GB/T 14949.11-2021Manganese ores—Determination of carbon content—Gravimetric method and infrared absorption method (English PDF)

4.1 Principle

Use phosphoric acid to decompose the sample, with oxygen as the carrier gas; use alkali asbestos to absorb carbon dioxide, and the gravimetric method to determine.

4.2 Reagents

Unless otherwise specified, use analytical reagents only.

4.2.1 Water, GB/T 6682, Grade III.

4.2.2 Chromium oxide.

4.2.3 Anhydrous copper sulfate, which is obtained by baking crystalline copper sulfate (CuSO4·5H2O) at 180 °C ~ 200 °C for more than 3 h.

4.2.4 Anhydrous magnesium perchlorate, which shall be dried at 120 °C ~ 150 °C before being loaded into the absorption tube.

4.2.5 Alkali asbestos.

4.2.7 Phosphoric acid, rho =

4.3 Instruments and devices

See Figure 1 for the diagram of the analysis device for the gravimetric method. slightly; keep it for 10 min, then, remove the electric hot plate (Figure 1A). During this process, keep the air flow rate through the drying tube at 3 ~ 4 air bubbles per second (Figure 1L); then, continue to maintain for 10 min to drive off the residual carbon dioxide.

Close the piston of the absorption tube; remove the absorption tube (Figure 1J and

Figure 1K); place it in a desiccant-free desiccator in the balance chamber; place it for 30 min to equilibrate the temperature. Open the piston of the absorber tube (Figure 1J and Figure 1K), and close it immediately, to allow the internal pressure to equilibrate atmospheric pressure. Weigh.

4.6 Calculation and presentation of results

4.6.1 Calculation of analysis results

Calculate the mass fraction wC of carbon according to Formula (1).

Where: wC - mass fraction of carbon; m - mass of the sample, in grams (g); m0 - mass of carbon dioxide measured in the blank test, in grams (g); m1 - mass of the absorption tube (Figure 1J and Figure 1K) before absorption, in grams (g); m2 - mass of the absorption tube (Figure 1J and Figure 1K) after absorption, in grams (g);

K' - 0.272 7, the conversion coefficient for converting carbon dioxide to carbon.

4.6.2 Determination and presentation of analysis results

If the absolute value of the difference between the two independent analysis results of the same sample is not greater than the repeatability limit r, take the arithmetic mean as the analysis result. If the absolute value of the difference between the two independent analysis results is greater than the repeatability limit r, increase the number of measurements and determine the analysis results in accordance with the provisions of Appendix A. Round off the analysis results according to GB/T 8170.

4.7 Precision

In this document, calculate the precision according to the statistical methods of GB/T 6379.1 and GB/T 6379.2; the precision of this method is shown in Table 2. See Table B.1 in Appendix B for raw data.

5.1 Principle

The sample is heated and burned in the oxygen flow of the high-frequency induction furnace; the generated carbon dioxide is carried by the oxygen to the measuring chamber of the infrared analyzer. The carbon dioxide absorbs infrared energy of a certain wavelength; its absorption energy is proportional to its concentration. The amount of carbon can be measured from the change in energy received by the detector.

5.2 Reagents and materials

Unless otherwise specified, only use analytical reagents.

5.2.2 Acetone, the carbon content of the residue after evaporation is less than 0.000 5%.

5.2.3 Magnesium perchlorate, anhydrous, granular.

5.2.4 Ascarite, granular.

5.2.5 Glass wool.

5.2.6 Tin particles, carbon content less than 0.002%, and particle size 0.4 mm ~ 0.8 mm. If necessary, use acetone (5.2.2) to clean the surface, and dry at room temperature.

5.2.7 Pure iron, carbon content less than 0.002%, chip or granular.

5.2.8 Tungsten particles, carbon content less than 0.002%, and particle size 0.8 mm ~ 1.4 mm.

5.2.9 Oxygen, purity greater than 99.95%; oxygen of other purity can also be used if a lower but consistent blank can be obtained.

5.2.1 Water, GB/T 6682, Grade III

6 - high-frequency induction furnace;

7 - combustion tube;

8 - dust collector;

10 - flow controller;

11 - converter for converting carbon monoxide to carbon dioxide;

12 - desulphurizer;

13 - carbon dioxide infrared detector.

Note: The caranalyzer provided with a carbon monoxide detection cell does not need a converter for converting carbon monoxide to carbon dioxide.

Figure 2 - Diagram of infrared absorption caranalyzer

5.3.2 Gas source

5.3.2.1 The gas carrier system includes an oxygen container, a two-stage pressure regulator and a sequential control part that ensures the supply of suitable pressure and rated flow.

5.3.2.2 The power gas source system includes the power gas (5.2.10), a two-stage pressure regulator and a sequential control part that ensures the supply of suitable pressure and rated flow.

5.3.3 High-frequency induction furnace

The requirements for melting temperature of the sample shall be met.

5.3.4 Control system

5.3.4.1 Microprocessor system includes the central processing unit, memory, keyboard input device, information center display screen, analysis result display screen and analysis result printer, etc.

5.3.4.2 Control functions include automatic loading and unloading of crucibles and lifting and drop of furnace table; automatic cleaning; selection and setting of analysis conditions; monitoring, alarming and interruption of analysis process; collection, calculation, correction and processing of analysis data.

5.3.5 Measuring system

It is mainly composed of an electronic balance controlled by a microprocessor, an infrared analyzer and an electronic measuring element.

The fluctuation of the measured results shall be within the allowable error range, so as to confirm the linearity of the system; otherwise, the linearity of the system shall be adjusted according to the instrument manual.

5.5.5 Determination

5.5.5.1 According to the carbon content range of the sample to be tested, respectively select the best analysis conditions of the instrument, such as the combustion integration time of the instrument, the setting of the comparison level (or set number), etc.

5.5.5.2 Place the weighed sample (5.5.1) evenly in the crucible (5.2.11) that is pre-filled with 0.30 g ± 0.01 g of tin particles (5.2.6); cover with 0.50 g ± 0.01 g of pure iron (5.2.7) and 1.20 g ± 0.01 g of tungsten particles (5.2.8); take the crucible and place it on the crucible base of the furnace table; operate according to the instrument manual; start the analysis and read the results.

5.6 Determination and presentation of analysis results

If the absolute value of the difference between the two independent analysis results of the same sample is not greater than the repeatability limit r, take the arithmetic mean as the analysis result. If the absolute value of the difference between the two independent analysis results is greater than the repeatability limit r, increase the number of measurements and determine the analysis results in accordance with the provisions of Appendix A. Round off the analysis results according to GB/T 8170.

5.7 Precision

In this document, calculate the precision according to the statistical methods of GB/T 6379.1 and GB/T 6379.2; the precision of this method is shown in Table 4. See Table B.2 in Appendix B for raw data.