Air mixing device for air mixing and spark capturing of grinding air return system

Abstract

An air mixing device for air mixing and spark catching of a grinding air return system comprises an air mixing column outer cylinder and an air outlet inner cylinder located in the air mixing column outer cylinder, a cyclone air duct is arranged between the inner wall of the air mixing column outer cylinder and the outer wall of the air outlet inner cylinder, and a spiral downward pressing top plate is arranged at the top of the cyclone air duct. The top of the cyclone duct is positioned in a closed space by spirally pressing the top plate; a cyclone dust separation chute is spirally arranged on the inner wall of the cyclone air duct; a conical barrel dust hopper is arranged at the bottom of the air mixing column outer cylinder; the air conditioner further comprises a two-inlet and three-outlet air mixing system. Air sources of the system come from part of waste heat return air after dust removal of the grinding system and low-temperature flue gas of other systems, energy conservation and emission reduction are achieved, waste heat is recycled, heat source energy consumption of a hot blast stove is reduced, meanwhile, the two air sources both have low-oxygen conditions, low-oxygen operation conditions are provided for the grinding system after air mixing, and it is guaranteed that the oxygen content of the grinding system is controlled to be 12% or below.

Description

Technical Field

[0001] The invention relates to a closed and semi-closed loop air mixing system for grinding, and an air mixing and spark eliminating device connecting a hot blast furnace and a grinding machine. Background Art

[0002] At present, the heat source for drying the grinding mill comes from hot air furnaces, exhaust gas systems, steam and flue gas heat exchange, pure gas heat exchange and other methods. Especially when flammable and explosive solid minerals are used on both sides of the grinding mill and the hot air furnace, it is necessary to add a spark catcher between the hot air furnace and the grinding mill. However, the unfavorable factors such as dust collector filter bag falling and damage, hot air furnace combustion instability and deflagration cannot be avoided, resulting 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 in the mill. The catcher has a single function on the return air duct, which only captures sparks in the return air duct, and has no function of mixing air and flue gas, and reducing dust on the return air dust. The air mixing tube mixes the flue gas with the high-temperature return air gas to stably control the wind temperature entering the mill, but has no dust removal or spark capture function. The purpose of mixing the flue gas is to reduce the oxygen content entering the mill, use the waste heat of the flue gas to dry it, increase the flue gas temperature, avoid condensation of sulfur-containing flue gas at various mixing points of the mill to corrode the pipes and mill, and centrally treat the flue gas for desulfurization and denitrification. Summary of the invention

[0003] The purpose of the present invention is to provide a device for uniform air mixing, stable temperature control, dust removal and dust reduction, spark capture, flue gas heating and avoiding sulfur condensation corrosion, and to provide a multi-purpose air mixing device between the hot blast furnace and the grinder.

[0004] The technical solution of the present invention is specifically as follows: A mixing device for mixing air and catching sparks in a grinding return air system comprises an outer cylinder of a mixing air column and an inner cylinder of an air outlet located in the outer cylinder of the mixing air column, a cyclone air duct is provided between the inner wall of the outer cylinder of the mixing air column and the outer wall of the inner cylinder of the air outlet, a spiral pressing top plate is provided on the top of the cyclone air duct, and the spiral pressing top plate makes the top of the cyclone air duct in a closed space; a cyclone dust separation chute is spirally provided on the inner wall of the cyclone air duct; a cone bucket ash hopper is provided at the bottom of the outer cylinder of the mixing air column; It also includes a "two-inlet and 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 exhaust port is arranged at the end of the cyclone dust separation chute, a second dust exhaust port is arranged at the bottom of the conical barrel ash hopper, and a first air outlet is arranged at the upper end of the air outlet inner cylinder.

[0005] The high-temperature return air inlet duct is a rectangular duct, which is located in the tangential air inlet direction of the outer tube of the mixing air column.

[0006] The low-temperature flue gas inlet duct is a cylindrical pipe, in which a plurality of cyclone blades are arranged. The end of the cyclone blades is a flue gas outer cone barrel that enlarges the space. The center of the air outlet of the flue gas outer cone barrel is the flue gas inner cone barrel. The bottom of the flue gas inner cone barrel is the flue gas dust outlet, and the flue gas dust outlet is connected to the cyclone dust separation chute.

[0007] The inner air outlet tube is a cylindrical pipe, which is concentric with the outer air mixing column tube. The bottom end plane of the inner air outlet tube is higher than the bottom end plane of the outer air mixing column tube.

