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Waste Recovery
Figure 3 . Vertical heat exchanger with radial inlet and bottom separator vessel .
Figure 4 . Filter tank with activated carbon or silica gel .
What is the importance of the biogas conditioning process ? First of all , biogas has a significant water vapour content , which depends on the degree of humidity ( usually 100 % under saturated conditions ), and on the operating pressure and temperature . The presence of this water vapour is particularly harmful to the engines where this biogas is consumed , but it can also damage the rest of the instruments and equipment in the WWTP valorisation system : blowers , compressors , etc . Similarly , the presence of water vapour can damage other biogas consumers , such as a gas turbine or a steam boiler . Secondly , biogas also contains a number of polluting or corrosive compounds that need to be removed because they can be very harmful to the waste recovery plant :
• Siloxanes . These come from silicones that are present in household products such as oils , detergents , shampoos , deodorants , toothpastes , cosmetics , etc . During the combustion of biogas , siloxanes can produce silicates , silica and other crystalline compounds whose incrustations cause abrasive wear on the internal parts of engines .
• Hydrogen sulphide . The presence of sulphur in organic matter and sulphates and / or sulphites in water can produce hydrogen sulphide during anaerobic digestion of biogas . This gas is corrosive to all machinery in the system , and can sometimes act as an inhibitor , or even interrupt biogas production .
Relative humidity = 100 %
Operating pressure = 20 mbarg
14 % 12 %
Water steam content (% -vol )
10 % 8 % 6 % 4 % 2 % 0 %
25 30 35 40 45 50 55 Operating temperature (º C )
Figure courtesy of SACOME .
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