Recycling method for producing alumina leaf filter cake from imported guinea ore

Abstract

The invention discloses a method for recycling filter cakes of an aluminum oxide leaf filter produced from imported guinea ores, relates to the technical field of nonferrous metallurgical aluminum oxide production, and solves the problems of high energy consumption, easiness in blockage, short service life of filter cloth, incomplete solid-liquid separation recovery and low efficiency in a filter pressing process. The method comprises the following steps: a recycling process comprises the following steps: carrying out size mixing pretreatment on a low-solid-content filter cake generated by a leaf filter, feeding the low-solid-content filter cake into a settling tank, carrying out deep cone settling so as to carry out solid-liquid separation, and returning the separated supernatant to a rear dilution tank; and the underflow of the settling tank for solid-liquid separation is subjected to spiral dehydration and mother liquor blending and then returns to an aluminum oxide dissolution system. The solid content and Nk concentration of the filter cake can be automatically controlled and flexibly adjusted, and stable separation under high-temperature ore pulp is achieved; goethite blockage can be avoided, continuous operation is guaranteed, and the annual failure rate is smaller than 5%; the solid recovery rate is greater than or equal to 95%, the filtrate is circulated after reaching the standard, and the filter cake recovery operation cost is effectively reduced by greater than or equal to 30%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of non-ferrous metallurgical alumina production, and relates to a recycling method of leaf filter cake of imported Guinea bauxite, in particular to a method for settling separation, mother liquor preparation and recycling of leaf filter cake of high goethite (such as Guinea bauxite). BACKGROUND

[0002] The alumina industry is an important basic raw material industry of the national economy. In the Bayer process for producing alumina from imported Guinea bauxite, after the bauxite is dissolved at high temperature and high pressure, the generated red mud slurry needs to be precisely separated by a leaf filter to obtain pure sodium aluminate liquor. During this leaf filtering process, a small amount of fine impurity particles containing iron and silicon are trapped on the surface of the leaf filter cloth, forming a layer of filter cake. As the production continues, this layer of filter cake will thicken and be periodically back-flushed and cleaned, forming so-called "leaf filter cake".

[0003] Currently, the conventional treatment method for this leaf filter cake in industrial production is to return it to the red mud settling system, and after being filtered by a pressure filter together with a large amount of red mud, red mud cake is formed, which is finally sent to a stockyard for storage. However, this traditional recycling method has a series of core technical defects and economic problems: First, the pressure filtration process itself has core defects, resulting in high operating costs and low efficiency: the pressure filter for treating red mud needs to be frequently replaced with special filter cloth, resulting in high material consumption. At the same time, the pressure filtration process is intermittent, and the equipment starts and stops frequently, resulting in high energy consumption for pressing, which leads to high operating costs. The filtration efficiency is low: the imported Guinea bauxite contains a large amount of Al-goethite with small crystal structure and high viscosity. During the pressure filtration process, it is easy to embed and block the filter cloth pores, resulting in an increase in the filtration resistance of the filter medium by more than 40%, which seriously restricts the filtration rate. The temperature of the leaf filter cake attached to the slurry entering the pressure filtration system is usually higher than 95℃. The high temperature environment accelerates the aging and embrittlement of the filter cloth material, reducing its service life by more than 50% compared to the case of treating normal temperature materials. In addition, the unloading, cleaning, and assembly of the pressure filter still require a large amount of manual intervention, and it is difficult to achieve continuous and automatic operation, which affects the overall operation efficiency.

[0004] Second, the characteristics of the leaf filter cake itself affect: the leaf filter cake has a very low solid content (usually only 30-50g / L), and is an extremely dilute slurry. Returning it directly to the red mud system not only greatly increases the load of the settling tank and the pressure filter, but also highly dilutes the trace valuable components (such as unreacted alumina and alkali) in the large amount of red mud, resulting in a very low economic value of the recovered material. The traditional pressure filtration recycling mode has poor economic efficiency and is difficult to achieve efficient resource utilization.

