Secondary aluminum ash treatment method and system

Abstract

The invention discloses a secondary aluminum ash treatment method and system, secondary aluminum ash and alkali liquor are fully mixed, and after denitrification and filtration pretreatment, a solution I rich in sodium aluminate and secondary aluminum ash slag are obtained; uniformly mixing the obtained secondary aluminum ash with red mud, sodium carbonate and limestone according to a set weight part ratio to obtain a mixture; the mixture is pressed and formed into green pellets; drying the obtained green pellets through a drying device to obtain dry pellets; roasting the obtained dry pellets through a roasting device to obtain roasted pellets; the roasted pellets are crushed through a crushing device and then pass through a dissolution device, and a solution II rich in sodium aluminate and a material rich in silicon and calcium are obtained; and performing precipitation treatment on the solution I and the solution II rich in sodium aluminate to obtain aluminum hydroxide, and calcining the aluminum hydroxide at high temperature to obtain an aluminum oxide product. According to the system, the dangerous characteristic of secondary aluminum ash is eliminated, aluminum oxide is recycled, the obtained tailings rich in silicon and calcium serve as silicon-calcium fertilizer raw materials, and full-quantitative utilization of solid waste is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of metallurgical solid waste, and more specifically, relates to a secondary aluminum ash treatment method and system. Background Art

[0002] Aluminum ash is a solid waste generated during the electrolytic aluminum, aluminum processing and recycled aluminum processing. According to the number of times aluminum ash is used in the aluminum recycling process and the content of elemental aluminum, aluminum ash can be divided into primary aluminum ash and secondary aluminum ash. Among them, secondary aluminum ash contains aluminum oxide (30% to 60% of aluminum), aluminum nitride, silicon oxide and fluoride, etc., which are very easy to react with water or in humid air to produce toxic, harmful, explosive and smelly gases, such as ammonia, methane, hydrogen, hydrogen sulfide, etc. Due to its own reactivity, toxicity and other dangerous characteristics, my country included aluminum ash in the "National List of Hazardous Wastes" in 2016. It belongs to the waste of metal smelting, but the aluminum content in secondary aluminum ash is higher, even higher than the aluminum content in bauxite (the content of alumina is usually between 40% and 60%), which gives it greater resource value. According to research, secondary aluminum ash contains 50% to 65% Al2O3. The cost of producing the same quality of Al2O3 using secondary aluminum ash as raw material is about half of that of using bauxite process. Therefore, realizing the resource utilization of secondary aluminum ash can not only eliminate environmental hazards, but also recycle the alumina resources therein at low cost, which has both environmental and economic benefits.

[0003] Chinese patent document CN 106892441A discloses a method for utilizing aluminum ash, wherein aluminum ash slag is poured into a reactor, water is added to the reactor and stirred to form a slurry, and a hydrolysis reaction is performed for deamination. The escaped ammonia generated by the hydrolysis reaction and deamination enters an absorption tower, and the escaped ammonia is collected by spraying water or acid in the absorption tower. The slurry remaining after deamination is loaded into a storage container and placed in a box-type electric furnace for drying to obtain a block aluminum slag, and the block aluminum slag is sent to a vibration mill for ball milling to obtain secondary aluminum ash. This patent document eliminates the dangerous characteristics of aluminum ash through deamination treatment, and only obtains secondary aluminum ash, but does not achieve the recycling of valuable substances therein.

[0004] Chinese patent document CN 105274346A discloses a process for recycling aluminum ash, specifically, aluminum ash and water are pre-treated by slurry mixing, and then the pre-treated aluminum ash slurry is added to a pressure reactor for pressurized water immersion, and the pressurized water immersion obtains leaching residue containing aluminum oxide or aluminum hydroxide and a chloride-containing salt leachate, and the chloride-containing salt leachate is evaporated, crystallized and concentrated to obtain a covering agent for aluminum alloy casting, or industrial salt is obtained by evaporation, crystallization and concentration after defluorination, and the pressurized water leaching residue is calcined at high temperature to obtain aluminum oxide. This patent document recycles aluminum ash by pretreatment + pressurized water immersion, and the purity of the obtained Al2O3 is not high, and the full quantitative utilization of solid waste is not achieved.

