Refining Bitumen Without Sulfur Oxide Emissions
Funded through Round 8: Oil and Gas in 2014, the project objective was to design, build and operate a 10 barrel per day (bpd) pilot plant using Enlighten Innovation’s (formerly called Field Upgrading) proprietary DSU® technology. This pilot aimed to scale the technology to a larger continuous process at pilot scale to prove the technology further and gather the data necessary to design a commercial unit.
Enlighten Innovation’s DSU® technology selectively targets the components of bitumen and other heavy petroleum feedstocks that reduce the value of an upgraded product without reducing the volumetric yield. This includes sulfur, heavy metals and the total acidic number (TAN). While the technology initially focused on upgrading transportation fuels, marine fuel was determined as the best initial market. This technology significantly increases the American Petroleum Institute (API) gravity – a measure of petroleum liquid heaviness with respect to water – and results in a near pipeline-ready product, with no sulfur oxide emissions and lower GHG lifecycle emissions.
How does it work? The DSU® process can be separated into three main process sections: (1) the reactor, (2) the oil-solids separator and (3) sodium recovery. First, sodium, hydrogen and heavy oil are mixed in a reactor. The sodium eliminates sulfur and metal atoms from the heavy oil molecules and the hydrogen helps make the product oil ‘lighter’. Next, the oil-solids separator separates the solid metals and sodium sulfide from the oil. Finally, in the sodium recovery section sodium is separated from the sodium sulfide and recycled back to the reactor. The ability to recover the sodium and reuse it in the reactor makes the DSU® process unique and cost-effective.
The Molten Salt Challenge
In terms of lessons learned, making molten sodium flow continuously was the largest challenge. From the beginning, the project struggled with the molten sodium feed system to the reactor, especially during the first month of pilot plant operations. The root problem is that molten sodium solidifies or ‘freezes’ easily, which makes it very difficult to pump into the high-pressure reactor. To rectify this issue, the project successfully demonstrated a standalone high-pressure sodium pumping design and incorporated it into the design for a reactor scale-up test.
The project also faced challenges around the metallurgy required to contain the reaction of sodium and sulphur. This was due to the potential for caustic stress corrosion cracking. To ensure the most effective materials were used for the reactor construction, the project conducted a corrosion study utilizing corrosion coupons installed within the reactor vessel that were exposed to run conditions for several months. The range of metallurgy evaluated for reactor construction includes carbon steel, stainless steel, Ni-200 and Inconel alloys. These learnings ultimately lead to the project utilizing dual certified stainless steel as the chosen construction material.
What’s next?
This project de-risked DSU® technology and was moving towards commercialization with the CleanSeas demonstration project, a follow up project also funded by ERA. However, in 2024, the project was canceled part way through the construction of the demonstration site. The technology was more complex to develop than originally anticipated, leading to financial stress and uncertainty for the success of the technology going forward.