Method for determining total sulfur in coal

Abstract

The invention belongs to the technical field of material chemical analysis and detection, and particularly discloses a method for determining total sulfur in coal, which comprises the following steps: converting the sulfur element in the coal into a measurable ion form by combining high-temperature combustion with chemical dissolution, and realizing accurate quantification by utilizing an ICP-MS / OES technology. The method comprises the following steps: mixing a coal sample with an Escherka reagent, and firing at 800-850 DEG C for 1-2 hours to generate sulfate; the residues are dissolved by 0.05% hot hydrochloric acid to a constant volume, and the burning time of incompletely combusted coal particles needs to be prolonged or the incompletely combusted coal particles need to be discarded and remeasured. A standard sample adopts a gradient dilution sulfur standard solution, determination is carried out under a selected wavelength through ICP-MS, a concentration-intensity standard curve is drawn, and the sulfur content is calculated. For the high-sulfur coal sample (gt; 0.01% hydrochloric acid is adopted for dilution to adapt to the linear range of an instrument. By optimizing the pretreatment process and instrument parameters, the problems of low efficiency and insufficient precision of a traditional method are solved, the correlation coefficient reaches 0.999 or above, the accuracy is larger than or equal to 98%, and the method is suitable for coal quality control and environmental protection monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of material chemical analysis and detection, and in particular to a method for determining total sulfur in coal. Background Art

[0002] As one of the world's primary energy sources, coal plays a vital role in industrial production and daily life. In my country, coal constitutes the majority of the country's mining fuel, and this basic pattern is unlikely to change in the near future. All coal contains sulfur, though the concentration varies, ranging from 0.3% to 0.5% to 3% to 5%, or even higher. With rapid economic development, sulfur dioxide emissions from coal combustion in my country have increased dramatically, and the scope of acid rain pollution caused by sulfur dioxide has continued to expand. Acid rain and sulfur dioxide pollution harm public health, corrode building materials, damage ecosystems, and cause significant economic losses, becoming a major factor restricting socioeconomic development. Therefore, accurately measuring the total sulfur content of coal is crucial for coal quality control, environmental protection, and industrial production.

[0003] Standard methods for analyzing total sulfur in coal, both domestically and internationally, primarily include infrared spectroscopy, the Aesculapius method, high-temperature neutralization, coulometry, and the oxygen bomb method. With the advancement of technology, traditional methods for total sulfur determination in coal have become cumbersome, time-consuming, and inaccurate. These methods are no longer meeting the needs of society, necessitating innovative approaches to monitoring and analyzing sulfur in coal. Inductively coupled plasma mass spectrometry (ICP-OES) / inductively coupled plasma spectrometry (ICP-MS), as an advanced analytical technique, offers advantages such as a wide linear range, excellent precision, and minimal matrix interference, making it suitable for large-volume sample analysis. Widely used in the field of inorganic element analysis, its application to the determination of total sulfur in coal is expected to improve accuracy and efficiency, providing more reliable technical support for the coal industry. However, because ICP-OES / ICP-MS require a high-temperature plasma to atomize and excite elements in the sample, it cannot be directly used to detect total sulfur in coal. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for determining total sulfur in coal, so as to solve the problem that ICP-MS / OES cannot directly detect total sulfur in coal.

[0005] To achieve the above object, the present invention provides a basic solution: a method for determining total sulfur in coal, comprising the following steps:

[0006] S1: Sample collection and storage: Coal samples shall be collected in accordance with the relevant provisions of GB / T475. The samples shall be stored in a sealed container that does not absorb water and is airtight and placed in a cool place;

[0007] S2: Sample preparation: Coal samples were prepared in accordance with the relevant provisions of GB / T474, with air-dried samples with a particle size of less than 0.2 mm as the coal samples;

