Double-circulation perlite ore sand gradient preheating system capable of utilizing waste heat of tail gas of gas expansion furnace

Abstract

The double-circulation perlite ore sand gradient preheating system utilizing the waste heat of the tail gas of the fuel gas expansion furnace is provided with the double-return-stroke channels, the material heating time is prolonged, the heating temperatures of the double-return-stroke channels are different, low-temperature preheating is conducted firstly, then medium-temperature preheating is conducted, and the heating efficiency is improved. And most free water and part of bound water in the ore sand are removed more slowly and mildly. According to the technical scheme, an outer-layer material channel is formed between an outer pipe and a middle pipe, and a first spiral conveying structure is arranged on the inner wall of the outer-layer material channel; an inner-layer material channel is formed between the middle pipe and the inner core pipe, and a second spiral conveying structure is arranged on the inner wall of the inner-layer material channel; the heating cavity consists of an inner cavity of the inner core tube; and the rotating direction of the first spiral conveying structure is opposite to that of the second spiral conveying structure, so that materials are conveyed from the first end to the second end in the outer-layer material channel, enter the inner-layer material channel from the second feeding hole in the second end and are conveyed from the second end to the first end in the inner-layer material channel.

Description

Technical Field

[0001] This utility model relates to the technical field of perlite expansion equipment, and in particular to a dual-circulation perlite ore gradient preheating system for utilizing waste heat from the tail gas of a gas-fired expansion furnace. Background Technology

[0002] A perlite expansion furnace is a specialized piece of equipment for producing expanded perlite. Vitrified microspheres are white granular materials with a honeycomb-like internal structure, produced by preheating and then instantaneously calcining perlite ore to expand it. The production process of expanded perlite is as follows: Perlite manufacturers select perlite raw material ore of different particle sizes according to different applications. The moisture content of the perlite raw material ore is generally 4-6%. Rapid evaporation of moisture can cause the perlite to crack. Therefore, the ineffective water content of the perlite raw material ore should be removed before expansion. Extensive testing by domestic and international laboratories and manufacturers has shown that the optimal expansion effect and the largest expansion ratio (i.e., the lowest loose density) are achieved when the effective water content of expanded perlite is between 2.2% and 2.4%. Therefore, the production process of expanded perlite includes two key steps: preheating and expansion.

[0003] However, the preheating furnaces currently used for expanded perlite typically employ electric heating or gas heating for preheating. For example, a Chinese patent for an expanded perlite preheating furnace, publication number CN206944710U, includes a horizontally arranged cylindrical furnace chamber, four support rollers located below the front and rear ends of the furnace chamber, a drive mechanism for rotating the furnace chamber, a refractory brick furnace shell located outside the furnace chamber, a gas inlet pipe, an air distribution pipe, and an air distribution fan. A furnace chamber is located between the refractory brick furnace shell and the furnace chamber. A heating port is located on the side wall of the refractory brick furnace shell directly below the furnace chamber. The end of the gas inlet pipe extends into the furnace chamber through the heating port. The air distribution fan is located at the inlet of the air distribution pipe, which is connected to the gas inlet pipe.

[0004] Therefore, it is evident that most existing technologies use an additional heating source to heat the perlite preheating furnace, neglecting the preheating generated by the expansion furnace itself, resulting in energy and economic waste. For example, a Chinese patent for an expanded perlite preheating furnace, publication number CN206944710U, includes a refractory brick shell, a gas inlet pipe, a furnace chamber, a furnace liner inside the furnace chamber, and multiple feeding plates inside the furnace liner. Natural gas is burned in the furnace chamber to heat the furnace liner, and materials are conveyed inside the furnace liner via the feeding plates, during which the materials are preheated. This design has the following drawbacks: 1. Because its inner liner channel is a single-pass channel, at the same conveying speed and the same inner liner length, a higher furnace temperature is required for sufficient preheating, resulting in energy waste; 2. Using additional heating energy also leads to energy waste. Utility Model Content

