Beneficiation process of a refractory lean iron ore

Abstract

The disclosure provides a beneficiation process for refractory lean iron ore, and belongs to the technical field of mineral processing. The tailings produced by the beneficiation process for the refractory lean iron ore are subjected to spiral chute gravity separation operation, flotation operation and reduction operation, the tailings of the refractory lean iron ore have high beneficiation efficiency and recovery rate, the total iron grade of the iron powder obtained by the reduction operation reaches more than 97.5%, efficient development and utilization of the tailings resources of the refractory lean iron ore are realized, and high economic benefit and environmental benefit are achieved. The beneficiation process for the refractory lean iron ore has simple process flow, stable equipment operation, high automation degree, and is easy to realize industrial production.

Description

Technical Field

[0001] This disclosure relates to the field of mineral processing technology, specifically to a mineral processing technology for difficult-to-process lean iron ore. Background Technology

[0002] Iron and steel, as an important metallic material, are widely used in construction, machinery, automobiles, railways, shipbuilding, light industry, and home appliances. The iron and steel industry is a fundamental industry of the national economy, and its development level is an important indicator of a country's comprehensive strength. With the continuous mining of iron ore both domestically and internationally, high-grade, easily beneficiated iron ore has been largely depleted, leaving a large quantity of low-grade, complex, and difficult-to-benefit iron ore awaiting rational development. The efficient development and utilization of this difficult-to-benefit iron ore is of paramount strategic importance for expanding the utilization rate of iron resources and supporting iron ore supply.

[0003] Currently, the process for separating lean iron ore typically employs a combined beneficiation process of grinding-gravity separation-strong magnetic separation-anion reverse flotation. However, the current beneficiation process has the following shortcomings: First, the flotation volume is large, and the reagent consumption is also large; second, the high grade of flotation tailings leads to the disposal of iron tailings with higher fine particle size (20-23.5% iron grade in flotation tailings and 8-1% iron grade in magnetic tailings) by burying, resulting in significant resource waste and environmental pollution. Summary of the Invention

[0004] The purpose of this disclosure is to overcome the shortcomings of the existing technology and provide a beneficiation process for difficult-to-process lean iron ore, so as to realize the efficient development and utilization of tailings resources.

[0005] To achieve the above objectives, the technical solution adopted in this disclosure is as follows: a beneficiation process for refractory lean iron ore is provided, comprising the following steps:

[0006] The difficult-to-process lean iron ore is subjected to the following processes: first grinding, first weak magnetic and strong magnetic separation, second grinding, second weak magnetic and strong magnetic separation, flotation, spiral sluice gravity separation, and reduction.

[0007] The overflow product from the first grinding operation enters the first weak magnetic and strong magnetic separation operation;

[0008] The concentrate product from the first weak magnetic and strong magnetic separation operation enters the second grinding operation;

[0009] The overflow product from the second grinding operation enters the second weak magnetic and strong magnetic separation operation;

[0010] The middlings from the second weak magnetic and strong magnetic separation operation enter the flotation operation;

[0011] The tailings products from the first weak magnetic and strong magnetic separation operation, the tailings products from the second grinding operation, the tailings products from the second weak magnetic and strong magnetic separation operation, and the tailings products from the flotation operation are combined as tailings and enter the spiral sluice gravity separation operation.

[0012] The primary concentrate product from the spiral sluice gravity separation operation enters the reduction operation; the secondary concentrate product from the spiral sluice gravity separation operation is returned to the flotation operation.

[0013] This disclosure describes a process for treating tailings from refractory lean iron ore beneficiation using spiral sluice gravity separation, flotation, and reduction operations. This process achieves high beneficiation efficiency and recovery rate for tailings from refractory lean iron ore. The iron concentrate obtained from the reduction operation has a total iron content of over 95.6%, realizing the efficient development and utilization of tailings resources from refractory lean iron ore, and yielding significant economic and environmental benefits.

