WO1990000238A1 - Four - Google Patents

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Publication number
WO1990000238A1
WO1990000238A1 PCT/AU1989/000278 AU8900278W WO9000238A1 WO 1990000238 A1 WO1990000238 A1 WO 1990000238A1 AU 8900278 W AU8900278 W AU 8900278W WO 9000238 A1 WO9000238 A1 WO 9000238A1
Authority
WO
WIPO (PCT)
Prior art keywords
flow passage
furnace
combustion chamber
chamber
furnace according
Prior art date
Application number
PCT/AU1989/000278
Other languages
English (en)
Inventor
John K. Cannell
Ivan P. Chugg
Anthony G. Leitch
Original Assignee
Airwall Pty. 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 Airwall Pty. Ltd. filed Critical Airwall Pty. Ltd.
Publication of WO1990000238A1 publication Critical patent/WO1990000238A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23B—METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL
    • F23B1/00—Combustion apparatus using only lump fuel
    • F23B1/16—Combustion apparatus using only lump fuel the combustion apparatus being modified according to the form of grate or other fuel support
    • 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
    • F23M5/00—Casings; Linings; Walls
    • 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
    • F23M5/00—Casings; Linings; Walls
    • F23M5/08—Cooling thereof; Tube walls
    • F23M5/085—Cooling thereof; Tube walls using air or other gas as the cooling medium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H3/00—Air heaters
    • F24H3/02—Air heaters with forced circulation
    • F24H3/06—Air heaters with forced circulation the air being kept separate from the heating medium, e.g. using forced circulation of air over radiators
    • F24H3/067—Air heaters with forced circulation the air being kept separate from the heating medium, e.g. using forced circulation of air over radiators using solid fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
    • F26B21/06—Controlling, e.g. regulating, parameters of gas supply

