CCS- Carbon Capture and Storage- what is it?

CCS…. What is it??

After a very interesting lecture on Monday on communicating about CCS, I realised that far all I sort of know what it stands for… I know very little else about it.. so I figured… id research what it is and post it!!!

CCS- Carbon Capture and Storage

CCS is the process of capturing waste carbon dioxide from sources such as fossil uel power plants and then taking it to a storage site and depositing it where It will not enter the atmosphere, normally some form of underground geological formation.

How it works- Capture

Energy from fossil fuels such as coal, oil and natural gas is released in the combustion (burning) process. The emission of CO2 is a by-product of this process.

Capture technology can be applied to any large-scale emissions process, including coal-fired power generation, gas and oil production, and manufacture of industrial materials such as cement, iron, steel and pulp paper. In fact, large CO2 emitter industries around the world have applied capture technology for decades. Captured CO2 is used, for example, in the food and beverage industry and in making fertiliser.

In systems where the coal is pulverised to a powder, which makes up the vast majority of coal-based power plants in North America, Australia, Europe and China, the CO2 must be separated at fairly diluted concentrations from the balance of the combustion flue gases (gas exiting via a chimney or ‘flue’). In other systems, such as coal gasification, the CO2 can be more easily separated.

There are three basic types of CO2 capture: pre-combustion, post-combustion and oxyfuel with post-combustion.

Pre-combustion capture

Pre-combustion processes convert fuel into a gaseous mixture of hydrogen and CO2. The hydrogen is separated and can be burnt without producing any CO2; the CO2 can be compressed for transport.

Pre-combustion capture is used in industrial processes but has not been demonstrated in much larger power generation projects. The fuel conversion steps required for pre-combustion are more complex than the processes involved in post-combustion, so the technology is more difficult to apply to existing power plants.

Pre-combustion capture increases the CO2 concentration of the flue stream, requiring smaller equipment and different solvents with lower regeneration energy requirements.

The process involves:

·         partially reacting the fuel at high pressure with oxygen or air and, in some cases, steam, to produce carbon monoxide and hydrogen

·         reacting the carbon monoxide with steam in a catalytic shift reactor to produce CO2 and additional hydrogen

·         separating the CO2 and, for electricity generation, using hydrogen as fuel in a combined cycle plant.

Although pre-combustion capture involves a more radical change to power station design, most elements of the technology are already well proven in other industrial processes.

Post-combustion capture

Post-combustion processes separate CO2 from combustion exhaust gases so that the CO2 can be captured using a liquid solvent. The CO2 is absorbed by the solvent and then released when it is heated to form a high purity CO2 stream.

The process involves scrubbing the flue with a suitable solvent, such as an amine solution, to form an amine–CO2 complex, which is then decomposed by heat to release high purity CO2. The regenerated amine is recycled to be reused in the capture process.

Post-combustion capture is applicable to coal-fired power stations but additional measures, such as desulphurisation of the gas stream, are required to prevent the impurities in the flue gas from contaminating the CO2 capture solvent.

Two significant challenges for post-combustion capture involve:

·         the large volumes of gas that must be handled, requiring large-scale equipment and creating high capital costs

·         the amount of additional energy needed to operate the process.

Post-combustion capture technology is used widely in the food and beverage industry.

Oxyfuel combustion

Oxyfuel with post-combustion processes uses oxygen rather than air for combustion of fuel. This produces exhaust gas that is mainly water vapour and CO2 that can be easily separated to produce a high purity CO2 stream.

The concentration of CO2 in flue gas can be increased by using pure or enriched oxygen instead of air for combustion, either in a boiler or gas turbine. The oxygen is produced by cryogenic air separation (already used on a large scale industrially), and the CO2-rich flue gas recycled to avoid the excessively high-flame temperature associated with combustion in pure oxygen.

The advantage of oxyfuel combustion is that, because the flue gas contains a high concentration of CO2, the CO2 separation stage is simplified. The main disadvantage is that cryogenic oxygen is expensive.

Oxyfuel combustion for power generation is currently being demonstrated at a refurbished power station in Biloela, Queensland.

How CCS works - transport

Safely and reliably transporting CO2 from where it is captured to a storage site is an important stage in the CCS process.

Transport of CO2 is already a reality, occurring daily in many parts of the world. CO2 is transported by pipeline, ship and road tanker, primarily for use in the food industry or to recover more oil and gas from oil and gas fields.

