Method for preparing high nickel-chromium-iron alloy by using electric furnace refining dust and blast furnace dedusting ash

Abstract

The invention belongs to the technical field of collaborative and comprehensive utilization of metallurgical solid waste resources, and particularly relates to a method for preparing a high-nickel ferrochrome alloy from electric furnace refining dust and blast furnace dedusting ash. The method comprises the following steps: uniformly mixing electric furnace refining dust, blast furnace dedusting ash and coking coal, and carrying out hot press molding to obtain a mixed briquette; carrying out high-temperature carbon thermal reduction on the mixed briquette; cooling the high-temperature carbon thermal reduction product under the protection of inert gas to obtain a high-nickel ferrochrome alloy and self-pulverization slag; according to the method for preparing the high-nickel ferrochrome alloy, a flux and a binder are not used. According to the method, the electric furnace refining dust and the blast furnace dedusting ash are combined, and a large amount of C contained in the blast furnace dedusting ash is used for efficiently reducing metal elements such as Fe, Cr and Ni in the electric furnace refining dust, so that the effect of turning waste into wealth is achieved, flux, binder and the like do not need to be added in the process, and the cost is low. And the energy consumption can be reduced while the collaborative utilization of solid waste resources is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of coordinated comprehensive utilization of metallurgical solid waste resources, and specifically relates to a method for preparing high-nickel-chromium iron alloy by utilizing electric furnace refining dust and blast furnace dust removal ash. Background Art

[0002] With the continuous development of the steel industry, stainless steel has also developed into an indispensable material in various modern industries. The production of stainless steel will produce a large amount of electric furnace refining dust. For every ton of stainless steel produced, about 20-30kg of electric furnace refining dust is produced. Electric furnace refining dust contains a large amount of metal elements such as Fe, Cr, Ni, etc. If properly handled, it has a very high recycling value; if improperly handled, it will produce some negative benefits. The most intuitive is that it will cause pollution to the environment in which we live. Take the Cr element in the dust as an example. After long-term stacking, the Cr element will become extremely unstable and easily oxidized to form toxic Cr. 6+ , which pollutes soil and groundwater, endangering human health. Therefore, if electric furnace refining dust can be efficiently recycled and reused, it will not only alleviate the environmental pollution caused by metal elements, but also reduce the supply of raw materials required for stainless steel production, alleviate dependence on imported ore raw materials, save costs, and reduce environmental pollution. Therefore, how to efficiently and harmlessly recycle the valuable metals in electric furnace refining dust and enhance its secondary resource value is currently a relatively important research issue. At the same time, blast furnace dust is also an inevitable solid waste in the production process of the steel industry. Every ton of crude steel produced will produce about 15-20kg of blast furnace dust. Blast furnace dust mainly contains elements such as Fe and C. The instability of blast furnace dust itself makes it highly flammable, and after combustion, it will produce CO2, increasing environmental pressure. At the same time, blast furnace dust also contains harmful metal elements, such as Zn, K and other metal elements. If the content is too high, it will not only be unable to enter the blast furnace for reduction treatment, but stacking will also cause harm to the environment, and it will also greatly increase industrial production costs. This also makes it impossible to effectively utilize the large amount of valuable metal resources such as Fe and C contained in it.

[0003] At present, there are many methods for treating electric furnace refining dust and blast furnace dust, but these methods often have the following problems: (1) A large amount of binders, additives, slag-forming agents and other ingredients need to be added during the preparation of reaction raw materials, which makes the raw material preparation process complicated and consumes a lot of heat energy; (2) Some methods require the addition of nearly half or more coking coal, which consumes a large amount of coking coal and does not conform to the development goal of energy conservation and emission reduction; (3) Some methods use electric furnace refining dust or blast furnace dust to prepare ferroalloys, but their metal recovery rate is low and the metal grade in the alloy is low. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems and provide a new method for preparing high-nickel-chromium-iron alloy using electric furnace refining dust, so as to improve the metal grade of Ni, Cr and Fe in the prepared nickel-chromium-iron alloy, reduce the energy consumption of resource processing and reduce the emission of CO2 during the processing process, and improve the utilization rate of metallurgical solid waste.

