Treatment method for avoiding generation of H2S during smelting of mixed rare earth concentrate

Abstract

The invention discloses a treatment method for avoiding H2S generation during mixed rare earth concentrate smelting, and belongs to the technical field of environmental protection. The method mainly comprises the following steps: carrying out reverse flotation desulfurization on mixed rare earth concentrate to remove pyrite, mixing the pyrite-removed rare earth concentrate with concentrated sulfuric acid, and carrying out an oxygen-enriched heating reaction. According to the method, pyrite and rich oxygen are removed through flotation, so that H2S is prevented from being generated through reduction of concentrated sulfuric acid, H2S in roasting tail gas is remarkably reduced, sulfur is prevented from being generated in the production process, the treatment process of H2S in waste gas is omitted, and the possibility of fire disasters is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a treatment method for avoiding the generation of H2S during the smelting of mixed rare earth concentrate. Background Art

[0002] As the "material of the 21st century", rare earths are a type of element that scientists at home and abroad pay special attention to. In recent years, rare earth elements have been widely used in various industries, such as metallurgy, industry, agriculture, materials, etc., and have played an important role in the development of science and technology. The continuous development of the times has led to the increasingly widespread application of rare earths, and the production of rare earths has increased year by year. my country has the world's largest rare earth deposits. In order to reasonably develop and utilize them, various rare earth separation and extraction methods are currently available, with the aim of increasing the recovery rate of rare earths as much as possible. In addition, with the increase of people's environmental awareness, high-pollution and high-energy consumption industries are facing great pressure. Therefore, it has become a primary issue to study the green separation of rare earths from rare earth ores, the efficient use of rare earth resources, and the establishment of environmentally friendly and efficient extraction smelting enterprises.

[0003] Fluorocarbon cerium ore and monazite are the main minerals of rare earth ores, and some areas obtain a small amount of rare earths from xenotime and ion adsorption rare earth ores. Among them, pure fluorocarbon cerium ore is mainly produced in Huishan Lake, Shandong, Mianning, Sichuan, and Pass Mountain in the United States, while monazite is generally produced in coastal placer mines. Baotou mixed rare earth concentrate belongs to the paragenetic mineral of fluorocarbon cerium ore (REFCO3) and monazite (REPO4) (referred to as mixed ore), which is an important resource for extracting rare earth elements. This mineral has many elements, complex mineral phases, and is difficult to decompose. Since the 1980s, the sulfuric acid decomposition method has been adopted by many rare earth smelting companies due to its low cost and good mineral adaptability. However, the waste gas generated by this method has complex components (containing sulfuric acid mist, SO2, SO3, H2S, HF, SiF4, CO2), and the treatment process is complex and the process is long. Among them, sulfuric acid mist, SO3, HF and SiF4 can be obtained through four-stage countercurrent washing, distillation, and ammonia absorption to obtain sulfuric acid, ammonium bifluoride (NH4HF2), white carbon black and other products, while SO2 in the waste gas is catalytically absorbed to generate concentrated sulfuric acid, effectively treating the main components in the waste gas. However, a small amount of H2S gas in the waste gas has not been effectively recovered and treated during the entire process, and most of it continues to exist in the tail gas, which may cause the tail gas to fail to meet environmental protection requirements. However, the H2S content in the tail gas is low and the treatment cost is high. Therefore, it is urgent to study the influencing factors of H2S generation in the production process, effectively adjust the smelting parameters, and avoid the generation of H2S in the smelting process. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a treatment method for avoiding the generation of H2S during the smelting of mixed rare earth concentrate.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A treatment method for avoiding H2S generation during smelting of mixed rare earth concentrates, wherein the mixed rare earth concentrates are first subjected to reverse flotation desulfurization to remove pyrite, and then the obtained rare earth concentrates without pyrites are mixed with concentrated sulfuric acid and subjected to oxygen-enriched heating reaction.

