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EP0747637A2 - Dispositif d'alimentation pour air de combustion - Google Patents

Dispositif d'alimentation pour air de combustion Download PDF

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Publication number
EP0747637A2
EP0747637A2 EP96660025A EP96660025A EP0747637A2 EP 0747637 A2 EP0747637 A2 EP 0747637A2 EP 96660025 A EP96660025 A EP 96660025A EP 96660025 A EP96660025 A EP 96660025A EP 0747637 A2 EP0747637 A2 EP 0747637A2
Authority
EP
European Patent Office
Prior art keywords
combustion
air duct
duct system
air
heat exchanger
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.)
Withdrawn
Application number
EP96660025A
Other languages
German (de)
English (en)
Other versions
EP0747637A3 (fr
Inventor
Tapani Keronen
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.)
Nunnanlahden Uuni Oy
Original Assignee
Nunnanlahden Uuni Oy
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 Nunnanlahden Uuni Oy filed Critical Nunnanlahden Uuni Oy
Publication of EP0747637A2 publication Critical patent/EP0747637A2/fr
Publication of EP0747637A3 publication Critical patent/EP0747637A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24B—DOMESTIC STOVES OR RANGES FOR SOLID FUELS; IMPLEMENTS FOR USE IN CONNECTION WITH STOVES OR RANGES
    • F24B1/00—Stoves or ranges
    • F24B1/18—Stoves with open fires, e.g. fireplaces
    • F24B1/185—Stoves with open fires, e.g. fireplaces with air-handling means, heat exchange means, or additional provisions for convection heating ; Controlling combustion
    • F24B1/189—Stoves with open fires, e.g. fireplaces with air-handling means, heat exchange means, or additional provisions for convection heating ; Controlling combustion characterised by air-handling means, i.e. of combustion-air, heated-air, or flue-gases, e.g. draught control dampers 
    • F24B1/19—Supplying combustion-air

