US2102618A - Automatic system for supplying pulverized fuel to furnaces - Google Patents

Description

E. v. FRANCIS 2,362,618 AUTOMATIC SYSTEM FOR SUPPLYiNG PULVERIZED FUEL T0 FURNACES- Dec. '21, 1937.

Filed Jan. 23, 1935 s ShetQs-Shetl [NI/ENTOR: Ear/e M Franc/s ATT'Y.

Dc. 21, 1937. E. V.IFRANCISY 4 2,162,618 I AUTOMATIC-SYSTEM FOR ISUPPLYING PULVERIZED FUEL TO FURNACES Filed Jan. 23, 1933 5 sheet s-sh-eem 2 //\/V.EN TOR: 47 far/e 1/ Francis ATT' Dec. 21, 937. v. FRANCIS 2,102,618

AUTOMATIC SYSTEM FOR SUPPLYING PULVERIZED FUEL TO FURNACES El M l6 we Elg- 9 Ear/g l Hands,

INVENTOR:

ATTY Patented Dec. 21, 1937 l UNITED STAT PATENT "OFFICE" ration of Ohio Application'January 2a, 1933. Serial No. 652,975

, h h 2 Claims. My invention relates to automatic systems for I controlling the supply of pulverized fuel to furnaces and one of the objects of the invention 'is the provision of improved and flicient thermostatically controlled apparatus for starting and stopping the operation of a furnace and feedin a mixture of powdered coal and air thereto in accordance with temperature requirements.

A further object of the invention is the provision of improved ignition mechanism associated with a nozzle for projecting a mixture of air and pulverulent combustible material into a furnace combustion chamber.

A further object of theinvention is the provision of an improved and efficient system of electrical control of the delivery of fuel to a furnace and providing safety'features for the em cient operation of the furnace.

Another object of the invention is to provide a system for burning pulverized coal in a domestic furnace, in which a, preliminary combustion chamber is provided within the main furnace combustion chamber which allows for free escape of ashes and hot gases of combustion. and in which combined gas and electric 'means is provided to ignite the pulverized coal until said preliminary combustion chamber has its interior walls heated to a temperature suflicient to support combustion of the pulverized coal. after which said ignition means'is shut off, while the pulverized coal is continued to be fed to said furv nace as dictated by thermostatic control means.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims Referring to the accompanying drawings, Fig. 1 is an elevational view of an automatic thermostatically controlled heating system embodying my invention; j

Fig. 2 is a sectional plan view of my improved preliminary combustion chamber with the fuel delivery nozzle and ignition mechanism connected thereto and shown in plan view; 7

Fig. 3 is an enlarged sectional elevation (on line 3-3 of Fig. 2) of a portion 'of the structure shown in Fig. 2; v P

Fig. 4 is an enlarged plan view partlyin sectionv of the electric and gas ignition mechanism embodiedin the construction shown in Figs. 1 and 2; V

Fig. 5 is a wiring diagram of the circuits and connections for the heating system shown in Fig. 1;

Fig. 6 is a wiring diagram with a modification; Fig. is an elevational view of the switch panel lay for operating a motor control switch, and a thermaltime limit cut-out switch.

Fig. 8 represents the position of the switches of Fig. 7 during the starting period of the heating system;

Fig. 9 is a view similar to Fig. 8 but showing the position of the switches during the running period; and h v Fig. 10 is a sectional elevation of the thermostatic stack element for operating the switches shown at the upper portion of Fig. 7.

In Fig. 1, l4 designates a furnace of thevertical type which may be either in a hot air heating system, vapor heating system or steam heating system. While my improvements are particularly adapted to be installed in connection with a furnace alreadyin operation for the burning of coal in the ordinary way, it should be understood that my system may be permanently or detachably connected to a furnace when initially installed. The only changes necessary for the installation of previously installed furnace are the removal of the usual fire grate and the provision of suitable openings for the connections shown in Fig. 2. My improved preliminary combustion device i5 is mounted on verticaladjustable standards l6, l6 and comprises a supporting ring I! on which is mounted a cylindrical casing ill with a semispherical topv or cover I9 mounted" thereon as shown in Fig. 1. Rectangular side openings 20, are provided in the diametrically opposite sides of the preliminary combustion device i5 and the walls of the latter are formed by sections of fire resisting material as shown at 2| in Figs. 1 and 2 and at 22 in Fig. 1. v y

Secured to the bottom of the ring H at 23 adjacent the front portion of the furnace i4 is a flattenedpipe 24 which is provided with an upwardly projecting passage 25 to afford a nozzle. 28 for the mixture of pulverized coal and air to be projected upwardly through the lower circular opening in the bottom of the combustion device i5.

