A method and device for removing arsenic from low-grade nickel-molybdenum ore

Abstract

The present application relates to non-ferrous metallurgy technical field, specifically to a kind of low-grade nickel-molybdenum ore arsenic removal processing method and device, by using the device of the present application, inert protective gas atmosphere, calcium oxide and specific temperature rising mechanism, make As element in nickel-molybdenum ore separate solidification, substantially reduce the As content in nickel-molybdenum ore, and inert protective gas atmosphere makes the oxidation of nickel-molybdenum and other metal elements reduce, reduce the volatilization of nickel-molybdenum, can reduce the volatilization loss of nickel, molybdenum and other elements in nickel-molybdenum ore, improve the purity of nickel-molybdenum iron alloy and the recovery rate of nickel, molybdenum element.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal metallurgy technology, specifically to a method and apparatus for removing arsenic from low-grade nickel-molybdenum ore. Background Technology

[0002] Nickel-molybdenum symbiotic deposits are commonly found in black shale-type deposits in Guizhou and Hunan provinces, and are a unique polymetallic mineral resource in my country. Nickel-molybdenum ores typically contain 0.5%-5% nickel, 2%-10% molybdenum, and 0.1%-5% arsenic, indicating a relatively high enrichment level of nickel and molybdenum. However, nickel-molybdenum ores also contain other metallic and non-metallic elements. Nickel exists in forms such as sulphite, pyrite, and organically bound forms; molybdenum is mainly found in molybdenite, molybdenite, and organic molybdenum; and arsenic is mainly found in arsenopyrite (FeAsS). Existing beneficiation technologies are insufficient for enrichment. Improved beneficiation methods include conventional flotation, bioleaching, and roasting leaching. However, conventional flotation has a narrow applicability, and bioleaching has a long cycle time.

[0003] The main approach to processing and utilizing nickel-molybdenum ore currently involves a combined roasting-leaching smelting process. The core of this process is to convert sulfides into oxides or soluble salts through oxidative roasting, followed by selective metal extraction via wet leaching. Another approach is a leaching smelting process, which selectively extracts metals by adding reagents. Both approaches involve leaching, consuming significant amounts of chemical reagents and water, and generating arsenic-containing industrial wastewater that is difficult to treat and causes severe environmental pollution upon discharge. Direct leaching of minerals also presents numerous challenges, including the difficulty of directly acid-leaching sulfide ores, interference from complex ore occurrence states, difficulties in selective leaching, low nickel-molybdenum separation efficiency, and interference from impurities. These challenges all affect metal recovery rates. When using roasting-leaching and leaching processes, the best molybdenum recovery rate is ≥90%, and the best nickel recovery rate is ≥85%, while the arsenic removal rate is >70%, although achieving this in actual industrial production is quite difficult.

[0004] To address this issue, many researchers have improved traditional processes. For example, patent application number CN201810317127.4 discloses a smelting process involving roasting and chlorination volatilization, which separates and recovers the generated tail gas; patent application number 202010955545.3 discloses a high-temperature reduction smelting process and apparatus, which directly reduces and smelts alloys at high temperatures using a vacuum furnace; and patent application number CN201410308642.8 discloses a process involving alkali-adding roasting desulfurization, medium-frequency furnace, and carbon-silicon-iron reduction smelting.

[0005] However, nickel, molybdenum and other elements in nickel-molybdenum ore can be recovered through methods such as chlorination volatilization and smelting. The problem is that the separated components are complex and there are many impurities such as arsenic in the smelted alloy. High arsenic content will have a significant negative impact on the performance of steel. Therefore, the research team of this invention proposes a method and apparatus for removing arsenic from nickel-molybdenum ore in a clean manner during the pretreatment stage of nickel-molybdenum ore, so as to improve the purity of subsequent smelting of nickel-molybdenum ferroalloy. Summary of the Invention

[0006] In order to overcome the above-mentioned defects in the prior art, the purpose of this invention is to provide a method and apparatus for arsenic removal from low-grade nickel-molybdenum ore.

