GB/T 3558-2014 PDF in English
GB/T 3558-2014 (GB/T3558-2014, GBT 3558-2014, GBT3558-2014)
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Determination of Chlorine in Coal
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Standards related to: GB/T 3558-2014
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GB/T 3558-2014: PDF in English (GBT 3558-2014) GB/T 3558-2014
GB
ICS 73. 040
D 21
National Standard of the People's Republic of China
Replacing GB/T 3558-1996
Determination of chlorine in coal
(ISO 587.1997, Solid mineral fuels -
Determination of chlorine using Eschka mixture, NEQ)
ISSUED ON. JUNE 09, 2014
IMPLEMENTED ON. OCTOBER 01, 2014
Issued by. General Administration of Quality Supervision, Inspection
and Quarantine (AQSIQ) of the People's Republic of China;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword... 3
1. Scope ... 4
2. Normative references ... 4
3. Method A. High temperature combustion hydrolysis - potentiometric titration ... 4
4. Method B. Eschka mixture melt sample – potassium hydrogen sulfate titration ... 12
5. Test report ... 15
Annex A ... 16
Foreword
This Standard is drafted according to the rules given by GB/T 1.1-2009.
This Standard replaces GB/T 3558-1996 Determination of chlorine in coal. Compared
with GB/T 3558-1996, except the editorial modifications, the main changes are as follows.
-- Change the preparation concentration (see 3.2.2, or 2.2.2 in 1996 version) and
adding amount (see 3.4.2, or 2.4.2 in 1996 version) of the sulfuric acid solution;
-- Change the concentration of the silver nitrate standard solution (see 3.2.6 or
2.2.9 in 1996 version);
-- Add a potentiometric titration assembly, using the silver-silver chloride reference
electrodes available on the market (see 3.3.2).
Using re-drafting method, this Standard is compiled with reference to ISO 587.1997 Solid
mineral fuels – Determination of chlorine using Eschka mixture. This Standard is not
equivalent to ISO 587.1997.
Determination of chlorine in coal
1. Scope
This Standard specifies the summary of method, reagents and materials, apparatus, test
procedure, calculation of results and precision for the determination of total chlorine content
in coal using the high temperature combustion hydrolysis - potentiometric titration and Aldrin
melt sample - potassium hydrogen sulfate titration.
This Standard is applicable to brown, bituminous coal and anthracite.
2. Normative references
The following documents are indispensable for the application of this Standard. For dated
reference, the versions dated apply to this Standard. For undated references, the latest
edition of the normative document (including all modifications) referred to applies.
GB/T 483 General rules for analytical and testing methods of coal
3. Method A. High temperature combustion hydrolysis -
potentiometric titration
3.1 Summary of method
A coal sample is combusted and hydrolyzed in the mixed gas flow of oxygen and water
vapor. All chlorines contained in the coal are converted to chlorides and dissolved in the
water quantitatively. Titrate the concentration of chlorine ions in the condensate directly by
silver nitrate potentiometric method. Use the silver as an indicator electrode and the silver-
silver chloride as a reference electrode. Calculate the total chlorine content in the coal
sample according to the consumed volume of silver nitrate standard solution.
3.2 Reagents and materials
During analysis, unless otherwise stated, use only reagents of recognized analytical grade
and only distilled water or deionized water or water of equivalent purity.
3.2.1 Absolute ethyl alcohol. C2H5OH, ρ20°C=0.79 g/mL.
3.2.2 Sulfuric acid solution. (1 + 23) (V1 + V2), add 1 volume of concentrated sulfuric acid
of reagent grade to 23 volumes of water slowly, and mix uniformly.
3.2.3 Sodium hydroxide solution. 10 g/L, dissolve 1 g of reagent grade sodium hydroxide
in 100 mL of water.
and hold for 15 min.
3.4.2.2 After completion of combustion-hydrolysis, take off the absorber; cut off the
supply of oxygen and water vapor; remove the sample injection rod; and withdraw the
porcelain boat by using the nichrome wire with a hook.
3.4.2.3 Pour the sample solution from absorption flasks to a 200 mL beaker. Wash the
flasks and gas tubing with distilled water. The washing lotion is transferred to the beaker
directly. Add the distilled water to (140 ± 10) mL. Then add 3 drops of the bromocresol
green indicator (see 3.2.7) to the beaker. Neutralize the solution with sodium hydroxide
solution (see 3.2.3) till the indicator becomes light blue. Then, add 1 mL of the sulfuric
acid solution (see 3.2.2), 3 mL of the saturated potassium nitrate solution (see 3.2.4), and
5 mL of the sodium chloride standard solution (see 3.2.5).
