Harmless treatment process for aluminum ash through semi-wet pre-deamination

Abstract

According to the semi-wet pre-deamination aluminum ash harmless treatment process provided by the invention, the inhibitor is adopted in the material preparation process, and before brick making is completed, severe hydrolysis reaction caused by contact of aluminum ash and water can be effectively inhibited, so that the ammonia release amount is reduced, and the operation environment is improved; the semi-wet pre-deamination process is adopted, the aluminum ash bricks are subjected to hydrolysis reaction in the solid aluminum ash bricks, ammonia gas escapes from the bricks orderly and stably, the situation that a large amount of combustible gas is generated instantly in the traditional wet process is avoided, meanwhile, aluminum hydroxide generated through hydrolysis is utilized, so that the aluminum ash bricks have certain strength and can be stacked into a tunnel kiln to be sintered, and the production cost is reduced. And carrying out deep deamination and fluorine fixation. Besides, compared with a traditional rotary kiln for calcination, the tunnel kiln for deamination has the advantages that the calcination temperature and time are controllable, the problems of rotary kiln wall ring formation and flue blockage caused by salt fusion and volatilization in the sintering process are solved, continuous production is easy, and flue gas waste heat can be effectively recycled.

Description

Technical Field

[0001] The invention relates to an aluminum ash treatment process, in particular to a semi-wet pre-deammoniation aluminum ash harmless treatment process. Background Art

[0002] In the process of melting and casting aluminum products, in order to obtain qualified performance, the aluminum liquid needs to be purified. Under the action of refining agent, impurities in the aluminum liquid float on the surface of the aluminum liquid, and the slag is removed by skimming. The removed slag is commonly known as aluminum ash.

[0003] Aluminum ash contains metallic aluminum, inclusions mainly composed of aluminum oxide, and salts left over from refining agents. There are a large number of toxic elements. The soluble fluoride and cyanide contained in it will be transferred or volatilized into the atmosphere through wind, sun, and rain, or mixed into rivers with rainwater, seep into the ground to pollute the soil and groundwater, causing great damage to the growth of animals and plants and the human body, destroying the ecological environment, and affecting the balance of agricultural ecology. Aluminum ash has been listed in the list of hazardous wastes by the Ministry of Ecology and Environment because of its reactivity and leaching toxicity. The research on the process of preparing materials using aluminum ash carried out by domestic and foreign research institutions and enterprises mainly includes pyrometallurgical process and hydrometallurgical process.

[0004] The principle of the pyrometallurgical process is: using a rotary kiln or rotary furnace, the metal aluminum powder in the aluminum ash is oxidized at high temperature, aluminum nitride is decomposed, fluorides and salts are separated by high-temperature gasification, and the aluminum oxide is activated under the action of auxiliary materials, and has solubility and reactivity, which is used to produce alumina, calcium aluminate powder, steel mill pre-melted slag, etc. The reaction process of the pyrometallurgical process includes: 4Al+3O2→2Al2O3; 2AlN+2O2→Al2O3+N2O; 4AlN+5O2→2Al2O3+4NO2. The problems of the pyrometallurgical process include: salt adhesion and clogging of the rotary kiln cylinder or flue and fluoride corrosion of the kiln lining, some aluminum ash is not suitable for the production of calcium aluminate, and the purification system of fluoride and nitrogen oxide gas using SCNR or other processes is costly and the purification effect is unstable.

[0005] The principle of the wet process is: aluminum ash and water are first mixed into a slurry, and the metal aluminum powder and aluminum nitride are hydrolyzed in the reactor, the fluoride is solidified and the salt is dissolved and separated, and the aluminum hydroxide produced by the decomposition is easily soluble and can continue to be used to produce alumina, aluminum hydroxide, ceramics, building materials, etc. The reaction process of the wet process includes: 2Al+6H2O→2Al(OH)3+3H2↑; AlN+3H2O→Al(OH)3+NH3↑; Ca(OH)2+2NaF→2NaOH+CaF2. The problems of the wet process include: the hydrolysis time of aluminum nitride is long, and Al(OH)3 will form aluminum ash particles wrapped in aluminum, preventing water from penetrating into it, and the nitrogen removal rate is low. Ammonia and hydrogen are flammable and explosive, salts corrode equipment, high aluminum material products have low added value, filter cakes have high water content, and ammonia is emitted when stacked.

