RU1788403C - Method of melting cast iron and cupola for performing the same - Google Patents

Abstract

Usage: in foundry, namely in heated cupolas, blowing due to the use of heat from the exhaust gases. Essence: the method includes melting the mixture with purging with hot air, suctioning the waste and their gas at the filling window level, blowing part of the exhaust gases, comprising 300-500 nm3 per ton of molten metal, into the cupola zone located at 500-800 mm above the melting point. To carry out the method, a cupola containing a shaft 1 with one main row of tuyeres 2, at the level of the filling window, is covered with a lid 3, interlocked with the loading device, and equipped with a chimney 4 with a diaphragm 5 and a smoke exhauster 6, which is connected to the vertical pipe 7. The lower end of the vertical pipe 7 through a dust collector 8 is connected to an additional series of tuyeres 9 made in the shaft 1 at a distance of 1500-2QOO mm above the main row of tuyeres 2. The upper end of the vertical pipe 7 through the control device 10 is connected to eroy afterburning 11, wherein nnutri r.ezme- Shchen recuperator 12 to preheat the combustion air. 2 s.p. f-ly, 1 ill.

Description

The invention relates to foundry, in particular melting of cast iron in heated cupola furnaces, by using the heat of the exhaust gases.

Known cupola with hot blast from the bottom up, in which the exhaust gas is sucked into the exhaust system by a smoke exhauster and passed through the afterburner, a recuperator in which heat is exchanged between the exhaust gases and the blast air, after which the exhaust basins are cooled in the refrigerator and cleaning in a dust collector ..

With this method of cast iron smelting in a cupola, the heat of the exhaust gases is used only for heat exchange with blast air, the exhaust gas exhaust system is a sequence of units extended into the process chain and takes up a lot of space.

In addition, with such a sequence of units in the cleaning system, when the dust collector and smoke exhauster are at a more distant position from the cupola, the flue gases contaminated with dust clog the recuperator, lowering heat transfer, cause an explosive situation in the afterburner, clogging the torches for afterburning with dust gases.

The aim of the invention is to increase the thermal efficiency of the cupola

The goal is achieved in that in the method of cast iron melting in a cupola, including melting the mixture with hot air and exhaust gas exhaust using heat to blow it, according to the invention, the exhaust gas is exhausted at the level of the filling window and some of them component of 300-500 nm3 per tonne of molten metal is blown into the cupola zone located 500-800 mm above the melting band.

To implement the proposed method, a cupola containing a shaft with a filling window and a main row of tuyeres, a charging device, an exhaust gas pump system with a smoke exhaust, a afterburner, a recuperator for heating blast air, a dust collector, pipelines and control devices, according to the invention, the cupola is equipped with a lid and additional tuyeres, the lid being located in the shaft at the level of the filling window and interlocked with the loading device, the flue with a smoke exhauster is placed at the filling level th window and connected to the riser, the upper end through which the control device is connected to the afterburning chamber and the lower end through a dust collector connected to an additional adjacent tuyeres formed in the shaft cupola furnace at 1500-2000 mm above the primary tuyere row. Providing a cupola with a lid that covers the cupola shaft at the level of the filling window and is interlocked with a loading device, minimizes the leakage of exhaust gases into the atmosphere and brings the proposed

0 cupola to cupboards of a closed type. Placement of a chimney with a smoke exhauster at the level of the filling window allows not only the exhaust of all exhaust gases, but also due to the suction of air at

5 open lid to prevent leakage of exhaust gases into the atmosphere at the time of loading.

The introduction of exhaust gases containing carbon monoxide with a smoke exhauster into

The cupola zone, located 500-800 mm above the melting bed, allows, firstly, to create a reducing atmosphere in this zone, which is the charge heating zone, and thereby reduce coke consumption, and secondly, the outgoing The gases supplied here directly from the smoke exhauster have a high temperature, which they give to heat the mixture, which also increases the thermal efficiency of the cupola. When the distance between the smelter and the additional row of tuyeres for introducing exhaust gases of less than 500 mm, it is difficult to introduce the exhaust gases into the cupola shaft due to the increase in the hydraulic resistance of the filling due to the beginning melting of the slag components of the charge and possible slagging of the tuyeres . With an increase in the distance of more than 800 mm, the heating efficiency of the charge column decreases and the thermal efficiency of the cupola is reduced. ....

The amount of blown off exhaust gases was chosen so that (300-500 nm3 per ton of liquid metal) so as not to disturb the movement of gases in the cupola upward, but at the same time to return a significant part of the heat carried away to the cupola. With a decrease in the amount of injected exhaust gases below 300 nm3 per ton

With liquid metal, the efficiency of heating the charge in front of the melting zone sharply decreases and the thermal efficiency of the cupola is reduced. Increase in the amount of supplied exhaust gases in excess of 500 nm3 per ton

5 liquid metal can lead to the creation of an undesirable counterflow to their moving from the bottom up the main gas stream.

The connection of the smoke exhaust with a vertical pipe allows along with a trans

By porting the exhaust gases, in a vertical pipeline, to separate dust particles falling down into the dust collector under the action of gravity with a sharp loss of speed due to the large cross-section of the pipeline. As a result, a part of the exhaust gases flowing from the upper part of the vertical pipeline through the regulating device to the afterburner with a recuperator is already dedusted and provides efficient and reliable operation of the afterburner and the recuperator located in it for heating the blast air.

