Method for extracting potassium from potassium ore by coupling magnesium-calcium slag circulation with iron ore sintering

Abstract

The present application belongs to the field of metal resource processing, and particularly relates to a method for coupling potassium extraction from potash ore and iron ore sintering with magnesium-calcium-containing slag circulation, which comprises the following steps: 1. dispersing potash ore, magnesium-calcium-containing slag and alkali with water to obtain a slurry, filling and sealing the slurry in a pressure-resistant container, pre-treating the slurry at a high temperature T1 for heat and pressure preservation, and then cooling the slurry to a low temperature T2 for heat and pressure preservation; subsequently, releasing the pressure for solid-liquid separation to obtain potassium extraction liquid and potassium extraction residue containing calcium, magnesium and C2SH (hydrated dicalcium silicate); the potash ore is a potassium-containing aluminosilicate mineral; 2. mixing the potassium extraction residue with iron ore, fuel, auxiliary flux and returned ore after granulation to obtain sintered ore and calcium-magnesium-containing sintered solid byproduct; and the sintered solid byproduct is recycled for use in the treatment of step 1. The present application can realize the coupling of potassium extraction from potash ore and iron ore sintering.

Description

Technical Field

[0001] This invention belongs to the field of metal resource processing, specifically relating to a method for the cyclic coupling of potassium extraction from potassium ore and iron ore sintering with magnesium-calcium slag. Background Technology

[0002] Potassium fertilizer is an indispensable nutrient source for agricultural production and plays a vital role in ensuring food security. The Bayan Obo region possesses vast reserves of potassium-rich slate, with K2O content typically ranging from 8% to 16%. Although these resources are abundant, potassium exists primarily as aluminosilicate minerals, making direct utilization difficult. Therefore, developing technologies for the efficient extraction of potassium from insoluble potassium-containing minerals is of great significance.

[0003] Currently, methods for extracting potassium from potassium-bearing aluminum silicate minerals mainly include roasting, acid leaching, sub-molten salt extraction, and hydrothermal extraction. Among these, hydrothermal potassium extraction has attracted widespread attention due to its relatively mild reaction conditions and high potassium leaching rate. In the hydrothermal potassium extraction process, calcium-containing materials such as calcium oxide are usually added as reaction aids. Calcium oxide provides an alkaline environment and provides calcium in the reaction system. 2+ Ions, through disrupting the structure of aluminosilicate minerals and promoting ion exchange reactions, facilitate the leaching of potassium from the minerals. During potassium extraction, a large amount of calcium reacts with silicon in the minerals to generate solid products, primarily calcium silicate, forming potassium extraction slag (commonly known as calcium silicate slag). This type of byproduct is typically rich in CaO and SiO2 components, with its main phases being hydrated calcium silicate (CSH) and hydrated dicalcium silicate (C2SH), exhibiting relatively stable chemical compositions. Currently, there is a lack of large-scale utilization pathways for this type of potassium extraction byproduct coupled with the main industrial process, and it is mostly disposed of through stockpiling. This not only occupies land resources but also wastes calcium and silicon resources, becoming one of the important factors affecting the economics of hydrothermal potassium extraction processes.

[0004] On the other hand, iron ore sintering is an important raw material preparation process in steel production. Its main function is to prepare sintered ore with certain strength and metallurgical properties by sintering fine-grained iron ore, fuel, and flux through a high-temperature sintering reaction. It is characterized by large raw material processing capacity and strong raw material adaptability. During the sintering process, calcium-containing fluxes such as limestone and quicklime are usually added to match the SiO2 content in the raw materials, thereby adjusting the basicity of the sintered ore, promoting the formation of high-quality binder phases such as composite calcium ferrite, and thus improving the strength and metallurgical properties of the sintered ore.

[0005] Against this backdrop, using the calcium-silica slag, a byproduct of hydrothermal potassium extraction, in the iron ore sintering process can replace some calcium-containing fluxes and achieve synergistic regulation of CaO and SiO2 components in the sinter. The abundant CaO and SiO2 in the calcium-silica slag can participate in the adjustment of sinter basicity, decomposing or reacting under high-temperature sintering conditions to assist in the formation of high-quality binder phases such as composite calcium ferrite. This reduces the consumption of traditional fluxes such as limestone and quicklime while ensuring sinter quality. Correspondingly, quicklime originally used for sintering can be incorporated into the hydrothermal potassium extraction process as a reaction aid, providing an alkaline environment and reacting with CaO. 2+ This process enhances the disruption of mineral structure and the potassium leaching reaction. Consequently, a recycling pathway for calcium-containing materials is established between the two processes, which not only eliminates potassium extraction byproducts and reduces storage and disposal pressure, but also optimizes the sintering flux structure, contributing to improved overall resource utilization efficiency and process economy.

[0006] However, currently, potassium extraction and iron ore sintering processes are typically operated as two independent systems in industrial production. Potassium extraction requires the addition of calcium-containing materials such as calcium oxide, while the sintering system continuously consumes large amounts of calcium-based flux, and there is a lack of an effective material recycling pathway between the two. Therefore, it is necessary to propose a new process method to couple the potassium extraction process from potassium-containing minerals with the iron ore sintering process, thereby achieving the recycling of calcium and silicon elements between the two process systems.

[0007] Directly coupling hydrothermal potassium extraction by-product slag with iron ore sintering still presents several challenges: First, the potassium extraction slag has a high moisture content, fine particle size, and often contains gel-like calcium silicate, which can easily worsen permeability when directly introduced into the sintering bed. Second, the simultaneous entry of CaO, SiO2, and MgO from the potassium extraction slag into the sintering system can easily cause fluctuations in liquid phase quantity and viscosity without basicity and MgO balancing. Third, ordinary calcium silicate slag is difficult to directionally generate a composite calcium ferrite binder phase during sintering, leading to a decrease in the strength and metallurgical properties of the sintered ore after the flux substitution rate increases. Fourth, when sintered return ore, dust removal ash, or flux undersize material is returned to the hydrothermal section, it is necessary to control the metallic iron content, particle size, and Ca / Si ratio to balance the hydrothermal potassium extraction reaction and subsequent sintering quality. Therefore, synergistic control is needed among hydrothermal phase regulation, potassium extraction slag granulation methods, and sintering recycling material pretreatment. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a method for recycling potassium extraction from potassium ore and sintering iron ore using magnesium-calcium slag, aiming to utilize the recycling of two types of resources: potassium extraction from potassium ore and sintering iron ore using magnesium-calcium slag.

[0009] A method for cyclically coupling potassium extraction from magnesium-calcium slag with iron ore sintering, comprising the following steps:

[0010] Step 1:

[0011] Potassium ore, magnesium-calcium slag, and alkali are dispersed in water to obtain a slurry. The slurry is filled and sealed in a pressure-resistant container and preheated and pressurized at a high temperature T1, then cooled to a low temperature T2 and pressurized again. Subsequently, the pressure is released and solid-liquid separation is performed to obtain potassium extraction liquid and potassium extraction slag containing calcium, magnesium, and C2SH.