Definitions

  • a furnace comprises a combustion chamber formed at least in part by side walls, a combustion air inlet into said chamber, and an exhaust outlet from said chamber, a fuel inlet into said chamber, and a combustion grate on which solid fuel admitted to the chamber is supported during combustion, characterised in that a flow passage for gaseous fluid is in contact with said chamber, said flow passage being formed at least in part from a stainless steel membrane which separates the interior of the flow passage from the combustion chamber, means being provided for causing gas to flow in said flow passage to thereby extract heat from said combustion chamber in use.
  • at least one of the side walls is formed having inner and outer skins and said flow passage is formed between said skins.
  • Said stainless steel membrane is preferably an austenitic steel stabilized by the addition of nitrogen thereto and is preferably a stainless steel such as "Avesta 253 MA” (trade mark) manufactured by Axel Johnson Corporation AB of Sweden.
  • the furnace may be used for curing timber.
  • Figure 1 shows a cross-sectional side view through a furnace according to the invention, taken along line II-II of Figure 2,
  • the furnace 1 is comprised of two sections, namely a radiant energy section 2 and a convective heat transfer section 3.
  • the radiant energy section 2 will comprise that part of the furnace 1 where combustion actually takes place and includes a combustion chamber 4 " having a furnace floor 5 and side walls 6.
  • the walls 6 are preferably formed having an inne skin 7 and an outer skin 8.
  • the two skins 7 and 8 are s ⁇ aced apart to form a flow passage 9 therebetweenT
  • the inner skin 7 is preferably formed from a corrugated sheet 10 as depicted in Figure 3, with the axes of the corrugations 12 being aligned substantially vertically and the corrugated sheet 10 defining the inner face of the furnace wall 6.
  • the inner skin 7 will be made from a material suitable for withstanding the high temperatures generated in the furnace and will also have a high coefficient of thermal conductivity.
  • the crests of the corrugated sheet 10 may be bonded or joined to the outer skin 8 at the points of contact between the crests and the outer skin so that the flow passage 9 is divided into a number of sub-passages 15.
  • Each sub-passage 15 is formed by a single corrugation.
  • those sub-passages can be individually shut off by means of a valve closure arrangement indicated diagrammatically at numeral 16.
  • the valve closure arrangement may include a valve closure gate 17 for each sub-passage 15 and each of those gates 17 may be independently controllable so they can be selectively closed off as required.
  • the valve closure arrangement will thus allow the total cross-sectional area of the flow passage 9 to be varied in accordance with combustion rates, heated air demand rates, temperature requirements and like factor.
  • the upper cover or roof 18 of the combustion chamber 4 is also of hollow wall constructions, and the central passage 19 in the roof 18 forms a continuation of the passage 9 in the walls 6.
  • air which is moving in the roof passage 19 will also be heated by the high temperatures in the combustion chamber in use.
  • the radiant energy section 2 of the furnace described is adapted to heat air which is forced through the flow passage 9 and is conveyed to apparatus (not shown) wherein heated air is required.
  • That apparatus may, for example, be a wood drying chamber which requires a source of heated air for effective and controlled drying, and wherein the temperature of the heated air can be carefully controlled.
  • the heated air form the furnace passes out through ducts depicted at numeral 14 in Figure 2.
  • the air to be heated is channelled into the flow passage 9 through a header 20 which is located below the furnace walls 6 and feeds the air directly into the passage 9 between the inner and outer skins.
  • the air which passes through the furnace in this manner serves to carry heat from the radiant energy section 2 for use elsewhere as well as serving to cool and thereby protect the furnace walls 6.
  • the floor 5 of combustion chamber 4 can take any convenient form but in a preferred form of the invention the floor is substantially horizontal grate 21 and is comprised of a plurality corrugated and perforated sheets 22.
  • the corrugations 23 are preferably of triangular shape in cross-section with the apexes 24 of the corrugations 23 uppermost, and the perforations 25 may be formed in the sloping sides of those corrugations 23.
  • Fuel to be combusted may be fed into the combustion chamber 4 by any suitable means.
  • the fuel is fed by means of a rotatable screw feed 26 through an elevated opening 27 in the floor 5. This screw type of feed 26 is particularly suitable where the fuel to be used in combustion is of particulate solid form such as wood pulp or chip or coal pieces.
  • Combustion air is fed into the interior of the furnace through pipes 30 located below the floor 5, and from the pipes
  • the perforations 25 are angled so as to direct incoming combustion air in different directions defined by the axis of the individual perforations 25.
  • the incoming combustion air serves to at least partially fluidize the fuel within the combustion chamber 4.
  • the form and position of those perforations 25 on the sloping sides of the corrugations 23 serves to ensure that when combustion air is switched off, the fuel does not fall through the grate of the furnace. In this condition the fuel will slump down onto the grate 21 but will not pass through the perforations 25 into the area below the grate 21.
  • the elevated opening 27 may be located in the centre of the floor 5 and the elevated nature of the opening serves to more evenly distribute the fuel over the floor 5.
  • a controlled induced draft fan is used since this will mean, as mentioned above, that the combustion chamber 4 operates at a pressure slightly below atmospheric pressure.
