Method for treating gibbsite through high-temperature calcification transformation based on source blocking

Abstract

The invention relates to the technical field of aluminum oxide clean production, in particular to a method for treating gibbsite through high-temperature calcification transformation based on source blocking, which comprises the following steps: mixing high-iron bauxite, a calcium compound and Bayer mother liquor, and then carrying out pulpifying to obtain ore pulp; conveying the ore pulp to a high-pressure dissolution reactor to obtain transformed red mud; separating and washing the transformed red mud by using a vortex rapid settling tank; and adding a binder into the washed and dried transformed red mud to prepare small balls, and roasting, hardening and solidifying to obtain ironmaking pellets. According to the method, Bayer process flow equipment can be directly adopted, the method has the characteristics of simple process and equipment, high production efficiency and the like, the transformed slag serves as a pellet raw material to be directly used for producing pellets, no solid waste is generated in the whole process, and finally harmless, high-valued and full-quantized consumption of the red mud is achieved; and the worldwide problem that a large amount of red mud is discharged in the aluminum oxide production process is thoroughly solved.

Description

Technical Field

[0001] The present invention relates to the technical field of clean production of alumina, and in particular to a method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking. Background Art

[0002] For a long time, the alumina industry has dealt with red mud by discharging it first and then treating it. However, in recent years, more and more researchers have begun to solve the problem of red mud from the source. The existing technology discloses "Active iron powder, and a method for treating high-iron gibbsite ore with comprehensive utilization of iron and aluminum, Publication No.: CN115608982A". The above-mentioned iron powder with high-temperature reaction activity is added to the slurry after the high-iron gibbsite ore is mixed with the sodium aluminate solution, and high-temperature dissolution is carried out. The relative dissolution rate of alumina is greater than 97%. The low-aluminum and iron-rich red mud is further treated by pyrometallurgy to achieve the recycling of activated iron powder. Although this method uses activated iron powder to separate the iron phase during the dissolution process, a certain amount of iron hydrate garnet phase will still be generated during the dissolution process, which not only affects the reduction effect of iron oxide, but also causes impurities to be included in the subsequent iron selection process. In addition, the red mud finally obtained by this method still has a high alkalinity, and it is still impossible to achieve harmless and large-scale utilization in the future. Summary of the Invention

[0003] (1) Technical issues to be resolved

[0004] Given the existing technology, the red mud in the existing alumina industry is discharged first and then treated, which makes it impossible to achieve harmless and large-scale utilization.

[0005] (2) Technical solution

[0006] To this end, the present invention provides a method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking, comprising:

[0007] Step 1: Slurry preparation: high-iron bauxite, calcium compound, and Bayer mother liquor are mixed and slurried to obtain slurry;

[0008] Step 2: Calcification transformation: The slurry is transported to a high-pressure dissolution reactor to redistribute the sodium, aluminum, silicon, and iron phases in the slurry, so that sodium alkali and alumina enter the solution, and part of the alumina enters the slag phase in the form of hydrated garnet. The alkali-containing sodium silicon slag phase is transformed into an alkali-free hydrated garnet phase to obtain transformed red mud;

[0009] Step 3: Liquid-solid separation, using a vortex rapid sedimentation tank to separate and wash the transition red mud;

[0010] Step 4: Add a binder to the washed and dried transition red mud to form small balls, which are then calcined and hardened to form ironmaking pellets.

[0011] Furthermore, the calcareous compound is calcium oxide, and the added mass of calcium oxide is 3% to 10% of the total mass of the ore.

[0012] Furthermore, the calcareous compound is at least one of lime or calcium aluminate.

[0013] Furthermore, the concentration of Na2O in the Bayer mother liquor is 180-300 g / L.

[0014] Furthermore, the biomass is one or a mixture of straw, bagasse, cellulose, wood, starch, sawdust, wheat straw, and rice husk.

[0015] Furthermore, the temperature of the calcification transformation dissolution process is 200° C. to 300° C., and the calcification transformation reaction time is 0.5 to 2 hours.

[0016] Furthermore, in step 3, separation and washing are performed in a vortex rapid sedimentation tank, and the sodium oxide content is <1%.

[0017] Furthermore, the caustic ratio αk in the Bayer mother liquor is 2-10.

