WO2015102136A1

WO2015102136A1 - Energy saving type method for removing acid gas through pretreatment using ammonia water

Info

Publication number: WO2015102136A1
Application number: PCT/KR2014/000086
Authority: WO
Inventors: 강기준
Original assignee: (주)에이엠티퍼시픽; 강기준
Priority date: 2014-01-06
Filing date: 2014-01-06
Publication date: 2015-07-09

Abstract

The present invention relates to an energy saving type method for removing acid gas through a pretreatment using ammonia water and, more specifically, to an energy saving type method for removing, through a pretreatment using ammonia water, acid gas included in a gas source selected from among natural gas, pre-combustion gas, post-combustion gas, synthetic gas, and reactor discharge gas, the method comprising the steps of: treating the gas source by introducing the gas source into a first absorption tower containing ammonia water as a first absorbent (first step); and treating an upper discharge gas of the absorption tower by introducing the upper discharge gas into a second absorption tower (second step). According to the method for removing acid gas, it is possible to: remove most carbon dioxide in advance through an ammonia water pretreatment; save energy by using waste heat generated during the process; re-use ammonia water through an enriching column; and downsize and simplify a carbon dioxide production process and a sulfur production process after the removal of acid gas by, from acid gas, separating and discharging an inorganic sulfur compound and an organic sulfur compound.

Description

Energy saving type acid gas removal method through pretreatment with ammonia water

The present invention is a process for removing acid gas from a gas source containing an acid gas, such as natural gas, pre-combustion gas, post-combustion gas, syngas or reactor exhaust gas, more specifically natural gas, pre-combustion gas, post-combustion The present invention relates to a method for removing acid gas through pretreatment with ammonia water from gas, syngas, reactor exhaust gas and the like.

In general, using methane (CH ₄ ), hydrogen (H ₂ ) and carbon monoxide (CO) in natural gas, pre-combustion gas, post-combustion gas, syngas, reactor exhaust gas, etc. in a reactor or combustor In order to remove the acid gas, impurities such as carbon dioxide (CO ₂ ), inorganic sulfur compounds (H ₂ S), and organic sulfur compounds (COS, CS _2, etc.) are removed.

Generally, absorbents are used in combination with additives to remove acid gases.

However, these absorbents should use medium pressure steam (3.0 kg / cm ² G to 5.0 kg / cm ² G) because the regeneration temperature is about 120 ℃ to 140 ℃ when removing the absorbed acid gas.

In this case, the selectivity of the absorbent to absorb acid gas is in the order of carbon dioxide (CO ₂ )-> inorganic sulfur compound (H ₂ S)-> organic sulfur compound (COS).

Therefore, the absorbent absorbs the highest amount of carbon dioxide in the gas and then absorbs the inorganic sulfur compound and the organic sulfur compound. Therefore, a large amount of the absorbent has to be circulated to remove the inorganic sulfur compound and the organic sulfur compound. It consumes energy.

In addition, even though circulating a large amount of absorbent, circulating the amount of absorbent necessary to remove 1 vol ppm or less of organic sulfur compounds is industrially unreasonable, and the syngas discharged to the top of the absorption tower contains about 30 vol ppm of organic sulfur compounds. have. Therefore, before the synthesis gas discharged to the absorption tower is used in the reaction process, a reactor for converting the organic sulfur compound into an inorganic sulfur compound to completely remove the sulfur component is needed, and a gas is introduced into the reactor for converting the organic sulfur compound into an inorganic sulfur compound. High temperature steam must be used (approximately 30 kg / cm ² ) since the temperature must be raised from about 45 ℃ to 150 ℃ before.

Meanwhile, even though Korean Patent No. 0572286 discloses a method of removing acid gas components such as carbon dioxide and inorganic sulfur compounds from a gas by using a specific absorption medium, it does not disclose an efficient removal process of acid gas through ammonia water pretreatment.

