Can citric acid really form a dust explosion hazard?

[jakhsl]

I've just read an MSDS which says that citric acid (anhydrous) can form a dust explosion hazard. How true is this? The same goes for sodium methoxide..

 

[unclesyd]

We make several organic acids and anhydrides and all are considered to be explosive hazards in anhydrous form. In this classification there are several parameters that have to met in order for the explosive conditions to exit. The main one is the particle size. In one manufacturing process we go to great lengths to remove fines.
Nearly all organic dust has the potential, given the right conditions, to explode.

 

[ash9144]

I worked in vitamin C plant and yes the dust can be explosive. However the dust concentration has to be so high that it is highly unlikely. Somewhere around 70-80% dust in the air.

 

[25362]

In addition to the necessary conditions for explosions involving dusts as explained above, Crowl and Louvar (Chemical Process Safety: Fundamentals with Applications-Prentice Hall) say:

For most dusts, the lower explosion limit is between 20 and 40 g/m[sup]3[/sup] and the upper explosion limit between 2 and 6 kg/m[sup]3[/sup]

Quoting Lees (Loss Prevention in the Process Industries), they also say

For dusts, deflagrations appear to be more common than detonations. The pressure waves from deflagrations, however, are powerful enough to destroy structures and kill or injure people.

 

[c2sco]

It depends very strongly on the particle size and dryness. If your particles are small, say substantially below 100microns, and dry, then yes it will be explosive at much lower concentrations than 70%! 20-40 g/m2 is a decent guess, and this is quite dense, enought to obscure a light bulb at say 5m away. (Don't try it!!!) Dust explosions are unpredictable and people who operate in lousy conditions think it's all a myth until it happens to them.

There's lots of good info on dust explosions in corn silos in the US.

Deflagrations always occur first (unless you start it with an explosive) but they can change to a detonation eg in long ducts. Either will kill you.

There are lots of good ways to deal with dust hazards, but is all starts with getting the process right and good housekeeping to minimise the dust and its escape.

Stuart

 

[sktestman]

Quote:
Physical Dangers
Dust explosion possible if in powder or granular form, mixed
with air.

http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc08/icsc0855.pdf

It seems likely.

 

[schnipp]

Citric acid dust is explosive in a similar fashion to sugar dust.

It is not as worrisome as say corn starches or corn dust, but still must be considered.

You shouldn't need intrinsically safe wiring in the dry process area. It is a good idea, though, to slightly pressurize the electrical cabinets as the dust can cause havoc on the terminal strips and connections inside.

 

[unclesyd]

One thing not mentioned is that a light accumulation of dust can cause a flash over on the walls and equipment if all allowed to accumulate. The accumulated dust doesn't have to very thick for this to happen.

We have had incidents with an organic acid and a polymer monomer having a blue halo for a couple of seconds. All incidents were on brick walls where the dust has accumulated on the little ledge where the motor was pointed.