Fly ash magnetic separation iron extraction system and method

Abstract

The invention discloses a coal ash magnetic separation iron extraction system and method. Comprising a bin pump system and a magnetic separation system, wherein the bin pump system comprises a first bin pump system (2) and a second bin pump (12); the magnetic separation system comprises first-stage magnetic separation and second-stage magnetic separation, the surge bin (5) is of a branch bin chamber structure, the lower part of the surge bin (5) is an ash bucket bin, each ash bucket bin is connected with an air locking feeder (6) and a first-stage magnetic separator (7), and each first-stage magnetic separator (7) is connected with a spiral conveyor (8); an outlet of the spiral conveyor (8) is connected with the secondary magnetic separator (9); and an inlet of the surge bin (5) is connected with the three-way switching valve (4). The invention has the advantages of strong adaptability, compact process flow, small occupied area and the like, and effectively solves the pollution problem of fly ash.

Description

Technical Field

[0001] The invention belongs to the technical field of fly ash resource comprehensive utilization, and specifically relates to a fly ash magnetic separation iron extraction system and method, which is suitable for the solid waste recovery field of fly ash from coal-fired power plants or industrial smoke containing magnetic iron oxide. Background Art

[0002] Fly ash is the fine ash captured by the electrostatic precipitator after the flue gas of coal combustion. It is one of the main solid wastes discharged by coal-fired power plants. Its main components are SiO2, Al2O3, Fe2O3, etc. Generally, the Fe2O3 mass content in fly ash is 5~10%, depending on factors such as coal type and combustion conditions. It is reported that my country's fly ash production in 2023 will reach 895 million tons, and its average comprehensive utilization rate is less than 70%. If 20% of fly ash is used to refine iron powder, it will generate greater economic benefits.

[0003] As a solid waste, fly ash was mainly treated by landfill and stacking in the early days. This method not only occupies a large area and pollutes the environment, but also causes huge waste of resources.

[0004] The existing magnetic separation processes are mainly divided into two types: wet magnetic separation and dry magnetic separation.

[0005] Patent document CN202211568752.9 discloses a method for preparing cement iron correction material using fly ash magnetic separation process, and proposes to use a wet separation method to use fly ash for magnetic separation-grinding-magnetic separation process to refine iron powder in fly ash.

[0006] Patent document CN221360413U discloses an online dry magnetic separation system for fly ash, in which fly ash first enters a fly ash storage tank through an ash conveying pipeline inlet, the bottom outlet of the fly ash storage tank is connected to a screw feeder, the screw feeder outlet is connected to a vacuum loader, the vacuum loader outlet is connected to the top of a buffer tank, the bottom outlet of the buffer tank is connected to an online dry magnetic separation device, magnetic separation is completed in the online dry magnetic separation device for fly ash, the obtained magnetic components enter a magnetic powder storage tank through a pipeline, the remaining fly ash enters a tail ash storage tank through a pipeline, and the fly ash in the tail ash storage tank returns to the storage tank of the original fly ash system through a unloading device; an air compressor is connected to the online dry magnetic separation device and provides the online dry magnetic separation device with compressed air that meets the requirements.

[0007] Although wet magnetic separation is widely used, it has problems such as large water consumption, large amount of wastewater generation, and easy environmental pollution. Compared with wet magnetic separation, dry magnetic separation has the advantages of no water source pollution, simple and flexible structure, and strong adaptability, but it also has the disadvantages of poor magnetic separation efficiency of a single device and difficulty in obtaining high-grade iron-rich products. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention provides a fly ash magnetic separation iron extraction system and method.

[0009] The inventors found through experimental research that setting up a first-stage magnetic separator can separate 20% to 30% of iron-containing materials in fly ash, and the magnetic separation efficiency of magnetic iron oxide in fly ash is over 95%. After setting up a two-stage magnetic separator, fly ash with an iron content of over 50% can be separated.

