US3358625A

US3358625A - Moist fuel furnace

Info

Publication number: US3358625A
Application number: US498918A
Authority: US
Inventors: Robert W Jones
Original assignee: BIGELOW LIPTAK CORP
Current assignee: BIGELOW LIPTAK CORP
Priority date: 1965-10-20
Filing date: 1965-10-20
Publication date: 1967-12-19
Anticipated expiration: 1984-12-19

Description

Dec. 19, 1967 R. w. JONES 3,

MOIST FUEL FURNACE Filed 001:. 20, 1965 4 Sheets-Sheet 1 I NVENTOR.

dF/VE/sf Dec. 19, 1967 R. w. JONES MOIST FUEL FURNACE 4 Sheets-Sheet 2 Filed Oct. 20, 1965 INVENTOR. /%Z=rz J? 716.5

4 SheetsSheet 4 #1 9/; li-l 11 I j INVENTOR.

5T mvz/r.

R. W. JONES MOIST FUEL FURNACE Dec. 19, 1967 Filed Oct. 20, 1965 United States Patent 3,358,625 MOIST FUEL FURNACE Robert W. Jones, Birmingham, Mich, assignor to Bagelow-Liptak Corporation, Detroit, Mich., a corporation of Michigan Filed Oct. 20, 1965, Ser. No. 498,918 13 Claims. (Cl. 110-101) This invention relates generally to industrial type furnaces, and more particularly relates to an automatic fuel feeding system for use in moist fuel burning furnace, such as bagasse furnaces.

In sugar mills it is convenient and economical to use bagasse as a fuel to heat the steam boilers instead of other known fuels such as oil. While automatic boiler firing control is readily available with conventional fuels such as oil, it has not been fully available with moist fibrous fuels such as bagasse. In bagasse burning furnaces it has been possible to automatically regulate the boiler outlet damper to maintain a constant furnace draft and the flow of combustion air to the furnace in accordance with steam demand, but no automatic means has been available to properly regulate the height of the fuel pile, i.e., the feeding of the fuel.

Therefore, it is the basic object of this invention to provide a control means to automatically regulate the height of the fuel pile in a moist fuel furnace, such as a bagasse furnace, and thereby, in conjunction with automatic regulation of the boiler outlet damper and flow of combustion air, enable the same degree of automatic control to be obtained with boilers fired by bagasse as those fired by fuel oil or other fuels.

Being wet, a moist fuel such as bagasse is on the border line between being combustible and non-combustible. The size, shape, and location of the fuel pile are important factors in this connection and in determining the efiiciency with which the fuel burns. In fact, if the bagasse pile is too high it may topple over and cut off combustion air so that the fire is extinguished. On the other hand, it is desirable to have the pile as high as possible while still self-sustaining. These factors relate solely to the peculiar nature of the fuel and, accordingly, it is an object of this invention to provide a means for automatically regulating the feeding of the moist fuel (e.g., begasse) which is responsive to the height of the fuel pile and is independent of extrinsic factors such as combustion air, furnace draft, or steam flow or demand. By means of such feed regulation optimum burning of the moist fuel is achieved automatically.

There are, of course, many bagasse furnaces now in operation and, accordingly, it is an object of the invention to provide a fuel feed control system that may be readily incorporated into existing furnace installations.

Existing bagasse furnace installations employ a feed chute for each cell and, ordinarily, a battery of chutes are fed bagasse by a conveyor or bagasse carrier system. Bagasse flow through each chute is controlled by a gate structure which is moved manually by a handwheel acting through shafts, bevel gears, pinions, and racks secured to the each slidable half of the gate. In accordance with the present invention, it is preferred to attach a reversible drive motor to the gate operating structure and to control the opertaion of the motor by means of a suitable device that senses the height of the fuel pile in the cell. When the pile reaches the desired maximum height the gate opening is decreased, and when the pile reaches the desired minimum height the gate opening is increased, thus adjusting the flow of bagasse to the cell to maintain the height of the pile within a desired range. The gate is pref erably at least partly open at all times so that there is continuous flow to the cell.

