RU2048551C1 - Method and device for remelting aluminium - Google Patents

Abstract

FIELD: remelting of aluminium waste. SUBSTANCE: method involves preliminary superheating of metal melt, pouring in the charge by portions equal to 9-10% of melt mass, delivered in a jet of inert gas at a time interval required for superheating of each portion by 100 C. The device with a perforated nozzle reduces the melting time and waste of metal. EFFECT: higher efficiency. 3 cl, 3 dwg

Description

 The invention relates to metallurgy, in particular to the remelting of aluminum waste.

 Known methods for remelting aluminum scrap and alloys (shavings, foils), which include melting clean waste in drum and induction furnaces with the separation of impurities by refining. Smelting of chips and foil in drum furnaces is carried out with liquid salt slag, including sodium chloride, potassium chloride and cryolite.

 A device is known for remelting aluminum, selected as a prototype, comprising a furnace (induction, resistance) and a filling device.

 The disadvantages of the method of remelting aluminum in a drum furnace are the loss of metal in the burned salt and the additional energy consumption for its melting.

 The disadvantages of the existing method and device for remelting shredded aluminum waste in an induction (resistance) furnace are the irrational backfill (remelting technology) of aluminum obtained after cable plant waste processing plants with particle sizes (length, diameter) of 1-7 mm.

The bulk density of the crushed aluminum is 1590-1610 kg / m ³ , which is 58-61% of the density of the aluminum melt. Pressing such particles leads to their further grinding. Remelting of metal waste in the crucible of existing furnaces (induction, resistance) occurs when they are fully loaded with aluminum. In this case, 40% of the volume of the crucible is occupied by air, which interacts with molten aluminum to form Al ₂ O ₃ oxide. A high percentage (30-40%) of metal waste is observed. After melting the first backfill of aluminum, it is necessary to re-fill the waste (3-4 times) into the furnace, which causes additional air penetration and increases the waste of metal. In addition, repeated backfilling of the crushed aluminum into the melt until the crucible is completely filled leads to significant supercooling of the liquid metal. As a result, control over the melting process (temperature measurement) becomes more difficult, and energy consumption increases. As a result, the resulting melt has to be further refined, the temperature equalized over the crucible cross-section, and filtered to remove aluminum oxide. To reduce the waste of metal in the furnace when the crucible is fully loaded, it is necessary to blow with an inert gas (nitrogen) to the entire height of the filling until the metal is completely melted. When aluminum is heated, heating of the injected gas also occurs, which leads to a decrease in its density and removal from the furnace. Lack of cold gas leads to air penetration.

The melting of aluminum with a bulk density of 1660 kg / m ³ (60% of the density of the metal) causes additional energy costs. This is due to the fact that in the case of heating the backfill from the walls of the mold (crucible), the temperature distribution in the contacting bodies during the passage of the heat flux (q) causes a temperature jump (Δt _k ), which is proportional to the density of the heat flux through the contact
q = α _to ^. Δ t _k , (1) where α _{k is} the contact heat transfer coefficient.

·

(t₁-t₂)
(3) где λ и Е соответственно коэффициент теплопроводности и модуль упругости алюминия; а радиус пятна контакта; Р давление на стенку тигля (определяется плотностью засыпки); ω0,4-0,5 показатель степени для волнистых поверхностей; t₁ и t₂ температура соответственно стенки тигля и частичек алюминия; h высота неровностей.The occurrence of a temperature jump causes thermal resistance R = 1 / α _to . The transferred heat flux during contact heat transfer consists of the heat flux resulting from the conductivity through the contact, the thermal conductivity of the heated gas layer in the gap, and the thermal radiation of the crucible wall:
q = q _p + q + q _{rad Ziz} (2)
The specific contact of the heat flux between aluminum particles and the crucible wall is determined by the following formula
q _p =

·

(t ₁ -t ₂ )
(3) where λ and E are the thermal conductivity and elastic modulus of aluminum, respectively; and the radius of the contact spot; P pressure on the wall of the crucible (determined by the density of the backfill); ω0,4-0,5 exponent for corrugated surfaces; t ₁ and t _{2 the} temperature, respectively, of the wall of the crucible and particles of aluminum; h the height of the bumps.

