A two-tower coke oven gas desulfurization process and apparatus

Abstract

The present disclosure relates to a two-tower coke oven gas desulfurization process method and equipment. The method comprises: inputting the coke oven gas to be desulfurized into a first desulfurization tower for two-stage desulfurization treatment to obtain intermediate product gas; and inputting the intermediate product gas into a second desulfurization tower for one-stage desulfurization treatment to obtain desulfurized coke oven gas. The two-tower coke oven gas desulfurization process method according to the embodiment of the present disclosure can perform three-stage desulfurization treatment through two desulfurization towers, improve the desulfurization efficiency, and ensure the desulfurization index of the coke oven gas. Two regeneration towers are used to complete the circulation of the desulfurization liquid, and a reaction tank is provided to supplement the catalyst and concentrated ammonia water, so as to ensure the quality of the desulfurization liquid. The desulfurization liquid that is not fully reacted in the second desulfurization tower is input into the lower stage of the first desulfurization tower, so as to fully utilize the desulfurization liquid and improve the utilization efficiency of the desulfurization liquid.

Description

Technical Field

[0001] This disclosure relates to the field of production process technology, and in particular to a two-tower coke oven gas desulfurization process method and equipment. Background Technology

[0002] During the coking process, approximately 15-35% of the sulfur is transferred into the coke oven gas, with over 95% existing as hydrogen sulfide, resulting in a sulfur content of 4-10 g / m³ in the coke oven gas. 3 Hydrogen sulfide is a significant component of coal gas. When coal gas containing hydrogen sulfide is burned as fuel, it generates large amounts of sulfur oxides, causing severe air pollution. Furthermore, using coal gas with high sulfur content as a raw material for downstream facilities increases the cost of subsequent processing, affects product quality, and hinders the improvement of enterprises' economic benefits.

[0003] Large metallurgical enterprises often use wet desulfurization technology due to the large volume of coke oven gas they process. Based on different reaction mechanisms, it is divided into wet oxidation process and wet absorption process.

[0004] Wet oxidation processes use sodium or ammonia from coal gas as the alkali source and employ different additives as catalysts to absorb hydrogen sulfide from the coal gas, which is then oxidized to elemental sulfur through a regeneration system. The biggest advantage of this process is its high desulfurization efficiency, making it particularly suitable for purifying high-sulfur coal gas. However, its drawback is that during the oxidation process, the sulfur-rich desulfurization liquid comes into contact with air, resulting in strong side reactions and the formation of large amounts of compounds such as thiocyanates, thiosulfates, and sulfates. When these salts reach a certain concentration in the desulfurization liquid, they will reduce the coal gas desulfurization efficiency and exacerbate the corrosion of equipment and pipelines, so they need to be removed from the system promptly.

[0005] Wet absorption processes use alkaline substances such as potassium, sodium, and ammonia as absorbents to absorb hydrogen sulfide from coal gas, then reduce it to acidic gas containing hydrogen sulfide through a desorption system. Using acid production technology or the Claus process, the acidic gas is converted into sulfuric acid or high-quality sulfur products. The advantages of this process are that it generates fewer difficult-to-treat salt compounds, and the generated acidic gas is easily processed into chemical products. However, its disadvantage is that, compared to wet oxidation processes, most wet absorption processes have lower desulfurization efficiency and are suitable for use when the sulfur content of the raw coal gas is low (4–6 g / m³). Summary of the Invention

[0006] This disclosure presents a two-tower coke oven gas desulfurization process and equipment.

[0007] According to a first aspect of this disclosure, a two-tower coke oven gas desulfurization process is provided, comprising:

[0008] The coal gas to be desulfurized is fed into the first desulfurization tower for two-stage desulfurization treatment to obtain intermediate product coal gas. The two-stage desulfurization treatment includes desulfurization treatment through desulfurization liquid from the first regeneration tower and desulfurization treatment through desulfurization liquid from the second desulfurization tower.

[0009] The intermediate product gas is fed into a second desulfurization tower for a first-stage desulfurization process to obtain desulfurized gas. The first-stage desulfurization process includes desulfurization treatment through desulfurization liquid from a second regeneration tower.

