Method for measuring co2 fixation amount

Abstract

To improve the accuracy of measuring the CO2 fixation amount in a cement composition.SOLUTION: There is provided a method for measuring the amount of CO2 fixation in a cement composition, the method including: acidifying a sample of the cement composition; converting inorganic carbon in the sample into CO2 gas; and detecting the CO2 gas by a nondispersive infrared absorption method. In the method, before the acidifying, the particle size of the sample is set to not more than a predetermined particle size, and pure water is dropped onto the sample.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for measuring the amount of CO2 fixed in a cement composition. [Background technology]

[0002] As a method for reducing carbon dioxide (CO2) emissions during the production of cement compositions such as concrete, techniques for immobilizing CO2 in cement compositions have been developed. In such techniques, to accurately grasp the effect of reducing CO2 emissions, it is necessary to accurately quantify (measure) the amount of CO2 fixed in the cement composition. A known method for measuring the amount of CO2 fixed in a cement composition is simultaneous differential thermal analysis-thermogravimetry (TG-DTA method) (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-168531 Summary of the Invention [Problem to be solved by the invention]

[0004] The TG-DTA method mainly targets CO2 derived from CaCO3. Therefore, if CO2 exists in a form other than CaCO3 in the cement composition, the amount of CO2 fixed may not be measured accurately.

[0005] Another known method for measuring CO2 fixation is the TOC method, which uses a total organic carbon analyzer equipped with a solid sample combustion device. This method involves aerating an acidified sample to convert inorganic carbon (IC) in the sample into CO2 gas, which is then detected using non-dispersive infrared absorption. This method can measure all carbonates, including CaCO3. Therefore, theoretically, it is possible to accurately quantify the amount of CO2 fixation in cement compositions. However, while there are several examples of TOC methods for evaluating CO2 fixation, no standardization has been achieved. Furthermore, no pretreatment method has been established to obtain accurate measurements.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to improve the accuracy of measuring the amount of CO2 fixed in a cement composition. [Means for solving the problem]

[0007] The main invention for achieving the above object is a method for measuring the amount of CO2 fixation, which comprises acidifying a cement composition sample, converting inorganic carbon in the sample into CO2 gas, and detecting the CO2 gas by non-dispersive infrared absorption, characterized in that, prior to the acidification treatment, the particle size of the sample is reduced to a predetermined particle size or less, and pure water is added dropwise to the sample.

[0008] Other features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the accuracy of measuring the amount of CO2 fixed in a cement composition. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic plan view of the TOC meter 10 and the SSM 20. [Figure 2] FIG. 2 is a diagram showing the peripheral configuration of a sample board 22 of the SSM 20. [Figure 3] FIG. 1 is a schematic cross-sectional view of SSM20. [Figure 4] FIG. 2 is a flow chart showing a method for measuring the amount of fixed CO2 in this embodiment. [Figure 5] 5A to 5C are explanatory diagrams of gas paths. [Figure 6] FIG. 1 is a simplified flow chart showing sample processing. [Figure 7] FIG. 10 shows particle size test results. [Figure 8] FIG. 1 is a graph showing the relationship between the particle size of a sample and the amount of CO2 fixed. [Figure 9] FIG. 10 is a diagram showing test results of the amount of pure water dropped. [Figure 10] FIG. 1 is a diagram showing the relationship between the amount of pure water dropped and the amount of CO2 fixed. DETAILED DESCRIPTION OF THE INVENTION

[0011] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0012] (Aspect 1) A method for measuring the amount of CO2 fixation, which comprises acidifying a cement composition sample, converting inorganic carbon in the sample into CO2 gas, and detecting the CO2 gas by non-dispersive infrared absorption, characterized in that, prior to the acidification treatment, the particle size of the sample is adjusted to a predetermined particle size or less, and pure water is dripped onto the sample.

[0013] According to the method for measuring the amount of CO2 fixation of aspect 1, it is possible to increase the reactivity in the acidification treatment, and to improve the accuracy of measuring the amount of CO2 fixation in the cement composition.

