Method and device for determining the concentration of amines in a carbon capture absorbent

Abstract

The present application belongs to the technical field of carbon capture, and particularly relates to a method and a device for determining the amine concentration in a carbon capture absorbent. The method comprises the following steps: (1) consistency calibration of the reference amine solution and the pH meter; (2) determination of the potential titration end point; and (3) determination of the amine concentration in the carbon capture absorbent. The detection method is simple and feasible, the determination device is simple in structure and easy to operate, and the amine concentration in the online running carbon capture absorbent can be monitored, so that the effective operation of the carbon capture device is ensured, and the problem that the color indicator method cannot be determined due to the inability to distinguish the titration end point when the sample color is deep is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon capture and specifically relates to a method and a device for determining the concentration of amines in a carbon capture absorbent. BACKGROUND

[0002] Carbon capture, utilization and storage (CCUS) is an internationally accepted technology for future climate change response and carbon emission reduction. Capturing and recycling CO2 has become one of the effective means to slow down the greenhouse effect.

[0003] Chemical absorption is the most mature and most potential technology for large-scale application in the current carbon capture technology. Among them, organic alcohol amine solution, as the most widely used CO2 absorbent, is widely used in the purification of natural gas, synthetic ammonia raw gas, refinery gas, flue gas and other gases. The carbon capture device captures CO2 through absorption and regeneration cycles. The process principle is to use organic alcohol amine solution to absorb CO2 to form a rich solution under low temperature (35-45℃) conditions, and release CO2 under high temperature (100-120℃) conditions, so as to realize the high concentration recovery of CO2.

[0004] It is found in the application process that the amine is oxidized and degraded, the amine and its degradation products are easy to volatilize during regeneration, and the introduction of impurities in the tail gas leads to the decrease of the amine concentration in the carbon capture absorbent, which further leads to the decrease of the absorption capacity. In order to ensure the effective operation of the carbon capture device, it is necessary to monitor the amine concentration in the carbon capture absorbent.

[0005] In addition, with the long-time operation of the carbon capture device, in addition to the decrease of the amine concentration, the color of the absorbent will also gradually deepen, which can be changed from colorless, light yellow to deep red brown. The color of the unused carbon capture absorbent is relatively shallow, and the amine concentration can be determined by the color indicator method. However, the carbon capture absorbent in online operation is often deep in color, and the titration end point cannot be determined according to the color change during titration, so the color indicator method is not suitable for the determination of the amine concentration in the carbon capture absorbent with deep color. In order to effectively monitor the amine concentration of the carbon capture absorbent, an easy and effective determination method is urgently needed. SUMMARY

[0006] In order to solve the problem that the amine concentration cannot be determined due to the deep color of the carbon capture absorbent in online operation and the titration end point cannot be distinguished, the application provides a method and a device for determining the concentration of amines in a carbon capture absorbent. The detection method is simple and feasible, the determination device is simple in structure and easy to operate, and the amine concentration of the carbon capture absorbent in online operation can be monitored, so as to ensure the effective operation of the carbon capture device.

[0007] Specifically, the application provides the following technical solutions:

[0008] A method for determining the amine concentration in a carbon capture absorbent, comprising the following steps:

[0009] (1) Consistency calibration of the reference amine solution and the pH meter

[0010] Mix the reference amine solution, water and color indicator uniformly, titrate with the standard hydrochloric acid titration solution, stir while titrating, until the solution changes color, i.e. the titration end point, record the volume of the titrated hydrochloric acid, denoted as V , and the pH value at the titration end point, denoted as pH A ;

[0011] According to formulas ① and ②, respectively calculate the amine concentration actually measured by the reference amine solution and the relative error of the amine concentration:

[0012]

[0013] Among them, is the amine concentration actually measured by the reference amine solution, mol / L; is the volume of the standard hydrochloric acid titration solution titrated in step (1), ml; is the molar concentration of the standard hydrochloric acid titration solution in step (1), mol / L; is the volume of the reference amine solution added in step (1), ml;

[0014]

[0015] Among them, δ is the relative error of the concentration of the reference amine solution; C 理 is the theoretical amine concentration of the reference amine solution, mol / L;

[0016] When the relative error δ of the concentration of the reference amine solution is ≤5%, and the pH A value is between 3.1-4.4, the consistency calibration is completed;

