Anyone had experience of classification of hazardous areas for biodiesel (fatty acid methyl ester) vacuum distillation plant?. BD flash point = 130C, BD autoignition temp = 570C. BD vacuum distillation temp = 250C. In my opinion no haz area is created. Vacuum prevents any release of flammable liquid. If it was released it would immediately cool to below the flash point. Can anyone provide info on this
Many thanks
Regards
GF

In my opinion you'd better avoid too much notice of any advice you get here, because you're not showing a P&ID of the whole plant, and you're not mentioning the process conditions during heat-up and shutdown, etc.
For example, the vac pump. Where is that vent?
Does the vent have light ends? Is it a continuous emission?
Is it flammable at any time during the distillation?
That said, I don't have experience of haz areas for biodiesel.
Search LinkedIn for people who have worked on other biodiesel installations.

When I worked for a Fine Chems company, one of the Engineers carried out a classification for a vacuum drying plant. He went through it meticulously. Took him 3 months. We were all gob-smacked that "management" didn't chase him up.
(Cambridge graduate. Always wanted to avoid errors on a site with previous multiple accidents).

I do have experience of biodiesel plant design / operation / HAC and as David wisely says a much more complete picture is required...could you get hazardous areas inside the equipment if air leaks in?

Thanks gents for your comments.
No question .. inside the vessel and the discharge point for the vacuum pump are hazardous areas.
I'm hoping to find example(s) of hazardous area classifications for a biodiesel distillation plant. Assuming it creates a Zone 2 area ("flammable atmosphere could exist under abnormal conditions") .. what radius would it have?

If you can provide some more info we can help. Need to know whether the process will be taking the fluids above Flash Point.

As mentioned by you, flash point of biodiesel is 130C and you are operating at 270C; hence definitely vapors will be there.

However if we talk about the distillation vessel itself, the operation is under vaccum. No probability of flammable atmosphere inside due to absence of oxygen/ oxidant. Hence inside vessel classification can be non hazardous, by maintaining low rate for vacuum failure. Since it is difficult to keep this failure rate low, hence can be Zone 2.


However for vacuum pump, its vent and other equipment it will be necessary to classify.

Biodiesel is above its flash point, so any leakage can cause an explosive volume.
To my opinion no leakage can occur from flanges of a unit under vacuum, instead some air could enter;leakage can occur fromextraction pump seal to the heat exchangers, where temperature gets down under flash point.
Vacuum pump discharge should not be above 40°C, so no explosion risk.
Inside the vessel can enter air from flange leakage, so you should consider what happens inside the condenser, something like vapor concentration vs. temperature.
Sergio Cagianelli
Consultant

Biodiesel is above its flash point, so any leakage can cause an explosive volume.
To my opinion no leakage can occur from flanges of a unit under vacuum, instead some air could enter;leakage can occur fromextraction pump seal to the heat exchangers, where temperature gets down under flash point.
Vacuum pump discharge should not be above 40°C, so no explosion risk.
Inside the vessel can enter air from flange leakage, so you should consider what happens inside the condenser, something like vapor concentration vs. temperature.
Sergio Cagianelli
Consultant

Thanks for the comments
I'm getting the picture that the plant needs to be defined as a hazardous area, Zone 2, and am now trying to formulate a credible release scenario ... something like ... vacuum failure + failure of auto-shutdown system + uncontrolled heating + leak from a pipe fitting??
I wish the standard (AS/NZS 60079.10.1, IEC 60079.10.1) allowed for a more risk based approach. Zone 2 " ... explosive gas atmosphere is not likely to occur in normal operation ..." is a pretty crude/broad definition. There must come a point where the likelihood of a release is so small (several simultaneous unlikely events are required) that the chance of a release is negligible and so no hazardous area is created
Any thoughts?

Hi Graham,
This is my understanding if you follow EI 15. There are some guidelines for each zone i.e.:
Zone 0 is >1000 hours hazardous atmosphere.
Zone 1 is <1000 but > 10 hours
Zone 2 is <10 hours but > 1 hour.

In the old copy I have here it justifies the 1 hr/yr criteria by saying that it is 1E-4 frequency, which combined with ignition probability and occupancy rates meets a risk criteria of 1E-5 in most cases (barring continuous ignition source present, or other dangerous cases)

You would have to check with your own project/plant criteria but you don't necessarily need to define a hazardous area as zone 2 to cater for multiple scenarios (all of low enough probability) occurring simultaneously if the risk is almost non-existent.

Thanks Amiir .. very helpful
I'm not familiar with EI 15 ... me thinks I need to get my hands on a copy
Cheers
GF

Graham,

Did you manage to get your HAC problem resolved satisfactorily?
Do you need any additional support?