A sludge drying system coupled with a thermal storage system and method of operation

Abstract

This invention relates to a sludge drying system coupled with a thermal storage system, comprising: a thermal storage module, a sludge drying module, a waste heat collection module, and a waste heat upgrading module; the thermal storage module is used to store the peak-shaving steam energy of a power plant; the sludge drying module is connected to the thermal storage module and includes multiple parallel dryers, utilizing low-pressure steam to dry the sludge; the waste heat collection module is connected to the sludge drying module and is used to recover waste heat from high-temperature exhaust gas; the waste heat upgrading module is connected to the waste heat collection module and is used to improve the quality of waste heat and recycle it. The beneficial effects of this invention are: this invention couples drying technology with a boiler system, converting difficult-to-store steam energy into storable and combustible fuel, which helps achieve deep peak shaving in power plants, reduces the size of the thermal storage system, and improves system economy.

Description

Technical Field

[0001] This invention relates to the field of sludge drying technology, and more specifically, to a sludge drying system coupled with a thermal storage system and its operation method. Background Technology

[0002] With the gradual increase in urbanization and the rapid development of industry, how to treat sludge efficiently and with low pollution has become a problem for many cities. Sludge combustion is a relatively economical and efficient treatment method, but it requires a certain amount of steam to dry the sludge during operation. At the same time, the energy of the drying exhaust is directly absorbed and dissipated by the condensate, resulting in significant energy waste. In addition, with the rapid increase in the installed capacity of new energy sources in China, traditional power generation technologies inevitably have to participate in peak shaving along with the power grid. However, deep peak shaving poses a serious challenge to the stability of the combustion system. How to achieve deep peak shaving in power plants while ensuring the safety and stability of the boiler system is a major problem. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing a sludge drying system coupled with a thermal storage system and its operation method.

[0004] In the first aspect, a sludge drying system coupled with a heat storage system is provided, including: a heat storage module, a sludge drying module, a waste heat collection module, and a waste heat upgrading module;

[0005] The heat storage module is used to store the peak-shaving steam energy of the power plant, and includes a heat storage medium heater, a heat storage tank, a first heat storage medium circulation pump, an electric heater, a second heat storage medium circulation pump, and a heat releaser. The sludge drying module is connected to the heat storage module and includes multiple parallel dryers. The sludge drying module uses low-pressure steam to dry the sludge. The waste heat collection module is connected to the sludge drying module and includes a cyclone separator, an electrostatic precipitator-heat exchanger, and a waste heat exchanger for recovering waste heat from high-temperature exhaust gas. The waste heat quality improvement module is connected to the waste heat collection module and includes a steam-electric dual-purpose compressor, a first speed regulating device, an expander, a second speed regulating device, a steam compressor, a third flash tank, a second electric heater, a condenser, a gas-liquid separator, an evaporator, an electronic expansion valve, a filter, a liquid storage tank, a subcooler, a third water circulation pump, a feedwater preheater, and a third pressurization pump for improving the quality of waste heat and recycling it.

[0006] Preferably, the heat exchanger includes a high-temperature heat storage heat exchanger and a medium-temperature heat storage heat exchanger; the heat storage tank, the high-temperature heat storage heat exchanger, the medium-temperature heat storage heat exchanger, and the second heat storage medium circulation pump are connected in sequence to form a circulation loop; the high-temperature heat storage heat exchanger is also connected to a first flash tank, a first water circulation pump, and a first pressurization pump; the medium-temperature heat storage heat exchanger is also connected to a second flash tank, a second water circulation pump, and a second pressurization pump.

[0007] Preferably, the heat storage medium stored in the heat storage tank is molten salt, heat transfer oil, or liquid metal.

[0008] Preferably, the electrostatic precipitator-heat exchanger includes several electrostatic precipitator-heat exchanger anodes, electrostatic precipitator-heat exchanger cathodes, and staggered high-temperature exhaust gas channels and low-temperature exhaust gas channels.

[0009] Preferably, the steam-electric dual-purpose compressor and the steam compressor are driven by an expander, or by electricity, or by a combination of expander and electricity, and the speed of the steam-electric dual-purpose compressor and the steam compressor is adjusted according to the first speed regulating device and the second speed regulating device.

[0010] In a second aspect, a method for operating a sludge drying system coupled to a thermal storage system as described in any of the first aspects is provided, comprising:

[0011] Step 1: During the off-peak period of power supply and heating at the power plant, the heat storage mode of the heat storage module is activated. Peak-shaving steam is heated by the steam-water heat exchanger to generate steam to drive the expander and supply the sludge drying module. The sludge drying module, waste heat collection module and waste heat upgrading module operate in conjunction.

