Method for detecting content of free silicon

Abstract

The invention provides a method for detecting the content of free silicon, which comprises the following steps: S1, mixing one of a siliceous heat generating agent and low-silicon ferrosilicon with water and nitric acid, adding hydrofluoric acid, mixing, adding an aluminum chloride solution, and cooling to obtain a prepared test solution; s2, mixing the prepared test solution and the yttrium solution, and filtering to obtain a sample filtrate; s3, preparing a series of standard sample filtrate from the ferrosilicon standard samples with different masses according to the step S1 and the step S2; s4, taking water as a calibration blank, measuring the relative emission intensity of silicon in a series of standard sample filtrate by using a plasma emission spectrometer, and establishing a working curve; and determining the relative emission intensity of silicon in the sample filtrate by using a plasma emission spectrometer, and obtaining the free silicon content of the siliceous heat generating agent or low-silicon ferrosilicon according to the working curve. The method provided by the invention can be used for accurately detecting the content of free silicon in the siliceous exothermic agent sample or the low-silicon ferrosilicon sample.

Description

Technical Field

[0001] The present invention relates to the technical field of analysis and detection, and in particular to a method for detecting free silicon content. Background Art

[0002] Since siliceous heating agents and low-silicon ferrosilicon contain free silicon and silicon dioxide, which can react with alkali and hydrofluoric acid, there is currently no method at home or abroad to accurately detect the free silicon content in a mixture containing free silicon and silicon dioxide.

[0003] Steel mills purchase hundreds of tons of siliceous exothermic agents and low-silicon ferrosilicon every year for smelting stainless steel. The free silicon content in the siliceous exothermic agents and low-silicon ferrosilicon directly affects their heating effect and the casting quality of the smelted stainless steel. However, existing technology still cannot accurately detect the free silicon content in siliceous exothermic agents and low-silicon ferrosilicon, making the quality of the siliceous exothermic agents uncontrollable, which will seriously affect the production of stainless steel.

[0004] The siliceous heating agent purchased by the steel plant costs about 14,000 yuan per ton, and it has three different specifications: free silicon content ≥45%, ≥60%, and ≥72%; if the steel plant can only detect the total silicon content in the siliceous heating agent (that is, the sum of the silicon content in free silicon and silicon dioxide in the siliceous heating agent) and only meets the total content, the supplier can use silica instead of ferrosilicon to prepare the siliceous heating agent. The maximum proportion of silica adulteration is 100%, 50%, and 10%, respectively, and the average adulteration ratio is 53%, which may cause the company to lose about 200×1.4×50%=1.4 million yuan each year.

[0005] Therefore, in order to ensure the quality control of siliceous heating agents, the error of the detection value of free silicon in siliceous heating agents and low-silicon ferrosilicon needs to be ≤2. Summary of the Invention

[0006] The technical problem solved by the present invention is to provide a method for detecting the content of free silicon. The method provided in this application can accurately measure the content of free silicon in siliceous heating agents or low-silicon ferrosilicon.

[0007] In view of this, the present application provides a method for detecting free silicon content, comprising the following steps:

[0008] S1. Mix one of the siliceous heating agent and low-silicon ferrosilicon with water and nitric acid, then add hydrofluoric acid, add aluminum chloride solution after mixing, and cool to obtain a prepared test solution;

[0009] S2. mixing the prepared test solution and the yttrium solution, and filtering to obtain a sample filtrate;

[0010] S3, prepare a series of standard sample filtrates with ferrosilicon standard samples of different masses according to step S1 and step S2;

[0011] S4. Using water as a calibration blank, measure the relative emission intensity of silicon in a series of standard sample filtrates using a plasma emission spectrometer to establish a working curve;

[0012] The relative emission intensity of silicon in the sample filtrate is measured by a plasma emission spectrometer, and the free silicon content of the siliceous heating agent or low-silicon ferrosilicon is obtained according to the working curve.

[0013] In some specific embodiments, the volume ratio of the water, the nitric acid and the hydrofluoric acid is (20-30) ml: (70-90) ml: (7.5-12.0) ml; and / or the temperature of the water is 25-35°C.

