Volume flow or mass flow measurements in synthesis gas (e.g. from wood gasifiers) are not trivial due to fluctuating gas compositions. Synthesis gas is a multi-component gas mixture, which essentially consists of a non-combustible portion of nitrogen/carbon dioxide and a combustible portion of hydrogen/carbon monoxide and small portions of hydrocarbons. Depending on the material to be gasified and fluctuations in material quality, the gas composition of the resulting gas also varies more or less. Each thermal mass flow meter of the COMBIMASS series is calibrated to one gas composition. If the actual gas composition deviates from the calibration conditions, greater measurement value falsifications may be expected. Especially, fluctuating hydrogen contents in the gas flow shift the measurement signal significantly.

An acceptable accuracy of the gas flow measurement can be achieved if the thermal sensor is combined with a heat conductivity sensor. With the help of the second sensor in the flow-calmed area, the hydrogen concentration in the gas can be determined. Resulting signal is read into the electronics of the thermal sensor via a 4-20 mA signal. The sensor then corrects its measured value accordingly. The COMBIMASS® syngas measuring system is thus a device combination in an in-line design with flanges on both ends.

Prior to delivery, each system is calibrated in our CAMASS® calibration laboratory, taking into consideration the actual operating conditions with regard to gas composition and installation situation (internal pipe diameter, flow direction, …) Officially pre-tested measuring sections, standard orifices and precision inclined tube manometers are used as references. In addition, calibrated pressure and temperature transmitters enable the exact determination of the operating conditions and volume flows on site. These measuring devices are regularly checked by external laboratories as part of ISO quality assurance. State-of-the-art computer and simulation programs based on decades of experience are used to calculate the calibration data and determine the correction factors for temperature compensation.