Production process for dry-wet combined cyclic utilization of secondary aluminum ash

Abstract

The invention discloses a production process for dry-wet combined cyclic utilization of secondary aluminum ash, which comprises the following steps: step (1), mixing the secondary aluminum ash and a deamination agent according to the ratio of 100: (0.5-5) in parts by weight to obtain a mixed material; (2) taking 1 part of the mixture obtained in the step (1), adding 1.5-4 parts of water, performing stirring hydrolysis in a hydrolysis tank, then performing first ball milling, then adding a fluorine fixing agent for fluorine fixing treatment, and after fluorine fixing is completed, performing second ball milling until the average particle size is 0.7-1.5 [mu] m, so as to obtain a denitrified material; and (3) dehydrating the denitrified material to obtain a filter cake and a filtrate with the water content of 35-55%, and respectively feeding the filter cake and the filtrate into a dry process line and a wet process line to prepare calcium aluminate and polyaluminum chloride. The invention relates to the field of aluminum slag resource recovery, and discloses a method for preparing calcium aluminate and polyaluminum chloride from materials with ammonia nitrogen compounds removed through a dry method and a wet method respectively, so that the cycle index of raw materials in the independent production process of the two products can be reduced, the sintering temperature of the calcium aluminate can be reduced, and low-cost continuous production can be realized.

Description

Technical Field

[0001] The invention relates to the field of aluminum slag resource recovery, and in particular to a production process for the dry-wet combined recycling of secondary aluminum ash. Background Art

[0002] Secondary aluminum ash, also known as black ash, is mainly the waste after the extraction of metallic aluminum from primary aluminum ash or the aluminum-containing waste slag produced during the aluminum refining process. Secondary aluminum ash is a hazardous waste that contains a large amount of toxic and harmful substances such as fluoride, cyanide, aluminum carbide, and aluminum amide. Since secondary aluminum ash contains a high content of alumina, it has a wide range of application value. After ball milling, iron tapping, and screening, it forms a powder. It also contains a large amount of impurities and requires secondary treatment to form a product. The secondary treatment is divided into two technical processes, one is a wet process, which eventually forms polyaluminum chloride (water purifier) ​​after various processing treatments, and the other is a pyrometallurgical process, which eventually forms calcium aluminate (deoxidizer and high-aluminum material).

[0003] CN112794353B proposes a method and device for preparing polyaluminium chloride by resource utilization of aluminium ash slag, comprising the following steps: step 1: washing the recovered aluminium ash in a hydrolysis bin, filtering, drying and crushing the washed aluminium ash slag to obtain secondary aluminium ash; step 2: separating the secondary aluminium ash into main reaction aluminium ash and side reaction aluminium ash, diverting the secondary aluminium ash by a lifting mechanism, adding recovered waste hydrochloric acid and water to the main reaction aluminium ash for reaction, and obtaining aluminium chloride solution; step 3: dividing the aluminium chloride solution into a main reaction solution and a side reaction solution according to a certain volume ratio, subjecting the main reaction solution to primary constant temperature aging and secondary constant temperature aging; and step 4: filtering and centrifuging to obtain polyaluminium chloride.

[0004] CN111908491B relates to the technical field of polyaluminium chloride production methods, and specifically to a process for producing polyaluminium chloride using waste aluminium slag and aluminium ash, comprising aluminium slag treatment, a primary polymerization reaction, a secondary polymerization reaction, a primary liquid treatment, a tertiary polymerization reaction, etc. The waste aluminium slag and aluminium ash are processed into filter cakes, polyaluminium chloride solutions and polyaluminium chloride slurries after multiple processing.

[0005] CN114853460B discloses a method for preparing calcium aluminate synchronously by treating secondary aluminum ash with a sintering machine. The method comprises the following steps: mixing the secondary aluminum ash with calcium-containing raw materials, return ore and fuel to form granules, feeding the obtained granules to the sintering machine, igniting and sintering, cooling and crushing the obtained sintered ore to obtain a sintered calcium aluminate product. The method makes full use of the heat release from oxidation of metal aluminum in the secondary aluminum ash, the combustion of fuel and the automatic heat storage of the material layer to heat the sintering material, adjusts the liquid phase by controlling the metal aluminum content and alkalinity of the mixed material, and controls the sintering speed by using the sintering negative pressure, so that harmful elements such as K, Na, Cl and N in the secondary aluminum ash are quickly removed under high temperature conditions, and a sintered calcium aluminate product with excellent performance is obtained.

