ASTM D6721-01

Standard Test Method for Determination of Chlorine in Coal by Oxidative Hydrolysis Microcoulometry

SCOPE
1.1 This test method covers the determination of total chlorine in coal.

General Information

• Status: Historical
• Publication Date: 09-Oct-2001
• ICS: 73.040 - Coals
• Technical Committee: D05 - Coal and Coke
• Drafting Committee: D05.29 - Major Elements in Ash and Trace Elements of Coal

Relations

• Replaced By: ASTM D6721-01(2006) - Standard Test Method for Determination of Chlorine in Coal by Oxidative Hydrolysis Microcoulometry
• Effective Date: 01-Apr-2006

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D 6721 – 01
Standard Test Method for
Determination of Chlorine in Coal by Oxidative Hydrolysis
Microcoulometry
This standard is issued under the fixed designation D 6721; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Significance and Use
1.1 This test method covers the determination of total 4.1 This test method permits measurements of the chlorine
chlorine in coal. content of coals.
2. Referenced Documents 5. Interferences
2.1 ASTM Standards: 5.1 Bromides and iodides, if present are calculated as
D 2013 Method of Preparing Coal Samples for Analysis chloride. However, fluorides are not detected by this test
D 3173 Test Method for Moisture in theAnalysis Sample of method.
Coal and Coke
6. Apparatus
D 3180 Practice for Calculating Coal and Coke Analyses
from As-Determined to Different Bases 6.1 Hydrolysis Furnace, which can maintain a minimum
temperature of 900°C.
D 4621 Guide forAccountability and Quality Control in the
Coal Analysis Laboratory 6.2 Hydrolysis Tube, made of quartz and constructed such
that when the sample is combusted in the presence of tungsten
D 5142 Test Methods for Proximate Analysis of the Analy-
sisSamplesofCoalandCokebyInstrumentalProcedures accelerator and humidified oxygen, the byproducts of combus-
tion are swept into a humidified hydrolysis zone. The inlet end
E 29 Practice for Using Significant Digits in Test Data to
Determine Conformance with Specifications shall allow for the introduction and advancement of the sample
boatintotheheatedzone.Theinletshallhaveasidearmforthe
2.2 Other Standards
ISO 5725-6:1994 Accuracy of measurement methods and introduction of the humidified oxygen gas.The hydrolysis tube
results-Part 6: Use in practice of accuracy values must be of ample volume, and have a heated zone with quartz
wool so that complete hydrolysis of the halogens is ensured.
3. Summary of Test Method
6.3 Titration Cell, containing a reference electrode, a work-
3.1 A 5.00 to 40.00 mg sample of coal is combusted with ing electrode, and a silver sensor electrode, a magnetic stirrer
tungstenacceleratorinahumidifiedoxygengasflow,at900°C. as well as an inlet from the hydrolysis tube.
Halogens are oxidized and converted to hydrogenated halides, 6.4 Microcoulometer, capable of measuring the potential of
which are flushed into a titration cell where they accumulate. the sensing-reference electrode pair, comparing this potential
Chlorineisconvertedtohydrochloricacid.Oncethechlorideis with a bias potential, and amplifying the difference to the
captured in the electrolyte of the titration cell, it can be working electrode pair to generate current. The microcoulom-
quantitatively determined by microcoulometery, where chlo- eter output voltage should be proportional to the generating
ride ions react with silver ions present in the electrolyte. The current.
silver ion thus consumed is coulometrically replaced and the 6.5 Controller, with connections for the reference, working,
total electrical work needed to replace it is proportional to the and sensor electrodes, for setting operating parameters and for
chloride in the test sample. data integration.
6.6 Hydration Tube, containing water, positioned before the
gasinletonthesidearmofthecombustiontube,throughwhich
This test method is under the jurisdiction of ASTM Committee D05 on Coal
oxygen gas bubbles to provide a hydrated gas flow.
and Coke and is the direct responsibility of Subcommittee D05.29 on Major
6.7 Dehydration Tube, positioned at the end of the hydroly-
Elements in Ash and Trace Elements of Coal.
Current edition approved Oct. 10, 2001. Published November 2001. sis tube so that effluent gases are bubbled through a 95 %
Annual Book of ASTM Standards, Vol 05.06.
sulfuric acid solution. Water vapor is subsequently trapped
Annual Book of ASTM Standards, Vol 14.02.
while other gases flow into the titration cell.
Available from International Organization for Standardization 1 Rue de
