| 主权项 |
1. A method for collecting carbon dioxide from flue gas of a power plant, the method comprising the following steps:
1) providing an organic amine and an ionic liquid in a molar ratio of (1-1.1):1, mixing the organic amine, the ionic liquid, and water to obtain an aqueous solution of a composite absorbent having a concentration of between 20 and 40 wt. %;
using the aqueous solution of the composite absorbent comprising the organic amine and the ionic liquid as a CO2 absorbent, evenly spraying the aqueous solution of the composite absorbent into the flue gas from a rear part of a power plant boiler after dust removal and desulfurization to allow the flue gas flowing upwardly to fully contact with the downwardly sprayed aqueous solution of the composite absorbent and to allow CO2 in the flue gas to react with the composite absorbent, controlling a liquid-gas ratio between 5 and 25 L/m3, a reaction temperature of between 40 and 55° C., and a reaction pressure of between 0.01 and 10 atm, whereby absorbing CO2 to yield a solution rich in A.CO2 and B.CO2, in which, A represents the organic amine and B represents the ionic liquid; 2) allowing the solution rich in A.CO2 and B.CO2 to stand and clarify under the action of self-aggregation to form different liquid layers comprising a lower layer being a mixed solution rich in A.CO2 and B.CO2 and an upper layer being the aqueous solution of the composite absorbent; separating the lower layer to obtain the mixed solution rich in A.CO2 and B.CO2;
conducting heat exchange on the separated mixed solution rich in A.CO2 and B.CO2 to enable CO2 gas dissolved or absorbed by the aqueous solution of the composite absorbent therein to evaporate whereby yielding a mixed solution rich in A.CO2 and B.CO2 after heat exchange; 3) thermally decomposing the mixed solution rich in A.CO2 and B.CO2 after heat exchange to release the chemically bound CO2, whereby obtaining high-concentrated CO2 gas and the aqueous solution of the composite absorbent; 4) returning the aqueous solution of the composite absorbent obtained in step 3) to step 1) as the CO2 absorbent for recycling; 5) cooling the high-concentrated CO2 gas separated from step 3) to condense water vapor therein; 6) conducting gas-liquid separation on the high-concentrated CO2 gas after the cooling treatment in step 5) to remove a condensed water therein, whereby yielding CO2 gas having a purity of exceeding 99%; and 7) desiccating, compressing, and condensing the CO2 gas having the purity of exceeding 99% obtained in step 6) to transform the CO2 gas into a liquid state. |
