CO2 recovery device and CO2 recovery method

A CO2 recovery method in which a CO2 absorption tower and an absorption-solution regeneration tower are used to reuse a lean solution, from which CO2 has been removed in the absorption-solution regeneration tower, in the CO2 absorption tower,

• the CO2 absorption tower bringing CO2-containing flue gas into contact with a basic amine compound so as to remove CO2,
• the absorption-solution regeneration tower separating CO2 from the CO2-absorbed basic amine compound to regenerate a CO2 absorption solution, and
• the method comprising:
• supplying an aldehyde-compound removing agent to washing water while washing decarbonated flue gas with the washing water in a water-washing section to simultaneously remove basic amine compounds and aldehyde compounds;
• and
• supplying an acid to the washing water to control pH thereof to be on an acidic side;
• wherein, on an upstream side of the CO2 absorption tower, flue gas containing CO2, a nitrogen oxide, and a sulfur oxide is brought into contact with alkali-added cooling water to cool the flue gas, and, after the contact, the alkali-added cooling water is used as circulating water of the water-washing section.