Inter-Distance between two flare stacks

[Sharjeel39]

I am looking for a standard / rule of thumb regarding placement of Amine acid gas flare and Common flare stacks Is this possible to place them close to each other, is their any standard practise that limits this placement.

[Sahiba]

Distance of flares is limited from heat released by the flares. See API 521 and 537

[mh_mahmoodieh]

i am working in a plant which has a stack with 3 flare one acid and 2 others

[Processor]

As far as I know, no standard directly addresses this issue. However, such information might be available in practices developed / followed by few of the companies like Fluor or JGC etc.

In case of acid gas flare (it shall be incinerator if H2S is higher than certain level) main concern is to keep the Ground Level Concentration less than the allowable limit. Dispersion study is performed for such calculations duly considering certain variables like wind speed, wind stability class etc. In this way height of stack is finalized.

Similarly for flares, main concern is to keep the ground level as well as sterile area boundary radiations within allowable limits at peak load. In this way height of flare is finalized.

In case their are multiple stacks whether two flares or one flare and one incinerator, then there are two options:
1- Place all stacks side by side (with common support) i.e. zero dostance between the stacks. In such cases, height of all stacks are kept equal i.e. equal to the height of tallest stack. Main objective is to avoid flame impingement from one stack over the other. Main advatage is requirement of lesser ground area (i.e. sterile area). While disadvantage is unnecessary high elevation of few stacks which may unlikely result in higher dia. requirement due to highback pressure. Radiation as well dispersion profiles are estimated for the worst possible cases (like simultaneous flaring thru two or more stacks).
2- If land availability is not an issue like plants are in deserts as in middle east, then this option is to keep the stacks at such a distance that there sterile areas don't overlap.

In case of different independent trains, generally option 2 is preferred while in case of single train or multiple stacks in a single train, option 1 is preferred.

Acid gas stacks are of CRA like SS while flares are of CS (except tip), so incase of side by side configuration of multiple stacks where atleast one stack is of acid gas then corrosion implications on flare stack also need to be addressed.

Generally acid gas flowrate is much smaller than main flare load (peak load), further acid gas incinerator also require refractory, so in case of incinerator, it is not economical to unnecessarily increase its height / dia. to match with flare height.

Hopefully I have answered oratleast addressed your query. Sterile area radius has not been specified in API or other standards. It varies from company to company (at expense of height) and is different for onshore and off-shore applications.

[josefreitas]

I propose an idea: use the thermal energy on the flare to produce electricity. 460 m3/h of flare gas normaly give 2,5 MW of electricity power. There are many projects that use this soluction.