A method for directly recovering ultra-fine-grained ilmenite inclined plate overflow material without pre-concentration

Abstract

This invention provides a direct flotation recovery method for ultrafine-grained ilmenite overflow material from inclined plate slabs without pre-enrichment, belonging to the field of vanadium-titanium magnetite beneficiation technology. This invention targets the ultrafine-grained material from the overflow of the second-stage strong magnetic concentrate from the inclined plate slab of vanadium-titanium magnetite, proposing a complete direct flotation process that eliminates the need for strong magnetic and gravity separation pre-enrichment throughout the entire process, completely abandoning the technical bias of existing technologies that require pre-enrichment. Based on the high-grade and high-liberation characteristics of this material, separation is completed directly through flotation, eliminating the need for a complete set of pre-enrichment equipment. This reduces equipment investment by more than 40% and operating costs by more than 30%, while completely avoiding the irreversible loss of ultrafine-grained ilmenite during the pre-enrichment stage. This invention's direct flotation without pre-enrichment simplifies the processing steps.

Description

Technical Field

[0001] This invention relates to the field of vanadium-titanium magnetite beneficiation technology, and in particular to a method for direct flotation recovery of ultrafine ilmenite overflow material without pre-enrichment using inclined plates. Background Technology

[0002] Vanadium-titanium magnetite is the core carrier of my country's titanium resources. The Panxi region accounts for more than 90% of the country's total vanadium-titanium magnetite reserves, making it the core resource foundation for the development of my country's titanium industry. Currently, domestic vanadium-titanium magnetite beneficiation plants generally adopt the mainstream process of "magnetic separation for iron - strong magnetic pre-enrichment - flotation for titanium extraction". In the titanium beneficiation stage, the concentrate from the second-stage strong magnetic separation needs to be classified and concentrated by a slant plate thickener. The underflow enters the flotation system for titanium extraction, while the overflow is an ultra-fine ilmenite material with an extremely fine particle size.

[0003] The overflow material from this inclined plate is characterized by high grade, ultrafine particle size, and high degree of monomer liberation. Its TiO2 grade generally reaches 20%~23%, with -0.075mm particles accounting for ≥98%, of which -0.019mm ultrafine particles account for over 40%. The degree of ilmenite monomer liberation is ≥85%, and over 92% of the titanium element exists in the form of recyclable ilmenite, making it a titanium resource with significant recycling value. However, current technologies and production practices face the following insurmountable technical defects and industry pain points in the recycling and processing of this material: Severe resource loss and insufficient attention to recycling: Existing concentrators generally discharge the overflow material from the inclined plate directly into the tailings system. This material contains more than 30% of the titanium resources lost by the concentrators, resulting in a huge waste of my country's titanium resources. The industry lacks a dedicated and efficient recycling process for this single material.

[0004] The pre-enrichment process has extremely poor adaptability, which exacerbates the loss of fine-grained ilmenite: A few existing technologies attempt to mix this material with strong magnetic tailings and then pre-enrich it through strong magnetic and gravity separation before flotation. However, the material has an extremely fine particle size and is easily lost with the slurry during the strong magnetic pre-enrichment stage. The gravity separation stage cannot achieve effective recovery at all. The recovery rate of ultrafine ilmenite during the pre-enrichment process is less than 30%, which instead causes irreversible resource loss.

[0005] The process is lengthy and redundant, with high investment and operating costs: Existing technologies for the recovery of this material all require a pre-enrichment system, which requires additional investment in a large number of equipment such as strong magnetic separators, gravity separation equipment, and classification equipment, increasing equipment investment by more than 40% and operating costs by more than 30%. At the same time, the pre-enrichment process will damage the slurry dispersion system, worsen the subsequent flotation environment, and lead to a significant increase in flotation reagent consumption.

[0006] There is no dedicated flotation process, resulting in extremely low separation efficiency: Existing flotation processes are designed for conventional particle size ilmenite and do not take into account the flotation characteristics of ultrafine ilmenite (-0.019mm). This leads to problems such as poor reagent selectivity, low probability of collision between fine mineral particles, low flotation recovery rate, and inability to consistently meet concentrate grade standards, making it impossible to achieve efficient separation of this ultrafine material.