The present invention was created in order to solve the problems as described above, by using ammonia water to remove the acidic gas to reduce the use of the medium pressure steam, and pre-treatment by ammonia water to increase the energy efficiency using waste heat generated in the process The purpose is to provide a method for removing energy-saving acid gas.

The present invention provides a method for removing an acid gas included in a gas source selected from natural gas, pre-combustion gas, post-combustion gas, syngas, or reactor exhaust gas, wherein the gas source is a first absorbent including ammonia water. Processing by introducing into an absorption tower (first step); And a step (second step) of flowing the upper exhaust gas of the first absorption tower into a second absorption tower using a second absorbent (second step), thereby providing an energy saving acid gas removing method. .

The energy saving acid gas removing method according to the present invention provides the following effects.

First, in the acid gas removal process using ammonia water, most of the carbon dioxide is removed in advance by using low-temperature waste heat, so the circulation amount of the absorbent can be reduced in the process using the second absorbent using medium pressure steam. Can be reduced.

Second, the energy generated in the process of removing acidic gas using the second absorbent can be used as the energy of the process of removing acidic gas using ammonia water, which further reduces energy in the acidic gas removal process using ammonia. can do.

Third, since the energy required for the process of removing the acidic gas using ammonia water is provided in the process of removing the acidic gas using the second absorbent, cooling energy required in the process using the second absorbent can be reduced.

Fourth, since inorganic sulfur compounds and organic sulfur compounds are separated and discharged from acidic gases, carbon dioxide production process and sulfur production process can be miniaturized and simplified after acidic gas removal.

1 is an acid gas removal process using a conventional second absorbent.

2 is an embodiment of the present invention, an acid gas removal process using a second absorbent after removing the acid gas through the absorption tower using ammonia water as the absorbent.

Figure 3 is an acid gas removal process through another embodiment of the present invention.

Figure 4 is an acid gas removal process through another embodiment of the present invention.

100: second absorption tower 200: second stripping tower

300: first absorption tower 400: first stripping tower

500: concentration tower

101, 301, 501, 601, 701: heat exchanger

102, 302, 502: Cooler 203, 403, 503: Reboiler

204, 404, 504: condenser

The present invention provides a method for removing an acid gas included in a gas source selected from natural gas, pre-combustion gas, post-combustion gas, syngas, or reactor exhaust gas, wherein the gas source is a first absorbent including ammonia water. Processing by introducing into an absorption tower (first step); And a step (second step) of introducing the upper exhaust gas of the first absorption tower into the second absorption tower using the second absorbent (second step), and energy saving type acid by pretreatment with ammonia water. Provide a method for degassing.

The first step may include introducing the gas source into a first absorption tower including ammonia water as a first absorbent to absorb acid gas into ammonia; Transferring the upper exhaust gas of the first absorption tower to a second absorption tower; Exchanging the lower discharge solution of the first absorption tower with the lower discharge solution of the first stripping tower and then introducing the lower discharge solution into the first stripping tower; Removing the acid gas absorbed by the ammonia from the first stripping column and discharging the acid gas upwardly; Heat-exchanging the lower discharge solution of the first stripping tower with the lower discharge solution of the first absorption tower and cooling the liquid to flow into the upper portion of the first absorption tower; Introducing ammonia water obtained by washing with water in the upper portion of the first absorption tower and ammonia water obtained by washing with water in the upper portion of the first stripping column to a concentration tower; And discharging the concentrated ammonia from the top of the concentration tower.

In addition, the second step, the step of introducing the upper exhaust gas of the first absorption tower into the second absorption tower; Discharging the gas source remaining after absorbing the acidic gas into the second absorbent in the second absorption tower; Exchanging the lower discharge solution of the second absorption tower with the lower discharge solution of the second stripping tower and then introducing the liquid into the second stripping tower; Removing the acid gas absorbed by the second absorbent from the second stripping tower and discharging the acid gas upwardly; The lower discharge solution of the second stripping tower may include heat exchange with the lower discharge solution of the second absorption tower and then cooled to flow into the upper portion of the second absorption tower.

