JP7552661B2 - Method for refining coke oven gas - Google Patents

Description

The present invention relates to coke oven gas purification, and in particular to a method for purifying coke oven gas that can reduce the amount of industrial water used.

Conventionally, gas generated when coal is inserted into the carbonization chamber of a coke oven and carbonized (hereinafter referred to as "C gas") contains a large amount of fuel components such as hydrogen, methane, and carbon monoxide, and has a high calorific value of more than 20,000 kJ/ ^m3 . Therefore, this gas has been recovered and reused as fuel gas for blast furnaces, coke ovens, heating furnaces, and boilers.

At that time, the C gas discharged from the coke oven contains various substances such as tar, moisture, ammonia, hydrogen sulfide, and cyanide, and in order to use it as fuel, it is necessary to remove these combustion-inhibiting and harmful substances. For this reason, it is common to turn it into fuel gas through purification to remove these combustion-inhibiting and harmful substances (see, for example, Patent Document 1).

In addition, during the refining process of the above-mentioned C gas, a large amount of water derived from coal is generated as wastewater. Because this wastewater contains a large amount of ammonia and organic matter, it is discharged into the sea after the ammonia and organic matter are removed in a wastewater treatment facility.

FIG. 1 is a diagram showing a general C gas refining flow. Specifically, C gas is refined into fuel gas as follows. That is, first, C gas 1 from which naphthalene, which causes equipment blockage, is recovered after cooling C gas discharged from a coke oven (not shown) is introduced into a desulfurization facility 2 to remove hydrogen sulfide (desulfurization process). Next, C gas 3 from which hydrogen sulfide has been removed is introduced into ammonia removal facility 4 to remove ammonia components, which cause nitrogen oxides (NO _x ), from C gas 3 (deammoni- zation process). Thereafter, C gas 5 from which ammonia has been removed is cooled, and the light oil components in C gas 5 are recovered to refine C gas discharged from a coke oven into fuel gas.

As a desulfurization method in the above-mentioned desulfurization step, wet desulfurization methods such as the Takahax method and the Fumax method are known, in which an absorbing liquid such as an alkaline aqueous solution is brought into contact with C gas to absorb the hydrogen sulfide contained in the C gas into the absorbing liquid. Another known wet desulfurization method is to spray an absorbing liquid into an absorption tower having a packed bed, pass C gas through the absorption tower, and allow the sprayed alkaline aqueous solution to absorb the hydrogen sulfide in the C gas.

2 is a diagram showing an example of a desulfurization facility based on such a wet desulfurization method. The desulfurization facility 2 shown in this figure has an absorption tower 21 for absorbing hydrogen sulfide contained in the C gas 1 into an absorption liquid _L1 , and a regeneration tower 22 for stripping (removing) hydrogen sulfide from the absorption liquid _L1 that has absorbed hydrogen sulfide and lost its activity, thereby regenerating the absorption liquid L1.

The desulfurization treatment of the C gas 1 in the desulfurization equipment 2 is carried out as follows. That is, first, an alkaline absorbing solution _L1 such as ammonia water is introduced to the upper part of the absorption tower 21 and sprayed with a spray, and the C gas 1 introduced into the absorption tower 21 and the absorbing solution _L1 are brought into contact with each other in a countercurrent manner. Then, since the alkaline absorbing solution _L1 has the ability to absorb hydrogen sulfide, it absorbs the hydrogen sulfide contained in the C gas 1 and drops into the absorbing solution _L1 remaining at the lower part of the absorption tower 21. In this way, the absorbing solution _L1 is circulated in the absorption tower 21, the hydrogen sulfide contained in the C gas 1 is absorbed by the sprayed absorbing solution _L1 , and the C gas 3 from which hydrogen sulfide has been removed is discharged from the top of the absorption tower 21.

