Low-carbon and energy-saving process for smelting manganese-rich slag from high-silicon manganese ore

Abstract

The present application relates to the technical field of metallurgical chemical industry, and discloses a low-carbon energy-saving process for smelting manganese-rich slag from high-silicon manganese ore, wherein the process comprises the following steps: mixing fine-grained carbon-containing high-silicon manganese ore with silicon carbide powder to prepare premixed ore powder; completing decarburization by selective heating with microwaves in an inert atmosphere to obtain decarburized ore powder with a residual carbon content of less than 0.5%; granulating the decarburized ore powder with a sodium carbonate and potassium carbonate composite alkali system; carrying out two-stage alkali roasting desilication through a continuous flow microwave reactor; obtaining decarburized and desilicated concentrate through pressure filtration after countercurrent hot water leaching; recycling the alkali liquor back to the granulation process after evaporation and concentration of the leachate; and reducing smelting the decarburized and desilicated concentrate by adding coke powder and dolomite, to obtain manganese-rich slag products with a MnO content of 50 to 65%.

Description

Technical Field

[0001] This invention relates to the field of metallurgical and chemical technology, and more specifically, to a low-carbon and energy-saving process for smelting manganese-rich slag from high-silicon manganese ore. Background Technology

[0002] Manganese ore resources contain a large amount of fine-grained, carbonaceous, high-silica manganese ore, with a particle size of less than 0.1 mm and a carbon content of 3% to 8%. These ores originate from beneficiation tailings or weathered ore containing organic carbon. Due to their high silicon content, these ores must be alkali-roasted to remove silicon before they can be used to smelt manganese-rich slag.

[0003] Existing technologies typically employ conventional alkali roasting processes to desiliconize carbonaceous high-silicon manganese ores. This involves mixing and granulating the ore powder with an alkali agent, then directly feeding it into a roasting furnace to simultaneously complete decarburization and desiliconization within a temperature range of 650 to 850°C.

[0004] However, this process has the following technical problems: the carbonaceous components slowly pyrolyze within the calcination temperature range, producing... The reaction with alkaline flux produces carbonates, consuming available alkali, leading to a decrease in desilication rate and an increase in alkali dosage. Simultaneously, pyrolysis gas generation increases internal pressure in the granulated pellets, causing them to crack and pulverize, disrupting the material's structural integrity, and affecting the leaching desilication effect and the uniformity of the reduction smelting batch. The decarburization and desilication processes interfere with each other within the same temperature window, resulting in high overall process energy consumption and high alkali consumption. Summary of the Invention

[0005] This invention provides a low-carbon and energy-saving process for smelting manganese-rich slag from high-silicon manganese ore, solving the technical problems of high energy consumption and low grade of manganese-rich slag caused by carbonaceous impurities and high silicon content in the reduction smelting of high-silicon manganese ore in related technologies.

[0006] This invention discloses a low-carbon and energy-saving process for smelting manganese-rich slag from high-silicon manganese ore, comprising the following steps:

[0007] Premixed mineral powder is obtained by mixing fine-grained carbonaceous high-silicon manganese ore with silicon carbide micro powder.

[0008] The premixed mineral powder is placed in a microwave reactor and heated to 800 to 1000°C under an inert atmosphere and held for 8 to 20 minutes to complete decarburization, resulting in decarburized mineral powder with a residual carbon content of less than 0.5%.

[0009] Decarbonized mineral powder is mixed with sodium carbonate and potassium carbonate, granulated, and dried to obtain alkali mineral granules.

[0010] The alkali ore granules are fed into a tubular continuous flow microwave reactor and undergo alkali roasting and desiliconization in a preheating section and a reaction section. The temperature of the reaction section is 700 to 850°C to obtain activated roasted granules.

[0011] The activated roasted particles were leached with hot water and separated into solid and liquid components to obtain a decarburized and desiliconized concentrate.

[0012] The decarburized and desiliconized concentrate is mixed with coke powder and dolomite and then reduced and smelted. The slag and iron are separated to obtain manganese-rich slag.

[0013] Furthermore, the silicon carbide micro powder is α-phase silicon carbide with a particle size of 0.01 to 0.05 mm and a purity of not less than 98%, and the amount used is 2% to 5% of the mass of fine-grained carbonaceous high-silicon manganese ore.

[0014] Furthermore, the power density of the microwave heating is 8 to 18 kW / kg, the microwave frequency is 2450 MHz, and the heating rate is 30 to 60 °C / min.

[0015] Furthermore, the microwave heating adopts a pulsed power modulation method: heating the premixed mineral powder to the target temperature for 3 to 5 minutes at a power density of 14 to 18 kW / kg, and then switching to a power density of 6 to 8 kW / kg to maintain the temperature for 8 to 12 minutes.

[0016] Furthermore, the amount of sodium carbonate used is 10% to 20% of the mass of the decarbonated mineral powder, the amount of potassium carbonate used is 5% to 12% of the mass of the decarbonated mineral powder, and the mass ratio of sodium carbonate to potassium carbonate is 1.5:1 to 2:1.

[0017] Furthermore, the preheating section of the tubular continuous flow microwave reactor has a microwave power density of 2 to 5 kW / kg, a temperature of 300 to 500 °C, and a residence time of 5 to 10 min; the reaction section has a microwave power density of 6 to 14 kW / kg and a residence time of 15 to 30 min; the tube rotates around the axis at a speed of 2 to 5 r / min.

[0018] Furthermore, the hot water leaching adopts a countercurrent leaching method, with a hot water temperature of 75 to 95°C, a liquid-to-solid mass ratio of 3.5:1 to 5.5:1, and a leaching residence time of 20 to 50 minutes.

[0019] Furthermore, after leaching, the leachate is evaporated and concentrated to an alkaline concentration of 25% to 35%, and then recycled back to the granulation step to be used in combination with fresh alkaline agent. The amount of fresh alkaline agent added is 15% to 30% of the total amount of alkaline agent used.

[0020] Furthermore, in the reduction smelting, the amount of coke powder used is 5% to 11% of the mass of the decarburized and desiliconized concentrate, the amount of dolomite used is 2% to 6% of the mass of the decarburized and desiliconized concentrate, the reduction smelting temperature is 1300 to 1420℃, and the smelting time is 45 to 75 minutes.

[0021] This invention discloses a manganese-rich slag prepared by the above-mentioned low-carbon and energy-saving process, wherein the MnO content in the manganese-rich slag is 50% to 65%.

[0022] This invention places the decarburization process separately before the alkali roasting and desilication process using microwave selective heating, thus solving the technical problem of mutual interference between the decarburization and desilication processes within the same temperature window, and achieving the following technical effects:

[0023] After the decarburization and desiliconization processes are decoupled, no carbonaceous pyrolysis is generated during the roasting stage. The effective amount of alkali consumed is used entirely by the alkali in the compound alkali system to react with... The reaction ensures the utilization efficiency of alkali, and the amount of alkali used is reduced accordingly; decarburization is completed in a loose powder state, and pyrolysis gas can escape quickly in the gaps between particles, eliminating the problem of pellet cracking and pulverization; the sodium carbonate and potassium carbonate composite alkali system forms a eutectic liquid phase at about 710℃, which changes the desilication reaction from solid-solid contact to liquid-solid contact, reducing the calcination temperature requirement; the recycling of alkali solution reduces the amount of fresh alkali added to 15% to 30% of the total alkali usage, reducing alkali consumption. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the preparation process of low-carbon and energy-saving process for smelting manganese-rich slag from high-silicon manganese ore according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram comparing the decarbonization rate and residual carbon content of each embodiment and comparative example provided in the embodiments of the present invention;

[0026] Figure 3 This is a schematic diagram comparing the pellet integrity rate and desilication rate of each embodiment and comparative example provided in the embodiments of the present invention;

[0027] Figure 4 This is a schematic diagram comparing the energy consumption and decarbonization rate of step 2 in the pulsed mode and the conventional microwave mode provided in the embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram comparing the MnO content of the manganese-rich slag and the alkali consumption in step 4 of each embodiment and comparative example provided in the present invention.