[0014] In some specific embodiments, the ratio of one of the silicon heat-generating agent and the low-silicon ferrosilicon to the water is (0.2-0.5) g: (20-30) ml.

[0015] In some specific embodiments, the mixing is performed by shaking for 2 to 3 seconds every 15 to 20 seconds after the addition of the hydrofluoric acid, for a period of 10 to 12 minutes.

[0016] In some specific embodiments, the yttrium solution is a mixture of an initial yttrium solution and nitric acid, and the concentration of the initial yttrium solution is 1.000 g / ml.

[0017] In some specific embodiments, the silicon content in the ferrosilicon standard sample is greater than 70%, and the mass of the ferrosilicon standard sample is 0.10 g, 0.13 g, 0.16 g, 0.19 g, or 0.25 g.

[0018] In some specific embodiments, the power of the plasma emission spectrometer is 1250 W, and / or the nebulizer flow rate of the plasma emission spectrometer is 0.80 L / min, and / or the filtrate lift volume of the plasma emission spectrometer is 1.5 mL / min, and / or the flushing time of the plasma emission spectrometer is 30 s, and / or the plasma flow rate of the plasma emission spectrometer is 15 L / min, and / or the auxiliary gas flow rate of the plasma emission spectrometer is 0.20 L / min, and / or the observation mode of the plasma emission spectrometer is horizontal, and / or the integration time of the plasma emission spectrometer is 5 s.

[0019] In some specific embodiments, the correlation coefficient of the working curve is greater than 0.999.

[0020] In some specific embodiments, the content of free silicon in the silicon heat-generating agent or the low-silicon ferrosilicon is ≥2.00 wt %.

[0021] In some specific embodiments, the free silicon content of the silicon-based exothermic agent or low-silicon ferrosilicon is calculated as follows:

[0022]

[0023] Where: k1-the ratio of the standard value of the standard sample measured for the first time to the test value;

[0024] k2-the ratio of the standard value of the second determination standard sample to the test value;

[0025] 0.1000-mass standard of sample silicon heating agent or low silicon ferrosilicon, g;

[0026] y- the detection value of the element to be tested in the sample silicon heating agent or low-silicon ferrosilicon on the working curve, %;

[0027] m-mass of sample silicon heating agent or low silicon ferrosilicon, g.

[0028] The present application provides a method for detecting free silicon, which comprises first mixing a siliceous exothermic agent and one of low-silicon ferrosilicon with water and nitric acid, then adding hydrofluoric acid, adding aluminum chloride solution after mixing, cooling to obtain a prepared test solution, then mixing the above-mentioned prepared test solution with yttrium solution, and filtering to obtain a sample filtrate; then using the same method to establish a series of standard sample filtrates; finally, according to a working curve of the relative emission intensity of silicon in the standard sample filtrate, the free silicon content of the siliceous exothermic agent or low-silicon ferrosilicon is obtained; in the detection method provided by the present application, the silicon in the siliceous exothermic agent or low-silicon ferrosilicon sample to be tested is decomposed by a nitric acid-hydrofluoric acid mixture, and then the hydrofluoric acid is masked by aluminum chloride, and the relative emission intensity of silicon in the standard filtrate and the filtrate to be tested is detected by a plasma emission spectrometer, thereby accurately calculating the mass fraction of free silicon; further, the present application controls the ratio and addition amount of the nitric acid-hydrofluoric acid mixture and the decomposition time by sufficient shaking, so that the free silicon is completely decomposed and the amount of silicon dioxide decomposed is less than 5%, thereby ensuring the accuracy of the free silicon content detection. DETAILED DESCRIPTION

[0029] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0030] In view of the need for detecting the free silicon content in siliceous exothermic agents or low-silicon ferrosilicon in the prior art, the present application provides a method for detecting the free silicon content, which decomposes the free silicon with a nitric acid-hydrofluoric acid mixed acid, and finally uses a plasma emission spectrometer to measure the relative emission intensity of silicon, thereby obtaining the free silicon content of the siliceous exothermic agent or low-silicon ferrosilicon; specifically, an embodiment of the present invention discloses a method for detecting the free silicon content, comprising the following steps:

