Household garbage incineration fly ash low-temperature pyrolysis treatment system and method
By using fly ash granulation and the addition of magnetic materials, the problems of high equipment investment, high operating costs, and easy wear of seals in rotary pyrolysis furnaces for processing municipal solid waste incineration fly ash have been solved, thereby improving the processing capacity and stability of the pyrolysis furnace.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-27
- Publication Date
- 2026-05-01
AI Technical Summary
Existing rotary pyrolysis furnaces face challenges in processing fly ash from municipal solid waste incineration, including high equipment investment, high operating costs, easy wear of seals, and frequent and difficult-to-solve caking issues.
By using fly ash granulation and adding magnetic materials, fly ash is granulated and mixed with magnetic materials through a granulator to form a mixture of different particle sizes. The magnetic materials are used to improve heat transfer, optimize furnace conditions, and reduce dust and caking.
It significantly improves the processing capacity and stability of the pyrolysis furnace, reduces equipment investment and operating costs, extends the life of seals, and reduces the frequency of caking.
Smart Images
Figure CN121945528A_ABST
Abstract
Description
Low-temperature pyrolysis treatment system and method for fly ash from municipal solid waste incineration Technical Field
[0001] This invention belongs to the field of municipal solid waste incineration fly ash treatment technology, and relates to a low-temperature pyrolysis treatment system and method for municipal solid waste incineration fly ash. Background Technology
[0002] In recent years, waste incineration technology has gradually become the research and development direction of waste reduction and resource utilization technology at home and abroad due to its advantages such as high degree of harmlessness, good volume reduction and size reduction effect, low final disposal pressure and recovery of some energy. However, because the fly ash produced by municipal solid waste incineration contains dioxins, heavy metals and soluble salts, it is defined as hazardous waste and needs to be treated before it can be utilized for resource utilization.
[0003] According to the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration (Trial) HJ1134-2020" standard, the resource utilization of fly ash must meet three conditions: ① The soluble chlorine content should not exceed 2%, preferably not higher than 1%; ② The leaching concentration of heavy metals in the fly ash treatment products should be prepared according to HJ557, and the leaching concentration of heavy metals should not exceed the maximum allowable emission concentration limit specified in GB 8978; ③ The total amount of dioxin residues should not exceed 50 ng-TEQ / kg (based on the dry weight of fly ash).
[0004] Currently, the most effective methods for dioxin treatment are high-temperature decomposition above 850℃ or low-temperature thermal degradation below 500℃. High-temperature decomposition is energy-intensive, resulting in high investment and operating costs. Low-temperature thermal degradation, on the other hand, offers milder conditions, lower temperatures, lower energy consumption, simpler processes, and lower facility construction and operating costs, and its reliability has been proven through testing.
[0005] There are two processes for the low-temperature resource utilization of fly ash: pyrolysis after fly ash washing and washing after fly ash pyrolysis. Washing after fly ash pyrolysis has the advantages of low energy consumption and low dioxin content in salt products.
[0006] Low-temperature pyrolysis of fly ash currently mainly uses rotary pyrolysis furnaces. Compared with shaftless spiral pyrolysis furnaces, rotary pyrolysis furnaces are tilting type with low filling rate, ensuring complete and uniform mixing of fly ash. The dioxin content after pyrolysis is low, and they are easy to manufacture, process, inspect and maintain. Thermal deformation has no effect on the furnace body, making them the mainstream furnace type for low-temperature pyrolysis of fly ash.
[0007] However, rotary pyrolysis furnaces still have shortcomings in practical applications: (1) Fly ash has the characteristics of low thermal conductivity and low bulk density. Relying solely on the heating method of the rotary furnace wall and outer wall, it is difficult to quickly transfer heat to the inside of the material layer. In order to ensure that the fly ash reaches the pyrolysis temperature (usually 400-500℃), it is necessary to use a low filling rate (8~15%) and a long residence time to ensure uniform heating. This results in a large volume of rotary pyrolysis furnace required per unit mass of fly ash, and high equipment investment and operating costs.
[0008] (2) As the rotary pyrolysis furnace is rotating, the dynamic sealing devices at its feed end and discharge end are subjected to the dual scouring and wear of dust and high-temperature gas for a long time. The sealing elements are prone to failure and leakage, which destroys the inert and slightly negative pressure pyrolysis process, forcing the production line to frequently stop to replace the sealing components. The maintenance workload is large and the cost is high.
[0009] (3) During the low-temperature pyrolysis process, due to the small size of fly ash particles and uneven heating, some low-melting-point salts soften or melt and adhere to the furnace wall. Over time, severe caking or ring formation occurs, which is frequent and extremely difficult to clean. Summary of the Invention
[0010] In view of this, the purpose of the present invention is to provide a low-temperature pyrolysis treatment system and method for municipal solid waste incineration fly ash, so as to improve fly ash treatment capacity and reduce equipment investment and operating costs.
