RU2361161C2 - 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. Furnace can operate on natural and artificial draw with gas purification system, that makes breakage remelting process as environmentally friendly. In furnace it is external heat insulation of walls consisting of 3 layers of heat-insulating materials: chamotte granulated material, fireproof cotton, double layer of asbestos cardboard. Inclined platform, accumulative bath are bricked of baked in the hearth blocks "ШСУ" 33-1, 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. In furnace it is installed special quick-detachable tapping brick in metal casing, which can be easily changed for the new one in case of its wear without disassembly of butt and two side walls.

EFFECT: design simplification and reduction of heat losses.

6 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 of scrap.

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

The furnace contains a housing 1 mounted on the floor (Figs. 1, 2, 3), formed by brickwork of red clay brick. 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 the remelting of secondary aluminum contains a housing 1 (Figs. 4, 5) formed by masonry of refractory outer side, front 15 and rear 16 end walls made of dense chamotte brick grade ШБ. 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 19 layer 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 19 layer of the pillow 0.8: 0.6.

The gap between the front 15 end wall 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 brick of the ШЛБ brand with a 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 chips with a thermal conductivity of 0.4 W / (m · K).

In the front 15 end wall of the housing, a loading window 10 is made, in the rear 16 end wall 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 place of impact of the burning jet of burners installed in the channel 24 (not shown) in solid scrap, the scrap is intensively heated 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 smelting aluminum, the pillow accumulates heat transferred 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, heat the top layer 19 of the cushion 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 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 to take 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 a simple design, which allows to reduce emissions of harmful gases into the atmosphere, to reduce the loss of metal and heat into the environment, and also to extend its life.

EFFECT: the developed furnace is simple in design, having great productivity, which allows: to use scrap unsorted from foreign inclusions, to reduce heat loss to the environment due to special thermal insulation, to conduct the process of remelting on artificial traction with a dust and gas cleaning system, which makes it environmentally friendly.

The specified technical result is achieved due to the fact that in the reflective furnace for the remelting of aluminum scrap, comprising a housing formed by refractory outer side, front and rear end walls, a storage bath and an inclined platform bounded by a hearth and walls, a roof, a drain drain and a flue, according to the present invention, introduced a welded frame, poured concrete and having a heat-insulating layer. The introduced heat-insulating layer reduces heat loss.

In addition, the storage tank and the inclined platform are made of hearth blocks ШСУ 33-1 GOST 7151-74, laid on three layers of asbestos board, and has padding of dry quartz sand. The service life of the furnace is increased due to the use of hearth blocks ШСУ 33-1 GOST 7151-74, which have high refractoriness and resistance (service life according to practical data 5-6 years). Thermal insulation, consisting of three layers of asbestos board and tamping dry quartz sand, allows you to further maintain the temperature of the metal in the bath.

It should be noted that to ensure front loading of the proposed reflective furnace for remelting aluminum scrap, loading and slag windows are placed in the side wall.

At the same time, the reflective furnace for remelting aluminum scrap has two slots made in quick-change bricks in the duct to allow their replacement without stopping the furnace. Replacing quick-change summer bricks in the box is carried out without destroying the walls and arch.

Moreover, the reflective furnace for remelting aluminum scrap is made with the possibility of working on natural and artificial traction with a dust and gas cleaning system to achieve an environmentally friendly process.

Moreover, a steel box is welded to the furnace frame, which has heat insulation between it and each wall, consisting of fireclay chips, refractory wool and a double layer of sheet asbestos board. This design solution significantly reduces heat loss to the environment.

Introduction to the furnace design of the above devices, materials, etc., provides a solution to the problem.

The presence of an inclined platform allows the melting of scrap unsorted from foreign inclusions in the furnace, since alterations (cast iron and steel rings, liners, bushings, studs, pushers, valves, etc.) do not fall into the molten metal.

Figure 6 is a longitudinal section of a furnace.

7 is a transverse section of the furnace (view of the burner belt).

On Fig - cross section of the furnace (view of the notch 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 of 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 SHSU 33-1 GOST 7151-74 (thickness 300 mm, width 400 mm, length 1000 mm). The walls of the stove are made of fireclay bricks. The hearth blocks are laid on the frame and sand packing, on top of which the 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, the thermal expansion joints are not laid out.

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 and (27) of channel No. 14 (28), is poured with concrete of grade B40 (≈ 200 mm remains to the upper cut) . To reduce heat loss through the concrete of the carcass, the upper part of the carcass ≈ 200 mm is poured with concrete, into which chamotte, crushed lightweight brick (crumb) is added. After the concrete has hardened, a sand packing is made on the welded frame under the furnace bottom. The hearth consists of 2 rows of hearth blocks SHSU - 33-1 GOST 7151-74, 5 pieces in each row. Hearth blocks are lined with direct fireclay bricks of the ShA brand - 1 product No. 5 GOST 8691-73. In the lower central part of the front wall there is a notch 12 in the summer brick. Flying brick is placed in a metal box.

