System, method and apparatus for controlling the flow direction, flow rate and temperature of solids

An apparatus for controlling flow of a material includes an inlet for receiving the material from a source, and a seal mechanism connected to the inlet, the seal mechanism having a fluidizing bed configured to receive the material from the inlet, a first discharge passageway and a second discharge passageway. The fluidizing bed includes a first transport zone associated with the first discharge passageway and a second transport zone associated with the second discharge passageway, wherein the first and second transport zones are configured to receive transport gas from a transport gas source. The transport gas is controllable to selectively divert a flow of the material into the first discharge passageway and the second discharge passageway.

BACKGROUND

Technical Field

Embodiments of the invention relate generally to power generation and, more particularly, to a system, method and apparatus for controlling the flow direction, flow rate, and temperature of solids utilized in a power generation process.

Discussion of Art

Fluidized bed combustion (FBC) is a combustion technology used in power plants, primarily to burn solid fuels. FBC power plants are more flexible than conventional power plants in that they can be fired on coal, coal waste or biomass, among other fuels. The term FBC covers a range of fluidized bed processes, including circulating fluidized bed (CFB) boilers, bubbling fluidized bed (BFB) boilers and other variations thereof. In an FBC power plant, fluidized beds suspend solid fuels on upward-blowing jets of gas during the combustion or chemical reaction process in a combustor, causing a mixing of gas and solids. The fluidizing action, much like a bubbling fluid, provides a means for effective chemical reactions and heat transfer in the combustor.

During the combustion process of fuels which have a sulfur-containing constituent, e.g., coal, sulfur is oxidized to form primarily gaseous SO2. In particular, FBC reduces the amount of sulfur emitted in the form of SO2by a desulfurization process. A suitable sorbent, such as limestone containing CaCO3, for example, is used to absorb SO2from flue gas during the combustion process. In order to promote both combustion of the fuel and the capture of sulfur, FBC power plants operate at temperatures lower than conventional combustion plants. Specifically, FBC power plants typically operate in a range between about 850° C. and about 900° C. Since this allows coal to combust at cooler temperatures, NOxproduction during combustion is lower than in other coal combustion processes.

To further increase utilization of the fuel and efficiency of sulfur capture, a cyclone separator is typically used to separate solids, e.g., unutilized fuel and/or limestone, entrained in flue gas leaving the combustor. The separated solids are then returned to the combustor via a recirculation means, e.g., a recirculation pipe, to be used again in the combustion process. A sealpot, sometimes referred to as a “j-leg,” maintains a seal between the combustor and the cyclone separator to prevent unwanted escape of flue gas from the combustor backward, e.g., in a direction opposite to flow of the separated solids into the combustor, through the recirculation pipe.

In connection with the above, air systems in an FBC power plant are designed to perform many functions. For example, air is used to fluidize the bed solids consisting of fuel, fuel ash and sorbent, and to sufficiently mix the bed solids with air to promote combustion, heat transfer and reduce emissions (e.g., SO2, CO, NOxand N2O). In order to accomplish these functions, the air system is configured to inject air, designated primary air (PA) or secondary air (SA), at various locations and at specific velocities and quantities.

In addition, fluidizing air or gas and transport air or gas are typically supplied to the sealpot to facilitate the flow of solids and gas through the sealpot, as disclosed in U.S. Pat. No. 9,163,830, which is hereby incorporated by reference herein in its entirety. In particular, as is known in the art, solids from the chemical process that move downward through a feedpipe into the sealpot from the cyclone separator are fluidized by the fluidizing air or gas. The fluidized solids are then transported to a discharge pipe by the fluidizing and/or transport air or gas and ultimately back to the combustor. Thus, the sealpot forms a seal, thereby preventing flue gases in the combustor from flowing backward through the sealpot, e.g., upward through the feedpipe back into the cyclone, as is known in the art.

More recently, sealpots have also found use in chemical looping systems. Chemical looping systems utilize a high temperature process, whereby solids such as calcium or metal-based compounds, for example, are “looped” between a first reactor, called an oxidizer, and a second reactor, called a reducer. In the oxidizer, oxygen from air injected into the oxidizer is captured by the solids in an oxidation reaction. The captured oxygen is then carried by the oxidized solids to the reducer to be used for combustion and/or gasification of a fuel such as coal. After a reduction reaction in the reducer, the solid products with some un-reacted solids are returned to the oxidizer to be oxidized again, and the cycle repeats. In such systems, a sealpot may be utilized to prevent a pressure differential that could cause backflow, as discussed above. For example, a sealpot may be utilized in between the output of the oxidizer and the input of the reducer to provide a flow of oxidized solids to the reducer and prevent backflow therefrom.

In both types of systems, the flow rate and temperature of the solids entering the combustor/reducer (e.g., coal in a traditional FBC system, and limestone/calcium oxide, or metal oxide, in a system that incorporates chemical looping) are important parameters that affect chemical reactions. In particular, the temperature of the circulating solids must often be reduced prior to entering the reactor in order to ensure a desired level of chemical reaction.

