Method for improving extraction rate of aluminum in fly ash through fly ash-ammonium sulfate roasting process

Abstract

The invention relates to the technical field of fly ash utilization, in particular to a method for improving the extraction rate of aluminum in fly ash by a fly ash-ammonium sulfate roasting process, which comprises the following steps: (1) pretreating fly ash; (2) calcining the pretreated coal ash and ammonium sulfate mixture, (3) carrying out impregnation reaction on the calcined solid powder product, and (4) extracting high-silicon slag: after solid-liquid separation, putting the filter residue into a drying oven, drying for a certain time, and then weighing, according to characterization, the method has high aluminum extraction rate, and the aluminum extraction rate is 93.05%. The method is simple in process, solves the problem of low aluminum extraction rate of an ammonium sulfate roasting method, and has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of fly ash utilization, and in particular relates to a method for improving the aluminum extraction rate in fly ash through a fly ash-ammonium sulfate roasting process. Background Art

[0002] Fly ash is the most common waste from coal-fired power plants. Finding suitable disposal sites, long-term maintenance costs, inefficient land use and adverse environmental impacts are important factors hindering fly ash disposal.

[0003] The efficient use of fly ash can buffer natural resources and energy and bring huge environmental benefits. Therefore, using fly ash as a backup resource for extracting aluminum metal is of great significance to the sustainable development of the aluminum industry and to improving the comprehensive utilization value of fly ash.

[0004] In recent years, research on the efficient utilization of fly ash has become a new hotspot, and new processes and methods have continued to emerge. However, these processes still have some shortcomings. The alkaline sintering method has the problem of high energy consumption, the acid method has the problem of high equipment investment, poor reliability, low extraction rate, etc., and the acid-base combined method has the problem of large reagent usage. The ammonium sulfate roasting method does not require the addition of any additives, and the high-silicon slag obtained can also be used as a high-silicon filler. It has the advantages of suitable reaction conditions and relatively low energy consumption, and has attracted widespread attention. However, it still has the problem of low aluminum extraction rate. Therefore, it needs to be solved urgently. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process. The method has a simple process and solves the problem of low aluminum extraction rate in the ammonium sulfate roasting method, and has good application prospects.

[0006] To achieve the above object, the technical solution of the present invention is implemented as follows: a method for improving the aluminum extraction rate in fly ash by a fly ash-ammonium sulfate roasting process, comprising the following steps:

[0007] (1) Fly ash pretreatment:

[0008] Weigh a certain amount of fly ash from a power plant, put it into a ball mill for grinding for a certain period of time, and break up the mullite crystals in the fly ash so that the fly ash can be roasted with ammonium sulfate in the future;

[0009] The ground fly ash is placed in a sodium hydroxide solution of a certain concentration to improve the activation degree of the fly ash, and the alkalized fly ash is further placed in a trifluoromethanesulfonic acid solution of a certain concentration after washing and drying to remove the crystalline substances remaining after grinding;

[0010] (2) Calcination of fly ash and ammonium sulfate mixture:

[0011] The pretreated fly ash and ammonium sulfate are fully mixed according to the mass ratio, placed in a muffle furnace, and calcined at a certain temperature by uniformly increasing the temperature. After calcination for a certain period of time, the mixture is taken out by uniformly decreasing the temperature to room temperature, and finally ground to obtain a calcined solid powder product;

[0012] (3) Carrying out an impregnation reaction on the calcined solid powder product:

[0013] The calcined solid powder product is weighed and mixed with an equal proportion of distilled water, and an impregnation reaction is carried out at a certain stirring speed and a certain temperature, and solid-liquid separation is carried out after a certain reaction time;

[0014] (4) High silicon slag extraction:

[0015] After solid-liquid separation, the filter residue is placed in an oven to dry for a certain period of time, then weighed and characterized and analyzed. According to the characterization, the aluminum extraction rate is 90-95%.

