US3541625A - Induction plasma torch - Google Patents

Induction plasma torch Download PDF

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Publication number
US3541625A
US3541625A US689143A US3541625DA US3541625A US 3541625 A US3541625 A US 3541625A US 689143 A US689143 A US 689143A US 3541625D A US3541625D A US 3541625DA US 3541625 A US3541625 A US 3541625A
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United States
Prior art keywords
gas
casing
plasma
apertures
supply
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Expired - Lifetime
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US689143A
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English (en)
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Anthonie Jan Burggraaf
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Individual
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Individual
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/30—Plasma torches using applied electromagnetic fields, e.g. high frequency or microwave energy

Definitions

  • the invention relates to an induction plasma torch for heating finely divided material.
  • the torch is provided with a cylindrical casing surrounded by an induction coil, the casing has a seal at one end through which are provided at least one supply aperture for a stream of gas, which travels along the inner wall of the casing.
  • a second supply aperture is provided for a stream of a mixture,
  • the torch is used for heating or melting pulverulent or gritty material having a high melting point such as refractory oxides or carbides of nuclear fuels.
  • the gas is conducted through the casing and out on a side other than through which the gas enters the casing.
  • a recurrent problem of the prior art torches occurs due to the relatively large quantity of gas required for the desired stability of the plasma; consequently the stay or period of suspension of the particles of the pulverulent or gritty material in the plasma is often too short to process an intended quantity of material.
  • a plurality of factors, such as the velocity of the gas along the wall, the quantity of mixture per unit of time, the composition of said mixture and the supplied radio-frequency energy must be relatively adjusted so as to achieve the desired stability of the plasma, and the adjustment is particularly critical especially if a longer stay of the pulverulent material in the plasma is desired. If the melting behaviour of the powder in a plasma obtained by radio-frequency induction does not satisfy the expectations and if one or more adjustments must be modified to this end, one is concerned time and again with the less satisfactorily controllable stability of the discharge.
  • An object therefore of this invention is to provide an induction plasma torch with which the said operating adjustments can be realized without too much critical interdependence.
  • the cylindrical casing is sealed in a gastight manner at one end; the other end is provided with a seal through which there are supply apertures for gas for pulverulent material mixed with gas, and, one or more exhaust apertures for conducting away the gas plasma from within the casing.
  • a radio frequency induction coil surrounds the casing at the gastight sealed end.
  • the gas stream enters and moves along the wall such that at the area near the coil there is present an outermost gas stream moving towards the sealed end of the casing and an inner gas stream moving in the opposite direction and displaced more towards the centre of the casing.
  • the stabilization of the gas plasma discharge generally improves when less heat is dissipated. It is an advantage therefore to have a gas flow produced such that the heat therein carried along the wall by the gas stream is fed back within the discharge area rather than being dissipated through the casing walls. It has been found that with such a torch, the quantity of gas to be supplied per unit of time under otherwise identical conditions may be considerably smaller than if the gas is conducted away from the casing at the end remote from the inlet side. This reduced supply of gas renders a longer stay of the finely divided material possible which is further increased because the direction of the gas stream towards the centre of the casing is opposite to that of the stream of the particles.
  • a further advantage of the plasma torch according to the invention is that the gas reversing its direction at the sealed end of the casing and supplied along the Wall supplies heat to the molten material collected in situ so that the melting bath provided for this purpose may be larger than if heating only took place by the plasma extended in the direction of the melting bath.
  • the orifice of at least one exhaust duct on the same side as the end of the casing where the gas is supplied is preferably located more closely to the axis than the apertures of one or more ducts for the supply of gas only.
  • said supply apertures are arranged concentrically about the axis, the orifices for a plurality of exhaust ducts being arranged concentrically at a smaller distance from the axis, the assembly of apertures and orifices being arranged concentrically about a duct in the axis for supplying a gas stream which is mixed with the pulverulent or gritty material.
  • the supply of grit may take place in a larger section through an annular aperture or a plurality of apertures around a central aperture, the latter being used in that case for conducting away the gas.