[0006] Secondary aluminum ash contains a large amount of ammonia nitrogen compounds. The collection and treatment of ammonia nitrogen compounds in the actual production process requires additional costs. The production process of polyaluminum chloride requires multiple polymerization, filter pressing and other processes. The filter residue needs to be repeatedly reused, which increases the number of raw material cycles and increases production costs. The production process of calcium aluminate requires high-temperature treatment. Due to the presence of ammonia nitrogen compounds in secondary aluminum ash, the sintering reaction temperature of the existing technology is even close to 1400°C. Summary of the invention

[0007] In order to solve the above problems, the present invention proposes a production process for the combined dry and wet recycling of secondary aluminum ash, in which the materials after removal of ammonia nitrogen compounds are used to prepare calcium aluminate and polyaluminum chloride respectively through dry and wet lines, which can reduce the number of raw material cycles in the separate production processes of the two products, reduce the sintering temperature of calcium aluminate, and realize low-cost continuous production.

[0008] To achieve the above object, the technical solution of the present invention is:

[0009] A production process for the dry-wet combined recycling of secondary aluminum ash, comprising the following steps:

[0010] Step (1) ingredients: by weight, secondary aluminum ash and deamination agent are mixed in a ratio of 100:0.5-5 to obtain a mixed material;

[0011] Step (2) denitrification: take 1 part of the mixed material obtained in step (1), add 1.5-4 parts of water, stir and hydrolyze in a hydrolysis tank, and then pass through the first ball milling, then add a fluorine fixing agent for fluorine fixing treatment, and after the fluorine fixing is completed, pass through the second ball milling until the average particle size is 0.7-1.5 μm to obtain a denitrified material;

[0012] Step (3) dehydration treatment: the denitrified material is dehydrated to obtain a filtrate and a filter cake with a moisture content of 35%-55%, the filtrate enters a wet process line to produce polyaluminium chloride; the filter cake enters a dry process line to produce calcium aluminate;

[0013] The dry process line comprises the following steps:

[0014] Step (a-1): uniformly mixing the filter cake with the mixed material in step (1) until the moisture content is 10%-20% to obtain a pre-treated material, and the pre-treated material is allowed to stand for a while and then formed into a blank;

[0015] Step (a-2): sintering the blank at 1250-1320° C. for 1-2 hours, cooling, and crushing to obtain calcium aluminate;

[0016] The wet process line comprises the following steps:

[0017] Step (b-1): adding 15%-20% of a polymerizing agent to the filtrate, adjusting the pH to 2-5, and obtaining wet polyaluminium chloride after sedimentation and dehydration;

[0018] Step (b-2): drying the wet polyaluminium chloride to obtain polyaluminium chloride.

[0019] In this scheme, the denitrification process of the secondary aluminum ash in step (2) is the key to the entire scheme. In the hydrolysis and deamination process, a deamination agent is added to accelerate the hydrolysis of aluminum nitride and other substances in the secondary aluminum ash, so that the aluminum element mainly exists in the form of aluminum oxide, aluminum hydroxide and metaaluminate; the first ball milling process further breaks the material particles, so that the residual aluminum nitride therein is further hydrolyzed, and the second ball milling reduces the average particle size of the material to 0.7-1.5μm, which reduces the temperature of the solid phase reaction of the dry process line and enables the reaction to be more complete. The solid fluorine agent is added because the raw material after grinding is in liquid form and is not easy to dehydrate. After adding the solid fluorine agent and stirring, the raw material is made into a fluid state, so that the dehydration can proceed normally. Since the generated sodium aluminate and potassium aluminate are soluble in water, they exist in the filtrate after dehydration treatment, that is, the aluminum source for the wet process line to produce polyaluminum chloride; aluminum oxide, aluminum hydroxide and insoluble calcium aluminate exist in the filter cake, which is the aluminum source for producing calcium aluminate in the dry process line. This solution removes ammonia nitrogen compounds in the material before entering the dry process line through hydrolysis and the first ball milling, and reduces the average particle size of the material before entering the dry process line through the second ball milling. The combined effect of the two reduces the overall ammonia nitrogen compound content of the dry process line material and reduces the particle size, so that the sintering temperature only needs to be around 1300°C.

