CN108658111A - A method of improving alumina producing Bayer process efficiency - Google Patents

Abstract

The present invention relates to a kind of methods improving alumina producing Bayer process efficiency, the piece alkali that this method must be supplemented with using alumina producer is reacted with Bayer-process seed-separating mother liquor or evaporation mother liquor, high severe alkali, high molecule ratio sodium aluminate solution are formed, does not need to exclude carbon alkali and its causticization by forcing the processes such as effect evaporation that pregnant Bayer liquor can be realized；By realizing the efficient crystallization process of intermediate products aluminate hydrates sodium, the cycle efficieny and the production capacity under existing weaponry and equipment that dissolution medium can be improved.The present invention can be under the premise of not inputting other materials or energy, you can synchronous to realize salt discharge causticization and improve medium circulation efficiency；Newly-increased aluminate hydrates sodium crystallization process mild condition, equipment investment is low, and industry is handling strong, and economic benefit is apparent.Alumina product produced by the invention and the alumina product of existing Bayer process are identical in quality, and no any newly-increased exhaust gas, waste liquid or solid waste generate, energy conservation and environmental protection.

Description

A method for improving the production efficiency of alumina by Bayer process

technical field

The invention relates to the technical field of alumina production, in particular to a method for improving the efficiency of alumina production by Bayer process.

Background technique

The metal aluminum and alumina industry is an important basic raw material industry for the development of the national economy. More than 90% of the total output of industrial alumina is used for electrolytic production of metal aluminum, and the rest is used in the fields of electronics, refractory materials, petroleum, chemical industry, ceramics, environmental protection and pharmaceuticals.

In 2017, my country's alumina output was 69.02 million tons, accounting for 56.2% of the world's output. At present, the industrial production method of alumina is basically alkali method, mainly including Bayer method, sintering method and Bayer-sintering combined method. Thanks to the advancement of technology and equipment, and subject to economic constraints, the existing metallurgical-grade alumina is basically produced by the Bayer process.

K.J.Bayer proposed the production principle of the Bayer method between 1889 and 1892, which can be described mainly by the closed cycle formed by the four processes of bauxite dissolution, dilution and desilication, semen sorting, and medium evaporation. Although more than 120 years of technological and equipment advancements have been made, the basic principle of the Bayer process has not changed, that is, in the dissolution process, the circulating medium with a molecular ratio of about 3 dissolves the diaspore and monohydrate in the bauxite. Gibbsite or gibbsite, the sodium aluminate solution with a molecular ratio of about 1.5 and saturated with alumina is obtained, and then refined to obtain a sodium aluminate semen solution with a molecular ratio of about 1.5 and suitable for species decomposition. During the seed decomposition process, the intermediate product of aluminum hydroxide and the seed mother liquor with a molecular ratio of about 3 are obtained. The final seed mother liquor is evaporated, drained and alkali supplemented to obtain a circulating mother liquor with a molecular ratio of about 3. The circulating mother liquor is used as a circulating medium to return to the dissolution process to dissolve aluminum Soil ore.

It can be seen from the above that one of the key processes of the existing Bayer process alumina production is the circulation of mother liquor with a molecular ratio of about 3 to dissolve bauxite to obtain a saturated solution of sodium aluminate with a molecular ratio of about 1.5. The production capacity of the unit dissolution medium (that is, the circulating mother liquor with a molecular ratio of about 3) to treat bauxite, that is, the medium circulation efficiency, is mainly determined by the constant state of the molecular ratio. Moreover, after the initial caustic concentration of the medium and the stripping temperature are determined, the molecular ratio of the prepared saturated sodium aluminate solution is determined. Therefore, one of the keys to improving the medium circulation efficiency of the Bayer process is how to increase the molecular ratio of the circulating mother liquor.

The sintering method can produce aluminum hydroxide through carbonation and decomposition, and the decomposition efficiency is much higher than 50%. However, the aluminum hydroxide or alumina products produced by the sintering method are not as good as the Bayer method, and because the comprehensive energy consumption level of the sintering method is much higher than The Bayer method, except for the preparation of chemical alumina, the existing alumina production enterprises basically no longer use the sintering process or the Bayer-sintering joint method.

