Coal power unit boiler primary air production and application system based on pinch point technology

Abstract

The utility model discloses a coal power unit boiler primary air production and application system based on the pinch point technology, and belongs to the technical field of waste heat utilization. Comprising a boiler, a steam turbine, a steam turbine generator, a second primary fan, a cold source loss utilization device, a heat supply gradient utilization device, a coal pulverizing system, an external heat supply header, a flow adjusting door and a hot air communication door. The cold source loss utilization device is used for avoiding cold source loss discharged to the cooling tower in the power generation process, the heat supply gradient utilization device is used for replacing an original heat supply steam temperature reduction device, the high temperature of primary air of the boiler can be kept when a unit is in low load, normal operation of a boiler pulverizing system and a combustion system is guaranteed, and deep peak regulation of a power plant is achieved. The problems that a traditional waste heat application system cannot recover original high-quality heat energy of a boiler to produce high-temperature primary air, the loss of the high-quality heat energy is large, meanwhile, the high temperature of the primary air of the boiler is difficult to keep when a unit is low in load, and normal operation of a boiler pulverizing system and a combustion system cannot be guaranteed are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of waste heat utilization, in particular to a primary air production and application system for a coal-fired power unit boiler based on a pinch point technology. Background Art

[0002] Coal-fired power plants are the main consumers of primary energy in China. The power generation of coal-fired power plants in China accounts for about 57% of the national power generation, and they are the focus of energy conservation and carbon reduction in the future. For many years, people have been committed to improving the power supply efficiency of coal-fired power plants. The main ways are: improving initial parameters, reducing final parameters, improving the structure of the steam circulation part, and reducing the irreversible loss of flow. However, due to the limitations of the nature of water vapor, these efforts have reached a certain limit at the technical and economic level. At present, the power supply efficiency of coal-fired power plants has reached about 48%. Domestically and even in the world, efforts are being made to improve the efficiency of steam turbines and boilers alone (including using the flue gas bypass of the air preheater to heat the feed water and condensate, and the low-temperature economizer and heater combined system, etc.). It is extremely difficult to improve the power supply efficiency. There are two types of steam turbine generator sets in coal-fired power plants: condensing type (including extraction condensing type) and back pressure type. Except for the back pressure heating units in thermal power plants, most steam turbine generator sets are condensing units (including extraction condensing type). According to the second law of thermodynamics, heat will not transfer spontaneously from the low temperature area to the high temperature area. In the thermal cycle where the steam turbine generator uses high temperature and high pressure steam to do work, there must be a cold end, that is, the point with the lowest steam temperature in the steam power cycle. For condensing units, after the steam passes through the turbine generator impeller to do all the work, it becomes exhaust steam (temperature 28-45°C), which is discharged to the exhaust cylinder and enters the cold end of the steam turbine - the condensate pump. The waste heat of the steam turbine generator that enters the condenser can no longer generate electricity, but is taken away by circulating water and finally discharged to the atmosphere through the cooling tower. The waste heat of the steam turbine generator that enters the condenser and can no longer generate electricity is generally called cold source loss. The main heat loss of the condensing unit is the cold source loss. The lost heat exceeds the heat energy used by the steam turbine to do work. The cold source loss accounts for about 60% of the power generation energy, which is the main reason for the low cycle thermal efficiency of thermal power plants. In the current academic community, from the fundamental conditions of the feasibility of the heat engine steam power cycle, it is believed that the loss of cold source is indispensable. The technical means to reduce the loss of cold source of steam turbine generators mainly include heat recovery steam extraction, back pressure steam turbine generators or adjustment steam extraction steam turbine generators, circulating water low vacuum heating, and heat pump technology application. Except for heat recovery steam extraction, the other three technical means to reduce the loss of cold source of steam turbine generators must supply heat to the outside, and this part of energy cannot be used or consumed inside the coal-fired power plant. The low cycle efficiency of coal-fired power plants and the heat lost by the cold end loss exceed the heat energy used by the steam turbine to do work. This problem is a global problem that plagues the improvement of the efficiency of coal-fired power plants. The applicant's prior patent application with application number CN202022390557.4 applies for a steam turbine generator waste heat application system that reduces cold source loss. It heats the boiler primary air through an air preheater to avoid cold source loss discharged to the cooling tower during the power generation process; however, it cannot recover the boiler's original high-quality heat energy to produce boiler high-temperature primary air. The boiler heating steam cooling device has a large loss of high-quality heat energy. At the same time, it is difficult to maintain the high temperature of the boiler primary air when the unit is under low load, and the normal operation of the boiler pulverizing system and combustion system cannot be guaranteed.

