2 replies to this topic

[betty]

Dears,

Atomizing steam should be at least 6-7 bar(g) at the burner inlet and at least 1.5 to 2 bar above the fuel oil pressure. Atomizing steam consumption would be about 0.25-0.5 kg per kg of fuel oil. Atomizing steam should be dry saturated or slightly superheated to prevent any condensate formation at the burner gun. Atomizing steam line should be sized considering 0.5 kg per kg of fuel oil consumption.


This atomizing steam is for fuel oil... What about fuel gas?
Regards

[ankur2061]

Betty,

Natural Gas-fired burners do not use atomizing steam.

For fuel oil also you can have a burner which does not require an atomizing media. Such burners are called self-atomizing fuel oil burners where the burner gun imparts enough velocity and shear forces to the entering fuel oil generating fine oil droplets or aerosol which enhances the combustion process inside the fired heater by creating a large surface area for a given volume of oil-combustion air mixture.

Hope this helps.

Regards,
Ankur.

[kkala]

Seeing that topic of heavy fuel oil atomization has been touched, below is a summary on atomizing media to my understanding.
Α. Steam atomization seems preferable for industrial burners using heavy fuel oil No 6, or similar. This is suggested by following.
Α1. Pressure atomization is most effective for lighter fuel oils (Perry, 7th ed, p 27-34).
A2. Although steam atomizing burners are expensive to operate, they are used widely in refineries because they can handle almost any fuel and steam is universally available (Nelson, Pet Refinery Engineering, 1958, p 425).
A3. Mechanical atomization is not used in local refinery boilers, burning heavy fuel oil. Five of such boilers known use atomizing steam for fuel oil. In a black startup (no steam available) diesel oil is burnt, atomized by compressed air. Typical local duty specification for boilers includes the option of compressed air for atomizing fuel oil, never chosen.
A4. Mechanical atomization was used in a rotary dryer of local NPK fertilizers (1976-81). The burner used fuel oil No1, or alternatively diesel. Burning efficiency was rather fair. Required atomizing pressure is reported as 600 - 1000 psig for heavy residuals. Imperfect atomization can result in unburnt fuel oil, which is corroding (Perry, 4th ed, 1963, p 9-27). There was explosion in a rotary drier of another unit, due to unburnt fuel oil accumulated there.
B. Fuel oil No 6 (of max viscosity) needs to be heated to 99-129 oC for mechanical atomization, versus 77-99 oC for steam atomization (Nelson, loc cit, p 72). So even fuel oil No 6 is susceptible of mechanical atomization, but it is not indicated according to above.
Γ. It is noted that in USA fuel oil per ASTM D 396 (No 1 to 6) is almost any fuel (http://en.wikipedia.org/wiki/Fuel_oil), while in Greece ( and consequently in EU) fuel oil concerns only the so called No 1 (180 cSt max at 50 oC) and No 3 (380 cSt max at 50 oC). Heavy fuel oils mentioned here include Greek No 3 and ASTM D 396 No 6.
Δ. Above represents a summary on the topic, useful when writing process duty specs for boilers or furnaces. If there are additional data on heavy fuel oil atomization, please advise to complete the picture, reporting (if possible) references or examples.

Edited by kkala, 25 December 2011 - 04:40 PM.