WO1989012786A1 - Dispositif pour la combustion de combustibles solides, comprenant une chambre de combustion pourvue d'inserts destines a reguler l'alimentation en air de combustion - Google Patents

Dispositif pour la combustion de combustibles solides, comprenant une chambre de combustion pourvue d'inserts destines a reguler l'alimentation en air de combustion Download PDF

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Publication number
WO1989012786A1
WO1989012786A1 PCT/SE1989/000335 SE8900335W WO8912786A1 WO 1989012786 A1 WO1989012786 A1 WO 1989012786A1 SE 8900335 W SE8900335 W SE 8900335W WO 8912786 A1 WO8912786 A1 WO 8912786A1
Authority
WO
WIPO (PCT)
Prior art keywords
insert
combustion
combustion chamber
inserts
air
Prior art date
Application number
PCT/SE1989/000335
Other languages
English (en)
Inventor
Karl Sigurd Herman Hultgren
Original Assignee
Hultgren Karl S H
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 Hultgren Karl S H filed Critical Hultgren Karl S H
Publication of WO1989012786A1 publication Critical patent/WO1989012786A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23B—METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL
    • F23B7/00—Combustion techniques; Other solid-fuel combustion apparatus
    • F23B7/002—Combustion techniques; Other solid-fuel combustion apparatus characterised by gas flow arrangements
    • F23B7/007—Combustion techniques; Other solid-fuel combustion apparatus characterised by gas flow arrangements with fluegas recirculation to combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23M—CASINGS, LININGS, WALLS OR DOORS SPECIALLY ADAPTED FOR COMBUSTION CHAMBERS, e.g. FIREBRIDGES; DEVICES FOR DEFLECTING AIR, FLAMES OR COMBUSTION PRODUCTS IN COMBUSTION CHAMBERS; SAFETY ARRANGEMENTS SPECIALLY ADAPTED FOR COMBUSTION APPARATUS; DETAILS OF COMBUSTION CHAMBERS, NOT OTHERWISE PROVIDED FOR
    • F23M9/00—Baffles or deflectors for air or combustion products; Flame shields
    • F23M9/02—Baffles or deflectors for air or combustion products; Flame shields in air inlets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L1/00—Passages or apertures for delivering primary air for combustion 
    • F23L1/02—Passages or apertures for delivering primary air for combustion  by discharging the air below the fire
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
    • F23L15/00—Heating of air supplied for combustion
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Definitions

