WO2013143335A1

WO2013143335A1 - Method for extracting aluminium oxide in fly ash by alkaline process

Info

Publication number: WO2013143335A1
Application number: PCT/CN2012/087467
Authority: WO
Inventors: 李旺兴; 尹中林; 杨志民; 吴拓宇
Original assignee: 中国铝业股份有限公司
Priority date: 2012-03-28
Filing date: 2012-12-26
Publication date: 2013-10-03
Also published as: CN102627305A; CN102627305B

Abstract

Disclosed is a method for extracting aluminium oxide in fly ash by an alkaline process comprising: step (1), adding lime or limestone in the fly ash, and adding an alkaline solution, to produce a raw slurry; step (2), firing the raw slurry into a wrought material; step (3), performing alkaline leaching on the wrought material and liquid-solid separation on the leached slurry, so as to obtain a solid phase residue 1 and a leachate 1; step (4), desilicating the leachate 1 and then performing liquid-solid separating on same; step (5), carbonation decomposing the desilicated liquid after separation by filtering, so as to obtain aluminium hydroxide; and step (6), calcinating the aluminium hydroxide to obtain the aluminium oxide product. The method of the present invention can be used to process raw materials of fly ash originating from various sources, so as to produce aluminium oxide.

Description

Method for extracting alumina from fly ash by alkali method

Technical field

The invention relates to a method for extracting alumina from fly ash by alkali method.

Background technique

Fly ash is a finely powdered material collected from the flue gas after combustion of coal. The mineral composition and chemical composition of fly ash are related to the source of coal. The phase composition is mainly composed of vitreous, mullite, quartz, hematite, magnetite, anhydrite, tricalcium phosphate and yellow feldspar. Powdery material; chemical composition is mainly A1 ₂ 0 ₃ , Si0 ₂ , Fe ₂ 0 ₃ , CaO, MgO, etc., and also contains a small amount of rare elements. Fly ash storage requires a large amount of land and also causes a certain degree of pollution to the surrounding environment. Therefore, research on the comprehensive utilization of fly ash, turning waste into treasure, is of great significance to environmental protection and resource utilization, and to building an environmentally-friendly society.

The process for extracting alumina (aluminum hydroxide) or aluminum salt from fly ash can be classified into an acid method, an alkali method, and an acid-base mixture method. These processes have their own characteristics in the process route. The advantage of the acid method is that the main component of the fly ash, Si0 _{2 ,} does not enter the solution, but the disadvantage is that the impurity metal element which is co-dissolved with the aluminum needs to be purified, the impurity removal process is long, the acid consumption is large, and acid-resistant equipment is required. Representative methods of the alkali method are a limestone sintering method and a soda lime sintering method. The advantage of fly ash alkali extraction of alumina is that metal impurities have little interference and the technology is mature. Due to the large amount of clinker, the alkali method causes excessive energy consumption, and the amount of slag formed after alumina extraction is large.

The solid waste produced during the extraction of alumina by the fly ash alkali method will contain a certain amount of alkali and alumina. Effectively reducing the alkali and alumina content in the solid waste residue is a necessary prerequisite for maximizing the economic benefits of the extraction of alumina from fly ash and alkali, and realizing large-scale resource utilization of solid waste. Summary of the invention

The object of the present invention is to provide a short process, a low alkali consumption, an easy to control product quality, and an alkali extraction method for comprehensive utilization of solid residue after extraction of alumina. The method of medium alumina.

The object of the present invention is to realize the alkali extraction of alumina in fly ash by the following technical scheme. Methods, including:

Step (1), adding lime or limestone to the fly ash, and adding a lye to prepare a raw slurry; step (2), firing the raw slurry into a mature material;

Step (3), the clinker is alkali leached, and the leaching slurry is subjected to liquid-solid separation to obtain solid phase residue 1 and leachate 1;

Step (4), after desiliconizing the leachate 1, performing liquid-solid separation;

Step (5), separating the desiliconized liquid separated by filtration, and performing carbonation decomposition to obtain aluminum hydroxide;

Step (6), aluminum hydroxide is calcined to obtain an alumina product. Further, the fineness of the fly ash is -0.18 mm; the fineness of the limestone powder or lime powder is -0.18 mm.

