0001]The present invention is a composite amine absorbent, CO 2 or H 2 about S or removing apparatus and method for both.
[0002]In recent years, the greenhouse effect due to CO 2 has been pointed out as one of the causes of global warming , and there is an urgent need for countermeasures internationally in order to protect the global environment. The sources of CO 2 are all areas of human activity that burn fossil fuels, and the demand for their emission control tends to increase. Along with this, for power generation equipment such as thermal power plants that use a large amount of fossil fuel, a method of contacting the combustion exhaust gas of the boiler with an amine-based CO 2 absorbing liquid to remove and recover CO 2 in the combustion exhaust gas. A method for storing the recovered CO 2 without releasing it into the atmosphere is being energetically studied. In addition, as a step of removing / recovering CO 2 from the combustion exhaust gas using the CO 2 absorption liquid as described above, the combustion exhaust gas and the CO 2 absorption liquid are brought into contact with each other in the absorption tower, and the absorption liquid that has absorbed CO 2 is used. A method has been adopted in which heating is performed in a regeneration tower to release CO 2 and the absorption liquid is regenerated and circulated to the absorption tower again for reuse (see, for example, Patent Document 1).
[0003]
Examples 　of CO 2 recovery technology from post-combustion exhaust gas include a chemical absorption method that chemically absorbs and separates CO 2 using a chemical absorption liquid such as an amine solution, or a physical absorption liquid that absorbs CO 2 under high pressure. A physical absorption method for separating carbon dioxide has been proposed. The chemical absorption method using a chemical absorption solution that chemically reacts with CO 2 using an amine solution or the like and strongly bonds with CO 2 has high reactivity, so low partial pressure CO 2 such as combustion exhaust gas (for example, 0.003 to 0.003) Although it is applied to 0.014 MPa), it requires a large amount of energy to release CO 2 from a chemically strongly bonded absorption solution and regenerate the CO 2 absorption solution. On the other hand, in the physical absorption method in which CO 2 is separated by using a physical dissolution phenomenon, the energy consumption for CO 2 regeneration is small, but the high partial pressure CO 2 (for example, 0.9 to 2.0 MPa) is used. ) Is required, and although it is suitable for CO 2 separation such as IGCC (Integrated Coal Gasification Combined Cycle), it is not suitable for low CO 2 partial pressure combustion exhaust gas.
[0004]
　CO of the chemical method 2 using the absorbing solution, for example, CO, such as flue gas from power plants 2 containing CO from the gas 2 in the method of absorbing and removing and recovering, these steps are installed in addition to combustion equipment Therefore, the operating cost must be reduced as much as possible. Especially among the processes, CO 2 CO after absorbing 2 CO from the absorption liquid 2 because in the step of reproducing by releasing consumes a large amount of heat energy (steam), is required to be energy-saving process as much as possible ..
[0005]
　As the CO 2 absorbent used in the physical absorption method, there is a proposal of an absorbent using, for example, polyethylene glycol monoalkyl ether (see, for example, Patent Document 2). Further, as a CO 2 absorption liquid used in the chemical absorption method, there is a proposal of an absorption liquid using, for example, polypropylene glycol ether (see, for example, Patent Document 3).
Prior art literature
Patent documents
[0006]
Patent Document 1: Japanese Patent Application Laid-Open No. 7-51537
Patent Document 2: US Patent Specification No. 4,705,673
Patent Document 3: Japanese Patent Application Laid-Open No. 2009-521313
Outline of the invention
Problems to be solved by the invention
[0007]
　However, since the CO 2 absorption liquid disclosed in Patent Document 2 is an absorption liquid of the physical absorption method at a high CO 2 partial pressure, when the CO 2 partial pressure is low as in the chemical absorption method, the inside of the regeneration tower There is a problem that the reduction rate of steam reboiler calorie is low. Further, the CO 2 absorbing liquid disclosed in Patent Document 3 includes an example of propylene glycol methyl ether as the CO 2 absorbing liquid, but the propylene glycol methyl ether has a low boiling point under atmospheric pressure and is a CO 2 absorbing tower. During the CO 2 absorption step in the above, the propylene glycol methyl ether is released to the outside of the system due to the accompanying gas due to evaporation, and there is a problem in improving operability and performance.
[0008]
　Thus, CO from the exhaust gas 2 To carry out the recovery by chemical absorption method, CO 2 in the regeneration of the absorbent liquid, CO 2 for the purpose of operating cost reduction in the recovery of the desired CO with a small amount of steam 2 can achieve recovery amount energy saving In order to express the sexuality, the emergence of a new composite amine absorbing solution having not only an absorbing ability but also a regenerating ability is eagerly desired.
[0009]
　In view of the above problems, the absorption capacity not only reproduction capability composite amine absorbent that combines, CO 2 or H 2 and to provide an S or removing apparatus and method for both.
Means to solve problems
[0010]
　The first aspect of the present invention to solve the problems described above, CO in the gas 2 or H 2 An absorbent solution to absorb S or both, and (1) straight chain monoamine, (2) a diamine And (3) the first ether bond-containing compound of the following chemical formula (I) are dissolved in water in a composite amine absorbing liquid.
　R 1- O- (R 2- O) n- R 3 ... (I)
　Here, in the formula (I), R 1 is a hydrocarbon group having 2 to 4 carbon atoms, and R 2 is a propylene group. , R 3 is hydrogen, and n is 1 to 3.
[0011]
　In the second invention, in the first invention, the first ether bond-containing compound of the chemical formula (I) of (3) is propylene glycol alkyl ether, and the alkyl ether in the propylene glycol alkyl ether is ethyl. It is in a complex amine absorber characterized by being any of ether, propyl ether, and butyl ether.
[0012]
　A third invention, CO in the gas 2 or H 2 An absorbent solution to absorb S or both, (1) with linear monoamine, and (2) a diamine, (4) the following formula (II) The second ether bond-containing compound is in a composite amine absorbing liquid characterized by being dissolved in water.
　R 4- O- (R 5- O) n- R 6 ... (II)
　Here, in Eq. (II), R 4 is an acetyl group, R 5 is an ethylene group, and R 6 is an alkyl group. , N is 1.
[0013]
　In the fourth invention, in the third invention, the second ether bond-containing compound of the chemical formula (II) of (4) is ethylene ethylene glycol alkyl ether, and the alkyl ether in the ethylene glycol alkyl ether acetate is used. , Methyl ether, or ethyl ether.