[0010] In one possible implementation, the method further includes:

[0011] The reacted desulfurization liquid at the bottom of the first desulfurization tower is fed into the first regeneration tower for regeneration treatment via a desulfurization liquid circulation pump to obtain desulfurization liquid.

[0012] In one possible implementation, the method further includes:

[0013] The desulfurization liquid at the bottom of the second desulfurization tower is fed into the first desulfurization tower through a desulfurization liquid circulation pump.

[0014] In one possible implementation, the gas to be desulfurized is fed into a first desulfurization tower for two-stage desulfurization treatment to obtain intermediate product gas, including:

[0015] The desulfurized liquid from the first regeneration tower is fed into the top of the first desulfurization tower;

[0016] The desulfurized liquid from the second desulfurization tower is fed into the lower section of the first desulfurization tower;

[0017] The gas to be desulfurized is fed into the bottom of the first desulfurization tower. During the upward movement of the gas, it undergoes desulfurization treatment with the desulfurization liquid sprayed from the top and bottom of the tower to obtain the intermediate product gas.

[0018] In one possible implementation, the method further includes:

[0019] The desulfurized liquid drawn from the middle of the first desulfurization tower is fed into the second regeneration tower for regeneration treatment to obtain desulfurized liquid.

[0020] In one possible implementation, the intermediate product gas is fed into a second desulfurization tower for a first-stage desulfurization treatment to obtain desulfurized gas, including:

[0021] The desulfurized liquid from the second regeneration tower is fed into the top of the second desulfurization tower;

[0022] The intermediate product gas is fed into the bottom of the second desulfurization tower, and during the upward movement of the intermediate product gas, it undergoes desulfurization treatment with the desulfurization liquid sprayed down from the top of the tower to obtain the desulfurized gas.

[0023] In one possible implementation, the method further includes:

[0024] Concentrated ammonia and catalyst are added to the desulfurization liquid drawn from the middle of the first desulfurization tower.

[0025] According to a second aspect of this disclosure, a two-tower coke oven gas desulfurization process device is provided, characterized in that it comprises: a first desulfurization tower, a second desulfurization tower, a first regeneration tower, and a second regeneration tower.

[0026] Desulfurized liquid from the first regeneration tower and from the second desulfurization tower is fed into the first desulfurization tower to perform two-stage desulfurization treatment on the coal gas to be desulfurized that is fed into the first desulfurization tower, so as to obtain intermediate product coal gas.

[0027] The desulfurized liquid from the second regeneration tower is fed into the second desulfurization tower to perform a first-stage desulfurization treatment on the intermediate product coal gas fed into the second desulfurization tower, thereby obtaining desulfurized coal gas.

[0028] In one possible implementation, the device further includes multiple desulfurization liquid circulation pumps.

[0029] The desulfurization liquid circulation pump is used for:

[0030] The reacted desulfurization liquid at the bottom of the first desulfurization tower is fed into the first regeneration tower for regeneration treatment to obtain desulfurization liquid;

[0031] The desulfurization liquid at the bottom of the second desulfurization tower is fed into the lower section of the first desulfurization tower; and

[0032] The desulfurized liquid drawn from the middle of the first desulfurization tower is fed into the second regeneration tower for regeneration treatment to obtain desulfurized liquid.

[0033] In one possible implementation, the apparatus further includes a reaction tank.

[0034] The reaction tank is located on the path from the desulfurization liquid drawn from the middle of the first desulfurization tower to the second regeneration tower, and is used to supplement concentrated ammonia and catalyst into the desulfurization liquid drawn from the middle of the first desulfurization tower.

[0035] According to the two-tower coke oven gas desulfurization process method of the present disclosure, three-stage desulfurization treatment can be carried out through two desulfurization towers to improve desulfurization efficiency and ensure the desulfurization index of the gas. Two regeneration towers are used to complete the circulation of the desulfurization liquid, and a reaction tank is set up to replenish catalyst and concentrated ammonia water to ensure the quality of the desulfurization liquid. Furthermore, the desulfurization liquid that has not fully reacted in the second desulfurization tower is fed into the lower section of the first desulfurization tower, thereby making full use of the desulfurization liquid and improving its utilization efficiency.

