A mixed air, spark catching device for a pulverized fuel return air system

Abstract

A kind of mixed air, mixed air device of spark catching for grinding air return system, including mixed air column outer tube and the air outlet inner tube in mixed air column outer tube, between mixed air column outer tube inner wall and air outlet inner tube outer wall is cyclone air duct, the top of cyclone air duct is provided with spiral down-pressing top plate, and spiral down-pressing top plate makes the top of cyclone air duct be in closed space;Spiral cyclone dust separation chute is arranged on the inner wall of cyclone air duct;Conical barrel hopper is arranged at the bottom of mixed air column outer tube;It further includes the mixed air system of " two in three out ".The air source of the present application comes from the part of waste heat return air after dust removal of grinding system and other system low-temperature flue gas, energy saving and emission reduction: waste heat recovery and reuse, reduce the energy consumption of hot blast furnace heat source, while the two air sources both have low oxygen conditions, provide low oxygen operation conditions for grinding system after mixing air, ensure that the oxygen content of grinding system is controlled below 12%.

Description

Technical Field

[0001] This invention relates to a closed or semi-closed loop air mixing system for grinding mills, and a device for mixing air and eliminating sparks between a hot blast stove and a mill. Background Technology

[0002] Currently, the heat source for drying in grinding mills comes from various methods, including hot air furnaces, flue gas systems, steam and flue gas heat exchange, and pure gas heat exchange. Especially when flammable and explosive solid minerals are used on both sides of the grinding mill and the hot air furnace, a spark arrestor needs to be added between the furnace and the mill. However, this cannot prevent the dust collector filter bags from falling off or breaking, unstable combustion in the hot air furnace, and the risk of deflagration. This results in a large amount of solid fuel sparks entering the grinding mill through the return air duct, causing the risk of combustion and explosion of solid combustibles inside the mill. The spark arrestor has a single function in the return air duct, only capturing sparks; it does not mix the flue gas or reduce dust in the return air. The mixing duct mixes the flue gas with the high-temperature return air, stabilizing the temperature of the air entering the mill, but it does not remove dust or capture sparks. The purpose of mixing flue gas is to reduce the oxygen content entering the mill, utilize the waste heat of the flue gas for drying, increase the flue gas temperature, prevent sulfur-containing flue gas from condensing and corroding pipes and the mill at various mixing points, and centrally treat the flue gas for desulfurization and denitrification. Summary of the Invention

[0003] The purpose of this invention is to provide a device for uniform air mixing, stable temperature control, dust removal and reduction, spark capture, and heating of flue gas to prevent sulfur-containing condensation and corrosion. It provides a multi-purpose air mixing device between a hot blast stove and a mill.

[0004] The specific technical solution of the present invention is as follows:

[0005] A mixing device for mixing air and capturing sparks in a grinding mill return air system includes a mixing column outer cylinder and an outlet inner cylinder located inside the mixing column outer cylinder. A cyclone duct is formed between the inner wall of the mixing column outer cylinder and the outer wall of the outlet inner cylinder. A spiral downward pressure plate is provided at the top of the cyclone duct, which makes the top of the cyclone duct a closed space. A cyclone dust separation chute is spirally arranged on the inner wall of the cyclone duct. A cone-shaped ash hopper is provided at the bottom of the mixing column outer cylinder.

[0006] It also includes a "two-inlet, three-outlet" mixed air system: the first air inlet is a low-temperature flue gas inlet duct, the second air inlet is a high-temperature return air inlet duct, and both the low-temperature flue gas inlet duct and the high-temperature return air inlet duct are connected to the cyclone duct; a first dust discharge port is set at the end of the cyclone dust separation chute, a second dust discharge port is set at the bottom of the cone ash hopper, and a first air outlet is set at the upper end of the air outlet inner cylinder.

[0007] The high-temperature return air intake duct is a rectangular pipe, which is located in the tangential air intake direction of the outer cylinder of the mixing column.

[0008] The low-temperature flue gas inlet duct is a cylindrical pipe with multiple cyclone blades inside. The ends of the cyclone blades are enlarged flue gas outer cones. The center of the outlet of the outer flue gas cone is the inner flue gas cone. The bottom of the inner flue gas cone is the flue gas dust outlet, which is connected to the cyclone dust separation chute.

[0009] The inner tube of the air outlet is a cylindrical pipe, concentric with the outer tube of the mixing column, and the bottom plane of the inner tube of the air outlet is higher than the bottom plane of the outer tube of the mixing column.

