Cryogenic air separation is a high-energy consumption process and contributes significantly to greenhouse gas emissions. Reduction potentials of the CO2 emissions for both the full-tower heat-integrated air separation columns (F-HIASC) and the top-tower heat-integrated air separation columns (T-HIASC) are investigated. The optimization models of the minimum CO2 emissions are further proposed. The unit CO2 emissions of F-HIASC and T-HIASC can be decreased significantly compared to the conventional air separation columns (CASC). Furthermore, the capital cost and total annual cost are analyzed so as to evaluate properly the economic feasibility of HIASC. The results demonstrate that the total annual costs of F-HIASC and T-HIASC are much lower than that of CASC.