Classifications

• • 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
  • F23L9/00—Passages or apertures for delivering secondary air for completing combustion of fuel 
  • F23L9/04—Passages or apertures for delivering secondary air for completing combustion of fuel  by discharging the air beyond the fire, i.e. nearer the smoke outlet
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23B—METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL
  • F23B5/00—Combustion apparatus with arrangements for burning uncombusted material from primary combustion
  • F23B5/04—Combustion apparatus with arrangements for burning uncombusted material from primary combustion in separate combustion chamber; on separate grate

Definitions

• the invention relates to a burner for solid fuels such as wood, chips and briquettes of combustible material, com ⁇ prising a combustion chamber which has a solid bottom and which has at one end an opening for receiving continuously supply fuel from a fuel conveyor, such as a screw convey ⁇ or, air jets in the side walls of the combustion chamber for supplying primary air to the combustion zone in the fuel at the rear end portion of the bottom, where ash and other uncombusted -taterial falls down onto a transverse screw conveyor beneath the rear end edge of the bottom plate, and a flue throat which extends upwards from the rear end portion of the combustion chamber and is provided with means for supplying secondary air to the combustion gases in the flue throat.
• a fuel conveyor such as a screw convey ⁇ or, air jets in the side walls of the combustion chamber for supplying primary air to the combustion zone in the fuel at the rear end portion of the bottom, where ash and other uncombusted -taterial falls down onto a transverse screw conveyor beneath the rear end edge of the bottom
• Solid fuel burners usually have a grate at the bottom of the combustion chamber. Primary air is supplied from below through the grate. In practice, it has, however, proved almost impossible in such a burner to obtain effective combustion of solid fuels which have a relatively high moisture content, i.e. up to about 50% or more.
• the purpose of the present invention is to further develop the type of burner which has a solid bottom and is of the type described in the preamble to Claim 1 so as to provide effective combustion of such fuels as chips with a mois- ture content of 15-50%, briquettes of chips, bark or paper, sawdust mixed with chips in essentially equal amounts and similar moist fuels.
• This is achieved with a burner of the type which according to the inv rention has the characteristics defined in the characterizing clause of the attached Claim 1.
• secondary air is added, in a manner known per se, to the gases in the flue throat to achieve after-combustion. This is highly depend ⁇ ent on how effectively the secondary air is mixed with the combustion gases.
• this mixing- _in is improved in a particularly simple manner by di ⁇ viding the gas flow, in the vicinity of the inlet end of the flue throat, into a number of partial flows in sub ⁇ channels in a throttling plate of ceramic material.
• the required amount of second- ary air is supplied essentially tangentially near the inlet end of each subchannel to produce a powerful vortex of secondary air in the subchannel at the same time as the partial flow of combustion gas flows through the sub ⁇ channel.
• Figure 1 is a longitudinal section through a burner according to the invention.
• Figure 2 is a horizontal section through the burner.
• Figure 3 is a separate partial view from above of the throttling plate with subchannels between the combustion chamber and the flue throat.
• Figure 4 is a schematic perspective view of a subchannel.
• the burner 10 is made simply of a few components and con ⁇ sists of a bottom plate 12 in the combustion chamber 14, two side walls 16 and 18, an end wall 20 and a ceiling in the form of a ceiling plate 22 and a throttling plate 24 with subchannels 26. Above the throttling plate there is a tubular flue throat 28 which can be connected to a heat exchanger (not shown).
• the above mentioned components are of ceramic material
• the ceramic throttling plate 24 has a thickness which is at least 4 cm so that the subchannels 26 have a corre- sponding length, designated H in Figure 4.
• the diameter of the subchannels is designated D. In the example shown, the diameter D is approximately 1.5 times the length H.
• the fuel is supplied continuously through a pipe 30 from a storage compartment to a screw conveyor 32 which feeds the fuel through an inlet opening at the front end of the com- bustion chamber. At this end, there is a connection 34 to an automatic lighter.
• the walls of the combustion chamber are insulated with an insulating material 36 in a known manner.
• the fuel 38 on the bottom plate 12 has a forward area 38A, where the fuel is dried at a temperature of 100-200°C, and a rear area 38B, where the moist fuel begins to be gas ⁇ ified as primary air is supplied through three jets 40 in the side walls 16, 18. The jets direct the primary air flows obliquely towards the rear so that the primary air tends to push ash and similar solid particles to the rear end edge 42 of the bottom plate, where the ash etc. falls down onto a transverse screw conveyor 44 for removal of ash and unburned particles.
• the partially uncombusted gases then flow up towards the throttling plate 24, where the gas flow is throttled by being led into the three subchannels 26, where the gas velocity is increased.
• each of the subchannels secondary air is supplied through a jet 46 which directs the secondary air flow tangentially into each subchannel, in the vicinity of the inlet end of each subchannel at a height h from the inlet edge of the channel.
• This height h is less than half of the length of the channel H, preferably less than 1/3 of its length.
• the total area of the subchannels is approximately half of the cross-sectional area of the flue throat. This ratio can, however, be adjusted so that the combined area of the subchannels is in the range of 30-70% of the cross-sectional area of the flue throat. If the burner capacity, i.e. the amount of fuel supplied per unit of time, is increased or decreased, the size and number of the subchannels is adjusted to the predetermined capacity. The amounts of primary and secondary air supplied are then adjusted to the feeding of the fuel in question, so that stable and effective combustion conditions are obtained.
• the throttling plate 24 is easily replaceable with another throttling plate with other suitable subchannels.
• the system is essentially air-tight with the exception of those places where primary air and secondary air are supplied. This is essential to obtain optimum combustion conditions r.
• the primary air and secondary air are supplied with the aid of individual fans which can be individually controlled.
• the combustion can be observed through an observation glass 52.

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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)
• Incineration Of Waste (AREA)
• Combustion Of Fluid Fuel (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=20376639

Family Applications (1)

Country Status (2)

Cited By (7)

Citations (5)

• 1989
  • 1989-08-04 SE SE8902683A patent/SE463576B/sv not_active IP Right Cessation
• 1990
  • 1990-08-07 WO PCT/SE1990/000518 patent/WO1992002762A1/en active Application Filing

Patent Citations (5)

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