Science reduces sulphur at Burnaby Refinery

Refineries have made huge strides in reducing sulphur from gasoline. Today, only the tiniest traces can be found in transportation fuels, and refineries are constantly working on eliminating that sulphur altogether.

At Chevron’s Burnaby Refinery, for example, a state-of-the-art sulphur recovery system was installed in 1993 to meet and exceed federal guidelines.

Lead process engineer Oswaldo Garcia said Chevron is committed to protecting the environment. “It’s about making sure that we remove this sulphur from the fuels consumers are using and lowering the atmospheric emissions at the source.”

How it works

Remarkably, the process used at Burnaby is based on a well-known and proven technology. The Claus process was originally patented by German chemist Carl Friedrich Claus in 1883. Of course, the processes have evolved over the years, starting with the introduction of the modified Claus process in 1938 and then gradually incorporating other cutting edge technologies to further increase the levels of sulphur recovery.

First, it’s important to note that sulphur is a naturally-occurring contaminant in crude oil; it is not an additive. As the refinery turns crude oil into gasoline, jet fuel and other products, the sulphur needs to be safely removed from these products.

During the processing of different hydrocarbon products, sulphur bonds with hydrogen to create hydrogen sulphide (H2S), a gas that cannot be released into the air. Therefore, in the Burnaby Refinery, H2S-laden streams are fed into a sulphur recovery unit (SRU), where they are transformed into water vapour and elemental sulphur.

“It’s a multistage sulphur recovery process,” Garcia explained. “We transform H2S into liquid sulphur first in a thermal reactor, and then catalytically in a series of reactors or converters... we achieve about 70 per cent recovery in the thermal reactor and with the catalytic steps we go up to more than 98 per cent recovery.”

The process is “dictated by thermodynamics and that has its limits,” he said. “In order to achieve higher levels of recovery, a different process is required to further process the remaining sulphur compounds in the tail gas.

So, once the “tail gas” leaves the Claus reactors (named, obviously, for the German chemist), it is fed into a SuperClaus reactor that uses a specially designed type of catalyst that boosts the sulphur recovery to more than 99 per cent.

As Garcia explains, the thermal stage can remove about 70 per cent of the sulphur. Going the next step, up to 98 per cent. “With the Superclaus reactor, we achieve more than 99.6 per cent sulphur recovery.”

“Any (refinery) with an SRU would have the modified Claus process in the front end as described before. Generally, the difference would be found on the technology used in the tail gas unit.”

The SRU stores the sulphur in an underground pit and sells it to third parties as liquid sulphur.

After the sulphur is removed and turned into a liquid sulphur product, it is dried and made into pellets or flakes for multiple other uses, including fertilizer.

Big environmental benefits

Chevron continually strives to not just meet, but exceed federal guidelines. The entire goal of the sophisticated SRU, with that final big “super step,” is to be environmentally responsible, said Garcia.

“If we don’t recover that sulphur in the SRU, we would be using it in the fuels we use in our daily lives,” he continued.

“It’s about keeping the environment free from atmospheric pollutants, and in this case the SO2 itself which is the ultimate product of sulphur compounds combustion. It’s about making sure that we remove this sulphur from the fuels consumers are using.”

For more on how Chevron is reducing the environmental impact of their Burnaby refinery, check out:

No smelly gas fumes: Burnaby Refinery captures gasoline vapour
How wastewater comes clean at the Burnaby Refinery

And learn more about how refineries are reducing GHG emissions.

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