A continuous grinding, magnetic-flotation short-process classification separation process for mixed iron ore

Abstract

The present invention relates to the technical field of mineral processing, and particularly to a continuous grinding, magnetic - flotation short - process classification and separation process for mixed iron ore. 1) The mixed iron ore mainly composed of magnetite and hematite is crushed to 0 - 12 mm and fed into the first - stage ball mill as raw ore; 2) The first - stage overflow product is fed into the second - stage ball mill; 3) The secondary overflow product is subjected to N - stage weak magnetic separation to obtain high - grade magnetite concentrate with a grade of 68% - 69%; 4) The first - stage weak magnetic tailing product is fed into a high - intensity magnetic separator for separation. After the second - to N - stage weak magnetic tailings are mixed with the high - intensity magnetic concentrate, they are all fed into the reverse flotation operation for separation, and the high - intensity magnetic tailings are discarded as part of the comprehensive tailings; 5) The obtained flotation concentrate and the weak magnetic separation concentrate are combined into comprehensive concentrate. The present invention has strong adaptability to changes in ore properties, significantly improves the recovery rate and grade of iron in iron concentrate, reduces production costs, and is of great significance for the efficient recovery of high - magnetic mixed iron ore.

Description

Technical Field

[0001] The present invention relates to the technical field of mineral processing, in particular to a mixed iron ore continuous grinding and magnetic-flotation short-process classification and separation process. Background Art

[0002] At present, my country's mineral processing plants mostly use a "stage grinding, coarse and fine separation, gravity-magnetic-flotation combined process" to process mixed iron ore containing magnetite and hematite. This process can first use gravity separation to separate out magnetite with a coarse embedded particle size, reducing the amount of grinding, lowering grinding costs, and avoiding the impact of over-grinding on flotation operations. However, with the continuous mining of ore, the embedded particle size of the minerals continues to become finer. Stage separation can no longer select iron concentrates of qualified grade. In addition, the fine screening operation often becomes blocked, affecting the operating rate. The coarse and fine classification of middlings exceeds 300%, and the load is large, resulting in a large amount of magnetic iron entering the sweeping magnetic and weak magnetic separation operations, causing serious entrainment, affecting the flotation feed grade, flotation concentrate grade, and recovery rate. Under the current high demand for ore, the sweeping magnetic separation discards a portion of the tailings, resulting in a low total iron recovery rate of this process, resulting in a huge waste of resources. Therefore, the use of continuous grinding has become an inevitable trend in mineral processing in the future.

[0003] However, the existing continuous grinding and magnetic-flotation combined separation process involves grinding the ore in two stages, followed by a weak-magnetic-strong-magnetic pre-enrichment process to obtain a mixed magnetic concentrate, which is then fed into reverse flotation. This results in a large flotation workload, impacting the plant's annual processing capacity and increasing flotation costs. Furthermore, combined flotation processing consumes a lot of reagents and increases slurry heating costs. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention provides a mixed iron ore continuous grinding and magnetic-flotation short-process classification and separation process, which has strong adaptability to changes in ore properties, significantly improves the recovery rate and grade of iron in iron concentrate, reduces production costs, and is of great significance for the efficient recovery of highly magnetic mixed iron ore.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A mixed iron ore continuous grinding and magnetic-flotation short-process classification and separation process specifically comprises the following steps:

[0007] 1) The mixed iron ore mainly composed of magnetite and hematite is crushed to 0-12mm and fed into a ball mill as the raw ore. It is then graded with a cyclone to form a closed-circuit grinding system. The overflow particle size is 50%-65% of -200 mesh.

[0008] 2) The primary overflow product is fed into the secondary ball mill and formed into a closed-circuit grinding system with a cyclone. The secondary overflow particle size is 85% to 95% of -200 mesh;

[0009] 3) The secondary overflow product is subjected to N-stage low-intensity magnetic separation, where N ≥ 3. Demagnetization is carried out by a demagnetizer between each stage of low-intensity magnetic separation to obtain high-grade magnetite concentrate with a grade of 68% - 69%.

