US2382483A - Ignition system for pulverized coal burners - Google Patents

Description

Au ..14, 1945. A gN 2,382,483

IGNJ ITION SYSTEM FOR PULVERIZED COAL BURNERS Filed Feb. 4, 1942 5 Sheets-Sheet l w E m &\

Q N 5.4mm MENTOR ED BY WM Aug. 14, 1945. E HOLDEN IGNITION SYSTEM FOR PULVERIZED COAL BURNERS Filed Feb. 4, 1942 3 Sheets-Sheet 2 R O m V m 1945. E. A. HOLDEN 2,382,483

IGNITION SYSTEM FOR PULVERIZED COAL BURNERS Filed Feb. 4, 1942 5 Sheets-Sheet 5 Patented Aug. 14, 1945 IGNITION SYSTEM FOR PULVERIZED COAL BURNERS Edward Allen Holden, Jamaica, N. Y., assignmto Engineer Company, New York, N.'Y., a corporation of New York Application February 4, 1942; Serial No. 429,480

11 Claims.

This invention relates to the use of a retractable electric sparking device and an oil, gas or similar burner used in combination to effect the ignition of a stream of pulverized coal or similar fuel delivered through any of the various types of pulverized coal burners or the like. This ignition is conveniently accomplished by a combination of electrical and mechanical means operated by distant control. The movements of the electrodes and of the oil or gas burners while correlated are independent of each other and allow, first, ignition of the ignition fuel by the sparking device; second, the withdrawal of the electrodes of the sparking device from the hot ignition flame zone after the ignition fuel is lighted and third, the withdrawal of the ignition fuel burner from the hot pulverized coal zone after coal ignition has taken place and the coal flame is stabilized. Other essential functions are more fully hereinafter described.

The object of the invention is to provide a simple, reliable and interlocking device for the safe,

rapid and convenient ignition of pulverized coal or similar fuel in furnaces of various types, particularly for re-igniting coal streams when igni tion has been lost.

Since the pulverized coal is burned in suspension, only a few seconds supply of fuel is in the furnace at any one time and on loss of ignition, either through failure of the mills pulverizing the coal, of the supply of coal to the mills or due to unfavorable furnace conditions, there instantly follows a complete loss of heat liberation in the furnace and with steam boilers, for example, by cessation of steam generation. The resulting loss of pressure in steam used for power or process or public utility work may result in serious interruption of plant operation and heavy financial loss. It is therefore essential that ignition be reestablished as promptly as possible.

Various means are used at the present time to accomplish this, the principal ones being hand manipulated torches which may be either oil soaked waste on the end of a steel rod, kerosene oil torch operated by compressed air or gas from a pipe. All of these methods involve the loss of time required to get the torch to the individual coal burners, frequently in the larger installations, up long iron ladders to firing platforms, light the torch itself, insert it in the individual coal burner and wait while the mill is started and coal ignition is established, to be followed by the withdrawal and storage of the torch.

pulverized coal burners in a furnace from the first one in order to prevent possible disastrous explosions. In this case there is a further delay while the torch is transferred to the other burners, mills for those burners started and coal ignition established in each.

By using the equipment hereinafter described, it is possible for the operator from a central position, preferably at the combustion control and instrument board now commonly used in large plants, to simultaneously, or in rapid succession,

ignite as many coal burners as may be required within a few seconds, irrespective of their location, with entire safety to the operating personnel and the furnaces, and using only the limited operating force commonly found in modern combustion controlled plants.

To illustrate the principles involved, an oil burner of the mechanical atomizing type is shown but other types of oil atomizers or gas under pressure may be used by slight modification of the apparatus detail. A number of different pulverizedcoal burners are in commercial use, all having in common, however, some method of delivering a stream of finely pulverized coal, picked up by a stream of air passing through the mill and carried through piping to an opening in the furnace wall and discharged into the furnace in such relation to a stream of seccndary air as to provide thorough intermixture of the air and fuel. The coal may be fired horizontally through a circular air register, vertically downward through a rectangular opening in an arch, or between water wall tubes or through any of the numerous other type burners in use.

