Boundary Dam
In 2011, construction began on a full scale integrated carbon capture and storage demonstration project at the SaskPower Boundary Dam lignite power plant, in Saskatchewan. Two years later and the facility is nearing completion. Boundary Dam is on course to being among the first low carbon fossil power plants in the world. The facility will capture one million tonnes of CO2 per annum from a 110 MW pulverised coal unit when it begins operation next year. The CO2 will becompressed and transported 60km for use in Enhanced Oil Recovery (EOR).
Construction of the CO2 capture facility is taking place in parallel to an overhaul of unit three in the coal power plant. The upgrades include boiler modifications and replacement of the steam turbine. As a result, even with the parasitic energy loss due to CO2removal the thermal efficacy of the unit will decrease.
The current upgrades will provide two services for the power plant: the removal of both SO2 and CO2, in a two stage process. In the first stage an optimised amine sorbent washes and binds with SO2 in the flue gas. This amine is then regenerated in a stripper column, releasing a pure stream of SO2. The SO2 is further reprocessed on site to produce sulphuric acid, a saleable commodity valuable in many industrial processes.
The CO2 removal process takes place after the flue gas has been sufficiently cleaned of SO2. The decalcified flue gas passes through a significantly larger absorber column where a different amine again washes the gas, this time binding and removing CO2. The CO2 rich amine is regenerated in a large stripper column, providing a high purity CO2 stream to the compressor room.
The scale of the facility, with the capacity to capture one million tonnes of CO2 per annum, is equivalent to a typical combined cycle gas power plant. In reality, if the process were employed at a gas power plant, the footprint and complexity would be smaller still as the SO2 removal and sulphuric acid conversion process would not be necessary, and lower volumes of CO2 would be produced.
Saskatchewan has significant coal reserves and a long-established coal mining industry. However, coal-fired generating units are responsible for 77% of greenhouse gas emissions from the electricity sector in Canada. The Federal Government of Canada therefore introduced a strict CO2emissions performance standard of 420 t/GWh for new coal-fired electricity generation units, and units that have reached the end of their useful life. The legislation will effectively outlaw unabated lignite and coal electricity generation from these plants when it comes into force in 2015.
SaskPower - an enterprise owned by the provincial state of Saskatchewan - has worked in close partnership with the Provincial government and local coal suppliers to make the Boundary Dam CCS project a reality. Several revenue streams helped make the business case for the project. The regulated electricity market in Saskatchewan provided valuable electricity price stability and predictability, assuring the plant of baseload dispatch. The Weyburn oil fields nearby meant that a sales contract for the CO2 produced has already been concluded: The purchaser - Cenovus Energy - will assume liability for storage. A supply contract is nearing agreement for the sulphuric acid the plant will produce. And finally, Federal Government support in the form of a Cdn$240 million grant with few strings attached helped the first movers involved in the project to fill a funding gap without compromising the commercial value of their learnings or their intellectual property.
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