A solar reheating flue gas drying sludge system

Abstract

The present invention discloses a solar reheated flue gas drying sludge system, comprising a sludge drying device, which includes at least a sludge dryer; a residual flue gas heating device, which includes a flue gas conveying component and a flue gas electric heater; the input end of the flue gas conveying component is connected to the flue gas outlet of the boiler, the output end of the flue gas conveying component is connected to the flue gas heat exchange input end of the flue gas electric heater, and the flue gas heat exchange output end of the flue gas electric heater is connected to the reheated flue gas input end of the sludge dryer; a solar power supply device, which is composed of a solar panel and a battery pack; the battery pack is connected to the power supply end of the flue gas electric heater. The embodiment of the present invention utilizes solar energy to convert into electrical energy to reheat the boiler's residual heat flue gas, and the heated flue gas is used to dry the sludge. This can reduce the amount of flue gas extracted and improve the utilization rate of flue gas thermal energy.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge drying, and in particular to a solar energy reheating flue gas drying sludge system. Background Art

[0002] Sludge generated after sewage treatment at urban sewage treatment plants is a type of solid waste with a complex composition, containing heavy metals, toxic and harmful pathogens, and inert, difficult-to-degrade organic matter. Improper sludge disposal can pollute water, soil, crops, and other areas, causing serious secondary pollution to the environment. Currently, the main sludge treatment methods in my country include landfill, land use, pyrolysis, and combustion. The advantage of landfill is its simplicity, but its disadvantages are also significant, such as the tendency to contaminate groundwater resources at the landfill site and the occupation of large amounts of land resources. Sludge contains a large amount of combustible organic matter. If the sludge is burned, a small amount of ash will be produced after combustion, and a large number of harmful substances in the sludge will also be destroyed during the combustion process, making it a better method for harmless and volume-reducing treatment.

[0003] In addition, mixing sludge with raw coal and feeding it into the boiler of a coal-fired power plant for co-combustion is also a way to properly treat sludge. This method can not only render the sludge harmless and reduce its volume, but also use the calorific value of the sludge to generate electricity, thus realizing the resource treatment of sludge.

[0004] Because the moisture content of sludge from sewage treatment plants is approximately 80%, if it is directly mixed with raw coal, the moisture content of the resulting mixed fuel will deviate from the moisture content of the boiler's designed coal type. If the sludge is directly mixed with the raw coal, it will have a negative impact on boiler operation and can easily cause blockage of the raw coal bunker and coal feeder. For this reason, existing coal-fired sludge power generation units are equipped with a sludge drying system to dry the wet sludge to a certain moisture content before mixing it with the raw coal. Depending on the process, the drying system can be divided into a flue gas direct drying system and a steam indirect drying system. The direct flue gas drying process can use the high temperature environment of the furnace to eliminate the odorous gases generated during the drying process. However, the flue gas extraction point in the direct flue gas drying process is very critical. If the flue gas is extracted before the dust collector, the flue gas will contain a large amount of dust. If the flue gas is extracted after the dust collector, the flue gas consumption will be large. Therefore, the flue gas drying sludge technology needs to be improved. Summary of the Invention

[0005] This invention provides a solar-powered flue gas reheating sludge drying system to improve existing flue gas sludge drying technology. By converting solar energy into electrical energy to reheat boiler waste heat, the heated flue gas is then used to dry the sludge. This reduces flue gas extraction volume and improves flue gas thermal energy utilization.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a solar reheating flue gas drying sludge system, comprising:

[0007] A sludge drying device, which comprises at least a sludge dryer;

[0008] The residual flue gas heating device comprises a flue gas conveying component and a flue gas electric heater; the input end of the flue gas conveying component is connected to the flue gas outlet of the boiler, the output end of the flue gas conveying component is connected to the flue gas heat exchange input end of the flue gas electric heater, and the flue gas heat exchange output end of the flue gas electric heater is connected to the reheated flue gas input end of the sludge dryer;

[0009] The solar power supply device is composed of a solar panel and a battery pack; the battery pack is connected to the power supply end of the flue gas electric heater.

[0010] In one embodiment of the present invention, the flue gas conveying assembly includes an induced draft fan and a booster fan; the induced draft fan and the booster fan are arranged on a pipeline between the boiler and the flue gas electric heater.

