Spiral sleeve type pulverized coal preheater and pulverized coal preheating system

Abstract

The application discloses a spiral sleeve type pulverized coal preheater and a pulverized coal preheating system, and belongs to the field of pulverized coal preheating. The spiral sleeve type pulverized coal preheater comprises an inner cylinder, a closed cavity is formed in the inner cylinder, the inner cylinder comprises an upper cone part, a cylindrical part and a lower cone part which are distributed along a vertical direction in sequence, the tip of the upper cone part is opposite to the tip of the lower cone part; an outer cylinder is sleeved to the outer side of the inner cylinder, the outer cylinder is penetrated at both ends; the outer cylinder comprises an upper platform part, a cylindrical part and a lower platform part which are distributed along a plumb direction in sequence; a heat exchange pipe group is arranged around the inner cylinder and comprises a plurality of layers of spiral pipes which are coaxially nested and are used for the flow of pulverized coal; the upper cone part and the upper platform part are in position correspondence, the cylindrical part and the cylindrical part are in position correspondence, and the lower cone part and the lower platform part are in position correspondence; the heat exchange pipe group is located between the cylindrical part and the circular platform part; a flue gas channel is formed between the inner cylinder and the outer cylinder, so that flue gas flows along the contour of the inner cylinder to heat the heat exchange pipe group. The preheater can fully utilize the heat of flue gas to efficiently heat pulverized coal.

Description

Technical Field

[0001] This invention relates to the field of pulverized coal preheating, and more specifically, to a spiral sleeve type pulverized coal preheater and pulverized coal preheating system. Background Technology

[0002] Currently, the steel industry commonly uses pulverized coal injection (PCI) technology in blast furnaces to replace coke, increasing the proportion of coal used to reduce coke and fuel consumption and lower ironmaking costs. However, as the proportion of coal increases, the coal-coke replacement ratio decreases significantly, mainly because pulverized coal is not fully burned in the blast furnace tuyeres. Incompletely burned pulverized coal or residual coke particles flow with the gas; some enter the coke pores, reducing their porosity and affecting the flowability of molten iron in the hearth, thus impacting hearth activity; another portion enters the slag-forming zone, increasing the viscosity of the initial slag and worsening the permeability of the furnace charge, thereby affecting blast furnace stability and iron production; the remaining pulverized coal is discharged with the gas and adheres to the dust collector ash.

[0003] To improve pulverized coal injection efficiency and reduce unburned pulverized coal production, the key lies in increasing the combustion efficiency of the pulverized coal. Preheating the pulverized coal can shorten its heating time at the tuyeres, thereby increasing the contact time between the pulverized coal and oxygen and improving combustion efficiency.

[0004] For example, Chinese patent document (CN113091481A) provides a bridge tube waste gas waste heat recovery device. The key points of its technical solution are: the bridge tube waste heat recovery heat exchanger includes a heat exchanger flange, a heat exchanger shell, a spiral tube, a water inlet, a water outlet, and a waste gas outlet; the upper part of the heat exchanger is provided with a bridge tube waste heat recovery heat exchanger flange, the bottom is the waste gas outlet, a spiral tube is arranged inside the heat exchanger shell, the heat exchanger shell is provided with a water inlet and a water outlet, and the water inlet and the water outlet are connected to the spiral tube placed inside the heat exchanger shell.

[0005] The above-mentioned device uses spiral heat exchange tubes, which can reduce the pressure loss inside the pipe to a certain extent. However, compared with the spiral arrangement, this parallel arrangement of heat exchange tubes does not significantly improve the heat exchange efficiency. Moreover, to a certain extent, the waste heat medium is not fully utilized, resulting in a large amount of waste heat being wasted.