[0010] To achieve the purpose of the present invention, one aspect of the present invention provides a fly ash magnetic separation and iron extraction system, including a silo pump system and a magnetic separation system, the silo pump system including a first silo pump system and a second silo pump; the magnetic separation system includes a primary magnetic separation and a secondary magnetic separation, the primary magnetic separation is first connected in parallel and then in series with the secondary magnetic separation; the buffer silo is a divided chamber structure, the upper part of the buffer silo is a frame structure, and the lower part is an ash hopper silo, each ash hopper silo is respectively connected to an air lock feeder and a primary magnetic separator, and each primary magnetic separator is connected to a screw conveyor; the outlet of the screw conveyor is connected to the secondary magnetic separator; a first pneumatic double gate valve is arranged on the pipeline of the first silo pump to the ash storage, and a second pneumatic double gate valve is arranged on the pipeline of the first silo pump to the magnetic separation system; the inlet of the buffer silo is connected to a three-way switching valve.

[0011] Furthermore, the first-stage magnetic separator and the second-stage magnetic separator are respectively provided with a waste ash hopper; the second-stage magnetic separator is provided with a product hopper; the waste ash hopper is connected to a transfer bin, and the transfer bin is connected to a second bin pump; the product hopper is connected to a spiral metering scale.

[0012] Furthermore, there are four first-stage magnetic separators arranged in parallel; and then arranged in series with the second-stage magnetic separator; the screw conveyor is a horizontal screw conveyor with four inlets and one outlet, and two sets of symmetrical and opposite spiral blades are arranged on the screw shaft, and four feed ports are arranged on the top cover, which are connected to the first-stage magnetic separator in corresponding quantity, and a discharge port is arranged in the middle of the bottom of the box body, which is connected to the feed hopper of the second-stage magnetic separator.

[0013] Furthermore, the transfer bin is a conical bucket-type square bin, and a balance pipe is provided between the transfer bin and the buffer bin.

[0014] Furthermore, the four wall panels of the ash hopper bin of the buffer bin are provided with fluidizing plates; the buffer bin is provided with a vacuum pressure release valve, a bin top dust collector, a first radar type continuous level meter, a first radio frequency admittance type high level meter, and a first radio frequency admittance type low level meter.

[0015] Furthermore, the transfer warehouse is provided with a second radar type continuous material level meter, a second radio frequency admittance type high material level meter, and a second radio frequency admittance type low material level meter.

[0016] Furthermore, the first-stage magnetic separator and the second-stage magnetic separator are dry magnetic separators, using two-stage permanent magnetic rollers with a magnetic strength of 6000-10000Gs, and are provided with a blowing device, a magnetic swing, and a brush assembly.

[0017] Furthermore, the spiral weighing scale adopts a hoisting type weighing spiral scale, which connects the electronic weighing sensor and the spiral scale body through a hinge and is hung for installation.

[0018] Another aspect of the present invention provides a method for extracting iron from fly ash by magnetic separation, the steps of which include: S1: The fly ash captured by the electrostatic precipitator is collected in the ash hopper and transported by the first bin pump; Open the first pneumatic double-disc valve, close the second pneumatic double-disc valve, and transport the fly ash to the ash storage; Close the first pneumatic double-disc valve, open the second pneumatic double-disc valve, and transport the fly ash to the magnetic separation system; S2: Fly ash is transported to the buffer bin through the three-way switching valve, and the three three-way switching valves are switched in sequence to achieve uniform distribution to the sub-bins; S3: Clean compressed air is introduced into the fluidizing plate of the buffer bin to fluidize the fly ash. The air lock feeder is turned on by the fly ash’s own weight to quantitatively feed the fly ash to the primary magnetic separator. S4: The primary magnetic separator uses magnetic adsorption and centrifugal action on magnetic iron oxide to achieve rough separation of fly ash, which can separate fly ash with an iron content of 20% to 30% and primary waste ash with an iron content of less than 5%; S5: On the one hand, the iron-containing fly ash after rough selection is collected by a screw conveyor, and on the other hand, the secondary waste ash is transported to the transfer bin; S6: The iron-containing fly ash is discharged from the outlet of the screw conveyor to the secondary magnetic separator, where it is finely magnetically separated under the action of a strong magnetic field of 6000~10000Gs, and iron-rich products with an iron content of more than 50% and secondary waste ash can be separated; S7: The selected iron-rich products are collected and transported by means of a spiral metering scale. The secondary waste ash is transported to the transfer bin and then to the ash storage via the second bin pump.