  • the present invention relates to an arrangement for combusting solid fuels, such as chips, pellets, coal or finely chopped wood, said an arrangement comprising a combustion chamber, a grate mounted adjacent the bottom of the combustion chamber, means for supplying com ⁇ bustion air to the combustion chamber through the grate, a flue gas outlet provided at the upper end of the combustion chamber, and means for delivering fuel to the combustion chamber, and further comprising a first and a second insert which are of tubular construction and arranged one above the other, and which divide the combustion chamber into an internal and an external part, in that said inserts have a diameter which is smaller than corresponding parts of the combustion chamber so as to form an annular space between the wall of the combustion chamber and the outer surfaces of respective inserts, wherein the mutually facing ends of respective inserts have a configuration such as to form therebetween a slot or gap through which secondary air of combustion can be delivered to the internal part of the combustion chamber.
  • the process strived for in the combustion of solid fuel can be divided into three stages, namely a first stage in which the solid fuel is gassified, a second stage in which the gassified fuel is combusted to form combustion products which contain no free heated carbon, but in which the carbon is bound constantly to other sub ⁇ stances, inter alia as a result of the formation of carbon monoxide, and a third stage in which final oxi ⁇ dation of the combustion products takes place, therewith generating carbon dioxide, among other products.
  • Com- bustion of this nature can be sustained with an air supply corresponding substantially to a combustion reaction of stoichio etric proportions between fuel and oxidizer, which is advantageous both with respect to pressure drop and thermal transmission.
  • combustion of this nature will result in cleaner waste gases and is thus advantageous also from an environ ⁇ mental aspect, since, inter alia, no oxides of nitrogen are formed.
  • the object of the present invention is to provide a solid fuel combustion arrangement in which the com ⁇ bustion achieved is a further improvement on the result achieved with the arrangement according to the aforesaid publication.
  • this object is achieved with an arrangement of the kind described in the introduction which is characterized in that at least one further tubular insert is mounted in the combustion chamber above the other two inserts, this further insert or inserts having a configuration such as to form an air inlet gap between the bottom edge surface of each fur ⁇ ther insert and the top edge surface of an underlying insert; and in that the bottom edge surface of the uppermost insert extends fully to the inner surface of the wall of the combustion chamber.
  • the further insert or inserts thus form a tertiary zone, in which the final oxidation process mainly takes place.
  • Figure 1 is a partial sectional view of an arrangement constructed in accordance with the invention
  • Figure 2 is a partial sectional view of the lower part of the arrangement illustrated in Figure 1.
  • Fig. 1 The arrangement illustrated in Fig. 1 includes an ash box 1, a fan means 2, a combustion chamber 3, a grate 10 which is connected to the bottom of the combustion chamber and operative in permitting air to pass into the combustion chamber, and a convection part 8 in which water is heated by the heat radiated from the hot flue gases.
  • a flue gas outlet 9 is provided on the convection part 8.
  • the combustion chamber 3 is encircled by a shell 22 of insulating material, said shell being spaced from the combustion chamber so as to form a peripheral gap between the inner surface of the shell and the outer surface of the combustion chamber wall.
  • This gap is open to atmosphere at the top thereof, whereas the lower part of the gap is connected to one or more conduits 27, which are, in turn, connected to the suction side of the fan means 2.
  • a conduit 19 extending from the flue gas outlet 9 is also connected to the suction side of the fan means.
  • the pressure side of the fan means is con ⁇ nected to the suction side thereof by means of a shunt conduit 25, and valves or dampers 24, 26, 28 are mounted in the conduits for the purpose of controlling the flow of gas therethrough.
  • the fuel supply system comprises a conveyer belt 7 on which solid fuel is conveyed to a storage tank 6, from which the fuel falls gravitationally down through a feed conduit, which discharges into the combustion chamber.
  • the amount of fuel falling through the feed conduit can be regu ⁇ lated by means of a control device 5.
  • the combustion chamber 3 incorporates three inserts 11, 13, 15.
  • Fig. 2 illustrates the bottom part of the arrangement shown in Fig. 1 in larger scale.
  • the grate 10 is operative in allowing combustion air to flow into the combustion chamber and, to this end, comprises a multiple of mutually parallel air distributing tubes 41, the ends of which are connected to respective collecting chambers 42, which may also consist of tubes and which are connected to the pressure side of the fan means 2 by means of one or more pipe connectors 33.
  • the tubes 41 are open upwardly towards the combustion 3 and, when seen in cross-section, the uppermost part of respective tubes has a nozzle-like configuration.
  • the tubes 41 preferably taper in the direction of air flow, as illustrated in Fig. 1.
  • narrow spacer bars 40 for instance in the form of edge-standing iron flats, extend centrally above the nozzle openings of the tubes 41 and centrally between said tubes, these flats being intended to support the solid fuel and to hold said fuel spaced from the nozzle openings.
  • the bars are not rigidly attached, but rest, for instance, in grooves or channels provided in the wall of the combustion chamber or on the top surface of the collecting chambers.
  • first tubular insert 11 Located above the grate 10 and in the immediate vicinity thereof is a first tubular insert 11.
  • This first insert preferably has the form of a truncated cone, with the cone base facing upwards and having an inwardly curved top edge surface.
  • the insert 11 has mounted on the bottom thereof a beam-cross 39 by means of which the first insert is supported on a rotatable shaft 32, which is driven for rotation by a motor 29 through the intermediary of some suitable system, for instance through a sprocket chain 30 connected to a sprocket wheel mounted on the shaft 32.
  • the insert will also preferably support against rollers 37 which project from the combustion chamber wall 35 and which coact with peripherally extending shoulders 36 or the like formed on the outer surface of the insert 11.
  • rollers 37 which project from the combustion chamber wall 35 and which coact with peripherally extending shoulders 36 or the like formed on the outer surface of the insert 11.
  • one or more of the rollers may have the form of a drive roller and may be arranged, in some suitable manner, to coact with the shoulders 36, for instance such that the insert will be rotated by the frictional forces engendered between roller and shoulder, therewith enabling the rollers 37 to be used for rotation of the insert.
  • a second tubular insert 13 is mounted above the first insert 11.
  • the second insert 13 has the form of a straight cylinder having inwardly curved top and bottom edge surfaces and having a larger diameter than the base of the first insert. Seen in a vertical direction, the beginning of the inwardly bent inner edge surface of the second insert 13 is located on the same level as the beginning of the inwardly bent top edge surface of the first insert 11, such as to form a relatively narrow, annular inlet gap for the passage of secondary air of combus- tion, the flow cross-section of which gap is defined by the curvature of respective inwardly curved edge sur ⁇ faces and by the height position or vertical position of the second insert.
