Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23B—METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL
  • F23B3/00—Combustion apparatus which is portable or removable with respect to the boiler or other apparatus which is heated
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
  • F23K3/00—Feeding or distributing of lump or pulverulent fuel to combustion apparatus
  • F23K3/10—Under-feed arrangements
  • F23K3/14—Under-feed arrangements feeding by screw

Definitions

• the present invention concerns a stoker for burning solid fuel, comprising a grate which is connected to a fan for supply of combustion air, and feeding means for controlled feeding of fuel from a reservoir to the grate which reservoir on one hand comprises a primary container located at the feeding means containing a smaller vol ⁇ me of the fuel, and on the other a secondary container which is connected to the primary container and is located at a distance from said primary container and having a main volume of the fuel, which primary container comprises detector means for controlling replenishment of fuel from the secondary container to the primary container, wherein an air distribution chamber is located between the grate and the primary container, which air distribution chamber is supplied with air via the fan and distributes the air to the grate bowl via a primary air pipe, and to the upper side of the grate via a secondary air outlet.
• Non-fossil solid fuel like for example pellets, wood, and wood chips
• Combustion of non-fossil solid fuel is normally performed in a grate.
• the solid fuel is slowly gasified within the grate under limited supply of air.
• the received gas is then burned in a secondary step under ample supply of air.
• the process results in a minimum discharge of environmental polluting gas, in comparison with most other types of combustion.
• the residual product is a fine ash which contains matter having a pH-increasing effect and being in shortage within acidificated ground.
• the development of furnaces for this purpose has been directed to furnaces which can be operated automatically, approximately in the same user friendly way as the existing oil burner.
• furnaces and burners for solid fuel have been designed as a complete furnace or as a dockable unit which can be docked to an existing furnace.
• One object of the present invention is to provide a stoker for burning solid fuel which fulfils the above mentioned fire safety demands and which has so small mounting space requirements, that it can replace conventional oil burners on a common heating boiler.
• the stoker according to the invention is characterized in that an outer ring is rotatable joumalled upon the upper edge of the grate bowl, and is provided with gear segments to rotate the ring in order to avoid accumulation of cinders at the opening of the grate.
• Fig. 1 is a side view schematically showing a stoker according to the invention
• Fig. 2 shows the stoker in Fig. 1 in a view from above.
• the stoker according to the invention is adapted to be mounted directly into the furnace opening which is used for mounting an oil burner at a common one-family house heating furnace.
• the stoker is provided with a mounting plate 10 with screw holes for mounting screws.
• a thick pipe 11 is rigidly connected to the mounting plate
• the pipe 11 forms a bearing for a feeding screw 12, which is driven intermittently with a very low speed by means of a stepping motor 13.
• the motor 13 drives the screw 12, so that its thread feeds in the direction towards the at the opposite end of the tube
• a primary reservoir.15 is placed with its bottom at an opening in the tube 11, in such a way that fuel, for example stick shaped pellets, can fall down into the tube 11 from the reservoir 15 and be fed in the direction towards the grate 14.
• the primary reservoir 15 is connected via a hose 16 (or a pipe) to a secondary reservoir 17, which is shown in reduced scale in Fig. 1 and is provided with a worm screw 18 which is operating obliquely upwards and is driven by a motor 19.
• the secondary reservoir 17 forms a main volume of fuel, which for example accommodates fuel for a month production of heat.
• the primary reservoir 15 forms a part volume which may be sufficient for about one hour production of heat.
• a level detector 20a in the primary reservoir 15 can for example be constituted by a photo cell, which is used for detection of the fuel level in this reservoir.
• a relay will switch on and start the motor 19 which will drive the screw 18, until a suitable level of fuel is reached inside the primary reservoir 15. Then the motor 19 is stopped. In this way it is ensured that only a limited amount of energy is present near to the fire in the grate 14.
• the tube 11 and the reservoir 15 are provided with temperature sensors (not shown in the drawings) which sense if anything unusual is would happen, wherein the motor 13 will increase its rate of feed and rapidly feed out the amount of fuel which is present in the reservoir 15, via the grate. Simultaneously, a signal is sent to the motor 19 so that its operation is stopped until the fault is corrected.
• An air distribution chamber 20b is located at the mounting plate 10 and is supplied with air via a fan 21.
• the chamber b is connected to the grate via a primary air pipe 22 and a secondary air pipe 23.
• the first mentioned pipe distributes air around the inside of the grate bowl 14 via slits 24 in a cast steel ring 25.
• the secondary air pipe 23 is directed towards to the upper edge of the grate bowl, above which the final combustion takes place.
• the secondary air also transports away the fine ash from the top of the grate bowl.
• An outer ring 26 is rotatable joumalled upon the upper edge of the grate bowl, and is provided with gear segments, which are actuated by a finger 28 protruding from the end of the screw shaft 12.
• a detection pipe 27 which extends from the air distribution chamber 20b through the mounting plate 10, is used for detection of the existence of combustion in the grate 14.
• the detector is cooled by means of leak air from the chamber 20b.
• Similar pipes can be used for detecting the level of ash in the furnace below the stoker, and for sucking out ash from said room.
• An electronic control system is used for indication of malfunction and for regulating the stoker with reference to feeding in of fuel via the screw 12.
• the stoker can be operated intermittently in the same manner as an oil burner, so that it can switch between a stand by mode (0 KW) and working mode (e.g. 2-12 KW), in accordance with thermostat control means.
• a stoker in accordance with the invention can for example have an output of 2-12 KW.
• the combustion efficiency is about 90%.
• the amount of ash is normally 0,5-1 % and the weight of the stoker without secondary reservoir is about 10 Kg.
• the invention is not limited to the above described embodiment, but several variations are possible within the scope of the accompanying claims.
• the grate 14 and the primary reservoir 15 can be designed differently.

Landscapes

• 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)
• Fuel-Injection Apparatus (AREA)
• Magnetic Resonance Imaging Apparatus (AREA)
• Gasification And Melting Of Waste (AREA)
• Incineration Of Waste (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=20392215

Family Applications (1)

Country Status (8)

Cited By (1)

Families Citing this family (3)

Family Cites Families (6)

• 1993
  • 1993-12-23 SE SE9304289A patent/SE502033C2/sv not_active IP Right Cessation
• 1994
  • 1994-12-23 DE DE69423366T patent/DE69423366T2/de not_active Expired - Fee Related
  • 1994-12-23 AU AU13951/95A patent/AU1395195A/en not_active Abandoned
  • 1994-12-23 PL PL94315254A patent/PL181372B1/pl not_active IP Right Cessation
  • 1994-12-23 AT AT95905282T patent/ATE190389T1/de not_active IP Right Cessation
  • 1994-12-23 WO PCT/SE1994/001252 patent/WO1995017627A1/en active IP Right Grant
  • 1994-12-23 DK DK95905282T patent/DK0731895T3/da active
  • 1994-12-23 EP EP95905282A patent/EP0731895B1/de not_active Expired - Lifetime

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events