BioWorks Energy LLC provides expertise in operations of wastewater treatment systems for industrial, agricultural, and municipal wastewater treatment processes. Its focus is on anaerobic digestion processes that capture biogas for electricity generation. BioWorks most recent project included the installation of a new digester that would require an instrument to read the flow of a changing biogas concentration from an anaerobic digester to an internal combustion engine as accurately as possible. The accuracy of the meter would help the operator to understand the gas usage and the efficiency of the engine. Drastic changes in the gas consumption can signify premature wear on the engine among several other issues. Keeping the measurement error as low as possible is paramount to monitoring consumptions, but finding a flowmeter designed to measure the flow of more than one gas or gas concentration wouldn't be easy.
When beginning the search for a meter that would be able to meet the challenges of this project, Chad Antle, CEO of BioWorks Energy LLC, hit a few walls. He needed a meter that could handle two very important aspects of this project: the meter must measure the flow of biogas at different concentrations of carbon dioxide and methane; and it couldn't break the bank.
Researching flow technologies such as ultrasonic, positive displacement, turbine, and Coriolis showed that the only technologies offering multiple calibration points were too expensive. This brought him back to the cost-effective thermal mass flowmeter, but a manufacturer was needed that could offer a highly accurate meter that could be adjusted for various gas compositions.
There are many manufacturers of thermal mass flowmeters, but it was the Model FT1 by Fox Thermal Instruments that offered the perfect solution. Not only is the price tag on the Model FT1 economical, but it also has a short lead time, is easy to install, and offers the technology needed to measure different biogas concentrations. The Gas-SelectX® gas selection menu available on the Model FT1 thermal mass flow meter and temperature transmitter allows the user to choose from Air, Argon, Carbon Dioxide, Helium, Methane, Natural Gas, Nitrogen, Oxygen, Propane, or any mix of these gases equaling 100%.
For this project, the methane concentration was expected to fluctuate between 68-71%; however, due to the occasional fluctuations from feedstock, this number could fall as low as 55% or jump up as high as 75%. A meter calibrated for 35% carbon dioxide and 65% methane, for example, would introduce a large measurement error. The Model FT1 allows the user to manually enter the concentration of up to three gases available in the Gas-SelectX® menu in order to create the ideal calibration for the most accurate reading possible.
The Model FT1 used in this case study has out-performed competitor meters in this application. Used in conjunction with a gas sampler, this meter has taken the need for recalibration at the factory due to gas concentration changes completely out of the picture. The Gas-SelectX® gas selection menu is convenient, easy to use, and has revolutionized how gas flow instrumentation can be used in the field.
Ria Edens, Marketing Communications Manager, Fox Thermal Instruments
Link to Article:
2015 Flow Control Magazine: Thermal Flowmeter & Temperature Transmitter Resolves Recalibration Issue for Wastewater Treatment Operator