RU2361162C2 - Reverberatory furnace for metal remelting - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: invention relates to reverberatory furnace for remelting of aluminium breakage. Furnace contains case, formed by side, front and back end walls, limited by bottom and walls accumulative bath, crown, two discharge tap holes, flue duct and fabricated frame, on which everything is located. In furnace it is external walls heat insulation, consisting of four layers of heat insulators: chamotte granulated material, fireproof cotton, triple layer of asbestos cardboard, asbestine granulated material. Inclined platform, accumulative bath are bricked of baked in the hearth blocks "£Üá-50", laid for three layers of asbestos cardboard and wadding made of dry high-silica sand, that provides heat keeping in furnace bath, interrupting its offtake to binding. Furnace binding inside is lined by moler brick, reducing heat loss from bath through the binding. Crown over inclined platform and furnace bath allows heat insulating patching material in two layers, consisting two layers of fireproof mats, layer of moler brick, which additionally reduce heat losses from the melting space of furnace. In furnace there are installed six injection burners of type "æÿ" 2-6 for introduction of forced melting operation. Furnace allows two tap holes, implemented in quick-change tapping bricks in metallic binding, that provides implementation of its change without furnace stopping for repair and excluding destruction of crown and walls. It is provided design simplification and reduction of heat losses. ^ EFFECT: design simplification and reduction of heat losses. ^ 7 cl, 9 dwg

Description

The invention relates to ferrous metallurgy, and in particular to smelting units for remelting secondary aluminum scrap and waste aluminum alloys into ingots and ingots. The furnace can be used for refining, producing alloys, averaging the chemical composition.

Known reflective furnace for melting metal (RF patent No. 2155304), which is an analogue of the invention.

The furnace contains a floor-mounted housing 1, Figs. 1, 2, 3, formed by red clay brick masonry. In the inner cavity of the housing with a gap relative to it, on the pillow 2 (from the diatom), there is an accumulative bath, limited by the hearth 3 and walls 4 made of refractory brick SB. The depth of the bath (500 mm) is limited by the inclined platform 5, which is the loading table. A large arch 6 is assembled above the storage bath, resting on the end walls 4 of the bath. Above the inclined platform 5, a small arch 7 is assembled, based on the end walls 8 of the platform. Small 7 and large 6 vaults are covered with heat-insulating crumb 9 from diatom brick. A loading window 10 is made above the inclined platform 5 in the furnace body. A gas duct 11 is mounted in the wall of the furnace body opposite to the loading table 11. In the bottom 3 there is a notch 12, opposite which a slag window 13 is mounted in the body for removing slag from the metal surface at a height of 500 mm relative to letki. Next to the slag window, parallel to the axis of the bath, a channel 14 is made for accommodating the nozzle therein. The arch 6 above the storage tank is made asymmetric with respect to its transverse axis, the radius increases towards the slag window 13.

The disadvantages of this furnace are:

1. The complexity of the design due to the presence of two arches (small above the loading table and large above the bathroom).

2. The lack of external thermal insulation of the furnace, reducing heat loss to the external environment.

Known reflective furnace for remelting metal (RF patent No. 2047663), which is the closest (prototype) to the proposed, which is intended for remelting secondary aluminum.

The described furnace for remelting secondary aluminum contains a housing 1, Figs. 4, 5, formed by brickwork of refractory outer side, front 15 and rear 16 end walls made of solid chamotte brick grade SB. The casing is mounted on the floor 17. A large arch 6 rests on the casing.

In the internal cavity of the furnace with a gap relative to the housing, a storage bath of 600 mm depth limited by the walls 4 and the hearth 3 is installed and an inclined platform 5 is mounted.

On the floor 17 in the inner perimeter of the walls of the casing there is a refractory heat storage pillow made of two layers. Its lower layer 18 is made of diatom brick masonry with a thermal conductivity of 0.4 W / (m · K), its upper layer 19 is filled with fine-grained fireclay chips with a thermal conductivity of 0.6 W / (m · K. ), with steel blooms placed in it 20.

The storage bath is installed on the top layer 19 of the pillow and is made of solid chamotte brick of grade ШБ with a thermal conductivity of 0.8 W / (m · K.). The ratio of thermal conductivity of the hearth 3 baths and the upper layer 19 of the pillow 0.8: 0.6.

The gap between the front end wall 15 of the housing and the corresponding wall 4 of the storage bath under the inclined platform 5 is filled with a monolithic heat-insulating layer 21 made of solid fireclay bricks of the ШЛБ brand with thermal conductivity of 0.75 W / (m · K.), and the rest of the gap 22 between the storage bath and the body is filled with a backfill of chamotte coarse-grained chips with a thermal conductivity of 0.4 W / (m · K.).

