Coke oven gas desulfurization apparatus and coke oven gas desulfurization method

Abstract

To provide desulfurization equipment for coke oven gas that can sufficiently regenerate an absorption liquid even if the amount of oxygen gas introduced into a regeneration tower is reduced.SOLUTION: Desulfurization equipment 100 for coke oven gas comprises: an absorption tower 20 that brings coke oven gas and an absorption liquid into countercurrent contact with each other to obtain a first reaction fluid S1 containing desulfurization products; a regeneration tower 30 that mixes the first reaction fluid S1 with oxygen-containing gas to oxidize the desulfurization products to regenerate the absorption liquid; and a first flow path L1 that introduces at least a portion of first exhaust gas containing oxygen gas generated in the regeneration tower 30 into a liquid reservoir part 24 of the absorption tower 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One aspect of the present disclosure relates to a desulfurization device for coke oven gas and a desulfurization method for coke oven gas.

Background Art

[0002] Coke oven gas generated when producing coke by carbonizing coal contains sulfides such as hydrogen sulfide in addition to combustible components such as hydrogen and hydrocarbons. Therefore, prior to using coke oven gas as fuel, it is necessary to remove sulfides in the coke oven gas. As a technology for removing sulfides, a desulfurization device that countercurrently contacts coke oven gas with an absorption liquid containing ammonia or sodium carbonate is known. As such a desulfurization device, one equipped with a regeneration tower that regenerates the absorption liquid by blowing air into the absorption liquid that has absorbed sulfides is used. In Patent Document 1, a technology for introducing an inert gas into the exhaust gas has been proposed to enhance safety when burning the exhaust gas from the regeneration tower of the desulfurization device or returning it to the COG main pipe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One effective method for reducing the oxygen concentration of exhaust gas generated by a desulfurization apparatus like the one described in Patent Document 1 is to reduce the amount of oxygen gas introduced into the regeneration tower that regenerates the absorbent through oxidation reactions. However, reducing the amount of oxygen gas introduced into the regeneration tower raises concerns that the oxidation of the desulfurization products contained in the absorbent will be insufficient. To ensure sufficient oxidation of the desulfurization products while reducing the amount of oxygen introduced into the regeneration tower, it is conceivable to increase the residence time in the regeneration tower. However, increasing the residence time requires increasing the volume of liquid held in the regeneration tower, which increases the cost of equipment installation and operation.

[0005] This disclosure provides a coke oven gas desulfurization apparatus and a coke oven gas desulfurization method that can sufficiently regenerate the absorbent even with a reduced amount of oxygen gas introduced into the regeneration tower. [Means for solving the problem]

[0006] A coke oven gas desulfurization apparatus according to one aspect of the present disclosure comprises an absorption tower that brings coke oven gas and an absorbent liquid into countercurrent contact to obtain a first reaction fluid containing desulfurization products, and a regeneration tower that mixes the first reaction fluid with an oxygen-containing gas to oxidize the desulfurization products and regenerate the absorbent liquid, the apparatus comprising a first flow path that introduces at least a portion of the first exhaust gas containing oxygen gas generated in the regeneration tower into the liquid reservoir of the absorption tower.

[0007] The coke oven gas desulfurization apparatus described above includes a first channel that introduces at least a portion of the first exhaust gas generated in the regeneration tower into the liquid reservoir of the absorption tower. When the oxygen-containing first exhaust gas is introduced into the liquid reservoir of the absorption tower through this first channel, the oxidation reaction of the desulfurization products contained in the first reaction fluid is initiated in the liquid reservoir. In this way, the oxidation reaction of the desulfurization products proceeds not only in the regeneration tower but also in the absorption tower. This makes it possible to increase the residence time of the first reaction fluid and oxygen gas, so that even if the amount of oxygen-containing gas mixed with the first reaction fluid in the regeneration tower is reduced, the oxidation of the desulfurization products contained in the absorbent liquid proceeds sufficiently, and the absorbent liquid can be sufficiently regenerated.

[0008] In the above-described desulfurization apparatus for coke oven gas, the oxygen concentration of the second exhaust gas generated from the liquid reservoir of the absorption tower may be 10% by volume or less. The mixed gas obtained by mixing such second exhaust gas and coke oven gas, and the desulfurized gas obtained by desulfurizing the mixed gas, are sufficiently safe and can be effectively used for various purposes such as fuel gas without the addition of inert gas. However, this does not preclude the addition of inert gas.

[0009] In any of the above-mentioned coke oven gas desulfurization apparatuses, the absorbent may contain ammonia. This allows for sufficiently smooth absorption (desulfurization) in the absorption tower and regeneration in the regeneration tower.

[0010] In any of the above-described coke oven gas desulfurization apparatuses, the first flow path may have a confluence section where the absorbent liquid and the first exhaust gas merge, and a discharge section that discharges a gas-liquid mixed fluid containing the absorbent liquid and the first exhaust gas into the first reaction fluid in the liquid reservoir section. This increases the contact efficiency between the oxygen gas contained in the first exhaust gas and the first reaction fluid in the liquid reservoir section, thereby sufficiently promoting the oxidation reaction of the desulfurization product. Consequently, the amount of oxygen-containing gas mixed into the first reaction fluid in the regeneration tower can be further reduced.

