CO2 load calculation and prediction method of amino absorbent

Abstract

The invention relates to the technical field of CO2 capture, and discloses a CO2 load calculation and prediction method of an amino absorbent, which comprises the following steps: constructing an amino absorbent and CO2 reaction thermodynamic model, comprising equilibrium constant expressions of all possible chemical reactions, equilibrium constants under standard temperature and pressure, a Van der Hough equation, a solution ion strength calculation formula, an H + activity coefficient calculation formula, a pH value calculation formula under an equilibrium state and a CO2 load calculation formula. The method comprises the following steps: acquiring initial parameters of an amino absorbent solution in a carbon capture system, inputting the initial parameters into a thermodynamic model, iteratively solving the change trend of the pH along with the CO2 load in the CO2 absorption process of the absorbent through an equation set, and substituting the change trend into the to-be-measured pH to obtain the CO2 load of a target amino absorbent under the to-be-measured pH. With the adoption of the method, the CO2 load can be accurately and quickly obtained only by arranging a pH probe in the carbon capture system without sampling or using dangerous chemicals, so that the method has relatively high safety and convenience, and operation errors are not easy to occur.

Description

Technical Field

[0001] This invention relates to the field of CO2 capture technology, and in particular to a method for calculating and predicting CO2 load using an amine absorbent. Background Technology

[0002] Carbon dioxide capture, utilization, and storage (CCUS) technology is a crucial technological option for addressing the global climate crisis and promoting energy transition. Carbon dioxide capture technology is the core component of the CCUS technology system, and its cost and efficiency directly determine the economic feasibility and emission reduction effectiveness of the entire CCUS project. Amine-based absorbents are currently the most widely used and technologically mature CO2 capture materials. Amine-based absorbent load determination is a key parameter for evaluating the performance of a carbon dioxide capture system, directly affecting capture efficiency, energy consumption, and operating costs.

[0003] Existing techniques for determining the load of amine absorbents typically employ the water displacement method (or gas volume displacement method). This method uses an excess of 30%–50% sulfuric acid solution as a titrant to react with the amine absorbent of unknown load, allowing CO2 in the amine absorbent to be fully desorbed and enter the gas measuring tube in gaseous form. Based on the principle of communicating vessels, the liquid levels in the water level bottle and the gas measuring cylinder are kept equal. The water level change data is recorded by visual reading, and the water displacement volume is converted into the molar amount of CO2, which is then further converted to obtain the load of the absorbent solution.

[0004] Besides the aforementioned drainage method, only Chinese patent CN120489844A discloses a device and method for online measurement of CO2 load of absorbent in a carbon capture system. This method uses several solenoid valves and a weighing mechanism to control the flow of a certain mass of the solution to be tested into a liquid chamber containing a certain mass of sulfuric acid solution. During the reaction, CO2 generated enters the gas chamber through a waterproof and breathable component and is discharged by a vacuum component. The weighing mechanism measures the change in the total mass of the reaction solution (i.e., the CO2 content in the solution to be tested), thus enabling real-time monitoring of the CO2 load of the absorbent in the carbon capture system. The main purpose of this technology is to replace the CO2 molar quantity calculation method in the drainage method with a direct measurement method using weight loss, and to achieve automated sampling and measurement through electrified equipment.

[0005] From the perspective of chemical reaction mechanism, both the water displacement method and the loss-of-gravity method for determining absorbent load face the challenges of convenience, safety, and accuracy associated with the use of sulfuric acid solution. The procedures are cumbersome, time-consuming, and labor-intensive, making rapid batch determination impossible. Furthermore, the addition of excessive sulfuric acid during the determination process generates acidic waste liquid, which can easily cause environmental pollution. In addition, if the sample is not fully mixed or the container is not sealed in time during sampling, the sample may come into contact with CO2 in the air, causing detection errors and affecting the accuracy of the measurement results. Summary of the Invention

[0006] To address the aforementioned technical problems—namely, existing techniques for determining the CO2 load of amine absorbents require the use of sulfuric acid solutions, which presents challenges in terms of convenience and safety, and is prone to operational errors—this invention provides a method for calculating and predicting the CO2 load of amine absorbents. Using this method, only a pH probe needs to be placed in the carbon capture system; sampling and the use of hazardous chemicals are unnecessary. This method allows for accurate and rapid determination of the CO2 load of the amine absorbent, offering high safety and convenience, and minimizing operational errors.