For the functioning of this invention, it is only necessary to arrange the igniting flame so that some part. of the pulverized coal stream in any of the various types of burners will pass through the ignition flame or close enough to it to ignite For the purpose of exemplification only, one

of the many commonly used types of coal burners is shown, being of the circular air register type. A mechanical oil atomizer is shown as typical of a fluid burner.

Referring to the accompanying drawings forming a part of the specifications in which like numerals designate like parts in all the views:

Fig. 1 is a diagrammatic view, partly in sec- In many plants firemen are forbidden to light tion, showing the ignition system with both the sparking device and the ignition burner in their retracted or off positions;

Fig.2 is a similar view showing both the device and the ignition burner in their projected or operative positions; and

Fig. 3 is a similar view showing the sparking device retracted after it has effected the ignition of the ignition burner fuel but with the ignition burner still projected to complete the ignition of the furnace fuel.

The same reference characters are used to designate the same parts in all views.

The figures all show by way of example a central longitudinal section of the register type of coal burner commonly used. Coal which has been pulverized in mills not shown, is carried by a stream of primary air through a, coal pipe I and a passage 2 through burner pipe l and discharged in a stream of-flne coal dust through opening 3 into the furnace throat opening 5 formed by a refractory ring 6. Secondary air for combustion is supplied through duct I.

A so called ignition tube 8 is commonly located' longitudinally along the center line of these coal burners. In this tube is shown an oil gun 9 having at its furnace end I0 an oil atomizer of the mechanical or pressure type which discharges a vey fine oil spray, usually in the form of a. hollow cone ll, into the furnace opening 5 and across the path of the pulverized coal when it issues from the opening 3 in coal burner The liquid fuel burner may be any one of many forms, and any readily combustible liquids, such as oil, may be used. Ga mayalso be used with a suitable burner tip at the furnace end of the fuel pipe 9.

The gun 9 is here shown supplied with fuel through an elbow I2 mounted on a, support I3, a flexible pipe Ila, a control valve 55, actuable by coil 54, a connecting pipe Nb and a pump I40 connected to a reservoir as indicated at Md.

The gun 9 is carried by plunger l5 carrying a piston I5a in a cylinder I6 which has pipe connections I1 and I8 at' opposite ends of the cylinder to which flexible pipes I6 and I8 alternately deliver and carry away fluid under pressure following operation of control valve II, as later described.

Referring to Fig. 1, application of pressure in cylinder I6 to connection I8 through flexible pipe I5 and connection of the opposite end to the drain by connection I1 and flexible pipe I8 will either retract or hold in retracted position the oil gun 9 as shown, in which position it is out of the hot pulverized coal fire zone. Conversely in Fig. 2 application of pressure to connection II and discharge through the opposite end connection I8 will advance the gun 9 into firing position as shown.

The electrodes 21b for igniting the oil spray are similarly mounted and may be located either in the same ignition tube as the oil gun 9 or they may be introduced through an auxiliary tube as will be necessary to adapt the equipment to existing types of pulverized coal, burners. These burners vary as to the size of ignition tube used and in other respects. The methods of operation, however, are substantially the same. For purpose of explanation only, the gun and the electrodes are both here shown in the ignition tube.

The electrodes 21b are carried by the plunger 30 carrying a piston 30a in a double acting cylinder 28 and admission of pressure through connection 31 and discharge through 36 retracts or holds in the retracted position the electrodes 2'Ib,'as shown in Figs. 1 and 3. Conversely, application of pressure to connection 36 and discharge through connection 31 will advance the electrodes 211) so that spark between their terminals 49, 50 will ignite the oil spray as shown in Fig. 2.