[0006] The relevant technologies do not provide effective solutions to the above problems. Summary of the Invention

[0007] To address the problem of low coal pulverized material preheating efficiency in related technologies, some embodiments of this application provide a spiral sleeve-type coal pulverized material preheater, comprising: an inner cylinder having a closed cavity inside, the inner cylinder including an upper conical portion, a cylindrical portion, and a lower conical portion distributed sequentially along a plumb line, the tips of the upper and lower conical portions facing opposite directions; an outer cylinder fitted onto the outside of the inner cylinder, the two ends of the outer cylinder being open; the outer cylinder including an upper platform portion, a cylindrical portion, and a lower platform portion distributed sequentially along a plumb line; and a heat exchange tube assembly arranged around the inner cylinder, comprising coaxially nested multi-layer spiral tubes for coal pulverized material flow; wherein the upper conical portion and the upper platform portion are positioned correspondingly, the cylindrical portion and the cylindrical portion are positioned correspondingly, and the lower conical portion and the lower platform portion are positioned correspondingly, the heat exchange tube assembly being located between the cylindrical portion and the lower platform portion; a flue gas channel is formed between the inner and outer cylinders, allowing flue gas to flow along the contour of the inner cylinder to heat the heat exchange tube assembly.

[0008] Furthermore, the height of the cylindrical portion is equal to the height of the cylindrical portion; the generatrix of the upper conical portion is parallel to the generatrix of the upper platform portion, and the generatrix of the lower conical portion is parallel to the generatrix of the lower platform portion.

[0009] Furthermore, the pulverized coal inlet of the heat exchange tube assembly and the flue gas outlet of the outer cylinder are located on the same side, and the pulverized coal outlet of the heat exchange tube assembly and the flue gas inlet of the outer cylinder are located on the same side, so that the flue gas and the pulverized coal flow in opposite directions.

[0010] Furthermore, the upper side of the heat exchange tube assembly is the pulverized coal inlet, and the lower side of the heat exchange tube assembly is the pulverized coal outlet; the lower side of the outer cylinder is provided with a flue gas inlet, and the upper side of the outer cylinder is provided with a flue gas outlet.

[0011] Furthermore, the diameter of the flue gas outlet is smaller than the diameter of the flue gas inlet.

[0012] Furthermore, the slopes of the upper and lower cones are the same.

[0013] Furthermore, the slope of the upper and lower conical portions is at its minimum value.

[0014] Furthermore, the spacing between adjacent inner and outer spiral tubes is 6mm to 10mm; the distance between all spiral tubes is consistent.

[0015] Furthermore, the diameter of the spiral tube is 20mm to 50mm, and the pitch of the spiral tube is 5mm to 300mm; the diameter of the innermost spiral tube is 1500mm to 2000mm.

[0016] Furthermore, the heat exchange tube assembly comprises an even number of spiral tube layers; wherein the inlets of every two spiral tube layers are connected in parallel, and the outlets of every two spiral tube layers are also connected in parallel.

[0017] Furthermore, the heat exchange tube assembly comprises 2 to 6 spiral tubes.

[0018] To achieve the above objectives, this application also provides a pulverized coal preheating system, including a flue gas furnace and the spiral sleeve type pulverized coal preheater described above; the flue gas furnace is used to generate flue gas; the flue gas inlet and the flue gas outlet are respectively connected to the flue gas furnace.

[0019] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0020] (1) Because the spiral sleeve type pulverized coal preheater of this application has a uniquely shaped inner cylinder, the flue gas enters the outer cylinder from the bottom and is diverted by the lower cone of the inner cylinder inside the outer cylinder. The flue gas makes as much contact as possible with the multi-layer spiral tubes surrounding the cylindrical part of the inner cylinder, thereby fully exchanging heat with the pulverized coal inside the spiral tubes. After heat exchange, it flows through the upper cone of the inner cylinder for convergence and is smoothly and unobstructedly output to the outside, so as to further maintain the heat. This design allows the flue gas to fully contact the multi-layer spiral tubes, maximizing the utilization of the heat of the flue gas in the outer cylinder. At the same time, the double cone design of the inner cylinder fully matches the outer cylinder, which can reduce the pressure loss during flue gas flow, thereby ensuring the flow rate of the flue gas.

[0021] (2) In the spiral sleeve type pulverized coal preheater of this application, the pulverized coal inlet of the heat exchange tube group and the flue gas outlet of the outer cylinder are located on the same side, and the pulverized coal outlet of the heat exchange tube group and the flue gas outlet of the outer cylinder are located on the same side, so that the flue gas and pulverized coal flow in opposite directions, thereby achieving countercurrent heat exchange. When the pulverized coal is about to be discharged, the flue gas has just entered the outer cylinder. At this time, the flue gas temperature is relatively high, which further fully heats the pulverized coal and helps to preheat the pulverized coal to the expected temperature. Compared with cocurrent heat exchange, countercurrent heat exchange significantly improves the heat exchange effect.

