A coal-fired boiler sludge combustion system

Abstract

The present invention discloses a sludge co-burning system for a coal-fired boiler, comprising a furnace, a pulverized coal burner and a sludge burner. The sludge burner is arranged on the furnace and above the uppermost pulverized coal burner. The number of the sludge burners is multiple, wherein at least two of the sludge burners are centrally symmetrically arranged about the central axis of the furnace. The sludge co-burning system for a coal-fired boiler of the present invention can effectively reduce the secondary pollution problem caused by direct landfilling of sludge, and at the same time reduce the problem of long sludge composting and natural drying treatment cycles and poor effects. Sludge incineration can achieve volume reduction and reduce treatment costs. By arranging the sludge burner, while fully burning the sludge, it can also avoid the impact on the original boiler pulverized coal burnout, improve combustion efficiency, and reduce energy waste. By reasonable combustion control and tail gas treatment, the emission of harmful gases (such as dioxins) generated during the incineration process can be reduced, and the impact on the environment can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of coal-fired boilers, and in particular to a sludge co-combustion system for coal-fired boilers. Background Art

[0002] With the rapid development of my country's economy and society, the urbanization process has accelerated, sewage treatment facilities have been continuously improved, and the urban sewage treatment capacity has been significantly improved. However, a large amount of residual sludge will be generated in the sewage treatment process, and the treatment and disposal of sludge has become a major challenge facing the current environmental protection field. Traditional sludge treatment methods mainly include landfill, composting, natural drying and incineration. Among them, landfill is the most common treatment method, but a large amount of sludge is directly landfilled without standardized treatment, which is easy to cause secondary pollution. The composting and natural drying treatment cycles are long and the effect is not good. Although incineration treatment can achieve reduction, the operating cost is high and it is easy to produce harmful substances such as dioxins. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, an embodiment of the present invention provides a system for burning sludge in a coal-fired boiler.

[0005] The sludge co-firing system of a coal-fired boiler according to an embodiment of the present invention comprises a furnace, a pulverized coal burner and a sludge burner. The number of the pulverized coal burners is multiple, and the multiple pulverized coal burners are arranged at intervals in the height direction of the furnace; the sludge burner is arranged on the furnace and above the uppermost pulverized coal burner, the number of the sludge burners is multiple, and the multiple sludge burners are arranged at intervals along the circumference of the furnace, wherein at least two of the sludge burners are arranged centrally symmetrically about the central axis of the furnace.

[0006] In some embodiments, the coal-fired boiler sludge co-firing system of the embodiment of the present invention also includes a tail flue and a sludge drying and crushing device, the tail flue is connected to the furnace, the tail flue is provided with a smoke extraction pipe for extracting part of the flue gas in the tail flue, the sludge drying and crushing device has a flue gas inlet, a sludge inlet and a smoke powder outlet, the flue gas inlet is connected to the smoke extraction pipe, the smoke powder outlet is connected to the sludge burner, the sludge drying and crushing device is used to receive part of the flue gas dried sludge discharged from the tail flue and grind the dried sludge into powder, so that the flue gas carries the powdered sludge to the sludge burner for combustion.

[0007] In some embodiments, the smoke extraction pipe includes a first branch pipe, a second branch pipe and a mixing main pipe. The first branch pipe and the second branch pipe are arranged at intervals in the height direction of the tail flue to extract smoke of different temperatures in the tail flue. The first branch pipe and the second branch pipe are both connected to the mixing main pipe, and the mixing main pipe is connected to the smoke inlet of the sludge drying and crushing device so that the smoke extracted by the first branch pipe and the second branch pipe are mixed in the mixing main pipe and then transported to the sludge drying and crushing device.

[0008] In some embodiments, the temperature of the flue gas extracted by the first branch pipe is 540°C-660°C, and the temperature of the flue gas extracted by the second branch pipe is 300°C-400°C.

[0009] In some embodiments, the flue gas flow rate of the mixing main pipe is 18 m / s-22 m / s.

[0010] In some embodiments, an SCR denitrification device is provided on the tail flue, and the first branch pipe is located above the SCR denitrification device.

[0011] In some embodiments, the coal-fired boiler sludge co-firing system of the embodiment of the present invention further includes an air preheater, which is located below the SCR denitrification device, and the second branch pipe is located between the SCR denitrification device and the air preheater.