"ice

Other features and objects of this invention will become apparent hereinafter in connection with the description of the accompanying drawings in which:

FIGURE 1 is a vertical section through one cell of a moist fuel burning furnace particularly illustrating the relationship of the feed chute with the fuel pile and also the relationship of one form of fuel level indicating device with respect to the fuel pile;

FIGURE 2 is another vertical section through a portion of a bagasse furnace partially illustrating two combustion cells of a three or more cell furnace and particularly illustrating the positioning of the fuel level indicating devices for an end cell and an intermediate cell;

FIGURE 3 is a representative schematic illustration in front elevation of the operating mechanism for the fuel feed gate control illustrating both the manual and automatic features of the control apparatus;

FIGURE 3A is an enlarged representative schematic illustration in plan view of a fuel gate operator drive train and limit switch arrangement which may be utilized in the control apparatus of FIGURE 3;

FIGURE 4 is a side view illustrating the details of a mechanical fuel pile level indicating device and the mounting features thereof, which device may be of the type described in greater detail in U.S. Patent No. 2,851,553;

FIGURE 5 is a schematic diagram of control circuitry utilized in conjunction with the fuel indicating device; and

FIGURE 6 is a schematic diagram illustrating the cir- 'cuitry for providing electrical energy to a magnetic clutch and to the fuel level indicating device.

Referring to the drawings and first to FIGS. 1-3, there .isillustrated a portion of a moist fuel burning furnace 10 having a horseshoe shaped combustion cell 11, such as is well known for the burning of bagasse. Generally the furnace comprises a plurality of combustion cells 11, one being shown in FIG. 1 and two in FIG. 2, which may be constructed of a slab hearth 12 and a tile wall construction 14. The wall 14 may be constructed of a series of horizontal courses formed from individual blocks of tile 16 which rest upon a lower course of air passage forming cast iron members 18 and follow the construction and details described in U.S. Patent 2,694,370 issued Nov. 16, 1964. Fuel for the furnace is fed by means of an inclined fuel chute 20 which is suitably positioned and angled as to provide the proper height and discharge angle for the fuel as it leaves the end of the chute, thereby building up the proper size and shape of the fuel pile 25 on the cell floor 12. Air for combustion of the fuel is provided by passageways within the wall 14 of the cell and is forced therethrough by means of blowers. The gaseous products resulting from the burning of the bagasse rises through the throat 22 and passes over the boiler tubes (not shown) to be heated. As is seen in FIGURE 1, the furnace may be of the well known Ward constricted neck design, as is commonly used in applications of this type. Each cell is provided with a suitable access door 24 to permit entry into the cell.

The size and shape of the fuel pile 25 is sensed by indicator means 28, 30, and 30' which extend into the cell in accordance with the particular position of the fuel chute 20 with respect to the hearth 12. The indicators illustrated in FIGS. l-4 are of the type shown a? of the pile is directly related to its width each device is responsive to and capable of providing signals to indicate the height of the pile 25. Preferably, the impeller 32 engages the side of pile on about the centerline of the pile and at about /3 of its minimum desired height along the inclined axis extending at an angle as indicated in the drawings. While two

indicators

28 and 30 are shown in the end cell 11 of FIGS. 1 and 2 only one of them is actually used and this is preferably device 30 which extends through the sidewall 14 rather than the indicator 28 which extends through the door 24. In this left cell of FIG. 2, the sidewalls are not available for mounting of the indicator 30' and it may therefore be mounted in the front wall of the cell, as shown, rather than the door 24.

The

indicator devices

28, 30, and 30' are of the type that open and close a switch with the rotating and stopping of the impellers 32 due to resistance of the pile 25. However, broadly, other types of signalling device may be utilized in the practice of the invention to indicate the sizeof the fuel pile 25. For example, an optical system may be used wherein a beam of light is allowed to shine on a receiving device or is cut off from the receiver, depending on the size and shape of the pile, thereby producing a control signal which is indicative of the condition of the fuel pile.

