CN113651346B - Purification method of sodium aluminate solution in alumina production process - Google Patents
Purification method of sodium aluminate solution in alumina production process Download PDFInfo
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- CN113651346B CN113651346B CN202111086684.8A CN202111086684A CN113651346B CN 113651346 B CN113651346 B CN 113651346B CN 202111086684 A CN202111086684 A CN 202111086684A CN 113651346 B CN113651346 B CN 113651346B
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- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
Abstract
The application particularly relates to a method for purifying sodium aluminate solution in the production process of aluminum oxide, which belongs to the technical field of aluminum oxide production and comprises the following steps: delivering the sodium aluminate solution to be purified and the diffusion solution into a cation exchange membrane diffusion dialysis device for treatment to obtain a sodium aluminate solution with high impurity concentration and a sodium aluminate solution with low impurity concentration; evaporating and filtering the sodium aluminate solution with high impurity concentration to obtain a crystallized and filtered sodium aluminate solution; recycling the sodium aluminate solution with low impurity concentration and the filtered sodium aluminate solution; the sodium oxalate and sodium carbonate in the Bayer process evaporation mother liquor or seed precipitation mother liquor sodium aluminate solution are treated by adopting a cation exchange membrane diffusion dialysis method, and under certain technological conditions, the sodium oxalate and sodium carbonate in the sodium aluminate solution can be efficiently separated and removed without electrifying or introducing other impurity components, and the flow is simple.
Description
Technical Field
The application belongs to the technical field of alumina production, and particularly relates to a method for purifying sodium aluminate solution in the alumina production process.
Background
With the rapid development of the alumina industry in China, the grade of domestic bauxite is reduced, the impurity content is increased, and the carbon content in the ore is obviously increased. In the process of producing alumina by the Bayer process, carbon-containing minerals in ores enter a solution in the leaching process, and the concentration of oxalate and carbonate in a production system is increased after long-term accumulation, so that the production is adversely affected.
The oxalate content of the system is increased, sodium oxalate and aluminum hydroxide are crystallized and separated out together in the process of crystal seed decomposition, so that the granularity of an aluminum hydroxide product is thinned, the decomposition rate is reduced, the vertical disc is difficult to filter, the sodium oxide content in the product alumina is increased, and the quality of the alumina product is reduced; and the decomposition tank collapses in severe cases, which affects normal production. The process for removing sodium oxalate from bayer process liquors mainly comprises: solution combustion, crystallization, precipitation, seed washing, neutralization with seawater, etc. However, the solution combustion method has higher energy consumption and more heat loss, needs to add solution roasting equipment and carbon dioxide waste gas treatment equipment, and has high investment cost in factory construction; the evaporation process of the crystallization method consumes energy, and the removal efficiency is low; lime is needed to be used for removing oxalate by a precipitation method, the lime consumption is large, the utilization rate is low, alumina loss can be caused, and trace calcium impurities enter a product to reduce the purity of the product; the neutralization method of seed washing and seawater occupies a large area, and the method needs to take the temporary seawater as a basic condition.
The carbon alkali content of the system is increased, so that the discharge is not smooth in the flash evaporation process of the dissolved pulp, and the dissolved steam consumption is increased; the forced effect salt discharge pressure in the evaporation process is increased, so that the evaporation steam consumption is increased, the forced effect is precipitated due to crystallization of carbon alkali, the evaporation capacity is rapidly attenuated, and the cleaning period is greatly shortened; the viscosity of the slurry in the production system is increased, and the electricity consumption for conveying slurry materials is increased; the increased viscosity of the sodium aluminate solution results in a decrease in the decomposition rate and a decrease in the alumina yield. The method for removing the carbon alkali from the production system mainly comprises high-concentration evaporation crystallization salt removal, red mud washing liquid causticizing salt removal, barium salt causticizing salt removal and the like. However, the high-concentration evaporation crystallization salt removal operation cost is high, the evaporation capacity is affected, and long-time operation is not facilitated; the causticizing method of the red mud washing liquid has slow effect of removing sodium carbonate and can cause alumina loss; ba (OH) used for discharging salt by barium salt causticization method 2 And the BaO has high price and high use cost, and meanwhile, the regeneration and recovery construction investment of the barium salt is high and the environment is easy to pollute.
