Low-grade sulfur-containing carbonate-iron ore mineral phase transformation-flue gas desulfurization synergistic beneficiation method and application thereof

Abstract

The application discloses a low-grade sulfur-containing carbonate refractory iron ore mineral phase conversion-flue gas desulfurization collaborative beneficiation method and application thereof, and belongs to the technical field of comprehensive utilization of refractory iron ore. The method mainly comprises the following steps: (1) grading of raw ore; (2) magnetic separation pre-concentration and high-intensity magnetic separation pre-concentration; (3) concentration and filtration of pre-concentration concentrate; (4) hydrogen-based mineral phase conversion of pre-concentration concentrate powder; (5) one-stage weak magnetic dry separation of the mineral phase conversion product, two-stage weak magnetic wet separation of the one-stage weak magnetic dry separation concentrate, and three-stage weak magnetic wet separation of the two-stage weak magnetic concentrate; (6) concentration and filtration of the three-stage weak magnetic concentrate; (7) preparation of alkaline ore slurry from pre-concentration tailings, and flue gas desulfurization of step (4); and (8) concentration and filtration of the mixed three-stage weak magnetic separation tailings. The application can overcome the defects of the existing process for selecting low-grade siderite, efficiently recovers iron elements, and simultaneously uses the tailings as building materials.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of refractory iron ore, specifically relating to a synergistic beneficiation method of ore phase transformation and flue gas desulfurization for low-grade sulfur-containing carbonate refractory iron ore and its application. Background Technology

[0002] Iron ore resources, as a fundamental raw material for the steel industry, are of significant strategic importance to national industrial development due to their efficient development and utilization. Given the current complex and volatile international situation, the security of iron ore resources is crucial to the safety of China's steel supply chain. The country is committed to establishing a long-term, stable, efficient, diversified, and high-quality resource security system to alleviate the supply and demand pressure of iron ore resources, reduce dependence on iron ore imports, and form a dual-circulation resource security pattern both domestically and internationally.

[0003] Based on the iron content, iron ore can be classified into rich ore (iron content > 60%) and lean ore (iron content < 60%). Sulfur-containing carbonate iron ore is a typical low-grade, complex, and difficult-to-process lean iron ore. Currently, my country's proven reserves of carbonate iron ore are approximately 1.8 billion tons, accounting for 5% of the country's total iron ore reserves, mainly distributed in Shaanxi, Gansu, Sichuan, and Guizhou provinces. Carbonate iron ore is primarily composed of siderite (FeCO3), with a theoretical iron content of only 48%. As iron is replaced by calcium, magnesium, manganese, and barium elements in an isomorphous manner, the iron content in the ore is even lower. Iron ore is usually recovered using magnetic separation, but carbonate iron ore is diamagnetic and cannot be directly recovered using magnetic separation. The rotary kiln roasting-magnetic separation process is relatively mature, but the iron recovery rate is only 65%-70%, resulting in serious resource waste. Existing technologies for this type of ore have three major drawbacks: first, traditional roasting flue gas requires separate treatment with limestone; second, flue gas desulfurization is an exothermic reaction, and this heat is not recovered and utilized, resulting in waste heat; and third, iron recovery faces low recovery rates and poor concentrate quality. Therefore, for low-grade, sulfur-containing carbonate iron ores that are difficult to beneficiate, there is an urgent need to develop green and efficient beneficiation processes. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a co-processing method for beneficiating low-grade sulfur-containing carbonate refractory iron ore by ore phase transformation and flue gas desulfurization. This method utilizes a synergistic process of grinding, pre-enrichment, hydrogen-based ore phase transformation, weak magnetic separation, and flue gas desulfurization for beneficiating low-grade sulfur-containing carbonate refractory iron ore. It can achieve efficient recovery and obtain high-grade iron concentrate with high recovery rate. At the same time, it has environmental protection and energy-saving characteristics by "treating waste with waste".