[0007] The method for preventing H2S from being generated during smelting of mixed rare earth concentrate specifically comprises the following steps:

[0008] At room temperature, the mixed rare earth concentrate is added to the flotation tank, water is added to prepare the slurry, and then the inhibitor, collector and frother are added in sequence, and the foam product and the product in the tank are collected; wherein the foam product is pyrite concentrate, and the product in the tank is rare earth concentrate;

[0009] The rare earth concentrate is filtered and dried to obtain a pyrite-free rare earth concentrate;

[0010] The rare earth concentrate without pyrite is mixed with concentrated sulfuric acid, and then natural gas and oxygen-enriched air are introduced for roasting.

[0011] The present invention first removes pyrite from the mixed rare earth concentrate to avoid the formation of pyrite, a sulfide mineral, in the concentrate, and then introduces oxygen-rich gas during sulfuric acid roasting to prevent sulfuric acid reduction at high temperature from generating hydrogen sulfide through oxygen-rich air blasting. The present invention achieves the purpose of significantly reducing hydrogen sulfide in tail gas and meeting emission standards through the synergistic effect of pyrite removal by flotation and oxygen-rich air.

[0012] Furthermore, the slurry adjustment refers to adjusting the slurry concentration to 25-30%.

[0013] Furthermore, the inhibitor is sodium silicate, and the addition amount is 2.3-2.8 kg / t.

[0014] Furthermore, the collector is potassium butyl xanthate, and the addition amount is 0.16-0.2 kg / t.

[0015] Furthermore, the foaming agent is pine oil, and the added amount is 0.04-0.08 kg / t.

[0016] Furthermore, the amount of natural gas introduced is 70m 3 Natural gas / 1 ton of concentrate.

[0017] Furthermore, the amount of oxygen-enriched air introduced is 10m 3 Air / 1m 3 natural gas.

[0018] Furthermore, the oxygen enrichment of the oxygen-enriched air is 25-30%.

[0019] Furthermore, the mass ratio of the pyrite-removed rare earth concentrate to concentrated sulfuric acid is 1:(1-1.5).

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] The present invention discloses a treatment method that can prevent the generation of H2S during the smelting of mixed rare earth concentrate. The present invention adopts the means of flotation removal of pyrite and oxygen enrichment to prevent concentrated sulfuric acid from reducing and generating H2S, significantly reducing the H2S in the roasting tail gas, and avoiding the generation of sulfur in the production process, eliminating the treatment process of H2S in the waste gas, and reducing the possibility of fire. DETAILED DESCRIPTION

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0024] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0025] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0026] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0027] Based on the analysis of the composition of the roasting flue gas, the generation of H2S is jointly determined by the content of pyrite (FeS) in the ore, the humidity of the gas, and the oxidizing property of the gas in the roasting flue gas. Although the humidity of the gas can be effectively controlled by dehumidification, it is difficult to achieve in practice because the roasting sulfuric acid itself contains some water, and some moisture is also produced during the decomposition of minerals by sulfuric acid, so the control of the generation of hydrogen sulfide by dehumidification has little effect. Therefore, the present invention starts from the other two factors that produce H2S (the content of FeS in pyrite and the oxidizing property of the gas in the roasting flue gas), firstly performs reverse flotation desulfurization on the mixed rare earth concentrate to remove pyrite, and then mixes the obtained rare earth concentrate without pyrite with sulfuric acid and performs an oxygen-enriched heating reaction, so that the generation of H2S is significantly reduced.

[0028] The following embodiment of the present invention provides a method for preventing the generation of H2S during the smelting of a mixed rare earth concentrate, which specifically comprises the following steps:

[0029] Grind the mixed rare earth concentrate to more than 200 meshes, add the mixed rare earth concentrate to the flotation tank at room temperature, add water to slurry, then add inhibitor, collector and frother in sequence, collect the foam product and the product in the tank; wherein the foam product is pyrite concentrate, and the product in the tank is rare earth concentrate;

[0030] Filtering and drying the foam product and the product in the tank to obtain a rare earth concentrate without pyrite;

[0031] The rare earth concentrate without pyrite is mixed with concentrated sulfuric acid, and then natural gas and oxygen-enriched air are introduced for roasting.

