A method for producing chromium-nickel stainless steel mother liquor by microwave enhanced pre-reduction-smelting

Abstract

The invention discloses a method for producing chromium-nickel stainless steel mother liquor by microwave-enhanced pre-reduction-smelting, wherein fine chromite powder, fine laterite nickel ore powder, a reducing agent and an additive are mixed to obtain a mixture, the mixture is pressed into a mass to obtain a green ball, the green ball is subjected to microwave pre-reduction to obtain a pre-reduced pellet, the pre-reduced pellet is smelted to obtain a chromium-nickel stainless steel mother liquor; the temperature of the microwave pre-reduction is 800-1100°C, and the time of the microwave pre-reduction is 1-3h. This method can not only effectively realize the synchronous reduction of laterite nickel ore and chromite to obtain a high-quality chromium-nickel stainless steel mother liquor product, but also greatly reduce production energy consumption and cost, and has many advantages such as high valuable metal grade and recovery rate, low production cost, environmental friendliness, simple process, etc., which provides a new direction for the resource utilization of low-grade laterite nickel ore and chromite and energy saving and consumption reduction in the stainless steel production process.

Description

Technical Field

[0001] The invention belongs to the field of valuable metal recovery, and in particular relates to a method for producing chromium-nickel stainless steel mother liquor by microwave-enhanced pre-reduction-smelting. Background Art

[0002] Stainless steel, as an important steel material, is widely used in many fields. Nickel and chromium, as important alloying elements, play an important role in improving the corrosion resistance, toughness, plasticity, weldability and strength of stainless steel products. At present, the production raw materials such as stainless steel scrap, ferrochrome, ferronickel and other alloys are mainly melted in EAF furnace or BOF furnace, and then refined in AOD / VOD furnace to obtain stainless steel crude products. The cost of stainless steel raw materials such as ferrochrome and ferronickel accounts for 70% of the total stainless steel smelting cost. Therefore, reducing the smelting and melting costs of ferrochrome and ferronickel is crucial to reducing the production cost of stainless steel.

[0003] The main nickel raw material for producing stainless steel is the nickel iron product produced by laterite nickel ore. The rotary kiln drying pre-reduction-electric furnace smelting process (RKEF) is the mainstream process for producing nickel iron products, with the advantages of mature technology, large production scale, good product quality and high production efficiency. However, the power consumption and fuel consumption costs of this process are high, accounting for more than 65% of the total cost, which is not friendly to areas with shortages of electricity and fuel. In addition, the RKEF process is greatly affected by the nickel grade of the raw material. For every 0.1% reduction in the nickel grade of laterite nickel ore, the process processing cost will increase by 1-2%. Therefore, for low-grade laterite nickel ore with a nickel grade of less than 1.5% (accounting for 54% of undeveloped nickel ore resources), the economic benefits of the RKEF process are greatly reduced. The main chromium raw material for producing stainless steel is ferrochrome, of which 91-93% is high-carbon ferrochrome, mainly derived from the ore-melting process of metallurgical-grade chromite. This process has problems such as high production temperature (~1700℃), high power consumption (2372~4024kW·h / t), low production efficiency, high requirements for chromite particle size, and high production cost.

