JP2001081479A - Purification method and purification equipment for coke oven gas - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the ammonia concentration in an absorption solution of a desulfurization tower using ammonia vapor having a high concentration and containing no impurities,
Provided is a method of purifying a coke oven gas and a purification facility capable of improving desulfurization efficiency. SOLUTION: A desulfurization step having a desulfurization tower using an aqueous ammonia solution as an absorbent and a desulfurization absorbent regenerating tower, an ammonia absorption tower using an aqueous solution of ammonium dihydrogen phosphate as an absorbent, an ammonia stripper, and an ammonia distillation tower are provided. A method for purifying coke oven gas comprising a deammonification step, wherein the bottom liquid flowing out of the bottom of the ammonia distillation tower is indirectly heated by the bottom liquid flowing out of the bottom of the ammonia stripper to evaporate the ammonia. And a purification method of a coke oven gas for supplying the obtained ammonia vapor to a desulfurization absorption liquid regeneration tower and / or a desulfurization tower, and a purification facility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for purifying coke oven gas for desulfurization and deammonification of coke oven gas, and more particularly to a method of purifying coke oven gas capable of improving desulfurization efficiency. And purification equipment.

[0002]

2. Description of the Related Art A coke oven gas contains a sulfur compound and ammonia. In the coke oven, a coke oven gas purification facility for desulfurization and deammonification of the coke oven gas is additionally provided. Sulfur compounds of the coke oven gas is mainly hydrogen sulfide (H ₂ S), the content thereof is about 3 to 7 g / Nm ^3.

As a desulfurization method of coke oven gas, there are a wet method and a dry method, and a wet method is often used for gas treatment of a large volume. As the wet desulfurization method, a diamond method, a Takahax method, a Humax-Rodax method, and the like are used. Further, as a method for deammonifying coke oven gas, a fossum method in which coke oven gas is brought into contact with an aqueous solution of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) is used.

[0004] In the diamond type method, which is the above-mentioned wet desulfurization method, hydrogen sulfide (H ₂ S) in coke oven gas is selected with ammonia water by bringing coke oven gas and ammonia water into contact in countercurrent in a desulfurization tower. The method comprises an absorption step of absorbing the liquid, and a regeneration step of the absorbing liquid for stripping H ₂ S from the absorbing liquid. The Humax-Rodax method and the Takahax method use NH as an absorbent for desulfurization absorption liquid.
_{Using 4} OH or Na ₂ CO ₃ , the coke oven gas is brought into contact with the absorbing solution in a desulfurization tower to absorb H ₂ S in the gas, and the sulfur compound in the absorbing solution after desulfurization is reacted with air and a catalyst. To generate colloidal sulfur and regenerate the absorbent.

As the wet desulfurization method, the diamondox method has an advantage that the amount of waste liquid to be treated is small, but the desulfurization rate is lower than other methods, and an improvement in the desulfurization rate has been demanded. Further, in the Humax-Rodax method and the Takahax method, further improvement in the desulfurization rate has been required. As means for increasing the absorption efficiency of hydrogen sulfide in the desulfurization tower, for example, the following methods are employed in the diamondox method, but in any case, an increase in energy consumption or an increase in equipment investment is caused.

Reduction of the average operating temperature of the absorption tower due to heat exchange Increase in the flow ratio between the absorption liquid and the coke oven gas Increase in the hydrogen sulfide removal rate in the regeneration step of the absorption liquid and the concentration of hydrogen sulfide in the absorption liquid at the inlet of the desulfurization tower Reduction Increasing the number of stages in the absorption tower and the number of spray pumps On the other hand, as a method of improving the desulfurization performance of the absorption liquid itself, in order to improve the desulfurization performance by increasing the ammonia concentration in the absorption liquid, a coke oven gas liquid (ams water) A method is known in which ammonia vapor stripped of is supplied to a desulfurization tower.

However, the ammonia vapor obtained by stripping the coke oven gas liquid has a low ammonia concentration, and it is difficult to increase the ammonia concentration in the absorbing solution. Further, in the case of the above-described method, a large amount of impurities such as hydrogen sulfide, carbon dioxide, and cyanide are contained in the ammonia vapor, and as a result, the desulfurization efficiency may decrease.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and increases the concentration of ammonia in the absorption solution of a desulfurization tower by using high-concentration ammonia vapor containing no impurities. It is an object of the present invention to provide a method and a facility for purifying a coke oven gas capable of improving efficiency.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found the following findings.
The present inventors have found (1) to (4) and have reached the present invention. (1) Recovery of excess heat in the fossum method deammonia equipment: In the deammonia equipment by the fossum method, excess heat is generated in the process because ammonia is stripped under high temperature and high pressure conditions.

