Heating the Atomizing Air 2

[gladkenn]

This is just a thought. I am planning to recover heat from continuous blowdown for heating the atomizing air before it goes into the boiler. Will this have greater impact or benefit regarding the efficiency of the boiler?

 

[hacksaw]

no measureable benefit

but your use of the term "atomizing air" is a bit unusual, in that it does not usually enter the fire box as a separate connection. can you elaborate?

 

[gladkenn]

hacksaw,
The boiler is CB600-600-150psig. Before, it fires with bunker fuel but due to environmental restriction it is now firing low sulfur fuel oil(LSFO). The atomizing air is the initial air entering into the boiler combined with the fuel. A secondary air from the forced draft fan then enters forcing the flue gas out to the smokestack. I thought this is elementary?
Anyway, does preheating the atomizing air give any difference?

gladkenn

 

[hacksaw]

the atomizing air goes to the oil gun not the boiler, as such. just wanted to make certain we were talking about the same sort of a system, rather than some new style of a premix burner

improvement, not much at least on a BTU basis, just look at the energy balance.

in the heavier fuels atomizing steam is used, not because of the heat gain but to improve atomization of the oil

 

[rmw]

Heating the atomizing air, assuming you are talking about the atomizing air that goes into the gun as hacksaw states, would increase the volume of the air, which would either increase the pressure drop of the air to the gun tip, robbing the tip of energy needed for atomization, or reduce the air flow (due to flow losses due to increased volume) again penalizing the atomization of the fuel oil at the gun tip.

The atomizing steam regime also mentioned by hacksaw is already sized (piping and gun tubing wise) for the steam at the operating conditions.

So, unless you system was initially designed for preheated atomizing air, (as some gas turbines using heated compressor discharge air are) I wouldn't do it.

There should be plenty of areas where you could recover the waste heat, like, for example preheating the fuel to the gun, rather than the air. Now there is a thought.

rmw

 

[gladkenn]

Rmw,you metioned preheating the fuel. We might have to consider also the flash point of the fuel. LSFO has a lower flash point than the bunker fuel which is why we no longer needed to preheat unlike what we had done for the bunker fuel before.

Anyway I will try other ways of improving our steam system. Thanks alot guys!

gladkenn