US20170356642A1 - Circulating fluidized bed boiler with bottom-supported in-bed heat exchanger - Google Patents
Circulating fluidized bed boiler with bottom-supported in-bed heat exchanger Download PDFInfo
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- US20170356642A1 US20170356642A1 US15/618,913 US201715618913A US2017356642A1 US 20170356642 A1 US20170356642 A1 US 20170356642A1 US 201715618913 A US201715618913 A US 201715618913A US 2017356642 A1 US2017356642 A1 US 2017356642A1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/01—Fluidised bed combustion apparatus in a fluidised bed of catalytic particles
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
- F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
- F22B31/0015—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed for boilers of the water tube type
- F22B31/0023—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed for boilers of the water tube type with tubes in the bed
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
- F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
- F22B31/0061—Constructional features of bed cooling
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
- F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
- F22B31/0069—Systems therefor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
- F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
- F22B31/0084—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed
- F22B31/0092—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed with a fluidized heat exchange bed and a fluidized combustion bed separated by a partition, the bed particles circulating around or through that partition
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/02—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
- F23C10/12—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated exclusively within the combustion zone
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/20—Inlets for fluidisation air, e.g. grids; Bottoms
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/22—Fuel feeders specially adapted for fluidised bed combustion apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C2206/00—Fluidised bed combustion
- F23C2206/10—Circulating fluidised bed
- F23C2206/102—Control of recirculation rate
Definitions
- the present disclosure generally relates to the field of circulating fluidized bed (CFB) reactors or boilers such as those used in electric power generation facilities and, in particular, to a new and useful CFB reactor arrangement which permits temperature control within the CFB reaction chamber and/or of the effluent solids with an in-bed heat exchanger (IBHX).
- the CFB reactor arrangement provides a bottom-supported IBHX wherein the enclosure that defines the IBHX is supported from the dormant solids hoppers for the CFB and bubbling fluidized bed (BFB) of the IBHX.
- Circulating fluidized bed (CFB) reactors or boilers are used in the production of steam for industrial processes and electric power generation; see, for example, U.S. Pat. Nos. 5,799,593, 4,992,085, 4,891,052, 5,343,830, 5,378,253, 5,435,820, and 5,809,940.
- CFB boilers see Steam/its generation and use, 42nd Edition, edited by G. L. Tomei, Copyright 2015, The Babcock & Wilcox Company, ISBN 978-0-9634570-2-8, the text of which is hereby incorporated by reference as though fully set forth herein.
- upward gas flow carries reacting and non-reacting solids to an outlet at the upper portion of the furnace where the solids are separated from the gas, often by a staggered array of impact-type particle separators.
- the solids are used within the combustion process to transfer heat from the chemical process to the boiler water-cooled enclosure walls and other heating surfaces. The solids thus help control the overall furnace temperature that results in reducing NOx and SO 2 .
- the bulk of the solids reaching the top of the furnace are collected and returned to the furnace bottom.
- U.S. Pat. No. 6,532,905 discloses a controllable solids heat exchanger called an in-bed heat exchanger (IBHX).
- IBHX in-bed heat exchanger
- BFB bubbling fluidized bed
- Heat transfer in the heat exchanger is controlled by controlling the rate of solids discharge from the lower part of the BFB into the furnace.
- the discharge control is accomplished using at least one non-mechanical valve being operated by controlling flow rate of fluidizing gas in the vicinity of the non-mechanical valve.
- the present disclosure improves reliability of the CFB boiler with IBHX while reducing its cost and widening the range of design options.
- the disclosure provides a configuration wherein the enclosure of the IBHX is supported from the dormant solids hoppers for CFB and IBHX located under the distribution grids.
- the disclosure provides a support configuration wherein the membranes between the tubes of the enclosure walls are removed to define loose tubes that extend through the hopper walls to accommodate thermal expansion.
- the disclosure provides a support configuration wherein a skirt is disposed inside the IBHX hopper to prevent gas leakage from the IBHX hopper to the CFB hopper around the enclosure supports.