[0020] Preferably, in step (1), the deamination agent is a mixture of sodium hydroxide, calcium oxide and sodium carbonate in a mass ratio of 1:0.3-0.5:0.3-0.5.

[0021] In order to accelerate the denitrification reaction, the hydrolysis reaction in the hydrolysis tank needs to maintain a certain temperature and pH, and sodium hydroxide and calcium oxide are added. The reaction of calcium oxide and water provides a certain temperature for the hydrolysis process. The large amount of hydroxide ions provided by sodium hydroxide is conducive to the conversion of ammonium ions generated by hydrolysis into ammonia. At the same time, the alkaline environment converts aluminum hydroxide generated by the hydrolysis reaction into aluminate, which also promotes the hydrolysis reaction. Sodium carbonate can precipitate calcium ions and reduce the generation of calcium aluminate.

[0022] Preferably, in step (2), the temperature of the stirring hydrolysis in the hydrolysis tank is 50-105° C., and the reaction time is 2-10 h.

[0023] Preferably, the hydrolysis tank comprises a tank body, an air outlet, a conduit, a feed port, and a discharge port, wherein the air outlet is arranged at the top of the tank body; the feed port is arranged at the upper end of the tank body; the discharge port is arranged at the lower end of the tank body; the conduit penetrates into the tank body, and the part of the conduit penetrating into the tank body is provided with a conduit end facing vertically downward, and a guide hole is provided on the surface of the conduit end, and a filter screen of 100-200 mesh is provided in the guide hole.

[0024] Preferably, one of air, water vapor or alkali solution with a temperature of 80-120° C. is introduced into the conduit, and the alkali solution is a sodium hydroxide solution with a mass concentration of 0.1%-2%.

[0025] In order to ensure the temperature in the hydrolysis tank, a conduit is passed through the tank body, which can be passed through high-temperature gas, high-temperature water vapor or high-temperature alkali solution. Since the high temperature in the hydrolysis tank will cause a large amount of water to evaporate, affecting the fluidity of the material, the introduction of high-temperature water vapor can not only maintain the high temperature in the hydrolysis tank, but also improve the fluidity of the material and supplement a certain amount of water; the target products of this scheme are calcium aluminate and polyaluminum chloride. The introduction of high-temperature alkali solution not only has a function similar to high-temperature water vapor, but also can adjust the content of sodium aluminate in the material after the hydrolysis reaction, that is, to adjust the output ratio of the final product calcium aluminate and polyaluminum chloride, which is conducive to flexible adaptation to production needs; the introduction of high-temperature air can accelerate the evaporation of water and adjust the pH. The ammonia discharged from the outlet can be collected and used as a dry process line sintering or wet process line drying fuel. The function of the conduit end and the filter is to prevent the pressure change in the conduit from causing the material to flow back.

[0026] Preferably, in step (2), the fluorine-fixing agent is calcium oxide, the fluorine-fixing treatment time is 1-3 hours, and the fluorine-fixing treatment temperature is 20-60°C.

[0027] Preferably, in step (a-1), the standing time is 3-5 hours.

[0028] Stirring not only mixes the materials evenly, but also hydrolyzes the newly introduced aluminum nitride in the materials and removes some ammonia nitrogen compounds.

[0029] Preferably, in step (a-2), during the sintering process, the oxygen concentration is 18%-22%.

[0030] The main purpose of ensuring sufficient oxygen for sintering is to convert a small amount of ferrous iron, iron, aluminum and other substances in the material into oxides to ensure the efficiency of the solid phase reaction, and at the same time react with ammonia nitrogen compounds to generate nitrogen.

[0031] Preferably, in step (b-1), the polymerization agent is aluminum chloride and sodium chloride in a mass ratio of 3-5:1, and the pH is adjusted by hydrochloric acid.

[0032] Preferably, in step (b-2), the drying condition is 60-80°C and kept warm for 2-3h.