3.5 Potentiometric titration
3.5.1 Preparation
Place the beaker containing 150 mL of the distilled water on a titration set. Insert an
indicator electrode. Connect the titration assembly (self-made silver-silver chloride
reference electrode) according to Figure 4. Connect to the self-made silver-silver chloride
reference electrode with a salt bridge; or connect the titration assembly (silver-silver
chloride reference electrode available on the market) according to Figure 5. Connect the
indicator electrode lead and reference electrode lead to measuring terminal of a millivolt
ammeter. Put the stirring bars inside. Start up the stirrer. At this point, the ammeter should
indicate the potential difference (±m V); otherwise, it shall verify if the connection of
measuring circuit is correct.
3.5.2 Potentiometric calibration of end point
3.5.2.1 Preparation of blank solution. Same as 3.4.2, except that no coal sample is added.
3.5.2.2 Potentiometric calibration of titration end point. Place a beaker containing the
blank solution on a titration set. Drip the silver nitrate standard solution that has a definite
dripping quantity at a rate of 0.03 mL/s. Record the potential value at this point. Carry out
the potential determinations twice as above. The difference between the measured values
shall not exceed ±3 mV. Use the mean as the potential of titration end point. For the first
determination or change of chemical reagents, draw the differential curve of titration
according to Annex A to determine the consumed volume (V1) of silver nitrate standard
solution when the potential of end point is calibrated.
3.5.3 Titration for sample solution
Place a beaker containing the sample solution on a titration set. Firstly, drip the silver
nitrate standard solution at a rate of 0.05 mL/s; observe the reading of millivolt ammeter.
When it is close to calibrated potential of end point, make titration at a rate of 0.02 mL/s
till the calibrated potential of end point is reached. After 1 min of stirring, write down the
4.4.1 Weigh (1 ± 0.1)g of the coal sample (accurate to 0.000 2 g) for general analytic test.
Place in a crucible in where 3 g (to the nearest 0.1 g) of the Eschka mixture is contained.
Mix thoroughly. Then, cover with a further 2 g of the Eschka mixture. Place the crucible in
the muffle furnace. Keep the furnace door half-opened. Raise the temperature to (680 ±
20)°C. Maintain this temperature for 3 h.
4.4.2 Withdraw the crucible from the muffle furnace. Cool to room temperature. Transfer
the incinerated mixture to a 250 mL beaker. Wash the inner wall of crucible with 50 mL ~
60 mL of hot water. Add the washing lotion to the beaker.
4.4.3 Filter the solution through a qualitative filter paper by decantation method. Wash
the residues with hot water once or twice. Then transfer the residues to a funnel. Wash
the residues and paper thoroughly with hot water till there is no chlorine ions (without
turbidity if it is examined with the silver nitrate solution). In the process of filtration and
residues washing, control the filtrate to a final volume of about 110 mL.
4.4.4 Add 1 drop of the phenolphthalein indicator to filtrate. Regulate with the nitric acid
until the red colour disappears, with an extra addition of 5 mL; add 5 mL of the sodium
chloride standard solution and 10 mL of the silver nitrate standard solution accurately with
a one-mark pipette. Stand over a period of 2 min ~ 3 min. Measure 3 mL of hexanol; cover
with a watch glass. Place the beaker on an electromagnetic stirrer and stir for 1 min rapidly.
Then add 1 mL of the ammonium iron sulfate solution. Titrate with the potassium hydrogen
sulfate standard solution. The end point is reached when the solution changes to light
orange from cream white. Write down the volume (V3) of consumed potassium hydrogen
sulfate standard solution.
4.4.5 Determination of blank value
Determine each lot of coal samples. Carry out two or more blank determinations by using
the same procedure as described in 4.4.1 ~ 4.4.4. Take the mean as the blank value (V4).
4.5 Calculation of results
The chlorine content of the coal is calculated according to Formula (3) and is recorded
with the mean of two repeated determinations by rounding off to the third decimal places
in according with GB/T 483.
Where.
Clad – is the chlorine content of the air-dried coal sample, expressed as a percentage
(%) by mass;
V3 – is the volume, in millilitres, of the potassium hydrogen sulfate standard solution used
in the determination;
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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