Method for preparing ferrochrome through chromium slag suspension roasting pre-reduction-electric furnace smelting

Abstract

A method for preparing ferrochrome through chromium slag suspension roasting pre-reduction-electric furnace smelting belongs to the field of mineral processing, and comprises the following steps: crushing chromium slag, and preheating to obtain a preheated material; the preheated materials are fed into a suspension roasting furnace, N2 gas is introduced into a furnace body, and the materials in a system are dehydrated under the action of high temperature; h2 and N2 are introduced into the suspension roasting furnace, the materials are in a suspension state under the action of ascending air flow, roasted product roasted sand is obtained and directly fed into the electric furnace through a pipeline for melting separation, ferrochrome obtained after melting separation of the electric furnace enters a cooling tower to be cooled and then is stored in a storage bin, and tailings enter a slag pool to be cooled and then are placed in a slag storage bin. The suspension magnetization roasting technology provided by the invention has the characteristic of large gas-solid contact area, the roasting time is greatly shortened, the roasting efficiency is improved, and the cost is reduced.

Description

Technical Field

[0001] The invention belongs to the field of mineral processing, and in particular relates to a method for preparing ferrochrome alloy by suspended roasting pre-reduction of chromium slag and then smelting in an electric furnace. Background Art

[0002] Chromium slag is a solid waste produced during the preparation of chromium compounds using chromite as raw material. The main hazards of these waste slags come from their toxicity, alkalinity and hydration expansion properties. Chromium slag contains sodium chromate and calcium chromate, which are the basic components of its toxicity. Firstly, the hexavalent chromium (Cr(VI)) in these compounds is highly oxidizing and corrosive and destructive to organisms, making it toxic. Secondly, calcium chromate is also considered to be carcinogenic.

[0003] Chromium slag is usually piled in the open air, and is affected by rain and snow, causing the hexavalent chromium in it to be dissolved and seep into groundwater, or enter rivers and lakes, thereby polluting the environment. In severely polluted areas, the concentration of hexavalent chromium in water may be as high as tens of milligrams per liter, far exceeding the drinking water standard. Hexavalent chromium, chromium compounds, and chromium compound aerosols are harmful to human and animal health in various forms. In addition, through weathering, chromium in the soil may be oxidized into soluble complex anions, and then enter surface water or groundwater through leaching. High concentrations of soil chromium inhibit the nitrification of organic matter and accumulate in plants. Both trivalent chromium and hexavalent chromium are lethal to aquatic organisms. In water bodies, trivalent chromium is mainly adsorbed on solid matter and exists in sediments, while hexavalent chromium is mostly soluble in water. Hexavalent chromium is relatively stable in water, but can be reduced to trivalent chromium under anaerobic conditions. Trivalent chromium salts can be hydrolyzed in neutral or weakly alkaline solutions to form water-insoluble chromium hydroxide and deposit on the bottom of the water. Generally speaking, natural water contains only trace amounts of chromium, which will be deposited on the seabed after flowing into the ocean through rivers. The chromium concentration in seawater is usually less than 1 ppb. Experiments have shown that when the chromium concentration in water is 1 ppm, it will stimulate crop growth; when it is 1 to 10 ppm, it will slow down crop growth; and when the concentration reaches 100 ppm, it will almost stop the growth of crops and put them in a dying state. The presence of chromium compounds in wastewater will reduce the efficiency of biochemical treatment of wastewater and cause serious damage to water resources.

[0004] Chromium has broad application prospects in many industries. Chromite is the main raw material of the chemical industry. Through processing and manufacturing, various chromium salts can be produced. Chromium salts are one of the important categories of inorganic salts, and their uses are wide-ranging, covering many fields. The main applications include electroplating, leather tanning, textile printing and dyeing, pharmaceutical preparation, fuel additives, catalyst preparation, oxidants, match manufacturing, and metal corrosion inhibitors.

[0005] In addition, metallic chromium is also considered one of the key materials in electroplating metals. In many cases, metal parts need to be covered with a layer of chromium film, which becomes the outermost protective layer. The thinner the chromium film, the more tightly it can adhere to the metal surface. For example, the chromium plating on the inner wall of some artillery barrels and gun barrels may be only a few thousandths of a millimeter thick. Although these chromium layers will experience extremely high stress and wear after firing hundreds of shells or bullets, they still remain on the surface of the parts. Without the physical properties provided by this layer of chromium plating, the service life of the parts will be greatly shortened due to wear and corrosion. Chromic acid and chromates are used as oxidants to oxidize certain compounds to higher-level products in organic synthesis. In addition, chromium salts are also used in the preparation of catalysts to promote various important reactions, such as oxidation, hydrogenation and hydrogenation reactions. Chromium salts can be used as intermediates for the preparation of certain drugs, and can also be used as stabilizers and color correctors for drugs.

