Method for reducing summer operation back pressure of unit by using dead steam waste heat recovery system

Abstract

The invention discloses a method for reducing the summer operation back pressure of a unit through a waste steam waste heat recovery system. The method comprises the following steps that S1, a waste steam heat exchange system is arranged; s2, a heat source water inlet of the exhaust steam heat exchange system is connected with an exhaust pipeline of the steam turbine through an exhaust steam adjusting valve, and a water outlet is connected into a water supply system; s3, a circulating water inlet and a circulating water outlet of the dead steam heat exchange system are connected into a heat supply network circulating water pipeline; s4, when the steam exhaust temperature tf of the steam turbine is larger than or equal to 60 DEG C, the dead steam adjusting valve is opened, and the opening degree M of the dead steam adjusting valve is 30%; and when tf-tr is smaller than or equal to 5 DEG C, the dead steam adjusting valve is closed, and the opening degree M of the dead steam adjusting valve is 0%.

Description

Technical Field

[0001] The invention relates to the technical field of optimization and energy-saving methods for the cold end of a steam turbine of a thermal power generating set, and in particular to a method for reducing the back pressure of a set during summer operation by utilizing an exhaust steam waste heat recovery system. Background Art

[0002] In the water-scarce areas in the north, in order to reduce the water consumption of thermal power generating units, newly built units in recent years have adopted direct air cooling towers or indirect air cooling towers to cool the turbine exhaust steam into saturated condensate.

[0003] In order to reduce construction costs, the cooling capacity of the air cooling tower is generally designed within the design range according to the annual average temperature and the unit back pressure within the guaranteed hours. During the hot summer weather, the cooling capacity of the air cooling tower is insufficient, causing the back pressure of the generator set to reach more than 32kPa and the condensate temperature to reach more than 72℃ in the afternoon. First, the failure temperature of the condensate polishing resin is around 72℃. In order to prevent the failure of the resin, the unit load needs to be reduced to maintain the condensate temperature; second, the turbine back pressure increases, that is, the cold end loss increases. The same power generation load requires more steam consumption, while the boiler rated load is a fixed value. When the actual evaporation of the boiler remains unchanged, the actual power generation will inevitably decrease. Taking the 350MW unit with indirect cooling as an example, when the summer temperature reaches about 34℃, the actual power generation of the unit decreases by about 60MW; third, due to the increase in power generation steam consumption, the unit power supply coal consumption index increases by more than 20% in the short term, which seriously affects the economic operation of the unit.

[0004] In order to reduce the impact of high temperature weather in summer on the power generation and coal consumption indicators of the unit, combined with the fact that the unit adopts exhaust steam waste heat recovery to provide heating and has the condition of converting exhaust steam waste heat to circulating water in the heating pipeline in summer, there is an urgent need for a method that can utilize the exhaust steam waste heat recovery system to reduce the back pressure of the unit during summer operation. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a method for reducing the back pressure of the unit during summer operation by utilizing an exhaust steam waste heat recovery system.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: The method of reducing the back pressure of the unit during summer operation by utilizing the exhaust steam waste heat recovery system comprises the following steps: S1. Lay out the exhaust steam heat exchange system; S2. Connect the heat source water inlet of the exhaust steam heat exchange system to the exhaust pipe of the steam turbine through the exhaust steam regulating valve, and connect the water outlet to the water supply system; S3, connecting the circulating water inlet and the circulating water outlet of the exhaust steam heat exchange system to the circulating water pipeline of the heat network; S4, when the turbine exhaust temperature tf ≥60℃, open the exhaust steam regulating valve to make its opening M=30%; when t f -t r When the temperature is ≤5℃, close the exhaust steam regulating valve and make its opening M=0%; Among them, t r is the circulating water temperature of the heating network.

[0007] The beneficial effects of the present invention are: 1. During the hot summer weather, the present invention can discharge part of the condenser exhaust steam of the generator set to the exhaust steam waste heat recovery system to exchange heat with the circulating water of the heat network, reduce the heat exchange intensity of the condensate circulating water system, and reduce the back pressure of the generator set.

[0008] 2. The present invention adopts a waste steam heat exchange system to exchange part of the exhaust heat of the turbine during high temperature weather in summer to the heat network circulating water system. First, it can reduce the operating back pressure of the unit and increase the power generation of the unit; second, it can reduce the condenser outlet water temperature and reduce the damage to the chemical finishing resin; third, it can reduce the coal consumption of the unit for power supply and improve the economic efficiency of the unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the present invention. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0011] like Figure 1 As shown, the method of using the exhaust steam waste heat recovery system to reduce the back pressure of the unit during summer operation includes the following steps: S1. Lay out the exhaust steam heat exchange system; S2. Connect the heat source water inlet of the exhaust steam heat exchange system to the exhaust pipe of the steam turbine through the exhaust steam regulating valve, and connect the water outlet to the water supply system; S3, connecting the circulating water inlet and the circulating water outlet of the exhaust steam heat exchange system to the circulating water pipeline of the heat network; S4, when the turbine exhaust temperature t f ≥60℃, open the exhaust steam regulating valve to make its opening M=30%; when t f -t r When the temperature is ≤5℃, close the exhaust steam regulating valve and make its opening M=0%; Among them, t r is the circulating water temperature of the heating network.

[0012] Among them, 1) t f When the temperature is ≥60℃, the exhaust steam regulating valve opens, and part of the exhaust steam waste heat is exchanged with the circulating water in the heat network to reduce the heat exchange pressure of the cooling tower.

[0013] 2) t f -t r When the temperature is ≤5℃, the heat exchange capacity of the exhaust steam waste heat exchange system fails and the exhaust steam regulating valve is closed.

[0014] The present invention recovers the exhaust steam evaporation latent heat during the winter operation of the unit for heating of residents, thereby reducing the heating cost. In the original operation mode, during the summer operation of the unit, the exhaust steam waste heat recovery system is a shutdown device. Because the exhaust steam waste heat system has the ability to transfer the exhaust steam waste heat of the steam turbine to the circulating water system in the heat network pipeline, it can be implemented during the summer operation to connect part of the exhaust steam of the steam turbine to the exhaust steam waste heat system and the circulating water in the heat network pipeline for heat exchange, so as to reduce the heat exchange pressure of the air cooling tower and realize the reduction of the exhaust steam back pressure of the unit.

[0015] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reducing the back pressure of a unit during summer operation by utilizing an exhaust steam waste heat recovery system, characterized in that: The following steps are involved: S1. Lay out the exhaust steam heat exchange system; S2. Connect the heat source water inlet of the exhaust steam heat exchange system to the exhaust pipe of the steam turbine through the exhaust steam regulating valve, and connect the water outlet to the water supply system; S3, connecting the circulating water inlet and the circulating water outlet of the exhaust steam heat exchange system to the circulating water pipeline of the heat network; S4, when the turbine exhaust temperature t f ≥60℃, open the exhaust steam regulating valve to make its opening M=30%; when t f -t r When the temperature is ≤5℃, close the exhaust steam regulating valve and make its opening M=0%; Among them, t r is the circulating water temperature of the heating network.

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