KR20210078986A - Apparatus and method for purifying flue gas comprising acid gas - Google Patents

Abstract

The present invention relates to an apparatus and a method for purifying flue gas containing acid gas generated during the chemical conversion process of a steelworks or sulfur manufacturing process. The flue gas purification apparatus includes: an absorption tower for absorbing acid gas in the flue gas by an absorption liquid to discharge the purified flue gas; and a regeneration tower connected to the absorption tower to remove the acid gas from the absorption liquid so as to regenerate the absorption liquid and discharge the acid gas, wherein the absorption tower includes a cleaning column for removing nonionic impurities in the flue gas with a cleaning solution, and includes a solid-liquid separation mechanism for regenerating the cleaning solution by removing nonionic impurities in the discharged cleaning solution.

Description

Exhaust gas purification apparatus and method for removing acid gas from exhaust gas containing acid gas {APPARATUS AND METHOD FOR PURIFYING FLUE GAS COMPRISING ACID GAS}

The present invention relates to an exhaust gas purification apparatus and method for purifying an exhaust gas containing an acid gas generated during a steelworks chemical conversion process or a sulfur manufacturing process.

In the present invention, exhaust gas such as COG generated by dry distillation of coal in the chemical conversion process of the ironmaking process or tail gas generated at the rear end of the COG refining process contains acid gases such as _{H 2 S or ammonia.} This acid gas contains sulfur, which is an emission control material, and causes corrosion of the exhaust gas transport pipe and is the main cause of blockage of the transport pipe. Therefore, these acid gases must be removed.

For example, in the chemical conversion process, impurities in COG (tar, dust, mist, H ₂ S, NH ₃ , refers to the process of refining BTX). The chemical conversion process of a steel mill is generally divided into a delivery facility, a refining facility, a by-product recovery facility such as tar, light oil, sulfur, and absorption oil, and a wastewater treatment facility.

Here, COG (Coke Oven Gas) refers to the gas generated from the dry distillation of coke, ^{and has a high calorific value of 4,400 kcal/Nm 3} , so it is used as a heat source in each process of the steel mill.

Ammonia water is a liquid containing a trace amount of ammonia generated by evaporation and condensation of moisture in coal, and is being treated as wastewater at the Hwaseong plant. On the other hand, the composition of COG is CO ₂ 1.6 to 2.8 vol%, O ₂ 0.1 to 1.0 vol%, C ₄ H ₄ 2.6 to 4.4 vol%, CO 5.0 to 7.0 vol%, H ₂ 53.3 to 62.4 vol%. , H ₂ S is contained in about 6.0 to 12.0 g/Nm ^{3 .}

_{Acid gases such as H 2} S contained in COG cause SOx generation, and such acid gases have been generally collected using _{ammonia water (NH 4 OH) generated during the refining process.}

For example, the primary cooling facility is the principle of heat exchange by indirect gas-liquid contact in the PGC (Primary Gas Cooler). After cooling the COG supplied at about 80°C to about 30°C, which is a temperature suitable for collection, H ₂ S in COG is configured to be collected by spraying in the absorption tower using dehydrated water and NH _{3 using soft water or surplus water.}

On the other hand, the BTX scrubber and light oil recovery facility collects BTX (Benzene, Toluene, Xylene) components in COG using Absorbing Oil, and the collected Reached Oil is heated in a heating furnace, It is separated into light oil and absorption oil using the difference in boiling point in the distillation column. The recovered light oil is sold, and the absorbed oil is reused for collection. In addition, the tar recovery facility is composed of a decanter and a receiver facility that separates the water and tar separated in the down comer by the difference in specific gravity (ordination: 1, tar: 1.17). .

However, ammonia water used for _{H 2} S capture has a problem with a low selectivity _{to H 2} S of 68% due to a competitive reaction with _{CO 2 and the like.} Therefore, it is necessary to use a large amount of hands, and due to this, the apparatus for refining the coke oven gas becomes large, and there are problems such as a decrease in productivity and an increase in pressure due to the presence of carbon dioxide in the post-process of producing elemental sulfur from hydrogen sulfide. .

