US3587489A - Furnaces for solid fuel - Google Patents

Furnaces for solid fuel Download PDF

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Publication number
US3587489A
US3587489A US820486A US3587489DA US3587489A US 3587489 A US3587489 A US 3587489A US 820486 A US820486 A US 820486A US 3587489D A US3587489D A US 3587489DA US 3587489 A US3587489 A US 3587489A
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Prior art keywords
grate
coal
gas
furnace
chamber
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Expired - Lifetime
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US820486A
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English (en)
Inventor
Viking Valentin Demar
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Ekman C O A
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Ekman C O A
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    • 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
    • F23B1/02—Combustion apparatus using only lump fuel for indirect heating of a medium in a vessel, e.g. for boiling water
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23B—METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL
    • F23B2700/00—Combustion apparatus for solid fuel
    • F23B2700/011—Combustion apparatus for solid fuel with fuel shaft for steam boilers

Definitions

  • a furnace for burning solid fuels such as bituminous coals comprises a grate, a fuel inlet shaft' which communicates only at its lower end with a combustion chamber FURNACES FOR SOLID FUEL above the grate by means of a restricted opening beneath a 21 Claims 5 Drawing solid transverse wall, the lower end portion of the fuel inlet [52] U.S. Cl 110/31, shaft forming a degassing chamber.
  • a gas duct is provided for 48/76 conveying gas from the degassing chamber for distribution [51] Int. Cl Cl0b 31/02 beneath a rearward section of the grate.
  • Field of Search 110/31 the invention, the bottom end of the degassing chamber por- 48/76 tion of the inlet shaft is closed.
  • FURNACES son soun FUEL This invention relates to furnaces for burning solid fuels 1 such as bituminous coals smokelessly, the furnaces being of the kind in which under normal working conditions gases and volatile matter including tar (hereinafter referred to generically as gas) from the green coal are released and mixed with air and the mixture is thereafler raised to a sufficiently high temperature to ignite by being passed through the incandescent fuel-bed at the rear of the grate.
  • gas volatile matter including tar
  • the principal object of the present invention is to ensure controlled and effective degassing.
  • a furnace for burning solid fuels having a gas content as defined above comprising a grate, a fuel inlet shaft which communicates only at its lower end with a combustion chamber above the grate by means of a restricted opening beneath a solid transverse wall, the lower end portion of the fuel inlet shaft forming a degassing chamber, and a gas duct for conveying gases from the degassing chamber for distribution beneath a rearward section of the grate, wherein the bottom end of the degassing chamber portion of the inlet shaft is closed.
  • FIG. 1 is a longitudinal sectional view of the furnace
  • FIG. 2 is a perspective view of some of the more important parts of the furnace, with some portions broken away,
  • FIG. 3 shows a fragment of a cross section on the line 3-3 of FIG. 2,
  • FIG. 4 is an elevational view of part of the furnace.
  • FIG. 5 is a longitudinal vertical sectional view of a hopper which may be used for feeding coal to the furnace shown in FIGS. 1 to 4.
  • Coal is fed to the furnace shown in FIGS. 1 to 4 from the outlet of a hopper and descends under gravity down a coal inlet shaft 11.
  • the bottom of the shaft 11 is formed by a dead plate '12 which extends over the width of a forward extension of a horizontal grate 13 between sidewalls 14 of the furnace.
  • the front wall of the coal inlet shaft 11 is formed by a coal guide 15 which is slightly inclined to the vertical to allow the descending coal to swell as it is degassed.
  • the rear wall of the shaft is formed by a transverse refractory arch block 16 disposed above the grate 13 so as to define a restricted opening 17 connecting the coal inlet shaft 11 with a combustion chamber 18 situated beneath a top refractory arch formed by a plate 19.
  • the space beneath the grate I3 is divided by transverse partitions 20 and 21 into an air inlet chamber 22 and a gas distributing chamber 23.