[0007] The specific technical solution of this invention is as follows: A method for calculating and predicting CO2 load using an amine absorbent, comprising: S1: Construct a thermodynamic model for the reaction between the target amine absorbent and CO2, including: equilibrium constant expressions for all possible chemical reactions and equilibrium constants at standard temperature and pressure, van der Hoff equation, formula for calculating solution ionic strength, and H2O. + Formulas for calculating activity coefficient, pH value under equilibrium conditions, and CO2 load; S2: Obtain the initial parameters of the target amine absorbent solution in the carbon capture system, input them into the thermodynamic model of S1, and obtain the pH change trend with CO2 load during CO2 absorption by the absorbent through the iterative equation system. Substitute the pH to be measured to obtain the CO2 load of the target amine absorbent at the pH to be measured.

[0008] Preferably, in step S1, the possible chemical reactions include: ; ; ; ; ; ; .

[0009] Preferably, in step S1, the formula for calculating the ionic strength of the solution is: half of the sum of the products of the molar concentration of each ion and the square of its charge number (i.e., the molar concentration of each ion is denoted as m). i Let z be the number of charges it carries. i According to 0.5·∑(m i ·z i 2 (The ionic strength of the solution is obtained).

[0010] Preferably, in step S1, the H +The activity coefficient is calculated using the Davis equation (i.e., denoted as A for the temperature-dependent constant, I for the ionic strength of the solution, and z for the ionic charge number, where z = +1, and H+ is used as the ionic constant). + The activity coefficient is denoted as f, according to -A·z 2 ·[I 1 / 2 / (1+I 1 / 2 )-0.3I], to obtain log f; where A is based on 1.8246×10 6 / T K 2 / 3 Calculations show that T K (Refers to the reaction environment temperature, expressed in Kelvin).

[0011] Preferably, in step S1, the formula for calculating the pH value under equilibrium conditions is: [Formula for calculating pH value under equilibrium conditions is missing from the original text]. + H in the expression for activity coefficient multiplied by equilibrium constant + After determining the concentration, take the logarithm to base 10, then multiply by -1 (i.e., multiply the H+ by the logarithm). + The activity coefficient is denoted as f, and H is in the equilibrium constant expression. + The concentration is denoted as c, according to -log 10 (f·c) yields the pH value at equilibrium.

[0012] Preferably, in step S1, the CO2 load calculation formula is: the rate of change of the concentration of free amine absorbent in the amine absorbent solution at the pH to be tested, divided by the stoichiometric ratio of the amine absorbent to CO2 (i.e., the rate of change of the concentration of free amine absorbent in the amine absorbent solution at the pH to be tested is denoted as λ, the stoichiometric ratio of the amine absorbent to CO2 is denoted as n, and the CO2 load is obtained based on λ / n).

[0013] Furthermore, the formula for calculating the rate of change of free amine absorbent concentration in the amine absorbent solution at the pH to be measured is: the initial concentration of the target amine absorbent solution in the carbon capture system, minus the simulated free amine absorbent concentration at the pH to be measured, and then divided by the initial concentration of the amine absorbent solution (i.e., the initial concentration of the target amine absorbent solution in the carbon capture system is denoted as [RR'NH)). x ] i The concentration of free amine absorbent in the target amine absorbent solution obtained from the simulated carbon capture system at the test pH is denoted as [RR'NH]. x ] pH According to ([RR'NH) x ] i -[RR'NH x ] pH ) / [RR'NH x ] iThe rate of change λ of the concentration of free amine absorbent in the amine absorbent solution at the pH to be tested was obtained.

[0014] Preferably, in step S2, the initial parameters include: amine absorbent concentration, density, reaction temperature, pressure, and pH.

[0015] Preferably, in step S2, the number of iterations of the equation system is 30 to 100.