[0029] Figure 6 This is a schematic diagram of the SEM morphology of decarburized and desiliconized concentrate provided in an embodiment of the present invention;

[0030] Figure 7 This is a schematic diagram of the XRD diffraction pattern of the water-quenched product with manganese-rich slag provided in an embodiment of the present invention;

[0031] Figure 8 This is a schematic diagram of the FTIR comparison spectra of alkali ore granules before and after roasting, provided in an embodiment of the present invention. Detailed Implementation

[0032] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0033] This invention discloses a low-carbon and energy-saving process for smelting manganese-rich slag from high-silicon manganese ore, with reference to... Figure 1 ,include:

[0034] Step 1: Preparation of premixed mineral powder containing microwave-sensitive components

[0035] 100 parts by weight of fine-grained, carbonaceous, high-silica manganese ore and 2 to 5 parts by weight of silicon carbide micropowder are added to a mixer and mixed evenly to obtain a premixed mineral powder containing microwave-sensitive components. The preferred amount of silicon carbide micropowder is 3 to 4 parts by weight. If the amount is less than 2 parts by weight, the microwave heating uniformity is insufficient; if it is more than 5 parts by weight, it will adversely affect the consumption of alkali solution during subsequent alkali roasting and leaching processes.

[0036] It should be noted that the particle size of the aforementioned silicon carbide micro powder is 0.01 to 0.05 mm, preferably 0.02 to 0.03 mm. Within this particle size range, the silicon carbide micro powder can be uniformly dispersed and adhered to the surface of fine-grained carbonaceous high-silicon manganese ore particles, forming uniformly distributed microwave absorption hotspots.

[0037] It should be noted that the aforementioned silicon carbide micro powder is α-phase silicon carbide with a purity of not less than 98% and a dielectric loss tangent of ( At 2450MHz and room temperature, the value is not less than 0.05, where This represents the ratio of dielectric loss to energy storage of the material in an alternating electromagnetic field. Alpha-phase silicon carbide was chosen because its chemical stability at high temperatures is superior to that of β-phase silicon carbide, allowing it to maintain its structural integrity during subsequent alkali roasting and reduction smelting processes, thus continuously exerting its selective heating effect as a permanent microwave absorber.

[0038] Furthermore, the mixing speed of the mixer is 100 to 300 r / min, and the mixing time is 10 to 20 min, preferably 150 to 200 r / min and 12 to 15 min, to ensure that the silicon carbide micro powder and the fine carbonaceous high-silicon manganese ore particles are fully and uniformly dispersed.

[0039] Furthermore, since silicon carbide micro powder is a dust-like material, mixing operations should be carried out in a closed or locally ventilated environment, and operators should wear dust masks to avoid prolonged inhalation of fine-particle dust.

[0040] Step 2, Microwave Selective Decarburization

[0041] Place the premixed ore powder containing microwave-sensitive components obtained in Step 1 into a tubular microwave reactor, introduce nitrogen to establish an inert atmosphere, and heat it to 800 to 1000 °C at a microwave frequency of 2450 MHz and a power density of 8 to 18 kW / kg, hold for 8 to 20 min, and then cool to obtain decarburized ore powder. Among them, the power density is preferably 10 to 14 kW / kg, the corresponding heating temperature is preferably 850 to 950 °C, and the holding time is preferably 10 to 15 min. The carbonaceous components in silicon carbide micropowder and fine-grained carbonaceous high-silicon manganese ore have high dielectric loss characteristics for 2450 MHz microwaves, and preferentially absorb electromagnetic energy and convert it into heat energy in the microwave field to achieve selective rapid volume heating. The carbonaceous components are centrally pyrolyzed and decomposed into CO and gas in this temperature range. Since the premixed ore powder containing microwave-sensitive components exists in the form of loose powder rather than dense pellets, the generated gas can quickly escape through the particle gaps, and there is no problem of structural damage caused by internal pressure accumulation. After cooling, sample and detect the residual carbon content of the decarburized ore powder. The residual carbon content is determined by the high-temperature combustion infrared absorption method, and the residual carbon content less than 0.5% (mass fraction) is qualified.

[0042] It should be noted that the nitrogen flow rate in the above inert atmosphere is 2 to 5 L / (min·L) based on the effective volume of the reactor, and the oxygen content in the reactor is maintained below 0.5% (volume fraction). The purpose of using an inert atmosphere is to prevent the uncontrollable combustion of carbonaceous components under aerobic conditions from causing local overheating and ensure that the decarburization process is mild and controllable.

[0043] Furthermore, the nitrogen purity is not less than 99.9% (volume fraction), and the gas injection method is to continuously inject from the bottom of the reactor and discharge from the top to ensure the uniform distribution of the inert atmosphere in the reactor and carry out the CO and[[ID=I2]] gas generated by pyrolysis out of the reaction zone in time.

[0044] Furthermore, the heating rate in the microwave heating and temperature-rising stage is controlled to be 30 to 60 °C / min, preferably 40 to 50 °C / min, to avoid local overheating of the material caused by too fast heating.

[0045] Furthermore, in order to further improve the decarburization efficiency and microwave energy utilization rate, a pulse power modulation method can be adopted during microwave heating: heat the premixed ore powder containing microwave-sensitive components to the target temperature quickly at a high power density of 14 to 18 kW / kg for 3 to 5 min, and then switch to a low power density of 6 to 8 kW / kg to maintain the holding for 8 to 12 min. This pulse power modulation method can avoid local overheating caused by continuous high-power heating and reduce the total energy consumption at the same time.

[0046] Furthermore, the reactor's tail gas outlet is connected to an alkaline absorption tower, where a 5-10% sodium carbonate solution is used to absorb and treat the CO in the tail gas, preventing direct CO emissions into the atmosphere and potential safety hazards. After treatment, the tail gas is tested for CO concentration, and emissions are only permitted after confirmation that the concentration is below 24 mg / m³.

[0047] Furthermore, since this step involves high-temperature operation and the generation of toxic gases such as CO, the operating area should be equipped with an online CO concentration alarm device. Operators must not open the inlet or outlet during reactor operation. The microwave reactor shell should be equipped with electromagnetic shielding and high-temperature warning signs to prevent microwave leakage and high-temperature burns.

[0048] Step 3, granulation of alkali ore

[0049] 100 parts by weight of the decarbonated mineral powder obtained in step 2 are mixed evenly with 10 to 20 parts by weight of sodium carbonate and 5 to 12 parts by weight of potassium carbonate in a granulator. Then, 2 to 5 parts by weight of water are added for wet granulation. The granulation speed is 200 to 400 r / min, and the granulation time is 8 to 15 min, to obtain spherical particles with a particle size of 1 to 3 mm. The obtained spherical particles are placed in an oven and dried at 110 to 130°C until the moisture content is less than 2%, to obtain alkali mineral granules. The preferred mass ratio of sodium carbonate to potassium carbonate is 1.5:1 to 2:1, the preferred amount of sodium carbonate is 13 to 17 parts by weight, and the preferred amount of potassium carbonate is 7 to 10 parts by weight. The composite alkali system of sodium carbonate and potassium carbonate utilizes the fact that the two form a eutectic at about 710°C (lower than the individual melting points of sodium carbonate (851°C) and potassium carbonate (891°C) to form a liquid phase coating on the decarbonated mineral powder particles at a lower temperature. On the particle surface, the solid-solid reaction is transformed into a liquid-solid reaction, reducing the required calcination temperature and accelerating the desilication reaction.

