Method for removing other impurities while retaining silicon and aluminum phases in fly ash based on magnetic thermal separation
By combining magnetothermal sorting and flotation, the problem of impurity removal in fly ash is solved, and the separation of high-purity silicon-aluminum phases is achieved, laying the foundation for the high-value utilization of fly ash.
Patent Information
- Application Number
- CN202510519031.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-24
- Publication Date
- 2025-07-11
AI Technical Summary
The existing fly ash removal methods are difficult to effectively remove impurities, resulting in low purity of silicon and aluminum and poor environmental protection, which limits the high-value utilization of fly ash.
Magnetothermal sorting technology combined with flotation method is used to remove magnetic impurities in fly ash and retain the silicon-aluminum phase through thermal reduction treatment, magnetic separation, pickling and flotation steps, avoid the use of chemical reagents, and reduce energy consumption and pollution.
High-purity silicon-aluminum phase separation is achieved, the mass fraction of iron element is reduced to 0.49%, and iron and carbon impurities are basically removed, providing a high-purity raw material for preparing molecular sieves, which is environmentally friendly and has low energy consumption.
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Figure CN120286179A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation, and belongs to the technical field of fly ash separation. Background Art
[0002] Fly ash is a powdery solid particulate matter captured from the flue gas generated during the coal combustion process, and is an important component of bulk industrial solid waste, with its main component being aluminosilicate. As coal is the main energy source, the output of fly ash has been continuously increasing in recent years, and the waste recycling of fly ash has become an urgent problem to be solved. However, most of the existing treatment schemes focus on aspects such as cement manufacturing, concrete, and low-end building materials, all in the low-value fields.
[0003] Research has found that fly ash has characteristics such as multi-porosity and a large specific surface area, and also has active groups such as SiO2 and Al2O3, and is a multi-functional powdery mineral resource that can be used to prepare molecular sieves. Molecular sieves are a class of artificially synthesized inorganic non-metallic porous crystal materials, which have broad application prospects in the fields of gas adsorption storage, catalysis, etc. However, in addition to the silicon-aluminum phase required for molecular sieves, fly ash also contains a large amount of impurities such as mullite, quartz phase, magnetite, hematite, gypsum, rutile, etc., which not only affect the color of the molecular sieve, but also seriously affect the synthesis, adsorption, catalysis and other properties of the molecular sieve. Therefore, fly ash needs to be pretreated for impurity removal before synthesizing molecular sieves.
[0004] The existing impurity removal methods generally use the acid method to extract aluminum, but iron also partially dissolves during this process. After the subsequent alkali roasting, the iron component is still together with the silicon-aluminum phase, so the obtained molecular sieve product still contains impurities such as iron and calcium. In addition, many impurity removal methods also involve the alkali fusion process, but there is no process of dissolving with an alkali solution and filtering to remove iron and calcium in the subsequent process, resulting in the limitation of the product purity.
[0005] Currently, the pretreatment methods of fly ash are divided into physical methods and chemical methods. Physical methods include separation, mechanical grinding and other technologies, and chemical methods include pre-desilication, roasting and other technologies. The separation and grinding pretreatment technologies have simple processes, low energy consumption, and less environmental pollution, but are limited in improving the activity of fly ash. The roasting pretreatment technology can remove unburned carbon and easily decomposable minerals in fly ash and achieve the separation of target elements, but has poor environmental protection. Summary of the Invention
[0006] The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation, which solves the problems of low silicon-aluminum purity and poor environmental protection after fly ash impurity removal, and provides ideas for improving the added value of fly ash utilization.
[0007] To achieve the above object, the present invention is implemented by the following technical solutions: The present invention provides a method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation, including: Performing thermal reduction treatment on fly ash and then preparing an aqueous fly ash solution by mixing with water; Using a magnetic separation tube to perform magnetic separation on the aqueous fly ash solution, and after suction filtration, dividing the aqueous fly ash solution into a magnetic phase and a non-magnetic phase; Drying the non-magnetic phase and then performing acid washing, and filtering to obtain fly ash precipitate; Drying the fly ash precipitate and then placing it in a flotation cell for flotation operation to obtain the silicon-aluminum phase of fly ash.
[0008] Further, the particle size range of the fly ash is 200-500 mesh.
[0009] Further, the thermal reduction treatment includes placing the fly ash in an alumina crucible, putting it into a tube furnace, heating it in an argon atmosphere at a heating rate of 10-15 °C / min to 600-700 °C, keeping it at a constant temperature for 1 h and then cooling it, and taking it out when the temperature drops to 180-200 °C.
[0010] Further, the solid-liquid mass ratio of fly ash to water in the aqueous fly ash solution is 1:1.
[0011] Further, the condition parameters for performing magnetic separation on the aqueous fly ash solution using the magnetic separation tube are magnetic separation 3-4 times under a magnetic field intensity of 380-420 mT.
