WO2018048032A1 - Method for purifying coke oven gas and apparatus for purifying coke oven gas - Google Patents

Abstract

A method for purifying coke oven gas, according to an embodiment of the present invention, comprises the steps of: absorbing, in an absorption column, hydrogen sulfide and ammonia contained in coke oven gas by using an aqueous solution of methyldiethanolamine which is an absorption solution, and discharging the absorption solution which has absorbed the hydrogen sulfide and the ammonia; separating, in a regeneration column, the hydrogen sulfide and the ammonia contained in the absorption solution which has absorbed the hydrogen sulfide and the ammonia, into a vapor phase and discharging the regenerated absorption solution; transferring the regenerated absorption solution to the absorption column; and removing heat stable salts (HSS) contained in the regenerated absorption solution transferred to the absorption column by means of an electrodialysis device. Due to this feature, the present invention has the effects of improving the absorption efficiency of hydrogen sulfide and ammonia contained in the coke oven gas and preventing performance deterioration of an absorbent by treating the heat stable salts.

Description

Coke oven gas purification method and stagnation device

The present invention relates to a method for purifying coke oven gas by removing hydrogen sulfide and ammonia contained in the coke oven gas and a purification apparatus thereof.

The coke oven for producing coke is additionally produced by coke oven gas (COG) during the dry distillation process, and the coke oven gas is a major by-product gas of the iron making process used for power generation or fuel in steel mills. . When coke oven gas is generated in a coke oven, it contains impurities such as hydrogen sulfide, ammonia and BTX, which requires a purification process before use.

Among these, hydrogen sulfide is not only the main material causing corrosion of the coke oven gas transfer pipe, but also contains sulfur which is an emission control material and must be removed. In addition, ammonia must be removed as it is a major substance that reacts with carbon dioxide in coke oven gas or other by-product gas to precipitate in the conveying piping in the form of ammonium carbonate and cause the blockage of the pipe.

In general, ammonia (NH ₃ ) or sodium hydroxide (NaOH) is mixed with water to remove hydrogen sulfide contained in the coke oven gas, and ammonia is removed using soft water. However, ammonia and sodium hydroxide, which are used as absorbents of hydrogen sulfide, compete not only with hydrogen sulfide but also with carbon dioxide (about 2-3 vol.%) Present in the coke oven gas, so the amount of absorbent due to simultaneous absorption of hydrogen sulfide and carbon dioxide This takes more than necessary. This increases the size of the coke oven gas refining device more than necessary, and in the regeneration process of regenerating hydrogen sulfide due to the absorption of carbon dioxide due to the excessive input of steam and the presence of carbon dioxide in the subsequent process of producing elemental sulfur from hydrogen sulfide. This causes problems such as an increase in the amount of processing gas and a resulting pressure rise.

On the other hand, in general, two ammonia scrubbers are removed to remove ammonia, and ammonia is removed using soft water, but a large amount of soft water is required to remove ammonia to a desired level. Significant cost is also required for construction and maintenance. Therefore, there is an urgent need for a single process to remove hydrogen sulfide selectively without removing carbon dioxide from the coke oven gas and to remove ammonia with high efficiency.

The present invention is to provide a coke oven gas stagnation method and apparatus for improving the absorption and removal efficiency of hydrogen sulfide and ammonia contained in the coke oven gas, and to prevent the performance degradation of the absorbent liquid by removing the heat stable salt that degrades the performance of the absorbent. do.

According to an embodiment of the present invention, by using an aqueous solution of methyldiethanolamine (MDEA; Methyldiethanolamine) in the absorption tower to absorb hydrogen sulfide and ammonia contained in the coke oven gas (COG), hydrogen sulfide and ammonia Discharging the absorbed liquid absorbed by the gas, separating hydrogen sulfide and ammonia contained in the absorbed liquid in which the hydrogen sulfide and the ammonia are absorbed in a gaseous phase and discharging the regenerated absorbent liquid to transfer the regenerated absorbent liquid to the absorption tower. It provides a method for purifying coke oven gas comprising the step of removing the heat stable salt (HSS; Heat Stable Salt) contained in the regenerated absorbent liquid transferred to the absorption tower using an electrodialysis apparatus.

The methyl diethanolamine aqueous solution may have a concentration of 30 to 50% by weight.

The thermally stable salt may be at least one selected from the group consisting of formate, thiocyanate, acetate, sulfate, chloride, thiosulfate, oxalate, glycolate or nitrate.

The electrodialysis apparatus may remove the heat stable salt contained in the absorbent liquid.

The electrodialysis apparatus may be applied voltage of 8 ~ 13V.

