JP2018162201A - Ammonium sulfate manufacturing method and ammonium sulfate manufacturing facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of ammonium sulfate and an ammonium sulfate manufacturing facility, capable of reducing used amount of sulfamic acid.SOLUTION: In a manufacturing method of ammonium sulfate in which diluted sulfuric acid is sprayed to C gas introduced to an ammonium sulfate saturated tower, then ammonium sulfate mother liquid, which is diluted sulfuric acid absorbing ammonium, is introduced to a 2 lineage ammonium sulfate crystallizer consisting of an ammonium sulfate crystallizer 4A and ammonium sulfate crystallizer 4B, the ammonium sulfate mother liquid Lis heated and concentrated, then solid solution separated to obtain an ammonium sulfate crystal with a first grain diameter 11A and a separated filtrate 12A is supplied to a device 4A in the device 4A, the ammonium sulfate mother liquid Lis heated and concentrated, then solid solution separated to obtain an ammonium sulfate crystal 11B, which is larger than the ammonium sulfate crystal 11A in the device 4B, a part of the filtrate 12B to which sulfamic acid is added is not supplied to the device 4A and returned to an ammonium sulfate crystallization tank 41B after adding a part 14 of ammonium sulfate concentrated water 8B to the filtrate 12B.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an ammonium sulfate production method and an ammonium sulfate production facility.

Conventionally, a gas (hereinafter also referred to as “C gas”) that is generated when coal is inserted into a coking chamber of a coke oven and dry-distilled includes a large amount of fuel components such as hydrogen, methane, and carbon monoxide, and is 20000 kJ / Since it has a high heat quantity exceeding m ³ , it is recovered and reused as fuel gas for blast furnaces, coke ovens, heating furnaces, and boilers.

  At that time, various substances such as tar, water, ammonia, hydrogen sulfide, and cyan are mixed in the C gas discharged from the coke oven. Substances and harmful substances need to be removed. Therefore, it is customary to use fuel gas through purification to remove these combustion-inhibiting substances and harmful substances.

Specifically, the purification of C gas into fuel gas is performed as follows. First, after C gas discharged from the coke oven is cooled, C gas from which naphthalene that causes equipment blockage is recovered is introduced into a desulfurization facility to remove hydrogen sulfide (desulfurization step). Next, the C gas from which hydrogen sulfide has been removed is introduced into a deammonia facility, and the ammonia component that causes nitrogen oxides (NO _x ) is removed from the C gas (deammonia process). Then, C gas from which ammonia was removed is cooled, and the light oil content in C gas is collect | recovered (light oil collection process). Through the above steps, the C gas discharged from the coke oven is purified into fuel gas.

In the deammonification step, C gas and dilute sulfuric acid are reacted to recover ammonia contained in C gas as ammonium sulfate crystals. FIG. 1 is a diagram illustrating an example of a deammonia process. In this deammonification step, the C gas 1 from which hydrogen sulfide has been removed through the desulfurization step is introduced into the ammonium sulfate saturated column 2, and dilute sulfuric acid is sprayed by spraying, and the C gas 1 introduced into the ammonium sulfate saturated column 2 and Contact with countercurrent. Then, the sprayed dilute sulfuric acid absorbs ammonia contained in the C gas 1 and falls and stays in the lower part of the ammonium sulfate saturated tower 2 as ammonium sulfate mother liquor L ₁ .

Here, the ammonium sulfate mother liquor L ₁ staying in the lower part of the ammonium sulfate saturated column 2 is discharged from the ammonium sulfate saturated column 2, and the ammonium sulfate mother solution 3 is introduced into the ammonium sulfate crystallizer 4. The introduced ammonium sulfate mother liquor 3 is heated and concentrated by the ammonium sulfate crystallizer 4, and ammonium sulfate contained in the ammonium sulfate mother liquor 3 is crystallized and recovered as a slurry 5 containing ammonium sulfate crystals.

  On the other hand, moisture (hereinafter also referred to as “ammonium sulfate-containing steam”) 6 evaporated from the ammonium sulfate mother liquor 3 by the concentration treatment is condensed by the condenser 7 to become ammonium sulfate condensed water 8 and transferred to the wastewater treatment facility 9. Drugs are added to make it harmless.

  Details of the ammonium sulfate crystallizer will be described below. FIG. 2 shows an example of an ammonium sulfate crystallization apparatus 4 that crystallizes ammonium sulfate contained in the ammonium sulfate mother liquor 3. The ammonium sulfate crystallization apparatus 4 shown in this figure has an ammonium sulfate crystallization tank 41, a heater 42, an evaporation tank 43, a condenser 7, and a separator 10.

