GB1581672A - Fluidised bed combustion - Google Patents

Fluidised bed combustion Download PDF

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Publication number
GB1581672A
GB1581672A GB21318/77A GB2131877A GB1581672A GB 1581672 A GB1581672 A GB 1581672A GB 21318/77 A GB21318/77 A GB 21318/77A GB 2131877 A GB2131877 A GB 2131877A GB 1581672 A GB1581672 A GB 1581672A
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GB
United Kingdom
Prior art keywords
bed
vessel
combustible
fluidised
combustible material
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
GB21318/77A
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Coal Industry Patents Ltd
Original Assignee
Coal Industry Patents Ltd
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 Coal Industry Patents Ltd filed Critical Coal Industry Patents Ltd
Priority to GB21318/77A priority Critical patent/GB1581672A/en
Publication of GB1581672A publication Critical patent/GB1581672A/en
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B01J8/24—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
    • B01J8/38—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed containing a rotatable device or being subject to rotation or to a circulatory movement, i.e. leaving a vessel and subsequently re-entering it
    • B01J8/382—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique with fluidised bed containing a rotatable device or being subject to rotation or to a circulatory movement, i.e. leaving a vessel and subsequently re-entering it with a rotatable device only
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/04—Waste materials; Refuse
    • C04B18/12—Waste materials; Refuse from quarries, mining or the like
    • C04B18/125—Slate residues, e.g. colliery shale or oil shale or oil shale ash
    • 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
    • F23C10/007—Fluidised bed combustion apparatus comprising a rotating bed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
    • F23G5/30—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having a fluidised bed
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/91—Use of waste materials as fillers for mortars or concrete