[0017] When the relative error δ of the concentration of the reference amine solution is >5%, or the pH A value is not between 3.1-4.4, the pH meter is calibrated again with a standard buffer solution until it meets the above standard;

[0018] (2) Determination of the potential titration end point

[0019] Mix the unused carbon capture absorbent, water and color indicator uniformly, titrate with the standard hydrochloric acid titration solution, stir while titrating, until the solution changes color, i.e. the titration end point, record the pH value at the titration end point, denoted as pH B ;

[0020] (3) Determination of the amine concentration of the carbon capture absorbent

[0021] Mix the carbon capture absorbent to be measured, water and color indicator evenly, titrate with hydrochloric acid standard titration solution, stir while titrating, until the pH value of the solution reaches pH V value, i.e. the titration end point, record the volume of hydrochloric acid titrated, denoted as

[0022] According to formula (3), the amine concentration of the carbon capture absorbent to be measured is calculated respectively:

[0023]

[0024] wherein, is the amine concentration of the carbon capture absorbent to be measured, mol / L; is the volume of the hydrochloric acid standard titration solution titrated in step (3), ml; is the molar concentration of the hydrochloric acid standard titration solution in step (3), mol / L; is the volume of the carbon capture absorbent to be measured added in step (3), ml.

[0025] In the present application, the carbon capture absorbent refers to organic alcohol amine carbon capture absorbent. Currently, the carbon capture absorbent running in the device is generally a composite organic alcohol amine solution, i.e. a composite formula solution composed of organic alcohol amines with different molecular structures and functions. At the same time, the unused carbon capture absorbent in step (2) refers to fresh carbon capture absorbent with the same formula as the carbon capture absorbent to be measured.

[0026] In step (3) of the present application, the determination of the titration end point must meet the following two points at the same time: one is that the pH value of the solution approaches pH V ; the other is that when one more drop of hydrochloric acid standard titration solution is added, the pH value is observed to decrease rapidly.

[0027] It is particularly necessary to point out that the inventors found in the test process that the pH value of the titration end point can be a certain point value or a certain range value, which may be related to the following aspects: one is the brand, accuracy, and set titration end point determination speed of the pH meter, and the influence of the equipment state at that time; two is that the organic alcohol amine salt hydrochloride is formed in the hydrochloric acid titration process of the organic alcohol amine solution, the composition is complex and changes with the titration, resulting in the fluctuation of the pH value of the solution; three is the influence of the stirring speed of the solution in the hydrochloric acid titration process, the hydrochloric acid titration of the organic alcohol amine solution belongs to a chemical reaction, and the stirring speed also has an influence on the uniformity of the liquid.

[0028] As a preferred, before step (1) is carried out, the pH meter is first calibrated with a standard buffer solution.

[0029] As a preferred, the color indicator is methyl orange.

[0030] As preferred, in step (1), the reference amine solution is a 30% by mass ethanolamine solution or a 30% by mass N-methyl diethanolamine solution. The reference amine solution uses the above-mentioned mass concentration of ethanolamine solution or N-methyl diethanolamine solution, which is closer to the actual working condition and is more favorable to the consistency calibration of the first step.

[0031] As preferred, in steps (1)-(3), the molar concentration of any of the standard hydrochloric acid titration solutions is 0.2-1.0 mol / L; more preferably, the molar concentrations of the standard hydrochloric acid titration solutions are all the same. If the concentration of the hydrochloric acid titration solution is too large, the error of one drop will be relatively large when titrated to the vicinity of the end point; if the concentration of the hydrochloric acid titration solution is too small, the volume of the hydrochloric acid used in titration will be relatively large.

[0032] As preferred, in step (1), the use amount of the reference amine solution, water and color indicator is 1 ml: 10-30 ml: 1-2 drops.

[0033] As preferred, in step (2), the use amount of the unused carbon capture absorbent, water and color indicator is 1 ml: 10-30 ml: 1-2 drops.

[0034] As preferred, in step (3), the use amount of the to-be-tested carbon capture absorbent, water and color indicator is 1 ml: 10-30 ml: 1-2 drops.

[0035] Further preferably, in steps (1)-(3), the use amount of the reference amine solution, the unused carbon capture absorbent and the to-be-tested carbon capture absorbent, and water and color indicator are all the same.

[0036] As preferred, in step (3), the titration speed of the standard hydrochloric acid titration solution is: when the pH of the solution is greater than 6.5, one drop of the standard hydrochloric acid titration solution is added every 1-2 seconds; when the pH of the solution is less than 6.5, one drop of the standard hydrochloric acid titration solution is added every 10-30 seconds.