[0022] (3) In the spiral sleeve type pulverized coal preheater of this application, the height of the cylindrical part is equal to the height of the cylindrical part, the generatrix of the upper cone part is parallel to the generatrix of the upper platform part, and the generatrix of the lower cone part is parallel to the generatrix of the lower platform part. This design allows the flue gas to pass as smoothly as possible in the flue gas channel and reduces the resistance of the flue gas passing between the inner and outer cylinders. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings:

[0024] Figure 1 This is a cross-sectional structural schematic diagram of a spiral sleeve type pulverized coal preheater and pulverized coal preheating system according to an embodiment of this application;

[0025] Figure 2 This is a top view of a heat exchanger tube assembly according to an embodiment of this application;

[0026] Label Explanation:

[0027] 100. Inner cylinder; 110. Upper conical part; 120. Cylindrical part; 130. Lower conical part;

[0028] 200. Outer cylinder; 210. Upper platform; 211. Flue gas outlet; 220. Cylindrical section; 230. Lower platform; 231. Flue gas inlet;

[0029] 300. Heat exchanger tube assembly; 310. Spiral tube;

[0030] 400. Flue gas passage;

[0031] 500. Connectors. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate for the embodiments of this application described herein.

[0034] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation. Furthermore, some of the above terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific circumstances.

[0035] This application provides a spiral sleeve type pulverized coal preheater, which is used to heat pulverized coal from about 80°C to about 280-315°C before injecting it into the blast furnace.

[0036] The spiral sleeve-type pulverized coal preheater includes an inner cylinder 100, an outer cylinder 200, and a heat exchange tube assembly 300, used for preheating pulverized coal. Specifically, the pulverized coal particles have a diameter of 300 mesh and are transported by mixing with high-pressure inert gas for subsequent pulverized coal injection.

[0037] The inert gas mentioned above can be nitrogen or coal gas, etc.

[0038] The inner cylinder 100 has a closed cavity inside. The inner cylinder 100 includes an upper conical portion 110, a cylindrical portion 120 and a lower conical portion 130 distributed sequentially along the plumb line. The pointed tip of the upper conical portion 110 and the pointed tip of the lower conical portion 130 face opposite directions.

[0039] The outer cylinder 200 is fitted onto the outside of the inner cylinder 100, and both ends of the outer cylinder 200 are open. The outer cylinder 200 includes an upper platform portion 210, a cylindrical portion 220, and a lower platform portion 230 distributed sequentially along the plumb line.

[0040] The heat exchange tube assembly 300 is arranged around the inner cylinder 100 and includes a multi-layer spiral tube 310 with coaxial nesting for the circulation of pulverized coal.

[0041] The upper conical portion 110 and the upper platform portion 210 are positioned correspondingly, the cylindrical portion 120 and the cylindrical portion 220 are positioned correspondingly, and the lower conical portion 130 and the lower platform portion 230 are positioned correspondingly. The heat exchange tube assembly 300 is located between the cylindrical portion 120 and the platform portion. A flue gas passage 400 is formed between the inner cylinder 100 and the outer cylinder 200, allowing the flue gas to flow along the contour of the inner cylinder 100 to heat the heat exchange tube assembly 300.

[0042] In this way, because the spiral sleeve type pulverized coal preheater of this application has a uniquely shaped inner cylinder 100, the flue gas enters the outer cylinder 200 from the bottom and is diverted by the lower cone 130 of the inner cylinder 100 inside the outer cylinder 200. The flue gas makes as much contact as possible with the multi-layer spiral tubes 310 surrounding the cylindrical part 120 of the inner cylinder 100, thereby fully exchanging heat with the pulverized coal inside the spiral tubes 310. After heat exchange, it flows through the upper cone 110 of the inner cylinder 100 for convergence and smooth and unobstructed external output to further maintain heat. This design allows the flue gas to have full contact with the multi-layer spiral tubes 310, maximizing the utilization of the heat of the flue gas inside the outer cylinder 200. At the same time, the double cone design of the inner cylinder 100 works well with the outer cylinder 200 to reduce pressure loss during flue gas flow, thereby ensuring the flow rate of the flue gas.