[0012] In some embodiments, the temperature of the flue gas entering the sludge drying and pulverizing device from the flue gas inlet is 500°C-550°C, and the temperature of the flue gas discharged from the flue gas powder outlet is 180°C-200°C.

[0013] In some embodiments, the coal-fired boiler sludge co-firing system of the embodiment of the present invention also includes a storage bin and a feeder, wherein the storage bin is used to store sludge, and the storage bin is connected to the sludge inlet through the feeder to transport the sludge to the sludge drying and crushing device.

[0014] In some embodiments, the coal-fired boiler sludge co-firing system of the embodiment of the present invention also includes a dust collector, a desulfurization tower and a chimney. The dust collector is connected to the tail flue to remove dust from the flue gas discharged from the tail flue, the desulfurization tower is connected to the dust collector to desulfurize the flue gas after dust removal, and the chimney is connected to the desulfurization tower to discharge the desulfurized flue gas.

[0015] The sludge-combustion system for coal-fired boilers of the embodiment of the present invention can effectively reduce the secondary pollution problem caused by direct landfill of sludge, and at the same time reduce the problem of long sludge composting and natural drying treatment cycles and poor results. Sludge burning can achieve reduction, reduce the volume of sludge, and reduce treatment costs. Using existing equipment in coal-fired boilers to burn sludge can save the investment cost and operating cost of new incineration facilities. By arranging the sludge burner, while fully burning the sludge, it can also avoid the impact on the burnout of the original boiler coal powder, improve combustion efficiency, and reduce energy waste. Through reasonable combustion control and tail gas treatment, the emission of harmful gases (such as dioxins) generated during the incineration process can be reduced, reducing the impact on the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a system for burning sludge in a coal-fired boiler according to an embodiment of the present invention.

[0017] Figure 2 It is a schematic diagram of the arrangement of a sludge burner according to an embodiment of the present invention.

[0018] Reference numerals:

[0019] 100. Coal-fired boiler sludge combustion system; 1. Furnace; 2. Pulverized coal burner; 3. Sludge burner; 4. Tail flue; 5. Sludge drying and crushing device; 501. Flue gas inlet; 502. Sludge inlet; 503. Flue gas pulverization outlet; 6. Smoke extraction pipe; 601. First branch pipe; 602. Second branch pipe; 603. Mixing main pipe; 7. SCR denitrification device; 8. Air preheater; 9. Storage silo; 10. Feeder; 11. Dust collector; 12. Desulfurization tower; 13. Chimney. DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0021] like Figure 1 and Figure 2 As shown, the sludge co-firing system 100 of a coal-fired boiler according to an embodiment of the present invention comprises a furnace 1, a pulverized coal burner 2 and a sludge burner 3. There are a plurality of pulverized coal burners 2, and the plurality of pulverized coal burners 2 are arranged at intervals in the height direction of the furnace 1. The sludge burner 3 is arranged on the furnace 1 and above the uppermost pulverized coal burner 2, and there are a plurality of sludge burners 3, and the plurality of sludge burners 3 are arranged at intervals along the circumference of the furnace 1, wherein at least two sludge burners 3 are arranged in a central symmetric manner about the central axis of the furnace 1.

[0022] It should be noted that the sludge entering the boiler is dry sludge powder with a moisture content of about 30%. The dry sludge has a low fixed carbon content and most of it is volatile matter. It is very easy to burn and burn out. The furnace temperature in the area above the wind of the pulverized coal burner 2 is above 1000°C, and the dry sludge is sufficient to burn out in this range. Since the dry sludge is sent into the boiler with flue gas, some sludge is sent into the boiler from the pulverized coal combustion area, which will lower the local furnace temperature and affect the burning of the pulverized coal. The pulverized coal above the wind of the pulverized coal burner 2 has basically been burned out. Sending dry sludge to this area can reduce the impact on the burning of the pulverized coal, etc.

[0023] In the coal-fired boiler sludge co-combustion system 100 of the embodiment of the present invention, a plurality of pulverized coal burners 2 are arranged at intervals in the height direction of the furnace 1, so that the pulverized coal can be fully burned in the furnace 1 and the combustion efficiency can be improved. The sludge burner 3 is located above the uppermost pulverized coal burner 2, and at least two of the sludge burners 3 are arranged centrally and symmetrically about the central axis of the furnace 1, so that the sludge can be mixed with the pulverized coal and burned after entering the furnace 1, making full use of the high temperature environment in the furnace 1, while avoiding the influence on the burnout of the pulverized coal.