[0003] Since the 1980s, with the development of process system engineering, energy conservation has entered the era of process system energy conservation. People have realized that in order to optimize the overall design of a process industrial plant, that is, to minimize energy consumption, cost and pollution, the entire system must be combined as an organic whole. Therefore, process integration has become the focus. The most practical process integration method is the pinch point technology. The pinch point technology is based on thermodynamics. It analyzes the distribution of energy flow along the temperature in the process system from a macroscopic perspective, finds the "bottleneck" of system energy consumption, and provides a "bottleneck solution". At present, the pinch point technology has successfully achieved significant energy-saving effects worldwide, especially in the chemical industry. How to use the pinch point technology and generalized heat recovery system in the energy conservation of thermal power units to utilize part of the cooling source loss of steam turbine generators in coal-fired thermal power plants and improve the cycle efficiency of coal-fired thermal power plants has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the utility model is to provide a coal-fired power unit boiler primary air production and application system based on pinch point technology in response to the above-mentioned problems, so as to solve the problems that the traditional steam turbine generator waste heat application system cannot recover the original high-quality thermal energy of the boiler to produce high-temperature primary air of the boiler, the high-quality thermal energy loss of the boiler heating steam cooling device is large, and it is difficult to maintain the high temperature of the boiler primary air when the unit is under low load, and the normal operation of the boiler pulverizing system and the combustion system cannot be guaranteed.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model is:

[0006] A primary air production and application system for a coal-fired power unit boiler based on pinch point technology 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, wherein the rotor output shafts of the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder are connected in sequence, the steam outlet of the boiler is respectively connected to the steam inlet of the high-pressure cylinder and the medium-pressure cylinder, the exhaust port 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 exhaust port of the low-pressure cylinder is connected to a condenser, the condenser is connected to the water inlet of a condensate pump, the condensate produced by the condenser is pressurized by the condensate pump, and then sequentially passes through a first low-pressure heater. The first and second sections of the high-pressure cylinder's steam extraction outlets are connected to the third and second high-pressure heater's steam extraction inlets, respectively; the third and fourth sections of the medium-pressure cylinder's steam extraction outlets are connected to the first high-pressure heater and the steam extraction inlet of the deaerator, respectively; the fifth, sixth, seventh and eighth sections of the low-pressure cylinder's steam extraction outlets are connected to the fourth, third, second and first low-pressure heater's steam extraction inlets, respectively. The exhaust steam inlet of the low-pressure heater is connected; the tail flue of the boiler is connected with an air preheater, and the bypass flue in parallel with the air preheater is connected with a high-temperature economizer and a low-temperature economizer in sequence, the flue gas outlet of the boiler is connected with the flue gas inlets of the air preheater and the high-temperature economizer respectively, and the flue gas outlets of the air preheater and the low-temperature economizer are connected to the flue gas treatment device after being connected; the condensate outlet of the second low-pressure heater is connected with the condensate inlet of the low-temperature economizer, and the condensate outlet of the low-temperature economizer is connected with the condensate inlet of the deaerator; the feed water inlet of the high-temperature economizer is connected with the outlet of the feed water pump, and the high-temperature economizer The water supply outlet of the device is connected to the water supply outlet of the third high-pressure heater and then connected to the boiler to form a circulation loop; the fourth section steam extraction outlet of the intermediate pressure cylinder is also connected to the steam inlet of the back pressure unit, and the back pressure unit directly provides power for the power plant; the exhaust port of the back pressure unit is respectively connected to the steam inlet of the secondary air heater, the air inlet of the primary air heater is connected to the air outlet of the blower, the air inlet of the secondary air heater is connected to the air outlet of the first primary air fan, and the air inlets of the blower and the first primary air fan are both connected to the air; the air outlets of the primary air heater and the secondary air heater are respectively connected to the air inlet of the boiler through the air preheater;It also includes a second primary fan, a cold source loss utilization device, a heat supply cascade utilization device, a powder making system and an external heat supply header. The second primary fan is connected to the cold source loss utilization device, the heat supply cascade utilization device, the powder making system and the boiler in sequence. The high-temperature steam inlet of the cold source loss utilization device is connected to the fourth stage steam extraction outlet of the intermediate pressure cylinder, the steam inlet of the heat supply cascade utilization device is connected to the external heat supply steam port of the boiler, and the hot steam outlet of the heat supply cascade utilization device is connected to the external heat supply header. ;