[0011] In any of the above-described desulfurization apparatuses for coke oven gas, the regeneration tower may include a mixing tank for mixing a first reaction fluid with an oxygen-containing gas to obtain a second reaction fluid, and a deaerating tank for receiving the second reaction fluid overflowing from the mixing tank and separating the gas from the second reaction fluid to regenerate the absorbent liquid. A second flow channel may also be provided at the confluence of the first flow channel for supplying the absorbent liquid regenerated in the deaerating tank. The absorbent liquid, from which the gas has been separated in this manner, can be smoothly transferred by a pump or the like. Therefore, the absorbent liquid can be smoothly merged with the first exhaust gas flowing through the first flow channel using the second flow channel.

[0012] In any of the above-described coke oven gas desulfurization apparatuses, the discharge section may discharge a gas-liquid mixed fluid such that a swirling flow is generated in the first reaction fluid in the liquid reservoir. This further increases the contact efficiency between the oxygen gas contained in the first exhaust gas and the first reaction fluid in the liquid reservoir, thereby further promoting the oxidation reaction of the desulfurization product. Consequently, the amount of oxygen-containing gas mixed into the first reaction fluid in the regeneration tower can be further reduced.

[0013] A method for desulfurizing coke oven gas according to one aspect of the present disclosure includes: a desulfurization step in which coke oven gas and an absorbent liquid are brought into countercurrent contact in an absorption tower to obtain a first reaction fluid containing desulfurization products; a regeneration step in which the first reaction fluid and an oxygen-containing gas are mixed in a regeneration tower to oxidize the desulfurization products and regenerate the absorbent liquid; and an introduction step in which at least a portion of the first exhaust gas containing oxygen gas generated in the regeneration step is introduced into the reaction fluid accumulating in the liquid reservoir of the absorption tower.

[0014] The above-described method for desulfurizing coke oven gas includes an introduction step in which at least a portion of the first exhaust gas generated in the regeneration process is introduced into the liquid reservoir of the absorption tower. By introducing the first exhaust gas containing oxygen gas into the first reaction fluid in this introduction step, the oxidation reaction of the desulfurization products contained in the first reaction fluid is initiated in the liquid reservoir. In this way, the oxidation reaction proceeds not only in the regeneration process but also in the desulfurization process. This makes it possible to increase the residence time of the first reaction fluid and oxygen gas, so that even if the amount of oxygen-containing gas mixed into the first reaction fluid in the regeneration process is reduced, the oxidation of the desulfurization products contained in the absorbent liquid can proceed sufficiently, and the absorbent liquid can be sufficiently regenerated.

[0015] In the above-described method for desulfurizing coke oven gas, the oxygen concentration of the second exhaust gas generated from the liquid reservoir during the introduction process may be 10% by volume or less. The mixed gas obtained by mixing such second exhaust gas and coke oven gas, and the desulfurized gas obtained by desulfurizing the mixed gas, are sufficiently safe and can be effectively used for various applications such as fuel gas without the addition of inert gas. However, this does not preclude the addition of inert gas.

[0016] In any one of the above-described desulfurization methods for coke oven gas, in the introduction step, the absorption liquid and the first exhaust gas may be merged, and the gas-liquid mixed fluid containing the absorption liquid and the first exhaust gas may be discharged into the first reaction fluid in the liquid reservoir section. Thereby, the contact efficiency between the oxygen gas contained in the first exhaust gas and the first reaction fluid in the liquid reservoir section can be increased, and the oxidation reaction of the desulfurization product can be sufficiently promoted. Therefore, the oxygen-containing gas mixed into the first reaction fluid in the regeneration step can be further reduced.

[0017] In any one of the above-described desulfurization methods for coke oven gas, in the introduction step, the gas-liquid mixed fluid may be discharged into the first reaction fluid in the liquid reservoir section to generate a swirling flow. Thereby, the contact efficiency between the oxygen gas contained in the first exhaust gas and the first reaction fluid in the liquid reservoir section can be increased, and the oxidation reaction of the desulfurization product can be further sufficiently promoted. Therefore, the oxygen-containing gas mixed into the first reaction fluid in the regeneration step can be even further reduced.

Advantages of the Invention

[0018] It is possible to provide a desulfurization apparatus for coke oven gas and a desulfurization method for coke oven gas capable of sufficiently regenerating the absorption liquid even when the amount of oxygen gas introduced into the regeneration tower is reduced.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram schematically showing a desulfurization apparatus for coke oven gas. [Figure 2] It is a diagram when looking at the liquid reservoir section of the absorption tower from above. <0​​​​​​​​​​​​Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, the following embodiments are examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant descriptions may be omitted as appropriate. Also, the positional relationships such as up, down, left, and right are based on the direction of the reference numerals in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[0021] The desulfurization device 100 for coke oven gas shown in FIG. 1 includes an absorption tower 20 that countercurrently contacts coke oven gas (COG) and an absorption liquid to obtain a first reaction fluid containing a desulfurization product, a regeneration tower 30 that mixes the first reaction fluid and an oxygen-containing gas to oxidize the desulfurization product and regenerate the absorption liquid, and a first flow path L1 that introduces at least a part of the first exhaust gas containing oxygen gas, which is generated in the regeneration tower 30, into the liquid reservoir portion 24 of the absorption tower 20. The first flow path L1 is composed of a flow path L1A formed by a pipe connecting the side wall of the regeneration tower 30 and a blower B1, a blower B1, a flow path L1B formed by a pipe connecting the blower B1 and a nozzle 12 disposed in the liquid reservoir portion 24, and the nozzle 12.

