DMF Extractability as a Predictor of Plasticity in Bituminous Coals
Plasticity is a phenomenon of certain coals that is not completely understood. Some bituminous coals go through a softening and swelling state upon heating before they re-solidify. It is this softening and swelling state that is labeled as the "plastic state" of the coal. Concurrent with t...
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| Format: | Others |
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TopSCHOLAR®
1983
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| Online Access: | https://digitalcommons.wku.edu/theses/2970 https://digitalcommons.wku.edu/cgi/viewcontent.cgi?article=3978&context=theses |
| Summary: | Plasticity is a phenomenon of certain coals that is not completely understood. Some bituminous coals go through a softening and swelling state upon heating before they re-solidify. It is this softening and swelling state that is labeled as the "plastic state" of the coal. Concurrent with the plastic state of the coal, thermal decomposition of the coal takes place. Several low molecular weight gases are also evolved. These occur at a temperature of approximately 450° C.
The plasticity of a coal is a good indication of the coking ability of a coal. Plastic coals tend to give higher yields in liquefaction reactions than do nonplastic coals, a fact very useful to the synfuel industry. Fluidized bed reactors are impaired by the use of plastic coals, as they tend to agglomerate in the bed. Currently the ASTM approved method used to determine plasticity is by using a Gieseler plastometer. Gieselers are inconsistent and an easier, more efficient method is needed.
It Is currently thought that the bitumen in the coal, the extractable portion of the coal, is responsible for Initiating the plasticity mechanism. It is logical, then, to assume that the amount of bitumen in the coal could be used as a predictor or the degree of plasticity.
Dimethylformamide (DMF) was used as the solvent for the Soxhlet extraction of 43 highly characterized bituminous coals. A correlation between the DMF extraction data and the coal plasticities shows that DMF extraction is a reasonable technique to use to predict plasticity. |
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