In the existing Bayer method seed decomposition process, the effect of improving the molecular ratio of mother liquor by optimizing the decomposition system is very limited. Use aliphatic alcohol or alkylphenol as the extractant to extract the alkali component in the sodium aluminate solution, or separate the alkali component and high molecular ratio sodium aluminate solution through the electrolysis process, or carry out the process by introducing a third component such as methanol The method of dissolution and crystallization has disadvantages such as high production cost or high energy consumption, introduction of organic components irrelevant to the Bayer system, and difficulty in industrial application.

Therefore, the existing method cannot economically and effectively improve the medium circulation efficiency of the existing Bayer process alumina production process.

Contents of the invention

In view of the problems existing in the prior art, the present invention uses caustic soda that must be supplemented by the alumina plant to react with the seed separation mother liquor or the evaporation mother liquor to form a high caustic alkali and high molecular ratio sodium aluminate solution, without the need for forced evaporation and other processes It can realize the synchronous removal of carbon alkali and causticization of Bayer mother liquor; by realizing the high-efficiency crystallization process of the intermediate product sodium aluminate hydrate, the circulation efficiency of the dissolution medium and the production capacity of the existing equipment can be improved. The invention can synchronously realize salt discharge causticization and improve medium circulation efficiency without inputting other substances or energy; newly added hydrated sodium aluminate crystallization process has mild conditions, low equipment investment, strong industrial controllability, and economic benefits obvious.

For reaching this purpose, the present invention adopts following technical scheme:

The invention provides a method for improving the efficiency of producing alumina by the Bayer process, which comprises the following steps:

(1) Use solid NaOH to mix and react with Bayer system seeding mother liquor or evaporated mother liquor, and adjust the caustic alkali concentration to above 300g/L;

(2) the slurry that step (1) obtains is mixed with sodium carbonate crystal seed, carries out sodium carbonate crystallization process; After crystallization finishes, obtain sodium carbonate slag phase and desalt mother liquor through liquid-solid separation;

(3) adjusting the caustic alkali concentration to not less than 350g/L with the salt discharge mother liquor whose caustic alkali concentration is lower than 350g/L, to obtain the liquid before crystallization;

(4) performing the sodium aluminate hydrate crystallization process on the pre-crystallization solution obtained in step (3); after the crystallization ends, crystal slag and crystallization mother liquor are obtained through liquid-solid separation;

(5) dissolving the crystal slag obtained in step (4), sending it to the dilution and desiliconization process in the Bayer production process, and then carrying out the seed separation process to obtain aluminum hydroxide precipitation;

(6) The crystalline mother liquor obtained in step (4) is sent to the dissolution process of the Bayer production process, and then the Bayer process dissolution slurry is obtained, and the precipitation of aluminum hydroxide is obtained through dilution and desiliconization, refining and decomposition processes;

(7) Dissolving the sodium carbonate slag obtained in step (2) and then causticizing to obtain NaOH solution and causticizing slag, and the NaOH solution is sent to the Bayer stripping process to dissolve the bauxite.

The method of the present invention adopts the solid NaOH to prepare the mother liquor or evaporate the mother liquor to a caustic concentration of 300g/L or more, and can realize the efficient carbon-alkali removal process of the mother liquor without forced evaporation, saving the investment in forced evaporation equipment Problems such as large size, difficult operation in the evaporation process, and steam consumption; the sodium aluminate solution obtained after deployment is suitable for the crystallization process of sodium aluminate hydrate, and an intermediate product of sodium aluminate hydrate that is easy to dissolve is obtained through the high-efficiency crystallization process of sodium aluminate hydrate And sodium aluminate solution with high molecular ratio and high caustic concentration; the intermediate product of sodium aluminate hydrate is dissolved to obtain a pre-separation solution with a molecular ratio of about 1.5 and suitable for the seed separation process, and then the aluminum hydroxide intermediate product is obtained. The medium circulation efficiency is improved; the sodium aluminate solution with high molecular ratio and high caustic concentration is directly returned to the dissolution process of the Bayer process, which can significantly increase the amount of dissolved ore and then increase the output of aluminum hydroxide or alumina in the Bayer process.