Therefore, how to remove oxalate and carbonate of a production system more simply and efficiently and reduce the adverse effect on production is always a technical problem which plagues the Bayer process for producing alumina.
Disclosure of Invention
The application aims to provide a purification method of sodium aluminate solution in the production process of alumina, so as to simply and efficiently remove oxalate and carbonate of a production system and reduce the adverse effect on production.
The embodiment of the application provides a method for purifying sodium aluminate solution in the production process of alumina, which comprises the following steps:
delivering the sodium aluminate solution to be purified and the diffusion solution into a cation exchange membrane diffusion dialysis device for treatment to obtain a sodium aluminate solution with high impurity concentration and a sodium aluminate solution with low impurity concentration;
evaporating and filtering the sodium aluminate solution with high impurity concentration to obtain a crystallized and filtered sodium aluminate solution;
recycling the low impurity concentration sodium aluminate solution and the filtered sodium aluminate solution;
wherein, the volume ratio of the sodium aluminate solution to be purified and the diffusion solution to be purified to the cation exchange membrane diffusion dialysis device is 1:1-2.5, the sodium aluminate solution to be purified and the diffusion liquid flow reversely.
Optionally, the sodium aluminate solution to be purified is evaporation mother liquor or seed precipitation mother liquor in the Bayer process flow.
Optionally, the evaporation mother liquor has a caustic concentration N k From 220g/L to 280g/L, the caustic ratio alpha of the evaporation mother liquor k ＞2.60。
Optionally, the caustic concentration N of the seed separation mother liquor k The caustic ratio alpha of the seed precipitation mother liquor is 140g/L to 180g/L k ＞2.60。
Optionally, the diffusion solution comprises a pan wash, a red mud wash, or water in a bayer process flow.
Optionally, the caustic concentration N of the flat-bed washing liquid and the red mud washing liquid k The caustic ratio alpha of the flat-bed washing liquid and the red mud washing liquid is 10g/L to 50g/L k ＞2.60。
Optionally, the use temperature of the cation exchange membrane is 20-80 ℃.
Optionally, the caustic ratio alpha of the sodium aluminate solution with high impurity concentration k From 1.5 to 2.0, the caustic ratio alpha of the sodium aluminate solution with low impurity concentration k ＞5.0。
Optionally, the method includes: and recycling the sodium aluminate solution with low impurity concentration to a Bayer process digestion system.
Optionally, the method includes: and recycling the filtered sodium aluminate solution to a Bayer process seed precipitation procedure for seed crystal decomposition.
One or more technical solutions in the embodiments of the present application at least have the following technical effects or advantages:
the method for purifying the sodium aluminate solution in the alumina production process provided by the embodiment of the application comprises the following steps: delivering the sodium aluminate solution to be purified and the diffusion solution into a cation exchange membrane diffusion dialysis device for treatment to obtain a sodium aluminate solution with high impurity concentration and a sodium aluminate solution with low impurity concentration; evaporating and filtering the sodium aluminate solution with high impurity concentration to obtain a crystallized and filtered sodium aluminate solution; recycling the low impurity concentration sodium aluminate solution and the filtered sodium aluminate solution; the volume ratio of the sodium aluminate solution to be purified and the diffusion solution to be sent into the cation exchange membrane diffusion dialysis device is 1:1-2.5, the sodium aluminate solution to be purified and the diffusion liquid flow reversely; the sodium oxalate and sodium carbonate in the Bayer process evaporation mother liquor or seed precipitation mother liquor sodium aluminate solution are treated by adopting a cation exchange membrane diffusion dialysis method, and under certain technological conditions, the sodium oxalate and sodium carbonate in the sodium aluminate solution can be efficiently separated and removed without electrifying or introducing other impurity components, so that the flow is simple, and the energy consumption and the cost are low; not only can the sodium oxalate and sodium carbonate of the production system be removed with high efficiency, but also the circulation efficiency of the Bayer process can be greatly improved.
The foregoing description is only an overview of the present application, and is intended to be implemented in accordance with the teachings of the present application in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present application more readily apparent.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method provided by an embodiment of the present application;
fig. 2 is a block diagram of a method provided by an embodiment of the present application.