[0006] In addition, the chromium content in stainless steel and other alloys improves the corrosion resistance and biocompatibility of medical devices, making it a common material for surgical instruments and implants. Chromium salts can be used in wastewater treatment to remove heavy metal ions and other pollutants from wastewater. Through methods such as precipitation, ion exchange or reduction, chromium salts can help purify wastewater to meet environmental standards, while also recovering and reusing chromium. Chromium salts are widely used in the preparation of anti-corrosion coatings and metal corrosion inhibitors. These coatings and additives can protect metal surfaces from corrosion by atmospheric oxygen, water and chemicals, thereby extending the service life of metal products.

[0007] Chromium salts also play a role in the energy sector. Chromates and lead chromates are used to produce batteries, such as lead-acid batteries, for backup power supplies and energy storage systems. Chromium salts are used as food additives in the food industry, mainly to adjust the color and stability of food. Chromium is also a cofactor for some enzymes and is essential for biochemical processes in some biological systems. Therefore, making full use of chromium resources plays an important role in social development and people's lives. Chromium slag detoxification is to reduce the toxic hexavalent chromium in the slag to non-toxic trivalent chromium or zero-valent chromium. There are mainly dry detoxification, wet detoxification and microbial detoxification technologies. Among them, dry detoxification technology mainly uses coal, sulfur and other reducing agents to detoxify chromium slag under high-temperature gas-solid conditions; wet detoxification technology mainly uses ferrous sulfate, sodium sulfide and other reducing agents to detoxify chromium slag under liquid-solid slurry heating conditions; microbial detoxification technology uses oxidation-resistant, alkali-resistant and salt-resistant microorganisms to detoxify chromium slag. Summary of the invention

[0008] The present invention aims to solve the problem that the chromium slag produced in industrial production is difficult to be effectively utilized and harms the environment. The present invention proposes to use the reducing atmosphere in the suspension roasting system to remove the Cr in the chromium slag. 6+ Converted into non-toxic Cr 3+or Cr, and the whole reaction is carried out in a high temperature environment, which can effectively reduce the alkalinity of the chromium slag and transform the hazardous chromium slag into traditional solid waste. At the same time, the suspended roasting pre-reduction electric furnace smelting process recycles a large amount of iron and chromium elements in the chromium slag, and can produce low-chromium iron products and harmless smelting slag, realizing the maximum resource utilization of chromium slag, avoiding resource waste and increasing process benefits.

[0009] A method for preparing ferrochrome alloy by chromium slag suspension roasting pre-reduction-electric furnace smelting, specifically comprising the following steps:

[0010] (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating to obtain preheated materials; the smoke discharged from the cyclone separator in the raw ore is cooled by a cooler, collected by a bag dust collector, and then fed into a suspension roasting furnace, and the smoke is discharged through a chimney;

[0011] (2) The preheated materials are fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, the materials in the system are dehydrated under the action of high temperature;

[0012] (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, the reduction roasting temperature is 700-900° C., the time is 15-30 min, and the roasting product calcine is obtained;

[0013] (4) feeding the roasted sand directly into an electric furnace through a pipeline for melting to obtain ferrochrome alloy and tailings. The temperature of the electric furnace is 1000-1200° C., and the roasted sand is retained for 1-2 hours;

[0014] (5) After melting in the electric furnace, the ferrochrome alloy enters the cooling tower for cooling and is then stored in the storage bin. The tailings enter the slag pool for cooling and is then placed in the slag storage bin.

[0015] in:

[0016] In the step (1), the components in the chromium slag are calculated by weight percentage: Cr2O6 2.5-3.8%, TFe 18-23%, SiO2 12-24%, Al2O3 6-9%, and MgO 28-36%.

[0017] In the step (1), the high-temperature flue gas after gas-solid separation in the cyclone separator is fed into the cyclone preheater to preheat the material.

[0018] In the step (2), the temperature of the material after preheating by the cyclone preheater is 400-600°C.

