US2090965A - Pulverized coal burner - Google Patents

Description

Aug. 24, 1937. D. c. RUTH 2,090,965

' PULVERIZED COAL BURNER I Filed May 22, 1933 2 Sheets-Sheet 1 Fl 3 f/vvE/yToFe:

Dav/b C.- FPu 777 Aug. 24, 1937. c, RUTH 2,090,965

PULVERIZED COAL BURNER Filed May 22, 1933 2 Sheets-Sheet 2 VEN TOR Dav/ 0 C Puf/v,

ATT Y Patented Aug. 24, 1937 UNE'EEQ STATES PULVERIZED David 0. Ruth, Denver, 0010.

Application May 22,

1 Claim.

The rapid introduction of gas and oil for fuel for use in the heating of buildings has reduced the demand for coal burning apparatus to such an extent that it has become necessary to develop means for burning coal in a way that makes it unnecessary to resort to the constant handling of the coal in the manner now quite common.

It is an object of the present invention to produce an apparatus for the burning of powdered coal which is so constructed and arranged that its operation is substantially automatic and comparable to the operation of an oil or gas burning device.

The present application is a continuation in part of my co-pending application Ser. No. 536,506, filed May 11, 1931.

Another object of the invention is the provision of a preliminary combustion chamber lined with fire resistant material in which a mixture of pulverulent fuel and air may be ignited and the heating of such lining or a portion thereof relied on to maintain combustion so long as the supply of air and fuel to such combustion chamber continues.

A further object of the invention is the provision in the combustion chamber of a furnace of a relatively small preliminary combustion chamber lined with fire resistant material adapted to be heated to incandescence by the combustion of an initial supply of air and powdered coal ignited automatically under the control of a room tl1ermostat,-such incandescence being relied on to continue the combustion of a continued supply of air and powdered coal after the ignition mechanism has been cut off and until the room thermostat automatically effects the stopping of such supply.

More particularly it is the object'of the present invention to provide a thermostatically controlled heating system in which a room thermostat starts and stops the operation of a motor driving feeding mechanism and a fan to supply a mixture of air and powdered coal to a preliminary relatively small combustion chamber lined with fire resistant material and communicating with the relatively large combustion chamber of the furnace of the heating system, and providing automatic ignition mechanism operated for a brief interval during the starting period or until the said lining of fire resistant material heats to incandescence whereupon said ignition mechanism is automatically cut off and such incandescence relied on to continue the ignition of the I incomingsupply of air and fueluntil the room COAL BURNER 1933, Serial No. 672,091

thermostat automatically stops the operating motor.

Other objects of the invention will appear hereinafter, the novel features and combinations being set. forth in the appended claims.

Reference will now be made to the accompanying drawings in which the preferred embodiment of the invention has been illustrated, and in which: 7

Fig. 1 is a side view of a furnace, parts thereof being shown in section, showing the same equipped with the present improved coal burning apparatus;

Fig. 2 is a section taken on the line 2-2 of Fig. 1; the motor being shown in elevation and the control circuits for the motor being shown diagrammatically;

Fig. 3 is a section taken on line 33 of Fig. 2;

Fig. 4 is a section taken on line 4-4 of Fig. 1;

Fig. 5 is atop plan view, partly in section, of a modified form of apparatus;

Fig. 6 is a section taken on line 66 of Fig. 5;

Fig. '7 is a section taken on line 'll of Fig. 5.

In the drawings, 1 represents the floor on which the furnace is supported. The furnace is of the conventional type and is provided with a hollow member 2 whose interior 3 forms the combustion chamber. The furnace is surrounded by the ordinary sheet metal jacket 4 and has a fiue 5 that connects with a chimney and a plurality of hot air ducts 6 that extend to the different rooms to be heated. Although thefurnace used for the purpose of illustrating the invention is a hot air furnace, it is evident that any other type of furnace or heating apparatus can be. employed.