[0036] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Other features and aspects of this disclosure will become clearer from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the specification, serve to illustrate the technical solutions of this disclosure.

[0038] Figure 1 This illustrates a two-tower coke oven gas desulfurization process method according to an embodiment of the present disclosure;

[0039] Figure 2 A schematic diagram of a two-tower coke oven gas desulfurization process equipment according to an embodiment of the present disclosure is shown.

[0040] Figure labels: First desulfurization tower 1, Second desulfurization tower 5, First regeneration tower 8, Second regeneration tower 4, Desulfurization liquid circulation pumps 3, 6, 7, Reaction tank 2. Detailed Implementation

[0041] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0042] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0043] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Furthermore, the term "at least one" in this document means any combination of at least two of any one or more elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0044] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0045] To improve the desulfurization efficiency of the desulfurization liquid, this disclosure adopts a wet oxidation process, using two desulfurization towers and two regeneration towers to carry out a three-stage desulfurization and two-stage regeneration process. This allows the desulfurization liquid to be regenerated in the regeneration tower after desulfurization treatment, maintaining the desulfurization efficiency of the desulfurization liquid, and improving the desulfurization effect of coal gas through three-stage desulfurization.

[0046] Figure 1 This illustrates a two-tower coke oven gas desulfurization process method according to an embodiment of the present disclosure, such as... Figure 1 As shown, the method includes:

[0047] Step S1: The gas to be desulfurized is fed into the first desulfurization tower for two-stage desulfurization treatment to obtain intermediate product gas. The two-stage desulfurization treatment includes desulfurization treatment through desulfurization liquid from the first regeneration tower and desulfurization treatment through desulfurization liquid from the second desulfurization tower.

[0048] Step S2: The intermediate product gas is fed into the second desulfurization tower for a first-stage desulfurization treatment to obtain desulfurized gas. The first-stage desulfurization treatment includes desulfurization treatment through desulfurization liquid from the second regeneration tower.

[0049] In one possible implementation, the gas to be desulfurized can undergo three stages of desulfurization treatment through two desulfurization towers (i.e., the first desulfurization tower and the second desulfurization tower), wherein the first desulfurization tower can undergo two stages of desulfurization treatment, and the second desulfurization tower can undergo one stage of desulfurization treatment.

[0050] In one possible implementation, desulfurization liquid from a first regeneration tower and desulfurization liquid from a second desulfurization tower may be input into the first desulfurization tower. Step S1 may include: inputting desulfurization liquid from the first regeneration tower into the top of the first desulfurization tower; inputting desulfurization liquid from the second desulfurization tower into the lower section of the first desulfurization tower; inputting the gas to be desulfurized into the bottom of the first desulfurization tower, and desulfurizing the gas with the desulfurization liquid sprayed down from the top and bottom sections of the tower during the upward movement of the gas to be desulfurized, thereby obtaining the intermediate product gas.

[0051] In one possible implementation, the height of the first regeneration tower may be higher than that of the first desulfurization tower. Compressed air may be introduced into the first regeneration tower so that the desulfurization liquid that has already reacted can be oxidized and regenerated, and flow to the top of the first regeneration tower. The regenerated desulfurization liquid can flow by gravity to the top of the first desulfurization tower and spray down from the top of the first desulfurization tower.

[0052] In one possible implementation, the desulfurization liquid at the bottom of the second desulfurization tower can be fed into the lower section of the first desulfurization tower by the action of a desulfurization circulation pump, and then sprayed down in the first desulfurization tower.

[0053] In one possible implementation, the gas to be desulfurized is input to the bottom of the first desulfurization tower and rises. During the rising process, it can come into countercurrent contact with the two sections of desulfurization liquid sprayed down and react with each other. This allows the desulfurization liquid to absorb hydrogen sulfide in the gas to be desulfurized, as well as ammonia in the gas, and to replenish the alkali source in the desulfurization liquid.

