A method for treating refractory industrial solid waste based on transient thermal shock activation and a method for recovering valuable elements.

Abstract

This invention belongs to the field of inorganic material treatment and solid waste resource utilization technology, specifically relating to a method for treating refractory industrial solid waste based on transient thermal shock activation and a method for recovering valuable elements. Addressing the problems of low extraction rates and high energy consumption of valuable elements in industrial solid waste containing stable crystalline phases such as mullite and quartz, this invention heats the pretreated solid waste powder from room temperature to ultra-high temperature in an extremely short time, holds it at that temperature for a very short time, and then cools it back to room temperature in an extremely short time using a quenching medium. This extreme temperature gradient generates enormous thermal stress within the crystals, inducing severe lattice distortion, fracture, and amorphization transformation in mullite and quartz crystals, thus compromising their thermodynamic stability. After treatment with this invention, the leaching activity of valuable elements in the solid waste is significantly improved, greatly reducing the acid and alkali consumption and reaction time in subsequent hydrometallurgical processes.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials science and solid waste resource utilization technology, specifically involving a method for treating refractory industrial solid waste based on transient thermal shock activation and a method for recovering valuable elements. Background Technology

[0002] With the progress of industrialization, a large amount of silicon-aluminum based industrial solid waste, such as fly ash and coal gangue, has been generated. These solid wastes are usually rich in aluminum, silicon, and key metal elements such as lithium, gallium, and rare earth elements, and have huge resource utilization potential.

[0003] However, most of these valuable elements are found in extremely stable mineral lattices such as mullite (3Al2O3·2SiO2) and quartz (SiO2). Mullite has strong covalent bonds and a dense chain structure, is resistant to acid and alkali corrosion, and has extremely high thermal stability; quartz has a high bond energy Si-O tetrahedral network structure.

[0004] Existing processing technologies mainly include:

[0005] 1) Traditional high-temperature roasting method: Solid waste is mixed with additives (such as sodium carbonate and calcium oxide) and roasted at 1000℃-1300℃ for a long time (1-4 hours). This method consumes a lot of energy and introduces a large number of impurities, generating secondary waste residue.

[0006] 2) High-pressure acid / alkali leaching method: requires extremely high acid and alkali concentrations and high-pressure reactor equipment, resulting in severe equipment corrosion and a high risk of operation.

[0007] 3) Mechanical ball milling activation: Although it can destroy crystals to a certain extent, it is inefficient, energy-intensive, and difficult to completely destroy the nanoscale lattice structure.

[0008] Therefore, there is an urgent need for a new technology that can destroy the stable crystal structure of mullite and quartz with low energy consumption, ultra-fast speed and high efficiency, in order to solve the "bottleneck" problem in the resource utilization of solid waste. Summary of the Invention

[0009] The purpose of this invention is to provide a method for treating refractory industrial solid waste based on transient thermal shock activation. By rapidly heating and cooling at the millisecond to second level, huge thermal mismatch stress is generated inside the crystal, achieving "explosive" destruction of the crystal structure.

[0010] Technical principle of the invention:

[0011] Unlike traditional heat treatment (which relies on thermal diffusion equilibrium), this invention utilizes the "thermal shock" effect. When mullite or quartz crystals are heated from room temperature to 1800–2500°C within 5 seconds, a huge transient temperature gradient is generated between the material surface and the core, as well as between the crystalline phases with different coefficients of thermal expansion. The tensile and shear stresses induced by this transient temperature gradient far exceed the theoretical fracture strength of the crystal, leading to instantaneous grain breakage, grain boundary slip, and a surge in lattice defects. The subsequent rapid cooling (queenching) "freezes" this disordered high-energy state (amorphous / glassy state) at high temperature, preventing crystal recrystallization. Atoms in the high-energy state are highly reactive and easily attacked by acid and base reagents, thereby releasing valuable elements locked in the crystal lattice.

[0012] A method for treating refractory industrial solid waste based on transient thermal shock activation includes the following steps:

[0013] Step S1, Raw material pretreatment: Dry, crush and grind industrial solid waste containing mullite and / or quartz crystal phase to obtain micron- or nano-sized solid waste precursor powder.

[0014] Step S2, Transient thermal shock activation: The solid waste precursor powder is placed in an ultra-fast heating environment and heated to a shock temperature of 1800℃~2500℃ at a heating rate of not less than 600℃ / s, and held for 0.5 seconds to 5 seconds.

