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

Abstract

The present invention discloses a method for preventing H2S generation during the smelting of mixed rare earth concentrate, belonging to the field of environmental protection technology. The method primarily involves performing reverse flotation desulfurization on the mixed rare earth concentrate to remove pyrite, then mixing the resulting pyrite-removed rare earth concentrate with concentrated sulfuric acid and subjecting it to an oxygen-enriched heating reaction. By removing pyrite through flotation and enriching the concentrate with oxygen to prevent H2S generation through reduction by concentrated sulfuric acid, the method significantly reduces H2S in roasting tail gas, avoids sulfur generation during the production process, eliminates the need for H2S treatment in waste gas, and reduces the potential for fires.

Description

Technical Field

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

[0002] Rare earth elements, considered the "materials of the 21st century," have garnered significant attention from scientists both domestically and internationally. In recent years, rare earth elements have found widespread application across a wide range of sectors, including metallurgy, industry, agriculture, and materials science, playing a crucial role in the advancement of science and technology. The continuous advancement of the times has led to an ever-increasing application of rare earth elements, and their production has increased annually. my country possesses the world's largest rare earth deposits. To effectively exploit and utilize these deposits, various rare earth separation and extraction methods have been developed, aiming to maximize rare earth recovery rates. Furthermore, with growing environmental awareness, highly polluting and energy-intensive industries are facing significant pressure. Therefore, research on green separation of rare earth elements from rare earth ores, efficient utilization of rare earth resources, and the establishment of environmentally friendly and efficient extraction smelting plants have become paramount.

[0003] Bastnaesite and monazite are the primary minerals in rare earth ore production, with smaller amounts of rare earth elements obtained from xenotime and ion-adsorption rare earth ores in some regions. Pure bastnaesite is primarily produced in Huishan Lake, Shandong Province, Mianning, Sichuan Province, and Mountain Pass, USA, while monazite is generally found in coastal placer mines. Baotou's mixed rare earth concentrate, a paragenetic mineral of bastnaesite (REFCO3) and monazite (REPO4) (referred to as a mixed ore), is a valuable resource for extracting rare earth elements. This mineral contains numerous elements, a complex ore phase, and is difficult to decompose. Since the 1980s, sulfuric acid decomposition has been adopted by many rare earth smelting companies due to its low cost and good mineral adaptability. However, this method produces waste gas with a complex composition (containing sulfuric acid mist, SO2, SO3, H2S, HF, SiF4, and CO2), making the treatment process complex and lengthy. Sulfuric acid mist, SO₃, HF, and SiF₄ are processed through four-stage countercurrent scrubbing, distillation, and ammonia absorption to produce products such as sulfuric acid, ammonium bifluoride (NH₄HF₂), and white carbon black. SO₂ in the exhaust gas is catalytically absorbed to produce concentrated sulfuric acid, effectively treating the primary component of the exhaust gas. However, a small amount of H₂S gas in the exhaust gas is not effectively recovered and treated throughout the entire process, with the majority remaining in the exhaust gas, potentially causing the exhaust gas to fail to meet environmental protection requirements. However, the H₂S content in the exhaust gas is low, and treatment costs are high. Therefore, it is urgent to study the factors influencing H₂S formation during the production process and effectively adjust smelting parameters to avoid H₂S formation during 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 the smelting of mixed rare earth concentrate comprises first subjecting the mixed rare earth concentrate to reverse flotation desulfurization to remove pyrite, then mixing the obtained pyrite-removed rare earth concentrate with concentrated sulfuric acid and subjecting it to oxygen-enriched heating reaction.

[0007] The method for preventing H2S from being generated during the 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 adjust the slurry, and then an inhibitor, a collector and a 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] Filtering and drying the rare earth concentrate to obtain a pyrite-free rare earth concentrate;

[0010] The pyrite-removed rare earth concentrate is mixed with concentrated sulfuric acid, and then natural gas and oxygen-enriched air are introduced for roasting.