[0005] To address the above technical problems, this utility model provides a dual-circulation perlite ore gradient preheating system for utilizing waste heat from the tail gas of a gas-fired expansion furnace. It has dual return channels, which extends the heating time of the material. The heating temperatures of the two return channels are different, with low-temperature preheating first and medium-temperature preheating, which allows for a slower and gentler removal of most of the free water and some of the bound water from the ore.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] A dual-circulation perlite sand gradient preheating system for utilizing waste heat from the exhaust gas of a gas-fired expansion furnace includes:

[0008] The three-layer tube structure is coaxially nested: from the outside to the inside, it consists of an outer tube, a middle tube, and an inner core tube.

[0009] Dual-circulation material channel:

[0010] a) An outer material channel is formed between the outer tube and the middle tube, and its inner wall is provided with a first spiral conveying structure;

[0011] b) An inner material channel is formed between the middle tube and the inner core tube, and its inner wall is provided with a second spiral conveying structure;

[0012] Rotary drive unit: A flipping drive mechanism connected to the outer tube, used to drive the tube body to rotate around the axis;

[0013] Feeding assembly: A hopper assembly located at the first end of the outer tube along the axial direction, comprising multiple circumferentially distributed hoppers and a first feed inlet connected thereto, the first feed inlet leading to the outer material channel;

[0014] Material diversion interface: The second feed port located at the second end of the central tube axis is used to introduce the material output from the outer material channel into the inner material channel;

[0015] Discharge port: The opening at the end of the middle tube extending axially to the first end of the outer tube;

[0016] Heating chamber: Consists of the inner cavity of the inner core tube;

[0017] Reverse conveying structure: The rotation direction of the first spiral conveying structure is opposite to that of the second spiral conveying structure, so that the material is conveyed from the first end to the second end in the outer material channel, and from the second end to the first end in the inner material channel.

[0018] Furthermore, the flipping drive mechanism includes:

[0019] The first tugboat is fixed at both ends of the outer tube;

[0020] A second tugboat that rolls in conjunction with each of the first tugboats;

[0021] The first support is rotatably fitted onto the first support;

[0022] Drive gear set: The first gear fixed to the outer tube meshes with the second gear driven by the motor.

[0023] Furthermore, the first spiral conveying structure includes:

[0024] The first continuous screw conveyor section adjacent to the first feed inlet;

[0025] The first intermittent push section adjacent to the second feed inlet is composed of a first inclined push plate (a) arranged along a spiral.

[0026] Furthermore, the second spiral conveying structure includes:

[0027] The second continuous screw conveyor section adjacent to the second feed inlet;

[0028] The second intermittent pushing section adjacent to the discharge port is composed of a second inclined pushing plate (a) arranged along a spiral.

[0029] Furthermore, the heating chamber is connected to an expansion furnace waste heat recovery device, which includes:

[0030] The elbow pipe connecting to the outlet of the expansion furnace has a circulating water cooling module on its outer wall;

[0031] The feed pipe connected to the elbow outlet has its end connected to the heating chamber of the inner core tube via a rotary joint.

[0032] The distributor located at the bottom of the feed tube includes a discharge port at the bottom of the feed tube and a finished product hopper that matches the discharge port.

[0033] Furthermore, the pusher plates of the intermittent pusher section are arranged in multiple rows in a circular pattern, with radially penetrating airflow channels formed between adjacent rows.

[0034] Furthermore, the preheating temperature range of the outer material channel is 200-250℃, and the preheating temperature range of the inner material channel is 300-400℃, forming a gradient heating path.

[0035] Furthermore, the outer wall of the outer tube is covered with an insulation layer.

[0036] Furthermore, the spiral conveying structure is composed of continuous spiral blades.

[0037] Furthermore, the first spiral conveying structure is fixed on the inner wall of the outer tube and located in the outer material channel; the second spiral conveying structure is fixed on the inner wall of the middle tube and located in the inner material channel.