In view of the above, while the design of existing sealpots is generally suitable for controlling a flow of solids along a single pathway and preventing backflow, control of the flow rate and the temperature of such solids, as well as control of the flow of solids along multiple paths, remains challenging and inefficient. Accordingly, there is a need for an integrated system and apparatus that provides for more precise and flexible control of the flow direction, flow rate, and temperature of solids.

BRIEF DESCRIPTION

In an embodiment, an apparatus for controlling material flow is provided. The apparatus includes an inlet for receiving the material from a source, and a sealpot connected to the inlet, the sealpot having a fluidizing bed configured to receive the material from the inlet, a first discharge passageway and a second discharge passageway. The fluidizing bed includes a first transport zone associated with the first discharge passageway and a second transport zone associated with the second discharge passageway, wherein the first and second transport zones are configured to receive transport air or gas from a transport air or gas source. The transport air or gas is controllable to selectively divert a flow of the material into the first discharge passageway and the second discharge passageway.

In another embodiment, an apparatus for controlling solids flow in a solid transport system is provided. The apparatus includes a solids feed-pipe having an upper end which receives solids from an upstream flow, and a lower end, a bed fluidly coupled to the lower end of the solids feed-pipe and configured to receive the solids from the solids feed-pipe, the bed including a first transport zone and a second transport zone, each transport zone being configured to receive fluidizing gas from a gas source, a first discharge passageway adjacent to the first transport zone, and a second discharge passageway adjacent to the second transport zone. Fluidized solids are transported to the first discharge passageway and the second discharge passageway using the fluidizing gas supplied to the first and second transport zones.

In yet another embodiment, a method of controlling solids flow is provided. The method includes the steps of receiving solids at a bed from a source, fluidizing the solids in the bed using a gas, and selectively transporting the fluidized solids to a first discharge passageway and a second discharge passageway by controlling a supply of fluidizing gas to a first fluidizing zone of the bed associated with the first discharge passageway and a second fluidizing zone of the bed associated with the second discharge passageway.

DETAILED DESCRIPTION

Reference will be made below in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference characters used throughout the drawings refer to the same or like parts. While embodiments of the invention are suitable for use in connection with chemical reaction processes such as fluidized bed combustion and/or chemical looping, embodiments of the invention may also be applicable for use in other types of chemical process systems and processes, including power generation. In addition, it is contemplated that embodiments of the invention may be utilized in any system where control over the flow direction, flow rate and temperature of a material is desired, including systems not related to power generation.

As used herein, “operatively coupled” refers to a connection, which may be direct or indirect. The connection is not necessarily a mechanical attachment. As used herein, “communication” means that two or more components are connected in such a manner to allow for the propagation of signals between such components, such as, but not limited to, through wires/cables, fiber optics, and wireless transmitters/receivers. As used herein, “fluidly coupled” or “fluid communication” refers to an arrangement of two or more features such that the features are connected in such a way as to permit the flow of fluid between the features and permits fluid transfer.

As used herein, “solids” refers to solid particles intended for use in a chemical reaction process such as, for example, coal particles. “Materials” as used herein, refers generally to non-liquid and non-gas materials, such as solid particles and the like, regardless of their intended use.

Embodiments of the invention relate to a system, method and apparatus for controlling the flow direction, flow rate and/or temperature of solids. Referring toFIG. 1, an integrated direction, flow rate and temperature control apparatus100according to an embodiment of the invention is illustrated. The apparatus100includes first and second control subassemblies110,112each having a separate inlet for receiving first and second flows114,116of solids from first and second sources (e.g., from respective cyclone separators of separate combustors), and a common outlet118. Other than sharing a common outlet118, the control subassemblies110,112can be fluidly separated from one another such that solids entering one of the inlets are not permitted to mix with solids entering the other of the inlets other than at the outlet118. In other embodiments, the solids entering the respective control subassemblies110,112may exit at separate outlets. In other embodiments, each flowpath of the respective control subassemblies110,112(as discussed hereinafter) may have its own, dedicated outlet.

As further shown inFIG. 1, the first control subassembly110includes a first seal mechanism120fluidly coupled to the inlet, a bypass pathway122and a heat exchange pathway124. The bypass pathway122and the heat exchange pathway124are fluidly coupled to the seal mechanism120and to the outlet118and are configured to receive a flow of solids from the seal mechanism120and to direct the solids to the outlet118or other downstream paths, as discussed in detail hereinafter. In an embodiment the first control subassembly110may also include an empty chamber126intermediate the seal mechanism120and the bypass pathway122and heat exchange pathway124. In an embodiment, a weir128separates the bypass pathway122from the heat exchange pathway124, and a weir129divides the empty chamber126from the pathways122,124. In an embodiment, the weir128is configured as a wall that prevents solids from flowing between the bypass pathway122and the heat exchange pathway124.