[0043] The flue gas can also enter the outer cylinder 200 from the top, first flow through the upper cone 110 of the inner cylinder 100, and then flow through the lower cone 130 of the inner cylinder 100.

[0044] As a comparison, the preheaters in the existing design are generally single-cylinder structures without an inner cylinder 100. After the flue gas enters the single cylinder, although it also comes into contact with the spiral tube 310, the flue gas in the center of the spiral tube 310 is often larger in volume, making it difficult to exchange heat efficiently with the spiral tube 310. In addition, the internal space of the single cylinder is relatively large, making it difficult to maintain high pressure after the flue gas enters the single cylinder, which reduces the flow velocity and easily causes stagnation inside the cylinder. The new high-temperature flue gas cannot quickly enter the single cylinder for heat exchange, further reducing the preheating efficiency of pulverized coal.

[0045] Specifically, the inner cylinder 100 is fixed to the inner wall of the outer cylinder 200 by a connector 500. There may be several connectors 500, wherein the connector 500 is disposed between the upper conical portion 110 and the upper platform portion 210, and / or, the connector 500 is disposed between the upper conical portion 110 and the upper platform portion 210 and between the lower conical portion 130 and the lower platform portion 230.

[0046] like Figure 1 As shown, the connector 500 is preferably rod-shaped to reduce the space occupied inside the preheater.

[0047] Preferably, the height of the cylindrical portion 120 is equal to the height of the cylindrical portion 220, the generatrix of the upper conical portion 110 is parallel to the generatrix of the upper platform portion 210, and the generatrix of the lower conical portion 130 is parallel to the generatrix of the lower platform portion 230. This design allows the flue gas to flow as smoothly as possible within the flue gas passage 400, reducing the resistance of the flue gas flowing between the inner cylinder 100 and the outer cylinder 200.

[0048] Specifically, the pulverized coal inlet of the heat exchange tube assembly 300 and the flue gas outlet 211 of the outer cylinder 200 are located on the same side, and the pulverized coal outlet of the heat exchange tube assembly 300 and the flue gas outlet 211 of the outer cylinder 200 are also located on the same side, causing the flue gas and pulverized coal to flow in opposite directions, thus achieving countercurrent heat exchange. When the pulverized coal is about to be discharged, the flue gas has just entered the outer cylinder 200. At this time, the flue gas temperature is relatively high, which further heats the pulverized coal and helps to preheat the pulverized coal to the expected temperature. Compared with co-current heat exchange, countercurrent heat exchange significantly improves the heat exchange effect.

[0049] In this design, the pulverized coal particles inside the spiral tube 310 are carried and transported by an inert gas. To prevent the pulverized coal particles from settling in the middle of the spiral tube 310, specifically, the upper side of the heat exchange tube assembly 300 is the pulverized coal inlet, and the lower side is the pulverized coal outlet. That is, the upper and lower sides of the multi-layer spiral tube 310 are the pulverized coal inlet and outlet, respectively. Figure 1As shown, a flue gas inlet 231 is provided on the lower side of the outer cylinder 200, and a flue gas outlet 211 is provided on the upper side of the outer cylinder 200. Specifically, the flue gas inlet 231 is formed by the lower platform 230, and the flue gas outlet 211 is formed by the upper platform 210. Thus, combined with the vertically arranged inner cylinder 100 and outer cylinder 200 structure in this application, the pulverized coal particles flow rapidly from top to bottom in the opposite direction of gravity, minimizing the problem of blockage inside the spiral tube 310, reducing the maintenance burden on users, and improving the preheating efficiency of pulverized coal.

[0050] Optionally, the diameter of the flue gas outlet 211 is smaller than the diameter of the flue gas inlet 231, so that a small amount of flue gas can stay inside the outer cylinder 200 for a short time to further heat the heat exchange tube assembly 300.

