A method for rapidly determining the contents of calcium oxide and magnesium oxide in blast furnace slag

Abstract

The application discloses a method for rapidly determining the content of calcium oxide and magnesium oxide in blast furnace slag, directly dissolves the sample by using hot nitric acid and hydrofluoric acid, does not need to use precious metal platinum gold crucible to treat the sample, directly reduces the analysis cost, does not need to use ammonia water to separate calcium and magnesium in the sample treatment process, adds triethanolamine to directly mask interfering ions such as iron, aluminum and manganese, then titrates, shortens the analysis time, and improves the work efficiency; when the total content of calcium and magnesium is determined, PAN is used as an indicator after Cu-EDTA solution is added, the total content of calcium and magnesium is determined by using EDTA to reversely titrate copper ions released after the Cu-EDTA solution is combined with calcium and magnesium; the titration end point changes from red to yellow, and is easier to observe and master. The method is simple and rapid in operation, can meet the production detection requirement, and has good popularization and application value.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical analysis technology, and in particular relates to a method for rapidly determining the content of calcium oxide and magnesium oxide in blast furnace slag. Background Technology

[0002] Blast furnace slag is a solid waste formed during the blast furnace ironmaking process from gangue in the ore, ash in the fuel, and non-volatile components in the limestone. It mainly contains oxides of calcium, silicon, aluminum, magnesium, and iron, and small amounts of sulfides.

[0003] The calculation of alkalinity requires the determination of calcium oxide content, with the ratio of calcium oxide to silicon dioxide content used in the alkalinity calculation formula. This ratio significantly impacts slag alkalinity removal and desulfurization, with contradictory effects. A high ratio enhances slag desulfurization but reduces alkalinity removal; a low ratio enhances alkalinity removal but reduces desulfurization. Increased magnesium oxide content promotes alkalinity removal but hinders desulfurization. Appropriate magnesium oxide content improves slag fluidity and stability, protecting the furnace lining, while excessive magnesium oxide increases slag viscosity, negatively impacting smelting efficiency. Therefore, calcium oxide and magnesium oxide are particularly important in the chemical composition analysis of blast furnace slag.

[0004] Currently, the methods for determining calcium oxide and magnesium oxide in slag typically employ EDTA direct complexation and X-ray fluorescence spectrometry. When using EDTA complexometric titration to determine calcium and magnesium, a mixture of sodium carbonate and boric acid flux is melted, extracted and dissolved with hydrochloric acid, and the pH is adjusted to approximately 7 with ammonia to separate interfering ions such as iron and aluminum. The solution is then diluted to a 250 mL volumetric flask. A certain amount of solution is then taken, and the pH is adjusted to be greater than 12. Using a calcium indicator as the endpoint, EDTA is used for complexometric titration until the solution changes from wine red to pure blue. The calcium content is calculated theoretically using the chemical reaction equation. A separate portion of the solution is taken, and the pH is adjusted to 10. Using Eriochrome Black T as an indicator, EDTA is used for complexometric titration until the solution changes from red to blue. The magnesium content is calculated theoretically by subtracting the amount of EDTA consumed in the calcium titration from the total amount of EDTA consumed in the calcium titration.

[0005] X-ray fluorescence spectroscopy, after calculating the loss on ignition, uses a melting method to prepare a molten sheet for determining the calcium and magnesium content.

