RU1792432C - Method of heating hearth furnace - Google Patents

Description

FIELD OF THE INVENTION The invention relates to ferrous metal, in particular to methods for heating hearth steel furnaces.

Known methods for heating the hearths with an upper fuel supply and oxidize 1, moreover, the fuel is supplied by a central jet, and the oxidizing agent is in the form of jets located in a circle surrounding the central nozzle;

The disadvantages of the known methods for heating hearth steel furnaces are the low efficiency of the heat of combustion and afterburning of gases and the lack of environmental friendliness of the process.

The closest technical solution to the claimed technical essence and the obtained result is the Known method for heating hearth furnaces with top fuel supply and an oxidizing agent, during which the fuel is supplied by a central jet, and the oxidizing agent is supplied by stream jets located around a circumference surrounding central nozzle, with direction parallel to the fuel stream. Partially the mixing of the components takes place in a chamber with an opening angle of 30-60 °. The oxidizer-gas ratio in the prechamber is maintained within 1.6-1.8. The air necessary for complete combustion of the fuel is supplied along the outer surface of the device.

The disadvantages of this method include low efficiency

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heat of combustion and afterburning of gases; insufficient environmental friendliness of the process. This is explained as follows. Fuel is supplied by the central jet, and the oxidizer is supplied by jets of jets arranged in a circle that surrounds the central nozzle with a parallel direction to the fuel jet, in the presence of a prechamber. causes intensive mixing of the components, which results in a narrow focus of the torch, a reduced temperature of the centrifuge, heat transfer, as well as increased noise during operation,

The aim of the invention is to increase the efficiency of the use of heat of combustion and afterburning of gases and the environmental friendliness of the processes.

This goal is achieved by the fact that the fuel is fed through the master burner with a central jet with an opening angle of 1626 °, and the oxidizer is fed with light brown jets located around a circle around the central jet, with alternating feed angles to the axis of the central fuel jet of 14-16 ° and 30- 45 °, respectively, with the ratio of the consumption of oxidizing agent. in alternating streams it is 0.5-2.0. at the same time, a slice of the burner stream during heating is placed at a height of 5-15 minimum diameters of the fuel stream from the surface of the loaded charge; the oxidizer is additionally fed with jets located around the first channel, the jets of the additional channel are directed alternating at angles to the axis of the central fuel jet 40-50 and 60-75 °, respectively, and the ratio of the oxidizer consumption in the jets of jets is kept within 0 , 1-10: the oxidizing-fuel ratio during periods of filling, heating the mixture and heating the bath is maintained within the range of 1-1.5, and during the purge period of the bath with oxygen 2-10.

On Fig, 1 is a schematic front view of the expiring and interacting jets of fuel 1 and oxidizer 2,3, supplied by the stream jets at angles 147) 6 °, and 30-45 °, respectively. and also a jet of additional oxidizing agent 4,5, supplied respectively at angles of 60-75 ° and 40-50 °. In this case, the option of mixing fuel and oxidizing agents with a feed at a height of 500 mm from a bath with eight alternating jets of an oxidizing agent of the first Rus and eight alternating jets of an additional oxidizing agent was considered: in Fig. 2, the degree of jamming of the fuel in four jets of oxidizer of the first bed 2 (angle. 14-16 °), flowing out of the nozzles, like fuel, at subcritical speed (angle of the jets about 26 °)

and a section of gentle angles of the oxidizer of the first Rus (angles 30-45 °) in the secondary combustion and stretching of the torch. The jets of additional oxidizing agent 4,5 either stretch the torch or participate in the afterburning of carbon monoxide over the bath; the spots of contact of these jets with the bath are significantly stretched with a large surface coverage.

This ratio of jets favorably affects the formation of the torch of burning, its. The surface and aerodynamic characteristics, as well as the conditions affecting the quiet course of burning without a sound effect.

At critical expiration rates in an off-design mode, the opening angle of the jet increases to 30 ° and the degree of compression of the gas stream increases, the conditions for its self-carburetion deteriorate somewhat, but the combustion is stable, without noise.