[0031] S1. Mix one of the siliceous heating agent and low-silicon ferrosilicon with water and nitric acid, then add hydrofluoric acid, add aluminum chloride solution after mixing, and cool to obtain a prepared test solution;

[0032] S2. mixing the prepared test solution and the yttrium solution, and filtering to obtain a sample filtrate;

[0033] S3, prepare a series of standard sample filtrates with ferrosilicon standard samples of different masses according to step S1 and step S2;

[0034] S4. Using water as a calibration blank, measure the relative emission intensity of silicon in a series of standard sample filtrates using a plasma emission spectrometer to establish a working curve;

[0035] The relative emission intensity of silicon in the prepared sample filtrate is measured by plasma emission spectrometer, and the free silicon content of the siliceous heating agent or low-silicon ferrosilicon is obtained according to the working curve.

[0036] In the method for detecting the free silicon content provided above, the present application first mixes one of the siliceous exothermic agent and low-silicon ferrosilicon with water and nitric acid, then adds hydrofluoric acid, adds aluminum chloride solution after mixing, and obtains the prepared test solution after cooling. In the above process, the siliceous exothermic agent and the low-silicon ferrosilicon are conventional siliceous exothermic agents and low-silicon ferrosilicon used by those skilled in the art, and there is no particular restriction on their sources. The siliceous exothermic agent and the low-silicon ferrosilicon both include free silicon, silicon dioxide and silicon carbide. The mass fraction of free silicon in the siliceous exothermic agent and the low-silicon ferrosilicon is ≥2.00wt%. The nitric acid and hydrofluoric acid are analytically pure reagents; the volume ratio of the water, the nitric acid, and the hydrofluoric acid is (20-30) ml: (70-90) ml: (7.5-12.0) ml. Specifically, the volume ratio of the water, the nitric acid, and the hydrofluoric acid is (20-26) ml: (73-86) ml: (9.0-11.0) ml. In a specific embodiment, the volume ratio of the water, the nitric acid, and the hydrofluoric acid is 20 ml: 80 ml: 10 ml. The ratio of the siliceous exothermic agent, one of the low-silicon ferrosilicon, and water is (0.2-0.5) g: (20-30) ml. Specifically, the ratio of the siliceous exothermic agent, one of the low-silicon ferrosilicon, and water is (0.3-0.4) g: (23-30) ml. In a specific embodiment, the ratio of the siliceous exothermic agent, one of the low-silicon ferrosilicon, and water is 0.2-0.5 g: 20 ml. The aluminum chloride solution is obtained by mixing 150 ml of aluminum chloride hexahydrate solution with a concentration of 500 g / L with 700 ml of water; the aluminum chloride is used to mask hydrofluoric acid to ensure the accuracy of silicon content detection. The siliceous heating agent or the low-silicon ferrosilicon is used as the test sample, which is mixed with water and nitric acid and then quickly shaken for 2 to 3 seconds every 15 to 20 seconds for 10 minutes. The aluminum chloride mixture is quickly added while stirring and cooled to room temperature. After adding the aluminum chloride solution, the ratio and addition amount of the nitric acid-hydrofluoric acid mixture are further controlled in a 25 to 35°C water bath. The decomposition time is controlled while shaking thoroughly so that the free silicon is completely decomposed and the amount of silicon dioxide decomposition is less than 5%. The silicon content is detected based on this. If the amount and duration of the water, nitric acid and hydrofluoric acid are not within the above range, the free silicon in the test sample will not be completely decomposed, or the amount of silicon dioxide decomposition will be greater than 5%, which will affect the accuracy of silicon detection.

