Modular Boilers Exhaust design

[rahim16]

Hi Guys,
I am looking assistance in finding exhaust header & stack sizes for 3 modular hot water boilers. Each boiler has 24" exhaust flange. I am planning to breach them in one common header & then connect to stack.
I have existing 2 stacks available each 16" big. How I find the common header size from 3 boilers exhausts & stack size. Can I use two stacks connected with one common header, this way size for required stack will be divided in two.
Appreciated for suggestions & any tech referneces.
Thanks

 

[athomas236]

rahim,

More information is required, what are exhaust gas flows and temperatures, lengths of ducting?

athomas236

 

[rahim16]

Thanks for the response. I am sorry I don't have exhaust gas details as I am choosing the boilers directly from vendor catologue, capable of providing required duty. What I know is the exhaust size of each module (24").
The 3 boilers will be fitted in a boiler room (in basement) having 28'X19' space, while each module is 5.5'X4.5' in size. The two existing stacks (16" each) is located on opposite corner of room.
Again I will ask in general, can we connect two stacks with one common exhaust header (each on two ends), this will divide the exhaust gas into halves & stack size will be half.
Thanks agian
rahim

 

[pmover]

Forced draft, induced draft, or natural draft boilers?

sorry, ya need to provide the data athomas236 stated or at least provide the boiler duty.

good luck!
-pmover

 

[rahim16]

Hi,
Guys appreciated your help. Its natural draft & 3 modular boilers each of 49 H.P.
Regards

 

[athomas236]

rahim,

Here are some numbers for you to think about:

49HP @ 33472BTU/h for 1HP = 1.64million BTU/h=0.4806MW

With boiler efficiency of 75% and GCV of oil of 41MJ/kg, fuel consumption is 0.4806/(41*0.75)=0.0156kg/s = 124lb/h

With 4% O2 in flue gas (dry volume basis) ratio of flue gas to fuel is 18.06, so flue gas flow is 2240lb/h.

With flue gas temperature of 300C, gas constant of 286.7J/kg K and limiting gas velocity of 15m/s, the required duct diameter is 8 inches.

Of course all these numbers are all rough estimates and are made without any knowledge of your actual plant, but at least you have numbers.

Regards,

athomas236