Question

To differentiate by an activity good quality coal and bad coal

Answer 1

Bad-Coals may contain a number of impurities (such as sulphur or phosphorous) which, while they may be in very small quantities become significant because they can result in atmospheric pollutants when burnt or can affect the properties of steel produced.

Good -high quality coal due to its high fixed carbon content (not a coking coal), once a premium coal for steaming purposes but now relatively rare and only utilized in specialist applications such as a graphitizing material for electrode paste and as a reductant for reducing metal oxide ores