[0011] This method first removes pyrite from the mixed rare earth concentrate to prevent the formation of pyrite sulfide minerals in the concentrate. Then, oxygen-enriched gas is introduced during the sulfuric acid roasting process. This oxygen-enriched air blast prevents the formation of hydrogen sulfide during sulfuric acid reduction at high temperatures. This method achieves significant reduction in hydrogen sulfide in tail gas, achieving emission standards through the synergistic effect of pyrite removal by flotation and oxygen-enriched 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] This invention discloses a treatment method that can prevent the generation of H2S during the smelting of mixed rare earth concentrates. By using flotation to remove pyrite and oxygen enrichment to prevent H2S from being reduced by concentrated sulfuric acid, this method significantly reduces H2S in roasting tail gas and avoids the generation of sulfur during the production process. This eliminates the need for H2S treatment processes in waste gas and reduces the potential for fires. 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 rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

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

[0024] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 any conflict with any incorporated document, the contents 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 described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative 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 roasting flue gas composition, the generation of H2S is determined by the pyrite (FeS) content in the ore, the humidity of the gas, and the oxidizing properties 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 water is also produced during the decomposition of minerals by sulfuric acid. Therefore, controlling the generation of hydrogen sulfide by dehumidification has little effect. Therefore, the present invention takes the other two factors that generate H2S (the FeS content of pyrite and the oxidizing properties of the gas in the roasting flue gas) into consideration. By first performing reverse flotation desulfurization on the mixed rare earth concentrate to remove pyrite, and then mixing the obtained pyrite-free rare earth concentrate with sulfuric acid and performing an oxygen-enriched heating reaction, the generation of H2S is significantly reduced.

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

[0029] Grind the mixed rare earth concentrate to a size of 200 mesh or more, add the mixed rare earth concentrate to a flotation tank at room temperature, add water to adjust the slurry, then add an inhibitor, a collector, and a frother in sequence, and 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 pyrite-free rare earth concentrate;

[0031] The pyrite-removed rare earth concentrate 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 within the aforementioned ranges.

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

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

[0036] In the H2S removal process, as oxygen-enriched air is added, 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 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 within the aforementioned ranges.

[0037] The present invention achieves the goal of controlling hydrogen sulfide production by investigating and controlling the oxidizing properties of the gas. Since the main components of air are nitrogen and oxygen, the present invention primarily uses nitrogen and oxygen cylinders to change the oxygen content and gas flow rate in the gas, thereby changing the atmosphere in the roasting furnace and the H2S content in the exhaust gas.

[0038] In the H2S removal process, adding concentrated sulfuric acid for high-temperature calcination is a necessary step. The amount of sulfuric acid added will vary adaptively depending on the specific process type. For example, in the following embodiments of the present invention, the pyrite-free rare earth concentrate and concentrated sulfuric acid are mixed in a mass ratio of 1: (1-1.5). For example, in the following embodiments of the present invention, the pyrite-free rare earth concentrate and concentrated sulfuric acid are mixed in a mass ratio of 1:1, 1:1.5, or any ratio within the aforementioned range.

[0039] An exemplary embodiment of the method for preventing H2S generation during smelting of a mixed rare earth concentrate comprises the following steps:

[0040] The mixed rare earth concentrate is finely ground to above 200 mesh, 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 undergoes a roughing test process.

[0041] After flotation, the collected foam product (pyrite concentrate) and the in-tank product (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 to a rotary kiln, and heated for reaction as required. Natural gas and oxygen-enriched air are introduced during the heating process. The gas flow rate remains unchanged, and air enriched with 25-30% oxygen is introduced to enhance the oxidizing property 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 exiting 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, which is the total time from entering the kiln to exiting the kiln. In actual production, the sample after exiting 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 combustion time are not specifically limited. In the entire process from entering the kiln to exiting 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 amount of H2S generated.

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

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

[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 examples.

[0049] Example 1

[0050] Mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 mesh to produce mixed rare earth concentrate particles. The chemical composition, by mass percentage, was 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%, with the remainder being other components. Pyrite accounted for 3.23% of the mineral.

[0051] A method for preventing H2S from being generated during the smelting of mixed rare earth concentrates comprises 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%, and sodium silicate (2.5 kg / t) is used as an inhibitor, potassium butyl xanthate (0.18 kg / t) as a pyrite collector, and pine oil (0.05 kg / t) as a frother is used to flotate the mixed rare earth concentrate to remove pyrite, and then undergo secondary mineral processing;

[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 in 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] Mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 mesh to produce mixed rare earth concentrate particles. The chemical composition, by mass percentage, was 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%, with the remainder being other components. Pyrite accounted for 3.23% of the mineral.