[0051] Optional, such as Figure 1 As shown, the slopes of the upper conical portion 110 and the lower conical portion 130 are the same. Preferably, the minimum slope of the upper conical portion 110 and the lower conical portion 130 is [value missing]. This allows the flue gas to flow within a better range.

[0052] Furthermore, when pulverized coal flows downward within the spiral tube 310, it may cause the spiral tube 310 to vibrate. In order to prevent the multi-layer spiral tubes 310 from colliding with each other and causing mechanical damage, preferably, the distance between adjacent inner and outer spiral tubes 310 is 6mm to 10mm, and the spacing between all spiral tubes 310 is consistent, thereby providing each other with clearance space to prevent contact. At the same time, the flue gas can also flow within this spacing to efficiently exchange heat with the spiral tubes 310.

[0053] Preferably, the distance between adjacent inner and outer spiral tubes 310 is 8 mm, thereby controlling the gap area to increase the flue gas velocity and enhance heat exchange.

[0054] Among them, the spiral tube 310 should be selected with appropriate dimensions, including pitch, tube diameter and spiral diameter. The dimensional parameters of the spiral tube 310 have a great influence on the pressure loss in the tube.

[0055] Furthermore, the diameter of the spiral tube 310 is 20mm to 50mm, the pitch of the spiral tube 310 is 5mm to 300mm, and the diameter of the innermost spiral tube 310 is 1500mm to 2000mm. The size of the spiral tube 310 is within this preferred range, which is beneficial to reducing the pressure loss of pulverized coal in the spiral tube 310.

[0056] Preferably, the heat exchange tube assembly 300 includes an even number of spiral tubes 310, wherein the inlet of every two spiral tubes 310 is connected to the pulverized coal feeding main pipe, and the outlet of every two spiral tubes 310 is also connected to the pulverized coal discharge main pipe, so as to reduce the pressure loss of pulverized coal when it flows in the heat exchange tube assembly 300.

[0057] Specifically, the heat exchanger tube assembly 300 includes 2 to 10 spiral tubes 310, the exact number of which can be flexibly adjusted according to product scale. A more optimal solution is 2 to 6 spiral tubes 310. For example, the heat exchanger tube assembly 300 includes 2, 4, or 6 spiral tubes 310. Under the same pulverized coal flow rate, setting the spiral tubes 310 within the above range can ensure the flow velocity of pulverized coal within the spiral tubes 310, preventing it from affecting the subsequent blast furnace pulverized coal injection heating efficiency. If the number of spiral tubes 310 is large, the spiral tubes 310 will be correspondingly thinner, which will affect the flow velocity of pulverized coal within the spiral tubes 310.

[0058] As a specific embodiment, this application also provides a pulverized coal preheating system, including a flue gas furnace and the spiral sleeve type pulverized coal preheater provided in the above embodiment. The flue gas furnace is used to generate flue gas. The flue gas inlet 231 and the flue gas outlet 211 are respectively connected to the flue gas furnace. The flue gas furnace delivers high-temperature flue gas to the spiral sleeve type through the flue gas inlet 231. Furthermore, the high-temperature flue gas that has undergone heat exchange from the outer cylinder 200 can also re-enter the flue gas furnace from the flue gas outlet 211 for recycling.

[0059] Optionally, the flue gas outlet 211 can also be connected to the waste flue pipe simultaneously, so that some of the flue gas can be directly discharged into the waste flue pipe without re-entering the circulation, thus providing space for new high-temperature flue gas.

[0060] Specifically, hot flue gas at approximately 480°C is generated. The hot flue gas flows through the spiral sleeve-type pulverized coal preheater described in this application to preheat the pulverized coal. After preheating, the flue gas temperature is approximately 180°C. Part of the hot flue gas is circulated back to the hot blast stove for reheating, and part of the hot flue gas is discharged into the waste flue pipe.

[0061] Preferably, the flue gas furnace is connected to the blast furnace, introduces blast furnace gas, and heats it through a heating device to use it as fuel for generating flue gas, so as to make full use of the energy in the system.

[0062] In this pulverized coal preheating system, the connecting pipes between the flue gas furnace, the spiral sleeve pulverized coal preheater, and the blast furnace are properly insulated. For example, the pipes can be wrapped with high-temperature resistant insulation material.

