The dewatering and drying of coal are important links before deep processing of low rank coal.The evaporative technologies

including use of hot air

hot steam

microwave

or solar enorgy

as well as the non-evaporative technologies

such as hydrothermal dewatering(HTD)

mechanical thermal expression(MTE)

and organic dissolvent dewatering etc.

have been presented and compared.The evaporative drying is simple in process

and lower cost for equipments

while in non-evaporative drying process HTD or MTE

the latent heat in gasification isn't cosumed

the characters of low rank coal can be deeply improved

and the moisture in low rank coal can be irreversibly dewatered

at the same time

the rank of coal and its calorific value can be enhanced

therefore

having wide prospect of application.