RU2808499C1 - Method for high-temperature heating of blast furnaces and device for its implementation - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used for high-temperature heating of blast furnaces. The combustion of the plasma arc is organized directly inside the gas path, in which the gas moves towards the blast furnace, on an organized section of the pipe, with the gas flow at the entrance to the heating section divided into several gas path sleeves, gas swirling when supplied to the common chamber - the pipe and the mixing chamber, with cooling of the chamber wall due to the supply and blowing of part of the gas through it, with arc burning in a swirling flow of heated gas on the axis, with subsequent collection of the heated swirling gas in the mixing chamber while maintaining the swirl, tangential gas exit from the mixing chamber of the heating section into the gas tract. The outer ends of each rod electrode are located outside the device, equipped with a mechanism for increasing each electrode, a mechanism for supplying current and holding, and moving the rod electrode; the rod electrodes are made of electrically conductive material and are enclosed in protective cylinders. The arc in the chamber is ignited by bringing the electrodes located on the axis closer together, after which the electrodes are moved apart from each other, and the arc length is maintained within the length of the cylindrical chamber.

EFFECT: invention makes it possible to obtain high-temperature blast with increased efficiency without restrictions on the resource of continuous operation.

6 cl, 5 dwg

Description

The invention relates to a method and device for heating gas and producing hot blast for industry, in particular for blast furnaces and devices.

A known method and device for high-temperature plasma heating of blast in chemical reactors and hypersonic wind tunnels is a group of linear plasmatrons mounted on the walls of a pipe, for example, a wind tunnel, with subsequent supply of heated gas jets simultaneously into a common container; gas jets heated in plasma torches are summed up in a common cable, mixed with each other and with the gas flow, and form a heated jet in a common cable, which is then used for its intended purpose (Technology of electric arc gas heating: Textbook / M.F. Zhukov, G.-N B. Dandaron, V.K. Litvinov; Edited by M. F. Zhukov; Ural, Polytechnic Institute, Institute named after S. M. Kirov, Magnitogorological Mining and Metallurgist, Institute named after G. I. Nosov. - Sverdlovsk: UPI, 1988. pp. 24-29. Plasma electrotechnological installations. B.C. Cheredn., 2005 with 263, 297).

The disadvantage of the known blast air heater and heating method is the low heating efficiency, due to high energy losses in the plasma torches, in the walls of the gas flow mixing chamber, the need to significantly overheat the gases to ensure the average mass temperature, the need to compress gases to high pressures before supplying them to the chamber, limited service life , due to the limited service life of the electrodes of linear plasma torches without replacing them. Replacing the electrodes leads to the cessation of the heating process, which is unacceptable in continuous industrial technology. In some cases, compression is technologically impractical and unjustified, as, for example, in blast furnace blasting, where at a flow rate of several hundred thousand cubic meters per hour through a pipe with a diameter of 2000 mm or more, gas with a temperature of 1000-1300 ° C, at a speed of 60-90 meters per second is fed to the blast furnace, and it must be heated by 100-200 degrees.

To obtain high-temperature blast, with increased efficiency, without restrictions on the resource of continuous operation of the blast heating system, a method and device for high-temperature blast heating is proposed, in which the combustion of a plasma arc is carried out directly inside the pipe of the gas path in which the gas moves, in the general gas flow, in a duct, without additional compression, with the organization of a heating section in a common gas path, while the total gas flow is divided into several parts, due to the geometry of the gas path, a section of a special profile and a special gas flow regime are organized in it, so that the electric arc in The channel turns out to be placed in a gas flow swirling along its entire length, stabilizes and moves away from the walls by this flow on the axis, while giving power to the gas. In this case, the entire gas flow of the blast participates in heat exchange with the arc. The section consists of three coaxially hermetically sealed cylindrical sections inside the section, the two outermost of which have inlet openings at ends opposite to one another, providing the inlet gas flow with a co-current twist in the cylindrical channel, and the central one, of larger diameter, has an opening located tangentially for gas outlet. The divided gas flow partially passes through swirl devices at opposite ends of the heating section, and partially through the permeable walls of the channel, cooling it from the heat flow from the arc. Gas flows inside the pipe pass through the arc, remove power from it, while the gas heats up, and behind the device it reconnects into one flow in the gas path, i.e. - in the same pipe. Being part of the pipe, the device provides low hydraulic resistance to the gas pumped through the section.

The device for high-temperature plasma heating of the blast includes pairs of identical electrode units with electrodes placed in the cylindrical part of the section, located on the axis of the cylindrical section, in the direction of gas movement in the general gas flow.