[0038] The beneficial effects of this utility model are:

[0039] 1. By setting up an outer material channel and an inner material channel, perlite ore raw material enters from the first feed port at the head of the outer material channel and is conveyed by a screw to the second feed port at the tail, thus entering the inner material channel. The inner material channel conveys the material through a screw to the discharge port at the head. Through double-pass conveying, the heating time and heating distance of the material are increased. Under the same preheating temperature, pipe length and speed, the preheating effect is improved. Moreover, due to the longer preheating time, the heating temperature of the material channel with a lower single-pass temperature can also achieve a good preheating effect, saving heating energy.

[0040] 2. The inner core tube is located inside the two material channels, and its inner cavity forms a heating chamber, making the temperature of the inner material channel higher than that of the outer material channel. The preheating temperature of perlite is generally between 200-400℃. In this invention, during the preheating process, the material first passes through the outer material channel and then the inner material channel, with the heating temperature increasing from low to high. This results in the outer low-temperature stage (e.g., 200-250℃): primarily removing free water and weakly bound water (desorption rate is slow). The inner medium-temperature stage (e.g., 300-400℃): remaining weakly bound water and strongly bound water are released controllably in the cleared moisture channels. Traditional technology directly preheats at medium temperatures (e.g., 350℃), causing rapid vaporization of moisture and a surge in internal steam pressure; direct high temperatures cause the particle surface to dry rapidly, forming a "hard shell," hindering the escape of internal steam and leading to localized pressure accumulation and microcracks. Therefore, compared with direct high-temperature preheating, the core advantages of this utility model are: more precise control of the moisture removal process, avoidance of thermal stress concentration, and significant reduction of the risk of particle breakage.

[0041] 3. In a screw conveyor structure with a combination of continuous spiral blades and pusher plates, continuous spiral blades are set at the feed inlet so that the material is quickly pushed forward after entering. Then, multiple pusher plates arranged in a spiral pattern are set intermittently, which increases the material cavity. During the overall tumbling process driven by the outer tube, the material becomes more loose and can come into more full contact with the hot air in the cavity. The intermittent pusher plates also save material.

[0042] 4. Using an expansion furnace waste heat recovery device to heat the heating chamber saves energy. Attached Figure Description

[0043] To more clearly illustrate the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a front view of a specific product embodiment of the present utility model;

[0045] Figure 2 for Figure 1 View from direction A;

[0046] Figure 3 for Figure 1 Top view;

[0047] Figure 4 This is a perspective view of the preheating furnace portion of this utility model;

[0048] Figure 5 This is a cross-sectional view of the present invention.

[0049] Figure 6 This is a two-section view from the perspective of this utility model;

[0050] Figure 7 This is a three-section view of the present invention.

[0051] Figure 8 This is a four-section view of the present invention.

[0052] Figure 9 This is a perspective view of the waste heat recovery device of this utility model;

[0053] Figure 10 This is a cross-sectional view of the waste heat recovery device of this utility model;

[0054] Figure 11 The shape of the preheating furnace part of this utility model Figure 1 ;

[0055] Figure 12 The shape of the preheating furnace part of this utility model Figure 2 .

[0056] Explanation of reference numerals in the attached drawings: Outer pipe 1, outer material channel 101, middle pipe 2, inner material channel 201, inner core pipe 3, heating chamber 301, first spiral conveying structure 4, first continuous spiral conveying section 401, first intermittent pushing section 402, first inclined pushing plate 402a, second spiral conveying structure 5, second continuous spiral conveying section 501, second intermittent pushing section 502, second inclined pushing plate 502a, flipping drive mechanism 6, first drag wheel 601, second drag wheel 602, first gear 603, second gear 604, motor 605, first support 606, hopper assembly 7, digging hopper 701, first feed inlet 702, second feed inlet 8, discharge outlet 9, elbow pipe 10, circulating water cooling module 11, guide pipe 12, distributor 13, discharge outlet 1301, finished product hopper 1302, insulation layer 14. Detailed Implementation

