Method for improving efficiency of Rankine cycle

1. A method for improving efficiency of a large Rankine cycle, comprising a heat source system, a steam turbine cycle system, and a cold end system, wherein, the steam turbine cycle system comprises a main steam system, a steam turbine system, a reheat steam system, and a shaft sealing steam system, wherein, the reheat steam system comprises a reheater, and the steam turbine system comprises a high-pressure cylinder, wherein the method comprises:

S 1000 : adjusting an equipment state or operating condition of the heat source system or the steam turbine cycle system to reduce heat absorption of the reheater, so that a temperature of steam entering a steam turbine subsequent to the high-pressure cylinder is lower than a rated temperature of reheat steam to reduce cold end loss, thereby improving cycle thermal efficiency of the steam turbine.

2. The method for improving efficiency of a large Rankine cycle according to claim 1 , wherein for a traditional power plant, adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system comprises:

S 1011 : adjusting fuel quantity and output of a burner of each relevant layer, specifically as follows: increasing fuel quantity of a lower-layer burner of a boiler and reducing fuel quantity of an upper-layer burner of the boiler; or,

S 1012 : when the reheater meets an adjustment condition for a reheat flue gas damper, specifically comprising: adjusting, i.e., decreasing an opening degree of the reheat flue gas damper; or,

S 1013 : when the reheater meets and/or does not meet the adjustment condition for the reheat flue gas damper, specifically comprising: adjusting, i.e., decreasing an inclination angle of the burner of the boiler.

3. The method for improving efficiency of a large Rankine cycle according to claim 2 , wherein for a traditional power plant, when the steam turbine system further comprises an intermediate-pressure cylinder, and a reheat steam bypass pipe is provided between an exhaust pipe of the high-pressure cylinder and an intake pipe of the intermediate-pressure cylinder, and a regulating valve is provided in the reheat steam bypass pipe, adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system comprises:

S 1020 : fully or partially opening the regulating valve, so that a part of exhaust steam of the high-pressure cylinder directly enters the intake pipe of the intermediate-pressure cylinder through the exhaust pipe of the high-pressure cylinder.

4. The method for improving efficiency of a large Rankine cycle according to claim 1 , wherein for a traditional power plant, adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system specifically comprises:

S 1031 : reducing a heat exchanging area of the reheater; or,

S 1032 : removing the reheater.

5. The method for improving efficiency of a large Rankine cycle according to claim 4 , wherein the step S 1032 further comprises:

replacing, on the basis of an original superheater for main steam and an original economizer, the reheater with a new economizer; or

wherein, for a traditional power plant with a regenerative steam extraction system, the step S 1032 further comprises:

adjusting fuel quantity and output of a burner of each relevant layer, specifically as follows: increasing fuel quantity of a lower-layer burner of a boiler and reducing fuel quantity of an upper-layer burner of the boiler; or,

adjusting, i.e., decreasing an inclination angle of the burner of the boiler;

so as to decrease a temperature of main steam between a rated temperature of the main steam and a saturation temperature of the main steam.

6. The method for improving efficiency of a large Rankine cycle according to claim 4 , wherein the step S 1032 further comprises:

removing the superheater.

7. The method for improving efficiency of a large Rankine cycle according to claim 6 , wherein the step S 1032 further comprises:

replacing an original superheater with a high-temperature economizer.

8. The method for improving efficiency of a large Rankine cycle according to claim 4 , wherein the step S 1032 further comprises:

adding desuperheating water for main steam to make the main steam become saturated steam or wet steam with an enthalpy value equal to or lower than that of saturated steam.

9. The method for improving efficiency of a large Rankine cycle according to claim 6 , wherein the step S 1032 comprises:

increasing capacity of a feed pump, or increasing opening of a regulating valve of the feed pump, or adding a new feed pump in a regenerative steam extraction loop other than 4 #steam extraction pipe, to increase water feed of the heat source system and the steam turbine cycle system.