[0007] Without a complete closed-loop design, environmental protection and resource benefits cannot be balanced: the existing process does not build a complete closed-loop system for this material, the disorderly discharge of middlings causes secondary resource loss, and the production wastewater cannot be fully recycled, bringing additional environmental pressure. Summary of the Invention

[0008] Addressing the core pain points of existing technologies for recovering ultrafine ilmenite from the overflow of vanadium-titanium magnetite two-stage strong magnetic concentrate using inclined plate flotation, such as increased resource loss due to pre-enrichment processes, lengthy and costly processes, lack of dedicated flotation processes, and low separation efficiency, the present invention aims to provide a complete recovery process that eliminates pre-enrichment and allows for direct flotation throughout the entire process. Specifically designed for the unique characteristics of ultrafine ilmenite overflow material, the invention optimizes the slurry preparation and dispersion system, reagent formulation, and flotation process structure to achieve low-cost, high-efficiency, and green recovery of ilmenite from this material. The core design is not covered by prior patents, possessing strong patent inventiveness and industrialization value.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for direct flotation recovery of ultrafine ilmenite sloping plate overflow material without pre-enrichment includes the following steps: Step 1: Homogenization and Dispersion Pretreatment without Pre-enrichment Take the overflow material from the inclined plate of the second stage strong magnetic concentrate of the vanadium-titanium magnetite beneficiation plant, add water to adjust the slurry mass concentration to 25%~35%, then add water glass as a dispersant, stir, and control the pH value of the slurry to 6~7 to obtain a uniformly dispersed flotation slurry to be treated; stirring can fully eliminate the agglomeration of ultrafine ilmenite and gangue minerals. Step 2: Flotation Desulfurization Pretreatment The slurry to be processed in step 1 is subjected to a roughing and scavenging flotation process to remove sulfide minerals, resulting in desulfurized slurry and sulfur concentrate by-products. The purpose of removing sulfide minerals is to avoid interference with the subsequent flotation of ilmenite. Step 3: Targeted flotation separation of ultrafine ilmenite particles The desulfurized slurry from step 2 was subjected to closed-circuit flotation with one roughing stage, five cleaning stages, and two scavenging stages to obtain titanium concentrate and flotation tailings.

[0010] Preferably, the amount of water glass added in step 1 is 300~800g / t of the overflow material.

[0011] Preferably, the roughing and scavenging flotation process described in step 2 includes the following steps: Desulfurization roughing: The feed is slurry to be processed, and the output is desulfurization roughing concentrate and desulfurization roughing tailings; First scavenging: The feed is desulfurization roughing tailings. After adding reagents, it is separated to produce desulfurization scavenging concentrate I and desulfurization scavenging tailings I. Desulfurization scavenging concentrate I is returned to the desulfurization roughing operation inlet, mixed with the raw ore, and then separated again. Second scavenging: The feed is desulfurization scavenging tailings I. After adding reagents, it is separated to produce desulfurization scavenging concentrate II and desulfurization scavenging tailings II. Desulfurization scavenging concentrate II is returned to the desulfurization scavenging I operation inlet. Product destination: Desulfurized roughing concentrate is combined with various scavenging concentrates as a by-product of sulfur concentrate; Desulfurized scavenging tailings II is the desulfurized slurry.

[0012] Preferably, the reagent regime used in the roughing and scavenging flotation process described in step 2 is as follows: Sulfuric acid 800~1500g / t, butyl xanthate 400~600g / t, pine oil 150~300g / t; The entire amount of reagent is added during the roughing process; The first screening process involves adding 30% butyl xanthate and 20% pine oil. The second sweep was supplemented with 20% butyl xanthate and 10% pine oil.