Similarly, the second control subassembly112includes a second seal mechanism130fluidly coupled to the inlet, a bypass pathway132and a heat exchange pathway134. The bypass pathway132and the heat exchange pathway134are fluidly coupled to the seal mechanism130and to the outlet118and are configured to receive a flow of solids from the seal mechanism130and to direct the solids to the outlet118, as discussed in detail hereinafter. As illustrated inFIG. 1, the heat exchange pathway134of the second subassembly includes112a plurality of heat exchange chambers136,138,140. Although three separate heat exchange chambers136,138,140are illustrated, more or fewer heat exchanger chambers may be utilized without departing from the broader aspects of the present invention. In an embodiment the second control subassembly112may also include an empty chamber142intermediate the seal mechanism130and the bypass pathway132and heat exchange pathway134. In an embodiment, a weir144separates the bypass pathway132from the heat exchange pathway134, and a weir146divides the empty chamber142from the pathways132,134. As also shown therein, a weir148may also be positioned adjacent to the outlet118downstream from the pathways of each control subassembly. As with weir128, weir144is configured as a wall that prevents solids from flowing between the bypass pathway132and the heat exchange pathway134.

Referring now toFIG. 2, the configuration of the first seal mechanism120is illustrated. Second seal mechanism130is similarly configured, however, only first seal mechanism120is shown for purposes of simplification. In an embodiment, the seal mechanisms120,130are generally similar to that disclosed in U.S. Pat. No. 9,163,830 (which is incorporated by reference herein in its entirety) and operate to move solids therethrough in a generally similar manner. As shown inFIG. 2, a solids flow feedpipe150defines the first inlet for receiving the first flow114of solids. The feedpipe150receives solids from, for example, a solids separator (not shown) such as a cyclone separator, but is not limited thereto in certain embodiments. The feedpipe150supplies the solids to a dual fluidizing and/or transport bed152of the seal mechanism120.

First and second fluidizing zones154,156are supplied with a fluidizing gas, such as fluidizing air, for example, from a fluidizing gas source158. In an embodiment, the fluidizing gas source158may be a single gas source configured to selectively provide a flow of fluidizing gas to both zones154,156, although separate gas sources are also possible. Alternatively (or additionally), first and second transport zones160,162of the fluidizing/transport bed152are supplied with a transport gas, e.g., transport gas, supplied from a transport gas source164. In an embodiment, the transport gas source164may be a single gas source configured to selectively provide a flow of transport gas to both zones160,162, although separate gas sources are also possible. Further, in an embodiment, the fluidizing gas source158and the transport gas source164may be separate components, as shown inFIG. 2, or, alternatively, may be included in a single gas source (not shown). In an embodiment, each of the transport zones or fluidizing zones (or the supply conduits leading to each zone) may be configured with a flow control device such as a damper or valve159that is selectively controllable/adjustable in order to regulate the flow of gas to the respective transport zone or fluidizing zone, for the reasons discussed hereinafter.

As further shown inFIG. 2, discharge pipes or passageways166,168are connected to the fluidizing/transport bed152in an area substantially corresponding to the transport zones160,162of the bed152. An orifice plate170, similar to that disclosed in the '830 patent, is disposed between each discharge pipe166,168and the fluidizing/transport bed152. Each orifice plate170has a plurality of apertures172which limits solids (prevents a surge of solids flow) and allows fluidized solids being transported from the fluidizing/transport bed152to the respective discharge pipes166,168.

The plurality of apertures of the orifice plate170can be disposed at a height above the fluidizing/transport bed152and include at least one solids aperture172and at least one gas aperture174. In an exemplary embodiment, the solids aperture172is located at a height below the gas aperture174. As is known in the art, fluidized solids maintained in the fluidizing/transport bed152, and the solids column within the feedpipe150act as a seal preventing backflow from downstream flow. As is also known in the art, solids flow through the apertures and into the discharge pipes166,168(i.e., solids flow rate) is regulated based on the number and arrangement of rows of solids apertures172, the area of such apertures, and the velocity of fluidizing/transport gas supplied to the bed152, as is disclosed in the '830 patent and further discussed therein.

For example, in an exemplary embodiment, a flow rate of solids into the discharge pipes166,168of the seal mechanism is based upon a velocity of the fluidizing gas and/or the transport gas supplied from the fluidizing gas source158and/or the transport gas source164, respectively. In general, the flow of solids is related to the velocity of the fluidizing gas and/or the transport gas, e.g., increasing the velocity of the fluidizing gas and/or the transport gas using valves159causes a corresponding increase in the flow rate of solids through the seal mechanism (via more exposed solids apertures172). Therefore, a desired flow rate of solids, based upon operation of a power plant (not shown), is maintained by adjusting the velocity of the fluidizing gas and/or the transport gas.