[0010] Particularly, in the deammonification equipment using the fossum method, the bottom liquid of the ammonia stripper has a high temperature, and there is room for heat recovery. (2) Utilization of the bottoms of the ammonia distillation column: The bottoms of the ammonia distillation column contain ammonia, although the concentration is low, but the ammonia vapor obtained by heating the above-mentioned bottoms is converted to the desulfurization absorption liquid. The desulfurization performance of the desulfurization absorbent can be improved by the addition.

(3) Evaporation and concentration of ammonia in the liquid withdrawn from the bottom of the ammonia distillation column by utilizing the sensible heat of the ammonia stripper at the bottom of the ammonia distillation tower: For example, by indirect heat exchange between the high-temperature column bottom liquid and the ammonia distillation column bottom liquid, the ammonia in the ammonia distillation column column liquid can be evaporated to obtain a high-concentration ammonia vapor.

Further, the desulfurization performance of the desulfurization absorbing solution can be improved by adding the obtained high-concentration ammonia vapor to the desulfurizing absorption solution. (4) By adopting the method of (3) above, while effectively utilizing both the ammonia extractor bottom draw liquid and the excess heat in the fosam method deammonification equipment, which have not been effectively utilized in the past, The desulfurization performance of the desulfurization absorption liquid can be improved.

That is, a first invention is a method of purifying a coke oven gas having a coke oven gas desulfurization step and a deammonification step, wherein the desulfurization step includes a desulfurization tower using an aqueous ammonia solution as an absorbing solution, In the desulfurization step having a desulfurization absorption liquid regeneration tower for regenerating the absorption liquid extracted from the desulfurization tower, the deammonification step includes an ammonia absorption tower using an aqueous solution of ammonium dihydrogen phosphate as an absorption liquid, and the ammonia absorption tower. Ammonium dihydrogen phosphate flowing out of the bottom of the ammonia stripper in a deammonification step having an ammonia stripper for evaporating ammonia in the withdrawn absorbent and an ammonia distillation column for purifying ammonia vapor flowing out of the ammonia stripper From the bottom of the ammonia distillation column by the bottom liquid which is an aqueous solution The refining of coke oven gas characterized in that the ammonia-containing bottom liquid to be discharged is indirectly heated to evaporate the ammonia, and the obtained ammonia vapor is supplied to the desulfurization-absorbing liquid regeneration tower and / or the desulfurization tower. Is the way.

The method of purifying a coke oven gas according to the first preferred embodiment of the first invention is a method of purifying a coke oven gas having a desulfurization step of a coke oven gas and a deammonification step subsequent to the desulfurization step. Wherein the desulfurization step is a desulfurization step including a desulfurization tower using an aqueous ammonia solution as an absorbing liquid, and a desulfurizing absorption liquid regenerating tower for regenerating the absorbing liquid extracted from the desulfurizing tower, wherein the deammonification step includes phosphorus. An ammonia absorption tower using an aqueous solution of ammonium dihydrogen oxide as an absorbing solution, an ammonia stripper for evaporating ammonia in the absorbing solution extracted from the ammonia absorbing tower, and an ammonia distillation tower for purifying ammonia vapor flowing out of the ammonia stripper. Ammonia dihydrogen phosphate flowing out of the bottom of the ammonia stripper in the deammonification step having The ammonia-containing bottom liquid flowing out of the bottom of the ammonia distillation tower is indirectly heated by the bottom liquid which is an aqueous solution to evaporate ammonia, and the obtained ammonia vapor is supplied to the desulfurization-absorbing liquid regeneration tower and / or the desulfurization tank. This is a method for purifying coke oven gas, which is supplied to a tower.