[0024] The sludge-combustion system 100 of a coal-fired boiler according to an embodiment of the present invention can effectively reduce the secondary pollution problem caused by direct landfilling of sludge, and at the same time reduce the problem of long sludge composting and natural drying treatment cycles and poor results. Sludge burning can achieve volume reduction, reduce the volume of sludge, and reduce treatment costs. Using existing equipment of coal-fired boilers to burn sludge can save the investment cost and operating cost of new incineration facilities. By arranging the sludge burner 3, while fully burning the sludge, it can also avoid the impact on the burnout of the original boiler coal powder, improve combustion efficiency, and reduce energy waste. Through reasonable combustion control and tail gas treatment, the emission of harmful gases (such as dioxins) generated during the incineration process can be reduced, reducing the impact on the environment.

[0025] In some embodiments, the sludge co-combustion system 100 of the coal-fired boiler of the embodiment of the present invention further includes a tail flue 4 and a sludge drying and crushing device 5. The tail flue 4 is connected to the furnace 1, and a smoke extraction pipe 6 is provided on the tail flue 4 for extracting part of the flue gas in the tail flue 4. The sludge drying and crushing device 5 has a flue gas inlet 501, a sludge inlet 502 and a smoke powder outlet 503, the flue gas inlet 501 is connected to the smoke extraction pipe 6, and the smoke powder outlet 503 is connected to the sludge burner 3. The sludge drying and crushing device 5 is used to receive part of the flue gas discharged from the tail flue 4 to dry the sludge and grind the dried sludge into powder, so that the flue gas carries the powdered sludge to the sludge burner 3 for combustion.

[0026] The dried sludge powder is easier to burn because its moisture content is reduced and it can release heat more quickly. The waste heat of the flue gas in the tail flue 4 is used to dry the sludge, which realizes the recycling of heat energy and improves the energy efficiency of the whole system. The drying and crushing device can reduce the volume of the sludge and reduce the emission of harmful substances that may be contained in the sludge during the combustion process. By mixing the sludge powder with the coal powder for combustion, the emission of harmful gases can be reduced, especially when the combustion process is precisely controlled. By improving the combustion efficiency and the utilization of heat energy, the operating cost can be reduced and the economic benefit can be improved. This system can adapt to different types of sludge and coal-fired boilers and has strong flexibility and applicability.

[0027] In some embodiments, the smoke extraction pipe 6 includes a first branch pipe 601, a second branch pipe 602 and a mixing main pipe 603. The first branch pipe 601 and the second branch pipe 602 are arranged at intervals in the height direction of the tail flue 4 to extract smoke of different temperatures in the tail flue 4. The first branch pipe 601 and the second branch pipe 602 are both connected to the mixing main pipe 603, and the mixing main pipe 603 is connected to the smoke inlet 501 of the sludge drying and crushing device 5, so that the smoke extracted by the first branch pipe 601 and the second branch pipe 602 is mixed in the mixing main pipe 603 and then transported to the sludge drying and crushing device 5.

[0028] The first branch pipe 601 and the second branch pipe 602 are arranged at intervals in the height direction of the tail flue 4, with the purpose of extracting flue gases of different temperatures in the tail flue 4. Usually, the temperature of the flue gases in the upper part of the tail flue 4 is higher, while the temperature of the flue gases in the lower part is lower. The first branch pipe 601 and the second branch pipe 602 are both connected to the mixing main pipe 603, and the function of the mixing main pipe 603 is to mix the flue gases extracted from the two branches. Flue gases of different temperatures from the first branch pipe 601 and the second branch pipe 602 are mixed in the mixing main pipe 603 to reach a suitable temperature range for use in the sludge drying process. The mixing main pipe 603 is connected to the flue gas inlet 501 of the sludge drying and crushing device 5 to transport the mixed flue gas to the drying and crushing device for drying the sludge.