In addition to newly adding equipment such as the normal temperature crystallization process of sodium aluminate hydrate, the method of the present invention can realize the obvious improvement of the production capacity of the existing alumina plant without adding additional Bayer process dissolution units, etc., with low equipment investment, low energy consumption, and economical Significant benefits.

Adjust the caustic concentration to more than 300g/L in step (1) of the present invention, for example, the caustic concentration can be 300g/L, 350g/L, 400g/L, 450g/L, 500g/L, 550g/L or 600g /L, the preferred caustic concentration is 300g/L～600g/L.

Preferably, the slurry obtained in step (1) has a molecular ratio of 4 to 11, such as 4, 4.5, 5, 5.3, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.2, 9.6, 10, 10.2, 10.5, 10.8 or 11.

Preferably, the temperature adopted in the sodium carbonate crystallization process described in step (2) is 80 to 110°C, such as 80°C, 82°C, 85°C, 90°C, 92°C, 95°C, 98°C, 100°C, 102°C, 105°C, 108°C or 110°C; the crystallization time is 1-3h, for example, it can be 1h, 1.2h, 1.5h, 2h, 2.2h, 2.5h or 3h.

Preferably, the adjustment of the caustic alkali concentration in step (3) is carried out through an evaporation process, and other methods can also be used for adjustment. The present invention does not specifically limit the adjustment method, as long as the concentration is adjusted to more than 350g/L.

Preferably, the caustic concentration of the pre-crystallization liquid in step (3) is 300g/L to 600g/L, such as 300g/L, 350g/L, 400g/L, 450g/L, 500g/L, 550g/L L or 600g/L, the molecular ratio is 4~11, such as 4, 4.2, 4.5, 5, 5.2, 5.5, 5.8, 6.2, 7.4, 7.5, 8, 8.4, 9.1, 9.2, 9.6, 10.2, 10.6, 10.8 or 11.

Preferably, the temperature used in the crystallization process of sodium aluminate hydrate described in step (4) is 30-60°C, such as 30°C, 32°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C °C; the crystallization time is at least 3h, for example it may be 3h, 5h, 8h, 10h, 15h.

The newly added sodium aluminate hydrate crystallization process of the present invention has mild conditions, and the required temperature is only 30-60°C, which is basically a crystallization process at room temperature. Therefore, it has low equipment requirements, low energy consumption, and strong industrial operability.

Preferably, the caustic concentration of the crystallization mother liquor in step (4) is 300g/L-600g/L, such as 300g/L, 350g/L, 400g/L, 450g/L, 500g/L, 550g/L Or 600g/L, the molecular ratio is 20 or more, such as 20, 22, 25, 28, 30, 34, 37, 40, 42, 45, 50, 55 or 58, preferably 25-55.

In the present invention, the sodium aluminate mother liquor with high caustic alkali and high molecular ratio is formed by reacting caustic soda which must be supplemented by the alumina plant with seed separation mother liquor or evaporated mother liquor, and the simultaneous removal of Bayer mother liquor can be realized without going through forced evaporation and other processes Carbon soda and its causticization; it also realizes the high-efficiency crystallization process of the intermediate product sodium aluminate hydrate, thereby greatly improving the circulation efficiency of the dissolution medium and the production capacity under the existing equipment.

Preferably, the crystalline slag in step (5) is washed with part of the seed semen, dissolved in hot water to obtain a sodium aluminate solution, and then the seeds are decomposed to obtain aluminum hydroxide precipitation.

Preferably, the crystallization mother liquor in step (6) is mixed with the Bayer system evaporation mother liquor, bauxite and lime, and then sent to the dissolution process of the Bayer production process.

