Innovation in Global Power - Parsons Brinckerhoff

Thermal – Achieving New Efficiencies, Reducing Carbon Emissions
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and sulphur dioxide, and to reduce nitrogen oxides before
entering the carbon capture process. The carbon dioxide is
absorbed into a chemical solution 1 to remove it from the flue
gas, which is then emitted to atmosphere. The carbon dioxide
gas is removed from the absorbent, compressed and transported
for long-term sequestration. The challenge with this
technology is the need to scale up to utility-size capture.
Oxyfuel. An oxyfuel plant is one in which the fuel is
combusted in oxygen supplied by an air separation plant
rather than air. The resulting flue gases are purified to remove
particulate matter and sulphur dioxide, and to reduce nitrogen
oxides. Some of the captured carbon dioxide is recycled and
mixed with the oxygen feed to the boiler plant to control
combustion temperature. The remaining carbon dioxide is
then purified, compressed and transported to long-term storage.
The aim of oxyfuel development is to use as much of the
existing and proven equipment as possible; although some
issues remain relating to the control of combustion temperatures
within the boiler and the scaling up of air separation
plant to the size necessary for use in power plant applications.
Carbon Dioxide Transport and Storage
Transport. Captured carbon dioxide is transported to a longterm
storage location by either pipeline, truck, train, or boat,
although only pipeline would be feasible for the quantities
resulting from large-scale power generation—millions of tonnes
per year. The pipeline could transport carbon dioxide in the
gaseous phase, at pressures below 71 bar, or at higher pressures
where the carbon dioxide is present as a supercritical
fluid giving benefits from lower frictional losses. The scale is
such that a new pipeline infrastructure would be needed.
Storage. Storage of carbon dioxide is assumed to be in
geological formations, such as depleted oil and gas reservoirs,
deep saline aquifers and unmineable coal seams. These
formations need to provide storage with negligible leakage
to ensure that the carbon is sequestered over geological
timescales—thousands, if not tens of thousands of years.
The estimated global potential for the storage of CO2 in
these various sinks is detailed in Table 1. As would be expected,
the capacities for the oil/gas and coal storage options are
considerably smaller than those for the saline aquifers.
Even with the present global carbon dioxide emissions of
about 25 billion tonnes per year, the available storage capacity
extends for about 55 years to about 435 years. Whilst
this is not a solution, it does provide us with a temporary
breathing space in which to find and implement alternative
means of energy provision to satisfy human, social and
economic aspirations.
Technology
Analysis and
Lifetime Cost of
Generation
For the purposes of
reviewing the position
of gas turbine technology
within a carbon
constrained world, it was
necessary to identify those
power generation technologies where gas turbines will
continue to have a use and, importantly, the competitor
technologies. The technologies reviewed included:
• Coal supercritical pulverised fuel plant with flue gas
desulphurisation with and without carbon capture
• Coal integrated gasification combined cycle plant (IGCC)
with and without carbon capture
• Gas fired combined cycle plant with low NOx burner
technology with and without carbon capture
• New generation nuclear power plant.
Table 1: Estimated Capacity of
CO 2 Storage Options.
(Source: IEA-GHG, 2004)
Our analysis considered the impact of carbon and capital
on the lifetime cost of electricity generation. The extent to
which carbon pricing ‘feeds through’ to the cost of electricity
generation depends on the amount of free allocations
provided by government to individual plants. Given that
different allocation methodologies will be adopted in different
countries globally, it was considered to be of more value to
assume no allocations and that the full cost of carbon flows
through to the end electricity generation cost.
The level of carbon captured within the carbon capture
options will be specific to each plant’s detailed design. The
costs associated with the transport and storage of carbon
were based on various reference sources—an indicative
value of $10/ton CO2 sequestered was used. 2 The Capital
costs and operation and maintenance costs were based on
those observed in the market and included adjustments for
the recent increases in the underlying materials costs, such as:
• Steel: 35 percent increase since 2002
• Copper: 400 percent increase since 2002
• Nickel: 400 percent increase since 2002.
The analysis showed that the addition of carbon capture
and associated transport and storage charges added about
35 percent to 63 percent to the lifetime cost of electricity
generation. Introducing a carbon cost payable by the
generation plants for all CO2 emitted increased the electricity
costs across the board, as would be expected. For example,
if a $25/ton charge were placed on all CO2 emissions, the gap
between non-carbon capture and carbon capture would be
narrowed to 6 percent to 22 percent due to the proportionately
larger impact the carbon cost has on the non-CCS plant.
1 A number of possible chemicals can be used. Amine, ammonia, and potassium bicarbonate are just a few.
2 Imperial College, Potential for Synergy between renewables and Carbon Capture and Storage.
PB Network #68 / August 2008 6