What difference could replacing a single heat exchanger make to the CO² emissions of an oil refinery? A big one. In fact, it’s had the same effect as taking 30,000 cars off the road, and meant a cost saving of more than USD 2 million per year. We visited the west coast of Sweden to find out more.
It is a frosty morning in Sweden’s western archipelago, a picture-postcard region where white and rust-red houses perch on bedrock worn smooth by wind and pounding waves. Fishing boats cut their way across the large fjord as a flock of seabirds circles overhead. Nestled in this idyllic landscape is one of Europe’s most modern and energy-efficient refineries – the Preem facility outside Lysekil.
Preem is Sweden’s largest fuel company and it has made sustainability central to its operations. It produces the first diesel in the world that has met the criteria of environmental sustainability certification – it’s made of 50 percent tall oil, a byproduct of the Swedish forest. The company also delivers extra energy from its two Swedish refineries – the other is in Gothenburg, just down the coast – to the surrounding area as heat, providing the energy equivalent of heating 36,000 homes. Its long-term ambition is to become entirely climate neutral. “Ultimately, we want to be part of the solution, not part of the problem,” says Gunnar Olsson, the company’s Technical Director.
The Lysekil refinary’s location by the sea is a source of inspiration for that work, says Olsson. “Being out here, so close to the coast, brings everything into sharper relief. We work and live side-by-side with nature.” Refining oil is a hugely energy-intensive process, so one area where the refinery has been focusing its efforts to reduce its environmental footprint is energy consumption. In 2012, Preem conducted a wide-ranging energy audit, when the refinery’s entire operations were analyzed for possible energy savings. The company’s management decided to replace four of its traditional shell-and-tube heat exchangers at the Lysekil refinery with an Alfa Laval Compabloc welded plate heat exchanger in the atmospheric distillation process. This is one of the refinery’s most critical and energy-intensive processes, where crude oil is separated into different fractions.
And the result? The single Compabloc exchanger delivers 22.6MW of energy recovery – 7MW more than the previous installation. “The investment lowered our energy use substantially, and it’s brought down CO², sulphur and nitrogen oxide emissions,” says Olsson. In all, Preem estimates that 14,600 tonnes of CO² emissions have been cut annually.
The energy intensity of refining oil makes energy the largest cost at the facility. The Alfa Laval Compabloc exchanger results in significantly higher energy efficiency, since the temperature difference between two fluids (what is called the temperature approach) in the exchanger can be low as 3-5°C for the Compabloc exchanger to work. This allows the exchanger to recover more heat than the shell-and-tube heat exchangers traditionally used by refineries, while using significantly less plot space. In purely economic terms, the resulting energy efficiency improvements of the new Alfa Laval exchanger are worth about USD 2.2 million per year at the Lysekil refinery alone.
As the next step in its improvements to the facility, Preem is building an entirely new vacuum distillation unit – the part of the refinery process where the heavy oil residue remaining at the bottom of the atmospheric distillation is further refined. And Preem has extended its investment in Alfa Laval’s Compabloc technology and is installing these welded plate heat exchangers extensively throughout the process. “It was a pretty straightforward decision,” says Olsson. “They are much more energy efficient and compact, and the technology works even with a temperature approach of just a few degrees.”
In the refinery process, there are often major problems with residue deposits on the surface of the heat exchangers, which reduces heat transfer efficiency and increases the hydraulic resistance – a factor that can lead to reduced capacity. But Alfa Laval Compabloc exchangers in these applications have fewer problems with fouling, which leads to greater overall efficiency and sustainability gains. Fouling is something that Ibrahim Tahric, Mechanical Engineer at Preem, has experienced first-hand. There is definitely less fouling on the Compablocs compared to the shell-and-tube exchangers we use otherwise, so they require less maintenance,” he says.
Due to the risks involved in the handling of fuel and other refinery products at high temperatures and pressures, the refinery business is known for being extremely conservative when it comes to introducing new technologies. Still, Eva Andersson, Refinery Industry Manager at Alfa Laval, sees a trend among refineries that they start with testing one Compabloc exchanger in the distillation process and then make a larger investment once they have seen the results. “Both the business case and the environmental benefits for the Alfa Laval Compabloc exchangers are so strong,” says Andersson. “When I list the advantages, people often don’t believe that all of it could be true, but then they try it out and they discover that it holds up. It’s encouraging that responsible players like Preem are leading the way.”
Learn more about process optimizations for oil refineries: