GPS-X Technical Reference

Suspended Growth Models 208
Estimation of Effluent Gas Composition
The open basin HPO considers the gas-liquid transfer of O 2, CO 2, N2, H 2 and CH 4 in
Mantis2 model. In Mnatis3 model, gas liquid transfer of N 2O is also modeled. The partial
pressure of each gas at the surface of the tank is estimated by assuming a virtual gas
headspace having a volume equivalent to the volume of the gas holdup in the tank. The
virtual head space thus represents the volume in the tank occupied by the bubbles.
The volume of the virtual headspace is estimated by using the following expression:
Equation 6.71
where:
V headspace = volume of headspace (m 3 )
V liquid = volume of liquid in tank (m 3 )
Φ holdup = gas holdup in tank (-)
The partial pressure of each gas in the headspace is then integrated using the following
derivative equation:
Equation 6.72
where:
g i,o
p total
= partial pressure of i gas, atm
= total pressure of the gas in headspace (atm)
r g,i = gas transfer rate for i gas, mole/m 3 /d
V liquid = volume of liquid, m 3
f molarvolume
g i,in
= molar volume of gas at standard condition
= partial pressure of feed gas, atm
Q gas, in = feed gas flow rate, m 3 /d
Q vent = outlet gas flow rate, m 3 /d
GPS-X Technical Reference