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Environmental & Geological Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • Treatment Of Sludge (AREA)
  • Processing Of Solid Wastes (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO FLUIDISED BED COMBUSTION (71) We, COAL INDUSTRY (PATENTS) LIMITED, a company organised in accordance with the laws of Great Britain of Hobart House, Grosvenor Place, London, S.W. IX 7AE England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-- This invention concerns improvements in or relating to the fluidised bed combustion of combustible material, particularly such material possessing a water content.
One type of material having a water content is colliery tailings which generally comprise a large proportion of clays, or minerals having a structure similar to that of clay materials, and shales, as well as coal and are normally available as an aqueous slurry. The tailings leaving a coal washery are conveniently thickened to give a solids content of between 30 and 65% by weight prior to combustion and one method for preparing a low density material from colliery tailings employing fluidised and combustion is disclosed in our U.K. Patent No. 1,355,031.
According to one aspect the invention provides a method for thermally treating a combustible material having a water content, the method including the steps, of forming a bed of particulate material in a rotatable vessel, fluidising the bed and rotating the vessel at such a speed as to maintain the fluidised bed in contact with a bounding wall of the vessel, and introducing the combustible material into the vessel for combustion in the fluidised bed which is maintained at an elevated temperature suitable for combustion.
The combustible material having a water content may conveniently be colliery tailings thickened to a solids content of between 30% and 65%by weight. The material is preferably in the form of an aqueous slurry in this instance may advantageously be sprayed on to the surface of the bed. Alternatively, the slurry may be injected directly into the bed.
The operating temperature of the fluidised bed is conveniently in the range 750"C and 950"C.
The fluidising velocity is preferably set at such a value that whilst the bed is well fluidised, it is not too high such as to cause excessive elutriation. The actual value will also depend upon the 'g' force exerted by rotating the vessel and thus the bed. It is expected that the 'g' force will be in the range 5 to 20 g. The fluidising velocity may be in the range 20 and 80 ft/s.
The size of the bed material may be of the order of minus l/8in.
According to a second aspect of the invention, apparatus when used in the method according to the first aspect, includes a vessel rotatably mounted, a gas permeable support arrangement for a fluidised bed within the vessel, an inlet for a fluidising medium, a gas outlet, a means of introducing combustible material to the vessel, a material outlet in the vessel, and means for rotating the vessel.
Conveniently, the vessel is of cylindrical form and is mounted for rotation about its longitudinal axis which may be disposed horizontally or vertically, or at an intermediate angle.
As a preference the vessel is mounted with its longitudinal axis vertical and the gas permeable support arrangement is provided with a base of conical shape in which is formed the material outlet, the conical shape in use assisting the flow of agglomerated oversized particles towards the material outlet.
By way of example only, a method for and apparatus when used in the method for thermally treating a combustible material having a water content according to the invention are described below with reference to the drawing accompanying the Provisional Specification which is a diagrammatic sectional view of the apparatus.
Referring to the drawing, there is shown apparatus indicated at 1 for thermally treating a combustible material having a water content, the apparatus 1 including a rotatably mounted cylindrical vessel 2 provided with an outlet 4 for a fluidising medium and a gas outlet 6. The vessel 2 is arranged such that its longitudinal axis is vertical.
Disposed co-axially within the vessel 2 is a gas permeable cylindrical support arrangement 8 which is attached at one end to an end wall 10 of vessel 2 circumjacent the gas outlet 6. The other end of the arrangement 8 is provided with a conical base 12 in which is formed a material outlet 14 to which is coupled a discharge conduit 16.
Means for introducing combustible mateial into the vesse 12 in this example comprises a spray assembly 18 including a spray head 20 and a feed pipe 22, the assembly 18 conveniently being disposed within the gas outlet 6 and extending into the vessel.
In operation of the apparatus, particulate material, for example ash, is placed within the cylindrical support arrangement 8 and upon rotation of the vessel 2 is thrown against the arrangement to form a bed 30 of material. Upon introduction of a fluidising medium through inlet 4 the bed 30 becomes fluidised, the air passing into an annular plenum chamber 32 defined between the arrangement 8 and vessel 2, prior to its passage into the bed 30.
The temperature of the bed may be raised to a level conducive to the combustion of the combustible material by conventional means, for example auxilary burners or the use of a gaseous starting fuel burnt in the bed. Once the requisite temperature has been attained, combustible material having a water content, for example colliery tailings thickened to a solids content of between 30% and 65% by weight, is introduced through the spray assembly 18 to issue through the head 20 in the form of a spray which impinges on the fluidised bed 30.
The combustible content of the tailings is wholly or partially burnt. The temperature of the bed 30 is controlled either by adjusting the feed rate of the colliery tailings if they are capable of auto thermal combustion or by varying the feed rate of an auxiliary fuel or water dilution rlts depending on whether the combustible content is low or high respectively.
When the colliery tailings in the form of a slurry are sprayed onto the surface of the fluidised bed 30, agglomerates generally spherical in shape are formed. The spherical agglomerates are formed from the droplets of the spray and by deposition of the tailings sprayed onto the particles of bed material as a coating, the water content being totally or substantially totally evaporated and a significant amount of the combustible content burnt off in both cases. The action of the fluidised bed 30 also tends to abrade the surface of the agglomerate or deposited material such that the particles are generally spherical when discharged from the bed 30 through outlet 14. The gas exhausting through outlet 6 will normally carry elutriated fines from the bed 30 and these may be removed from the the gas stream by conventional gas cleaning techniques.
The solid products discharged from the bed may be used in their dry state as an aggregate or may be mixed with untreated colliery tailings slurry to give a product suitable for tipping. The exhaust gases may be passed through heat recuperative systems prior to their discharge to atmosphere.
The apparatus when used in this method of the present invention tends to alleviate one problem attendant upon conventional nonrotating fluidised beds. This concerns the removal from the bed of oversize particles which can accumulate in a bed of large crosssectional area causing partial defluidisation of the bed and necessitating plant shut down.
The compact nature of a rotating fluidised bed will assist in overcoming this problem.
As an example, if the support arrangement 8 and thus the bed 30 has a diameter of 4 ft, the speed of rotation of the vessel would be of the order of 150 rpm. It has been estimated that typical treatment rates would be 800 to 3200 lb/ft2 (bed area) with a 'g' force of 5 to 20g. A unit of this specification would be capable of treating approximately 20 ton/h of colliery tailings.
