Method for determining carbon content in molten salt chlorination residue and use of the method

Abstract

This invention relates to the field of carbon content determination, specifically to a method for determining the carbon content in molten salt chlorination slag and its applications. The method includes the following steps: sample preparation, sample pretreatment, sample measurement, plotting a standard curve, and calculating the carbon content in the sample. The technical solution of this invention solves the problems existing in directly using a high-frequency infrared carbon-sulfur analyzer to determine the carbon content in molten salt chlorination slag during titanium tetrachloride industrial production, improving the oxidation melting rate and carbon release rate during the high-frequency infrared carbon-sulfur analyzer measurement process. Furthermore, the technical solution of this invention maintains good stability in determining the carbon content in molten salt chlorination slag.

Description

Technical Field

[0001] This invention relates to the field of carbon content determination, and in particular to a method for determining the carbon content in molten salt chlorination slag and the application of this method. Background Technology

[0002] Molten salt chlorination is the main preparation method in the industrial production of titanium tetrachloride. Molten salt chlorination slag is the molten salt medium used in the reaction of high-titanium slag with petroleum coke and Cl2 in a molten salt chlorination furnace to produce TiCl4. During production, the ore-to-coke ratio is calculated by measuring the carbon and titanium dioxide content in the molten salt, and then the operating conditions of the chlorination furnace are adjusted accordingly. Typically, molten salt chlorination slag contains 1-7% carbon, 40-60% sodium chloride, 15-30% ferrous chloride, 5-10% aluminum oxide, 1-5% titanium dioxide, and a small amount of chlorine gas.

[0003] The principle of detecting carbon content in molten salt is that carbon in molten salt reacts with oxygen at high temperature to produce carbon dioxide, and the carbon content in molten salt is calculated by measuring the amount of carbon dioxide.

[0004] There are three commonly used analytical methods for determining the carbon content in molten chloride salts: ① High-temperature gravimetric method: The molten salt is burned in a high-temperature furnace, and the carbon content is calculated based on the difference in mass before and after burning. However, due to the complex composition of the molten salt slag, some metal chlorides decompose under high-temperature conditions, leading to an overestimation of the measured result. Furthermore, the decomposed hydrogen chloride gas corrodes the resistance wire, causing a deterioration of the environment inside the high-temperature furnace. ② Combustion non-aqueous titration method: When the molten salt is burned and decomposed at 1200℃, hydrogen chloride gas and chlorine gas escape, interfering with the measurement and failing to meet the titration requirements. ③ Direct infrared carbon-sulfur method: This method also suffers from severe equipment corrosion and unstable data. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for determining the carbon content in molten salt chlorination slag and its application in the industrial production of titanium tetrachloride. The technical solution of this invention reduces the influence of interfering components on the carbon content determination results, improves the oxidation melting rate and carbon release rate during the high-frequency infrared carbon-sulfur analyzer determination process, and effectively reduces the corrosion problem of equipment caused by hydrogen chloride gas, thereby extending the service life of the equipment.

[0006] The technical solution provided by this invention is as follows:

[0007] This invention provides a method for determining the carbon content in molten salt chlorination slag, comprising the following steps:

[0008] S1. Sample preparation: The molten salt chlorination slag sample taken from the production line is crushed and sealed for later use;

[0009] S2. Sample pretreatment: Weigh the sample treated in S1 and place it in a container. Add calcium oxide and / or magnesium oxide, add water until the sample is fully moistened, and then dry it for later use.

[0010] S3. Sample Measurement: Add flux to the sample after S2 treatment and measure it with a high-frequency infrared carbon-sulfur analyzer to obtain the integrated area of ​​the CO2 infrared absorption signal.

[0011] S4. Plot the standard curve: Process and measure the molten salt chlorination slag calibration materials with different carbon contents in the order of steps S1-S3, and then plot the standard curve with the carbon content of the standard material as the abscissa and the integral area of ​​the measured CO2 infrared absorption signal as the ordinate.

[0012] S5. Substitute the integral area of ​​the CO2 infrared absorption signal measured in S3 into the standard curve plotted in S4 to obtain the carbon content in the sample.

