In-bed solids control valve with improved reliability

Abstract

A non-mechanical valve arrangement for use with circulating fluidized bed (CFB) boilers has a CFB reaction chamber and a bubbling fluidized bed (BFB) within an enclosure in the lower portion of the CFB reaction chamber, the BFB containing an in-bed heat exchanger (IBHX). Solids flowing from the BFB enclosure to the CFB reaction chamber may be controlled using one or more non-mechanical valves. Each non-mechanical valve is independently controlled using independently controlled fluidizing means. The non-mechanical valve has collectors to collect solids backsifting into the fluidizing means of the valve. Agglomerates are removed which could block the valve. Channel walls parallel to the direction of solids flow through the valve opening may be provided to reduce external interference with local fluidization to maintain the proper functionality of the non-mechanical valve.

What is claimed is: 
     
         1 . 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.   
     
     
         2 . A circulating fluidized bed boiler comprising:
 a circulating fluidized bed boiler reaction chamber comprising side walls and a distribution grid for providing fluidizing gas into the circulating fluidized bed boiler reaction chamber;   a bubbling fluidized bed in a compartment including at least one enclosure wall;   at least one controllable in-bed heat exchanger, the in-bed heat exchanger being located within the compartment comprising the bubbling fluidized bed;   at least one non-mechanical valve adapted to control 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, and including at least one independently controlled fluidizing means located at least at one of upstream and downstream of the opening;   the independently controlled fluidizing means each being connected to 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; and   collectors linked to the one or more independently controlled fluidizing means, 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 a supply of fluidizing medium.   
     
     
         3 . The circulating fluidized bed boiler of  claim 2 , wherein the non-mechanical valve further comprises:
 one or more solids removal means, the solids removal means being adapted to provide a passage for removal of agglomerates, and being located at least one of upstream and downstream of said at least one opening in the bubbling fluidized bed enclosure wall.   
     
     
         4 . The circulating fluidized bed boiler of  claim 3 , wherein the bubbling fluidized bed is located within a lower portion of the circulating fluidized bed boiler reaction chamber, wherein the bubbling fluidized bed is bound by enclosure walls and by the floor of the circulating fluidized bed boiler reaction chamber; and
 wherein the in-bed heat exchanger occupies part of the circulating fluidized bed boiler reaction chamber floor and is within the enclosure walls of the bubbling fluidized bed.   
     
     
         5 . The circulating fluidized bed boiler of  claim 3 , wherein the removal means are sealed against furnace pressure. 
     
     
         6 . The circulating fluidized bed boiler of  claim 3 , further comprising:
 one or more screw coolers, each being connected to the one or more solids removal means and being adapted for cooling discharged solids and for sealing against furnace pressure.   
     
     
         7 . The circulating fluidized bed boiler of  claim 2 , further comprising:
 means for sealing at least one of the collectors, the fluidizing means, and the fluidizing medium supply sources, to allow removal of backsifted solids from the collectors during operation of the circulating fluidized bed boiler.   
     
     
         8 . The circulating fluidized bed boiler of  claim 2 , further comprising:
 a plurality of channel 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.   
     
     
         9 . The circulating fluidized bed boiler of  claim 8 , wherein at least one opening is complemented by a channel wall on each side of the opening and wherein said walls both protrude into at least one of the bubbling fluidized bed and the circulating fluidized bed by a distance of at least one half the width of the opening. 
     
     
         10 . The circulating fluidized bed boiler of  claim 9 , further comprising:
 one or more bridging surfaces linking the tops of a plurality of channel walls, the bridging surfaces being adapted to reduce vertical movement of bed material near at least one opening in the enclosure wall.   
     
     
         11 . The circulating fluidized bed boiler of  claim 3 , further comprising:
 independently controlled fluidizing means located at least at one of upstream and downstream of each solids removal means.   
     
     
         12 . The circulating fluidized bed boiler of  claim 2 , further comprising:
 one or more rotary valves each connected to at least one collector for removal of backsifted solids from the collectors during operation of the circulating fluidized bed boiler furnace.   
     
