Classifications

• • 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
  • F23G5/02—Incineration of waste; Incinerator constructions; Details, accessories or control therefor with pretreatment
  • F23G5/027—Incineration of waste; Incinerator constructions; Details, accessories or control therefor with pretreatment pyrolising or gasifying stage
  • F23G5/0273—Incineration of waste; Incinerator constructions; Details, accessories or control therefor with pretreatment pyrolising or gasifying stage using indirect heating
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
  • F23G7/10—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of field or garden waste or biomasses
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
  • F23G7/10—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of field or garden waste or biomasses
  • F23G7/105—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of field or garden waste or biomasses of wood waste

Definitions

• the present invention relates to a boiler of the kind stated in the preamble of claim 1.
• a boiler of this type is disclosed in DE "Offenle- gungsschrift" no. 24 00 778 and is described as being parti ⁇ cularly well suited for the burning of various kinds of waste and in particular waste containing material from the scrapping of cars, such as rubber from car tyres.
• the flame from the secondary burner is di ⁇ rected towards the mouth of the tube and heats the waste in the mouth to such a degree that it continues to burn, when the secondary fuel supply is stopped.
• the fuel in the mouth of the tube is exposed to a very strong air flow, which in the case of essentially dry and comminuted fuel will disperse it in the combustion chamber without reachx.g the high combustion temperatures necessary for maintaining the combustion.
• the object of the present invention is to provide a boi ar, which does not have these drawbacks, and which in connection with burning of comminuted fuel is particularly well suited for intermittent operation and where, in a simple way, variations in the thermal value of the fuel used and its ability to gasify are compensated for.
• This object is met thereby that the boiler according to t' present invention is characteristic by the subject matt - of the characterizing clause of claim 1.
• the tube By letting the tube project freely into the combustion chamber in the area of the combustion zone of the secondary burner, the tube is exposed to a heavy heat radia ⁇ tion, which develops a strong gasification in the fuel sup ⁇ plied by means of the helical conveyor. Simultaneously with the supplying of the fuel the helical conveyor carries out a stirring to such an extent that the heat supplied is distri ⁇ ubbed in the part of the fuel, which is present in the free ⁇ ly projecting part of the tube.
• the formation of gas gene ⁇ rated by the strong heating causes the gas to be pressed out through the mouth of the tube and by means of the two-sided deflector to be mixed effectively with the combustion air from the secondary burner.
• the secondary fuel supply can be reduced, but the resulting flame in the combustion chamber will essentially have the same shape and extension, as when secondary fuel is burned, and will ensure a combustion pattern in the boiler, which may therefore be constructed to yield a high degree of effiency. Firing of the boiler can take place immediately by starting the secondary burner at full effect, the secondary fuel supply being adjusted for the attainment of an approxi ⁇ mately full exploitation of the hydrogen supplied in the combustion air. Gradually along with the heating of the gas tube, the organic fuel supplied by the helical conveyor gives off an increasing amount of gas, and it will then be possible to throttle down or perhaps completely stop the supply of secondary fuel.
• the deflector protects the secon ⁇ dary burner against superheating from the combustion of the gas formed and contributes to ensure a safe control of where the flames from the combustion will be in the combustion chamber irrespective of the ratio between the fuels used.
• the smoke flue of the boiler is placed opposite to the secondary burner and preferably below the point of entrance of the tube with the helical conveyor.
• the uttermost part of the tube with the helical conveyor tapers conically in the di- rection of the secondary burner.
• the secondary burner is an oil or gas burner, preferably a natural gas burner controlled by a lambda probe in the smoke flue.
• This arrangement is described in claim 7.
• Natural gas burners available on the market are adapted to this kind of control of the gas supply, and the necessary automatic control for regulating the yield is therefore in many cases present as an integrated part of for instance na ⁇ tural gas burners. Natural gas is therefore the preferred fuel for the secondary burner.
• the present invention relates to a boiler, in which a fuel that when heated at least partly can be transformed in ⁇ to a combustible gas is utilized.
• a fuel may typically be a socalled bio fuel, which may for instance be cut straw, wooden flakes, sawdust or the like, which in a suitable com ⁇ minuted shape when heated to over 300 ⁇ C liberates approx. 75% of its weight and the major part of its thermal value in the form of gases.
• the boiler according to the invention is shown in a longitudinal section in the drawing and comprises a combustion chamber 1 surrounded by a hood 2, which com ⁇ prises hollow spaces 3 for a heat transmission medium, nor- mally water.
• the hood is in the embodiment shown in the shape of a horizontally extending cylinder, which at one end is closed by means of a front wall 4, in the middle of which a primary air supply in the form of a blower 5 is placed, said blower being adapted to blow combustion air into the combustion chamber through a mouth piece 6.
• the front wall may advantageously have the shape of a preheating device 7 for the combustion air, whereby part of the heat delivered from the combustion chamber to the front wall 4 is transfer ⁇ red to the blown in air.