[0022] The absorption tower 20 has a gas outlet 22, an absorption liquid inlet 23, a gas inlet 21, and a reaction fluid outlet 25 from top to bottom. The absorption tower 20 has a plurality of stages of packing layers 26 between the absorption liquid inlet 23 and the gas inlet 21. The packing layers 26 are provided to improve the gas-liquid contact efficiency. For example, Raschig rings or the like may be filled in the packing layers 26. The structure and number of the packing layers 26 are not particularly limited, and the packing layers 26 may not be provided.

[0023] The coke oven gas is introduced through a gas inlet 21 located at the bottom of the absorption tower 20 and rises within the tower. The coke oven gas contains hydrogen and other combustible components such as hydrocarbons, as well as sulfides such as hydrogen sulfide. The absorbent liquid is introduced through an absorbent liquid inlet 23 located at the top of the absorption tower 20 and descends within the tower. The absorbent liquid is, for example, water containing ammonia. The coke oven gas introduced through the gas inlet 21 and the absorbent liquid introduced through the absorbent liquid inlet 23 come into countercurrent contact within the absorption tower 20.

[0024] In the absorption tower 20, sulfides contained in the coke oven gas are absorbed into the absorbent liquid. At this time, sulfides and ammonia react to produce desulfurization products. For example, hydrogen sulfide, a type of sulfide, reacts with ammonia contained in the absorbent liquid as follows to produce NH4HS as a desulfurization product. NH3 + H2O → NH4OH (1) NH4OH + H2S → NH4HS + H2O (2)

[0025] Inside the absorption tower 20, the desulfurization reaction described above proceeds as the coke oven gas and the absorbent liquid come into countercurrent contact, generating desulfurization products. The desulfurization reaction is not limited to the reaction equations (1) and (2) described above, and various reactions may proceed depending on the type of sulfide contained in the coke oven gas. The reaction fluid S1 (first reaction fluid) containing the desulfurization products generated by the reaction remains in the liquid reservoir 24 at the bottom of the absorption tower 20. The desulfurization products may be contained as solids in the reaction fluid S1 or may be dissolved in the reaction fluid S1.

[0026] A nozzle 12, which is the tip of a first flow path L1 that introduces at least a portion of the first exhaust gas containing oxygen gas generated in the regeneration tower 30, is positioned in the liquid reservoir section 24. A connecting pipe 43 is also connected to the liquid reservoir section 24 to transfer the stagnant reaction fluid S1 to the mixing tank 40 in the regeneration tower 30. Therefore, the liquid level in the liquid reservoir section 24 and the liquid level in the mixing tank 40 may be the same. The base end of the first flow path L1 is connected to the side wall of the regeneration tower 30.

[0027] The first flow channel L1 introduces the first exhaust gas containing oxygen gas, generated in the mixing tank 40 and degassing tank 50 of the regeneration tower 30, into the liquid reservoir 24. The reaction fluid S1 accumulating in the liquid reservoir 24 is introduced with the first exhaust gas containing oxygen gas that has flowed through the first flow channel L1. A portion of the desulfurization products contained in the reaction fluid S1 is oxidized by the oxygen gas contained in the first exhaust gas. The oxidation reaction that occurs here may include, for example, the reactions shown in the following reaction equations (3) and (4). In equation (4), x is any positive value. 2NH4HS + O2 → 2NH4OH + 2S (3) NH3+NH4HS+xS → (NH4)2S x+1 (4)

[0028] In the liquid reservoir 24, the oxidation reactions of the desulfurization products as described in (3) and (4) above proceed, so the reaction fluid S1 that remains in the liquid reservoir 24 contains oxidation products such as sulfur in addition to the desulfurization products. The reaction fluid S1 containing these components is discharged from the reaction fluid outlet 25 and flows through the connecting pipe 43. A catalyst introduction section 48 is connected to the connecting pipe 43, and a catalyst is added to the reaction fluid S1 from the catalyst introduction section 48. Picric acid is an example of a catalyst. Oxidation reactions such as those in equations (3) and (4) are promoted by catalysts such as picric acid. The absorbent liquid introduced into the absorption tower 20 is circulated and therefore contains a catalyst. For this reason, oxidation reactions such as those in equations (3) and (4) proceed smoothly in the liquid reservoir 24 as well.

[0029] After the catalyst is added from the catalyst introduction section 48, the reaction fluid S1 flows through the connecting pipe 43 and is introduced into the regeneration tower 30. The regeneration tower 30 includes a mixing tank 40 that mixes the reaction fluid S1 with an oxygen-containing gas to obtain a reaction fluid S2 (second reaction fluid) containing oxidation reactants, and a degassing tank 50 that surrounds the mixing tank 40, receives the reaction fluid S2 overflowing from the mixing tank 40, separates the gas from the reaction fluid S2 to regenerate the absorbent liquid.

