Efficient power production requires plant operators to monitor boiler tubes for slag deposits that prevent boilers from running at peak efficiency. Proactively maintaining boilers helps plant operators to improve boiler uptime by reducing the number of manual cleaning cycles and decreasing tube erosion that may be caused by excessive cleaning.
“In the past,” says Lenny Shaver, director of business development with LumaSense Technologies, “this process was performed manually by operators who viewed the combustion process and internal components of the boiler through observation ports. Not only is this not accurate or repeatable, it is also hazardous since boiler temperatures are often as high as 1100°C. What makes it even more complicated is that the human eye is sensitive to light from between 400 and 700 μm, so boiler tubes cannot be accurately visualised during the combustion process.”
To overcome these problems, LumaSense has developed BoilerSpection for continuous infrared (IR) imaging inside the boilers. The system uses a 320x240-pixel camera with 0,08-K sensitivity and 3,9 μm bandpass filter to image boiler tubes during the combustion process. The imaging system is fitted with a borescope that is placed through the observation port of the furnace and the camera system is then mounted to this external port. Cooled air is passed through the borescope and the camera housing to lower the temperature of both the lens and camera and allowing the system to be purged of any contaminants that may adversely affect the operation.
Images captured at up to 30 frames/s are transferred either digitally over an Ethernet interface to a host PC or via an NTSC interface to a colour monitor. In this way, images can be processed and displayed on the host PC and simultaneously viewed in real time. After images are transferred, they are processed to determine specific characteristics.
To check the build-up of ash and slag, for example, specific regions of interest within each image can be programmed so the operator can monitor how the temperature within them changes over time. Based on these comparisons, the system can be used to automatically alert an operator, trigger an alarm, or control cleaning equipment on the boiler.
By monitoring these images over a specific time period, the system also provides data on how the coal burning process is performing, which helps to maximise the efficiency of the entire process. Historical data can be crucial for evaluating the effect of other changes to the process, such as new fuel sources or maintenance to the burners or coal pulverisers.
To further extend access to images captured by the IR cameras, the host PC software broadcasts the images as streaming JPEGs to a Web page, any user that is granted access on the plan network can view the images using via browser.
The system is already in use at a number of coal-powered facilities. One such facility, Alabama Power’s Miller Steam Plant, has deployed numerous cameras to monitor two of its four 720-MW boilers. The 12 storey boilers each use six BoilerSpection cameras to monitor the combustion process at various locations.
Prior to using BoilerSpection, the Alabama plant operators estimate they performed approximately 51 de-slag operations on the boilers annually. During a six-month period using the BoilerSpection system, only 12 of these processes were performed, resulting in huge savings to the site. The plant is now planning to outfit its remaining two boilers with the vision system.
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