Rotary hearth pellet cooling and drying coupled system and method

Abstract

The application discloses a rotary hearth furnace pellet cooling and drying coupling system and method, and the coupling system comprises four coupling devices, a pellet outlet conveying device and a pellet inlet conveying device; each coupling device comprises a cooling zone, a heat exchange zone and a drying zone, the top of the coupling device is provided with an air inlet, and the lower part of the coupling device is connected with an air outlet; the air inlet of the first coupling device is used for introducing a first cooling medium, and the air outlet of the first coupling device is connected with the air inlet of the second coupling device through a high-temperature circulating pipeline provided with a high-temperature circulating fan; the air inlet of the fourth coupling device is used for introducing a second cooling medium, and the air outlet of the fourth coupling device is connected with the air inlet of the third coupling device through a low-temperature circulating pipeline provided with a low-temperature circulating fan. The application can fully utilize the DRI waste heat and effectively improve the heat energy utilization rate.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, to the utilization of thermal energy in a rotary hearth furnace for treating metallurgical dust and sludge, and particularly to a coupled system and method for cooling and drying pellets in a rotary hearth furnace. Background Technology

[0002] For bulk metallurgical solid waste containing iron, carbon, and zinc, large-scale integrated iron and steel enterprises currently often use rotary hearth furnace technology for processing, producing DRI pellets for recycling. The raw materials for rotary hearth furnace production require the addition of water to granulate them into green pellets. These green pellets, with a moisture content of ~14%, are then dried on a chain grate to a moisture content of 1%~2% before being fed into the furnace for reduction. Inside the rotary hearth furnace, the dry pellets are reduced by combustion using coal gas and high-temperature combustion air to obtain high-temperature DRI pellets. The 1100℃ high-temperature DRI pellets are typically cooled to below 200℃ in a horizontal cylindrical cooler using indirect water spray cooling, with the vaporized steam naturally discharged. No heat is recovered from the DRI pellets. The drying of the green pellets and the heating of the combustion air require a dedicated hot blast stove, which consumes a large amount of fuel gas.

[0003] Currently, heat recovery from high-temperature DRI cooling is being considered, using membrane wall coolers to produce hot water or steam. However, the rotary joints of the membrane coolers are not resistant to high pressure, limiting them to producing only low-pressure steam or hot water, and the equipment suffers from severe wear. The hot air required for the chain grate machine used in green pellet drying and the combustion air for the rotary hearth furnace are still heated using gas-fired hot air furnaces. This results in high energy consumption, high operating costs, and poor economic efficiency for the rotary hearth furnace, necessitating equipment upgrades and process optimization to improve heat energy utilization.

[0004] Existing patent CN103436653B discloses a water-cooled cylinder device for direct reduced iron, including a cooling cylinder and a water spray assembly. An outer casing is fitted over the cooling cylinder, with a gap between the outer casing and the cooling cylinder. The side wall of the outer casing has an inlet for the cooling water sprayed by the water spray assembly to enter, and the bottom of the outer casing has a drain outlet. However, this technology only considers the cooling of direct reduced iron and does not recover residual heat. It relies on the evaporation of the sprayed water to remove heat, wasting heat and consuming a large amount of water.

[0005] Existing patent CN105758205B discloses a combined waste heat recovery system for a rotary hearth furnace, including a DRI cooling furnace connected to the bottom of the rotary hearth furnace. The exhaust chimney is connected to a high-pressure blower via a pipe. Cooling air drawn in by the high-pressure blower enters the cooling air circulation channel of the DRI cooling furnace, passes through the duct, and exchanges heat with the hot material inside the furnace. The gas after heat exchange enters the settling chamber through a pipe. This achieves waste heat recovery from the hot material generated by the rotary hearth furnace process. A portion of the purified low-temperature flue gas can be self-circulated and used as a cooling medium in the hot DRI cooling furnace to exchange heat and cool the hot material. However, although this patent considers waste heat recovery during DRI cooling, the waste heat is only used to generate hot air, which is sent to the original boiler system to produce steam. It is not used as a heat source for the dryer or for heating the combustion air within the system. Using only hot flue gas to cool the DRI results in low cooling capacity and limited cooling range and effect. Summary of the Invention

[0006] The purpose of this invention is to provide a coupled system and method for cooling and drying pellets in a rotary hearth furnace, which can fully utilize the waste heat from the DRI process and effectively improve the thermal energy utilization rate.

[0007] The objective of this invention can be achieved using the following technical solutions: This invention provides a coupled cooling and drying system for rotary hearth furnace pellets, comprising: Four coupling devices are arranged adjacent to each other in a horizontal direction, and are respectively the first coupling device, the second coupling device, the third coupling device and the fourth coupling device; The furnace-outfeeding pellet conveying device and the furnace-infeeding pellet conveying device are arranged in parallel vertical intervals, with opposite conveying directions and parallel to the horizontal direction; both the furnace-outfeeding pellet conveying device and the furnace-infeeding pellet conveying device pass through four coupling devices in sequence, and their respective ends pass through the first coupling device and the fourth coupling device respectively; both the furnace-outfeeding pellet conveying device and the furnace-infeeding pellet conveying device are provided with multiple through holes. Each coupling device includes a cooling zone, a heat exchange zone, and a drying zone arranged sequentially from top to bottom. The cooling zone is located above the pellet conveying section of the pellet conveying device, the heat exchange zone is located below the pellet conveying section and is equipped with a heat exchange device, and the drying zone is located above the pellet conveying section of the pellet conveying device. The top of the coupling device has an air inlet, and the lower part of the coupling device, located below the pellet conveying section, is connected to an air outlet. The air inlet of the first coupling device is used to introduce the first cooling medium, and the air outlet of the first coupling device is connected to the air inlet of the second coupling device through a high-temperature circulation pipeline equipped with a high-temperature circulation fan. The air inlet of the fourth coupling device is used to introduce the second cooling medium, and the air outlet of the fourth coupling device is connected to the air inlet of the third coupling device through a low-temperature circulation pipeline equipped with a low-temperature circulation fan.

[0008] The present invention also provides a coupled method for cooling and drying pellets in a rotary hearth furnace, employing the above-mentioned coupled system for cooling and drying pellets in a rotary hearth furnace. The coupled method for cooling and drying pellets in a rotary hearth furnace includes: A first cooling medium is introduced into the air inlet of the first coupling device; A second cooling medium is introduced into the air inlet of the fourth coupling device; The gas from the outlet of the first coupling device is introduced into the inlet of the second coupling device; The gas from the outlet of the fourth coupling device is introduced into the inlet of the third coupling device; The DRI pellets produced by the rotary hearth furnace are fed into the first coupling device from the feed end of the pellet conveying device. The DRI pellets are cooled in the cooling zones of the first coupling device, the second coupling device, the third coupling device and the fourth coupling device in sequence during the conveying process of the pellet conveying device, so as to obtain cooled finished DRI pellets at the discharge end of the pellet conveying device. Green pellets are fed into the fourth coupling device from the feed end of the pellet conveying device. The green pellets are then dried in the drying zones of the fourth coupling device, the third coupling device, the second coupling device, and the first coupling device in sequence as the pellet conveying device is conveyed, so that dry pellets are obtained at the discharge end of the pellet conveying device.

[0009] As described above, the rotary hearth furnace pellet cooling and drying coupling system and method of the present invention is divided into four coupling devices, each with a cooling zone, a heat exchange zone, and a drying zone. This integrates DRI pellet cooling, green pellet drying, and waste heat utilization, achieving coupling between DRI finished product cooling and green pellet drying in the rotary hearth furnace. It features high integration, a small footprint, and energy savings. The outgoing pellet conveying device and the incoming pellet conveying device are designed with opposite moving directions, ensuring that the DRI pellets and green pellets move in opposite directions, resulting in higher heat exchange efficiency. Simultaneously, after cooling and drying the DRI pellets and green pellets in the first coupling device using the first cooling medium, it is introduced into the second coupling device to cool and dry the DRI pellets and green pellets thereafter. Similarly, after cooling and drying the green pellets using the second cooling medium at the top of the fourth coupling device, it is introduced into the third coupling device to cool and dry the DRI pellets and green pellets thereafter. This further enhances the utilization of DRI waste heat and effectively improves thermal energy utilization. Attached Figure Description

[0010] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein: Figure 1 This is a partial structural schematic diagram of the rotary hearth furnace pellet cooling and drying coupling system provided by the present invention.

[0011] Figure 2 forFigure 1 A cross-sectional view along the MM line.

[0012] Figure 3 This is a schematic diagram of the rotary hearth furnace pellet cooling and drying coupling system provided by the present invention.