[0008] The trough section of the cyclone dust separation chute is L-shaped, and the vertical side is close to the axial center of the outer cylinder of the air mixing column. The L-shaped cyclone dust separation chute and the inner wall of the outer cylinder of the air mixing column form an open U-shaped chute.

[0009] The spiral line of the cyclone dust separation chute is consistent with the pitch and diameter of the spiral downward pressure top plate.

[0010] The first dust discharge port adopts a pulse venturi tube, which is located at the end of the cyclone dust separation chute, changing from an open U-shaped chute to a closed rectangular contraction port, and a pulse venturi tube is arranged at the center of the contraction port section.

[0011] A pulse valve interface is arranged at the closed rectangular contraction port.

[0012] Two pressure transmitters and two temperature transmitter interfaces are respectively provided in the high-temperature return air inlet duct and the air outlet inner tube.

[0013] A vortex cover is arranged in the cone barrel ash hopper, and the vortex cover is located above the second dust exhaust port.

[0014] The beneficial effects of the present invention are as follows: the wind source comes from part of the residual heat return air after dust removal of 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 energy consumption of the hot blast furnace heat source is reduced. At the same time, both wind sources have low-oxygen conditions. After mixed air, low-oxygen operating conditions are provided 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.

[0015] When the hot air furnace uses solid combustible fuel, sparks will appear in the pipe entering the grinder. The series spark catcher can solve this problem. In the face of emergencies, the dust collector filter bag of the grinding system is damaged or falls off, and a large number of sparks will be generated after passing through the hot air furnace. At this time, the mixed air column can cope with this emergency. In addition, the mixed air device uses the cyclone principle to handle a large amount of dust, which is better than the processing capacity of the spark catcher.

[0016] The incoming flue gas may contain nitrogen and sulfides, especially sulfides. When the dew point is lower than the sulfide dew point, condensation will occur on the pipe wall. After being heated by high-temperature return air, the dew point will be higher than the sulfide dew point to avoid corrosion to the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the appearance diagram of the air mixing device for the grinding return air system and the spark capture device; Figure 2 This is a cross-sectional view of the interior of the air mixing device; Figure 3 Low-temperature flue gas inlet duct swirl structure; Figure 4 This is a schematic diagram of air-powder separation in the low-temperature flue gas inlet duct; Figure 5 It is the dust confluence of low temperature flue gas inlet duct; Figure 6 This is a schematic diagram of the L-type cyclone dust separation chute discharging powder; Figure 7 It is the inlet and outlet pressure and temperature monitoring diagram. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0020] like Figure 1 As shown, a mixing device for mixing air and catching sparks in a grinding return air system includes a mixing air column outer cylinder 12 and an air outlet inner cylinder 8 located inside the mixing air column outer cylinder 12. A cyclone duct 13 is provided between the inner wall of the mixing air column outer cylinder 12 and the outer wall of the air outlet inner cylinder 8. A spiral downward pressing top plate 11 is provided on the top of the cyclone duct 13. The spiral downward pressing top plate 11 makes the top of the cyclone duct 13 in a closed space. A cyclone dust separation chute 2 is spirally provided on the inner wall of the cyclone duct 13; a cone ash hopper 10 is provided at the bottom of the mixing air column outer cylinder 12; It also includes a "two-in-three-out" air 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. The low-temperature flue gas inlet duct 4 and the high-temperature return air inlet duct 5 are both connected to the cyclone duct 13. In this way, the two air inlets serve as two heat source airflows of the air mixing cylinder. The two air inlets are mixed in the cyclone duct 13 space between the outer cylinder 12 of the air mixing column and the inner cylinder 8 of the air outlet. By extending the length of the inner cylinder of the air outlet, the mixing time of the two air inlets is increased to ensure the stability of the air temperature at the air outlet at the end of the inner cylinder of the air outlet. The first dust discharge port 1 is set at the end of the cyclone dust separation chute 2, the second dust discharge port 14 is set at the bottom of the cone bucket ash hopper 10, and the first air outlet 15 is set at the upper end of the air outlet inner cylinder 8. In this way, the dust discharge port of the cone bucket ash hopper 10, the first dust discharge port 1, and the inner cylinder 8 of the air outlet together constitute the "three-out" channel of the air mixing device, two dust discharge ports and one air mixing outlet.

[0021] 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 tube 12 of the air mixing column. Under the action of the spiral downward pressure top plate 11, the return air is forced to form a stable cyclone.