[0019] In the step (2), the temperature at which the material is dehydrated in the suspension roasting furnace is 700-900° C., and the dehydration reaction lasts for 5-10 minutes.

[0020] In the step (3), the main chemical reaction formula of the material in the suspension roasting furnace is:

[0021] Cr2O6+3H2(g)=Cr2O3+3H2O(g)

[0022] In the step (5), the temperature of the material after passing through the cooling tower and the slag pool is 20-50°C.

[0023] The ferrochrome alloy prepared by the method has, by weight percentage, the following contents: 9-12% Cr2O3, 35-40% Fe2O3, 2-4% SiO2, 30-36% Al2O3 and 12-15% MgO.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The heat source required for the preheating process in the suspension roasting system of the present invention can make full use of the high-temperature gas already existing in the factory, thereby avoiding energy waste.

[0026] (2) The suspended magnetization roasting technology provided by the present invention has the characteristics of large gas-solid contact area, which greatly shortens the roasting time, improves the roasting efficiency and reduces the cost.

[0027] (3) In the roasting process, the present invention uses high-temperature roasted sand to enter the furnace, thereby reducing the energy consumption of the electric furnace.

[0028] (4) In the process of producing low-chromium iron in an electric furnace, the products obtained by the present invention include vanadium slag and low-chromium iron. The obtained vanadium slag can be sold to steel companies for smelting and preparing vanadium alloys and metallic vanadium to increase process benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the process flow of preparing ferrochrome by suspended roasting pre-reduction of chromium slag and electric furnace smelting according to the present invention. DETAILED DESCRIPTION

[0030] Example 1

[0031] The chromium slag used in the embodiment of the present invention contains 2.8% Cr2O6, 20.4% TFe, 16.2% SiO2, 7.5% Al2O3 and 29.3% MgO by weight.

[0032] A method for preparing ferrochrome by suspended roasting pre-reduction of chromium slag and electric furnace smelting, the process flow chart of which is as follows: Figure 1 As shown, the specific steps include:

[0033] (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating to obtain preheated materials; the smoke discharged from the cyclone separator in the raw ore is cooled by a cooler, collected by a bag dust collector and then fed into a suspension roasting furnace, the smoke is discharged through a chimney, and the high-temperature smoke after gas-solid separation in the cyclone separator is fed into a cyclone preheater to preheat the materials;

[0034] (2) The temperature of the material after preheating by the cyclone preheater is 450°C. The preheated material is fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, high-temperature protective flue gas is generated in the system. At the same time, the material will be dehydrated under the action of the high-temperature gas. The temperature is 750°C and the duration is 8 minutes;

[0035] (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, and the reduction roasting temperature is 700° C. for 25 min to obtain a roasted product, calcine;

[0036] (4) feeding the roasted sand directly into an electric furnace through a pipeline for melting to obtain ferrochrome alloy and tailings. The temperature of the electric furnace is 1000° C. and the roasted sand is retained for 1.5 hours;

[0037] (5) After melting in the electric furnace, the ferrochrome enters the cooling tower. The material temperature after cooling is 45°C. After cooling, it is stored in the storage bin. The tailings enter the slag pool and are cooled to room temperature before being placed in the slag storage bin.

[0038] The ferrochrome prepared in this embodiment has, by weight percentage, 10.27% Cr2O3, 38.26% Fe2O3, 2.56% SiO2, 31.55% Al2O3 and 13.49% MgO.

[0039] Example 2

[0040] The chromium slag used in the embodiment of the present invention contains 2.5% Cr2O6, 18.7% TFe, 13.3% SiO2, 6.4% Al2O3 and 28.5% MgO by weight.

[0041] A method for preparing ferrochrome by suspended roasting pre-reduction of chromium slag and electric furnace smelting, specifically comprising the following steps:

[0042] (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating to obtain preheated materials; the smoke discharged from the cyclone separator in the raw ore is cooled by a cooler, collected by a bag dust collector and then fed into a suspension roasting furnace, the smoke is discharged through a chimney, and the high-temperature smoke after gas-solid separation in the cyclone separator is fed into a cyclone preheater to preheat the materials;

[0043] (2) The temperature of the material after preheating by the cyclone preheater is 500°C. The preheated material is fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, high-temperature protective flue gas is generated in the system. At the same time, the material will be dehydrated under the action of the high-temperature gas. The temperature is 790°C and the duration is 7 minutes;

[0044] (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, and the reduction roasting temperature is 750° C. for 20 min to obtain a roasted product, calcine;

[0045] (4) The roasted sand is directly fed into an electric furnace through a pipeline for melting to obtain ferrochrome alloy and tailings. The temperature of the electric furnace is 1100° C. and the roasted sand is retained for 1.2 h.

