What physical and chemical processes transform lignite to bituminous coal?

Question

Quizplus · Accepted Answer

Lignite is transformed into bituminous coal through a combination of heating to drive off water and volatile gases, and pressure for compaction. These processes cause the carbon content of the coal to increase, resulting in a higher energy content and a darker appearance. Coking in industrial ovens without oxygen is a process used to transform bituminous coal into higher-grade forms of coal, such as coke and anthracite. Weathering and further transport do not play a significant role in the transformation of lignite to bituminous coal. Mining and drying in the sun may be involved in the extraction and preparation of the coal, but these processes do not actually transform the coal from one grade to another.

What Physical and Chemical Processes Transform Lignite to Bituminous Coal