 As follows from expression (3), an increase in the heat flux between the crucible wall and the aluminum particles (and also between the particles themselves) is primarily determined by the size of the contact spot and the size of the particles. A decrease in a and h increases the heat flux. In addition, an increase in pressure on the mold wall and between the particles themselves also increases the heat flux. The pressure on the wall is determined by the bulk density of aluminum. An increase in backfill density increases the heat flux. The maximum value of the heat flux is at a filling density close to the density of the molten (solid) metal.

·(t₁+t₂)
(4) где λ коэффициент теплопроводности газа при температуре (t₁+t₂)/2; g₁ и g₂ длины температурных скачков на границах зазора; δ- зазор между поверхностями стенки тигля и частичек ( δh).The specific heat flux through the gas gap is determined by the expression
q _zaz =

(T ₁ + t ₂ )
(4) where λ is the thermal conductivity of the gas at a temperature of (t ₁ + t ₂ ) / 2; g ₁ and g ₂ lengths of temperature jumps at the boundaries of the gap; δ is the gap between the surfaces of the crucible wall and particles (δh).

 From the expression (4) it follows that reducing the gap between the contacting surfaces increases the heat flux, i.e. the melting time of the filled aluminum waste, and, accordingly, the energy consumption are determined by the bulk density of aluminum and the completeness of filling the working volume of the crucible.

 The purpose of the invention, reducing waste and improving the quality of remelted aluminum, reducing energy consumption.

 This is achieved by the fact that in the method of remelting aluminum in a crucible furnace, comprising filling metal and supplying an inert gas, according to the invention, 60-70% of the crushed waste is introduced into a preheated melt in an inert gas stream with a time interval necessary for heating, melting and overheating of the melt.

,
D_в/2=300-100.n, H ≅ 300 мм,
n=0,1,2,3.12, α12-45^o.The goal is also achieved by the fact that in the device for producing metal containing a crucible furnace, a heated hopper and a tube with holes for distributing inert gas, according to the invention, the inner diameter of the crucible D _in , the distance from the outlet of the nozzle of the tube to the mirror of the liquid metal H, the angle of inclination α the axis of the nozzle outlet openings to the horizon are interconnected by the following relationships:
tgα

,
D _in /2=300-100.n, H ≅ 300 mm,
n = 0,1,2,3.12, α12-45 ^o .

c·h·n δ /c=1-1,5,

tgγ γ0-22^o,
где δ(d_н-d_в)/2.For the purpose of uniform distribution of metal particles on the surface of the liquid melt, the relation between the inner and outer _in d _n d nozzle diameters, with width and height h holes, number of holes n, δ and angle γ reversal edges of holes are installed on the wall thickness dependences

c · h · n δ / c = 1-1.5,

tgγ γ0-22 ^o ,
where δ (d _n -d _in ) / 2.

Serial filling of 9-10% of the crushed metal to the mass of superheated melt in an inert gas stream in the amount of 60-70% of the crucible capacity, as well as the established ratios of the internal D _{in the} crucible diameter, the distance from the nozzle outlet holes N to the liquid metal mirror, and the angle of inclination of the outlet axis holes to the horizon α with diameters d _in and d _n nozzle, width and height h of the outlet holes, the number of holes n and the angle of rotation of the edge of the holes γ achieve the goal of the invention.

When the crucible is completely filled with ground aluminum, the heat flux densities from the wall are determined by expressions (1) - (4). Heat transfer in contacted bodies and through the gas gap causes an increase in the cost of electricity for the melting of the loaded material. This is due to the fact that heat transfer occurs from the surface of the crucible F ₁ to the total area of aluminum particles F ₂ in contact with it. For example, particles of aluminum in contact with the crucible surface F ₁ = 0.275 m ² with a common surface F ₂ = 0.046 m ² , the area ratio F ₁ / F ₂ = 6 times.

-

(5) где ε приведенная степень черноты; С_о постоянная Стефана-Больцмана; t₁ и t₂ соответственно температуры стенки тигля и засыпки.From the remaining surface of the particles, heat transfer occurs through the gas gap and radiation. Pressing aluminum particles (d = (1-2) ^. 10 ^-3 m and l = (3-7) ^. 10 ^-3 m) leads to their further grinding and increase the contact surface with air. When the crucible wall temperature ^of 730-800 C the amount of heat transferred by radiation filling is less than 5% compared with the value obtained from the expression (3)
QC

-

(5) where ε is the reduced degree of blackness; S _o Stefan-Boltzmann constant; t ₁ and t _2, respectively, the temperature of the wall of the crucible and backfill.

