Energy-saving smelting process for secondary aluminum production

Abstract

The invention discloses an energy-saving smelting process for secondary aluminum production. The energy-saving smelting process comprises the following steps: pretreating raw materials; a medium-frequency induction furnace is used as a main smelting furnace; carrying out gradient heating smelting; and the low-consumption refining process comprises the steps that at the temperature of 660-670 DEG C, a composite refining agent is adopted, mechanical vibration is applied for refining and heat preservation casting, a three-stage waste heat utilization system of tail gas waste heat drying, combustion-supporting air preheating and ingot casting waste heat recycling is constructed, and the tail gas waste heat utilization rate is increased to 60% or above; the intermediate frequency furnace double-layer heat preservation design is matched with a closed-loop cooling system, the heat loss is reduced by 40%, the oxidation burning loss of molten aluminum is reduced through a gradient temperature rising strategy, energy is saved by 25%-30% compared with a traditional technology, the production cost is reduced by 15%-20%, raw material pretreatment is conducted through crushing, magnetic separation and classified batching, impurities are controlled from the source, and a composite refining agent is matched with mechanical vibration and vacuum degassing to cooperate, so that the production efficiency is improved. And the non-metal impurity removal rate is increased, the cast ingot purity is improved, the mechanical property is stable, and the high-end secondary aluminum application requirement is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recycled aluminum processing, in particular to an energy-saving smelting process for recycled aluminum production. BACKGROUND

[0002] As the core component of aluminum industry circular economy, recycled aluminum production is the core link of realizing the recycling of aluminum resources, and the energy saving and impurity removal efficiency of its smelting process directly affect the purity of aluminum liquid, the performance of ingot and the production cost.

[0003] At present, the traditional smelting furnace mostly uses single insulation material, the heat loss is serious, the tail gas heat is directly discharged, the waste heat utilization rate is less than 10%, the raw material drying relies on extra energy, the heating rate control is unreasonable, too fast can easily lead to oxidation of aluminum liquid, too slow can prolong the smelting time and increase the energy consumption, and the temperature fluctuation is large during smelting process, the oxidation loss rate of aluminum liquid is high, which leads to the decrease of the quality of recycled aluminum, and it is difficult to meet the production demand of high-end profiles. In view of the above problems, an energy-saving and efficient smelting process is needed, which can completely remove impurities, fully recover waste heat and stably maintain the quality of recycled aluminum, so as to reduce the production cost and improve the product competitiveness. SUMMARY

[0004] The purpose of the present application is to provide an energy-saving smelting process for recycled aluminum production, which aims to solve the above problems existing in the prior art.

[0005] To achieve the above purpose, the technical scheme of the present application is an energy-saving smelting process for recycled aluminum production, comprising the following steps: S1, raw material pretreatment: the sorted waste aluminum is crushed to 30-80mm, the non-meltable impurities are removed manually, the waste heat drying box using the waste heat of smelting furnace tail gas is used for low-temperature drying and water removal at 80-100℃ for 1.5-2h, so that the water content is reduced to ≤0.08%, then the electromagnetic separator with magnetic field strength of 1000-1200Gs is used for magnetic separation to remove iron, the iron impurity removal rate is ≥95%, and finally the classification and batching are carried out according to AL content ≥95%, Si content 0.5-1.0%; S2, smelting equipment configuration: a medium-frequency induction furnace with power of 400-600kW and electric efficiency ≥85% is used as the main smelting furnace, the furnace body adopts double-layer insulation of nano heat insulation material + aluminum silicate fiber, a flue gas heat exchanger is installed at the furnace mouth to recover the tail gas heat for raw material drying and preheating combustion-supporting air, and the induction furnace coil adopts industrial cooling water closed loop circulation, and the cooling water temperature is controlled at 25-35℃; S3, gradient temperature melting: the combustion-supporting air at 150-200 DEG C after preheating is used to preheat the furnace at a temperature rising rate of 5-6 DEG C / min from room temperature to 400-450 DEG C, and then the temperature rising rate is increased to 8-10 DEG C / min, the power output is 60-70%, the temperature is increased from 450 DEG C to 650-660 DEG C, and then the temperature is kept at 660-670 DEG C for 1-1.2 h for rapid melting, and then the temperature is kept at 660-670 DEG C for 20-30 min for temperature adjustment, and pure nitrogen with a purity of 99.5% is introduced throughout the process; S4, low-consumption refining process: at 660-670 DEG C, a composite refining agent composed of NaCl+KCl+CaF2 in a mass ratio of 5:3:2 is added in an amount of 0.8-1.0%, and mechanical vibration with a frequency of 20-30 Hz and an amplitude of 0.8-1.2 mm is applied for refining, and the refining time is 15-20 min, and then vacuum degassing is performed at a vacuum degree of 0.06-0.08 MPa for 10-15 min; S5, temperature holding and casting: the temperature of the aluminum liquid is controlled at 650-660 DEG C, the power is maintained at 30-40% for temperature holding, a semi-continuous casting mode is adopted, the casting temperature is 640-650 DEG C, the drawing speed is 100-140 mm / min, the crystallizer adopts a closed-loop cooling water flow rate of 12-18 L / min, and the residual heat of the cast ingot is transferred to the raw material preheating area through a heat conduction device to assist the preheating of the raw material.

