Overall pressure within the bioreactor

760 mm Hgb


Enthalpy of vaporization of water

2.414x106 J kg-water-1


Density of the air phase

1.14 kg-dry-air m-3 c


Density of the bioreactor wall

7820 kg m-3

a The program converts all variables and parameters to

a consistent set of units.

where "biomass" appears within the units, this represents dry biomass. b Needed for the calculation of the air water activity.

c Used in the calculation of the headspace gas mass (G, kg) and to calculate the mass flow rate of air (Fin, kg-dry-air s-1) from the value input as vvm.

As shown in Fig. 22.1(a), it is also assumed that the relative humidity of the off-gases is monitored. When the water activity (i.e., the relative humidity divided by 100) falls below a set point value (awg*), then sufficient water is added to the bed to bring the water activity of the solids back to the initial value. Note that it is assumed that this water is added at the temperature of the bed.

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