- the disclosure provides a support configuration wherein a secondary gas conduit is supported by the CFB hopper with a secondary gas duct carried by the IBHX enclosure with nozzles to provide secondary gas to the CFB.
- a circulating fluidized bed (CFB) boiler comprising: a CFB reaction chamber having side walls and an open-bottom grid defining a floor at a lower end of the CFB reaction chamber for providing fluidizing gas into the CFB reaction chamber; at least one bubbling fluidized bed (BFB) located within a lower portion of the CFB reaction chamber and being bound by enclosure walls and the floor of the CFB reaction chamber, with the fluidizing gas feed to the BFB portion of the grid controlled separately from the fluidizing gas feed to the CFB portion of the grid; at least one controllable in-bed heat exchanger (IBHX), the IBHX occupying part of the CFB reaction chamber floor and being surrounded by the enclosure walls of the BFB; bottom-supported hoppers containing dormant solids disposed under the CFB and the BFB; the enclosure walls of the BFB being supported off the bottom-supported hoppers; the enclosure walls of the BFB are of cooled membrane gas-tight design around the perimeter of the BFB, including: at least one top
- a circulating fluidized bed (CFB) boiler comprising: a CFB reaction chamber having walls and an open-bottom grid defining a floor at a lower end of the CFB reaction chamber for providing fluidizing gas into the CFB reaction chamber; at least one bubbling fluidized bed (BFB) located within a lower portion of the CFB reaction chamber and being bound by enclosure walls and the floor of the CFB reaction chamber, with the fluidizing gas feed to the BFB portion of the grid controlled separately from the fluidizing gas feed to the CFB portion of the grid; at least one controllable in-bed heat exchanger (IBHX), the IBHX occupying part of the CFB reaction chamber floor and being surrounded by the enclosure walls of the BFB; hoppers containing dormant solids disposed under the CFB and the BFB; and the enclosure walls of the BFB being supported off the bottom-supported hoppers.
- a CFB reaction chamber having walls and an open-bottom grid defining a floor at a lower end of the CFB reaction chamber for providing fluidizing gas into the C
- a circulating fluidized bed (CFB) boiler comprising: a CFB reaction chamber having walls and an open-bottom grid defining a floor at a lower end of the CFB reaction chamber for providing fluidizing gas into the CFB reaction chamber; at least one bubbling fluidized bed (BFB) located within a lower portion of the CFB reaction chamber and being bound by enclosure walls and the floor of the CFB reaction chamber, with the fluidizing gas feed to the BFB portion of the grid controlled separately from the fluidizing gas feed to the CFB portion of the grid; the enclosure walls of the BFB are of cooled membrane gas-tight design; at least one controllable in-bed heat exchanger (IBHX), the IBHX occupying part of the CFB reaction chamber floor and being surrounded by the enclosure walls of the BFB; hoppers containing dormant solids disposed under the CFB and the BFB; and the enclosure walls of the BFB being connected to at least one of the bottom-supported hoppers with supports and becoming of a loose design with sufficient flexibility
- FIG. 1 is a sectional side elevation view of a CFB boiler depicting a first exemplary configuration of the disclosure, illustrating a bubbling fluidized bed (BFB) enclosure within the CFB boiler.
- BFB bubbling fluidized bed
- FIG. 2 is an enlarged view of a portion of the BFB enclosure disposed below the distribution grid of the CFB.
- FIG. 2A is a view taken along line 2 A- 2 A of FIG. 2 .
- FIG. 3 is a plan view looking down along line 3 - 3 of FIG. 1 .
- FIG. 4 is a section view taken along line 4 - 4 of FIG. 3 .
- a circulating fluidized bed (CFB) furnace 1 includes walls 2 (including roof 2 a ) and an in-bed heat exchanger (IBHX) 3 immersed in bubbling fluidized bed (BFB) 4 .
- the circulating fluidized bed of furnace 1 predominantly includes solids made up of the ash of fuel 5 , sulfated sorbent 6 and, in some cases, external inert material 7 fed through at least one of walls 2 and fluidized by fluidizing gas (typically, primary air) 8 supplied through a distribution grid 9 fed from pipes 10 .