Detailed Description
The advantages and various effects of the present application will be more clearly apparent from the following detailed description and examples. It will be understood by those skilled in the art that these specific embodiments and examples are intended to illustrate the application, not to limit the application.
Throughout the specification, unless specifically indicated otherwise, the terms used herein should be understood as meaning as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. In case of conflict, the present specification will control.
Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present application are commercially available or may be prepared by existing methods.
The technical scheme of the embodiment of the application aims to solve the technical problems, and the overall thought is as follows:
according to an exemplary embodiment of the present application, there is provided a method for purifying a sodium aluminate solution in an alumina production process, the method comprising:
s1, delivering a sodium aluminate solution to be purified and a diffusion solution into a cation exchange membrane diffusion dialysis device for treatment to obtain a sodium aluminate solution with high impurity concentration and a sodium aluminate solution with low impurity concentration;
specifically, a cation exchange membrane diffusion dialysis device is adopted to treat sodium aluminate solution, the sodium aluminate solution and diffusion solution are respectively introduced into a dialysis chamber and a diffusion chamber of a cation exchange membrane diffusion dialysis separator according to a certain proportion, so that sodium aluminate solution A with high impurity concentration and sodium aluminate solution B with low impurity concentration are obtained, and most sodium oxalate and sodium carbonate in the original solution are enriched in the sodium aluminate solution A.
As an alternative embodiment, the sodium aluminate liquor to be purified is selected from the evaporation mother liquor or seed precipitation mother liquor in the bayer process, the evaporation mother liquor N k 220-280g/L、α k > 2.60, said seed precipitation mother liquor N k 140-180g/L、α k ＞2.60。
As an alternative embodiment, the diffusion solution is selected from the flat-bed wash, red mud wash or water in the Bayer process flow, the flat-bed wash and red mud wash N k 10-50g/L、α k ＞2.60。
As an alternative embodiment, the volume ratio of the sodium aluminate solution to be purified and the diffusion solution to be purified to be sent to the cation exchange membrane diffusion dialysis device is 1:1-2.5, the sodium aluminate solution and the diffusion liquid reversely flow at two sides of the cation exchange membrane;
the volume ratio of the sodium aluminate solution to be purified and the diffusion solution to be sent into the cation exchange membrane diffusion dialysis device is controlled to be 1:1-2.5, on one hand, considering the practical economy of the application process of the technology, ensuring that the evaporation energy consumption in the subsequent process flow cannot be too high, on the other hand, ensuring higher impurity purification efficiency, wherein the adverse effect of too small a ratio value is that the concentration of the sodium aluminate solution B obtained after purification is too low to directly return to the Bayer process flow, or the energy consumption of the subsequent evaporation concentration is too high, which is not beneficial to the application of the technology, and the solution concentration difference is reduced due to the too large value and the impurity purification effect is poor.
As an alternative embodiment, the cation exchange membrane is used at a temperature of 20-80 ℃.
The use temperature of the cation exchange membrane is controlled to be 20-80 ℃, so that on one hand, the cation exchange membrane is guaranteed to have good purification performance, on the other hand, the material is guaranteed to have good fluidity, the cation exchange membrane performance is poor due to the fact that the temperature is too high, the purification effect on impurity ions is poor, and the adverse effect that the viscosity of the sodium aluminate solution is increased under the low-temperature condition is poor.
As an alternative embodiment, alpha of sodium aluminate solution A is obtained by diffusion dialysis separation through a cation exchange membrane k Alpha of sodium aluminate solution B of 1.5-2.0 k ＞5.0。
S2, evaporating and filtering the sodium aluminate solution with high impurity concentration to obtain a crystallized and filtered sodium aluminate solution;
specifically, evaporating the sodium aluminate solution A to separate sodium oxalate and sodium carbonate crystals; the filtered sodium oxalate and sodium carbonate crystals are exported or causticized and returned to the alumina production system.
S3, recycling the sodium aluminate solution with low impurity concentration and the filtered sodium aluminate solution;
specifically, the sodium aluminate solution B is directly returned to a Bayer process digestion system or is sent to the Bayer process digestion system after evaporation concentration; and delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation procedure for seed crystal decomposition.