On the other hand, a part of the absorbing solution _L1 that has been inactivated by absorbing hydrogen sulfide and that is retained in the lower part of the absorption tower 21 is introduced into the regeneration tower 22, and the regeneration air G _A is introduced into the regeneration tower 22 to remove the hydrogen sulfide absorbed in the absorbing solution _L1 , thereby regenerating the absorbing solution _L1 . The removed hydrogen sulfide is discharged to the outside of the tower as waste air G _B , and the regenerated active absorbing solution _L1 is introduced to the upper part of the absorption tower 21 and used again to absorb hydrogen sulfide. In this way, the absorbing solution _L1 is circulated between the absorption tower 21 and the regeneration tower 22, whereby the C gas 1 can be continuously desulfurized.

In the above-described desulfurization equipment 2, in order to extract impurities and the like contained in the absorbing solution _L1 and to keep the properties of the absorbing solution _L1 constant, a predetermined amount of the absorbing solution _L1 discharged from the absorption tower 21 is extracted to the outside of the desulfurization equipment 2. Then, in order to replenish the extracted absorbing solution _L1 , industrial water is added to the absorption tower 21. Also, in order to increase the absorption efficiency of hydrogen sulfide in the absorbing solution _L1 , ammonia water is also added separately.

The absorption liquid _L1 extracted from the desulfurization equipment 2 is called desulfurization waste liquid 6, and is supplied to a wet oxidation equipment 7, where the sulfur content contained in the desulfurization waste liquid 6 is oxidized to sulfate or sulfuric acid. The desulfurization waste liquid 6 from which the sulfur content has been oxidized (hereinafter referred to as "oxidized liquid" 8) is then subjected to a dechlorination equipment 9 to remove chlorine content (dechlorination step).

Figure 3 is a diagram showing an example of a dechlorination facility 9. The dechlorination facility 9 shown in this figure has a dechlorination resin tower 43 that absorbs the chlorine contained in the oxidation liquid 8 into a resin, an ammonium sulfate condensed water tank 41 that stores industrial water to be supplied as regenerating liquid to the dechlorination resin that has absorbed chlorine and lost its absorbing power, and an ammonium sulfate condensed water pump 42 that supplies the industrial water stored in the ammonium sulfate condensed water tank 41 to the dechlorination resin tower 43.

The oxidized liquid 8 discharged from the wet oxidation equipment 7 is introduced into the dechlorination resin tower 43 of the dechlorination equipment 9, where the chlorine contained in the oxidized liquid 8 is absorbed into the dechlorination resin. The oxidized liquid 8 from which the chlorine has been removed is discharged from the dechlorination resin tower 43 as ammonium sulfate mother liquor (first ammonium sulfate mother liquor) 10, and introduced into the ammonium sulfate crystallizer 11 described below.

The dechlorination resin stored in the dechlorination resin tower 43 loses its absorbing power as it repeatedly absorbs the chlorine contained in the oxidizing liquid 8. Therefore, as necessary, industrial water stored in the ammonium sulfate condensate tank 41 is introduced into the dechlorination resin tower 43 by the ammonium sulfate condensate pump 42 and supplied to the dechlorination resin to regenerate the dechlorination resin. The industrial water used to regenerate the dechlorination resin is sent to the wastewater treatment facility 15, which will be described later.

Returning to FIG. 1, the C gas 3 that has undergone the desulfurization process is introduced into the deammonification equipment 4, where the ammonia contained in the C gas 3 is removed. This ammonia removal can be achieved by reacting the C gas with dilute sulfuric acid and recovering it as ammonium sulfate (hereinafter referred to as "ammonium sulfate"). FIG. 4 is a diagram showing an example of a deammonification equipment. The deammonification equipment 4 shown in this figure has an ammonium sulfate saturation tower 51, a mother liquor circulation tank 52, and a pump 53.