[0006] Preferably, the waste aluminum in the raw material pre-treatment includes waste profiles and waste pop cans.

[0007] Preferably, the magnetic field strength of the electromagnetic sorting machine in step S1 is 1000-1200Gs.

[0008] Preferably, the power of the intermediate frequency induction furnace in step S2 is 400-600 kW, and the electric efficiency is greater than or equal to 85%.

[0009] Preferably, the temperature of the combustion-supporting air in step S3 is 150-200 DEG C.

[0010] Preferably, the mass ratio of NaCl, KCl and CaF2 in the composite refining agent in step S4 is 5:3:2.

[0011] Preferably, the frequency of the mechanical vibration in step S4 is 20-30 Hz, and the amplitude is 0.8-1.2 mm.

[0012] Preferably, the vacuum degree of the vacuum degassing method in step S4 is 0.06-0.08 MPa.

[0013] The beneficial effects of the present application are: 1. A three-stage waste heat utilization system is constructed for tail gas waste heat drying, combustion air preheating, and ingot waste heat recovery, and the tail gas waste heat utilization rate is increased to more than 60%; the double-layer insulation design of the intermediate frequency furnace is combined with the closed-loop cooling system, the heat loss is reduced by 40%, the gradient heating strategy reduces the oxidation loss of aluminum liquid, and the energy saving is 25%-30% compared with the traditional process, and the production cost is reduced by 15%-20%.

[0014] 2. The raw material pretreatment is crushed, magnetically separated, and classified and dosed to control impurities from the source, and the composite refining agent is combined with mechanical vibration and vacuum degassing to improve the removal rate of non-metallic impurities, improve the purity of the ingot, stabilize the mechanical properties, and meet the application requirements of high-end recycled aluminum.

[0015] 3. The gradient heating shortens the melting period, the process is compatible with various raw materials such as waste profiles and waste pop cans, classified dosing ensures uniform composition, and there is no need to frequently adjust parameters, semi-continuous casting is combined with a closed-loop cooling system, the ingot forming rate is ≥99%, and the production efficiency is improved.

[0016] 4. The water resource utilization rate of the closed-loop cooling system is increased to 95%, waste is avoided, nitrogen protection reduces aluminum liquid oxidation and harmful gas emissions, the composite refining agent has no heavy metal components, waste slag is easy to handle, conforms to environmental protection policies, there is no secondary pollution in the whole process, and green smelting is achieved. DETAILED DESCRIPTION

[0017] The application will be further described below in conjunction with examples. EMBODIMENT

[0018] A recycled aluminum production energy-saving smelting process includes the following steps: S1, raw material pretreatment: crushed waste aluminum after sorting to 30mm, manually remove non-meltable impurities, use a waste heat drying box using smelting furnace tail gas waste heat to dry at 80℃ for 1.5h to remove water, reduce the water content to ≤0.08%, then use an electromagnetic separator with a magnetic field strength of 1000Gs to remove iron, the iron impurity removal rate is ≥95%, and finally classify and dose according to AL content ≥95%, Si content 0.5%; S2, smelting equipment configuration: use a 400-600kW, electric efficiency ≥85% intermediate frequency induction furnace as the main smelting furnace, the furnace body uses nano heat insulation material + aluminum silicate fiber double-layer insulation, the furnace mouth is equipped with a flue gas heat exchanger to recover tail gas heat for raw material drying and preheating combustion air, the induction furnace coil uses industrial cooling water closed-loop circulation, and the cooling water temperature is controlled at 25℃; S3, Gradient heating melting: Using the residual heat to preheat the combustion air to 150℃, the furnace temperature is raised from room temperature to 400℃ at a heating rate of 5℃ / min, and held for 30 minutes for preheating. Then the heating rate is increased to 8℃ / min, the power output is 60%, and the temperature is raised from 450℃ to 650℃. The temperature is held for 1 hour for rapid melting. After that, the temperature is stabilized at 660℃, the power is reduced to 40%, and the temperature is held for 20 minutes for temperature adjustment. Nitrogen gas with a purity of ≥99.5% is introduced throughout the process. S4. Low-consumption refining process: At 660℃, a composite refining agent composed of NaCl+KCl+CaF2 in a mass ratio of 5:3:2 is added at a rate of 0.8%, and mechanical vibration of 20Hz and amplitude of 0.8mm is applied for refining for 15 minutes. Then, vacuum degassing is carried out for 10 minutes using a vacuum degassing method with a vacuum degree of 0.06MPa. S5. Insulation casting: The temperature of the aluminum liquid is controlled at 650℃, and the power is maintained at 30% for insulation. A semi-continuous casting method is adopted, with a casting temperature of 640℃, a billet pulling speed of 100mm / min, and a closed-loop cooling water flow rate of 12L / min in the crystallizer. The residual heat of the cast ingot after casting is transferred to the raw material pretreatment area through a heat conduction device to assist in the preheating of raw materials. Example