my.improved apparatus in connection with a The ignition apparatus associated with the noz- 2 members 32 and 33. The forward end of the rod- 80 screw-threaded into the contacting as shown in Fig.4, The exposed terminal 31 ofthe rod 35 is located as shown in Fig.- 4 adjacent V the metal pin 38 which has one end embedded in insulated member 36 with the other end extending to the center of the opening 39 to a position adjacent the upper end' ofthe terminal 49. The latter as shown in Figs. 3 and 4 is mounted on the metal holder 42 which in turn is supported by the pipe 59. The lead 29 of the transformer 21 being grounded on the pipe 24 is in electrical connection with the terminal 46' while the lead 28 is connected to the insulated terminal 31. There are, therefore, two spark gaps in series with each other, one being relatively short to produce a hot spark-while the other gap between the terminals 38 and 49 is relatively long to effect a flaming arc. When the primary of the transformer is closed through the terminals 43, 43 a hot spark will be produced between the terminals 31, 38 and at the same time a flaming arc will be produced between the terminals 38. 40. The terminals 31, 38, and 40 are composed of metal of a composition usual in spark plugs.

A gas supply pipe 44 is connected through a regulating valve 45 to the electro-magnetically operated valve 46. The latter is connected by means of the pipe 41 to the gas jet 48 which projects into the flaring mouth 49 of the pipe 56, the latter being in communication with the chamher having opening 39 and the upwardly extending passage way 25 leading to the nozzle 26. Air openings 5| are provided at the rear of the mouth 49 as shown in Fig. 4. As hereinafter explained the electro-magnetic valve 46 will be opened at the same time that-the ignition transformer 21 is operated to produce the sparks between the terminals 31 and 38 and between the terminals 38 and 40.

If the electric ignition mechanism is omitted or is out of operation a constantly burning gas pilot flame at 52 may be-relied on to ignite the gas flowing from the gas jet 48 when the electromagnetic valve 46 is opened. The pilot tube 53 is connected to a pilot regulating valve 54. The

pipe 53 is connected through the valve 54 to the supply pipe 44 in advance of the regulating valve 45 so that the pilot flame may be cut off without interfering with the operation of the electro-magnetic valve 46.

The outer end of the flat pipe 24 is metallically connected to the metal connector 55 and the latter is connected at its outer end to the pipe 56 which leads to and is connected to the fan casing 51 of the pulverized fuel feed mechanism 66.

The powdered fuel such as pulverized coal is adapted to be stored in the large bin 59 the lower end of which is conical or hopper shaped as shown at 69 in Fig. 1. The lower end of the hopper 60 is secured as shown in Fig. 1 to a hopper shaped casting 62 of the pulverized fuel feeding mechanism 66 which is disclosed in detail in my divisional application Serial No. 727,270 flied May 24, 1934, said application being a division of my chute 83 is provided for delivering pulverized fuel' from the feeding mechanism 66 to the fan in cas-' ing 51. Leveling screws H4 are provided to level the base 63.

block 34 so as to electrically connect the rod 39 to another rod 35 which is mounted in the in- 'An electric motor 89 mounted on the base frame 63 has it armature shaft 99 connected by the coupling 9i to the shaft 92. Said shaft 92 drives the feeding mechanism 66 and also drives the fan in the casing 51 which fan delivers a mixture of pulverized fuel and air to the pipe 56.

The stack switch device H8 is mounted on the flue II9 which leads from the furnace I4 as shown in Fig. 1. Fig. 7 shows the front of the ,stack switch device H8 with the cover removed and Fig. 10 is a sectional elevation of the upper portion of the stack switch device H8 including the stack switch element I20 which projects into the flue H9 to be heated thereby.

By referring to Fig. 5 it will be seen that when the room thermostat switch I2I is moved to closed position while the main lineswitch I22 is closed a circuit will be completed from the secondary winding I23 of the transformer-relay I24 through the conductor I25, main pull-in mercury switch I26, conductor I21, auxiliary pull-in mercury switch I28, conductor I29, safety heating resistance I 39, conductor I3I, thermostat switch I2I and conductor I32 to the other terminal of the secondary I23.

When the'main line switch I22 is closed a circuit is established from the main I33 through the conductor I34, lock-out mercury switch I35, conductor I35, primary winding I23, and conductor I38 to the other main I332 I Fig. 7 shows that the secondary winding I23 of the transformer-relay I24 acts as an electromagnetic winding for an electro-magnet having a pole I36 adjacent to which is a movable armature I36 which is pivoted to the frame of the electro-magnet and carries the motor mercury switch I31.

It will thus be seen that when the thermostat switch I2I closes the armature I36 will be attracted to the pole I36 to effect closure of the mercury switch I31. Thereupon a circuit will be established from the conductor I35 through the conductor I39, switch I31, conductors I49,

'I4I, motor 89, and conductors I42, I38 to the main I33.