With a low position of the burner above the bath (300-500 mm), both fuel and oxidizing jets flowing from the nozzles hit the surface, deform, reflect, and spread over it. This leads to additional mixing of the components and burning in contact with the heated surface.

The invention is as follows.

Fuel (gas) is supplied through a central nozzle with a jet opening angle of 16-26 ° (gas outflow velocity at the nozzle exit is 100-300 m / s) at a height of 5-15 nozzle diameters (practically at a burner power of 12-18 million kcal / h, this amounts to 300-1000 mm), and the oxidizing agent (oxygen) is fed with alternating jets diverging from the center at angles of 14-16 ° and 30-45 °. This creates the conditions for steeper angle oxidizer jets (14-16 °) to softly pressurize the fuel in an oxidizing medium, partially move with the fuel and reform it if it is not burned, and then the oxidizer jets supplied at 30-45 ° angles diluted with the environment they pick up the reformed gas in the stream or reflected from the surface, burn it in jets and direct it to the surface of the mixture or bath.

The oxidizer-gas ratio at the nozzle exit is maintained in the range of 1.0-1.5, and the oxidizer flow ratio between steep and gentle angles is maintained in the range of 0.5-2. At the same time, for the low position of the burner in operation (300-600 mm) for heating the bath during the refining period, the oxidizer-gas ratio of 1.5 is used, and the ratio of the oxidizer consumption to steep and gentle angles is 0.5-1. For high

the position of the burner (700-1000 Mm) - heating the charge during the warm-up period, the oxidizer-gas ratio of 1 is applied, and the ratio of the oxidizer consumption to steep and gentle angles is 1-2.

When applying additional oxidizing agents with alternating jets at angles of 40-50 ° 30-75 ° in a ratio of 0.1-10, you can control the position of the torch

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d bath or charge. So, when

burners from the bath at a height of 500 mm, the maximum diameter of the zone of influence of the torch from the jets of the first channel (angles 14-45 °) will be 1000 mm. When the additional oxidizing agent jets are activated (angles 4C-750), the diameter of the torch exposure zone expands to 4000 mm. This is convenient for expanding the zone of the torch impact on the Non-heated mixture during filling and heating of the mixture, as well as the burning of carbon monoxide with oxygen over the bath purge area. The oxidizer: gas ratio in the heating periods of the charge or the bath is set to 1.0-1.5, and the purging periods are maintained within 2-10 and this ensures an excess of oxidizing agent for burning carbon monoxide over the bath.

The outflow of fuel (gas) with a jet opening angle of 16 ° is provided at a speed of l / 10 m / s. For conditions of good gas reformation vi of production due to its high radiation characteristics, such speeds and even lower (i.e., with a smaller opening angle) are highly desirable. However, the design of the burner, its dimensions in this case are significantly increased. The latter leads to large ps of heat with the cooling water of the burner and the likelihood of overgrowing of the fuel nozzle increases even with accepted protection standards (supply of small amounts of fuel, air and inert gases). At an angle of opening of the gas stream of 26 °, its expiration rate is close to critical (m / s). In this case, the gas stream mixes well with the oxidizing agent, the gas is reformed worse, which reduces the radiation characteristics of the plume and the heat transfer from the plume to the bath.

An opening angle of a gas stream greater than 26 ° is undesirable, because outflow velocities approach critical (350 m / s), mixing gas with an oxidizing agent enhances

due to increased turbulization,

This and due to the greater penetration of one gas into another, gas reforming is deteriorating and combustion begins to be accompanied by LUVMOM and the greater the larger the angle of the fuel jet.

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The supply of a part of the oxidizer of the first Rus by jets at an angle of 14 ° promotes a soft, limited displacement of the gas with the oxidizer and its good reforming. However, when the oxidant supply ratio along the paths is 2, the undesired noise effect and some deterioration of gas reforming appear in the off-design mode at this angle of meeting and the critical flow rate in the off-design mode. When the oxidizing agent is supplied at an angle of 16 °, these drawbacks are not manifested, however, at low feed ratios of 0.5, there is some deterioration in gas reforming.