More specifically, the energy-saving acid gas removal method, the step of introducing the gas source into the first absorption tower containing ammonia water as the first absorbent to absorb the acid gas in the first absorbent; Introducing a lower discharge solution of the first absorption tower into a first stripping tower; Removing the acid gas absorbed by the first absorbent from the first stripping tower and discharging the acid gas to an upper portion of the first stripping tower; Absorbing the remaining acid gas into the second absorbent by introducing the upper discharge solution of the first absorbent into the second absorbent including the second absorbent; Removing the acid gas absorbed by the second absorbent from the second stripping tower and discharging the acid gas to an upper portion of the second stripping tower; And heat-exchanging the lower discharge solution of the second stripping column with the lower discharge solution of the first absorption tower and then introducing the lower discharge solution into the first stripping tower.

In addition, the acid gas may be any one or a combination of two or more selected from the group consisting of carbon dioxide, inorganic sulfur compounds and organic sulfur compounds.

In addition, the energy-saving acid gas removal method, the gas source is introduced into a first absorption tower including ammonia water as a first absorbent to absorb the acid gas to ammonia; Exchanging the lower discharge solution of the first absorption tower with the lower discharge solution of the first stripping tower and then introducing the lower discharge solution into the first stripping tower; Removing the acid gas absorbed by the ammonia from the first stripping column and discharging the acid gas upwardly; Heat-exchanging the lower discharge solution of the first stripping tower with the lower discharge solution of the first absorption tower and cooling the liquid to flow into the upper portion of the first absorption tower; Introducing ammonia water obtained by washing with water in the upper portion of the first absorption tower and ammonia water obtained by washing with water in the upper portion of the first stripping column to a concentration tower; Discharging the concentrated ammonia from the top of the concentration tower; Introducing a lower discharge solution of the concentration tower into a first absorption tower; Introducing an upper discharge gas of the first absorption tower into a second absorption tower; Discharging the gas source remaining after absorbing the acidic gas into the second absorbent in the second absorption tower; Exchanging the lower discharge solution of the second absorption tower with the lower discharge solution of the second stripping tower and then introducing the liquid into the second stripping tower; Removing the acid gas absorbed by the second absorbent from the second stripping tower and discharging the acid gas upwardly; Heat-exchanging the lower discharge solution of the second stripping tower with the lower discharge solution of the second absorption tower and cooling the liquid to flow into the upper portion of the second absorption tower; And heat-exchanging the lower discharge solution of the second stripping tower with the first absorption tower lower discharge solution flowing into the first stripping tower, and then introducing the lower discharge solution into the first stripping tower.

That is, according to the present invention, the first discharge tower bottom discharge solution flowing into the first stripping column is heat-exchanged with the bottom discharge solution of the first stripping tower, and then heat exchanged once more with the bottom discharge solution of the second stripping tower To the first stripping column.

The second absorbent may be selected from the group consisting of amine compounds, calcium absorbents and sodium absorbents.

In addition, the ammonia water introduced into the concentration tower may be introduced into the concentration tower by exchanging heat again with the lower discharge solution of the second stripping column.

In addition, the first absorption tower and the first stripping tower using ammonia water may be provided with a washing unit for absorbing and recovering the lost ammonia as water, by cooling the water discharged to the lower portion of the concentration tower to enter the washing unit ammonia Can be used for absorption. At this time, the water discharged to the bottom of the concentration tower may be used after cooling the heat exchanged with the solution washed in the upper portion of the first absorption tower and the first stripping tower.

Hereinafter, the energy saving type acid gas removal method through pretreatment with ammonia water according to the present invention will be described in more detail with one embodiment of removing acid gas from bunker-C oil. At this time, the composition of the gas discharged from the reactor is as follows.