As indicated in FIGURE 3, electrical energy from a suitable source is supplied to the indicating device. 30 through a control panel and motor starter 48 by means of a cable 46. The control signal generated. by the indicator 30 (as well as electrical energy) is fed' from the control panel 48 through a cable 52 to a fuel gate operator mechanism 49 which may be suitably connected to the conventional rack, pinion, and bevel gear structure 49A that is used to open and close the gate. means 56 for the chute 20..

The fuel gate operator mechanism 42 has an output shaft 63 that is connected by means, of the chain and sprocket 55 to an operating shaft 58, such as the, pinion shaft of the fuel gate operating structure 49A. Rotation. of shaft 63 in one direction will increase the gate opening and rotation in the opposite directionwill, decrease the opening thereby providing means for controlling the rate of bagasse flow through the chute 20. Bagasse is fedto the mouth of each chute 20 over th gate means 56 by means of a conventional bagasse carrier or conveyor 62.

The fuel gate operating mchanism 49 includes a. reversible motor 50 which is connected-througha magnetic clutch 67 to theoutput shaft 63. By deenergizing the clutch 67 the motor is disconnected from the gear structure 49A which may then be manually operated by means of the chain fall 66 which rotates sprocket 68 that is afiixed to the shaft 58. Thus, the gate- 56 can be manually operated or its position can be set asdesired at the time automatic operation commences.

As shown schematically in FIGURE 3A, the gate drive system 49 includes the reversible motor 50 which is adapted to provide forward and reverse power to its shaft 69 which is connected to a speed reducer 65 .which in turn, is connected by shaft 70 to the. magnetic clutch 67. The shaft 63 isdriven by the clutch 67. The drive system includes a pair of

rotary limit switches

71 and 73 to control the length of stroke of the gate movement and the location of theextreme open and closed positions, respectively, of the gate means 56. These switches therefore provide a simulated modulated control of the fuel flow, it being noted that it is desirable that at all times the gate means be at least partially open for fuel passage.

The rotary limit switch 71 has a shaft 77 that is rotated:by the gear reducer shaft 70 through sprockets 75 and 79 and interconnecting chain 88. The limits of switch 71 are set to a predetermined number of revolutions of the shaft and through suitable electrical circuitry controlthe number. of revolutions of

shafts

70 and 63 and the length of stroke of the gate means 56, i.e., the extent of its opening and closing movement.

The second rotary limit switch 73 has a shaft 8 that is rotated by output shaft 63 through sprockets and 39 which are connected together by means of a chain 88. The limit switch 73 is initally settodetermine the location of extreme open or closed position of the gate 56, i.e., the indexed position of the gate opening. This can be adjusted manually by the furnace operator from the floor by means of chain 66. When the magnetic clutch 67 is deenergized rotation of shaft 58 by means of the chain 66will rotate shaft 63 and therefore limit switch shaft 87 to reset the switch. Thus, the operator changes the extreme open or closed position of the gate opening but the length of the stroke of the gate remains fixed by the number of revolutions of shaft 70 as determined by switch 71. The actual location of the gate opening with respect to the larger cross sectional area of the chute 29 can affect the flow of bagasse from the conveyor 62 into the chute, and the switch 73, as just described, enables this to be adjusted at any time in accordance with fuel conditions.

FIGURE 4 illustrates on larger scale one form of indicator device 30 referred to above. Additional details are disclosed in US. Patent 2,851,553 and the device is available on the open market. The indicator has. a rotary impeller 32 which is rotated by a motor in housing 36 and, continues to rotate until the fuel pile has covered the impeller by a predetermined amount, depending on the characteristics of the fuel, whereupon the resistance becomes too great and rotation stops. Inside housing 36 there is a switch means responsive to torque on the floating housing of a synchronous motor driving the impeller so that this, or rotation and stoppage of the impeller, is used to operate the switch means and generate a mechanical signal indicative of the height of the pile.