[0006] This method directly dissolves the sample using hot nitric acid and hydrofluoric acid, eliminating the need for expensive platinum crucibles compared to the methods mentioned above, thus directly reducing analytical costs. During sample preparation, there is no need for ammonia to separate calcium and magnesium; triethanolamine is added to directly mask interfering ions such as iron, aluminum, and manganese before titration. When determining the combined calcium and magnesium content, Cu-EDTA solution is added, with PAN as an indicator. The determination is completed by back titration after EDTA releases copper ions from the Cu-EDTA solution. The titration endpoint changes from red to yellow, making it easier to observe and control. Summary of the Invention

[0007] The purpose of this invention is to provide a rapid method for determining the calcium oxide and magnesium oxide content in blast furnace slag. During sample processing, there is no need to use ammonia for calcium and magnesium separation; triethanolamine is added to directly mask interfering ions such as iron, aluminum, and manganese before titration. When determining the combined calcium and magnesium content, Cu-EDTA solution is added, with PAN as an indicator. EDTA releases copper ions from the Cu-EDTA solution, and the determination is completed via back titration. The titration endpoint changes from red to yellow, making it easier to observe and control; this directly reduces analytical costs.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] This invention provides a method for rapidly determining the calcium oxide and magnesium oxide content in blast furnace slag, comprising:

[0010] The sample was rapidly dissolved using hot nitric acid and hydrofluoric acid, and then diluted to 100 mL in a polyethylene volumetric flask with grade III water.

[0011] A certain amount of solution was taken and placed in two 500 mL Erlenmeyer flasks. Triethanolamine was added to mask interfering ions such as iron, aluminum, and manganese. The pH of the solutions was adjusted to be greater than 12 and to 10, respectively. Disodium ethylenediaminetetraacetate standard solution was used as the titrant. The color change of calcium indicator indicated the endpoint of the complexometric titration. After recording the volume of titrant consumed, the calcium content in the sample was calculated from the theoretical value. In the other flask, PAN was used as the indicator. The solution was titrated with disodium ethylenediaminetetraacetate standard solution until the solution changed from red to yellow. The volume of titrant consumed was recorded as the combined consumption of calcium and magnesium. The magnesium content in the sample was calculated from the theoretical value obtained by subtracting the volume of titrant consumed by the first flask for calcium titration.

[0012] Furthermore, it is applicable to the determination of calcium oxide and magnesium oxide content in blast furnace slag, with the determination range for calcium oxide being less than 50% and the determination range for magnesium oxide being less than 30%.

[0013] Further, accurately weigh 0.05 g of sample and place it in a 200 mL polyethylene beaker. Add 20 mL of preheated nitric acid solution to boiling and stir continuously with a plastic rod. Then, add 1 mL of hydrofluoric acid using a plastic pipette and continue stirring. After adding 20 mL of saturated boric acid solution, transfer the solution to a 100 mL polyethylene volumetric flask and dilute to the mark.

[0014] Further determination of calcium oxide content:

[0015] Pipette 25 mL of the above solution into a 500 mL Erlenmeyer flask, add 30 mL of triethanolamine and 10 mL of sodium hydroxide solution, shake well, add 0.1 g of calcium indicator, and titrate with disodium ethylenediaminetetraacetate standard solution until the solution changes from wine red to pure blue. Record the volume consumed as V. 02 ;

[0016] Perform a blank test along with the sample, and record the volume of standard solution consumed as V. 01 .

[0017] Further determination of magnesium oxide content:

[0018] Pipette 25 mL of the above solution into a 500 mL Erlenmeyer flask. Add 5 mL of triethanolamine, 20 mL of water, 10 mL of ammonia buffer solution, 3 mL of Cu-EDTA solution, and 2-3 drops of PAN indicator. Titrate with disodium ethylenediaminetetraacetate standard solution until the solution changes from red to yellow. Record the volume consumed as V. 03 .

[0019] Perform a blank test along with the sample, and record the volume of standard solution consumed as V. 04 .

[0020] Further, the calculation of the analysis results

[0021]

[0022]

[0023] Where: m: sample mass (g);

[0024] K: Sample liquid-liquid ratio;

[0025] V 01 The volume of EDTA standard solution consumed in the blank titration of calcium (mL);

[0026] V 02 The volume of EDTA standard solution consumed during calcium titration (mL);

[0027] C: Concentration of the standard titration solution of disodium ethylenediaminetetraacetate (EDTA) in mol / L;

[0028] V03 The volume of EDTA standard solution consumed in the titration of calcium and magnesium (mL);

[0029] V 04 The volume of EDTA standard solution consumed in the titration of the calcium-magnesium balance blank (mL);

[0030] M(MgO): Molar mass of magnesium oxide, 40.30 g / mol;

[0031] M(CaO): Molar mass of calcium oxide, 56.08 g / mol.

