A method for granulating and crystallizing molten nickel-iron slag by air quenching and its application

Abstract

The present application discloses a method and application for air quenching granulation and crystallization treatment of molten nickel-ferronickel slag, comprising mixing molten nickel-ferronickel slag with a tempering agent in a set mass ratio, melting the mixture, and obtaining liquid slag that meets preset indicators; sequentially subjecting the liquid slag to multi-stage diversion and spray granulation to obtain hot granulated slag beads; and directly subjecting the hot granulated slag beads to crystallization treatment and cooling to obtain a granulated slag product, thereby solving the technical problems of low utilization rate of nickel-ferronickel slag and unstable performance of the granulated slag product.

Description

Technical Field

[0001] The present application relates to a method and application for air quenching granulation and crystallization of molten nickel-iron slag, and in particular to a process for air quenching granulation of molten nickel-iron slag and crystallization of hot granulated slag, belonging to the field of resource utilization technology. Background Art

[0002] During the nickel-iron alloy production process, nickel-iron slag is a solid waste generated during the smelting process. Every ton of nickel produced produces 6-16 tons of nickel-iron slag. The current global stockpile has reached hundreds of millions of tons, but the comprehensive utilization rate is only around 12%. This large amount of unused nickel-iron slag not only consumes land resources, but also poses a potential threat to the ecological environment through the leaching of heavy metal components. Finding ways to recycle nickel-iron slag is a key issue in the field of metallurgical solid waste management.

[0003] The existing technology for treating nickel-iron slag mainly uses water quenching or air quenching. However, the water quenching method not only consumes a large amount of water resources, but also wastes a large amount of sensible heat of the high-temperature slag. Moreover, most of the slag after water quenching can only be used as low-value-added materials such as mine filling materials. As a widely studied method of utilizing slag, the air quenching method can not only save water resources and effectively utilize the sensible heat of the slag compared to the traditional water quenching method, but also the ejected gas will not cause harm to the environment. However, the air quenching method is more stringent on the cooling conditions. The process often uses a treatment process of air quenching plus water quenching, which not only wastes secondary resources and the sensible heat of the granulated slag, but also limits the application scope of the granulated slag. At the same time, in the existing nickel-iron slag air quenching granulation process, after the high-temperature slag is granulated by air quenching, its physical heat energy is dissipated in the form of high-temperature slag beads and tail gas, which not only causes a decrease in the overall thermal efficiency of the system, but also requires additional energy consumption to maintain the operating temperature of the remaining process links. The direct discharge of high-temperature tail gas is also prone to cause environmental thermal pollution problems.

[0004] The patent with publication number CN110747302A discloses a steel slag air quenching device and a steel slag granulation method. This method uses a variety of cooling media such as air, nitrogen, and water to force cooling of the granulated slag, effectively improving the granulation efficiency. However, the purpose of the forced cooling method is to control the high glass content of the product, which restricts its application in the field of foundry sand. The patent with publication number CN117025863A discloses a method for enhanced cooling of granulated blast furnace slag. High-pressure gas is mixed with hollow glass beads and amorphous slag beads to form a gas-solid two-phase flow, and the cooling of the granulated slag beads is accelerated by "cold slag hot core". Although the dependence on the water quenching process is reduced, the "cold slag hot core" mechanism aggravates the energy consumption of the system and does not solve the problem of sensible heat recovery. The patent with publication number CN114247848A uses nickel-iron slag as raw material for air quenching and granulation to obtain granulated slag, but the resulting slag beads have a high proportion of amorphous phase, resulting in fluctuations in refractory performance, which limits their reliability in high-temperature application scenarios.