Further, the lye added is a mixture of sodium carbonate and a carbonated decomposition mother liquor after evaporation.

Further, the addition amount of the raw slurry mixing process, the lime or limestone system is determined by the amount of Si0 _2, the amount of limestone or lime is added in a molar ratio of CaO and SiO ₂ is 0.8 to 2.2 the control, sodium carbonate was added The amount is controlled in accordance with a molar ratio of Na ₂ O to Al ₂ O ₃ + Fe ₂ 0 ₃ of 0.9 to 1.7. Using a low molar ratio of CaO and SiO ₂ , the material flow rate is small, the amount of solid slag after extraction of alumina is small, and the system efficiency is high.

Further, in the mixing process of the raw slurry, the addition amount of limestone or lime is determined by the amount of SiO ₂ in the system, and the addition amount of limestone or lime is controlled according to the molar ratio of CaO and SiO ₂ of 0.8 to 2.2, and sodium carbonate is added. The amount is controlled in accordance with the molar ratio of Na ₂ O to A1 ₂ 0 ₃ + Fe ₂ 0 ₃ of 1.7 to 3.0.

Further, the raw slurry is fired at a temperature of 900 to 1380 ° C and the firing time is 10 to 120 minutes. A suitable range of sintering temperatures is wide and easy to control.

Further, the alkaline leaching of the clinker is performed by leaching the clinker with a conditioning liquid at a temperature of 40 to 105 °C.

Further, part or all of the solid residue obtained in the step (4) is returned to the step (1). Raw material for the preparation of raw slurry.

Further, the mother liquor after the carbonation decomposition of the step (5) is returned to the step (1) after evaporation, and is used for the preparation of the raw slurry.

Further, the conditioning liquid for the leaching clinker is prepared by mixing the solid residue of the slurry after the solid solution of the leaching clinker.

Further, the method further includes:

Step (7), the solid phase residue 1 obtained in the step (3) is further subjected to alkali leaching, and the leaching slurry is subjected to liquid-solid separation to obtain a solid phase residue 2 and a leaching solution 2, and alumina and a base are further recovered.

Further, the method further includes:

Step (8), using the leachate 2 to adjust the molecular ratio of the system during the desiliconization treatment in the step (4).

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the method further comprises:

Step (9), adding lime to the leachate obtained in the step (7), filtering after the reaction, and the obtained filter residue is used for the desiliconization process in the step (4).

A method of extracting alumina from fly ash by an alkali method according to claim 1, wherein

Step (10), using the solid residue 2 obtained in the step (7) as a raw material for producing a cement building material.

Further, the concentration of the solution for performing alkali leaching in the step (7) is Na ₂ 0 _K 30 to 250 g/L.

Further, the solution for performing alkali leaching in the step (7) is a polymer ratio sodium aluminate solution having an oc _k of 10 to 60 and a Na ₂ 0 _K of 30 to 250 g/L.

Further, the leaching temperature for performing alkali leaching in the step (7) is 60 to 250 °C. Further, the leaching time for performing alkali leaching in the step (7) is 5 to 360 minutes. Further, the liquid-solid ratio at the time of alkali leaching in the step (7) is 1 to 5. Further, in the step (7), the liquid-solid ratio when the polymer is subjected to alkali leaching than the sodium aluminate solution is 5-8. Further, the leach solution 2 obtained in the step (7) is used to adjust the molecular ratio of the system during desiliconization in the step (4), and the molecular ratio of the desiliconization liquid solution can be adjusted to 1.4 to 2.0.

Further, lime is added to the leachate 2 obtained in the step (7), and after the reaction, it is filtered, and the obtained filter residue is used for the desiliconization process in the step (4).

Further, the solid phase residue 2 obtained in the step (7) is used as a raw material for producing a building material.

