Determination method and determination device for amine concentration in carbon capture absorbent

Abstract

The invention belongs to the technical field of carbon capture, and particularly relates to a method and a device for measuring the concentration of amine in a carbon capture absorbent. The determination method comprises the following steps: (1) calibrating the consistency of a reference amine solution and a pH meter; (2) judging a potentiometric titration end point; and (3) determining the amine concentration of the carbon capture absorbent. The detection method is simple and feasible, the determination device is simple in structure and convenient to operate, and the concentration of the amine in the online running carbon capture absorbent can be monitored, so that the effective running of the carbon capture device is ensured, and the problem that determination cannot be performed due to the fact that a sample is dark in color and cannot be distinguished at a titration end point in a color indicator method is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon capture, and in particular relates to a method and a device for determining the concentration of amines in a carbon capture absorbent. Background Art

[0002] Carbon capture utilization and storage (CCUS) is a widely accepted technology for future response to climate change and reduction of carbon emissions. Capturing and recycling CO2 has become one of the effective means to mitigate the greenhouse effect.

[0003] Chemical absorption is the most mature and promising carbon capture technology. Among them, organic alcohol amine solution is the most widely used CO2 absorbent and is widely used in the purification of natural gas, synthetic ammonia feed gas, refinery gas, flue gas and other gases. The carbon capture device captures CO2 through absorption and regeneration cycle. The process principle is to use organic alcohol amine solution to absorb CO2 at a relatively low temperature (35-45°C) to form a rich liquid, and the rich liquid releases CO2 at a relatively high temperature (100-120°C), thereby achieving high-concentration recovery of CO2.

[0004] During the application process, it was found that amines undergo oxidative degradation, amines and their degradation products are easily volatilized during regeneration, and the introduction of impurities in the tail gas leads to a decrease in the amine concentration in the carbon capture absorbent, which in turn leads to a decrease in 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, as the carbon capture device operates for a long time, in addition to the decrease in amine concentration, the color of the absorbent will gradually deepen, from colorless and light yellow to dark reddish brown. Unused carbon capture absorbents are lighter in color, and the amine concentration can be determined by the color indicator method. However, online carbon capture absorbents are often darker in color, and the titration endpoint cannot be determined based on the color change during titration. Therefore, the color indicator method is not suitable for the determination of amine concentration in carbon capture absorbents with darker colors. In order to effectively monitor the amine concentration of carbon capture absorbents, an easy and effective determination method is urgently needed. Summary of the invention

[0006] Aiming at the problem that the color indicator method cannot measure the amine concentration because the carbon capture absorbent in online operation has a dark color and cannot be distinguished at the titration endpoint, the present invention provides a method and a device for measuring the amine concentration in the carbon capture absorbent. The detection method is simple and feasible, and the measuring device has a simple structure and is easy to operate. It can realize the monitoring of the amine concentration of the carbon capture absorbent in online operation, thereby ensuring the effective operation of the carbon capture device.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] A method for determining the concentration of amines in a carbon capture absorbent comprises the following steps:

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

[0010] Mix the reference amine solution, water and color indicator evenly, and titrate with hydrochloric acid standard titration solution, stirring while titrating until the solution changes color, which is the titration endpoint. Record the volume of hydrochloric acid titrated, which is recorded as and the pH value at the titration endpoint, recorded as pH A ;

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

[0012]

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

[0014]

[0015] Where, δ refers to the relative error of the concentration of the reference amine solution; C 理 It refers to the theoretical amine concentration of the benchmark amine solution, mol / L;

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

[0017] When the relative error of the concentration of the reference amine solution is greater than 5%, or the pH A If the value is not between 3.1 and 4.4, recalibrate the pH meter with standard buffer solution until it meets the above standards;

[0018] (2) Determination of the endpoint of potentiometric titration

[0019] Mix unused carbon capture absorbent, water and color indicator evenly, titrate with hydrochloric acid standard titration solution, stirring while titrating until the solution changes color, which is the titration end point, and record the pH value at the titration end point, which is recorded as pH B ;

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

[0021] Mix the carbon capture absorbent to be tested, water and color indicator evenly, and titrate with hydrochloric acid standard titration solution while stirring until the pH value of the solution reaches pH V The value is the titration endpoint, and the volume of hydrochloric acid titrated is recorded as

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

[0023]

[0024] in, It refers to the amine concentration of the carbon capture absorbent to be tested, mol / L; is the volume of the standard hydrochloric acid 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 tested added in step (3), ml.