The tube portion 40 of the indicator 30 serves as a housing for shaft 74 and threads on an extension 82 of the housing 36 of the motor and signal producing means. A hearing pin 84 may be provided at one end of the tube 40 to provide a bearing surface for the shaft 74 thereby concentrically positioning the two parts. A mounting sleeve 86 is selectively, slidably mounted on the xterior surface of the tube. 40 and is fixed thereto in a desired position by means of a set screw 88, the screw 88 being adapted to engage anyone of several longitudinally spaced indented portions (not shown) provided on the tube 40. The sleeve 86 is provided with an angled mounting plate 90 which provides a mounting flange for attachment of the indicator 30 on the wall of the furnace. Suitable holes (not shown) may be provided in the mounting plate 90 for receiving bolts therethrough for fastening the plate to the wall of the furnace. By shifting the position of the sleeve 86 on the tube 40 the immersion depth of the impeller 32 can be adjusted until it extends into the furnace and bagasse pile 25 to a depth that causes it to stop rotating when the desired maximum pile height is obtained and resume full rotation when the desired minimum height is reached. The signal producing means in housing 36 comprises any device which will produce a first signalin response to the rotating of the impeller and a second signal in response. to the stoppage of the impeller (or predetermined maximum and minimum speeds of rotation of the impeller). The signals may take any form, and, for example, may be a digital or analogue signal or the presence or absence of a voltage or current, etc. Such a device may be a motor enclosed in a resiliently mounted housing whereby 0 the normal rotation of the impeller closes a first set of contacts and the stoppage of the impeller closes a second set of contacts. This second closing may be due to the angular movement of the motor housing with respect to the outer casing 36 of the signal means against the bias of a spring connected therebetween. As an alternative, the switching mechanism may comprise a flyball type switch assembly mounted on the motor shaft wherein a first switch is closed by the governor when the shaft is stopped and a second switch is closed when the shaft is rotating. Reference is made to US. Patent 2,851,553 for a suitable motor and signal producer for impeller 32.

Referring now to FIGS. 5 and 6, there is illustrated a schematic diagram of a suitable circuit interconnecting the parts of the fuel control system described above and forming the control panel 48. The reversible motor 50 is supplied with three-phase alternating current by means of

conductors

192, 104, and 166 which is fed through a set of

contactors

108, 110, and 112 and

conductors

114, 116 and 118 to the motor. The reversing function is performed by a second set of

conductors

120, 122 and 124 and a second set of

contactors

126, 128, 130 which reverses two of the phases with respect to the third phase thereby reversing the rotation of the motor when the second set of conductors is energized. The control circuitry for the two sets of contactors is connected across conductors 104 and 1&6 and generally comprises a switching mechanism 134 which is contained within the signal producing means in housing 36, the limit switch 73, the limit switch 71, and the coils for the two sets of motor starting contactors 138. Also a normally open start-stop contactor 149 is provided to control the manual or automatic operation of the system. When contactor 140 is opened, the automatic portion of the system is disabled thereby allowing the manual operation of the gate means 56.

The signal producing means in housing 36 contains the switch 134 which has an armature or blade 142 movable between a pair of

terminals

144 and 146. When the impeller is rotating the blade 142 is in contact with terminal 144 and when it has been stopped the blade 142 is in contact with terminal 146. Terminal 144 is connected to a contactor 148 by means of conductor 147, contactor 148 being part of rotary limit switch 71 which is set to a predetermined number of revolutions of shaft 70 to determine the length of the travel or stroke of the gate opening movement. A relay coil 150 is also connected in series circuit with the limit switches 71 and 73 including a contactor 151 by means of conductors 152 thereby energizing the coil 1513 at such time as the switch 142 is in contact with terminal 144 and the feed gate is in closed position thereby closing

contacts

148 and 151. A coil 1:56 and a pair of contactors 158 and 159 are connected in series circuit between the terminal 146 at one end thereof and the contacts 140 at the other end and in parallel circuit to

contacts

148 and 151 and coil 15%.