[0057] The following will refer to the appendix in the embodiments of this utility model. Figure 1-12 The technical solutions in the embodiments of this utility model are clearly and completely described herein. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0058] This utility model discloses a dual-circulation perlite sand gradient preheating system for utilizing waste heat from the tail gas of a gas-fired expansion furnace, comprising a preheating furnace, wherein the preheating furnace includes:

[0059] A coaxially nested three-layer tubular structure: from the outside to the inside, it consists of an outer tube 1, a middle tube 2, and an inner core tube 3; in this embodiment, the tubular structure is placed horizontally, and the first and second ends of the outer tube 1 and the middle tube 2 are sealed (the orientation in this embodiment is...). Figure 1 In the orientation shown, the first end is the right end and the second end is the left end. The second end of the middle tube 2 is fixed to the inner wall of the second end of the inner tube 1, and the first end of the middle tube 2 extends out of the first end of the outer tube 1. The first and second ends of the inner core tube 3 extend out of the first and second ends of the middle tube 2, respectively, and the second end of the outer tube 1 is sealed to the inner core tube 3.

[0060] Dual-circulation material channel:

[0061] a) An outer material channel 101 is formed between the outer pipe 1 and the middle pipe 2, and a first spiral conveying structure 4 is provided on its inner wall; the outer material channel 101 is used to preheat the perlite ore raw material in the first stage of low temperature section; the first spiral conveying structure 4 is fixed on the inner side wall of the outer pipe 1 and located in the outer material channel 101.

[0062] (b) An inner material channel 201 is formed between the middle tube 2 and the inner core tube 3, and a second spiral conveying structure 5 is provided on its inner wall; the inner material channel 201 performs a second-stage medium-temperature preheating of the perlite ore. The second spiral conveying structure 5 is fixed on the inner side wall of the middle tube 2 and located inside the inner material channel 201.

[0063] Rotary drive unit: The flipping drive mechanism 6 connected to the outer tube 1 is used to drive the tube body to rotate around the axis. The rotary drive unit drives the tube body to flip. During the flipping process, the spiral conveying structure works to transport the material. The flipping of the tube body causes the material in the outer material channel 101 and the inner material channel 201 to move axially driven by the spiral structure. At the same time, the tube wall carries the material to a high place and then it falls freely, forming continuous scattering. The dynamic tumbling ensures that the surface of each mineral sand is continuously exposed to the hot airflow, avoiding uneven heating caused by static accumulation.

[0064] Feeding assembly: A hopper assembly 7 located at the first axial end of the outer tube 1 includes multiple circumferentially distributed digging hoppers 701 and a first feed inlet 702 connected to them. The first feed inlet 702 leads to the outer material channel 101. A feeding bin is fitted at the bottom of each digging hopper 701. During the tube's rotation, the multiple digging hoppers 701 sequentially feed material from the feeding bins into the outer material channel 101 through the first feed inlet 702. This forms a continuous feeding system for the preheating furnace.

[0065] Material diversion interface: The second feed port 8 is located at the second end of the axial direction of the middle tube 2 and is used to guide the material output from the outer material channel 101 into the inner material channel 201; there are multiple second feed ports 8, which are evenly distributed around the circumference of the middle tube 2.

[0066] Discharge port 9: The opening at the end of the middle tube 2 extending axially to the first end of the outer tube 1;

[0067] Heating chamber 301: Composed of the inner cavity of inner core tube 3;

[0068] Reverse conveying structure: The first spiral conveying structure 4 rotates in the opposite direction to the second spiral conveying structure 5, causing the material to be conveyed from the first end to the second end in the outer material channel 101, and from the second end to the first end in the inner material channel 201. The reverse spiral design achieves double the preheating path within a finite length. Both the first and second spiral structures can be composed of continuous spiral blades.