The mechanism of adopting a cation exchange membrane diffusion dialysis method to treat Bayer process evaporation mother liquor or seed precipitation mother liquor sodium aluminate solution to realize simple and efficient removal of oxalate and carbonate of a production system and reducing adverse effects on production is that the oxalate and the carbonate are efficiently enriched into sodium aluminate solution A through membrane separation and purification treatment, and then are subjected to evaporation and filtration treatment through a single process, so that various harmful effects on production caused by accumulation of oxalate and carbonate in the production process for a long time are avoided.
The purification method of sodium aluminate solution in the alumina production process of the present application will be described in detail with reference to examples, comparative examples and experimental data.
Example 1
The caustic alkali concentration N of the decomposed mother solution is obtained after the seed crystal is decomposed in the Bayer production process k 145.00g/L, al 2 O 3 The concentration is 82.25g/L, and the concentration of carbon alkali N C 20.12g/L, sodium oxalate concentration of 1.04g/L, alpha k 2.90.
Cooling the decomposed mother liquor to 50deg.C to 0.80L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 43.56g/L, al 2 O 3 The concentration is 42.50g/L, and the concentration of carbon alkali N C 10.63g/L, sodium oxalate concentration of 0.53g/L, alpha k 1.69, evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process to carry out seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; water at 1.32L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B has low impurity concentrationCaustic concentration N of sodium aluminate solution B k 135.69g/L of Al 2 O 3 The concentration is 6.90g/L, and the concentration of carbon alkali N C 1.18g/L, sodium oxalate concentration of 0.10g/L, alpha k And the sodium aluminate solution B is subjected to evaporation concentration and then sent to a Bayer process digestion system at 32.37.
Example 2
The caustic alkali concentration N of the decomposed mother solution is obtained after the seed crystal is decomposed in the Bayer production process k 169.00g/L, al 2 O 3 The concentration is 97.55g/L, and the concentration of carbon alkali N C 21.50g/L, sodium oxalate concentration of 1.58g/L, alpha k 2.85.
Cooling the decomposed mother liquor to 50deg.C to 1.00L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 68.94g/L, al 2 O 3 The concentration is 56.87g/L, and the concentration of carbon alkali N C 12.87g/L, sodium oxalate concentration of 0.79g/L, alpha k 1.99, evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process to carry out seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; caustic concentration N of the diffusion liquid k 10.00g/L of Al 2 O 3 The concentration is 5.98g/L, and the concentration of carbon alkali N C 3.12g/L, alpha k At 2.75, at 1.65L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 144.53g/L of Al 2 O 3 The concentration is 12.21g/L, and the concentration of carbon alkali N C 5.41g/L, sodium oxalate concentration of 0.27g/L, alpha k 19.48, and the sodium aluminate solution B is sent to a Bayer process digestion system after being evaporated and concentrated.
Example 3
The caustic alkali concentration N of the decomposed mother solution is obtained after the seed crystal is decomposed in the Bayer production process k 175.00g/L，Al 2 O 3 The concentration is 104.68g/L, and the concentration of the carbo-alkali is N C 20.22g/L, sodium oxalate concentration of 1.14g/L, alpha k 2.75.
Cooling the decomposed mother liquor to 20deg.C to 1.20L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 104.29g/L, al 2 O 3 The concentration is 86.73/L, and the concentration of carbon alkali N C 14.94g/L, sodium oxalate concentration of 0.77g/L, alpha k 1.98, evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process for seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; caustic concentration N of the diffusion liquid k 20.00g/L of Al 2 O 3 The concentration is 11.92g/L, and the concentration of carbon alkali N C 2.22g/L, alpha k At 2.76 and 1.20L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 160.52g/L, al 2 O 3 The concentration is 14.11g/L, and the concentration of carbon alkali N C 5.28g/L, sodium oxalate concentration of 0.26g/L, alpha k The sodium aluminate solution B is directly sent to a Bayer process digestion system for 18.72.
Example 4
The caustic alkali concentration N of the evaporation mother liquor is obtained by evaporation after the seed crystal is decomposed in the Bayer production process k 240.00g/L, al 2 O 3 The concentration is 141.00g/L, and the concentration of the carbo-alkali is N C 35.26g/L, sodium oxalate concentration of 1.29g/L, alpha k 2.80.