[0005] The technical system generally has the following defects: (1) The existing slag air quenching granulation process generally adopts forced rapid cooling to increase the glass content in the slag beads. The resulting granulated slag has a high proportion of amorphous phase and is mainly used as a cement admixture, which limits its application field. (2) The forced cooling process consumes a large amount of water / electricity resources, and fluctuations in the cooling rate can easily cause uneven stress distribution inside the slag beads, resulting in unstable product performance. (3) The high-temperature exhaust gas generated during the air quenching process is mostly discharged directly, resulting in sensible heat loss and insufficient overall thermal efficiency of the system. Therefore, it is of great practical significance to develop a nickel-iron slag processing technology that combines efficient granulation, controllable crystallization and waste heat recovery. Summary of the Invention

[0006] The purpose of this application is to overcome the deficiencies in the prior art and provide a method and application for the air quenching granulation and crystallization treatment of molten nickel-ferronickel slag, so as to solve the technical problems of low utilization rate of nickel-ferronickel slag, unstable performance of granulated slag products and limited application range.

[0007] To achieve the above objectives, this application adopts the following technical solutions:

[0008] Provided is a method for air quenching, granulating and crystallizing molten nickel-ferronickel slag, comprising:

[0009] Mixing molten nickel-iron slag and a tempering agent in a mass ratio of 3:1 to 100:0, and melting the mixture to obtain liquid slag meeting preset specifications;

[0010] The liquid slag is subjected to multi-stage diversion and injection granulation in sequence to obtain hot granulated slag beads;

[0011] The hot granulated slag beads are directly crystallized and cooled to obtain the finished granulated slag product.

[0012] In combination with the first aspect, further, the liquid slag that meets the preset indicators includes the following mass percentage components: SiO2: 40%~60%, MgO: 16%~38%, Fe2O3: 2%~16%, FeO: 0.8%~8%, Al2O3: 3%~12%, CaO: 0.3%~6%, Cr2O3: 0.1%~5%, MnO: 0.01%~0.8%, Na2O and K2O: 0.01%~0.8%.

[0013] Furthermore, the conditioning agent is any one or more mixtures of feldspar, quartz sand, borax, fluorite and soda ash.

[0014] Furthermore, the temperature range of the liquid slag is 1480° C. to 1580° C., and the viscosity range is 0.09 Pa·s to 0.8 Pa·s.

[0015] Furthermore, the pressure of the spray granulation is 0.3MPa~0.8MPa.

[0016] Furthermore, the temperature of the hot granulated slag beads ranges from 700°C to 1000°C.

[0017] Furthermore, the gas pressure of the spray granulation is 0.3MPa~0.8MPa, and the aperture of the spray nozzle is 2~7mm.

[0018] Furthermore, the temperature of the crystallization treatment is 830° C. to 940° C., and the crystallization time is 15 min to 75 min.

[0019] Furthermore, the cooling includes: setting a temperature drop program cooling of 4-10°C / min, placing in the air for natural cooling and water spray cooling.

[0020] In a second aspect, the granulated slag product prepared by the air quenching granulation and crystallization treatment method of molten nickel-iron slag according to any of the above items is used in foundry sand or petroleum filler.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present application provides a method and application for air quenching granulation and crystallization of molten nickel-ferro slag, which fully utilizes the sensible heat of the slag and does not require a forced cooling process. Crystal precipitation is controlled by heat treatment, thereby improving the product yield rate, saving resource consumption in the cooling process while ensuring performance stability. After granulation, the hot granulated slag beads do not need to be cooled and are directly hot-charged and sent to a high-temperature furnace for heat treatment, effectively utilizing the sensible heat of the hot granulated slag beads and reducing energy loss.

[0023] The raw materials consist only of nickel-iron slag and a small amount of tempering agent, which has simple requirements on equipment. It not only reduces production costs but also increases the utilization rate of nickel-iron slag to 75%~100%. The obtained granulated slag has good performance in terms of particle size, bulk density, water content, loss on ignition, and acid consumption value. All performances are higher than the requirements of the foundry sand industry standards. It can be used as foundry sand and petroleum filler, which broadens the application range of granulated slag and has strong market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A process flow chart of a method for air quenching, granulating and crystallizing molten nickel-ferro slag provided in an embodiment of the present application;

[0025] Figure 2 The macroscopic morphology of the samples obtained in Examples 1 to 5 is shown;

[0026] Figure 3 This is the XRD pattern of the sample obtained in Example 1;

[0027] Figure 4 This is the XRD diagram of raw nickel-iron slag. DETAILED DESCRIPTION

[0028] The technical solution of the present application is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application.

