A method for comprehensive utilization of resources of bayer process leaf filter cake of recycled alumina

Abstract

The present application relates to a kind of resource comprehensive utilization method of recycling bayer process leaf filter cake of alumina, belong to alumina production technical field.The method is produced in the leaf filter cake slurry of bayer process crude liquid refining process is separated by deep-cone settling tank liquid-solid, solid content is increased to 200-300g / l, and the underflow of settling tank is filtered by plate-and-frame filter press, and filtrate returns bayer process crude liquid tank for refining, and the leaf filter cake with moisture content of 25-35% is transported to sintering method raw material mill and bayer process red mud, limestone, soda ash are prepared into raw slurry, and the raw slurry is adjusted to C / S for 1.93-1.99, N / R for 0.93-0.99, and then sintered into clinker at 1100-1200 DEG C in clinker kiln, and the clinker is dissolved, red mud is separated and washed, atmospheric desilication, seed fraction decomposition, calcination and other processes, to produce aluminum hydroxide or alumina.The method can make the dissolution rate of alumina in bayer process leaf filter cake reach more than 86%, and the dissolution rate of sodium oxide can reach more than 92%, the valuable material recovery rate is greatly improved, and the waste is turned into treasure, energy saving and emission reduction is realized.

Description

Technical Field

[0001] This invention relates to a method for the comprehensive utilization of resources from the Bayer process leaf filter cake of alumina, belonging to the field of alumina production technology. Background Technology

[0002] Currently, the main method for alumina production is the Bayer process, which involves leaching alumina from bauxite using caustic alkali under specific pressure and temperature. After dilution, red mud separation, and washing, the leached slurry yields a sodium aluminate solution (crude solution). This crude solution is then refined in a leaf filter to obtain the refined solution required for alumina production, ensuring product quality. During the leaf filter refining process, lime slurry is used as the medium for filtration. The lime slurry reacts with the sodium aluminate during filtration, causing some alumina loss from the solution, which enters the leaf filter cake. This leaf filter cake is backwashed with the refined solution and enters the cake filter tank. It is then pumped to the post-leaching dilution tank. After red mud separation and washing, the leaf filter cake is discharged along with the waste red mud to the red mud dump.

[0003] Current methods for processing Bayer process leaf filter cake typically involve transferring the Bayer leaf filter slurry to a leaching and dilution tank for liquid-solid separation of the sodium aluminate solution. This allows for the recovery of the sodium aluminate solution, but the Bayer leaf filter cake is discharged into the red mud dump along with the discarded red mud. The A / S ratio of the Bayer leaf filter cake is as high as 3.5-7.1, and the cake contains large amounts of valuable materials such as alumina, sodium oxide, and calcium hydroxide, resulting in resource waste. Another method involves transferring the Bayer leaf filter cake to a pre-desiliconization tank for re-leaching with adjusted raw ore slurry. This can replace some of the lime, and some alumina can be leached out. However, even under high-pressure leaching conditions, the leaching rate of tricalcium aluminate in the Bayer leaf filter cake is very low, and the valuable materials in the Bayer leaf filter cake cannot be largely recovered.

[0004] In the Bayer process for alumina production, approximately 0.6-0.8 tons of leaf filter cake are generated for every ton of alumina produced. The leaf filter cake contains approximately 24-30% alumina, 38-45% calcium oxide, 1.5-2.2% sodium oxide, 3.2-6.1% silicon dioxide, and 0.8-2.1% iron oxide, resulting in an A / S ratio as high as 3.5-7.1. Currently, alumina resources are becoming increasingly scarce, and valuable materials such as alumina, sodium oxide, and calcium oxide in the leaf filter cake should be extensively recycled and utilized. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the comprehensive utilization of resources from Bayer process leaf filter cake of alumina, in order to solve the technical problem that valuable materials in Bayer process leaf filter cake cannot be largely recycled and utilized, and can only be piled up with red mud, resulting in resource waste.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for the comprehensive utilization of resources from the recovery of alumina Bayer process leaf filter cake includes the following steps: S1. The leaf filter cake slurry produced during the Bayer process crude liquor refining process is transported to a deep cone settling tank for liquid-solid separation, increasing the solid content to 200-300 g / l. The overflow from the settling tank is returned to the Bayer process crude liquor tank for refining. S2. The underflow from the deep cone settling tank is filtered through a plate and frame filter press. The filtrate is returned to the Bayer process coarse liquid tank for refining to obtain a leaf filter cake with a moisture content of 25-35%. S3. The leaf filter cake is fed to the sintering process raw material mill and mixed with Bayer process red mud, limestone and soda ash to make raw meal slurry. The raw meal slurry is adjusted to C / S of 1.93-1.99 and N / R of 0.93-0.99. S4. The prepared raw material slurry is sprayed into the clinker kiln from the tail end of the clinker kiln through a spray gun and sintered into clinker at a temperature of 1100-1200℃. S5. The clinker is leached in a leaching mill using a washing solution with a caustic ratio ak of 1.15-1.25. After separation in a settling tank, the overflow is desilication under normal pressure and purified by leaf filtration to obtain a refined solution. The refined solution is then subjected to seed decomposition and calcination to obtain aluminum hydroxide or aluminum oxide products.