Further, the method for purifying a coke oven gas according to the second preferred embodiment of the first aspect of the present invention is directed to a coke oven gas having a deammonification step of the coke oven gas and a desulfurization step after the deammonification step. The desulfurization step, wherein the desulfurization step includes a desulfurization tower using an aqueous ammonia solution as an absorbent, and a desulfurization absorbent regenerating tower for regenerating the absorbent extracted from the desulfurization tower; Is an ammonia absorbing tower using an aqueous solution of ammonium dihydrogen phosphate as an absorbing solution, an ammonia stripper for evaporating ammonia in the absorbing solution extracted from the ammonia absorbing tower, and an ammonia for purifying ammonia vapor flowing out of the ammonia stripper. In the deammonification step having a distillation column, the phosphoric acid distilling out of the bottom of the ammonia stripper The ammonia-containing bottom liquid flowing out of the bottom of the ammonia distillation tower is indirectly heated by the bottom liquid which is an aqueous ammonium ammonium solution to evaporate ammonia, and the obtained ammonia vapor is supplied to the desulfurization absorption liquid regeneration tower and / or A method for purifying a coke oven gas, comprising supplying the gas to the desulfurization tower.

A second aspect of the present invention relates to a coke oven gas refining facility having a coke oven gas desulfurization facility and a deammonia facility, wherein the desulfurization facility includes a desulfurization column 1 using an aqueous ammonia solution as an absorbing solution; A desulfurization absorption liquid regeneration tower 2 for regenerating the absorption liquid withdrawn from the desulfurization tower 1, wherein the deammonification equipment comprises: an ammonia absorption tower 3 using an aqueous solution of ammonium dihydrogen phosphate as an absorption liquid; An ammonia stripper 4 for evaporating the ammonia in the absorbing liquid extracted from the ammonia stripper 3 and an ammonia distillation column 5 for purifying the ammonia vapor flowing out of the ammonia stripper 4, and the phosphorus flowing out from the bottom of the ammonia stripper 4 The bottom liquid, which is an aqueous solution of ammonium dihydrogen oxide, and the liquid flowing out of the bottom of the ammonia distillation tower 5 A near-containing bottoms liquid to indirect heat exchange, the ammonia concentrator for obtaining ammonia vapor vaporized ammonia from the ammonia-containing bottoms liquid 6
And the ammonia vapor obtained by the ammonia concentrating device 6 is transferred to the desulfurization absorption liquid regeneration tower 2 and / or the desulfurization tower 1
A coke oven gas refining facility having ammonia vapor supply piping systems 7 and 9 for supplying gas to a coke oven.

The coke oven gas refining facility of the first preferred embodiment of the second invention is a coke oven gas refining facility having a coke oven gas desulfurization facility and a deammonia facility in a post-process of the desulfurization facility. Wherein the desulfurization equipment comprises: a desulfurization tower 1 using an aqueous ammonia solution as an absorbing solution;
Desulfurization absorption liquid regeneration tower 2 for regenerating the absorption liquid extracted from
An ammonia absorbing tower 3 using an aqueous solution of ammonium dihydrogen phosphate as an absorbing liquid; and an ammonia stripper 4 for evaporating ammonia in the absorbing liquid extracted from the ammonia absorbing tower 3.
And an ammonia distillation column 5 for purifying ammonia vapor flowing out of the ammonia stripper 4.
Indirect heat exchange is performed between the bottom liquid, which is an aqueous solution of ammonium dihydrogen phosphate, flowing out of the bottom of the ammonia stripper 4 and the bottom liquid containing ammonia flowing out of the bottom of the ammonia distillation column 5 to remove ammonia from the bottom liquid containing ammonia. An ammonia concentrator 6 for evaporating ammonia vapor, an ammonia vapor supply piping system 7 for supplying the ammonia vapor obtained by the ammonia concentrator 6 to the desulfurization absorbent regenerating tower 2 and / or the desulfurization tower 1, 9 is a coke oven gas refining facility,

