Oxyfuel technology has been retrofitted at a 700-MW coal-fired power plant in Queensland, Australia, and is now capturing carbon dioxide from one of the plant’s six steam boilers. The Callide Oxyfuel project is being closely watched because—since Sweden’s Vattenfall in December cancelled a key 300-MW demonstration of oxyfuel combustion and postcombustion at the Janschwalde power plant in Brandenburg, Germany—it is one of only a handful of carbon capture coal-fired projects that use this technology to move past concept to construction.
Brisbane-based CS Energy began work in 2008 to modify one of six steam boilers at its Callide A Power Station near Biloela to enable it to produce power in oxyfiring mode for three years. Air Liquide built both the 660-metric ton-per-day oxygen plant and the carbon capture plant, which began operating in March (Figure 4). The oxyfuel boiler and carbon dioxide capture plant are expected to be fully operational later this year.
|4. Oxygen for life. Oxyfuel systems developed by Air Liquide were retrofitted in a 1970-built, 1998-recommissioned 30-MW steam boiler at CS Energy’s 700-MW black coal–firing Callide A power station. With oxygen available, the boiler can be started up, first on air and slowly moved to oxyfiring—a process where the flue gas is recycled and mixed with oxygen to take the place of the air. The oxygen production plant has a capacity of 660 metric tons per day at an oxygen purity of 98%. The carbon dioxide capture plant has been designed to produce 75 metric tons of carbon dioxide per day. This image shows the air separation plant. Courtesy: Global CCS Institute|
Callide Oxyfuel Project Director Dr. Chris Spero said that the first stage of commissioning of the plant under oxyfiring conditions had now commenced, with the successful integration of the oxygen production units with the coal-fired boiler. “This signals a major step forward for the project and the demonstration of how carbon capture technology can be integrated with existing coal-fired power stations,” Spero said.
The technology entails two air separation units that produce oxygen, which is mixed with a portion of exhaust gas from the boiler and recycled back into the process. Burning coal in this mixture results in a concentration of carbon dioxide in the final exhaust stream, where it can be more readily separated from the other exhaust gases in the carbon dioxide capture plant. Commissioning was critical to ensuring all of the elements of electricity generation and the oxyfuel and carbon dioxide capture processes are safe and thoroughly tested, Spero said.
The construction and initial commissioning phases of the project required more than 150 staff and contractors, who worked more than 400,000 man-hours. The A$206 million ($131 million) project is a joint venture between CS Energy, the Australian Coal Association, Xstrata Coal, Schlumberger, and Japanese participants J-POWER, Mitsui & Co. Ltd., and IHI Corp. It has so far been awarded A$50 million from the Australian Government under the Low Emissions Technology Demonstration Fund and A$17.5 million from the Japanese Government. The Callide Oxyfuel Project has also received financial support from the Queensland Government and technical support from JCOAL.
The project began at a pilot project scale at “about one hundredth of the size of Callide A Power Station,” CS Energy said. Pending the outcome of the 30-MW demonstration, the second phase of the project will include building a larger demonstration plant that produces 150,000 tons of CO2 per year for a test period of three to four years.
The Callide Oxyfuel Project team is now also assessing potential geosequestration sites to the west of Biloela in the Denison Trough. Studies have suggested that the area is ideal for storing CO2, as it has securely stored large volumes of gas for millions of years and has a very low level of seismic activity. The liquid CO2 produced at Callide A will be transported approximately 300 kilometers by truck to the Denison Trough.
CS Energy predicts the technology could be applied at commercial scale by 2020. If the project demonstration is successful, the next step would entail applying the technology to its existing coal-fired power stations and actively marketing oxyfuel to power stations in Australia and overseas.
The Callide CCS project is Australia’s only large-scale effort to develop carbon capture technology. In December 2010, the Queensland government scrapped the planned A$4.3 billion integrated gasification combined cycle ZeroGen project, after taxpayers had pumped A$150 million into the initiative. The government was advised to withdraw from ZeroGen after a report described it as “speculative.” In October 2011, the main company behind the ZeroGen project was placed in liquidation, confirming that ZeroGen is officially cancelled.
—Sonal Patel is POWER’s senior writer.