[0011] To achieve the above objectives, the present invention provides the following technical solution: a low-temperature pyrolysis treatment system for fly ash from municipal solid waste incineration, comprising a fly ash flaking and granulation system, a fly ash pyrolysis and magnetic material circulation system, and a dust collection system; the fly ash flaking and granulation system includes a feeding device, a flaking machine, a crusher, and a fly ash feeding hopper arranged sequentially along the material flow direction; the flaking machine's feeding hopper cover is provided with a fly ash inlet; the lower part of the fly ash feeding hopper is provided with a fly ash discharge port, and a fly ash discharge valve is provided at the fly ash discharge port; the fly ash pyrolysis and magnetic material circulation system includes a magnetic material feeding hopper, a pyrolysis furnace feeding screw, a low-temperature fly ash pyrolysis furnace, and a belt conveyor arranged sequentially along the material flow direction. The system includes an iron separator located above the belt conveyor; a magnetic material feed hopper with a feeding port and a circulating feed port at the top, and a magnetic material discharge port at the bottom, with a magnetic material discharge valve at the discharge port; a circulating feed port connected to the iron separator via a magnetic material conveying device; a magnetic material discharge valve interlocked with a fly ash discharge valve; the magnetic material feed hopper and fly ash feed hopper located above the pyrolysis furnace feed screw, with the fly ash discharge port and magnetic material discharge port connected to the pyrolysis furnace feed screw; and a dust collection system using negative pressure dust collection, including a sealing cover installed above the belt conveyor to seal the space above the belt conveyor, and a dust collection hood connected to the sealing cover.
[0012] This invention, through granulation and the addition of magnetic materials, can improve the thermal conductivity of fly ash, enhance heat transfer, ensure uniform heating between fly ash particles, improve fly ash processing capacity, and reduce equipment investment and operating costs. On the other hand, it can optimize furnace operating conditions, reduce dust, reduce wear, and prevent caking, thus solving problems such as frequent maintenance and high maintenance costs.
[0013] Optionally, the dust hood is connected to the dust inlet of the tablet press via a dust conveying pipe, and the dust inlet is located on the feed hopper cover of the tablet press.
[0014] Optionally, the feed screw of the tablet press is a shaftless screw, and the screw diameter gradually decreases from top to bottom along with the diameter of the feed hopper of the tablet press.
[0015] Optionally, the tablet press is a roller press, and the roller surface model of the tablet press is detachable. The tablet press can adjust the tablet size by changing the roller surface model.
[0016] Optionally, the crusher is an impact crusher, so that the particle size of the crushed fly ash is in the range of 50μm~10mm and the bulk density is 1~1.5t / m³.
[0017] Optionally, the fly ash low-temperature pyrolysis furnace is a rotary pyrolysis furnace.
[0018] Optionally, the magnetic material feed hopper is equipped with a level gauge to trigger an alarm and remind users to add material when the material level is lower than the required level.
[0019] Alternatively, the magnetic material conveying device may be a screw conveyor or a belt conveyor.
[0020] Optionally, the feeding device is a feeding screw.
[0021] Optionally, the iron separator is a bag separator.
[0022] A method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash, based on the aforementioned treatment system, employs a low-temperature pyrolysis process. The fly ash is granulated through a flaking and crushing process, eliminating the need for screening and forming a mixture of different particle sizes, including shaped granulated fly ash and unshaped powdered fly ash. The method includes the following steps: S1 Fly ash is fed into a flaking machine via a feeding device. The flaked and unflaked fly ash are then directly crushed in a crusher to form a mixture with a particle size of 50μm to 10mm; S2 Fly ash and magnetic materials are fed into a pyrolysis furnace feed screw conveyor at a ratio of 100:10 to 100:30 via interlocked fly ash discharge valves and magnetic material discharge valves, respectively; S3 The mixture is pyrolyzed in the low-temperature fly ash pyrolysis furnace, with heat transfer enhanced by the magnetic material; S4 The pyrolysis products are conveyed by a belt conveyor. During conveying, the magnetic material is separated by an iron separator and returned to the magnetic material feed hopper. Simultaneously, dust is collected by a dust collection system.
[0023] Optionally, the circulation volume of the magnetic material is 10-30% of the fly ash treatment volume, and the initial circulation volume of the magnetic material is 30% of the fly ash treatment volume, which is then increased to 30% when it drops to 10%.
[0024] Optionally, in step S4, the dust collected by the dust collection system is returned to the tablet press.
