Biogas+burners

Biogas need to be burnt in a burner that is designed for the gas. Since biogas usually contains roughly 58% methane and 42% carbon dioxide, it will not burn properly in a normal natural gas burner. The carbon dioxide content means that the fuel/air ratio is increased and also means the flame speed is slower, making flames less stable The properties of biogas are gioven in the table below.

The combustion properties of fuel gases are summerised by the Wobbe number:

Properties of biogas
The attached PDF file lists the various equations required to design a burner: ([|BiogasBurner.pdf]). Using the equations and the properties listed in the table, it should be possible to design a burner that works on biogas.
 * Biogas: assumed 58% CH4 and 42% CO2, saturated with water vapour at 30°C and standard pressure (1 bar) ||
 * Calorific value || 21.5 MJ m-3 || (20.1 to 25.9) ||
 * Effective molecular weight || 27.35 || (24 to 29) ||
 * Density || 1.0994 kg m-3 || (0.96 to 1.17) ||
 * Specific gravity || 0.94 || (0.82 to 1.00) ||
 * Viscosity || 12.97 10-6 Pa s ||  ||
 * Optimum air to fuel ratio || 5.5:1 || (15% biogas) ||
 * Flammability limits || 9% to 17% biogas in air ||  ||
 * Wobbe number || 22.2 MJ m-3 ||  ||
 * Burning velocity || 0.25 m s-1 in air ||  ||

A useful study of [|biogas burners for stoves and lights] was done by SNV (Netherlands Development Organisation) in 2009.

Here is a contribuition by Hoysall Chanakya.

This spreadsheet may also be helpful in burner design - the calculations are based on Dr David Fulford's book "Running a biogas project: a handbook" If you need help with Storage and Pipe Calculations here is another spreadsheet.