KR101417214B1 - Absorbent for the removal of carbon dioxide - Google Patents

Abstract

The present invention relates to a carbon dioxide absorbent, and more particularly to a carbon dioxide absorbent containing an amine, an acid and a glycol. The carbon dioxide absorbent of the present invention is useful for the process of collecting and separating carbon dioxide from exhaust gas and natural gas by using fossil fuel because it can reduce energy consumption and absorbent loss by excellent carbon dioxide absorbing ability even when it is repeatedly regenerated at low temperature can do.

Description

BACKGROUND ART [0002] Absorbent for the removal of carbon dioxide

The present invention relates to a carbon dioxide absorbent, and more particularly to a carbon dioxide absorbent containing an amine, an acid and a glycol.

Carbon dioxide (CO ₂ ), which is inevitably emitted in the process of consuming fossil fuels, is one of the representative greenhouse gases. Global warming has become a global concern, and efforts are being made to control its emissions. Therefore, research has been conducted on methods for obtaining energy with high efficiency while consuming the same fossil fuel. On the other hand, researches for reuse of captured carbon dioxide by collecting carbon dioxide emitted from existing industrial facilities and reducing the amount of emissions are also actively carried out It is progressing.

Absorption method, adsorption method, and membrane method are used to separate carbon dioxide from exhaust gas from steel mills, chemical plants, power plants, large boilers, and natural gas. The dual absorption method is capable of treating a large amount of exhaust gas with a high carbon dioxide removal efficiency even at a low CO 2 emission concentration of about 8 to 20% by volume. Therefore, compared to other recovery technologies such as an adsorption method and a separation membrane method, Is estimated to be high.

The process of using alkanolamine as the absorbent to be applied to the absorption method has been developed for a long time. Initially, triethanolamine was mainly used as an absorbent, and then many amines have been developed. Currently, many amines have been developed and are currently used as monoethanolamine, diethanolamine, methyldiethanolamine, diisopropylamine, piperazine, methylpiperazine, Amino-2-methyl-1-propanol, 2-ethylamino ethanol, 2-methylamino ethanol, 2-diethylamino ethanol and the like are applied as an absorbent. In addition, several tens of amine-based absorbents exist, and they are usually used in a solvent such as water at a concentration range of 20 to 50 wt%.

The absorption of carbon dioxide using an amine-based absorbent is explained in detail. The amine having a strong affinity for carbon dioxide absorbs the carbon dioxide contained in the exhaust gas supplied into the absorption tower, and the absorbent containing a large amount of carbon dioxide absorbs , The original amine solution is separated into carbon dioxide, and the high-purity carbon dioxide is stored in another reservoir. The regenerated amine solution is circulated to the absorption tower after the heat is removed from the heat exchanger, And recovered. However, in this process, since the absorbent is regenerated by heating to a high temperature in order to break the chemical bond between the carbon dioxide and the amine-based absorbent, there is a serious problem requiring high energy. Generally, the cost of CO2 recovery using the chemical absorption method accounts for more than 50% of the energy cost, and the energy cost of carbon dioxide absorbent regeneration accounts for more than 80% of the energy cost. Therefore, in order to lower the cost of recovering carbon dioxide, it is necessary to develop an absorbent having a low renewable energy consumption.

In order to overcome the drawbacks of such an amine-based absorbent, US Patent Publication Nos. 2005-0169825 and 7,459,134 disclose an ionic liquid which does not volatilize and maintains a liquid state at a low temperature of 100 DEG C there has been an attempt to use ionic liquid as a carbon dioxide absorbent. Ionic liquids are polar compound salts composed of organic cations and organic or inorganic anions, the solubility of the gas absorbed in the ionic liquid depends on the degree of interaction between the gas and the ionic liquid. Thus, by modifying the polarity, acidity, basicity, and nucleophilicity of an ionic liquid by appropriately modifying the cation and anion of the ionic liquid, the solubility in a specific gas can be controlled to some extent. However, these ionic liquid absorbers have a problem in that the amount of carbon dioxide absorbed at low pressure (1 to 10 atm) is lower than that of amine type absorbers, which increases the process and increases the amount of absorbent used. There is a problem that the manufacturing cost is excessively high. Therefore, there is a problem in that the economical efficiency of using an ionic liquid as a carbon dioxide absorbent is greatly reduced.

In order to overcome this problem, Korean Patent Laid-Open Publication No. 2011-99466 proposes a carbon dioxide absorbent containing an amine, an ionic liquid and a glycol solvent. In addition to solving the problem of high energy consumption in the regeneration process and the low thermal stability of the absorbent, which is a disadvantage of the conventional amine-based absorbent, solved the problem of low carbon dioxide absorption at low pressure which is a disadvantage of the existing ionic liquid absorbent, The cost of manufacturing the absorbent could be reduced. However, the problem that the ionic liquid is still used, which complicates the process of producing the absorbent, has not been solved, and the necessity of development of a technology capable of further reducing the cost of producing the absorbent has been raised.

