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I'm going to visit flare stack unit in a gas plant in another two weeks. My client gave some information that the current flare which was operated since 1992 (without blower) is having black smoke issue.

Can anyone share what can be the possibilities of having black smoke? thanks

RE: Flare

A change in what they're flaring? Something with more hydrocarbons perhaps?

If the stack mixes air with the flare medium it could be a failed blower. If it's velocity drafted the air inlets could be clogged with debris like bird nests, rat nests, bats, etc. As can be the inlet on a forced draft blower.

If there is an "assist" fuel it could be a valve is not working the fuel is absent so the flare is way under temperature preventing a complete burn.

A change in the ambient should be considered. Could be the flare medium is condensing in the plumbing and piling up somewhere.

A temp sensor could be bad so the flare isn't controlled or augmented correctly.

Of course someone may have "turned a knob" somewhere too.

Be interesting to hear what you find.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Flare

If this is related to you other query where the flare tip is designed for 1.25bcfd, it is very likely that this flare is operating at high turndown in normal operations ( low rate operational vents + some leaks ). Hence the black smoke - incomplete combustion of low flow flare stream due to insufficient aeration.

This problem may be made worse if these operational vent streams are high molecular weight.

Would suggest steam or air assist for these normal operating vent streams.

RE: Flare

Both posts thus far are spot on. Typically,when the flare tips have degraded, or there is change in service conditions or composition of the flared gas,then you will have incomplete combustion indicated by black smoke.

The reason for the change must first be understood. So check condition of the flare tips and gas composition.

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