A blast furnace slag waste heat recovery device and a recovery method

Abstract

The present invention provides a blast furnace slag waste heat recovery device composed of a first heat exchange chamber (1), a second heat exchange chamber (2), a hopper (3), a sand discharge port (4), and a blast furnace (5) for recovering the waste heat of the slag. The present invention also provides a corresponding waste heat recovery method: according to the intermittent slag discharge characteristics of the blast furnace (5), for each batch of slag, first transfer its heat to fine sand in the first heat exchange chamber (1); let the heated fine sand fall into the second heat exchange chamber (2) to heat the iron-making raw materials; discharge the fine sand to absorb the heat of the next batch of slag; utilize the time interval between two slag discharges to simultaneously carry out the operations of recovering the waste heat of the slag and absorbing the heat of the iron-making raw materials; after the heated iron-making raw materials are put into the blast furnace (5) for iron-making, the heat supply of the hot blast stove is saved, achieving the indirect recovery effect of the waste heat of the slag. The blast furnace slag waste heat recovery device of the present invention has a simple structure and low cost; the corresponding waste heat recovery method has a short process, is reliable and stable, and does not pollute the environment.

Description

Technical Field

[0001] The present invention relates to the field of iron-making blast furnaces, and particularly to a blast furnace slag waste heat recovery device and a recovery method. Background Art

[0002] Blast furnace ironmaking is the main way to industrially produce iron. The process of blast furnace ironmaking is to put raw materials such as iron ore, coke and flux (limestone, dolomite) into the blast furnace from the top, use the hot air blown into the blast furnace to heat the materials, and intermittently discharge molten iron and slag. Usually, about 300 kg of blast furnace slag is produced for every ton of iron smelted, and the slag tapping temperature is as high as about 1400 °C. Therefore, the slag discharged during the blast furnace ironmaking process contains a large amount of heat energy.

[0003] At present, a large amount of water is generally used in industry to cool blast furnace slag. The cooled slag is used for purposes such as building materials, and the water is heated to become hot water at 80-90 °C. However, this hot water is difficult to utilize because it contains solid particle impurities and sulfur. Some current new technologies have proposed various blast furnace slag waste heat recovery schemes, but most of them have long processes, complex equipment and large investments. For example, Chinese Patent 201821528753.X proposes to recover the waste heat of the slag for power generation. However, since the slag tapping from the blast furnace is intermittent, it is difficult to ensure a stable energy supply during the power generation process; at the same time, the relevant equipment process is relatively complex and the investment payback period is long.

[0004] Therefore, there is an urgent need to develop new blast furnace slag waste heat recovery technologies that are simple in equipment, low in cost, short in process, reliable and stable in operation, and do not pollute the environment. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a blast furnace slag waste heat recovery device with a simple structure and low cost, and provides a corresponding waste heat recovery method with a short process, reliability, stability and no environmental pollution.

[0006] According to one aspect of the present invention, there is provided a blast furnace slag waste heat recovery device for recovering the waste heat of slag. The device is provided with a first heat exchange chamber, a second heat exchange chamber, a hopper and a sand discharge port from top to bottom; two opposite sides of the top of the first heat exchange chamber are respectively provided with a first feed port and a slag inlet, two opposite sides of the bottom are respectively provided with a first block pusher and a first discharge port, the bottom is provided with a first screen and a first movable partition, and the first screen is located above the first partition, and a first limiting groove is provided on the wall surface of the first heat exchange chamber to restrict the first movable partition; a second feed port is provided on the side of the top of the second heat exchange chamber, two opposite sides of the bottom are respectively provided with a second block pusher and a second discharge port, the bottom is provided with a second screen and a second movable partition, and the second screen is located above the second partition, and a second limiting groove is provided on the wall surface of the second heat exchange chamber to restrict the second movable partition; the hopper is a flared structure that gradually narrows from top to bottom, and a sand discharge port is provided at the center of its bottom; the first block pusher is composed of a hydraulic cylinder, a push rod and a push block, and the second block pusher is composed of a hydraulic cylinder, a push rod and a push block.

[0007] For the above-mentioned blast furnace slag waste heat recovery device, the first feed port is connected to a first feed trough, the slag inlet is connected to a blast furnace slag discharge trough, and the second feed port is connected to a second feed trough.

[0008] For the above-mentioned blast furnace slag waste heat recovery device, a first gate and a second gate are provided on both the first discharge port and the second discharge port, and when the gates are closed, the corresponding discharge ports are also in a closed state.