[0012] The potassium ore is a potassium-aluminum silicate mineral;

[0013] The temperature T1 is 200~300℃; the ratio of temperature T2 to temperature T1 is 0.55~0.75;

[0014] Step 2:

[0015] The potassium-extracting slag obtained in step 1 is used as a calcium- and magnesium-containing flux. It is mixed with iron ore, fuel, auxiliary flux and return ore, granulated and then sintered to obtain sintered ore and sintered solid by-products containing calcium and magnesium.

[0016] The sintering solid by-products are sorted, crushed and / or screened to obtain magnesium-calcium slag, which is then mixed with calcium-magnesium flux in the iron ore sintering system and recycled for use in step 1.

[0017] The "magnesium-calcium slag-mediated coupling" described in this invention is not simply a matter of re-sintering potassium-extraction slag, but rather a process centered on the continuous phase transformation of the Ca-Mg component in both the hydrothermal and sintering sections: in the hydrothermal section, the magnesium-calcium slag releases Ca... 2+ and Mg 2+ Ca 2+ Fixing silicon released from potassium-containing minerals and inducing the formation of C2SH, Mg 2+ It participates in the perturbation of the aluminosilicate lattice and enhances potassium release together with KOH. In the sintering section, the potassium-extracting slag containing C2SH is used as a calcium-magnesium flux in the sintering mixture. During the sintering process, C2SH is dehydrated to generate active dicalcium silicate C2S, which is transformed into a composite calcium ferrite binder phase in the local high CaO activity and iron oxide enrichment areas. The calcium- and magnesium-containing sintering solid by-products generated during sintering are treated and returned to the hydrothermal section as magnesium-calcium slag, thus forming a closed-loop coupled cycle of "magnesium-calcium slag - hydrothermal potassium extraction - C2SH potassium extraction slag - iron ore sintering - sintering solid by-products - magnesium-calcium slag".

[0018] In this invention, the magnesium-calcium slag in step 1 includes at least one of metallurgical lime, sintered return ore, flux undersize, and sintering dust; the magnesium-calcium slag contains 10-90 wt% CaO, 1-5 wt% MgO, 0.5-35 wt% SiO2, and no more than 10 wt% Al2O3; further, when the magnesium-calcium slag is metallurgical lime, the CaO content is 50-90 wt%, wherein the active CaO content is no less than 45 wt%, and the remainder is unavoidable impurities and other metal oxides.

[0019] In this invention, the potassium ore includes at least one of potassium-rich slate, potassium feldspar, potassium nepheline, biotite, illite, and muscovite;

[0020] In this invention, the alkali is potassium hydroxide;

[0021] In this invention, the Ca / Si weight ratio in the slurry is 2.0~3.0; the alkali concentration is 5~30g / L; preferably, the Ca / Si weight ratio is 2.2~3.0; and the alkali concentration is 10~25g / L.

[0022] In this invention, the heat preservation and pressure holding time at temperature T1 is 0.5 to 4 hours, preferably 1.5 to 2 hours; the heat preservation and pressure holding time at temperature T2 is 3 to 8 hours, preferably 5 to 6 hours.

[0023] Furthermore, to improve the coupling effect between the hydrothermal section and the sintering section, the solid content of the slurry is controlled to be 20wt%~50wt% in step 1, and the filling rate of the pressure vessel is 50%~80%; the cooling process is kept closed without solid-liquid separation, so that the Si, Al, K and Ca, Mg ions released in the high-temperature section continue to participate in the low-temperature rearrangement.

[0024] In this invention, the potassium extraction residue contains 40-60% CaO, the weight ratio of CaO to SiO2 is 1.8-2.8, and the content of dicalcium silicate hydrate is above 50%, preferably above 60%; after drying, crushing and sieving, the proportion of particles smaller than 3mm is not less than 90wt%.

[0025] In this invention, the potassium extraction solution also contains aluminum impurities; the potassium extraction solution is subjected to carbonation treatment to obtain potassium carbonate.

[0026] In this invention, in step 2, the potassium-extracting slag obtained in step 1 is used as a calcium- and magnesium-containing flux and granulated with iron ore, fuel, auxiliary flux and return ore to obtain sintered pellets, which are then sintered.

[0027] Furthermore, the granulation process includes two stages. The first stage involves adding water to potassium slag, iron ore powder (30%–60% of the total dry weight of iron ore), and fuel (30%–60% of the total dry weight of fuel) to form mother pellets. The second stage involves mixing the remaining iron ore powder, remaining fuel, auxiliary flux, and return ore with the mother pellets and performing the second stage of granulation to encapsulate the mother pellets, thus obtaining sintered pellets (also known as sintered mixture, which includes iron ore, fuel, auxiliary flux, and return ore).

[0028] In this invention, in step 2, the content of potassium extraction slag in the sintered agglomerates is 0.5wt%~6wt%, preferably 1wt%~4wt%, and more preferably 1.5wt%~3.5wt%. The proportions of iron ore, fuel, limestone, dolomite, quicklime, return ore, and potassium extraction slag are adjusted according to the target basicity and MgO content of the sintered ore. The CaO / SiO2 basicity in the sintered agglomerates is 1.95~2.20, the MgO content is 1.8wt%~2.3wt%, and the moisture content is 7.4wt%~8.5wt%.

[0029] In this invention, the ignition temperature of the sintering process is 1050~1200℃, the ignition time is 60~120s, the thickness of the sintering material layer is 700~1000mm, the negative pressure of the exhaust is 10~16kPa, the maximum sintering temperature is 1280~1380℃, and the atmosphere is air or an oxygen-containing atmosphere.

[0030] In this invention, by concentrating the potassium extraction slag inside the mother ball and coexisting it with some iron ore powder and fuel, the active C2S generated by C2SH dehydration is preferentially transformed into a composite calcium ferrite binder phase in a local micro-region with high CaO activity.

[0031] Compared to conventional one-time mixing and granulation, this invention uses two-stage granulation to form a micro-region in which potassium slag, some iron ore powder, and some fuel coexist closely inside the mother pellet. The local high temperature generated by fuel combustion and the high CaO activity provided by potassium slag promote the directional conversion of C2S to the SFCA binder phase, which is beneficial to taking into account the potassium slag disposal, sintering strength, and adaptability to recycled materials.

[0032] In this invention, the sintering solid by-products include sintered return ore with a particle size of less than 5 mm, flux undersize material, and / or sintering dust.

[0033] Further, the sintering solid by-product is crushed and screened to less than 3 mm, and optionally subjected to magnetic separation or gravity separation to reduce the iron-rich particle content. After adjusting the proportion of the sintering solid by-product with metallurgical lime and / or other calcium-containing materials according to the Ca / Si weight ratio required in step 1, it is returned to step 1 as magnesium-calcium slag.

[0034] Furthermore, the sintering re-mixing in step 2 adopts a two-stage granulation method of "potassium slag core formation" to avoid the uniform dispersion of fine potassium slag in the mixture, which would lead to a decrease in air permeability. At the same time, the MgO in the potassium slag is incorporated into the sintering MgO balance, and the amount of dolomite or other magnesium-containing flux is adjusted accordingly to keep the MgO content of the sinter within the target range.