Similarly, and as discussed in detail hereinafter, the ratio of solids entering discharge pipe166to discharge pipe168may be controlled by adjusting the amount/velocity of fluidizing and/or transport air provided to the transport and fluidizing zones associated with the respective discharge pipes166,168. For example, if it is desired that more solids be diverted to the discharge pipe166, then the flow of air into the fluidizing zone158and/or transport zone160associated with the discharge pipe166may be increased (relative to the flow or air into the zones associated with discharge pipe169) using, for example, valve159. This increase in air flow causes a corresponding increase in solids flow into the discharge pipe166.

In other embodiments, the flow rate of solids into each discharge pipe166,168is based upon the total number of solids apertures exposed to the solids. More specifically, the flow rate of solids is substantially proportional to the total number solid apertures172exposed to the solids; increasing the total number of solids apertures172exposed to the solids increases the flow rate of solids through the discharge pipes166,168. Therefore, the desired flow rate of solids, based upon operation of a transport system (not shown) having the seal mechanism, is maintained by adjusting the bed expansion height with fluidizing gas and gas injection to the feed pipe through the total number of solids apertures172. In still another exemplary embodiment, the flow rate of solids is based upon a height of a bed expansion line of relative to heights of the solids apertures172, as more particularly discussed in the '830 patent.

Turning now toFIG. 3, a detailed, schematic illustration of the first control subassembly110is shown. As illustrated, discharge pipe168of the first seal mechanism120is fluidly coupled to the bypass pathway122, and the discharge pipe166is fluidly coupled to the heat exchange pathway124. The amount of solids entering the heat exchange pathway124is first controlled by the gas velocity in transport zone160and162. In general, higher gas velocity promotes greater solids flow. As shown, the bypass pathway122leads directly to outlet118. The heat exchange pathway124includes a fluidized bed heat exchanger through which solids are configured to pass, to facilitate the mixing, cooling or heating of such solids, before being passed to the outlet118. As shown therein, the heat exchange pathway124includes empty chamber126and a heat exchange chamber176separated by weir129. The heat exchange chamber176includes a heat exchanger180associated therewith. Each chamber126,176is supplied with fluidizing and/or transport gas from a fluidizing/transport gas source182, which may be the same or different from gas sources158and164. Each of the fluidizing gas sources182may be configured with a control device such as a damper or valve183that allows for control over the flow rate and/or velocity of gas entering the chambers126,176, respectively.

Solids entering the heat exchange pathway124may be adjustably cooled (or heated) to a desired degree by controlling the velocity of gas provided to the empty chamber126and the heat exchange chamber176. For example, solids flowing into the empty chamber126may be slumped by decreasing the flow of gas from source182into the empty chamber126, or passed quickly to the heat exchange chamber176over the weir129by increasing the flow of gas into the empty chamber126. Likewise, once solids enter the heat exchange chamber176, the velocity of gas provided to the chamber176may be controlled in order to either increase or decrease the mixing of such solids and gas within the chamber176(which increases or decreases the amount of heat transfer that takes place). Once the solids exit the heat exchange pathway124, they are passed to the outlet118.

Turning now toFIG. 4, a detailed, schematic illustration of the second control subassembly112is shown. The second control subassembly112is configured similarly to the first control subassembly110, but instead of a single fluidized bed heat exchanger, uses a series of fluidized bed heat exchangers to more precisely control the temperature of solids. As illustrated inFIG. 4, discharge pipe168of the second seal mechanism130is fluidly coupled to the bypass pathway132, and the discharge pipe166is fluidly coupled to the heat exchange pathway134. As shown, the bypass pathway132leads directly to outlet118. The heat exchange pathway134includes a plurality of fluidized bed heat exchangers through which solids are configured to pass, to facilitate the cooling or heating of such solids, before being passed to the outlet118. As shown therein, the heat exchange pathway134includes empty chamber142and a series of heat exchange chambers136,138,140. The heat exchange chambers are separated from the empty chamber142by weir146, which the heat exchange chambers are separated from one another by weirs184. The heat exchange chambers136,138,140each include a respective heat exchanger186,188,190associated therewith. Each chamber146,136,138,140is supplied with gas from a gas source192, which may be the same or different from gas sources158,164,182. As illustrated, each of the gas sources192may be configured with a control device such as a damper or valve193that allows for control over the flow rate and/or velocity of gas entering the chambers136,138,140,142, respectively.

Solids entering the heat exchange pathway134may be adjustably cooled (or heated) to a desired degree by controlling the velocity of fluidized gas provided to the empty chamber146and the heat exchange chambers136,138,140. For example, solids flowing into the empty chamber142may be slumped by decreasing the flow of gas from source192into the empty chamber142, or passed quickly to the first heat exchange chamber136over the first weir146by increasing the flow of gas into the empty chamber142. Likewise, once solids enter the first heat exchange chamber136, the velocity of gas provided to the chamber136may be controlled in order to either increase or decrease the mixing of such solids and gas within the chamber136(which increases or decreases the amount of heat transfer that takes place). Similar slumping or flow of the solids within or out of the chambers138,140is controlled in the same manner, i.e., by increasing or decreasing the flow of gas within each such chamber138,140. Once the solids exit the heat exchange pathway134, they are passed to the outlet118.

