CN111573699A - Method for removing sodium oxalate in production process of aluminum oxide - Google Patents
Method for removing sodium oxalate in production process of aluminum oxide Download PDFInfo
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- CN111573699A CN111573699A CN202010438917.5A CN202010438917A CN111573699A CN 111573699 A CN111573699 A CN 111573699A CN 202010438917 A CN202010438917 A CN 202010438917A CN 111573699 A CN111573699 A CN 111573699A
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- sodium oxalate
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/021—After-treatment of oxides or hydroxides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
Abstract
The invention relates to a method for removing sodium oxalate in the production process of alumina, which comprises the following steps: washing and filtering aluminum hydroxide containing crystallized sodium oxalate by using soft water to obtain finished aluminum hydroxide and first filtrate, conveying the first filtrate to a washing tank with a heat preservation device, and adding seed crystal aluminum hydroxide into the washing tank; washing the seed crystal aluminum hydroxide by using the first filtrate under the stirring condition, and filtering to obtain washed seed crystal aluminum hydroxide and second filtrate; conveying the washed seed crystal aluminum hydroxide to a seed crystal decomposition system, and conveying the second filtrate to a sodium oxalate crystallization tank with a cooling device; adding sodium hydroxide into a sodium oxalate crystallization tank with a temperature reduction device, cooling, stirring to obtain slurry containing sodium oxalate crystals, and filtering to obtain caustic alkali filtrate and solid sodium oxalate. The method can reduce the accumulation of sodium oxalate in the sodium aluminate solution, effectively reduce the influence degree of the sodium oxalate on the production process, and is favorable for the smooth production by the Bayer process and the improvement of the product quality.
Description
Technical Field
The invention belongs to the technical field of alumina production, and particularly relates to a method for removing sodium oxalate in an alumina production process.
Background
At present, more than 95 percent of the alumina yield in China is produced by adopting a Bayer process, and along with the reduction of the ore grade in China and the great improvement of the use proportion of imported ores, the adverse effect of organic matters in the ores on the production is increasingly prominent. The organic matters are divided into two categories of humic acid and asphalt, and the asphalt in the bauxite is insoluble in an alkaline solution and is discharged out of a production system along with the red mud. The organic matter of humic acid reacts with alkali to generate various sodium humate, and then gradually changes into low molecular weight organic compounds such as sodium oxalate and sodium carbonate. In the circulation process of the sodium aluminate solution, sodium oxalate can be rapidly accumulated, so that the concentration of the sodium oxalate in the solution is rapidly increased, the production of alumina is obviously influenced, mainly in the decomposition process of seed precipitation, due to the reduction of temperature, the sodium oxalate and aluminum hydroxide are crystallized together, the agglomeration of aluminum hydroxide crystals is prevented, the grain refining phenomenon is facilitated, the strength of the crystals is reduced in the roasting process, and a series of adverse effects are brought to the aspects of production, maintenance, yield, quality and the like of products.
In order to eliminate the harm of sodium oxalate in industrial sodium aluminate solution to alumina production, a great deal of research is carried out on the mechanism and method for removing sodium oxalate in the alumina production process at home and abroad, and various control and removal methods are provided, mainly comprising the following steps: crystallization, seed washing, organic oxidation, adsorption, solution combustion, and the like. The crystallization method is to carry out some pretreatments on sodium aluminate solution to reduce the stability of sodium oxalate in the solution, usually, the solution is evaporated, concentrated or cooled to crystallize sodium oxalate, or proper crystal seeds are added to promote sodium oxalate to crystallize and separate out from the solution, so as to achieve the purpose of removing sodium oxalate from the solution. The solution combustion method has higher energy consumption and production and application cost; the adsorption method can only remove certain specific organic matters to reduce the critical concentration of the sodium oxalate, but has no removal effect on the sodium oxalate; the chemical precipitation method is widely applied, mainly utilizes lime milk for causticization, and can effectively remove sodium oxalate in the sodium aluminate solution, but can cause the loss of alumina, so the method is only limited to treating the solution with low alkali concentration and has less application; the crystallization method has the advantages of low energy consumption, less equipment investment and lower production and application cost.
