Method for simultaneous removal of hydrogen sulfide (H2S) and hydrogen cyanide (HCN) from concentrated ammonia

Abstract

The present invention provides a method for removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) from concentrated ammonia water, the method comprising: a catalyst treatment step of contacting concentrated ammonia water containing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) with an iron oxide catalyst; and a regeneration step of supplying a regeneration solution to the iron oxide catalyst to regenerate the iron oxide catalyst. According to the present invention, by simultaneously removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) contained in concentrated ammonia water, it is possible to improve the absorption efficiency of hydrogen sulfide (H2S) and hydrogen cyanide (HCN) of coke oven gas (COG) when using concentrated ammonia water in an H2S scrubber (H2S / S).

Description

Technical Field

[0001] This invention relates to a method for removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) contained in concentrated ammonia water used in an H2S scrubber (H2S / S) in a coking plant for refining coke oven gas (COG), and more specifically, to a method for removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) contained in concentrated ammonia water using an iron oxide catalyst. Background Technology

[0002] A coke oven with multiple carbonization chambers, after being loaded with coal using a charging car, heats it at a temperature of approximately 1240°C or higher in the absence of external air for about 19 hours to produce grayish-white coke, from which volatile components in the coal have been removed. This is a type of coal dry distillation. Furthermore, the coke after dry distillation is discharged from the carbonization chamber using an extruder and then transported to a quenching tower for quenching.

[0003] On the one hand, although not shown in a separate figure, when the carbon is charged into the carbonization chamber, the aforementioned COG is produced through thermal decomposition. This COG is then transported to the refining equipment (coking plant) via riser pipes located above each carbonization chamber.

[0004] COG contains hydrogen sulfide (H2S) and hydrogen cyanide (HCN). When COG is burned, hydrogen sulfide (H2S) is converted to sulfur dioxide (SO2), and hydrogen cyanide (HCN) is converted to nitrogen oxides (NOx). x This process, which involves the removal of tar, hydrogen sulfide, and hydrogen cyanide from COG, contributes to smog. Therefore, COG transported to coking plants requires pre-refining to remove tar, hydrogen sulfide, and hydrogen cyanide before combustion. However, with increasingly stringent environmental regulations, there is a growing demand for higher COG quality. Consequently, methods to improve the absorption efficiency of H2S absorption towers for removing hydrogen sulfide and hydrogen cyanide from COG in coking plants include adding H2S absorption towers and utilizing sodium hydroxide (NaOH), ammonia (NH3), or amine compounds.

[0005] In addition, Korean Patent No. 10-0467774 discloses the following structure: ammonia water used in the H2S absorption tower is transported to an ammonia regeneration tower, and after separating and refining hydrogen sulfide, it is recycled back to the H2S absorption tower.

[0006] Thus, a method for removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) from the concentrated ammonia water supplied to the H2S absorption tower using a relatively simple process is expected to be applicable in related fields. Summary of the Invention

[0007] Technical issues

[0008] The present invention aims to provide a simple and economical method for removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) from concentrated ammonia using an iron oxide catalyst.

[0009] Technical solution

[0010] According to one aspect of the present invention, a method for removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) from concentrated ammonia water is provided, the method comprising: a catalyst treatment step of contacting concentrated ammonia water containing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) with an iron oxide catalyst; and a regeneration step of supplying a regeneration solution to the iron oxide catalyst to regenerate the iron oxide catalyst.

[0011] Invention Effects

[0012] According to the present invention, by simultaneously removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) contained in concentrated ammonia water, the absorption efficiency of hydrogen sulfide (H2S) and hydrogen cyanide (HCN) in coke oven gas (COG) can be improved when concentrated ammonia water is used in an H2S scrubber (H2S / S). Attached Figure Description

[0013] Figure 1 A simplified schematic diagram of an exemplary processing apparatus for performing the method of removing hydrogen sulfide (H2S) and hydrogen cyanide (HCN) from concentrated ammonia water according to the present invention is shown.

[0014] Figure 2 The concentrations of hydrogen sulfide and hydrogen cyanide in concentrated ammonia water before and after removal of hydrogen sulfide and hydrogen cyanide from concentrated ammonia water using an iron oxide catalyst according to the present invention are shown.