The coke oven gas refining equipment according to the second preferred embodiment of the second aspect of the present invention includes a coke oven gas deammonia equipment, and a coke oven gas having a desulfurization equipment in a post-process of the deammonia equipment. The desulfurization facility, wherein the desulfurization facility is a desulfurization tower 1 using an aqueous ammonia solution as an absorbing solution.
And a desulfurization absorbent regenerating tower 2 for regenerating the absorbent extracted from the desulfurization tower 1, wherein the deammonification equipment comprises an ammonia absorbing tower 3 using an aqueous solution of ammonium dihydrogen phosphate as an absorbing liquid; An ammonia stripper 4 for evaporating the ammonia in the absorption liquid extracted from the ammonia absorption tower 3 and an ammonia distillation tower 5 for purifying the ammonia vapor flowing out of the ammonia stripper 4 are provided from the bottom of the ammonia stripper 4. An indirect heat exchange between the bottom liquid which is an aqueous solution of ammonium dihydrogen phosphate and the bottom liquid containing ammonia flowing out of the bottom of the ammonia distillation column 5 to evaporate ammonia from the bottom liquid containing ammonia to obtain ammonia vapor. Ammonia concentrator 6 and obtained by the ammonia concentrator 6 A purification equipment of the coke oven gas that comprises said the ammonia vapor desulfurization absorbent regenerator 2 and / or ammonia steam supply piping system 7, 9 to be supplied to the desulfurization tower 1.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. FIG. 1 shows an example of the coke oven gas purification equipment of the present invention by a flow sheet (side view). In FIG. 1, 1 is a desulfurization tower, 2 is a desulfurization absorbent regenerating tower, 3 is an ammonia absorption tower, 4 is an ammonia stripper, 5 is an ammonia distillation tower, and 6 is an ammonia concentrator for recovering high-concentration ammonia vapor (: An indirect heat exchanger), 7 is an ammonia vapor supply piping system, 8 is a flow pipe for bottom liquid of the ammonia stripper tower bottom provided in the ammonia concentrator,
f ₁ is the flow direction of the coke oven gas (hereinafter referred to as COG), f ₂ is the liquid sending direction of the desulfurization absorbing fluid, f ₃ is the liquid sending direction ammonia stripper bottoms bottoms liquid, f ₄ ammonia distillation column bottom Bottom feeding direction of the liquid, f ₅ denotes the flow direction of the high-concentration ammonia vapor.

In the coke oven gas purification equipment shown in FIG. 1, desulfurization and deammonification of the coke oven gas are performed as described below. That is, coke oven gas (: COG)
In the desulfurization tower 1, H ₂ S is removed by an aqueous ammonia solution. The absorption liquid extracted from the desulfurization tower is regenerated by steam heating in the desulfurization absorption liquid regeneration tower 2, and is recycled to the desulfurization tower 1.

In the desulfurization according to the above-mentioned diamond method, COG desulfurization and regeneration of a desulfurization absorbent are carried out according to the following reaction formulas (1) and (2). Desulfurization tower: H ₂ S + NH ₃ → NH ₄ HS ……………… (1) Desulfurization absorption liquid regeneration tower: NH ₄ HS → NH ₃ + H ₂ S …… (2) In step 1, a desulfurization step of selectively absorbing hydrogen sulfide (H ₂ S) in COG with ammonia water by bringing coke oven gas (: COG) and ammonia water into countercurrent, and desulfurization of stripping hydrogen sulfide It consists of a regeneration step of the absorbing liquid.

The desulfurized COG is fed to an ammonia absorption tower 3 using an aqueous solution of ammonium dihydrogen phosphate as an absorbing solution, and deammoniaated to obtain purified COG. The absorption liquid withdrawn from the bottom of the ammonia absorption tower 3 is sent to an ammonia stripper 4, where the ammonia is evaporated by steam heating, the ammonia vapor is purified in the ammonia distillation tower 5, and the purified ammonia is cooled by the subsequent cooling. Collected as cheap.

In the above-described deammonification by the Fossum method, COG is calculated by the following reaction formulas (3) and (4).
Of ammonia and regeneration of the absorbent. Ammonia absorption tower: NH ₃ + NH ₄ H ₂ PO ₄ → (NH ₄ ) ₂ HPO ₄ ………… (3) Ammonia stripper: (NH ₄ ) ₂ HPO ₄ → NH ₄ H ₂ PO ₄ + NH ₃ …… ( 4) As shown in FIG. 1, in the present invention, a high-temperature bottom liquid (ammonia stripper bottom liquid) which is an aqueous solution of ammonium dihydrogen phosphate flowing out of the bottom of the ammonia stripper 4 of the deammonification equipment (fosam method) is used. ) Is used as a heat source to evaporate ammonia in the bottom liquid of the bottom of the ammonia distillation column 5, and the resulting high-concentration ammonia vapor is supplied to the desulfurization absorption liquid regeneration column 2.

