RU2661368C1 - Induction crucible furnace - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy and can be used for the processing of scrap and waste of ferrous metals. Induction crucible furnace operating at an average frequency of 500 Hz contains a steel furnace body with a rotatable lined cover mounted on it, hydraulic mechanisms for lifting the lid and tilting the furnace. It is equipped with a device connected to the lid for evacuation of flue gases formed during smelting in the furnace, connected to a two-stage dust and gas cleaning system, including a smoke exhauster installed in front of it a mixing chamber with two gate valves, four-section gas cleaning unit for cleaning flue gases from harmful substances in the fluidized bed of the adsorbent and a cyclone unit for cleaning dust from the gas stream coming from said gas cleaning. Lid is lined with mullite non-shrinkage stuffed mass with a crust of garlic, and the refractory packed mass of the crucible has the following composition, weight %: crystalline quartzite with an average grain size of 0.14–0.2 mm 72, zirconium concentrate with an average grain size 0.05–0.063 mm 23, sodium tripolyphosphate 1.5, kaolin 3.5.

EFFECT: invention provides low heat loss, increases productivity and extends the life of the furnace.

1 cl, 10 dwg, 1 tbl

Description

The invention relates to ferrous metallurgy, and in particular to smelting units for processing (remelting) scrap and waste of ferrous metals. The furnace can be used for refining, producing ferrous alloys, and averaging the chemical composition of scrap.

Known induction furnace (RF patent No. 2092761), which is an analogue of the invention, containing, like the claimed induction crucible furnace, a refractory crucible, a water-cooled inductor located around the crucible, a steel furnace body, a hearth, a lining.

The disadvantages of this furnace are:

1. The presence of channels in the refractory wall of the crucible, which are made in the form of hollow rings connected by hollow racks make the induction furnace difficult to manufacture and unreliable in operation.

2. The absence of dust and gas cleaning, which would reduce the harmful effects on the environment.

3. Inadequate mechanization of the induction furnace.

Due to the above disadvantages, the furnace cannot solve the technical problem.

Also known is an induction crucible furnace for processing scrap and waste of secondary aluminum (Information source MS Shklyar "Furnaces of secondary non-ferrous metallurgy", publishing house "Metallurgy", 1987. p. 120-126), which is an analogue of the proposed. The induction crucible furnace described in the information source contains, like the proposed one, a refractory crucible, a water-cooled induction coil (inductor) located around the crucible, a steel furnace body, a hearth, a crucible wear (eating) indicator, a lining.

The disadvantages of this furnace are:

1. The low resistance of the lining of the induction crucible furnace.

2. The absence of dust and gas cleaning, which would reduce the harmful effects on workers in the workshop and the environment.

3. Inadequate mechanization of the induction furnace.

Due to the above disadvantages, the furnace cannot solve the technical problem.

The closest analogue (prototype) with respect to the inventive induction crucible furnace is an induction crucible furnace (source of information VA Grachev "Furnaces of foundries" .- M .: MGOU, 1994, S. 472-475 and S. 533-541 ), containing, as the claimed induction furnace, a refractory crucible, a water-cooled induction coil (inductor) located around the crucible, a steel furnace body, a hearth, a crucible wear (eating) indicator, a lining.

The prototype of the inventive furnace has the following disadvantages:

1. Low durability of the lining of the induction furnace.

2. The lack of dust and gas cleaning, which would reduce the harmful effects on the environment.

3. Inadequate mechanization of the induction furnace.

4. The furnace operates at an industrial frequency.

5. The furnace does not include a compact modern cooling station.

Due to the above disadvantages, the furnace cannot solve the technical problem.

The objective of the invention is the creation of a highly mechanized cooling station equipped with a mid-frequency induction crucible furnace for processing (re-melting) scrap and waste of ferrous metals, which allows to reduce emissions of harmful gases into the atmosphere, reduce heat loss to the environment, and also increase its life.

EFFECT: developed furnace is a high-mechanized mid-frequency induction crucible furnace equipped with a cooling station having a long service life, which allows: to reduce heat loss to the environment through the use of a lined furnace cover, to conduct a re-melting process on artificial traction with a gas-cleaning dust system, which makes it environmentally friendly.