[0010] The cross-section of the cyclone dust separation chute is L-shaped, with the vertical side close to the axial center of the outer cylinder of the mixing column. The L-shaped cyclone dust separation chute and the inner wall of the outer cylinder of the mixing column form an open U-shaped chute.

[0011] The spiral of the cyclone dust separation chute is consistent with the pitch and diameter of the spiral downward pressure plate.

[0012] The first dust discharge port adopts a pulse venturi tube. The pulse venturi tube dust discharge port is located at the end of the cyclone dust separation chute. It changes from an open U-shaped chute to a closed rectangular contraction port, and a pulse venturi tube is set at the center of the contraction port cross section.

[0013] A pulse valve interface is provided at the closed rectangular contraction port.

[0014] Two pressure transmitters and two temperature transmitter interfaces are installed in the high-temperature return air inlet duct and the outlet air cylinder, respectively.

[0015] A vortex hood is installed inside the cone-shaped dust hopper, and the vortex hood is located above the second dust discharge port.

[0016] The beneficial effects of this invention are as follows: the air source comes from the residual heat return air after dust removal in the grinding system and low-temperature flue gas from other systems, which saves energy and reduces emissions: waste heat is recovered and reused, and the heat source energy consumption of the hot blast stove is reduced. At the same time, both air sources have low oxygen conditions. After mixing, they provide low oxygen operating conditions for the grinding system, ensuring that the oxygen content of the grinding system is controlled below 12%, which can meet the explosion-proof safety regulations (GB16543-2008) for blast furnace bituminous coal injection systems.

[0017] When the hot blast furnace uses solid combustible fuel, sparks may appear in the pipes entering the mill. A series of spark catchers can solve this problem. In the event of a sudden situation, the dust collector filter bags in the grinding system may be damaged or fall off, resulting in a large number of sparks being generated as they pass through the hot blast furnace. The mixing column can handle this sudden situation. Furthermore, this mixing device utilizes the cyclone principle and can handle a large amount of dust, which is superior to the processing capacity of the spark catcher.

[0018] The intake flue gas may contain nitrogen and sulfides, especially sulfides. When the temperature is below the sulfide dew point, condensation will form on the pipe wall. After being heated by the high-temperature return air, the temperature will be above the sulfide dew point, thus preventing corrosion of the equipment. Attached Figure Description

[0019] Figure 1 A schematic diagram of the mixing and spark capture device for the grinding mill return air system;

[0020] Figure 2 This is a cross-sectional view of the internal structure of the air mixing device;

[0021] Figure 3 Low-temperature flue gas inlet duct swirl structure;

[0022] Figure 4 A schematic diagram of air-powder separation in the low-temperature flue gas inlet duct;

[0023] Figure 5 Dust collection in the low-temperature flue gas inlet duct;

[0024] Figure 6 Schematic diagram of L-shaped cyclone dust separation chute for dust discharge;

[0025] Figure 7 This is a graph showing the pressure and temperature monitoring for import and export. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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, they should not be construed as limitations on this invention.

[0028] like Figure 1 As shown, a mixing device for a grinding mill return air system, comprising a mixing column outer cylinder 12 and an outlet inner cylinder 8 located within the mixing column outer cylinder 12, wherein a cyclone duct 13 is formed between the inner wall of the mixing column outer cylinder 12 and the outer wall of the outlet inner cylinder 8, and a spiral downward pressing top plate 11 is provided at the top of the cyclone duct 13, which makes the top of the cyclone duct 13 a closed space. A cyclone dust separation chute 2 is spirally arranged on the inner wall of the cyclone duct 13; and a cone-shaped ash hopper 10 is provided at the bottom of the mixing column outer cylinder 12.

[0029] It also includes a "two-in, three-out" mixing system: the first air inlet is a low-temperature flue gas inlet duct 4, and the second air inlet is a high-temperature return air inlet duct 5. Both the low-temperature flue gas inlet duct 4 and the high-temperature return air inlet duct 5 are connected to the cyclone duct 13. In this way, the two air inlets serve as two heat source airflows for the mixing duct. The two air inlets mix within the space of the cyclone duct 13 between the outer cylinder 12 of the mixing column and the inner cylinder 8 of the outlet. By extending the length of the inner cylinder of the outlet, the mixing time of the two air inlets is increased, ensuring a stable air temperature at the outlet of the inner cylinder. A first dust discharge port 1 is set at the end of the cyclone dust separation chute 2, a second dust discharge port 14 is set at the bottom of the cone ash hopper 10, and a first air outlet 15 is set at the upper end of the inner cylinder of the outlet. Thus, the dust discharge port of the cone ash hopper 10, the first dust discharge port 1, and the inner cylinder of the outlet 8 together form the "three-outlet" channel of the mixing device, with two dust discharge ports and one mixing outlet.

