Method and system for co-processing of aluminum dross in an alumina clinker kiln

Abstract

The present application relates to a kind of bauxite clinker kiln method and system for disposing aluminum ash, belong to metallurgical environmental protection technical field, the method includes the following steps: pretreatment aluminum ash, obtain fine powder aluminum ash;Fine powder aluminum ash is added to bauxite slurry, so that fine powder aluminum ash and the dry raw material and calcined coal ash in bauxite slurry are mixed, and mixed sintering is carried out, and then cooling is carried out, to obtain clinker;The present application carries out resource utilization to aluminum ash, replaces part of aluminum ore, and is used in the production of aluminum-based new material product, while reducing the production cost of aluminum-based new material product, realizes the harmless treatment of aluminum ash.

Description

TECHNICAL FIELD

[0001] The application relates to the field of metallurgical environmental protection, and in particular to a method and system for cooperatively disposing aluminum ash in an alumina clinker kiln. BACKGROUND

[0002] The alumina clinker rotary kiln adopts a wet process. Raw slurry is prepared by mixing circulating mother liquor, aluminum ore, soda ash, limestone ore (or lime) and white coal, and after multiple index adjustments, the raw slurry is atomized into the rotary kiln by a high-pressure pump spray gun. The dried material passes through the kiln tail preheating zone, the decomposition zone, the sintering zone and the cooling zone in sequence, is sintered into clinker, and then the heat is recovered by a single-cylinder cooling machine or a grate cooler to obtain qualified clinker. The clinker is prepared into sodium aluminate crude liquid through wet grinding, liquid-solid separation in a settling tank and washing, and the crude liquid is refined, decomposed, washed and (calcined) to obtain an aluminum-based new material product.

[0003] As the world's largest producer of aluminum products, the domestic aluminum industry produces nearly 3.5 million tons of aluminum ash annually. The National Hazardous Waste List (2021 Edition) lists aluminum ash produced in the electrolytic aluminum, aluminum processing and recycled aluminum industries as hazardous waste (HW48), and requires that aluminum ash be disposed of in accordance with the relevant requirements for hazardous waste. According to the number of times aluminum ash is used in the recycling process and the content of metallic aluminum, aluminum ash can be divided into primary aluminum ash and secondary aluminum ash. Primary aluminum ash contains a large amount of metallic aluminum and has high recycling value, and recycling is common. The content of metallic aluminum in secondary aluminum ash is generally less than 5%, and the current disposal methods for aluminum ash are mainly landfill and cement kiln co-processing. Due to the limited disposal capacity, illegal dumping of aluminum ash across provinces occurs from time to time. Secondary aluminum ash is the residue after physical or chemical methods are used to extract metallic aluminum from primary aluminum ash or other waste aluminum, and has a low content of metallic aluminum and relatively complex composition, mainly containing a small amount of aluminum, salt flux, oxides and aluminum nitride, of which the content of alumina can be more than 60%. Since aluminum ash contains many useful substances, resource utilization of aluminum ash not only has good economic benefits, but also has good environmental benefits.

[0004] After one or more recoveries of metallic aluminum, the content of aluminum in aluminum ash is very low, and mainly contains alumina, aluminum nitride, iron-silicon-magnesium oxides, chlorides, fluorides and the like. The harmless disposal of aluminum ash mainly involves denitrification, fluorine fixation, salt removal, and making the products produced meet the corresponding national or industry product quality standards. Currently, domestic enterprises can divide the harmless disposal of secondary aluminum ash into wet and dry methods. Wet aluminum ash recycling generally refers to placing aluminum ash in a leaching solution, and the leached metallic aluminum and its compounds and leaching residue are treated as solid waste. The dry method is to mix aluminum ash with limestone at a certain ratio, sieve it after ball milling, uniformly send it into a rotary kiln for calcination (calcination temperature is 1,100-1,300 DEG C), and then cool and process it to produce calcium aluminate products.

