GB/T 1574-2007Test method for analysis of coal ash (English PDF)

6.1 Preparation of Test Solution

6.1.1 Reagents

6.1.2 Preparation for sample solution

Weigh 0.10 g (accurate to 0.0002 g) of ash sample; place into a silver crucible; wet it with a few drops of ethanol; add 2 g of sodium hydroxide;

6.1.3 Preparation of blank solution

Same as 6.1.2, but ash sample is not added. This solution is named as solution B.

6.2 Determination of Silicon Dioxide (Silicon Molybdenum Blue

Spectrophotometric Method)

6.2.1 Method summary

With the existence of ethanol, in hydrochloric acid [c(HCl) = 0.1 mol/L] medium, metasilicic acid reacts with molybdic acid to generate stable silicon-molybdenum yellow. Raise the acidity to 2.0 mol/L or above, use ascorbic acid to reduce the silicon-molybdenum yellow into silicon molybdenum blue; and determine silicon dioxide content with spectrophotometric method.

6.2.2 Reagents

6.2.2.7 Standard stock solution of silicon dioxide. 1 mg/mL

Accurately weigh 0.5000 g (accurate to 0.0002 g) of spectral-pure silicon dioxide which has been burnt at 1000 °C + 10°C for 30 min; place into a platinum crucible that contains 5 g of anhydrous sodium carbonate (GB/T 639); mix it uniformly;

6.2.2.8 Standard working solution of silicon dioxide. 0.05 mg/mL

Accurately pipet 25 mL of standard stock solution of silicon dioxide; place it into a 400 mL beaker that contains 100mL of hydrochloric acid solution (6.2.2.3).

6.2.3 Analysis procedures

6.2.3.1 Drawing of working curve

6.2.3.1.1 Accurately pipet 0 mL, 5 mL, 10mL, 15 mL, 20 mL, 25 mL, 30 mL of standard working solution of silicon dioxide (6.2.2.8). Respectively inject them into 100mL volumetric flasks; successively add 5 mL, 4 mL, 3 mL, 2 mL, 1 mL, 0 mL of hydrochloric acid solution (6.2.2.4); add water to 27 mL; add 8 mL of ethanol; add 5 mL of ammonium molybdate solution; shake well; place it at 20°C ~30°C for 20 min.

6.2.3.2 Determination of sample

6.2.3.2.1 Accurately pipet 5 mL of solution A (6.1.2) and 5 mL of solution B (6.1.3) respectively; respectively inject into 100mL volumetric flasks; add 8 mL of ethanol, about 20 mL of water, 5 mL of ammonium molybdate solution; shake well; place it at 20°C ~30°C for 20 min.

6.2.3.2.2 It's operated according to 6.2.3.1.2 […]

6.2.5 Method precision

Precision of determination result for silicon dioxide is shown in Table 1.

6.3 Continuous Determination of Ferric Oxide and Titanium Dioxide

(Spectrophotometric Method with Ferrotitanium Reagent)

6.3.1 Method summary

Under the condition of pH= 4.7~4.9, ferric ion reacts with ferrotitanium reagent to generate purple complex; use spectrophotometric method to determine ferric oxide.

Add adequate amount of ascorbic acid, so that purple of the solution disappears; titanic ion reacts with ferrotitanium reagent to generate yellow complex, use spectrophotometric method to determine titanium dioxide.

6.3.2 Reagents and materials

6.3.2.1 Ascorbic acid.

6.3.2.2 Ferrotitanium reagent solution. 20 g/L. Weigh 2 g of ferrotitanium reagent (C6H4O8S2Na2); dissolve it into water; dilute to 100 mL with water.

6.3.2.8 Standard working solution of ferric oxide. 0.1 mg/mL

Accurately pipet 10mL of standard stock solution of ferric oxide; place into a 100mL volumetric flask; dilute to the mark with the hydrochloric acid solution (6.3.2.4); shake well.

6.3.2.11 Congo red test paper.

6.3.3 Analysis procedures

6.3.3.1 Drawing of working curve

6.3.3.2 Determination

6.3.3.2.1 Accurately pipet 5 mL of solution A and 5mL of solution B; respectively pour them into 50 mL volumetric flasks; add 10 mL of ferrotitanium reagent solution; shake well. Drop-add ammonia water until the solution accurately appears in red (if ferrum content is very low, small piece of Congo red test paper may be added; drop-add ammonia water until the test paper becomes red); add 5 mL of buffer solution; dilute to the mark with water; shake well. After being placed for 1h, use a 1cm cuvette to determine its absorbance at wave length of 570 nm.

6.3.5 Method precision

7 Macro-analysis Method of Silicon Dioxide, Ferric Oxide, Aluminum Oxide, Calcium Oxide, Magnesium Oxide and Titanium Dioxide

7.1 Determination of Silicon Dioxide (Animal Glue Condensing Mass Method)

7.1.1 Method summary

Add sodium hydroxide into ash sample for melting; place it into boiling water for leaching; acidify it with hydrochloric acid; evaporate it to dryness; in the medium of hydrochloric acid, use animal glue to condense silicic acid; precipitate and filter it; burn and weigh it.

7.1.2 Reagents and materials

7.1.3 Test procedure

7.1.5 Method precision

Precision of determination result of silicon dioxide is shown in Table 8.

7.2 Continuous Determination of Ferric Oxide and Aluminum Oxide

(Complexometric Titration with EDTA)

7.2.1 Method summary

Under the condition of PH=1.8~ 2.0, use sulfosalicylic acid as the indicator; use EDTA standard solution to titrate. Add excessive EDTA for complex with aluminum ion and titanium ion, etc. Under the condition of pH = 5.9, use xylenol orange as the indicator; use zinc salt to titrate the remaining EDTA; then add villiaumite to replace the EDTA that has been complex with aluminum ion and titanium ion; use zinc acetate standard solution to titrate.

