The invention discloses a CO2 / N2 switching type double-circulation extraction process. The process comprises: mixing oil-containing
solid waste and
organic acid, separating to obtain mixed liquid A and
solid waste, adding a polyetheramine
aqueous solution into the
mixed solution A, separating to obtain an
oil phase and a
mixed solution B, introducing CO2 into the
mixed solution B, protonating, separating to obtain an
organic acid and a mixed solution C, returning the
organic acid to the oily
solid waste, introducing N2 into the mixed solution C, deprotonating to obtain CO2 and a polyetheramineaqueous solution, returning the polyetheramine
aqueous solution to the mixed solution A, and returning CO2 to the mixed solution B, wherein the
temperature control range of the whole extraction process is 30-70 DEG C. The method has the advantages that (1) the organic acid
aqueous solution and the polyether amine aqueous solution are combined for use, so that the purpose of oil removal is achieved, the organic acid aqueous solution and the polyether amine aqueous solution are recycled, the method is environment-friendly and safe to operate, and the oil removal cost is saved, the
recovery rateof oil products is high, other impurities are not introduced, and the
recovery rate of conventional oil products, especially heavy oil products, can reach 90% or above.