So far, after five-month operation, all the indicators of two sets of impure nitrogen heat exchangers have reached the design capacity for the revamped air compressor of oxygen-making equipment in Chaoyang Iron and Steel. The emitted air heat energy from air compressor was used efficiently. The heat exchange effect between emitted air and impure nitrogen is obvious. The temperature of emitted air reduces 10℃ while the temperature of impure nitrogen will rise 65 to 84℃, which reduced electrical heating energy consumption of impure nitrogen, saving 2.2million degree of electricity per year.