• Afghan Youth Association

Introduction to Carbon Captur Storage (CCS)

Author(s): Hamed Al-Busaidi, Shabiha Begum, George Done, Parwiz Karimi, Temitayo Ken-Afolabi Carbon Capture Storage (CCS) is a combination of technologies purposefully designed to prevent the release of CO2 generated through intensive industrial production processes and conventional power generation into the atmosphere. The technology separates the CO2 from emissions of chemical processes. The CO2 is compressed and transported to appropriate geological storage locations. The bulk of research and development has been focused on improving the efficiency of CO2 separation processes from the released compounds by heavy industrial processes (GRI.,2018). The methods through which CO2 is captured falls into three main categories: pre-combustion, post-combustion and oxy-fuel combustion (Climate Technology Centre & Network.,2019). In 1996, the first ever CCS began operation in Sleipner, Norway. In addition to 5 large scale CCS plant under construction, there are 18 large scale CCS operating globally. According to a report by Global CCS Institute (GCCSI), the existing CCS facilities have the capacity to capture 31 million tonnes of CO2 annually (GRI.,2018). CCS is considered the only technology which has the potential to reduce emissions released by large scale industrial facilities. The GCCSI has stated that to meet the global temperature rise limit of 2.0˚C, an estimated 2500 CCS facilities are needed by 2040 if each CCS facility captures 1.50 million tonnes of CO2 annually (GRI.,2018). The waste incineration plant run by ABKDK Ltd. produces a significantly large volume of flue gas. In addition to CO2, the flue gas is composed of other environmental air pollutants including sulphur oxides (SOx), nitrogen oxides (NOx) and particulates. These are environmentally harmful substances and limit the CO2 absorption within the CCS plant. The pre-treatment processes of the flue gas require high operating temperatures which increases the energy consumption of the plant. The three main CCS technologies used in power plants and industrial processes are post-combustion, pre-combustion and oxyfuel combustion (Sood & Vyas, 2017). Pre-combustion carbon capture comprises of the removal of carbon from the combustible material before combustion so is therefore not applicable to treating waste incineration flue gas (Sood & Vyas, 2017). Oxy-fuel combustion involves burning fuel in pure oxygen (Sood & Vyas,2017). It requires the use of an air separation unit (ASU) that produces a rich oxygen stream used for combustion in the boiler (Simpson & Simon, 2007). The flue gas produced is rich in water (H2O) and CO2 which is then cooled to produce a dry CO2 rich stream (Simpson & Simon,2007). Although certain oxy-fuel combustion processes can be retrofitted to existing plants, the efficiency of the furnace significantly reduces (Simpson & Simon, 2007). The system’s air efficiency also needs to be high enough to offset the extra cost of requiring a carbon separation unit (CSU) at the end of the process (Simpson & Simon,2007). Post-combustion is the most commonly used method for carbon capture in industry (Herzog, H et al, 2009) and can be retrofitted onto existing power plants to treat the flue gas (Sood & Vyas, 2017). This process first reduces the level of contaminants in the flue gas (Wang et al., 2017), then the CO2 is removed from the flue gas and the treated flue gas is released into the atmosphere (Wang et al., 2017). After this the CO2 is dried, compressed and transported for storage (Wang et al., 2017). One of the issues with this process is the low partial pressure of CO2 in the flue gas which causes a low driving force for separation (Wang et al., 2017) whereas oxy-fuel combustion has a higher CO2 partial pressure as it avoids dilution of the gas with nitrogen (N2). Post Combustion Carbon Capture 1. Chemical absorption Chemical absorption is one of the most developed carbon capture processes that can be used in large scale industries. CO2 from the flue gas is captured using an amine-based solvent that absorbs the CO2 in an exothermic reaction that occurs in an absorption tower, the product of the reaction is a soluble carbonate salt (Karamé, 2018). The reaction is then reversed, and the captured CO2 can be de-absorbed in a stripper tower by heating the carbonate solution (Karamé, 2018). Chemical absorption is favoured by CO2 capture at low partial pressure, with amine solution being the predominant solvent (Rackley, 2010). 