In this deammonification equipment 4, C gas 3 from which hydrogen sulfide has been removed through a desulfurization process is introduced into an ammonium sulfate saturation tower 51, and dilute sulfuric acid is sprayed onto it by a spray and brought into countercurrent contact with the C gas 3 introduced into the ammonium sulfate saturation tower 51. Then, the ammonia contained in the C gas 3 is absorbed, and the ammonium sulfate mother liquid _L2 falls and accumulates at the bottom of the ammonium sulfate saturation tower 51.

Here, a portion of the ammonium sulfate mother liquor _L2 remaining in the lower part of the ammonium sulfate saturation tower 51 is recovered in the mother liquor circulation tank 52, and after concentrated sulfuric acid S is added in the mother liquor circulation tank 52, it is introduced by the pump 53 to the upper part of the ammonium sulfate saturation tower 51 and sprayed again. In this manner, the ammonium sulfate mother liquor _L2 is circulated between the ammonium sulfate saturation tower 51 and the mother liquor circulation tank 52 to continuously remove the ammonia content in the C gas 3, and the C gas 5 from which the ammonia has been removed is discharged from the ammonium sulfate saturation tower 51.

Meanwhile, the remainder of the ammonium sulfate mother liquor _L2 remaining in the lower portion of the ammonium sulfate saturation tower 51 is discharged from the ammonium sulfate saturation tower 51 as ammonium sulfate mother liquor (second ammonium sulfate mother liquor) 10. The discharged ammonium sulfate mother liquor 10 is introduced into an ammonium sulfate crystallizer 11 together with the ammonium sulfate mother liquor (first ammonium sulfate mother liquor) 10 discharged from the dechlorination equipment 9, where the ammonium sulfate contained in the ammonium sulfate mother liquor 10 is crystallized and recovered as crystalline ammonium sulfate. FIG. 5 shows an example of an ammonium sulfate crystallizer that crystallizes the ammonium sulfate contained in the ammonium sulfate mother liquor 10. The ammonium sulfate crystallizer 11 shown in this figure has an ammonium sulfate crystallization tank 71, a heater 72, an evaporation tank 73, and a condenser 74.

The ammonium sulfate mother liquor 10 discharged from the dechlorination equipment 9 and the ammonium sulfate saturation tower 51 is introduced into the ammonium sulfate crystallization tank 71 of the ammonium sulfate crystallization device 11. The introduced ammonium sulfate mother liquor 10 is heated by the heater 72 and supplied to the evaporation tank 73, where the water contained in the ammonium sulfate mother liquor 10 is evaporated and concentrated. The concentrated ammonium sulfate mother liquor 10 is returned to the ammonium sulfate crystallization tank 71, heated again by the heater 72, and supplied to the evaporation tank 73. In this way, the ammonium sulfate mother liquor 10 is circulated between the ammonium sulfate crystallization tank 71 and the evaporation tank 73, where ammonium sulfate is crystallized and precipitated. The precipitated slurry containing crystalline ammonium sulfate is discharged from the bottom of the ammonium sulfate crystallization tank 71 and transported to an ammonium sulfate drying facility (not shown) where it is dried using a centrifuge, a dryer, or the like. In this way, the dried crystalline ammonium sulfate can be recovered.

Meanwhile, steam 12 containing ammonium sulfate is discharged from the top of the evaporation tank 73. The discharged ammonium sulfate-containing steam 12 is condensed by a condenser 74, and the resulting ammonium sulfate condensate 13 is sent to wastewater treatment equipment 15, where the ammonia contained in the ammonium sulfate condensate 13 is decomposed, and then discharged into the sea as discharge water 16.

The ammonium sulfate condensate 13 obtained by the condenser 74 contains a large amount of free ammonia derived from the ammonium sulfate mother liquor 10, but if such ammonium sulfate condensate 13 is treated in the wastewater treatment facility 15, the load on the wastewater treatment facility 15 increases. Furthermore, a shortage of industrial water has become evident, particularly in industrial areas, and reducing the amount of industrial water used has also become an issue for factories.

