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GB/T 214-2007 English PDF (GBT214-2007)

GB/T 214-2007 English PDF (GBT214-2007)

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GB/T 214-2007: Determination of total sulfur in coal

This Standard specifies the method principle, reagents and materials, apparatus, test procedures, results calculation and precision, etc. of the Eschka method, coulometric titration, high temperature combustion neutralization method for the determination of sulfur in coal. For the arbitration analysis, the Eschka method shall be taken.
GB/T 214-2007
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 75.160.10
D 21
Replacing GB/T 214-1996, GB/T 18856.8-2002
Determination of Total Sulfur in Coal
(ISO 334:1992, Solid Mineral Fuels - Determination of Total Sulfur - Eschka Method, NEQ; ISO 351:1996, Solid Mineral Fuels ?€? Determination
of Total Sulfur ?€? High Temperature Combustion Method, NEQ)
ISSUED ON: NOVEMBER 01, 2007
IMPLEMENTED ON: JUNE 01, 2008
Issued by: General Administration of Quality Supervision, Inspection
and Quarantine;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Eschka Method ... 5
4 Coulometric Titration Method ... 8
5 High Temperature Combustion Neutralization Method ... 12
6 Test Report ... 18
Determination of Total Sulfur in Coal
1 Scope
This Standard specifies the method principle, reagents and materials, apparatus, test procedures, results calculation and precision, etc. of the Eschka method, coulometric titration, high temperature combustion neutralization method for the determination of sulfur in coal. For the arbitration analysis, the Eschka method shall be taken. This Standard is applicable to the lignite, bituminous coal, anthracite, and coke; it is also applicable to the dry coal samples of the water-coal-slurry.
2 Normative References
The provisions in following documents become the provisions of this Standard through reference in this Standard. For dated references, the subsequent amendments (excluding corrigendum) or revisions do not apply to this Standard, however, parties who reach an agreement based on this Standard are encouraged to study if the latest versions of these documents are applicable. For undated references, the latest edition of the referenced document applies.
GB/T 212 Proximate Analysis of Coal (GB/T 212-2001, eqv ISO 11722:1999; eqv ISO 1171:1997; eqv ISO 562:1998)
GB/T 483 General Rules for Analytical and Testing Methods of Coal
3 Eschka Method
3.1 Principle
The coal sample was mixed with the Eschka reagent and burned. The sulfur in the coal was converted into sulfate; and then the sulfate ion generated the barium sulfate precipitate. The total sulfur content in the coal shall be calculated based on the mass of the barium sulfate.
3.2 Reagents and Materials
3.2.1 Eschka reagent (hereinafter referred to as Drinox): evenly mix the 2 pieces of the mass of chemically pure light magnesium oxide (GB/T 9857) and 1 piece of mass of chemically pure anhydrous sodium carbonate (GB/T 639); and grind them to the substance with the particle size of less than 0.2mm; then store in a sealed container. 4.3.2 Electrolytic cell and electromagnetic stirrer
The electrolytic cell has a height of (120~180) mm, a capacity of no less than 400mL; equipped with platinum electrolytic electrode pair with an area of about 150mm2, and platinum indicator electrode pair with an area of about 15mm2. The response time of the indicator electrode shall be less than 1s; the speed of the electromagnetic stirrer is about 500r/min, which can be adjusted continuously.
4.3.3 Coulomb integrator
The integral linear error in the range of electrolytic current (0~350) mA shall be less than 0.1%; equipped with (4~6) digital display or printer.
4.3.4 Sample-delivery program controller
It can move forward and backward flexibly according to the prescribed programs. 4.3.5 Air supply and purification device
It consists of the electromagnetic pump and purification tube. The air supply volume is about 1500mL/min; and the air extraction volume is about 1000mL/min. The purification tube contains sodium hydroxide and color-changing silica gel. 4.4 Test procedures
4.4.1 Test preparation
4.4.1.1 Raise the temperature of tubular high temperature furnace to 1150??C; use another set of platinum rhodium-platinum thermocouple pyrometer to determine the position ad length of high temperature zone, and the position at 500??C. 4.4.1.2 Adjust the sample-delivery program controller, so that the pre-decomposition and pyrolysis of the coal samples are at the positions of 500??C and 1150??C, respectively.
4.4.1.3 Fill the outlet of the combustion tube with cleaned and dried glass fiber cotton. Fill the aluminum silicate cotton with a thickness of about 3 mm at a distance of (80 ~ 100) mm from the outlet end.
4.4.1.4 Assemble the following devices together, such as program controller, tubular high temperature furnace, Coulomb integrator, electrolytic cell, electromagnetic stirrer, and air supply and purification device. The connection among the combustion tube, piston and the electrolytic cell shall be close to each other, and sealed with a silicone rubber tube.
4.4.1.5 Start the air extraction and air supply pumps; adjust the air extraction flow to 1000mL/min. Then close the piston between the electrolytic cell and combustion tube. 4.4.3.2 Start the air supply pump and the air extraction pump; and adjust the air extraction flow to 1000mL/min. Under air extraction condition, add the electrolyte to the electrolytic cell and start the electromagnetic stirrer.