[0004] In general, the main costs of stainless steel production currently come from three aspects: 1) the different reduction conditions of laterite nickel ore and chromite cause the reduction of the two to be asynchronous, resulting in high equipment and cycle costs for the separate process production of nickel-iron alloy and chromium-iron alloy; 2) the high process costs such as power consumption caused by the high smelting temperatures of stainless steel raw materials (nickel-iron: 1550-1600°C, chromium-iron: ~1700°C); 3) the increase in the operating cost of stainless steel production caused by the process of cooling the nickel-iron / chromium-iron hot alloy liquid and then heating it for smelting; therefore, the present invention takes measures to achieve synchronous reduction of laterite nickel ore and chromite, promotes efficient co-reduction of the mixed system of laterite nickel ore and chromite, thereby reducing the energy consumption and equipment cost of raw material production, and then reducing the production cost of stainless steel smelting, which is of great economic and social significance for ensuring the healthy and sustainable development of my country's stainless steel industry. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the problems of low recovery rate of valuable metals, long production process of stainless steel raw materials, high production, equipment and operation costs in the existing stainless steel smelting process, and provide a method for microwave-enhanced low-grade laterite nickel ore-chromite co-reduction with simple process, low production cost, high recovery rate of valuable metals, high resource utilization rate and environmental friendliness. The present invention has the advantages of high quality of chromium-nickel-iron alloy products, low energy consumption, low pollution, simple process, low production cost and high production efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The invention discloses a method for producing chromium-nickel stainless steel mother liquor by microwave enhanced pre-reduction-smelting. The method comprises the following steps: uniformly mixing chromite fine powder, laterite nickel ore fine powder, a reducing agent and an additive to obtain a mixture, pressing the mixture into a mass to obtain a green ball, performing microwave pre-reduction on the green ball to obtain a pre-reduced pellet, and smelting the pre-reduced pellet to obtain the chromium-nickel stainless steel mother liquor. The microwave pre-reduction temperature is 800-1100° C., and the microwave pre-reduction time is 1-3 hours.

[0008] During the reduction process of the mixed system of laterite nickel ore and chromite, the inventors found that the chromium-containing spinel structure is difficult to destroy in conventional reduction, while the chromium component in chromite mainly exists in the form of chromium spinel. Therefore, the reduction conditions of chromium spinel are very harsh, and in the case of conventional heating treatment, it is often accompanied by long-term high-temperature treatment (>1500℃,>5h), and the energy consumption and cost are very large. The reduction conditions of the nickel component in laterite nickel ore (1000~1100℃, 1~2h) are extremely mismatched with the reduction conditions of the chromium component in chromite, and it is difficult to achieve the simultaneous reduction of laterite nickel ore and chromite. In order to destroy the chromite structure under conventional heating, the reduction temperature needs to be higher than 1250℃, and the reduction time needs to be more than 3h. Therefore, in conventional heating, when the pre-reduction-smelting two-step method is used to treat the mixed system of laterite nickel ore and chromite, two situations will occur: either the treatment conditions in the pre-reduction stage are improved to ensure the reduction of chromite, resulting in an increase in the cost and energy consumption of the pretreatment process; or only the reduction of laterite nickel ore is considered in the pretreatment process while the reduction of chromite is ignored, which will increase the difficulty of treatment during the smelting process. When the mixed system of laterite nickel ore and chromite is directly reduced in one step to produce stainless steel mother liquor, in order to completely recover the chromium component in the chromite, the high-temperature treatment (1500-1700℃) time is very long (>5h), so the production energy consumption is high and the equipment pressure is high.

[0009] Therefore, the reduction of the conditions for destroying the chromium-containing spinel structure and the increase in the degree of spinel destruction are very critical for the reduction of chromium and nickel metals in the mixed system of laterite nickel ore and chromite, the subsequent smelting effect and the saving of stainless steel mother liquor production costs. The present invention adopts a two-step process of microwave pre-reduction-electric furnace smelting of a mixed system of laterite nickel ore and chromite to prepare chromium-nickel stainless steel mother liquor. The inventor unexpectedly found that due to the strong microwave responsiveness of chromite itself, the chromium spinel stably existing in the chromite can be greatly destroyed at a low temperature in the microwave field, releasing the chromium-containing component, thereby realizing the synchronous reduction and recovery of laterite nickel ore / chromite, while reducing the subsequent electric furnace smelting cost and energy consumption.

[0010] Specifically, the present invention conducted a large number of comparative tests on conventional pre-reduction and microwave pre-reduction of a mixed system of laterite nickel ore and chromite and found that although the metallization rate of the chromium component was not significantly improved by the microwave external field at low temperature, the degree of destruction of the chromium spinel structure by the microwave external field was significantly better than that of conventional reduction, which not only made the reduction degree of the chromium spinel in the pre-reduction stage higher, but more importantly, the inventors found that the destruction of the spinel structure was conducive to the release of chromium-containing components, which significantly promoted the reduction of subsequent smelting conditions and the improvement of smelting effect.