[0015] Figure 3 The invention illustrates the measurement of hydrogen sulfide concentration changes in recovered concentrated ammonia water using both regenerated and new catalysts. This confirms that the catalyst can be used semi-permanently through regeneration.

[0016] Preferred Implementation

[0017] Hereinafter, preferred embodiments of the present invention will be described. However, embodiments of the present invention can be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0018] This invention relates to a method for reducing the concentration of hydrogen sulfide (H2S) and hydrogen cyanide (HCN) dissolved in concentrated ammonia water during the treatment of COG generated in coke ovens. The concentrated ammonia water is the absorbent supplied to the H2S absorbent tower to absorb the hydrogen sulfide and hydrogen cyanide contained in the COG. Generally, it is an aqueous solution containing NH3, H2S, CO2, HCN, BTX (benzene, toluene, xylene), etc., with a pH value of 9.5–10.5.

[0019] More specifically, it includes: a catalyst treatment step, in which concentrated ammonia water containing hydrogen sulfide and hydrogen cyanide is contacted with the iron oxide catalyst; and a regeneration step, in which a regeneration solution is supplied to the iron oxide catalyst to regenerate it.

[0020] Concentrated ammonia water used in the purification of COG is used to absorb hydrogen sulfide and hydrogen cyanide contained in the COG. Therefore, by using concentrated ammonia water, which removes hydrogen sulfide and hydrogen cyanide and reduces their concentration, in the H2S absorption tower, the efficiency of absorbing hydrogen sulfide and hydrogen cyanide from COG can be improved.

[0021] A catalyst treatment step involving contacting concentrated ammonia with an iron oxide catalyst can remove hydrogen sulfide and hydrogen cyanide from concentrated ammonia. The iron oxide that can be used in this step can be selected from the group consisting of ferrous oxide (FeO), magnetite (Fe3O4), iron oxide (Fe2O3), and iron hydroxide (Fe(OH)2, Fe(OH)3), with iron oxide (Fe2O3) and iron hydroxide (Fe(OH)3) being preferred.

[0022] There are no particular limitations on the contact step, but for example, it can be achieved by spraying concentrated ammonia water onto the iron oxide catalyst or by immersing the iron oxide catalyst in concentrated ammonia water. However, there are no particular limitations on the contact method. For example, spraying concentrated ammonia water can more effectively contact the concentrated ammonia water and the iron oxide catalyst, thereby increasing the efficiency of removing hydrogen sulfide and hydrogen cyanide from the concentrated ammonia water.

[0023] Particulate iron oxide catalyst is preferred. Specifically, since it may mix with solid sulfur or the like generated in the catalyst treatment step, granular form other than powder is preferred in order to easily separate the solid sulfur and perform catalyst regeneration in the regeneration step. More preferably, particles with an average particle size of 2 to 10 mm are used, and most preferably, particles with an average particle size of 3 to 8 mm are used, but are not limited thereto. As long as it can be easily separated from solid sulfur in the regeneration step and the size of the regenerated catalyst is not limited, it can be used without restriction.

[0024] Simultaneously, air, oxygen, or a combination thereof can be supplied to the iron oxide catalyst to perform the catalyst treatment step. When concentrated ammonia water comes into contact with the iron oxide catalyst, the air, oxygen, or combination thereof can be supplied to the iron oxide catalyst in the same direction as the flow direction of the concentrated ammonia water. When the activity of the iron oxide catalyst decreases while removing hydrogen sulfide and hydrogen cyanide contained in the concentrated ammonia water, the activity of the iron oxide catalyst can be restored. For example, when concentrated ammonia water is sprayed onto the iron oxide catalyst, air can be supplied in the same direction as the spray direction of the concentrated ammonia water. At this time, the oxygen in the air can restore the activity of the iron oxide catalyst. The appropriate amount can be supplied according to the amount of concentrated ammonia water to be treated, and the amount and concentration of hydrogen sulfide and hydrogen cyanide contained in the concentrated ammonia water.

[0025] For example, when air, oxygen, or a combination thereof is supplied to the iron oxide catalyst along with the regeneration solution during the catalyst treatment step, the following reaction occurs.

