US3697229A

US3697229A - Automatic ignition system for flaring waste combustible gases

Info

Publication number: US3697229A
Application number: US75542A
Authority: US
Inventors: Donald J Frey; Warren P Opp
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1970-09-25
Filing date: 1970-09-25
Publication date: 1972-10-10
Anticipated expiration: 1989-10-10
Also published as: CA935899A

Abstract

AN AUTOMATIC IGNITION SYSTEM FOR FLARING WASTE COMBUSTIBLE GASES BEING EXHAUSTED THROUGH A STACK, WHICH UTILIZES AN IGNITOR BURNER WHICH IS AUTOMATICALLY ENERGIZED WHEN GASES ARE PASSED TO THE STACK. A MAIN FLAME SCANNER, IGNITOR BURNER SCANNER, AND A TIMER ARE SO INTERRELATED THAT A SAFE, ECONOMICAL, AND EFFICIENT OPERATION IS PERFORMED.

Description

BEST AVALABLE Y 06!. 10, 1972 FREY EI'AL 3,691,229

AUTOMATIC IGNITION SYSTEM FOR FLARING WASTE COMBUSTIBLE GASES Filed Sept. 25, 1970 64 La o o e {9 45 hn 5 07 887 I INVENTOR. DONALD J FEEY WARREN P. OPP

ATTOZNEY United States Patent "ice 3,697,229 AUTOMATIC IGNITION SYSTEM FOR FLARING WASTE COMBUSTIBLE GASES Donald J. Frey, North Canton, and Warren P. Opp, Simsbury, Conn., assignors to Combustion Engineering, Inc., Windsor, Conn.

Filed Sept. 25, 1970, Ser. No. 75,542 Int. Cl. F23d 13/20; F2311 9/08 US. Cl. 23-277 C 3 Claims ABSTRACT OF THE DISCLOSURE An automatic ignition system for flaring waste combustible gases being exhausted through a stack, which utilizes an ignitor burner which is automatically energized when gases are passed to the stack. A main flame scanner, ignitor burner scanner, and a timer are so interrelated that a safe, economical, and efficient operation is performed.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION The ignition system of the present invention has an ignitor burner positioned in the upper portion of a stack which is automatically energized upon passage of waste gases to the stack, and which is de-energized upon ignition of the combustibles inthe waste gases. Flame scanners for both the ignitor burner and the main gas stream assure safe, efiicient operation.

BRIEF DESCRIPTION OF THE DRAWING The figure is a combined schematic and diagrammatic representation of the improved ignition system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Looking now to the figure, numeral :10 designates a duct through which waste gases containing combustibles, such as blast furnace gas, is conveyed. When these gases are not utilized, such as burning in a furnace, they are generally exhausted through a stack, such as 12, to the atmosphere. In the arrangement illustrated when it is desired to exhaust the gas through stack 12, a damper 14 is opened. Connected to the damper and rotatable therewith is a switch 16 which closes its associated contacts when the damper 14 is in its open position. This energizes the main flame scanner 1-8 by completing a circuit through

conductors

20 and 22 to power source 24.

Upon energization of scanner 18, rod 26 is moved to the right, closing normally open switch 28. Closure of switch 28 completes two circuits, as hereinbelow described. A timer 40 is energized through conductors 37 and 38, and normally closed switch 74. Also, an ignitor burner flame scanner 34 is simultaneously energized, through conductors 32 and 36.

Upon energization of timer 40, a valve 44 in the fuel line to the ignitor burner 46 is opened, for example by a solenoid, by closure of switch 84 upon movement to the left. Closure of switch 84 completes a circuit to Patented Oct. 10, 1972 the solenoid of valve 44 through conductors 50, 52 and 42, 43. Closure of switch 84 also energizes an ignition source, such as spark plug 48 for the ignitor burner 46. This circuit is completed through conductors 54, 56 and 42, 43. Air is being supplied to the ignitor burner 46 continuously by a fan, not shown.

Upon establishment of flame at the ignitor burner 46, the flame scanner 34 will detect such flame, moving the associated switch 45' to its closed position. Closure of switch 45 energizes relay 72 through

conductors

76, 78, and 82. Relay 72 will then open normally closed switch 74, de-energizing the timer 40.

The ignitor burner will then ignite the combustibles in the blast furnace gas flowing up through the stack 12. When this flame is detected by scanner 18, switch arm 26 moves to the left, opening switch 28 and closing switch 30. Opening of switch 28 de-activates the ignitor burner and the ignitor flame scanner. The closing of switch 30 completes a circuit to indicating light 66 through conductors 68 and 70, which lets the operator known that the waste gas is being burned.

