Gas Pressure required for generator

[digimart]

Hi,
I am planning a project, whereby a biogas unit be setup for producing gas through cow-waste and other organic wastes.
The gas thus produced will be used to run a power generator ( NG generator ).
The generator is to be of power rating 15 KVA.
Please advise, how much gas pressure be required to run a 15KVA power generator ?

Thanks

Omar Sharif
Digimart
Lahore, PK

 

[daddles]

I doubt that's the proper way to look at things -- you can run one from a variety of pressures. It's likely that the mass flow will be the thing that's important. You can make back-of-the-envelope estimates as follows. Many hydrocarbon fuels (gasoline, diesel, etc.) have on the order of 30-40 MJ/kg of energy in them as the heat of combustion. Since 15 kVA is about 15 kW or 0.015 MW = 0.015 MJ/s, you can then get that the mass flow will have to be about (0.015 MJ/s)/(30 MJ/kg) or 0.5 g/s. Of course, this is at 100% efficiency, so you'll want to multiply by the reciprocal of efficiency. If the efficiency is 15%, then the mass flow rate is 0.5(1/0.15) = 3.3 g/s.

Anyway, that's how I'd get some estimates. Then you'll have to make some calculations to estimate what pressures you'll need to get that flow rate assuming some piping/pumping system. It's probably mostly straightforward engineering; you can look up the stuff you need in e.g. Perry & Chilton's "Chemical Engineering Handbook".