The specified technical result is achieved due to the fact that in an induction crucible furnace for processing scrap and waste of ferrous metals containing a refractory crucible, a water-cooled induction coil (inductor) located around the crucible, a steel furnace body, a hearth, a crucible wear (eating) indicator , lining, according to the invention, introduced having a high resistance refractory packing mass of the following composition:

crystalline quartzite with an average grain size of 0.14-0.2 mm, wt.% 72 zircon concentrate with an average grain size of 0.05-0.063 mm, wt.% 23 sodium tripolyphosphate, wt.% 1,5 kaolin, wt.% 3,5

At the same time, the service life of the induction crucible furnace is increased due to the use of refractory ramming mass, which has high refractoriness and resistance.

Moreover, the furnace is designed to operate on artificial traction with a two-stage dust removal system for gas cleaning to achieve an environmentally friendly process, including a smoke exhauster, a four-section gas treatment unit, and a cyclone unit.

It should be noted that the lining introduced into the composition of the induction crucible furnace is lined with a mullite non-shrink packing material with a crust crust and reduces the heat loss to the environment, and also makes it possible to additionally maintain the temperature of the metal in the furnace for processing scrap and waste ferrous metals. Mullite non-shrink packing material with a crust crust has high refractoriness and resistance, so the furnace has a long service life.

Further, the lid of the induction crucible furnace is equipped with a device for removing the flue gases generated during smelting in the furnace, consisting of: a connector, duct, transition pipe and a pipe through which the flue gases are supplied to a two-stage dust-cleaning gas treatment system.

Moreover, a hydraulic mechanism for tilting the furnace has been introduced into the furnace, as well as a hydraulic mechanism for lifting the lid of the furnace, which allows the furnace to be classified as highly mechanized.

In this case, water cooling from the inductor, as well as the frequency converter and the capacitor bank, is performed in the cooling station. The cooling station is compact and allows you to automatically control the process of cooling the water of the inductor, as well as the frequency converter and the capacitor bank using a control rack and a computer. It is important to note that the proposed induction crucible furnace does not work at an industrial frequency, but at an average frequency of 500 Hz. At the same time, the energy consumption is half as much as that of the HPPI operating in a continuous melting cycle, lining costs are reduced, unproductive labor costs are eliminated, and the heat engineering efficiency of the furnace is increased.

Finally, the two-bath furnace is equipped with a two-stage gas-cleaning dust system to achieve an environmentally friendly process, the first stage being a DN-15 smoke exhauster four-section gas-cleaning unit, and the second block of cyclones, while the gas-cleaning dust unit has the following characteristic: gas purification capacity 31000 m ³ / h, the degree of dust removal 82%, the degree of purification by hydrogen fluoride 62%, the degree of purification by copper oxide 85%, the degree of purification by carbon monoxide 80%, the degree of purification by nitric oxide 81%, degree 80% alumina purification; sound level no more than 74 TWA. From the above data it follows that the four-section gas purification unit has a wide range of purification of harmful substances contained in flue gases, and dust is cleaned in the cyclone unit.

Introduction to the furnace design of the above devices, materials, two-stage dust and gas cleaning systems, etc., provides a solution to the problem.

In the design part of the application for an invention is depicted:

in FIG. 1 type of stoves in plan with boot devices;

in FIG. 2 section AA of a complex of induction crucible furnaces with a service platform;

in FIG. 3 is a front view of an induction crucible furnace;

in FIG. 4 type B furnace (top);

in FIG. 5 view In the furnace (side);

in FIG. 6 section of the furnace;

in FIG. 7 is a plan view of equipment located under a service site;

in FIG. 8 is a plan view of a two-stage dust-cleaning gas treatment system;

in FIG. 9 four-section gas cleaning unit;

in FIG. 10 block of cyclones;

The proposed induction crucible furnace relates to ferrous metallurgy, namely to melting units for processing (remelting) scrap and waste of ferrous metals. An induction crucible furnace (hereinafter referred to as the furnace) can be used for refining, producing ferrous alloys, and averaging the chemical composition of scrap.