[0012] Step 2: During the peak power and heat supply period of the power plant, start the heat release mode of the thermal storage module to release the stored thermal energy to generate medium-pressure and low-pressure steam. Part of the steam drives the expander and supplies it to the sludge drying module. The sludge drying module, waste heat collection module and waste heat upgrading module operate in conjunction.

[0013] Step 3: During the power plant's power and heat supply period, based on the temperature of the heat storage medium and the sludge inventory, choose to directly use steam extracted from the turbine or continue to release the stored heat energy to drive the expander and supply it to the sludge drying module. The sludge drying module, waste heat collection module, and waste heat upgrading module operate in conjunction.

[0014] Preferably, in step 1, the thermal storage mode includes steam heat source thermal storage and steam-electric combined heating:

[0015] The steam heat source storage includes:

[0016] Steam passes through the heat storage medium heater, starts the first heat storage medium circulation pump, and the heat storage medium comes out from the bottom of the heat storage tank and enters the heat storage medium heater and the first electric heater in sequence. The first electric heater is turned off, the heat storage medium is heated by steam, and then the heat storage medium enters the heat storage tank.

[0017] The steam-electric combined heating includes: activating a first electric heater to supplement heat based on the heat storage of the steam heat source.

[0018] Preferably, in step 2, the heat release mode includes: medium-pressure-low-pressure steam mode, medium-pressure steam mode, and low-pressure steam mode;

[0019] The medium-pressure-low-pressure steam mode includes:

[0020] The second thermal storage medium circulation pump is started. After the thermal storage medium comes out from the top of the thermal storage tank, it enters the high-temperature thermal storage heat exchanger and the medium-temperature thermal storage heat exchanger in sequence, and then returns to the thermal storage tank. The ambient temperature demineralized water is pressurized by the second pressurizing pump, mixed with the drainage from the second flash tank, and then enters the medium-temperature thermal storage heat exchanger to be heated, and then enters the second flash tank to flash and generate steam. The ambient temperature demineralized water is pressurized by the first pressurizing pump, mixed with the drainage from the first flash tank, and then enters the first water circulation pump to be heated, and then enters the first flash tank to flash and generate steam.

[0021] Preferably, the medium-pressure steam mode includes: based on the medium-pressure-low-pressure steam mode, shutting off the second water circulation pump and the second booster pump; the low-pressure steam mode includes: based on the medium-pressure-low-pressure steam mode, shutting off the first water circulation pump and the first booster pump.

[0022] Preferably, the sludge drying module, waste heat collection module, and waste heat upgrading module operate in combination, including:

[0023] Steam enters the expander, which drives the steam-electric compressor and the steam compressor. The steam-electric compressor causes the refrigerant to circulate. The refrigerant absorbs heat during phase change in the evaporator, and is then compressed and heated by the steam-electric compressor. It then enters the condenser to release heat and become a saturated liquid. It then enters the subcooler for further cooling and becomes a subcooled liquid. After passing through the liquid receiver and filter, it is throttled and cooled by the electronic expansion valve and finally returns to the evaporator.

[0024] The sludge absorbs heat from the water vapor in the dryer, causing the water in the sludge to evaporate. It then sequentially enters the cyclone separator for dust removal, the electrostatic precipitator-heat exchanger, the waste heat exchanger, and the electrostatic precipitator-heat exchanger before finally entering the boiler air supply system. The water vapor in the dryer undergoes phase change and condenses into condensate, which then enters the condensate tank for flash evaporation. The resulting liquid water is transported through pipelines to the boiler deaerator. The hot water generated by the waste heat exchanger passes through the evaporator and feedwater preheater of the waste heat upgrading module before returning to the waste heat exchanger.

[0025] The demineralized water sequentially enters the feedwater preheater, subcooler, third flash tank, condenser, and third flash tank. The saturated steam generated by heat absorption and temperature rise, together with the saturated steam generated by the condensate tank, is drawn into the steam compressor for compression. Then, it is mixed with the steam from the expander outlet and enters the drying module.

[0026] The beneficial effects of this invention are:

[0027] 1. Traditional dryers use throttled and depressurized steam as a heat source, resulting in energy loss. This invention utilizes an expander to perform work, outputting mechanical work while depressurizing, thus improving energy utilization efficiency. Compared to electrically driven compressors, steam-driven systems have higher primary energy utilization efficiency.

[0028] 2. In traditional dryers, the waste heat from the exhaust gas is directly dissipated by the condensate, resulting in significant energy waste. This invention alleviates scaling on the waste heat exchanger by combining electrostatic dust removal and heat exchange, and recovers some of the waste heat. Furthermore, it utilizes high-temperature heat pump technology and steam compression technology to recover most of the waste heat from the drying system, thereby reducing its energy consumption.

