Publications

Factsheets

What is carbon capture and storage (CCS)? [view PDF] PDF

Carbon capture and storage, also known as CCS or geosequestration, refers to the separation of carbon dioxide (CO2) from major industrial sources and its deep geological storage, safely and permanently deep underground.
The fossil fuels coal, oil and natural gas currently supply around 85 per cent of the world's energy needs, however they are a major source of CO2. CO2 is the most common greenhouse gas after water vapour and the gas contributing most to global warming.

The International Energy Agency predicts that fossil fuels will continue to be heavily used around the world for many years to come, especially as the demand for energy is increasing. The urgent need to reduce atmospheric concentrations of CO2 means we need a portfolio of solutions to tackle our emissions, including energy efficiency, using less carbon-intensive fuels, enhancing natural carbon sinks (vegetation), and harnessing renewable energy from the wind, earth, sun and tides. Carbon capture and storage is an important part of this portfolio.

CCS is currently the only technology that will allow us to decrease greenhouse gas emissions while using fossil fuels and retaining our existing energy-distribution infrastructure. CCS can reduce emissions from fossil fuel-burning power stations, whether gas or coal-fired, by as much as 90 percent. It is an important technology for Australia, which is heavily reliant on fossil fuels and has extensive potential geological storage resources.

While CCS is often referred to as 'clean coal', it is also applicable to a wide range of other CO2-producing industries such as oil and natural gas processing, cement manufacture, fertiliser manufacture, iron and steel manufacture and the petrochemical industry.

While the concept of CCS as a means of reducing greenhouse gas emissions has arisen only in the past decade or so, CCS uses technologies that have been widely practiced in different industries for many years. Over 50 million tonnes of CO2 are currently stored geologically every year around the world, often as part of oil recovery operations.

The CO2CRC research effort focuses on developing and demonstrating efficient, economic and safe methods of capturing carbon dioxide and geologically storing it in the deep subsurface.

CCS_cycle

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Capturing cabon dioxide (CO2) [view PDF] PDF

Capturing carbon dioxide (CO2) from a stationary source such as a power plant involves separating it from the flue gas stream to prevent the gas from being released to the atmosphere.
The main sources for CO2 capture are natural gas processing, industrial processes, electricity generation and, potentially in the future, hydrogen production. Natural gas production often involves separating naturally occurring CO2 mixed with the gas in its natural state before the gas can be sold. As Australia's natural gas industry expands this will be an increasing source of emissions that will need to be dealt with.

Other industrial processes where CO2 capture is applicable include fertiliser and ammonia production, and cement manufacture; however the total quantity of CO2 produced by these processes is relatively small.

A far larger source of CO2, accounting for approximately half of all CO2 emissions in Australia, is fossil fuel electricity generation from coal, oil or natural gas. The technology for capturing CO2 from these sources is currently available, and research is underway to make the process more efficient and cost-effective.

There are three categories of CO2 capture systems that could be used at power stations: post-combustion, pre-combustion and oxy-firing. In post-combustion capture CO2 is separated from the flue gas after fuel is burnt. This process can be added, or retro-fitted, to existing power stations, either coal or natural gas-fired.

During pre-combustion capture the fossil fuel is reacted with steam and oxygen, producing a synthetic gas (syngas) which is made up of mostly carbon monoxide (CO), carbon dioxide and hydrogen (H2). An additional reaction with water (known as a water gas shift) can be used to convert the residual carbon monoxide to CO2 and additional hydrogen. The CO2 is removed and the hydrogen can then be burned in gas turbines to produce electricity. Such plants exist today.

This process, where the solid fuel is gasified in either an oxygen or air-blown gasifier, can be applied to all fossil fuels. Examples of this process are Integrated Gasification Combined Cycle (IGCC) or Integrated Drying Gasification Combined Cycle (IDGCC) an Australian-developed technology.

Oxy-firing combustion capture involves the combustion of fuel (coal or gas) in pure oxygen or oxygen-enriched air. The process can produce about 75 per cent less flue gas than air-fueled combustion and the exhaust consists of between 80 and 90 per cent CO2. The remaining gas is water vapour, which simplifies the CO2 separation step. An air separation plant is required to produce pure oxygen for the process from air.

CO2 capture has been practised commercially for many years. While the capture of CO2 for geological storage is a relatively new concept, CO2 capture for commercial markets has been practised in Australia and overseas for many years.

