Electric arc plasma torch

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to electric arc gas heaters – plasma torches, used to produce low-temperature plasma jets with stable mass and thermal characteristics based on various gases – oxidizing, reducing, aggressive, condensing and their mixtures, and can be used in the metallurgical and chemical industries, mechanical engineering, energy, and ecology. The electric arc plasma torch consists of a common mixing chamber with a side opening for the plasma jet to exit, and two identical vortex chambers on either side of the common mixing chamber. Each vortex chamber includes a cooled cylindrical channel, a magnetic system in the form of a solenoid, a diaphragm, a rod-shaped extendable electrode placed at the end of the vortex chamber, and gas chambers for supplying plasma-forming gas. A mechanism for holding and feeding the rod electrode and current-carrying elements are installed on the rod-type extendable electrode. Both vortex chambers are hermetically mounted on a common mixing chamber. The rod electrode continuously grows during operation.EFFECT: increase in the reliability, continuous operation life and thermal efficiency of the electric arc plasma torch.2 cl, 3 dwg

Description

[0001] The proposed invention relates to the field of electrical engineering, namely to electric arc gas heaters (plasma torches) used for the purpose of obtaining stable, in terms of mass and thermal characteristics, jets of low-temperature plasma based on various gases - oxidizing, reducing, aggressive, condensing and their mixtures, and can be used in the metallurgical and chemical industries, mechanical engineering, energy, and ecology.

[0002] The closest plasma torch in terms of operating principle and design (prototype) is the one described in the book (Plasma torches: designs, characteristics, calculation / A.S. Koroteev, V.M. Mironov, Yu.S. Svirchuk. - M: Mashinostroenie, 1993, pp. 27-29, 55-58). The plasma torch consists of a common mixing chamber with a side opening for the plasma jet outlet and two vortex chambers, each of which includes a cylindrical electrode with a magnetic coil mounted on it in the form of a solenoid, a narrowing profiled channel - a confuser, and an igniting needle electrode. The confuser can be made either solid or formed by a set of interconnected water-cooled washers, on one side of the inner surface of which a visor is made, and on the opposite side of the washer a cut is made.A plasma gas supply ring made of electrically insulating material is installed between the cylindrical electrode and the confuser. It contains gas supply holes located tangentially to the inner surface of the plasma torch's gas discharge chamber. All plasma torch components are firmly secured longitudinally through insulators with studs, forming a sealed inner chamber. The arc's electrical column in this type of plasma torch burns along the entire channel, and the near-electrode spots, driven by the magnetic field and gas vortex, circulate circumferentially and move longitudinally along the cylindrical electrodes, subsequently forming a narrow, circular, eroded groove on them.

[0003] The described plasma torch circuit has a number of disadvantages:

[0004] 1) High dependence of the stabilization of the electric arc on the plasma torch axis on a number of factors: the current value, the flow rate and speed of the plasma-forming gas (circumferential and longitudinal), the physical characteristics and quantitative distribution of the plasma-forming gas across all supply units.

[0005] 2) Limited time resource of continuous operation of electrodes, primarily the cathode, and the need for periodic replacement of worn-out cylindrical electrodes with new ones, which is associated with the shutdown of the plasma torch.

[0006] 3) Change in the length of the electric arc caused by the movement of near-electrode spots along the cylindrical electrodes in the circumferential and longitudinal directions, leading to pulsation of the power and temperature of the outgoing plasma jet.

[0007] The technical problem, which the proposed invention is aimed at solving, is to ensure a long-term continuous operation mode of the electrodes (from 1000 hours and more), to increase the thermal efficiency of the plasma torch, with the possibility of precise regulation of the mass and thermal parameters of the plasma outflowing jet over a wide range and the possibility of using inert, oxidizing, aggressive and condensing media as plasma-forming gases.

[0008] The technical result of the proposed group of inventions consists in increasing the reliability and service life of continuous operation of the plasma torch and increasing the thermal efficiency.

[0009] To solve the specified technical problem and achieve the technical result, an electric arc plasma torch is proposed, consisting of a common mixing chamber, with a side opening for the exit of the plasma jet, and two identical vortex chambers (anode and cathode), each of which contains a cooled cylindrical channel, a magnetic system in the form of a solenoid, a diaphragm, a rod-shaped extendable electrode placed at the end of the vortex chamber, and gas chambers for supplying plasma-forming gas.

[0010] The common mixing chamber is a solid metal element of the plasma torch, containing a cooling jacket. Both vortex chambers are sealed and secured to it on both sides through an insulator. The axis of the plasma jet outlet channel of the common mixing chamber can be configured to either cross or intersect with the axis of the plasma torch.

[0011] At the ends of the cooled cylindrical channel, for each of the vortex chambers, chambers (vortex and straight-through) for supplying plasma-forming gas are installed, with the vortex chamber installed at the end, on the side of the common mixing chamber, and the straight-through chamber located at the opposite end, on the side where the mechanism for holding and feeding the electrode is located.

[0012] The common mixing chamber and both cooled cylindrical channels have a floating potential during plasma torch operation.

[0013] The common mixing chamber and both swirl chambers have a closed cooling circuit consisting of short, parallel-connected electrically insulating cooling channels connected to the inlet and outlet cooling manifolds.

[0014] Rod-type, extendable electrodes placed on the ends of the plasma torch allow for a fixed arc length along the axis. This allows for the power input to be maintained over a wide range of plasma gas flow rates, without power or temperature fluctuations in the outgoing plasma jet, and facilitates arc stabilization along the plasma torch axis.

