Quality-divided enrichment-stepped suspension roasting-iron separation and copper leaching method for copper-containing limonite difficult to separate

Abstract

The invention discloses a quality-divided enrichment-stepped suspension roasting-iron separation and copper leaching method for copper-containing limonite difficult to separate, and belongs to the technical field of beneficiation metallurgy. The method mainly comprises five sections of operations of recovering strong magnetic iron minerals by low-intensity magnetic separation, separating and enriching by high-intensity magnetic separation, carrying out stepped suspension roasting, extracting copper from roasted products by a wet method and extracting iron by low-intensity magnetic separation. The method comprises the following steps: carrying out raw ore crushing and grinding on refractory copper-containing limonite, recovering strong magnetic iron minerals through low-intensity magnetic separation, carrying out high-intensity magnetic separation quality-divided enrichment on low-intensity magnetic separation tailings, carrying out acid leaching on strong roughing tailings to obtain copper-rich acid leaching liquid, carrying out gradient suspension roasting on high-intensity magnetic separation concentrate, and carrying out acid leaching on roasted products to obtain copper-rich acid leaching liquid and iron-rich leaching residues; and the iron-rich leaching residues are subjected to ore grinding dissociation and low-intensity magnetic separation recovery, and iron ore concentrate is obtained. Compared with the prior art, copper and iron in the refractory copper-containing limonite can be comprehensively and efficiently recycled, and the resource utilization rate of the refractory copper-containing limonite is greatly increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of mineral processing and metallurgy, and particularly relates to a method for separate enrichment - cascade suspension roasting - iron separation and copper leaching of refractory copper - bearing limonite. Background Technique

[0002] Limonite is an important iron ore resource, characterized by high iron content and wide occurrence. However, some limonite often associates with valuable metals such as copper in relatively high contents. Among them, the refractory copper - bearing limonite in Yulong, Tibet is the most representative, with large scale, complete ore body types, and a well - developed secondary oxidation zone. The refractory copper - bearing limonite mainly consists of iron oxides and secondary clay, with high copper and iron grades (Cu grade 1% - 2%, TFe grade 35% - 50%). The refractory copper - bearing limonite often has a high combined water content under natural conditions, and the iron minerals and copper minerals form a tightly - bound structure. In addition, the mineral composition of the refractory copper - bearing limonite is complex and the dissemination particle size is fine, making it difficult for conventional physical mineral processing or a single metallurgical process to achieve an ideal separation effect.

[0003] Chinese Patent CN104056714A discloses a beneficiation process for refractory fine-grained iron copper ores. In this invention, grinding and flotation are used to obtain rough flotation concentrates and tailings I. The rough flotation concentrates are further finely ground, floated, and magnetically separated to obtain copper concentrate I and iron concentrate I. The flotation tailings I are screened. The coarse-grained tailings are floated to obtain copper concentrate II and tailings II, and the fine-grained tailings are processed by magnetic separation and gravity separation processes to obtain iron concentrate II, iron concentrate III, and iron concentrate IV. However, this method can only process copper ores containing magnetic iron and with copper not being encapsulated and being easy to float, and is applicable to easily beneficiated copper iron ore resources with low combined magnetic iron, and cannot process refractory copper-bearing limonite with high combined state. Chinese Patent CN104815746A discloses a recovery method for refractory copper oxide ores with high iron and high argillaceous alkaline gangue, which is used to recover copper in copper iron ores. In this invention, the copper iron ores are first ground and floated to obtain flotation concentrates, then the flotation concentrates are subjected to high-gradient magnetic separation to obtain high-gradient magnetic separation concentrates and magnetic separation tailings. The high-gradient magnetic separation concentrates are further magnetically separated to obtain magnetic separation concentrates and magnetic separation middlings. Finally, copper in the magnetic separation middlings is recovered by hydrometallurgical leaching. However, in refractory copper-bearing limonite, copper minerals exist in limonite in the form of lattice substitution. This method has problems such as low leaching efficiency of combined copper minerals and serious iron loss in the leaching solution, which affects subsequent copper recovery, and does not consider the recovery of iron minerals. CN117165778A proposes a method for recovering iron and copper from high-iron copper ores by modified magnetic separation-acid leaching. In this invention, the high-iron copper ores are subjected to modified roasting to reduce weakly magnetic iron ores to strongly magnetic iron ores, and the iron minerals in the ore samples are recovered by a two-stage magnetic separation process. The magnetic separation tailings are further acid leached to obtain a copper-containing leaching solution. The roasting method in this patent is high-temperature static roasting, with a high roasting temperature (850°C - 950°C), which has problems such as high energy consumption, large carbon emissions, and uneven reduction process. Summary of the Invention

[0004] Based on problems such as the complex nature and difficult separation of refractory copper-bearing limonite, and aiming at the deficiencies of the existing technology, the present invention provides a method for fractional enrichment - cascade suspension roasting - iron separation and copper leaching of refractory copper-bearing limonite, aiming to achieve the efficient resource utilization of iron and copper in refractory copper-bearing limonite.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for fractional enrichment - cascade suspension roasting - iron separation and copper leaching of refractory copper - bearing limonite, which mainly includes five sections of operations: weakly magnetic separation to recover strongly magnetic iron minerals, high - intensity magnetic separation for fractional enrichment, cascade suspension roasting, wet copper extraction from the roasted product, and weakly magnetic separation for iron extraction; the refractory copper - bearing limonite is subjected to multi - stage crushing and grinding, and after weakly magnetic separation, strongly magnetic iron mineral iron concentrate I and weakly magnetic separation tailings are obtained; the weakly magnetic separation tailings are subjected to high - intensity magnetic separation, and fractional enrichment is carried out to obtain high - intensity magnetic separation concentrate and high - intensity magnetic separation tailings. The high - intensity magnetic separation concentrate is combined - state copper - bearing limonite concentrate, and the high - intensity magnetic separation tailings are non - combined - state copper - rich tailings; the high - intensity magnetic separation tailings are acid - leached to obtain copper - rich leachate I and tailing leaching residue; the high - intensity magnetic separation concentrate is subjected to cascade suspension roasting. Cascade suspension roasting is to first carry out de - hydroxylation roasting and then reduction roasting in a suspension roasting device. Air is continuously introduced at the bottom of the roasting device for de - hydroxylation roasting to obtain de - hydroxylated minerals, and then the air supply is stopped. Reducing gas and inert gas are continuously introduced at the bottom of the roasting device for reduction roasting to obtain roasted products; the roasted products are subjected to selective iron - controlled acid leaching for copper extraction to obtain copper - rich acid leachate II and iron - rich leaching residue; the iron - rich leaching residue is ground and dissociated, and then weakly magnetic separation is carried out to obtain magnetic separation concentrate iron concentrate II and magnetic separation tailings.