[0025] Optionally, the dust feed rate at the dust inlet is 2 to 5% of the total fly ash feed rate.
[0026] Optionally, the particle size of the magnetic material is 1~5mm.
[0027] Optionally, the hydraulic pressure used for tablet compression shall not exceed 5 MPa.
[0028] Optionally, the tablets are 50-100 mm long, 5-10 mm wide, and 1-5 mm thick.
[0029] Optionally, the bulk density of the fly ash after crushing is 1~1.5t / m³.
[0030] Alternatively, the mixing of fly ash and magnetic materials can be carried out solely through the feed screw of the pyrolysis furnace, without the need for additional mechanical mixing using a stirrer.
[0031] The beneficial effects of the present invention are as follows: 1. The processing system of the present invention is applied in the field of low-temperature pyrolysis of fly ash. During the low-temperature pyrolysis process, very few substances are volatilized from fly ash, and the gas in the furnace is mainly nitrogen in a protective inert atmosphere. Since there is less dust generated by fly ash volatilization, the present invention does not require all fly ash to be granulated. Granulation only uses the pressing and crushing process, without the need for screening equipment, which simplifies the system and reduces operating costs.
[0032] 2. This invention uses fly ash to form granules without sieving, creating a mixture of different particle sizes containing shaped fly ash particles and unshaped powdered fly ash. The unshaped powdered fly ash fills the gaps between the shaped fly ash particles, increasing the bulk density of the granulated fly ash to 1~1.5 t / m³. 3 The bulk density is 10-20% higher than that of fly ash that is entirely composed of shaped granules. Bulk density is a major factor affecting the throughput of low-temperature pyrolysis furnaces. The granulation method of this invention can increase the fly ash throughput by 10-20%, significantly improving the processing capacity of the pyrolysis furnace.
[0033] 3. In this invention, the amount of magnetic material added is 10-30% of the fly ash treatment amount. The magnetic material is only used to improve the heat transfer effect, so its content range is relatively wide. The control requirements for the magnetic material are low, and no precise control is required, which significantly reduces the complexity of the process operation and makes the system operation easier to control.
[0034] 4. In this invention, since the magnetic material is only used to improve the heat transfer effect, the requirement for uniformity of mixing is low. There is no need for fly ash and magnetic material to be fully and uniformly mixed. Therefore, fly ash and magnetic material are mixed only through the feed screw of the pyrolysis furnace. There is no need to configure an additional stirrer for mechanical mixing. The system is relatively simple and the equipment investment and operating costs are low.
[0035] 5. This invention adds magnetic particles to the pyrolysis furnace, which increases the heat conduction and radiative heat absorption of the materials in the furnace, thereby enhancing the heat transfer of fly ash and increasing the processing capacity of the pyrolysis furnace by more than 1.5 times.
[0036] 6. When this invention utilizes both fly ash granulation and the addition of magnetic particles simultaneously in a pyrolysis furnace, it increases the overall processing capacity of the furnace by more than two times, significantly improving its throughput and stability. The mechanism is as follows: This invention uses fly ash granulation followed by crushing to form a mixture of different particle sizes, including shaped fly ash particles and unshaped powdered fly ash, increasing the bulk density of the fly ash by 1.5 to 2 times. Generally, the original bulk density of fly ash is around 0.5 to 0.7 t / m³, and the fly ash filling rate in the pyrolysis furnace is 8 to 15%. Industrial pyrolysis furnaces are designed and their dimensions are determined based on the volumetric filling rate. That is, when the furnace size is determined, the volumetric filling rate is a key factor in its processing capacity. With a fixed volume, increasing the bulk density can improve the processing quality. Therefore, when the density of fly ash is increased by 2 times, the mass of the same volume of fly ash fed into the pyrolysis furnace increases by 2 times. However, due to the overall heat transfer within the furnace, a pyrolysis furnace of the same size cannot process fly ash with a mass greater than 2 times after the density is increased by 2 times; experimental data shows a mass increase of approximately 1.5 to 2 times. This invention achieves synergistic optimization of the material's packing structure and thermal conductivity through the combined effects of functional material addition, tableting, crushing and granulation, granulation molding, and the formation of particle size distribution among unformed fly ash. This increases the processing capacity of the pyrolysis furnace by more than 2 times.
[0037] 7. This invention can extend the service life of seals by 2 to 3 times or more. The mechanism is that after fly ash is granulated and pressed, the number of tiny particles smaller than 100 mesh in the fly ash is reduced by 50 to 70%, thus reducing the wear of seals caused by dust from tiny particles and extending the service life of seals by 2 to 3 times or more.