[0025] In the present invention, the carbon capture absorbent refers to an organic alcohol amine carbon capture absorbent. The carbon capture absorbent currently in operation is generally a composite organic alcohol amine solution, that is, 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 a fresh carbon capture absorbent with the same formula as the carbon capture absorbent to be tested.

[0026] In step (3) of the present invention, the determination of the titration endpoint must simultaneously meet the following two points: first, the pH value of the solution is close to pH V value; secondly, when one more drop of hydrochloric acid standard titration solution is added, it is clearly observed that the pH value drops rapidly.

[0027] It is particularly important to note that the inventors discovered during the experiment that the pH value of the titration endpoint may be a certain point value or a certain range of values, which may be related to the following aspects: first, the brand and accuracy of the pH meter, the speed of setting the titration endpoint determination, and the influence of the equipment status at the time; second, the organic alcohol amine solution will form organic alcohol amine hydrochloride during the hydrochloric acid titration process, which has a complex composition and changes at any time with the titration, resulting in fluctuations in the pH value of the solution; third, the influence of the stirring speed of the solution during the hydrochloric acid titration process. The hydrochloric acid titration of the organic alcohol amine solution is a chemical reaction, and the stirring speed also affects the uniformity of the liquid.

[0028] Preferably, before performing step (1), the pH meter is first calibrated using a standard buffer solution.

[0029] Preferably, the color indicator is methyl orange.

[0030] Preferably, in step (1), the reference amine solution is a 30% by mass ethanolamine solution or a 30% by mass N-methyldiethanolamine solution. The reference amine solution is an ethanolamine solution or N-methyldiethanolamine solution of the above mass concentration, which is closer to actual working conditions and is more beneficial for the consistency calibration of the first step.

[0031] Preferably, in step (1) to step (3), the molar concentration of any of the hydrochloric acid standard titration solutions is 0.2-1.0 mol / L; more preferably, the molar concentrations of the hydrochloric acid standard titration solutions are the same. If the concentration of the hydrochloric acid titration solution is too high, the error of one drop will be relatively large when titrating near the end point; if the concentration of the hydrochloric acid titration solution is too low, a large volume of hydrochloric acid will be used during titration.

[0032] Preferably, in step (1), the reference amine solution, water and color indicator are used in a ratio of 1 ml: 10-30 ml: 1-2 drops.

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

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

[0035] Further preferably, in steps (1) to (3), the reference amine solution, the unused carbon capture absorbent and the carbon capture absorbent to be tested are each used in the same ratio with water and the color indicator.

[0036] Preferably, in step (3), the titration rate 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 dripped 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 dripped every 10-30 seconds.

[0037] The present invention also provides a measuring device for the above-mentioned method for measuring the amine concentration in the carbon capture absorbent, comprising:

[0038] The iron frame is fixed with a burette clamp, an acid burette is clamped on the burette clamp, a magnetic stirrer is arranged below the acid burette, a titration container is placed on the upper surface of the magnetic stirrer, and a magnet and a pH electrode of a pH meter are arranged inside.

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

[0040] The beneficial effects of the present invention are at least:

[0041] 1) The present invention provides a method for determining the amine concentration in a carbon capture absorbent, which can determine the amine concentration of the carbon capture absorbent in use, thereby solving the problem that the color indicator method cannot be determined due to the dark color of the sample and the inability to distinguish at the titration end point;

[0042] 2) The present invention provides a method for determining the amine concentration in a carbon capture absorbent, using a color indicator method as a reference to optimize the titration endpoint value. Experiments have shown that the method is easy and effective, and can monitor the amine concentration of an online carbon capture absorbent, thereby ensuring the effective operation of the carbon capture device;

[0043] 3) In the method for determining the amine concentration in a carbon capture absorbent provided by the present invention, the reference amine solution is preferably a 30% by mass ethanolamine solution or a 30% by mass N-methyldiethanolamine solution, which is closer to actual working conditions and is more beneficial for the first step of consistency calibration;

[0044] 4) The present invention provides a method for determining the concentration of amines in a carbon capture absorbent, and the measurement equipment used is simple in structure and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the structure of the measuring device used in the example, wherein: 1-iron stand, 2-acid burette, 3-burette clamp, 4-beaker, 5-magnetic stirrer, 6-pH. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product manual shall be followed.

[0047] In the following examples, the measuring device used is as follows Figure 1 As shown, it includes:

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

[0049] The pH meter is an S40 PH / conductivity / ion comprehensive tester produced by Mettler-Toledo Instruments (Shanghai) Co., Ltd., which has an automatic temperature compensation function and a set accuracy of 0.01.