[0014]
　A fifth aspect of the invention is characterized in that, in the first or third invention, the linear monoamine of (1) contains at least one of a primary linear monoamine, a secondary linear monoamine, and a tertiary linear monoamine. It is in the complex amine absorber.
[0015]
　A sixth invention is a composite amine absorbing liquid according to the first or third invention, wherein the diamine of (2) contains at least one of a primary linear polyamine, a secondary linear polyamine, and a cyclic polyamine. It is in.
[0016]
　The seventh invention is characterized in that, in the first or third invention, the total concentration of the linear monoamine of (1) and the diamine of (2) is 40 to 60% by weight of the entire absorption liquid. It is in the composite amine absorber.
[0017]
　In the eighth invention, in the first invention, the blending ratio of the diamine of (2) and the first ether bond-containing compound of (3) with respect to the linear monoamine of (1) is (diamine + fifth). 1 is an ether bond-containing compound) / a composite amine absorbing solution characterized by having a linear monoamine of 0.35 to 1.1.
[0018]
　In the ninth invention, in the first invention, the compounding ratio of the diamine of (2) and the first ether bond-containing compound of (3) is the weight ratio of the first ether bond-containing compound / diamine linear monoamine. , 0.99-7.8.
[0019]
　In the tenth invention, in the third invention, the compounding ratio of the diamine of (2) and the second ether bond-containing compound of (4) to the linear monoamine of (1) is (diamine + ether). The composite amine absorber is characterized in that the bond-containing compound) / linear monoamine is 0.35 to 1.1.
[0020]
　In the eleventh invention, in the third invention, the blending ratio of the diamine of (2) and the second ether bond-containing compound of (4) is such that the weight ratio of the ether bond-containing compound / diamine linear monoamine is 0. It is in a complex amine absorber characterized by being 99-7.8.
[0021]
　A twelfth aspect of the present invention is, CO 2 or H 2 S or both contacting the gas containing the absorbed liquid and CO Part 2 or H 2 and S or absorption tower to remove the both, CO 2 or H 2 S or both of the and a absorbent regenerator for reproducing the absorbed solution, wherein the absorbent regenerator with CO 2 or H 2 reuse S or solution was regenerated to remove both of the above absorption tower, CO CO 2 or H 2 S or a device for removing 2 or H 2 S or both, which comprises using the composite amine absorbing solution of the invention according to any one of 1 to 11. It is in both removal devices.
[0022]
　A thirteenth invention, CO in the twelfth invention, the absorption temperature of the absorption tower, along with a 30 ~ 80 ° C., the regeneration temperature of the absorbent regenerator, characterized in that at 110 ° C. or higher 2 or H 2 S or removal device of both.
[0023]
　A fourteenth invention is the invention of the first 12 or 13, CO of the absorption tower inlet 2 partial pressure, CO is characterized by a low partial pressure 2 or H 2 in apparatus for removing S or both.
[0024]
　In the fifteenth invention, a gas containing CO 2 or H 2 S or both is brought into contact with an absorbing liquid to remove CO 2 or H 2 S or both in an absorption tower, and CO 2 or H 2 S is removed. or reproduces the solution which has absorbed the both absorption solution regeneration tower, the absorbing solution regeneration tower with CO 2 or H 2 reuse S or solution was regenerated to remove both of the above absorption tower, CO 2 or H 2 a S or method of removing the both, CO using the composite amine absorbent of the invention described in any one of the first to 11 2 or H 2 , characterized in that the removal of S or both It is in the method of removing CO 2 and / or H 2 S.
[0025]
　A sixteenth invention, in the fifteenth invention, the absorption temperature of the absorption tower, along with a 30 ~ 80 ° C., the regeneration temperature of the absorbent solution regeneration tower, CO and wherein the at 110 ° C. or higher 2 H or 2 in S or method for removing both.
[0026]
　A seventeenth invention is the invention of a 15 or 16, CO of the absorption tower inlet 2 partial pressure, CO is characterized by a low partial pressure 2 or H 2 in the S or method for removing both.
The invention's effect
[0027]
　According to the present invention, the linear monoamine of (1), the diamine of (2), and the ether bond-containing compound ether of the formula (I) (3) are dissolved in water to prepare an absorption liquid. Due to these synergistic effects, the absorbency of CO 2 or H 2 S or both is good, and the dissipative property of absorbed CO 2 or H 2 S during regeneration of the absorption liquid is good. This makes it possible to reduce the amount of water vapor used when regenerating the absorption liquid in the CO 2 recovery facility.
A brief description of the drawing
[0028]
FIG. 1 is a schematic view showing a configuration of a CO 2 recovery device according to a first embodiment .
FIG. 2 is a diagram showing a reboiler calorific value reduction rate according to Test Example 1-8.
FIG. 3 is a diagram showing a reboiler calorific value reduction rate according to Test Example 9-17.
FIG. 4 is a diagram showing a reboiler calorie reduction rate according to Test Examples 18-19.
FIG. 5 is a graph showing the relationship between the weight ratio of the absorbent liquid composition {(b + c) / a} and the reboiler calorific value reduction rate (%).
Mode for carrying out the invention
[0029]
　Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to this example, and when there are a plurality of examples, the present invention also includes a combination of the respective examples.
Example
[0030]
　Composite amine absorbent according to an embodiment of the present invention, CO in the gas 2 or H 2 An absorbent solution to absorb S or both, linear monoamine (a component) of (1), (2) Diamine (component b) and (3) the first ether bond-containing compound ether (component c) of the following chemical formula (I), which is an absorption liquid of the chemical absorption method, are dissolved in water (component d). Is. In the present invention, the linear monoamine of (1), the diamine of (2), and the first ether bond-containing compound ether of (3) are dissolved in water to prepare an absorption liquid in a complex manner. Due to the entanglement and the synergistic effect of these, the absorbability of CO 2 or H 2 S or both is good, and the dissipative property of the absorbed CO 2 or H 2 S at the time of regeneration of the absorbing liquid becomes good, and CO 2 The amount of water vapor used when regenerating the absorption liquid in the recovery facility can be reduced.
[0031]
　Here, (1) the linear monoamine (a component) contains at least one of a primary linear monoamine (a1 component), a secondary linear monoamine (a2 component), and a tertiary linear monoamine (a3 component). It's a waste. Further, a combination of a two-component linear amine of a primary linear monoamine and a secondary linear monoamine, a combination of a two-component linear amine of a primary linear monoamine and a tertiary linear monoamine, and a primary linear chain. It may be a combination of a three-component linear amine of a monoamine, a secondary linear monoamine and a tertiary linear monoamine.