[0016] Preferably, the amine absorbent is an alcohol amine CO2 absorbent.

[0017] Compared with the prior art, the present invention has the following advantages: (1) Using the method of the present invention, only the pH monitoring data of the target amine absorbent solution in the carbon capture system at a certain time point is needed. Combined with the thermodynamic model, the CO2 load of the target amine absorbent in the carbon capture system at that time point can be obtained. The calculation and prediction results have high accuracy and do not require the use of hazardous chemicals such as sulfuric acid, thus having high safety.

[0018] (2) Using the method of the present invention, no sampling is required. Only a pH probe needs to be placed in the carbon capture system to accurately and efficiently obtain the CO2 load of the amine absorbent. Therefore, remote and continuous real-time monitoring of CO2 load can be achieved, which has both low cost and high timeliness. Attached Figure Description

[0019] Figure 1 The results show the trend of pH change with CO2 load and the accuracy of the calculation prediction of the ethanolamine solution obtained in Example 1.

[0020] Figure 2 The results show the pH trend of the 2-amino-2-methyl-1-propanol solution obtained in Example 2 as a function of CO2 load and the accuracy of the calculated prediction. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] A method for calculating and predicting CO2 load using an amine absorbent, comprising: S1: Construct a thermodynamic model for the reaction between the target amine absorbent and CO2, including: equilibrium constant expressions for all possible chemical reactions and equilibrium constants at standard temperature and pressure, van der Hoff equation, formula for calculating solution ionic strength, and H2O. + Formulas for calculating activity coefficient, pH value under equilibrium conditions, and CO2 load; S2: Obtain the initial parameters of the target amine absorbent solution in the carbon capture system, input them into the thermodynamic model of S1, and obtain the pH change trend with CO2 load during CO2 absorption by the absorbent through the iterative equation system. Substitute the pH to be measured to obtain the CO2 load of the target amine absorbent at the pH to be measured.

[0023] In the method of this invention, only the pH monitoring data of the target amine absorbent solution in the carbon capture system at a certain time point is needed. Combined with the thermodynamic model of the reaction between the target amine absorbent and CO2 provided by this invention, the CO2 load of the target amine absorbent in the carbon capture system at that time point can be obtained, and the calculation and prediction results have high accuracy. Furthermore, the method of this invention does not require the use of hazardous chemicals such as sulfuric acid, has high safety, and does not generate environmentally polluting waste liquid. At the same time, since the method of this invention only requires the placement of a pH probe in the carbon capture system without sampling, non-destructive real-time monitoring can be carried out during system operation, and remote and continuous monitoring can be achieved, combining the characteristics of low cost and high timeliness.

[0024] In some specific embodiments, the possible chemical reactions in step S1 include: ; ; ; ; ; ; .

[0025] In some specific embodiments, in step S1, the formula for calculating the ionic strength of the solution is: the sum of the products of the molar concentration of each ion and the square of its charge number, and then taking half of the sum (i.e., the molar concentration of each ion is denoted as m). i Let z be the number of charges it carries. i According to 0.5·∑(m i ·z i 2 (The ionic strength of the solution is obtained).

[0026] In some specific embodiments, in step S1, the H + The activity coefficient is calculated using the Davis equation (i.e., denoted as A for the temperature-dependent constant, I for the ionic strength of the solution, and z for the ionic charge number, where z = +1, and H+ is used as the ionic constant). + The activity coefficient is denoted as f, according to -A·z 2 ·[I 1 / 2 / (1+I1 / 2 )-0.3I], to obtain log f; where A is based on 1.8246×10 6 / T K 2 / 3 Calculations show that T K (Refers to the reaction environment temperature, expressed in Kelvin).

[0027] In some specific embodiments, in step S1, the pH value calculation formula under equilibrium state is: H + H in the expression for activity coefficient multiplied by equilibrium constant + After determining the concentration, take the logarithm to base 10, then multiply by -1 (i.e., multiply the H+ by the logarithm). + The activity coefficient is denoted as f, and H is in the equilibrium constant expression. + The concentration is denoted as c, according to -log 10 (f·c) yields the pH value at equilibrium.

