The conventional high back pressure heating has high requirements on the thermal net circulating water volume. In order to solve this technical obstacle

this study proposes a reconstruction technology of local high back pressure heating technology for three-exhaust unit. The cores of this technology are to use the duplex cooling method to increase the back pressure of exhaust steam from the exhaust outlet of the unit

and adopt exhaust steam to heat the thermal net circulating water. Thereby

this technology significantly improves the heating capacity and the heating economy of the unit. At present

this technology has achieved good engineering application results. Taking a 200 MW pumping and condensing three-exhaust cogeneration unit as an example

after the transformation using the high back pressure heating technology based on duplex cooling

the coal consumption of power generation has been decreased by more than 30 g/(kW·h) compared to the conventional medium and low-pressure connectingtube extraction methods. In addition

it can take an addition 1.7×10~6 m~2 of heating area. This technical route has important reference value for the 600 MW grade four-exhaust unit with high back pressure technology transformation.