[0029] 3. This invention couples drying technology with a boiler system, converting difficult-to-store steam energy into storable and combustible fuel. This facilitates deep peak shaving in power plants, reduces the size of the thermal storage system, and improves system economy. Furthermore, the tiered heat absorption / release of the thermal storage medium in this invention meets the steam parameter requirements of different scenarios, offering high flexibility. In addition, this invention further enhances the subcooling of the refrigerant at the heat pump condenser end by preheating the feedwater, thereby increasing the heat pump's COP. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a sludge drying system coupled with a thermal storage system.

[0031] Figure 2 This is a schematic diagram of an electrostatic precipitator-heat exchanger.

[0032] Explanation of reference numerals in the attached drawings: 1. First electric valve; 2. Heat storage medium heater; 3. Heat storage tank; 4. First heat storage medium circulation pump; 5. First electric heater; 6. High-temperature heat storage heat releaser; 7. Medium-temperature heat storage heat releaser; 8. Second heat storage medium circulation pump; 9. First check valve; 10. First flash tank; 11. First water circulation pump; 12. Second check valve; 13. Third check valve; 14. First pressurization pump; 15. Second electric valve; 16. Second flash tank; 17. Second water circulation pump; 18. Fourth check valve; 19. Fifth check valve; 20. Second pressurization pump; 21. Third electric valve; 22. Sixth check valve; 23. Fourth electric valve; 24. Steam-electric dual-purpose compressor; 25. First speed control device; 26. Expander; 27. Second speed control device; 28. Steam compressor; 29. ​​Seventh check valve; 20. Eighth check valve; 20. First electric valve; 21. First electric valve; 22. Second electric valve; 23. Steam compressor; 24. First speed control device; 25. Expander; 26. Second speed control device; 27. Steam compressor; 28. Seventh check valve; 29. ​​Eighth check valve; 20. First electric valve; 20. First electric valve; 20. First electric valve; 21. First electric valve; 22. Second electric valve; 23. Second electric valve; 24. First speed control device; 25. First speed control device; 26. Second speed control device; 27. Second speed control device; 28. Steam compressor; 29. ​​Seventh check valve; 20. First electric valve; 20. Second electric valve; 20. First electric valve; 21. First electric valve; 22. Second electric valve; 20. First electric valve; 21. First electric valve 30. Directional valve, 31. Fifth electric valve, 32. Sixth electric valve, 33. Dryer, 35. Cyclone separator, 36. Electrostatic precipitator-heat exchanger, 37. Cleaning nozzle, 38. Waste heat exchanger, 39. Drain tank, 40. Third flash tank, 41. Second electric heater, 42. Condenser, 43. Gas-liquid separator, 44. Evaporator, 45. Electronic expansion valve, 46. Filter, 47. Liquid storage tank, 48. Subcooler, 49. Third water circulation pump, 50. Feed water preheater, 51. Third pressurization pump, 52. Condensate waste liquid pipe, 53. Seventh electric valve, 54. High-pressure water, 55. Eighth electric valve, 56. Ninth electric valve, 57. Steam-water heat exchanger, 58. Electrostatic precipitator-heat exchanger anode, 59. Electrostatic precipitator-heat exchanger cathode, 60. High-temperature waste gas passage, 61. Low-temperature waste gas passage. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0034] Example 1:

[0035] To address the problems of the prior art, Embodiment 1 of this application provides a sludge drying system coupled with a thermal storage system, comprising: a thermal storage module, a sludge drying module, a waste heat collection module, and a waste heat upgrading module;

[0036] The heat storage module is used to store peak-shaving steam energy from the power plant and includes a heat storage medium heater 2, a heat storage tank 3, a first heat storage medium circulation pump 4, an electric heater 5, a second heat storage medium circulation pump 8, and a heat releaser. The sludge drying module is connected to the heat storage module and includes multiple parallel dryers 33. The sludge drying module uses low-pressure steam to dry the sludge. The waste heat collection module is connected to the sludge drying module and includes a cyclone separator 35, an electrostatic precipitator-heat exchanger 36, and a waste heat exchanger 38 for recovering high-temperature heat. Waste heat from exhaust gas; the waste heat improvement module is connected to the waste heat collection module and includes a steam-electric dual-purpose compressor 24, a first speed regulating device 25, an expander 26, a second speed regulating device 27, a steam compressor 28, a third flash tank 40, a second electric heater 41, a condenser 42, a gas-liquid separator 43, an evaporator 44, an electronic expansion valve 45, a filter 46, a liquid storage tank 47, a subcooler 48, a third water circulation pump 49, a water preheater 50, and a third pressurizing pump 51, used to improve the quality of waste heat and recycle it.