[0035] Beneficial effects

[0036] (1) This invention constructs a cross-process material circulation path between potassium extraction from potassium-containing minerals and iron ore sintering. The potassium extraction slag obtained from hydrothermal potassium extraction is returned to the sintering system as a calcium-magnesium flux. The calcium- and magnesium-containing solid by-products obtained from sintering are processed and returned to the hydrothermal potassium extraction system as magnesium-calcium slag. This realizes a closed-loop circulation of magnesium-calcium slag between potassium extraction and sintering processes, reduces the consumption of traditional calcium-magnesium flux, and realizes the resource utilization of potassium extraction by-products.

[0037] (2) This invention employs a segmented hydrothermal potassium extraction process, first at high temperature and then at low temperature. The high-temperature stage achieves rapid decomposition of potassium-containing aluminum silicate minerals, while the low-temperature stage promotes the regular crystallization of hydrated dicalcium silicate C2SH. In the magnesium-calcium slag, CaO and MgO form an alkaline-earth synergistic effect in the hydrothermal system, Ca... 2+ Promotes silicon fixation and calcium silicate phase formation, Mg 2+ It participates in the perturbation of aluminosilicate lattice and, together with KOH, promotes the decomposition of potassium-containing minerals and the release of potassium.

[0038] (3) The potassium extraction slag obtained by this invention mainly contains hydrated dicalcium silicate C2SH, which can be dehydrated during sintering to generate active dicalcium silicate C2S, serving as a precursor for the formation of the composite calcium ferrite binder phase. Through a two-stage granulation process, the potassium extraction slag, some iron ore powder, and fuel are constructed into a micro-region reaction environment with close coexistence inside the mother sphere, so that C2S can be efficiently converted into the composite calcium ferrite binder phase under local high CaO activity and iron oxide enrichment conditions, thereby improving the strength and metallurgical performance of sintered ore while disposing of the potassium extraction slag.

[0039] (4) By controlling the proportion of potassium slag added to the sintering mixture, the basicity of CaO / SiO2 in the sintering mixture, the content of MgO, the moisture content and the particle size of the granulation, this invention can avoid excessive dispersion of fine potassium slag, which would lead to a decrease in the permeability of the sintering material layer, and achieve the synergy between the resource utilization of potassium slag and the stable operation of the sintering process.

[0040] (5) This invention is applicable to potassium-containing aluminum silicate minerals from different sources, including at least one of potassium-rich slate, potassium feldspar, potassium nepheline, biotite, illite, and muscovite. The chemical composition and C2SH phase structure of the potassium extraction slag are used as the sintering remixing and matching indicators, which has good raw material adaptability and process universality.

[0041] (6) The potassium-rich aluminum leaching solution (potassium extraction solution) of the present invention can achieve preferential separation of aluminum and transformation of potassium by CO2 carbonation treatment. The aluminum-free solution is evaporated and crystallized to obtain potassium carbonate product. The crystallization mother liquor can be returned to the hydrothermal system for recycling, which is beneficial to reduce wastewater discharge and alkali consumption. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the process flow of the method described in this invention.

[0043] Figure 2 The image shows the XRD pattern of the potassium extraction residue obtained in Example 1.

[0044] Figure 3 The images shown are SEM-EDS images of the potassium extraction residue obtained in Example 1; where (a) is an SEM image, (b) is an EDS image of Ca, (c) is an EDS image of Al, (d) is an EDS image of Si, (e) is an EDS image of Mg, (f) is an EDS image of Na, and (g) is an EDS image of K. Detailed Implementation

[0045] To better understand the present invention, the following examples and comparative examples further illustrate the content of the invention, but the content of the invention is not limited thereto. Unless otherwise stated, all percentage contents in the following examples are mass percentages, and all sintering ratios are based on a dry basis.

[0046] The present invention provides an optional method for the cyclic coupling of potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag, comprising the following steps:

[0047] Step a: Calcium source preparation

[0048] Magnesium-calcium slag is prepared from the iron ore sintering system for use in the hydrothermal potassium extraction process. The magnesium-calcium slag includes at least one of metallurgical lime, sintering return ore, flux undersize, and sintering dust.

[0049] Metallurgical lime is a commonly used calcium-containing flux in iron ore sintering systems, with CaO as its main component and MgO as a secondary component. Sintered return ore, flux undersize, and sintering dust are calcium- and magnesium-containing solid byproducts generated or recycled in iron ore sintering systems. For sintered return ore, flux undersize, and / or sintering dust, magnetic separation or gravity separation can be performed first to reduce the content of iron-rich particles. Then, after crushing and screening, the particle size is reduced to less than 3 mm. Based on the Ca / Si weight ratio required for hydrothermal potassium extraction, the composition is adjusted with metallurgical lime and / or other calcium-containing materials to obtain magnesium-calcium slag for hydrothermal potassium extraction.

[0050] Step b: Hydrothermal potassium extraction

[0051] Potassium aluminum silicate minerals, magnesium-calcium slag obtained in step a, and KOH are dispersed in water to form a slurry. The slurry is filled and sealed in a pressure-resistant container and subjected to a staged hydrothermal treatment, first at high temperature and then at low temperature. The high-temperature stage, T1, is 200~300℃ and is held at that temperature and pressure for 0.5~4 hours. Subsequently, without solid-liquid separation, the system is cooled to the low-temperature stage, T2, and held at that temperature and pressure for another 3~8 hours. The ratio of T2 to T1 is 0.55~0.75 in Celsius. The Ca / Si weight ratio in the slurry is 2.0~3.0, and the KOH concentration is 5~30 g / L.

[0052] In magnesium-calcium slag, CaO and MgO form a synergistic effect on alkaline earth during hydrothermal processes, where Ca... 2+ Promotes silicon fixation and calcium silicate phase formation, Mg 2+ It participates in the perturbation of the aluminosilicate lattice and, together with KOH, promotes the decomposition of potassium-containing minerals and the release of potassium. After hydrothermal treatment, pressure relief and solid-liquid separation are performed to obtain potassium extraction solution and potassium extraction residue containing calcium, magnesium, and C2SH.

[0053] Step c: Leachate treatment

[0054] The potassium extraction solution obtained in step b is subjected to CO2 carbonation treatment to separate aluminum impurities and prepare potassium carbonate. Specifically, the potassium extraction solution is heated to 50-90°C, and CO2 gas with a volume concentration of 10-100% is introduced under stirring to reduce the pH value of the solution to 9.5-10.5 within 0.5-3 hours, causing aluminum to preferentially precipitate out as aluminum hydroxide. After solid-liquid separation, the aluminum-removed clear liquid is evaporated and crystallized to obtain potassium carbonate product. The mother liquor from crystallization is returned to the hydrothermal system for recycling.

[0055] Step d: Treatment of potassium extraction residue

[0056] The potassium extraction slag obtained in step b is dried, crushed, and sieved to ensure that the proportion of particles smaller than 3 mm is not less than 90 wt%. The potassium extraction slag contains 40-60 wt% CaO, with a CaO to SiO2 weight ratio of 1.8-2.8, and a C2SH phase content of over 50%. The MgO contained in the potassium extraction slag is included in the MgO balance in subsequent sintering batching calculations, and the amount of dolomite or other magnesium-containing fluxes is adjusted accordingly.