CO2 is captured from natural gas wells in South Australia, near Mt Gambier and in southern Victoria, near Port Campbell. The CO2 is then used for various commercial processes including carbonation of beverages and dry-ice production.

In the United States, CO2 capture at power plants using chemical absorption based on the monoethanolamine solvent has been practised since the late 1970s, with the captured CO2 being used for enhanced oil recovery as well as smaller scale CO2 beverage manufacture.

Capture processes

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CO2CRC Capture Research [view PDF] PDF

Carbon dioxide (CO2) capture represents up to 80 per cent of the cost of a carbon capture and storage system. The CO2CRC Capture Program researches, develops and demonstrates technologies that can reduce capture costs by 75 to 80 per cent.

These reductions are being achieved by focusing on a number of themes including:

  • selecting the best separation medium and/or process;
  • designing for optimal heat integration within the power plant; and
  • selecting equipment that is fit-for-purpose for the CO2 removal application.

We have over 60 lead researchers, post doctoral fellows and doctoral students working at five universities around
the country on a range of cost-effective CO2 separation techniques, such as:

  • gas separation and capture technologies for the full range of carbon dioxide-producing applications, including post-combustion, pre-combustion and oxyfuels, power and natural gas production, and for all fossil fuel energy sources, such as black and brown coal, natural gas and biofuels;
  • gas absorption processes;
  • gas separation and gas absorption membranes;
  • solid adsorption products and processes;
  • cryogenic and hydrate gas separation processes; and
    other hybrid applications.

This work has resulted in innovative techniques to reduce costs and resulted in several worldwide patents. An important aspect of commercialising technologies is to demonstrate them at ever increasing scale, thus moving from laboratory and desk-based studies to plant-based installations. CO2CRC has been or is involved in several major capture demonstration projects.

  • The UNO MK3 Project, at Hazelwood power station in Victoria's Latrobe Valley, which is currently trialling the CO2CRC-developed UNO capture technology as well as adsorption and membrane technologies. The system has a range of potential environmental and energy saving benefits and is the subject of world-wide patents.
  • The H3 Capture project, completed in 2011, which trialled
    three post-combustion capture technologies at Hazelwood power station. This project was part of the Latrobe Valley
    Post-Combustion Capture Project and was supported by International Power and the Victorian Government
  • The CO2CRC/HRL Mulgrave Capture Project, completed in 2010, which used a research gasifier to trial three pre-combustion capture technologies. The world-first project was supported by HRL Developments and the Victorian Government.

Each of these projects are providing data and experience to reduce emissions and capture costs for all fossil fuel-fired power stations and support our vision of a low-emission future.

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Storing CO2 [view PDF] PDF

The storage of carbon dioxide (CO2) secures the gas deep underground in a geological rock formation.
Geological reservoirs into which CO2 can be injected include depleted oil and natural gas fields, and deep saline formations. Since the stored CO2 will be buoyant, as it is less dense than the water in and around the reservoir rocks, it needs to be geologically trapped to ensure that it does not reach the surface. The exact trapping mechanism depends on the geology.

In depleted oil and gas reservoirs geological traps contain the CO2. In some cases these are anticlines, or folds; in other cases fault traps. In the case of deep saline formations, an impermeable caprock above the formation is not needed as small amounts of CO2 are trapped in the pores of the rock as it moves through the formation. This is known as residual trapping.

Solubility and mineral trapping are two other important mechanisms. Solubility trapping involves the dissolution of CO2 into the saline water in the reservoir. Mineral trapping results from the CO2 reacting with minerals in the rocks to form stable carbonate minerals.

CO2CRC collaborates with leading research institutions and industry to investigate the storage potential of Australia's sedimentary basins.

CO2CRC has produced studies of Australian and international CO2 storage resources, computer modelling and software to maximise the storage potential of reservoirs and publications such as the CO2 Storage Atlas of New South Wales.

CO2CRC also conducts world-leading storage research at the CO2CRC Otway Project, Australia's first operational CO2 storage project. This facility allows international teams to conduct experiments 'in the field'; generating tools to improve the efficiency and safety of CO2 storage for large-scale CCS projects.

CO2CRC research at the Otway Project has confirmed that storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of carbon dioxide.

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CO2CRC Otway Project Stage 2 [view PDF] PDF

Project aim

The CO2CRC Otway Project is a world-leading international research project investigating the geological storage of carbon dioxide (CO2). In Stage 1, over 65,000 tonnes of carbon dioxide-rich gas was stored in a depleted gas reservoir and comprehensively monitored.