[0012] Further, the step of drying the non-magnetic phase and then performing acid washing, and filtering to obtain fly ash precipitate includes: Placing the non-magnetic phase in a constant temperature blast drying oven and drying it at 105-120 °C to obtain a solid non-magnetic phase; Placing the solid non-magnetic phase in hydrochloric acid, performing a water bath reaction at 80-90 °C for 3-5 h, and filtering to obtain fly ash precipitate.
[0013] Further, the solid-liquid volume ratio of the solid non-magnetic phase to the hydrochloric acid is 3:1.
[0014] Further, the step of drying the fly ash precipitate and then placing it in a flotation cell for flotation operation to obtain the silicon-aluminum phase of fly ash includes: Drying the fly ash precipitate and then placing it in a flotation cell, adding water and stirring, sequentially adding a dispersant, a collector, and a foaming agent, aerating for a period of time and then skimming the foam until no minerals float out from the foam layer to obtain the silicon-aluminum phase of fly ash.
[0015] Further, the dispersant is sodium silicate, the collector is kerosene, and the foaming agent is sec-octanol; and / or, the volume ratio of sodium silicate, kerosene, and sec-octanol is 80:123:7-8.
[0016] Further, the stirring time is 5 - 6 min; and / or, the aeration time is 10 - 15 s.
[0017] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention combines thermology and magnetism to remove magnetic impurities in fly ash, such as magnetite and hematite, and retains non-magnetic useful components. The method does not involve the use of chemical reagents, is environmentally friendly, does not produce additional pollution, and has relatively low energy consumption compared to powder activation and acid solution activation; Using the method of the present invention for impurity removal can reduce the mass fraction of iron elements in fly ash to 0.49%, and it can be basically considered that iron is completely removed. After magnetic-thermal separation, flotation decarbonization treatment is carried out on fly ash. After double treatment of magnetic-thermal separation and flotation decarbonization, the main impurities of fly ash, iron and carbon, are basically removed, and high-purity raw materials for preparing molecular sieves are obtained. Description of the Drawings
[0018] Figure 1 It is a schematic flow chart of a method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic-thermal separation in an embodiment of the present invention. Detailed Embodiments
[0019] The present invention will be further described below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention. Embodiment 1
[0020] As Figure 1 shown, the embodiment of the present invention provides a method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic-thermal separation, including the following steps: (1) Pass the fly ash through a 200-mesh sieve to remove large particle impurities.
[0021] (2) Place the sieved fly ash in an alumina crucible, put it into a tube furnace together, pass argon for 10 - 15 min, heat it at a heating rate of 10 °C / min to 700 °C, keep it at a constant temperature for 1 h, wait until the temperature in the furnace drops below 200 °C, close the argon, and take out the sample.
[0022] (3) Prepare a mixed solution by mixing fly ash and water at a solid-liquid mass ratio of 1:1, and use a CXG500 / 50 magnetic separation tube to perform magnetic separation for iron removal three times at 400 mT. After magnetic separation, the fly ash is divided into a magnetic phase and a non-magnetic phase. Among them, the magnetic phase is solid and the non-magnetic phase is liquid. Solid-liquid separation is carried out by suction filtration, and then it is placed in a constant temperature blast drying oven and dried at 105 °C.
[0023] (4)Pickle the non-magnetic phase with hydrochloric acid to dissolve the remaining iron and calcium oxide in the acid, and then remove them by filtration.
[0024] (5)Dry the product at a temperature of 90 °C for 2 h; weigh 500 g of fly ash and place it in a 1 L flotation cell, add water to exceed the scale line; turn on the impeller to stir and adjust the pulp for 5 min, add the collector kerosene at a rate of 123 L / h for 3 min, and add the foaming agent sec-octanol at a rate of 23 L / h for 1 min. The aeration rate is 120 L / h. After turning on the aeration for 10 s, start skimming the foam until no minerals float out of the foam layer, and end the flotation to obtain the silicon-aluminum phase of fly ash.
[0025] In this example, after carbothermal reduction and hydrochloric acid pickling, the mass ratio of SiO2 and Al2O3 in fly ash reaches 5.65, the mass fraction of Fe content reaches 0.49%, and the mass fraction of CaO content reaches 2.08%. The lowest loss on ignition of fly ash after flotation is 2.31%, and the yield can reach 84.00%, basically meeting the requirements for the next step of synthesizing molecular sieve. Example 2
[0026] The difference between this example and Example 1 is only that a dispersant sodium silicate is added, and the specific steps are as follows: Sieve the fly ash through a 200-mesh sieve to remove large particle impurities.
