Carbon capture and storage |
Supercritical* Supercritical*
Above: Evolution of unit size and steam conditions for CEGB pulverised fuel steam power plant Data from S. Maimari, UK power plants, Imperial College internal report, 2004
* Drakelow
by the authors. At the first of the PCC power projects, the Boundary Dam 3 (BD3) unit in Saskatchewan, replacement costs of the order of $20/tCO2
were reported for the selected
solvent in evidence to a government committee and also suggested in the 2019 GCCSI global status report, and improved reclaiming methods were apparently sought.
At the second PCC power project, the Petra Nova (PN) facility in Texas – a 50:50 joint venture of utility NRG and JX Nippon – the capture plant was not restarted in 2020 after a planned shut- down, with low oil prices stated as the reason (the captured CO2
The critical point of failure at the Kemper County IGCC project was the gasifier, but
were suggested in the 2019 GCCSI report. The new 100% owner, JX Nippon, has, however, said they “aim to be ready for resuming operation of the CO2
capturing facility in the second quarter next year”.
At the time of closure Petra Nova had operated for about three years (with some outages). The solvent used at PN had previously been tested at large pilot scale at Plant Barry for over 13 000 hours, but these tests obviously still could not give advance warning of any issues arising after a more extended period of operation.
was used for enhanced oil recovery). But, since the plant was not subsequently restarted when oil prices rose and the 50% share owned by NRG has recently been sold for $3.6 million to JX Nippon – less than 1% of its original value – it is possible that net operating revenues, even when sunk capital costs are discounted, are unattractive. Solvent management costs of the order of $10/ tCO2
this was a key enabler to allow a proven CO2 separation technology to be used and so an integral part of the whole CCS package. While much of the project cost over-run (> $7bn spent vs. ~$2.5bn estimated at FID) may be attributed to ‘mega project’ factors (ie, project management issues that are not technology- specific) the ‘show-stopper’ appears to have been the failure of the refractory lining of the gasifier when the plant finally commenced operation. The gasifier technology had been extensively tested at a pilot scale of 50 tonnes of coal per day but was then scaled up by a factor of over two orders of magnitude in throughput for Kemper County.
Evidence underlying the ‘factor of two scale- up plus two years operation’ recommendation comes from the, largely successful, history of steam plant development over a period of about 30 years in the second half of the 20th century, as, for example, undertaken by the CEGB in the UK. This involved significant innovation in both static high-temperature and high-pressure components in the boilers and also in rotating machinery subject to very high thermal and mechanical stresses in the turbines. As shown in the graphs above, unit sizes were never increased by more than a factor of two, and often much less, and the limits of high-pressure steam temperature and pressure for sub-critical units were tested before the major increase in unit output. Very importantly, although the
18 | October 2022|
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developments involved a number of technology suppliers the CEGB was able to take an overview of technical progress and ensure that effective knowledge transfer, and supporting investigations and research, took place at all stages.
The rest of this decade promises to see a number of new power CCS projects being built and, if successful, these can provide the reference plants for a rapid roll-out in the next decade to help avoid the risk of dangerous climate change. Some technical teething problems are to be expected but these can also be very valuable learning opportunities for the whole industry if proper knowledge transfer arrangements are in place for publicly- supported projects. However, provided a few simple precautions as outlined here are adopted, fundamental show-stoppers will be much less likely to be encountered and the current record, with one power CCS project currently running out of three built, will be converted to the necessarily high success level needed to encourage new investment and government policy support.
Declaration of interests:
The authors’ research work includes the use of non-proprietary solvents for post-combustion capture and also the development of small-scale test equipment for very long term on-site assessment of solvent management and corrosion (as recommended in this article).
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