[0005] The objective of this invention is achieved through the following technical solution: This invention provides a method for the synergistic beneficiation of low-grade sulfur-containing carbonate refractory iron ore through ore phase transformation and flue gas desulfurization, comprising the following steps: (1) Grinding, classifying and slurrying the raw ore to obtain pre-enriched raw materials; (2) Perform magnetic pre-enrichment and strong magnetic scavenging pre-enrichment operations to obtain pre-enriched concentrate and pre-enriched tailings; (3) The pre-enriched concentrate is concentrated and filtered to obtain pre-enriched concentrate powder. The overflow water and filtrate are recycled to the pre-enriched raw material slurry preparation operation in step (1) for slurry concentration adjustment to achieve closed-loop water return. (4) The pre-enriched concentrate powder is placed in a suspension roasting furnace and a reducing and inert gas is introduced to roast the pre-enriched concentrate in a suspension state. The siderite is converted into magnetite through hydrogen-based mineral phase conversion to obtain mineral phase conversion product. (5) The mineral phase transformation product is subjected to a first stage of weak magnetic dry separation to obtain weak magnetic dry separation concentrate and weak magnetic dry separation tailings; the weak magnetic dry separation concentrate is ground, classified and slurry adjusted, and then subjected to a second stage of weak magnetic wet separation to obtain weak magnetic concentrate 1 and weak magnetic tailings 1; the weak magnetic concentrate 1 is subjected to a third stage of weak magnetic wet separation to obtain weak magnetic concentrate 2 and weak magnetic tailings 2. (6) The weak magnetic concentrate 2 is concentrated and filtered to obtain the final iron concentrate product. The overflow water and filtrate are recycled to the weak magnetic dry separation concentrate slurry preparation operation in step (5) for slurry concentration adjustment to realize water return closed loop. (7) The pre-enriched tailings are slurried to make alkaline slurry, which is then introduced into the flue gas generated by the suspension roasting in step (4). The alkaline slurry desulfurizes the flue gas to generate sulfate substances. At the same time, under the high temperature of the flue gas, the siderite in the alkaline slurry is transformed into goethite tailings through mineral phase transformation. Goethite tailings can be subsequently used in pigments, catalysts, adsorption materials and other fields. (8) The weak magnetic dry separation tailings, weak magnetic tailings 1 and weak magnetic tailings 2 are mixed, concentrated and filtered to obtain the final tailings. The overflow water and filtrate are reused in step (7) pre-enriched tailings slurry preparation to achieve closed-loop water return. The final tailings can be further used as raw materials for building materials.

[0006] Further, in step (1), grinding and classifying to -0.074mm particles account for 60wt.%-80wt.%, and adding water to adjust the slurry to a concentration of 50wt.%-60wt.% for pre-enriched raw materials.

[0007] Further, in step (2), the magnetic pre-enrichment is divided into two stages. First, a weak magnetic pre-enrichment operation is performed to obtain pre-enriched concentrate 1 and pre-enriched tailings 1. Then, a strong magnetic pre-enrichment operation is performed on the pre-enriched tailings 1 to obtain pre-enriched concentrate 2 and pre-enriched tailings 2. A strong magnetic scavenging pre-enrichment operation is performed on the pre-enriched tailings 2 to obtain pre-enriched concentrate 3 and pre-enriched tailings. The pre-enriched concentrate 1, pre-enriched concentrate 2 and pre-enriched concentrate 3 are mixed to obtain pre-enriched concentrate.

[0008] Furthermore, the magnetic field strength for weak magnetic pre-enrichment is 800 Oe-1000 Oe, and the magnetic field strength for strong magnetic pre-enrichment and strong magnetic scanning pre-enrichment is 5000 Oe-8000 Oe. The TFe grade in the pre-enriched concentrate is >28%.

[0009] Further, in step (4), the reducing gas is a mixture of CO and H2, the inert gas is N2, and the volume ratio of CO, H2 and N2 is (50-60):(140-150):(390-410); the calcination temperature is 450℃-600℃, and the calcination time is 10min-30min.

[0010] Furthermore, the TFe grade in the mineral phase transformation product is >35%.

[0011] Furthermore, in step (5), the magnetic field strength of the first, second and third weak magnetic separation is 800Oe-1000Oe, and the weak magnetic dry separation concentrate is ground and classified to a particle content of -0.038mm ≥ 90wt.%.

[0012] Further, in step (7), the pre-enriched tailings are adjusted to a pH of 10-12; and an alkaline slurry is prepared using the natural alkali source (calcium carbonate, etc.) in the pre-enriched tailings.

[0013] This invention provides an application of a co-processing method for ore phase transformation and flue gas desulfurization in low-grade sulfur-containing carbonate refractory iron ore.

[0014] Furthermore, the TFe grade in the iron concentrate product is >60%, the recovery rate is >80%, the desulfurization efficiency after flue gas desulfurization is >99%, and the SO2 emission concentration is <35mg / m³. 3 .

[0015] Advantages and effects of the present invention: 1. The present invention provides a co-processing method for the ore phase transformation and flue gas desulfurization of low-grade sulfur-containing carbonate refractory iron ore, which can overcome the defects of existing processes for the beneficiation of refractory low-grade siderite, achieve efficient recovery of iron elements in the ore, and at the same time, the tailings can be used as building materials.