[0038] 8. This invention can extend the caking cycle of fly ash in the furnace by more than 2 times. The mechanism is as follows: after fly ash is granulated and pressed, the specific surface area and contact points of the fly ash are reduced, which effectively improves the bridging polymerization of fly ash. Therefore, the fluidity is increased, and it is not easy to cake on the furnace wall, thus extending the caking cycle of fly ash in the furnace by more than 2 times.
[0039] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description
[0040] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 is a schematic diagram of the low-temperature pyrolysis treatment system for municipal solid waste incineration fly ash of the present invention.
[0041] Figure reference numerals: 1. Feeding device; 2. Fly ash inlet; 3. Tableting machine; 3.1 Feeding screw of tableting machine; 3.2 Feeding hopper cover of tableting machine; 3.3 Feeding hopper of tableting machine; 3.4 Tableting machine body; 3.5 Hydraulic system; 4. Fly ash outlet; 5. Crusher; 6. Crusher outlet; 7. Fly ash feeding hopper; 8. Fly ash discharge valve; 9. Feeding port; 10. Circulating feed port; 11. Magnetic material feeding hopper; 12. Magnetic material discharge valve; 13. Magnetic material discharge port; 14. Pyrolysis furnace feeding screw; 15. Fly ash low-temperature pyrolysis furnace; 16. Pyrolysis furnace discharge port; 17. Belt conveyor; 18. Iron separator; 19. Sealing cover; 20. Dust suction hood; 21. Dust conveying pipeline; 22. Dust inlet; 23. Iron separator outlet; 24. Magnetic material conveying device; 25. Detailed Implementation
[0042] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.
[0043] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.
[0044] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.
[0045] Fly ash has low thermal conductivity and low bulk density. Therefore, increasing the thermal conductivity and bulk density of the material inside the furnace can increase the unit throughput of the rotary pyrolysis furnace, reduce investment, and improve operational economics. Fly ash is prone to caking and damaging seals inside the rotary pyrolysis furnace. Therefore, improving the properties of fly ash can slow down the caking and unclogging cycle and reduce the frequency of seal replacement.
[0046] This invention increases the bulk density of fly ash by granulation and adds magnetic particles to increase thermal conductivity, thereby increasing the unit throughput of the rotary pyrolysis furnace and reducing equipment investment and operating costs. Granulation and the addition of magnetic particles also improve the flowability of fly ash, making it less prone to caking in the conveying pipeline and pyrolysis furnace, thus extending the caking and unclogging cycle. Granulation also reduces dust generation in the pyrolysis furnace, reduces wear on seals, and reduces the frequency of seal replacement.
[0047] Example 1 (Refer to Figure 1) illustrates a low-temperature pyrolysis treatment system for fly ash from municipal solid waste incineration. The figure shows the following structures and their relative positions: 1. Feeding device; 2. Fly ash inlet; 3. Tableting machine; 3.1. Feeding screw of the tableting machine; 3.2. Feed bin cover of the tableting machine; 3.3. Feed bin of the tableting machine; 3.4. Tableting machine body; 3.5. Hydraulic system; 4. Fly ash outlet; 5. Crusher; 6. Crusher outlet; 7. Fly ash feed bin; 8. Fly ash discharge bin. The system comprises a fly ash granulation system (8), a fly ash discharge port (9), a feeding port (10), a circulating feed port (11), a magnetic material feed hopper (12), a magnetic material discharge valve (13), a magnetic material discharge port (14), a pyrolysis furnace feed screw (15), a fly ash low-temperature pyrolysis furnace (16), a pyrolysis furnace discharge port (17), a belt conveyor (18), an iron remover (19), a sealing cover (20), a dust collection hood (21), a dust conveying pipeline (22), a dust feed port (23), an iron remover discharge port (24), and a magnetic material conveying device (25). The system consists of a fly ash granulation and pelletizing system, a fly ash pyrolysis and magnetic material circulation system, and a dust collection system.
[0048] The fly ash tableting and granulation system includes a feeding device 1, a tablet press 3, a crusher 5, and a fly ash feed hopper 7 arranged sequentially along the material flow direction; the feed hopper cover 3.2 of the tablet press is provided with a fly ash feed inlet 2 and a dust feed inlet 23; the lower part of the fly ash feed hopper 7 is provided with a fly ash discharge port 9, and a fly ash discharge valve 8 is provided at the fly ash discharge port.