In addition, if the H ₂ S removal efficiency is low, first, a SOx penalty is generated due to the total amount of air emission regulation, second, the increase in STS 304 steel cold-rolled ship flaws increases the production cost by using LNG mixed with it, and third, the pipe Because clogging and corrosion are causing an increase in maintenance costs, a new concept of refining and removal technology is needed.

Patent Document 1: Republic of Korea Patent No. 1839225

The present invention is to provide a purification method and apparatus capable of collecting _{H 2} S in COG generated in a steelworks chemical plant to be 98% or more, that is, H ₂ S present in COG is 0.1 g/Nm ^{3 or less.}

Furthermore, the present invention is to provide a technology capable of prolonging the life of the absorbent liquid used for _{H 2 S collection.}

As an embodiment, the present invention provides an exhaust gas purification apparatus for purifying an exhaust gas containing an acid gas generated in a steelworks chemical conversion process or a sulfur manufacturing process, wherein the apparatus absorbs the acid gas in the exhaust gas as an absorption liquid to produce purified exhaust gas. a discharging absorption tower; and a regeneration tower connected to the absorption tower and configured to remove acid gas from the absorption liquid to regenerate the absorption liquid and discharge acid gas, wherein the absorption tower includes a cleaning column for removing nonionic impurities in the exhaust gas with a cleaning liquid and a solid-liquid separation means for regenerating the washing solution by removing nonionic impurities in the discharged washing solution.

As another aspect, the present invention provides a flue gas purification method for purifying flue gas generated in a steelworks chemical conversion process or a sulfur manufacturing process, wherein the method washes the acid gas-containing flue gas supplied to the absorption tower with a washing solution to remove at least nonionic impurities. A washing step of removing a portion and separating the discharged washing solution into solid-liquid to remove non-ionic impurities, an absorption step of absorbing the acid gas in the flue gas containing the washed acid gas with an absorbent liquid, and discharging the purified flue gas, and from the absorption tower It includes a regeneration step of supplying an acid gas-containing absorption liquid that has absorbed the acid gas to the regeneration tower, and removing the acid gas and regenerating the acid gas into an absorption liquid.

_{The present invention can simultaneously collect H 2} S and NH ₃ using an absorbent such as MDEA, and reduce the absorbent liquid consumption by prolonging the life of the absorbent. can promote

Furthermore, according to the present invention, it is easy to respond to regulations on the total amount of air emissions due to the generation of fine dust and SOx, and it is possible to reduce the cost due to the use of LNG mixed with the increase of STS 304 steel cold-rolled ship defects in the stainless process, and residual It is possible to prevent pipe clogging and corrosion caused by _{H 2 S, thereby reducing operating costs.}

1 is a view schematically showing an exhaust gas purification apparatus and method for purifying an exhaust gas containing an acid gas generated in an ironworks chemical conversion process or a sulfur manufacturing process according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiment 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.

An object of the present invention is to provide a method and apparatus for purifying flue gas containing acid gas generated during an ironmaking process, and specifically, a method for refining COG generated during coal distillation or tail gas generated from a COG refining process, and We want to provide a device.

The present invention is an exhaust gas purification apparatus for purifying an exhaust gas containing an acid gas generated in a steelworks chemical conversion process or a sulfur manufacturing process, and includes an absorption tower and a regeneration tower. An example of an exhaust gas purification apparatus according to the present invention is schematically shown in FIG. 1 .

As can be seen from FIG. 1 , in the absorption tower 200 , the exhaust gases 11 and 12 containing acid gas from the lower part are supplied to the exhaust gas inlet 201 and move to the upper part, and from the upper part of the absorption tower 200 , Acid gas in the exhaust gas is absorbed and removed by the injected absorption liquid 15 , and is discharged through the purified exhaust gas outlet 220 at the top of the tower. The absorbent liquid 15 is injected through the absorption liquid inlet 211 located at the lower end of the purified exhaust gas outlet 220, and the injected absorbent liquid 15 absorbs the acid gas in the exhaust gas and then the exhaust gas inlet 201. It is discharged through the acid gas-containing exhaust gas outlet 212 located at the top.