[0007] One objective of this invention is to provide a method for removing arsenic from low-grade nickel-molybdenum ore, comprising the following steps:

[0008] Nickel-molybdenum ore and calcium oxide were spread evenly on multi-layer refractory plates in a 1:5 ratio and placed in a heating furnace. Nitrogen gas was first introduced into the sealed heating furnace to create a nitrogen atmosphere. Then, a certain amount of calcium oxide was placed at the gas outlet of the heating furnace, and inert protective gas and a small amount of air were introduced to make the furnace reach a low oxygen condition. Under a certain heating mechanism, high-temperature roasting was carried out to obtain roasted sand with extremely low arsenic content.

[0009] The heating mechanism is as follows: the furnace temperature is raised to 200℃~300℃ within 15 minutes, held at 200℃~300℃, and then raised to 900℃-1100℃ and held.

[0010] The low-oxygen conditions are defined as an oxygen concentration of 1%-5%; under high-temperature conditions, when the oxygen concentration is greater than 1%, arsenic oxide and calcium oxide can react.

[0011] FeAsS and other compounds in nickel-molybdenum ore decompose under high temperature and inert protective gas conditions:

[0012] ;

[0013] ;

[0014] Arsenic vapor and .

[0015] A small portion of gaseous arsenic is physically adsorbed onto the CaO surface, while most of the arsenic reacts with calcium oxide at high temperatures to form calcium arsenate.

[0016] .

[0017] This invention uses nitrogen as an inert protective gas and adjusts the air input pressure to achieve low oxygen conditions inside the furnace, thereby reducing the generation and volatilization of molybdenum oxide, improving the recovery rate of alloying elements, and reducing production costs.

[0018] Furthermore, nickel-molybdenum ore and calcium oxide are spread separately on multi-layer refractory boards without mixing. The thickness of the nickel-molybdenum ore is about 1-3 cm. The refractory boards are placed in the heating furnace, and 1-3 kg of calcium oxide is placed at the gas outlet of the heating furnace.

[0019] Preferably, nickel-molybdenum ore and calcium oxide are laid flat on multiple layers of refractory boards without mixing. The thickness of the nickel-molybdenum ore is 2cm. The refractory boards are placed inside the heating furnace, and 2kg of calcium oxide is placed at the gas outlet of the heating furnace.

[0020] Furthermore, the nickel-molybdenum ore is mined ore that has been crushed into powder blocks of <3mm by a crusher, and the weight content of water in the crushed nickel-molybdenum ore is 5%-10%.

[0021] Furthermore, the calcium oxide is steelmaking calcium oxide with CaO ≥ 92%, activity ≥ 380 ml, S ≤ 0.05%, and C ≤ 0.5%.

[0022] The calcium oxide can react with arsenic oxide at high temperatures to form calcium arsenate, thus solidifying As. Calcium oxide can also adsorb sulfur, reducing the concentration of acidic substances in the atmosphere and mitigating the environmental impact of harmful elements.

[0023] Furthermore, the inert protective gas is used in steelmaking. , ≥99.99%, air supply pressure 0.01-0.1MPa; the air is compressed air supplied by the compressor.

[0024] Furthermore, the heating mechanism involves holding the temperature at 200℃~300℃ for 30 minutes; then continuing to heat the temperature from 200℃~300℃ to 900℃~1100℃ for 60-80 minutes and holding for 120 minutes.

[0025] Furthermore, before heating, the inert protective gas supply pressure is 0.1 MPa, the gas flow rate is 20-40 L / min, and the holding time is 30 min, so that the furnace is in a positive pressure nitrogen atmosphere; after heating, the inert protective gas supply pressure is 0.01-0.1 MPa, and the air supply pressure is 2-5 kPa.

[0026] Preferably, the inert protective gas supply pressure is 0.1 MPa before heating and is maintained for 30 minutes to make the furnace pressure positive; after heating, the inert protective gas supply pressure is 0.02 MPa and the air supply pressure is 2-5 kPa.

[0027] Another object of the present invention is to provide a treatment apparatus for removing arsenic from low-grade nickel-molybdenum ore.