[0007] Further, the method for fractional enrichment - cascade suspension roasting - iron separation and copper leaching of refractory copper - bearing limonite specifically includes the following steps:

[0008] (1) Raw ore crushing and grinding: The refractory copper - bearing limonite is subjected to multi - stage crushing and grinding. After particle fine - crushing, particle classification, and material de - humidification, refractory copper - bearing limonite ore powder is obtained;

[0009] (2) Weakly magnetic separation to recover strongly magnetic iron minerals: The refractory copper - bearing limonite ore powder is subjected to weakly magnetic separation to separate and recover the strongly magnetic minerals therein to obtain iron concentrate I;

[0010] (3) High - intensity magnetic separation for fractional enrichment: The weakly magnetic separation tailings generated in step (2) are subjected to high - intensity magnetic separation, and fractional enrichment is carried out to obtain combined - state copper - bearing limonite concentrate and non - combined - state copper - rich tailings;

[0011] (4) Acid leaching of copper from high - intensity magnetic separation tailings: The non - combined - state copper - rich tailings are added to a sulfuric acid leaching solution, and acid leaching is carried out at normal temperature and pressure. The acid - leaching products are filtered and washed by suction to obtain copper - rich leachate I and tailing leaching residue;

[0012] (5) Stepwise suspension roasting of strongly magnetic separated concentrate: Add the copper-bearing limonite concentrate in combined state to the suspension roasting device. Continuously introduce air at the bottom of the suspension roasting device. First, carry out dehydroxylation roasting. After obtaining the dehydroxylated minerals, stop introducing air. Continuously introduce reducing gas and inert gas at the bottom of the suspension roasting device, and then carry out reduction roasting. Cool down the suspension roasting device to obtain the roasted product. During the stepwise suspension roasting process, not only the transformation of iron minerals from weak magnetism to strong magnetism is enhanced, but also the copper in combined state undergoes grain boundary dislocation with iron minerals, which is beneficial to the release of copper;

[0013] (6) Wet copper extraction from the roasted product: Prepare sulfuric acid leaching solution. Add the roasted product to the sulfuric acid leaching solution and carry out acid leaching at normal temperature and pressure to selectively leach copper and control iron loss. Filter and wash the acid leaching product to obtain copper-rich acid leaching solution II and iron-rich leaching residue;

[0014] (7) Grinding and dissociation: Place the iron-rich leaching residue in a mill and add water for wet grinding. After the iron-rich leaching residue is dissociated, carry out drying to obtain the grinding product;

[0015] (8) Weak magnetic separation for iron extraction: Carry out weak magnetic separation on the grinding product, and then carry out drying to obtain magnetic separation concentrate iron concentrate II and magnetic separation tailings.

[0016] Furthermore, in step (1), the multi-stage crushing and grinding is to crush the refractory copper-bearing limonite raw ore with a jaw crusher, and further crush the crushed minerals with a disc crusher until the proportion of particles with a particle size of -0.2 mm is more than 85%.

[0017] Furthermore, in step (2), the magnetic field intensity of the weak magnetic separation is 0.1 T - 0.2 T.

[0018] Furthermore, in step (3), the magnetic field intensity of the strong magnetic separation is 1 T - 1.2 T.

[0019] Furthermore, in step (4), the sulfuric acid mass concentration of the acid leaching is 5% - 10%, the liquid-solid mass ratio is (4 - 8):1, the leaching time is 60 min - 150 min, and a small amount of deionized water is used to wash the filter cake.

[0020] Furthermore, in step (5), the roasting temperature of the dehydroxylation roasting is 400 °C - 550 °C, the air flow rate is 300 mL / min - 700 mL / min, and the roasting time is 3 min - 6 min;

[0021] The reducing gas for reductive roasting is H2 or a mixture of H2 and CO. The flow rate of the reducing gas is 50 mL / min - 150 mL / min. The inert gas is nitrogen, and the flow rate of the inert gas is 300 mL / min - 600 mL / min. The roasting temperature is 480°C - 600°C, and the roasting time is 10 min - 30 min. The suspension roasting device is cooled to below 150°C.

[0022] Furthermore, in step (6), the sulfuric acid mass concentration for acid leaching is 3% - 7%, the liquid-solid mass ratio is (3 - 6):1, the leaching time is 30 min - 90 min, and a small amount of deionized water is used to wash the filter cake.

[0023] Furthermore, in step (7), the mill for wet grinding is a ball mill or a rod mill, the liquid-solid mass ratio is 1:1, the grinding time is 3 min - 6 min, and drying is carried out using a dryer.

[0024] Furthermore, in step (8), the magnetic field intensity for weak magnetic separation is 0.1 T - 0.2 T, and the magnetic separation time is 3 min - 6 min.

[0025] Advantages and effects of the present invention:

[0026] 1. Compared with the flotation - magnetic separation - gravity separation method: The flotation - magnetic separation - gravity separation method can only treat copper ores containing magnetic iron and with copper not being wrapped and being easy to float, and is not applicable to copper-bearing limonite with high combined state. The method of fractional enrichment - cascade roasting - magnetic separation leaching developed in the present invention can comprehensively and efficiently recover copper and iron from refractory copper-bearing limonite with weak magnetism, avoiding the problem that the existing methods are not applicable to treating refractory copper-bearing limonite.

[0027] 2. Compared with the flotation - magnetic separation - leaching method: When treating refractory copper-bearing limonite by the flotation - magnetic separation - leaching method, on the one hand, copper minerals are hosted in limonite in the form of lattice substitution, resulting in low copper leaching rate and serious iron loss in the leaching solution, thus affecting subsequent copper recovery. On the other hand, the comprehensive recovery of iron ore resources is not considered and there is a problem of low leaching efficiency of combined copper minerals. In the present invention, a small amount of iron in magnetite is recovered in advance by weak magnetic separation, and the copper-bearing limonite is fractionally enriched - cascade roasted by high-gradient magnetic separation, which not only enhances the magnetism of iron minerals but also promotes the grain boundary dislocation between combined copper minerals and iron minerals, thereby improving the leaching efficiency of combined copper minerals. At the same time, the content of iron ions in the solution is reduced during the leaching process, greatly improving the resource utilization rate of refractory copper-bearing limonite.