[0050] It should be noted that the sodium carbonate mentioned above is industrial-grade sodium carbonate with a purity of not less than 99% and a particle size of 0.075 to 0.15 mm; the potassium carbonate is industrial-grade potassium carbonate with a purity of not less than 98% and a particle size of 0.075 to 0.15 mm.

[0051] By controlling the granulation speed to 200 to 400 r / min and the granulation time to 8 to 15 min, spherical particles with a diameter of 1 to 3 mm and uniform density can be obtained. Since the residual carbon content in the decarbonized mineral powder is less than 0.5%, the alkaline mineral granules will not crack or pulverize due to carbon pyrolysis gas generation during subsequent roasting.

[0052] Furthermore, the heating rate of the drying step is controlled at 1 to 3 °C / min, preferably 1.5 to 2 °C / min, to avoid excessively rapid heating that could cause the surface moisture of the spherical particles to evaporate rapidly and generate cracks.

[0053] Furthermore, the water used for granulation is deionized water or softened water, and the water is added by atomized spraying at a rate of 0.2 to 0.5 parts by mass per minute to ensure that the moisture is evenly distributed in the material and to avoid uneven particle size caused by local over-wetting.

[0054] Furthermore, sodium carbonate and potassium carbonate powders are alkaline and irritating. During the batching and granulation operations, operators should wear protective gloves and goggles to avoid dust contact with the skin and eyes.

[0055] Step 4: Continuous flow microwave alkaline roasting for desilication

[0056] The alkali ore granules obtained in step 3 are continuously fed into a tubular continuous flow microwave reactor via a screw feeder. The reactor has two temperature zones: a preheating zone and a reaction zone. In the preheating zone, the microwave power density is 2 to 5 kW / kg, the temperature is 300 to 500°C, and the residence time is 5 to 10 min; preferably, the power density is 3 to 4 kW / kg, the temperature is 350 to 450°C, and the residence time is 6 to 8 min. In the reaction zone, the microwave power density is 6 to 14 kW / kg, the temperature is 700 to 850°C, and the residence time is 15 to 30 min; preferably, the power density is 8 to 12 kW / kg, the temperature is 720 to 800°C, and the residence time is 18 to 25 min. Activated roasted granules are obtained by continuous discharge.

[0057] The preheating section serves to uniformly heat the alkali ore granules, preventing them from fracturing due to thermal stress when directly introduced into the high-temperature zone. In the reaction section, the sodium carbonate and potassium carbonate composite alkali system forms a eutectic liquid phase around 710℃. This eutectic liquid phase wets and coats the decarbonized ore powder particles. The particle surface transforms the desilication reaction from a solid-solid contact to a liquid-solid contact, increasing the reaction interface area and accelerating the desilication reaction rate. Since the decarburization process is completed independently in step 2, no further action is required during the calcination stage. The effective alkali content is entirely used to react with... The reaction produces soluble silicates, thus ensuring the efficient utilization of the alkali.

[0058] Furthermore, the heating rate between the preheating section and the reaction section is controlled at 5 to 15°C / min, preferably 8 to 12°C / min, to ensure that the pellets are heated uniformly in the temperature transition range and to avoid thermal stress cracks caused by excessive temperature gradient.

[0059] Furthermore, in order to further improve the uniformity of heating of materials in the reactor, the tube of the tubular continuous flow microwave reactor rotates around the axis at a speed of 2 to 5 r / min, so that the spherical particles continuously tumble and move forward in the tube, and each particle is uniformly irradiated by microwaves.

[0060] Furthermore, a nitrogen protective atmosphere is introduced into the tubular continuous flow microwave reactor, with a nitrogen purity of not less than 99.9% (volume fraction) and a nitrogen flow rate of 1 to 3 L / (min·L) based on the effective volume of the reactor. This is to prevent local overheating of the alkali ore granules during high-temperature roasting due to the oxidation and combustion of residual trace carbon or organic matter, while also avoiding the volatilization loss of the composite alkali system in an aerobic atmosphere.

[0061] Furthermore, tubular continuous flow microwave reactors should be equipped with comprehensive electromagnetic shielding measures. The microwave leakage power density at the reactor inlet / outlet and tube connection should be less than 5 mW / cm². Operators must not approach unshielded areas during reactor operation, and high-temperature warning signs should be installed on the outside of the equipment.

[0062] Step 5, hot water leaching for desilication

[0063] The activated roasted particles obtained in step 4 are continuously fed into a countercurrent leaching device, where hot water at a temperature of 75 to 95°C is sprayed from the top at a liquid-to-solid mass ratio of 3.5:1 to 5.5:1. The material moves from top to bottom, and the leaching residence time is 20 to 50 minutes. The dissolved sodium silicate and potassium silicate enter the liquid phase, while the desilication concentrate slurry is discharged from the bottom. The desilication concentrate slurry is dewatered by pressure filtration, and the filter cake is washed 2 to 3 times with clean water and dried in an oven at 110 to 130°C until the moisture content is below 2%. The decarburized and desilicon concentrate contains 5-12% silica and less than 0.5% carbon. The preferred hot water temperature is 80-90℃, the preferred liquid-to-solid mass ratio is 4:1-5:1, and the preferred leaching residence time is 30-40 minutes. Countercurrent leaching is used to contact fresh hot water with the partially leached material, maintaining a high concentration gradient in the leachate, which is beneficial for the continued dissolution of silicates. In the decarburized and desilicon concentrate... The content and carbon content were determined by X-ray fluorescence spectroscopy and high-temperature combustion infrared absorption spectroscopy, respectively.

[0064] Furthermore, the pH value of the leachate in the countercurrent leaching device is monitored in real time by an online detector, and the pH value is controlled within a range of 10 to 13, preferably 11 to 12. When the pH value is lower than 10, the pH value is adjusted to the target range by adding sodium carbonate solution to maintain the solubility of silicate in the liquid phase and prevent silicate hydrolysis and precipitation.

[0065] Furthermore, the washing water temperature of the filter cake obtained by pressure filtration is 60 to 80°C, and the amount of water used for each washing is 0.5 to 1.0 times the mass of the filter cake. After washing, the wash water is combined with the leachate and sent to step 6 for alkali recovery to reduce alkali loss.

[0066] Furthermore, the leachate is a strongly alkaline solution (pH 10 to 13). Operators must wear alkali-resistant protective gloves, goggles, and protective aprons during the leaching and filtration processes to prevent skin and eye burns from alkaline splashes. An emergency flushing water source should be provided around the leaching unit.

[0067] Step 6, Alkali solution recycling

[0068] The leachate obtained from pressure filtration in step 5 is sent to a multi-effect evaporator for evaporation and concentration. After concentration to a alkali concentration of 25% to 35%, the sodium carbonate and potassium carbonate in the concentrate are recycled back to step 3 to be reused with fresh alkali. The amount of recycled alkali replenished is determined based on the alkali recovery rate in the leachate, and the amount of fresh alkali added is 15% to 30% (mass fraction) of the total alkali used. The alkali concentration is determined by acid-base titration.

[0069] Furthermore, the multi-effect evaporator operates at a temperature of 60 to 90°C, an operating pressure of 0.02 to 0.08 MPa (absolute pressure), and an evaporation and concentration time of 1 to 3 hours. Preferably, the operating temperature is 70 to 80°C, the operating pressure is 0.03 to 0.05 MPa (absolute pressure), and the evaporation and concentration time is 1.5 to 2 hours, in order to achieve energy-saving evaporation at a lower temperature and prevent the decomposition of carbonates at high temperatures.