[0005] To achieve the above object, the present invention provides a method for preparing a high-nickel-chromium ferroalloy by using electric furnace refining dust and blast furnace dust removal ash, the method comprising: Step 1) Electric furnace refining dust, blast furnace dust, and coking coal are uniformly mixed, and then hot-pressed to obtain mixed briquettes; Step 2) subjecting the mixed compact obtained in step 1) to high-temperature carbothermal reduction; Step 3) Cooling the high-temperature carbon thermal reduction product obtained in step 2) to room temperature under the protection of an inert gas to obtain a mixture of a high-nickel-chromium iron alloy and self-pulverizing slag; The above method for preparing high nickel-chromium iron alloy does not use flux and binder.

[0006] In the above method for preparing high nickel chromium iron alloy, the method for separating the mixture of high nickel chromium iron alloy and self-pulverizing slag can be: sorting magnetic material and non-magnetic material, the magnetic material is high nickel chromium iron alloy, and the non-magnetic material is self-pulverizing slag.

[0007] The reduction of metal oxides is only possible with an appropriate carbon content, and the separation of reduction products is only possible with an appropriate basicity. Based on the calculation of the carbon content and the adjustment of the basicity, as a preferred embodiment, in the above-mentioned method for preparing a high-nickel-chromium ferroalloy using electric furnace refining dust and blast furnace dust, the mass ratio of electric furnace refining dust to blast furnace dust is (70-80):(20-30), and the coking coal content is 5-10% of the total mass of the electric furnace refining dust and blast furnace dust.

[0008] As a preferred solution, the electric furnace refining dust meets at least one of the following conditions: The total iron mass fraction is not less than 31%; The chromium mass fraction is not less than 8%; The nickel mass fraction is not less than 2%.

[0009] The benefit of the electric furnace refining dust satisfying at least one of the above conditions is that it can achieve a high recovery rate of the reduction product and a high recycling value.

[0010] As a preferred solution, the blast furnace dust ash meets at least one of the following conditions: The total iron mass fraction is not less than 29%; The carbon mass fraction shall not be less than 20%.

[0011] The benefits of blast furnace dust that meets at least one of the above conditions are that it can achieve a high recovery rate of reduced products and high recycling value. The high carbon content can provide a reducing agent, reduce the proportion of coking coal, and reduce the amount of coking coal used.

[0012] As a preferred solution, the coking coal meets at least one of the following conditions: The fixed carbon mass fraction is not less than 60%; Ash content not higher than 10%; Volatile matter does not exceed 30%; The colloid layer index is not less than 12mm.

[0013] The benefit of coking coal meeting at least one of the above conditions is that the coking coal has a high carbon content, which can provide more reducing agents; the high colloidal layer index can provide more colloidal bodies during the hot pressing process, improve the compressive strength of the mixed briquette, and meet the strength requirements of subsequent processing.

[0014] As a preferred solution, the electric furnace refined dust is obtained by at least one of drying, crushing, and screening through a 200-mesh sieve.

[0015] As a preferred solution, the blast furnace dust ash is obtained by at least one of drying, crushing, and screening through a 200-mesh sieve.

[0016] As a preferred solution, the coking coal is obtained by at least one of drying, crushing, and screening through a 200-mesh sieve.

[0017] As a preferred embodiment, step 2) of the above method for preparing high-nickel-chromium ferroalloy using electric furnace refining dust and blast furnace dust ash is carried out under the protection of inert gas.

[0018] As a preferred embodiment, in step 3) of the above-mentioned method for preparing a high-nickel-chromium ferroalloy using electric furnace refining dust and blast furnace dust removal ash, the cooling rate under inert gas protection is 18-23°C / min. This is because controlling the cooling rate appropriately facilitates the pulverization and separation of the reduction product, thereby increasing the yield of the high-nickel-chromium ferroalloy. Furthermore, cooling under an inert atmosphere prevents oxidation of the reduction product.