[0005] The current practice of simply mixing leaf filter cake into the red mud system is essentially a crude "end-of-pipe mixing" treatment rather than an independent resource recovery system. Existing technologies lack a continuous treatment system adapted to the characteristics of leaf filter cake with low solids content and high viscosity, and have not formed an integrated, closed-loop operation process of "pretreatment-sedimentation-dewatering-blending". This results in a discontinuous and unstable recovery process, incomplete solid-liquid separation, and low resource recovery efficiency.

[0006] In summary, existing methods for treating leaf filter cake generated during alumina production from Guinea mines have significant shortcomings in terms of technology, cost, efficiency, and system design. There is an urgent need to develop a targeted, complete, economical, and efficient dedicated recycling method. Summary of the Invention

[0007] To address the above shortcomings, this invention provides a method for recycling filter cake from alumina leaf filter presses produced using imported Guinean ore. This method solves the problems of high energy consumption, easy clogging, short filter cloth life, and incomplete solid-liquid separation and low efficiency in pressure filtration processes. It achieves automated control by linking all monitoring equipment and pump groups through an online density meter and flow meter-linked PLC system. This allows for flexible adjustment of the filter cake solid content and Nk concentration (caustic alkali concentration); stable separation under high-temperature slurry conditions (80-100℃); prevention of goethite clogging; ensuring continuous operation with an annual failure rate of <5%; and improved filter cake dewatering efficiency, ensuring a solid recovery rate of ≥95% and filtrate recycling to meet standards. This effectively reduces filter cake recycling operating costs by ≥30%, achieving green and high-value recycling of waste resources. The specific technical solution is as follows: A method for recycling filter cake from a leaf filter machine produced from imported Guinean ore includes the following steps: The low-solids filter cake produced by the leaf filter machine is pre-treated by slurry preparation and then enters a settling tank for deep cone settling to separate solids and liquids. The supernatant separated from the filter cake is returned to the dilution tank. The bottom flow from the settling tank after solid-liquid separation is dewatered by a spiral and mixed with mother liquor before being returned to the alumina leaching system.

[0008] Preferably, the recycling method specifically includes the following steps: (1) Pretreatment of filter cake: Add oxime acid type flocculant to the filter cake, stir and heat to adjust the slurry to obtain mineral slurry; (2) Deep cone settling separation: After the slurry pretreated in step (1) is sent into the settling tank, solid-liquid separation is carried out with a goethite settling rate of ≥5m / h to obtain supernatant and underflow; (3) Filtrate recovery: The supernatant from step (2) is sent to the alumina production dilution tank system; (4) Deep dewatering of the underflow: Deep dewatering of the underflow from the settling tank in step (2) to obtain filter cake; (5) Dynamic adjustment of mother liquor: Inject circulating mother liquor into the filter cake after dehydration in step (4), and then send it to the alumina leaching system for recycling.

[0009] Preferably, in step (1), the solid content of the filter cake is 30-50 g / L.

[0010] Preferably, in step (1), the oxime acid type flocculant is sodium hydroxamate, and the oxime acid type flocculant is added at a dosage of 0.5 to 1.5 kg / t of dry material.

[0011] Preferably, in step (1), the stirring rate is 30-50 r / min and the heating temperature is 80-100℃.

[0012] Preferably, in step (2), the Al2O3 content of the supernatant is ≤5g / L.

[0013] Preferably, in step (2), the solid content of the underflow is 500-600 g / L and the water content is <50%.

[0014] Preferably, in step (4), the deep dewatering is carried out in a screw dewatering machine with a screw speed of 15-25 r / min, a feed rate of 10-20 m³ / h, a pressing pressure of 0.3-0.5 MPa, and a filter cake moisture content of ≤25% and a solid recovery rate of ≥95%.

[0015] Preferably, in step (4), the filter cake is rich in Al2O3 and CaO.