[0028] In some specific embodiments, in step S1, the CO2 load calculation formula is: the rate of change of the concentration of free amine absorbent in the amine absorbent solution at the pH to be tested, divided by the stoichiometric ratio of the amine absorbent to CO2 (i.e., the rate of change of the concentration of free amine absorbent in the amine absorbent solution at the pH to be tested is denoted as λ, the stoichiometric ratio of the amine absorbent to CO2 is denoted as n, and the CO2 load is obtained based on λ / n).

[0029] In the above specific embodiments, the formula for calculating the rate of change of free amine absorbent concentration in the amine absorbent solution at the pH to be tested is: the initial concentration of the target amine absorbent solution in the carbon capture system, minus the simulated free amine absorbent concentration at the pH to be tested, and then divided by the initial concentration of the amine absorbent solution (i.e., the initial concentration of the target amine absorbent solution in the carbon capture system is denoted as [RR'NH)). x ] i The concentration of free amine absorbent in the target amine absorbent solution obtained from the simulated carbon capture system at the test pH is denoted as [RR'NH]. x ] pH According to ([RR'NH) x ] i -[RR'NH x ] pH ) / [RR'NH x ] i The rate of change λ of the concentration of free amine absorbent in the amine absorbent solution at the pH to be tested was obtained.

[0030] In some specific embodiments, the initial parameters in step S2 include: amine absorbent concentration, density, reaction temperature, pressure, and pH.

[0031] In some specific implementations, in step S2, the equation system is iterated 30 to 100 times.

[0032] In some specific embodiments, the amine absorbent is an alcohol amine CO2 absorbent.

[0033] The present invention will now be described with reference to specific embodiments and comparative examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0034] Example 1: Calculation and prediction of CO2 load of ethanolamine This embodiment uses ethanolamine, a typical amine-based absorbent, as an example. The CO2 load of the amine-based absorbent (ethanolamine) is calculated and predicted using the following method, and the accuracy of the predicted results is verified: S1: Establish a database of physical properties of amine absorbents Ethanolamine (represented as RNH2, hereinafter the same) has the chemical structural formula NH2CH2CH2OH, a molar molecular mass of 61.08 g / mol, an alkalinity of 0, and a hydrolysis equilibrium constant pK. b The standard enthalpy change ΔH for the CO2 absorption reaction is 4.49. 0 It is -85 kJ / molCO2.

[0035] S2: Constructing a thermodynamic model for the reaction between the target amine absorbent and CO2. A thermodynamic model for the reaction of ethanolamine with CO2 is constructed, consisting of the following set of chemical reaction equations: (1) According to the literature, the possible thermodynamic reaction processes and their equilibrium constants during the absorption of CO2 by ethanolamine are as follows: 1) RNH2 + H2O = RNH3 + + OH - log_k1 = -4.49; 2) 2RNH2 + CO2 = RNHCOO - + RNH3 + log_k2 = 3.74; 3) RNHCOO - + H2O = RNH2 + HCO3 - log_k3 = -1.61; 4) RNH3 + = RNH2+ H + , log_k4 = -10.01; 5) H2O = H + + OH - log_k5 = -14.03; 6) CO2 + H2O = H + + HCO3 - log_k6 = -6.36; 7) HCO3 - = H + + CO3 2- , log_k7 = -10.34.

[0036] (2) Van der Hoff equation (i.e., the equilibrium constant, enthalpy change, standard temperature, and standard pressure under standard temperature and pressure conditions are denoted as K0, ΔH, and ΔH, respectively). 0 Let T0 be 298.13 K and P0 be 1 atm. Let the gas constant be R, which is 8.314 J / mol·K. Let the equilibrium constant under a specific temperature T1 be K1 and the equilibrium constant under a specific pressure P1 be K2. P The change in total molar amount before and after the reaction is denoted as Δn; according to -ΔH 0 From / R·(1 / T1-1 / T0), we can obtain lnK1 / K0, and thus K1; according to K0·(P1 / P0) Δn , obtain K P ).