[0032]
　The primary linear monoamine (a1 component) is preferably a primary monoamine (a1L component) having low steric hindrance or a primary monoamine (a1H component) having high steric hindrance.
　Here, in the primary linear monoamine, examples of the primary monoamine (a1L component) having low steric hindrance include monoethanolamine (MEA), 3-amino-1-propanol, 4-amino-1-butanol, and di. At least one selected from glycolamines can be mentioned. In addition, you may combine these.
[0033]
　Further, in the primary linear monoamine, the primary monoamine (a1H component) having high steric hindrance is preferably a compound represented by the chemical formula (1) represented by the following “Chemical formula 1”.
[Chemical 1]

[0034]
　Specifically, examples of the primary monoamine (a1H component) having high steric damage include 2-amino-1-propanol (2A1P), 2-amino-1-butanol (2A1B), and 2-amino-3-methyl. Select from at least one of -1-butanol (AMB), 1-amino-2-propanol (1A2P), 1-amino-2-butanol (1A2B), 2-amino-2-methyl-1-propanol (AMP) and the like. However, the present invention is not limited thereto. In addition, you may combine these.
[0035]
　The secondary linear monoamine (a2) is preferably a compound represented by the chemical formula (2) represented by "Chemical Formula 2" below.
[Chemical 2]

[0036]
　Specifically, as the secondary linear monoamine (2a), a compound selected from at least one of, for example, N-methylaminoethanol, N-ethylaminoethanol, N-propylaminoethanol, N-butylaminoethanol and the like is used. The present invention is not limited to this, although it can be mentioned. In addition, you may combine these.
[0037]
　The tertiary linear monoamine (a3) ​​is preferably a compound represented by the chemical formula (3) represented by "Chemical Formula 3" below.
[Chemical 3]

[0038]
　Specifically, examples of the tertiary linear monoamine (a3) ​​include N-methyldiethanolamine, N-ethyldiethanolamine, N-butyldiethanolamine, 4-dimethylamino-1-butanol, 2-dimethylaminoethanol, and 2-diethylamino. Selected from at least one of ethanol, 2-di-n-butylaminoethanol, N-ethyl-N-methylethanolamine, 3-dimethylamino-1-propanol, 2-dimethylamino-2-methyl-1-propanol and the like. However, the present invention is not limited thereto. In addition, you may combine these.
[0039]
　Here, as the formulation of the above-mentioned two-component system of the linear monoamine, the following formulation is preferable. The weight ratio of the primary linear monoamine (a1H component) having high steric hindrance / the primary linear monoamine (a1L component) having low steric hindrance is (a1H) / (a1L) = 0.3 to 2.5. It is preferably in the range of. Further, it is more preferably set in the range of (a1H) / (a1L) = 0.3 to 1.2, and further preferably in the range of (a1H) / (a1L) = 0.3 to 0.7. This is because, at a ratio other than the above, the absorption performance is lower than that when the absorption performance of 30% by weight as the monoethanolamine (MEA) concentration generally used in the past is used as a reference.
[0040]
　The weight ratio of the tertiary linear monoamine (a3 component) / secondary linear monoamine (a2 component) is preferably in the range of (a3) ​​/ (a2) = 0.3 to 2.5. Further, it is more preferable that the range is (a3) ​​/ (a2) = 0.6 to 1.7, and more preferably the range is (a3) ​​/ (a2) = 0.6 to 1.0. This is because if it is lower than the above range, the reproduction performance deteriorates, and if it is higher than the above range, the absorption performance deteriorates.
[0041]
　The weight ratio of the primary linear monoamine (a1H component) / secondary linear monoamine (a2 component) having high steric hindrance is in the range of (a1H) / (a2) = 0.3 to 2.5. It is preferable to do so. Further, it is more preferable that the range is (a1H) / (a2) = 0.6 to 1.7, and more preferably the range is (a1H) / (a2) = 0.6 to 1.0. This is because if it is lower than the above range, the reproduction performance deteriorates, and if it is higher than the above range, the absorption performance deteriorates.
[0042]
　The weight ratio of the primary linear monoamine (a1H component) / tertiary linear monoamine (a3 component) having high steric hindrance is in the range of (a1H) / (a3) ​​= 0.3 to 2.5. It is preferable to do so. Further, it is more preferable that the range is (a1H) / (a3) ​​= 0.6 to 1.7, and more preferably the range is (a1H) / (a3) ​​= 0.6 to 1.0. This is because if it is lower than the above range, the absorption performance deteriorates, and if it is higher than the above range, the reproduction performance also deteriorates.
[0043]
　The diamine (b component) of (2) preferably contains at least one of a primary linear polyamine, a secondary linear polyamine, and a cyclic polyamine.
[0044]
　Here, examples of the primary linear polyamine or the secondary linear polyamine group include ethylenediamine (EDA), N, N'-dimethylethylenediamine (DMEDA), N, N'-diethylethylenediamine (DEEDA), and propanediamine (PDA). ), N, N'-dimethylpropanediamine (DMPDA) and the like, but the present invention is not limited thereto. In addition, you may combine these.
[0045]
　Examples of cyclic polyamines include piperazine (PZ), 1-methylpiperazine (1MPZ), 2-methylpiperazine (1MPZ), 2,5-dimethylpiperazine (DMPZ), and 1- (2-aminoethyl) piperazine (AEPRZ). ), 1- (2-Hydroxyethyl) piperazine (HEP) and the like, but the present invention is not limited thereto. In addition, you may combine these.
[0046]
　Moreover, as the 1st ether bond containing compound ether (c component) of (3), the 1st ether bond containing compound of the following chemical formula (I) can be mentioned.
　R 1- O- (R 2- O) n- R 3 ... (I)
　　Here, in the formula (I),
　　R 1 is a hydrocarbon group having 2 to 4 carbon atoms, and
　　R 2 is a propylene group. ,
　　R 3 is hydrogen, and
　　n is 1 to 3.