[0037] The application also provides a measuring device for the determination method of the amine concentration in the carbon capture absorbent.

[0038] The iron stand is fixed with a burette clamp, the acid burette is clamped on the burette clamp, the magnetic stirrer is arranged below the acid burette, the titration container is placed on the upper surface of the magnetic stirrer, and the interior is provided with a magnetic sub and a pH electrode of the pH meter.

[0039] The accuracy of the pH meter is not less than 0.1 level, preferably not less than 0.01 level, and is equipped with an automatic temperature compensation function.

[0040] The application has at least the following beneficial effects:

[0041] 1) The application provides a method for determining the amine concentration in a carbon capture absorbent, which can determine the amine concentration in the carbon capture absorbent, solves the problem that the color indicator method cannot be determined due to the inability to distinguish the titration end point when the sample color is deep;

[0042] 2) The method for determining the amine concentration in a carbon capture absorbent provided by the application optimizes the titration end point value by taking the color indicator method as a reference. Experiments prove that the method is easy and effective, and can realize the monitoring of the amine concentration of the online running carbon capture absorbent, thereby ensuring the effective operation of the carbon capture device;

[0043] 3) The method for determining the amine concentration in a carbon capture absorbent provided by the application preferably uses a mass fraction of 30% ethanolamine solution or a mass fraction of 30% N-methyl diethanolamine solution as the reference amine solution, which is closer to the actual working condition and is more favorable for the consistency calibration of the first step;

[0044] 4) The method for determining the amine concentration in a carbon capture absorbent provided by the application uses a simple structure of the determination equipment, which is easy to operate. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The structure of the determination device used in the embodiment is shown in the figure, wherein 1 is an iron stand, 2 is an acid burette, 3 is a burette clamp, 4 is a beaker, 5 is a magnetic stirrer, and 6 is a pH. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely in combination with the drawings in the embodiments of the application. The following embodiments are used to illustrate the application, but not to limit the scope of the application. If the specific technology or condition is not specified in the embodiments, it is carried out according to the technology or condition described in the literature in the art, or according to the product instruction.

[0047] In the following embodiments, the determination device used is shown in the figure, which includes: Figure 1

[0048] The iron stand 1 is fixed with the burette clamp 3, the acid burette 2 with a specification of 50ml is clamped on the burette clamp 3, the magnetic stirrer 5 is arranged below the acid burette 2, the beaker 4 is placed on the upper surface of the magnetic stirrer 5, and the inside is provided with a magnetic sub and a pH electrode of the pH meter 6;

[0049] The pH meter is derived from the S40 type PH / conductivity / ion comprehensive tester of Mettler-Toledo Instrument (Shanghai) Co., Ltd., has an automatic temperature compensation function, and the setting precision is 0.01 level. ​

[0050] The adopted acid burette is from Beijing Glass Instrument Factory, brand is Bomei, and specification is 50ml.

[0051] The adopted pipette is from Tianjin Tianke Glass Instrument Manufacturing Co., Ltd., brand is Tianbo, and specification is 2ml.

[0052] The carbon capture absorbent is 30% ethanolamine-N-methyl diethanolamine composite formula aqueous solution, and the new sample is light yellow. After continuous operation in the absorption-regeneration device for a period of time, the color of the absorbent changes to dark red-brown liquid. The rich liquid sampled in the regeneration tower is marked as R liquid; the lean liquid sampled in the regeneration tower is marked as L liquid.

[0053] Example 1

[0054] 1) Consistency calibration of the reference amine solution and the pH meter

[0055] First, the pH meter is calibrated and set by using standard buffer solutions 4.0 and 11.0;

[0056] 2ml of 30% ethanolamine aqueous solution is accurately taken by using a 2ml pipette, placed in a 100ml beaker, added with water to 30ml, dropped with 2 drops of methyl orange indicator with a concentration of 0.1wt%, and placed in a magnetic stirrer; the beaker containing the test solution is placed on the magnetic stirrer and immersed in the pH meter test electrode; the stirrer and the pH meter are turned on, and the solution is slowly titrated with 0.5034mol / L hydrochloric acid standard titration solution until the solution changes color, and the volume of hydrochloric acid consumed is recorded as 19.9ml, and the pH value is 3.35-4.22.

