A cross-system collaborative and thickening pretreatment process for re-concentration of phosphate rock ore

Abstract

This invention discloses a cross-system synergistic and thickening pretreatment middlings re-selection process for phosphate rock, belonging to the field of phosphate ore beneficiation technology. Addressing the technical problems of high middlings circulation load and deteriorating separation environment in single-unit flotation systems, this invention proposes a dual innovative solution: at the process level, a cross-system middlings synergistic processing loop is constructed, concentrating the scavenged middlings produced by multiple single-reverse flotation magnesium removal systems for thickening, fractionation, pretreatment, and dedicated re-selection, achieving targeted middlings upgrading and system circulation load reduction; at the reagent level, a composite flocculant composed of low-acyl gellan gum, Xanthomonas oryzae polysaccharide, sodium hexametaphosphate, and calcium chloride is innovatively used to achieve selective flocculation and pre-desliming of gangue minerals, significantly improving middlings floatability. This invention, through a cross-system synergistic and selective flocculation middlings re-selection process, solves the problem of ineffective recovery of middlings in phosphate rock, improving the phosphate ore resource recovery rate.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, specifically to a cross-system collaborative and thickening pretreatment process and system for the re-selection of phosphate rock ore. Background Technology

[0002] Phosphate rock is a major source of phosphate fertilizers and phosphate chemical products, making its beneficiation and purification crucial. Reverse flotation, as a mature and efficient deimpurification method, dominates the phosphate rock beneficiation field. Within reverse flotation processes, single-stage reverse flotation for magnesium removal is widely used due to its advantages such as simple process, low investment, and ease of operation. However, industrial practice shows that single-stage reverse flotation for magnesium removal systems faces a common problem—the ineffective treatment of middlings, resulting in a consistently high internal circulating load that restricts the improvement of beneficiation indicators.

[0003] In traditional processes, middlings are often directly returned to the main system for circulation. Although the process is simple, the fine mud and intermediate-grade minerals in the middlings increase the system load and reduce flotation efficiency. CN114682387B reduces the mutual influence between the two stages by adding a hydrocyclone and a thickener for dewatering and defoaming between the first and second reverse flotation stages, but it is mainly aimed at concentrates rather than middlings.

[0004] For the recovery of fine-grained minerals, CN115870087B employs a combined microbial flocculation-magnetic flotation process to treat fine-grained ilmenite, which involves multiple steps and a complex process, making it unsuitable for middlings in phosphate rock. CN110369120A discloses a combined gravity-flotation process for phosphate rock, which first concentrates the gravity separation tailings, then performs forward flotation, and finally reverse flotation, primarily processing the raw ore and not optimizing the middlings for further processing.

[0005] CN114405684A proposes a "slime dispersion + mineral flocculation" re-beneficiation method for fine-grained molybdenum tailings, which is a good approach, but the reagents and parameters are not directly applicable to phosphate rock. CN118287252A recovers low-grade phosphorus from iron ore tailings, but the raw material is tailings rather than middlings from phosphate rock.

[0006] The current process suffers from several problems: First, in a single flotation system, the middlings circulation load is too high, resulting in low concentration and poor quality middlings in the third stage of flotation. This gradual return of middlings within the system worsens the separation environment. Second, directly returning middlings to the front end not only increases the burden on the main system but also introduces fine mud and difficult-to-separate components, interfering with normal separation. Third, each system operates independently, lacking a multi-system middlings co-processing solution, leading to insufficient resource integration. Fourth, conventional flocculants have weak selectivity, making it difficult to effectively separate valuable minerals from gangue. These problems, combined, restrict the recovery efficiency and resource utilization rate of middlings in collophane. Summary of the Invention

[0007] To address the technical problems of low middlings recovery efficiency in phosphate ore beneficiation caused by severe mud formation, high circulating load, and large fluctuations in middlings properties in single-unit flotation systems, and to achieve the technical effects of improving phosphate ore resource recovery rate, reducing production costs, and significantly improving middlings floatability, this invention provides a cross-system collaborative and thickening pretreatment middlings re-concentration process for phosphate ore.