[0007] Furthermore, the chemical composition of the leaf filter cake, by dry weight percentage, is: 24-30% aluminum oxide, 38-45% calcium oxide, 1.5-2.2% sodium oxide, 3.2-6.1% silicon oxide, 0.8-2.1% iron oxide, with the balance being moisture and other impurities; the A / S ratio of the leaf filter cake is 3.5-7.1.

[0008] Furthermore, in step S3, the mass ratio of the Bayer red mud, leaf filter cake, limestone, and soda ash is 4:2:1:1 by dry weight.

[0009] Further, in step S4, the main components of the clinker are solid sodium aluminate, sodium ferrite and calcium orthosilicate, and the clinker has a C / S ratio of 1.93-1.99, an N / R ratio of 0.93-0.99, a bulk density of 1.15-1.35 kg / l and a particle size of 3-10 mm.

[0010] Furthermore, in step S5, the feed temperature of the leaching solution is 70-80℃, the feed L / S ratio of the leaching solution is 8-12, and the alumina concentration of the leaching solution is 100-115g / l.

[0011] Furthermore, in step S5, the atmospheric pressure desilication involves increasing the silicon content index of the sodium aluminate solution to over 300 while stirring with added seed crystals.

[0012] Furthermore, in step S5, the underflow from the separation settling tank is discharged after being washed seven times in reverse to recover the alumina and sodium oxide.

[0013] The beneficial effects of this invention are as follows: (1) The present invention uses Bayer process leaf filter cake as raw material for sintering. Through high-temperature sintering, the insoluble compounds such as tricalcium aluminate in the leaf filter cake are converted into soluble sodium aluminate and hydrolyzable sodium ferrite, which fundamentally solves the problem of low dissolution rate in the traditional high-pressure re-dissolution method. The alumina dissolution rate can reach more than 86%, the sodium oxide dissolution rate can reach more than 92%, and the recovery rate of valuable materials is greatly improved.

[0014] (2) The present invention adopts a two-stage liquid-solid separation pretreatment process of deep cone settling tank and plate and frame filter press. The leaf filter cake slurry with low solid content is first increased to 200-300 g / l by deep cone settling, and then the water content is reduced to 25-35% by plate and frame filter press, which creates conditions for subsequent sintering and batching. At the same time, the settling overflow and filter press filtrate are returned to the Bayer process coarse liquid tank for refining, maximizing the recovery of sodium aluminate solution.

[0015] (3) The filter cake of the leaf filter of the present invention contains a large amount of calcium oxide (38-45%), which can replace part of the limestone in the sintering batch, thus reducing the production cost.

[0016] (4) This invention realizes the comprehensive utilization of Bayer leaf filter cake resources, reduces red mud discharge, and achieves the purpose of turning waste into treasure, saving energy and reducing emissions, with significant economic and environmental benefits. Attached Figure Description

[0017] Appendix Figure 1 This is a schematic diagram of the process flow for the comprehensive utilization of resources from the Bayer process leaf filter cake of alumina, as provided in an embodiment of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0019] Example 1

[0020] A comprehensive resource utilization method for recovering alumina Bayer process leaf filter cake, with a process flow diagram as follows: Figure 1 As shown, the specific steps include: First, the Bayer process leaf filter cake slurry undergoes liquid-solid separation in a deep cone settling tank to increase the solid content to 200-300 g / L. Then, it is filtered by a plate and frame filter press, and the filtrate is returned to the Bayer process coarse liquid tank for refining.