[0028] A treatment device for removing arsenic from low-grade nickel-molybdenum ore includes a gas supply channel, a heating furnace, a tail gas treatment device, and a temperature controller.

[0029] The gas supply channel includes an inert protective gas pipeline and an air pipeline, and the inert protective gas pipeline and the air pipeline are respectively connected to the lower side of the heating furnace.

[0030] The heating furnace is a resistance wire heating furnace, wherein the resistance wire is set on the inner side of the fireplace. The top of the heating furnace is detachably equipped with a furnace cover. The heating furnace is filled with refractory bricks and refractory cotton from the outside to the inside. The heating furnace has a multi-layered refractory frame structure inside, wherein the top is an inverted V-shaped structure, and a refractory plate is provided between two adjacent refractory frames. The heating furnace has an air outlet on the upper part of the side away from the gas supply pipe. The air outlet is connected to the cyclone dust collector of the exhaust gas treatment device through the first exhaust pipe.

[0031] The exhaust gas treatment device includes a cyclone dust collector, a condenser, a spray tower, and an induced draft fan. The cyclone dust collector has a dust outlet at the bottom and is connected to the condenser at the top through a second exhaust pipe. The condenser is connected to the spray tower through an exhaust gas pipe, and the spray tower is connected to the induced draft fan through a pipe.

[0032] The temperature controller controls the temperature inside the heating furnace.

[0033] The beneficial effects of this invention are:

[0034] 1. The method of the present invention uses an inert protective gas atmosphere, calcium oxide and a specific heating mechanism to separate and solidify the As element in nickel-molybdenum ore, which greatly reduces the As content in nickel-molybdenum ore, making it easier to smelt a relatively pure nickel-molybdenum-iron alloy. The arsenic removal rate is stable at over 90%, and can reach over 99% in some cases.

[0035] 2. The device of the present invention can efficiently and significantly reduce the arsenic content in nickel-molybdenum ore through a sealed heating furnace and multi-layer heat-resistant plates. At the same time, precise control of inert protective gas and oxygen can reduce the volatilization loss of nickel, molybdenum and other elements in nickel-molybdenum ore, and improve the purity of nickel-molybdenum ferroalloy and the recovery rate of nickel and molybdenum.

[0036] 3. High-purity nickel-molybdenum-iron alloys can be widely used in the production of nickel-molybdenum-containing steels and high-alloy steels; compared with steel produced using pure nickel and pure molybdenum, the high-purity nickel-molybdenum-iron alloys produced using the method of this invention can significantly reduce smelting costs; compared with the current nickel-molybdenum ore roasting-leaching process, the apparatus and method of this invention can greatly reduce the pollution of the surrounding environment during the production process. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the arsenic removal treatment device for low-grade nickel-molybdenum ore according to the present invention.

[0038] Explanation of reference numerals in the attached diagram: 1. Inert protective gas pipeline; 2. Air pipeline; 3. Heating furnace; 4. Multi-layer refractory board; 5. Resistance wire; 6. Refractory brick; 7. Furnace cover; 8. Refractory cotton; 9. Furnace wall; 10. First exhaust pipeline; 11. Cyclone dust collector; 12. Second exhaust pipeline; 13. Condenser; 14. Tail gas pipe; 15. Spray tower; 16. Exhaust fan; 17. Air outlet; 19. Dust outlet; 21. Temperature controller. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0040] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0041] The chemical composition of the crushed nickel-molybdenum ore is approximately (%): Mo 4%, Ni 2%, Fe 15%, Zn 2.5%. 18% It contains 2% S, 22% C, 6% As, etc., and belongs to low-grade nickel-molybdenum ore.

