Ignition of vegetable oils under pressure ?

[Externet]

Hello.

How to find at which pressure, which edible oils ignite/decompose ?  Where to look for such data ?

Say plain soybean oil; will it withstand being pumped/compressed at 6000 psi / 400 atm ?  And other edible oils...

[Sensei]

1 hour ago, Externet said:

How to find at which pressure, which edible oils ignite/decompose ?  Where to look for such data ?

Say plain soybean oil; will it withstand being pumped/compressed at 6000 psi / 400 atm ?  And other edible oils...

...you need oxidizer to have ignition...

 

 

[OldChemE]

Pure vegetable oil is usable in diesel engines.  That does require oxygen (as noted by Sensei).  Ignition under those conditions is achieved a t 15-120 atm.  For ignition or decomposition without oxygen it will depend on temperature as well as pressure-- so there is no single correct answer.  While I do not know for certain. I suspect that since the oil is essentially not compressible, it will not significantly heat up as it is compressed and therefore high pressure alone will neither cause it to ignite nor decompose.

[MigL]

I guess that's a good thing.
Reduces hydraulic systems fires.

[StringJunky]

14 hours ago, OldChemE said:

Pure vegetable oil is usable in diesel engines.  That does require oxygen (as noted by Sensei).  Ignition under those conditions is achieved a t 15-120 atm.  For ignition or decomposition without oxygen it will depend on temperature as well as pressure-- so there is no single correct answer.  While I do not know for certain. I suspect that since the oil is essentially not compressible, it will not significantly heat up as it is compressed and therefore high pressure alone will neither cause it to ignite nor decompose.

Oil needs to at least be aerosolized for it to ignite under pressure, doesn't it? Gasoline will autoignite at 234psi, apparently.

[studiot]

15 hours ago, OldChemE said:

Pure vegetable oil is usable in diesel engines.  That does require oxygen (as noted by Sensei).  Ignition under those conditions is achieved a t 15-120 atm.  For ignition or decomposition without oxygen it will depend on temperature as well as pressure-- so there is no single correct answer.  While I do not know for certain. I suspect that since the oil is essentially not compressible, it will not significantly heat up as it is compressed and therefore high pressure alone will neither cause it to ignite nor decompose.

Yup +1

Used to be one of the standing instructions for wartime foraging (for fuel)  -  find some cooking oil, preferably clean.

[Externet]

Thanks, gentlemen.

Do you see a convenient way to compress air with no toxic contaminants as from synthetic/mineral oils ?

 

The intention is to explore using a hydraulic pump to compress air above oil surface.  Is there such contraption in the market ?  Using water could  corrode the pump.

 

[John Cuthber]

What flow rate are you looking at?
For a few ml/min you can use a 2nd hand HPLC pump.
However, remember that a 6 KPSI liquid reservoir  that bursts just spills oil and makes a bit of a mess, but a vessel containing air at that pressure is a bomb.

 

The pressure won't affect the oil.

[Externet]

Thank you.  25 litres/minute.  Am very aware of dangers for gases under high pressure.

Lubrication in an air high pressure piston compressor I had took a very special synthetic oil MIL6085A  to avoid it from combusting as diesel fuel when exposed to high pressures and destroying the compressor;  and wondered how worse would the similar risk of vegetable oils be.

[John Cuthber]

400 bar is  40 Mpa
That's 40 MJ/ m3 or 40 KJ/ litre

25 litres per minute at that pressure is  40,000 * 25 i.e. 1 MJ/ min

16.7 KW of power at 100 % efficiency.

At any credible efficiency it's not going to be the pressure that causes problems, but the temperature rise will set stuff on fire.

 

What are you planning to do with about 20 horsepower of compressed air?

 

 

Edited September 2, 2020 by John Cuthber

[Externet]

Thanks.

25 litres per minute is the atmospheric air pressure inlet before compression.  Like at start of every cycle; 25 atmospheric litres are fed above the oil surface, then compressed and delivered trough a non-return valve and 25 more litres are admitted for the next (1 minute) cycle.

25 l/min is not the flow at 6000psi.