[0032] In some embodiments, the slurry adjustment refers to adjusting the slurry concentration to 25-30%. For example, in the following embodiments of the present invention, the slurry concentration can be adjusted to 25%, 28%, 29%, 30% or any value between the aforementioned ranges.

[0033] In some embodiments, the inhibitor may be sodium silicate, and the addition amount is 2.3-2.8 kg / t. For example, in the following embodiments of the present invention, the addition amount of the inhibitor may be 2.3 kg / t, 2.5 kg / t, 2.6 kg / t, 2.8 kg / t or any value in the aforementioned range.

[0034] In some embodiments, the collector may be potassium butyl xanthate, and the amount added is 0.16-0.2 kg / t. For example, in the following embodiments of the present invention, the amount of the collector added may be 0.16 kg / t, 0.18 kg / t, 0.2 kg / t or any value between the aforementioned ranges.

[0035] In some embodiments, the foaming agent may be pine oil, and the amount added is 0.04-0.08 kg / t. For example, in the following embodiments of the present invention, the amount of the foaming agent added may be 0.04 kg / t, 0.05 kg / t, 0.06 kg / t, 0.07 kg / t, 0.08 kg / t or any value between the aforementioned ranges.

[0036] In the H2S removal process, with the addition of oxygen-enriched air, the amount of natural gas introduced remains unchanged. Therefore, in some embodiments, the amount of natural gas introduced is 70m 3 Natural gas / 1 ton of concentrate. The amount of oxygen-enriched air introduced is 10m 3 Air / 1m 3 Natural gas. The oxygen enrichment of the oxygen-enriched air is 25-30%. In the following embodiments of the present invention, the oxygen enrichment of the oxygen-enriched air is 25%, 26%, 27%, 28%, 29%, 30% or any value between the aforementioned ranges.

[0037] The present invention achieves the purpose of controlling the amount of hydrogen sulfide produced by investigating and controlling the oxidizing property of the gas. Since the main components of air are nitrogen and oxygen, the present invention mainly changes the oxygen content and gas flow rate in the gas through nitrogen cylinders and oxygen cylinders to achieve the purpose of changing the atmosphere in the roasting furnace and changing the H2S content in the tail gas.

[0038] In the H2S removal process, adding concentrated sulfuric acid for high-temperature calcination is a necessary step, and the amount of addition will vary adaptively according to the specific process type. Exemplarily, in the following embodiments of the present invention, the pyrite-free rare earth concentrate is mixed with concentrated sulfuric acid in a mass ratio of 1: (1-1.5). Exemplarily, in the following embodiments of the present invention, the pyrite-free rare earth concentrate is mixed with concentrated sulfuric acid in a mass ratio of 1: 1, 1: 1.5 or any ratio between the aforementioned range values.

[0039] An exemplary example of a treatment method for avoiding the generation of H2S during the smelting of a mixed rare earth concentrate specifically comprises the following steps:

[0040] The mixed rare earth concentrate is finely ground to more than 200 meshes, and water is added to adjust the pulp concentration to 25-30% at room temperature. Sodium silicate (2.3-2.8 kg / t) is used as an inhibitor, potassium butyl xanthate (0.16-0.2 kg / t) is used as a pyrite collector, and pine oil (0.04-0.08 kg / t) is used as a frother. The mixed rare earth concentrate is subjected to reverse flotation desulfurization, and a roughing test process is carried out;

[0041] After flotation, the collected foam product (pyrite concentrate) and the product in the tank (rare earth tailings) are filtered and dried to obtain a pyrite-free rare earth concentrate; the purpose of collecting the foam product (pyrite concentrate) is to recycle it, but it is not within the scope of the present invention, so the subsequent treatment will not be described in detail;

[0042] The obtained pyrite-free rare earth concentrate is mixed with concentrated sulfuric acid as required, added into a rotary kiln, and heated as required. Natural gas and oxygen-enriched air are introduced during the heating process. The gas flow remains unchanged, and air enriched with 25-30% oxygen is introduced to enhance the oxidizability in the furnace.

