Molten ferronickel slag air quenching granulation and crystallization treatment method and application

Abstract

The invention discloses a molten ferronickel slag air-quenching granulation and crystallization treatment method and application, and the method comprises the following steps: mixing molten ferronickel slag and a tempering agent according to a set mass ratio, and melting to obtain liquid slag meeting a preset index; the liquid slag is sequentially subjected to multi-stage flow division and injection granulation, and hot-state granulated slag beads are obtained; and the hot-state granulated slag beads are directly crystallized and cooled to obtain a granulated slag finished product, and the technical problems that the utilization rate of the ferronickel slag is low, and the performance of the granulated slag finished product is unstable are solved.

Description

Technical Field

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

[0002] In the production process of nickel-iron alloy, nickel-iron slag, as a solid waste generated during the smelting process of nickel-iron alloy, 6 - 16 tons of nickel-iron slag are generated per ton of nickel product. The current global cumulative stockpile has reached the scale of hundreds of millions of tons, but the comprehensive utilization rate is only about 12%. A large amount of unutilized nickel-iron slag not only occupies land resources, but also the leaching of its heavy metal components poses a potential threat to the ecological environment. Seeking a way for the resource utilization of nickel-iron slag is an important topic in the current field of metallurgical solid waste treatment.

[0003] The existing technologies for nickel-iron slag treatment mainly include water quenching method or air quenching method. 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 molten slag. Moreover, most of the slag after water quenching can only be used as materials with low added value such as mine filling materials. As a widely studied way of slag utilization, the air quenching method, compared with the traditional water quenching method, can not only save water resources and effectively utilize the sensible heat of the molten slag, but also the ejected gas will not cause harm to the environment. However, the air quenching method has strict requirements for cooling conditions, and the process mostly uses the treatment process of air quenching plus water quenching, which not only causes waste of secondary resources and sensible heat of granulated slag, but also limits the application range of granulated slag. At the same time, in the existing nickel-iron slag air quenching granulation process, after the high-temperature molten slag is air quenched and granulated, 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 emission of high-temperature tail gas is also likely to cause environmental heat pollution problems.

[0004] The patent with the publication number CN110747302A discloses a steel slag air quenching device and a steel slag granulation method, which uses a variety of cooling media such as air, nitrogen, and water to forcibly cool the granulated slag, effectively improving the granulation efficiency. However, the purpose of the forced cooling method is to control the high vitreous content of the product, which is restricted to a certain extent in the application in the field of casting sand. The patent with the publication number CN117025863A discloses a method for strengthening the cooling and granulation of blast furnace slag, which forms a gas-solid two-phase flow by mixing high-pressure gas with hollow glass beads and amorphous slag beads, and accelerates the cooling of granulated slag beads through the "cold slag hot core". Although it reduces the dependence on the water quenching process, the "cold slag hot core" mechanism increases the system energy consumption and does not solve the problem of sensible heat recovery. The patent with the publication number CN114247848A uses nickel-iron slag as a raw material for air quenching granulation to obtain granulated slag, but the obtained slag beads have fluctuating refractory properties due to the too high proportion of amorphous phase, which limits their reliability in high-temperature application scenarios.

[0005] The technical system generally has the following defects: (1) In the existing slag air-quenching granulation process, forced rapid cooling is generally used to increase the vitreous content in slag beads. The granulated slag obtained has a high proportion of amorphous phase and is mainly used as a cement admixture, with limited application fields; (2) A large amount of water / electricity resources are consumed during the forced cooling process, and the fluctuation of the cooling rate is likely to cause uneven stress distribution inside the slag beads, resulting in unstable product performance. (3) The high-temperature tail gas generated during the air-quenching process is mostly directly discharged, causing sensible heat loss and insufficient overall thermal efficiency of the system. Therefore, it is of great practical significance to develop a nickel-iron slag treatment technology with the functions of 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, provide a method and application for air-quenching granulation and crystallization treatment of molten nickel-iron slag, and solve the technical problems of low utilization rate of nickel-iron slag, unstable performance of granulated slag products and limited application scope.

