Capture the dream

Tore Torp, a pioneer of CO₂ capture and the coordinator of StatoilHydro’s Europe-wide CO₂ capture and storage research programme at the Sleipner gas and oil field in the North Sea, says the project is an important step forward. “This technology is applicable to all types of fossil fuel and could have major environmental benefits,” he says, “but research is needed to reduce the costs and improve  performance and reliability. The results will be highly significant for future capture plants.”

The project will create two pilot plants to test the most promising CO₂ capture technologies at the new combined heat and power plant at the Mongstad complex, which also comprises an oil refinery, a fractionation plant and a crude oil terminal. The power plant is fuelled by both natural gas and refinery gas. StatoilHydro and government-owned Gassnova have also committed to building a full-scale plant based on the technology that proves most successful.

The approaches to be tested are based on absorption of CO₂ in either amine or chilled ammonia. The technology centre will verify their relative effectiveness and assess which gives the best overall economy – a critical factor. Both have been used commercially in removing CO₂ from natural gas, but this is the first application with purely environmental motives. Aker ASA and Alstom Power have been contracted to build the pilot plants, which will use amine and chilled ammonia respectively.

“Mongstad is a result of the escalating debate around global warming,” says Hans-Jacob Svensen, Segment Manager, Energy & Environment, Alfa Laval Nordic. “Private vehicle emissions have long been a political issue, but in fact they only account for around 5 percent of global CO₂ discharge. Power plants burning fossil fuels are responsible for around eight times as much. CO₂ capture technology could reduce total emissions by up to 20 percent. We’re proud that Alfa Laval heat exchangers play a part in this.”

Another of the project’s goals is to develop the market for CO₂ capture technology, which can be applied to power plants fired by any type of fossil fuel. “There are around 7,500 coal-fired power plants, which contribute a large chunk to the total CO₂ discharge,” Svensen says. “And more than 500 plants are scheduled to become operational in the coming five years.”

StatoilHydro and Alfa Laval have a 10-year history of partnership in pioneering CO₂ capture at Sleipner, for which Alfa Laval supplied all the heat exchangers, and the companies recently signed a global preferred supplier agreement for heat exchangers that will pave the way for more Alfa Laval heat exchangers to be used in projects to come. Alfa Laval will also contribute knowledge, as well as information regarding other products and developments.

The biggest challenges are economic rather than technical, Torp says. “Energy consumption is the toughest issue,” he says. “This accounts for 70 to 80 percent of the cost of capture; the chemical reaction in the absorption process is strong, so a lot of energy is required to strip the CO₂ afterwards. Absorption is most effective at low temperatures and separation is most effective at high temperatures, so the circulating absorption medium must be repeatedly cooled and heated. Heat exchangers are therefore a critical part of the process.”

Safe storage of the stripped CO₂ is another important area for developing a widespread market for the technology, and this continues to be researched at Sleipner. “More than 11 million tonnes of CO₂ have so far been injected into an aquifer more than 800 metres below the seabed and successfully contained,” Torp says.

Other challenges for the Mongstad project include the difference in CO₂ concentrations between natural gas and power plant flue gases (exhaust gases that leave through the chimney), as well as scaling up from pilot to full-scale operation. “The performance of the heat exchangers will also be even more critical due to the high temperature of the flue gases,” Torp says.

The pilot plants are expected to be completed in 2011 and operative in 2012. The Norwegian government will make a final decision on the full-scale plant when the test results are clear.