In this ammonium sulfate crystallizer 4, ammonium sulfate crystals are produced as follows. First, the ammonium sulfate mother liquor 3 is introduced into the ammonium sulfate crystallization tank 41. The introduced ammonium sulfate mother liquor L ₂ is heated by the heater 42 and supplied to the evaporation tank 43, and the water contained in the ammonium sulfate mother liquor L ₂ is evaporated and concentrated. The ammonium sulfate-containing steam 6 discharged from the evaporation tank 43 is condensed by the condenser 7, and the obtained ammonium sulfate condensed water 8 is sent to the wastewater treatment facility 9, and the pH is adjusted by adding a chemical agent, followed by wastewater treatment. The

On the other hand, the ammonium sulfate mother liquor L ₂ concentrated in the evaporation tank 43 is returned to the ammonium sulfate crystallization tank 41. By thus ammonium sulfate mother liquor L ₂ is circulated between the ammonium sulfate crystallization vessel 41 and the evaporation tank 43, by increasing the ammonium sulfate concentration of ammonium sulfate mother liquor L ₂ to issue a ammonium sulphate crystals crystals.

  Subsequently, the slurry 5 containing the crystallized ammonium sulfate crystal 11 is discharged from the lower part of the ammonium sulfate crystallization tank 41 and separated into the ammonium sulfate crystal 11 and the filtrate 12 by the separator 10 such as a centrifugal separator. The ammonium sulfate crystal 11 is transported to a drying facility (not shown) in the next process and commercialized. On the other hand, the filtrate 12 is returned to the ammonium sulfate crystallization tank 41. In this way, ammonium sulfate crystals can be produced.

  By the way, ammonium sulfate produced as described above is distinguished by size, and is mainly classified into three types: fine grains (~ 2mm), medium grains (2mm ~ 3mm), and large grains (3mm ~ 4mm). . Then, using the three types of ammonium sulfate crystallizer comprising an ammonium sulfate crystallizer for producing fine and medium ammonium sulfate crystals and an ammonium sulfate crystallizer for producing large particles of ammonium sulfate, the above three types of ammonium sulfate crystals are used. May be manufactured (for example, see Patent Document 1).

  FIG. 3 shows a flow chart of a conventional ammonium sulfate production method using an ammonium sulfate production facility equipped with two systems of ammonium sulfate crystallizer. The ammonium sulfate production equipment shown in this figure is an equipment equipped with two ammonium sulfate crystallization apparatuses shown in FIG. 2, and the ammonium sulfate mother liquor 3 discharged from the ammonium sulfate saturation tower 2 shown in FIG. The apparatus 4A and the lower ammonium sulfate crystallizer 4B are introduced separately.

The upper ammonium sulfate crystallization apparatus 4A includes a first ammonium crystallization tank 41A, a first heater 42A, a first evaporation tank 43A, a first condenser 7A, and a first separator 10A. Have Manufacture of ammonium sulfate crystals using this ammonium sulfate crystallization apparatus 4A is performed in the same manner as the apparatus shown in FIG. That is, first, the ammonium sulfate mother liquor 3A is introduced into the first ammonium sulfate crystallization tank 41A. The introduced ammonium sulfate mother liquor L ₃ is heated by the first heater 42A and supplied to the first evaporation tank 43A, and the water contained in the ammonium sulfate mother liquor L ₃ is evaporated and concentrated. The ammonium sulfate-containing steam 6A discharged from the first evaporation tank 43A is condensed by the first condenser 7A. Then, the obtained ammonium sulfate condensate 8A is sent to the first waste water treatment facility 9A, and after the chemical is added and the pH is adjusted, the waste water is treated.

On the other hand, the ammonium sulfate mother liquor L ₃ concentrated in the first evaporation tank 43A is returned to the first ammonium sulfate crystallization tank 41A. By thus circulated between the ammonium sulfate mother liquor L ₃ and first ammonium sulfate crystallizer 41A and the first evaporator tank 43A, by increasing the ammonium sulfate concentration of ammonium sulfate mother liquor L ₃ to precipitate ammonium sulphate crystals.