The method for extracting alumina in fly ash by the alkali method of the invention can be used for processing alumina produced by fly ash raw materials of different sources, different chemical compositions and mineral compositions, and the solid residue has low alkali content and can be used as building materials. The raw material of the invention is mature and reliable. Compared with the existing alkali production process, the material flow rate is small, the solid residue is small, and the zero discharge of the whole process can be realized, which is beneficial to environmental protection. The high output rate and low energy consumption of the whole process of producing fly ash alumina are realized, and the solid residue after extracting alumina can realize large-scale resource utilization.

detailed description

The method for extracting alumina in fly ash by the alkali method provided by the embodiment of the invention comprises the steps of: 1) removing fly ash (fine grinding if necessary, fineness is preferably -80 mesh), grinding Fine limestone powder or lime powder (fineness is preferably -80 mesh), and sodium carbonate and evaporated carbonation decomposition mother liquor are mixed in a certain ratio to form a raw slurry; 2) raw slurry at a certain temperature The mature material is fired under the condition; 3) the clinker is leached with a solution containing sodium carbonate and sodium hydroxide under certain conditions, and the leaching slurry is subjected to liquid-solid separation; 4) the leaching solution is desiliconized and then carbonized. Decomposition to obtain aluminum hydroxide; 5) aluminum hydroxide is calcined to obtain an alumina product; 6) the solid phase product formed during the desiliconization process can be returned to the raw slurry preparation stage as a raw material for preparing the raw slurry; 7) carbonation The decomposed mother liquor is returned after evaporation and used to prepare the raw slurry; 8) the adjusting solution for leaching clinker is prepared by the washing liquid of the solid phase residue after the solid solution of the leaching clinker; 9) 3) Solid residue obtained in OK alkali leaching, the leaching of the slurry liquid-solid separation, and a base for further recovery of alumina; obtained leachate system for adjusting 4) the molecular desiliconization Ratio; it is also possible to add lime to the obtained leachate, and then filter after the reaction, and the obtained filter residue is used for

4) Desiliconization process; 10) The resulting solid phase residue is used as a raw material for the production of building materials such as cement.

Example 1

The raw material is a kind of thermal ash fly ash, the main chemical composition is Al ₂ 0 ₃ 39 °/. , Si0 ₂ 44.1 % , after grinding, the fineness of -80 mesh limestone powder or lime powder and sodium carbonate and the evaporated carbonation decomposition mother liquor are controlled according to the molar ratio of CaO and SiO ₂ of 1.0, sodium carbonate (including after evaporation) carbonation decomposition of Na ₂ 0 in the mother liquor) is added in an amount in a molar ratio of Na ₂ 0 and _{_{_{Al 2 O 3 + Fe 2 O}}} 3 is 1.1 control formulation prepared raw slurry; raw slurry at a temperature of 1110 ° C Under the conditions of firing, the qualified clinker is obtained; the clinker is leached with the adjusting solution at 80-90 ° C, the leaching rate of alumina in the clinker can reach 69.97%, and the leaching rate of sodium oxide in the clinker can reach 70.46%. The clinker leaching solution is decarburized and then carbonized and decomposed to obtain aluminum hydroxide. The aluminum hydroxide is calcined to obtain metallurgical grade oxidation.

^吕? .

The solid residue after the clinker is dissolved is leached for 360 minutes at a temperature of 90 ° C with an alkali solution having a caustic alkali concentration of Na ₂ 0 _K 50 g/L. The solid solution ratio is 2, and the solid phase residue is A1 ₂ 0 ₃ The leaching rate was 15%, and the leaching rate of Na ₂ 0 in the solid residue was 91%. The finally obtained solid phase residue is used as the raw example 2

The raw material is fly ash of a thermal power plant. The main chemical composition is Al ₂ 0 ₃ 41 % and Si0 ₂ 47 %. The fineness after grinding is -80 mesh limestone powder or lime powder and sodium carbonate and carbonation after evaporation. The mother liquor is controlled according to a molar ratio of CaO to SiO ₂ of 1.3, and sodium carbonate (including Na ₂ 0 in the carbonation decomposition mother liquor after evaporation) is added in a molar ratio of Na ₂ O to Al ₂ O ₃ + Fe ₂ 0 ₃ . 1.0 Control the preparation of the raw slurry by batching; the raw slurry is fired at a temperature of 1200 ° C to obtain qualified clinker; the clinker is leached with the adjusting solution at 80-90 ° C, and the alumina in the clinker The leaching rate can reach 77.76%, and the leaching rate of sodium oxide in clinker can reach 82.78%. The clinker leaching solution is decarburized and then carbonized and decomposed to obtain aluminum hydroxide. The aluminum hydroxide is calcined to obtain metallurgical grade oxidation. 4 Lu products.