In other embodiments, the heat exchange pathway134may be configured to provide a serpentine-like flow of solids through the pathway. For example, in an embodiment, weir146may have an aperture or space at the bottom thereof that allows solids to flow under the weir146(into the chamber136into the bottom thereof). Weir184between chambers138and140may be similarly configured. In operation, therefore, solids may flow into empty chamber142, beneath weir146, and into heat exchange chamber136. The solids may then flow out of chamber136over weir184and into chamber138. Once entering chamber138, the solids may flow under weir184into chamber190, and ultimately over weir148and to outlet118. In this embodiment, by entering chambers136,140at the bottom thereof (under the respective weirs), the solids are permitted to more closely interact with the heat exchangers186,190associated therewith (such as be passing through the heat exchangers) in order to better facilitate heat transfer.

In other embodiments, each of the heat exchange chambers136,138,140may have a width wherein different zones (indicated by the dashed lines inFIG. 1.) are defined along the width. The different zones may be provided with differing amounts of transport air in order to selectively pass or slump the solids within the respective chambers to more precisely control the temperature of the solids.

In connection with the above, each of the inlets of respective control subassemblies110,112may be configured with a temperature sensor configured to detect the inlet temperature of the solids from the first and second source. In an embodiment, each of the heat exchange pathways124,134may also be configured with one or more temperature sensors for detecting a temperature of solids at various points as they flow therethrough. Likewise, in an embodiment, the apparatus100may include a temperature sensor associated with the outlet118for detecting a temperature of the solids at the outlet118. Moreover, the system of the present invention may include a control unit200, as shown inFIG. 1, electrically or communicatively coupled to the apparatus100. The control unit200is configured to receive temperature data for the solids, including the inlet temperature of the solids and the outlet temperature of the solids, and to store a target temperature in a database. Moreover, the control unit200is configured to control the supply of fluidizing gas and transport gas provided to the bed152and the empty chambers126,142and heat exchange chambers176,136,138,140, as well as control operation of the heat exchangers within the respective heat exchange passageways. In connection with the above, the control unit200is configured to control the amount or velocity of transport gas and/or fluidizing gas provided to the respective transport zones in160,162and/or fluidizing zones154,156of the bed in dependence upon the detected inlet temperature of the solids in relation to the target temperature, as well as to the heat exchange chambers, as discussed in detail below. Such control may be provided by controlling the position of valves159,183and193.

Referring toFIGS. 1 and 2, in operation, solids from a first source are provided to the first control subassembly110through feedpipe150. As the solids enter the feedpipe150, or prior thereto, a temperature of the solids may be detected. Once entering the seal mechanism120the solids are provided to the fluidizing and/or transport bed152, where they mix with fluidizing gas supplied from one or more of the fluidizing gas sources158and/or transport gas supplied from one or more of the transport gas sources164to form fluidized solids in the fluidizing zones of the bed152. Depending on the inlet temperature of the solids in relation to a target temperature of the solids, they are either passed to the bypass pathway122or to the heat exchange pathway124. For example, if the temperature of the solids is close to the target temperature, the velocity of fluidizing gas and/or transport gas provided to the fluidizing zone154and transport zone160associated with the heat exchange pathway124is reduced, while the velocity of fluidizing gas and/or transport gas provided to the fluidizing zone156and transport zone162associated with the bypass pathway122is increased in order to direct the flow of solids into discharge pipe168leading to the bypass pathway122and ultimately to outlet118for subsequent use (rather than the discharge pipe166leading to the heat exchange pathway124). As used herein, “inlet temperature” is a temperature of the solids upstream from the bed152. As used herein, “target temperature” is a predetermined, optimal temperature or temperature range of the solids required for subsequent use of the solids.

If, however, the temperature of the solids is higher than the target temperature, the velocity (or amount/flow rate) of fluidizing gas and/or transport gas provided to the fluidizing zone154and transport zone160associated with the heat exchange pathway124is increased, while the velocity (or amount/flow rate) of fluidizing gas and/or transport gas provided to the fluidizing zone156and transport zone162associated with the bypass pathway122is reduced in order to direct the flow of solids into discharge pipe166leading to the heat exchange pathway124. As will be readily appreciated, therefore, the velocity of gas provided to the respective fluidizing zones154,156and transport zones160,162may be controlled in order to direct the flow of solids into multiple paths (i.e., a bypass path or heat exchange path).

