A steam turbine waste heat application system for reducing cooling source loss

Abstract

The present invention relates to the technical field of waste heat utilization, in particular to a steam turbine waste heat application system for reducing cold source loss, comprising a boiler, a steam turbine, a steam turbine generator, a blower, a primary blower, a back pressure generator, a first air heater, a second air heater, a high temperature economizer, a low temperature economizer, and an air preheater, wherein the boiler steam outlet is connected to the steam turbine, and the fourth stage steam extraction of the steam turbine is connected to the back pressure generator; the boiler smoke outlet is connected to the air preheater, and the high temperature economizer and the low temperature economizer are connected to the flue in parallel with the air preheater; the exhaust steam of the back pressure generator is respectively connected to the first air heater and the second air heater; the air outlets of the blower and the primary blower are respectively connected to the first air heater and the second air heater, and the air outlets of the first air heater and the second air heater are respectively connected to the boiler through the air preheater. The waste heat of boiler flue gas can be recycled and utilized to reduce the cold source loss of the steam turbine.

Description

Technical Field

[0001] The invention relates to the technical field of waste heat utilization, and in particular to a steam turbine waste heat utilization system capable of reducing cold source loss. Background Art

[0002] As the international community and the Chinese government's requirements for energy conservation, emission reduction and environmental protection continue to increase, my country has put forward clear requirements on the energy consumption level of coal-fired power units. However, most of the energy consumption indicators of the current units still fail to meet this requirement, and there is still a lot of room for improvement. It is necessary to improve the unit operation level through energy-saving optimization and further transformation, thereby improving the economic and social benefits of power plants.

[0003] As a result, a variety of energy-saving and emission-reduction technologies have emerged, and many technical routes have been proposed to reduce the cooling source loss of steam turbines. However, the technical routes used still have the following problems: 1. When there is no external heat supply, there is still a lot of room for the utilization of steam turbine waste heat, but there are not many ways to reduce the cooling source loss of steam turbines, and it is difficult to improve the utilization of steam turbine waste heat and further reduce the cooling source loss; 2. When there is no external heat supply, there is still a certain room for the utilization of boiler flue gas waste heat, which has not been fully utilized and there is room for further improvement; 3. The low-temperature corrosion and ash blockage of the heat exchange elements in the low-temperature section of the boiler air preheater are still serious. Summary of the invention

[0004] The purpose of the present invention is to provide a steam turbine waste heat utilization system that reduces cold source loss, reduces the cold source loss of the steam turbine, improves the cycle efficiency of the steam turbine, and can solve the problems of ash blockage and low-temperature corrosion of the air preheater.

[0005] In order to achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: A steam turbine waste heat application system for reducing cold source loss comprises a boiler, a steam turbine and a steam turbine generator, wherein the steam turbine comprises a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder, and the rotor output shafts of the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder are connected in sequence;

[0006] The steam outlet of the boiler is connected to the steam inlets of the high-pressure cylinder and the medium-pressure cylinder respectively, the steam outlet of the medium-pressure cylinder is connected to the steam inlet of the low-pressure cylinder, the rotor output shaft of the low-pressure cylinder is connected to the steam turbine generator, the steam outlet of the low-pressure cylinder is connected to the steam inlet of the condenser, the condensate produced by the condenser is pressurized by the condensate pump, and then passes through the first low-pressure heater, the second low-pressure heater, the third low-pressure heater, and the fourth low-pressure heater to be connected to the deaerator, and the feed water at the outlet of the deaerator is pressurized by the feed water pump and then flows through the first The high-pressure heater, the second high-pressure heater and the third high-pressure heater are finally connected to the boiler; the first and second extraction steam outlets of the high-pressure cylinder are respectively connected to the extraction steam inlets of the third high-pressure heater and the second high-pressure heater, the third and fourth extraction steam outlets of the medium-pressure cylinder are respectively connected to the extraction steam inlets of the first high-pressure heater and the deaerator, and the fifth, sixth, seventh and eighth extraction steam outlets of the low-pressure cylinder are respectively connected to the extraction steam inlets of the fourth low-pressure heater, the third low-pressure heater, the second low-pressure heater and the first low-pressure heater;