Therefore, the problem of high energy consumption in the process of regenerating the absorbent, which is a disadvantage of the conventional amine-based absorbent, and the problem of low thermal stability of the absorbent are solved and problems of low carbon dioxide absorption at low pressure, which is a disadvantage of the conventional ionic liquid absorbent, It is necessary to develop a new carbon dioxide absorbent which can overcome the problem of high manufacturing cost due to complicated manufacturing process of drying.

It is an object of the present invention to provide a novel carbon dioxide absorbent which can overcome the above problems at once.

The present invention is characterized by a carbon dioxide absorbent containing an amine, an acid, and a glycol.

Since the carbon dioxide absorbent of the present invention is prepared by mixing amines, acids, and glycols only by stirring without washing or drying, the manufacturing process is simple.

The carbon dioxide absorbent of the present invention has an effect of reducing the consumption of renewable energy by 45% or more as compared with the conventional amine-based absorbent.

The carbon dioxide absorbent of the present invention has an extremely high carbon dioxide absorption amount and a very low manufacturing cost compared to the conventional ionic liquid absorbent.

The carbon dioxide absorbent of the present invention is simple in manufacturing process compared to conventional absorbents including amines, ionic liquids and glycols, and has a manufacturing cost lower by 70% or more.

1 is a schematic view of an apparatus for absorbing carbon dioxide.

The present invention relates to a carbon dioxide absorbent prepared by mixing an amine, an acid and a glycol solvent only by stirring without a special washing process or a drying process.

The amine used in the present invention refers to a compound in which the hydrogen atom of ammonia (NH ₃ ) is substituted with an alkyl group or aryl group, which is a hydrocarbon residue. Depending on the number of hydrocarbon residues, it can be divided into primary amine (R ¹ NH ₂ ), secondary amine (R ¹ R ² NH) and tertiary amine (R ¹ R ² R ³ N) Amines, diamines, triamines, and tetraamines, and the amines include aromatic amines or aliphatic amines. The aforementioned amine is specifically an aliphatic amine selected from a primary amine represented by R ¹ NH ₂ , a secondary amine represented by R ¹ R ² NH, or a tertiary amine represented by R ¹ R ² R ³ N, wherein R ¹ , R ^2, and R ³ are the same or different represents a C _1-10 alkyl group and as one to three hydroxy is substituted C _1-10 alkyl group); C _1-10 alkyl, C _1-10 hydroxyalkyl, and C _1-10 substituted or unsubstituted by one or two substituents selected from the group consisting of aminoalkyl piperazine; And piperidines substituted or unsubstituted with one or two substituents selected from C _1-10 alkyl, C _1-10 hydroxyalkyl, and C _1-10 aminoalkyl. More specifically, the amine may be monoethanolamine (MEA), diethanolamine (DEA), triethanolamine, methylmonoethanolamine, methyldiethanolamine, dimethylmonoethanolamine diisopropanolamine, diisopropanolamine, piperazine, 1-methylpiperazine, 2-methylpiperazine (hereinafter referred to as "dimethylmonoethanolamine"), diethylmethanolamine, diethylmonoethanolamine, monoisopropanolamine, diisopropanolamine, 2-methylpiperazine, dimethylpiperazine, 1-ethylpiperazine, 1- (2-aminoethyl) piperazine, 1- 2-hydroxyethyl piperazine, 2-piperidinemethanol, 2-piperidineethanol, 2-amino-2-methyl- Propanol (2-amino-2-methyl-1-propanol), 2-amino- 2-amino-2-ethyl-1-propanediol, 3-aminopropanol, 2-amino- At least one selected from the group consisting of 2-ethylaminoethanol, 2-methylaminoethanol and 2-diethylaminoethanol.

The content of the amine in the carbon dioxide absorbent of the present invention is preferably 20 to 40% by weight. If the content of the amine is too small, the carbon dioxide absorbing ability at low pressure may be lowered. Conversely, if the content is too large, Can be.

The acid used in the present invention includes an organic acid or an inorganic acid. The acid is specifically selected from the group consisting of carbonic acid, citric acid, formic acid, oxalic acid, propionic acid, acetic acid, butanoic acid, hexanoic acid, benzoic acid, phosphoric acid, and phosphorous acid.

