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Boiler Horsepower Calculation

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RJB32482

RJB32482

Chemical
Jan 19, 2005
271
Hello,

I'm looking to have someone double check my calculation for the capacity of a 250 BHP boiler assuming:

Feedwater Temperature = 270 degrees F (Specific Enthalpy of the Liquid = 239.17 BTU/lb)
Steam Pressure Desired = 250 PSIG (Specific Enthalpy of Liquid = 381.76 BTU/lb, Latent Heat of Evaporation of Steam = 820.44 BTU/lb)
Boiler Horsepower = 250

So calculate the heat to raise the water to 250 PSIG Saturation Temperature:

381.76-239.17 = 142.59 BTU/lb

Calculate Total Heat:

820.44+142.59 = 963.03 BTU/lb

250*33475 = 8,368,750 BTU/hr

8,368,750/963.03 = 8,690 lbs/hr steam

But the boiler manufacturer we are talking to says that the boiler has an input of 9,900,000 BTU/hr also. This is much different than the 250 BHP rating. I guess we can discuss with them, but thoughts from my calculation based on just BHP and how BTU/hr input calculates to BHP?

Thanks.
 
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RJB
You are missing heat losses and boiler efficiency in your boiler HP calculation. That's why you need about 10MMBtu/hr to get the 250 BHP.

Regards
StoneCold
 
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Boiler horsepower is currently based on either burner heat input or output. The current equivalency is either 41,844 btu/hr heat input or 33,475 heat output from burners. Efficiency of the burners is assumed 80%. Now if you have an older fire tube boiler, the boiler horsepower is based on heating surface and the equivalency is 1 BoHp= 10 sq.ft. of heating surface.
 
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You are calculating the heat output after losses.

The boiler manufacturer is telling you the heat input required to get the output you are looking for.
 
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