[0011] In one embodiment of the present invention, the fume conveying assembly further comprises a dust collector;

[0012] The input end of the dust collector is connected to the smoke outlet end of the boiler, the output end of the dust collector is connected to the input end of the booster fan through the induced draft fan, and the output end of the booster fan is connected to the flue gas heat exchange input end of the flue gas electric heater.

[0013] In one embodiment of the present invention, the output end of the flue gas conveying assembly is connected to the flue gas power generation equipment through a flue gas treatment device.

[0014] In one embodiment of the present invention, the solar reheating flue gas drying sludge system further includes:

[0015] A control device configured to:

[0016] When the monitored inlet flue gas temperature of the sludge dryer meets the preset flue gas temperature adjustment condition, the heating power of the flue gas electric heater is regulated to maintain the inlet flue gas temperature of the sludge dryer within the preset working flue gas temperature range.

[0017] In one embodiment of the present invention, the control device is further configured to:

[0018] When starting the sludge dryer, controlling the operation of the sludge dryer at a medium-speed heating power;

[0019] When it is monitored that the inlet flue gas temperature of the sludge dryer is lower than the first flue gas temperature endpoint value, the flue gas electric heater is controlled to operate at a high heating power;

[0020] When it is monitored that the inlet flue gas temperature of the sludge dryer rises from the first flue gas temperature endpoint value to the second flue gas temperature endpoint value, the heating power is switched back to the middle gear to control the operation of the flue gas electric heater.

[0021] In one embodiment of the present invention, the control device is further configured to:

[0022] When it is monitored that the inlet flue gas temperature of the sludge dryer is higher than the third flue gas temperature endpoint value, the flue gas electric heater is controlled to operate at a low-speed heating power;

[0023] When it is monitored that the inlet flue gas temperature of the sludge dryer drops from the third flue gas temperature endpoint value to reach the fourth flue gas temperature endpoint value, switching back to the middle heating power to control the operation of the flue gas electric heater;

[0024] The second smoke temperature endpoint value is smaller than the fourth smoke temperature endpoint value, and the fourth smoke temperature endpoint value is smaller than the third smoke temperature endpoint value.

[0025] In one embodiment of the present invention, the sludge drying device further comprises a sludge silo; a sludge output end of the sludge silo is connected to a sludge input end of the sludge dryer via a conveying pipeline.

[0026] In one embodiment of the present invention, the sludge drying device further includes a pulverizing system; the dried sludge outlet of the sludge dryer is connected to the pulverizing system through a conveying mechanism, and the output end of the pulverizing system is connected to the input end of the boiler.

[0027] In one embodiment of the present invention, the sludge dryer is a hybrid heat exchanger.

[0028] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0029] (1) By converting solar energy into electrical energy and then heating the boiler waste heat flue gas, and then using the heated flue gas to dry the sludge, not only can the thermal energy of low-grade flue gas be fully utilized, but also a better sludge drying effect can be achieved with a smaller amount of flue gas extraction.

[0030] (2) When there is no sludge that needs to be dried, the flue gas conveying components and the flue gas electric heater are kept in a shutdown state, and the battery pack is used to supply power to the DC load of the power plant to improve energy utilization.

[0031] (3) When there is sludge that needs to be processed, the flue gas conveying component is started to guide the flue gas from the boiler to the flue gas electric heater, and the electricity converted from solar energy is used for reheating, thereby achieving reheating of the residual smoke and reducing the amount of flue gas extracted. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of a solar reheating flue gas drying sludge system according to one embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of a method for using a solar reheating flue gas drying sludge system according to one embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of a method for using a solar reheating flue gas drying sludge system according to one embodiment of the present invention;

[0035] The reference numerals in the accompanying drawings of the specification are as follows:

[0036] 1. Photovoltaic panels; 2. Battery pack; 3. Flue gas electric heater; 4. Pulverizing system; 5. Dried sludge; 6. Sludge dryer; 7. Flue gas thermometer; 8. Sludge conveying equipment; 9. Wet sludge; 10. Sludge silo; 11. Boiler; 12. Electric door; 13. Booster fan; 14. Dust collector; 15. Induced draft fan; 16. Flue gas treatment equipment; 17. Flue gas power generation equipment. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] See Figure 1 The embodiment of the present invention provides a solar reheating flue gas drying sludge system, comprising:

[0039] The sludge drying device includes a sludge dryer 6, a sludge silo 10, and a pulverizing system 4; the sludge output end of the sludge silo 10 is connected to the sludge input end of the sludge dryer 6 through a sludge conveying device 8, and the dried sludge outlet of the sludge dryer 6 is connected to the pulverizing system 4 through a conveying mechanism. The output end of the pulverizing system 4 is connected to the input end of the boiler 11, and the conveying mechanism transports the dried sludge 5 to the pulverizing system 4.