[0030] Furthermore, the high-temperature return air inlet duct 5 is a rectangular duct, which is located in the tangential air inlet direction of the outer cylinder 12 of the mixing column. Under the action of the spiral downward pressure top plate 11, it forces the return air to form a stable cyclone.

[0031] Furthermore, the low-temperature flue gas inlet duct 4 is a cylindrical pipe, inside which multiple cyclone blades 4.1 are installed. The ends of the cyclone blades 4.1 are enlarged space flue gas outer cone 4.2, the center of the outlet of the flue gas outer cone 4.2 is the flue gas inner cone 4.3, and the bottom of the flue gas inner cone 4.3 is the flue gas dust outlet 4.4, which is connected to the cyclone dust separation chute 2. In this way, the low-temperature flue gas forms a swirling flow inside the cylindrical pipe, and finally the exhaust direction of the flue gas dust outlet 4.4 is consistent with the cyclone rotation direction of the mixing column outer cylinder 12.

[0032] It should be noted that the outer flue gas cone 4.2 and the inner flue gas cone 4.3 are coaxial, i.e., concentric circles. They are perpendicular to the axis of the mixing column outer cylinder 12. The outer flue gas cone 4.2 and the inner flue gas cone 4.3 are welded to the upper part of the mixing column outer cylinder 12. The inner flue gas cone 4.3 is a hollow structure at both ends, and the gas can enter the interior of the mixing column outer cylinder 12 from the small end to the large end. The gas can also enter the interior of the mixing column outer cylinder 12 from the fan-shaped opening at the bottom of the mixing column outer cylinder 12 between the outer flue gas cone 4.2 and the inner flue gas cone 4.3.

[0033] Therefore, the high-temperature return air inlet duct 5 and the low-temperature flue gas inlet duct 4 form a "dual air inlet" channel for the air mixing device, which uniformly mixes the hot air from different systems to form a stable, safe, and spark-free heat source for drying inside the mill. It should also be noted that there are various cyclone dust collector inlet forms, including round tubes, rectangular tubes, and volutes, all of which can provide stable cyclone dust collection conditions for this device.

[0034] Furthermore, the air outlet inner cylinder 8 is a cylindrical pipe, concentric with the mixing column outer cylinder 12, and the bottom plane of the air outlet inner cylinder 8 is higher than the bottom plane of the mixing column outer cylinder 12.

[0035] Furthermore, the cross-section of the cyclone dust separation chute 2 is L-shaped, with its vertical side close to the axial center of the mixing column outer cylinder 12. The L-shaped cyclone dust separation chute and the inner wall of the mixing column outer cylinder 12 form an open U-shaped chute. Under the action of the centrifugal force of the cyclone, the particulate dust is driven to move downward along the U-shaped chute. The other side plate of the U-shaped chute separates the dust and air in the mixing air, preventing the falling dust from escaping the U-shaped chute due to air turbulence. The spiral of the cyclone dust separation chute 2 is consistent with the pitch and diameter of the spiral downward pressing top plate 11, and the first dust discharge port 1 is set at the end.

[0036] Furthermore, the first dust outlet 1 adopts a pulse venturi tube. The pulse venturi dust outlet is located at the end of the cyclone dust separation chute 2, changing from an open U-shaped chute to a closed rectangular contraction outlet. A pulse jet pipe is set at the center of the contraction outlet cross-section. This closed contraction outlet utilizes the Venturi principle to form a low negative pressure when there is no jet blowing. When high-pressure, high-speed pulse air is jetted, a high negative pressure is formed at the end of the pulse venturi tube. The high and low negative pressures alternately carry the dust collected at the front end of the pulse venturi tube out of the mixing device.

[0037] Even better, a pulse valve interface 3 is provided at the closed rectangular contraction port. The pulse valve interface 3 opens at regular intervals, and the high-speed high-pressure jet expands the pulse venturi effect to form a high negative pressure zone.

[0038] Furthermore, two pressure transmitters 6 and two temperature transmitter interfaces 7 are installed in the high-temperature return air inlet duct 5 and the outlet air cylinder 8 respectively to monitor the pressure difference and temperature at the inlet and outlet, and adjust the air volume and air temperature of the inlet duct to ensure the air temperature at the outlet.

[0039] Furthermore, a vortex hood 9 is installed inside the cone-shaped dust hopper 10, and the vortex hood 9 is located above the second dust outlet 14.