When replacing a worn summer brick, the box is removed from the niche, the old summer brick is removed, a new box is put in the box, and the box with the new brick installed is put in a niche. The furnace walls 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 metal armor, there is a heat-insulating layer consisting of fireclay stuffing, a double layer of sheet asbestos board, and fire-resistant cotton wool. The armor is attached to the frame by vertical channels No. 20 (29) of 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 and slag windows have arches 7 and 31, respectively, laid out according to the patterns in 5 rows from the chamotte end wedge of Fig.6. The masonry of the arch of the loading window stands for a steel box (armor) of 60 mm. In the rear wall 16 there are two openings for two injection burners BIG1 - 11 TU 51-464-89 (32) Fig.7. Heel beams 33 are welded from channels No. 24.

The furnace can operate on natural traction with the power off due to the use of two injection burners of the BIG 1-11 type TU 51-464-89. The burners are located at an angle to the inclined platform 5 of the furnace and the hearth, which allows more complete use of heat during combustion to heat the mixture and its melting. Each burner has a 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 34 Fig. 8 in two layers.

In the rear wall 16 there is a gas duct 11 of FIG. 6, which has an arched vault. The flue has two control flaps (one for regulating artificial draft, the other for regulating natural draft). It is important to note that the furnace can operate both on artificial draft and on natural draft. When using dust and gas cleaning plants (for example, installations of the Gas Institute of Ukraine or others), the process becomes environmentally friendly. At the top behind the side wall of the furnace, the gas duct 11 bifurcates: one branch (straight-hog) goes to the chimney 35, the other (inclined hog) 36 goes to the mixing chamber, a smoke exhauster and dust and gas cleaning Fig. 9. The borovka branch going to the exhaust fan has a mixing chamber in which two gates are installed: one of which 37 closes or opens the exhaust gas supply to the exhaust fan, the other 38 regulates the supply of fresh air to dilute the combustion products with it Fig. 9. The same valves (gates) control the amount of vacuum in the furnace. With artificial traction, a vacuum is created by a smoke exhaust (not shown).

By means of a smoke exhaust, the combustion products, having been cleaned of dust and harmful gases, are pumped through a metal return duct 39 into a chimney 35. The melted metal is poured out of the furnace through the chute 40 into the molds 41, mounted (for example) on the carousel 42 of Fig. 9. 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 two gas injection burners 32 of Fig. 7, walled up in special openings, heats the scrap to the melting temperature. The metal melts and flows down an inclined platform 5 into the furnace bath. The burners are installed obliquely, so the flame of the burners is inclined at an angle to the inclined platform 5, the bathtub, and it slides along the burden lying on the inclined platform and the bath with molten metal, strikes the rear 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. In the process, heat is accumulated in a large vault 6, from where it is reflected on the metal. Coating layers of the arch 34, thermal insulation of the walls, the hearth, the inclined platform 5 and the heat-insulating layer of the furnace frame, sanding of dry quartz sand and sheet refractory material 26 provide high thermal insulation of the melting unit. At the same time, the concrete of the furnace frame provides additional thermal resistance to the heat flux emanating from the loading table and the bath down. 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 (loading table), 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 at the end of the smelting they are 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, the flux metal is treated with flux, the metal is thoroughly mixed in the bath and the spectral analysis laboratory confirms the grade of the alloy obtained, a notch is opened and the alloy is cast into molds 41.

It is important to note that when the furnace is operated on artificial traction, when the gate 43 is closed and the gate 37, 38, 44 are open, the combustion products, having passed through the inclined bore 35 and the mixing chamber, are woken up (diluted) in the workshop air, then they are cleaned of dust and harmful compounds enter the chimney 35 through the return metal duct 39 (the dust and gas cleaning installation with a smoke exhaust is not shown in the diagram). Flue gas cleaning makes the process environmentally friendly.

The operation of the furnace on natural draft is carried out if the dimensions of the sanitary protection zone allow, during calcination, casting of deposited metal into molds or during a power outage, when the operation of the smoke exhauster and dust and gas cleaning system is impossible.

The gate valves 37, 38, 44 are closed while 43 is open.

After casting the liquid metal, the bath is cleaned of slag, the tap hole 12 is plugged and the cycle repeats.

Claims (6)

1. Reflective furnace for remelting aluminum scrap, comprising a housing formed by refractory outer side, front and rear end walls, a storage bath and an inclined platform bounded by a hearth and walls, a vault, a drain passage and a duct, characterized in that the housing is placed on a welded frame filled with concrete and having a heat-insulating layer. 2. The furnace according to claim 1, characterized in that the storage bath and inclined platform are made of hearth blocks SHSU 33-1 GOST 7151-74, laid on three layers of asbestos board, and has a pad of dry quartz sand. 3. The furnace according to claim 1, characterized in that the loading and slag windows are placed in the side wall to provide front loading. 4. 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. 5. The furnace according to claim 1, characterized in that it is configured to operate on natural and artificial traction with a dust and gas cleaning system to achieve an environmentally friendly process. 6. 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 and a double layer of sheet asphalt board.

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