[0013] Preferably, step 3, the closed-circuit flotation process involving one roughing, five cleaning, and two sweeping steps, includes the following steps: (1) Coarse selection operation: After adding roughing reagents to the desulfurized slurry, the slurry is separated to produce roughing concentrate and roughing tailings; the roughing concentrate is sent to the cleaning series and the roughing tailings are sent to the scavenging series. (2) Five carefully selected assignments: Selected Concentrate I: The feed is the rougher concentrate. After adding sulfuric acid to adjust the pH, it is separated to produce Selected Concentrate I and Selected Concentrate I tailings. The Selected Concentrate I tailings are returned to the rougher operation inlet. Selected Concentrate II: The feed is Selected Concentrate I. After adding sulfuric acid to adjust the pH, it is separated to produce Selected Concentrate II and Selected Concentrate II tailings. The Selected Concentrate II tailings are returned to the Selected Concentrate I operation inlet. Selected III: The feed is Selected II concentrate, which is then separated to produce Selected III concentrate and Selected III tailings; Selected III tailings are returned to the Selected II operation entry point. Selected IV: The feed is Selected III concentrate, which is then separated to produce Selected IV concentrate and Selected IV tailings; Selected IV tailings are returned to the Selected III operation entry point. Selected V: The feed is Selected IV concentrate, which is separated to produce Selected V concentrate (foam) and Selected V tailings; Selected V tailings are returned to the Selected IV operation entry; Final product: Selected V concentrate is titanium concentrate; (3) Secondary scanning operation Scavenging I: The feed is roughing tailings. After adding collector, it is separated to produce scavenging I concentrate and scavenging I tailings. The scavenging I concentrate is returned to the roughing operation inlet. Scavenging II: The feed is scavenging I tailings. After adding collector, it is separated to produce scavenging II concentrate and scavenging II tailings; scavenging II concentrate is returned to the scavenging I operation inlet; Final product: Scavenging II tailings, also known as flotation tailings, are sent to the tailings treatment system.

[0014] Preferably, the reagent regimen for the roughing process in step 3 is as follows: sulfuric acid 4500~5500 g / t, modified water glass 3500~4500 g / t, collector 1000~1800 g / t, and diesel oil 500~600 g / t; wherein sulfuric acid acts as a pH adjuster to control the pH value of the pulp to be stable at 5.0~5.5; modified water glass acts as a gangue inhibitor and pulp dispersant to enhance the inhibition effect of ultrafine gangue particles; it is a collector specifically for ilmenite, possessing strong collecting ability and high selectivity, and is suitable for the flotation characteristics of ultrafine ilmenite particles; diesel oil acts as an auxiliary collector to enhance the collecting effect and increase the floating probability of fine ilmenite particles.

[0015] Preferably, in step 3, sulfuric acid is added to adjust the pH of the slurry to 5.0-5.5 during the refining process; no additional collectors or inhibitors are added during this process, and the grade of titanium concentrate is gradually improved through multiple refining processes to ensure that the final product meets the standards.

[0016] Preferably, in step 3, 30% to 40% of the collector is added during the first scavenging process, and 15% to 20% of the collector is added during the second scavenging process; this can maximize the recovery of ilmenite that has not floated to the surface in the slurry and improve the overall recovery rate.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses the ultrafine particles from the overflow of the inclined plate of the second-stage strong magnetic concentrate of vanadium-titanium magnetite. It proposes a direct flotation process that eliminates the need for strong magnetic concentrating and gravity separation pre-enrichment throughout the entire process, completely overcoming the technical bias of existing technologies that require pre-enrichment. Based on the high grade and high liberation degree of this material, separation is achieved directly through flotation, eliminating the need for a complete pre-enrichment system. This reduces equipment investment by over 40% and operating costs by over 30%, while also completely preventing the irreversible loss of ultrafine ilmenite particles during the pre-enrichment stage. This invention, with its direct flotation without pre-enrichment, simplifies the processing steps.

[0018] This invention constructs two fully closed-loop systems: a closed-loop system for the sorting process and a closed-loop system for water circulation, thereby maximizing resource recovery and achieving green and clean production. Closed-loop circulation in the sorting process: Desulfurized scavenging concentrate is returned to the desulfurized roughing operation for enrichment; tailings from flotation cleaning I are returned to the titanium roughing operation, and tailings from cleaning II to cleaning V are returned to the previous cleaning operation step by step; scavenging I and scavenging II concentrates are returned to the titanium roughing operation. All middlings are circulated in a closed loop, with no valuable minerals discharged or lost, and secondary loss of ultrafine ilmenite is prevented.

[0019] Water circulation closed loop: After all mineral processing wastewater is concentrated by a high-efficiency thickener, the clarified water is 100% returned to the slurry preparation, separation and equipment flushing processes for recycling, with no production wastewater discharged externally; after the thickener underflow and flotation tailings are combined, all of them are transported to the tailings dam for centralized and compliant disposal through a closed pipeline, and the tailings dam return water is further incorporated into the water circulation closed loop system to achieve a closed loop throughout the entire process. Detailed Implementation

[0020] The technical solution of the present invention will now be described in detail through examples and comparative examples.

