Cottam Power Stations --- Before Apply CCS Technology

Before we start to talk about CCS at power stations, let’s look at some news about CCS from Research Councils UK.

“In April 2012, The Engineering and Physical Sciences Research Council (EPSRC) and the Department of Energy and Climate Change (DECC) announced a £13 million investment to establish a UK Carbon Capture and Storage (CCS) Research Centre.”

“EPSRC plans to invest approximately £10 million over a five-year period while DECC has started its CCS commercialisation programme and roadmap which will set out the Government’s vision for achieving commercial deployment of CCS in the UK in the 2020s, including investing £125 million in CCS research and development from the year 2011 to 2015.”

Now let’s look at the application of carbon capture and storage in power stations. There are many proposals of CCS in power stations in the UK, today I will focus on Cottam power stations.

A view of the coal-fuelled Cottam power station in Retford, U.K.

Cottam power stations has a pair of power stations (Cottam power station and Cottam development centre), located at Cottam near Retford in Nottinghamshire. Cottam power station is owned by EDF energy , whereas Cottam development centre is owned by E.ON UK.

Cottam power station is a coal- filled power station which has a generating capacity of 2 million kilowatts (kW) per year. It generates about 4% of total electricity supply of the UK market. In 2007, WWF ranked Cottam power station as the second of UK’s worst climate polluting power station, and the 20th in the EU (WWF, 2007). In the year 2006, it has around 10,029,024 Tonnes of carbon dioxide emission with near 940g carbon dioxide released per kWh electricity generated.

Next post I will talk about how CCS works at Cottam power station, how much carbon emission can be reduced and what is the cost.

Reference:

• Research Councils UK. http://www.rcuk.ac.uk/Pages/Home.aspx
• EDF Energy's coal-fired power stations.

  http://www.edfenergy.com/energyfuture/edf-energys-approach-why-edf-energy/coal-and-edf-energy
• Europe’s Dirty 30, WWF (2007). http://awsassets.panda.org/downloads/european_dirty_thirty_may_2007.pdf
• Photo from Talea Miller (2009).  Experts Sound Off on U.S. Role, Expectations for Copenhagen. http://www.pbs.org/newshour/updates/north_america/july-dec09/climate_11-25.html

A New Number, A New Peak

On 5th December, 2012, the Mauna Loa Observatory: Scripps Institutionof Oceanography gave the average value of concentration of atmospheric carbon dioxide in November. Two months ago, before I wrote the first post, the mean atmospheric CO₂ concentration in September was 391.07ppm.The concentration of carbon dioxide in the atmosphere in November 2012 hit a new peak - 392.92ppm. 

A paper by James Hansen from the NASA Goddard Institute for Space Studies stated that “350 parts per million” is the safe upper limit for the atmospheric carbon dioxide concentration, otherwise there may have a risk of seeding irreversible catastrophic effects. Another research from Ken Caldeira suggested that anthropogenic carbon dioxide released in the future may need to be eliminated in order to stabilise the global-mean temperatures.

Reference:

• Mauna Loa dataset. Mauna Loa Observatory: Scripps Institution of Oceanography。 
• Caldeira, K., Matthews, H. (2008), Stabilizing climate requires near-zero emissions,Geophys. Res. Lett., 35, L04705
• Hansen, J. et al (2008). If emissions of greenhouse gases are reduced, how quickly do their concentrations in the atmosphere decrease. 

CCS in the UK

The CCSA published a paper on 5th December 2012 discussed about “gas will support decarbonisation of the electricity mix.”

The UK government confirmed a number of steps that would be taken to stimulate investment in gas generation in its Gas Generation Strategy on 5th December 2012. New gas-fired power stations which emits at least have less carbon are going to be built over the following twenty years to replace retiring coal, older gas and nuclear power stations. Also those power stations need to provide the flexibility to balance out increasing amounts of wind and nuclear energy.

Secretary of State Edward Davey said that “The Gas Generation Strategy also confirms the Government’s commitment to supporting the development and commercialisation of Carbon Capture and Storage (CCS) technology, which will help to decarbonise gas, as well as coal, in future.”

On 03 April 2012 the UK government launched a new CCS Commercialisation Programme Competition in order to support practical experience in the design, construction and operation of CCS.

There are many CCS project proposals are planned in the UK. Here are two examples given by CCSA.

Don Valley Power Project, Yorkshire.

On February 10 2011, it was announced that bids had been submitted to the EU NER300 process to fund CCS projects for two projects in Hatfield. The first is a 900 MW IGCC plant in a consortium with National Grid, which was awarded 180 million euros funds from the EU's EEPR competition. The second project, a joint venture with Calix, was announced in November 2010 and is a 450MW gas fired Endex NGCC plant.