In the front end wall of the housing 15, a loading window 10 is made, in the rear end wall 16 there is a gas duct 11 equipped with a control flap 23, and in the hearth 3 of the storage bath there is a notch 12.

In the side walls of the casing above the inclined platform 5, channels 24 and 25 are made opposite each other to accommodate burners (not shown).

The longitudinal axis of the channel 24 is perpendicular to the vertical plane passing through the horizontal axis of the furnace, and the longitudinal axis of the channel 25 is located at an angle to the specified vertical plane.

The furnace operates as follows.

An aluminum scrap with ambient temperature is loaded into a preheated furnace through a loading window 10 onto an inclined platform 5. In this case, fuel combustion and scrap heating occur in the furnace volume. At the point of impact of a burning jet of flame of the burners installed in channel 24 (not shown), the solid scrap is intensely heated to the melting point of the scrap to the melting temperature of aluminum and its alloys. After the formation of the liquid phase, the metal flows down an inclined platform 5 into the storage bath.

All combustible components burn out, moisture evaporates, decomposing into oxygen and hydrogen, and all non-metallic inclusions and inclusions, whose melting point is higher than aluminum, remain on the inclined platform 5. This waste is removed from the inclined platform 5 and does not enter the molten metal.

The burners installed in the channels 25 (not shown) carry out the heating of the metal in the storage bath and the heating of the notch 12.

The gases resulting from the combustion of the fuel are discharged through the gas duct 11, regulating their removal by the valve 23, in order to maintain the thermal regime in the furnace and maintain the optimum temperature in it at any stage of melting and casting.

In the process of aluminum smelting, the pillow accumulates heat transmitted through under 3 baths and the inclined platform 5 down, and prevents it from going to floor 17. The essence of the process of accumulation and constant maintenance of the temperature of the hearth 3 and the inclined platform 5 of the furnace is as follows.

Heated above the melting point of aluminum (750-800 ° C) under 3 baths heats the top layer 19 of the pillow and the steel blooms 20 contained therein to the melting temperature of aluminum (658-660 ° C). Blooms 20 retain heat for a long time, having a high heat capacity, and being in the hot space filled with backfill 19, they seem to accumulate heat.

The bottom layer 18 of the cushion has a very low thermal conductivity and serves as a heat insulator that prevents heat from escaping from the furnace to the concrete floor 17 (the upper level of layer 18 has a temperature of 600 ° C, and the lower one is 40 ° C). Since the temperature difference between the bottom of the 3 baths and the layer 19 of the pillow is constantly small (50-150 ° C), the heat flux directed from the bottom of the 3 baths to the pillow is also small, i.e. heat loss from the furnace to the environment is minimized. The thermal efficiency of the furnace is above 70%. In addition, the heat storage cushion is constantly heated to the melting point of aluminum.

The function of the monolithic layer 21 is to collect heat from the interior of the furnace and from the pillow and direct it to maintain a stable temperature of the inclined platform 5. At the same time, the monolithic layer 21 provides additional thermal resistance to the heat flux emanating from the inclined platform 5 downward. For this, its thermal conductivity is less than the thermal conductivity of the inclined platform 5. This is necessary in order to reduce the heat flux directed from the inclined platform 5 to the pillow and, therefore, also minimize heat loss to the environment.

The ratio of thermal conductivity of the hearth 3 of the bath and the layer 19 of the pillow, equal to 0.8: 0.6, provides stability and optimality of the thermal regime of the furnace.

The bottom layer 18 of the cushion provides optimal thermal insulation of the furnace.

As the metal accumulates in the bath, the tap hole 12 is opened and the metal from the bath enters an appropriate container (not shown).

After the release of metal, the tap hole 12 is closed and the cycle repeats.

The disadvantages of this furnace are:

1. The high cost and complexity of the accumulating heat pillows (lightweight refractory bricks, blooms).

2. The large depth of the liquid metal in the bath makes the mixing process difficult, as a result of which the liquid metal will not be homogeneous.

The objective of the invention is the creation of a gas bath of a reflective type furnace for remelting aluminum scrap of simple design, reducing the loss of metal and heat in the environment, as well as increasing its life and productivity.

EFFECT: developed furnace is simple in construction, has high productivity, low metal waste, which allows the use of scrap unsorted from foreign inclusions, reduces heat loss to the environment due to special thermal insulation, and allows the remelting process without the use of electricity due to the installation of six injection burners.

The specified technical result is achieved due to the fact that in the reflective furnace for remelting aluminum scrap, containing a housing formed by refractory outer side, front and rear end walls, a storage bath and an inclined platform, limited by the hearth and walls, the arch, drain holes and the flue are introduced welded the frame, which inside has a diatom brick lining. Diatom brick helps reduce heat loss from the bath through the frame to the floor.