Cooling the above evaporation mother liquor to 50deg.C to 1.20L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 74.03g/L of Al 2 O 3 The concentration is 73.26g/L, and the concentration of the carbo-alkali is N C 18.54g/L, sodium oxalate concentration of 0.65g/L, alpha k 1.66, evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process to carry out seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; water at 1.68L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 219.52g/L, al 2 O 3 The concentration is 11.57g/L, and the concentration of carbon alkali N C 2.43g/L, sodium oxalate concentration of 0.15g/L, alpha k And 31.22, the sodium aluminate solution B is sent to a Bayer process digestion system after being evaporated and concentrated.
Example 5
The caustic alkali concentration N of the evaporation mother liquor is obtained by evaporation after the seed crystal is decomposed in the Bayer production process k 270.00g/L, al 2 O 3 The concentration is 167.60g/L, and the concentration of the carbo-alkali is N C 35.15g/L sodium oxalate concentration 1.37g/L, alpha k 2.65.
Cooling the above evaporation mother liquor to 50deg.C to make it at 1.4L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 131.77g/L, al 2 O 3 The concentration is 109.02g/L, and the concentration of the carbo-alkali is N C 22.78g/L, sodium oxalate concentration of 0.83g/L, alpha k 1.99, evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process to carry out seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; caustic concentration N of the diffusion liquid k 45.00g/L of Al 2 O 3 The concentration is 25.60g/L, and the concentration of the carbo-alkali is N C 4.35g/L, alpha k 2.89 at 1.96L/m 2 H diffusion into cation exchange membranesThe diffusion chamber at the other side of the dialysis separator and the decomposing mother liquor are countercurrent to the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, and the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 228.63g/L, al 2 O 3 The concentration is 41.31g/L, and the concentration of the carbo-alkali is N C 7.41g/L, sodium oxalate concentration of 0.15g/L, alpha k The sodium aluminate solution B is directly sent to a Bayer process digestion system at 9.11.
Example 6
The caustic alkali concentration N of the evaporation mother liquor is obtained by evaporation after the seed crystal is decomposed in the Bayer production process k 240.00g/L, al 2 O 3 The concentration is 139.33g/L, and the concentration of the carbo-alkali is N C 30.36g/L, sodium oxalate concentration of 1.36g/L, alpha k 2.83. Cooling the above evaporation mother liquor to 60deg.C to obtain a solution with a concentration of 2.4L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 102.12g/L, al 2 O 3 The concentration is 85.48g/L, and the concentration of carbon alkali N C 16.22g/L, sodium oxalate concentration of 0.75g/L, alpha k 1.97, evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process to carry out seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; water at 2.88L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 225.91g/L, al 2 O 3 The concentration is 17.10g/L, and the concentration of carbon alkali N C 8.60g/L, sodium oxalate concentration of 0.33g/L, alpha k 21.73, sodium aluminate solution B is directly sent to the Bayer process digestion system.
Example 7
The caustic alkali concentration N of the evaporation mother liquor is obtained by evaporation after the seed crystal is decomposed in the Bayer production process k 240.00g/L, al 2 O 3 The concentration is 141.00g/L, and the concentration of the carbo-alkali is N C 30.48g/L, sodium oxalate concentration of 1.34g/L, alpha k 2.80. Cooling the above evaporation mother liquor to 60deg.C to obtain a solution with a concentration of 1.4L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 83.21g/L, al 2 O 3 The concentration is 68.83g/L, and the concentration of the carbo-alkali is N C 14.52g/L, sodium oxalate concentration of 0.55g/L, alpha k 1.99, evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process to carry out seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; caustic concentration N of the diffusion liquid k 30.00g/L of Al 2 O 3 The concentration is 17.95g/L, and the concentration of carbon alkali N C 3.15g/L, alpha k At 2.75 and 3.08L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 202.97g/L, al 2 O 3 The concentration is 34.91g/L, and the concentration of carbon alkali N C 6.75g/L, sodium oxalate concentration of 0.18g/L, alpha k 9.56, the sodium aluminate solution B is sent to a Bayer process digestion system after being evaporated and concentrated.