[0018] Furthermore, the mass ratio of liquid to solid in the slurry is (2-8):1.

[0019] Furthermore, the high-iron bauxite is gibbsite.

[0020] (3) Beneficial effects

[0021] The beneficial effects of the present invention are as follows: the present invention mentions a method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking, including: slurry preparation, mixing high-iron bauxite, calcium compounds and Bayer mother liquor and then slurrying to obtain slurry; calcification transformation, transporting the slurry to a high-pressure dissolution reactor, redistributing the sodium, aluminum, silicon and iron phases in the slurry, so that sodium alkali and most of the alumina enter the solution, part of the alumina enters the slag phase in the form of hydrated garnet, and the alkali-containing sodium silicon slag phase is converted into an alkali-free hydrated garnet phase to obtain transformed red mud; liquid-solid separation, separating and washing the transformed red mud with a vortex rapid sedimentation tank; adding a binder to the washed and dried transformed red mud to form small balls, which are then hardened and consolidated into ironmaking pellets through roasting.

[0022] To overcome the current practice of red mud being discharged prior to treatment in the alumina industry, this invention proposes a method for clean production of bauxite trihydrate based on source-blocking calcification transformation. Through high-temperature calcification transformation, boehmite, which cannot be dissolved at low temperatures, can be dissolved at high temperatures. The aluminous goethite in the dissolution process is transformed into hematite during the calcification process, releasing the alumina contained therein, further enhancing the dissolution of the alumina. The transformation process achieves an alumina dissolution rate exceeding 80%, a 3% to 8% improvement over the existing low-temperature Bayer process. Sodium and alkali recovery exceeds 90%, and the final sodium oxide content in the transformed red mud is less than 1%. The transformed red mud can be directly used in pellet production. This method can directly utilize Bayer process equipment, offering simple process and equipment, high production efficiency, and direct use of the transformed slag as pellet feedstock in pellet production. The entire process generates no solid waste, ultimately achieving harmless, high-value, and fully quantified disposal of red mud, completely resolving the global challenge of large-scale red mud emissions during alumina production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart of a method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking mentioned in this application;

[0024] Figure 2 This is another process flow chart of a method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking mentioned in this application. DETAILED DESCRIPTION

[0025] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0026] When amount, concentration or other value or parameter are represented with range, preferred range or the range that a series of upper preferred value and lower preferred value limit are expressed, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, and no matter whether this scope is disclosed separately.For example, when disclosing scope " 1-5 ", described scope should be interpreted as including scope " 1-4 ", " 1-3 ", " 1-2 ", " 1-2 and 4-5 ", " 1-3 and 5 " etc.When numerical range is described in this article, unless otherwise stated, otherwise this scope is intended to include its end value and all integers and fractions within this range.

[0027] In these embodiments, unless otherwise indicated, the parts and percentages are all measured by mass. "Parts by mass" refers to the basic unit of measurement for expressing the mass ratio relationship of multiple components. 1 part can represent any unit mass, such as 1g, 3.527g, etc. If we say that the mass parts of component A are a parts and the mass parts of component B are b parts, then it means that the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiplication factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0028] refer to Figure 2 The present invention relates to a method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking, comprising:

[0029] Step 1: Slurry preparation

[0030] The high iron bauxite (gibbsite ore), calcium compounds (calcium oxide, lime or calcium aluminate, etc.) and Bayer mother liquor are mixed and pulped to obtain ore pulp.

[0031] It should be noted that the raw materials are fully mixed to form a uniform slurry, which provides a good material basis and reaction interface for the subsequent calcification transformation reaction, so that the various components can fully contact and undergo chemical reactions.

[0032] It should be noted that the use of Bayer mother liquor for slurrying realizes the recycling of mother liquor, reduces resource waste and the use of new water, and reduces production costs.

[0033] It should be noted that by controlling the added mass of calcium compounds (the added mass of calcium oxide is 3%-10% of the total mass of the ore), the Na2O concentration in the Bayer mother liquor (180-300g / L), the caustic ratio αk of the Bayer mother liquor (2-10), and the liquid to solid mass ratio in the slurry (2-8:1), the chemical composition and physical properties of the reaction system can be precisely controlled, which is beneficial to the subsequent calcification transformation reaction and the generation of products.

