Catch it and keep it.
Energy industry-related emissions of carbon dioxide into the earth's atmosphere amounted to 31.6 gigatonnes last year. That figure seems unlikely to decline in the foreseeable future through any decrease in the type of electricity generation activities that produce C[O.sub.2]--continued investments in coal-fired power stations in India and China will see to that.
If such emissions are to be reduced there is only one solution--widespread deployment of carbon capture and storage (CCS) technologies that intercept C[O.sub.2] after it has been generated and convey it to reliable long-term storage.
These technologies are not futuristic. On the contrary they have been employed in piecemeal fashion for some time. Indeed the whole concept is "well understood and has been used for decades at a large scale in certain applications".
That is the verdict of the Global CCS Institute --whose 370 members range from governments to universities--as delivered in its latest annual report. This document, The Global Status of CCS 2013, says there are three main established applications of elements of the overall approach.
The first is the C[O.sub.2] separation done as a matter of routine in gas processing and other industrial systems. Second is the transport of C[O.sub.2] in pipelines. And third is the injection and geological storage of C[O.sub.2], which has been safely performed in saline reservoirs for more than 15 years and in oil and gas reservoirs for decades. In the latter instances it is usually part of enhanced oil recovery procedures, in which the C[O.sub.2] is used to help force residual reserves of the hydrocarbons to the surface.
The financial potential of the technique is considerable. The International Energy Agency estimates that the exclusion of CCS from the roster of technologies used to prevent carbon emissions from the electricity sector would increase total mitigation costs by $2 trillion by 2050 if the internationally agreed C[O.sub.2] targets were to be achieved.
Purely industrial activities currently account for more than 20% of the world's C[O.sub.2] emissions, so the applicability of CCS across both the power generation and manufacturing arenas is an important factor in its favour.
There is an increasing volume of research aimed at refining the technologies involved. The institute's report says there are 65 large-scale projects under way across the globe, of which 12 are in operation and eight under construction. China now has 12 projects across all stages of planning, compared to just five in 2010--it is second only to the US, which has 20 schemes.
The UK is showing serious ambition to implement CCS at large scale. The Department of Energy and Climate Change is putting up 1 billion [pounds sterling] for a commercialisation competition and has selected two preferred bidders. The two projects should be given the go-ahead for construction in the early part of 2015.
The first of the pair, the Peterhead project, aims to capture 90% of the C[O.sub.2] from part of an existing gas-fired power station in Aberdeenshire. The C[O.sub.2] will be transported to a depleted gas field beneath the North Sea for storage. The project involves Shell and utility company SSE.
The second scheme, the White Rose project, will capture 90% of the carbon dioxide from a new coal-fired power station at the Drax site in North Yorkshire, followed by its transport to and storage in a saline aquifer beneath the southern North Sea. The project involves Alstom, Drax Power, BOC and the National Grid.
Two other bidders, the Teesside Low-Carbon project and the Captain Clean Energy scheme, were put on a reserve list. On Teesside, a hydrogen-rich 'syngas' will be created from coal to fuel a gas-turbine power generation facility. Surplus C[O.sub.2] will be conveyed to storage under the North Sea. The backers are a consortium formed of BOC, International Power, Premier Oil and Progressive Energy.
The Captain Clean Energy project will also create syngas from coal to run a new 570MW power station at Grangemouth in Scotland. The resulting C[O.sub.2] will be conveyed first by 280km of undergound onshore pipeline and then by 78km of offshore pipeline beginning at St Fergus to storage 2km below the North Sea. The partners in the scheme are developer Summit Power, Scottish CCS specialist C[O.sub.2] DeepStore, Siemens and the National Grid.
The Captain project was outlined in more detail at a recent symposium at the Institution of Mechanical Engineers' headquarters in London. Chris Brookhouse, vice-president of Summit Power, said the initiative is intended to comprise a mix of new facilities with the judicious reuse of existing infrastructure.
The new power station will "burn only hydrogen" after the coal has been reduced to its "basic building blocks" of CO and [H.sub.2]. Impurities such as mercury and sulphur will be removed, while carbon will be taken out as C[O.sub.2]. Powering a gas turbine with hydrogen, he added, "is not the the norm" but is available commercially.
Both sections of pipeline that will be used to convey the C[O.sub.2] already exist, having been built to transport gas from North Sea wells. Brookhouse said that the onshore section, which skirts the eastern seaboard of Scotland, bypassing Aberdeen on the way, could also constitute a trunk line into which industrial C[O.sub.2] generators could feed their own output. Its maximum capacity of 10 million tonnes of C[O.sub.2] a year would allow for this possibility. Almost all Scotland's big emitters are situated close by the line.