7.2.2 Reagents

7.2.3 Analysis procedures

7.2.3.1 Accurately pipet 20 mL of solution C; place into a 250mL beaker; dilute with water to about 50mL; the remaining procedures are operated in accordance with calibration method in 7.2.2.9.

7.2.4 Result calculation

7.2.4.1 The mass fraction w(Fe2O3)(%) of ferric oxide is calculated according to Formula (14).

7.2.4.2 The mass fraction w(Al2O3)(%) of aluminum oxide is calculated according to Formula (15).

7.2.5 Method precision

7.3 Determination of Calcium Oxide (EDTA Complexometric Titration)

7.3.1 Method summary

Use triethanolamine to mask ferrum icon, aluminum icon, titanium icon and manganese icon. Under the condition of pH >=12.5, use calcein-thymolphthalein as indicator; use EDTA standard solution to titrate.

7.3.2 Reagents

7.5.5 Method precision

The precision of determination result of titanium dioxide is shown in Table 13.

8.1 Barium Sulfate Mass Method

8.1.1 Method summary

Leach the sulfur in ash sample with hydrochloric acid; filter the solution; neutralize the filtered solution with ammonium hydroxide; and precipitate ferrum. Add barium chloride into the solution to generate barium sulfate sediment; and weigh it.

8.1.2 Reagent

8.1.2.1 Hydrochloric acid (GB/T 622) solution. volume ratio is (1+3).

8.1.2.2 Ammonia (GB/T 631) solution. volume ratio is (1+1).

8.1.2.3 Hydrochloric acid (GB/T 622) solution. volume ratio is (1+1).

8.1.2.4 Barium chloride solution. 100 g/L. Weigh 10g of barium chloride (GB/T 652); dissolve it in water; dilute to 100 mL with water.

8.1.2.5 Silver nitrate solution. 10g/L. Weigh 1g of silver nitrate (GB/T 670); dissolve it in water; dilute to 100 mL with water; add several drops of nitric acid (GB/T 626); store in a brown bottle.

8.1.2.6 Methyl orange indicator. 2g/L. Weigh 0.2 g of methyl orange; dissolve in water; dilute to 100 mL with water.

8.1.2.7 Filter paper. medium-speed qualitative filter paper.

8.1.2.8 Filter paper. slow-speed qualitative filter paper.

8.1.3 Analysis procedure

8.1.4 Result calculation

The mass fraction w(SO3)(%) of sulfur trioxide is calculated according to Formula (21).

8.1.5 Method precision

The precision of determination result of sulfur trioxide is shown in Table 14.

8.2 Combustion Neutralization Method

8.2.1 Method summary

Use activated carbon powder as additive; ash sample is decomposed in 1300°C airflow; use hydrogen oxide solution to absorb; use methyl red - bromocresol green as indicator; use sodium hydroxide standard solution to titrate.

8.2.2 Reagents and materials

8.2.3 Instruments and equipment

8.2.3.5 T-shaped glass tube. used for installation of push rod and air inlet.

8.2.3.6 Gas flowmeter. the maximum measuring range is 1 L/min.

8.2.3.7 Gas filter. glass melting plate made from the sintering of glass sand; model of melting plate. G2; pore size. 4.9 µm~9 µm; used for gas dispersion.

8.2.3.8 Conical flask. 250mL.

8.2.3.9 Gas bottle. 250 mL, 2 pieces; one with potassium hydroxide solution (8.2.2.4) and the other with concentrated sulfuric acid (8.2.2.2).

8.2.3.10 Drying tower. 250 mL, with allochroic silicagel inside.

8.2.3.11 A water suction pump or vacuum pump.

9.1 Method 1

9.1.1 Method summary

Use hydrofluoric acid - perchloric acid to decompose ash sample to remove silicon dioxide; pipet some solution; add it in ammonium molybdate and ascorbic acid solution to generate phosphorous molybdenum blue; use spectrophotometric method to determine.

9.1.2 Reagent

9.1.2.9 Reagent solution. add 10 mL of ascorbic acid solution (9.1.2.5) and 5 mL of antimony potassium tartrate solution (9.1.2.8) into 35 mL of ammonium aluminate - sulfuric acid solution (9.1.2.7); mix up uniformly. The solution shall be prepared immediately before use.

9.1.3 Analysis procedure

9.1.3.1 Preparation of to-be-tested sample solution

Weigh 0.1000g of ash sample (accurate to 0.0002g); put it into a 30 mL PTFE crucible; wet it with water; add 2 mL of perchloric acid and 10 mL of hydrofluoric acid;

9.1.3.2 Preparation of blank solution

It is as specified in 9.1.3.1, but ash sample is not included.

9.1.3.3 Drawing of working curve

9.1.3.3.1 Accurately pipet 0mL, 1mL, 2mL, and 3mL of standard working solution of phosphorus pentoxide; respectively pour them into 50mL volumetric flasks; add 5 mL of reagent solution (9.1.2.9); maintain for 1 min ~2 min; then dilute to the mark with water; shake well. After being placed at 20°C~30°C for 1h, use a 1cm~3 cm cuvette to determine its absorbance at wave length of 650 nm on spectrophotometer.

9.2.2 Reagent

9.2.2.1 Hydrofluoric acid (GB/T 620).

9.2.2.2 Sulfuric acid (GB/T 625). relative density is 1.84.

9.2.2.3 Sulfuric acid (GB/T 625) solution. c(1/2H2SO4)=0.2 mol/L.

9.2.3 Analysis procedure

9.2.4 Result calculation

The mass fraction w(P2O5)(%) of phosphorus pentoxide is calculated according to Formula (26). […]