[0028] 3. Compared with the static roasting - leaching method: When the static roasting - leaching method is used to treat refractory copper - bearing limonite, the roasting temperature is high (850°C - 950°C), and there are problems such as high energy consumption, large carbon emissions, and uneven reduction process. In contrast, in the present invention, through a two - stage magnetic separation process, the copper - bearing limonite is pre - enriched by quality, reducing the treatment amount of the roasted ore. The stepped suspension roasting not only reduces the roasting temperature but also increases the efficiency and uniformity of the reduction process.

[0029] 4. First, the present invention uses a magnetic separation process to divide the raw ore into strongly magnetic magnetite concentrate, weakly magnetic iron ore rich in bound copper, and magnetic separation tailings rich in unbound copper. By enriching the raw ore by quality and further treating minerals of different properties by quality, the treatment amount of the roasted minerals is reduced, and the energy consumption is lowered. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow schematic diagram of a method for quality - enrichment - stepped suspension roasting - iron separation and copper leaching of refractory copper - bearing limonite according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention provides a method for quality - enrichment - stepped suspension roasting - iron separation and copper leaching of refractory copper - bearing limonite. Using the refractory copper - bearing limonite in Yulong, Tibet, according to the Figure 1 shown process flow, five - stage operations of weak magnetic separation to recover strongly magnetic iron minerals, high - intensity magnetic separation for quality enrichment, stepped suspension roasting, wet selective enhanced copper extraction, and weak magnetic separation of roasted products to extract iron are carried out on the refractory copper - bearing limonite. The refractory copper - bearing limonite is subjected to multi - stage crushing and grinding. After weak magnetic separation, strongly magnetic iron mineral concentrate I and weak magnetic separation tailings are obtained. The weak magnetic separation tailings are subjected to high - intensity magnetic separation to obtain high - intensity magnetic separation concentrate and high - intensity magnetic separation tailings by quality enrichment. The high - intensity magnetic separation concentrate is bound copper - bearing limonite concentrate, and the high - intensity magnetic separation tailings are unbound copper - rich tailings. The high - intensity magnetic separation tailings are acid - leached to obtain copper - rich leachate I and tailing leaching residue. The high - intensity magnetic separation concentrate is subjected to stepped suspension roasting. The stepped suspension roasting is to first carry out dehydroxylation roasting and then reduction roasting in a suspension roasting device. Air is continuously introduced at the bottom of the roasting device for dehydroxylation roasting to obtain dehydroxylated minerals. Then, air introduction is stopped, and a reducing gas (H2 or a mixture of H2 and CO) and an inert gas (N2 or Ar) are continuously introduced at the bottom of the roasting device for reduction roasting to obtain roasted products. During the stepped suspension roasting process, the materials are always in a suspended fluidized state. The roasted products are acid - leached to selectively control iron and leach copper to obtain copper - rich acid leachate II and iron - rich leaching residue. The iron - rich leaching residue is ground and dissociated, and then subjected to weak magnetic separation to obtain magnetic separation concentrate iron concentrate II and magnetic separation tailings.

[0032] The present invention will be described in detail below with reference to the embodiments.

[0033] Example 1

[0034] A method for fractional enrichment - cascade suspension roasting - iron separation and copper leaching of refractory copper - bearing limonite in the present invention. The refractory copper - bearing limonite has a TFe grade of 47.41% and a Cu grade of 1.72%. The method specifically includes the following steps:

[0035] (1) Crushing and grinding of raw ore: Use a jaw crusher to crush the particles of refractory copper - bearing limonite into fine particles. The crushed minerals are further crushed by a disc crusher, and then the particles are classified and the material is dehumidified so that the proportion of particles with a particle size of - 0.2 mm is 85%, obtaining refractory copper - bearing limonite ore powder;

[0036] (2) Weak magnetic separation to recover strongly magnetic iron minerals: At a magnetic field intensity of 0.2 T, use a wet magnetic separator to perform weak magnetic separation on the refractory copper - bearing limonite ore powder to separate and recover the strongly magnetic minerals therein, obtaining iron concentrate I;

[0037] (3) High - intensity magnetic separation for fractional enrichment: At a magnetic field intensity of 1.2 T, use a wet magnetic separator to perform high - intensity magnetic separation on the tailings of weak magnetic separation produced in step (2), and fractional enrichment to obtain combined - state copper - bearing limonite concentrate and non - combined - state copper - rich tailings;

[0038] (4) Acid leaching of copper from the tailings of high - intensity magnetic separation: Add the non - combined - state copper - rich tailings to the sulfuric acid leaching solution, and perform acid leaching at normal temperature and pressure. The mass concentration of sulfuric acid is 5%, the liquid - solid mass ratio is 6:1, and the leaching time is 150 min. After the acid - leaching product is washed 3 times with deionized water in suction filtration, copper - rich leaching solution I and tailings leaching residue are obtained;

[0039] (5) Cascade suspension roasting of high - intensity magnetic separation concentrate: Add the combined - state copper - bearing limonite concentrate to a suspension roasting device at 400 °C, continuously introduce air at 500 mL / min from the bottom of the suspension roasting device for de - hydroxylation roasting. After roasting for 5 min, de - hydroxylated minerals are obtained; Stop introducing air, and continuously introduce a reducing gas of 100 mL / min of H2 and an inert protective gas of 300 mL / min of N2 from the bottom of the suspension roasting device, and perform reduction roasting at 480 °C. After roasting for 30 min, the temperature of the suspension roasting device is cooled to below 150 °C, and the roasting product is taken out;

[0040] (6) Wet copper extraction from the roasting product: Prepare a sulfuric acid leaching solution with a sulfuric acid mass concentration of 4%. Add the roasting product to the sulfuric acid leaching solution, with a liquid - solid mass ratio of 5:1, and perform acid leaching at normal temperature and pressure. The leaching time is 90 min. After the acid - leaching product is suction - filtered and washed 3 times, copper - rich acid leaching solution II and iron - rich leaching residue are obtained;

[0041] (7) Grinding and dissociation: Place the dried iron - rich leaching residue after suction filtration and washing in a rod mill, and perform wet grinding with water with a liquid - solid mass ratio of 1:1 for 3 min. The iron - rich leaching residue is dissociated and dried in a dryer to obtain the grinding product;

[0042] (8) Weak magnetic separation for iron extraction: Conduct weak magnetic separation on the ground product in a magnetic separation device. Set the magnetic field intensity at 0.1 T and the magnetic separation time at 6 min. Further dry the magnetic separation product in an oven to obtain magnetic separation concentrate iron concentrate II and magnetic separation tailings.