[0049] The fly ash pyrolysis and magnetic material circulation system includes a magnetic material feed hopper 12, a pyrolysis furnace feed screw 15, a fly ash low-temperature pyrolysis furnace 16, a belt conveyor 18, and an iron separator 19 located above the belt conveyor 18, arranged sequentially along the material flow direction. The magnetic material feed hopper 12 has a feeding port 10 and a circulating feed port 11 at its upper part and a magnetic material discharge port 14 at its lower part. A magnetic material discharge valve 13 is provided at the magnetic material discharge port. The circulating feed port 11 is connected to the iron separator 19 through a magnetic material conveying device 25. The magnetic material discharge valve 13 is interlocked with the fly ash discharge valve 8. The magnetic material feed hopper 12 and the fly ash feed hopper 7 are located above the pyrolysis furnace feed screw 15, and the fly ash discharge port 9 and the magnetic material discharge port 14 are connected to the pyrolysis furnace feed screw 15.
[0050] The dust collection system includes a sealing cover 20 installed above the belt conveyor 18 to seal the space above the belt conveyor, and a dust collection cover 21 connected to the sealing cover 20. The dust collection cover 21 is connected to the dust inlet 23 of the tablet press through a dust conveying pipe 22.
[0051] In this embodiment, the tablet press 3 can be a roller press, the magnetic material conveying device 25 can be a screw conveyor or a belt conveyor, the feeding device 1 can be a feeding screw, and the iron remover 19 can be a bag iron remover.
[0052] Fly ash enters the tablet press 3 from the feeding device 1 through the fly ash inlet 2 connected to it. The fly ash after tableting and the fly ash before tableting both enter the crusher 5 through the fly ash outlet 4. The crusher 5 crushes the mixture of tableted and un-tableted fly ash and then enters the fly ash feed hopper 7 through the crusher outlet 6.
[0053] The tablet press 3 has two feed inlets on its feed hopper cover 3.2: a fly ash feed inlet 2 and a dust feed inlet 23. The dust feed inlet 23 receives dust from the system conveyed by the dust conveying pipe 22. The tablet press's feed screw 3.1 is a shaftless screw, and its diameter gradually decreases from top to bottom along with the diameter of the feed hopper 3.3, allowing the fly ash to enter the tablet press body 3.4 more effectively. Within the tablet press body 3.4, the fly ash is compressed into tablets by two rollers.
[0054] Below the fly ash feed hopper 7 is a fly ash discharge valve 8, which is connected to the pyrolysis furnace feed screw 15 via the fly ash discharge port 9. Above the magnetic material feed hopper 12 are two feed ports: a circulation feed port 11 and a feeding port 10. The feeding port 10 is for adding new magnetic material, while the circulation feed port receives the system-circulated magnetic material conveyed by the magnetic material conveying device 25.
[0055] The magnetic material feed hopper 12 is equipped with a level gauge. When the material level falls below the level gauge, an alarm is triggered to remind the user to add material. Magnetic material can also be added manually. The magnetic material discharge valve 13 below the magnetic material feed hopper 12 is interlocked with the fly ash discharge valve 8. Parameters can be set to adjust the frequency of the magnetic material discharge valve 13 and the fly ash discharge valve 8 to regulate the ratio of magnetic material to fly ash. The discharge valve 13 and the fly ash discharge valve 8 are connected to the pyrolysis furnace feed screw 15 through the magnetic material discharge port 14 and the fly ash discharge port 9, respectively. Magnetic material and fly ash are conveyed to the fly ash low-temperature pyrolysis furnace 16 through the pyrolysis furnace feed screw 15. The positions of the magnetic material feed hopper 12 and the fly ash feed hopper 7 above the pyrolysis furnace feed screw 15 are not differentiated by front or back; they only need to be added in a certain proportion and mixed in the pyrolysis furnace feed screw 15 without needing to be uniformly mixed.
[0056] The fly ash low-temperature pyrolysis furnace 16 is connected to the belt conveyor 18 via the pyrolysis furnace discharge port 17. A magnetic separator 19 is suspended above the belt conveyor 18. The magnetic separator 19 uses magnetic adsorption to separate the magnetic material from the fly ash mixture. The separated magnetic material enters the magnetic material conveying device 25 through the magnetic separator discharge port 24, and is then conveyed to the circulating feed port 11, and finally into the magnetic material feed hopper 12. The space above the belt conveyor is sealed by a sealing cover 20 to prevent dust leakage. A dust collection hood 21 is connected above the sealing cover, and the collected dust enters the tablet press 3 through the dust conveying pipe 22 and the dust feed port 23.
[0057] Fly ash enters the tablet press 3 through the feeding device 1 and the fly ash inlet 2 connected to the feeding device 1. The tablet press 3, based on the model dimensions of the two support rollers, compresses a portion of the fly ash into blocks 50-100 mm long, 5-10 mm wide, and 1-5 mm thick. The block size can be adjusted by changing the support roller model. The tablet press 3 has a tableting success rate of approximately 50-70%. This invention does not require classifying the fly ash from the tablet press 3 outlet into powder and block forms, eliminating the need for screening equipment. The fly ash feeding speed is primarily adjusted by the feeding screw 3.1 of the tablet press, which is controlled by adjusting the motor frequency of the feeding screw 3.1.