Stage 2B of the project focussed on CO2 storage in saline formations in deep porous rocks containing formation water. Saline formations are very common worldwide and have the potential to store many years' worth of CO2 emissions.

Key risks for large-scale commercial projects include uncertainties regarding how much CO2 can be stored and how well the CO2 is contained. This research is helping reduce these uncertainties and provide the basis for a cost-effective process to evaluate saline formations.

Storing CO2

CO2 is held underground in several ways, known as trapping mechanisms.

In Stage 1 the CO2 was stored in a depleted gas reservoir – trapped by a seal rock above the formation and a sealing fault at the side of the formation. This is known as structural trapping.

The Stage 2B experiment was designed to test two non-structural trapping mechanisms: residual gas trapping and dissolution trapping. Residual gas trapping and dissolution trapping are important mechanisms in geological storage but have not been demonstrated to the extent of structural trapping – the 2B experiment provided valuable information on how much CO2 is trapped in this way.

Residual gas trapping occurs when a small amount of CO2 becomes disconnected or 'snaps off' from the CO2 plume as the CO2 moves through the porous rock. The CO2 is stored in the pores in tiny bubbles, trapped by surface tension. The CO2 can't move out of the pore space and remains fixed underground.

Dissolution trapping refers to the portion of CO2 that is dissolved in the formation water. Once the CO2 dissolves, the water becomes denser, sinks towards the bottom of the formation and is more securely stored.

Sandeep & Peter

The experiment

Stage 2 work began with the drilling of a new 1565 metre well, CRC-2, in February 2010.
During the drilling, over 176 metres of rock samples, known as core, were obtained. These samples have been tested extensively to evaluate the amount of storage space in the rock (porosity) and how easily CO2 can move through it (permeability).

Researchers were able to compare these data with the results of the test injections to fine tune their computer models of storage capacity and security.
To test the trapping capacity of the rocks, the research team undertook a series of small scale injections into the Paaratte Formation, using a series of instruments installed in the injection well at depths of around 1400 metres. The instruments include temperature and pressure sensors, as well as a system of U-tubes for deep formation sampling, similar to those used in Stage 1.

The aim was to break up the CO2 within the rock pores (residual gas saturation), then remove any remaining mobile CO2. A range of measurement techniques helped evaluate how much CO2 was left behind (permanently stored). By correlating that information with their understanding of the formation rock qualities, the researchers were able to estimate the storage capacity of the formation using these mechanisms and extend that knowledge through modelling to similar formations.

Experiment plan

The experiment took about two months and involved a series of extractions and injections.

  1. Before the residual gas test, formation water was extracted from the Paaratte Formation and stored on the surface in tanks. This water was used for injections later in the experiment. A range of downhole instruments gathered baseline data on the water saturated formation. Small quantities of tracer gases were injected in order to track how the CO2 moves through the rock.
  2. A relatively small amount of pure CO2, around 150 tonnes, was injected into the formation. This mimicked the storage of CO2 as part of a Carbon Capture and Storage (CCS) operation and filled the rock pores with CO2.
  3. After a period, formation water saturated with CO2 was re-injected to drive the formation to residual gas saturation.
  4. The amount of CO2 trapped was evaluated in a range of ways including water extraction, pressure sensors, tracer concentrations, temperature sensors and borehole logging measurements. By using a variety of testing methods, the experiment reduced variation in results.

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The Lake Nyos Gas Burst [view PDF] PDF

In August 1986 at Lake Nyos, in Cameroon, West Africa, a volcanic crater lake released a large volume of carbon dioxide (CO2). This was not a volcanic eruption, but a gas burst.

Being denser than air, the CO2 did not disperse but flowed down into nearby populated valleys resulting in the deaths of about 1700 people.

What happened at Lake Nyos?

Cameroon is situated on the Cameroon Volcanic Line, an area of volcanic activity that makes it susceptible to the release of volcanic CO2. After degassing from the hot magma, the CO2 gas is either trapped underground or escapes to the surface. In the case of Lake Nyos, the CO2 slowly moved into natural pathways feeding into the lake as well as directly into the lake. CO2 is soluble in water and so dissolved into Lake Nyos.

The lake is very deep and contained a very large volume of stratified or layered water. When these layers become unstable through seasonal turnover, the CO2 is circulated to upper layers where it is released from the water in
non-catastrophic events.