[0047]
　The first ether bond-containing compound of the chemical formula (I) of (3) is propylene glycol alkyl ether, and the alkyl ether in the propylene glycol alkyl ether is ethyl ether, propyl ether, or butyl ether. It is preferably any of ether, propylene glycol propyl ether, and propylene glycol butyl ether. This is because when the alkyl ether in the propylene glycol alkyl ether contains propylene glycol methyl ether which is a methyl ether, for example, the boiling point under atmospheric pressure is as low as 120 ° C., and when CO 2 is absorbed, gas accompanies due to evaporation. This is because the ether bond-containing compound is released to the outside of the system due to the above, and there is a problem in improving operability and performance.
[0048]
　Here, as the first ether bond-containing compound of the chemical formula (I) of (3), propylene glycol ethyl ether has a boiling point of 132 ° C., propylene glycol propyl ether has a boiling point of 149 ° C., and propylene glycol butyl ether has a boiling point of 170 ° C. Since the boiling point of dipropylene glycol propyl ether is 212 ° C. and the boiling point of tripropylene glycol butyl ether is 275 ° C., the above-mentioned problems as in the case of blending propylene glycol methyl ether having a low boiling point do not occur.
[0049]
　Further, in the present invention, as the ether bond-containing compound ether of (3), instead of the first ether bond-containing compound of the chemical formula (I), the second ether bond-containing compound of the following chemical formula (II) of (4) is contained. A compound may be blended.
　R 4- O- (R 5- O) n- R 6 ... (II)
　　Here, in the formula (I),
　　R 4 is an acetyl group,
　　R 5 is an ethylene group, and
　　R 6 is an alkyl group. ,
　　N is 1.
[0050]
　The second ether bond-containing compound of the chemical formula (II) of (4) is ethylene glycol alkyl ether acetate, and the alkyl ether in the ethylene glycol alkyl ether acetate is methyl ether or ethyl ether, ethylene glycol acetate. It is preferably either methyl ether or ethylene glycol ethyl ether acetate. This is because when ethylene glycol propyl propyl acetate and ethylene glycol butyl ether acetate having an alkyl group having 3 (C3) or more carbon atoms (for example, propyl ether and butyl ether) are applied, the solubility is lowered and the miscibility is not good. Is.
[0051]
　Next, it is preferable to specify the blending ratio of each component (component a, component b, component c) as follows. The total concentration of the linear monoamine (component a) of (1) and the diamine (component b) of (2) is preferably 40 to 60% by weight, more preferably 40% by weight of the entire absorption liquid. It is preferably 47 to 55% by weight of the whole. This is because if it is out of this range, it does not function well as an absorbing liquid.
[0052]
　The mixing ratio of the diamine (b component) of (2) and the first ether bond-containing compound (c component) of (3) with respect to the linear monoamine (a component) of (1) is (b + c). ) / A = 0.35 to 1.1, more preferably (b + c) / a = 0.40 to 0.94.
[0053]
　Similarly, the compounding of the second ether bond-containing compound of (4) is also the same as that of the linear monoamine (a component) of (1), the diamine (b component) of (2) and the second of (4). The compounding ratio of the above with the ether bond-containing compound (c component) is (b + c) / a = 0.35 to 1.1, and more preferably (b + c) / a = 0.40 to 0.94. Is preferable.
[0054]
　FIG. 5 is a graph showing the relationship between the weight ratio of the composition of the absorbing liquid {(b + c) / a} and the reboiler calorific value reduction rate (%). As shown in FIG. 5, if the blending condition is less than the low concentration blending condition (b + c) / a = 0.35), the effect of reducing the calorific value of the reboiler is limited, while the high concentration blending condition (b + c) / a = 1.1). This is because if it exceeds the above, the reboiler reduction rate due to an increase in liquid viscosity or the like drops sharply, which is not efficient in terms of practical use.
[0055]
　The mixing ratio of the diamine (b component) of (2) and the ether bond-containing compound (c component) of (3) is 0 for the weight ratio of the ether bond-containing compound (c component) / diamine linear monoamine (b component). The ratio is preferably .99 to 7.8. Similarly, in the blending of the second ether bond-containing compound, the blending ratio of the diamine (b component) of (2) and the second ether bond-containing compound (c component) of (4) is the ether bond-containing compound. The weight ratio of (component c) / diamine linear monoamine (component b) is preferably 0.99 to 7.8. This is because the effect of reducing the calorific value of the reboiler is limited under the low ratio condition of this blending ratio, while it is not efficient in terms of practical use such as an increase in liquid viscosity under the high ratio condition.
[0056]
　As for the mixing ratio (% by weight) of water (d component), the weight ratio of water is the balance of the total concentration of the linear monoamine of (1) and the diamine of (2) plus the ether compound. ..
[0057]
　In the present invention, for example, the absorption temperature of the absorption tower of the chemical absorption method at the time of contact with exhaust gas containing CO 2 or the like is preferably in the range of 30 to 80 ° C. Further, a corrosion inhibitor, a deterioration inhibitor and the like are added to the absorbent liquid used in the present invention, if necessary.
[0058]
　In addition, the CO 2 partial pressure at the inlet of the CO 2 absorption tower at the time of absorption to absorb CO 2 in the gas to be processed is chemically absorbed to be a low CO 2 partial pressure (for example, 0.003 to 0.1 MPa). Preferred from the application of the law.
[0059]
　In the present invention, CO 2 from the absorbing solution that has absorbed the like, CO 2 regeneration temperature in the regenerator to emit the like, when reproducing tower pressure is 130 ~ 200 kPa (absolute pressure), the bottom of the absorbing solution regeneration tower The temperature is preferably 110 ° C. or higher. This is because regeneration at a temperature lower than 110 ° C. requires an increase in the circulation amount of the absorbing liquid in the system, which is not preferable from the viewpoint of regeneration efficiency. More preferably, regeneration at 115 ° C. or higher is preferable.
[0060]
　Examples of the gas processed by the present invention include, but are not limited to, coal gasification gas, synthetic gas, coke oven gas, petroleum gas, natural gas, etc., but are not limited to CO 2 and H 2. Any gas may be used as long as it contains an acidic gas such as S.
[0061]
　CO in the gas of the present invention 2 or H 2 processes that can be employed in the methods of removing S, or both is not particularly limited, CO 2 an example of a removal device for removing be described with reference to FIG.