Definitions

  • the present invention relates to a combustion air duct system as defined in the preamble of claim 1.
  • combustion air is supplied into a fireplace is of great importance for combustion.
  • the primary combustion air is passed via an ash scuttle and a grate into the combustion process directly from indoor or outdoor air.
  • Secondary air can be passed to the space above the burning material through scuttles or via separate ducts or even into a separate upper secondary combustion space.
  • combustion air is passed into the combustion process either directly at ambient temperature or after preheating.
  • preheating takes place in the combustion chamber, in other words, generally the combustion chamber is provided with heating channels or pipes in which air is heated and is then discharged at a suitable point into the combustion process.
  • prior-art preheating arrangements have significant drawbacks.
  • the cold air flowing into the system cools down the combustion chamber, thus lowering the combustion temperature and leading to imperfect combustion and impure flue gases.
  • part of the burning gases is cooled down so that the gases are passed unburnt into the exit flue.
  • use of the furnace becomes more expensive and requires more maintenance, such as chimney sweeping.
  • the object of the invention is to eliminate the aforementioned drawbacks.
  • a specific object of the invention is to produce a new type of combustion air duct system structure, allowing the preheating of the combustion air in a fireplace to be so implemented that it does not interfere with the combustion process in the furnace and that the combustion will be as efficient and perfect as possible.
  • the air duct system of the invention has been mainly developed for soapstone furnaces, but the invention is not restricted to soapstone structures alone; instead, it can be used in furnaces made of other fireplace materials as well, such as brick.
  • the invention is intended for use in batch furnaces, fireplaces with a heat storage capacity in which the storage mass consists of a solid material capable of storing and delivering heat.
  • the structural material as well as the heat storing material may consist of metal, soapstone or other stone material, brick or other burnt mass or equivalent.
  • the combustion air duct system of the invention for supplying combustion air into the combustion space of a furnace comprises one or more air inlets, a heat exchanger for heating the air flowing from the air inlet through the supply air duct system, and one or more outlets through which the heated air is passed to a suitable point or suitable points in the combustion space.
  • the heat exchanger is in direct heat transfer contact with the flue gas flow after combustion.
  • the heat exchanger is placed in the flow of flue gases flowing out of the combustion space.
  • an essential feature of the invention is that the combustion air is heated, i.e. the energy for its heating is taken from the flue gas flow at a sufficient distance from the combustion process so that at this point all combustion has already taken place and the transfer of heat from the flue gas flow does not interfere with the combustion process.
  • the thermal energy used to heat the combustion air is taken from those areas of the duct system or those parts of the furnace structures whose cooling does not reduce the temperature of the combustion process, preferably from a point as close to the flue gas exit flue as possible.
  • the heat exchanger is preferably placed in a cheek duct, e.g. in its lower part. It may also be placed in the bottom duct after a cheek duct, before the flue. In certain applications, the heat exchanger can also be partially or completely placed in the first part of the flue.
  • the combustion air duct system may be designed only for the preheating of primary air, in which case the outlet of the duct system preferably opens into the space below the grate.
  • the duct system is designed only for the heating of secondary air, in which case the outlets direct the preheated combustion air into the upper part of the combustion chamber or into a secondary combustion space.
  • the combustion air duct system branches after the heat exchanger, directing one portion of the preheated air for use as primary combustion air and another portion for use as secondary combustion air. It is naturally also possible within the scope of the inventive idea to use separate heat exchangers for the preheating of primary air and secondary air.
  • the air inlet of the combustion air duct system of the invention may be placed freely as appropriate for each furnace either in the top, bottom, front, back or side part of the furnace.
  • the air inlet can be provided with a separate shutter to enable the inlet opening to be closed and the air flow rate to be adjusted.
  • the air inlet can be placed in a coal box or ash box below the combustion chamber, in which case it will be unnecessary to provide a separate shutter or regulator in the structure because the adjustment can be done simultaneously with the primary air adjustment performed via the ash box.
  • a correct ratio between primary air supplied via the grate and preheated secondary air supplied into the combustion chamber can be implemented via correct design of the secondary air duct system.
  • the heat exchanger is placed in a cheek duct of the fireplace so that it is surrounded by hot flue gases. It is also possible to place the heat exchanger in the immediate vicinity of a cheek duct, i.e. at the edge of a cheek duct or in contact with the edge so that the heat of the flue gases is effectively transferred to the combustion air to be heated.
  • the heat exchanger is so constructed that the combustion air to be heated is separated from a suitable part of the flue gas channel with a material having a good heat conductivity, such as a relatively thin soapstone sheet or a wall of steel, cast iron or other fire-resistant material with good heat conduction properties.
  • a material having a good heat conductivity such as a relatively thin soapstone sheet or a wall of steel, cast iron or other fire-resistant material with good heat conduction properties.
  • the heat exchanger consists of separate, possibly ribbed heat exchanger elements of e.g. cast iron placed in the flue gas channel.
  • Such elements may comprise tubular, platelike or other suitable structures.
  • the heat exchanger by machining grooves, holes, cavities or canals in the massive stone structures of a stone furnace.
  • these structures are disposed near the surface of the flue gas channel, i.e. on the other surface of the massive stone used, so that they effectively heat the combustion air flow.
  • the fireplace with a heat storage capacity as illustrated by Fig. 1 and 2 comprises an ash box 6 under the grate 5 and a combustion space 4 above the grate, from where the flue gases ascend and, having reached the top part of the combustion chamber, turn downward into the cheek ducts 7, flowing down toward the bottom ducts at the bottom of the fireplace, from where the flue gases pass further into the flue, which is not shown in the figure.
  • the whole structure is surrounded by a massive envelope 9 with a good heat storage capacity.
  • the envelope 9 is provided with air inlets 1 placed on either side of the envelope and going through it.
  • the air inlets lead to ring-shaped heat exchangers 2 surrounding the cheek ducts 7 at the lower part of the cheek ducts, roughly at the level of the grate or combustion chamber.
  • the ring-shaped heat exchanger made of cast iron or steel, is so embedded in the massive structures of the fireplace that it does not reduce the cross-sectional flow area of the cheek ducts 7.
  • the ring-shaped heat exchanger 2 opens downward into the ash box 6 via a primary air duct 10 and upward via a secondary air duct 11 above the fuel material in the combustion chamber 4. In this way, both primary air and secondary air in the fireplace is preheated before entering into the combustion process.
  • the heat for the preheating of the air is taken from the flue gases in the cheek duct 7 at a point far enough from the combustion chamber to ensure that this heat transfer will not interfere with or deteriorate the combustion process in any way.
  • Fig. 3 presents another embodiment of the invention, in which the heat exchanger 2 is also placed in the lower part of the cheek ducts, but only at one edge of the cheek ducts, i.e. at the rear edge.
  • the air inlets 1 are located on the rear side of the fireplace while the outlets 3 are placed in the back wall of the combustion chamber and likewise in the back wall of the ash chest.
  • Fig. 4 presents a third embodiment of the invention, in which a corner fireplace has an exit flue 12 in the rear corner, with a ring-shaped heat exchanger 2 disposed around the exit flue.
  • the flue gases flow up from the combustion space 4 and down through the cheek ducts on either side of the fireplace and further via the bottom ducts into the flue, where the heat exchanger 2 recovers some of the heat and passes it into the combustion air.
  • the air inlet 1 is located in the rear part of the fireplace and the primary air duct 13 runs in a substantially horizontal direction through the bottom structures 15 of the combustion chamber 2 to a point under the grate 16.
  • the secondary air duct 17 goes through the back wall 18 of the combustion chamber 4, opening into the combustion chamber at a point clearly above the grate 16.
  • Fig. 5 and 6 present an embodiment of the invention in which a soapstone fireplace with a heat storage capacity is only provided with a secondary air duct system according to the invention.
  • the air inlets 1 of the duct system are located on the front side of the fireplace at the level of the lower edge of the door, on either side of it.
  • the air inlets 1 open inwards into the fireplace, where they expand to form a sheetlike heat exchanger 2, which forms in the cheek ducts on either side of the combustion chamber, at the level of the combustion chamber of the fireplace, an air space of a width substantially equal to the width of the cheek ducts and a height substantially equal to the height of the combustion chamber.
  • outlets 3 which lead through the thick side walls 20 of the combustion chamber into the combustion chamber, passing the air heated by the flue gases in the heat exchanger 2 into the combustion chamber 19. It is to be noted that it would be possible in this embodiment, too, to use primary air ducts to pass part of the preheated air as primary air e.g. via the ash chest and grate.
  • Fig. 7 shows an embodiment of the invention in which spaces disposed in the outer surfaces of the side stones 21 of the combustion chamber act as a heat exchanger 2.
  • outlets 3 go through the side stones 21 in the upper heat exchanger area into the combustion space 4.
  • Fig. 8 presents alternative structures for implementing the heat exchanger 2 of the invention.
  • the cheek ducts 25 are located on either side of the combustion space or combustion chamber 4, and the relatively thick mass with a good heat storage capacity between the combustion chamber and the cheek ducts is provided with outlets 3, through which warm secondary combustion air can be discharged into the combustion space.
  • the heat exchanger 2a is placed behind the cheek duct 25, with a relatively thin casing 26 with a good thermal conductivity between them.
  • Another possibility is to place the heat transfer component 2c in front of the cheek duct, separated from the latter by a corresponding thin casing 27.
  • a third application is a heat exchanger 2b placed beside the cheek duct on the opposite side relative to the combustion space 4, with a corresponding, relatively thin casing 28 with a good thermal conductivity separating the heat exchanger from the cheek duct.
  • outlets 3 placed above the door of the combustion chamber in the front part of the fireplace as well, in addition to the outlets 3 on either side of the combustion chamber 4.
  • the heat exchangers 2 are preferably placed on either side of the combustion chamber near the cheek ducts 29, with a suitable channel 30 to pass heated secondary air into the combustion space through the front outlets as well.
  • Fig. 10 presents an embodiment in which the structure of the invention is applied in a corner fireplace.
  • the cheek ducts are now at right angles to each other, with a tubular, vertical heat exchanger 32 disposed at the juncture between them, i.e. in the corner area.
  • the combustion air duct system of the invention can be implemented in several different ways and the heat exchanger of the invention can be disposed in several different locations in fireplaces of different forms, made of soapstone or other fireplace materials and designed to be used for different purposes or in different modes.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Air Supply (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
EP96660025A 1995-06-09 1996-06-06 Dispositif d'alimentation pour air de combustion Withdrawn EP0747637A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI952868A FI952868A0 (fi) 1995-06-09 1995-06-09 Kanalsystem foer sekundaerluft
FI952868 1995-06-09