Preferably, the causticizing in the step (7) uses milk of lime for causticizing.

As a preferred technical solution of the present invention, the method for improving the efficiency of Bayer process for producing alumina according to the present invention comprises the following steps:

(1) Mix and react with solid NaOH and Bayer system seeding mother liquor or evaporated mother liquor, adjust the caustic alkali concentration to above 300g/L, and the molecular ratio is 4-11;

(2) The slurry obtained in step (1) is mixed with sodium carbonate seed crystals, and the sodium carbonate crystallization process is carried out at a temperature of 80 to 110 ° C. The crystallization time is 1 to 3 hours; after the crystallization ends, sodium carbonate is obtained through liquid-solid separation Slag phase and mother liquor of salt discharge;

(3) adjusting the caustic concentration of the salt-discharging mother liquor with a caustic concentration lower than 350g/L to not less than 350g/L to obtain a pre-crystallization solution with a caustic concentration above 350g/L and a molecular ratio of 4 to 11;

(4) The pre-crystallization liquid obtained in step (3) is subjected to the crystallization process of sodium aluminate hydrate at a temperature of 30-60 ° C, and the crystallization time is at least 3 hours; after the crystallization is completed, the crystal slag and the caustic concentration 300g/L～600g/L, crystallization mother liquor with a molecular ratio of 20 or more;

(5) washing the crystal slag obtained in step (4) with part of the seed semen, dissolving in hot water to obtain a sodium aluminate solution, and then decomposing the seeds to obtain aluminum hydroxide precipitation;

(6) Mix the crystallization mother liquor obtained in step (4) with the Bayer system evaporation mother liquor, bauxite and lime, and then send it to the dissolution process of the Bayer production process, and then obtain the Bayer method dissolution slurry, which is diluted and desiliconized, refined and decomposed Process, obtain aluminum hydroxide precipitation;

(7) After dissolving the sodium carbonate slag phase obtained in step (2), causticize with milk of lime to obtain NaOH solution and causticizing slag, and the NaOH solution is sent to the Bayer dissolution process to dissolve the bauxite.

Compared with the prior art, the present invention has at least the following beneficial effects:

(1) The present invention effectively couples the existing alkali supplementation process and the high-efficiency crystallization process of sodium aluminate hydrate in the Bayer process alumina production process, and obtains high caustic alkali and high molecular ratio aluminate through the newly added hydrated sodium aluminate crystallization process Sodium solution can increase the circulation efficiency of the Bayer process medium by more than 1.5%, and the economic benefits are obvious;

(2) The newly added sodium aluminate hydrate crystallization process of the present invention also produces aluminum hydroxide or alumina products, which can realize the improvement of Bayer process production capacity without inputting substances or energy irrelevant to the existing Bayer system;

(3) The present invention can realize the elimination and causticization of sodium carbonate in the Bayer mother liquor without setting the forced evaporation and salt discharge process, saving corresponding equipment investment and energy consumption;

(4) The equipment investment of the present invention is low, the comprehensive energy consumption level is low, and industrial maneuverability is good;

(5) The quality of the alumina product of the present invention is the same as that of the existing Bayer process, without any additional waste gas, waste liquid or solid waste, energy saving and environmental protection.

Description of drawings

Fig. 1 is a process flow chart of the method for improving the effect of Bayer process for producing alumina provided by the present invention.

The present invention will be further described in detail below. However, the following examples are only simple examples of the present invention, and do not represent or limit the protection scope of the present invention, and the protection scope of the present invention shall be determined by the claims.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation methods.