[0033] Compared with the existing technology, the advantages of this solution are:

[0034] 1. Process: By removing the ammonia nitrogen compounds from the materials, the materials are fed into the dry process line and the wet process line in the form of filter cake and filtrate to prepare calcium aluminate and polyaluminium chloride, respectively. This can reduce the number of raw material cycles in the separate production of the two products, reduce the sintering temperature of calcium aluminate, and achieve low-cost continuous production;

[0035] 2. Equipment: By designing the hydrolysis tank, the hydrolysis reaction in the hydrolysis tank can be flexibly controlled. At the same time, the output of the dry process line and the wet process line, the material flow state, and the pH can be controlled by changing the medium entering the conduit, thereby improving production flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 It is a production line equipment diagram for the production process of secondary aluminum ash dry-wet combined recycling utilization described in Example 1 of the present invention;

[0038] Figure 2 It is a cross-sectional structural diagram of the hydrolysis tank of the present invention;

[0039] Figure 3 This is a structural diagram of the conduit end of the hydrolysis tank of the present invention;

[0040] Figure 4 This is a structural diagram of the guide holes of the hydrolysis tank of the present invention;

[0041] In the figure: 1. primary batching tank; 2. transfer machine; 3. dry batching tank; 4. central control system; 5. hydrolysis tank; 5-1. tank body; 5-2. air outlet; 5-3. conduit; 5-4. feed inlet; 5-5. discharge outlet; 5-3-1. conduit end; 5-3-2. guide hole; 5-3-3. filter; 6. first ball mill; 7. fluorine fixation device; 8. second ball mill; 9. dehydration system; 10. wet batching device; 11. wet dehydrator; 12. drying machine; 13. molding machine; 14. water treatment equipment; 15. dust removal equipment; 16. cooling equipment; 17. crushing and packaging equipment; 18. ammonia pipeline; 19. sintering equipment. DETAILED DESCRIPTION

[0042] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. 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 creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] A production process for the dry-wet combined recycling of secondary aluminum ash (combined Figure 1 The production line equipment for the production process of secondary aluminum ash dry-wet combined recycling) includes the following steps:

[0045] Step (1) batching: by weight, the secondary aluminum ash and the deamination agent are mixed in a ratio of 100:1 through a primary batching tank 1 to obtain a mixed material; the deamination agent is a mixture of sodium hydroxide, calcium oxide and sodium carbonate in a mass ratio of 1:0.5:0.5; the mixed material is divided into two paths through a transfer machine 2, one of which enters a hydrolysis tank 5 and the other enters a dry batching tank 3 for standby use;

[0046] Step (2) Nitrogen removal: Take 1 part of the mixture obtained in step (1) (i.e., the mixture entering the hydrolysis tank 5), add 4 parts of water, stir and hydrolyze in the hydrolysis tank 5 at 100°C for 5 hours, and then pass it into the first ball mill 6 for the first ball milling, which is mainly to promote the hydrolysis of residual aluminum nitride. Then the material enters the fluorine fixation device 7, adds calcium oxide at 50°C for fluorine fixation treatment for 2 hours, and then passes it into the second ball mill 8 for the second ball milling, ball milling to an average particle size of 1.0 μm to obtain a denitrified material; the structure of the hydrolysis tank 5 is shown in FIG. Figure 2-4 As shown, it includes a tank body 5-1, an air outlet 5-2, a conduit 5-3, a feed port 5-4, and a discharge port 5-5. The air outlet 5-2 is arranged at the top of the tank body 5-1 and connected to the ammonia pipeline 18. The generated ammonia is collected and enters the sintering equipment 19 to serve as fuel; the feed port 5-4 is arranged at the upper end of the tank body 5-1, and the discharge port 5-5 is arranged at the lower end of the tank body 5-1; the conduit 5-3 penetrates into the tank body 5-1, and the part of the conduit 5-3 that penetrates into the tank body 5-1 is provided with a conduit end 5-3-1 that is vertically downward, and a guide hole 5-3-2 is provided on the surface of the conduit end, and a 100-mesh filter screen 5-3-3 is provided in the guide hole 5-3-2, and water vapor with a temperature of 100°C is passed into the conduit 5-3;

[0047] Step (3) dehydration treatment: the denitrified material is dehydrated in the dehydration system 9 to obtain a filter cake and a filtrate with a moisture content of 50%, and the filter cake enters the dry process line to produce calcium aluminate; the filtrate enters the wet process line to produce polyaluminium chloride; the central control system 4 is used to control the process parameters of the equipment of this production line, such as temperature control in the hydrolysis tank 5, medium type control in the conduit 5-3, sintering temperature control and oxygen content control in the dry process line, and automatic pH control in the wet process line; the water treatment equipment 14 processes the dehydration of each part (such as the denitrified material is dehydrated in the dehydration system 9) so that the production water meets the discharge standard or production reuse standard;

