RU2360983C2 - Reverberatory furnace for metal remelting - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: furnace contains body, formed by side, front and back end walls, limited by bottom and walls accumulative bath, crown, exhaust notch, flue duct and fabricated frame, at which everything is located. In furnace it is external walls heat-insulation, consisting of three layers of heat insulators: chamotte granulated material, fireproof cotton, double layer of asbestos cardboard. Inclined platform, accumulative bath are lined from car-top blocks "£Üá-50", lined in three layers of asbestos cardboard and tamping made of dry high-silica sand, that provides to keep heat in furnace bath, interrupting its withdrawal to the binding. Furnace binding is poured by concrete with additions of chamotte granulated material, and in top part of which are lined in two layers lightweight chamotte bricks, reducing thermolysis from bath through binding. Crown over the inclined platform and furnace bath allows heat insulating coating material in two layers and two layers of fireproof mats, which additionally reduce heat losses from melting area of furnace. In furnace there are installed seven injection burners of type "æÿ" for implementation of melting forced operation. ^ EFFECT: design simplification and heat losses reduction. ^ 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 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, a channel 14 is made parallel to the axis of the bath to accommodate 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), s 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 of the 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 of dense chamotte brick grade SHB 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 point of impact of a burning jet of flame of the 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 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 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 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 design, having a high productivity, which allows using scrap unsorted from foreign inclusions, reducing heat loss to the environment due to special thermal insulation, and conducting the remelting process 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 the weld is introduced welded into the reflective furnace for remelting aluminum scrap, containing a casing formed by refractory outer side front and rear end walls, an accumulation bath and an inclined platform limited by the hearth and walls, a concrete-filled frame with the addition of fireclay chips and having a heat-insulating layer consisting of two layers of lightweight fireclay brick laid in a frame under the bottom of the storage bath and onnoy platform. Two layers of lightweight fireclay bricks in the frame can dramatically reduce heat loss from the bath through the frame to the floor. Adding fireclay chips to concrete can reduce heat loss from the bath to the frame.

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

At the same time, to ensure front loading, loading and slag windows are placed in the side wall of the furnace.

It is important to note that a steel box is welded to the furnace frame, which has thermal insulation between it and each wall, consisting of fireclay chips, fire-resistant cotton wool and a double layer of sheet asphalt board. Such thermal insulation significantly reduces heat loss to the environment.

Moreover, the arch of the proposed reflective furnace for remelting aluminum scrap has a layer with double heat-insulating coating and two layers of refractory heat-insulating mats on it to further retain heat in the furnace.

Further, five burners are located in the rear end wall and two burners in the side wall. In order to maintain the temperature in the furnace bath, to heat up the notch and, if necessary, to overheat the alloy, as well as to increase the productivity, two injection burners BIT 2-6 TU 51-464-89 are installed obliquely to the bottom of the furnace. Five injection burners are installed at an angle to the inclined platform, which allows more complete use of heat during combustion to heat the mixture and its melting.

Finally, a gas duct and threshold are provided in the front wall to provide secondary heating of the molten metal.

The developed design of the proposed furnace can work with the power off due to the use of seven injection burners of the BIG 2-6 type TU 51-464-89.

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

Figure 6 is a longitudinal section of a furnace.

In Fig.7 is a transverse section of the furnace (on the loading window, the view burned full-time belt).

On Fig - cross section of the furnace (on the slag window, 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 (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 walls of the stove are made of fireclay bricks. The blocks are laid on the frame and sand packing, on top of which laid asbokarton 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 poured with concrete of grade B40 with the addition of fireclay chips to reduce heat loss through concrete frame. After the concrete has hardened, sanding is done on the welded frame under the furnace bottom. The hearth consists of 2 rows of MKRS-50 hearth blocks (1000 × 400 × 300), seven in each row and one row of MKRS-50 blocks (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 central part of the front wall there are two slots 12.

Three walls of the furnace are laid out in two bricks and one side, in which filling and slag windows are located, is laid out in two and a half 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 fastening of the steel box (armor) to the frame is carried out by vertical channels No. 20 (29) (Figure 6).

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

The loading and slag windows have arches 7 and 31, respectively, laid out according to templates in 5 rows of chamotte end wedges (Figs. 7, 8). 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 five openings for five injection burners BIG 2-6 TU 51-464-89 (32) (Fig. 7). Two injection burners 33 BIG 2-6 TU 51-464-89 are installed in the side wall at an angle to the bottom, blocked by a block ШСУ 33-1 GOST 7151-74 (34). Heel beams 35 are welded from channels No. 24 (Fig.7, 8).

The burners in the rear wall 16 are located at an angle to the inclined platform 5 of the furnace for quick melting of the loaded mixture. 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 36 (Fig.7) in two layers. To reduce heat loss through the arch of the furnace 6 on top of the coating two layers of refractory mats 37 are laid (Fig. 7).

To reduce heat loss under the inclined platform 5, two layers of lightweight fireclay brick 38 are laid in the frame 38 (Fig. 7), and to reduce heat loss under the hearth 3 in the frame two rows of lightweight brick 39 are also laid. The duct 11 is laid in the rear wall 16 (Fig. .8), which has an arched vault 40. At the top behind the side wall of the furnace, the flue 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 smelted metal is poured from the furnace along the first trough 43 into the molds 44 placed on the chill casting line, and along the second 45 into the molds mounted on the carousel 46 (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 five gas injection burners 32 (Fig.7), walled up in special openings, heat 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 tilted at an angle to the inclined platform 5, the bath and it seems to slide along the charge lying on the inclined platform and the bath with molten metal, smoothly bends around the back wall 16 and the threshold in it, then, twisting, rises to 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 36, two layers of refractory mats 37, thermal insulation of walls, a hearth, an inclined platform 5 and a double heat-insulating layer of the furnace frame 39, sand bed and sheet refractory material 26 provide high thermal insulation of the melting unit. At the same time, concrete with the addition of fireclay chips from the furnace frame provides additional thermal resistance to the heat flux emanating from the inclined platform 5 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 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, the liquid metal is flux-treated, 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 44 and carousel 46.

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 bath and an inclined platform limited by a hearth and walls, a vault, a drain passage and a gas duct, characterized in that the furnace body is placed on a welded a framework poured with concrete with the addition of fireclay chips and having a heat-insulating layer consisting of two layers of lightweight fireclay bricks laid in a framework under the bottom of the storage bath and an inclined platform. 2. The furnace according to claim 1, characterized in that the storage tank and the inclined platform are made of hearth blocks MKRS-50, laid on three layers of asbestos board with tamping 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 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. 5. The furnace according to claim 1, characterized in that the arch of the furnace has a layer with double heat-insulating coating and on it two layers of refractory heat-insulating mats for additional heat storage in the furnace. 6. The furnace according to claim 1, characterized in that five burners are placed in the rear end wall and two burners in the side wall. 7. The furnace according to claim 1, characterized in that a gas duct and a threshold are provided in the front wall to provide secondary heating of the liquid metal.

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