Increasing the temperature of the crucible above 800 ^{° C} leads to oxidation of the melt. So, for liquid steel, the amount of heat transferred by radiation at t ₁ = 1500 ^o С, compared with aluminum at t = 800 ^o С increases 13 times, i.e. backfilling of the entire crucible and heating of aluminum lead to additional energy consumption and an increase in the process time. In addition, a significant consumption of inert gas is necessary to protect the entire volume of backfill, which is also undesirable. In the case of initial backfill, 30-40% of aluminum of the volume of the total backfill into the crucible is intensified. In the case of the first filling and melting of less than 30% by weight of the metal in a completely filled crucible, the amount of additional fillings in the superheated melt increases in the amount of 9-10%. In addition, it is necessary to more accurately dosage. An increase in backfill over 40% is also impractical, since it increases the heating time, the consumption of electricity and nitrogen, and worsens the quality of the metal. The mass of additional filling of the crushed metal in the amount of 9-10% to the mass of the superheated melt in the crucible follows from the equation of the heat balance during aluminum overheating at 100 ^o C.

^M. from ₂ ^. Δ t = m _. c ₁ (t _c -t _o ) + r ^. m (6)
where M and m, respectively, the mass of the melt and the backfill; с ₁ and с ₂ specific heat of solid aluminum and melt; Δt melt overheating. After substituting the initial aluminum data from (3) for an arbitrary mass of the melt, we obtain the relation m = (0.09-0.1) M.

α коэффициент теплоотдачи расплава; λ коэффициент теплопроводности металла; δ характерный размер (толщина теплового пограничного слоя), Re= U^.x/ ν критерий Рейнольдса; U скорость металла на границе с частичками; Рr критерий Прандтля, ν коэффициент кинематической вязкости.After the first charge is melted, heat is transferred to the melt from almost the entire surface of the crucible in contact with the melt. In addition, nitrogen flow is only necessary to protect the surface of the metal mirror and several layers of backfill. The difference in the densities of solid and liquid aluminum (2868> 2380 kg / m ³ ) leads to the immersion of particles in the melt, their intense heating and melting, which follows from equation (3)
N _and = 0.343 ^. Re ^0.5. Pr ^0.4 , (7)
where nu

α melt heat transfer coefficient; λ metal thermal conductivity; δ characteristic dimension (thickness of the thermal boundary layer), Re = ^U. x / ν Reynolds test; U is the metal velocity at the particle boundary; Pr test Prandtl, ν coefficient of kinematic viscosity.

x расстояние от стенки тигля до рассматриваемого сечения.δ

x distance from the crucible wall to the section under consideration.

The heat flux transferred by the melt to the backfill is determined by the expression
q = α ˙ F˙ Δ t, W (8)
where α is the heat transfer coefficient of the melt backfill; F is the surface area of the particles in contact with the melt; Δ t is the temperature difference between the melt and the backfill.

 A comparison of expressions (3) and (8) shows that the value of the heat flux determined by (8) is ten times higher than the value obtained by (3). This suggests that during the same time, the heating of aluminum particles during loading into an overheated melt will occur to a higher temperature due to the generation of heat, tens of times higher than the heat obtained during the total heat transfer through the gap, contact and radiation. In addition, the oxidation of particles, their fumes and the consumption of protective gas are reduced. After each filling of particles into the superheated metal, the mass of the melt obtained after melting aluminum increases. Accordingly, the amount of subsequent backfill also increases, which in percentage terms is 9-10% of the mass of the melt.

The amount of crushed aluminum loaded into the crucible can be determined by the marks applied on the inner and outer surfaces of the hopper with the sight of the remaining quantity. The temperature of the melt in the crucible is measured by two thermocouples that simultaneously control the temperature of the charge and the melt. At the initial moment of feeding the crushed aluminum, a decrease in the temperature of the melt due to the accumulation of heat by particles is observed. This temperature decrease should not exceed 100 ^about C.