[0030] The reaction fluid S1 is introduced into the mixing tank 40 through an inlet 44 to which a connecting pipe 43 is connected. The mixing tank 40 has a bottom plate 41 and a cylindrical side wall 41a that opens upward. A nozzle 42 for supplying oxygen-containing gas is provided at the bottom of the mixing tank 40. The oxygen-containing gas is, for example, air.

[0031] In the mixing tank 40, the reaction fluid S1 introduced from the inlet 44 and the oxygen-containing gas supplied from the nozzle 42 are mixed. In the mixing tank 40, the desulfurization products remaining in the reaction fluid S1 react with the oxygen gas contained in the oxygen-containing gas to produce oxidation products such as sulfur. The reaction may include the reactions shown in the reaction equations (3) and (4) described above.

[0032] The reaction fluid S2, which contains oxidation products such as sulfur produced by the oxidation of sulfur compounds, overflows from the upper end of the side wall 41a of the mixing tank 40 and flows out into the degassing tank 50. In the degassing tank 50, the reaction fluid S2 containing bubbles undergoes gas-liquid separation. The liquid obtained by gas-liquid separation may contain solid components such as sulfur. At least a portion of the liquid obtained in this way (which may contain solid components) can be reused as an absorbent liquid and flows through a channel L9 equipped with a pump P1 to be introduced into the absorption tower 20 from the absorbent liquid inlet 23. The tip of the absorbent liquid inlet 23 may be configured as a distributor.

[0033] Flow path L9 is connected downstream of pump P1 to flow path L7, flow path L10 for discharging absorbent liquid from the system, and flow path L11 for replenishing absorbent liquid. Flow path L10 discharges a portion of the absorbent liquid when the solid content concentration in the absorbent liquid increases or when the amount of absorbent liquid used in circulation becomes excessive. Flow path L11 introduces absorbent liquid into flow path L9 to replenish the absorbent liquid when it becomes insufficient due to discharge from flow path L10, etc. Examples of liquids introduced from flow path L11 include ammonia and water. If the coke oven gas introduced from the gas inlet 21 contains ammonia, the water introduced from flow path L11 absorbs the ammonia. This maintains the concentration of ammonia in the circulating absorbent liquid within an appropriate range. Flow path L7 branches into two, flow path L7a and flow path L7b, which supply absorbent liquid to nozzle 12 and nozzle 42, respectively.

[0034] The first exhaust gas obtained by gas-liquid separation in the degassing tank 50 contains oxygen gas derived from the oxygen-containing gas. The concentration of oxygen gas in the first exhaust gas may be, for example, 10 to 18 volume percent. In this specification, "volume percent" of gas refers to the volume ratio under standard conditions (0°C, 1 atm). The first exhaust gas flows through the first flow path L1 connected to the side wall of the regeneration tower 30 toward the liquid reservoir 24 of the absorption tower 20.

[0035] The nozzle 12, located at the end (tip) of the first flow path L1 on the absorption tower 20 side, has a confluence section 12A where the first exhaust gas and the absorbent liquid merge, and a discharge section 12B that discharges the gas-liquid mixed fluid produced by the confluence of the first exhaust gas and the absorbent liquid. The confluence section 12A of the nozzle 12 is connected to a flow path L7a (second flow path). At the confluence section 12A, a gas-liquid mixed fluid is produced when the first exhaust gas containing oxygen gas and the absorbent liquid, which is a liquid, merge. The nozzle 12 discharges this gas-liquid mixed fluid into the reaction fluid S1 in the liquid reservoir section 24. As a result, the first exhaust gas and the reaction fluid S1 are thoroughly mixed, and the oxidation of the desulfurization products contained in the reaction fluid S1 proceeds efficiently.

[0036] A nozzle 42, located at the bottom of the mixing tank 40, has a confluence section 42A where the oxygen-containing gas and the absorbent liquid merge, and a discharge section 42B that discharges the gas-liquid mixed fluid produced by the confluence of the oxygen-containing gas and the absorbent liquid. In the confluence section 42A, a gas-liquid mixed fluid is produced by the confluence of the gaseous oxygen-containing gas and the liquid absorbent liquid. The nozzle 42 discharges this gas-liquid mixed fluid from the discharge section 42B into the reaction fluid S1 in the mixing tank 40. This ensures that the oxygen-containing gas and the reaction fluid S1 are thoroughly mixed, and the oxidation of desulfurization products contained in the reaction fluid S1 proceeds efficiently. In this way, a reaction fluid S2 containing oxidation products such as sulfur is obtained.

[0037] In the coke oven gas desulfurization unit 100, the oxidation reaction of the desulfurization products generated in the desulfurization reaction in the absorption tower 20 by oxygen gas proceeds in both the liquid reservoir 24 of the absorption tower 20 and the mixing tank 40 of the regeneration tower 30. Therefore, it is possible to extend the residence time of the oxidation reaction without changing the height and diameter of the regeneration tower 30 (mixing tank 40). As a result, the reaction can proceed sufficiently even if the amount of oxygen-containing gas (air) supplied from the nozzle 42 is reduced. Therefore, it is possible to reduce the amount of oxygen contained in the desulfurization gas discharged from the coke oven gas desulfurization unit 100, thereby improving safety.

