Gasoline demand has fallen to its lowest level in decades, and refineries have reduced production as a result. However, low throughputs frequently result in unfavorable conditions that lead to more coking, fouling, hot spots, etc. The severity of these conditions is difficult to predict, which makes furnace condition monitoring the preferred way to understand equipment characteristics and maximize preparedness when demand improves again.
Stay-at-home orders, travel restrictions, and other proactive measures have prevented roughly 530 million new cases of COVID-19around the globe and slowed its spread. This is excellent news. However, it is undeniable that shutdowns have hurt the oil and gas industry as demand plummeted for motor gasoline, distillate fuel oil (primarily diesel), and jet fuel. Of these three products, distillate fuel oil has seen the least decline since the transport and agricultural sectors are essential services and, thus, remain fairly active even as many airplanes and personal vehicles sit idle.
Refinery Operations Before and During a Pandemic
Most U.S. refineries are configured for gasoline production. Before many businesses were shut down and stay-at-home orders were issued, motor gasoline product supplied an average of 8.9 million b/d, based on 2020 data through March. Since then, this figure has fallen 40% to 5.3 million b/d as of the week ending April 17.
With lower demand, refineries have had to reduce their overall production. But since long-haul trucks, trains, and agricultural machines are still running near pre-pandemic levels, some facilities moved toward producing diesel. This shift is doable but not always simple, depending on the refinery configuration. For example, a furnace’s atmospheric and vacuum columns may have to be set up differently to produce distillate fuel instead of gasoline. But regardless of the finished fuel, storage capacity is limited, and refineries are forced to reduce feed rates until demand increases again.
Lower throughput is not an issue in “clean service” heaters, such as what is found in hydrodesulfurization units, hydrotreaters, and catalytic reformers. These furnaces handle relatively clean process fluids and do not typically coke or foul when working with lower feed rates. The same can’t be said for the heaters with heavier feed, such as crude, vacuum, and coker units.
Coking and Fouling in Furnaces
In coking/fouling heaters, the flow regime of liquid and vapor is stable at high throughput. At low throughput, however, the vapor and liquid velocities decrease, which could lead to higher film temperatures, flow issues (stratified, plug, slug), and dry points, resulting in hot spots, localized overheating, and accelerated coke formation.
Furthermore, when demand increases again and refineries ramp up production, these units would reach their tube skin temperature threshold at lower severity due to the effect of internal coking/fouling layer buildup over time.
Example of an IR scan
Furnace Condition Monitoring by WIKA USA
It is difficult to predict or quantify the severity of coking/fouling deposition at low throughout operation without information on the tube skin temperatures, infrared (IR) images, and operating data. That’s why furnace condition monitoring is important for identifying and managing issues of enhanced coking, fouling, and hot spots resulting from non-uniform firing, flow non-uniformity, flame impingement, etc.
WIKA USA’s Furnace Condition Monitoring (FCM) services use IR scans and tube skin temperature monitoring analyses to compile a thorough profile of the process tubes in the radiant/convection section of fired heater equipment. Our temperature specialists then share this information with refineries so they can make any necessary changes to the operations. FCM services can also provide onsite support to evaluate the effects of any modifications. Several refineries in the U.S. and elsewhere have already benefited from our furnace condition monitoring services and recommendations.
The global pandemic will ease someday, and the demand for fossil fuels will once again rise. Furnace condition monitoring is a proactive method to keep heaters in good working condition and to identify/rectify issues at their incipient stages. Doing so helps avoid unplanned shutdowns and allows refineries to optimize their assets’ operation. WIKA USA is a global leader in innovative ETM (electronic temperature measurement) solutions for the refining and petrochemical industry. For more information on whether your refinery could benefit from WIKA’s Furnace Condition Monitoring services, contact our electronic temperature specialists.