[0013] Explanation of icon numbers: 101. First coupling device; 102. Second coupling device; 103. Third coupling device; 104. Fourth coupling device; A. Coupling segment I; B. Coupling segment II; C. Coupling segment III; D. Coupling segment IV; E. Coupling segment V; F. Coupling segment VI; 1. Air inlet; 11. Cooling fan; 111. Cooling air duct; 2. Cooling area; 3. Heat exchange zone; 31. Heat exchange device; 311. Heat exchanger; 32. Combustion fan; 321. Combustion air duct; 33. Cold fluid duct; 34. Steam duct; 4. Collecting hopper; 41. Collecting hopper body; 411. First collecting inclined plate; 412. Second collecting inclined plate; 42. Collecting pipe; 43. First airtight valve; 44. Finished product powder silo; 5. Drying area; 6. Air outlet; 61. High-temperature circulating fan; 611. High-temperature circulating pipeline; 62. Low-temperature circulating fan; 621. Low-temperature circulating pipeline; 7. Return hopper; 71. Return hopper body; 711. First return inclined plate; 712. Second return inclined plate; 72. Return pipe; 73. Second airtight valve; 8. Waste material hopper; 81. Waste material pipe; 200. Pelletizing conveyor; 201. Pelletizing conveyor section; 202. First grate; 203. Upper support structure; 204. Lower support structure; 205. High-temperature DRI pellet inlet; 206. Finished DRI pellet outlet; 207. Finished pellet bin; 300. Pellet feeding conveyor; 301. Pellet feeding conveyor section; 302. Second grate; 303. Upper support structure; 304. Lower support structure; 305. Green pellet inlet; 306. Dry pellet outlet; 400. Return material conveying device; 500, rotary hearth furnace; 600. Flue gas pipeline; 601. Waste heat boiler; 602. First dust collector; 603. First dust collector fan; 604. First chimney; 700. Discharge pipeline; 701. Second dust collector; 702. Second dust collector fan; 703. Second chimney. Detailed Implementation

[0014] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0015] like Figures 1 to 3 As shown, this application provides a rotary hearth furnace pellet cooling and drying coupled system, comprising: Four coupling devices are arranged adjacent to each other in a horizontal direction, namely the first coupling device 101, the second coupling device 102, the third coupling device 103 and the fourth coupling device 104. The pellet conveying device 200 for exiting the furnace and the pellet conveying device 300 for entering the furnace are arranged in parallel at intervals. Their conveying directions are opposite and parallel to the horizontal direction mentioned above. Both the pellet conveying device 200 for exiting the furnace and the pellet conveying device 300 for entering the furnace pass through four coupling devices in sequence, and their two ends pass through the first coupling device 101 and the fourth coupling device 104 respectively. Both the pellet conveying device 200 for exiting the furnace and the pellet conveying device 300 for entering the furnace are provided with multiple through holes. Each coupling device includes, from top to bottom, a cooling zone 2, a heat exchange zone 3, and a drying zone 5. The cooling zone 2 is located above the outlet pellet conveying section 201 of the outlet pellet conveying device 200. The heat exchange zone 3 is located below the outlet pellet conveying section 201 and is equipped with a heat exchange device 31. The drying zone 5 is located above the inlet pellet conveying section 301 of the inlet pellet conveying device 300. The top of the coupling device has an air inlet 1, and the lower part of the coupling device is located above the inlet pellet conveying section 301. The lower area is connected to an air outlet 6; the air inlet 1 of the first coupling device 101 is used to introduce the first cooling medium, and the air outlet 6 of the first coupling device 101 is connected to the air inlet 1 of the second coupling device 102 through a high-temperature circulation pipe 611 equipped with a high-temperature circulation fan 61; the air inlet 1 of the fourth coupling device 104 is used to introduce the second cooling medium, and the air outlet 6 of the fourth coupling device 104 is connected to the air inlet 1 of the third coupling device 103 through a low-temperature circulation pipe 621 equipped with a low-temperature circulation fan 62.

[0016] The adjacent coupling devices are separated by corresponding partitions. The outlet pellet conveying device 200 and the inlet pellet conveying device 300 can pass through the corresponding partitions, which have openings for passage. The outlet pellet conveying device 200 is used to convey DRI pellets. The outlet pellet conveying section 201 can transport high-temperature DRI pellets from the high-temperature end to the low-temperature end, achieving cooling of the high-temperature DRI pellets to obtain cooled finished DRI pellets. The inlet pellet conveying device 300 is used to convey pellets to be fed into the furnace. The inlet pellet conveying section 301 can transport green pellets from the low-temperature end to the high-temperature end, achieving drying of the green pellets to obtain dry pellets. Here, DRI refers to direct reduced iron, which is the product of a rotary hearth furnace; green pellets refer to wet lumps formed by pelletizing or pressing materials, and the dried pellets obtained after drying can be used as feed material for the rotary hearth furnace.

[0017] The exiting pellet conveyor 200 and the entering pellet conveyor 300 move in opposite directions. The two ends of the exiting pellet conveyor 200 extending from the first coupling device 101 and the fourth coupling device 104 respectively form the feeding end and the discharging end, i.e., the high-temperature DRI pellet inlet 205 and the finished DRI pellet outlet 206. The two ends of the entering pellet conveyor 300 extending from the fourth coupling device 104 and the first coupling device 101 respectively form the feeding end and the discharging end, i.e., the green pellet inlet 305 and the dry pellet outlet 306. The gas introduced through the air inlet 1 at the top of the coupling device cools the pellets on the exiting pellet conveyor 200 and then enters the corresponding heat exchanger 31 through the through holes on the exiting pellet conveyor 200 for heat exchange and cooling. The cooled gas can then dry the pellets on the entering pellet conveyor 300.

[0018] The coupling system of this application is divided into four coupling devices, each with a cooling zone 2, a heat exchange zone 3, and a drying zone 5. It integrates DRI pellet cooling, green pellet drying, and waste heat utilization, achieving coupling between DRI finished product cooling and green pellet drying in the rotary hearth furnace 500. This system boasts high integration, a small footprint, and energy savings. The outgoing pellet conveying device 200 and the incoming pellet conveying device 300 are designed to move in opposite directions, resulting in higher heat exchange efficiency. Simultaneously, after cooling and drying the DRI pellets in the first coupling device 101 using the first cooling medium, the gas is then introduced into the second coupling device 102 to cool and dry the DRI pellets in the second coupling device 102. A second cooling medium is then introduced into the top of the fourth coupling device 104 to cool the DRI, and the gas after drying the green pellets is then introduced into the third coupling device 103 to cool and dry the DRI pellets in the third coupling device 103. This better achieves full utilization of the waste heat from the DRI and effectively improves the thermal energy utilization rate.

[0019] Furthermore, the temperature of the first cooling medium is lower than that of the high-temperature DRI pellets produced in the rotary hearth furnace 500. The first cooling medium can be an inert gas, rotary hearth furnace flue gas, or other hot flue gas with low oxygen content (such as blast furnace hot blast stove flue gas). The second cooling medium can be air or an inert gas.

[0020] The preferred cooling medium is cooled rotary hearth furnace flue gas, which eliminates the need for inert gas consumption and enables the utilization of rotary hearth furnace flue gas.

[0021] The preferred second cooling medium is room temperature air, which provides good cooling performance and eliminates the need for inert gas consumption. (Refer to...) Figure 3 The air inlet 1 of the fourth coupling device 104 is connected to the atmosphere through a cooling air duct 111 equipped with a cooling fan 11.

[0022] Optionally, the heat exchange device 31 in the first coupling device 101 includes an air preheater. The inlet end of the air preheater is connected to the atmosphere through a combustion air duct 321 equipped with a combustion air fan 32. The outlet end of the air preheater is used to provide combustion air to the rotary hearth furnace 500, thereby realizing the use of the heat released by the high-temperature DRI cooling for the preheating of the combustion air, further improving the thermal energy utilization rate.

[0023] Alternatively, the heat exchange device 31 within the first coupling device 101 may further include a steam superheater to utilize the heat released from the high-temperature DRI cooling for saturated steam heating, thereby further improving thermal energy utilization.

[0024] In this way, the system can recover the heat released during the high-temperature DRI cooling process of the rotary hearth furnace and use the heat for drying green pellets, heating the combustion air of the rotary hearth furnace, and generating superheated steam. It combines the functions of the conventional rotary hearth furnace hot blast stove system, green pellet drying system, and DRI cooling system into one, saving system space, eliminating the gas consumption of the traditional hot blast stove, and eliminating the water consumption of DRI cooling, thereby reducing the energy medium consumption of the system and ultimately reducing the production cost of DRI.

[0025] In practical applications, the heat exchange device 31 within each coupling device may include at least one heat exchanger 311. When at least two heat exchangers 311 are included, the multiple heat exchangers 311 are arranged side by side along the aforementioned horizontal direction. The specific type of heat exchanger 311 can be determined according to the actual heat exchange needs and functions.

[0026] For example, optionally, the heat exchange device 31 in the second coupling device 102 includes an evaporator and / or a steam superheater, the heat exchange device 31 in the third coupling device 103 includes an evaporator, and the heat exchange device 31 in the fourth coupling device 104 includes an economizer and / or a hot water heat exchanger.

[0027] The medium in each heat exchanger 311 can be externally input gas or liquid, or it can be gas or liquid generated inside the entire coupling body, as needed.