The contactors 158 and 159 provide a limit switch function limiting the closing movement of the feed gate so that it is open at least a minimum amount to feed a small portion of fuel to the furnace at all times, preferably about 15% of the rate at which the fuel is burned. The coil 150 is operatively associated with

contactors

108, 110 and 112 to close these contacts when actuated, thereby energizing the reversible motor in a first direction to open the feed gate. Similarly, coil 156 is operatively associated with

contactors

126, 128 and 130 to reverse the operation of the motor 1019 thereby moving feed gate 56 toward closed position reducing the flow of fuel to the cell to the desired minimum rate, (e.g., the 15% referred to above).

In operation, and assuming that the fuel gate is open and fuel is being fed by gravity from chute 20 into the combustion cell of the furnace, the contacts 148 are open and the switch blade 142 is in contact with terminal 144 due to the fact that the shaft of the signal means 36 is rotating. When sufiicient fuel has been fed to the furnace, the impeller 32 will be stopped and the switch 134 will shift to the position wherein blade 142 is in contact with terminal 146. Thus, the coil 156 will 6 be energized thereby closing the contacts 126, 128, to reverse the operation of the motor and reduce the fuel gate opening. When the fuel gate has closed sufliciently to activate the limit switch 71 (or 73 if it is set for extreme closing) and open either of selected contactors 158, 159, the motor 51) will then be stopped.

As the fuel is being burned down, the fuel pile will recede from the blades of the impeller section 32, and at such time as the fuel resistance is reduced sufliciently the impeller will resume rotation. With the gate 56 in the near closed position, the

contacts

148, 151 will be closed, the switch blade 142 will be in contact with terminal 144, and the coil 15% will be energized thereby closing

contacts

108, 110 and 112, With these latter contacts closed, the motor 160 will again reverse and open the feed gate until such time as the limit switch 71 (or 73 if it is set for extreme opening) is activated to open

contacts

148 or 151. This cycling is repeated during the entire combustion of the fuel pile. When it is desired to deenergize the system, contacts are opened and the control portion of the system will be deenergized.

Referring to FIG. 6, there is illustrated a schematic diagram of a system for feeding electrical energy to the magnetic clutch of the motor and also the windings or other devices within the indicator 30. The indicator could be driven by a synchronous motor type, the hysteresis motor type, or any other suitable means for providing the switching function as described. In most of these switching arrangements, a source of electrical energy is required and thus a source 166 of alternating current energy is connected to the active portion 162 of the signal means in housing 36 by means of a pair of

conductors

164, 166 and 168, 170. As was described above, the motor 50 illustrated in FIG. 3A, is provided with a magnetic clutch 67 to couple and decouple the motor from the operating mechanism 49 and the feed gate 56, and this clutch 67 is also fed from the source 160 through

conductors

164, 166 and a pair of

contactors

174 and 176. The contactors 174 are magnetically connected to the coil and the contactors 176 are magnetically connected to the coil 156, Thus, the magnetic clutch is energized whenever the motor 50 is energized in either direction, thereby coupling the motor to the feed gate. As an alternative arrangement, the

contactors

174, 176 may be combined into a single contact in the control panel 48, and thus the magnetic clutch will be continuously energized as long as the automatic system is being used. However, if it is decided to resort to manual operation, the single contact may be opened.

While the above invention has been described with an electromechanical indicating means 30, it is to be understood that other suitable types of signal producing indicating means may be utilized. One such indicating means is a modulated type beam indicator in the walls of the furnace to provide a beam of light which will be broken by the fuel pile when it has reached the prescribed size. In this latter case the transmitter portion of the optical system comprises a projector with two focusing lenses, a light source, and a motor driven aperture disc; and the receiver comprises a pair of lenses, a photocell, an amplifier and control output relays. The beam indicator employs a modulated signal beam which is unaffected by extraneous light, falling particles, flame or smoke. The two signal beams are stacked, one on top of the other, in each of the projector and receiver. By successive interruption of the top beam and clearing of the bottom beam, a control signal is provided to regulate the control system and thus the fuel gate operator in a manner similar to that described in conjunction with electromechanical system above.