[0019] An energy-saving smelting process for producing recycled aluminum includes the following steps: S1. Raw material pretreatment: The sorted waste aluminum is crushed to 60mm, and infusible impurities are manually removed. Low-temperature drying and dehydration are carried out in a waste heat drying box using the waste heat of the smelting furnace tail gas at 90℃ for 1.7h, so that the moisture content is reduced to ≤0.08%. Then, the iron is removed by magnetic separation using an electromagnetic separator with a magnetic field strength of 1100Gs. The iron impurity removal rate is ≥95%. Finally, the raw materials are sorted and batched according to the AL content ≥95% and the Si content 0.8%. S2. Smelting equipment configuration: A 500kW medium-frequency induction furnace with an electrical efficiency of ≥85% is used as the main smelting furnace. The furnace body is insulated with nano-insulation material + aluminum silicate fiber double layer. A flue gas heat exchanger is installed at the furnace mouth to recover the heat of the tail gas for raw material drying and preheating of combustion air. The induction furnace coil adopts closed-loop circulation of industrial cooling water, and the cooling water temperature is controlled at 35℃. S3, Gradient heating melting: Using the residual heat to preheat the combustion air to 180℃, the furnace temperature is raised from room temperature to 430℃ at a heating rate of 5℃ / min, and held for 35 minutes for preheating. Then the heating rate is increased to 9℃ / min, the power output is 65%, and the temperature is raised from 450℃ to 650℃. The temperature is held for 1.1 hours for rapid melting. After that, the temperature is stabilized at 665℃, the power is reduced to 45%, and the temperature is held for 25 minutes for temperature adjustment. Nitrogen gas with a purity of ≥99.5% is introduced throughout the process. S4. Low-consumption refining process: At 665℃, a composite refining agent composed of NaCl+KCl+CaF2 in a mass ratio of 5:3:2 is added at a rate of 0.9%, and mechanical vibration of 25Hz and 1.0mm amplitude is applied for refining for 17min. Then, vacuum degassing is carried out for 13min with a vacuum degree of 0.07MPa. S5. Insulation casting: The temperature of the aluminum liquid is controlled at 655℃, and the power is maintained at 35% for insulation. A semi-continuous casting method is adopted, with a casting temperature of 645℃, a billet pulling speed of 120mm / min, and a closed-loop cooling water flow rate of 15L / min in the crystallizer. The residual heat of the cast ingot after casting is transferred to the raw material pretreatment area through a heat conduction device to assist in the preheating of raw materials. Example

[0020] An energy-saving smelting process for producing recycled aluminum includes the following steps: S1. Raw material pretreatment: The sorted waste aluminum is crushed to 80mm, and infusible impurities are manually removed. Low-temperature drying and dehydration are carried out in a waste heat drying box using the waste heat of the smelting furnace tail gas at 100℃ for 2 hours, so that the moisture content is reduced to ≤0.08%. Then, the iron is removed by magnetic separation using an electromagnetic separator with a magnetic field strength of 1200Gs. The iron impurity removal rate is ≥95%. Finally, the raw materials are sorted and batched according to AL content ≥95% and Si content 1.0%. S2. Smelting equipment configuration: A 400-600kW medium-frequency induction furnace with an electrical efficiency of ≥85% is used as the main smelting furnace. The furnace body is insulated with nano-insulation material and aluminum silicate fiber double layer. A flue gas heat exchanger is installed at the furnace mouth to recover the heat of the tail gas for raw material drying and preheating of combustion air. The induction furnace coil adopts closed-loop circulation of industrial cooling water, and the cooling water temperature is controlled at 35℃. S3, Gradient heating melting: Using the residual heat to preheat the combustion air to 200℃, the furnace temperature is raised from room temperature to 450℃ at a heating rate of 6℃ / min, and held for 40 minutes for preheating. Then the heating rate is increased to 10℃ / min, the power output is 70%, and the temperature is raised from 450℃ to 660℃. The temperature is held for 1.2 hours for rapid melting. After that, the temperature is stabilized at 670℃, the power is reduced to 50%, and the temperature is held for 30 minutes for temperature adjustment. Nitrogen gas with a purity of ≥99.5% is introduced throughout the process. S4. Low-consumption refining process: At 670℃, a composite refining agent composed of NaCl+KCl+CaF2 in a mass ratio of 5:3:2 is added at a rate of 1.0%, and mechanical vibration of 30Hz and 1.2mm amplitude is applied for refining for 20 minutes. Then, vacuum degassing is carried out for 15 minutes using a vacuum degassing method with a vacuum degree of 0.08MPa. S5. Insulation casting: The temperature of the aluminum liquid is controlled at 660℃, and the power is maintained at 40% for insulation. A semi-continuous casting method is adopted, with a casting temperature of 650℃, a billet pulling speed of 140mm / min, and a closed-loop cooling water flow rate of 18L / min in the crystallizer. The residual heat of the cast ingot after casting is transferred to the raw material pretreatment area through a heat conduction device to assist in the preheating of raw materials.

