Method and device for controlling the content of by-product salt in coal gas HPF ammonia desulfurization solution

Abstract

This application relates to a method and apparatus for controlling the by-product salt content in the HPF ammonia desulfurization liquid of coal gas. The method includes the following steps: S1: Compressed air is introduced into the aeration plate at the bottom of the regeneration tower to contact the HPF ammonia desulfurization raw liquid / desulfurization circulating liquid from the reaction tank and regenerate the desulfurization liquid; S2: The regenerated desulfurization liquid overflows from the top of the regeneration tower and enters the reaction tank for recycling; and the sulfur foam generated at the top of the regeneration tower enters the sulfur foam tank through the sulfur foam pipeline. The method of this application can effectively prolong the reaction time between oxygen and desulfurization liquid, resulting in a more complete reaction, effective utilization of oxygen, and effective reduction of by-product salt formation.

Description

Technical Field

[0001] This invention belongs to the field of coal gas purification, specifically relating to a method and apparatus for controlling the content of by-product salts in the HPF ammonia desulfurization liquid of coal gas. Background Technology

[0002] Coal gas desulfurization is a crucial step in the coal gas purification process of the coking industry. The removal of hydrogen sulfide and hydrogen cyanide from coal gas is essential, as it affects the quality of subsequent synthetic industrial products and can cause catalyst poisoning and deactivation. If hydrogen sulfide removal is ineffective, the organic sulfur contained in the coal gas will be oxidized into sulfur dioxide when used as fuel in industrial kilns such as coke ovens and tubular furnaces, resulting in acid rain and environmental pollution. Currently, most coking enterprises in China primarily use the HPF ammonia desulfurization process.

[0003] The HPF ammonia desulfurization process is a wet desulfurization process that uses ammonia as the alkali source and hydroquinone, dinuclear cobalt phthalocyanine sulfonate (PDS), and ferrous sulfate as catalysts. The basic principle is to absorb hydrogen sulfide from the coal gas into a solution and react it with ammonia to generate ammonium hydrosulfide or ammonium polysulfide. The catalyst acts as an oxygen carrier, oxidizing the hydrogen sulfide into elemental sulfur or sulfur foam, thus achieving desulfurization. However, while achieving desulfurization, the HPF ammonia process in coking plants produces large amounts of byproduct salts such as ammonium thiocyanate, ammonium thiosulfate, and ammonium sulfate, commonly known as "three salts." In winter, when temperatures are low, the desulfurization effect is often better controlled, and the growth rate of the three salts in the desulfurization solution is slow. Conversely, in summer, when temperatures are high, the desulfurization effect is difficult to control, and the content of the three salts increases rapidly. Increased content of the three salts inhibits the formation of ammonium polysulfide, resulting in a decrease in the desulfurization effect of the coal gas.

[0004] Therefore, reducing the content of trichlorides in desulfurization liquid has become crucial for the coking industry to ensure desulfurization efficiency. Currently, most coking enterprises in China use salt extraction or acid production processes to reduce by-product salts, which leads to increased energy consumption and hinders energy conservation and emission reduction. Summary of the Invention

[0005] This invention provides a method and related apparatus for controlling the content of by-product salts in the HPF ammonia desulfurization liquid of coal gas.

[0006] On one hand, the present invention provides a method for controlling the content of by-product salts in the HPF ammonia desulfurization liquid of coal gas, the method comprising the following steps:

[0007] S1: Compressed air is introduced into the aeration disc with a bottom aperture of 4.5mm-9mm in the regeneration tower, and comes into contact with the coal gas HPF ammonia desulfurization raw liquid / desulfurization circulating liquid from the reaction tank at a volume ratio of 2.7:1 to 2.0:1 to regenerate the desulfurization liquid. During the regeneration process, some of the ammonium hydrosulfide in the desulfurization raw liquid is oxidized into suspended sulfur, and some of the ammonium polysulfide is oxidized into sulfur foam.

[0008] S2: The regenerated desulfurization liquid overflows from the top of the regeneration tower and enters the reaction tank for recycling; and the sulfur foam generated at the top of the regeneration tower enters the sulfur foam tank through the sulfur foam pipeline.

[0009] In a specific embodiment, the desulfurization raw solution has an ammonium thiocyanate content ≥150g / L, an ammonium thiosulfate content ≥100g / L, and a total content of the three salts of ammonium thiocyanate, ammonium thiosulfate, and ammonium sulfate ≥300g / L.