[0007] Furthermore, it also includes a flow regulating door, and the external heating steam port of the boiler is connected to the external heating manifold through the flow regulating door.

[0008] Furthermore, it also includes a hot air communication door, through which the hot primary air of the air preheater and the hot primary air generated by the heat supply cascade utilization device are connected to the boiler.

[0009] 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.

[0010] Furthermore, a denitrification device is connected to the tail flue of the boiler, the flue gas inlet of the denitrification device is connected to the flue gas outlet of the boiler, and the flue gas outlet of the denitrification device is respectively connected to the flue gas inlets of the air preheater and the high-temperature economizer.

[0011] 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.

[0012] 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.

[0013] Furthermore, it also includes a static mixer, the exhaust steam outlet of the back pressure unit is connected to the static mixer after passing through the secondary air heater, and the drain outlet of the static mixer is connected to the condensate pump after passing through the primary air heater.

[0014] Due to the adoption of the above technical solution, the beneficial effects of the utility model are:

[0015] 1. The utility model utilizes the exhaust heat of the back pressure unit and part of the condensate heat after being heated by the last low-temperature heater, preheats the boiler air through the secondary air heater and the primary air heater, recovers part of the waste heat originally discharged to the cooling tower, improves the air inlet temperature of the air preheater, realizes the utilization of part of the turbine generator cold source loss, and avoids low-temperature corrosion and ash blockage of the low-temperature section heat exchange element of the boiler air preheater; at low load, the unit deep peak regulation is achieved by increasing the primary and secondary air temperatures.

[0016] 2. Utilize the flue gas heat of the original heating boiler cold air, through the newly added bypass flue in parallel with the air preheater, heat the feed water and condensate according to the flue gas energy level, and recover the heat of the flue gas in the bypass flue. The bypass flue is installed with a bypass economizer consisting of a high-pressure economizer and a low-pressure economizer: the high-temperature part of the flue gas heat is used to heat the feed water through the high-pressure economizer, and the low-temperature part of the flue gas heat is used to heat the condensate through the low-pressure economizer, and the feed water and condensate are heated to the temperature of the original heat recovery system. Part of the steam extraction of the original heating stages 1, 2, 3, 4, 5, and 6 is excluded.

[0017] 3. The part of the steam that was originally used to heat the feed water and condensate is used to generate electricity and heat the boiler air. The first, second and third sections of the steam continue to work in the high and medium pressure cylinders of the steam turbine generator to generate electricity. After working in the medium pressure cylinder, it is combined with the fourth section of the steam that is squeezed out to enter the back pressure steam turbine generator to generate electricity. The fifth and sixth sections of the steam continue to work in the low pressure cylinder of the steam turbine generator to generate electricity.

[0018] 4. After the back-pressure steam turbine generator generates electricity, the exhaust pressure drops to atmospheric pressure. The exhaust steam passes through the secondary air heater in the outlet duct of the blower to heat the boiler secondary air, and the boiler secondary air is heated from the original blower outlet air temperature of 20°C to about 85°C, replacing the low-temperature section of the air preheater to preheat the boiler secondary air; through the static mixer, the condensate at the outlet of the second low-pressure heater is used to draw the drain of the secondary air heater, and after the pressure is increased and combined, it is sent to the primary air heater to heat the cold air, and the boiler primary air is heated from the original first primary fan outlet air temperature of 20°C to about 85°C, replacing the low-temperature section of the air preheater to preheat the boiler primary air, while avoiding the safety problems of heat loss of the heater drain and vibration caused by the drain.