[0026] 3H₂S + Fe₂O₃ → Fe₂S₃ + ​​3H₂O

[0027] 3H₂S + 2Fe(OH)₃ → Fe₂S₃ + ​​6H₂O

[0028] 2Fe₂S₃ + ​​3O₂ → 2Fe₂O₃ + 3S₂

[0029] S2+CN - →2SCN -

[0030] SCN - +2O₂ + 2H₂O → SO₄²⁻ 2- +CO2+NH4 +

[0031] 4S2→S8

[0032] That is, the solid sulfur (S2 to S8) generated when hydrogen sulfide (H2S) reacts with the iron oxide catalyst reacts with hydrogen cyanide (HCN) to remove hydrogen cyanide. Therefore, both hydrogen sulfide and hydrogen cyanide can be removed together.

[0033] Then, the carbon dioxide produced during the reaction is released in gaseous form, and ammonium ions and sulfate ions exist in concentrated ammonia water in ionic form.

[0034] Based on 1L of concentrated ammonia water, it is preferable to use 10 to 30g of the iron oxide catalyst, more preferably 15 to 25g. When the weight of the iron oxide catalyst is less than 10g, the catalyst action is insufficient, resulting in a decrease in removal efficiency. When it exceeds 30g, the additional increase in removal efficiency is negligible, making it uneconomical.

[0035] In this invention, the catalyst treatment step of contacting concentrated ammonia water with an iron oxide catalyst can reduce the concentration of hydrogen sulfide in concentrated ammonia water to 80% to 90% and the concentration of hydrogen cyanide in concentrated ammonia water to 60% to 70%.

[0036] Meanwhile, the present invention includes a regeneration step of supplying a regeneration solution to the iron oxide catalyst after contacting concentrated ammonia with the iron oxide catalyst to regenerate the iron oxide catalyst.

[0037] The regeneration step can be carried out using an oxidative regeneration solution, which can cause the following reaction.

[0038] 2Fe2S3+6H2O2→2Fe2O3+6H2O+3S2

[0039] 2Fe₂S₃ + ​​6H₂O₂ → 4Fe(OH)₃ + 3S₂

[0040] 2Fe2S3+6ClO - →2Fe₂O₃ + 6Cl - +3S2

[0041] 2Fe2S3+3ClO2 - →2Fe₂O₃ + 3Cl - +3S2

[0042] In addition, the regeneration solution can wash away the solid sulfur formed on the catalyst surface.

[0043] Preferably, the regeneration solution is an oxidation regeneration solution selected from the group consisting of water, ozone water, chlorine dioxide water, H2O2, NaOCl, NaClO2, NaClO3, NaClO4, KMnO4, and HNO3.

[0044] In the regeneration step, the regeneration solution may be supplied to the iron oxide catalyst along with at least one oxidizing gas selected from the group consisting of air, oxygen, ozone and ClO2 gas, preferably oxygen.

[0045] 2Fe₂S₃ + ​​3O₂ → 2Fe₂O₃ + 3S₂

[0046] 2Fe2S3+3O2+6H2O→4Fe(OH)3+3S2

[0047] As described above, by supplying the oxidizing gas and the regeneration solution together to the iron oxide catalyst, small particles such as solid sulfur can be separated from the iron oxide catalyst.

[0048] Compared to virgin catalysts, catalysts regenerated through the regeneration step can achieve a catalytic efficiency of over 80%. Considering the time and cost required for catalyst regeneration, it is preferable to regenerate the catalyst to achieve a catalytic efficiency of 80% to 90% compared to virgin catalysts. This regeneration step allows for the semi-permanent use of the iron oxide catalyst, thereby reducing costs.

[0049] In this invention, a recovery step may also be included to recover concentrated ammonia water obtained from the catalyst treatment step.

[0050] The recovery step may include a solid-liquid separation process. For example, in the recovery step of the concentrated ammonia water, in order to further remove solid sulfur particles, etc., solid-liquid separation may be performed by methods such as sedimentation based on specific gravity difference or centrifugation, so that only concentrated ammonia water can be recovered, but it is not limited to this.

