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1. Scope of application This standard applies to coal, coal coke, water-coal slurry, and coal gangue. 2. Reagents: The water mentioned is deionized water or distilled water of equivalent purity. 3. Instrumentation and Equipment 3.1 High-temperature muffle furnace: Equipped with a temperature control system that enables maintenance of a temperature of (1000±10)°C. 3.2 Analytical balance: sensitivity of 0.1g. 3.3 Atomic absorption spectrophotometer. 3.4 Ceramic crucibles. 3.5 Ash dish 4. Preparation of ash sample: Weigh a certain amount of coal sample for general analysis or coal water slurry sample into the ash dish (for coal samples used in general analysis, the weight per square centimeter should not exceed 0.15 g; for coal water slurry samples, 15 g to 18 g is used, and these samples are pre-dried at 105°C to 110°C). The ash dish is then placed in a muffle furnace with a temperature not exceeding 100°C; under conditions of natural ventilation with a gap of about 15 mm left in the furnace door, the temperature is raised slowly to 500°C over 30 minutes. After remaining at this temperature for 30 minutes, the temperature is increased to (815±10)°C, and the sample is burned there for 2 hours. Once taken out and allowed to cool, the ash sample is ground to a particle size of 0.1 mm using an agate mortar. Then, in the ash tray, it is burned at (815±10)°C for another 30 minutes, until the change in its mass does not exceed one thousandth of the mass of the ash sample, at which point the mass becomes constant. Remove it, place it in the air for about 5 minutes, and then transfer it to a desiccator. If sampling is not carried out promptly, it is necessary to calcine at (815±10)°C for another 30 minutes before sampling. 5. Methods for the determination of potassium, sodium, iron, calcium, magnesium, and manganese (atomic absorption method) 5.1 Method overview: The ash sample is decomposed using hydrofluoric acid and perchloric acid; in a hydrochloric acid medium, a releasing agent such as lanthanum or strontium is added to eliminate the interference of elements like aluminum and titanium on the determination of calcium and magnesium. Atomic absorption analysis is then performed using an air-acetylene flame. 5.2 Reagents 5.2.1 Hydrofluoric acid: 40% or higher. 5.2.2 Perchloric acid: 70.0% or more. 5.2.3 Hydrochloric acid solution: volume ratio of (1+1). 5.2.4 Hydrochloric acid solution: volume ratio of (1+3). 5.2.5 Potassium oxide standard reserve solution: 1 mg/mL. Weigh 1.5829 g of high-purity potassium chloride (99.9%), which has been calcined at 500°C for 30 minutes, into a 400 mL beaker. Dissolve it in water, transfer the solution to a 1000 mL volumetric flask, dilute with water to the mark, mix well, and then transfer it to a plastic bottle. 5.2.6 Sodium oxide standard reserve solution: 1 mg/mL. Weigh 1.885 g of high-purity sodium chloride (99.99%), which has been calcined at 500°C for 30 minutes, into a 400 mL beaker. Dissolve it in water, transfer the solution to a 1000 mL volumetric flask, dilute with water to the mark, mix well, and then transfer it to a plastic bottle. 5.2.7 Mixed standard working solution for potassium, sodium, and manganese: containing 50 μg/mL of K2O, 50 μg/mL of Na2O, and [amount] μg/mL of MnO2. Accurately transfer 25 mL each of the potassium oxide standard reserve solution, sodium oxide standard reserve solution, and manganese dioxide standard reserve solution into a 500 mL volumetric flask, dilute with water to the mark, mix well, and transfer to a plastic bottle. 5.3 Analysis Steps 5.3.1 Preparation of the sample solution Weigh 0.1 g ± 0 of the ash sample. 01 g (accurately weighed to 0.0002 g) is placed in a polytetrafluoroethylene crucible, moistened with water, to which 2 mL of perchloric acid and 10 mL of hydrofluoric acid are added. The mixture is then heated slowly on an electric heating plate at a low temperature (not exceeding 250°C) until it is nearly dry; after that, the temperature is increased further until almost no white smoke remains. The solution is continued to be heated until it is completely dry without becoming blackened. Remove the crucible and let it cool slightly; then add 10 mL of hydrochloric acid solution (1+1) and 10 mL of water. Place it back on an electric heating plate and heat it to near boiling point, maintaining that temperature for 2 minutes. Remove the crucible, transfer the solution contained in it to a 100 mL volumetric flask using hot water, cool it to room temperature, dilute to the mark with water, and mix well. 5.3.2 Preparation of the sample blank solution: When analyzing a batch of samples, a sample blank solution should be prepared simultaneously. The preparation of this blank solution involves the same procedures as those described in 5.3.1, with the exception that no sample is added. 5.3.3 Preparation of the sample solution to be analyzed: 5.3.3.1 Sample solution for potassium, sodium, and manganese analysis: Accurately transfer 5 mL each of the sample solution (5.3.1) and the sample blank solution (5.3.2) into a 50 mL volumetric flask, add 1 mL of hydrochloric acid solution (1+4), and then dilute to the mark with water. 5.4 Preparation of mixed standard solutions: 5.4.1 Mixed standard series solutions for potassium, sodium, and manganese: Transfer 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, 6 mL, 7 mL, 8 mL, 9 mL, and 10 mL respectively of the mixed standard working solutions for potassium, sodium, and manganese into a 100 mL volumetric flask, add 4 mL of hydrochloric acid solution (5.2.4), dilute to the mark with water, and mix well. 5.4.2 Determination of potassium and sodium 5.4.2.1 Determination of instrument operating conditions: Apart from the analysis lines for each element specified in Table 1 and the flame gases used, other parameters of the instrument, such as lamp current, bandwidth, burner height and angle, as well as the flow rates and pressures of the fuel gas and oxidizing gas, should be adjusted to their optimal values. Table 1 Recommended operating conditions for the instrument Element analysis line/nm Flame gas K 766.5 Acetylene-air Na 589.0 Acetylene-air Fe 248.3 Acetylene-air Ca 422.7 Acetylene-air Mg 285.2 Acetylene-air Mn 279.5 Acetylene-air 5.4.2.2 Measurement: Under the operating conditions for the instrument determined in 5.4.2.1, the absorbance of the corresponding elements in the standard series solutions (5.4.1) and the sample solutions to be analyzed (5.3.3.1) is measured respectively. 5.4.2.3 Preparation of working curves: The mass concentration of each component measured in the standard series solutions (in μg/mL) is used as the horizontal axis, while the corresponding absorbance value is used as the vertical axis, to plot the working curves for each component. 5.5 Calculation of results: The mass fraction of each component is calculated using equation (1): ………………………… (1) Where: ----- is the mass concentration of the component determined from the working curve, expressed in micrograms per milliliter (μg/mL) ； m----- is the mass of the gray sample, in grams (g). 6. Source of the method The method is derived from GB/T 1574-2007