[0029] By extracting flue gas at different heights and mixing them, flue gas with a more uniform temperature can be obtained, which helps to improve the efficiency and uniformity of the sludge drying process. Using flue gas with a higher temperature can remove moisture from the sludge more quickly, thereby improving the drying efficiency. Since the temperature of the flue gas is uniform, the corrosion and wear of the tail flue 4 and the smoke extraction pipe 6 by the high-temperature flue gas can be reduced. By rationally allocating and utilizing the flue gas heat in the tail flue 4, the thermal energy utilization efficiency can be maximized and energy consumption can be reduced. The design of the mixing main pipe 603 helps to maintain the stability of the system operation and avoid affecting the sludge drying effect due to flue gas temperature fluctuations. Improving the performance of the sludge drying and crushing device 5 helps to reduce the emission of harmful gases during the combustion process of the sludge, thereby reducing the impact on the environment.

[0030] In some embodiments, the temperature of the flue gas extracted by the first branch pipe 601 is 540°C-660°C, and the temperature of the flue gas extracted by the second branch pipe 602 is 300°C-400°C. By adjusting the ratio of the flue gas extracted by the first branch pipe 601 and the second branch pipe 602, the temperature of the mixed flue gas can be flexibly adjusted to adapt to different types of sludge and different drying requirements. Reasonable use of flue gas at different temperatures can reduce energy waste and improve the thermal efficiency of the entire system.

[0031] In some embodiments, the flue gas flow rate of the mixing main pipe 603 is 18 m / s-22 m / s.

[0032] The appropriate flue gas flow rate helps to transfer heat to the sludge more effectively, accelerates the evaporation of water, and thus improves the drying efficiency. If the flue gas flow rate is too fast, it may cause fine sludge particles to be blown away, affecting the drying effect and possibly causing equipment wear. The flue gas flow rate in the mixing main pipe 603 is controlled at 18m / s-22m / s. This flow rate range can ensure that the flue gas and the sludge are fully in contact, and can prevent the sludge particles from being blown away due to excessive flow rate.

[0033] In some embodiments, an SCR denitrification device 7 is provided on the tail flue 4 , and the first branch pipe 601 is located above the SCR denitrification device 7 .

[0034] The SCR denitrification device 7 is located on the tail flue 4 and is used to treat the denitrification of the flue gas after combustion to reduce the emission of nitrogen oxides. The first branch pipe 601 is located above the SCR denitrification device 7, which means that it extracts the flue gas after the SCR denitrification treatment. The purpose is to use the flue gas with reduced nitrogen oxide content to dry the sludge. Since the flue gas extracted by the first branch pipe 601 has been processed by the SCR denitrification device 7, the nitrogen oxide content therein has been reduced, which can further reduce the emission of nitrogen oxides during the sludge combustion process.

[0035] In some embodiments, the coal-fired boiler sludge co-firing system 100 of the embodiment of the present invention further includes an air preheater 8, which is located below the SCR denitrification device 7, and the second branch pipe 602 is located between the SCR denitrification device 7 and the air preheater 8.

[0036] The air preheater 8 is a device for preheating the air entering the furnace 1. By preheating the air, the combustion efficiency can be improved because the preheated air can provide more oxygen to support combustion. The second branch pipe 602 is located between the SCR denitration device 7 and the air preheater 8, which means that it extracts the flue gas that has been treated by the SCR denitration but has not yet entered the air preheater 8. This part of the flue gas has a moderate temperature and can be used for drying sludge.

[0037] In some embodiments, the temperature of the flue gas entering the sludge drying and pulverizing device 5 through the flue gas inlet 501 is 500°C-550°C, and the temperature of the flue gas discharged from the flue gas powder outlet 503 is 180°C-200°C.

[0038] The flue gas inlet 501 of the sludge drying and crushing device 5 is designed to receive flue gas with a temperature of 500°C-550°C. The flue gas in this temperature range can provide enough heat to dry the sludge, while not being too high to destroy the properties of the sludge or cause the equipment to overheat. The flue gas temperature at the flue gas powder outlet 503 after drying and crushing is controlled at 180°C-200°C. The flue gas in this temperature range has released a large amount of heat for the sludge drying process, and the temperature is relatively low, which is conducive to the subsequent exhaust gas treatment and discharge.