[0043] In this process, the heating reaction refers to the process in which a mixture of rare earth concentrate and concentrated sulfuric acid is burned under the mixed gas after natural gas and oxygen-enriched air are introduced. The combustion process of the mixture continues from entering the kiln to leaving the kiln, and the highest combustion temperature range can reach about 500-600°C. As the combustion is completed, its temperature will show a downward trend. The entire combustion process lasts about 120 minutes, that is, the total time from entering the kiln to leaving the kiln. In actual production, the sample after leaving the kiln can immediately enter the next stage as the raw material for the next stage. The present invention reduces the generation rate of H2S through this optimized treatment process. In the following embodiments of the present invention, the combustion temperature and the combustion time are not specifically limited. In the entire process from entering the kiln to leaving the kiln, the present invention regulates the amount of natural gas and oxygen-enriched air introduced according to different processes, thereby completing the high-temperature roasting process, thereby achieving the purpose of reducing the generation of H2S.

[0044] In the following examples of the present invention, the rare earth element oxide content is determined by plasma method; the pyrite content is determined by a method combining mineral analysis and element analysis; and the H2S in the gas is determined by gas chromatography. The specific determination methods can be conventional methods in the art.

[0045] The "normal temperature" mentioned in the present invention refers to 25±10°C unless otherwise specified.

[0046] The raw materials used in the present invention are all purchased from the market.

[0047] The concentration of concentrated sulfuric acid is 90-98%.

[0048] The technical solution of the present invention is further illustrated by the following embodiments.

[0049] Example 1

[0050] The mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 meshes to obtain mixed rare earth concentrate particles. After measurement, the chemical composition by mass percentage is as follows: rare earth element oxide (REO) 54.21%, CaO 11.63%, FeO 4.21%, SiO2 2.53%, F 6.75%, P 5.91%, S 1.20%, and the balance is other components. Pyrite in the mineral is 3.23%.

[0051] A method for preventing H2S from being generated during the smelting of mixed rare earth concentrates, specifically comprising the following steps:

[0052] (1) At room temperature, water is added to the mixed rare earth concentrate particles to adjust the slurry concentration to 27%, sodium silicate (2.5 kg / t) is used as an inhibitor, potassium butyl xanthate (0.18 kg / t) is used as a pyrite collector, and pine oil (0.05 kg / t) is used as a frother to flotate the mixed rare earth concentrate to remove pyrite, and then secondary mineral processing is performed;

[0053] (2) After flotation is completed, the product in the tank (rare earth tailings) is collected, filtered, and dried to obtain a rare earth concentrate without pyrite;

[0054] (3) The rare earth concentrate without pyrite was mixed with concentrated sulfuric acid at a mass ratio of 1:1.5, added to the rotary kiln, and natural gas (70m 3 Natural gas / 1 ton of concentrate) and oxygen-enriched air (10m 3 Air / m 3 Natural gas), the oxygen content in the oxygen-enriched air is 28%, which enhances the oxidizability in the furnace and obtains the roasted product after roasting.

[0055] The results show that the rare earth loss rate is 3.26%, the pyrite removal rate is 85.56%, and the H2S content in the treated flue gas is 4.5 mg / m 3 , compared with the original process (the H2S content in the flue gas in the original process is 2250mg / m 3 ), the H2S content in the flue gas is reduced by 99.80%.

[0056] Example 2

[0057] The mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 meshes to obtain mixed rare earth concentrate particles. After measurement, the chemical composition by mass percentage is as follows: rare earth element oxide (REO) 54.21%, CaO 11.63%, FeO 4.21%, SiO2 2.53%, F 6.75%, P 5.91%, S 1.20%, and the balance is other components. Pyrite in the mineral is 3.23%.