     
         13 . The circulating fluidized bed boiler of  claim 2 , wherein the openings in the bubbling fluidized bed enclosure wall comprise passages having depth to height ratios of  1 . 4  or greater, and wherein the openings are adapted to substantially prevent solids flow through the openings in the absence of fluidization by one or more independently controlled fluidizing means. 
     
     
         14 . The circulating fluidized bed boiler of  claim 2 , wherein the openings are adapted to substantially prevent solids flow out of the bubbling fluidized bed compartment in the absence of fluidization by one or more independently controlled fluidizing means. 
     
     
         15 . The circulating fluidized bed boiler of  claim 2 , wherein one or more openings comprise a pipe. 
     
     
         16 . The circulating fluidized bed boiler of  claim 2 , further comprising:
 a plurality of channel walls projecting on each side of one or more openings in the bubbling fluidized bed enclosure wall, the channel walls projecting 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; and   bridging surfaces linking the tops of a plurality of channel walls and adapted to reduce vertical movement of bed material near at least one opening in the enclosure wall;   wherein the channel walls and bridging surfaces are adapted to collectively extend the effective length of one or more openings in the enclosure wall; and   wherein the one or more openings, together with their respective channel walls and bridging surfaces, are collectively adapted to substantially prevent solids flow out of the bubbling fluidized bed compartment in the absence of fluidization by one or more independently controlled fluidizing means adjacent to those openings.   
     
     
         17 . The circulating fluidized bed boiler of  claim 2 , wherein the bubbling fluidized bed enclosure comprises tubes cooled by at least one of water and steam. 
     
     
         18 . The circulating fluidized bed boiler of  claim 2 , wherein the bubbling fluidized bed is located within a lower portion of the circulating fluidized bed boiler reaction chamber, wherein the bubbling fluidized bed is bound by enclosure walls and by the floor of the circulating fluidized bed boiler reaction chamber; and
 wherein the in-bed heat exchanger occupies part of the circulating fluidized bed boiler reaction chamber floor and is within the enclosure walls of the bubbling fluidized bed.   
     
     
         19 . The circulating fluidized bed boiler of  claim 2 , wherein the enclosure wall comprises at least two non-mechanical valves, each valve being adapted to independently control solids discharge from the bubbling fluidized bed into the circulating fluidized bed boiler reaction chamber, and wherein each valve comprises at least one independently controlled fluidizing means located at least one of upstream and downstream of its respective opening. 
     
     
         20 . The circulating fluidized bed boiler of  claim 19 , the boiler having a partially-opened condition wherein at least one non-mechanical valve is in a closed state while at least one other non-mechanical valve is in an open state;
 wherein said partially-opened state is characterized by at least one independently controlled fluidizing means of the closed non-mechanical valve being in a non-fluidizing state; and   wherein said partially-opened state is characterized by at least one independently controlled fluidizing means of the open non-mechanical valve being in a fluidizing state.   
     
     
         21 . The circulating fluidized bed boiler of  claim 2 , wherein at least one opening comprises a channel with a depth to height ratio of not less than 1.0. 
     
     
         22 . The circulating fluidized bed boiler of  claim 2 , wherein at least one opening comprises a channel with a depth to height ratio of not less than 1.4. 
     
     
         23 . The circulating fluidized bed boiler of  claim 2 , wherein at least one opening is defined by materials comprising one or a combination of ceramic, firebrick, and refractory covered tubes. 
     
     
         24 . The circulating fluidized bed boiler of  claim 2 , wherein each independently controlled fluidizing means is connected to a fluidizing medium source by a path which passes through a collector, the fluidizing medium being supplied through the collector at an elevation above a maximum level of backsifted solids collected by the collector. 
     
     
         25 . The circulating fluidized bed boiler of  claim 2 , comprising at least one source of fluidizing medium adapted to provide fluidizing medium having reduced oxygen content to at least one independently controlled fluidizing means. 
     