[0013] Furthermore, the specific steps of the crushing process in S1 are as follows: first, the molten salt chlorination slag sample taken from the production process is crushed into small particles, and then crushed in a crusher. The particle size of the crushed sample is less than 200 mesh. The grinding disc of the crusher is heated before use. Preferably, the temperature of the heating treatment is 50-100℃, the heating time is 10-60 min, and the crushing and sample preparation time is 2-5 min.

[0014] The particle size of molten salt chlorination slag directly affects the extent of subsequent chemical reactions. If the particle size is too large, the ferrous chloride in the molten salt chlorination slag may not be completely converted into ferric oxide, leading to the generation of hydrogen chloride gas during subsequent combustion. Furthermore, the carbon source in the molten salt chlorination slag may not be fully oxidized, resulting in a lower carbon content reading. Therefore, the particle size of the molten salt chlorination slag sample is crucial to the technical solution of this invention. Extensive experiments by the inventors have shown that controlling the particle size of the molten salt chlorination slag sample to less than 200 mesh avoids the problems of ferrous chloride residue and insufficient carbon source oxidation during sample pretreatment.

[0015] Furthermore, the mass ratio of the sample to calcium oxide and / or magnesium oxide in S2 is 1:1 to 1:2.

[0016] Calcium oxide and / or magnesium oxide can convert ferrous chloride in molten salt chlorination slag samples into ferric oxide and CaCl2 and / or MgCl2, and neutralize the small amount of Cl2 in the molten salt chlorination slag samples. The remaining calcium oxide and / or magnesium oxide can also synergistically work with flux to lower the melting point of the pretreated molten salt chlorination slag samples, increase the fluidity of the molten salt chlorination slag, improve the carbon oxidation melting rate and release rate, and at the same time reduce the amount of flux used.

[0017] Furthermore, the calcium oxide and / or magnesium oxide in S2 are subjected to high-temperature calcination treatment before use; preferably, the high-temperature calcination temperature is 850-950℃ and the time is 2-5h.

[0018] Since calcium oxide and / or magnesium oxide readily react with moisture and CO2 in the air to produce Ca(OH)2 / Mg(OH)2 and CaCO3 / MgCO3, impurities may be present in conventional calcium oxide and / or magnesium oxide. High-temperature calcination can decompose CaCO3 / MgCO3, thus avoiding the introduction of new carbon sources.

[0019] Furthermore, in S2, drying is performed using a vacuum drying oven at a temperature of 100-110°C for 30-60 minutes, protected by an inert gas, which is at least one of nitrogen or argon.

[0020] After the calcium oxide and / or magnesium oxide added in S2 react fully with the molten salt chlorination slag, there will still be residual calcium oxide and / or magnesium oxide. In order to prevent calcium oxide and / or magnesium oxide from reacting with moisture and CO2 in the air, a vacuum drying oven needs to be used during the drying process, and the protection effect with inert gas is even better.

[0021] Furthermore, the container in S2 is a special crucible for carbon and sulfur, which needs to be preheated before use at a temperature of 850-950℃ for 2-5 hours.

[0022] Furthermore, the water mentioned in S2 is pure water.

[0023] Furthermore, the flux mentioned in S3 is at least one of pure iron particles, tungsten particles, tin particles, and copper particles, and the mass ratio of flux to molten salt chlorination slag is 15:1-20:1.

[0024] Furthermore, the flux is pure iron particles and tungsten particles.

[0025] The main function of flux is to provide heat for sample oxidation, alter melting characteristics, stabilize combustion, and cover the sample to prevent splashing. Appropriate flux selection and dosage can accelerate sample oxidation and melting, improving carbon and sulfur release rates and measurement accuracy. Therefore, the choice of flux varies depending on the specific component. Commonly used metallic fluxes include tungsten, tin, pure iron, and copper. The inventors of this application conducted flux selection experiments and found that the use of tungsten and pure iron particles as fluxes in the technical solution of this application significantly reduces chlorine volatilization and results in better oxidation melting rates and carbon release rates.

