Method for reducing lime consumption in process of producing aluminum oxide by Bayer process

Abstract

The invention relates to a method for reducing lime consumption in a process of producing aluminum oxide by a Bayer process, which comprises the following steps: adding 1.5-3g of calcium-silicon slag into desiliconized sodium aluminate crude liquid per liter of the desiliconized sodium aluminate crude liquid, and uniformly stirring to obtain sodium aluminate crude liquid to be finely filtered; feeding the sodium aluminate crude liquid to be finely filtered into a leaf filter for finely filtering, and keeping the pressure in the leaf filter below 0.35 MPa to obtain sodium aluminate fine liquid. According to the method, the filter residue calcium-silicon residue in the desilicication process is used as a filter aid, so that the consumption of lime in the process of producing the aluminum oxide by the Bayer process is reduced, the production cost is reduced, and suspended matters in the sodium aluminate fine liquid are less than or equal to 0.01 g / L; meanwhile, lime milk is replaced by the solid calcium-silicon slag, so that the problems that the concentration of the sodium aluminate crude liquid is diluted due to the fact that the lime milk brings water and the lime milk reacts with sodium metaaluminate in the crude liquid to cause aluminum loss are solved, and the yield of aluminum oxide is increased.

Description

Technical Field

[0001] The invention relates to the technical field of preparing alumina by the Bayer process, and in particular to a method for reducing lime consumption in the process of producing alumina by the Bayer process. Background Art

[0002] In the Bayer process of producing alumina, the ore is crushed, ground, pre-desiliconized, dissolved and separated by red mud sedimentation to obtain red mud and sodium aluminate crude liquid, and the sodium aluminate crude liquid is desiliconized and finely filtered to obtain sodium aluminate fine liquid. At present, in the refining process of sodium aluminate crude liquid, lime milk is usually added to the crude liquid before the crude liquid passes through the leaf filter, and tricalcium aluminate generated by the reaction of lime milk and crude liquid is used as a filter aid for filtering the crude liquid. Tricalcium aluminate has the characteristics of high hardness, large particles, looseness and porosity, which can increase the looseness and air permeability of the filter cake on the leaf filter, reduce the resistance during the filtration of sodium aluminate crude liquid, and increase the production capacity. However, the lime consumption is large and the production cost is high when using this method. The lime milk reacts with the sodium metaaluminate in the crude liquid to form aluminum hydroxide precipitation, resulting in the loss of aluminum in the crude liquid, which in turn leads to a decrease in the yield of alumina. In addition, adding a large amount of lime milk to the sodium aluminate crude liquid will dilute the concentration of the sodium aluminate crude liquid, thereby affecting the yield of alumina. Therefore, it is of great significance to develop a method to reduce the lime consumption in the Bayer process of producing alumina. Summary of the invention

[0003] In view of the problems in the above-mentioned prior art such as large lime consumption, serious aluminum loss in crude liquor, and dilution of the concentration of sodium aluminate crude liquor, the present invention provides a method for reducing lime consumption in the process of producing alumina by the Bayer process. The method uses calcium silicon slag as a filter aid, which reduces lime consumption and increases the output of alumina.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A method for reducing lime consumption in a Bayer process for producing alumina, comprising the following steps:

[0006] (1) adding lime to the sodium aluminate crude liquid in the desiliconization process to desiliconize the crude liquid, and after the reaction is completed, the reaction slurry is subjected to solid-liquid separation, and the resulting filter residue is calcium-silicon slag;

[0007] (2) adding a filter aid to the desiliconized sodium aluminate crude liquid, wherein the filter aid includes calcium silicate slag, and the filter aid is added to the desiliconized sodium aluminate crude liquid at a ratio of 1.5-3 g of calcium silicate slag per liter of sodium aluminate crude liquid, and stirring evenly to obtain a sodium aluminate crude liquid to be finely filtered;

[0008] (3) The sodium aluminate crude liquid to be finely filtered is sent to a leaf filter by a sodium aluminate crude liquid pump for fine filtration. The pressure in the leaf filter is maintained below 0.35 MPa to obtain sodium aluminate fine liquid.

