In the process of coal formation, there are various
intermediate stages. These stages are referred to as the
ranks of coal. Lignite or brown coal is one such rank.
Lignite is soft, brown and high in moisture content
(35 to 40%). It weathers quickly, ignites spontaneously
and has a low calorific value.
Coals are analyzed in two ways. The ultimate
analysis determines the total percentage of elements
present in coal. The proximate analysis gives an
empirical estimate of the amounts of moisture, ash,
volatile matter and fixed carbon in coal.