- fluidizing gas typically, primary air
- the dormant solids under CFB and BFB are contained in hoppers ( 26 and 27 , correspondingly) equipped with outlets for draining solids from CFB and BFB ( 28 and 29 , correspondingly).
- Pipes 10 and 25 are supported off hoppers 26 and 27 , correspondingly (supports are not shown).
- BFB 4 is separated from the CFB by an enclosure 30 made of gas-tight cooled membrane panels.
- Enclosure 30 surrounds the perimeter of BFB 4 but is essentially open from the top allowing solids influx from CFB into BFB (arrow 19 ).
- Enclosure 30 includes overflow ports (that can be formed as vertical slots connected to top opening 31 ; see FIG. 3 ) 32 , which lowest elevation essentially defines the height of BFB 4 .
- Enclosure 30 also includes underflow ports 34 . Controlling rate of solids recycle 35 through underflow ports 34 allows controlling the heat duty of IBHX 3 . The rate of solids recycle 35 is controlled by separately controlling (not shown) feed rate of fluidizing medium 22 to BFB plan areas adjacent to underflow ports 34 .
- the pressure within enclosure 30 equals the pressure outside of it at the elevation of the top of BFB 4 . Due to higher bulk density of BFB compared to CFB, the pressure below that elevation is higher on the BFB side, i.e. within enclosure 30 .
- the highest pressure differential is at the elevation of the distribution grids ( 9 and 24 , located essentially at the same elevation).
- Cooled membrane panels 60 are used as stiffeners of enclosure walls 30 providing the rigidity necessary to withstand the pressure differential.
- the height of panels 60 depends on the amount of heat transfer surface required for the furnace heat duty. They can extend all the way through the furnace roof 2 A or be cut shorter and topped with headers 65 , from which pipes 70 continue up to roof 2 A.
- the lower ends of panels 60 penetrate through hoppers 27 and terminate with headers 61 .
- Enclosure 30 is topped with a header 72 that is connected with the outside of the furnace through pipes 74 . If temperature of the cooling medium in enclosure 30 and/or panels 60 differs from that of walls 2 , corresponding penetrations through roof 2 A are equipped with expansion joints 76 and 78 . The lower part of enclosure 30 extends below grid 24 . The weight of enclosure 30 is supported off hoppers 26 and 27 .
- An exemplary configuration of a supports 79 and 80 for supporting enclosure 30 is depicted in FIGS. 2 and 2A . Support 79 is welded to the walls of the hoppers 26 and 27 while support 80 is welded to membranes 81 . Horizontal pads 82 and 83 are welded to supports 79 and 80 , respectively.
- FIGS. 2 and 2A depict one exemplary configuration but other support arrangements can be used to support enclosure 30 from one or both of hoppers 26 and 27 .
- the membranes 81 in the panels forming enclosure 30 terminate, and the resulting configuration of loose tubes 84 provides flexibility to accommodate differences in thermal expansion of tubes 84 and hoppers 26 and 27 as tubes 84 penetrate the walls of hopper 26 .
- Skirt 86 is attached to the inside of enclosure 30 above support 80 and extends into hopper 27 .
- Loose tubes 84 are connected to headers 88 outside hoppers 26 and 27 .
- IBHX 3 can be supported off platework between hoppers 27 or off enclosure 30 or some combination thereof. IBHX 3 terminates at headers 89 .
- Enclosure 30 also includes a duct 92 for supplying part of secondary gas (typically, secondary air) 95 through nozzles 98 into the CFB.
- Nozzles 98 can be formed of enclosure 30 tubes.
- Another part of secondary gas 95 is supplied through nozzles 99 on walls 2 .
- the combination of nozzles 98 and 99 allows effective coverage of furnace 1 plan area by secondary gas 95 .
- One type of nozzle that can be used is disclosed in U.S. Pat. No. 8,622,029, the text of which is hereby incorporated by reference as though fully set forth herein. At certain conditions, e.g. for smaller furnace sizes, it is possible to provide an acceptable secondary gas coverage by using only nozzles 99 on walls 2 . In such a configuration, duct 92 is not required and can be removed.