[0016] 2. The pre-enrichment process of the siderite in this invention not only reduces the processing capacity of the roasting furnace but also ensures a high iron recovery rate. At the same time, the TFe grade of the pre-enriched concentrate is increased by more than 9% compared with the original ore. Under a reducing atmosphere, the minerals in the pre-enriched concentrate are thermally decomposed, and weakly magnetic minerals are transformed into strongly magnetic minerals. Volatile substances are separated from the minerals, and the TFe grade of the mineral phase transformation product reaches more than 35%. The magnetic minerals are separated by a weak magnetic dry separation process to obtain magnetic iron concentrate while reducing water consumption. The final iron concentrate product has a TFe grade of more than 60% and a TFe recovery rate of more than 80%.

[0017] 3. This invention enables "waste treatment with waste." By using alkaline slurry to absorb flue gas from suspension roasting, it can achieve flue gas desulfurization and fully utilize the waste heat from suspension roasting, further transforming the siderite in the pre-enriched tailings into goethite. The siderite in the tailings is of low grade and has no direct utilization value, making it a type of solid waste. However, after being transformed into goethite, its grade is improved, and it can be used in pigments, catalysts, adsorbent materials, and other fields, thereby reducing the accumulation of low-grade tailings and reducing the pressure of solid waste treatment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow for Example 1. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the embodiments.

[0020] Example 1 A co-processing method for phase transformation and flue gas desulfurization of low-grade, sulfur-containing carbonate refractory iron ore tailings is proposed for the separation of tailings from a difficult-to-process low-grade, sulfur-containing iron ore with a TFe grade of 19.14%. Figure 1 The process flow shown includes the following steps: (1) The siderite recovery tailings are crushed and ground until the proportion of -0.074mm reaches 80wt.%, and water is added to adjust the slurry to 60wt. to obtain sulfur-containing iron ore tailings powder as pre-enrichment raw material; (2) Place the sulfur-containing iron ore tailings powder in a magnetic separator, adjust the magnetic field strength to 1000 Oe, and perform weak magnetic pre-enrichment operation to obtain pre-enriched concentrate 1 and pre-enriched tailings 1. Perform strong magnetic pre-enrichment operation on pre-enriched tailings 1 with a magnetic field strength of 7000 Oe to obtain pre-enriched concentrate 2 and pre-enriched tailings 2. Perform strong magnetic scavenging pre-enrichment operation on pre-enriched tailings 2 with a magnetic field strength of 7000 Oe to obtain pre-enriched concentrate 3 and pre-enriched tailings. Mix pre-enriched concentrate 1, pre-enriched concentrate 2 and pre-enriched concentrate 3 to obtain pre-enriched concentrate. (3) The pre-enriched concentrate is concentrated and filtered to obtain pre-enriched concentrate powder with a moisture content of less than 8% and a TFe grade of 30.05%. The overflow water and filtrate are recycled to the water used for slurry preparation of pre-enriched raw materials in step (1) to achieve closed-loop water return. (4) The pre-enriched concentrate powder is placed in a suspension roasting furnace, and CO, H2 and N2 are introduced. The volume ratio of CO:H2:N2 is 60:140:400. The flow rate of the mixed gas is adjusted to 600 mL / min, so that the pre-enriched concentrate is roasted in a suspension state. The roasting temperature is 600℃ and the roasting time is 30 min. Siderite is converted into magnetite through hydrogen-based mineral phase conversion to obtain mineral phase conversion product. The grade of mineral phase conversion product TFe is 38.24%. (5) The mineral phase transformation product is subjected to a first stage of weak magnetic dry separation with a magnetic field strength of 1000 Oe to obtain weak magnetic dry separation concentrate and weak magnetic dry separation tailings; the weak magnetic dry separation concentrate is ground and classified to a -0.038mm content of 90 wt.%, water is added to adjust the slurry to a concentration of 60 wt.%, and then a second stage of weak magnetic wet separation is performed with a magnetic field strength of 1000 Oe to obtain weak magnetic concentrate 1 and weak magnetic tailings 1; the weak magnetic concentrate 1 is subjected to a third stage of weak magnetic wet separation with a magnetic field strength of 1000 Oe to obtain weak magnetic concentrate 2 and weak magnetic tailings 2; (6) The weak magnetic concentrate 2 is concentrated and filtered to obtain the final iron concentrate product. The iron concentrate product has a TFe grade of 63.53% and a TFe recovery rate of 85.09%. The overflow water and filtrate are recycled to step (5) as slurry water for the weak magnetic dry separation concentrate operation to achieve a closed-loop water return. (7) The pre-enriched tailings are slurry-prepared, and the natural alkaline substances in the pre-enriched tailings are used to prepare an alkaline slurry with a pH of 12. This slurry is then introduced into the flue gas generated by the suspension roasting in step (4). The alkaline slurry desulfurizes the flue gas to generate sulfates, with a desulfurization efficiency of 99.38% and an SO2 emission concentration of 32.62 mg / m³. 3 Meanwhile, under the high temperature of the flue gas, the siderite in the alkaline slurry is transformed into goethite tailings through mineral phase transformation; the goethite tailings can be subsequently used in pigments, catalysts, adsorbent materials and other fields. (8) The weak magnetic dry separation tailings, weak magnetic tailings 1 and weak magnetic tailings 2 are mixed, concentrated and filtered to obtain the final tailings. The overflow water and filtrate are reused in the pre-enriched tailings slurry preparation operation to realize the water return closed loop. The final tailings can be further used as raw materials for building materials.