[0070] Furthermore, before returning to step 3, the concentrated liquid obtained from evaporation and concentration is filtered to remove suspended solid impurities. The filter screen has a pore size of 0.1 to 0.5 mm to prevent solid impurities from accumulating during the alkali circulation process and mixing into the alkali ore granules, thus affecting the granulation quality.

[0071] Furthermore, the alkali recycling process allows for the reuse of alkali, with the amount of fresh alkali added being only 15% to 30% of the total alkali consumption, significantly reducing alkali consumption and the total amount of alkali-containing wastewater discharged. The condensate generated during the evaporation and concentration process, after being tested to have a neutral pH, can be recycled as leaching water in step 5, achieving a closed-loop circulation of process water.

[0072] Furthermore, small amounts of waste alkali that cannot be used due to the accumulation of impurities during the alkali recycling process must be collected and handed over to a professional waste liquid treatment agency for harmless treatment, and must not be directly discharged into sewers or natural water bodies.

[0073] Step 7: Preparation of manganese-rich slag by reduction smelting

[0074] 100 parts by weight of the decarburized and desilicationized concentrate obtained in step 5 are mixed evenly with 5 to 11 parts by weight of coke powder and 2 to 6 parts by weight of dolomite. The mixture is then pressed into briquettes and fed into a submerged arc furnace for reduction smelting at 1300 to 1420°C for 45 to 75 minutes. After slag-iron separation, the manganese-rich slag melt is rapidly cooled by water quenching to obtain a manganese-rich slag product with a MnO content of 50 to 65%. The preferred amounts of coke powder and dolomite are 7 to 9 parts by weight, the preferred reduction smelting temperature is 1350 to 1400°C, and the preferred smelting time is 55 to 65 minutes. The MnO content in the manganese-rich slag product is determined by X-ray fluorescence spectrometry.

[0075] It should be noted that the coke powder has a particle size of 0.5 to 3 mm and a fixed carbon content of not less than 85%. The dolomite has a particle size of 1 to 5 mm and a total CaO and MgO content of not less than 50%.

[0076] Furthermore, the pressing pressure for briquetting is 10 to 30 MPa, preferably 15 to 25 MPa, and the briquetting particle size is 20 to 40 mm, to ensure that the briquetting has sufficient mechanical strength in the electric arc furnace and to prevent it from breaking during the high-temperature reduction process and affecting the permeability of the furnace.

[0077] Furthermore, when mixing the decarburized and desilication concentrate, coke powder, and dolomite, the feeding sequence is to first mix the decarburized and desilication concentrate and dolomite evenly, and then add the coke powder. The mixing speed is 100 to 200 r / min, and the mixing time is 5 to 10 min, to ensure that the coke powder is evenly distributed among the decarburized and desilication concentrate particles and to ensure sufficient contact between carbon and manganese oxides during the reduction smelting process.

[0078] Furthermore, the manganese-rich slag product obtained by water quenching and cooling is filtered and dehydrated, and then dried at 110 to 130°C until the moisture content is less than 1%. The dried manganese-rich slag product is then tested for MnO content by X-ray fluorescence spectroscopy and characterized by phase composition by X-ray diffraction to confirm that the product quality meets the requirements.

[0079] Furthermore, the CO-containing flue gas generated during the reduction smelting process in the electric arc furnace must be fully combusted in a secondary combustion chamber and converted into CO. Afterwards, the flue gas passes through a bag filter to remove particulate matter before being discharged through the chimney. An online CO concentration monitoring and alarm device should be installed in the operating area of ​​the submerged arc furnace. Operators should wear respirators and stay away from areas prone to molten metal splashing during open operations such as tapping iron and slag, and should wear high-temperature resistant protective clothing.

[0080] Furthermore, the waste slag generated from reduction smelting (a small amount of furnace bottom residue other than manganese-rich slag products) and the wastewater containing suspended solids generated during water quenching must be collected and treated separately. The waste slag, after being tested and confirmed to be free of excessive harmful substances, can be used as aggregate for building materials; the water quenching wastewater, after being filtered and treated to remove suspended solids, should be recycled and must not be directly discharged.

[0081] This invention decouples the decarburization and desiliconization processes by placing the decarburization process independently before the alkaline roasting desiliconization process using microwave selective heating, thus eliminating the interference of carbonaceous components on the alkaline roasting desiliconization process.

[0082] In step 2, silicon carbide micropowder acts as a permanent microwave absorber, synergistically absorbing microwave energy with the carbonaceous components in fine-grained carbonaceous high-silica manganese ore. In a loose powder state, concentrated decarburization is completed within 8 to 20 minutes. The loose powder morphology allows the gases generated by pyrolysis to escape rapidly through the interparticle gaps, avoiding the problem of cracking and pulverization caused by gas generation inside dense pellets. After decarburization, the residual carbon content in the decarburized ore powder is less than 0.5%. During the subsequent granulation process in step 3 and alkali roasting in step 4, there is no longer any carbonaceous pyrolysis gas generation inside the pellets, and the pellet structure remains intact. Simultaneously, no gas is generated during the roasting stage. In this complex alkali system, the effective alkali content is not consumed by carbonate formation; it is entirely used to react with... The reaction produces soluble silicates, ensuring the utilization efficiency of the alkali and reducing the amount of alkali required.

[0083] In step 4, the sodium carbonate and potassium carbonate composite alkali system forms a eutectic liquid phase at approximately 710°C, which is lower than the individual melting points of sodium carbonate (851°C) and potassium carbonate (891°C). This allows the desilication reaction to occur at the liquid-solid interface, reducing the required calcination temperature compared to conventional single-alkali processes. The tubular continuous flow microwave reactor ensures uniform heating and continuous feeding and discharging of the material, shortening the calcination residence time compared to batch calcination. In step 6, the alkali solution recycling reduces the amount of fresh alkali added to 15% to 30% of the total alkali consumption, thus reducing alkali consumption.

[0084] The combination of the above processes enables the present invention to solve the technical problems in the following aspects: the decoupling of the decarburization and desiliconization processes eliminates the consumption of effective alkali by carbonaceous components and the damage to the integrity of the pellet structure; microwave selective heating shortens the reaction time of each stage of decarburization and roasting and reduces heat energy consumption; the composite alkali eutectic liquid phase reduces the roasting temperature requirement; and alkali circulation reduces alkali agent consumption.

[0085] Example 1

[0086] Step 1: Take fine-grained, carbonaceous, high-silica manganese ore (particle size less than 0.1 mm, carbon content 5%). 100 parts by weight of silicon carbide micro powder (32% content) and 2 parts by weight of silicon carbide micro powder (particle size 0.01mm, α phase, purity 98%). Add the mixture to the mixer and mix at 100 r / min for 10 min to obtain premixed mineral powder containing microwave-sensitive components.

[0087] Step 2: Place the premixed mineral powder in a tubular microwave reactor, introduce 99.9% pure nitrogen gas at a flow rate of 2 L / (min·L), heat at a rate of 30℃ / min, heat to 800℃ at a microwave frequency of 2450MHz and a power density of 8kW / kg, hold for 8 min, and after cooling, take a sample to test the residual carbon content using high-temperature combustion infrared absorption method. The exhaust gas is treated by absorption with a 5% sodium carbonate solution.

