Fly ash pelletizing system, fly ash low temperature pyrolysis processing system and method

Abstract

This invention relates to a fly ash granulation and pelletizing system, a fly ash low-temperature pyrolysis treatment system and method, belonging to the technical field of fly ash treatment for municipal solid waste incineration. The fly ash granulation and pelletizing system includes a feeding device, a granulator, a crusher, and a fly ash feed hopper arranged sequentially along the material flow direction; the feed hopper cover of the granulator is provided with a fly ash inlet; the lower part of the fly ash feed hopper is provided with a fly ash discharge port, and a fly ash discharge valve is provided at the fly ash discharge port. This invention granulates fly ash through a granulation and crushing process, forming a mixture with a particle size of 50μm~10mm and a bulk density of 1~1.5t / m³. 3 This significantly improves the throughput and operational stability of the pyrolysis process.

Description

Technical Field

[0001] This invention belongs to the field of fly ash treatment technology for municipal solid waste incineration, and relates to fly ash granulation and pelletizing system, fly ash low-temperature pyrolysis treatment system and method. 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 kiln wall and the 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 adopt 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 fly ash tableting and granulation system, a fly ash low-temperature pyrolysis treatment system and method, 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 fly ash tableting and granulation system includes a feeding device, a tablet press, a crusher, and a fly ash feed hopper arranged sequentially along the material flow direction; the feed hopper cover of the tablet press is provided with a fly ash inlet; the lower part of the fly ash feed hopper is provided with a fly ash discharge port, and a fly ash discharge valve is provided at the fly ash discharge port.

[0012] 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.

[0013] 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.

[0014] Optionally, the crusher is an impact crusher so that the particle size of the crushed fly ash ranges from 50μm to 10mm.

[0015] Optionally, the feeding device is a feeding screw.

[0016] A low-temperature pyrolysis treatment system for fly ash includes a fly ash tableting and granulation system, a pyrolysis furnace feeding device, and a low-temperature pyrolysis furnace arranged sequentially along the material flow direction. The fly ash tableting and granulation system is the fly ash tableting and granulation system described above.

[0017] Optionally, the fly ash low-temperature pyrolysis furnace is a rotary pyrolysis furnace.

[0018] Optionally, the pyrolysis furnace feeding device is a pyrolysis furnace feeding screw.

[0019] A method for low-temperature pyrolysis treatment of fly ash, the aforementioned treatment system employing a low-temperature pyrolysis process, granulates the fly ash through a granulation and crushing process, without screening, forming a mixture of different particle sizes, comprising shaped granulated fly ash and unshaped powdered fly ash, including the following steps: S1 fly ash enters the tablet press via the feeding device for tableting. The tableted and unpressed fly ash are directly fed into the crusher for crushing, forming a mixture with a particle size of 50μm~10mm. S2 fly ash enters the pyrolysis furnace feeding device through the fly ash discharge valve; S3 fly ash enters the fly ash low-temperature pyrolysis furnace for pyrolysis through the pyrolysis furnace feeding device.

[0020] Optionally, the bulk density of the fly ash after crushing is 1~1.5t / m³.

[0021] Optionally, the tablets are 50-100 mm long, 5-10 mm wide, and 1-5 mm thick.

[0022] Optionally, the hydraulic pressure used for tablet compression shall not exceed 5 MPa.

[0023] The beneficial effects of this invention are as follows: 1. This invention uses fly ash granulation to form a mixture of different particle sizes, including shaped fly ash particles and unshaped powdered fly ash. This allows the bulk density of the crushed fly ash to reach 1~1.5 t / m³, increasing the bulk density of fly ash by 1.5~2 times. Generally, the original bulk density of fly ash is around 0.5~0.7 t / m³, and the fly ash filling rate in the pyrolysis furnace is 8~15%. Therefore, this invention significantly improves the bulk density of fly ash and increases the throughput of the pyrolysis furnace.