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

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

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

[0053] Example 1

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

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

[0056] Use a 2ml pipette to accurately draw 2ml of 30% ethanolamine aqueous solution, place it in a 100ml beaker, add water to 30ml, drip 2 drops of 0.1wt% methyl orange indicator, and put in a magnet; place the beaker containing the test solution on a magnetic stirrer and immerse the pH test electrode; turn on the stirrer and pH meter, slowly titrate with 0.5034mol / L hydrochloric acid standard titration solution until the solution changes color, record the volume of hydrochloric acid consumed (19.9ml) and the pH value (3.35-4.22).

[0057]

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

[0059]

[0060] δ≤5%, and the pH value of the titration endpoint is between 3.1-4.4, completing the consistency calibration.

[0061] 2) Determination of the endpoint of potentiometric titration

[0062] Use a 2ml pipette to accurately draw 2ml of new carbon capture absorbent solution, place it in a 100ml beaker, add water to 30ml, drip 2 drops of 0.1wt% methyl orange indicator, and put in a magnet; place the beaker containing the test solution on a magnetic stirrer and immerse the pH test electrode; turn on the stirrer and the pH meter, slowly titrate with a 0.5034mol / L hydrochloric acid standard titration solution until the solution changes color, record the pH value of the titration end point as 3.62-3.74, and use this pH value as the titration end point of the carbon capture absorbent in use.

[0063] 3) Determination of amine concentration in carbon capture absorbent R liquid

[0064] Use a 2ml pipette to accurately draw 2ml of the carbon capture absorbent R solution in use, place it in a 100ml beaker, add water to 30ml, drip 2 drops of 0.1wt% methyl orange indicator, and put in a magnet; place the beaker containing the test solution on a magnetic stirrer and immerse the pH test electrode; turn on the stirrer and pH meter, slowly titrate with 0.5034mol / L hydrochloric acid standard titration solution, when the solution pH value reaches 6.5, observe 20S after each drop of hydrochloric acid solution, drop until the pH value of the test solution is 3.18-3.76, which is close to the preferred pH value of 3.62-3.74 in step 2, and when another drop of hydrochloric acid solution is dripped, it is obviously observed that the pH value drops rapidly, and the pH value is regarded as 3.18-3.76 as the titration end point, record the volume of hydrochloric acid consumed 3.4ml, and calculate its amine concentration.

[0065]

[0066] Example 2

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

[0068] First, the pH meter was calibrated using standard buffer solutions 4.0 and 11.0;

[0069] Use a 2ml pipette to accurately draw 2ml of 30% N-methyldiethanolamine aqueous solution, place it in a 100ml beaker, add water to 30ml, drip 2 drops of 0.1wt% methyl orange indicator, and put in a magnet; place the beaker containing the test solution on a magnetic stirrer and immerse the pH test electrode; turn on the stirrer and pH meter, slowly titrate with 0.5034mol / L hydrochloric acid standard titration solution until the solution changes color, record the volume of hydrochloric acid consumed (10.2ml) and the pH value (3.23-4.00).

[0070]

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

[0072]

[0073] δ≤5%, and the pH value of the titration endpoint is between 3.1-4.4, completing the consistency calibration.

[0074] 2) Determination of the endpoint of potentiometric titration

[0075] Use a 2ml pipette to accurately draw 2ml of new carbon capture absorbent solution, place it in a 100ml beaker, add water to 30ml, drip 2 drops of 0.1wt% methyl orange indicator, and put in a magnet; place the beaker containing the test solution on a magnetic stirrer and immerse the pH test electrode; turn on the stirrer and the pH meter, slowly titrate with a 0.5034mol / L hydrochloric acid standard titration solution until the solution changes color, record the pH value of the titration end point as 3.48-3.69, and use this pH value as the titration end point of the carbon capture absorbent in use.

[0076] 3) Determination of amine concentration in carbon capture absorbent L liquid

[0077] Use a 2ml pipette to accurately draw 2ml of the carbon capture absorbent L solution, place it in a 100ml beaker, add water to 30ml, drip 2 drops of 0.1% methyl orange indicator, and put in a magnet; place the beaker containing the test solution on a magnetic stirrer and immerse the pH test electrode; turn on the stirrer and pH meter, slowly titrate with 0.5034mol / L hydrochloric acid standard titration solution, when the solution pH value reaches 6.5, observe for 20s after each drop of hydrochloric acid solution, drop until the test solution pH value is 3.22-3.99, which is close to the preferred pH value of 3.48-3.69 in step 2, and when another drop of hydrochloric acid solution is dripped, the pH value is obviously observed to drop rapidly, and the pH value is considered to be 3.22-3.99 as the titration end point. Record the volume of hydrochloric acid consumed, 3.3ml, and calculate its amine concentration.

