RU2787915C1 - Device for high-temperature plasma blast heating - Google Patents

Abstract

FIELD: high-temperature blast.

SUBSTANCE: invention relates to devices for producing hot blast for industry, in particular, for blast furnaces. The device integrated into the gas path and designed to heat the blast contains electrode assemblies of the plasma torch, mechanisms for moving plasma electrode assemblies, a mechanism for building up electrodes, a mechanism for feeding new electrode sections. After the arc is ignited between the electrodes of the plasma electrode assemblies, by moving the hot ends of the plasma electrode assemblies, the arc is set to the desired position, ensuring arc burning in a perpendicular position relative to the axis of the pipe, providing a transverse vortex flow of gas around the hot ends of the electrodes and the arc with temperature control of the walls. In this case, the arc burns in the vortex channel, its position is stabilized by the vortex, without the arc being demolished by the gas flow lower in the direction of gas movement in the channel, thus stabilizing the parameters of the heated gas.

EFFECT: invention makes it possible to obtain a high-temperature blast with increased efficiency without restrictions on the resource of continuous operation, while the plasma arc is burning directly inside the gas path.

4 cl, 6 dwg

Description

The invention relates to devices for producing hot blast for industry, in particular for blast furnaces and devices.

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

The disadvantage of the known blast air heater is the low heating efficiency, due to high energy losses in the plasma torches, in the design of the wind tunnel, as well as high heat losses in the walls of the gas flow mixing 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 termination of the heating process, which is unacceptable in continuous industrial technology.

To obtain a high-temperature blast, with increased efficiency, without restrictions on the resource of continuous operation, a device for high-temperature plasma heating of the blast is proposed, in _which the plasma arc is burned directly inside the pipe (gas duct), in the gas flow, while in the pipe, as an integral part of the heater , due to its geometry, a special gas flow regime is organized, through a local smooth narrowing and subsequent sharp expansion behind the ledge, the electrode assemblies of the plasma heater and the plasma arc of the plasma torch are placed in the zone of the vortex axis, behind the ledge. The device for high-temperature plasma heating of the blast also includes pairs of identical electrode assemblies of the plasma heater with electrodes located perpendicular to the flow. There can be several such nodes, they are located inside the pipe (gas duct), in the gas flow, one after the other, while in the pipe, in front of each node, a local smooth narrowing and subsequent sharp expansion behind the step are organized, and the electrode nodes of the plasma heater are placed, and the plasma arc burns in the zone of the vortex axis behind the step.

The ledge is formed by the fact that inside the pipe is made with an asymmetric one-sided narrowing of the section in the direction of gas flow by 30-80% of its cross-sectional area on the one hand, in the form of a smoothly tapering section of the gas path pipe, with a length of 100-300% of the height and pipe wall width (or diameter).

The electrode assemblies of the plasma heater behind the ledge are placed in such a way that the generatrix of the electrode is hidden from the gas flow by the ledge and does not protrude above the upper point of the ledge. This ensures that there is no stretching and drift along the plasma arc flow.

The distance between the pairs of electrode assemblies of the plasma heater is chosen to be at least three characteristic dimensions of the pipe (diameter or side) so that the gas flow sufficiently reduces the turbulence in front of the next ledge to form a vortex behind it.

Each of the electrodes is equipped with a casing, which is made in the form of a closed pipe, covering the entire electrode along the perimeter, so that only the end part of the electrode protrudes from the casing in the pipe, while the length of the electrode part protruding from the casing is selected from the condition of ensuring protection of the casing surface from ingress arcs. A gap is made between the casing of the electrode assembly of the plasma heater and the electrode, with the possibility of supplying a protective gas between them. The electrode casing is provided with cooling channels and channels for supplying a protective gas along the electrode, for example, argon or nitrogen, the flow rate and speed of the protective gas are selected from the conditions for protecting the working part of the electrode in the arc burning zone in the pipe (gas duct) by blowing with protective gas. Protective gas reduces the harmful effect of the gas heated in the pipe on the electrodes and increases the service life. In particular, it has been experimentally established that the replacement of 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 assemblies of the plasma heater, with the electrodes placed in them, are taken out through the hermetic seal outside the walls of the gas path pipe, electrically insulated from each other and the pipe body, fixed 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 assembly of the plasma heater is provided on the outer side of the walls of the gas channel pipe with a device for supplying and a device for building up electrodes during operation, without stopping the process. This allows, when the electrode is consumed from the side of the working end, to continuously compensate for the consumable part, feed it in the direction of another electrode, and, as it is consumed, build it up from the outside, for example, by screwing, using additional sections of electrodes that are fed into the device for build-up of electrodes in the course of work, without a stop for process.

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

After ignition of the arc between the electrodes of the electrode assemblies of the plasma heater, by moving the hot ends of the electrode assemblies of the plasma heater, the arc is set to the required position, ensuring that the arc burns in a perpendicular position relative to the pipe axis, providing a transverse-vortex gas flow around the hot ends of the electrodes and the arc with wall temperature control. In this case, the arc burns in the vortex channel, its position is stabilized by the vortex, without the arc being blown 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 assemblies of the plasma heater for high-temperature plasma heating of the blast can be in operation.