[0016] Preferably, in step (5), circulating mother liquor is injected at the inlet of the spiral dewatering machine into the slurry mixing tank to dilute the solid content of the filter cake to 200-250 g / L and increase the Nk concentration of the leached slurry to >200 g / L; the Nk concentration of the circulating mother liquor is 200-220 g / L.

[0017] The present invention achieves at least the following beneficial effects: 1. This invention utilizes the low solids content of filter cake (30-50 g / L) and adds an oxime acid-type flocculant (preferably sodium hydroxamate, dosage 0.5-1.5 kg / ton dry material). Filter cake pretreatment accelerates goethite settling (settling velocity ≥ 5 m / h). A deep cone settling tank enhances solid-liquid separation in the compression zone, increasing the underflow solids content to 500-600 g / L (moisture content < 50%). The deep cone settling tank design enhances solid-liquid separation in the compression zone, increasing underflow solids content and reducing moisture content. During the dynamic adjustment stage of the mother liquor, circulating mother liquor (Nk concentration: 200-220 g / L) is injected at the inlet of the slurry preparation tank of the spiral dewatering machine. This dilutes the filter cake solids content to 200-250 g / L, preventing pipe blockage, and also increases the Nk concentration of the leaching slurry to a critical value (> 200 g / L), preventing a decrease in leaching rate.

[0018] 2. This invention installs online density meters, flow meters, and level gauges at the inlet and outlet of the slurry preparation tank, settling tank, dilution tank, and spiral dewatering machine to achieve automation. The online density meter and flow meter are linked to a PLC system to control all monitoring equipment and pump sets, adjusting the flocculant dosage, mother liquor injection volume (see attached control loop), and dewatering machine speed in real time to ensure stable parameters at each stage and achieve automated control.

[0019] 3. The recycling method of this invention flexibly adjusts the solid content and Nk concentration (caustic alkali concentration) of the filter cake through automated control; achieves stable separation under high-temperature slurry (80-100℃); avoids goethite clogging, ensures continuous operation, and has an annual failure rate of <5%; improves the filter cake dewatering efficiency, ensures a solid recovery rate of ≥95%, and ensures that the filtrate meets the recycling standards, thereby effectively reducing the operating cost of filter cake recycling by ≥30%.

[0020] 4. This invention is the first to combine oxime acid flocculant, slurry conditioning tank, deep cone settling tank, dilution tank, and spiral dewatering machine in the recovery of high-grade goethite filter cake, constructing an integrated process of "slurry conditioning pretreatment, deep cone settling, filtrate recovery, spiral dewatering, and mother liquor preparation". It discovers the settling adaptability of low-solids filter cake and eliminates the traditional pressure filtration step. The "mother liquor injection before pump" design achieves the dual goals of adjusting nitrogen content (Nk) and diluting solids content while preventing pipe blockage, solving the core pain points of high-temperature high-grade goethite slurry recovery. The filter cake moisture content is ≤28%, operating costs are reduced by ≥30%, the annual failure rate is <1.5%, and the recovery rate of calcium oxide (CaO) and alumina (Al2O3) is ≥87%. At the same time, it reduces ore consumption and lime digestion costs and adapts to the flexible adjustment needs of different production lines.

[0021] 5. The core objective of this invention is to recover calcium oxide (CaO) and alumina (Al2O3) from the leaf filter cake. This recovery can effectively reduce ore consumption and lime digestion costs. By installing a spiral dewatering machine at the bottom outlet of the settling tank, the moisture content of the bottom stream is reduced to below 25%. Furthermore, the addition of circulating mother liquor significantly reduces the amount of returned liquid. The αk of the returned liquid is only 1.60, while the αk of the circulating mother liquor is 3.25. If the αk of the returned liquid is too low, it will affect the amount of ore fed into the tank, thereby affecting the output. The recycling process of this invention is as follows: leaf filter cake (solid content of about 50 g / L) → sedimentation (to increase the solid content to 600 g / L) → spiral dewatering machine (to reduce the moisture content to 25%) → blending tank (to add circulating mother liquor to reduce the solid content to 300 g / L, which facilitates pump delivery and increases αk from 1.60 to 2.8) → high-pressure leaching (at a temperature above 240°C, to dissolve alumina Al2O3, and CaO to replace lime milk in the reaction to produce hydrated garnet and reduce alkali consumption). Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This invention presents a process flow diagram for the recycling of filter cake from imported Guinean ore used in the production of alumina leaf filter presses. Detailed Implementation