[0019] In the process of the present invention, the fly ash captured by the electrostatic precipitator enters the magnetic separation system through the first bin pump system, and a three-way switching valve is arranged on the pipeline between the first bin pump system and the buffer bin. The reversing function of the three-way switching valve can realize the uniform distribution of the fly ash in different zones.

[0020] In the process of the present invention, the buffer bin is provided with multiple chambers, and an air lock feeder and a primary magnetic separator are arranged under each chamber. The fly ash can be quantitatively fed through the air lock feeder and roughly separated through the primary magnetic separator. After the rough separation, primary waste ash and iron-containing fly ash can be obtained. The primary waste ash enters the transfer bin, and the iron-containing fly ash is transported to the secondary magnetic separator by a screw conveyor.

[0021] In the process of the present invention, secondary waste ash and iron-rich products can be obtained after fine magnetic separation in the secondary magnetic separator; the secondary waste ash also enters the transfer bin and is finally transported to the ash storage through the bin pump, while the iron-rich product is collected and transported after accurate weighing by a spiral metering scale.

[0022] The three-way switching valve is a pneumatic switching valve that can achieve fast and automatic switching. The center line angle of the two outlet directions is 30°, and it has a reversing function.

[0023] The buffer bin is a sub-chamber with a connected structure without partitions inside. By cooperating with a three-way switching valve, fly ash can be evenly distributed in the buffer bin.

[0024] The four wall plates of the ash hopper of the buffer bin are provided with fluidizing plates, and the introduction of clean compressed air can keep the fly ash in the bin in a fluidized state without dead corners.

[0025] The buffer bin is provided with a vacuum pressure release valve, which adopts a 508 diaphragm vacuum pressure release valve, and can automatically release overpressure and vacuum pressure to ensure the safety of the equipment and the system.

[0026] The buffer bin is provided with a bin top dust collector, and the processing capacity is designed according to the amount of compressed air supplied to the electrostatic precipitator, so as to ensure that the conveying pressure is released quickly.

[0027] The buffer bin adopts a combination of a radar type continuous material level meter and a radio frequency admittance type high and low material level meter, which can realize over-material level alarm and real-time monitoring of material level height.

[0028] The magnetic separator is a dry magnetic separator, which adopts a "parallel + series" two-stage magnetic separation layout mode and has the functions of blowing and dust collection. It can realize the efficient separation of magnetic iron oxide in fly ash and improve the iron grade. The magnetic separation rate of magnetic iron oxide in fly ash is as high as 95%. After secondary fine magnetic separation, an iron-rich product with an iron content of more than 50% can be obtained.

[0029] The spiral metering scale can realize the functions of quantitative conveying and weighing of materials.

[0030] Fluidizing plates are arranged on the wall plates on both sides of the cone hopper of the transfer bin, and compressed air is introduced to make the materials fluidized, thereby effectively preventing the materials from being blocked.

[0031] A balance pipe is installed between the transfer bin and the buffer bin to balance the pressure between the two bins and ensure stable operation of the system.

[0032] The transfer warehouse is provided with a radar type continuous material level meter and a radio frequency admittance type high and low material level meter, which can realize over-material level alarm and real-time monitoring of material level height.

