A copper smelting slag heat preservation and slow cooling ladle and a slow cooling method for improving copper recovery rate

Abstract

This application belongs to the field of resource utilization and efficient recycling technology of solid waste in non-ferrous metallurgy, and more specifically, relates to a copper smelting slag heat-insulating and slow-cooling slag bag and a slow-cooling method for improving copper recovery rate. The heat-insulating and slow-cooling slag bag of this invention is a cast ladle, which is an integral cast structure. The casting of the slag bag has a dispersed porous structure generated during the casting process. This porous structure helps to reduce the thermal conductivity of the slag bag, thereby facilitating heat insulation and slow cooling after slag collection. During slow cooling, it can effectively prolong the high-temperature liquid phase maintenance time of the copper smelting slag, reduce or even remelt the instantaneous solidified shell layer generated at the ladle wall, and reduce copper loss caused by the thick instantaneous solidified shell layer on the ladle wall. The heat-insulating and slow-cooling cast ladle and slow-cooling method proposed in this invention can significantly improve copper phase particle size and mineral processing recovery rate, and has good economic and environmental benefits.

Description

Technical Field

[0001] This application belongs to the field of resource utilization and efficient recycling technology of solid waste in non-ferrous metals metallurgy, and more specifically, relates to a copper smelting slag heat preservation and slow cooling slag bag and slow cooling method to improve copper recovery rate. Background Technology

[0002] In the copper smelting process, high-temperature copper smelting slag (temperature of about 1200-1400℃) generated by smelting furnace or blowing furnace is continuously discharged from the furnace. The copper grade in the slag is usually higher than that of the copper ore entering the beneficiation process. Therefore, it is necessary to achieve safe and efficient recovery of copper from copper smelting slag.

[0003] The currently widely used traditional processing technology is: using 12m 3 Slag ladles of molten slag and below are collected at the furnace front to receive high-temperature molten slag, and then transported to the slag yard. If there are no limitations on the space and the number of slag ladles, they can be directly subjected to slow cooling in the ladle for several days to allow the copper particles to grow as large as possible. However, this method has a very low slag ladle turnover efficiency, occupies a large area, and the tailings slag has a very high copper content. Therefore, in order to improve efficiency and shorten the production cycle, the more common practice is to transport the slag ladles that have received high-temperature molten slag to the slag yard and subject them to natural slow cooling for about 72 hours, followed by in-ladle water cooling. Generally, after 8-24 hours of natural slow cooling, water is added to the slag ladle for in-ladle water cooling, which takes about 72 hours in total. After the slag has completely solidified, it is then transported to the slag dump for slag dumping, mechanical crushing and screening, multi-stage grinding, and flotation operations, ultimately realizing the recovery and utilization of matte or metallic copper contained in the copper slag.

[0004] The existing high-temperature copper smelting slag slow cooling devices have the following prominent problems: (1) The slag bales are occupied for a long time, the slow cooling cycle is long, the equipment turnover rate is low, and a large number of slag bales and a large area of ​​slow cooling space are required; (2) 12m 3 Thick, dense, instantaneous solidified shells are easily formed on the walls and openings of the slag bag. The copper particles in this part are small and cannot be recovered by flotation. (3) At present, the copper content in the tailings after flotation is as high as 0.25% (25% copper concentrate grade), and the copper recovery rate in copper smelting slag needs to be improved. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a copper smelting slag heat preservation and slow cooling slag bag and slow cooling method to improve copper recovery rate. It aims to solve the technical problem that insufficient copper particle growth during the slow cooling process of the slag bag used in the prior art for slow cooling of copper smelting slag leads to high copper loss in tailings and low copper recovery rate.

[0006] To achieve the above objectives, in a first aspect, this application provides a copper smelting slag heat-insulating and slow-cooling slag bag for improving copper recovery rate. The slag bag is a casting bag, and the casting bag is an integral casting structure.

[0007] During the casting process of the slag ladle, by setting external chills in the conical areas of the inner and outer walls of the slag ladle and using an inverted pouring method, i.e., bottom up and slag ladle opening down, the slag ladle casting has a diffusely distributed porous structure inside. This porous structure helps to reduce the thermal conductivity of the slag ladle, which in turn helps to keep it warm and cool it slowly after receiving the slag, thereby promoting the growth of copper particles in the molten copper smelting slag.

[0008] Preferably, the volume of the casting ladle is 12-30m³. 3 Further preferred is 18-30m 3 More preferably 20-26 m 3 .

[0009] Preferably, the casting ladle is made of low-carbon, high-strength, heat-resistant cast steel.

[0010] Preferably, the specific composition of the low-carbon, high-strength, heat-resistant cast steel material, by mass percentage, includes: C: 0.15~0.2%, Si: 0.40~0.80%, Mn: 0.60~1.20%, Cr: 0.9~1.5%, Ni: 0.8~1.75%, Mo: 0.3~0.5%, S ≤0.015%, P ≤0.015%, RE: 0.001-0.1%, with the balance being Fe and unavoidable impurities.

[0011] Preferably, the slag bag includes a slag bag body and a trunnion, with a circular opening and a sluice gate at the top, and lifting lugs at both ends of the upper part;

[0012] The wall thickness of the slag bag is gradually varied within the range of 90~150mm according to the size of the slag bag. A rounded transition with a radius of 30-80mm is set at the connection between the side wall and the bottom plate to reduce the concentration of thermal stress.

[0013] The outer wall is equipped with ring-shaped reinforcing ribs with a spacing of 600~800mm and a height of 50~80mm to enhance the overall structural rigidity and resistance to thermal deformation.

[0014] Preferably, the casting process of this casting ladle adopts an inverted pouring method, that is, the bottom is on top and the slag ladle opening is at the bottom, and the initial solidification temperature of the casting is controlled at 1480-1540℃ during the pouring process.

[0015] Preferably, the pore structure is dispersed in the middle part of the slag pack wall thickness direction, and the distribution thickness is further preferably 20-40 mm; the size of the dispersed pore structure is <0.1 mm.

[0016] Preferably, the top of the slag bag is provided with a movable heat-insulating cover.

