Effect of CO2 Concentration of Gas on Energy Efficiency Performance

“The concentration of CO2 in the flue gas varies, especially in different power plants which use different coal and operating equipment or different industrial senses. This is a key parameter in the input of the CCS system and Figure 8 and Figure 9 show the effect of variable CO2 concentrations of gas from 8% to 16%, which is suitable for the component of flue gas of coal-fired power plants.

Figure 8. The regeneration heat changes with the CO2 concentration variation.
Figure 9. The energy efficiency performance with the CO2 concentration variation.
At low concentrations, the energy consumption is apparently high both in the thermodynamic cycle and equilibrium model at 3.43 and 4.97 GJ/t, respectively, which may be similar to the effect a high L/G brings. Then, as the CO2 concentration increases, the regeneration heat declines sharply. However, it has a limitation as when the concentration is higher than the absorption capacity for a certain L/G value, the regeneration heat will not continue to decline. The lowest value is 2.82 and 3.89 GJ/t, respectively. On the other hand, when it comes to the energy conversion efficiency, the higher CO2 concentration is good news. The Wmin decreases from 201.1 to 128.2 kJ/kg continuously and COPCO2 continuously increase to 2.80. The η2nd has a similar trend with Wmin, which decreases from 27.8% to 20.0%, with lower values indicating more room for improvement of energy performance.
In summary, the higher the CO2 concentration, the higher the result of energy conversion. However, the actual solvent could not achieve such an ideal level and the existing technological process of absorption is also a limitation, which hinders the energy performance.”

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