[0046] (5) After melting in the electric furnace, the ferrochrome enters the cooling tower. The material temperature after cooling is 40°C. After cooling, it is stored in the storage bin. The tailings enter the slag pool and are cooled to room temperature before being placed in the slag storage bin.

[0047] In the ferrochrome prepared in this embodiment, by weight percentage, the Cr2O3 content is 11.86%, the Fe2O3 content is 38.74%, the SiO2 content is 3.82%, the Al2O3 content is 31.61%, and the MgO content is 14.01%.

[0048] Example 3

[0049] The chromium slag used in the embodiment of the present invention contains 3.6% Cr2O6, 22.4% TFe, 18.2% SiO2, 8.5% Al2O3 and 31.3% MgO by weight.

[0050] A method for preparing ferrochrome by suspended roasting pre-reduction of chromium slag and electric furnace smelting, specifically comprising the following steps:

[0051] (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating to obtain preheated materials; the smoke discharged from the cyclone separator in the raw ore is cooled by a cooler, collected by a bag dust collector and then fed into a suspension roasting furnace, the smoke is discharged through a chimney, and the high-temperature smoke after gas-solid separation in the cyclone separator is fed into a cyclone preheater to preheat the materials;

[0052] (2) The temperature of the material after preheating by the cyclone preheater is 600°C. The preheated material is fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, high-temperature protective flue gas is generated in the system. At the same time, the material will be dehydrated under the action of the high-temperature gas. The temperature is 850°C and the duration is 6 minutes;

[0053] (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, and the reduction roasting temperature is 800° C. for 15 min to obtain a roasted product, calcine;

[0054] (4) feeding the roasted sand directly into an electric furnace through a pipeline for melting to obtain ferrochrome alloy and tailings. The temperature of the electric furnace is 1200° C. and the roasted sand is kept for 1 hour.

[0055] (5) After melting in the electric furnace, the ferrochrome enters the cooling tower. The material temperature after cooling is 38°C. After cooling, it is stored in the storage bin. The tailings enter the slag pool and are cooled to room temperature before being placed in the slag storage bin.

[0056] In the ferrochrome prepared in this embodiment, by weight percentage, the Cr2O3 content is 11.49%, the Fe2O3 content is 37.44%, the SiO2 content is 3.85%, the Al2O3 content is 35.75%, and the MgO content is 13.66%.

[0057] Example 4

[0058] The chromium slag used in the embodiment of the present invention contains 2.76% Cr2O6, 20.42% TFe, 19.24% SiO2, 8.71% Al2O3 and 30.49% MgO by weight.

[0059] A method for preparing ferrochrome by suspended roasting pre-reduction of chromium slag and electric furnace smelting, specifically comprising the following steps:

[0060] (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating to obtain preheated materials; the smoke discharged from the cyclone separator in the raw ore is cooled by a cooler, collected by a bag dust collector and then fed into a suspension roasting furnace, the smoke is discharged through a chimney, and the high-temperature smoke after gas-solid separation in the cyclone separator is fed into a cyclone preheater to preheat the materials;

[0061] (2) The temperature of the material after preheating by the cyclone preheater is 518°C. The preheated material is fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, high-temperature protective flue gas is generated in the system. At the same time, the material will be dehydrated under the action of the high-temperature gas. The temperature is 734°C and the duration is 8 minutes;

[0062] (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, and the reduction roasting temperature is 826° C. for 18 min to obtain a roasted product, calcine;

[0063] (4) The roasted sand is directly fed into an electric furnace through a pipeline for melting to obtain ferrochrome alloy and tailings. The temperature of the electric furnace is 1175° C. and the roasted sand is retained for 1.14 h.

[0064] (5) After melting in the electric furnace, the ferrochrome enters the cooling tower. The material temperature after cooling is 27.42°C. After cooling, it is stored in the storage bin. The tailings enter the slag pool and are cooled to room temperature before being placed in the slag storage bin.