[0028] To further utilize thermal energy, preferably, the inlet end of the heat exchanger 31 of the fourth coupling device 104 is used to introduce cold fluid, the outlet end of the heat exchanger 31 of the fourth coupling device 104 can be connected to the inlet end of the evaporator of the third coupling device 103 through a pipe, the outlet end of the evaporator of the third coupling device 103 is connected to the inlet end of the heat exchanger 31 of the second coupling device 102 through a pipe, and the outlet end of the heat exchanger 31 of the second coupling device 102 is connected to the inlet end of the steam superheater in the first coupling device 101 through a pipe. After this connection arrangement, only a liquid (cold fluid), such as demineralized water, needs to be introduced outside the heat exchanger 311 in the fourth coupling device 104. After being heated, it can be gradually heated in the third coupling device 103, the second coupling device 102, and the first coupling device 101 to obtain superheated steam.

[0029] Alternatively, if the heat exchange devices 31 in the fourth coupling device 104, the third coupling device 103, the second coupling device 102 and the first coupling device 101 are connected in series, an outlet pipe can be connected to the outlet end of the heat exchange device 31 of the third coupling device 103 and an outlet pipe can be connected to the outlet end of the heat exchange device 31 of the second coupling device 102 to extract saturated steam from the process.

[0030] Further optionally, a hopper 4 is provided in each coupling device and below the heat exchange device 31, and a collecting pipe 42 that can communicate with the hopper 4 is provided on the side of the coupling device. The hopper 4 is configured to allow only gas to pass through.

[0031] The collecting hopper 4 is specifically located between the heat exchange zone 3 and the drying zone 5. The wall of the collecting hopper 4 does not allow material to pass through, but only gas. The collecting hopper 4 can be used to collect the leaked material from the pellet conveying device 200. The flue gas after the DRI pellets are cooled can continue to flow downward through the collecting hopper 4 to dry the green pellets below.

[0032] The hopper 4 can be constructed using any structural method to achieve a gas-solid separation structure that allows only unidirectional gas flow while blocking the penetration of solid materials. For example, at least part of the wall surface of each hopper 4 can be a louvered structure, with the blades of the louvered structure inclined towards the center of the hopper 4. The inclination of the blades forms a blocking surface for the solid aggregate, preventing the material from passing through and providing a flow channel for the gas. The inclination angle between the blades of the louvered structure and the wall surface of the hopper 4 can be designed according to the gas flow rate and the particle size of the solid material. The gap between adjacent blades needs to be determined according to the gas parameters and the particle size of the material to be blocked, to ensure that the gas can pass through while preventing material leakage from the gap between adjacent blades.

[0033] Alternatively, to facilitate the automatic falling of materials into the side collecting pipe 42 and the natural discharge of materials from the collecting hopper 4, refer to... Figure 1 and Figure 2 Each hopper 4 includes two symmetrically arranged hopper bodies 41. Each hopper body 41 includes a first hopper inclined plate 411 and two second hopper inclined plates 412 symmetrically arranged on both sides of the first hopper inclined plate 411. The tops and sides of the two second hopper inclined plates 412 are connected to the corresponding side walls of the coupling device. The tops of the two first hopper inclined plates 411 of the two hopper bodies 41 are connected. The first hopper inclined plate 411, the two second hopper inclined plates 412 and the corresponding side walls of the coupling device enclose a bucket-shaped structure with a gradually decreasing cross-section. The first hopper inclined plate 411 and the two second hopper inclined plates 412 are all louvered. Two collection pipes 42 are symmetrically arranged on both sides of the coupling device and are respectively connected to the bottom of the two hopper bodies 41.

[0034] The coupling device can adopt a rectangular structure, and the coupling body composed of four coupling devices is also a rectangular structure, with its length parallel to the aforementioned horizontal direction. Two collecting pipes 42 are symmetrically arranged on both sides of the two side walls along the conveying direction of the pellet conveying section 201, corresponding to the position of each collecting hopper 4. The two collecting pipes 42 are also symmetrically arranged relative to the conveying direction of the pellet conveying device 200. Each collecting hopper 4 is formed by three inclined plates and the corresponding vertical wall of the coupling device. The upper end of the collecting pipe 42 is connected to the bottom of the three inclined plates and the vertical wall. The upper part of the collecting pipe 42 is an inclined pipe arranged downwards from the side wall of the coupling device. After leaking material falls into the collecting hopper 4, it will fall into the collecting pipe 42 under the guidance of the three inclined plates. Generally, there is a first airtight valve 43 on the collecting pipe 42 to control the corresponding opening and closing.

[0035] Furthermore, referring to Figure 3The rotary hearth furnace pellet cooling and drying coupling system also includes a finished pellet bin 207 and a finished powder bin 44. The finished pellet bin 207 is connected to the discharge end of the pellet conveying device 200, and the finished powder bin 44 is connected to the outlet end of each collecting pipe 42.

[0036] The finished product pellet bin 207, also known as the DRI pellet bin, is connected to the finished DRI pellet outlet 206 and is used to collect finished DRI pellets; the finished product powder bin 44, also known as the DRI powder bin, is connected to the collection pipe 42 through the first airtight valve 43 and is used to collect DRI leakage.

[0037] Further optionally, a return hopper 7 is provided in each coupling device and below the pellet conveying section 301 of the furnace. The wall of the return hopper 7 is a closed surface, and a return pipe 72 that can communicate with the return hopper 7 is provided on the side of the coupling device.

[0038] The return hopper 7 is specifically located below the drying zone 5. The wall of the return hopper 7 can be sealed with steel plates, for example, to prevent materials and gases from passing through. It is mainly used for the collection and extraction of drying gases, as well as the collection of leaked materials from the pellet conveying device 300.

[0039] Alternatively, to facilitate the automatic falling of materials into the side return pipe 72 and the natural discharge of materials from the return hopper 7, refer to Figure 1 and Figure 2 Each return hopper 7 includes two symmetrically arranged return hopper bodies 71. Each return hopper body 71 includes a first return inclined plate 711 and two second return inclined plates 712 symmetrically arranged on both sides of the first return inclined plate 711. The tops and sides of the two second return inclined plates 712 are connected to the corresponding side walls of the coupling device. The tops of the two first return inclined plates 711 of the two return hopper bodies 71 are connected. The first return inclined plate 711, the two second return inclined plates 712 and the corresponding side walls of the coupling device enclose a bucket-shaped structure with a downwardly decreasing cross-section. Two return pipes 72 are symmetrically arranged on both sides of the coupling device corresponding to the position of each return hopper 7, and are respectively connected to the bottom of the two return hopper bodies 71.

[0040] The structure of the return hopper 7 is similar to that of the collection hopper 4 described above. The two return hoppers 7 are arranged symmetrically with respect to the conveying direction of the pellet conveying section 301. The upper end of the return pipe 72 is connected to the bottom of the vertical wall of the three inclined plates and the coupling device. The upper part of the return pipe 72 is an inclined pipe that is inclined outward and downward from the side wall of the coupling device. After the leaked material falls into the return hopper 7, it will fall into the return pipe 72 under the guidance of the three inclined plates. Generally, a second airtight valve 73 is also provided on the return pipe 72 to control the corresponding opening and closing.

[0041] Alternatively, a residual material hopper 8 is provided at the bottom of the coupling device and below the return hopper 7, with a residual material pipe 81 connected to the bottom end of the residual material hopper 8.

[0042] The wall of the waste hopper 8 can be sealed with a steel plate, for example, to collect leaked material. The waste hopper 8 can be configured as follows: Figure 1 and Figure 2 The image shows a conical hopper with a cross-section that gradually decreases downwards. The bottom center of the waste hopper 8 is connected to the vertically arranged waste pipe 81.

[0043] The number of collecting hoppers 4, return hoppers 7, and surplus hoppers 8 in each coupling device can be the same or different, depending on the needs. Optionally, the heat exchange device 31 of the coupling device includes one heat exchanger 311 or at least two heat exchangers 311 arranged side by side along the horizontal direction. The number of collecting hoppers 4, return hoppers 7, and surplus hoppers 8 in each coupling device is the same as the number of heat exchangers 311 in the coupling device. Each heat exchanger 311 is provided with a collecting hopper 4, a return hopper 7, and a surplus hopper 8 below it, which facilitates the smooth discharge of leaked material. Each collecting hopper 4 corresponds to two collecting pipes 42, and each return hopper 7 corresponds to two return pipes 72, which facilitates the collection of leaked material. In addition, each return hopper 7 corresponds to two symmetrical air outlets 6, and each air outlet 6 is connected to the vertical side wall of the coupling device corresponding to the return hopper 7, which facilitates ventilation.

[0044] Alternatively, the rotary hearth furnace pellet cooling and drying coupling system also includes a return material conveying device 400, whose conveying direction is parallel to the aforementioned horizontal direction. The return material conveying device 400 passes through the bottom of the four-section coupling device and is located below the residual material hopper 8 of each coupling device. The outlet ends of the return material pipe 72 and the residual material pipe 81 are arranged directly opposite the return material conveying device 400.

