Contaminant Removal

Common Gas Contaminant Removal

activated carbon gas cleaningBiogas  and  LFG  always  contains hydrogen sulphide (H2S).  This is usually in the range  of  1,000  to  6,000  ppm  but  may  also reach  2%  Vol (20 000 ppm)  or  more.  H2S, Ammonia (NH3) and Silicone compounds  often need  to  be  reduced  –  either  for reasons of environmental protection or because of  the  corrosion  hazard to engines and upstream processes.


For relatively small amounts of H2S and Siloxanes, activated carbon (AC) filtering can be employed. This process involves routing the gas through a bed of activated carbon where contaminants and impurities in the gas are exposed to the filter media and captured through the absorption process. Carbon is then replaced once saturated.


The non-chemical biological  process is usually preferred and this involves injecting a  limited amount of air (10 – 15% in relation to  the  gas  throughput) into the process. Bacteria known as Thiobacillus Spp convert  the  H2S  to elementary sulphur and sulphuric acid.
In order for the bacteria to grow it only needs:
•  Oxygen
•  A small amount of added nutrients and trace elements (readily available in South Africa)
•  A growing surface