[0040] The residual flue gas heating device includes a flue gas conveying component and a flue gas electric heater 3; the input end of the flue gas conveying component is connected to the flue gas outlet end of the boiler 11, the output end of the flue gas conveying component is connected to the flue gas heat exchange input end of the flue gas electric heater 3, and the flue gas heat exchange output end of the flue gas electric heater 3 is connected to the reheated flue gas input end of the sludge dryer 6;

[0041] The flue gas conveying assembly includes an induced draft fan 15, a booster fan 13, and a dust collector 14. These fans are installed in the pipeline between the boiler 11 and the electric flue gas heater 3. Specifically, the input of the dust collector 14 is connected to the flue gas outlet of the boiler 11, while the output of the dust collector 14 is connected to the input of the booster fan 13 via the induced draft fan 15. The output of the booster fan 13 is connected to the flue gas heat exchange input of the electric flue gas heater 3. Furthermore, the output of the flue gas conveying assembly is connected to the flue gas power generation equipment 17 (chimney) via the flue gas treatment device 16 (FGD).

[0042] The solar power supply device consists of a solar panel and a battery bank 2; the battery bank 2 is connected to the power supply terminal of the flue gas electric heater 3. The photovoltaic panel 1 converts solar energy into electricity and stores it in the battery bank 2. The battery bank 2 is in a floating charge state, and the flue gas electric heater 3 is supplied with electricity by the battery bank 2. When the flue gas electric heater 3 is not needed, the battery bank 2 supplies power to the power plant's DC loads.

[0043] In this embodiment, the solar reheated flue gas drying sludge system mainly consists of a photovoltaic subsystem and a reheated flue gas subsystem coupled together through a flue gas electric heater 3, which are described in detail below:

[0044] Reheated flue gas subsystem: A portion of the flue gas from the boiler 11 is drawn out of the induced draft fan 15 after the dust collector 14. It is pressurized by the booster fan 13 and then sent to the electric flue gas heater 3. The flue gas from the electric flue gas heater 3 is then sent to the sludge dryer 6 to dry the wet sludge 9. The sludge dryer 6 is a hybrid heat exchanger, where the high-temperature flue gas directly contacts the wet sludge. After drying the wet sludge, the flue gas carries the sludge-water mixture to the upper part of the furnace, where it also introduces a large amount of malodorous gases for decomposition. When designing the reheated flue gas subsystem, thermal calculations are performed to determine the flue gas temperature and volume required for maximum sludge drying (80% moisture content for wet sludge, 30% moisture content for dried sludge). This, in turn, determines the specifications of the booster fan 13 and the power of the electric flue gas heater 3. The booster fan 13 can adjust the flue gas flow rate by adjusting the rotor blade opening. A "sludge volume-flue gas flow rate" curve is plotted through thermal calculations and on-site commissioning. The power of the flue gas electric heater 3 is set to high, medium and low, corresponding to the flue gas flow from large to small, ensuring that most of the flow range is covered and the flue gas can be heated to 130℃~220℃. The medium gear is used by default after startup.

[0045] It should be noted that the flue gas generated by combustion in a coal-fired power plant's boiler 11 undergoes a dedusting process to remove most of the dust. It is then fed to the FGD via an induced draft fan 15 to remove SO2 before being discharged to the atmosphere through a chimney. A flue gas path is drawn from the outlet of induced draft fan 15, where it is pressurized by a booster fan 13 and fed to an electric flue gas heater 3. The high-temperature flue gas is then fed to a sludge dryer 6, a hybrid heater that dries the wet sludge by direct contact between the flue gas and the dryer. The flue gas, carrying moisture, malodorous gases, and a sludge-water mixture, is then fed to the furnace above the primary combustion zone, where the malodorous gases are decomposed in the high-temperature region.