[0032] Furthermore, the sample weight was accurate to ±0.1 mg.

[0033] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0034] This method uses hot nitric acid and hydrofluoric acid to directly dissolve the sample, eliminating the need for precious platinum crucibles and directly reducing analytical costs. During sample preparation, there is no need for ammonia to separate calcium and magnesium; triethanolamine is added to directly mask interfering ions such as iron, aluminum, and manganese before titration, shortening analysis time and improving efficiency. When determining the combined calcium and magnesium content, Cu-EDTA solution is added, with PAN as an indicator. EDTA complexes with calcium and magnesium in the Cu-EDTA solution, releasing copper ions, followed by back titration to determine the combined calcium and magnesium content. The titration endpoint changes from red to yellow, making it easier to observe and control. Detailed Implementation

[0035] A rapid method for determining the calcium oxide and magnesium oxide content in blast furnace slag:

[0036] 1 range

[0037] This method is applicable to the determination of calcium oxide and magnesium oxide content in blast furnace slag, with the determination range for calcium oxide being less than 50% and the determination range for magnesium oxide being less than 30%.

[0038] 2 Principles

[0039] The sample was dissolved in hot nitric acid and hydrofluoric acid. Boric acid was added to mask and complex excess fluoride ions. The calcium content was determined by titration with disodium ethylenediaminetetraacetate standard solution. A quantitative Cu-EDTA solution was added, and the total amount of calcium and magnesium was determined by displacement titration. The magnesium content was obtained by subtracting the calcium content from the total amount of calcium and magnesium.

[0040] 3. Main Instruments and Reagents

[0041] Acid burette: 50 ml.

[0042] Nitric acid: (1+3).

[0043] Hydrofluoric acid: 40%.

[0044] Sodium hydroxide solution: 25%.

[0045] Saturated boric acid solution.

[0046] Triethanolamine (4.5%): Take 45 ml of triethanolamine, add 3 g of hydroxylamine hydrochloride, and dilute with water to 1000 ml.

[0047] Triethanolamine: (1+1).

[0048] Calcium indicator 1%.

[0049] Disodium ethylenediaminetetraacetate standard solution: 0.0500 mol / L.

[0050] PAN indicator: 0.2% ethanol solution.

[0051] Cu-EDTA solution: 0.005M. Take 0.05M copper sulfate solution, add 5 mL of acetic acid, heat to 80℃, add 3-4 drops of PAN indicator, titrate with 0.05M disodium ethylenediaminetetraacetate solution until the solution turns green, then add water to 200 mL.

[0052] Ammonia buffer solution: Dissolve 54 g of ammonium chloride in an appropriate amount of water, add 350 ml of concentrated ammonia solution, and then dilute with water to 1000 ml.

[0053] 4. Sample condition and requirements

[0054] The samples must be homogeneous and representative. The samples should pass through a 200-mesh sieve.

[0055] 5. Analysis Steps

[0056] 5.1 Sample Size

[0057] Weigh 0.2 mg of the sample, accurate to ±0.1 mg.

[0058] 5.2 Blank Test

[0059] Perform blank tests along with the sample.

[0060] 5.3 Measurement

[0061] Accurately weigh 0.05 g of sample (accurate to ±0.1 mg) and place it in a 200 mL polyethylene beaker. Add 20 mL of preheated nitric acid (1+3) solution and stir continuously with a plastic rod. Then, add 1 mL of hydrofluoric acid using a plastic pipette and continue stirring. Next, add 20 mL of saturated boric acid solution and transfer the mixture to a 100 mL polyethylene volumetric flask. Dilute to the mark.