It will now be seen that the invention provides an automatic bagasse or moist fuel feed system in which the bagasse is continuously fed by gravity to the cell at a minimum rate which is below the rate of fuel consumption and at a maximum rate which is greater than the rate of fuel consumption, the rate of flow being controlled by an indicator means 30 which is sensitive directly or indirectly only to the height of the fuel pile. The indicator means is set to maintain the height of the bagasse pile between levels that provide optimum combustion of the fuel.

While it will be apparent that the embodiment of the invention herein disclosed fulfills the objects of the invention, it will be appreciated that the invention is susceptible t-o modification without departing from its spirit and scope.

I claim:

1. The method of supplying fuel to the hearth of a moist fuel combustion cell which comprises feeding'moist fuel continuously through a partially open gate to a gravity feed chute which deposits the fuel in a pile on the hearth, sensing the height and location of portions of the sides of the pile of fuel with a signal producing means and using the signal to open said gate wider when the height falls to apredetermined minimum, and sensing the height of the pile with a signal producing means and using the signal to at least partially close the gate when the height of the pile reaches a predetermined maximum.

2. The method of supplying fuel to the hearth of a moist fuel combustion cell which comprisesfeedingmoist fuel through a movable gate controlled opening to a gravity feed chute which deposits the fuel in a pile on'the hearth, sensing the height and location of portions of the sides of the fuel pile with a signal producing means and usingthe signals produced by said means to control the position of the movable gate and the size of the gate controlled opening and therefore the rate of fuel supply to the chute.

3. A moist fuel burning furnace having a hearth for supporting a fuel pile, a chute for supplying the fuel to the hearth in a pile, a fuel gate for controlling the flow of fuel to the chute, and a fuel feeding control system comprising signal producing indicating means for sensing the size and location of portions of the sides of the fuel pile, said indicating means producing a signal having a characteristic in accordance with the size of the pile, means operatively connected to the fuel gate and responsive to the signal of said indicating means for controlling the operation of the fuel gate, and control means energizing said fuel gate operating means in accordance with said signal characteristic.

4. A moist fuel burning furnace having a hearth for supporting a fuel pile, a chute for supplying the fuel to the hearth in a pile, a fuel gate for controlling the fiow of fuel to the chute, and a fuel feeding control system comprising signal producing indicating rneanis for sensing the height and location of portions of the sides of the fuel pile, said indicating means producing a signal having a characteristic in accordance with the height of said pile, a reversible motor operatively connected to the fuel gate to move the gate and responsive to the signal of said indicating means, and control means energizing said motor in one or the other direction in accordance With said signal characteristic.

5. A moist fuel burning furnace having a hearth for supporting a fuel pile, a chute for supplying the fuel to the hearth in a pile, a fuel gate for controlling the flow of fuel to the chute, and a fuel feeding control system comprising signal producing indicating means for sensing the size of the fuel pile, said indicating means having a reversing switch for producing a signal having a characteristic in accordance with the size of said pile, a reversible motor operatively connected to the fuel gate and responsive to the signal of said indicating means, and control means including a first coil and a first set of contactors for energizing said motor in a forward direction and a second coil and a second set of contactors for energizing said motor in a reverse direction, said coils being selectively energized in accordance with said signal characteristic, said control means including disconnect means for disabling said control means for providing manual operation of said fuel gate.

6. The invention of claim 5 wherein said disconnectmeans includes a magnetic clutch operatively associated with said first and second coil for interconnecting said motor and said fuel gate.

7. The invention of claim 5 wherein said indicating means includes an impeller to be embedded in the fuel pile, and motor driving said impeller and having a floating housing and said reversing switch being selectively operated between two positions in accordance with the torque on said housing.

