Monitoring of flames using optical fibers and video camera vision system

Abstract

This invention relates to a flame detection method and apparatus. More specifically, this invention relates to a flame d on method and apparatus designed for simultaneously monitoring several flames of different types such as pilot flames and main flames of differing sizes and intensity. These detected flames can be in one combustion unit or in several combustion units such as industrial furnaces or ground flares. The underlying principle of the invention is to collect and transmit light from each of the flames by use of optical fibers and to insect the collected light by a video camera vision system at the other end of the optical fibers and to transmit the “live” images of the glows as well as the “on / off” status of the burners to the control room, through modern electronic communication techniques such as Ethernet and / or wireless radio units.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] U.S. Pat. No. 6,278,374 B1 [0002] USPTO's Number for the provisional application of this patent: 6052 0535 [0003] Provisional Application filing date: Nov. 17, 2003FEDERALLY SPONSORED RESEARCH [0004] Not applicable SEQUENCE LISTING OF PROGRAM [0005] not applicable BACKGROUND OF THE INVENTION [0006] Heaters, boilers, furnaces, flares, ovens, incinerators, driers, heated baths and other combustion equipment have single or multiple burners. The term furnace will be used in all of the text below to cover all the combustion units mentioned above. Some large heat capacity burners, both gas and oil fired, modulated and fixed capacity, are fitted with smaller heat capacity pilot burners. In many cases both Pilot and the Main flames are continuously monitored for the safety of the furnace. [0007] Well-known flame detection methods are Ultra Violet scanners, thermocouples and flame rods. The currently available flame detection technologies have se...

AI Technical Summary

Benefits of technology

[0028] The present invention relates to a new technology in the furnace flame detection, both in principle and in the choice of detection equipments. Optical fibers are used to collect the light from several flames from the burners at the furnace end and transmit the light through a desired distance to a video camera box, which is protected from external light sources and located in a safe area and convenient place. Thus the operator at the control center can conveniently and continuously view the “live” images of the glows and the status data on the burners.

[0034] That it can reliably and accurately sense small variations in the intensity of the flame as evidenced by the intensity of illumination, and

[0042] 2. The camera views several tips simultaneously. The camera's functionality is confirmed as long as the monitor displays some glows from the fiber tips.

[0051] Another big advantage of this invention is that each burner can be fitted with 2 optical fiber heads, for a small cost addition, for back up and for redundancy. The second set of fibers from all the burners can be viewed by a duplicate camera system and give the plant additional margin of safety.

[0057] Yet another preferred embodiment of the present invention provides a method for monitoring the status of flames of a plurality of burners from several independently operated combustion units. Optical fibers are run from all the burners of the different said combustion units, (from both the main flame and the pilot flame of each burner if so required), to the dark chamber. A digital image of all the “full moons” is acquired by the video camera. The decision making process to declare a flame failure is the same as described in the first embodiment above. The monitor screen can have split sections to show the furnaces as separate entities on the screen; monitoring results on flames belonging to each furnace can thus be seen separately. Such split screen vision technology is readily available.

Problems solved by technology

They fail frequently if the flame intensity or composition of the fuel fluctuates and / or dust settles on the viewing glass of the scanner.

This is a big limitation.

Oil fired burners, which make a good percentage of burners in the world, cannot use them.

In addition, the sensitivity of the UV scanners reduces with shelf life and the operating life.

The UV scanning technique also presents great difficulty when desired to monitor pilot flames.

Due to the small size of the pilots and their inaccessible locations, great difficulties are encountered in finding a suitable location for the scanner.

But continued exposure to flame and high temperatures leads to thermal degradation leading to extremely short lifespan, typically a few months.

Replacement and even maintenance are difficult since the sensor locations and the insulated mounting arrangements are difficult to access.

Such shutdowns result in high operating costs for the facility.

Thermocouples fail after sometime due to their close proximity to the flame and pose similar difficulties as Flame Rods to access and higher costs.

All the abovementioned flame sensors have the common disadvantage of requiring multiple sensors for multiple burners, since these sensors are capable of monitoring only one flame at a time.

One disadvantage of this method is the unavailability in practice of such view glasses in desirable locations.

A large number of existing furnaces do not have sight ports where the camera can be mounted to view the flames.

Often existing or planned sight ports are not ideally located to view all the burners.

That makes the method difficult to apply especially since installation of a new sight port can be done only when the furnace is shut down.

This difficulty results in continued reliance on less reliable UV detection methods for flame monitoring and control, raising safety concerns.

Even when such maintenance shut down is scheduled, mounting of the camera in a suitable location requires extensive advance planning and significant additional costs in the necessary extension of the shut down period (leading to charges for lost production), as well as in the costs of the modification itself.

They add to the cost in addition to a lot of engineering and planning.

This also increases the system cost considerably.

Additionally, in many cases, the field of the camera does not permit the entire range of burners to be viewed comprehensively and allows viewing only a few burners well.

This will increase the cost and make the controls more complicated.

Another disadvantage of the before mentioned patent is that in many furnaces, such as industrial boilers, code regulations require both the pilot flame and the main flame of all burners to be monitored directly.

A camera directly viewing the flames may find it difficult to distinguish the presence of small pilot behind larger main flame envelopes.

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