The solid residue after the clinker is dissolved is leached with an alkali solution having a caustic alkali concentration of Na ₂ 0 _K 100g/L at a temperature of 12 CTC for 20 minutes, and the leaching liquid solid ratio is 2, and the leaching of A1 ₂ 0 ₃ in the solid residue is carried out. The rate was 16%, and the leaching rate of Na ₂ 0 in the solid residue was 89%. The resulting solid phase residue is used as a raw material for the production of cement.

Example 3

The raw material is fly ash of a thermal power plant, the main chemical composition is Al ₂ 0 ₃ 47 °/. , Si0 ₂ 43 % , after grinding, the fineness of -80 mesh limestone powder or lime powder and sodium carbonate and the evaporated carbonation decomposition mother liquor are controlled according to the molar ratio of CaO and SiO ₂ of 1.5, sodium carbonate (including after evaporation) The Na ₂ 0 in the carbonation decomposition mother liquor is added according to the molar ratio of Na ₂ 0 and A1 ₂ 0 ₃ + Fe ₂ 0 ₃ to prepare the raw slurry; the raw slurry is at a temperature of 1 120 ° C-fired to obtain qualified clinker; leaching clinker with adjusting liquid at 80-90 °C, the leaching rate of alumina in clinker can reach 84.97%, and the leaching rate of sodium oxide in clinker can reach 92.82% . The clinker leaching solution is decarburized and then carbonized and decomposed to obtain aluminum hydroxide. After calcination, the aluminum hydroxide is obtained by metallurgical oxidation. .

The solid residue after the clinker is dissolved is leached with an alkali solution having a caustic alkali concentration of Na ₂ 0 _K 140 g/L at a temperature of 160 ° C for 15 minutes, and the leaching liquid-solid ratio is 3, and the solid phase residue is A1 ₂ 0 ₃ The leaching rate was 17%, and the leaching rate of Na ₂ 0 in the solid residue was 88%. The finally obtained solid phase residue is used as the raw example 4

The raw material is a thermoelectric fly ash, the main chemical composition is Al ₂ 0 ₃ 51 ° /. , Si0 ₂ 38 % , after grinding, the fineness of -80 mesh limestone powder or lime powder and sodium carbonate and the evaporated carbonation decomposition mother liquor are controlled according to the molar ratio of CaO and SiO ₂ of 1.4, sodium carbonate (including after evaporation) carbonation decomposition of Na ₂ 0 in the mother liquor) is added in an amount in a molar ratio of Na ₂ 0 and _{_{_{A1 2 0 3 + Fe 2 0}}} 3 1.05 control the formulation to raw slurry; raw slurry at a temperature of 1250 ° C Boiled under conditions to obtain qualified clinker; leaching clinker with adjusting liquid at 80-90 °C, the leaching rate of alumina in clinker can be In order to reach 84.17%, the leaching rate of sodium oxide in clinker can reach 88.21%. The clinker leaching solution is decarburized and then carbonized and decomposed to obtain aluminum hydroxide. The aluminum hydroxide is calcined to obtain metallurgical grade oxidation.

^吕? .

The solid residue after the clinker is dissolved is leached with an alkali solution having a caustic alkali concentration of Na0 _2K 200g/L at a temperature of 200 ° C for 10 minutes, and the leaching liquid-solid ratio is 3, and the leaching of A1 ₂ 0 ₃ in the solid residue is carried out. The rate was 18%, and the leaching rate of Na ₂ 0 in the solid residue was 89%. The resulting solid phase residue is used as a raw material for the production of cement.