[0019] As a preferred embodiment, in step 1) of the method for preparing a high-nickel-chromium ferroalloy using electric furnace refining dust and blast furnace dust removal ash, the operating conditions of the hot pressing satisfy at least one of the following conditions: Hot pressing pressure is 20-40MPa; Hot pressing temperature is 200-300℃; The holding time is 0.5-4min.

[0020] The reason is that coking coal produces colloids at high temperatures. By maintaining pressure for a certain period of time, the colloids can fully contact and bond with the raw material powder particles, thereby improving the compressive strength of the mixed briquette to meet the requirements of subsequent reduction.

[0021] As a preferred embodiment, in step 2) of the method for preparing a high-nickel-chromium ferroalloy using electric furnace refining dust and blast furnace dust removal ash, the operating conditions of the high-temperature carbothermal reduction meet at least one of the following conditions: The temperature of high-temperature carbothermal reduction is 1300-1500℃; The time for high-temperature carbothermal reduction is 30-60 min; The CO2 partial pressure of high-temperature carbothermal reduction does not exceed 10%.

[0022] Controlling the CO2 gas partial pressure to no more than 10% can ensure the CO gas partial pressure and ensure the provision of a reducing atmosphere.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides a method for preparing a high-nickel-chromium-iron alloy using electric furnace refining dust and blast furnace dust ash. The method uses solid waste electric furnace refining dust, blast furnace dust ash, and relatively low-addition coking coal as raw materials, and obtains a high-nickel-chromium-iron alloy with a high metal grade through a high-temperature carbon thermal reduction process. Due to the synergistic reduction effect of the blast furnace dust ash and solid waste electric furnace refining dust, the reduction efficiency of the entire preparation process is greatly improved. Without adding any flux or binder, the reduction product alloy particles and self-pulverizing slag can be efficiently separated by cooling to room temperature in an inert atmosphere, thereby reducing energy consumption and production costs. Furthermore, the method for preparing a high-nickel-chromium-iron alloy using electric furnace refining dust and blast furnace dust ash provided by the present invention uses a relatively small amount of coking coal, generates less volatile matter and ash during the reduction process, and has relatively low environmental pollution. Furthermore, the self-pulverizing slag produced does not contain metals such as Ni, Cr, and Fe, further reducing environmental pollution. At the same time, the method provided by the present invention for preparing high-nickel-chromium iron alloy using electric furnace refining dust and blast furnace dust removal ash has a simple process flow and low requirements for process conditions such as reaction temperature. It can save resources, protect the environment and reduce emissions, and has high economic benefits, and has broad industrial application prospects.

[0024] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1The present invention is a process flow chart of a specific embodiment of a method for preparing high-nickel-chromium ferroalloy by utilizing electric furnace refining dust and blast furnace dust removal ash. DETAILED DESCRIPTION

[0026] In the following description, exemplary embodiments according to the present invention will be described in more detail. However, these exemplary embodiments can be implemented in a variety of different forms and should not be construed as being limited to the embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art.

[0027] In the examples and comparative examples of the present invention, the electric furnace refining dust was sourced from a domestic stainless steel manufacturer; the blast furnace dust was sourced from a domestic stainless steel manufacturer; and the coking coal was sourced from a domestic stainless steel manufacturer. The total iron content of the electric furnace refining dust was no less than 31% by mass; the chromium content was no less than 8% by mass; and the nickel content was no less than 2% by mass. The total iron content of the blast furnace dust was no less than 29% by mass; and the carbon content was no less than 20% by mass. The coking coal had a fixed carbon content of no less than 60% by mass; an ash content no greater than 10%; a volatile matter content no greater than 30%; and a colloidal layer index no less than 12 mm.