[0034] Step 2: Calcification transformation The slurry is transported to a high-pressure dissolution reactor to redistribute the sodium, aluminum, silicon, and iron phases in the slurry, so that sodium alkali and most of the alumina enter the solution, and part of the alumina enters the slag phase in the form of hydrated garnet. The alkali-containing sodium silicon slag phase is transformed into an alkali-free hydrated garnet phase to obtain transformed red mud.

[0035] It should be noted that sodium alkali and most of the aluminum oxide enter the solution, realizing the effective recovery of sodium and aluminum resources, improving resource utilization and reducing resource waste.

[0036] It should be noted that converting the original alkali-containing sodium silicate slag phase into an alkali-free hydrated garnet phase reduces the alkali content in the slag phase, reduces the impact of alkali on subsequent treatment processes and the environment, and is also beneficial to the comprehensive utilization of red mud.

[0037] It should be noted that the temperature for controlling the calcification transformation and dissolution process is 200℃-300℃, and the reaction time is 0.5-2h. Under such high temperature and high pressure conditions, the reaction rate can be accelerated, the reaction can be carried out more fully, and the reaction efficiency and product quality can be improved.

[0038] Step 3: Liquid-solid separation The transition red mud is separated and washed using a vortex rapid sedimentation tank, and the sodium oxide content is <1%.

[0039] It should be noted that the vortex rapid sedimentation tank has efficient separation capabilities, which can quickly achieve liquid-solid separation of transformed red mud and improve production efficiency.

[0040] It should be noted that through separation and washing, the sodium oxide content in the transition red mud can be effectively reduced to <1%, reducing the impact of impurities on the subsequent preparation of ironmaking pellets and improving the purity and quality of the red mud.

[0041] Step 4: Preparation of ironmaking pellets: Add a binder to the washed and dried transition red mud to form small balls, which are then calcined and hardened to form ironmaking pellets.

[0042] It should be noted that converting the previously difficult-to-process red mud into ironmaking pellets with certain physical and chemical properties realizes the resource utilization of red mud and reduces the environmental impact of red mud storage. - Providing ironmaking raw materials: The prepared ironmaking pellets can be used as raw materials for ironmaking, providing a new resource source for the steel industry and reducing its dependence on traditional iron ore.

[0043] To overcome the current practice of red mud being discharged prior to treatment in the alumina industry, this invention proposes a method for clean production of bauxite trihydrate based on source-blocking calcification transformation. Through high-temperature calcification transformation, boehmite, which cannot be dissolved at low temperatures, can be dissolved at high temperatures. The aluminous goethite in the dissolution process is transformed into hematite during the calcification process, releasing the alumina contained therein, further enhancing the dissolution of the alumina. The transformation process achieves an alumina dissolution rate exceeding 80%, a 3% to 8% improvement over the existing low-temperature Bayer process. Sodium and alkali recovery exceeds 90%, and the final sodium oxide content in the transformed red mud is less than 1%. The transformed red mud can be directly used in pellet production. This method can directly utilize Bayer process equipment, offering simple process and equipment, high production efficiency, and direct use of the transformed slag as pellet feedstock in pellet production. The entire process generates no solid waste, ultimately achieving harmless, high-value, and fully quantified disposal of red mud, completely resolving the global challenge of large-scale red mud emissions during alumina production.

[0044] To better understand the technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0045] The bauxite used in the embodiment of the present invention is high-iron trihydrate bauxite imported from Guinea by a domestic alumina enterprise, and its chemical composition by mass percentage is: Al2O3 is 41.19%, SiO2 is 3.30%, Fe2O3 is 31.33%, and sodium oxide is 0.029%.

[0046] Example 1

[0047] Process such as Figure 1 、 Figure 2 As shown:

[0048] A sodium aluminate solution having a sodium oxide concentration of 220 g / L and a caustic ratio of 3.0 is mixed with high-iron bauxite and calcium oxide at a liquid-solid ratio of 2.5 ml / g, wherein the amount of calcium oxide added is 6% of the amount of the ore, to prepare a mixed slurry;

[0049] The mixed slurry was heated to 240°C under stirring conditions for dissolution reaction, the stirring speed was 300 rpm, and the dissolution reaction time was 60 min to obtain a dissolution material;

[0050] The dissolved materials were quickly separated, washed and then dried in a vortex rapid sedimentation tank. The percentage of sodium oxide in the transformed red mud was 0.8%, and the aluminum oxide recovery rate was 85.6%.