Once the solids are passed into the heat exchange pathway124, the flow and temperature of such solids may be controlled by controlling the respective slumping or fluidizing of the solids within the empty chamber126and the heat exchange chamber176, as discussed above. In particular, if the temperature of the solids must be substantially reduced to meet the predetermined target temperature, the flow of fluidizing gas provided to the heat exchange chamber176may be increased in order to increase the mixing of the solids and gas within the chamber176, and hence the heat transfer rate from solids/gas to the heat exchanger. While in the heat exchange chamber176, heat is transferred from the solids to the fluid flowing through the heat exchanger180in order to reduce the temperature of the solids to the target temperature. The solids may then be passed to the outlet118by the fluidizing gas or other means, for subsequent use in a chemical process.

Similarly, as shown inFIG. 4, and simultaneously with flow and temperature control of solids within the first control subassembly110, solids from a second source may be provided to the second control subassembly112through solids feed-pipe150of the second seal mechanism130. As the solids enter the feed-pipe150, or prior thereto, a temperature of the solids may be detected. Once entering the seal mechanism130the solids are provided to the dual fluidizing and/or transport bed152, where they mix with fluidizing gas supplied from one or more of the fluidizing gas sources158and/or transport gas supplied from one or more of the transport gas sources164to form fluidized solids in the fluidizing zones of the bed152. Depending on the inlet temperature of the solids in relation to a target temperature of the solids, they are either passed to the bypass pathway132or to the heat exchange pathway134. For example, if the temperature of the solids is close to the target temperature, the velocity of fluidizing gas and/or transport gas provided to the fluidizing zone154and transport zone160associated with the heat exchange pathway134is reduced, while the velocity of fluidizing gas and/or transport gas provided to the fluidizing zone156and transport zone162associated with the bypass pathway132is increased in order to direct the flow of solids into discharge pipe168leading to the bypass pathway132and ultimately to outlet118for subsequent use (rather than the discharge pipe166leading to the heat exchange pathway134).

If, however, the temperature of the solids is higher than the target temperature (or, in other embodiments, lower than the target temperature), the velocity of fluidizing gas and/or transport gas provided to the fluidizing zone154and transport zone160associated with the heat exchange pathway134is increased, while the velocity of fluidizing gas and/or transport gas provided to the fluidizing zone156and transport zone162associated with the bypass pathway132is reduced in order to direct the flow of solids into discharge pipe166leading to the heat exchange pathway134. As indicated above, therefore, the velocity of gas provided to the respective fluidizing zones154,156and transport zones160,162may be controlled in order to direct the flow of solids into multiple paths (i.e., a bypass path132or heat exchange path134).

Once the solids are passed into the heat exchange pathway124, the flow and temperature of such solids may be controlled by controlling the respective slumping or fluidizing of the solids within the empty chamber126and the heat exchange chambers136,138,140, as discussed above. In particular, if the temperature of the solids must be substantially reduced to meet the predetermined target temperature, the flow of fluidizing gas provided to one or more of the heat exchange chambers136,138,140may be decreased in order to increase the residence time of the solids within one or more of the chambers136,138,140. While in the heat exchange chambers136,138,140, heat is transferred from the solids to the fluid flowing through the heat exchangers186,188,190in order to reduce the temperature of the solids to the target temperature. The solids may then be passed to the outlet118by the fluidizing gas, for subsequent use in a chemical process. Use of multiple heat exchangers rather than a single heat exchanger allows the temperature of the solids to be more precisely controlled while keeping the solids moving through the heat exchange pathway134.

In an embodiment, the empty chambers126,146are provided to help prevent the backup of fluidized solids and to aid in solids fluidization. In certain embodiments, the empty chambers126,146may be omitted from the apparatus100. While the apparatus100is illustrated as having two discharge flow paths (i.e., to the bypass pathway or the heat exchange pathway), the present invention is not limited in this regard. In particular, the seal mechanism of each control subassembly may include any number of discharge pipes or pathways, each having a fluidizing zone and transport zone supplied with fluidizing gas and transport gas, respectively, associated therewith. Accordingly, the velocity of transport gas supplied to each transport zone may be adjusted in order to selectively control the flow of solids into one or more pathways (i.e., in one or more directions). Indeed, rather than using mechanical valves or the like to control the direction and flow rate of solids along multiple pathways, transport gas may be utilized to selectively move the solids through the respective bypass or heat exchange loops, which is much less costly, more precise and much easier to implement that mechanical devices.

By combining a seal mechanism having two or more discharge pathways (i.e., one or more heat exchange pathways and a bypass pathway), the apparatus100provides the flexibility needed to meet a wide range of operating conditions and is effective in distributing solids at a controlled direction, flow rate and temperature. In particular, the apparatus may be designed to have any number of subassemblies configured to accept any number of source flows of solids having a variety of different inlet temperatures and pressures. The apparatus100is operable to control the flow of solids through the apparatus in order that the temperature of the solids at the outlet is precisely controlled, regardless of the temperature of the solids at the inlet.

In an embodiment, rather than employing weirs within the heat exchange pathways to separate the chambers within the respective heat exchange pathways, a large gap defining a non-fluidizing zone may be utilized to effectively separate the chambers from one another.