[0058] A method for preventing H2S from being generated during the smelting of mixed rare earth concentrates, specifically comprising the following steps:

[0059] (1) At room temperature, water is added to the mixed rare earth concentrate particles to adjust the slurry concentration to 27%, sodium silicate (2.3 kg / t) is used as an inhibitor, potassium butyl xanthate (0.16 kg / t) is used as a pyrite collector, and pine oil (0.04 kg / t) is used as a frother to flotate the mixed rare earth concentrate to remove pyrite, and then secondary mineral processing is performed;

[0060] (2) After flotation is completed, the product in the tank (rare earth tailings) is collected, filtered, and dried to obtain a rare earth concentrate without pyrite;

[0061] (3) The rare earth concentrate without pyrite was mixed with concentrated sulfuric acid at a mass ratio of 1:1.5, added to the rotary kiln, and natural gas (70m 3 Natural gas / ton of concentrate) and oxygen-enriched air (10m 3 Air / m 3 Natural gas), the oxygen content in the oxygen-enriched air is 30%, which enhances the oxidizability in the furnace and obtains the roasted product after roasting.

[0062] The results show that the rare earth loss rate is 3.54%, the pyrite removal rate is 82.47%, and the H2S content in the treated flue gas is 5.0 mg / m 3 , compared with the original process (the H2S content in the flue gas in the original process is 2250mg / m 3 ), the H2S content in the flue gas is reduced by 99.78%.

[0063] Example 3

[0064] The mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 meshes to obtain mixed rare earth concentrate particles. After measurement, the chemical composition by mass percentage is as follows: rare earth element oxide (REO) 54.21%, CaO 11.63%, FeO 4.21%, SiO2 2.53%, F 6.75%, P 5.91%, S 1.20%, and the balance is other components. Pyrite in the mineral is 3.23%.

[0065] A method for preventing H2S from being generated during the smelting of mixed rare earth concentrates, specifically comprising the following steps:

[0066] (1) At room temperature, water is added to the mixed rare earth concentrate particles to adjust the slurry concentration to 25%, sodium silicate (2.8 kg / t) is used as an inhibitor, potassium butyl xanthate (0.2 kg / t) is used as a pyrite collector, and pine oil (0.08 kg / t) is used as a frother, and the mixed rare earth concentrate is subjected to flotation to remove pyrite, and then subjected to secondary mineral processing;

[0067] (2) After flotation is completed, the product in the tank (rare earth tailings) is collected, filtered, and dried to obtain a rare earth concentrate without pyrite;

[0068] (3) The rare earth concentrate without pyrite was mixed with concentrated sulfuric acid at a mass ratio of 1:1.5, added to the rotary kiln, and natural gas (70m 3 Natural gas / 1 ton of concentrate) and oxygen-enriched air (10m 3 Air / 1m 3 Natural gas), the oxygen content in the oxygen-enriched air is 25%, which enhances the oxidizability in the furnace and obtains the roasted product after roasting.

[0069] The results show that the rare earth loss rate is 3.19%, the pyrite removal rate is 89.08%, and the H2S content in the treated flue gas is 3.0 mg / m 3 , compared with the original process (the H2S content in the flue gas in the original process is 2250mg / m 3 ), the H2S content in the flue gas is reduced by 99.87%.

[0070] Example 4

[0071] The mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 meshes to obtain mixed rare earth concentrate particles. After measurement, the chemical composition by mass percentage is as follows: rare earth element oxide (REO) 60.10%, CaO 4.35%, FeO 4.11%, SiO21.81%, F 7.80%, P6.50%, S1.26%, and the balance is other components. Pyrite in the mineral is 3.31%.