[0029] The present application provides a method for quenching granulation and crystallization of molten nickel-iron slag. The process flow is as follows: Figure 1 As shown, the following steps are included:

[0030] (1) The molten nickel-iron slag discharged from the smelting process is subjected to a determination of whether to add a tempering agent based on its composition characteristics: when the slag composition does not meet the preset index, a tempering agent is added and a high-temperature tempering treatment is performed in a tempering furnace until the slag is in a liquid state with a temperature greater than 1480°C; when the slag composition meets the preset index, the slag is subjected to a high-temperature treatment to be in a liquid state and then directly enters step S2.

[0031] Furthermore, the temperature range of the liquid slag is 1480°C~1580°C, and the viscosity is 0.09Pa·s~0.8Pa·s.

[0032] (2) The liquid slag after quenching and tempering or the original molten nickel-iron slag without quenching and tempering is diverted into multiple stages and then introduced into the slag trough inlet. The slag is blown by the high-pressure gas ejected from the Laval nozzle below the slag trough inlet to obtain granulated slag beads. The diameter of the slag trough inlet is 30-50 mm, and the Laval nozzle is located 0.2-0.5 m below the slag trough inlet. The aperture of the Laval nozzle is 2-7 mm. The pressure of the high-pressure gas is 0.3 MPa-0.8 MPa.

[0033] The waste heat of the high-temperature tail gas generated during the air quenching process in this step can be used to supply energy to other process links by setting up a gas-solid heat exchange device.

[0034] (3) The granulated slag beads are collected on a collection platform and then directly hot-charged and sent to a high-temperature furnace for crystallization at a temperature of 700-1000°C. The crystallization temperature is 830-940°C and the crystallization time is 15-75 minutes. The waste heat generated in this step can be recovered through a circulation pipeline to the gas-solid heat exchange device in step (2).

[0035] (4) After the crystallization is completed, you can choose to set the temperature in the furnace to cool at a rate of 4~10℃ / min, put it into the air for natural cooling, or spray a small amount of water on the surface to accelerate cooling. After cooling, the particle size is screened to obtain the granulated slag product.

[0036] The liquid slag obtained in step (1) comprises:

[0037] SiO2: 40%~60%, MgO: 16%~38%, Fe2O3: 2%~16%, FeO: 0.8%~8%, Al2O3: 3%~12%, CaO: 0.3%~6%, Cr2O3: 0.1%~5%, MnO: 0.01%~0.8%, Na2O and K2O: 0.01%~0.8%, and the rest are impurities.

[0038] In some other embodiments of the present application, the composition of the liquid slag involved in the air quenching and granulation is:

[0039] SiO2: 44.27%, MgO: 34.31%, Fe2O3: 12.14%, FeO: 1.42%, Al2O3: 3.42%, CaO: 0.98%, Cr2O3: 1.18%, MnO: 0.63%, Na2O and K2O: 0.15%.

[0040] Or: SiO2: 48.63%, MgO: 32.13%, Fe2O3: 8.96%, FeO: 1.61%, Al2O3: 3.22%, CaO: 1.44%, Cr2O3: 1.03%, MnO: 0.58%, Na2O and K2O: 0.23%.

[0041] In the specific examples of the present application, unless otherwise specified, the experimental environment and parameter conditions of each group in the examples remain consistent except for the differences clearly stated.

[0042] Example 1:

[0043] This embodiment provides a molten nickel-iron slag crystallization process, the process is as follows:

[0044] (1) The raw materials include nickel-iron slag and a tempering agent, wherein the nickel-iron slag accounts for 90% of the total mass percentage; the tempering agent accounts for 10% of the total mass percentage, and the tempering agent is a mixture of quartz sand and feldspar.

[0045] (2) The molten nickel-iron slag and the tempering agent are melted in a tempering furnace and kept warm at 1550°C.

[0046] (3) The tempered liquid slag is diverted into multiple stages and then introduced into the slag trough inlet. At this time, the composition of the slag is SiO2: 44.27%, MgO: 34.31%, Fe2O3: 12.14%, FeO: 1.42%, Al2O3: 3.42%, CaO: 0.98%, Cr2O3: 1.18%, MnO: 0.63%, Na2O and K2O: 0.15%, the temperature is 1550℃, and the viscosity is 0.6 Pa·s.