[0021] Table 1. Composition of Bayer process leaf filter cake solution 179.27 168 1.54 56.77

[0022] Table 2 Chemical composition of Bayer Falch filter cake 6.13% 2.0% 24.20% 36.80% 1.62% 3.95

[0023] Leaf filter cake with a moisture content of approximately 30% is fed to a sintering process feed mill and mixed with Bayer process red mud, limestone, and soda ash to form a raw meal slurry. In this embodiment, Bayer process red mud, leaf filter cake, limestone, and soda ash are mixed and ground in a mass ratio of 4:2:1:1 to form a raw meal slurry (mass calculated by dry weight). The raw meal slurry ratio requires C / S 1.93-1.99 and N / R 0.93-0.99, and is then prepared into a raw meal slurry that meets the above ratio requirements through a slurry tank.

[0024] Table 3 Chemical composition of Bayer process red mud 18.90% 11.55% 24.00% 16.22% 10.94% 3.12% 1.27 Table 4 Chemical composition of limestone 1.10% 0.71% 0.90% 52.70% The raw meal slurry is injected into the clinker kiln from the tail end through three spray guns for clinker sintering. The clinker is sintered into clinker at a temperature of 1100-1200℃. The main components of the clinker are solid sodium aluminate, sodium ferrite, and calcium orthosilicate. Clinker quality requirements: C / S ratio 1.93-1.99, N / R ratio 0.93-0.99, bulk density 1.15-1.35 kg / l (particle size: 3-10 mm), and a grayish-black porous appearance.

[0025] Table 5 Chemical composition of clinker 14.96% 8.5% 23.8% 30.3% 18.16% 2.24% 1.59 The clinker is leached in a dissolving mill using a washing solution with a low caustic ratio (ak 1.15-1.25). During the clinker leaching process, sodium aluminate dissolves in the solution, sodium ferrite hydrolyzes to generate sodium oxide and Fe2O3·H2O solid precipitates, and most of the calcium orthosilicate remains in the red mud, except for a small amount that is decomposed by sodium hydroxide, sodium carbonate and sodium aluminate in the solution to allow silicon dioxide to enter the solution.

[0026] The leachate is pumped by a centrifugal pump to a settling tank for rapid separation. The settling separation technical requirements are as follows: leachate feed temperature: 70-80℃, leachate feed L / S: 8-12, leachate alumina concentration: 100-115g / l, underflow L / S: 3.0-4.5.

[0027] The overflow from the separation settling tank is sent to the desiliconization tank for atmospheric pressure desiliconization under stirring with added seed crystals. The silicon index of the sodium aluminate solution is increased to over 300. The crude liquid is then purified into sodium aluminate solution by passing it through a leaf filter. The suspended solids in the purified liquid do not exceed 0.015 g / L. After seed removal, decomposition, and calcination, the purified liquid can be used to produce aluminum hydroxide or alumina.

[0028] The underflow from the separation settling tank undergoes seven reverse washing cycles to recover alumina and sodium oxide. After the seven reverse washing cycles, the underflow is pumped by an oil separator pump to a red mud dump for damming.

[0029] Table 6. Composition of the washing solution 52.97 40 1.25 Table 7 Chemical composition of red mud after clinker leaching 21.98% 4.51% 44.8% 2.18% 87.2% 92.5% In this embodiment, after the Bayer process leaf filter cake is sintered and dissolved in the clinker kiln, the alumina dissolution rate in the leaf filter cake is 87.2% and the sodium oxide dissolution rate is 92.5%, which greatly improves the recovery rate of valuable materials and reduces red mud discharge.

[0030] This invention features stable technical performance, low operating costs, and is suitable for industrial application. A Bayer process alumina plant with an annual production capacity of 2 million tons produces approximately 140,000 tons of leaf filter cake annually, containing about 34,000 tons of alumina, 2,500 tons of sodium oxide, and 56,000 tons of calcium oxide. Through clinker sintering and leaching, assuming an alumina leaching rate of 86% and a sodium oxide leaching rate of 92%, approximately 29,000 tons of alumina, 2,300 tons of sodium oxide, and 56,000 tons of calcium oxide can be recovered annually. This improves resource utilization while achieving the goals of increasing production, reducing energy consumption, and reducing emissions.

[0031] Example 2 This embodiment shares the same basic process flow and raw material source as Embodiment 1, with the main process parameters as follows: In step S1, the solid content is increased to 200 g / L after liquid-solid separation in the deep cone settling tank.

[0032] In step S2, the moisture content of the filter cake after plate and frame filtration is 35%.