[0062]
　FIG. 1 is a schematic view showing the configuration of the CO 2 recovery device according to the first embodiment . As shown in FIG. 1, the CO 2 recovery device 12 according to the first embodiment cools the exhaust gas 14 containing CO 2 and O 2 discharged from the industrial combustion equipment 13 such as a boiler and a gas turbine with the cooling water 15. an exhaust gas cooling device 16 for the cooled CO 2 gas 14 and CO containing 2 CO absorbs 2 absorbing solution (hereinafter, also referred to as "absorbing solution".) 17 and is brought into contact with and CO from the exhaust gas 14 2 a CO removing 2 CO having a recovery section 18A 2 and the absorption tower 18, CO 2 CO absorbed 2 absorbing solution (hereinafter, also referred to as "rich solvent".) 19 CO from 2 to release by CO 2 play absorbing solution It has an absorbing liquid regeneration tower 20 and the like. Then, the CO 2 in the recovery device 12, in the absorbent regenerator 20 CO 2Play CO removing the 2 absorbing solution (hereinafter, also referred to as "lean solvent".) 17 CO 2 CO in absorption tower 18 2 is reused as the absorption liquid.
[0063]
　In FIG. 1, reference numeral 13a is a flue, 13b is a chimney, and 34 is steam condensed water. The CO 2 recovery device 12 may be retrofitted to recover CO 2 from an existing exhaust gas source, or may be simultaneously attached to a new exhaust gas source. A damper that can be opened and closed is installed in the exhaust gas 14 line, and is opened when the CO 2 recovery device 12 is in operation. Although the exhaust gas source is operating, it is set to be closed when the operation of the CO 2 recovery device 12 is stopped.
[0064]
　In the CO 2 recovery method using the CO 2 recovery device 12 , first, the exhaust gas 14 from the industrial combustion equipment 13 such as a boiler or a gas turbine containing CO 2 is boosted by the exhaust gas blower 22, and then the exhaust gas cooling device. It is sent to 16, where it is cooled by the cooling water 15 and sent to the CO 2 absorption tower 18.
[0065]
　The CO 2 in the absorption tower 18, the exhaust gas 14 CO is an amine absorbent solution according to the present embodiment 2 absorbing solution 17 and then countercurrent contact, CO in the exhaust gas 14 2 is, CO by chemical reaction 2 absorbed into the absorbing solution 17 Will be done. CO 2 CO in the recovery portion 18A 2 CO after was removed 2 removing exhaust gases, CO 2 CO supplied from the nozzle washing section 18B in the absorption tower 18 2 wash water 21 circulating containing absorption liquid and gas-liquid Upon contact, the CO 2 absorbing liquid 17 accompanying the CO 2 removed exhaust gas is recovered, and then the CO 2 removed exhaust gas 23 is released to the outside of the system. Moreover, CO 2 CO was absorbed 2 rich solution 19 is absorbed fluid is pressurized by the rich solution pump 24, the rich-lean solution heat exchanger 25, reproduced by the absorbent regenerator 20 CO 2 absorbing solution 17 It is heated by the lean solution and supplied to the absorption liquid regeneration tower 20.
[0066]
　The rich solution 19 released from the upper part of the absorption liquid regeneration tower 20 to the inside causes an endothermic reaction by the water vapor supplied from the bottom part, and releases most of CO 2 . The CO 2 absorption liquid that has released a part or most of CO 2 in the absorption liquid regeneration tower 20 is called a semi-lean solution. By the time the semi-lean solution reaches the bottom of the absorption liquid regeneration tower 20, it becomes a CO 2 absorption liquid (lean solution) 17 from which almost all CO 2 has been removed . A part of this lean solution 17 is superheated by water vapor 27 in the reboiler 26, and water vapor for CO 2 desorption is supplied to the inside of the absorption liquid regeneration tower 20 .
[0067]
　On the other hand, from the top of the absorption liquid regeneration tower 20, a CO 2 accompanying gas 28 accompanied by water vapor released from the rich solution 19 and the semi-lean solution is derived in the tower, the water vapor is condensed by the condenser 29, and the separation drum 30 is used. The water is separated at, the CO 2 gas 40 is released to the outside of the system , and the CO 2 gas 40 is separately compressed by the compressor 41 and recovered. After passing through the separation drum 43, the compressed / recovered CO 2 gas 42 is press-fitted into an oil field using an enhanced oil recovery method (EOR) or stored in an aquifer to warm up. We are taking measures. The recirculated water 31 separated and recirculated from the CO 2 companion gas 28 accompanied by water vapor by the separation drum 30 is supplied to the upper part of the absorption liquid regeneration tower 20 and the washing water 21 side by the recirculation water circulation pump 35, respectively. The regenerated CO 2 absorbent (lean solution) 17 is cooled by the rich solution 19 in the rich lean solution heat exchanger 25, then boosted by the lean solution pump 32, and further by the lean solution cooler 33. After being cooled, it is supplied into the CO 2 absorption tower 18. In addition, in this embodiment, only the outline thereof is explained, and the attached device is partially omitted.
[0068]
　Hereinafter, suitable test examples showing the effects of the present invention will be described, but the present invention is not limited thereto.
[0069]
[Test Example]
　CO 2 was absorbed using an absorption test device (not shown ). In FIGS. 2 to 3, the three-component composite amine absorbent (linear monoamine (a component), diamine (b component), and first ether bond-containing compound (c component) in Test Example 1-17 is added to water (d). It is a figure which shows the riboira calorific value reduction rate of the thing dissolved in the component). FIG. 4 shows the three-component composite amine absorbent (linear monoamine (a component), diamine (b component), and second ether bond-containing compound (c component) in Test Examples 18-19 in water (d component). It is a figure which shows the riboira calorific value reduction rate of (dissolved). Further, as a comparative example, the amount of heat of reboiler under the same conditions as that of the test example was obtained from the formulation of each test example except that the first ether bond-containing compound or the second ether bond-containing compound (component c) was not contained. The reduction rate (%) of each reboiler calorie was calculated based on the reboiler calorific value of the comparative example. A list of components of the test examples is shown in [Table 1] below.
[0070]
[table 1]

[0071]
[Test Example 1-4] In
　Test Example 1, N-ethylaminoethanol is used as the linear monoamine (component a) and 2-methylpiperazine is used as the diamine (component b), and the first ether bond-containing compound ether is used. As (component c), propylene glycol monopropyl ether was used, and the mixture was dissolved and mixed with water (component d) to prepare an absorption liquid.
[0072]
　In Test Example 2, the absorption liquid had the same composition as that of Test Example 1 except that piperazine was used as the diamine (component b) in Test Example 1.
