Abstract
The concentration of carbon dioxide has been abnormally increasing over the years. In the year 2016, its concentration exceeded the limitations, and has been considered as a dangerous situation. As a response to the increasing carbon dioxide content in the Earth’s atmosphere, different processes are being suggested in order to lower the concentration. Carbon Capture and Storage, or CCS, is one of these processes. Generally, there are three different phases of this process: the pre-combustion, the oxyfuel, and the post-combustion. These three phases have different processes in which the carbon dioxide content is being separated from the other components. These processes are responsible for the maintenance of coal power plants. This is for the purpose of lowering the carbon emissions, as power plants are one of the biggest contributors of carbon dioxide in the atmosphere. As of now, CCS is proven to be efficient, but expensive, but a further solution suggests the improvement of the facilities in order to accumulate more carbon dioxide content.
Introduction
It is in September when the concentration of carbon dioxide in the atmosphere is usually at its lowest for a year. However, this 2016, the concentration of carbon dioxide in the atmosphere did not go below 400 parts per million, an inevitable threshold that marks the failure of efforts to maintain or lower concentrations of carbon dioxide in the atmosphere. The concentration going over the month where it should be the lowest meant that the carbon dioxide in the atmosphere had permanently gone over the threshold (Kahn 2016). This also meant that if humanity fail to devise better ways to lower the said concentration of carbon dioxide in the atmosphere, then the survival of many species could be at stake. With that urgency to reduce carbon dioxide concentrations in the atmosphere, carbon dioxide capture and storage or CCS is acknowledged to be a strategy that could lower carbon dioxide emissions and reduce the detrimental effects of reaching the threshold. Furthermore, post-combustion, pre-combustion and oxy-fuel are the main technologies used for carbon capture in plants that are powered by coal. This paper will likewise review the applications of these technologies and assess their appropriate uses, challenges in each technology and possible solution to such challenges.
Body
Carbon Dioxide Capture and Storage
Carbon dioxide capture and storage or CCS is a strategy or a technology that can lower carbon dioxide emissions in the atmosphere and consequently the current concentrations by capturing the carbon dioxide emitted by the utilization of large industries of fossil fuels. This technology is currently more applicable to large industries rather than on smaller scale producers of carbon dioxide, such as households and other institutions (Carbon Capture & Storage Association 2017). Reducing the emissions of industrial plants that run on fossil fuel is important and highly critical since they contribute a significant amount to the carbon emissions of the world. Thus, controlling emissions in this area will guarantee a significant reduction in the carbon dioxide emissions. This would mean a more hospitable environment for everyone in the society and species that are at the brink of extinction (Global CSS Institute 2016).
Moreover, carbon dioxide capture and storage has three stages or phases. The first one is the actual capture of the carbon dioxide. It is at this stage when the carbon dioxide is isolated from industries dependent on fossil fuels. This is followed by the transportation of the captured carbon dioxide. Finally, the captured and transported carbon dioxide from are stored underground to make sure that the emitted carbon dioxide will not go to the atmosphere and make global warming and climate change worse (Carbon Capture & Storage Association 2017).
Furthermore, there are many options when it comes to capturing carbon dioxide: post-combustion, pre-combustion and oxyfuel combustion. Each of the said options in capturing carbon dioxide has their own appropriate applications when it comes to a specific type of coal-fired power plant, and their own limitations and challenges.
Pre-Combustion
As for the pre-combustion capture of carbon dioxide, this option is often taken by the coal-gasification plants. In here, coal is made into a gas to produce a gas mainly composed of hydrogen and carbon monoxide. The said components are then allowed to undergo a chemical reaction with water, forming higher amounts of hydrogen and carbon dioxide. The carbon dioxide is then transported and securely stored. The hydrogen from this process may be used to produce electricity through turbines or used to fuel hydrogen cells that may power other motors without the problem of producing carbon dioxide as a by-product.
Advantages:
The pre-combustion process generally uses a less amount of sources. From the solid waste to the amount of water required, less than 50 percent of each of them is only required (TESEP). Also, the process is a very efficient one. 95 percent of the Carbon dioxide and Sulfur were removed during the process. Above all that, different fuels can be used for the process, which makes it easier to be implemented in the power plant (TESEP).
Challenge:
Among the challenges that the use of pre-combustion capture faces is that it cannot be retrofitted into older coal plants unlike post-combustion capture (Jha 2008). As such, it cannot be used in the majority of the plants already existing, making it problematic to depend on such capturing technology to minimize carbon dioxide emissions. Aside from these, in order to proceed for the operation, the power plant must be well-maintained, and it requires a high initial cost (TESEP).