[0005] Current alumina clinker kiln processing methods involve either feeding the ash directly to the clinker rotary kiln tail for sintering via an elevator, or mixing the ash with raw materials and granulating it before feeding it to the kiln tail. Both of these processes negatively impact the kiln system. Direct feeding of the ash to the kiln tail without granulation allows the elemental aluminum contained in the ash to enter the electrostatic precipitator (ESP) under wind power, impacting its efficiency and causing increased particulate matter. Furthermore, due to the wet process environment at the kiln tail, strict control of ash handling is required to ensure safe operation of the ESP. When granulation is employed, water or recycled mother liquor reacts with the ash during the granulation process, releasing ammonia and hydrogen, which can cause secondary environmental pollution. Summary of the Invention

[0006] To solve the above problems, the present invention provides a method and system for the coordinated disposal of aluminum ash in an alumina clinker kiln, which utilizes the aluminum ash as a resource, replaces part of the aluminum ore, and is used for the production of aluminum-based new material products. While reducing the production cost of aluminum-based new material products, the present invention achieves harmless treatment of aluminum ash.

[0007] In a first aspect, the present invention provides a method for co-processing aluminum ash in an alumina clinker kiln, the method comprising the following steps:

[0008] Pre-treating aluminum ash to obtain fine powder aluminum ash;

[0009] Add dry raw meal and burnt coal ash to the fine powdered aluminum ash, mix and sinter, and then cool to obtain clinker.

[0010] Furthermore, the particle size of the fine powder aluminum ash is 100-200 mesh.

[0011] Furthermore, the pretreatment of aluminum ash to obtain fine powdered aluminum ash comprises the following steps:

[0012] The aluminum ash is ball-milled and then sieved to obtain undersize material;

[0013] The material under the sieve is subjected to secondary grinding and passed through a mesh sieve of a preset particle size to obtain fine powder aluminum ash.

[0014] Furthermore, the preset particle size is 145 mesh to 155 mesh.

[0015] Furthermore, the aluminum ash includes primary aluminum ash and / or secondary aluminum ash.

[0016] Furthermore, the weight ratio of the fine powder aluminum ash, the dry raw meal and the burnt coal ash is 2.5-15:95.6-83.1:1.9.

[0017] Furthermore, the indicators of the clinker include an alkali ratio of 0.95 to 1.01, a calcium ratio of 1.97 to 2.10, an iron-aluminum ratio of 0.065 to 0.075, and a bulk density of 1.10 to 1.35.

[0018] Further, the following is satisfied between the clinker and the alumina slurry:

[0019] The delivered raw material alkali ratio = the clinker alkali ratio ± K1, and the raw material calcium ratio = the clinker calcium ratio ± K2;

[0020] Wherein, K1, K2 are historical delivery raw material and clinker difference values.

[0021] Further, the method further comprises: dissolving the clinker to obtain a sodium aluminate crude liquid.

[0022] In a second aspect, the embodiments of the present application provide an alumina clinker kiln system for co-processing aluminum ash, which is used to implement the method of the first aspect, and the system comprises a ball mill, a vibrating screen, a Raymond mill, a fine powder bin, a clinker kiln and a clinker bin connected in sequence.

[0023] The clinker kiln comprises an aluminum ash kiln inlet pipeline and a coal injection pipeline, and the aluminum ash kiln inlet pipeline is arranged above the coal injection pipeline.

