System and method for utilizing waste heat of non-ferrous metal smelting slag

Abstract

The invention relates to a non-ferrous metal smelting slag waste heat utilization system and method, and belongs to the technical field of non-ferrous metal smelting slag treatment and waste heat recovery. Aiming at the problems of low smelting slag waste heat recovery efficiency, poor spray cooling safety, unreliable connection of different cooling processes and the like in the prior art, a composite heat exchange top cover unit comprising a water cooling wall cover, an inverted funnel-shaped air duct and a multi-cavity coil heat exchanger is arranged, and a cooling gas supply unit, a spray device and a control system are combined; the staged and controlled cooling process that cooling gas is used for conducting air cooling on the high-temperature molten slag firstly, after the surface temperature of the high-temperature molten slag is reduced to the safety threshold value, spraying water cooling is started, and in the process, waste heat is continuously recycled through a circulating working medium. The device is mainly used for safely and efficiently recycling waste heat released in the cooling process of the non-ferrous metal smelting slag, and steam and hot water are produced and supplied to factories for use.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal smelting slag treatment and waste heat recovery technology, and in particular to a system and method for utilizing waste heat from non-ferrous metal smelting slag. Background Technology

[0002] In the pyrometallurgical process of non-ferrous metals, a large amount of high-temperature molten slag is generated, with temperatures typically exceeding 1100℃. Effectively recovering the waste heat released during the cooling and solidification of this slag is of great significance for energy conservation and emission reduction. Currently, the industry still faces several technical bottlenecks in the cooling and waste heat treatment methods for such high-temperature molten slag.

[0003] Conventional natural slow cooling methods mainly rely on the outer wall of the slag tank to dissipate heat to the environment. The cooling cycle is long, and the heat is mostly lost in the form of radiation and convection, which is difficult to be collected and utilized by the system, resulting in significant energy waste.

[0004] While direct water spray cooling can accelerate cooling, its application at high temperatures (such as when the slag temperature is significantly higher than the boiling point of water) can easily lead to safety risks due to rapid water vaporization. Furthermore, the evaporation of the sprayed water can easily precipitate salt scale, which adheres to the tank walls and internal structures, reducing heat exchange efficiency and exacerbating equipment corrosion. Rapid water cooling also hinders the crystal formation of non-ferrous metal smelting slag, negatively impacting subsequent mineral processing operations.

[0005] While forced air cooling is relatively safe, its cooling capacity is limited, making it difficult to lower the slag temperature to the lower temperatures required for subsequent processing (e.g., below 50°C). If an attempt is made to combine air cooling and water cooling into a continuous process, the question arises of how to safely and reliably determine the switching point between the two cooling modes. Switching too early poses safety risks, while switching too late results in low efficiency and lacks a reliable automatic judgment and execution mechanism.

[0006] Regarding the structure of waste heat recovery equipment, the placement of heat exchange elements inside the slag pot presents a challenge: if they are too close to the molten slag surface, there is a risk of them being splashed or stuck by the molten slag; if they are too far away, the heat exchange effect will be poor. In addition, efficiently removing the heated heat transfer medium (such as hot air) from the slag pot and maintaining a suitable pressure environment inside the pot to avoid cold air backflow and ensure heat transfer efficiency also places high demands on the system integration design.

[0007] Therefore, existing technologies for treating high-temperature smelting slag have shortcomings in terms of waste heat recovery efficiency, process safety, reliability of process connection, equipment layout and system integration, and urgently need to be improved. Summary of the Invention

[0008] This invention provides a system and method for utilizing waste heat from non-ferrous metal smelting slag, aiming to safely and efficiently recover the waste heat released by smelting slag during the cooling process, and to solve the problems of low waste heat recovery efficiency, poor safety of spray cooling, and unreliable process connection in the prior art through a phased and controlled cooling process.

[0009] To achieve the above objectives, the present invention provides a system for utilizing waste heat from non-ferrous metal smelting slag, comprising: Slag pots are used to hold smelting slag. The composite heat exchange top cover unit includes: A water-cooled wall cover is sealed at the top opening of the slag tank. The water-cooled wall cover is a pressure-bearing cover plate with an internal circulating water channel. The inlet and outlet of the circulating water channel are used to connect to the external steam drum circulation system. The air duct is sealed at its lower end to the central area of ​​the upper surface of the water-cooled wall cover and passes through the water-cooled wall cover to communicate with the internal space of the slag tank. Its upper end is connected to a hot air output pipe. The air duct is cylindrical or inverted funnel-shaped. A multi-cavity coil heat exchanger includes a sleeve fitted inside the air duct, a first coil heat unit disposed in an annular cavity between the sleeve and the air duct, and a second coil unit disposed inside the sleeve. The working fluid inlet and outlet of the multi-cavity coil heat exchanger pass through the air duct and are used to connect to an external steam drum circulation system. A spray device is installed on the lower surface of the water-cooled wall cover and connected to the cooling water circulation unit via a pipe. The cooling water circulation unit includes a water storage tank and a circulation pump. A cooling gas supply unit includes a cooling gas source and an air supply duct. The air outlet of the air supply duct is connected to the upper part of the side wall of the slag pot or a dedicated air inlet on the water-cooled wall cover, for delivering cooling gas to the space above the smelting slag inside the slag pot. The control system is used to first start the cooling gas supply unit to air-cool the smelting slag; after the surface temperature of the smelting slag drops to a safe threshold, it then controls the cooling water circulation unit to start, so that the spraying device sprays cooling water onto the surface of the smelting slag for spray water cooling; during the air cooling and spray water cooling processes, the working fluid in the external steam drum circulation system is controlled to circulate in the circulating water channel of the water-cooled wall cover and the multi-cavity coil heat exchanger to recover waste heat.

[0010] Preferably, both the first coil heating unit and the second coil heating unit are spiral coils, with their axes arranged perpendicular to the plane of the water-cooled wall cover.

[0011] Preferably, the hot air output pipe is sequentially connected to a pressure regulating valve and at least one indirect heat exchanger.

[0012] Preferably, the preset safety threshold in the control system is 700℃-850℃; and the control system monitors the temperature of the smelting slag in real time during the spray water cooling stage, and controls the cooling water circulation unit to stop operating when the temperature drops to 50℃-100℃.

[0013] Preferably, the cooling gas supply unit further includes an air compressor and a buffer tank; the air compressor is used to compress the cooling gas to a preset pressure, and the buffer tank is connected between the air compressor and the air supply duct to stabilize the pressure and flow rate of the cooling gas.

[0014] Preferably, the spraying device includes an annular main pipe and multiple atomizing nozzles; the annular main pipe is fixedly installed on the lower surface of the water-cooled wall cover, and the multiple atomizing nozzles are evenly distributed along the circumference of the annular main pipe.

