Question

why it is necessary to purify raw coal prior to its chemical processing to obtain several useful products?
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Answer 1

Answer:

Refined coal is the product of the application of a coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals and raising their calorific values.[1] Coal refining or upgrading technologies are typically pre-combustion treatments and/or processes that alter the characteristics of a coal before it is burned.