The swirl chamber on each side of the pipe is formed from a local section of the gas duct, while the local section of the gas duct is formed into a cylindrical hollow working chamber formed by two cylindrical sections and a cylindrical central part located between them, a mixing chamber located symmetrically from each of the cylindrical sections, made by the cavity of the larger diameter, gas enters the swirl chamber tangentially from each of the ends of the pipes, and in this case the diameters of the outer cylindrical sections have a smaller diameter relative to the central section in the ratio of 1.1-3.0. Electrode units in cylindrical sections are placed coaxially in such a way that the gas flow along a vortex trajectory washes them, the hot ends of the electrode units and the plasma arc. This ensures the absence of stretching and drift along the plasma arc flow. The arc is blown by co-twirling flows moving counter to the mixing chamber, connecting in the center of the mixing chamber, after which the total flow is removed through a tangential hole in the mixing chamber.

Each of the electrodes is equipped with a casing, which is made in the form of a pipe covering the entire electrode along the perimeter with a gap, so that only the end part of the electrode protrudes from the casing in the pipe, and the length of the part of the electrode protruding from the casing is selected from the condition that the arc does not hit the casing. There is a gap between the casing of the electrode unit and the electrode, with the possibility of supplying a protective gas between them, for example, nitrogen, argon. The electrode casing is equipped with cooling channels and supply channels along the electrode of protective gas, for example, argon or nitrogen, the flow rate and speed of the protective gas are selected from the conditions for ensuring protection of the working part of the electrode in the arc burning zone in the pipe (flue) by blowing with protective gas. Shielding gas reduces the harmful effects of gas heated in the pipe on the electrodes and increases the service life. In particular, it has been experimentally established that replacing air with nitrogen increases the service life of the graphite electrode under the above-described operating conditions of this plasma heater by more than three times.

The second ends of each of the electrode units of the plasma heater, with the electrodes placed in them, are brought out through a hermetically sealed seal outside the walls of the gas path pipe, electrically insulated from each other and the pipe body, mounted on movable bases, with the possibility of their mutual movement relative to each other in the gas channel of the pipe and relative to the pipe body. Thus, by controlling the movement of each electrode, the required position of the electrode in the pipe, the position of the arc and the length of the arc are achieved.

The electrode unit is equipped on the outside of the gas channel pipe walls with a supply device and a device for extending electrodes during operation, without stopping the gas heating process. This allows, when the electrode is consumed from the side of the working end, to continuously compensate for the consumed part, feed it in the direction of another electrode, and, as it is consumed, increase it from the outside, for example, by screwing, using additional sections of electrodes that are fed into the device for building electrodes during operation, without stopping the process.

Each of the electrodes of the electrode units is connected by corresponding current leads to the plasma arc power source.

After igniting the arc between the electrodes of the plasma electrode units, moving the hot torns of the plasma electrode units, the arc is set to the required position, the required arc length and arc current are set to provide the specified heating power. A vortex flow of gas around the hot ends of the electrodes and arc is ensured, with control of the wall temperature. In this case, the arc burns in the vortex channel, its position is stabilized by the vortex, without the arc being carried away by the gas flow lower in the direction of gas movement in the channel, which stabilizes the parameters of the heated gas.

Depending on the requirements for the temperature of the gas flow, one, two or more pairs of electrode units of the device for high-temperature plasma heating of the blast may be in operation. They are located inside the pipe (gas duct), in the general gas flow, one after the other, or parallel to one another, while in the pipe each pair of electrode units, forming a heating device, is located in a chamber with swirling gas, which together with the units forms a heating device , with the subsequent release of the preheated gas into the direct-flow gas path, the electrode units of the plasmatron and the plasma arc burns in the zone of the vortex axis.

The device operates as follows, see Fig. 1-5.

In the gas path of blast, for example, blast furnace, preheated gas with a temperature of 900-1200 degrees, called cold blast, is supplied at full flow rate to a device for high-temperature heating. Cold blast from channel pos. 1 is divided into two or three gas flows, pos. 2, 3, and after heating in the device it again enters through hole 4 into the common gas channel pos. 5 heated, hot blast.

The high-temperature heating device consists of a gas rope section assembled from three parts - a cylindrical section with a swirler pos. 6, left, pos. 7. right, pos. 8 and central part, mixing chamber, pos. 9. The entire flow of supplied gas through the swirlers pos. 6 in pos. 8 and 7, fed into the device. In a cylindrical section, positions 8 and 7 can be additionally installed at the end of each section, in front of the central part of pos. 9, swirlers, i.e. - two swirlers for each section. The purpose of the swirler is to spin all the gas relative to the pipe axis with minimal pressure loss.

The temperature of the gas supplied to the inlet of the heater does not exceed the maximum operating temperature of the walls of the gas path, and can reach 1000 or more degrees Celsius. The gas passes in transit through a device for high-temperature heating of the blast, which is part of the specified gas path, and thanks to the swirlers, the gas supplied through the swirler paths is swirled in the cylindrical and central sections.

