This test method is a relative measure of the degree of oxidation present in coal. It does not determine the quantitative amount of oxidized coal present. It is only intended to serve as a guide to the supplier, buyer, and user for selecting coals for metallurgical use.
Note 18212;The values shown in Table 1 are based on the transmittance obtained using the original procedure4 (wavelength at 520 nm, 17-mm light path, 2– to 3-min boiling time, dilution of the extract to 80 mL). At these conditions, coals that had transmittance values greater than 90 % were considered to be unoxidized, coals less than 80 % were considered to be oxidized, and coals between 80 and 90 % were considered suspect. As this procedure becomes accepted as the standard and more experimental data are gathered, modifications to these cutoff values are expected. Note that lower rank bituminous coals are more easily extracted than higher rank coal.
TABLE 1 Guidelines for General Acceptance/Rejection Levels of Oxidized Coal
| Percent Transmittance at 520 nm, 17-mm Light Path | Interpretation of Results |
|---|---|
| >90 | Coal is not oxidized. Suitable for metallurgical usage. |
| 80 to 90 | Coal may be oxidized. If it is being used metallurgically, it should be monitored closely for further changes in oxidation. |
| <80 | Coal is oxidized. Coal at this level may cause coke quality and coke plant operating problems. |
1.1 This colorimetric method describes the determination of the relative degree of oxidation by alkali extraction of coals that are high volatile A bituminous to low volatile bituminous in rank.
1.2 This test cannot be sensitive to thermally oxidized coal. It is intended for coals that may be oxidized as a result of weathering.
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 and health practices and determine the applicability of regulatory limitations prior to use.
1.4 The values stated in SI units shall be regarded as standard.
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