The absorption liquid 15 can be suitably used in the present invention as long as it is conventionally used to absorb acid gas in the exhaust gas, for example, aqueous ammonia, methylethylamine (MEA), methyldiethanolamine (MDEA), etc. can Among them, methyldiethanolamine has excellent selectivity with respect _{to H 2} S and ammonia contained in the flue gases 11 and 12, and thus, it is more preferable to use methyldiethanolamine having a characteristic less competitive reaction with _{CO 2 .}

The concentration of the aqueous solution of methyldiethanolamine is preferably 30 to 50% by weight, more preferably 35 to 45% by weight. If the concentration of the aqueous solution of methyldiethanolamine is less than 30% by weight, the circulating amount of the absorbent solution 15 may increase and thus the size of the device may be increased. If it exceeds 50% by weight, corrosion problems and viscosity may increase, causing problems in process operation. have.

Meanwhile, in the exhaust gases 11 and 12, _{nonionic impurities such as naphthalene, tar, dust, mist, etc. are included in addition to H 2} S to be removed by the absorption liquid 15, which are also removed by the absorption liquid 15. do. However, when these nonionic impurities are included, there is a problem in that the regeneration rate of the absorbent liquid 15 such as methyldiethanolamine is lowered and the lifespan is shortened. In addition, these nonionic impurities may cause obstacles such as clogging of pipes in the process while continuously circulating the absorption tower 200 and the regeneration tower 300 . Therefore, it is more preferable to remove them before being absorbed by the absorbent liquid 15 .

To this end, the present invention includes a step of cleaning the exhaust gas, including a cleaning column 202 for cleaning the exhaust gas (11, 12) supplied to the absorption tower 200, as shown in FIG. The cleaning column 202 is located between the exhaust gas inlet 201 to which the exhaust gases 11 and 12 are supplied and the acid gas-containing absorbent liquid outlet 212 from which the acid gas-containing absorbent liquid 16 absorbing the acid gas is discharged.

At least a portion of the nonionic impurities contained in the exhaust gases 11 and 12 are washed and removed by spraying the cleaning liquid 13 to the exhaust gases 11 and 12 passing through the cleaning column 202, and the used cleaning liquid 14 is It is discharged to the bottom of the absorption tower (200). Thereby, it is possible to reduce the amount of nonionic impurities contained in the exhaust gases 11 and 12 that are removed by the absorption liquid 15, so that the deterioration of the absorption liquid 15 can be suppressed or delayed, and pipe clogging can be prevented. have. The cleaning solution 13 may be aqueous ammonia.

Although not limited thereto, the exhaust gases 11 and 12 of about 50° C. are introduced through the exhaust gas inlet 201. At this time, by spraying the cleaning liquid 13 into the cleaning column 202, the exhaust gases 11 and 12. Nonionic impurities such as naphthalene, tar, dust, and mist in the flue gases 11 and 12 can be collected and removed by gas-liquid contact with the gas. In this case, the cleaning liquid 13 may be sprayed in an amount of 1 to 7 tons or 3 to 5 tons per hour based on, for example, the exhaust gas 90000 Nm ^{3 /hr.}

On the other hand, since the exhaust gases 11 and 12 supplied to the absorption tower 200 have passed through a blower (not shown), it is a relatively high temperature of 40 to 50° C., and in the washing column 202, ammonia water, etc. By spraying the cleaning liquid 13 , the exhaust gases 11 and 12 can be cooled. The cleaning column 202 preferably has a temperature of 35° C. or less, and if necessary, the temperature of the cleaning column 202 can be lowered to about 20° C. by using a chiller.

By lowering the temperature of the flue gases 11 and 12 in this way, it is possible to more easily remove a significant amount of nonionic impurities such as tar and naphthalene contained in the flue gases 11 and 12, and the absorption tower 200 absorbs the acid gas. Thus, it is possible to keep the circulating absorbent liquid clean. On the other hand, when the temperature of the washing column 202 exceeds 35° C., since the moisture content in the exhaust gases 11 and 12 supplied to the absorption tower 200 increases, there is a problem of increasing the moisture content in the absorption liquid.