[0021] Example 2 A co-processing method for ore phase transformation and flue gas desulfurization of low-grade, refractory sulfur-containing carbonate iron ore is disclosed for the beneficiation of a certain low-grade, refractory iron ore with a raw ore grade of 21.83% TFe. The method includes the following steps: (1) The siderite recovery tailings are crushed and ground until the proportion of -0.074mm reaches 80wt.%, and water is added to adjust the slurry to 60wt. to obtain sulfur-containing iron ore tailings powder as pre-enrichment raw material; (2) Place the sulfur-containing iron ore tailings powder in a magnetic separator, adjust the magnetic field strength to 950 Oe, and perform weak magnetic pre-enrichment operation to obtain pre-enriched concentrate 1 and pre-enriched tailings 1. Perform strong magnetic pre-enrichment operation on pre-enriched tailings 1 with a magnetic field strength of 6500 Oe to obtain pre-enriched concentrate 2 and pre-enriched tailings 2. Perform strong magnetic scavenging pre-enrichment operation on pre-enriched tailings 2 with a magnetic field strength of 6500 Oe to obtain pre-enriched concentrate 3 and pre-enriched tailings. Mix pre-enriched concentrate 1, pre-enriched concentrate 2 and pre-enriched concentrate 3 to obtain pre-enriched concentrate. (3) The pre-enriched concentrate is concentrated and filtered to obtain pre-enriched concentrate powder with a moisture content of less than 8% and a TFe grade of 31.35%. The overflow water and filtrate are recycled to the water used for slurry preparation of pre-enriched raw materials in step (1) to achieve closed-loop water return. (4) The pre-enriched concentrate powder is placed in a suspension roasting furnace, and CO, H2 and N2 are introduced. The volume ratio of CO:H2:N2 is 55:145:400. The flow rate of the mixed gas is adjusted to 600 mL / min, so that the pre-enriched concentrate is roasted in a suspension state. The roasting temperature is 600℃ and the roasting time is 25 min. Siderite is converted into magnetite through hydrogen-based mineral phase conversion to obtain mineral phase conversion product. The grade of mineral phase conversion product TFe is 37.81%. (5) The mineral phase transformation product is subjected to a first stage of weak magnetic dry separation with a magnetic field strength of 950 Oe to obtain weak magnetic dry separation concentrate and weak magnetic dry separation tailings; the weak magnetic dry separation concentrate is ground and classified to a -0.038mm content of 90 wt.%, water is added to adjust the slurry to a concentration of 60 wt.%, and then a second stage of weak magnetic wet separation is performed with a magnetic field strength of 950 Oe to obtain weak magnetic concentrate 1 and weak magnetic tailings 1; the weak magnetic concentrate 1 is subjected to a third stage of weak magnetic wet separation with a magnetic field strength of 950 Oe to obtain weak magnetic concentrate 2 and weak magnetic tailings 2; (6) The weak magnetic concentrate 2 is concentrated and filtered to obtain the final iron concentrate product. The iron concentrate product has a TFe grade of 63.83% and a TFe recovery rate of 84.91%. The overflow water and filtrate are recycled to step (5) as slurry water for the weak magnetic dry separation concentrate operation to achieve a closed-loop water return. (7) The pre-enriched tailings are slurry-prepared, and the natural alkaline substances in the pre-enriched tailings are used to prepare an alkaline slurry with a pH of 10. This slurry is then introduced into the flue gas generated by the suspension roasting in step (4). The alkaline slurry desulfurizes the flue gas to generate sulfates, with a desulfurization efficiency of 99.27% ​​and an SO2 emission concentration of 33.51 mg / m³. 3 Meanwhile, under the high temperature of the flue gas, the siderite in the alkaline slurry is transformed into goethite tailings through mineral phase transformation; the goethite tailings can be subsequently used in pigments, catalysts, adsorbent materials and other fields. (8) The weak magnetic dry separation tailings, weak magnetic tailings 1 and weak magnetic tailings 2 are mixed, concentrated and filtered to obtain the final tailings. The overflow water and filtrate are reused in the pre-enriched tailings slurry preparation operation to realize the water return closed loop. The final tailings can be further used as raw materials for building materials.

