Determination method for calcium fluoride content in desulfurizing agent

Abstract

The invention discloses a method for measuring the content of calcium fluoride in a desulfurizing agent, and belongs to the technical field of analytical chemistry and metallurgical detection. The method comprises the following specific steps: grinding, sieving and drying a desulfurizer sample to obtain a sample; weighing a sample material, adding a calcium-containing acetic acid solution, placing at normal temperature and intermittently stirring to selectively dissolve calcium oxide while calcium fluoride is basically insoluble; adding perchloric acid, heating until concentrated white smoke is emitted, and removing fluorine ions in the solution; acidifying, heating to dissolve salts, cooling, and then transferring to a volumetric flask for constant volume; measuring the spectral intensity of the test solution under a calcium element characteristic spectral line by using ICP-OES; and calculating the calcium content according to a pre-drawn calcium element working curve, and converting the calcium content into the calcium fluoride mass fraction. Through the pretreatment process of normal-temperature selective dissolution of calcium-containing acetic acid and fluorine removal of perchloric acid, transmission interference and spectral line interference of fluorine ions on ICP-OES calcium measurement are effectively eliminated, and the method is suitable for wide-range measurement of the content of calcium fluoride in the desulfurizing agent.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry and metallurgical testing technology, and specifically relates to a method for determining the calcium fluoride content in desulfurizing agents. Background Technology

[0002] Desulfurizers are widely used in the steelmaking process to remove sulfur from steel. Calcium fluoride (CaF2) is a key component, and its content directly affects desulfurization efficiency and slag characteristics. Therefore, accurately determining the calcium fluoride content in desulfurizers is crucial for quality control in steel enterprises.

[0003] Currently, common methods for determining calcium fluoride in desulfurizing agents include chemical titration (such as EDTA titration) and X-ray fluorescence spectrometry (XRF). Chemical titration involves multiple manual steps, such as sample dissolution, separation of interfering ions, and multiple titrations. The process is lengthy, time-consuming, and cumbersome. Furthermore, the results are easily affected by the operator's experience and skill level, making it difficult to guarantee precision and accuracy, resulting in low efficiency and unsuitability for the daily batch testing needs of steel enterprises. While XRF offers faster analysis speed, its sensitivity for detecting low-content components is limited, especially when the calcium fluoride content is low, leading to increased measurement errors. Simultaneously, this method is sensitive to matrix effects, making it less applicable to industrial desulfurizing agent samples with varying matrix compositions (such as containing different proportions of calcium oxide, silicates, and sulfates). It requires the establishment of complex standard sample libraries for calibration, resulting in significant equipment investment and high maintenance costs, hindering its widespread application in most steel enterprise testing centers.

[0004] Furthermore, existing instrumental analysis methods often face interference from fluoride ions when directly applied to desulfurizers. Fluoride ions readily react with calcium to form non-volatile calcium fluoride particles, reducing sample transport efficiency and causing spectral interference in ICP-OES measurements, affecting the accurate determination of calcium. Traditional pretreatment methods struggle to completely eliminate this interference, leading to significant deviations in measurement results. Steel enterprises urgently need a calcium fluoride content determination method with a clear operating procedure, fast analysis speed, high precision, accuracy, reliability, moderate cost, and suitability for batch testing to meet the requirements of real-time production monitoring and stable quality. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to solve the above problems and provide a method for determining the calcium fluoride content in a desulfurizing agent.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for determining the calcium fluoride content in a desulfurizing agent includes the following steps: a) Grind the desulfurizing agent sample until it passes through a 240-mesh sieve, and dry it at 105±1℃ to obtain the sample; b) Weigh the sample, add calcium acetic acid solution, place at room temperature and stir intermittently, so that the calcium oxide in the sample is selectively dissolved by the calcium acetic acid solution, while the calcium fluoride is basically insoluble; c) Add perchloric acid to the mixture in step b) and heat until thick white fumes are emitted to remove fluoride ions from the solution; d) After acidification, dissolution of salts, and cooling, transfer the test solution to a volumetric flask and dilute to volume. e) Measure the spectral intensity of the test solution under the characteristic spectral lines of calcium using an inductively coupled plasma atomic emission spectrometer; f) Calculate the calcium content in the test solution based on the pre-plotted calcium element working curve, and convert it to the mass fraction of calcium fluoride.

[0007] Furthermore, the calcium-containing acetic acid solution is used to selectively dissolve calcium oxide at room temperature, thereby fixing the form of calcium in calcium fluoride and thus identifying the calcium to be tested as originating from calcium fluoride.

[0008] Furthermore, step c) is used to efficiently remove fluoride ions, eliminating the transmission and spectral interference of fluoride on calcium in inductively coupled plasma emission spectroscopy.

[0009] Furthermore, the linear correlation coefficient of the calcium element working curve is greater than 0.999.

[0010] Furthermore, in step d), acidification is achieved by adding hydrochloric acid and heating to dissolve the soluble salts.

