Influence of the viscosity and moisture during flow measurements of energy gases

Important results from the project

The study presents a method to correct flow rates measured with a Laminar Flow Element flowmeter pre-set on methane while used for gas mixtures of unknown composition. The method has several applications inclusive for the sampling of biogas and biomethane onto sorbent tubes for conformity assessment. During the sampling, the composition of the gas is often not known at the time of the sampling. The method proposed implies to pre-set the LFE flowmeter on methane and to correct the value using a factor based on the later-determined viscosity of the gas once the composition has been obtained.

Expected long term effects

The method proposed here implies to pre-set the LFE flowmeter on methane and to correct the value using a factor based on the later-determined viscosity of the gas once the composition has been precisely obtained. The method has several applications inclusive for the sampling of biogas and biomethane onto sorbent tubes for conformity assessment. The bias on the volume sampled with the method proposed here.has to be taken into account and will impact the measurement uncertainties of the method which includes the uncertainty due to the sampling and the analytical method.

Approach and implementation

Five different models were evaluated to calculate the viscosity for binary mixtures of methane and carbon dioxide and for multi-component gases containing up to nine components commonly found in biogases. The method has been applied for flow rates ranging from 40 to 100 Nml/min.The results of these evaluations showed that the factor using the viscosity of the mixtures calculated with the models of Reichenberg and Carr showed the smallest biases for binary mixtures. For multi-component mixtures, the best results were obtained when using the models of Lucas and Carr.