Of the various methods for controlling and removing sodium oxalate, only the seed crystal washing method, the crystallization method and the oxidation method are industrially applied, and the other methods are difficult to industrially apply due to the complex process flow, high cost, poor sodium oxalate removal effect and the like. The seed crystal washing method has the defects that the washing water amount is large, and the evaporation burden is increased; the mother liquor concentration crystallization in the crystallization method is difficult to realize solid-liquid separation, while the seed crystal of the seed crystal crystallization method is easy to lose activity, and the regeneration treatment or preparation leads to the complication of the process; although the organic matter oxidation method has good sodium oxalate removal effect, a great potential safety hazard exists in the use process.
Disclosure of Invention
The invention aims to provide an economic, simple, effective and easily-realized method for removing sodium oxalate in sodium aluminate solution in the alumina production process aiming at the defects of the technology.
The purpose of the invention is realized by the following technical scheme.
A method for removing sodium oxalate in the production process of alumina is characterized by comprising the following steps:
(1) washing and filtering aluminum hydroxide containing crystallized sodium oxalate by soft water at 50-100 ℃ to obtain finished aluminum hydroxide and first filtrate, and conveying the first filtrate to a washing tank with a heat preservation device;
(2) adding seed crystal aluminum hydroxide into the washing tank with the heat preservation device in the step (1), washing the seed crystal aluminum hydroxide by using the first filtrate under the stirring condition, and filtering to obtain washed seed crystal aluminum hydroxide and second filtrate;
(3) conveying the washed seed crystal aluminum hydroxide to a seed crystal decomposition system, and conveying the second filtrate to a sodium oxalate crystallization tank with a cooling device;
(4) adding sodium hydroxide into a sodium oxalate crystallization tank with a cooling device to obtain a mixed material;
(5) cooling the mixed material and stirring to obtain slurry containing sodium oxalate crystals;
(6) the slurry containing sodium oxalate crystals was filtered to obtain a caustic filtrate and solid sodium oxalate.
The method for removing sodium oxalate in the production process of alumina is characterized in that the temperature of the first filtrate for washing the seed crystal aluminum hydroxide in the step (2) is 40-90 ℃.
The method for removing sodium oxalate in the production process of alumina is characterized in that the seed crystal aluminum hydroxide is mixed with the first filtrate in the step (2), and the solid content of the seed crystal aluminum hydroxide is 800 g/L-1500 g/L.
The method for removing sodium oxalate in the production process of alumina is characterized in that the process conditions of washing the seed crystal aluminum hydroxide by using the first filtrate under the stirring condition in the step (2) are as follows: the washing temperature is 40-90 ℃, the washing time is 10-60 min, and the stirring speed is 100-150 r/min.
The method for removing the sodium oxalate in the production process of the alumina is characterized in that Na in the mixed material in the step (4)2OkThe concentration is 200 g/L-400 g/L.
The method for removing sodium oxalate in the production process of alumina is characterized in that the mixed material is cooled to 40-60 ℃ in the step (5), and then stirred for 50-200 min to obtain slurry containing sodium oxalate crystals.
The invention has the beneficial technical effects that: the method is realized by using the product aluminum hydroxide washing liquid sent to an evaporation system under the conventional production condition to wash seed crystal aluminum hydroxide which is not washed under the conventional production condition, leading the crystallized sodium oxalate attached to the surface of the seed crystal aluminum hydroxide and the sodium oxalate contained in the attached liquid to enter the washing liquid, and removing the seed crystal aluminum hydroxide out of the production system by improving the alkali concentration of the seed crystal washing liquid and reducing the temperature of the solution to promote the crystallization of the sodium oxalate. The method is particularly suitable for removing impurity sodium oxalate in sodium aluminate solution when the sodium oxalate content is higher in the process of producing alumina by a Bayer process.