[0037] Specifically, the heat exchanger includes a high-temperature heat storage heat exchanger 6 and a medium-temperature heat storage heat exchanger 7; the heat storage tank 3, the high-temperature heat storage heat exchanger 6, the medium-temperature heat storage heat exchanger 7, and the second heat storage medium circulation pump 8 are connected in sequence to form a circulation loop; the high-temperature heat storage heat exchanger 6 is also connected to a first flash tank 10, a first water circulation pump 11, and a first pressurization pump 14; the medium-temperature heat storage heat exchanger 7 is also connected to a second flash tank 16, a second water circulation pump 17, and a second pressurization pump 20.

[0038] The heat storage medium stored in the heat storage tank 3 is molten salt, heat transfer oil, or liquid metal.

[0039] In the sludge drying module, low-pressure steam (above 0.3 MPa, above 150°C) enters the drying system, which consists of multiple dryers 33 connected in parallel. This low-pressure steam can come from the second flash tank 16 or from steam extracted from the power plant turbine. The steam undergoes a phase change and condenses within the dryer 33, becoming hydrophobic, and then enters the hydrophobic condensate tank 39 for flash evaporation. The resulting liquid water is transported via pipeline to the boiler deaerator. The sludge within the dryer 33 absorbs heat from the steam, and as its temperature rises, the moisture in the sludge evaporates and is discharged from the top with the air, then enters the cyclone separator 35 for dust removal.

[0040] Example 2:

[0041] Based on Example 1, Example 2 of this application provides a more specific sludge drying system coupled with a thermal storage system, such as... Figure 1 As shown, it includes: a heat storage module, a sludge drying module, a waste heat collection module, and a waste heat upgrading module.

[0042] In the waste heat collection module, the high-temperature and high-humidity air (90-120℃) discharged from the cyclone separator 35 enters the electrostatic precipitator-heat exchanger 36 through port a, heating the low-temperature waste gas. At the same time, the electrostatic precipitator further removes dust and other impurities from the air, reducing the air temperature to above the dew point temperature. The air then flows out through port b and enters the tube side of the waste heat exchanger 38, where the temperature drops to below 60℃. It then enters the electrostatic precipitator-heat exchanger 36 through port d and is heated, with the temperature rising to above 80℃. After exiting through port c, it enters the boiler air supply system. The organic matter it contains has a combustion-supporting effect. The condensate from the air and water vapor in the waste heat exchanger 38 is discharged through the condensate waste liquid pipe 52. Low-temperature demineralized water (30-50°C) enters from the lower shell side of waste heat exchanger 38, is heated to 50-70°C, then flows out from the upper shell side of waste heat exchanger 38, enters evaporator 44 to absorb heat and cool down, then enters feedwater preheater 50 for further cooling, and finally returns to waste heat exchanger 38. In addition, tube-side fouling can be cleaned either by opening the fourth electric valve 23 to purge with low-pressure steam, or by opening the seventh electric valve 53 to clean with high-pressure water 54. Wastewater is discharged through condensate waste liquid pipe 52.

[0043] In the waste heat recovery module, the second electric heater 41 is activated until the liquid water temperature in the third flash tank 40 reaches above 75°C. Medium-temperature, high-pressure refrigerant flows out from the storage tank 47, is filtered by the filter 46, and then enters the electronic expansion valve 45, becoming a low-temperature, low-pressure refrigerant. It then enters the evaporator 44, absorbs heat, and becomes a low-pressure superheated gas. Next, it enters the gas-liquid separator 43, where the gaseous refrigerant enters the steam-electric dual-purpose compressor 24, where it is compressed into a high-temperature, high-pressure gaseous refrigerant. It then enters the condenser 42 to release heat, and then enters the subcooler 48 to further release heat. Finally, it returns to the storage tank 47 to begin the next cycle. The demineralized water is pressurized to 0.1-0.3 MPa by the third pressurizing pump 51, and then enters the feedwater preheater 50 to absorb heat and increase its temperature to 30-50°C. It then enters the subcooler 48 to further increase its temperature to 40-60°C, and then enters the third flash tank 40. The mixed liquid water is sent to the condenser 42 by the third water circulation pump 49 to absorb heat and increase its temperature to 100-130°C. It then enters the third flash tank 40 to flash and generate steam. The steam is mixed with the steam discharged from the top of the condensate tank 39 and then compressed to above 0.3 MPa by the steam compressor 28. After mixing with the steam discharged from the expander 26, it enters the sludge drying module.

[0044] It should be noted that the steam-electric dual-purpose compressor 24 and the steam compressor 28 can be driven entirely by the expander 26, or they can be partially driven by electricity or driven entirely by electricity. The speed of the steam-electric dual-purpose compressor 24 and the steam compressor 28 is adjusted according to the first speed regulating device 25 and the second speed regulating device 27.