[0015] Preferably, an external wall heat exchanger is installed on the outer wall of the slag pot, and a base heat exchanger is installed at the bottom of the slag pot; the external wall heat exchanger and the base heat exchanger are respectively connected to an external waste heat utilization system through pipes; and a closed-cell vibrator is installed on the outer wall of the slag pot.

[0016] This invention provides a method for utilizing waste heat from non-ferrous metal smelting slag, employing the aforementioned system and including the following steps: S1, Air-cooling stage: After the high-temperature molten slag is injected into the slag pot, cooling gas is sent into the slag pot through the cooling gas supply unit to force air cooling of the slag. At the same time, waste heat is recovered through the circulating water channel of the water-cooled wall cover and the multi-cavity coil heat exchanger. S2. Temperature monitoring and judgment: Monitor the surface temperature of the smelting slag in real time. When it drops to the safe threshold of 700℃-850℃, proceed to step S3. S3, Water Slow Cooling Stage: Start the cooling water circulation unit and spray cooling water onto the surface of the smelting slag through the spray device for spray water cooling. At the same time, continue to recover waste heat through the water-cooled wall cover and multi-cavity coil heat exchanger. S4. Termination and subsequent treatment: When the temperature of the smelting slag drops to 50℃-100℃, stop spraying cooling water to complete the waste heat recovery and slag cooling.

[0017] Preferably, in step S1, the cooling gas introduced is compressed air or nitrogen, and the pressure is maintained at 0.8-1.2 MPa to maintain a slightly positive pressure state inside the slag pot.

[0018] Preferably, the working fluid generated by recovering waste heat in steps S1 and S3 is saturated steam. The saturated steam is transported to a steam drum for steam-water separation. The separated steam is used for at least one of the following purposes: power generation, heating, or driving a heat pump. In step S1, the hot air discharged from the duct passes through pressure regulation and at least one stage of indirect heat exchange in sequence to heat the demineralized water to produce hot water, thus making cascade utilization of the waste heat of the hot air.

[0019] The present invention has the following beneficial effects: First, this invention fundamentally avoids the risks of violent vaporization, splashing, and even explosion caused by direct contact between high-temperature molten slag (>700℃) and liquid water by setting up a phased, controlled cooling process that first uses air cooling and then water cooling, and automatically switches according to a preset safe temperature threshold. The pre-emptive, controlled forced air cooling stage creates safe conditions for water cooling, allowing the two cooling methods to be safely and efficiently connected. This achieves continuous and complete recovery of waste heat from both the high-temperature and medium-low-temperature stages while ensuring operational safety.

[0020] Secondly, this invention employs a composite heat exchange top cover unit, integrating a water-cooled wall cover, a multi-cavity coil heat exchanger, and air ducts to construct a three-dimensional, multi-path synchronous waste heat recovery system. During both air-cooling and water-cooling processes, the system can recover radiant heat through the water-cooled wall cover, recover convective and radiant heat from the gas phase space through the suspended coils, and collect and export hot air through the air ducts for subsequent utilization. This integrated design achieves efficient and synchronous capture of different forms of heat (radiative heat and sensible heat in the gas phase) inside the slag pot, significantly improving the total waste heat recovery of a single device or a single cooling stage.

[0021] Third, this invention arranges the annular main pipe of the spray device around the multi-cavity coil heat exchanger, and controls the spray water to act only on the slag surface in the central area surrounded by the coil. This arrangement achieves physical isolation between the spray cooling area and the core heat exchange equipment, effectively preventing the direct impact and rapid cooling of the high-temperature coil surface by the low-temperature water mist, and avoiding the risk of damage to the heat exchange tubes due to uneven thermal stress. This protects the critical heat exchange equipment, extends its service life, and ensures that the spray water absorbs heat in the designated area, optimizing the synergistic effect of cooling and heat recovery.

[0022] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the system pipeline connection for the utilization of waste heat from non-ferrous metal smelting slag according to the present invention. Figure 2 This is a schematic diagram of the process for utilizing waste heat from non-ferrous metal smelting slag according to the present invention. Figure 3 This is a detailed view of the composite heat exchange top cover unit of the present invention; Figure 4 This is a schematic diagram showing the distribution of the air duct, hot air output pipe, multi-chamber coil heat exchanger, and spray device of the present invention.

[0024] The following are the reference numerals in the accompanying drawings: 1. Slag tank; 2. Water-cooled wall cover; 3. Air duct; 4. Hot air output pipe; 5. Ventilation hole; 6. Multi-chamber coil heat exchanger; 61. First coil heat unit; 62. Second coil heat unit; 63. Sleeve; 7. Spray device; 8. Air supply pipe; 9. Dedicated air inlet; 10. External wall heat exchanger; 11. Base heat exchanger; 12. External steam drum circulation system; 13. Composite heat exchange top cover unit. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] like Figures 1 to 4 As shown, this invention provides a system for utilizing waste heat from non-ferrous metal smelting slag. The system mainly includes a slag pot 1, a composite heat exchange top cover unit 13, a cooling gas supply unit, a cooling water circulation unit, and a control system.

[0027] The slag pot 1 is used to contain molten metallurgical slag at high temperatures.

[0028] The composite heat exchange top cover unit is sealed and installed at the top opening of the slag tank 1. The composite heat exchange top cover unit specifically includes: Water-cooled wall cover 2: This is a pressure-bearing cover plate with an internal circulating water channel, sealed to the top opening of the slag tank via a flange or mechanical locking device. The inlet and outlet of the circulating water channel are used to connect to the external steam drum circulation system 12. Specifically, the external steam drum circulation system includes a steam drum, downcomer, riser, circulation pump, and related valves and instruments. The steam drum is used for steam-water separation and storage. The downcomer transports water from the steam drum to the water-cooled wall cover and the multi-chamber coil heat exchanger. The steam-water mixture formed after heat absorption returns to the steam drum via the riser, realizing natural or forced circulation of the working fluid.

[0029] To facilitate rapid and safe separation of the composite heat exchange top cover unit from the slag tank after cooling, the upper surface of the water-cooled wall cover 2 is equipped with several lifting lugs or lifting flanges for connection to the workshop overhead crane or a dedicated lifting device. A quick-release snap-fit ​​or hydraulic locking sealing structure is used between the water-cooled wall cover 2 and the sealing flange at the top of the slag tank 1. Guide columns or rails can be installed on the outer side of the sealing surface to ensure smooth and centered lifting of the top cover, preventing collisions with internal components. All pipes requiring connection to external systems, including the inlet and outlet of the circulating water channel, the inlet of the spray device, and the hot air output pipe, are connected to flexible hoses (or metal hoses) of appropriate length via quick-connect fittings with self-sealing valves. The other end of the flexible hose is connected to the workshop's fixed piping network. This design allows the flexible hose to hang naturally or be supported by a simple bracket before lifting the top cover, without disassembling any rigid pipes, greatly simplifying the operation and improving system maintainability and turnover efficiency.