For the distribution of aluminum particles over the surface of the metal mirror, the particle sizes (diameter, length), the distance h ₁ from the place where the particles fall from the hopper to the nozzle outlet openings, the location of the outlet openings around the nozzle perimeter, the parameters of the hole, the gas velocity at the outlet of the hole are essential. For crushed particles with parameters d = 2-3 mm, l = 3-5 mm, the volume and mass of particles are respectively equal: V = (9.4-35.4) ^. 10 ^-9 m ³ , m = (25-95) ^. 10 ^-6 kg. Depending on the particle orientation (end face, side surface), the contact area with the gas flow is F = (3.1-23.6) ^. 10 ^-6 m ² .

 To transfer a particle to a different distance (depending on the inner diameter of the crucible), a certain pressure of gas (nitrogen) is necessary, which ensures a change in the path of the particle at the minimum gas pressure. The height of the point of interaction of the particle with the gas to the metal mirror H, the angle between the axis of the outlet with the horizon α, the design of the atomizing device (nozzle), and the number of particles delivered per unit time play a role in the range of particle movement at a given gas pressure.

(см/с)
(9)
где D диаметр отверстия, см; d средняя крупность частиц, мм; ν коэффициент вариации размера частиц, ед. При D=25^.10^-3 м значение а=0,35 м/с.For the given parameters of the particles, the volumetric flow rate with the hopper open is determined by (4), which is 86 ^. 10 ^-6 cm ³ / s with a hole diameter of 25 ^. 10 ^-3 m. In the same work, the speed of particles in the center of the hole of the hopper is determined by the diameter of the hole and particle size distribution
a

(cm / s)
(nine)
where D is the diameter of the hole, cm; d average particle size, mm; ν coefficient of variation of particle size, units At D = 25 ^. 10 ^-3 m value a = 0.35 m / s.

The particle velocity in front of the nozzle outlet will be equal to
V = a + g ^. τ (10)
where a = 0.35 m / s initial velocity; g = 9.81 m / s ² gravity acceleration; τ particle fall time.

The outlet openings of the atomizer are slotted (in the form of a rectangle) located at a distance of h ₁ from the hopper.

 For example, with an additional backfill mass of m = 3.5 kg, the dosing time is τ26 s, with m = 21 kg τ151 s.

(11)
где скорость частицы V определяется по выражению (10).An increase in the distance h ₁ from the hopper (feeder) to the nozzle openings leads to an increase in the rate of fall of particles and, accordingly, their energy, which follows from the formulas
E

(eleven)
where the particle velocity V is determined by the expression (10).

откуда v

(12)
Расстояние h₁ определяется количеством расплава в тигле и его высотой. Увеличение энергии падающей частицы приводит к необходимости увеличения скорости истечения газа из отверстий насадка. При оптимальном расстоянии h₁ энергия струи газа (азота) расходуется только на искривление траектории движения частичек, обладающих своей кинетической энергией. Наличие щелевых отверстий увеличивает фронт струи, а соответственно, и время взаимодействия газа с частичкой, т.е. обеспечивается большая эффективность струй. Чрезмерное увеличение h₁ увеличивает объем пространства тигля (печи). Кроме этого, при резком изменении траектории движения частиц (угол 70-90^о) происходит потеря энергии частички на трение с газом. В результате дальность полета уменьшается, поэтому лучше несколько увеличить расстояние Н до зеркала металла и придать траекторию движения частицы более плавную. Т.е. значительное уменьшение угла наклона оси отверстия с горизонтом α нецелесообразно. Значительное увеличение угла α также нецелесообразно, так как при этом уменьшается дальность полета частиц и для достижения периферийных слоев зеркала металла необходимо будет увеличить высоту Н.Particle fall time is determined by the formula
τ

where v

(12)
The distance h _{1 is} determined by the amount of melt in the crucible and its height. An increase in the energy of the incident particle makes it necessary to increase the rate of gas outflow from the nozzle openings. At an optimal distance h _{1, the} energy of a gas (nitrogen) jet is spent only on the curvature of the trajectory of motion of particles having their kinetic energy. The presence of slotted holes increases the front of the jet, and, accordingly, the time of interaction of the gas with the particle, i.e. greater jet efficiency. Excessive increase in h ₁ increases the volume of the space of the crucible (furnace). Additionally, the sudden change in the particle trajectories (angle ^of 70-90) particles occurs energy loss due to friction with the gas. As a result, the flight range decreases, so it is better to slightly increase the distance H to the metal mirror and make the particle trajectory smoother. Those. a significant decrease in the angle of inclination of the axis of the hole with the horizon α is impractical. A significant increase in the angle α is also impractical, since this reduces the flight range of the particles and to achieve the peripheral layers of the metal mirror it will be necessary to increase the height N.

