Dealing With Carbon Dioxide

CO2 sequestration captures R&D funding

15 March 2004

Against a background of persistently rising atmospheric CO2 levels, some key projects addressing power plant carbon dioxide capture and sequestration have recently received funding in Europe and the USA

The eventual objective of the Castor project is no less than the capture and geological storage of 10% of European CO2 emissions, or 30% of the emissions of large industrial facilities (mainly conventional power stations). Over the first four years the project has a total budget of u15.8 million, of which u8.5 million is in the form of a contribution from the European Commission (under FP6).

On 2-3 February 2004, the launch meeting was held for Castor at the Institut Français du Pétrole (IFP), which is leading the project and can build on its expertise in the full CO2 chain (capture, transport, and sequestration). At the launch meeting there were 65 delegates representing the 30 European companies and research institutions involved, from 11 different EU countries.

To accomplish Castor’s goals, new technologies must be developed for the capture and separation of CO2 from flue gases and its geological storage. In addition tools and methods are needed to quantify and minimise the uncertainties and risks associated with the storage of CO2. In this context, the Castor project programme is aimed more specifically at reducing the costs of capture and separation of CO2 (from u40-60/ton CO2 to u20-30/ton CO2), improving the performance, safety, and environmental impact of geological storage concepts, and, finally, validating the concept at actual sites.

Work on capture, which accounts for 70% of the budget, is aimed at developing new CO2 separation processes suited to the problems of capture of CO2 at low concentrations in large volumes of gases at low pressure. The processes will be tested in a pilot capture unit capable of absorbing 1 to 2 tons of CO2 per hour, from real flue gas. The pilot unit, the largest such capture system in the world, will be installed at Elsam’s 400 MWe Esbjerg 3 coal-fired plant. It is hoped to have the pilot unit in operation by the third quarter of 2005.

The work on storage will provide the European industrial community with four new storage facility case studies representative of the geological variety of existing sites across Europe: storage in an abandoned reservoir in the Mediterranean (the Casablanca field, operated by Repsol, Spain); storage in a deep saline aquifer (Snohvit, North Sea, operated by Statoil, Norway); storage in two

depleted gas reservoirs, one deep, 2500 m down (North Sea, Netherlands, operated by Gaz de France), and the other closer to the

surface and on land, 500 m down (Austria,

operated by Rohoel). Risk and environmental impact studies will be conducted and methodologies for predicting the future of these sites and for monitoring them will be developed, with the aim of enriching current knowledge in these areas.

Eight US DoE projects

Meanwhile in the United States the Department of Energy has just announced support for further projects addressing capture and storage of carbon dioxide from power plants. For a country that is declining to ratify the Kyoto protocol, the United States

government is supporting what look like some substantial research projects in this field.

In March the DoE’s Office of Fossil Energy announced it was funding eight new projects investigating new ways to capture carbon dioxide. Described as “revolutionary and experimental”, the new projects will explore innovative technologies that could lead to practical and cost-effective means of capturing and sequestering carbon dioxide. The projects support the President’s Global Climate Change Initiative, which aims to cut US greenhouse gas intensity by 18% by 2012.

The projects were selected under a solicitation announced in May 2003 by the National Energy Technology Laboratory, which will manage them for the Office of Fossil Energy. The solicitation called for proposals to conduct research in four areas: advanced separation techniques; advanced subsurface technologies; advanced geochemical methods for

sequestering carbon; and “novel niches”.

These topics were identified in February 2003 during a workshop conducted for the Energy Department by a committee of the National Research Council. About 70 participants from the private sector, academia, government, and other institutions met to discuss new approaches for reducing the amount of carbon dioxide entering the atmosphere from fossil-fuel-based energy systems. The report generated from the workshop was considered in developing the solicitation.

Four of the newly selected projects will focus on advanced separation techniques to capture carbon dioxide and hydrogen from fossil-

fuelled power plants. Two of these will study high-temperature membranes, one will investigate a new carbon dioxide absorbent, and one will look at nanoscale materials – on a scale

approximately 40 000 times smaller than the width of a human hair – as separation agents.

Three of the remaining projects will focus on advanced subsurface technologies and geochemical methods for sequestering carbon. Sequestration with these methods could offer permanent disposal of carbon dioxide by forming geologically stable rock-like structures called mineral carbonates. Carbonates are formed when minerals such as limestone, olivine, and serpentine react with carbon dioxide.

The eighth project falls under the heading “novel niches”, which include innovative concepts involving carbon dioxide recycling and products. For this project, biocatalysts – microorganisms and their enzymes – will cause chemical reactions that can potentially convert carbon dioxide to value-added products, and ensure permanent storage of carbon dioxide.

The new projects are outlined below:

• A new concept for the fabrication of hydrogen selective silica membranes (three year project, total cost $237 393)

Researchers at the University of Minnesota’s Department of Chemical Engineering and Materials Science will develop a new method for making extremely thin, high-temperature, hydrogen-selective silica membranes from byproduct materials. The membranes, called molecular sieves, work like filters with ultra-small pores that allow only hydrogen molecules to pass through, leaving a carbon-dioxide-rich gas behind for sequestration. These types of membranes will potentially be used in future fossil-fueled power plants that produce hydrogen under conditions of high temperatures and pressures.