[0008] The technical solution adopted in this invention is: to provide a cross-system collaborative and thickening pretreatment process for the re-concentration of phosphate rock, comprising the following steps:

[0009] (1) Mid-ore collection: The mid-ore produced by two or more independent single-reverse magnesium demagnesification main systems is collected and collected in a centralized manner; (2) Selective flocculation and thickening: The collected middlings from the scavenging section are transported to a high-efficiency thickener, and a composite flocculant with multiple functions of inhibition, flocculation and pre-desliming is added for selective flocculation treatment to obtain a bottom flow with a concentration of 50%-60%. Most of the ultrafine sludge is discharged with the overflow, thus realizing the pre-treatment of middlings desliming. (3) Slurry conditioning and activation: The thick underflow is introduced into the slurry conditioning tank, and high-phosphorus wastewater is added to adjust the pH to 4.0-4.5. At the same time, the slurry concentration is adjusted to about 18-22%, and magnesium removal collector is added to activate the slurry conditioning. (4) Middlings re-concentration: The slurry after slurry preparation is fed into a dedicated middlings re-concentration flotation system independent of the main system for directional upgrading to obtain re-concentrated concentrate and re-concentrated tailings; (5) Product feedback: The re-selected concentrate is returned to the roughing stage of any of the main systems, and the re-selected tailings are merged with the system tailings into the tailings thickener after entering the subsequent two scavenging operations.

[0010] Preferably, the composite flocculant in step (2) is composed of the following components by mass fraction: 35%-50% low acyl gellan gum, 25-30% Xanthomonas oryzae polysaccharide (also known as xanthan gum, hereinafter referred to as XCT), 15%-30% sodium hexametaphosphate, and 3%-10% calcium chloride.

[0011] Furthermore, the amount of composite flocculant added in step (2) is 200-500 g / t. When adding it, it is prepared into an aqueous solution of 1‰-3‰ in advance and added to the thickener through a multi-point dosing method.

[0012] Furthermore, the ore in the scavenging section comes from at least two independent single-reverse magnesium removal flotation systems, with a concentration of 3-8% and a phosphorus grade of 13-20%.

[0013] Preferably, the high-efficiency thickener is a deep cone thickener, and its underflow concentration is controlled at 50-60%.

[0014] Furthermore, the selective magnesium removal collector is XF-01, and the addition amount is 800-1500 g / t.

[0015] Preferably, the dedicated middlings re-flotation system adopts a flotation process structure of one roughing and two scavenging stages, and the phosphorus grade of the re-concentrated concentrate is 25-28%, with a concentration of about 15-20%, and the phosphorus grade of the re-concentrated tailings is 4.0-4.5%.

[0016] The present invention also provides a composite flocculant specifically for the above-mentioned process, which is composed of low-acyl gellan gum, Xanthomonas oryzae polysaccharide (XCT), sodium hexametaphosphate and calcium chloride, and does not contain polyacrylamide.

[0017] Preferably, by mass fraction, its composition is: 35%-50% low acyl gellan gum, 25-30% XCT, 15%-30% sodium hexametaphosphate, and 3%-10% calcium chloride.

[0018] Furthermore, the composite flocculant is a dry powder formulation that can be directly added.

