A method for extracting silicon and aluminum from coal-based solid waste by alkali leaching

Abstract

The present application belongs to the technical field of coal-based solid waste comprehensive treatment, and discloses a method for extracting silicon and aluminum from coal-based solid waste by alkali leaching, which comprises the following steps: placing mineral materials and auxiliary materials in a condition of 90-120 DEG C and 300 r / min to mix and ball mill for 120-180 min; wherein, the mineral materials comprise fly ash, Fe2O3 and activated carbon; the auxiliary materials comprise one or more of Na2CO3, CaO, La2O3, TiO2 and Ga2O3; under the protection of nitrogen atmosphere, low-temperature reduction roasting is carried out at 200 DEG C for 10 min; high-temperature reduction roasting is carried out at 1200-1300 DEG C for 60 min, and natural cooling is carried out for 15 min to obtain reduction roasting materials; under an oxidation atmosphere, the reduction roasting materials are placed in a condition of 1000-1100 DEG C and 0.4 r / min to carry out oxidation roasting for 150 min; natural cooling is carried out to room temperature to obtain roasting clinker; the roasting clinker is mixed with sodium carbonate solution to carry out primary alkali leaching reaction to obtain primary leaching solution and primary leaching residue; the primary leaching residue is mixed with sodium peroxide solution to carry out secondary alkali leaching reaction to obtain secondary leaching solution and secondary leaching residue.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of comprehensive treatment of coal-based solid waste, and particularly relates to a method for extracting silicon and aluminum from coal-based solid waste by alkali leaching. BACKGROUND

[0002] Coal-based solid waste mainly refers to fly ash and other main solid waste discharged by coal-fired power plants and city central heating boilers, and is the largest single solid waste in China at present, with a cumulative stock of more than 3 billion tons and an annual output of 900 million tons. Fly ash mainly includes SiO2 (20% to 60%) and Al2O3 (10% to 50%) oxides. Extracting aluminum from fly ash not only can improve the comprehensive utilization benefit of fly ash, but also is beneficial to the sustainable development of the aluminum oxide industry.

[0003] In the prior art, the method for extracting aluminum from fly ash includes an alkali method, an acid method and an acid-alkali combined method. However, whether the acid method or the alkali method is used to extract aluminum, there is a problem of low additional value and little by-product of aluminum extraction, which greatly affects the economy of fly ash aluminum extraction. Moreover, due to the high silicon content in fly ash, a large amount of solid waste containing silicon is generated after aluminum extraction, which still has a great resource waste problem. SUMMARY

[0004] In view of this, in order to solve the problems raised in the background art, the purpose of the present application is to provide a method for extracting silicon and aluminum from coal-based solid waste by alkali leaching.

[0005] In order to achieve the above purpose, the present application provides the following technical scheme:

[0006] A method for extracting silicon and aluminum from coal-based solid waste by alkali leaching, comprising:

[0007] S1. Mechanical activation pretreatment: placing the mineral material and auxiliary materials in a mixed ball mill under the condition of 90 to 120 DEG C and 300 r / min for 120 to 180 min;

[0008] The mineral material includes fly ash, Fe2O3 and activated carbon.

[0009] The auxiliary material includes one or more of Na2CO3, CaO, La2O3, TiO2 and Ga2O3.

[0010] S2. Reduction roasting: under the protection of nitrogen atmosphere, heating to 200 DEG C at a heating rate of 5 DEG C / min, and low-temperature reduction roasting at 200 DEG C for 10 min; heating to 1200 to 1300 DEG C at a heating rate of 8 DEG C to 10 DEG C / min, and high-temperature reduction roasting at 1200 to 1300 DEG C for 60 min to obtain reduction roasting material.