[0015] The electrode holding and feeding mechanism automatically feeds the growing rod electrodes axially into the plasma torch's gas-discharge chamber, based on the potential difference between the growing rod electrode and the diaphragm of the cooled cylindrical channel. Combined with the ability to grow the rod electrodes by fastening them together, it compensates for rod electrode erosion by feeding them as they burn out. This, along with protecting the rod electrode with a gas inert to the electrode material, ensures a long service life of 1000 hours or more for the plasma torch. Furthermore, the plasma torch's internal chamber is not subject to arc erosion and can be used indefinitely.

[0016] Figure 1 shows an electric arc plasma torch consisting of a common mixing chamber 1 connected through insulators 2 with anode and cathode vortex chambers 3 and 4, respectively. Each of the vortex chambers includes a cooled cylindrical channel with a diaphragm 5, a magnetic system 6 for stabilizing the arc, a vortex 7 and a straight-through 8 chamber for feeding the plasma-forming gas, a butt plate 9 connected to the vortex chamber through an insulator 10 and an electrode holding and feeding mechanism 11.

[0017] To cool the plasma torch components, its design incorporates parallel cooling circuits 12, 13, 14, 15, and 16, which are connected to the inlet and outlet cooling manifolds via short electrically insulating channels. At the start, cascade arc breakdown occurs across gaps 17, 18, 19, and 20.

[0018] Figures 2 and 3 show options for organizing the channel for the plasma jet flowing out of the nozzle from a common mixing chamber. The figures depict:

[0019] Figure 2: A section of the common mixing chamber showing that the axis of the nozzle 21 outlet jet channel intersects with the axis of the plasma torch 22.

[0020] Figure 3: a section of the common mixing chamber, which shows that the axis of the outlet jet channel of the nozzle 21 does not intersect with the axis of the plasma torch 22.

[0021] The electric arc plasma torch operates as follows.

[0022] The required coolant flow rate, with a temperature above the plasma gas dew point, is supplied through the plasma torch cooling jackets, thereby preventing gas condensation on the surface of the plasma torch working chamber. The specified plasma gas flow rate is then supplied to the gas-vortex rings for supplying the plasma gas. Magnetic solenoids located on the vortex chambers are activated. Open-circuit voltage is applied from the plasma torch power source to the growing rod electrodes via the current-carrying elements of the end electrode assembly. An oscillator causes a cascade breakdown of four gaps, followed by stabilization of the electric arc on the gas-discharge chamber axis. In the plasma torch gas-discharge chamber, the plasma gas interacts with the arc, heats up, and exits the common mixing chamber into the external environment, to the consumer. In this case, the growing rod electrodes are protected by a gas that is inert to them.

[0023] Example.

[0024] An electric arc plasma torch with the following internal dimensions of the vortex chambers: length L1=0.01÷0.04 m, diameter D1=0.02÷0.03 m, and internal dimensions of the common mixing chamber: l1=0.05÷0.06 m, l2=0.15÷0.2 m, d1=0.02÷0.025 m, d2=0.01÷0.015 m, was tested on an experimental bench. The plasma-forming gas in the form of "dry" water vapor with a temperature of 150-300°C, with a total flow rate of 10÷15 kg / h is fed into the plasma torch chamber through the vortex chambers for supplying the plasma-forming gas. A protective plasma-forming gas (argon) was supplied to protect the rod electrodes (in this case, graphite) through straight-through plasma-forming gas supply chambers with a total flow rate of 50 l / min. Distilled water circulated under excess pressure through the plasma torch element cooling jackets with a total flow rate of 25 m3 / h at a temperature in the range of 105-120°C.The lower value of the cooled water temperature is explained by the prevention of condensation on the structural elements of the plasma torch, and the upper value of the temperature is explained by the prevention of boiling of water in the cavities of the closed water-cooling system, at the lowest pressure of 0.2 MPa. The temperature difference of the cooling channel at the inlet and outlet of the vortex chamber lies in the range of 2 ÷ 6 °C. The arc current varied in the range of 170 ÷ 500 A, the arc voltage - from 300 to 1200 V. The power input to the arc varied in the range of 55 to 500 kW, while the thermal efficiency of the plasma torch was more than 80%, with the main heat flow falling on the common mixing chamber. The remaining thermal power is removed by the coolant into the cooling system. The plasma torch operating mode is stable and continuous.

Claims

1. An electric arc plasma torch consisting of a common mixing chamber with a side opening for the outlet of a plasma jet and two vortex chambers, characterized in that each of the vortex chambers is equipped on the side opposite the common mixing chamber with extendable rod electrodes located coaxially with the vortex chamber, and both cylindrical channels included in the vortex chambers and the common mixing chamber are under a floating potential and are electrically isolated from each other and from both end electrode assemblies, the outer ends of the extendable rod electrode are designed with the possibility of extension by fastening / screwing during continuous operation of the plasma torch through a mechanism for holding and feeding the rod electrode.

2. An electric arc plasma torch according to paragraph 1, characterized in that both vortex chambers are installed and hermetically secured on a common mixing chamber through electrical insulators from each other, wherein the cooled cylindrical channels of both vortex chambers and the common mixing chamber are under a floating potential, the axis of the output nozzle of the common mixing chamber, perpendicular to the longitudinal axes of the vortex chambers, is made not intersecting with the axis of the plasma torch, and wherein the ratio of the diameter of the internal channel of the common mixing chamber, coaxial with the plasma torch, to the diameter of the channel of the vortex chambers is 0.3÷1.

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