The mechanism of applying low-vacuum circulating water for heat supply was presented.Taking the 135 MW and 300 MW condensing units as the examples

issues should be considered and solved during retrofitting of low-vacuum circulating water heating system were discussed.After the low vacuum circulating water heating system was adopted

the available waste exhaust heat of the 135 MW and 300 MW unit were 727 GJ/h and 1 382 GJ/h

and the increased heating area of them were 4.0×106 m2 and 7.7×106 m2

respectively

making the unit achieve its best economy during the whole year's running.With no supplement of the unit installed capacity and no increase of local pollutant emission

it should be better to enlarge the heating area and save amount of circulating cooling water lost by evaporation.