Example 8
The caustic alkali concentration N of the evaporation mother liquor is obtained by evaporation after the seed crystal is decomposed in the Bayer production process k 220.00g/L, al 2 O 3 The concentration is 129.71g/L, and the concentration of the carbo-alkali is N C 25.53g/L sodium oxalate concentration 1.39g/L, alpha k 2.79. Cooling the above evaporation mother liquor to 80deg.C to make it at 1.4L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 70.89g/L, al 2 O 3 The concentration is 64.73g/L, and the concentration of carbon alkali N C 12.78g/L, sodium oxalate concentration of 0.51g/L, alpha k The number of the components is 1.80,evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation procedure for seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; caustic concentration N of the diffusion liquid k 25.00g/L of Al 2 O 3 The concentration is 14.95g/L, and the concentration of carbon alkali N C 4.23g/L, alpha k At 2.75 and 3.50L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 183.03g/L, al 2 O 3 The concentration is 14.33g/L, and the concentration of carbon alkali N C 21.01g/L, sodium oxalate concentration of 0.17g/L, alpha k 21.01, sodium aluminate solution B is sent to a Bayer process digestion system after evaporation concentration.
Comparative example 1
The caustic alkali concentration N of the decomposed mother solution is obtained after the seed crystal is decomposed in the Bayer production process k 145.00g/L, al 2 O 3 The concentration is 82.25g/L, and the concentration of carbon alkali N C 20.12g/L, sodium oxalate concentration of 1.04g/L, alpha k 2.90.
Heating the decomposed mother liquor to 85deg.C to 0.80L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 51.86g/L, al 2 O 3 The concentration is 37.60g/L, and the concentration of the carbo-alkali is N C 4.61g/L, sodium oxalate concentration of 0.29g/L, alpha k 2.27, evaporating the sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process for seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; water at 1.32L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B has low impurity concentrationCaustic concentration N of sodium aluminate solution B k 95.78g/L, al 2 O 3 The concentration is 16.70g/L, and the concentration of carbon alkali N C 12.23g/L, sodium oxalate concentration of 0.54g/L, alpha k 9.43, the sodium aluminate solution B is sent to a Bayer process digestion system after evaporation concentration.
Comparative example 2
The caustic alkali concentration N of the decomposed mother solution is obtained after the seed crystal is decomposed in the Bayer production process k 169.00g/L, al 2 O 3 The concentration is 97.55g/L, and the concentration of carbon alkali N C 21.50g/L, sodium oxalate concentration of 1.58g/L, alpha k 2.85.
Heating the decomposed mother liquor to 90deg.C to 1.00L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 73.15g/L, al 2 O 3 The concentration is 53.71g/L, and the concentration of the carbo-alkali is N C 6.00g/L, sodium oxalate concentration of 0.34g/L, alpha k 2.24, evaporating the sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process for seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; caustic concentration N of the diffusion liquid k 10.00g/L of Al 2 O 3 The concentration is 5.98g/L, and the concentration of carbon alkali N C 3.12g/L, alpha k At 2.75, at 1.65L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 121.58g/L, al 2 O 3 The concentration is 22.56g/L, and the concentration of carbon alkali N C 17.16g/L, sodium oxalate concentration of 1.05g/L, alpha k And the sodium aluminate solution B is subjected to evaporation concentration and then sent to a Bayer process digestion system, wherein the sodium aluminate solution B is 8.87.
Comparative example 3
The caustic alkali concentration N of the decomposed mother solution is obtained after the seed crystal is decomposed in the Bayer production process k Is 169.00g/L，Al 2 O 3 The concentration is 97.55g/L, and the concentration of carbon alkali N C 21.50g/L, sodium oxalate concentration of 1.58g/L, alpha k 2.85.
Cooling the decomposed mother liquor to 5 deg.C to 1.00L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 72.48g/L, al 2 O 3 The concentration is 53.72g/L, and the concentration of carbon alkali N C 6.36g/L, sodium oxalate concentration of 0.40g/L, alpha k 2.22, evaporating the sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process for seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; caustic concentration N of the diffusion liquid k 10.00g/L of Al 2 O 3 The concentration is 5.98g/L, and the concentration of carbon alkali N C 3.12g/L, alpha k At 2.75, at 1.65L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 133.94g/L, al 2 O 3 The concentration is 18.31g/L, and the concentration of carbon alkali N C 17.99g/L, sodium oxalate concentration of 1.02g/L, alpha k And (3) evaporating and concentrating the sodium aluminate solution B to obtain 12.03, and sending the sodium aluminate solution B to a Bayer process digestion system.