[0057] Step e: Sintering and recombining

[0058] The potassium-extracting slag obtained in step d is used as a calcium- and magnesium-containing flux. It is mixed with iron ore, fuel, auxiliary flux, and return ore, granulated, and then sintered to obtain sintered ore and calcium- and magnesium-containing sintered solid byproducts. The proportion of potassium-extracting slag added to the sintering mixture is 0.5 wt% to 6 wt%, preferably 1 wt% to 4 wt%. The CaO / SiO2 basicity of the sintering mixture is controlled at 1.95 to 2.20, the MgO content is controlled at 1.8 wt% to 2.3 wt%, and the moisture content is controlled at 7.4 wt% to 8.5 wt%.

[0059] Preferably, the sintering mixture adopts a two-stage granulation method. In the first stage of granulation, all potassium slag, a portion of iron ore powder accounting for 30% to 60% of the total dry weight of iron ore, and fuel accounting for 30% to 60% of the total dry weight of fuel are granulated with water to form mother pellets. In the second stage of granulation, the remaining iron ore powder, remaining fuel, auxiliary flux, and return ore are mixed with the mother pellets and granulated, so that the mother pellets are coated to form sintered agglomerates.

[0060] The ignition temperature for sintering is 1050~1200℃, the ignition time is 60~120s, the sintering material layer thickness is 700~1000mm, the exhaust negative pressure is 10~16kPa, the maximum sintering temperature is 1280~1380℃, and the atmosphere is air or an oxygen-containing atmosphere. By concentrating the potassium extraction slag inside the mother pellet and coexisting it with some iron ore powder and fuel, the active C2S generated by C2SH dehydration is preferentially converted into a composite calcium ferrite binder phase in localized high CaO activity micro-regions.

[0061] Step f: Sieving and Recycling

[0062] After sintering, the sintered products are crushed and screened to obtain finished sintered ore and sintered return ore with a particle size of less than 5 mm. The sintered return ore, flux undersize material, and / or sintering dust are sintered solid by-products containing calcium and magnesium. After being crushed and screened to less than 3 mm, the content of iron-rich particles is reduced by magnetic separation or gravity separation. The proportion of these particles with metallurgical lime and / or other calcium-containing materials is adjusted according to the Ca / Si weight ratio required in step b, and then the sintered ore is returned to the hydrothermal potassium extraction process as magnesium-calcium slag.

[0063] To clearly demonstrate the effects of this invention, a benchmark sintering ore blending scheme is first defined (Table 1). The benchmark group uses conventional sintering ore blending without adding the potassium extraction slag obtained in this invention. The MgO content in the benchmark sintering mixture is 2.03 wt%; the sintering process parameters are: material thickness 840 mm, ignition temperature 1150~1200℃, ignition time not less than 90 s, main exhaust fan negative pressure 10~15 kPa, sintering machine speed 1.3~1.6 m / min, and mixture moisture content 7.4~8.5%.

[0064] Table 1. Benchmark sintering ore blending scheme (basicity (CaO / SiO2): 2.11)

[0065] The sintering performance test results show that the vertical sintering speed of the benchmark group is 23.8 mm / min, and the utilization factor is 1.42 t / (m). 2 The solid fuel consumption was 52.6 kg / t, the drum strength was 77.6%, the yield was 71.8%, the reduction index (RI) was 82.4%, and the low-temperature reduction pulverization index (RDI) was [missing information]. +3.15 It is 70.6%.

[0066] Examples 1-6 below were all carried out according to steps a-f above. Each example verified the applicability of the method of the present invention under different raw materials and process parameters by adjusting the type of potassium ore, the amount of magnesium-calcium slag blended, the hydrothermal conditions, and the proportion of potassium slag recovery. In each example, the names of the same raw materials, the names of the same phases, and the same sintering evaluation indicators remained consistent.

[0067] In the hydrothermal process, in addition to adding magnesium-calcium slag, limestone and other components are also added to adjust the Ca / Si ratio during the treatment process.

[0068] Example 1

[0069] In step a, metallurgical lime, accounting for 1.0 wt% of the total sintering proportion, is added from the iron ore sintering system as magnesium-calcium slag. The metallurgical lime contains 66.64 wt% CaO and 1.89 wt% MgO.

[0070] In step b, the potassium ore and the magnesium-calcium slag from step a and KOH are slurried with water and then subjected to hydrothermal treatment, followed by solid-liquid separation to obtain potassium extraction liquid and potassium extraction slag.

[0071] The potassium ore used was potassium-rich slate with a K₂O content of 9.16 wt% and a particle size of -200 mesh. The hydrothermal potassium extraction conditions were as follows: T₁ was 250℃, held at the high-temperature stage for 2 hours; T₂ was 180℃, held at the low-temperature stage for 6 hours; the T₂ / T₁ ratio was 0.72; the Ca / Si weight ratio was 2.6; and the KOH concentration was 20 g / L. The resulting potassium leaching rate was 96.80%.

[0072] In step c, the obtained potassium extraction solution is treated with carbonation by passing a gas with a CO2 volume concentration of 30% at 75°C, and the pH value of the solution is controlled to drop to 10.2 within 1.5 hours. Aluminum is preferentially precipitated out in the form of aluminum hydroxide. After solid-liquid separation, the aluminum-free clear liquid is evaporated and crystallized to obtain potassium carbonate product, and the crystallization mother liquor is returned to the hydrothermal system of step b.

[0073] In step d, after drying, crushing, and sieving, the proportion of potassium extraction residue with a particle size smaller than 3 mm is not less than 90 wt%. The main components and phase composition of the potassium extraction residue are shown in Table 3. The phase and microstructure of the potassium extraction residue obtained in Example 1 were characterized. Figure 2 As shown, the main diffraction peaks of the potassium extraction slag basically correspond to the positions of the C2SH standard peaks, indicating that a calcium-silicon phase, mainly composed of dicalcium silicate hydrate, was formed in the system after staged hydrothermal treatment; Figure 3 As shown, the potassium extraction slag has a fine-grained agglomerate structure with certain pores between the particles. The elemental distribution is mainly Ca and Si, with a small amount of Mg signal. This is consistent with the composition characteristics of the potassium extraction slag in Table 3, which is mainly composed of CaO and SiO2 with a small amount of MgO. This indicates that the magnesium and calcium components participate in the hydrothermal reaction and enter the solid phase structure of the potassium extraction slag.

[0074] In step e, based on the CaO-SiO2-MgO material balance calculation, 1.27 wt% of potassium extraction slag is equivalent to approximately 0.97 wt% of metallurgical lime. After comprehensively adjusting limestone, dolomite, and other ingredients, the amount of quicklime added to the sintering mixture in Example 1 was adjusted from 4.25 wt% in the baseline group to 2.28 wt%. The sintering remixing scheme and the basicity and MgO content of the mixture are shown in Table 4.

