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Author
Arregui Balbuena, Carlos
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CO2 emissions have become a problem since technological progress caused an overproduction of this gas, having as a consequence the so-called greenhouse effect on the planet. Today, there is a huge concern to mitigate its effects and different options to sort this issue out are being studied. Most of them go through the capture and subsequent storage, or reuse, of CO2 (CCUS). Since the capture of CO2 from the atmosphere is not efficient due to its low concentration (around 0.04%), it is necessary to capture it directly at the source of emission. These emission sources are, in a significant percentage, electricity generation plants, since they are based on the combustion of fossil fuels. As emissions levels for newly built CCGT plants without carbon capture is today around 350 kgCO2/MWh, it is expected that they will not be able to operate without CCUS beyond 2030, according to most European regulations.
One of the most widely used forms of capture is chemical absorption with monoethanolamine (MEA) in solution at 30% by weight, due to the rapid kinetics, it presents when reacting with CO2 and its regeneration capacity, changing the temperature and pressure conditions of the process. However, the main problem with capturing CO2 from natural gas combustion is that it is highly diluted by a large amount of air used in a gas turbine, coming into a low concentration (3-4%). This leads to inefficient absorption, requiring a large amount of solute to absorb CO2. In addition, the excess of oxygen creates problems of solvent degradation and corrosion in equipment.
In this work, a complete simulation study of the combination of a cycle power generation plant by natural gas combustion coupled to a carbon capture plant with MEA is presented. In particular, the effect of the enrichment of the CO2 content in the combustion chamber by injection of this gas together with air at the compressor inlet is evaluated to see how both, the electricity generation plant and the carbon capture plant, are affected.
The gas natural reaction is simulated using CHEMKIN®, a program specialized in modeling the combustion reaction of hydrocarbons that uses the GRIMECH 3.0 kinetic mechanism. Additionally, a steam cycle with an SGT6-2000E gas turbine from the Siemens catalog is studied using Aspen HYSYS v10. Finally, the capture plant is evaluated through a simulation with the Aspen Plus v10 program. The generation and consumption results of both plants are integrated to see how the complete system behaves as a function of different CO2 concentrations.
Finally, an economic study is carried out to check the viability of this combined installation as a function of the CO2 enrichment, discussing the effects on power generation vs.CO2 recovered.
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