[0007] An air preheater is connected to the tail flue of the boiler, and a high-temperature economizer and a low-temperature economizer are sequentially connected to the bypass flue in parallel with the air preheater. The flue gas outlet of the boiler is respectively connected to the flue gas inlets of the air preheater and the high-temperature economizer, and the flue gas outlets of the air preheater and the low-temperature economizer are connected to the flue gas treatment device; the condensate outlet of the second low-pressure heater is connected to the condensate inlet of the low-temperature economizer, and the condensate outlet of the low-temperature economizer is connected to the condensate inlet of the deaerator; the feed water inlet of the high-temperature economizer is connected to the outlet of the feed water pump, and the feed water outlet of the high-temperature economizer is connected to the feed water outlet of the third high-pressure heater and then connected to the boiler to form a circulation loop;

[0008] The fourth section steam extraction outlet of the medium pressure cylinder is also connected to the steam inlet of the back pressure generator, and the back pressure generator directly provides power for the power plant; the exhaust port of the back pressure generator is respectively connected to the steam inlets of the first air heater and the second air heater, the air inlet of the first air heater is connected to the air outlet of the blower, and the air inlet of the second air heater is connected to the air outlet of the primary air fan, and the air inlets of the blower and the primary air fan are both connected to the air; the air outlets of the first air heater and the second air heater are respectively connected to the air inlet of the boiler through the air preheater.

[0009] Furthermore, it also includes a drain cooler, wherein the drain outlet of the first heater is connected to the drain outlet of the second heater and then connected to the drain inlet of the drain cooler, and the drain outlet of the drain cooler is connected to the drain inlet of the condenser; the condensate inlet of the drain cooler is connected to the outlet of the condensate pump, and the condensate outlet of the drain cooler is connected to the condensate outlet of the second low-pressure heater and then connected to the condensate inlet of the low-temperature economizer.

[0010] Furthermore, a static mixer is connected to the connecting pipeline between the drain cooler and the condenser, the drain inlet of the static mixer is connected to the drain outlet of the drain cooler, the drain outlet of the static mixer is connected to the drain inlet of the condenser, and the condensate inlet of the static mixer is connected to the condensate outlets of the drain cooler and the condensate pump, respectively.

[0011] Furthermore, a pressure regulating valve is connected to the condensate connecting pipeline between the second low-pressure heater and the third low-pressure heater.

[0012] Furthermore, the flue gas treatment device includes a dust collector, an induced draft fan, a desulfurization tower and a smoke window. The flue gas outlet of the low-temperature economizer is connected to the flue gas outlet of the air preheater and then connected to the inlet of the dust collector. The outlet of the dust collector is connected to the inlet of the desulfurization tower through the induced draft fan, and the outlet of the desulfurization tower is connected to the atmosphere through the smoke window.

[0013] Furthermore, a denitrification tower is connected to the tail flue of the boiler, the flue gas inlet of the denitrification tower is connected to the flue gas outlet of the boiler, and the flue gas outlet of the denitrification tower is respectively connected to the flue gas inlets of the air preheater and the high-temperature economizer.

[0014] Furthermore, it also includes a cooling tower, wherein the circulating water inlet of the cooling tower is connected to the circulating water outlet of the condenser, and the circulating water outlet of the cooling tower is connected to the circulating water inlet of the condenser through a circulating water pump.

[0015] Furthermore, the drain outlet of the third high-pressure heater is connected to the drain inlet of the second high-pressure heater, the drain outlet of the second high-pressure heater is connected to the drain inlet of the first high-pressure heater, the drain outlet of the first high-pressure heater is connected to the drain inlet of the deaerator, the drain outlet of the fourth low-pressure heater is connected to the drain inlet of the third low-pressure heater, the drain outlet of the third low-pressure heater is connected to the drain inlet of the second low-pressure heater, and the drain outlet of the second low-pressure heater is connected to the drain inlet of the first low-pressure heater.