[0011] S3. Reduction cooling: under the protection of nitrogen atmosphere, the reduction roasted material is naturally cooled for 15 min;

[0012] S4. Oxidation roasting: under the oxidation atmosphere, the cooled reduction roasted material is placed under the condition of 1000-1100℃ and 0.4r / min for oxidation roasting for 150 min; and naturally cooled to room temperature to obtain a roasted material;

[0013] S5. Primary alkali leaching: the roasted material is mixed with a sodium carbonate solution according to a mass-volume ratio of 2:15 to perform a primary alkali leaching reaction to obtain a primary leaching solution and a primary leaching residue;

[0014] S6. Secondary alkali leaching: the primary leaching residue is mixed with a sodium hydroxide solution according to a mass-volume ratio of 1:12 to perform a secondary alkali leaching reaction to obtain a secondary leaching solution and a secondary leaching residue.

[0015] Preferably, the molar ratio of aluminum oxide, Fe2O3 and activated carbon in the fly ash is 2:1-1.2:1.2.

[0016] Preferably, the mass ratio of the mineral material to the auxiliary material is 4:0.1-0.8.

[0017] Preferably, when the auxiliary material includes Ga2O3, the mass ratio of the mineral material to the auxiliary material is 4:0.1.

[0018] Preferably, when the auxiliary material includes TiO2, the mass ratio of the mineral material to the auxiliary material is 4:0.8.

[0019] Preferably, in the step S5, the alkali solution for primary alkali leaching is a 4mol / L sodium carbonate solution.

[0020] Preferably, in the step S5, the primary alkali leaching reaction condition is set as: the reaction temperature is 110-150℃, the reaction time is 90-120 min, and the rotation speed is 50rpm.

[0021] Preferably, in the step S6, the alkali solution for secondary alkali leaching is an 8mol / L sodium hydroxide solution.

[0022] Preferably, in the step S6, the secondary alkali leaching reaction condition is set as: the reaction temperature is 220-270℃, the reaction time is 90-120 min, and the rotation speed is 50rpm.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] In the present application, firstly, the fly ash, Fe2O3, activated carbon and auxiliary materials are mixed, ball milled and calcined, and then the silicon and aluminum in the fly ash are fully extracted through one-time alkali leaching and two-time alkali leaching. Among them: the mixed ball milling is used to increase the contact between Fe2O3 and fly ash, so as to improve the magnetic separation effect of Fe2O3; the calcination includes a reduction calcination stage and an oxidation calcination stage, which can cooperate with the two-time alkali leaching to dissolve more silicon and aluminum in the calcined clinker, thereby greatly improving the resource utilization rate and economic value of the fly ash. In addition, the auxiliary materials include one or more of Na2CO3, CaO, La2O3, TiO2 and Ga2O3, which can promote further reaction with aluminum oxide in the fly ash, thereby improving the leaching rate of aluminum. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A flow chart of the method for extracting silicon and aluminum from coal-based solid waste by alkali leaching according to the present application;

[0026] Figure 2 A calcination temperature curve diagram of Example 1;

[0027] Figure 3 A calcination temperature curve diagram of Comparative Example 1. DETAILED DESCRIPTION

[0028] In order to further understand the content of the present application, the present application is described in detail in combination with the drawings and examples. The structures, proportions, sizes and the like shown in the drawings of the present specification are only used to cooperate with the content disclosed in the specification, so as to be understood and read by those skilled in the art, and do not have technical significance, any modification of structure, change of proportion relationship or adjustment of size, which does not affect the effect and purpose that can be achieved by the present application, should still fall within the scope covered by the disclosed technical content. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and the like in the present specification are only for the convenience of clear understanding of the description, and are not used to limit the implementable range, the change or adjustment of relative relationship without substantial change of technical content is also regarded as the implementable scope of the present application. It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so as to describe the embodiments of the present application.