10. The method for improving efficiency of a large Rankine cycle according to claim 5 , wherein adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system further comprises:

S 1040 : increasing a pressure of main steam and/or increasing the number of impeller stages of a rotor of a steam turbine to increase power of the steam turbine and improve work efficiency of the steam turbine.

11. The method for improving efficiency of a large Rankine cycle according to claim 1 , wherein for a nuclear generator set, adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system comprises:

S 1050 : reducing a flow rate of fresh steam input to a steam-water separation reheater or removing the steam-water separation reheater to reduce a temperature of reheat steam to a temperature which is less than a rated temperature of main steam by 10° C. or more.

12. The method for improving efficiency of a large Rankine cycle according to claim 1 , wherein for a combined-cycle generator set, adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system comprises:

S 1061 : reducing a heat exchanging area of a heat absorbing element of a low-pressure heating system or an intermediate-pressure heating system to reduce heat absorption of the low-pressure heating system or the intermediate-pressure heating system; or,

S 1062 : removing the low-pressure heating system or the intermediate-pressure heating system.

13. The method for improving efficiency of a large Rankine cycle according to claim 12 , wherein the step S 1062 further comprises:

replacing, on the basis of an original superheater for main steam and an original economizer, the removed low-pressure heating system or intermediate-pressure heating system with a new high-pressure economizer.

14. The method for improving efficiency of a large Rankine cycle according to claim 1 , wherein for a solar thermal generator set, adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system comprises:

S 1071 : reducing a heat exchanging area of the reheater to reduce heat absorption of the reheat steam; or,

S 1072 : removing the reheater.

15. The method for improving efficiency of a large Rankine cycle according to claim 14 , wherein the step S 1072 further comprises:

replacing, on the basis of an original superheater for main steam and an original economizer, the removed reheater with a new high-pressure economizer.

16. A method for improving efficiency of a small Rankine cycle, comprising a heat source system, a steam turbine cycle system, and a cold end system, wherein, the steam turbine cycle system comprises a main steam system, a steam turbine system, a regenerative steam extraction system, and a shaft sealing steam system, wherein a working medium of a steam turbine is steam or another low boiling point medium, wherein the steam turbine system comprises a high-pressure cylinder, wherein the method comprises:

S 2000 : adjusting an equipment state or operating condition of the heat source system or a steam turbine cycle system, reducing an enthalpy value of main steam, and increasing a proportion of regenerative extracted steam to reduce cold end loss, thereby increasing cycle thermal efficiency of the steam turbine.

17. The method for improving efficiency of a small Rankine cycle according to claim 16 , wherein adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system comprises:

adjusting fuel quantity and output of a burner of each relevant layer, specifically as follows:

S 2011 : increasing fuel quantity of a lower-layer burner of a boiler and reducing fuel quantity of an upper-layer burner of the boiler; or, S 2012 : decreasing an inclination angle of the burner;

so as to reduce a temperature of main steam between a rated temperature of the main steam and a saturation temperature of the main steam;

or wherein adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system comprises:

S 2020 : removing a superheater.

18. The method for improving efficiency of a small Rankine cycle according to claim 17 , further comprising:

S 3010 : replacing an original superheater with a high-temperature economizer;

or wherein, the method further comprises:

S 3020 : adding desuperheating water for main steam to make the main steam become saturated steam or wet steam with an enthalpy value equal to or lower than that of saturated steam.

19. The method for improving efficiency of a small Rankine cycle according to claim 16 , wherein adjusting the equipment state or operating condition of the heat source system or the steam turbine cycle system comprises:

S 2030 : increasing capacity of a feed pump, or increasing opening of a regulating valve of the feed pump, or adding a new feed pump in a regenerative steam extraction loop other than 4 #steam extraction pipe, to increase water feed of the heat source system and the steam turbine cycle system.

20. The method for improving efficiency of a small Rankine cycle according to claim 17 , wherein the method further comprises:

S 4000 : increasing a pressure of main steam and/or increasing the number of impeller stages of a rotor of a steam turbine to increase power of the steam turbine and improve work efficiency of the steam turbine.