9.5
Removal of Trace Components
9.5.1 Removal of Ammonia
Protein degradation process results in the formation of ammonia, and the ammonia
content quantity depends upon the pH settings in the digester and the substrate
composition. Hence, the biogas upgradation must be done to rectify the problem of
ammonia generation. The separation of ammonia can be done by drying the biogas
by cooling technique without the involvement of separate cleaning process
(Petersson and Wellinger 2009; Report 2012).
9.5.2 Removal of Siloxanes
Siloxanes, the compound with silicon-oxygen bond, are widely used in shampoos
and deodorants, and its presence can be easily detected in biogas produced from a
sewage sludge treatment plants. The problem with siloxanes exists when it is burned
to form silicon oxide in gas engines, and hence it must be removed by adsorption
process or by cooling the gas or by absorption process or during hydrogen sulphide
separation process. The adsorption process can be performed using activated aluminium or activated silica gel or activated carbon. For absorption process, liquid
mixture of hydrocarbons is used (Petersson and Wellinger 2009; Report 2012).
9.5.3 Removal of Water
Corrosion is one of the major problems arising due to the reaction of water condensate (formed during the saturation of biogas with the water vapour while leaving the
digester) in the gas pipeline with that of the sulphur oxides. So, it is necessary to
remove the water vapour from the biogas itself before leaving the digester by
reducing the temperature and maximising the pressure. Reduction in temperature
leads to cooling, and it is achieved using an electric cooler (refrigeration) or
condensate trap. Activated charcoal, silicon dioxide or molecular sieves (zeolites)
(Report 2012) can also be applied to remove the water vapour by the process of
adsorption. Hygroscopic salts or glycol solutions can also be used to remove water
vapour by uploading the absorption process (Petersson and Wellinger 2009).
9.5.4 Removal of Particulates
In gas turbines and gas engines, the presence of particulates in biogas leads to
mechanical wear, and it can be eradicated by using special mechanical filters sized
0.01–1 μm (Report 2012; Petersson and Wellinger 2009).
9 Recent Trends in Biogas Upgrading Technologies for Biomethane Production
261
Removal of Trace Components
9.5.1 Removal of Ammonia
Protein degradation process results in the formation of ammonia, and the ammonia
content quantity depends upon the pH settings in the digester and the substrate
composition. Hence, the biogas upgradation must be done to rectify the problem of
ammonia generation. The separation of ammonia can be done by drying the biogas
by cooling technique without the involvement of separate cleaning process
(Petersson and Wellinger 2009; Report 2012).
9.5.2 Removal of Siloxanes
Siloxanes, the compound with silicon-oxygen bond, are widely used in shampoos
and deodorants, and its presence can be easily detected in biogas produced from a
sewage sludge treatment plants. The problem with siloxanes exists when it is burned
to form silicon oxide in gas engines, and hence it must be removed by adsorption
process or by cooling the gas or by absorption process or during hydrogen sulphide
separation process. The adsorption process can be performed using activated aluminium or activated silica gel or activated carbon. For absorption process, liquid
mixture of hydrocarbons is used (Petersson and Wellinger 2009; Report 2012).
9.5.3 Removal of Water
Corrosion is one of the major problems arising due to the reaction of water condensate (formed during the saturation of biogas with the water vapour while leaving the
digester) in the gas pipeline with that of the sulphur oxides. So, it is necessary to
remove the water vapour from the biogas itself before leaving the digester by
reducing the temperature and maximising the pressure. Reduction in temperature
leads to cooling, and it is achieved using an electric cooler (refrigeration) or
condensate trap. Activated charcoal, silicon dioxide or molecular sieves (zeolites)
(Report 2012) can also be applied to remove the water vapour by the process of
adsorption. Hygroscopic salts or glycol solutions can also be used to remove water
vapour by uploading the absorption process (Petersson and Wellinger 2009).
9.5.4 Removal of Particulates
In gas turbines and gas engines, the presence of particulates in biogas leads to
mechanical wear, and it can be eradicated by using special mechanical filters sized
0.01–1 μm (Report 2012; Petersson and Wellinger 2009).
9 Recent Trends in Biogas Upgrading Technologies for Biomethane Production
261