[0039] The flue gas temperature of 500℃-550℃ can efficiently transfer heat to the sludge, promote the rapid evaporation of water, and thus achieve efficient drying. By controlling the temperature of the inlet flue gas, the sludge can be prevented from being over-dried, which helps to maintain the physical and chemical properties of the sludge, especially for some heat-sensitive sludge components. During the sludge drying and crushing process, the reduction in flue gas temperature means that the heat is effectively utilized. In this way, the thermal efficiency of the system is improved and energy consumption is reduced. Lower temperatures (180℃~200℃) help reduce wear and corrosion inside the sludge drying and crushing device 5 and the tail flue 4. Lower temperatures help reduce the generation and emission of harmful gases, such as nitrogen oxides and sulfur oxides, thereby reducing the impact on the environment.

[0040] In some embodiments, the coal-fired boiler sludge co-firing system 100 of the embodiment of the present invention also includes a storage bin 9 and a feeder 10. The storage bin 9 is used to store sludge. The storage bin 9 is connected to the sludge inlet 502 through the feeder 10 to transport the sludge to the sludge drying and crushing device 5.

[0041] The main function of the storage silo 9 is to store sludge. It can provide a temporary storage space for the sludge to ensure that the sludge can be stored safely and orderly before it needs to be processed. The storage silo 9 also has a buffering effect and can adjust between the sludge supply and processing capacity to cope with possible imbalances in supply and demand. The storage silo 9 can optimize the logistics process of the sludge and reduce losses during transportation and processing through centralized storage and batch processing. The feeder 10 is responsible for conveying the sludge in the storage silo 9 to the sludge inlet 502 of the sludge drying and crushing device 5 to ensure that the sludge can enter the drying and crushing system continuously and evenly. The feeder 10 can usually control the conveying speed and amount of the sludge to ensure the stability of the sludge treatment process.

[0042] The storage bin 9 is connected to the sludge inlet 502 of the sludge drying and crushing device 5 through the feeder 10, forming a complete sludge treatment process. Through the coordinated use of the storage bin 9 and the feeder 10, it can be ensured that the sludge treatment system can still maintain stable operation when the sludge supply is unstable or the treatment demand changes. When the sludge treatment equipment needs maintenance or overhaul, the storage bin 9 can provide sufficient sludge storage space to reduce the downtime of the system. The feeder 10 can adjust the sludge delivery volume according to the real-time needs of the system to improve the sludge treatment efficiency. The design of the storage bin 9 and the feeder 10 can adapt to sludge of different types and properties, improving the adaptability of the system. The use of the storage bin 9 and the feeder 10 reduces the direct exposure and manual operation of the sludge and improves the working environment. Through a closed conveying system, the impact of dust and odor generated during the sludge treatment process on the environment can be reduced.

[0043] In some embodiments, the coal-fired boiler sludge co-firing system 100 of the embodiment of the present invention also includes a dust collector 11, a desulfurization tower 12 and a chimney 13. The dust collector 11 is connected to the tail flue 4 to remove dust from the flue gas discharged from the tail flue 4. The desulfurization tower 12 is connected to the dust collector 11 to desulfurize the flue gas after dust removal. The chimney 13 is connected to the desulfurization tower 12 to discharge the desulfurized flue gas.

[0044] The dust collector 11 is a device for capturing solid particulate matter in the flue gas. It separates the particulate matter from the flue gas by physical, chemical or electrical methods. The dust collector 11 is connected to the tail flue 4 to remove dust from the flue gas discharged from the tail flue 4 to reduce the emission of particulate matter in the flue gas. The desulfurization tower 12 is a device for removing acidic gases such as sulfur dioxide (SO) from the flue gas. It usually converts SO into solid or liquid form through chemical reactions, thereby reducing its emission. The desulfurization tower 12 is connected to the dust collector 11 to desulfurize the flue gas after dust removal to further reduce pollutants in the flue gas. The chimney 13 is a device for discharging the desulfurized flue gas. The height and diameter design of the chimney 13 helps to reduce the pollution of the flue gas to the ground, and also helps to diffuse and dilute the flue gas.

[0045] The sludge treatment coupled coal-fired boiler system of the embodiment of the present invention is effectively removed from the flue gas by the dust collector 11 and the desulfurization tower 12, thereby reducing air pollution. The dust collector 11 can remove particulate matter from the flue gas, improve combustion efficiency, and reduce energy waste. The system design of the embodiment of the present invention helps to meet strict environmental regulations and emission standards. Reducing pollutant emissions helps to improve air quality and protect the environment and human health.

