Spiral sleeve type pulverized coal preheater and pulverized coal preheating system

Abstract

The invention discloses a spiral sleeve type pulverized coal preheater and a pulverized coal preheating system, and belongs to the field of pulverized coal preheating. According to the spiral sleeve type pulverized coal preheater bag, a closed cavity is formed in an inner barrel, the inner barrel comprises an upper conical part, a cylindrical part and a lower conical part which are sequentially distributed in the vertical direction, and the pointed cone of the upper conical part and the pointed cone of the lower conical part are opposite in direction; the inner cylinder is sleeved with the outer cylinder, and the two ends of the outer cylinder are through. The outer cylinder comprises an upper table part, a cylinder part and a lower table part which are sequentially distributed in the plumb bob direction; the heat exchange tube group is arranged around the inner cylinder, comprises a plurality of layers of spiral tubes which are coaxially nested and is used for circulating pulverized coal; the upper conical part corresponds to the upper table part in position, the cylindrical part corresponds to the cylinder part in position, the lower conical part corresponds to the lower table part in position, and the heat exchange tube set is located between the cylindrical part and the circular table part; a smoke channel is formed between the inner cylinder and the outer cylinder, so that smoke flows along the outline of the inner cylinder to heat the heat exchange tube set. The preheater can make full use of flue gas heat to efficiently heat pulverized coal.

Description

Technical Field

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

[0002] Currently, the iron and steel industry generally adopts the technology of injecting pulverized coal into blast furnaces to replace coke, increasing the proportion of coal materials used, thereby reducing the consumption of coke and fuel and achieving a reduction in the ironmaking cost. However, as the proportion of coal materials increases, the coal-coke replacement ratio will decrease significantly, mainly because the pulverized coal fails to burn sufficiently in the blast furnace tuyere area. The unburned pulverized coal or residual carbon particles will flow with the gas. Part of them will enter the pores of the coke, reducing its porosity and affecting the fluidity of the molten iron in the hearth, and further affecting the activity of the hearth; another part will enter the slag-forming area, resulting in an increase in the viscosity of the primary slag and deteriorating the permeability of the burden, thus affecting the stability of the blast furnace and the molten iron output; the remaining pulverized coal will be discharged with the gas and adhere to the dust.

[0003] In order to improve the effect of coal injection and reduce the generation of unburned pulverized coal, the key lies in improving the combustion efficiency of the pulverized coal. Preheating the pulverized coal can shorten its heating time at the tuyere, thereby increasing the contact time between the pulverized coal and oxygen and improving the combustion efficiency.

[0004] For example, Chinese patent document (CN113091481A) provides a waste heat recovery device for bridge pipe raw gas. The key points of its technical solution are as follows: The bridge pipe waste heat recovery heat exchanger includes a heat exchanger flange, a heat exchanger housing, a spiral pipe, a water inlet, a water outlet, and a heat exchanger raw gas outlet; the upper part of the outer side of the heat exchanger is provided with a bridge pipe waste heat recovery heat exchanger flange, the bottom is the heat exchanger raw gas outlet, the spiral pipe is arranged inside the heat exchanger housing, and the heat exchanger housing is provided with a water inlet and a water outlet, and the water inlet and outlet are communicated with the spiral pipe placed inside the heat exchanger housing.

[0005] The above device adopts a spiral heat exchange pipe, which can reduce the pressure loss inside the pipeline to a certain extent. However, compared with the spiral arrangement method, this parallel arrangement method of heat exchange pipes cannot significantly improve the heat exchange efficiency, and to a certain extent, the waste heat medium is not fully utilized, resulting in a large amount of waste heat being wasted.

[0006] In response to the above problems, the related technologies do not provide effective solutions. Summary of the Invention

[0007] To solve the problem of low pulverized coal preheating efficiency in related technologies, some embodiments of the present application provide a spiral sleeve type pulverized coal preheater, including: an inner cylinder, which forms a closed cavity inside, and the inner cylinder includes an upper cone part, a cylindrical part, and a lower cone part that are sequentially distributed along the plumb direction, and the tips of the upper cone part and the lower cone part face in opposite directions; an outer cylinder, which is sleeved outside the inner cylinder, and both ends of the outer cylinder are through; the outer cylinder includes an upper table part, a cylindrical part, and a lower table part that are sequentially distributed along the plumb direction; a heat exchange tube group, which is arranged around the inner cylinder and includes multiple layers of spiral tubes nested coaxially for the pulverized coal to flow through; wherein, the upper cone part and the upper table part are in corresponding positions, the cylindrical part and the cylindrical part are in corresponding positions, the lower cone part and the lower table part are in corresponding positions, and the heat exchange tube group is located between the cylindrical part and the frustum part; 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 group.