[0045] Furthermore, such as Figure 2As shown, the electrostatic precipitator-heat exchanger 36 includes an anode 58 and a cathode 59. The high-temperature exhaust gas passage 60 carries the exhaust gas discharged from the cyclone separator 35, and dust or other impurities in the exhaust gas are adsorbed onto the outer surface of the anode 58. The low-temperature exhaust gas passage 61 carries the exhaust gas discharged from the waste heat exchanger 38. The high-temperature exhaust gas passage 60 and the low-temperature exhaust gas passage 61 are arranged alternately and vertically.

[0046] Example 3:

[0047] Based on Examples 1 and 2, Example 3 of this application provides an operation method for a sludge drying system coupled with a thermal storage system, including:

[0048] Step 1: During the off-peak period of power supply and heating in the power plant, the heat storage mode of the heat storage module is activated. Peak-shaving steam is heated by the steam-water heat exchanger 57 to generate steam to drive the expander 26 and supply the sludge drying module. The sludge drying module, waste heat collection module and waste heat upgrading module operate in conjunction.

[0049] In step 1, the thermal storage mode includes steam heat source thermal storage and steam-electric combined heating:

[0050] The steam heat source storage includes:

[0051] Open the first electric valve 1, and steam passes through the heat storage medium heater 2. The outlet steam temperature is not lower than 200℃. Start the first heat storage medium circulation pump 4. After the heat storage medium comes out from the bottom of the heat storage tank 3, it enters the heat storage medium heater 2 and the first electric heater 5 in sequence. Turn off the first electric heater 5. The heat storage medium is heated to 300-600℃. The heat storage medium is heated by steam and then enters the heat storage tank 3.

[0052] The steam-electric combined heating includes: supplementing the heat by activating the first electric heater 5 based on the heat storage of the steam heat source. The power of the first electric heater 5 can come from off-peak electricity from the power grid or from renewable energy sources.

[0053] In addition, in step 1, the ninth electric valve 56 needs to be opened, and the peak-shaving steam releases heat through the steam-water heat exchanger 57; the second electric valve 15 is opened, and the ambient temperature demineralized water is pressurized to 1-1.6 MPa by the second pressurization pump 20, mixed with the drainage from the second flash tank 16, and then enters the steam-water heat exchanger 57 to absorb heat. It then enters the second flash tank 16 to flash and generate steam. This steam first serves as the driving energy for the expander 26, and finally as the heat source for the sludge drying module. The number of dryers started is related to the peak-shaving level; the higher the peak-shaving level, the greater the steam flow, and the more dryers are started. If the peak-shaving steam is low, but there is abundant renewable energy power, or if there is off-peak electricity on the grid, the thermal storage module operates in thermal storage mode with steam-electric combined heating, while the rest remains unchanged.

[0054] Step 2: During the peak power and heat supply period of the power plant, the heat release mode of the heat storage module is activated to release the stored heat energy to generate medium-pressure and low-pressure steam. Part of the steam drives the expander 26 and supplies it to the sludge drying module. The sludge drying module, waste heat collection module and waste heat upgrading module operate in conjunction.

[0055] In step 2, the heat release mode includes: medium-pressure-low-pressure steam mode, medium-pressure steam mode, and low-pressure steam mode;

[0056] The medium-pressure-low-pressure steam mode includes:

[0057] The second thermal storage medium circulation pump 8 is started. After exiting from the top of the thermal storage tank 3, the thermal storage medium sequentially enters the high-temperature thermal storage heat exchanger 6 and the medium-temperature thermal storage heat exchanger 7, and then returns to the thermal storage tank 3. The outlet temperature of the thermal storage medium in the high-temperature thermal storage heat exchanger 6 is not lower than 300℃, and the outlet temperature of the thermal storage medium in the medium-temperature thermal storage heat exchanger 7 is not lower than 200℃. The ambient temperature demineralized water is pressurized to 1-1.6MPa by the second pressurizing pump 20, mixed with the drainage from the second flash tank 16, and then enters the medium-temperature thermal storage heat exchanger 7 for heating, and then enters the second flash tank 16 for flash evaporation to generate steam. The ambient temperature demineralized water is pressurized to 1.6-4MPa by the first pressurizing pump 14, mixed with the drainage from the first flash tank 10, and then enters the first water circulation pump 11 for heating, and then enters the first flash tank 10 for flash evaporation to generate steam.