On the axis of the chambers there are two electrodes pos. 10, made, for example, of graphite. The electrodes are enclosed in a protective cylinder pos. 11, equipped with cooling ropes pos. 12, Between the protective cylinder pos. 11 and the electrodes pos. 10, protective gas can be supplied through the protective gas input channel 13. for example, nitrogen, argon. Electrodes in the protective cylinder pos. 11 pass on the rope axis through the hole in the end of pos. 14 cylindrical sections left, pos. 7, right, pos. 8, through the seal, pos. 15.

The electrodes in the protective cylinder are attached to the movement mechanism pos. 16, and with the help of the movement mechanisms, the electrode assemblies move through the seals along the axis. and the electrodes in the protective cylinder are installed on the axis of the heater in the working position relative to each other, with a gap. The electrodes are extended from the protective cylinders.

By moving the electrode units of the heater, the specified length of the plasma arc (pos. 17) and arc power are ensured. The position of the electrode units is chosen based on the consideration of stable combustion of the plasma arc; the arc burns in a vortex gas flow.

The electrode extension mechanism, pos. 18, and current supply pos. 19.

Cold blast flow from channel pos. 1, divided into two - three gas flows, pos. 2, 3, controlled using control valves pos. 20 installed in the gas path.

There can be two or more heating devices in the gas path, and they can be located either sequentially one after another, pos. 21, 22, or in parallel. pos. 24, 23.

To reduce heat losses into the walls of the heating area, its walls are made of permeable material, for example, permeable ceramics, for example, based on oxides (ceramic foam, lightweight materials, etc.). In this case, gas for cooling the walls enters through the third gas flow path, pos. 3, and then through the collectors pos. 25 goes to the outer walls of the cylindrical sections, left, pos. 7, right, pos. 8 and the central part, mixing chamber, pos. 9, and through them - into the chamber, cooling the walls and maintaining their temperature at a level close to the cold blast temperature.

When the device is operating, the electrodes in the protective cylinder at a set flow rate of cold blast gas through the heater section are inserted through the seals in the hole at the end of the cylindrical sections, installed in the working position opposite each other, by contact or voltage breakdown, an electric arc is ignited between them, and then spread along the axis , and set the arc length corresponding to the specified operating mode in terms of voltage and current, in accordance with the required temperature of the heated blast. Subsequently, the magnitude of current and voltage is controlled within the capabilities of the power source to establish the required heating mode. On the power source of the arc heating units and the units themselves, the installation of technological parameters (position, currents, voltages, shielding gas flow) corresponding to the required operating mode is ensured. Passing the gas path - the swirler, the gas flow is twisted, due to which the arc is established in the area of the channel axis, and the gas completely washes the plasma arc, as a result of which it is heated to the required level.

The gas in the heater moves towards each other in two swirling flows, and is partially diluted with gas entering the chamber through the permeable walls, entraining this gas into rotation. The gas blown through the walls reduces the harmful abrasive effect of the vortex, preventing dust particles from entering the chamber walls. The heated swirling gas flow on both sides occurs in the area of the central part, the mixing chamber, pos. 9. To ensure that the arc does not move toward the chamber wall when the flow turns in the area where the heated gas exits, and that the stabilizing effect of the vortex swirl is not disrupted, the mixing chamber is made short and of large diameter. The swirling gas flow, due to centrifugal forces, “dives” into a pocket of larger diameter, and through a hole in the wall of the channel, made tangential to the surface, is removed from the heating section into the gas path, heated to a given temperature.

As a rule, for example, in blast furnace blasting, the flow rate cannot be changed for technological reasons; it can only be redistributed along parallel paths. Consequently, temperature control is carried out only by the power of the arc discharge in the heater.

If there are two or more pairs of heaters located in series one after the other, a coordinated power distribution between them is ensured, taking into account preheating from the first heater. If it is necessary to regulate the temperature or turn off one of the plasma torches, the remaining ones change the power to maintain the gas temperature at a given level.

As the working sections of the electrodes are used up, a new section of electrodes 26 is added to the outer end of the electrode, for example, by feeding and screwing, using special mechanisms, without stopping work, and joined to the electrode assembly, pos. 27, after which the feed mechanism pos. 29 the electrode moves, if necessary, a specified distance.