[0043] In this example, iron concentrate I and iron concentrate II products are mixed. The final iron concentrate product has an iron grade of 63.97% and an iron recovery rate of 88.96%. Rich copper leaching solution I and rich copper acid leaching solution II are mixed. The copper leaching rate in the final obtained copper leaching solution is 92.96%.

[0044] Example 2

[0045] A method for fractional enrichment - cascade suspension roasting - iron extraction and copper leaching of refractory copper-bearing limonite in the present invention. The refractory copper-bearing limonite has a TFe grade of 48.49% and a Cu grade of 1.62%. It specifically includes the following steps:

[0046] (1) Raw ore crushing and grinding: Use a jaw crusher to crush the refractory copper-bearing limonite particles into fine particles. The crushed ore is further finely crushed by a disk crusher, followed by particle sizing and material dehumidification to make the proportion of particles with a particle size of -0.2 mm reach 90%, obtaining refractory copper-bearing limonite ore powder.

[0047] (2) Weak magnetic separation for recovering strongly magnetic iron minerals: Conduct weak magnetic separation on the refractory copper-bearing limonite ore powder using a wet magnetic separator at a magnetic field intensity of 0.2 T to separate and recover the strongly magnetic minerals therein, obtaining iron concentrate I.

[0048] (3) High-intensity magnetic separation for fractional enrichment: Conduct high-intensity magnetic separation on the weak magnetic separation tailings produced in step (2) using a wet magnetic separator at a magnetic field intensity of 1 T to fractionally enrich and obtain combined copper-bearing limonite concentrate and non-combined rich copper tailings.

[0049] (4) Acid leaching of copper from high-intensity magnetic separation tailings: Add the non-combined rich copper tailings to a sulfuric acid leaching solution and conduct acid leaching at normal temperature and pressure. The mass concentration of sulfuric acid is 8%, the liquid-solid mass ratio is 5:1, and the leaching time is 60 min. After the acid leaching product is washed 3 times with deionized water in suction filtration, rich copper leaching solution I and tailing leaching residue are obtained.

[0050] (5) Stepwise suspension roasting of strongly magnetic separated concentrate: Add the combined copper-bearing limonite concentrate into a suspension roasting device at 550 °C, continuously introduce air at 300 mL / min from the bottom of the suspension roasting device for dehydroxylation roasting. After roasting for 6 min, dehydroxylated minerals are obtained. Stop introducing air, and continuously introduce reducing gas from the bottom of the suspension roasting device. The reducing gas is 100 mL / min of H2 and 50 mL / min of CO, as well as 400 mL / min of N2 as inert protective gas. Continue reduction roasting at 500 °C. After roasting for 20 min, the temperature of the suspension roasting device is cooled to below 150 °C, and the roasted product is taken out;

[0051] (6) Wet copper extraction from roasted product: Prepare a sulfuric acid leaching solution with a sulfuric acid mass concentration of 7%. Add the roasted product into the sulfuric acid leaching solution with a liquid-solid mass ratio of 3:1, and perform acid leaching at normal temperature and pressure for 30 min. After the acid leaching product is filtered by suction and washed 3 times, a copper-rich acid leaching solution II and an iron-rich leaching residue are obtained;

[0052] (7) Grinding and dissociation: Place the dried iron-rich leaching residue after suction filtration and washing in a rod mill, and perform wet grinding with water with a liquid-solid mass ratio of 1:1 for 6 min. The iron-rich leaching residue is dissociated and dried in a dryer to obtain a grinding product;

[0053] (8) Weak magnetic separation for iron extraction: Perform weak magnetic separation on the grinding product in a magnetic separation device. The magnetic field intensity is set at 0.15 T, and the magnetic separation time is set at 5 min. Further dry the magnetic separation product to obtain a magnetic separation concentrate (iron concentrate II) and a magnetic separation tailing.

[0054] In this example, the iron concentrates I and II are mixed. The final iron concentrate product has an iron grade of 62.5% and an iron recovery rate of 84.26%; the copper-rich leaching solution I and the copper-rich acid leaching solution II are mixed. The copper leaching rate in the final copper leaching solution is 90.38%.

[0055] Example 3

[0056] A method for fractional enrichment-stepwise suspension roasting-iron separation and copper leaching of refractory copper-bearing limonite in the present invention. The refractory copper-bearing limonite has a TFe grade of 48.67% and a Cu grade of 1.62%, and specifically includes the following steps:

[0057] (1) Primary ore crushing and grinding: Use a jaw crusher to finely crush the refractory copper-bearing limonite particles. The crushed minerals are further finely crushed by a disc crusher, and particle classification and material dehumidification are carried out to make the proportion of particles with a particle size of -0.2 mm reach 95% to obtain a refractory copper-bearing limonite ore powder;

[0058] (2) Weak magnetic separation for recovering strongly magnetic iron minerals: At a magnetic field intensity of 0.1 T, a wet magnetic separator is used to perform weak magnetic separation on the refractory copper-bearing limonite ore powder to separate and recover the strongly magnetic minerals therein, obtaining iron concentrate I;

[0059] (3) Medium enrichment by strong magnetic separation: At a magnetic field intensity of 1.1 T, a wet magnetic separator is used to perform strong magnetic separation on the tailings from weak magnetic separation in step (2) to achieve medium enrichment and obtain copper-bearing limonite concentrate in combined state and copper-rich tailings in uncombined state;