[0010] 4) The product of the first-stage low-intensity magnetic tailings is fed into a high-intensity magnetic separator for separation. The second to N-stage low-intensity magnetic tailings are mixed with the high-intensity magnetic concentrate and then fed into a reverse flotation operation for separation. The high-intensity magnetic tailings are discarded as part of the comprehensive tailings.

[0011] 5) The reverse flotation process adopts one-stage roughing. The roughing concentrate undergoes one-stage cleaning operation, and the cleaning tailings are returned to the roughing. The roughing tailings undergo three-stage scavenging operations. The scavenging concentrates are returned to the previous-stage scavenging, and the first-stage scavenging is returned to the roughing operation. The cleaning concentrate and the low-intensity magnetic separation concentrate are combined into the comprehensive concentrate with a grade above 67%. The flotation tailings and the high-intensity magnetic tailings are combined into the comprehensive tailings with a grade between 10% - 12%.

[0012] Furthermore, in the said step 1), the magnetite content in the mixed iron ore is above 60%.

[0013] Furthermore, in the said step 1), the feed concentration of the primary classification hydrocyclone is controlled at 65% - 70%.

[0014] Furthermore, in the said step 3), the number of low-intensity magnetic separation stages is determined according to the actual properties of the ore. The number of low-intensity magnetic separation stages is 3 - 5 stages or two stages of low-intensity magnetic separation are replaced by a fine magnetic separation device. Low-intensity magnetic concentrate is obtained through low-intensity magnetic separation.

[0015] Furthermore, the said fine magnetic separation device is a elutriation machine, a magnetic separation column or a magnetic vibrator.

[0016] Furthermore, in the said step 4), the first-stage low-intensity magnetic tailings are concentrated so that the feed concentration of the high-intensity magnetic operation is controlled at 35% - 45%. The high-intensity magnetic concentrate and the second to N-stage low-intensity magnetic tailings are mixed to form the feed for flotation and then concentrated again so that the feed concentration for flotation is controlled at 40% - 45%.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. First, after two-stage closed-circuit continuous grinding, the present invention is directly fed into low-intensity magnetic separation to first separate out a part of the low-intensity magnetic concentrate, reducing the feed amount for flotation. The tailings of the first-stage low-intensity magnetic separation are fed into high-intensity magnetic separation, and the other low-intensity magnetic tailings and the high-intensity magnetic concentrate are fed into the reverse flotation operation together. Under the condition of unchanged concentrate grade, the total iron recovery rate is improved.

[0019] 2. The present invention eliminates the gravity separation, scavenging magnetic separation, and fine screening operations, reducing the equipment maintenance and manual labor intensity, and avoiding problems such as fine screen blockage, low grade of gravity separation concentrate, and large load of coarse-fine classification and scavenging magnetic separation operations.

[0020] 3. The weak magnetic separation concentrate does not enter the flotation operation. Through the weak magnetic re-separation operation, the weak magnetic concentrate is directly used as part of the combined concentrate, solving the problems of high content of magnetic iron, serious entrainment in the first-stage weak magnetic separation, and low grade of the feed to the flotation operation.

[0021] 4. By adopting multi-stage weak magnetic separation, the weak magnetic concentrate and the flotation concentrate are mixed into a combined concentrate. Compared with a single flotation operation, it is easier to control the grade of the weak magnetic concentrate by adjusting the number of weak magnetic stages and operation parameters, and then control the grade of the combined iron concentrate, which can meet iron concentrates of different grades.

[0022] 5. In view of the increasing content of magnetic iron in the current ore, the magnetic iron is separated in advance through a magnetic separation operation to obtain the weak magnetic concentrate, reducing the feed amount to the flotation operation and alleviating the burden of the flotation operation, and solving the drawback of the total processing capacity of the concentrator being restricted by the flotation operation.