[0028] In the embodiments and comparative examples of the present invention, separation of magnetic material and non-magnetic material refers to separation of a mixture of high-nickel-chromium-iron alloy and self-pulverizing slag by magnetic adsorption, wherein the magnetic material is high-nickel-chromium-iron alloy and the non-magnetic material is self-pulverizing slag.

[0029] In the examples and comparative examples of the present invention, the inert gas used is argon.

[0030] Example 1 This embodiment provides a method for preparing high-nickel-chromium ferroalloy by utilizing electric furnace refining dust and blast furnace dust removal ash.

[0031] Figure 1 The process flow chart of a specific embodiment of the method for preparing high nickel-chromium ferroalloy using electric furnace refining dust and blast furnace dust ash of the present invention is shown. Figure 1 The separation method here refers to the separation of magnetic and non-magnetic materials. Figure 1 : Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 70:30:10 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under a hot pressing pressure of 30 MPa, a hot pressing temperature of 200°C and a holding time of 1 minute to obtain a mixed briquette.

[0032] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to a high-temperature carbothermal reduction and cooling process. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag. The high-temperature reduction temperature was 1400°C, the reduction time was 40 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 20°C / min. The resulting high-grade nickel-chromium iron alloy contained 62% by weight of Fe, 13% by weight of Cr, and 4% by weight of Ni. The harmful components P and S were both less than 0.05% by weight, and the proportion of particles ≤74 μm (below 200 mesh) in the self-pulverizing slag exceeded 70%. The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 91%, 90%, and 92%, respectively.

[0033] Example 2 This embodiment provides a method for preparing high-nickel-chromium ferroalloy by utilizing electric furnace refining dust and blast furnace dust removal ash.

[0034] Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 75:25:5 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under the conditions of a hot pressing pressure of 35 MPa, a hot pressing temperature of 200°C and a holding time of 1 minute to obtain a mixed briquette.

[0035] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to high-temperature carbothermal reduction and cooling. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag, respectively. The high-temperature reduction temperature was 1450°C, the reduction time was 45 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 20°C / min. The resulting high-grade nickel-chromium iron alloy contained 60% Fe, 12% Cr, and 4% Ni by mass. The harmful components P and S were both less than 0.05% by mass. Over 70% of the self-pulverizing slag contained particles ≤74 μm (below 200 mesh). The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 91%, 90%, and 91%, respectively.

[0036] Example 3 This embodiment provides a method for preparing high-nickel-chromium ferroalloy by utilizing electric furnace refining dust and blast furnace dust removal ash.

[0037] Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 80:20:5 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under the conditions of a hot pressing pressure of 35 MPa, a hot pressing temperature of 200°C and a holding time of 1 minute to obtain a mixed briquette.

[0038] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to high-temperature carbothermal reduction and cooling. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag, respectively. The high-temperature reduction temperature was 1450°C, the reduction time was 50 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 20°C / min. The resulting high-grade nickel-chromium iron alloy contained 58% by weight Fe, 12% by weight Cr, and 4% by weight Ni. The harmful components P and S were both less than 0.05% by weight, and the proportion of particles ≤74 μm (below 200 mesh) in the self-pulverizing slag exceeded 70%. The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 90%, 89%, and 91%, respectively.

[0039] Example 4 This embodiment provides a method for preparing high-nickel-chromium ferroalloy by utilizing electric furnace refining dust and blast furnace dust removal ash.

[0040] Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 80:20:5 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under the conditions of a hot pressing pressure of 40 MPa, a hot pressing temperature of 200°C and a holding time of 2 minutes to obtain a mixed briquette.

[0041] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to a high-temperature carbothermal reduction and cooling process. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag, respectively. The high-temperature reduction temperature was 1450°C, the reduction time was 55 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 20°C / min. The resulting high-grade nickel-chromium iron alloy contained 59% by weight Fe, 12% by weight Cr, and 5% by weight Ni. The harmful components P and S were both less than 0.05% by weight. Over 70% of the self-pulverizing slag contained particles ≤74 μm (below 200 mesh). The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 90%, 90%, and 92%, respectively.