[0026] Furthermore, the specific steps for preparing calibrating materials for molten salt chlorination slag with different carbon contents in S4 are as follows:

[0027] SS1, Matrix preparation: The matrix is ​​prepared according to the composition of the molten salt chlorination slag. The matrix includes sodium chloride, iron oxide, titanium dioxide, calcium chloride, and calcium chloride. The matrix also includes at least one of manganese chloride, magnesium chloride, silicon dioxide, and aluminum oxide. The matrix is ​​mixed and then calcined. The slag is then removed and crushed according to step S1 for later use.

[0028] SS2, Preparation of calibration materials: Weigh different amounts of carbon source references into containers, add the matrix prepared in SS1 respectively, and obtain molten salt chlorination slag calibration materials with different carbon contents;

[0029] Preferably, the carbon content in the matrix should be less than 0.002%;

[0030] The carbon content of the matrix is ​​controlled to be less than 0.002% to avoid introducing new carbon sources.

[0031] Preferably, the carbon content in the molten salt chlorination slag calibration material is 2%-10%;

[0032] Preferably, the temperature at which the matrix mixture is calcined is 650-750°C, and the time is 1-5 hours.

[0033] Furthermore, the carbon source is calcium carbonate; preferably, the calcium carbonate is subjected to calcination treatment before use at a temperature of 100-110°C for 1-5 hours.

[0034] After sample pretreatment, the main components of molten salt chlorination slag changed from carbon, sodium chloride, ferrous chloride, and titanium dioxide to carbon, sodium chloride, ferric oxide, titanium dioxide, and calcium chloride. Therefore, the composition of the matrix was adjusted accordingly when plotting the standard curve.

[0035] Calcium carbonate is a convenient carbon source for obtaining reference reagents, and it is stable at room temperature.

[0036] Furthermore, the matrix is ​​composed of 35-60% sodium chloride, 8-20% iron oxide, 7-25% calcium chloride, 5-12% manganese chloride, 3-14% silicon dioxide, 1-10% titanium dioxide, and 7-12% aluminum oxide, where % refers to mass percentage.

[0037] The present invention also provides the application of the method for determining the carbon content in molten salt chlorination slag in the industrial production of titanium tetrachloride.

[0038] In summary, compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] 1. Due to the high ferrous chloride content (up to 25%) in molten salt chlorination slag, direct measurement using a high-frequency infrared carbon-sulfur analyzer would generate a large amount of hydrogen chloride gas. This hydrogen chloride gas not only corrodes the equipment but also reacts with iron or tungsten particles in the flux, significantly reducing flux efficiency and increasing flux usage. Furthermore, the infrared absorption peaks of hydrogen chloride and CO2 overlap during high-frequency infrared carbon-sulfur analysis, directly affecting CO2 measurement results. This application addresses this issue by pretreating the sample, adding calcium oxide and / or magnesium oxide, along with pure water, to the molten salt chlorination slag sample before high-frequency infrared carbon-sulfur analysis. This not only neutralizes the acidic environment of the molten salt chlorination slag but also converts the interfering component, ferrous chloride, into iron oxide and calcium chloride or magnesium chloride, which are less volatile at 1200°C, thus avoiding hydrogen chloride gas generation and reducing interference with CO2 measurement. Furthermore, in the molten salt chlorination slag system, chlorides react with calcium oxide and / or magnesium oxide to form calcium magnesium chloride. Sodium chloride and calcium magnesium chloride together form low-melting-point chlorides. Excess calcium oxide and / or magnesium oxide have a synergistic effect with flux, which significantly reduces chlorine volatilization. In addition, it also effectively reduces equipment corrosion problems and improves the service life of the equipment.