Syngas: 93.8% by volume (vol%)

Carbon dioxide: 5% by volume (vol%)

Inorganic Sulfur Compounds: 0.7% by volume (vol%)

Organic Sulfur Compounds: 0.03% by volume (vol%)

Inert gas (N ₂ ): 0.47% by volume (vol%)

1 illustrates a prior art, according to FIG. 1, an acidic gas is introduced into the absorption tower 100 using diisopropanolamine (DIPA) at 39% by weight (wt%) using the gas having the composition 10. (25) Carbon dioxide, inorganic sulfur compound, organic sulfur compound must be removed before synthesis gas can be used in reaction process. Sulfur compounds, in particular, have an adverse effect on the catalyst in the reaction process and should be removed below 1 vol ppm. The selectivity for the second absorbent 32 to absorb the acidic gas 25 is in the order of carbon dioxide-> inorganic sulfur compound-> organic sulfur compound. Therefore, diisopropanolamine as the second absorbent absorbs the most carbon dioxide in the gas and then the inorganic sulfur compound and the organic sulfur compound. Therefore, the amount (kg) of the absorbent (30,32) to be circulated to remove the inorganic sulfur compound and organic sulfur compound is about 3.5 times the amount of the synthesis gas (Nm ³ ), which consumes a lot of energy in the absorption-regeneration process. .

The amount of absorbent consumed to absorb carbon dioxide and inorganic sulfur compounds per 1 Nm ^{3 of} syngas is 3.48 kg as shown in the following formula,

3.5 kg x (5 + 0.7 vol%) / (5 + 0.7 + 0.03 vol%) = 3.48 kg

The amount of absorbent consumed to absorb the organic sulfur compound per 1 Nm ^{3 of the} synthesis gas is 0.02 kg as shown in the following formula,

3.5 kg-3.48 kg = 0.02 kg

In this case, 220 kg of medium pressure steam is used per 1000 Nm ³ of syngas.

Even though circulating such a large amount of absorbent, it is industrially unreasonable to circulate the amount of absorbent necessary to remove the organic sulfur compound to 1 vol ppm or less, and the syngas 15 discharged to the upper part of the absorption tower has about 30 vol ppm of organic matter. Contains sulfur compounds. Therefore, before the synthesis gas discharged to the absorption tower is used in the reaction process, a reactor for converting the organic sulfur compound into an inorganic sulfur compound to completely remove the sulfur component is needed, and a gas is introduced into the reactor for converting the organic sulfur compound into an inorganic sulfur compound. Since the temperature must be raised from about 45 ℃ to 150 ℃ before, a high pressure steam of about 30 kg / cm ² should be used, and this also requires a lot of energy because 60 kg of high pressure steam per 1000 Nm ³ syngas.

However, in the present invention, the exhaust gas of the synthesis gas production reactor is first introduced 40 into the first absorption tower 300 using ammonia water using low temperature energy as an absorbent to first remove carbon dioxide and inorganic sulfur compounds. .

Synthesis gas 45 discharged to the upper portion of the absorption tower using ammonia water as the absorbent contains an organic sulfur compound, so that the second absorbent is introduced into the second absorption tower 100 to remove the organic sulfur compound.

Theoretical circulation amount of the absorbent for reducing the organic sulfur compound to 30 vol ppm or less is 0.02 kg / synthetic gas 1 Nm ³ , and the theoretical absorbent circulation amount for the organic sulfur compound to 1 vol ppm or less is 0.4 kg / synthetic gas 1 Nm ³ .

Therefore, the amount of medium pressure steam used to reduce the organic sulfur compound to 1 vol ppm or less is about 220 kg x 0.4 kg / 3.5 kg, thus about 25 kg per 1000 Nm ³ of syngas. This medium pressure steam amount is about 11% compared to using only the second absorbent as the absorbent. In addition to these effects, as shown in Figs. 3 and 4, by exchanging heat with the stripping column bottom solution 30 using the second absorbent and the stripping column inflow liquid 51 or the concentrated tower inflow liquid 71 using the ammonia water as the absorbent. The amount of low pressure steam can also be reduced.