[0075] The sintering granulation adopts a two-stage granulation method. In the first stage granulation, all potassium slag, homogenized ore accounting for 45% of the total dry weight of iron ore, and coke powder accounting for 50% of the total dry weight of fuel are granulated with water to form mother pellets. In the second stage granulation, the remaining homogenized ore, remaining coke powder, dolomite, quicklime, limestone, dust collector ash, internal return and high return are added and mixed with the mother pellets to obtain sintered pellets.

[0076] In step f, the sintering product is crushed and screened to obtain finished sintered ore and sintered return ore. The sintered return ore with a particle size of less than 5 mm can be crushed and screened to less than 3 mm, and then mixed with metallurgical lime according to the Ca / Si weight ratio and returned to the hydrothermal potassium extraction process as magnesium-calcium slag.

[0077] The sintering parameters of Example 1 are shown in Table 5. The vertical sintering speed is 24.3 mm / min, the utilization coefficient is 1.45 t / (m²·h), the solid fuel consumption is 51.8 kg / t, the drum strength is 78.5%, the yield is 72.6%, the RI is 83.2%, and the RDI is... +3.15 It is 72.0%.

[0078] Example 2

[0079] The difference between this embodiment and Embodiment 1 is that in step a, the magnesium-calcium slag source is a portion of the sintering solid by-product generated by the iron ore sintering system, which is then compounded with metallurgical lime. Sintering return ore with a particle size less than 5mm, flux undersize, and sintering dust are mixed at a mass ratio of 60:30:10. After magnetic separation to remove iron-rich particles, the mixture is crushed and sieved to a particle size less than 3mm to obtain a pretreated sintering solid by-product. This pretreated by-product is then mixed with metallurgical lime at a mass ratio of 65:35 to form magnesium-calcium slag. Testing revealed that the magnesium-calcium slag contains 43.8 wt% CaO, 2.16 wt% MgO, 12.6 wt% SiO2, and 2.42 wt% Al2O3.

[0080] In step b, T2=160℃, T2 / T1=0.64, Ca / Si=2.4, and the potassium leaching rate is 95.60%; the remaining steps are the same as in Example 1. The composition and phase composition of the potassium extraction slag are shown in Table 3, the sintering remixing scheme and the basicity and MgO content of the mixture are shown in Table 4, and the sintering indexes are shown in Table 5.

[0081] The results show that sintering byproducts, after pretreatment and compounding with metallurgical lime, can stably participate in hydrothermal potassium extraction and generate potassium extraction slag with high C2SH content for sintering reprocessing.

[0082] Example 3

[0083] The difference between this embodiment and Embodiment 1 is that the magnesium-calcium slag in step a is obtained by compounding sintering solid by-products with metallurgical lime. Specifically, sintering return ore, flux undersize material, and dust collector ash are mixed in a mass ratio of 70:20:10. After removing iron-rich particles by magnetic separation, the mixture is crushed and sieved to a particle size of less than 3 mm to obtain pretreated sintering solid by-products. Subsequently, the pretreated sintering solid by-products are mixed with metallurgical lime in a mass ratio of 60:40 to form magnesium-calcium slag for hydrothermal potassium extraction. The metallurgical lime contains 66.64 wt% CaO and 1.89 wt% MgO. Testing revealed that the compounded magnesium-calcium slag contains 36.4 wt% CaO, 2.17 wt% MgO, 11.0 wt% SiO2, and 2.00 wt% Al2O3.

[0084] In step b, the potassium ore was the same as in Example 1, but the hydrothermal potassium extraction conditions were adjusted as follows: T1 was 200℃, with a high-temperature holding period of 2 hours; T2 was 148℃, with a low-temperature holding period of 6 hours; the ratio of T2 to T1 was 0.74 based on the Celsius temperature values; by adjusting the dosage of potassium-rich slate and compound magnesium-calcium slag, the Ca / Si weight ratio in the slurry was made 2.2; the KOH concentration was 25 g / L. The resulting potassium leaching rate was 95.70%.

[0085] The remaining steps are the same as in Example 1. The composition and phase composition of the potassium extraction slag are shown in Table 3, the sintering remixing scheme and the basicity and MgO content of the mixture are shown in Table 4, and the sintering indexes are shown in Table 5.

[0086] The results show that, after pretreatment and compounding with metallurgical lime, the sintering solid by-products can maintain a high utilization rate while improving the effective Ca supply capacity in the hydrothermal system, thus keeping the Ca / Si weight ratio of the slurry stably controlled within the range specified in this invention. The resulting potassium extraction slag has a high C2SH content, and the potassium extraction slag remixing ratio is controlled within a reasonable range. Through two-stage granulation and CaO-SiO2-MgO balance regulation, the permeability of the sintering bed is not significantly deteriorated, and the sintering speed, drum strength, yield, and low-temperature reduction pulverization performance are all superior to the benchmark group, verifying the feasibility of compounding sintering solid by-products with metallurgical lime to participate in the potassium extraction-sintering cycle coupling.

[0087] Example 4

[0088] The difference between this embodiment and Embodiment 1 is that in step b, the potassium ore used is potassium feldspar (K2O content 12.5wt%, particle size -200 mesh). The hydrothermal conditions are shown in Table 2: T1 is 240℃, with a high-temperature holding time of 1.5 hours; T2 is 170℃, with a low-temperature holding time of 5 hours; T2 / T1 is 0.71; and the KOH concentration is 10 g / L. The obtained potassium leaching rate is 97.33%. The remaining steps are the same as in Embodiment 1. The composition and phase composition of the potassium extraction slag are shown in Table 3, the sintering remixing scheme and the basicity and MgO content of the mixture are shown in Table 4, and the sintering indices are shown in Table 5.

[0089] The results show that when potassium feldspar is used as a potassium-containing raw material, potassium extraction slag with high C2SH content can also be obtained under optimized hydrothermal conditions, and the sintering index is better than that of Example 1, which verifies the good applicability of the method of the present invention to different potassium-containing aluminum silicate minerals.

[0090] Example 5

[0091] The difference between this embodiment and Embodiment 4 is that the hydrothermal conditions in step b are shown in Table 2, where T1 is 300℃ with a high-temperature holding time of 1.5 hours; T2 is 200℃ with a low-temperature holding time of 5 hours; T2 / T1 is 0.67; and the Ca / Si weight ratio is 3.0. The KOH concentration is the same as in Embodiment 4. The obtained potassium leaching rate is 97.53%. The remaining steps are the same as in Embodiment 4. The composition and phase composition of the potassium extraction slag are shown in Table 3, the sintering remixing scheme and the basicity and MgO content of the mixture are shown in Table 4, and the sintering indices are shown in Table 5.

[0092] The results show that, under the condition that the hydrothermal Ca / Si weight ratio and T1 are both close to the upper limit of the present invention, although the proportion of potassium slag reprocessing is increased to 2.94 wt%, the sintering index is still better than the benchmark group by adjusting the alkalinity and MgO balance and by two-stage granulation, which verifies the stability of the method of the present invention under the process boundary conditions.