The powdered coal is contained in a hopper 1 that is made preferably in the shape of an inverted cone. The bottom of the hopper terminates in a casting or housing 8 having an opening in which is located a circular feeder 9. This feeder is mounted on an axle It and is provided on its periphery with a plurality of pockets or teeth H. When the apparatus is in operation, the cylindrical feeder is turned in the direction of the arrow in Figj 3. Since the hopper is filled with powdered coal, it is evident that the pockets will become filled with coal as the feeder turns, and this coal will be carried downwardly along the circular side 12 of the housing and into the inlet opening [3 of the fan housing [4. Located within the fan housing is a fan having blades l5. This fan is adapted to be rotated at a high rate of speed and produces a flow of air that passes inwardly through-the inlet opening l3 and outwardly through the outlet opening [6. The outlet opening of the fan housing is connected with a conduit or pipe I? that extends to the combus tion chamber I 8' that is located in the door opening of the furnace, in the manner shown in Fig.

ing l9.-

1. The combustion chamber I8 is preferably formed from fire clay or of metal lined with fire clay l8", and is made in the form of a rectangular box I 8 whose bottom is provided with an open- This box I8 is of the proper size and shape to fit the door of the furnace and to project inwardly into the combustion chamber 3, a distance equal to the width of the opening IS. The outer end of the box-like chamber 18' has 5 an opening 20 and the conduit IT is provided with a flaring end 2| that is secured to the end of the box-like member is in the manner shownin Fig. 4. Two electrode plugs 22 are secured in the conical end portion 2| in the manner shown in 0 Fig. 4 and the electrodes 23 project towards each other so as to form a spark gap. The electrodes are connected to the ends of the high tension secondary winding 24 of a transformer whose primary winding has been designated by reference numeral 25. When the stream of air and powdered coal is to be ignited an electric spark is passed between the electrodes 23 and this ignites the mixture in a manner that will be referred to hereinafter. Associated with the fan 0 is reduction gearing that is housed in the gear casing 26, shown in Fig. 2. The power for operating the fan and the feeder is provided by means of an electric motor 21, whose drive shaft 28 is connected with the shaft 29 by means 'of a shaft coupling 30. Shaft 10 extends through the gear casing in the manner shown, and carries three gear wheels. The gear wheels 3| and 32 are connected together and are freely rotatable on the shaft l0. Gear wheel 3| is in mesh 0 with the pinion 33 on shaft 29, and gear wheel 32 is in mesh with a large gear 34 that is formed integral with the small gear 35. The two gears 34 and 35 are connected together and are rotatable on shaft 29, but gear 33 is keyed to the shaft 45 29. A gear 38 is fastened to shaft l0 and therefore when the motor operates the fan will rotate at the same speed as the motor while the feederdisk 9 will rotate at a much slower speed. It is evident that when the fan is operating, air 0 will enter through the opening l3 and pass outwardly through the exhaust opening [6 and into the conduit 91. While the fan is operating, the feeder 9 will turn also and thiswill convey coal from the hopper to the intake opening, in a man- 55 ner quite apparent from an inspection of Figs.

2 and 3. The stream of air that enters the fan will pass across the edge of feeder 9 and will tend to remove the coal from the pockets and in this way the feeder will be kept from clogging up so 0 that the amount of coal fed will always remain the same; whereas, if means were not provided for removing the coalfrom the pockets, the coal might stick and be returned, thus making the operation ineffective. For the purpose of stir- 65 ring or agitating the coal, a metal frame, like 75 switch, located in one of the rooms that are heated, and which can be adjusted to start the motor at any desired temperature, and to stop it when the temperature exceeds the predetermined value. The automatic switching apparatus is illustrated in Fig. 2 and may be standard equipment, the apparatus that is now used in connection with the gas and oil heaters being suitable for this purpose. When the motor is started, the high tension current is turned on to the electrode plugs for a short time for the purpose of igniting the mixture, after which the high tension current is disconnected until the motor has been brought to a stop and is again started. I