[0058] The fly ash mixture formed by the tableting process of the tablet press 3 and the unformed fly ash enters the crusher 5 through the fly ash outlet 4. The crusher 5 crushes the fly ash mixture, and the crushed fly ash mixture then enters the fly ash feed hopper 7 through the crusher outlet 6. The fly ash exiting the crusher 5 is mainly a mixture of fly ash particles with a diameter of 50μm~10mm. By filling the voids in the larger formed fly ash particles with small-diameter fly ash powder, the bulk density of the fly ash can be increased to 1~1.5t / m³. 3 Crusher 5 should preferably be an impact crusher, utilizing high-speed rotating blades to impact and crush the fly ash during tableting. The tablet press's feed hopper cover 3.2 has two feed inlets: a fly ash feed inlet 2 and a dust feed inlet 23. The dust feed inlet receives dust from the system conveyed by the dust conveying pipe 22. The amount of dust fed through the dust feed inlet 23 is very small, approximately 2-5% of the total fly ash feed, and has minimal impact on the bulk density of fly ash in the fly ash feed hopper 7.
[0059] The circulation volume of magnetic material is approximately 10-30% of the fly ash treatment volume. This ratio effectively improves the heat transfer efficiency of fly ash while having minimal impact on system wear and load. The magnetic material feed hopper 12 has a level gauge; when the material level falls below the level mark, an alarm is triggered to remind the user to add material. Because the magnetic material circulates within the system, the daily loss is approximately 2-3%, requiring infrequent additions. Manual addition is possible, eliminating the need for automation. For example, if the initial circulation volume of magnetic material is 30% of the fly ash treatment volume, it takes 7-10 days to reduce it to 10%, during which time no additional magnetic material is needed. To ensure proper mixing of the magnetic material with the fly ash while minimizing the amount of magnetic material carried by the fly ash, a particle size of 1-5 mm is recommended for the magnetic material.
[0060] The magnetic material discharge valve 13 below the magnetic material feed hopper 12 is interlocked with the fly ash discharge valve 8. The frequency of the magnetic material discharge valve 13 and the fly ash discharge valve 8 can be adjusted by setting parameters to regulate the ratio of magnetic material to fly ash. The magnetic material discharge valve 13 and the fly ash discharge valve 8 are connected to the pyrolysis furnace feed screw 15 through the magnetic material discharge port 14 and the fly ash discharge port 9, respectively. The magnetic material and fly ash are transported to the fly ash low-temperature pyrolysis furnace 16 through the pyrolysis furnace feed screw 15. The magnetic material feed hopper 12 and the fly ash feed hopper 7 are not positioned in a front-to-back manner above the pyrolysis furnace feed screw 15. They only need to be fed in a certain proportion and mixed in the pyrolysis furnace feed screw 15, and uniform mixing is not required.
[0061] The fly ash low-temperature pyrolysis furnace 16 adopts a rotary pyrolysis furnace. During the forward conveying process of magnetic materials and fly ash in the fly ash low-temperature pyrolysis furnace 16, the mixture of magnetic materials and fly ash is continuously stirred and mixed. Magnetic materials have characteristics such as high thermal conductivity and strong radiation absorption capacity, and have good absorption of radiation and heat transfer properties of the pyrolysis furnace. Through heat transfer by mixing and contacting with fly ash, magnetic materials can quickly transfer the heat absorbed by them to fly ash, improve the heat transfer effect of fly ash, and accelerate the heating time of fly ash.
[0062] After the fly ash and magnetic material mixture is discharged from the fly ash low-temperature pyrolysis furnace 16 to the belt conveyor 18, the magnetic material is separated from the mixture by the iron separator 19. The separated magnetic material enters the magnetic material conveying device 25 through the iron separator outlet 24, and is then conveyed to the circulating feed inlet 11, and then into the magnetic material feed hopper 12 to complete the cycle. The magnetic material conveying device 25 can be a screw conveyor or a belt conveyor. During operation, it needs to automatically convey the magnetic material back to the magnetic material feed hopper 12 to ensure the normal operation of production.
[0063] The space above the belt conveyor is vacuumed using a negative pressure dust extraction method to prevent dust from being generated and overflowing during the separation of magnetic materials and fly ash. The extracted dust enters the tablet press 3 through the dust conveying pipe 22 and the dust inlet 23 and returns to the processing system.