[0040] In the calibration substance preparation method, the matrix addition method makes the CO2 quantification results more accurate and stable, thereby minimizing the error of the standard curve. Based on the composition of the pretreated molten salt chlorinated slag sample, the inventors of this application determined the matrix components to be 35-60% sodium chloride, 8-20% iron oxide, 7-25% calcium chloride, 5-12% manganese chloride, 3-14% silicon dioxide, 1-10% titanium dioxide, and 7-12% aluminum oxide, where % refers to mass percentage. This composition covers at least 98% of the components of the molten salt chlorinated slag. Using the method of this application to prepare the calibration substance results in a smaller error in the plotted standard curve and more accurate carbon quantification results.

[0041] 3. This application solves the problem of easy hydrolysis of samples through standardized and strict operation, laying a solid foundation for obtaining accurate results. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0043] Example 1

[0044] The method protected in this application and a comparative experiment on the determination of carbon content in five carbon standard samples using the high-frequency infrared carbon-sulfur method:

[0045] The composition tables of the five carbon standard samples are as follows:

[0046] Table 1. Composition of 5 carbon standard samples

[0047]

[0048] The above five carbon standard samples were purchased from the Shandong Metallurgical Research Institute Co., Ltd., which produces standard materials.

[0049] The specific steps for determining the carbon content in five carbon standard samples using the method protected in this application are as follows:

[0050] Step 1: Weigh 0.04g of carbon standard sample from each sample;

[0051] Step 2: Place the 5 carbon standard samples processed in Step 1 into a carbon-sulfur crucible that has been pre-calcined at high temperature, add 0.05g of calcium oxide, add 2 drops of pure water until the samples are fully moistened, and then place them in a vacuum drying oven at 105℃ for 45 minutes. Nitrogen gas is used for protection during drying. The carbon-sulfur crucible is calcined at 900℃ for 2 hours.

[0052] Step 3: Add 0.35g of pure iron particles and 0.35g of tungsten particles to the sample after step 2, and measure it with a high-frequency infrared carbon-sulfur analyzer to obtain the integrated area of ​​the CO2 infrared absorption signal.

[0053] Step 4: Prepare calibration materials with different carbon contents. Process and measure the calibration materials with different carbon contents in the order of steps 1 to 3. Then, plot a standard curve with the carbon content of the standard material as the x-axis and the integral area of ​​the measured CO2 infrared absorption signal as the y-axis. The correlation coefficient r > 0.999 can be used to calculate the sample content; otherwise, prepare the calibration materials again.

[0054] Step 5: Substitute the integrated area of ​​the CO2 infrared absorption signal measured in Step 3 into the standard curve plotted in Step 4 to obtain the carbon content in the sample.

[0055] The specific steps for determining the carbon content in five carbon standard samples using the high-frequency infrared carbon-sulfur method are basically the same as those for determining the carbon content in five carbon standard samples using the method protected in this application, except that there is no second step.

[0056] The results of the two methods for determining the carbon content in five carbon standard samples are shown in the table below:

[0057] Table 2. Results of carbon content determination in five carbon standard samples using two methods.

[0058] Carbon Standard Material Numbering batch The carbon content (%) determined by the method of this application Carbon content (%) determined directly using the high-frequency infrared carbon-sulfur method. GBW11103 m 81.30 79.50 GBW11104 L 71.52 69.44 GBW11109 n 65.00 63.50 GBW11112 k 68.30 65.90 GBW11126 f 74.00 72.50

[0059] As shown in the table above, the method protected in this application and the direct use of high-frequency infrared carbon-sulfur method have relatively small errors in determining the carbon content of carbon standard samples. The method protected in this application not only does not have a negative impact on the determination of carbon content in carbon standard samples after sample pretreatment, but also improves the accuracy of carbon content determination in carbon standard samples.

[0060] Example 2

[0061] In Example 1, the fluxes 0.35g of pure iron granules and 0.35g of tungsten granules in both methods were replaced with 0.7g of pure iron granules or 0.7g of tungsten granules, while keeping everything else unchanged. The results of the two methods after the replacement for determining the carbon content in five carbon standard samples are shown in the table below:

[0062] Table 3. Results of carbon content determination in five carbon standard samples using the two methods after flux replacement.

