Burning Purg Gases from Biogas Upgrading
Biogas from AD fermenter or from landfills can be upgraded to replace natural gas in the gas grids or for transportation fuels. To produces the so called renewable natural gas (RNG) CO2 and eventually N2 has to be precipitated.
Depending on the type of gas upgrading residual methan is part of the purg gas of the upgrading process. As methane has a high climate potential it mus be oxidized before emitting it to the atmosphere. Otherwise it would deteriorate the climate impact of the biogas upgrading process. E-flox developed tailor made plant to oxidize these gases, which are primarily used in combination with PSA (pressure swing absorption) and membrane type gas upgrading systems. Combusiton air and purge gas is preheated with flue gas heat prior to their injection into the combusiton chamber. Depending on the type of preheater differeant authtermal methane concentraitons can be reached. This is the minimum methane concentraiton in the purge gas which can be burned without supplementary gas. Beside the methane concentraitons other hazardeous constitutents like H2S or Siloxanes might influence the choice of burners to be used. In the download section a document shows a comparison of differen burner types and their performance.
The flue gas downstream of the preheaters is still hot. Depending on the methane concentraitons and the burner type temperatures of 250-800°C are achieved. This flue gas can be used to produce warm water. The efficience of such a waste heat recovery is typically between 60 and 85%.