ASTM D7348-21

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Designation: D7348 − 13 D7348 − 21
Standard Test Methods for
Loss on Ignition (LOI) of Solid Combustion Residues
This standard is issued under the fixed designation D7348; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These test methods cover the determination of the mass loss from solid combustion residues upon heating in an air or oxygen
atmosphere to a prescribed temperature. The mass loss can be due to the loss of moisture, carbon, sulfur, and so forth, from the
decomposition or combustion of the residue.
1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this The
values given in parentheses after SI units are provided for information only and are not considered standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D121 Terminology of Coal and Coke
D3174 Test Method for Ash in the Analysis Sample of Coal and Coke from Coal
D3180 Practice for Calculating Coal and Coke Analyses from As-Determined to Different Bases
D3682 Test Method for Major and Minor Elements in Combustion Residues from Coal Utilization Processes
D3683 Test Method for Trace Elements in Coal and Coke Ash by Atomic Absorption (Withdrawn 2018)
D4326 Test Method for Major and Minor Elements in Coal Ash By X-Ray Fluorescence
D6316 Test Method for Determination of Total, Combustible and Carbonate Carbon in Solid Residues from Coal and Coke
D6349 Test Method for Determination of Major and Minor Elements in Coal, Coke, and Solid Residues from Combustion of
Coal and Coke by Inductively Coupled Plasma—Atomic Emission Spectrometry
D6357 Test Methods for Determination of Trace Elements in Coal, Coke, and Combustion Residues from Coal Utilization
Processes by Inductively Coupled Plasma Atomic Emission Spectrometry, Inductively Coupled Plasma Mass Spectrometry,
and Graphite Furnace Atomic Absorption Spectro
D7582 Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis
D8146 Guide for Evaluating Test Method Capability and Fitness for Use
These test methods are under the jurisdiction of ASTM Committee D05 on Coal and Coke and isare the direct responsibility of Subcommittee D05.29 on Major Elements
in Ash and Trace Elements of Coal.
Current edition approved Sept. 1, 2013Oct. 1, 2021. Published September 2013November 2021. Originally approved in 2007. Last previous edition approved in 20082013
as D7348 – 08E1.13. DOI: 10.1520/D7348-13.10.1520/D7348-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service as service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7348 − 21
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions—For definitions of terms used in these test methods, refer to Terminology D121.
4. Summary of Test Method
4.1 Loss on ignition (LOI) is determined by measuring the loss in mass of the test specimen when heated under controlled
conditions of temperature, time, atmosphere, specimen mass, and equipment specifications. The LOI can be determined by
measuring the mass loss in a single procedure or in a two-step procedure in which mass losses, equivalent to the moisture and ash
values of the test specimen, are determined.
5. Significance and Use
5.1 LOI refers to the mass loss of a combustion residue whenever it is heated in an air or oxygen atmosphere to high temperatures.
In the cement industry, use of the term LOI normally refers to a mass loss in a sample heated to 950°C.950 °C. To combustion
engineers, the term LOI normally refers to mass losses in samples heated to temperatures normally less than 950°C.950 °C. These
test methods establish a procedure for determining LOI values for combustion residues heated to 750°C750 °C or 950°C.950 °C.
LOI values from these test methods can be used by industries that utilize combustion residues in various processes and products.
5.2 If the solid combustion residue is heated to estimate the combustible or unburned carbon in the sample, it has been shown that
LOI and estimation of unburned carbon do not necessarily agree well with each other and that LOI should not be used as an
estimate of unburned carbon in all combustion residues. . Direct determination of unburned (combustible) carbon can be carried
out using Test Method D6316.
5.3 If the solid combustion residue is heated to prepare an ash for the determination of the concentrations mass fractions of major
and minor elements, use the heating procedure described in Test Methods D3682, D4326, and D6349, or the procedures for the
750°C750 °C LOI determination described in these test methods (Method A).
5.4 If the solid combustion residue is heated to prepare an ash for the determination of the concentrations mass fractions of trace
elements, use the heating procedure described in Test Methods D3683 and D6357.
NOTE 1—Combustion residues produced in furnace operations or other combustion systems can differ from the ash yield, as determined in Test Methods
D3174 and D7582, because combustion conditions influence the chemistry and amount of ash. Combustion causes an expulsion of all water, the loss of
carbon dioxide from carbonates, the conversion of metal sulfides into metal oxides, metal sulfates and sulfur oxides, and other chemical reactions.
Likewise, the “ash” obtained after igniting combustion residues can differ in composition and amount from Test Methods D3174 and D7582 ash yields
because of different heating procedures, combustion of unburned carbon, and decomposition of materials in the residue.