[0051] Example 2

[0052] A sodium aluminate solution having a sodium oxide concentration of 260 g / L and a caustic ratio of 4 is mixed with high-iron bauxite and calcium oxide at a liquid-solid ratio of 3 ml / g, wherein the amount of calcium oxide added is 7.5% of the amount of the ore, to prepare a mixed slurry;

[0053] The mixed slurry was heated to 260° C. under stirring conditions for dissolution reaction, the stirring speed was 300 rpm, and the dissolution reaction time was 50 min to obtain the dissolution material;

[0054] The dissolved materials were quickly separated, washed and then dried in a vortex rapid sedimentation tank. The percentage of sodium oxide in the transformed red mud was 0.71%, and the aluminum oxide recovery rate was 89.6%.

[0055] Example 3

[0056] A sodium aluminate solution having a sodium oxide concentration of 280 g / L and a caustic ratio of 5 is mixed with high-iron bauxite and calcium oxide at a liquid-solid ratio of 5 ml / g, wherein the amount of calcium oxide added is 10% of the amount of the ore, to prepare a mixed slurry;

[0057] The mixed slurry was heated to 280°C under stirring conditions for dissolution reaction, the stirring speed was 300 rpm, and the dissolution reaction time was 60 min to obtain a dissolution material;

[0058] The dissolved material was quickly separated, washed and then dried in a vortex rapid sedimentation tank. The percentage of sodium oxide in the transformed red mud was 0.47% and the aluminum oxide recovery rate was 90.1%.

[0059] The above describes the basic principles, main features, and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any person skilled in the art without departing from the technical solution of the present invention should be included in the patent scope of the present invention.

[0060] In the description of the present invention, each embodiment focuses on the differences from other embodiments, and reference can be made to the same or similar parts between the embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0061] In the description of the present invention, relational terms such as first and second are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined. Moreover, the term "comprises", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements includes not only those elements, but also includes other elements not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the statement "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or equipment comprising the elements.

[0062] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0063] In the description of this specification, the terms "one embodiment", "some embodiments", "embodiments", "examples", "specific examples" or "some examples" refer to the specific features, structures, materials or characteristics described in conjunction with the embodiment or example and included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0064] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking, characterized in that: include: Step 1: Slurry preparation: high-iron bauxite, calcium compound, and Bayer mother liquor are mixed and slurried to obtain slurry; Step 2: Calcification transformation: The slurry is transported to a high-pressure dissolution reactor to redistribute the sodium, aluminum, silicon, and iron phases in the slurry, so that sodium alkali and alumina enter the solution, and part of the alumina enters the slag phase in the form of hydrated garnet. The alkali-containing sodium silicon slag phase is transformed into an alkali-free hydrated garnet phase to obtain transformed red mud; Step 3: Liquid-solid separation, using a vortex rapid sedimentation tank to separate and wash the transition red mud; Step 4: Add a binder to the washed and dried transition red mud to form small balls, which are then calcined and hardened to form ironmaking pellets.

2. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: The calcium compound is calcium oxide, and the added mass of calcium oxide is 3% to 10% of the total mass of the ore.

3. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: The calcium compound is at least one of lime or calcium aluminate.

4. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: The concentration of Na2O in Bayer mother liquor is 180-300 g / L.

5. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: The biomass is one or a mixture of straw, bagasse, cellulose, wood, starch, sawdust, wheat straw, and rice husk.

6. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: The temperature of the calcification transformation dissolution process is 200°C to 300°C, and the calcification transformation reaction time is 0.5 to 2 hours.

7. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: In step 3, separation and washing are performed in a vortex rapid sedimentation tank, and the sodium oxide content is <1%.

8. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: The caustic ratio αk in Bayer mother liquor is 2 to 10.

9. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: The mass ratio of liquid to solid in the slurry is (2-8):

1.

10. The method for treating bauxite trihydrate by high-temperature calcification transformation based on source blocking according to claim 1, characterized in that: The high iron bauxite is gibbsite.

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