[0023] 6. The mineral dissemination size is gradually becoming finer, and a finer grinding size is required to achieve the required dissociation degree for ore dressing. Continuous grinding results in a finer grinding size compared to the existing stage grinding, adapting to the minerals with a fine dissemination size at present. Description of the Drawings

[0024] Figure 1 It is the process flow chart of the present invention. Detailed Embodiments

[0025] Next, the technical solution of the present invention will be clearly and completely described in combination with the examples of the present invention. Obviously, the described embodiments are only one of the embodiments of the present invention, and those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve it. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and those related can obviously make changes or appropriate modifications and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0026] As Figure 1 shown, a continuous grinding, magnetic-flotation short process classification and separation process for a mixed iron ore specifically includes the following steps:

[0027] (1) The mixed iron ore mainly composed of magnetite and hematite is crushed to 0 - 12 mm and fed into the first-stage ball mill as raw ore, and forms a closed-circuit grinding system with a hydrocyclone classifier. The particle size of the first overflow is 50% - 65% - 200 mesh, and the feed concentration of the first-stage hydrocyclone is controlled at 65% - 70%; the magnetite content in the mixed iron ore is above 60%.

[0028] (2) Feed the primary overflow product into the secondary ball mill and form a closed-circuit grinding system with the hydrocyclone. Control the feed concentration of the secondary classification hydrocyclone at 30%-40%, and the particle size of the secondary overflow is 85%-95% -200 mesh.

[0029] (3) Conduct four-stage weak magnetic separation on the secondary overflow product (the number of weak magnetic separation stages is determined by the actual properties of the ore). Demagnetization should be carried out by a demagnetizer between each stage of weak magnetic separation to obtain high-grade (grade 68%-69%) magnetite concentrate.

[0030] The number of weak magnetic separation stages is determined according to the actual properties of the ore. Generally, the number of weak magnetic separation stages is 3-5. Or fine magnetic separation equipment such as a elutriator, magnetic separation column, and magnetic vibrating machine can replace two stages of weak magnetic separation. After weak magnetic separation, weak magnetic concentrate with a grade of 68%-69% can be obtained.

[0031] Perform a demagnetization operation on the concentrate product of each stage of the four-stage weak magnetic separation to eliminate the influence of magnetic agglomeration on the separation operation. Among them, the tailings of the first-stage weak magnetic separation are fed into the high-intensity magnetic operation, and the tailings of the second, third, and fourth-stage weak magnetic separations are fed into the reverse flotation operation. Semi-countercurrent magnetic separators or fine separation equipment such as elutriators, magnetic separation columns, and magnetic vibrating machines are used for the weak magnetic separators.

[0032] (4) Feed the product of the first-stage weak magnetic tailings into a high-intensity magnetic separator for separation. The tailings of the second, third, and fourth-stage weak magnetic separations are mixed with the high-intensity magnetic concentrate and then fed into the reverse flotation operation for separation. The high-intensity magnetic tailings are discarded as part of the comprehensive tailings.

[0033] Concentrate the tailings of the first-stage weak magnetic separation to control the feed concentration of the high-intensity magnetic operation at 35%-45%. The high-intensity magnetic concentrate is mixed with the tailings of the second, third, and fourth-stage weak magnetic separations to form the feed for flotation, and then concentrate it to control the feed concentration for flotation at 40%-45%.

[0034] (5) The reverse flotation process uses one-stage roughing. The roughing concentrate undergoes one-stage cleaning operation. The cleaning tailings are returned to the roughing. The roughing tailings undergo three-stage scavenging operations. The scavenging concentrates are returned to the previous-stage scavenging, and the first-stage scavenging is returned to the roughing operation. The cleaning concentrates and the weak magnetic concentrates are combined into the comprehensive concentrate with a grade above 67%. The flotation tailings and the high-intensity magnetic tailings are combined into the comprehensive tailings with a grade between 10%-12%.

[0035]

Example

[0036] In the example of the present invention, the selected mixed iron ore is taken from the Anshan area of Liaoning. The total iron grade in the ore is about 33%, the gangue minerals are mainly quartz, and the magnetite content is about 75%.

[0037] Example 1

[0038] The selected mixed iron ore in this example has a total iron grade of 34.5%, the gangue minerals are mainly quartz, and the magnetite content is 75%. A continuous grinding, magnetic-flotation short-process classification separation process is adopted.

[0039] (1) The mixed ore mainly composed of magnetite and hematite is crushed to 0 - 12 mm as the raw ore and fed into the first-stage ball mill, and forms a closed-circuit grinding system with hydrocyclone classification. The particle size of the first overflow is 55% - 200 mesh.