To facilitate the adjustment of the electrodes 21b and the ignition spray II relative to each other and to the coal stream, a. carrier I9 is provided, said carrier being supported on the tube 8 in which the ignition burner and electrodes are located. Said tube is shown as passing through a central aperture in said carrier. The carrier is shown as also provided with oppositely disposed side apertures through which the cylinders I6 and 28, respectively, pass and in which they are supported. The single cylinder carrier I9, or if the burner and electrodes are located in separate tubes both cylinder carriers are slidably adjustable longitudinally along the tube or tubes. The cylinders I6 and 2B are themselves slidably adjustable longitudinally relative to each other in the carrier or carriers to permit adjustment of the electrodes relative to the ignition burner to facilitate ignition of the ignition fuel, which when ignited is employed in turn to ignite the fuel of the main fuel burner. To permit adjustment of the ignition flame relative to the main fuel burner the cylinders I6 and 28 are moved as a unit by proper adjustment of the carrier I9, which supports them, along the tube 8. When the adjustments have been made the cylinders l6 and 28 and carrier I 9, or carriers, are preferably secured in adjusted position by suitable conventional means, such as set screws K, K, K", respectively. The above adjustments are permitted by reason of the flexibility of the feed pipes 16, 11, I8 and 19.

To operate the plunger I5 carrying the oil gun 9 and the plunger 30 carrying the electrodes 21b, any fluid such as oil or water or compressed air may be used. Assuming, for the purpose of explanation. a liquid is used, it is pumped by a pump I3 from a suitable reservoir I4 under pressure through pipe 15 to the control valve II. This control valve has three operating positions and these positions and the resulting flow of liquid and the resulting positions of plungers I5 and 30 are shown in Figs. 1, 2 and 3 respectively. Pipe I5 supplies liquid under pressure and pipe I2 connects to the drain in all positions.

Referring to Fig. 1, the first position of the control valve is shown. Liquid is supplied under pressure through flexible pipes I6 and TI to the inner ends of cylinders 16 and 28 and drained from the outer ends through flexible pipes I8 and I9 retracting both plungers.

Referring to Fig. 2, the second position of the control valve is shown. Liquid under pressure then is supplied through flexible pipes I8 and I9 to the outer ends of both cylinders and drained through I6 and I1, advancing both plungers.

Referring to Fig. 3, the third position of the control valve is shown. Liquid under pressure is being supplied to the inner end of cylinder 28 through flexible pipe 11 and drained from the opposite end through flexible pipe I9, retracting the electrodes 21b while simultaneously, pressure is maintained on the outer end of cylinder I6 through flexible pipe I8, the inner end assacas being still connected to the drain through 15. The ignition burner is thus held in firing position where it can continue to maintain an oil flame until the pulverized coal is ignited. The electrodes are meanwhile held out of the hot zone of the ignition flame.

' To coordinate and synchronize the movement of the ignition burner and the electrodes, and to safeguard lighting of! both the oil and pul-- verized coal, both of which are, under certain conditions, capable of producing serious explosions in the furnace, as well as to maintain the apparatus in working condition and in constant readiness for use, the electrical equipment as hereinafter described is provided.

Electric current is obtained from any satisfactory source. To establish the electric spark and also control the flow of fuel to the ignition burner, a. combination of contact switches, relays and other electrical devices are provided.

Referring to Figs. 1 and 2. The spark between electrode points 49, 50 isestablished as follows: Spring contact switch 34 is mounted on or near cylinder 28 in'such position that the inward movement of the arm 3| carried by the plunger 30, will close the switch, allowing cur-- rent from supply line 4| to flow to and through relay coil 45, closing both relay switches 45 and 41 as shown in Fig. 2. The closure of switch 45 permits current topass from supply line S, through 4i, 42 to the primary of transformer 48, returning through 4 IR. The transformer secondary, being thus energized, causes sparks to pass between the terminals 49, 50 at the outer ends of the electrodes 21b. I

