Method for preparing 4N quartz sand by taking granite tailings as raw material

Abstract

The invention relates to a method for preparing 4N quartz sand by taking granite tailings as a raw material, which comprises the following steps: firstly, removing impurities from the granite tailings to obtain a quartz sand crude product with the SiO2 purity of more than or equal to 99.6%; the method comprises the following steps: roasting a quartz sand crude product of which the SiO2 purity is greater than or equal to 99.6% at a high temperature, and then carrying out cold gathering on the quartz sand crude product by adopting liquid CO2; the obtained quartz sand is subjected to secondary impurity removal, and a high-purity quartz sand product with the SiO2 purity larger than or equal to 99.99% is obtained. According to the invention, liquid CO2 is adopted for cold gathering of quartz sand, dependence on water resources is effectively reduced, surface pollution to the quartz sand is also reduced, the impurity removal end point of each step is judged according to analysis and test results, and the impurity removal efficiency is greatly improved.

Description

Technical Field

[0001] The present invention relates to a method for preparing 4N quartz sand from granite tailings, belonging to the technical fields of solid waste environmental protection utilization and deep processing of non-metallic minerals. Background Art

[0002] As is well known, granite stone, as a decorative material in the construction industry, is widely used in public places such as subways, airports, stations, docks, shopping malls, hotels, schools, parks, and squares. A large amount of solid waste residue will be generated during the production of granite stone. If the solid waste comprehensive utilization is not well done, it will cause serious pollution to the (dust) air, (sewage) water body, and (waste residue) solid waste environment where the stone production is located. Therefore, doing a good job in the solid waste comprehensive utilization problem during the granite stone production process is a key issue related to the healthy development of the granite industry. Taking a certain granite stone industry as an example, the annual output value is 30 billion yuan, and the output of solid waste granite tailings is more than 10 million tons. Currently, such solid waste is mainly consumed as construction sand. However, a single flow direction may bring problems of untimely consumption due to changes in the industry development, and the large amount of accumulated tailings has become an urgent problem to be solved. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing high-purity quartz sand with 4N (SiO 2 purity ≥ 99.99%).

[0004] The solution adopted by the present invention to solve the above technical problems is:

[0005] A method for preparing 4N quartz sand from granite tailings, comprising the following steps:

[0006] (1) Primary impurity removal: removing impurities from the granite tailings to obtain a crude quartz sand product with SiO 2 purity ≥ 99.6% (mass percentage, the same below);

[0007] (2) High-temperature roasting and rapid cooling: performing high-temperature roasting on the obtained crude quartz sand product with SiO 2 purity ≥ 99.6%, and then rapidly cooling the crude quartz sand product with liquid CO 2 ;

[0008] (3) Secondary impurity removal: performing secondary impurity removal on the quartz sand obtained in step (2) to obtain a high-purity quartz sand product with SiO 2 purity ≥ 99.99%.

[0009] Furthermore, the primary impurity removal includes the following steps:

[0010] (1a) Wet classification: Select tailings mortar with a mesh size of 60 - 150, dehydrate it after magnetic separation for standby.

[0011] (1b) Flotation: Until the SiO₂ purity in the sand after flotation ≥ 99%. 2 Purity ≥ 99%.

[0012] (1c) Acid pickling for impurity removal: Until the SiO₂ purity in the obtained sand ≥ 99.6%, and dry the tailings after acid pickling for standby. 2 Purity ≥ 99.6%, and dry the tailings after acid pickling for standby.

[0013] Furthermore, the wet classification is water washing and screening. For example, use a cylindrical classifier with three or more stages for quantitative water washing and screening, so that classification and desliming are carried out in one process, improving efficiency.

[0014] Furthermore, in step (1b), dodecylamine is used as the flotation reagent for at least one flotation until the SiO₂ in the tailings ≥ 99%. As an example, the conditions for the flotation are: solid - liquid ratio 3% - 30%, pH value 2 - 3, and flotation reagent concentration 80 - 120 g / t. 2 ≥ 99%. As an example, the conditions for the flotation are: solid - liquid ratio 3% - 30%, pH value 2 - 3, and flotation reagent concentration 80 - 120 g / t.

[0015] Furthermore, the acid pickling solution used in step (1c) includes HF and one or more of HCl, sulfuric acid, and oxalic acid.

[0016] Furthermore, the concentration of HF in the acid pickling solution is 5% - 20%, HCl is 20% - 25%, sulfuric acid is 10% - 20%, and oxalic acid is 5% - 10%.