[0017] More preferably, the thickness of the insulation cover is 200-500mm, and the insulation cover is a composite insulation cover, which includes: a heat-resistant steel frame and an insulation material with a heat-reflective coating on the surface.

[0018] According to another aspect of the present invention, a method for slow cooling using the aforementioned heat-insulating and slow-cooling slag bag is provided, comprising the following steps: using the aforementioned heat-insulating and slow-cooling slag bag to collect molten copper smelting slag with a slag discharge temperature of 1200-1400℃, covering the slag bag with a heat-insulating cover after collection, and slowly cooling it inside the heat-insulating and slow-cooling slag bag, so that copper particles in the molten copper smelting slag agglomerate and grow.

[0019] This invention aims to overcome the problems of insufficient copper particle growth, equipment dispersion, and short lifespan in existing slow-cooling slag bags for copper smelting, and provides an integral slow-cooling slag bag for cast copper slag with heat preservation and slow cooling effects, as well as its slow cooling method. By optimizing the slag bag structure design, the residence time in the high-temperature liquid zone is significantly extended, promoting sufficient crystallization and coarsening of copper particles, reducing the copper content in tailings, and improving copper recovery rate. Simultaneously, it reduces the number of equipment and floor space required, and extends service life. Overall, compared with existing technologies, the above-described technical solution has the following beneficial effects:

[0020] (1) The copper smelting slag heat preservation and slow cooling slag bag provided by the present invention is a casting bag with an integral casting structure. The casting of the slag bag wall has a fine pore structure dispersed inside. Compared with the welded bag (also known as the structural bag), it has a smaller thermal conductivity. When the slag is slow cooled, it can effectively prolong the high temperature liquid phase maintenance time of the copper smelting slag, so that the copper particles have enough time to complete the physical evolution process of "segregation → aggregation and growth → sedimentation". Moreover, at the end of the slow cooling, more than 90% of the copper smelting slag is still in the liquid phase state, which provides conditions for the subsequent direct air quenching and granulation of copper smelting slag. Compared with the traditional 72-hour slow cooling cycle, the bag processing time is shortened by more than 60 hours, which greatly improves the slag bag turnover rate and production efficiency.

[0021] (2) In the preferred embodiment, a large-capacity casting ladle (18-30m) is used. 3 The casting process employs an inverted pouring method, with an initial solidification temperature of 1480-1540℃. During casting, external chills are installed on the conical surfaces of the inner and outer walls of the casting ladle. This allows for the formation of a fine, dispersed pore structure in the middle of the ladle wall thickness. This pore structure distribution has been shown to effectively prolong the high-temperature (above 1205℃) liquid phase maintenance time of copper smelting slag and promote the rapid enrichment and growth of copper-containing particles in the smelting slag.

[0022] (3) This invention optimizes the slag bag design and improves cooling uniformity: Through simulation, it was found that compared to 12 m 3 Slag bags, 24 m 3The casting process is more conducive to the formation of a loosely distributed microporous structure, which in turn facilitates the formation of a "heat-insulating layer" with low thermal conductivity and small specific surface area, effectively slowing down the heat dissipation rate; at the same time, it avoids the 12 m 3 The problem of a thick instantaneous solidified shell easily forming on the slag bag wall is addressed by remelting the instantaneous solidified shell layer during the slag receiving process, which is conducive to the uniform distribution of internal heat and the continuous settling, aggregation, and growth of copper particles.

[0023] (4) The novel casting bag provided by this invention can promote the full growth of copper phase particles, thereby improving the copper recovery rate of flotation and reducing the copper content in tailings: the large-capacity slag bag has a large heat capacity and slow heat dissipation, which significantly enhances macroscopic segregation and Stokes settling effect, and promotes the migration, collision and coarsening of fine copper-containing droplets. This method can significantly increase the average particle size of copper particles, reduce the residual copper content in slag tailings by more than 20%, and significantly improve the copper resource recovery rate. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the pore distribution in casting ladles and welded ladles;

[0025] Figure 2 It is 12m 3 Casting package and 12m 3 Simulation results of solidification color temperature of weldment;

[0026] Figure 3 This is a schematic diagram of the overall casting structure of the casting package according to an embodiment of this application;

[0027] Figure 4 This is a comparison diagram of the distribution of internal pore structure in castings under different casting conditions;

[0028] Figure 5 This is a diagram showing the porosity distribution within a 24 m³ casting ladle at different initial solidification temperatures.

[0029] Figure 6 Analysis of the thickness, volume, and copper weight at the solidification crust for different slag bag types;

[0030] Figure 7 The thickness and variation of the solidified shell at the end of different slag filling types (red indicates the solidified shell part).

[0031] Figure 8 This is a sampling plan diagram of an embodiment of the present application for on-site sampling of slag samples from a copper enterprise's slag bag;

[0032] Figure 9 It is a comparison of the instantaneous solidified shell thickness of the foundry ladle wall and the welded ladle wall after 1000s of solidification following slag collection.

[0033] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0034] A-Foundry ladle; 1-Spherical slag ladle; 2-Conical slag ladle; 3-External chill; 4-Gating and riser system; 5-Lifting lug assembly. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0036] The slow cooling and heat preservation of high-temperature copper smelting slag (1200-1400℃) is a core step in promoting the crystallization and growth of copper particles and achieving efficient copper recovery. Slag ladles used for slow cooling and heat preservation of high-temperature copper smelting slag are typically of two types: welded ladles and cast ladles. The steel outer shell of a welded ladle is obtained through welding (joining together cut and shaped steel plates); the steel structure of a cast ladle is obtained through casting (pouring molten steel into a mold).

[0037] In actual industrial production, given that the rolled steel plates used in welded ladles have better toughness and strength stability than most castings, and considering that casting defects such as shrinkage cavities, porosity, sand holes, and gas holes are easily generated during the casting process, welded ladles are generally preferred for receiving and slowly cooling high-temperature copper smelting slag. Even when some smelters use casting ladles for receiving and slowly cooling slag, considering that shrinkage cavities and porosity defects are inevitably generated during the casting process, the industry usually adjusts process parameters or sets internal / external chills to concentrate these defects as much as possible in the riser and gating area.