[0024] 2. 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.

[0025] 3. 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.

[0026] 4. 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.

[0027] 5. 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.

[0028] 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

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the fly ash tableting and granulation system of the present invention; Figure 2 This is a schematic diagram of the fly ash low-temperature pyrolysis treatment system of the present invention.

[0030] Figure reference numerals: 1. Feeding device; 2. Fly ash inlet; 3. Tableting machine; 3.1 Feeding screw of tableting machine; 3.2 Feeding bin cover of tableting machine; 3.3 Feeding bin 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 bin; 8. Fly ash discharge valve; 9. Pyrolysis furnace feeding device; 10. Fly ash low-temperature pyrolysis furnace; 11. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] This invention increases the bulk density of fly ash by granulating it into pellets, thereby increasing the unit throughput of the rotary pyrolysis furnace and reducing equipment investment and operating costs. Granulation also improves 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. Furthermore, granulation reduces dust generation in the pyrolysis furnace, reduces wear on seals, and decreases the frequency of seal replacement.

[0036] Example 1 Please see Figure 1The figure shows a fly ash tableting and granulation system, including the following structures and their relative positions: feeding device 1, fly ash inlet 2, tablet press 3, feeding screw 3.1 of the tablet press 3, feeding hopper cover 3.2 of the tablet press 3.3, tablet press body 3.4, hydraulic system 3.5, fly ash outlet 4, crusher 5, crusher outlet 6, fly ash feed hopper 7, fly ash discharge valve 8, and fly ash discharge port 9. The system comprises a feeding device 1, tablet press 3, crusher 5, and fly ash feed hopper 7 arranged sequentially along the material flow direction. The feeding hopper cover 3.2 of the tablet press has a fly ash inlet 2. The feeding screw 3.1 of the tablet press is a shaftless screw, and its diameter gradually decreases from top to bottom along with the diameter of the feeding hopper 3.3 of the tablet press, allowing the fly ash to enter the tablet press body 3.4 more effectively. Fly ash is compressed into tablets by two rollers in the tablet press body 3.4. A fly ash discharge port 9 is located at the bottom of the fly ash feed hopper 7, and a fly ash discharge valve 8 is located at the fly ash discharge port. In this embodiment, the tablet press 3 can be a roller press, and the feeding device 1 can be a feeding screw.

[0037] 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.

[0038] The tablet press 3, based on the model dimensions of the two idler rollers, compresses a portion of the fly ash into blocks 50-100mm long, 5-10mm wide, and 1-5mm thick. The block size can be adjusted by changing the idler 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 feed rate of the fly ash tablets is primarily adjusted by the feed screw 3.1 of the tablet press, which is controlled by adjusting the motor frequency of the feed screw 3.1.

[0039] The fly ash from the outlet of crusher 5 is mainly a mixture of fly ash particles with a diameter of 50μm to 10mm. By filling the voids in the larger shaped 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 be an impact crusher, which uses high-speed rotating blades to impact and crush the fly ash of the crusher.

[0040] Example 2 Please see Figures 1-2This is a low-temperature pyrolysis treatment system for fly ash, comprising a fly ash granulation and pelletizing system, a pyrolysis furnace feeding device 10, and a low-temperature pyrolysis furnace 11 arranged sequentially along the material flow direction; a fly ash discharge valve 8 is connected to the pyrolysis furnace feeding device 10 through a fly ash discharge port 9; the low-temperature pyrolysis furnace is a rotary pyrolysis furnace; and the pyrolysis furnace feeding device is a pyrolysis furnace feeding screw.