[0064] Example 2: A method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash. Based on the above-mentioned treatment system, a low-temperature pyrolysis process is adopted. The fly ash is granulated through a flaking and crushing process without screening, forming a mixture of different particle sizes, including shaped granulated fly ash and unshaped powdered fly ash. The method includes the following steps: S1: Fly ash is fed into a flaking machine 3 via a feeding device 1 and flaked. The flaked and unflaked fly ash are directly fed into a crusher 5 for crushing, forming a mixture of 50μm~10mm particle sizes; S2: Fly ash and magnetic materials are fed into the pyrolysis furnace feeding screw 15 at a ratio of 100:10~100:30 through an interlocked fly ash discharge valve 8 and a magnetic material discharge valve 13, respectively; S3: The mixture is fed into a low-temperature fly ash pyrolysis furnace 16 for pyrolysis at 300~500℃, and heat transfer is enhanced by magnetic materials; S4: The pyrolysis products are conveyed by belt conveyor 18. During the conveying process, magnetic materials are separated by iron separator 19 and returned to magnetic material feed hopper 12. At the same time, dust is collected by dust collection system and returned to tablet press 3. The fly ash products after separation of magnetic materials are then washed, desalinated and recycled.
[0065] This invention is applied in the field of low-temperature fly ash pyrolysis. During low-temperature pyrolysis, very few substances volatilize from the fly ash, and the gas inside the furnace is mainly nitrogen in a protective inert atmosphere. Therefore, the amount of dust generated from fly ash volatilization is minimal. This invention does not require all fly ash to be granulated; it only uses a pressing and crushing process, resulting in a relatively simplified device structure. Furthermore, because it is a mixture of fly ash with different particle sizes, the bulk density of the fly ash is approximately 10-20% higher than that of fly ash composed entirely of particles. In low-temperature pyrolysis furnaces where bulk density is a major factor affecting throughput, the granulation method of this invention can increase throughput by 10-20%. Since low-temperature pyrolysis does not change the particle morphology, dioxins will volatilize from the granulation voids. To avoid affecting dioxin decomposition, this invention controls the hydraulic pressure of the pressing process, ensuring that the hydraulic pressure of the granulation does not exceed 5 MPa. The fly ash granulation method of this invention not only significantly improves the bulk density of fly ash but also improves fly ash flowability, slows down caking, and extends the sealing cycle.
[0066] This invention increases the bulk density of fly ash through granulation and pelletizing, thereby enhancing the throughput of the rotary pyrolysis furnace. Granulation and pelletizing also improves the flowability of the fly ash, alleviating caking within the furnace. Furthermore, it reduces the number of fine particles in the material, minimizing wear on seals caused by dust and extending their service life. By granulating and pelletizing fly ash, the invention achieves the goals of increasing the throughput and operational stability of the pyrolysis furnace, and extending maintenance cycles. Adding magnetic particles to the pyrolysis furnace increases the thermal conductivity and radiative heat absorption of the materials within the furnace, thus enhancing heat transfer from the fly ash and improving the furnace's processing capacity.
[0067] This invention significantly improves the unit processing capacity of the pyrolysis furnace by granulating fly ash and adding magnetic materials, improves the flowability of fly ash, reduces caking and wear of seals in the furnace, realizes the recycling of magnetic materials and low-cost collection and treatment of dust, and has the advantages of high processing efficiency, low operating cost and simple maintenance.
[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A low-temperature pyrolysis treatment system for fly ash from municipal solid waste incineration, characterized in that: The system includes a fly ash tableting and granulation system, a fly ash pyrolysis and magnetic material circulation system, and a dust collection system. The fly ash tableting and granulation system includes a feeding device (1), a tablet press (3), a crusher (5), and a fly ash feed hopper (7) arranged sequentially along the material flow direction. The feed hopper cover (3.2) of the tablet press is provided with a fly ash inlet (2). The lower part of the fly ash feed hopper (7) is provided with a fly ash discharge port (9), and a fly ash discharge valve (8) is provided at the fly ash discharge port. The fly ash pyrolysis and magnetic material circulation system includes a magnetic material feed hopper (12), a pyrolysis furnace feed screw (15), a fly ash low-temperature pyrolysis furnace (16), a belt conveyor (18), and an iron remover (19) located above the belt conveyor (18). The upper part of the magnetic material feed hopper (12) is provided with a fly ash discharge port (9). The feeding port (10) and the circulating feeding port (11) are equipped with a magnetic material discharge port (14) at the bottom and a magnetic material discharge valve (13) at the magnetic material discharge port; the circulating feeding port (11) is connected to the iron remover (19) through the magnetic material conveying device (25); the magnetic material discharge valve (13) is interlocked with the fly ash discharge valve (8); the magnetic material feeding bin (12) and the fly ash feeding bin (7) are located above the pyrolysis furnace feeding screw (15), and the fly ash discharge port (9) and the magnetic material discharge port (14) are connected to the pyrolysis furnace feeding screw (15); the dust collection system uses negative pressure dust collection to collect dust, including a sealing cover (20) set above the belt conveyor (18) to seal the space above the belt conveyor, and a dust collection cover (21) connected to the sealing cover (20).