[0030] Air duct 3: Its upper end is sealed and connected to the central area of ​​the upper surface of the water-cooled wall cover, and passes through the water-cooled wall cover to communicate with the internal space of the slag tank. Its lower end is connected to the hot air output pipe 4. The air duct is cylindrical or inverted funnel-shaped.

[0031] Multi-chamber coil heat exchanger 6: It is fixedly suspended inside the air duct 3 by a bracket. It includes a sleeve 63 fitted inside the air duct, a first coil heat exchanger unit 61 disposed in the annular cavity between the sleeve and the air duct, and a second coil heat exchanger unit 62 disposed in the sleeve. Both the first coil heat exchanger unit and the second coil heat exchanger unit are spiral coils with their axes perpendicular to the plane of the water-cooled wall cover. The working fluid inlet and outlet of the multi-chamber coil heat exchanger pass through the water-cooled wall cover and are connected to the external steam drum circulation system.

[0032] Spray device 7: It is installed on the lower surface of the water-cooled wall cover and connected to the cooling water circulation unit through a pipe.

[0033] The cooling water circulation unit includes a water storage tank and a circulation pump. The water storage tank is preferably an existing water storage tank in the plant area. The inlet of the circulation pump is connected to the water storage tank through a pipe, and the outlet is connected to the spray device through a pipe, thereby forming a cooling water supply loop.

[0034] The cooling gas supply unit includes a cooling gas source and an air supply duct 8. The air outlet of the air supply duct is connected to a dedicated air inlet 9 opened on the upper part of the side wall of the slag pot or on the water-cooled wall cover, for delivering cooling gas to the space above the smelting slag inside the slag pot.

[0035] The control system is electrically connected to the cooling gas supply unit, the cooling water circulation unit, the temperature measuring device installed inside the slag tank, and the external steam drum circulation system. The temperature measuring device installed inside the slag tank is preferably a non-contact device, such as an infrared thermometer or a colorimetric pyrometer. This device measures the temperature of the slag surface through a dedicated observation window or mounting sleeve installed on the top or side wall of the slag tank. The temperature measuring device transmits the real-time detected temperature signal to the control system. Specifically, the control system includes a programmable logic controller (PLC), a temperature measuring device and a pressure measuring device, and actuators that control the air compressor, circulating pump, and pressure regulating valve; it internally stores preset temperature thresholds and control programs, and is capable of receiving sensor signals and issuing control commands according to the program.

[0036] During the slow water cooling stage, the cooling water sprayed from the spray device rapidly absorbs heat and vaporizes upon contact with the surface of the high-temperature smelting slag, while the rest forms a liquid water film or droplets. The system precisely adjusts the spray water volume through a flow control system to match the cooling requirements at the current slag temperature, aiming to achieve controlled slow cooling rather than pursuing complete instantaneous vaporization of the water. Some unvaporized cooling water is allowed to remain at the bottom of the slag pot or on the slag surface. The entire cooling process (from approximately 1100℃ to 50℃-100℃) can be controlled to a total time of approximately 4 days (96 hours) by adjusting the intensity and duration of air cooling and spray cooling. This meets the process requirements for the slow formation of the smelting slag's crystal structure, which is beneficial for subsequent mineral processing operations.

[0037] The typical workflow or operation method of this system is as follows: (1) System initialization and feeding: High-temperature molten slag at a temperature of about 1100℃ is injected into the slag pot.

[0038] (2) Air-cooled and high-temperature waste heat recovery stage: The control system controls the start-up of the cooling gas supply unit. The air compressor compresses the cooling gas (such as air or nitrogen) to 0.8MPa-1.2MPa, and after being stabilized by the buffer tank, it is sent into the space above the smelting slag in the slag pot through the air supply pipe for forced convection cooling. At the same time, the working fluid (water) in the external steam drum circulation system circulates in the circulating water channel of the water-cooled wall cover and the multi-cavity coil heat exchanger, absorbing the heat transferred by the radiation of the high-temperature slag and the convection of the hot air, and partially vaporizes to recover the high-temperature waste heat. The hot air after heat exchange is discharged through the air duct. The cooling rate in this high-temperature stage is controlled to ensure slow cooling, which is conducive to the formation of mineral crystals in the slag that are beneficial to mineral beneficiation.

[0039] (3) Spray water cooling and low-temperature waste heat recovery stage: The slag surface temperature is monitored in real time by a temperature measuring device. When the temperature drops to the preset safety threshold (700℃-850℃), the control system controls the cooling water circulation unit to start, spraying atomized cooling water onto the slag surface through the spray device. The spray water further cools the slag, partially vaporizing and partially existing in liquid form. During this stage, the water-cooled wall cover and multi-cavity coil heat exchanger continue to operate to recover waste heat. When the slag temperature drops to the preset termination temperature (50℃-100℃), the control system stops spraying. The duration and intensity of the spray water cooling stage are also adjusted according to the total cooling time target.

[0040] (4) Comprehensive utilization of waste heat products: During the entire operation, the saturated steam generated by the external steam drum circulation system is transported to the steam drum for steam-water separation. The separated steam can be used for power generation, heating, or driving a heat pump. At the same time, the hot air discharged from the duct can be introduced into subsequent waste heat recovery equipment (such as a partition heat exchanger) to heat demineralized water to produce hot water, realizing the cascade utilization of thermal energy.

[0041] After the cooling process is complete, the control system confirms that all equipment has stopped operating. Operators or the automatic program sequentially disconnect all quick-connect fittings (including pipelines for circulating water, spray water, hot air output, and cooling gas supply) connected to the composite heat exchanger top cover unit. Release the mechanical locking or snap-lock seals between the water-cooled wall cover and the slag pot. Using a workshop overhead crane or a dedicated lifting device, lift the entire composite heat exchanger top cover unit (including the water-cooled wall cover, air ducts, multi-chamber coil heat exchanger, and spray system) smoothly and vertically upwards via lifting lugs or lifting flanges, completely separating it from the slag pot. The separated slag pot can be transported by a transfer vehicle to the next work area (such as slag yard slow cooling or the mineral processing workshop), while the composite heat exchanger top cover unit can be moved to the next slag pot to be processed for installation, preparing for the next work cycle.

[0042] Through the aforementioned phased and controlled operation process, the system can efficiently recover the sensible and latent heat released during the cooling of smelting slag from a high-temperature molten state to a medium-low temperature state, while ensuring safety.