Therefore, the present applicant has proposed in Patent Document 2 a method for reducing the load on the wastewater treatment facility 15 and reducing the amount of industrial water used by using the ammonium sulfate condensate 13 as the hydrogen sulfide absorbing liquid _L1 in the desulfurization facility 2.

JP 2001-81479 A JP 2016-035015 A

The method described in Patent Document 2 above can reduce the load on the wastewater treatment facility 15 and reduce the amount of industrial water used. However, the demand for reducing the amount of industrial water used is becoming more stringent every year, and there is still room for improvement in reducing the amount of industrial water used.

The present invention was made in consideration of the above problems, and its purpose is to propose a method for refining coke oven gas that can reduce the amount of industrial water used.

The inventors have thoroughly investigated ways to solve the above problems. As a result, they have discovered that it is extremely effective to supply at least a portion of the ammonium sulfate condensate, which has conventionally been supplied as an absorption liquid for hydrogen sulfide in wastewater treatment equipment and the desulfurization process, as a regenerating liquid for the dechlorination resin used in the dechlorination process, and have completed the present invention.

That is, the gist and configuration of the present invention are as follows.
(1) A method for purifying coke oven gas, which comprises treating coke oven gas containing hydrogen sulfide to produce an oxidized liquid, removing chlorine contained in the oxidized liquid by absorbing it into a dechlorination resin, and recovering ammonium sulfate crystals from the resulting ammonium sulfate mother liquor,
A method for purifying coke oven gas, comprising supplying at least a portion of ammonium sulfate-containing ammonium sulfate condensate produced during crystallization of the crystalline ammonium sulfate as a regenerating liquid for the dechlorination resin.

(2) A method for purifying coke oven gas, comprising contacting coke oven gas discharged from a coke oven with an absorbing liquid to remove hydrogen sulfide contained in the coke oven gas by absorbing it into the absorbing liquid, spraying dilute sulfuric acid onto the coke oven gas from which the hydrogen sulfide has been removed to remove ammonia contained in the coke oven gas by absorbing it into the dilute sulfuric acid, and refining the coke oven gas into a fuel gas, while oxidizing a part of the absorbing liquid that has absorbed the hydrogen sulfide to form an oxidized liquid, and then absorbing and removing chlorine contained in the oxidized liquid by a dechlorination resin to obtain a first ammonium sulfate mother liquor, and recovering crystalline ammonium sulfate from the second ammonium sulfate mother liquor that is the dilute sulfuric acid that has absorbed the ammonia,
A method for purifying coke oven gas, comprising supplying at least a portion of ammonium sulfate-containing ammonium sulfate condensate produced during crystallization of the crystalline ammonium sulfate as a regenerating liquid for the dechlorination resin.

(3) A method for purifying coke oven gas according to (1) or (2), in which the pH of at least a portion of the ammonium sulfate-containing ammonium sulfate condensate is adjusted to 4 or more and 7 or less, and then supplied as a regenerating liquid for the dechlorination resin.

(4) A method for purifying coke oven gas according to any one of (1) to (3), in which a portion of the ammonium sulfate-containing ammonium sulfate condensate produced during crystallization of the crystalline ammonium sulfate is supplied as make-up water for the absorption liquid during recovery of hydrogen sulfide from the coke oven gas.

(5) A method for purifying coke oven gas according to any one of (2) to (4), wherein the absorption liquid is ammonia water.

(6) A method for purifying coke oven gas according to any one of (2) to (5), in which a portion of the ammonium sulfate-containing ammonium sulfate condensate produced during crystallization of the crystalline ammonium sulfate is supplied as makeup water when a portion of the absorption liquid that has absorbed the hydrogen sulfide is oxidized to produce an oxidized liquid.

According to the present invention, the ammonium sulfate condensate that was previously supplied to wastewater treatment equipment is now supplied as a regenerating liquid for dechlorination resin in dechlorination equipment, thereby reducing the amount of industrial water used.

