2
2GENERAL INFORMATION
Anaerobic biodegradation processes are gaining in interest among industry and local
governments, due to their ability to produce energy and reduce sludge yields.
In the anaerobic biodegradation process, gas flow rate represents a key parameter for evaluating
the performance of a process. In laboratory scale experiments, the bioreactor volume ranges from
1 to 50 l with a low gas production, especially during the start-up period, often within several
hundreds millilitres per hour. Measuring such a low volume of gas accurately is not an easy task
using commercially available gas flow meters since they do not measure such low flow rates.
A gas flow meter for laboratory-scale reactors has higher demands compared with a meter
adapted for a large-scale anaerobic reactor. This includes no gas losses, stable calibration
through time, and higher sampling rates, and ultimately more reliable gas measurements. The
µFlow meets all the needs of the most demanding biogas/biofuel labs and user applications.
2.1 Conventional Gas Flow Meters
Conventional gas flow meters (i) utilise techniques (e.g., thermal, Coriolis mass, ultrasonic,
turbine, vortex shedding etc.) that measure parameters such as velocity or mass of the flowing
stream to indirectly determine the volumetric flow or (ii) measure the volume of the gas directly
by liquid displacement. Although use of the liquid displacement technique is simple and
straightforward, errors associated with volume determination still exist when the investigated gas
is soluble in the displaceable liquid and the barrier solution is in direct and continuous contact
with the atmosphere. Moreover, in order to compare the data obtained from different
laboratories, correction factors need to be included in volume calculations to obtain gas volumes
at standard temperature and pressure, thus reducing or eliminating the error from this source.
2.2 Advantages of µFlow over Conventional Flow Meters
The µFlow provides several unique functionalities that are important for monitoring the gas flow
rate during a biodegradation process:
•Large linear detection range (20 to 4000 ml/h) that fits perfectly with most lab- and small
pilot-scale applications
•Real-time pressure and temperature compensation for gas flow rate and volume
measurements ensure that all gas flow measurements are accurate
•Real-time gas flow rate and normalisation allow for gas measurements to be standardised