[0033] In step S3, Bayer red mud, leaf filter cake, limestone, and soda ash are mixed in a mass ratio of 4:2:1:1, and the raw slurry is adjusted to C / S 1.93 and N / R 0.93.

[0034] In step S4, the sintering temperature of the clinker kiln is 1100℃.

[0035] In step S5, the clinker is leached in a leaching mill using a washing solution with a caustic ratio of ak 1.15. The feed temperature of the leaching solution is 70℃, the feed rate of the leaching solution is 8 L / S, the alumina concentration of the leaching solution is 100 g / L, and the underflow rate is 3.0 L / S.

[0036] The remaining raw material composition and process steps are the same as in Example 1.

[0037] In this embodiment, the alumina dissolution rate in the leaf filter cake was 86.3%, and the sodium oxide dissolution rate was 91.6%.

[0038] Example 3 This embodiment shares the same basic process flow and raw material source as Embodiment 1, with the main process parameters as follows: In step S1, the solid content is increased to 300 g / L after liquid-solid separation in the deep cone settling tank.

[0039] In step S2, the moisture content of the filter cake after plate and frame filtration is 25%.

[0040] In step S3, Bayer red mud, leaf filter cake, limestone, and soda ash are mixed in a mass ratio of 4:2:1:1, and the raw slurry is adjusted to C / S 1.99 and N / R 0.99.

[0041] In step S4, the sintering temperature of the clinker kiln is 1200℃.

[0042] In step S5, the clinker is leached in a leaching mill using a washing solution with a caustic ratio of ak 1.25. The feed temperature of the leaching solution is 80℃, the feed rate of the leaching solution is 12 L / S, the alumina concentration of the leaching solution is 115 g / L, and the underflow rate is 4.5 L / S.

[0043] The remaining raw material composition and process steps are the same as in Example 1.

[0044] In this embodiment, the alumina dissolution rate in the leaf filter cake was 85.8%, and the sodium oxide dissolution rate was 91.4%.

[0045] Example 4 This embodiment has the same basic process flow and raw material source as Embodiment 1: In step S1, the solid content is increased to 250 g / L after liquid-solid separation in the deep cone settling tank.

[0046] In step S2, the moisture content of the filter cake after plate and frame filtration is 30%.

[0047] In step S3, Bayer red mud, leaf filter cake, limestone, and soda ash are mixed in a mass ratio of 4:2:1:1, and the raw slurry is adjusted to C / S 1.93 and N / R 0.93.

[0048] In step S4, the sintering temperature of the clinker kiln is 1100℃.

[0049] In step S5, the clinker is leached in a leaching mill using a washing solution with a caustic ratio of ak 1.25. The feed temperature of the leaching solution is 80℃, the feed rate of the leaching solution is 12 L / S, the alumina concentration of the leaching solution is 115 g / L, and the underflow rate is 4.5 L / S.

[0050] The remaining raw material composition and process steps are the same as in Example 1.

[0051] In this embodiment, although the sintering temperature is set to the lower limit of 1100°C, the leaching effect is enhanced by increasing the caustic solubility ratio and leaching temperature. The alumina leaching rate in the leaf filter cake is 87%, and the sodium oxide leaching rate is 92%.

[0052] Example 5 This embodiment has the same basic process flow and raw material source as Embodiment 1: In step S1, the solid content is increased to 250 g / L after liquid-solid separation in the deep cone settling tank.

[0053] In step S2, the moisture content of the filter cake after plate and frame filtration is 30%.

[0054] In step S3, Bayer red mud, leaf filter cake, limestone, and soda ash are mixed in a mass ratio of 4:2:1:1, and the raw slurry is adjusted to C / S 1.99 and N / R 0.99.

[0055] In step S4, the sintering temperature of the clinker kiln is 1200℃.

[0056] In step S5, the clinker is leached in a leaching mill using a washing solution with a caustic ratio of ak 1.15. The feed temperature of the leaching solution is 70℃, the feed rate of the leaching solution is 8 L / S, the alumina concentration of the leaching solution is 100 g / L, and the underflow rate is 3.0 L / S.

[0057] The remaining raw material composition and process steps are the same as in Example 1.

[0058] In this embodiment, the sintering temperature was set to the upper limit of 1200℃ to ensure more complete sintering of the clinker. Even with relatively mild leaching conditions, the alumina leaching rate in the leaf filter cake still reached 86.8%, and the sodium oxide leaching rate was 92.3%. This indicates that under conditions of high-temperature and complete sintering, even with a lower leaching caustic solubility ratio and feed temperature, a high leaching rate can still be obtained.