FIG. 1 is a flow diagram of a conventional method for purifying C gas. FIG. 1 is a diagram showing an example of a desulfurization facility. FIG. 1 is a diagram showing an example of a dechlorination facility. FIG. 1 is a diagram showing an example of a deammonification facility. FIG. 1 is a diagram showing an example of an ammonium sulfate crystallizer. FIG. 1 is a flow diagram of a method for purifying C gas according to the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Fig. 6 shows a flow diagram of the method for purifying C gas according to the present invention. The same components as those shown in Fig. 1 are given the same reference numerals. As shown in this figure, the method for purifying C gas according to the present invention is characterized in that at least a part of the ammonium sulfate condensed water 13 generated when ammonium sulfate is crystallized from the ammonium sulfate mother liquor is replenished as a substitute for industrial water when regenerating the dechlorination resin that has absorbed chlorine in the dechlorination step.

In the process of thoroughly studying ways to reduce the amount of industrial water used in factories such as steelworks, the inventors focused on the industrial water used in the dechlorination equipment 9. As described above, the dechlorination resin contained in the dechlorination resin tower 43 of the dechlorination equipment 9 loses its chlorine absorption capacity as it continues to absorb chlorine, so the absorption capacity of the dechlorination resin is regenerated using industrial water. The industrial water used in this process is introduced into the wastewater treatment equipment 15, where it is treated before being discharged into the sea.

Meanwhile, the ammonium sulfate condensate 13 obtained by the condenser 74 of the ammonium sulfate crystallizer 11 is also introduced into the wastewater treatment facility 15, where the ammonia contained in the ammonium sulfate condensate 13 is decomposed and then discharged into the sea.

The inventors then came up with the idea of replenishing at least a portion of the ammonium sulfate condensate 13 sent to the wastewater treatment facility 15 as a replacement for the industrial water conventionally used to regenerate the dechlorination resin, and thus completed the present invention. Each step of the C gas purification method of the present invention will be described below.

First, the coke oven gas discharged from the coke oven is at a high temperature of around 1000°C, so it is directly cooled by contacting it with ammonia water (ammonia water) in a dry main, and then cooled to around 35°C using a direct and/or indirect primary cooler, etc.

Next, the cooled C gas is introduced into a naphthalene recovery facility, and naphthalene, which causes the equipment to clog, is recovered from the cooled C gas. A method for removing naphthalene using absorbent oil is widely known as a method for recovering naphthalene, and this method can also be used in the present invention.

Then, the C gas 1 from which naphthalene has been removed is introduced into the desulfurization equipment 2, and the hydrogen sulfide contained in the C gas 1 is removed. The specific desulfurization method using the desulfurization equipment 2 shown in Figure 2 is as described above, and therefore will not be described here.

Then, the C gas 3 from which hydrogen sulfide has been removed is introduced into the deammonification equipment 4, and the ammonia contained in the C gas 3 is removed. The specific deammonification method using the deammonification equipment 4 shown in FIG. 4 is as described above, and will not be described further. In the conventional method shown in FIG. 1, all of the ammonium sulfate condensate 13 obtained by the condenser 74 was supplied to the wastewater treatment equipment 15 for treatment, but in the present invention, as shown in FIG. 6, at least a portion of the ammonium sulfate condensate 13 is supplied to the dechlorination equipment 9 as a regenerating liquid for the dechlorination resin in the dechlorination process. This makes it possible to reduce the amount of industrial water used.

Then, the C gas 5 from which the ammonia has been removed and discharged from the top of the ammonium sulfate saturation tower 51 is introduced into a light oil recovery facility (not shown) to recover the light oil contained in the C gas 5. The light oil is generally recovered by an absorption method using absorbent oil, in which the C gas 5 and the absorbent oil are brought into countercurrent contact to physically absorb the light oil contained in the C gas 5.

