The COMBIMASS® eco-bio+ flow meter is developed particularly for the agricultural anaerobic digestion market using thermal dispersion technology. This principle determines directly the gas flow rate at standard pressure and standard temperature. The sensor consists of a heated and a non-heated reference electrode. When the flow is crossing the sensor, the heated one is cooling down an represents thus a measure for the number of molecules (mass flow). However the dampness portion of the biogas is measured too. Therefore the flow rate at standard conditions according to the German standard paper DIN 1343 (0°C, 1,01325 bar, 0% rel. humidity) cannot be measured directly, since the request 0% rel. humidity is not fulfilled.
The maximum waterdamp portion at saturation point depends only on gas temperature and is represented by a well-known equation. The temperature information of the non-heated reference sensor is used to determine and compensate the humidity in the biogas directly in the electronic board of the flow meter. Thus the dry gas mass flow can be determined at standard conditions finally, if the installation point is chosen well at a place where the gas is waterdamp saturated.
So the use of the COMBIMASS® eco-bio+ for verification of annual gas production (e.g. in CDM-projects) becomes possible. Further manipulation-poor and -safe instruments are available for special applications.
Thermal mass flow meter are suited particularly well for the use in wet biogas compared to other technologies (e.g. Vortex, ultrasonic, mechanical counters), since even at low gas speeds the measurement is very precise.
A further substancial advantage is that all necessary compensation can take place directly in that one measuring instrument. No further sensor, hardware or compensation computer are necessary.
The installation is not more simply at lower costs, the failure of probability is lower than using a combination of three measuring instruments (temperature, pressure and flow rate) and no error summarization will take place.
