Industrial Electronics

Vegetable oil hydrogenation process relies on H2 gas measurement with thermal flow meter

28 June 2022

Process and plant engineers in the food/beverage industries who are responsible for vegetable oil hydrogenation processes will find the precision ST80L series thermal mass flow meter from Fluid Components International (FCI) provides accurate hydrogen gas mass flow measurement that helps them deliver a tasty product.

No matter the food product, oil hydrogenation can be expensive due to the relatively high cost of H2 gas, its storage and plant safety requirements. Food industry process engineers have found that not all air/gas flow measurement technologies are suitable for this application because the process requires a 435 psig (30 bar[g]) pressure level, which results in an H2 density that is too low for some flow measurement technologies, such as Coriolis, to offer sufficient range-ability and high accuracy.

Source: FCISource: FCIFCI’s ST80L series thermal mass flow meter is a wide-ranging direct mass flow instrument well suited for H2 measurement in small 1 inch to 2 inch (DN25-DN50) sizes in pressures up to 70 bar (g), 1,000 psig. It features accuracy of up to ±1% of reading with ±0.5% repeatability over a wide flow range of 0.0062 SCFM to 838 SCFM (0,01 Nm3/h to 1425 Nm3/h) under variable process temperatures, making it ideal for measuring many other process gases, waste gases and compressed air applications in food/beverage industry plants.

All FCI flow meters are calibrated in the company’s own one-of-a-kind Calibration Laboratory where the instruments are calibrated in the actual gas they are to measure under the customer’s unique pressure and temperature conditions, such as H2 at up to a pressure of 70 bar(g). Flow meter calibration using the actual gas method under customer plant operating conditions helps ensure accurate, consistent measurement rather than using the inferred gas method used by most manufacturers.

The ST80L inline flow meter’s thermal dispersion flow sensor’s design is elegant in that it does not utilize any moving parts by employing solid-state platinum resistance temperature detection sensors that are precision matched and embedded in equal mass thermowells. The sensor’s design requires virtually no cleaning and is less prone to fouling than other flow measurement technologies when there is a concern about particulate laden gas streams.

Hydrogen molecules are extremely small and can leak through the threaded connections typically provided with many flow meters. FCI’s inline H2 flow meters, however, with their all-welded design in which the sensor is welded to the inline pipe spool eliminates concerns about potential instrument H2 leaks for user peace-of-mind. Additionally the process connections of the inline pipe spool can be flanged or provided with a butt-weld joint that allows the inline thermal mass flowmeter to be welded directly into the user’s piping or application equipment.

The ST80L inline thermal mass flow meter (pipe spool length of 9xDN) can be delivered with a unique low pressure drop Vortab Flow Conditioner. This flow conditioner is welded at the inlet of the flow meter allowing for very short piping installation lengths (only 3xDN required for upstream straight length) to provide accurate measurement in crowded plant equipment areas.

The durable and highly reliable ST80L inline flow meter is optionally available with remote mounting capabilities where space is at a premium or the measurement point is not easily accessed. The remote mount transmitter, which has an option for local indication of flow, temperature and totalized flow, can be mounted up to 1,000 feet (300 meters) away from the local flow element in the process piping.

The ST80L flow meter series features scalable dual 4 mA to 20 mA outputs that are standard. They are user assignable to flow rate or temperature. Outputs are user programmable to full flow range or subsets of full flow range. They are also isolated and have fault indication per NAMUR NE43 guidelines and are user selectable for high (greater than 21.0 mA) or low (less than 3.6 mA). Standard digital outputs available include: HART (v7 compliant), Modbus RS-485 RTU/ASCII and USB Serial I/O. Optional: digital outputs that can be added are Foundation Fieldbus H1, PROFIBUS-PA, or PROFIBUS-DP.

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