[0038] However, unlike traditional design approaches, this invention proposes a copper smelting slag heat preservation and slow cooling slag bag that improves copper recovery rate. The slag bag is a cast slag bag with an integral casting structure. The casting of the slag bag has a diffusely distributed pore structure generated during the casting process. This pore structure helps to reduce the thermal conductivity of the slag bag, thereby facilitating heat preservation and slow cooling after slag collection, and promoting the growth of copper particles in the molten copper smelting slag.

[0039] It is speculated that the slag pockets formed by casting are not dense, which hinders heat dissipation. Furthermore, the greater the thickness of the slag pocket, the more likely the casting process will introduce a porous structure. In contrast, the welded ladle, made from forged steel, has a denser matrix, allowing for faster heat dissipation without obstruction. A schematic diagram of the porosity distribution in both casting and welded ladles is shown below. Figure 1 As shown. According to the formula for calculating effective thermal conductivity, , where k eff It is the effective thermal conductivity of the composite material, V f It is the volume fraction of pores or the second phase, k f It is the thermal conductivity of the pores or second phase, k. mIt is the thermal conductivity of the matrix material, while k f < <k m Therefore, the effective thermal conductivity, or thermal conductivity coefficient, of a cast ladle with a diffusely distributed pore structure in its wall is lower than that of a forged and welded ladle without pores.

[0040] This invention analyzes the slow cooling performance of copper smelting slag bales through a combination of actual field sampling and numerical simulation. The mathematical model employs commonly used filling and solidification mechanism models in this field for simulation analysis.

[0041] In some embodiments, a mathematical model of the fluid forming flow field and a discretization scheme are used to simulate the filling process. Calculations of the actual fluid are performed using the Eulerian equations to the Navier-Stokes equations. Discretization using the energy conservation equations (Navier-Stokes equations) and the continuity equations facilitates the solution. Heat transfer during the filling process is simulated through flow-heat coupling. The solidification process is simulated using a temperature field mathematical model and finite difference (Fourier's law and the differential equation of heat conduction). Finite difference is used for discrete calculations in both time and space during solidification.

[0042] In the following simulation examples, experiments and simulations were conducted on copper slag, and the results of 12m tests were examined and compared. 3 Foundry ladle, 12m 3 Welding package, 24m 3 The different performances of casting ladles in delaying heat dissipation, inhibiting the formation of solidified shells, and promoting the enrichment of copper-containing particles.

[0043] The initial input conditions for the simulation are as follows: the shape of the slag bag is set to a conical shape plus a spherical shape. The temperature is set to 1250℃ when the copper slag is poured into the slag bag (i.e., when receiving the slag), and the temperature of the slag bag during slag receiving is set to 25℃. The slag composition is input, and the solidus of the slag is set to 1057℃, and the liquidus is set to 1200℃. The ambient temperature is set to 20℃. The simulation includes a 12m³ welding bag and a 12m... 3 The calculation parameters for the casting ladle are obtained by inverse calculation of thermophysical properties after actual temperature measurement, 24m. 3 The calculation parameters for the casting ladle are based on a 12m diameter. 3 The casting ladle parameters were obtained by scaling up the scale. 24m 3 The casting ladle design incorporates external chills on the inner and outer conical surfaces of the ladle wall, an initial solidification temperature of 1500℃, and inverted pouring. Interface parameters (interfacial heat transfer coefficient, cal / cm²) are calculated. 2 s ℃): 12m 3 Foundry ladle, 12m 3The welding package is as follows: casting / air: 0.023000, casting / mold: 0.023000, air / mold: 0.023000; 24m 3 The casting package specifications are: casting / air: 0.023000, casting / mold: 0.01000, air / mold: 0.023000. 12m 3 The thickness of the casting ladle gradually changes from 90-135mm, 24m 3 The thickness of the casting ladle gradually changes from 120-145mm; the material of the casting ladle is low-carbon, high-strength, heat-resistant cast steel (C 0.20%, Si 0.60%, Mn 0.80%, Cr 1.0%, Ni 1.5%, Mo 0.4%, S 0.015%, P 0.01%, RE: 0.02%, balance Fe). The welding ladle is made of Q345R, with a wall thickness of 80mm and a bottom thickness of 100mm. The input slag composition is: SiO2 32wt%, FeO 10wt%, Fe2O3 40wt%, Cu 3wt%, S 0.5wt%, Al2O3 5wt%, CaO 5wt%, MgO 4.5wt%.

[0044] For 12m 3 Casting package and 12m 3 A simulation comparison of welding packages revealed that 12m 3 The air-cooled cooling rate of the casting ladle was mostly below 0.01℃ / s, which is consistent with the field measurement of 0.0016℃ / s (indicating the accuracy of the simulation results); the cooling rate of the parts in contact with air was much higher, reaching a maximum of 0.4℃ / s. A simulation comparison of 12m... 3 Casting and welding packages were found, 12m 3 The casting process involves a slower temperature drop in the filling mold and a longer solidification time (12m). 3 Foundry ladle: 172200s, 12m 3 Welding package: 114646s), with a thinner condensed shell layer on the package wall (12m). 3 Casting ladle: 3.57 mm, 12m 3 Welding ladle: 37.72 mm). Solidification time refers to the time required for copper smelting slag to fully solidify within the ladle. It is evident that casting ladles and welding ladles of the same volume exhibit significant differences in their performance during the slow cooling process. Figure 2 12m 3 Casting package and 12m 3 Simulation results of solidification color temperature of the welded ladle. The comparison of solidification color temperatures shows that the cast ladle requires a longer solidification time to match the structural color temperature of the welded ladle.

[0045] A chill is a metal object (usually made of cast iron, steel, copper, graphite, etc.) with strong cooling capacity placed inside the sand mold or casting during the casting process to control the solidification sequence of the casting. Its core function is to accelerate the solidification rate in local areas and, in conjunction with the adjustment of casting process parameters, to concentrate porosity defects mainly in the riser and gating areas, thereby eliminating porosity defects as much as possible. However, this invention, through simulation and experimental testing, has found that during the casting process, by specifically controlling one or more of the casting method, pouring temperature, slag ladle thickness, and the position of the external chill, a portion of the porosity structure can be retained and dispersed on the slag ladle wall. This is beneficial for the heat preservation and slow cooling of copper smelting slag, thereby improving the copper recovery rate. It is possible that these measures reduce the thermal conductivity of the slag ladle.