[0014] (Aspect 2) In the method for measuring a CO2 fixation amount according to aspect 1, the predetermined particle size is preferably 150 μm.

[0015] According to the method for measuring the amount of fixed CO2 in aspect 2, by reducing the particle size of the sample (to 150 μm or less), it is possible to obtain measurement results with high accuracy (close to the theoretical value).

[0016] (Aspect 3) In the method for measuring a CO2 fixation amount according to the first or second aspect, the amount of the pure water dropped is preferably 4 mL / g or more.

[0017] According to the method for measuring the amount of CO2 fixation of the third aspect, it is possible to obtain measurement results with high accuracy (close to the theoretical value).

[0018] (Aspect 4) In the method for measuring a CO2 fixation amount according to any one of Aspects 1 to 3, it is preferable that the sample that has been subjected to the acidification treatment is subjected to an aeration treatment.

[0019] According to the method for measuring the amount of fixed CO2 in aspect 4, the generated CO2 gas can be sent to a detector (CO2 detector) that uses non-dispersive infrared absorption.

[0020] (Aspect 5) In the method for measuring a CO2 fixation amount according to any one of Aspects 1 to 4, it is preferable that, when converting the inorganic carbon into the CO2 gas, the inorganic carbon is maintained at a predetermined temperature that promotes the conversion into the CO2 gas.

[0021] According to the method for measuring the amount of CO2 fixation of the fifth aspect, CO2 gas can be generated more reliably, and the accuracy of detecting the amount of CO2 fixation can be improved.

[0022] === Implementation form === <<About the measuring device>> In this embodiment, a total organic carbon meter (TOC-L) equipped with a solid sample combustion device (SSM-5000A) is used to measure the amount of CO2 fixed in a cement composition sample. CPHThis equipment uses a solid sample combustion apparatus (hereafter referred to as SSM) to acidify the sample, converting inorganic carbon (IC) in the sample into CO2 gas, and then detects the generated CO2 gas using a total organic carbon analyzer (hereafter referred to as TOC analyzer) using non-dispersive infrared absorption.

[0023] In addition, since the simultaneous thermogravimetric differential thermal analysis (TG-DTA method) mainly targets CO2 derived from CaCO3, if CO2 is present in a form other than CaCO3 in the cement composition, the amount of fixed CO2 may not be measured accurately.

[0024] In contrast, the measurement method using a TOC analyzer (TOC method) can measure all carbonates and can quantify CO2 present in forms other than CaCO3. For example, it can detect carbonates such as magnesium carbonate (MgCO3) and monocarbonate (3CaO·Al2O3·CaCO3·nH2O), as well as CO2 absorbed by amorphous calcium silicate carbonate. This theoretically allows for a higher accuracy in the amount of CO2 fixed.

[0025] However, although there are several examples of methods for evaluating the amount of CO2 fixation using the TOC method, they have not yet been standardized. Furthermore, pretreatment methods for obtaining accurate measurements have not yet been established. Therefore, in this embodiment, we investigated pretreatment methods for the TOC method to improve the measurement accuracy of the amount of CO2 fixation.

[0026] Fig. 1 is a schematic plan view of the TOC meter 10 and the SSM 20. Fig. 2 is a diagram showing the configuration of the periphery of the sample board 22 of the SSM 20. Fig. 3 is a schematic cross-sectional view of the SSM 20.

[0027] In this embodiment, as shown in FIG. 1, two horizontal directions (front-rear direction and left-right direction) are defined. The front-rear direction is the depth direction of the apparatus. The side (rear side) to which the air ducts 50 and 52 are connected is defined as "rear", and the opposite side (front side) is defined as "front". The left-right direction is the direction orthogonal to the front-rear direction (the width direction of the apparatus). In FIG. 1, the side where the SSM 20 is arranged with respect to the TOC meter 10 is defined as "right", and the opposite side is defined as "left".