The used cleaning solution 14 may be discharged to the outside of the process as it is, but it is preferable to circulate it and reuse it after removing the nonionic impurities. When the used cleaning solution is reused, the nonionic impurities may be removed by solid-liquid separation means between the nonionic impurities and the cleaning solution. The solid-liquid separation means may include, for example, a decanter 204 for precipitating and removing nonionic impurities using a specific gravity difference. After removing the nonionic impurities, the regenerated cleaning solution 13 may be supplied to the cleaning column 202 by the circulation pump 203 or the like.

Meanwhile, the acid gas-containing absorption liquid 16 may include some nonionic impurities that are not removed by the cleaning liquid 13 together with the acid gas. It is also preferable to remove nonionic impurities contained in the acid gas-containing absorbent liquid 16 by solid-liquid separation. The solid-liquid separation means is not particularly limited, but a settling drum 214 may be used. Impurities in the acid gas-containing absorbent liquid 16 may be precipitated and removed using the sedimentation drum 214 , and the supernatant may be sent to the regeneration tower 300 to be regenerated as an absorbent liquid. Thereafter, if necessary, a filter 216 may be provided to further remove impurities.

The absorbent liquid 16 containing acid gas, such as hydrogen sulfide and ammonia, discharged through the acid gas-containing absorbent liquid outlet 212 in the lower portion of the absorption tower 200 is transferred by a pump or the like, and is transferred by a heat exchanger 205 at 60 to 120° C. It is supplied to the regeneration tower 300 in a preheated state to a temperature of

In the regeneration tower 300, regeneration is performed with the absorption liquid at a temperature of 100 to 130° C., by heating the absorption liquid 16 containing the acid gas by applying high-temperature steam as a thermal energy source by the steam reboiler 307, the acid gas is produced It can be separated in the gas phase and regenerated as an absorbent liquid. The regenerated absorbent liquid 17 is discharged to the regenerated absorbent liquid outlet 302 at the bottom of the regeneration tower 300 , is cooled to 40° C. or less through the heat exchanger 250 , and then transferred to the absorption tower 200 and recirculated. .

On the other hand, the acid gas containing the acid gas separated from the absorption liquid 16 containing the acid gas due to the high temperature as described above is discharged through the acid gas outlet 308 at the upper part of the regeneration tower 300, and the reflux drum ( 309) and discharged outside the process. The discharged gas containing the acid gas may be transferred to the Klaus system as the tail gas 12 of the sulfur recovery process and treated.

The purification process of the flue gas containing the acid gas according to the present invention is basically an absorption process of absorbing the acid gas in the flue gas in the absorption tower 200, and the absorption by applying high-temperature steam as a thermal energy source in the regeneration tower 300 The regeneration process of separating the acid gas of hydrogen sulfide and ammonia into gas phase is repeated. At this time, the absorption liquids 15 and 17 react with carbon monoxide (CO), hydrogen cyanide (HCN), and hydrogen sulfide contained in the flue gases 11 and 12 by continuously circulating the absorption tower 200 and the regeneration tower 300 to react with formate ions. (HCCOO ^- ), thiosulfate ion (SCN ^- ), etc. These acidic substances are combined with MDEA to form a stable salt, that is, a heat stable salt (HSS), which deteriorates the performance of the absorbent.

These thermally stable salts are at 100 to 130 °C. As it is not separated in the regeneration tower 200 operated at a temperature of a certain degree, it is accumulated in the absorption liquid and corrodes process equipment or decreases the performance of the absorption liquid, which may eventually cause replacement of the absorption liquid. The thermally stable salt may be, for example, at least one selected from the group consisting of formate, thiocyanate, acetate, sulfate, chloride, thiosulfate, oxalate, glycolate, and nitrate.