[0008] Further, 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 table part, and the generatrix of the lower cone part is parallel to the generatrix of the lower table part.

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

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

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

[0012] Further, the slopes of the upper cone part and the lower cone part are the same.

[0013] Further, the minimum slope of the upper cone part and the lower cone part is

[0014] Further, the distance between adjacent spiral tubes inside and outside is 6 mm to 10 mm; the distances between all spiral tubes are the same.

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

[0016] Further, the heat exchange tube group includes an even number of layers of spiral tubes; wherein, the inlets of every two layers of spiral tubes are connected in parallel with each other, and the corresponding outlets of every two layers of spiral tubes are also connected in parallel with each other.

[0017] Furthermore, the heat exchange tube group includes 2 to 6 spiral tubes.

[0018] To achieve the above object, the present application also provides a pulverized coal preheating system, including a flue gas furnace and the spiral sleeve type pulverized coal preheater in the above solution; the flue gas furnace is used to generate flue gas; the flue gas inlet and the flue gas outlet are respectively communicated with the flue gas furnace.

[0019] Adopting the technical solution provided by the present invention, compared with the prior art, it has the following beneficial effects:

[0020] (1) Since the spiral sleeve type pulverized coal preheater of the present application is provided with an inner cylinder with a unique shape, after the flue gas enters the outer cylinder from the lower side, it is diverted by the lower conical part of the inner cylinder inside the outer cylinder, and the flue gas makes as much contact as possible with the multi-layer spiral tubes surrounding the outer cylinder of the inner cylinder, so as to fully exchange heat with the pulverized coal in the spiral tubes. After heat exchange, it then flows through the upper conical part of the inner cylinder for confluence and is smoothly output externally to further maintain heat. This design can make the flue gas fully contact with the multi-layer spiral tubes, making the most of the heat of the flue gas in the outer cylinder. At the same time, the double conical part design of the inner cylinder fully cooperates with the outer cylinder, which can reduce the pressure loss during the flow of the flue gas, thereby ensuring the flow rate of the flue gas.

[0021] (2) In the spiral sleeve type pulverized coal preheater of the present application, the pulverized coal inlet of the heat exchange tube group and the flue gas outlet of the outer cylinder are 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 on the same side, so that the flue gas and the pulverized coal flow in opposite directions for countercurrent heat exchange. When the pulverized coal is about to be output externally, the flue gas just enters the outer cylinder. At this time, the flue gas temperature is relatively high, which further fully heats the pulverized coal and is conducive to preheating the pulverized coal to the expected temperature. Compared with co-current heat exchange, the countercurrent heat exchange significantly improves the heat exchange effect.

[0022] (3) In the spiral sleeve type pulverized coal preheater of the present application, the height of the cylindrical part is equal to the height of the cylindrical part, the generatrix of the upper conical part is parallel to the generatrix of the upper table part, and the generatrix of the lower conical part is parallel to the generatrix of the lower table part. This design makes the flue gas flow as smoothly as possible in the flue gas channel and reduces the resistance of the flue gas flowing between the inner cylinder and the outer cylinder. Description of the Drawings

[0023] The drawings constituting a part of the present application are used to provide a further understanding of the present application, making other features, objects, and advantages of the present application more obvious. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

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

[0025] Figure 2 Schematic top view structure diagram of a heat exchange tube group according to an embodiment of the present application;

[0026] Label description:

[0027] 100, inner cylinder; 110, upper conical part; 120, cylindrical part; 130, lower conical part;

[0028] 200, outer cylinder; 210, upper platform part; 211, flue gas outlet; 220, cylindrical part; 230, lower platform part; 231, flue gas inlet;

[0029] 300, heat exchange tube group; 310, spiral tube;

[0030] 400, flue gas passage;

[0031] 500, connecting piece. Detailed implementation manners

[0032] In order to enable those skilled in the art of the present technology to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0033] It should be noted that the terms "first", "second", etc. in the description and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so as to describe the embodiments of the present application herein.