[0006] Therefore, a safer, more efficient and lower-cost process is needed for the harmless treatment of aluminum ash. Summary of the invention

[0007] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a semi-wet pre-deammoniation aluminum ash harmless treatment process.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A semi-wet pre-deammoniation aluminum ash harmless treatment process comprises the following steps:

[0010] S1. Ingredients: According to the mass fraction, 1-5% of the fluorine-fixing agent, 0.5-1% of the inhibitor, secondary aluminum ash, and dust removal water are mixed according to 10-20% of the weight of the aluminum ash, added into a strong mixer and stirred for 5-10 minutes to mix into a uniform slurry; wherein the inhibitor is an acidic inhibitor used to react with the aluminum ash to produce ammonium salt and inhibit the hydrolysis reaction;

[0011] S2, molding; the evenly mixed slurry is conveyed to the feeding bin of the hydraulic molding machine through a belt, so that the slurry is hydraulically molded into aluminum ash bricks;

[0012] S3, curing; stacking the aluminum ash bricks and transferring them to the curing tunnel behind the kiln car. At this time, after the inhibitor is consumed, the aluminum nitride and metal aluminum in the aluminum ash bricks react with water to produce ammonia and hydrogen, which escape from the aluminum ash bricks. A layer of adhesive Al(OH)3 is formed on the surface of the aluminum ash particles to harden the bricks as a whole, while releasing heat; the ammonia is absorbed and processed to form a by-product of ammonia water, and the aluminum ash bricks are dried by using the heat released by the hydrolysis reaction. At the end of the curing tunnel, the aluminum ash bricks are completely dry and no ammonia is released;

[0013] S4, calcination; stacking the cured aluminum ash bricks in the kiln car of the tunnel kiln, and taking them out of the kiln after preheating, calcining and cooling, wherein the calcination temperature is 800-1200°C and the calcination time is 2-4 hours; during the calcination process, the Al and AlN remaining in the aluminum ash bricks and the Al(OH)3 generated during the curing process are all reacted to form Al2O3;

[0014] S5. Obtain harmless aluminum ash bricks.

[0015] Preferably, the inhibitor in step S1 is an inorganic salt containing aluminum acid, or an organic acid that can be calcined and decomposed at high temperature.

[0016] Preferably, the fluorine-fixing agent in step S1 contains CaCl2, and in steps S1-S4, soluble fluorine is combined with calcium element to form calcium fluoride.

[0017] Preferably, in step S1, a powerful mixer is used to evenly mix all the raw materials, and a spray tower is arranged next to the powerful mixer to spray fresh water to suppress dust during the feeding process.

[0018] Preferably, step S3 includes a brick-making waste gas treatment process, that is, the waste ammonia generated during the curing process is absorbed by chilled pure water to produce ammonia water as a by-product.

[0019] Preferably, step S4 includes a calcination flue gas treatment process, that is, a reducing agent injection port is set on the flue gas circulation device of the tunnel kiln. In the process of flue gas circulation driven by the flue gas circulation device, the reducing agent reacts with nitrogen oxides in the flue gas, and then the particulate matter is collected by bag dust removal, and finally the acid gas is absorbed by alkali spraying.

[0020] Preferably, the reducing agent is ammonia water obtained as a byproduct in step S3.

[0021] Preferably, in step S2, the molding pressure of the hydraulic molding machine is 100-300 tons, and the holding time is 5 seconds.

[0022] Preferably, in step S3, the aluminum ash bricks are stacked in 1-20 layers according to needs by a stacking machine and transferred into a maintenance tunnel.