[0016] Due to the adoption of the above technical scheme, the present invention has the following beneficial effects: the present invention arranges an air preheater, a high-temperature economizer, a low-temperature economizer, a back-pressure generator, a first air heater, a second air heater, a blower, a primary fan, and a drain cooler; the back-pressure generator uses part of the waste heat of the fourth stage steam extraction of the steam turbine as a heat source to generate electricity, thereby providing power for the power plant and increasing the power supply of the power plant; the first air heater and the second air heater use the exhaust steam of the back-pressure generator as a heating heat source, respectively heating the cold air sent into the first air heater and the second air heater by the blower and the primary fan Heating greatly increases the inlet air temperature of the air preheater. At the same time, the exhaust steam of the back-pressure generator is converted into drain through the first and second heaters and enters the drain cooler. In the drain cooler, the condensate from the condensate pump is used to fully absorb the heat of the drain from the first and second heaters and then returns to the condenser for recycling. This can minimize the cold source loss of the exhaust steam part of the back-pressure generator and achieve the best energy-saving effect. The high-temperature economizer and the low-temperature economizer are sequentially arranged on the bypass flue in parallel with the air preheater. When the inlet air temperature of the air preheater rises, First, it reduces the heat of boiler flue gas used to heat the air in the air preheater, allowing more boiler flue gas to enter the bypass flue in parallel with the air preheater, and be used by the high-temperature economizer and low-temperature economizer to heat feed water and condensate, ultimately saving the extraction steam used to heat feed water and condensate, so that more extraction steam can continue to work in the high- and medium-pressure cylinders of the steam turbine to generate electricity and drive the back-pressure generator to generate electricity, increase the power generation of the power plant, reduce coal consumption for power generation, and provide heat source for the heater, creating a virtuous cycle. Second, it avoids low-temperature corrosion of the heat exchange elements in the low-temperature section of the air preheater Corrosion and ash blocking can be prevented, and the safety of thermal power plants can be improved; high-temperature economizer and low-temperature economizer jointly utilize the flue gas heat bypassed by the air preheater to realize energy hierarchical utilization, making the system more energy-efficient. The high-temperature economizer utilizes the waste heat of the boiler flue gas to heat the feed water from the feed water pump, and the first-level utilization of the waste heat of the boiler flue gas can utilize the higher-quality heat energy in the flue gas. The low-temperature economizer utilizes the waste heat of the flue gas from the high-temperature economizer to heat the condensate from the drain cooler and the condensate pump, and the second-level utilization of the waste heat of the boiler flue gas can make full use of the waste heat of the boiler flue gas and reduce the exhaust temperature. The various parts of the system are interrelated and work together to effectively reduce the cooling source loss of the steam turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a structural schematic diagram of a steam turbine waste heat utilization system for reducing cold source loss.

[0018] The reference numbers in the figure are: 1- boiler, 2- turbine, 201- high pressure cylinder, 202- medium pressure cylinder, 203- low pressure cylinder, 3- back pressure generator, 4- blower, 5- static mixer, 6- primary fan, 7- first air heater, 8- second air heater, 9- air preheater, 10- low temperature economizer, 11- denitrification tower, 12- drain cooler, 13- flue gas treatment device, 131- dust collector, 132- induced draft fan, 133- desulfurization tower , 134-smoke stack, 14-high temperature economizer, 15-steam turbine generator, 16-condensate pump, 17-first low-pressure heater, 18-second low-pressure heater, 19-pressure regulating valve, 20-third low-pressure heater, 21-fourth low-pressure heater, 22-deaerator, 23-feed water pump, 24-first high-pressure heater, 25-second high-pressure heater, 26-third high-pressure heater, 27-condenser, 28-cooling tower, 29-circulating water pump. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0021] like Figure 1 As shown, a steam turbine waste heat application system for reducing cold source loss includes a boiler 1, a steam turbine 2 and a steam turbine generator 15, wherein the steam turbine includes a high-pressure cylinder 201, a medium-pressure cylinder 202 and a low-pressure cylinder 203, and the rotor output shafts of the high-pressure cylinder 201, the medium-pressure cylinder 202 and the low-pressure cylinder 203 are connected in sequence.

