Info

Power Efficiency Guide

Ultimate Guide to Power Efficiency

Get Instant Access

Total

7,887

13,466

1 "Known technological options" refer to technologies that exist in operation or in the pilot plant stage at the present time, as referenced in the mitigation scenarios discussed in the TAR. It does not include any new technologies that.will require profound technological breakthroughs. Known technological options are explained in the TAR and several mitigation scenarios include CCS

2 Storage of CO2 as mineral carbonates does not cover deep geological carbonation or ocean storage with enhanced carbonate neutralization as discussed in Chapter 6 (Section 7.2).

3 Saline formations are sedimentary rocks saturated with formation waters containing high concentrations of dissolved salts. They are widespread and contain enormous quantities of water that are unsuitable for agriculture or human consumption. Because the use of geothermal energy is likely to increase, potential geothermal areas may not be suitable for CO2 storage (see Section 5.3.3).

1 "Known technological options" refer to technologies that exist in operation or in the pilot plant stage at the present time, as referenced in the mitigation scenarios discussed in the TAR. It does not include any new technologies that.will require profound technological breakthroughs. Known technological options are explained in the TAR and several mitigation scenarios include CCS

2 Storage of CO2 as mineral carbonates does not cover deep geological carbonation or ocean storage with enhanced carbonate neutralization as discussed in Chapter 6 (Section 7.2).

3 Saline formations are sedimentary rocks saturated with formation waters containing high concentrations of dissolved salts. They are widespread and contain enormous quantities of water that are unsuitable for agriculture or human consumption. Because the use of geothermal energy is likely to increase, potential geothermal areas may not be suitable for CO2 storage (see Section 5.3.3).

Figure SPM.1. Schematic diagram of possible CCS systems showing the sources for which CCS might be relevant, transport of CO2 and storage options (Courtesy of CO2CRC).

emissions (see Figure SPM.1) (Sections 1.2, 1.4, 2.2, Table 2.3).

4. The net reduction of emissions to the atmosphere through CCS depends on the fraction of CO2 captured, the increased CO2 production resulting from loss in overall efficiency of power plants or industrial processes due to the additional energy required for capture, transport and storage, any leakage from transport and the fraction of CO2 retained in storage over the long term. Available technology captures about 85-95% of the CO2 processed in a capture plant. A power plant equipped with a CCS system (with access to geological or ocean storage) would need roughly 10-40%4 more energy than a plant of equivalent output without CCS, of which most is for capture and compression. For secure storage, the net result is that a power plant with CCS could reduce CO2 emissions to the atmosphere by approximately 80-90% compared to a plant without CCS (see Figure SPM.2). To the extent that leakage might occur from a storage reservoir, the fraction retained is defined as the fraction of the cumulative amount of injected CO2 that is retained over a specified period of time. CCS systems with storage as mineral carbonates would need 60-

Reference Plant

Plant with CCS

CO2 avoided

CO2 captured

CO2 produced (kg/kWh)

Figure SPM.2. CO2 capture and storage from power plants. The increased CO2 production resulting from the loss in overall efficiency of power plants due to the additional energy required for capture, transport and storage and any leakage from transport result in a larger amount of "CO2 produced per unit of product" (lower bar) relative to the reference plant (upper bar) without capture (Figure 8.2).

4 The range reflects three types of power plants: for Natural Gas Combined Cycle plants, the range is 11-22%, for Pulverized Coal plants, 24—40% and for Integrated Gasification Combined Cycle plants, 14—25%.

180% more energy than a plant of equivalent output without CCS. (Sections 1.5.1, 1.6.3, 3.6.1.3, 7.2.7).

What is the current status of CCS technology?