[0059] Comparative Example 1 The Bayer process leaf filter cake is treated using a high-pressure re-leaching method, which is an existing technology, without the batching and sintering process in steps S3-S4. Specifically, the leaf filter cake (pretreated by deep cone settling and plate and frame filtration) from the same source and composition as in Example 1 is transported to a pre-desilicon tank, mixed with the adjusted raw ore slurry, and then re-leached under high-pressure leaching conditions (leaching temperature 260℃, pressure 6MPa, leaching time 60min). After leaching, the slurry is diluted, red mud is separated and washed, and the sodium aluminate solution is recovered.

[0060] In Comparative Example 1, the alumina dissolution rate in the leaf filter cake was only about 35%, and the sodium oxide dissolution rate was only about 40%. This is because the alumina in the Bayer process leaf filter cake mainly exists in the form of tricalcium aluminate (3CaO·Al2O3), which is difficult to dissolve effectively even under alkaline conditions and high temperature and pressure. However, this invention converts tricalcium aluminate into soluble solid sodium aluminate at a high temperature of 1100-1200℃ through a sintering method, fundamentally changing the phase composition and thus significantly improving the dissolution rate.

[0061] Comparative Example 2 The difference between this comparative example and Example 1 is that the deep cone settling and plate and frame filter press pretreatment processes in steps S1 and S2 are omitted. The leaf filter cake slurry (with a solid content of only 56.77 g / L, i.e., extremely high water content) is directly transported to the sintering process feed mill without pretreatment and is mixed with Bayer red mud, limestone, and soda ash. The remaining sintering and leaching process parameters are the same as in Example 1.

[0062] In Comparative Example 2, due to the excessively low solid content of the leaf filter cake slurry, a large amount of water was introduced during batching, resulting in a raw slurry moisture content far exceeding normal requirements. This severely affected the mixing accuracy and uniformity of the raw slurry. The excessive water evaporated in the clinker kiln, consuming a large amount of heat energy, making it difficult to maintain a stable sintering temperature of 1100-1200℃. Simultaneously, the large amount of water evaporation caused large local temperature fluctuations within the clinker kiln, leading to uneven clinker sintering, insufficient sintering of some materials, and incomplete reactions. Ultimately, the alumina dissolution rate in the leaf filter cake was only about 73.5%, and the sodium oxide dissolution rate was only about 81.2%, with significantly increased energy consumption and poor economic efficiency during production.

[0063] Comparative Example 3 The only difference between this comparative example and Example 1 is that in step S4, the clinker kiln sintering temperature is 1050℃ (lower than the lower limit of the 1100-1200℃ range specified in this invention). The remaining raw material composition and process steps are exactly the same as in Example 1.

[0064] In Comparative Example 3, because the sintering temperature was 1050℃, which is lower than the minimum temperature required for the complete formation of sodium aluminate and sodium ferrite, the clinker was not fully sintered. Tricalcium aluminate was not completely converted into sodium aluminate, and sodium ferrite formation was also incomplete. The clinker was yellowish in appearance, mostly powdery, with a bulk density of only 0.95 kg / l, far below the requirement of 1.15-1.35 kg / l for normal clinker. The alumina dissolution rate in the leaf filter cake was only about 68.4%, and the sodium oxide dissolution rate was only about 72.9%, significantly lower than the results of Examples 1-3 in the range of 1100-1200℃, indicating that 1100℃ is the critical temperature for ensuring complete sintering of the clinker.

[0065] The results of the above embodiments and comparative examples are summarized as follows: Table 8 Comparison of effects of each embodiment and comparative example Example 1 87.2 92.5 Example 2 86.3 91.6 Example 3 85.8 91.4 Example 4 87 92 Example 5 86.8 92.3 Comparative Example 1 35 40 Comparative Example 2 73.5 81.2 Comparative Example 3 68.4 72.9 As shown in Table 8, in Examples 1-5 using the method of the present invention, within the process parameter range defined by the present invention, the alumina dissolution rate all reached over 86%, and the sodium oxide dissolution rate all reached over 92%, demonstrating stable results. Examples 4 and 5 respectively employed a combination of low-temperature sintering with strong dissolution conditions and high-temperature sintering with mild dissolution conditions, indicating that different combinations within the process parameter range of the present invention can achieve good results, demonstrating strong process adaptability.