[0024] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0025] The present application provides a method and system for co-processing aluminum ash in an alumina clinker kiln. The aluminum ash is pretreated, and the fine powder aluminum ash after pretreatment is fed into the kiln head of the clinker kiln from the alumina production process by dense phase pneumatic conveying. Under the action of its own kinetic energy and the wind force of the kiln tail exhaust fan, it passes through the firing zone (temperature up to 1200℃-1450℃) with the wind. Part of the elemental aluminum and aluminum nitride in the alumina slurry burns and decomposes, and provides heat energy for the kiln. In the kiln tail, the aluminum ash collides with the raw material of the alumina slurry raised by the raising plate area, loses kinetic energy and falls into the raw material. Then, it returns to the kiln head with the raw material to the firing zone. Part of the ultra-fine aluminum ash is captured and agglomerated by the atomized slurry in the kiln tail drying zone. The aluminum ash collected in the raising plate and drying zone area is mixed with dry raw material under the continuous rotation of the rotary kiln, returns from the kiln tail, passes through the decomposition zone and the firing zone, and undergoes various reactions, including: aluminum fluoride is converted into calcium fluoride and alumina, elemental aluminum is burned into alumina, aluminum nitride is converted into nitrogen oxide and alumina, alumina and soda ash are converted into sodium aluminate, and nitrogen oxide is converted into nitrogen by SCR denitrification after the kiln. The produced clinker is dissolved, separated by liquid-solid separation in a settling tank, and washed to produce sodium aluminate crude liquid required for the production of new aluminum-based materials. The separated solid becomes red mud and is discharged for storage. The above process has high utilization rate of aluminum ash, no additional secondary pollution, and because of the high content of alumina in the aluminum ash, the process reduces the requirement for the grade of aluminum ore, and compared with the original process, the A / S of aluminum ore is reduced by 0.8-1.2, which is suitable for digesting low-grade bauxite and reduces the cost of raw materials. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1 A schematic flow chart of a method for collaboratively disposing aluminum ash in an alumina clinker kiln provided in an embodiment of the present application;

[0029] Figure 2 Schematic diagram of the workflow of the system for collaborative disposal of aluminum ash in an alumina clinker kiln provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0031] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0032] like Figure 1 As shown, in a first aspect, the present invention provides a method for co-processing aluminum ash in an alumina clinker kiln, the method comprising the following steps:

[0033] S1. Pre-treating aluminum ash to obtain fine powder aluminum ash;

[0034] S2. Add the fine powdered aluminum ash to the alumina slurry to mix the fine powdered aluminum ash and the dry raw meal in the alumina slurry with the burnt coal ash, and sinter the mixture, and then cool it to obtain clinker.

[0035] In the embodiment of this application, Figure 2As shown, the above process is specifically: the aluminum ash is pretreated, the treated aluminum ash is metered by a screw, and then is sent into the kiln by air, and the aluminum ash in the kiln runs to the kiln tail under the action of the wind of the large kiln exhaust fan and its own kinetic energy, collides with the raised material (or atomized slurry) at the kiln tail raising plate (or drying area), loses kinetic energy, and then is mixed and agglomerated with the drying slurry, and runs to the kiln head, in the running process, the aluminum ash and the drying slurry continuously mix and react, and after the preheating zone, the decomposition zone, the sintering zone and the cooling zone, the aluminum ash enters the cooler to be cooled into qualified clinker. The clinker is subjected to processes such as dissolution, refining, decomposition and washing, and finally the aluminum-based new material product is obtained.

[0036] In some optional embodiments, the aluminum ash includes primary aluminum ash and secondary aluminum ash.

[0037] In the embodiments of the present application, the specific type of aluminum ash can cover most of the aluminum ash waste generated in the alumina production process, thereby improving the universality of the treatment method.

[0038] In some optional embodiments, the particle size of the fine powder aluminum ash is 100-200 mesh.

[0039] In the embodiments of the present application, the specific particle size of the fine powder aluminum ash can facilitate the subsequent mixing and sintering process.

[0040] In some optional embodiments, the pretreated aluminum ash is obtained by the following steps:

[0041] S101. Ball milling the aluminum ash and screening to obtain undersize material;

[0042] S102. Secondary grinding the undersize material through a mesh screen with a preset particle size to obtain fine powder aluminum ash.

[0043] In the embodiments of the present application, by refining the specific pretreatment steps, fine powder aluminum ash with a preset particle size can be obtained through two grinding processes, thereby facilitating the subsequent mixing and sintering process.

[0044] In some optional embodiments, the preset particle size is 145-155 mesh.

[0045] In the embodiments of the present application, by controlling the specific preset particle size, fine powder aluminum ash with a suitable particle size can be obtained, which facilitates the subsequent mixing and sintering process.

[0046] In some optional embodiments, the fine powder aluminum ash is sent into the kiln from the kiln head of the alumina clinker kiln by dense phase air conveying, the inlet pipe is parallel to the coal injection pipe and is arranged above the coal injection pipe, and the inlet pipe is externally cast with refractory material.

[0047] In some alternative embodiments, the weight ratio of the fine aluminum ash, the dry raw material and the calcined coal ash is 2.5-15: 95.6-83.1: 1.9.