In a washing system for producing a product aluminum hydroxide from aluminum oxide, the temperature of washing water is generally not lower than 95 ℃, so that crystalline sodium oxalate attached to the surface of the unwashed product aluminum hydroxide and sodium oxalate contained in an attached solution enter washing liquid after washing, and the washing liquid contains sodium oxalate with a certain concentration. Meanwhile, the crystal seeds are not washed by new water independently, so that water resources can be saved, the distilled water amount of the water can be reduced, and the energy consumption of evaporation is reduced. The activity of the crystal seeds is increased after washing, the decomposition of the sodium aluminate solution can be strengthened, the decomposition rate is improved, and the particle size distribution of the aluminum hydroxide product is optimized. The invention uses the circulating water of the alumina plant as the cooling medium of the solution with high caustic alkali concentration, and the cooling cost of the solution is low. Filtering and separating the slurry containing sodium oxalate crystals to obtain a solution with high caustic alkali and low sodium oxalate content, directly sending the solution to an evaporation system, mixing the solution with mother liquor, and taking the mixture after the solution is qualified as circulating mother liquor to dissolve out the next batch of ores.
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FIG. 1 is a schematic process flow diagram of the present invention.
Detailed Description
Referring to fig. 1, the method for removing sodium oxalate in the production process of alumina of the present invention comprises the following steps: (1) filtering and separating the aluminum hydroxide containing the crystallized sodium oxalate, washing with soft water at 50-100 ℃, filtering to obtain a filter cake finished product aluminum hydroxide and a first filtrate, and pumping the first filtrate into a washing tank with a heat preservation device by a pump. The aluminum hydroxide containing crystalline sodium oxalate comes from a seed precipitation system and has a coarser particle size. (2) Adding seed crystal aluminum hydroxide into a washing tank with a heat preservation device in the step (1), washing the seed crystal aluminum hydroxide by using the first filtrate under the stirring condition, and filtering to obtain washed seed crystal aluminum hydroxide and second filtrate, namely crystalThe content of-45 mu m particles in the seed aluminum hydroxide is 30-40%, the washed seed aluminum hydroxide is taken as seed crystal and conveyed to a main process seed crystal decomposition system, and the temperature of the first filtrate for washing the seed aluminum hydroxide is 40-90 ℃. And mixing the seed crystal aluminum hydroxide with the first filtrate, wherein the solid content of the seed crystal aluminum hydroxide is 800-1500 g/L. The process conditions for washing the seed crystal aluminum hydroxide by the first filtrate under the stirring condition are as follows: the washing temperature is 40-90 ℃, the washing time is 10-60 min, and the stirring speed is 100-150 r/min. (3) And conveying the washed seed crystal aluminum hydroxide to a seed crystal decomposition system, conveying the second filtrate to a sodium oxalate crystallization tank with a temperature reduction device, and increasing the caustic alkali concentration of the solution. (4) Adding sodium hydroxide into a sodium oxalate crystallization tank with a cooling device to obtain a mixed material, wherein the mixed material is a sodium aluminate solution with high caustic alkali and high sodium oxalate content; na in the mixed material2OkThe concentration is 200 g/L-400 g/L. The added sodium hydroxide is solid or liquid alkali. (5) Cooling the mixed material by using circulating water, stirring, and promoting sodium oxalate to crystallize and separate out to obtain slurry containing sodium oxalate crystals; preferably, the mixed material is cooled to 40-60 ℃, stirred and crystallized for 50-200 min, and slurry containing sodium oxalate crystals is obtained. (6) Filtering the slurry containing sodium oxalate crystals by using a vacuum filter and then separating to obtain filtrate, namely the sodium aluminate filtrate with high caustic alkali and low sodium oxalate content. And directly sending the filtrate to an evaporation system of a main flow of a Bayer process, blending the filtrate with evaporation mother liquor, sending the filtrate serving as circulating mother liquor to a wet grinding ingredient after the concentration is qualified, dissolving out the next batch of ore, adding lime milk to causticize and recover caustic alkali after the filter cake is dissolved by hot water, or directly discarding the filter cake.
Example 1
Filtering and separating aluminum hydroxide containing crystallized sodium oxalate, washing with soft water at 50 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 30 percent (minus 45 mu m) with the first filtrate at the temperature of 40 ℃ under the condition of stirring rotation speed of 120r/min for 10min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 1500g/L, and adding sodium hydroxide into the second filtrate to obtain a mixtureMaterials, mixing Na in the materials2OkAnd when the concentration reaches 200g/L, cooling the mixed material to 40 ℃, stirring and crystallizing for 50min at the stirring speed of 100r/min to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 5.4 g/L.
