Granular bed filter apparatus and method

Claim 1

Filter apparatus comprising a housing having an inlet chamber and an outlet chamber, said housing having a wall separating said chambers, said housing having a dirty gas inlet communicating with the inlet chamber and clean gas outlet communicating with the outlet chamber, a plurality of hollow filter stacks, means in said housing supporting said stacks so that said clean gas outlet communicates with the interior of said stacks while the stacks are disposed in said inlet chamber, each stack including a series of discrete annular members, said annular members including an outer wall connected to an imperforate inner wall by an intermediate wall, said members being superimposed over one another so that the inner and outer walls are generally aligned and coaxial, the inner wall on one member cooperating with an outer wall on another member to define an annular filter bed containing inert granular material, the diameter of said stacks being approximately five to six times the radial width of the filter bed, an inlet screen surrounding the upper end of each filter bed and coaxial therewith to define an inlet from said inlet chamber to the filter bed, a generally horizontal screen across the bottom of each filter bed so that gas to be cleaned may flow axially through the bed and enter the interior of the stack, a discharge conduit at one end of each stack communicating with the interior thereof to facilitate discharge of cleaned gas in an axial direction to said outlet chamber, means for fluidizing the granular material into the space above its bed and radially inwardly from its respective inlet screen by introducing pulses of air into said discharge conduits at a pressure in excess of that required for fluidizing said granular material, and said last-mentioned means including a nozzle aligned with said discharge conduits.