Great Plains Synfuels Plant
17.4 million (as of end 2008) tonnes/CO2
The $2.1-billion Great Plains Synfuels Plant near Beulah, North Dakota, began operating in 1984 and is currently one of just eight CCS schemes operating worldwide. Sequestration began in 2000 and the project continues to inject around 3 million tonnes of CO2 a year.
The US government supported its construction in order to encourage the development of alternative fuel sources. The goal was to produce methane (CH4) from coal. The synfuels plant is the only commercial-scale coal gasification plant in the US that manufactures natural gas. In 1997, the Dakota Gasification Company (DGC) agreed to sell captured CO2 from its Great Plains Synfuels Plant through a pipeline to the Weyburn and Midale oilfields across the border in Saskatchewan, Canada. Delivery of the first CO2 began in September 2000.
The plant has been owned and operated by Dakota Gas since 1988. About $477 million has been invested in the Synfuels plant since 1988 to achieve environmental compliance, improve efficiency, and invest in new byproduct development.
Dakota Gas, which is a subsidiary of Basin Electric Power Cooperative, shares natural gas sales revenue with the US Department of Energy (DoE) through an agreement established in 1988 when Dakota Gas purchased the plant from the DoE. The government has now recovered more than $1.3 billion of its investment through revenue sharing and foregone production tax credits of $754 million.
CO2 capture and storage
Using Lurgi gasifiers, the Synfuels plant gasifies lignite coal to produce gases and liquids. More than 16,000 tonnes of crushed lignite coal per day is fed into gasifiers, where it is mixed with steam and oxygen and then partially burned at a temperature of 1200°C (2200°F). This breaks down the coal to produce a mixture of gases. The gas is cooled to condense tar, water, and other impurities. Then it is passed through methanol at 70°C (-94°F) to removes compounds of sulphur and naphtha, and capture most of the CO2. This separates the synthetic natural gas from other compounds—mostly CO2. The daily production is 3050 tonnes of SNG, which is fed through gas pipelines to customers, and 13,000 tonnes of waste gas, 96% of which is CO2.