Abstract: The cold end system is an important auxiliary system of power generation unit of thermal power plant, and its working condition and operational characteristics influence on stability, safety and economical efficiency of the unit greatly. Taking the 300MW unit of a power plant in Inner Mongolia as example, the influence of the back pressure variation on the unit economical efficiency under several typical conditions was analyzed. The influences of the working water temperature variation of the vacuum pump on the air inflow, the condenser pressure, the heat consumption rate and the coal consumption rate of the unit were analyzed emphatically. A reformation measure was adopted, in which an industrial water flow was added and used as cooling water. The test result shows that the result of the reformation is favorable, and the economical efficiency of the unit was improved obviously.

Key words: cold end system, economical efficiency, vacuum pump, back pressure, heat consumption rate, coal consumption rate, cooling water, optimization