As described above, the ammonium sulfate condensate 13 contains a large amount of free ammonia that absorbs the hydrogen sulfide contained in the C gas 1 in the desulfurization process, and is an alkaline solution. Therefore, if the ammonium sulfate condensate 13 is supplied to the dechlorination equipment 9 as is, the calcium contained in the oxidizing liquid 8 may precipitate and cause the dechlorination equipment 9 to become clogged. Therefore, as shown in FIG. 6, it is preferable to provide a pH adjustment tank 14 on the upper stage of the dechlorination equipment 9 and adjust the pH of the ammonium sulfate condensate 13 to 4 to 7 before supplying it as a regenerating liquid for the dechlorination resin. This prevents the calcium contained in the oxidizing liquid 8 from precipitating in the dechlorination equipment 9, and prevents the dechlorination equipment 9 from becoming clogged.

In this way, at least a portion of the ammonium sulfate condensate 13 that was previously supplied to the wastewater treatment facility 15 is now replenished as a regenerating liquid for the dechlorination resin used in the dechlorination process, making it possible to reduce the amount of industrial water used to refine coke oven gas.

In addition to the above-mentioned method of the present invention, it is preferable to supply a part of the ammonium sulfate condensate 13 as makeup water for the absorption solution _L1 when recovering hydrogen sulfide from the C gas 1 in the desulfurization equipment 2, as described in Patent Document 3. This makes it possible to further reduce the amount of industrial water used.

It is also preferable to supply a part of the ammonium sulfate condensed water 13 as makeup water when a part of the absorption liquid _L1 (desulfurization waste liquid 6) that has absorbed hydrogen sulfide is oxidized in the wet oxidation equipment 7 to produce the oxidation liquid 8. The supplied ammonium sulfate condensed water 13 can be used as seal water for a pump or makeup water for diluting the desulfurization waste liquid 6. This can further reduce the amount of industrial water used.

In the above explanation, when crystallizing ammonium sulfate crystals in the ammonium sulfate crystallizer 11, both the ammonium sulfate mother liquor (first ammonium sulfate mother liquor) 10, which is the oxidized liquid 8 from which chlorine has been removed in the dechlorination equipment 9, and the ammonium sulfate mother liquor (second ammonium sulfate mother liquor) 10 discharged from the ammonium sulfate saturation tower 51 are introduced into the ammonium sulfate crystallizer 11. However, as a result of further investigation by the present inventor, it has been found that it is also possible to crystallize ammonium sulfate crystals by introducing only the ammonium sulfate mother liquor (first ammonium sulfate mother liquor) 10 discharged from the dechlorination equipment 9 into the ammonium sulfate crystallizer 11. In this case, the amount of industrial water used can also be reduced.

The following describes examples of the present invention, but the present invention is not limited to these examples.