Example 5

The raw material is fly ash of a thermal power plant. The main chemical composition is Al ₂ 0 ₃ 55 % and Si0 ₂ 37 %. The fineness after grinding is -80 mesh limestone powder or lime powder and sodium carbonate and carbonation after evaporation. The mother liquor is controlled according to a molar ratio of CaO to SiO ₂ of 1.6, and sodium carbonate (including Na ₂ 0 in the carbonation decomposition mother liquor after evaporation) is added in a molar ratio of Na ₂ O to Al ₂ O ₃ + Fe ₂ 0 ₃ . 1.0 Control the preparation of raw slurry by batching; the raw slurry is fired at a temperature of 1 150 ° C to obtain qualified clinker; the clinker is leached with the adjusting solution at 80-90 ° C, and the clinker is oxidized. The leaching rate of aluminum can reach 86.21%, and the leaching rate of sodium oxide in clinker can reach 94.12%. The clinker leaching solution is decarburized and then carbonized and decomposed to obtain aluminum hydroxide, and the aluminum hydroxide is calcined to obtain a metallurgical grade oxidized product.

The solid residue after the clinker is dissolved is leached with an alkali solution having a caustic alkali concentration of Na ₂ 0 _K 200 g/L at a temperature of 220 ° C for 8 minutes, and the leaching liquid-solid ratio is 3, and the solid phase residue is A1 ₂ 0 ₃ The leaching rate was 18%, and the leaching rate of Na ₂ 0 in the solid residue was 87%. The resulting solid phase residue is used as a raw material for the production of cement.

Example 6

The raw material is fly ash of a thermal power plant. The main chemical composition is Al ₂ 0 ₃ 53 % and Si0 ₂ 38 %. The fineness after grinding is -80 mesh limestone powder and sodium carbonate and evaporated carbonation decomposition mother liquor according to CaO. The molar ratio to SiO ₂ is 1.5, and the amount of sodium carbonate (including Na ₂ 0 in the carbonation decomposition mother liquor after evaporation) is controlled according to a molar ratio of Na ₂ 0 and A1 ₂ 0 ₃ + Fe ₂ 0 ₃ of 0.98. Match Raw slurry is prepared; the raw slurry is fired at a temperature of 1230 ° C to obtain qualified clinker; the clinker is leached with the adjusting solution at 80-90 ° C, and the alumina leaching rate in the clinker can be It reaches 84.46%, and the leaching rate of sodium oxide in clinker can reach 92.78%. The clinker leaching solution is decarburized and then carbonized and decomposed to control the carbonation decomposition conditions to obtain a pseudo-boehmite product.

The solid residue after the clinker is dissolved is leached with an alkali solution having a caustic alkali concentration of Na ₂ 0 _K 70 g/L at a temperature of 100 ° C for 240 minutes, and the leaching liquid-solid ratio is 3, and the solid phase residue is A1 ₂ 0 ₃ The leaching rate was 13%, and the leaching rate of Na ₂ 0 in the solid residue was 81%. The resulting solid phase residue is used as a raw material for the production of cement.

Example 7

The raw material is a thermoelectric fly ash, the main chemical composition is Al ₂ 0 ₃ 55 ° /. , Si0 ₂ 37 % , the fineness of -80 mesh limestone powder or lime powder after grinding and sodium carbonate and the carbonation decomposition mother liquor after evaporation are controlled according to the molar ratio of CaO and SiO ₂ of 2.05, sodium carbonate (including after evaporation) carbonation decomposition of Na ₂ 0 in the mother liquor) is added in an amount in a molar ratio of Na ₂ 0 and _{_{_{A1 2 0 3 + Fe 2 0}}} 3 0.97 control the formulation to raw slurry; raw slurry at a temperature of 1250 ° C Under the conditions of firing, the qualified clinker is obtained; the clinker is leached with the adjusting solution at 80-90 ° C, the leaching rate of alumina in the clinker can reach 88.21%, and the leaching rate of sodium oxide in the clinker can reach 96.16%. The clinker leaching solution is decarburized and then carbonized and decomposed to obtain aluminum hydroxide, and the aluminum hydroxide is calcined to obtain a metallurgical grade oxidized product.