[0040] (2) The first-stage overflow product is fed into the second-stage ball mill and forms a closed-circuit grinding system with the hydrocyclone. The particle size of the second overflow is 85% - 200 mesh.

[0041] (3) The second overflow product is subjected to four-stage weak magnetic separation. Demagnetization is carried out by a demagnetizer between each stage of weak magnetic separation to obtain magnetite concentrate with a grade of 68%.

[0042] (4) The product of the first-stage weak magnetic tailings is fed into a high-intensity magnetic separator for separation. The second, third, and fourth-stage weak magnetic tailings are mixed with the high-intensity magnetic concentrate and then fed into the reverse flotation operation for separation. The high-intensity magnetic tailings are discarded as part of the combined tailings.

[0043] (5) The reverse flotation process adopts one-stage roughing. The roughing concentrate undergoes one-stage cleaning operation. The cleaning tailings are returned to the roughing. The roughing tailings undergo three-stage scavenging operations. The scavenging concentrates are returned to the previous-stage scavenging, and the first-stage scavenging is returned to the roughing operation. The cleaning concentrate and the weak magnetic separation concentrate are combined into the combined concentrate with a grade of 67.7%. The flotation tailings and the high-intensity magnetic tailings are combined into the combined tailings with a grade of 11.5%.

[0044] Example 2

[0045] The mixed iron ore selected in this example has a total iron grade of 34%, the gangue minerals are mainly quartz, and the magnetite content is 73%. A continuous grinding, magnetic - flotation short - process classification separation process is adopted.

[0046] (1) The mixed ore mainly composed of magnetite and hematite is crushed to 0 - 12 mm as the raw ore and fed into the first-stage ball mill, and forms a closed-circuit grinding system with hydrocyclone classification. The particle size of the first overflow is 56% - 200 mesh.

[0047] (2) The first-stage overflow product is fed into the second-stage ball mill and forms a closed-circuit grinding system with the hydrocyclone. The particle size of the second overflow is 87% - 200 mesh.

[0048] (3) The second overflow product is subjected to four-stage weak magnetic separation. Demagnetization is carried out by a demagnetizer between each stage of weak magnetic separation to obtain magnetite concentrate with a grade of 67.8%.

[0049] (4) The product of the first-stage weak magnetic tailings is fed into a high-intensity magnetic separator for separation. The second, third, and fourth-stage weak magnetic tailings are mixed with the high-intensity magnetic concentrate and then fed into the reverse flotation operation for separation. The high-intensity magnetic tailings are discarded as part of the combined tailings.

[0050] (5) The reverse flotation process adopts one-stage roughing. The roughing concentrate undergoes one-stage cleaning operation, and the tailings from cleaning are returned to roughing. The tailings from roughing undergo three-stage scavenging operations. The scavenging concentrates are returned to the previous-stage scavenging, and the first-stage scavenging tailings are returned to the roughing operation. The cleaning concentrates and the weak magnetic separation concentrates are combined into the comprehensive concentrate with a grade of 67.5%. The flotation tailings and the strong magnetic tailings are combined into the comprehensive tailings with a grade of 11.3%.

[0051] In the present invention, after two-stage closed-circuit continuous grinding, it is directly fed into weak magnetic separation to first separate out a part of the weak magnetic concentrates, reducing the feed amount to flotation. The tailings from the first-stage weak magnetic separation are fed into strong magnetic separation, and the other weak magnetic separation tailings and the strong magnetic separation concentrates are fed into the reverse flotation operation together. Under the condition of unchanged concentrate grade, the total iron recovery rate is increased. In the present invention, the gravity separation, scavenging magnetic separation, and fine screening operations are removed, reducing the equipment maintenance and manual labor intensity, and avoiding problems such as fine screen clogging, low grade of gravity separation concentrates, and large loads in the coarse-fine classification and scavenging magnetic separation operations. The weak magnetic separation concentrates do not enter the flotation operation. Through the re-selection of weak magnetic separation, the weak magnetic concentrates are directly used as part of the comprehensive concentrates, solving the problems of high magnetic iron content, serious entrainment in the first-stage weak magnetic separation, and low feed grade to flotation. By adopting multi-stage weak magnetic separation, the weak magnetic concentrates and the flotation concentrates are mixed into the mixed concentrates. Compared with the single flotation operation, it is easier to control the grade of the weak magnetic concentrates by adjusting the number of weak magnetic stages and operation parameters, and then control the grade of the mixed iron concentrates, which can meet iron concentrates with different grades. In view of the increasing magnetic iron content in the current ore, the magnetic iron is separated in advance through magnetic separation operation to obtain weak magnetic concentrates, reducing the feed amount to flotation and alleviating the burden of the flotation operation, and solving the drawback of the total processing capacity of the concentrator being restricted by the flotation operation. The mineral dissemination size gradually becomes finer, and finer grinding particle size is required to achieve the required dissociation degree for ore dressing. Continuous grinding has a finer grinding particle size than the existing stage grinding, adapting to the minerals with fine dissemination size at present.

