What can I do to reduce the likelihood of an explosion?
The key to reducing the probability of a coal-fired power plant fire or explosion is preparation. Fires generate from several different sources: coal dust, oil, or hydrogen. It is necessary to be knowledgeable about fire ignition in order to avoid it. The main causes of plant fires and explosions are coal dust, equipment error, and human error. Training plant personnel on proper housekeeping and machinery maintenance along with proper fire protection will greatly reduce the chances of a fire or explosion.
Housekeeping
Without a stringent housekeeping regimen, even the most advanced fire suppression system will not be able to stop an explosion from happening. A documented housekeeping routine is necessary to reduce the odds of a fire or explosion. According to the Mine Safety and Health Administration, with a robust housekeeping schedule, the fuel source would be eradicated, eliminating secondary explosions. Secondary explosions have the largest death toll of all coal-fired power plant combustions.
Dust collectors alone will not adequately dispose of dust; in fact, 40% of fires and explosions were caused by the dust collectors. An effective option is to wet the dust to weigh it down so it does not float into hidden crevices. Because the dust is microscopic, microscopic water spray must be used. Plants should use a wash down system to keep coal dust at a minimum. Industry surveys have shown that plant personnel who have utilized wash down systems have been happy with the results.
During an outage, it is essential to clear dust completely from bunkers, silos, and conveyor belts. Idle dust can explode. When preparing for the outage, wash down all walls of the bunkers or silos to eliminate the source for explosions.
Carbon Dioxide
If dust cannot be completely cleared, another option is to pump carbon dioxide into a sealed bunker or silo. The carbon dioxide would eliminate the possibility of dust combustion by taking away its oxygen.
Design
A bunker or silo should be designed as if a fire is imminent. Access points should be installed on several levels to allow for entrance of fire extinguishment tools. It is important for the water to directly contact the source of the fire in a bunker or silo. Another design choice that will reduce the chances of a fire or explosion is a cone shaped floor or a free flow bottom cone. Many bunkers or silos have a funnel-flow pattern that occurs when the walls inhibit the coal from flowing freely. Most coal will flow down the center, while the remaining coal that has accumulated on the sides will linger stagnantly. Stagnant coal can create a heat source. The key to reduce the likelihood of a bunker or silo fire is in the design.
What are my fire protection options?
Detection Devices
Several different detectors are needed throughout the facility, depending on the location. Silos, bunkers, and dust collectors are at a high risk for explosions due to the congregation of PRB dust. It is necessary to choose the correct detection device. Carbon monitors, infrared scanning, temperature scanning, or linear heat detectors are adequate options. Linear heat detectors, such as Protectowire, can detect heat along a length of space, instead of a singular spot. This works extremely well along conveyor belts, which are a major fire hazard because they easily create heat through movement or from idler or roller bearing failure.
Fire Suppression Systems
Sprinkler systems must be installed throughout a plant. The main fire culprits are silos, bunkers, conveyor belts, crusher buildings, dust collectors, coal pulverizers, turbines, generators, and transformers as seen in Diagram B. Hazard location will determine the best system type. Temperature controlled locations are best protected by a wet-pipe system. Non-temperature controlled areas need a dry-pipe system to avoid frozen pipes. Transformers and other areas where quick suppression is important and water damage is not a concern are effectively protected by deluge sprinkler systems.
Diagram B
Three main suppressants dominate coal-fired power plants: water, CO2, foam and/or f500 solutions. It is essential in coal dust-related bunker/silo fires to use a piercing rod or inerting system to smother the fire at its source. In all other areas of a plant, various types of sprinkler systems will effectively suppress fires.
An integral part of finding a solution to fire protection is choosing a company with experience and expertise to implement a comprehensive system. Fire protection providers must have the design capability to plan custom solutions for site obstructions and plant nuances. Each fire susceptible location of a plant must have a fixed sprinkler system that is designed specifically for that area. High value – high risk facilities are vastly more complicated than other industries; a fire protection solution provider should be experienced in providing fire protection for plant environments to ensure solutions that are suitable for the specific application. With proper housekeeping schedules, diligence, and fire suppression systems, the safety of people, plant, and production is greatly increased.
