Here is a great article from Industrial Fuels and Power Magazine, explaining fire and explosion risks in coal fired power plants, but relevant to all industrial processing plants with combustible dust. Topics include Understanding, Measuring and Reducing Risk. Utilizing Technology to help Mitigate. Understanding Layers of Protection. Successful Combustible Dust Risk Management. A good read...
An explosive issue | Industrial Fuels and Power
Geof Brazier and Mitch Rooker, members of the US-based NFPA committee on explosion venting and protection systems discuss coal dust explosion risks in power plants.
In February 2009, a silo at a coal-fired power plant exploded, severely injuring six workers and resulting in US$300,000 in fines. This recent power plant explosion, located in the Midwest United States, serves as another dangerous reminder of the risks faced by power plants that handle combustible coal dust.
Coal handling, processing and storage systems can produce hazardous conditions with the potential to produce a dust explosion. Explosions occur as a result of ignition of a combustible material (dust, gas, or vapour) when mixed with oxygen, typically that which is present in the air. When this takes place inside a confined enclosure, such as a dust collector or a conveyor gallery at a power plant, a rapid pressure rise is developed in addition to the expected flame of combustion. This pressure could develop to over 100psig in a fraction of a second if the dust explosion is not mitigated in some way, exerting destructive forces within a few milliseconds that will place both personnel and equipment at risk. Examples of potential ignition sources within the coal systems of a power plant are:
• tramp metal producing sparks within milling, grinding and conveying systems
• pyrites producing impact sparks
• static electricity
• hot surfaces
• smouldering fire nests which can self-ignite at relatively low temperatures, as low as 160°C, compared to a dust cloud self ignition temperature as low as 440°C
• easily ignited pockets of “coal gas” that can generate a secondary dust explosion.
In this recent example of a combustible dust explosion within a power plant, the event occurred at a silo used to collect fugitive before the dust is then used as fuel. Contract workers were onsite setting up scaffolding on the outside of the silo when the explosion occurred. Flames, embers and dust rained down on the workers causing severe burns which required hospitalisation.
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