[0078]

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the concentration of amines in a carbon capture absorbent, characterized in that: (1) Consistency calibration of reference amine solution and pH meter Mix the reference amine solution, water and color indicator evenly, and titrate with hydrochloric acid standard titration solution, stirring while titrating until the solution changes color, which is the titration endpoint. Record the volume of hydrochloric acid titrated, which is recorded as and the pH value at the titration endpoint, recorded as pH A ; According to formulas ① and ②, the measured amine concentration of the reference amine solution and the relative error of the amine concentration are calculated respectively: in, It refers to the measured amine concentration of the reference amine solution, mol / L; is the volume of the standard hydrochloric acid solution titrated in step (1), ml; is the molar concentration of the hydrochloric acid standard titration solution in step (1), mol / L; is the volume of the reference amine solution added in step (1), ml; Where, δ refers to the relative error of the concentration of the reference amine solution; C 理 It refers to the theoretical amine concentration of the benchmark amine solution, mol / L; When the relative error of the concentration of the reference amine solution is ≤5%, and the pH A When the value is between 3.1-4.4, the consistency calibration is completed; When the relative error of the concentration of the reference amine solution is greater than 5%, or the pH A If the value is not between 3.1 and 4.4, recalibrate the pH meter with standard buffer solution until it meets the above standards; (2) Determination of the endpoint of potentiometric titration Mix unused carbon capture absorbent, water and color indicator evenly, titrate with hydrochloric acid standard titration solution, stirring while titrating until the solution changes color, which is the titration end point, and record the pH value at the titration end point, which is recorded as pH B ; (3) Determination of amine concentration in carbon capture absorbent Mix the carbon capture absorbent to be tested, water and color indicator evenly, and titrate with hydrochloric acid standard titration solution while stirring until the pH value of the solution reaches pH B The value is the titration endpoint, and the volume of hydrochloric acid titrated is recorded as According to formula ③, the amine concentration of the carbon capture absorbent to be tested is calculated respectively: in, It refers to the amine concentration of the carbon capture absorbent to be tested, mol / L; is the volume of the standard hydrochloric acid 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 tested added in step (3), ml.

2. The method for determining the amine concentration in the carbon capture absorbent according to claim 1, characterized in that: Before performing step (1), the pH meter is first calibrated using a standard buffer solution.

3. The method for determining the amine concentration in the carbon capture absorbent according to claim 1 or 2, characterized in that: The color indicator is methyl orange.

4. The method for determining the amine concentration in the carbon capture absorbent according to claim 1 or 2, characterized in that: In step (1), the reference amine solution is a 30% by mass ethanolamine solution or a 30% by mass N-methyldiethanolamine solution.

5. The method for determining the amine concentration in the carbon capture absorbent according to claim 1 or 2, characterized in that: In steps (1) to (3), the molar concentration of any of the hydrochloric acid standard titration solutions is 0.2-1.0 mol / L.

6. The method for determining the amine concentration in the carbon capture absorbent according to claim 1 or 2, characterized in that: In step (1), the dosage ratio of the reference amine solution, water and color indicator is 1 ml: 10-30 ml: 1-2 drops.

7. The method for determining the amine concentration in the carbon capture absorbent according to claim 1 or 2, characterized in that: In step (2), the ratio of the unused carbon capture absorbent, water and color indicator is 1 ml: 10-30 ml: 1-2 drops; In step (3), the dosage ratio of the carbon capture absorbent to be tested, water and color indicator is 1 ml: 10-30 ml: 1-2 drops.

8. The method for determining the amine concentration in a carbon capture absorbent according to claim 1 or 2, characterized in that: In step (3), the titration rate of the hydrochloric acid standard titration solution is: when the pH value of the solution is greater than 6.5, one drop of the hydrochloric acid standard titration solution is dripped every 1-2 seconds; when the pH value of the solution is less than 6.5, one drop of the hydrochloric acid standard titration solution is dripped every 10-30 seconds.

9. A measuring device for the method for measuring the amine concentration in the carbon capture absorbent according to any one of claims 1 to 8, characterized in that: include: The iron frame is fixed with a burette clamp, an acid burette is clamped on the burette clamp, a magnetic stirrer is arranged below the acid burette, a titration container is placed on the upper surface of the magnetic stirrer, and a magnet and a pH electrode of a pH meter are arranged inside.

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