[0007] To achieve the above purpose, this application adopts the following technical solutions: Provide a method for air-quenching granulation and crystallization treatment of molten nickel-iron slag, including: Mix molten nickel-iron slag and a conditioning agent in a mass ratio of 3:1 to 100:0, melt to obtain liquid slag meeting preset indexes; Perform multi-stage shunting and spray granulation on the liquid slag in sequence to obtain hot granulated slag beads; Directly perform crystallization treatment on the hot granulated slag beads, cool to obtain granulated slag products.

[0008] Combined with the first aspect, further, the liquid slag meeting preset indexes 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%.

[0009] Further, the conditioning agent is any one or a mixture of feldspar, quartz sand, borax, fluorite, soda ash.

[0010] Further, the temperature range of the liquid slag is 1480°C - 1580°C, and the viscosity range is 0.09 Pa·s - 0.8 Pa·s.

[0011] Further, the pressure of the spray granulation is 0.3 MPa - 0.8 MPa.

[0012] Further, the temperature range of the hot granulated slag beads is 700°C - 1000°C.

[0013] Further, the gas pressure for the spray granulation is 0.3 MPa to 0.8 MPa, and the nozzle aperture for the spraying is 2 to 7 mm.

[0014] Further, the temperature for the crystallization treatment is 830 °C to 940 °C, and the crystallization time is 15 min to 75 min.

[0015] Further, the cooling includes: cooling by setting a temperature reduction program of 4 to 10 °C / min, natural cooling in air, and any one or more of water spraying cooling.

[0016] In a second aspect, an application of the granulated slag product prepared by the method for wind quenching granulation and crystallization treatment of molten nickel-iron slag according to any one of the above in foundry sand or petroleum filler.

[0017] Compared with the prior art, the beneficial effects achieved by the present application are as follows: The method for wind quenching granulation and crystallization treatment of molten nickel-iron slag and the application provided by the present application make full use of the sensible heat of the molten slag and do not require a forced cooling process. By controlling the crystal precipitation through heat treatment, the product yield is improved. It not only saves the resource consumption in the cooling process but also ensures the performance stability; the hot granulated slag beads after granulation do not need to be cooled and are directly hot charged and hot sent to a high-temperature furnace for heat treatment, effectively utilizing the sensible heat of the hot granulated slag beads and reducing the energy loss. The raw material components are only nickel-iron slag and a small amount of conditioning agent, and the equipment requirements are simple. It not only has a low production cost but also improves the utilization rate of nickel-iron slag to 75% to 100%; the performance of the obtained granulated slag product in terms of particle size, bulk density, water content, ignition loss, and acid consumption value is good, and each performance is higher than the requirements of the foundry sand industry standard. It can be used as foundry sand and petroleum filler, broadening the application range of granulated slag and having strong market competitiveness. Description of the Drawings

[0018] Figure 1 It is a process flow chart of a method for wind quenching granulation and crystallization treatment of molten nickel-iron slag provided by an embodiment of the present application; Figure 2 It is a macroscopic morphology diagram of the samples obtained in Examples 1 to 5; Figure 3 It is an XRD diagram of the sample obtained in Example 1; Figure 4 It is an XRD diagram of the original nickel-iron slag. Detailed Embodiments

[0019] The technical solution of the present application will be described in detail below with reference to 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.

[0020] The present application provides a method for air quenching granulation and crystallization treatment of molten nickel-iron slag. The process flow is as Figure 1 shown and includes the following steps: (1) According to the composition characteristics of the molten nickel-iron slag discharged during the smelting process, determine whether to add a conditioning agent: when the slag composition does not reach the preset index, add the conditioning agent and perform high-temperature conditioning treatment in a conditioning furnace until the molten slag reaches a temperature greater than 1480 °C; when the slag composition meets the preset index, directly enter step S2 after high-temperature treatment to obtain molten slag.

[0021] Furthermore, the temperature range of the molten slag is 1480 °C to 1580 °C, and the viscosity is 0.09 Pa·s to 0.8 Pa·s.