  • the figure shows an induction plasma torch having a space 1 enclosed by a casing 2 within which the electric gas discharge, called plasma, takes place.
  • the casing 2 is made of an insulating material having a high melting point and causing no considerable dielectric losses when using a radio-frequency induction field.
  • the casing usually consists of quartz or of a double-walled quartz tube, a coolant being led through the interspace.
  • An induction coil 3 consisting of one or few turns surrounding the casing may be connected to a radio-frequency generator of known construction which is therefore not shown.
  • the coil 3 Upon energizing, the coil 3 induces a magnetic field of high frequency in the space 1 within the casing 2, and a suitable gas atmosphere for producing a plasma is created.
  • argon is used as a filler gas for the ignition, however once the plasma is obtained other gases for example, nitrogen is usable for maintaining the plasma.
  • the argon gas is supplied in known manner and is replaced by nitrogen gas when the tube is normally operating.
  • Supply ducts in transverse wall or seal 4 terminate in the space 1 within the casing and admit a gas flow which travels along the inner wall of the casing, the path of travel being indicated by dashed line 6.
  • the gas flows along the casing wall to the opposite end of the casing, there it is deflected inwardly and then flows in the reverse direction toward the direction of entry.
  • the plasma gas is conducted away, through exhaust apertures 7 provided in the seal 4 said apertures being located at a shorter radial distance from the centre than the supply apertures 5.
  • the material to be melted is supplied through tube in the centre in the seal 4 which tube has anaperture 11 for axial passage of a gas stream carrying with it the grit or powder to be melted.
  • the casing 2 is sealed against the passage of gas at the opposite end by a transverse wall 8 having a cup-like depression 9 in which the molten material is collected and forms a melt.
  • the direction of the probable gas flow as shown is obtained when the supply ducts 5 terminating through the seal 4 are to some extent placed tangentially at an angle. It has been found that with a gas flow of sufiicient intensity for stabilizing the plasma, the stream will convey the plasma away from the casing wall and thus prevent melting. The flow will follow the wall and deflect upward at the sealed end of the casing whereas with an axial supply of gas, the gas density along the wall is smaller and a stronger flow is necessary for sufficient stabilization and heat insulation. The plasma will become unstable either with too high or too low a velocity of the gas. It has been found that with an adjustment of the gas supply between 5 and L/min.
  • the inside diameter of the casing is between 70 and 95 mms.
  • Such a plasma torch may be loaded with 18 to 25 kw. Observations proved that the gas moving along the transverse wall 8 contributes considerably to maintaining the collected, molten material in the cup-like depression 9 at its melting point and if the melting bath is not heated separately, an etfective engagement of the diameter of the melting bath is obtained in that the plasma widens on the melting surface.
  • the location of the exhaust apertures is not limited to the region within the ring of supply apertures.
  • the exhaust apertures may be provided between the supply apertures such that the conducting away of the gas does not interfere with the supply of gas.
  • An induction plasma torch for heating finely divided material comprising a cylindrical casing, an induction coil surrounding the casing, a first seal at one end of the casing, a second seal at the other end of the casing, said first seal defining at least one gas supply aperture therein for supplying a stream of gas along the inner wall of the casing in the area of the coil, said stream being reversed at the opposite and sealed end of the casing and deflected inwardly and in the direction of entry, at least one additional aperture defined by said first seal for supplying a stream of gas contained finely divided material, the last mentioned stream being directed along the axis of the casing, and at least one exhaust aperture defined by said first seal for conducting away gas from within the casing.
  • a plasma torch as claimed in claim 2 wherein gas supply apertures and exhaust apertures are arranged concentrically about a central aperture.
  • An induction plasma torch for heating finely divided material comprising a cylindrical casing, transverse walls sealing both ends of the casing, an induction coil surrounding the casing, a central aperture and a plurality of concentric apertures defined by one of the transverse walls, wherein a gas is supplied through the radially outermost aperture, a gas containing finely divided materials is supplied through the central aperture and the resultant plasma gas is removed through exhaust apertures positioned radially intermediate the central and outermost apertures.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Electromagnetism (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Plasma Technology (AREA)
US689143A 1967-01-06 1967-12-08 Induction plasma torch Expired - Lifetime US3541625A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6700212A NL6700212A (ja) 1967-01-06 1967-01-06