Example 2
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with soft water at 100 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 40% of minus 45 mu m with the first filtrate at the temperature of 90 ℃ under the condition of stirring rotation speed of 120r/min for 60min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 1200g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkAnd when the concentration reaches 400g/L, cooling the mixed material to 40 ℃, stirring and crystallizing for 200min at the stirring speed of 120r/min to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 10.8 g/L.
Example 3
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with soft water at 70 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 35 percent (45 mu m) with the first filtrate at 60 ℃ under the condition of stirring at the rotating speed of 120r/min for 30min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 800g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkAnd when the concentration reaches 350g/L, cooling the mixed material to 40 ℃, stirring and crystallizing for 150min at the stirring speed of 150r/min to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 6.8 g/L.
Example 4
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with soft water at 95 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 35 percent (45 mu m) with the first filtrate at 85 ℃ under the condition of stirring at the rotating speed of 120r/min for 20min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 1000g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkAnd when the concentration reaches 400g/L, cooling the mixed material to 60 ℃, stirring and crystallizing for 100min at the stirring speed of 120r/min to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 6.5 g/L.
Example 5
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with soft water at 80 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 35 percent (45 mu m) with the first filtrate at 70 ℃ under the condition of stirring at the rotating speed of 120r/min for 50min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 1000g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkConcentration ofAnd cooling the mixed material to 50 ℃ and stirring and crystallizing for 200min when the concentration reaches 350g/L, wherein the stirring speed is 120r/min, so as to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. After the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 7.2 g/L.
Example 6
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with soft water at 95 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 35 percent (45 mu m) with the first filtrate at 85 ℃ under the condition of stirring at the rotating speed of 120r/min for 40min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 1300g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkAnd when the concentration reaches 300g/L, cooling the mixed material to 45 ℃, stirring and crystallizing for 120min at the stirring speed of 130r/min to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 9.5 g/L.
Example 7
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with soft water at 100 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 36 percent (45 mu m) with the first filtrate at the temperature of 90 ℃ under the condition of stirring rotation speed of 120r/min for 20min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 1500g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkThe concentration reaches 2000g/L, and the mixture is mixedAnd cooling the material to 55 ℃, stirring and crystallizing for 120min, wherein the stirring speed is 120r/min, and obtaining slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 8.9 g/L.
Example 8
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with soft water at 95 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 35 percent (45 mu m) with the first filtrate at 85 ℃ under the condition of stirring at the rotating speed of 120r/min for 60min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 800g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkAnd when the concentration reaches 250g/L, cooling the mixed material to 50 ℃, and stirring and crystallizing for 80min at the stirring speed of 120r/min to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 5.3 g/L.
Example 9
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with 90 ℃ soft water, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing with 80 ℃ first filtrate at the condition of stirring speed of 120r/min to obtain 35% crystal seed aluminum hydroxide with the content of minus 45 mu m for 30min, filtering to obtain second filtrate, wherein the adding amount of the crystal seed aluminum hydroxide is 800g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkThe concentration reaches 300g/L, and then the mixed material is cooled to 40 ℃ and stirredCrystallizing for 150min, and stirring at 130r/min to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 6.2 g/L.
Example 10
Filtering and separating aluminum hydroxide containing crystalline sodium oxalate, washing with soft water at 95 ℃, filtering to obtain filter cake finished product aluminum hydroxide and first filtrate, washing seed crystal aluminum hydroxide with the content of 36 percent (45 mu m) with the first filtrate at 85 ℃ under the condition of stirring at the rotating speed of 120r/min for 40min, filtering to obtain second filtrate, wherein the addition amount of the seed crystal aluminum hydroxide is 1500g/L, adding sodium hydroxide into the second filtrate to obtain a mixed material, and enabling Na in the mixed material to be2OkAnd when the concentration reaches 400g/L, cooling the mixed material to 50 ℃, stirring and crystallizing for 180min at the stirring speed of 120r/min to obtain slurry containing sodium oxalate crystals. Filtering the serous fluid containing the sodium oxalate crystals to obtain filtrate and filter cakes, and directly sending the filtrate after removing the sodium oxalate to an evaporation system of a main flow of a Bayer process. The filter cake is solid sodium oxalate, and the filter cake is dissolved by hot water and then sent to a causticization procedure to recover caustic alkali or directly discarded. Through the treatment, the content of sodium oxalate in the solution returned to the main production flow of the Bayer process is reduced by 9.3 g/L.