[0038] The total residence time of the desulfurization product and oxygen gas in the liquid reservoir 24 and the mixing tank 40 may be 2.6 to 5 minutes, or it may be 3 to 4 minutes. This makes it possible to achieve both a reduction in the oxygen concentration of the second exhaust gas mixed with the coke oven gas (COG) generated from the liquid reservoir 24 and oxidation of the desulfurization product at a sufficiently high level.

[0039] A gas-liquid mixed fluid is discharged from the discharge section 12B of the nozzle 12 into the reaction fluid S1 that remains in the liquid reservoir section 24 of the absorption tower 20. As a result, the gas bubbles become sufficiently small, and the frequency of contact between the reaction fluid S1 and the oxygen gas contained in the first exhaust gas can be sufficiently increased. This allows the oxidation reaction of the desulfurization product to proceed efficiently. The completion of the oxidation reaction can be determined by measuring the oxygen concentration of the second exhaust gas generated from the liquid reservoir section 24, or by measuring the potential of the absorbent liquid regenerated in the regeneration tower 30.

[0040] Of the gas-liquid mixed fluid discharged into the reaction fluid S1 in the liquid reservoir section 24, at least a portion of the oxygen gas is consumed in the oxidation reaction, and the remaining oxygen gas and other gases (e.g., nitrogen gas) rise through the reaction fluid S1 and undergo gas-liquid separation. Subsequently, it is mixed with coke oven gas (COG) introduced from the gas inlet 21 of the absorption tower 20 and rises within the absorption tower 20 while in countercurrent contact with the absorbent liquid. Finally, it is discharged from the gas outlet 22 into the flow path L4 as desulfurized gas.

[0041] The desulfurized gas is obtained by desulfurizing a mixed gas of coke oven gas containing combustible components such as hydrogen and hydrocarbons and the second exhaust gas in the absorption tower 20. The desulfurized gas may contain oxygen gas derived from the second exhaust gas and other gases (e.g., nitrogen gas). The oxygen gas contained in the first exhaust gas is consumed by its reaction with the desulfurization products contained in the reaction fluid S1. Therefore, the amount of oxygen in the second exhaust gas mixed with the coke oven gas is sufficiently less than the lower explosion limit, thereby improving safety. The oxygen concentration in the second exhaust gas generated from the liquid reservoir 24 may be 10% by volume or less. From the viewpoint of keeping the oxygen concentration in the second exhaust gas within the above range, the surplus rate of oxygen gas supplied to the mixing tank 40 (surplus air rate if the oxygen-containing gas is air) may be 80% or less, or 60% or less. This surplus rate is the surplus ratio based on the theoretical amount of oxygen required to oxidize hydrogen sulfide contained in the coke oven gas to sulfur by formulas (2) and (3) as the base (100%). For example, if 1.5 times the theoretical amount of oxygen is supplied, the oxygen gas surplus rate will be 50%.

[0042] The oxygen concentration in the second exhaust gas generated from the liquid reservoir 24 can be adjusted by changing the amount of oxygen gas contained in the oxygen-containing gas supplied from the nozzle 42 in the mixing tank 40. By reducing the amount of oxygen gas contained in the oxygen-containing gas supplied from the nozzle 42 in the mixing tank 40, the oxygen concentration in the second exhaust gas can be lowered. However, if the amount of oxygen gas contained in the oxygen-containing gas supplied from the nozzle 42 is reduced too much, the oxidation reaction of the desulfurization product may not proceed sufficiently in the mixing tank 40, and the absorbent liquid may not be sufficiently regenerated in the regeneration tower 30. From the viewpoint of ensuring that the oxidation reaction of the desulfurization product proceeds sufficiently, the oxygen concentration in the second exhaust gas generated from the liquid reservoir 24 may be 6% by volume or more, or 8% by volume or more. From a similar viewpoint, the surplus rate of oxygen gas supplied to the mixing tank 40 may be 30% or more, or 40% or more.

[0043] There are no restrictions on the shape, arrangement, or number of nozzles 12 provided in the liquid reservoir 24 of the absorption tower 20. For example, multiple nozzles 12 may be provided at the bottom of the absorption tower 20. In the example shown in Figure 2, four nozzles 12 (nozzles 12a, 12b, 12c, 12d) are provided in the liquid reservoir 24. Each nozzle 12 forms the tip of the first flow path L1 (L1B) and has a confluence section 12A where the first exhaust gas and the absorbent liquid flowing through the flow path L7a merge, and a discharge section 12B located on the tip side (downstream side) of the confluence section 12A. Each nozzle 12 discharges a gas-liquid mixed fluid containing the first exhaust gas (oxygen gas) into the reaction fluid S1 accumulating in the liquid reservoir 24 from the discharge section 12B.