According to an embodiment of the present invention, the absorption tower for absorbing hydrogen sulfide and ammonia contained in the coke oven gas with an aqueous solution of methyldiethanolamine as an absorption liquid, and discharges the absorption liquid absorbed with hydrogen sulfide and ammonia to the bottom, the absorption tower and A regeneration tower connected between the absorption tower and the regeneration tower to remove hydrogen sulfide and ammonia contained in the absorption liquid discharged from the absorption tower in a gaseous phase, and to remove the heat stable salt contained in the absorption liquid discharged from the regeneration tower. Provided is a coke oven gas purification device comprising an electrodialysis device.

The thermally stable salt may be at least one selected from the group consisting of formate, thiocyanate, acetate, sulfate, chloride, thiosulfate, oxalate, glycolate or nitrate.

The electrodialysis apparatus may remove the heat stable salt contained in the absorbent liquid.

The electrodialysis apparatus may be applied voltage of 8 ~ 13V.

According to one embodiment of the present invention, the absorption efficiency of hydrogen sulfide and ammonia contained in the coke oven gas is improved, and thermal stability salts are treated to prevent the deterioration of the absorbent.

1 is a view schematically showing a coke oven gas purification process according to an embodiment of the present invention.

Figure 2 is a graph showing the hydrogen sulfide concentration and hydrogen sulfide removal efficiency contained in the coke oven gas before and after the absorption tower supply.

3 is a graph showing the carbon dioxide concentration contained in the coke oven gas before and after the absorption tower supply.

4 is a graph showing the removal efficiency of ammonia in the absorption tower over time.

Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a method for purifying coke oven gas by removing hydrogen sulfide and ammonia contained in the coke oven gas together, and the present invention to improve the absorption efficiency of hydrogen sulfide and ammonia contained in the coke oven gas, SUMMARY A coke oven gas stagnation method and apparatus for treating thermally stable salts that degrade the performance of an absorbent are provided.

1 is a view schematically showing a coke oven gas purification process according to an embodiment of the present invention, the coke oven gas stagnation device is an absorption tower 201, regeneration tower 202, electrodialysis apparatus 203, pump 204, reflux drum 205, filter 206, heat exchanger 207, and the like.

The coke oven gas 101 additionally generated during the drying of the coke oven is supplied to the lower portion of the absorption tower 201. The coke oven gas contains impurities such as hydrogen sulfide, ammonia, and BTX. Meanwhile, an aqueous solution of methyldiethanolamine (MDEA) is supplied to the absorption tower as an absorption liquid.

In the absorption tower 201, aqueous methyldiethanolamine solution and coke oven gas are in countercurrent contact, and the absorber absorbs hydrogen sulfide and ammonia contained in the coke oven gas. The absorbing liquid 103 in which the hydrogen sulfide and ammonia are absorbed is discharged to the lower portion of the absorption tower. On the other hand, among the gases contained in the coke oven gas, gases such as hydrogen, methane, carbon monoxide, etc., which do not react with the methyldiethanolamine aqueous solution, that is, the coke oven gas 102 from which hydrogen sulfide and ammonia have been removed, is located at the top of the absorption tower 201. Can be discharged through.

Conventionally, aqueous ammonia and sodium hydroxide solution used as an absorbent of hydrogen sulfide were required to excessively increase the amount of the absorption liquid by reacting not only with hydrogen sulfide but also with carbon dioxide, and carbon dioxide absorbed with hydrogen sulfide in a subsequent process of producing sulfur using hydrogen sulfide. This caused problems such as an increase in the amount of processing gas and an increase in pressure. However, according to one embodiment of the present invention, by using only methyldiethanolamine aqueous solution as the absorbent liquid to remove only hydrogen sulfide can prevent the problem caused by the conventional carbon dioxide absorption.

In addition, the conventional coke oven gas purification process is a process for cooling the coke oven gas, removing hydrogen sulfide contained in the coke oven gas, removing the ammonia contained in the coke oven gas, BTX contained in the coke oven gas It was made in the order of removal process. However, the coke oven gas purification process of the present invention can remove hydrogen sulfide and ammonia contained in the coke oven gas at the same time by using methyldiethanolamine aqueous solution as an absorption liquid, so that the process of removing hydrogen sulfide and the process of removing ammonia are separately. Since there is no need to operate the system, the cost of refining process is reduced and the facility itself is simplified.

It is preferable that it is 30-50 weight%, and, as for the density | concentration of the said methyldiethanolamine aqueous solution, it is more preferable that it is 35-45 weight%. If the concentration of the aqueous solution of methyl diethanolamine is less than 30% by weight may increase the size of the device due to the increase in the amount of circulation of the absorbent liquid, and if more than 50% by weight may cause problems in the process operation due to the increase in corrosion and viscosity.

