BPC instruments AMPTS III Operation And Maintenance Manual page 11

2) CO -absorption Unit (Unit B): Different amounts of biogas is generated during the AD
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process based on the content of the reactors (blank, positive control, negative control,
and samples). Biogas is mainly made of methane (CH ) and carbon dioxide (CO ). The
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unit B is where the CO and traces of hydrogen sulphide are removed through a
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chemical reaction with a 3 mol/L NaOH solution (Figure 5). The absorption efficiency
is higher than 98% even at high flow rates.
Figure 5. Bottler holder designed for 9 glass bottles (250 mL). AMPTS III is equipped with two bottle
holders.
Carbon dioxide reacts with sodium hydroxide in an acid-base reaction to generate
sodium carbonate and sodium bicarbonate:
In this case, only methane will reach the detection unit (single gas measurements). If
the test aims to measure biogas, the Unit B is not needed, where the setup should
present the following configuration (Figure 6).
Figure 6. Setup for total gas (e.g., biogas) measurements.
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