The principle of operation of the device is as follows. Through the pipe of the supply gas path 2, the full flow of gas 1 is supplied to the consumer object, possibly preheated (see Fig. 1). The pipe of the supply gas path 3 can have a round or rectangular cross section, while the aspect ratio (height and width) is any, moreover, in Fig. 2 and 3 show cases where the narrowing of the cross section in the direction of gas flow can be up to 30% of the total cross section, and in Fig. 4 shows the case when the narrowing of the section in the direction of the gas flow can be up to 80% of the total section, the length of the narrowing section is 100-300% of the pipe diameter, or an equivalent diameter, if the pipe has a rectangular cross section. The entire gas flow passes through the plasma node - a device for high-temperature plasma heating of the blast, which is part of the specified gas path.

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 degrees Celsius or more.

Using the movement mechanisms 5, the arc heating electrode assemblies of the plasma heater 4 are set to the working position. The arc heating units are set in working position, the plasma arc is ignited. On the power source of the arc heating units and the units themselves, the installation of technological parameters (position, currents, voltages, shielding gas consumption) corresponding to the required operating mode is provided. The gas flow in the pipe, passing the swirler 3, is partially blown through the plasma arc 9 and additionally heated under the action of the plasma discharge formed on the section element by the plasma unit, and partially passes by it along the gas duct.

The position of the electrode assemblies of the plasma heater is chosen from the consideration of stable burning of the plasma arc, in a perpendicular arrangement relative to the axis of the pipe. The length of the part of the electrode protruding from the casing is chosen from the condition of ensuring the protection of the casing surface from arcing. The arc burns in a vortex flow stabilized by a ledge.

Part of the thermal power from the arc reaches the swirler 3 by radiation, and then it is dissipated by radiation and convection along the general gas flow and heats up the displaced gas flow.

By moving the electrode assemblies of the plasma heater, a given length of the plasma arc and the power of the plasma torches are provided.

In the presence of two or more pairs of plasma torches located in series one after the other, a consistent power distribution between the plasma torches is ensured. If it is necessary to regulate the temperature, or turn off one of the plasmatrons, the remaining ones change the power to maintain the gas temperature at a given level.

As the working sections of the plasmatron electrodes are consumed, a new section of electrodes 7 is built up on the outer part of the electrode, for example, by feeding and screwing, using special mechanisms 6, without stopping work, after which the electrode feed mechanism 8 in the electrode assembly of the plasma heater moves, with necessary, in the working space, at a given distance.

In FIG. 2-5 shows the possible designs of the swirler 3 and the choice of which is determined by a specific set of technical requirements, depending on the tasks to be solved for heating the blast.

In FIG. 6 shows the electrode assembly of the plasma heater, which is integrated into the existing section of the gas duct or pipe 2 and includes a graphitized electrode 11 located in a protective casing 12 and blown along the side surface with protective gas 15 entering through the protective gas inlet channel 10. The protective casing is made water-cooled , where water circulates through the water cooling channels 13, the electrode assembly of the plasma heater is also equipped with a current lead 14. As the graphite electrode is consumed, a new section of the buildup electrode 7 is installed from the cold end.

Claims (4)

1. A device for high-temperature plasma heating of the blast, comprising two opposite electrode assemblies of a plasma heater with an arc burning between them, characterized in that the body of the device is made in the form of a section of a gas path pipe with heat-insulated walls, inside the section of the gas path pipe is made in the form of a smoothly tapering section with an asymmetric unilateral narrowing of the section in the direction of gas flow by 30-80% of its cross-sectional area on one side, the length of the narrowing section is 100-300% of the height and width of the pipe or its diameter, followed by a sharp expansion of the pipe with a ledge from the side of the narrowing , while the electrode assemblies of the plasma heater, with electrodes fixed in them, are placed in the channel of the gas path pipe perpendicular to the axis of the channel, directly behind the ledge, in the zone of recirculating gas movement - the vortex to the ledge, in such a way that the generatrix of the electrode does not protrude above the ledge, is located below the top of the ledge a and is hidden from the gas flow by a ledge, while each of the electrodes is provided with a casing, which is made in the form of a closed pipe, covering the entire electrode along the perimeter, so that only the end part of the electrode protrudes from the casing in the pipe section of the gas path, while the length of the protruding a part of the electrode from the casing is selected from the condition of ensuring the protection of the surface of the casing from arcing, a gap is made between the casing of the electrode assembly of the plasma heater and the electrode with the possibility of supplying a protective gas between them, and the second ends of each of the electrode assemblies of the plasma heater, with electrodes placed in them through a sealed the seals are placed outside the walls of the gas path pipe, electrically insulated from each other and the pipe body, the electrode assemblies of the plasma heater are fixed on movable bases, with the possibility of their mutual movement relative to each other and relative to the pipe body, each of the electrodes is connected by appropriate current leads to a power source plasma arc. 2. The device according to claim 1, characterized in that each of the electrode assemblies of the plasma heater is electrically connected to the electrodes, is equipped with a displacement drive, is movable in the gas channel of the pipe and is equipped on the outside of the pipe walls of the gas channel with a device for feeding and a mechanism for build-up of electrodes in the course of work without a stop for process. 3. The device according to claim 1 or 2, characterized in that the electrode casing is provided with cooling channels and channels for supplying a protective gas along the electrode, for example, argon or nitrogen, the flow rate and speed of the protective gas is selected from the condition of ensuring protection of the working part of the electrode in the arc burning zone in the pipe of the gas path by blowing with protective gas. 4. The device according to any one of paragraphs. 1-3, characterized in that it contains one or more pairs of electrode assemblies of the plasma heater, with each pair of electrode assemblies of the plasma heater installed on the pipe section of the gas path one after the other, behind the ledge, perpendicular to the flow, and the distance between the pairs of electrode assemblies plasma heater - at least three characteristic dimensions of the pipe in the form of a diameter or sides.

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