That is, as described above, in the deammonification equipment by the Fossum method using an aqueous solution of ammonium dihydrogen phosphate as an absorbing solution, since the stripping of ammonia is performed under high temperature and high pressure conditions, the bottom liquid of the ammonia stripper column bottom is not removed. High temperature. In the present invention, the sensible heat of the high-temperature bottom bottom liquid of the ammonia stripper is used, and preferably, the ammonia distillation column is indirectly heat-exchanged between the high-temperature bottom bottom liquid and the ammonia distillation column bottom liquid. The ammonia in the bottom liquid of the tower is evaporated to obtain a high concentration of ammonia vapor.

Incidentally, the ammonia concentration of the ammonia vapor can be controlled by controlling the operating temperature of the ammonia distillation column 5. The ammonia concentration in the desulfurization absorption solution is determined by the gas-liquid equilibrium with the ammonia concentration in the coke oven gas. To increase the ammonia concentration in the desulfurization absorption solution,
It is necessary to supply a sufficiently high concentration of ammonia vapor to the desulfurization absorber for the vapor-liquid equilibrium of the coke oven gas and the ammonia concentration of the absorber in the desulfurization tower, and it has been difficult to increase the ammonia concentration of the conventional desulfurization absorber. there were.

On the other hand, according to the present invention, the high-concentration ammonia vapor obtained is used as a part of the stripping vapor of the desulfurization absorption liquid regenerating tower of the desulfurization equipment, whereby the ammonia in the desulfurization absorption liquid is used. The concentration increased to about twice the conventional value, and the desulfurization rate of the coke oven gas was improved. The apparatus for heating the bottom liquid flowing out of the bottom of the ammonia distillation tower 5 with the bottom liquid flowing out of the bottom of the ammonia stripper 4 to evaporate ammonia includes a high-temperature bottom liquid flowing out of the bottom of the ammonia stripper 4. Indirect heat exchange between the liquid (aqueous solution of ammonium dihydrogen phosphate) and the bottom liquid flowing out of the bottom of the ammonia distillation column 5 to evaporate ammonia from the bottom liquid of the ammonia distillation column to obtain a high-concentration ammonia vapor. Apparatus 6 can be used.

That is, the above-described ammonia concentrator 6
For example, as shown in FIG. 1, a high-temperature ammonia stripper column bottom liquid distribution pipe (finned tube) 8 is disposed inside a heat exchanger, and the ammonia distillation column column bottom liquid is circulated outside the pipe. Indirect heat exchangers can be used. Further, as the above-mentioned distribution pipe 8, it is preferable to use a finned flexible pipe having fins attached to the outer surface of the flexible pipe.

In the above-described indirect heat exchanger, the bottom liquid of the ammonia distillation tower is heated, ammonia is evaporated, and high-concentration ammonia vapor flows out into the upper pipe,
Ammonia is supplied to the desulfurization absorbent regenerating tower 2 by the ammonia vapor supply piping system 7 and water of the ammonia distillation tower bottom bottom liquid from which ammonia has been removed is discharged into the lower piping.

According to the present invention, the following effects (1) to (3) can be obtained by employing the above method. (1) Improvement of the desulfurization performance of the desulfurization absorption liquid: By recovering ammonia from the bottom liquid extracted from the ammonia distillation column,
A high-concentration ammonia vapor that does not contain impurities such as hydrogen sulfide, carbon dioxide, and cyanide that causes a decrease in the desulfurization efficiency is obtained, and the obtained ammonia vapor is added to the desulfurization absorption liquid to improve the desulfurization performance of the desulfurization absorption liquid. Can be improved.

(2) Efficient use of waste liquid and excess heat: Both the waste liquid extracted from the bottom of the ammonia distillation column and the excess heat in the defoaming method using the Fosam method, which have not been effectively utilized in the past, can be effectively utilized. . (3) Since ammonia is supplied to the desulfurization and absorption liquid regeneration tower in a vapor state, stripping steam in the desulfurization and absorption liquid regeneration tower can be reduced.

The case where the present invention is applied to a coke oven gas refining method and a refining facility having a desulfurization facility based on the diamox method has been described. The present invention has a desulfurization facility based on the Humax Rodax method or the Takahax method. It is also possible to apply to a coke oven gas purification method and purification equipment. FIG. 2 is a flow sheet (side view) showing an example of a coke oven gas purification facility of the present invention in which the above-described desulfurization facility is provided.