[0022] Example 3 A co-processing method for ore phase transformation and flue gas desulfurization of low-grade sulfur-containing carbonate iron ore, used for the separation of a certain refractory low-grade carbonate iron ore with a TFe grade of 23.46%, specifically includes the following steps: (1) The siderite recovery tailings are crushed and ground until the proportion of -0.074mm reaches 70wt.%, and water is added to adjust the slurry to 55wt.% to obtain sulfur-containing iron ore tailings powder as pre-enrichment raw material; (2) Place the sulfur-containing iron ore tailings powder in a magnetic separator, adjust the magnetic field strength to 850 Oe, and perform weak magnetic pre-enrichment operation to obtain pre-enriched concentrate 1 and pre-enriched tailings 1. Perform strong magnetic pre-enrichment operation on pre-enriched tailings 1 with a magnetic field strength of 8000 Oe to obtain pre-enriched concentrate 2 and pre-enriched tailings 2. Perform strong magnetic scavenging pre-enrichment operation on pre-enriched tailings 2 with a magnetic field strength of 8000 Oe to obtain pre-enriched concentrate 3 and pre-enriched tailings. Mix pre-enriched concentrate 1, pre-enriched concentrate 2 and pre-enriched concentrate 3 to obtain pre-enriched concentrate. (3) The pre-enriched concentrate is concentrated and filtered to obtain pre-enriched concentrate powder with a moisture content of less than 8% and a TFe grade of 32.87%. The overflow water and filtrate are recycled to the water used for slurry preparation of pre-enriched raw materials in step (1) to achieve closed-loop water return. (4) The pre-enriched concentrate powder is placed in a suspension roasting furnace, and CO, H2 and N2 are introduced. The volume ratio of CO:H2:N2 is 60:150:390. The flow rate of the mixed gas is adjusted to 600 mL / min, so that the pre-enriched concentrate is roasted in a suspension state. The roasting temperature is 600℃ and the roasting time is 15 min. The siderite is converted into magnetite through hydrogen-based mineral phase conversion to obtain the mineral phase conversion product. The grade of the mineral phase conversion product TFe is 39.88%. (5) The mineral phase transformation product is subjected to a first stage of weak magnetic dry separation with a magnetic field strength of 850 Oe to obtain weak magnetic dry separation concentrate and weak magnetic dry separation tailings; the weak magnetic dry separation concentrate is ground and classified to a -0.038mm content of 90 wt.%, water is added to adjust the slurry to a concentration of 60 wt.%, and then a second stage of weak magnetic wet separation is performed with a magnetic field strength of 850 Oe to obtain weak magnetic concentrate 1 and weak magnetic tailings 1; the weak magnetic concentrate 1 is subjected to a third stage of weak magnetic wet separation with a magnetic field strength of 850 Oe to obtain weak magnetic concentrate 2 and weak magnetic tailings 2; (6) The weak magnetic concentrate 2 is concentrated and filtered to obtain the final iron concentrate product. The iron concentrate product has a TFe grade of 63.74% and a TFe recovery rate of 84.63%. The overflow water and filtrate are recycled to step (5) as slurry preparation water for the weak magnetic dry separation concentrate operation to achieve a closed-loop water return. (7) The pre-enriched tailings are slurry-prepared, and the natural alkaline substances in the pre-enriched tailings are used to prepare an alkaline slurry with a pH of 11. This slurry is then introduced into the flue gas generated by the suspension roasting in step (4). The alkaline slurry desulfurizes the flue gas to generate sulfates, with a desulfurization efficiency of 99.16% and an SO2 emission concentration of 33.42 mg / m³. 3 Meanwhile, under the high temperature of the flue gas, the siderite in the alkaline slurry is transformed into goethite tailings through mineral phase transformation; the goethite tailings can be subsequently used in pigments, catalysts, adsorbent materials and other fields. (8) The weak magnetic dry separation tailings, weak magnetic tailings 1 and weak magnetic tailings 2 are mixed, concentrated and filtered to obtain the final tailings. The overflow water and filtrate are reused in the pre-enriched tailings slurry preparation operation to realize the water return closed loop. The final tailings can be further used as raw materials for building materials.