(13)
где Н расстояние от выходных отверстий насадка до зеркала металла; D_в/2= 300+100^. n радиус тигля, n=0,1,2,3.12, Н ≅ 300 мм, α=12-45^о. Практически для всех тиглей высота Н не должна превышать 300 мм. Наиболее оптимальный угол α 45^о для тиглей с D_в=0,6 м. Для диаметров тиглей D_в>0,6 м для обеспечения постоянства Н (экономия объема тигля) целесообразно уменьшать угол наклона оси отверстия α Минимальное значение α12^о для тиглей с D_в=3000 мм.Based on the foregoing, we can write
tgα

(13)
where H is the distance from the nozzle outlet to the metal mirror; D _in / 2 = 300 + 100 ^. n crucible radius, n = 0,1,2,3.12, Н Н 300 mm, α = 12-45 ^о . For almost all crucibles, the height H should not exceed 300 mm. The most optimal angle is α 45 ^о for crucibles with D _в = 0.6 m. For crucible diameters D _в > 0.6 m, to ensure constant Н (saving the volume of the crucible), it is advisable to reduce the angle of inclination of the hole axis α. The minimum value is α12 ^о for crucibles with D _in = 3000 mm.

 The gas flow through the nozzle orifice can be determined as follows.

cosβ (14)
где С_х= 1,2 коэффициент; 2^.L высота выходного отверстия; ρ плотность газа (азота); V скорость; β угол между струей газа и вертикалью (направлением падения частицы).The force of a gas jet on a particle (5)
PC _x · (2L) ·

cosβ (14)
where C _x = 1.2 coefficient; 2 ^. L outlet height; ρ density of gas (nitrogen); V speed; β angle between the gas stream and the vertical (direction of particle fall).

Particle Gravity
F = m ^. g, (15)
where m is the mass of the particle.

(16)
Масса частиц m в выражении 16 определяется с учетом массы всей засыпки в течение времени τ и количества отверстий n.In the case of equality (14) and (15), the mode of particle “wandering” is ensured. In practice, there is no need for a gas velocity that ensures the "soaring" of particles, but only their deflection with movement of the metal onto the mirror. The numerical value obtained by expression (15), to ensure a given gas flow rate, should be 2-3 times higher than the value obtained by (14). With this in mind, the gas velocity at the outlet of the hole nozzle is determined by the expression
v

(sixteen)
Particle mass m in expression 16 is determined taking into account the mass of the entire backfill over time τ and the number of holes n.

c·h·n (или F_н=F_отв) говорит о равенстве площадей центрального канала насадка и выходных отверстий. Расход газа через канал определяется площадью проходного сечения и скоростью газа. Увеличение площади отверстий (F_отв>F_н) приводит к уменьшению скорости газа на выходе из них, а соответственно, к уменьшению силы воздействия на частички металла. В итоге уменьшается расстояние, на которое они перемещаются. В случае (F_отв<F_н) (сумма площадей выходных отверстий насадка меньше площади центрального канала) увеличивается сопротивление течению газа через отверстия, а соответственно, возрастают потери давления.Equality of relations

c · h · n (or F _n = F _resp ) indicates the equality of the areas of the central channel of the nozzle and the outlet openings. The gas flow through the channel is determined by the area of the bore and the gas velocity. Increasing the area of the holes (F _otv> F _n) leads to a decrease in gas velocity at the exit from them and, consequently, to a decrease in the impact strength of the metal particles. As a result, the distance they move is reduced. In the case of (F _holes <F _n) (sum of areas of the nozzle outlet openings smaller than the area of the central channel) increases resistance to flow of gas through the openings, and accordingly, the pressure loss increases.

 The ratio of the nozzle wall thickness δ (channel length) to the hole width c, equal to δ / c = 1-1.5, is determined by the fact that for δ / c <1 the gas flow does not have time to form in the outlet, and, accordingly, the parameters of the outflow jet (its expansion increases, the continuity of the jet decreases). At δ / s> 1.5, the resistance to the flow in the nozzle opening increases, and, accordingly, its speed decreases.

tgγ определяет степень различия ширины выходного отверстия. Различие ширины выходного отверстия на входе (а) и выходе из него (с) преследует цель увеличения площади поверхности, перекрываемой струями для равномерного распределения частиц на поверхности зеркала металла.Attitude

tgγ determines the degree of difference in the width of the outlet. The difference in the width of the outlet at the inlet (a) and exit from it (c) is aimed at increasing the surface area covered by the jets for uniform distribution of particles on the surface of the metal mirror.