[0024] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] like Figure 1 As shown, the recycling method of the present invention includes the following core equipment and processes: 1. Feeding process: Leaf filter → Inlet pipe → Slurry preparation tank (including flocculant addition device, stirring device, and insulation layer); 2. Separation process: Slurry preparation tank → Deep cone settling tank; 3. Filtrate recovery: Deep cone settling tank (overflow port) → Post-dilution tank → Circulating post-dilution tank system; 4. Dewatering process: Deep cone settling tank (underflow outlet) → Underflow pump → Spiral dewatering machine (including the inlet of the circulating mother liquor injection mixing tank); 5. Finished product conveying: Screw dewatering machine → dissolution system; 6. Control components: Online density meter, flow meter, level gauge → PLC control system (linking all equipment).

[0027] Example 1 A method for recycling filter cake from alumina leaf filter produced using imported Guinean ore includes the following steps: (1) Filter cake pretreatment: The 50g / L low solid content filter cake produced by the leaf filter is directly fed into the slurry preparation tank through the inlet pipe. The volume of a single slurry preparation tank is 55m³. The effective volume of the slurry preparation tank is adapted to the production line capacity. The filter cake is homogenized and stirred in the slurry preparation tank at a stirring rate of 50r / min. At the same time, oxime acid type flocculant (sodium hydroxamic acid) is added at a dosage of 1.5kg / t dry material to lay the foundation for the subsequent sedimentation process. The temperature of the slurry is maintained at 100℃ through the insulation layer of the slurry preparation tank to avoid temperature fluctuations affecting the flocculation effect and obtain the slurry. (2) Deep cone settling separation: a deep cone settling tank is used to enhance the solid-liquid separation effect in the compression zone and increase the underflow concentration. After the slurry pretreated in step (1) is sent into the settling tank, the goethite settling rate is 7 m / h, so that the slurry can achieve rapid solid-liquid stratification and obtain a supernatant with an Al2O3 content of 5 g / L and an underflow with a solid content of 600 g / L and a water content of 43%. (3) Supernatant recovery: The supernatant separated in the settling tank in step (2) is introduced into the dilution tank through the overflow pipe. The dilution tank is equipped with a liquid level monitoring device to prevent overflow. The supernatant in the dilution tank is pumped to the alumina production circulating mother liquor system to realize the recovery of water resources and residual caustic alkali, and reduce the consumption of fresh water and alkali. (4) Deep dewatering of the underflow: The underflow of the settling tank is transported to the screw dewatering machine through the pipeline for deep dewatering. The feed rate is 20 m³ / h, which is matched with the processing capacity of the dewatering machine. During deep dewatering, the screw speed of the screw dewatering machine is 25 r / min, and the pressing pressure is 0.5 MPa to achieve deep dewatering. The moisture content of the filter cake after dewatering is 23%, and the solid recovery rate is 96%. The dewatered filter cake (rich in Al2O3 and CaO) is directly sent to the alumina leaching system to avoid resource waste. (5) Dynamic adjustment of mother liquor: Inject circulating mother liquor (Nk concentration of 220g / L) into the inlet of the spiral dewatering machine into the slurry tank to dilute the solid content of the filter cake to 250g / L and prevent pipeline blockage; at the same time, increase the Nk concentration of the leaching slurry to >200 / L to avoid a decrease in leaching rate.