[0028] The TOC meter 10 equipped with the SSM 20 can separately measure total carbon (TC) and inorganic carbon (IC) in a sample. Then, total organic carbon (TOC) can be determined from the difference (TC - IC). In this embodiment, the configuration and the like necessary for measuring inorganic carbon (IC) will be described, and descriptions of other parts will be omitted. Also, in FIG. 1, illustration of a pure air supply unit (and air duct) that supplies carrier gas (pure air) to the TOC meter 10 and a phosphoric acid container 30 (described later) arranged in the SSM 20 is omitted.

[0029] In FIG. 1, an air duct 50 is provided between the oxygen supply unit 40 and the SSM 20. And a carrier gas (oxygen gas (O2 gas)) is supplied from the oxygen supply unit 40 to the SSM 20 (specifically, a heating furnace 21 described later) through the air duct 50.

[0030] Also, an air duct 52 is provided between the TOC meter 10 and the SSM 20. And a carrier gas (O2 gas) and CO₂ gas generated from the sample are supplied from the SSM 20 to the TOC meter 10 (specifically, a CO₂ detection unit 12 described later) through the air duct 52 (described later). Also, a carrier gas (pure air) is supplied from a pure air supply unit (not shown) to the TOC meter 10 (CO₂ detection unit 12).

[0031] <Regarding the TOC meter 10> As shown in Figure 1, the TOC meter 10 includes a CO2 detector 12. The CO2 detector 12 detects CO2 using non-dispersive infrared absorption. The non-dispersive infrared absorption method is a measurement method that utilizes the fact that CO2 gas absorbs specific wavelengths in the infrared region. Although a detailed explanation is omitted, the amount of CO2 can be measured by irradiating infrared light onto the supplied CO2 gas and detecting the infrared light absorbed by the CO2 gas.

[0032] <SSM20について> As shown in FIGS. 1 to 3, the SSM 20 includes a heating furnace 21, a sample board 22, a lid 23, and a lever 24.

[0033] The heating furnace 21 is a furnace that heats the sample to a predetermined temperature (here, 200°C). As described above, a carrier gas (oxygen gas (O2 gas)) is supplied to the heating furnace 21 from the oxygen supply unit 40. The gas discharged from the heating furnace 21 is sent to the CO2 detection unit 12 of the TOC meter 10 through an air conduit 52. The heating furnace 21 also communicates with the space at the set position of the sample board 22, which will be described later.

[0034] The sample board 22 is a dish-shaped container on which a sample (a cement composition in this embodiment) is placed. At the position where the sample is placed on the sample board 22 (hereinafter referred to as the set position), the top of the device is open (see FIG. 2), allowing the sample to be placed on the sample board 22.

[0035] The lid 23 is provided so as to be movable in the left-right direction, and when it is moved to the right, the top of the sample board 22 can be opened, and when it is moved to the left (above the sample board 22), the sample board 22 can be shut off from the atmosphere (closed). Also, as shown in Figures 2 and 3, a tube 32 extending from the phosphoric acid container 30 is passed through the lid 23, and when the lid 23 is placed on the sample board 22 (closed), phosphoric acid solution can be dripped from the phosphoric acid container 30 onto the sample on the sample board 22.

[0036] The lever 24 is movable in the front-back direction, and the sample board 22 slides (moves) in the front-back direction according to the operation of the lever 24. When the lever 24 is pulled forward, the sample board 22 is at the set position (the sample loading position) (see FIGS. 1 to 3). Then, by moving (pushing) the lever 24 backward, the sample board 22 (and the sample) can be inserted into the heating furnace 21. Also, by moving (pulling) the lever 24 forward, the sample board 22 can be taken out of the heating furnace 21.

[0037] <<Regarding the measurement procedure of the CO2 fixation amount>> In the TOC method, by acidifying the sample with a phosphoric acid solution (acidification treatment), the inorganic carbon (IC) in the sample is converted into CO2 gas. Therefore, in order to accurately grasp the CO2 fixation amount, it is important to sufficiently react the sample with the phosphoric acid solution.

[0038] Therefore, in the present embodiment, in order to enhance the reactivity between the sample (cement composition) and the phosphoric acid solution, before performing the acidification treatment, a treatment of pulverizing the sample and a treatment of dropping pure water onto the sample are performed.