[0063]

[0064] As shown in the table above, after replacing the flux with 0.7g of pure iron particles or 0.7g of tungsten particles instead of 0.35g of pure iron particles and 0.35g of tungsten particles, there was no significant difference between the carbon content determined directly by the high-frequency infrared carbon-sulfur method and the carbon content determined by the method protected in this application. The sample pretreatment in the method protected in this application did not affect the accuracy of the carbon content determination.

[0065] Based on the results of Examples 1 and 2, it can be seen that there may be a synergistic effect among calcium oxide, flux iron particles, and tungsten particles, which can improve the oxidation melting rate and carbon release efficiency of carbon standard samples, thereby improving the accuracy of carbon content determination of carbon standard samples.

[0066] Example 3

[0067] A method for determining the carbon content in molten salt chlorination slag, the specific steps of which are as follows:

[0068] S1. Sample preparation: After sealing the molten salt chlorination slag sample taken from the production line and sending it to the testing room, first crush the molten salt chlorination slag sample into small particles, and then quickly put it into the grinding disc of the pulverizer to grind for 3 minutes. The particle size of the sample after grinding should be less than 200 mesh. Then quickly take out the sample and seal it in a self-sealing bag for testing. The grinding disc is heated before use at a temperature of 80°C for 30 minutes.

[0069] S2. Sample pretreatment: Weigh 0.04g of the sample treated in S1 and place it in a carbon-sulfur crucible that has been pre-calcined at high temperature. Add 0.05g of calcium oxide and 2 drops of pure water until the sample is fully moistened. Then place it in a vacuum drying oven at 105℃ for 45 minutes. Use nitrogen gas for protection during drying. The high temperature of the carbon-sulfur crucible is 900℃ and the time is 2 hours.

[0070] S3. Sample determination: Add 0.35g of pure iron particles and 0.35g of tungsten particles to the sample after S2 treatment, and measure it with a high-frequency infrared carbon-sulfur analyzer to obtain the integrated area of ​​the CO2 infrared absorption signal.

[0071] The specific steps for preparing molten salt chlorination slag calibration materials with different carbon contents are as follows:

[0072] SS1. Matrix Preparation: Based on the composition of the molten salt chlorination slag, weigh out 50% sodium chloride, 10% iron oxide, 10% calcium chloride, 6% manganese chloride, 7% silicon dioxide, 9% titanium dioxide, and 8% aluminum oxide (%). After mixing, calcine in a 700℃ high-temperature furnace for 1 hour. Remove and pulverize according to step S1 for later use. The carbon content in the matrix should be controlled to be less than 0.002%.

[0073] SS2, Preparation of calibration materials: Weigh 0.01g, 0.02g, 0.03g, 0.05g, 0.08g, and 0.1g (accurate to 0.0001g) of calcium carbonate standard into sulfuric acid crucibles respectively, and add 0.05g of the matrix prepared in SS1 to obtain molten salt chlorination slag calibration materials with different carbon contents;

[0074] The calcium carbonate is subjected to a calcination treatment before use, and the calcination temperature is 105℃ in a high-temperature furnace for 2 hours.

[0075] S4. Plot the standard curve: Process and measure the calibration materials of molten salt chlorination slag with different carbon contents in the order of steps S1-S3. Then plot the standard curve with the carbon content of the standard material as the abscissa and the integral area of ​​the measured CO2 infrared absorption signal as the ordinate. The correlation coefficient r > 0.999 can be used to calculate the sample content; otherwise, repeat the process.

[0076] S5. Substitute the integral area of ​​the CO2 infrared absorption signal measured in S3 into the standard curve plotted in S4 to obtain the carbon content in the sample.

[0077] The carbon content measured in this embodiment is 5.52%.

[0078] Example 4

[0079] A method for determining the carbon content in molten salt chlorination slag, the specific steps of which are as follows:

[0080] S1. Sample preparation: After sealing the molten salt chlorination slag sample taken from the production line and sending it to the testing room, first crush the molten salt chlorination slag sample into small particles, then quickly put it into the grinding disc of the pulverizer and grind it for 2 minutes. Then quickly take out the sample and seal it in a self-sealing bag for testing. The grinding disc is heated before use at a temperature of 50°C for 60 minutes.