[0027] Place the sieved fly ash in an alumina crucible, put it into a tubular furnace together, pass argon for 10 - 15 min, heat it up to 700 °C at a heating rate of 10 °C / min, keep it at a constant temperature for 1 h, wait until the temperature in the furnace drops below 200 °C, turn off the argon, and take out the sample.
[0028] Prepare a mixed solution of fly ash and water according to a solid-liquid mass ratio of 1:1, and use a CXG500 / 50 magnetic separation tube to perform magnetic separation to remove iron three times at 400 mT. After magnetic separation, the fly ash is divided into a magnetic phase and a non-magnetic phase, and solid-liquid separation is carried out by suction filtration, and then it is dried in a constant temperature blast drying oven at 105 °C.
[0029] Pickle the non-magnetic phase with hydrochloric acid to dissolve the remaining iron and calcium oxide in the acid, and then remove them by filtration.
[0030] Dry the product at 90 °C for 2 h; Weigh 500 g of fly ash and place it into a 1 L flotation cell, then add water to exceed the scale line; Start the impeller to stir and adjust the pulp for 5 min, add the dispersant sodium silicate at a rate of 120 L / h for 2 min, add the collector kerosene at a rate of 123 L / h for 3 min, and add the frother sec-octanol at a rate of 23 L / h for 1 min. The aeration rate is 120 L / h. After starting the aeration for 10 s, start skimming the foam until no minerals float out of the foam layer, then end the flotation to obtain the silicon-aluminum phase of fly ash.
[0031] In this example, after carbothermal reduction and hydrochloric acid pickling, the mass ratio of SiO2 and Al2O3 in fly ash reaches 5.65, the mass fraction of Fe content reaches 0.49%, and the mass fraction of CaO content reaches 2.08%. The lowest loss on ignition of the fly ash after flotation is 1.71%, and the yield can reach 84.86%, basically meeting the requirements for the next step of synthesizing molecular sieve.
[0032] Compared with Example 1, the loss on ignition of the fly ash in this example is reduced by 0.60%, and the yield is increased by 0.86%. It can be seen that adding the dispersant sodium silicate can significantly improve the flotation effect. Example 3
[0033] The difference between this example and Example 1 is only that the dispersant sodium silicate is added and the number of magnetic separation times is increased to four, which specifically includes the following steps: Sieve the fly ash through a 200-mesh sieve to remove large particle impurities.
[0034] Place the sieved fly ash in an alumina crucible and put it into a tubular furnace together. Pass argon for 10 - 15 min, heat it up to 700 °C at a heating rate of 10 °C / min, keep it at a constant temperature for 1 h, wait until the temperature in the furnace drops below 200 °C, then close the argon and take out the sample.
[0035] Prepare a mixed solution of fly ash and water according to a solid-liquid mass ratio of 1:1, and use a CXG500 / 50 magnetic separation tube to perform magnetic separation four times to remove iron at 400 mT. After magnetic separation, the fly ash is divided into a magnetic phase and a non-magnetic phase, and solid-liquid separation is carried out by suction filtration, and then it is placed in a constant temperature blast drying oven and dried at 105 °C.
[0036] Pickle the non-magnetic phase with hydrochloric acid to dissolve the remaining iron and calcium oxide in the acid, and then remove them by filtration.
[0037] Dry the product at 90 °C for 2 h; weigh 500 g of fly ash and place it in a 1 L flotation cell, add water to submerge the scale line; turn on the impeller to stir and adjust the pulp for 5 min, add the dispersant sodium silicate at 120 L / h for 2 min, add the collector kerosene at 123 L / h for 3 min, and add the foaming agent sec-octanol at 23 L / h for 1 min. The air inflow rate is 120 L / h. Start blowing air, and start skimming the foam 10 s later until no minerals float out of the foam layer. End the flotation to obtain the silicon-aluminum phase of fly ash.
[0038] In this example, after carbothermal reduction and hydrochloric acid pickling, the mass ratio of SiO2 and Al2O3 in fly ash reaches 5.65, the mass fraction of Fe content reaches 0.47%, and the mass fraction of CaO content reaches 2.08%. The lowest loss on ignition of the fly ash after flotation is 1.71%, and the yield can reach 84.86%. It basically meets the requirements for the next step of synthesizing molecular sieve.
[0039] After increasing the number of magnetic separation times, there are no significant changes in the mass ratio of SiO2 and Al2O3, the mass fraction of Fe content, and the mass fraction of CaO content in fly ash. It can be seen that after the number of magnetic separation times reaches a certain number, the impurity removal effect will no longer change significantly. Therefore, it can be judged that three magnetic separation times are the best.
[0040] Compared with Example 1, the loss on ignition of fly ash is reduced by 0.60%, and the yield is increased by 0.86%, which further proves that adding the dispersant sodium silicate can significantly improve the flotation effect. Example 4
[0041] The difference between this example and Example 1 is only that the number of magnetic separation times is increased to four times, and the flotation operation is omitted. It includes the following steps: Pass the fly ash through a 200-mesh sieve to screen out large particle impurities.
