EP0090641B1 - Fluidized bed heat exchanger - Google Patents

Fluidized bed heat exchanger Download PDF

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Publication number
EP0090641B1
EP0090641B1 EP19830301758 EP83301758A EP0090641B1 EP 0090641 B1 EP0090641 B1 EP 0090641B1 EP 19830301758 EP19830301758 EP 19830301758 EP 83301758 A EP83301758 A EP 83301758A EP 0090641 B1 EP0090641 B1 EP 0090641B1
Authority
EP
European Patent Office
Prior art keywords
bed
drain
heat exchanger
air
plate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19830301758
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0090641A3 (en
EP0090641A2 (en
Inventor
Robert D. Steward
Thomas E. Taylor
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Foster Wheeler Energy Corp
Original Assignee
Foster Wheeler Energy Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Foster Wheeler Energy Corp filed Critical Foster Wheeler Energy Corp
Publication of EP0090641A2 publication Critical patent/EP0090641A2/en
Publication of EP0090641A3 publication Critical patent/EP0090641A3/en
Application granted granted Critical
Publication of EP0090641B1 publication Critical patent/EP0090641B1/en
Expired legal-status Critical Current

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Classifications

    • 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
    • F23C10/24—Devices for removal of material from the bed

Definitions

  • This invention relates to a fluidized bed heat exchanger and, more particularly, to a heat exchanger in which heat is generated by the combustion of particulate fuel in a fluidized bed and a method of operation thereof.
  • fluidized beds have long been recognized as an attractive way of generating heat.
  • air is passed through a perforated plate or grid supporting particulate material which usually includes a mixture of a fuel material, such as high sulphur bituminous coal, and an adsorbent material for adsorbing the sulphur released as a result of the combustion of the coal.
  • a fuel material such as high sulphur bituminous coal
  • an adsorbent material for adsorbing the sulphur released as a result of the combustion of the coal.
  • the bed behaves like a coiling liquid which promotes the combustion of the fuel.
  • the basic advantage of such an arrangement include a relatively high heat transfer rate, substantially uniform bed temperature, combustion at relatively low temperatures, ease of handling the coal, a reduction in corrosion and boiler fouling and a reduction in heat exchanger (e.g. boiler) size.
  • the coal and adsorbent are continuously introduced into the bed by suitable feeders, injectors, or the like, and coal ash and adsorbent are discharged from the lower portion of the bed to a screw cooler, conveyor belt or the like, usually through gravity drain pipes having entrances registering with discharge openings formed in the heat exchanger housing at the sides of the perforated support plate, as disclosed for example in DE-A-2 929 056 wherein a plurality of special pockets for receiving the upper ends of a corresponding plurality of drain pipes are provided in the housing side walls, and the lower end of the pipes communicating with said screw cooler, conveyor belt, or the like.
  • a fluidized bed heat exchanger comprises an enclosure, a perforated support plate within said enclosure supporting a bed of particulate material which includes a fuel material and an adsorbent material, means for introducing air through perforations in the plate to fluidize said bed, means for starting combustion in said bed by which relatively heavy fuel ash particles are formed, means for introducing additional particulate material to said bed, and a drain for discharging spent particulate material from said bed, characterised in that said drain comprises a substantially vertical tubular means which extends through the perforated plate in a perforated region thereof so as to define a drain inlet for particulate material within said bed, said tubular means including separating means for providing a classifying flow of air through said drain and into said bed such as to produce within said bed at said inlet and coaxially with said drain a substantially vertical, generally conical, region of low density whereby said relatively heavy fuel ash particles migrate toward the said low density region and sink into the drain whilst the particles of said adsorbent material
  • the air flow can of course be varied to control the return of the adsorbent particles which are drawn into the drain pipe by the fuel ash particles.
  • a fluidized bed heat exchanger can be operated in such a way that substantially all of the fuel, normally coal, is fluidized and in which the ash, though prevented from clogging the drain pipe, is permitted to discharge through it while adsorbent material is selectively prevented from doing so.
  • the exchanger can also be operated in such a manner that the level of the fluidized bed is precisely controlled.
  • a fluidized bed heat exchanger embodying the present invention has a perforate plate supporting a fluidized bed of particulate material and a drain pipe to which a source of compressed air is connected to flow upwardly through the drain pipe and into the material of the fluidized bed above the drain pipe, thereby preventing the heavy pieces of coal ash from accumulating.