Fig. 1 shows the process flow sheet of the method for improving the Bayer process production alumina effect of the present invention, and it specifically comprises the following steps:

(1) Use solid NaOH to mix and react with Bayer system seeding mother liquor or evaporated mother liquor, and adjust the caustic alkali concentration to above 300g/L;

(2) the slurry that step (1) obtains is mixed with sodium carbonate crystal seed, carries out sodium carbonate crystallization process; After crystallization finishes, obtain sodium carbonate slag phase and desalt mother liquor through liquid-solid separation;

(3) adjusting the caustic alkali concentration to not less than 350g/L with the salt discharge mother liquor whose caustic alkali concentration is lower than 350g/L, to obtain the liquid before crystallization;

(4) performing the sodium aluminate hydrate crystallization process on the pre-crystallization solution obtained in step (3); after the crystallization ends, crystal slag and crystallization mother liquor are obtained through liquid-solid separation;

(5) dissolving the crystal slag obtained in step (4), sending it to the dilution and desiliconization process in the Bayer production process, and then carrying out the seed separation process to obtain aluminum hydroxide precipitation;

(6) The crystalline mother liquor obtained in step (4) is sent to the dissolution process of the Bayer production process, and then the Bayer process dissolution slurry is obtained, and the precipitation of aluminum hydroxide is obtained through dilution and desiliconization, refining and decomposition processes;

(7) Dissolving the sodium carbonate slag obtained in step (2) and then causticizing to obtain NaOH solution and causticizing slag, and the NaOH solution is sent to the Bayer stripping process to dissolve the bauxite.

In order to facilitate understanding of the present invention, the present invention enumerates the following examples. It should be clear to those skilled in the art that the examples are only for helping to understand the present invention, and should not be regarded as specific limitations on the present invention.

Example 1

This embodiment provides a method for improving the efficiency of alumina production by the Bayer process. The mother liquor of a certain Bayer process alumina plant is used as a raw material. The main composition of the mother liquor of the alumina plant (g/L, the same below) is shown in Table 1 mentioned.

Table 1

Its production process includes the following steps:

( ₁ ) Mix the seed separation mother liquor with solid NaOH, prepare a slurry with a liquid phase _Na2Ok concentration of 400g/L and a molecular ratio of 5.5, discharge salt with sodium carbonate seed crystals at 100°C for 3 hours, and filter to obtain Sodium carbonate filter cake and _Na2Ok concentration are _400g /L, molecular ratio is the pre-crystallization liquid of 5.5;

( ₂ ) Cool the pre-crystallization solution with a _Na2Ok concentration of 400g/L and a molecular ratio of 5.5 to 45°C and crystallize for 15 hours to obtain a sodium aluminate hydrate filter cake with a caustic concentration of 395g/L and a molecular ratio of 25 crystallization mother liquor;

(3) After washing the sodium aluminate hydrate filter cake with part of the seed separation mother liquor and dissolving it in hot water, a sodium aluminate solution with a _Na2Ok concentration of _175g /L and a molecular ratio of 1.46 was obtained, and then decomposed the seeds to obtain Aluminum hydroxide;

(4) Based on a certain total caustic quality, after mixing the crystallization mother liquor with a caustic concentration of 395g/L and a molecular ratio of 25 with the A-effect evaporation mother liquor, the Bayer method dissolution process is carried out with diaspore ore, etc., converted The concentration change of the dissolution medium before and after dissolution, the calculated medium circulation efficiency is 167.5kg/m ³ ;

(5) After dissolving the sodium carbonate filter cake obtained in step (1), causticize with milk of lime to obtain NaOH solution and causticizing slag, and the NaOH solution is sent to the Bayer dissolution process to dissolve the bauxite.

Example 2:

This embodiment provides a method for improving the efficiency of alumina production by the Bayer process, using the evaporated mother liquor of a certain Bayer process alumina plant described in Table 1 as a raw material, and the production process is as follows:

( ₁ ) Mix the A-effect evaporation mother liquor with solid NaOH, prepare a liquid phase _Na2Ok concentration of 500g/L, and a slurry with a molecular ratio of 7.7, discharge salt with sodium carbonate seed crystals for 3 hours at 100°C, and filter Obtain _sodium carbonate filter cake and Na O _K concentration is 500g/L, the molecular ratio is the pre-crystallization liquid of 7.7;