2. The low-temperature pyrolysis treatment system for municipal solid waste incineration fly ash according to claim 1, characterized in that: The dust hood (21) is connected to the dust inlet (23) of the tablet press (3) through the dust conveying pipe (22). The dust inlet (23) is located on the feed hopper cover (3.2) of the tablet press.
3. The low-temperature pyrolysis treatment system for municipal solid waste incineration fly ash according to claim 1, characterized in that: The feed screw (3.1) of the tablet press is a shaftless screw, and the screw diameter gradually decreases from top to bottom along with the diameter of the feed hopper (3.3) of the tablet press.
4. The low-temperature pyrolysis treatment system for municipal solid waste incineration fly ash according to claim 1, characterized in that: The tablet press (3) is a roller press. The roller surface model of the tablet press (3) is detachable. The tablet press (3) can adjust the tablet size by changing the roller surface model.
5. The low-temperature pyrolysis treatment system for municipal solid waste incineration fly ash according to claim 1, characterized in that: The crusher (5) is an impact crusher so that the particle size of the fly ash after crushing is in the range of 50μm~10mm.
6. The low-temperature pyrolysis treatment system for municipal solid waste incineration fly ash according to claim 1, characterized in that: The magnetic material feeding hopper (12) is equipped with a material level gauge to trigger an alarm to remind the user to add material when the material level is lower than the required level.
7. The low-temperature pyrolysis treatment system for municipal solid waste incineration fly ash according to claim 1, characterized in that: The fly ash low-temperature pyrolysis furnace (16) is a rotary pyrolysis furnace, the magnetic material conveying device (25) is a screw conveyor or belt conveyor, the feeding device (1) is a feeding screw, and the iron remover (19) is a bag iron remover.
8. A method for low-temperature pyrolysis treatment of fly ash from municipal solid waste incineration, characterized in that: Based on the processing system described in any one of claims 1 to 7, a low-temperature pyrolysis process is adopted to granulate fly ash through a tableting and crushing process without screening, forming a mixture of different particle sizes, including shaped granulated fly ash and unshaped powdered fly ash, including the following steps: S1 Fly ash enters the tableting machine (3) through the feeding device (1) for tableting, and the tableted and un-tableted fly ash directly enters the crusher (5) for crushing to form a mixture of 50μm~10mm particle size; S2 Fly ash and magnetic materials are respectively mixed by the fly ash discharge valve (8) and magnetic material discharge valve (13) controlled by interlocking at a ratio of 100:10~100:30 into the pyrolysis furnace feeding screw (15); S3 The mixture enters the fly ash low-temperature pyrolysis furnace (16) for pyrolysis, and heat transfer is enhanced by the magnetic material; S4 The pyrolysis products are transported by the belt conveyor (18), and the magnetic material is separated by the iron remover (19) during the transport process. The magnetic material is returned to the magnetic material feeding hopper (12), and the dust is collected by the dust collection system.
9. The method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash according to claim 8, characterized in that: The circulation volume of magnetic material is 10-30% of the fly ash treatment volume. The initial circulation volume of magnetic material is 30% of the fly ash treatment volume, and it is added back to 30% when it drops to 10%.
10. The method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash according to claim 8, characterized in that: In step S4, the dust collected by the dust collection system is returned to the tablet press (3).
11. The method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash according to claim 8, characterized in that: The dust feed rate at the dust inlet (23) is 2% to 5% of the total fly ash feed rate.
12. The method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash according to claim 8, characterized in that: The particle size of the magnetic material is 1~5mm.
13. The method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash according to claim 8, characterized in that: The hydraulic pressure used for tablet compression should not exceed 5 MPa.
14. The method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash according to claim 8, characterized in that: The tablets are 50-100mm long, 5-10mm wide, and 1-5mm thick.
15. The method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash according to claim 8, characterized in that: The bulk density of the fly ash after crushing is 1~1.5t / m³.
16. The method for low-temperature pyrolysis treatment of municipal solid waste incineration fly ash according to claim 8, characterized in that: The mixing of fly ash and magnetic materials is carried out only by the feed screw (15) of the pyrolysis furnace, without the need for additional mechanical mixing by a stirrer.