  • the upward flow of air also results in a low density area in the fluidized bed in a generally conical region above the inlet to the drain pipe, thereby providing less support for the particulate material in the region above the drain pipe.
  • the heavier particles of the fluidized bed tend to migrate toward the low density region and to sink into the drain pipe.
  • the flow of compressed air is selected so that it forms a separating air screen by which the relatively light particles of adsorbent material are buoyed and lifted upwardly, while the heavier coal ash particles are pulled by gravity down through the upwardly flowing compressed air into the drain pipe.
  • the area in the fluidized bed around the inlet to the drain pipe is kept substantially free of any accumulation of material, and the light adsorbent material particles are retained in the fluidized bed, while the heavier coal ash particles are allowed to continuously and freely discharge through the drain pipe. Since the coal ash particles in a heat exchanger of the invention can drain relatively freely, they discharge at a relatively constant rate. The rate of particulate material flowing into the fluidized bed can then be adjusted whereby the level of the fluidized bed can be precisely controlled.
  • Reference numeral 6 refers in general to an enclosure forming a major portion of the fluidized bed heat exchanger which may be in the form of a boiler, a combustor, a process reactor or any similar device.
  • the enclosure 6 comprises a front wall 8, a rear wall 10, and two sidewalls, one of which is shown by the reference numeral 12.
  • Each wall is formed by a plurality of vertically extending tubes 14 disposed in spaced, parallel relationship and connected together by a plurality of elongated fins 16 extending for the entire lengths of the tubes 14 and connected to diametrically opposed surfaces of the tubes in a conventional manner.
  • the upper portion of the enclosure 6 is not shown for the convenience of presentation, it being understood that it comprises a convection section, a roof and an outlet for allowing the combustion gases to discharge, also in a conventional manner.
  • a bed of particulate material shown in general by the reference numeral 18, is disposed within the heat exchanger 6 and rests on a plate 20 extending horizontally in the lower portion of the heat exchanger and having a plurality of perforations 21.
  • the bed 18 can comprise a mixture of discrete particles of fuel material, such as bituminous coal, and an adsorbent, such as limestone, for adsorbing the sulphur released by the combustion of the fuel material.
  • An air plenum 22 is provided immediately below the perforated plate 20 and an air inlet pipe 24 is provided through the plenum for distributing air from an external source (not shown) to the plenum under the control of a valve 26. Since the valve 26 can be of a conventional design, it will not be described in any further detail.
  • a bed light-off burner 28 is mounted through the front wall 18 immediately above the plate 20 for initially lighting off the bed 18 during startup.
  • the feeders 30, 32 and 34 receive particulate coal from inlet ducts or the like, and are controlled by valves or other flow control devices to feed the coal particles onto the upper surface of the bed 18.
  • the feeders 30, 32 and 34 can operate by gravity discharge or can be in the form of spreader feeders or any other similar device. It is understood that feeders identical to the feeders 30, 32 and 34 and controlled by identical devices can also be provided through one or more of the front wall 8, the rear wall 10 and the other side wall 12, and that similar feeders and control devices can also be provided for discharging the adsorbent onto the bed 18.
  • a pair of horizontal headers 40 are connected in fluid communication with the tubes 14 forming the front wall 8 and the rear wall 10, and another pair of horizontal headers 42 are connected in fluid communication with the tubes 14 forming the side walls 12. It is understood that headers similar to the headers 40 and 42 are provided in communication with the upper ends of the walls 8, 10 and 12. As a result, a fluid to be heated can be sequentially or simultaneously passed through the walls 8, 10 and 12 to pick up the heat from the fluidized bed in a.conventional manner.
  • a drain 43 extends through the air plenum 22 and includes an outer pipe 44, an inner pipe 46 defining a throat concentrically disposed within the outer pipe 44, and a bevelled collar 48 secured between the outer and inner discharge pipes 44 and 46 at their upper ends so that an upper edge of the bevelled collar 48 is level with the lower surface of the perforated plate 20 to form a gradually narrowing inlet for the particulate coal ash entering the drain 43.
  • the inlet is positioned at an opening 49 defined in the perforated plate 20.
  • the bevelled collar 48 may be secured in any suitable manner, as by threadedly connecting the bevelled collar to the external surface of the inner pipe 46 and welding the bevelled collar to the outer pipe 44.
  • the outer pipe 44 is supported by a threaded connection or other suitable connection to an annular flange 50 depending from the lower surface of the perforated plate 20.
  • the outer and inner pipes 44 and 46 extend downwardly through a bottom wall 52 of the plenum 22 where they are guided by a collar 54 interposed between the outer pipe 44 and an annular flange 56 depending from the lower wall 52 of the plenum 22.