(2) Cool the pre-crystallization solution with a Na ₂ O _k concentration of 500g/L and a molecular ratio of 7.7 to 60°C and crystallize for 5 hours to obtain a sodium aluminate hydrate filter cake with a caustic concentration of 492g/L and a molecular ratio of 37 crystallization mother liquor;

(3) After washing the sodium aluminate hydrate filter cake with part of the seed separation mother liquor and dissolving it with hot water, a sodium aluminate solution with a _Na2Ok concentration of _175g /L and a molecular ratio of 1.45 is obtained, and then decomposed the seeds to obtain Aluminum hydroxide;

(4) Based on a certain total caustic quality, after mixing the crystallization mother liquor with a caustic concentration of 492g/L and a molecular ratio of 37 with the A-effect evaporation mother liquor, the Bayer method dissolution process is carried out with diaspore ore, etc., converted The concentration change of the dissolution medium before and after dissolution, the calculated circulation efficiency of the medium is 167.6kg/m ³ ;

(5) After dissolving the sodium carbonate filter cake obtained in step (1), causticize with milk of lime to obtain NaOH solution and causticizing slag, and the NaOH solution is sent to the Bayer dissolution process to dissolve the bauxite.

Example 3:

This embodiment provides a method for improving the efficiency of alumina production by the Bayer process, using the evaporated mother liquor of a certain Bayer process alumina plant described in Table 1 as a raw material, and the production process is as follows:

(1) Mix the B-effect evaporation mother liquor with solid NaOH to prepare a slurry with a liquid phase Na ₂ O _k concentration of 600g/L and a molecular ratio of 10.6. Use sodium carbonate seed crystals at 100°C to remove salt for 3 hours and filter The sodium carbonate filter cake and the pre-crystallization solution with a _Na2Ok concentration of _600g /L and a molecular ratio of 10.6 were obtained;

( ₂ ) Cool the pre-crystallization solution with a _Na2Ok concentration of 600g/L and a molecular ratio of 10.6 to 50°C and crystallize for 10 hours to obtain a sodium aluminate hydrate filter cake with a caustic concentration of 583g/L and a molecular ratio of 42 crystallization mother liquor;

(3) After washing the sodium aluminate hydrate filter cake with part of the seed separation mother liquor and dissolving it in hot water, a sodium aluminate solution with a _Na2Ok concentration of _175g /L and a molecular ratio of 1.46 was obtained, and then decomposed the seeds to obtain Aluminum hydroxide;

(4) Based on a certain total caustic quality, after mixing the crystalline mother liquor with a caustic concentration of 583g/L and a molecular ratio of 42 with the A-effect evaporation mother liquor, the diaspore ore and the like are used to carry out the Bayer dissolution process, converted The concentration change of the dissolution medium before and after dissolution, the calculated medium circulation efficiency is 167.9kg/m ³ ;

(5) After dissolving the sodium carbonate filter cake obtained in step (1), causticize with milk of lime to obtain NaOH solution and causticizing slag, and the NaOH solution is sent to the Bayer dissolution process to dissolve the bauxite.

Example 4:

This embodiment provides a method for improving the efficiency of alumina production by the Bayer process. The mother liquor of a certain Bayer process alumina plant described in Table 1 is used as a raw material, and the production process is as follows:

( ₁ ) Mix the seed separation mother liquor with solid NaOH to form a slurry with a liquid phase _Na2Ok concentration of 300g/L and a molecular ratio of 4.2, discharge salt with sodium carbonate seed crystals at 100°C for 3 hours, and filter to obtain sodium carbonate _Filter cake and _Na2Ok concentration are 300g/L, molecular ratio is the discharge salt filtrate of 4.2;

( ₂ ) _Na2Ok concentration is 300g/L, molecular ratio is 4.2 and evaporates to the _Na2Ok concentration is _550g /L, molecular ratio is the pre-crystallization liquid of 4.2;

(3) Cool the pre-crystallization solution with a _Na2Ok concentration of _550g /L and a molecular ratio of 4.2 to 45°C and crystallize for 30 hours to obtain a sodium aluminate hydrate filter cake with a caustic concentration of 538g/L and a molecular ratio of 55 crystallization mother liquor;