[0022] Furthermore, the low-temperature flue gas inlet duct 4 is a cylindrical pipe, and a plurality of cyclone blades 4.1 are arranged in the cylindrical pipe, and the ends of the cyclone blades 4.1 are flue gas outer cone barrels 4.2 that enlarge the space, and the center of the air outlet of the flue gas outer cone barrel 4.2 is the flue gas inner cone barrel 4.3, and the bottom of the flue gas inner cone barrel 4.3 is the flue gas dust outlet 4.4, and the flue gas dust outlet 4.4 is connected to the cyclone dust separation chute 2. In this way, the low-temperature flue gas forms a swirl inside the cylindrical pipe, and finally the air outlet direction through the flue gas dust outlet 4.4 is consistent with the cyclone rotation direction of the air mixing column outer cylinder 12.

[0023] It should be noted that the smoke outer cone barrel 4.2 and the smoke inner cone barrel 4.3 are coaxial, that is, concentric circles, and they are perpendicular to the axis of the outer tube 12 of the air mixing column. The smoke outer cone barrel 4.2 and the smoke inner cone barrel 4.3 are welded on the outer tube 12 of the air mixing column at the same time. The smoke inner cone barrel 4.3 is a hollow structure at both ends. The gas can pass through the small end to the big end and enter the interior of the outer tube 12 of the air mixing column; the gas can also enter the interior of the outer tube 12 of the air mixing column from the fan-shaped opening opened on the top of the outer tube 12 of the air mixing column at the bottom between the smoke outer cone barrel 4.2 and the smoke inner cone barrel 4.3.

[0024] Therefore, the high-temperature return air inlet duct 5 and the low-temperature flue gas inlet duct 4 are the "double air inlet" channels of the air mixing device, which evenly mix the hot air from different systems to form a stable wind temperature, safe and spark-free in-mill drying heat source. In addition, it should be noted that there are many forms of cyclone dust removal air inlet, including circular tubes, rectangular tubes, and volutes, which can provide stable cyclone dust removal conditions for this device.

[0025] Furthermore, the air outlet inner cylinder 8 is a cylindrical pipe, which is concentric with the air mixing column outer cylinder 12 , and the bottom end plane of the air outlet inner cylinder 8 is higher than the bottom end plane of the air mixing column outer cylinder 12 .

[0026] Furthermore, the cross section of the cyclone dust separation chute 2 is L-shaped, with the vertical side close to the axial center of the outer cylinder 12 of the air mixing column. The L-shaped cyclone dust separation chute and the inner wall of the outer cylinder 12 of the air mixing column form an open U-shaped chute. Under the centrifugal force of the cyclone, the particle dust drives the dust to move downward along the U-shaped chute. The other side plate of the U-shaped chute separates the dust and air in the mixed air to prevent the falling dust from running out of the U-shaped chute due to air turbulence. The spiral line of the cyclone dust separation chute 2 is consistent with the pitch and diameter of the spiral downward pressure top plate 11, and the first dust discharge port 1 is set at the end.

[0027] Furthermore, the first dust exhaust port 1 adopts a pulse venturi, and the pulse venturi dust exhaust port is located at the end of the cyclone dust separation chute 2, and changes from an open U-shaped chute to a closed rectangular contraction port. A pulse blowing pipe is arranged at the center of the contraction port cross section. The closed contraction port utilizes the Venturi principle to form a low negative pressure in the absence of blowing. When high-pressure and high-speed pulse air is blown, a high negative pressure is formed at the end of the pulse venturi. The high and low negative pressure cycles alternately bring the dust gathered at the front end of the pulse venturi out of the air mixing device.

[0028] Preferably, a pulse valve interface 3 is provided at the closed rectangular contraction port, the pulse valve interface 3 is opened at a fixed time, and the high-speed high-pressure jet expands the pulse venturi effect to form a high negative pressure area.

[0029] Furthermore, two pressure transmitters 6 and two temperature transmitter interfaces 7 are respectively provided in the high-temperature return air inlet duct 5 and the air outlet inner tube 8 to monitor the pressure difference and temperature of the air inlet and outlet, and adjust the air volume and air temperature of the air inlet duct to ensure the air temperature of the air outlet.

[0030] Furthermore, a vortex cover 9 is provided in the conical barrel ash hopper 10 , and the vortex cover 9 is located above the second dust exhaust port 14 .