[0045] The return material conveying device 400 may be a return material belt, for example, which is used to return the material collected by the return material hopper 7 and the surplus material hopper 8 to the batching system for re-batching.

[0046] Alternatively, an external insulation layer may be provided on the outer walls of the return hopper 7 and the surplus hopper 8.

[0047] Alternatively, the above-mentioned pellet conveying device 200 for exiting the furnace and pellet conveying device 300 for entering the furnace are both chain grate machines, and the working section chain grate assembly of the chain grate machine constitutes the pellet conveying section 201 for exiting the furnace or the pellet conveying section 301 for entering the furnace.

[0048] The chain grate machine itself uses an existing structure, including a ring chain grate assembly and a drive unit. The ring chain grate assembly includes a ring chain and a grate assembly made up of multiple grate plates hinged together. The grate plates are fixedly connected to the ring chain and have multiple through holes for ventilation. The upper part of the ring chain grate assembly is the working section, and the lower part is the return section (also known as the lower unloaded chain grate assembly). The drive unit drives the ring chain to rotate, thereby moving the grate plates and enabling the conveying of pellets.

[0049] The driving device may include a drive motor and two sets of sprocket structures. The two sets of sprocket structures are located at both ends of the entire coupling body along its length. The two sets of sprocket structures are spaced apart along the aforementioned horizontal direction on the inner side of the annular chain to tension the annular chain. The drive motor drives one set of sprocket structures to rotate, thereby moving the annular chain.

[0050] Further optional, refer to Figures 1 to 3 Each sprocket structure includes two sprockets spaced vertically apart. The chain grate machine also includes two sets of support structures (upper support structure and lower support structure) spaced vertically apart. Each support structure includes a frame and rollers to support the ring chain and grate. The chain grate assembly on the upper support structure constitutes the working section chain grate assembly, and the chain grate assembly on the lower support structure constitutes the return section chain grate assembly. The upper support structure 203 of the chain grate machine corresponding to the pellet conveying device 200 is located above the heat exchange device 31, and the lower support structure 204 is located below the collecting hopper 4. The material leaking from the grate of the pellet conveying section 201 will naturally settle in the collecting hopper 4 below.

[0051] The upper support structure 303 of the chain grate corresponding to the feed pellet conveyor 300 is located below the lower support structure 204 of the discharge pellet conveyor 200 and above the return hopper 7. The lower support structure 304 is located between the return hopper 7 and the waste hopper 8. The return hopper 7 can collect the material leaking from the grate plate of the feed pellet conveyor section 301 and the return waste material from the grate plate in the return section of the discharge pellet conveyor 200. The waste hopper 8 can collect the return waste material from the grate plate in the return section of the chain grate assembly of the feed pellet conveyor 300 and the material leaking from the system. The arrangement of the upper and lower support structures of the chain grate corresponding to the discharge pellet conveyor 200 and the feed pellet conveyor 300 in this way is more conducive to the rotation of the chain.

[0052] Further optionally, the first coupling device 101 and the second coupling device 102 each include two coupling structures arranged side by side along the horizontal direction, separated by a partition. Each coupling structure is provided with a cooling zone 2, a heat exchange zone 3 and a drying zone 5, and each coupling structure is provided with at least one heat exchanger 311.

[0053] Dividing the first coupling device 101 and the second coupling device 102 into two parallel coupling structures and separating them with corresponding partitions can make the airflow distribution more uniform and improve the utilization rate of thermal energy.

[0054] Each heat exchange device 31 within the coupling device includes at least one heat exchanger 311. The specific number of heat exchangers 311 can be determined according to the actual heat balance and heat exchange requirements. For example, referring to... Figure 1 and Figure 3 The first coupling device 101 has two heat exchangers 311 in each of its two coupling structures, the second coupling device 102 has two heat exchangers 311 in each of its two coupling structures, the third coupling device 103 has three heat exchangers 311 in each of its two coupling structures, and the fourth coupling device 104 has two heat exchangers 311 in each of its two coupling structures. This makes it easier to maintain thermal balance, facilitates heat exchange, improves the utilization of thermal energy, and makes it easier to inspect and replace the heat exchangers 311.

[0055] In this example, the heat exchangers have the same heat exchange area. The inlet ends of the heat exchangers 311 in each coupling structure are connected (to the same pipe), and the outlet ends are connected (to the same pipe). The inlet ends of the heat exchangers 311 in the third coupling device 103 are connected (to the same pipe), and the outlet ends are connected (to the same pipe). The inlet ends of the heat exchangers 311 in the fourth coupling device 104 are connected (to the same pipe), and the outlet ends are connected (to the same pipe).

[0056] The fourth coupling device 104, the third coupling device 103, the two coupling structures of the second coupling device 102, and the steam superheater in the first coupling structure of the first coupling device 101 are connected in series. This allows for the gradual heating of the cold fluid to obtain superheated steam, eliminating the need for each heat exchanger 311 to be connected to an external cold medium, thus further improving thermal energy utilization and resource utilization. Optionally, the outlet end of any heat exchanger 311 in the third coupling device 103 can be connected to an outlet pipe, and the outlet end of any heat exchanger 311 in each coupling structure of the second coupling device 102 can be connected to an outlet pipe to extract steam with different parameters from the process.

[0057] Furthermore, the rotary hearth furnace 500 pellet cooling and drying coupling system also includes a rotary hearth furnace 500. The discharge port of the rotary hearth furnace 500 is connected to the feed end of the discharge pellet conveying device 200, the feed port of the rotary hearth furnace 500 is connected to the discharge end of the feed pellet conveying device 300, the flue gas outlet of the rotary hearth furnace 500 is connected to the air inlet 1 of the first coupling device 101 through the flue gas pipeline 600, and a cooling and dust removal device is provided on the flue gas pipeline 600.

[0058] The discharge port of the rotary hearth furnace 500 is connected to the high-temperature DRI pellet inlet 205, used to feed the high-temperature DRI pellets into the pellet conveying device 200. The feed port of the rotary hearth furnace 500 is connected to the dry pellet outlet 306, used to feed the obtained dry pellets into the rotary hearth furnace 500. The flue gas from the flue gas outlet of the rotary hearth furnace 500 is cooled and purified by a cooling and dust removal device before being introduced into the first coupling device 101.

[0059] Optionally, the cooling and dust removal device is mainly used for cooling and dust removal of the rotary hearth furnace flue gas. The cooling and dust removal device includes a waste heat boiler 601, a first dust collector 602, and a first dust removal fan 603 arranged sequentially along the flue gas conveying direction. The first dust collector 602 may be, for example, a bag filter.

[0060] Generally, a first chimney 604 is connected to the flue gas duct 600 and located behind the first dust removal fan 603. After the high-temperature flue gas from the rotary hearth furnace 500 is cooled and purified, part of it is introduced into the first coupling device 101, and the other part is discharged into the atmosphere through the first chimney 604.

[0061] Furthermore, the burner of the rotary hearth furnace 500 is connected to the outlet end of the air preheater in the first coupling device 101 to introduce preheated combustion air into the rotary hearth furnace 500.

[0062] Furthermore, referring to Figure 3 The rotary hearth furnace pellet cooling and drying coupling system also includes an exhaust pipe 700. Each air outlet 6 of the second coupling device 102 and the third coupling device 103 can be connected to the exhaust pipe 700. An exhaust dust removal device is also sequentially installed on the exhaust pipe 700.

[0063] The exhaust pipe 700 and the exhaust dust removal device are mainly used for dust removal and exhaust of the gas discharged from the outlet 6 of the second coupling device 102 and the third coupling device 103. The exhaust dust removal device includes a second dust collector 701, a second dust collector fan 702, and a second chimney 703 arranged in sequence, with the second chimney 703 located at the outlet end of the exhaust pipe. The second dust collector 701 can be, for example, a bag filter dust collector, and the dust collector can also be connected to the aforementioned return material conveying device 400.

[0064] Generally, corresponding chute structures are provided at the high-temperature DRI pellet inlet 205, finished DRI pellet outlet 206, green pellet inlet 305, and dry pellet outlet 306 to facilitate the entry or exit of pellets.

[0065] in addition, Figure 1 The connections of the various parts in the coupling entity shown are as follows: gas is mainly connected by pipes and valves, while materials are mainly connected by conveying equipment and chutes, which will not be described in detail.

[0066] Furthermore, to better understand the working process of the entire coupled system, the following will be used as an example. Figure 1 and Figure 3 The first coupling device 101 and the second coupling device 102 shown in the figure each include two coupling structures, and each coupling structure is provided with two heat exchangers 311. The third coupling device 103 is provided with three heat exchangers 311, and the fourth coupling device 104 is provided with two heat exchangers 311. These are examples for illustration.