[0019] 5. The newly added second primary fan produces boiler primary air. At the same time, the original air preheater is replaced by the cold source loss utilization device, and the steam heat of the final stage (four-stage extraction) of the steam turbine generator is used to heat the temperature of the first primary fan from the atmospheric temperature (about 20°C) to 140°C, while avoiding the cold source loss discharged to the cooling tower during the power generation process; the original heating steam cooling device is replaced by the heating cascade utilization device, and the original high-quality heat energy is recovered to produce 310°C boiler high-temperature primary air, avoiding the high-quality heat energy loss of the heating steam cooling device. At the same time, it can maintain the high temperature of the boiler primary air when the unit is under low load, ensuring the normal operation of the boiler pulverizing system and the combustion system, and realizing deep peak regulation of the power plant. The original air preheater is replaced by a heat cascade utilization device and a cold source loss utilization device to produce boiler primary air, displacing the high-temperature flue gas heat of the original air preheater to generate primary air, and the displaced high-temperature flue gas heat is used to heat feed water and condensate. The steam originally used to heat feed water and condensate is squeezed out and used to generate electricity in the steam turbine generator, realizing the indirect improvement of low-quality thermal energy to high-quality electric energy. It can realize heat cascade utilization and reduce cold source loss, and realize energy saving and deep peak regulation of power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the system structure of the utility model;

[0021] In the attached drawings, 1- boiler, 2- turbine, 201- high pressure cylinder, 202- medium pressure cylinder, 203- low pressure cylinder, 3- back pressure unit, 4- first primary fan, 5- static mixer, 6- blower, 7- primary air heater, 8- secondary air heater, 9- air preheater, 10- low pressure economizer, 11- denitrification device, 12- back pressure generator, 13- flue gas treatment device, 131- dust collector, 132- induced draft fan, 133- desulfurization tower, 134- smoke window, 14- high pressure economizer, 15- turbine generator, 16- condenser, 1 7-first low-pressure heater, 18-second low-pressure heater, 19-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 30-cold source loss utilization device, 31-heating cascade utilization device, 32-second primary fan, 33-external heating manifold, 34-pulverizing system, 35-hot air communication door, 36-flow regulating door. DETAILED DESCRIPTION

[0022] The specific implementation of the utility model is further described below with reference to the accompanying drawings.

[0023] In the description of the present invention, it should be understood that the terms "center", "length", "width", "up", "down", "vertical", "horizontal", "top", "bottom", "inside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0026] See also Figure 1A primary air production application system for a coal-fired power unit boiler 1 based on pinch point technology includes a boiler 1, a steam turbine 2, a steam turbine generator 15, a second primary air fan 32, a cold source loss utilization device 30, a heat supply cascade utilization device 31, a pulverizing system 34, an external heat supply header 33, a flow regulating door 36 and a hot air communication door 35. The steam turbine 2 includes a high-pressure cylinder 201, a medium-pressure cylinder 202 and a low-pressure cylinder 203. 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. 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, and the low-pressure cylinder The exhaust port of 203 is connected to the condenser 16, and the condenser 16 is connected to the water inlet of the condensate pump. The condensate produced by the condenser 16 is pressurized by the condensate pump, 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 to be connected to the deaerator 22. The feed water at the outlet of the deaerator 22 is pressurized by the feed water pump 23, and then flows through the first high-pressure heater 24, the second high-pressure heater 25 and the third high-pressure heater 26 to be 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, and 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, the deaerator 22, and the deaerator 22. The fifth, sixth, seventh and eighth extraction steam outlets of the low-pressure cylinder 203 are connected to the extraction steam 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 respectively; 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 sequentially connected with a high-temperature economizer and a low-temperature economizer, the flue gas outlet of the boiler 1 is respectively connected to the flue gas inlets of the air preheater 9 and the high-temperature economizer, and the flue gas outlets of the air preheater 9 and the low-temperature economizer are connected to the flue gas treatment device 13; the condensate outlet of the second low-pressure heater 18 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 22; The water feed inlet of the warm economizer is connected to the outlet of the water feed pump 23, and the water feed outlet of the high-temperature economizer is connected to the water feed outlet of the third high-pressure heater 26 and then connected to the boiler 1 to form a circulation loop; the fourth-stage steam extraction outlet of the medium-pressure cylinder 202 is also connected to the steam inlet of the back-pressure unit 3, and the back-pressure generator 12 of the back-pressure unit 3 directly provides power for the power plant; the exhaust port of the back-pressure unit 3 is connected to the steam inlet of the secondary air heater 8, the air inlet of the primary air heater 7 is connected to the air outlet of the blower 6, and the air inlet of the secondary air heater 8 is connected to the air outlet of the first primary air fan 4, and the air inlets of the blower 6 and the first primary air fan 4 are both connected to the air; the air outlets of the primary air heater 7 and the secondary air heater 8 are respectively connected to the air inlet of the boiler 1 through the air preheater 9;The second primary air blower 32 is connected to the cold source loss utilization device 30, the heat supply step utilization device 31, the powder making system 34 and the boiler 1 in sequence. The high-temperature steam inlet of the cold source loss utilization device 30 is connected to the fourth stage steam extraction outlet of the medium pressure cylinder 202, the steam inlet of the heat supply step utilization device 31 is connected to the external heat supply steam port of the boiler 1, and the hot steam outlet of the heat supply step utilization device 31 is connected to the external heat supply header 33. The external heat supply steam port of the boiler 1 is connected to the external heat supply header 33 through a flow regulating door 36. The hot primary air of the air preheater 9 and the hot primary air generated by the heat supply step utilization device 31 are both connected to the boiler 1 through a hot air communication door 35. ;

