Patent Application
20110155027
This invention relates to an apparatus for transporting particulate material from a hopper along a transportation duct including an auger flight to a discharge duct arranged at right angles to the transportation duct with a discharge opening at a remote end of the discharge duct.
Such apparatus is particularly but not exclusively designed for use in a burner for particulate fuel, such as coal or pellets, in which the discharge duct extends vertically upwardly from the transportation duct thus releasing the particulate material from an upper open end of the discharge duct for combustion within a combustion chamber.
In U.S. Pat. No. 5,823,123 (Waldner) issued Oct. 20, 1998 is disclosed a combustion system for particulate fuel including a combustion chamber with an opening at the base of the combustion chamber and a vertical discharge duct pushing the particulate fuel through the opening. There is provided a hopper spaced from the combustion chamber and a transportation duct for carrying the particulate fuel from hopper to the discharge duct.
The system is particularly designed for burning coal in particulate form but can also take any other solid particulate fuel such as pellets formed from wood or other materials including straw. The particulate material is generally provided in larger chunks which are more affective for combustion due to the larger spaces necessary between the chunks into which the air can flow more readily.
In the transportation duct there is provided an auger shaft with a first long auger flight rotated to carry the material from the hopper to the discharge duct. A second shorter flight is arranged in a short tube portion on a side of the discharge duct opposite to the hopper and is rotated in the direction to feed the material back toward the discharge duct. The two flight portions cooperate in pushing the material into the vertical discharge duct as the shaft of the flight is rotated.
Apparatus of this general type is well known and includes a stoker generally of the above type in which a hopper discharges downwardly into the transportation duct with the auger flight arranged for transporting the particulate material along the transportation duct to the vertically upwardly extending discharge duct which extends into the combustion chamber of the furnace.
This arrangement has had some disadvantages and difficulties in properly feeding the particulate fuel through the discharge duct into the furnace. Blockages can occur in the horizontal section of the auger tube and this problem has been ongoing for many years with no solution having been made available despite the knowledge in the industry that such blockages can occur due to the nature of the particular material to be transported.
It is one object of the present invention to provide an improved apparatus for transporting such particulate material for movement to the discharge opening.
According to one aspect of the invention there is provided a combustion apparatus comprising:
a combustion chamber;
a transportation duct for transporting a particulate fuel material to the combustion chamber including a substantially horizontal transportation tube having a first feed end and a second end;
a hopper for discharging into the transportation tube at said first feed end for transportation therealong;
an auger mounted in the transportation tube for transporting the particulate material therealong including a shaft extending along the transportation tube and a flight mounted on the shaft for rotation therewith arranged such that rotation of the shaft tends to move the particulate material toward the combustion chamber;
the tube having therein at least one abutment member fixedly mounted on an inside surface of the tube and extending longitudinally of the tube with an inside surface of the abutment member located inwardly of the inside surface of the tube and with the flight having an outside edge at or inwardly of the inside surface of the abutment member.
Preferably the abutment member extends axially of the tube, although it may be helical with a helix angle much smaller than that of the flight.
Preferably there is provided a plurality of abutment members at angularly spaced positions around the tube.
Preferably there are two bottom abutment members adjacent a bottom of the tube with each located on a respective side of a bottom center line of the tube.
Preferably the outer edge of the flight rests on the inside surface of the two abutment members so as to be supported spaced from the inside surface of the tube.
Preferably there is at least one additional abutment member at a position spaced angularly from the two bottom abutment members. This may be located at a position spaced angularly from the two bottom abutment members and located at a position spaced angularly from the top center line of the tube. Preferably this is located at a position spaced angularly from the top center line of the tube toward the side of the top center line which side is angularly advanced relative to the direction of rotation of the flight in the tube.
For simplicity of construction there may be only a single additional abutment member and the location of this to the advanced side of the top center line ensures that it is located in the area of the tube which is filled with the particulate material to be transported. However there may be more.