[0034] In the present application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation, or be constructed and operated in a specific orientation. And, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present application can be understood according to specific circumstances.

[0035] The present 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 and then inject 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 group 300, which is used to preheat pulverized coal. Specifically, the diameter of the pulverized coal particles is 300 mesh, and they are transported by mixing with high-pressure inert gas for dedicated subsequent pulverized coal injection work.

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

[0038] A closed cavity is formed inside the inner cylinder 100. The inner cylinder 100 includes an upper conical part 110, a cylindrical part 120 and a lower conical part 130 distributed in sequence along the plumb direction. The tip cones of the upper conical part 110 and the lower conical part 130 face in opposite directions.

[0039] The outer cylinder 200 is sleeved on the outside of the inner cylinder 100, and both ends of the outer cylinder 200 are through. The outer cylinder 200 includes an upper table part 210, a cylindrical part 220 and a lower table part 230 distributed in sequence along the plumb direction.

[0040] The heat exchange tube group 300 is arranged around the inner cylinder 100 and includes multiple layers of spiral tubes 310 nested coaxially for the pulverized coal to flow through.

[0041] Among them, the upper conical part 110 and the upper table part 210 are in corresponding positions, the cylindrical part 120 and the cylindrical part 220 are in corresponding positions, the lower conical part 130 and the lower table part 230 are in corresponding positions, and the heat exchange tube group 300 is located between the cylindrical part 120 and the frustum part. A flue gas channel 400 is formed between the inner cylinder 100 and the outer cylinder 200, so that the flue gas flows along the contour of the inner cylinder 100 to heat the heat exchange tube group 300.

[0042] In this way, due to the unique-shaped inner cylinder 100 of the spiral sleeve type pulverized coal preheater of the present application, after the flue gas enters the outer cylinder 200 from the lower side, it is diverted by the lower conical part 130 of the inner cylinder 100 inside the outer cylinder 200. The flue gas makes as much contact as possible with the multiple layers of spiral tubes 310 surrounding the cylindrical part 120 of the inner cylinder 100, so as to fully exchange heat with the pulverized coal in the spiral tubes 310. After heat exchange, it then flows through the upper conical part 110 of the inner cylinder 100 for confluence and is smoothly output externally to further maintain heat. This design can make the flue gas fully contact with the multiple layers of spiral tubes 310, maximize the utilization of the heat of the flue gas in the outer cylinder 200. At the same time, the double conical part design of the inner cylinder 100 fully cooperates with the outer cylinder 20, which can reduce the pressure loss during the flow of the flue gas and thus ensure the flow rate of the flue gas.

[0043] Among them, the flue gas can also enter the outer cylinder 200 from the upper side, first flow through the upper conical part 110 of the inner cylinder 100, and then flow through the lower conical part 130 of the inner cylinder 100.

[0044] As a comparative example, the preheater in the existing design is generally of a single-cylinder structure without an inner cylinder 100. After the flue gas enters the single cylinder, although it also contacts the spiral tube 310, the flue gas in the center of the spiral tube 310 is often larger in volume, making it difficult to efficiently exchange heat with the spiral tube 310. Moreover, the internal space of the single cylinder is large, and it is difficult to maintain high pressure after the flue gas enters the single cylinder, resulting in a weakened flow velocity and easy formation of stagnation in the cylinder. Subsequently, the new high-temperature flue gas cannot quickly enter the single cylinder for heat exchange, further weakening the pulverized coal preheating efficiency.

[0045] Specifically, the inner cylinder 100 is fixed to the inner wall of the outer cylinder 200 through a connecting member 500. There can be several such connecting members 500. Among them, the connecting member 500 is arranged between the upper conical part 110 and the upper table part 210, and / or the connecting member 500 is arranged between the upper conical part 110 and the lower conical part 130 and the lower table part 230.

[0046] As Figure 1 shown, the connecting member 500 is preferably rod-shaped to reduce the occupation of space inside the preheater.