[0047] (4) A Laval nozzle with a diameter of 3.5 mm is used to quench the slag to obtain granulated slag beads. The Laval nozzle is located 0.4 m below the chute mouth. The gas pressure of the spray is 0.6 MPa. The exhaust gas is passed through the gas-solid heat exchange device and the pipeline to provide energy for high-temperature tempering and crystallization.

[0048] (5) The granulated slag beads at 800 °C are hot-charged and sent to the crystallization furnace for crystallization treatment through the collection platform. The crystallization temperature is 900 °C and the crystallization time is 30 min.

[0049] (6) After crystallization is completed, the slag is cooled to below 180°C at a cooling rate of 6°C / min to obtain a granulated slag product.

[0050] like Figure 2 As shown in Figure a, it is a picture of the granulated slag product before screening. It can be seen from the figure that the particle size of the granulated slag product is basically less than 4mm and the sphericity is good.

[0051] The granulated slag product was subjected to particle size screening to obtain samples. The XRD results of the samples were as follows: Figure 3 As shown, the sample has obvious crystallization peaks, and the main crystal phase is magnesian olivine. The XRD of the original slag is as follows Figure 4 As shown, the main crystal phases are enstatite and mafic olivine. Figure 3 It can be seen that the crystal phase is effectively controlled by the crystallization treatment in this embodiment, which promotes the transformation of enstatite to mafic olivine and effectively improves the performance of the sample. The sample density is 2965 kg / m 3 , bulk density 1795kg / m 3 , water content 0.03%, loss on ignition 0.01%, acid consumption value 4.9ml, and excellent performance indicators.

[0052] Example 2:

[0053] This embodiment provides a molten nickel-iron slag crystallization process, the process is as follows:

[0054] (1) The raw material is 100% molten nickel-iron slag.

[0055] (2) The molten nickel-iron slag was directly diverted into the slag trough after multi-stage diversion. The slag composition at this time was SiO2: 48.63%, MgO: 32.13%, Fe2O3: 8.96%, FeO: 1.61%, Al2O3: 3.22%, CaO: 1.44%, Cr2O3: 1.03%, MnO: 0.58%, Na2O and K2O: 0.23%. The temperature was 1480°C and the viscosity was 0.8 Pa·s.

[0056] (3) A Laval nozzle with a diameter of 7 mm is used to granulate the slag by air quenching to obtain granulated slag beads. The Laval nozzle is located 0.5 m below the chute mouth. The gas pressure of the spray is 0.3 MPa. The exhaust gas is sent to the high-temperature tempering and crystallization stage through a gas-solid heat exchange device through a pipeline.

[0057] (4) The granulated slag beads at 1000 °C are hot-charged and sent to the crystallization furnace for crystallization treatment through the collection platform. The crystallization temperature is 940 °C and the crystallization time is 75 min.

[0058] (5) After crystallization is completed, the mixture is cooled to below 180°C at a cooling rate of 10°C / min to obtain granulated slag.

[0059] The granulated slag is screened to obtain the sample, as shown in the sample picture. Figure 2 As shown in b, the sample particle size is basically less than 4mm and the sphericity is good. The sample density is 3015kg / m 3 , bulk density 1810kg / m 3 , water content 0.04%, loss on ignition 0.03%, acid consumption value 4.3ml, and excellent performance indicators.

[0060] Example 3:

[0061] This embodiment provides a molten nickel-iron slag crystallization process, the process is as follows:

[0062] (1) The raw materials mainly include nickel-iron slag and tempering agent, with nickel-iron slag accounting for 75% of the total mass percentage; the tempering agent accounts for 25% of the total mass percentage, and the tempering agent is a mixture of quartz sand, borax and fluorite.

[0063] (2) Place the molten nickel-iron slag and the tempering agent in a tempering furnace and keep it warm at 1580°C.