- Duct 92 is supplied with secondary gas 95 through a conduit 102 made of membrane panels 104 . As shown in FIG. 4 , part of the panel 104 between duct 92 and conduit 102 turns into screen 105 to allow a passage for the secondary gas from conduit 102 into duct 92 . Panels 104 at the upper end can terminate at header 72 and/or dedicated headers (not shown). Their lower ends extend downward to essentially the same elevation as where gas-tight BFB enclosure 30 turns into a loose-tube type design. At that elevation conduit 102 made of panels 104 is connected gas-tightly to plate-type conduit 106 that continues to the wall of hopper 26 and penetrates the wall.
- Conduit 106 is equipped with expansion joints 107 on its both ends for accommodating its thermal expansion versus conduit 102 and hopper 26 .
- membrane panels 104 turn into loose tubes 108 , which configuration allows accommodation of the difference in thermal expansion between tubes 108 and hopper 26 as the tubes penetrate the hopper wall and terminate at header 109 .
- Furnace walls 2 are supported off top steel 110 and expand downwards. Hoppers 26 and 27 have bottom supports 115 and expand upwards. A pressure seal allowing both expansions is provided by expansion joint 120 around the perimeter of furnace 1 . At certain conditions, e.g. lower furnace height due to high fuel reactivity and/or relaxed combustion efficiency requirements and/or relaxed emissions requirements, etc., the entire boiler can be bottom-supported. This would eliminate the need in expansion joint 120 .
Abstract
Description
- This patent application claims priority to U.S. Provisional Patent Application No. 62/349,627 filed Jun. 13, 2016 and titled “CIRCULATING FLUIDIZED BED BOILER WITH BOTTOM-SUPPORTED IN-BED HEAT EXCHANGER.” The complete text of this patent application is hereby incorporated by reference as though fully set forth herein in its entirety.
- The present disclosure generally relates to the field of circulating fluidized bed (CFB) reactors or boilers such as those used in electric power generation facilities and, in particular, to a new and useful CFB reactor arrangement which permits temperature control within the CFB reaction chamber and/or of the effluent solids with an in-bed heat exchanger (IBHX). The CFB reactor arrangement provides a bottom-supported IBHX wherein the enclosure that defines the IBHX is supported from the dormant solids hoppers for the CFB and bubbling fluidized bed (BFB) of the IBHX.
- Circulating fluidized bed (CFB) reactors or boilers are used in the production of steam for industrial processes and electric power generation; see, for example, U.S. Pat. Nos. 5,799,593, 4,992,085, 4,891,052, 5,343,830, 5,378,253, 5,435,820, and 5,809,940. For an overview of the design and operation of CFB boilers, see Steam/its generation and use, 42nd Edition, edited by G. L. Tomei, Copyright 2015, The Babcock & Wilcox Company, ISBN 978-0-9634570-2-8, the text of which is hereby incorporated by reference as though fully set forth herein.
- In a CFB boiler, upward gas flow carries reacting and non-reacting solids to an outlet at the upper portion of the furnace where the solids are separated from the gas, often by a staggered array of impact-type particle separators. The solids are used within the combustion process to transfer heat from the chemical process to the boiler water-cooled enclosure walls and other heating surfaces. The solids thus help control the overall furnace temperature that results in reducing NOx and SO2. The bulk of the solids reaching the top of the furnace are collected and returned to the furnace bottom.
- U.S. Pat. No. 6,532,905 discloses a controllable solids heat exchanger called an in-bed heat exchanger (IBHX). The heat exchanger is immersed within a bubbling fluidized bed (BFB). Heat transfer in the heat exchanger is controlled by controlling the rate of solids discharge from the lower part of the BFB into the furnace. The discharge control is accomplished using at least one non-mechanical valve being operated by controlling flow rate of fluidizing gas in the vicinity of the non-mechanical valve. Reducing or completely shutting off fluidizing gas flow to the controlling fluidizing device (typically, a plurality of bubble caps are used to distribute the fluidizing gas) hampers local fluidization and, correspondingly, slows down solids movement through the non-mechanical valve thus allowing the control of the solids discharge from the BFB to the CFB. U.S. Pat. No. 8,434,430 discloses an example of a controllable non-mechanical valve for an IBHX in FIG. 3 of the patent.