[0093] Example 6

[0094] The difference between this embodiment and Embodiment 4 is that, in step a, the sintered return ore with a particle size of less than 5 mm obtained after sintering treatment in Embodiment 4, flux undersize, and sintering dust are mixed at a mass ratio of 65:25:10. After removing iron-rich particles by magnetic separation, the mixture is crushed and sieved to a particle size of less than 3 mm, and then mixed with metallurgical lime at a mass ratio of 55:45 to obtain magnesium-calcium slag. Testing revealed that the magnesium-calcium slag contained 45.6 wt% CaO, 2.12 wt% MgO, 11.8 wt% SiO2, and 2.20 wt% Al2O3.

[0095] In step b, the potassium ore used was a mixture of potassium-rich slate and potassium feldspar in a 1:1 mass ratio. The hydrothermal conditions are shown in Table 2, differing from those in Example 4 in that: T1 was 260℃, with a high-temperature holding period of 2 hours; T2 was 155℃, with a low-temperature holding period of 5 hours; the T2 / T1 ratio was 0.60; the Ca / Si weight ratio was 2.3; and the KOH concentration was 15 g / L. The resulting potassium leaching rate was 95.85%.

[0096] The remaining steps are the same as in Example 1. The composition and phase composition of the potassium extraction slag are shown in Table 3, the sintering remixing scheme and the basicity and MgO content of the mixture are shown in Table 4, and the sintering indexes are shown in Table 5.

[0097] The results show that under the condition that T2 / T1 is close to the lower limit, the magnesium-calcium slag obtained by compounding the circulating by-products with metallurgical lime can still produce potassium-enriching slag with a C2SH content of more than 60%, and the sintering index is better than the benchmark group. This verifies that the method of the present invention can still achieve a stable cyclic coupling effect under the boundary conditions of a low proportion in the low temperature range.

[0098] Table 2. Hydrothermal potassium extraction conditions and results for each embodiment.

[0099] Table 3 Chemical composition and phase composition of potassium extraction residue from each embodiment

[0100] Table 4 Sintering Ore Blending Schemes for Each Embodiment

[0101] Table 5 Comparison of sintering indices of each embodiment with the baseline group

[0102] Comparative Example 1: Traditional Sintering Process

[0103] This comparative example represents a traditional iron ore sintering process. The difference from Example 1 is that metallurgical lime, sintered return ore, flux undersize, or sintering dust from the iron ore sintering system were not introduced as magnesium-calcium slag into the hydrothermal potassium extraction system, and potassium extraction slag containing C2SH was not obtained and recycled. The sintering ore blending was exactly the same as the baseline group.

[0104] The sintering parameters in this comparative example use baseline data. The baseline data shows that, without constructing a cyclic coupling pathway of "magnesium-calcium slag - hydrothermal potassium extraction - C2SH potassium extraction slag - iron ore sintering - sintering solid byproducts - magnesium-calcium slag," the sintering process relies solely on traditional fluxes such as quicklime, limestone, and dolomite to adjust basicity and MgO content. This prevents the recycling of hydrothermal potassium extraction byproducts and the cyclic return of sintering solid byproducts to the hydrothermal potassium extraction stage.

[0105] This comparative example illustrates that without constructing a cyclic coupling path for magnesium-calcium slag, it is impossible to achieve the synergistic effect of potassium slag resource utilization, sintering flux substitution, and sintering solid by-product recycling.

[0106] Comparative Example 2: Insufficient MgO content in magnesium-calcium slag

[0107] Compared with Example 1, the difference is that metallurgical lime from the sintering system is not used as the magnesium-calcium slag in step a. Instead, analytical grade CaO is used as the calcium-containing additive for hydrothermal potassium extraction. The MgO content in the analytical grade CaO is less than 0.01 wt%, which does not meet the requirement that the MgO content in the magnesium-calcium slag is 1 wt% to 5 wt%. Other hydrothermal potassium extraction conditions are the same as in Example 1.

[0108] The hydrothermal potassium extraction conditions were as follows: the potassium ore used was potassium-rich slate; T1 was 250℃, with a high-temperature holding time of 2 hours; T2 was 180℃, with a low-temperature holding time of 6 hours; T2 / T1 was 0.72; the Ca / Si weight ratio was 2.6; and the KOH concentration was 20 g / L. The obtained potassium leaching rate was 89.3%, which was lower than that of Example 1.

[0109] In this comparative example, since analytical grade CaO contains virtually no MgO, the hydrothermal system lacks Mg. 2+ The perturbation effect on the crystal lattice of potassium-aluminum silicate minerals, Ca 2+ With Mg 2+ No synergistic effect between alkaline and earth elements can be formed. Even with the same Ca / Si weight ratio, KOH concentration, and segmented hydrothermal temperature as in Example 1, the potassium leaching rate still decreased significantly.

[0110] This comparative example demonstrates that MgO in magnesium-calcium slag is not a common impurity component, but rather an important synergistic component that participates in promoting the decomposition of potassium-aluminum silicate minerals and the release of potassium during the hydrothermal potassium extraction process.

[0111] Comparative Example 3: The hydrothermal treatment sequence is low temperature first, then high temperature.

[0112] This comparative example illustrates the effect of a high-temperature followed by a low-temperature hydrothermal sequence on potassium leaching and C2SH formation. The difference from Example 1 is that the hydrothermal treatment sequence is adjusted to low temperature first, followed by high temperature; that is, the low-temperature stage is performed first at temperature T2, and then the temperature is increased to T1 for the high-temperature stage. All other conditions are the same as in Example 1.

[0113] Specifically, the potassium ore used was potassium-rich slate, and the magnesium-calcium slag was made of metallurgical lime. The leaching process involved first holding at 180℃ for 6 hours, then raising the temperature to 250℃ and holding for 2 hours; the Ca / Si weight ratio was 2.6, and the KOH concentration was 20 g / L. The resulting potassium leaching rate was 91.8%. The potassium extraction slag obtained from the hydrothermal treatment contained approximately 38.6% C₂SH, with the main phases being CSH gel, incompletely converted calcium silicate, and a small amount of C₂SH, failing to meet the requirement of a C₂SH content exceeding 50%.

[0114] The potassium extraction slag was dried, crushed, and sieved to a particle size of less than 3 mm, then added to the sintering mixture at a ratio of 1.30 wt%. The basicity and MgO content of the sintering mixture were adjusted according to the CaO-SiO2-MgO material balance. The calculated basicity of the sintering mixture was 1.98, and the MgO content was 2.04 wt%. A two-stage granulation method was used for sintering.

[0115] The sintering test results show that the vertical sintering rate of this comparative example is 20.1 mm / min, and the utilization coefficient is 1.16 t / (m). 2 The solid fuel consumption was 55.6 kg / t, the drum strength was 61.2%, the yield was 65.2%, the RI was 81.2%, and the RDI was [missing information]. +3.15 The basicity and MgO content of the sintering mixture were within the target range, but due to the insufficient C2SH content in the potassium extraction slag, it was difficult to form enough active C2S precursors during the sintering process, resulting in a weak directional formation effect of the composite calcium ferrite binder phase.