[0060] (4) Acid leaching of copper from the tailings of strong magnetic separation: The copper-rich tailings in uncombined state are added to the sulfuric acid leaching solution, and acid leaching is carried out at normal temperature and pressure. The mass concentration of sulfuric acid is 10%, the liquid-solid mass ratio is 4:1, and the leaching time is 90 min. After the acid leaching product is washed 3 times with deionized water in suction filtration, copper-rich leaching solution I and tailings leaching residue are obtained;

[0061] (5) Stepwise suspension roasting of the concentrate of strong magnetic separation: The copper-bearing limonite concentrate in combined state is added to a suspension roasting device at 400 °C, and air is continuously introduced from the bottom of the suspension roasting device at a rate of 700 mL / min for dehydroxylation roasting. After roasting for 3 min, dehydroxylated minerals are obtained; Stop introducing air, and continuously introduce reducing gas from the bottom of the suspension roasting device. The reducing gas is H2 at 50 mL / min and inert protective gas N2 at 500 mL / min, and reduction roasting is continued at 600 °C. After roasting for 10 min, the temperature of the suspension roasting device is cooled to below 150 °C, and the roasting product is taken out;

[0062] (6) Wet copper extraction from the roasting product: Prepare a sulfuric acid leaching solution with a mass concentration of sulfuric acid of 3%. Add the roasting product to the sulfuric acid leaching solution, with a liquid-solid mass ratio of 6:1, and perform acid leaching at normal temperature and pressure for 60 min. After the acid leaching product is suction filtered and washed 3 times, copper-rich acid leaching solution II and iron-rich leaching residue are obtained;

[0063] (7) Grinding and dissociation: The dried iron-rich leaching residue after suction filtration and washing is placed in a rod mill, and wet grinding is carried out with water at a liquid-solid mass ratio of 1:1 for 4 min. The iron-rich leaching residue is dissociated and dried in a dryer to obtain the grinding product;

[0064] (8) Iron extraction by weak magnetic separation: The grinding product is subjected to weak magnetic separation in a magnetic separation device. The magnetic field intensity is set at 0.2 T, and the magnetic separation time is set at 3 min. The magnetic separation product is further dried to obtain magnetic separation concentrate iron concentrate II and magnetic separation tailings.

[0065] In this example, the iron concentrates I and II are mixed. The final iron concentrate product has an iron grade of 62.73% and an iron recovery rate of 86.38%; The copper-rich leaching solution I and copper-rich acid leaching solution II are mixed. The leaching rate of copper in the final obtained copper leaching solution is 91.32%.

[0066] Example 4

[0067] A method for fractional enrichment - cascade suspension roasting - iron separation and copper leaching of refractory copper - bearing limonite of the present invention, the refractory copper - bearing limonite has a TFe grade of 48.67% and a Cu grade of 1.62%, and specifically includes the following steps:

[0068] (1) Raw ore crushing and grinding: Use a jaw crusher to finely crush the refractory copper - bearing limonite particles, and further finely crush the crushed minerals with a disc crusher. Perform particle sizing and material dehumidification to make the proportion of particles with a particle size of -0.2 mm reach 100%, obtaining refractory copper - bearing limonite ore powder;

[0069] (2) Weak magnetic separation to recover strongly magnetic iron minerals: At a magnetic field intensity of 0.15 T, use a wet magnetic separator to perform weak magnetic separation on the refractory copper - bearing limonite ore powder, separate and recover the strongly magnetic minerals therein, obtaining iron concentrate I;

[0070] (3) High - intensity magnetic separation for fractional enrichment: At a magnetic field intensity of 1.2 T, use a wet magnetic separator to perform high - intensity magnetic separation on the tailings from the weak magnetic separation in step (2), and fractionally enrich to obtain combined - state copper - bearing limonite concentrate and non - combined - state copper - rich tailings;

[0071] (4) Acid leaching of copper from high - intensity magnetic separation tailings: Add the non - combined copper - rich tailings to the sulfuric acid leaching solution, perform acid leaching at normal temperature and pressure, with a sulfuric acid mass concentration of 6%, a liquid - to - solid mass ratio of 8:1, and a leaching time of 90 min. After the acid - leaching product is washed 3 times with deionized water in suction filtration, obtain copper - rich leaching solution I and tailing leaching residue;

[0072] (5) Cascade suspension roasting of high - intensity magnetic separation concentrate: Add the combined - state copper - bearing limonite concentrate to a suspension roasting device at 520 °C, continuously introduce air at 500 mL / min from the bottom of the suspension roasting device for dehydroxylation roasting. After roasting for 5 min, obtain dehydroxylated minerals; Stop introducing air, and continuously introduce a reducing gas at the bottom of the suspension roasting device. The reducing gas is 50 mL / min of H2 and 50 mL / min of CO, and an inert protective gas of 600 mL / min of N2. Continue to perform reduction roasting at 500 °C. After roasting for 20 min, cool the suspension roasting device to below 150 °C and take out the roasting product;

[0073] (6) Wet copper extraction from the roasting product: Prepare a sulfuric acid leaching solution with a sulfuric acid mass concentration of 5%, add the roasting product to the sulfuric acid leaching solution, with a liquid - to - solid mass ratio of 5:1, perform acid leaching at normal temperature and pressure, with a leaching time of 60 min. After the acid - leaching product is suction - filtered and washed 3 times, obtain copper - rich acid leaching solution II and iron - rich leaching residue;

[0074] (7) Grinding and dissociation: Place the dried iron-rich leaching residue after suction filtration and washing in a ball mill, and grind it with water at a liquid-solid mass ratio of 1:1 for 4 minutes. Dissociate the iron-rich leaching residue and dry it in a dryer to obtain the grinding product;

[0075] (8) Weak magnetic separation for iron extraction: Conduct weak magnetic separation on the grinding product in a magnetic separation device. Set the magnetic field intensity at 0.12 T and the magnetic separation time at 5 minutes. Further dry the magnetic separation product to obtain magnetic separation concentrate iron concentrate II and magnetic separation tailings.

[0076] In this example, iron concentrate I and iron concentrate II products are mixed. The final iron concentrate product has an iron grade of 63.18% and an iron recovery rate of 85.61%; rich copper leaching solution I and rich copper acid leaching solution II are mixed, and the copper leaching rate in the final obtained copper leaching solution is 90.66%.

