An annual symposium organised by Saskpower, the Canadian utility behind the world’s first carbon capture power plant, was this year timed to follow on from the ‘PCCC3’ conference on post-combustion capture held at the same venue in Regina, Canada. Almost a year on from the opening of the pioneering plant at Boundary Dam, the symposium offered a rare chance to hear some first-hand operational experience and details of the utility’s business case for the project.
Saskpower’s decision to invest in such an ambitious project owes much to its status as a government-owned, monopoly supplier of electricity to the Canadian province of Saskatchewan, with a heavy dependence on the local lignite for its generating capacity. A federal cap on power plant carbon emissions seeming likely, the company made a financially based decision to use CCS as a means of retaining some of the value of its extensive coal infrastructure whilst ensuring a low cost fuel supply for the future. Gas and wind generating capacity on the grid has also been greatly expanded, but a total dependence on the whims of the natural gas market was considered an excessive risk, despite North America’s current low gas prices putting the project in a somewhat less favourable light. The resulting conversion of an existing 140 MW Unit 3 at Boundary Dam carried a price tag of 1.47 billion Canadian dollars, including a complete upgrade of the turbine and boiler which was responsible for over a third of the total expenditure and all of an 18% budget overspend. Around half the money was spent on the carbon capture plant supplied by Shell Cansolv, with the remainder going on upstream controls for conventional emissions. The repowered boiler now generates 160 MW – reduced to around 120 MW when the carbon capture is operating.
A blow-by-blow analysis of the past year’s operation at the plant was refreshingly open, detailing a series of problems described as mundane teething issues. Of these, the most serious has been inadequate control of the temperature and flow rate of the steam used in solvent regeneration, leading to excessive solvent degradation and therefore a reduced capture rate and greater expenditure on replacement solvent. This problem now seems to have been rectified with a replacement steam attemperator, allowing the capture plant to return to full load. Fortuitously, low oil prices and a resulting low demand for the CO2 for enhanced oil recovery over this period has meant that a more manageable 65% of the flue gas was being sent to the capture plant anyway, although this did raise the question of whether there could be a CO2 surplus once the capture plant resumes normal service. Some other problems mentioned included slagging due to incinerating the sodium-rich solvent waste in the furnace, issues with pressure control in the boiler, and excessive fly ash build up in the amine absorber, although all of these difficulties appear to have been resolved or are being addressed in a current shutdown.
On the positive side, key components such as the flue gas cooler and CO2 dehydrator and compressors have been running more smoothly than may have been expected, and the plant has had generally good availability. An apparently unexpected benefit was that rapid shutdown of the capture facility could allow the plant to easily generate another 35 MW during times of peak demand – a capability which has been called upon on several occasions over the year. Saskpower’s willingness to share these kind of findings and operational experience from the world’s first carbon capture plant is a major benefit to progress of the technology, and also the aim of a new partnership with mining company BHP Bulliton that was announced to much fanfare and media presence during the day.
Plans for future capture units were much discussed but not confirmed, with the most likely candidate being the combined flue gas of Boundary Dam’s other two units. Capital costs are projected to be significantly lower for a second plant, based on reducing excessive design margins and implementing cost-saving measures revealed by the first project. It was found, for example, that as much of the plant as possible should be manufactured off-site in modules and shipped in. Of note is the fact that the CO2 limit of 420 kg/MWh since introduced by the federal government would only require 85% capture rather than the 90% demonstrated by Boundary Dam 3, from which significant cost savings could also be derived. Operating costs could also be reduced by around 10%, through measures such as combining the capture and power plant control rooms and reducing overstaffing.
As mentioned above, the CO2 produced by the plant is used for enhanced oil recovery in Saskatchewan’s ageing oil fields, with some also used in a saline aquifer storage test project called Aquistore. Unfortunately, I had to leave Regina before a final talk concerning this aspect of the process, but for those interested in obtaining the full story a detailed report on the whole project produced by Saskpower and IEAGHG is now available from the IEAGHG website.