[0021] In a specific embodiment of the present invention, the raw material overflow material is the overflow material from the inclined plate of the second stage strong magnetic concentrate of the Chongqing Iron and Steel Xichang Mining Co., Ltd. beneficiation plant. The properties of this material are as follows: TiO2 grade 22.85%, TFe grade 21.33%, -0.075mm particle size percentage 98.47%, -0.019mm particle size percentage 41.46%, ilmenite monomer liberation degree 87%, TiO2 content in ilmenite 92.76%, S content 0.39%, and P content 0.31%.

[0022] In the following embodiments of the present invention, the collector is a novel flotation collector DTX-CT produced by Henan Tianhong New Material Technology Co., Ltd., material code C8057271; the modified water glass is prepared by mixing water glass with medium modulus and sodium tripolyphosphate at a mass ratio of 99:1, and the medium modulus is 2.5.

[0023] Example 1 A method for direct flotation recovery of ultrafine ilmenite overflow material from inclined plate without pre-enrichment, comprising the following steps: Step 1: Homogenization and Dispersion Pretreatment without Pre-enrichment Take the overflow material from the inclined plate of the second stage strong magnetic concentrate of the vanadium-titanium magnetite beneficiation plant, add water to adjust the slurry mass concentration to 30%, then use water glass as a dispersant at a dosage of 600g / t of raw ore, stir for 5 minutes, control the pH value of the slurry to 6.5, and obtain a uniformly dispersed flotation slurry to be processed. Step 2: Flotation Desulfurization Pretreatment The slurry to be processed in step 1 is subjected to a roughing and scavenging flotation process to remove sulfide minerals, resulting in desulfurized slurry and sulfur concentrate by-products. The purpose of removing sulfide minerals is to avoid interference with the subsequent flotation of ilmenite. The flotation process, consisting of one roughing and two scavenging stages, comprises the following steps: Desulfurization roughing: The feed is slurry to be processed, and the output is desulfurization roughing concentrate and desulfurization roughing tailings; First scavenging: The feed is desulfurization roughing tailings. After adding reagents, it is separated to produce desulfurization scavenging concentrate I and desulfurization scavenging tailings I. Desulfurization scavenging concentrate I is returned to the desulfurization roughing operation inlet, mixed with the raw ore, and then separated again. Second scavenging: The feed is desulfurization scavenging tailings I. After adding reagents, it is separated to produce desulfurization scavenging concentrate II and desulfurization scavenging tailings II. Desulfurization scavenging concentrate II is returned to the desulfurization scavenging I operation inlet. Product destination: Desulfurized rougher concentrate is combined with scavenging concentrate from each stage as a by-product of sulfur concentrate; Desulfurized scavenging tailings II is the desulfurized slurry. The reagent regime used in the first roughing and second scavenging flotation process is as follows: Sulfuric acid 800~1500g / t, butyl xanthate 400~600g / t, pine oil 150~300g / t; The entire amount of reagent is added during the roughing process; The first screening process involves adding 30% butyl xanthate and 20% pine oil. The second sweep was supplemented with 20% butyl xanthate and 10% pine oil.