[0116] This comparative example illustrates that simply controlling the temperature range in the hydrothermal section is insufficient to obtain potassium-rich slag suitable for sintering and reprocessing. The high-temperature-then-low-temperature treatment sequence is beneficial for first achieving the deconstruction of potassium-aluminum silicate minerals, and then promoting the regular crystallization of C2SH. If the sequence is changed to low-temperature followed by high-temperature, the C2SH content in the potassium-rich slag will be insufficient, and the sintering improvement effect will be significantly weakened.

[0117] Comparative Example 4: The Ca / Si weight ratio is lower than that of this invention.

[0118] This comparative example illustrates the effect of a Ca / Si weight ratio in the hydrothermal system below 2.0 on hydrothermal potassium extraction and sintering reprocessing. Compared to Example 4, the difference lies in the following: potassium feldspar is used as the potassium ore, and metallurgical lime is used as the magnesium-calcium slag; however, the Ca / Si weight ratio in the hydrothermal system is adjusted to 1.8, which is below the range defined in this invention. Other hydrothermal potassium extraction conditions are the same as in Example 4.

[0119] The hydrothermal potassium extraction conditions were as follows: T1 was 240℃, with a high-temperature holding time of 1.5 hours; T2 was 170℃, with a low-temperature holding time of 5 hours; T2 / T1 was 0.71; and the KOH concentration was 10 g / L. The obtained potassium leaching rate was 91.53%, lower than that of Example 4. The potassium extraction slag obtained from hydrothermal treatment accounted for approximately 2.34 wt% of the total sintering composition, with a CaO / SiO2 weight ratio of 1.82. The main phase was CSH gel, and the degree of C2SH crystallinity was significantly lower than that of the examples. Its chemical composition is shown in Table 6.

[0120] Table 6 Chemical composition of potassium extraction residue obtained in Comparative Example 4

[0121] During sintering and remixing, the aforementioned potassium-extracting slag is added to the sintering mixture at a ratio of 2.34 wt%. Based on material balance calculations, the final sintering remixing scheme is as follows: 57.22 wt% homogenized ore, 15.38 wt% internal remixing, 7.69 wt% high-grade remixing, 5.60 wt% dolomite, 1.30 wt% quicklime, 5.60 wt% limestone, 3.59 wt% coke powder, 1.28 wt% dust collector ash, and 2.34 wt% potassium-extracting slag, totaling 100 wt%. The calculated basicity of the sintering mixture is 1.98, and the MgO content is 2.05 wt%.

[0122] Sintering test results show that, compared with the baseline group, the vertical sintering speed of this comparative example increased by only 0.5%, the utilization coefficient by only 0.7%, and the drum strength by only 1.0%, with virtually no improvement in reducibility. Due to the excessively low Ca / Si weight ratio, the calcium activity in the hydrothermal system is insufficient, which is detrimental to the complete decomposition of potassium-aluminum silicate minerals and to the regular crystallization of C2SH. The resulting potassium-extraction slag, mainly composed of CSH gel, is difficult to effectively transform into a composite calcium ferrite binder phase during sintering, significantly weakening the sintering improvement effect.

[0123] This comparative example illustrates that when the Ca / Si weight ratio is below 2.0, it is difficult to simultaneously achieve efficient potassium extraction, C2SH potassium extraction slag formation, and subsequent sintering and re-blending effects.

[0124] Comparative Example 5: The Ca / Si weight ratio is higher than that of this invention.

[0125] This comparative example illustrates the adverse effects of a Ca / Si weight ratio in the hydrothermal system exceeding 3.0 on the composition of the potassium extraction slag and the sintering remixing. Compared to Example 4, the difference lies in the following: potassium feldspar is used for the potassium ore, and metallurgical lime is used for the magnesium-calcium slag; however, the Ca / Si weight ratio in the hydrothermal system is adjusted to 3.3, which is higher than the range defined in this invention. Other hydrothermal potassium extraction conditions are the same as in Example 4.

[0126] The hydrothermal potassium extraction conditions were as follows: T1 was 240℃, with a high-temperature holding time of 1.5 hours; T2 was 170℃, with a low-temperature holding time of 5 hours; the T2 / T1 ratio was 0.71; and the KOH concentration was 10 g / L. The obtained potassium leaching rate was 98.12%. The potassium extraction slag accounted for approximately 1.62 wt% of the total sintering composition, with C2SH as the main phase, but containing free Ca(OH)2, and the local CaO activity in the potassium extraction slag was relatively high.

[0127] During sintering and remixing, the aforementioned potassium-extracting slag is added to the sintering mixture at a ratio of 1.62 wt%. Based on material balance calculations, the final sintering remixing scheme is as follows: 58.65 wt% homogenized ore, 15.38 wt% internal remixing, 7.69 wt% high-grade remixing, 5.50 wt% dolomite, 1.29 wt% quicklime, 5.00 wt% limestone, 3.59 wt% coke powder, 1.28 wt% dust collector ash, and 1.62 wt% potassium-extracting slag, totaling 100 wt%. The calculated basicity of the sintering mixture is 1.98, and the MgO content is 2.02 wt%.

[0128] Sintering test results showed that although the basicity and MgO content of the sintered mixture were within the target range, the presence of free Ca(OH)2 in the potassium extraction slag led to excessively high local CaO concentrations during sintering, resulting in localized overmelting of the material layer and an imbalance between liquid phase quantity and viscosity. The vertical sintering speed decreased to 18.5 mm / min, and the utilization coefficient dropped to 1.02 t / (m²). 2 ·h), solid fuel consumption increased to 57.5 kg / t, yield dropped to 64.2%, and drum strength dropped to 60.5%.

[0129] This comparative example illustrates that when the Ca / Si weight ratio is higher than 3.0, even if the overall basicity and MgO content of the sintering mixture are within the target range after batching adjustments, the excessively high local calcium activity in the potassium-extracting slag will still cause imbalance in the sintering liquid phase, affecting the stability of the sintering process and the quality of the sintered ore.

[0130] Comparative Example 6: Excess potassium extraction residue was added and conventional one-time mixing and granulation were used.

[0131] This comparative example illustrates the influence of the proportion of potassium-extracting slag added and the sintering granulation method on the sintering remixing effect. Compared to Example 5, the difference lies in the following: a higher proportion of metallurgical lime is added from the sintering system to the potassium feldspar hydrothermal potassium extraction system, resulting in a potassium-extracting slag addition ratio of 6.46 wt% in the sintering mixture, which is higher than the 0.5 wt%~6 wt% range specified in this invention; simultaneously, the sintering granulation adopts a conventional one-stage mixing granulation method, instead of the two-stage granulation method that concentrates the potassium-extracting slag inside the mother pellet.

[0132] In the hydrothermal potassium extraction stage, potassium feldspar was used as the potassium ore, and the potassium extraction process conditions were the same as in Example 4. The potassium extraction process produced potassium extraction slag, which accounted for approximately 6.46 wt% of the total sintering composition. Its main chemical composition was similar to that of the potassium extraction slag obtained in Example 4, with C2SH as the main phase.