At the same time, the control valve 1| being in the second position, the ignition burner plunger I5 is moving forward from the position shown in Fig. 1 to that shown in Fig. 2. A contact switch 25, located relative to the cylinder IS in a manner similar to that already described for cylinder 28, is closed by pressure of arm 24 on plunger 25a. Circuit from supply line 43 is thus closed to relay coil 53, but current will not flow unless relay switch 41 has already been closed by relay coil 45. In other words, the oil cannot be turned on even though the gun 9 is in firing position, until the electrodes are in position and the spark current established. If, however, switch 41 has been closed by coil 45, current from line 43 will pass through coil 53 which will be energized and switches 5| and 52 will be closed. If the by-pass switch 80 is also closed, current will then flow from line 44 across switch 5i to solenoid 54, opening oil supply valve and also lighting signal lamp 61, showing oil pressure is on the ignition burner line.

If the electrodes reach firing position first and spark current is turned on by closing of switch 34, the fuel valve 55 will open when the atomizer gun 9 reaches firing position and closes switch such time as the pulverized coal is lighted ofl, which maybe immediately or some time later.

The control valve II is therefore moved into its third position, Fig. 3. The electrodes are retracted as previously explained and the resulting release of pressure of plunger arm II onspring contact switch 24, immediately opens switch 54 and deenergizes relay coil 45,; which in turn opens switches 45 and 41 and discontinues the spark at 45, 50

It will be noted that the above described opening of switch 41 opens the circuit from the relay coil 53 through said switch to line 43R. However, the previous closing of switch 52 by relay coil 55 provided a path in parallel with that through relay switch 41 for maintaining current from line 45 across switch 52 to keep coil 55 energized after switch 41 is op ned. Since the relay 55 will keep the switch 5| closed as long as the coil is energized, current from line. 44 will continue to flow across switch 5! to the fuel valve 54, 55, keeping it open and supplying fuel to the ignition burner until the current through coil 53 is interrupted by retraction of ignition burner and resulting opening of contact switch 25.

When the pulverized coal is turned on, it may ignite promptly from the ignition flame, but may be unstable for a time. and .the ignition flame may then be kept in service as long as desired. When ready to discontinue it, the control valve is turned back to the first position, Fig. 1. The pressure is thereby applied to the inner end of cylinder l5 and relieved from its outer end and the gun is retracted. As a result of the initial movement, the contact switch 25 is opened, as previously descrl d, permitting the fuel valve 54, 55 to close. The pressure is meanwhile maintained on the inner end of cylinder 28 and the electrodes remain in their retracted position which they assumed from previous movement of control valve to secend position, as previously described.

It will be noted that if the oil gun be partly retracted, opening contact switch 25 and cutting off current to the solenoid fuel valve 54, 55 and the gun is then returned to firing position, closing switch 25, the oil will not turn on until the electrodes are advanced and spark current established as previously explained. This provides against spraying unignited oil into the furnace, 4

switch 62 in line 44. A relay coil 63 is used .to

operate switch 64. An electric eye 65 is directed at the flame, either ignition or coal. Signal lights 66 and 61 are provided to show that lines in which they are located are energized-connecting lines 58, 58a, 59, 10 and 10a are provided for the purposes hereinafter described.

The operation is as follows: After the operator has put the control H in the second position, Fig. 2, the spark current is established by the closing of relay 45 and the relay 53 is also closed, closing the circuit of line 44 as far as the relay switch 52, which will be open. The operator now closes the momentary switch 60 manually, allowing current from 4311 to flow through lines 58 and- 68a through coil Bl, energizing that relay and passing through line 68R to the return line R.

When relay 6| is thus energized, switch 62 is thereby closed and current in line 44 opens solenoid valve 54, 55, the signal lamp 6! is lighted and oil flows to the atomizer. If the spray ignites, then the electric eye 65 is actuated to permit current from 43a to flow through lines 10 and 10a. energizing relay 63 and lighting signal lamp 66. When relay 63 is energized it closes, switch 64 establishing the circuit 69, 64, 69a in parallel with that through momentary switch 60. When the operator releases the momentary switch 60 after a suitable interval, if'the spray has not been ignited, the electric eye switch will not have closed circuit 10, 10a, 10R, the switch 64 will not have closed, the signal light 66 will not have lighted. The current being cut off from relay coil 6| by the opening of the momentary switch 60, the line 44 is opened by switch 62 and the solenoid valve 54, 55 shuts off the oil.