[0019] The beneficial effects of this invention are mainly reflected in two aspects: process and reagents. Firstly, in terms of process, the middlings from the scavenging section of multiple single-stage magnesium removal systems are centrally processed. First, a thickening and separation pretreatment is performed before the middlings enter an independent re-selection loop. This improves the quality of the middlings, reduces the cyclic burden on the main system, and maximizes the potential of the equipment through cross-system coordinated control. Secondly, in terms of reagents, a composite flocculant composed of low-acyl gellan gum, XCT, sodium hexametaphosphate, and calcium chloride is used. The synergistic effect of gellan gum and XCT dual-microbial polysaccharides, combined with the activation of gangue by calcium chloride and the dispersion and protection of sodium hexametaphosphate phosphate minerals, is utilized through Ca... 2+ / Mg 2+ The dual recognition and multi-level network structure allow for the selective flocculation, activation, and removal of gangue minerals such as dolomite, significantly improving the floatability of middlings. Through dual innovations in both process and reagents, this invention effectively solves the long-standing problems of middlings mud formation interference and high circulating load leading to ineffective middlings recovery, thereby significantly improving the system's phosphorus recovery rate. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0021] Figure 1This is the process flow diagram of the present invention. The diagram clearly shows the process flow of middlings in collophane ore with cross-system collaboration and thickening pretreatment, specifically including the following steps: (1) collecting middlings from the scavenging section produced by multiple single reverse magnesium removal systems; (2) selectively flocculating and settling the collected middlings, with most of the ultrafine sludge being discharged as return water with the overflow, and the underflow being activated by adding pH adjuster and magnesium removal collector before entering the middlings re-selection process; (3) the re-selection process includes one reverse flotation operation, and the obtained re-selection concentrate is returned to the roughing stage of any main system, and the froth product is treated as tailings by two consecutive scavenging and reverse flotation processes; (4) the middlings obtained from scavenging are returned to the aforementioned flocculation and settling process for recycling, and finally the scavenging froth tailings and the main system tailings are merged and discharged.

[0022] Example 1 This embodiment focuses on a single reverse flotation magnesium removal system for a calcareous phosphate rock in Hubei Province. The raw ore has a P2O5 grade of 24.56% and an MgO content of 5.01%. The specific processing steps are as follows: (1) Middlings collection: The middlings from the three independently operating single-reverse flotation demagnesification systems are transported to the middlings collection pool via pipeline. The middlings have a P2O5 grade of 18.35%, MgO content of 8.56%, -200 mesh particle size content of 87.21%, pulp concentration of 7.5%, and pH of 4.8. The pulp is stirred evenly to ensure stable pulp properties.

[0023] (2) Selective flocculation and thickening: The collected middlings are pumped to a deep cone high-efficiency thickener with a middlings flow rate of 465-535 m³ / h. 3 With a dry ore volume of 35-40 t / h, a composite flocculant consisting of low-acyl gellan gum, XCT, sodium hexametaphosphate, and calcium chloride in a mass ratio of 45%:25%:25%:5% is added to prepare a 2‰ (mass fraction) aqueous solution. The dosage of the composite flocculant is 400 g / t. After thickening treatment of the middlings, the underflow concentration is controlled at around 55%, achieving preliminary pretreatment.

[0024] (3) Slurry preparation and activation: The thick underflow is introduced into the slurry preparation tank, and the slurry flow rate is controlled at 60 m³ / s. 3 / h. Add high-phosphorus wastewater (12.0m³) with a pH of 2.1. 3 / h) and return water (60 m 3 Adjust the slurry pH to 4.2, add 1200g / t of XF-01 magnesium removal collector, and the slurry concentration after conditioning and activation is about 25%.

[0025] (4) Middlings re-concentration: The activated slurry is sent to a dedicated re-concentration flotation system independent of the main system, using a reverse flotation process of "one roughing and two scavenging". During the flotation process, gangue minerals such as dolomite enter the froth product and are discharged, while phosphate minerals remain in the tank to form re-concentration concentrate.

[0026] (5) Product feedback: The concentrate in the tank is returned to the mixing tank of any main system through a special pump and pipeline system, and after being fully mixed with the raw ore, it enters the roughing section to ensure that the stable operation of the main system is not affected.

[0027] Example 2 This embodiment focuses on a single reverse flotation magnesium removal system for a calcareous phosphate rock in Hubei Province. The raw ore has a P2O5 grade of 24.34% and an MgO content of 5.12%. The specific processing steps are as follows: (1) Middlings collection: The middlings from the three independently operating single-reverse flotation demagnesification systems are transported to the middlings collection pool via pipeline. The collected middlings have a P2O5 grade of 15.27%, MgO content of 9.35%, -200 mesh particle size content of 89.15%, pulp concentration of 6.98%, and pH of 4.92. The mixture is stirred evenly to ensure the stability of the pulp properties.