  • the second insert may optionally be connected to the wall of the combustion chamber in a manner such as to enable the height position of the second insert to be adjusted, and therewith also the width of the inlet gap.
  • the diameter of the second insert is smaller than the diameter of the combustion chamber 3, such that an annular space is formed between the combustion chamber wall 35 and the outer surfaces of the first and second inserts.
  • the combus ⁇ tion chamber and the inserts have a circular cross- section, which is the preferred cross-section.
  • the preferred cross-section it will be understood that other cross-sectional shapes are possible, although less advantageous from the aspect of air flow, since rotation of the first insert is then liable to disturb the ho ogenity of the flow within the arrangement.
  • a third tubular insert 15 which, similar to the first insert 11, has the form of a frustated cone, although with the base facing downwards in contra ⁇ distinction to the base of the first insert. Further ⁇ more, the bottom edge surface of the third insert ex- tends fully to the wall 35 of the combustion chamber. and the third insert will thus form an upper limitation of the annular base between the combustion chamber wall 35 and the outer surfaces of the first and second inserts.
  • the wall of the third insert coacts with the inwardly curved top edge surface of the second insert, such as to form an inlet gap for tertiary air of combustion.
  • the walls of the gas passages 20 in the convection part 8 are configured in accordance with Swedish patent 80900799.0, the vortex-laminar gas flow in the gas passageways resulting in highly effective heat transfer to the radiator water.
  • the fan means 2 draws in fresh air by suction, through the conduit 27, fresh air from the peripheral gap lo ⁇ cated between the inner surface of the shell 22 and the outer surface of the combustion chamber wall 35.
  • the fresh air Prior to entering the fan, the fresh air is admixed with hot flue gases drawn by suction from the flue gas outlet 9, through the conduit 19, and also with an air-gas mixture taken optionally from the pressure side of the fan means, through the shunt conduit 25.
  • the fresh air flowing in the peripheral gap cools the wall 35 of the combustion chamber, and is, of course, thereby pre ⁇ heated prior to entering the fan means.
  • the combustion air in the form of an air/flue gas mixture, passes from the fan means to the collecting chambers 42 and into the air distributing tubes 41, therewith cooling the grate and further heating the combustion air.
  • the combustion air then flows out through the nozzle- like openings of the tubes 41, and is deflected locally by the bars 40 and enters the combustion chamber 3 in the form of two distinct flows separated by the wall of the insert 11, namely a primarily flow within the insert 11 and a secondary flow in the annulus space lying externally of the insert 11.
  • the primary flow shall comprise about 60% of the total flow, so as to ensure that the oxygen present will be sufficient to achieve desired gassification of the fuel. Since, when seen in total, there is only a small air surplus during operation of the arrangement, it will be understood that the oxygen content of the primary flow will not suffice to provide stoichiometric combustion conditions in the actual fuel hearth. Conseguently, mainly gassification of solid fuel takes place in the fuel hearth. Thus, gassified solid fuel mixed with the primary flow will flow upwards from the lower part of the insert 11.
  • Part of the secondary flow will flow into the interior of the inserts through the gap between the first and second inserts 11, 13.
  • the proportion of combustion air which flows in through this gap is determined substan ⁇ tially by the relationship between the restistance to flow afforded by respective inlet gaps between the inserts 11, 13 and 13, 15 and, when the height positions or vertical positions of the inserts 13, 15 can be adjusted, can thus be adapted to suitable values for mutually different solid fuels.
  • a pre-heated mixture of fresh air and recycled flue gases will thus flow at high speed into the central part of the combustion chamber defined by the inserts, at a height location which is level with the top edge surface of the first insert 11.
  • the secondary air of combustion is guided by the inwardly curved insert edge surfaces defining the inlet gap between the first and second inserts 11, 13, and the mixture will flow radially inwards from the top edge of the insert 11. As indicated in the Figures, this results in local turbulent flow, which produces a highly effective mixture from the gassified fuel contained by the primary flow and the in ⁇ flowing secondary air of combustion. This inflow is effective in supplyling sufficient oxygen to the gassified fuel to achieve the desired oxidation of carbon to carbon monoxide without forming free carbons.
  • the effective mixing and recycling process engendered by said vortex motion greatly assists in generating fav ⁇ ourable conditions for the primary combustion process.
  • the first insert is rotated at a speed adapted to the fuel combustion cycle, such that the quantity of solid fuel falling from the fuel infeed system along a gen- eratrice of the first insert wall will be totally com ⁇ busted (gassified) subsequent to one revolution of the insert, at which point the generatrice will again be located opposite the outlet of the infeed system in the combustion chamber.
  • the following combustion values were achieved when feeding pellets substantially continuously into a com ⁇ bustion chamber constructed in accordance with the invention and having a nominal rating of 500 kW: C0 2 17-20% soot index 0-1 flue gas temperature 1500-1700°C
  • the carbon dioxide content was decreased by one or two units, by successively closing the valve or damper 24, whereas the soot index remained unchanged.
  • the load could be stepped down to about 20%.
  • the measuring values attained indicate that the desired stages in the combustion process were successfully achieved with an arrangement of apparatus constructed in accordance with the invention.
  • soot index values attained show that the greater part of the fuel was combusted in a gassified state. said soot index being graduated in a scale from 0-10 and being a measurement of the extent to which free carbon is formed during the combustion process.
  • the carbon dioxide content is directly proportional to the air surplus present during the combustion process and is theoretically between 20-21% during combustion under stoichiometric conditions.
  • the resultant carbon dioxide content values thus show that combustion in an inventive arrangement is effected with a very small air surplus and therewith under substantially stoichiometric conditions.
  • the first insert may be stationary instead of rotatable, in which case the fuel feed system must be constructed to distribute the fuel uniformly over the grate, which can be achie- ved, for instance, by causing the fuel to fall onto a distributing cone mounted in the central part of the combustion chamber.
  • a rotating first insert is preferred, since conventional distributing arrangements have a tendency to disturb excessively the flow in the combustion chamber.
  • final combustion can be achieved in several final stages, by introducing additional gap-forming inserts between the illustrated second and third inserts.
  • the curvature of the inwardly curved edge surfaces of the inserts can be varied, in order to achieve desired gap cross-sections, such as to impart the desired direction and speed to the combustion air flowing into the interior of the combustion chamber.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Solid-Fuel Combustion (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)