[0081] S2. Sample pretreatment: Weigh 0.04g of the sample treated in S1 and place it in a carbon-sulfur crucible that has been pre-calcined at high temperature. Add 0.04g of calcium oxide and 3 drops of pure water until the sample is fully moistened. Then place it in a vacuum drying oven at 100℃ for 60 minutes. Argon gas is used for protection during drying. The high temperature of the carbon-sulfur crucible is 850℃ and the time is 5 hours.

[0082] S3. Sample Measurement: Add 0.4g of pure iron particles and 0.4g of tungsten particles to the sample after S2 treatment, and measure it with a high-frequency infrared carbon-sulfur analyzer to obtain the integrated area of ​​the CO2 infrared absorption signal.

[0083] The specific steps for preparing molten salt chlorination slag calibration materials with different carbon contents are as follows:

[0084] SS1. Matrix preparation: Based on the composition of molten salt chlorination slag, weigh out 45% sodium chloride, 8% iron oxide, 17% calcium chloride, 5% manganese chloride, 3% silicon dioxide, 10% titanium dioxide, and 12% aluminum oxide (the percentages are by mass). After mixing, calcine in a high-temperature furnace at 650℃ for 5 hours, remove and crush according to step S1 for later use. The carbon content in the matrix should be controlled to be less than 0.002%.

[0085] SS2, Preparation of calibration materials: Weigh 0.01g, 0.02g, 0.03g, 0.05g, 0.08g, and 0.1g (accurate to 0.0001g) of calcium carbonate standard into sulfuric acid crucibles respectively, and add 0.05g of the matrix prepared in SS1 to obtain molten salt chlorination slag calibration materials with different carbon contents;

[0086] The calcium carbonate is subjected to calcination treatment at 100°C for 5 hours before use;

[0087] S4. Plot the standard curve: Process and measure the calibration materials of molten salt chlorination slag with different carbon contents in the order of steps S1-S3. Then plot the standard curve with the carbon content of the standard material as the abscissa and the integral area of ​​the measured CO2 infrared absorption signal as the ordinate. The correlation coefficient r > 0.999 can be used to calculate the sample content; otherwise, repeat the process.

[0088] S5. Substitute the integral area of ​​the CO2 infrared absorption signal measured in S3 into the standard curve plotted in S4 to obtain the carbon content in the sample.

[0089] The carbon content measured in this embodiment is 5.85%.

[0090] Example 5

[0091] A method for determining the carbon content in molten salt chlorination slag, the specific steps of which are as follows:

[0092] S1. Sample preparation: After sealing the molten salt chlorination slag sample taken from the production line and sending it to the testing room, first crush the molten salt chlorination slag sample into small particles, then quickly put it into the grinding disc of the pulverizer and grind it for 5 minutes. Then quickly take out the sample and seal it in a self-sealing bag for testing. The grinding disc is heated before use at a temperature of 100°C for 10 minutes.

[0093] S2. Sample pretreatment: Weigh 0.04g of the sample treated in S1 and place it in a carbon-sulfur crucible that has been pre-calcined at high temperature. Add 0.08g of calcium oxide and 5 drops of pure water until the sample is fully moistened. Then place it in a vacuum drying oven at 110℃ for 30 minutes. Use nitrogen gas for protection during drying. The high temperature of the carbon-sulfur crucible is 950℃ and the time is 1 hour.

[0094] S3. Sample determination: Add 0.3g of pure iron particles and 0.3g of tungsten particles to the sample after S2 treatment, and measure it with a high-frequency infrared carbon-sulfur analyzer to obtain the integrated area of ​​the CO2 infrared absorption signal.

[0095] The specific steps for preparing molten salt chlorination slag calibration materials with different carbon contents are as follows:

[0096] SS1. Matrix preparation: Based on the composition of molten salt chlorination slag, weigh out 40% sodium chloride, 20% iron oxide, 8% calcium chloride, 7% manganese chloride, 14% silicon dioxide, 3% titanium dioxide, and 8% aluminum oxide (the percentages are by mass). After mixing, calcine in a high-temperature furnace at 750℃ for 1 hour, remove and crush according to step S1 for later use. The carbon content in the matrix should be controlled to be less than 0.002%.