The absorbing liquid 103 absorbed with hydrogen sulfide and ammonia discharged from the lower portion of the absorption tower 201 is transferred by the pump 204 and supplied to the regeneration tower 202 in a preheated state by the heat exchanger 207. . In the regeneration tower, the absorption liquid is regenerated at a temperature of 100 to 130 ° C. Due to such a high temperature, the hydrogen sulfide and ammonia-containing gas 104 may be discharged from the absorbing liquid absorbed by the hydrogen sulfide and ammonia after passing through the flux drum 205. The discharged gas containing hydrogen sulfide and ammonia may be transferred to a sulfur recovery process or a treatment process and used depending on the purpose.

The regenerated absorbing liquid 105, in which hydrogen sulfide and ammonia are separated, is discharged to the lower portion of the regeneration tower 202, cooled to 40 ° C or lower through the heat exchanger 207, and then transferred to the absorption tower and recycled.

The coke oven gas purification process according to the present invention basically absorbs hydrogen sulfide and ammonia in the absorption tower 201 and hydrogen sulfide and ammonia absorbed by applying thermal energy in the form of hot steam in the regeneration tower 202. The regeneration process of separating into the gas phase is repeated. The absorbing liquid is caused by continuously circulating the absorption tower and the regeneration tower of the carbon monoxide (CO) hydrogen cyanide (HCN), by reaction with hydrogen sulfide formate ion (HCCOO ^-) contained in the coke oven ^gas, such as, thiosulfate ion (SCN) It will make acidic material. These acidic substances are combined with MDEA to produce a stable salt, that is, heat stable salt (HSS), which degrades the performance of the absorbent liquid.

These thermally stable salts are salts that do not separate in the regeneration tower 202 operated at a temperature of about 100 to 130 ° C., which may cause corrosion of the process equipment or deteriorate the performance of the absorbent liquid, which may eventually cause absorbent liquid replacement. . Such thermally stable salts can be, for example, one or more selected from the group consisting of formate, thiocyanate, acetate, sulfate, chloride, thiosulfate, oxalate, glycolate or nitrate.

According to one embodiment of the invention, an electrodialysis apparatus 203 is used to remove the thermally stable salts contained in the regenerated absorbent liquid. Due to the electrodialysis method, the anion and the cation of the thermally stable salt may be selectively permeated and then removed to maintain the performance of the aqueous solution of methyldiethanolamine as an absorbent liquid. The aqueous dimethyldiethanolamine solution passed through the electrodialysis apparatus, that is, the absorbent liquid 106 from which the heat stable salt is removed is supplied to the absorption tower 201 to remove hydrogen sulfide and ammonia contained in the coke oven gas.

The electrodialysis apparatus 203 is provided between the absorption tower 201 and the regeneration tower 202, the voltage is applied to the electrodialysis apparatus to remove the thermal stability salt contained in the regenerated absorbent liquid discharged from the regeneration tower It is preferable that it is 8-13V, and it is more preferable that it is 9-11V. If the voltage applied to the electrodialysis apparatus is less than 8V, the ion removal rate may be slow.

On the other hand, the trace amount of ammonia which could not be separated in the regeneration tower 202 may be discharged together with the absorption liquid regenerated to the bottom of the regeneration tower. The regenerated absorbent liquid is supplied to the electrodialysis apparatus 203 for removing the thermally stable salt contained therein, in which part of the ammonia absorbed in the regenerated absorbent liquid may also be removed.

On the other hand, the coke oven gas purification device of the present invention can be used to modify or replace the existing equipment. Specifically, the coke oven gas purification process comprises a hydrogen sulfide scrubber contained in the coke oven gas, an ammonia scrubber contained in the coke oven gas and a BTX scrubber contained in the coke oven gas, in particular for the removal of ammonia Place ammonia scrubber and remove ammonia with soft water.

However, a large amount of soft water is required to remove the ammonia to the desired level, and construction and maintenance of the ammonia scrubber requires a considerable cost.

The coke oven gas purification apparatus of the present invention may be included to replace one or more of two when two ammonia scrubbers are installed, and may preferably be located between the hydrogen sulfide scrubber and the ammonia scrubber and the BTX scrubber.

As described above, the coke oven gas purifying apparatus of the present invention has the advantage of simplifying the chemical conversion process by simultaneously purifying hydrogen sulfide and ammonia. Thus, when replacing the ammonia scrubber in the existing equipment, hydrogen sulfide and ammonia 2 Because of the effect of refining with tea, high-efficiency purification of hydrogen sulfide and ammonia is possible.

In addition, even in applying the existing equipment including two ammonia scrubber, there is little change, so installation and construction are simple and cost advantages can be expected.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The following examples are merely examples to help understanding of the present invention, but the scope of the present invention is not limited thereto.

Example

A 40% by weight aqueous methyldiethanolamine solution (absorbent solution) and a coke oven gas were supplied to the absorption tower so that the aqueous methyldiethanolamine solution (absorbent solution) and the coke oven gas were in countercurrent contact.