[0027] 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 is connected to the flue gas outlet of the air preheater 9 and then connected to the inlet of the dust collector 131. The outlet of the dust collector 131 is connected to the inlet of the desulfurization tower 133 through the induced draft fan 132, and the outlet of the desulfurization tower 133 is connected to the atmosphere through the smoke window 134.

[0028] In this embodiment, a denitrification device 11 is also connected to the tail flue of the boiler 1, and the flue gas inlet of the denitrification device 11 is connected to the flue gas outlet of the boiler 1, and the flue gas outlet of the denitrification device 11 is respectively connected to the flue gas inlets of the air preheater 9 and the high-temperature economizer.

[0029] In this embodiment, a cooling tower 28 is further included. The circulating water inlet of the cooling tower 28 is connected to the circulating water outlet of the condenser. The circulating water outlet of the cooling tower 28 is connected to the circulating water inlet of the condenser through a circulating water pump 29.

[0030] In this embodiment, 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.

[0031] Furthermore, it also includes a static mixer 5, the exhaust steam outlet of the back pressure unit 3 is connected to the static mixer 5 after passing through the secondary air heater 8, and the drain outlet of the static mixer 5 is connected to the condensate pump after passing through the primary air heater 7.

[0032] The specific working principle is as follows:

[0033] 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, 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 11. The feed water is heated by the boiler 1 and becomes steam to form a circulation loop. 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 respectively use the heat of the fourth, fifth, sixth, seventh, and eighth sections of the steam turbine 2 to heat the condensate, and the third high-pressure heater 26, the second high-pressure heater 25, and the first high-pressure heater 24 respectively use the first, second, and third sections of the steam turbine 2 to heat the feed water, so that the feed water temperature is increased and then returned to the boiler 1 for recycling. 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.

[0034] The back-pressure generator 12 utilizes the fourth-stage partial steam extraction to drive the rotor to generate power, thereby directly providing power for the power plant. The exhaust steam of the back pressure generator 12 enters the secondary air heater 8, and the cold air from the blower 6 enters the secondary air heater 8. The exhaust steam of the back pressure generator 12 is used to heat the cold air in the secondary air heater 8, so that the temperature of the cold air increases from 20°C at the inlet of the secondary air heater 8 to 75°C at the outlet; the cold air generated by the first primary fan 4 enters the primary air heater 7, and the 99°C drain from the secondary air heater 8 is combined with the 105°C condensate from the outlet of the cold source loss utilization device 30 (or the 100°C condensate from the outlet of the second low-pressure heater 18) and enters the static mixer 5. The drain from the secondary air heater 8 is sucked by the pressure of the condensate, and the pressure is increased. After the combination, it enters the primary air heater 7, so that the temperature of the cold air increases from 20°C at the inlet of the primary air heater 7 to 75°C at the outlet, thereby increasing the temperature of the air inlet of the air preheater 9, and at the same time, the condensate temperature of the primary air heater 7 drops to 45°C. 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; secondly, the average temperature difference between the flue gas and the cold air at the cold end of the air preheater is reduced from 105°C to 50°C, avoiding low-temperature corrosion and ash blocking of the heat exchange elements in the low-temperature section of the air preheater 9, and improving the safety of the coal-fired thermal power plant; thirdly, the primary and secondary hot air temperatures of the boiler 1 at low load are increased, which can achieve stable combustion of the boiler 1 at lower loads, creating conditions for deep peak regulation of the unit. After the exhaust steam of the back pressure generator 12 is heated by the cold air in the secondary air heater 8, the exhaust steam changes from 170°C steam at the inlet of the secondary air heater 8 to 99°C drain at the outlet. The 45°C condensed water at the outlet of the primary air heater 7 is directly returned to the condenser 27 for recycling. The cold source loss of the exhaust steam part of the back pressure generator 12 can be minimized to achieve the best energy saving effect.