[0005] Chinese patent document CN 103695656A discloses a method for recycling aluminum ash, which specifically involves scraping out the hot aluminum ash on the surface of the smelting furnace and conveying the hot aluminum ash to an aluminum ash frying pan within 5 minutes for stirring, controlling the temperature of the aluminum ash in the frying pan, melting the aluminum in the aluminum ash into aluminum liquid and stratifying it with the slag, and then recovering the aluminum liquid from the bottom of the frying pan; the slag is continuously crushed and ground during the cooling process, and the crushed and ground slag is sent to a screening barrel for screening to screen out fine ash, medium screen ash and coarse ash. The patent document solution only realizes the recycling of metallic aluminum in the aluminum ash, but does not extract the alumina resources therein. Summary of the invention

[0006] In order to solve the above-mentioned technical problems, the present invention provides a secondary aluminum ash treatment method and system while eliminating the hazardous characteristics of secondary aluminum ash and recovering the aluminum oxide therein. The tailings can be used as a raw material for silicon-calcium fertilizer to achieve full quantitative utilization of solid waste.

[0007] The technical solutions adopted are as follows:

[0008] In one aspect, the present invention provides a secondary aluminum ash treatment method, the method comprising the following steps:

[0009] Step 1, fully mixing the secondary aluminum ash with the alkali solution, and obtaining a sodium aluminate-rich solution I and secondary aluminum ash slag after denitrification and filtration pretreatment;

[0010] Step 2, mixing the obtained secondary aluminum ash with red mud, soda ash and limestone in a set weight ratio to obtain a mixture;

[0011] Step 3, pressing the mixture into green pellets;

[0012] Step 4, drying the obtained green pellets to obtain dry pellets;

[0013] Step 5, calcining the obtained dry pellets to obtain calcined pellets;

[0014] Step 6, crushing the obtained calcined pellets to obtain calcined pellet particles;

[0015] Step 7, subjecting the roasted pellet particles to a dissolution treatment to obtain a solution II rich in sodium aluminate and a material rich in calcium silicon;

[0016] Step 8, subjecting the obtained sodium aluminate-rich solution I and solution II to precipitation treatment to obtain an aluminum hydroxide product;

[0017] Step 9, calcining the aluminum hydroxide product at high temperature to obtain an aluminum oxide product.

[0018] Among them, in step 2, the weight ratios of secondary aluminum ash, red mud, soda ash and limestone in the mixture are (65-85):(15-35):(30-50):(40-55).

[0019] Preferably, in step 2, the weight ratios of secondary aluminum slag, red mud, soda ash and limestone in the mixture are (75-80):(17-34):(30-40):(42-48).

[0020] Preferably, in step 4, the moisture content of the dry pellets obtained after drying is less than 2%.

[0021] Preferably, the calcination temperature used in step 5 is 1180-1280° C., and the calcination time is 60-120 min.

[0022] Preferably, the particle size of the calcined pellets in step 6 is not greater than 20 mm.

[0023] Preferably, the high temperature calcination temperature used in step 9 is 1000-1200°C.