[0097] SS2, Preparation of calibration materials: Weigh 0.01g, 0.02g, 0.03g, 0.05g, 0.08g, and 0.1g (accurate to 0.0001g) of calcium carbonate standard into sulfuric acid crucibles respectively, and add 0.05g of the matrix prepared in SS1 to obtain molten salt chlorination slag calibration materials with different carbon contents;

[0098] The calcium carbonate is subjected to calcination treatment at 110°C for 1 hour before use;

[0099] S4. Plot the standard curve: Process and measure the calibration materials of molten salt chlorination slag with different carbon contents in the order of steps S1-S3. Then plot the standard curve with the carbon content of the standard material as the abscissa and the integral area of ​​the measured CO2 infrared absorption signal as the ordinate. The correlation coefficient r > 0.999 can be used to calculate the sample content; otherwise, repeat the process.

[0100] S5. Substitute the integral area of ​​the CO2 infrared absorption signal measured in S3 into the standard curve plotted in S4 to obtain the carbon content in the sample.

[0101] The carbon content measured in this embodiment was 5.38%.

[0102] Example 6

[0103] A method for determining the carbon content in molten salt chlorination slag, the specific steps of which are as follows:

[0104] S1. Sample preparation: After sealing the molten salt chlorination slag sample taken from the production line and sending it to the testing room, first crush the molten salt chlorination slag sample into small particles, then quickly put it into the grinding disc of the pulverizer and grind it for minutes. Then quickly take out the sample and seal it in a self-sealing bag for testing. The grinding disc is heated before use at a temperature of 85°C for 50 minutes.

[0105] S2. Sample pretreatment: Weigh 0.04g of the sample treated in S1 and place it in a carbon-sulfur crucible that has been pre-calcined at high temperature. Add 0.08g of calcium oxide and add drops of pure water until the sample is fully moistened. Then place it in a vacuum drying oven at 105℃ for 45 minutes. Use nitrogen gas for protection during drying. The high temperature of the carbon-sulfur crucible is 900℃ and the time is 2 hours.

[0106] S3. Sample determination: Add 0.35g of pure iron particles and 0.35g of tungsten particles to the sample after S2 treatment, and measure it with a high-frequency infrared carbon-sulfur analyzer to obtain the integrated area of ​​the CO2 infrared absorption signal.

[0107] The specific steps for preparing molten salt chlorination slag calibration materials with different carbon contents are as follows:

[0108] SS1. Matrix Preparation: Based on the composition of the molten salt chlorination slag, weigh out the matrix consisting of 50% sodium chloride, 10% iron oxide, 10% calcium chloride, 6% manganese chloride, 7% silicon dioxide, 9% titanium dioxide, and 8% aluminum oxide (the percentages are by mass). After mixing, calcine the matrix in a high-temperature furnace at 700℃ for 1 hour. Remove the matrix and crush it according to step S1 for later use. The carbon content in the matrix should be controlled to be less than 0.002%.

[0109] SS2, Preparation of calibration materials: Weigh 0.01g, 0.02g, 0.03g, 0.05g, 0.08g, and 0.1g (accurate to 0.0001g) of calcium carbonate standard into sulfuric acid crucibles respectively, and add 0.05g of the matrix prepared in SS1 to obtain molten salt chlorination slag calibration materials with different carbon contents;

[0110] The calcium carbonate is subjected to calcination treatment at 110°C for 2 hours before use;

[0111] S4. Plot the standard curve: Process and measure the calibration materials of molten salt chlorination slag with different carbon contents in the order of steps S1-S3. Then plot the standard curve with the carbon content of the standard material as the abscissa and the integral area of ​​the measured CO2 infrared absorption signal as the ordinate. The correlation coefficient r > 0.999 can be used to calculate the sample content; otherwise, repeat the process.