6. Interferences
6.1 There are no known interferences for these test methods.
7. Apparatus
7.1 Furnace—The apparatus shall consist of a furnace with a cavity large enough to accept multiple crucibles. The furnace shall
be constructed so the cavity is surrounded by a suitable refractory and insulated so as to develop a uniform temperature in all parts
of the cavity but with a minimum free space. The furnace shall be capable of being heated rapidly (10°C/min(10 °C ⁄min or faster)
from ambient to 950°C.950 °C. The temperature shall be monitored and maintained at values specific to each of the determinations.
Provisions shall be made to introduce drying and oxidizing gases and to remove products of drying, decomposition, and
combustion. A recommended flow rate is one furnace volume change per minute, but higher flow rates (that is, two furnace
volumes per minute, as in some other standard test methods for coal and coke) are acceptable. The furnace can be a stand alone
muffle furnace or a computer-controlled macrothermogravimetric macro thermogravimetric analyzer (macro TGA) system. In
Burris S.C. , S.C., Li, D., and Riley J.T, “Comparison of Heating Losses and Macro Thermogravimetric Analysis Procedures for Estimating Unburned Carbon in
Combustion Residues,” Energy Fuels Vol 19, 2005, pp. 1493-1502.–1502.
D7348 − 21
macro TGA, a sample size of 1 g (or larger) is used. In a typical analysis, the temperature is ramped from ambient to a specific
temperature and held at that temperature for a prescribed length of time. In thermogravimetric analysis, the mass of a sample in
a controlled atmosphere is recorded repeatedly as a function of temperature or time.
7.2 Drying Oven—For determining the moisture in solid combustion residue samples, use a drying oven with openings for drying
gas circulation and capable of temperature regulation between the limits of 104104 °C and 110°C.110 °C. A drying gas flow rate
of approximately one volume change per minute is recommended but higher flow rates, that is, two volume changes per minute,
as in some other standard test methods for coal and coke, are acceptable.
7.3 Crucibles, use a crucible of a convenient form that allows extensive contact between the specimen and reactant gas. The
crucibles can be made of porcelain, fused silica, or similar materials. The crucibles shall have the dimensions specified by the
instrument manufacturer.
7.4 Balance, sensitive to 0.1 mg. In the macro TGA, the balance is an integral part of the system. For other systems, the balance
is a separate piece of apparatus.
7.5 Operation of the instrumental system in its entirety shall be verified in accordance with the manufacturer’s operating
instructions.
7.6 Venting Equipment—Combustion and decomposition gases evolved during the test procedures shall be vented from the
laboratory and suitable venting equipment shall be installed in the vicinity of the apparatus.
8. Reagents and Materials
8.1 Drying Gases—Air dried to a moisture content of 1.91.9 mg mg/L ⁄L or less (dew point –10°C–10 °C or less). Nitrogen
(99.5 % purity) is normally used with the macro TGA system. Argon can also be used.
8.2 Oxidizing Gases—Oxygen (99.5 % purity) or air.
9. Hazards
9.1 The user shall insure acceptable documented safety procedures are in place for the handling of all reagents and test materials
and for the operation of laboratory equipment specified for these test methods.
10. Sampling, Test Specimens, and Test Units
10.1 The sample used for analysis shall be thoroughly mixed and of such fineness to pass through a 250-μm250 μm (No. 60) sieve.
Pulverizing the sample to this fineness is required.
11. Preparation of Apparatus
11.1 For LOI determinations using a macro TGA, follow the manufacturer’s recommended procedure for verifying system
stability and for loading and taring the crucibles. Various modes of operation are possible depending on the instrument used and
the manner in which the determinations are completed. The instrument can be programmed to terminate the test whenever the test
specimens and crucibles have reached a constant mass. Typically, crucibles are weighed the mass of a crucible is determined
automatically at specified intervals, and the analysis is complete whenever three successive weighings mass determinations agree
within a plateau deviation specified for the instrument. Constant mass is defined as a point where the mass change is ≤ 0.05 %
≤ 0.05 % of a nine-minute9 min period, either by using three successive weighings mass determinations (for some TGAs) or a fixed
nine-minute9 min period (for some TGAs). This mass change of 0.05%0.05 % is equivalent to 0.0005 g 0.0005 g for a 1.0000 g
1.0000 g sample. Alternately, the instrument can be programmed to allow for moisture determination by heating the test specimens
for a specified time period (for example, 1 h) at the prescribed temperature limits.
11.2 When using a muffle furnace for LOI determinations, always start the test with the muffle furnace at ambient temperature.
12. Conditioning
12.1 Heat new crucibles for use in these test methods under the conditions of the test and cool before use.
D7348 − 21
13. Procedure
13.1 In these procedures Method A refers to LOI determinations at 750°C750 °C whereas Method B refers to LOI determinations
at 950°C.950 °C.
13.2 For LOI determinations using a macro TGA, the analyses are normally complete when the sample reaches a constant mass
as defined in the instrumental operating parameters. (See 11.1.)