The content of the acid in the carbon dioxide absorbent of the present invention is preferably 1 to 10% by weight. If the content of the acid is too small, the desorbing temperature and energy of the carbon dioxide increases and the energy consumption can be increased. Conversely, The viscosity of the adsorbent is increased, the operation stability of the absorption tower is lowered, the pressure loss is increased, and the cost of the absorber feed pump power may be increased.

The glycol used in the present invention is a diol compound containing two hydroxyl groups (-OH), the two hydroxyl groups each having an alcoholic property, and each hydroxyl group is a primary alcohol, a secondary alcohol, or 3 It has the structure of tea alcohol. The glycol specifically includes at least one member selected from the group consisting of C _1-10 alkylene glycol, di (C _1-10 alkylene) glycol, and tri (C _1-10 alkylene) glycol. More specifically, the glycol may be selected from the group consisting of ethylene glycol (EG), propylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol dipropylene glycol, and triethylene glycol.

The content of the glycol in the carbon dioxide absorbent of the present invention is preferably 50 to 70% by weight. If the content of glycol is too small, the regeneration temperature of the absorbent may be high. Conversely, if the content of carbon dioxide is excessively large, .

When carbon dioxide is absorbed using the carbon dioxide absorbent of the present invention, the temperature is in the range of -20 to 80 ° C, preferably 40 to 70 ° C, the pressure is in the range of 1 to 100 atm, preferably 1 to 20 atm It is good. Generally, when absorbing carbon dioxide, the lower the temperature and the higher the pressure, the more the absorption amount increases. However, if the temperature and the pressure range are out of the above range, the cost during the operation is excessively increased and the efficiency of the absorption process is lowered. . When the carbon dioxide is regenerated by degassing, the temperature is in the range of 70 to 180 ° C, preferably 90 to 120 ° C, the pressure is in the range of 0.01 to 20 atm, preferably 0.1 to 6 atm It is good to degas.

The present invention as described above will be described in more detail based on the following examples. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Lt; / RTI >

[Example]

Examples 1 to 3 and Comparative Examples 1 to 4. Manufacture of absorbent

Were mixed at the composition ratios shown in Table 1 below to prepare a carbon dioxide absorbent.

Absorbent composition
(weight%) Example Comparative Example One 2 3 One 2 3 4
Amine Monoethanolamine 30 30 30 30 2-Amino-2-methyl-propanol 30 2-methylpiperazine 30
mountain Propionic acid 10 Oxalic acid 10 Phosphorous acid 10 Ionic liquid [BMIM] [BF ₄ ] 100 [DMIM] [MHPO ₃ ] 10
menstruum Ethylene glycol 60 60 70 60 Propylene glycol 60 water 70 [BMIM] [BF ₄ ]: 1-Butyl-3-methylimidazolium tetrafluoroborate
[DMIM] [MHPO ₃ ]: Dimethylimidazolium methylphosphite

[Experimental Example]

EXPERIMENTAL EXAMPLE 1. Sorbent Renewable Energy Consumption Consumed in Carbon Dioxide Recovery

In order to compare the amount of renewable energy consumed between the carbon dioxide absorbent of the present invention (Examples 1 to 3) and the conventional amine absorbent (Comparative Examples 1 and 2), the recycle energy was calculated by the following formula (1). The results are shown in Table 2 below.

[Equation 1]

Renewable energy = H _d + H _s + H _v

In the above equation (1), H _d represents desorption heat, H _s represents latent heat, and H _v represents vaporization heat.

Absorbent renewable energy consumed when recovering 1 ton of carbon dioxide Absorbent  Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Renewable Energy Consumption (GJ) 2.0 2.2 2.1 2.7 3.8

1) Measurement of desorption heat (H _d )

Since the heat of desorption (H _d ) of CO2 is the same size as the heat of absorption (H _a ) and the direction of heat input and output is different, the absorption heat is measured using a micro reaction calorimeter (THT) To determine the desorption heat (H _d = - H _a )

For absorption heat measurement, 0.3 g of sample was placed in a reactor (SUS, PEEK tube) dedicated to absorption heat measurement of a micro reaction calorimeter, and the amount of energy generated by flowing carbon dioxide at a constant flow rate to the reactor was measured to obtain an absorption heat .

2) Latent heat (H _s ) measurement

The latent heat was measured by using a calorimeter and the heat capacity of each absorbent was measured according to the temperature. The change of the carbon dioxide loading before and after the measurement was analyzed using a TOC analyzer and then calculated using the following equation (2).

&Quot; (2) "

In the above formula (2), ρ represents the absorbent density, Cp represents the heat capacity value, ΔT represents the temperature difference before and after the reaction, α represents the carbon dioxide loading value before and after the reaction, and C _amine represents the amine concentration.