[0028] (2) Selective flocculation and thickening: The collected middlings are pumped to a deep cone high-efficiency thickener with a middlings flow rate of 430-500 m³ / h. 3 With a dry ore volume of 30-35 t / h, a composite flocculant consisting of low-acyl gellan gum, XCT, sodium hexametaphosphate, and calcium chloride in a mass ratio of 50%:20%:25%:5% is added to prepare a 2‰ (mass fraction) aqueous solution. The amount of composite flocculant added is 400 g / t. After thickening treatment of the middlings, the underflow concentration is controlled at around 55%, achieving preliminary pretreatment.

[0029] (3) Slurry preparation and activation: The thick underflow is introduced into the slurry preparation tank, and the slurry flow rate is controlled at 60 m³ / s. 3 / h. Add high-phosphorus wastewater with a pH of 2.1 (13 m³). 3 / h) and return water (59 m 3 Adjust the slurry pH to 4.2, add 1200g / t of XF-01 magnesium removal collector, and the slurry concentration after conditioning and activation is 25%.

[0030] (4) Middlings re-concentration: The activated slurry is sent to a dedicated re-concentration flotation system independent of the main system, using a reverse flotation process of "one roughing and two scavenging". During the flotation process, gangue minerals enter the froth product, while phosphate minerals remain in the tank to form re-concentration concentrate.

[0031] (5) Product feedback: The concentrate in the tank is returned to the mixing tank of any main system through a special pump and pipeline system, and after being fully mixed with the raw ore, it enters the roughing section to ensure that the stable operation of the main system is not affected.

[0032] Example 3 This embodiment focuses on a single reverse flotation magnesium removal system for a calcareous phosphate rock in Hubei Province. The raw ore has a P2O5 grade of 24.75% and an MgO content of 4.89%. The specific processing steps are as follows: (1) Middlings collection: The middlings from the three independently operating single-reverse flotation demagnesification systems are transported to the middlings collection pool via pipeline. The collected middlings have a P2O5 grade of 19.56%, an MgO content of 7.59%, a -200 mesh particle size content of 88.45%, a pulp concentration of 6.98%, and a pH of 4.75. The mixture is stirred evenly to ensure the stability of the pulp properties.

[0033] (2) Selective flocculation and thickening: The collected middlings are pumped to a deep cone high-efficiency thickener with a middlings flow rate of 430-500 m³ / h. 3 With a dry ore volume of 30-35 t / h, a composite flocculant consisting of low-acyl gellan gum, XCT, sodium hexametaphosphate, and calcium chloride in a mass ratio of 45%:20%:27%:8% is added to prepare a 2‰ (mass fraction) aqueous solution. The dosage of the composite flocculant is 450 g / t. After thickening of the middlings, the underflow concentration is controlled at around 57%, achieving preliminary separation.

[0034] (3) Slurry preparation and activation: The thick underflow is introduced into the slurry preparation tank, and the slurry flow rate is controlled at 60 m³ / s. 3 / h. Add high-phosphorus wastewater (13.5m³) with a pH of 2.1. 3 / h) and return water (75 m 3 Adjust the slurry pH to 4.15, add 1200g / t of XF-01 magnesium removal collector, and the slurry concentration after conditioning and activation is 23%.

[0035] (4) Middlings re-concentration: The activated slurry is sent to a dedicated re-concentration flotation system independent of the main system, using a reverse flotation process of "one roughing and two scavenging". During the flotation process, gangue minerals such as dolomite enter the froth product and are discharged, while phosphate minerals remain in the tank to form re-concentration concentrate.

[0036] (5) Product feedback: The concentrate in the tank is returned to the mixing tank of any main system through a special pump and pipeline system, and after being fully mixed with the raw ore, it enters the roughing section to ensure that the stable operation of the main system is not affected.