[0023] Preferably, in step S2, the aluminum ash is pressed into aluminum ash plates instead of aluminum ash bricks, and in step S4, a roller kiln is used instead of a tunnel kiln for sintering.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. Adding inhibitors in the batching step can effectively inhibit the violent hydrolysis reaction between aluminum ash and water before the curing operation, improve the operating environment, avoid safety accidents, and the inhibitors remain in the aluminum ash bricks and will not affect the subsequent use of the aluminum ash bricks;

[0026] 2. The treatment process of the present invention is mixed into a slurry in the batching step, which has a higher slurry concentration than that of the aluminum ash wet treatment process. It can be directly pressed into aluminum ash bricks by hydraulic equipment, and the amount of water theoretically required for the deamination hydrolysis reaction can be controlled to avoid a large amount of excess water adhering to the filter cake after the traditional wet treatment. The inhibitor reacts with AlN in the aluminum ash to generate ammonium salt and gelled aluminum hydroxide to harden the bricks, so that the aluminum ash bricks have a certain strength, can be stacked and sintered in the tunnel kiln, and deep deamination and fluorine fixation are carried out. After curing and deamination, they are directly calcined. The process steps are simpler and the treatment effect is better.

[0027] 3. In the wet treatment process, aluminum ash is added with water to form a solution, which needs to be transferred to a special reactor by a pump for reaction, and the reaction rate needs to be strictly controlled to avoid excessive reaction and slurry overflowing from the tank. In the present invention, aluminum ash bricks are hydrolyzed and deaminated during the curing process, and do not need to be transferred to a reactor. The process is simpler and effectively reduces costs; even if ammonia escapes from the bricks in large quantities, no safety accidents will occur, and the reaction efficiency can be appropriately improved, which is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 This is a brief process flow chart of a semi-wet pre-deammoniation aluminum ash harmless treatment process;

[0030] Figure 2 The present invention is an operation flow chart of a semi-wet method for pre-deammoniation of aluminum ash harmless treatment process. DETAILED DESCRIPTION

[0031] In order to further understand the purpose, structure, characteristics, and functions of the present invention, this section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0032] Reference below Figure 1 and Figure 2 A semi-wet pre-deammoniation aluminum ash harmless treatment process of the present invention is described in detail, which specifically includes the following steps:

[0033] S1. Ingredients: According to the mass fraction, 1-5% of the fluorine-fixing agent, 0.5-1% of the inhibitor, secondary aluminum ash, and dust removal water are mixed according to 10-20% of the weight of the aluminum ash, added into a strong mixer and stirred for 5-10 minutes to mix into a uniform wet mixture; wherein the inhibitor is an acidic inhibitor used to react with the aluminum ash to produce ammonium salt and inhibit the hydrolysis reaction;

[0034] In this step, the mixed wet mixture is thicker and has less water than the slurry prepared by the traditional wet process. The inhibitor reacts with AlN in the aluminum ash to inhibit the hydrolysis reaction. On the one hand, ammonium salt is generated to prevent the release of ammonia generated by hydrolysis; on the other hand, Al(OH)3 is generated to form a gelatinous protective layer on the surface of the slurry, thereby further inhibiting the hydrolysis reaction. Therefore, the inhibitor added in the present invention has a dual effect of inhibiting the hydrolysis reaction.

[0035] S2, molding; the evenly mixed wet material is conveyed to the feeding bin of the hydraulic molding machine through a belt, so that the wet material is hydraulically molded into aluminum ash bricks;

[0036] In this step, depending on the thickness of the slurry prepared in step S1, it can be directly pressed into wet aluminum ash bricks by the hydraulic press. Due to the continuous reaction of the inhibitor, a layer of Al(OH)3 will be formed on the surface of the formed aluminum ash bricks, which can effectively harden the aluminum ash bricks so that they can be stacked. Preferably, the forming pressure of the hydraulic forming machine is 100-300 tons, and the holding time is 5 seconds.

[0037] S3, curing; stacking the aluminum ash bricks and transferring them into the curing tunnel, at which time the inhibitor is consumed, and the water in the aluminum ash bricks begins to react with the aluminum ash particles to hydrolyze. The hydrolysis reaction produces ammonia gas that escapes from the aluminum ash bricks, and a layer of adhesive Al(OH)3 is generated on the surface of the particles in the aluminum ash bricks to harden the bricks as a whole, while releasing heat; the ammonia gas is absorbed and processed to form ammonia water as a byproduct, and the heat released by the hydrolysis reaction is used to dry the aluminum ash bricks. At the end of the curing tunnel, the aluminum ash bricks are completely dry and no ammonia gas is released;