[0042] Example 5 This embodiment provides a method for preparing high-nickel-chromium ferroalloy by utilizing electric furnace refining dust and blast furnace dust removal ash.

[0043] Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 75:25:10 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under a hot pressing pressure of 40 MPa, a hot pressing temperature of 200°C and a holding time of 3 minutes to obtain a mixed briquette.

[0044] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to a high-temperature carbothermal reduction and cooling process. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag. The high-temperature reduction temperature was 1500°C, the reduction time was 40 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 20°C / min. The resulting high-grade nickel-chromium iron alloy contained 59% by weight Fe, 11% by weight Cr, and 4% by weight Ni. The harmful components P and S were both less than 0.05% by weight, and the proportion of particles ≤74 μm (below 200 mesh) in the self-pulverizing slag exceeded 70%. The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 91%, 89%, and 91%, respectively.

[0045] Comparative Example 1 The difference from Example 1 is that blast furnace dust is not used, and the mass ratio of electric furnace refined dust to coking coal is 100:10.

[0046] The electric furnace refined dust and coking coal with a mass ratio of 100:10 were fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under the conditions of a hot pressing pressure of 30 MPa, a hot pressing temperature of 200°C, and a holding time of 1 minute to obtain a mixed briquette.

[0047] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to a high-temperature carbothermal reduction and cooling process. After cooling to room temperature, a mixed reduction product of high-nickel-chromium-iron alloy and harmless slag was obtained. The high-temperature reduction temperature was 1400°C, the reduction time was 40 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction did not exceed 10%, and the cooling rate was 20°C / min. The resulting reduction product could not be separated from the high-grade nickel-chromium-iron alloy and slag phases by sorting magnetic and non-magnetic materials. The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 83%, 81%, and 86%, respectively.

[0048] Comparative Example 2 The difference from Example 2 is that the mass ratio of electric furnace refining dust to blast furnace dust is 85:15.

[0049] Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 85:15:5 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under a hot pressing pressure of 35 MPa, a hot pressing temperature of 200°C and a holding time of 1 minute to obtain a mixed briquette.

[0050] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to a high-temperature carbothermal reduction and cooling process. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag, respectively. The high-temperature reduction temperature was 1450°C, the reduction time was 45 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 20°C / min. The resulting high-grade nickel-chromium iron alloy contained 58% by weight Fe, 10% by weight Cr, and 3% by weight Ni. The harmful components P and S were both less than 0.05% by weight, and the proportion of particles ≤74 μm (below 200 mesh) in the self-pulverizing slag exceeded 40%. The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 89%, 87%, and 87%, respectively.

[0051] Comparative Example 3 The difference from Example 3 is that the mass ratio of electric furnace refining dust to blast furnace dust is 65:35.

[0052] Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 65:35:5 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under a hot pressing pressure of 35 MPa, a hot pressing temperature of 200°C and a holding time of 1 minute to obtain a mixed briquette.

[0053] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to a high-temperature carbothermal reduction and cooling process. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag, respectively. The high-temperature reduction temperature was 1450°C, the reduction time was 50 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 20°C / min. The resulting high-grade nickel-chromium iron alloy contained 56% by weight of Fe, 11% by weight of Cr, and 3% by weight of Ni. The harmful components P and S were both less than 0.05% by weight, and the proportion of particles ≤74 μm (below 200 mesh) in the self-pulverizing slag exceeded 60%. The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 88%, 87%, and 90%, respectively.

[0054] Comparative Example 4 The difference from Example 4 is that the cooling rate under the protection of inert gas is 15° C. / min.

[0055] Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 80:20:5 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under the conditions of a hot pressing pressure of 40 MPa, a hot pressing temperature of 200°C and a holding time of 2 minutes to obtain a mixed briquette.

