Thermal flow measurement in wet gas scrubber systems enhances accuracy in air pollution control

In industrial locations where air pollution control is vital, wet gas scrubbers are widely used to capture and neutralise pollutants before atmospheric release. These systems depend on injected liquid streams to absorb harmful compounds such as sulphur dioxide (SO₂) and nitrogen oxides (NOₓ). They are essential for compliance with environmental regulations concerning particulate and gas-phase emissions.

Accurate measurement of gas flow into these scrubbers, especially under saturated and variable flow conditions, is essential for maintaining consistent system performance. However, moisture presents a major challenge for traditional flow measurement methods. Devices like pitot tubes are prone to fouling and blockage, often requiring frequent maintenance and recalibration to stay functional.

To address this issue, thermal dispersion-based instrumentation, such as the ST80 Series Flow Meter from Fluid Components International (FCI), is increasingly selected for deployment in wet gas scrubber applications. This technology provides direct mass flow measurement using a no-moving-parts design and a single pipe penetration, thereby reducing both the complexity of installation and the maintenance burden.

FCI’s ST80 is built to perform reliably in conditions typical of scrubber inlet streams, which may involve 2% moisture content in round ducts ranging from 15 to 54 inches (381 to 1371.6 mm) in diameter, with flow ranges from 66.56 to 100,000 SCFM, under pressures of 5 psia in H₂O (g) and temperatures between 21.1°C and 35°C. It features a wide turndown ratio of 1000:1, accuracy of ±1.0% of reading (±0.5% full scale), and repeatability of ±0.5% of reading. These specifications make it ideal for use in variable and low-pressure gas flow regimes.

Critical to its operation in saturated gas environments is the inclusion of FCI’s AST™ thermal measurement mode and the proprietary Wet Gas MASSter coating, which serves to redirect moisture away from the sensing element. These features help ensure signal stability and extend instrument service life.

The meter’s advanced transmitter electronics enable integration with various communication protocols, such as HART, Foundation Fieldbus, PROFIBUS PA/DP, and Modbus. A configurable display provides real-time readings of flow, temperature, totalized volume, and alarm status. The ST80 is approved by numerous international certifications, including ATEX, IECEx, UKEX, and SIL1, demonstrating its suitability for use in regulated and potentially explosive environments.

As industrial facilities seek to enhance the accuracy, reliability, and traceability of their emissions monitoring systems, thermal flow meters like the ST80 provide a dependable and proven solution to support wet gas scrubbing technologies.