[0046] In some embodiments, the present invention specifically sets high thermal conductivity external chills in the conical regions of the inner and outer walls of the slag ladle mold. The external chills can be a single piece or multiple pieces joined together in the conical region. Because the solidification rate is fast in the area of ​​the ladle wall near the external chills, forming a fine-grained structure, while the central part of the ladle wall, relatively far from the external chills, solidifies more slowly, resulting in a coarse-grained structure in the middle, achieving a fine, dispersed porous structure with a pore size typically <0.1 mm. Compared to casting processes that use internal chills or only locally set external chills in the hot spot region, the external chill setting method of the present invention can accelerate the solidification of the slag ladle while retaining a portion of dispersed fine porous structure in the middle part of the ladle wall thickness direction, thereby reducing the thermal conductivity without reducing the strength of the slag ladle. In a preferred embodiment, by adjusting parameters such as the thickness, material, and distance of the external chills from the sand mold surface, a 20-40 mm thick coarse-grained structure and a fine, dispersed porous structure with a size <0.1 mm are formed in the middle part of the ladle wall thickness direction.

[0047] In some embodiments, the present invention employs, for example, the following methods during the production of casting ladles: Figure 3 The external chill setup shown refers to the installation of external chills on both the inner and outer conical surfaces of the slag pot. Specific parameters are as follows:

[0048] Material of external chill: rolled steel plate or graphite, etc. For example, ordinary carbon structural steel with a thermal conductivity ≥50W / (m·K).

[0049] External chill locations: A single complete external chill is installed on the conical surface of the outer wall of the slag bag, and another single complete external chill is installed on the conical surface of the inner wall, or multiple external chills are installed on the conical surface of the inner wall. Each external chill measures 150mm × 200mm × 50mm, with a gap of 20-30mm between the chills. The dimensions of the external chills can be adjusted according to actual needs.

[0050] Figure 3 Some preferred embodiments are shown, in which the present invention employs a 24m3 The integral casting structure of a cast steel slag ladle (i.e., a foundry ladle). The ladle includes the ladle body and trunnions, with a circular opening at the top and a chute. Lifting lugs are located at both ends of the upper part. The casting process is generally the same as that of existing foundry ladles, but differs in that, to disperse a fine, diffuse porosity in the middle of the ladle wall along its thickness, external chills are specifically installed at the inner and outer conical surfaces of the ladle wall. Figure 3 As shown, A-casting ladle; 1-spherical slag ladle; 2-conical slag ladle; 3-external chill; 4-gating and riser system; 5-lifting lug assembly.

[0051] In a preferred embodiment, different casting processes are simulated to examine whether an external chill is placed in the slag-filled conical region and to compare the distribution of porosity within the casting when different pouring methods are used. Figure 4 As shown, content (a) is inverted casting without external chills; content (b) is upright casting with external chills; content (c) is as follows... Figure 3 The conical region shown is equipped with an external chill and is cast in an inverted manner. The external chill is made of graphite.

[0052] It can be seen that, in content (a) without external chills, the internal pore structure of the casting is mainly concentrated in the riser area, and the pores are not dispersed; in content (b) although external chills are set in the upright pouring method, the pores are mainly distributed at the slag pot opening and bottom; only when external chills are set in the cone area of ​​the slag pot and the pouring is inverted (content (c)) are a large number of fine and dispersed pore structures generated on the slag pot wall (the red area in the figure indicates shrinkage cavities and porosity). The rolled and forged steel plates used in the welding ladle are non-porous. In the casting ladle, shrinkage cavities and porosity may exist in the casting slag pot. These shrinkage cavities and porosity will reduce the thermal conductivity of the slag pot, thereby forming a thinner solidified shell layer, and also providing an opportunity for the copper particles in the molten slag to segregate → settle → aggregate and grow, achieving rapid and slow cooling.

[0053] The preferred embodiment of this invention integrates a casting process optimization method that combines local chilling with precise control of pouring temperature. This method aims to significantly reduce the volume of shrinkage cavities (also known as porosity or pore structure) and refine the pore distribution by controlling the solidification sequence and suppressing the formation of isolated liquid phase regions. Initial solidification temperature optimization during pouring: The initial solidification temperature is controlled within the range of 1500℃ to 1580℃. Combined with numerical simulation of the casting process, the influence of temperature on the evolution of solidification defects is systematically studied.

[0054] Simulation results show that as the initial solidification decreases, the total volume of shrinkage cavities and porosity inside the casting decreases significantly, while the porosity distribution tends to become more dispersed and fine. Specific data are shown in Table 1:

[0055] Table 1. Shrinkage cavities and porosity inside castings under different initial solidification temperatures.

[0056]

[0057] Under the condition of a high initial solidification temperature of 1580℃, such as Figure 5 As shown, the high superheat of the molten metal leads to a slow overall cooling rate of the casting, causing the hot spots to remain liquid for extended periods, forming large, isolated liquid phase regions. Due to the premature solidification of the feeding channels, effective feeding becomes impossible, ultimately resulting in concentrated shrinkage cavities (large in volume but few in number) and continuous shrinkage porosity along the slag baffle and at corners. These defects significantly reduce local density, easily becoming crack initiation points and readily leading to early failure under thermal shock conditions.

[0058] As the initial solidification temperature decreases from 1580℃ to 1560℃, ( Figure 5 (Not shown in the image) The initial enthalpy of the molten metal decreases, and the overall heat dissipation efficiency of the mold relatively improves. The effect of the external chill begins to appear, the cooling rate of the hot spot area accelerates, and the volume of the isolated liquid phase region shrinks. The number of shrinkage cavities increases slightly (e.g., to about 92), indicating that the shrinkage cavities are beginning to disperse, but the overall volume decrease is limited, and the shrinkage porosity is still in a localized clustered state.