[0009] Furthermore, the filter aid in step (2) also includes lime milk, and the ratio of the calcium silicate slag to the lime milk is 1-4:1.

[0010] Furthermore, the calcium-silica slag includes hydrated garnet.

[0011] Furthermore, the suspended matter in the sodium aluminate semen is less than or equal to 0.01 g / L.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The invention provides a method for reducing lime consumption in a process of producing alumina by the Bayer process. The method uses calcium-silicon slag, a filter residue in a desiliconization process, as a filter aid, thereby reducing lime consumption in a process of producing alumina by the Bayer process and reducing production costs. Furthermore, the suspended matter in the sodium aluminate concentrate is less than or equal to 0.01 g / L. Meanwhile, solid calcium-silicon slag is used to replace lime milk, thereby avoiding the problem that the concentration of sodium aluminate crude liquid is diluted due to water brought into the lime milk and aluminum loss caused by the reaction of the lime milk with sodium metaaluminate in the crude liquid, thereby increasing the yield of alumina. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail by specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0015] A method for reducing lime consumption in a Bayer process for producing alumina, comprising the following steps:

[0016] (1) adding lime to the sodium aluminate crude liquid in the desiliconization process to desiliconize the crude liquid, and after the reaction is completed, the reaction slurry is subjected to solid-liquid separation, and the resulting filter residue is calcium-silicon slag;

[0017] (2) adding a filter aid to the desiliconized sodium aluminate crude liquid, wherein the filter aid comprises calcium silicate slag, and the filter aid is added to the desiliconized sodium aluminate crude liquid at a ratio of 1.5-3 g of calcium silicate slag per liter of sodium aluminate crude liquid, and stirring evenly to obtain a sodium aluminate crude liquid to be finely filtered;

[0018] (3) The sodium aluminate crude liquid to be finely filtered is sent to a leaf filter by a sodium aluminate crude liquid pump for fine filtration. The pressure in the leaf filter is maintained below 0.35 MPa to obtain sodium aluminate fine liquid.

[0019] Example 1

[0020] Lime is added to the crude sodium aluminate liquid in the desiliconization process to desiliconize the crude sodium aluminate liquid, and after the reaction is completed, the reaction slurry is separated into solid and liquid to obtain calcium-silicon slag; calcium-silicon slag is added to the crude sodium aluminate liquid after desiliconization at a ratio of 1.5 g of calcium-silicon slag per liter of the crude sodium aluminate liquid, and the mixture is stirred evenly to obtain the crude sodium aluminate liquid to be finely filtered; the crude sodium aluminate liquid to be finely filtered is sent to a leaf filter by a crude liquid pump for fine filtration, and the pressure in the leaf filter is maintained at 0.35 MPa to obtain sodium aluminate semen, the suspended matter content of the obtained sodium aluminate semen is 0.008 g / L, and the concentration difference of sodium aluminate in the semen and the crude liquid before the desiliconization process is 1.07 g / L.

[0021] Example 2

[0022] Lime is added to the sodium aluminate crude liquid in the desiliconization process to desiliconize the sodium aluminate crude liquid, and after the reaction is completed, the reaction slurry is solid-liquid separated to obtain calcium-silicon slag; calcium-silicon slag is added to the sodium aluminate crude liquid after desiliconization at a ratio of 3g of calcium-silicon slag per liter of sodium aluminate crude liquid, and lime milk is added to the sodium aluminate crude liquid after desiliconization at a ratio of calcium-silicon slag: lime milk=3:1, and the mixture is stirred evenly to obtain sodium aluminate crude liquid to be finely filtered; the sodium aluminate crude liquid to be finely filtered is sent to a leaf filter by a crude liquid pump for fine filtration, and the pressure in the leaf filter is maintained at 0.3MPa to obtain sodium aluminate semen, the suspended matter content of the obtained sodium aluminate semen is 0.006g / L, and the concentration difference of sodium aluminate in the semen and the crude liquid before the desiliconization process is 1.73g / L.

