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Fly Ash Silo Explosion

Fly Ash Silo Explosion

Fly Ash Silo Explosion

A silo holding fly ash exploded the other day. Blew the roof off and landed 250m away. News story linked below. I read another story that said the silo was pressurized. Not so much an engineering failure, but maybe a failure to provide some engineered controls to prevent this.


RE: Fly Ash Silo Explosion

There are several different chemicals involved with fly ash, depending on the coal from which it came. In particular calcium oxide can be a very beneficial ingredient for use in concrete mixes because it combines with water to create a strong bonding material when then combining with carbon.. It might have happened that some water got into the silo and started the reaction of that first combination, which can be very violent.

RE: Fly Ash Silo Explosion

I've never heard of fly ash dust being explosive, but it is typically moved around using air slides, etc, and the compressed air supply can be a source of energy to cause structural damage.

I've seen a case where they blew the lids off a bank of four inter-connected cement silos by running the air slides over a weekend to de-humidify the silos at the end of construction before they went into service, but they hadn't installed the roof-top pressure relief valves. Even though the volumetric rate of air being introduced into the silos was low, it "inflated" the silos over time until the seam weld between the roof and the wall split, venting the silos. No-one was on site when the lids blew in the middle of the night - the steel plate roofs stayed attached to the tops of the silos, but a lot of ancillary steelwork and piping was blown off.

In another incident (at a different cement plant), the big dust collector (about 2 m x 2 m x 2 m in size) on the top of a large concrete silo was blown clear off and landed about 50 metres away. No-one was injured, which was quiet amazing. We struggled to work out what would cause such an explosion in a cement silo. Eventually, the maintenance team admitted that they had been using explosives inside the silo to "rattle the walls" and dislodge the caked-on cement which had built-up and adhered to the silo walls. I guess they used a bit too much gelignite that day!


RE: Fly Ash Silo Explosion

I wonder if there's any chance that there was some waste incinerator ash mixed in? There was an explosion a year or two ago on a ship in the UK loaded with incinerator ash that had got damp while stored in a barn. The water reacted with metal residues and the resultant hydrogen did what it does best once able to accumulate in the ship's hold.


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