[0024] On the other hand, the present invention also provides a secondary aluminum ash processing system, the system comprising:

[0025] A pretreatment device is used to mix the secondary aluminum ash with the alkali solution, perform denitrification and filtering treatment, and obtain a solution I rich in sodium chlorate and a secondary aluminum ash slag;

[0026] A mixing device is used to mix the obtained secondary aluminum ash slag with red mud, soda ash and limestone according to a set weight ratio to obtain a mixture;

[0027] A molding device, used for pressing the mixed material into green pellets;

[0028] A drying device, used for drying the raw pellets to obtain dry pellets;

[0029] A roasting device, used for roasting the dry pellets to obtain roasted pellets;

[0030] A crushing device, used for crushing the roasted pellets to obtain roasted pellet particles;

[0031] A dissolution device is used to dissolve the roasted pellet particles to obtain a solution II rich in sodium aluminate and a material rich in calcium silicon;

[0032] A precipitation device is used to precipitate the obtained sodium aluminate-rich solution I and solution II to obtain aluminum hydroxide;

[0033] The calcining device is used to calcine the obtained aluminum hydroxide at high temperature to obtain an aluminum oxide product.

[0034] Preferably, the weight ratios of secondary aluminum ash, red mud, soda ash and limestone in the mixing device are (75-80):(17-34):(30-40):(42-48).

[0035] Preferably, the roasting temperature in the roasting device is 1180-1280° C., and the roasting time is 60-120 min.

[0036] The technical solution of the present invention has the following advantages:

[0037] A. The method and system provided by the present invention utilizes secondary aluminum ash to be mixed with alkali solution for denitrification and filtration pretreatment to obtain a solution I rich in sodium aluminate and a secondary aluminum ash slag, and then the obtained secondary aluminum ash slag ingredients are mixed and successively subjected to ball pressing, drying, roasting, crushing and dissolution treatment to obtain a solution II rich in sodium aluminate, and the two obtained solutions I and II are mixed and subjected to precipitation treatment, and then calcined at high temperature to obtain an alumina product with a purity of more than 95%, thereby eliminating the hazardous characteristics of the secondary aluminum ash and recovering the alumina therein. At the same time, the obtained silicon-calcium tailings can be used as a raw material for silicon-calcium fertilizer, thereby realizing the full quantitative utilization of solid waste.

[0038] B. The method and system of the present invention calcines the obtained aluminum hydroxide at high temperature, thereby removing low-melting-point chlorides and fluorides to prevent them from dissolving into the sodium aluminate solution, thereby significantly improving the quality of the alumina product. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are 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.

[0040] Figure 1 It is a flow chart of the secondary aluminum ash treatment method provided by the present invention;

[0041] Figure 2 It is a process flow chart of the secondary aluminum ash treatment system provided by the present invention;

[0042] Figure 3 It is a schematic diagram of the overall structure of the secondary aluminum ash treatment system provided by the present invention.

[0043] The following are marked in the figure:

[0044] 1- Pretreatment device; 2- Mixing device; 3- Forming device; 4- Drying device; 5- Roasting device

[0045] 6-crushing device; 7-dissolution device; 8-precipitation device; 9-calcination device. DETAILED DESCRIPTION

[0046] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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.

[0047] like Figure 1 As shown, the present invention provides a secondary aluminum ash treatment method, comprising the following steps:

[0048] [S01] The secondary aluminum ash is fully mixed with the alkali solution, and after denitrification and filtration pretreatment, a solution I rich in sodium aluminate and secondary aluminum ash slag are obtained.

[0049] [S02] The obtained secondary aluminum ash slag is mixed with red mud, soda ash and limestone in a set weight ratio to obtain a mixture. The weight ratio of the secondary aluminum ash slag, red mud, soda ash and limestone is (65-85): (15-35): (30-50): (40-55), and the preferred ratio of the present invention is (75-80): (17-34): (30-40): (42-48).

[0050] [S03] Press the mixture into green pellets.

[0051] [S04] Drying the obtained green pellets to obtain dry pellets, wherein the moisture content of the obtained dry pellets is less than 2%.

[0052] [S05] The obtained dry pellets are calcined to obtain calcined pellets; wherein the calcination temperature is 1180-1280° C., and the calcination time is 60-140 min, preferably 60-120 min.

[0053] [S06] The obtained calcined pellets are crushed to obtain calcined pellet particles, wherein the particle size of the calcined pellet particles is not greater than 20 mm.