(Example 1)
Coke oven gas was refined according to the refining flow of C gas shown in Fig. 6. That is, first, C gas 1 discharged from a coke oven and cooled to remove naphthalene was introduced into a desulfurization facility 2 to remove hydrogen sulfide.
Next, the C gas 3 from which hydrogen sulfide has been removed is introduced into ammonia removal equipment 4, where ammonia, which causes nitrogen oxides, is removed from the C gas 3 from which hydrogen sulfide has been removed.
On the other hand, the desulfurization waste liquid 6 discharged from the desulfurization tower 21 of the desulfurization equipment 2 was introduced into a wet oxidation equipment 7, where the sulfur content was oxidized, and the obtained oxidized liquid 8 was introduced into a dechlorination equipment 9, where the chlorine contained in the oxidized liquid 8 was removed. The obtained ammonium sulfate mother liquid (first ammonium sulfate mother liquid) 10 was introduced into an ammonium sulfate crystallizer 11.
In addition, the ammonium sulfate mother liquor (second ammonium sulfate mother liquor) 10 discharged from the ammonium sulfate saturation tower 51 of the deammonification facility 4 was introduced into the ammonium sulfate crystallizer 11 together with the ammonium sulfate mother liquor 10 obtained from the dechlorination facility 9, and the ammonium sulfate contained in the ammonium sulfate mother liquor 10 was crystallized to obtain crystalline ammonium sulfate. At that time, the ammonium sulfate-containing steam 12 discharged from the evaporation tank 73 was condensed by the condenser 74 to obtain ammonium sulfate condensed water 13. Of the ammonium sulfate condensed water 13 obtained per day (432 tons), 151 tons were supplied as makeup water for the absorption liquid _L1 of the desulfurization facility 2, 120 tons were supplied as makeup water for the wet oxidation facility 7, and 144 tons were supplied as a regenerating liquid for the dechlorination resin of the dechlorination facility 9, and the remaining 17 tons and the factory wastewater were introduced into the wastewater treatment facility 15, where the ammonia contained in the ammonium sulfate condensed water 13 was decomposed, and then discharged into the sea as the discharged water 16. In addition, a pH adjustment tank 14 was provided above the dechlorination equipment 9, and the pH of the ammonium sulfate condensate 13 was adjusted to 6 to 8 before being supplied to the condensate tank 41 of the dechlorination equipment 9.
On the other hand, the C gas 5 from which ammonia was removed and discharged from the ammonium sulfate saturator of the deammonification equipment 4 was cooled and then the light oil contained in the C gas 5 was removed. In this way, the C gas discharged from the coke oven was refined into a fuel gas. The conditions for refining the C gas are shown in Table 1.

Comparative Example
C gas discharged from a coke oven was purified according to the C gas purification flow shown in Figure 1. That is, all of the ammonium sulfate condensate 13 obtained in the invention example was supplied to a wastewater treatment facility 15. In addition, 151 tons of industrial water was supplied per day to the desulfurization facility 2, 120 tons of industrial water was supplied per day to the wet oxidation facility 7, and 144 tons of industrial water was supplied per day to the dechlorination facility 9. All other conditions were the same as those in the invention examples. The conditions for C gas purification are shown in Table 1.

(Example 2)
As in Example 1, coke oven gas was purified according to the purification flow of C gas shown in Fig. 6. However, the ammonium sulfate mother liquor (second ammonium sulfate mother liquor) 10 discharged from the ammonium sulfate saturation tower 51 of the deammonification equipment 4 was not introduced into the ammonium sulfate crystallizer 11, and only the ammonium sulfate mother liquor (first ammonium sulfate mother liquor) 10 obtained from the dechlorination equipment 9 was introduced into the ammonium sulfate crystallizer 11, and the ammonium sulfate contained in the ammonium sulfate mother liquor (first ammonium sulfate mother liquor) 10 was crystallized to obtain crystalline ammonium sulfate. Of the ammonium sulfate condensate water 13 (312 tons) obtained per day, 144 tons was supplied as makeup water for the absorption liquid _L1 of the desulfurization equipment 2, 24 tons was supplied as makeup water for the wet oxidation equipment 7, and 144 tons was supplied as regenerating liquid for the dechlorination resin of the dechlorination equipment 9. In addition, a pH adjustment tank 14 was provided on the upper stage of the dechlorination equipment 9, and the pH of the ammonium sulfate condensate 13 was adjusted to 6 to 8 before being supplied to the condensate tank 41 of the dechlorination equipment 9.
On the other hand, the C gas 5 from which ammonia was removed and discharged from the ammonium sulfate saturator of the deammonification equipment 4 was cooled, and then the light oil contained in the C gas 5 was removed. In this manner, the C gas discharged from the coke oven was refined into a fuel gas. All other conditions were the same as those in Example 1. The conditions for refining the C gas are shown in Table 1.

As is clear from Table 1, in Examples 1 and 2, there is no need to supply industrial water to the dechlorination equipment 9, and the amount of industrial water used is reduced compared to the comparative example.