[0048] In the embodiments of the present application, the specific weight ratio of the fine aluminum ash, the dry raw material and the calcined coal ash can make the fine aluminum ash, the dry raw material and the calcined coal ash mixed and sintered to form the clinker.

[0049] In some alternative embodiments, the indexes of the clinker include an alkali ratio of 0.95-1.01, a calcium ratio of 1.97-2.10, an iron-aluminum ratio of 0.065-0.075, and a bulk density of 1.10-1.35.

[0050] In some alternative embodiments, to ensure that the clinker indexes meet the expectations, the proportion of the stable fine aluminum ash is added, the clinker indexes are taken as the target, the raw material is ground, and then is adjusted for multiple times to ensure that the delivered raw material alkali ratio = clinker alkali ratio ± K1, and the raw material calcium ratio = clinker calcium ratio ± K2, wherein K1 and K2 are the difference between the delivered raw material and the clinker in the history (the first three shifts of the alumina production).

[0051] In some alternative embodiments, the method further comprises:

[0052] S3. Dissolving the clinker to obtain a sodium aluminate crude solution.

[0053] In the embodiments of the present application, the sodium aluminate in the clinker is leached out by introducing the dissolving method, so as to obtain the sodium aluminate crude solution.

[0054] As shown in Figure 2 Based on the same inventive concept, the embodiments of the present application provide an alumina clinker kiln system for cooperatively disposing aluminum ash, which is used to implement the method and includes a ball mill, a vibrating screen, a Raymond mill, a fine powder bin, a clinker kiln and a clinker bin which are sequentially connected;

[0055] The clinker kiln includes an aluminum ash kiln pipeline and a coal injection pipeline, and the aluminum ash kiln pipeline is arranged above the coal injection pipeline.

[0056] The system is based on the method of the first aspect described above, and therefore at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described here one by one.

[0057] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods not specified in the following examples are generally determined according to the national standards. If there is no corresponding national standard, the international standard, the conventional condition or the condition suggested by the manufacturer is used.

[0058] Example 1

[0059] This example provides a method for co-processing aluminum ash in an alumina clinker kiln. Figure 1 As shown, the method comprises: pre-treating aluminum ash to obtain fine powder aluminum ash; adding the fine powder aluminum ash into an alumina clinker kiln, mixing with dry raw meal and burnt coal ash, sintering, and cooling to obtain clinker; the specific process is:

[0060] After ball milling, screening, and pre-treatment with a Raymond mill, the aluminum ash is converted into fine powder secondary aluminum ash with a mesh size below 150. This is then blown from the kiln head into the rotary kiln by air. At the lifting plate area at the kiln tail, the aluminum ash collides with the lifted raw meal, loses kinetic energy, and falls into the raw meal, returning to the kiln head firing zone along with the raw meal. Some ultrafine aluminum ash is captured and agglomerated by the atomized slurry in the kiln tail drying zone. The aluminum ash collected in the lifting plate and drying zone is mixed with the dry raw meal under the continuous rotation of the rotary kiln. It then returns from the kiln tail, passing through the decomposition zone and firing zone, where various reactions occur. Aluminum fluoride is converted into calcium fluoride and aluminum oxide, elemental aluminum burns to form aluminum oxide, aluminum nitride generates nitrogen oxides and aluminum oxide, and aluminum oxide reacts with soda ash to form sodium aluminate, which enters the solution during the subsequent dissolution process, forming a sodium aluminate solution. Nitrogen oxides are converted into nitrogen through SCR denitrification after the kiln.

[0061] This process has a high resource utilization rate of aluminum ash, no secondary pollution in the process, and is beneficial to reducing ore and combustion costs; the fine powder aluminum ash is transported from the kiln head of the alumina clinker kiln into the kiln through dense phase air, the kiln inlet pipe is parallel to the coal injection pipe and is arranged above the coal injection pipe, and refractory material is cast on the outside of the kiln inlet pipe; the weight ratio of the fine powder aluminum ash, the dry raw meal, and the burned coal ash is 10:90:1.9; the indicators of the clinker include alkali ratio 0.95-1.01, calcium ratio 1.97-2.10, iron-aluminum ratio 0.065-0.075, and bulk density 1.10-1.35; the alkali ratio of the delivered raw meal = clinker alkali ratio ± K1, and the calcium ratio of the raw meal = clinker calcium ratio ± K2, where K1 and K2 are the differences between the historical delivered raw meal and clinker.