[0008] S3: Preparation of sample: Weigh 1g of coal sample and 2g of Aska reagent, place them in a 30ml porcelain crucible and mix them, then cover them with 1g of Aska reagent, move the porcelain crucible containing the sample into a well-ventilated muffle furnace, gradually heat it from room temperature to 800℃-850℃ within 1h-2h, and keep it at 1h-2h. Then take out the crucible and cool it to room temperature to obtain the burned product of the sample, stir and crush the burned product in the porcelain crucible with a glass rod, dissolve the burned product of the sample in a 250ml volumetric flask with 0.05% hot hydrochloric acid solution, repeatedly rinse the inner wall of the porcelain crucible with 0.05% hot hydrochloric acid solution, add the washing liquid to the volumetric flask, dilute the volume to the mark of the 250ml volumetric flask with pure water, mix thoroughly, and obtain the sample to be tested;

[0009] S4: Preparation of standard samples: Accurately pipette 1.00, 2.00, 3.00, 5.00, 7.00, 9.00, and 10.00 mL of the sulfur standard working solution into a 50 mL volumetric flask. Dilute to the mark on the volumetric flask with 0.01% hydrochloric acid and shake well to obtain standard solutions of known concentrations.

[0010] S5: Place the certified reference material into the ICP-MS / OES instrument and perform a full-band scan of the standard solution sample to identify all possible characteristic spectral lines. Use the instrument's built-in background correction function or software algorithm to verify interference effects. Compare the detection limits and calibration curve slopes at different wavelengths. Select the wavelength with the highest sensitivity within the response range of 0-1,000,000.

[0011] S6: After the ICP-MS / OES instrument is tuned, set the instrument wavelength parameter to 186 nm and measure the standard solution, blank, certified reference material, and test sample in increasing order of concentration. Repeat the measurement three times for each sample and take the average value. Draw a working curve with concentration as the horizontal axis and response intensity as the vertical axis. Fit the working curve to the standard working curve to quantitatively calculate the sample concentration.

[0012] S7: Calculation of total sulfur content in coal

[0013] WP%=(C 样 -C 空白 )*D*V*Aad*10-4 / m

[0014] Where: C 样 Indicates the mass concentration of sulfur in the sample calculated from the standard curve, mg / L

[0015] C 空白 Indicates the mass concentration of sulfur calculated from the standard curve of the laboratory blank sample, mg / L

[0016] D represents the dilution factor

[0017] Aad stands for air dry basis

[0018] m represents the sample mass

[0019] V represents the constant volume.

[0020] The principles and beneficial effects of the present invention are:

[0021] 1. The working principle of ICP-MS / OES is to atomize and excite the elements in the sample through high-temperature plasma, emit light of a specific wavelength, and determine the element concentration through spectral analysis. The coal sample and the Aesculapius reagent are burned at 800℃~850℃ for 1~2 hours to ensure that the organic matter is completely decomposed and the sulfur element is converted into stable sulfate. The residue after the coal sample and the Aesculapius reagent are mixed and burned is dissolved in 0.05% hot hydrochloric acid, and the sulfate is converted into sulfate ions (SO4 2- After constant volume, a homogeneous solution is formed. This solution is then atomized in the atomizer of the plasma emission spectrometer and carried into the plasma torch by argon carrier gas. The target element is vaporized, ionized, excited, and radiates a characteristic spectral line in the plasma torch. The intensity of the characteristic spectrum is proportional to the content of the element in the sample within a certain range.

[0022] 2. Prepare standard solutions of varying concentrations using standard working solutions. Detect the standard solutions using ICP-MS / OES to obtain instrument responses. A working curve is then plotted. The intensity of the characteristic spectrum is proportional to the content of the element in the sample within a certain range. By fitting the response of the sample to the working curve, the sulfur concentration of the sample can be determined. Coal quality analysis is performed on an air-dried basis to ensure accuracy and comparability of the results.

[0023] 3. When a coal sample is placed under normal laboratory conditions, i.e., room temperature of 20 degrees Celsius and relative humidity of 60 percent, it will lose some moisture. The remaining stable moisture is called the air-dried moisture under normal laboratory conditions. The composition based on the air-dried coal sample is called the air-dried basis composition.

[0024] 4. In S5, a certified reference material is a substance or material that has been determined to have one or more sufficiently uniform characteristic values ​​to serve as a "measuring tool" in the analytical measurement industry.