Possible industrial applications

According to the present invention, at least a portion of the ammonium sulfate condensate that was previously supplied to wastewater treatment equipment is replenished as regenerating liquid for the dechlorination resin in the dechlorination process, which reduces the amount of industrial water used and is therefore useful in the steel industry.

1, 3, 5 C gas 2 Desulfurization equipment 4 Deammonia equipment 6 Desulfurization waste liquid 7 Wet oxidation equipment 8 Oxidized liquid 9 Dechlorination equipment 10 Ammonium sulfate mother liquor 11 Ammonium sulfate crystallization device 12 Ammonium sulfate-containing steam 13 Ammonium sulfate condensed water 14 pH adjustment tank 15 Wastewater treatment equipment 16 Discharge water 21 Absorption tower 22 Regeneration tower 41 Ammonium sulfate condensed water tank 42 Ammonium sulfate condensed water pump 43 Dechlorination resin tower 51 Ammonium sulfate saturation tower 52 Mother liquor circulation tank 53 Pump 71 Ammonium sulfate crystallization tank 72 Heater 73 Evaporation tank 74 Condenser G _A Regeneration air G _B Waste air L ₁ Absorption liquid L ₂ Ammonium sulfate mother liquor

Claims (6)

A method for purifying coke oven gas, comprising treating coke oven gas containing hydrogen sulfide to produce an oxidized liquid, removing chlorine contained in the oxidized liquid by absorbing it into a dechlorination resin, and recovering ammonium sulfate crystals from the resulting ammonium sulfate mother liquor, comprising:
A method for purifying coke oven gas, comprising supplying at least a portion of ammonium sulfate-containing ammonium sulfate condensate produced during crystallization of the crystalline ammonium sulfate as a regenerating liquid for the dechlorination resin. A method for purifying coke oven gas, comprising the steps of: bringing coke oven gas discharged from a coke oven into contact with an absorbing liquid to remove hydrogen sulfide contained in the coke oven gas by absorbing it into the absorbing liquid; spraying dilute sulfuric acid onto the coke oven gas from which the hydrogen sulfide has been removed to remove ammonia contained in the coke oven gas by absorbing it into the dilute sulfuric acid; refining the coke oven gas into a fuel gas; and oxidizing a portion of the absorbing liquid which has absorbed the hydrogen sulfide to form an oxidized liquid, and then removing chlorine contained in the oxidized liquid by absorbing it into a dechlorination resin to obtain a first ammonium sulfate mother liquor; and recovering crystalline ammonium sulfate from the second ammonium sulfate mother liquor which is the dilute sulfuric acid which has absorbed the ammonia,
A method for purifying coke oven gas, comprising supplying at least a portion of ammonium sulfate-containing ammonium sulfate condensate produced during crystallization of the crystalline ammonium sulfate as a regenerating liquid for the dechlorination resin. The method for purifying coke oven gas according to claim 1 or 2, wherein the pH of at least a portion of the ammonium sulfate-containing ammonium sulfate condensate is adjusted to 4 or more and 7 or less, and then the ammonium sulfate condensate is supplied as a regenerating liquid for the dechlorination resin. The method for purifying coke oven gas according to claim 1 or 2, wherein a portion of the ammonium sulfate-containing ammonium sulfate condensate produced during crystallization of the crystalline ammonium sulfate is supplied as make-up water for the absorption liquid during recovery of hydrogen sulfide from the coke oven gas. The method for purifying coke oven gas according to claim 2, wherein the absorption liquid is aqueous ammonia. 3. The method for purifying coke oven gas according to claim 2, wherein a part of ammonium sulfate-containing ammonium sulfate condensed water generated when the crystalline ammonium sulfate is crystallized is supplied as makeup water when a part of the absorption liquid having absorbed the hydrogen sulfide is oxidized to obtain an oxidized liquid.

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