[0073]
　In Test Example 3, an absorption liquid having the same composition was used except that N-butylaminoethanol was used as the linear monoamine (component a) in Test Example 1.
[0074]
　In Test Example 4, an absorption liquid having the same composition was used except that piperazine was used as the diamine (component b) in Test Example 3.
[0075]
[Test Example 5-17] In
　Test Example 5, two types of the linear monoamine (component a) of (1) are used, monoethanolamine is used as the first linear monoamine, and 2 is used as the second linear monoamine. -Amino-2-methyl-1-propanol was used.
　Further, piperazine is used as the diamine (b component) of (2), and propylene glycol monopropyl ether is used as the first ether bond-containing compound ether (c component) of (3), and the mixture is dissolved and mixed in water (d component). It was made into an absorption liquid.
[0076]
　In Test Example 6, an absorption liquid having the same composition as that of Test Example 5 was used except that propanediamine was used as the diamine (b component) of (2) in Test Example 5.
[0077]
　In Test Example 7, the absorbent solution having the same composition as that of Test Example 5 except that dipropylene glycol monopropyl ether was used as the first ether bond-containing compound ether (component c) of (3) in Test Example 5. bottom.
[0078]
　In Test Example 8, as will be described later, in Test Example 5, the weight ratio of {(b component) and (c component)} / (a ​​component) and the added weight ratio of (c component) and water (d component) ( An absorption liquid having the same composition as that of Test Example 5 was used, except that the concentrations of (c) / (b)) and water (d component) were changed.
[0079]
　In Test Example 9, an absorption liquid having the same composition as that of Test Example 5 was used except that N-ethylaminoethanol was used as the first linear monoamine in Test Example 5.
[0080]
　In Test Example 10, an absorption liquid having the same composition as that of Test Example 9 was used, except that N-butylaminoethanol was used as the first linear monoamine in Test Example 9.
[0081]
　In Test Example 11, an absorption liquid having the same composition as that of Test Example 9 was used, except that N-methyldiethanolamine was used as the first linear monoamine in Test Example 9.
[0082]
　In Test Example 12, the absorption liquid had the same composition as that of Test Example 11 except that N-ethylaminoethanol was used as the second linear monoamine in Test Example 11.
[0083]
　In Test Example 13, an absorption liquid having the same composition as that of Test Example 12 was used except that N-butylaminoethanol was used as the second linear monoamine in Test Example 12.
[0084]
　In Test Example 14, an absorption liquid having the same composition as that of Test Example 11 was used, except that N-ethyldiethanolamine was used as the first linear monoamine in Test Example 11.
[0085]
　In Test Example 15, an absorption liquid having the same composition as that of Test Example 14 was used, except that N-ethylaminoethanol was used as the second linear monoamine in Test Example 14.
[0086]
　In Test Example 16, the absorption liquid had the same composition as that of Test Example 14 except that N-butylaminoethanol was used as the second linear monoamine in Test Example 14.
[0087]
　In Test Example 17, an absorption liquid having the same composition as that of Test Example 11 was used, except that 4-dimethylamino-1-butanol was used as the first linear monoamine in Test Example 11.
[0088]
[Test Example 18-19] In
　Test Example 18, two types of the linear monoamine (component a) of (1) are used, monoethanolamine is used as the first linear monoamine, and 2 is used as the second linear monoamine. -Amino-2-methyl-1-propanol was used. Further, piperazine is used as the diamine (b component) of (2), and ethylene ethylene glycol monomethyl ether acetate is used as the second ether bond-containing compound ether (c component) of (4), and the mixture is dissolved and mixed in water (d component). It was made into an absorption liquid.
[0089]
　In Test Example 19, in Test Example 18, an absorbent solution having the same composition as that of Test Example 18 was used, except that ethylene glycol monoethyl ether acetate was used as the second ether bond-containing compound ether (component c) of (4). bottom.
[0090]
　Here, in Test Example 1-19, the total concentration range of the linear monoamine of the component (a) and the diamine of the component (b) was in the range of 47 to 55% by weight.
　Further, the weight ratio of {(b component) and (c component)} / (a ​​component) in Test Example 1-4 was set to 0.53 to 0.94, and {(b component) and ((b component) in Test Example 5-6 ( The weight ratio of {(b component)} / (a ​​component) was 0.84, and the weight ratio of {(b component) and (c component)} / (a ​​component) in Test Example 7 was 0.40, and Test Example 8 The weight ratio of {(b component) and (c component)} / (a ​​component) in is 0.35 to 1.1, and {(b component) and (c component)} / (a) in Test Example 9-17. The weight ratio of (component) was 0.61, and the weight ratio of {(b component) and (c component)} / (a ​​component) in Test Examples 18-19 was 0.84.
　The added weight ratio ((c) / (b)) of the (c component) and the diamine (b component) in Test Example 1-7 was 1.2 to 7.8, and the (c component) in Test Example 8 was set. ) And diamine (b component) are added in a weight ratio ((c) / (b)) of 0.99 to 5.0, and addition of (c component) and diamine (b component) in Test Example 9-19. The weight ratio ((c) / (b)) was set to 1.2 to 7.8.
　The water (d component) concentration in Test Example 1-7 was 22 to 45% by weight, the water (d component) concentration in Test Example 8 was 17 to 46% by weight, and the water (d component) concentration in Test Example 9-19. Was 22 to 45% by weight.
[0091]
　The absorption conditions in these tests were 40 ° C. and 10 kPaCO 2, and the regeneration conditions were 120 ° C., and the reboiler calorific value reduction rate (%), which is the reduction rate based on the reboiler calorific value of the comparative example, was determined.
[0092]
　The results of Test Example 1-8 are shown in FIG. 2, the results of Test Example 9-17 are shown in FIG. 3, and the results of Test Example 18-19 are shown in FIG. In Test Example 8, a plurality of tests were carried out by changing the compounding conditions in the compounding range, and the average thereof was used. As shown in FIGS. 2 to 4, in Test Example 1-19, the revolving calorie reduction rate was all higher than the standard of the comparative example. In particular, Test Examples 1-6, Test Examples 9-16, and Test Examples 18 and 19 had a revolving calorie reduction rate of more than 5%, and Test Example 16 had a revolving calorie reduction rate of more than 10%, which were good.