Caledonia Clean Energy Project, Scotland

Summit Power Group, National Grid, Petrofac - coal feedstock CCS plant;

On 20 March 2012 Summit Power Group announced entering into agreement with National Grid  to seek funding to develop a full-chain commercial-scale CCS plant in the Port of Grangemouth, west of Edinburgh on the Firth of Forth. The plant will use coal feedstock and produce hydrogen gas for commercial use. Carbon dioxide will be captured and transported via pipeline to St Fergus by National Grid Carbon and stored under the North Sea by CO2DeepStore, a Petrofac subsidiary.

Reference:

•     CCSA weekly newsletters, 06 December 2012. http://www.ccsassociation.org/news-and-events/ccsa-weekly-newsletter/
•     Government confirms role of gas in decarbonisation strategy. Theengineer. http://www.theengineer.co.uk/sectors/energy-and-environment/news/government-confirms-role-of-gas-in-decarbonisation-strategy/1014861.article#ixzz2EOH1WGgP
•     Don Valley Power Project . 2CoEnergy. http://www.2coenergy.com/don_valley_power_project.html
•     Summit Power, National Grid and Petrofac Team Up on Decc Carbon Capture Programme in UK. http://co2deepstore.com/co2-storage-for-caledonia-clean-energy-project 

Carbon Capture at Power Plants

The process of capture of atmospheric carbon dioxide and store it in geology for a long term is called carbon sequestration. Reduce the emission of carbon dioxide produced in power plant is a major geo-engineering method to mitigate the increase of atmospheric carbon dioxide concentration.

Carbon dioxide can be stored in deep sedimentary formations. Here is a map of sedimentary basins showing suitability as sequestration sites (Benson, 2008).

  

Combustion-based systems provide most electricity today. There are three capture techniques that can be used at fossil fuel power plans. They are pre-combustion, post- combustion and oxyfuel.

This is an amine-based postcombustion CO₂ capture system from a coal-fired power plant in Oklahoma, USA.

Post-combustion capture technology is the use after the burning of fossil fuels in the air. Carbon dioxide is separated by scrubbing from flue gas. Typically about 85%-90% carbon dioxide is captured by this “scrubbing process”. Post-combustion capture technology can be retrofitted to existing fossil fuel power stations. It can also be used at natural gas combined cycle (NGCC) power stations (Rubin, 2008).

Pre- combustion capture technology is used before the combustion of fossil fuels. Fossil fuels can be converted to a form amenable to capture. Fossil fuels are to a gas mixture of carbon dioxide and hydrogen firstly, and the carbon dioxide converted can be separated by scrubbing and then be stored. IGCC (Integrated Gasification Combined Cycle) is a process that electricity is through gas turbines and steam-powered stations. It costs less energy to remove CO₂, therefore, this process improves overall efficiency of power stations.

This is a precombustion CO₂ capture system used to produce synthetic natural gas from coal at the Dakota Gasification Plant in North Dakota.

Oxyfuel technology is “oxycombustion capture technology”. This technique uses pure oxygen during the fossil fuel combustion. Hence the flue gas produced contains only carbon dioxide and steam. Carbon dioxide and water can be separated by a cooling process, after that the flue contains almost only carbon dioxide left. Oxycombustion is the most efficient carbon capture method but cost more than other two methods.

Carbon dioxide under super critical state will be in to the target formation and stored after it is in power plants. There is growing agreement that exceptionally high retention rates are for carbon dioxide sequestration. Hepple and Benson (2005) considered that the goal of retention should be between 90 per cent and 99 per cent over a thousand years if sequestration is on a large scale.

There are four types of trapping modes: structural and stratigraphy trapping, residual CO₂ trapping, solubility trapping and mineral trapping. This graph shows the evolution of trapping mechanisms over time (IPCC 2005).

Reference:

• Benson, SM. Cole, DR. (2008) CO₂ Sequestration in deep sedimentary formation. Elements 4: 325-331
• Benson SM, Hoversten M, Gasperikova E, Haines M (2005) Monitoring protocols and life-cycle costs for geologic storage of carbon dioxide.
• Hepple RP, Benson SM (2005) Geologic storage of carbon dioxide as a climate change mitigation strategy: Performance requirements and the implications of surface seepage. Environmental Geology 47: 576-585   
• IPCC (2005) Underground geological storage. In: Metz B, Davidson O, de Coninck HC, Loos M, Meyer LA (eds) IPCC Special Report on Carbon Dioxide Capture and Storage, prepared by Working Group III of the Intergovernmental Panel on Climate Change. Cambridge University Press.
• Edward S. Rubin. (2008) CO₂ Capture and Transport

Carbon Capture and Storage - CCS

The website of the Department of Energy & Climate Change of the UK givesn a description of “What is CCS?” and “How does it work?” Also, it mentioned that the British Geological Survey had estimated that the minimum UK carbon dioxide storage is 7. 8GT and the capacity may range from 24GT to 240GT for a hundred years storage.

Here is a video from BGS about CCS in the UK.