However, Lake Nyos existed in long-term physical and chemical equilibrium and there was no seasonal turnover. These circumstances produced stratified lake waters with very high CO2 concentrations. Either the addition of simply too much CO2 (the water was supersaturated in CO2) or external mechanical forces (underwater land slip or earthquake) caused the equilibrium of the lake to be disturbed.

This disturbance caused the stratified lake layers to mix; the CO2-rich waters were suddenly exposed to lower pressures and became unstable. This sudden destabilisation caused large amounts of the CO2 to be released out of the lake as a gas burst.

This event is not the only sudden release of CO2 from a lake that has been documented. In 1984 a gas burst also occurred at Lake Monoun, Cameroon, only 100km away from Lake Nyos, releasing a large volume of CO2, fortunately into largely unpopulated areas.

Does the Lake Nyos incident suggest that geological storage of carbon dioxide is unsafe?

The answer is no. Storage sites are carefully characterised, over several years, to ensure they provide safe and permanent storage. Sites are selected that lack any of the readily identifiable natural pathways or the active volcanic activity that is present in Cameroon.

Potential CO2 storage sites have:

  • simple geology to avoid movement and leakage of CO2;
  • the depth to maintain the CO2 as a liquid beneath the Earth's surface (at least 800m);
  • the right type and capacity of permeable rocks to absorb the CO2; and
  • the necessary rocks or structures to trap or seal in the CO2.

Large spontaneous releases of many tonnes of CO2, as happened at Lake Nyos, cannot occur at such sites. Our research to date strongly suggests that in many of Australia's sedimentary basins CO2 emissions could be safely stored for thousands of years and longer.

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Pre-combustion capture of carbon dioxide

Pre-combustion solvent absorption [view PDF] PDF

Advanced power generation technologies are under development that can make much cleaner and more efficient use of fossil fuels such as coal. Integrated Gasification Combined Cycle (IGCC) is one such technique, converting coal to a combustible gas known as syngas (containing hydrogen, carbon monoxide and carbon dioxide) at high temperature and pressure. IGCC uses a gas turbine followed by a steam turbine to generate electricity.

Solvent absorption is the current industry method for removing carbon dioxide (CO2) from syngas. Liquid chemicals are used to absorb the CO2 and then release it at an elevated temperature in another vessel.

After the gasification of the coal and various gas cleaning steps, the gas enters the absorption column. There it comes into contact with the solvent which absorbs the CO2. The other gases leave the absorption column, and the “rich” solvent containing the CO2 is then pumped to another column called a stripping column.

The "rich" solvent is then heated to about 120°C, causing the CO2 to be released from the solvent. The CO2 emerges at the top of the stripper column where it is cooled, allowing the removal of water and traces of solvents. The liquid is returned to the top of the stripper column and the "lean" solvent is pumped from the bottom back to the absorber.

On the way, the hot, lean solvent passes through a heat exchanger, along with the rich solvent leaving the absorber column. This cools the lean solvent, ready for more CO2 absorption, and heats the rich solvent on its way to the stripper column. The solvent can be used over and over again to perform the separation of CO2.

Solvent

The CO2CRC Mulgrave Capture Project is undertaking research into solvent capture. The research aims to:

  • trial a potassium carbonate-promoted solvent system and compare its performance to the traditional amine solvent (MEA);
  • reduce the energy required to heat the solvent to release the CO2 and to cool the lean solvent and the CO2;
  • control or prevent the solvent degrading or corroding equipment;
  • improve the amount of CO2 captured/released by the solvent through the use of novel packing material in the columns;
  • understand the interaction between the solvent system and impurities present in the syngas, including H2S, CH4 and CO; and
  • reduce the cost of carbon capture and make solvent absorption technologies more commercially viable.

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Pre-combustion membrane separation [view PDF] PDF

Membranes, made of either polymers or ceramics, can be used to separate carbon dioxide (CO2) from other gases. CO2CRC is investigating new types of membranes and processes to improve their effectiveness. One of the challenges with membrane technologies is making them robust enough to withstand the harsh environment of industrial waste gases.

Membranes can be used in two ways; either as a method of allowing CO2 to be absorbed from a gas stream into a solvent (membrane gas absorption) or on their own, much like a filter (gas separation membranes).

Membrane Gas Absorption

In membrane gas absorption, a membrane separates the feed gas from a liquid solvent. The CO2 is absorbed into the solvent via pores in the membrane, while the other gases are not. The CO2 can then be removed from the solvent as in solvent absorption.