  Subsequently, the slurry 5A containing the precipitated ammonium sulfate crystal 11A is discharged from the lower part of the first ammonium sulfate crystallization tank 4A, and the ammonium sulfate crystal 11A and the first filtrate 12A are separated by the first separator 10A such as a centrifugal separator. To separate. The ammonium sulfate crystal 11A is transported to a drying facility (not shown) in the next process and commercialized. On the other hand, the first filtrate 12A is returned to the first ammonium sulfate crystallization tank 41A. In this way, ammonium sulfate crystals are produced. In the first ammonium sulfate crystallizer 4A, relatively small and medium-sized ammonium sulfate crystals are produced.

On the other hand, the second ammonium sulfate crystallization apparatus 4B in the lower stage includes a second ammonium sulfate crystallization tank 41B, a second heater 42B, a second evaporation tank 43B, and a second condenser 7B. And a second separator 10B. The ammonium sulfate crystal using the second ammonium sulfate crystallizer 4B is performed as follows. First, the ammonium sulfate mother liquor 3B is introduced into the second ammonium sulfate crystallization tank 41B. The introduced ammonium sulfate mother liquor L ₄ is heated by the second heater 42B and supplied to the second evaporating tank 43B, and the water contained in the ammonium sulfate mother liquor L ₄ is evaporated and concentrated. The ammonium sulfate-containing steam 6B discharged from the second evaporation tank 43B is condensed by the second condenser 7B. And the obtained ammonium sulfate condensate 8B is sent to the 2nd waste water treatment equipment 9B, and after chemical | medical agent is added and pH is adjusted, it is drained.

On the other hand, the ammonium sulfate mother liquor L ₄ concentrated in the second evaporation tank 43B is returned to the second ammonium sulfate crystallization tank 41B. By thus circulated between the ammonium sulfate mother liquor L ₄ and the second ammonium sulfate crystallizer 41B and the second evaporator tank 43B, by increasing the ammonium sulfate concentration of ammonium sulfate mother liquor L ₄ to precipitate ammonium sulphate crystals. The slurry 5B containing the precipitated ammonium sulfate crystal 11B is discharged from the lower part of the second ammonium sulfate crystallization tank 4B and separated into the ammonium sulfate crystal 11B and the second filtrate 12B by the second separator 10B such as a centrifugal separator. . The ammonium sulfate crystal 11B is conveyed to a drying facility (not shown) in the next process and commercialized. In this second ammonium sulfate crystallizer 4B, relatively large and large ammonium sulfate crystals are produced.

  Further, the second filtrate 12B is returned to the second ammonium sulfate crystallization tank 41B after adding sulfamic acid which is effective for precipitation of ammonium sulfate having a large particle diameter, but the specific gravity of the filtrate 12B is too high. In the process of returning to the second ammonium sulfate crystallization tank 41B, for example, in a tank or the like (not shown) for temporarily storing the second filtrate 10B, there is a possibility that the ammonium sulfate crystals will precipitate and block the apparatus. . Therefore, a part of the second filtrate 12B is supplied to the upper first ammonium sulfate crystallizer 4A, and the remaining second filtrate 12B is returned to the second ammonium sulfate crystallizer 41B.

JP 2014-237666 A

  In the lower second ammonium sulfate crystallizer 4B shown in FIG. 3, the amount of sulfamic acid added can be reduced because the sulfamic acid added to the filtrate 12B to produce large ammonium sulfate is expensive. There is a need for a method for producing ammonium sulfate.

  Therefore, an object of the present invention is to propose an ammonium sulfate production method and an ammonium sulfate production facility capable of reducing the amount of sulfamic acid used.

The present invention for solving the above problems is as follows.
(1) The dilute sulfuric acid that has introduced the coke oven gas that has passed through the desulfurization step to the ammonium sulfate saturation tower, sprayed dilute sulfuric acid on the coke oven gas, absorbed ammonia contained in the coke oven gas, and then absorbed ammonia. The ammonium sulfate mother liquor was led to two systems of ammonium sulfate crystallizer comprising a first ammonium sulfate crystallizer and a second ammonium sulfate crystallizer, and the ammonium sulfate mother liquor was concentrated by heating in the first ammonium sulfate crystallizer. In the second ammonium sulfate crystallizer, after solid-liquid separation to obtain an ammonium sulfate crystal having a first particle size and supplying the separated first filtrate to the first ammonium sulfate crystallizer, In the method for producing ammonium sulfate, the ammonium sulfate mother liquor is heated and concentrated, followed by solid-liquid separation to obtain an ammonium sulfate crystal having a second particle size larger than the first particle size.
A portion of the second filtrate to which sulfamic acid has been added is not supplied to the first ammonium sulfate crystallizer, and water evaporated during the concentration of the ammonium sulfate mother liquor in the second ammonium sulfate crystallizer is removed. A method for producing ammonium sulfate, comprising adding a part of condensed ammonium sulfate condensed water to the second filtrate to which sulfamic acid has been added, and then supplying the second ammonium sulfate crystallizer.