Referring toFIG. 5, a combustion power plant300and, more particularly, a fluidized bed combustion (FBC) power plant300includes the combustor310, the solids separator312, e.g., the cyclone separator312, and the integrated flow direction, flow rate and temperature control apparatus100according to an exemplary embodiment. The furnace310of the FBC power plant is supplied with primary gas (PA)314, secondary gas (SA)316and fuel318. In addition, other materials such as limestone (not shown), for example, may be supplied to the furnace310, but alternative exemplary embodiments are not limited to the foregoing components or materials.

In an exemplary embodiment, the combustor310is an FBC-type combustor such as a circulating fluidized bed (CFB) combustor, but alternative exemplary embodiments are not limited thereto. For example, the combustor310may be a bubbling fluidized bed (BFB) combustor, a moving fluidized bed combustor or a chemical looping combustor.

As the combustor310burns the fuel318, combustion products, including gases and solids, exit the combustor310via a flue320and enter the cyclone separator312. The cyclone separator312separates the solids and supplies the solids to the feedpipe150of the seal mechanism120(or seal mechanism130). The gases exit the cyclone separator312via a central duct322and are delivered to other components of the FBC power plant300such as atmosphere control equipment (not shown) via a tangential duct324.

The solids separated by the cyclone separator312are delivered to the feedpipe150of the seal mechanism120. In an exemplary embodiment, the solids are then returned to the combustor310via the outlet118of the apparatus100, as described above in greater detail with reference toFIGS. 1-4.

As alluded to above, the integrated flow direction, flow rate and temperature control apparatus100may also be incorporated into a chemical looping power generation system of the type known in the art. For example, the input to seal mechanism120could be an oxidizer loop of a chemical looping system. In such system, the apparatus100may be utilized to control the temperature and flow rate of solids from the oxidizer of the system to the reducer. Indeed, the apparatus100may be utilized to selectively cool oxidized solids to a temperature required to facilitate the chemical reaction within the reducer.

Thus, the integrated flow path, flow rate and/or temperature control apparatus100according to an exemplary embodiment provides a multiple orifice exit design and a method for controlling a flow rate of solids. Therefore, the apparatus has a substantially increased or effectively improved solids flow control range, as well as increased precision of regulation of the solids flow control range. In addition, the apparatus has increased steady state seal maintainability, decreased flue gas escape, decreased solids loss from the system, improve chemical reactions, and increased turndown ratio. The apparatus100also provides for precise temperature control of the solids passing therethrough, which facilitates more efficient combustion or better control of chemical reactions, and power generation, as a whole.

It will be noted that while exemplary embodiments have been described with reference to an apparatus including a dual-fluidized bed seal mechanism associated with fluidized bed combustion power plants such as circulating fluidized bed boilers and chemical process reactors, alternative exemplary embodiments are not limited thereto. Rather, an apparatus according to other embodiments may be utilized in any type of chemical process plant including power plants, but not limited to, CFB, BFB, transport bed or combined CFB, BFB and transport bed and other variations of fluidized bed process plants, as well as conventional power plants.

In addition, while the apparatus100has been described to control the process of a power plant, the present invention contemplates that the apparatus may be used with any process needing to control solids flow rate, pressure, flow direction and/or temperature within such a process system.

In an embodiment, an apparatus for controlling a flow direction, flow rate and/or temperature of a material is provided. The apparatus includes an inlet for receiving the material from a source, and a seal mechanism connected to the inlet, the seal mechanism having a fluidizing bed configured to receive the material from the inlet, a first discharge passageway and a second discharge passageway. The fluidizing bed includes a first transport zone associated with the first discharge passageway and a second transport zone associated with the second discharge passageway, wherein the first and second transport zones are configured to receive transport gas from a transport gas source. The transport gas is controllable to selectively divert a flow of the material into the first discharge passageway and the second discharge passageway. In an embodiment, the apparatus may further include a bypass pathway fluidly coupled to the first discharge passageway, and a heat exchange pathway fluidly coupled to the second discharge passageway. The heat exchange pathway may include at least one heat exchanger associated therewith for controlling a temperature of the material. In an embodiment, the heat exchange pathway includes a heat exchange chamber housing the heat exchanger and an empty chamber upstream from the heat exchange chamber, the heat exchange chamber and the empty chamber being separated by a weir. In an embodiment, the heat exchange chamber and the empty chamber are supplied with fluidizing gas for selectively passing the material through, or slumping the material within, each chamber. In an embodiment, the apparatus may also include an outlet fluidly coupled to the heat exchange pathway and the bypass pathway. In an embodiment, the apparatus may include a first orifice plate adjacent to the first discharge passageway and separating the first discharge passageway from the fluidizing bed, and a second orifice plate adjacent to the second discharge passageway and separating the second discharge passageway from the fluidizing bed. The first orifice plate and the second orifice plate each have a plurality of apertures disposed at a height above the bed which allow the transport of fluidized material and gas through the plurality of apertures of the orifice plate from the bed to the first and second discharge passageways, respectively. In an embodiment, the flow rate of the material into the first and second passageways is controlled based on at least one of a total number of the plurality of apertures, a diameter of an aperture of the plurality of apertures, a cross-sectional shape of an aperture of the plurality of apertures, an area of an aperture of the plurality of apertures and a height of an aperture of the plurality of apertures. In an embodiment, the apparatus is configured to control the flow direction, the flow rate and the temperature of the material in a chemical process plant. The chemical process plant may include at least one of a fluidized bed reactor, a circulating fluidized bed reactor, a bubbling fluidized bed reactor, a moving fluidized bed, and a transport reactor, or a combination of the above. In an embodiment, the fluidizing bed is configured to fluidize the material using a gas supplied from a fluidizing gas source. In an embodiment, the material is one of a solids fuel, a reactant and inert particles.