Oxyfuel System
In the burning of carbon dioxide, a sufficient amount of energy is required to separate oxygen from it. In this process, Carbon Capture and Storage is required in order to extract the carbon dioxide and water vapor separately. Afterwards, carbon dioxide will be condensed, while water vapor will be stored. Oxyfuel system enters into the process this time. Using the system, the air components will be converted into their liquid states, and this comprises 15 percent of the power being used (Jha 2008).
Advantages:
Among the processes involved, oxyfuel system is considered as one of the most efficient process of all. It has almost, if not complete, carbon dioxide capture. Since the combustion is almost complete, there is a less amount of emission (TESEP). It can be also subjected to retrofit, which means that it can be transferred from one power plant to another, or from an older plant to the newer one (TESEP).
Challenge:
Since there is an almost complete combustion process, the energy required for the operation is considerably higher, as well. As such, this can also entail a high operating cost (TESEP).
Post-Combustion
The carbon dioxide from the combustion of coal may be captured by using a solvent that could absorb carbon dioxide from the exhaust of the plants. This type of capture is called post-combustion simply because it collects the carbon dioxide after the coal had been combusted and the carbon dioxide had been emitted in the exhausts. There are of course other ways to capture the carbon dioxide emitted post-combustion aside from the use of an absorbing solvent. The use “May be retrofitted to existing plants or used in new ones Fuel injected into boiler and combusted in air Produces steam to power turbines and generate electricity Gas of CO2, nitrogen and water Chemical wash separates CO2 Capture, compressed and dehydrated Ready for transport and storage” (Global CSS Institute 2016).
Post-combustion processes separate CO2 from combustion exhaust gases. CO2 can be captured using a liquid solvent or other separation methods. In an absorption-based approach, once absorbed by the solvent, the CO2 is released by heating to form a high purity CO2 stream. This technology is widely used to capture CO2 for use in the food and beverage industry (Jho 2008).
Advantages:
Post combustion process may be retrofitted to the older plants or in new ones. Thus, it only means that there is no need to set up a new one when a plant will be renovated or relocated (Teacher Earth Science Education Programme [TESEP]). However, because of its critical role, the retrofitting skills must be highly taken into consideration. Another thing is that post-combustion process is flexible, because not only energy sources such as coal is applicable, but also the other renewable energy sources (TESEP). Thus, this process can be used on a wide range of energy sources.
Challenges:
Despite the advantages brought about by retrofitting, the main problem is that it entails a high operating and maintenance cost. In the post-combustion process, retrofitting and solvent are the ones responsible for the most of the expenses required. Also, in order to effectively operate in this process, the required energy is equally high, as well. These requirements also must conform to the skills of the operator, as retrofitting requires a huge amount of experience from the workers (TESEP).
Future Solutions
Overall, it can be determined that the coal plant operation is very expensive because of the high amount of energy required. As such, it is a good recommendation for the improvement of energy efficiency. It is not that the cost will be lowered significantly. However, with the operating energy being spent effectively, more operations will be done through time. However, this will also require a significant renovation of the facilities. As such, it is recommended to allocate improvement costs from time to time. Also, it is best to hire an expert consultant regarding the maintenance of the power plant. Hiring an expert will be more efficient because this will further prevent more errors and inaccuracies.
Conclusion
Operations in a coal power plant require a huge amount of effort and resources. Spending a large amount of investment and maintenance costs cannot be avoided. As such, there is a need to consider the skills and management of the workers, as well as the plant supervisors. The quality of the output of the operation, in order to avoid wasting all the important resources.
References
Jha, A., 2008, ‘Explainer: How carbon is captured and stored,’ The Guardian, viewed 11 January, 2017, from https://www.theguardian.com/environment/2008/sep/05/carboncapturestorage.carbonemi ssions1.
Kahn, B., 2016, ‘The World Passes 400 PPM Threshold. Permanently,’ Climate Central, viewed 11 January, 2017, from http://www.climatecentral.org/news/world-passes-400-ppm- threshold-permanently-20738.
‘Understanding CCS,’ 2016, Global CCS Institute, viewed 11 January, 2017, from https://www.globalccsinstitute.com/content/capture.
‘What is CCS?,’ Carbon Capture and Storage Association, viewed 11 January, 2017, from http://www.ccsassociation.org/what-is-ccs/