  • This reduced pressure chamber will mean that, should any leaks occur in the wall of the chamber, rather than gas from the combustion chamber being forced out of the combustion chamber, ambient air will be sucked into the combustion chamber. This is particularly important where a leak may occur between the flow passage 9 and the combustion chamber 4.
  • a reduced pressure combustion chamber will ensure that combustion gasses are not inadvertently forced into the flow passage 9 which would thereby contaminate the air or other gas in that flow passage 9.
  • Secondary combustion air may be directed into the combustion chamber at a position above the fluidized bed to thereby enhance combustion within the combustion chamber.
  • the secondary combustion air will serve to provide additional combustion oxygen for any combustible products which remain unburnt after combustion has taken place in the fluidized bed.
  • the grate 21 is preferably supported on a plurality of spaced joists 32 which are situated at an elevated position to define a gap or gaps 33 below the grate 21.
  • This gap 33 can provide a space in which a fuel feed mechanism is located as well as providing an area through which combustion air can be supplied.
  • Air heated in the radiant energy section 2 of the furnace 1 may be directed towards and collect in a plenum 35 mounted above the radiant energy section 2.
  • the plenum 35 may then carry the heated air towards the outlet ducts 14 of the furnace 1.
  • the plenum 35 is basically a large manifold mounted on top of the combustion chamber 4 and the passage 9 in the walls 6 and the passage 19 in the roof 18 all lead into this plenum which in turn leads into a duct 36 which connects the passages 9 and 19 with the outlet duct 14.
  • This duct 36 and the outer skin 8 of the combustion chamber are both preferably formed of or covered by a heat insulating material so that heated air retains its heat on its passage to the outlet ducts 14. It is envisaged that air will be heated by the chamber to between 250°C and 400°C, but it may be significantly higher than this, up to approximately 1000°C.
  • the inner skin 7 is preferably made from a stainless steel material which is a fully austenitic steel.
  • the austenite is stabilized by the addition of nitrogen.
  • This type of material is known and is manufactured by Axel Johnson Corporation AB of Sweden under the trade mark "Avesta 253 MA” .
  • Such a material has the following chemical composition: Chemical Composition %
  • the relatively high level of chromium and silicon in this material would normally give rise to a two phase microstructure - an austenitic-ferritic steel.
  • the microstructure contains carbides. The material thus possess a very high stability against sigma phase precipitation. It therefore does not become embrittled, even after a long period of high temperature operation.
  • the material contains rare earth metals added in very small but carefully controlled amounts. They provide resistance to oxidation and good creep strength.
  • the rare earth metals consist primarily of lanthanides, i.e., cerium, lanthanum, neodymium, praseodymium, etc.
  • the material has a very high scaling temperature in air, and scaling does not occur to any significant extent below approximately 1150°C.
  • the oxide which forms in the material has a good adhesive power which is responsible for the resistence to scaling in the face of large and rapid temperature fluctuations. Growth of the oxide layer is inhibited by the high silicon content and the addition of the rare earth metals.
  • 253 MA possesses a coefficient of thermal conduction which is less than that of steel. At 20°C the material will have a thermal conduction of approximately 15 /m C. This is not significantly different from other stainless steel materials.
  • the inner wall 7 will be made from a relatively thin sheet of material, approximately 1.5 to 1.6 millimetres thick. Heat transfer for a material with a wall thickness as thin as that is not too critical.
  • 253 MA has physical and mechanical properties which are more than satisfactory for the requirements of a furnace as described above. This is so, particularly since the flow passage 9 is a relatively low pressure passage and the combustion chamber 4 is also a low pressure chamber.
  • a furnace as described above is advantageous in that it heats air, or other gas which may be used, directly, that is, combustion within the furnace serves to heat the gas which can then be ,used where necessary.
  • a transfer medium such as oil which is heated and then in turn is used through a heat exchanger to heat air
  • the direct heating of air in the furnace allows for a simple and efficient system of heating to be employed.
  • the hollow wall construction enables lightweight metal components to be used which are able to withstand the high temperatures generated in the combustion chamber. This is possible because the air which is being heated in that hollow wall serves to remove heat continuously from the combustion chamber directly, ensuring that the sheet material from which the hollow walls 6 are made does not reach unacceptably high temperatures.
  • FIG. 5 of the drawings illustrates diagrammatically one possible application for the furnace 1.
  • a combustion chamber 4 is coupled to a timber curing chamber 60.
  • Ducting 14 links the two chambers 4 and 60 and supplies heated air generated in the flow passage 9 of the furnace to the curing chamber 60.
  • a control valve 61 controls the supply of heated air to' the curing chamber 60.
  • Combustion air is supplied to the chamber through pipes 30 and a control facility 62 controls the supply of combustion air.
  • Fuel is fed to the combustion chamber 4 through fuel supply passage 26 and fuel supply is controlled by fuel control means 63.
  • Water is supplied to the curing chamber 60 through spray nozzles 64. Those spray nozzles 64 are fed heated water from a tank 65 which is heated to just below boiling point in the convection section 3 of the furnace 1.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)