[0064] (3) The tempered liquid slag is diverted into multiple stages and then introduced into the slag trough inlet. At this time, the composition of the slag is SiO2: 44.27%, MgO: 34.31%, Fe2O3: 12.14%, FeO: 1.42%, Al2O3: 3.42%, CaO: 0.98%, Cr2O3: 1.18%, MnO: 0.63%, Na2O and K2O: 0.15%, the temperature is 1580℃, and the viscosity is 0.09 Pa·s.

[0065] (4) A Laval nozzle with a diameter of 2 mm is used to granulate the slag by air quenching to obtain granulated slag beads. The Laval nozzle is located 0.2 m below the chute mouth. The gas pressure of the spray is 0.8 MPa. The exhaust gas is sent to the high-temperature tempering and crystallization stage through a gas-solid heat exchange device through a pipeline.

[0066] (5) The granulated slag beads at 700 °C are hot-charged and sent to the crystallization furnace for crystallization treatment through the collection platform. The crystallization temperature is 830 °C and the crystallization time is 15 min.

[0067] (6) After crystallization is completed, the mixture is cooled to below 180°C at a cooling rate of 4°C / min to obtain granulated slag.

[0068] (7) The granulated slag is screened to obtain samples. The sample pictures are as follows: Figure 2 As shown in c, the sample particle size is basically less than 4mm and the sphericity is good. The sample density is 2933kg / m 3 , bulk density 1774kg / m 3 , water content 0.02%, loss on ignition 0.01%, acid consumption value 4.6ml, and excellent performance indicators.

[0069] Example 4:

[0070] This embodiment provides a molten nickel-iron slag crystallization process, the process is as follows:

[0071] (1) The raw materials mainly include nickel-iron slag and tempering agent, with nickel-iron slag accounting for 92% of the total mass percentage; the tempering agent accounts for 8% of the total mass percentage, and the tempering agent is a mixture of borax, fluorite and soda ash.

[0072] (2) Place the molten nickel-iron slag and the tempering agent in a tempering furnace and keep it warm at 1530°C.

[0073] (3) The liquid slag after quenching and tempering is diverted into multiple stages and then introduced into the inlet of the slag trough. At this time, the composition of the slag is SiO2: 44.27%, MgO: 34.31%, Fe2O3: 12.14%, FeO: 1.42%, Al2O3: 3.42%, CaO: 0.98%, Cr2O3: 1.18%, MnO: 0.63%, Na2O and K2O: 0.15%, the temperature is 1530℃, and the viscosity is 0.6 Pa·s.

[0074] (4) A Laval nozzle with a diameter of 3.5 mm is used to quench the slag to obtain granulated slag beads. The Laval nozzle is located 0.4 m below the chute mouth. The gas pressure of the spray is 0.6 MPa. The exhaust gas is sent to the high-temperature tempering and crystallization stage through a gas-solid heat exchange device through a pipeline to provide energy.

[0075] (5) The granulated slag beads at 800 °C are hot-charged and sent to the crystallization furnace for crystallization treatment through the collection platform. The crystallization temperature is 900 °C and the crystallization time is 30 min.

[0076] (6) After crystallization is completed, it is placed in the air to cool naturally to obtain granulated slag.

[0077] The granulated slag is screened to obtain the sample, as shown in the sample picture. Figure 2 As shown in (d), the sample particle size is basically less than 4mm and the sphericity is good. The sample density is 3042kg / m 3 , bulk density 1833kg / m 3 , water content 0.06%, loss on ignition 0.04%, acid consumption value 5.0ml, and excellent performance indicators.

[0078] Embodiment 5:

[0079] In this embodiment, the crystallization process in Example 1 is removed, and the nickel-iron slag is subjected to air quenching and granulation to directly obtain the finished product. By comparing the role of the crystallization process in this application, the process is as follows:

[0080] (1) The raw materials mainly include nickel-iron slag and tempering agent, with nickel-iron slag accounting for 90% of the total mass percentage; the tempering agent accounts for 10% of the total mass percentage, and the tempering agent is a mixture of quartz sand, borax and fluorite.

[0081] (2) Place the molten nickel-iron slag and the tempering agent in a tempering furnace and keep it warm at 1550°C.