(2) Ammonium sulfate saturated tower that sprays dilute sulfuric acid on coke oven gas that has undergone the desulfurization process to absorb ammonia contained in the coke oven gas, and ammonium sulfate mother liquor that is the diluted sulfuric acid that has absorbed ammonia is concentrated to produce ammonium sulfate crystals. The first ammonium sulfate crystallizer comprises a first ammonium sulfate crystallizer and a second ammonium sulfate crystallizer, and the first ammonium sulfate crystallizer stores the first ammonium sulfate mother liquor. An ammonium sulfate crystallization tank, a first heater for heating the ammonium sulfate mother liquor, a first evaporation tank for evaporating water contained in the ammonium sulfate mother liquor, and water condensed from the first evaporation tank is condensed. A first separator, a first separator obtained by solid-liquid separation of the heated ammonium sulfate mother liquor to obtain an ammonium sulfate crystal having a first particle size, and a first separator separated by the first separator. And a first filtrate supply pipe for returning the filtrate to the first ammonium sulfate crystallization tank, The second ammonium sulfate crystallization apparatus includes: a second ammonium crystallization tank that stores the ammonium sulfate mother liquor; a second heater that heats the ammonium sulfate mother liquor; and a second that evaporates water contained in the ammonium sulfate mother liquor. An evaporating tank; a second separator for solid-liquid separation of the heated ammonium sulfate mother liquor to obtain an ammonium sulfate crystal having a second particle size; and a second filtrate separated by the second separator. A second filtrate supply pipe for supplying a part of the second filtrate to the first ammonium sulfate crystallization apparatus, and a third filtrate supply pipe for returning the remainder of the second filtrate to the second ammonium sulfate crystallization tank. In an ammonium sulfate production facility having
Without providing the second filtrate supply pipe, all the second filtrate is returned to the second ammonium sulfate crystallization tank by the third filtrate supply pipe, and obtained by the second condenser. An ammonium sulfate production facility comprising an ammonium sulfate condensed water supply pipe for supplying a part of the produced ammonium sulfate condensed water to the second ammonium sulfate crystallization tank.

  ADVANTAGE OF THE INVENTION According to this invention, the usage-amount of the sulfamic acid used when manufacturing an ammonium sulfate can be reduced.

It is a figure which shows an example of a deammonification process. It is a figure which shows an example of an ammonium sulfate crystallization apparatus. It is a flowchart of the manufacturing method of the conventional ammonium sulfate using the ammonium sulfate manufacturing equipment provided with two systems of ammonium sulfate crystallizer. It is a flowchart of the manufacturing method of the ammonium sulfate by this invention.

(Ammonium sulfate production method)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 shows a flow chart of the method for producing ammonium sulfate according to the present invention. In addition, the same code | symbol is attached | subjected to the structure same as the structure shown by FIG. As shown in FIG. 4, the method for producing ammonium sulfate according to the present invention separates a part of the second filtrate 12B, which is separated by the second separator 10B in the lower stage and to which sulfamic acid is added, from the first ammonium sulfate in the upper stage. not supplied to the crystallizer 4A, the lower second ammonium sulfate condensed water 8B condensed the discharged ammonium sulfate containing vapor 6B from the second evaporation chamber 43B when the concentration of ammonium sulfate crystallizer ammonium sulfate mother liquor L ₄ in 4B Is added to the second filtrate 12B to which sulfamic acid has been added, and then supplied to the second ammonium sulfate crystallization tank 41B in the lower stage.

  As described above, in the conventional method for producing ammonium sulfate shown in FIG. 3, in order to prevent the apparatus from being blocked, a part 13 of the second filtrate 12B separated by the second condenser 10B is removed from the upper stage. Although being supplied to the first ammonium sulfate production apparatus 4A, expensive sulfamic acid is added to the second filtrate 12B as a crystallizing agent in order to produce large particles of ammonium sulfate. However, ammonium sulfate produced using the upper first ammonium sulfate crystallizer 4A is smaller than that produced by the lower ammonium sulfate crystallizer 4B, and therefore sulfamic acid is not required. Therefore, in the conventional method, expensive sulfamic acid is wastefully supplied to the upper ammonium sulfate crystallizer 4A.