[0016] Furthermore, the particle size of the fly ash particles in step (1) is 100-300 microns, and the mass of the fly ash weighed once is 100 g.

[0017] Furthermore, the ball mill grinding time in step (1) is 8 hours.

[0018] Furthermore, the concentration of the sodium hydroxide solution in step (1) is 1 mol / L; the concentration of the trifluoromethanesulfonic acid solution is 1 mol / L.

[0019] Furthermore, in step (2), the mass ratio of ammonium sulfate to fly ash is controlled between 3:1 and 4:1.

[0020] Furthermore, in step (2), the heating rate of the muffle furnace is 5°C / min, and the cooling rate is 20°C / min.

[0021] Furthermore, in step (2), the calcination temperature of the fly ash and ammonium sulfate is 400-500° C., and the calcination time is 1-2 h.

[0022] Furthermore, in step (3), the mass ratio of the calcined solid powder product to distilled water is 1:2-1:3.

[0023] Furthermore, in step (3), the impregnation reaction needs to be stirred, and the stirring speed ranges from 300 to 500 rpm, the impregnation reaction temperature is 80 to 100° C., and the impregnation reaction time is 3 hours.

[0024] Furthermore, in step (4), the drying temperature of the oven is 100-120° C., and the drying time is 6-8 hours.

[0025] The beneficial effects of the present invention are embodied in:

[0026] The present invention constructs a method for extracting aluminum from fly ash according to parameters such as specific pretreatment process, ratio, calcination temperature, calcination time and impregnation time of fly ash, which has a good aluminum extraction rate. The method has the advantages of simple application, low energy consumption, high extraction rate, etc., and has good advantages in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a line graph of aluminum extraction rate under different mass ratios of ammonium sulfate and fly ash;

[0028] Figure 2 It is a line graph of aluminum extraction rate of fly ash and ammonium sulfate mixture at different calcination temperatures;

[0029] Figure 3 It is a line graph of aluminum extraction rate of calcined product at different impregnation times. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] Example

[0032] 1. Pretreatment of fly ash:

[0033] Weigh 100g of fly ash and grind it in a ball mill for 8h to break up the mullite crystals in the fly ash so that the fly ash can be roasted with ammonium sulfate in the future;

[0034] The ground fly ash is placed in a 1 mol / L sodium hydroxide solution to increase the activation degree of the fly ash. The alkalized fly ash is further washed and dried and then placed in a 1 mol / L trifluoromethanesulfonic acid solution to remove crystalline substances remaining after grinding.

[0035] 2. Calcination of fly ash and ammonium sulfate mixture:

[0036] The fly ash ground by ball mill is fully mixed with the raw material in a ratio of 4:1, placed in a muffle furnace, and calcined at a heating rate of 5°C / min to 400°C. After calcination for 2 hours, it is cooled to room temperature at a cooling rate of 20°C / min, taken out, and ground to obtain a calcined solid powder product.

[0037] 3. Impregnation experiment of calcined product:

[0038] The calcined product was weighed and mixed with an equal proportion of distilled water, with the mass ratio of the calcined product to distilled water being 1:3. The immersion reaction was carried out at 300 rpm and 80°C, and solid-liquid separation was carried out after the reaction for 3 hours.

[0039] 4. High silicon slag extraction:

[0040] After solid-liquid separation, the filter residue was placed in an oven at 120° C. and dried for 8 hours and then weighed. According to the characterization, it was found that the present invention had a high aluminum extraction rate of 93.05%.

[0041] According to the method provided in the above embodiment, the mass ratio of ammonium sulfate to fly ash is adjusted to 1:1-5:1, and the aluminum extraction rate is statistically analyzed. The results are as follows: Figure 1 As shown in the figure: with the increase of the ammonium sulfate / fly ash mass ratio, the aluminum extraction rate in the calcined product shows an upward trend. When the ammonium sulfate / fly ash mass ratio reaches 3, the aluminum extraction rate can reach more than 90%. When the ammonium sulfate / fly ash mass ratio is 4, the aluminum extraction rate can reach 93.05%. When the aluminum extraction rate exceeds 4, there is no obvious upward trend in the aluminum extraction rate. Therefore, the optimal mass ratio of ammonium sulfate to fly ash should be controlled at 3-4.