[0047] Preferably, the height of the cylindrical part 120 is equal to the height of the cylindrical part 220, the generatrix of the upper conical part 110 is parallel to the generatrix of the upper table part 210, and the generatrix of the lower conical part 130 is parallel to the generatrix of the lower table part 230. This design enables the flue gas to flow as smoothly as possible in 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 group 300 and the flue gas outlet 211 of the outer cylinder 200 are on the same side, and the pulverized coal outlet of the heat exchange tube group 300 and the flue gas outlet 211 of the outer cylinder 200 are on the same side, enabling the flue gas and the pulverized coal to flow in opposite directions for countercurrent heat exchange. When the pulverized coal is about to be output, the flue gas has just entered the outer cylinder 200. At this time, the flue gas temperature is relatively high, which can further fully heat the pulverized coal, facilitating the preheating of the pulverized coal to the expected temperature. Compared with concurrent heat exchange, countercurrent heat exchange significantly improves the heat exchange effect.

[0049] Among them, the pulverized coal particles in the spiral tube 310 are carried and conveyed by an inert gas. To prevent the pulverized coal particles from settling in the middle of the spiral tube 310, more specifically, the upper side of the heat exchange tube group 300 is the pulverized coal inlet, and the lower side of the heat exchange tube group 300 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 the pulverized coal outlet respectively. As 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 table portion 230, and the flue gas outlet 211 is formed by the upper table portion 210. Thus, in combination with the vertically arranged inner cylinder 100 and outer cylinder 200 structures in this application, the pulverized coal particles flow rapidly from top to bottom against the direction of gravity, minimizing the problem of blockage inside the spiral tube 310 as much as possible, reducing the maintenance burden on users, and improving the pulverized coal preheating efficiency.

[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 slightly inside the outer cylinder 200 to further heat the heat exchange tube group 300.

[0051] Optionally, as Figure 1 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 so that the fluidity of the flue gas is within a better range.

[0052] Furthermore, when the pulverized coal flows downward in the spiral tube 310, it may cause the spiral tube 310 to vibrate. To prevent mechanical damage caused by collisions between the multi-layer spiral tubes 310, preferably, the distance between the adjacent inner and outer spiral tubes 310 is 6 mm to 10 mm, and the spacing between all the spiral tubes 310 is the same, so as to provide a clearance space for each other to prevent contact, and 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 the adjacent inner and outer spiral tubes 310 is 8 mm, so as to control the clearance area, increase the flue gas flow rate, and enhance heat transfer.

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

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

[0056] Preferably, the heat exchange tube group 300 includes an even number of layers of spiral tubes 310. Among them, the inlets of every two layers of spiral tubes 310 are merged and connected to the powder supply main pipe, and the outlets corresponding to every two layers of spiral tubes 310 are also merged and connected to the powder discharge main pipe to reduce the pressure loss when the pulverized coal flows through the heat exchange tube group 300.

[0057] Specifically, the heat exchange tube group 300 includes 2 to 10 spiral tubes 310, and the specific quantity can be flexibly adjusted according to the product scale. A more optimal solution is 2 to 6 spiral tubes 310. For example, the heat exchange tube group 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 passing speed of the pulverized coal in the spiral tubes 310 and prevent the impact on the heating efficiency of pulverized coal injection into the blast furnace at the back. If the number of spiral tubes 310 is large, the spiral tubes 310 will be correspondingly thinner, which will affect the passing speed of the pulverized coal in the spiral tubes 310.

[0058] As a specific embodiment, the present application also provides a pulverized coal preheating system, which includes 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 communicated with the flue gas furnace. The flue gas furnace conveys high-temperature flue gas to the spiral sleeve type through the flue gas inlet 231, and moreover, the high-temperature flue gas that has undergone heat exchange from the outer cylinder 200 can enter the flue gas furnace again through the flue gas outlet 211 for recycling.

[0059] Optionally, the flue gas outlet 211 can also be synchronously communicated with a waste flue gas pipeline, so that part of the flue gas is directly discharged into the waste flue gas pipeline without entering the cycle again, in order to provide space for new high-temperature flue gas.