5. There are different types of CO2 capture systems: postcombustion, pre-combustion and oxyfuel combustion (Figure SPM.3). The concentration of CO2 in the gas stream, the pressure of the gas stream and the fuel type (solid or gas) are important factors in selecting the capture system. Post-combustion capture of CO2 in power plants is economically feasible under specific conditions5. It is used to capture CO2 from part of the flue gases from a number of existing power plants. Separation of CO2 in the natural gas processing industry, which uses similar technology, operates in a mature market6. The technology required for pre-combustion capture is widely applied in fertilizer manufacturing and in hydrogen production. Although the initial fuel conversion steps of pre-combustion are more elaborate and costly, the higher concentrations of CO2 in the gas stream and the higher pressure make the separation easier. Oxyfuel combustion is in the demonstration phase7 and uses high purity oxygen. This results in high CO2 concentrations in the gas stream and, hence, in easier separation of CO2 and in increased energy requirements in the separation of oxygen from air (Sections 3.3, 3.4, 3.5).

6. Pipelines are preferred for transporting large amounts of CO2 for distances up to around 1,000 km. For amounts smaller than a few million tonnes of CO2 per year or for larger distances overseas, the use of ships, where applicable, could be economically more attractive. Pipeline transport of CO2 operates as a mature market technology (in the USA, over 2,500 km of pipelines transport more than 40 MtCO2 per year). In most gas pipelines, compressors at the upstream end drive the flow, but some pipelines need intermediate compressor stations. Dry CO2 is not corrosive to pipelines, even if the CO2 contains contaminants. Where the CO2 contains moisture, it is removed from the CO2 stream to prevent corrosion and to avoid the costs of constructing pipelines of corrosion-

Figure SPM.3. Schematic representation of capture systems. Fuels and products are indicated for oxyfuel combustion, pre-combustion (including hydrogen and fertilizer production), post-combustion and industrial sources of CO2 (including natural gas processing facilities and steel and cement production) (based on Figure 3.1) (Courtesy CO2CRC).

5 "Economically feasible under specific conditions" means that the technology is well understood and used in selected commercial applications, such as in a favourable tax regime or a niche market, processing at least 0.1 MtCO2 yr-1 , with few (less than 5) replications of the technology.

6 "Mature market" means that the technology is now in operation with multiple replications of the commercial-scale technology worldwide.

7 "Demonstration phase" means that the technology has been built and operated at the scale of a pilot plant but that further development is required before the technology is ready for the design and construction of a full-scale system.

Figure SPM.4. Overview of geological storage options (based on Figure 5.3) (Courtesy CO2CRC).

Figure SPM.4. Overview of geological storage options (based on Figure 5.3) (Courtesy CO2CRC).

resistant material. Shipping of CO2, analogous to shipping of liquefied petroleum gases, is economically feasible under specific conditions but is currently carried out on a small scale due to limited demand. CO2 can also be carried by rail and road tankers, but it is unlikely that these could be attractive options for large-scale CO2 transportation (Sections 4.2.1, 4.2.2, 4.3.2, Figure 4.5, 4.6).

7. Storage of CO2 in deep, onshore or offshore geological formations uses many of the same technologies that have been developed by the oil and gas industry and has been proven to be economically feasible under specific conditions for oil and gas fields and saline formations, but not yet for storage in unminable coal beds8 (see Figure SPM.4).

If CO2 is injected into suitable saline formations or oil or gas fields, at depths below 800 m9, various physical and geochemical trapping mechanisms would prevent it from migrating to the surface. In general, an essential physical trapping mechanism is the presence of a caprock10. Coal bed storage may take place at shallower depths and relies on the adsorption of CO2 on the coal, but the technical feasibility largely depends on the permeability of the coal bed. The combination of CO2 storage with Enhanced Oil Recovery (EOR11) or, potentially, Enhanced Coal Bed Methane recovery (ECBM) could lead to additional revenues from the oil or gas recovery. Well-drilling technology, injection technology, computer simulation of storage reservoir performance and monitoring methods from existing applications are being

8 A coal bed that is unlikely to ever be mined - because it is too deep or too thin - may be potentially used for CO2 storage. If subsequently mined, the stored CO2 would be released. Enhanced Coal Bed Methane (ECBM) recovery could potentially increase methane production from coals while simultaneously storing CO2. The produced methane would be used and not released to the atmosphere (Section 5.3.4).