[0022] The steam outlet of the boiler 1 is connected to the steam inlets of the high-pressure cylinder 201 and the medium-pressure cylinder 202 respectively, the exhaust port of the medium-pressure cylinder 202 is connected to the steam inlet of the low-pressure cylinder 203, the rotor output shaft of the low-pressure cylinder 203 is connected to the steam turbine generator 15, the exhaust port of the low-pressure cylinder 203 is connected to the steam inlet of the condenser 27, the condensate produced by the condenser 27 is pressurized by the condensate pump 16, and is connected to the deaerator 22 through the first low-pressure heater 17, the second low-pressure heater 18, the third low-pressure heater 20, and the fourth low-pressure heater 21 in sequence, the condensate at the outlet of the deaerator 22 is pressurized by the feed water pump 23, and is sequentially It flows through the first high-pressure heater 24, the second high-pressure heater 25 and the third high-pressure heater 26, and is finally connected to the boiler 1; the first and second steam extraction outlets of the high-pressure cylinder 201 are respectively connected to the steam extraction inlets of the third high-pressure heater 26 and the second high-pressure heater 25, the third and fourth steam extraction outlets of the medium-pressure cylinder 202 are respectively connected to the steam extraction inlets of the first high-pressure heater 24 and the deaerator 22, and the fifth, sixth, seventh and eighth steam extraction outlets of the low-pressure cylinder 203 are respectively connected to the steam extraction inlets of the fourth low-pressure heater 21, the third low-pressure heater 20, the second low-pressure heater 18 and the first low-pressure heater 17. The drain outlet of the third high-pressure heater 26 is connected to the drain inlet of the second high-pressure heater 25, the drain outlet of the second high-pressure heater 25 is connected to the drain inlet of the first high-pressure heater 24, the drain outlet of the first high-pressure heater 24 is connected to the drain inlet of the deaerator 22, the drain outlet of the fourth low-pressure heater 21 is connected to the drain inlet of the third low-pressure heater 20, the drain outlet of the third low-pressure heater 20 is connected to the drain inlet of the second low-pressure heater 18, and the drain outlet of the second low-pressure heater 18 is connected to the drain inlet of the first low-pressure heater 17. The steam turbine 2 utilizes the steam generated by the boiler 1 to drive the rotor of the steam turbine 2 to rotate and perform work. The steam after performing work is discharged from the exhaust port of the steam turbine 2 and is re-condensed into condensed water in the condenser 27. The condensed water is then converted into feed water through multiple low-pressure heaters and the deaerator 22. The feed water is then passed into the boiler 1 after passing through multiple high-pressure heaters to be heated into steam and then recycled. Since the condensed water is heated by the steam extraction from the low-quality section of the steam turbine in the multiple low-pressure heaters and the deaerator 22, and the feed water is heated by the steam extraction from the high-quality section of the steam turbine in the multiple high-pressure heaters, the feed water temperature entering the boiler 1 is increased, and the energy consumption of the boiler 1 is reduced.

[0023] The tail flue of the boiler 1 is connected with an air preheater 9, and the bypass flue in parallel with the air preheater 9 is connected with a high-temperature economizer 14 and a low-temperature economizer 10 in sequence. The flue gas outlet of the boiler 1 is connected with the flue gas inlets of the air preheater 9 and the high-temperature economizer 14 respectively. The air preheater 9 is connected with the flue gas inlet of the low-temperature economizer 10 and then connected with the flue gas treatment device 13. In this embodiment, the flue gas treatment device 13 includes a dust collector 131, an induced draft fan 132, a desulfurization tower 133 and a smoke window 134. The flue gas outlet of the low-temperature economizer 10 is connected with the flue gas outlet of the air preheater 9 and then connected with the inlet of the dust collector 131. The outlet of the dust collector 131 is connected with the inlet of the desulfurization tower 133 through the induced draft fan 132, and the outlet of the desulfurization tower 133 is connected with the atmosphere through the smoke window 134. After the flue gas is dedusted by the dust collector 131, it enters the desulfurization tower 133 for desulfurization under the action of the induced draft fan 132. The clean flue gas from the desulfurization tower 133 is discharged into the atmosphere through the chimney 134, reducing air pollution. The condensate outlet of the second low-pressure heater 18 is connected to the condensate inlet of the low-temperature economizer 10, and the condensate outlet of the low-temperature economizer 10 is connected to the condensate inlet of the deaerator 22; the feed water inlet of the high-temperature economizer 14 is connected to the outlet of the feed water pump 23, and the feed water outlet of the high-temperature economizer 14 is connected to the feed water outlet of the third high-pressure heater 26 and then connected to the boiler 1 to form a circulation loop. The air preheater 9 utilizes the flue gas from the boiler 1 to heat the air which is returned to the boiler 1 for recycling. By arranging a high-temperature economizer 14 and a low-temperature economizer 10 in the parallel bypass flue of the air preheater 9, the high-temperature economizer 14 and the low-temperature economizer 10 are utilized to gradedly recover and utilize the waste heat of the boiler flue gas, thereby further improving the utilization of the waste heat of the boiler flue gas and reducing the exhaust temperature of the boiler. The function of the high-temperature economizer 14 and the low-temperature economizer 10 is to utilize the waste heat of the boiler flue gas to heat part of the feed water from the feed water pump 23 and part of the condensate from the second low-pressure heater 18, respectively, thereby reducing the partial extraction steam of the first, second and third stages used to heat the feed water in the third high-pressure heater 26, the second high-pressure heater 25 and the first high-pressure heater 24 and the partial extraction steam of the fourth, fifth and sixth stages used to heat the condensate in the deaerator 22, the fourth low-pressure heater 21 and the third low-pressure heater 20, so that more extraction steam can be used in the high-pressure cylinder 201 and the medium-pressure cylinder 202 of the steam turbine 2 to continue to generate work and drive the back-pressure generator 3 to generate work, and provide a heat source for the first heater 7 and the second heater 8. This can increase the power generation of the power plant, reduce the coal consumption for power generation, and make the system more energy-efficient. Since the high-temperature economizer 14 and the low-temperature economizer 10 are sequentially arranged on the parallel bypass flue of the air preheater 9, the high-temperature economizer 14 and the low-temperature economizer 10 can utilize the flue gas in a graded manner, so that the heat of the bypass flue gas of the air preheater 9 can be fully utilized, thereby improving the thermal energy utilization efficiency of the power plant.The condensate from the second low-pressure heater 18 is heated by the flue gas in the high-temperature economizer 14, the flue gas temperature is reduced, and then enters the low-temperature economizer 10 for secondary utilization, the flue gas temperature is further reduced, and finally merges with the flue gas from the air preheater 9 and enters the flue gas treatment device 13 for treatment and then is discharged into the air, which effectively reduces the exhaust temperature of the boiler 1.