[0042] Example 1

[0043] A method for removing arsenic from low-grade nickel-molybdenum ore includes the following steps:

[0044] Nickel-molybdenum ore and calcium oxide were spread separately on multi-layer refractory boards at a weight ratio of 1:5, without mixing. The nickel-molybdenum ore was 2 cm thick. The refractory boards were then placed in a heating furnace. Nitrogen gas was first introduced into the sealed furnace for 30 minutes at a flow rate of 30 L / min and a supply pressure of 0.1 MPa to create a nitrogen atmosphere. 2 kg of calcium oxide was placed at the furnace outlet. The nitrogen supply pressure was then adjusted to 0.02 MPa, and the air supply pressure to 5 kPa. The furnace temperature was raised to 300°C within 15 minutes and held at 300°C for 30 minutes. Then, the temperature was increased from 300°C to 1000°C within 70 minutes and held at 1000°C for 120 minutes. This process allowed the arsenic (As) element in the nickel-molybdenum ore to separate and react with the calcium oxide to form calcium arsenate, which was then roasted to obtain calcined ore.

[0045] The nickel-molybdenum ore is mined and pulverized into powder or lumps of approximately 2mm. The calcium oxide is steelmaking grade calcium oxide with CaO ≥ 92%, activity ≥ 380ml, S ≤ 0.05%, and C ≤ 0.5%. This calcium oxide can react with arsenic oxide at high temperatures to form calcium arsenate, thus solidifying As. The inert protective gas is used in steelmaking. , ≥99.99%, air supply pressure 0.01-0.1MPa; the air is compressed air supplied by the compressor.

[0046] Example 2

[0047] A method for removing arsenic from low-grade nickel-molybdenum ore includes the following steps:

[0048] Nickel-molybdenum ore and calcium oxide were spread separately on multi-layer refractory boards at a weight ratio of 1:5, without mixing. The nickel-molybdenum ore was 2 cm thick. The refractory boards were then placed in a heating furnace. Nitrogen gas was first introduced into the sealed heating furnace for 30 minutes at a flow rate of 20 L / min and a supply pressure of 0.1 MPa to create a nitrogen atmosphere. 2 kg of calcium oxide was placed at the furnace outlet. The nitrogen supply pressure was then adjusted to 0.02 MPa, and the air supply pressure was 5 kPa. The furnace temperature was raised to 300 °C within 15 minutes and held at 300 °C for 30 minutes. Then, the temperature was raised from 300 °C to 1100 °C within 90 minutes and held at 1100 °C for 120 minutes to allow the As element in the nickel-molybdenum ore to volatilize and separate. The roasting was then completed to obtain roasted ore.

[0049] The nickel-molybdenum ore is mined and pulverized into powder or lumps of approximately 3mm. The calcium oxide is steelmaking grade calcium oxide with CaO ≥ 92%, activity ≥ 380ml, S ≤ 0.05%, and C ≤ 0.5%. This calcium oxide can react with arsenic oxide at high temperatures to form calcium arsenate, thus solidifying As. The inert protective gas is used in steelmaking. , ≥99.99%, air supply pressure 0.01-0.1MPa; the air is compressed air supplied by the compressor.

[0050] Example 3

[0051] A method for removing arsenic from low-grade nickel-molybdenum ore includes the following steps:

[0052] Nickel-molybdenum ore and calcium oxide were spread separately on multi-layer refractory boards at a weight ratio of 1:5, without mixing. The nickel-molybdenum ore thickness was 2 cm. The refractory boards were then placed in a heating furnace. Nitrogen gas was first introduced into the sealed heating furnace for 30 minutes at a flow rate of 40 L / min and a supply pressure of 0.1 MPa to create a nitrogen atmosphere. 2 kg of calcium oxide was placed at the furnace outlet. The nitrogen supply pressure was then adjusted to 0.02 MPa, and the air supply pressure was 5 kPa. The furnace temperature was raised to 300 °C within 15 minutes and held at 300 °C for 30 minutes. Then, the temperature was raised from 300 °C to 1000 °C within 70 minutes and held at 1000 °C for 120 minutes to allow the As element in the nickel-molybdenum ore to volatilize and separate. The roasting was then completed to obtain roasted ore.

