Process for extracting aluminum in fly ash by two-step method

Abstract

The invention relates to the technical field of fly ash utilization, in particular to a process for extracting aluminum in fly ash by a two-step method, which comprises the following steps: 1) extraction of amorphous aluminum in fly ash: weighing fly ash, firstly dipping in sulfuric acid, dissolving amorphous aluminum oxide in fly ash, filtering, drying, and grinding in a ball mill for 8 hours; 2) extraction of crystalline aluminum in fly ash: 21) fully mixing the fly ash ground in the step 1) with ammonium sulfate according to a ratio, placing the mixture in a muffle furnace, heating to 400 DEG C at a constant speed, and calcining for 2 hours; 22) taking out and weighing the calcined product, mixing the calcined product with distilled water according to a mass ratio of 1: 2, dipping for 3 hours under the conditions of 400 DEG C and 300rpm, and carrying out solid-liquid separation; and 23) drying the solid subjected to solid-liquid separation in a drying oven at 120 DEG C for 6 hours to obtain a high-silicon slag solid. 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 two-step process for extracting aluminum from fly ash. Background Art

[0002] As a common byproduct of coal-fired power plants, fly ash has an annual output of more than 600 million tons, becoming an environmental and resource management problem that needs to be solved urgently. The traditional treatment method - landfilling, not only consumes a large amount of precious land resources, but also triggers a chain reaction, including obstruction of ecosystem circulation, increased soil erosion, and even potential threats to human health, especially interfering with the repair mechanism of human DNA. Therefore, the effective management and resource utilization of fly ash has become a key issue that needs to be overcome worldwide. Faced with the challenges of land occupation, environmental damage and high long-term maintenance costs brought about by fly ash treatment, it is particularly urgent to find innovative solutions. Against the background of increasingly tight global resources, the efficient conversion and utilization of fly ash is regarded as an effective way to alleviate resource shortages and promote environmental friendliness. In particular, in my country, aluminum resources are relatively scarce, and the proven bauxite reserves account for only a very small proportion of the world's total. The alumina resources contained in fly ash have therefore become a new hope to alleviate this dilemma. Its potential as an alternative resource for aluminum metal is huge, which is of great significance to ensuring the sustainable development of the aluminum industry and improving the comprehensive utilization level of fly ash.

[0003] In recent years, the research on efficient utilization of fly ash has become the focus of scientific research and industry, and a series of new processes and technologies have emerged to explore more environmentally friendly and economical fly ash treatment solutions. However, these emerging processes still face many challenges in practical applications: the alkaline sintering method has huge energy consumption, the acid extraction method faces problems such as high equipment investment, poor operating stability and low extraction efficiency, and the acid-base combined method is difficult to be widely promoted due to the large consumption of reagents. In this context, the ammonium sulfate roasting method has gradually attracted the attention of the industry due to its advantages such as no need to add additional additives, the product high silicon slag can be reused, the reaction conditions are mild and the energy consumption is relatively low. Despite this, the deficiency of this process in aluminum extraction rate is still a major bottleneck restricting its widespread application. Therefore, it needs to be solved urgently. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a two-step process for extracting aluminum from fly ash. The method is simple in process and solves the problem of low aluminum extraction rate in the ammonium sulfate roasting method, and has good application prospects.

[0005] To achieve the above object, the technical solution of the present invention is implemented as follows: a two-step process for extracting aluminum from fly ash, comprising the following steps:

[0006] 1) Extraction of amorphous aluminum from fly ash:

[0007] Weigh a certain weight of fly ash, soak it in sulfuric acid for a period of time to dissolve the amorphous aluminum oxide in the fly ash, filter it, dry it, and grind it in a ball mill for 8 hours;

[0008] 2) Extraction of crystalline aluminum from fly ash:

[0009] 21) The fly ash ground in step 1) is fully mixed with ammonium sulfate in proportion, placed in a muffle furnace, and calcined at 400° C. for 2 hours at a uniform temperature increase;

[0010] 22) The calcined product was taken out and weighed, mixed with distilled water at a mass ratio of 1:2, immersed at 400°C and 300 rpm for 3 hours, and then solid-liquid separation was performed;

[0011] 23) The solid after solid-liquid separation is placed in an oven at 120° C. and dried for 6 hours to obtain a high-silicon slag solid.

[0012] Furthermore, the particle size of the fly ash in step 1) is 100-300 microns, and the mass of the fly ash weighed once is 100g.

[0013] Furthermore, the concentration of sulfuric acid in step 1) is 1 mol·L-1, and the volume of sulfuric acid is 200 mL.

[0014] Furthermore, the fly ash in step 1) is impregnated for 1 hour, and is stirred during impregnation at a stirring speed of 300 rpm and at a temperature of 80°C.

[0015] Furthermore, the grinding power of the ball mill in step 1) is 10 kW. By improving the collision efficiency of the ball mill, the extraction efficiency of aluminum in fly ash is also improved.