[0077] Comparative Example 1

[0078] This comparative example uses the existing static roasting-leaching method to treat copper-bearing limonite, which specifically includes the following steps:

[0079] (1) Raw ore pretreatment: Use a jaw crusher to crush the refractory copper-bearing limonite particles with a TFe grade of 47.4% and a Cu grade of 1.72%. Further finely crush the crushed ore with a disc crusher to make the proportion of particles with a particle size of -0.2 mm reach 85%;

[0080] (2) Static roasting: Uniformly mix the copper-bearing limonite strong magnetic separation concentrate with carbon powder and then conduct reduction roasting. Take out the material when the temperature in the roasting furnace drops below 150 °C. The carbon powder dosage is 15% of the ore powder mass, the roasting temperature is 900 °C, and the roasting time is 60 minutes;

[0081] (3) Wet copper extraction from the roasted product: Prepare a chemical extraction solution by mixing the leaching reagent sulfuric acid and water in a certain proportion. The sulfuric acid mass concentration is 5%, the liquid-solid mass ratio is 5:1, and the leaching time is 60 minutes. After suction filtering and washing the acidic leaching sample 3 times, obtain rich copper leaching solution and iron-rich leaching residue;

[0082] (4) Grinding and dissociation: Put the dried iron-rich leaching residue after suction filtration and washing into a rod mill, and grind it with water at a liquid-solid mass ratio of 1:1 for 4 minutes. Further dry the grinding product in a dryer;

[0083] (5) Weak magnetic separation for iron extraction: Conduct magnetic separation on the iron-rich leaching residue after grinding and dissociation in a magnetic separation tube. Set the magnetic field intensity at 0.12 T and the magnetic separation time at 5 minutes. Further dry the magnetic separation product to obtain magnetic separation concentrate and magnetic separation tailings.

[0084] The iron grade of the iron concentrate product finally obtained in this comparative example is 60.54%, the iron recovery rate is 81.3%, and the leaching rate of copper in the finally obtained copper leaching solution is 83.22%. This shows that the existing static roasting - leaching method not only has a high roasting temperature, high energy consumption and large carbon emissions, but also has an uneven reduction process. Therefore, the recovery effects of iron and copper are poor, and it is impossible to achieve the iron grade, iron recovery rate and copper leaching rate of the products obtained by the method of staged enrichment - cascade suspension roasting - iron separation and copper leaching of refractory copper - bearing limonite in the present invention.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is that dehydroxylation roasting is not carried out, but direct reduction roasting is carried out on the copper - bearing limonite concentrate in the bound state, which specifically includes the following steps:

[0087] (1) Ore crushing and grinding: Use a jaw crusher to crush the refractory copper - bearing limonite particles into fine particles, and further crush the crushed minerals with a disc crusher, followed by particle sizing and material dehumidification to make the proportion of particles with a particle size of -0.2 mm reach 85%, obtaining the refractory copper - bearing limonite ore powder.

[0088] (2) Weak magnetic separation to recover strongly magnetic iron minerals: At a magnetic field intensity of 0.2 T, use a wet magnetic separator to perform weak magnetic separation on the refractory copper - bearing limonite ore powder to separate and recover the strongly magnetic minerals therein, obtaining iron concentrate I.

[0089] (3) High - intensity magnetic separation for staged enrichment: At a magnetic field intensity of 1.2 T, use a wet magnetic separator to perform high - intensity magnetic separation on the tailings from the weak magnetic separation in step (2) to obtain copper - bearing limonite concentrate in the bound state and non - bound copper - rich tailings through staged enrichment.

[0090] (4) Acid leaching of copper from the tailings of high - intensity magnetic separation: Add the non - bound copper - rich tailings to the sulfuric acid leaching solution and carry out acid leaching at normal temperature and pressure. The mass concentration of sulfuric acid is 5%, the liquid - solid mass ratio is 6:1, and the leaching time is 150 min. After the acid - leaching product is washed 3 times with deionized water in suction filtration, copper - rich leaching solution I and tailings leaching residue are obtained.

[0091] (5) Cascade suspension roasting of high - intensity magnetic separation concentrate: Add the copper - bearing limonite concentrate in the bound state to a suspension roasting device at 400 °C, continuously introduce reducing gas H2 at 100 mL / min and inert protective gas N2 at 300 mL / min from the bottom of the suspension roasting device, and carry out reduction roasting at 480 °C. After roasting for 30 min, the temperature of the suspension roasting device is cooled to below 150 °C, and the roasted product is taken out.

[0092] (6)Wet copper extraction from roasted product: Prepare a sulfuric acid leaching solution with a sulfuric acid mass concentration of 4%. Add the roasted product to the sulfuric acid leaching solution with a liquid-solid mass ratio of 5:1. Conduct acid leaching at normal temperature and pressure for 90 minutes. After the acid leaching product is filtered by suction and washed 3 times, a copper-rich acid leaching solution II and an iron-rich leaching residue are obtained;

[0093] (7)Grinding and dissociation: Place the dried iron-rich leaching residue after suction filtration and washing in a rod mill, and conduct wet grinding with a liquid-solid mass ratio of 1:1 for 3 minutes. Dissociate the iron-rich leaching residue and dry it in a dryer to obtain a grinding product;

[0094] (8)Weak magnetic separation for iron extraction: Conduct weak magnetic separation on the grinding product in a magnetic separation device with a magnetic field intensity set at 0.1 T and a magnetic separation time set at 6 minutes. Further dry the magnetic separation product in an oven to obtain a magnetic separation concentrate, iron concentrate II, and a magnetic separation tailing.

[0095] In this comparative example, iron concentrate I and iron concentrate II products are mixed. The final iron concentrate product has an iron grade of 61.44% and an iron recovery rate of 81.79%; copper-rich leaching solution I and copper-rich acid leaching solution II are mixed. The leaching rate of copper in the final obtained copper leaching solution is 88.83%. Its iron grade, iron recovery rate, and copper leaching rate are all inferior to those of Example 1 because dehydroxylation roasting can generate a large number of pores and cracks on the mineral surface, improving the diffusion rate of reducing gases in the subsequent reduction fluidized bed roasting.