[0011] In addition, the pre-reduction temperature and time in the microwave pre-reduction process have a great influence on the degree of destruction of the spinel structure and the degree of synchronous reduction of the mixed system of laterite nickel ore and chromite. When the microwave pre-reduction temperature is low and the pre-reduction time is insufficient, the nickel-iron components in the laterite nickel ore are reduced to form nickel-iron metal, but the chromium spinel structure in the chromite is not destroyed, and the reduction effect of the chromite is poor, so the purpose of synchronous reduction and recovery of the laterite nickel ore / chromite mixed system cannot be achieved. When the microwave pre-reduction temperature is too high and the pre-reduction time is too long, the nickel and iron components in the easily reduced laterite nickel ore are completely reduced. At this time, although the chromite achieves a good reduction effect, the chromium grade is low, and there is still a phenomenon of asynchronous reduction of laterite nickel ore and chromite, which leads to increased energy consumption in the pre-reduction stage. Therefore, it is necessary to explore suitable microwave pre-reduction conditions in the microwave pre-reduction stage to achieve the synchronous reduction of laterite nickel ore and chromite, so as to achieve the purpose of reducing energy consumption in the pre-reduction stage and reducing energy consumption in the chromium-nickel stainless steel mother liquor production process. The inventors have discovered through a large number of experimental explorations that synchronous reduction of laterite nickel ore and chromite can be achieved under specific microwave reduction temperature and reduction time, thereby not only reducing the energy consumption of pre-reduction production but also facilitating the subsequent smelting process.

[0012] In a preferred embodiment, the particle sizes of the chromite fine powder and the laterite nickel ore fine powder are both less than 74 μm.

[0013] In a preferred embodiment, the chromite fine powder is obtained by grinding chromite.

[0014] In a preferred embodiment, the laterite nickel ore fine powder is obtained by grinding laterite nickel ore.

[0015] In a preferred embodiment, in the chromite fine powder, the mass fraction of Cr2O3 is 40.1-42.5wt%, and the mass ratio of Cr2O3 / FeO is 2.0-2.19.

[0016] In a preferred embodiment, in the laterite nickel ore fine powder, the mass fraction of iron is 33.35-38.47 wt %, and the mass fraction of nickel is 1.45-1.49 wt %.

[0017] In a preferred embodiment, the amount of the chromite fine powder added is 10-50wt% of the mass of the laterite nickel ore fine powder, preferably 20-30wt%.

[0018] In a preferred embodiment, the reducing agent is selected from at least one of small coke pieces, lignite and coke powder, preferably small coke pieces.

[0019] In a preferred embodiment, the particle size of the reducing agent is less than 74 μm.

[0020] In a preferred embodiment, the reducing agent is added in an amount of 17-20 wt % of the total mass of the chromite fine powder and the laterite nickel ore fine powder.

[0021] In a preferred embodiment, the additive is selected from at least one of calcium oxide, calcium carbonate and calcium hydroxide.

[0022] In a preferred embodiment, the additive is added in an amount of 8 to 12 wt % of the total mass of the chromite fine powder and the laterite nickel ore fine powder.

[0023] In the actual operation process, according to the different water contents of the chromite fine powder and the laterite nickel ore fine powder, a small amount of water is added as a binder to make the mixture better for compacting and forming.

[0024] In a preferred embodiment, the mixture is pressed into a mass and dried to obtain green balls.

[0025] In a preferred embodiment, the pressure for compacting the mixture is 5 to 20 MPa.

[0026] In a preferred embodiment, the microwave pre-reduction is carried out under a protective atmosphere, and the flow rate of the protective atmosphere is 0.1 to 0.3 L / min.

[0027] The inventors found that controlling the flow rate of the protective atmosphere within the above range will ultimately achieve the best microwave pre-reduction effect. If the flow rate is too low, there will be a risk of the newly generated reduction product being oxidized again. If the flow rate of the protective atmosphere is too large, the generated CO will be quickly blown away from the reaction furnace chamber, resulting in insufficient gas reduction during the reduction process.

[0028] Further preferably, the protective atmosphere is nitrogen.

[0029] In a preferred embodiment, the microwave pre-reduction temperature is 1000-1100° C., preferably 1050-1100° C., and the microwave pre-reduction time is 1.5-2.5 hours, preferably 2-2.5 hours. The microwave pre-reduction effect is optimal when the microwave pre-treatment is carried out within the scope of this preferred embodiment.