[0022] (2) After multi-stage diversion of the conditioned molten slag or the original unconditioned molten nickel-iron slag, introduce it into the inlet of the slag flow tank, and blow the molten slag with high-pressure gas ejected from the Laval nozzle below the inlet of the slag flow tank to obtain granulated slag beads; the diameter of the inlet of the slag flow tank is 30 to 50 mm, the Laval nozzle is located 0.2 to 0.5 m directly below the inlet of the slag flow tank, and the aperture of the Laval nozzle is 2 to 7 mm. The pressure of the high-pressure gas is 0.3 MPa to 0.8 MPa.

[0023] During the air quenching process in this step, the waste heat of the high-temperature tail gas can be used to supply energy to other process links by setting up a gas-solid heat exchange device.

[0024] (3) The granulated slag beads are collected through a collection platform and directly hot-charged and hot-transported to a high-temperature furnace at a temperature of 700 to 1000 °C for crystallization treatment. The crystallization temperature is 830 to 940 °C, and the crystallization time is 15 to 75 min. The waste heat generated in this step can be recovered through a circulation pipeline to the gas-solid heat exchange device in step (2).

[0025] (4) After crystallization, any one or more of the following three cooling methods can be selected: cooling at a rate of 4 to 10 °C / min in the furnace, cooling in the air naturally, and accelerating cooling by spraying a small amount of water on the surface. After cooling, perform particle size screening to obtain the finished granulated slag.

[0026] The molten slag obtained in step (1) includes: 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%, the rest are impurities.

[0027] In some other embodiments of the present application, the composition of the liquid slag participating in air quenching granulation 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%.

[0028] 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%.

[0029] In the specific embodiments of the present application, unless otherwise specified, except for the clearly pointed out differences, the experimental environments and parameter conditions of each group in the embodiments are kept consistent.

[0030] Example 1:

[0031] This embodiment provides a crystallization treatment of molten nickel - iron slag, and the process is as follows: (1) The raw materials include nickel - iron slag and a conditioning agent. The nickel - iron slag accounts for 90% of the total mass percentage; the conditioning agent accounts for 10% of the total mass percentage, and the conditioning agent is a mixture of quartz sand and feldspar.

[0032] (2) Melt the molten nickel - iron slag and the conditioning agent in a conditioning furnace and keep it at 1550 °C for heat preservation.

[0033] (3) After multi - stage diversion of the conditioned liquid slag, introduce it into the inlet of the slag flow tank. 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 °C, and the viscosity is 0.6 Pa·s.

[0034] (4) The molten slag is granulated by air quenching using a Laval nozzle with a diameter of 3.5 mm to obtain granulated slag beads. The Laval nozzle is located 0.4 m directly below the chute opening, and the gas pressure for injection is 0.6 MPa. The tail gas is used to supply energy for high-temperature conditioning and crystallization through a gas-solid heat exchange device and pipelines.

[0035] (5) The granulated slag beads at 800 °C are hot-charged and hot-transported to a crystallization furnace through a collection platform for crystallization treatment. The crystallization temperature is 900 °C, and the crystallization time is 30 min.

[0036] (6) After crystallization is completed, it is cooled to below 180 °C at a cooling rate of 6 °C / min to obtain the finished granulated slag product.

[0037] As Figure 2 shown in a of the figure, it is a picture of the finished granulated slag product before screening. It can be seen from the figure that the particle size of the finished granulated slag product is basically less than 4 mm, and the sphericity is good.

[0038] After the finished granulated slag product is subjected to particle size screening to obtain a sample, the XRD results of the sample are as Figure 3 shown. The sample has obvious crystallization peaks, and the main crystal phase is magnesium iron olivine. The XRD of the original slag is as Figure 4 shown, and the main crystal phases are enstatite and magnesium iron olivine. By comparison Figure 3 it can be known that in this embodiment, the crystal phase is effectively controlled through crystallization treatment, promoting the transformation of enstatite to magnesium iron olivine, effectively improving the performance of the sample. The density of the sample is 2965 kg / m 3 , the bulk density is 1795 kg / m 3 , the water content is 0.03%, the loss on ignition is 0.01%, and the acid consumption value is 4.9 ml. The performance indicators are excellent.

