Reliable biogas percent methane content and flow rate with ultrasonic flow meters

Measurements that matter.

Innovation in flow measurement:

Biogas flow measurements have always been difficult due to wet gas conditions and changing compositions of methane and carbon dioxide. Traditional technologies have struggled to achieve a consistent and reliable measurements without field optimization or repair. Today, because of advanced electronics and transducer designs, ultrasonic flow meters are now being installed more and more in biogas applications as they have broken the stigma of only being suitable for clean applications.

Ultrasonic flow meters are an excellent fit for biogas flow measurements since they are well suited for low pressure gas, low to medium velocities, changing stream compositions, and tolerance to wet gas installations. However, not until recently have ultrasonic flow meters utilized their naturally measured sound speed and more readily accessible diagnostics.

With a transit time ultrasonic flow meter, two transducers are mounted on opposite sides at an angle so that one transducer is upstream of the flow and the other transducer is downstream of the flow. The transducers act as a pair and both transmit and receive ultrasonic signals. With flow, the signal from the downstream transducer will slow down as it is going against the process fluid to the upstream transducer and while the signal speeds up going from the upstream transducer to the downstream transducer. With the difference in transit time and knowing the spacing between transducers, the fluid velocity is calculated.

Innovation in flow measurement:

The exact transit time it takes an ultrasonic soundwave to acquire from one transducer to the other transducers is based on sound speed. Sound speed is property of a specific fluid (gas, liquid, or solid) but also changes with temperature. With sound speed, temperature, and pressure, a Panametrics ultrasonic flowmeter can now also provide a constant percent methane concentration in a biogas fluid eliminating a need and the maintenance associate with a separate gas analyzer.

With both a dependable percent methane content and flow measurement in a single pipe penetration, wastewater treatment plants are now able to better optimize operations and improve efficiency.