[0048] The dry process line includes the following steps:

[0049] Step (a-1): the filter cake and the mixed material in step (1) (i.e., the mixed material entering the dry process batching tank 3 through the transfer machine 2) are uniformly mixed until the moisture content is 15% to obtain a pretreated material, and the pretreated material is allowed to stand for 3 hours and then molded into a blank by a molding machine 13;

[0050] Step (a-2): placing the blank in a sintering device 19, sintering at 1270° C. for 2 hours under an oxygen concentration of 20%, then cooling in a cooling device 16, and crushing in a crushing and packaging device 17 to obtain calcium aluminate; wherein dust is removed by a dust removal device 15 during the sintering process and then discharged;

[0051] The wet process line comprises the following steps:

[0052] Step (b-1): after the filtrate is passed into the wet batching device 10, 20% of a polymerizing agent is added to the filtrate, wherein the polymerizing agent is aluminum chloride and sodium chloride in a mass ratio of 3:1, and the pH is adjusted to 3 with hydrochloric acid. After sedimentation, the filtrate is dehydrated in a wet dehydrator 11 to obtain a wet polyaluminum chloride material;

[0053] Step (b-2): introducing the wet polyaluminium chloride into a dryer 12 and drying it at 70° C. for 2 h to obtain polyaluminium chloride.

[0054] Example 2

[0055] The difference from Example 1 is that in step (1), the secondary aluminum ash and the deammoniation agent are mixed in a ratio of 100:5.

[0056] Example 3

[0057] The difference from Example 1 is that in step (2), 1.5 parts of water are added to 1 part of the mixed material.

[0058] Example 4

[0059] The difference from Example 1 is that in step (2), after the solid fluorine is completed, a second ball milling is performed to an average particle size of 1.5 μm.

[0060] Example 5

[0061] The difference from Example 1 is that in step (2), an alkali solution with a temperature of 100° C. is introduced into the conduit 5 - 3 , and the alkali solution is a sodium hydroxide solution with a mass concentration of 1%.

[0062] Example 6

[0063] The difference from Example 1 is that in step (2), hot air with a temperature of 100° C. is introduced into the conduit 5 - 3 .

[0064] Comparative Example 1

[0065] The difference from Example 1 is that calcium aluminate is prepared using a dry process line alone.

[0066] Comparative Example 2

[0067] The difference from Example 1 is that polyaluminium chloride is prepared solely by using a wet process line.

[0068] Comparative Example 3

[0069] The difference from Example 1 is that in step (1), the secondary aluminum ash and the deammoniation agent are mixed in a ratio of 100:0.1.

[0070] Comparative Example 4

[0071] The difference from Example 1 is that in step (1), the secondary aluminum ash and the deammoniation agent are mixed in a ratio of 100:6.

[0072] Comparative Example 5

[0073] The difference from Example 1 is that in step (2), 1 part of water is added to 1 part of the mixed material.

[0074] Comparative Example 6

[0075] The difference from Example 1 is that in step (2), after the solid fluorine is completed, a second ball milling is performed to an average particle size of 2.0 μm.

[0076] Comparative Example 7

[0077] The difference from Example 1 is that in step (2), after the solid fluorine is completed, a second ball milling is performed to an average particle size of 0.6 μm.

[0078] Comparative Example 8

[0079] The difference from Example 1 is that in step (2), the conduit 5 - 3 is closed.

[0080] Comparative Example 9

[0081] The difference from Example 1 is that in step (2), no second ball milling is performed.

[0082] Comparative Example 10

[0083] The difference from Example 1 is that in step (2), the first ball milling is not performed.

[0084] Comparative Example 11

[0085] The difference from Example 1 is that in step (2), no fluorine-fixing agent is added.

[0086] Comparative Example 12

[0087] The difference from Example 1 is that in step (2), 30° C. dry air is introduced into conduit 5 - 3 .

[0088] Comparative Example 13

[0089] The difference from Example 1 is that in step (2), an alkali solution at 30° C. is introduced into the conduit 5 - 3 , and the alkali solution is a sodium hydroxide solution with a mass concentration of 1%.