At the same time that the motor circuit is closed a circuit will be established through the conductor I43, ignition mercury switch I44, conductor I45, and primary I46 of the ignition transformer '21, which will effect sparking between the terminals 31, 38 and 38, 40. I At the same time that the motor is started and the electric ignition mechanism is operated a circuit is established through the conductor I49, electro-magnet 46, and conductor I59, to effect opening of the valve l5l for passage of the gas through the gas supply pipe 44.

The closure of the thermostat switch I2I there- 'fore effects starting of the motor 89,0peration of the electric ignition mechanism and flow of gas from the nozzle-48 shown in Fig. 4. When the motor starts, the feeding mechanism shown in Fig. 1 operates to deliver amixture of air and powdered coal to the preliminary combustion device I5 for burning therein preliminarily. the combustion being completed in the furnace chamber I52.

In some installations it is desirable to prolong the starting period and I have therefore mounted the auxiliary pull-in mercury switch I28 on the same carrier I53 on which the hold-in mercury switch I54 is mounted. As shown in Figs. 7 and 10 the carriers I53 and I55 are connected by spring operated frictional devices I56 and I51 on the rock shaft I58 the inner end of which is connected to the stack thermostat element I20. The I 26 and I28 are closed can. sumcient current be adjustments are such that when the combustion of the fuel begins, the heating in the flue II9 will be suflicient to cause the thermostat element "I3I, thermostat switch HI, and conductor I32 to the other terminal of the secondary I23. The

resistance I60 is thus placed in series with the resistance I30 to cut down the current through the latter sufllciently to prevent thelatter from .effecting operation of the tripping mechanism I63, and sumcient current will flow through winding I23 'to maintain switch I31 closed.

. Asshown in Fig. 7 an expansion device I64 is located adjacent the heating resistance When sumcient current passes through the latter it will heat to cause such expansion of the device I64 as to operate the tripping device I63 and "thereby permit the look-out mercury switch I35 to tilt toopened position thereby cutting off the current from the supply mains and necessitatvirigresetting by manually operating the knob I65.v By the arrangement of'the circuits shown in Fig. and the adjustments illustrated in Figs. '7. 8, and9. I have provided a prolonged starting period in such installations as require prolonged heating of the furnace,- before the stack element 5 I20 becomes sufficiently heated to rotate the shaft.

I53 sufliciently to move the carrier I55 against the limit stop I66. In other words, the time element for operation preliminarily of the heating element I30 to trip the switch I35 to opened position has beeneliminated. .When the furnace has been sumciently heated to move the carrier I55-against the stoprl66 the main'pull-in switch I26 is opened and at the same time the ignition switch I44 is opened. whereupon the electric ignition will discontinue in its operation and the valve I5I will close automatically. The-'motor 89 and the fan will continue in operation how-- ever until a predetermined room temperature has been reached, whereupon the thermostat switch I2I will be opened and the armature I36 will move away from the pole I36 to open the motor switch I31, whereupon'the motor and fan will automatically stop and soalso the fuel feeding mechanism.

The thermostatic control switch comprises two pairs of contacts I 2I and I61 and when contacts I2I open in response to an increase in teinperature of the space to be heated, contacts I61 will be closed and a circuit will be established from a low voltage secondary I68 through the conductors I69, -I6I, hold-in. switch I54, conductor I62, resistance I30,'conductor I3I, contacts I61 and conductor I to the other terminal of the secondary I68. The resistance I30 may be so proportioned that it will act to operate the tripping mechanism. I63 if the stack element I20 does not 0001 within a predetermined time to open the hold-in switch I54. During normal operation, however, within such predetermined closed. It should also be noted that an interval 'timethe hold-in switch I54 will be opened and 'bothof the pull-in switches I26 and I28 will be will be established before the closure of the thermostat I2I can restart the supply of fuel to the furnace because not until both of the switches passed to operate the armature I36. When the fuel supply has been automatically cut off by the opening of the thermostat I2Iv the preliminary return of the carrier I53 against the stop "I will effect opening of the hold-in switch I54 and closure of the auxiliary pull-in switch I28,

but the main pull-in switch I26 is still open and will remain open until after the shaft I58 has been rocked farther by further cooling of the stack element I20. When the carrier I55 reaches the stop I12 the main pull-in switch I26 will be closed and the ignition switch I44 will he closed in readiness for restarting when the. thermostat switch I2I is again closed.

after a pre-determined length of time. For in-,

stance, if the stack element I20 does not rock the shaft I58 at all within a period of say 1% minutes the circuit through the resistance I30 will cause the latter to effect the opening of the lock-out switch I35.