[0038] In this step, the aluminum ash bricks are in the curing tunnel, and first wait for the inhibitor to react completely, and ammonia continues to accumulate in the water, so that the alkalinity is sufficient to dissolve the newly generated Al(OH)3. After the coating is destroyed, the hydrolysis reaction is no longer inhibited, and then water is added according to the actual situation to promote the hydrolysis reaction. The hydrolysis reaction in this step is roughly the same as the hydrolysis reaction in the wet process. The components such as Al and AlN in the aluminum ash undergo hydrolysis reaction with water:

[0039] 2Al+6H2O→2Al(OH)3+3H2↑;

[0040] AlN+3H2O→Al(OH)3+NH3↑;

[0041] It can be seen that in this step, the hydrolysis reaction converts most of the aluminum-containing elements such as Al and AlN in the aluminum gray brick into Al(OH)3, and due to the gel-like properties of Al(OH)3 itself, the aluminum gray brick is further hardened. In addition, the hydrolysis reaction generates a large amount of heat, which is conducive to accelerating the drying of the aluminum gray brick. A large amount of ammonia will also be released in this step, but it is different from the hydrolysis reaction of the wet process to release ammonia. In the wet process, the hydrolysis reaction is a solution-like slurry in the reactor. If there is too much ammonia, the bubble is released from the solution and fills the reactor, which is very likely to cause the liquid to burst the tank. At the same time, a large amount of ammonia quickly fills the reactor to form a high-pressure environment, and there is also an explosion risk. Therefore, it is not only necessary to provide a specific reactor, but also to accurately control the reaction rate, and the processing cost is high and dangerous; and the processing process of the present invention, the hydrolysis reaction is carried out in the aluminum gray brick, and the generated ammonia escapes stably from the aluminum gray brick, and the amount of ammonia generated will not fluctuate violently, so the hydrolysis reaction rate can be controlled according to the actual situation, and it is safe and cost-effective.

[0042] S4, calcination; stacking the cured aluminum ash bricks in the kiln car of the tunnel kiln, and taking them out of the kiln after preheating, calcining and cooling, wherein the calcination temperature is 800-1200°C and the calcination time is 2-4 hours; during the calcination process, the residual Al, AlN and Al(OH)3 produced by hydrolysis in the aluminum ash bricks are all reacted to Al2O3;

[0043] In this step, the aluminum-containing components such as Al(OH)3, Al, and AlN in the aluminum ash brick are calcined and converted into Al2O3. The specific reaction process includes:

[0044] 2Al(OH)3→Al2O3+3H2O;

[0045] 4Al+3O2→2Al2O3;

[0046] 2AlN+2O2→Al2O3+N2O;

[0047] 4AlN+5O2→2Al2O3+4NO2;

[0048] It can be seen that in this step, the conversion of aluminum components in aluminum ash can be achieved only through calcination treatment, and the N element is converted into N2O. After calcination treatment, the nitrogen removal rate of aluminum ash brick reaches more than 99%, and the soluble fluorine combines with calcium elements to form calcium fluoride. The leached fluoride ion concentration can meet the national standard.

[0049] S5. Obtain harmless aluminum ash bricks.

[0050] The present invention adopts an inhibitor in the batching process, which can effectively inhibit the aluminum ash from contacting with water and causing violent hydrolysis reaction before brick making is completed, thereby reducing the difficulty of operation and avoiding safety accidents. In addition, the present invention adopts a semi-wet pre-deammoniation process, and after the aluminum ash brick is made, a hydrolysis reaction is carried out in the solid aluminum ash brick, and ammonia escapes from the brick, avoiding the traditional wet process of deammoniation aluminum ash adhering a large amount of water, resulting in ammonia remaining in the water, and needing to continue drying before it can be used as a downstream raw material. At the same time, the aluminum hydroxide produced by hydrolysis is used to make the aluminum ash brick have a certain strength, which can be stacked into the tunnel kiln for sintering, and deep deammoniation and fluorine fixation are carried out. In addition, the use of tunnel kiln deammoniation is more than the traditional rotary kiln calcination, and the calcination temperature and time are controllable, which solves the problems of rotary kiln wall ringing and flue blockage, is easy to produce continuously, and the flue gas waste heat can be effectively recycled.