[0037] The present application then mixes the above-mentioned prepared test solution and yttrium solution, and obtains a sample filtrate after filtration; in this process, the yttrium solution is the internal standard measured by the plasma emission spectrometer to eliminate the influence of instrument fluctuations and differences in the prepared test solution on the test solution composition; the yttrium solution is an yttrium solution having a concentration of the initial yttrium solution and nitric acid mixed, and the initial yttrium solution has a concentration of 1.000 mg / ml.

[0038] Furthermore, the present application then prepares a series of standard sample filtrates using ferrosilicon standard samples of different masses according to the above steps; the silicon content in the ferrosilicon standard samples is greater than 70%, and the masses of the ferrosilicon standard samples are 0.10g, 0.13g, 0.16g, 0.19g, and 0.25g.

[0039] According to the present invention, water is then used as a calibration blank, and the relative emission intensity of silicon in a series of standard sample filtrates is measured using a plasma emission spectrometer to establish a working curve; the relative emission intensity of silicon in the prepared sample filtrate is measured using a plasma emission spectrometer, and according to the working curve, the free silicon content of the siliceous heat-generating agent or low-silicon ferrosilicon is obtained; in this application, the power of the plasma emission spectrometer is 1250W, the atomizer flow rate of the plasma emission spectrometer is 0.80L / min, the filtrate lift volume of the plasma emission spectrometer is 1.5mL / min, the flushing time of the plasma emission spectrometer is 30s, and / or the plasma flow rate of the plasma emission spectrometer is 15L / min, the auxiliary gas flow rate of the plasma emission spectrometer is 0.20L / min, the observation mode of the plasma emission spectrometer is horizontal, and the integration time of the plasma emission spectrometer is 5s. The above working curve is automatically drawn by the instrument software with the concentration of silicon as the horizontal axis and the relative emission light intensity intensity ratio as the vertical axis. The correlation coefficient of the working curve is greater than 0.999, which indicates that there is a strong linear relationship between concentration and signal, and the data points are closely distributed around the regression line. The working curve has a good fitting effect and good linearity and can be used for quantitative analysis.

[0040] According to the above working curve and the relative emission intensity of silicon in the detected sample filtrate, the free silicon content of the siliceous heating agent or low-silicon ferrosilicon is calculated. The specific calculation formula is:

[0041]

[0042] Where: k1-the ratio of the standard value of the standard sample measured for the first time to the test value;

[0043] k2-the ratio of the standard value of the second determination standard sample to the test value;

[0044] 0.1000-sample mass reference, g;

[0045] y- the detection value of the element to be tested in the sample silicon heating agent or low-silicon ferrosilicon on the working curve, %;

[0046] m-mass of sample silicon heating agent or low silicon ferrosilicon, g.

[0047] The above calculation process is automatically calculated by a computer. During the detection process, the standard sample with a content of the element to be detected similar to that of the sample is first detected, then the content of the element to be detected in the sample is detected, and then the standard sample is detected.

[0048] In order to further understand the present invention, the method for detecting free silicon content provided by the present invention is described in detail below with reference to the examples. The protection scope of the present invention is not limited by the following examples.

[0049] Example

[0050] The instruments, reagents, and relevant information of the plasma emission spectrometer used in this embodiment, as well as the detection of the free silicon content in the sample are specifically as follows:

[0051] 1. Instruments and Equipment

[0052] 1.1 Balance (sensitivity 0.1 mg);

[0053] 1.2 Plasma emission spectrometer;

[0054] 2 Sample preparation

[0055] Prepare the sample according to GB / T 4010;

[0056] 3 Reagents

[0057] Unless otherwise stated, only reagents confirmed to be of analytical grade and distilled or deionized water or water of equivalent purity were used in the analyses;

[0058] 3.1 Nitric acid (ρ1.42 g / mL);

[0059] 3.2 Hydrofluoric acid (ρ1.15 g / mL);

[0060] 3.3 Aluminum chloride hexahydrate solution (500 g / L);

[0061] 3.4 Aluminum chloride mixture;

[0062] Add 150.0 ml of aluminum chloride hexahydrate solution (3.3) to a 1000 ml wide-mouth plastic beaker, add water to make up to 700 ml, and stir well.