[0023] Example 3

[0024] Lime is added to the sodium aluminate crude liquid in the desiliconization process to desiliconize the sodium aluminate crude liquid, and after the reaction is completed, the reaction slurry is solid-liquid separated to obtain calcium-silicon slag; calcium-silicon slag is added to the sodium aluminate crude liquid after desiliconization at a ratio of 2g of calcium-silicon slag per liter of sodium aluminate crude liquid, and lime milk is added to the sodium aluminate crude liquid after desiliconization at a ratio of calcium-silicon slag: lime milk=4:1, and stirred evenly to obtain sodium aluminate crude liquid to be finely filtered; the sodium aluminate crude liquid to be finely filtered is sent to a leaf filter for fine filtration by a crude liquid pump, and the pressure in the leaf filter is maintained at 0.25MPa to obtain sodium aluminate semen, the obtained sodium aluminate semen has a suspended matter content of 0.007g / L, and the concentration difference of sodium aluminate in the semen and the crude liquid before the desiliconization process is 1.24g / L.

[0025] Example 4

[0026] Lime is added to the sodium aluminate crude liquid in the desiliconization process to desiliconize the sodium aluminate crude liquid, and after the reaction is completed, the reaction slurry is separated into solid and liquid to obtain calcium-silicon slag; calcium-silicon slag is added to the sodium aluminate crude liquid after desiliconization at a ratio of 2.5g of calcium-silicon slag per liter of sodium aluminate crude liquid, and lime milk is added to the sodium aluminate crude liquid after desiliconization at a ratio of calcium-silicon slag: lime milk=1:1, and stirred evenly to obtain sodium aluminate crude liquid to be finely filtered; the sodium aluminate crude liquid to be finely filtered is sent to a leaf filter by a crude liquid pump for fine filtration, and the pressure in the leaf filter is maintained at 0.35MPa to obtain sodium aluminate semen, the obtained sodium aluminate semen has a suspended matter content of 0.005g / L, and the concentration difference of sodium aluminate in the semen and the crude liquid before the desiliconization process is 1.96g / L.

[0027] The invention provides a method for reducing lime consumption in a process of producing alumina by the Bayer process. The method uses calcium-silicon slag, a filter residue in a desiliconization process, as a filter aid, thereby reducing lime consumption in a process of producing alumina by the Bayer process and reducing production costs. Furthermore, the suspended matter in the sodium aluminate concentrate is less than or equal to 0.01 g / L. Meanwhile, solid calcium-silicon slag is used to replace lime milk, thereby avoiding the problem that the concentration of sodium aluminate crude liquid is diluted due to water brought into the lime milk and aluminum loss caused by the reaction of the lime milk with sodium metaaluminate in the crude liquid, thereby increasing the yield of alumina.

[0028] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A method for reducing lime consumption in the Bayer process for producing alumina, characterized in that: The following steps are involved: (1) adding lime to the sodium aluminate crude liquid in the desiliconization process to desiliconize the crude liquid, and after the reaction is completed, the reaction slurry is subjected to solid-liquid separation, and the resulting filter residue is calcium-silicon slag; (2) adding a filter aid to the desiliconized sodium aluminate crude liquid, wherein the filter aid comprises calcium silicate slag, and the filter aid is added to the desiliconized sodium aluminate crude liquid at a ratio of 1.5-3 g of calcium silicate slag per liter of sodium aluminate crude liquid, and stirring evenly to obtain a sodium aluminate crude liquid to be finely filtered; (3) The sodium aluminate crude liquid to be finely filtered is sent to a leaf filter by a sodium aluminate crude liquid pump for fine filtration. The pressure in the leaf filter is maintained below 0.35 MPa to obtain sodium aluminate fine liquid.

2. A method for reducing lime consumption in the Bayer process for producing alumina according to claim 1, characterized in that: The filter aid in step (2) further comprises lime milk, and the ratio of the calcium silicate slag to the lime milk is 1-4:

1.

3. The method for reducing lime consumption in the Bayer process for producing alumina according to claim 1, characterized in that: The calcic silica slag includes hydrated garnet.

4. The method for reducing lime consumption in the Bayer process for producing alumina according to claim 1, characterized in that: The suspended matter in the sodium aluminate semen is less than or equal to 0.01 g / L.