[0058] A method for preventing H2S from being generated during the smelting of mixed rare earth concentrates comprises 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. The mixed rare earth concentrate is subjected to flotation to remove pyrite, and then undergoes secondary mineral processing;

[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 in 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] Mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 mesh to produce mixed rare earth concentrate particles. The chemical composition, by mass percentage, was 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%, with the remainder being other components. Pyrite accounted for 3.23% of the mineral.

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

[0066] (1) At room temperature, water is added to the mixed rare earth concentrate particles to adjust the pulp 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. The mixed rare earth concentrate is subjected to flotation to remove pyrite, and then undergoes 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 in 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] Mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 mesh to produce mixed rare earth concentrate particles. The chemical composition, by mass percentage, was as follows: rare earth element oxide (REO) 60.10%, CaO 4.35%, FeO 4.11%, SiO2 1.81%, F 7.80%, P 6.50%, S 1.26%, with the remainder being other components. Pyrite accounted for 3.31% of the mineral.

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

[0073] (1) At room temperature, water is added to the mixed rare earth concentrate particles to adjust the pulp 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. The mixed rare earth concentrate is subjected to flotation to remove pyrite, and then undergoes 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 in 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] Mixed rare earth concentrate (Baotou Bayan Obo mixed rare earth ore) was ground to a particle size of less than 200 mesh to produce mixed rare earth concentrate particles. The chemical composition, by mass percentage, was as follows: rare earth element oxide (REO) 65.10%, CaO 4.35%, FeO 4.11%, SiO2 1.63%, F 7.80%, P 4.10%, S 1.36%, with the remainder being other components. Pyrite accounted for 3.18% of the mineral.

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

[0080] (1) At room temperature, water is added to the mixed rare earth concentrate particles to adjust the pulp 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. The mixed rare earth concentrate is subjected to flotation to remove pyrite, and then undergoes 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 in 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] 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 H2S removal was improved, the rare earth leaching rate dropped to below 90%. This is mainly because the high oxygen content leads to excessive oxidizing properties, which oxidizes Ce, Pr, and Tb from trivalent to tetravalent rare earth elements, making them difficult to leach, reducing the rare earth leaching rate.

[0087] Comparative Example 2

[0088] 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 enrichment content resulted in low oxidizing properties within the furnace, causing some sulfuric acid to be locally reduced to form hydrogen sulfide within the furnace, resulting in substandard hydrogen sulfide emissions in the exhaust gas.

[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 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 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 858 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 decreased by 62.09%. Although oxygen enrichment reduces the production of hydrogen sulfide, it is still possible to avoid the production of hydrogen sulfide during the decomposition of pyrite.

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

Claims

1. A method for preventing H2S from being generated 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; 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 adjust the slurry, and then an inhibitor, a collector and a 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 pyrite-free rare earth concentrate is mixed with concentrated sulfuric acid, and then natural gas and oxygen-enriched air are introduced for roasting; the roasting temperature is 500-600°C; The oxygen enrichment amount of the oxygen-enriched air is 25-30%.

2. The method for avoiding H2S generation during smelting of mixed rare earth concentrate according to claim 1, characterized in that: The slurry adjustment refers to adjusting the slurry concentration to 25-30%.

3. The method for avoiding H2S generation during smelting of mixed rare earth concentrate according to claim 1, characterized in that: The inhibitor is sodium silicate, and the addition amount is 2.3-2.8 kg / t.

4. The method for preventing H2S generation during smelting of mixed rare earth concentrate according to claim 1, characterized in that: The collector is potassium butyl xanthate, and the addition amount is 0.16-0.2 kg / t.

5. The method for preventing H2S generation during smelting of mixed rare earth concentrate according to claim 1, characterized in that: The foaming agent is pine oil, and the addition amount is 0.04-0.08 kg / t.

6. The method for preventing H2S generation during smelting of mixed rare earth concentrate according to claim 1, characterized in that: The amount of natural gas introduced is 70m 3 Natural gas / ton of concentrate.

7. The method for avoiding H2S generation during smelting of mixed rare earth concentrate according to claim 1, characterized in that: The amount of oxygen-enriched air introduced is 10m 3 Air / m 3 natural gas.

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