[0014] In some embodiments, the first grinding operation consists of a first ball mill and a first hydrocyclone; the refractory lean iron ore enters the first ball mill, and the product of the first ball mill enters the first hydrocyclone; the overflow product of the first hydrocyclone enters the first weak magnetic and strong magnetic separation operation as the overflow product of the first grinding operation, and the sand product of the first hydrocyclone is returned to the first ball mill for ball milling.

[0015] In some embodiments, the first weak magnetic separation operation consists of a first weak magnetic separator, a first thickener and desliming machine, and a first strong magnetic separator; the overflow product of the first grinding operation enters the first weak magnetic separator, the tailings product of the first weak magnetic separator enters the first thickener and desliming machine, the concentrate product of the first thickener and desliming machine enters the first strong magnetic separator, the tailings product of the first thickener and desliming machine and the tailings product of the first strong magnetic separator are combined as tailings and enter the spiral sluice gravity separation operation, and the concentrate product of the first weak magnetic separator and the concentrate product of the first strong magnetic separator are combined as the concentrate product of the first weak magnetic separation operation and enter the second grinding operation.

[0016] Specifically, the magnetic force of the first weak magnetizer is 1500-2000 GS; the magnetic force of the first strong magnetizer is 5000-8000 GS.

[0017] In some embodiments, the second grinding operation consists of a second hydrocyclone and a second ball mill; the concentrate product from the first weak magnetic and strong magnetic separation operation enters the second hydrocyclone, the underflow product from the second hydrocyclone enters the second ball mill, and the product from the second ball mill returns to the second hydrocyclone; the overflow product from the second hydrocyclone enters the second weak magnetic and strong magnetic separation operation as the overflow product of the second grinding operation.

[0018] In some embodiments, the second weak magnetic and strong magnetic separation operation comprises a second thickener / desliming machine, a second weak magnetic separator, a magnetic gravity separator, a third thickener / desliming machine, and a fourth thickener / desliming machine. The overflow product from the second grinding operation enters the second thickener / desliming machine, the concentrate product from the second thickener / desliming machine enters the second weak magnetic separator, the concentrate product from the second weak magnetic separator enters the magnetic gravity separator, and the concentrate product from the magnetic gravity separator becomes the final concentrate product. The tailings products from the second thickener / desliming machine and the tailings products from the magnetic gravity separator are combined and enter the third thickener / desliming machine, the concentrate product from the third thickener / desliming machine enters the fourth thickener / desliming machine, and the concentrate product from the fourth thickener / desliming machine becomes the middlings product for flotation. The tailings products from the third thickener / desliming machine and the tailings products from the fourth thickener / desliming machine are combined as tailings for spiral sluice gravity separation.

[0019] Specifically, the magnetic force of the second weak magnetic separator is 1500-2000GS; the magnetic force of the magnetic gravity separator is 5000-8000GS.

[0020] In some embodiments, the flotation operation includes a first flotation, a second flotation, a first scavenging, and a first magnetic screen; the middlings product from the second weak magnetic strong magnetic separation operation enters the first flotation; the concentrate product from the first flotation enters the second flotation, the tailings product from the second flotation is returned to the first flotation, the concentrate product from the first flotation enters the first scavenging; the tailings product from the first scavenging enters the first magnetic screen, the tailings product from the first scavenging and the tailings product from the first magnetic screen are combined as tailings and enter the spiral sluice gravity separation operation, the tailings product from the first magnetic screen is returned to the first flotation, and the concentrate product from the second flotation is the final concentrate product.

[0021] Specifically, the magnetic force of the first magnetic sieve is 1500-2000GS.

[0022] Specifically, the present invention employs a reverse flotation process.

[0023] In some embodiments, the spiral sluice gravity separation operation consists of a first spiral sluice, a second spiral sluice, and a third spiral sluice; the tailings products from the first weak magnetic and strong magnetic separation operation, the second grinding operation, and the second weak magnetic and strong magnetic separation operation are combined and enter a tailings pond; the tailings products from the tailings pond enter a tailings dam; the tailings products from the first magnetic screen enter a tailings dam; the products from the tailings dam enter the first spiral sluice; the dewatered tailings products from the tailings pond enter the second spiral sluice; the tailings products from the first scavenging operation enter the third spiral sluice; the primary concentrate products from the first, second, and third spiral sluices are combined as primary concentrate products and enter the reduction operation; the secondary concentrate products from the first, second, and third spiral sluices are returned as secondary concentrate products to the flotation operation.