CO2CRC trials use a hollow fibre membrane module to:

  • test a range of membrane materials with a range of solvents; and
  • evaluate the performance of each configuration.

hollow fibre membrane

Gas Separation Membranes

CO2 can selectively pass through gas separation membranes, allowing CO2 to be removed from the feed gas.

CO2CRC trials aim to:

  • test a number of gas separation membrane strategies (for example, removing H2 first, then the CO2 second);
  • investigate the influence syngas and minor gas components have on membrane performance and plasticization; and
  • investigate the separation performance of a number of molecular sieving membranes at high temperatures. These membranes separate gases based on their size.
  • They are particularly suited for use when the process includes a water gas shift reaction which will maximise CO2 capture.

flat sheet membrane

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Pre-combustion adsorption technologies [view PDF] PDF

Adsorbent capture technologies for separating carbon dioxide (CO2) from industrial gas streams have the potential to be highly cost-effective, as they require less energy and could have less impact on the environment.
Adsorbents are solids, typically minerals called zeolites, that can capture CO2 on their surface, release the CO2 following a change in temperature or pressure and be reused in a cyclical process.

In current CO2CRC trials, the CO2 is released from the adsorption material by reducing the pressure. This is known as Pressure Swing Adsorption (PSA). The adsorbents are being tested at about 250°C, a much higher feed gas temperature than is possible for other gas separation technologies. This ability may lower the capture cost by reducing the need to cool the gas for capture and then reheat it for entry into the gas turbine in a power plant.

Current CO2CRC trials aim to:

  • identify and test suitable adsorbents and process conditions over a range of temperature and pressure conditions; and
  • investigate the performance of adsorbents at higher temperatures.

adsorption

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Post-combustion capture of carbon dioxide

Solvent absorption [view PDF] PDF

Solvent absorption is currently the preferred option for removing carbon dioxide (CO2) from industrial waste gas and for purifying natural gas.

It is the method used by the International Power Capture Plant  at Hazelwood power station and involves passing the flue gas through liquid chemicals that absorb CO2 and then release it at an elevated temperature in another vessel. The same chemical can be used over and over again to separate CO2.

In post-combustion capture from power stations, the flue gas is at atmospheric pressure and contains mainly nitrogen, CO2, oxygen and water. At Hazelwood Power Station the CO2 makes up about 11 per cent of the flue gas.

The cooled flue gas comes into contact with the solvent in the absorber and the CO2 is absorbed into the solvent at a temperature of between 40-60°C. The other gases leave the absorber column and the "rich" solvent containing the CO2 is then pumped to another column (called a stripper or desorber) via a heat exchanger. The "rich" solvent is then heated to about 120°C, causing the CO2 to be released from the solvent.

The CO2 emerges at the top of the desorber where it is cooled to remove water. The water is returned to the desorber and the “lean” solvent pumped back to the absorber. On the way, the hot, lean solvent passes through a heat exchanger, where it exchanges heat with the rich solvent leaving the absorber column.

Solvent
Solvent-based absorption CO2 capture.

The CO2CRC H3 Capture Project, completed in 2011, used the International Power Capture Plant at Hazelwood power station to conduct research into solvent absorption for CO2 capture. The International Power Capture Plant was constructed by The Process Group and, in the first phase, is designed to capture 25 tonnes per day of CO2 from flue gas.

The project:

  • trialled a number of solvents including a hot potassium carbonate-promoted solvent;
  • investigated reducing the energy consumption for solvent regeneration;
  • assessed the energy integration options for the power plant and capture processes;
  • researched solvent degradation and corrosion;
  • improved understanding of the interaction between the solvent system and impurities present in the flue gas, including SOx and NOx; and
  • reviewed the technical and economic issues for commercial use of post combustion capture in existing and new Victorian brown coal power stations.

The H3 project was part of the Latrobe Valley Post-combustion Capture Project, supported by the Victorian Government, through the Energy Technology Innovation Strategy (ETIS) Brown Coal R&D funding.
CO2CRC is supported through the Australian Government’s Cooperative Research Centre Program.

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Membrane technologies [view PDF] PDF

Membranes, generally made of polymers or ceramics, can be used to effectively sieve out carbon dioxide (CO2) from gas streams. The membrane material is specifically designed to preferentially separate the molecules in the mixture. The process has not yet been applied on a large scale and there are challenges related to the composition and temperature of the flue gases.