In addition, the storage bath and the inclined platform are made of MKRS-50 hearth blocks laid on three layers of asbestos board and have a pad of dry quartz sand. Hearth blocks have high fire resistance and resistance (service life up to 6 years according to practical data). Three layers of asphalt board and dry quartz sand allow you to further maintain the temperature of the metal in the furnace bath.

However, the furnace has two slots for the release of molten metal located in the rear end wall.

At the same time, a steel box is welded to the furnace frame, which has thermal insulation between it and each wall, consisting of fireclay chips, refractory wool, a triple layer of sheet asbestos board and asbestos chips.

It is important to note that the arch of the proposed furnace has a layer with double heat-insulating coating and on it two layers of refractory heat-insulating mats and a layer of diatom brick for additional heat storage in the furnace.

Six burners are located in the side walls of the furnace. In the process of smelting aluminum scrap, all burners are switched on to achieve high furnace productivity, i.e. to ensure forced melting. In order to maintain the temperature in the furnace bath, to warm the tap hole and, if necessary, to overheat the alloy, as well as to increase the productivity in the side wall, where the furnace slag window is located, one burner directed to an inclined platform, and two BIG 2-6 TU injection burners 51-464-89 directed to the bottom of the furnace.

Moreover, two tap holes made in quick-change tap-hole bricks in the box are introduced into the design of the proposed furnace to ensure the possibility of their replacement without stopping the furnace.

Finally, the proposed reflective furnace for remelting aluminum scrap can operate with the power off due to the use of six injection burners of the BIG 2-6 type TU 51-464-89. Installation of injection burners is carried out at an angle to the inclined platform and the bath, which allows more complete use of heat during combustion to heat the mixture and its melting.

Introduction to the proposed furnace of the above provides a solution to the problem.

Figure 6 presents a longitudinal section of the furnace.

7 is a transverse section of the furnace (view of the loading window).

On Fig - cross section of the furnace along the slag window (view of the notches and chimney).

Figure 9 is a plan view of the furnace.

The proposed furnace contains a housing formed by brickwork of the outer side, front 15 and rear 16 end walls, Fig.6, laid out of fireclay bricks.

The body is mounted on a metal frame. Under the furnace 3 and the inclined platform 5 are laid out from the hearth blocks MKRS-50 (thickness 300 mm, width 400 mm, length 1000 mm or 500 mm). The threshold of the loading window of the furnace is also laid out from the hearth blocks MKRS-50 (thickness 300 mm, width 400 mm, length 1000 mm). The walls of the stove are made of fireclay bricks. The blocks are laid on a frame and sand packing, on top of which asbokarton is laid in three layers 26, Fig.6.

As a binder, a refractory solution is used, consisting of refractory clay (20%), fireclay powder (75%), water glass (3%) and AHPS (aluminochromophosphate mixture, 2%).

The thickness of the seams is 1-2 mm.

Four walls are laid on the metal frame of the furnace, under 3, an inclined platform 5. The welded furnace frame, welded from I-beams No. 24, 36 (27) and channels No. 14 (28), is lined with diatom brick inside. After calcining the masonry with portable burners, a sanding is done on the welded frame under the furnace bottom. The hearth consists of 2 rows of hearth blocks MKRS-50 (1000 × 400 × 300), seven in each row and one row consisting of seven blocks MKRS-50 (500 × 400 × 300). Hearth blocks are lined with direct fireclay bricks of the ShA-1 brand, product No. 5 GOST 8691-73. In the lower part of the rear wall 16 there are two slots 12. A loading window 10 is made in the front end wall 15 of the housing.

All four walls of the furnace are laid out in two bricks. To reduce heat loss, increase efficiency and the life of the furnace, between the masonry of the furnace and the steel casing (armor) there is a heat-insulating layer consisting of fireclay stuffing, a triple layer of sheet asbestos board, fire-resistant cotton wool and asbestos chips. The armor is attached to the frame by vertical channels No. 20 (29), Fig.6.

To prevent the expansion of the masonry furnace vertical channels have a bunch of horizontal channels No. 20 (30), Fig.6.

The loading 10 and slag 13 windows have arches 7 and 31, respectively, laid out according to the patterns of the chamotte end wedge, Fig.6, 8. In the side wall there is a slag window 13 of Fig.8, the arch of which, like the large arch 6, is supported on heel bricks 32 SHA-1 product No. 67 GOST 8691-73, Fig. 8. For rapid melting of the charge in the side wall at an angle to the inclined platform 5, three injection burners 33 BIG 2-6 TU 51-464-89 are stacked together, blocked by the ШСУ 33-1 block GOST 7151-74 (34). The centers of the three burners located in the opposite side wall are offset relative to the above by 600 mm, one of which is directed at an angle to the inclined platform 5, and the other two burners - to the bottom 3 of the furnace. Each burner has its own gas control valve. Heel beams 35 are welded from channels No. 30, Fig.7, 8.