[0046] Photovoltaic subsystem: Solar panels convert solar energy into electricity and store it in battery bank 2. During normal operation, battery bank 2 is in a floating charge state. This power is primarily used to power the flue gas heater 3 for flue gas heating. Its secondary function is to power the DC loads of the coal-fired power plant. The energy consumed by the batteries is supplied by photovoltaic power generation. The capacity of the photovoltaic subsystem is designed based on the power output of the flue gas heater 3, with an average output that can meet the maximum power output of the flue gas heater 3.

[0047] In one embodiment of the present invention, the solar reheating flue gas drying sludge system further includes:

[0048] A control device configured to:

[0049] When the monitored inlet flue gas temperature of the sludge dryer 6 meets the preset flue gas temperature adjustment condition, the heating power of the flue gas electric heater 3 is adjusted to maintain the inlet flue gas temperature of the sludge dryer 6 within the preset working flue gas temperature range;

[0050] When the sludge dryer 6 is started, the sludge dryer 6 is controlled to operate at a medium-speed heating power;

[0051] When it is monitored that the inlet flue gas temperature of the sludge dryer 6 is lower than the first flue gas temperature endpoint value, the flue gas electric heater 3 is controlled to operate at a high heating power;

[0052] When the inlet flue gas temperature of the sludge dryer 6 is monitored to rise from the first flue gas temperature endpoint value to the second flue gas temperature endpoint value, the heating power is switched back to the middle gear to control the operation of the flue gas electric heater 3;

[0053] When it is monitored that the inlet flue gas temperature of the sludge dryer 6 is higher than the third flue gas temperature endpoint value, the flue gas electric heater 3 is controlled to operate at a low heating power;

[0054] When the inlet flue gas temperature of the sludge dryer 6 is detected to drop from the third flue gas temperature endpoint value to the fourth flue gas temperature endpoint value, the heating power is switched back to the middle gear to control the operation of the flue gas electric heater 3;

[0055] The second smoke temperature endpoint value is smaller than the fourth smoke temperature endpoint value, and the fourth smoke temperature endpoint value is smaller than the third smoke temperature endpoint value.

[0056] For ease of understanding, as an example, Figure 2 、 Figure 3 As shown, one method of using the solar reheating flue gas drying sludge system is:

[0057] When the sludge needs to be dried, the control device starts the booster fan 13, opens its inlet and outlet electric doors 12, and pre-sets the blade opening of the booster fan 13 according to the amount of sludge to be processed so that the flue gas flow reaches the required value for drying the sludge.

[0058] The control device activates the flue gas electric heater 3, which defaults to mid-range operation, and constantly monitors the flue gas temperature at the inlet of the sludge dryer 6 via the flue gas temperature meter 7. To ensure sludge drying efficiency and prevent explosions, the control device switches to high-range operation when the inlet flue gas temperature falls below 130°C, switches back to mid-range operation when the temperature rises to 150°C, switches to low-range operation when the temperature rises above 220°C, and switches back to mid-range operation when the temperature drops to 200°C, ensuring that the flue gas temperature throughout the drying process remains primarily between 130°C and 220°C.

[0059] Furthermore, when the flue gas temperature at the inlet of the sludge dryer 6 falls below 130°C, the entire sludge transport system stops loading sludge. Loading will resume only when the flue gas temperature rises above 150°C after falling below 130°C. The flue gas temperature at the outlet of the sludge dryer 6 is also monitored during operation and compared with the flue gas temperature at the inlet of the sludge dryer 6. The operating status of the sludge dryer 6 is evaluated based on the temperature drop.

[0060] When there is no sludge to be dried, the booster fan 13 remains stopped, its inlet and outlet electric doors 12 are closed, the flue gas electric heater 3 remains stopped, and the power of the battery pack 2 is supplied to the DC load of the power plant, thereby making full use of solar energy.

[0061] In summary, the embodiments of the present invention have the following beneficial effects:

[0062] (1) By converting solar energy into electrical energy and then heating the boiler waste heat flue gas, and then using the heated flue gas to dry the sludge, not only can the thermal energy of low-grade flue gas be fully utilized, but also a better sludge drying effect can be achieved with a smaller amount of flue gas extraction.

[0063] (2) When there is no sludge that needs to be dried, the flue gas conveying components and the flue gas electric heater are kept in a shutdown state, and the battery pack is used to supply power to the DC load of the power plant to improve energy utilization.

[0064] (3) When there is sludge that needs to be processed, the flue gas conveying component is started to guide the flue gas from the boiler to the flue gas electric heater, and the electricity converted from solar energy is used for reheating, thereby achieving reheating of the residual smoke and reducing the amount of flue gas extracted.