[0062] In summary, the present invention provides a method and system for the coordinated disposal of aluminum ash in an alumina clinker kiln, which utilizes the aluminum ash as a resource, replaces part of the aluminum ore, and is used for the production of aluminum-based new material products. While reducing the production cost of aluminum-based new material products, the harmless treatment of aluminum ash is achieved.

[0063] Various embodiments of the present application can take on a variety of scopes; it should be understood that a scope in the form of a range is described merely for the sake of convenience and brevity, and should not be construed as a rigid limitation of scope unless specifically called out as such; therefore, it should be considered that a range description recited has specifically disclosed all possible sub-ranges and individual numerical values within that range. For example, it should be considered that a range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is recited herein, any cited number (fractional or integral) within the recited range is expressly included.

[0064] In the present application, unless otherwise stated, the orientation words such as "upper" and "lower" are specifically the direction of the drawing surface in the drawings. In addition, in the description of the present application, the terms "comprise", "include" and the like mean "including but not limited to". In the present text, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In the present text, "and / or", describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent: the case of A alone, the case of A and B together, and the case of B alone. Where A and B can be singular or plural. In the present text, "one or more" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0065] The above description is merely a specific implementation of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application should not be limited to the embodiments shown herein, but should be consistent with the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for co-processing aluminum ash in an alumina clinker kiln, characterized in that: The method comprises the following steps: Pre-treating aluminum ash to obtain fine powder aluminum ash; The fine powdered aluminum ash is added to the alumina slurry to mix the fine powdered aluminum ash with the dry raw meal in the alumina slurry and the burned coal ash, and the mixture is sintered and then cooled to obtain clinker; wherein the fine powdered aluminum ash is conveyed from the kiln head of the alumina clinker kiln by dense phase air into the kiln, the kiln inlet pipe is parallel to and arranged above the coal injection pipe, and passes through the firing zone with the wind, and the firing zone temperature is 1200° C. to 1450° C.; The aluminum ash includes primary aluminum ash and / or secondary aluminum ash; The particle size of the fine powder aluminum ash is 100 mesh to 200 mesh; The weight ratio of the fine powdered aluminum ash, the dry raw meal and the burnt coal ash is 2.5-15:95.6-83.1:1.9; The indicators of the clinker include alkali ratio of 0.95 to 1.01, calcium ratio of 1.97 to 2.10, iron-aluminum ratio of 0.065 to 0.075, and bulk density of 1.10 to 1.35; The clinker and the alumina slurry satisfy the following conditions: The alkali ratio of the raw meal delivered = the alkali ratio of the clinker ± K1, and the calcium ratio of the raw meal = the calcium ratio of the clinker ± K2; Among them, K1 and K2 are the differences between raw materials and clinker delivered in the first three shifts of alumina production.

2. The method according to claim 1, characterized in that The pre-treatment of aluminum ash to obtain fine powdered aluminum ash comprises the following steps: The aluminum ash is ball-milled and then sieved to obtain undersize material; The material under the sieve is subjected to secondary grinding and passed through a mesh sieve of a preset particle size to obtain fine powder aluminum ash.

3. The method according to claim 2, characterized in that The preset particle size is 145 mesh to 155 mesh.

4. The method according to claim 1, wherein The method further comprises: The clinker is dissolved to obtain a crude sodium aluminate solution.

5. A system for co-processing aluminum ash in an alumina clinker kiln, characterized in that: The system is used to implement the method according to any one of claims 1 to 4, and the system comprises a ball mill, a vibrating screen, a Raymond mill, a fine powder bin, a clinker kiln and a clinker bin connected in sequence; The clinker kiln comprises an aluminum ash inlet pipe and a coal injection pipe. The aluminum ash inlet pipe is parallel to the coal injection pipe and is arranged above the coal injection pipe.

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