[0029] Example 1

[0030] A method for extracting silicon and aluminum from coal-based solid waste by alkali leaching, comprising:

[0031] S1. Mechanical activation pretreatment: the mineral material and the auxiliary material are mixed and ball milled at 120°C and 300r / min for 180min according to a mass ratio of 4:0.1 to obtain the mixed raw material; specifically, 0.1g of auxiliary material is added to every 4g of mineral material; wherein:

[0032] The mineral material includes 42.5g of fly ash (alumina content in fly ash is 48%, and silicon oxide content is 43%), 19.2g of Fe2O3, and 1.44g of activated carbon in a molar ratio of 2:1.2:1.2;

[0033] The auxiliary material includes Ga2O3.

[0034] S2. Reduction roasting

[0035] S21. The mixed raw material obtained in step S1 is placed in a quartz tube, the quartz tube is placed in a roasting furnace, nitrogen is introduced into the roasting furnace at a ventilation rate of 120mL / min for 30min, then heated to 200°C at a temperature rising rate of 5°C / min, and low-temperature reduction roasting is performed for 10min;

[0036] S22. Heated to 1200°C at a temperature rising rate of 10°C / min, high-temperature reduction roasting is performed for 60min to obtain a reduction roasted material;

[0037] S3. Reduction cooling: the reduction roasted material is naturally cooled for 15min under the protection of a nitrogen atmosphere;

[0038] S4. Oxidation roasting: air is introduced into the roasting furnace, and the cooled reduction roasted material is placed in the roasting furnace for oxidation roasting at 1000°C and 0.4r / min for 150min in an oxidizing atmosphere; naturally cooled to room temperature to obtain a roasted material;

[0039] In this embodiment, the roasting temperature curve is as shown in Figure 2 The reduction roasting is divided into two stages of low-temperature reduction roasting and high-temperature reduction roasting, compared with direct heating to 1200-1300°C, the segmented roasting of this embodiment ensures that the mixed raw material can perform sufficient reduction roasting; during the oxidation roasting process, rotation is performed at 0.4r / min to ensure that the reduction roasted material can perform sufficient oxidation roasting, avoiding incomplete roasting and affecting the aluminum-silicon leaching rate.

[0040] S5. First alkali leaching

[0041] S51. A 4mol / L sodium carbonate solution of 30mL is prepared and placed in a reaction kettle;

[0042] S52. 3g of the roasted material is poured into an agate mortar and ground uniformly, then mixed into the above reaction kettle;

[0043] S53. After tightening the reaction kettle, install it in the homogeneous reactor, set the reaction temperature to 115°C, the reaction time to 120 min, and the rotation speed to 50 rpm, and perform the first alkali leaching reaction;

[0044] S5.4. After the reaction, use a 0.22 µm polytetrafluoroethylene filter membrane to perform suction filtration, obtain the first leaching solution and the first leaching residue, and dry the first leaching residue to constant weight.

[0045] S6. Second alkali leaching

[0046] S61. Prepare 36 mL of 8 mol / L sodium hydroxide solution and place it in the reaction kettle;

[0047] S62. Take 1.5 g of the first leaching residue after drying, pour it into a maroon mortar, grind it evenly, and then mix it into the above reaction kettle;

[0048] S63. After tightening the reaction kettle, install it in the homogeneous reactor, set the reaction temperature to 220°C, the reaction time to 120 min, and the rotation speed to 50 rpm, and perform the second alkali leaching reaction;

[0049] S64. After the reaction, use a 0.22 µm polytetrafluoroethylene filter membrane to perform suction filtration, obtain the second leaching solution and the second leaching residue.

[0050] The first leaching solution and the second leaching solution of the above Example 1 were determined as follows:

[0051] ① SiO2 content determination

[0052] Dilute the alkali leaching solution to 250 mL in a volumetric flask to obtain the stock solution.

[0053] Transfer 1 mL of the stock solution to a 100 mL volumetric flask, dilute to the mark with water, shake well; then transfer 8 mL to a 100 mL volumetric flask, add water to 60 mL, shake well to obtain the test solution (not constant volume). When the concentration is high, take 1 mL of the stock solution and dilute to 250 mL in a volumetric flask, then take 1 mL of the dilution solution for analysis, and set up a blank group at the same time.