[0065] (4) The thermal energy of low-grade flue gas is utilized without affecting the boiler thermal system.

[0066] (5) After the flue gas for drying is taken from the dust collector, the amount of dust brought into the sludge by the flue gas is very small.

[0067] (6) The electric heater uses the electricity converted from solar energy to heat the flue gas and then dries the sludge. In this way, only a small amount of flue gas needs to be extracted to complete the sludge drying, and a large system is not required.

[0068] (7) The direct flue gas drying process sends part of the malodorous gases in the sludge into the high-temperature environment of the furnace for decomposition, thus achieving the deodorization function.

[0069] Solar energy is used to generate electricity, which is stored in batteries and supplied to flue gas electric heaters or power plant DC loads when needed, which is environmentally friendly.

[0070] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A solar reheating flue gas drying sludge system, characterized in that: include: A sludge drying device, which comprises at least a sludge dryer; The residual flue gas heating device comprises a flue gas conveying component and a flue gas electric heater; the input end of the flue gas conveying component is connected to the flue gas outlet of the boiler, the output end of the flue gas conveying component is connected to the flue gas heat exchange input end of the flue gas electric heater, and the flue gas heat exchange output end of the flue gas electric heater is connected to the reheated flue gas input end of the sludge dryer; A solar power supply device, which consists of a solar panel and a battery pack; the battery pack is connected to the power supply terminal of the flue gas electric heater; the electric energy of the flue gas electric heater is supplied by the battery pack; a control device configured to, when the monitored flue gas temperature at the inlet of the sludge dryer meets a preset flue gas temperature adjustment condition, regulate the heating power of the flue gas electric heater so as to maintain the flue gas temperature at the inlet of the sludge dryer within a preset operating flue gas temperature range; The device is further configured to: when the sludge dryer is started, control the operation of the sludge dryer at a medium-range heating power; when it is monitored that the inlet flue gas temperature of the sludge dryer is less than a first flue gas temperature endpoint value, control the operation of the flue gas electric heater at a high-range heating power; when it is monitored that the inlet flue gas temperature of the sludge dryer rises from the first flue gas temperature endpoint value to a second flue gas temperature endpoint value, switch back to the medium-range heating power to control the operation of the flue gas electric heater, and; When it is monitored that the inlet flue gas temperature of the sludge dryer is higher than the third flue gas temperature endpoint value, the flue gas electric heater is controlled to operate at a low-speed heating power; When it is monitored that the inlet flue gas temperature of the sludge dryer drops from the third flue gas temperature endpoint value to reach the fourth flue gas temperature endpoint value, switching back to the middle heating power to control the operation of the flue gas electric heater; The second smoke temperature endpoint value is smaller than the fourth smoke temperature endpoint value, and the fourth smoke temperature endpoint value is smaller than the third smoke temperature endpoint value.

2. The solar reheating flue gas drying sludge system according to claim 1, characterized in that: The smoke conveying assembly includes an induced draft fan and a booster fan; The induced draft fan and the booster fan are arranged on the pipeline between the boiler and the flue gas electric heater.

3. The solar reheating flue gas drying sludge system according to claim 2, characterized in that: The flue gas conveying assembly also includes a dust collector; The input end of the dust collector is connected to the smoke outlet end of the boiler, the output end of the dust collector is connected to the input end of the booster fan through the induced draft fan, and the output end of the booster fan is connected to the flue gas heat exchange input end of the flue gas electric heater.

4. The solar reheating flue gas drying sludge system according to claim 1 or 3, characterized in that: The output end of the flue gas conveying component is connected to the flue gas power generation equipment through the flue gas treatment equipment.

5. The solar reheating flue gas drying sludge system according to claim 1, characterized in that: The sludge drying device also includes a sludge silo; The sludge output end of the sludge silo is connected to the sludge input end of the sludge dryer through a sludge conveying device.

6. The solar reheating flue gas drying sludge system according to claim 1, characterized in that: The sludge drying device also includes a pulverizing system; The dried sludge outlet of the sludge dryer is connected to the pulverizing system through a conveying mechanism, and the output end of the pulverizing system is connected to the input end of the boiler.

7. The solar reheating flue gas drying sludge system according to claim 1, characterized in that: The sludge dryer is a hybrid heat exchanger.

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