[0046] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0048] 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 one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0050] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0051] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A coal-fired boiler sludge combustion system, characterized in that: include: Furnace (1); A pulverized coal burner (2), wherein the number of the pulverized coal burners (2) is multiple, and the multiple pulverized coal burners (2) are arranged at intervals in the height direction of the furnace (1); A sludge burner (3), wherein the sludge burner (3) is arranged on the furnace (1) and is located above the uppermost pulverized coal burner (2), and the number of the sludge burners (3) is multiple, and the multiple sludge burners (3) are arranged at intervals along the circumference of the furnace (1), wherein at least two of the sludge burners (3) are arranged in a centrally symmetrical manner with respect to the central axis of the furnace (1).

2. The coal-fired boiler sludge combustion system according to claim 1, characterized in that: The invention also comprises a tail flue (4) and a sludge drying and pulverizing device (5), wherein the tail flue (4) is connected to the furnace (1), and a smoke extraction pipe (6) is provided on the tail flue (4) for extracting part of the flue gas in the tail flue (4). The sludge drying and pulverizing device (5) comprises a flue gas inlet (501), a sludge inlet (502) and a smoke powder outlet (503), wherein the flue gas inlet (501) is connected to the smoke extraction pipe (6), and the smoke powder outlet (503) is connected to the sludge burner (3). The sludge drying and pulverizing device (5) is used to receive part of the flue gas discharged from the tail flue (4) to dry the sludge and grind the dried sludge into powder, so that the flue gas carries the powdered sludge to the sludge burner (3) for combustion.

3. The coal-fired boiler sludge combustion system according to claim 2, characterized in that: The smoke extraction pipe (6) comprises a first branch pipe (601), a second branch pipe (602) and a main mixing pipe (603); the first branch pipe (601) and the second branch pipe (602) are arranged at intervals in the height direction of the tail flue (4) to extract smoke of different temperatures in the tail flue (4); the first branch pipe (601) and the second branch pipe (602) are both connected to the main mixing pipe (603); the main mixing pipe (603) is connected to the smoke inlet (501) of the sludge drying and pulverizing device (5) so that the smoke extracted by the first branch pipe (601) and the second branch pipe (602) are mixed in the main mixing pipe (603) and then transported to the sludge drying and pulverizing device (5).

4. The coal-fired boiler sludge combustion system according to claim 3, characterized in that: The temperature of the flue gas extracted by the first branch pipe (601) is 540°C-660°C, and the temperature of the flue gas extracted by the second branch pipe (602) is 300°C-400°C.

5. The coal-fired boiler sludge combustion system according to claim 4, characterized in that: The flue gas flow rate of the mixing main pipe (603) is 18m / s-22m / s.

6. The coal-fired boiler sludge combustion system according to claim 4, characterized in that: The tail flue (4) is provided with an SCR denitration device (7), and the first branch pipe (601) is located above the SCR denitration device (7).

7. The coal-fired boiler sludge combustion system according to claim 6, characterized in that: It also includes an air preheater (8), the air preheater (8) is located below the SCR denitrification device (7), and the second branch pipe (602) is located between the SCR denitrification device (7) and the air preheater (8).

8. The coal-fired boiler sludge combustion system according to claim 4, characterized in that: The temperature of the flue gas entering the sludge drying and pulverizing device (5) through the flue gas inlet (501) is 500°C-550°C, and the temperature of the flue gas discharged from the flue gas powder outlet (503) is 180°C-200°C.

9. The coal-fired boiler sludge combustion system according to claim 1, characterized in that: It also includes a storage bin (9) and a feeder (10), wherein the storage bin (9) is used to store sludge, and the storage bin (9) is connected to the sludge inlet (502) via the feeder (10) to transport the sludge to the sludge drying and crushing device (5).

10. The coal-fired boiler sludge combustion system according to claim 2, characterized in that: It also includes a dust collector (11), a desulfurization tower (12) and a chimney (13), wherein the dust collector (11) is connected to the tail flue (4) to remove dust from the flue gas discharged from the tail flue (4), the desulfurization tower (12) is connected to the dust collector (11) to desulfurize the flue gas after dust removal, and the chimney (13) is connected to the desulfurization tower (12) to discharge the desulfurized flue gas.

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