[0037] (3) Formula for calculating the ionic strength of a solution: Sum the products of the molar concentration of each ion and the square of its charge, and take half of the sum (i.e., denote the molar concentration of each ion as m). i Let z be the number of charges it carries. i According to 0.5·∑(m i ·z i 2 (The ionic strength of the solution is obtained).

[0038] (4) H + The activity coefficient calculation formula is the Davis equation (i.e., denoted by A for the temperature-related constant, I for the ionic strength of the solution, and z for the ionic charge number, where z = +1, and H+...). + The activity coefficient is denoted as f, according to -A·z 2 ·[I 1 / 2 / (1+I 1 / 2 )-0.3I], to obtain log f; where A is based on 1.8246×10 6 / T K 2 / 3 Calculations show that T K (Refers to the reaction environment temperature, expressed in Kelvin).

[0039] (5) Formula for calculating pH value under equilibrium conditions: H +H in the expression for activity coefficient multiplied by equilibrium constant + After determining the concentration, take the logarithm to base 10, then multiply by -1 (i.e., multiply the H+ by the logarithm). + The activity coefficient is denoted as f, and H is in the equilibrium constant expression. + The concentration is denoted as c, according to -log 10 (f·c) yields the pH value at equilibrium.

[0040] (6) CO2 Load Calculation Formula: The rate of change of free ethanolamine concentration in the ethanolamine absorbent at the test pH is divided by the stoichiometric ratio of the ethanolamine absorbent to CO2 (i.e., the rate of change of free ethanolamine concentration in the ethanolamine absorbent at the test pH is denoted as λ, and the stoichiometric ratio of the ethanolamine absorbent to CO2 is denoted as n; the CO2 load is obtained based on λ / n). The formula for calculating the rate of change of free ethanolamine concentration in the ethanolamine absorbent at the test pH is: the initial concentration of the ethanolamine absorbent in the carbon capture system minus the simulated free ethanolamine concentration at the test pH, then divided by the initial concentration of the ethanolamine absorbent (i.e., the initial concentration of the ethanolamine absorbent in the carbon capture system is denoted as [RNH2]). i The concentration of free ethanolamine in the simulated carbon capture system at the target pH is denoted as [RNH2]. pH According to ([RNH2]) i -[RNH2] pH ) / [RNH2] i The rate of change λ of the concentration of free ethanolamine in the ethanolamine absorbent at the pH to be tested was obtained.

[0041] S3: Obtain the pH and initial parameters of the amine absorbent solution. The initial parameters of the ethanolamine solution obtained in the carbon capture system are as follows: initial concentration of 30 wt.%, initial pH of 10.89, initial density of 1.02 g / mL, initial reaction temperature of 25℃, and initial pressure of 1 atm.

[0042] The pH values ​​detected during the CO2 absorption process were 10.25, 9.94, and 9.71 at three different times.

[0043] S4: Calculation of CO2 load of amine absorbent using thermodynamic model The initial parameters obtained in step S3 were imported into the thermodynamic model constructed in step S2. The pH variation with CO2 load during ethanolamine CO2 absorption was obtained through iterative equation processing (50 iterations). The results are shown in […]. Figure 1 Based on this trend, the CO2 load of the ethanolamine solution at pH values ​​of 10.25, 9.94, and 9.71 was 0.16, 0.25, and 0.32, respectively.

[0044] S5: Verify the accuracy of the calculated prediction results The accuracy of the calculated prediction results obtained in this embodiment was verified using the water displacement method recommended in the power industry standard DL / T 2763-2024 "Technical Specification for Performance Testing of Chemical Absorption Solution for Carbon Dioxide in Flue Gas of Thermal Power Plants". The CO2 load test method provided in this standard is as follows: A volume of absorbent solution V (in mL) is measured using a pipette and placed into the outer chamber of the reaction flask; an excess of sulfuric acid solution is measured using a pipette and placed into the inner chamber of the reaction flask, the volume of sulfuric acid solution being greater than the volume of absorbent solution; the reaction flask is then covered, ensuring the inner chamber is connected to the top of the gas measuring tube via a connecting tube; a high-level water bottle is held (the bottom of the water bottle is connected to the bottom of the gas measuring tube via a connecting tube). Connect the tube to the gas measuring tube and keep the liquid level level with the liquid level in the gas measuring tube. When the liquid level stabilizes, record the scale value V1 (in mL). Slowly tilt the reaction bottle to allow the sulfuric acid solution to flow from the inner chamber to the outer chamber and react with the sample to be tested. Adjust the height of the water level bottle to be level with the liquid level in the gas measuring tube. When the liquid level stabilizes, record the scale value V2 (in mL). At the same time, record the room temperature T1 (in K) and the pressure P1 (in kPa). Record the molar concentration of the absorbent solution as C1. According to (V2-V1)·273.15·P1 / (22.4·V·C1·T1·101.3), the CO2 load is obtained.