[0051] In some embodiments, the inhibitor in step S1 is an inorganic salt containing aluminum acid, or an organic acid that can be calcined and decomposed at high temperature. The inorganic salt containing aluminum acid can be selected from aluminum sulfate, aluminum chloride, aluminum nitrate, etc., dissolved into a solution and mixed with aluminum ash; the organic acid can be selected from formic acid, oxalic acid, acetic acid, etc. that can be calcined and decomposed at high temperature. In summary, the selection of the inhibitor needs to meet the following requirements: 1. It can first react with AlN in aluminum ash to generate ammonium salt, thereby inhibiting the hydrolysis reaction and preventing it from generating ammonia; 2. The compounds generated by the reaction of the inhibitor with AlN in aluminum ash, except for ammonium salt, should not affect the reaction in the subsequent steps, and the residue in the aluminum ash brick should not affect the subsequent use.

[0052] In some embodiments, the fluorine-fixing agent in step S1 contains CaCl2. In steps S1-S4, soluble fluorine reacts with calcium element in water or at high temperature to form calcium fluoride, thereby completing the fluorine-fixing effect.

[0053] In some embodiments, a powerful mixer is used in step S1 to mix all the raw materials evenly, and a spray tower is set up next to the powerful mixer to spray fresh water to suppress dust during the feeding process. The processing workshop is kept clean and tidy, and the raw materials are mixed evenly to avoid affecting subsequent reactions.

[0054] In some embodiments, step S3 includes a brick-making waste gas treatment process, that is, the waste ammonia generated during the curing process is absorbed by frozen pure water to produce ammonia water as a by-product.

[0055] In some embodiments, step S4 includes a calcination flue gas treatment process, that is, a reducing agent injection port is set on the flue gas circulation device of the tunnel kiln, and the reducing agent reacts with nitrogen oxides in the flue gas during the flue gas circulation driven by the flue gas circulation device, and then the particulate matter is collected by bag dust removal, and the final acid gas is absorbed by alkali spraying. Preferably, the reducing agent can be selected from the byproduct ammonia water obtained in step S3.

[0056] In some embodiments, in step S3, the aluminum ash bricks are stacked in 10 layers by a stacking machine and transferred into a curing tunnel. The process of the present invention is not limited to stacking 10 layers, which is specifically set according to the size of the curing tunnel and the size of the aluminum ash bricks in actual conditions.

[0057] In some embodiments, in the treatment process of the present invention, the aluminum ash can also be pressed into aluminum ash plates instead of aluminum ash bricks in step S2. Correspondingly, in the calcination step, the aluminum ash plates are placed in a roller kiln for calcination, and the overall treatment process principle remains the same.

[0058] The semi-wet pre-deammoniation aluminum ash harmless treatment process of the present invention is as follows: Figure 2 As shown, workers put various raw materials, including secondary aluminum ash, fluorine-fixing agent, inhibitor, etc. into a high-power mixer. A spray tower is also set up next to the high-power mixer, and fresh water is added to spray in the high-power mixer for spray dust removal, which has the effect of collecting dust. After mixing evenly, a hydraulic molding machine is used to press the wet material into pieces of aluminum ash bricks, and a stacking machine is used to stack the drop hammer bricks on the kiln car, and the shuttle bus enters the track in the maintenance tunnel, that is, the deammoniation tunnel for deammoniation. In the process of deammoniation by hydrolysis reaction of aluminum ash bricks, ammonia is collected and then used to absorb the waste ammonia into ammonia water with chilled water using an absorption device, forming one of the by-products of this treatment process. After the deamination tunnel is completed and the aluminum ash bricks are completely dried, the aluminum ash bricks are stacked and placed in the tunnel kiln for calcination. The tail gas generated during the calcination process is introduced into a special exhaust gas treatment device for SNCR denitrification. Specifically, a reducing agent injection port is set on the flue gas circulation device. In the process of the flue gas circulation driven by the flue gas circulation device, the reducing agent reacts with nitrogen oxides in the flue gas, and then the particulate matter is collected by bag dust removal. The final acid gas is absorbed by alkali spraying. The aluminum ash bricks calcined in the tunnel kiln are harmless aluminum ash bricks and can be reused.