[0058] The medium-pressure steam mode includes: based on the medium-pressure-low-pressure steam mode, shutting off the second water circulation pump 17 and the second booster pump 20, at which time low-pressure steam cannot be generated; the low-pressure steam mode includes: based on the medium-pressure-low-pressure steam mode, shutting off the first water circulation pump 11 and the first booster pump 14, at which time medium-pressure steam cannot be generated.

[0059] In addition, in step 2, the medium-pressure steam generated by the medium-pressure-low-pressure steam mode enters the medium-pressure steam header through the first one-way valve 9, increasing the supply of medium-pressure steam. Part of the generated low-pressure steam passes through the third electric valve 21 and the sixth one-way valve 22, and then enters the low-pressure steam header, increasing the supply of low-pressure steam. The other part of the low-pressure steam first serves as the driving energy for the expander 26, and then enters the sludge drying module as a heat source. When the medium temperature of the heat storage module is below 200°C, the heat storage module stops operating. If the power plant has sufficient sludge fuel reserves after drying, the sludge drying module, waste heat collection module, and waste heat upgrading module stop operating. If the power plant has insufficient sludge fuel reserves after drying, the eighth electric valve 55 opens, and steam is directly extracted from the power plant turbine as a heat source, allowing the sludge drying module, waste heat collection module, and waste heat upgrading module to operate normally.

[0060] Step 3: During the power plant's power and heat supply period, based on the temperature of the heat storage medium and the sludge inventory, select to directly use the steam turbine to extract steam or continue to release the stored heat energy to drive the expander 26 and supply it to the sludge drying module. The sludge drying module, waste heat collection module, and waste heat upgrading module operate in conjunction.

[0061] Specifically, during the off-peak period before the peak power and heating season of the power plant, the eighth electric valve 55 is opened, and steam extracted from the power plant turbine is used directly as the heat source. The sludge drying module, waste heat collection module, and waste heat upgrading module operate normally. During the off-peak period after the peak power and heating season, if the medium temperature of the thermal storage module is below 200℃, it operates as before; if the medium temperature of the thermal storage module is above 200℃, it operates according to the peak power and heating season mode, freeing up thermal storage space for the off-peak period until the medium temperature of the thermal storage module falls below 200℃.

[0062] The sludge drying module, waste heat collection module, and waste heat upgrading module operate in conjunction, including:

[0063] Steam enters the expander 26, which drives the steam-electric compressor 24 and the steam compressor 28. The steam-electric compressor 24 causes the refrigerant to circulate. The refrigerant undergoes a phase change and absorbs heat in the evaporator 44, and is then compressed and heated by the steam-electric compressor 24. It then enters the condenser 42 to release heat and become a saturated liquid. It then enters the subcooler 48 for further cooling and becomes a subcooled liquid. After passing through the liquid storage tank 47 and the filter 46, it is throttled and cooled by the electronic expansion valve 45 and finally returns to the evaporator 44.

[0064] The sludge in the dryer 33 absorbs heat from the water vapor, causing the water in the sludge to evaporate. It then sequentially enters the cyclone separator 35 for dust removal, the electrostatic precipitator-heat exchanger 36, the waste heat exchanger 38, and finally the boiler air supply system. The water vapor in the dryer 33 undergoes a phase change and condenses into condensate, which then enters the condensate tank 39 for flash evaporation. The resulting liquid water is transported to the boiler deaerator via pipeline. The hot water produced in the waste heat exchanger 38 passes through the evaporator 44 and feedwater preheater 50 of the waste heat upgrading module before returning to the waste heat exchanger 38.

[0065] The demineralized water sequentially enters the feed water preheater 50, subcooler 48, third flash tank 40, condenser 42, and third flash tank 40. The saturated steam generated by absorbing heat and raising the temperature, together with the saturated steam generated by the condensate tank 39, is drawn into the steam compressor 28 for compression, and then mixed with the steam from the outlet of the expander 26 and enters the drying module.