3) Measurement of vaporization heat (H _v )

The heat of vaporization was obtained by measuring the vapor pressure and substituting it into the Clausius-Clapeyron equation shown in the following equation (3).

&Quot; (3) "

In Equation (3), P ^sat represents a saturated vapor pressure and T represents a measurement temperature.

Experimental Example 2. Absorption amount of carbon dioxide per 1 L of absorbent

The following experiments were conducted to compare the amounts of carbon dioxide absorbed between the carbon dioxide absorbent of the present invention (Examples 1 to 3) and the conventional ionic liquid absorbent (Comparative Examples 3 and 4).

1 is a carbon dioxide absorption experiment device. The experimental apparatus consisted of a 100 mL stainless steel absorption reactor equipped with a thermometer and a pressure gauge, a 370 mL gas storage reservoir, a magnetic stirrer, and a vacuum pump with a thermometer and a pressure gauge . After the weight of the absorbent was weighed, it was put in a stainless steel absorption reactor together with a magnet rod, and vacuum-dried at 40 DEG C for one hour with stirring. After the valve connected to the stainless steel absorption reactor was closed, the pressure and temperature in the equilibrium state were recorded (initial value) by adding 5 atm of carbon dioxide to the gas storage cylinder (S1). Likewise, after opening the valve, the pressure and temperature at equilibrium were recorded and the stirrer was started and after 30 minutes the final pressure and temperature were recorded (equilibrium value). The degree of decrease in the pressure of the carbon dioxide storage cylinder was measured, and the amount of carbon dioxide absorbed in the absorbent was calculated using the gas-phase equation. The absorption amount of carbon dioxide per 1 L of the absorbent was measured in the same manner as described in Table 3 below.

Absorption amount of carbon dioxide per 1 L of absorbent (condition: 40 ° C, 5 atm) Absorbent  Example 1 Example 2 Example 3 Comparative Example 3 Comparative Example 4 CO ₂ absorption amount (g) 140 165 137 15 124

As described above, the carbon dioxide absorbent according to the present invention significantly reduced the consumption of renewable energy compared to the conventional amine-type absorbent (Comparative Examples 1 and 2), and the conventional ionic liquid absorbents (Comparative Examples 3 and 4) The carbon dioxide absorbing amount is greatly increased. In addition, compared with the conventional absorbent using an ionic liquid, the manufacturing cost is remarkably reduced.

Claims (8)

Amine;
But are not limited to, carbonic acid, citric acid, formic acid, oxalic acid, propionic acid, acetic acid, butanoic acid, hexanoic acid, At least one acid selected from the group consisting of benzoic acid, phosphoric acid, and phosphorous acid; And
Glycol;
Wherein the carbon dioxide absorbent is a carbon dioxide absorbent.
The method according to claim 1,
20 to 40% by weight of the amine;
1 to 10% by weight of the acid; And
50 to 70% by weight of the glycol;
Wherein the carbon dioxide absorbent is a carbon dioxide absorbent.
3. The method according to claim 1 or 2,
The amines R ¹ primary amine, R ¹ R ² NH secondary amine, or R ¹ R ² R aliphatic amine selected from tertiary amines represented by ³ N (wherein R ^1, R ² represented by the represented by NH ₂ and R ³ is the same or different represents a C _1-10 alkyl group and as one to three hydroxy is substituted C _1-10 alkyl group); C _1-10 alkyl, C _1-10 hydroxyalkyl, and C _1-10 substituted or unsubstituted by one or two substituents selected from the group consisting of aminoalkyl piperazine; And piperidines substituted or unsubstituted with one or two substituents selected from C _1-10 alkyl, C _1-10 hydroxyalkyl, and C _1-10 aminoalkyl, and carbon dioxide Absorbent.
The method of claim 3,
The amine may be selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, methylmonoethanolamine, methyldiethanolamine, dimethylmonoethanolamine, diethylmonoethanolamine, monoisopropanolamine, diisopropanolamine, (2-aminoethyl) piperazine, 1- (2-hydroxyethyl) piperazine, 2-piperidinemethanol, 2-methylpiperazine, dimethylpiperazine, 1-ethylpiperazine, 1- 2-methyl-1-butanol, 2-amino-2-ethyl-1-propanediol, 3-aminopropanol, 2- ethyl Aminoethanol, 2-methylaminoethanol, and 2-diethylaminoethanol.
3. The method according to claim 1 or 2,
_Wherein the glycol is at least one selected from the group consisting of C _1-10 alkylene glycol, di (C _1-10 alkylene) glycol, and tri (C _1-10 alkylene) glycol.
6. The method of claim 5,
Wherein the glycol is at least one selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol, and triethylene glycol.
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