However, the scale of transportation required for widespread deployment of CCS is much more substantial than the current scale of transport and will involve moving dense, concentrated CO2.

How is CO2 transported?

Once separated from other elements of the flue gas (gas exiting via a chimney or ‘flue’), the CO2 is compressed to make it easier to transport.

Pipelines are—and are likely to continue to be—the most common method used to transport the very large quantities of CO2 involved in CCS. There are already millions of kilometres of pipelines around the world that transport various gases, includingCO2.

Transport of CO2 by truck and rail is possible for small quantities. Trucks are used at some project sites, moving the CO2 from where it is captured to a nearby storage location. Given the large quantities of CO2 that would be captured via CCS in the long-term, it is unlikely that truck and rail transport will be significant.

Ship transportation can be an alternative option for many regions of the world. Shipment of CO2 already takes place on a small scale in Europe, where ships transport food-quality CO2 (around 1,000 tonnes) from large point sources to coastal distribution terminals.

Larger scale shipment of CO2, with capacities in the range of 10,000 to 40,000 cubic metres, is likely to have much in common with the shipment of liquefied petroleum gas (LPG). There is already a great deal of expertise in transporting LPG, which has developed into a worldwide industry over a period of 70 years.

How CCS works - storage

Storing CO₂ underground is not a new or emerging technology—it is an existing reality on an industrial scale. In fact, there are geological systems that naturally contain CO₂ and many others throughout the world that experts have determined can retain centuries’ worth of injected CO₂. This will help abate climate change by removing and keeping this greenhouse gas out of the atmosphere.

What can be done with captured CO₂?

Generally speaking, the CO₂ can be:

• stored in secure deep underground geological formations
• used as a value-added commodity. This can result in a portion of the CO₂ being permanently stored—for example, in concrete that has been cured using CO₂ or in plastic materials derived from biomass that uses CO₂ as one of the ingredients 
• converted into biomass. This can be achieved, for example, through algae farming using CO₂ as a feedstock. The harvested algae can then be processed into biofuels that take the place of non-biological carbon sources.

How does geological storage of CO₂ work? 

Geological storage involves injecting CO₂ captured from industrial processes into rock formations deep underground. The formations are selected for their huge capacity to store and retain injected greenhouse gases indefinitely. This way, the CO₂ is effectively removed and isolated from the atmosphere.

The following geologic characteristics are associated with effective storage sites:

• storage formations have enough voids, or pores, in the rock to allow the injection of CO₂
• pores in the rock are connected well enough, a feature called ‘permeability’, so that the CO₂ can move and spread out within the formation, providing the capacity needed to accept the amount of CO₂
• formations must have an extensive cap or barrier at the top to contain the CO₂ for hundreds to thousands of years, and longer.

Fortunately, there are many locations around the world that have formations with these characteristics. Most are found in vast geological features called ‘sedimentary basins’. Almost all oil and gas production is associated with sedimentary basins. The types of geologic formations that trap oil and gas (and also naturally occurring CO₂) include sandstones, limestones and dolomites that are similar to those that make good CO₂ storage reservoirs.

It is the natural geologic characteristics that resulted in oil and gas being trapped for millions of years before they were discovered that make secure geologic storage of CO₂ such a viable option for greenhouse gas mitigation.

How is CO₂ injected underground and why does it stay there?

Once captured, the CO₂ is compressed into a ‘supercritical state’—a fluid almost as dense as water—and then pumped down through a well into a porous geological formation, as described above.

The pores in underground formations are initially filled with a fluid, either oil, gas or, much more commonly, very salty water. CO₂ can be injected into oil reservoirs to help with oil recovery but most future large–scale projects will target saline water-bearing formations for storage because they are more common and can have enormous capacity. In general, depths greater than 800 metres are desired to keep the CO₂ in the compressed, or dense, state.

Because the CO₂ is initially slightly more buoyant than water, a portion will migrate to the top of the formation, where it will become trapped beneath the caprock, which acts as a seal. In most natural systems, there are numerous thick barriers between the deep reservoir and the surface. Some of the CO₂ will start to dissolve slowly into the saline water and become trapped indefinitely, whereas another portion of CO₂ may become residually trapped in tiny pore spaces.

The ultimate trapping process involves dissolved CO₂ reacting with the reservoir rocks to form a mineral, much like snails or clams use calcium and carbon from seawater to form their hard shells. Depending on the reservoir minerals present, this process can be relatively quick or very slow, but it effectively transforms the CO₂ into a solid mineral.