[0054] [S07] The calcined pellet particles are subjected to dissolution treatment to obtain a solution II rich in sodium aluminate and a material rich in calcium silicon.

[0055] [S08] subjecting the obtained sodium aluminate-rich solution I and solution II to precipitation treatment to obtain aluminum hydroxide. Specifically, the obtained sodium aluminate-rich solution I and solution II are mixed, and then aluminum hydroxide seeds are added to precipitate the aluminum hydroxide product under the conditions of continuous stirring and gradual cooling.

[0056] [S09] The aluminum hydroxide product is calcined at high temperature to obtain an aluminum oxide product. Specifically, the aluminum hydroxide product obtained by precipitation is calcined at a high temperature of 1000°C to 1200°C to remove attached water and crystallization water to obtain an aluminum oxide product.

[0057] The reaction principle of the present invention is as follows: the secondary aluminum ash and the aluminum oxide in the red mud react with the added sodium carbonate and calcium carbonate during high temperature roasting. The main reaction formula is as follows:

[0058] Al2O3+Na2CO3=Na2O·Al2O3+CO2(g);

[0059] Al2O3+2SiO2+Na2CO3=Na2O·Al2O3·2SiO2+CO2(g);

[0060] Na2O·Al2O3·2SiO2+4CaCO3=Na2O·Al2O3+2(2CaO·2SiO2)+CO2(g);

[0061] Na2O·Al2O3+4H2O=2NaAl(OH)4;

[0062] NaAl(OH)4=NaOH+Al(OH)3(s);

[0063] 2Al(OH)3=Al2O3+3H2O(g).

[0064] The present invention converts the aluminum oxide in the secondary aluminum ash and red mud into soluble sodium aluminate, and the soluble sodium aluminate is dissolved into water, and a sodium aluminate-rich solution and solid calcium silicon material are obtained after filtration and separation. The sodium aluminate is dissolved and precipitated to obtain an aluminum hydroxide product, and the aluminum hydroxide product is further calcined at a high temperature of 1000°C to 1200°C to obtain an alumina product. During the high-temperature calcination process, low-melting-point chlorides and fluorides are removed to prevent them from dissolving into the sodium aluminate solution, thereby improving the quality of the alumina product.

[0065] like Figure 2 and Figure 3As shown, the present invention also provides a secondary aluminum ash processing system, which includes: a pretreatment device 1, a mixing device 2, a forming device 3, a drying device 4, a roasting device 5, a crushing device 6, a dissolution device 7, a precipitation device 8, a calcining device 9 and a connecting and conveying device between the devices. The pretreatment device 1 mixes the secondary aluminum ash with the alkali solution, performs denitrification and filtering treatment, and obtains a solution I rich in sodium chlorate and a secondary aluminum ash slag; the mixing device 2 mixes the obtained secondary aluminum ash slag with red mud, soda ash and limestone according to a set weight ratio to obtain a mixture; the molding device 3 presses the mixture into green pellets; the drying device 4 dries the green pellets to obtain dry pellets; the roasting device 5 roasts the dry pellets to obtain roasted pellets; the crushing device 6 crushes the roasted pellets to obtain roasted pellet particles; the dissolution device 7 dissolves the roasted pellet particles to obtain a solution II rich in sodium aluminate and a material rich in calcium silicate; the precipitation device 8 precipitates the obtained solution I and solution II rich in sodium aluminate to obtain aluminum hydroxide; the calcining device 9 calcines the obtained aluminum hydroxide at a calcination temperature of 1000-1200°C to obtain an alumina product. The weight ratio of the secondary aluminum ash, red mud, soda ash and limestone in the mixing device 2 is (65-85): (15-35): (30-50): (40-55), and the further preferred weight ratio is (75-80): (17-34): (30-40): (42-48). The roasting temperature in the roasting device 5 is 1180-1280° C., and the roasting time is 60-120 min.