[0043] In one specific embodiment of the present invention, the multi-cavity coil heat exchanger is configured as a spiral coil structure. Specifically, the spiral coil heat exchanger is fixedly suspended on the lower surface of the water-cooled wall cover, with its axis perpendicular to the plane of the water-cooled wall cover. Multiple spiral coil heat exchangers are evenly distributed circumferentially along the air duct.

[0044] The spiral coil is made of high-temperature resistant metal tubing, such as stainless steel or nickel-based alloy tubing. The outer diameter of the tubing can be selected within the range of 50mm-150mm, and the spiral pitch can be designed within the range of 1.5 to 3 times the outer diameter of the tubing. The overall height of the spiral coil's suspended arrangement can be determined according to the internal space of the slag pot, for example, between 1.0m and 2.5m, thereby ensuring a safe non-contact distance between the coil portion and the surface of the smelting slag.

[0045] The working fluid inlet and outlet of each spiral coil heat exchanger pass through a pre-set connection interface on the water-cooled wall cover and are reliably connected to the piping of the external steam drum circulation system. All spiral coil heat exchangers are arranged at equal angular intervals around the central axis of the air duct, for example, 4, 6 or 8 independent spiral coil units can be evenly arranged circumferentially.

[0046] During operation, the working fluid from the external steam drum circulation system flows in from the upper inlet of each spiral coil heat exchanger and flows downward along the spiral pipes under the action of gravity or a circulating pump. During this process, the working fluid absorbs heat radiated from the high-temperature smelting slag below and heat convected by the rising hot air through the pipe walls, gradually increasing its temperature. The heated working fluid exits from the lower outlet of each coil and returns to the external steam drum circulation system.

[0047] This spiral coil structure and circumferentially uniform arrangement effectively increase the heat exchange area within the arrangement space, promote heat exchange uniformity, and facilitate smooth flow and efficient heat exchange of the working fluid. Those skilled in the art can adapt the number, specific structural dimensions, and arrangement radius of the spiral coils according to the actual slag tank size and heat recovery requirements.

[0048] In one specific embodiment of the present invention, the upper end of the air duct is connected to the hot air output pipe, which is sequentially connected in series with a pressure regulating valve and at least one stage of indirect heat exchanger, as well as an induced draft fan and an exhaust gas treatment unit. The lower part of the indirect heat exchanger is provided with a condensate collection port, and the condensate flows back to the plant's hot water system or a water storage tank through a pipe. The induced draft fan provides the system's exhaust power, and the exhaust gas treatment unit includes a whitening tower or a spray section in the water storage tank for final purification before discharge.

[0049] The pressure regulating valve is installed on the hot air output pipe, downstream of the duct outlet. Its function is to receive and regulate the pressure of the hot air discharged from the slag pot, maintaining a slightly positive pressure in the first half of the system (i.e., inside the slag pot and duct), for example, 0.5 kPa-2.0 kPa higher than ambient pressure, to prevent backflow of external cold air and ensure stable hot air discharge. Specifically, the pressure regulating valve is an electrically operated valve, installed on the hot air output pipe, downstream of the duct outlet and before the indirect heat exchanger. The pressure regulating valve is connected to a pressure sensor located at the top of the slag pot, receiving commands from the control system and controlling the exhaust back pressure by adjusting the valve opening, thereby maintaining a slightly positive pressure (0.5-2.0 kPa) inside the slag pot and duct system. The induced draft fan is located at the end of the waste heat recovery system; its suction force, together with the upstream air supply pressure and the pressure regulating valve, works in conjunction to maintain a stable slightly positive pressure in the slag pot and duct system and ensure smooth airflow discharge.

[0050] The indirect heat exchanger is connected downstream of the pressure regulating valve. In a preferred embodiment, a two-stage indirect heat exchanger is used for cascaded waste heat recovery of hot air: The first partition-type heat exchanger: its hot-side inlet is connected to the outlet pipe of the pressure regulating valve, receiving hot air whose temperature has dropped to below 300°C. Demineralized water flows through its cold side. The hot air and demineralized water exchange heat through the partition without contacting each other, heating the demineralized water from ambient temperature (e.g., 20°C-30°C) to a first temperature (e.g., 80°C-90°C). The resulting hot water at this first temperature is piped to the plant's deaerator as boiler feedwater or a deoxygenation heat source.

[0051] The second wall-mounted heat exchanger has its hot-side inlet connected to the hot-side outlet of the first wall-mounted heat exchanger, receiving hot air whose temperature has been further reduced after the first stage of heat exchange. Its cold side also receives demineralized water at normal temperature. The hot air transfers its remaining heat to the demineralized water, heating it to a second temperature (e.g., 50°C-70°C). The resulting hot water at this second temperature is connected to the plant's hot water network for production and domestic use.

[0052] In the above process, the high-temperature, high-humidity gas (mainly composed of hot air and water vapor) from the slag tank flows through the first and second indirect-contact heat exchangers, where its sensible heat is recovered stage by stage to heat the demineralized water. Simultaneously, most of the water vapor in the gas condenses on the low-temperature heat exchange surfaces of the indirect-contact heat exchangers (especially the second stage), releasing latent heat of vaporization, further improving waste heat recovery efficiency. The condensate and the produced hot water are transported together to the plant's hot water system or deaerator, achieving water resource recovery. A small amount of uncondensed moisture is sent to the storage tank along with the subsequent exhaust gas by an induced draft fan for "whitening" treatment, where the water vapor is completely absorbed by the tank water. This completes the closed-loop process of the spray water from liquid injection to final capture and recovery by the system, essentially achieving near-zero discharge of liquid wastewater.

[0053] Through the above connections and configurations, effective pressure control of the hot air discharged from the slag tank and deep, tiered recovery of waste heat are achieved, converting low-grade heat energy into usable hot water and improving overall energy utilization efficiency. Those skilled in the art can design and adjust the number of stages, heat exchange area, and specific process parameters of the indirect heat exchanger based on the initial temperature and flow rate of the hot air.

[0054] In one specific embodiment of the present invention, the temperature control logic of the control system is described in detail. The control system includes a temperature measuring device disposed inside the slag tank, a programmable logic controller, and an actuator connected to the cooling gas supply unit and the cooling water circulation unit.

[0055] The control system has a preset safe temperature threshold for switching cooling modes. This safe temperature threshold is set within the range of 700℃-850℃. This range is set based on the following considerations: its upper limit ensures that the smelting slag has been sufficiently cooled from its initial molten state (approximately 1100℃), increasing its overall mechanical strength and stability; its lower limit ensures that the slag temperature is still significantly higher than the boiling point of water, at which point the injected cooling water will rapidly vaporize, helping to prevent liquid water from accumulating on the high-temperature slag surface and causing violent vaporization or localized stress. Specific values ​​can be selected and fine-tuned according to the specific composition and properties of the smelting slag, for example, set to 750℃ or 800℃.