[0030] In a preferred embodiment, the power of the microwave pre-reduction is 900-1100W, preferably 1000-1100W.

[0031] The inventors have found that when the power of microwave pre-reduction is controlled within the above range, the ultimate microwave pre-reduction effect is optimal.

[0032] In a preferred embodiment, the pre-reduced pellet cap coal is smelted at a temperature of 1400 to 1600° C., for a time of 1 to 3 hours, and at a smelting basicity of 1 to 1.5.

[0033] Further preferably, the smelting temperature is 1500-1600° C., and the smelting time is 1.5-2.5 h.

[0034] In the present invention, after the spinel structure of chromite is destroyed by microwave pre-reduction, smelting can be carried out at a lower temperature, avoiding the difficulty of slag metallographic phase separation caused by too high smelting temperature, and improving the metal grade and recovery rate of nickel, chromium and iron in stainless steel mother liquor.

[0035] In actual operation, the pre-reduced pellets are placed in a graphite crucible / corundum crucible and covered with coal for smelting. The inventors found that the performance of the stainless steel mother liquor obtained by smelting with covered coal is optimal.

[0036] Principles and advantages of the present invention:

[0037] The innovation of the present invention lies in the use of microwave pre-reduction-melting two-step method to coordinately treat the laterite nickel ore / chromite mixed system to prepare chromium-nickel stainless steel mother liquor. The main technical key point of the invention is to make full use of the strong microwave responsiveness of chromite itself, so that the stable chromium spinel in the chromite can be greatly destroyed under microwave low temperature conditions, releasing chromium-containing components, thereby realizing the synchronous reduction and recovery of laterite nickel ore / chromite, while reducing the subsequent electric furnace smelting cost and energy consumption. The present invention adopts microwave pre-reduction-melting two-step method to coordinately treat the laterite nickel ore / chromite mixed system to prepare chromium-nickel stainless steel mother liquor, which can reduce the high electricity consumption cost of stainless steel raw materials such as chromium-iron alloy and nickel-iron alloy due to different process production, and save the operating cost of the subsequent hot alloy liquid cooling and remelting process. Furthermore, the mixed pre-reduction and smelting of laterite nickel ore and chromite can not only use the mutual coordination of the components in the two materials to adjust the slag smelting performance to reduce the addition of external additives, but also avoid the problems of increased slag discharge, large differences in slag composition, and difficult slag utilization caused by the separate treatment of nickel-iron alloy and chromium-iron alloy. More importantly, by regulating the degree of reduction of chromium, nickel and iron-containing phases during the pre-reduction process, the melting point of the Cr-Ni-Fe alloy and the melting point of the slag can be adjusted, the fluidity of the stainless steel mother liquor can be improved, the difficulty of slag metallographic phase separation caused by excessively high smelting temperature can be avoided, and the nickel, chromium and iron metal grade and recovery rate in the stainless steel mother liquor can be increased. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0039] To avoid repetition, the raw materials involved in this specific implementation are described as follows, and will not be repeated in the specific examples:

[0040] In the chromite fine powder used in the implementation, the mass fraction of Cr2O3 is 40.1-42.5wt%, the mass ratio of Cr2O3 / FeO is 2.0-2.19, and the mass fraction of iron in the laterite nickel ore fine powder used is 33.35-38.47wt%, and the mass fraction of nickel is 1.45-1.49wt%.

[0041] Example 1

[0042] The chromite ore and laterite nickel ore raw materials are ground separately, and the reducing agent and additives are added in proportion to prepare and uniformly obtain a mixture. The mixture is pressed and dried to obtain green balls, which are placed in a microwave tube furnace for pre-reduction under a protective atmosphere to obtain pre-reduced pellets, and the pre-reduced pellets are smelted in an electric furnace to obtain a chromium-nickel stainless steel mother liquor product.