[0059] When the temperature drops further to 1540℃, such as Figure 5 As shown, the fluidity of the molten metal decreased slightly, but remained within an acceptable range. The external chill, combined with the lower pouring temperature, resulted in a more uniform advancement of the solidification front in the hot spot region. The number of shrinkage cavities increased significantly, indicating that large shrinkage cavities were "broken down" into multiple smaller shrinkage cavities; the number of porosity cavities increased simultaneously, and the volume of individual porosity cavities decreased, indicating that the porosity began to improve. At this stage, the initial transformation from "concentrated defects" to "dispersed micropores" has been achieved.

[0060] 1520℃ is the performance inflection point, such as Figure 5 As shown, the total volume of shrinkage porosity decreased significantly and its distribution became more uniform. The strong cooling gradient formed by the external chill at the corner effectively suppressed the connectivity of micro-shrinkage porosity between dendrites. According to solidification theory, when the cooling rate increases, the dendrite spacing decreases, the feeding channels become finer, and the liquid phase migration path shortens, which is conducive to the micropores being "encased" by the subsequent solidified metal rather than expanding. At this point, the internal microstructure and mechanical properties of the slag bag reach a better balance.

[0061] At a low temperature of 1500℃, such as Figure 5 As shown, the molten metal had the lowest superheat and the casting solidified the fastest overall. The external chill formed a strong heat flow guide in the hot spot region, causing the solidification front to quickly pass through the corner and upper edge areas, greatly compressing the existence time of the isolated liquid phase. Although the total volume of shrinkage porosity was slightly higher than 1520℃ (possibly due to insufficient micro-feeding caused by excessively rapid local cooling), the number of shrinkage porosity blocks reached 10607, indicating that the porosity was highly dispersed and the individual volume was extremely small (average <10 cm³), which meets the core objective of "dispersed miniaturization".

[0062] When the initial solidification temperature drops to 1500℃, the total volume of shrinkage cavities decreases by approximately 4.7% compared to the 1580℃ condition; the total volume of shrinkage porosity decreases by approximately 8.7%; the number of shrinkage porosity blocks increases significantly (from 9,378 to 10,607), and the volume of individual shrinkage porosity blocks decreases, indicating a more dispersed and finer pore distribution; the solidification time is shortened by approximately 12.4%, which helps improve production efficiency. It is evident that as the initial solidification temperature decreases, the total volume of shrinkage cavities and porosity shows a decreasing trend, and the shrinkage porosity distribution becomes finer (the number of shrinkage porosity blocks increases), which is beneficial for improving slag bag performance. In actual production, it is recommended to control the initial solidification temperature at 1480-1540℃, preferably 1500-1520℃.

[0063] In metallurgy, the impact of micropores on mechanical properties is far less than that of large shrinkage cavities. According to the Hall-Petch relation and fracture mechanics theory, the smaller the defect size, the lower the stress concentration factor, and the significantly improved the material's resistance to thermal fatigue and cracking. Simultaneously, rapid solidification helps refine grains, further enhancing strength and toughness. Furthermore, a 12.4% reduction in solidification time means faster production cycles and lower energy consumption, resulting in significant economic benefits.

[0064] Based on the above systematic research, this invention proposes a slow-cooling slag bag for copper smelting slag that can improve copper recovery rate. The slag bag is a casting bag with an integral casting structure. The casting of the slag bag has a fine and dispersed pore structure inside, and the pores are dispersed in the middle part of the thickness direction of the slag bag wall.

[0065] Specifically, in a preferred embodiment, the casting process of the casting ladle of the present invention adopts an inverted pouring method, that is, the bottom is on top and the slag ladle opening is below. During the pouring process, the initial solidification temperature of the casting is controlled at 1480-1540℃, more preferably 1500-1520℃, which makes it easier to generate dispersed shrinkage cavities, thereby helping to reduce the thermal conductivity of the slag ladle.

[0066] In a preferred embodiment, during the casting process of the casting ladle, by setting external chills in the conical area of ​​the inner and outer walls of the slag ladle, fine and dispersed pores are distributed in the middle part of the wall thickness direction of the casting ladle, and the pores have a thickness of 30-40 mm.

[0067] In a preferred embodiment, the casting ladle is made of low-carbon, high-strength, heat-resistant alloy steel as the base material. During the casting process, the molten steel may be modified as needed. In some embodiments, the specific composition of this low-carbon, high-strength, heat-resistant cast steel material, by mass percentage, includes: C: 0.15~0.2%, Si: 0.40~0.80%, Mn: 0.60~1.20%, Cr: 0.9~1.5%, Ni: 0.8~1.75%, Mo: 0.3~0.5%, S ≤ 0.015%, P ≤ 0.015%, RE: 0.001-0.1%, with the balance being Fe and unavoidable impurities.

[0068] In some embodiments, the slag bag is divided into a slag bag body and a trunnion. The upper opening is a circular structure with a spout, and the upper two ends are provided with lifting lugs. The wall thickness of the slag bag is gradually changed from 90 to 150 mm (this thickness range can be adjusted according to the volume of the slag bag during actual production). A circular arc transition with a radius of 30-80 mm is provided at the connection between the side wall and the bottom plate to reduce thermal stress concentration. The outer wall is provided with annular reinforcing ribs with a spacing of 600-800 mm and a height of 50-80 mm to enhance the overall structural rigidity and resistance to thermal deformation.

[0069] It is generally believed that the larger and thicker the casting, the more porosity and defects are produced, and the worse the slag inclusion quality. Therefore, in current industrial production practice, smaller volumes, such as 12 m³, are preferred. 3 The slag bag. However, through simulation, it was learned that the 24 m provided by this invention... 3 The casting ladle compared to 12 m 3 The casting ladle is more conducive to the crystal growth of copper particles and improves the copper recovery rate. This is likely due to the large volume and thickness of the slag ladle, and the control of the casting process to obtain a dispersed microporous structure, which helps to reduce the thermal conductivity. At the same time, the large volume, thickness, and slag capacity of the slag ladle result in a large heat storage capacity and a small specific surface area, which also slows down the solidification of the copper smelting slag, facilitating subsequent heat recovery. Therefore, this invention provides a copper smelting slag slow-cooling ladle with an integral casting structure, with a volume of 12~30m³. 3 The optimal slag bag volume is 18-30 m³. 3 20-26 m is preferred. 3 The slag bale thickness gradually changes from 120-145 mm. On the other hand, this invention controls the porosity obtained within the casting ladle during the casting process to be a microscopically dispersed pore structure. In the metallurgical process, the negative impact of microscopic pores on the material's mechanical properties is significantly less than that of macroscopic shrinkage cavities. According to the Hall-Petch relation and fracture mechanics theory, reducing defect size can effectively reduce stress concentration, thereby significantly enhancing the material's resistance to thermal fatigue and cracking. The innovative slag bale design adopted in this invention, while achieving a low thermal conductivity and promoting copper particle aggregation and growth, still ensures the overall mechanical properties remain stable.