[0023] Example 4 A co-processing method for phase transformation and flue gas desulfurization of low-grade sulfur-containing carbonate refractory iron ore is used for the separation of tailings from a refractory low-grade siderite ore with a raw ore grade of 15.91% TFe. The method includes the following steps: (1) The siderite recovery tailings are crushed and ground until the proportion of -0.074mm reaches 60wt.%, and water is added to adjust the slurry to 50wt. to obtain siderite powder as a pre-enrichment raw material; (2) Place the siderite powder in a magnetic separator, adjust the magnetic field strength to 800 Oe, and perform weak magnetic pre-enrichment operation to obtain pre-enriched concentrate 1 and pre-enriched tailings 1. Perform strong magnetic pre-enrichment operation on pre-enriched tailings 1 with a magnetic field strength of 5000 Oe to obtain pre-enriched concentrate 2 and pre-enriched tailings 2. Perform strong magnetic scavenging pre-enrichment operation on pre-enriched tailings 2 with a magnetic field strength of 5000 Oe to obtain pre-enriched concentrate 3 and pre-enriched tailings. Mix pre-enriched concentrate 1, pre-enriched concentrate 2 and pre-enriched concentrate 3 to obtain pre-enriched concentrate. (3) The pre-enriched concentrate is concentrated and filtered to obtain pre-enriched concentrate powder with a moisture content of less than 8% and a TFe grade of 28.63%. The overflow water and filtrate are recycled to the water used for slurry preparation of pre-enriched raw materials in step (1) to achieve closed-loop water return. (4) The pre-enriched concentrate powder is placed in a suspension roasting furnace, and CO, H2 and N2 are introduced. The volume ratio of CO:H2:N2 is 50:140:410. The flow rate of the mixed gas is adjusted to 600 mL / min, so that the pre-enriched concentrate is roasted in a suspension state. The roasting temperature is 550℃ and the roasting time is 10 min. Siderite is converted into magnetite through hydrogen-based mineral phase conversion to obtain mineral phase conversion product. The grade of mineral phase conversion product TFe is 35.57%. (5) The mineral phase transformation product is subjected to a first stage of weak magnetic dry separation with a magnetic field strength of 800 Oe to obtain weak magnetic dry separation concentrate and weak magnetic dry separation tailings; the weak magnetic dry separation concentrate is ground and classified to a -0.038mm content of 90 wt.%, water is added to adjust the slurry to a concentration of 50 wt.%, and then a second stage of weak magnetic wet separation is performed with a magnetic field strength of 800 Oe to obtain weak magnetic concentrate 1 and weak magnetic tailings 1; the weak magnetic concentrate 1 is subjected to a third stage of weak magnetic wet separation with a magnetic field strength of 800 Oe to obtain weak magnetic concentrate 2 and weak magnetic tailings 2; (6) The weak magnetic concentrate 2 is concentrated and filtered to obtain the final iron concentrate product. The iron concentrate product has a TFe grade of 60.86% and a TFe recovery rate of 80.14%. The overflow water and filtrate are reused in step (5) as slurry preparation water for the weak magnetic dry separation concentrate operation to achieve a closed-loop water return. (7) The pre-enriched tailings are slurry-prepared, and the natural alkaline substances in the pre-enriched tailings are used to prepare an alkaline slurry with a pH of 10. This slurry is then introduced into the flue gas generated by the suspension roasting in step (4). The alkaline slurry desulfurizes the flue gas to generate sulfates, with a desulfurization efficiency of 99.32% and an SO2 emission concentration of 34.13 mg / m³. 3 Meanwhile, under the high temperature of the flue gas, the siderite in the alkaline slurry is transformed into goethite tailings through mineral phase transformation; the goethite tailings can be subsequently used in pigments, catalysts, adsorbent materials and other fields. (8) The weak magnetic dry separation tailings, weak magnetic tailings 1 and weak magnetic tailings 2 are mixed, concentrated and filtered to obtain the final tailings. The overflow water and filtrate are reused in the pre-enriched tailings slurry preparation operation to realize the water return closed loop. The final tailings can be further used as raw materials for building materials.