[0009] For the above-mentioned blast furnace slag waste heat recovery device, the mesh numbers of both the first screen and the second screen are between 1 mesh and 5 mesh.

[0010] For the above-mentioned blast furnace slag waste heat recovery device, a heat insulation layer is provided on the outer wall surface of the device.

[0011] According to another aspect of the present invention, there is provided a waste heat recovery method for the above-mentioned blast furnace slag waste heat recovery device. The first movable partition and the second movable partition are default to be in a state of separating the materials in the device. Before the current batch of slag is discharged from the blast furnace, fine sand and ironmaking raw materials are pre-loaded in the second heat exchange chamber; after the current batch of slag is discharged from the blast furnace, the following steps are performed:

[0012] Step S1: Keep the material separation state of the first movable partition, and load fine sand with a volume of 10% to 30% of the first heat exchange chamber into the first heat exchange chamber through the first feed port;

[0013] Step S2: Discharge the high-temperature slag into the first heat exchange chamber through the slag inlet;

[0014] Step S3: Load fine sand into the first heat exchange chamber through the first feed port until the internal space of the first heat exchange chamber is filled;

[0015] Step S4: Leave it for a period of time;

[0016] Step S5: Pull out the second movable partition board, so that the fine sand in the second heat exchange chamber falls into the hopper through the second screen and is discharged through the sand discharge port for recycling, and then insert the second movable partition board again to keep the second heat exchange chamber and the hopper separated;

[0017] Step S7: Open the second discharge port, push out the ironmaking raw materials in the second heat exchange chamber through the second pusher for blast furnace ironmaking, and then close the second discharge port;

[0018] Step S8: Load ironmaking raw materials with a volume of 10% to 30% of the second heat exchange chamber into the second heat exchange chamber through the second feed port;

[0019] Step S9: Pull out the first movable partition board, so that the fine sand in the first heat exchange chamber falls into the second heat exchange chamber through the first screen, and then insert the first movable partition board again to keep the first heat exchange chamber and the second heat exchange chamber separated;

[0020] Step S10: Open the first discharge port, push out the slag in the first heat exchange chamber through the first pusher, and then close the first discharge port.

[0021] In the above waste heat recovery method, before the current batch of slag is discharged from the blast furnace, the fine sand contained in the second heat exchange chamber is the fine sand that was heated in the first heat exchange chamber by the previous batch of slag and then fell into the second heat exchange chamber.

[0022] In the above waste heat recovery method, the particle size of the fine sand is less than 0.5 mm, and the ironmaking raw materials are any one or any mixture of iron ore, coke and flux, where the flux is any one or a mixture of limestone and dolomite.

[0023] In the above waste heat recovery method, the leaving time in Step S4 is 90% to 95% of the time interval between two adjacent batches of slag discharge from the blast furnace.

[0024] In the leaving process of Step S4 in the above waste heat recovery method, the fine sand in the first heat exchange chamber absorbs the heat of the current batch of slag, and at the same time, the fine sand that was heated by the previous batch of slag in the second heat exchange chamber transfers its own heat to the ironmaking raw materials.

[0025] According to the characteristics of intermittent slag discharge from the blast furnace, for each batch of molten slag, its heat is first transferred to fine sand in the first heat exchange chamber; then the heated fine sand falls into the second heat exchange chamber under the action of gravity to heat the iron-making raw materials; finally, the fine sand is discharged to absorb the heat of the next batch of molten slag, realizing the recycling of the fine sand. When the current batch of molten slag heats the fine sand in the first heat exchange chamber, the fine sand heated by the previous batch of molten slag in the second heat exchange chamber is heating the iron-making raw materials, thus ensuring the stable and reliable heat recovery process, making full use of the time interval between two slag discharges, and simultaneously carrying out the operations of molten slag waste heat recovery and iron-making raw material heat absorption. After the heated iron-making raw materials are put into the blast furnace for iron-making, it is equivalent to partially transferring the thermal energy of the molten slag back to the blast furnace, thereby saving the heat supply of the hot blast stove and achieving the indirect recovery effect of molten slag waste heat.

