acid; and a crystallization step of crystallizing ammonium sulfate from the ammonium sulfate mother liquor. Spray saturator and second
And a spray saturator of (1) are connected in series, and a part of the ammonium sulfate mother liquor reacted in the first spray saturator is sent to the second spray saturator to complete the reaction in the first spray saturator. When it reacts with the furnace gas again and is withdrawn to the crystallization process, and when the concentration of free sulfuric acid in the ammonium sulphate mother liquor in the crystallization process reaches a prescribed concentration, the production of granular ammonium sulfate in the crystallization process is temporarily stopped and the whole process is stopped. Dissolve and transfer the ammonium sulphate mother liquor from this crystallization step to the first saturator and replace it with the ammonium sulphate mother liquor with low free sulfuric acid concentration charged from the second saturator, and then produce granular ammonium sulphate in the crystallization step. 1. A method for producing granular ammonium sulfate, which comprises restarting