Combustion Calculations - Boilers Biomass

[fritzgrey]

Hi,

I would like to do a combustion calculation from first principles to determine % by volume of Carbon Dioxide and Oxygen in the flue gas (Exhaust gas) of biomass power station boilers.
The following is the breakdown of Pine (as received around 30% moisture content)

Carbon 36%
Hydrogen 4%
Oxygen 30%
Nitrogen 0%
Sulphur 0%
Moisture 30%

For a biomass fired boiler on a fixed grate I can work on 120% excess air (as opposed to around 40% for coal and 25% for oil).

Unrelated useful info is that for the above fuel the Net average calorific value is around 11.75 MJ/kg (if it was completely dry and had no ash the Net calorific value would increase to 18.31 MJ/kg).

I would also like you to research the difference between the following:
1. Net calorific value and gross calorific value
2. Net boiler efficiency and gross boiler efficiency

How do I calculate the Net and gross boiler efficiency?

Could someone please point me in a direction??

 

[macmet]

The first thing I'd recommend you do is look at the B&W book "Steam". It's a great book that is surprisingly cheap.

I'm not sure how I'd say it's meant for biomass fuels but the same theories can be applied.

 

[boilerone]

For combustion and flue gas calculations you can find in different books. For detailed efficiency calculation method I'd recommend ASME boiler performance test code PTC 4.1. It also explains net efficiency in section 6.2. In short, net efficiency takes into account of all parasite power consumptions and heat losses so is lower than net efficiency.

 

[25362]

HANDBOOK OF HEAT AND MASS TRANSFER Vol 1, Editor: Nicholas P. Cheremisinoff (Gulf Publishing Co.)

 

[FOURe]

Hi there:

Here is a URL for a free spreadsheet that deals with basic combustion calculations:

http://www.engineering-4e.com/eng-tips/combustionwithplots.xls

Thanks,

Gordan

http://www.engineering-4e.com