[0088] Step 3: Take 100 parts by weight of the decarbonated mineral powder obtained in Step 2, add 10 parts by weight of sodium carbonate (particle size 0.075 mm) and 5 parts by weight of potassium carbonate (particle size 0.075 mm), with a sodium carbonate to potassium carbonate mass ratio of 2:1, add 2 parts by weight of deionized water (atomized spray, spray rate 0.2 parts by weight / min), granulate at 200 r / min for 8 min to obtain spherical particles with a particle size of 1 mm. Heat the spherical particles to 110℃ at a heating rate of 1℃ / min and dry until the moisture content is less than 2% to obtain alkali mineral granules.

[0089] Step 4: The alkali ore granules are fed into a tubular continuous flow microwave reactor via a screw feeder. The tube rotates at a speed of 2 r / min, and nitrogen is introduced at a flow rate of 1 L / (min·L). The preheating section has a power density of 2 kW / kg, a temperature of 300℃, and a residence time of 5 min. The preheating to reaction section has a heating rate of 5℃ / min. The reaction section has a power density of 6 kW / kg, a temperature of 700℃, and a residence time of 15 min. Activated roasted granules are continuously discharged.

[0090] Step 5: The activated roasted particles are fed into a countercurrent leaching device and sprayed with 75°C hot water at a liquid-to-solid mass ratio of 3.5:1 for 20 minutes, with the pH value controlled at 10. The desilication concentrate slurry is discharged from the bottom, dewatered by pressure filtration, and the filter cake is washed three times with 60°C hot water (each time using 0.5 times the mass of the filter cake). It is then dried at 110°C until the moisture content is less than 2%, yielding a decarburized and desilication concentrate.

[0091] Step 6: The leachate obtained by pressure filtration is sent to a multi-effect evaporator, with an operating temperature of 60℃ and an operating pressure of 0.02MPa, and evaporated and concentrated for 1 hour until the alkali concentration reaches 25%. After filtration through a 0.1mm pore size filter, the concentrated solution is recycled back to Step 3 for reprocessing, with the amount of fresh alkali added being 15% of the total alkali usage.

[0092] Step 7: Take 100 parts by weight of the decarburized and desilicationized concentrate obtained in Step 5, mix it with 2 parts by weight of dolomite (particle size 1 mm) at 100 r / min for 5 min, then add 5 parts by weight of coke powder (particle size 0.5 mm, fixed carbon content 85%), and continue mixing until uniform. Press it into 20 mm pellets at 10 MPa, and send it to a submerged arc furnace for reduction smelting at 1300℃ for 45 min. After slag and iron separation, the manganese-rich slag melt is water-quenched, filtered and dehydrated, and then dried at 110℃ until the moisture content is less than 1%, to obtain the manganese-rich slag product.

[0093] Example 2

[0094] Step 1: Take 100 parts by weight of fine-grained carbonaceous high-silica manganese ore from the same batch as in Example 1, and 3 parts by weight of silicon carbide micro powder (particle size 0.02 mm, α phase, purity 98%). Add the mixture to the mixer and mix at 150 r / min for 12 min to obtain premixed mineral powder containing microwave-sensitive components.

[0095] Step 2: Place the premixed mineral powder in a tubular microwave reactor, introduce nitrogen gas at a flow rate of 3.5 L / (min·L), heat at a rate of 40℃ / min, heat to 850℃ at a microwave frequency of 2450MHz and a power density of 10kW / kg, hold for 10 min, and after cooling, take a sample to test the residual carbon content. The tail gas is treated by absorption with a 7.5% sodium carbonate solution.

[0096] Step 3: Take 100 parts by weight of the decarbonated mineral powder obtained in Step 2, add 13 parts by weight of sodium carbonate (0.1 mm particle size) and 7 parts by weight of potassium carbonate (0.1 mm particle size), with a sodium carbonate to potassium carbonate mass ratio of approximately 1.9:1, and add 3.5 parts by weight of deionized water (atomized spray, spraying rate 0.35 parts by weight / min). Granulate at 300 r / min for 11.5 min to obtain spherical particles with a particle size of 2 mm. Heat the spherical particles to 120℃ at a heating rate of 1.5℃ / min and dry until the moisture content is less than 2% to obtain alkali mineral granules.

[0097] Step 4: The alkali ore granules are fed into a tubular continuous flow microwave reactor via a screw feeder. The tube rotates at a speed of 3.5 r / min, and nitrogen is introduced at a flow rate of 2 L / (min·L). The preheating section has a power density of 3 kW / kg, a temperature of 350℃, and a residence time of 6 min. The preheating to reaction section has a heating rate of 8℃ / min. The reaction section has a power density of 8 kW / kg, a temperature of 720℃, and a residence time of 18 min. Activated roasted granules are continuously discharged.

[0098] Step 5: The activated roasted particles are fed into a countercurrent leaching device and sprayed with 80°C hot water at a liquid-to-solid mass ratio of 4:1 for 30 minutes, with the pH value controlled at 11. The desilication concentrate slurry is discharged from the bottom, dewatered by pressure filtration, and the filter cake is washed three times with 70°C hot water (each time using 0.75 times the mass of the filter cake). It is then dried at 120°C until the moisture content is less than 2%, yielding a decarburized and desilication concentrate.

[0099] Step 6: The leachate obtained by pressure filtration is sent to a multi-effect evaporator, with an operating temperature of 70℃ and an operating pressure of 0.03MPa, and evaporated and concentrated for 1.5 hours until the alkali concentration reaches 30%. After filtration through a 0.3mm pore size filter, the concentrated solution is recycled back to Step 3 for reprocessing, with the amount of fresh alkali added being 22.5% of the total alkali usage.

[0100] Step 7: Take 100 parts by weight of the decarburized and desilicationized concentrate obtained in Step 5, mix it with 3 parts by weight of dolomite (3mm particle size) at 150 r / min for 7.5 min, then add 7 parts by weight of coke powder (1.75mm particle size, fixed carbon content 85%), and continue mixing until uniform. Press it into 30mm pellets at 15 MPa and send it to a submerged arc furnace for reduction smelting at 1350℃ for 55 min. After slag and iron separation, the manganese-rich slag melt is water-quenched, filtered and dehydrated, and then dried at 120℃ until the moisture content is less than 1%, to obtain the manganese-rich slag product.

[0101] Example 3

[0102] Step 1: Take 100 parts by weight of fine-grained carbonaceous high-silica manganese ore from the same batch as in Example 1, and 5 parts by weight of silicon carbide micro powder (particle size 0.05 mm, α phase, purity 98%). Add the mixture to a mixer and mix at 300 r / min for 20 min to obtain a premixed mineral powder containing microwave-sensitive components.

[0103] Step 2: Place the premixed mineral powder in a tubular microwave reactor, introduce nitrogen gas at a flow rate of 5 L / (min·L), heat at a rate of 60℃ / min, heat to 1000℃ at a microwave frequency of 2450MHz and a power density of 18kW / kg, hold for 20 min, and after cooling, take a sample to test the residual carbon content. The tail gas is treated by absorption with a 10% sodium carbonate solution.

[0104] Step 3: Take 100 parts by weight of the decarbonated mineral powder obtained in Step 2, add 20 parts by weight of sodium carbonate (0.15 mm particle size) and 10 parts by weight of potassium carbonate (0.15 mm particle size), with a sodium carbonate to potassium carbonate mass ratio of 2:1, add 5 parts by weight of deionized water (atomized spray, spraying rate 0.5 parts by weight / min), granulate at 400 r / min for 15 min to obtain spherical particles with a particle size of 3 mm. Heat the spherical particles to 130℃ at a heating rate of 3℃ / min and dry until the moisture content is less than 2% to obtain alkali mineral granules.