[0039] Example Two:

[0040] This embodiment provides a crystallization treatment of molten nickel-iron slag, and the process is as follows: (1) The raw material is 100% molten nickel-iron slag.

[0041] (2) The original molten nickel-iron slag is directly subjected to multi-stage diversion and then introduced into the inlet of the slag chute. At this time, the composition of the molten slag is 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 is 1480 °C, and the viscosity is 0.8 Pa·s.

[0042] (3) The molten slag is granulated by air quenching using a Laval nozzle with a diameter of 7 mm. The Laval nozzle is located 0.5 m directly below the chute opening, and the gas pressure for injection is 0.3 MPa. The tail gas is sent through a gas-solid heat exchange device via a pipeline to high-temperature conditioning for energy supply in the crystallization stage.

[0043] (4) The granulated slag beads at 1000 °C are hot-charged and hot-transported through a collection platform to a crystallization furnace for crystallization treatment. The crystallization temperature is 940 °C, and the crystallization time is 75 min.

[0044] (5) After crystallization is completed, it is cooled to below 180 °C at a cooling rate of 10 °C / min to obtain granulated slag.

[0045] After the granulated slag is screened by particle size, a sample is obtained. The sample picture is as shown in Figure 2 b in the figure. The particle size of the sample is basically less than 4 mm, and the sphericity is good. The density of the sample is 3015 kg / m 3 , and the bulk density is 1810 kg / m 3 , the water content is 0.04%, the loss on ignition is 0.03%, and the acid consumption value is 4.3 ml. The performance indicators are excellent.

[0046] Example 3:

[0047] This example provides a crystallization treatment for molten nickel-iron slag, and the process is as follows: (1) The raw materials mainly include nickel-iron slag and a conditioning agent. The nickel-iron slag accounts for 75% of the total mass percentage; the conditioning agent accounts for 25% of the total mass percentage, and the conditioning agent is a mixture of quartz sand, borax, and fluorite.

[0048] (2) The molten nickel-iron slag and the conditioning agent are kept warm in a conditioning furnace at 1580 °C.

[0049] (3) After conditioning, the liquid molten slag is introduced into the inlet of the slag chute through multi-stage diversion. At this time, the composition of the molten 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 °C, and the viscosity is 0.09 Pa·s.

[0050] (4) The molten slag is granulated by air quenching using a Laval nozzle with a diameter of 2 mm. The Laval nozzle is located 0.2 m directly below the chute opening, and the gas pressure for injection is 0.8 Mpa. The tail gas is sent through a gas-solid heat exchange device via a pipeline to high-temperature conditioning for energy supply in the crystallization stage.

[0051] (5) The granulated slag beads at 700 °C are hot charged and sent to the crystallization furnace through the collection platform for crystallization treatment. The crystallization temperature is 830 °C and the crystallization time is 15 min.

[0052] (6) After crystallization is completed, it is cooled to below 180 °C at a cooling rate of 4 °C / min to obtain granulated slag.

[0053] (7) After the granulated slag is subjected to particle size screening, a sample is obtained. The sample picture is as shown in Figure 2 c below. The particle size of the sample is basically less than 4 mm and the sphericity is good. The density of the sample is 2933 kg / m 3 , and the bulk density is 1774 kg / m 3 , the water content is 0.02%, the loss on ignition is 0.01%, and the acid consumption value is 4.6 ml. The performance indicators are excellent.

[0054] Example 4:

[0055] This example provides a crystallization treatment of molten nickel-iron slag, and the process is as follows: (1) The raw materials mainly include nickel-iron slag and a conditioning agent. The nickel-iron slag accounts for 92% of the total mass percentage; the conditioning agent accounts for 8% of the total mass percentage. The conditioning agent is a mixture of borax, fluorite, and soda ash.

[0056] (2) The molten nickel-iron slag and the conditioning agent are kept warm in the conditioning furnace at 1530 °C.

