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Thermal imaging in the protection of coal conveyors

Challenges

Coal starts to oxidize when exposed to air, which induces a temperature rise. However, when transporting the coal to silos, crushers, or boilers with several kilometers-long conveyor belts, spontaneous combustion is even easier than coal pile storage due to the movement. In addition, during the pre-combustion oxidization process, the coal might produce large amounts of toxic and explosive methane and carbon monoxide gases, causing more difficulties to control any subsequent fire.


When the bituminous coal ignites, the fire would not only harm the plant's personnel and likely destroy part of the conveyor system, causing the power generation to stop completely.


The heavy fire of the conveyor belt Hot inclusions in the belt


Solution

Since hot inclusions on coal or coke conveyors can go undetected and the rise in temperature of coal could not be seen by the naked eye, as non-contact remote tools, infrared cameras are the best choice to monitor the coal and belt conveyors to control risks. Infrared cameras should be widely adopted along the belt to monitor the entire coal mass’s temperature during transportation, not just the upper surface of coal, and allow the appropriate measures before causing substantial damage to coal power plants.


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Cameras need to be small enough as the FOTRIC 600 series fixed-mount infrared cameras since under certain circumstances they have to be placed under a belt just beyond the point where the material has been transferred. A surveillance system consisting of FOTRIC cameras with either auto or manual focus can provide stable and accurate 24/7 monitoring. Hot spots can be discovered and localized immediately.



The cameras can be installed independently or as part of a protection system that ensures complete archiving of data, events, and measured values through the FOTRIC open-source API SDK which offers versatile modular functions tailored to users’ demands.


They can see through dust, smoke, rain, and fog even in darkness at -25° to 65°C, which is practical in harsh conditions, meanwhile, 30Hz live streaming with radiometric data can be recorded manually or by an automatic SDK trigger.


FOTRIC 600 cameras have a detection range of -20°C to 2000°C for extreme temperatures e.g. in chemical processing and steel plants, and an imaging resolution of up to 640x480 with a sensitivity of 0.03°C for detecting minute heat anomalies e.g. in storage facilities of coal, Li-ion batteries, and waste, and lens options from 10° to 92°, enough for either distant targets or wide view purposes e.g. in substations, belt conveyors, and manufacturing bases.


Deployment

Infrared cameras need to monitor the entire belt surface and an alarm connecting to an automated control will be raised if any areas reach a designated temperature, which can trigger water sprays or suppression systems (fire extinguisher system), alternatively hot material might be diverted to a safe area for not passing to the next processing stage such as crushers or boilers.


Cameras should be placed in three key locations: 1) In front of the curtain of coal when falling from one section of the belt to another for scanning deeper into the coal to detect hot inclusions; 2) Under the second belt just after a transfer point. The freshly uncovered belt will have an infrared fingerprint of any hot items that have been in contact with the surface; 3) Above the coal conveyor belt to detect hot inclusions on or close to the surface. In addition, the system can be set to monitor equipment temperature too such as conveyor rollers, and thus reduce the fire risk caused by a technical failure.


Cameras can be installed on a fixed mount, a pan/tilt head, or other positioning devices.


The coal conveyor belt monitored by FOTRIC 600 cameras


Benefits

For coal spontaneous combustion, initially, it’s slightly above the ambient temperature, but if left unchecked it can rise to above 400°C, causing the coal to burst into flame. Early detection of any temperature rise is critical to help eliminate costly conveyor belt repairs and reduce downtime.


[1] Thermal imaging systems: Fire protection of stockyards, industrial and security use. https://www.enelex.cz/?page_id=1238&lang=en

[2] Milesight Retransforms Infrastructure for Coal-Fired Power Plant in China

https://www.milesight-iot.com/success-stories/temperature-gateway-power-plant-china/

[3] Coal-fired power plant diagram

https://en.wikipedia.org/wiki/File:Coal_fired_power_plant_diagram.svg



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