Flow Meters Dependable Gas Flow Measurement for Industrial Pollution Control

Editor: Ahlam Rais

The engineering team at a coal-fired electric power plant utilizing ammonia (NH3) for nitrous oxide (NOx) removal by its pollution control system installed the ST100 Series Thermal Flow Meter from Fluid Components International (FCI) based on its superior repeatability in measuring NH3 under harsh operating conditions.

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Fluid Components International’s ST100 series thermal flow meter continuously displays all process measurements and instrument status for easy on-site viewing by technicians.
Fluid Components International’s ST100 series thermal flow meter continuously displays all process measurements and instrument status for easy on-site viewing by technicians.
(Source: FCI)

The ST100 Series Thermal Flow Meter allowed the plant team to optimize its selective catalytic reduction (SCR) system. This step improved performance while substantially reducing NH3 consumption and costs, states the company. The meter, with its rugged thermal dispersion sensor head, provides a highly repeatable measurement solution to control vaporized NH3 in such applications.

The engineers at the electric power plant were experiencing problems with inconsistent measurement of the vaporized NH3 injected into their flue gas as a means to reduce NOx emissions. The original system utilized a volumetric flow sensor, which wasn’t well suited for controlling the NH3 gas injection system. Switching to the mass flow sensing meter, as opposed to taking a volumetric measurement, solved the false readings issue, adds the firm.

Given the Flow Meter’s standard wide flow turndown ratio of 100:1 (up to 1000:1 based on application), and the ability to measure mass flow, instead of volumetric flow, the engineers decided to conduct a pilot test. They installed the insertion style thermal flow meters on the primary vaporized ammonia feed lines to their nozzle grid for the test.

With the resulting improved measurement reliability, they took the project one-step further and installed in-line style ST100AL thermal flow meters at each of their nozzle locations. After proving out the benefits in one operating unit, they eventually instrumented the ammonia injection systems for all of the units within the facility, mentions the company.

The meter can be factory calibrated to measure virtually any popular process gas as well as mixed gases. The technology is suitable for use in wet and dirty gas applications, having no small ports prone to fouling, opines the firm. The basic insertion style air/gas meter features a thermal flow sensing element that measures flow from 0.25 up to 1000 SFPS (0.07 NMPS to 305 NMPS) with accuracy of ±0.75 percent of reading, ±0.5 percent of full scale. The basic in-line style meter is available for 2-inch and smaller line sizes.

The meter’s transmitter is unsurpassed in meeting both a plant’s current and future need for outputs, process information and communications. Whether the output required is traditional 4-20 mA analog, frequency/pulse or advanced digital bus communications such as Hart, Modbus, Profibus, or Foundation Fieldbus, the Series will meet your instrumentation integration needs, claims the firm. Its advanced bus communications are all third party certified and registered.

Developed with a graphical, multivariable backlit LCD display, the meter brings new meaning to the term ‘process information’. Its sophisticated readout continuously displays all process measurements and instrument status for easy on-site viewing by technicians, and it has the ability to query for service diagnostics via an integral, optical HMI that does not require declassification of hazardous areas.

Designed for extreme industrial process and plant conditions, the meter can be used in service up to 850ºF (454ºC) and is available with both integral and remote (up to 1000 feet [300 meters]) electronics versions, mentions the company. The meter is agency approved for hazardous environments, including the entire instrument, the transmitter and the rugged, NEMA 4X/IP67 rated enclosure.

Global approvals include: Atex, CPA, CRN, EAC/TRU CU, FM, FMc, FDT, Gost, IECEx, Inmetro and Nepsi. Third party failure rate data per IEC 61508 is available that demonstrates suitability of the hardware architecture for SIL 1 (HFT=0) applications, concludes the firm.

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