As a rule, currently factories, enterprises, manufacturers of products are increasingly buying two melting furnaces, which are called a complex of melting furnaces. Operation of melting furnace complexes makes production continuous. two furnaces can work at the same time, or one is in operation and the other is under repair, so it would be correct, modern to describe the complex of melting furnaces, and also to simultaneously describe the design and operation of the induction crucible furnace.

The complex of melting furnaces consists of the following main units:

- from two melting furnaces 1;

- two capacitor banks 2;

- two mid-frequency thyristor converter 3;

- a set of water-cooled cables 4;

- two vibro-loading machines for filling the charge into the furnace 5;

- signaling devices for eating the lining of the crucible 6;

- cooling stations (not shown);

- a hydraulic station for tilting the furnace and lifting the lid.

- two control panels tilting the furnace forward 7;

- two control panels tilting the furnace back 8;

- two transformers 9;

- two sets of busbars 10;

- control racks of the furnace complex 11 of FIG. 1, 2, 7.

In addition, the proposed furnace for melting cast iron and steel, unlike the prototype, does not work at an industrial frequency, but at an average 500 Hz.

Compared to induction furnaces of industrial frequency (IPPC), smelting of cast iron at medium frequency also has the following advantages: - energy consumption is half as much as that of IPPC operating in a continuous melting cycle with partial discharge of metal and periodic reloading of the charge; - charge mode melting, i.e. without the use of liquid metal residue (“bogs”), which passes from the smelting to the smelting, it eliminates the preliminary drying of the charge and the costs associated with it, in addition, reduces the cost of lining, since the longevity of the lining under the batch mode of smelting increases, and, finally, to eliminate unproductive costs of labor, electricity and materials associated with the impossibility of shutting down the IPPC for interruptions in the operation of the foundry; - the allowable specific power supplied to the metal is 3 times higher than in the IPPCH (IPSC - 1000 kW × h / t, IPPC - 300 kW × h / t), which provides short melting cycles (40-45 min), increases thermotechnical efficiency and allows to optimize the process of formation of crystallization centers, due to a one-time heating of the metal and lower average temperature during melting than that of IPPCH 14 working with a “swamp”; - the ability to work in the stabilization mode of active power throughout the melting cycle, starting with the “cold” state of the charge, in which the transfer of active power at medium frequencies occurs due to the ferromagnetic properties of the charge, and ending with the molten metal, when the active power is supplied by the flow of eddy currents in a narrow layer of the melt pool, which allows to increase the efficiency of using the installed capacity of electrical equipment with high quality indicators of the consumed electricity.

The furnace body 12 has a welded steel structure, which is equipped with convenient support and fasteners for installing a water-cooled inductor 13 and wiring of FIG. 3, 6. The water-cooled inductor 13 of the furnace is a multi-turn coil made of a hollow thick-walled profile of rectangular cross section made of high-quality electrotechnical copper. On the outside, the profile of the inductor 13 is covered with a layer of insulating material 14 having a high breakdown voltage and high resistance to elevated temperatures and mechanical loads. The inductor coil 13 has early warning sensors or alarms 15 for eating through the lining of the crucible, indicating wear of the lining 16 of FIG. 6. The electric current is supplied to the inductor 13 by flexible water-cooled cables 4, and busbars 10 are installed in front of them, the cooling water supply by rubber-fabric sleeves of FIG. 2, 7. To cool the inductors 13 of the melting furnaces 1, distilled water will be used, which will circulate in galvanized pipes so that there is no rust formation. Cooling water will be supplied from the cooling station (not shown, which is located in the next room) by pumps under a pressure of 6 atm. The tilt of the furnace 1 is carried out by two hydraulic cylinders 17, fed from the pumping station, and the forward tilt is made from the control panel tilting the furnace forward 7, and the tilt back is made from the control panel tilting the furnace back 8 FIG. 13.

The furnace body 1 is closed by a rotary cover 18. It should be noted that the lid 18 of the furnace 1, lined with a mullite non-shrinkable packing mass with a crust crust, introduced into the induction crucible furnace, allows to reduce heat loss to the environment, and also makes it possible to further maintain the temperature of the metal in furnace 1 for processing scrap and waste of ferrous metals, in addition, the mullite non-shrink packing material with a crust crust has high refractoriness and resistance, therefore furnace 1 has a long service life ui. The cover 18 is rotated by two hydraulic cylinders 19. Further, the cover 18 is equipped with a device for removing flue gases generated during smelting in the furnace, consisting of: a connector 20, a duct 21, a transition pipe 22 and a pipe 23, through which the flue gases are fed into a two-stage dust system gas cleaning.