[0052] The present invention has strong adaptability to the changes in ore properties, significantly improves the recovery rate and grade of iron in iron concentrates, reduces production costs, and has important significance for the efficient recovery of high-magnetic mixed iron ores.

[0053] The present invention uses the above embodiments to illustrate the detailed process flow of the present invention, but the present invention is not limited to the above detailed process flow, that is, it does not mean that the present invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the products of the present invention, the addition of auxiliary components, the selection of specific implementation manners, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A continuous grinding, magnetic-float short-process classification separation process for mixed iron ore, characterized in that, Specifically, it includes the following steps: 1) Crush the mixed iron ore mainly composed of magnetite and hematite to 0 - 12 mm, feed it as the raw ore into the first-stage ball mill, and form a closed-circuit grinding system with the hydrocyclone classification. The particle size of the first-stage overflow is 50% - 65% - 200 mesh; the magnetite content in the mixed iron ore is over 60%; the feed concentration of the first-stage classification hydrocyclone is controlled at 65% - 70%; 2) Feed the first-stage overflow product into the second-stage ball mill and form a closed-circuit grinding system with the hydrocyclone. The particle size of the second-stage overflow is 85% - 95% - 200 mesh; 3) Conduct N-stage weak magnetic separation on the second-stage overflow product, where N ≥ 3. Demagnetization must be carried out by a demagnetizer between each stage of weak magnetic separation to obtain high-grade magnetite concentrate with a grade of 68% - 69%; 4) Feed the tailings product of the first-stage weak magnetic separation into a high-intensity magnetic separator for separation. The tailings of the second to N-stage weak magnetic separation are mixed with the high-intensity magnetic concentrate and then fed into the reverse flotation operation for separation. The high-intensity magnetic tailings are discarded as part of the comprehensive tailings; the first-stage weak magnetic tailings are concentrated to control the feed concentration of the high-intensity magnetic operation at 35% - 45%. The high-intensity magnetic concentrate is mixed with the tailings of the second to N-stage weak magnetic separation to form the feed for flotation, and then concentrated to control the feed concentration for flotation at 40% - 45%; 5) The reverse flotation process adopts one-stage roughing. The roughing concentrate undergoes one-stage cleaning operation, and the cleaning tailings are returned to the roughing. The roughing tailings undergo three-stage scavenging operations. The scavenging concentrates are returned to the previous-stage scavenging, and the first-stage scavenging is returned to the roughing operation. The cleaning concentrate and the weak magnetic separation concentrate are combined into the comprehensive concentrate with a grade above 67%. The flotation tailings and the high-intensity magnetic tailings are combined into the comprehensive tailings with a grade between 10% - 12%.

2. The continuous grinding, magnetic-float short-process classification and separation process for mixed iron ore according to claim 1, characterized in that, In step 3), the number of weak magnetic separation stages is determined according to the actual properties of the ore. The number of weak magnetic separation stages is 3 - 5 stages or two stages of weak magnetic separation are replaced by a fine magnetic separation device to obtain weak magnetic concentrate through weak magnetic separation.

3. A continuous grinding, magnetic-flotation short-process classification and separation process for mixed iron ore according to claim 2, characterized in that The fine magnetic separation device is a washing machine, a magnetic separation column or a magnetic vibrator.

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