- An undesired drawback of reducing the flow rate of the fluidizing gas in the vicinity of the non-mechanical valve is bed material agglomeration. The decrease of the local fluidizing velocity and corresponding reduction of the bed mixing (while combustion takes place) can result in a local bed temperature rise sufficient for bed material agglomeration. Solids agglomeration may also happen elsewhere in the bed of the IBHX because generally lower fluidizing velocity in the BFB (compared to CFB) results in less vigorous mixing and thus higher potential for temperature and chemical non-uniformity leading to forming agglomerates. To be discharged from the IBHX through a dedicated drain opening, the agglomerates have to be moved towards this opening by the solids discharge flow. If the flow is not sufficient to move the agglomerates, they will eventually accumulate in the IBHX rendering its inoperable.
- Using an open bottom design (see Steam: Its Generation and Use, 41st ed., page 17-3 (2005; The Babcock & Wilcox Company, Barberton, Ohio) allows draining agglomerates from any location of the IBHX thus greatly improving its operation reliability. Using an open bottom design with an IBHX, however, is associated with a substantial weight of bed material in the hopper(s) below the IBHX and corresponding load increase on the boiler support steel.
- The present disclosure improves reliability of the CFB boiler with IBHX while reducing its cost and widening the range of design options.
- The disclosure provides a configuration wherein the enclosure of the IBHX is supported from the dormant solids hoppers for CFB and IBHX located under the distribution grids.
- The disclosure provides a support configuration wherein the membranes between the tubes of the enclosure walls are removed to define loose tubes that extend through the hopper walls to accommodate thermal expansion.
- The disclosure provides a support configuration wherein a skirt is disposed inside the IBHX hopper to prevent gas leakage from the IBHX hopper to the CFB hopper around the enclosure supports.
- The disclosure provides a support configuration wherein a secondary gas conduit is supported by the CFB hopper with a secondary gas duct carried by the IBHX enclosure with nozzles to provide secondary gas to the CFB.
- One embodiment of the invention discloses a circulating fluidized bed (CFB) boiler comprising: a CFB reaction chamber having side walls and an open-bottom grid defining a floor at a lower end of the CFB reaction chamber for providing fluidizing gas into the CFB reaction chamber; at least one bubbling fluidized bed (BFB) located within a lower portion of the CFB reaction chamber and being bound by enclosure walls and the floor of the CFB reaction chamber, with the fluidizing gas feed to the BFB portion of the grid controlled separately from the fluidizing gas feed to the CFB portion of the grid; at least one controllable in-bed heat exchanger (IBHX), the IBHX occupying part of the CFB reaction chamber floor and being surrounded by the enclosure walls of the BFB; bottom-supported hoppers containing dormant solids disposed under the CFB and the BFB; the enclosure walls of the BFB being supported off the bottom-supported hoppers; the enclosure walls of the BFB are of cooled membrane gas-tight design around the perimeter of the BFB, including: at least one top opening for CFB solids influx into the BFB; at least one overflow port for setting the BFB height; at least one underflow port for BFB solids controlled recycle back into the CFB; the gas-tight BFB enclosure extending below the grid to the elevation sufficient for not exceeding a preset percentage of leakage of the fluidizing gas from the BFB into the CFB through the bed of the dormant solids between the aforementioned elevation and the grid; and the tubes of the BFB enclosure below that elevation becoming of a loose design with sufficient flexibility for accommodating differences in thermal expansion of the tubes and the hoppers as the tubes penetrate the walls of the hoppers.
- Another embodiment of the invention discloses a circulating fluidized bed (CFB) boiler comprising: a CFB reaction chamber having walls and an open-bottom grid defining a floor at a lower end of the CFB reaction chamber for providing fluidizing gas into the CFB reaction chamber; at least one bubbling fluidized bed (BFB) located within a lower portion of the CFB reaction chamber and being bound by enclosure walls and the floor of the CFB reaction chamber, with the fluidizing gas feed to the BFB portion of the grid controlled separately from the fluidizing gas feed to the CFB portion of the grid; at least one controllable in-bed heat exchanger (IBHX), the IBHX occupying part of the CFB reaction chamber floor and being surrounded by the enclosure walls of the BFB; hoppers containing dormant solids disposed under the CFB and the BFB; and the enclosure walls of the BFB being supported off the bottom-supported hoppers.