[0057]

[0058] C 理 = 4.91mol / L (i.e. the theoretical amine concentration of 30% ethanolamine aqueous solution)

[0059]

[0060] δ≤5%, and the pH value at the titration end point is between 3.1-4.4, and the consistency calibration is completed.

[0061] 2) Determination of the potential titration end point

[0062] Using 2ml pipette accurately take 2ml carbon capture absorbent new liquid, placed in 100ml beaker, add water to 30ml, drop in 2 drops of 0.1wt% methyl orange indicator, put into the magnetic; the test solution in the beaker placed on the magnetic stirrer, immersed in pH test electrode; open the stirrer and pH meter, slowly titrate with 0.5034mol / L hydrochloric acid standard titration solution, until the solution appears color change, record the titration end point pH value is 3.62-3.74, and the pH value as in the carbon capture absorbent titration end point.

[0063] 3) in the determination of the concentration of R liquid amine with carbon capture absorbent

[0064] Using 2ml pipette accurately take 2ml in the carbon capture absorbent R liquid, placed in 100ml beaker, add water to 30ml, drop in 2 drops of 0.1wt% methyl orange indicator, put into the magnetic; the test solution in the beaker placed on the magnetic stirrer, immersed in pH test electrode; open the stirrer and pH meter, slowly titrate with 0.5034mol / L hydrochloric acid standard titration solution, when the solution pH value shows to 6.5, every drop of hydrochloric acid solution, after 20S, drop to the test solution pH value is 3.18-3.76, similar to the preferred pH value 3.62-3.74 of step two, at the same time when again drop of hydrochloric acid solution, obviously observed the pH value rapidly decreased, the pH value as 3.18-3.76 is the titration end point, record the consumption of hydrochloric acid volume 3.4ml, and calculate its amine concentration.

[0065]

[0066] Example 2

[0067] 1) the consistency of the reference amine solution and pH meter calibration

[0068] First, the standard buffer solution 4.0 and 11.0 for pH meter calibration settings;

[0069] Using 2ml pipette accurately take 2ml 30% N-methyl diethanolamine aqueous solution, placed in 100ml beaker, add water to 30ml, drop in 2 drops of 0.1wt% methyl orange indicator, put into the magnetic; the test solution in the beaker placed on the magnetic stirrer, immersed in pH test electrode; open the stirrer and pH meter, slowly titrate with 0.5034mol / L hydrochloric acid standard titration solution, until the solution appears color change, record the consumption of hydrochloric acid volume 10.2ml, pH value is 3.23-4.00.

[0070]

[0071] C 理= 2.52 mol / L (i.e. the theoretical amine concentration of 30% N-methyldiethanolamine aqueous solution)

[0072]

[0073] δ≤5%, and the pH value at the titration end point is between 3.1 and 4.4, and the consistency calibration is completed.

[0074] 2) Determination of the end point of the potential titration

[0075] 2 ml of the carbon capture absorbent new solution is accurately taken using a 2 ml pipette, placed in a 100 ml beaker, water is added to 30 ml, 2 drops of 0.1 wt% methyl orange indicator are added dropwise, and the beaker is placed in a magnetic stirrer; the beaker containing the test solution is placed on the magnetic stirrer, immersed in the pH electrode; the stirrer and pH meter are turned on, and the 0.5034 mol / L hydrochloric acid standard titration solution is slowly titrated until the solution changes color, and the pH value at the titration end point is recorded as 3.48-3.69, which is used as the pH value at the end point of the carbon capture absorbent titration.

[0076] 3) Determination of the amine concentration of the carbon capture absorbent L solution

[0077] 2 ml of the carbon capture absorbent L solution is accurately taken using a 2 ml pipette, placed in a 100 ml beaker, water is added to 30 ml, 2 drops of 0.1% methyl orange indicator are added dropwise, and the beaker is placed in a magnetic stirrer; the beaker containing the test solution is placed on the magnetic stirrer, immersed in the pH electrode; the stirrer and pH meter are turned on, and the 0.5034 mol / L hydrochloric acid standard titration solution is slowly titrated, and when the pH value of the solution shows 6.5, one drop of hydrochloric acid solution is added every 20 s, and the pH value of the test solution is 3.22-3.99, which is similar to the preferred pH value of 3.48-3.69 in step two, and when another drop of hydrochloric acid solution is added, the pH value is observed to decrease rapidly, and the pH value of 3.22-3.99 is considered as the end point of the titration. The volume of hydrochloric acid consumed is recorded as 3.3 ml, and the amine concentration is calculated.