Claims (6)
1. A method for removing sodium oxalate in the production process of alumina is characterized by comprising the following steps:
(1) washing and filtering aluminum hydroxide containing crystallized sodium oxalate by soft water at 50-100 ℃ to obtain finished aluminum hydroxide and first filtrate, and conveying the first filtrate to a washing tank with a heat preservation device;
(2) adding seed crystal aluminum hydroxide into the washing tank with the heat preservation device in the step (1), washing the seed crystal aluminum hydroxide by using the first filtrate under the stirring condition, and filtering to obtain washed seed crystal aluminum hydroxide and second filtrate;
(3) conveying the washed seed crystal aluminum hydroxide to a seed crystal decomposition system, and conveying the second filtrate to a sodium oxalate crystallization tank with a cooling device;
(4) adding sodium hydroxide into a sodium oxalate crystallization tank with a cooling device to obtain a mixed material;
(5) cooling the mixed material and stirring to obtain slurry containing sodium oxalate crystals;
(6) the slurry containing sodium oxalate crystals was filtered to obtain a caustic filtrate and solid sodium oxalate.
2. The method for removing sodium oxalate in the production process of aluminum oxide according to claim 1, wherein the temperature of the first filtrate for washing the seed aluminum hydroxide in the step (2) is 40 ℃ to 90 ℃.
3. The method for removing sodium oxalate in the production process of aluminum oxide according to claim 1, wherein the seed crystal aluminum hydroxide is mixed with the first filtrate in the step (2), and the solid content of the seed crystal aluminum hydroxide is 800 g/L-1500 g/L.
4. The method for removing sodium oxalate in the production process of aluminum oxide according to claim 1, wherein the process conditions for washing the seed crystal aluminum hydroxide with the first filtrate under stirring in the step (2) are as follows: the washing temperature is 40-90 ℃, the washing time is 10-60 min, and the stirring speed is 100-150 r/min.
5. The method for removing sodium oxalate in the production process of alumina as claimed in claim 1, wherein Na in the mixed material in the step (4)2OkThe concentration is 200 g/L-400 g/L.
6. The method for removing sodium oxalate in the production process of aluminum oxide according to claim 1, wherein the mixed material is cooled to 40-60 ℃ and then stirred for 50-200 min in the step (5), so as to obtain slurry containing sodium oxalate crystals.
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| CN112939040A (en) * | 2021-03-31 | 2021-06-11 | 中铝集团山西交口兴华科技股份有限公司 | Method for removing sodium oxalate in production process of alumina and fine alumina |
| CN116640936A (en) * | 2023-05-25 | 2023-08-25 | 中铝郑州有色金属研究院有限公司 | Method for producing high-grade vanadium concentrate |
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| CN101575111A (en) * | 2008-05-08 | 2009-11-11 | 沈阳铝镁设计研究院 | System and method for removing oxalate in sodium aluminate solution |
| CN105480994A (en) * | 2014-09-18 | 2016-04-13 | 沈阳铝镁设计研究院有限公司 | Efficient method for enriching oxalate through washing of fine seeds |
| CN105668598A (en) * | 2016-01-19 | 2016-06-15 | 中国铝业股份有限公司 | Method for removing sodium oxalate during aluminum oxide production process |
| CN107572570A (en) * | 2017-09-15 | 2018-01-12 | 臧海伟 | A kind of method that oxalates is removed in the washing lotion from Bayer process |
| CN108002415A (en) * | 2017-12-06 | 2018-05-08 | 中国铝业股份有限公司 | The processing method of the crystal of sodium oxalate is removed in aluminum oxide production process |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112939040A (en) * | 2021-03-31 | 2021-06-11 | 中铝集团山西交口兴华科技股份有限公司 | Method for removing sodium oxalate in production process of alumina and fine alumina |
| CN116640936A (en) * | 2023-05-25 | 2023-08-25 | 中铝郑州有色金属研究院有限公司 | Method for producing high-grade vanadium concentrate |
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