[0133] During sintering remixing, based on material balance calculations, 6.46 wt% of potassium-extracting slag can replace approximately 5.33 wt% of quicklime, therefore no further quicklime will be added at the sintering end. The final sintering remixing scheme is as follows: 54.50 wt% homogenized ore, 15.38 wt% internal remixing, 7.69 wt% high-grade remixing, 5.60 wt% dolomite, 0 wt% quicklime, 5.50 wt% limestone, 3.59 wt% coke powder, 1.28 wt% dust collector ash, and 6.46 wt% potassium-extracting slag, totaling 100 wt%. The calculated basicity of the sintering mixture is 2.04, and the MgO content is 2.08 wt%.

[0134] Sintering test results showed that although the basicity and MgO content of the sintering mixture were within the target range, the excessive proportion of potassium-extracting slag and the failure to concentrate the slag within the mother pellets through two-stage granulation resulted in excessive dispersion of fine-grained potassium-extracting slag in the sintering mixture, leading to decreased permeability of the material bed. When the main suction negative pressure increased to 20.5 kPa, the vertical sintering speed decreased to 19.2 mm / min, and the utilization coefficient decreased to 1.08 t / (m²). 2 ·h), solid fuel consumption increased to 57.2 kg / t, yield decreased to 64.5%, drum strength decreased to 60.8%, and the proportion of <5mm increased to 13.2%.

[0135] This comparative example illustrates that higher amounts of potassium slag added are not necessarily better. If the proportion of potassium slag added exceeds a reasonable range, and a cored micro-region is not formed within the mother pellet where potassium slag, some iron ore powder, and fuel coexist, even if the overall basicity and MgO content meet the standards, it will still lead to decreased permeability of the sintering bed and a decline in the quality of the sinter. Therefore, it is necessary to control the proportion of potassium slag added, and a two-stage granulation method is preferred to achieve a reasonable distribution of potassium slag in the sintered pellets.

[0136] The above embodiments are merely examples to clearly illustrate the method of the present invention and are not intended to limit the specific implementation methods. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here; therefore, any obvious variations or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for cyclically coupling potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag, characterized in that the steps include: include: Step 1: Potassium ore, magnesium-calcium slag, and alkali are dispersed in water to obtain a slurry. The slurry is filled and sealed in a pressure-resistant container and pre-treated at a high temperature T1 and then cooled to a low temperature T2 and treated at the same temperature and pressure. Subsequently, the pressure is released and solid-liquid separation is performed to obtain potassium extraction solution and potassium extraction slag containing calcium, magnesium, and hydrated dicalcium silicate. The magnesium-calcium slag contains 10-90 wt% CaO and 1-5 wt% MgO. The potassium ore is a potassium-aluminum silicate mineral; The temperature T1 is 200~300℃; the ratio of temperature T2 / temperature T1 is 0.55~0.75; Step 2: The potassium-extracting slag obtained in step 1 is used as a calcium- and magnesium-containing flux. It is mixed with iron ore, fuel, auxiliary flux and return ore, granulated and then sintered to obtain sintered ore and sintered solid by-products containing calcium and magnesium. The sintering solid by-products are sorted, crushed and / or screened to obtain magnesium-calcium slag, which is then mixed with calcium-magnesium flux in the iron ore sintering system and recycled for use in step 1.

2. The method for cyclically coupling potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag as described in claim 1, characterized in that, The magnesium-calcium slag in step 1 includes at least one of metallurgical lime, sintering return ore, flux screening material, and sintering dust removal ash. The magnesium-calcium slag contains 0.5-35 wt% SiO2 and no more than 10 wt% Al2O3. When the magnesium-calcium slag is metallurgical lime, the CaO content is 50~90wt%, of which the active CaO content is not less than 45wt%.

3. The method for cyclically coupling potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag as described in claim 1, characterized in that, Potassium deposits include at least one of the following: potassium-rich slate, potassium feldspar, potassium nepheline, biotite, illite, and muscovite. The alkali is potassium hydroxide; In the slurry, the Ca / Si weight ratio is 2.0~3.0; the alkali concentration is 5~30g / L.

4. The method for cyclically coupling potassium extraction from magnesium-calcium slag with iron ore sintering as described in claim 1, characterized in that, The heat preservation and pressure holding time at temperature T1 is 0.5~4 hours; the heat preservation and pressure holding time at temperature T2 is 3~8 hours.

5. The method for cyclically coupling potassium extraction from magnesium-calcium slag with iron ore sintering as described in claim 1, characterized in that, The potassium extraction residue contains 40-60% CaO, with a CaO to SiO2 weight ratio of 1.8-2.8 and a dicalcium silicate hydrate content of over 50%. After drying, crushing, and sieving, the proportion of particles smaller than 3mm is not less than 90wt%.

6. The method for cyclically coupling potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag as described in claim 1, characterized in that, The potassium extraction solution also contains aluminum impurities; The potassium extraction solution is passed through a CO2-containing gas for carbonation treatment, and the pH is controlled at 9.5~10.5 to precipitate and separate aluminum impurities. The resulting aluminum-free solution is then evaporated and crystallized to obtain potassium carbonate.

7. The method for cyclically coupling potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag as described in claim 1, characterized in that, In step 2, the potassium-extracting slag obtained in step 1 is used as a calcium-magnesium flux to granulate with iron ore, fuel, auxiliary flux and return ore to obtain sintered pellets, which are then sintered. The granulation process includes two stages. The first stage involves adding water to potassium extraction slag, iron ore powder (30%–60% of the total dry weight of iron ore), and fuel (30%–60% of the total dry weight of fuel) to form mother pellets. The second stage involves mixing the remaining iron ore powder, remaining fuel, auxiliary flux, and return ore with the mother pellets and performing the second stage of granulation to encapsulate the mother pellets and obtain sintered pellets.

8. The method for cyclically coupling potassium extraction from potassium ore and sintering iron ore with magnesium-calcium slag as described in claim 7, characterized in that, In step 2, the content of potassium slag in the sintered pellets is 0.5wt%~6wt%; the basicity of CaO / SiO2 is 1.95~2.20, the content of MgO is 1.8wt%~2.3wt%, and the moisture content is 7.4wt%~8.5wt%.

9. The method for cyclically coupling potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag as described in claim 7 or 8, characterized in that, The ignition temperature for sintering is 1050~1200℃, the ignition time is 60~120s, the sintering material layer thickness is 700~1000mm, the exhaust negative pressure is 10~16kPa, the maximum sintering temperature is 1280~1380℃, and the atmosphere is an oxygen-containing atmosphere.

10. The method for cyclically coupling potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag as described in claim 9, characterized in that, The atmosphere is air.

11. The method for cyclically coupling potassium extraction from potassium ore and sintering of iron ore with magnesium-calcium slag as described in claim 3, characterized in that, The sintering solid by-products include sintered return ore with a particle size of less than 5 mm, flux undersize and / or sintering dust. The sintering solid by-products are crushed and screened to less than 3 mm, and the iron-rich particle content is reduced by magnetic separation or gravity separation. The proportion of the sintering solid by-products to metallurgical lime and / or other calcium-containing materials is adjusted according to the Ca / Si weight ratio required in step 1, and then returned to step 1 as magnesium-calcium slag.

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