[0039] FIG. 4 is a flowchart showing the method for measuring the CO2 fixation amount in the present embodiment. FIGS. 5A to 5C are explanatory diagrams of the gas path (gas flow). Also, FIG. 6 is a flowchart simply showing the treatment for the sample.

[0040] First, a carrier gas (O2 gas, pure air gas) is flowed through the apparatus, and the apparatus is started (the heating furnace 21 of the SSM20 is heated to 200 ° C) and warmed for 1 hour or more (S01 in FIG. 4). At this time, as shown in FIG. 5A, since the lid 23 is open in the SSM20, the carrier gas (O2 gas) supplied from the oxygen supply unit 40 flows out of the apparatus system.

[0041] Next, a sample of the cement-based material (cement composition) is pulverized to 150 μm or less (see Examples) using a pulverizing device (S02 in FIG. 4). Note that this pulverization treatment may be performed before step S01.

[0042] Then, the powder sample (50 mg) obtained by pulverization is placed on the sample board 22 (S03 in FIG. 4). Hereinafter, the powder sample will also be referred to as sample S.

[0043] Next, pure water is dropped onto the sample S using a micropipette (not shown) (S04 in FIG. 4) to wet the sample S. The amount of pure water dropped is preferably 4 mL / g or more (see Examples).

[0044] Next, the lid 23 is closed (moved onto the sample board 22) and left for two minutes (S05 in FIG. 4). By closing the lid 23, as shown in FIG. 5B, the carrier gas (O2 gas) is sent to the CO2 detection unit 12 of the TOC analyzer 10 via the SSM 20 (heating furnace 21, sample board 22) and flows out of the system, so that the atmosphere around the sample S is filled with the carrier gas (O2 gas). In other words, the atmosphere and the carrier gas are exchanged (replaced) within the SSM 20. This prevents the CO2 detection unit 12 of the TOC analyzer 10 from detecting CO2 gas in the atmosphere, thereby improving the accuracy of CO2 detection.

[0045] Next, phosphoric acid solution (200 μL) is dropped onto the sample S from the phosphoric acid container 30 (S06 in FIG. 4), and the sample board 22 is pushed into the heating furnace 21 and heated to 200°C (S07 in FIG. 4). By acidifying the sample S (to pH 3 or less) with the phosphoric acid solution, the inorganic carbon contained in the sample S is converted into CO2 gas. Furthermore, by maintaining the heating furnace 21 at 200°C, the conversion of inorganic carbon into CO2 gas can be promoted.

[0046] As shown in FIG. 5C, the CO2 gas generated from the sample S is sent to the CO2 detection unit 12 of the TOC meter 10 via a carrier gas (O2 gas).

[0047] Then, the CO2 detection unit 12 of the TOC meter 10 detects the CO2 gas by non-dispersive infrared absorption (S08 in FIG. 4).

[0048] As explained above, in this embodiment, before the sample of cement-based material is acidified with the phosphoric acid solution, the sample is crushed (to a particle size of 150 μm or less) and pure water is dripped onto the sample. This increases the reactivity of the sample with the phosphoric acid solution, thereby improving the accuracy of measuring the amount of CO2 fixed in the cement composition.

[0049] <<<Example>>> In this example, the measurement of the amount of CO2 fixation was evaluated by varying the conditions of pretreatment (particle size of the sample, amount of pure water dripped). In the example, a total organic carbon meter (TOC-L) equipped with a solid sample combustion device (SSM-5000A) manufactured by Shimadzu Corporation was also used. CPH ) was used.

[0050] <<About the particle size of the sample>> If the sample particle size is large, the reaction with the phosphoric acid solution may be insufficient, which may result in an underestimation of the amount of CO2 fixed. Therefore, after crushing the sample (limestone with a CaCO3 purity of 98.44%), it was classified according to particle size and the amount of CO2 fixed for each was measured.

[0051] <Particle size conditions> The samples were classified using sieves with openings of 75 μm, 0.15 mm, 0.3 mm, 0.6 mm, 1.2 mm, and 2.5 mm, and the amount of CO2 fixation was measured for each sample. In other words, the particle size of each sample after classification was within the following range.