[0010] In a specific embodiment, the pH of the desulfurization stock solution is ≥9.0.

[0011] In a specific embodiment, the desulfurization raw solution has a volatile ammonia content ≥8.5 g / L, a suspended sulfur content ≥2.0 g / L, and a PDS content ≥60 mg / L.

[0012] In a specific embodiment, the pressure of the compressed air is ≥0.4MPa.

[0013] In a specific embodiment, the volume ratio of compressed air to desulfurization raw liquid is 2.4:1 to 2.2:1, and preferably, the volume ratio of compressed air to desulfurization raw liquid is 2.2:1.

[0014] In a specific embodiment, the method further includes filtering the sulfur foam that entered the sulfur foam tank in step S2 using a filter press.

[0015] On the other hand, the present invention relates to an apparatus for controlling the content of by-product salts in the HPF ammonia desulfurization liquid of coal gas, which includes the following units:

[0016] The reaction tank is used to contain the raw gas desulfurization solution from the HPF ammonia process of the reaction tank and the desulfurization circulating liquid that has been regenerated by the regenerator and overflows from the top of the regeneration tower.

[0017] The regenerator, connected to the reaction tank via pipeline, receives the HPF ammonia desulfurization feedstock from the reaction tank and the desulfurization circulating liquid regenerated by the regenerator. It is also connected to a compressed air supply pipeline to receive compressed air. Its bottom is equipped with an aeration disc with orifices of 4.5mm-9mm for compressed air to pass through.

[0018] The sulfur foam tank, which is connected to the regenerator via a sulfur foam pipeline, is used to receive sulfur floated from the top of the regenerator and to process it.

[0019] In a specific embodiment, the device further includes:

[0020] A desulfurization liquid circulation pump is installed on the pipeline connecting the reaction tank and the regenerator to regulate the volume ratio of compressed air to desulfurization raw liquid or desulfurization circulating liquid.

[0021] Flow meters and control valves are installed on the compressed air supply line to regulate the volume ratio of compressed air to desulfurization raw material or desulfurization circulating liquid.

[0022] In a specific embodiment, the device further includes a filter press connected to a sulfur foam tank, which is used to filter the sulfur foam in the sulfur foam tank.

[0023] Beneficial effects

[0024] The inventors discovered that during the regeneration of desulfurization liquid, reducing the aperture of the aeration disc reduces the bubble volume and increases the number of bubbles. Oxygen in the air oxidizes some ammonium hydrosulfide into suspended sulfur (S) and some ammonium polysulfide into sulfur foam, which flows out through the overflow weir at the top of the regeneration tower. This reduces the content of ammonium hydrosulfide and ammonium polysulfide in the desulfurization liquid, thus disrupting the equilibrium of the by-salt reaction. The by-salt reaction changes from a forward reaction to a reverse reaction (as shown below), and the concentrations of ammonium thiocyanate, ammonium thiosulfate, and ammonium sulfate in the desulfurization liquid decrease accordingly, thus completing this invention.

[0025] By-salt reaction:

[0026]

[0027]

[0028]

[0029] Therefore, the method for controlling the content of by-product salts in the HPF ammonia desulfurization liquid of coal gas provided by the present invention has the following excellent effects: it can effectively prolong the reaction time between oxygen and desulfurization liquid, the reaction is more complete, oxygen is effectively utilized, and the amount of by-product salts generated is effectively reduced. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the device for controlling the content of by-product salts in the HPF ammonia desulfurization liquid of coal gas, and the desulfurization liquid regeneration process.

[0031] Figure 2 The aeration disc is provided in the regeneration tower included in the apparatus of this application.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Reaction tank

[0034] 2. Desulfurization liquid circulation pump

[0035] 3. Regeneration Tower

[0036] 4. Sulfur foam tank

[0037] 5. Flow meter

[0038] 6. Control valve

[0039] 7. Aeration disc

[0040] 8. Aeration disc holes in the regeneration tower Detailed Implementation

[0041] The following examples demonstrate the effectiveness of the present invention in controlling the byproduct salt content of the HPF ammonia desulfurization liquid for coal gas, but are not limited to the following embodiments. Unless otherwise specified, the equipment and methods used are conventional equipment and methods in the art.

[0042] the term

[0043] Desulfurization feedstock: In this article, the desulfurization fluid in the reaction tank before the start of the desulfurization fluid regeneration process will be referred to as desulfurization feedstock.