[0024] Example 5 A co-processing method for beneficiation of low-grade sulfur-containing carbonate iron ore, involving phase transformation and flue gas desulfurization, is used for the separation of a difficult-to-process low-grade sulfur-containing siderite ore with a TFe grade of 22.34%. The method specifically includes the following steps: (1) The siderite recovery tailings are crushed and ground until the proportion of -0.074mm reaches 70wt.%, and water is added to adjust the slurry to 55wt.% to obtain sulfur-containing siderite powder as a pre-enrichment raw material; (2) Place the sulfur-containing siderite powder in a magnetic separator, adjust the magnetic field strength to 900 Oe, and perform weak magnetic pre-enrichment operation to obtain pre-enriched concentrate 1 and pre-enriched tailings 1. Perform strong magnetic pre-enrichment operation on pre-enriched tailings 1 with a magnetic field strength of 6000 Oe to obtain pre-enriched concentrate 2 and pre-enriched tailings 2. Perform strong magnetic scavenging pre-enrichment operation on pre-enriched tailings 2 with a magnetic field strength of 6000 Oe to obtain pre-enriched concentrate 3 and pre-enriched tailings. Mix pre-enriched concentrate 1, pre-enriched concentrate 2 and pre-enriched concentrate 3 to obtain pre-enriched concentrate. (3) The pre-enriched concentrate is concentrated and filtered to obtain pre-enriched concentrate powder with a moisture content of less than 8% and a TFe grade of 31.41%. The overflow water and filtrate are recycled to the water used for slurry preparation of pre-enriched raw materials in step (1) to achieve closed-loop water return. (4) The pre-enriched concentrate powder is placed in a suspension roasting furnace, and CO, H2 and N2 are introduced. The volume ratio of CO:H2:N2 is 50:150:400. The flow rate of the mixed gas is adjusted to 600 mL / min, so that the pre-enriched concentrate is roasted in a suspension state. The roasting temperature is 500℃ and the roasting time is 20 min. Siderite is converted into magnetite through hydrogen-based mineral phase conversion to obtain mineral phase conversion product. The grade of mineral phase conversion product TFe is 36.17%. (5) The mineral phase transformation product is subjected to a first stage of weak magnetic dry separation with a magnetic field strength of 900 Oe to obtain weak magnetic dry separation concentrate and weak magnetic dry separation tailings; the weak magnetic dry separation concentrate is ground and classified to a -0.038mm content of 90 wt.%, water is added to adjust the slurry to a concentration of 56 wt.%, and then a second stage of weak magnetic wet separation is performed with a magnetic field strength of 900 Oe to obtain weak magnetic concentrate 1 and weak magnetic tailings 1; the weak magnetic concentrate 1 is subjected to a third stage of weak magnetic wet separation with a magnetic field strength of 900 Oe to obtain weak magnetic concentrate 2 and weak magnetic tailings 2; (6) The weak magnetic concentrate 2 is concentrated and filtered to obtain the final iron concentrate product. The iron concentrate product has a TFe grade of 62.53% and a TFe recovery rate of 83.42%. The overflow water and filtrate are recycled to step (5) as slurry preparation water for the weak magnetic dry separation concentrate operation to achieve a closed-loop water return. (7) The pre-enriched tailings are slurry-prepared, and the natural alkaline substances in the pre-enriched tailings are used to prepare an alkaline slurry with a pH of 11. This slurry is then introduced into the flue gas generated by the suspension roasting in step (4). The alkaline slurry desulfurizes the flue gas to generate sulfates, with a desulfurization efficiency of 99.41% and an SO2 emission concentration of 31.19 mg / m³. 3 Meanwhile, under the high temperature of the flue gas, the siderite in the alkaline slurry is transformed into goethite tailings through mineral phase transformation; the goethite tailings can be subsequently used in pigments, catalysts, adsorbent materials and other fields. (8) The weak magnetic dry separation tailings, weak magnetic tailings 1 and weak magnetic tailings 2 are mixed, concentrated and filtered to obtain the final tailings. The overflow water and filtrate are reused in the pre-enriched tailings slurry preparation operation to realize the water return closed loop. The final tailings can be further used as raw materials for building materials.