[0035] The high-pressure economizer 14 uses the flue gas bypassing the air preheater 9 to heat the feed water from the feed water pump 23, and the low-pressure economizer 10 uses the flue gas waste heat after the high-pressure economizer 14 is used to heat part of the condensed water from the outlet of the second low-pressure heater 18. The high-pressure economizer 14 and the low-pressure economizer 10 are arranged in series on the flue gas side, 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-pressure 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 passes into the boiler 1, and the flue gas temperature drops from 385°C at the inlet to 220°C at the outlet, and then enters the low-temperature economizer for reuse. After part of the condensate from the outlet of the second low-pressure heater 18 is heated by the flue gas in the low-temperature economizer, the condensate temperature increases from 106°C at the inlet to 165°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 125°C at the outlet, and then enters the flue gas treatment device 13 for treatment and is discharged into the atmosphere.

[0036] The second primary air blower 32 produces the primary air of the second boiler 1, and replaces the original air preheater 9 through the cold source loss utilization device 30, and utilizes the steam heat of the last stage (four-stage extraction steam) of the steam turbine 2 to heat the temperature of the first primary air blower 4 from the atmospheric temperature (about 20°C) to 150°C, and at the same time cools the high-temperature steam of the last stage (four-stage extraction steam) of the steam turbine 2 from 330°C to condensate of 105°C, and the condensate of 105°C is then cooled to 45°C through the primary air heater; The stage utilization device 31 replaces the original heating steam cooling device, heats the 150℃ primary air to 310℃, and reduces the original 540℃ external heating steam temperature to 270℃, recovers the original high-quality heat energy to produce 315℃ boiler 1 high-temperature primary air, avoids the loss of high-quality heat energy of the heating steam cooling device, and at the same time can maintain the high temperature (315℃) of the boiler 1 primary air when the unit is under low load, ensure the normal operation of the boiler 1 powder making system 34 and the combustion system, and realize deep peak regulation of the power plant.

[0037] The above description is a detailed description of the preferred feasible embodiment of the utility model, but the embodiment is not used to limit the scope of the patent application of the utility model. All equivalent changes or modified changes completed under the technical spirit suggested by the utility model should fall within the patent scope covered by the utility model.