(4) After washing the sodium aluminate hydrate filter cake with part of the seed separation mother liquor and dissolving it with hot water, a sodium aluminate solution with a _Na2Ok concentration of _175g /L and a molecular ratio of 1.45 is obtained, and then decomposed the seeds to obtain Aluminum hydroxide;

(5) Based on a certain total caustic quality, after mixing the crystallization mother liquor with a caustic concentration of 538g/L and a molecular ratio of 55 with the A-effect evaporation mother liquor, it is equipped with diaspore ore and the like to carry out the Bayer dissolution process, converted The concentration change of the dissolution medium before and after dissolution, the medium circulation efficiency is calculated to be 177.8kg/m ³ ;

(6) After dissolving the sodium carbonate filter cake obtained in step (1), causticize with milk of lime to obtain NaOH solution and causticizing slag, and the NaOH solution is sent to the Bayer dissolution process to dissolve the bauxite.

Comparative example 1:

With the mother liquor of a certain Bayer process alumina plant described in Table 1 as raw material, adopt the Bayer process to produce alumina, and its production process is as follows:

(1) Get a part of the A-effect evaporation mother liquor and enter the forced-effect evaporator to evaporate, and obtain the forced-effect mother liquor after desalting;

(2) mix part A effect evaporation mother liquor, step (1) gained strong effect mother liquor and system need to supplement solid _NaOH , make Bayer process circulating mother liquor, its Na O concentration is _245g /L, and molecular ratio is 3.38;

(3) The recirculating mother liquor, diaspore ore etc. that mixing step (2) make carry out Bayer method stripping process, convert the concentration change before and after stripping of stripping medium, calculate and obtain circulating mother liquor circulation efficiency to be 165.0kg/m ³ ;

(4) After dissolving the sodium carbonate filter cake obtained in step (1), causticize with milk of lime to obtain NaOH solution and causticizing slag, and the NaOH solution is sent to the Bayer dissolution process to dissolve the bauxite.

After comparing the medium circulation efficiency calculated in Examples 1 to 4 with the circulation mother liquid circulation efficiency calculated in Comparative Example 1, it is drawn that the Bayer method medium circulation efficiency of Example 1 has improved by 1.52% compared with Comparative Example 1; 2 Compared with the Bayer method medium circulation efficiency of comparative example 1, the circulation efficiency of Bayer method has been improved by 1.58%; the Bayer method medium circulation efficiency of embodiment 3 has been improved by 1.76% compared with comparative example 1; the Bayer method medium circulation efficiency of embodiment 4 has been improved by 7.76% %.

From the above results, it can be drawn that the present invention utilizes caustic soda that must be supplemented by an alumina factory to react with the Bayer method seed separation mother liquor or evaporated mother liquor to form a high caustic alkali and high molecular ratio sodium aluminate solution without forced forced evaporation. It can realize the removal of carbon and alkali of Bayer mother liquor and its causticization; by realizing the high-efficiency crystallization process of the intermediate product sodium aluminate hydrate, the circulation efficiency of the dissolution medium is effectively improved.

The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of selected components in the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (7)

1. a kind of method improving alumina producing Bayer process efficiency, which is characterized in that include the following steps：

(1) solid NaOH and Bayer system seed precipitation solution or evaporation mother liquor is used to mix, react, adjust severe alkali concentration to 300g/L with On；

(2) slurries that step (1) obtains are mixed with sodium carbonate crystal seed, carries out sodium carbonate crystallization process；After crystallization, through liquid Gu isolated sodium carbonate slag phase and salt discharge mother liquor；

(3) severe alkali concentration is adjusted into severe alkali concentration to 350g/L is not less than less than the salt discharge mother liquor of 350g/L, obtains crystallizing preceding liquid；

(4) liquid carries out aluminate hydrates sodium crystallization process before the crystallization for obtaining step (3)；After crystallization, obtained through solid-liquor separation To crystal slag and crystalline mother solution；