In another embodiment, an apparatus for controlling flow of solids in a chemical process plant is provided. The apparatus includes a solids feed-pipe having an upper end which receives solids of the power plant, and a lower end, a bed fluidly coupled to the lower end of the solids feed-pipe and configured to receive the solids from the solids feed-pipe, the bed including a first transport zone and a second transport zone, each transport zone being configured to receive transport gas from a transport gas source, a first discharge passageway adjacent to the first transport zone, and a second discharge passageway adjacent to the second transport zone. Fluidized solids are transported to the first discharge passageway and the second discharge passageway using the transport gas supplied to the first and second transport zones. In an embodiment, the apparatus further includes a bypass pathway fluidly coupled to the first discharge passageway, and a heat exchange pathway fluidly coupled to the second discharge passageway, the heat exchange pathway having at least one heat exchanger associated therewith for controlling a temperature of the solids. In an embodiment, the at least one heat exchanger is a plurality of heat exchangers, each heat exchanger being associated with a separate heat exchange chamber within the heat exchange pathway. In an embodiment, the apparatus includes an empty chamber within the heat exchange pathway and positioned upstream from the plurality of heat exchange chambers. The heat exchange chambers and the empty chamber are supplied with fluidizing gas for selectively passing the material through, or slumping the material within, each chamber to heat or cool the fluidized solids to a target temperature. In an embodiment, the apparatus may also include an outlet fluidly coupled to the heat exchange pathway and the bypass pathway for receiving the fluidized solids at approximately the target temperature. In an embodiment, the power plant includes at least one of a fluidized bed combustion power plant, a circulating fluidized bed boiler, a bubbling fluidized bed boiler, a moving fluidized bed boiler and a chemical looping combustor. In an embodiment, the feedpipe receives the solids from a first source and the apparatus further includes a second feedpipe having an upper end which receives solids of the power plant from a second source, a second bed fluidly coupled to the lower end of the second feedpipe and configured to receive the solids from the second feedpipe, the second bed including a first transport zone and a second transport zone, each transport zone being configured to receive transport gas from the transport gas source, a second bypass pathway in communication with the first transport zone of the second bed, and a second heat exchange pathway in communication with the second transport zone of the second bed. Fluidized solids from the second source are transported to the second bypass pathway and the second heat exchange pathway using the transport gas supplied to the first and second transport zones of the second bed. In an embodiment, the second heat exchange pathway and the second bypass pathway are fluidly coupled to the outlet.

In yet another embodiment, a method of controlling a flow direction, flow rate and/or temperature of solids is provided. The method includes the steps of, at a bed, receiving solids from a source, fluidizing the solids in the bed using a gas, and selectively transporting the fluidized solids to a first discharge passageway and a second discharge passageway by controlling a supply of transport gas to a first fluidizing zone of the bed associated with the first discharge passageway and a second fluidizing zone of the bed associated with the second discharge passageway. In an embodiment, the first discharge passageway is fluidly coupled to a bypass pathway, the second discharge passageway is fluidly coupled to a heat exchange pathway having at least one heat exchanger associated therewith for controlling a temperature of the fluidized solids, and the method includes the step of varying at least one of an amount and velocity of the transport gas provided to at least one of the first fluidizing zone and the second fluidizing zone in dependence upon an inlet temperature of the solids. In an embodiment, the method may also include the step of, if the inlet temperature of the solids is greater than a target temperature, increasing at least one of the amount and velocity of the transport gas provided to the second fluidizing zone to transport the fluidized solids into the heat exchange passageway to decrease the temperature of the fluidized solids. In an embodiment, the method may also include the step of, if the inlet temperature of the solids is approximately equal to or less than a target temperature, increasing at least one of the amount and velocity of the transport gas provided to the first fluidizing zone to transport the fluidized solids into the bypass passageway. In an embodiment, in addition to solids/gas temperature control, the same concept can be used in controlling a chemical reaction for specific materials/solids at a desired temperature and pressure. For example, the flow rate of solids through the system may be precisely controlled in the various manners discussed above in order to more precisely one or more chemical reactions within the system.