Induction Crucible Lining

General requirements

The lining 16 of the furnace 1 should have high thermal resistance, mechanical strength, not corroded by liquid metal and slag, have a minimum coefficient of linear expansion.

The refractory lining of 16 melting crucibles should provide:

- relatively high resistance of the crucible with a minimum wall thickness;

- lack of electrical conductivity;

- minimum volumetric changes in materials during operation: sufficient erosion resistance against the effects of metal and slag;

- high mechanical strength;

- thermal stability.

The furnace used developed by the author, having high refractoriness and durability refractory ramming mass for the crucible (acid lining) of the following composition:

crystalline quartzite with an average grain size of 0.14-0.2 mm, wt.% 72 zircon concentrate with an average grain size of 0.05-0.063 mm, wt.% 23 sodium tripolyphosphate, wt.% 1,5 kaolin, wt.% 3,5

At the same time, the service life of the induction crucible furnace is increased due to the use of refractory ramming mass, which has high refractoriness and resistance. Monitoring the status of the crucible is carried out visually and using the signaling device 15 of eating the crucible.

Production of a hearth and a concrete ring.

For the manufacture of hearth 24 and concrete ring 25, the author recommends using the materials listed in table No. 1.

Thoroughly mix the mixture of alumina cement and quartzite powders in a forced-action mixer in a dry form, then add water in an amount of 10-12 liters per 100 kg of a dry powder mixture of FIG. 6. The prepared concrete must be used within an hour.

Hearth stone 24 and concrete ring 25 pour ready-to-use refractory concrete from a mixture of powders (see table. 1).

To increase the density of concrete, it is recommended to prepare

refractory concrete of normal consistency, which, when compressed in a hand, crumbles, lay in a formwork and compact it under the action of a press.

Dry the hearth 24 and the concrete ring 25 within 3 days. For lining the drain toe 26 and collar 27 of the furnace 1, the author recommends using the materials indicated in table No. 1.

Inductive Melting Inductor Coating

The inductor 13 is designed to create an alternating magnetic current of a given strength. In addition to its main purpose, it also serves as an important structural element, perceiving mechanical and thermal load from the side of the melting crucible and largely determining the reliability of the induction furnace 1 as a whole.

The inductor 13 of the induction furnace must provide:

- minimal electrical loss,

- the required flow rate of cooling water,

- the necessary mechanical strength and sufficient rigidity,

- reliable electrical insulation of turns.

The inductor 13 is coated during the manufacture of kiln 1, as well as during the repair of kiln 1, by special refractory concrete based on quartzite and alumina cement powders (the composition is given earlier in table 1). After applying a coating layer, it is necessary to dry (during drying, do not apply water to the inductor) with incandescent lamps for 3 days. After the inductor coating has dried 13, it is necessary to lay GOST 6122-75 micanite or 5 mm thick asbestos cardboard according to GOST 2850-95 from the inner surface of the side walls of the crucible and to the hearth 24. Then, according to the template, fill the crucible with a pneumatic vibrator with a rammed ram or manually above refractory ramming mass for the crucible.

Crucible drying and sintering

Sintering is carried out with a lid tightly closed to release water vapor.

Drying of the crucible to start with reduced voltage at the inductor 13.

Shutter speed at 25 kW for 2 hours

Then increase the power to 50 kW and continue heating for 2 hours.

After that, the furnace 1 switch to full power and continue heating until the mixture and the template are completely melted.

As the charge is melted into the furnace 1, load the charge in portions until the liquid metal deposits to the collar level 27.

After complete melting of the charge, proceed to sintering the crucible. Overheat the metal to a temperature of 1500 ° C and withstand at least 15-20 minutes. The specified firing mode is necessary for sintering the working layer of the lining 16 in order to give it the necessary mechanical strength.

After the first melting, it is recommended to conduct another 3-4 melts without interruption, for fixing and good sintering of the crucible.