[0043] The average particle size of the laterite nickel ore and chromite fine powder particles is 74 μm;

[0044] The m(chromite) / m(latite nickel ore)=10wt%;

[0045] The additive is CaCO3, and the amount of CaCO3 added is 12wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0046] The reducing agent is lignite, and the amount of lignite added is 17wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0047] The green ball forming pressure is 10MPa;

[0048] The microwave pre-reduction temperature is 800°C, the pre-reduction time is 1h, and the microwave reduction power is 900W;

[0049] The protective atmosphere is N2, and the gas flow rate is 0.1L / min;

[0050] The smelting temperature is 1500°C, the smelting time is 1h, and the smelting basicity R=1.0;

[0051] In this Example 1, the metallization rates of chromium, nickel and iron in the pre-reduction product are 5.7%, 83.2% and 60.2% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 33%, 79% and 83% respectively.

[0052] Example 2

[0053] The chromite ore and laterite nickel ore raw materials are ground separately, and the reducing agent and additives are added in proportion to prepare and uniformly obtain a mixture. The mixture is pressed and dried to obtain green balls, which are placed in a microwave tube furnace for pre-reduction under a protective atmosphere to obtain pre-reduced pellets, and the pre-reduced pellets are smelted in an electric furnace to obtain a chromium-nickel stainless steel mother liquor product.

[0054] The average particle size of the laterite nickel ore and chromite fine powder particles is 74 μm.

[0055] The m(chromite) / m(latite nickel ore)=20wt%;

[0056] The additive is CaCO3, and the amount of CaCO3 added is 11.3wt% of the total mass of the laterite nickel ore and chromite raw materials.

[0057] The reducing agent is lignite, and the amount of lignite added is 18wt% of the total mass of the laterite nickel ore and chromite raw materials.

[0058] The green ball forming pressure is 15MPa.

[0059] The microwave pre-reduction temperature is 900°C, the pre-reduction time is 1h, and the microwave reduction power is 950W;

[0060] The protective atmosphere is N2, and the gas flow rate is 0.2L / min;

[0061] The smelting temperature is 1500°C, the smelting time is 1.5h, and the smelting basicity R=1.1;

[0062] The metallization rates of chromium, nickel and iron in the pre-reduction product of Example 2 are 10.94%, 84.1% and 78.5% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 56%, 83% and 90% respectively.

[0063] Example 3

[0064] The chromite ore and laterite nickel ore raw materials are ground separately, and the reducing agent and additives are added in proportion to prepare and uniformly obtain a mixture. The mixture is pressed and dried to obtain green balls, which are placed in a microwave tube furnace for pre-reduction under a protective atmosphere to obtain pre-reduced pellets, and the pre-reduced pellets are smelted in an electric furnace to obtain a chromium-nickel stainless steel mother liquor product.

[0065] The average particle size of the laterite nickel ore and chromite fine powder particles is 74 μm;

[0066] The m(chromite) / m(nickel laterite)=30wt%;

[0067] The additive is Ca(OH)2, and the amount of Ca(OH)2 added is 10.8wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0068] The reducing agent is coke powder, and the amount of coke powder added is 19wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0069] The green ball forming pressure is 15MPa;

[0070] The microwave pre-reduction temperature is 950° C., the pre-reduction time is 1.5 h, and the microwave reduction power is 1000 W;

[0071] The protective atmosphere is N2, and the gas flow rate is 0.2L / min;

[0072] The smelting temperature is 1550°C, the smelting time is 2h, and the smelting basicity R=1.2;

[0073] The metallization rates of chromium, nickel and iron in the pre-reduction product of Example 3 are 11.6%, 97.0% and 87.7% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 64.8%, 96% and 97% respectively.

[0074] Example 4

[0075] The chromite ore and laterite nickel ore raw materials are ground separately, and the reducing agent and additives are added in proportion to prepare and uniformly obtain a mixture. The mixture is pressed and dried to obtain green balls, which are placed in a microwave tube furnace for pre-reduction under a protective atmosphere to obtain pre-reduced pellets, and the pre-reduced pellets are smelted in an electric furnace to obtain a chromium-nickel stainless steel mother liquor product.

