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1. Introduction - Firenze University Press

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Net Coal Consumption Rate g/kWh 305<br />

Net Heat Rate kJ/kWh 8937.1<br />

Overall Plant CO2 Emissions<br />

Carbon Dioxide Emissions g/kWh 867.8<br />

3.2. Amine scrubbing process for post-combustion CO2 capture<br />

In this study, the process design of CO2 capture was based on a standard monoethanolamine (MEA)<br />

absorption-desorption method. Fig. 5 shows the process of the CO2 separation unit. As is shown in<br />

Fig. 5, flue gas from the power plant is first cooled (down to a temperature of 40-50oC)and<br />

desulphurized in a flue gas desulfurization unit (FGD). Then, after passing through a booster fan,<br />

flue gas is absorbed by MEA in an absorber. The treated flue gas, from which most of the CO2 gas<br />

has been separated, is vented to the atmosphere. Rich solvent from the bottom of CO2 absorber is<br />

delivered to a cross heat exchanger by a pump (P1). Having been heated in the heat exchanger, it is<br />

delivered to a stripper to desorb CO2 by thermal treatment at 100oC up to 140oC. The CO2-H2O<br />

stream desorbed from the stripper is condensed and the moisture is removed to get more pure CO2<br />

in a condenser and a separator (Sp). The lean solvent is delivered to the cross heat exchanger by a<br />

pump (P2), and then to the absorber after cooling the stream to the designed temperature by a cooler<br />

(C1). Considering the degradation and volatilization of MEA, makeup of MEA solvent is also<br />

added to the absorber. Usually the CO2 separated from the stripper is compressed to the required<br />

pressure and temperature by the multistage compressor (CP) for CO2 transportation.<br />

Fig. 5. The typical CO2 capture process based on MEA<br />

The main parameters of the absorption process based on MEA are listed in Table 2. The pressure of<br />

the stripper is set as 2.1bar, and the stripper temperature is 115oC. The entire flue gas stream enters<br />

the absorber tower and the CO2 recovery ratio can reach over 90%. And the mass purity of CO2<br />

can reach 99.8%, which is high enough for CO2 storage or many industrial applications.<br />

Table 2. Main performance parameters with MEA-based CO2 capture process<br />

Title Number<br />

Desorber <strong>Press</strong>ure (bar) 2.1<br />

Temperature of reboiler (°C) 115<br />

CO2 recovery ratio (%) 90<br />

CO2 lean loading(molCO2/molMEA) 0.3<br />

24

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