[0056] The control system also presets a termination temperature threshold for stopping operation during the spray water cooling stage. This termination temperature threshold is set within the range of 50℃-100℃. This range is set based on the following considerations: the upper limit (100℃) ensures that the slag has been sufficiently cooled, the main stage of waste heat recovery has been completed, and the basic temperature requirements of subsequent processing steps for the slag are met; the lower limit (50℃) avoids excessive cooling leading to energy waste and, under safe conditions, allows for the recovery of potentially very low-grade waste heat. Specific values ​​can be set according to the production rhythm and the economics of heat recovery, for example, 50℃.

[0057] During operation, the control system executes the following control flow: 1. Air-cooling stage control: After the system starts, the controller continuously monitors the surface temperature of the smelting slag based on feedback from the temperature measuring device. As long as the temperature is higher than the safe temperature threshold (e.g., >750℃), the controller controls the cooling gas supply unit to continue operating for air cooling.

[0058] 2. Mode switching judgment: When the temperature measuring device detects that the surface temperature of the smelting slag drops to equal to or below the safe temperature threshold (e.g., ≤750℃), the controller generates a switching command.

[0059] 3. Water slow cooling stage control: According to the switching command, the controller can first gradually reduce or shut down the cooling gas supply, then start the cooling water circulation unit to start spray water cooling, and continue to monitor the temperature.

[0060] 4. Process termination control: During the spray water cooling process, when the temperature measuring device detects that the temperature of the smelting slag drops to or below the termination temperature threshold (e.g., ≤80℃), the controller generates a stop command, shuts down the cooling water circulation unit, and ends the cooling process.

[0061] Through the specific temperature threshold settings and phased control logic described above, the control system achieves safe, automatic, and precise control of the pre-air cooling and subsequent water cooling process, effectively preventing risks that may arise from the high-temperature slag encountering water, and optimizing the energy recovery process. Those skilled in the art can select appropriate threshold values ​​within the stated range based on actual process requirements and equipment characteristics.

[0062] In one specific embodiment of the present invention, the specific structure and connection method of the cooling gas supply unit are described. The cooling gas supply unit mainly consists of a cooling gas source, an air compressor, a buffer tank, and an air supply duct.

[0063] The cooling gas source provides the initial cooling medium, which is air or nitrogen. The air compressor's inlet is connected to the cooling gas source via a pipe. The air compressor compresses the intake cooling gas to a preset pressure required for system operation. This preset pressure can be set according to the system resistance and the required cooling intensity, for example, between 0.8 MPa and 1.2 MPa. The compressed high-pressure gas is discharged from the air compressor's outlet.

[0064] The inlet of the buffer tank is connected to the outlet of the air compressor via a high-pressure pipeline. The volume of the buffer tank is designed according to the air compressor's discharge capacity and the system's allowable pressure fluctuation range. Its interior may be hollow or equipped with a flow stabilizing element. The main function of the buffer tank is to store a certain amount of compressed gas and, utilizing its gas volume buffering characteristics, eliminate pressure pulsations caused by the periodic discharge of the air compressor, thereby providing the subsequent system with relatively stable pressure and flow rate of cooling gas.

[0065] The inlet end of the air supply duct is connected to the outlet end of the buffer tank. The outlet end of the air supply duct is divided into one or more branches, which are respectively connected to the air inlet on the upper side wall of the slag tank or a dedicated air inlet on the water-cooled wall cover. A flow regulating valve and a pressure gauge can be installed on the air supply duct to monitor and regulate the gas conditions supplied to the slag tank.

[0066] During operation, the cooling gas supply unit operates according to the following process: the gas from the cooling gas source is drawn in by the air compressor and compressed to a preset pressure; the compressed gas enters the buffer tank for pressure stabilization and flow equalization; then, the gas with stable pressure is transported through the air supply pipe to the space above the smelting slag in the slag tank to complete forced air cooling heat exchange.

[0067] By configuring the air compressor and the buffer tank, the cooling gas supply unit can provide a continuous, stable, and pressure-controllable supply of cooling gas for the entire air-cooling process. This is a crucial foundation for ensuring the efficient, safe, and stable operation of the system. Those skilled in the art can select and design the power, discharge capacity of the air compressor, and the volume of the buffer tank based on the system scale and gas consumption.

[0068] In one specific embodiment of the present invention, the spraying device includes an annular main pipe and a plurality of atomizing nozzles.

[0069] The annular header is made of corrosion-resistant metal tubing (such as stainless steel) and is shaped like a closed ring. This annular header is fixed to the lower surface of the water-cooled wall cover by multiple brackets or clamps. The diameter of the annular header can be selected according to the required total water spray volume; for example, the outer diameter can be between 50mm and 100mm. This arrangement achieves the following beneficial effects: First, it physically isolates the direct contact between the sprayed water mist and the multi-chamber coil heat exchanger, avoiding thermal shock to the high-temperature coil caused by the low-temperature water mist and protecting the core heat exchange equipment. Second, it ensures that the water mist sprayed from all sides can evenly and without dead angles cover the central slag area surrounded by the coil heat exchanger, achieving uniform cooling of the slag surface. Third, it allows the sprayed water to vaporize in the central area, and the steam can fully mix with the hot air before flowing through the coil area, reducing disturbance to the radiative and convective heat exchange environment of the coil.

[0070] The number of atomizing nozzles is multiple, for example, 8 to 16. These atomizing nozzles are installed at equal intervals at the lower part of the annular main tube or on the side facing the center of the slag pot via threaded or flanged connections. The spray axis of each atomizing nozzle is preferably set vertically downward or slightly inclined towards the center of the annulus, and its atomization angle can be selected between 60° and 120° to ensure that the sprayed water mist can cover the surface of the smelting slag in the area surrounded by the multi-chamber coil heat exchanger.

[0071] The annular header is provided with one or more water inlet ports, which pass through the water-cooled wall cover or extend from its side and are connected to the outlet of the circulating pump in the cooling water circulation unit via pipes.

[0072] During operation, cooling water from the cooling water circulation unit is pressurized by the circulation pump and then transported to the annular header, where it is distributed to each atomizing nozzle. After passing through the atomizing nozzle, the pressurized water is atomized into fine droplets and sprayed onto the surface of the pre-cooled smelting slag below, achieving efficient and uniform spray cooling.

[0073] This annular header combined with circumferentially distributed atomizing nozzles ensures that cooling water can act on the slag surface in a manner that covers a large area and is evenly distributed, improving cooling efficiency and uniformity. Simultaneously, its circumferential arrangement avoids interference with the working space of the multi-chamber coil heat exchanger. Those skilled in the art can specifically select and set the diameter of the annular header, the number and type of atomizing nozzles, and the installation angle according to the diameter of the slag pot and the required spray intensity.