[0066] Comparative Example 1 uses the existing high-pressure re-dissolution method without sintering, and the alumina dissolution rate is only about 35%, which is much lower than that of the embodiment of the present invention. This proves that the sintering method is the key to achieving a large-scale recovery of valuable materials in the leaf filter cake.

[0067] Comparative Example 2 omitted the two-stage pretreatment process of deep cone sedimentation and plate and frame filter press. The direct batching of low solid content slurry resulted in excessively high moisture content in the raw slurry, uneven sintering, an alumina dissolution rate of 73.5%, and a significant increase in energy consumption. This demonstrates the necessity of the two-stage pretreatment process to ensure the subsequent sintering effect.

[0068] The sintering temperature of Comparative Example 3 (1050℃) is lower than the lower limit of 1100℃ of the range defined in this invention, and the alumina dissolution rate is only about 68.4%, indicating that the sintering temperature range of 1100-1200℃ is the key parameter range to ensure the full sintering of clinker and achieve a high dissolution rate.

Claims

1. A method for the comprehensive utilization of resources from alumina Bayer process leaf filter cake, characterized in that, Includes the following steps: S1. The leaf filter cake slurry produced during the Bayer process crude liquor refining process is transported to a deep cone settling tank for liquid-solid separation, increasing the solid content to 200-300 g / l. The overflow from the settling tank is returned to the Bayer process crude liquor tank for refining. S2. The underflow from the deep cone settling tank is filtered through a plate and frame filter press. The filtrate is returned to the Bayer process coarse liquid tank for refining to obtain a leaf filter cake with a moisture content of 25-35%. S3. The leaf filter cake is fed to the sintering process raw material mill and mixed with Bayer process red mud, limestone and soda ash to make raw meal slurry. The raw meal slurry is adjusted to C / S of 1.93-1.99 and N / R of 0.93-0.

99. S4. The prepared raw material slurry is sprayed into the clinker kiln from the tail end of the clinker kiln through a spray gun and sintered into clinker at a temperature of 1100-1200℃. S5. The clinker is leached in a leaching mill using a washing solution with a caustic ratio ak of 1.15-1.

25. After separation in a settling tank, the overflow is desilication under normal pressure and purified by leaf filtration to obtain a refined solution. The refined solution is then subjected to seed decomposition and calcination to obtain aluminum hydroxide or aluminum oxide products.

2. The method for comprehensive resource utilization of alumina Bayer process leaf filter cake according to claim 1, characterized in that, The chemical composition of the leaf filter cake, by dry weight percentage, is: 24-30% aluminum oxide, 38-45% calcium oxide, 1.5-2.2% sodium oxide, 3.2-6.1% silicon oxide, 0.8-2.1% iron oxide, with the balance being moisture and other impurities; the A / S ratio of the leaf filter cake is 3.5-7.

1.

3. The method for comprehensive resource utilization of alumina Bayer process leaf filter cake according to claim 1, characterized in that, In step S3, the mass ratio of the Bayer red mud, leaf filter cake, limestone, and soda ash is 4:2:1:1 by dry weight.

4. The method for comprehensive resource utilization of alumina Bayer process leaf filter cake according to claim 1, characterized in that, In step S4, the main components of the clinker are solid sodium aluminate, sodium ferrite and calcium orthosilicate. The clinker has a C / S ratio of 1.93-1.99, an N / R ratio of 0.93-0.99, a bulk density of 1.15-1.35 kg / l and a particle size of 3-10 mm.

5. The method for comprehensive resource utilization of alumina Bayer process leaf filter cake according to claim 1, characterized in that, In step S5, the feed temperature of the leaching solution is 70-80℃, the feed L / S ratio of the leaching solution is 8-12, and the alumina concentration of the leaching solution is 100-115g / l.

6. The method for comprehensive resource utilization of alumina Bayer process leaf filter cake according to claim 1, characterized in that, In step S5, the atmospheric pressure desilication involves increasing the silicon content index of the sodium aluminate solution to over 300 under stirring with added seed crystals.

7. The method for comprehensive resource utilization of alumina Bayer process leaf filter cake according to claim 1, characterized in that, In step S5, the underflow from the separation settling tank is discharged after being washed seven times in reverse to recover the alumina and sodium oxide.

8. The method for comprehensive resource utilization of alumina Bayer process leaf filter cake according to claim 1, characterized in that, After step S5, the alumina leaching rate in the leaf filter cake is ≥86%, and the sodium oxide leaching rate is ≥92%.

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