Claims

1. A sludge drying system coupled with a thermal storage system, characterized in that, include: Thermal storage module, sludge drying module, waste heat collection module and waste heat upgrading module; The heat storage module is used to store the peak-shaving steam energy of the power plant, including a heat storage medium heater (2), a heat storage tank (3), a first heat storage medium circulation pump (4), a first electric heater (5), a second heat storage medium circulation pump (8), and a heat exchanger; the sludge drying module is connected to the heat storage module and includes multiple parallel dryers (33), which use low-pressure steam to dry the sludge; the waste heat collection module is connected to the sludge drying module and includes a cyclone separator (35), an electrostatic precipitator-heat exchanger (36), and a waste heat exchanger (38), which are used to recover the waste heat from high-temperature exhaust gas; the waste heat upgrading module is connected to the waste heat collection module and includes a steam-electric dual-purpose compressor (24), a first speed regulating device (25), an expander (26), a second speed regulating device (27), a steam compressor (28), a third flash tank (40), and a condenser (42). The system includes a gas-liquid separator (43), an evaporator (44), an electronic expansion valve (45), a filter (46), a liquid storage tank (47), a subcooler (48), a third water circulation pump (49), a feedwater preheater (50), and a third pressurizing pump (51), used to improve the quality of waste heat and recycle it; the first speed regulating device (25) is connected to the steam-electric dual-purpose compressor (24) and the expander (26) at both ends, and the second speed regulating device (27) is connected to the expander (26) and the steam compressor (28) at both ends; the gas-liquid separator (43) is connected to the steam-electric dual-purpose compressor (24) and the evaporator (44) at both ends; the third water circulation pump (49) is connected to the third flash tank (40) and the condenser (42) at both ends; the third pressurizing pump (51) is connected to the feedwater preheater (50); and the third flash tank (40) is equipped with a second electric heater (41). The heat exchanger includes a high-temperature heat storage heat exchanger (6) and a medium-temperature heat storage heat exchanger (7); the heat storage tank (3), the high-temperature heat storage heat exchanger (6), the medium-temperature heat storage heat exchanger (7), and the second heat storage medium circulation pump (8) are connected in sequence to form a circulation loop; the high-temperature heat storage heat exchanger (6) is also connected to a first flash tank (10), a first water circulation pump (11), and a first pressurization pump (14); the medium-temperature heat storage heat exchanger (7) is also connected to a second flash tank (16), a second water circulation pump (17), and a second pressurization pump (20); a steam-water heat exchanger (57) is provided between the medium-temperature heat storage heat exchanger (7) and the second water circulation pump (17); The sludge drying module, waste heat collection module, and waste heat upgrading module operate in conjunction, including: steam entering the expander (26), the expander (26) driving the steam-electric compressor (24) and the steam compressor (28); the steam-electric compressor (24) causing the refrigerant to circulate, the refrigerant absorbs heat in the evaporator (44) through phase change, and is then compressed and heated by the steam-electric compressor (24), and then enters the condenser (42) to release heat and become a saturated liquid, and then enters the subcooler (48) to further cool down and become a subcooled liquid, and then passes through the liquid storage tank (47) and filter (46), and is then throttled and cooled down by the electronic expansion valve (45), and finally returns to the evaporator (44); The sludge in the dryer (33) absorbs heat from the water vapor, and the water in the sludge evaporates. The generated exhaust gas enters the cyclone separator (35) for dust removal, the electrostatic dust removal-heat exchanger (36), the waste heat exchanger (38), and the electrostatic dust removal-heat exchanger (36) in sequence, and finally enters the boiler air supply system. The water vapor in the dryer (33) undergoes phase change and condenses into hydrophobic water, and then enters the hydrophobic condensate tank (39) for flash evaporation. The generated liquid water is transported to the boiler deaerator through pipelines. The hot water generated by the waste heat exchanger (38) passes through the evaporator (44) and feedwater preheater (50) of the waste heat upgrading module, and then returns to the waste heat exchanger (38). The demineralized water sequentially enters the third pressurization pump (51), feed water preheater (50), subcooler (48), third flash tank (40), third water circulation pump (49), condenser (42), and third flash tank (40). The saturated steam generated by heat absorption and temperature rise is drawn into the steam compressor (28) and compressed together with the saturated steam generated by the condensate tank (39). Then it is mixed with the steam from the outlet of the expander (26) and enters the sludge drying module.

2. The sludge drying system coupled with a thermal storage system according to claim 1, characterized in that, The heat storage medium stored in the heat storage tank (3) is molten salt, heat transfer oil or liquid metal.

3. The sludge drying system coupled with a thermal storage system according to claim 1, characterized in that, The electrostatic precipitator-heat exchanger (36) includes several electrostatic precipitator-heat exchanger anodes (58), electrostatic precipitator-heat exchanger cathodes (59), and staggered high-temperature exhaust gas channels (60) and low-temperature exhaust gas channels (61).

4. The sludge drying system coupled with a thermal storage system according to claim 1, characterized in that, The steam-electric compressor (24) and the steam compressor (28) are driven by an expander (26), or by electricity, or by a combination of expander (26) and electricity. The speed of the steam-electric compressor (24) and the steam compressor (28) is adjusted according to the first speed regulating device (25) and the second speed regulating device (27).