Once out at sea, the initial plan would be for the C[O.sub.2] to be stored in the Captain sandstone formation to the north-east of St Fergus. But Brookhouse said that it is intended that the C[O.sub.2] will subsequently be used to support enhanced oil recovery (EOR) operations further out into the North Sea. These have the potential to produce "three billion-plus" barrels.
The storage and oil recovery aspects of the project cleverly dovetail into each other. The ability to inject C[O.sub.2] into the Captain formation would help to reconcile the requirement common to all power generation facilities to run at a constant level for maximum efficiency with the likely variability of demand for the gas for EOR operations. The possible EOR aspects of the project, though, would constitute a breakthrough in terms of North Sea oil recovery. So far, Brookhouse said, no use of C[O.sub.2] for EOR has been implemented there at all.
Brookhouse added that the 2 billion [pounds sterling]-plus cost of the project could be met entirely from commercial sources provided that an appropriate contract for difference--which guarantees revenue for low-carbon power generation--could be agreed for the Grangemouth facility.
The Captain scheme has a forerunner in the US using a similar approach. This is the Texas Clean Energy project, an initiative to build a 400MW power generation facility at Penwell. Some three million tonnes of C[O.sub.2] a year will be captured--90% of the total produced--of which two thirds will be used for EOR in nearby oilfields. Brookhouse said that this scheme, Summit Power's "first major CCS project", is running two to three years ahead of its UK counterpart and construction should start in 2013.
Even though full-scale CCS projects are now realistic propositions, there is as yet no convergence on just a few primary technologies --at least where initial capture is involved. On the contrary, instead of a single obvious candidate, there are a plethora of contenders. So says Professor Jon Gibbins, director of the UK Carbon Capture and Storage Research Centre, which is based at the University of Edinburgh but operates as a virtual institution involving 200 academics across the country.
Gibbins says there are three broad approaches to the issue of how C[O.sub.2] generation and capture can be handled. These are: the pre-combustion separation of C[O.sub.2], as at Grangemouth; the burning of fuel in a conventional manner followed by post combustion capture of the resulting C[O.sub.2], usually by chemical absorption; and the oxyfuel burning of fuel in a mix of oxygen and recycled flue gas that produces C[O.sub.2] in a manner that does not require a chemical process to capture it.
But the variables that might come into play at specific locations mean that within these basic parameters many microscopic decisions will need to be made about the details of how CCS will be implemented. Gibbins mentions as more macroscopic factors, for instance, whether gas or coal will be the fuel, whether the installation will be new-build or retrofit, the operational pattern of the facility, the availability of water, and even the ambient temperature of the location.
Gibbins says there is a long way to go before it becomes evident which CCS technologies will turn out to be the most effective. For example, the post-combustion capture process by chemical absorption requires a subsequent reheating of the liquid solvent to release the captured C[O.sub.2] so that it can be compressed and transported. That imposes a significant energy penalty on the overall efficiency of the installation.
He says he regards the state of CCS in the early part of the 21st century as being analogous to that of the automotive industry at the beginning of the 20th, when it was not obvious what fundamental technologies would become predominant. A mix of basic research and demonstration projects therefore seems likely to continue for some time to come even while full-scale implementations of the approach are getting under way.
In the UK, Gibbins says, funding for basic research which barely existed a decade ago is now being ramped up. The total amount either spent over the past five years or committed for the next two to three is in the order of 70 million [pounds sterling]. Most of that is allocated by the research councils. His research centre also has a relatively small amount--4 million [pound sterling]--at its disposal.
One initiative that the centre runs on its own account is a test facility known as Pact--pilot-scale advanced capture technology--operated jointly by the universities of Sheffield and Leeds at Beighton, with satellite operations at Cranfield and Edinburgh.
In addition, CCS is beginning to enter the engineering curriculum. A couple of MSc courses have been established, and Gibbins says that relevant project work is also now carried out by third-year undergraduates at his own university.
Relevant research is also taking place under the auspices of the Electric Power Research Institute, a global organisation with 700 employees that is funded by the industry. Karl Bindemann, technical executive at the organisation, says that CCS is now a distinct strand of activity that is growing in importance.
The institute has already been involved in two big demonstration projects in the US. But Bindemann admits that, to become a major enabler of carbon mitigation in the power industry, CCS will have to surmount problems of public perception and concern about the transport and safe storage of the C[O.sub.2]--ironically the aspects of the process that are arguably the most well-established and secure.
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|Publication:||Professional Engineering Magazine|
|Date:||Dec 1, 2013|
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