According to an embodiment of the present invention, an ion exchange resin reclaimer 218 including an ion exchange resin may be used to remove the thermally stable salt contained in the regenerated absorbent liquid. By passing the regenerated absorbent liquid 17 through the ion exchange resin reclaimer 218, thermal stability salts in the form of anions contained in the regenerated absorbent liquid 17 are selectively removed, thereby improving the performance of the regenerated absorbent liquid 17. to be able to keep

When 15% or more of the regenerated absorbent liquid 17 is passed through the ion exchange resin reclaimer 218, the performance of the regenerated absorbent liquid 17 can be maintained, and the lifespan of the regenerated absorbent liquid 17 can be prolonged. More preferably, 20% or more of the regenerated absorbent liquid 17 is passed through the reclaimer 218 . However, as the amount of the regenerated absorbent liquid 17 passing through the ion exchange resin reclaimer 218 increases, the thermal stability salt content in the regenerated absorbent liquid 17 can be reduced, but the Since the facility has to be enlarged, it is more preferable to pass 50% or less, for example, 30% or less, of the regenerated absorbent liquid 17 through the ion exchange resin reclaimer 218 in terms of removal of thermal stability salts and equipment optimization. Do.

Therefore, a portion of the regenerated absorption liquid 17 containing the thermal stability salt is supplied to the absorption liquid inlet 211 of the absorption tower 200 through the bypass pipe, and a portion passes through the ion exchange resin reclaimer 218 after It is supplied to the absorption liquid inlet 211 of the absorption tower 200 together with the regenerated absorption liquid 17 and/or the new absorption liquid 15 to be bypassed.

On the other hand, in the case of using the ion exchange resin reclaimer 218, the ion exchange resin reaches a saturated state with a thermally stable salt. In this case, the ion exchange resin is periodically washed using externally supplied washing water. , regenerate the ion exchange resin with a regenerating material such as sodium hydroxide.

Washing water after washing the ion exchange resin can be recycled as an absorbent solution because it contains a high concentration of amine compounds. At this time, since the washing water contains a large amount of water compared to the existing absorbent liquid, when it is added as an absorbent liquid, the acid gas absorption performance is deteriorated due to the increase in the absorbent liquid capacity and the low concentration of the amine aqueous solution. Therefore, when the ion exchange resin washing water is recycled as the process circulating fluid, it is preferable to remove moisture from the process circulating fluid.

After washing the ion exchange resin with the washing water, the washing water remains in the pores of the ion exchange resin. The water remaining in these pores may be removed in the process of passing a part of the regenerated absorbent solution through the ion exchange resin.

On the other hand, the acid gas (tail gas) discharged through the upper portion of the regeneration tower 300 _{contains a large amount of sulfur components such as S, H 2} S, SO ₂ , and COS. From this tail gas, the method of the present invention as described above And it can purify the sulfur component using the device.

However, the tail gas is H ₂ S in addition to reproducing the tower is 300 discharged to the upper portion, which contains S, SO _2, COS, such as bars, it is necessary to convert them to H ₂ S. Therefore, it is preferable to perform the purification process after preparing _{the tail gas as H 2} S by supplying the tail gas together with hydrogen to the hydrogenation reactor 104 for hydrogenation reaction.

The tail gas supplied to the hydrogenation reaction is heated by injecting LNG and air through the burner 102, and then S, SO _{2 by reaction with hydrogen in the presence of Mo or Co catalyst in the hydrogenation reactor 104.} , it can be prepared as _{H 2} S from sulfur components such as COS. Thereafter, after removing the water by cooling to the sink 106, it is introduced into the absorption tower 200 through a blower or the like to perform the purification process of the exhaust gas (tail gas, 12) containing the acid gas.

The exhaust gas purified according to the present invention (including the purified tail gas) may be stored in the gas holder 221 and used as an energy source.

According to the present invention as described above, it is possible to selectively remove the acid gas from the exhaust gas containing the acid gas, and it is possible to suppress problems such as clogging of the pipe due to the nonionic impurities contained in the exhaust gas.