[0067] Along the aforementioned horizontal direction, the two coupling structures in the first coupling device 101, the two coupling structures in the second coupling device 102, the third coupling device 103, and the fourth coupling device 104 can be respectively designated as coupling segment I (A), coupling segment II (B), coupling segment III (C), coupling segment IV (D), coupling segment V (E), and coupling segment VI (F). These six coupling segments are separated by corresponding partitions, and the pellet conveying device 200 (outgoing pellets) and the pellet conveying device 300 (incoming pellets) can pass through each partition. Each coupling segment has a cooling zone 2, a heat exchange zone 3, and a drying zone 5 arranged sequentially from top to bottom, respectively achieving cooling of the high-temperature DRI, heat recovery during the DRI cooling process (including heating combustion air and generating steam), and drying of the green pellets. The inner walls of the cooling zone 2, heat exchange zone 3, and drying zone 5 can all be insulated with high-temperature castable refractory or spray coating. The six cooling zones 2 corresponding to these six coupling sections are sequentially named Cooling Section I, Cooling Section II, Cooling Section III, Cooling Section IV, Cooling Section V, and Cooling Section VI along the conveying direction of the pellet conveying section 201. The six heat exchange zones 3 are sequentially named Heat Exchange Section I, Heat Exchange Section II, Heat Exchange Section III, Heat Exchange Section IV, Heat Exchange Section V, and Heat Exchange Section VI in the same direction. The six drying zones 5 are sequentially named Drying Section I, Drying Section II, Drying Section III, Drying Section IV, Drying Section V, and Drying Section VI in the same direction.

[0068] The heat exchanger 311 in coupling segment VI F is an economizer and / or a hot water heat exchanger 311; the heat exchanger 311 in coupling segment V E is an evaporator; the heat exchanger 311 in coupling segment IV D is an evaporator; the heat exchanger 311 in coupling segment III C is an evaporator and / or a steam superheater; the heat exchanger 311 in coupling segment II B is an air preheater; and the heat exchanger 311 in coupling segment I A is a steam superheater. The inlet ends and outlet ends of the two heat exchangers 311 in coupling section VI F are connected; the inlet ends and outlet ends of the three heat exchangers 311 in coupling section V E are connected; the inlet ends and outlet ends of the two heat exchangers 311 in coupling section IV D are connected; the inlet ends and outlet ends of the two heat exchangers 311 in coupling section III C are connected; the inlet ends and outlet ends of the two heat exchangers 311 in coupling section II B are connected; and the inlet ends and outlet ends of the two heat exchangers 311 in coupling section I A are connected.

[0069] The outlet ends of the two heat exchangers 311 in the VI coupling section F are connected to the inlet ends of the three heat exchangers 311 in the V coupling section E via the same pipe. The outlet ends of the three heat exchangers 311 in the V coupling section E are connected to the inlet ends of the two heat exchangers 311 in the IV coupling section D via the same pipe. The outlet ends of the two heat exchangers 311 in the IV coupling section D are connected to the inlet ends of the two heat exchangers 311 in the III coupling section C via the same pipe. The outlet ends of the two heat exchangers 311 in the III coupling section C are connected to the inlet ends of the two heat exchangers 311 in the I coupling section A via the same pipe. The heat exchange devices 31 in these five coupling sections are connected in series to gradually heat the cold fluid to obtain superheated steam. In an alternative configuration, an outlet pipe can be connected to any of the three heat exchangers 311 in the V coupling section E, an outlet pipe can be connected to any of the two heat exchangers 311 in the IV coupling section D, and an outlet pipe can be connected to any of the two heat exchangers 311 in the III coupling section C, so as to obtain steam with different parameters from different coupling sections in the process.

[0070] The entire system has a high-temperature DRI pellet inlet 205, a finished DRI pellet outlet 206, a green pellet inlet 305, a dry pellet outlet 306, a cold fluid pipe 33, and a steam pipe 34. The high-temperature DRI pellet inlet 205 and the finished DRI pellet outlet 206 are located at both ends of the coupling body along the aforementioned horizontal direction, and the green pellet inlet 305 and the dry pellet outlet 306 are located at both ends of the coupling body along the aforementioned horizontal direction. The green pellet inlet 305 is located below the finished DRI pellet outlet 206, and the dry pellet outlet 306 is located below the high-temperature DRI pellet inlet 205. The cold fluid pipe 33 is connected to the inlet ends of the two heat exchangers 311 in the VI coupling section F for introducing cold fluid, such as demineralized water. The steam pipe 34 is connected to the outlet ends of the two heat exchangers 311 in the I coupling section A for outputting steam.

[0071] Each of the six coupling sections has an air inlet 1 at the top and an air outlet 6 at the bottom. The inlet of the aforementioned high-temperature circulating fan 61 is connected to all the air outlets 6 of coupling section I (A) and coupling section II (B) via a high-temperature circulating pipe 611, and the outlet of the high-temperature circulating fan 61 is connected to all the air inlets 1 of coupling section III (C) and coupling section IV (D) via a high-temperature circulating pipe 611. The inlet of the aforementioned low-temperature circulating fan 62 is connected to all the air outlets 6 of coupling section VI (F) via a low-temperature circulating pipe 621, and the outlet of the low-temperature circulating fan 62 is connected to all the air inlets 1 of coupling section V (E) via a low-temperature circulating pipe 621. The inlet of the aforementioned cooling fan 11 is atmospheric, and its outlet is connected to all the air inlets 1 of coupling section VI (F). The inlet of the aforementioned combustion fan 32 is atmospheric, and its outlet is connected to the inlet ends of both air preheaters in coupling section II (B).

[0072] ReferenceFigure 3 The specific process flow of the entire coupling system is as follows: High-temperature DRI pellets produced by the rotary hearth furnace 500 enter the cooling zone 2 of the first coupling section A through a chute and the high-temperature DRI pellet inlet 205. The high-temperature DRI pellets are spread flat on the first grate 202 corresponding to the pellet conveying section 201. As the first grate 202 moves from right to left, it passes through cooling sections I to VI in sequence and contacts the cooling medium for heat exchange. The cooled finished DRI pellets enter the DRI pellet silo for storage through the finished DRI pellet outlet 206. During the movement of the first grate 202, DRI powder leaks into the collection hopper 4 below and is then sent to the DRI powder silo for storage via the first airtight valve 43 and the corresponding conveying equipment.

[0073] Green pellets enter the drying zone 5 of the coupling section VI through the green pellet inlet 305 and are spread flat on the second grate 302 corresponding to the pellet conveying section 301. As the second grate 302 moves from left to right, it passes through the drying sections VI to I in sequence and comes into contact with each heating medium for drying. The temperature of the heating medium gradually increases, and the resulting dry pellets enter the rotary hearth furnace 500 as raw material through the dry pellet outlet 306 and the corresponding feeding device.

[0074] The high-temperature flue gas generated by the rotary hearth furnace 500 is cooled sequentially by the waste heat boiler 601, purged by the first dust collector 602, and then a portion of the clean flue gas is sent to the cooling section I and cooling section II by the first dust collector fan 603. The excess flue gas is discharged through the first chimney 604. In the cooling section I and cooling section II, the flue gas absorbs heat from the high-temperature DRI pellets and rises in temperature, and then enters the heat exchange section I and heat exchange section II through the gaps in the first grate 202. The temperature rise of the flue gas in the cooling section I is greater than that in the cooling section II. Therefore, the heat exchanger 311 in the heat exchange section I is a steam superheater for producing superheated steam, and the heat exchanger 311 in the heat exchange section II is an air preheater for preheating the combustion air.

[0075] After being cooled by heat exchange stage I and heat exchange stage II, the flue gas enters drying stage I and drying stage II respectively through the louvers of collecting hopper 4 to dry the green pellets. The flue gas is further cooled and then enters return hopper 7 for collection and is led out through outlet 6. It is then sent to cooling stage III and cooling stage IV by high-temperature circulating fan 61 to continue cooling the cooled DRI pellets. The generated hot flue gas passes through the first grate 202 and enters heat exchange stage III and heat exchange stage IV. The heat exchangers 311 in heat exchange stage III and heat exchange stage IV are evaporators used for steam generation. After being cooled by heat exchange stage III and heat exchange stage IV, the flue gas enters drying stage III and drying stage IV respectively through the louvers of the corresponding collecting hopper 4 to dry the green pellets. The flue gas is further cooled and then enters return hopper 7 for collection and is led out through outlet 6 to enter the second dust collector 701 for dust removal. Finally, it is sent to the second chimney 703 for discharge by the second dust collector fan 702.

[0076] Combustion blower 32 sends ambient air into heat exchange section II, where cold air is heated into high-temperature hot air in the air preheater, and then sent to each burner of rotary hearth furnace 500 as combustion air.