[0042] According to the method provided in the above embodiment, the calcination temperature of the fly ash and ammonium sulfate mixture was adjusted to 100-600°C, and the aluminum extraction rate was statistically analyzed. The results are as follows: Figure 2 As shown in the figure: With the increase of calcination temperature, the extraction rate of aluminum in the calcined product shows a trend of first increasing and then decreasing. When the calcination temperature is in the range of 300-450℃, the extraction rate of aluminum in fly ash can reach more than 85%, and the best aluminum extraction rate temperature point is reached at 400℃, and the aluminum extraction rate reaches 93.05%. Therefore, from the perspective of energy saving, the best calcination temperature of the fly ash and ammonium sulfate mixture should be 400℃;

[0043] According to the method provided in the above embodiment, the immersion time of the calcined product was adjusted to 1-6 hours, and the aluminum extraction rate was statistically analyzed. The results are as follows: Figure 3 As shown in the figure: with the increase of impregnation time, the extraction rate of aluminum in the calcined product shows an upward trend. When the impregnation time reaches 8h, the aluminum extraction rate reaches 93.05%. After that, the increase of impregnation time has no obvious effect on the improvement of aluminum extraction rate. Therefore, the optimal impregnation time is 8h.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the aluminum extraction rate in fly ash by fly ash-ammonium sulfate roasting process, characterized in that: The following steps are involved: (1) Fly ash pretreatment: Weigh fly ash and grind it in a ball mill; The ground fly ash is placed in a sodium hydroxide solution for alkalization, and the alkalized fly ash is washed and dried and then placed in a trifluoromethanesulfonic acid solution to remove crystalline substances remaining after grinding; (2) Calcination of fly ash and ammonium sulfate mixture: The pretreated fly ash and ammonium sulfate are fully mixed according to the mass ratio, placed in a muffle furnace, and calcined by uniform heating. After calcination, the mixture is cooled to room temperature by uniform cooling, taken out, and finally ground to obtain a calcined solid powder product; (3) Carrying out an impregnation reaction on the calcined solid powder product: The calcined solid powder product is weighed, mixed with an equal proportion of distilled water, and then impregnated for reaction, followed by solid-liquid separation; (4) High silicon slag extraction: After solid-liquid separation, the filter residue is placed in an oven to dry, then weighed, and characterized and analyzed. According to the characterization, the aluminum extraction rate is 90-95%.

2. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: The particle size of the fly ash particles in step (1) is 100-300 microns, and the mass of the fly ash weighed once is 100g.

3. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: The ball mill grinding time in step (1) is 8 hours.

4. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: The concentration of the sodium hydroxide solution in step (1) is 1 mol / L; the concentration of the trifluoromethanesulfonic acid solution is 1 mol / L.

5. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: In step (2), the mass ratio of ammonium sulfate to fly ash is 3:1-4:

1.

6. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: In step (2), the heating rate of the muffle furnace is 5°C / min, and the cooling rate is 20°C / min.

7. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: In step (2), the calcination temperature of the fly ash and ammonium sulfate is 400-500° C., and the calcination time is 1-2 hours.

8. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: In step (3), the mass ratio of the calcined solid powder product to distilled water is 1:2-1:

3.

9. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: In step (3), the impregnation reaction needs to be stirred, and the stirring speed ranges from 300 to 500 rpm, the impregnation reaction temperature is 80 to 100° C., and the impregnation reaction time is 3 hours.

10. The method for improving the aluminum extraction rate in fly ash by using a fly ash-ammonium sulfate roasting process according to claim 1, characterized in that: In step (4), the drying temperature of the oven is 100-120° C., and the drying time is 6-8 hours.

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