13.3 For LOI determinations using a single-step procedure, add approximately 1 g 1 g of solid combustion residue to each
successive crucible and weigh. determine the mass. Select oxygen or air as the furnace atmosphere and gradually raise the
temperature of the furnace at a rate such that the furnace temperature reaches 500500 °C 6 10°C10 °C at the end of 1 h. 1 h. For
Method A, continue the gradual heating until the temperature rises from 500500 °C 6 10°C10 °C to 750750 °C 6 15°C15 °C at
the end of 1 h. 1 h. For Method B, continue the gradual heating until the temperature rises from 500500 °C 6 10°C10 °C to
950950 °C 6 20°C20 °C at the end of 1 h. 1 h. Maintain the higher temperature until the combustion residue test specimens reach
a constant mass or for an additional 2 h.2 h.
13.4 For LOI determinations using a two-step procedure, add approximately 1 g 1 g of solid combustion residue to each successive
crucible and weigh. determine the mass. For moisture determinations with the macro TGA, turn on the drying gas (see 8.1) and
heat the weighed test specimens of known mass in crucibles without covers at 104104 °C to 110°C.110 °C. A recommended flow
rate is one furnace volume change per minute, but higher flow rates (that is, two furnace volumes per minute, as in other standard
test methods for coal and coke) are acceptable. Ash determinations on the residues (dried test specimens) from the moisture
determination are made by changing the macro TGA furnace atmosphere to oxidizing gas (see 8.1), and gradually raising the
temperature of the furnace at a rate such that the furnace temperature reaches 500500 °C 6 10°C10 °C at the end of 1 h. For
Method A, continue the gradual heating until the temperature rises from 500500 °C 6 10°C10 °C to 750750 °C 6 15°C15 °C at
the end of 1 h. For Method B, continue the gradual heating until the temperature rises from 500500 °C 6 10°C10 °C to 950950 °C
6 20°C20 °C at the end of 1 h. 1 h. Maintain the higher temperature until the combustion residue test specimens reach a constant
mass or for an additional 2 h.
13.5 LOI can be determined in a single-step procedure using a muffle furnace (see 7.1). Place approximately 1 g 1 g of combustion
residue into a preweighed crucible and weigh the crucible of known mass and determine the mass of the test specimen to the
nearest 0.1 mg. 0.1 mg. Place the crucible with the test specimen, without a cover, into the cold furnace. Turn on the oxidizing
gas (see 8.2) and adjust the flow to approximately one furnace volume change per minute. Gradually raise the temperature of the
furnace at a rate such that the furnace temperature reaches 500500 °C 6 10°C10 °C at the end of 1 h. For Method A, continue the
gradual heating of the samples until the temperature rises from 500500 °C 6 10°C10 °C to 750750 °C 6 15°C15 °C at the end
of 1 h. For Method B, continue the gradual heating until the temperature rises from 500500 °C 6 10°C10 °C to 950950 °C 6
20°C20 °C at the end of 1 h. 1 h. Maintain the higher temperature until the combustion residue test specimens reach a constant
mass or for an additional 2 h.2 h.
13.6 LOI can be determined in a two-step procedure using a muffle furnace and a drying oven (see 7.2). To determine moisture,
place approximately 1 g of combustion residue into a preweighed crucible and weigh the crucible of known mass and determine
the mass of the test specimen to the nearest 0.1 mg. Place the crucible with the test specimen, without a cover, into the preheated
drying oven (104(104 °C to 110°C)110 °C) through which passes a current of preheated drying gas (see 8.1). Close the oven and
heat for 1 h. Remove the test specimen crucibles, cover immediately, allow to cool to ambient temperature in a desiccator, and
weigh. determine the mass. (Additional heatings and weighings mass determinations may be necessary for some solid combustion
residues if the 1-h1 h time period is insufficient to bring the test specimen to a constant weight.)mass.) For ash determination, place
the crucible, without covers, with the dry test specimen in a cold furnace. Gradually raise the temperature of the furnace at a rate
such that it reaches 500500 °C 6 10°C10 °C at the end of 1 h. 1 h. For Method A, continue the gradual heating until the
temperature rises from 500500 °C 6 10°C10 °C to 750750 °C 6 15°C15 °C at the end of 1 h. 1 h. For Method B, continue the
gradual heating until the temperature rises from 500500 °C 6 10°C10 °C to 950950 °C 6 20°C20 °C at the end of 1 h. 1 h.
Maintain the higher temperature until the combustion residue test specimens reach a constant mass or for an additional 2 h.2 h.
13.7 If the solid combustion residue is heated to prepare an ash for the determination of the concentrations mass fractions of major
and minor elements, use the heating procedure described in Test Methods D3682 (, 7.1), D4326 (, 7.1), and D6349 (9.2), , or the
750°C750 °C procedure (Method A) described previously.
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