The solid residue after the clinker is dissolved is leached for 8 minutes at a temperature of 220 ° C with an alkali solution having a caustic alkali concentration of Na ₂ 0 _K 200 g/L. The solid solution ratio is 3, and the solid phase residue is A1 ₂ 0 ₃ The leaching rate was 11%, and the leaching rate of Na ₂ 0 in the solid residue was 81%. The resulting solid phase residue is used as a raw material for the production of cement.

Example 8

The raw material is a kind of thermal ash fly ash, the main chemical composition is Al ₂ 0 ₃ 35 °/. , Si0 ₂ 44 % , after grinding, the fineness of -80 mesh limestone powder or lime powder and sodium carbonate and the evaporated carbonation decomposition mother liquor are controlled according to the molar ratio of CaO and SiO ₂ of 0.98, sodium carbonate (including after evaporation) Carbon Under the raw slurry at a temperature of 1240 ° C condition; Na ₂ 0) was added an amount of acidified decomposition mother liquor compounded prepared raw slurry was 2.2 controlled in accordance with a molar ratio of Na ₂ 0 and _{_{_{A1 2 0 3 + Fe 2 0}}} 3 of After firing, the qualified clinker is obtained; the clinker is leached with the adjusting solution at 80-90 ° C, the leaching rate of alumina in the clinker can reach 87.55%, and the leaching rate of sodium oxide in the clinker can reach 97.98%. The clinker leaching solution is decarburized and then carbonized and decomposed to obtain aluminum hydroxide. The aluminum hydroxide is calcined to obtain metallurgical grade oxidation.

^吕^^ ? .

The solid residue after the clinker is dissolved is leached for 300 minutes at a temperature of 98 ° C with a sodium aluminate solution having a caustic alkali concentration of Na ₂ 0 _K 45 g/L and a molecular ratio a _k = 10, and the leaching ratio is 8 The leaching rate of Α1 ₂ Ο ₃ in the solid residue was 9.6%, and the leaching rate of Na ₂ 0 in the solid residue was 89%. The resulting solid phase residue is used as a raw material for the production of cement.

Example 8 illustrates that the molar ratio of the compound Na ₂ O to Al ₂ O ₃ + Fe ₂ 0 ₃ is increased to 2.2, and the polymer is more leached at a liquid-solid ratio of 8 than the sodium aluminate solution, and the alumina content can be treated lower. Fly ash, the effect is as good as the above method for treating fly ash with high alumina content.

Example 9

The raw material is a thermoelectric fly ash, the main chemical composition is Al ₂ 0 ₃ 32 ° /. , Si0 ₂ 41 % , after grinding, the fineness of -80 mesh limestone powder or lime powder and sodium carbonate and the evaporated carbonation decomposition mother liquor are controlled according to the molar ratio of CaO to SiO ₂ of 1.02, sodium carbonate (including after evaporation) carbonation decomposition of Na ₂ 0 in the mother liquor) was added an amount of prepared furnish raw slurry to 3.0 to control the molar ratio of Na ₂ 0 and _{_{_{Al 2 O 3 + Fe 2 O}}} 3 ; a raw material slurry at a temperature of 1250 ° C Under the conditions of firing, the qualified clinker is obtained; the clinker is leached with the adjusting solution at 82 ° C, the leaching rate of alumina in the clinker can reach 87.96%, and the leaching rate of sodium oxide in the clinker can reach 99.12%. The clinker leaching solution is decarburized and then carbonized and decomposed to obtain aluminum hydroxide. After the aluminum hydroxide is calcined, the metallurgical grade alumina production port σ is obtained.

The solid residue after the clinker is dissolved is leached for 320 minutes at a temperature of 98 ° C with a sodium aluminate solution having a caustic alkali concentration of Na ₂ 0 _K 40 g/L and a molecular ratio of a _k = 60. The leaching ratio is 6 The leaching rate of A1 ₂ 0 ₃ in the solid residue was 10.6%, and the leaching rate of Na ₂ 0 in the solid residue was 93%. Most The resulting solid residue is used as a raw material for the production of cement.

Example 9 illustrates that the molar ratio of the compounded Na ₂ O and Al ₂ O ₃ + Fe ₂ 0 ₃ is further increased to 3.0, and the fly ash having a lower alumina content can be treated, and the powder having a high alumina content is treated by the aforementioned method. As good as coal ash.

