Combustion air

[shom]

I need to calculate the air flow (lb/hr) required for burning No#2 oil (Higher calorific value= 20,516 Btu/lb). Here 16.8 lb(allowing 25% excess air) of air is required for burning 1 lb oil. Any help is appreciated.

Thank you.

 

[RossABQ]

What more do you need? I asusme you know the oil burn rate, you have stated the HHV of the oil, and you know the amount of air per pound of fuel. Fuel is somewhere around 7.5 lbs/cu ft as I recall, I can't think what else you need?

 

[25362]

Do you mean that you wish to review the air figure used "here"?

 

[Feric]

Hi there:

Here is an MS Excel spreadsheet that deals with combustion calculations for oil and coal type fuels.

http://engware.i-dentity.com/eng-tips/combustion.xls

Thanks,

Gordan

http://members.aol.com/engware

 

[shom]

Thanks so much for all your responses. The air is heated beforehand in a preheater by steam (maximum flow 250,000 lb/hr) and then fed to the burner. Actually I need the max air flow to this heater which I am trying to figure out from the combustion data.

Is it logical to consider the heated air to give up all the heat to burn the fuel?

heat lost by steam = heat gained by air = heat lost by air= heat gained by fuel
ms(hi-ho)= mf*HCV and ma=16.8*mf
where, m is the lb/hr for steam,fuel & air.

Regards

 

[25362]

In theory the sensible heat of the air is added to that of the fuel to produce a certain flame temperature.

However, the pressure drop and the expansion of preheated air, vs cold air, could lead to upsets in burning speed and rate, subjects that should be discussed with the burner manufacturer.

 

[Feric]

shom:

My suggestion is to plug in the numbers in the spreadsheet.

Thanks,

Gordan

http://members.aol.com/engware

 

[Feric]

shom:

Here are a few plots for ideal and complete stoichiometric combustion of coal, oil and gas with standard air:

I do hope that the above plots will be useful to you.

Thanks,

Gordan

http://members.aol.com/engware

 

[Feric]

shom:

I missed one plot.

Thanks,

Gordan

http://members.aol.com/engware

 

[shom]

Thanks a lot Feric for your plots & also for your spreadsheet where I did pug in my numbers and calculated HHV in Btu/lb. However I calculated the fuel flow from my previously mentioned equation and calculated boiler efficiency that gave me a reasonable figure (74%). Thank you 25362 for your opinion.

Does anyone have idea about the range of power boiler efficiency?

Regards

 

[Feric]

shom:

I glad to be of some help.

http://engware.i-dentity.com

 

[Feric]

To All:

My last post sounds like broken English.

I have to admit that it is just being too fast on the trigger.

It was supposed to say:

"I am glad to be of some help ... "

In the future, I will try to take more time before releasing my post.

http://engware.i-dentity.com