11: COG 12: tail gas
13: cleaning liquid or regenerated cleaning liquid 14: used cleaning liquid
15: absorbent liquid 17: regenerated absorbent liquid
16: acid gas containing absorption liquid 102: burner
104: Hydrogenation Reactor 106: Accumulator
108: blower 200: absorption tower
201: exhaust gas inlet 202: cleaning column
203, 305: circulation pump 204: decanter
205, 250: heat exchanger 211: absorption liquid inlet
212: acid gas-containing absorption liquid outlet 214: sedimentation drum
216, 217: filter 218: ion exchange resin reclaimer
220: purified flue gas outlet 221: gas holder
300: regeneration tower 301: acid gas containing absorption liquid inlet
302: regenerated absorbent liquid outlet 307: steam reboiler
308: acid gas outlet 309: reflux drum

Claims (14)

As an exhaust gas purification apparatus for purifying exhaust gas containing acid gas generated during the chemical conversion process of a steelworks or sulfur manufacturing process,
an absorption tower for absorbing acid gas in the exhaust gas as an absorption liquid and discharging purified exhaust gas; and a regeneration tower connected to the absorption tower, removing acid gas from the absorption liquid to regenerate the absorption liquid and discharging the acid gas,
The absorption tower includes a washing column for removing nonionic impurities in the exhaust gas with a washing solution,
and a solid-liquid separation means for regenerating the washing solution by removing nonionic impurities in the discharged washing solution. The flue gas purification apparatus according to claim 1, wherein the washing column is located between the flue gas inlet and the absorbent liquid outlet. The flue gas purification apparatus according to claim 1, wherein the washing liquid is discharged to the bottom of the absorption tower, and at least part of it is circulated to the washing column. The exhaust gas purification apparatus according to claim 1, wherein the solid-liquid separation means is a decanter. The exhaust gas purification apparatus according to claim 1, further comprising a settling drum for precipitating and removing nonionic impurities in the absorbing liquid that has absorbed the acid gas. The flue-gas purification apparatus according to claim 1, further comprising a hydrogenation reactor for supplying the flue gas to the absorption tower after generating hydrogen sulfide by reacting sulfur in the sulfur-containing flue gas with hydrogen. The flue gas purification apparatus according to claim 1, further comprising a purification flue gas holder for storing the purified flue gas. According to claim 1,
a pipe for transferring the regenerated absorbent liquid discharged from the regeneration tower to the absorption tower;
and an ion exchange resin reclaimer that branches from the pipe to supply at least a portion of the regenerated absorbent liquid, and removes thermally stable salts from the regenerated absorbent liquid by ion exchange,
An exhaust gas purification device for supplying the regenerated absorbent liquid that has passed through the ion exchange resin reclaimer to the absorption tower through the pipe. As an exhaust gas purification method for refining the exhaust gas generated in the steelworks chemical conversion process or sulfur manufacturing process,
a washing step of removing at least a portion of nonionic impurities by washing the acid gas-containing exhaust gas supplied to the absorption tower with a washing solution, and solid-liquid separation of the discharged washing solution to remove nonionic impurities;
an absorption step of absorbing the acid gas in the cleaned acid gas-containing exhaust gas with an absorption liquid and discharging the purified exhaust gas; and
An exhaust gas purification method comprising a regeneration step of supplying an acid gas-containing absorption liquid that has absorbed the acid gas from the absorption tower to a regeneration tower, and removing the acid gas and regenerating it into an absorption liquid. The method of claim 9, wherein the washing liquid is aqueous ammonia. The flue gas purification method according to claim 9, wherein nonionic impurities are removed by solid-liquid separation of the acid gas-containing absorbent liquid discharged in the absorption step and supplied to the regeneration tower. The method of claim 9, wherein the absorption liquid is methyldiethanolamine. 10. The method of claim 9, further comprising the step of injecting 15 to 50% of the regenerated absorption liquid into an absorption tower after passing through an ion exchange resin to remove thermally stable salts. The method of claim 13, further comprising washing the ion exchange resin of the reclaimer with washing water, discharging the washing water as an absorption liquid, and removing some moisture from the absorption liquid.

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