4 replies to this topic

[sheiko]

Hello,

Could someone please explain me why do burners manufacturers specify a minimun deltaP between Fuel Oil and steam?

I believe it promotes good atomization and thus good air/fuel mixing, but how does it work and what if the requirement is not achieved?

Thanks for your time and help.

Edited by sheiko, 27 November 2012 - 06:50 AM.

[breizh]

Hi Sheiko ,

This paper may help you .

Breizh

Edited by breizh, 22 November 2012 - 12:01 AM.

[kkala]

1. Let us look at the burner lance presented in http://www.steamesteem.com/?fuel-atomizing/internal-mix. According to the description, oil and steam are met in small peripheral nozzles to form an emulsion, ending to the central lance out. Expansion of this mixture along its way out produces a spray of atomized oil.
2. Perry shows the same burner (Fig 27-27 in 7th edition, Combustion of Liquid Fuels, Y-jet twin fluid atomizer) confirming that steam pressure is maintained 1.4-2.8 bar over the oil pressure. Description says that the liquid fuel stream is exposed to a stream of steam flowing at high velocity in the peripheral nozzles, then it continues as before.
3. "Atomizing fluid ports" (better distinguished in Perry's figure) are narrow steam passages upstream of oil - steam mixing. Steam undergoes a generous ΔP there, to increase velocity during mixing. This ΔP corresponds to necessary excess pressure of steam supplied, seeing that oil and steam have same pressure at mixing point.
4. Above is a personal interpretation and for a specific burner type. If pressure difference between steam and oil is reduced, steam velocity in the small peripheral nozzles (exit ports per Perry) will be less. This can result in non uniform oil-steam mixture, poor fuel atomization and eventually inefficient burning.
5. Injecting steam into liquid fuel as above is the usual procedure. According to info from bids, a few burners inject liquid fuel into steam.
Above is valid for fuel oil burners with steam atomization (most usual case). It does not concern gas burners (Perry, Combustion of gaseous Fuels).

[sheiko]

It's clearer.
I understand that the deltaP is specific to the burner design (manufacturer).
Moreover, the range given by Perry (1.4 - 2.8 bar) matches with the values shown on the burners data sheet I have at hands.
Thanks Kostas.

And thanks Breizh for the pdf (even though I have not found info about steam atomization).

Edited by sheiko, 26 November 2012 - 08:04 PM.

[kkala]

Burner designs are proprietary, including steam atomizers; so deltaP as above varies from one design to another.
I wonder whether this deltaP increases or decreases as burner load gets lower and lower (not having relevant PID available). Probably steam to fuel ratio (kg/kg) increases in such a case, "trying" to maintain high steam velocity in atomizing fluid ports.