In FIG. 2, 9 is an ammonia vapor supply piping system, 10 is a solid-liquid separation device, 11 is a waste liquid treatment device,
Numeral 12 denotes sulfur, and other symbols indicate the same contents as in FIG. In desulfurization equipment of the Humax-Rodax method and the Takahax method, the desulfurization tower 1
Although NH ₄ OH or Na ₂ CO ₃ is used, a method of purifying a coke oven gas using NH ₄ OH as an absorbent of the desulfurization absorption liquid according to the present invention and a purification facility will be described below.

In the desulfurization equipment of the Humax-Rodax method, picric acid is used as a catalyst, and in the desulfurization equipment of the Takahax method, sodium naphthoquinone sulfonate is used as a catalyst. The principle of the desulfurization method of the desulfurization equipment shown in FIG. 2 is as follows. That is, the coke oven gas is brought into contact with a desulfurization absorbing solution containing NH ₄ OH in the desulfurization tower 1 to absorb and remove H ₂ S in the gas.

At this time, other acid gas (HCN, CO ₂ etc.)
Is also absorbed at the same time. The desulfurized absorbing solution that has absorbed H ₂ S is sent to the desulfurizing absorbing solution regenerating tower 2, where sulfur compounds in the absorbing solution are oxidized by the action of air and a catalyst to produce colloidal sulfur. Is regenerated into a desulfurization absorption solution containing NH ₄ OH. If the absorbent is circulated, rodane and thiosulfate are generated and accumulated as side reactions, so a part of the circulating absorbent is extracted and colloidal sulfur is separated into a solid-liquid separator.
After separation at 10, a part of the absorption liquid is treated by the waste liquid treatment device 11.

The deammonification equipment of the coke oven gas purification equipment shown in FIG. 2 is a deammonification equipment using the same fosam method as that of FIG. The method for recovering high-concentration ammonia vapor is the same as that of FIG. 1 described above, except that the high-temperature bottom liquid (aqueous ammonium dihydrogen phosphate) flowing out from the bottom of the ammonia stripper 4 of the deammonification equipment is used as a heat source. This is a method in which ammonia in the bottom liquid of the tower 5 is evaporated to recover high-concentration ammonia vapor.

On the other hand, in the coke oven gas purification equipment shown in FIG. 2, the obtained high-concentration ammonia vapor is supplied to the desulfurization tower 1 by the ammonia vapor supply piping system 9. As a result, according to the present invention, it is possible to effectively utilize both the ammonia extractor bottom draw liquid and the excess heat in the fosam method deammonia equipment, which have not been effectively utilized, and to supply high-concentration ammonia vapor. As a result, the ammonia concentration in the desulfurization absorption liquid increases, and the desulfurization efficiency can be improved.

In the above, the method of purifying a coke oven gas and the purifying equipment provided with a deammonia equipment as a post-process of the desulfurizing equipment as exemplified in FIGS. 1 and 2 have been described. From the basic configuration and principle of the present invention, the present invention can be applied to a coke oven gas purification method and a purification facility in which a desulfurization facility is provided as a post-process of the deammonification facility.

[0038]

EXAMPLES The present invention will be described below more specifically based on examples. The coke oven gas was purified using the coke oven gas purification equipment shown in FIG. In addition,
The throughput of the coke oven gas is 75000 Nm ³ / H. As the ammonia concentrator 6, a high-temperature ammonia stripper bottom bottom liquid circulation pipe (a finned serpentine pipe) 8 is provided inside a heat exchanger, An indirect heat exchanger that circulates the bottom liquid of the ammonia distillation column was used.

In this embodiment, the ammonia in the bottom liquid of the ammonia distillation column 5 is evaporated by using the high-temperature bottom liquid (aqueous ammonium dihydrogen phosphate) flowing out from the bottom of the ammonia stripper 4 of the deammonia equipment as a heat source. The obtained high-concentration ammonia vapor was supplied to the desulfurization-absorbing-liquid regenerating tower 2. As a result, the concentration of free ammonia in the desulfurization absorption liquid increased from about 10 g / l to about 15 g / l, and the desulfurization rate (H ₂ S removal rate) increased from about 90% to about 95%
Improved.

In the above-described embodiment, the test results in the coke oven gas purification equipment provided with the deammonia equipment as a post-process of the desulfurization equipment have been described. However, the present invention is not limited to the basic configuration and principle of the present invention. Therefore, the present invention can be applied to a coke oven gas purification method and a purification facility in which a desulfurization facility is provided as a post-process of the deammonification facility.

