The invention relates to a method taking composite solvents, such as
dimethyl ether of polyethlene glycol and the like, as an absorbent to purify industrial
tail gas rich in CO, which belongs to the technical field of the clean production of
chemical industry. In the method, the counterflow physical absorption of the
impurity components of H2S, PH3, HCN, HF, AsH3 and the like in the
tail gas is carried out in an absorption
tower by utilizing the composite solvents of the method under the conditions of low temperature or normal temperature and 0.1 to 3.5 MPa (gage pressure) after the industrial
tail gas rich in the CO is washed by water and dewatered, and the removal rate of the main
impurity components reaches more than 99 percent. Absorption liquid which flows out from the bottom of the absorption
tower and is rich in the
impurity components is throttled, decompressed and heated by a flash
evaporator to escape most of the impurity components, the absorption liquid enters a regenerating
tower after being reheated and is in counterflow contact with part of refluent purified gas, and impurities are further desorbed. The absorption liquid after being desorbed by the regenerating tower is delivered to the absorption tower for recycle, and the
desorption gas of the regenerating tower is delivered back to an inlet of a purification
system. The high-concentration foreign gas escaping from the flash
evaporator is utilized after alkali washing or
copper sulfate liquid washing.