[0044] When the absorption tower 20 is viewed from above, each nozzle 12 discharges a gas-liquid mixed fluid F1 from the discharge section 12B along the tangential direction of the side wall of the cylindrical absorption tower 20. As a result, a swirling flow C1 is formed in the reaction fluid S1 in the liquid reservoir section 24, centered on the center C0 of the absorption tower 20. By forming such a swirling flow C1, gas-liquid contact is efficiently performed, and the oxidation of desulfurization products contained in the reaction fluid S1 proceeds smoothly.

[0045] In the example shown in Figure 2, four nozzles 12 are provided, but in other examples, there may be three or fewer, or five or more. Furthermore, multiple nozzles 12 may be arranged in a row along the discharge direction of the gas-liquid mixed fluid F1. In yet another example, the first exhaust gas flowing through the first flow path L1 may be discharged into the reaction fluid S1 not as a gas-liquid mixed fluid, but as a gas (first exhaust gas). This simplifies the nozzle structure.

[0046] The nozzle 42 provided at the bottom of the mixing tank 40 may have the same shape as the nozzle 12 provided in the liquid reservoir 24 of the absorption tower 20. The nozzle 42 may also discharge a gas-liquid mixed fluid from its discharge section 42B along the tangential direction of the cylindrical side wall 41a. This allows a swirling flow to be formed in the reaction fluid S2 of the mixing tank 40. This enables efficient gas-liquid contact in the mixing tank 40, facilitating smooth regeneration of the absorbent liquid.

[0047] A pre-cooling tower may be provided upstream of the absorption tower 20 to cool the coke oven gas. In the pre-cooling tower, the coke oven gas may be cooled to 35-50°C by bringing it into contact with water.

[0048] A method for desulfurizing coke oven gas according to one embodiment includes: a desulfurization step in which coke oven gas and an absorbent liquid are brought into countercurrent contact in an absorption tower to obtain a first reaction fluid containing desulfurization products; a regeneration step in which the first reaction fluid and an oxygen-containing gas are mixed in a regeneration tower to oxidize the desulfurization products and regenerate the absorbent liquid; and an introduction step in which at least a portion of the first exhaust gas containing oxygen gas generated in the regeneration step is introduced into the first reaction fluid accumulating in the liquid reservoir of the absorption tower. This cooling method may also be carried out using a coke oven gas desulfurization apparatus 100. Therefore, the description of the coke oven gas desulfurization apparatus 100 described above also applies to the coke oven gas desulfurization method of this embodiment.

[0049] For example, in the regeneration process, a catalyst (e.g., picric acid) may be added to the reaction fluid S1, and then an oxygen-containing gas may be mixed to oxidize the desulfurization product and regenerate the absorbent. From the viewpoint of reducing the oxygen concentration in the second exhaust gas generated from the liquid reservoir 24, the surplus rate of oxygen gas supplied to the mixing tank 40 in the regeneration process (or the surplus air rate if the oxygen-containing gas is air) may be 80% or less, or 60% or less. From a similar viewpoint, the oxygen concentration in the second exhaust gas generated from the liquid reservoir 24 may be 10% by volume or less. From the viewpoint of ensuring sufficient oxidation of the desulfurization product in the regeneration process, the above surplus rate of oxygen gas may be 30% or more, or 40% or more. From a similar viewpoint, the oxygen concentration in the second exhaust gas generated from the liquid reservoir 24 may be 6% by volume or more, or 8% by volume or more.

[0050] In the introduction process, the absorbent liquid and the first exhaust gas from the regeneration tower 30 may be combined at the confluence section 12A of the nozzle 12 provided at the tip of the first flow path L1 to obtain a gas-liquid mixed fluid containing the absorbent liquid and the first exhaust gas. By discharging this gas-liquid mixed fluid containing the first exhaust gas into the reaction fluid S1 in the liquid reservoir section 24, the frequency of contact between the desulfurization product and oxygen gas is increased, allowing the oxidation reaction to proceed smoothly. In the regeneration process, the gas-liquid mixed fluid obtained by combining the oxygen-containing gas and the absorbent liquid may also be discharged into the reaction fluid S1 in the mixing tank 40 to mix the oxygen-containing gas and the reaction fluid S1. This increases the frequency of contact between the desulfurization product and oxygen gas, allowing for the smooth acquisition of a reaction fluid S2 containing oxidation products such as sulfur. Therefore, the absorbent liquid can be regenerated smoothly.

[0051] With the coke oven gas desulfurization apparatus 100 and coke oven gas desulfurization method of each embodiment described above, the absorbent liquid can be sufficiently regenerated even if the amount of oxygen gas (oxygen-containing gas) introduced into the reaction fluid S2 of the mixing tank 40 is reduced. Therefore, the oxygen concentration in the second exhaust gas generated from the liquid reservoir 24 can be sufficiently reduced. The desulfurized gas mixed with such second exhaust gas has a high level of safety because the oxygen concentration is well below the lower explosive limit, and can be effectively utilized as fuel gas, etc. Note that the coke oven gas desulfurization method of this embodiment may be carried out using a gas cooling device different from the coke oven gas desulfurization apparatus 100 described above.

