The abundance of discounted crude oil, or opportunity crudes, as they are known in refinery parlance, has shifted refinery operators’ mindsets over the past few years.In a Hydrocarbon Engineering article, Equip for Opportunity Crudes, Emerson’s Marcelo Carugo and Tim Olsen describe ways that technology can help refiners avoid the challenges of processing crude oils with different properties that what is normally refined.
…the refiner does have flexibility in selecting catalyst and which crude oils to process. Although the catalyst loaded will be fixed until the next turnaround, there are options to change it depending on expected crude oil feedstocks, product quality and yield.
Marcelo and Tim describe the main challenges in processing opportunity crudes, including:
…crude blending to match a refiner’s configuration and processing capabilities, crude switch disturbances, fouling and accelerated fouling from incompatible crude blends, corrosion, energy balancing across the crude unit preheat exchangers, tight oils which have additional challenges related H2S (treated with amine-based H2S scavengers), paraffin waxes, filterable solids, API gravity variability, and catalyst performance related to higher levels of calcium and iron.
…can accurately measure tank level with a wide variety of crude oil gravity. In addition, as per API 2350, a second level measurement is required to avoid overfilling the tank.
When blending crude oils, Marcelo and Tim recommend having [hyperlink added]:
…coriolis mass meters to measure and control the crude blend ration. A volume base may not provide the desired blend unless lab samples are taken in a timely manner…
Hydrogen sulfide (H2S) is a very poisonous, corrosive, flammable and explosive gas that poses safety hazards unless properly treated and removed [hyperlink added]:
The mixing of the railcar [crude oil transportation] during movement along with a change in temperature can result in higher vapour pressure and the release of entrained H2S making the offloading a potential safety hazard. Hydrogen sulfide monitoring should be standard for loading and offloading…
Read the article for how additional measurements, analytics, final control and control strategies can help with corrosion monitoring & desalter levels, fired heater optimization and safety, atmospheric fractionators and personnel performance via training.
Tim and Marcelo conclude:
Opportunity crudes can be discounted and too tempting not to buy. As their properties can vary, a traditional crude assay does not always represent the crude oil delivered to the refinery. Hence, there is a needed for additional measurements, predictive analytics and advance process control to effectively handle these varying feedstocks. Automation technology and behaviour to utilise the new information is advancing to meet the new challenges with opportunity crude oil supply.
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