A total of four processes were carried out (Examples 1 to 4), and in each example, the concentrations of hydrogen sulfide and carbon dioxide contained in the coke oven gas were measured before feeding the coke oven gas to the bottom of the absorption tower. In addition, the concentrations of hydrogen sulfide and carbon dioxide contained in the purified coke oven gas discharged to the top of the absorption tower were measured. The removal rate of hydrogen sulfide, carbon dioxide, and ammonia was confirmed in the absorption tower based on the measurement result.

2 is a graph showing the hydrogen sulfide concentration and the removal efficiency included in the coke oven gas before and after the absorption tower supply, Figure 3 is a graph showing the carbon dioxide concentration contained in the coke oven gas before and after the absorption tower supply.

According to Figure 2 it was confirmed that the hydrogen sulfide removal efficiency is 91% or more in the absorption tower using the methyldiethanolamine aqueous solution as the absorption liquid and the hydrogen sulfide concentration is 150ppm or less. On the other hand, according to Figure 3 it was confirmed that the removal rate of carbon dioxide in the absorption tower using a methyldiethanolamine aqueous solution as the absorption liquid is significantly low. Therefore, it was confirmed that the methyldiethanolamine aqueous solution can selectively remove only hydrogen sulfide contained in the coke oven gas.

Meanwhile, in Example 1, the concentration of ammonia contained in the coke oven gas was measured with time before supplying the coke oven gas to the bottom of the absorption tower, and the concentration of ammonia contained in the purified coke oven gas discharged to the upper portion of the absorption tower was measured. The concentration was measured over time to calculate the ammonia removal efficiency in the absorption tower, and the results are shown in FIG. 4.

According to Figure 4 it was confirmed that the removal efficiency of the ammonia in the absorption tower is 96% or more.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and changes can be made without departing from the technical spirit of the present invention described in the claims. It will be obvious to those of ordinary skill in the field.

[Description of the code]

101: coke oven gas

102: Coke oven gas with hydrogen sulfide and carbon dioxide removed

103: absorbing liquid in which hydrogen sulfide and carbon dioxide are absorbed

104: gas containing hydrogen sulfide and carbon dioxide

105: regenerated absorbent liquid

106: Absorbent without thermally stable salts

201: absorption tower

202: regeneration tower

203: electrodialysis apparatus

204: pump

205: reflux drum

206: filter

207: heat exchanger

Claims (9)

1. Absorbing hydrogen sulfide and ammonia contained in a coke oven gas (COG) using an aqueous solution of methyldiethanolamine (MDEA) as an absorption liquid in the absorption tower, and discharging the absorption liquid containing hydrogen sulfide and ammonia;

   Discharging hydrogen sulfide and ammonia contained in the absorbent liquid in which the hydrogen sulfide and ammonia are absorbed in a gaseous phase in a regeneration tower to discharge the regenerated absorbent liquid;

   Transferring the regenerated absorbent liquid to the absorption tower; And

   Removing a heat stable salt (HSS) contained in the regenerated absorbent liquid transferred to the absorption tower by using an electrodialysis apparatus;

   Coke oven gas purification method comprising a.
2. The method of claim 1, wherein the methyldiethanolamine aqueous solution has a concentration of 30 to 50% by weight coke oven gas purification method.
3. The method of claim 1, wherein the thermally stable salt is at least one selected from the group consisting of formate, thiocyanate, acetate, sulfate, chloride, thiosulfate, oxalate, glycolate or nitrate.
4. The method of claim 1, wherein the electrodialysis device is a coke oven gas purification method for removing the heat stable salt contained in the absorbent liquid.
5. The method of claim 1, wherein the electrodialysis apparatus is a coke oven gas purification method of the applied voltage is 8 ~ 13V.
6. An absorption tower for absorbing hydrogen sulfide and ammonia contained in the coke oven gas with an aqueous methyldiethanolamine solution as an absorption liquid, and discharging the absorption liquid containing hydrogen sulfide and ammonia downward;

   A regeneration tower connected to the absorption tower and separating hydrogen sulfide and ammonia contained in the absorption liquid discharged from the absorption tower in a gas phase; And

   An electrodialysis apparatus provided between the absorption tower and the regeneration tower to remove thermally stable salts contained in the absorption liquid discharged from the regeneration tower;

   Coke oven gas purification apparatus comprising a.
7. The coke oven gas purifier according to claim 6, wherein the thermally stable salt is at least one selected from the group consisting of formate, thiocyanate, acetate, sulfate, chloride, thiosulfate, oxalate, glycolate or nitrate.
8. The coke oven gas purification device according to claim 6, wherein the electrodialysis device removes the heat stable salt contained in the absorbent liquid.
9. The coke oven gas purifier according to claim 6, wherein the electrodialysis apparatus has an applied voltage of 8 V to 13 V.

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