[0044] Desulfurization circulating fluid: In this article, the desulfurization fluid that enters the regeneration tower and is circulated and regenerated thereafter after the desulfurization regeneration process begins is referred to as desulfurization circulating fluid.

[0045] In this paper, the regeneration process of the desulfurization circulating liquid in the regeneration tower includes the oxidation of the reduced catalyst and the flotation separation of the resulting elemental sulfur.

[0046] Example 1: Pilot-scale sideline performance evaluation:

[0047] like Figure 1 As shown, the device of the present invention includes: a reaction tank 1, a desulfurization liquid circulation pump 2, a regeneration tower 3, a sulfur foam tank 4, a flow meter 5, a control valve 6, and an aeration disc 7. The desulfurization raw liquid in the reaction tank 1 is pressurized by the desulfurization liquid circulation pump 2 and enters the bottom of the regeneration tower 3. Compressed air (≥0.4MPa) is controlled by the control valve 5 and the flow meter 6 to maintain a certain volume ratio of 2.2 with the desulfurization liquid circulation volume, and enters the aeration disc at the bottom of the desulfurization regeneration tower 3. Bubbles are formed through the air holes (pore diameter 4.5mm-9mm, which can be used for biological wastewater treatment). These bubbles fully contact the desulfurization raw liquid (which becomes the desulfurization circulating liquid after the regeneration process begins), causing the tri-salts in the desulfurization raw liquid / desulfurization circulating liquid to be converted into sulfur foam, reducing the content of by-product salts such as ammonium thiocyanate, ammonium thiosulfate, and ammonium sulfate in the desulfurization raw liquid / desulfurization circulating liquid. The sulfur foam generated at the top of regeneration tower 3 enters sulfur foam tank 4 through sulfur foam pipe; the desulfurization liquid at the top of regeneration tower 3 enters reaction tank 1 through desulfurization liquid pipe.

[0048] The above-mentioned desulfurization feedstock comes from the high-salt desulfurization liquid discharged from the HPF ammonia desulfurization unit. Its specifications are as follows: Ammonium thiocyanate content ≥150g / L; Ammonium thiosulfate content ≥100g / L; Total content of ammonium thiocyanate, ammonium thiosulfate, and ammonium sulfate ≥300g / L; pH ≥9.0; Volatile ammonia ≥8.5g / L; Suspended sulfur ≥2.0g / L; PDS content ≥60mg / L. (Note: Generally, the discharged desulfurization liquid meets the specifications. If the discharged desulfurization liquid does not meet the above requirements, the HPF ammonia desulfurization unit is operating stably and does not require the discharge of desulfurization liquid; therefore, there is no need to reduce the three salts in the desulfurization liquid.)

[0049] Taking a coking plant in Hebei Province as an example, 2500m 3 Performance evaluation was conducted on a portion of the / h coke oven gas desulfurization side-stream unit. Specific experimental process operation parameters were defined. The test period was from July 25th to July 30th, 2023, with a desulfurization liquid circulation rate of 50m³. 3 / h, air flow rate 90m 3 / h-140m 3 At an air pressure of 0.40 MPa-0.60 kPa, the contents of ammonium thiosulfate and ammonium sulfate were determined by titration, and the contents of ammonium thiocyanate were determined by colorimetry (spectrophotometry). The results are shown in Table 1 below.

[0050] Table 1

[0051]

[0052] The trichloride content in the desulfurization system is higher than 300 g / L, while the trichloride content in the desulfurization liquid in the side-stream system is less than 300 g / L. Although the side-stream system discharges a portion of the trichloride, it cannot be completely emptied. Therefore, when the desulfurization system is introduced for desulfurization, the desulfurization liquid in the desulfurization system and part of the original desulfurization liquid in the side-stream system are mixed. The trichloride content of the mixed desulfurization liquid is 285.94 g / L.

[0053] The reduction rate of by-product salts is calculated using the following formula:

[0054]

[0055] In actual circulation operation, byproduct salts in the desulfurization liquid can be converted into sulfur foam through their reverse reaction. The data in Table 1 shows that when the desulfurization liquid circulation rate is 50 m³ / s... 3 At a rate of / h, the optimal air volume entering the regeneration tower is 110m³. 3 / h, the byproduct salt in the desulfurization liquid decreased from 285.94 g / L to 231.25 g / L through a reverse reaction, with a reduction rate of 19.12%. The data above demonstrates that the method and apparatus of this application can effectively control the byproduct salt content in the HPF ammonia desulfurization liquid from coal gas, and have industrial applicability.