8. A fuel burning furnace having a hearth for supporting a fuel pile, chute means for supplying the fuel to the hearth in a pile, a fuel gate for controlling the flow of fuel to the chute means, and a fuel feeding control system comprising signal producing indicating means for sensing the size of the fuel pile, said indicating means having. a. reversing switch for producing a signal. having a characteristic in accordance with the size of, said pile, a reversible motor operatively connected to the fuel gate and responsive. to the signal v of said indicating, means, control means including a first coil and a first set of contactors for energizing said motor in a forward direction and a second coil and a secondset of .contactors for energizing said motor in a reverse direction, said coils being selectively energized in accordance with said signal characteristic, and limit circuit means for selectively controlling the open and closed positions of the fuel gate including first andsecond switch means connected in circuit controlling relation with said coils for controlling the energization of the coils in accordance with the position of the fuel gate and the length of stroke of the fuel gate.

9. The invention of claim 8 including manually operated remote setting means for adjusting the setting of said first switch means to adjust the indexed position of the fuel gate.

10. A moist fuel burning furnace having a hearth for supporting a fuel pile, a chute for supplying the fuel to the hearth in a pile, a fuel gate for controlling the fiow of fuel to the chute, and a fuel feeding control system comprising signal producing indicating means for sensing the size of the fuel pile, said indicating means having a reversing switch for producing a signal having a characteristic in accordance with the condition of said pile, a reversible motor operatively connected to the fuel gate and responsive to the signal of said indicating means, and control means including a first coil and a first set of contactors for energizing said motor in a forward direction and a second coil and a second set of contactors for energizing said motor in a reverse direction, said coils being selectively energized in accordance with said'signal characteristic, said indicating means including switch means being selectively connected in series circuit with one of said first and second coils in accordance with said signal characteristic.

11. The fuel burning furnace of claim 10 further including a magnetic clutch interconnecting said reversible motor and the fuelgate, means for selectively energizing and deenergizing said magnetic clutch, and manual means connected to the fuel gate for manually controlling the fuel gate when said magnetic clutch is deenergized.

12. The method of supplying bagasse or the like to a combustion cell having a floor during operation of the cell comprising continuously depositing the bagasse in a pile on the floor at a first rate substantially less than the rate of bagasse consumption by combustion in the cell, sensing the height and location of portions of. the sldes of the bagasse pile, and increasing the rate of deposition of bagasse to greater than the rate of fuel consumption when the height of the pile reaches a predetermined minimum and continuing such increased rate until the height reaches a predetermined maximum and then returning to said first rate of deposition.

13. A moist fuel burning furnace having a hearth for supporting a fuel pile, a chute for supplying the fuel to the hearth in a pile, a fuel gate for controlling the flow of fuel to the chute, and a fuel feeding control system comprising signal producing indicating means for sensing the height and location of portions of the sides of the fuel pile, said indicating means producing a signal having a characteristic in accordance with the height of said pile, a reversible motor operatively connected to the fuel gate to move the gate and responsive to the signal of said indicating means, and control means energizing said motor in one or the other direction in accordance with said signal characteristic, indicating means including rotatable impeller which is embeddable in the fuel pile,

10 said signal being one of rotation and non-rotation of the impeller.

References Cited UNITED STATES PATENTS 2,114,619 4/1938 Ward l10-10 X 2,299,727 10/ 1942 Blauvelt et al 1l010l 2,426,347 8/1947 Fulton 110101 X FOREIGN PATENTS 463,003 7/ 1928 Germany. 396,039 7/ 1933 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner.

Claims

5. A MOIST FUEL BURNING FURNACE HAVING A HEARTH FOR SUPPORTING A FUEL PILE, A CHUTE FOR SUPPLYING THE FUEL TO THE HEARTH IN A PILE, A FUEL GATE FOR CONTROLLING THE FLOW OF FUEL TO THE CHUTE, AND A FUEL FEEDING CONTROL SYSTEM COMPRISING SIGNAL PRODUCING INDICATING MEANS FOR SENSING THE SIZE OF THE FUEL PILE, SAID INDICATING MEANS HAVING A REVERSING SWITCH FOR PRODUCING A SIGNAL HAVING A CHARACTERISTIC IN ACCORDANCE WITH THE SIZE OF SAID PILE, A REVERSIBLE MOTOR OPERATIVELY CONNECTED TO THE FUEL GATE AND RESPONSIVE TO THE SIGNAL OF SAID INDICATING MEANS, AND CON-