Membranes are used to separate CO2 from other gases (gas separation membranes) and to allow CO2 to be absorbed from a gas stream into a solvent (membrane gas absorption). There are a range of membrane types for these processes.

Membrane Gas Absorption

A membrane can be used with a solvent to capture the CO2. The CO2 diffuses between the pores in the membrane and is then absorbed by the solvent. The membrane maintains the surface area between gas and liquid phases. This type of membrane is useful when the CO2 has a low partial pressure, such as in flue gases, because the driving force for gas separation is small.

Membrane gas absorption

In the diagram above, the porous membrane allows gases to come into contact with the solvent. Only CO2 is absorbed because of the selectivity of the solvent. The membrane itself does not separate the CO2 from other gases, but rather maintains a barrier between the liquid and gas with permeability through the pores.

In a traditional solvent absorption process, the liquid and the gas are together, which leads to flow problems such as foaming and channelling. The physical separation of the gas flow from the liquid flow in a membrane absorber eliminates these problems.

Using a compact membrane can reduce the size of the equipment required to absorb the CO2. Research is focused on developing appropriate materials that ensure that solvent does not penetrate the membrane pores.

The CO2CRC H3 Capture Project at International Power’s Hazelwood Power Station conducted research into membrane gas absorption for CO2 capture.

The project:

  • tested a range of membrane materials with a range of solvents; and
  • evaluated the performance of each configuration.

Gas separation membranes

The advantage of using gas separation membranes is that the equipment is much smaller and there is no solvent involved. At the current stage of development, the main cost is the energy required to create a large enough pressure difference across the membrane to drive separation. A membrane acts as a semi-permeable barrier. The CO2 passes through this barrier more easily than other gases. In general, the rate at which a particular gas will move through the membrane can be determined by the size of the molecule, the concentration of gas, the pressure difference across the membrane and the affinity of the gas for the membrane material.

flat sheet membrane

While the equipment is smaller, gas separation membranes require a large pressure difference to drive separation.

The CO2CRC H3 Capture Project at International Power’s Hazelwood Power Station, completed in 2011, conducted research into gas separation membranes for CO2 capture.

The project:

  • tested a range of gas separation membranes;
  • investigated the separation performance of these membranes under real flue gas conditions; and
  • monitored the effects of minor gas components in the flue gas.

The H3 project was part of the Latrobe Valley Post-combustion Capture Project, supported by the Victorian Government, through the Energy Technology Innovation Strategy (ETIS) Brown Coal R&D funding.

CO2CRC is supported through the Australian Government’s Cooperative Research Centre Program.

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Adsorption technologies

Adsorbent capture technologies for separating carbon dioxide (CO2) from industrial gas streams have the potential to be highly cost-effective, as they require less energy and could have less impact on the environment.

Adsorbents are solids, typically minerals called zeolites, that can capture CO2 on their surface, release the CO2 following a change in temperature or pressure and be reused in a cyclical process.

In CO2CRC trials, the CO2 is released from the adsorption material by reducing the pressure.

This is known as Pressure Swing Adsorption (PSA) or, where the pressure is reduced to very low pressure, Vacuum Swing Adsorption (VSA). This process is widely used in air separation, natural gas purification and hydrogen gas generation.


principles of adsorption

In CO2CRC trials, the adsorber column contains multiple layers to deal with the complex composition of the flue gas.

Multilayer adsorption_two beds
A water-selective and acidic gas-resistant adsorbent is used to remove the water and the SOx and NOx in the flue gas.

The CO2CRC H3 Capture Project at International Power's Hazelwood Power Station, completed in 2011, conducted research into adsorption technologies for COcapture.

The project:

  • demonstrated adsorption for CO2 capture from flue gas;
  • assessed adsorption process, equipment and different adsorbents under various working conditions and equipment configurations;
  • assessed the effect of impurities, temperature and load on the vacuum swing adsorption process; and
  • assessed economic and engineering issues for scale-up

The H3 project was part of the Latrobe Valley Post-combustion Capture Project, supported by the Victorian Government, through the Energy Technology Innovation Strategy (ETIS) Brown Coal R&D funding.

CO2CRC is supported through the Australian Government’s Cooperative Research Centre Program.

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The chemistry of solvent absorption of carbon dioxide [view PDF] PDF

Solvents used in carbon dioxide capture are either chemical solvents or physical solvents.