[0066] The contents of Al and Na in the secondary aluminum ash used in the embodiment of the present invention are Al: 39.61%, Na: 1.03% respectively; the mass ratios of the components in the red mud are Al2O3: 25.5%, Na2O: 6.5%, SiO2: 20.4%; CaO in limestone: 49.5%, and Na2CO3 in soda ash: 98%.

[0067] Example 1

[0068] The secondary aluminum ash and alkali solution are fully mixed in the pretreatment device, and after denitrification and filtration pretreatment, a solution I rich in sodium aluminate and a secondary aluminum ash slag are obtained; the secondary aluminum ash slag, red mud, soda ash and limestone are mixed and pressed into balls according to a mass ratio of 75:25:30:45 in the mixing device, and sent to the drying device for drying, and the water content is controlled below 2%. The dry pellets are roasted at 1180°C for 120 minutes in the roasting device, and the roasted pellets are first crushed to form particles, and then sent to the dissolution device for dissolution, and a solution II rich in sodium aluminate is obtained after dissolution. The solution I and the solution II are sent to the precipitation device for precipitation, and the obtained aluminum hydroxide product is sent to the calcination device. After high-temperature calcination, the Al2O3 content (%) of the aluminum oxide product is ≥97.5%.

[0069] Example 2

[0070] The secondary aluminum ash and alkali solution are fully mixed in the pretreatment device, and after denitrification and filtration pretreatment, a solution I rich in sodium aluminate and a secondary aluminum ash slag are obtained; the secondary aluminum ash slag, red mud, soda ash and limestone are mixed and pressed into balls according to a mass ratio of 67:34:30:48 in the mixing device, and sent to the drying device for drying, and the water content is controlled below 2%. The dry pellets are roasted at 1220°C for 90 minutes in the roasting device, and the roasted pellets are first crushed to form particles, and then sent to the dissolution device for dissolution, and a solution II rich in sodium aluminate is obtained after dissolution. The solution I and the solution II are sent to the precipitation device for precipitation, and the obtained aluminum hydroxide product is then sent to the calcination device. After high-temperature calcination, the Al2O3 content (%) in the alumina product is obtained to be ≥97.9%.

[0071] Example 3

[0072] The secondary aluminum ash and alkali solution are fully mixed in the pretreatment device, and after denitrification and filtration pretreatment, a solution I rich in sodium aluminate and a secondary aluminum ash slag are obtained; the secondary aluminum ash slag, red mud, soda ash and limestone are mixed in a mass ratio of 83:17:35:42, pressed into balls in a forming device to obtain green pellets, and sent to a drying device for drying to obtain dry pellets, and the water content is controlled below 2%. The dry pellets are roasted at 1200°C for 100 minutes in a roasting device to obtain roasted balls, and the roasted pellets are first crushed by a crushing device to form particles, and then sent to a dissolution device for dissolution, and a solution II rich in sodium aluminate is obtained after dissolution, and solution I and solution II are sent to a precipitation device for precipitation, and the obtained aluminum hydroxide product is then sent to a calcining device, and after high-temperature calcination, the Al2O3 content (%) in the aluminum oxide product is obtained to be ≥98.3%.

[0073] Example 4

[0074] The secondary aluminum ash and alkali solution are fully mixed in the pretreatment device, and after denitrification and filtration pretreatment, a solution I rich in sodium aluminate and a secondary aluminum ash slag are obtained; the secondary aluminum ash slag, red mud, soda ash and limestone are mixed in a mass ratio of 80:20:40:45, pressed into balls in a forming device to obtain green pellets, and sent to a drying device for drying to obtain dry pellets, and the water content is controlled below 2%. The dry pellets are roasted at 1280°C for 60 minutes in a roasting device to obtain roasted balls, and the roasted pellets are first crushed by a crushing device to form particles, and then sent to a dissolution device for dissolution, and a solution II rich in sodium aluminate is obtained after dissolution, and solution I and solution II are sent to a precipitation device for precipitation, and the obtained aluminum hydroxide product is then sent to a calcining device, and after high-temperature calcination, the Al2O3 content (%) in the alumina product is obtained to be ≥95.8%.