[0024] Step 3: Targeted flotation separation of ultrafine ilmenite particles The desulfurized slurry from step 2 was subjected to closed-circuit flotation with one roughing stage, five cleaning stages, and two scavenging stages to obtain titanium concentrate and flotation tailings. The specific steps are as follows: (1) Coarse selection operation: After adding roughing reagents to the desulfurized slurry, the slurry is separated to produce roughing concentrate and roughing tailings; the roughing concentrate is sent to the cleaning series and the roughing tailings are sent to the scavenging series. (2) Five carefully selected assignments: Selected Concentrate I: The feed is the rougher concentrate. After adding sulfuric acid to adjust the pH, it is separated to produce Selected Concentrate I and Selected Concentrate I tailings. The Selected Concentrate I tailings are returned to the rougher operation inlet. Selected Concentrate II: The feed is Selected Concentrate I. After adding sulfuric acid to adjust the pH, it is separated to produce Selected Concentrate II and Selected Concentrate II tailings. The Selected Concentrate II tailings are returned to the Selected Concentrate I operation inlet. Selected III: The feed is Selected II concentrate, which is then separated to produce Selected III concentrate and Selected III tailings; Selected III tailings are returned to the Selected II operation entry point. Selected IV: The feed is Selected III concentrate, which is then separated to produce Selected IV concentrate and Selected IV tailings; Selected IV tailings are returned to the Selected III operation entry point. Selected V: The feed is Selected IV concentrate, which is separated to produce Selected V concentrate (foam) and Selected V tailings; Selected V tailings are returned to the Selected IV operation entry; Final product: Selected V concentrate is titanium concentrate; (3) Secondary scanning operation Scavenging I: The feed is roughing tailings. After adding collector, it is separated to produce scavenging I concentrate and scavenging I tailings. The scavenging I concentrate is returned to the roughing operation inlet. Scavenging II: The feed is scavenging I tailings. After adding collector, it is separated to produce scavenging II concentrate and scavenging II tailings; scavenging II concentrate is returned to the scavenging I operation inlet; Final product: Scavenging II tailings, also known as flotation tailings, are sent to the tailings treatment system; Roughing reagent system: sulfuric acid 5000g / t, modified water glass 4000g / t, 1400g / t, diesel 550g / t, control the slurry pH value to 5.2; for cleaning I to cleaning V, sulfuric acid is added to adjust the pH to 5.2; for scavenging I, 500g / t is added, and for scavenging II, 250g / t is added.

[0025] The titanium concentrate obtained had a TiO2 grade of 47.62% and a TiO2 recovery rate of 77.35% in the flotation operation, which fully met the standards for high-quality titanium concentrate products, verifying the feasibility and advanced nature of the method of this invention.

[0026] Example 2 Based on an annual processing capacity of 386,000 tons of overflow material from the inclined plate of the second-stage strong magnetic concentrate, with an annual operating time of 330 days and 24-hour continuous production; The method described in Embodiment 1 of this invention is used for processing without strong magnetic fields or reselection pre-enrichment operations throughout the entire process; The final titanium concentrate obtained has a stable TiO2 grade of ≥46%, with an annual output of 35,800 tons of titanium concentrate with a TiO2 grade of 46%, and a TiO2 recovery rate of ≥75% in the flotation process; Economic benefits: Based on a price of 2,000 yuan / ton for titanium concentrate, the annual output value will increase by 71.6 million yuan, the annual production cost will be over 22 million yuan, and the annual profit and tax will increase by over 49 million yuan. The total investment of the project is 18 million yuan, and the investment payback period is only 4.4 months. Environmental benefits: 100% of production wastewater is recycled, with no wastewater discharge, achieving green and clean production without additional environmental risks.

[0027] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for direct flotation recovery of ultrafine ilmenite sloping plate overflow material without pre-enrichment, characterized in that, Includes the following steps: Step 1: Homogenization and Dispersion Pretreatment without Pre-enrichment Take the overflow material from the inclined plate of the second stage strong magnetic concentrate of the vanadium-titanium magnetite beneficiation plant, add water to adjust the slurry mass concentration to 25%~35%, then add water glass as a dispersant, stir, and control the pH value of the slurry to 6~7 to obtain a uniformly dispersed flotation slurry to be processed. Step 2: Flotation Desulfurization Pretreatment The slurry to be processed in step 1 is subjected to a first roughing and second scavenging flotation process to remove sulfide minerals, resulting in desulfurized slurry and sulfur concentrate by-products. Step 3: Targeted flotation separation of ultrafine ilmenite particles The desulfurized slurry from step 2 was subjected to closed-circuit flotation with one roughing stage, five cleaning stages, and two scavenging stages to obtain titanium concentrate and flotation tailings.

2. The method for direct flotation recovery of ultrafine ilmenite inclined plate overflow material without pre-enrichment according to claim 1, characterized in that, The amount of water glass added in step 1 is 300~800g / t of the overflow material.