[0054] In the example, a desulfurization tray can be installed in the middle of the first desulfurization tower, allowing the gas to be desulfurized to pass through the tray, but preventing the desulfurization liquid from passing through. In the lower section of the first desulfurization tower, the gas to be desulfurized can come into countercurrent contact with the desulfurization liquid sprayed down from the bottom of the second desulfurization tower for desulfurization treatment, but cannot come into contact with the desulfurization liquid sprayed down from the top of the first regeneration tower. In the upper section of the first desulfurization tower, the gas to be desulfurized can come into countercurrent contact with the desulfurization liquid sprayed down from the top of the first regeneration tower for desulfurization treatment, and the desulfurization liquid sprayed down from the top of the first regeneration tower is intercepted by the desulfurization tray and discharged from the first desulfurization tower, preventing it from flowing to the lower section and the bottom of the tower. That is, in the first regeneration tower, the gas to be desulfurized can undergo two-stage desulfurization treatment.

[0055] In one possible implementation, the method further includes: using a desulfurization liquid circulation pump to input the reacted desulfurization liquid at the bottom of the first desulfurization tower into a first regeneration tower for regeneration treatment to obtain desulfurization liquid. After desulfurization treatment, the desulfurization liquid sprayed from the first desulfurization tower can be input into the first regeneration tower for regeneration via the desulfurization circulation pump, thereby allowing the desulfurization liquid to be recycled, maintaining its quality while improving its utilization rate.

[0056] In one possible implementation, the method further includes: feeding the desulfurized liquid from the bottom of the second desulfurization tower into the first desulfurization tower via a desulfurization liquid circulation pump. The intermediate product gas entering the second desulfurization tower has a low sulfur content; therefore, the desulfurized liquid in the second desulfurization tower has not fully reacted, meaning it can still absorb more hydrogen sulfide. If the desulfurized liquid from the second desulfurization tower is directly fed into the regeneration tower, it may waste the function and energy consumption of the regeneration tower. Therefore, the insufficiently reacted desulfurized liquid in the second desulfurization tower can be fed into the lower section of the first desulfurization tower via a desulfurization circulation pump to react directly with the gas to be desulfurized, which has a higher hydrogen sulfide content, thereby absorbing more hydrogen sulfide and improving the utilization rate of the desulfurized liquid.

[0057] In one possible implementation, the method further includes: inputting the desulfurization liquid drawn from the middle of the first desulfurization tower into the second regeneration tower for regeneration treatment to obtain desulfurization liquid. As described above, the middle of the first desulfurization tower may be provided with a tower cut-off plate to intercept the desulfurization liquid sprayed from the top of the first desulfurization tower, and the desulfurization liquid drawn from the middle of the first desulfurization tower is input into the second regeneration tower for regeneration treatment via a desulfurization liquid circulation pump. For example, similar to the first regeneration tower, the desulfurization liquid is regenerated by compressed air and transported to the top of the second regeneration tower, thereby flowing into the second desulfurization tower.

[0058] In one possible implementation, step S2 may include: inputting desulfurization liquid from the second regeneration tower to the top of the second desulfurization tower; inputting the intermediate product gas to the bottom of the second desulfurization tower, and performing desulfurization treatment with the desulfurization liquid sprayed down from the top of the tower during the upward process of the intermediate product gas to obtain the desulfurized gas.

[0059] In one possible implementation, the intermediate product gas can enter the bottom of the second desulfurization tower and, during its ascent, come into countercurrent contact with the desulfurization liquid sprayed down from the top of the tower. The desulfurization liquid can absorb the hydrogen sulfide in the intermediate product gas to obtain desulfurized gas. If the sulfur content in the desulfurized gas meets the standard, it can proceed to subsequent processes.