[0026] The device of the present invention has a simple structure and low cost. Except for the first pusher and the second pusher, it basically does not involve dynamic equipment. Since recycled and inert fine sand is used as the heat exchange medium instead of conventional water or gas, the cost is low, resources are saved, the corrosion of the equipment is very small, and no pollutants are discharged into the external environment. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of the waste heat recovery device in the embodiment of the present invention. In the figure, 1 is the first heat exchange chamber, 2 is the second heat exchange chamber, 3 is the hopper, 4 is the sand discharge port, 5 is the blast furnace, 11 is the first feed inlet, 12 is the first feed chute, 13 is the first discharge outlet, 14 is the first gate, 15 is the molten slag inlet, 16 is the blast furnace slag discharge chute, 17 is the hydraulic cylinder of the first pusher, 18 is the push rod of the first pusher, 19 is the push block of the first pusher, 21 is the second feed inlet, 22 is the second feed chute, 23 is the second discharge outlet, 24 is the second gate, 25 is the hydraulic cylinder of the second pusher, 26 is the push rod of the second pusher, 27 is the push block of the second pusher, 28 is the second screen, 29 is the second movable partition, 110 is the first screen, 111 is the first movable partition, 112 is the first limiting groove, and 210 is the second limiting groove.

[0028] Figure 2 It is a sectional view taken along the line A-A of the waste heat recovery device in the embodiment of the present invention. In the figure, 1 is the first heat exchange chamber, 2 is the second heat exchange chamber, 3 is the hopper, 4 is the sand discharge port, 11 is the first feed inlet, 12 is the first feed chute, 14 is the first gate, 15 is the molten slag inlet, 21 is the second feed inlet, 22 is the second feed chute, 24 is the second gate, 28 is the second screen, 29 is the second movable partition, 110 is the first screen, 111 is the first movable partition, 112 is the first limiting groove, 210 is the second limiting groove. In the figure, the omitted part 5 is the blast furnace, 15 is the molten slag inlet, and 16 is the blast furnace slag discharge chute.

[0029] Figure 3 This is the B-B cross-sectional view of the waste heat recovery device in the embodiment of the present invention. In the figure, 1 is the first heat exchange chamber, 2 is the second heat exchange chamber, 3 is the hopper, 4 is the sand discharge port, 19 is the push block of the first material pusher, 27 is the push block of the second material pusher, 28 is the second screen, 29 is the second movable partition, 110 is the first screen, 111 is the first movable partition, 112 is the first limit groove, and 210 is the second limit groove.

[0030] Figure 4 This is the waste heat recovery flow chart in the embodiment of the present invention. Specific Embodiments

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] As Figures 1 to 3 shown, a blast furnace slag waste heat recovery device is used to recover the waste heat of the slag. The device is provided with a first heat exchange chamber 1, a second heat exchange chamber 2, a hopper 3 and a sand discharge port 4 from top to bottom; two opposite sides of the top of the first heat exchange chamber 1 are respectively provided with a first feed port 11 and a slag inlet 15, and two opposite sides of the bottom are respectively provided with a first material pusher and a first discharge port 13. The bottom is provided with a first screen 110 and a first movable partition 111, and the first screen 110 is located above the first partition. A first limit groove 112 is provided on the wall surface of the first heat exchange chamber 1 to restrict the first movable partition 111; a second feed port 21 is provided on the side of the top of the second heat exchange chamber 2, and two opposite sides of the bottom are respectively provided with a second material pusher and a second discharge port 23. The bottom is provided with a second screen 28 and a second movable partition 29, and the second screen 28 is located above the second partition. A second limit groove 210 is provided on the wall surface of the second heat exchange chamber 2 to restrict the second movable partition 29; the hopper 3 is in the shape of a flared mouth that gradually narrows from top to bottom, and a sand discharge port 4 is provided at the center of its bottom; the first material pusher is composed of a hydraulic cylinder 17, a push rod 18 and a push block 19, and the second material pusher is composed of a hydraulic cylinder 25, a push rod 26 and a push block 27.

[0033] In the above blast furnace slag waste heat recovery device, the first feed port 11 is connected to the first feed tank 12, the slag inlet 15 is connected to the slag discharge tank of the blast furnace 5, and the second feed port 21 is connected to the second feed tank 22.

[0034] In the above blast furnace slag waste heat recovery device, first gates 14 and second gates 24 are provided on both the first discharge port 13 and the second discharge port 23. When the gates are closed, the corresponding discharge ports are also in a closed state.

[0035] In the above blast furnace slag waste heat recovery device, the mesh numbers of both the first screen 110 and the second screen 28 are between 1 mesh and 5 meshes.

