Argonne and KPM Developing New Efficient Process for Extracting Hydrogen from Hydrogen Sulfide in Unrefined Petroleum, Including Oil Sands

26 August 2008

Researchers at the US Department of Energy’s Argonne National Laboratory and Kingston Process Metallurgy Inc. (KPM) of Kingston, Ontario are developing a new process to extract and reuse pure hydrogen from the hydrogen sulfide that naturally contaminates unrefined oil, including oil sands. The hydrogen can then be used to upgrade and clean crude oil and petroleum products and aid in a number of refining processes.

The process uses a molten copper reactor invented by Argonne and KPM researchers. Hydrogen sulfide gas is first separated from the crude oil stock in the reactor, using technology already in place. This gas is then bubbled though molten copper, which releases pure hydrogen, which is captured. As the sulfur reacts with the copper, the copper is gradually turned into copper sulfide.

The copper sulfide is subsequently reacted with air to recover the pure copper. This copper is then reused in the process with negligible losses, according to Gregory Krumdick, an engineer in Argonne’s Energy Systems Division. This reaction of copper sulfide with air also releases a concentrated stream of sulfur dioxide, which is reacted with water to create concentrated sulfuric acid, used widely in the chemical industry and which has become a valued agricultural commodity.

The reactions between the hydrogen sulfide and copper and the copper sulfide and air release energy that helps to heat the system, enabling the researchers to harvest the products efficiently, Krumdick said. The system operates at a temperature of about 1,200° Celsius.

Technologies that are in use today, including the widely used Claus process, are more energy- and capital-intensive. In addition, they also lose the hydrogen in the process. Instead of capturing the hydrogen from the hydrogen sulfide, the Claus process ends up converting it into water.

—Gregory Krumdick

The multi-step Claus gas desulfurizing process was invented more than 100 years ago and is the most widely used method for removing the hydrogen sulfide that is present in crude oil and raw natural gas and recovering elemental sulfur.

In the Claus process, an acid gas feed is partially oxidized to generate sulfur dioxide (SO₂), which then reacts with the remaining hydrogen sulfide (H₂S) over a catalyst to produce sulfur and water. Most Claus sulfur plants contain two or three catalytic stages after the thermal stage and can achieve 94-97% sulfur recovery efficiency. A number of enhancements to the Claus process have emerged over the years, including the use of oxygen or liquid redox systems to boost efficiency further.

However, the Claus process is also believed to be more limited than the Argonne-KPM process in terms of the other types of impurities it can handle, according to the researchers. Costly energy-intensive modules that scrub other contaminants, such as ammonia, methane and carbon dioxide from raw oil and natural gas must be separately attached to Claus processing facilities.

Argonne computer modeling strongly indicated that the Argonne-KPM process would deal with those other impurities, a conclusion that was later experimentally proven. Contaminants such as ammonia and various hydrocarbons are reformed to their elemental constituents, providing an added benefit to the process, Krumdick said.

Argonne and KPM continue to scale up their experimental work to further test the process with a pilot scale reactor. Argonne and KPM began working on the technology in 2003 as a laboratory-directed research and development proof-of-concept project. Argonne is collaborating with KPM, a bench-scale process development firm, under a work-for-others agreement. KPM is supported in part by Natural Resources Canada (NRCan), which has provided C$600,000 (Canadian) for the research over the last three years.