- Yet another embodiment of the invention discloses a circulating fluidized bed (CFB) boiler comprising: a CFB reaction chamber having walls and an open-bottom grid defining a floor at a lower end of the CFB reaction chamber for providing fluidizing gas into the CFB reaction chamber; at least one bubbling fluidized bed (BFB) located within a lower portion of the CFB reaction chamber and being bound by enclosure walls and the floor of the CFB reaction chamber, with the fluidizing gas feed to the BFB portion of the grid controlled separately from the fluidizing gas feed to the CFB portion of the grid; the enclosure walls of the BFB are of cooled membrane gas-tight design; at least one controllable in-bed heat exchanger (IBHX), the IBHX occupying part of the CFB reaction chamber floor and being surrounded by the enclosure walls of the BFB; hoppers containing dormant solids disposed under the CFB and the BFB; and the enclosure walls of the BFB being connected to at least one of the bottom-supported hoppers with supports and becoming of a loose design with sufficient flexibility for accommodating differences in thermal expansion of the tubes and the hopper as the tubes penetrate the hopper wall.
- The preceding non-limiting aspects, as well as others, are more particularly described below. A more complete understanding of the processes and equipment can be obtained by reference to the accompanying drawings, which are not intended to indicate relative size and dimensions of the assemblies or components thereof. In those drawings and the description below, like numeric designations refer to components of like function. Specific terms used in that description are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure.
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FIG. 1 is a sectional side elevation view of a CFB boiler depicting a first exemplary configuration of the disclosure, illustrating a bubbling fluidized bed (BFB) enclosure within the CFB boiler. -
FIG. 2 is an enlarged view of a portion of the BFB enclosure disposed below the distribution grid of the CFB. -
FIG. 2A is a view taken alongline 2A-2A ofFIG. 2 . -
FIG. 3 is a plan view looking down along line 3-3 ofFIG. 1 . -
FIG. 4 is a section view taken along line 4-4 ofFIG. 3 . - As shown in
FIGS. 1-4 , a circulating fluidized bed (CFB)furnace 1 includes walls 2 (including roof 2 a) and an in-bed heat exchanger (IBHX) 3 immersed in bubbling fluidized bed (BFB) 4. The circulating fluidized bed offurnace 1 predominantly includes solids made up of the ash offuel 5, sulfated sorbent 6 and, in some cases, externalinert material 7 fed through at least one ofwalls 2 and fluidized by fluidizing gas (typically, primary air) 8 supplied through adistribution grid 9 fed frompipes 10. Dormant solids belowgrid 9 effectively define a part of the furnace floor. Some solids are entrained by gases resulting from the fuel combustion and move upward (arrows 15) eventually reaching aparticle separator 16 at the furnace exit. While some of the solids (arrow 17) passseparator 16, the bulk of them (arrow 18) are captured and recycled back to the furnace. Those solids along with others (arrow 19), falling out ofupflow solids stream 15, feed BFB 4 that is being fluidized by fluidizing gas (typically, air) 22 supplied through aBFB distribution grid 24 fed frompipes 25. Dormant solids belowgrid 24 effectively define another part of the furnace floor. The dormant solids under CFB and BFB are contained in hoppers (26 and 27, correspondingly) equipped with outlets for draining solids from CFB and BFB (28 and 29, correspondingly).Pipes hoppers - BFB 4 is separated from the CFB by an
enclosure 30 made of gas-tight cooled membrane panels.Enclosure 30 surrounds the perimeter ofBFB 4 but is essentially open from the top allowing solids influx from CFB into BFB (arrow 19).Enclosure 30 includes overflow ports (that can be formed as vertical slots connected totop opening 31; seeFIG. 3 ) 32, which lowest elevation essentially defines the height ofBFB 4.Enclosure 30 also includesunderflow ports 34. Controlling rate of solids recycle 35 throughunderflow ports 34 allows controlling the heat duty ofIBHX 3. The rate of solids recycle 35 is controlled by separately controlling (not shown) feed rate of fluidizingmedium 22 to BFB plan areas adjacent to underflowports 34. - The pressure within