  • the fuel on the grate 13 forms a burning fuel-bed 25 which slopes away from the restricted opening 17 to the rear end of the grate 13 where the ash and any clinker which may have formed drop on to an ash-removing screw-conveyor 26 which extends across the full width of the furnace. From this point it may be removed in any appropriate manner depending upon the location of the furnace. In the embodiment illustrated, it is taken out through one side wall 14.
  • the grate is formed by a plurality of reciprocable parallel grate bars 27 of generally triangular or tapering cross section as shown in FIGS. 2 and 3.
  • the grate bars 27 have three sets of laterally projecting abutments, namely: abutments 28 at their forward ends, abutments 29 at their rear ends and abutments 30 at an intermediate region above the transverse partition 20.
  • the abutments 28, 29, 30 on each bar 27 abut the corresponding abutments on the adjacent bar so that the portions ofeach grate bar 27 between the abutments 28 and 30 and between the abutments 30 and 29 are spaced from the corresponding portions of the adjacent bars.
  • a primary air flow channel 31 is formed between the air inlet chamber 22 and the fuel-bed 25.
  • a secondary gas flow channel 32 is formed between the gas distributing chamber 23 and the rearend of the fuel-bed 25.
  • the two outermost grate bars should be of rectangular cross section as shown at 33 in FIG. 2. In this way a more uniform air distribution across the fuel-bed is maintained.
  • All the grate bars 27 and 33 are slidably supported at their forward ends on a transverse bar 34 and at their rear ends by the top of the rear wall partition 21 of the gas distributing chamber 23.
  • the coal guide 15 forms a boundary between the coal inlet shaft 11 and a gas receiving chamber 35 at the front of the furnace.
  • the lower part of the coal inlet shaft 11 communicates with the gas receiving chamber 35 through gaps between downwardly projecting teeth 36 in the lower part of the guide 15 and a horizontal opening 37 beneath the teeth 36.
  • the gas receiving chamber 35 is connected to the gas distribution chamber 23 by two gas ducts 38 and 39 (FIG. 4).
  • the entry to the gas duct 38 is shown at 40 in FIG. 1 and its outlet at 41. It is preferred that the gas ducts have a uniform circular cross section throughout their length in order to minimize their frictional resistance.
  • a reciprocating mechanism for the grate bars 27 comprises a rotationally driven shaft 42 carrying radial arms 43, one for each grate bar.
  • Each grate bar has a cam surface 44 engaged by a roller 45 carried by the corresponding radial arm 43.
  • the radial arms 43 are divided alternately into two angularly spaced groups as shown in FIG. 1.
  • As the shaft 42 rotates in the clockwise direction (FIG. 1) one group of corresponding grate bars is retracted to the forward end position before the other group.
  • a crossbar 46 interconnecting the two outermost bars 33 ensures that all the grate bars are then returned to the rear position shown in FIG. 1 simultaneously as a result of engagement of the cross bar 46 with abutments 47 on the grate bars.
  • the top surfaces of the grate bars may slope as shown at 48. The relative movement between adjacent grate bars will then cause the top surface of the grate to undulate, thereby opening up the fuel-bed and discouraging the formation of clinker.
  • the shaft 42 is driven by an electric motor 49 through a chain drive 50.
  • the voltage supplied to the motor 49 may be varied in order to control the speed of the motor.
  • the ash removal screw conveyor 26 is driven by the same motor 49 through a chain drive 51 (FIG. 4). Any adjustment.
  • a reciprocating pusher bar 52 projects rearwardly over the dead plate 12 with a running clearance forming effectively a seal between the pusher bar and the lower edge 53 of the bottom of the gas receiving chamber 35.
  • the pusher bar 52 is secured by bolts 54 (FIG. 2) to the outermost grate bars 33 so as to move with them.
  • the shafi 11 is filled with coal and the burning fuel on the grate 13 forms a bed of the general shape indicated at 25.
  • the draught above the fuel-bed 25 in the combustion chamber 18 causes air to be drawn through the inlet channel 31 in the direction of the arrow 55.
  • the upper portion of the partition 20 and the front surfaces of the abutments 30 are inclined upwards and rearwards and are aligned to guide part of the airflow to follow the arrow 55.
  • a smaller airflow is diverted in the direction of the arrow 56 to pass through small channels 57 provided between the tops of the abutments 30 and the top surface of the grate 13 as shown in FIGS. 1, 2 and 3 so as to cool the grate bars in this region.
  • the tops of the abutments 30 have a length, measured longitudinally of the grate bars, at least equal to the reciprocatory stroke of the grate so that in all relative positions of the grate bars an effective seal is provided between the channels 31 and 32 other than in the region of the channels 57.