[0090] The main components of the secondary aluminum ash selected in the above embodiments and comparative examples are shown in Table 1:

[0091] Table 1

[0092] Al Fe Si Mg Na+K Cl+F O N other 41.3％ 1.5％ 0.62％ 4.9％ 0.51％ 3.2％ 45.15％ 1.02％ 1.80％

[0093] The prepared calcium aluminate is tested with reference to GBT 29341-2012 "Calcium Aluminate for Water Treatment Agents";

[0094] The prepared polyaluminium chloride is tested with reference to GB 15892-2020 "Polyaluminium chloride for drinking water";

[0095] Also calculate the unit energy consumption cost.

[0096] The results are shown in Table 2.

[0097] Table 2

[0098]

[0099]

[0100]

[0101] As can be seen from Table 2, Example 1-5 has a significant cost advantage over Comparative Example 1-11. At the same time, in terms of quality, the calcium aluminate prepared in Example 1-5 can meet the requirements of GBT 29341-2012 "Calcium Aluminate for Water Treatment Agents", and the prepared polyaluminium chloride can meet the requirements of GB 15892-2020 "Polyaluminium Chloride for Drinking Water", and is even slightly better than commercially available products. In the present invention, the presence of conduit 5-3 can be used to adjust the output structure of calcium aluminate and polyaluminium chloride. If the main product is calcium aluminate, hot water vapor or hot air is introduced into conduit 5-3 to reduce the moisture in the hydrolysis tank, while ensuring fluidity and sufficient hydrolysis. The total amount of aluminum elements entering the filtrate after subsequent dehydration will be reduced, and the wet line output will decrease.

[0102] The main problem of Comparative Examples 1 and 2 is that the advantages and disadvantages of the dry process and the wet process are not fully combined, resulting in an increase in the number of material circulation times and higher costs.

[0103] Comparative Examples 3 and 4 are the effects of the denitrification agent content. When the denitrification agent is too little, that is, in Comparative Example 3, the denitrification reaction is incomplete, resulting in residual ammonia nitrogen compounds, which in turn leads to the inability to obtain qualified products at the same sintering temperature in the dry method. At the same time, the high-temperature volatilization process of ammonia nitrogen compounds requires the absorption of heat, which results in a portion of the heat in the sintering process being consumed, increasing costs; the addition of the denitrification agent introduces aluminate ions. When the denitrification agent is too little, the aluminate ions in the filtrate after dehydration in step (3) are less, and the unreacted aluminum nitride is hydrolyzed to produce aluminum ions, resulting in less polyaluminum chloride output, resulting in an increase in unit cost. In Comparative Example 4, excessive denitrification agent leads to a reduction in calcium aluminate production, and excessive sodium ions lead to a decrease in the purity of calcium aluminate.

[0104] In Comparative Example 5, too little water is added in step (2), which will lead to incomplete hydrolysis. In addition, the solid content of the material discharged from the hydrolysis tank 5 and entering the first ball mill is too high, resulting in poor fluidity and easy blockage. Similar examples of the material solid content of the material discharged from the hydrolysis tank 5 and entering the first ball mill being too high include Comparative Example 8 and Comparative Example 12. As can be seen from Comparative Example 8, when the conduit 5-3 is closed, the material water evaporates due to the high temperature in the hydrolysis tank 5, which makes the material fluidity poor and makes it difficult to discharge; in Comparative Example 12, the low-temperature air takes away part of the water, and at the same time, the temperature drops, the hydrolysis slows down, and the fluidity of the material is also poor due to incomplete hydrolysis, which ultimately leads to a decline in product quality; in Comparative Example 13, cold alkali liquid is passed into the conduit, which also causes the temperature of the hydrolysis tank to drop. Comparative Example 10 did not go through the first ball mill, and both of them are cases of incomplete hydrolysis.

[0105] Comparative Examples 6, 7 and 9 are all about the effect of the average particle size on the process and product after the second ball milling after the solid fluorine is completed. If the average particle size is too large, a higher temperature will be required when sintering calcium aluminate in the dry process line, which will increase the cost. Comparative Example 7 shows that if the particle size is too fine, it will affect the dehydration, resulting in a higher solid content of the filtrate entering the wet process line, and a reduced supply of filter cake entering the dry process line, which will increase the cost and deteriorate the quality. Comparative Example 11 is the same as Comparative Example 7 without the addition of a fluorine agent.

