Granular media filters

Claim 1

IN A GRANULAR BED FILTER HAVING ENTRANCE AND EXIT SIDES IN WHICH A BED OF GRANULAR MATERIAL IS SUPPORTED IN A FILTER COMPARTMENT BY SCREEN MEANS AND IN WHICH A STREAM OF DUSTY GAS FIRST PASSES THROUGH SAID GRANULAR MATERIAL WHERE SUSPENDED PARTICLES ARE REMOVED FROM SAID GAS STEAM AND FILTERED GAS EXITS THROUGH THE SCREEN MEANS, THE METHOD OF OPERATING AND CLEANING SAID FILTER OF PARTICLES REMOVED FROM THE DUSTY GAS WHICH METHOD COMPRISES STEPS OF INTRODUCING THE DUSTY GAS TO THE ENTRANCE OF THE FILTER IN A CONTINUOUS NON-INTERRUPTED STREAM, PERIODICALLY CLEANING SAID GRANULAR MATERIAL OF ACCUMULATED PARTICLES FILTERED FROM THE DUSTY GAS BY FEEDING A PULSE OF CLEAN GAS THROUGH SAID FILTER COMPARTMENT IN A REVERSE DIRECTION SUFFICIENT TO FLUIDIZE THE GRANULAR MATERIAL IN SAID FILTER COMPARTMENT, REDUCING THE FLOW OF CLEAN GAS TO A LEVEL BELOW THE INCIPIENT FLUIDIZATION RATE TO ALLOW THE GRANULAR MATERIAL TO SETTLE FROM ITS FLUIDIZED STATE INTO A BED AT BUT SUFFICIENT TO MAINTAIN A PRESSURE ON THE EXIT SIDE OF SAID FILTERR COMPARTMENT HIGHER THAN THE PRESSURE MAINTAINED ON THE ENTRANCE SIDE OF SAID FILTER COMPARTMENT BY THE DUSTY GAS STREAM WHEREBY THE FLOW OF DUSTY GAS INTO THE FILTER COMPARTMENT IS PREVENTED PRIOR TO SETTLEMENT OF THE GRANULAR MATERIAL INTO A BED SUPPORTED ON THE SCREEN MEANS, AND, AFTER THE GRANULAR MATERIAL HAS SETTLED INTO A BED AT REST, ARRESTING THE FLOW OF CLEAN GAS ALLOW THE DUSTY GAS TO FLOW INTO THE FILTER COMPARTMENT AND BE FILTERED OF ENTRAINED DUST PARTICLES.