[0057] (3) After conditioning, the liquid slag is subjected to multi-stage diversion and then introduced into the inlet of the slag chute. 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 °C, and the viscosity is 0.6 Pa·s.

[0058] (4) The slag is quenched and granulated with a Laval nozzle with a diameter of 3.5 mm to obtain granulated slag beads. The Laval nozzle is located 0.4 m directly below the chute opening, and the gas pressure of the jet is 0.6 MPa. The tail gas is sent to high-temperature conditioning through a gas-solid heat exchange device through a pipeline to supply energy for the crystallization process.

[0059] (5) The granulated slag beads at 800 °C are hot charged and sent to the crystallization furnace through the collection platform for crystallization treatment. The crystallization temperature is 900 °C and the crystallization time is 30 min.

[0060] (6) After crystallization is completed, it is naturally cooled in the air to obtain granulated slag.

[0061] After the granulated slag is subjected to particle size screening, a sample is obtained. The sample picture is as shown inFigure 2 As shown in d, the particle size of the sample is basically less than 4 mm and the sphericity is good. The density of the sample is 3042 kg / m 3 , and the bulk density is 1833 kg / m 3 , the water content is 0.06%, the loss on ignition is 0.04%, the acid consumption value is 5.0 ml, and the performance indicators are excellent.

[0062] Example Five:

[0063] In this example, the crystallization treatment process in Example 1 is removed, and the nickel-iron slag is directly granulated by air quenching to obtain the finished product. To compare the role of the crystallization treatment process in this application, the process is as follows: (1) The raw materials mainly include nickel-iron slag and a conditioning agent. The nickel-iron slag accounts for 90% of the total mass percentage; the conditioning agent accounts for 10% of the total mass percentage. The conditioning agent is a mixture of quartz sand, borax, and fluorite.

[0064] (2) The molten nickel-iron slag and the conditioning agent are kept warm in a conditioning furnace at 1550 °C.

[0065] (3) After conditioning, the liquid slag is divided into multiple streams and then introduced into the inlet of the slag chute. 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 °C, and the viscosity is 0.6 Pa·s.

[0066] (4) The slag is granulated by air quenching using a Laval nozzle with a diameter of 3.5 mm. The Laval nozzle is located 0.4 m directly below the chute opening, and the gas pressure for spraying is 0.6 MPa. After air quenching granulation, granulated slag is obtained, and the tail gas is sent through a gas-solid heat exchange device through a pipeline to the high-temperature conditioning link for energy supply.

[0067] (5) After granulated slag is screened by particle size, a sample is obtained. The sample picture is as shown in Figure 2 e. The particle size of the sample is basically less than 4 mm and the sphericity is good. The density of the non-crystallized sample is 3032 kg / m 3 , and the bulk density is 1753 kg / m 3 , the water content is 0.4%, the loss on ignition is 0.01%, and the acid consumption value is 8.7 ml. 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.

[0068] This application also provides an application of the method for air quenching granulation and crystallization treatment of molten nickel-iron slag, and the application includes preparing foundry sand or petroleum filling agent.

[0069] The above are only the preferred embodiments of the present application. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present application, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. A method for air quenching granulation and crystallization treatment of molten nickel-iron slag, characterized in that, Comprising: Mixing molten nickel-iron slag and a conditioning agent in a mass ratio of 3:1 to 100:0, melting to obtain a liquid slag that meets preset indicators; Successively performing multi-stage shunting and spray granulation on the liquid slag to obtain hot granulated slag beads; Directly performing crystallization treatment on the hot granulated slag beads and cooling to obtain a finished product of granulated slag.

2. The method according to claim 1, wherein 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%.

3. The method according to claim 1, wherein 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 - 1580°C, and the viscosity range is 0.09 Pa·s - 0.8 Pa·s.

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

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

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

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

9. The method according to claim 1, characterized in that The cooling includes any one or more of setting a cooling program with a temperature drop of 4 - 10°C / min, natural cooling in air, and spray cooling.

10. Application of the finished product of granulated slag prepared by the method according to any one of claims 1 - 9 in foundry sand or petroleum filling agent.

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