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Hydrocarbon Engineering,

Refiners face a multitude of challenges today. While global fuel demand will likely decline in the mid-term as a result of the energy transition, leading to overcapacities and decreasing prices, demand will instead continue to shift to high-quality and clean products. The task therefore resembles modern hydrocarbon alchemy: efficiently converting crude oil of varying and increasingly lower quality into marketable products.

Feedstock variability impacts product quality and unit reliability. One crucial factor is the processing of heavy crude oil fractions – the so-called ‘bottom of the barrel’. These mixtures, composed of long-chain hydrocarbons that remain as residue during atmospheric and vacuum distillation, place the highest demand on equipment. As such, the profitability of any refinery depends on efficient operations. It is therefore of huge importance that refinery operators enhance the reliability of equipment in order to extend run lengths and minimise the impact of shutdown. Plant availability is crucial.

High-temperature flow measurement

Reliable and accurate flow control is a prerequisite for safe and efficient refinery operation. Measuring residue flow is a particularly demanding task. The main challenges are high viscosity of the fluid, entrained abrasive particles, and high temperatures. Despite their well-known shortcomings, conventional flow measurement instrumentation still depends upon differential pressure (?P) measurements. These wetted devices suffer from coke formation on the primary element and, more importantly, clogging of the small pressure taps. As a result, they tend to require a lot of maintenance. Further disadvantages of ?P measurements are resulting pressure losses, impaired energy efficiency, and limited measurement dynamics (turndown).

Due to its practical advantages, external flow measurement with clamp-on ultrasonic transducers has become a standard measuring technique across a broad range of industries and applications. Experts are happy to resort to non-invasive technology when it comes to measuring the flow of complex media. Measuring with clamp-on transducers mounted on the outside of the pipe means measuring from the safe side. Since the transducers do not come into direct contact with the medium flowing inside, they do not suffer wear and tear. Non-intrusive measurement also means no pressure loss and no risk of leakage. Furthermore, the acoustic method provides high accuracy over an extremely large measuring range, independent of the flow direction...

Written by Carolina Stopkoski, FLEXIM AMERICAS Corp., USA, and Jörg Sacher, FLEXIM GmbH, Germany.

This article was originally published in the April 2022 issue of Hydrocarbon Engineering magazine. To read the full article, sign in here or register for a free trial subscription.

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