[0093]
　Based on the above, according to the present invention, the linear monoamine (component a) of (1), the diamine (component b) of (2), and the first or second ether bond of (3) or (4) are contained. Since the compound (c component) is dissolved in water (d component), it is possible to provide a composite amine absorbing liquid having excellent energy saving properties as compared with the conventional one, and CO 2 or H 2 S in the gas or its thereof. It was possible to reduce the amount of heat of the reboiler when regenerating the absorbent liquid that absorbed both.
[0094]
[Test Example 20]
　Comparison of the calorific value of reboiler between the absorbent solution of Test Example 11 and the absorbent solution having the composition of Example 1 of Patent Document 2 (US Patent Specification No. 4,705,673) proposed by the physical absorption method. Was done. The results are shown in [Table 2] below. Here, in the composition of Test Example 10, two types of the linear monoamine (component a) of (1) are used, N-methyldiethanolamine is used as the first linear monoamine, and 2- as the second linear monoamine. Amino-2-methyl-1-propanol was used, piperazine was used as the diamine (b component) of (2), and propylene glycol monopropyl ether was used as the first ether bond-containing compound ether (c component) of (3). It is used and dissolved and mixed in water (component d). The composition of Example 1 of Patent Document 2 (US Patent Specification No. 4,705,673) is methyldiethanolamine (MDEA), methoxytriglycol (MTG), and water. The revolving calorie reduction rate in [Table 2] is water by the concentration of the ether bond-containing compound in the comparative example under the same conditions as the performance example in [Table 2], except that it does not contain the ether bond-containing compound. It is the reduction rate for the amount of calorie of reboiler in [Example of conditions in which the concentration of is increased].
[0095]
[Table 2]

[0096]
　As shown in [Table 2], in the absorption liquid of Compound 1 (methyldiethanolamine (MDEA), methoxytriglycol (MTG), water) of Patent Document 2 (US Patent Specification No. 4,705,673), For example, when the gas condition is not high pressure near normal pressure, the riboira calorific value reduction rate is low, and the riboira calorific value is worse (reduction rate -5%) than when the ether bond-containing compound is not added. In this idea, the amount of revolving heat can be reduced.
[0097]
[Test Example 21]
　The first ether bond-containing compound (propylene glycol monopropyl ether) of Test Example 1 and the first ether bond-containing compound (dipropylene glycol monopropyl ether) of Test Example 7 and R 2 in the chemical formula I. The solubility of the compound with an ether bond-containing compound (butylene glycol monobutyl ether) having 4 (C4) or more carbon atoms in water was compared. The results are shown in [Table 3] below.
[0098]
[Table 3]

[0099]
　As shown in [Table 3], the first ether bond-containing compound (propylene glycol monopropyl ether) of Test Example 1 and the first ether bond-containing compound (dipropylene glycol monopropyl ether) of Test Example 7 are water. The solubility in both was 20% by weight or more. On the other hand, the ether bond-containing compound (butylene glycol monobutyl ether) having R 2 having 4 or more carbon atoms in Chemical Formula I had a low solubility in water of about 1% by weight. As a result, the ether bond-containing compound having R 2 having 4 (C4) or more carbon atoms in the chemical formula I is difficult to apply as an aqueous solution, and there is a problem in improving operability and performance. The ether bond-containing compounds (propylene glycol monopropyl ether, dipropylene glycol monopropyl ether) of No. 7 have high solubility in water, and can reduce the problem of deterioration of operability and the calorific value of reboiler.
[0100]
[Test Example 22]
　The first ether bond-containing compound (propylene glycol monopropyl ether) of Test Example 1, the ether bond-containing compound (dipropylene glycol monopropyl ether) of Test Example 7, and R 3 in the chemical formula I are alkyl groups. The solubility of the above ether bond-containing compound (propylene glycol dibutyl ether) in water was compared. The results are shown in [Table 4] below.
[0101]
[Table 4]

[0102]
　As shown in [Table 4], the ether bond-containing compound (propylene glycol monopropyl ether) of Test Example 1 and the ether bond-containing compound (dipropylene glycol monopropyl ether) of Test Example 7 both have a solubility in water of 20. It was more than% by weight. On the other hand, the ether bond-containing compound (propylene glycol dibutyl ether) in which R 3 is an alkyl group in Chemical Formula I had a low solubility in water of less than 1% by weight. As a result, it is difficult to apply it as an aqueous solution, and there are problems in improving operability and performance. On the other hand, the ether bond-containing compounds (propylene glycol monopropyl ether, dipropylene glycol monopropyl ether) of Test Examples 1 and 7 are used. Has high solubility in water, and can reduce the problem of deterioration of operability and reduce the amount of riboylyl heat.
[0103]
[Test Example 23]
　The second ether bond-containing compound of Test Example 18 (ethylene glycol monomethyl ether acetate: 5 carbon atoms), the second ether bond compound of Test Example 19 (ethylene glycol monoethyl ether acetate: 6 carbon atoms). The boiling point of the ether bond-containing compound (ethylene glycol ethyl methyl ether (5 carbon atoms), ethylene glycol diethyl ether (6 carbon atoms)) in which R 1 in the chemical formula II is an alkyl group was compared. The results are shown in [Table 5] below.
[0104]
[Table 5]

[0105]
As shown in [Table 5], the boiling point of the second ether bond-containing compound (ethylene glycol monomethyl ether acetate) of Test Example 18 is 143 ° C., and the second ether bond compound (ethylene glycol monomethyl ether acetate) of Test Example 19 Ethylene ether) had a boiling point of 156 ° C. On the other hand, the boiling point of ethylene glycol ethyl methyl ether, which is an ether bond-containing compound in which R 1 is an alkyl group in Chemical Formula II, is 100 to 102 ° C, and the boiling point of ethylene glycol diethyl ether is 120 ° C, which are low under atmospheric pressure. There are problems in improving operability and performance, such as the release of ether bond-containing compounds to the outside of the system due to the accompanying gas due to evaporation. On the other hand, the second ether bond-containing compound of Test Example 18 (ethylene glycol monomethyl ether acetate: 5 carbon atoms) and the second ether bond compound of Test Example 19 (ethylene glycol monoethyl ether acetate: 6 carbon atoms) Even if the number of carbon atoms is the same, R 1 of the chemical formula II has a higher boiling point than the ether bond-containing compound of the alkyl group, so that the problem of deterioration of operability can be reduced and the amount of revolving heat can be reduced.