[0072] A method for preventing H2S from being generated during the smelting of mixed rare earth concentrates, specifically comprising the following steps:

[0073] (1) At room temperature, water is added to the mixed rare earth concentrate particles to adjust the slurry concentration to 28%, sodium silicate (2.6 kg / t) is used as an inhibitor, potassium butyl xanthate (0.18 kg / t) is used as a pyrite collector, and pine oil (0.06 kg / t) is used as a frother, and the mixed rare earth concentrate is subjected to flotation to remove pyrite, and then subjected to secondary mineral processing;

[0074] (2) After flotation is completed, the product in the tank (rare earth tailings) is collected, filtered, and dried to obtain a rare earth concentrate without pyrite;

[0075] (3) The rare earth concentrate without pyrite was mixed with concentrated sulfuric acid at a mass ratio of 1:1.5, added to the rotary kiln, and natural gas (70m 3 Natural gas / ton of concentrate) and oxygen-enriched air (10m 3 Air / m 3Natural gas), the oxygen content in the oxygen-enriched air is 28%, which enhances the oxidizability in the furnace and obtains the roasted product after roasting.

[0076] The results show that the rare earth loss rate is 3.01%, the pyrite removal rate is 88.15%, and the H2S content in the treated flue gas is 3.5 mg / m 3 , compared with the original process (the H2S content in the flue gas in the original process is 2250mg / m 3 ), the H2S content in the flue gas is reduced by 99.84%.

[0077] Example 5

[0078] The mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 meshes to obtain mixed rare earth concentrate particles. After measurement, the chemical composition by mass percentage is as follows: rare earth element oxide (REO) 65.10%, CaO 4.35%, FeO 4.11%, SiO21.63%, F 7.80%, P4.10%, S1.36%, and the balance is other components. Pyrite in the mineral is 3.18%.

[0079] A method for preventing H2S from being generated during the smelting of mixed rare earth concentrates, specifically comprising the following steps:

[0080] (1) At room temperature, water is added to the mixed rare earth concentrate particles to adjust the slurry concentration to 27%, sodium silicate (2.5 kg / t) is used as an inhibitor, potassium butyl xanthate (0.18 kg / t) is used as a pyrite collector, and pine oil (0.07 kg / t) is used as a frother, and the mixed rare earth concentrate is subjected to flotation to remove pyrite, and then subjected to secondary mineral processing;

[0081] (2) After flotation is completed, the product in the tank (rare earth tailings) is collected, filtered, and dried to obtain a rare earth concentrate without pyrite;

[0082] (3) The rare earth concentrate without pyrite was mixed with concentrated sulfuric acid at a mass ratio of 1:1.5, added to the rotary kiln, and natural gas (70m 3 Natural gas / ton of concentrate) and oxygen-enriched air (10m 3 Air / m 3 Natural gas), the oxygen content in the oxygen-enriched air is 29%, which enhances the oxidizability in the furnace and obtains the roasted product after roasting.

[0083] The results show that the rare earth loss rate is 3.41%, the pyrite removal rate is 87.13%, and the H2S content in the treated flue gas is 4.2 mg / m 3 , compared with the original process (the H2S content in the flue gas in the original process is 2250mg / m 3), the H2S content in the flue gas is reduced by 99.81%.

[0084] Comparative Example 1

[0085] The same as Example 1, except that in step (3), the oxygen content in the oxygen-enriched air is 35%.

[0086] The results show that the rare earth loss rate is 3.26%, the pyrite removal rate is 85.56%, and the H2S content in the treated flue gas is 4.1 mg / m 3 , compared with the original process (the H2S content in the flue gas in the original process is 2250mg / m 3 ), the H2S content in the flue gas was reduced by 99.82%. Although the removal of H2S was better, the rare earth leaching rate decreased to below 90%. This was mainly because the high oxygen content led to high oxidizability, and Ce, Pr, and Tb in the rare earth were oxidized from trivalent to tetravalent, which made it difficult to leach, reducing the leaching rate of rare earth.

[0087] Comparative Example 2

[0088] The same as Example 1, except that in step (3), the oxygen content in the oxygen-enriched air is 20%.