WHAT WE CLAIM IS: 1. A method for thermally treating a combustible material having a water content, the method including the steps of forming a bed of particulate material in a rotatable vessel, fluidising the bed and rotating the vessel at such a speed as to maintain the fluidised bed in contact with a bounding wall of the vessel, and introducing the combustible material into the vessel for combustion in the fluidised bed which is maintained at an elevated temperature suitable for combustion.
2. A method according to claim 1 in which the combustible material is colliery tailings.
3. A method according to claim 2 in which the colliery tailings are thickened to a solids content of between 30% and 65% by weight prior to introduction into the fluidised bed.
4. A method according to any of the preceding claims in which the combustible
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. having a water content according to the invention are described below with reference to the drawing accompanying the Provisional Specification which is a diagrammatic sectional view of the apparatus. Referring to the drawing, there is shown apparatus indicated at 1 for thermally treating a combustible material having a water content, the apparatus 1 including a rotatably mounted cylindrical vessel 2 provided with an outlet 4 for a fluidising medium and a gas outlet 6. The vessel 2 is arranged such that its longitudinal axis is vertical. Disposed co-axially within the vessel 2 is a gas permeable cylindrical support arrangement 8 which is attached at one end to an end wall 10 of vessel 2 circumjacent the gas outlet 6. The other end of the arrangement 8 is provided with a conical base 12 in which is formed a material outlet 14 to which is coupled a discharge conduit 16. Means for introducing combustible mateial into the vesse 12 in this example comprises a spray assembly 18 including a spray head 20 and a feed pipe 22, the assembly 18 conveniently being disposed within the gas outlet 6 and extending into the vessel. In operation of the apparatus, particulate material, for example ash, is placed within the cylindrical support arrangement 8 and upon rotation of the vessel 2 is thrown against the arrangement to form a bed 30 of material. Upon introduction of a fluidising medium through inlet 4 the bed 30 becomes fluidised, the air passing into an annular plenum chamber 32 defined between the arrangement 8 and vessel 2, prior to its passage into the bed 30. The temperature of the bed may be raised to a level conducive to the combustion of the combustible material by conventional means, for example auxilary burners or the use of a gaseous starting fuel burnt in the bed. Once the requisite temperature has been attained, combustible material having a water content, for example colliery tailings thickened to a solids content of between 30% and 65% by weight, is introduced through the spray assembly 18 to issue through the head 20 in the form of a spray which impinges on the fluidised bed 30. The combustible content of the tailings is wholly or partially burnt. The temperature of the bed 30 is controlled either by adjusting the feed rate of the colliery tailings if they are capable of auto thermal combustion or by varying the feed rate of an auxiliary fuel or water dilution rlts depending on whether the combustible content is low or high respectively. When the colliery tailings in the form of a slurry are sprayed onto the surface of the fluidised bed 30, agglomerates generally spherical in shape are formed. The spherical agglomerates are formed from the droplets of the spray and by deposition of the tailings sprayed onto the particles of bed material as a coating, the water content being totally or substantially totally evaporated and a significant amount of the combustible content burnt off in both cases. The action of the fluidised bed 30 also tends to abrade the surface of the agglomerate or deposited material such that the particles are generally spherical when discharged from the bed 30 through outlet 14. The gas exhausting through outlet 6 will normally carry elutriated fines from the bed 30 and these may be removed from the the gas stream by conventional gas cleaning techniques. The solid products discharged from the bed may be used in their dry state as an aggregate or may be mixed with untreated colliery tailings slurry to give a product suitable for tipping. The exhaust gases may be passed through heat recuperative systems prior to their discharge to atmosphere. The apparatus when used in this method of the present invention tends to alleviate one problem attendant upon conventional nonrotating fluidised beds. This concerns the removal from the bed of oversize particles which can accumulate in a bed of large crosssectional area causing partial defluidisation of the bed and necessitating plant shut down. The compact nature of a rotating fluidised bed will assist in overcoming this problem. As an example, if the support arrangement 8 and thus the bed 30 has a diameter of 4 ft, the speed of rotation of the vessel would be of the order of 150 rpm. It has been estimated that typical treatment rates would be 800 to 3200 lb/ft2 (bed area) with a 'g' force of 5 to 20g. A unit of this specification would be capable of treating approximately 20 ton/h of colliery tailings. WHAT WE CLAIM IS:
1. A method for thermally treating a combustible material having a water content, the method including the steps of forming a bed of particulate material in a rotatable vessel, fluidising the bed and rotating the vessel at such a speed as to maintain the fluidised bed in contact with a bounding wall of the vessel, and introducing the combustible material into the vessel for combustion in the fluidised bed which is maintained at an elevated temperature suitable for combustion.
2. A method according to claim 1 in which the combustible material is colliery tailings.
3. A method according to claim 2 in which the colliery tailings are thickened to a solids content of between 30% and 65% by weight prior to introduction into the fluidised bed.
4. A method according to any of the preceding claims in which the combustible
material is in the form of an aqueous slurry which is sprayed onto the bed.
5. A method according to any one of the preceding claims in which the operating temperature of the fluidised bed lies in the range 750"C to 9500C.
6. A method according to any one of the preceding claims in which the size of the fluidised bed material is of the order of minus 1/8in.
7. Apparatus when used in the method according to any one of preceding claims including a vessel rotatably mounted, a gas permeable support arrangement for a fluidised bed within the vessel, an inlet for a fluidising medium, a gas outlet, a means of introducing combustible material to the vessel, a material outlet in the vessel, and means for rotating the vessel.
8. Apparatus according to claim 7 in which the vessel is of cylindrical form and is mounted for rotation about its longitudinal axis
9. Apparatus according to claim 8 in which the vessel is disposed with its axis its axis horizontal or vertical, or at an intermediate angle.
10. Apparatus according to claim 9 in which the vessel is mounted with its longitudinal axis vertical and the gas permeable support arrangement is provided with a base of conical shape in which is formed the material outlet.
11. Apparatus according to any one of claims 7 to 10 in which the means of introducing combustible material comprises a spray assembly.
12. A method for thermally treating a combustible material having a water content substantially as hereinbefore described with reference to the drawing accompanying the Provisional Specification.
13. Apparatus when used in the method for thermally treating a combustible material substantially as hereinbefore described with reference to the drawing accompanying the Provisional Specification.
GB21318/77A 1978-05-16 1978-05-16 Fluidised bed combustion Expired GB1581672A (en)