Chemical solvents

With chemical solvents, the absorption primarily depends on chemical reactions between the solvent and CO2 . Post capture, heat is required to release the CO2 and regenerate the solvent.

chemical solvents

Physical solvents

Absorption in a physical solvent relies on the solubility of CO2 in the solvent rather than a chemical reaction
with the solvent. The solvent is regenerated by changing pressure or temperature. Examples of physical
solvents are methanol, dimethyl ethers of polyethylene glycol and N - methyl - 2 - pyrrolidone (NMP).

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The International Power Capture Plant

Why is carbon capture important?

Carbon dioxide (CO2) is the most significant man-made greenhouse gas emitted worldwide. As in the rest of the world, Australian emissions of CO2 are growing steeply.

While the energy sector is the largest source of Australian CO2 emissions, it is also initiating, supporting and funding research into ways to reduce the amount of CO2 emitted to the atmosphere. Carbon capture and storage (CCS) is one of those ways and will be an important part of reducing global greenhouse gas emissions, along with energy efficiency and renewable energy technologies.

Why post-combustion capture?

Brown coal, or lignite, is the cheapest source of fossil fuel for power generation in Australia. Australia has enough coal for hundreds of years. Significant improvements in how we burn brown coal for power, as well as the ability to capture carbon dioxide from coal-fired power plants, will mean we can continue to use this abundant resource in a carbon-constrained world.

Post-combustion capture involves the removal of CO2 after the coal is burned. Given the large number of coal-fired power plants in Australia and in the world, post-combustion capture offers an opportunity to make significant cuts in greenhouse gas emissions.

Post-combustion capture has the advantage that it can be retrofitted to existing plants, integrated into new plants, has high operational flexibility – as it can be added in stages and operated independently of the power station – and, importantly for this project, has significant development potential through process improvements, new sorbents and new technologies.
By demonstrating the technology at scale, this project will reduce the technical risk and cost of post-combustion capture for coal-fired power stations around the world.

What is the International Power Capture Plant?

International Power Australia has built a solvent capture plant at Hazelwood power station to capture up to 50 tonnes of CO2 per day, with 25 tonnes per day captured during the initial phase. It is the largest post-combustion capture plant in Australia and significant on a world scale. The technology partners in the project are CO2CRC and Process Group.

The system uses the BASF solvent PuraTreatTM, a recyclable water-based solvent. Additionally, much of the CO2 captured will be used in the neutralisation of ash water, producing calcium carbonate and effectively sequestering the CO2.

The plant has been funded by International Power with support from the Federal Government’s Low Emission Technology Development Fund (LETDF) and the Victorian Government's Energy Technology Innovation Strategy Large Scale Demonstration Plant fund (ETIS LSDP).

The Hazelwood Carbon Capture Project aims to:

  • Demonstrate the application of carbon dioxide capture to a power plant
  • Demonstrate post-combustion capture, in Australia’s largest capture facility, at Hazelwood power station
  • Gain operating experience in post-combustion capture for power plant personnel
  • Reduce CO2 emissions
  • Provide CO2 for neutralising plant ash water and in doing so, replace mineral acids used in this process
  • Effectively sequester CO2 in a mineral form as part of the neutralisation process
  • Provide the basis for subsequent R&D into post-combustion capture in association with CO2CRC.

International Power Australia is a wholly owned subsidiary of International Power plc, a UK-based independent power generation and operation company.
Since becoming established in Australia in 1996, International Power Australia has invested in excess of A$5 billion and focused on becoming a leading player in the energy industry.

The company owns and operates more than 3700 MW of renewable, gas-fired and brown coal-fired generating plants in Victoria, South Australia and Western Australia. It also has an energy retailing operation in Victoria and South Australia called Simply Energy.

International Power Australia is participating in a number of research projects aimed at reducing carbon dioxide emissions from brown coal-fired power stations.

The Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) is one of the world’s leading collaborative research organisations focused on CCS.

CO2CRC is a joint venture between Australian and international industry, universities and other research bodies from Australia and New Zealand, and Australian Commonwealth, State and international government agencies.

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The chemistry of storage [view PDF] PDF

CO2 is not dissolved in formation water immediately after it is injected. It is said to be free-phase or immiscible. As it is supercritical, it is less dense than the formation water and so it rises upwards.