When you turn on a cold furnace with a sintered crucible (after a break in melting), a heating time of 8-10 hours is necessary to ensure uniform heating of the crucible to a red state, this helps to increase the service life of the refractory lining 16 of the crucible. Avoid loading cold furnace 1 with chips or molten metal.

It is important to note that the wall thickness of the crucible, i.e., the distance between the inductor 13 and the liquid metal, affects the electrical parameters of the furnace: the thicker the wall, the greater the number of magnetic lines of force penetrating the inductor 13, is not involved in the heating of the metal and the smaller cos ^ϕ furnace 1. The magnetic flux from the outside of the inductor 13 passes through radially arranged packets of transformer steel - magnetic circuit 28. The magnetic circuit 28 is fixed in the furnace 1 by pins 29, which are arranged in several rows. The magnetic permeability of transformer steel is many times greater than that of air, so almost the entire magnetic flux passes through the magnetic circuit 28. It should be noted that the magnetic circuit 28 is advisable to be located as close as possible to the inductor 13, which increases its rigidity and reduces the size of furnace 1. From Due to the presence of a crucible, furnace 1 has a small cos ^ϕ . In order not to load the network with high reactive power, a capacitor bank 2 is connected in parallel with the inductor 13, the number of capacitors in the course of melting changes, since when heated, the electrical resistance of the charge, and in some cases its magnetic properties, changes. The proposed furnace 1 (complex of furnaces) does not work at an industrial frequency of 50 Hz, but at a frequency of 500 ± 15%, so each furnace 1 of the complex of furnaces has a frequency converter 3 with a capacity of 2500 kW. Two capacitor banks 2, as well as two frequency converters 3 are mounted under the service site of the furnace complex of FIG. 7. Although crucible induction furnaces have a lower cos ^ϕ and require more expensive and complex electrical equipment, it is advisable to use them for remelting low-grade waste. The preparation of alloys in these furnaces on a low-grade charge with subsequent refining ensures high quality castings in the mold and foundry. In the design of furnace 1, the following should be noted: it rests on a base 30, in which two posts 31 are fixed, in the upper part of which there are axes 32, around which the furnace 1 rotates when the molten metal deposited in the furnace is drained. Racks 31 for stiffness have welded jibs 33. The furnace 1 also rests on a pedestal 34, which is welded to the base 30. Stiffening ribs 35 of the FIG. 3, 5, 6. Each furnace 1 included in the furnace complex is equipped with a vibro-loading machine 5, which moves along steel rails 36. Vibro-loading machines 5 are loaded with a bridge crane 37, which moves along the span of the warehouse of the mixture along crane tracks 38 Fig 1. Service platform equipped with two ladders 39 and has a perimeter fence 40. Between the vibro-loading machines 5 in the center there is a room 41 for smelters, in which there is a rack 11 for controlling the complex of furnaces and a computer 42.

Let us briefly analyze the water cooling system of furnaces 1. The cooling water treatment system (cooling station) will be located in the water treatment room (not shown) located next to the dust and gas treatment room. Inductors of melting furnaces 13, capacitor banks 2 and frequency converters 3 will be cooled by water. Currently, cooling stations are widely used, the author also chose a cooling station for cooling, but I do not describe it in detail. Closed-type cooling station with a plate heat exchanger and with an emergency water tank with a volume of 30 m3. According to industrial safety requirements, it is necessary to have an emergency furnace cooling system. The author introduced an emergency capacity, which is at around 5 m. When the main input power is turned off, if melting occurs, it is necessary to turn on the emergency cooling system. At the same time, the taps of the existing cooling system are closed and the taps of the emergency cooling system are opened, and the diesel pump of the emergency cooling system is turned on. The emergency water cooling system provides emergency operation of the furnaces for 5 hours. It should be noted that in the cooling system of the inductors 13 of the furnaces, capacitor banks 2 and frequency converters 3, distilled water is used. Under the service platform, there is a panel of internal water distribution 43, as well as collector No. 1 pos. 44 and collector No. 2 pos. 45 of FIG. 7.