[0028] Example 2 A method for recycling filter cake from alumina leaf filter produced using imported Guinean ore includes the following steps: (1) Filter cake pretreatment: The 30g / L low solid content filter cake produced by the leaf filter is directly fed into the slurry preparation tank through the inlet pipe. The single tank volume of the slurry preparation tank is 50m³. The effective volume of the slurry preparation tank is adapted to the production line capacity. The filter cake is homogenized and stirred in the slurry preparation tank at a stirring rate of 30r / min. At the same time, oxime acid type flocculant (sodium hydroxamic acid) is added at a dosage of 0.5kg / t dry material to lay the foundation for the subsequent sedimentation process. The temperature of the slurry is maintained at 80℃ through the insulation layer of the slurry preparation tank to avoid temperature fluctuations affecting the flocculation effect and obtain the slurry. (2) Deep cone settling separation: a deep cone settling tank is used to enhance the solid-liquid separation effect in the compression zone and increase the underflow concentration. After the slurry pretreated in step (1) is sent into the settling tank, the goethite settling rate is 5 m / h, which realizes rapid solid-liquid stratification and obtains a supernatant with an Al2O3 content of 3 g / L and an underflow with a solid content of 500 g / L and a water content of 50%. (3) Supernatant recovery: The supernatant separated in the settling tank in step (2) is introduced into the dilution tank through the overflow pipe. The dilution tank is equipped with a liquid level monitoring device to prevent overflow. The supernatant in the dilution tank is pumped to the alumina production circulating mother liquor system to realize the recovery of water resources and residual caustic alkali, and reduce the consumption of fresh water and alkali. (4) Deep dewatering of the underflow: The underflow of the settling tank is transported to the screw dewatering machine through the pipeline for deep dewatering. The feed rate is 10-20 m³ / h, and the feed rate is matched with the processing capacity of the dewatering machine. During deep dewatering, the screw speed of the screw dewatering machine is 15 r / min and the pressing pressure is 0.3 MPa to achieve deep dewatering. The moisture content of the filter cake after dewatering is 25%, and the solid recovery rate is 95%. The dewatered filter cake (rich in Al2O3 and CaO) is directly sent to the alumina leaching system to avoid resource waste. (5) Dynamic adjustment of mother liquor: Inject circulating mother liquor (Nk concentration of 200g / L) into the inlet of the spiral dewatering machine into the slurry tank to dilute the solid content of the filter cake to 200g / L and prevent pipeline blockage; at the same time, increase the Nk concentration of the leaching slurry to >180 / L to avoid a decrease in leaching rate.

[0029] Example 3 A method for recycling filter cake from alumina leaf filter produced using imported Guinean ore includes the following steps: (1) Filter cake pretreatment: The 40g / L low solid content filter cake produced by the leaf filter is directly fed into the slurry preparation tank through the inlet pipe. The single tank volume of the slurry preparation tank is 53m³. The effective volume of the slurry preparation tank is adapted to the production line capacity. The filter cake is homogenized and stirred in the slurry preparation tank at a stirring rate of 40r / min. At the same time, oxime acid type flocculant (sodium hydroxamic acid) is added at a dosage of 1.0kg / t dry material to lay the foundation for the subsequent sedimentation process. The temperature of the slurry is maintained at 90℃ through the insulation layer of the slurry preparation tank to avoid temperature fluctuations affecting the flocculation effect and obtain the slurry. (2) Deep cone settling separation: a deep cone settling tank is used to enhance the solid-liquid separation effect in the compression zone and increase the underflow concentration. After the slurry pretreated in step (1) is sent into the settling tank, the goethite settling rate is 6 m / h, which realizes rapid solid-liquid stratification and obtains a supernatant with an Al2O3 content of 4 g / L and an underflow with a solid content of 550 g / L and a water content of 46%. (3) Supernatant recovery: The supernatant separated in the settling tank in step (2) is introduced into the dilution tank through the overflow pipe. The dilution tank is equipped with a liquid level monitoring device to prevent overflow. The supernatant in the dilution tank is pumped to the alumina production circulating mother liquor system to realize the recovery of water resources and residual caustic alkali, and reduce the consumption of fresh water and alkali. (4) Deep dewatering of the underflow: The underflow of the settling tank is transported to the screw dewatering machine through the pipeline for deep dewatering. The feed rate is 15 m³ / h, which is matched with the processing capacity of the dewatering machine. During deep dewatering, the screw speed of the screw dewatering machine is 20 r / min, and the pressing pressure is 0.4 MPa to achieve deep dewatering. The moisture content of the filter cake after dewatering is 22%, and the solid recovery rate is 97%. The dewatered filter cake (rich in Al2O3 and CaO) is directly sent to the alumina leaching system to avoid resource waste. (5) Dynamic adjustment of mother liquor: Inject circulating mother liquor (Nk concentration of 210g / L) into the inlet of the spiral dewatering machine into the slurry tank to dilute the solid content of the filter cake to 230g / L and prevent pipeline blockage; at the same time, increase the Nk concentration of the leaching slurry to >190 / L to avoid a decrease in leaching rate.