[0059] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0060] The present invention has been described by the above-mentioned relevant embodiments, but the above-mentioned embodiments are only examples for implementing the present invention, which are used to help understand the technical solutions and core ideas of the present application. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention; on the contrary, the technical solutions recorded in the above-mentioned embodiments can still be modified, or some of the technical features therein can be replaced by equivalents; modifications and embellishments made without departing from the spirit and scope of the present invention are all within the scope of patent protection of the present invention.

Claims

1. A semi-wet pre-deammoniation aluminum ash harmless treatment process, characterized in that: The following steps are involved: S1. Ingredients: According to the mass fraction, 1-5% of the fluorine-fixing agent, 0.5-1% of the inhibitor, secondary aluminum ash, and dust removal water are mixed according to 10-20% of the weight of the aluminum ash, added into a strong mixer and stirred for 5-10 minutes to mix into a uniform wet mixture; wherein the inhibitor is an acidic inhibitor used to react with the aluminum ash to produce ammonium salt and inhibit the hydrolysis reaction; S2, molding; the evenly mixed wet material is conveyed to the feeding bin of the hydraulic molding machine through a belt, so that the wet material is hydraulically molded into aluminum ash bricks; S3, curing; stacking the aluminum ash bricks and transferring them into the curing tunnel, at which time the inhibitor is consumed, and the water in the aluminum ash bricks begins to undergo a hydrolysis reaction with the aluminum ash particles, the hydrolysis reaction produces ammonia gas that escapes from the aluminum ash bricks, and a layer of adhesive Al(OH)3 is generated on the surface of the particles in the aluminum ash bricks to harden the bricks as a whole, while releasing heat; the ammonia gas is absorbed and processed to form a byproduct of ammonia water, and the aluminum ash bricks are dried using the heat released by the hydrolysis reaction, until the end of the curing tunnel, the aluminum ash bricks are completely dry and no ammonia gas is released; S4, calcination; stacking the cured aluminum ash bricks in the kiln car of the tunnel kiln, and taking them out of the kiln after preheating, calcining and cooling, wherein the calcination temperature is 800-1200°C and the calcination time is 2-4 hours; during the calcination process, Al, AlN and Al(OH)3 in the aluminum ash bricks are all reacted to Al2O3; S5. Obtain harmless aluminum ash bricks.

2. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 1, characterized in that: The inhibitor in step S1 is an inorganic salt containing aluminum acid, or an organic acid that can be calcined and decomposed at high temperature.

3. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 1, characterized in that: The fluorine-fixing agent in step S1 contains CaCl2, and in step S4, soluble fluorine is combined with calcium element to form calcium fluoride.

4. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 1, characterized in that: In step S1, a powerful mixer is used to mix all the raw materials evenly, and a spray tower is set up next to the powerful mixer to spray fresh water to suppress dust during the feeding process.

5. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 1, characterized in that: Step S3 includes a brick-making waste gas treatment process, that is, the waste ammonia generated during the curing process is absorbed by frozen pure water to produce ammonia water as a by-product.

6. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 1, characterized in that: Step S4 includes a calcination flue gas treatment process, that is, a reducing agent injection port is set on the flue gas circulation device of the tunnel kiln. In the process of flue gas circulation driven by the flue gas circulation device, the reducing agent reacts with nitrogen oxides in the flue gas, and then the particulate matter is collected by bag dust removal, and finally the acid gas is absorbed by alkali spraying.

7. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 5, characterized in that: The reducing agent is the byproduct ammonia water obtained in step S3.

8. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 1, characterized in that: In step S2, the molding pressure of the hydraulic molding machine is 100-300 tons, and the holding time is 5 seconds.

9. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 1, characterized in that: In step S3, the aluminum ash bricks are stacked 1-20 layers as required by a stacking machine and transferred into a maintenance tunnel.

10. The semi-wet pre-deammoniation aluminum ash harmless treatment process according to claim 1, characterized in that: In step S2, the aluminum ash is pressed into aluminum ash plates or spheres to replace aluminum ash bricks, wherein the spherical aluminum ash is contained in a corundum sagger, and in step S4, a roller kiln is used instead of a tunnel kiln for sintering.

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