[0056] Meanwhile, in the HPF ammonia desulfurization station, no aeration discs are installed. Compressed air is directly introduced into the DN200 or DN250 desulfurization liquid pipeline through DN25 or DN50 pipes for mixing (i.e., the current form of air-desulfurization liquid contact in the regeneration tower). The mixture then enters the regeneration tower for reaction. Under these conditions, the tri-salt composition of the desulfurization liquid was also tested, and the results are shown in Table 2 below.

[0057] Table 2

[0058]

[0059] As can be seen from the data in Table 2, the tri-salt content of the desulfurization liquid increased when no aeration disc was installed. This is because the reaction was incomplete and the reaction time was short, resulting in excessive oxygen in some areas, which led to an increase in the concentration of ammonium thiosulfate and ammonium sulfate.

Claims

1. A method for controlling the content of by-product salts in the HPF ammonia desulfurization liquid of coal gas, the method comprising the following steps: S1: Compressed air is introduced into the aeration disc with a bottom aperture of 4.5mm-9mm in the regeneration tower, and comes into contact with the coal gas HPF ammonia desulfurization raw liquid or desulfurization circulating liquid from the reaction tank at a volume ratio of 2.7:1~2.0:1 to regenerate the desulfurization liquid. During the regeneration process, some of the ammonium hydrosulfide in the desulfurization raw liquid is oxidized into suspended sulfur, and some of the ammonium polysulfide is oxidized into sulfur foam. S2: The regenerated desulfurization liquid overflows from the top of the regeneration tower and enters the reaction tank for recycling; and the sulfur foam generated at the top of the regeneration tower enters the sulfur foam tank through the sulfur foam pipeline. The pressure of the compressed air is ≥0.4MPa.

2. The method according to claim 1, wherein, The desulfurization raw solution has an ammonium thiocyanate content ≥150g / L, an ammonium thiosulfate content ≥100g / L, and a total content of ammonium thiocyanate, ammonium thiosulfate and ammonium sulfate trisalts ≥300g / L.

3. The method according to claim 1, wherein, The pH of the desulfurization stock solution is ≥9.

0.

4. The method according to claim 1, wherein, The desulfurization raw liquid has a volatile ammonia content ≥8.5 g / L, a suspended sulfur content ≥2.0 g / L, and a PDS content ≥60 mg / L.

5. The method according to claim 1, wherein, The volume ratio of compressed air to desulfurization raw liquid is 2.4:1 to 2.2:

1.

6. The method according to claim 1, wherein, The volume ratio of compressed air to desulfurization raw liquid is 2.2:

1.

7. The method according to claim 1, wherein, The method further includes filtering the sulfur foam that entered the sulfur foam tank in step S2 using a filter press.

8. An apparatus for controlling the content of by-product salts in the HPF ammonia desulfurization liquid of coal gas using the method described in any one of claims 1-7, wherein... Includes the following units: The reaction tank is used to contain the raw gas desulfurization solution from the HPF ammonia process of the reaction tank and the desulfurization circulating liquid that has been regenerated by the regenerator and overflows from the top of the regeneration tower. The regenerator is connected to the reaction tank via pipeline to receive the coal gas HPF ammonia desulfurization raw liquid from the reaction tank and the desulfurization circulating liquid regenerated by the regenerator. It is also connected to the compressed air supply pipeline to receive compressed air. The bottom of the regenerator is equipped with an aeration disc with an aperture of 4.5mm-9mm for compressed air to pass through. as well as The sulfur foam tank, which is connected to the regenerator via a sulfur foam pipeline, is used to receive sulfur floated from the top of the regenerator and to process it.

9. The apparatus according to claim 8, further comprising: A desulfurization liquid circulation pump is installed on the pipeline connecting the reaction tank and the regenerator to regulate the volume ratio of compressed air to the desulfurization raw liquid or desulfurization circulating liquid from the HPF ammonia method of coal gas from the reaction tank. Flow meters and control valves are installed on the compressed air supply line to regulate the volume ratio of compressed air to desulfurization raw material or desulfurization circulating liquid.

10. The apparatus according to claim 8, further comprising: A filter press connected to a sulfur foam tank is used to filter the sulfur foam in the tank.

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