[0060] In one possible implementation, the method further includes supplementing the desulfurization liquid drawn from the middle of the first desulfurization tower with concentrated ammonia and a catalyst. For example, a reaction tank can be installed along the path from the middle of the first desulfurization tower to the second regeneration tower; that is, the desulfurization liquid drawn from the middle of the first desulfurization tower first enters the reaction tank and then enters the second regeneration tower. Concentrated ammonia and a catalyst can be added to the reaction tank to replenish the ammonia and catalyst in the desulfurization liquid, thereby maintaining the quality of the desulfurization liquid.

[0061] In one possible implementation, sulfur foam can be generated at the top of the two regeneration towers due to the regeneration process. The height of the regeneration towers can be used to allow the sulfur foam to flow into a foam tank for subsequent applications. This can increase the byproducts of the desulfurization process.

[0062] In one possible implementation, the flow path of the gas to be desulfurized in the above process is as follows: bottom of the first desulfurization tower, two-stage desulfurization in the first desulfurization tower, top of the first desulfurization tower, bottom of the second desulfurization tower, one-stage desulfurization in the second desulfurization tower, top of the second desulfurization tower, and then leaving the second desulfurization tower after desulfurization.

[0063] In one possible implementation, the flow path of the desulfurization liquid in the above process is as follows: lower section of the first desulfurization tower, bottom of the first desulfurization tower, first regeneration tower, top of the first desulfurization tower, middle section of the first desulfurization tower, reaction tank, second regeneration tower, top of the second desulfurization tower, bottom of the second desulfurization tower, and then back to the lower section of the first desulfurization tower, thus completing the recycling of the desulfurization liquid.

[0064] According to the two-tower coke oven gas desulfurization process method of the present disclosure, three-stage desulfurization treatment can be carried out through two desulfurization towers to improve desulfurization efficiency and ensure the desulfurization index of the gas. Two regeneration towers are used to complete the circulation of the desulfurization liquid, and a reaction tank is set up to replenish catalyst and concentrated ammonia water to ensure the quality of the desulfurization liquid. Furthermore, the desulfurization liquid that has not fully reacted in the second desulfurization tower is fed into the lower section of the first desulfurization tower, thereby making full use of the desulfurization liquid and improving its utilization efficiency.

[0065] Figure 2 A schematic diagram of a two-tower coke oven gas desulfurization process device according to an embodiment of the present disclosure is shown, such as... Figure 2 As shown, the equipment includes: a first desulfurization tower 1, a second desulfurization tower 5, a first regeneration tower 8, and a second regeneration tower 4.

[0066] Desulfurization liquid from the first regeneration tower 8 and the second desulfurization tower 5 is fed into the first desulfurization tower 1 to perform two-stage desulfurization treatment on the coal gas to be desulfurized that is fed into the first desulfurization tower, and to obtain intermediate product coal gas.

[0067] The desulfurized liquid from the second regeneration tower 4 is fed into the second desulfurization tower to perform a first-stage desulfurization treatment on the intermediate product coal gas fed into the second desulfurization tower, thereby obtaining desulfurized coal gas.

[0068] In one possible implementation, the apparatus further includes multiple desulfurization liquid circulation pumps (desulfurization liquid circulation pump 3, desulfurization liquid circulation pump 6, and desulfurization liquid circulation pump 7).

[0069] The desulfurization liquid circulation pump 7 is used to input the reacted desulfurization liquid at the bottom of the first desulfurization tower into the first regeneration tower for regeneration treatment to obtain desulfurization liquid;

[0070] The desulfurization liquid circulation pump 6 is used to input the desulfurization liquid at the bottom of the second desulfurization tower into the lower section of the first desulfurization tower; and

[0071] The desulfurization liquid circulation pump 3 is used to input the desulfurization liquid drawn from the middle of the first desulfurization tower into the second regeneration tower for regeneration treatment to obtain desulfurization liquid.

[0072] In one possible implementation, the device further includes a reaction tank 2, which is located on the path from the middle of the first desulfurization tower to the second regeneration tower, for replenishing concentrated ammonia and catalyst to the desulfurization liquid drawn from the middle of the first desulfurization tower.