[0074] In one specific embodiment of the present invention, the slag tank is equipped with an outer wall heat exchanger 10, a base heat exchanger 11, and a closed-chamber vibrator.

[0075] The external wall heat exchanger is installed on the outer wall of the slag tank. Specifically, it adopts a plate or finned tube structure, and its heat exchange surface is tightly attached to the outer wall surface of the slag tank by welding or fasteners to maximize the conduction of heat from the tank wall. The external wall heat exchanger has an independent medium flow channel inside, and its inlet and outlet are connected to an external waste heat utilization system, such as a low-temperature hot water circulation network or a raw material preheating system, through pipelines. The working medium (such as water or heat transfer oil) circulates in the flow channel, absorbing the heat lost from the tank wall.

[0076] The base heat exchanger is installed on the bottom outer surface of the slag pot. Its structure can be either coiled or flat, and it is also installed in close contact with the bottom outer surface of the slag pot. The base heat exchanger also has independent inlet and outlet, and is connected via pipes to the external waste heat recovery system or another independent heat-using unit to recover heat lost from the bottom of the slag pot.

[0077] The closed-chamber vibrator is installed on the outer wall of the slag pot, typically located in the lower-middle part of the pot. There can be one or more vibrators arranged symmetrically around the circumference. Each vibrator includes a vibrating motor and a connecting base, which is fixedly connected to the outer wall of the slag pot by high-strength bolts. An eccentric block is mounted on the shaft of the vibrating motor, generating a periodic high-frequency excitation force when it is energized and rotates. The vibrator operates intermittently during the air-cooling and / or water-cooling stages, with each run lasting 1-3 minutes and an interval of 5-15 minutes, at a vibration frequency of 15-30Hz, to prevent the slag from adhering to the pot wall and to promote uniform cooling. Its start and stop are automatically controlled by the control system according to the cooling stage and a preset program.

[0078] The excitation force is transmitted through the slag pot wall to the smelting slag inside, causing the slag body to vibrate slightly. This vibration effectively overcomes the adhesion and friction between the slag particles and between the slag and the slag pot wall, preventing the smelting slag from sticking to the pot wall during cooling and promoting uniform distribution and compaction of the slag within the slag pot. This facilitates uniform cooling and smooth discharge of the cooled slag. The operation of the closed-chamber vibrator can be controlled intermittently or continuously by the control system, and its start-up timing and running time can be set according to the cooling process stage.

[0079] By incorporating the external wall heat exchanger, base heat exchanger, and closed-chamber vibrator, comprehensive recovery of waste heat dissipated from the slag pot is achieved, effectively solving the engineering challenge of slag adhesion and further improving the overall system's heat recovery efficiency and operational reliability. Those skilled in the art can design specific structural forms and areas of the heat exchangers, as well as the number, installation location, and vibration parameters of the closed-chamber vibrators, based on the size and shape of the slag pot.

[0080] This invention provides a method for utilizing waste heat from non-ferrous metal smelting slag, which employs the aforementioned system. The method includes the following steps performed sequentially: S1, Air-cooled stage: Molten slag at approximately 1100°C is injected into the slag pot. Subsequently, the cooling gas supply unit is activated. Specifically, the air compressor is turned on, compressing the cooling gas (e.g., air or nitrogen) to 0.8MPa-1.2MPa. After pressure stabilization in a buffer tank, the gas is supplied into the slag pot through a dedicated air inlet on the upper side wall or water-cooled wall cover via an air supply duct. This allows the gas to flow above the slag, resulting in forced convection heat exchange. During this stage, the temperature of the high-temperature slag begins to decrease from its initial temperature of approximately 1100°C. Simultaneously, the working fluid (water) in the external steam drum circulation system circulates in the circulating water channels of the water-cooled wall cover and the multi-chamber coil heat exchanger, continuously absorbing heat transferred by radiation and convection. Part of the working fluid vaporizes, achieving preliminary recovery of waste heat. The heated air rises, enters the air duct through the ventilation holes on the water-cooled wall cover, and is discharged through the hot air output pipe. The cooling rate of the entire air cooling stage is controlled by adjusting the flow rate and temperature of the cooling gas to ensure coordination with the subsequent water slow cooling stage. The total time for cooling the smelting slag from about 1100℃ to 50℃-100℃ is controlled within a predetermined range (e.g., about 4 days), meeting the requirements of the slow cooling process for slag crystal structure.

[0081] S2. Temperature Monitoring and Judgment: During the air-cooling stage, the surface temperature of the smelting slag is monitored in real time by a temperature measuring device installed inside the slag pot. The control system continuously receives temperature signals and compares them with a preset safe temperature threshold (set within the range of 700℃-850℃). When the monitored surface temperature of the smelting slag drops to or below this safe temperature threshold, it is determined that the air-cooling stage is basically complete, and the smelting slag has been cooled to a state where it can be safely cooled by spray water. Subsequently, the control system issues a command to prepare for the next stage.

[0082] S3, Water Slow Cooling Stage: The control system activates the cooling water circulation unit and precisely controls the spray water flow rate based on the slag temperature. The circulation pump delivers cooling water from the storage tank to the spraying device, which atomizes the water and sprays it evenly onto the slag surface, where the temperature is still above 700°C. Upon contact with the slag, the spray water rapidly absorbs heat, partially vaporizing and partially forming a liquid water film or droplets, achieving controlled slow cooling. This process absorbs a large amount of sensible heat and latent heat of vaporization from the slag, achieving continuous cooling. The generated water vapor mixes with the hot air inside the tank, forming a high-temperature, high-humidity gas. During this stage, the water-cooled wall cover and the multi-cavity coil heat exchanger operate simultaneously, continuing to recover radiant heat and convective heat from the space. Under the negative pressure of the system, the high-temperature, high-humidity gas enters the air duct through the ventilation holes on the water-cooled wall cover and proceeds to the subsequent processing steps.

[0083] S4. Termination and Follow-up Processing: During the water-cooling phase, the temperature of the smelting slag continues to be monitored in real time using a temperature measuring device. The control system compares the monitored temperature with a preset termination temperature threshold (set within the range of 50℃-100℃). When the smelting slag temperature drops to or below this termination temperature threshold, the water-cooling phase is considered complete. Subsequently, the control system issues a command to stop the cooling water circulation unit (i.e., shut down the circulation pump), ending the spray water cooling. At this point, the smelting slag has completed the waste heat recovery and main cooling process and can be used for subsequent transfer, slow cooling, or ore beneficiation operations.

[0084] Furthermore, during the air-cooling stage (S1), the hot air discharged from the air duct can be introduced into subsequent waste heat recovery equipment. For example, the hot air can be passed sequentially through a pressure regulating valve and at least one indirect heat exchanger to heat the demineralized water, producing hot water for use in the plant area, thus realizing the cascade utilization of thermal energy.