[0105] Step 4: The alkali ore granules are fed into a tubular continuous flow microwave reactor via a screw feeder. The tube rotates at a speed of 5 r / min, and nitrogen is introduced at a flow rate of 3 L / (min·L). The preheating section has a power density of 5 kW / kg, a temperature of 500℃, and a residence time of 10 min. The preheating to reaction section has a heating rate of 15℃ / min. The reaction section has a power density of 14 kW / kg, a temperature of 850℃, and a residence time of 30 min. Activated roasted granules are continuously discharged.

[0106] Step 5: The activated roasted particles are fed into a countercurrent leaching device and sprayed with 95℃ hot water at a liquid-to-solid mass ratio of 5.5:1 for 50 minutes, with the pH value controlled at 13. The desilication concentrate slurry is discharged from the bottom, dewatered by pressure filtration, and the filter cake is washed three times with 80℃ hot water (each time using 1.0 times the mass of the filter cake). It is then dried at 130℃ until the moisture content is less than 2%, yielding a decarburized and desilication concentrate.

[0107] Step 6: The leachate obtained by pressure filtration is sent to a multi-effect evaporator, with an operating temperature of 90℃ and an operating pressure of 0.08MPa, and evaporated and concentrated for 3 hours until the alkali concentration reaches 35%. After filtration through a 0.5mm pore size filter, the concentrated solution is recycled back to Step 3 for reprocessing, with the amount of fresh alkali added being 30% of the total alkali usage.

[0108] Step 7: Take 100 parts by weight of the decarburized and desilicationized concentrate obtained in Step 5, mix it with 6 parts by weight of dolomite (particle size 5 mm) at 200 r / min for 10 min, then add 11 parts by weight of coke powder (particle size 3 mm, fixed carbon content 85%), and continue mixing until uniform. Press the mixture into 40 mm pellets at 30 MPa, and send it to a submerged arc furnace for reduction smelting at 1420℃ for 75 min. After slag-iron separation, the manganese-rich slag melt is water-quenched, filtered and dehydrated, and then dried at 130℃ until the moisture content is less than 1%, to obtain the manganese-rich slag product.

[0109] Example 4

[0110] The parameters for steps 1 and 3 through 7 are the same as in Example 2.

[0111] Step 2 employs a pulsed power modulation method: nitrogen gas is introduced at a flow rate of 3.5 L / (min·L), and the heating rate is 40℃ / min. Initially, the premixed mineral powder is heated at a high power density of 14 kW / kg for 3 minutes to rapidly raise its temperature to 850℃. Then, the temperature is maintained at a low power density of 6 kW / kg for 8 minutes. After cooling, samples are taken to detect the residual carbon content. The exhaust gas is treated by absorption with a 7.5% sodium carbonate solution.

[0112] Example 5

[0113] The parameters for steps 1 and 3 through 7 are the same as those in Example 3.

[0114] Step 2 employs a pulsed power modulation method: Nitrogen gas is introduced at a flow rate of 5 L / (min·L), and the heating rate is 50℃ / min. First, the premixed mineral powder is heated at a high power density of 18 kW / kg for 5 minutes to rapidly raise its temperature to 950℃. Then, the temperature is maintained at a low power density of 8 kW / kg for 12 minutes. After cooling, samples are taken to detect the residual carbon content. The exhaust gas is treated by absorption with a 10% sodium carbonate solution.

[0115] Example 6

[0116] The parameters for steps 1 and 3 through 7 are the same as in Example 2.

[0117] Step 2 employs a pulsed power modulation method: nitrogen gas is introduced at a flow rate of 3.5 L / (min·L), and the heating rate is 40℃ / min. Initially, the premixed mineral powder is heated at a high power density of 16 kW / kg for 4 minutes to rapidly raise its temperature to 850℃. Then, the temperature is maintained at a low power density of 7 kW / kg for 10 minutes. After cooling, samples are taken to detect the residual carbon content. The exhaust gas is treated by absorption with a 7.5% sodium carbonate solution.

[0118] Example 7

[0119] Step 1: Take 100 parts by weight of fine-grained carbonaceous high-silica manganese ore from the same batch as in Example 1, and 4 parts by weight of silicon carbide micro powder (particle size 0.03 mm, α phase, purity 98%). Add the mixture to the mixer and mix at 200 r / min for 15 min to obtain premixed mineral powder containing microwave-sensitive components.

[0120] Step 2: Place the premixed mineral powder in a tubular microwave reactor, introduce nitrogen gas at a flow rate of 3.5 L / (min·L), heat at a rate of 50℃ / min, and heat to 950℃ at a microwave frequency of 2450MHz and a power density of 14kW / kg. Hold at this temperature for 15 minutes, and after cooling, take a sample to test the residual carbon content. The exhaust gas is treated by absorption with a 7.5% sodium carbonate solution.

[0121] Step 3: Take 100 parts by weight of the decarbonated mineral powder obtained in Step 2, add 17 parts by weight of sodium carbonate (0.1 mm particle size) and 10 parts by weight of potassium carbonate (0.1 mm particle size), with a sodium carbonate to potassium carbonate mass ratio of approximately 1.7:1, and add 3.5 parts by weight of deionized water (atomized spray, spraying rate 0.35 parts by weight / min). Granulate at 300 r / min for 11.5 min to obtain spherical particles with a particle size of 2 mm. Heat the spherical particles to 120℃ at a heating rate of 2℃ / min and dry until the moisture content is less than 2% to obtain alkali mineral granules.

[0122] Step 4: The alkali ore granules are fed into a tubular continuous flow microwave reactor via a screw feeder. The tube rotates at a speed of 3.5 r / min, and nitrogen is introduced at a flow rate of 2 L / (min·L). The preheating section has a power density of 4 kW / kg, a temperature of 450℃, and a residence time of 8 min. The preheating to reaction section has a heating rate of 12℃ / min. The reaction section has a power density of 12 kW / kg, a temperature of 800℃, and a residence time of 25 min. Activated roasted granules are continuously discharged.

[0123] Step 5: The activated roasted particles are fed into a countercurrent leaching device and sprayed with 90°C hot water at a liquid-to-solid mass ratio of 5:1 for 40 minutes, with the pH value controlled at 12. The desilication concentrate slurry is discharged from the bottom, dewatered by pressure filtration, and the filter cake is washed three times with 70°C hot water (each time using 0.75 times the mass of the filter cake). It is then dried at 120°C until the moisture content is less than 2%, yielding a decarburized and desilication concentrate.

[0124] Step 6: The leachate obtained by pressure filtration is sent to a multi-effect evaporator, with an operating temperature of 80℃ and an operating pressure of 0.05MPa, and evaporated and concentrated for 2 hours until the alkali concentration reaches 30%. After filtration through a 0.3mm pore size filter, the concentrated solution is recycled back to Step 3 for reprocessing, with the amount of fresh alkali added being 22.5% of the total alkali usage.

[0125] Step 7: Take 100 parts by weight of the decarburized and desilicationized concentrate obtained in Step 5, mix it with 5 parts by weight of dolomite (3mm particle size) at 150 r / min for 7.5 min, then add 9 parts by weight of coke powder (1.75mm particle size, fixed carbon content 85%), and continue mixing until uniform. Press it into 30mm pellets at 25 MPa and send it to a submerged arc furnace for reduction smelting at 1400℃ for 65 min. After slag and iron separation, the manganese-rich slag melt is water-quenched, filtered and dehydrated, and then dried at 120℃ until the moisture content is less than 1%, to obtain the manganese-rich slag product.

[0126] Comparative Example 1

[0127] Step 2 is omitted, and the premixed mineral powder containing microwave-sensitive components obtained in step 1 of Example 2 is directly fed into step 3 for granulation. The remaining parameters for steps 3 to 7 are the same as in Example 2. Since the residual carbon content in the premixed mineral powder is still at the level of the original ore (approximately 5%), the carbonaceous components in the alkali ore granules undergo pyrolysis at high temperature during the alkali roasting process in step 4, generating… and gas.

