for operation the steam separator can be used to adjust the pressure of the fluid to the bed the temperature of the fluid being a function of the separation pressure flashing in the bed can also be prevented by cooling the bed with cooling coils within the bed a similar result can be obtained by utilizing a booster pump in the line to increase the pressure of the fluid it is essential to the invention for a sustained continuous operation to keep the particles in the fluidized bed at a relatively uniform constant size to obtain the desired amount of silica separation from the fluid for this purpose the sand is recycled to remove all or a substantial portion of the silica polymer coating this can be done by passing quantities of the coated sand through conduit 9 and a control 10 into separator 11 the coated sand particles are conveyed to the separator by screw conveyor or the like after removal of the coating the sand is returned through conduit 12 to chamber 3 the fine silica coating residue is separated from the sand and the sand recycled without the coating residue to the fluidized column perferably at the top of the column the removed coating is passed to a collection hopper 13 this silica coating is very fine high grade silica which has a variety of uses such as in glass making ceramics and the like as an alternate procedure the coating on the sand particles can be dissolved in a strong base such as sodium hydroxide and the resulting solution separated from the coating free sand particles a typical arrangement for a fluidized bed would be a chamber approximately three meters.