The above operation takes place if everything performs as it should. If, for some reason, the main flame scanner 18 fails to detect flame in the main gas stream flow, a different operation takes place. The switch 28 will remain closed, and switch 30 remains open. ,The circuit for the ignitor scanner 34 thus stays energized. Although the circuits for the solenoid valve 44 and ignition spark 48 are tie-energized by opening of switch 74, and thus also switch 84, new circuits for solenoid valve 44 and ignition spark plug 48 are completed through switch 45 and

conductors

88, 89 and 90, 91. This will keep the ignitor burner in operation continuously in the'event the main flame scanner 18 fails to detect a flame.

The above situation can occur either because the scanner 18 is malfunctioning and needs repair or be-v cause the blast furnace gas does not in fact ignite. In any event, the operator will be made aware of the fact that something is amiss when bulb 66 fails to light up. Thus the ignitor burner scanner 34 acts to override the main flame scanner 18 and keep the system in operation even though no flame is detected by the main scanner 18. If at any later time scanner 18 does detect a flame, swith 28 will be opened and switch 30 closed, indicating to the operator that the trouble has been overcome.

An alternative operation takes place if the ignitor burner fails to ignite after a predetermined period of time when it is initially placed in operation. If this happens the ignitor burner scanner 34 will not detect flame and thus switch 45 remains open. This keeps relay 72 de-energized, switch 74 remains closed and timer 40 continues to run. After timer 40 has run for its full length of time, which can be set for 30 or 60 seconds, it moves the switch arm along with switches 84 and 86 to the right and is latched in that position. This opens switch 84, and since switch 45 attached to the ignitor scanner 34 is in its open position, shuts off valve 44 and ignition spark plug 48. The simultaneous closing of switch 86 completes a circuit through

conductors

58, 60 and 42, 43 to alarm light 62 and motor drive 64 of the damper 14. Motor 64 will close valve 14, opening switch =16, thus stopping the flow of gas to the stack and deenergizing the entire control system. Light 62 indicates this situation to the operator, so that appropriate maintenance can be performed.

From the above it can be seen that an ignitor burner has been provided for igniting the combustibles in waste gases at the top of a stack which is highly reliable and efficient in operation. In normal operation as soon as a flame is established in the main gas stream, the ignitor is shut off. If for some reason the main flame scanner does not detect a flame but the ignitor burner is performing satisfactorily, the waste gases continue to be discharged to the atmosphere with the ignitorjburner remaining in operation as insurance. In the event the ignitor flame scanner does not detect flame at the ignitor burner within a predetermined period of time after it is energized, the flow of waste gases to the stack is stopped; and a signal device makes the operator aware of the malfunction.-

What is claimed is:

1. In combination, a stack through which waste gas containing combustibles is to be discharged to the atmosphere, duct means connectedto the bottom of the stack, damper means positioned in the duct means, said damper means having a first closed position which prevents flow of the waste gas to the stack and a second open position whichpermits flow of the waste gas to the stack, first flame detector means located adjacent the top of the stack for detecting the presence or absence of flame in the main stream of waste gas, saidfirst flame detector means being electrically associated with the damper means such that it is energized when the damper means is in its open position, an ignitor burner located adjacent the top of the stack for igniting the combustibles contained in the waste gas, second flame detector means for detecting the presence or absence of flame in the ignitor burner, said second flame detector means being electrically associated with the first flame detector means such that it is energized when the first flame detector means senses no flame, and is de-energized when the first flame detector means senses a flame, said ignitor burner having spark ignition means and fuel supply means, said second flame detector means being electrically associated with the ignitor burner such that when no flame exists in the ignitor burner the spark ignition means is energized and fuel is supplied thereto, and whena flame is detected by the flrst flame detector means, the second flame detector is de-energized, thus de-ener-gizing the spark ignition means and shutting ofi the fuel supply to the ignitor burner.

2. The combination set forth in claim 1, including timer means electrically associated with the ignitor burner which de-energizes the spark ignition means and shuts off the fuel to the ignitor burner after a predetermined period of time after the second flame detector means is energized, if no flame is detected by the first and second flame detector means.

3. The combination set forth in claim 2, wherein the timer means is electrically associated with the damper means such that it closes the damper. means after a predetermined period of time after the second flame detector means is energized, if no flame is detected by the first and second flame detector means.

References Cited UNITED STATES PATENTS 2,306,073 12/1942 Metcalf 250-217 F 2,656,008 10/1953 Engel 23277 C 3,447,880 6/1969 Potts et a1. 431 X 1,473,716 11/ 1923 Willcox 431202 X 2,888,981 6/1959 Ripple 431202 X JAMES H. TAYMAN, ]R., Primary Examiner US. Cl. X.R.

23232 E, 2 C; 43l-5, 14, 60, 71, 45, 202, 51; 26615, 31; 8 R, 18 R; 356-207; 2502l.7 F