Claims

1. A co-processing method for ore phase transformation and flue gas desulfurization of low-grade, sulfur-containing, refractory iron ore, characterized in that, Includes the following steps: (1) Grinding, classifying and slurrying the raw ore to obtain pre-enriched raw materials; (2) Perform magnetic pre-enrichment and strong magnetic scavenging pre-enrichment operations to obtain pre-enriched concentrate and pre-enriched tailings; (3) The pre-enriched concentrate is concentrated and filtered to obtain pre-enriched concentrate powder. The overflow water and filtrate are reused in step (1) pre-enriched raw material slurry preparation. (4) The pre-enriched concentrate powder is placed in a suspension roasting furnace, and reducing and inert gases are introduced to keep the pre-enriched concentrate in a suspension state for roasting. Siderite is converted into magnetite through hydrogen-based mineral phase conversion to obtain mineral phase conversion product; wherein, the reducing gas is a mixture of CO and H2, the inert gas is N2, and the volume ratio of CO, H2 and N2 is (50-60):(140-150):(390-410); the roasting temperature is 450℃-600℃, and the roasting time is 10min-30min; the TFe grade in the mineral phase conversion product is >35%; (5) The mineral phase transformation product is subjected to a first stage of weak magnetic dry separation to obtain weak magnetic dry separation concentrate and weak magnetic dry separation tailings; the weak magnetic dry separation concentrate is ground, classified and slurry adjusted, and then subjected to a second stage of weak magnetic wet separation to obtain weak magnetic concentrate 1 and weak magnetic tailings 1; the weak magnetic concentrate 1 is subjected to a third stage of weak magnetic wet separation to obtain weak magnetic concentrate 2 and weak magnetic tailings 2. (6) The weak magnetic concentrate 2 is concentrated and filtered to obtain the final iron concentrate product. The overflow water and filtrate are recycled to the weak magnetic dry separation concentrate slurry preparation operation in step (5). Among them, the TFe grade in the iron concentrate product is >60% and the recovery rate is >80%. (7) The pre-enriched tailings are slurried to a pH of 10-12. An alkaline slurry is made using the natural alkali source in the pre-enriched tailings and introduced into the flue gas generated by the suspension roasting in step (4). The alkaline slurry desulfurizes the flue gas to generate sulfates. At the same time, under the high temperature of the flue gas, the siderite in the alkaline slurry is transformed into goethite tailings through mineral phase conversion. The desulfurization efficiency of the flue gas after desulfurization is >99%, and the SO2 emission concentration is <35mg / m³. 3 ; (8) The weak magnetic dry separation tailings, weak magnetic tailings 1 and weak magnetic tailings 2 are mixed, concentrated and filtered to obtain the final tailings. The overflow water and filtrate are reused in step (7) pre-enriched tailings slurry preparation to realize the water return closed loop.

2. The method for synergistic beneficiation of low-grade sulfur-containing carbonate refractory iron ore by ore phase transformation and flue gas desulfurization as described in claim 1, characterized in that, In step (1), the ore is ground and classified to a particle size of -0.074mm, which accounts for 60wt.%-80wt.%. Water is added to adjust the slurry to a concentration of 50wt.%-60wt.%. This is a pre-enriched raw material.

3. The method for synergistic beneficiation of low-grade sulfur-containing carbonate refractory iron ore by ore phase transformation and flue gas desulfurization as described in claim 1, characterized in that, In step (2), the magnetic pre-enrichment is divided into two stages. First, a weak magnetic pre-enrichment operation is performed to obtain pre-enriched concentrate 1 and pre-enriched tailings 1. Then, a strong magnetic pre-enrichment operation is performed on the pre-enriched tailings 1 to obtain pre-enriched concentrate 2 and pre-enriched tailings 2. A strong magnetic scavenging pre-enrichment operation is performed on the pre-enriched tailings 2 to obtain pre-enriched concentrate 3 and pre-enriched tailings. The pre-enriched concentrate 1, pre-enriched concentrate 2 and pre-enriched concentrate 3 are mixed to obtain pre-enriched concentrate.

4. The method for synergistic beneficiation of low-grade sulfur-containing carbonate refractory iron ore by ore phase transformation and flue gas desulfurization as described in claim 3, characterized in that, The magnetic field strength for weak magnetic pre-enrichment is 800 Oe-1000 Oe, and the magnetic field strength for strong magnetic pre-enrichment and strong magnetic scanning pre-enrichment is 5000 Oe-8000 Oe. The TFe grade in the pre-enriched concentrate is >28%.

5. The method for synergistic beneficiation of low-grade sulfur-containing carbonate refractory iron ore by ore phase transformation and flue gas desulfurization as described in claim 1, characterized in that, In step (5), the magnetic field strength of the first, second and third weak magnetic separation is 800Oe-1000Oe. The weak magnetic dry separation concentrate is ground and classified to a content of -0.038mm particles ≥90wt.

6. The application of the ore phase transformation-flue gas desulfurization synergistic beneficiation method for low-grade sulfur-containing carbonate refractory iron ore as described in any one of claims 1-5 in low-grade sulfur-containing carbonate refractory iron ore.

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