[0024] In some embodiments, the reduction operation involves the following steps: the primary concentrate product from the spiral chute gravity separation operation, carbon powder, sodium salt, binder, and water are mixed evenly and then pelletized; the pellets are reduced at 800-1200℃ for 1-3 hours, and the resulting reduced product is screened, crushed, and magnetically separated to obtain iron concentrate.

[0025] This disclosure describes the reduction, screening, and magnetic separation of the primary concentrate product from a spiral chute gravity separation operation to obtain iron concentrate powder. After testing, the total iron content of the obtained iron concentrate powder reaches over 95.6%.

[0026] Specifically, the average particle size of the spheres obtained by the pelletizing process is 10-20 mm, for example, but not limited to 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, and 20 mm.

[0027] In different implementations, the reduction temperature can be, but is not limited to, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C.

[0028] In different implementations, the restoration time is 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0029] In some embodiments, the sodium salt is sodium carbonate and / or sodium chloride; the binder is at least one of bentonite, starch, and bamboo fiber.

[0030] In some embodiments, based on 100 parts by weight of a primary concentrate product, the carbon powder weighs 40-60 parts, the sodium salt weighs 15-30 parts, the binder weighs 2-4 parts, and the water weighs 10-20 parts.

[0031] In this invention, if the sodium chloride or sodium carbonate content is below a certain range, the reduction process reaction will be insufficient; if too little or too much binder is added, the pelletizing effect will be poor; if too little or too much water is added, the pelletizing effect will be poor.

[0032] In different embodiments, the weight of the toner can be, but is not limited to, 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, or 60 parts.

[0033] In different embodiments, the weight of the sodium salt can be, but is not limited to, 15 parts, 17 parts, 19 parts, 21 parts, 23 parts, 25 parts, 28 parts, or 30 parts.

[0034] In different embodiments, the weight of the adhesive may be, but is not limited to, 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts.

[0035] In different embodiments, the weight of the water may be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, or 20 parts.

[0036] Compared with the prior art, the beneficial effects of this disclosure are as follows: This disclosure uses spiral sluice gravity separation, flotation and reduction operations on the tailings generated by the beneficiation process of refractory lean iron ore, which has high beneficiation efficiency and recovery rate for tailings of refractory lean iron ore. The total iron grade of the iron concentrate obtained from the reduction operation reaches more than 95.6%, realizing the efficient development and utilization of tailings resources of refractory lean iron ore, with high economic and environmental benefits.

[0037] The disclosed beneficiation process for refractory lean iron ore is simple, the equipment operates stably, the degree of automation is high, and it is easy to achieve industrial production. Attached Figure Description

[0038] Figure 1 This is a flow chart of the beneficiation process for difficult-to-process lean iron ore. Detailed Implementation

[0039] To facilitate understanding of this disclosure, a more complete description will be provided below. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0040] As used in this article:

[0041] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0042] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0043] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1-5” is disclosed, the described range should be interpreted as including ranges “1-4”, “1-3”, “1-2”, “1-2 and 4-5”, “1-3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0044] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0045] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0046] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0047] To further illustrate the present invention, the beneficiation process for refractory lean iron ore provided by the present invention will be described in detail below with reference to the accompanying drawings, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0048] like Figure 1 As shown, this disclosure provides a beneficiation process for refractory lean iron ore, including the following steps:

[0049] (1) The refractory lean iron ore with a grade of 10-50% is subjected to jaw crusher and medium crusher in sequence to obtain ore particles with an average particle size of 10-50mm.