Docked burners have a common burner tunnel for sustainable torch burning.

The large vault 6 is made according to the template from the end wedge and has a coating of 36 in two layers. To reduce heat loss through the furnace arch 6, two layers of refractory mats 37 are laid over the coating, and a layer of diatom brick 38 is laid over the mats, Fig. 8.

To reduce heat loss under the inclined platform 5 and under the hearth 3, rows of diatom bricks 39 are laid out inside the entire frame.

In the rear wall 16 there is a gas duct 11, Fig. 8, which has an arched vault 40. At the top, behind the side wall of the furnace, the gas duct 11 goes to the chimney 41, Fig. 9. On the duct 11 there is a gate 42, which controls the amount of vacuum in the furnace.

The molten metal is poured from the furnace through the chute 43 into the molds 44 placed on the carousel, and along the chute 45 into the molds fixed on the chill casting line 46, Fig. 9. In the event of wear of a quick-change summer brick (cracks, a significant increase in the diameter of a notch, potholes, slagging, etc.), it can be replaced without stopping the furnace for repair and without destroying the walls and arch.

The furnace operates as follows.

In the calcined furnace on an inclined platform 5 through the loading window 10 is loaded unfinished aluminum scrap with an ambient temperature. The flame of four gas injection burners 32, Fig. 7, walled up in special openings of the side walls, heats the scrap to the melting temperature. The metal melts and flows down an inclined platform 5 into the furnace bath, to which two more burners are directed (their heat is necessary to maintain the temperature in the furnace bath, warm two years 12, and also to increase productivity when the scrap does not contain cast iron, carbon and stainless steel, it is loaded not only on the inclined platform 5, but also on the bottom (in the bathtub) 3. The burners are installed obliquely, so the flame of the burners is inclined at an angle to the inclined platform 5, the bath and it kind of glides along the charge lying on the inclined platform and the bath with p alloyed metal, smoothly bends around the back wall 16, then, twisting, rises to the large arch 6, flows around part of it in the opposite direction, passes a second time on the surface of the liquid metal, providing its secondary heating. During operation, the heat is accumulated in the large arch 6, from which it is reflected metal coating layers 36 of the arch 36, two layers of refractory mats 37, a layer of diatom brick 38, thermal insulation of walls, a hearth, an inclined platform 5 and a heat-insulating layer of a furnace frame made of diatom brick 39, sand bed and sheet fire ornogo material 26 provide excellent thermal insulation melting unit. In the smelting process include, if necessary, four, five, six burners. All burners are turned on to achieve high furnace performance, i.e. to ensure forced melting. The thermal efficiency of the furnace is above 65%.

During the melting process, the scrap melts, the moisture in it evaporates, decomposing into oxygen and hydrogen, and all inclusions remain on the inclined platform 5, the melting temperature of which is higher than that of the aluminum alloy. These wastes (alterations: cast iron and steel rings, liners, bushings, studs, pushers, valves, etc.) do not fall into the molten metal, since they are periodically removed with a scraper from the surface of the inclined platform 5 to the slag. After the molten scrap loaded into the furnace is completely melted, molten metal is processed with flux, the metal is thoroughly mixed in the bath and the spectral analysis laboratory confirms the grade of the alloy obtained, two openings 12 are opened and the alloy is cast into molds of the chill-casting line 46 and carousel 44.

Flue gases released during the melting of metal in the furnace pass through the gas duct 11 and then enter the atmosphere through the chimney 41, Fig.9.

The gate valve 42 is open.

After casting the liquid metal, the bath is cleaned of slag, two plugs 12 are plugged and the cycle repeats.

Claims (7)

1. Reflective furnace for remelting aluminum scrap, comprising a housing formed by refractory outer side, front and rear end walls, an accumulation bathtub and an inclined platform defined by a hearth and walls, a vault, a drain passage and a gas duct, characterized in that the housing is placed on a welded frame which inside has a diatom brick lining. 2. The furnace according to claim 1, characterized in that the storage bath and inclined platform are made of MKRS-50 hearth blocks laid on three layers of asbestos board and have a pad of dry quartz sand. 3. The furnace according to claim 1, characterized in that it has two slots for the release of molten metal located in the rear end wall. 4. The furnace according to claim 1, characterized in that a steel box is welded to the furnace frame, having heat insulation between it and each wall, consisting of fireclay chips, refractory wool, a triple layer of sheet asbestos board and asbestos chips. 5. The furnace according to claim 1, characterized in that the furnace arch has a layer with double heat-insulating coating and two layers of refractory heat-insulating mats on it, a layer of diatom brick for additional heat storage in the furnace. 6. The furnace according to claim 1, characterized in that six burners are placed in the side walls of the furnace. 7. The furnace according to claim 1, characterized in that it has two slots made in quick-change bricks in the box to allow replacement without stopping the furnace.

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