[0024] The fourth stage steam extraction outlet of the intermediate pressure cylinder 202 is also connected to the steam inlet of the back pressure generator 3, and the back pressure generator 3 directly provides power for the power plant; the exhaust port of the back pressure generator 3 is respectively connected to the steam inlet of the first air heater 7 and the second air heater 8; the air inlet of the first air heater 7 is connected to the air outlet of the blower 4, and the air inlet of the second air heater 8 is connected to the air outlet of the primary air fan 6, and the air inlets of the blower 4 and the primary air fan 6 are both connected to the air; the air outlets of the first air heater 7 and the second air heater 8 are respectively connected to the air inlet of the boiler 1 through the air preheater 9. The fourth stage partial steam extraction of the steam turbine 2 is used to provide work heat energy for the back pressure generator 3, directly providing power for the power plant, and at the same time, the exhaust heat of the back pressure generator 3 is used as the heat source of the heater, and the exhaust steam of the back pressure generator 3 is used to heat the cold air entering the heater, greatly increasing the temperature of the air inlet of the air preheater 9. Since the high-temperature economizer 14 and the low-temperature economizer 10 are arranged on the bypass flue in parallel with the air preheater 9, when the air inlet temperature of the air preheater 9 is increased, the flue gas heat used to heat the air in the air preheater 9 is reduced, and the heat absorption of the air preheater 9 is reduced, so that more flue gas can be diverted to the bypass flue in parallel with the air preheater 9 to heat the feed water and condensate in the high-temperature economizer 14 and the low-temperature economizer 10, and finally save the extraction steam used to heat the feed water and condensate the feed water, so that more extraction steam continues to work in the high-pressure cylinder 201 and the medium-pressure cylinder 202 of the steam turbine 2 to generate electricity and drive the back pressure generator 3 to generate electricity, increase the power generation of the power plant, reduce the coal consumption of power generation, and provide heat source for the first heater 7 and the second heater 8, so as to produce a virtuous cycle. Since the air inlet temperature of the air preheater 9 is increased, the low-temperature corrosion and ash blocking of the heat exchange elements in the low-temperature section of the air preheater 9 are avoided, and the safety of the thermal power plant is improved.

[0025] It also includes a drain cooler 12, the drain outlet of the first heater 7 is connected to the drain outlet of the second heater 8 and then connected to the drain inlet of the drain cooler 12, the drain outlet of the drain cooler 12 is connected to the drain inlet of the condenser 27; the condensate inlet of the drain cooler 12 is connected to the outlet of the condensate pump 16, the condensate outlet of the drain cooler 12 is connected to the condensate outlet of the second low-pressure heater 18 and then connected to the condensate inlet of the low-temperature economizer 10. The drain cooler 12 uses the drain heat from the heater to heat the condensate from the condensate pump 16, so that the condensate rises and then enters the low-temperature economizer 10, and returns to the deaerator 22 after being heated by the flue gas waste heat. The drain cooler 12 uses the condensate to fully absorb the drain heat of the heater, which can minimize the cold source loss of the exhaust part of the back pressure generator 3 and achieve the best energy saving effect.

[0026] The connection pipeline between the drain cooler 12 and the condenser 27 is connected with a static mixer 5, the drain inlet of the static mixer 5 is connected with the drain outlet of the drain cooler 12, the drain outlet of the static mixer 5 is connected with the drain inlet of the condenser 27, and the condensate inlet of the static mixer 5 is respectively connected with the condensate outlets of the drain cooler 12 and the condensate pump 16. The condensate from the drain cooler 12 and the condensate pump 16 is used as the driving water source of the static mixer 5, and the pressure of the condensate is used to drive the static mixer 5 to suck the drain from the drain cooler 12, thereby increasing the drain pressure and allowing the drain to return to the condenser 27 smoothly.