In the process of induction crucible furnaces 1 emits a large amount of flue gas. The amount of flue gases generated during the operation of two furnaces 1 with a capacity of 5 tons each, according to enlarged estimates, is 31,000 m3 / h. The temperature of the flue gas is an average of 150 ° C. The furnace is equipped with a two-stage dust and gas cleaning system to achieve an environmentally friendly process, and the first stage is a mixing chamber 46, smoke exhauster DN-15 pos. 47, a four-section gas treatment unit 48, and a second cyclone unit 49 of FIG. 8. Purification of flue gases from harmful substances occurs in a four-section gas cleaning unit 48, developed by the author and depicted in FIG. 9, which has a wide range of purified harmful substances in flue gases. Each section of the four-section gas treatment unit 48 is a prefabricated steel rectangular sectional body 50, in the lower part of which there is a lower rotary loading grill 51 with holes. Above the lower rotary loading grill 51, a lower loading nozzle 52 of FIG. 9. In the middle part of the steel casing 50 there is an upper swivel loading grill 53 with openings. The rotation of the gratings around the axes is carried out using the handles 54, mounted on the axes of the gratings. The upper loading nozzle 55 is located above the upper rotary loading grill 53. The cover 56 opens and closes the chamber 57, through which the repair technicians service and repair the four-section gas cleaning unit 48. The four-section unit 48 is supported by ten supports 58, in the upper part a service platform is attached to it 59. The spent adsorbent and dust are collected in the conical part 60 of the steel casing 50. The cleaned gases are supplied to the dust and gas cleaning unit through two inlet pipes 61. At the service site 59 a frame 62, on which a blower 63 with an electric motor 64 is mounted, spent adsorbent contaminated with dust from the lower rotary loading lattice 51 and the upper rotary loading lattice 53 with the help of handles 54 is discharged into the conical part 60 of the steel case 50, and then by turning the handles 65 of each section, the spent adsorbent is poured through the lower neck 66 of the steel casing 50 into a container (not shown) and taken to a dump. Fresh adsorbent is loaded twice a week with two shift furnaces and three times a week with three-shift furnaces. Purified flue gases are supplied from each section through pipes 67 to blowers 63 and then through pipe 68 to cyclone unit 49 of FIG. 8, 9. To monitor the progress of the flue gas cleaning process, two eyes 69 are made in the steel case 50. Since the flue gases leaving the furnace have a temperature of 150 ° C, a mixing chamber 46 is usually installed in front of the exhaust fan 47, in which the flue gases are diluted the air of the workshop, while their temperature decreases. In the mixing chamber 46, two gates are installed: one of which 70 closes or opens the supply of exhaust gases to the exhaust fan 47, the other 71 regulates the supply of fresh air to dilute the combustion products of FIG. 8. As a smoke exhaust, a smoke exhaust mod is adopted. DN-15. The four-section gas treatment unit in accordance with the requirements of technical and industrial safety 48 has a guard 72. The principle of operation of the gas treatment unit 48 is as follows: from the furnaces 1, flue gases are pumped by the exhaust fan 47 through pipe 73 into the inlet pipes 61 and an adsorbent layer passes under pressure, forming an adsorbent layer "fluidized bed", as a result of which the harmful substances in the flue gases are adsorbed by an adsorbent: slaked lime and activated carbon. The adsorbent is loaded into the loading nozzles 52, 55 by the operator of the gas treatment unit from a ladder.

After cleaning the flue gases from harmful substances, they are cleaned of dust in the cyclone unit 49 (Fig. 8, 10). The cyclone block consists of eight single cyclones welded together. Each single cyclone consists of a welded steel cylindrical body 74 having a welded cone 75 at the bottom. A pipe 76 for entering the dusty gas into a rectangular cyclone is tangent to the cylindrical cyclone body 74. An exhaust pipe 77 is mounted in the upper part of each single cyclone with an outlet pipe 78 through which the purified gas leaves the cyclone. A common steel dust bin 79 is welded to the bottom of the cones 75 of the cyclone unit 49. The steel dust bin 79 has a rectangular part 80 at the top, and a conical part that is divided into two parts (small bins) 81, in which technological hatches 82 are made. Small bins 81 have dust outlets 83 at the bottom. The dusty gas stream is supplied to the cyclone unit 49 through the inlet pipe 76. The cyclone unit 49 is supported by four supports 84.

