In-bed solids control valve with improved reliability

A circulating fluidized bed boiler comprising:

• a circulating fluidized bed boiler reaction chamber comprising side walls and a distribution grid defining a floor at a lower end of the circulating fluidized bed boiler reaction chamber, the distribution grid being adapted for providing fluidizing gas into the circulating fluidized bed boiler reaction chamber;
• a bubbling fluidized bed located within a lower portion of the circulating fluidized bed boiler reaction chamber and being bound by enclosure walls and by the floor of the circulating fluidized bed boiler reaction chamber;
• at least one controllable in-bed heat exchanger, the in-bed heat exchanger occupying part of the circulating fluidized bed boiler reaction chamber floor and being within the enclosure walls of the bubbling fluidized bed;
• at least one non-mechanical valve designed to permit the control of solids discharge from the bubbling fluidized bed into the circulating fluidized bed boiler reaction chamber, the valve comprising at least one opening in the enclosure wall of the bubbling fluidized bed, and including at least one independently controlled fluidizing means located at least at one of upstream and downstream of the opening;
• the at least one independently controlled fluidizing means each being connected to corresponding fluidizing medium supply means, the independently controlled fluidizing means being adapted for controlling a flow rate of solids from the bubbling fluidized bed to the circulating fluidized bed boiler reaction chamber, the independently controlled fluidizing means being controlled separately from the distribution grid;
• the independently controlled fluidizing means and the fluidizing medium supply means being at least one of connected to and comprising collectors, the collectors being adapted for collecting solids in the event of backsifting of solids into the fluidizing means such that the collected solids do not obstruct the supply of fluidizing medium;
• valves for sealing at least one of the collectors, the fluidizing means, and the fluidizing medium supply means, to allow removal of backsifted solids from the collectors during operation of the circulating fluidized bed furnace;
• the non-mechanical valve further comprising at least one solids removal means, being adapted for removal of agglomerates, located at least one of upstream and downstream of said at least one opening in the bubbling fluidized bed enclosure wall;
• the removal means each being connected to at least one screw cooler adapted for sealing against furnace pressure, for controlling solids discharge rate through the removal means, and for cooling discharged solids and agglomerates;
• the bubbling fluidized bed enclosure wall comprising a plurality of channel walls adjacent to one or more openings in the bubbling fluidized bed enclosure wall, the walls projecting generally away from the enclosure wall into at least one of the circulating fluidized bed and the bubbling fluidized bed, the channel walls being adapted to reduce lateral movement of solids in one or more directions perpendicular to the direction of solids discharge from the bubbling fluidized bed to the circulating fluidized bed.