[0011] Furthermore, the method is applicable to the determination of calcium fluoride content in desulfurizing agents ranging from 0.15% to 30%.

[0012] Furthermore, the preparation method of the calcium-containing acetic acid solution is as follows: weigh 5g of calcium carbonate into a beaker, cover it with a watch glass, add 100mL of acetic acid solution, heat it in a water bath to dissolve it, transfer it into a 1000mL volumetric flask and dilute it to the mark with acetic acid solution, and shake well.

[0013] Furthermore, the acetic acid solution is prepared by mixing acetic acid and water in a volume ratio of 1:9.

[0014] Furthermore, after measuring the spectral intensity of calcium using an inductively coupled plasma atomic emission spectrometer, if the difference between two independent test results does not exceed the allowable difference specified in the standard, the average value is taken as the final analysis result.

[0015] The beneficial effects of this invention are as follows: 1. High accuracy: Through selective dissolution with calcium-containing acetic acid at room temperature (calcium-containing acetic acid solution is used to selectively dissolve calcium oxide at room temperature, fixing the form of calcium element in calcium fluoride, thereby locking the source of the calcium to be tested to calcium fluoride), the detection target is accurately locked to calcium in calcium fluoride, avoiding interference from other calcium sources; then step c) heating to produce dense white fumes efficiently removes fluoride ions, eliminating the interference of non-volatile particles formed by fluoride transmission and spectral interference, ensuring the reliability of ICP-OES calcium measurement results.

[0016] 2. Rapid analysis: Compared with traditional chemical titration, this method greatly reduces manual operation and waiting time. After pretreatment, the instrument can quickly measure the sample, making it suitable for batch sample testing. The efficiency of the entire process is significantly improved.

[0017] 3. High sensitivity and wide linear range: ICP-OES itself has high sensitivity. After optimizing the pretreatment, this method can effectively determine the calcium fluoride content in a wide range from 0.15% to 30%, meeting the diverse needs of industrial desulfurizers. Moreover, the linear correlation coefficient of the working curve is greater than 0.999, ensuring accurate calculation.

[0018] 4. Relatively safe and simple operation: The pretreatment steps are clear and standardized, the acid dosage is controllable, the operation in the fume hood is highly safe, no complicated equipment or automated instruments are required, and it is easy to promote in the laboratory and train operators.

[0019] 5. Excellent cost-effectiveness: It mainly relies on conventional ICP-OES instruments, and the equipment investment and operating costs are far lower than XRF. It also does not require a special standard sample library, making it particularly suitable for daily applications in steel enterprise testing centers. It has good economic efficiency and practicality.

[0020] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic flowchart of the method for determining the calcium fluoride content in the desulfurizing agent in this embodiment of the invention. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0024] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0025] Example 1 Please see Figure 1 This is a method for determining the calcium fluoride content in a desulfurizing agent, comprising the following steps: 1. Preparation of calcium-containing acetic acid solution: Weigh 5g of analytical grade calcium carbonate (CaCO3) into a 250mL beaker and cover with a watch glass. Slowly add 100mL of acetic acid solution (acetic acid to water volume ratio of 1:9, i.e., prepared by mixing 10mL of glacial acetic acid with 90mL of pure water). Heat in a water bath (temperature controlled at 80-90℃) and stir until the calcium carbonate is completely dissolved (the solution is clear and no bubbles are produced). After cooling to room temperature, transfer the entire solution to a 1000mL volumetric flask and dilute to the mark with the above acetic acid solution (volume ratio 1:9). Shake thoroughly to obtain the calcium-containing acetic acid solution. This solution is used to selectively dissolve calcium oxide. The calculated calcium concentration is approximately 2g / L (calculated as Ca), which is sufficient to meet the dissolution requirements of calcium oxide in 0.1000g of sample.

[0026] 2. Sample Preparation: Take an appropriate amount of desulfurizing agent sample and grind it in an agate mortar until it passes through a 240-mesh standard sieve. Place the sieved sample in a drying oven and dry it at 105±1℃ for 2 hours. Remove it and cool it to room temperature in a desiccator to obtain the sample.

[0027] 3. Sample Pretreatment: Accurately weigh 0.1000g of the above sample (accurate to 0.0001g) and place it in a 200mL polytetrafluoroethylene or glass beaker. Add 20mL of the prepared calcium acetic acid solution and let it stand at room temperature (about 20-25℃) for 30 minutes. During this time, stir intermittently with a glass rod every 5-10 minutes for 3-5 times to selectively dissolve the calcium oxide (CaO) in the sample, while keeping the calcium fluoride (CaF2) essentially insoluble, thereby fixing the calcium element to be tested as calcium in calcium fluoride.

[0028] Next, add 5 mL of perchloric acid (HClO4, preferably 70%–72% concentration) to the beaker, place it on a hot plate, and heat it gradually until the solution boils and continue heating until dense white fumes are emitted (approximately 5–10 minutes). This step completely removes fluoride ions (F ions) from the solution. - This eliminates the interference of fluoride on the subsequent ICP-OES determination of calcium (due to non-volatile calcium fluoride particles) and spectral interference. Remove the beaker and allow it to cool slightly.

