What are the reasons that are responsible for back fire or reverse flow of flame in the furnace? What measures should be taken to prevent these incidents?
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02/07/2010
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Jigish Jepal, Yokogawa, jigish_jepal@yahoo.com
The best way to avoid reverse flow of flame in the furnace is to have alarms and interlocks. As mentioned in other reply, maintain negative pressure (draft) inside the furnace. You can have an alarm, if pressure is nearing atmospheric pressure and can have trip if the negative pressure inside the furnace is not sufficient. Earlier fast responding draft pressure transmitters were not available. But now a days transmitters with as fast as 150 miliseconds are available.
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05/01/2010
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Matloob Hassan, National Refinery Limited, matloobhassan296@yahoo.com
if you don't maintain draught in negative position then back fire occurs.
you should check if your furnace damper is in correct position to create draught and second thing is that your fuel gas or fuel oil must be burnt completely.
For fuel oil burning you have to make accurate mixture of oil + automizing steam(MP steam).
the indication of unburnt fuel oil is that dark clouds will appear from your furnace stack and if you don't take attention then after a being of time back fire will occur.
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22/11/2009
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Lindsay McRae, Pall Corporation, Lindsay_McRae@pall.com
Flame instability can be caused by burner fouling if the fuel gas is not properly treated. Low NOX and Ultra low NOX burners are particularly susceptible to fouling due to particles ( FeS corrosion products & sometimes ammonium chloride), and liquid contaminants in fuel gas network because the orifice is smaller (2-3mm) than for conventional burners (6-8 mm). Flame instability, and furnace 'barking' can be prevented by a regular burner cleaning program with some refiners having to clean 20% of burners every month! However, burner cleaning is only addressing the symptom and re-installing burners after cleaning can result in incorrect burner set up if the maintenance people are not taking enough care to correctly re-install the burner tips.
We find that KO pots, mesh pads, cyclonic devices and basket strainers are usually ineffective at properly protecting burners from fouling and resulting flame stability problems. High efficiency SepraSol LG coalescers are widely used to treat fuel gas to remove virtually all liquid aerosol & solid contaminants down to 1um in size.
Refiners with SepraSol LG coalescers installed find that the need for a regular burner cleaning program is reduced or eliminated altogether which creates safer furnace operation as flame stability problems can require regular burner cleaning to avoid burner flameout and potential catastrophic failure of the furnace (explosion). I might add also that the pilot burner can be protected with small fuel gas filters or coalescers also.
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22/11/2009
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
I would first be sure that you are not overloading the furnace in terms of available draft. Your furnace manufacturer can calculate the draft based on the current operating conditions. Then you will know if you are on the ragged edge of draft availability.
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