  The present inventors diligently studied how to reduce the amount of sulfamic acid used in such conventional methods. If all of the second filtrate 12B separated by the second separator 10B at the lower stage is returned to the second ammonium sulfate crystallization tank 41B, the amount of sulfamic acid used is eliminated and the amount used is reduced. But can cause device blockage.

  The blockage of the device can be prevented by adjusting the specific gravity of the second filtrate 12B by adding industrial water to the second filtrate 12B. However, the cost for procuring industrial water is newly generated, and the effect of reducing the amount of sulfamic acid used is reduced.

  Therefore, the present inventors diligently studied how to reduce the specific gravity of the second filtrate 12B and prevent blockage of the apparatus without using industrial water. As a result, attention was paid to the ammonium sulfate-containing steam 6B discharged from the second evaporation tank 43B of the second ammonium sulfate crystallizer 4B. As described above, the ammonium sulfate-containing steam 6B is condensed by the second condenser 7B, and the obtained ammonium sulfate condensate 8B is sent to the wastewater treatment facility 9B and adjusted in pH, and is subjected to wastewater treatment. It has not been effectively utilized until. Therefore, the present inventors have conceived that a part of the ammonium sulfate condensed water 8B is added to the second filtrate 12B to which sulfamic acid is added. Thereby, the usage-amount of sulfamic acid can be reduced, adjusting the specific gravity of the 2nd filtrate 12B and preventing apparatus obstruction | occlusion without additional cost like industrial water. The ammonium sulfate condensate 8B contains oil, sludge and free ammonia, but the amount thereof is very small and most of it is moisture, so there is no problem even if it is used as a substitute for industrial water.

  Further, since a part of the ammonium sulfate condensate 8B is added to the second filtrate 12B to which sulfamic acid has been added, the amount of the chemical added to the ammonium sulfate condensate 8B in the wastewater treatment facility 9B can also be reduced. . Hereinafter, with reference to FIG. 4, the manufacturing method of the ammonium sulfate by this invention is demonstrated.

First, the production of ammonium sulfate in the upper first ammonium sulfate crystallizer 4A is the same as the conventional method shown in FIG. That is, first, the ammonium sulfate mother liquor 3A is introduced into the first ammonium sulfate crystallization tank 41A. The introduced ammonium sulfate mother liquor L ₃ is heated by the first heater 42A and supplied to the first evaporation tank 43A, and the water contained in the ammonium sulfate mother liquor L ₃ is evaporated and concentrated. The ammonium sulfate-containing steam 6A discharged from the first evaporation tank 43A is condensed by the first condenser 7A, and the obtained ammonium sulfate condensed water 8A is sent to the first wastewater treatment facility 9A, and the chemical is added to the pH. After adjustment, the wastewater is treated.

On the other hand, the ammonium sulfate mother liquor L ₃ concentrated in the first evaporation tank 43A is returned to the first ammonium sulfate crystallization tank 41A. By thus circulated between the ammonium sulfate mother liquor L ₃ and first ammonium sulfate crystallizer 41A and the first evaporator tank 43A, by increasing the ammonium sulfate concentration of ammonium sulfate mother liquor L ₃ to precipitate ammonium sulphate crystals.

  Subsequently, the slurry 5A containing the precipitated ammonium sulfate crystal 11A is discharged from the lower part of the first ammonium sulfate crystallization tank 4A and separated into the ammonium sulfate crystal 11A and the filtrate 12A by the first separator 10A such as a centrifugal separator. . The ammonium sulfate crystal 11A is transported to a drying facility (not shown) in the next process and commercialized. On the other hand, the filtrate 12A is returned to the first ammonium sulfate crystallization tank 41A. In this way, ammonium sulfate crystals are produced. In the first ammonium sulfate crystallizer 4A, relatively small and medium-sized ammonium sulfate crystals are produced.

On the other hand, in the manufacture of ammonium sulfate in the second ammonium sulfate crystallizer 4B in the lower stage, first, the ammonium sulfate mother liquor 3B is introduced into the second ammonium sulfate crystallizer 41B. The introduced ammonium sulfate mother liquor L ₄ is heated by the second heater 42B and supplied to the second evaporating tank 43B, and the water contained in the ammonium sulfate mother liquor L ₄ is evaporated and concentrated. The ammonium sulfate-containing steam 6B discharged from the second evaporation tank 43B is condensed by the second condenser 7B, and the obtained ammonium sulfate condensed water 8B is sent to the second wastewater treatment facility 9B, and the chemical is added to the pH. After adjustment, the wastewater is treated.