[0077] Cooling fan 11 blows ambient air into cooling section VI, ultimately cooling the DRI pellets to below 120°C. The cold air is heated into hot air and then flows through the second grate 302 into heat exchange section VI. Heat exchanger 311, using either an economizer or a hot water heat exchanger 311, performs a heat recovery process on the hot air. Subsequently, the hot air enters drying section VI through the louvers of collecting hopper 4 to preheat the green pellets. The air is further cooled and then collected in return hopper 7 and led out through outlet 6, where it is cooled by low-temperature circulating fan 6. 2. The air is sent to the cooling section V and continues to cool the DRI. The generated hot air passes through the first grate 202 and enters the heat exchange section V. The heat exchangers 311 in the heat exchange section V are all evaporators for steam generation. After the hot air is cooled in the heat exchange section, it enters the drying section V through the louvers of the collecting hopper 4 to dry the green balls. The flue gas is further cooled and then enters the return hopper 7 for collection and is led out through the air outlet 6 to enter the second dust collector 701 for dust removal. Finally, it is sent to the second chimney 703 for discharge by the second dust removal fan 702.

[0078] The heat exchanger 311 in the heat exchange stage III can also be a superheater. By setting the system pressure and adjusting the function of the heat exchanger 311, it can produce single-pressure or dual-pressure saturated steam and superheated steam.

[0079] During the movement of the second grate 302, the pulverized material of the green pellets leaks into the return hopper 7 below, and then flows through the second airtight valve 73 and chute to the return conveyor belt of the return conveyor device 400. The remaining material shaken off by the second grate 302 during its return stroke and the material leaking from the coupling device are all collected in the remaining material hopper 8, and then flow from the bottom of the remaining material hopper 8 into the return conveyor belt. The dust collected by the dryer dust collector is also discharged to the return conveyor belt through the conveying equipment. Finally, the return conveyor belt sends the above materials back to the rotary hearth furnace 500 batching system to participate in the batching again.

[0080] Furthermore, a specific embodiment is provided below, and the process flow is as follows: The 1100℃ high-temperature DRI pellets produced by the rotary hearth furnace 500 enter the cooling zone 2 of the first coupling section A through a chute and the high-temperature DRI pellet inlet 205. The high-temperature DRI pellets are spread flat on the first grate 202 corresponding to the pellet conveying section 201. As the grate moves from right to left, they pass through cooling sections I to VI in sequence and come into contact with each cooling medium for heat exchange, finally cooling down to obtain finished DRI pellets at 120℃. The finished DRI pellets enter the DRI pellet silo for storage through the finished DRI pellet outlet 206. During the movement of the first grate 202, the DRI powder leaks into the collection hopper 4 below and is sent to the finished powder silo 44 for storage via the first airtight valve 43 and the corresponding conveying equipment.

[0081] Green pellets with a moisture content of 14% enter the drying zone 5 of the coupling section VI through the green pellet inlet 305 and are spread flat on the second grate 302 corresponding to the pellet conveying section 301. As the grate moves from left to right, it passes through the drying sections VI to I in sequence and comes into contact with each heating medium for dehydration and drying. The temperature of the heating medium gradually increases, and dry pellets with a moisture content of 1% to 2% are obtained and enter the rotary hearth furnace 500 as raw material through the dry pellet outlet 306 and the corresponding feeding device.

[0082] The high-temperature flue gas generated by the rotary hearth furnace 500 at 1050℃ is cooled to below 200℃ by the waste heat boiler 601, then further cooled to 170℃ by the zinc dust collector. A portion of the clean flue gas (below 160℃) is then sent to cooling section I and cooling section II by the first dust collector fan 603, while the excess flue gas is discharged through the first chimney 604. The DRI pellets at the inlet of cooling section I are at 1100℃. After being cooled by the clean flue gas, the temperature drops to 850℃ before entering cooling section II, where they are further cooled to 700℃ by the clean flue gas.

[0083] Furthermore, in the cooling section I, the clean flue gas passes through the 1100°C DRI bed, where its temperature rises to 800°C and enters the heat exchange section I via the first grate 202. The heat exchanger 311 in the heat exchange section I is a steam superheater. The heat from the flue gas is absorbed by the saturated steam in the superheater, reducing the temperature to 350°C and generating superheated steam at 2.3 MPa and 310°C~350°C. The 350°C hot flue gas enters the drying section I through the louvers of the collecting hopper 4, where the green pellets are finally dried to obtain dry pellets. The flue gas temperature is further reduced to 250°C, and then it is collected by the return hopper 7 via the second grate 302 and led out through the outlet 6.

[0084] In the cooling section II, the clean flue gas passes through the 850°C DRI bed, where its temperature rises to 600°C~700°C. It then passes through the first grate 202 and enters the heat exchange section II. The heat exchanger 311 in the heat exchange section uses an air preheater, where the flue gas heat is absorbed by the combustion air, reducing the temperature to 300°C. The combustion air fan 32 sends ambient air into the heat exchange section II, where the cold air is heated to 450°C in the air preheater and then sent to the burners of the rotary hearth furnace 500 as combustion air. The 300°C hot flue gas enters the drying section II through the louvers of the collecting hopper 4 to dry the green pellets, further reducing the flue gas temperature to 200°C. It then passes through the second grate 302 into the return hopper 7 for collection and is led out through the outlet 6.

[0085] Furthermore, the flue gas from the outlet 6 of the drying section I and drying section II is mixed with the flue gas at a temperature of about 220°C. This flue gas is sent to the cooling section III and cooling section IV by the high-temperature circulating fan 61, and continues to cool the cooled DRI pellets. The DRI pellets at the inlet of the cooling section III are 700°C. After being cooled by the circulating flue gas, the temperature drops to 580°C, and then enters the cooling section IV, where they are further cooled by the circulating flue gas to 450°C.

[0086] In the cooling stage III, the circulating flue gas passes through a 700°C DRI bed, where its temperature rises to 550°C. It then passes through the first grate 202 and enters the heat exchange stage III. The heat exchanger 311 in the heat exchange stage is an evaporator. The heat from the flue gas is absorbed by the steam-water mixture in the evaporator, reducing the temperature to 250°C and generating saturated steam at 2.3 MPa and 220°C. The 250°C hot flue gas then passes through the louvers of the DRI powder collection hopper 4 into the drying stage III to dry the green pellets. The flue gas temperature is further reduced to 150°C, and then it is collected by the return hopper 7 via the second grate 302 and led out through the outlet 6.

[0087] In the cooling IV section, the circulating flue gas passes through the 580°C DRI bed, where the temperature rises to 450°C and enters the heat exchange IV section through the first grate 202. The heat exchanger 311 in the heat exchange IV section is an evaporator. The heat of the flue gas is absorbed by the steam-water mixture in the evaporator, and the temperature drops to 220°C, generating saturated steam at 2.3MPa and 220°C. Then, the flue gas enters the drying IV section through the louvers of the collecting hopper 4 to dry the green pellets. The flue gas temperature is further reduced to 120°C, and then it is collected by the return hopper 7 through the second grate 302 and led out through the air outlet 6.

[0088] Cooling fan 11 blows ambient air into cooling section VI, ultimately cooling the DRI to below 120°C. In cooling section VI, the ambient air passes through the 280°C DRI bed, its temperature rises to 220°C, and it enters heat exchange section VI via the first grate 202. Heat exchanger 311 in heat exchange section VI employs either an economizer or a hot water heat exchanger 311. The heat from the flue gas is absorbed by the demineralized water in the economizer or hot water heat exchanger 311, reducing the temperature to 150°C and producing 2.3 MPa saturated water or hot water. The 150°C air then enters drying section VI through the louvers of the DRI powder collection hopper 4, preheating the green pellets. The air temperature is further reduced to 70°C, and then it is collected by the return hopper 7 via the second grate 302 and led out through the outlet 6.

[0089] Air drawn from the return hopper 7 of the drying section VI is sent to the cooling section V by the low-temperature circulating fan 62. In the cooling section V, the circulating air passes through the 450°C DRI bed, its temperature rises to 380°C, and it enters the heat exchange section V through the first grate 202. The heat exchanger 311 in the heat exchange section is an evaporator. The heat of the flue gas is absorbed by the steam-water mixture in the evaporator, and the temperature drops to 200°C, producing saturated water or steam at 220°C and 2.3MPa. The 200°C air enters the drying section V through the louvers of the DRI powder collection hopper 4 to heat the green pellets. The circulating air temperature is further reduced to 90°C, and then it enters the return hopper 7 through the second grate 302 for collection and is drawn out through the air outlet 6.

[0090] Furthermore, the DRI temperature at the inlet of cooling section V is 450°C. After being cooled by circulating air, it is reduced to 280°C before entering cooling section VI, where it is further cooled by ambient air to 120°C.

[0091] Furthermore, the flue gas drawn from the return hopper 7 outlet 6 of drying section III, drying section IV and drying section V merges at a temperature of about 100℃~150℃ and enters the drying dust collector for dust removal. Finally, it is sent to the second chimney 703 for discharge by the second dust removal fan 702.

[0092] During the movement of the second grate 302, the pulverized material of the green pellets leaks into the return hopper 7 below, and then flows through the second airtight valve 73 and chute to the return conveyor belt. The remaining material shaken off by the second grate 302 during its return stroke and the material leaking from the coupling device are all collected in the remaining material hopper 8, and then flow from the bottom of the hopper into the return conveyor belt. The dust collected by the dryer dust collector is also discharged to the return conveyor belt through the conveying equipment. Finally, the return conveyor belt sends the above materials back to the rotary hearth furnace 500 batching system to participate in the batching again.