Abstract

La présente invention se rapportre à un four et plus particulièrement à un four destiné à chauffer un fluide gazeux traversant le four pour être utilisé ailleurs. Le four comprend une chambre de combustion (4) formée au moins en partie par des parois latérales (6). La chambre de combustion est destinée à effectuer la combustion d'un combustible solide, lequel est soutenu sur une grille (5) formant le sol de la chambre de combustion. Un passage d'écoulement (9) pour le fluide gazeux se trouve en contact avec la chambre de combustion et est formé au moins en partie d'une membrane en acier inoxydable qui sépare l'intérieur du passage d'écoulement de la chambre de combustion. L'écoulement de gaz à l'intérieur du passage d'écoulement entraîne l'extraction de chaleur de la chambre de combustion et le four peut ainsi fournir de l'air chauffé propre pouvant être utilisé pour d'autres opérations de traitement ou pour d'autres applications. Le matériau à base d'acier inoxydable avec lequel est fabriquée la membrane est de préférence composé d'un acier austénitique dont l'un des constituants est du silicium. Un matériau préféré pour la membrane est une tôle de type Avesta 253 MA. Le passage d'écoulement (9) est de préférence ménagé dans l'une des parois latérales de la chambre de combustion. Cette paroi latérale comporte de préférence une chemise interne et une chemise externe, lesquelles sont espacées pour définir le passage d'écoulement. La chemise interne est formée du matériau à base d'acier inoxydable. La chemise interne peut éventuellement être formée par un matériau ondulé, dont les ondulations définissent chacune des sous-passages séparés pouvant être séparément obturés, de façon à faire varier la section transversale du passage d'écoulement.
PCT/AU1989/000278 1988-06-29 1989-06-28 Four WO1990000238A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPI9045 1988-06-29
AUPI904588 1988-06-29

Publications (1)

Publication Number Publication Date
WO1990000238A1 true WO1990000238A1 (fr) 1990-01-11

Family

ID=3773188

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1989/000278 WO1990000238A1 (fr) 1988-06-29 1989-06-28 Four

Country Status (1)

Country Link
WO (1) WO1990000238A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006041391A1 (fr) * 2004-10-14 2006-04-20 Lindstroem Sture Grille et bruleur comportant cette grille
EP2420744A1 (fr) * 2010-08-18 2012-02-22 Eloma GmbH Echangeur thermique à gaz pour appareils de traitement d'aliments et un tel appareil
CN111288751A (zh) * 2020-03-10 2020-06-16 广西格卡环保科技有限公司 一种农副产品的烘干设备

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB763722A (en) * 1950-10-20 1956-12-19 Andre Huet Improvements in combustion chamber linings
AU3483463A (en) * 1963-08-30 1966-03-03 D. McALLISTER Improvements in and relating to air heaters

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB763722A (en) * 1950-10-20 1956-12-19 Andre Huet Improvements in combustion chamber linings
AU3483463A (en) * 1963-08-30 1966-03-03 D. McALLISTER Improvements in and relating to air heaters

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DERWENT ABSTRACT ACCESSION NO. 84-040813/07, Class Q74; & SE,A,8203473 (OSBYVARME AB), 23 January 1983 (23.01.83). *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006041391A1 (fr) * 2004-10-14 2006-04-20 Lindstroem Sture Grille et bruleur comportant cette grille
GB2434203A (en) * 2004-10-14 2007-07-18 Sture Lindstroem Fire grate and burner comprising such a fire grate
GB2434203B (en) * 2004-10-14 2008-02-27 Sture Lindstroem Fire grate and burner comprising such a fire grate
EP2420744A1 (fr) * 2010-08-18 2012-02-22 Eloma GmbH Echangeur thermique à gaz pour appareils de traitement d'aliments et un tel appareil
WO2012022546A1 (fr) * 2010-08-18 2012-02-23 Eloma Gmbh Échangeur de chaleur à gaz pour appareils de traitement de produits alimentaires ainsi qu'appareil de ce type
CN111288751A (zh) * 2020-03-10 2020-06-16 广西格卡环保科技有限公司 一种农副产品的烘干设备

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