[0025] Option 2, which is the preferred option of the basic option, is to discard the test if black coal particles still float after dilution with hydrochloric acid in S2. If there are undissolved black coal particles in the solution, it indicates incomplete combustion and needs to be discarded and retested.

[0026] Option 3, which is the preferred option of the basic option, is that in S2, if there are unburned coal particles in the muffle furnace, they should be burned for another 0.5 h at 800°C to 850°C. The burning time of unburned coal particles should be extended to prevent residual carbon from interfering with subsequent dissolution.

[0027] Option 4, a preferred alternative to the basic option, uses the Aiska reagent in S2, which is a mixture of light magnesium oxide and anhydrous sodium carbonate in a 2:1 ratio and ground to a particle size of less than 0.2 mm. During combustion, MgO provides an alkaline environment, preventing sulfur from volatilizing and losing in gaseous form (such as SO2). Na2CO3 acts as a flux, lowering the combustion temperature and promoting the oxidation of sulfur to sulfate.

[0028] Option 5, the preferred alternative to the basic option, involves centrifuging or filtering the coal sample for sulfur content ≤2% and then directly measuring the supernatant. If the sulfur content is >2%, dilute the supernatant with 0.01% hydrochloric acid before measuring. To ensure accuracy, the ICP-MS instrument's response should be controlled between 0 and 1,000,000. The response is proportional to the concentration of the element in the sample within a certain range. Excessively high concentrations can result in excessively high response values, affecting accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a working curve diagram of a method for determining total sulfur in coal of the present invention at a wavelength of 186 nm;

[0030] Figure 2 This is a working curve diagram of a method for determining total sulfur in coal according to the present invention at a wavelength of 187 nm;

[0031] Figure 3 It is a working curve diagram of a method for determining total sulfur in coal according to the present invention at a wavelength of 185 nm. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below through specific embodiments:

[0033] Example 1

[0034] A method for determining total sulfur in coal comprises the following steps:

[0035] S1: Sample collection and storage: Coal samples shall be collected in accordance with the relevant provisions of GB / T475. The samples shall be stored in a sealed container that does not absorb water and is airtight and placed in a cool place;

[0036] S2: Sample preparation: Coal samples were prepared in accordance with the relevant provisions of GB / T474, with air-dried samples with a particle size of less than 0.2 mm as the coal samples;

[0037] S3: Preparation of sample: Weigh 1g of coal sample and 2g of Aska reagent, place them in a 30ml porcelain crucible and mix them, then cover them with 1g of Aska reagent, move the porcelain crucible containing the sample into a well-ventilated muffle furnace, gradually heat it from room temperature to 800℃-850℃ within 1h-2h, and keep it at 1h-2h. Then take out the crucible and cool it to room temperature to obtain the burned product of the sample, stir and crush the burned product in the porcelain crucible with a glass rod, dissolve the burned product of the sample in a 250ml volumetric flask with 0.05% hot hydrochloric acid solution, repeatedly rinse the inner wall of the porcelain crucible with 0.05% hot hydrochloric acid solution, add the washing liquid to the volumetric flask, dilute the volume to the mark of the 250ml volumetric flask with pure water, mix thoroughly, and obtain the sample to be tested;

[0038] S4: Preparation of standard samples: Accurately pipette 1.00, 2.00, 3.00, 5.00, 7.00, 9.00, and 10.00 mL of the sulfur standard working solution into a 50 mL volumetric flask. Dilute to the mark on the volumetric flask with 0.01% hydrochloric acid and shake well to obtain standard solutions of known concentrations.

[0039] S5: Place the certified reference material into the ICP-MS / OES instrument and perform a full-band scan of the standard solution sample to identify all possible characteristic spectral lines. Use the instrument's built-in background correction function or software algorithm to verify interference effects. Compare the detection limits and calibration curve slopes at different wavelengths. Select the wavelength with the highest sensitivity within the response range of 0-1,000,000.