[0030] Comparative Example 1 The difference from Example 1 is that the filter cake is not pretreated, while other conditions remain unchanged. In this comparative example, the inability to effectively mix the filter cake and flocculant in the leaf filter directly affects the settling effect of the filter cake, leading not only to an increase in flocculant usage but also to a lower solids content in the sedimentation underflow, thus increasing treatment costs.

[0031] Comparative Example 2 The difference from Example 1 is that in step (1), a deep cone settling tank is not used; instead, a regular settling tank is used for settling separation, while other conditions remain unchanged. This comparative example cannot improve the solids content of the leaf filter cake, leading to increased operating costs in subsequent steps.

[0032] Comparative Example 3 The difference from Example 1 is that step (4) does not add a spiral dewatering machine at the bottom outlet for deep dewatering, but instead uses a regular dewatering machine, while other conditions remain unchanged. The moisture content of the filter cake after dewatering in this comparative example is too high, which increases the operating cost of subsequent steps.

[0033] Comparative Example 4 Unlike Example 1, a horizontal filter press was used instead of a deep cone settling tank and a spiral dewatering machine. The filtrate was returned for dilution, and the filter cake was returned for dissolution, while other conditions remained unchanged. This comparative example required the addition of a filter press feeding buffer tank, a feeding pump, and devices and heat exchange media for cooling the material, which significantly increased operating costs.

[0034] Comparative Example 5 The difference from Example 1 is that a deep cone settling tank and a spiral dewatering machine were not used; instead, a cyclone classifier was used for classification. The overflow was returned to the dilution tank, and the underflow was returned to the dissolution process; all other conditions remained unchanged.

[0035] This comparative example only performed simple grading of the leaf filter cake, resulting in a high moisture content in the cake. This significantly impacted the output of the filter cake after it entered the leaching unit. Furthermore, the high content of suspended solids in the overflow returned to the dilution tank after grading drastically reduced the recovery rates of alumina and calcium oxide.

[0036] The methods of Examples 1-3 and Comparative Examples 1-5 were used to recover and reuse the filter cake of alumina leaf filters produced from imported Guinea ore. The filter cake moisture content (%), operating cost (yuan / m³ filter cake), failure rate (%), and alumina and calcium oxide recovery rate (%) of each method are shown in Table 1 below.

[0037] Table 1 As shown in Table 1, the filter cake moisture content of Examples 1 to 3 was slightly lower than that of Comparative Example 4, but significantly higher than that of Comparative Example 5. Furthermore, the operating costs of Examples 1 to 3 were significantly higher than those of Comparative Examples 2 and 5, and their failure rates were also significantly higher than those of Comparative Examples 3 and 5. This indicates that the method of recovering leaf filter cake using a settling tank and dewatering machine in this application has significant technical advantages compared to existing technologies.