[0062] 5.3.1 Determination of calcium oxide content

[0063] Pipette 25 mL of the above solution into a 500 mL Erlenmeyer flask, add 30 mL of triethanolamine (4.5%) and 10 mL of sodium hydroxide solution (25%), shake well, add 0.1 g of calcium indicator, and titrate with disodium ethylenediaminetetraacetate standard solution until the solution changes from wine red to pure blue. Record the volume consumed as V. 02 .

[0064] Perform a blank test along with the sample, and record the volume of standard solution consumed as V. 01 .

[0065] 5.3.2 Determination of magnesium oxide content

[0066] Pipette 25 mL of the above solution into a 500 mL Erlenmeyer flask. Add 5 mL of triethanolamine (1+1), 20 mL of water, 10 mL of ammonia buffer solution, 3 mL of Cu-EDTA solution, and 2-3 drops of PAN indicator. Titrate with disodium ethylenediaminetetraacetate standard solution until the solution changes from red to yellow. Record the volume consumed as V. 03 .

[0067] Perform a blank test along with the sample, and record the volume of standard solution consumed as V. 04 .

[0068] 5.3.3 Calculation of Analysis Results

[0069]

[0070]

[0071] Where: m: sample mass (g)

[0072] K: Sample liquid-to-liquid ratio

[0073] V 01 Volume (mL) of EDTA standard solution consumed during calcium titration (blank)

[0074] V 02 Volume (mL) of EDTA standard solution consumed during calcium titration.

[0075] C: Concentration of the disodium ethylenediaminetetraacetate standard titration solution (mol / L)

[0076] V 03 Volume (mL) of EDTA standard solution consumed in titrating the calcium and magnesium content.

[0077] V 04 Volume (mL) of EDTA standard solution consumed in the titration of the calcium-magnesium balance blank.

[0078] M(MgO): Molar mass of magnesium oxide (40.30 g / mol)

[0079] M (CaO): Molar mass of calcium oxide (56.08 g / mol)

[0080] 6. Allowable difference

[0081]

[0082] 7. Accuracy Verification

[0083] 7.1 Sample Precision Test

[0084] This method is used for number 1 # The blast furnace slag samples were tested six times. The relative standard deviations (RSDs) of this method were 0.51% and 1.63%, both less than 5%, indicating good precision. The experimental results are shown in Table 1.

[0085] Table 1 Precision Experiment

[0086]

[0087] 7.2 Sample Accuracy Experiment

[0088] By comparing with certified reference materials for blast furnace slag, the difference from the standard value was less than the allowable deviation, thus demonstrating good accuracy of this method. Experimental results are shown in Table 2.

[0089] Table 2. Comparison of calcium oxide and magnesium oxide in blast furnace slag with standard substances (%)

[0090]

[0091] 8. Conclusion

[0092] This method directly dissolves samples using hot nitric acid and hydrofluoric acid, eliminating the need for expensive platinum crucibles and significantly reducing analytical costs. During sample preparation, ammonia is not required for calcium and magnesium separation; triethanolamine is added to directly mask interfering ions such as iron, aluminum, and manganese before titration, shortening analysis time and improving efficiency. For determining the combined calcium and magnesium content, Cu-EDTA solution is added, with PAN as an indicator. EDTA complexes with calcium and magnesium in the Cu-EDTA solution, releasing copper ions, followed by back titration to determine the combined calcium and magnesium content. The titration endpoint changes from red to yellow, making it easier to observe and control. Practical experience has proven that this method is simple and rapid, meeting production testing needs and possessing significant potential for widespread application.