2. Membrane separation This technology uses a membrane to separate CO2 from a mixture of gases such as flue gas. Depending on the design and the material of the membrane, filtration involves a number of physical and chemical processes. Porosity and pore size are the key characteristics that determine the permeate transportation mechanism (Baker, R. 2004). The membrane material is divided into three categories: hybrid membrane, ceramic membrane and polymeric membrane (Wang, Y., Zhao, L, 2017). Membranes consist of thin polymeric films to separate gas mixtures depending on the rate at which molecules permeate, this is also called selectivity. The partial pressure at different sides of the membrane determines the permeation driving force (Wang, m. and Lawal, A., 2011). two-stage membrane has been experimented to capture >80 % of CO2 with a CO2 purity of >95% from a flue gas feed of 18260 kmol/h with 1.02 GJ/ton CO2 energy consumption (Xuezhong He, 2015). 3. Chemical and physical adsorption Adsorption is a new potential method for the removal of CO2 from a gas stream mixture using a solid rather than an aqueous mixture or membrane. This is advantageous as it has the potential to remove some of the major drawbacks of liquid solvent CO2 capture (Unveren et al, 2016). The main disadvantages of using a liquid amine is the energy required for the stripper column, the corrosive product formed when the CO2 is absorbed and degradation of the solvent which can all be reduced by the use of solid adsorption (Verma et al., 2015). There are two main methods for the adsorption and desorption; pressure swing adsorption (PSA) and temperature swing adsorption (TSA). PSA utilises varying pressure to adsorb the gas to the sorbent and then desorb it at constant temperature. However, TSA varies the temperature to do the same and is normally at ambient pressure which makes TSA much more useful for flue gas treatment (Ntiamoah et al., 2015). There are two methods by which the sorbent can remove the CO2 from the mixture; physical or chemical adsorption. Physical adsorption using carbon based sorbents or zeolites permits low concentrations of CO2 as well as a high degree of separation with a capacity of 10-15% by weight, however, it does not have a high N2/CO2 selectivity (Hinkov et al., 2016). We express our gratitude to Hamed Al-Busaidi, Shabiha Begum, George Done, Parwiz Karimi and Temitayo Ken-Afolabi for sharing their work with us. We wish them all the very best in thier future careers as successful engineers.  References 1. Grantham Research Institute on climate change and the environment (GRI). (2018). what is carbon capture and storage and what role can it play in tackling climate change? - Grantham Research Institute on climate change and the environment. [online] Available at: [Accessed 1 Dec. 2019] 2. Climate Technology Centre & Network. (2019). CO2 capture technologies. [online] Available at: [Accessed 1 Dec. 2019]. 3. Sood, A. and Vyas, S. 2017. Carbon Capture and Sequestration- A Review. IOP Conference Series: Earth and Environmental Science. [Online]. 83,p.012024. [Accessed 9 October 2019]. Available from: 4. Simpson, A.P. Simon, A.J. 2007. Second law comparison of oxy-fuel combustion and post-combustion carbon dioxide separation. Stanford, USA. 5. Wang, Y., Zhao, L., Otto, A., Robinius, M. and Stolten, D. 2017. A Review of Post-combustion CO2 Capture Technologies from Coal-fired Power Plants. Energy Procedia. [Online]. 114,pp.650-665. [Accessed 9 October 2019]. Available from: C837FBA07A924A1D20F7A0048DB45F89A0ABDEEEC05294DD74949610F2D9A7ACEBDB 06270D3DBD0. 6. Karamé, I. (2018). Carbon dioxide chemistry capture and oil recovery. London: IntechOpen, pp.142-158, 103-106. 7. Rackley, S. (2010). Carbon capture and storage. Burlington, MA: Butterworth-Heinemann, p.Chapter 6. 8. Baker, R. (2004). Membrane Technology and Applications, John Wiley and Sons, Chichester, UK. 9. Wang, Y., Zhao, L., Otto, A., Robinius, M. and Stolten, D. 2017. A Review of Post-combustion CO2 Capture Technologies from Coal-fired Power Plants. Energy Procedia. [Online]. 114,pp.650-665. [Accessed 9 October 2019]. Available from: C837FBA07A924A1D20F7A0048DB45F89A0ABDEEEC05294DD74949610F2D9A7ACEBDB 06270D3DBD0. 10. Xuezhong He , Chao Fu, May-Britt Hägg (2015) Membrane system design and process feasibility analysis for CO2 capture from flue gas with a fixed-site-carrier membrane, Available at: file:///C:/Users/kziau/Downloads/1-s2.0-S1385894714017288-main.pdf (Accessed: 12 November 2019). 11. Unveren, E., Monkul, B., Sarioglan, S., Karademir, N. and Alper, E. 2016. solid amine sorbents for co2 capture by chemical adsorption: a review. Petroleum. 12. Verma, M., Joahnn, P., Pelletier, F., Godbout, S., Brar, S., Tyagi, R. and Surampalli, R. 2015. Carbon Capture and Sequestration: Physical/Chemical Technologies. 13. Ntiamoah, A., Ling, J., Xiao, P., Webley, P.A. and Zhai, Y. 2015. CO 2 Capture by Temperature Swing Adsorption: Use of Hot CO 2-Rich Gas for Regeneration. 14. Hinkov, I., Lamari, F., Langlois, P., Dicko, M., Chilev, C. and Pentchev, I. 2016. Carbon Dioxide Capture by Adsorption (Review). Journal of chemical technology and metallurgy.

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