[0075] Anything not described in the present invention is applicable to the prior art.

[0076] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. However, the obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A secondary aluminum ash treatment method, characterized in that: The method comprises the following steps: Step 1, fully mixing the secondary aluminum ash with the alkali solution, and obtaining a sodium aluminate-rich solution I and secondary aluminum ash slag after denitrification and filtration pretreatment; Step 2, mixing the obtained secondary aluminum ash with red mud, soda ash and limestone in a set weight ratio to obtain a mixture; Step 3, pressing the mixture into green pellets; Step 4, drying the obtained green pellets to obtain dry pellets; Step 5, calcining the obtained dry pellets to obtain calcined pellets; Step 6, crushing the obtained calcined pellets to obtain calcined pellet particles; Step 7, subjecting the roasted pellet particles to a dissolution treatment to obtain a solution II rich in sodium aluminate and a material rich in calcium silicon; Step 8, subjecting the obtained sodium aluminate-rich solution I and solution II to precipitation treatment to obtain an aluminum hydroxide product; Step 9, calcining the aluminum hydroxide product at high temperature to obtain an aluminum oxide product.

2. The secondary aluminum ash treatment method according to claim 1, characterized in that: In step 2, the weight ratios of secondary aluminum ash, red mud, soda ash and limestone in the mixture are (65-85):(15-35):(30-50):(40-55).

3. The secondary aluminum ash treatment method according to claim 2, characterized in that: In step 2, the weight ratios of secondary aluminum ash, red mud, soda ash and limestone in the mixture are (75-80):(17-34):(30-40):(42-48).

4. The secondary aluminum ash treatment method according to claim 1, characterized in that: In step 4, the moisture content of the dry pellets obtained after drying is less than 2%.

5. The secondary aluminum ash treatment method according to claim 1, characterized in that: The calcination temperature used in step 5 is 1180-1280° C., and the calcination time is 60-120 min.

6. The secondary aluminum ash treatment method according to claim 1, characterized in that: The particle size of the calcined pellets in step 6 is no more than 20 mm.

7. The secondary aluminum ash treatment method according to claim 1, characterized in that: The high temperature calcination temperature used in step 9 is 1000-1200°C.

8. A secondary aluminum ash treatment system, characterized in that: The system comprises: A pretreatment device is used to mix the secondary aluminum ash with the alkali solution, perform denitrification and filtering treatment, and obtain a solution I rich in sodium chlorate and a secondary aluminum ash slag; A mixing device is used to mix the obtained secondary aluminum ash slag with red mud, soda ash and limestone according to a set weight ratio to obtain a mixture; A molding device, used for pressing the mixed material into green pellets; A drying device, used for drying the raw pellets to obtain dry pellets; A roasting device, used for roasting the dry pellets to obtain roasted pellets; A crushing device, used for crushing the roasted pellets; A dissolution device is used to dissolve the crushed roasted pellets to obtain a solution II rich in sodium aluminate and a material rich in calcium silicon; A precipitation device is used to precipitate the obtained sodium aluminate-rich solution I and solution II to obtain aluminum hydroxide; The calcining device is used to calcine the obtained aluminum hydroxide at high temperature to obtain an aluminum oxide product.

9. The secondary aluminum ash treatment system according to claim 8, characterized in that: The weight ratios of secondary aluminum ash, red mud, soda ash and limestone in the mixing device are (75-80):(17-34):(30-40):(42-48).

10. The secondary aluminum ash processing system according to claim 8, characterized in that: The roasting temperature in the roasting device is 1180-1280° C., and the roasting time is 60-120 minutes.

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