[0052] Particle size: 75μm or less 150-75μm 0.3-0.15mm 0.6-0.3mm 1.2-0.6mm 2.5-1.2mm

[0053] <Evaluation results> Figure 7 shows the results of particle size tests. Figure 8 shows the relationship between the particle size of the sample and the amount of CO2 fixed. The horizontal axis of Figure 8 shows particle size, and the vertical axis shows the amount of CO2 fixed (%). Note that particle size increases toward the right side of the figure. Figure 8 also shows the theoretical value of the amount of CO2 fixed (43.29%).

[0054] As shown in Figures 7 and 8, the smaller the particle size of the sample, the greater the amount of CO2 fixed that was quantified, and a value close to the theoretical value (43.29%) was obtained. This is thought to be because reducing the particle size increases the specific surface area, making it easier to react with the phosphoric acid solution.

[0055] It was confirmed that if the particle size is 150 μm (0.15 mm) or less, the error between the theoretical value and the measured value is about 2%, and highly accurate results can be obtained.

[0056] <<About the amount of pure water dripped>> Because the phosphoric acid solution is highly viscous, it does not spread easily over the entire sample, but wetting the sample with pure water before adding the phosphoric acid solution (before acidification treatment) is expected to increase the reactivity with the sample. In this example, the amount of pure water added was varied to evaluate the amount of CO2 fixation.

[0057] <Dripping amount conditions> The amount of CO2 fixation was measured when the amount of pure water dropped onto the sample was 0, 2, 4, 6, 10, and 20 mL / g. CaCO3 reagent (purity 99.5%, average particle size 20 μm) was used as the sample.

[0058] <Evaluation results> Figure 9 shows the test results for the amount of pure water dropped. Figure 10 shows the relationship between the amount of pure water dropped and the amount of CO2 fixed. The horizontal axis of Figure 10 shows the amount of pure water dropped, and the vertical axis shows the amount of CO2 fixed (%). Figure 10 also shows the theoretical value of the amount of CO2 fixed (43.75%).

[0059] 9 and 10, the measured amount of CO2 fixation without adding pure water was 30.71%, which was about 70% of the theoretical value. This shows that adding pure water is necessary to fully react the sample with the phosphoric acid solution.

[0060] Furthermore, if the amount of pure water dropped is 4 mL / g or more, the difference between the theoretical value and the measured value is kept to about 2%, confirming that highly accurate measurement results can be obtained.

[0061] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof. [Explanation of symbols]

[0062] 10 Total organic carbon meter (TOC meter) 12 CO2 detector 20 Solid Sample Combustion Apparatus (SSM) 21 Furnace 22 Sample Board 23 Lid 24 Lever 30 Phosphoric acid container 32 tubes 40 Oxygen supply unit 50 Air duct 52 Air duct

Claims

1. A sample of the cement composition is acidified to remove inorganic carbon from the sample. ２ converting the CO ２ CO gas detection by non-dispersive infrared absorption ２ A method for measuring a fixed amount, comprising: Prior to the acidification treatment, the particle size of the sample is adjusted to a predetermined particle size or less, and pure water is added dropwise to the sample. CO characterized by ２ How to measure the amount of fixation.

2. The CO according to claim 1 ２ A method for measuring a fixed amount, comprising: The predetermined particle size is 150 μm. CO characterized by ２ How to measure the amount of fixation.

3. The CO according to claim 1 ２ A method for measuring a fixed amount, comprising: The amount of pure water dropped is 4 mL / g or more. CO characterized by ２ How to measure the amount of fixation.

4. The CO according to claim 1 ２ A method for measuring a fixed amount, comprising: subjecting the acidified sample to an aeration treatment; CO characterized by ２ How to measure the amount of fixation.

5. The CO according to claim 1 ２ A method for measuring a fixed amount, comprising: The inorganic carbon is ２ When converted into gas, the CO ２ maintaining the temperature at a level that promotes conversion to gas; CO characterized by ２ How to measure the amount of fixation.

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