[0085] In the air-cooling stage (S1) and the water-cooling stage (S3), the saturated steam generated by the water-cooled wall cover and the multi-cavity coil heat exchanger is transported to the steam drum for steam-water separation. The separated steam can be used for power generation, heating, or driving heat pumps, depending on the needs of the plant area.

[0086] This method, through the aforementioned phased and controlled cooling process, maximizes the recovery of sensible and latent heat released during the cooling of non-ferrous metal smelting slag from a high-temperature molten state to a medium-low temperature state, while ensuring safety, thus achieving efficient energy utilization.

[0087] In one specific embodiment of the present invention, during the air-cooling stage described in step S1, the cooling gas fed into the slag tank is compressed air or nitrogen. When air is selected, its source is ambient air; when nitrogen is selected, its source is the plant's nitrogen generation unit or liquid nitrogen vaporization system. Using nitrogen provides an inert atmosphere in the process, further reducing the risk of oxidation or explosion.

[0088] The operating pressure of the cooling gas is maintained within the range of 0.8 MPa to 1.2 MPa. This pressure range is achieved by adjusting the output of the air compressor in the cooling gas supply unit or by using a pressure regulating valve after the buffer tank. The control system can set a target pressure value, such as 1.0 MPa, and uses pressure sensor feedback for closed-loop control to maintain stable air supply pressure. Specifically, the cooling gas supply unit is equipped with a pressure reducing valve or throttling device on the air supply pipeline to reduce the pressure of the 0.8 MPa-1.2 MPa high-pressure gas output from the air compressor to an appropriate pressure before sending it into the slag tank. By adjusting the balance between the air supply flow rate and the exhaust pressure, the system maintains a slight positive pressure inside the tank within the range of 0.5 kPa to 2.0 kPa.

[0089] One of the core purposes of maintaining this pressure range is to ensure that the interior of the slag pot remains under a slightly positive pressure throughout the air-cooling process. Specifically, this means that the pressure inside the slag pot and its connected air ducts is slightly higher than the atmospheric pressure of the external environment. This pressure difference is typically controlled between 0.5 kPa and 2.0 kPa.

[0090] The micro-positive pressure state is achieved and maintained by continuously supplying pressurized cooling gas into the slag tank at a certain flow rate, serving as a make-up gas source; while the gas inside the tank is discharged through the air duct and hot air output pipe, forming an exhaust passage. By precisely controlling the gas supply pressure and flow rate to be slightly greater than the exhaust system's pumping capacity under corresponding operating conditions, a stable micro-positive pressure can be established and maintained within the system.

[0091] Maintaining a slightly positive pressure state has the following beneficial effects: First, it can effectively prevent cold air from the external environment from being drawn into the system through gaps in the slag tank or pipes, avoiding interference with the established temperature field and airflow organization inside the tank, and ensuring the stability of heat exchange efficiency; Second, it helps to suppress instantaneous negative pressure inside the tank that may be caused by unexpected situations (such as sudden temperature changes), improving the safety of system operation; Third, it provides power for positive pressure exhaust, ensuring that hot air can be smoothly guided to subsequent waste heat recovery equipment.

[0092] Those skilled in the art can select a specific operating pressure value within the pressure range based on the sealing performance of the slag pot, the resistance characteristics of the system pipeline, and the required cooling intensity, and achieve precise and stable pressure control through the PID regulation function of the control system.

[0093] In one specific embodiment of the present invention, the specific utilization path of the recovered products in the method includes the utilization of saturated steam and the cascade recovery of waste heat from hot air.

[0094] In the air-cooling stage (S1) and the water-cooling stage (S3), the working fluid generated by recovering waste heat in the circulating water channel of the water-cooled wall cover and the multi-cavity coil heat exchanger is saturated steam. Specifically, feedwater from the external steam drum circulation system absorbs heat in the aforementioned heat exchange equipment and partially vaporizes to form a steam-water mixture. This steam-water mixture is then transported to a steam drum through pipelines.

[0095] Inside the steam drum, gravity and built-in steam-water separation devices (such as cyclone separators and steam equalization orifice plates) are used to separate the steam-water mixture. The separated saturated steam accumulates in the upper space of the steam drum, while the separated water is located in the lower part of the steam drum. The water in the lower part of the steam drum is then returned to the water-cooled wall cover and the multi-chamber coil heat exchanger through downcomers and a circulating pump to complete the circulation.

[0096] The saturated steam drawn from the steam drum is distributed to different utilization pathways through the main steam pipeline, including but not limited to at least one of the following: 1. Power generation: Saturated steam is introduced into a medium-low temperature waste heat power generation system to drive a steam turbine or screw expander to do work, which in turn drives a generator to generate electricity.

[0097] 2. Heating: Saturated steam is connected to the steam heating network in the plant area and used directly for heating, heat preservation or domestic heating in the production process.

[0098] 3. Driving a heat pump: A portion of the saturated steam serves as the driving heat source, entering a high-temperature heat pump unit. This heat pump unit consumes a small amount of electricity to upgrade the quality of the steam or a portion of its heat, producing higher-temperature steam or hot water for specific processes or for further power generation.

[0099] During the air-cooling stage (S1), the hot air discharged from the air duct enters the subsequent waste heat deep recovery system via the hot air output pipe.

[0100] First, hot air flows through a pressure regulating valve. This valve automatically adjusts its opening based on a set positive pressure value (e.g., 0.5 kPa-2.0 kPa above ambient pressure) to stabilize the operating pressure in the first half of the system.

[0101] Then, the pressurized hot air enters at least one indirect heat exchanger for cooling and waste heat recovery. In a specific two-stage recovery scheme: First-stage heat exchange: Hot air enters the shell side (or tube side) of the first indirect heat exchanger. Simultaneously, demineralized water at a temperature of 20℃-30℃ is pumped into the tube side (or shell side) of the same heat exchanger. Heat exchange occurs between the two through the indirect heat exchanger, heating the demineralized water to 80℃-90℃, and then it is transported to the plant's deaerator as a preheating source for boiler feedwater.

[0102] Second-stage heat exchange: The cooled hot air discharged from the first wall-mounted heat exchanger enters the second wall-mounted heat exchanger. At room temperature demineralized water (20℃-30℃) is also pumped into this heat exchanger. After another heat exchange, the demineralized water is heated to 50℃-70℃, and the resulting hot water is directly connected to the plant's low-pressure hot water network for production and domestic washing purposes.

[0103] After undergoing multiple heat exchange stages, the hot air exhaust gas, which has been cooled to near ambient temperature, is extracted by an exhaust fan located at the end of the system. It can then be piped into an existing water storage tank for water bath de-whitening treatment before being discharged.