  • the outer and inner pipes 44 and 46 terminate at lower ends which are welded or otherwise suitably secured to a flat annular plate 58 which extends radially outward from the lower end of the inner pipe 46.
  • the flat annular plate 58 includes a plurality of apertures 62 spaced outward from the outer -pipe 44 for receiving fasteners, such as nuts and bolts 63, to connect the flange 58 t& a compressed air inlet assembly 64.
  • the compressed air inlet assembly 64 includes a compressed air inlet pipe 66 having a lateral inlet port 68 which is connected to a source of compressed air (not shown), the flow of compressed air to the inlet pipe 66 being controlled by a valve 70.
  • the compressed air inlet pipe 66 includes a radially extending upper flange 72 including a plurality of apertures 74 by which the nuts and bolts 63 can connect the flange 72 to the flange 58.
  • An inner pipe 76 including at its upper end an outwardly flaring frustoconical plate 78 having a plurality of perforations 80, is positioned concentrically within the compressed air inlet pipe 66.
  • the frustoconical plate 78 includes a central aperture 81 through which the draining coal ash particles can pass.
  • the upper end of the frustoconical plate 78 includes an outwardly extending flange 82 which overlies the flange 72 and includes apertures 84 in alignment with the apertures 74, so that the flange 82 can be clamped between the flanges 72 and 58 when the appropriate fasteners are installed.
  • a lower annular flange 86 extends radially outward from the lower end of the inner pipe 76 beyond the air inlet pipe 66 so as to define, with the air inlet pipe 66, the inner pipe 76 and the frustoconical plate 78, an annular plenum chamber 88.
  • a suitable device such as a rotary feeder 90, is secured at the lower end of the inner pipe 76 to control the discharge of the coal ash.
  • a rotary feeder has been indicated in the drawings, other suitable discharge devices, such as screw feeders, can be employed.
  • valve 26 associated with the air inlet pipe 24 is opened to allow air to pass up through the plenum 22 and through the perforations 21 in the perforated plate 20.
  • the light-off burner 28 is then fired to heat the material in the bed until the temperature of the material reaches a predetermined level, whereby combustion is started and relatively heavy coal ash particles begin to form, at which time particulate fuel is discharged from the feeders 30, 32 and 34, and adsorbent material is discharged from other feeders (not shown) onto the upper surface of the bed 18 as needed.
  • the light-off burner 28 is turned off while the feeders 30, 32 and 34 continue to distribute particulate fuel to the upper surface of the bed in accordance with predetermined feed rates.
  • Fluid, such as water, to be heated is passed into the headers 40 and 42 where it passes simultaneously, or in sequence, through the tubes 14 forming the walls 8, 10 and 12 to add heat from the fluidized bed to the fluid before it is passed to external apparatus for further processing.
  • Compressed air is admitted to the annular plenum chamber 88 through the compressed air inlet port 68 by the manipulation of the valve 70.
  • the compressed air flows through the perforations 80 in the frustoconical plate 78 and increases in velocity when it enters the throat defined by the inner drain pipe 46, from which it flows directly upward through the fluidized bed 18, creating a generally conical low density region in the fluidized bed above the drain 43.
  • the bed material over the drain 43 is prevented from accumulating around the inlet to the drain.
  • the material of the fluidized bed 18 tends to migrate toward the low density region over the drain 43.
  • the diameter of the inner drain pipe 46 and the flow of air from the compressed air source are selected so that the air flowing up through the drain 43 defines an air screen separating the relatively lightweight adsorbent material particles from the heavier coal ash particles.
  • the adsorbent particles are normally eliminated in the flue gas, the coal ash particles are continuously discharged through the drain 43 and additional adsorbent and coal is continuously supplied to the top of the fluidized bed 18 to maintain a continuous circulation of material and a constant level in the fluidized bed 18.
  • the flow of coal ash particles into the drain 43 occurs freely, rather than being unpredictably restricted or blocked by accumulations around the entrance to the drain 43, it occurs at a relatively constant rate, so that the rate of particulate material being fed to the fluidized bed 18 can be adjusted, whereby the level of the fluidized bed 18 can be precisely controlled. If it is desired to increase the rate of removal of the adsorbent material from the fluidized bed 18, the flow of compressed air through the drain pipe 43 can be reduced so that the lighter adsorbent material particles will fall through the drain pipe 43 along with the heavier coal ash particles. By adjusting the amount of compressed air flowing through the drain 43 into the fluidized bed 18 the size of particles which will be allowed to fall through the drain 43 can be controlled.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
EP19830301758 1982-03-31 1983-03-29 Fluidized bed heat exchanger Expired EP0090641B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US36416382A 1982-03-31 1982-03-31
US364163 1982-03-31