[0093] Optionally, in practical applications, to ensure that the DRI pellets are cooled sequentially through the four coupling devices (specifically, within the six coupling sections) along the pellet conveying section 201, the temperature of the DRI pellets in each cooling zone 2 decreases gradually along the conveying direction; it is also necessary to ensure that the flue gas temperature in each drying zone 5 increases gradually along the conveying direction when the pellets entering the furnace are dried sequentially through the four coupling devices (specifically, within the six coupling sections) along the pellet conveying section 301, to prevent green pellet bursting due to rapid heating. This can be achieved by adjusting the operating parameters of the heat exchanger 311, the number of heat exchangers 311, and the relevant process parameters of the system.

[0094] Optionally, the high-temperature DRI pellet temperature is 1050~1100℃, the finished product DRI temperature is 100~130℃, the high-temperature flue gas temperature generated by the rotary hearth furnace 500 is 1050~1100℃, the flue gas temperature after exiting the first coupling section A and the second coupling section B and entering the high-temperature circulating fan 61 is 200-250℃, and the gas temperature after exiting the sixth coupling section F and entering the low-temperature circulating fan 62 is 70~95℃.

[0095] The "high" and "low" in the high-temperature circulating fan 61 and low-temperature circulating fan 62 mentioned above are only used to distinguish the relative high and low flue gas temperatures they correspond to; the specific flue gas temperatures depend on the actual situation. Optionally, multi-tube dust collectors can be added to the inlet pipes of the high-temperature circulating fan 61 and the low-temperature circulating fan 62 to reduce fan wear.

[0096] Furthermore, this application also provides a coupled method for cooling and drying pellets in a rotary hearth furnace, employing the aforementioned coupled system. The coupled method includes: A first cooling medium is introduced into the air inlet 1 of the first coupling device 101; A second cooling medium is introduced into the air inlet 1 of the fourth coupling device 104; The gas from the outlet 6 of the first coupling device 101 is introduced into the inlet 1 of the second coupling device 102. The gas from the outlet 6 of the fourth coupling device 104 is introduced into the inlet 1 of the third coupling device 103. The DRI pellets produced by the rotary hearth furnace 500 are fed into the first coupling device 101 from the feed end of the pellet conveying device 200. The DRI pellets are cooled in the cooling zones 2 of the first coupling device 101, the second coupling device 102, the third coupling device 103 and the fourth coupling device 104 in sequence during the conveying process of the pellet conveying device 200, so as to obtain cooled finished DRI pellets at the discharge end of the pellet conveying device 200. Green pellets are fed into the fourth coupling device 104 from the feed end of the pellet conveying device 300. The green pellets are then dried in the drying zones 5 of the fourth coupling device 104, the third coupling device 103, the second coupling device 102 and the first coupling device 101 in sequence during the conveying process of the pellet conveying device 300, so as to obtain dry pellets at the discharge end of the pellet conveying device 300.

[0097] This method uses the aforementioned system to couple the cooling of the DRI finished product in the rotary hearth furnace with the drying of the green pellets entering the furnace, thereby making full use of the waste heat from the DRI process and achieving energy conservation and consumption reduction.

[0098] Optionally, the rotary hearth furnace 500 pellet cooling and drying coupling method further includes: introducing combustion air into the inlet end of the air preheater within the first coupling device 101, utilizing the heat of the gas in the heat exchange zone 3 of the first coupling device 101 to exchange heat with the combustion air in the air preheater, so that preheated combustion air is obtained at the outlet end of the air preheater. This achieves the coupling of DRI finished product cooling with furnace-entry green pellet drying and combustion air preheating, improving the utilization of waste heat.

[0099] Further optionally, the heat exchange device 31 in the first coupling device 101 further includes a steam superheater, the heat exchange device 31 in the second coupling device 102 includes an evaporator and / or a steam superheater, the heat exchange device 31 in the third coupling device 103 includes an evaporator, and the heat exchange device 31 in the fourth coupling device 104 includes an economizer and / or a hot water heat exchanger; the rotary hearth furnace 500 pellet cooling and drying coupling method further includes: introducing liquid into the heat exchanger 311 of the fourth coupling device 104, and sequentially passing it through the heat exchanger 311 in the third coupling device 103, the heat exchanger 311 in the second coupling device 102, and the steam superheater in the first coupling device 101 to obtain superheated steam.

[0100] In summary, the coupled system and method of this application have the following advantages: (1) By adopting the system and method of this application, the coupling of high-temperature DRI cooling with green pellet drying and combustion air heating is realized. The heat released by high-temperature DRI cooling is used for green pellet drying, combustion air heating and steam generation. Compared with the traditional process, the waste heat of DRI cooling is recovered and there is no water dissipation in the cooling process; green pellet drying and combustion air heating do not require the configuration of a heating furnace, and there is no additional gas consumption, saving a lot of gas; at the same time, the waste heat of DRI cooling can also generate steam.

[0101] (2) This application combines the three systems of the traditional hot blast stove system, green ball drying system and DRI cooling system of the rotary hearth furnace 500 into one, which has a high degree of equipment concentration, greatly reduces the floor space, and reduces the number of pipe connections between equipment, thus reducing heat loss.

[0102] (3) Using hot flue gas to cool the high-temperature section of DRI, the inert atmosphere of the flue gas can replace high-value inert gases such as nitrogen; at the same time, the hot flue gas carries heat, which is more conducive to the full utilization of the waste heat of DRI than using room temperature cooling gas.

[0103] (4) Cooling the low-temperature section DRI with ambient air has a good cooling effect, the heat exchange area can be reduced, the equipment size is small, and the reaction between the low-temperature DRI and the air can be ignored in a short time, saving the consumption of inert gas in conventional cooling processes.

[0104] (5) The cooling medium and the hot DRI are in counter-current cascade contact, and the drying medium and the green pellets are in counter-current cascade contact, resulting in higher heat exchange efficiency. The six-stage refined cooling and green pellet drying process, compared with the traditional extensive single-stage cooling and two-stage drying, provides more thorough cooling of the DRI finished product and more complete drying of the green pellets. The temperature of the hot medium for green pellet drying gradually increases, avoiding green pellet cracking caused by rapid heating, thereby reducing the green pellet powdering rate.

[0105] (6) Heat exchangers 311 are installed below the cooling zone 2 corresponding to each coupling section. By adjusting the number of heat exchangers 311 and the medium parameters, the hot air temperature of the green pellet drying can be easily controlled, and the quality of the dried pellets is guaranteed.

[0106] (7) The inlet and outlet of the high-temperature DRI are opposite to the inlet and outlet of the green pellets, and the material flow direction of the DRI is opposite to that of the green pellets. The hot air generated by the high-temperature DRI thoroughly dries the green pellets, and the hot air generated by the low-temperature DRI preheats the green pellets, so the heat energy is fully utilized.

[0107] (8) Each coupling device has upper-layer DRI cooling, middle-layer waste heat recovery and combustion air heating, and lower-layer green pellet drying. This equipment integrates DRI cooling, combustion air heating, green pellet drying and waste heat recovery functions, with high equipment concentration and small footprint.

[0108] (9) By setting up the collecting hopper 4 and the return hopper 7 respectively, the collecting hopper 4 is set below the grate corresponding to the pellet conveying section 201 of the furnace exit, and the return hopper 7 is set below the grate corresponding to the pellet conveying section 301 of the furnace inlet. The collecting hopper 4 is a louvered structure with the louvers tilting inward and downward, allowing airflow to pass through and the material to be collected into the hopper. This can achieve separate collection of DRI powder and return material without mixing.

[0109] (10) The coupling system can replace the traditional hot air furnace system, DRI cooling system, and green pellet drying system, realizing the functions of three systems and using surplus thermal energy to produce steam. The coupling system uses hot flue gas and ambient air to cool the high and low temperature sections of the DRI respectively, replacing the traditional inert gas, reducing operating costs, providing good DRI cooling effect, and more complete heat recovery. The hot flue gas and ambient air are in counter-current cascade contact with the DRI, with temperature changing segment by segment, resulting in more complete heat exchange and effectively preventing green pellet bursting.