[0128] Comparative Example 2

[0129] In step 1, no silicon carbide micropowder was added (the amount of silicon carbide micropowder used was 0), the mixing speed was 150 r / min, and the mixing time was 12 min. The remaining parameters of step 1 were the same as in Example 2. The parameters of steps 2 to 7 were the same as in Example 2. Due to the lack of microwave absorption hotspots provided by silicon carbide micropowder, the uniformity of microwave heating decreased, and the decarburization efficiency was affected.

[0130] Comparative Example 3

[0131] In step 3, only sodium carbonate (15 parts by mass, 0 parts by mass of potassium carbonate) is used, without potassium carbonate. The total amount of alkali ore used is basically the same as in Example 2. The parameters for steps 1 to 2 and steps 4 to 7 are the same as in Example 2. Since the melting point of the sodium carbonate system is 851°C, which is higher than the eutectic temperature of approximately 710°C for the sodium carbonate and potassium carbonate composite system, a sufficient liquid phase cannot be formed in the reaction section of step 4 at 720°C, and the desilication reaction is mainly solid-solid contact.

[0132] Experimental verification:

[0133] Examples 1 to 7 were used to verify the coverage and consistency of the process parameter range (including conventional microwave mode and pulsed power modulation mode) of the present invention in terms of decarburization efficiency, pellet structure integrity, desiliconization rate, and MnO content in manganese-rich slag. Comparative Examples 1 to 3 were used to verify the following three controls: the necessity of microwave selective decarburization in step 2, the necessity of silicon carbide micropowder as a microwave-sensitive component, and the superiority of the sodium carbonate and potassium carbonate composite alkali system over the single sodium carbonate system.

[0134] Experimental sample preparation:

[0135] The raw materials are all from the same batch of fine-grained, carbonaceous, high-silica manganese ore, with a particle size of less than 0.1 mm and an initial carbon content of 5% (mass fraction). The content is 32% (mass fraction), and the initial MnO content is approximately 38% (mass fraction). The silicon carbide micropowder is in the α phase and has a purity of 98%. (2450MHz, room temperature). Sodium carbonate purity not less than 99%, potassium carbonate purity not less than 98%. Coke powder fixed carbon content not less than 85%, dolomite CaO and MgO total content not less than 50%. Each example and comparative example was prepared independently according to its own parameters and specifications. The preparation amount of each group was based on 100 parts by mass of fine-grained carbonaceous high-silica manganese ore (approximately 500g in laboratory scale).

[0136] Experimental conditions

[0137] The microwave reactor operates at a fixed frequency of 2450MHz, with comprehensive electromagnetic shielding and a microwave leakage power density of less than 5mW / cm². The inert atmosphere nitrogen purity is no less than 99.9% (volume fraction), and the oxygen content within the reactor is less than 0.5% (volume fraction). The countercurrent leaching unit monitors the pH value online. The submerged arc furnace operates under a standard reducing atmosphere. All operators wear protective equipment as required throughout the process.

[0138] Experimental steps:

[0139] Step A: Complete Step 1 (Preparation of Premixed Mineral Powder Containing Microwave-Sensitive Components) according to the formulation specified in each embodiment and comparative example. Determine the initial carbon content of the premixed mineral powder by high-temperature combustion infrared absorption method as the input reference for Step B.

[0140] Step B: Complete Step 2 (microwave selective decarburization) according to the parameters specified in each embodiment and comparative example (this step is skipped in Comparative Example 1). Determine the residual carbon content (mass fraction) of the decarburized mineral powder using high-temperature combustion infrared absorption spectrometry and record the decarburization rate. Decarburization rate Calculate using the following formula:

[0141]

[0142] in This refers to the initial carbon content (mass fraction) of the premixed mineral powder. This refers to the residual carbon content (mass fraction) of decarbonized mineral powder.

[0143] Step C: Complete step 3, granulation of alkali ore, according to the parameters specified in each embodiment and comparative example, and record the particle size of spherical particles and the granulation qualification rate.

[0144] Step D: Complete step 4, continuous flow microwave alkaline roasting and desilication, according to the parameters specified in each embodiment and comparative example. After roasting, visually inspect and sieve to detect the pellet integrity rate (the percentage of intact particles to the total number of particles), and record the pellet cracking and pulverization status.

[0145] Step E: Complete step 5, hot water leaching desilication, according to the parameters specified in each embodiment and comparative example, and determine the concentration of silica in the decarburized and desilication concentrate by X-ray fluorescence spectroscopy. Content (mass fraction), calculate desilication rate :

[0146]

[0147] in For the initial raw ore Content (mass fraction) In decarbonized and desiliconized concentrate Content (mass fraction).

[0148] Step F: Complete the alkali recycling in step 6 according to the parameters specified in each embodiment and comparative example, determine the mass concentration of the concentrated alkali solution by acid-base titration, and record the proportion of the actual amount of fresh alkali added to the total amount of alkali used.

[0149] Step G: Complete the reduction smelting in step 7 according to the parameters specified in each embodiment and comparative example, determine the MnO content (mass fraction) in the manganese-rich slag product by X-ray fluorescence spectroscopy, and characterize the phase composition by X-ray diffraction.

[0150] Experimental or test results such as Figures 2-8 And as shown in the table below:

[0151]

[0152] As shown in Table 1, the residual carbon content of Examples 1 to 7 is all below 0.5%, and the decarburization rate is between 90.4% and 96.8%, which meets the requirement that the granulated alkali ore will not crack or pulverize due to carbonaceous pyrolysis gas generation during the subsequent roasting process. Comparative Example 1 omits step 2, and the residual carbon content of the material entering the subsequent process is still 5.00%, without any decarburization treatment. In Comparative Example 2, without the addition of silicon carbide micropowder, the microwave heating uniformity decreases, the decarburization rate is only 63.6%, and the residual carbon content is 1.82%, far exceeding the 0.5% acceptable line. Compared with Example 2, the decarburization rate decreases by about 30 percentage points, indicating that silicon carbide micropowder, as a microwave-sensitive component, plays an irreplaceable role in improving microwave heating uniformity and decarburization efficiency. Comparative Example 3 has the same decarburization results as Example 2 (the parameters in step 2 are the same), with the difference lying in the subsequent steps.

[0153]

[0154] As shown in Table 2, the pellet integrity rate of Examples 1 to 7 was between 96.2% and 98.6%, and the concentrate... The content is between 6.2% and 10.8%, all of which meet the requirements. For content below 12%, the desiliconization rate should be between 66.3% and 81.3%.

[0155] Comparative Example 1 showed a pellet integrity rate of only 61.3%, a decrease of approximately 37 percentage points compared to Example 2. This indicates that the large amount of pyrolysis gas generated by the carbonaceous components during the roasting stage led to severe cracking and pulverization of the pellets; simultaneously, the concentrate... The content was as high as 18.6%, with a desilication rate of only 41.9%, a decrease of approximately 32 percentage points compared to Example 2. This is because the pellet cracking damaged the integrity of the material structure and... The consumption of effective alkali severely disrupts the desilication process.

[0156] Comparative Example 2, due to incomplete decarburization (residual carbon content 1.82%), had a pellet integrity rate of 78.4% and a desiliconization rate of 55.3%, which were about 20 percentage points and 18 percentage points lower than Example 2, respectively. This further proves that the improvement of decarburization efficiency by silicon carbide micro powder directly affects the quality of subsequent processes.