[0096] Comparative Example 3

[0097] The difference between this comparative example and Example 1 is that instead of using cascade suspension roasting, direct magnetic separation leaching is carried out on copper-bearing limonite, which specifically includes the following steps:

[0098] (1)Raw ore crushing and grinding: Use a jaw crusher to crush the particles of refractory copper-bearing limonite into fine particles. The crushed ore is further finely crushed by a disc crusher, and the particles are classified and the material is dehumidified so that the proportion of particles with a particle size of -0.2 mm is 85% to obtain a refractory copper-bearing limonite ore powder;

[0099] (2)Weak magnetic separation to recover strongly magnetic iron minerals: Conduct weak magnetic separation on the refractory copper-bearing limonite ore powder with a wet magnetic separator at a magnetic field intensity of 0.2 T to separate and recover the strongly magnetic minerals therein to obtain iron concentrate I;

[0100] (3)Strong magnetic separation for medium enrichment: Conduct strong magnetic separation on the weak magnetic separation tailing produced in step (2) with a wet magnetic separator at a magnetic field intensity of 1.2 T to conduct medium enrichment to obtain a combined copper-bearing limonite concentrate and an uncombined copper-rich tailing;

[0101] (4) Acid leaching of copper from the tailings of high-intensity magnetic separation: Add the unbound copper-rich tailings to the sulfuric acid leaching solution, and carry out acid leaching at normal temperature and pressure. The mass concentration of sulfuric acid is 5%, the liquid-solid mass ratio is 6:1, and the leaching time is 150 min. After the acid leaching product is washed 3 times with deionized water by suction filtration, copper-rich leaching solution I and tailings leaching residue are obtained;

[0102] (5) Acid leaching of copper from the concentrate of high-intensity magnetic separation: Prepare a sulfuric acid leaching solution with a sulfuric acid mass concentration of 4%. Add the roasted product to the sulfuric acid leaching solution, with a liquid-solid mass ratio of 5:1, and carry out acid leaching at normal temperature and pressure for 90 min. After the acid leaching product is suction filtered and washed 3 times, copper-rich acid leaching solution II and iron-rich leaching residue are obtained;

[0103] (6) Grinding and dissociation: Place the dried iron-rich leaching residue after suction filtration and washing in a rod mill, and carry out wet grinding with a liquid-solid mass ratio of 1:1 for 3 min. The iron-rich leaching residue is dissociated and dried in a dryer to obtain the grinding product;

[0104] (7) Weak magnetic separation for iron extraction: Carry out weak magnetic separation on the grinding product in a magnetic separation equipment, set the magnetic field intensity at 0.1 T and the magnetic separation time at 6 min. Further dry the magnetic separation product in an oven to obtain magnetic separation concentrate iron concentrate II and magnetic separation tailings.

[0105] In this comparative example, iron concentrate I and iron concentrate II products are mixed. The iron grade of the finally obtained iron concentrate product is 54.49% and the iron recovery rate is 73.38%; copper-rich leaching solution I and copper-rich acid leaching solution II are mixed. The leaching rate of copper in the finally obtained copper leaching solution is 59.21%. It can be seen that the lack of the cascade suspension roasting process will seriously affect the grade and recovery rate of the products. The cascade suspension roasting enhances the magnetism of iron minerals and also promotes the grain boundary dislocation between the bound copper ore and iron minerals, thereby improving the leaching efficiency of the bound copper minerals.

[0106] Comparative Example 4

[0107] The difference between this comparative example and Example 1 is that instead of using magnetic separation for medium enrichment, the refractory copper-bearing limonite is directly subjected to cascade suspension roasting - leaching - magnetic separation, which specifically includes the following steps:

[0108] (1) Ore crushing and grinding: Use a jaw crusher to crush the refractory copper-bearing limonite particles into fine particles, and further crush the crushed minerals with a disc crusher. The particles are classified and the material is dehumidified so that the proportion of particles with a particle size of -0.2 mm is 85% to obtain the refractory copper-bearing limonite ore powder;

[0109] (2) Stepwise suspension roasting: Add refractory copper-bearing limonite ore powder into a suspension roasting device at 400 °C, continuously introduce air at 500 mL / min from the bottom of the suspension roasting device for dehydroxylation roasting. After roasting for 5 min, dehydroxylated minerals are obtained. Stop introducing air, continuously introduce reducing gas, i.e., 100 mL / min of H2 and 300 mL / min of inert protective gas N2, from the bottom of the suspension roasting device, and conduct reduction roasting at 480 °C. After roasting for 30 min, cool the suspension roasting device to below 150 °C and take out the roasted product;

[0110] (3) Wet copper extraction from roasted product: Prepare a sulfuric acid leaching solution with a sulfuric acid mass concentration of 4%. Add the roasted product into the sulfuric acid leaching solution with a liquid-solid mass ratio of 5:1, and conduct acid leaching at normal temperature and pressure for 90 min. After the acid leaching product is filtered and washed 3 times, a copper-rich acid leaching solution and an iron-rich leaching residue are obtained;

[0111] (4) Grinding and dissociation: Place the dried iron-rich leaching residue after filtration and washing in a rod mill, and conduct wet grinding with water with a liquid-solid mass ratio of 1:1 for 3 min. Dissociate the iron-rich leaching residue and dry it in a dryer to obtain a grinding product;

[0112] (5) Low-intensity magnetic separation for iron extraction: Conduct low-intensity magnetic separation on the grinding product in a magnetic separation device, set the magnetic field intensity at 0.1 T, and set the magnetic separation time at 6 min. Further dry the magnetic separation product in an oven to obtain magnetic separation concentrate iron concentrate II and magnetic separation tailings.

[0113] The iron grade of the iron concentrate product finally obtained in this comparative example is 61.45%, the iron recovery rate is 82.51%, and the copper leaching rate in the finally obtained copper leaching solution is 89.31%. This shows that the lack of the process of magnetic separation and medium enrichment will reduce the leaching efficiency of refractory copper-bearing limonite.