5. A method for operating a sludge drying system coupled with a thermal storage system as described in claim 1, characterized in that, include: Step 1: During the off-peak period of power supply and heating in the power plant, the heat storage mode of the heat storage module is started. The peak steam is heated by the steam-water heat exchanger (57) to generate steam to drive the expander (26). The water vapor at the outlet of the expander (26) is mixed with the water vapor at the outlet of the steam compressor (28) and enters the sludge drying module together. The sludge drying module, the waste heat collection module and the waste heat upgrading module operate in conjunction. Step 2: During the peak power and heat supply period of the power plant, start the heat release mode of the heat storage module to release the heat storage energy to generate medium and low pressure steam. Part of the steam drives the expander (26) and supplies it to the sludge drying module. The sludge drying module, waste heat collection module and waste heat upgrading module operate together. Step 3: During the power supply and heating period of the power plant, depending on the temperature of the heat storage medium and the sludge inventory, choose to directly use the steam turbine to extract steam or continue to release the heat storage energy to drive the expander (26) and supply it to the sludge drying module. The sludge drying module, waste heat collection module and waste heat upgrading module operate together. The sludge drying module, waste heat collection module, and waste heat upgrading module operate in conjunction, including: steam entering the expander (26), the expander (26) driving the steam-electric compressor (24) and the steam compressor (28); the steam-electric compressor (24) causing the refrigerant to circulate, the refrigerant absorbs heat in the evaporator (44) through phase change, and is then compressed and heated by the steam-electric compressor (24), and then enters the condenser (42) to release heat and become a saturated liquid, and then enters the subcooler (48) to further cool down and become a subcooled liquid, and then passes through the liquid storage tank (47) and filter (46), and is then throttled and cooled down by the electronic expansion valve (45), and finally returns to the evaporator (44); The sludge in the dryer (33) absorbs heat from the water vapor, and the water in the sludge evaporates. The generated exhaust gas enters the cyclone separator (35) for dust removal, the electrostatic dust removal-heat exchanger (36), the waste heat exchanger (38), and the electrostatic dust removal-heat exchanger (36) in sequence, and finally enters the boiler air supply system. The water vapor in the dryer (33) undergoes phase change and condenses into hydrophobic water, and then enters the hydrophobic condensate tank (39) for flash evaporation. The generated liquid water is transported to the boiler deaerator through pipelines. The hot water generated by the waste heat exchanger (38) passes through the evaporator (44) and feedwater preheater (50) of the waste heat upgrading module, and then returns to the waste heat exchanger (38). The demineralized water sequentially enters the third pressurization pump (51), feed water preheater (50), subcooler (48), third flash tank (40), third water circulation pump (49), condenser (42), and third flash tank (40). The saturated steam generated by heat absorption and temperature rise is drawn into the steam compressor (28) and compressed together with the saturated steam generated by the condensate tank (39). Then it is mixed with the steam from the outlet of the expander (26) and enters the sludge drying module.

6. The operation method of the sludge drying system coupled with the thermal storage system according to claim 5, characterized in that, In step 1, the thermal storage mode includes steam heat source thermal storage and steam-electric combined heating: The steam heat source storage includes: Steam passes through the heat storage medium heater (2), the first heat storage medium circulation pump (4) is started, and the heat storage medium comes out from the bottom of the heat storage tank (3) and enters the heat storage medium heater (2) and the first electric heater (5) in sequence. The first electric heater (5) is turned off, the heat storage medium is heated by steam, and then the heat storage medium enters the heat storage tank (3). The steam-electric combined heating includes: activating the first electric heater (5) to supplement heat based on the heat storage of the steam heat source.

7. The operation method of the sludge drying system coupled with the thermal storage system according to claim 5, characterized in that, In step 2, the heat release mode includes: medium-pressure-low-pressure steam mode, medium-pressure steam mode, and low-pressure steam mode; The medium-pressure-low-pressure steam mode includes: The second heat storage medium circulation pump (8) is started. After the heat storage medium comes out from the top of the heat storage tank (3), it enters the high temperature heat storage heat exchanger (6) and the medium temperature heat storage heat exchanger (7) in sequence, and then returns to the heat storage tank (3). The ambient temperature demineralized water is pressurized by the second pressurizing pump (20), mixed with the drainage of the second flash tank (16), and enters the medium temperature heat storage heat exchanger (7) to be heated, and then enters the second flash tank (16) to flash and generate steam. The ambient temperature demineralized water is pressurized by the first pressurizing pump (14), mixed with the drainage of the first flash tank (10), and enters the first water circulation pump (11), then enters the high temperature heat storage heat exchanger (6) to be heated, and then enters the first flash tank (10) to flash and generate steam.

8. The operation method of the sludge drying system coupled with the thermal storage system according to claim 7, characterized in that, The medium-pressure steam mode includes: based on the medium-low pressure steam mode, shutting off the second water circulation pump (17) and the second booster pump (20); the low-pressure steam mode includes: based on the medium-low pressure steam mode, shutting off the first water circulation pump (11) and the first booster pump (14).

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