Connection of the smoke exhaust with a vertical pipe to which a afterburner with a recuperator located in it is connected to the top and a dust collector is connected to the bottom, i.e. the vertical arrangement of these devices along the cupola shaft makes the whole installation more compact.

The drawing is a schematic illustration of a cupola for implementing the proposed method.

The cupola contains a shaft 1 with a main row of tuyeres 2 for supplying blast air. At the filling window level, the cupola shaft is covered by a lid 3, interlocked by electric sensors with a loading device and equipped with a chimney 4 with a diaphragm 5 and a smoke exhauster 6 included in the exhaust exhaust system. The smoke exhaust fan 6 is connected to a vertical pipe 7, the cross-section of which greatly exceeds the cross-section of the smoke exhaust pipe 6. The lower end of the vertical pipe 7 is connected to a dust collector 8 and through it with an additional series of tuyeres 9 made in the cupola shaft 1 at a distance of 500-800 mm above the melting band, which corresponds to 1500-2000 mm above the main row of tuyeres 2. The upper end of the vertical pipe 7 through the regulating device 10, which can be made in the form of a damper, is adjustable. The electric one-turn mechanism is connected to the afterburning chamber 11, inside of which there is a recuperator 12 for heating the blast air supplied through the pipe 13 from the blower 14 to the tuyeres 2.

The proposed method for melting cast iron in a cupola is carried out as follows.

During smelting, the exhaust gases sucked from the mine cupola shaft 1 at the level of the filling window through the flue pipe 4 with the help of a smoke exhauster 6 enter the vertical pipe 7 where, under the action of force

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severity and speed loss due to a sharp change in the cross section of the pipeline, solid particles fall down into the dust collector 8.

In the vertical conduit 7, the exhaust gas stream is divided into two streams, one of which goes down and is blown through the tuyeres 9 into the mine, where it creates a reducing atmosphere and, when rising upward, gives off its heat to the filling. From the upper part of the other vertical pipe 7, part of the exhaust gas flow through the control device 10 enters the afterburning chamber 11, inside which, simultaneously with the burning of carbon monoxide from the exhaust gases, heat is exchanged between these gases and the blast air pipes of the recuperator 12. Amount of waste of the flue gases injected into the cupola is determined by the control device 10. From the afterburner 11, the flue gases enter the recovery system 15, where they can be used, for example, to dry sand with a fluidized bed or rods.

PRI me R 1. In the existing cupola, an additional row of tuyeres was placed at a height of 1500 mm above the main tuyere series, which corresponds to 500 mm above the level of the melting bed. During smelting of pig iron, an additional series of tuyeres was used to blow off exhaust gases in an amount of 300 nm per tonne of molten metal, as a result of which coke consumption was reduced by 10 kg per tonne of molten metal.

Example 2. Through an additional row of tuyeres, also located at an altitude of 1500 mm above the main tuyere tuyere, off-gases in the amount of 400 nm per ton of molten metal were blown into the cupola during melting. At the same time, a decrease in coke consumption amounted to 12 kg per ton of liquid metal.

Example 3. An additional row of tuyeres was placed at a height of 2000 mm above the main tuyere range, which corresponds to 800 mm above the level of the melting band. By blowing off exhaust gases through them in an amount of 500 nm3 per tonne of liquid metal, a decrease in coke consumption by 15 kg per tonne of liquid metal was obtained.

With a decrease in the amount of injected exhaust gas below 300 nm3 per tonne of liquid metal, the coke economy decreased and had no practical value. An increase in the amount of injected exhaust gases in excess of 500 nm3 per tonne of liquid metal brought down the flame in the melting zone, which led to a decrease in the temperature of the exhausted metal. .

Thus, the proposed method for melting cast iron in a cupola, carried out using the proposed design of a cupola, allows using the waste gases to heat the charge column in the cupola of the cupola to increase the temperature of liquid metal by 20-30 ° C and reduce the consumption of blast air to 500 -600 nm3 per tonne of molten metal, by using exhaust gases to create a reducing atmosphere in the charge heating zone, reduce coke consumption by 10% and increase the cupola productivity by increasing the metal filling rate, by cleaning the exhaust gas from dust in front of the afterburner, increase the reliability of the cupola exhaust gas purification system, and by placing vertically along the cupola shaft of the cleaning system units, increase the compactness of the entire installation.

SUMMARY OF THE INVENTION 1. A method for melting cast iron in a cupola furnace, comprising melting a mixture with blowing with hot air and suction of the exhaust gases using their heat to preheat blowing, characterized in that in order to increase the thermal efficiency of the cupola, the exhaust gases are sucked out at the level of the filling window and part of them, which is 300-500 nm3 per 1 ton of molten metal, is blown into the cupola zone located 500-800 mm above the melting

by sa.

2. A cupola for cast iron melting, comprising a shaft with a filling window and a main row of tuyeres, a loading device, an exhaust gas extraction system with a smoke exhaust,

a afterburner, a recuperator for heating blast air, a dust collector, pipelines and control devices, so that, in order to increase the thermal efficiency of the cupola,

it is equipped with a lid and an additional series of tuyeres, while the lid is located in the shaft at the level of the filling window and is locked with the loading device, the chimney and smoke exhauster are placed at

a filling window and connected to a vertical pipeline, the upper end of which is connected to the afterburning chamber through a regulating device, and the lower end is connected through an dust collector to an additional series of tuyeres made in the cupola shaft 1500-2000 mm higher than the main tuyere series.