[0021] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An energy-saving smelting process for producing recycled aluminum, characterized in that, Includes the following steps: S1. Raw material pretreatment: The sorted waste aluminum is crushed to 30-80mm, and infusible impurities are manually removed. Low-temperature drying and dehydration are carried out in a waste heat drying box using the residual heat of the smelting furnace tail gas at 80-100℃ for 1.5-2h, so that the moisture content is reduced to ≤0.08%. Then, the iron is removed by magnetic separation using an electromagnetic separator, with an iron impurity removal rate of ≥95%. Finally, the raw materials are sorted and batched according to AL content ≥95% and Si content 0.5-1.0%. S2. Smelting equipment configuration: A medium-frequency induction furnace is used as the main smelting furnace. The furnace body is insulated with nano-insulation material and aluminum silicate fiber double layer. A flue gas heat exchanger is installed at the furnace mouth to recover the heat of the tail gas for raw material drying and preheating of combustion air. The induction furnace coil adopts closed-loop circulation of industrial cooling water, and the cooling water temperature is controlled at 25-35℃. S3, Gradient Heating Melting: Using the waste heat to preheat the combustion air, the furnace temperature is raised from room temperature to 400-450℃ at a heating rate of 5-6℃ / min, and held for 30-40min for preheating. Then, the heating rate is increased to 8-10℃ / min, and the power output is 60-70%, raising the temperature from 450℃ to 650-660℃. The temperature is held for 1-1.2h for rapid melting. After that, the temperature is stabilized at 660-670℃, the power is reduced to 40-50%, and the temperature is held for 20-30min for adjustment. Nitrogen gas with a purity of ≥99.5% is introduced throughout the process. S4. Low-consumption refining process: At 660-670℃, a composite refining agent composed of NaCl+KCl+CaF2 is added at a rate of 0.8-1.0%, and mechanical vibration is applied for refining for 15-20 minutes. Then, vacuum degassing is performed for 10-15 minutes. S5. Insulation casting: The temperature of the aluminum liquid is controlled at 650-660℃, and the power is maintained at 30-40% for insulation. A semi-continuous casting method is adopted, with a casting temperature of 640-650℃ and a billet pulling speed of 100-140mm / min. The crystallizer adopts a closed-loop cooling water flow rate of 12-18L / min. The residual heat of the cast ingot after casting is transferred to the raw material pretreatment area through a heat conduction device to assist in the preheating of raw materials.

2. The energy-saving smelting process for producing recycled aluminum according to claim 1, characterized in that, The waste aluminum in the raw material pretreatment includes waste profiles and waste beverage cans.

3. The energy-saving smelting process for producing recycled aluminum according to claim 2, characterized in that, In step S1, the magnetic field strength of the electromagnetic separator is 1000-1200 Gs.

4. The energy-saving smelting process for producing recycled aluminum according to claim 1, characterized in that, The medium-frequency induction furnace mentioned in step S2 has a power of 400-600kW and an electrical efficiency of ≥85%.

5. The energy-saving smelting process for producing recycled aluminum according to claim 1, characterized in that, In step S3, the temperature of the combustion air is 150-200℃.

6. The energy-saving smelting process for producing recycled aluminum according to claim 1, characterized in that, The mass ratio of NaCl, KCl, and CaF2 in the composite refining agent described in step S4 is 5:3:

2.

7. The energy-saving smelting process for producing recycled aluminum according to claim 1, characterized in that, In step S4, the frequency of mechanical vibration is 20-30Hz and the amplitude is 0.8-1.2mm.

8. The energy-saving smelting process for producing recycled aluminum according to claim 7, characterized in that, The vacuum degree of the vacuum degassing method described in step S4 is 0.06-0.08 MPa.