[0045] Using the CO2 load test method in DL / T 2763-2024, the CO2 loads of the ethanolamine solution at pH 10.25, 9.94, and 9.71 were measured to be 0.16, 0.25, and 0.33, respectively. These values ​​are essentially the same as the calculated predictions (0.16, 0.25, and 0.32) obtained in this example, with an error within 3%. The measured results all fall within the 95% confidence interval of the calculated predictions (a comparison of the measured results and the calculated predictions can be found in...). Figure 2 ).

[0046] Example 2: Calculation and prediction of CO2 load of 2-amino-2-methyl-1-propanol This embodiment uses 2-amino-2-methyl-1-propanol, a typical sterically hindered amine absorbent, as an example. The CO2 load of the amine absorbent (2-amino-2-methyl-1-propanol) is calculated and predicted using the following method, and the accuracy of the predicted results is verified: S1: Establish a database of physical properties of amine absorbents 2-Amino-2-methyl-1-propanol (represented by RR'NH2, the same below) has the chemical structural formula (CH3)2C(NH2)CH2OH, a molar molecular mass of 89.14 g / mol, an basicity of 0, and a hydrolysis equilibrium constant pK. b The standard enthalpy change ΔH for the CO2 absorption reaction is 4.31. 0 The value is -79 kJ / mol CO2.

[0047] S2: Constructing a thermodynamic model for the reaction between the target amine absorbent and CO2. A thermodynamic model for the reaction of 2-amino-2-methyl-1-propanol with CO2 is constructed, consisting of the following set of chemical reaction equations: (1) According to literature review, the possible thermodynamic reaction processes and their equilibrium constants during the absorption of CO2 by 2-amino-2-methyl-1-propanol are as follows: 1) RR'NH2 + H2O = RR'NH3 + + OH - log_k1 = -4.74; 2) RR'NH2 + CO2 + H2O = RR'NH3 + + HCO3 - , log_k2 = 3.10; 3) RR'NH3 + = RR'NH2+ H + log_k4 = -9.69; 4) H2O = H + + OH - log_k5 = -14.03; 5) CO2 + H2O = H + + HCO3 - log_k6 = -6.36; 6) HCO3 - = H + + CO3 2- , log_k7 = -10.34.

[0048] (2) Van der Hoff equation (i.e., the equilibrium constant, enthalpy change, standard temperature, and standard pressure under standard temperature and pressure conditions are denoted as K0, ΔH, and ΔH, respectively). 0 Let T0 be 298.13 K and P0 be 1 atm. Let the gas constant be R, which is 8.314 J / mol·K. Let the equilibrium constant under a specific temperature T1 be K1 and the equilibrium constant under a specific pressure P1 be K2. P The change in total molar amount before and after the reaction is denoted as Δn; according to -ΔH 0 From / R·(1 / T1-1 / T0), we can obtain lnK1 / K0, and thus K1; according to K0·(P1 / P0) Δn , obtain K P ).

[0049] (3) Formula for calculating the ionic strength of a solution: Sum the products of the molar concentration of each ion and the square of its charge, and take half of the sum (i.e., denote the molar concentration of each ion as m). i Let z be the number of charges it carries. i According to 0.5·∑(m i ·z i 2 (The ionic strength of the solution is obtained).