Publications (2)

Publication Number Publication Date
EP0747637A2 true EP0747637A2 (fr) 1996-12-11
EP0747637A3 EP0747637A3 (fr) 1998-12-09

Family

ID=8543583

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96660025A Withdrawn EP0747637A3 (fr) 1995-06-09 1996-06-06 Dispositif d'alimentation pour air de combustion

Country Status (2)

Country Link
EP (1) EP0747637A3 (fr)
FI (1) FI952868A0 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1150073A3 (fr) * 2000-04-28 2005-05-04 Nunnanlahden Uuni Oy Cheminée d'accumulateur de chaleur
EP3324122A1 (fr) 2016-11-17 2018-05-23 Toni Klement Four de cheminée

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4349009A (en) * 1980-03-03 1982-09-14 Overhead Door Corporation Combustion air system
CA1260786A (fr) * 1984-02-22 1989-09-26 Andrew S. Robertson Systeme de chauffage

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1150073A3 (fr) * 2000-04-28 2005-05-04 Nunnanlahden Uuni Oy Cheminée d'accumulateur de chaleur
EP3324122A1 (fr) 2016-11-17 2018-05-23 Toni Klement Four de cheminée

Also Published As

Publication number Publication date
EP0747637A3 (fr) 1998-12-09
FI952868A0 (fi) 1995-06-09

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