The supply of a part of the oxidizer of the first Rus by jets at an angle of less than 14 ° contributes to a greater clamping of the fuel flow, increased mixing, which leads to a decrease in gas reforming and the appearance of a noise effect.

The supply of an oxidizing agent with an angle greater than 16 ° stretches the combustion zone until the fuel flows to the surface, the luminosity of the flame decreases, and the combustion process in the reflected flow is more developed.

The supply of a part of the oxidizer of the first Rus by jets at an angle of 30 ° promotes the formation of a compact dense plume with an underdeveloped surface coverage area. An oxidant supply at an angle of 45 ° expands the plume's ability to cover a heated surface, but spotting coverage appears.

The supply of a part of the oxidizer of the first Rus by jets at an angle of less than 30 ° makes the torch even more compact and dense, and the impact zone is smaller. A significant decrease in the angle of inclination can adversely affect the reform of the gas and its radiation characteristics. The supply of oxidizing agent at an angle of more than 45 ° still stretches the zone of influence of the torch, but some part of the area is outside the direct influence of the torch due to the significant development of spotting.

The supply of an oxidizing agent of the first Rus in the ratio of costs between steep and gentle angles equal to 0.5 contributes to a soft, slightly reformed, elongated core with reduced radiation characteristics and. more rigid turning flow. Rationally, such a combination is advantageous for the low position of the burner above the bath with afterburning of the reflected and flowing gas stream. With a ratio of 2, a stiff core with insufficient luminosity and soft edges is obtained. It must be assumed that the optimum ratio is in the range of 1-1.3.

The supply of an oxidizing agent of the first Rus in a ratio of flow rates between steep and gentle angles of more than 2 ensures that the oxidizing agent is supplied to the reforming in a larger quantity than is necessary for the reforming. Therefore, an excessive amount of it goes to combustion without providing the necessary reform; the radiation characteristics of the torch, the coverage area of the heated surface and the total heat transfer are reduced. The supply of an oxidizing agent in a ratio of less than 0.5 further reduces the portion of the oxidizing agent used for gas reforming, and thereby worsens its radiation characteristics and heat transfer, despite the increased intensity of the influence of gentle angles on the coverage area.

The location of the burner at a height of 5 minimum diameters of the fuel stream (300-400 mm) is advisable with a soft gas flow. Suitable for heating molten bath or for arranging afterburning of carbon monoxide over an oxygen bath. The location of the burner at an altitude of less than 5 diameters narrows the coverage area of the surface by a torch, reflected flows intensively develop, and during liquid periods spray formation and purge effect. The location of the burner at a height of 15 minimum diameters of the fuel jet (900-1000 mm) is advisable with a hard torch, designed to receive a large area of the torch exposure (periods of filling and heating). The location of the burner at a height of more than 15 diameters removes the torch from the surface, increases the heat loss for heating the working space, the convective component in the heat transfer decreases, although the heat transfer from the increase in the coverage area increases.

The supply of additional oxidizing agent with alternating jets with angles of inclination of 40-50 ° and 60-75 ° is advisable in cases where it is necessary to organize the heating of large areas of the bath with an average and low location of the burner (5-8 diameters), as well as to organize the supply of oxidizer over a larger surface to burn off carbon monoxide above it. Moreover, the alternation of jets in this case is mainly necessary to take into account the profile of the bath. The width of the jet is directed at an angle of 40-50 °, and the length of 60-75 °. The lower limits (40 ° and 60 ° are used for a high position of the burner in operation (800-1000 mm), and the upper ones (50 ° and 75 °) for the low (300-500 mm).

The addition of an additional oxidizing agent increases the efficiency of heat utilization and afterburning of gases. The supply of an oxidizing agent with an inclination angle of jets of less than 40 ° reduces the area of action of the torch and oxidizing agent and the efficiency of heat transfer. The supply of an oxidizing agent with an inclination angle of jets greater than 75 ° causes a portion of the oxidizing agent expiring at a critical speed to begin to detach from the bath and thereby detach the torch from the surface. The same is true for the carbon monoxide afterburning process ..