[0054] Add 3.50 mL of hydrochloric acid (3 mol / L) to the test solution (add 7.00 mL of hydrochloric acid when the NT in the solution is higher than 100 g / L), shake well to dissolve all the aluminum hydroxide precipitate, and add 2.50 mL of HCI (3 mol / L) to the blank group and shake well.

[0055] In the blank group, the test solution was added with 5% ammonium molybdate solution 5 mL, and shaken. After standing for a certain time (20 min at room temperature below 20℃; 15 min at 20℃-30℃; 10 min at 30℃-40℃), 20 mL of sulfuric acid-oxalic acid-ammonium ferrous sulfate mixed solution was added, diluted with water to the specified scale, shaken, and stood for 5 min. The absorbance was measured at wavelength 700 nm in a 1 cm cuvette with air as the reference, and the content of SiO2 was obtained from the standard curve.

[0056] ②Al2O3 content determination

[0057] The alkaline leaching solution was diluted to 250 mL in a volumetric flask to obtain the stock solution.

[0058] 2 mL of the stock solution was taken and added to a 250 mL conical flask, followed by 5 mL of EDTA solution (0.05 mol / L) and 20 mL of hydrochloric acid (6 mol / L). After heating and boiling for 2 min, the test solution was removed. Then 4 drops of green light phenothalin indicator were added, and 6 mol / L sodium hydroxide was titrated to a light red color. The consumption of sodium hydroxide titration solution was recorded. 10 mL of acetic acid-sodium acetate buffer (80 g of anhydrous sodium acetate + 7.7 mL of acetic acid diluted to 1 L) was added, and 3 drops of dimethyl phenol orange indicator was added. Zinc nitrate standard solution was titrated to rose red color, which was the end point. The consumption of zinc nitrate was recorded.

[0059] The Al2O3 content was calculated according to the following formula:

[0060] In the formula: ρAl2O3 represents the concentration of Al2O3 (mol / L); C EDTA represents the concentration of EDTA standard solution (mol / L); V EDTA represents the volume of EDTA standard solution added (mL); C Zn represents the concentration of zinc nitrate standard solution (mol / L); V Zn represents the volume of consumed zinc nitrate standard solution (mL); V 样 represents the volume of test solution added (mL).

[0061] The determination results are as follows:

[0062]

[0063] Example 2

[0064] A method for extracting silicon and aluminum from coal-based solid waste by alkaline leaching, comprising:

[0065] S1. Mechanical activation pretreatment: the mineral material and the auxiliary material are mixed and ball milled at 120°C and 300r / min for 180min according to a mass ratio of 4:0.2 to obtain the mixed raw material; specifically, 0.2g of auxiliary material can be added to 4g of mineral material; wherein:

[0066] The mineral material includes 42.5g of fly ash (the content of alumina in the fly ash is 48% and the content of silicon oxide is 45%), 19.2g of Fe2O3 and 1.44g of activated carbon in a molar ratio of 2:1.2:1.2;

[0067] The auxiliary material includes TiO2.

[0068] S2. Reduction roasting: the same as in Example 1 above;

[0069] S3. Reduction cooling: the same as in Example 1 above;

[0070] S4. Oxidation roasting: the same as in Example 1 above;

[0071] S5. Primary alkaline leaching: the same as in Example 1 above;

[0072] S6. Secondary alkaline leaching: the same as in Example 1 above.

[0073] The primary leaching solution and the secondary leaching solution obtained in this example are determined by using the same determination method as in Example 1 above, and the determination results are shown in the following table:

[0074] The determination results are shown in the following table:

[0075]

[0076] Comparative Example 1

[0077] This comparative example is used to verify the influence of the addition of auxiliary material on the extraction rate of silicon and aluminum.