[0089] The results show that the rare earth loss rate is 3.26%, the pyrite removal rate is 85.56%, and the H2S content in the treated flue gas is 456 mg / m 3 , compared with the original process (the H2S content in the flue gas in the original process is 2250mg / m 3 ), the H2S content in the flue gas was reduced by 79.73%. The low oxygen content made the oxidation in the furnace too low, causing some sulfuric acid to be locally reduced in the furnace to generate hydrogen sulfide, and the emission of hydrogen sulfide in the tail gas did not meet the standard.

[0090] Comparative Example 3

[0091] The same as Example 1, except that steps (1)-(2) are not performed, and the raw material mixed rare earth concentrate particles are directly mixed with concentrated sulfuric acid to perform the operation of step (3), specifically: the raw material mixed rare earth concentrate particles and concentrated sulfuric acid are mixed in a mass ratio of 1:1.5, added to a rotary kiln, and natural gas (70m 3 Natural gas / 1 ton of concentrate) and oxygen-enriched air (10m 3 Air / 1m 3 Natural gas), the oxygen content in the oxygen-enriched air is 28%, which enhances the oxidizability in the furnace and obtains the roasted product after roasting.

[0092] The results show that the rare earth loss rate is 0%, the pyrite removal rate is 0%, and the H2S content in the treated flue gas is 858mg / m 3, compared with the original process (the H2S content in the flue gas in the original process is 2250mg / m 3 ), the H2S content in the flue gas decreased by 62.09%. Although oxygen enrichment reduces the generation of hydrogen sulfide, it is still unavoidable that hydrogen sulfide is still generated when pyrite decomposes.

[0093] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preventing H2S from being produced during the smelting of mixed rare earth concentrate, characterized in that: The mixed rare earth concentrate is first subjected to reverse flotation desulfurization to remove pyrite, and then the obtained rare earth concentrate without pyrite is mixed with concentrated sulfuric acid and subjected to oxygen-enriched heating reaction.

2. The method for avoiding the generation of H2S during the smelting of mixed rare earth concentrate according to claim 1, characterized in that: The method specifically comprises the following steps: At room temperature, the mixed rare earth concentrate is added to the flotation tank, water is added to prepare the slurry, and then the inhibitor, collector and frother are added in sequence, and the foam product and the product in the tank are collected; wherein the foam product is pyrite concentrate, and the product in the tank is rare earth concentrate; filtering and drying the rare earth concentrate to obtain a pyrite-free rare earth concentrate; The rare earth concentrate without pyrite is mixed with concentrated sulfuric acid, and then natural gas and oxygen-enriched air are introduced for roasting.

3. The method for avoiding the generation of H2S during the smelting of mixed rare earth concentrate according to claim 2, characterized in that: The slurry adjustment refers to adjusting the slurry concentration to 25-30%.

4. The method for avoiding the generation of H2S during the smelting of mixed rare earth concentrate according to claim 2, characterized in that: The inhibitor is sodium silicate, and the addition amount is 2.3-2.8 kg / t.

5. The method for avoiding H2S generation during smelting of mixed rare earth concentrate according to claim 2, characterized in that: The collector is potassium butyl xanthate, and the addition amount is 0.16-0.2 kg / t.

6. The method for avoiding the generation of H2S during the smelting of mixed rare earth concentrate according to claim 2, characterized in that: The foaming agent is pine oil, and the added amount is 0.04-0.08 kg / t.

7. The method for avoiding the generation of H2S during the smelting of mixed rare earth concentrate according to claim 2, characterized in that: The amount of natural gas introduced is 70m 3 Natural gas / ton of concentrate.

8. The method for avoiding H2S generation during smelting of mixed rare earth concentrate according to claim 2, characterized in that: The amount of oxygen-enriched air introduced is 10m 3 Air / m 3 natural gas.

9. The method for avoiding H2S generation during smelting of mixed rare earth concentrate according to claim 8, characterized in that: The oxygen-enriched air has an oxygen enrichment content of 25-30%.

10. The method for avoiding H2S generation during smelting of mixed rare earth concentrate according to claim 2, characterized in that: The mass ratio of the pyrite-removed rare earth concentrate to concentrated sulfuric acid is 1:(1-1.5)1.5.