[0053] The nickel-molybdenum ore is mined and pulverized into powder or lumps of approximately 3mm. The calcium oxide is steelmaking grade calcium oxide with CaO ≥ 92%, activity ≥ 380ml, S ≤ 0.05%, and C ≤ 0.5%. This calcium oxide can react with arsenic oxide at high temperatures to form calcium arsenate, thus solidifying As. The inert protective gas is used in steelmaking. , ≥99.99%, air supply pressure 0.01-0.1MPa; the air is compressed air supplied by the compressor.

[0054] Example 4

[0055] A method for removing arsenic from low-grade nickel-molybdenum ore includes the following steps:

[0056] Nickel-molybdenum ore and calcium oxide were spread separately on multi-layer refractory boards at a weight ratio of 1:5, without mixing. The nickel-molybdenum ore thickness was 1 cm. The refractory boards were then placed in a heating furnace. Nitrogen gas was first introduced into the sealed heating furnace for 30 minutes at a flow rate of 30 L / min and a supply pressure of 0.1 MPa to create a nitrogen atmosphere. 3 kg of calcium oxide was placed at the gas outlet of the heating furnace. The nitrogen supply pressure was then adjusted to 0.1 MPa, and the air supply pressure was 2 kPa. The furnace temperature was raised to 200°C within 15 minutes and held at 200°C for 30 minutes. Then, the temperature was raised from 200°C to 900°C within 60 minutes and held at 900°C for 120 minutes to allow the As element in the nickel-molybdenum ore to volatilize and separate. The roasting was then completed to obtain roasted ore.

[0057] The nickel-molybdenum ore is mined and pulverized into powder or lumps of approximately 1 mm. The calcium oxide is steelmaking grade calcium oxide with CaO ≥ 92%, activity ≥ 380 ml, S ≤ 0.05%, and C ≤ 0.5%. This calcium oxide can react with arsenic oxide at high temperatures to form calcium arsenate, thus solidifying As. The inert protective gas is used in steelmaking. , ≥99.99%, air supply pressure 0.01-0.1MPa; the air is compressed air supplied by the compressor.

[0058] Example 5

[0059] A method for removing arsenic from low-grade nickel-molybdenum ore includes the following steps:

[0060] Nickel-molybdenum ore and calcium oxide were spread separately on multi-layer refractory boards at a weight ratio of 1:5, without mixing. The nickel-molybdenum ore thickness was 3 cm. The refractory boards were then placed in a heating furnace. Nitrogen gas was first introduced into the sealed heating furnace for 30 minutes at a flow rate of 40 L / min and a supply pressure of 0.1 MPa to create a nitrogen atmosphere. 1 kg of calcium oxide was placed at the furnace outlet. The nitrogen supply pressure was then adjusted to 0.07 MPa, and the air supply pressure to 3.5 kPa. The furnace temperature was raised to 250 °C within 15 minutes and held at 250 °C for 30 minutes. Then, the temperature was raised from 250 °C to 1100 °C within 80 minutes and held at 1100 °C for 120 minutes to allow the As element in the nickel-molybdenum ore to volatilize and separate. The roasting was then completed to obtain roasted ore.

[0061] The nickel-molybdenum ore is mined and pulverized into powder or lumps of approximately 1 mm. The calcium oxide is steelmaking grade calcium oxide with CaO ≥ 92%, activity ≥ 380 ml, S ≤ 0.05%, and C ≤ 0.5%. This calcium oxide can react with arsenic oxide at high temperatures to form calcium arsenate, thus solidifying As. The inert protective gas is used in steelmaking. , ≥99.99%, air supply pressure 0.01-0.1MPa; the air is compressed air supplied by the compressor.

[0062] Example 6

[0063] A treatment device for removing arsenic from low-grade nickel-molybdenum ore includes a gas supply channel, a heating furnace 3, a tail gas treatment device, and a temperature controller 21.

[0064] The gas supply channel includes an inert protective gas pipeline 1 and an air pipeline 2. The inert protective gas pipeline 1 and the air pipeline 2 are respectively connected to the lower side of the heating furnace 3.