Preferably the abutment member comprises an elongate bar having a width in the angular direction of the tube which is greater than a height in a radial direction of the tube. That is the bar is preferably a simple flat bar. However other constructions are also possible to provide the abutment or stop projecting inwardly from the inside surface of the tube outside the flight edge. For example the bar could be a round bar or rod or a different flat bar of different dimensions. Typically the auger tube is 6 inches with a 5 inch flight but the tube may be a smaller or a larger diameter pipe. The bar is easily attached using welding but other similar elements can be welded or bolted into the pipe.
Preferably the abutment member extends substantially along the full length of the tube from the hopper to the combustion chamber. However the length may be shorter provided it acts to restrict the rotation of the material sufficiently to prevent or inhibit the blockage.
Preferably the radius of the outside edge of the flight is smaller than the distance of the inside surface of the abutment member from the axis of the tube.
Preferably there is provided a substantially vertical discharge tube having a bottom end attached to the transportation tube and a top end communicating with the combustion chamber for feeding the particulate fuel material from the transportation tube upwardly into the combustion chamber.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:
In the drawings like characters of reference indicate corresponding parts in the different figures.
Reference is made to the above patent of Waldner from which some of the drawings are taken and modified to show the arrangement of the present invention.
An apparatus for burning coal is shown in the figure and comprises a hopper 10 containing a particulate fuel 11 which is, for example, coal in the form of chunks as opposed to a very fine particulate of dust form. The apparatus further includes a combustion chamber 12 in which the coal is burnt. The shape and arrangement of the combustion chamber is shown only schematically since this is well known to one skilled In the art and commercial arrangements are available for purchase from the present assignees.
The combustion chamber 12 is fed from below through a circular discharge opening 13 so the material moves vertically upwardly through a discharge duct 14 to the upper mouth of the duct forming the discharge opening and onto a support surface 15 on which the combustion occurs.
The particulate fuel is transported from the hopper to the discharge duct 14 through a transportation duct 16. The transportation duct 16 comprises a horizontal tube 17 having an opening 18 connected to a base of the hopper 10. The tube extends beyond the hopper to an end flange 19 to which is attached a motor M for driving an auger shaft 20 which extends along the full length of the tube 17 and carries an auger flight 21. The auger flight 21 extends from a feed end 21A underlying the hopper to a discharge end 21B at the discharge duct 14.
In general, therefore, the motor is arranged to drive the shaft in a direction D which is counter-clockwise as shown in
The tube 17 is arranged so that It extends beyond the discharge duct 14 to an end portion 17a which is relatively short but provides an open portion of the tube from the adjacent edge of the discharge duct 14 to an end plate 23 carrying bearing 24 for the end of the shaft 20. Within the end portion 17A of the tube 17 is provided a second flight section 25 which is carried on the shaft 20 for rotation there with and provides at least one turn of the flight. The flight 25 is arranged relative to the direction of rotation of the shaft so as to tend to feed material from the end plate 23 toward the discharge duct 14. Each of the flights 21 and 25 terminates at an edge of the flight which is vertical and is substantially axially aligned with those portions of the duct 14 which lie on a vertical central plane of the tube 17.
The discharge duct 14 is of course a short length of tube which is shaped at its lower end to extend over the top surface of the tube 17 so the lower edge of the tube 14 follows the cylindrical surface of the tube 17. A hole is cut in the tube 17 which matches the contact of the lower edge of the tube 14 with the tube 17 and the tube 14 is then welded at its lower edge to the edge of the opening indicated at 17B. The end edges of the flights 21 and 25 which are indicated 21B and 25A respectively. These terminate at positions aligned at the edges of the duct 14 so that underneath the duct 14 there is no flight portion and the shaft is therefore exposed. In order to assist in causing movement in the material between the two flight portions underneath the duct 14, the shaft carries a plurality of projections which are conveniently a plurality of rods parallel to the shaft and welded to the shaft at angularly spaced position there around. There are preferably three such rods 20A which are thus carried with the shaft as it rotates and thus impact on the particular material sitting on the shaft or around the shaft.
