Ultrasonic Gas Flow Meter Helps Steel Mill Achieve Reliable Low-Pressure Flue Gas Measurement

Summary

A major steel mill in China, with a production capacity of tens of millions of tons per year, has a long and successful track record using ultrasonic flow meters. Already very familiar with Panametrics products, the customer has used many Panametrics liquid, gas, and flare flow meters with great success. However, it was also using a competing ultrasonic flow meter for flue gas measurement. The customer found it unreliable and wanted to replace it.

Application

Fig. 1: Welding the downstream transducer nozzle onto the flue gas duct.

Fluid	Flue gas
Pipe Size and Material	2410 × 4000 mm (7.9 × 13.1 ft), carbon steel
Process Temperature	101 – 129 °C (214 – 264 °F)
Process Pressure	-11 Pa to 93 kPa (-0.0016 to 13.5 psig)
Fluid Sound Speed	~390 m/s (~1,280 ft/s)

Benefits:

Measures down to very slight vacuum pressure
No pressure drop
Low maintenance
Long-term stability
Works on rectangular pipes
Wide measuring range

Challenge

The flow meter had to be installed on a large 2.4 m × 4 m rectangular duct. The installation location offered only about 1.5 pipe diameters of straight run upstream, resulting in a non-fully-developed flow profile. With the two nozzles positioned far apart, achieving correct alignment was difficult — any offset risked losing signal capture and producing inaccurate, unreliable readings. There was no room for error: the measurement data feeds directly into the plant’s continuous emission monitoring system (CEMS).

Solution

Given the very long acoustic path, the Panametrics team recommended its DigitalFlow XGM868i gas ultrasonic flow transmitter with T5 transducers operating at 50 kHz. The wide beam angle of these transducers ensured an accurate measurement across the long path. In parallel, the Panametrics Services team used a laser alignment tool to achieve precise nozzle alignment. Following successful installation and commissioning, the flow meter delivered accurate and reliable data, and the customer was able to properly feed its CEMS with the required flow measurement data. Following this success, the Panametrics team is already discussing similar applications at other steel mills around the world.

Technician welding a transducer mounting nozzle onto a large flue gas duct

Source: Panametrics Application Note PANA013AN (panametrics.com) — © Panametrics LLC. Localized and prepared by INTECH CONTROL, the official Panametrics representative for Slovakia and Hungary.

APPLICATION NOTE

Steel mill with molten metal ladle at dusk

Ultrasonic Gas Flow Meter Helps Steel Mill Safely Control LD Converter Gas Recovery

Summary

A major steel mill in India operates one of the most advanced production lines in the country, including a high-precision Cut-to-Length line capable of processing steel coils up to 25 mm thick with edge trimming. Looking to further optimize its operations, the customer wanted to install a bidirectional gas flow meter on its Linz-Donawitz gas (LD gas) holder. The 100,000 Nm³/h LD gas holder collects gas from the SMS (Steel Melt Shop) converter and exports it through two DN1000 (40″) lines, each operating at roughly 1,000–1,200 mmWC when its booster is active. These lines feed into a DN1600 (64″) booster fan gas (BFG) network running at 900–1,100 mmWC. The customer wanted to feed LD gas into the BF gas network, but faced a safety concern: if a booster motor failed to keep the line pressure above the BFG network’s 900–1,100 mmWC during spillback, BFG gas could flow back into the LD gas holder undetected, creating a safety risk for the entire LD gas holder setup.

Application

Fig. 1: T5 Bias 90 installation with XAMP preamplifiers on the 64″ (DN1600) BFG line.

Pipe Size and Material	64″ (DN1600) Sch. 40, carbon steel (API 5L)
Gas Flow Range	0 – 100,000 Nm³/h
Gas Temperature	Ambient – 70 °C
Gas Pressure	Atmospheric – 1,600 mmWC
Gas Composition	~13–15% CO₂ / ~50–70% CO / ~0.4–1.2% O₂ / ~2–3% H₂ / ~5–20 mg/Nm³ dust / moisture

Benefits:

Bidirectional flow measurement
Accurate, cost-effective measurement on large pipelines
Wide rangeability
Handles difficult gases (CO₂ / CO / H₂), works up to 100% CO₂
Local support from INTECH CONTROL

Challenge

The plant had already tried a differential pressure device and several other flow technologies, but none of them could cope with the low operating pressure, the bidirectional flow, the very wide rangeability (from almost zero flow through reverse flow up to maximum flow) and the dust content in the gas. Ultrasonic flow meters, however, can handle all of these challenges — including the signal absorption caused by high CO₂ content that defeats many other technologies.

Solution

The Panametrics sales and application engineering team reviewed the process conditions and the customer’s requirements. Drawing on extensive experience with steel mill gas applications, the team proposed the DigitalFlow XGM868i with T5 (100 kHz) transducers in a Bias 90 configuration. The flow meter was successfully installed and commissioned by the Panametrics Services team. The customer was very satisfied with the result — the measured data matched expectations — and has since deployed Panametrics ultrasonic flow meter technology on other LD gas lines throughout the same plant.

XGM868i transducers installed on a large gas pipeline

Panametrics DigitalFlow XGM868i process gas ultrasonic flow meter

Datasheet (PDF) Panametrics DigitalFlow XGM868i

Source: Panametrics Application Note PANA018AN (panametrics.com) — © Panametrics LLC. Localized and prepared by INTECH CONTROL, the official Panametrics representative for Slovakia and Hungary.