[0078] S1. Mechanical activation pretreatment: 42.5g of fly ash (the mass fraction of alumina in the fly ash is calculated as 48%), 19.2g of Fe2O3 and 1.44g of activated carbon are mixed and ball milled at 120°C and 300r / min for 180min according to a molar ratio of 2:1.2:1.2 to obtain the mixed raw material.

[0079] S2. Reduction roasting: the same as in Example 1 above;

[0080] S3. Reduction cooling: the same as in Example 1 above;

[0081] S4. Oxidation roasting: the same as in Example 1 above;

[0082] S5. Primary alkaline leaching: the same as in Example 1 above;

[0083] S6. Secondary alkali leaching: same as Example 1 above.

[0084] The primary and secondary leaching solutions obtained in this example were measured in the same manner as Example 1 above, and the measurement results are shown in the following table:

[0085] The measurement results are shown in the following table:

[0086]

[0087] This shows that the addition of auxiliary materials for co-calcination has a significant effect on the dissolution of SiO2 and Al2O3, and in particular, the dissolution rate of SiO2 is significantly improved.

[0088] Comparative Example 2

[0089] This comparative example is used to verify the effect of the calcination step on the extraction rate of silicon and aluminum.

[0090] S1. Mechanical activation pretreatment: same as Example 1 above.

[0091] S2. Reduction calcination:

[0092] S21. The mixed raw materials obtained from the pretreatment in step S1 were placed in a quartz tube, and the quartz tube was placed in a calcination furnace. Nitrogen was introduced into the calcination furnace at a flow rate of 120 mL / min for 30 min, and then heated to 200°C at a heating rate of 5°C / min, and reduction calcination was performed at low temperature for 10 min.

[0093] S22. The temperature was raised to 1100°C at a rate of 10°C / min, and reduction calcination was performed at high temperature for 60 min. The sample was naturally cooled to room temperature, and a calcined clinker was obtained. In this example, the temperature curve of the calcination is shown in Figure 3

[0094] S3. Primary alkali leaching: same as step S5 of Example 1 above.

[0095] S4. Secondary alkali leaching: same as step S6 of Example 1 above.

[0096] The primary and secondary leaching solutions obtained in this example were measured in the same manner as Example 1 above, and the measurement results are shown in the following table:

[0097]

[0098] This shows that the addition of auxiliary materials for co-calcination has a significant effect on the dissolution of SiO2 and Al2O3, and in particular, the dissolution rate of SiO2 is significantly improved.

[0099] Comparative Example 3 ​

[0100] A method for extracting silicon and aluminum from coal-based solid waste by alkali leaching, comprising:

[0101] S1. Mechanical activation pretreatment: the mineral material and the auxiliary material are mixed and ball milled at 90°C and 300r / min for 180min according to a mass ratio of 4:0.1, to obtain a mixed raw material; specifically, 0.1g of auxiliary material can be added for every 4g of mineral material; wherein:

[0102] The mineral material includes 42.5g of fly ash (alumina content in fly ash is 48%, and silicon oxide content is 43%), 19.2g of Fe2O3 and 1.44g of activated carbon in a molar ratio of 2:1.2:1.2;

[0103] The auxiliary material includes Ga2O3.

[0104] S2. Reduction roasting: the same as in Example 1 above;

[0105] S3. Reduction cooling: the same as in Example 1 above;

[0106] S4. Oxidation roasting: the same as in Example 1 above;

[0107] S5. First alkali leaching: the same as in Example 1 above;

[0108] S6. Second alkali leaching: the same as in Example 1 above.