[0036] For the above blast furnace slag waste heat recovery device, a heat insulation layer is provided on the outer wall surface of the device.

[0037] To facilitate the observation and understanding of the structural composition of the recovery device, Figure 3 the state when a part of the first movable partition 111 and the second movable partition 29 are each drawn out is drawn in the figure.

[0038] Please combine Figure 4 to understand a waste heat recovery method for the above blast furnace slag waste heat recovery device. For this method, the first movable partition 111 and the second movable partition 29 are default in the state of separating the materials in the device. Before the current batch of molten slag is discharged from the blast furnace 5, fine sand and ironmaking raw materials are previously installed in the second heat exchange chamber 2; after the current batch of molten slag is discharged from the blast furnace 5, the following steps are performed:

[0039] Step S1: Keep the material separation state of the first movable partition 111, and load fine sand with a volume of 10% to 30% of the volume of the first heat exchange chamber 1 into the first heat exchange chamber 1 through the first feed port 11;

[0040] Step S2: Discharge the high-temperature molten slag into the first heat exchange chamber 1 through the molten slag inlet 15;

[0041] Step S3: Load fine sand into the first heat exchange chamber 1 through the first feed port 11 until the internal space of the first heat exchange chamber 1 is filled;

[0042] Step S4: Set aside for a period of time;

[0043] Step S5: Draw out the second movable partition 29, so that the fine sand in the second heat exchange chamber 2 falls into the hopper 3 through the second screen 28 and is discharged through the sand discharge port 4 for recycling, and then insert the second movable partition 29 again to keep the second heat exchange chamber 2 and the hopper 3 separated;

[0044] Step S7: Open the second discharge port 23, and push out the ironmaking raw materials in the second heat exchange chamber 2 through the second pusher for ironmaking in the blast furnace 5, and then close the second discharge port 23;

[0045] Step S8: Load ironmaking raw materials with a volume of 10% to 30% of the volume of the second heat exchange chamber 2 into the second heat exchange chamber 2 through the second feed port 21;

[0046] Step S9: Draw out the first movable partition 111, so that the fine sand in the first heat exchange chamber 1 falls into the second heat exchange chamber 2 through the first screen 110, and then insert the first movable partition 111 again to keep the first heat exchange chamber 1 and the second heat exchange chamber 2 separated;

[0047] Step S10: Open the first discharge port 13, push out the molten slag in the first heat exchange chamber 1 through the first pusher, and then close the first discharge port 13.

[0048] In the above waste heat recovery method, before the current batch of molten slag is discharged from the blast furnace 5, the fine sand contained in the second heat exchange chamber 2 is the fine sand that fell into the second heat exchange chamber 2 after being heated by the previous batch of molten slag in the first heat exchange chamber 1.

[0049] In the above waste heat recovery method, the particle size of the fine sand is less than 0.5 mm, and the iron-making raw material is a mixture of any one or any combination of iron ore, coke, and flux, where the flux is any one or a mixture of limestone and dolomite.

[0050] In the above waste heat recovery method, the shelving duration in step S4 is 90% to 95% of the time interval between two adjacent batches of slag discharge from the blast furnace 5.

[0051] In the above waste heat recovery method, during the shelving process of step S4, the fine sand in the first heat exchange chamber 1 absorbs the heat of the current batch of molten slag, and at the same time, the fine sand that was heated by the previous batch of molten slag in the second heat exchange chamber 2 transfers its own heat to the iron-making raw material.

[0052] Embodiment

[0053] Please refer to Figures 1 to 4 Understand the embodiments of the present invention.

[0054] For a certain iron-making blast furnace, iron is tapped 6 times per day at equal time intervals, and high-temperature molten slag is also discharged each time iron is tapped. After a certain batch of molten slag is discharged from the blast furnace 5, the following steps are performed:

[0055] Step S1: Maintain the material isolation state of the first movable partition 111, and load fine sand with a volume of 30% of the volume of the first heat exchange chamber 1 into the first heat exchange chamber 1 through the first feed port 11;

[0056] Step S2: Discharge the high-temperature molten slag into the first heat exchange chamber 1 through the molten slag inlet 15;

[0057] Step S3: Load fine sand into the first heat exchange chamber 1 through the first feed port 11 until the internal space of the first heat exchange chamber 1 is filled;