enclosure 30 equals the pressure outside of it at the elevation of the top ofBFB 4. Due to higher bulk density of BFB compared to CFB, the pressure below that elevation is higher on the BFB side, i.e. withinenclosure 30. The highest pressure differential is at the elevation of the distribution grids (9 and 24, located essentially at the same elevation). Cooledmembrane panels 60 are used as stiffeners ofenclosure walls 30 providing the rigidity necessary to withstand the pressure differential. The height ofpanels 60 depends on the amount of heat transfer surface required for the furnace heat duty. They can extend all the way through thefurnace roof 2A or be cut shorter and topped withheaders 65, from whichpipes 70 continue up toroof 2A. The lower ends ofpanels 60 penetrate throughhoppers 27 and terminate withheaders 61. -
Enclosure 30 is topped with aheader 72 that is connected with the outside of the furnace throughpipes 74. If temperature of the cooling medium inenclosure 30 and/orpanels 60 differs from that ofwalls 2, corresponding penetrations throughroof 2A are equipped withexpansion joints enclosure 30 extends belowgrid 24. The weight ofenclosure 30 is supported offhoppers supports enclosure 30 is depicted inFIGS. 2 and 2A .Support 79 is welded to the walls of thehoppers support 80 is welded to membranes 81.Horizontal pads supports pads enclosure 30 andhoppers FIGS. 2 and 2A depict one exemplary configuration but other support arrangements can be used to supportenclosure 30 from one or both ofhoppers membranes 81 in thepanels forming enclosure 30 terminate, and the resulting configuration ofloose tubes 84 provides flexibility to accommodate differences in thermal expansion oftubes 84 andhoppers tubes 84 penetrate the walls ofhopper 26.Skirt 86 is attached to the inside ofenclosure 30 abovesupport 80 and extends intohopper 27. Positive pressure in hopper 27 (compared to hopper 26) pushesskirt 86 against the wall ofhopper 27 creating a seal (along with the resistance of the layer of dormant solids below grid 24) that essentially eliminates fluidizing gas leakage betweenhoppers Loose tubes 84 are connected toheaders 88outside hoppers -
IBHX 3 can be supported off platework betweenhoppers 27 or offenclosure 30 or some combination thereof.IBHX 3 terminates atheaders 89. -
Enclosure 30 also includes aduct 92 for supplying part of secondary gas (typically, secondary air) 95 throughnozzles 98 into the CFB.Nozzles 98 can be formed ofenclosure 30 tubes. Another part ofsecondary gas 95 is supplied throughnozzles 99 onwalls 2. The combination ofnozzles furnace 1 plan area bysecondary gas 95. One type of nozzle that can be used is disclosed in U.S. Pat. No. 8,622,029, the text of which is hereby incorporated by reference as though fully set forth herein. At certain conditions, e.g. for smaller furnace sizes, it is possible to provide an acceptable secondary gas coverage by usingonly nozzles 99 onwalls 2. In such a configuration,duct 92 is not required and can be removed. -
Duct 92 is supplied withsecondary gas 95 through aconduit 102 made ofmembrane panels 104. As shown inFIG. 4 , part of thepanel 104 betweenduct 92 andconduit 102 turns intoscreen 105 to allow a passage for the secondary gas fromconduit 102 intoduct 92.Panels 104 at the upper end can terminate atheader 72 and/or dedicated headers (not shown). Their lower ends extend downward to essentially the same elevation as where gas-tight BFB enclosure 30 turns into a loose-tube type design. At thatelevation conduit 102 made ofpanels 104 is connected gas-tightly to plate-type conduit 106 that continues to the wall ofhopper 26 and penetrates the wall.Conduit 106 is equipped withexpansion joints 107 on its both ends for accommodating its thermal expansion versusconduit 102 andhopper 26. Upon the connection withconduit 106,membrane panels 104 turn intoloose tubes 108, which configuration allows accommodation of the difference in thermal expansion betweentubes 108 andhopper 26 as the tubes penetrate the hopper wall and terminate atheader 109. -
Furnace walls 2 are supported offtop steel 110 and expand downwards.Hoppers bottom supports 115 and expand upwards. A pressure seal allowing both expansions is provided byexpansion joint 120 around the perimeter offurnace 1. At certain conditions, e.g. lower furnace height due to high fuel reactivity and/or relaxed combustion efficiency requirements and/or relaxed emissions requirements, etc., the entire boiler can be bottom-supported. This would eliminate the need inexpansion joint 120. - The foregoing description has been made with reference to exemplary embodiments. Modifications and alterations of those embodiments will be apparent to one who reads and understands this general description. The present disclosure should be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or equivalents thereof.