  • the gas distributing chamber 23 As the gas distributing chamber 23 is sealed by the partitions 20 and 21 and the abutments 29 and 30, a suction created by the chimney or induced draught fan is created in this chamber due to the draught above the fuel-bed 25.
  • the gas distributing chamber 23 is connected to the gas receiving chamber 35 and this suction is of the same magnitude as that existing above the fuel-bed 25 less the resistance presented by the coal in the inlet shaft 11, the gas ducts 38 and 39, the grate l3 and the fuel-bed on the grate.
  • the shaft 11 In order to minimize this resistance the shaft 11 is made relatively narrow by the coalguide and the gas ducts are short and have a uniform circu lar cross section throughout their length.
  • This mixture has a very low temperature (for example 50 C.) and is continuously evacuated through the gas ducts 38 and 39 to the gas distributing chamber 23 and is then passed up in the direction of the arrow 61 through the channel 32 and the burning fuel-bed on the grate 13 in a very hot region where the mixture is raised to ignition temperature (700 to 800 C.) and is ignited above the hot fuel-bed.
  • ignition temperature 700 to 800 C.
  • the transverse block is made of refractory material of sufficiently low thermal conductivity to maintain a sufficiently high temperature at its lower rear edge 63 to ignite the gases and at the same time to limit the heat conducted from the combustion chamber to the inlet shaft 11 and thereby to limit premature necessityication of the coal in the shaft.
  • the airflow through the air inlet chamber 22 may be regulated in accordance with the speed of the coal feed.
  • the airflow may be controlled by a damper while with a forced or induced draught the driving motor for the fan may be under the same control as the motor 49.
  • the furnace may be mounted in a boiler having its front wall located in a position shown by the broken lines 64.
  • the top plate 19 and the side plates 14 will then be made of a refractory material having relatively high thermal conductivity.
  • a feeding device for feeding coal from a gravity supply to its outlet, in which a weir defines a free surface for coal descending under gravity through the device and only the coal in the layer adjacent to this free surface has access to the outlet of the device.
  • FIG. 5 shows a feeding device in the form of a hopper base for feeding coal to the inlet shaft 11 without subjecting the coal in the shaft to the weight of the coal in the hopper above the hopper base.
  • the hopper base shown in FIG. 5 forms the lower end of a vertically extending coal hopper 101 of rectangular section. Normally the coal in the'hopper forms an air seal for the outlet 10 but a detachable cover 102 may be provided if necessary.
  • the rear wall 103 of the hopper is inclined downwardly and forwardly at an angle of not less than 45 to the horizontal.
  • a baffle plate 104 is slidably mounted on the wall 103 and carries a screw-threaded rod 105 extending through a slot in the inclined wall 103. On this rod 105 is screwed a correspondingly internally screw-threaded knob 106 by means of which the baffle plate 104 can be fixed in any desired position.
  • the lower edge 107 of the baffle plate 104 forms a weir for the coal descending from the hopper 101. Since coal has an angle of repose of about 45, the baffle plate edge 107 'determines the position of a coal surface 108 which slopes at about 45 to the horizontal. Coal from the hopper 101 cannot reach the space above and to the left of the surface 108 in the FIG. irrespective of the quantity of coal in the hopper 101.
  • the baffle plate 104 can be moved to a lower position in which its edge 107 is advanced to the position shown at 109 and thereby moves the coal surface to the position shown at 114. in this position, the coal surface at 114 lies to the right of the edge 110 of the outlet 10. Accordingly no coal from the hopper 101 can enter the furnace through the outlet 10.
  • the baffle plate 104 In order to feed coal to the outlet 10, the baffle plate 104 must be moved upwards until its lower edge 107 defines the free surface 108 shown in the F16. Coal from the surface 108 is then able to slide over the edge 110 of the coal outlet 10 until the latter becomes completely filled with coal. As soon as this occurs the lower end of the surface layer of coal will be supported so that no further coal can discharge down the face 108 until the coal level in the outlet 10 drops.
  • an agitator 110 may be employed instead of relying on the free discharge of coal down the face 108.