[0157] Comparative Example 3 used a single sodium carbonate system. The reaction temperature of 720℃ was lower than the melting point of sodium carbonate alone (851℃), making it impossible to form a sufficient liquid phase. The desilication reaction was mainly solid-solid contact, with a desilication rate of only 57.2%, and the concentrate... With a content of 13.7%, the desilication rate decreased by about 16 percentage points compared with Example 2, indicating that the sodium carbonate and potassium carbonate composite alkali system transforms the solid-solid reaction into a liquid-solid reaction through a eutectic liquid phase at about 710°C, which has a significant effect on improving the desilication efficiency.

[0158]

[0159] Note: The actual alkali consumption in step 4 is based on Example 1 with a baseline value of 1.00; the energy consumption in step 2 is based on Example 1 with a baseline value of 1.00; step 2 is omitted in Comparative Example 1, so there is no energy consumption data for step 2.

[0160] As shown in Table 3, the MnO content of the manganese-rich slag in Examples 1 to 7 ranges from 51.3% to 58.7%, all meeting the product index requirement of 50% to 65% MnO content. Examples 4 to 6 adopted a pulsed power modulation method, and the relative energy consumption of step 2 was 0.88 to 0.91, which is about 5 to 8 percentage points lower than that of Example 2 (0.96) using the conventional mode. This indicates that pulsed power modulation effectively reduces microwave energy consumption while ensuring decarburization efficiency.

[0161] Comparative Example 1 suffered from excessive consumption of effective alkali due to carbonaceous components, resulting in an actual alkali consumption of approximately 41% higher in step 4 compared to Example 2. The MnO content in the manganese-rich slag was only 44.2%, below the product specification limit of 50%, making the product substandard. Comparative Example 2 suffered from incomplete decarburization, leading to residual carbon consuming effective alkali during the roasting stage. The actual alkali consumption in step 4 was approximately 27% higher than in Example 2, and the MnO content in the manganese-rich slag was 47.5%, also below the product specification limit. Comparative Example 3 suffered from low desilication efficiency due to the single alkali agent system, resulting in an MnO content in the manganese-rich slag of 46.8%, below the product specification limit. The actual alkali consumption in step 4 was approximately 34% higher than in Example 2.

[0162] Based on the results in Tables 1 to 3, the process of the present invention solves the corresponding technical problems through the following points:

[0163] Firstly, step 2, microwave selective decarburization, independently removes carbonaceous components before alkali roasting, achieving a decarburization rate of 90.4% to 96.8%, resulting in a residual carbon content of less than 0.5% in the alkali ore granules entering step 4. Compared to Comparative Example 1, the pellet integrity rate increased by approximately 37 percentage points, the desiliconization rate increased by approximately 32 percentage points, the alkali consumption in step 4 decreased by approximately 29%, and the MnO content in the manganese-rich slag increased by approximately 10 to 14 percentage points.

[0164] Secondly, silicon carbide micropowder, as a microwave-sensitive component, significantly improves the uniformity of microwave heating. Compared with Comparative Example 2, the decarburization rate increased by approximately 30 percentage points, the pellet integrity rate increased by approximately 20 percentage points, and the desiliconization rate increased by approximately 18 percentage points.

[0165] Third, the sodium carbonate and potassium carbonate composite alkali system transforms the desilication reaction from a solid-solid contact to a liquid-solid contact through a eutectic liquid phase at approximately 710°C. Compared to Comparative Example 3, the desilication rate is increased by approximately 16 percentage points at the same reaction temperature (720°C), and the alkali consumption in step 4 is reduced by approximately 25%.

[0166] Fourth, the pulsed power modulation method (Examples 4 to 6) reduces the energy consumption of step 2 by about 5 to 8 percentage points while maintaining a decarbonization rate comparable to the conventional mode, thus verifying the energy-saving effect of this method.

[0167] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A low-carbon and energy-saving process for smelting manganese-rich slag from high-silicon manganese ore, characterized in that, Includes the following steps: Premixed mineral powder is obtained by mixing fine-grained carbonaceous high-silicon manganese ore with silicon carbide micro powder. The premixed mineral powder is placed in a microwave reactor and heated to 800 to 1000°C under an inert atmosphere and held for 8 to 20 minutes to complete decarburization, resulting in decarburized mineral powder with a residual carbon content of less than 0.5%. Decarbonized mineral powder is mixed with sodium carbonate and potassium carbonate, granulated, and dried to obtain alkali mineral granules. The alkali ore granules are fed into a tubular continuous flow microwave reactor and undergo alkali roasting and desiliconization in a preheating section and a reaction section. The temperature of the reaction section is 700 to 850°C to obtain activated roasted granules. The activated roasted particles were leached with hot water and separated into solid and liquid components to obtain a decarburized and desiliconized concentrate. The decarburized and desiliconized concentrate is mixed with coke powder and dolomite and then reduced and smelted. The slag and iron are separated to obtain manganese-rich slag.

2. The low-carbon and energy-saving process according to claim 1, characterized in that, The silicon carbide micro powder is α-phase silicon carbide with a particle size of 0.01 to 0.05 mm and a purity of not less than 98%. The dosage is 2% to 5% of the mass of fine-grained carbonaceous high-silicon manganese ore.

3. The low-carbon and energy-saving process according to claim 1, characterized in that, The power density of the microwave heating is 8 to 18 kW / kg, the microwave frequency is 2450 MHz, and the heating rate is 30 to 60 °C / min.

4. The low-carbon and energy-saving process according to claim 3, characterized in that, The microwave heating adopts a pulsed power modulation method: heating the premixed mineral powder to the target temperature for 3 to 5 minutes at a power density of 14 to 18 kW / kg, and then switching to a power density of 6 to 8 kW / kg to maintain the temperature for 8 to 12 minutes.

5. The low-carbon and energy-saving process according to claim 1, characterized in that, The amount of sodium carbonate used is 10% to 20% of the mass of the decarbonated mineral powder, and the amount of potassium carbonate used is 5% to 12% of the mass of the decarbonated mineral powder. The mass ratio of sodium carbonate to potassium carbonate is 1.5:1 to 2:

1.

6. The low-carbon and energy-saving process according to claim 1, characterized in that, The preheating section of the tubular continuous flow microwave reactor has a microwave power density of 2 to 5 kW / kg, a temperature of 300 to 500°C, and a residence time of 5 to 10 min; the reaction section has a microwave power density of 6 to 14 kW / kg and a residence time of 15 to 30 min; the tube rotates around its axis at a speed of 2 to 5 r / min.

7. The low-carbon and energy-saving process according to claim 1, characterized in that, The hot water leaching adopts a countercurrent leaching method, with a hot water temperature of 75 to 95°C, a liquid-to-solid mass ratio of 3.5:1 to 5.5:1, and a leaching residence time of 20 to 50 minutes.

8. The low-carbon and energy-saving process according to claim 1, characterized in that, The leachate after leaching is evaporated and concentrated to an alkaline concentration of 25% to 35%, and then recycled back to the granulation step to be used in combination with fresh alkaline agent. The amount of fresh alkaline agent added is 15% to 30% of the total amount of alkaline agent used.

9. The low-carbon and energy-saving process according to claim 1, characterized in that, In the reduction smelting process, the amount of coke powder used is 5% to 11% of the mass of the decarburized and desiliconized concentrate, the amount of dolomite used is 2% to 6% of the mass of the decarburized and desiliconized concentrate, the reduction smelting temperature is 1300 to 1420℃, and the smelting time is 45 to 75 minutes.

10. A manganese-rich slag smelted by the low-carbon and energy-saving process described in any one of claims 1 to 9, characterized in that, The manganese-rich slag contains 50% to 65% MnO.

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