Is underground storage of CO₂ safe?

Three industrial–scale storage projects that inject up to two million tonnes of CO₂ annually into saline formations have been operating for many years, along with other smaller projects actively capturing and storing CO₂.

These industrial–level projects are complemented by numerous research–scale CCS projects, intergovernmental and industry partnerships, research programs, and stakeholder networks. No adverse safety, health, or environmental effects have ever been documented from any of these operations.

How do we know that it works?

There are decades of operational experience from projects that are very similar to CCS, including underground CO₂ injection for enhanced oil recovery (EOR) and the use of technologies analogous to CCS, such as acid gas (a combination of hydrogen sulphide and CO₂) injection, and natural gas storage.

The oil and natural gas industries have more than 40 years’ experience injecting CO₂ into geologic reservoirs to increase oil production. This process is a type of EOR and uses the properties of CO₂ to mix with the oil to move it out of the reservoir more effectively. In most operations, the CO₂ is recycled and will remain in the reservoir indefinitely at the end of the life of the oil field.

These sites have been injecting many millions of tonnes of CO₂ safely into the subsurface for decades. The success of these projects and the increasing number of research demonstrations provides considerable confidence in the potential to store large quantities of CO₂ underground safely, securely and for very long periods.

How much CO₂ can be stored underground?

The United Nations Intergovernmental Panel on Climate Change estimates the world’s potential capacity at two trillion tonnes, although there could be a “much larger potential”. Several regions around the world—the United States, Canada, China, South Africa, Europe and Australia—are doing significant amounts of work on characterising potential storage sites.

The 2012 North American Carbon Storage Atlas indicates there is more than 1,600 billion tonnes of CO₂ storage potential in saline formations alone in the United States, Canada and Mexico. This means that there is centuries’ worth of CO₂ geological storage for the region.

A European Union project estimates the CO₂ storage capacity in oil and gas fields, in and around the North Sea alone, at 37 billion tonnes, which would enable this region to inject CO₂ for several decades once the fields are depleted.

The Sleipner project, located some 240 kilometres off the coast of Norway in the North Sea, is storing more than 2,700 tonnes of CO₂ per day, injected nearly 800 metres below the seabed. Over the lifetime of the project, it is expected that more than 20 million tonnes of CO₂ will be injected into the saline formation.

Monitoring surveys of the injected CO₂ indicate that over the past 15 years, the gas has spread out over nearly 10 square kilometres underground, without moving upwards or out of the storage reservoir.

Long-term simulations also suggest that over hundreds to thousands of years, the CO₂ will eventually dissolve in the saline water, becoming heavier and less likely to migrate away from the reservoir.

A month ago the first coal power plant with CCS opened in Canada-

Country: Canada

Project type: Capture

Scale: Large

Status: Operative

Capital cost: $600 million (canadian $)

Year of operation 2014

Industry: Coal Power Plant

MW capacity: 120

Capture method: Post-combustion

Capture technology: Amine

New or retrofit: Retrofit

Transport of CO2 by: Pipeline

Type of storage: EOR

Volume: 1 million tonnes/CO2

The retrofitted capture plant captures 1 million tonnes per year of CO2 - or 95% - from one of Boundary Dam’s aging combustion units, which has a generating capacity of around 130MW. That’s equivalent to taking more than 400,000 cars off Norwegian roads annually.

The total amount of CO2 produced, for all generating units at Boundary Dam Power station, is 5.5 to 6 million tonnes annually.

This $1,24 billion (of which 600 million is for CCS and the rest is for modernizing the plant) integrated carbon capture & storage project has retrofitted SaskPower's coal-fired Boundary Dam Power Station in Estevan, Saskatchewan with a carbon capture system. Captured CO2 is used for enhanced oil recovery and stored in deep saline aquifers.

The provincial government approved the proposals in April 2011, which cleared the way for construction to begin immediately. The capture facility is opening in October 2014, after a test period since April.

The majority of the captured gas is sold to operator Cenovus for enhanced oil recovery (EOR) at its Weyburn oilfield. Cenovus has set up injection wells and built a 40 mile-long pipeline connecting Weyburn with Boundary Dam. SaskPower and Petroleum.

Hopefully over the next few years many more of these projects will be finished and come online- expecially with the new “backing” from the IPCC….

Anyway… there it it… CCS!!! Enjoy!