[0076] The average particle size of the laterite nickel ore and chromite fine powder particles is 74 μm;

[0077] The m(chromite) / m(latite nickel ore)=35wt%;

[0078] The additive is Ca(OH)2, and the amount of Ca(OH)2 added is 10.3wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0079] The reducing agent is coke powder, and the amount of coke powder added is 19.1wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0080] The green ball forming pressure is 20MPa;

[0081] The microwave pre-reduction temperature is 1000°C, the pre-reduction time is 2.0h, and the microwave reduction power is 1050W;

[0082] The protective atmosphere is N2, and the gas flow rate is 0.2L / min;

[0083] The smelting temperature is 1550°C, the smelting time is 2.0h, and the smelting basicity R=1.3;

[0084] The metallization rates of chromium, nickel and iron in the pre-reduction product of Example 4 are 27.0%, 97.1% and 87.3% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 75.1%, 98.8% and 98.1% respectively.

[0085] Example 5

[0086] The chromite ore and laterite nickel ore raw materials are ground separately, and the reducing agent and additives are added in proportion to prepare and uniformly obtain a mixture. The mixture is pressed and dried to obtain green balls, which are placed in a microwave tube furnace for pre-reduction under a protective atmosphere to obtain pre-reduced pellets, and the pre-reduced pellets are smelted in an electric furnace to obtain a chromium-nickel stainless steel mother liquor product.

[0087] The average particle size of the laterite nickel ore and chromite fine powder particles is 74 μm;

[0088] The m(chromite) / m(latite nickel ore)=40wt%;

[0089] The additive is CaO, and the amount of CaO added is 9.9wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0090] The reducing agent is small coke, and the addition amount of small coke is 19.3wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0091] The green ball forming pressure is 20MPa;

[0092] The microwave pre-reduction temperature is 1050°C, the pre-reduction time is 2.5h, and the microwave reduction power is 1100W;

[0093] The protective atmosphere is N2, and the gas flow rate is 0.2L / min;

[0094] The smelting temperature is 1600°C, the smelting time is 1h, and the smelting basicity R=1.4;

[0095] The metallization rates of chromium, nickel and iron in the pre-reduction product of Example 5 are 35.0%, 94.5% and 85.2% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 84.5%, 99.2% and 99.1% respectively.

[0096] Example 6

[0097] The chromite ore and laterite nickel ore raw materials are ground separately, and the reducing agent and additives are added in proportion to prepare and uniformly obtain a mixture. The mixture is pressed and dried to obtain green balls, which are placed in a microwave tube furnace for pre-reduction under a protective atmosphere to obtain pre-reduced pellets, and the pre-reduced pellets are smelted in an electric furnace to obtain a chromium-nickel stainless steel mother liquor product.

[0098] The average particle size of the laterite nickel ore and chromite fine powder particles is 74 μm;

[0099] The m(chromite) / m(latite nickel ore)=50wt%;

[0100] The additive is CaO, and the amount of CaO added is 9.3wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0101] The reducing agent is small coke, and the addition amount of small coke is 19.5wt% of the total mass of the laterite nickel ore and chromite raw materials;

[0102] The green ball forming pressure is 15MPa;

[0103] The microwave pre-reduction temperature is 1100° C., the pre-reduction time is 3 h, and the microwave reduction power is 1100 W;

[0104] The protective atmosphere is N2, and the gas flow rate is 0.3L / min;

[0105] The smelting temperature is 1600°C, the smelting time is 2h, and the smelting basicity R=1.5;

[0106] The metallization rates of chromium, nickel and iron in the pre-reduction product of Example 6 are 45.5%, 95.1% and 86.7% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 98.6%, 99.3% and 99.2% respectively.

[0107] Comparative Example 1

[0108] The other conditions were the same as those in Example 1, except that a conventional tube furnace was used for pre-reduction.

[0109] In this comparative example 1, the metallization rates of chromium, nickel and iron in the pre-reduction product are 1.1%, 34.1% and 50.2% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 29.1%, 30.4% and 53.0% respectively.

[0110] Comparative Example 2

[0111] The other conditions were the same as those in Example 6, except that a conventional tube furnace was used for pre-reduction.

[0112] The metallization rates of chromium, nickel and iron in the pre-reduction product of Comparative Example 2 are 32.1%, 78.3% and 89.3% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 78.3%, 90.3% and 91.3% respectively.