[0037] Comparative Example 1 This comparative example is used to examine the impact of not processing the middlings separately and returning them directly according to the original process on the phosphorus yield of the main system.

[0038] Specific operation: Unlike Example 1, the ore from the third scavenging stage does not undergo independent thickening pretreatment. Instead, it follows the original process and is directly returned to the second scavenging stage. It is then combined with the tailings from the first scavenging stage and carried out together in the second scavenging stage. The remaining process conditions are consistent with those in Example 1.

[0039] Comparative Example 2 This comparative example is used to examine the effect of directly re-selecting middlings without thickening pretreatment.

[0040] Specific operation: Unlike Example 1, the thickening pretreatment step (2) of the three-stage ore is omitted and it directly enters the re-selection flotation system. The remaining process conditions are the same as in Example 1.

[0041] Comparative Example 3 This comparative example is used to examine the contribution of ore aggregation in multiple systems to the process efficiency.

[0042] Specific operation: Unlike Example 1, only the middlings produced by a single reverse flotation demagnesification system is taken and not mixed with the ore from other systems. The same thickening pretreatment and reselection steps as in Example 1 are performed directly, and the remaining process conditions are the same as in Example 1.

[0043] Comparative Example 4 This comparative example is used to examine the impact of the return location of the reprocessed concentrate on the stability of the main system.

[0044] Specific operation: Unlike Example 1, in step (5), the re-selected concentrate is not returned to the main system rough concentrate, but is returned to the scavenging section of the main system. The remaining process conditions are the same as in Example 1.

[0045] Comparative Example 5 This comparative example is used to examine the effect of replacing the composite flocculant of the present invention with a traditional cationic polyacrylamide flocculant.

[0046] Specific operation: Unlike Example 1, in the thickening pretreatment step, the composite flocculant of the present invention is replaced with conventional cationic polyacrylamide with a molecular weight of 12 million, while the addition amount and other process conditions remain the same as in Example 1.

[0047] Comparative Example 6 This comparative example was used to investigate the effect of not adding Xanthomonas oryzae polysaccharide (XCT) to the composite flocculant.

[0048] Specific operation: Unlike Example 1, the composite flocculant used in the thickening pretreatment step does not contain XCT, but is composed of only three components: low-acyl gellan gum, sodium hexametaphosphate, and calcium chloride, in a mass ratio of 60%:33.3%:6.7%. The total amount of flocculant added and other process parameters remain the same as in Example 1.

[0049] Comparative Example 7 This comparative example is used to investigate the gangue activation effect of calcium chloride.

[0050] Specific operation: Unlike Example 1, the composite flocculant used in the thickening pretreatment step does not contain calcium chloride, but is composed of three components: low acyl gellan gum, XCT and sodium hexametaphosphate, in a mass ratio of 45%:25%:30%. The total amount of flocculant added and other process parameters are consistent with those in Example 1.

[0051] Comparative Example 8 This comparative example is used to investigate the dispersing and phosphorus-retaining effect of sodium hexametaphosphate.

[0052] Specific operation: Unlike Example 1, the composite flocculant used in the thickening pretreatment step does not contain sodium hexametaphosphate, but is composed of three components: low acyl gellan gum, XCT and calcium chloride, with a mass ratio of 45%:25%:30%. The total amount of flocculant added and other process parameters are consistent with those in Example 1.

[0053] Comparative Example 9 This comparative example is used to examine the necessity of flocculants in thickening pretreatment.

[0054] Specific operation: Unlike Example 1, no flocculant is added in step (2), and thickening is achieved solely by gravity settling. The remaining process conditions are consistent with those in Example 1.

[0055] Comparative Example 10 This comparative example is used to examine the synergistic effect of the optimal ratio of composite flocculants.

[0056] Specific operation: Unlike Example 1, the ratio of composite flocculant used in the thickening pretreatment step is adjusted to low acyl gellan gum: XCT: sodium hexametaphosphate: calcium chloride = 20%: 40%: 30%: 10%, while the total amount of flocculant added and other process parameters remain the same as in Example 1.