In addition, since the content of inorganic sulfur compounds and organic sulfur compounds can be reduced to 1 vol ppm or less in the upper exhaust gas 45 of the absorption tower using ammonia water as an absorber, a reactor for converting organic sulfur compounds into synthetic sulfur compounds to remove sulfur is required. You can't.

At this time, the concentration of ammonia in the ammonia water flowing into the first absorption tower is preferably from 2% by weight to 25% by weight. If the concentration of ammonia is too low, the amount of ammonia water used is too high. If the concentration of ammonia is too high, the amount of ammonia that is volatilized and lost in the process may be high, and excessive freezing energy must be used to reduce this volatilization. to be.

In more detail, it demonstrates with reference to each drawing.

1 is a process chart of a conventional acid gas removal method.

2 is a process chart of a method for removing acid gas through pretreatment with ammonia water according to an embodiment of the present invention, and FIG. 3 is a process diagram of an energy saving method according to another embodiment of the process diagram shown in FIG. 2. 4 is a flowchart illustrating another embodiment of the energy saving method of the flowchart illustrated in FIG. 3. Here, the same reference numerals as those shown in Figs. 1, 2, 3, and 4 are the same members having the same configuration and function, and thus repetitive description thereof will be omitted.

In addition, the first absorption tower 300 and the first stripping tower 400 may further include a washing unit at the top, re-boilers (203, 403, 503) of the stripping tower (200, 400) and concentration tower (500) ) Using steam (98) and in the condenser (204, 404, 504) with cooling water (97). In addition, the

coolers

102, 302, and 502 use the coolant 97 to cool.

Referring to FIG. 3, a gas source 40 selected from natural gas, pre-combustion gas, post-combustion gas, syngas, or reactor exhaust gas flows into the first absorption tower 300 using ammonia water as an absorbent. In the first absorption tower 300, the acid gas is collected in ammonia water and discharged (50) to the lower portion of the first absorption tower 300 is introduced into the first stripping tower (400).

The acid gas collected in the ammonia water in the first stripping tower 400 is discharged through the upper part of the first stripping column 55, and after the acid gas is removed, the ammonia water is discharged into the lower portion of the first stripping column 60 to obtain the first gas. It is introduced into the absorption tower 300 (60, 61, 62).

The solution 54 washed in the first stripping tower upper washing unit is introduced into the concentration tower 500 with the solution 44 washed in the first absorption tower upper washing unit 70, and concentrated ammonia Discharge 75. The concentrated tower bottom discharge solution 80 is circulated and introduced into the upper washing part of the first absorption tower 300 and the upper washing part of the first stripping tower 400. (Stage 1)

The upper exhaust gas 45 of the first absorption tower 300 is introduced into the second absorption tower 100 using the second absorbent. In the second absorption tower 100, the organic sulfur compound is collected in the second absorbent and flows into the second stripping tower 200 through the lower portion of the second absorption tower 100 (20, 21). In the second stripping tower 200, the second absorbent and the organic sulfur compound are discharged to the lower 30 and the upper 25 of the second stripping tower 200, respectively. In this case, the organic sulfur compound is discharged to the upper portion 25 of the second stripping tower 200, and the second absorbent is discharged to the lower portion 30 of the second stripping tower 200. Inflow 32 to the top of 100). (Step 2)

During the process, the second stripping tower

bottom discharge solution

30, 31 and the first absorption tower

bottom discharge solution

50, 51, 53 are heat-exchanged through the heat exchanger 601 to be generated in the second stripping tower 400. Using waste heat saves energy.

According to another embodiment of the present invention

As shown in FIG. 4, the ammonia water 44 obtained by washing the waste heat generated in the second stripping tower 200 with water at the top of the first absorption tower and the ammonia water obtained by washing with water at the top of the first stripping tower (54). ) Is introduced into the enrichment tower 500, so the heat is exchanged through the heat exchanger 701 to use waste heat generated in the second stripping tower, thereby saving energy.