[0106]
　That is, when a compound having a low boiling point, such as an ether bond-containing compound having an alkyl group in R 1 in Chemical Formula II, is applied as the second ether bond-containing compound , a gas due to evaporation during CO 2 absorption. There is a problem of increasing emissions due to the release of the ether bond-containing compound from the absorption tower to the outside of the system due to the accompanying release, and in addition to this, the concentration of the ether bond-containing compound in the absorption liquid decreases with the release to the outside of the system. As a result, it becomes impossible to improve the performance of the amount of heat recovered by CO 2 (the amount of heat of reboiler).
Code description
[0107]
　12 CO 2 recovery unit
　13 industrial combustion facility
　14 exhaust
　16 exhaust gas cooler
　17 CO 2 absorbing solution (lean
　solution) 18 CO 2 absorption tower
　19 CO 2 CO absorbed 2 absorbing solution (rich
　solution) 20 absorbent regenerator
　21 wash water　

WE CLAIM

[Claim 1]CO in the gas 2 or H 2 A S or absorbent that absorbs both,
　(1) straight and monoamine,
　(2) a diamine and,
　(3) the first ether linkage containing the following formula (I) A composite amine absorbing liquid characterized by dissolving a compound in water.
　R 1- O- (R 2- O) n- R 3 ... (I)
　　Here, in the formula (I),
　　R 1 is a hydrocarbon group having 2 to 4 carbon atoms, and
　　R 2 is a propylene group. ,
　　R 3 is hydrogen, and
　　n is 1 to 3.
[Claim 2]
　In claim 1,
　the first ether bond-containing compound of the chemical formula (I) of (3) is a propylene glycol alkyl ether, and the
　alkyl ether in the propylene glycol alkyl ether is ethyl ether, propyl ether, or butyl ether. A composite amine absorber characterized by being either.
[Claim 3]
　CO in the gas 2 or H 2 A S or absorbent that absorbs both,
　(1) straight and monoamine,
　(2) a diamine,
　(4) a second ether bond-containing the following formula (II) A composite amine absorbing liquid characterized by dissolving a compound in water.
　R 4- O- (R 5- O) n- R 6 ... (II)
　　Here, in Eq. (II),
　　R 4 is an acetyl group,
　　R 5 is an ethylene group, and
　　R 6 is an alkyl group. ,
　　N is 1.
[Claim 4]
　In claim 3,
　the second ether bond-containing compound of the chemical formula (II) of (4) is ethylene ethylene glycol alkyl ether
　acetate, and the alkyl ether in the ethylene glycol alkyl ether acetate is methyl ether or ethyl ether. A composite amine absorber characterized by being either.
[Claim 5]
　The
　composite amine absorbing liquid according to claim 1 or 3, wherein the linear monoamine of (1) contains at least one of a primary linear monoamine, a secondary linear monoamine, and a tertiary linear monoamine.
[Claim 6]
　The
　composite amine absorbing liquid according to claim 1 or 3, wherein the diamine of (2) contains at least one of a primary linear polyamine, a secondary linear polyamine, and a cyclic polyamine.
[Claim 7]
　The
　composite amine absorption liquid according to claim 1 or 3, wherein the total concentration of the linear monoamine of (1) and the diamine of (2) is 40 to 60% by weight of the entire absorption liquid.
[Claim 8]
　In claim 1,
　the blending ratio of the diamine of (2) and the first ether bond-containing compound of (3) to the linear monoamine of (1) is (diamine + first ether bond-containing compound). / A composite amine absorber characterized by having a linear monoamine of 0.35 to 1.1.
[Claim 9]
　In claim 1,
　the mixing ratio of the diamine of (2) and the first ether bond-containing compound of (3) is such that the weight ratio of the first ether bond-containing compound / diamine linear monoamine is 0.99 to 7. A composite amine absorbing solution characterized by being 8.
[Claim 10]
　In claim 3,
　the blending ratio of the diamine of (2) and the second ether bond-containing compound of (4) to the linear monoamine of (1) is (diamine + ether bond-containing compound) / linear. A composite amine absorbing solution characterized by having a monoamine of 0.35 to 1.1.
[Claim 11]
　In claim 3,
　the blending ratio of the diamine of (2) and the second ether bond-containing compound of (4) is such that the
weight ratio of the ether bond-containing compound / diamine linear monoamine is 0.99 to 7.8. A complex amine absorber characterized by this.
[Claim 12]
　CO 2 or H 2 S or a gas containing absorbing solution and is contacted with and CO that both 2 or H 2 and S or absorption tower to remove the both, CO 2 or H 2 solution having absorbed S or both, and a absorbent regenerator for reproducing, the absorbing solution regeneration tower with CO 2 or H 2 reuse S or solution was regenerated to remove both of the above absorption tower, CO 2 or H 2 S or a device for removing both,
　composite amine absorbent CO and characterized by using the according to any one of claims 1 to 11 2 or H 2 S or both of the removal device.
[Claim 13]
　According to claim 12,
　the absorption temperature of the absorption tower is 30 to 80 ° C., and the regeneration temperature of the absorption liquid regeneration tower is 110 ° C. or higher, that is, CO 2 or H 2 S, or both of them. Removal device.
[Claim 14]
　The device for removing CO 2 and / or H 2 S according to claim 12 or 13,
　wherein the CO 2 partial pressure at the inlet of the absorption tower is a low partial pressure .
[Claim 15]
　The gas containing CO 2 or H 2 S or both was brought into contact with the absorbing liquid to remove CO 2 or H 2 S or both in the absorption tower, and CO 2 or H 2 S or both were absorbed. the solution was reproduced in the absorbing solution regeneration tower, the absorbing solution regeneration tower with CO 2 or H 2 reuse S or solution was regenerated to remove both of the above absorption tower, CO 2 or H 2 S or a both method of removing,
　CO using the composite amine absorbent according to any one of claims 1 to 11 2 or H 2 , characterized in that the removal of S or both CO 2 or H 2 A method for removing S or both.
[Claim 16]
　According to claim 15,
　the absorption temperature of the absorption tower is 30 to 80 ° C., and the regeneration temperature of the absorption liquid regeneration tower is 110 ° C. or higher, that is, CO 2 or H 2 S, or both of them. How to remove.
[Claim 17]
　The method for removing CO 2 and / or H 2 S according to claim 15 or 16,
　wherein the CO 2 partial pressure at the inlet of the absorption tower is a low partial pressure .