[0069] As one embodiment of this utility model, the flipping drive mechanism 6 includes:

[0070] The first tugboat 601 is fixed at both ends of the outer tube 1;

[0071] A second tug wheel 602 is rolled in cooperation with each of the first tug wheels 601; preferably, the second tug wheel 602 has flanges at both ends along its axial direction, and the first tug wheels are fitted into the annular grooves formed by the flanges at both ends. This arrangement can effectively prevent the first tug wheel 601 from disengaging from the second tug wheel 602;

[0072] The first support 606, the first tug wheel 602 is rotatably fitted on the first support 606; the second tug wheel 602 provides support for the first tug wheel 601.

[0073] Drive gear set: The first gear 603, fixed to the outer tube 1, meshes with the second gear 604 driven by the motor 605. The motor 605 drives the second gear 604, which in turn drives the first gear 603 to rotate. The first gear rotates the outer tube 1, which in turn rotates the first rollers 601 at both ends. The first rollers 601 drive the second rollers 602 to rotate. Simultaneously, this drives the first spiral conveyor structure 4 and the second spiral conveyor structure 5 to convey materials in opposite directions. The roller structures at both ends effectively support the tube structure.

[0074] As an embodiment of the present invention, the first spiral conveying structure 4 includes:

[0075] The first continuous screw conveyor section 401 is adjacent to the first feed inlet 702;

[0076] The first intermittent pushing section 402 adjacent to the second feed inlet 8 is composed of a first inclined pushing plate 402a arranged along a spiral. The first spiral conveying structure 4 is located within the outer material channel 101.

[0077] The second spiral conveyor structure 5 includes:

[0078] The second continuous screw conveyor section 501 is adjacent to the second feed inlet 8;

[0079] The second intermittent pushing section 502 adjacent to the discharge port 9 is composed of a second inclined pushing plate 502a arranged along a spiral. The second spiral conveying structure 5 is located within the inner material channel 101.

[0080] In this embodiment, the continuous spiral conveyor section consists of continuous spiral blades. The continuous spiral conveyor section at the inlet enhances the material conveying capacity. When the material passes through the pusher plate area, it loses the constraint of the continuous blades and disperses fully under gravity. The centrifugal force generated by the rotation of the tube throws the material against the outer wall of the channel; when the material rises to a certain height (approximately 60°-90°) with the tube wall, gravity overcomes the centrifugal force, and the material falls freely; the intermittent pusher plate area forms a material waterfall, fully dispersing the particles. This creates a "splashing-falling" cycle. As a specific example, the pusher plate maintains a gap of 0.5-1mm with the outer tube wall.

[0081] In a preferred embodiment, the pusher plates of the intermittent pushing section (402, 502) are arranged in multiple rows in a circular pattern, with radially penetrating airflow channels 403 formed between adjacent rows. Exhaust gas at a certain temperature radiates heat radially from the inner core tube (heating chamber); as the material tumbles, airflow channels are formed between the pusher plates, allowing hot gas to penetrate the material layer; the particle surface continuously renews its interface with the hot gas. During radial heat radiation from the heating chamber, the inner and outer material channels sequentially form a medium-temperature heating section (300-400℃) and a low-temperature heating section (200-250℃), creating a gradient heating path.

[0082] In one embodiment of this utility model, the heating chamber 301 is connected to an expansion furnace waste heat recovery device, which includes:

[0083] The elbow pipe 10 connected to the outlet of the expansion furnace has a circulating water cooling module 11 on its outer wall;

[0084] The feed pipe 12, which is connected to the outlet of the elbow pipe 10, is connected at its end to the heating chamber 301 of the inner core tube 3 via a rotary joint.

[0085] The distributor 13 located at the bottom of the guide pipe 12 includes a discharge port 1301 at the bottom of the guide pipe 12 and a finished product hopper 1302 that cooperates with the discharge port 1301.