[0112] S5. Substitute the integral area of ​​the CO2 infrared absorption signal measured in S3 into the standard curve plotted in S4 to obtain the carbon content in the sample.

[0113] The carbon content measured in this embodiment was 5.02%.

[0114] As can be seen from the above embodiments, the technical solution of the present invention solves the problem of directly using a high-frequency infrared carbon-sulfur analyzer to determine the carbon content in molten salt chlorination slag in the industrial production of titanium tetrachloride, and may improve the oxidation melting rate and carbon release efficiency during the high-frequency infrared carbon-sulfur analyzer determination process. At the same time, the technical solution of the present invention can maintain good stability in determining the carbon content in molten salt chlorination slag.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the carbon content in molten salt chlorination slag, characterized in that, Includes the following steps: S1. Sample preparation: The molten salt chlorination slag sample taken from the production line is crushed and sealed for later use; S2. Sample pretreatment: Weigh the sample treated in S1 and place it in a container. Add calcium oxide and / or magnesium oxide, add water until the sample is fully moistened, and then dry it for later use. S3. Sample Measurement: Add flux to the sample after S2 treatment and measure it with a high-frequency infrared carbon-sulfur analyzer to obtain the integrated area of ​​the CO2 infrared absorption signal. S4. Plot the standard curve: Process and measure the molten salt chlorination slag calibration materials with different carbon contents in the order of steps S1-S3, and then plot the standard curve with the carbon content of the standard material as the abscissa and the integral area of ​​the measured CO2 infrared absorption signal as the ordinate. S5. Substitute the integral area of ​​the CO2 infrared absorption signal measured in S3 into the standard curve plotted in S4 to obtain the carbon content in the sample. During drying in S2, a vacuum drying oven is used at a temperature of 100-110°C for 30-60 minutes, protected by an inert gas, which is at least one of nitrogen or argon.

2. The method for determining the carbon content in molten salt chlorination slag according to claim 1, characterized in that, The specific steps of the crushing process in S1 are as follows: First, the molten salt chlorination slag sample taken from the production process is crushed into small particles, and then crushed in a crusher. The particle size of the crushed sample is less than 200 mesh. The grinding disc of the crusher is heated before use.

3. The method for determining the carbon content in molten salt chlorination slag according to claim 1, characterized in that, The flux mentioned in S3 is at least one of pure iron particles, tungsten particles, tin particles, and copper particles, and the mass ratio of flux to molten salt chlorination slag is 15:1-20:

1.

4. The method for determining the carbon content in molten salt chlorination slag according to claim 3, characterized in that, The flux is pure iron granules and tungsten granules.

5. A method for determining the carbon content in molten salt chlorination slag according to any one of claims 1-4, characterized in that, The specific steps for preparing calibrating materials for molten salt chlorination slag with different carbon contents in S4 are as follows: SS1, Matrix preparation: The matrix is ​​prepared according to the composition of the molten salt chlorination slag. The matrix includes sodium chloride, iron oxide, titanium dioxide, and calcium chloride. The matrix also includes at least one of manganese chloride, magnesium chloride, silicon dioxide, and aluminum oxide. The matrix is ​​mixed and then calcined. The slag is then removed and crushed according to step S1 for later use. SS2, Preparation of calibration materials: Weigh different amounts of carbon source references into containers, add the matrix prepared in SS1 respectively, and obtain molten salt chlorinated slag calibration materials with different carbon contents.

6. The method for determining the carbon content in molten salt chlorination slag according to claim 5, characterized in that, The carbon source is reference calcium carbonate.

7. The method for determining the carbon content in molten salt chlorination slag according to claim 5, characterized in that, The matrix is ​​composed of 35-60% sodium chloride, 8-20% iron oxide, 7-25% calcium chloride, 5-12% manganese chloride, 3-14% silicon dioxide, 1-10% titanium dioxide, and 7-12% aluminum oxide, where % refers to mass percentage.

8. The application of the method for determining the carbon content in molten salt chlorination slag according to claim 7 in the industrial production of titanium tetrachloride.

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