(5) the crystal slag for obtaining step (4) dissolves, and send to Bayer production process and dilutes desiliconization process, then carries out kind and divided Journey obtains aluminum hydroxide precipitation；

(6) crystalline mother solution for obtaining step (4) is sent into Bayer production process and dissolves out process, then obtains Bayer Process digestion material Slurry obtains aluminum hydroxide precipitation through diluting desiliconization, refined, decomposable process；

(7) causticization after the sodium carbonate slag phase dissolving obtained step (2), is made NaOH solution and causticization slag, and NaOH solution is sent into Bayer dissolution process removes dissolving bauxite.

2. the method as described in claim 1, which is characterized in that step (1) the severe alkali concentration is 300g/L~600g/L；

Preferably, the slurries that step (1) obtains, molecular proportion are 4~11.

3. method as claimed in claim 1 or 2, which is characterized in that warm used by step (2) the sodium carbonate crystallization process Degree is 80~110 DEG C；Crystallization time is 1~3h；

Preferably, the adjustment of step (3) the severe alkali concentration is carried out by evaporation process；

Preferably, the severe alkali concentration of liquid is 300g/L~600g/L before step (3) described crystallization, and molecular proportion is 4~11.

4. the method as described in one of claim 1-3, which is characterized in that step (4) the aluminate hydrates sodium crystallization process institute The temperature used is 30~60 DEG C；Crystallization time is at least 3h；

Preferably, the severe alkali concentration of the crystalline mother solution be 300g/L~600g/L, molecular proportion be 20 or more, preferably 25~ 55。

5. the method as described in one of claim 1-4, which is characterized in that step (5) the crystallization slag part kind divides sperm Washing, after hot water dissolving, obtains sodium aluminate solution, then carries out seeded precipitation again and aluminum hydroxide precipitation is made.

6. the method as described in one of claim 1-5, which is characterized in that step (6) crystalline mother solution is steamed with Bayer system Hair mother liquor, bauxite and lime are mixed, and Bayer production process dissolution process is re-fed into；

Preferably, step (7) described causticization carries out causticization using milk of lime.

7. the method as described in one of claim 1-6, which is characterized in that the described method comprises the following steps：

(1) solid NaOH and Bayer system seed precipitation solution or evaporation mother liquor is used to mix, react, adjust severe alkali concentration to 300g/L with On, molecular proportion is 4~11；

(2) slurries that step (1) obtains are mixed with sodium carbonate crystal seed, sodium carbonate crystallization is carried out at a temperature of 80~110 DEG C Process, crystallization time are 1~3h；After crystallization, sodium carbonate slag phase and salt discharge mother liquor are obtained through solid-liquor separation；

(3) severe alkali concentration is adjusted into severe alkali concentration to 350g/L is not less than less than the salt discharge mother liquor of 350g/L, obtains severe alkali concentration In 350g/L or more, molecular proportion liquid before 4~11 crystallization；

(4) liquid carries out aluminate hydrates sodium crystallization process at a temperature of 30~60 DEG C before the crystallization for obtaining step (3), when crystallization Between be at least 3h；After crystallization, it is 300g/L~600g/L to obtain crystal slag and severe alkali concentration through solid-liquor separation, and molecular proportion is 20 or more crystalline mother solution；

(5) divide the crystal slag part kind that step (4) obtains to semen washing, after hot water dissolving, obtain sodium aluminate solution, so It carries out seeded precipitation again afterwards and aluminum hydroxide precipitation is made；

(6) crystalline mother solution that step (4) obtains is mixed with Bayer system evaporation mother liquor, bauxite and lime, is re-fed into Bayer production process dissolves out process, then obtains Bayer Process digestion slurry, through diluting desiliconization, refined, decomposable process, obtains hydrogen-oxygen Change aluminum precipitation；

(7) milk of lime causticization is used after the sodium carbonate slag phase dissolving obtained step (2), NaOH solution and causticization slag, NaOH is made Solution is sent into Bayer dissolution process and removes dissolving bauxite.