[0016] Furthermore, in step 21), the optimal mass ratio of fly ash to ammonium sulfate is between 1:3 and 1:4.

[0017] Furthermore, in step 21), the calcination heating rate is 5°C / min, the calcination temperature is 400°C, the calcination time is 2 hours, and the cooling rate is 40°C / min.

[0018] Furthermore, the sulfuric acid filtrate obtained in step 1) and the filtrate and filter residue in step 23) are all recovered, the filtrate is used for subsequent extraction of metals such as aluminum, and the filter residue is used as a silicon-containing filler or catalyst.

[0019] Furthermore, the grinding time of the ball mill in step 1) is 8 hours.

[0020] The beneficial effects of the present invention are embodied in:

[0021] (1) In the method provided by the present invention, fly ash is treated in a two-step process, and a two-step process and application of aluminum in fly ash are constructed through processes such as acid leaching, filtration, calcination, impregnation, filtration, washing and drying. The process has good aluminum extraction rate and extraction efficiency, and the process has the advantages of simple application, low energy consumption, and high extraction rate, and has good advantages in practical applications.

[0022] (2) The method provided by the present invention performs acid leaching treatment on fly ash, which has an important influence on the activity of active components in fly ash, such as silica, calcium oxide, magnesium oxide, etc.; acid leaching treatment can release and increase the content of these active components, thereby increasing the activity of fly ash. After the activity is increased, it is convenient to subsequently extract amorphous aluminum and other metal elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the extraction rate of aluminum from fly ash at different impregnation times;

[0024] Figure 2 This is a comparison chart between the two-step process for extracting aluminum from fly ash and the traditional ammonium sulfate-fly ash roasting method;

[0025] Figure 3 The application of a two-step process for extracting aluminum from fly ash with different aluminum contents is presented. DETAILED DESCRIPTION

[0026] 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.

[0027] Embodiment 1:

[0028] Extraction process of amorphous aluminum in fly ash:

[0029] Weigh 100g of fly ash, soak it in sulfuric acid for 1 hour to dissolve the amorphous aluminum oxide in the fly ash, filter and dry it, and then grind it in a ball mill for 8 hours. The filtrate is recovered and used later;

[0030] Extraction process of crystalline aluminum from fly ash:

[0031] The fly ash ground by a ball mill was fully mixed with ammonium sulfate in proportion, placed in a muffle furnace, and calcined at 400°C for 2 hours at a uniform temperature. The calcined product was taken out and weighed, mixed with distilled water in a mass ratio of 1:2, and immersed at 400°C and 300rpm for 3 hours. The solid-liquid separation was performed, and the obtained high-silicon slag solid was placed in a 120°C oven and dried for 6 hours to obtain the final high-silicon slag solid.

[0032] The control group was ground in a ball mill for 8 hours and then operated according to the extraction process system of crystalline aluminum in fly ash to obtain the following Figure 2 The experimental results show that the aluminum leaching rate of the ammonium sulfate-fly ash roasting process after acid leaching is higher. When the ball milling time is 8 hours, the aluminum leaching rate is 10.60% higher than that of the ammonium sulfate-fly ash roasting process without acid leaching.

[0033] Therefore, compared with the traditional ammonium sulfate-fly ash roasting method, the two-step process for extracting aluminum from fly ash has a higher aluminum extraction rate and faster efficiency.

[0034] Embodiment 2:

[0035] The two-step process for extracting aluminum from fly ash with different aluminum contents is applied, as shown in the attached Figure 3 The two-step extraction process of aluminum from fly ash was applied with fly ash having aluminum oxide contents of 11.35%, 15.02%, 19.05%, 24.05%, 26.06%, 28.05%, 31.07% and 33.05%.

[0036] The specific implementation of each group of fly ash experiments is mainly divided into two steps:

[0037] Extraction process of amorphous aluminum in fly ash:

[0038] Weigh 100g of fly ash, soak it in sulfuric acid for 1 hour to dissolve the amorphous aluminum oxide in the fly ash, filter and dry it, and then grind it in a ball mill for 8 hours. The filtrate is recovered and used later;

[0039] Extraction process of crystalline aluminum from fly ash:

[0040] The fly ash ground by a ball mill was fully mixed with ammonium sulfate in proportion, placed in a muffle furnace, and calcined at 400°C for 2 hours at a uniform temperature. The calcined product was taken out and weighed, mixed with distilled water in a mass ratio of 1:2, and immersed at 400°C and 300rpm for 3 hours. The solid-liquid separation was performed, and the obtained high-silicon slag solid was placed in a 120°C oven and dried for 6 hours to obtain the final high-silicon slag solid.

[0041] The experimental results show that the aluminum leaching rates of fly ash with aluminum oxide contents of 11.35%, 15.02%, 19.05%, 24.05%, 26.06%, 28.05%, 31.07% and 33.05% are 94.05%, 94.25%, 93.54%, 95.05%, 94.06%, 95.93%, 96.05% and 95.82% respectively. The aluminum leaching rates are all over 90%.