[0050] (4) H + The activity coefficient calculation formula is the Davis equation (i.e., denoted by A for the temperature-related constant, I for the ionic strength of the solution, and z for the ionic charge number, where z = +1, and H+...). + The activity coefficient is denoted as f, according to -A·z 2 ·[I 1 / 2 / (1+I 1 / 2 )-0.3I], to obtain log f; where A is based on 1.8246×10 6 / T K 2 / 3 Calculations show that T K (Refers to the reaction environment temperature, expressed in Kelvin).

[0051] (5) Formula for calculating pH value under equilibrium conditions: H + H in the expression for activity coefficient multiplied by equilibrium constant + After determining the concentration, take the logarithm to base 10, then multiply by -1 (i.e., multiply the H+ by the logarithm). + The activity coefficient is denoted as f, and H is in the equilibrium constant expression. + The concentration is denoted as c, according to -log 10 (f·c) yields the pH value at equilibrium.

[0052] (6) CO2 load calculation formula: The rate of change of free 2-amino-2-methyl-1-propanol concentration in the 2-amino-2-methyl-1-propanol absorbent at the pH to be measured is divided by the stoichiometric ratio of the 2-amino-2-methyl-1-propanol absorbent to CO2 (i.e., the rate of change of free 2-amino-2-methyl-1-propanol concentration in the carbon capture system at the pH to be measured is denoted as λ, and the stoichiometric ratio of the 2-amino-2-methyl-1-propanol absorbent to CO2 is denoted as n. The CO2 load is obtained based on λ / n). The formula for calculating the rate of change of free 2-amino-2-methyl-1-propanol concentration in the 2-amino-2-methyl-1-propanol absorbent at the test pH is: Initial concentration of the 2-amino-2-methyl-1-propanol absorbent in the carbon capture system, minus the simulated free 2-amino-2-methyl-1-propanol concentration at the test pH, then divided by the initial concentration of the 2-amino-2-methyl-1-propanol absorbent (i.e., the initial concentration of the 2-amino-2-methyl-1-propanol absorbent in the carbon capture system is denoted as [RR'NH2]). i The concentration of free 2-amino-2-methyl-1-propanol in the simulated carbon capture system at the tested pH is denoted as [RR'NH2]. pH According to ([RR'NH2]) i -[RR'NH2] pH ) / [RR'NH2] i The rate of change in the concentration of free 2-amino-2-methyl-1-propanol at the pH to be tested is denoted as λ.

[0053] S3: Obtain the pH and initial parameters of the amine absorbent solution. The initial parameters of the 2-amino-2-methyl-1-propanol solution obtained in the carbon capture system are as follows: initial concentration of 27 wt.%, initial pH of 11.46, initial density of 0.92 g / mL, initial reaction temperature of 40℃, and initial pressure of 1 atm.

[0054] The pH values ​​detected during the CO2 absorption process were 9.50, 9.25, 8.96, and 8.60 at four different times.

[0055] S4: Calculation of CO2 load of amine absorbent using thermodynamic model The initial parameters obtained in step S3 were imported into the thermodynamic model constructed in step S2. The pH variation with CO2 load during CO2 absorption by 2-amino-2-methyl-1-propanol was obtained through iterative equation calculation (50 iterations). The results are shown in […]. Figure 2Based on this trend, the CO2 load of the 2-amino-2-methyl-1-propanol solution at four time points with pH values ​​of 9.50, 9.25, 8.96, and 8.60 were 0.35, 0.49, 0.65, and 0.82, respectively.

