Abstract: In recent years, all boilers for civic heat supply units have been equipped with flue gas denitrification device due to the increasingly severe consequences of environmental pollutions. However, the operation of the flue gas denitrification device has exhibited some side effects on the high pressure heat supply system. In this paper, through the analysis on the thermodynamic properties of the heat supply system, it is concluded that the boiler minimum denitrification load is the major factor restricting the high pressure heating system economic operation. As a result the retrofit plan is proposed to fully take advantage of denitrification device for high back pressure heating unit under all loading conditions of. The case analysis of a 135-MW such unit indicates that the net coal consumption rate will be reduced by 8.67 g/(kW·h) once the plan is implemented. In this way the potential of energy saving in high back pressure steam turbines can be further explored.

Key words: thermal generation unit, high back pressure heating unit, denitrification device, economic performance