Varembé, Case Postale 56, CH-1211, Geneva 20, Switzerland
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6721–01
6.8 Gas-Tight Sampling Syringe, having a 50 µL capacity, 9. Sampling
capable of accurately delivering 10 to 40 µL of standard
9.1 Prepare the analysis sample in accordance with Method
solution.
D 2013 to pass a 250-µm (60 mesh) sieve.
6.9 Sample Boats, made of quartz, ceramic or platinum.
9.2 Analyze a separate portion of the analysis sample for
6.10 Balance, analytical, with a sensitivity to 0.00001 g.
moisture content in accordance with Test Method D 3173 or
Test Methods D 5142.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be
10. Preparation of Apparatus
used in all tests. Unless otherwise indicated, it is intended that
10.1 Fill the hydration tower with water and connect it to
allreagentsshallconformtothespecificationoftheCommittee
the quartz furnace tube inlet.
on Analytical Reagents of the American Chemical Society,
10.2 Set the furnace temperature to 900°C.
where such specifications are available. Other grades may be
10.3 Adjust the gas flows according to manufacturers speci-
used, provided that the reagent is of sufficiently high purity to
fication, typically 200 mL/min for oxygen and 100 mL/min for
permit its use without lessening the accuracy of the determi-
the carrier gas.
nation.
10.4 Prepare the sulfuric acid dehydration scrubber, and
7.2 PurityofWater—Unless otherwise indicated, references
connect it to the outlet of the quartz furnace combustion tube.
to water shall be understood to mean reagent water conforming
10.5 Clean and prepare the electrode system for the titration
to Specification D 1193, Type II or Type III.
cell per instrument specifications.
7.3 Acetic Acid (sp gr. 1.05), glacial acetic acid
10.6 Fill the titration cell with fresh electrolyte solution to
(CH COOH).
just above the top fill mark.
7.4 Argon or Helium, carrier gas, minimum 99.9 % purity.
10.7 Place the titration cell on the magnetic stirring device
7.5 SodiumAcetate, anhydrous, (NaCH CO ), fine granular.
3 2
and connect the electrode system to the controller. Do not
7.6 Cell Electrolyte Solution—Dissolve 1.35 g sodium ac-
connect the gas flow from the dehydration scrubber to the
etate (NaCH CO ) in 100 mL water. Add to 850 mL of acetic
3 2
titration cell.
acid (CH COOH) and dilute to 1000 mL with water.
10.8 Initiate a conditioning run of the titration cell to
7.7 Tungsten Powder, combustion accelerator, (-100 mesh)
establish titration gain and endpoint values.
minimum 99.9 % purity.
10.9 Once the titration cell is properly conditioned, connect
7.8 Oxygen, combustion gas minimum 99.6 % purity.
the gas flow from the dehydration scrubber to the titration cell.
7.9 Gas Regulators—Use two-stage gas regulators for the
10.10 Let the titration cell stabilize to a background poten-
carrier and combustion gases.
tial of less then 1.0 mv.
7.10 Potassium Nitrate (KNO ), fine granular.
10.11 To ensure quality data, care must be taken to avoid
7.11 Potassium Chloride (KCl), fine granular.
contaminating the sample boats during the course of the
7.12 Working Electrode Solution (10% KNO ), Dissolve
analytical procedure. Do not touch the boats with fingers.
50 g potassium nitrate (KNO ) in 500 mL of water.
Handle and transfer the boats using tongs and store said boats
7.13 Inner Chamber Reference Electrode Solution (1 M
in a sealed container such as a glass desiccator, containing no
KCl)—Dissolve 7.46 g potassium chloride (KCl) in 100 mLof
desiccant. Prepare the combustion boats by heating them in the
water.
combustion tube with oxygen flow for a minimum of five min.
7.14 Outer Chamber Reference Electrode Solution (1 M
KNO )—Dissolve 10.1 g potassium nitrate (KNO ) in 100 mL
3 3
11. Recovery Factor
of water.
7.15 Sodium Chloride (NaCl), fine granular.
11.1 Confirm the instrument carrier gas and time delay
7.16 Sulfuric Acid (sp gr. 1.84), (H SO ), concentrated.
settings. Typical delays for solvent injections are 2.0 min for
2 4
7.17 2,4,6-Trichlorophenol (TCP) (C H OCl ), fine granu-
carrier gas and 2.5 min to titration start.
6 3 3
lar.
11.2 Inject 10 µL of chlorine standard solution through the
7.18 Methanol (MeOH) (CH OH), 99.9 % minimum purity.
injection port into a prepared combustion boat. Advance the
7.19 Working Chlorine Standard (1µg/µL)—Weigh accu-
combustion boat slowly into the heated zone of the furnace.
rately 0.1856 g of 2,4,6-Trichlorophenol to the nearest 0.1 mg.
Record the recovered µg Chlorine as RC.
Transfer to a 100 mLvolumetric flask. Dilute to
...