[0041] Example 3 A method for low-temperature pyrolysis treatment of fly ash, based on the above-mentioned treatment system, employs a low-temperature pyrolysis process to granulate fly ash through a granulation and crushing process, without the need for sieving, forming a mixture of different particle sizes, including shaped granulated fly ash and unshaped powdered fly ash, comprising the following steps: S1 fly ash enters the tablet press 3 through the feeding device 1 for tableting. The hydraulic pressure used for tableting is not higher than 5 MPa. The size of the tablet is 50~100 mm long, 5~10 mm wide, and 1~5 mm thick. The tablets and unpressed fly ash are directly fed into the crusher 5 for crushing to form a mixture with a particle size of 50 μm~10 mm. S2 fly ash enters the pyrolysis furnace feeding device 10 through fly ash discharge valve 8; S3 fly ash enters the fly ash low-temperature pyrolysis furnace 11 through the pyrolysis furnace feeding device 10 for pyrolysis; the fly ash products after pyrolysis are then subjected to subsequent water washing, desalination and resource utilization.

[0042] 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.

[0043] This invention increases the bulk density of fly ash through granulation and pelletizing, thereby improving the throughput of the rotary pyrolysis furnace. Granulation and pelletizing also improves the flowability of fly ash, alleviating caking within the furnace. Furthermore, granulation and pelletizing reduce the number of fine particles in the material, minimizing wear on seals caused by dust and extending their service life. Ultimately, granulation and pelletizing achieves the goals of increasing the throughput and operational stability of the pyrolysis furnace, and extending maintenance cycles.

[0044] This invention significantly improves the unit processing capacity of the pyrolysis furnace by granulating fly ash into pellets, improves the fluidity of fly ash, reduces caking in the furnace and wear of seals, and has the advantages of high processing efficiency, low operating cost and simple maintenance.

[0045] 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 fly ash tableting and granulation system, characterized in that: It 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.

2. The fly ash tableting and granulation system 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.

3. The fly ash tableting and granulation system 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.

4. The fly ash tableting and granulation system 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.

5. The fly ash low-temperature pyrolysis treatment system according to claim 1, characterized in that: The feeding device (1) is a feeding screw.

6. A fly ash low-temperature pyrolysis treatment system, comprising a fly ash granulation and pelletizing system, a pyrolysis furnace feeding device (10), and a fly ash low-temperature pyrolysis furnace (11) arranged sequentially along the material flow direction, characterized in that: The fly ash tableting and granulation system is the fly ash tableting and granulation system as described in any one of claims 1 to 5.

7. The fly ash low-temperature pyrolysis treatment system according to claim 6, characterized in that: The fly ash low-temperature pyrolysis furnace (11) is a rotary pyrolysis furnace.

8. The fly ash low-temperature pyrolysis treatment system according to claim 6, characterized in that: The pyrolysis furnace feeding device (10) is a pyrolysis furnace feeding screw.

9. A method for low-temperature pyrolysis treatment of fly ash, characterized in that: Based on the processing system described in claim 6, a low-temperature pyrolysis process is used to granulate fly ash through a tableting and crushing process, without the need for sieving, forming a mixture of different particle sizes, including shaped fly ash particles and unshaped powdered fly ash, comprising the following steps: S1 fly ash enters the tablet press (3) through the feeding device (1) for tableting. The tableted and unpressed fly ash directly enter the crusher (5) for crushing to form a mixture of particles with a diameter of 50μm~10mm. S2 fly ash enters the pyrolysis furnace feeding device (10) through the fly ash discharge valve (8); S3 fly ash enters the fly ash low-temperature pyrolysis furnace (11) through the pyrolysis furnace feeding device (10) for pyrolysis.

10. The method for low-temperature pyrolysis treatment of fly ash according to claim 9, characterized in that: The bulk density of the fly ash after crushing is 1~1.5t / m³.

11. The method for low-temperature pyrolysis treatment of fly ash according to claim 9, characterized in that: The tablets are 50-100mm long, 5-10mm wide, and 1-5mm thick.

12. The method for low-temperature pyrolysis treatment of fly ash according to claim 9, characterized in that: The hydraulic pressure used for tablet compression should not exceed 5 MPa.

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