[0015] Step S3, rapid quenching: After the heat preservation is completed, the solid waste precursor powder that has been heated is immediately cooled to below 200°C within 5 seconds by rapid cooling method to complete the transient thermal shock activation and obtain activated slag.

[0016] Further, in step S2, the heating rate is 600℃ / s to 1000℃ / s, and the heating time from room temperature to the impact temperature is controlled within 5 seconds; the impact temperature is 2000℃±100℃; and the holding time is 1 second to 5 seconds.

[0017] Furthermore, in step S3, the rapid cooling method cools the heated solid waste precursor powder to room temperature at a rate of not less than 600°C / s.

[0018] Furthermore, the ultrafast heating environment described in step S2 employs one of the following: flash Joule heating (FJH), high-frequency thermal plasma heating, or high-power laser irradiation heating. When using flash Joule heating, conductive additives (such as carbon sources) need to be doped into the solid waste precursor powder in step S1, and the powder is placed in a quartz tube or insulating container. Ultrafast heating is achieved by applying a pulsed current through capacitor discharge.

[0019] Furthermore, the rapid cooling method described in step S3 is liquid nitrogen spray quenching, inert gas high-speed airflow impact cooling, or water-cooled copper roller spinning cooling.

[0020] Furthermore, the industrial solid waste is at least one of fly ash, coal gangue, red mud, kaolin tailings, aluminum ash, or smelting slag.

[0021] Furthermore, the processes in steps S2 and S3 need to be carried out in an inert atmosphere (such as argon or nitrogen) or a reducing atmosphere to prevent excessive oxidation or volatilization of valuable elements.

[0022] The method for recovering valuable elements using the above method includes: treating the activated residue obtained in step S3 with acid or alkali leaching, filtering and separating to obtain a leachate containing valuable metal ions, and then purifying and precipitating to obtain the target product.

[0023] Furthermore, compared with the original industrial solid waste that has not been activated by transient thermal shock, the activated slag has a leaching rate of aluminum (Al), lithium (Li) or gallium (Ga) that is increased by more than 30% under the same leaching conditions, and the leaching reaction temperature is reduced by 20°C to 50°C.

[0024] The beneficial effects of this invention are:

[0025] (1) Extremely high activation efficiency: It can achieve the activation effect that traditional roasting takes several hours in a few seconds, transforming mullite and quartz into highly active amorphous aluminosilicates.

[0026] (2) Energy saving and consumption reduction: Although the instantaneous power is high, the total energy consumption per unit mass of material is much lower than that of traditional long-term high-temperature roasting due to the extremely short processing time (seconds).

[0027] (3) Significantly improved leaching rate: After treatment, the leaching rate of elements such as aluminum and lithium can be increased from 20%-40% before treatment to more than 85%-95%.

[0028] (4) Wide applicability: Applicable to various industrial waste residues containing refractory silicate minerals. Detailed Implementation

[0029] The embodiments of the technical solution of the present invention will be described in detail below. These embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.

[0030] Example 1: Transient thermal shock activation of fly ash;

[0031] (1) Raw material pretreatment: High-alumina fly ash from a thermal power plant was taken, and XRD analysis showed that the main phases were mullite and quartz. It was dried, crushed, and ball-milled to D50=10μm to obtain solid waste precursor powder, and a small amount of conductive carbon black (10% of the mass of solid waste precursor powder) was mixed in as the Joule heating medium.

[0032] (2) Transient thermal shock activation: The mixed powder is loaded into a pulse heating device and nitrogen gas is introduced into the device. The discharge parameters are set so that the sample is heated from room temperature (25°C) to 2000°C in 3 seconds and held at 2000°C for 2 seconds.

[0033] (3) Rapid quenching: Immediately afterward, the power is cut off and liquid nitrogen mist is introduced to cool the sample to room temperature within 3 seconds.

[0034] Results analysis: XRD analysis showed that the intensity of the characteristic diffraction peaks of mullite and quartz in the treated powder disappeared by more than 90%, and obvious "bun peaks" appeared, indicating that the crystal structure had been transformed into an amorphous glassy state.