[0056] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to high-temperature carbothermal reduction and cooling. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag. The high-temperature reduction temperature was 1450°C, the reduction time was 55 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 15°C / min. The resulting high-grade nickel-chromium iron alloy contained 60% Fe, 12% Cr, and 5% Ni by mass. The harmful components P and S were both less than 0.05% by mass. The proportion of particles ≤74 μm (below 200 mesh) in the self-pulverizing slag exceeded 75%. The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 92%, 90%, and 92%, respectively.

[0057] Comparative Example 5 The difference from Example 5 is that the cooling rate under the protection of inert gas is 25° C. / min.

[0058] Electric furnace refined dust, blast furnace dust removal ash and coking coal with a mass ratio of 75:25:10 are fully dried, crushed, sieved through a 200-mesh sieve, mixed evenly, and then pressed under a hot pressing pressure of 40 MPa, a hot pressing temperature of 200°C and a holding time of 3 minutes to obtain a mixed briquette.

[0059] The crucible containing the mixed compacts was placed in a high-temperature furnace and, under inert gas protection, subjected to a high-temperature carbothermal reduction and cooling process. After cooling to room temperature, magnetic and non-magnetic materials were separated to produce a high-nickel-chromium iron alloy and harmless self-pulverizing slag, respectively. The high-temperature reduction temperature was 1500°C, the reduction time was 40 minutes, the CO2 partial pressure during the high-temperature carbothermal reduction was no more than 10%, and the cooling rate was 25°C / min. The resulting high-grade nickel-chromium iron alloy contained 57% Fe, 10% Cr, and 4% Ni by mass. The harmful components P and S were both less than 0.05% by mass. The proportion of particles ≤74 μm (below 200 mesh) in the self-pulverizing slag exceeded 60%. The metal recoveries of Fe, Cr, and Ni in the overall electric furnace refining dust and blast furnace dust removal ash were 90%, 88%, and 91%, respectively.

[0060] The main parameters of Examples 1-5 and Comparative Examples 1-5 are shown in Table 1: Table 1

[0061] In Table 1, the parameters and their units are: hot pressing pressure (MPa), hot pressing temperature (°C), holding time (min), high-temperature reduction temperature (°C), reduction time (min), and cooling rate (°C / min).

[0062] From Table 1 we can see that: 1) Comparative Example 1 differs from Example 1 only in that blast furnace dust is not used. In this case, Comparative Example 1 fails to separate the high-grade nickel-chromium-iron alloy from the slag phase; the metal recoveries of Fe, Cr, and Ni drop from 91%, 90%, and 92% to 83%, 81%, and 86%, respectively.

[0063] 2) Comparative Example 2 differs only in that the mass ratio of electric furnace refining dust to blast furnace dust is changed from 75:25 to 85:15. The fraction of particles ≤74 μm in the self-pulverized slag decreases from 70% to 40%, and the metal recoveries of Fe, Cr, and Ni decrease from 91%, 90%, and 91% to 89%, 87%, and 87%, respectively.

[0064] 3) Comparative Example 3 differs from Example 3 only in that the mass ratio of electric furnace refining dust to blast furnace dust is changed from 80:20 to 65:35. The fraction of particles ≤74 μm in the self-pulverized slag decreases from 70% to 60%, and the metal recoveries of Fe, Cr, and Ni decrease from 90%, 89%, and 91% to 88%, 87%, and 90%, respectively.

[0065] 4) Comparative Example 4 differs from Example 4 only in that the cooling rate is reduced from 20°C / min to 15°C / min. Although the fraction of the self-pulverized slag with a particle size ≤74 μm in Comparative Example 4 is higher than that in Example 4, and the metal recovery rate is also slightly higher than that in Example 4, the cooling rate in Comparative Example 4 is too low, resulting in an excessively long recovery process and high energy consumption, rendering the recovery process meaningless.