The ratio of the oxidizing agent consumption of the first and additional Russes during operation is maintained within the range of 0.1 ... 10. A ratio of 0.1 is used when using a carbon monoxide burner over a blown bath, when there is a need for an oxidizing jet to be fed to a large surface, and the gas nozzle is protected by special blowing. In this case, 1 part of the oxidizing agent is fed in the first channel to organize the protection of the nozzle from clogging and partial burning of carbon monoxide in the area. A ratio of 107 is applied when using a burner to heat a liquid bath with a low and medium position of the burner and a charge with an average and high position of the burner. In this version of the work, 10 parts of the oxidizing agent flows in the first rus and 1 part in the additional one, which serves mainly as a protection factor for nozzles from clogging with slag and metal spatter coming from both the burner and the blowing tuyeres.

The ratio is less than 0.1. Can lead to the sealing of slag and metal nozzles of the first Rus. A ratio greater than 10 may result in sealing nozzles of the auxiliary channel. The working practical range of the ratios for filling-heating is 10. Heating the metal in a finishing 7-10, while burning carbon monoxide with a small amount of fuel (400 m3 / h for blowing) - 0.3-0.7.

The oxidizer-fuel ratio in the periods of filling and heating is maintained within 1 in the medium and high burner arrangement variants (700-1000 mm), since the amount of oxygen introduced by the jets in this embodiment is high and the gas burning is complete. With a low location of the burner (300-500 mm) and for the most part. When using it to heat the metal in the finishing process, the amount of oxygen introduced by the jets due to their low development and low oxygen concentration in

environment decreases and, accordingly, set equal to 1.5.

: During the purge period of the bath with oxygen, the oxidizer-fuel ratio is assumed to be 2 in the low-carbon purge options (0.5% and below), when the metal is mainly heated not from the combustion of carbon monoxide, but from the burning of the fuel. The ratio (equal to 10 is taken in the variants of carbon monoxide afterburning when the bath is filled with oxygen from a high carbon angle (0.6% and higher), when the bath is heated mainly by burning 5 carbon monoxide, and the fuel is supplied only for protect the nozzle from clogging slag and metal.

The oxidizer-fuel ratio in the supply / heating and heating less than 1 will lead to a lack of fuel and loss of heat absorption, and more / more than 1.5 will lead to an excess of oxidizer; in the period of purging the bath with oxygen, a ratio of less than 2 does not provide combustion and

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kigani - reduction of heat absorption,

greater than 10 to irrational consumption of oxidizing agent.

Examples of specific performance.

The proposed method for heating hearth furnaces can be carried out both independently and in combination with other conventional ones.

Melting was carried out in the open-hearth furnace of the Zaporizhstal plant with a 250 t batch with the use of the actual end section. The burner was installed in the center: the main arch of the furnace, as an additional means of boosting the thermal operation of the furnace: by heating the charge during the warm-up period, heating the bath to melting by burning carbon monoxide, and the molten bath during the finishing period. The thermal modality of the burner is 16 million kcal / h; gas nozzle diameter 60 mm; gas flow rate of 1500-2000 m / h with a jet opening angle of 16-26 °, the oxidizer of the main path with a flow rate of up to 3000 m / h was supplied through 8 nozzles of Diameter 15 mm with alternating angles of 14-16 ° and 30-45 °; the oxidizer of the additional path was also fed through 8 nozzles with a diameter of 15JMM with alternating angles of 40–50 ° and 60–75 :, the path throughput was up to 25 ().

After loading the metal charge during the pre-heating period, the burner was seated in the working space and 1000 m / h of gas and oxygen were supplied. After verifying the normal course of combustion, the burner was seated 15-8 diameters (1000-700 mm) from the charge and added |) and instructions the rest of the gas (500 m / h) and Oxygen to a ratio of 1. During the heating and deposition of the charge, the position of the burner above the charge was adjusted. The use of additional heating provides heating of the metal charge 50-100 ° C higher, and this reduces the consumption of cast iron by 10-12 kg / teel and reduces the duration of the heating period by 30-50%, which means that the melting time is 5-8%, at the same time, specific fuel consumption was reduced by 5-7 kg / t and 1-2 m3 / t

0 oxygen.