[0065] In the ferrochrome prepared in this embodiment, by weight percentage, the Cr2O3 content is 9.26%, the Fe2O3 content is 35.83%, the SiO2 content is 2.08%, the Al2O3 content is 35.71%, and the MgO content is 13.85%.

[0066] Example 5

[0067] The chromium slag used in the embodiment of the present invention contains 2.74% Cr2O6, 20.33% TFe, 20.83% SiO2, 8.22% Al2O3 and 34.28% MgO by weight.

[0068] A method for preparing ferrochrome by suspended roasting pre-reduction of chromium slag and electric furnace smelting, specifically comprising the following steps:

[0069] (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating. The smoke discharged from the cyclone separator in the raw ore is cooled in a cooler, collected by a bag dust collector, and then fed into a suspension roasting furnace. The smoke is discharged through a chimney. The high-temperature smoke after gas-solid separation in the cyclone separator is fed into a cyclone preheater to preheat the material;

[0070] (2) The temperature of the material after preheating by the cyclone preheater is 498°C. The preheated material is fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, high-temperature protective flue gas is generated in the system. At the same time, the material will be dehydrated under the action of the high-temperature gas. The temperature is 798°C and the duration is 7.5 minutes;

[0071] (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, and the reduction roasting temperature is 822° C. for 15 min to obtain a roasted product, calcine;

[0072] (4) The roasted sand is directly fed into an electric furnace through a pipeline for melting to obtain ferrochrome alloy and tailings. The temperature of the electric furnace is 1160° C. and the roasted sand is retained for 1.2 h.

[0073] (5) After melting in the electric furnace, the ferrochrome enters the cooling tower. The material temperature after cooling is 30.44°C. After cooling, it is stored in the storage bin. The tailings enter the slag pool and are cooled to room temperature before being placed in the slag storage bin.

[0074] In the ferrochrome prepared in this embodiment, by weight percentage, the Cr2O3 content is 10.39%, the Fe2O3 content is 36.44%, the SiO2 content is 3.88%, the Al2O3 content is 34.44%, and the MgO content is 13.28%.

[0075] Example 6

[0076] The chromium slag used in the embodiment of the present invention contains 3.47% Cr2O6, 21.88% TFe, 22.86% SiO2, 8.61% Al2O3 and 29.43% MgO by weight.

[0077] A method for preparing ferrochrome by suspended roasting pre-reduction of chromium slag and electric furnace smelting, specifically comprising the following steps:

[0078] (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating to obtain preheated materials; the smoke discharged from the cyclone separator in the raw ore is cooled by a cooler, collected by a bag dust collector and then fed into a suspension roasting furnace, the smoke is discharged through a chimney, and the high-temperature smoke after gas-solid separation in the cyclone separator is fed into a cyclone preheater to preheat the materials;

[0079] (2) The temperature of the material after preheating in the cyclone preheater is 537°C. The preheated material is fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, high-temperature protective flue gas is generated in the system. At the same time, the material will be dehydrated under the action of the high-temperature gas. The temperature is 757°C and the duration is 7.5 minutes;

[0080] (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, and the reduction roasting temperature is 857° C. for 26 min to obtain a roasted product, calcine;

[0081] (4) The roasted sand is directly fed into an electric furnace through a pipeline for melting to obtain ferrochrome alloy and tailings. The temperature of the electric furnace is 1195° C. and the roasted sand is retained for 2 hours;

[0082] (5) After melting in the electric furnace, the ferrochrome enters the cooling tower. The material temperature after cooling is 37.5°C. After cooling, it is stored in the storage bin. The tailings enter the slag pool and are cooled to room temperature before being placed in the slag storage bin.

[0083] In the ferrochrome prepared in this embodiment, by weight percentage, the Cr2O3 content is 11.84%, the Fe2O3 content is 38.85%, the SiO2 content is 2.11%, the Al2O3 content is 31.43%, and the MgO content is 13.47%.

[0084] Example 7

[0085] The chromium slag used in the embodiment of the present invention contains 2.83% Cr2O6, 19.84% TFe, 23.95% SiO2, 8.62% Al2O3 and 34.76% MgO by weight.