• Novel dual-functional membrane for controlling carbon dioxide emissions from fossil fired power plants (three year project, total cost $871 997)

Researchers at the University of New Mexico’s Center for Micro-Engineered Materials, with collaboration from T3 Scientific in Arden Hills, Minnesota, will develop a new, dual-functional membrane that will use both the membrane pore structure, and an amine chemical adhered to the membrane, to increase the removal of carbon dioxide from fossil fuelled power plants. Researchers anticipate that the strong interactions between the carbon dioxide molecules and the amine-coated membrane pores will help spread the carbon dioxide on the pore walls and block other gases, such as oxygen, nitrogen and sulphur dioxides, that are also present in power plant stacks. The new membrane is expected to exhibit higher carbon dioxide selectivity than other types of silica-based membranes that separate carbon dioxide based only on the difference in pore size. This new membrane-based carbon dioxide capture process may be an attractive alternative to costly amine-based absorption processes currently available for carbon dioxide capture in power plants.

• Design and evaluation of ionic liquids as novel carbon dioxide absorbents (three year project, total cost $399 409)

This project, to be conducted by the Department of Chemical and Biomolecular Engineering at the University of Notre Dame, will focus on the development of liquid absorbents that fall within a relatively new class of compounds called ionic liquids. Ionic liquids are typically organic salts that, in their pure state, are liquid under atmospheric conditions at room temperature. They have unusual properties that suggest they could be extremely effective as carbon dioxide absorbents, possibly replacing current amine-based technology to capture carbon dioxide from power plants stacks. Unlike amines, which are corrosive and costly to operate, organic salts are typically benign, and can be disposed of in landfills. Building upon and extending their previous work with other chemicals, the researchers will use computer modelling to design and evaluate ionic liquids to determine their affinity for capturing carbon dioxide. They will also assess the economics of different ionic liquids against conventional absorbents.

• Carbon dioxide separation with novel microporous metal organic frameworks (three year project, total cost $900 000)

This project will be a collaborative effort among UOP LLC, in Des Plaines, Illinois, the University of Michigan, and Northwestern University to identify novel microporous metal organic frameworks (MOFs) suitable for carbon dioxide separation. MOFs are hybrid organic/inorganic structures at the nanoscale to which carbon dioxide will stick. Researchers plan to use molecular modelling on computers to design, tailor, and assess MOFs with the best properties for adsorbing carbon dioxide, and to predict structures of new MOFs. Successful completion of this project could lead to a low-cost, novel sorbent to remove carbon dioxide from the gases emitted from power plant stacks.

• Carbon dioxide sequestration in carbonate sediments below the sea floor (three year project, total cost of $797 210)

Scientists from Harvard University will collaborate with scientists from Columbia University, Carnegie-Mellon University, and the University of California at Santa Cruz to investigate the feasibility of sequestering carbon dioxide by injecting it below the sea floor in calcium carbonate sediments. These sediments could act as absorbents for the carbon dioxide, but they need study because the chemistry, temperature, and pressure conditions below the sea floor are different from those encountered in underground sequestration on land. Pressurised tanks in a laboratory will be used as a modelling tool to simulate the conditions below the sea floor. The researchers will seek to understand the mechanical and chemical behaviour of carbon dioxide and carbon-dioxide/water mixtures injected into carbonate sediments under a range of pressures and temperatures, and with a range of sediment compositions.

• A novel approach to mineral carbonation: enhancing carbonation while avoiding mineral pretreatment process costs (two year project, total cost $558 663)

This project, to be conducted by researchers at the Center for Solid State Science at Arizona State University, will study the chemistry and kinetics of carbonation using commonly occurring minerals such as olivine as the geochemical method for sequestering carbon dioxide. The approaches taken by the researchers will include using sonic frequencies to increase the exfoliation and particle cracking of the minerals to enhance carbon dioxide sequestration. They will also perform chemical and fluid studies to determine optimal exfoliation of the mineral and the kinetics involved. Using modelling and experimental investigations, the scientists will attempt to speed up, control, and tailor the carbonation process. This research should indicate whether or not carbon dioxide sequestered underground in this manner will be permanently stored.

• A novel approach to experimental studies of mineral dissolution kinetics (three year project, total cost $426 701)

This project, an experimental study incorporating modelling and bench-scale testing, will study geological sequestration of carbon dioxide using the carbonation process. Scientists from the Department of Geology and Planetary Science at the University of Pittsburgh will try to store carbon dioxide with sulphur dioxide in redbed sandstones containing feldspar and iron oxides. They will use an electron microscope to determine what reactions have occurred at the molecular and atomic levels, and will seek to answer such questions as: What happens to the carbon dioxide and the minerals when they come into contact? Are iron carbonates developed? Will the porosity of the minerals change, and, 50 years later, will the carbon dioxide leak out over a large area?

• Process design for the biocatalysis of value-added chemicals from carbon dioxide (three year project, total cost $384 275)

Researchers from the Faculty of Engineering at the University of Georgia Research Foundation will conduct the most novel of all the eight projects. They will perform metabolic engineering to create strains of microbes that feed off carbon dioxide and produce byproducts such as succinic, malic, and fumeric acids, all of which have commercial uses. The advantage of the proposed process is that microbial strains will be placed in direct contact with the gases emitted from power plants, thereby avoiding the cost of commercial carbon dioxide capture systems.

All this research is taking place against the background of progressively rising atmospheric CO2 levels, as for example measured by the US National Oceanic and Atmospheric Administration’s Mauna Loa Observatory in Hawaii (see graph). Such a pattern of measurements suggests the overall trend is attributable to human activity in general, and fossil fuel burning in particular.

Schematic of pilot CO2 capture plant Schematic of pilot CO2 capture plant
The Esbjerg 3 plant The Esbjerg 3 plant
Atmospheric CO2, as measured at the NOAA's Mauna Loa Observatory Atmospheric CO2, as measured at the NOAA's Mauna Loa Observatory

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