You are hereRemoval of trace components: water, ammonia, siloxanes, particulates

Removal of trace components: water, ammonia, siloxanes, particulates

Biogas is saturated with water vapour when it leaves the digester. This water tends to condensate in apparatuses and pipelines and together with sulphur oxides may cause corrosion. By increasing the pressure and decreasing the temperature water will condense from the biogas and can thereby be removed. Cooling can either be realised by using the surroundings temperature (air, soil) or by electric cooling (refrigeration). Water can also be removed by scrubbing with glycol or by adsorption on silicates, activated charcoal or molecular sieves (zeolites).

Ammonia is usually separated when the biogas is dried by cooling as its solubility in liquid water is high. Furthermore, most technologies for carbon dioxide removal are also selective for the removal of ammonia. A separate cleaning step is therefore usually not necessary.

Siloxanes are used in products such as deodorants and shampoos, and can therefore be found in biogas from sewage sludge treatment plants and landfill gas. These substances can create serious problems when burned in gas engines or combustion facilities. Siloxanes can either be removed by gas cooling, by adsorption on activated carbon, activated aluminium or silica gel or by absorption in liquid mixtures of hydrocarbons.

Particulates and droplets can be present in biogas and landfill gas and can cause mechanical wear in gas engines, turbines and pipelines. Particulates that are present in the biogas are separated by fine mechanical filters (0,01µm – 1µm).