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GB21318/77A GB1581672A (en) 1978-05-16 1978-05-16 Fluidised bed combustion

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Application Number Priority Date Filing Date Title
GB21318/77A GB1581672A (en) 1978-05-16 1978-05-16 Fluidised bed combustion

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4559071A (en) * 1981-07-30 1985-12-17 Ppg Industries, Inc. Ablating liquefaction method
US4564379A (en) * 1981-07-30 1986-01-14 Ppg Industries, Inc. Method for ablating liquefaction of materials
DE3426640A1 (en) * 1984-07-19 1986-01-23 Thyssen Industrie Ag, 4300 Essen Process and equipment for the heat treatment of coarse-grained material
USRE32317E (en) * 1981-07-30 1986-12-30 Ppg Industries, Inc. Glass batch liquefaction
US4654068A (en) * 1981-07-30 1987-03-31 Ppg Industries, Inc. Apparatus and method for ablating liquefaction of materials
US4710356A (en) * 1983-12-23 1987-12-01 Krauss-Maffei A.G. Apparatus to accelerate the transfer of material between two media reacting in a fluidized bed
GB2212736A (en) * 1987-11-27 1989-08-02 John Hunter Rotary fluidised bed gasifier
US5050374A (en) * 1990-08-01 1991-09-24 John Hunter Gasification/combustion system
WO1998013648A1 (en) * 1996-09-27 1998-04-02 The University Of Sheffield Rotatable fluidised bed incinerator

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4559071A (en) * 1981-07-30 1985-12-17 Ppg Industries, Inc. Ablating liquefaction method
US4564379A (en) * 1981-07-30 1986-01-14 Ppg Industries, Inc. Method for ablating liquefaction of materials
USRE32317E (en) * 1981-07-30 1986-12-30 Ppg Industries, Inc. Glass batch liquefaction
US4654068A (en) * 1981-07-30 1987-03-31 Ppg Industries, Inc. Apparatus and method for ablating liquefaction of materials
US4710356A (en) * 1983-12-23 1987-12-01 Krauss-Maffei A.G. Apparatus to accelerate the transfer of material between two media reacting in a fluidized bed
US4801336A (en) * 1983-12-23 1989-01-31 Krauss-Maffei A.G. Process for accelerating the transfer of media in a fluidized bed
DE3426640A1 (en) * 1984-07-19 1986-01-23 Thyssen Industrie Ag, 4300 Essen Process and equipment for the heat treatment of coarse-grained material
GB2212736A (en) * 1987-11-27 1989-08-02 John Hunter Rotary fluidised bed gasifier
GB2212736B (en) * 1987-11-27 1991-10-23 John Hunter Fluidised bed gasification/combustion system
US5050374A (en) * 1990-08-01 1991-09-24 John Hunter Gasification/combustion system
WO1998013648A1 (en) * 1996-09-27 1998-04-02 The University Of Sheffield Rotatable fluidised bed incinerator
US6220189B1 (en) * 1996-09-27 2001-04-24 The University Of Sheffield Rotatable fluidized bed incinerator

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Legal Events

Date Code Title Description
PS Patent sealed
746 Register noted 'licences of right' (sect. 46/1977)
PCNP Patent ceased through non-payment of renewal fee