[0063] 3.5 Yttrium solution (0.01000g / L)

[0064] Pipette 20.00 ml of yttrium solution (1.000 mg / ml, purchased standard solution) into a 2000 ml volumetric flask, add 25.0 ml of nitric acid (3.1), mix well, dilute to the mark with water, and mix well;

[0065] 4 Spectral lines and parameters

[0066] 4.1 After the instrument is started and preheated and can be used normally, select the analysis elements and spectral lines according to Table 1 and set the analysis parameters according to Table 2;

[0067] 4.2 Analytical Spectral Lines

[0068] Table 1 lists the analytical lines used in this method. When selecting analytical lines, the interference must be carefully checked and, if necessary, the matrix matching method and the interference coefficient correction method should be used for correction.

[0069] Table 1 Recommended analysis line data table

[0070] element Analysis line wavelength / nm Possible interfering elements Si 251.611 Y (internal standard element) 371.030

[0071] 4.3 Analysis parameters

[0072] Table 2 Analysis parameter setting data table

[0073]

[0074] 5 Analysis Steps

[0075] 5.1 Sample size

[0076] Weigh 0.2-0.5g of sample, accurate to 0.0001g;

[0077] 5.2 Sample processing

[0078] Place the sample in a plastic cup, add 20.0 ml of water and 80.0 ml of nitric acid (3.1), mix well, add 10.0 ml of hydrofluoric acid (3.2), shake quickly, shaking for 2 to 3 seconds every 15 to 20 seconds for 10 minutes, quickly add the aluminum chloride mixture (3.4) while stirring, and cool to room temperature;

[0079] Pipette 20.00 ml of yttrium solution (3.5) into a 1000 ml volumetric flask, transfer the test solution prepared above into the volumetric flask, dilute to the mark with water, mix well, dry filter with slow filter paper, remove the initial part of the filtrate, obtain the filtrate, and measure on the instrument;

[0080] 5.3 Drawing of working curve

[0081] Weigh 0.10, 0.13, 0.16, 0.19, 0.22, and 0.25 g of a standard ferrosilicon sample with a silicon content greater than 70% into a plastic beaker, add 20.0 ml of water and 80.0 ml of nitric acid (3.1), mix thoroughly, add 10.0 ml of hydrofluoric acid (3.2), shake rapidly, and shake for 2-3 seconds every 15-20 seconds for 10 minutes. Rapidly add the aluminum chloride mixture (3.4) while stirring, and cool to room temperature.

[0082] Pipette 20.00 ml of yttrium solution (3.5) into a 1000 ml volumetric flask, transfer the test solution prepared above into the volumetric flask, dilute to the mark with water, mix well, dry filter with slow filter paper, remove the initial part of the filtrate, obtain the filtrate, and measure on the instrument;

[0083] Using water as the calibration blank, measure the relative emission light intensity of silicon in the filtrate of the standard sample from low to high; plot a working curve with the silicon concentration as the abscissa and the relative emission light intensity ratio of the analytical line as the ordinate (the working curve is automatically plotted by the instrument software);

[0084] The correlation coefficient of the established working curve should be greater than 0.999.

[0085] 5.4 Sample measurement

[0086] Determine the relative emission intensity of silicon in the sample filtrate, and the computer automatically calculates the silicon content from the working curve;

[0087] 5.5 Result calculation

[0088] First, test the standard sample with a similar content of the element to be tested, then test the content of the element to be tested in the sample, and then test the standard sample again, and calculate according to the following formula:

[0089]

[0090] Where: k1-the ratio of the standard value of the standard sample measured for the first time to the test value;

[0091] k2-the ratio of the standard value of the second determination standard sample to the test value;

[0092] 0.1000-sample mass reference, g;

[0093] y-detection value of the element to be tested in the sample on the working curve, %;

[0094] m-sample mass, g.

[0095] Note 3: When k1 and k2 are |k1-k2|≤0.005 during the test, 2 to 4 samples can be tested between the test control standard steels. If the instrument volatility is large, only one sample can be tested between the test control standard steels.