3. The method for direct flotation recovery of ultrafine ilmenite inclined plate overflow material without pre-enrichment according to claim 1, characterized in that, Step 2, the first roughing and second scavenging flotation process, includes the following steps: Desulfurization roughing: The feed is slurry to be processed, and the output is desulfurization roughing concentrate and desulfurization roughing tailings; First scavenging: The feed is desulfurization roughing tailings. After adding reagents, it is separated to produce desulfurization scavenging concentrate I and desulfurization scavenging tailings I. Desulfurization scavenging concentrate I is returned to the desulfurization roughing operation inlet, mixed with the raw ore, and then separated again. Second scavenging: The feed is desulfurization scavenging tailings I. After adding reagents, it is separated to produce desulfurization scavenging concentrate II and desulfurization scavenging tailings II. Desulfurization scavenging concentrate II is returned to the desulfurization scavenging I operation inlet. Product destination: Desulfurized roughing concentrate is combined with various scavenging concentrates as a by-product of sulfur concentrate; Desulfurized scavenging tailings II is the desulfurized slurry.

4. The method for direct flotation recovery of ultrafine ilmenite inclined plate overflow material without pre-enrichment according to claim 1, characterized in that, The reagent regime used in the roughing and scavenging flotation process described in step 2 is as follows: Sulfuric acid 800~1500g / t, butyl xanthate 400~600g / t, pine oil 150~300g / t; The entire amount of reagent is added during the roughing process; The first screening process involves adding 30% butyl xanthate and 20% pine oil. The second sweep was supplemented with 20% butyl xanthate and 10% pine oil.

5. The method for direct flotation recovery of ultrafine ilmenite inclined plate overflow material without pre-enrichment according to claim 1, characterized in that, Step 3, the closed-circuit flotation process involving one roughing step, five cleaning steps, and two sweeping steps, includes the following steps: (1) Coarse selection operation: After adding roughing reagents to the desulfurized slurry, the slurry is separated to produce roughing concentrate and roughing tailings; the roughing concentrate is sent to the cleaning series and the roughing tailings are sent to the scavenging series. (2) Five carefully selected assignments: Selected Concentrate I: The feed is the rougher concentrate. After adding sulfuric acid to adjust the pH, it is separated to produce Selected Concentrate I and Selected Concentrate I tailings. The Selected Concentrate I tailings are returned to the rougher operation inlet. Selected Concentrate II: The feed is Selected Concentrate I. After adding sulfuric acid to adjust the pH, it is separated to produce Selected Concentrate II and Selected Concentrate II tailings. The Selected Concentrate II tailings are returned to the Selected Concentrate I operation inlet. Selected III: The feed is Selected II concentrate, which is then separated to produce Selected III concentrate and Selected III tailings; Selected III tailings are returned to the Selected II operation entry point. Selected IV: The feed is Selected III concentrate, which is then separated to produce Selected IV concentrate and Selected IV tailings; Selected IV tailings are returned to the Selected III operation entry point. Selected V: The feed is Selected IV concentrate, which is separated to produce Selected V concentrate and Selected V tailings; Selected V tailings are returned to the Selected IV operation entry; Final product: Selected V concentrate is titanium concentrate; (3) Secondary scanning operation Scavenging I: The feed is roughing tailings. After adding collector, it is separated to produce scavenging I concentrate and scavenging I tailings. The scavenging I concentrate is returned to the roughing operation inlet. Scavenging II: The feed is scavenging I tailings. After adding collector, it is separated to produce scavenging II concentrate and scavenging II tailings; scavenging II concentrate is returned to the scavenging I operation inlet; Final product: Scavenging II tailings, also known as flotation tailings, are sent to the tailings treatment system.

6. The method for direct flotation recovery of ultrafine ilmenite inclined plate overflow material without pre-enrichment according to claim 5, characterized in that, The reagent regimen for the roughing process is as follows: sulfuric acid 4500~5500g / t, modified water glass 3500~4500g / t, collector 1000~1800g / t, and diesel oil 500~600g / t.

7. The method for direct flotation recovery of ultrafine ilmenite inclined plate overflow material without pre-enrichment according to claim 5, characterized in that, During the refining process, sulfuric acid is added to adjust the pH of the slurry to 5.0-5.

5.

8. The method for direct flotation recovery of ultrafine ilmenite inclined plate overflow material without pre-enrichment according to claim 5, characterized in that, The first scavenging process adds 30% to 40% of the collector, and the second scavenging process adds 15% to 20% of the collector.