[0058] Step S4: Shelve for a period of time, with a shelving duration of approximately 215 minutes, so that the high-temperature molten slag has enough time to transfer heat to the fine sand in the first heat exchange chamber 1. At the same time, the fine sand heated by the previous batch of molten slag in the second heat exchange chamber 2 and the iron-making raw material are also exchanging heat;

[0059] Step S5: Withdraw the second movable partition 29, allowing the fine sand in the second heat exchange chamber 2 to fall into the hopper 3 through the second screen 28 and be discharged through the sand discharge port 4 for recycling (for heat exchange with the blast furnace slag of the next batch), and then insert the second movable partition 29 again to keep the second heat exchange chamber 2 and the hopper 3 separated;

[0060] Step S7: Open the second discharge port 23, and push out the iron-making raw materials in the second heat exchange chamber 2 through the second pusher for iron-making in the blast furnace 5, and then close the second discharge port 23;

[0061] Step S8: Load iron-making raw materials with a volume of 30% of the volume of the second heat exchange chamber 2 into the second heat exchange chamber 2 through the second feed port 21;

[0062] Step S9: Withdraw the first movable partition 111, allowing the fine sand in the first heat exchange chamber 1 to fall into the second heat exchange chamber 2 through the first screen 110, and then insert the first movable partition 111 again to keep the first heat exchange chamber 1 and the second heat exchange chamber 2 separated;

[0063] Step S10: Open the first discharge port 13, and push out the slag in the first heat exchange chamber 1 through the first pusher, and then close the first discharge port 13.

[0064] Before the current batch of slag is discharged from the blast furnace 5, the fine sand in the second heat exchange chamber 2 is the fine sand that fell into the second heat exchange chamber 2 after being heated by the previous batch of slag in the first heat exchange chamber 1.

[0065] It should be noted that the operations of the above steps S1 to S10 are actually carried out cyclically: before the current batch of blast furnace slag is discharged, the waste heat recovery of the previous batch of blast furnace slag just completes the operation of step S10, and the iron-making raw materials heated by it can be put into the blast furnace for iron-making during the current batch of iron tapping, thus completing the utilization of the slag waste heat.

[0066] According to the characteristics of intermittent slag discharge of the blast furnace in the embodiment of the present invention, for each batch of slag, first transfer its heat to the fine sand in the first heat exchange chamber; then allow the heated fine sand to fall into the second heat exchange chamber under the action of gravity for heating the iron-making raw materials; finally, discharge the fine sand for absorbing the heat of the next batch of slag to realize the recycling of the fine sand. When the current batch of slag heats the fine sand in the first heat exchange chamber, the fine sand heated by the previous batch of slag in the second heat exchange chamber is heating the iron-making raw materials, thus ensuring the stable and reliable waste heat recovery process, making full use of the time between two slag discharges, and simultaneously carrying out the operations of waste heat recovery of the slag and heat absorption of the iron-making raw materials. After the heated iron-making raw materials are put into the blast furnace for iron-making, it is equivalent to partially transferring the thermal energy of the slag back to the blast furnace, thereby saving the heat supply of the hot blast stove and achieving the indirect recovery effect of the slag waste heat.

[0067] The device structure in the embodiments of the present invention is simple and the cost is low. Except for the first material pusher and the second material pusher, it basically does not involve dynamic equipment. Since recycled and inert fine sand is used as the heat exchange medium instead of conventional water or gas, the cost is low, resources are saved, the corrosion of the equipment is very small, and no pollutants are discharged into the external environment.

Claims

1. A blast furnace slag waste heat recovery device for recovering the waste heat of slag, characterized in that From top to bottom, there are a first heat exchange chamber (1), a second heat exchange chamber (2), a hopper (3) and a sand discharge port (4) respectively; on two opposite sides at the top of the first heat exchange chamber (1), there are a first feed inlet (11) and a slag inlet (15) respectively, on two opposite sides at the bottom, there are a first lump pusher and a first discharge port (13) respectively, at the bottom, there is a first screen (110) and a first movable partition (111), and the first screen (110) is located above the first movable partition, and on the wall surface of the first heat exchange chamber (1), there is a first limiting groove (112) to restrict the first movable partition (111); on the side at the top of the second heat exchange chamber (2), there is a second feed inlet (21), on two opposite sides at the bottom, there are a second lump pusher and a second discharge port (23) respectively, at the bottom, there is a second screen (28) and a second movable partition (29), and the second screen (28) is located above the second movable partition, and on the wall surface of the second heat exchange chamber (2), there is a second limiting groove (210) to restrict the second movable partition (29); the hopper (3) is a flared structure that gradually narrows from top to bottom, and at the center of its bottom, there is a sand discharge port (4); the first lump pusher is composed of a hydraulic cylinder (17), a push rod (18) and a push block (19), and the second lump pusher is composed of a hydraulic cylinder (25), a push rod (26) and a push block (27).