[0033] The beneficial technical effects of the present invention are: (1) The use of multi-chamber buffer bin, three-way switching valve and interlocking control of air lock feeder can achieve uniform distribution and quantitative feeding of fly ash in different zones; (2) A two-stage magnetic separation layout mode of "parallel + series" is adopted to separate the magnetic iron oxide in fly ash. The magnetic separation efficiency of the magnetic iron oxide in fly ash is as high as over 95%, which improves the iron grade of the iron-rich product. The iron grade of the iron-rich product after magnetic separation is as high as over 50%, reaching the iron grade of iron-rich ore. It can be used as a raw material in the metal smelting process, realizing the high-value utilization of fly ash and effectively solving the pollution problem of fly ash. (3) The overall process of the present invention adopts a vertical arrangement, which has the advantages of strong adaptability, compact process flow, and small footprint; (4) It is easy to transform in situ and realize industrial production, and can be applied to the recycling of fly ash from coal-fired power plants or industrial smoke solid waste containing magnetic iron oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a process flow chart of a fly ash high-efficiency magnetic separation and iron extraction system.

[0035] In the figure: 1—first pneumatic double-disc valve; 2—first silo pump system; 3—second pneumatic double-disc valve; 4—three-way switching valve; 5—buffer silo; 6—air lock feeder; 7—first magnetic separator; 8—screw conveyor; 9—second magnetic separator; 10—screw metering scale; 11—transfer silo; 12—second silo pump; 13—vacuum pressure release valve; 14—first radar type continuous material level meter; 15—silo top dust collector; 16—first radio frequency admittance type high material level meter; 17—fluidizing plate; 18—first radio frequency admittance type low material level meter; 19—second radio frequency admittance type low material level meter; 20—second radio frequency admittance type high material level meter; 21—second radar type continuous material level meter. DETAILED DESCRIPTION

[0036] The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0037] like Figure 1As shown, a fly ash magnetic separation and iron extraction system includes a silo pump system and a magnetic separation system, the silo pump system includes a first silo pump system and a second silo pump; the magnetic separation system includes a primary magnetic separation and a secondary magnetic separation, the primary magnetic separation is first connected in parallel and then in series with the secondary magnetic separation; the buffer silo 5 is a divided chamber structure, the upper part of the buffer silo 5 is a frame structure, and the lower part is an ash hopper silo, each ash hopper silo is respectively connected to an air lock feeder 6 and a primary magnetic separator 7, each primary magnetic separator 7 is connected to a screw conveyor 8; the outlet of the screw conveyor 8 is connected to a secondary magnetic separator 9; a first pneumatic double gate valve 1 is arranged on the pipeline of the first silo pump 2 to the ash storage, and a second pneumatic double gate valve 3 is arranged on the pipeline of the first silo pump 2 to the magnetic separation system; the inlet of the buffer silo 5 is connected to a three-way switching valve 4.

[0038] The first-stage magnetic separator 7 and the second-stage magnetic separator 9 are respectively provided with a waste ash hopper; the second-stage magnetic separator 9 is provided with a product hopper; the waste ash hopper is connected to a transfer bin 11, and the transfer bin 11 is connected to a second bin pump 12; the product hopper is connected to a spiral metering scale 10.

[0039] There are four primary magnetic separators 7, which are arranged in parallel; and then they are arranged in series with the secondary magnetic separator 9; the screw conveyor 8 is a horizontal screw conveyor with four inlets and one outlet, and two sets of symmetrical and opposite spiral blades are arranged on the screw shaft. The top cover is provided with four feed ports, which are connected to the primary magnetic separator 7 in corresponding numbers, and a discharge port is arranged in the middle of the bottom of the box body, which is connected to the feed hopper of the secondary magnetic separator 9.

[0040] The transfer bin 11 is a cone-shaped square bin, and a balance pipe is arranged between the transfer bin 11 and the buffer bin 5 .

[0041] The four wall panels of the ash hopper bin of the buffer bin 5 are provided with fluidizing plates 17; the buffer bin 5 is provided with a vacuum pressure release valve 13, a bin top dust collector 15, a first radar type continuous material level meter 14 and a first radio frequency admittance type high material level meter 16, and a first radio frequency admittance type low material level meter 18.

[0042] The transfer warehouse 11 is provided with a second radar type continuous material level meter 21 , a second radio frequency admittance type high material level meter 20 , and a second radio frequency admittance type low material level meter 19 .