  • the agitator shown in FIG. 5 consists of a shaft 111 carrying two short wings 112. Conveniently the shaft 111 is connected by a chain and sprocket drive to the shaft 42 of the furnace but may of course be driven in any other appropriate manner.
  • the rotating wings 112 skim the surface layer of the coal and cause it to discharge through the outlet 10.
  • the agitator may be arranged to feed the coal towards the outlet at a slightly greater rate than the rate of consumption in the furnace. Coal will then build up to the position indicated at 118. No further coal can be fed by the agitator until the coal level in the outlet 10 drops.
  • baffle plate 104 downwards a short distance so as to move the coal surface 108 towards the position 114 until the coal is beyond the reach of the wings 112 and the lower end of the coal surface is supported on the bottom wall 119 of the hopper at a position spaced from the edge 110.
  • the force required to move the bafile plate 104 through this short distance is relatively small compared with the force which would be required to drive it fully through the coal into contact with the opposite wall 120.
  • a furnace for burning solid fuels having a gas content comprising: a grate having forward and rearward sections; means including side walls defining a combustion chamber above said grate; a depending fuel inlet shaft having a lower end portion disposed above the forward section of said grate and forming a restricted opening between said fuel inlet shaft and said combustion chamber, said means including a solid transverse plate, said wall being disposed above said plate and defining the upper surface of said restricted opening and said plate closing the lower end of said degassing chamber and defining the lower surface of said restricted opening; and duct means for conveying gas from said degassing chamber and for distributing the gas below said rearward section of said grate.
  • a furnace for burning solid fuels having a gas content comprising: a grate having forward and rearward sections; said grate including .a plurality of substantially horizontally disposed bars, means for imparting reciprocatory motion to said bars; means including side walls defining a combustion chamber above said grate; a depending fuel inlet shaft having a lower end portion disposed above the forward section of said grate and fonning a fuel degauing chamber; means forming a restricted opening between said fuel inlet shaft and said means including a solid transverse plate, said wall being disposed above said plate and defining the upper surface of said restricted opening and said plate closing the lower end of said degassing chamber and defining the lower surface of said restricted opening; and duct means for conveying gas from said degassing chamber and for distributing the gas below said rearward section of said grate.
  • a furnace according to claim 2 wherein the restricted opening is formed by a refractory block extending between the side walls of the furnace to define a substantially constant height for the restricted opening throughout its length between its inlet and outlet.
  • a furnace according to claim 6, wherein the block defining the restricted opening is made of a refractory material of relatively low thermal conductivity while the roof and the side walls of the furnace are formed of material having a relatively high thermal conductivity.
  • a furnace according to claim 2 wherein a reciprocatory pusher at the front edge of the degassing chamber bottom serves to urge the fuel towards the grate.
  • a furnace according to claim 10 wherein the rear edge of the transverse plate forms an abutment for the fuel-bed on the grate as the grate is retracted to its forward end position.
  • adjacent grate bars define primary and secondary through-flow channels defined by lateral abutments on the bars which make sealing contact with corresponding abutments on the adjacent bars, the abutments separating the primary and secondary throughflow channels being located above the front wall of a gas distributing chamber beneath the grate, the primary throughflow channel extending between the said front wall and the rear edge of the bottom of the degassing chamber, and the gas duct opens into the gas distributing chamber.
  • a furnace according to claim 14 wherein the longituv 19.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Solid-Fuel Combustion (AREA)
  • Incineration Of Waste (AREA)
  • Filling Or Emptying Of Bunkers, Hoppers, And Tanks (AREA)
US820486A 1968-05-02 1969-04-30 Furnaces for solid fuel Expired - Lifetime US3587489A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2096068 1968-05-02