[0066] 5) The only difference between Comparative Example 5 and Example 5 is that the cooling rate is reduced from 20°C / min to 25°C / min, the fraction of the pulverized slag with a particle size of ≤74 μm is reduced from 70% to 60%, and the metal recoveries of Fe, Cr, and Ni are reduced from 91%, 89%, and 91% to 90%, 88%, and 91%, respectively.

[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing high nickel-chromium ferroalloy using electric furnace refining dust and blast furnace dust removal ash, characterized in that: The method includes: Step 1) Electric furnace refining dust, blast furnace dust, and coking coal are uniformly mixed, and then hot-pressed to obtain mixed briquettes; Step 2) subjecting the mixed compact obtained in step 1) to high-temperature carbothermal reduction; Step 3) Cooling the high-temperature carbon thermal reduction product obtained in step 2) to room temperature under the protection of an inert gas to obtain a mixture of a high-nickel-chromium iron alloy and self-pulverizing slag; The above method for preparing high nickel-chromium iron alloy does not use flux and binder; The mass ratio of electric furnace refining dust and blast furnace dust is (70-80): (20-30); The content of coking coal is 5-10% of the total mass of electric furnace refining dust and blast furnace dust; The carbon mass fraction of the blast furnace dust is not less than 20%.

2. The method for preparing high nickel-chromium ferroalloy by using electric furnace refining dust and blast furnace dust ash according to claim 1, characterized in that: Also includes: Step 4) Separating the mixture of high nickel chromium iron alloy and self-pulverizing slag: sorting magnetic materials and non-magnetic materials, the magnetic materials are high nickel chromium iron alloy, and the non-magnetic materials are self-pulverizing slag.

3. The method for preparing high nickel-chromium ferroalloy by using electric furnace refining dust and blast furnace dust ash according to claim 1, characterized in that: The electric furnace refining dust meets at least one of the following conditions: The total iron mass fraction is not less than 31%; The chromium mass fraction is not less than 8%; The nickel mass fraction is not less than 2%.

4. The method for preparing high nickel-chromium ferroalloy by using electric furnace refining dust and blast furnace dust ash according to claim 1, characterized in that: The total iron mass fraction of the blast furnace dust is not less than 29%.

5. The method for preparing high nickel-chromium ferroalloy by utilizing electric furnace refining dust and blast furnace dust ash according to claim 1, characterized in that: The coking coal meets at least one of the following conditions: The fixed carbon mass fraction is not less than 60%; Ash content not higher than 10%; Volatile matter does not exceed 30%; The colloid layer index is not less than 12mm.

6. The method for preparing high nickel-chromium ferroalloy by using electric furnace refining dust and blast furnace dust ash according to claim 1, characterized in that: At least one of the following conditions must be met: The electric furnace refined dust is obtained by at least one of drying, crushing, and screening through a 200-mesh sieve; The blast furnace dust ash is obtained by at least one of drying, crushing, and screening through a 200-mesh sieve; The coking coal is obtained through at least one of drying, crushing, and screening through a 200-mesh sieve.

7. The method for preparing high nickel-chromium ferroalloy by using electric furnace refining dust and blast furnace dust ash according to claim 1, characterized in that: In step 3), the cooling rate under the protection of inert gas is 18-23°C / min.

8. The method for preparing high nickel-chromium ferroalloy by using electric furnace refining dust and blast furnace dust ash according to claim 1, characterized in that: In step 1), the operating conditions of the hot pressing molding meet at least one of the following conditions: Hot pressing pressure is 20-40MPa; Hot pressing temperature is 200-300℃; The holding time is 0.5-4min.

9. The method for preparing high nickel-chromium ferroalloy by using electric furnace refining dust and blast furnace dust ash according to claim 1, characterized in that: In step 2), the operating conditions of the high-temperature carbothermal reduction meet at least one of the following conditions: The temperature of high-temperature carbothermal reduction is 1300-1500℃; The time for high-temperature carbothermal reduction is 30-60 min; The CO2 partial pressure of high-temperature carbothermal reduction does not exceed 10%.

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