[0017] The main purpose of flotation is to remove feldspar from quartz sand. When the flotation end - point is set too low, the consumption of HF in the acid pickling solution needs to be increased to fully remove feldspar impurities. However, when the SiO₂ content at the end - point is less than 99%, even if the amount of HF is increased, it is difficult to achieve the goal of SiO₂ purity ≥ 99.6%. And when the flotation end - point is set too high, for example, the SiO₂ content at the end - point exceeds 99.6%, it will increase the flotation cost and reduce the SiO₂ output. 2 content is less than 99%, even if the amount of HF is increased, it is difficult to achieve the goal of SiO₂ 2 purity ≥ 99.6%. And when the flotation end - point is set too high, for example, the SiO₂ 2 content exceeds 99.6%, it will increase the flotation cost and reduce the SiO₂ 2 output.

[0018] Furthermore, an oxidant is added to the acid pickling solution used in step (1c); the oxidant is selected from any one or more of halogen oxyacids, halogen oxyacid salts, nitrates, or nitrites, such as: nitric acid, nitrates, or perchloric acid and perchlorates, or chloric acid, hypochlorous acid, and chlorates, hypochlorites. The dosage of the oxidant is 0.1% - 0.5% of the mass of the acid pickling solution. When the material to be pickled contains sulfur components, adding an oxidant can oxidize sulfide minerals.

[0019] Further, in step (1c), fluidized heating pickling is adopted, the pickling temperature is 75 - 80 °C, and the pickling time is 5h - 8h.

[0020] Further, in steps (1) to (3), XRF (X-ray fluorescence spectrometry) is used to analyze the components in the product, and the production is guided by the analysis results of XRF, ensuring the effective operation of the quality control and quality assurance systems during the product production process.

[0021] Further, the temperature of high-temperature roasting in step (2) is 1000 - 1100 °C.

[0022] Further, in step (2), the liquid CO used for quenching 2 The dosage is not less than 1.2 times the mass of the material.

[0023] Further, the secondary impurity removal includes one or more of the following treatments: secondary pickling, flotation, and water washing and drying.

[0024] The present invention uses liquid CO 2 to quench the quartz sand, and using liquid CO 2 The advantages of quenching are as follows: 1. It avoids the problem that the sand containing moisture after water cooling needs to be dried, and the water in the sand will dilute the acid solution during the subsequent pickling process, affecting the purification effect; 2. It avoids the problem that chemical reactions occur between the surface of the high-temperature quartz material and water during the water quenching process, generating alcohol groups or hydroxyl groups; 3. Using CO 2 for quenching can keep the outer surface of the material clean; 4. It is beneficial for directly sampling the material for XRF analysis after cooling, and judging the end point of each impurity removal step based on the analysis and test results, which not only greatly improves the impurity removal efficiency, but also saves the cost of drying the sample after water cooling and avoids the risk of material contamination during water cooling. Specific Embodiments

[0025] To better understand the present invention, the following embodiments further illustrate the present invention, but the content of the present invention is not limited to the following embodiments only.

[0026] Example 1

[0027] The process of the present invention is implemented using the tailings generated during the processing of white duck mountain granite in Macheng, Hubei:

[0028] (1) Pretreat the granite tailings: Use a forklift to send the tailings into the silo of a three-stage cylindrical classifier (20 mesh, 50 mesh, 150 mesh), then quantitatively perform water washing, screening, and classification, collect the 50 - 150 mesh mortar, and use an electromagnetic separator with a magnetic field strength of 1.5T and perform magnetic separation at least three times, and then collect the slurry after magnetic separation and dehydrate it for standby.

[0029] (2) Flotation: (1) The obtained materials are fed into a flotation machine, water is added to make the solid-liquid ratio 25%, an appropriate amount of HF regulator is added to adjust the pH value between 2.0 - 3.0, stirred for 30 min, then dodecylamine is added to make its concentration reach 100 g / t, and stirred for 40 min. A foaming agent is added, and air is inflated for flotation for 30 min. Sampling is carried out, and the quartz content in the sample is analyzed by XRF. When the quartz content is 99.5%, flotation is stopped; otherwise, flotation is carried out multiple times under the same process conditions until the quartz content meets the requirements.

[0030] (3) Acid pickling for impurity removal: The acid solution formula is designed with reference to the XRF analysis results. The quartz sand after separating feldspar in (2) is subjected to fluidized heating and acid pickling. Since the analysis results show that there is no sulfur in the quartz sand, the acid solution is a mixed acid solution of industrial hydrofluoric acid + hydrochloric acid, with a concentration of HF: 5%; HCl: 25%, the acid pickling temperature is 75 °C, and the acid pickling time is 8 hours, then dried for standby. The acid-pickled quartz sand is analyzed by XRF.

[0031] (4) High-temperature roasting and polycooling: The quartz sand obtained in (3) is roasted at a high temperature of 1000 °C for 1 h, and then polycooled using liquid CO 2 where the usage amount of liquid CO 2 is not less than 1.2 times the mass of the quartz sand material.

[0032] (5) Secondary impurity removal: The quartz sand in (4) is subjected to secondary acid pickling and purification with 55% hydrofluoric acid, then the acid solution is removed, and then flotation, ultra-pure water fine washing, centrifugal dehydration, and high-temperature drying are carried out. Sampling is carried out to analyze the SiO 2 content according to the GB / T 3284 - 2015 standard.