[0052] Although embodiments of the present disclosure have been described above, the present disclosure is not limited in any way to the above embodiments. For example, it is not necessary to introduce all of the first exhaust gas obtained by gas-liquid separation in the degassing tank 50 of the regeneration tower 30 into the reaction fluid S1 from the discharge section 12B of the nozzle 12. For example, a portion of the first exhaust gas obtained by gas-liquid separation in the degassing tank 50 may be combined with the desulfurized gas discharged from the gas outlet 22 of the absorption tower 20, or it may be combined with an oxygen-containing gas and circulated to the nozzle 42. The gas introduced from the gas inlet 21 may be a mixed gas containing COG and a gas other than COG. [Examples]

[0053] The contents of this disclosure will be described in more detail with reference to examples and comparative examples, but this disclosure is not limited to the following specific examples.

[0054] (Comparative Example 1) A coke oven gas (COG) desulfurization apparatus 200 was prepared, as shown in Figure 4, comprising a regeneration tower 130 having an absorption tower 120, a mixing tank 140, and a degassing tank 150. In the absorption tower 120, COG was desulfurized by countercurrent contact with an absorbent liquid containing ammonia. The reaction fluid S11, containing the desulfurization products generated in the absorption tower 120, flowed through a connecting pipe 143, and after a catalyst (picric acid) was added, it was introduced into the mixing tank 140. A gas-liquid mixed fluid containing air and absorbent liquid was discharged into the reaction fluid S12 from a nozzle 142 located at the bottom of the mixing tank 140 to oxidize the desulfurization products. The absorbent liquid regenerated by the oxidation of the desulfurization products overflowed from the mixing tank 140 into the degassing tank 150 and was degassed. A portion of the degassed absorbent liquid was circulated and supplied back to the absorption tower 120 via pump P1 and flow path L9. The remaining portion of the degassed absorbent liquid was supplied to the confluence 142A of the nozzle 142 via pump P1 and flow path L7.

[0055] In this coke oven gas desulfurization apparatus 200, the oxygen concentration in the exhaust gas from the regeneration tower 130 was measured when the amount of air supplied to the nozzle 142 was changed. At the confluence 142A of the nozzle 142, air and absorbent liquid merged to form a gas-liquid mixed fluid, which was discharged from the discharge 142B into the mixing tank 140 to obtain a reaction fluid S12 containing oxidation products. The calculated amount of air required to oxidize all the desulfurization products generated by desulfurizing the sulfides contained in the coke oven gas used in operation (theoretical air amount) was 24 Nm³ 3 The amount of air supplied to nozzle 142 was 68 Nm³ / h. 3 The excess air ratio was kept constant at / h (183%), and the residence time of the desulfurization product (reaction fluid) and oxygen gas was changed by altering the liquid level in the mixing tank 140. In this way, the change in oxygen concentration in the exhaust gas discharged from the regeneration tower 130 due to the residence time was investigated. The results are shown in Figure 3.

[0056] (Comparative Examples 2, 3) The operation was carried out using the same procedure as in Comparative Example 1, except that the amount of air supplied to nozzle 142 was changed as shown in Table 1. Then, using the same procedure as in Comparative Example 1, the oxygen concentration in the exhaust gas discharged from the regeneration tower 130 was measured when the residence time of the desulfurization product and oxygen gas was changed. The results are shown in Figure 3.

[0057] In the reaction fluid S12 obtained in the mixing tank 140, the timing of the completion of oxidation of the desulfurization product can be determined as the point at which the oxygen concentration of the exhaust gas no longer changes even when the residence time is increased. From the results shown in Figure 3, it is estimated that in Comparative Example 1, where the excess air ratio was 183%, the oxidation of the desulfurization product was completed in less than 2.5 minutes of residence time. However, in Comparative Example 1, the oxygen concentration in the exhaust gas was 15% by volume or higher. In Comparative Examples 2 and 3, where the excess air ratios were 121% and 83%, respectively, the oxygen concentration of the exhaust gas was lower than in Comparative Example 1.

[0058] (Example 1) The coke oven gas desulfurization apparatus 200 shown in Figure 4 was modified to prepare the coke oven gas desulfurization apparatus 100 shown in Figure 1. Specifically, a nozzle 12 was installed at the bottom of the liquid reservoir 24 of the absorption tower 20, and the nozzle 12 was connected to a first flow path L1 through which the exhaust gas (first exhaust gas) generated in the regeneration tower 30 flows, and to a flow path L7a through which the absorbent liquid regenerated in the regeneration tower 30 flows. Except for using this coke oven gas desulfurization apparatus 100, the apparatus was operated in the same manner as in Comparative Examples 1 to 3. The amount of air supplied to the nozzle 42 was 37 Nm³. 3 The ratio of excess air was kept constant at / h (excess air ratio: 54%), and the residence time of the desulfurization products (reaction fluid) and oxygen was changed by altering the liquid level in the liquid reservoir 24 of the mixing tank 40 and the absorption tower 20. In this way, the change in oxygen concentration of the exhaust gas (second exhaust gas) generated from the liquid reservoir 24 due to the residence time was investigated. The results are shown in Figure 3. As shown in Figure 3, it was confirmed that the oxidation of the desulfurization products was completed at a residence time of 3.33 minutes.