[0038] A comparison of Example 1 with Comparative Examples 1 to 4 revealed that different filter cake moisture contents resulted in different operating costs and varying alumina and calcium oxide recovery rates. Only when the moisture content was within the range of 25%–28%, the Nk concentration of the injected circulating mother liquor was 190–220 g / L, and the filter cake solids content was diluted to 200–250 g / L, did the technical effect of low operating costs and high alumina and calcium oxide recovery rates emerge.

[0039] This application uses a settling tank + dewatering machine method, and strictly controls the Nk concentration of the injected circulating mother liquor and the solid content of the filter cake dilution, which significantly improves the recovery rate of alumina and calcium oxide.

[0040] Compared with the methods of Comparative Examples 1-3, the method of recycling imported Guinean ore to produce alumina leaf filter cake showed that the investment cost and operating cost were reduced by ≥30%, the annual failure rate was <5%, and the solid recovery rate was ≥95%.

[0041] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for recycling filter cake from alumina leaf filter produced using imported Guinean ore, characterized in that, Includes the following steps: The recycling process involves pre-treating the low-solids filter cake produced by the leaf filter and then subjecting it to deep cone settling in a settling tank to separate the solids and liquids. The supernatant is then returned to the dilution tank. After being dehydrated by a spiral and mixed with mother liquor, the bottom stream of the solid-liquid separation settling tank returns to the alumina leaching system.

2. The recycling method according to claim 1, characterized in that, Specifically, the following steps are included: (1) Pretreatment of filter cake: Add oxime acid type flocculant to the filter cake, stir and heat to adjust the slurry to obtain mineral slurry; (2) Deep cone settling separation: After the slurry pretreated in step (1) is sent into the settling tank, solid-liquid separation is carried out with a goethite settling rate of ≥5m / h to obtain supernatant and underflow; (3) Recover the supernatant: Send the supernatant from step (2) to the alumina production dilution tank system for recycling; (4) Deep dewatering of the underflow: Deep dewatering of the underflow from the settling tank in step (2) to obtain filter cake; (5) Dynamic adjustment of mother liquor: Inject circulating mother liquor into the filter cake after dehydration in step (4), and then send it to the alumina leaching system for recycling.

3. The recycling method according to claim 2, characterized in that, In step (1), the solid content of the filter cake is 30-50 g / L.

4. The recycling method according to claim 2, characterized in that, In step (1), the oxime acid type flocculant is sodium hydroxamate, and the oxime acid type flocculant is added at a dosage of 0.5 to 1.5 kg / t of dry material.

5. The recycling method according to claim 2, characterized in that, In step (1), the stirring rate is 30-50 r / min, and the heating temperature is 80-100℃.

6. The recycling method according to claim 2, characterized in that, In step (2), the Al2O3 content of the supernatant is ≤5g / L.

7. The recycling method according to claim 2, characterized in that, In step (2), the solid content of the underflow is 500-600 g / L and the water content is <50%.

8. The recycling method according to claim 2, characterized in that, In step (4), the deep dewatering is carried out in a screw dewatering machine with a screw speed of 15-25 r / min, a feed rate of 10-20 m³ / h, a pressing pressure of 0.3-0.5 MPa, and a filter cake moisture content of ≤25% and a solid recovery rate of ≥95%.

9. The recycling method according to claim 2, characterized in that, In step (4), the filter cake is rich in Al2O3 and CaO.

10. The recycling method according to claim 2, characterized in that, In step (5), circulating mother liquor is injected at the inlet of the spiral dewatering machine into the slurry mixing tank to dilute the solid content of the filter cake to 200-250 g / L and increase the Nk concentration of the leached slurry to >200 g / L; the Nk concentration of the circulating mother liquor is 200-220 g / L.

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