Residual trapping

The CO2 plume migrates with the formation waters which generally have low flow velocities (typically less than 10 cm/year). At the tail of the CO2 plume, the concentration of the CO2 falls and it becomes trapped by capillary pressure from the water in the pore spaces between the rock and stops flowing. Over time, this residually trapped CO2 can dissolve into the formation water.

residual trapping

The tail of the carbon dioxide plume is snapped off and trapped residually

Solubility Trapping

The solubility of CO2 in water increases with increasing pressure and decreases with increasing temperature and increasing water salinity. As some CO2 dissolves in water, the water becomes denser, and begins to sink downwards. This leads to convective mixing of the formation water with the CO2, increasing the amount of CO2 dissolved in the formation water.

Aqueous CO2 will form carbonic acid, a weak acid, in the reaction

solubility trapping

This is the reaction that occurs in carbonated soft drinks and soda water.

Mineral Trapping

When dissolved CO2 reacts with the reservoir rock, carbonate minerals can form and precipitate, trapping CO2 in the most stable form. While there is some reaction in the early years of storage, the time line for this trapping mechanism is generally over thousands of years. The potential to form these minerals depends on the composition of the reservoir rock (eg the presence of aluminosilicates), the temperature and pressure of the rock, the chemical composition of the water, the water/rock contact area and the rate of fluid flow through the rock.

One mineral which can be formed is calcite (calcium carbonate) in the following reaction:

mineral trapping

Figure 2: Calcite filling pores Katnook Field, Pretty Hill Formation, Otway Basin. Watson, M N, Boreham, C J, and Tingate, P R, 2004. Carbon dioxide and carbonate cements in the Otway Basin: implications for
geological storage of carbon dioxide. APPEA Journal, Vol. 44(1), pp. 703-720.

A typical mineral reaction that occurs in the natural accumulations of CO2 in the Otway Basin is that of iron-rich chlorite forming kaolinite and siderite. The reaction below shows the formation of siderite:

mineral reaction

Geological Storage of natural gas

TRUenergy’s Iona Gas Facility is a good example of how natural gas can be safely injected, stored and withdrawn
from a geological reservoir.

The Iona reservoir was identified as being suitable for a gas storage facility in the 1990s. Its development was
accelerated following the Longford gas plant explosion in 1998, when Victoria’s gas supplies were disrupted for three
weeks. Adjacent reservoirs at North Paaratte and Wallaby Creek have also been developed for storage.
Natural gas is generally a seasonal fuel, with demand much higher in winter for heating. By storing large amounts
of gas when demand is low and supplying it when demand is high suppliers can guarantee a consistent supply,
especially in the case of unforeseen accidents or disasters.

Large quantities of purified natural gas have been stored in porous, underground rocks since 1915. The first natural
gas storage project was in Weland County, Ontario Canada, which used the porous rocks of a depleted natural gas
field to store natural gas.

As Australia’s electricity generation becomes increasingly powered by gas, supplies need to be assured for the
summer months, to deal with peak demand for air-conditioning, or to fill in for variable supplies such as renewable
sources like wind. This means that gas storage facilities such as Iona will be more and more important.

There are now more than 500 facilities geologically storing natural gas in over 20 countries around the world,
including large facilities under parts of Berlin and Paris. They are well understood, safe and considered
uncontroversial by surrounding communities.

Truenergy’s Iona gas facility

An example of safe and efficient underground gas storage

The geology

The geology and structure at Iona has a number of similarities with
Stage 1 of the Otway Project:

  • Gas injection is into the highly permeable Waarre C sandstone
  • Gas is trapped structurally in a depleted gas field
  • The trap is bound by large faults, forming a juxtaposition seal for gas

Operations

  • Methane storage at a depth of ~ 1300 metres below surface
  • Five injection/withdrawal wells, two observation wells at Iona and 3 injection/withdrawal wells at remote sites.
  • 22 petajoules total storage
  • 380 terajoules per day withdrawal deliverability
  • 155 terajoules per day injection deliverability

Dynamics of storage

CO2CRC, in collaboration with Schlumberger, have conducted
a detailed 3D geomechanical modelling study designed to
understand the mechanical effects of gas injection and withdrawal
at Iona. Results suggest little structural change and preservation
of fault and seal integrity.

  • Maximum predicted ground subsidence and heave were 9 millimetres and 2 millimetres, respectively, during periods of highest gas withdrawal and injection.
  • The cumulative plastic strain along faults is <0.1 per cent, indicating a high degree of fault stability.

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