The operation of each cyclone is based on the use of centrifugal forces arising from the rotation of the gas-dust flow inside the welded steel cylindrical body 74 of the cyclone. The rotation is achieved by tangentially introducing the pulverized flow into the cyclone with an inclination downward at an angle of 15 °. As a result of the action of centrifugal forces, dust particles suspended in the stream are thrown onto the walls of the cylindrical body 74, fall out of the stream. The clean gas stream, continuing to rotate, rotates 180 ° and exits the cyclone through an axially arranged exhaust pipe 77. Dust particles reaching the walls of the cylindrical body 74, under the action of the axially moving flow and gravity, move towards the dust outlet of the cone 75 and accumulate in the dust bunker, then settle in small bins 81. Pure gas flows from all individual cyclones through the exhaust pipes 77 enter the common outlet 85 and then into the chimney 86 of FIG. 1, 10. At the same time, the gas treatment dust installation has the following characteristic: the gas treatment dust installation has the following characteristic: the gas to be cleaned is 31,000 m ³ / h, the dust removal rate is 82%, the hydrogen fluoride treatment rate is 62%, the gas treatment degree is copper oxide 85%, purification by carbon monoxide 80%, purification by nitric oxide 81%, purification by alumina 80%, sound level not more than 74 DBA. From the above data it follows that the four-section gas purification unit has a wide range of purification of harmful substances contained in flue gases, and dust is cleaned in the cyclone unit.

Description and operation of the induction furnace

Before each start-up of the induction furnace, a thorough inspection of the crucible is necessary. The crucible should not have cracks, bulges, dips. After draining the metal, the crucible must be carefully cleaned of scraps with a scraper. During operation of the electric furnace, mechanical impacts on the lining are not allowed. At the beginning of the start-up of the furnaces or after a long stop of the oven, it is necessary to carefully inspect the inductor, blow it with compressed air to remove dust, check the connections of the water supply hoses, let the water in the inductor 13 and the water-cooled cables, the capacitor bank 2, the frequency converter 3, check the passage of water through each hose separately , check the pressure with a pressure gauge.

Attention! It is forbidden to melt in a faulty crucible, which will inevitably lead to an accident!

Ferroalloys and slag-forming, seated in the furnace should be dried. When smelting metal, it is forbidden to use lime with traces of quenching and a shelf life of more than one day.

The procedure for filling a metal charge is as follows: a fine charge should be placed on the bottom of the crucible to mitigate the impact of large pieces, and, if necessary, carburization is loaded with an electrode charge or coke along with the fine charge. On a small charge, refractory and largest pieces of the charge at the crucible walls should be loaded at 2/3 of the inductor height so that the magnetic lines of force intersect the maximum cross-sectional area of the pieces. The rest of the charge load small fusible charge. To reduce heat loss, it is recommended to cover the crucible with a lid 18. It is recommended to lay the mixture tightly when loading the crucible, taking into account that when the mixture is heated, its linear expansion (increase in volume) takes place, therefore, excessive charge density is not allowed, otherwise the furnace lining will high pressure is applied, which leads to accelerated wear of the lining. The dense loading provides the speed of melting, less oxidizability of the metal and less wear of the crucible with reduced energy consumption. So, in accordance with the calculation of the charge, the first (right) vibro-loading machine 5 is loaded with a bridge crane 37, while the second (left) vibro-loading machine 5 loads the second furnace 1 with charge. Next, the smelters include a dust and gas cleaning system (pre-fill the adsorbent in a four-section gas cleaning unit) and after download furnaces 1 charge begin to melt the metal. It is only allowed to turn on the furnace if it is in working order: lining, furnace cooling system, mechanical and electrical equipment. After loading, close the crucible with a lid and start melting. After loading the charge, turn on furnace 1. If melting is carried out in a cold crucible, then the first 15-20 minutes, furnace 1 should work at reduced power. When working with a hot crucible, the supply of reduced power continues for 5-7 minutes. The power supplied to the electric furnace is gradually increased to the maximum, supporting it until the end of metal melting. As the metal melts, the charge lowers, settles and melts, freeing the upper part of the crucible to load the remaining part of the charge. When filling the charge and conducting melting, it is necessary to strictly monitor that jamming of the pieces of the mixture does not work, as this can lead to their welding and the formation of “bridges”. In the case of the formation of a bridge, it must be destroyed and precipitated. Untimely destruction of the bridge leads to overheating of the molten metal and the destruction of the crucible. To eliminate the sticking of the charge in the melting process, it is necessary to periodically upset using a crowbar with rubber-insulated handles. As the charge settles, gradually load the remaining part of it, making sure that the cold pieces do not fall into the liquid metal, as this can cause foaming of the metal and welding of the cold charge in the upper part of the crucible with the formation of difficult to remove bridges. As the formation of liquid metal and throughout the melting should be poured into the crucible slag mixture, avoiding exposure of the metal.