[0065] The heating furnace 3 is a resistance wire heating furnace, in which the resistance wire 5 is set on the inner side of the fireplace 9. The top of the heating furnace 3 is detachably equipped with a furnace cover 7, in which the lower surface of the furnace cover 4 is provided with a protrusion, and the upper end of the heating furnace 3 is provided with a groove that matches the protrusion. The four corners of the furnace cover 7 are detachably connected to the heating furnace 3 by bolts to achieve a sealing effect. The heating furnace 3 is filled with refractory bricks 6 and refractory cotton 8 from the outside to the inside. The heating furnace 3 is equipped with a multi-layer structure of refractory frames 4, in which the top is an inverted V-shaped structure, and refractory plates are provided between two adjacent refractory frames 4. The refractory frames 4 and the refractory plates are made of high-temperature alloy steel. The main frame has four layers. The heating furnace 3 has an air outlet 17 on the upper part of the side away from the gas supply pipe. The air outlet 17 is connected to the cyclone dust collector 11 of the exhaust gas treatment device through the first exhaust pipe 10.

[0066] The exhaust gas treatment device includes a cyclone dust collector 11, a condenser 13, a spray tower 15, and an induced draft fan 16. The cyclone dust collector 11 has a dust outlet 19 at the bottom and is connected to the condenser 13 at the top through a second exhaust pipe 12. The dust outlet 19 can remove and collect dust in the exhaust gas. The condenser 13 is connected to the spray tower 15 through an exhaust gas pipe 14. The spray tower 15 is connected to the induced draft fan 16 through a pipe to discharge the qualified exhaust gas.

[0067] The temperature controller 21 controls the temperature inside the heating furnace 3.

[0068] The working principle is as follows: First, the crushed low-grade nickel-molybdenum ore and calcium oxide are laid on the multi-layer refractory frame 4 inside the heating furnace 3. Then, the furnace cover 7 is closed and the four corner bolts are tightened to ensure that the U-shaped protrusion fits tightly with the groove on the upper part of the furnace wall 9, ensuring the airtightness of the heating furnace 3. A certain amount of calcium oxide is placed at the gas outlet 17 of the heating furnace 3. After the preparation is completed, nitrogen gas is introduced into the sealed heating furnace 3 to form a nitrogen atmosphere inside the furnace. The heating program is set by the temperature controller 21, and inert gas and air are continuously introduced into the furnace through the inert protective gas pipeline 1 and the air pipeline 2. At the same time, the resistance wire 5 starts heating, and the temperature inside the heating furnace 3 rises. When the temperature reaches the target range, the temperature is maintained to allow the arsenides to undergo thermal decomposition and volatilization, transforming into gaseous arsenides. Most of the As elements react with calcium oxide under high temperature conditions to form calcium arsenate. The arsenic-containing gas released is discharged from the outlet 17 by the suction of the induced draft fan 16. The calcium oxide at the outlet 17 adsorbs sulfur (S) and a small amount of gaseous arsenic (As), which then enters the first exhaust pipe 10. This gas first enters the cyclone dust collector 11, where the carried dust particles are separated and collected through the dust outlet 19. The preliminarily purified gas then enters the condenser 13 through the second exhaust pipe 12, where the gaseous arsenic compounds are condensed into a solid and recovered. Afterward, the remaining exhaust gas enters the spray tower 15 through the exhaust pipe 14 to neutralize and absorb any residual harmful substances. Finally, the purified gas that meets the standards is discharged by the induced draft fan 16, completing the entire treatment process.

[0069] To verify the effectiveness of this invention, the inventors conducted verification experiments, excerpts of which are as follows:

[0070] The chemical composition of the crushed nickel-molybdenum ore is approximately (%): Mo 4%, Ni 2%, Fe 15%, Zn 2.5%. 18% It contains 2% S, 22% C, 6% As, etc., and belongs to low-grade nickel-molybdenum ore.