[0050] The mineral particles with an average particle size of 10-50mm are screened, and the 10-20mm product obtained from the screening is finely crushed. The finely crushed product is returned to the screening. The 10-20mm product obtained from the screening is then fed into the first ball mill for ball milling. The 21-50mm product obtained from the screening is returned to the jaw crusher for crushing. The materials obtained from the screening, such as silica, calcium oxide, and ferric oxide, with an iron content of less than 20%, are used as dry-disposal tailings.

[0051] The product obtained from the first ball mill is fed into a Φ500mm hydrocyclone for primary classification. The overflow product from the Φ500mm hydrocyclone is fed into a Φ350mm hydrocyclone for secondary classification. The sediment products from the Φ500mm hydrocyclone and the sediment products from the Φ350mm hydrocyclone are returned to the first ball mill.

[0052] (2) The overflow product of the Φ350mm hydrocyclone in step (1) is fed into the first weak magnetic separator for magnetic separation. The tailings product of the first weak magnetic separator is fed into the first thickener and desliming machine. The concentrate product of the first thickener and desliming machine is fed into the first strong magnetic separator. The tailings product of the first thickener and desliming machine and the tailings product of the first strong magnetic separator are combined as tailings and fed into the spiral sluice gravity separation operation. The concentrate product of the first weak magnetic separator and the concentrate product of the first strong magnetic separator are combined as the concentrate product of the first weak magnetic and strong magnetic separation operation and fed into the second grinding operation.

[0053] (3) The concentrate product obtained in step (2) of the first weak magnetic and strong magnetic separation operation is fed into a Φ150mm hydrocyclone, the sand product of the Φ150mm hydrocyclone is fed into the second ball mill, and the product of the second ball mill is returned to the Φ150mm hydrocyclone; the overflow product of the Φ150mm hydrocyclone is fed into the second weak magnetic and strong magnetic separation operation as the overflow product of the second grinding operation.

[0054] (4) The overflow product of the second grinding operation obtained in step (3) is fed into the second thickener and desliming machine. The concentrate product of the second thickener and desliming machine is fed into the second weak magnetic separator. The concentrate product of the second weak magnetic separator is fed into the magnetic gravity separator. The concentrate product of the magnetic gravity separator is used as the final concentrate product. The tailings product of the second thickener and desliming machine and the tailings product of the magnetic gravity separator are combined and fed into the third thickener and desliming machine. The concentrate product of the third thickener and desliming machine is fed into the fourth thickener and desliming machine. The concentrate product of the fourth thickener and desliming machine is used as the middlings product and fed into the flotation operation. The tailings product of the third thickener and desliming machine and the tailings product of the fourth thickener and desliming machine are combined as tailings and fed into the spiral sluice gravity separation operation.

[0055] (5) The middlings product obtained from the second weak magnetic and strong magnetic separation operation in step (4) is fed into the first flotation machine for roughing, the concentrate product of the first flotation machine is fed into the second flotation machine for fine selection, the tailings product of the second flotation is returned to the first flotation machine, the concentrate product of the first flotation machine is fed into the first scavenging machine for scavenging, the tailings product of the first scavenging machine is fed into the first magnetic screen for magnetic screening, the tailings product of the first scavenging machine and the tailings product of the first magnetic screen are combined as tailings and fed into the spiral sluice gravity separation operation, the tailings product of the second flotation fine selection machine is returned to the first flotation machine, and the iron concentrate product of the second flotation machine is used as the final concentrate product;

[0056] (6) The tailings products of the first thickener and desliming machine in step (2), the tailings products of the first strong magnetic separator, and the tailings products of the third thickener and desliming machine and the fourth thickener and desliming machine in step (4) are combined and put into the tailings pond. The tailings products of the first magnetic screen in step (5) are put into the tailings dam. The products in the tailings pond are pumped to the spiral sluice. The dewatered tailings products are put into the tailings dam. The products in the tailings dam are put into the first spiral sluice. The dewatered tailings products in the tailings pond are put into the second spiral sluice. The tailings products of the first scavenging are put into the third spiral sluice. The primary concentrate products of the first spiral sluice, the primary concentrate products of the second spiral sluice, and the primary concentrate products of the third spiral sluice are combined as primary concentrate products and put into the reduction operation. The secondary concentrate products of the first spiral sluice, the secondary concentrate products of the second spiral sluice, and the secondary concentrate products of the third spiral sluice are combined as secondary concentrate products and all are returned to the flotation operation.

