Closed Drain Recovery System

A closed drain recovery system comprising:

• a steam boiler configured to supply steam to a loading apparatus;
• a closed-type drain tank for reserving drain discharged from the loading apparatus through a drain return line, and configured to supply the reserved drain to the steam boiler through a drain supply line;
• an air-open-type makeup water tank configured to supply makeup water to the drain tank through a makeup water line;
• a steam introduction line for introducing a first flush steam within the drain tank to the makeup water tank;
• a surplus drain introduction line for introducing surplus drain to the makeup water tank from one of the drain tank and the loading apparatus;
• and
• a condensing unit provided for the makeup water tank, and configured to condense one or both of the first flush steam and a second flush steam by bringing the one or both of the first flush steam and the second flush steam into contact with the makeup water within the makeup water tank, the second flush steam being generated from the surplus drain.