In Fig. 2 there is shown for illustrative purposes a simplified diagram of electric circuits and connections for securing automatic operation of the furnace, including the starting and stopping thereof, under the control of a thermostat shown at 67. When the main line switch 68 is closed, a circuit will be established from the supply main 69 through the conductor 70 to the solenoid H, to the conductor I2 and thence through the thermostat 61, when the latter is closed, to the other supply main 13. Therefore, when the thermostat 61 closes the electric circuit of the solenoid H, the latter pulls up its plunger 14 against the retarding action of the dash-pot which is connected by the vertical rod 16 to the plunger M, Cross bars 1'! and 18 are mounted on and insulated from the vertical rod 16 in position to be below and out of contact with the stationary contact plates 19 and 80. When the solenoid H is de-energized the bar I! may rest on the supports 8|. When the solenoid is energized and the cross cars 11 and 18 are moved upwardly, they may both engage simultaneously the fixed contacts 79 and 80. Consequently, as soon as the motor 21 is operated, the transformer 25, 24 will also be operated. The feeding mechanism and the fan will therefore be operated by the motor 21 simultaneously with the beginning of the operation of the pilot ignition device comprising the electrodes 23 shown in Fig. 4.

When the cross bar 'l'l engages the contact 19 and the thermostat 61 is closed, a circuit will be established from the supply main 69 through the primary 25 of the transformer, conductor 82, switch 11, 19, conductor 12, and thermostat B1 to the other supply main 13. The motor 21 is connected in parallel to the transformer winding 25 by means of the conductor 83, switch 18, 80, conductor 84, motor 21, conductor 85, and thermostat 61 to the other supply main 13.

As stated above, the high tension current is turned on to the electrode plugs 22, 23 for a short time for the purpose of igniting the mixture, after which the high tension current is disconnected until the motor 21 is stopped and again started. The contact 19 may be of such a length that the cross bar 11 remains in contact therewith for such short period of time. When the cross bar 11 reaches its dotted line position 71', the cross bar 18 will occupy its dotted line position 18' against the abutment stops 86 with the cross bar 18 still in engagement with the contact 80. It will thus be seen that the operation of the transformer 24, 25 is discontinued when the cross bar TI moves out of contact with the plate 19 into its dotted line position 11 but the cross bar 18 remains in engagement with the plate 80. Therefore, after a starting period the electric ignition device discontinues operating but the motor 21 continues to operate the fan and the feeder so long as the thermostat 61 remains closed. When the latter opens the solenoid 1| becomes de-energized, and the dash pot 15 permits the plunger 14 and the cross bars Hand 18 to drop quickly back to their initial positions. The restoration of the cross bar d1- from its dotted lineposition to its full line position doesnot affect the transformer because when the bar H re-engages the contact 19, the circuit through the transformer winding 25 is open at the thermostat 67. The opening of the thermostat thereforerestoresthe parts to initial positions in readiness to .be automatically operated whenever the-thermostat is closed again.

In Figs. 5, 6 and 7, a slightly modified form of apparatus has been shown which is adapted more particularly for large power installations, such as boilers for power and heating purposes. The fan that corresponds to fan M in Figs. 1 to 4 has a casing 46) that is supported on a base 4|. The motor 21 is directly connected with the fan and a conduit l1 extends from the outlet port of the fan to the combustion chamber as already described. The hopper instead of being located directly above the fan is located a short distance away and the rotary feeder instead of being a disk provided with teeth, is a squirrel cage drum having radial blades 42. This drum is mounted for rotation on an axis 43 and is rotated by means of a belt 44 that extends from the pulley 45 to the pulley 46. The bars 42 are spaced apart so as to form in conjunction with an arcuate plate 41, pockets for the reception of coal. The arcuate plate 41 is located inside of the squirrel cage drum and against the inner edges of the blades in the manner shown in Fig. 7. When the drum is rotated, the powdered coal will fill the pockets above the plate 41 and will be carried with the drum as the latter rotates. A conduit 48 connects theinlet opening 49 of the fan with an outlet opening 50 in the circular housing 5| within which the rotary drum is located. This housing is also provided with an inlet opening 52. The radial blades are so shaped and positioned that when the fan is operating, it produces a suction that causes a stream of air to flow in the direction of the arrows in Fig. 7. The air entering through the opening 52 tends to remove the powdered coal from the pockets and to carry the coal into the conduit 48. Any coal that drops to the bottom of the housing will be caught by the blades 42 and carried upwardly into the path of the air stream as it passes into the outlet opening 50. The powdered coal is carried by the air stream into the fan and then through the conduit I! as above explained. The modified construction just described is provided with an agitator 31 like the one shown in Fig. 2. A slide 53 is located directly above the squirrel cage drum and by moving this slide inwardly and outwardly the capacity of the feeder can be changed so as to adapt it to different requirements.