Abstract

La présente invention se rapporte à un dispositif pour la combustion de combustibles solides, comprenant une chambre de combustion (3) divisée en une partie interne et une partie externe au moyen d'inserts (11, 13, 15) mutuellement différents. De l'air de combustion est amené à la chambre de combustion par en dessous et est divisé en un flux primaire, lequel s'écoule dans la partie interne de la chambre de combustion, et en un flux secondaire, lequel s'écoule dans la partie externe de la chambre de combustion. Des parties du flux secondaire sont insufflées dans la partie interne de la chambre de combustion, par des ouvertures définies entre les différents inserts. La présente invention permet d'obtenir une chambre de combustion dans laquelle la combustion s'effectue dans la phase dite bleutée.
PCT/SE1989/000335 1988-06-14 1989-06-13 Dispositif pour la combustion de combustibles solides, comprenant une chambre de combustion pourvue d'inserts destines a reguler l'alimentation en air de combustion WO1989012786A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8802223A SE461295B (sv) 1988-06-14 1988-06-14 Anordning foer foerbraenning av fasta braenslen, foersedd med i braennkammaren anordnade insatser foer styrning av tillfoerseln av foerbraenningsluft
SE8802223-1 1988-06-14

Publications (1)

Publication Number Publication Date
WO1989012786A1 true WO1989012786A1 (fr) 1989-12-28

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PCT/SE1989/000335 WO1989012786A1 (fr) 1988-06-14 1989-06-13 Dispositif pour la combustion de combustibles solides, comprenant une chambre de combustion pourvue d'inserts destines a reguler l'alimentation en air de combustion

Country Status (4)

Country Link
EP (1) EP0393161A1 (fr)
AU (1) AU3839289A (fr)
SE (1) SE461295B (fr)
WO (1) WO1989012786A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001022004A1 (fr) * 1999-09-24 2001-03-29 Kubi Ab Four de combustion
DE102009014010A1 (de) * 2009-03-19 2010-10-07 Georg Fischer Gmbh & Co. Kg Brenner für festes, stückiges Brennmaterial

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE377422C (de) * 1922-09-14 1923-06-19 Otto Schulz Lufterhitzer
SE449916B (sv) * 1981-07-23 1987-05-25 Hultgren Karl S H Anordning for forbrenning av fast brensle
CH665468A5 (de) * 1983-05-20 1988-05-13 Theodor Koch Verfahren zur sekundaerluftzufuehrung, sekundaerlufteinlass zur ausfuehrung des verfahrens sowie anwendung des verfahrens.

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE377422C (de) * 1922-09-14 1923-06-19 Otto Schulz Lufterhitzer
SE449916B (sv) * 1981-07-23 1987-05-25 Hultgren Karl S H Anordning for forbrenning av fast brensle
CH665468A5 (de) * 1983-05-20 1988-05-13 Theodor Koch Verfahren zur sekundaerluftzufuehrung, sekundaerlufteinlass zur ausfuehrung des verfahrens sowie anwendung des verfahrens.

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001022004A1 (fr) * 1999-09-24 2001-03-29 Kubi Ab Four de combustion
DE102009014010A1 (de) * 2009-03-19 2010-10-07 Georg Fischer Gmbh & Co. Kg Brenner für festes, stückiges Brennmaterial
DE102009014010B4 (de) * 2009-03-19 2012-02-23 Georg Fischer Gmbh & Co. Kg Brenner für festes, stückiges Brennmaterial

Also Published As

Publication number Publication date
AU3839289A (en) 1990-01-12
SE461295B (sv) 1990-01-29
SE8802223L (sv) 1989-12-15
SE8802223D0 (sv) 1988-06-14
EP0393161A1 (fr) 1990-10-24

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