[0078]

[0079] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of determining amine concentration in a carbon capture absorbent, characterized by, (1) Consistency calibration of the reference amine solution with the pH meter A reference amine solution, water and a color indicator are mixed well, titrated with a standard titration solution of hydrochloric acid, while stirring, until the solution changes color, i.e. the end point of the titration, and the volume of hydrochloric acid titrated is recorded, noted as , and the pH value at the end point of the titration, noted as ; the color indicator is methyl orange; According to the formula ① and ②, the amine concentration and the relative error of the amine concentration of the reference amine solution are calculated respectively: = ① wherein, is the measured amine concentration of the reference amine solution, mol / L; is the volume of the standard hydrochloric acid titration solution used in step (1), ml; is the molar concentration of the standard hydrochloric acid titration solution used in step (1), mol / L; is the volume of the reference amine solution added in step (1), ml; δ = 0.5 2) wherein δ refers to the relative error of the reference amine solution concentration; C 理 refers to the theoretical amine concentration of the reference amine solution, mol / L; When the relative error δ of the reference amine solution concentration is ≤ 5%, and When the value is between 3.1-4.4, then the uniformity calibration is completed; when the relative error δ of the reference amine solution concentration is > 5%, or when the value is not between 3.1 and 4.4, the pH meter is recalibrated with a standard buffer solution until the above criteria are met; (2) Determination of the end point of the potential titration A fresh carbon capture absorbent, water and a colour indicator are mixed well and titrated with a standard titration solution of hydrochloric acid, with stirring, until a colour change occurs in the solution, i.e. the end point of the titration, and the pH at the end point of the titration is recorded as ; (3) Determination of the amine concentration of the carbon capture absorbent The carbon capture absorbent under test, water and a colour indicator are mixed well and titrated with a standard titration solution of hydrochloric acid, with stirring, until the pH of the solution reaches a value, i.e. the end point of the titration, of 3.5 The volume of hydrochloric acid titrated is recorded as ; According to the formula ③, the amine concentration of the carbon capture absorbent to be measured is calculated: = ③ wherein, is the amine concentration of the carbon capture absorbent to be measured, mol / L; is the volume of the standard hydrochloric acid titration solution titrated in step (3), ml; is the molar concentration of the standard hydrochloric acid titration solution in step (3), mol / L; is the volume of the carbon capture absorbent to be measured added in step (3), ml.

2. The method of claim 1, wherein the method is performed in a carbon capture plant. Before step (1), the pH meter is calibrated by using the standard buffer solution.

3. The method of claim 1 or 2, wherein the method is characterized by, In step (1), the reference amine solution is a 30% ethanolamine solution or a 30% N-methyl diethanolamine solution.

4. The method of claim 1 or 2, wherein the method is characterized by, In steps (1)-(3), the molar concentration of any of the standard hydrochloric acid titration solution is 0.2-1.0 mol / L.

5. The method of claim 1 or 2, wherein the method is performed in a time period of 1 to 10 minutes. In step (1), the amount of the reference amine solution, water and color indicator is 1 ml: 10-30 ml: 1-2 drops.

6. The method of claim 1 or 2, wherein the method is performed in a time period of 1 to 10 minutes. In step (2), the amount of the unused carbon capture absorbent, water and color indicator is 1 ml: 10-30 ml: 1-2 drops. In step (3), the amount of the carbon capture absorbent to be measured, water and color indicator is 1 ml: 10-30 ml: 1-2 drops.

7. The method of claim 1 or 2, wherein the method is performed in a time period of 1 to 10 minutes. In step (3), the titration speed of the standard hydrochloric acid titration solution is: when the pH of the solution is greater than 6.5, drop one drop of the standard hydrochloric acid titration solution every 1-2 seconds, and when the pH of the solution is less than 6.5, drop one drop of the standard hydrochloric acid titration solution every 10-30 seconds.

8. A measuring device for the method of determining the concentration of amines in a carbon capture absorbent according to any one of claims 1 to 7, characterized in that It comprises: A stand fixed with a burette clamp, an acid burette clamped on the burette clamp, a magnetic stirrer arranged below the acid burette, a titration container placed on the upper surface of the magnetic stirrer, and a pH electrode of a pH meter arranged inside the magnetic stirrer.

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