[0033] Example 2

[0034] The raw materials used in this example are the same as those in Example 1. The differences in the implementation process from Example 1 are as follows:

[0035] (2) Flotation is stopped when the SiO 2 content reaches 99%.

[0036] (3) The HF concentration in the acid solution is 20%; HCl: 25%.

[0037] Comparative Example 1

[0038] The raw materials used in this comparative example are the same as those in Example 1. The differences in the implementation process from Example 1 are as follows:

[0039] (2) Flotation is stopped when the SiO 2 content reaches 89.1%.

[0040] (3) The HF concentration in the acid solution is 20%; HCl: 25%.

[0041] Example 3

[0042] The raw materials used in this example are the same as those in Example 1. The difference in the implementation process from Example 1 is as follows:

[0043] (3) The acid solution used is a mixed acid solution of industrial hydrofluoric acid + sulfuric acid, with a concentration of HF: 20%; H 2 SO 4 : 10%, the pickling temperature is 75 - 80 °C, and the pickling time is 5 hours.

[0044] Comparative Example 2

[0045] The raw materials used in this comparative example are the same as those in Example 1. The difference in the implementation process from Example 1 is as follows:

[0046] (4) Quenching is carried out with tap water. After quenching, the material is dehydrated and dried, and then sampled for XRF analysis.

[0047] Example 4

[0048] Using the tailings generated during the processing of granite in Suizhou, Hubei, the implementation process is the same as that in Example 1. The XRF analysis results show that the flotation material contains sulfur elements. Therefore, 0.5% nitric acid is added as an oxidant to the acid solution.

[0049] Example 5

[0050] The raw materials used in this example are the same as those in Example 4. The difference in the implementation process from Example 4 is as follows:

[0051] (3) 0.1% chloric acid is added as an oxidant to the acid solution.

[0052] The SiO of quartz sand in the above steps 2 content is determined according to the "Determination of Loss on Ignition and Silicon Dioxide Content in Chemical Composition Analysis Method of Quartz Glass" in GB / T3284 - 2015 --- Ignition Subtraction Method, and the test results are as follows:

[0053] Table 1 Detection Results of Quartz Sand Content in Examples and Comparative Examples

[0054]

[0055] It should be noted that the technical indicators of the final products obtained in the above examples all meet the requirements of the standard of GB / T32649 - 2016 "High - purity Quartz Sand for Photovoltaic Use".

[0056] The above is the preferred embodiment of the present invention. Of course, it cannot be used to limit the scope of the rights of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A method for preparing 4N quartz sand using granite tailings as raw materials, characterized in that: The steps include: (1) primary impurity removal, wherein the granite tailings are subjected to impurity removal to obtain a crude quartz sand product having a SiO2 purity of ≥99.6%; (2) high temperature calcination and cooling, the obtained quartz sand crude product with SiO2 purity ≥99.6% is calcined at high temperature and then cooled with liquid CO2; (3) secondary impurity removal, the quartz sand obtained in step (2) is subjected to secondary impurity removal to obtain a high-purity quartz sand product with a SiO2 purity of ≥99.99%.

2. The method according to claim 1, characterized in that The one-time impurity removal comprises the following steps: (1a) Wet classification: select 60-150 mesh tailings mortar, dehydrate after magnetic separation and set aside; (1b) flotation, until the SiO2 purity in the sand after flotation is ≥99%; (1c) Pickling and removing impurities until the SiO2 purity of the obtained sand is ≥99.6%, and the tailings after pickling are dried for later use.

3. The method according to claim 2, characterized in that In step (1b), dodecylamine is used as a flotation agent to carry out at least one flotation until SiO2 in the tailings is ≥99%.

4. The method according to claim 2, characterized in that: The pickling solution used in step (1c) includes hydrofluoric acid and at least one of hydrochloric acid, sulfuric acid and oxalic acid.

5. The method according to claim 2, characterized in that: The pickling solution used in step (1c) is added with an oxidant; the oxidant is selected from any one or more of halogen oxygen-containing acids, halogen oxygen-containing salts, nitrates or nitrites; the amount of the oxidant is 0.1%-0.5% of the mass of the pickling solution.

6. The method according to claim 2, characterized in that Step (1c) adopts fluidized heating pickling, the pickling temperature is 75-80°C, and the pickling time is 5h-8h.

7. The method according to claim 1, characterized in that In steps (1) to (3), XRF is used to analyze the components in the product.

8. The method according to claim 1, characterized in that The temperature of high temperature calcination in step (2) is 1000-1100°C.

9. The method according to claim 1, characterized in that: The amount of liquid CO2 used for condensation in step (2) is not less than 1.2 times the mass of the material.

10. The method according to claim 1, characterized in that The secondary impurity removal includes at least one of the following treatments: pickling, flotation, water washing and drying.

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