[0070] Other unlisted slag bag casting process parameters can be performed according to the standard operating parameters.

[0071] In some embodiments, the top of the slag bag of the present invention is provided with an openable heat-insulating cover, with a thickness of 200-500mm. The heat-insulating cover is a composite heat-insulating cover, comprising: a heat-resistant steel frame and heat-reflective coating on the surface of the heat-insulating material, which is heat-insulating cotton or refractory brick. The outer heat-resistant steel frame is located away from the slag bag opening, and the heat-reflective coating on the surface of the heat-insulating material is located near the slag bag opening.

[0072] One simulation embodiment compared the instantaneous solidification shell formation after slag receiving of different slag bag types (in this invention, the instantaneous solidification shell or solidification shell refers to the slag layer solidified within 1100 seconds after slag receiving), as shown in Table 2 and... Figure 6 As shown.

[0073] Table 2. Analysis of the thickness and volume of the slag bag wall and surface crust for different slag bag types at 1000s.

[0074]

[0075] Figure 6 Table 2 shows that under air-cooled conditions (i.e., cooling directly in air after slag collection), 12m 3 The thickness and volume of the solidified shell layer on the welded package wall are 12m. 3 More than 10 times the size of the casting ladle, and 12m 3 The thickness and volume of the solidified shell layer on the ladle wall are 24m. 3 The difference is 4-7 times greater in the casting ladle, and the same significant difference is also reflected in the surface solidified shell layer. This indicates that casting ladles, especially large-volume casting ladles, do indeed have a significantly better heat preservation and slow cooling effect due to the dispersed porous structure of the ladle wall reducing its thermal conductivity.

[0076] Based on the slag bag type, the thickness of the solidified shell, and the copper content of different slag types, the copper weight at the solidified shell was calculated, as shown in Table 3. The copper content in the smelting slag was assumed to be 1.8%, and the copper content in the converter slag was assumed to be 4%. The densities of the smelting slag and converter slag were 3.5 g / cm³, respectively. 3 and 3.8 g / cm 3 The copper particles in the solidified shell are small and difficult to float and recover, resulting in a reduced copper recovery rate. As shown in Table 4, at 1000 seconds after slag collection, the copper recovery rate was 12 m 3 The thickness of the solidified shell layer in the casting cladding is only 3.57 mm, while the thickness of the 12 m cladding shell layer is only 3.57 mm. 3 The weld bead is 37.72mm, 24m. 3The casting ladle is even smaller, only 0.543mm. Based on the copper content of 1wt% in the smelting slag and 4wt% in the converter slag, with a copper smelting slag to converter slag ratio of 4.5:1, and a slag density of 3.5g / cm³, the final product is as follows: 3 The copper loss was calculated based on the thickness of the solidified shell, and the results are shown in Table 3. The calculation shows that, compared to welded ladles, using a casting ladle can reduce the copper content in the tailings from 0.25% to below 0.15%, or even below 0.12%, increasing the copper recovery rate by more than 20%. It can be seen that the copper content in the solidified shell is significantly reduced in a casting ladle compared to a welded ladle, and the copper content is further significantly reduced in a large-volume casting ladle compared to a small-volume casting ladle. Therefore, in the preferred embodiment of this invention, a 24 m... 3 The large casting ladle serves as the core slow-cooling container. It is speculated that because the ladle is integrally cast from low-conductivity, heat-resistant cast steel, the central part of the ladle wall contains a diffusely distributed microporous structure, forming a "heat-insulating layer" that effectively reduces the thermal conductivity.

[0077] Table 3. Thickness, volume, and copper content of the wall and surface crust of different slag bags.

[0078]

[0079] The experimental results show that choosing a casting ladle can improve copper recovery; larger slag ladles have better remelting effects and lower solidified shell thickness than smaller slag ladles, so larger slag ladles are beneficial to improving copper recovery; the matte particles in the slag ladle that are farther from the ladle wall are larger, which is more conducive to flotation, so larger slag ladles are also beneficial to flotation recovery; the higher the temperature of the copper slag, the more conducive it is to the segregation, enrichment and sedimentation of matte, which is also due to the better heat preservation effect of the casting ladle.

[0080] During the experiment, a 12m simulation was also specifically used for comparison. 3 Casting ladle and 24m 3 The thickness of the solidified shell at different times after the slag collection in the casting ladle is shown in Table 4.

[0081] Table 4 12m 3 Casting ladle and 24m 3 Ladle wall solidification layer thickness corresponding to different slag collection times

[0082]

[0083] As can be seen, 26 seconds after the slag collection was completed, 12m 3 Casting ladle and 24m 3 The solidified shell thickness of both casting ladles was 0 mm. At 105 seconds after slag collection, the temperature of both casting ladle types was still above the liquidus, and solidification had not yet begun, with a solidification thickness of 0 mm. At 236 seconds after slag collection, solidification began to form on the casting ladle, but the solidified shell was very thin, 24 m thick. 3 The thickness of the solidified shell is greater than 12m3 The amount is small; 315 seconds after slag collection, the solidified shell of the casting ladle begins to grow slowly, while at 24 m 3 The thickness of the solidified shell in the casting ladle is approximately 12 m. 3 Half the thickness of the casting ladle; 498 seconds after slag collection, 12 m 3 Casting cladding solidified shell ratio 24 m 3 The casting ladle is large; at 1000 seconds after slag collection, 12 m 3 The solidified shell layer in the casting cladding is still relatively small, approximately 3.57 mm, while the 24 m... 3 The thickness of the solidified shell layer in the casting ladle was less than 0.543 mm; at 1758 seconds after slag collection, 12 m 3 Casting ladle and 24 m 3 The thickness of the solidified shell layer in the casting ladle varies significantly. This indicates that using the large-capacity slow-cooling slag ladle of this invention can significantly reduce copper loss in the solidified shell layer, thereby significantly reducing the copper content in the tailings slag.