2. The blast furnace slag waste heat recovery device according to claim 1, characterized in that, The first feed inlet (11) is connected to a first feed trough (12), the slag inlet (15) is connected to the slag discharge trough of a blast furnace (5), and the second feed inlet (21) is connected to a second feed trough (22).

3. The blast furnace slag waste heat recovery device according to claim 1, characterized in that, On both the first discharge port (13) and the second discharge port (23), there are a first gate (14) and a second gate (24), and when the gates are closed, the corresponding discharge ports are also in a closed state.

4. The blast furnace slag waste heat recovery device according to claim 1, characterized in that, The mesh numbers of both the first screen (110) and the second screen (28) are between 1 mesh and 5 meshes.

5. The blast furnace slag waste heat recovery device according to claim 1, characterized in that, There is a heat insulation layer on the outer wall surface of the device.

6. A waste heat recovery method for the waste heat recovery device of the blast furnace slag according to any one of claims 1-5, characterized in that, The first movable partition (111) and the second movable partition (29) are default in a state of separating the materials in the device. Before the current batch of molten slag is discharged from the blast furnace (5), fine sand and iron-making raw materials are previously loaded in the second heat exchange chamber (2); after the current batch of molten slag is discharged from the blast furnace (5), the following steps are carried out: Step S1: Keep the state of the first movable partition (111) separating the materials, and load fine sand with a volume of 10% to 30% of the first heat exchange chamber (1) into the first heat exchange chamber (1) through the first feed inlet (11). Step S2: Discharge the high-temperature molten slag into the first heat exchange chamber (1) through the slag inlet (15). Step S3: Load fine sand into the first heat exchange chamber (1) through the first feed inlet (11) until the internal space of the first heat exchange chamber (1) is filled. Step S4: Leave it for a period of time. Step S5: Pull out the second movable partition (29) to enable the fine sand in the second heat exchange chamber (2) to fall into the hopper (3) through the second screen (28) and be discharged through the sand discharge port (4) for recycling, and then insert the second movable partition (29) again to keep the second heat exchange chamber (2) and the hopper (3) separated. Step S7: Open the second discharge port (23), and push out the iron-making raw materials in the second heat exchange chamber (2) through the second material pusher for iron-making in the blast furnace (5), and then close the second discharge port (23); Step S8: Load iron-making raw materials with a volume of 10% to 30% of the second heat exchange chamber (2) into the second heat exchange chamber (2) through the second feed port (21); Step S9: Pull out the first movable partition (111) to allow the fine sand in the first heat exchange chamber (1) to fall into the second heat exchange chamber (2) through the first screen (110), and then insert the first movable partition (111) to keep the first heat exchange chamber (1) and the second heat exchange chamber (2) separated; Step S10: Open the first discharge port (13), and push out the molten slag in the first heat exchange chamber (1) through the first material pusher, and then close the first discharge port (13).

7. The waste heat recovery method according to claim 6, wherein Before the current batch of molten slag is discharged from the blast furnace (5), the fine sand contained in the second heat exchange chamber (2) is the fine sand that was heated in the first heat exchange chamber (1) by the previous batch of molten slag and then fell into the second heat exchange chamber (2).

8. The waste heat recovery method according to claim 6, characterized in that, The particle size of the fine sand is less than 0.5 mm, and the iron-making raw materials are any one or any mixture of iron ore, coke, and flux, where the flux is any one or a mixture of limestone and dolomite.

9. The waste heat recovery method according to claim 6, characterized in that, The shelving duration in Step S4 is 90% to 95% of the time interval between two adjacent batches of slag discharge in the blast furnace (5).

10. The waste heat recovery method according to claim 6, characterized in that, During the shelving process of Step S4, the fine sand in the first heat exchange chamber (1) absorbs the heat of the current batch of molten slag, and at the same time, the fine sand that was heated by the previous batch of molten slag in the second heat exchange chamber (2) transfers its own heat to the iron-making raw materials.

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