[0040] S6: After the ICP-MS / OES instrument is tuned, set the instrument wavelength parameter to 187 nm. Measure the standard solution, blank, certified reference material, and each sample in ascending order of concentration. Repeat the measurement three times and take the average value. Draw a working curve with concentration as the horizontal axis and response intensity as the vertical axis. Fit the working curve to the standard working curve to quantitatively calculate the sample concentration.

[0041] S7: Calculation of total sulfur content in coal

[0042] WP%=(C 样 -C 空白 )*D*V*Aad*10-4 / m

[0043] Where: C 样 Indicates the mass concentration of sulfur in the sample calculated from the standard curve, mg / L

[0044] C 空白 Indicates the mass concentration of sulfur calculated from the standard curve of the laboratory blank sample, mg / L

[0045] D represents the dilution factor

[0046] Aad stands for air dry basis

[0047] m represents the sample mass

[0048] V represents the constant volume.

[0049] As shown in Table 1, Table 2 and Figure 1 As shown: when the concentration of the standard working solution is 250 mg / L and the wavelength of the ICP-MS instrument is set to 186 nm, the response value of the blank sample is 82.250, the response value of the sample with a concentration of 150 mg / L is 704302.250, and the correlation coefficient is 0.99968.

[0050] Table 1: Standard sample response value table

[0051]

[0052] Table 2: 186nm spectral detection standard sample response table

[0053]

[0054] Example 2

[0055] A method for determining total sulfur in coal comprises the following steps:

[0056] S1: Sample collection and storage: Coal samples shall be collected in accordance with the relevant provisions of GB / T475. The samples shall be stored in a sealed container that does not absorb water and is airtight and placed in a cool place;

[0057] S2: Sample preparation: Coal samples were prepared in accordance with the relevant provisions of GB / T474, with air-dried samples with a particle size of less than 0.2 mm as the coal samples;

[0058] S3: Preparation of sample: Weigh 1g of coal sample and 2g of Aska reagent, place them in a 30ml porcelain crucible and mix them, then cover them with 1g of Aska reagent, move the porcelain crucible containing the sample into a well-ventilated muffle furnace, gradually heat it from room temperature to 800℃-850℃ within 1h-2h, and keep it at 1h-2h. Then take out the crucible and cool it to room temperature to obtain the burned product of the sample, stir and crush the burned product in the porcelain crucible with a glass rod, dissolve the burned product of the sample in a 250ml volumetric flask with 0.05% hot hydrochloric acid solution, repeatedly rinse the inner wall of the porcelain crucible with 0.05% hot hydrochloric acid solution, add the washing liquid to the volumetric flask, dilute the volume to the mark of the 250ml volumetric flask with pure water, mix thoroughly, and obtain the sample to be tested;

[0059] S4: Preparation of standard samples: Accurately pipette 1.00, 2.00, 3.00, 5.00, 7.00, 9.00, and 10.00 mL of the sulfur standard working solution into a 50 mL volumetric flask. Dilute to the mark on the volumetric flask with 0.01% hydrochloric acid and shake well to obtain standard solutions of known concentrations.

[0060] S5: Place the certified reference material into the ICP-MS / OES instrument and perform a full-band scan of the standard solution sample to identify all possible characteristic spectral lines. Use the instrument's built-in background correction function or software algorithm to verify interference effects. Compare the detection limits and calibration curve slopes at different wavelengths. Select the wavelength with the highest sensitivity within the response range of 0-1,000,000.

[0061] S6: After the ICP-MS / OES instrument is tuned, set the instrument wavelength parameter to 186 nm. Measure the standard solution, blank, certified reference material, and each sample in ascending order of concentration. Repeat the measurement three times and take the average value. Draw a working curve with concentration as the horizontal axis and response intensity as the vertical axis. Fit the working curve to the standard working curve to quantitatively calculate the sample concentration.

[0062] S7: Calculation of total sulfur content in coal

[0063] WP%=(C 样 -C 空白) *D*V*Aad*10-4 / m

[0064] Where: C 样 Indicates the mass concentration of sulfur in the sample calculated from the standard curve, mg / L

[0065] C 空白 Indicates the mass concentration of sulfur calculated from the standard curve of the laboratory blank sample, mg / L

[0066] D represents the dilution factor

[0067] Aad stands for air dry basis

[0068] m represents the sample mass

[0069] V represents the constant volume.