The second absorbent is monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), diisopropanolamine (Diisopropanolamine; DIPA), Diglycolamine (DGA), aminomethylpropanol (AMP), piperidine ethanol (PE) potassium hydroxide (KOH) and sodium hydroxide (NaOH) An amine compound which is one or a combination of two or more selected from the group consisting of, calcium-based absorbents such as limestone and slaked lime, sodium-based absorbents such as sodium carbonate (Na ₂ CO ₃ ) or sodium hydrogen carbonate (NaHCO ₃ ), and the like can be used. It is not limited to this.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims

In the method of removing the acid gas contained in the gas source selected from natural gas, pre-combustion gas, post-combustion gas, syngas or reactor exhaust gas,

Treating the gas source by introducing it into a first absorption tower including ammonia water as a first absorbent (first step); And

And a step (second step) of introducing the upper exhaust gas of the first absorption tower into a second absorption tower using a second absorbent and treating the second absorption tower.
The method according to claim 1,

The energy saving acid gas removal method,

Introducing the gas source into a first absorption tower including ammonia water as a first absorbent to absorb acid gas into the first absorbent;

Introducing a lower discharge solution of the first absorption tower into a first stripping tower;

Removing the acid gas absorbed by the first absorbent from the first stripping tower and discharging the acid gas to an upper portion of the first stripping tower;

Absorbing the remaining acid gas into the second absorbent by introducing the upper discharge solution of the first absorbent into the second absorbent including the second absorbent;

Removing the acid gas absorbed by the second absorbent from the second stripping tower and discharging the acid gas to an upper portion of the second stripping tower; And

And exchanging the bottom discharge solution of the second stripping column with the first stripping solution after exchanging heat with the first stripping solution.
The method according to claim 1 or 2,

The acid gas is carbon dioxide, inorganic sulfur compounds and organic sulfur compounds, characterized in that any one or a combination of two or more selected from the group consisting of, energy saving acid gas removal method.
The method according to claim 1 or 2,

The second absorbent is selected from the group consisting of amine compounds, calcium-based absorbents and sodium-based absorbents, energy saving acid gas removal method.
The method according to claim 1 or 2,

The energy saving acid gas removal method,

Absorbing the acid gas into ammonia by introducing the gas source into a first absorption tower including ammonia water as a first absorbent;

Exchanging the lower discharge solution of the first absorption tower with the lower discharge solution of the first stripping tower and then introducing the lower discharge solution into the first stripping tower;

Removing the acid gas absorbed by the ammonia from the first stripping column and discharging the acid gas upwardly;

Heat-exchanging the lower discharge solution of the first stripping tower with the lower discharge solution of the first absorption tower and cooling the liquid to flow into the upper portion of the first absorption tower;

Introducing ammonia water obtained by washing with water in the upper portion of the first absorption tower and ammonia water obtained by washing with water in the upper portion of the first stripping column to a concentration tower;

Discharging the concentrated ammonia from the top of the concentration tower;

Introducing a lower discharge solution of the concentration tower into a first absorption tower;

Introducing an upper discharge gas of the first absorption tower into a second absorption tower;

Discharging the gas source remaining after absorbing the acidic gas into the second absorbent in the second absorption tower;

Exchanging the lower discharge solution of the second absorption tower with the lower discharge solution of the second stripping tower and then introducing the liquid into the second stripping tower;

Removing the acid gas absorbed by the second absorbent from the second stripping tower and discharging the acid gas upwardly;

Heat-exchanging the lower discharge solution of the second stripping tower with the lower discharge solution of the second absorption tower and cooling the liquid to flow into the upper portion of the second absorption tower; And

And exchanging the lower discharge solution of the second stripping column with the first absorbing tower lower discharge solution flowing into the first stripping tower and then introducing the lower stripping solution into the first stripping tower. How to remove gas.
The method according to claim 5,

The ammonia water introduced into the concentration tower further comprises the step of heat-exchanging with the lower discharge solution of the second stripping column to be introduced into the concentration tower, energy saving acidic gas removal method.