[0071] Comparative Example 1 (Nitrogen Atmosphere Comparison)

[0072] Nickel-molybdenum ore and calcium oxide were placed in a heating furnace at a weight ratio of 1:5. The furnace temperature was raised to 300℃ within 15 minutes and held at 300℃ for 30 minutes. Then, the temperature was raised from 300℃ to 1000℃ within 70 minutes and held at 1000℃ for 120 minutes, allowing the As element in the nickel-molybdenum ore to volatilize and separate, reacting with calcium oxide to form calcium arsenate. After roasting, roasted sand was obtained. After cooling, samples were taken for analysis. The nickel, molybdenum, iron, and arsenic composition (mass percentage) in the roasted sand was determined by inductively coupled plasma atomic emission spectrometry as follows: Ni 3.3%, Mo 4.16%, Fe 13.47%, As 0.3266%. The calculated arsenic removal rate was 75.4%.

[0073] Comparative Example 2 (Temperature Comparison)

[0074] Nickel-molybdenum ore and calcium oxide were placed in a heating furnace at a weight ratio of 1:5. Nitrogen gas was first introduced into the sealed furnace for 30 minutes at a pressure of 0.1 MPa to create a nitrogen atmosphere. The nitrogen pressure was then adjusted to 0.02 MPa, and the air pressure to 5 kPa. The furnace temperature was raised to 300°C within 15 minutes and held at 300°C for 30 minutes. Subsequently, the temperature was increased from 300°C to 900°C within 60 minutes and held at 900°C for 120 minutes, allowing the As element in the nickel-molybdenum ore to separate and react with the calcium oxide to form calcium arsenate. After roasting, calcined ore was obtained. Samples were taken and analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The nickel, molybdenum, iron, and arsenic composition (mass percentage) of the calcined ore was as follows: Ni 3.75%, Mo 7.13%, Fe 17.5%, As 0.1671%. The calculated arsenic removal rate was 87.6%.

[0075] Comparative Example 3 (Comparison of nitrogen atmosphere and calcium oxide)

[0076] Nickel-molybdenum ore (same weight as in Example 1) was placed in a heating furnace. The furnace temperature was raised to 300°C within 15 minutes and held at 300°C for 30 minutes; then, the temperature was raised from 300°C to 1000°C within 70 minutes and held at 1000°C for 120 minutes, allowing the As element in the nickel-molybdenum ore to separate and volatilize. Roasted sand was obtained after roasting, and samples were taken for analysis after cooling. The nickel, molybdenum, iron, and arsenic composition (mass percentage) in the roasted sand was determined by inductively coupled plasma atomic emission spectrometry as follows: Ni 2.8%, Mo 3.4%, Fe 11.22%, As 0.423%. The calculated arsenic removal rate was 68.2%.

[0077] After cooling, the calcined sand obtained in Example 1 was sampled and analyzed. The nickel, molybdenum, iron and arsenic composition (mass percentage) in the calcined sand was determined by inductively coupled plasma atomic emission spectrometry as follows: Ni 3.85%, Mo 7.93%, Fe 18.4%, As 0.0096%. The arsenic removal rate was calculated to be 99.2%.

[0078] After cooling, the calcined sand obtained in Example 2 was sampled and analyzed. The nickel, molybdenum, iron and arsenic composition (mass percentage) in the calcined sand was determined by inductively coupled plasma atomic emission spectrometry as follows: Ni 3.19%, Mo 6.4%, Fe 19.96%, As 0.0227%. The arsenic removal rate was calculated to be 98.2%.

[0079] After cooling, the calcined sand obtained in Example 3 was sampled and analyzed. The nickel, molybdenum, iron and arsenic composition (mass percentage) in the calcined sand was determined by inductively coupled plasma atomic emission spectrometry as follows: Ni 3.75%, Mo 7.13%, Fe 13.6%, As 0.0508%. The arsenic removal rate was calculated to be 95.8%.

[0080] The comparison of arsenic removal rates in the above experiments is shown in Table 1, and the comparison of nickel and molybdenum contents before and after arsenic removal is shown in Table 2.