[0086] The circulating water-cooled module is a water-cooled tank, through which cooling water is circulated to cool the elbow pipe. This cooling water circulation system supplies cooling water to the tank to cool the elbow pipe 10 inside. The expanded perlite material is in a molten state before entering the elbow pipe 10. Because the material channel inside the elbow pipe 10 is cooled by the cooling water, the temperature of the molten material flow decreases from a high-temperature stage of 900-1050℃ to a medium-temperature stage of 680-780℃ upon entering the elbow pipe, changing the material from a molten state to a granular state. This cooling prevents the high-speed molten material from sticking to the curved part of the elbow pipe 10, causing material accumulation. The cooling water circulation system consists of circulation pipelines, a circulation pump, and a cooling unit, which is existing technology and will not be described in detail here.

[0087] The material flow enters the horizontally placed guide pipe 12 through the elbow pipe 1. A discharge port 1301 is located at the bottom of the guide pipe 12. Most of the material particles fall into the discharge hopper through the discharge port 1301. The material in the finished product hopper 1302 is conveyed to the finished product bin. A portion of the lighter material enters the heating chamber of the preheating 8 under the action of the system's induced draft, heating the heating chamber. Afterward, the material flow passes through a cyclone separator to separate the waste gas, and the remaining material enters the finished product bin. This utility model is a preheating furnace for supplying waste heat. The expanded perlite falling from the feed inlet 1301 of the feed pipe falls under its own weight, while the lighter materials and the medium-temperature (680-780℃) exhaust gas containing dust are drawn into the cyclone separator through the horizontally arranged inner core tube 3 channel of the preheating furnace by the system's induced draft. Under the action of centrifugal force, the finished product falls to the bottom and is conveyed by air to the finished product silo for storage. The exhaust gas containing dust enters the multi-tube dust collector for depressurization, cooling and dust collection. After depressurization and cooling, the exhaust gas enters the pulse bag dust collector for secondary filtration, further filtering out the dust in the exhaust gas. The treated exhaust gas is discharged through the chimney in compliance with standards. The finished product is packaged through the receiving port at the bottom of the silo and then stored or sold. The heating chamber of the inner core tube is designed in a straight line, which is more conducive to the passage of exhaust gas and material flow from the expansion furnace. The feed pipe 12 and the elbow pipe 10 are both made of thermally conductive materials, such as aluminum and stainless steel. At the same time, the inner core tube and the middle tube are also made of thermally conductive materials such as stainless steel. The outer tube can also be made of stainless steel, but for heat preservation, an insulation layer 14 is wrapped around the outside of the outer tube. This insulation layer 14 is made of 100mm thick aluminum silicate insulation cotton.

[0088] Since the temperature of the heating chamber introduced into the inner core tube is 680-780℃, which is lower than that of natural gas heating or electric heating, it requires a longer heating stroke. However, increasing the length of a single channel is not conducive to site layout. Therefore, this utility model innovatively solves the problem by using a double return path.

[0089] The process of using this utility model is as follows:

[0090] The equipment motor is started, causing the pipe to rotate. Perlite ore is evenly distributed around the circumference of the hopper into the outer material channel. Driven by the first spiral conveyor structure, the material moves along the pipe axis from the feed end to the turning end. At this point, it enters the 200-250℃ low-temperature section: free water is removed (the gap between the pusher plates increases the material's looseness). The material then turns through the second feed inlet into the inner material channel, where it is driven by the reverse second spiral conveyor structure, moving along the axis from the turning end to the discharge end. At this point, it enters the 300-400℃ medium-temperature section: some bound water escapes through the air gap of the pusher plate. The energy recovery process of this utility model is as follows: expansion furnace tail gas → water-cooled dust suppression in the elbow pipe → hot gas injection into the inner core pipe; after preheating, the ore enters the expansion furnace through the discharge port.