Claims (6)

1. A method for high-temperature heating of blast in a gas heating path with gas supply through a heating device with an arc, characterized in that the entire volume of heated gas from a common gas channel is divided into at least three parts by control devices, one of the parts is supplied to the first swirling apparatus, the other part - into the second twisting apparatus, the third part - into a common channel with an arc through the permeable walls of the channel, all separated gas flows are connected in a common channel - the cylindrical mixing chamber of the heating device, while the gas supply through the first and second paths into the cylindrical mixing chamber is ensured with twisting and parallel, on the axis of the mixing chamber, electrodes are placed opposite each other, the arc is ignited and maintained on the axis, the distribution of flow rates along the paths is ensured in such a way that the peripheral gas velocity is sufficient to hold the arc between the electrodes without touching the wall, and the gas flow rate into the permeable wall of the channel - to prevent overheating of the wall material, while the arc is ignited by bringing the electrodes located on the axis closer together until electrical breakdown and the occurrence of an arc between them; after ignition of the arc, the electrodes are separated from each other using movement drives, moving along the axis maintains the length of the arc within the length of the cylindrical mixing chamber of the heating device, by controlling the flow rates, they eliminate the spatial instability of the arc and the displacement of the arc from the axis to the wall of the heating device and its destruction, while controlling the position of the electrodes and changing the current value ensures the specified power on the arc, changing the gas flow rate along each of the paths and power control the temperature of the gas and the permeable wall of the channel and ensure the spatial position of the arc in the mixing chamber of the heating device, and as the electrodes are consumed, they are continuously increased from the outside, while the increase is carried out mechanically using sensors that control the length of the electrodes as they are consumed, without removing the voltage and turning off heating device, wherein the gas heated in the heating device is fed further through an opening in the heating device into the blast gas supply path behind the heating device. 2. The method according to claim 1, characterized in that two or more heating devices are located in the heating path, and the position of the heating sections can be located parallel or in series one after the other. 3. The method according to claim 1, characterized in that as the electrodes are consumed, they are continuously built up from the outside by screwing together parts outside the heating device. 4. A device for high-temperature heating of blast by the method according to claim 1, characterized in that it contains a common gas supply path, a gas flow separation section at the entrance to the device, at least two gas inlet pipes and a common mixing chamber of the heating device, made in the form of three fastened between each other, each of which is equipped with a cylindrical channel inside, the cylindrical channels of the parts are coaxial, the central of the three parts, the common mixing chamber of the heating device is equipped with a cylindrical channel, the side cylindrical channels - vortex chambers - are equipped with a gas entry channel into the cylinders from the side opposite the common mixing chamber , with gas supply holes for each of them from the devices swirling the gas flow, with gas swirling in them in a co-direction relative to each other, while the ratio of the diameter of the central part of the cylindrical channel of the common mixing chamber to the diameter of the side cylindrical channels is 1.1-3, 0, and the length of the central part of the cylindrical channel of the common mixing chamber along the axis is 0.1-2.0 of the diameter of the side cylindrical channel, at each of the ends of the cylinders of the side channels on the axis there are holes with rods located in them, fixed with the ability to move in the protective cylinder stackable electrodes, one electrode on each side of the chamber, located coaxially with the cylinder, a hermetic seal and electrical insulation are made between the hole and the protective cylinder with the electrode, while the outer ends of each rod electrode are brought outside the device, equipped with a movement mechanism and a mechanism for extending each electrode by make-up during continuous operation of the device, a mechanism for supplying current and holding, and moving the rod electrode, the rod electrodes are made of electrically conductive material, enclosed in protective cylinders with a gap between the electrode and the protective cylinder, on the outside of the device there are pipes for supplying gas protecting the electrodes to the protective cylinders cylinders, into the gap between the cylinders and the electrodes, the drive for moving the electrodes along the axis has a stroke to move the electrode from the end of the cylindrical channel to contact with each other inside the chamber, both mentioned side cylindrical channels and the common mixing chamber of the heating device are under a floating potential and electrically isolated from both end electrode units and each other, while the mixing chamber of the heating device has a hole for the gas outlet, located perpendicular to the axis of the vortex chambers, tangential to the generatrix of the internal diameter of the mixing chamber in the direction of the gas rotation vector, while the upper point of the generatrix of the hole is a continuation of the surface of the generatrix mixing chamber, with each of the gas input channels equipped with a gas flow control device. 5. The device according to claim 4, characterized in that both vortex chambers and the mixing chamber are made of material permeable to gas, equipped with external casings - collectors for organizing their cooling by supplying gas through the walls, each of the casings is equipped with a gas duct connected to a common channel gas supply through an additional channel, with flow control devices for supplying gas through their permeable walls into the chamber of the device, and both cylinders on the side of the mixing chamber are equipped with additional swirling devices that form vortex chambers that supply gas through each of them, with gas swirling into them in in a co-direction relative to each other and the general gas flow. 6. The device according to claim 4, characterized in that the rod electrodes are made of electrically conductive material in the form of graphite.

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