[0043] The primary magnetic separator 7 and the secondary magnetic separator 9 are dry magnetic separators, which use two-stage permanent magnetic rollers with a magnetic strength of 6000-10000 Gs, and are provided with a blowing device, a magnetic swing, and a brush assembly.

[0044] The spiral weighing scale 10 is a hanging type weighing spiral scale, in which an electronic weighing sensor and a spiral scale body are connected by a hinge and hung for installation.

[0045] Take a 300MW coal-fired power plant as an example.

[0046] Close the first pneumatic double-disc valve 1, start the second pneumatic double-disc valve 3, and the fly ash collected by the electrostatic precipitator is transported to the magnetic separation system through the first bin pump system. The designed ash transport capacity is 12t / h.

[0047] Buffer bin 5 is a hopper bin with separate chambers. It is connected inside and has no partition structure. The designed capacity is 36m 3 , through the three-way switching valve, the fly ash is evenly distributed in the sub-chamber.

[0048] A "parallel + series" two-stage magnetic separation layout mode is adopted. According to the amount of fly ash, four first-stage magnetic separators 7 are connected in parallel and connected in series with one second-stage magnetic separator 9. The design processing capacity of a single magnetic separator is 3t / h.

[0049] Furthermore, the fly ash is quantitatively conveyed to the primary magnetic separator 7 through the air lock feeder 6, and 10% of the iron-containing fly ash is separated through rough selection to obtain about 1.2 t / h of iron-containing fly ash with an iron content of 20% to 30%.

[0050] Furthermore, the iron-containing fly ash falls into the screw conveyor 8 by its own weight. The screw conveyor 8 has a designed processing capacity of 1.2 t / h and is equipped with a variable frequency adjustable motor with a frequency adjustment range of 0-50 Hz.

[0051] Furthermore, the iron-containing fly ash enters the secondary magnetic separator 9, and is finely selected through adsorption, ejection, re-adsorption, and re-ejection to separate an iron-rich product with an iron content of more than 50%, thereby obtaining about 0.6 t / h of an iron-rich product.

[0052] At this time, the comprehensive magnetic separation rate of magnetic iron oxide in fly ash can reach more than 95%, and the iron grade of the iron-rich product after fine magnetic separation can reach more than 50%, reaching the iron grade of iron-rich ore.

[0053] The above detailed description of the implementation scheme in conjunction with the accompanying drawings is only a preferred implementation scheme of the present invention. However, the present invention is not limited to the specific implementation details in the above scheme. Any modification or substitution made within the concept and principle of the present invention is within the protection scope of the present invention.

Claims

1. A fly ash magnetic separation iron extraction system, comprising a silo pump system and a magnetic separation system, characterized in that The silo pump system comprises a first silo pump system (2) and a second silo pump (12); the magnetic separation system comprises a primary magnetic separation system and a secondary magnetic separation system, wherein the primary magnetic separation system is first connected in parallel and then connected in series with the secondary magnetic separation system; the buffer silo (5) is a compartment structure, wherein the upper portion of the buffer silo (5) is a frame structure and the lower portion is an ash hopper silo, wherein each ash hopper silo is respectively connected to an air lock feeder (6) and a primary magnetic separator (7), and each primary magnetic separator (7) is connected to a screw conveyor (8); the outlet of the screw conveyor (8) is connected to a secondary magnetic separator (9); a first pneumatic double-disc valve (1) is arranged on a pipeline of the first silo pump (2) to the ash storage, and a second pneumatic double-disc valve (3) is arranged on a pipeline of the first silo pump (2) to the magnetic separation system; and the inlet of the buffer silo (5) is connected to a three-way switching valve (4).

2. A fly ash magnetic separation iron extraction system according to claim 1, characterized in that The first-stage magnetic separator (7) and the second-stage magnetic separator (9) are each provided with a waste ash hopper; the second-stage magnetic separator (9) is provided with a product hopper; the waste ash hopper is connected to a transfer bin (11), and the transfer bin (11) is connected to a second bin pump (12); the product hopper is connected to a spiral metering scale (10).