It should be noted that the above specific embodiments are merely illustrative of the technical solutions of the present invention, and the present invention is not limited thereto. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be Modifications or equivalents are intended to be included within the scope of the appended claims.

Claims

Claim

A method for extracting alumina from fly ash by an alkali method, comprising: step (1), adding lime or limestone to fly ash, and adding alkali liquid to prepare a raw slurry; 2), the raw slurry is fired into a mature material;

Step (6), aluminum hydroxide is calcined to obtain an alumina product.

2. The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the fineness of the fly ash is -0.18 mm; the fineness of limestone powder or lime powder is -0.18 mm .

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the added alkali liquid is a mixed liquid of sodium carbonate and a carbonated decomposition mother liquid after evaporation.

4. The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the mixing process of the raw slurry, the amount of limestone or lime added is determined by the amount of Si0 ₂ in the system, limestone Or the amount of lime added is controlled according to a molar ratio of CaO to SiO ₂ of 0.8 to 2.2, and the amount of sodium carbonate added is controlled by a molar ratio of Na ₂ 0 and A1 ₂ 0 ₃ + Fe ₂ O ₃ of 0.9 to 1.7.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the raw slurry is fired at a temperature of 900 to 1380 ° C and the firing time is 10 to 120 minutes.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the alkali leaching of the clinker is leaching clinker with a conditioning liquid at a temperature of 40 to 105 °C. .

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein part or all of the solid residue obtained in the step (4) is returned to the raw material prepared in the raw slurry. .

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the mother liquor after the carbonation decomposition in the step (5) is returned to the step (1) after evaporation, and is used for raw Slurry preparation.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the adjusting liquid for leaching clinker is washed by solid-phase residue after slurry separation of slurry of leaching clinker酉己ι3⁄4 ϋ.

The method for extracting alumina from fly ash by an alkali method according to any one of claims 1 to 9, further comprising:

The method for extracting alumina from fly ash by an alkali method according to claim 10, further comprising:

The method for extracting alumina from fly ash by an alkali method according to claim 11, further comprising:

A method of extracting alumina from fly ash by an alkali method according to claim 11, wherein

Step (10), using the solid phase residue 2 obtained in the step (7) as a raw material for producing cement building materials.

The method for extracting alumina from fly ash by an alkali method according to claim 10, wherein a concentration of the solution for performing alkali leaching in the step (7) is Na ₂ 0 _K 30 to 250 g/L.

The method for extracting alumina from fly ash by an alkali method according to claim 10, wherein the leaching temperature for performing alkali leaching in the step (7) is 60 to 250 V.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the leaching time for performing alkali leaching in the step (7) is 5 to 360 minutes.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the liquid-solid ratio at the time of alkali leaching in the step (7) is 1 to 5.

18. The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the leach solution 2 obtained in the step (7) is used for adjusting a molecule of the system during desiliconization in the step (4). The molecular ratio of the desiliconized stock solution can be adjusted to 1.4 to 2.0.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein lime is added to the leach solution 2 obtained in the step (7), and the reaction is followed by filtration, and the obtained filter residue is used in the step. Desiliconization process in (4).

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the solid phase residue 2 obtained in the step (7) is used as a raw material for producing a building material.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the mixing process of the raw slurry, the amount of limestone or lime added is determined by the amount of Si0 ₂ in the system, limestone Alternatively, the amount of lime added is controlled by a molar ratio of CaO to SiO ₂ of 0.8 to 2.2, and the amount of sodium carbonate added is controlled by a molar ratio of Na ₂ 0 to A1 ₂ 0 ₃ + Fe ₂ O ₃ of 1.7 to 3.0.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the solution for performing alkali leaching in the step (7) is a _k at 10 to 60, Na ₂ 0 _K The polymer is in a ratio of 30 to 250 g/L than the sodium aluminate solution.

The method for extracting alumina from fly ash by an alkali method according to claim 1, wherein the liquid-solid ratio of the polymer in the step (7) when the base is leached by the sodium aluminate solution is 5 ~8.