[0041]

According to the present invention, the following excellent effects can be obtained. (1) Improvement of the desulfurization performance of the desulfurization absorption liquid: By recovering ammonia from the bottom liquid extracted from the ammonia distillation column,
A high-concentration ammonia vapor that does not contain impurities such as hydrogen sulfide, carbon dioxide, and cyanide, which lowers the desulfurization efficiency, can be obtained.

By adding the high-concentration ammonia vapor obtained as described above to the desulfurization absorption liquid, the desulfurization performance of the desulfurization absorption liquid can be improved. (2) Efficient use of waste liquid and excess heat: Both the waste liquid extracted from the bottom of the ammonia distillation tower and the excess heat in the defoaming method using the fosam method, which have not been effectively utilized in the past, can be effectively utilized.

(3) In a method for purifying a coke oven gas using a diamond method as a desulfurization method, ammonia is supplied in a vapor state to the desulfurization absorption liquid regenerating tower, whereby the desulfurization absorption liquid regenerating tower is stopped. Ripping steam can be reduced.

[Brief description of the drawings]

FIG. 1 is a flow sheet (side view) showing an example of a coke oven gas purification facility of the present invention.

FIG. 2 is a flow sheet (side view) showing an example of a coke oven gas purification facility of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Desulfurization tower 2 Desulfurization absorption liquid regeneration tower 3 Ammonia absorption tower 4 Ammonia stripper 5 Ammonia distillation tower 6 Ammonia concentrator (: Indirect heat exchanger) 7, 9 Ammonia vapor supply piping system 8 Ammonia stripper tower bottom liquid distribution pipe 10 Solid-liquid separation unit 11 Waste liquid treatment unit 12 Sulfur f ₁ Flow direction of coke oven gas (: COG) f ₂ Flow direction of desulfurization absorption liquid f ₃ Feed direction of bottom liquid of ammonia stripper tower f ₄ Bottom of ammonia distillation tower the direction of flow of the ammonia vapor in the liquid sending direction f ₅ a high concentration of the bottom liquid

Claims (2)

[Claims] 1. A method of purifying a coke oven gas comprising a coke oven gas desulfurization step and a deammonification step,
The desulfurization step is a desulfurization step including a desulfurization tower using an aqueous ammonia solution as an absorbent, and a desulfurization absorbent regenerating tower for regenerating the absorbent extracted from the desulfurization tower. A deammonification step comprising an ammonia absorption tower using an aqueous solution as an absorption liquid, an ammonia stripper for evaporating ammonia in the absorption liquid extracted from the ammonia absorption tower, and an ammonia distillation tower for purifying ammonia vapor flowing out of the ammonia stripper. Indirectly heating the ammonia-containing bottom liquid flowing out of the bottom of the ammonia distillation column with the bottom liquid that is an aqueous solution of ammonium dihydrogen phosphate flowing out of the bottom of the ammonia stripper to evaporate the ammonia, The ammonia vapor was supplied to the desulfurization absorption liquid regeneration tower and / Or purification process of the coke oven gas and supplying to the desulfurization tower. 2. A coke oven gas refining facility having a coke oven gas desulfurization facility and a deammonia facility,
The desulfurization equipment comprises a desulfurization tower (1) using an aqueous ammonia solution as an absorbent, and a desulfurization absorbent regenerating tower (2) for regenerating the absorbent extracted from the desulfurizer (1). Equipment comprising an ammonia absorption tower (3) using an aqueous solution of ammonium dihydrogen phosphate as an absorbing solution;
An ammonia stripper (4) for evaporating ammonia in the absorbing liquid extracted from (3), and an ammonia distillation column (5) for purifying ammonia vapor flowing out of the ammonia stripper (4). (4) The bottom liquid which is an aqueous solution of ammonium dihydrogen phosphate flowing out from the bottom of the column and the ammonia distillation column
An ammonia concentrator (6) for indirect heat exchange with the ammonia-containing bottom liquid flowing out from the bottom of (5) to evaporate ammonia from the ammonia-containing bottom liquid to obtain ammonia vapor; and A coke oven gas characterized in that it has an ammonia vapor supply piping system (7, 9) for supplying the ammonia vapor obtained in the above to the desulfurization absorption liquid regeneration tower (2) and / or the desulfurization tower (1). Refining equipment.