[0029] Add approximately 10 mL of hydrochloric acid (1+1 volume ratio, i.e., concentrated hydrochloric acid mixed with water in a 1:1 ratio) and an appropriate amount of pure water (approximately 20–30 mL) to a beaker. Continue heating until the soluble salts are completely dissolved (the solution is clear and there is no obvious precipitate). After cooling to room temperature, transfer the entire solution to a 100 mL volumetric flask, dilute to the mark with pure water, and shake thoroughly to obtain the test solution.

[0030] 4. Instrument Measurement: Use an inductively coupled plasma optical emission spectrometer (ICP-OES) and select the characteristic spectral lines of calcium (recommended wavelengths are 317.933 nm or 315.887 nm to avoid interference). Under optimized instrument operating conditions (RF power 1.2 kW, nebulizer gas flow rate 0.8 L / min, auxiliary gas flow rate 1.0 L / min, observation height 12 mm, etc.; specific parameters should be fine-tuned according to the instrument model and laboratory conditions), take a sample solution and measure, recording the spectral emission intensity of calcium.

[0031] Simultaneously, blank solution (prepared without sample and following the same pretreatment steps) and a series of standard calcium solutions were measured, and a working curve of calcium element was plotted (concentration range covering the expected sample content, linear correlation coefficient r>0.999).

[0032] 5. Result Calculation: Based on the spectral intensity value of the test solution, find or calculate the concentration of calcium in the solution (μg / mL) from the working curve, multiply it by the fixed volume (100mL) to obtain the total calcium mass (mg), and convert it to the mass fraction of calcium fluoride (CaF2).

[0033] To ensure precision, the same sample is measured twice in parallel. When the difference between the two independent test results does not exceed the allowable difference specified in the national standard or the company's internal control standard, the average value is taken as the final analysis result; if it exceeds the allowable difference, the test must be repeated.

[0034] This embodiment is performed entirely within a fume hood, ensuring safe and controllable operation. The entire pretreatment process takes approximately 1–1.5 hours. The instrument provides rapid measurement and is suitable for batch processing in the laboratory (multiple samples can be processed simultaneously). Practical verification has shown that this method exhibits good accuracy and precision for samples with CaF2 content ranging from 0.15% to 30% in the desulfurizing agent. The results show deviations less than the allowable error compared to known standard samples, meeting the daily quality control requirements of steel enterprises.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for determining the calcium fluoride content in a desulfurizing agent, characterized in that, Includes the following steps: a) Grind the desulfurizing agent sample until it passes through a 240-mesh sieve, and dry it at 105±1℃ to obtain the sample; b) Weigh the sample, add calcium acetic acid solution, place at room temperature and stir intermittently, so that the calcium oxide in the sample is selectively dissolved by the calcium acetic acid solution, while the calcium fluoride is basically insoluble; c) Add perchloric acid to the mixture in step b) and heat until thick white fumes are emitted to remove fluoride ions from the solution; d) After acidification, dissolution of salts, and cooling, transfer the test solution to a volumetric flask and dilute to volume. e) Measure the spectral intensity of the test solution under the characteristic spectral lines of calcium using an inductively coupled plasma atomic emission spectrometer; f) Calculate the calcium content in the test solution based on the pre-plotted calcium element working curve, and convert it to the mass fraction of calcium fluoride.

2. The method according to claim 1, characterized in that, The calcium-containing acetic acid solution is used to selectively dissolve calcium oxide at room temperature, thereby fixing the calcium element in calcium fluoride and thus identifying the calcium to be tested as originating from calcium fluoride.

3. The method according to claim 1, characterized in that, Step c) is used to efficiently remove fluoride ions and eliminate the transmission and spectral interference of fluoride on calcium in inductively coupled plasma emission spectroscopy.

4. The method according to claim 1, characterized in that, The linear correlation coefficient of the calcium element working curve is greater than 0.

999.

5. The method according to claim 1, characterized in that, In step d), acidification is achieved by adding hydrochloric acid and heating to dissolve the soluble salts.

6. The method according to claim 1, characterized in that, The method is applicable to the determination of calcium fluoride content in desulfurizing agents ranging from 0.15% to 30%.

7. The method according to claim 1, characterized in that, The method for preparing the calcium-containing acetic acid solution is as follows: Weigh 5g of calcium carbonate into a beaker, cover it with a watch glass, add 100mL of acetic acid solution, heat it in a water bath to dissolve it, transfer it to a 1000mL volumetric flask and dilute it to the mark with acetic acid solution, and shake well.

8. The method according to claim 7, characterized in that, The acetic acid solution is prepared by mixing acetic acid and water in a volume ratio of 1:

9.

9. The method according to claim 1, characterized in that, After measuring the spectral intensity of calcium using an inductively coupled plasma atomic emission spectrometer, if the difference between two independent test results does not exceed the allowable difference specified in the standard, the average value is taken as the final analysis result.

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