Comparative example 4
The caustic alkali concentration N of the evaporation mother liquor is obtained by evaporation after the seed crystal is decomposed in the Bayer production process k 270.00g/L, al 2 O 3 The concentration is 167.60g/L, and the concentration of the carbo-alkali is N C 35.15g/L sodium oxalate concentration 1.37g/L, alpha k 2.65.
Cooling the above evaporation mother liquor to 50deg.C to make it at 1.4L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 210 is given as.25g/L，Al 2 O 3 The concentration is 139.08g/L, and the concentration of the carbo-alkali is N C 19.07g/L, sodium oxalate concentration of 0.66g/L, alpha k 2.49, evaporating the sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process for seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; caustic concentration N of the diffusion liquid k 45.00g/L of Al 2 O 3 The concentration is 25.60g/L, and the concentration of the carbo-alkali is N C 4.35g/L, alpha k 2.89 at 1.12L/m 2 H, entering the diffusion chamber at the other side of the cation exchange membrane diffusion dialysis separator, and carrying out countercurrent flow on the decomposition mother liquor and the decomposition mother liquor through the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, wherein the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 252.65g/L, al 2 O 3 The concentration is 31.05g/L, and the concentration of the carbon alkali N C 25.45g/L, sodium oxalate concentration of 0.94g/L, alpha k The sodium aluminate solution B was sent directly to the Bayer process digestion system at 13.38.
Comparative example 5
The caustic alkali concentration N of the evaporation mother liquor is obtained by evaporation after the seed crystal is decomposed in the Bayer production process k 240.00g/L, al 2 O 3 The concentration is 141.00g/L, and the concentration of the carbo-alkali is N C 35.26g/L, sodium oxalate concentration of 1.29g/L, alpha k 2.80.
Cooling the above evaporation mother liquor to 50deg.C to 1.20L/m 2 H, entering a dialysis chamber of a cation exchange membrane diffusion dialysis separator to obtain a sodium aluminate solution A with high impurity concentration, wherein the sodium aluminate solution A with high impurity concentration has caustic alkali concentration N k 57.25g/L, al 2 O 3 The concentration is 55.64g/L, and the concentration of the carbo-alkali is N C 14.06g/L, sodium oxalate concentration of 0.49g/L, alpha k 1.69, evaporating sodium aluminate solution A to separate out sodium oxalate and sodium carbonate crystals, delivering the filtered sodium aluminate solution to the existing Bayer process seed precipitation process to carry out seed crystal decomposition, and returning the filtered sodium oxalate and sodium carbonate crystals to an alumina production system after export or causticization; water at 3.60L/m 2 H diffusion into cation exchange membranesThe diffusion chamber at the other side of the dialysis separator and the decomposing mother liquor are countercurrent to the diffusion chamber to obtain a sodium aluminate solution B with low impurity concentration, and the sodium aluminate solution B with low impurity concentration has caustic alkali concentration N k 109.85g/L, al 2 O 3 The concentration is 5.85g/L, and the concentration of carbon alkali N C 1.25g/L, sodium oxalate concentration of 0.08g/L, alpha k 30.88, the sodium aluminate solution B is sent to a Bayer process digestion system after being evaporated and concentrated.