[0059] [Table 1]

[0060] Table 1 shows the oxygen concentration in the exhaust gas discharged from the regeneration tower 130 when the residence time is 2.5 minutes in the Comparative Examples 1-3 column. The Example 1 column shows the oxygen concentration of the exhaust gas (second exhaust gas) generated from the liquid reservoir 24 when the residence time is 3.33 minutes. In addition, Table 1 shows the height from the discharge portion 12B of the nozzle 12 to the liquid surface of the liquid reservoir 24 (effective contact height), which is the region in the absorption tower 20 where the oxidation reaction occurs.

[0061] Under the operating conditions of Example 1 shown in Table 1, the liquid level in both the absorption tower 20 and the mixing tank 40 was 5m, which was lower than the liquid level in Comparative Examples 1-3. In Example 1, the oxidation reaction of the desulfurization product is carried out in two locations: the liquid reservoir 24 of the absorption tower 20 and the mixing tank 40 of the regeneration tower 30. Therefore, even with a low air surplus rate, the residence time can be extended and the oxidation reaction can proceed sufficiently without increasing the liquid level in the absorption tower 20 and the mixing tank 40. [Industrial applicability]

[0062] This invention provides a coke oven gas desulfurization apparatus and a coke oven gas desulfurization method that can sufficiently regenerate the absorbent even with a reduced amount of oxygen gas introduced into the regeneration tower. [Explanation of Symbols]

[0063] 12, 12a, 12b, 12c, 12d, 42, 142… Nozzles, 12A, 42A, 142A… Confluence section, 12B, 42B, 142B… Discharge section, 20, 120… Absorption tower, 21… Gas inlet, 22… Gas outlet, 23… Absorbent liquid inlet, 24… Liquid reservoir section, 25… Reaction fluid outlet, 26… Packed bed, 30, 130… Regeneration tower, 40, 140… Mixing tank, 41… Bottom plate, 41a… Side wall, 43, 143... Connecting pipe, 44... Inlet, 48... Catalyst introduction section, 50, 150... Degassing tank, 100, 200... Desulfurization equipment for coke oven gas, B1... Blower, C0... Center, C1... Swirling flow, F1... Gas-liquid mixed fluid, L1... First flow path, L1A, L1B, L4, L7, L7a, L7b, L9, L10, L11... Flow paths, P1... Pump, S1, S2, S11, S12... Reaction fluid.

Claims

1. A coke oven gas desulfurization apparatus comprising: an absorption tower that brings coke oven gas and an absorbent liquid into countercurrent contact to obtain a first reaction fluid containing desulfurization products; and a regeneration tower that mixes the first reaction fluid with an oxygen-containing gas to oxidize the desulfurization products and regenerate the absorbent liquid, wherein The regeneration tower is equipped with a first flow path that introduces at least a portion of the first exhaust gas containing oxygen gas generated in the aforementioned regeneration tower into the liquid reservoir of the absorption tower, The desulfurization apparatus for coke oven gas has a first flow path comprising a confluence section where the absorbent liquid and the first exhaust gas merge, and a discharge section that discharges a gas-liquid mixed fluid containing the absorbent liquid and the first exhaust gas into the first reaction fluid in the liquid reservoir section.

2. The coke oven gas desulfurization apparatus according to claim 1, wherein the oxygen concentration of the second exhaust gas generated from the liquid reservoir of the absorption tower is 10% by volume or less.

3. The coke oven gas desulfurization apparatus according to claim 1, wherein the absorbent liquid contains ammonia.

4. The regeneration tower includes a mixing tank that mixes the first reaction fluid and the oxygen-containing gas to obtain a second reaction fluid, and a degassing tank that receives the second reaction fluid overflowing from the mixing tank and separates the gas from the second reaction fluid to regenerate the absorbent liquid. The coke oven gas desulfurization apparatus according to claim 1, further comprising a second channel for supplying the absorbent liquid regenerated in the degassing tank to the confluence of the first channel.

5. The coke oven gas desulfurization apparatus according to claim 1, wherein the discharge unit discharges the gas-liquid mixed fluid such that a swirling flow is generated in the first reaction fluid of the liquid reservoir.

6. In an absorption tower, a desulfurization step is performed to obtain a first reaction fluid containing desulfurization products by bringing coke oven gas and absorbent liquid into countercurrent contact, In the regeneration tower, a regeneration step is performed in which the first reaction fluid and an oxygen-containing gas are mixed to oxidize the desulfurization product and regenerate the absorbent, The process includes an introduction step of introducing at least a portion of the first exhaust gas containing oxygen gas generated in the regeneration step into the first reaction fluid that is retained in the liquid reservoir of the absorption tower. A method for desulfurizing coke oven gas, wherein in the introduction step, the absorbent liquid and the first exhaust gas are combined, and the gas-liquid mixed fluid containing the absorbent liquid and the first exhaust gas is discharged into the first reaction fluid in the liquid reservoir.

7. The method for desulfurizing coke oven gas according to claim 6, wherein the oxygen concentration of the second exhaust gas generated from the liquid reservoir in the introduction step is 10% by volume or less.

8. The method for desulfurizing coke oven gas according to claim 6, wherein in the introduction step, the gas-liquid mixed fluid is discharged into the first reaction fluid in the liquid reservoir to generate a swirling flow.

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