[0084] Simulations were also conducted on continuously injecting high-temperature molten slag at 1200-1400℃ into 12 m³ welding ladles, 12 m³ casting ladles, and 24 m³ casting ladles, respectively. The results are shown in […]. Figure 7 As shown in the image, the 24 m³ large-capacity casting ladle has a large capacity and high heat capacity. The solidified shell layer formed on the ladle wall in the initial slag-feeding stage is gradually remelted under the continuous impact and heat conduction of the subsequent high-temperature molten slag, and eventually disappears completely when the ladle is 80% full. Figure 7 It can be seen that the 12 m³ welding ladle was not remelted at all, while the 12 m³ casting ladle was only partially remelted.

[0085] In one embodiment, a copper enterprise slag bag (including 12 m) 3 Casting package and 12 m 3 Sampling of solidified slag from both types of welding packages was carried out on-site. The sampling plan diagram is shown below. Figure 8 As shown. After sampling, the mineral particles were refined through multi-stage grinding before analysis. Analysis revealed that 12 μm... 3 Welding package is 12 m 3 The proportion of copper matte particles smaller than or equal to 43 micrometers in the foundry was significantly higher, consistent with the simulation results. Furthermore, sampling analysis revealed that the copper matte particles in the solidified crust were extremely fine (≤10μm), making mineral processing difficult. Therefore, it is necessary to control the volume of the solidified crust to be as small as possible.

[0086] The present invention also provides a method for slow cooling using the aforementioned heat-insulating and slow-cooling slag bag, comprising the following steps: using the aforementioned heat-insulating and slow-cooling slag bag to collect molten copper smelting slag with a slag discharge temperature of 1200-1400℃, covering the slag bag with a heat-insulating cover after collection, and slowly cooling it inside the heat-insulating and slow-cooling slag bag, so that copper particles in the molten copper smelting slag segregate, aggregate, grow, and settle.

[0087] In some embodiments, the slow cooling method specifically includes the following steps:

[0088] Slag receiving stage: Molten copper slag with a slag discharge temperature of 1200-1400℃ is poured into the large-capacity slag ladle, and the slag receiving amount of a single ladle is controlled at 55-75 tons;

[0089] Standing and slow cooling stage: Immediately cover with the insulation cover and place the slag bag in the closed insulation room to allow the molten slag to cool slowly and fully.

[0090] High-temperature liquid residence control: Utilizing the low specific surface area and high heat capacity of the large-capacity casting ladle with a porous structure provided in the preferred embodiment of the present invention, the residence time of the slag in the liquid state above 1205℃ is extended to 8 hours or more, promoting the segregation, diffusion, collision, and aggregation growth of copper phase droplets. After the copper phase droplets have fully segregated, collided, and aggregated, since the liquid slag content is still maintained above 90%, it can be directly hoisted to the air-quenching heat collection chamber for air-quenching granulation and waste heat recovery, and subsequently enters the grinding-flotation process to recover copper metal.

[0091] In some embodiments, the temperature of the insulation chamber and the slag body is monitored in real time during the slow cooling process using the slag bag of the present invention to ensure that the cooling meets the target thermal regime for slow cooling: that is, the insulation temperature is controlled between the initial temperature of slag receiving (1200-1400℃) and the melting point of fir olivine (1205℃), and the insulation time is 8-12 hours.

[0092] The slag bag and slow cooling method for promoting the crystallization and growth of copper phase in copper smelting slag proposed in this invention are applicable to copper smelting slag produced by various pyrometallurgical copper smelting processes. Copper smelting slag includes, but is not limited to, smelting slag and converter slag produced by flash smelting or molten pool smelting, etc., and the temperature of the slag is 1200-1400℃.

[0093] In one simulation example, a 12m² directly air-cooled... 3 Foundry ladle, 12m 3 Welding package, 24m 3 The casting ladle, and a 24m³ container equipped with an insulated cover and insulated chamber for slow cooling under insulated conditions. 3The casting ladle (insulated) was simulated, and the liquid phase content was tested 8-12 hours after slag collection and solidification. The liquid phase (red area) indicates that the slag temperature is above 1205℃, as shown in Table 5. It can be seen that the insulation effect of the casting ladle is better than that of the welded ladle, and the large-volume casting ladle is better than the small-volume casting ladle. Under the condition of insulation and slow solidification, the high-temperature liquid phase is still 88.7% after 12 hours of solidification (it can be inferred that it is still above 90% after 8 hours of solidification). Moreover, the small-volume slag ladle has a clear solidified shell layer on the ladle wall after 12 hours of slow cooling, while the 24 m 3 The casting ladle was kept at a high temperature and cooled slowly for 12 hours, and no solidified shell layer was found on the ladle wall. This indicates that the casting ladle of the present invention uses a high temperature liquid phase window of 8-12 hours above 1205℃, which is conducive to the rapid growth of copper particles.

[0094] Table 5. Comparison of liquid phase content of copper smelting slag of different slag bag types 8-12 hours after solidification

[0095]

