Question

gaseous fuels are preferred over solid fuels in chemical industries.why

Answer 1

Calorific value is defined as the amount of heat energy produced on complete combustion of 1 kilogram of a fuel. It is expressed in a unit called kilojoule per kg. The higher the calorific value of a fuel, the more is its efficiency.The calorific value of gaseous fuels are more.When a gaseous fuel  burns, it gives off a great deal of energy. And unlike other solid and liquid fuels it does not leaves any ash. 
and it produces very little air pollution.
Due to the above reasons gaseous fuel is always better than solid and liquid fuels.

Answer 2

'coz the calorific value of gaseous fuels are more.when a gaseous fuel is burn ,it gives tremendous amount of energy nd does n't leave behind ash on burning like other solid or liquid fuels nd moreover gaseous fuels are easier to handle than the solid fuels and they can be transported through windpipes as well.
hope it helps!!