[0040] The working principle of this invention is:

[0041] The first dust discharge port 1 is a pulse venturi dust discharge port, located at the end of the cyclone dust separation chute 2. The cyclone dust separation chute 2 and the inner wall of the mixing column outer cylinder 12 together form a U-shaped chute. Swirls are formed within the cyclone channels of the two dust-laden airflows: the low-temperature flue gas inlet duct 4 and the high-temperature return air inlet duct 5. Under centrifugal force and neutralization, air-dust separation is achieved. Because the dust has a larger mass, its centrifugal force is also greater, causing it to move along the outer side of the cyclone channel. The dust in the high-temperature return air inlet duct 5 moves downwards along the outer cyclone dust separation chute 2. The swirling structure of the low-temperature flue gas inlet duct 4 is shown below. Figure 3Dust particles form a cyclone along the cyclone blades 4.1, and similarly move along the outer side of the flue gas outer cone 4.2, flowing from the flue gas dust outlet 4.4 into the cyclone dust separation chute 2. Figure 5 The collected dust is finally discharged from the outer cylinder 12 of the mixing column through the pulse venturi tube of the first dust outlet 1. Figure 6 The separated flue gas is mixed with the high-temperature flue gas in the mixing duct from the inner flue gas cone 4.3. The air-powder separation process is described in [link to relevant documentation]. Figure 4 .

[0042] The second dust outlet is located at the bottom of the cone-shaped dust hopper 10, and a vortex hood 9 is installed inside the cone-shaped dust hopper. Dust that has not been discharged from the first dust outlet 1 will continue to separate under the action of centrifugal force and gravity. Finally, the dust passes through the outside of the vortex hood 9 and collects in the cone-shaped dust hopper 10. The vortex airflow in the center collides with the vortex hood 9 and moves upward in a spiral motion, and is finally discharged from the third outlet, i.e., the air outlet inner cylinder 8.

[0043] To accelerate the discharge of dust from the end of the L-shaped cyclone dust separation chute 2, a converging funnel-shaped opening is designed at the end. Utilizing the principle of a venturi tube, when the airflow passes through the converging opening at the end of the venturi tube, a low negative pressure is created. Dust near the first dust discharge port 1 is drawn away by this negative pressure, achieving immediate dust removal. A pulse valve interface 3 is installed at the converging opening. The pulse valve opens periodically, and the high-speed, high-pressure jet amplifies the venturi effect, creating a high negative pressure zone and forming intermittent high and low negative pressures for better dust removal. The pulsed venturi tube function is similar to an air cannon. If needed, the first dust discharge port 1 can be connected to the dust collector inlet to create a continuous and stable negative pressure zone.

[0044] By mixing air, separating dust with a cyclone separator, and extending the mixing air path, sparks entering the mixing column are extinguished by hitting the walls and are separated from the mixing column, preventing sparks from entering the mill. Cyclone separation and pulse venturi tubes extinguish the sparks and discharge them from the mixing device, allowing clean air to enter the mill through the central inner cylinder.

[0045] like Figure 7As shown, the "two-in, three-out" mixing scheme has two temperature transmitter interfaces 7 and two pressure transmitters 6 installed at the upper ends of the high-temperature return air inlet duct 5 and the outlet air cylinder 8. Through inlet air temperature monitoring (TE01) and outlet air temperature monitoring (TE02), the airflow and temperature of the high-temperature return air inlet duct 5 are adjusted to ensure that the air temperature of the outlet air cylinder 8 is within the normal mill drying temperature of 230-250℃, and does not exceed 300℃. When the dust collector bag breaks or falls, some of the solid combustible dust will be discharged from the chimney through the dust collector outlet return air duct, while the rest will be ignited by the hot air furnace, forming a large amount of spark dust. This spark dust then enters the mixing device through the high-temperature return air inlet duct 5. When the hot air furnace uses solid fuel, sparks will also enter the mixing device. When a large amount of dust passes through the mixing device, the change in the air-to-dust ratio causes a change in the pressure difference between the pressure transmitter in the local high-temperature return air inlet duct 5 and the pressure transmitter in the local outlet air cylinder 8. This pressure difference (PD05) is calculated using inlet pressure monitoring (PT04) and outlet pressure monitoring (PT03) and displayed visually. (See...) Figure 7 The mixing duct incorporates measures such as extended mixing time, low-temperature flue gas cooling, spark collision with the walls, and swirling dust removal to promptly expel sparks from the mixing device, preventing them from entering the mill and causing dust explosion or other risks.