On the other hand, the ammonium sulfate mother liquor L ₄ concentrated in the second evaporation tank 43B is returned to the second ammonium sulfate crystallization tank 41B. By thus circulated between the ammonium sulfate mother liquor L ₄ and the second ammonium sulfate crystallizer 41B and the second evaporator tank 43B, by increasing the ammonium sulfate concentration of ammonium sulfate mother liquor L ₄ to precipitate ammonium sulphate crystals. The slurry 5B containing the precipitated ammonium sulfate crystal 11B is discharged from the lower part of the second ammonium sulfate crystallization tank 4B and separated into the ammonium sulfate crystal 11B and the filtrate 12B by the second separator 10B such as a centrifugal separator. The ammonium sulfate crystal 11B is conveyed to a drying facility (not shown) in the next process and commercialized. In this second ammonium sulfate crystallizer 4B, relatively large and large ammonium sulfate crystals are produced.

  On the other hand, the second filtrate 12B returns all of the second filtrate 12B to the second ammonium sulfate crystallization tank 41B without supplying a part of the second filtrate 12B to the first ammonium sulfate crystallization apparatus 4A. A part of the ammonium sulfate condensate 8B obtained by condensing the ammonium sulfate-containing vapor discharged from the second evaporation tank 43B during the concentration of the ammonium sulfate mother liquor in the ammonium sulfate crystallizer 4B is supplied to the second ammonium crystallizer 4B.

  In this way, a part 14 of the second ammonium sulfate condensed water 8B is supplied to the ammonium sulfate crystallization tank 41B, and the part 13 of the second filtrate 12B is changed as in the conventional method shown in FIG. Since it is not wastefully supplied to the first ammonium sulfate crystallizer 4A, the amount of sulfamic acid used can be reduced. In addition, as described above, a part 14 of the ammonium sulfate condensate 8B supplied to the ammonium sulfate crystallizer 4B has been sent to the waste water treatment facility 9B and processed, and thus industrial water is not used. In addition to the need for additional costs as in the case of the case, the amount of chemicals used in the wastewater treatment facility 9B can be reduced.

  In addition, as shown in FIG. 4, the supply of the part 14 of the second ammonium sulfate condensed water 8B to the second ammonium crystallization tank 41B is performed by adding to the second filtrate 12B. Alternatively, it may be configured to be supplied directly to the second ammonium sulfate crystallization tank 41B.

(Ammonium sulfate production facility)
Next, an ammonium sulfate production facility according to the present invention will be described. For this purpose, first, an ammonium sulfate production facility equipped with two conventional ammonium sulfate crystallizing apparatuses will be described with reference to FIG. A conventional ammonium sulfate production facility includes an ammonium sulfate saturation tower (not shown) that sprays dilute sulfuric acid on C gas 1 that has undergone a desulfurization process and absorbs ammonia contained in C gas 1, and ammonium sulfate that is dilute sulfuric acid that has absorbed ammonia. It comprises two systems of ammonium sulfate crystallizers consisting of a first ammonium sulfate crystallizer 4A and a second ammonium sulfate crystallizer 4B, which concentrate the mother liquor 3 to obtain ammonium sulfate crystals.

The first ammonium sulfate crystallizer 4A includes a first ammonium sulfate crystallization tank 41A for storing the ammonium sulfate mother liquor L _3, a first heater 42A for heating the ammonium sulfate mother liquor L _3, the ammonium sulfate mother liquor L ₃ Solid-liquid separation of the first evaporation tank 43A for evaporating moisture, the first condenser 7A for condensing the ammonium sulfate-containing vapor 6A discharged from the first evaporation tank 43A, and the ammonium sulfate mother liquor L ₃ concentrated by heating. The first separator 10A for obtaining ammonium sulfate crystals of the first particle size, and the first filtrate 12A separated by the first separator 10A is returned to the first ammonium sulfate crystallization tank 41A. And a filtrate supply pipe.

Further, the second ammonium sulfate crystallizer. 4B, a second ammonium sulfate crystallization tank 41B for storing the ammonium sulfate mother liquor L _4, and the second heater 42B for heating the ammonium sulfate mother liquor L _4, the ammonium sulfate mother liquor L ₄ A second evaporation tank 43B for evaporating the contained water, a second condenser 7B for condensing the ammonium sulfate-containing vapor 6B discharged from the second evaporation tank 43B, and an ammonium sulfate mother liquor L ₄ concentrated by heating are solidified. A second separator 10B that obtains ammonium sulfate crystals having a second particle size by liquid separation, and a part of the second filtrate 12B separated by the second separator 10B is used as a first ammonium sulfate crystallizer. It has a second filtrate supply pipe for supplying to 4A, and a third filtrate supply pipe for returning the remainder of the second filtrate to the second ammonium sulfate crystallization tank 41B.