[0093] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for rapidly determining the calcium oxide and magnesium oxide content in blast furnace slag, characterized in that: include: The sample was rapidly dissolved using hot nitric acid and hydrofluoric acid, and then diluted to 100 mL in a polyethylene volumetric flask with grade III water. A certain amount of solution was taken and placed in two 500 mL Erlenmeyer flasks. Triethanolamine was added to mask interfering ions such as iron, aluminum, and manganese. The pH of the solutions was adjusted to be greater than 12 and to 10, respectively. Disodium ethylenediaminetetraacetate standard solution was used as the titrant. The color change of calcium indicator indicated the endpoint of the complexometric titration. After recording the volume of titrant consumed, the calcium content in the sample was calculated from the theoretical value. In the other flask, PAN was used as the indicator. The solution was titrated with disodium ethylenediaminetetraacetate standard solution until the solution changed from red to yellow. The volume of titrant consumed was recorded as the combined consumption of calcium and magnesium. The magnesium content in the sample was calculated from the theoretical value obtained by subtracting the volume of titrant consumed by the first flask for calcium titration.

2. The method for rapidly determining the calcium oxide and magnesium oxide content in blast furnace slag according to claim 1, characterized in that: It is applicable to the determination of calcium oxide and magnesium oxide content in blast furnace slag, with the determination range of calcium oxide being less than 50% and magnesium oxide being less than 30%.

3. The method for rapidly determining the calcium oxide and magnesium oxide content in blast furnace slag according to claim 1, characterized in that: Accurately weigh 0.05 g of sample and place it in a 200 mL polyethylene beaker. Add 20 mL of preheated nitric acid solution to boiling and stir continuously with a plastic rod. Then, add 1 mL of hydrofluoric acid using a plastic pipette and continue stirring. Next, add 20 mL of saturated boric acid solution and transfer the mixture to a 100 mL polyethylene volumetric flask. Dilute to the mark.

4. The method for rapidly determining the calcium oxide and magnesium oxide content in blast furnace slag according to claim 3, characterized in that: Determination of calcium oxide content: Pipette 25 mL of the above solution into a 500 mL Erlenmeyer flask, add 30 mL of triethanolamine and 10 mL of sodium hydroxide solution, shake well, add 0.1 g of calcium indicator, and titrate with disodium ethylenediaminetetraacetate standard solution until the solution changes from wine red to pure blue. Record the volume consumed as V. 02 ; Perform a blank test along with the sample, and record the volume of standard solution consumed as V. 01 .

5. The method for rapidly determining the calcium oxide and magnesium oxide content in blast furnace slag according to claim 4, characterized in that: Determination of magnesium oxide content: Pipette 25 mL of the above solution into a 500 mL Erlenmeyer flask. Add 5 mL of triethanolamine, 20 mL of water, 10 mL of ammonia buffer solution, 3 mL of Cu-EDTA solution, and 2-3 drops of PAN indicator. Titrate with disodium ethylenediaminetetraacetate standard solution until the solution changes from red to yellow. Record the volume consumed as V. 03 . Perform a blank test along with the sample, and record the volume of standard solution consumed as V. 04 .

6. The method for rapidly determining the calcium oxide and magnesium oxide content in blast furnace slag according to claim 5, characterized in that: Calculation of analysis results Where: m: sample mass (g); K: Sample liquid-liquid ratio; V 01 The volume of EDTA standard solution consumed in the blank titration of calcium (mL); V 02 The volume of EDTA standard solution consumed during calcium titration (mL); C: Concentration of the standard titration solution of disodium ethylenediaminetetraacetate (EDTA) in mol / L; V 03 The volume of EDTA standard solution consumed in the titration of calcium and magnesium (mL); V 04 The volume of EDTA standard solution consumed in the titration of the calcium-magnesium balance blank (mL); M(MgO): Molar mass of magnesium oxide, 40.30 g / mol; M(CaO): Molar mass of calcium oxide, 56.08 g / mol.

7. The method for rapidly determining the calcium oxide and magnesium oxide content in blast furnace slag according to claim 3, characterized in that: The sample weight was accurate to ±0.1 mg.

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