[0070] As shown in Table 1, Table 3 and Figure 2 As shown: when the concentration of the standard working solution is 250 mg / L and the wavelength of the ICP-MS instrument is set to 187 nm, the response value of the blank sample is 111.833, the response value of the sample with a concentration of 150 mg / L is 441552.583, and the correlation coefficient is 0.99972.

[0071] Table 3: 187nm spectral detection standard sample response table

[0072]

[0073] Example 3

[0074] A method for determining total sulfur in coal comprises the following steps:

[0075] S1: Sample collection and storage: Coal samples shall be collected in accordance with the relevant provisions of GB / T475. The samples shall be stored in a sealed container that does not absorb water and is airtight and placed in a cool place;

[0076] S2: Sample preparation: Coal samples were prepared in accordance with the relevant provisions of GB / T474, with air-dried samples with a particle size of less than 0.2 mm as the coal samples;

[0077] S3: Preparation of sample: Weigh 1g of coal sample and 2g of Aska reagent, place them in a 30ml porcelain crucible and mix them, then cover them with 1g of Aska reagent, move the porcelain crucible containing the sample into a well-ventilated muffle furnace, gradually heat it from room temperature to 800℃-850℃ within 1h-2h, and keep it at 1h-2h. Then take out the crucible and cool it to room temperature to obtain the burned product of the sample, stir and crush the burned product in the porcelain crucible with a glass rod, dissolve the burned product of the sample in a 250ml volumetric flask with 0.05% hot hydrochloric acid solution, repeatedly rinse the inner wall of the porcelain crucible with 0.05% hot hydrochloric acid solution, add the washing liquid to the volumetric flask, dilute the volume to the mark of the 250ml volumetric flask with pure water, mix thoroughly, and obtain the sample to be tested;

[0078] S4: Preparation of standard samples: Accurately pipette 1.00, 2.00, 3.00, 5.00, 7.00, 9.00, and 10.00 mL of the sulfur standard working solution into a 50 mL volumetric flask. Dilute to the mark on the volumetric flask with 0.01% hydrochloric acid and shake well to obtain standard solutions of known concentrations.

[0079] S5: Place the certified reference material into the ICP-MS / OES instrument and perform a full-band scan of the standard solution sample to identify all possible characteristic spectral lines. Use the instrument's built-in background correction function or software algorithm to verify interference effects. Compare the detection limits and calibration curve slopes at different wavelengths. Select the wavelength with the highest sensitivity within the response range of 0-1,000,000.

[0080] S6: After the ICP-MS / OES instrument is tuned, set the instrument wavelength parameter to 185nm, and measure the standard solution, blank, certified reference material, and each sample in increasing order of concentration. Repeat the measurement three times, take the average value, and draw a working curve with concentration as the horizontal axis and response intensity as the vertical axis. Fit the working curve to the standard working curve to quantitatively calculate the sample concentration;

[0081] S7: Calculation of total sulfur content in coal

[0082] WP%=(C 样 -C 空白 )*D*V*Aad*10-4 / m

[0083] Where: C 样Indicates the mass concentration of sulfur in the sample calculated from the standard curve, mg / L

[0084] C 空白 Indicates the mass concentration of sulfur calculated from the standard curve of the laboratory blank sample, mg / L

[0085] D represents the dilution factor

[0086] Aad stands for air dry basis

[0087] m represents the sample mass

[0088] V represents the constant volume.

[0089] As shown in Table 1, Table 4 and Figure 3 As shown: when the concentration of the standard working solution is 250 mg / L and the wavelength of the ICP-MS instrument is set to 185 nm, the response value of the blank sample is 19.417, the response value of the sample with a concentration of 150 mg / L is 116233.667, and the correlation coefficient is 0.99992.

[0090] Table 4: 185nm spectral detection standard sample response table

[0091]

[0092] The response value of the ICP-MS instrument should be controlled between 0-1000000. To ensure detection accuracy, the correlation coefficient of the working curve should be greater than 0.999.