[0027] A pressure regulating valve 19 is connected to the condensate connection pipeline between the second low-pressure heater 18 and the third low-pressure heater 20. The regulating valve 19 is used to control the flow of condensate entering the low-temperature economizer 10, thereby allocating and regulating the flow of condensate entering the low-temperature economizer 10 and the third low-pressure heater 20.

[0028] The system further comprises a denitrification tower 11, the flue gas inlet of the denitrification tower 11 is connected to the boiler 1, and the flue gas outlet of the denitrification tower 11 is respectively connected to the air preheater 9 and the high temperature economizer 14. The denitrification tower 11 is conducive to removing harmful substances such as NO2 in the flue gas.

[0029] The system further includes a cooling tower 28, the circulating water inlet of the cooling tower 28 is connected to the circulating water outlet of the condenser 27, and the circulating water outlet of the cooling tower 28 is connected to the circulating water inlet of the condenser 27 through a circulating water pump 29. The cooling tower 28 can discharge the waste heat in the circulating water to the atmosphere, reduce the temperature of the circulating water, and the cooled circulating water can be reused, and is pumped back into the condenser 27 through the circulating water pump 29 to cool the exhaust steam of the steam turbine 2 for recycling.

[0030] The working process of the present invention is:

[0031] The steam generated by the boiler 1 enters the high-pressure cylinder 201 and the medium-pressure cylinder 202 respectively, and the exhaust steam of the medium-pressure cylinder 202 enters the low-pressure cylinder 203. The low-pressure cylinder 203 drives the steam turbine generator 15 through the rotor output shaft, so that the steam turbine generator 15 supplies power to the power grid. The exhaust steam of the low-pressure cylinder 203 enters the condenser 27 to produce condensed water. The condensed water of the condenser 27 is pressurized by the condensate pump 16, and then passes through the first low-pressure heater 17, the second low-pressure heater 18, the third low-pressure heater 20, and the fourth low-pressure heater 21 in sequence and enters the deaerator 22. The condensed water deoxygenated by the deaerator 22 becomes the feed water of the boiler 1. The feed water at the outlet of the deaerator 22 is pressurized by the feed water pump 23 and then enters the first high-pressure heater 24, the second high-pressure heater 25 and the third high-pressure heater 26 in sequence and then passes into the boiler 1. The feed water is heated by the boiler 1 and becomes steam to form a circulation loop. In the deaerator 22, the fourth low-pressure heater 21, the third low-pressure heater 20, the second low-pressure heater 18, and the first low-pressure heater 17, the heat of the fourth, fifth, sixth, seventh, and eighth sections of the steam turbine 2 is used to heat the condensate to convert it into feed water. In the third high-pressure heater 26, the second high-pressure heater 25, and the first high-pressure heater 24, the heat of the first, second, and third sections of the steam turbine 2 is used to heat the feed water, so that the feed water temperature is increased and then returned to the boiler 1 for recycling, thereby reducing the energy consumption of the boiler 1. The circulating water in the condenser 27 circulates between the condenser 27 and the cooling tower 28, and after being cooled in the cooling tower 28, it is pumped back into the condenser 27 through the circulating water pump 29 for recycling.

[0032] The flue gas of the boiler 1 passes through the denitrification tower 11 and enters the air preheater 9 and the high-pressure economizer 14 connected in parallel with the air preheater 9 respectively. The flue gas in the high-pressure economizer 14 is utilized in the primary stage and then enters the low-temperature economizer 10 for secondary utilization. The flue gas from the air preheater 9 and the low-temperature economizer 10 are combined and then enter the flue gas treatment device 13 for treatment and then discharged to the atmosphere. At the same time, part of the steam extraction from the fourth section of the medium-pressure cylinder 202 enters the back-pressure generator 3, part of the feed water from the feed water pump 23 enters the high-temperature economizer 14, and part of the condensate from the second low-pressure heater 18 enters the low-temperature economizer 10.