[0046] The "two-in, three-out" mixed air system effectively utilizes the residual heat of the return air after dust removal and the low-oxygen conditions of other flue gas systems to provide a safe air temperature and low-oxygen environment for grinding solid combustibles. If the flue gas temperature is low and the sulfur content is high, the acidic liquid formed by condensation will cause acid corrosion to the subsequent pipelines and equipment. The air temperature is raised again to above the exposure point by the high-temperature return air in the mixed air device, thereby achieving the function of energy saving and emission reduction.

[0047] This invention is applicable to mixed air under both positive and negative conditions, and the dust discharge port of the pulse venturi tube can be connected to the inlet of the dust collector.

[0048] It should be noted that this solution involves multiple base support structures, offering various installation support methods: steel columns, welded steel plate bases, concrete bases, steel structure bases, etc. To reduce equipment placement elevation, even a foundation pit method may be used; however, these will not be elaborated upon in this solution. The common solid combustibles in this solution's hot blast stoves are primarily coal, biomass fuel, charcoal, and other high-calorific-value solids. Solid combustibles inside the mill include: coal, petroleum coke, semi-coke, iron powder formed from nickel matte grinding, and natural ferrous sulfide powder, etc.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several changes and improvements without departing from the overall concept of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A mixing device for mixing air and capturing sparks in a grinding mill return air system, characterized in that: The system includes an outer cylinder (12) for mixing air and an inner cylinder (8) for air outlet located inside the outer cylinder (12). A cyclone duct (13) is located between the inner wall of the outer cylinder (12) and the outer wall of the inner cylinder (8). A spiral downward pressure plate (11) is provided at the top of the cyclone duct (13), which makes the top of the cyclone duct (13) a closed space. A cyclone dust separation chute (2) is spirally provided on the inner wall of the cyclone duct (13). A cone-shaped ash hopper (10) is provided at the bottom of the outer cylinder (12). It also includes a "two-inlet, three-outlet" mixed air system: the first air inlet is a low-temperature flue gas inlet duct (4), the second air inlet is a high-temperature return air inlet duct (5), and both the low-temperature flue gas inlet duct (4) and the high-temperature return air inlet duct (5) are connected to the cyclone duct (13); a first dust discharge port (1) is set at the end of the cyclone dust separation chute (2), a second dust discharge port (14) is set at the bottom of the cone ash hopper (10), and a first air outlet (15) is set at the upper end of the air outlet inner cylinder (8); The high-temperature return air intake duct (5) is a rectangular duct, which is located in the tangential air intake direction of the outer cylinder (12) of the mixing column; The low-temperature flue gas inlet duct (4) is a cylindrical pipe. Multiple cyclone blades (4.1) are installed inside the cylindrical pipe. The end of the cyclone blades (4.1) is the flue gas outer cone (4.2) with enlarged space. The center of the outlet of the flue gas outer cone (4.2) is the flue gas inner cone (4.3). The bottom of the flue gas inner cone (4.3) is the flue gas dust outlet (4.4). The flue gas dust outlet (4.4) is connected to the cyclone dust separation chute (2). The air outlet inner cylinder (8) is a cylindrical pipe, concentric with the mixing column outer cylinder (12), and the bottom plane of the air outlet inner cylinder (8) is higher than the bottom plane of the mixing column outer cylinder (12); The cross-section of the cyclone dust separation chute (2) is L-shaped, with the vertical side close to the axial center of the mixing column outer cylinder (12). The L-shaped cyclone dust separation chute and the inner wall of the mixing column outer cylinder (12) form an open U-shaped chute. The first dust discharge port (1) adopts a pulse venturi tube. The pulse venturi tube dust discharge port is located at the end of the cyclone dust separation chute (2). It changes from an open U-shaped chute to a closed rectangular contraction port. A pulse jet pipe is set at the center of the contraction port cross section.

2. The air mixing device for mixing air and capturing sparks in a grinding mill return air system according to claim 1, characterized in that: The spiral of the cyclone dust separation chute (2) is consistent with the pitch and diameter of the spiral downward pressure plate (11).

3. The air mixing device for mixing air and capturing sparks in a grinding mill return air system according to claim 1, characterized in that: A pulse valve interface (3) is provided at the closed rectangular contraction port.

4. The air mixing device for mixing air and capturing sparks in a grinding mill return air system according to claim 1, characterized in that: A pressure transmitter (6) and a temperature transmitter interface (7) are installed in the high-temperature return air inlet duct (5), and a pressure transmitter (6) and a temperature transmitter interface (7) are installed in the outlet air cylinder (8).

5. The air mixing device for mixing air and capturing sparks in a grinding mill return air system according to claim 1, characterized in that: A vortex hood (9) is installed inside the cone-shaped dust hopper (10), and the vortex hood (9) is located above the second dust outlet (14).

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