[0031] The working principle of the present invention is: 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 air mixing column outer tube 12 together form a U-shaped chute. The dust-containing airflows in the low-temperature flue gas inlet duct 4 and the high-temperature return air inlet duct 5 form swirls in their respective cyclone channels, and the air and dust separation is achieved under the action of centrifugal force and neutrality. Since the dust mass is larger, its centrifugal force is also greater, and it moves along the outside of the cyclone channel. The dust in the high-temperature return air inlet duct 5 moves downward along the outer cyclone dust separation chute 2. The swirl structure of the low-temperature flue gas inlet duct 4 is shown in FIG. Figure 3The dust forms a cyclone along the cyclone blades 4.1, and also moves along the outside of the flue gas outer cone barrel 4.2, and flows into the cyclone dust separation chute 2 from the flue gas dust outlet 4.4. Figure 5 The collected dust is finally discharged from the outer cylinder 12 of the mixed air column through the pulse venturi of the first dust exhaust port 1. Figure 6 The separated flue gas is mixed with the high-temperature flue gas in the air mixing tube from the flue gas inner cone barrel 4.3. The air-powder separation process is shown in Figure 4 .

[0032] The second dust discharge port is located at the bottom of the conical barrel ash hopper 10, and a vortex cover 9 is arranged inside the conical barrel ash hopper. The dust that is not discharged through the first dust discharge port 1 will continue to separate under the action of centrifugal force and gravity, and finally the dust passes through the outside of the vortex cover 9 and gathers in the conical barrel ash hopper 10; the vortex airflow in the center collides with the vortex cover 9 and spirals upward, and is finally discharged from the third outlet, i.e., the air outlet inner cylinder 8.

[0033] In order to accelerate the discharge of dust at the end of the L-shaped cyclone dust separation chute 2, a contraction trumpet is designed at the end, that is, using the principle of the Venturi tube, when the airflow passes through the contraction port at the end of the Venturi tube, a low negative pressure will be formed at the contraction port, and the dust near the first dust discharge port 1 will be sucked away by the negative pressure, achieving the function of immediate dust discharge, and a pulse valve interface 3 is set at the contraction port. The pulse valve opens at a fixed time, and the high-speed high-pressure jet expands the effect of the Venturi tube to form a high negative pressure area, forming intermittent high and low negative pressures, achieving a better dust discharge effect. The pulse Venturi tube acts like an air cannon. The first dust discharge port 1 can be connected to the air inlet of the dust collector as needed to form a continuous and stable negative pressure area.

[0034] By mixing air, separating dust with cyclones, and extending the mixed air path, sparks entering the mixed air column will hit the wall and extinguish, and then be separated from the mixed air column to prevent sparks from entering the mill. Cyclone separation and pulse venturi will extinguish sparks and discharge them out of the mixed air device, and clean air will enter the mill through the central inner cylinder.

[0035] like Figure 7As shown, the "two-in and three-out" mixed air scheme is provided with two temperature transmitter interfaces 7 and two pressure transmitters 6 at the upper ends of the high-temperature return air inlet duct 5 and the outlet inner tube 8. Through the inlet air temperature monitoring (TE01) and outlet air temperature monitoring (TE02), the air volume and air temperature of the high-temperature return air inlet duct 5 are adjusted to ensure that the air temperature of the outlet inner tube 8 is at the normal mill drying air temperature of 230-250°C, and the maximum does not exceed 300°C. When the dust collector bag is broken and falls, part of the solid combustible dust will be discharged from the chimney through the dust collector outlet return air duct, and the other part will be ignited through the hot air furnace, forming a large amount of spark dust, which will enter the mixed air device through the high-temperature return air inlet duct 5. When the hot air furnace uses solid fuel, sparks will also be formed and enter the mixed air device. When a large amount of dust passes through the air mixing device, the air-dust ratio changes, which will cause the pressure difference between the pressure transmitter of the local high-temperature return air inlet duct 5 and the pressure transmitter of the local air outlet inner tube 8 to change. The pressure difference (PD05) between the two is calculated through the inlet pressure monitoring (PT04) and outlet pressure monitoring (PT03) for intuitive display, see Figure 7 The inside of the air mixing tube is equipped with measures such as extended air mixing time, low-temperature flue gas cooling, sparks hitting the wall, and swirl dust removal to promptly discharge sparks from the air mixing device to prevent sparks from entering the mill and causing dust deflagration and explosion risks in the mill.