[0042] According to the method provided in the above embodiment, the fly ash acidification time was adjusted to 0-90min, and the aluminum leaching rate was statistically analyzed. The results are as follows: Figure 1 As shown in the figure: with the increase of impregnation time, the aluminum impregnation efficiency shows a trend of first increasing and then stabilizing. When the sulfuric acid impregnation time is within 60 minutes, the aluminum impregnation efficiency shows an upward trend. When the sulfuric acid impregnation time is greater than 60 minutes, the aluminum impregnation efficiency is stable. When the sulfuric acid impregnation time reaches 60 minutes, the aluminum impregnation efficiency reaches 95.63%. Therefore, from the perspective of energy saving, the acid leaching time of fly ash should be controlled within 60 minutes.

[0043] According to the method provided in the above embodiment, the ball milling time of fly ash was adjusted to 0-11h, and the aluminum leaching rate was statistically analyzed. The results are as follows: Figure 2 As shown in the figure: with the increase of ball milling time, the aluminum leaching rates of the two-step process for extracting aluminum from fly ash and the traditional ammonium sulfate-fly ash roasting method both increase with time. When the ball milling time reaches 8 hours, the aluminum leaching rates of the two-step process for extracting aluminum from fly ash and the traditional ammonium sulfate-fly ash roasting method are 95.63% and 85.03%, respectively. Therefore, from the perspective of energy saving, the optimal ball milling time is 8 hours.

[0044] according to Figure 2 It can be seen that the aluminum leaching rate of the ammonium sulfate-fly ash roasting process after acid leaching is higher. When the ball milling time is 8 hours, the aluminum leaching rate is 10.60% higher than that of the ammonium sulfate-fly ash roasting process without acid leaching. Therefore, the two-step process for extracting aluminum from fly ash has a higher aluminum extraction rate and faster efficiency than the traditional ammonium sulfate-fly ash roasting method.

[0045] According to the method provided in the above embodiment, the aluminum leaching rate of fly ash in the range of different aluminum contents of 10%-35% is statistically analyzed. The results are as follows: Figure 3 As shown in the figure: The two-step process for extracting aluminum from fly ash has a good aluminum leaching rate, which can reach 90% or above, and has good application prospects.

[0046] Therefore, the two-step process for extracting aluminum from fly ash of the present invention also has good prospects in practical applications.

[0047] 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 two-step process for extracting aluminum from fly ash, characterized in that: The following steps are involved: 1) Extraction of amorphous aluminum from fly ash: Weigh fly ash, soak it in sulfuric acid to dissolve the amorphous aluminum oxide in the fly ash, filter it, dry it, and grind it in a ball mill; 2) Extraction of crystalline aluminum from fly ash: 21) The fly ash ground in step 1) is fully mixed with ammonium sulfate according to a mass ratio, placed in a muffle furnace, and calcined at 400° C. for 2 hours at a uniform temperature increase; 22) The calcined product was taken out and weighed, mixed with distilled water at a mass ratio of 1:2, immersed at 400°C and 300 rpm for 3 hours, and then solid-liquid separation was performed; 23) The solid after solid-liquid separation is placed in an oven at 120° C. and dried for 6 hours to obtain a high-silicon slag solid.

2. A two-step process for extracting aluminum from fly ash 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 two-step process for extracting aluminum from fly ash according to claim 1 is characterized in that: The concentration of sulfuric acid in step 1) is 1 mol·L -1 , the volume of sulfuric acid is 200mL.

4. The two-step process for extracting aluminum from fly ash according to claim 1 is characterized in that: The fly ash in step 1) is impregnated for 1 hour and stirred during impregnation at a stirring speed of 300 rpm and at a temperature of 80°C.

5. The two-step process for extracting aluminum from fly ash according to claim 1 is characterized in that: The grinding power of the ball mill in step 1) is 10 kW.

6. The two-step process for extracting aluminum from fly ash according to claim 1 is characterized in that: In step 2), the mass ratio of fly ash to ammonium sulfate is 1:3-1:

4.

7. The two-step process for extracting aluminum from fly ash according to claim 1 is characterized in that: The calcination heating rate in step 2) is 5°C / min, the calcination temperature is 400°C, the calcination time is 2 hours, and the cooling rate is 40°C / min.

8. The two-step process for extracting aluminum from fly ash according to claim 1 is characterized in that: The sulfuric acid filtrate obtained in step 1) and the filtrate and filter residue in step 23) are all recovered, the filtrate is used for subsequent aluminum extraction, and the filter residue is used as a silicon-containing filler or catalyst.

9. The two-step process for extracting aluminum from fly ash according to claim 1, characterized in that: The grinding time of the ball mill in step 1) is 8 hours.

Images