an apparatus for the direct fluorination of solid particles of polymeric resins capable of being fluorinated in which the solid particles are contacted by a flow of a mixture of fluorine and carrier fluid in a solid - gas reactor . in the solid - gas reactor , the fluid flow continuously agitates or fluidizes the solid particles to maintain the solid particles in motion . the degree of motion of the solid particles is a function of the linear velocity of the fluid and of the physical properties of the solid particles such as the solid bulk density , particle size , geometry of the solid particle , and adhesion or agglomeration of solid particles . the solid - gas reactor can be arranged with single or multi - reactors in batch or continous mode .