[0036] The "two-in-three-out" mixed air 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 wind temperature and low oxygen environment for solid combustible grinding. If the flue gas temperature is low and the sulfur content is high, the acidic liquid formed by condensation will cause acid corrosion to subsequent pipelines and equipment. The wind temperature is raised again to above the exposure point by the high-temperature return air in the air mixing device, thereby achieving the function of energy saving and emission reduction.

[0037] The invention is suitable for mixed air under positive and negative conditions, and the dust discharge port of the pulse venturi tube can be connected to the inlet of the dust collector.

[0038] It should be noted that this solution has many base support structures, and can provide a variety of installation support methods: steel columns, steel plate welded bases, concrete bases, steel structure bases, etc. In order to reduce the height of the equipment, it can even be a foundation pit method, which is not explained in detail in this solution. Common hot blast furnace solid combustibles in this solution are mostly coal, biomass fuel, charcoal, and other solids with high calorific value. Solid combustibles in the mill include: coal, petroleum coke, semi-coke, iron powder formed by nickel matte powder grinding, and natural ferrous sulfide powder.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several changes and improvements can be made without departing from the overall concept of the present invention, which should also be regarded as the scope of protection of the present invention.

Claims

1. An air mixing device for mixing air and catching sparks in a grinding return air system, characterized in that: It comprises an air mixing column outer cylinder (12) and an air outlet inner cylinder (8) located inside the air mixing column outer cylinder (12); a cyclone duct (13) is provided between the inner wall of the air mixing column outer cylinder (12) and the outer wall of the air outlet inner cylinder (8); a spiral downward pressing top plate (11) is provided at the top of the cyclone duct (13); the spiral downward pressing top plate (11) makes the top of the cyclone duct (13) in a closed space; a cyclone dust separation chute (2) is spirally provided on the inner wall of the cyclone duct (13); and a cone ash hopper (10) is provided at the bottom of the air mixing column outer cylinder (12); It also includes a "two-inlet and 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 the low-temperature flue gas inlet duct (4) and the high-temperature return air inlet duct (5) are both connected to the cyclone duct (13); a first dust discharge port (1) is provided at the end of the cyclone dust separation chute (2), a second dust discharge port (14) is provided at the bottom of the conical barrel ash hopper (10), and a first air outlet (15) is provided at the upper end of the air outlet inner cylinder (8).

2. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 1, characterized in that: The high-temperature return air inlet duct (5) is a rectangular duct, and the rectangular duct is located in the tangential air inlet direction of the air mixing column outer tube (12).

3. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 1, characterized in that: The low-temperature flue gas air inlet duct (4) is a cylindrical pipe, and a plurality of cyclone blades (4.1) are arranged in the cylindrical pipe. The ends of the cyclone blades (4.1) are flue gas outer cone barrels (4.2) that enlarge the space. The center of the air outlet of the flue gas outer cone barrel (4.2) is the flue gas inner cone barrel (4.3). The bottom of the flue gas inner cone barrel (4.3) is the flue gas dust outlet (4.4), and the flue gas dust outlet (4.4) is connected to the cyclone dust separation chute (2).

4. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 1, characterized in that: The air outlet inner cylinder (8) is a cylindrical pipe, which is concentric with the air mixing column outer cylinder (12), and the bottom end plane of the air outlet inner cylinder (8) is higher than the bottom end plane of the air mixing column outer cylinder (12).

5. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 1, characterized in that: The cyclone dust separation chute (2) has an L-shaped cross section, with the vertical side close to the axial center of the air mixing column outer cylinder (12). The L-shaped cyclone dust separation chute and the inner wall of the air mixing column outer cylinder (12) form an open U-shaped chute.

6. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 5, characterized in that: The helical line of the cyclone dust separation chute (2) is consistent with the pitch and diameter of the spiral downward pressing top plate (11).

7. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 5, characterized in that: The first dust discharge port (1) adopts a pulse venturi tube, which is located at the end of the cyclone dust separation chute (2) and changes from an open U-shaped chute to a closed rectangular contraction port. A pulse venturi tube is arranged at the center of the contraction port cross section.

8. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 7, characterized in that: A pulse valve interface (3) is provided at the closed rectangular contraction port.

9. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 1, characterized in that: Two pressure transmitters (6) and two temperature transmitter interfaces (7) are respectively provided on the high-temperature return air inlet duct (5) and the air outlet inner cylinder (8).

10. The air mixing device for mixing air and catching sparks in a grinding return air system according to claim 1, characterized in that: A vortex cover (9) is arranged in the conical barrel ash hopper (10), and the vortex cover (9) is located above the second dust discharge port (14).

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