• the primary air supply is a gas or possibly an oil burner with variable gas or oil supply 8.
• the gas or the oil serves as a secondary fuel in the boiler, but the supply should be adjustable with an interval so wide that it is possible to fire the engine so ⁇ lely with the secondary fuel or solely with the primary fuel.
• the burner consisting of the blower 5 and the fuel supply 8 is used for firing the boiler and as an additional fuel supply source during the running.
• the boiler is provided with a back wall 9, wh;. .1 like the hood of the boiler is provided with hollow spaces 10 for the heat transmission medium.
• a tube 11 with a helical conveyor is provided, said tube extending throughout the length of the boiler and with closed walls to the mouthpiece 6 for the air supply.
• the mouthpiece 6 and the tube with the helical conveyor have a common axis extending horizontally approXaimately in the middle of the boiler.
• the tube with the hel.- 5 ⁇ 1 conveyor tapers in the direction of its mouth 12 at a sL.rt distance in front of the mouthpiece 6.
• the distance between the mouth 12 and the mouthpiece 6 is of the same size as the diameter of the mouth 12.
• a deflector 13 In front of the mouth 12 a deflector 13 is provided, the purpose of which is to deflect, the gas streaming out of the mouth 12 of the tube with the helical conveyor in a direction radially outwards.
• the deflector is however two-sided and also serves to de ⁇ flect e stream of gaseous or atomized secondary fuel out ⁇ wards, so that the combustion of both the fuel supplied to the fuel supply 8 and gas streaming from the mouth 12 takes place by means of a flame starting in the area around the deflector 13, said flame extending along the tube 11 with the helical conveyor on all sides thereof.
• the tube 11 with the helical conveyor is outside the back wall 9 of the boiler connected with a supply tube 14 with a helic .
• conveyor 15 supplying comminuted bio fuel to the supply tube from a storage silo 16.
• the storage silo 16 may be closed by a cover 17 preventing gas from entering backwards through the silo.
• the helical conveyor 15 trans ⁇ ports the bio fuel through the tube 11 at su a speed that the fuel stays in the tube for approx. 1 - 5 minutes. During this period the bio fuel is heated to a temperature of more than 300*C and thereby gives off its gas content.
• the gas can only flow in the direction towards the mouth 12, and the gas formation is so heavy that the not transformed grains or corn in the conically tapering part are swept along out through the mouth and mixed with the combustion air blown in from the mouthpiece 6.
• an outlet 18 for smoke and ashes In the back wall there is furthermore an outlet 18 for smoke and ashes.
• Ashes deposited in the lower part of the combustion chamber, may advantageously be blown out in the smoke flue by means of a compressed air blower 19, the ash being separated from the smoke in a (not shown) device for cleaning of the smoke flue placed before the flue is taken to a chimney.
• Start of the boiler is carried out by means of the burner placed in the front wall, said burner being supplied with the secondary fuel.
• the helical conveyor is started, the bio fuel being thereby gra ⁇ dually pressed forwards through the tube with the helical conveyor and an increasing amount of gas will be produced, until a stationary stage has been attained.
• the supply of secondary fuel to the burner in the front plate will be re ⁇ cuted.
• the air supply remains unchanged.
• the regu ⁇ lation of the secondary fuel supply may advantageously be controlled by means of a measuring of the oxygen surplus in the flue gas, an automatic control taking care of ensuring that the supply of secondary fuel will exactly be enough for obtaining an oxygen surplus of for instance 2%.
• a regu ⁇ lation is commonly known in connection with burners for heating with natural gas and need not be further described in this connection.
• Tests with the prototype show that it is possible to produce a boiler which is capable of operating effectively at varying ratios between bio fuel and a support fuel, such as natural gas, and which is capable of working with a con- stantly high effect both in case of a combined burning of bio fuel and natural gas and in case of pure bio fuel being burned.
• a support fuel such as natural gas
• the tube with the helical conveyor and the deflector are to be made from a heat-resistant material which can re ⁇ sist temperatures of approx. 7-800°c.
• the embodiment shown in the drawing of the mouth piece 6 and the mouth 12 with the intermediary deflector is a preferred and simple embodi- ment of the invention, and the -gas developed can by re ⁇ covered by means of guiding plates or the like means placed in the mouths and which impart a turbulent, rotating move ⁇ ment to the air of the primary air supply and the gas flow.
• the boiler is constructed with a view to the desired combination of fuel, for instance na ⁇ tural gas, as a secondary fuel, and straw or sawdust as a primary fuel.
• the principle of the boiler described may, however, also be used in certain types of already existing boilers, which are provided with a tube with a helical con- veyor introduced in the wall opposite to the oil or gas bur ⁇ ner and directed towards the oil or gas burner.
• a tube with a helical con- veyor introduced in the wall opposite to the oil or gas bur ⁇ ner and directed towards the oil or gas burner.

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• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Wood Science & Technology (AREA)
• Combustion Of Fluid Fuel (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 1990
  • 1990-08-01 DK DK183490A patent/DK183490A/da not_active Application Discontinuation
• 1991
  • 1991-07-31 WO PCT/DK1991/000220 patent/WO1992002763A1/en not_active Application Discontinuation
  • 1991-07-31 EP EP19910914450 patent/EP0541677A1/de not_active Withdrawn
  • 1991-07-31 AU AU83134/91A patent/AU8313491A/en not_active Abandoned

Non-Patent Citations (1)

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