[0082] (3) The tempered liquid slag is diverted into multiple stages and then introduced into the slag trough inlet. At this time, the composition of the slag is SiO2: 44.27%, MgO: 34.31%, Fe2O3: 12.14%, FeO: 1.42%, Al2O3: 3.42%, CaO: 0.98%, Cr2O3: 1.18%, MnO: 0.63%, Na2O and K2O: 0.15%, the temperature is 1550℃, and the viscosity is 0.6 Pa·s.

[0083] (4) A Laval nozzle with a diameter of 3.5 mm is used to granulate the slag by air quenching to obtain granulated slag beads. The Laval nozzle is located 0.4 m below the chute mouth. The gas pressure of the spray is 0.6 MPa. Granulated slag is obtained after air quenching and granulation. The exhaust gas is sent to the high-temperature tempering link through a gas-solid heat exchange device and a pipeline for energy supply.

[0084] (5) The granulated slag is screened to obtain samples. The sample pictures are as follows: Figure 2 As shown in Figure e, the sample particle size is basically less than 4 mm and the sphericity is good. The density of the uncrystallized sample is 3032 kg / m 3 , bulk density 1753kg / m 3 , water content 0.4%, loss on ignition 0.01%, acid consumption value 8.7ml. The density, loss on ignition and other properties of the non-crystallized sample are not much different from those after crystallization, but the water content and acid consumption value are significantly higher, which does not meet the performance requirements of foundry sand.

[0085] The present application also provides an application of a method for air quenching, granulating and crystallizing molten nickel-iron slag, which includes preparing foundry sand or petroleum filler.

[0086] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for quenching, granulating and crystallizing molten nickel-ferronickel slag, characterized in that: include: Mixing molten nickel-iron slag and a tempering agent in a mass ratio of 3:1 to 100:0, and melting the mixture to obtain liquid slag meeting preset specifications; The liquid slag is sequentially diverted into the slag trough inlet through multi-stage diversion, and granulated by the high-pressure gas sprayed from the Laval nozzle below the slag trough inlet to obtain hot granulated slag beads; The slag trough inlet has a diameter of 30-50 mm, and the Laval nozzle is located 0.2-0.5 m below the slag trough inlet. The high-temperature exhaust heat generated during the air quenching process is supplied to other process steps through a gas-solid heat exchange device. The hot granulated slag beads are collected and directly hot-charged and sent to a high-temperature furnace at a temperature of 700-1000°C for crystallization treatment, and then cooled to obtain the granulated slag product; the waste heat generated in this step is recovered to the gas-solid heat exchange device through a circulation pipeline.

2. The method according to claim 1, characterized in that The liquid slag meeting the preset indicators includes the following mass percentage components: SiO2: 40%~60%, MgO: 16%~38%, Fe2O3: 2%~16%, FeO: 0.8%~8%, Al2O3: 3%~12%, CaO: 0.3%~6%, Cr2O3: 0.1%~5%, MnO: 0.01%~0.8%, Na2O and K2O: 0.01%~0.8%.

3. The method according to claim 1, characterized in that The conditioning agent is any one or more of feldspar, quartz sand, borax, fluorite and soda ash.

4. The method according to claim 1, wherein The temperature range of the liquid slag is 1480° C. to 1580° C., and the viscosity range is 0.09 Pa·s to 0.8 Pa·s.

5. The method according to claim 1, wherein The pressure of the spray granulation is 0.3MPa~0.8MPa.

6. The method according to claim 1, characterized in that The temperature of the hot granulated slag beads ranges from 700°C to 1000°C.

7. The method according to claim 1, characterized in that The gas pressure of the spray granulation is 0.3MPa~0.8MPa, and the aperture of the spray nozzle is 2~7mm.

8. The method according to claim 1, characterized in that The temperature of the crystallization treatment is 830° C. to 940° C., and the crystallization time is 15 min to 75 min.

9. The method according to claim 1, characterized in that The cooling includes: setting a temperature drop program of 4-10°C / min for cooling, placing the product in the air for natural cooling, and spraying water for cooling.

10. Use of the granulated slag product prepared by the method according to any one of claims 1 to 9 in foundry sand or petroleum filler.

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