[0060] Specifically, hot flue gas at about 480°C is generated, and the hot flue gas flows through the spiral sleeve type pulverized coal preheater in the present application to preheat the pulverized coal. After preheating, the temperature of the flue gas is about 180°C. Part of the hot flue gas is circulated to the hot blast stove for reheating, and part of the hot flue gas enters the waste flue gas pipeline for discharge.

[0061] Preferably, the flue gas furnace is communicated with the blast furnace, introduces blast furnace gas, and is heated by a heating device to be used as the 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 pipelines among the flue gas furnace, the spiral sleeve type pulverized coal preheater and the blast furnace are well insulated. For example, the pipeline can be wrapped with high-temperature resistant thermal insulation materials outside.

[0063] Generally speaking, a closed inner cylinder 100 is arranged inside the spiral sleeve type pulverized coal preheater in the present application, which can reduce the flue gas flow rate of the fluid in the outer cylinder 200, and the inner cylinder 100 is adapted to the shape of the outer cylinder 200, increasing the flow rate of the flue gas and performing efficient heat exchange with the coal gas in the multi-layer spiral tubes 310, effectively improving the heat exchange efficiency.

[0064] In this application, the terms "installed", "set up", "provided with", "connected", "linked", and "socketed" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral structure; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, or there may be internal communication between two devices, components, or parts. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0065] The above are only the preferred embodiments of this application and are not intended to limit this application. For those skilled in the art, various changes and modifications can be made to this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A spiral sleeve type pulverized coal preheater, characterized in that, Comprising: An inner cylinder, inside which a closed cavity is formed. The inner cylinder includes an upper conical part, a cylindrical part, and a lower conical part that are sequentially distributed in the plumb direction. The tip cones of the upper conical part and the lower conical part face opposite directions. An outer cylinder, which is sleeved outside the inner cylinder and both ends of the outer cylinder are through. The outer cylinder includes an upper table part, a cylindrical part, and a lower table part that are sequentially distributed in the plumb direction. A heat exchange tube group, which is arranged around the inner cylinder and includes multiple layers of coaxial nested spiral tubes for the circulation of pulverized coal. Wherein, the upper conical part and the upper table part are in corresponding positions, the cylindrical part and the cylindrical part are in corresponding positions, the lower conical part and the lower table part are in corresponding positions, and the heat exchange tube group is located between the cylindrical part and the frustum part. A flue gas passage 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 group.

2. The spiral sleeve type pulverized coal preheater according to claim 1, wherein: The height of the cylindrical part is equal to the height of the cylindrical part. The generatrix of the upper conical part is parallel to the generatrix of the upper table part, and the generatrix of the lower conical part is parallel to the generatrix of the lower table part.

3. The spiral sleeve type pulverized coal preheater according to claim 1, wherein: The pulverized coal inlet of the heat exchange tube group and the flue gas outlet of the outer cylinder are on the same side, and the pulverized coal outlet of the heat exchange tube group and the flue gas inlet of the outer cylinder are 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, wherein: The upper side of the heat exchange tube group is the pulverized coal inlet, and the lower side of the heat exchange tube group is the pulverized coal outlet. A flue gas inlet is arranged on the lower side of the outer cylinder, and a flue gas outlet is arranged on the upper side of the outer cylinder.

5. The spiral sleeve type pulverized coal preheater according to claim 4, wherein: 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, wherein: The slopes of the upper conical part and the lower conical part are the same.

7. The spiral sleeve type pulverized coal preheater according to claim 6, wherein: The minimum slope of the upper conical part and the lower conical part is 8. The spiral sleeve type pulverized coal preheater according to claim 1, wherein: The distance between adjacent inner and outer spiral tubes is 6 mm to 10 mm; the distances between all spiral tubes are the same.

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

10. The spiral sleeve type pulverized coal preheater according to claim 1, wherein: The heat exchange tube group includes an even number of layers of spiral tubes; wherein, the inlets of every two layers of spiral tubes are connected in parallel with each other, and the corresponding outlets of every two layers of spiral tubes are also connected in parallel with each other.

11. The spiral sleeve type pulverized coal preheater according to claim 10, wherein: The heat exchange tube group includes 2 to 6 spiral tubes.

12. A pulverized coal preheating system, wherein: It includes a flue gas furnace and the 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 communicated with the flue gas furnace.

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