[0063] In summary, the spiral sleeve type pulverized coal preheater of this application has a closed inner cylinder 100, which can reduce the flue gas flow rate of the fluid in the outer cylinder 200. In addition, the inner cylinder 100 and the outer cylinder 200 are matched in shape to increase the flow velocity of the flue gas and achieve efficient heat exchange with the coal gas in the multi-layer spiral tube 310, thereby effectively improving the heat exchange efficiency.

[0064] In this application, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0065] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A spiral sleeve type coal powder preheater, characterized by, include: The inner cylinder has a closed cavity inside, and the inner cylinder includes an upper conical part, a cylindrical part and a lower conical part distributed sequentially along the plumb line, with the tips of the upper conical part and the tips of the lower conical part facing opposite directions; An outer cylinder is fitted onto the outside of the inner cylinder, with both ends of the outer cylinder being open; the outer cylinder comprises an upper platform, a cylindrical section, and a lower platform distributed sequentially along the plumb line. A heat exchange tube assembly, which is arranged around the inner cylinder, includes coaxially nested multi-layer spiral tubes for supplying pulverized coal flow. The upper conical portion and the upper platform portion are in corresponding positions, the cylindrical portion and the cylindrical portion are in corresponding positions, and the lower conical portion and the lower platform portion are in corresponding positions. The heat exchange tube assembly is located between the cylindrical portion and the truncated cone portion. A flue gas channel is formed between the inner cylinder and the outer cylinder, so that the flue gas flows along the contour of the inner cylinder to heat the heat exchange tube assembly.

2. The spiral sleeve type pulverized coal preheater according to claim 1, characterized in that: The height of the cylindrical portion is equal to the height of the cylindrical portion; The generatrix of the upper cone is parallel to the generatrix of the upper platform, and the generatrix of the lower cone is parallel to the generatrix of the lower platform.

3. The spiral sleeve type pulverized coal preheater according to claim 1, characterized in that: The pulverized coal inlet of the heat exchange tube assembly and the flue gas outlet of the outer cylinder are located on the same side, and the pulverized coal outlet of the heat exchange tube assembly and the flue gas inlet of the outer cylinder are located on the same side, so that the flue gas and the pulverized coal flow in opposite directions.

4. The spiral sleeve type pulverized coal preheater according to claim 3, characterized in that: The upper side of the heat exchange tube assembly is the pulverized coal inlet, and the lower side of the heat exchange tube assembly is the pulverized coal outlet; the lower side of the outer cylinder is provided with a flue gas inlet, and the upper side of the outer cylinder is provided with a flue gas outlet.

5. The spiral sleeve type pulverized coal preheater according to claim 4, characterized in that: The diameter of the flue gas outlet is smaller than the diameter of the flue gas inlet.

6. The spiral sleeve type pulverized coal preheater according to claim 1, characterized in that: The slopes of the upper and lower cones are the same.

7. A spiral sleeve type pulverized coal preheater according to claim 6, characterized in that: The minimum slope of the upper and lower taper is 8. The spiral sleeve type pulverized coal preheater according to claim 1, characterized in that: The distance between adjacent inner and outer spiral tubes is 6 mm to 10 mm; the distance between all spiral tubes is the same.

9. The spiral sleeve type pulverized coal preheater according to claim 1, characterized in that: The diameter of the spiral tube is 20mm to 50mm, and the pitch of the spiral tube is 5mm to 300mm; the diameter of the innermost spiral tube is 1500mm to 2000mm.

10. A spiral sleeve type pulverized coal preheater according to claim 1, characterized in that: The heat exchange tube assembly comprises an even number of spiral tube layers; wherein the inlets of every two spiral tube layers are connected in parallel, and the outlets of every two spiral tube layers are also connected in parallel.

11. A spiral sleeve type pulverized coal preheater according to claim 10, characterized in that: The heat exchange tube assembly comprises 2 to 6 spiral tubes.

12. A pulverized coal preheating system, characterized in that: Includes a flue gas furnace and a spiral sleeve type pulverized coal preheater according to any one of claims 1-11; The flue gas furnace is used to generate flue gas; the flue gas inlet and the flue gas outlet are respectively connected to the flue gas furnace.

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