Publications (1)

Publication Number Publication Date
US3541625A true US3541625A (en) 1970-11-24

Family

ID=19798922

Family Applications (1)

Application Number Title Priority Date Filing Date
US689143A Expired - Lifetime US3541625A (en) 1967-01-06 1967-12-08 Induction plasma torch

Country Status (9)

Country Link
US (1) US3541625A (ja)
AT (1) AT284286B (ja)
BE (1) BE708971A (ja)
CH (1) CH473472A (ja)
DE (1) DE1286241B (ja)
FR (1) FR1550698A (ja)
GB (1) GB1149473A (ja)
NL (1) NL6700212A (ja)
SE (1) SE342731B (ja)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4169962A (en) * 1974-10-02 1979-10-02 Daidoseiko Kabushikikaisha Heat treating apparatus
US5046145A (en) * 1990-04-20 1991-09-03 Hydro-Quebec Improved arc reactor with advanceable electrode
US5949193A (en) * 1995-10-11 1999-09-07 Valtion Teknillinen Tutkimuskeskus Plasma device with resonator circuit providing spark discharge and magnetic field
US20160096241A1 (en) * 2014-10-07 2016-04-07 Caterpillar Inc. Consumable insert for welding

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4266113A (en) * 1979-07-02 1981-05-05 The United States Of America As Represented By The Secretary Of The Navy Dismountable inductively-coupled plasma torch apparatus
NO174180C (no) * 1991-12-12 1994-03-23 Kvaerner Eng Innföringsrör for brenner for kjemiske prosesser
GB2490355B (en) * 2011-04-28 2015-10-14 Gasplas As Method for processing a gas and a device for performing the method
WO2020041597A1 (en) 2018-08-23 2020-02-27 Transform Materials Llc Systems and methods for processing gases
US11633710B2 (en) 2018-08-23 2023-04-25 Transform Materials Llc Systems and methods for processing gases

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3210454A (en) * 1962-05-17 1965-10-05 Alloyd Electronics Corp High temperature apparatus
US3296410A (en) * 1962-06-20 1967-01-03 Atomic Energy Authority Uk Induction coupled plasma generators
US3343027A (en) * 1963-08-10 1967-09-19 Siemens Ag Arc plasma device having gas cooled electrodes containing low work function material

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3210454A (en) * 1962-05-17 1965-10-05 Alloyd Electronics Corp High temperature apparatus
US3296410A (en) * 1962-06-20 1967-01-03 Atomic Energy Authority Uk Induction coupled plasma generators
US3343027A (en) * 1963-08-10 1967-09-19 Siemens Ag Arc plasma device having gas cooled electrodes containing low work function material

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4169962A (en) * 1974-10-02 1979-10-02 Daidoseiko Kabushikikaisha Heat treating apparatus
US5046145A (en) * 1990-04-20 1991-09-03 Hydro-Quebec Improved arc reactor with advanceable electrode
US5949193A (en) * 1995-10-11 1999-09-07 Valtion Teknillinen Tutkimuskeskus Plasma device with resonator circuit providing spark discharge and magnetic field
US20160096241A1 (en) * 2014-10-07 2016-04-07 Caterpillar Inc. Consumable insert for welding
US9545693B2 (en) * 2014-10-07 2017-01-17 Caterpillar Inc. Consumable insert for welding

Also Published As

Publication number Publication date
GB1149473A (en) 1969-04-23
CH473472A (de) 1969-05-31
FR1550698A (ja) 1968-12-20
BE708971A (ja) 1968-07-04
SE342731B (ja) 1972-02-14
DE1286241B (de) 1969-01-02
NL6700212A (ja) 1968-07-08
AT284286B (de) 1970-09-10

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