[0081]

[0082] As shown in Table 1, the arsenic removal rate of this application is consistently above 90%, and can reach over 99% in some cases. In contrast, Comparative Example 1 did not introduce gas according to the technical solution of this application, Comparative Example 2 used a non-preferred roasting temperature, and Comparative Example 3 introduced gas according to the technical solution of this application but did not add calcium oxide. The comparison shows that the arsenic removal rate using the non-preferred temperature of this application is the highest among the three comparative examples, reaching 87.6%, while the arsenic removal rates of Comparative Examples 1 and 3 are relatively low, only about 60-70%. This proves that this application uses an inert protective gas atmosphere, calcium oxide, and a specific heating mechanism to separate and solidify the As element in nickel-molybdenum ore, significantly reducing the As content in the nickel-molybdenum ore, which facilitates the subsequent smelting of a relatively pure nickel-molybdenum ferroalloy.

[0083]

[0084] As shown in Table 2, after high-temperature roasting, moisture and elements in the nickel-molybdenum ore volatilize, and the content of each element in the nickel-molybdenum ore changes. The nickel and molybdenum contents of Examples 1-3 of this application are all relatively high, and the nickel and molybdenum contents of Comparative Example 2 at a non-preferred roasting temperature are also relatively high. However, the nickel and molybdenum contents of Comparative Examples 1 and 3 are relatively low, with the molybdenum content being only half that of the examples of this application, and the fluctuation is large. This proves that the inert protective gas and oxygen control of this application can reduce the volatilization loss of elements such as nickel and molybdenum in the nickel-molybdenum ore, and improve the purity of nickel-molybdenum ferroalloy and the recovery rate of nickel and molybdenum elements.

[0085] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for removing arsenic from low-grade nickel-molybdenum ore, characterized in that, Includes the following steps: Nickel-molybdenum ore and calcium oxide are spread separately on multi-layer refractory boards at a weight ratio of 1:5, without mixing. The nickel-molybdenum ore is 1-3 cm thick. The refractory boards are placed in a heating furnace. Nitrogen gas is first introduced into the sealed heating furnace to create a nitrogen atmosphere. Then, 1-3 kg of calcium oxide is placed at the gas outlet of the heating furnace. Inert protective gas and a small amount of air are then introduced to create low-oxygen conditions in the furnace. High-temperature roasting is carried out under a certain heating mechanism to obtain roasted sand. The heating mechanism is as follows: the furnace temperature is raised to 200℃~300℃ within 15 minutes, and held at 200℃~300℃ for 30 minutes; then, the temperature is raised from 200℃~300℃ to 1000℃~1100℃ and held for 120 minutes over 60-80 minutes. The aforementioned low-oxygen conditions involve an oxygen concentration of 1%-5%. The nickel-molybdenum ore is mined and crushed into powder blocks <3mm by a crusher. After crushing, the weight content of the nickel-molybdenum ore is 5%-10%. The calcium oxide is steelmaking calcium oxide with CaO ≥ 92%, activity ≥ 380 ml, S ≤ 0.05%, and C ≤ 0.5%. The inert protective gas is used in steelmaking. , ≥99.99%, air supply pressure 0.01-0.1MPa; the air is compressed air supplied by the compressor; Before heating, the inert protective gas supply pressure is 0.1 MPa, the gas flow rate is 20-40 L / min, and the holding time is 30 min, so that the furnace is in a positive pressure nitrogen atmosphere; after heating, the inert protective gas supply pressure is 0.01-0.1 MPa, and the air supply pressure is 2-5 kPa.

2. The method for removing arsenic from low-grade nickel-molybdenum ore according to claim 1, characterized in that, The nickel-molybdenum ore and calcium oxide are laid flat on multiple layers of refractory boards without mixing. The nickel-molybdenum ore is 2 cm thick. The refractory boards are placed inside the heating furnace, and 2 kg of calcium oxide is placed at the gas outlet of the heating furnace.

3. The method for removing arsenic from low-grade nickel-molybdenum ore according to claim 1, characterized in that, Before heating, the inert protective gas supply pressure is 0.1 MPa and the holding time is 30 min to make the furnace pressure positive; after heating, the inert protective gas supply pressure is 0.02 MPa and the air supply pressure is 5 kPa.

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