Carbon Sequestration

Only available on StudyMode
  • Download(s) : 395
  • Published : May 19, 2009
Open Document
Text Preview
INTRODUCTION
Since carbon dioxide concentration in the atmosphere is accumulating rapidly because of burning fossil fuel, coal, oil and natural gas for power generation, transportation, industrial and domestic uses, our earth has been facing global warming, sea level rising, flooding and other adverse changes which damage to our ecosystem. To address this challenge, we need to find out other alternative ways that do not produce carbon dioxide or that reduce the release of enormous amount of carbon dioxide gases. Carbon dioxide capture and storage (CSS) or sequestration, which will be discussed in this report, is a new technology that secures emissions reductions and cost effective so that it’s quite critical to long-term emission reductions to rescue our globe. HOW WILL THE GAS BE INTRODUCED INTO THE ROCK SYSTEM

CSS is four-step processes to be carried out that are capturing, compressing, transporting, storing and injecting carbon dioxide into the storage site. Capture
First of all, carbon dioxide emitted from electrical generation plants and other combustion sources as a flue gas can be captured by three engineering techniques. The first is end-of-pipe or pre combustion approach in which chemical processes are used to gasify the fossil fuel to extract H2 before it is combusted. Another way to capture CO2 can be done by post combustion whereby carbon dioxide is recovered from the flue gas by scrubbing it with an aqueous solution. Alternatively, the last approach uses oxygen instead of air in the burner so that CO2 and water compounds are produced from which the CO2 is easily separated. Among these technologies, only post-combustion capture is closest to implementation that could be applied broadly today, but costs and energy demands are high while the other options require more research to achieve much higher energy efficiency.

Comparative benefits of post-combustion, pre-combustion and oxygen-combustionTechnology Advantages Drawbacks
Post-Combustion

• Mature technology for other applications (e.g. separation of CO2 from natural gas)

• Standard retrofit of existing power generation capability

• Technology improvements and cost reductions possible with additional development

• High energy penalty (~30%)

• High cost

Pre-Combustion

• Lower costs than post-combustion capture

• Lower energy penalties than post-combustion capture

• High pressure of CO2 reduces compression costs

• Combine with H2 production for transportation sector

• Technology improvements and cost reductions possible with additional development

• Complex chemical process required for gasification

• Repowering of existing capacity needed

• Large capital investment needed for repowering

Oxygen-Combustion

• Avoid the need for complex post-combustion separation

• Potentially higher generation efficiencies

• Technology improvements and cost reductions possible with additional development

• New high temperature materials are needed for optimal performance

• On-site oxygen separation unit needed

• Repowering of existing capacity needed

Compression, Transport
Once the gas is capture, it is compressed by the higher pressures and becomes a liquid to be able to trap in the pore space between the grains of rock. The safe transportation method of gas to storage sites are considered to use pipelines for transporting large amounts of CO2 to a well characterised storage site. CO2 can also be transported as a liquid on road tankers or railcar in insulated tanks at low temperature and by ships where CO2 has to be moved over large distances or overseas.

Injection and Storage (State of the gas when stored)
it is injected as a supercritical fluid (dense and liquid-like) at sufficiently high pressures and temperatures through an injection well into the target reservoir formation, generally at a depth of 800m or more. A reservoir rock could be sandstone, in which...
tracking img