[0104] Through the above specific implementation methods, the efficient, classified, and tiered utilization of saturated steam and hot air, two waste heat carriers generated during the smelting slag cooling process, is achieved, maximizing the overall energy utilization efficiency and economy of the entire system. Those skilled in the art can optimize the specific allocation ratio of steam and hot water, as well as the number of stages of the indirect heat exchanger, according to the actual energy demand structure of the plant.

[0105] This invention achieves complete vaporization of the spray water by precisely controlling the water-to-air ratio during the spray cooling stage, and utilizes the system's hot air handling process (wall heat exchange + whitening) to efficiently recover the water vapor and its carried energy. This design not only simplifies the slag tank structure (eliminating the need for complex high-temperature resistant drain valves and pipelines), fundamentally avoiding the risk of high-temperature molten slag leakage or drain blockage, but also achieves complete dual recovery of water and heat, demonstrating the system's high integration and safety.

[0106] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. Those skilled in the art can make modifications and variations to the current embodiments without departing from the scope and spirit of the invention, and all such modifications and variations fall within the scope defined by the invention.

Claims

1. A system for utilizing waste heat from non-ferrous metal smelting slag, characterized in that, include: Slag pots are used to hold smelting slag. The composite heat exchange top cover unit includes: A water-cooled wall cover is sealed at the top opening of the slag tank. The water-cooled wall cover is a pressure-bearing cover plate with an internal circulating water channel. The inlet and outlet of the circulating water channel are used to connect to the external steam drum circulation system. The air duct is sealed at its lower end to the central area of ​​the upper surface of the water-cooled wall cover and passes through the water-cooled wall cover to communicate with the internal space of the slag tank. Its upper end is connected to a hot air output pipe. The air duct is cylindrical or inverted funnel-shaped. A multi-cavity coil heat exchanger includes a sleeve fitted inside the air duct, a first coil heat unit disposed in an annular cavity between the sleeve and the air duct, and a second coil unit disposed inside the sleeve. The working fluid inlet and outlet of the multi-cavity coil heat exchanger pass through the air duct and are used to connect to an external steam drum circulation system. A spray device is installed on the lower surface of the water-cooled wall cover and connected to the cooling water circulation unit via a pipe. The cooling water circulation unit includes a water storage tank and a circulation pump. A cooling gas supply unit includes a cooling gas source and an air supply duct. The air outlet of the air supply duct is connected to the upper part of the side wall of the slag pot or a dedicated air inlet on the water-cooled wall cover, for delivering cooling gas to the space above the smelting slag inside the slag pot. The control system is used to first start the cooling gas supply unit to air-cool the smelting slag; after the surface temperature of the smelting slag drops to a safe threshold, it then controls the cooling water circulation unit to start, so that the spraying device sprays cooling water onto the surface of the smelting slag for spray water cooling; during the air cooling and spray water cooling processes, the working fluid in the external steam drum circulation system is controlled to circulate in the circulating water channel of the water-cooled wall cover and the multi-cavity coil heat exchanger to recover waste heat.

2. The system for utilizing waste heat from non-ferrous metal smelting slag according to claim 1, characterized in that, Both the first coil heating unit and the second coil heating unit are spiral coils, with their axes arranged perpendicular to the plane of the water-cooled wall cover.

3. The system for utilizing waste heat from non-ferrous metal smelting slag according to claim 1, characterized in that, The hot air output pipe is sequentially connected to a pressure regulating valve and at least one indirect heat exchanger.

4. The system for utilizing waste heat from non-ferrous metal smelting slag according to claim 1, characterized in that, The preset safety threshold in the control system is 700℃-850℃; and the control system monitors the temperature of the smelting slag in real time during the spray water cooling stage, and controls the cooling water circulation unit to stop operating when the temperature drops to 50℃-100℃.

5. The system for utilizing waste heat from non-ferrous metal smelting slag according to claim 1, characterized in that, The cooling gas supply unit also includes an air compressor and a buffer tank; the air compressor is used to compress the cooling gas to a preset pressure, and the buffer tank is connected between the air compressor and the air supply pipe to stabilize the pressure and flow rate of the cooling gas.

6. The system for utilizing waste heat from non-ferrous metal smelting slag according to claim 1, characterized in that, The spraying device includes an annular main pipe and multiple atomizing nozzles; the annular main pipe is fixedly installed on the lower surface of the water-cooled wall cover, and the multiple atomizing nozzles are evenly distributed along the circumference of the annular main pipe.

7. The system for utilizing waste heat from non-ferrous metal smelting slag according to claim 1, characterized in that, An external wall heat exchanger is installed on the outer wall of the slag pot, and a base heat exchanger is installed at the bottom of the slag pot; the external wall heat exchanger and the base heat exchanger are respectively connected to an external waste heat utilization system through pipes; a closed-chamber vibrator is installed on the outer wall of the slag pot.

8. A method for utilizing waste heat from non-ferrous metal smelting slag, characterized in that, The system according to any one of claims 1-7 includes the following steps: S1, Air-cooling stage: After the high-temperature molten slag is injected into the slag pot, cooling gas is sent into the slag pot through the cooling gas supply unit to force air cooling of the slag. At the same time, waste heat is recovered through the circulating water channel of the water-cooled wall cover and the multi-cavity coil heat exchanger. S2. Temperature monitoring and judgment: Monitor the surface temperature of the smelting slag in real time. When it drops to the safe threshold of 700℃-850℃, proceed to step S3. S3, Water Slow Cooling Stage: Start the cooling water circulation unit and spray cooling water onto the surface of the smelting slag through the spray device for spray water cooling. At the same time, continue to recover waste heat through the water-cooled wall cover and multi-cavity coil heat exchanger. S4. Termination and subsequent treatment: When the temperature of the smelting slag drops to 50℃-100℃, stop spraying cooling water to complete the waste heat recovery and slag cooling.

9. The method for utilizing waste heat from non-ferrous metal smelting slag according to claim 8, characterized in that, In step S1, the cooling gas introduced is compressed air or nitrogen, and the pressure is maintained at 0.8-1.2 MPa to maintain a slightly positive pressure state inside the slag pot.

10. The method for utilizing waste heat from non-ferrous metal smelting slag according to claim 8, characterized in that, In steps S1 and S3, the working fluid generated by recovering waste heat is saturated steam. The saturated steam is transported to a steam drum for steam-water separation. The separated steam is used for at least one of the following purposes: power generation, heating, or driving a heat pump. In step S1, the hot air discharged from the duct passes through pressure regulation and at least one stage of indirect heat exchange in sequence to heat the demineralized water to produce hot water, thus making cascade utilization of the waste heat of the hot air.

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