[0035] Leaching experiment: The activated slag was leached for 2 hours at 100℃ and normal pressure using 20% ​​hydrochloric acid. The leaching rate of alumina reached 92%, while the leaching rate of the untreated raw ash obtained in step (1) was only 35% under the same conditions.

[0036] Example 2: Plasma thermal shock of coal gangue;

[0037] (1) Raw material pretreatment: Coal gangue is dried, crushed and ground to 200 mesh.

[0038] (2) Transient thermal shock activation: High-temperature plasma stream is generated using a high-frequency thermal plasma generator. Coal gangue powder is injected into the central region of the plasma (temperature > 2500℃) through nitrogen carrier gas, and the residence time of the powder in the stream is about 0.5 to 1 second.

[0039] (3) Rapid quenching: The ejected molten droplets fall directly into the circulating cooling water for water quenching (cooling rate > 1000℃ / s).

[0040] Results: The obtained quenched slag is mainly amorphous, and the lithium leaching rate is increased from 25% in the original ore to 88%.

[0041] Comparative Example 1: Traditional roasting;

[0042] The same fly ash as in Example 1 was placed in a muffle furnace and heated to 1000°C at a rate of 10°C / min, held at that temperature for 2 hours, and then cooled with the furnace. XRD showed that the mullite crystal phase remained intact, and the aluminum extraction rate from acid leaching was only 45%.

Claims

1. A method for treating refractory industrial solid waste based on transient thermal shock activation, characterized in that, Includes the following steps: Step S1, Raw material pretreatment: Dry, crush and grind industrial solid waste containing mullite and / or quartz crystal phase to obtain micron- or nano-sized solid waste precursor powder. Step S2, Transient thermal shock activation: The solid waste precursor powder is placed in an ultra-fast heating environment and heated to a shock temperature of 1800℃~2500℃ at a heating rate of 600℃ / s~1000℃ / s, and held for 0.5 seconds~5 seconds. Step S3, rapid quenching: After the heat preservation is completed, the solid waste precursor powder that has been heated is immediately cooled to below 200°C within 5 seconds by a rapid cooling method to complete the transient thermal shock activation and obtain the activated slag. The rapid cooling method mentioned in step S3 is liquid nitrogen spray quenching, inert gas high-speed airflow impact cooling, or water-cooled copper roller strip cooling.

2. The method for treating refractory industrial solid waste based on transient thermal shock activation according to claim 1, characterized in that: In step S2, the heating rate is 600℃ / s to 1000℃ / s, and the heating time from room temperature to the impact temperature is controlled within 5 seconds; the impact temperature is 2000℃±100℃; and the holding time is 1 second to 5 seconds.

3. The method for treating refractory industrial solid waste based on transient thermal shock activation according to claim 1, characterized in that: In step S3, the rapid cooling method cools the heated solid waste precursor powder to room temperature at a rate of not less than 600°C / s.

4. The method for treating refractory industrial solid waste based on transient thermal shock activation according to claim 1, characterized in that: The ultra-fast heating environment described in step S2 is one of Joule flash heating, high-frequency thermal plasma heating, or high-power laser irradiation heating. When Joule flash heating is used, conductive additives need to be doped into the solid waste precursor powder in step S1 and placed in a quartz tube or insulating container. Ultra-fast heating is achieved by applying pulse current through capacitor discharge.

5. The method for treating refractory industrial solid waste based on transient thermal shock activation according to claim 1, characterized in that: The industrial solid waste is at least one of the following: fly ash, coal gangue, red mud, kaolin tailings, aluminum ash, or smelting slag.

6. The method for treating refractory industrial solid waste based on transient thermal shock activation according to claim 1, characterized in that: The processes described in steps S2 and S3 need to be carried out in an inert or reducing atmosphere.

7. A method for recovering valuable elements using the transient thermal shock activation treatment method for refractory industrial solid waste as described in any one of claims 1-6, characterized in that, include: The activated residue obtained in step S3 is subjected to acid or alkali leaching, filtered and separated to obtain a leachate containing valence metal ions, and then purified and precipitated to obtain the target product.

8. The method according to claim 7, characterized in that: Compared with raw industrial solid waste that has not been activated by transient thermal shock, the activated slag increases the leaching rate of aluminum, lithium or gallium by more than 30% under the same leaching conditions, and reduces the leaching reaction temperature by 20°C to 50°C.