When using the method for burning carbon monoxide over the blown bath (oxygen consumption for blowing 2500 m / h), the burner was seated in the working

5 space, a small amount of gas was supplied (up to 500 m / h) and primary and additional oxygen at 500 m / h. Then the burner was seated at a height of 5-7. diameters of the gas nozzle (300-500 mm) from the bath and

The remaining oxygen was supplied to an additional nozzle bed to a ratio of 0.33 (15, m / h), the oxidizer: fuel ratio was maintained equal to 4. During the afterburning operation (0.5-1 hour), or the metal temperature increased by 50-90 ° C or the process was carried out with reduced fuel consumption. The savings in terms of cast iron consumption was 10-15 kg / t or fuel 5-7 kg / t with an increase in oxygen consumption

0 to 4-6 m3 / t.

When using the method for heating the metal during the finishing period, the burner was seated in the working space, gas and oxygen were supplied in the first rus

5 nozzles of 1000 m / h. Then she sat down on the bathtub at a height of 5-7 diameters (300-500 mm), the rest was supplied with gas (500 m / h) and oxygen in the first rus - 1000 m / h and additional. Rusu

0 250 m3 / h, maintaining an oxygen: gas ratio of 1.5. The heating rate of the metal, depending on the state of the furnace, is 1.5-2.5 ° C / min. Fuel and oxygen savings averaged 5-7% of the specific

5 furnace costs.

The proposed heating method can be implemented on any hearth of a melting furnace consuming natural gas and oxygen.

The application of the proposed method of heating in hearth furnaces in comparison with the known methods allows to increase the efficiency of using the heat of combustion and afterburning of gases and the environmental friendliness of the process, which is manifested in the application of the method for heating the charge during its heating (it is possible to use it in filling), which It allows the process to be carried out to reduce the duration of the smelting period v as a whole, providing an increase in the unit productivity or an additional heat input to the batch with high efficiency and a reduction in the process consumption energy resources (cast iron, fuel); in the application of a method for re-burning carbon monoxide over a blown bath, which allows to introduce more heat into the bath by increasing the KIT of re-burning carbon monoxide and thereby reduce the period and cost of energy resources (cast iron, fuel); in the application of the method for heating the metal for fine-tuning, which allows to reduce the period duration and energy costs (cast iron, fuel, oxygen); in increasing the durability of the unit in connection with less intensification of its operation; in increasing the environmental friendliness of the process, as low noise and a reduction in the rate of formation of brown smoke during melting are provided; in high economic effect. V-. - .; .

Claims (3)

SUMMARY OF THE INVENTION 1. A method of heating a baking oven, comprising supplying fuel and an oxidizing agent through a vault and end burners during periods of filling the scrap, heating the charge and heating the bath, purging the bath with oxygen, and so on, so that , in order to increase the efficiency of using the heat of combustion and the environmental friendliness of the process, through the fuel is supplied by a central burner with a central jet with an opening angle of 16-26 °, and the oxidizing agent is fed with a light brown jet located around a circle around the central jets with alternating feed angles to the axis of the central fuel jet of 14-16 and 30-45 °, respectively, wherein the ratio of the oxidizer flow rate in alternating jets is 0.5-2.0. at the same time the slice of the vault burners during the heating period are located at a height of 5-15 minimum diameters of the fuel stream from the surface of the loaded charge. 2. The method according to claim 1, about t l and h a y u and s the fact that, in order to increase the efficiency of carbon monoxide afterburning, the oxidizing agent is additionally supplied with jets located around the first channel, the additional gas jets being directed alternating at angles to the axis of the central fuel jet of 40-50 and 60-75 °, respectively, and the expense ratio the oxidizing agent in the stream jets is maintained within the range of 0.1-10. - ...; 3. The method according to claims 1 and 2, with reference to the fact that the oxidizer-fuel ratio during periods of filling, heating the charge and heating the bath is maintained within 1-1.5, and during the purge period baths with oxygen-2-10.