Claims

1. A method for fractionation and enrichment of refractory copper-containing limonite - stepwise suspension roasting - iron selection and copper leaching, characterized in that: It mainly includes five operations: weak magnetic separation to recover strongly magnetic iron minerals, strong magnetic separation and enrichment, cascade suspension roasting, wet copper extraction of roasting products and weak magnetic separation to extract iron; multi-stage crushing and grinding of the difficult-to-select copper-containing limonite, weak magnetic separation and separation to obtain strong magnetic iron mineral iron concentrate I and weak magnetic separation tailings; strong magnetic separation tailings are subjected to strong magnetic separation, and enrichment is carried out to obtain strong magnetic separation concentrate and strong magnetic separation tailings. The strong magnetic separation concentrate is a bound copper-containing limonite concentrate, and the strong magnetic separation tailings are unbound copper-rich tailings; the strong magnetic separation tailings are subjected to acid leaching to obtain copper-rich leaching solution I and tailings leaching residue; strong magnetic separation concentrate The ore is subjected to step-by-step suspension roasting, which is to first carry out dehydroxylation roasting and then reduction roasting in a suspension roasting device, continuously introduce air into the bottom of the roasting device for dehydroxylation roasting to obtain dehydroxylated ore, stop introducing air, continuously introduce reducing gas and inert gas into the bottom of the roasting device for reduction roasting to obtain roasting products; the roasting products are subjected to selective iron-controlled acid leaching of copper to obtain copper-rich acid leaching solution II and iron-rich leaching slag; the iron-rich leaching slag is ground and dissociated, and then subjected to weak magnetic separation to obtain magnetic concentrate iron concentrate II and magnetic tailings.

2. The method for fractionation and enrichment of refractory copper-containing limonite-stepped suspended roasting-iron selection and copper leaching as claimed in claim 1, characterized in that: The specific steps include: (1) Ore crushing and grinding: The refractory copper-containing limonite is subjected to multi-stage crushing and grinding, and the particles are finely crushed, graded, and the material is dehumidified to obtain the refractory copper-containing limonite powder; (2) Weak magnetic separation to recover strongly magnetic iron minerals: Weak magnetic separation is performed on the hard-to-separate copper-containing limonite ore powder to separate and recover the strongly magnetic minerals therein to obtain iron concentrate I; (3) Strong magnetic separation and enrichment: The weak magnetic separation tailings produced in step (2) are subjected to strong magnetic separation to obtain bound copper-containing limonite concentrate and unbound copper-rich tailings; (4) Strong magnetic separation tailings acid leaching copper: adding the unbound copper-rich tailings into the sulfuric acid leaching solution, acid leaching is carried out at room temperature and pressure, and the acid leaching product is filtered and washed to obtain the copper-rich leaching solution I and the tailings leaching residue; (5) Stepwise suspension roasting of the concentrated ore with strong magnetic separation: the combined copper-containing limonite concentrate is added to a suspension roasting device, air is continuously introduced into the bottom of the suspension roasting device, and dehydroxylation roasting is first performed. After the dehydroxylation mineral is obtained, the introduction of air is stopped, and reducing gas and inert gas are continuously introduced into the bottom of the suspension roasting device, and reduction roasting is performed again. The suspension roasting device is cooled to obtain a roasted product. (6) Wet copper extraction from the roasted product: preparing a sulfuric acid leaching solution, adding the roasted product to the sulfuric acid leaching solution, and performing acid leaching at room temperature and pressure to selectively leach copper and control iron loss. The acid leaching product is filtered and washed to obtain copper-rich acid leaching solution II and iron-rich leaching residue; (7) Grinding and dissociation: The iron-rich leaching residue is placed in a mill, and water is added for wet grinding. After the iron-rich leaching residue is dissociated, it is dried to obtain a grinding product; (8) Weak magnetic separation: The grinding products are subjected to weak magnetic separation and then dried to obtain magnetic concentrate iron concentrate II and magnetic tailings.

3. The method for fractionation and enrichment of refractory copper-containing limonite-stepped suspended roasting-iron selection and copper leaching as claimed in claim 2, characterized in that: In step (1), the multi-stage crushing and grinding is to use a jaw crusher to crush the hard-to-select copper-containing limonite ore, and the crushed ore is further crushed by a disc crusher to a particle size of -0.2 mm, accounting for more than 85%.

4. The method for fractionation and enrichment of refractory copper-containing limonite-stepped suspended roasting-iron selection and copper leaching as claimed in claim 2, characterized in that: The magnetic field strength of the weak magnetic separation in step (2) is 0.1T-0.2T.

5. The method for fractionation and enrichment of refractory copper-containing limonite-stepped suspended roasting-iron selection and copper leaching as claimed in claim 2, characterized in that: The magnetic field strength of the strong magnetic separation in step (3) is 1T-1.2T.

6. The method for fractionation and enrichment of refractory copper-containing limonite-stepped suspended roasting-iron selection and copper leaching as claimed in claim 2, characterized in that: In step (4), the mass concentration of sulfuric acid for acid leaching is 5%-10%, the liquid-to-solid mass ratio is (4-8):1, the leaching time is 60min-150min, and the filter cake is washed with deionized water.

7. The method for fractionation and enrichment of refractory copper-containing limonite-stepped suspended roasting-iron selection and copper leaching as claimed in claim 2, characterized in that: The dehydroxylation calcination in step (5) is carried out at a temperature of 400°C to 550°C, an air flow rate of 300 mL / min to 700 mL / min, and a calcination time of 3 min to 6 min; The reducing gas for reduction roasting is H2 or a mixture of H2 and CO, the reducing gas flow rate is 50mL / min-150mL / min, the inert gas is nitrogen, the inert gas flow rate is 300mL / min-600mL / min, the roasting temperature is 480℃-600℃, and the roasting time is 10min-30min; the suspension roasting device is cooled to below 150℃.

8. The method for fractionation and enrichment of refractory copper-containing limonite according to claim 2 - stepwise suspension roasting - iron selection and copper leaching, characterized in that: In step (6), the mass concentration of sulfuric acid for acid leaching is 3%-7%, the liquid-solid mass ratio is (3-6):1, the leaching time is 30min-90min, and the filter cake is washed with deionized water.

9. The method for fractionation and enrichment of refractory copper-containing limonite-stepped suspended roasting-iron selection and copper leaching as claimed in claim 2, characterized in that: In step (7), the wet grinding mill is a ball mill or a rod mill, the liquid-solid mass ratio is 1:1, and the grinding time is 3 min-6 min; a dryer is used for drying.

10. The method for fractionation and enrichment of refractory copper-containing limonite - stepwise suspension roasting - iron selection and copper leaching as claimed in claim 2, characterized in that: The magnetic field strength of the weak magnetic separation in step (8) is 0.1T-0.2T, and the magnetic separation time is 3min-6min.

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