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US3587489A true US3587489A (en) 1971-06-28

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US820486A Expired - Lifetime US3587489A (en) 1968-05-02 1969-04-30 Furnaces for solid fuel

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US (1) US3587489A (enrdf_load_stackoverflow)
JP (1) JPS4911091B1 (enrdf_load_stackoverflow)
BE (1) BE732346A (enrdf_load_stackoverflow)
BG (1) BG17645A3 (enrdf_load_stackoverflow)
CS (1) CS169792B2 (enrdf_load_stackoverflow)
DE (1) DE1921881C3 (enrdf_load_stackoverflow)
ES (1) ES366696A1 (enrdf_load_stackoverflow)
FR (1) FR2007642A1 (enrdf_load_stackoverflow)
GB (1) GB1227764A (enrdf_load_stackoverflow)
NL (1) NL6906788A (enrdf_load_stackoverflow)
SE (1) SE356355B (enrdf_load_stackoverflow)
SU (1) SU506328A3 (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4430094A (en) 1981-12-21 1984-02-07 Foster Wheeler Energy Corporation Vapor generating system having a plurality of integrally formed gasifiers extending to one side of an upright wall of the generator
US8961626B1 (en) * 2006-01-25 2015-02-24 Randall J. Thiessen Rotating and movable bed gasifier
US10501696B2 (en) 2014-10-23 2019-12-10 Randall J. Thiessen Rotating and movable bed gasifier producing high carbon char
CN112143509A (zh) * 2020-09-11 2020-12-29 谷建兴 一种煤炭焦化处理方法

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IE49855B1 (en) 1979-08-10 1985-12-25 Ekman C O A Process and furnace for burning solid fuel
RU2175421C1 (ru) * 2000-11-09 2001-10-27 Аристархов Дмитрий Викторович Топочное устройство

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4430094A (en) 1981-12-21 1984-02-07 Foster Wheeler Energy Corporation Vapor generating system having a plurality of integrally formed gasifiers extending to one side of an upright wall of the generator
US8961626B1 (en) * 2006-01-25 2015-02-24 Randall J. Thiessen Rotating and movable bed gasifier
US10501696B2 (en) 2014-10-23 2019-12-10 Randall J. Thiessen Rotating and movable bed gasifier producing high carbon char
US11111447B2 (en) 2014-10-23 2021-09-07 Randall J. Thiessen Rotating and movable bed gasifier producing high carbon char
CN112143509A (zh) * 2020-09-11 2020-12-29 谷建兴 一种煤炭焦化处理方法
CN112143509B (zh) * 2020-09-11 2021-05-28 内蒙古汉生源科技有限公司 一种煤炭焦化处理方法

Also Published As

Publication number Publication date
DE1921881A1 (de) 1969-11-27
FR2007642A1 (enrdf_load_stackoverflow) 1970-01-09
CS169792B2 (enrdf_load_stackoverflow) 1976-07-29
BG17645A3 (bg) 1973-11-10
ES366696A1 (es) 1971-03-16
DE1921881C3 (de) 1978-08-10
JPS4911091B1 (enrdf_load_stackoverflow) 1974-03-14
DE1921881B2 (de) 1977-12-08
GB1227764A (enrdf_load_stackoverflow) 1971-04-07
NL6906788A (enrdf_load_stackoverflow) 1969-11-04
BE732346A (enrdf_load_stackoverflow) 1969-10-01
SU506328A3 (ru) 1976-03-05
SE356355B (enrdf_load_stackoverflow) 1973-05-21

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