[0109] The first leaching solution and the second leaching solution obtained in this example are determined by the same determination method as in Example 1 above, and the determination results are as follows:

[0110]

[0111] Comparative Example 4

[0112] A method for extracting silicon and aluminum from coal-based solid waste by alkali leaching, comprising:

[0113] S1. Mechanical activation pretreatment: the mineral material and the auxiliary material are mixed and ball milled at 90°C and 300r / min for 120min according to a mass ratio of 4:0.1, to obtain a mixed raw material; specifically, 0.1g of auxiliary material can be added for every 4g of mineral material; wherein:

[0114] The mineral material includes 42.5g of fly ash (alumina content in fly ash is 48%, and silicon oxide content is 43%), 19.2g of Fe2O3 and 1.44g of activated carbon in a molar ratio of 2:1.2:1.2;

[0115] The auxiliary material includes Ga2O3.

[0116] S2. Reduction roasting: the same as in Example 1 above;

[0117] S3. Reduction cooling: same as Example 1 above;

[0118] S4. Oxidative roasting: same as Example 1 above;

[0119] S5. Primary alkaline leaching: same as Example 1 above;

[0120] S6. Secondary alkaline leaching: same as Example 1 above.

[0121] The primary leachate and secondary leachate obtained in this example were measured in the same manner as Example 1 above, and the measurement results are shown in the following table:

[0122]

[0123] In combination with Comparative Examples 3 and 4 above, it is shown that milling of the ore material and the auxiliary material at 120°C for 180 min can significantly improve the SiO2 leaching rate and the Al / Si ratio of the leach residue.

[0124] Note that the above merely provides preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described above, and that various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above examples, the present application is not limited to the above examples, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A method for extracting silicon and aluminum from coal-based solid waste by alkaline leaching, characterized in that, include: S1. Mechanical activation pretreatment: The ore and auxiliary materials are mixed and ball-milled at 120℃ and 300r / min for 180min; The mineral material includes fly ash, Fe2O3, and activated carbon; the molar ratio of alumina, Fe2O3, and activated carbon in the fly ash is 2:1.2:1.

2. The auxiliary materials include Ga2O3 or TiO2; When the auxiliary material includes Ga2O3, the mass ratio of the ore to the auxiliary material is 4:0.1; When the auxiliary material includes TiO2, the mass ratio of the mineral to the auxiliary material is 4:0.2; S2. Reduction calcination: Under nitrogen atmosphere protection, the temperature is increased to 200℃ at a heating rate of 5℃ / min, and then reduced and calcined at 200℃ for 10 min; the temperature is increased to 1200-1300℃ at a heating rate of 8℃~10℃ / min, and then reduced and calcined at 1200-1300℃ for 60 min to obtain the reduced calcined material; S3. Reduction and cooling: Under nitrogen atmosphere protection, allow the reduced roasted material to cool naturally for 15 minutes; S4. Oxidative roasting: Under an oxidizing atmosphere, the cooled reduction roasted material is oxidized and roasted at 1000-1100℃ and 0.4r / min for 150min; then naturally cooled to room temperature to obtain roasted clinker; S5. First alkaline leaching: The roasted clinker is mixed with a 4 mol / L sodium carbonate solution at a mass-to-volume ratio of 1:10 to carry out a first alkaline leaching reaction, resulting in a first leaching solution and a first leaching residue; S6. Secondary alkaline leaching: The primary leaching residue is mixed with an 8 mol / L sodium hydroxide solution at a mass-to-volume ratio of 1:24 to carry out a secondary alkaline leaching reaction, resulting in a secondary leaching solution and a secondary leaching residue.

2. The method for extracting silicon and aluminum from coal-based solid waste by alkaline leaching according to claim 1, characterized in that, In step S5, the conditions for the first alkaline leaching reaction are set as follows: reaction temperature is 110-150℃, reaction time is 90-120 min, and rotation speed is 50 rpm.

3. The method for extracting silicon and aluminum from coal-based solid waste by alkaline leaching according to claim 1, characterized in that, In step S6, the conditions for the secondary alkali leaching reaction are set as follows: reaction temperature of 220-270℃, reaction time of 90-120 min, and rotation speed of 50 rpm.

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