9 At depths below 800-1,000 m, CO2 becomes supercritical and has a liquid-like density (about 500-800 kg m-3) that provides the potential for efficient utilization of underground storage space and improves storage security (Section 5.1.1).

10 Rock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir.

11 For the purposes of this report, EOR means CO2-driven Enhanced Oil Recovery.

Figure SPM.5. Overview of ocean storage concepts. In "dissolution type" ocean storage, the CO2 rapidly dissolves in the ocean water, whereas in "lake type" ocean storage, the CO2 is initially a liquid on the sea floor (Courtesy CO2CRC).

developed further for utilization in the design and operation of geological storage projects.

Three industrial-scale12 storage projects are in operation: the Sleipner project in an offshore saline formation in Norway, the Weyburn EOR project in Canada, and the In Salah project in a gas field in Algeria. Others are planned (Sections 5.1.1, 5.2.2, 5.3, 5.6, 5.9.4, Boxes 5.1, 5.2, 5.3).

8. Ocean storage potentially could be done in two ways: by injecting and dissolving CO2 into the water column (typically below 1,000 meters) via a fixed pipeline or a moving ship, or by depositing it via a fixed pipeline or an offshore platform onto the sea floor at depths below 3,000 m, where CO2 is denser than water and is expected to form a "lake" that would delay dissolution of CO2 into the surrounding environment (see Figure SPM.5). Ocean storage and its ecological impacts are still in the research phase13.

The dissolved and dispersed CO2 would become part of the global carbon cycle and eventually equilibrate with the CO2 in the atmosphere. In laboratory experiments, small-scale ocean experiments and model simulations, the technologies and associated physical and chemical phenomena, which include, notably, increases in acidity (lower pH) and their effect on marine ecosystems, have been studied for a range of ocean storage options (Sections 6.1.2, 6.2.1, 6.5, 6.7).

9. The reaction of CO2 with metal oxides, which are abundant in silicate minerals and available in small quantities in waste streams, produces stable carbonates. The technology is currently in the research stage, but certain applications in using waste streams are in the demonstration phase. The natural reaction is very slow and has to be enhanced by pre-treatment of the minerals, which at present is very energy intensive (Sections 7.2.1, 7.2.3, 7.2.4, Box 7.1).

12 "Industrial-scale" here means on the order of 1 MtCO2 per year.

13 "Research phase" means that while the basic science is understood, the technology is currently in the stage of conceptual design or testing at the laboratory or bench scale and has not been demonstrated in a pilot plant.

10. Industrial uses14 of captured CO2 as a gas or liquid or as a feedstock in chemical processes that produce valuable carbon-containing products are possible, but are not expected to contribute to significant abatement of CO2 emissions.

The potential for industrial uses of CO2 is small, while the CO2 is generally retained for short periods (usually months or years). Processes using captured CO2 as feedstock instead of fossil hydrocarbons do not always achieve net lifecycle emission reductions (Sections 7.3.1, 7.3.4).

11. Components of CCS are in various stages of development

(see Table SPM.2). Complete CCS systems can be assembled from existing technologies that are mature or economically feasible under specific conditions, although the state of development of the overall system may be less than some of its separate components.

There is relatively little experience in combining CO2 capture, transport and storage into a fully integrated CCS system. The utilization of CCS for large-scale power plants (the potential application of major interest) still remains to be implemented (Sections 1.4.4, 3.8, 5.1).

What is the geographical relationship between the sources and storage opportunities for CO2?

12. Large point sources of CO2 are concentrated in proximity to major industrial and urban areas. Many such sources are within 300 km of areas that potentially holdformations suitable for geological storage (see Figure SPM.6). Preliminary research suggests that, globally, a small proportion of large point sources is close to potential ocean storage locations.

Table SPM.2. Current maturity of CCS system components. The X's indicate the highest level of maturity for each component. For most components, less mature technologies also exist.

CCS component

CCS technology

Research phase 13

Demonstration phase 7

Economically feasible under specific conditions 5

Mature market 6

Capture

Post-combustion

Was this article helpful?

0 0
Guide to Alternative Fuels

Guide to Alternative Fuels

Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future.

Get My Free Ebook


Post a comment