     
         26 . The circulating fluidized bed boiler of  claim 2 , comprising at least one source of fluidizing medium adapted to provide fluidizing medium having an oxygen content not exceeding 15% by volume to at least one independently controlled fluidizing means. 
     
     
         27 . The circulating fluidized bed boiler of  claim 2 , comprising at least one source of fluidizing medium adapted to provide fluidizing medium having an oxygen content not exceeding 12% by volume to at least one independently controlled fluidizing means. 
     
     
         28 . The circulating fluidized bed boiler of  claim 2 , comprising at least one source of fluidizing medium adapted to provide fluidizing medium having an oxygen content not exceeding 9% by volume to at least one independently controlled fluidizing means. 
     
     
         29 . The circulating fluidized bed boiler of  claim 2 , comprising at least one source of fluidizing medium adapted to provide fluidizing medium having an oxygen content not exceeding 6% by volume to at least one independently controlled fluidizing means. 
     
     
         30 . A non-mechanical valve arrangement for selectively controlling a flow of particulate solids between two compartments wherein at least one of said compartments comprises a fluidized bed, the non-mechanical valve arrangement comprising:
 an enclosure wall separating the two compartments;   an opening in the enclosure wall linking the two compartments;   independently controlled fluidizing means located at least one of upstream and downstream of the opening, the independently controlled fluidizing means being connected to fluidizing medium supply means and being adapted for selectively controlling the flow of particulate solids through the opening;   one or more collectors connected to the independently controlled fluidizing means, the collectors being adapted for collecting any solids entering the fluidizing means such that the collected solids do not obstruct the supply of fluidizing medium to the fluidizing means; and   one or more independently controlled solids removal means located at least one of upstream and downstream of the opening, the removal means being adapted for removal of solids and agglomerates.   
     
     
         31 . The non-mechanical valve arrangement of  claim 30 , the non-mechanical valve arrangement further comprising:
 A plurality of channel walls projecting away from the enclosure wall into at least one compartment comprising a fluidized bed, wherein one or more channel walls are adjacent to the opening, and wherein the channel walls are adapted for reducing lateral movement of solids in at least one direction perpendicular to the direction of solids flow through the non-mechanical valve.   
     
     
         32 . The non-mechanical valve arrangement of  claim 30 , wherein a plurality of independently controlled fluidizing means are provided in at least one row, each row being parallel to a wall comprising a non-mechanical valve, wherein the independently controlled fluidizing means in each row can be turned on and off as a group. 
     
     
         33 . A method for preventing agglomeration of solids in the circulating fluidized bed boiler of  claim 2  when one or more non-mechanical valves are in a closed state, the closed state being characterized by the independently controlled fluidizing means of the closed valves not emitting fluidizing medium, the method comprising periodically emitting fluidizing medium from at least one independently controlled fluidizing means of each valve for not less than 10% of a span when said valves are in the closed state. 
     
     
         34 . A method for preventing agglomeration of solids in the circulating fluidized bed boiler of  claim 2  when one or more non-mechanical valves are in a closed state, the closed state being characterized by the independently controlled fluidizing means of the closed valves not emitting fluidizing medium, the method comprising periodically emitting fluidizing medium from at least one independently controlled fluidizing means of each valve for not less than 5% of a span when said valves are in the closed state. 
     
     
         35 . A method for preventing agglomeration of solids in the circulating fluidized bed boiler of  claim 2  when one or more non-mechanical valves are in a closed state, the closed state being characterized by the independently controlled fluidizing means of the closed valves not emitting fluidizing medium, the method comprising periodically emitting fluidizing medium from at least one independently controlled fluidizing means of each valve for not less than 2% of a span when said valves are in the closed state. 
     
     
         36 . A method for preventing agglomeration of solids in the circulating fluidized bed boiler of  claim 2  when one or more non-mechanical valves are in a closed state, the closed state being characterized by the independently controlled fluidizing means of the closed valves not emitting fluidizing medium, the method comprising periodically emitting fluidizing medium from at least one independently controlled fluidizing means of each valve no less than every five minutes.