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A Shell-and-tube heat exchanger enhancement that increases Energy Efficiency in the Oil, Gas, Power & Chemical Process Sectors

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Prevention rather than intervention minimises one of the biggest problems for refineries

For years, engineers have grappled with the problem of heat exchanger fouling in the preheating phase of crude oil fractionation. Researchers discovered the problem lies upstream – and solved it with technology for retrofit of heat exchanger designs or design into new.

Industrial Technologies icon Industrial Technologies

Global oil demand is expected to reach 100.6 million barrels per day by the end of 2022, with refining capacity increasing annually over the next 5 years. It is thus the perfect time for refineries to tackle the fouling problem of heat exchanger technology responsible for tremendous energy consumption, emissions and billions of dollars of lost revenue. The EU-funded FlowEnhancer project has developed Flow Optimiser, a shell-and-tube heat exchanger inlet flow modulator that can be retrofit or built into the inlet of new heat exchangers. It distributes the flow more evenly over the exchanger tubes, reducing fouling ‘hotspots’ in the exchanger and significantly enhancing heat exchanger efficiency.

The preheat train barrels into the future

Oil refineries ‘refine’ crude oil into higher-value commodities in a three-step process that begins with the fractionation of crude into smaller molecules. To achieve adequate fractionation, the crude stream must be fed into the distillation column at a very high temperature. Typically, a so-called crude preheat train precedes the fractionation step, utilising heat exchangers and waste heat from other process streams to reduce energy consumption. Total fouling-related costs in heat exchangers and boilers for major industrialised nations is estimated to exceed USD 4.4 billion annually. Computational fluid dynamics (CFD) modelling in the context of the previous FP7-funded CLEANEX project unexpectedly identified the inlet as the source of the problem. FlowEnhancer reduced the analyses’ computational load and focused on the relevant regions with brilliant results. According to Derek Sumsion, R&D Manager at Tube Tech International, “extensive high-resolution CFD modelling, far beyond that planned for FlowEnhancer, led to the design of an insert for the inlet that evenly distributes the inlet flow of different crude oil compositions in a multitude of exchangers with different tube volumes, minimising fouling.”

The first of its kind

Heat exchanger design has not changed much over the last four decades. Anti-fouling solutions, when employed, are located in the heat exchangers. As FlowEnhancer demonstrated, the problem is upstream. The Flow Optimiser reduces turbulence while enabling a 10 % increase in tube inflow velocity and a corresponding 7 °C increase in outlet temperature. This increases the exchanger efficiency, drastically reducing energy consumption, global CO2 emissions and costs while extending the asset’s life. The potential savings to refineries could reach up to EUR 1.8 million per year and a 9:1 return on investment per heat exchanger. Sumsion expands on outcomes, planned and unforeseen: “In addition to discovering the non-uniform inlet flow distribution, tests at Shell India conceived in light of pandemic-related challenges supported the expansive CFD analyses behind the Flow Optimiser concept, novel pulsation technology to reduce fouling at lower velocities, and potentially a long-awaited redesign of heat exchangers. We have many new projects for the future.” The new Flow Optimiser will be installed at a Shell site in October 2021 to provide information about fouling in the field. Meanwhile, the management team is raising capital and liaising with customers to accelerate the growth and uptake of Flow Optimiser. Flow Optimiser for the preheat train has left the station.

Keywords

FlowEnhancer, heat exchanger, fouling, Flow Optimiser, fractionation, preheat train, crude oil, refineries, CFD, computational fluid dynamics

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