The magnitude of the disclosure of the jet can be determined by the expression (5)
b = tg β _o (x + x _o ), (17)
where tg β _o = 0.22; H = x _o = 2.3 ^. b _o pole distance; x distance along the axis of the jet to the section in question; 2b _{o the} width of the outlet.

It can be seen from expression (17) that an increase in the width of the hole leads to an increase in the magnitude of the opening of the jet (front of the jet). However, an increase of 2b _o leads to an increase in the area of the outlet openings, and accordingly, to a decrease in the gas velocity at the outlet of the hole. An increase in the jet front with a slight decrease in gas velocity can be achieved by profiling the outlet openings. Moreover, the width of the hole c, measured by the outer diameter of the nozzle, exceeds the width a of the inner diameter. The maximum value of c must be such as to ensure δ / c = 1. Choosing an arbitrary wall thickness δ taking into account the ratio δ / c = 1-1.5, we obtain γ0-22 ^about . The maximum value of the angle γ22 ^{о is} advisable to apply in the case when the ratio of hole parameters h / c> 3. The minimum value of γ0 in the case of h / c = 1.5-2.

 Figure 1 shows the appearance of the claimed device.

 The proposed device consists of a furnace 1, inside of which there is a crucible 2, a heated hopper 3, valves 9, tubes 4 and 5 for supplying gas, a nozzle 6 with holes 7, a fume hood 8, a duct 10.

The operation of the device is as follows. Previously, the necessary amount of crushed aluminum is loaded into the hopper 3, the furnace is turned on, and at the same time as the crucible is heated, the hopper and backfill are heated. When the temperature reached 100-120 ^{° C.} hopper made crucible metal loading of 30% of its capacity. Download and stop the metal supply by rotating the two shutters 9.

The shutter is a round disk with a slot connecting the edge and the middle and designed for the free movement of the tube with gas. Turn on the gas supply, after immersing the tube 4 in the backfill. Backfill melting is carried out with a constant supply of gas (nitrogen). The temperature of the resulting melt and backfill is constantly monitored by thermocouples. When the melt overheats at 100 ^° C, backfill is supplied in the amount of 9-10% of the mass of the melt. The outlet openings of the nozzle are located at a distance H from the metal mirror. The exhaust gases through the duct 10 are fed to the heating of the hopper 3, and then removed into a fume hood 8. The sequence of operations of filling the metal and melting it in the crucible is repeated. After melting all the backfill and emptying the hopper, the melt in the crucible is purged with nitrogen to the entire depth with mixing of the metal and equalization of its temperature. If necessary, the melt is additionally purged with gaseous chlorine. The prepared aluminum settles in the furnace to casting start temperature (650-680 ° ^C).

и Нуссельта Nu

где а, α γ соответственно коэффициенты температуропроводности, теплоотдачи и теплопроводности алюминия, τ время процесса; l высота засыпки; х характерный размер (размер частичек алюминия).The inventive method of casting was tested in laboratory conditions with particulate aluminum remelting furnace SNOL-1,6.2,5.1 / 9-4I (TU 16-681.051-84) power of 1.8 kW at a temperature within the oven to 900 ^C. The heating and melting of backfill It was produced in a container measuring 0.25x0.15x0.12 m made of stainless steel with a wall thickness of 1 mm and coated with zinc paint from the inside. The outer surface of the tank was insulated. The container was closed by a lid, through an opening in which inert gas (nitrogen) was supplied. The simulation was carried out in compliance with the equality of the Fourier criteria F _o =

and Nusselt Nu

where a, α γ, respectively, are the coefficients of thermal diffusivity, heat transfer and thermal conductivity of aluminum, τ is the process time; l backfill height; x characteristic size (particle size of aluminum).

 In the first case, the tank was fully loaded with backfill in an amount of 7.2 kg, in the second case (the claimed method) 1.5 kg of aluminum was loaded into the tank. The mass of molten aluminum in a fully filled tank is 11 kg. In the process of remelting, it was found that in the inventive method, the process time is reduced (up to 15-20%), and accordingly, the energy consumption, the quality of the metal improves.