[0033] The back pressure generator 3 uses the fourth section of partial steam extraction to drive the rotor to generate electricity, directly providing power for the power plant. The exhaust steam of the back pressure generator 3 enters the first air heater 7 and the second air heater 8 respectively, and the cold air generated by the blower 4 and the primary fan 6 enters the first air heater 7 and the second air heater 8 respectively. The exhaust steam of the back pressure generator 3 is used to heat the cold air in the first air heater 7 and the second air heater 8, so that the temperature of the cold air is increased from 20°C at the inlet of the first air heater 7 and the second air heater 8 to 90°C at the outlet, thereby increasing the temperature of the air inlet of the air preheater 9. When the air inlet temperature of the air preheater 9 is increased, firstly, the flue gas waste heat used to heat the air in the air preheater 9 is reduced, that is, the heat absorption of the air preheater 9 is reduced. Since the high-temperature economizer 14 and the low-temperature economizer 10 are arranged on the bypass flue in parallel with the air preheater 9, more flue gas can be diverted to the bypass flue in parallel with the air preheater 9. Secondly, the low-temperature corrosion and ash blocking of the heat exchange element in the low-temperature section of the air preheater 9 are avoided, thereby improving the safety of the thermal power plant. After the exhaust steam of the back pressure generator 3 passes through the cold air in the heating heater, the temperature of the exhaust steam is reduced from 170°C steam at the inlet of the first heater 7 and the second heater 8 to 95°C-105°C water at the outlet. The drain water at the outlet of the first air heater 7 and the second air heater 8 are combined and enter the drain cooler 12, in which the drain water from the first air heater 7 and the second air heater 8 is used to heat the condensed water from the condensate pump 16, so that the drain water of the drain cooler 12 is reduced from 95°C-105°C at the inlet to 55°C at the outlet, and the condensed water of the drain cooler 12 is increased from 40°C at the inlet to about 90°C at the outlet, and is combined with the condensed water at the outlet of the second low-pressure heater 18 to enter the low-temperature economizer 10. By utilizing the condensed water to fully absorb the heat of the drain water from the first air heater 7 and the second air heater 8 and then return to the condenser 27 for recycling, the cold source loss of the exhaust part of the back-pressure generator 3 can be minimized, thereby achieving the best energy-saving effect. The drain from the drain cooler 12 is combined with the condensate from the condensate pump 16 and enters the static mixer 5. The pressure of the condensate is used to suck the drain from the drain cooler 12, thereby increasing the drain pressure and allowing the drain to smoothly return to the condenser 27 for recycling.

