At the recent American Fuel & Petrochemical Manufacturers (AFPM) 2013 Q&A and Technology Forum, Emerson’s Tim Olsen had an article in the conference daily publication. You may recall Tim from earlier posts and as the past Chair for the AIChE Fuels and Petrochemicals Division.
The article, New challenges with shale oil refining and crude blending, explored impacts of the growing North American shale oil (light tight oil) and gas production on downstream operations.
Tim opens noting the refining challenge:
…these typically lighter crude oils don’t come without some processing challenges. For starters, because they are lighter, they need to be blended with other crudes to get the right balance for best utilization of existing process units.
Without consistent blends, the operators must constantly adjust the crude unit operations. Without any blending:
…the greater percentage of lighter components can bottleneck the crude overhead and naphtha processing units, with limited production of other fuel products like diesel and jet fuel.
When two different crude sources with varying properties are blended, it:
…can introduce unknown issues with crude incompatibilities. When crudes are incompatible, accelerated fouling occurs in the crude unit heat exchanger train due to a rapid increase in asphaltene precipitation. Accelerated fouling can lead to additional energy costs with the crude unit fired heater, limiting throughput when the fired heater becomes duty limited, or causing an earlier shutdown for exchanger cleaning.
To address some of these challenges, some refiners are:
…adding temperature measurements around all the crude unit heat exchanger bundles that were not included in the original process design, and using software applications to monitor heat exchanger fouling to gain a better understanding of accelerated fouling due to crude incompatibilities, and to identify which tube bundles require cleaning.
…wireless temperature and differential pressure measurements for online process conditions… and monitor the condition or “health” of process equipment, not just heat exchangers but also process pumps, control valves, and other assets.
Tim explains that refiners must balance the cleaning costs of the heat exchange bundle versus the additional energy required for the heat transfer process as the tubes foul. With block and bypass valves, cleaning can be done without shutting the unit down, but throughput is reduced. An automated monitoring strategy can optimize availability and maintenance costs:
Online indication of asset health provides advanced warning and allows enough time for spare equipment to be safely brought online, eliminating process upsets, off-spec product and safety incidents that result from an unexpected trip. Advanced warning arms maintenance staff with the information they need to determine when servicing is necessary to prevent a failure, even on assets that do not have spares.
Tim concludes noting that online measurements, automated analysis, and automated alerts help reduce the risks associated with manual monitoring and provide earlier identification of abnormal situations.
Here’s more on heat exchanger monitoring, if you’d like additional detail.