[0057] (7) After mixing the primary concentrate product obtained in step (6), carbon powder, sodium salt, bentonite and water evenly, pelletize them to obtain pellets with an average particle size of 10-20 mm. After drying the pellets with an average particle size of 10-20 mm, place them in a crucible, and then place the crucible containing the pellets in a heating furnace. Heat the furnace to 1000 °C at a heating rate of 10 °C / min, hold the temperature for 2 hours, and then cool the furnace to room temperature to obtain the reduced product. Among them, based on 100 parts of the weight of the primary concentrate product, the weight of the carbon powder is 50 parts, the weight of the sodium salt is 20 parts, the weight of the bentonite is 3 parts, and the weight of the water is 15 parts.

[0058] The reduced product is sieved, with the material on the sieve being reduced balls and the material under the sieve being non-magnetic powders such as mineral powder and coal powder.

[0059] The reducing spheres were crushed to obtain reducing powder with an average particle size of 150-200 mesh;

[0060] Iron concentrate was obtained by wet magnetic separation of reduced powder with an average particle size of 150-200 mesh.

[0061] Testing revealed that the total iron content of the obtained iron concentrate reached over 97.5%, and the recovery rate was over 94%.

[0062] To prevent the iron concentrate from oxidizing, the obtained iron concentrate needs to be dried and sealed.

[0063] Through the beneficiation process of the present invention for difficult-to-process lean iron ore, the concentrate product of the magnetic gravity separator in step (4) and the iron concentrate product of the second flotation machine in step (5) are used as the final concentrate product. The iron grade of the final concentrate product is 61%, the yield is 85%, and the recovery rate is 85%.

[0064] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this disclosure and not to limit the scope of protection of this disclosure. Although this disclosure has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this disclosure without departing from the substance and scope of the technical solutions of this disclosure.

Claims

1. A beneficiation process of a refractory lean iron ore, characterized by, The method comprises the following steps: the first grinding operation, the first low-intensity magnetic separation operation, the second grinding operation, the second low-intensity magnetic separation operation, the flotation operation, the spiral chute gravity separation operation and the reduction operation are performed on the refractory lean iron ore; the overflow product of the first grinding operation enters the first low-intensity magnetic separation operation; the concentrate product of the first low-intensity magnetic separation operation enters the second grinding operation; the overflow product of the second grinding operation enters the second low-intensity magnetic separation operation; the middling product of the second low-intensity magnetic separation operation enters the flotation operation; the tailing product of the first low-intensity magnetic separation operation, the tailing product of the second grinding operation, the tailing product of the second low-intensity magnetic separation operation and the tailing product of the flotation operation are combined as tailings and enter the spiral chute gravity separation operation; the primary concentrate product of the spiral chute gravity separation operation enters the reduction operation; the secondary concentrate product of the spiral chute gravity separation operation returns to the flotation operation; the flotation operation comprises the first flotation, the second flotation, the first scavenging and the first magnetic screen; the middling product of the second low-intensity magnetic separation operation enters the first flotation; the concentrate product of the first flotation enters the second flotation, the tailing product of the second flotation returns to the first flotation, and the tailing product of the first flotation enters the first scavenging; the concentrate product of the first scavenging enters the first magnetic screen, the tailing product of the first scavenging and the tailing product of the first magnetic screen are combined as tailings and enter the spiral chute gravity separation operation, the concentrate product of the first magnetic screen returns to the first flotation, and the concentrate product of the second flotation is the final concentrate product; the spiral chute gravity separation operation comprises the first spiral chute, the second spiral chute and the third spiral chute; the tailing product of the first low-intensity magnetic separation operation, the tailing product of the second grinding operation, the tailing product of the second low-intensity magnetic separation operation are combined and enter a tailing pool, the tailing product of the first magnetic screen enters a tailing pool, the product of the tailing pool enters the first spiral chute, the dewatered tailing product of the tailing pool enters the second spiral chute, the tailing product of the first scavenging enters the third spiral chute, the primary concentrate product of the first spiral chute, the second spiral chute and the third spiral chute is combined as the primary concentrate product and enters the reduction operation, and the secondary concentrate product of the first spiral chute, the second spiral chute and the third spiral chute returns to the flotation operation as the secondary concentrate product; the steps of the reduction operation are as follows: the primary concentrate product of the spiral chute gravity separation operation, carbon powder, sodium salt, a binder and water are uniformly mixed to form balls; the balls are reduced at 800-1200℃ for 1-3h, the obtained reduction product is screened, crushed and magnetically separated to obtain iron concentrate powder; the weight of the carbon powder is 40-60 parts, the weight of the sodium salt is 15-30 parts, the weight of the binder is 2-4 parts and the weight of the water is 10-20 parts based on 100 parts of the weight of the primary concentrate product.