Claims

1. A dual-circulation perlite sand gradient preheating system for utilizing waste heat from the exhaust gas of a gas-fired expansion furnace, characterized in that, include: The three-layer tube structure is coaxially nested: from the outside to the inside, it consists of an outer tube (1), a middle tube (2), and an inner core tube (3); Dual-circulation material channel: a) An outer material channel (101) is formed between the outer tube (1) and the middle tube (2), and its inner wall is provided with a first spiral conveying structure (4); b) An inner material channel (201) is formed between the middle tube (2) and the inner core tube (3), and a second spiral conveying structure (5) is provided on its inner wall; Rotation drive unit: a flipping drive mechanism (6) connected to the outer tube (1) for driving the tube body to rotate around the axis; Feeding assembly: A hopper assembly (7) located at the first axial end of the outer tube (1) includes a plurality of circumferentially distributed hoppers (701) and a first feed port (702) connected thereto, the first feed port (702) leading to the outer material channel (101); Material diversion interface: The second feed port (8) located at the second end of the axial direction of the middle tube (2) is used to introduce the material output from the outer material channel (101) into the inner material channel (201); Outlet (9): The opening at the end of the middle tube (2) extending axially to the first end of the outer tube (1); Heating chamber (301): Composed of the inner cavity of the inner core tube (3); Reverse conveying structure: The first spiral conveying structure (4) rotates in the opposite direction to the second spiral conveying structure (5), so that the material is conveyed from the first end to the second end in the outer material channel (101) and from the second end to the first end in the inner material channel (201).

2. The system according to claim 1, characterized in that, The flipping drive mechanism (6) includes: The first tugboat (601) is fixed at both ends of the outer tube (1); A second tugboat (602) that rolls in cooperation with each of the first tugboats (601); The first support (606) is rotatably fitted on the first support (606); Drive gear set: The first gear (603) fixed on the outer tube (1) meshes with the second gear (604) driven by the motor (605).

3. The system according to claim 1, characterized in that, The first spiral conveying structure (4) includes: The first continuous screw conveyor section (401) is adjacent to the first feed inlet (702); The first intermittent push section (402) adjacent to the second feed port (8) is composed of a first inclined push plate (402a) arranged along a spiral.

4. The system according to claim 1, characterized in that, The second spiral conveyor structure (5) includes: The second continuous screw conveyor section (501) adjacent to the second feed inlet (8); The second intermittent pushing section (502) adjacent to the discharge port (9) is composed of a second inclined pushing plate (502a) arranged along a spiral line.

5. The system according to claim 1, characterized in that, The heating chamber (301) is connected to an expansion furnace waste heat recovery device, which includes: The elbow pipe (10) connected to the outlet of the expansion furnace has a circulating water cooling module (11) on its outer wall; The feed pipe (12) connected to the outlet of the elbow pipe (10) has its end connected to the heating chamber (301) of the inner core tube (3) via a rotary joint; The distributor (13) located at the bottom of the guide pipe (12) includes a discharge port (1301) at the bottom of the guide pipe (12) and a finished product hopper (1302) that cooperates with the discharge port (1301).

6. The system according to claim 3 or 4, characterized in that, The pusher plates of the intermittent pusher section (402, 502) are arranged in multiple rows in a circular pattern, and a radially penetrating airflow channel (403) is formed between adjacent rows.

7. The system according to claim 1, characterized in that, The preheating temperature range of the outer material channel (101) is 200-250℃, and the preheating temperature range of the inner material channel (201) is 300-400℃, forming a gradient heating path.

8. The system according to claim 1, characterized in that, The outer wall of the outer tube (1) is covered with a heat insulation layer (14).

9. The system according to claim 1, characterized in that, The spiral conveyor structure is composed of continuous spiral blades.

10. The system according to claim 1, characterized in that, The first spiral conveying structure (4) is fixed on the inner wall of the outer tube (1) and located in the outer material channel (101); the second spiral conveying structure (5) is fixed on the inner wall of the middle tube (2) and located in the inner material channel (201).

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