  The conventional ammonium sulfate production facility supplies a part of the second filtrate 12B separated by the separator 10B such as a centrifugal separator to the first ammonium sulfate crystallizer 4A by the second filtrate supply pipe. As a result, the apparatus was prevented from being blocked. On the other hand, in the ammonium sulfate production facility according to the present invention, as shown in FIG. 4, ammonium sulfate condensate obtained by the second condenser 7B without providing the second filtrate supply pipe in the conventional facility described above. An ammonium sulfate condensed water supply pipe for supplying a part 14 of the water 8B to the second ammonium sulfate crystallization tank 41B is provided.

  With the ammonium sulfate condensed water supply pipe, the specific gravity of the second filtrate 12B can be adjusted, and the apparatus can be prevented from being blocked. In addition, in the conventional equipment, a part of the second filtrate 12B containing expensive sulfamic acid is supplied to the first first ammonium sulfate crystallizer 4A that does not require sulfamic acid to waste sulfamic acid. As a result, in the facility according to the present invention, all of the second filtrate 12B is returned to the second ammonium sulfate crystallization tank 41B. As a result, the amount of sulfamic acid used can be reduced.

  Examples of the present invention will be described below, but the present invention is not limited to the examples.

(Invention example)
Ammonium sulfate was produced according to the flow chart shown in FIG. Specifically, C gas was introduced into an ammonium sulfate saturated tower (not shown) at 134,000 Nm ³ / h, and the ammonia content in the C gas was chemically absorbed in dilute sulfuric acid, and then 20.9 to the ammonium sulfate crystallizer 4A. The ammonium sulfate mother liquor was supplied to the m ³ / h, ammonium sulfate crystallizer 4B at 8.6 m ³ / h. Next, the slurry containing ammonium sulfate crystals was extracted from the bottom of each ammonium sulfate crystallizer and introduced into a centrifuge to separate into solid and liquid. By the solid-liquid separation, the second filtrate 12B was generated at 1.1 m ³ / h, and the whole amount was returned to the ammonium sulfate crystallization tank 41B. 25 kg of sulfamic acid was introduced per day into the separated second filtrate 12B. The second ammonium sulfate condensate 8B is generated at 3.0 m ³ / h, the ammonium sulfate condensate is introduced at 0.5 m ³ / h into the filtrate 12B containing the sulfamic acid, and the specific gravity of the second filtrate 12B is adjusted. This prevents the device from being blocked. The remaining 2nd ammonium sulfate condensate 8B 2.5 m ³ / h and 1st ammonium sulfate condensate 8A 17 m ³ / h were adjusted to pH by adding 1974 kg of chemicals per day, and were subjected to wastewater treatment.

(Comparative example)
Ammonium sulfate was produced according to the flow chart shown in FIG. Similarly to the inventive example, the ammonium sulfate mother liquor was supplied to the ammonium sulfate crystallizer 4A at 20.9 m ³ / h and to the ammonium sulfate crystallizer 4B at 8.6 m ³ / h. By the solid-liquid separation, 1.1 m ³ / h of the second filtrate 12B was generated. 75 kg of sulfamic acid per day was introduced into the second filtrate 12B. The 0.65 m ³ / h of the second filtrate 12B ammonium sulfate crystallization vessel 41A, was returned to 0.45 m ³ / h ammonium sulfate crystallization tank 41B. The second ammonium sulfate condensate 8B is generated at 3.0m ³ / h and is not added to the filtrate 12B containing sulfamic acid, but 2024kg of chemicals is added together with the first ammonium sulfate condensate 8A 17m ³ / h Then, the pH was adjusted and the waste water was treated. Other conditions are the same as those of the invention examples.

  The sulfamic acid used in the inventive example was 25 kg, whereas the sulfamic acid used in the comparative example was 75 kg, indicating that the amount of sulfamic acid used could be reduced by 50 kg. Further, in the inventive example, the amount of the chemical used for the treatment of the ammonium sulfate condensed water was 1974 kg, whereas the amount of the chemical used in the comparative example was 2024 kg, and the amount of the chemical used could be reduced by 50 kg. I understand. Thus, according to the present invention, it was possible to achieve a reduction in the amount of sulfamic acid and chemicals used for the treatment of condensed ammonium sulfate without affecting the production of ammonium sulfate.