Publications (3)

Publication Number Publication Date
EP0090641A2 EP0090641A2 (en) 1983-10-05
EP0090641A3 EP0090641A3 (en) 1984-08-01
EP0090641B1 true EP0090641B1 (en) 1988-01-07

Family

ID=23433320

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19830301758 Expired EP0090641B1 (en) 1982-03-31 1983-03-29 Fluidized bed heat exchanger

Country Status (5)

Country Link
EP (1) EP0090641B1 (ja)
JP (1) JPH0236877B2 (ja)
CA (1) CA1192792A (ja)
DE (1) DE3375197D1 (ja)
IN (1) IN159258B (ja)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT382227B (de) * 1985-04-30 1987-01-26 Simmering Graz Pauker Ag Verfahren und vorrichtung zur verbrennung von festen, fluessigen, gasfoermigen oder pastoesen brennstoffen in einem wirbelschichtofen
FI85758C (fi) * 1990-01-29 1992-05-25 Tampella Oy Ab Foerbraenningsanlaeggning.
KR100706697B1 (ko) 2000-08-09 2007-04-11 아사히 테크 가부시키가이샤 열풍 불어넣음형 유동층로, 회전식 열처리로, 열처리장치,및 열처리방법
FR3022611B1 (fr) 2014-06-19 2016-07-08 Ifp Energies Now Procede et installation de combustion par oxydo-reduction en boucle chimique avec un controle des echanges de chaleur

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3370938A (en) * 1965-07-30 1968-02-27 Allied Chem Method and apparatus for controlling particle size of fluidized beds
US3776150A (en) * 1972-03-06 1973-12-04 Awt Systems Inc Fluidized bed system for solid wastes
US3935825A (en) * 1975-02-24 1976-02-03 Institute Of Gas Technology Coal ash agglomeration device
US4196676A (en) * 1978-07-21 1980-04-08 Combustion Power Company, Inc. Fluid bed combustion method and apparatus
US4330502A (en) * 1980-06-16 1982-05-18 A. Ahlstrom Osakeyhtio Fluidized bed reactor
US4335661A (en) * 1980-09-24 1982-06-22 Foster Wheeler Energy Corporation Fluidized bed heat exchanger having an air assisted bed drain

Also Published As

Publication number Publication date
IN159258B (ja) 1987-04-18
JPH0236877B2 (ja) 1990-08-21
DE3375197D1 (en) 1988-02-11
JPS58213187A (ja) 1983-12-12
CA1192792A (en) 1985-09-03
EP0090641A3 (en) 1984-08-01
EP0090641A2 (en) 1983-10-05

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