[0057] Table 1. Test results of Examples 1-3 and Comparative Examples 1-10

[0058] The experimental results of Examples 1-3 show that the phosphorus recovery rate of the main system is above 94.5%, and the P2O5 grade of the re-selected concentrate exceeds 27.5% and the MgO content is below 3.1%, indicating that the process of the present invention has good adaptability to middlings of different properties. The experimental results of Comparative Examples 1-4 show that each step in the process route of "middling aggregation in multiple systems - thickening pretreatment - independent re-selection - return of re-selected concentrate to rougher selection" is indispensable. The experimental results of Comparative Examples 5-10 show that the four components of the composite flocculant and their optimal ratio are key to achieving selective flocculation, efficient removal of dolomite, and protection of phosphate minerals. The present invention combines the above closed-loop process with a low-acyl gellan gum / XCT / calcium chloride / sodium hexametaphosphate composite flocculant, which significantly improves the middlings re-selection effect, increases the phosphorus recovery rate of the main system, reduces phosphorus loss in tailings, and ensures the stable operation of the main system, achieving efficient resource recovery of low-grade gellan phosphate middlings.

[0059] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A process for re-cleaning of collophanite middlings in cross-system synergy with densification pretreatment, characterized by that, Includes the following steps: (1) Mid-mineral collection: The mid-minerals produced by the scavenging section of at least two independent single-reverse magnesium demagnesification main systems are collected in a centralized manner; (2) Selective flocculation thickening: The scavenged ore collected in step (1) is transported to a high-efficiency thickener, and a composite flocculant is added for selective flocculation pretreatment to obtain a high-concentration underflow rich in phosphorus minerals; the composite flocculant is composed of low-acyl gellan gum, Xanthomonas oryzae polysaccharide XCT, sodium hexametaphosphate and calcium chloride. (3) Slurry preparation and activation: The thick underflow obtained in step (2) is introduced into the slurry preparation tank, and high-phosphorus wastewater is added to adjust the pH to 4.0-4.5, while adjusting the slurry concentration to 18-22%; and magnesium removal collector is added to the slurry preparation tank. (4) Middlings reprocessing: The slurry after slurry conditioning in step (3) is subjected to reverse flotation to improve the quality of the phosphate concentrate and foam product in the tank; (5) Product feedback: The phosphate concentrate obtained in step (4) is returned to the roughing stage of any of the main systems.

2. The process according to claim 1, characterized in that, In step (1), the phosphorus grade of the collected scavenged ore is 13%-20%, and the concentration is 3%-8%.

3. The process of claim 2, wherein, The composite flocculant mentioned in step (2) has the following composition by mass fraction: 35%-50% low acyl gellan gum, 25%-30% XCT, 15%-30% sodium hexametaphosphate, and 3%-10% calcium chloride.

4. The process of claim 1, wherein, The composite flocculant mentioned in step (2) has the following composition by mass fraction: 45% low acyl gellan gum, 25% XCT, 25% sodium hexametaphosphate, and 5% calcium chloride.

5. The process of claim 1, wherein, The amount of composite flocculant added in step (2) is 200-500 grams per ton of dry middlings ore, and it is prepared as a 1%-3‰ aqueous solution before addition.

6. The process of claim 1, wherein, The high-efficiency thickener mentioned in step (2) is a deep cone thickener, and its underflow concentration is controlled at 50%-60%.

7. The process of claim 1, wherein, In step (3), the amount of magnesium collector used is 800-1500 g / t.

8. A composite flocculant specific to the process of any one of claims 1 to 7, characterized in that, It is composed of low-acyl gellan gum, Xanthomonas oryzae polysaccharide, sodium hexametaphosphate and calcium chloride.

9. The composite flocculant according to claim 8, characterized in that, The mass ratio of the low-acyl gellan gum to the auxiliary flocculant XCT is 1:0.3-0.

5.

10. The composite flocculant according to claim 8, characterized in that, The composite flocculant is a dry powder formulation that can be added directly.

Images