[0086] A method for preparing ferrochrome by suspended roasting pre-reduction of chromium slag and electric furnace smelting, specifically comprising the following steps:

[0087] (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating. The smoke discharged from the cyclone separator in the raw ore is cooled in a cooler, collected by a bag dust collector, and then fed into a suspension roasting furnace. The smoke is discharged through a chimney. The high-temperature smoke after gas-solid separation in the cyclone separator is fed into a cyclone preheater to preheat the material;

[0088] (2) The temperature of the material after preheating by the cyclone preheater is 588°C. The preheated material is fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, high-temperature protective flue gas is generated in the system. At the same time, the material will be dehydrated under the action of the high-temperature gas. The temperature is 732°C and the duration is 9 minutes;

[0089] (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, and the reduction roasting temperature is 867° C. for 27.5 min to obtain a roasted product, calcine;

[0090] (4) The roasted sand is directly fed into an electric furnace through a pipeline for melting to obtain ferrochrome alloy and tailings. The temperature of the electric furnace is 1158° C. and the roasted sand is retained for 1.5 h.

[0091] (5) After melting in the electric furnace, the ferrochrome enters the cooling tower. The material temperature after cooling is 29.43°C. After cooling, it is stored in the storage bin. The tailings enter the slag pool and are cooled to room temperature before being placed in the slag storage bin.

[0092] In the ferrochrome prepared in this embodiment, by weight percentage, the Cr2O3 content is 10.82%, the Fe2O3 content is 37.49%, the SiO2 content is 3.76%, the Al2O3 content is 32.43%, and the MgO content is 14.66%.

Claims

1. A method for preparing ferrochrome alloy by suspended roasting pre-reduction of chromium slag and electric furnace smelting, characterized in that: The specific steps include: (1) The chromium slag is crushed to less than -1 mm and fed into a cyclone preheater through a screw feeder for preheating to obtain preheated materials; the smoke discharged from the cyclone separator in the raw ore is cooled by a cooler, collected by a bag dust collector, and then fed into a suspension roasting furnace, and the smoke is discharged through a chimney; (2) The preheated materials are fed into the suspension roasting furnace, and N2 gas is introduced into the furnace body. At this time, the materials in the system are dehydrated under the action of high temperature; (3) introducing H2 and N2 into the suspension roasting furnace, the material is in a suspended state under the action of the ascending airflow, the reduction roasting temperature is 700-900° C., the time is 15-30 min, and the roasting product calcine is obtained; (4) The roasted sand is directly fed into an electric furnace through a pipeline for melting. The temperature of the electric furnace is 1000-1200° C. and the roasted sand is retained for 1-2 hours. (5) After melting in the electric furnace, the ferrochrome alloy enters the cooling tower for cooling and is then stored in the storage bin. The tailings enter the slag pool for cooling and is then placed in the slag storage bin.

2. The method for preparing ferrochrome alloy by chromium slag suspension roasting pre-reduction-electric furnace smelting according to claim 1, characterized in that: In the step (1), the components in the chromium slag are calculated by weight percentage: Cr2O6 2.5-3.8%, TFe 18-23%, SiO2 12-24%, Al2O3 6-9%, and MgO 28-36%.

3. The method for preparing ferrochrome alloy by chromium slag suspension roasting pre-reduction-electric furnace smelting according to claim 1, characterized in that: In the step (1), the high-temperature flue gas after gas-solid separation in the cyclone separator is fed into the cyclone preheater to preheat the material.

4. The method for preparing ferrochrome alloy by chromium slag suspension roasting pre-reduction-electric furnace smelting according to claim 1, characterized in that: In the step (2), the temperature of the material after preheating by the cyclone preheater is 400-600°C.

5. The method for preparing ferrochrome alloy by chromium slag suspension roasting pre-reduction-electric furnace smelting according to claim 1, characterized in that: In the step (2), the temperature at which the material is dehydrated in the suspension roasting furnace is 700-900° C., and the dehydration reaction lasts for 5-10 minutes.

6. The method for preparing ferrochrome alloy by chromium slag suspension roasting pre-reduction-electric furnace smelting according to claim 1, characterized in that: In the step (5), the temperature of the material after passing through the cooling tower and the slag pool is 20-50°C.

7. The method for preparing ferrochrome alloy by chromium slag suspension roasting pre-reduction-electric furnace smelting according to claim 1, characterized in that: The prepared ferrochrome alloy has, by weight percentage, 9-12% Cr2O3, 35-40% Fe2O3, 2-4% SiO2, 30-36% Al2O3 and 12-15% MgO.

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