Claims

1. A primary air production and application system for a coal-fired power unit boiler based on pinch point technology, 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, wherein the rotor output shafts of the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder are connected in sequence, wherein the steam outlet of the boiler is respectively connected to the steam inlet of the high-pressure cylinder and the medium-pressure cylinder, wherein the exhaust port of the medium-pressure cylinder is connected to the steam inlet of the low-pressure cylinder, wherein the rotor output shaft of the low-pressure cylinder is connected to the steam turbine generator, wherein the exhaust port of the low-pressure cylinder is connected to a condenser, wherein the condenser is connected to the steam inlet of a condensate pump, wherein the condensate produced by the condenser is pressurized by the condensate pump and then sequentially passes through a first low-pressure heater , the second low-pressure heater, the third low-pressure heater, and the fourth low-pressure heater are connected to the deaerator. The feed water at the outlet of the deaerator is pressurized by the feed water pump, and then flows through the first high-pressure heater, the second high-pressure heater, and the third high-pressure heater in sequence and is connected to the boiler; the first and second extraction steam outlets of the high-pressure cylinder are connected to the extraction steam inlets of the third high-pressure heater and the second high-pressure heater, respectively, the third and fourth extraction steam outlets of the medium-pressure cylinder are connected to the extraction steam inlets of the first high-pressure heater and the deaerator, respectively, and the fifth, sixth, seventh, and eighth extraction steam outlets of the low-pressure cylinder are connected to the fourth low-pressure heater, the third low-pressure heater, the second low-pressure heater, and the first low-pressure heater, respectively. The exhaust steam inlet is connected; the tail flue of the boiler is connected with an air preheater, and the bypass flue in parallel with the air preheater is connected with a high-temperature economizer and a low-temperature economizer in sequence, and the flue gas outlet of the boiler is connected with the flue gas inlets of the air preheater and the high-temperature economizer respectively, and the flue gas outlets of the air preheater and the low-temperature economizer are connected to the flue gas treatment device after being connected; the condensate outlet of the second low-pressure heater is connected with the condensate inlet of the low-temperature economizer, and the condensate outlet of the low-temperature economizer is connected with the condensate inlet of the deaerator; the feed water inlet of the high-temperature economizer is connected with the outlet of the feed water pump, and the feed water outlet of the high-temperature economizer is connected to the first The water supply outlets of the three high-pressure heaters are connected to the boiler to form a circulation loop; the fourth section steam extraction outlet of the medium-pressure cylinder is also connected to the steam inlet of the back pressure unit, and the back pressure generator of the back pressure unit directly provides power for the power plant; the exhaust port of the back pressure unit is respectively connected to the steam inlet of the secondary air heater, the air inlet of the primary air heater is connected to the air outlet of the blower, the air inlet of the secondary air heater is connected to the air outlet of the first primary air fan, and the air inlets of the blower and the first primary air fan are both connected to the air; the air outlets of the primary air heater and the secondary air heater are respectively connected to the air inlet of the boiler through the air preheater; it is characterized in that: It also includes a second primary fan, a cold source loss utilization device, a heat step utilization device, a powder making system and an external heat supply manifold. The second primary fan is connected to the cold source loss utilization device, the heat step utilization device, the powder making system and the boiler in sequence. The high-temperature steam inlet of the cold source loss utilization device is connected to the fourth section steam extraction outlet of the medium-pressure cylinder, the steam inlet of the heat step utilization device is connected to the external heat supply steam port of the boiler, and the hot steam outlet of the heat step utilization device is connected to the external heat supply manifold.

2. According to claim 1, a coal-fired power unit boiler primary air production and application system based on pinch point technology is characterized in that: It also includes a flow regulating door, through which the external heating steam port of the boiler is connected to the external heating manifold.

3. The primary air production and application system for coal-fired power plant boiler based on pinch point technology according to claim 1 is characterized by: It also includes a hot air communication door, through which the hot primary air of the air preheater and the hot primary air generated by the heat supply step utilization device are connected to the boiler.

4. The primary air production and application system for coal-fired power plant boiler based on pinch point technology according to claim 1 is characterized by: 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.

5. The primary air production and application system for coal-fired power plant boiler based on pinch point technology according to claim 1 is characterized by: A denitrification device is also connected to the tail flue of the boiler, the flue gas inlet of the denitrification device is connected to the flue gas outlet of the boiler, and the flue gas outlet of the denitrification device is respectively connected to the flue gas inlets of the air preheater and the high-temperature economizer.

6. The primary air production and application system for coal-fired power plant boiler based on pinch point technology according to claim 1 is characterized by: It also includes a cooling tower, wherein the circulating water inlet of the cooling tower is connected to the circulating water outlet of the condensate water pump, and the circulating water outlet of the cooling tower is connected to the circulating water inlet of the condensate water pump through the circulating water pump.

7. The primary air production and application system for coal-fired power plant boiler based on pinch point technology according to claim 1 is characterized by: 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.

8. The primary air production and application system for coal-fired power plant boiler based on pinch point technology according to claim 1 is characterized by: It also includes a static mixer. The exhaust steam outlet of the back pressure unit is connected to the static mixer after passing through a secondary air heater, and the drain outlet of the static mixer is connected to a condensate pump after passing through a primary air heater.

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