 Amurkabel JSC has created a pilot plant for remelting aluminum from the waste processing site.

The installation includes a SAT-02n crucible furnace with a capacity of 250 mg of aluminum and a capacity of 60 mW, a hopper for backfilling and dosing of metal, a tube with nozzles for supplying gaseous nitrogen to the crucible of the furnace. The mass of the first filling 38 kg, the pressure on the wall of the mold 284 N / m ² . The value of the specific contact heat flux from the backfill of aluminum pressed against the mold at a temperature difference Δt = 500 ^о С is 51.7 kW / m ³ , the specific heat flux through the gas gap is 14 kW / m ² , also when radiation from the surface of the crucible is 1, 92 kW / m ² , the total specific heat flux is 67.6 kW / m ² . the heat flux from the crucible wall to a bed of aluminum with a lateral contact surface of 0.275 m ² is 18.6 kW. The amount of heat used for heating, melting and overheating of liquid aluminum, respectively, equals 21.8; 15 and 3.4 MJ. With an average diameter of the crucible of 0.4 m, the contact surface with liquid metal is 0.126 m ² , the thickness of the filled layer with a mass of 3.5 kg reaches 16-18 mm. With an average value of the heat transfer coefficient of the melt backfill 3260 W / m ² .K the amount of heat of overheating of the metal transferred to the backfill is 52 kW.

 In the proposed embodiment, the melting time of the backfill and the burning of the metal are reduced, and its quality is increased.

 In FIG. 2 and 3 show the nozzle for supplying inert gas to the crucible of the furnace, respectively, longitudinal and transverse sections.

When processing ground aluminum waste in a device containing a SAT-025N crucible furnace with a crucible capacity of 250 kg of metal, the parameter values are as follows: hopper volume for filling 200 kg of aluminum 0.125 m ³ , shape and dimensions of the hopper, a truncated cone 0.79 m high with base diameters 0 , 7 and 0.14 m; the melting time of the first backfill (38 kg) of aluminum is 2160 s; superheat time 38 kg per 100 ^о С 183 s; the filling time of the filling of 3.5 kg of aluminum in the melt is 67 s, the distance from the metal mirror to the outlet openings of the nozzle is N = 0.3 m; the angle of inclination of the axis of the outlet to the horizon α45 ^about ; the inner diameter of the nozzle d _in = 15 mm; the number of holes n = 6, the size of the hole hxa = 7.5x4 mm; the nozzle wall thickness is δ6 mm, the maximum gas flow rate for feeding 21 kg of aluminum through the nozzles is G = 0.11 m ³ , the maximum gas velocity at the outlet from the hole during the filling period is U = 3.8-4.6 m / s.

 The inventive method of producing aluminum in a crucible furnace and a device for its implementation can reduce the melting time of the backfill, and accordingly, the energy consumption, reduce the waste of metal and improve its quality.

Claims (3)

1. The method of remelting aluminum, which includes sequential filling of the charge into the metal melt in batches as the previous batches melt, melting and refining, characterized in that the metal is preheated and the filling is carried out in an amount of 60 70% of the volume of the crucible charge, refining is carried out with an inert gas, wherein each portion of the backfill is 9 10% of the mass of the melt and it is fed in a stream of inert gas with an interval of time necessary for overheating of each portion of the backfill at 100 ^o C. 2. Device for remelting aluminum, containing a crucible furnace and nozzles, characterized in that it is equipped with a hopper with a valve, an inert gas supply pipe connected to the nozzle made with holes, while the inner diameter D _{in the} crucible, the distance H from the outlet nozzle to the liquid metal mirror, angle α of inclination of the axis of the outlet openings of the nozzle to the horizon are interconnected by the following mathematical relationship:

where D _in / 2 300 + 100 · n;
n 0 12 is an integer;
α = 12-45 ^° ;
H ≅ 300 mm. 3. The device according to p. 2, characterized in that the ratio between the inner diameter (d _in ) of the nozzle, the width of the outlet openings at the inlet (a) and outlet (c), the height h of the holes, the number n of holes, the thickness δ of the wall and the angle g hole edge reversal set according to

δ / c = 1-1.5;

γ = 0-22 ^° .

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