If, however, the spray has lighted, the electric eye switch will have closed the circuit through line 10, 10a and MR and relays 63 and 6| will continue to be energized after the momentary switch has been opened by the operator and the solenoid valve 54, 55 will remain open supplying oil to the atomizer until either the control valve isoperated to retract the. gun 9 or the flame goes out. In the first case, that of retraction of gun 9, the current to the solenoid valve 54, 55 is cut off at relay switch as previously described. In the second case, that of flame failure, the current to the solenoid valve 54, 55 is cut ofl at relay switch 62 by action of the electric eye 65 which will open circuit 10, a, deenergizing relays 63 and GI.

It is obvious that those skilled in the art may vary the details of construction as well as the arrangement of the parts without departing from the spirit of the invention. I, therefore, do not wish to be limited to the above disclosure except as may be required by the claims.

I claim:

1. In an ignition system for a fuel burner, inv

combination; mechanism for igniting the burner fuel comprising means movable to operative position to discharge ignition fuel to ignite the burner fuel; means movable to operative position to ignite said ignition fuel; means for advancing said two means to their respective operative positions and for retracting said last mentioned means to a position 'out of range of the burner and ignition flames and for independently re-' tions and for retracting said last mentioned means to a position out of range of the burner and ignition flames and for independently retracting said first mentioned means to a position out of range of the burner flame; and means for adjusting said first two means relative to each other and also for independently adjusting said first two means as a unit relative to said burner.

3. In an ignition system for a fuel burner, in combination; mechanism for igniting the burner fuel comprising means movable to operative position to discharge ignition fuel to ignite the burner fuel; means movable to operative position to ignite said ignition fuel; means for advancing said two means to their respective operative positions and for retracting said last mentioned means to a position out of range of the burner and ignition flames and for independently retracting said first mentioned means to a position out of range of the burner flame; and means for adjusting said first two means relative to each other.

4. In an ignition system for a fuel burner, in combination; mechanism for igniting the burner fuel comprising means movable to operative position to discharge ignition fuel to ignite the burner fuel; means movable to operative position to ignite said ignition fuel; and means for advancing said two means to their respective operative positions and for retracting said last mentioned means to a position out of range of the burner and ignition flames and for independently retracting said first mentioned means to a position out of range of the burner flame.

5. The combination defined in claim 4 in which there is provided means for preventing discharge of ignition fuel unless said means for discharging said fuel is in normal operating position.

6. The combination defln'ed in claim 4 in which there is provided means for preventing flow of ignition fuel before said means for igniting it is in operation.

'7. The combination defined in claim4 in which there is provided means for shutting off .flow of ignition fuel on loss of ignition; said means comprising an electric eye in the path of radiant energy transmitted from burner fuel combustion.

8. In an ignition system for a fuel burner, in combination; mechanism for igniting the burner fuel comprising means movable to operative position to discharge ignition fuel to ignite the burner fuel;' means movable to operative position to ignite said ignition fuel; and means at all times under control of the operator for advancing or retracting said ignition fuel discharging means and for independently advancing or retracting said means for igniting the ignition fuel.

9. In an ignition system for a fuel burner, in combination; mechanism for igniting the burner fuel comprising means movable to operative position to discharge ignition fuel to ignite the burner fuel; means movable to operative position to ignite said ignition fuel; means at all times under control of the operator for advancing or retracting said ignition fuel discharging means and for independently advancing or retracting said means for igniting the ignition fuel; and means for preventing the flow of ignition fuel until said means for igniting it is in operation.

10. The combination defined in claim 4 in which there is provided means for preventing flow of ignition fuel until said means for igniting it is in extended position.

11. The combination defined in claim 4 in which there is provided means for shutting off flow of ignition fuel on loss of ignition.

EDWARD A. HOLDEN.

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