[0110] The above are merely illustrative embodiments of the present invention and are not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A coupled cooling and drying system for pellets in a rotary hearth furnace, characterized in that, include: Four coupling devices are arranged adjacent to each other in a horizontal direction, and are respectively the first coupling device, the second coupling device, the third coupling device and the fourth coupling device; The furnace-outfeeding pellet conveying device and the furnace-infeeding pellet conveying device are arranged in parallel vertically, with opposite conveying directions and parallel to the horizontal direction; both the furnace-outfeeding pellet conveying device and the furnace-infeeding pellet conveying device pass through four coupling devices in sequence, and their respective ends pass through the first coupling device and the fourth coupling device respectively; both the furnace-outfeeding pellet conveying device and the furnace-infeeding pellet conveying device are provided with multiple through holes. Each coupling device includes a cooling zone, a heat exchange zone, and a drying zone arranged sequentially from top to bottom. The cooling zone is located above the pellet conveying section of the pellet conveying device, the heat exchange zone is located below the pellet conveying section and is equipped with a heat exchange device, and the drying zone is located above the pellet conveying section of the pellet feeding device. The top of the coupling device has an air inlet, and the lower part of the coupling device, located below the pellet feeding section, is connected to an air outlet. The air inlet of the first coupling device is used to introduce a first cooling medium, and the air outlet of the first coupling device is connected to the air inlet of the second coupling device through a high-temperature circulation pipeline equipped with a high-temperature circulation fan. The air inlet of the fourth coupling device is used to introduce a second cooling medium, and the air outlet of the fourth coupling device is connected to the air inlet of the third coupling device through a low-temperature circulation pipeline equipped with a low-temperature circulation fan.

2. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 1, characterized in that, The first cooling medium is the cooled rotary hearth furnace flue gas, and the second cooling medium is ambient temperature air.

3. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 1, characterized in that, The heat exchange device in the first coupling device includes an air preheater. The inlet end of the air preheater is connected to the atmosphere through a combustion air duct equipped with a combustion air fan. The outlet end of the air preheater is used to provide combustion air to the rotary hearth furnace.

4. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 1, characterized in that, The heat exchange device within the first coupling device also includes a steam superheater.

5. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 4, characterized in that, The heat exchange device in the second coupling device includes an evaporator and / or a steam superheater, the heat exchange device in the third coupling device includes an evaporator, and the heat exchange device in the fourth coupling device includes an economizer and / or a hot water heat exchanger.

6. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 5, characterized in that, The inlet end of the heat exchanger of the fourth coupling device is used to introduce cold fluid. The outlet end of the heat exchanger of the fourth coupling device can be connected to the inlet end of the evaporator of the third coupling device through a pipe. The outlet end of the evaporator of the third coupling device is connected to the inlet end of the heat exchanger of the second coupling device through a pipe. The outlet end of the heat exchanger of the second coupling device is connected to the inlet end of the steam superheater in the first coupling device through a pipe.

7. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 1, characterized in that, A hopper is provided within each of the coupling devices and below the heat exchange device. A collection pipe is provided on the side of the coupling device that can communicate with the hopper. The hopper is configured to allow only gas to pass through.

8. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 7, characterized in that, At least a portion of the wall surface of each of the hoppers is a louvered structure, with the blades of the louvered structure inclined toward the center of the hopper.

9. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 7, characterized in that, Each of the aforementioned hoppers includes two symmetrically arranged hopper bodies. Each hopper body includes a first collecting inclined plate and two second collecting inclined plates symmetrically arranged on both sides of the first collecting inclined plate. The tops and sides of the two second collecting inclined plates are connected to the corresponding sidewalls of the coupling device. The tops of the two first collecting inclined plates of the two hopper bodies are connected. The first collecting inclined plate, the two second collecting inclined plates, and the corresponding sidewalls of the coupling device enclose a bucket-shaped structure with a gradually decreasing cross-section. Two collecting pipes are symmetrically arranged on both sides of the coupling device and are respectively connected to the bottoms of the two hopper bodies.

10. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 7, characterized in that, The rotary hearth furnace pellet cooling and drying coupling system also includes a finished pellet bin and a finished powder bin. The finished pellet bin is connected to the discharge end of the pellet conveying device, and the finished powder bin is connected to the outlet end of each of the collecting pipes.

11. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 7, characterized in that, A return hopper is provided in each of the coupling devices and below the pellet conveying section into the furnace. The wall of the return hopper is a closed surface. A return pipe that can communicate with the return hopper is also provided on the side of the coupling device.

12. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 11, characterized in that, Each of the return hoppers includes two symmetrically arranged return hopper bodies. Each return hopper body includes a first return inclined plate and two second return inclined plates symmetrically arranged on both sides of the first return inclined plate. The tops and sides of the two second return inclined plates are connected to the corresponding sidewalls of the coupling device. The tops of the two first return inclined plates of the two return hopper bodies are connected. The first return inclined plate, the two second return inclined plates, and the corresponding sidewalls of the coupling device enclose a bucket-shaped structure with a gradually decreasing cross-section. Two return pipes are symmetrically arranged on both sides of the coupling device and are respectively connected to the bottoms of the two return hopper bodies.

13. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 11, characterized in that, At the bottom of the coupling device and below the return hopper, there is also a residual material hopper, and the bottom end of the residual material hopper is connected to a residual material pipe.

14. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 13, characterized in that, The heat exchange device of the coupling device includes one heat exchanger or at least two heat exchangers arranged side by side along the horizontal direction. The number of the collecting hopper, the number of the return hopper, and the number of the surplus hopper in each coupling device are the same as the number of the heat exchangers in the coupling device.

15. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 13, characterized in that, The rotary hearth furnace pellet cooling and drying coupling system also includes a return material conveying device, the conveying direction of which is parallel to the horizontal direction. The return material conveying device is installed at the bottom of the four coupling devices and located below the waste material hopper of each coupling device. The outlet ends of the return material pipe and the waste material pipe are arranged directly opposite the return material conveying device.

16. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 1, characterized in that, Both the first coupling device and the second coupling device include two coupling structures arranged side by side along the horizontal direction, separated by a partition. Each coupling structure is provided with a cooling zone, a heat exchange zone and a drying zone, and each coupling structure is provided with at least one heat exchanger.

17. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 16, characterized in that, Each of the two coupling structures of the first coupling device is provided with two heat exchangers, each of the two coupling structures of the second coupling device is provided with two heat exchangers, the third coupling device is provided with three heat exchangers, and the fourth coupling device is provided with two heat exchangers.

18. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 1, characterized in that, The rotary hearth furnace pellet cooling and drying coupling system also includes a rotary hearth furnace. The discharge port of the rotary hearth furnace is connected to the feed end of the pellet conveying device, the feed port of the rotary hearth furnace is connected to the discharge end of the pellet conveying device, the flue gas outlet of the rotary hearth furnace is connected to the air inlet of the first coupling device through a flue gas pipeline, and a cooling and dust removal device is provided on the flue gas pipeline.

19. The rotary hearth furnace pellet cooling and drying coupled system as described in claim 1, characterized in that, The rotary hearth furnace pellet cooling and drying coupling system also includes an exhaust pipeline. Each air outlet of the second coupling device and the third coupling device can be connected to the exhaust pipeline. An exhaust dust removal device is also sequentially installed on the exhaust pipeline.

20. A coupled method for cooling and drying pellets in a rotary hearth furnace, characterized in that, The rotary hearth furnace pellet cooling and drying coupling system as described in any one of claims 1-19, wherein the rotary hearth furnace pellet cooling and drying coupling method comprises: A first cooling medium is introduced into the air inlet of the first coupling device; A second cooling medium is introduced into the air inlet of the fourth coupling device; The gas from the outlet of the first coupling device is introduced into the inlet of the second coupling device; The gas from the outlet of the fourth coupling device is introduced into the inlet of the third coupling device; The DRI pellets produced by the rotary hearth furnace are fed into the first coupling device from the feed end of the pellet conveying device. The DRI pellets are cooled in the cooling zones of the first coupling device, the second coupling device, the third coupling device and the fourth coupling device in sequence during the conveying process of the pellet conveying device, so as to obtain cooled finished DRI pellets at the discharge end of the pellet conveying device. Green pellets are fed into the fourth coupling device from the feed end of the pellet conveying device. The green pellets are dried sequentially in the drying zones of the fourth coupling device, the third coupling device, the second coupling device, and the first coupling device during the conveying process of the pellet conveying device, so as to obtain dry pellets at the discharge end of the pellet conveying device.

21. The rotary hearth furnace pellet cooling and drying coupling method as described in claim 20, characterized in that, The rotary hearth furnace pellet cooling and drying coupling method further includes: Combustion air is introduced into the inlet of the air preheater in the first coupling device, and the heat of the gas in the heat exchange zone of the first coupling device is used to exchange heat with the combustion air in the air preheater, so as to obtain preheated combustion air at the outlet of the air preheater.

22. The rotary hearth furnace pellet cooling and drying coupling method as described in claim 20, characterized in that, The heat exchange device in the first coupling device further includes a steam superheater; the heat exchange device in the second coupling device includes an evaporator and / or a steam superheater; the heat exchange device in the third coupling device includes an evaporator; and the heat exchange device in the fourth coupling device includes an economizer and / or a hot water heat exchanger. The rotary hearth furnace pellet cooling and drying coupling method further includes: The liquid is introduced into the heat exchanger of the fourth coupling device, and then sequentially passes through the heat exchanger in the third coupling device, the heat exchanger in the second coupling device, and the steam superheater in the first coupling device to obtain superheated steam.

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