[0051] The present invention will now be described in more detail through specific embodiments. These embodiments are merely examples to aid in understanding the invention and are not intended to limit its scope. Specific Implementation

[0052] Example

[0053] Example 1

[0054] 1 L of concentrated ammonia solution at room temperature (25°C) containing dissolved 953 mg / L hydrogen sulfide (H₂S) and 524 mg / L hydrogen cyanide (HCN) was sprayed into a reaction vessel filled with 20 g of granular iron oxide (Fe₂O₃) catalyst with an average particle size of 4 mm. Simultaneously, air was circulated within the catalyst reaction vessel. The concentrated ammonia solution passing through the iron oxide catalyst was then recovered. The concentration of hydrogen sulfide in the recovered concentrated ammonia solution was analyzed by ion chromatography, and the concentration of hydrogen cyanide in the recovered concentrated ammonia solution was analyzed by continuous flow chromatography. The results were... Figure 2 As shown in the image.

[0055] like Figure 2 As shown, the hydrogen sulfide content in concentrated ammonia water is reduced to 160 mg / L, and the hydrogen cyanide content is reduced to 200 mg / L.

[0056] Example 2

[0057] After regenerating the catalyst by injecting air while using distilled water as the regeneration solution, to compare the catalytic efficiency of the regenerated catalyst and the new catalyst, the same method as in Example 1 was performed, except that either the regenerated catalyst or the new catalyst was used. Then, the concentration change of hydrogen sulfide in the concentrated ammonia solution over time was measured. Figure 3 As shown in the image.

[0058] like Figure 3As shown, under the same reaction time, after 120 minutes, the hydrogen sulfide concentration decreased from 889 mg / L to 30 mg / L with the new catalyst, and from 953 mg / L to 160 mg / L with the regenerated catalyst. Therefore, the hydrogen sulfide removal efficiency of the new catalyst was approximately 96.6%, and the removal efficiency of the regenerated catalyst was approximately 83.2%. Since the regenerated catalyst showed a hydrogen sulfide removal efficiency of 86.1% compared to the new catalyst, it is confirmed that the catalyst can be used semi-permanently by regenerating it.

[0059] The embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the technical spirit of the present invention as set forth in the claims.

[0060] [Symbol Explanation]

[0061] 10, 40: Oxygen storage tank

[0062] 12: Concentrated ammonia tank before treatment

[0063] 14, 20: Solenoid valves used for concentrated ammonia solution

[0064] 16, 26: Catalyst reaction vessel

[0065] 18, 28: Iron oxide catalyst

[0066] 22: Solid-liquid separator

[0067] 24: Treated concentrated ammonia water tank

[0068] 30, 32: Solenoid valves used to supply air, oxygen, ozone, or ClO2 gas.

[0069] 42: Regeneration solution storage tank

[0070] 44, 46: Solenoid valves used for regeneration solutions

[0071] 48, 50: Solenoid valves used to supply air, oxygen, ozone, or ClO2 gas.

Claims

1. A method for removing hydrogen sulfide and hydrogen cyanide from concentrated ammonia water, the method comprising: The catalyst treatment step involves contacting concentrated ammonia water containing hydrogen sulfide and hydrogen cyanide with the iron oxide catalyst. as well as In the regeneration step, an oxidative regeneration solution is supplied to the iron oxide catalyst to regenerate the iron oxide catalyst. The catalyst treatment step is performed by supplying air, oxygen, or a combination thereof.

2. The method for removing hydrogen sulfide and hydrogen cyanide from concentrated ammonia water according to claim 1, wherein, The iron oxide catalyst is in particulate form.

3. The method for removing hydrogen sulfide and hydrogen cyanide from concentrated ammonia water according to claim 1, wherein, The oxidation regeneration solution is an oxidation regeneration solution selected from at least one of the following groups: water, ozone water, chlorine dioxide water, H2O2, NaOCl, NaClO2, NaClO3, NaClO4, KMnO4, and HNO3.

4. The method for removing hydrogen sulfide and hydrogen cyanide from concentrated ammonia water according to claim 1, wherein, The regeneration step is performed together with an oxidizing gas selected from the group consisting of air, oxygen, ozone and ClO2.

5. The method for removing hydrogen sulfide and hydrogen cyanide from concentrated ammonia water according to any one of claims 1 to 4, wherein, Also includes: The recovery step recovers the concentrated ammonia water obtained from the catalyst treatment step.

6. The method for removing hydrogen sulfide and hydrogen cyanide from concentrated ammonia water according to claim 5, wherein, The recycling step includes a solid-liquid separation process.

Images