The separation capacities of the sodium carbonates and the sodium oxalate of examples 1 to 8 and comparative examples 1 to 5 are shown in the following table:
as can be seen from the above table, the method provided in this example can efficiently separate and remove sodium oxalate and sodium carbonate from a sodium aluminate solution, the separation capacity of sodium carbonate is more than 79%, the separation capacity of sodium oxalate is more than 81%, and the phenomenon that the separation capacity of sodium carbonate and the separation capacity of sodium oxalate are greatly reduced occurs when the use temperature of a cation exchange membrane or the volume ratio of a sodium aluminate solution to be purified and a diffusion solution fed into a cation exchange membrane diffusion dialysis device are not within the range provided in this example can be obtained by comparing comparative examples 1 to 3 with examples 1 to 2 and comparing comparative examples 4 with example 5; as can be obtained by comparing comparative example 5 with example 4, the volume ratio of the sodium aluminate solution to be purified and the diffusion liquid fed into the cation exchange membrane diffusion dialysis apparatus is defined by 1:1.20 drops to 1:3.00, the separation capacity for sodium carbonate and sodium oxalate does not vary much, but the sodium aluminate solution B obtained is N k The concentration is reduced by nearly one time, the sodium aluminate solution B in the embodiment 4 can be directly returned to the Bayer process flow, while the sodium aluminate solution B obtained in the comparative example 5 needs to be evaporated by 50 percent of liquid quantity to reach the same concentration as the sodium aluminate solution B and returned to the Bayer process flow, and under the technical condition, the energy consumption is high and the economy is realizedAnd (3) difference.
One or more technical solutions in the embodiments of the present application at least have the following technical effects or advantages:
(1) According to the method provided by the embodiment of the application, the sodium oxalate and the sodium carbonate in the Bayer process evaporation mother liquor or the seed precipitation mother liquor sodium aluminate solution are treated by adopting a cation exchange membrane diffusion dialysis method, and under certain technological conditions, the sodium oxalate and the sodium carbonate in the sodium aluminate solution can be efficiently separated and removed without electrifying or introducing other impurity components, so that the flow is simple, and the energy consumption and the cost are low;
(2) The method provided by the embodiment of the application not only can remove sodium oxalate and sodium carbonate in a production system with high efficiency, but also can greatly improve the circulation efficiency of the Bayer process.
Finally, it is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (5)
1. A method for purifying a sodium aluminate solution in an alumina production process, the method comprising:
delivering the sodium aluminate solution to be purified and the diffusion solution into a cation exchange membrane diffusion dialysis device for treatment to obtain a sodium aluminate solution with high impurity concentration and a sodium aluminate solution with low impurity concentration;
evaporating and filtering the sodium aluminate solution with high impurity concentration to obtain a crystallized and filtered sodium aluminate solution;
recycling the low impurity concentration sodium aluminate solution and the filtered sodium aluminate solution;
wherein, the volume ratio of the sodium aluminate solution to be purified and the diffusion solution to be purified to the cation exchange membrane diffusion dialysis device is 1:1-2.5, the sodium aluminate solution to be purified and the diffusion liquid flow reversely, the sodium aluminate solution to be purified is evaporation mother liquor or seed precipitation mother liquor in the Bayer process flow, and the caustic alkali concentration N of the evaporation mother liquor k From 220g/L to 280g/L, the caustic ratio alpha of the evaporation mother liquor k Caustic concentration N of the seed separation mother liquor > 2.60 k The caustic ratio alpha of the seed precipitation mother liquor is 140g/L to 180g/L k > 2.60, the diffusion liquid comprises a flat-bed wash, a red mud wash in a bayer process flow, the caustic concentration N of the flat-bed wash and the red mud wash k The caustic ratio alpha of the flat-bed washing liquid and the red mud washing liquid is 10g/L to 50g/L k More than 2.60 percent, the purification method realizes the separation capacity of sodium carbonate reaching more than 79 percent and the separation capacity of sodium oxalate reaching more than 81 percent.
2. The method for purifying sodium aluminate solution in alumina production process according to claim 1, wherein the cation exchange membrane is used at a temperature of 20 ℃ to 80 ℃.
3. The method for purifying sodium aluminate solution in alumina production process according to claim 1, wherein the caustic ratio α of the sodium aluminate solution with high impurity concentration is k From 1.5 to 2.0, the caustic ratio alpha of the sodium aluminate solution with low impurity concentration k ＞5.0。
4. The method for purifying sodium aluminate solution in alumina production process according to claim 1, wherein the method comprises: and recycling the sodium aluminate solution with low impurity concentration to a Bayer process digestion system.
5. The method for purifying sodium aluminate solution in alumina production process according to claim 1, wherein the method comprises: and recycling the filtered sodium aluminate solution to a Bayer process seed precipitation procedure for seed crystal decomposition.
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