Decarbonisation Technology - February 2025 Issue

Figure 3 The Rosemount ET410 Corrosion and Erosion Transmitter allows high-temperature online thickness monitoring, ideal for biofuel applications

operators to detect and address corrosion issues before they lead to significant damage or failure.

Managing corrosion risks Traditional methods for measuring the risk of corrosion are based on processes that have existed for many decades, such as rudimentary corrosion modelling, manual inspection, and risk-based inspection (RBI). The main challenge posed by using these techniques is that in many of these novel processes, the process is far less predictable, introducing previously unforeseen levels of risk. To properly manage these unknown levels of risk, refiners are adopting innovative strategies, with a particular focus on advanced monitoring technologies. One increasingly popular approach is the use of online, non- intrusive corrosion monitoring systems. Emerson’s Rosemount Wireless Corrosion and Erosion Transmitters (see Figure 3 ) are designed to measure wall thickness in real-time, allowing operators to detect corrosion quickly and take preventive action. They can be installed without the need to penetrate the pipe or vessel wall, minimising installation costs and allowing monitoring in previously inaccessible locations. These transmitters employ a patented Adaptive Cross-Correlation (AXC) technique, which significantly improves measurement accuracy, especially in challenging conditions such as those encountered in biofuel production (see Figure 4 ). This technology allows the transmitters to achieve a repeatability of up to 2.5 microns (0.0001in) in field conditions.

The transmitters typically transmit wall thickness measurements twice daily using wireless data retrieval, giving operators a high level of insight into the health of their assets directly from the desk (see Figure 5 ). This frequent data collection allows for the early detection of corrosion trends, enabling proactive maintenance strategies and potentially preventing costly shutdowns or equipment failures. A case study from a major European refiner illustrates the effectiveness of this approach. The refiner repurposed an old hydrotreating unit to utilise renewable feedstocks such as vegetable oils and used cooking oil. Recognising the increased corrosion risk, they installed Rosemount Wireless Corrosion and Erosion Transmitters. The transmitters were strategically placed in areas prone to corrosion, such as reactor effluent systems, high-temperature zones, and areas with potential for ammonium chloride or amine corrosion. By providing continuous data on wall thickness, the transmitters allowed the refiner to correlate corrosion rates with specific feedstocks and operating conditions. This insight has been invaluable in optimising processes and maintenance schedules. Moreover, thanks to their non-intrusive nature, the transmitters could be installed without any modifications to the existing equipment, minimising downtime and installation costs.

AXC

Figure 4 Adaptive Cross-Correlation (AXC) significantly improves the accuracy of the wall thickness and corrosion rate calculation