What is heat source / steam of dryer? / raw materials drying, sludge drying, slurry drying

What is heat source / steam of dryer?
What is “steam” precisely? Normally in many factories, steam is generated by steam generators or by boilers and used for various purposes.Steam is one of gaseous substances. The gaseous substance is roughly divided into steam and gas.
When the substance is distincted between steam and gas, the substance that its state is more changeable, such as the state close to evaporation or condensation, is called steam. The substance being in a state in which evaporation or condensation will hardly occurred is called gas.For example, LP gas, natural gas and biogas which is attracting attention recently is categorized to gas as its name suggests.Also, water vapor and steam are often used as equivalent words though, water vapor is a sort of steam in the strict sense. In addition, gas is often called as ideal gas but the term of real gas is used for steam and its characteristics is complicated.
The words of steam used for our dryer indicates water vapor and it is a gaseous substance generated by heating water and with no taste, no smell and no color.If water vapor is used as heat source of a dryer, running cost can be kept low by using surplus steam in a factory or exhaust steam from steam turbine.

Please also see this about steam for your reference.