The preliminary combustion chamber I8 must not be confused with the combustion chamber of the furnace as it performs a separate function. It has been explained herein that the mixture of air and coal is ignited in chamber l8, and it has been found that without this it is impracticable to use electrical ignition. The widening of the throat 21 decreases the velocity of the mixture which is further decreased when the mixture passes into the chamber I8. Since the capacity of the chamber I8 is ismall and since coal dust cannot accumulate therein due to the opening I9 in the bottom, there is never enough coal dust present to produce a serious explosion when the mixture is ignited. Any coal. dust that enters the combustion chamber 3 and is not burned therein will fall through the grate and will not cause any explosion by reason of any flame issuing at any time from the opening IS. The chamber I8 at the end of the tube [1 is a valuable element of the present combination and is an important element of this invention, there being produced thereby the necessary conditions for electric ignition and for the prevention of explosions. intense heat due to combustion of the initial-supply of the mixture of coal and air in the boxlike device 18 will heat the lining I8" of fire resistant material to such incandescence as to maintain ignition of the continued incoming mixture of fuel and air after the electric ignition has been out 01f.

Another inherent advantage of the arrangement shown in Fig. 1 is that an accumulation of ash from the burned coal is prevented from clogging or interfering with any of the burner passageways or the free flow of the mixture for combustion in the preliminary combustion chamber and thence into furnace chamber. The bottom opening I9 is widely spaced above the grate at the bottom of the furnace chamber so that the flame, as indicated by the curved arrow in Fig. 1, spreads from the bottom opening I9 into the central portion of the furnace chamber while solid particles, such as ash, may fall through the grate at the bottom of the furnace chamber into the ash pit at the bottom of the furnace.

From the foregoing description it will be seen that the apparatus shown in the drawings and described in this specification is so constructed and arranged that predetermined small quantities of powdered coal Will be positively fed into a regulated air stream in accordance with combustion requirements, the properly proportioned mixture of air and powdered coal being delivered in a continuous stream to the relatively small preliminary combustion chamber where it can be ignited by means of an electric ignition device which is preferably operated only during a short interval of time or until the fire resistant lining has been heated to sufficient incandescence to continue the combustion of the powdered coal flowing into such preliminary com- The bustion chamber after the ignition mechanism is I automatically cut off. By referring to Figs. 2 and 3 it will be seen that the small pockets of powdered coal fall continuously into the stream of air indicated by the arrow in Fig. 2 and the fan thoroughly separates the particles of coal by commingling them with the air and the mixture thus produced is caused to flow along the delivery pipe I! to the combustion chamber l8, shown in Figs. 1 and 4.

From the drawing it will be apparent that the invention shown and described is provided with means whereby the incoming air currents serve to remove the powdered coal from the rotary feeder and in this manner a positive operation is obtained, whereas, if this feature of construction were not present, the pockets might readily become clogged with coal with the result that the operation would become very erratic and intermittent, or would fail altogether, and therefore this feature of the invention is considered to be of great importance in a device of the kind described and claimed herein.

In the drawings the coal has been shown a being fed into the air stream as it enters the fan and this is believed to be the preferable way. It is desired to be understood, however,

til

- l 10 restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:

In apparatus for burning pulverized fuel, the combination with a furnace having a main combustion chamber with a substantially vertical wall provided" with an opening through which an auxiliary combustion chamber may be inserted, of a horizontally extending-auxiliary combustion chamber having an outlet opening in the bottom thereof and extending through said opening in the furnace wall withsaid outlet opening spaced from said wall, said auxiliary chamber being lined with refractory material and having an inner rear vertical refractory wall adjacent said outlet opening, a duct for carrying a mixture of powdered coal and air, a flaring connection establishing communication between said duct and the outer end of said auxiliary chamber, and ignition means in said flaring connection.

DAVID C. RUTH.

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