, In Fig. 6 under normal operations the preliminary rocking of the shaft I58 will cause the mer-' cury I14 in the device I13'to connect the contacts I54 beforethe'switch I28 is opend. Therefore, the hold-in switch I54 will be closed before the switch I28 is opened. The movement of the carrier I53 from the stop "I to the stop I50 will effect closure of the switch I54 and immediately afterward the opening of the switch I28. The resistance I60 will thereby be thrown into circuit with the resistance l 30 so as to prolong the starting period indefinitely or until the stack elements I20 has been heated sufliciently to move the carrier I55 from the stop I12 to the stop, I66.

When this occurs the main pull-in switch I26 will be opened. Otherwise the operation of the system illustrated in Fig. 6 is the same as that illustrated in Fig. 5.. s

It should be understood that both in the system shown in Fig. '5 and the system shown. in Fig. 6 the secondary I23 is relatively high voltage and of sufllcient'strength to cause the armature I36 to move to the pole I36. The secondary I68 is, however, of relativelylow voltage and of insuflicient'strength to cause the armature I34" to move to the pole I36. The secondary I50 merely acts as the secondary. of a transformer to obtain the safety features above pointed out.

While in some furnaces a pulverized fuel burner may be provided without having connected, thereto the preliminary combustion device I5, such burner would require-continued burning of gas coal may be sufflcient to cause the same to be exttnguished if the gas flame from the' nozzle 26 is not maintained. Therefgre'when the preliminary combustion device I5 is omitted, I prefer to so arrange the electro-magnetic -valve structure 46 as to be dependent on the motor switch I31 alone. This maybe done by placing the electro-magnet of this valve structure in the motor circuit direct-in the conductor I or In or I 38 shown in Fig. 6. Then the gas will continue to burn at the nozzle 8 whenever the pulverized fuel burns at the nozzle 26 and the fuel flame will not be extinguished but will be maintained so long as the motor 89 operates the feedin mechanism and the blower.

However, it is highly desirable to reduce the 7 consumption of the gas and I therefore prefer to include the preliminary combustion device l so that the gas may be cut oil? during the running period of the furnace. The refractory walls of the preliminary combustion chamber become sufficiently heated during the starting period to act continuously during the running period to maintain the pulverized fuel flame.- For instance, such refractory walls may reach a temperature during the running period of approximately 2400 F. so that irrespective of the temperature of the walls of the main furnace chamber I52 the burning of the fuelwill be maintained. Furthermore, the preliminary chamber l5 confines the mix-- ture of the pulverized coal and air for ignition to a limited space without preventing gradual For instance, I have found by actual test of a practical heating system such as that disclosed herein, that the feed of the pulverized coal to the fan need be no greater than one cubic foot in a period of twelve hours while burning of the pulverized coal in 'the furnace is being continuously sustained without the burning ofany gas from the pipe 44 and the burner nozzle 48 during the running period.

Obviously those skilled in the art various changes'in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I wish therefore not to be restricted 'to the precise construction herein disclosed.

Having thus described and shown an embodiment of my invention what I desire to secure by may make and contacts of a main switch which close in response to a determined lowering of the temperature of the space to be heated, a second control circuit including a resistance and a third switch in parallel with said first and second switches and in series with said heater, a third control circuit including said third switch, the resistance heater and the contacts of the main control switch which close in response to a determined rise in temperature of the space to be heated, and combustion responsive switching mechanism operable upon the establishment of' bination with a furnace, of a fuel burning apparatus comprising a power circuit and a control circuit, a safety cut-out switch which when operated disables both of said circuits, fuel supply control means in said power circuit, fuel ignition means in said power circuit, a switch common to both 01' said means, a furnace heat responsive switch individual to said ignition means, said control circuit comprising a series circuit including a room temperature responsive switch, a relay coil, a pair of furnace heat responsive switches and a time responsive operating means for said cut-out switch, a shunt circuit bridging said pair of furnace heat responsive switches comprising a resistor and a furnace heat responsive switch, said room temperatureswitch being effective responsive to a predetermined minimum room temperature to close its contacts and thereby close said series circuit whereby said relay coil and said time responsive operating means are energized, means for closing said switch common to both said fuel supply control'means and said fuel ignition means responsive to the energization of said relay coil, said furnace heat responsive switch in said shunt circuit operating responsive to an initial furnace heat to close said shunt circuit, one of said pair of furnace heat responsive switches in said main series circuit operating responsive to an initial furnace heat to open its contacts whereby the said series circuit includes said shunt resistor which is effective to disable the operation of 'said time responsive operating means to prevent operation of said cut-out'switch, said furnace heat responsive switch individual to said ignition means operating responsive to advanced furnace heat ,to disable said ignition means, and the other of said pair of furnace heat responsive switches operating responsive to advanced furnace heat to open its contacts, said switch-common to said fuel control means and said .fuel ignition means remaining under the control of said room temperature responsive switch. I

. EARLE V, FRANCIS.

Images