[0093] In summary, when the wavelength of the ICP-MS instrument is set to 186 nm, the response value is within the range of 0-1000000, and the correlation coefficient is greater than 0.999, and the accuracy of the measurement result is ≥98%.

[0094] The above is only an embodiment of the present invention, and the common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for determining total sulfur in coal, characterized in that: The steps include: S1: Sample collection and storage: Coal samples shall be collected in accordance with the relevant provisions of GB / T475. The samples shall be stored in a sealed container that does not absorb water and is airtight and placed in a cool place; S2: Sample preparation: Coal samples were prepared in accordance with the relevant provisions of GB / T474, with air-dried samples with a particle size of less than 0.2 mm as the coal samples; S3: Preparation of sample: Weigh 1g of coal sample and 2g of Aska reagent, place them in a 30ml porcelain crucible and mix them, then cover them with 1g of Aska reagent, move the porcelain crucible containing the sample into a well-ventilated muffle furnace, gradually heat it from room temperature to 800℃-850℃ within 1h-2h, and keep it at 1h-2h. Then take out the crucible and cool it to room temperature to obtain the burned product of the sample, stir and crush the burned product in the porcelain crucible with a glass rod, dissolve the burned product of the sample in a 250ml volumetric flask with 0.05% hot hydrochloric acid solution, repeatedly rinse the inner wall of the porcelain crucible with 0.05% hot hydrochloric acid solution, add the washing liquid to the volumetric flask, dilute the volume to the mark of the 250ml volumetric flask with pure water, mix thoroughly, and obtain the sample to be tested; S4: Preparation of standard samples: Accurately pipette 1.00, 2.00, 3.00, 5.00, 7.00, 9.00, and 10.00 mL of the sulfur standard working solution into a 50 mL volumetric flask. Dilute to the mark on the volumetric flask with 0.01% hydrochloric acid and shake well to obtain standard solutions of known concentrations. S5: Place the certified reference material into the ICP-MS / OES instrument and perform a full-band scan of the standard solution sample to identify all possible characteristic spectral lines. Use the instrument's built-in background correction function or software algorithm to verify interference effects. Compare the detection limits and calibration curve slopes at different wavelengths. Select the wavelength with the highest sensitivity within the response range of 0-1,000,000. S6: After the ICP-MS / OES instrument is tuned, set the instrument wavelength parameter to 186 nm and measure the standard solution, blank, certified reference material, and test sample in increasing order of concentration. Repeat the measurement three times for each sample and take the average value. Draw a working curve with concentration as the horizontal axis and response intensity as the vertical axis. Fit the working curve to the standard working curve to quantitatively calculate the sample concentration. S7: Calculation of total sulfur content in coal WP%=(C sample-C blank)*D*V*Aad*10-4 / m Where: Sample C represents the mass concentration of sulfur in the sample calculated from the standard curve, mg / L Cblank represents the mass concentration of sulfur calculated from the standard curve of the laboratory blank sample, mg / L D represents the dilution factor Aad stands for air dry basis m represents the sample mass V represents the constant volume.

2. The method for determining total sulfur in coal according to claim 1, wherein After dilution with hydrochloric acid in S2, if there are still black coal particles floating, the measurement will be invalid.

3. The method for determining total sulfur in coal according to claim 1, wherein: In S2, if there are unburned coal particles in the muffle furnace, they should continue to be burned at 800℃~850℃ for 0.5h.

4. The method for determining total sulfur in coal according to claim 1, wherein: In S2, the Aishika reagent is composed of a mixture of light magnesium oxide and anhydrous sodium carbonate, which are mixed in a ratio of 2:1 and ground to a particle size of less than 0.2 mm.

5. The method for determining total sulfur in coal according to claim 1, wherein If the sulfur content in the coal sample is ≤2%, the sample should be centrifuged or filtered to obtain the supernatant for direct measurement. If the sulfur content is greater than 2%, the supernatant should be diluted with 0.01% hydrochloric acid and then measured.

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