4.4.3.3 Put a small amount of non-measured coal sample into the porcelain boat; perform the endpoint potential adjustment test as described in 4.4.3.4. If the display value of the Coulomb integrator is 0 after the test, the measurement shall be repeated until the display value is no longer to be 0.
4.4.3.4 Take (0.05??0.005) g (accurate to 0.0002g) of air-dry coal sample in a porcelain boat with a particle size of less than 0.2mm; and cover the coal sample with a thin layer of tungsten trioxide. Place the porcelain boat on the quartz tray for sample delivery, start the sample-delivery program controller, and the coal sample shall be automatically sent into the furnace, and the coulometric titration shall begin immediately. After the test, the Coulomb integrator displays the milligrams or mass fraction of sulfur, or printed by a printer.
4.4.4 Calibration inspection
During the measurement of the instrument, coal reference materials or other control samples should be used regularly (after every 10 ~ 15 measurements are
recommended) to verify the stability and validity of the sulfur analyzer. If the measurement value of the coal reference material or other control samples exceed the uncertainty range (control limit) of the standard value; the instrument shall be re- calibrated according to the above procedures; and re-measure the samples since the previous inspection.
4.5 Result calculation
If the Coulomb integrator finally displays the milligrams of sulfur, the total sulfur mass fraction shall be calculated as per Formula (2):
Where:
St,ad ?€? total sulfur mass fraction in the coal samples for general analysis, in %; m1 ?€? display value of Coulomb integrator, in mg;
m ?€? mass of coal sample, in mg.
4.6 Precision of method
The repeatability and reproducibility for the determination of total sulfur by Coulometric titration method can refer to the provisions of Table 2.
5.2.9 Sodium hydroxide standard solution: c (NaOH) = 0.03mol/L.
5.2.9.1 Preparation of sodium hydroxide standard solution
Take 6.0g of guarantee reagent of sodium hydroxide (GB/T 629); dissolve it in 5000mL of distilled water that has been boiled and cooled; mix well; put it in the bottle; and plug it with a rubber stopper.
5.2.9.2 Calibration of the concentration of sodium hydroxide standard solution Take (0.2~0.3) g (accurate to 0.0002g) of potassium hydrogen phthalate that has been dried at 120??C for 1h in advance; place it into 250mL conical flask; dissolve by about 20mL water; take phenolphthalein as an indicator; titrate with sodium hydroxide standard solution to red; calculate its concentration according to Formula (3): Where:
c ?€? concentration of sodium hydroxide standard solution, in mol/L;
m ?€? mass of potassium hydrogen phthalate, in g;
V ?€? consumed amount of sodium hydroxide standard solution, in mL;
0.2042 ?€? molar mass of potassium hydrogen phthalate, in g/mmol.
5.2.9.3 Calibration of titer of sodium hydroxide standard solution:
Take about 0.2g (accurate to 0.0002g) of coal reference material, place it in a combustion boat, and cover it with a thin layer of tungsten trioxide. Test according to 5.4 and record the amount of sodium hydroxide solution at the time of titration. Calculate the titer according to Formula (4):
Where:
T - the titer of sodium hydroxide standard solution, in g/mL;
m ?€? the mass of coal reference material, in g;
S?€?t,ad ?€? the mass fraction of air dry basis total sulfur in coal reference material (see 4.4.2.2.1), in %;
V ?€? the consumed amount of sodium hydroxide solution, in mL.
1300??C above; length is about 77mm; upper width is about 12mm; height is about 8mm. 5.4 Test procedures
5.4.1 Test preparation
5.4.1.1 Insert the combustion tube into the high-temperature furnace so that the end of the small-diameter tube extends out of the furnace mouth 100mm, and connect a section of silicone rubber tube with a length of about 30mm.
5.4.1.2 The high temperature furnace is heated and stabilized at (1200??10) ??C, and the position and length of the high temperature constant temperature zone and 500 ??C temperature zone in the combustion tube are measured.
5.4.1.3 Connect the drying tower, oxygen flowmeter, combustion tube and absorption bottle of high temperature furnace; and check the air tightness of the devices. 5.4.2 Measurement procedures
5.4.2.1 Heat and control the high temperature furnace at (1200??10) ??C.
5.4.2.2 Separately take 100mL of neutralized hydrogen peroxide solution by a measuring cylinder; pour them into 2 absorption bottles; plug the stopper with a gas filter and connect it to the small-diameter end of the combustion tube. Check its air tightness again.
5.4.2.3 Take an air-dried coal sample (0.20??0.01) g (accurate to 0.0002 g) with the particle size of less than 0.2 mm in the combustion boat and cover a thin layer of tungsten trioxide.
5.4.2.4 Put the combustion boat containing coal samples on the inlet end of the combustion tube; then plug it with a T-shaped tube with a rubber stopper; and then introduce oxygen at a flow rate of 350 mL/min. Use a nichrome wire push rod to push the combustion boat to the 500??C temperature zone and keep it for 5 minutes; then push the boat to the high temperature zone, and immediately withdraw the push rod to burn the coal sample in the zone for 10 minutes.
5.4.2.5 Stop supplying oxygen; remove the absorption bottle near the combustion tube; and then remove the other absorption bottle.
5.4.2.6 Take off the T-shaped tube with rubber stopper; and take out the combustion boat by the nichrome wire hook.
5.4.2.7 Remove the stopper of the absorption bottle and clean the gas filter for (2 ~ 3) times by distilled water. When cleaning, press the rubber suction bulb to discharge the lotion.

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