[0073] It is understood that the embodiments mentioned above in this disclosure can be combined with each other to form combined embodiments without violating the principle and logic. Due to space limitations, this disclosure will not elaborate further. Those skilled in the art will understand that in the above methods of specific implementation, the specific execution order of each step should be determined by its function and possible internal logic.

[0074] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used in this disclosure is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable other those skilled in the art to understand the embodiments disclosed herein.

Claims

1. A desulfurization process for coke oven gas from a two-tower furnace, characterized in that, include: The coal gas to be desulfurized is fed into the first desulfurization tower for two-stage desulfurization treatment to obtain intermediate product coal gas. The two-stage desulfurization treatment includes desulfurization treatment through desulfurization liquid from the first regeneration tower and desulfurization treatment through desulfurization liquid from the second desulfurization tower. include: The desulfurized liquid from the first regeneration tower is fed into the top of the first desulfurization tower; The desulfurized liquid from the second desulfurization tower is fed into the lower section of the first desulfurization tower; The gas to be desulfurized is fed into the bottom of the first desulfurization tower. During the upward movement of the gas, it is desulfurized by the desulfurization liquid sprayed from the top and bottom of the tower to obtain the intermediate product gas. The intermediate product gas is fed into the second desulfurization tower for a first-stage desulfurization treatment to obtain desulfurized gas, wherein the first-stage desulfurization treatment includes desulfurization treatment through desulfurization liquid from the second regeneration tower; The desulfurized liquid drawn from the middle of the first desulfurization tower is fed into the second regeneration tower for regeneration treatment to obtain desulfurized liquid.

2. The method according to claim 1, characterized in that, The method further includes: The reacted desulfurization liquid at the bottom of the first desulfurization tower is fed into the first regeneration tower for regeneration treatment via a desulfurization liquid circulation pump to obtain desulfurization liquid.

3. The method according to claim 1, characterized in that, The method further includes: The desulfurization liquid at the bottom of the second desulfurization tower is fed into the first desulfurization tower through a desulfurization liquid circulation pump.

4. The method according to claim 1, characterized in that, The intermediate product gas is fed into a second desulfurization tower for a first-stage desulfurization treatment to obtain desulfurized gas, including: The desulfurized liquid from the second regeneration tower is fed into the top of the second desulfurization tower; The intermediate product gas is fed into the bottom of the second desulfurization tower, and during the upward movement of the intermediate product gas, it undergoes desulfurization treatment with the desulfurization liquid sprayed down from the top of the tower to obtain the desulfurized gas.

5. The method according to claim 1, characterized in that, The method further includes: Concentrated ammonia and catalyst are added to the desulfurization liquid drawn from the middle of the first desulfurization tower.

6. A two-tower coke oven gas desulfurization process equipment, characterized in that, include: First desulfurization tower, second desulfurization tower, first regeneration tower, and second regeneration tower. Desulfurized liquid from the first regeneration tower and from the second desulfurization tower is fed into the first desulfurization tower to perform two-stage desulfurization treatment on the coal gas to be desulfurized that is fed into the first desulfurization tower, so as to obtain intermediate product coal gas. The desulfurized liquid from the second regeneration tower is fed into the second desulfurization tower to perform a first-stage desulfurization treatment on the intermediate product gas fed into the second desulfurization tower to obtain desulfurized gas. It also includes multiple desulfurization liquid circulation pumps, The desulfurization liquid circulation pump is used for: The reacted desulfurization liquid at the bottom of the first desulfurization tower is fed into the first regeneration tower for regeneration treatment to obtain desulfurization liquid; The desulfurization liquid at the bottom of the second desulfurization tower is fed into the lower section of the first desulfurization tower; as well as The desulfurized liquid drawn from the middle of the first desulfurization tower is fed into the second regeneration tower for regeneration treatment to obtain desulfurized liquid.

7. The device according to claim 6, characterized in that, It also includes a reaction tank, The reaction tank is located on the path from the desulfurization liquid drawn from the middle of the first desulfurization tower to the second regeneration tower, and is used to supplement concentrated ammonia and catalyst into the desulfurization liquid drawn from the middle of the first desulfurization tower.

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