[0113] Comparative Example 3

[0114] Other conditions are the same as those in Example 6, the smelting basicity is natural basicity (R=0.03), and the CaO addition amount is 0wt%.

[0115] The metallization rates of chromium, nickel and iron in the pre-reduction product of this comparative example 3 are 30.3%, 76.5% and 76.3% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 21.2%, 42.0% and 39.0% respectively.

[0116] Comparative Example 4

[0117] The other conditions were the same as those in Example 6, except that the microwave pre-reduction temperature was 500°C.

[0118] The metallization rates of chromium, nickel and iron in the pre-reduction product of Comparative Example 4 were 1.26%, 20.1% and 31.2%, respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product were 11.45%, 15.45% and 28.01%, respectively.

[0119] Comparative Example 5

[0120] The other conditions were the same as those in Example 6, except that the melting temperature was 1400°C.

[0121] The metallization rates of chromium, nickel and iron in the pre-reduction product of Comparative Example 5 are 45.5%, 95.1% and 86.7% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 18.2%, 65.3% and 67.3% respectively.

[0122] Comparative Example 6

[0123] The other conditions were the same as those in Example 6, except that the melting temperature was 1700°C.

[0124] In this comparative example 6, the metallization rates of chromium, nickel and iron in the pre-reduction product are 45.5%, 95.1% and 86.7% respectively, and the metal recovery rates of chromium, nickel and iron in the smelting product are 98.9%, 99.5% and 99.7% respectively, indicating that the recovery rate will not increase if the smelting temperature continues to increase.

[0125] It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the appended claims rather than the above description, and it is therefore intended that all changes within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0126] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for producing chromium-nickel stainless steel mother liquor by microwave enhanced pre-reduction-smelting, characterized in that: The chromite fine powder, the laterite nickel ore fine powder, the reducing agent and the additive are mixed to obtain a mixture, the mixture is pressed into a mass to obtain a green ball, the green ball is subjected to microwave pre-reduction to obtain a pre-reduced pellet, and the pre-reduced pellet is smelted to obtain a chromium-nickel stainless steel mother liquor; the microwave pre-reduction temperature is 800-1100° C., and the microwave pre-reduction time is 1-3 h; In the chromite fine powder, the mass fraction of Cr2O3 is 40.1-42.5 wt%, and the mass ratio of Cr2O3 / FeO is 2.0-2.19; In the laterite nickel ore fine powder, the mass fraction of iron is 33.35-38.47 wt %, and the mass fraction of nickel is 1.45-1.49 wt %; The amount of the chromite fine powder added is 10-50wt% of the mass of the laterite nickel ore fine powder; The additive is selected from at least one of calcium oxide, calcium carbonate and calcium hydroxide; The additive is added in an amount of 8-12wt% of the total mass of the chromite fine powder and the laterite nickel ore fine powder; The pressure of the mixture pressing and forming is 5~20 MPa; The microwave pre-reduction is carried out under a protective atmosphere, and the flow rate of the protective atmosphere is 0.1-0.3 L / min.

2. The method for producing chromium-nickel stainless steel mother liquor by microwave enhanced pre-reduction-smelting according to claim 1, characterized in that: The particle sizes of the chromite fine powder and the laterite nickel ore fine powder are both less than 74 μm.

3. The method for producing chromium-nickel stainless steel mother liquor by microwave enhanced pre-reduction-smelting according to claim 1, characterized in that: The reducing agent is selected from at least one of small coke pieces, lignite and coke powder; The particle size of the reducing agent is less than 74 µm; The amount of the reducing agent added is 17-20wt% of the total mass of the chromite fine powder and the laterite nickel ore fine powder.

4. The method for producing chromium-nickel stainless steel mother liquor by microwave enhanced pre-reduction-smelting according to claim 1, characterized in that: The temperature of the microwave pre-reduction is 1000-1100° C., and the time of the microwave pre-reduction is 1.5-2.5 hours.

5. The method for producing chromium-nickel stainless steel mother liquor by microwave enhanced pre-reduction-smelting according to claim 1, characterized in that: The pre-reduced pellet cap coal is smelted at a temperature of 1400-1600° C., a smelting time of 1-3 h, and a smelting basicity of 1-1.5.