[0096] In another embodiment, for a copper enterprise 12 m 3 Casting package and 12 m 3 After the weld bead solidifies, samples of the solidified slag on the bead wall are taken, and the copper phase content distribution is analyzed by XRF. Figure 9 As shown, there is a significant difference in the copper phase distribution on the walls of the foundry ladle and the welded ladle in the direction away from the ladle wall. The copper phase distribution is more concentrated on the welded ladle wall, while the copper distribution is very low near the wall of the foundry ladle. The copper phase that can be recovered by flotation in copper smelting slag is mainly matte particles. Since the solidus of copper slag is 1057℃ and that of matte is 940-1000℃, combined with... Figure 6 Analysis results of the instantaneous condensed shell and Figure 9 XRF analysis results suggest that the preferentially solidifying slag phase pushes matte into the liquid phase, leading to matte segregation, and the segregation effect is positively correlated with temperature. Higher copper slag temperatures are more conducive to matte segregation. Due to the dispersed pore structure of this invention, the casting ladle has a low thermal conductivity and good insulation effect, thus further promoting segregation. The data for the instantaneous solidified shell layer, segregation layer, and enrichment layer are shown in the figure. It can be seen that there are significant differences in the thickness distribution of each layer between the casting ladle and the welded ladle. Thus, this invention, through a special casting process, enables a dispersed, fine pore structure on the ladle wall, resulting in a significant difference in the growth and enrichment of copper particles, significantly thinning or even remelting the instantaneous solidified shell layer, and significantly increasing the size of copper particles. These factors directly lead to a significant increase in copper recovery rate during the final flotation process, resulting in substantial economic benefits. In actual production, by improving the casting process and controlling the pore structure distribution of the casting ladle, the insulation effect of copper smelting slag can be effectively improved, thereby increasing the copper recovery rate.

[0097] Application Example 1

[0098] This application is used in a copper smelter with an annual output of 400,000 tons of crude copper. The total copper smelting slag from smelting and converter slag is 1.3 million tons, with an overall copper grade of 2.16%.

[0099] The original process used 12m 3 The welding package underwent a cooling cycle of 72 hours (natural slow cooling + in-package water cooling). After cooling, sample analysis revealed that 73.31% of the copper particles were >43μm.

[0100] This process uses 24m 3 Experiments were conducted on an integral casting ladle. The slag ladle material composition was: C 0.20%, Si 0.60%, Mn 0.80%, Cr 1.0%, Ni 1.2%, Mo 0.4%, S 0.014%, P 0.013%, RE 0.02%, with the balance being Fe. The wall thickness gradually changed from 120 to 145 mm, with a 50 mm radius arc transition at the connection between the sidewall and the bottom plate to reduce thermal stress concentration. Annular reinforcing ribs were installed on the outer wall, spaced 600 mm apart and 50 mm high, to enhance the overall structural rigidity and resistance to thermal deformation. During the casting process, multiple external chills (each measuring 150 mm × 200 mm × 50 mm, with a 20-30 mm gap between them) were placed on both the inner and outer conical surfaces of the ladle wall. The external chills were made of graphite, and the initial solidification temperature was 1500℃, with inverted casting.

[0101] The operation process is as follows:

[0102] 65 tons / bag of molten slag at 1250℃ were introduced; the bag was covered with an insulated cover and placed in a closed insulated chamber for slow cooling for 9 hours to promote the growth and aggregation of small copper phase particles. After cooling, the sample was taken for analysis and it was found that the proportion of copper particles >43μm was 91.25%. The increase in copper particle size can significantly improve the flotation recovery rate.

[0103] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A copper smelting slag holding and slow cooling ladle for improving the recovery of copper, characterized in that, The slag bag is a casting bag, and the casting bag is an integral casting structure; During the casting process of the slag ladle, external chills are placed in the conical areas of the inner and outer walls of the ladle, and an inverted pouring method is adopted, i.e., the bottom is on top and the ladle opening is below, so that the interior of the slag ladle casting has a diffusely distributed porous structure. Because the solidification rate is fast in the area of ​​the ladle wall near the external chill, forming a fine-grained structure, while the central part of the ladle wall is relatively far from the external chill and the solidification rate is slower, the porous structure is diffusely distributed in the middle part of the thickness direction of the ladle wall, and the size of the diffusely distributed porous structure is <0.1mm. This porous structure helps to reduce the thermal conductivity of the slag ladle, thereby facilitating heat preservation and slow cooling after slag collection, and promoting the growth of copper particles in the molten copper smelting slag.

2. The heat-insulating gradual cooling slag pot according to claim 1, wherein The volume of the casting ladle is 12-30 m 3 .

3. The heat-insulating and slow-cooling slag bag as described in claim 1, characterized in that, The casting ladle is made of low-carbon, high-strength, heat-resistant cast steel.

4. The heat-insulating and slow-cooling slag bag as described in claim 3, characterized in that, The specific composition of the low-carbon, high-strength, heat-resistant cast steel material, by mass percentage, includes: C: 0.15~0.2%, Si: 0.40~0.80%, Mn: 0.60~1.20%, Cr: 0.9~1.5%, Ni: 0.8~1.75%, Mo: 0.3~0.5%, S ≤ 0.015%, P ≤ 0.015%, RE: 0.001-0.1%, with the balance being Fe and unavoidable impurities.

5. The heat-insulating and slow-cooling slag bag as described in claim 1, characterized in that, The slag bag includes a slag bag body and a trunnion, with a circular opening at the top and a sluice structure, and lifting lugs at both ends of the upper part. The wall thickness of the slag bag is gradually varied within the range of 90~150mm according to the size of the slag bag, and a rounded transition with a radius of 30-80mm is set at the connection between the side wall and the bottom plate; The outer wall is equipped with ring-shaped reinforcing ribs with a spacing of 600~800mm and a height of 50~80mm.

6. The heat-insulating and slow-cooling slag bag as described in claim 1, characterized in that, The initial solidification temperature of the casting is controlled at 1480-1540℃ during the casting process.

7. The heat-insulating and slow-cooling slag bag as described in claim 1, characterized in that, The top of the slag bag is equipped with a movable heat-insulating cover.

8. The heat-insulating and slow-cooling slag bag as described in claim 7, characterized in that, The thickness of the insulation cover is 200-500mm. The insulation cover is a composite insulation cover, which includes a heat-resistant steel frame and an insulation material with a heat-reflective coating on the surface.

9. A method for slow cooling using a heat-insulating and slow-cooling slag bag as described in any one of claims 1 to 8, characterized in that, Includes the following steps: The slag receiving operation of molten copper smelting slag with a slag discharge temperature of 1200-1400℃ is carried out using the heat-insulating and slow-cooling slag bag as described in any one of claims 1 to 8. After receiving the slag, the heat-insulating cover is covered and the slag is slowly cooled in the heat-insulating and slow-cooling slag bag, so that the copper particles in the molten copper smelting slag agglomerate and grow.

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