Effect of altitude on capacity & design of steam boiler

[Davkoo]

Hello,

I am wondering if the altitude of the site have an effect on a HFO fired steam boiler capacity and its design.

The reason that I am asking this question is that we intend to purchase a HFO fire steam boiler of 1Ton/hr but the manufacturer is telling us that the 1Ton/hr will not be enough since the boiler is located at a high altitude (approx 1300m) and hence we should opt for 2Ton/hr. The explanation we received from the manufacturer is as follows:

Calculation of burner power:
Boiler capacity=1T/hr
Boiler efficiency=90%
Altitude of site=1276m thus Atmospheric pressure=0.845MPa
Pressure correction factor=1.2

Burner power= 700/0.9 *1.2=933kW

The 1Ton/hr manufacturer's boiler has been designed for light fuel oil and is not suitable for high altitudes.
The furnace size is also not suitable for HFO firing

The boiler should be designed for HFO and at high altitude and consequently their 2Ton/hr boiler will be the most suitable for these conditions.


I am kinda confused on the logic behind this explanation, so if anyone could enlighten me.

Thanks!

 

[chicopee]

the boiler manufacturer is in all likelihood thinking about the burner's output which will require more combustion air CFM for proper combustion for an oil pump designed to deliver a specified amount of fuel oil at sea level. Hence the next size boiler for the increase CFM will need to be greater than that provided for the 1 Ton/hr boiler.

 

[crshears]

Gotta agree with chicopee; the air up there, being less dense, can't support as much combustion, so the next size boiler up would likely have the bigger flue cross-sectional area needed to pass the required air without engendering excessive frictional losses. The size of burner on the other hand should not need upsizing from the original.

A question worth asking, though, is whether there is some margin left in the boiler steaming capacity over and above the peak expected load; if so, depending on just how much margin, it might be possible to use the original size boiler but place an upper limit on the fuel firing rate so as to not exceed the amount of air available.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[EmmanuelTop]

One thing that changes with elevation is actual kg/h of combustion air delivered by the fan. The fan always pushes constant volumetric flow, so as the elevation increases the density of air and Oxygen content decrease, resulting in smaller mass flow of air/Oxygen to the burners.

http://www.higherpeak.com/altitudechart.html

http://www.engineeringtoolbox.com/standard-atmosphere-d_604.html

I'm still not sure though if this calls for a boiler double the size. It just seems they don't have the right equipment for you available off the shelf. And it is not designed for HFO, and not for high altitudes. Perhaps you can talk to other potential suppliers.

Dejan IVANOVIC
Process Engineer, MSChE

 

[MJCronin]

You probably will not need the full capacity of the new boiler at all times. For the 2TPH boiler option, I assume you will be running at significant turn-down

I would be very interested in the partial capacity of both boilers offered boilers at your elevation

Additionally, what is the fuel efficiency at the various offered partial efficiencies ?

Can you meet the license emissions requirements if you need to run the 2 TPH boiler at partial capacity ????

Tell us more about performance .....

MJCronin
Sr. Process Engineer

 

[chicopee]

Your are probably buying a package boiler, so if you stayed with that same rated boiler, you could change the burner heat output by reducing the oil consumption, however, you will not get the desired steam output. While the 2T/hr steaming capacity may seem excessive, it does allow you flexibility to increase productivity.