2. The beneficiation process of a refractory lean iron ore as claimed in claim 1, wherein, the first grinding operation comprises the first ball mill and the first cyclone; the refractory lean iron ore enters the first ball mill, and the product of the first ball mill enters the first cyclone; the overflow product of the first cyclone enters the first low-intensity magnetic separation operation as the overflow product of the first grinding operation, and the sand product of the first cyclone returns to the first ball mill for ball milling.

3. The beneficiation process of a refractory lean iron ore as claimed in claim 1, wherein, The first weak-magnetic and strong-magnetic separation operation is composed of a first weak-magnetic machine, a first thickening and desliming machine and a first strong-magnetic machine; the overflow product of the first grinding operation enters the first weak-magnetic machine, the tailing product of the first weak-magnetic machine enters the first thickening and desliming machine, the concentrate product of the first thickening and desliming machine enters the first strong-magnetic machine, the tailing product of the first thickening and desliming machine and the tailing product of the first strong-magnetic machine are combined to enter the spiral chute gravity separation operation as tailings, and the concentrate product of the first weak-magnetic machine and the concentrate product of the first strong-magnetic machine are combined to enter the second grinding operation as concentrate products of the first weak-magnetic and strong-magnetic separation operation.

4. The beneficiation process of a refractory lean iron ore as claimed in claim 1, wherein, The second grinding operation is composed of a second cyclone and a second ball mill; the concentrate product of the first weak-magnetic and strong-magnetic separation operation enters the second cyclone, the sand product of the second cyclone enters the second ball mill, and the product of the second ball mill returns to the second cyclone; the overflow product of the second cyclone enters the second weak-magnetic and strong-magnetic separation operation as the overflow product of the second grinding operation.

5. The beneficiation process of a refractory lean iron ore as claimed in claim 1, wherein, The second weak-magnetic and strong-magnetic separation operation is composed of a second thickening and desliming machine, a second weak-magnetic machine, a magnetic and heavy separation device, a third thickening and desliming machine and a fourth thickening and desliming machine; the overflow product of the second grinding operation enters the second thickening and desliming machine, the concentrate product of the second thickening and desliming machine enters the second weak-magnetic machine, the concentrate product of the second weak-magnetic machine enters the magnetic and heavy separation device, the concentrate product of the magnetic and heavy separation device is the final concentrate product; the tailing product of the second thickening and desliming machine and the tailing product of the magnetic and heavy separation device are combined to enter the third thickening and desliming machine, the concentrate product of the third thickening and desliming machine enters the fourth thickening and desliming machine, the concentrate product of the fourth thickening and desliming machine enters the flotation operation as a middling product; the tailing product of the third thickening and desliming machine and the tailing product of the fourth thickening and desliming machine are combined to enter the spiral chute gravity separation operation as tailings.

6. The beneficiation process of a refractory lean iron ore as claimed in claim 1, wherein, The sodium salt is sodium carbonate and / or sodium chloride; the binder is at least one of bentonite, starch and bamboo fiber.

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