https://doi.org/10.3390/pr10050859
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The process for CO2 separation is conventional. The flue gases are first compressed to compensate for losses in the absorption column and where ammonia solutions have been used to avoid NH3 losses. They enter a heat exchanger where they are cooled, after which they are counter currently backwashed with an aqueous ammonia solution. The chemical solvent rich in CO2 is pumped before the regeneration column, in order to compensate for losses and minimize the final compression effort. The chemical solvent rich in CO2 is pre-heated in a second heat exchanger by the recovered lean solvent at the bottom of the absorption column. The heat required for the chemical solvent regeneration is supplied by the condensation of water vapor at low pressure. Regeneration reduces the solvent CO2 charge to a low charge. Afterward, before being reintroduced into the absorption column, the solvent is pumped out and cooled. The lower the charging rate, the greater the amount of steam for regeneration. The recovered CO2 flow at the top of the desorption column was compressed to 65 bars with intermediate cooling. This was dehydrated by the triethylene glycol (TEG) process. The residual mole fraction was set at 20 ppm to minimize the hydrate formation risk and corrosion during pipeline transport. The CO2 flow was finally compressed to 150 bars and cooled to 30 °C to increase the density of the CO2 and reach the value required for transport. The chemistry of the CO2 capture process based on ammonia is illustrated in Figure 1 [29], and in Reactions (1) and (2), the absorption and desorption process between MEA and CO2 is shown [30,31].


Parameter | CAP Using NH3 (2, 5, 7, 15% wt.) |
CAP Using MEA (30% wt.) |
---|---|---|
Flue gases temperature at the inlet at absorption column, °C | 20 | 20 |
Temperature of the chemical solvent at the inlet of the absorption column, °C | 0 | 40 |
Flue gases pressure, bar | 1.2 | 1.1 |
Chemical solvent pressure, bar | 1.1 | 1.1 |
Number of absorption column steps, – | 19 | 19 |
Number of desorption column steps, – | 15 | 15 |
SCH temperature CO2 lean/rich solvent, °C | 70 | 70 |
CO2 lean loading solvent, molCO2/molNH3/MEA | 0.3 | 0.21 |
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