3. A fly ash magnetic separation iron extraction system according to claim 1, characterized in that The first-stage magnetic separators (7) are four in number and arranged in parallel; they are then arranged in series with the second-stage magnetic separator (9); the screw conveyor (8) is a horizontal screw conveyor with four inlets and one outlet, two sets of symmetrical and opposite spiral blades are arranged on the screw shaft, four feed ports are arranged on the top cover, and the four ports are connected to the first-stage magnetic separators (7) in corresponding numbers; a discharge port is arranged in the middle of the bottom of the box body and is connected to the feed hopper of the second-stage magnetic separator (9).

4. A fly ash magnetic separation iron extraction system according to claim 1, characterized in that The transfer bin (11) is a conical bucket-shaped square bin, and a balance pipe is provided between the transfer bin (11) and the buffer bin (5).

5. A fly ash magnetic separation iron extraction system according to claim 1, characterized in that The four wall panels of the ash hopper bin of the buffer bin (5) are provided with fluidizing plates (17); the buffer bin (5) is provided with a vacuum pressure release valve (13), a bin top dust collector (15), a first radar type continuous material level meter (14), a first radio frequency admittance type high material level meter (16), and a first radio frequency admittance type low material level meter (18).

6. A fly ash magnetic separation iron extraction system according to claim 1, characterized in that The transfer bin (11) is provided with a second radar-type continuous material level meter (21), a second radio frequency admittance-type high material level meter (20), and a second radio frequency admittance-type low material level meter (19).

7. A fly ash magnetic separation iron extraction system according to claim 1, characterized in that The first-stage magnetic separator (7) and the second-stage magnetic separator (9) are dry-type magnetic separators, using two-stage permanent magnetic rollers with a magnetic strength of 6000-10000 Gs, and are provided with a blowing device, a magnetic swing, and a brush assembly.

8. A fly ash magnetic separation iron extraction system according to claim 1, characterized in that The spiral weighing scale (10) is a hanging type weighing spiral scale, in which an electronic weighing sensor and a spiral scale body are connected via a hinge and are hung for installation.

9. A method for extracting iron from fly ash by magnetic separation using any one of the systems of claims 1 to 8, wherein the characteristic steps are: include: S1: The fly ash captured by the electrostatic precipitator is collected in the ash hopper and transported by the first bin pump (2); The first pneumatic double-disc valve (1) is opened, and the second pneumatic double-disc valve (3) is closed, and the fly ash is transported to the ash storage; The first pneumatic double-disc valve (1) is closed, and the second pneumatic double-disc valve (3) is opened, so that the fly ash is transported to the magnetic separation system; S2: fly ash is transported to the buffer bin (5) through the three-way switching valve (4), and three three-way switching valves (4) are switched in sequence to achieve uniform distribution of fly ash to the sub-bins; S3: Clean compressed air is introduced into the fluidizing plate (17) of the buffer bin (5) to fluidize the fly ash. The fly ash is then fed quantitatively to the primary magnetic separator (7) by the fly ash's own weight. S4: The primary magnetic separator (7) is used to perform magnetic adsorption and centrifugal action on the magnetic iron oxide to achieve rough separation of fly ash, thereby separating fly ash with an iron content of 20% to 30% and primary waste ash with an iron content of less than 5%; S5: On the one hand, the iron-containing fly ash after rough selection is collected by a screw conveyor (8), and on the other hand, the secondary waste ash is conveyed to a transfer bin (11); S6: The iron-containing fly ash is discharged from the outlet of the screw conveyor (8) to the secondary magnetic separator (9), where fine magnetic separation is performed under the action of a strong magnetic field of 6000-10000 Gs, thereby separating an iron-rich product with an iron content of more than 50% and secondary waste ash; S7: The selected iron-rich product is weighed, collected and transported by a spiral metering scale (10), and the secondary waste ash is transported to the transfer bin (11), and then transported to the ash storage via the second bin pump (12).

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