The smelter during the smelting process must:

- to monitor the water cooling of the electric furnace (the pressure and temperature of the water in the water cooling branches), to prevent the inductor from fogging;

- maintain a given power during melting.

To control the melting mode from the control cabinet (control rack and computer). The mixture should be fed into the furnace in batches as the previous batches are melted. In the case of rapid mixing of the metal, accompanied by the release of metal from the furnace 1, it is necessary to immediately switch the furnace 1 to a lower power or turn off the furnace if the metal is ready for casting. The end of the smelting is determined by obtaining the desired chemical composition (pa based on the obtained metal samples), as well as the required temperature of the liquid metal.

At the end of the heat, perform the necessary technological operations (alloying, refining, modification, etc.). After carrying out these operations, a sample of liquid metal is taken for chemical. analysis. If chem. the analysis corresponds to the lost wax mark, a command is given to drain the liquid metal.

After melting and stress relieving from the furnace, proceed to tilt furnace 1 and drain the metal. Tilt the furnace using the tilt mechanism of the furnace from the console 7. Tilt the furnace 1 to produce evenly, observing the speed of the jet of metal being poured. The finished metal is drained from the furnace into a ladle, previously dried and heated (calcined). A bucket with a capacity of 15 tons is installed in the furnace pit pos. 87.

After the smelting, stop the operation of the Converter 3, but the circulation of cooling water must be maintained in the inductor 13 until the crucible becomes warm, only then turn it off. It is important to note that in the process of filling furnace 1 with charge, operation of furnace 1, discharge of deposited metal from it, flue gases are cleaned of harmful substances and dust according to the scheme: from furnace 1, connector 20, duct 21, adapter pipe 22 and pipe 23, chamber mixing 46, exhaust fan 47, pipe 73, four-section gas treatment unit 48, cyclone unit 49, chimney 86.

So, the developed furnace is a high-mechanized mid-frequency induction crucible furnace equipped with a cooling station, which has a long service life, which allows: to reduce heat loss to the environment through the use of a lined furnace cover, to conduct a re-melting process on artificial traction with a gas-cleaning dust system, which makes it environmentally friendly .

Claims (3)

Induction crucible furnace for processing scrap and waste of ferrous metals, operating at an average frequency of 500 Hz, containing a steel furnace body with a rotatable lined lid installed on it, hydraulic mechanisms for lifting the lid and tilting the furnace, a crucible with an alarm indicator mounted on the bottom and made of refractory ramming mass wear of the lining and a water-cooled induction coil located around the crucible, a two-stage dust and gas cleaning system, characterized in that it is equipped with a lid connected a device for removing flue gases generated during smelting in the furnace, connected to a two-stage dust and gas cleaning system, including a smoke exhauster, a mixing chamber installed in front of it with two gates, one of which is configured to close or open to supply exhaust flue gases to the said exhauster, and the other for regulating the air supply for their dilution, a four-section gas purification unit for cleaning flue gases from harmful substances in a fluidized bed of adsorbent and a cyclone unit for cleaning gas dust the flow coming from the aforementioned gas treatment, while the said lid is lined with a mullite non-shrink packing material with a crust crust, and the refractory packing mass of the crucible has the following composition, weight. %: crystalline quartzite with an average grain size of 0.14-0.2 mm 72 zircon concentrate with an average grain size of 0.05-0.063 mm 23 sodium tripolyphosphate 1,5 kaolin 3,5

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