[0034] The high-temperature economizer 14 uses the flue gas bypassing the air preheater 9 to heat the feed water from the feed water pump, and the low-temperature economizer 10 uses the flue gas waste heat after the first-level utilization of the high-temperature economizer 14 to heat the condensed water from the second low-pressure heater 18 and the drain cooler 12. The high-temperature economizer 14 and the low-temperature economizer 10 are arranged in series, which can grade the heat of the flue gas bypassing the air preheater 9 and improve the thermal energy utilization efficiency of the power plant. After the feed water of the feed water pump 23 is heated by the flue gas of the high-temperature economizer 14, the feed water temperature increases from 170°C at the inlet to 270°C at the outlet, and then merges with the feed water of the third high-pressure heater 26 and is passed into the boiler 1 for recycling. The flue gas temperature drops from 380°C at the inlet to 220°C at the outlet, and then enters the low-temperature economizer 10 for reuse. After the condensate from the second low-pressure heater 18 and the drain cooler 12 is heated by the flue gas in the low-temperature economizer 10, the temperature of the condensate increases from 90°C at the inlet to 170°C at the outlet, and then enters the deaerator 22 for recycling, while the flue gas temperature drops from 220°C at the inlet to 120°C at the outlet, and then enters the flue gas treatment device 13 for treatment and is discharged to the atmosphere. The various parts of the system are interrelated and work together to effectively reduce the cold source loss of the steam turbine 2.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A steam turbine waste heat application system for reducing cold source loss, comprising a boiler, a steam turbine and a steam turbine generator, wherein the steam turbine comprises a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder, and the rotor output shafts of the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder are connected in sequence, characterized in that: The steam outlet of the boiler is connected to the steam inlets of the high-pressure cylinder and the medium-pressure cylinder respectively, the steam outlet of the medium-pressure cylinder is connected to the steam inlet of the low-pressure cylinder, the rotor output shaft of the low-pressure cylinder is connected to the steam turbine generator, the steam outlet of the low-pressure cylinder is connected to the steam inlet of the condenser, the condensate produced by the condenser is pressurized by the condensate pump, and then passes through the first low-pressure heater, the second low-pressure heater, the third low-pressure heater, and the fourth low-pressure heater to be connected to the deaerator, and the feed water at the outlet of the deaerator is pressurized by the feed water pump and then flows through the first The high-pressure heater, the second high-pressure heater and the third high-pressure heater are finally connected to the boiler; the first and second extraction steam outlets of the high-pressure cylinder are respectively connected to the extraction steam inlets of the third high-pressure heater and the second high-pressure heater, the third and fourth extraction steam outlets of the medium-pressure cylinder are respectively connected to the extraction steam inlets of the first high-pressure heater and the deaerator, and the fifth, sixth, seventh and eighth extraction steam outlets of the low-pressure cylinder are respectively connected to the extraction steam inlets of the fourth low-pressure heater, the third low-pressure heater, the second low-pressure heater and the first low-pressure heater; An air preheater is connected to the tail flue of the boiler, and a high-temperature economizer and a low-temperature economizer are sequentially connected to the bypass flue in parallel with the air preheater. The flue gas outlet of the boiler is respectively connected to the flue gas inlets of the air preheater and the high-temperature economizer, and the flue gas outlets of the air preheater and the low-temperature economizer are connected to the flue gas treatment device; the condensate outlet of the second low-pressure heater is connected to the condensate inlet of the low-temperature economizer, and the condensate outlet of the low-temperature economizer is connected to the condensate inlet of the deaerator; the feed water inlet of the high-temperature economizer is connected to the outlet of the feed water pump, and the feed water outlet of the high-temperature economizer is connected to the feed water outlet of the third high-pressure heater and then connected to the boiler to form a circulation loop; The fourth-stage steam extraction outlet of the intermediate pressure cylinder is also connected to the steam inlet of the back-pressure generator, and the back-pressure generator directly provides power for the power plant; the exhaust port of the back-pressure generator is respectively connected to the steam inlets of the first air heater and the second air heater, the air inlet of the first air heater is connected to the air outlet of the blower, and the air inlet of the second air heater is connected to the air outlet of the primary air fan, and the air inlets of the blower and the primary air fan are both connected to the air; the air outlets of the first air heater and the second air heater are respectively connected to the air inlet of the boiler through the air preheater; The steam turbine waste heat application system for reducing cold source loss also includes a drain cooler, the drain outlet of the first heater is connected to the drain outlet of the second heater and then connected to the drain inlet of the drain cooler, the drain outlet of the drain cooler is connected to the drain inlet of the condenser; the condensate inlet of the drain cooler is connected to the outlet of the condensate pump, the condensate outlet of the drain cooler is connected to the condensate outlet of the second low-pressure heater and then connected to the condensate inlet of the low-temperature economizer; A static mixer is connected to the connecting pipeline between the drain cooler and the condenser, the drain inlet of the static mixer is connected to the drain outlet of the drain cooler, the drain outlet of the static mixer is connected to the drain inlet of the condenser, and the condensate inlet of the static mixer is connected to the condensate outlets of the drain cooler and the condensate pump respectively; A pressure regulating valve is connected to the condensate connecting pipeline between the second low-pressure heater and the third low-pressure heater.

2. A steam turbine waste heat utilization system for reducing cold source loss according to claim 1, characterized in that: The flue gas treatment device includes a dust collector, an induced draft fan, a desulfurization tower and a smoke window. The flue gas outlet of the low-temperature economizer is connected to the flue gas outlet of the air preheater and then connected to the inlet of the dust collector. The outlet of the dust collector is connected to the inlet of the desulfurization tower through the induced draft fan, and the outlet of the desulfurization tower is connected to the atmosphere through the smoke window.

3. The steam turbine waste heat utilization system for reducing cold source loss according to claim 1, characterized in that: A denitrification tower is also connected to the tail flue of the boiler, the flue gas inlet of the denitrification tower is connected to the flue gas outlet of the boiler, and the flue gas outlet of the denitrification tower is respectively connected to the flue gas inlets of the air preheater and the high-temperature economizer.

4. The steam turbine waste heat utilization system for reducing cold source loss according to claim 1, characterized in that: It also includes a cooling tower, wherein the circulating water inlet of the cooling tower is connected to the circulating water outlet of the condenser, and the circulating water outlet of the cooling tower is connected to the circulating water inlet of the condenser through a circulating water pump.

5. The steam turbine waste heat utilization system for reducing cold source loss according to claim 1, characterized in that: The drain outlet of the third high-pressure heater is connected to the drain inlet of the second high-pressure heater, the drain outlet of the second high-pressure heater is connected to the drain inlet of the first high-pressure heater, the drain outlet of the first high-pressure heater is connected to the drain inlet of the deaerator, the drain outlet of the fourth low-pressure heater is connected to the drain inlet of the third low-pressure heater, the drain outlet of the third low-pressure heater is connected to the drain inlet of the second low-pressure heater, and the drain outlet of the second low-pressure heater is connected to the drain inlet of the first low-pressure heater.

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