[0096] Since there are no standard samples of siliceous heating agents or low-silicon ferrosilicon standard samples in the prior art, the free silicon content in siliceous heating agent samples or low-silicon ferrosilicon samples synthesized from ferrosilicon (silicon content>70%, wherein the silicon dioxide content is negligible) and silica standard samples can only be tested. The amounts of ferrosilicon and silica used and the test results are shown in Table 3.

[0097] Table 3 Data table of ferrosilicon and silica dosage and test results

[0098]

[0099] From the above results, it can be seen that the difference between the detection value obtained by the detection method provided in the present application and the standard value is less than 2, which shows that the method for detecting free silicon provided in the present application has high accuracy.

[0100] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0101] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting free silicon content, comprising the following steps: S1. Mix one of the siliceous heating agent and low-silicon ferrosilicon with water and nitric acid, then add hydrofluoric acid, add aluminum chloride solution after mixing, and cool to obtain a prepared test solution; S2. mixing the prepared test solution and the yttrium solution, and filtering to obtain a sample filtrate; S3, prepare a series of standard sample filtrates with ferrosilicon standard samples of different masses according to step S1 and step S2; S4. Using water as a calibration blank, measure the relative emission intensity of silicon in a series of standard sample filtrates using a plasma emission spectrometer to establish a working curve; The relative emission intensity of silicon in the sample filtrate is measured by a plasma emission spectrometer, and the free silicon content of the siliceous heating agent or low-silicon ferrosilicon is obtained according to the working curve.

2. The method according to claim 1, characterized in that The volume ratio of the water, the nitric acid and the hydrofluoric acid is (20-30) ml: (70-90) ml: (7.5-12.0) ml; and / or the temperature of the water is 25-35°C.

3. The method according to claim 2, characterized in that The ratio of one of the siliceous heating agent and the low-silicon ferrosilicon to the water is (0.2-0.5) g: (20-30) ml.

4. The method according to claim 1 or 2, characterized in that The mixing method is as follows: shaking for 2 to 3 seconds every 15 to 20 seconds after adding the hydrofluoric acid, and continuing for 10 to 12 minutes.

5. The method according to claim 4, characterized in that The yttrium solution is a mixture of an initial yttrium solution and nitric acid, and the concentration of the initial yttrium solution is 1.000 g / ml.

6. The method according to claim 4, characterized in that The silicon content of the ferrosilicon standard sample is greater than 70%, and the masses of the ferrosilicon standard sample are 0.10g, 0.13g, 0.16g, 0.19g, and 0.25g.

7. The method according to claim 6, characterized in that The power of the plasma emission spectrometer is 1250 W, and / or the nebulizer flow rate of the plasma emission spectrometer is 0.80 L / min, and / or the filtrate lifting amount of the plasma emission spectrometer is 1.5 mL / min, and / or the flushing time of the plasma emission spectrometer is 30 s, and / or the plasma flow rate of the plasma emission spectrometer is 15 L / min, and / or the auxiliary gas flow rate of the plasma emission spectrometer is 0.20 L / min, and / or the observation mode of the plasma emission spectrometer is horizontal, and / or the integration time of the plasma emission spectrometer is 5 s.

8. The method according to claim 6, characterized in that The correlation coefficient of the working curve is greater than 0.

999.

9. The method according to any one of claims 1 to 8, characterized in that The content of free silicon in the silicon heat-generating agent or the low-silicon ferrosilicon is ≥2.00 wt %.

10. The method according to any one of claims 1 to 8, characterized in that The calculation formula of the free silicon content of the silicon heating agent or low-silicon ferrosilicon is: Where: k1-the ratio of the standard value of the standard sample measured for the first time to the test value; k2-the ratio of the standard value of the second determination standard sample to the test value; 0.1000-mass standard of sample silicon heating agent or low silicon ferrosilicon, g; y- the detection value of the element to be tested in the sample silicon heating agent or low-silicon ferrosilicon on the working curve, %; m-mass of sample silicon heating agent or low silicon ferrosilicon, g.

Images