Smokeless flare with compressed air supply 1

[PAN]

I have read API STD 521 (5th edition). There is only one paragraph indicated about high pressure air for prevent smoke prevention.

After consult the flare vendor, almost all famous flare vendors commented that I can not meet Ringleman 1 for this design.

I realized that this approach is less common because compressed air is more expensive than steam. However, I would like to discuss with the one who have experience in this design. If it cannot meet Ringleman 1, why API committees add this paragraph in 5th edition?

Please comment.

 

[Flareman]

Pan
There are a number of problems with compressed air as a smoke suppressant
- unlike steam it does not reduce the flame temperature so it is not as effective in slowing down the chemical action of producing carbon in the flame,
- in fact it speeds up combustion and increases the flame temperature so, to be effective, it needs a significant proportion of the stoichimetric quantity
- steam might be effective with around 0.4 kg of steam per kg of gas but air might need as much as 6 kg air per kg of gas to have an equivalent smoke suppressing effect,
- air injected at pressure will have a benefit because of the high velocity energy, but the cost of compressed air in quantity is prohibitive
- most air assisted flares are specially designed to use low pressure, high volume, fan-blown air rather than compressed air which minimizes the horsepower needed to move the air
documents like RP-521 include it because it is a possible technique, but the efficiency is poor and your specific case may just need a lot more air than is practical.

David

http://www.flareman.com

 

[PAN]

David,

Thanks for your advice. I started with API 521 because, it changed from "recommended practice" to "standard" in 5th edition. In my case, there is no steam on platform. The compressed air concept was used several years before I got the work here.

API refers to the required air pressure ~7 barg. At first, I understand that this is fixed pressure for any flare gas rate the high pressure air will suck the air surround flare tip for complete combustion. However, a manufacturer advise me that I can varied the air pressure with the changed of flare gas and smokeless condition. It seems that 7 barg is maxmimum pressure. However, there is no information about the required minimum pressure.

Anyone who has expereince in this design, please comment advise me about engineering references for the subject.