[0042] Place the sieved fly ash in an alumina crucible, put it into a tubular furnace, pass argon for 10 - 15 min, heat it at a heating rate of 10 °C / min to 700 °C, keep it at a constant temperature for 1 h, wait until the temperature in the furnace drops below 200 °C, turn off the argon, and take out the sample.
[0043] Prepare a mixed solution by mixing fly ash and water at a solid-liquid mass ratio of 1:1, and use a CXG500 / 50 magnetic separation tube to perform four magnetic separation operations to remove iron at 400 mT. After magnetic separation, the fly ash is divided into a magnetic phase and a non-magnetic phase, and solid-liquid separation is carried out by suction filtration, and then it is placed in a constant temperature blast drying oven and dried at 105 °C.
[0044] Use hydrochloric acid pickling for the non-magnetic phase to dissolve the remaining iron and calcium oxide in the acid, and then remove them by filtration.
[0045] Wash it with distilled water until it is neutral, dry the filter cake, grind it finely and reserve it for use.
[0046] In this embodiment, after carbothermal reduction and hydrochloric acid pickling, the mass ratio of SiO2 to Al2O3 in fly ash reaches 5.65, the mass fraction of Fe content reaches 0.47%, and the mass fraction of CaO content reaches 2.08%. There is no significant change compared with the data in Example 1, which once again confirms that the three-stage magnetic separation is the best. The loss on ignition of fly ash in this embodiment is 2.41%, and the yield is only 83.84%. Compared with Example 1 using flotation for decarbonization, the effect of omitting the flotation operation in this embodiment is poor.
[0047] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.
Claims
1. A method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation, characterized in that, Including: Performing thermal reduction treatment on fly ash and then preparing an aqueous fly ash solution by mixing with water; Performing magnetic separation on the aqueous fly ash solution using a magnetic separation tube, and after suction filtration, dividing the aqueous fly ash solution into a magnetic phase and a non-magnetic phase; Drying the non-magnetic phase and then performing acid washing, and taking fly ash precipitate after filtration; Drying the fly ash precipitate and then placing it in a flotation cell for flotation operation to obtain fly ash silicon-aluminum phase.
2. The method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation according to claim 1, wherein The particle size range of the fly ash is 200-500 mesh.
3. The method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation according to claim 1, wherein The thermal reduction treatment includes placing the fly ash in an alumina crucible, putting it into a tube furnace, heating it at a heating rate of 10-15 °C / min in an argon atmosphere to 600-700 °C, keeping it at a constant temperature for 1 h and then cooling it, and taking it out when the temperature drops to 180-200 °C.
4. The method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation according to claim 1, characterized in that The solid-liquid mass ratio of fly ash to water in the aqueous fly ash solution is 1:
1.
5. The method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation according to claim 1, characterized in that, The condition parameters for performing magnetic separation on the aqueous fly ash solution using a magnetic separation tube are magnetic separation 3-4 times under a magnetic field intensity of 380-420 mT.
6. The method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation according to claim 1, characterized in that, The drying the non-magnetic phase and then performing acid washing, and taking fly ash precipitate after filtration includes: Placing the non-magnetic phase in a constant temperature blast drying oven and drying it at 105-120 °C to obtain a solid non-magnetic phase; Placing the solid non-magnetic phase in hydrochloric acid, performing a water bath reaction at 80-90 °C for 3-5 h, and filtering to obtain fly ash precipitate.
7. The method for removing the remaining impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation according to claim 6, characterized in that, The solid-liquid volume ratio of the solid non-magnetic phase to the hydrochloric acid is 3:
1.
8. The method for removing the remaining impurities while retaining the silicon-aluminum phase of fly ash based on magnetic-thermal separation according to claim 1, characterized in that The drying the fly ash precipitate and then placing it in a flotation cell for flotation operation to obtain fly ash silicon-aluminum phase includes: Drying the fly ash precipitate and then placing it in a flotation cell, adding water and stirring, sequentially adding a dispersant, a collector and a foaming agent, aerating for a period of time and then skimming the foam until no minerals float out in the foam layer to obtain fly ash silicon-aluminum phase.
9. The method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation according to claim 8, characterized in that, The dispersant is sodium silicate, the collector is kerosene, and the foaming agent is sec-octanol; and / or, the volume ratio of sodium silicate, kerosene and sec-octanol is 80:123:7-8.
10. The method for removing other impurities while retaining the silicon-aluminum phase of fly ash based on magnetic thermal separation according to claim 8, characterized in that, The stirring time is 5-6 min; and / or, the aeration time is 10-15 s.