The flight 21 operates as previously described to carry the particulate fuel from the hopper to the discharge duct 14 however at the discharge duct the particulate material sits in effect in a pool underneath the discharge duct and tends to spread into the portion 17A of the tube 17. When the shaft is rotated the flight portions tend to sweep the pool of the particulate material toward the open lower end of the discharge duct and to push the material into the discharge duct for movement upwardly within the discharge duct. This double pushing action from the two flight portions provides an effective movement of the material In the discharge duct so that it is carried upwardly without the necessity for additional lifting elements actually in the discharge ducts. The projections on the shaft in the area underneath the discharge duct tend to vibrate or move the particulate material to prevent jamming and to assist in this upward pushing movement. In this way the particulate material is effectively moved upwardly the discharge duct to the mouth 13 without jamming or crushing the particulate material thus allowing the chunks to remain effectively intact.
The above described arrangement is shown in the above Waldner patent. The present invention provides an improvement for effecting transfer of the particulate fuel along the transportation tube 17.
As shown in the Figures, the auger 20 is mounted in the transportation tube 17 for transporting the particulate material therealong including the shaft 20 extending along the transportation tube and the flight 21 mounted on the shaft for rotation therewith in the counter clockwise direction D such that rotation of the shaft tends to move the particulate material toward the combustion chamber.
The tube has therein three abutment members 30, 31 and 32 fixedly mounted on an inside surface 17A of the tube and extending longitudinally of the tube 17 with an inside surface 33 of the abutment members located inwardly of the inside surface 17A of the tube and with the flight 21 having an outside edge 34 in contact with or spaced inwardly of the inside surface 33 of the abutment members 30, 31 and 32.
Each of the abutment members 30, 31 and 32 extends directly along the tube in the axial direction that is axially of the axis A of the tube 17. The abutment members are arranged at angularly spaced positions around the axis A of the tube so that for example the abutment member 30 is located at the 5-oclock position, the abutment member 31 is located at the 7-oclock position and the abutment member 32 is located at the 2-oclock position.
Thus there are two bottom abutment members 30 and 31 adjacent a bottom of the tube with each located on a respective side of a bottom center line CB of the tube. As the shaft 20 tends to sag under the weight of the flight, the outer edge 34 of the flight rests on the inside surface 33 of the two abutment members 30 and 31 so as to be supported spaced from the inside surface 17A of the tube 17. The abutment member 32 provides a single additional abutment member at a position spaced angularly from the two bottom abutment members 30 and 31 and located at a position spaced angularly from the top center line CT of the tube 17. As the abutment member 32 is located at the 2-oclock position it is located on a side of the center line CT which is angularly advanced relative to the direction of rotation of the flight in the tube. The tube 17 in use tends to be filled with the material in the area from the 12-oclock position to approximately the 7-oclock position as the rotation in the counter clockwise direction tends to carry the material around the tube away from the top toward the 7-oclock position. Thus the positioning of the abutment members in this area ensures that they engage into the material in the filled zone with the tendency to prevent that material from rotating around the tube at least in the area adjacent the inside surface 17A. This acts to prevent the whole body of the material in the tube from rotating with the flight which would halt longitudinal movement of the material since the required longitudinal movement is obtained by the relative movement between the flight and the material.
The abutment members can be formed of any suitable construction which allows easy attachment to the tube while locating the inside surface of the abutment member outwardly to the edge of the flight. However the abutment member preferably is simply formed from an elongate flat bar or strap of metal which is welded to the inside surface 17A. The bar has a width W in the angular direction of the tube which is greater than a height T in a radial direction of the tube. For example the bar maybe of 1 inch width and ΒΌ inch high.
The abutment members extend substantially along the full length of the tube from the hopper to the combustion chamber, that is from end 30A at or adjacent the hopper to end 30B at or adjacent the combustion chamber.
The radius of the outside edge 34 of the flight 21 is smaller than the distance of the inside surface 33 of the abutment members from the axis A of the tube so that the outside surface 34 tends to sit on the inside surface of the bottom member 30 and 31 and thus to be spaced slightly from the member 32.
Surprisingly this simple solution using simply the three bars or straps 30, 31 and 32 has provided a solution to a very long standing problem of blocking of the movement of the particulate material in the tube 17. This solution has been found only after long and extensive trials which determined initially the behaviour of the material in the tube and secondly the reason for the blockages which have plagued the system for many years.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.