- The relevant portion(s) of any specifically referenced patent and/or published patent application is/are incorporated herein by reference.
Claims (19)
Priority Applications (8)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US15/618,913 US20170356642A1 (en) | 2016-06-13 | 2017-06-09 | Circulating fluidized bed boiler with bottom-supported in-bed heat exchanger |
EP17175855.0A EP3306189A1 (en) | 2016-06-13 | 2017-06-13 | Circulating fluidized bed boiler with bottom-supported in-bed heat exchanger |
CL2017001518A CL2017001518A1 (en) | 2016-06-13 | 2017-06-13 | Circular fluidized bed boiler with a built-in lower support heat exchanger. |
CN201710444334.1A CN107490003A (en) | 2016-06-13 | 2017-06-13 | The CFBB of bed inside heat exchanger with bottom support |
BR102017012587-4A BR102017012587A2 (en) | 2016-06-13 | 2017-06-13 | CIRCULATING FLUIDIZED BED BOILER WITH BACKGROUND HEAT EXCHANGE |
CONC2017/0005825A CO2017005825A1 (en) | 2016-06-13 | 2017-06-13 | Circulating fluidized bed boiler with bottom supported bed heat exchanger |
PH12017000173A PH12017000173A1 (en) | 2016-06-13 | 2017-06-13 | Circulating fluidized bed boiler with bottom-supported in-bed heat exchanger |
RU2017120537A RU2017120537A (en) | 2016-06-13 | 2017-06-13 | BOILER WITH A CIRCULATING BOILING LAYER WITH A HEAT EXCHANGER WITH LOWER SUPPORT |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201662349627P | 2016-06-13 | 2016-06-13 | |
US15/618,913 US20170356642A1 (en) | 2016-06-13 | 2017-06-09 | Circulating fluidized bed boiler with bottom-supported in-bed heat exchanger |
Publications (1)
Publication Number | Publication Date |
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US20170356642A1 true US20170356642A1 (en) | 2017-12-14 |
Family
ID=60572562
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US15/618,913 Abandoned US20170356642A1 (en) | 2016-06-13 | 2017-06-09 | Circulating fluidized bed boiler with bottom-supported in-bed heat exchanger |
Country Status (8)
Country | Link |
---|---|
US (1) | US20170356642A1 (en) |
EP (1) | EP3306189A1 (en) |
CN (1) | CN107490003A (en) |
BR (1) | BR102017012587A2 (en) |
CL (1) | CL2017001518A1 (en) |
CO (1) | CO2017005825A1 (en) |
PH (1) | PH12017000173A1 (en) |
RU (1) | RU2017120537A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
ES2915695A1 (en) * | 2020-12-24 | 2022-06-24 | Waste To Energy Advanced Solutions S L | Installation and thermochemical conversion procedure of a Solid fuel in a synthesis gas (Machine-translation by Google Translate, not legally binding) |
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Also Published As
Publication number | Publication date |
---|---|
CO2017005825A1 (en) | 2017-10-20 |
CL2017001518A1 (en) | 2018-04-20 |
BR102017012587A2 (en) | 2018-02-06 |
EP3306189A1 (en) | 2018-04-11 |
CN107490003A (en) | 2017-12-19 |
RU2017120537A (en) | 2018-12-14 |
PH12017000173A1 (en) | 2018-07-23 |
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