  According to the present invention, when ammonium sulfate is produced from coke oven gas, the amount of sulfamic acid used can be reduced, which is useful in the steel industry.

1 Coke oven gas 2 ammonium sulfate saturation tower _{3,3A, 3B, L 1, L} 2, L 3, L 4 ammonium sulfate mother liquor 4, 4A, 4B ammonium sulfate crystallizer 5, 5A, 5B slurry 6, 6A, 6B ammonium sulfate-containing vapor 7, 7A, 7B Condenser 8, 8A, 8B, 14 Ammonium sulfate condensate 9, 9A, 9B Wastewater treatment facility 10, 10A, 10B Separator 11, 11A, 11B Ammonium sulfate crystal 12, 12A, 12B, 13 Filtrate 41, 41A, 41B Ammonium sulfate crystallization tank 42, 42A, 42B Heater 43, 43A, 43B Evaporation tank

Claims (2)

The coke oven gas that has passed through the desulfurization process is guided to an ammonium sulfate saturation tower, and the sulfuric acid is sprayed on the coke oven gas to absorb ammonia contained in the coke oven gas, and then the ammonium sulfate mother liquor that is the diluted sulfuric acid that has absorbed ammonia is added. The solution is led to two systems of ammonium sulfate crystallizer comprising a first ammonium sulfate crystallizer and a second ammonium sulfate crystallizer. In the first ammonium sulfate crystallizer, the ammonium sulfate mother liquor is heated and concentrated, and then a solid liquid. Separating, to obtain an ammonium sulfate crystal having a first particle size, and returning the separated first filtrate to the first ammonium sulfate crystallization tank, while in the second ammonium sulfate crystallization apparatus, In the method for producing ammonium sulfate, which is concentrated by heating and solid-liquid separation to obtain an ammonium sulfate crystal having a second particle size larger than the first particle size,
A portion of the second filtrate to which sulfamic acid has been added is not supplied to the first ammonium sulfate crystallizer, and water evaporated during the concentration of the ammonium sulfate mother liquor in the second ammonium sulfate crystallizer is removed. A method for producing ammonium sulfate, wherein a part of condensed ammonium sulfate condensed water is added to the second filtrate to which sulfamic acid has been added, and then returned to the second ammonium crystallization tank. Ammonium sulfate saturated tower for absorbing ammonia contained in the coke oven gas by spraying dilute sulfuric acid on the coke oven gas that has undergone the desulfurization step, and an ammonium sulfate mother liquor that is the diluted sulfuric acid that has absorbed ammonia are concentrated to obtain an ammonium sulfate crystal. The first ammonium sulfate crystallizing apparatus includes two systems of ammonium sulfate crystallizers each including a first ammonium sulfate crystallizer and a second ammonium sulfate crystallizer, and the first ammonium sulfate crystallizer stores the first ammonium sulfate crystal. A first evaporating tank, a first heater for heating the ammonium sulfate mother liquor, a first evaporating tank for evaporating the water contained in the ammonium sulfate mother liquor, and a first for condensing the water evaporated from the first evaporating tank. A condenser, a first separator obtained by solid-liquid separation of the ammonium sulfate mother liquor which has been heated and concentrated to obtain an ammonium sulfate crystal having a first particle size, and a first filtrate separated by the first separator And a first filtrate supply pipe that returns the first ammonium sulfate crystallization tank to the first ammonium sulfate crystallization tank. The ammonium sulfate crystallization apparatus comprises: a second ammonium crystallization tank that stores the ammonium sulfate mother liquor; a second heater that heats the ammonium sulfate mother liquor; and a second evaporation tank that evaporates water contained in the ammonium sulfate mother liquor. A second separator for solid-liquid separation of the ammonium sulfate mother liquor concentrated by heating to obtain an ammonium sulfate crystal having a second particle size, and a part of the second filtrate separated by the second separator A second filtrate supply pipe for supplying the first ammonium sulfate crystallizer to the first ammonium sulfate crystallizer, and a third filtrate supply pipe for returning the remainder of the second filtrate to the second ammonium sulfate crystallizer. In the ammonium sulfate production facility,
Without providing the second filtrate supply pipe, all the second filtrate is returned to the second ammonium sulfate crystallization tank by the third filtrate supply pipe, and obtained by the second condenser. An ammonium sulfate production facility comprising an ammonium sulfate condensed water supply pipe for supplying a part of the produced ammonium sulfate condensed water to the second ammonium sulfate crystallization tank.

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