After 30 years of development

the discrete element method (DEM) has developed to be a kind of numerical method of particle systems widely used in process engineering. In particular

the CFD-DEM coupling method has been widely used in the researches of fluidization. The DEM models are reviewed firstly

including the basic principles of DEM model

the particle shape model

the contact force model

the non-contact force model

and the fluid force model. Then the CFD-DEM coupling methods and the applications to fluidization are introduced

including the applications in fluidized bed

pneumatic conveying

and some other fields of process engineering. Finally

the future development of DEM and CFD-DEM coupling methods are presented

hoping to promote the development of DEM and its applications in process engineering.