[0106] In summary, the production process for the combined dry-wet recycling of secondary aluminum ash provided in this scheme has great cost advantages and can produce calcium aluminate and polyaluminum chloride that meet performance requirements.

Claims

1. A production process for the dry-wet combined recycling of secondary aluminum ash, characterized in that: The following steps are involved: Step (1) ingredients: by weight, secondary aluminum ash and deamination agent are mixed in a ratio of 100:0.5-5 to obtain a mixed material; Step (2) denitrification: take 1 part of the mixed material obtained in step (1), add 1.5-4 parts of water, stir and hydrolyze in a hydrolysis tank (5), and then pass through a first ball milling, then add a fluorine fixation agent for fluorine fixation treatment, and after fluorine fixation, pass through a second ball milling to an average particle size of 0.7-1.5 μm to obtain a denitrified material; the hydrolysis tank (5) includes a tank body (5-1), an air outlet (5-2), a conduit (5-3), a feed port (5-4), and a discharge port (5-5), wherein the air outlet (5-2) is arranged at the top of the tank body (5-1); the feed port (5-4) is arranged on the upper surface of the tank body (5-1). end; the discharge port (5-5) is arranged at the lower end of the tank body (5-1); the conduit (5-3) penetrates into the tank body (5-1), the part of the conduit (5-3) penetrating into the tank body (5-1) is provided with a conduit end head (5-3-1) vertically downward, the surface of the conduit end head is provided with a guide hole (5-3-2), and the guide hole (5-3-2) is provided with a filter screen (5-3-3) of 100-200 meshes; the conduit (5-3) is passed into one of air, water vapor or alkali liquid with a temperature of 80-120°C, and the alkali liquid is a sodium hydroxide solution with a mass concentration of 0.1%-2%; Step (3) dehydration treatment: the denitrified material is dehydrated to obtain a filtrate and a filter cake with a moisture content of 35%-55%, the filtrate enters a wet process line to produce polyaluminium chloride; the filter cake enters a dry process line to produce calcium aluminate; The dry process line comprises the following steps: Step (a-1): uniformly mixing the filter cake with the mixed material in step (1) until the moisture content is 10%-20% to obtain a pre-treated material, and the pre-treated material is allowed to stand for a while and then formed into a blank; Step (a-2): sintering the blank at 1250-1320° C. for 1-2 hours, cooling, and crushing to obtain calcium aluminate; The wet process line comprises the following steps: Step (b-1): adding 15%-20% of a polymerizing agent to the filtrate, adjusting the pH to 2-5, and obtaining wet polyaluminium chloride after sedimentation and dehydration; Step (b-2): drying the wet polyaluminium chloride to obtain polyaluminium chloride.

2. The production process for the dry-wet combined recycling of secondary aluminum ash according to claim 1, characterized in that: In step (1), the deamination agent is a mixture of sodium hydroxide, calcium oxide and sodium carbonate in a mass ratio of 1:0.3-0.5:0.3-0.

5.

3. The production process for the dry-wet combined recycling of secondary aluminum ash according to claim 1, characterized in that: In step (2), the temperature of stirring hydrolysis in the hydrolysis tank is 50-105° C., and the reaction time is 2-10 h.

4. The production process for the dry-wet combined recycling of secondary aluminum ash according to claim 1, characterized in that: In step (2), the fluorine-fixing agent is calcium oxide, the fluorine-fixing treatment time is 1-3 hours, and the fluorine-fixing treatment temperature is 20-60°C.

5. The production process for the dry-wet combined recycling of secondary aluminum ash according to claim 1, characterized in that: In step (a-1), the stirring time of the pretreated material is 3-5 hours.

6. The production process for the dry-wet combined recycling of secondary aluminum ash according to claim 1, characterized in that: In step (a-2), during the sintering process, the oxygen concentration is 18%-22%.

7. The production process for the dry-wet combined recycling of secondary aluminum ash according to claim 1, characterized in that: In step (b-1), the polymerization agent is aluminum chloride and sodium chloride in a mass ratio of 3-5:1, and the pH is adjusted by hydrochloric acid.

8. The production process for the secondary aluminum ash dry-wet combined recycling as claimed in claim 1, characterized in that: In step (b-2), the drying condition is 60-80° C. and kept warm for 2-3 hours.

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