Catalyst backflow prevention device

Claim 1

IN AN APPARATUS FOR CONTACTING A FLUID WITH A DENSE BED OF FLUIDIZED SOLIDS, SAID APPARATUS COMPRISING A CHAMBER HAVING INLET AND OUTLET MEANS AT A LOWER PART THEREOF, AN OUTLET MEANS AT AN UPPER PART THEREOF, SAID OUTLET MEANS AT SAID UPPER PART THEREOF BEING PROVIDED WITH SOLIDS-FROM-FLUID SEPARATING MEANS, THE IMPROVEMENT WHICH COMPRISES, IN COMBINATION: CONDUIT MEANS ADAPTED TO RETURN SEPARATED SOLIDS FROM SAID SEPARATING MEANS INTO SAID DENSE BED, SAID CONDUIT MEANS COMPRISING AN UPPER SECTION, A LOWER SECTION, AND AN INTERMEDIATE SECTION OF LARGER DIAMETER THAN SAID UPPER AND LOWER SECTIONS AND POSITIONED ABOVE THE UPPER LEVEL OF SAID DENSE BED; MEANS POSITIONED WITHIN SADI INTERMEDIATE SECTION AND RESPONSIVE TO THE WEIGHT OF THE ACCUMULATED SOLIDS WITHIN SAID UPPER SECTION TO OPEN THE LOWER END OF SAID UPPER SECTION WHEN THE HEAD OF ACCUMULATED SOLIDS WITHIN SAID UPPER SECTION EXCEEDS A PREDETERMINED PRESSURE AND TO CLOSE SAID LOWER END WHEN SAID HEAD IS LESS THAN SAID PRESSURE.