[0056] S5: Verify the accuracy of the calculated prediction results The accuracy of the calculated prediction results obtained in this embodiment was verified using the water displacement method recommended in the power industry standard DL / T 2763-2024 "Technical Specification for Performance Testing of Chemical Absorption Solution for Carbon Dioxide in Flue Gas of Thermal Power Plants". The CO2 load test method provided in this standard is as follows: A volume of absorbent solution V (in mL) is measured using a pipette and placed into the outer chamber of the reaction flask; an excess of sulfuric acid solution is measured using a pipette and placed into the inner chamber of the reaction flask, the volume of sulfuric acid solution being greater than the volume of absorbent solution; the reaction flask is then covered, ensuring the inner chamber is connected to the top of the gas measuring tube via a connecting tube; a high-level water bottle is held (the bottom of the water bottle is connected to the bottom of the gas measuring tube via a connecting tube). Connect the tube to the gas measuring tube and keep the liquid level level with the liquid level in the gas measuring tube. When the liquid level stabilizes, record the scale value V1 (in mL). Slowly tilt the reaction bottle to allow the sulfuric acid solution to flow from the inner chamber to the outer chamber and react with the sample to be tested. Adjust the height of the water level bottle to be level with the liquid level in the gas measuring tube. When the liquid level stabilizes, record the scale value V2 (in mL). At the same time, record the room temperature T1 (in K) and the pressure P1 (in kPa). Record the molar concentration of the absorbent solution as C1. According to (V2-V1)·273.15·P1 / (22.4·V·C1·T1·101.3), the CO2 load is obtained.

[0057] Using the CO2 load test method in DL / T 2763-2024, the CO2 loads of the 2-amino-2-methyl-1-propanol solution at four times with pH values ​​of 9.50, 9.25, 8.96, and 8.60 were measured to be 0.34, 0.48, 0.65, and 0.82, respectively. These results are essentially the same as the calculated predictions (0.35, 0.49, 0.65, and 0.82) obtained in this example, with an error within 3%. The measured results all fall within the 95% confidence interval of the calculated predictions (a comparison of the measured results and the calculated predictions can be found in...). Figure 2 ).

Claims

1. A method for calculating and predicting CO2 load using an amine-based absorbent, characterized in that, include: S1: Construct a thermodynamic model for the reaction between the target amine absorbent and CO2, including: equilibrium constant expressions for all possible chemical reactions and equilibrium constants at standard temperature and pressure, van der Hoff equation, formula for calculating solution ionic strength, and H2O. + Formulas for calculating activity coefficient, pH value under equilibrium conditions, and CO2 load; S2: Obtain the initial parameters of the target amine absorbent solution in the carbon capture system, input them into the thermodynamic model of S1, and obtain the pH change trend with CO2 load during CO2 absorption by the absorbent through the iterative equation system. Substitute the pH to be measured to obtain the CO2 load of the target amine absorbent at the pH to be measured.

2. The calculation and prediction method according to claim 1, characterized in that, In step S1, the possible chemical reactions include: ； ； ； ； ； ； 。 3. The calculation and prediction method according to claim 1, characterized in that, In step S1, the formula for calculating the ionic strength of the solution is: the sum of the product of the molar concentration of each ion and the square of its charge number, and then taking half of that sum.

4. The calculation and prediction method according to claim 1, characterized in that, In step S1, the H + The activity coefficient is calculated using the Davis equation.

5. The calculation and prediction method according to claim 1, characterized in that, In step S1, the pH value calculation formula under equilibrium state is: [The formula is missing from the original text, so the translation ends here.] + H in the expression for activity coefficient multiplied by equilibrium constant + After determining the concentration, take the logarithm to the base 10, then multiply by -1.

6. The calculation and prediction method according to claim 1, characterized in that, In step S1, the CO2 load calculation formula is: the rate of change of free amine absorbent concentration in the amine absorbent solution at the pH to be tested, divided by the stoichiometric ratio of the amine absorbent to CO2.

7. The calculation and prediction method according to claim 6, characterized in that, The formula for calculating the rate of change of free amine absorbent concentration in the amine absorbent solution at the pH to be tested is: the initial concentration of the target amine absorbent solution in the carbon capture system, minus the simulated free amine absorbent concentration at the pH to be tested, and then divided by the initial concentration of the amine absorbent solution.

8. The calculation and prediction method according to claim 1, characterized in that, In step S2, the initial parameters include: amine absorbent concentration, density, reaction temperature, pressure, and pH.

9. The calculation and prediction method according to claim 1, characterized in that, In step S2, the system of equations is iterated 30 to 100 times.

10. The calculation and prediction method according to claim 1 or 2, characterized in that, The amine absorbent is an alcohol amine CO2 absorbent.

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