Large wastewater treatment plants and landfill facilities often embark on waste-to-energy co-generation projects. The digester gas is used to create electricity or heat the facility. At times, however, the digester gas does not sustain the engines’ BTU levels, so natural gas blending becomes a practical alternative.

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Cogeneration Power Production Engines

Wastewater Digester Gas at WW Treatment Plant as Energy Source
Anaerobic digestion at WW treatment plants produces wastewater digester gas, a methane-rich byproduct that can be an energy source.

Waste-to-energy co-generation projects are increasingly popular because they offer both environmental benefits as well as cost incentives. It is common for wastewater treatment plants and landfill facilities to install multiple large reciprocating power production engines for power generation. The site’s digester gas production may even fuel these engines. The engines generate electricity, and when used for onsite power, there is little energy loss in the distribution and transportation of the energy. The machines are known to have high electrical efficiency and low environmental impact.

The engines’ co-gen energy may power the site, including the machines, and at times, these plants require continuous electricity. Unfortunately, not all facilities can generate enough digester gas to fuel the sizeable reciprocating power production engines. In these cases, a blend of digester gas and natural gas may power the engines to sustain the required BTU levels.

The power generation engines require that the natural gas and the digester gas be separately measured and adequately blended. Both gases require accurate flow meters that are not affected by the engines’ continuous vibration or the dirty environment.

Measuring Natural Gas and Digester Gas

biogas application guide
Biogas Application Guide

Thermal mass flow meters are suitable for measuring natural gas and digester gas before they are blended and fed to the engines.

Insertion-style thermal mass flow meters, such as the Sage Prime, Sage Paramount, or Sage Rio, may be installed in both the natural gas line and digester gas lines. Both models feature industrial enclosures. The Prime and Paramount have a robust yet lightweight, dual-sided NEMA 4 enclosure, is CE compliant, and meets UL and CSA standards for Class I Division 2 hazardous service. The Rio has the added hazardous area approval of Class I Division 1 Group B, C, D, and ATEX Zone 1 Flameproof approval. Please note that Sage Metering discontinued the RIO. If you require Class 1 Div 1 status, contact us.

One of the advantages of using the thermal mass flow meter in these applications is that the meters do not require the added expense of having pressure, temperature, or density devices like other air or gas flow meters. Additionally, since the meters have no moving parts, there is the added comfort that there will be minimal maintenance costs versus alternative measurement technologies.

Sage Meters

If you would like more information on using thermal mass flow meters in these applications, or if you have an application of your own, call us today to discuss how Sage Meters can satisfy your needs (866-677-7243).