US3818845A - Low temperature plasma incinerator and method of stabilizing impedance therein - Google Patents

Low temperature plasma incinerator and method of stabilizing impedance therein Download PDF

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Publication number
US3818845A
US3818845A US00209879A US20987971A US3818845A US 3818845 A US3818845 A US 3818845A US 00209879 A US00209879 A US 00209879A US 20987971 A US20987971 A US 20987971A US 3818845 A US3818845 A US 3818845A
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United States
Prior art keywords
tube
incinerator
gas
zone
incineration
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Expired - Lifetime
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US00209879A
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English (en)
Inventor
H Nakane
A Uehara
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Tokyo Ohka Kogyo Co Ltd
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Tokyo Ohka Kogyo Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
    • F23G5/08—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having supplementary heating
    • F23G5/10—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having supplementary heating electric
    • 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

  • ABSTRACT Rapid incineration of organic materials in a low tem- I 30 F A perature plasma incinerator for generation into a 1 Drug pphcauon nomy Data plasma by an applied high frequency electric field sup- DCC. 21, I970 Japan; yg g and maintained at a uumby a vacuum pump is promoted by introducing a b51050?
  • a cylindrical reaction tube of quartz or glass is evacuated to a pressure less than about Torrs with a vacuum pump and a high-frequency high voltage is applied to electrode plates disposed on the outside of the reaction tube by a high-frequency oscillator connected to the electrode plates, whereby a plasma of the gas remaining in the reaction tube is generated. If oxygen gas is introduced under such conditions into the reaction tube containing organic material, an oxygen plasma is produced, the material is incinerated to ashes by the action of this oxygen plasma.
  • theincineration rate is affected by various factors such as, for example, the level of voltage applied, the kind of gas introduced (such as oxygen, nitrogen, hydrogen and the like), the rate of introduction of such gas, and the nature of its flow (either laminar flow or turbulent flow).
  • the most important factor, however, is the matching of the impedance at the, electrical output of the oscillator with the impedance at the incineration reaction tube. The effect of such matching of impedance is great, particularly in the case of an apparatus of large processing capacity.
  • Another cause of a variation in impedance is a change in the flow rate of the gas introduced. It often occurs that the incineration operation is carried out by changing the flow rate of the gas introduced while keeping the power output constant. For instance, where the amount of the material to be treated is large, the gas may be initially introduced in a great quantity and gradually reduced in amount as theprocess proceeds. Also, when treating a wafer, the gas flow rate is adjusted according to the thickness of the photo-resist layer thereupon. In general, impedance decreases in proportion to increases in the level of vacuum, resulting in increased consumption of electric power. On the other hand, if the level of vacuum is lowered, the impedance increases and the power consumption is reduced. There exists, however, a level of vacuum below which it may become impossible to generate any plasma. 7 I
  • a method and apparatus for preventing variation in the impedance of the system in question characterized in that a suitable flow of a secondary gas is introduced through a secondary gas inlet provided between the exhaust port of the reaction tube and the vacuum pump, in accordance with any increase or decrease of the rate of primary gas flow into the reaction tube, while the interior of the reaction tube is kept in a high vacuum condition by use of a vacuum pump having a large dis charge capacity, thereby maintaining constant the level of vacuum in the reaction tube by maintaining the total flow of the two gases through the system substantially constant.
  • the incinerator reaction tube may include a cover or tion.
  • the feature of the invention has the further ad vance that even if the operator inadvertently neglects to disconnect the vacuum pump to restore normal pressure after completion of the incineration operation, no back flow of oil to the vacuum pump will result since air or other secondary gas is allowed to flow in gradually through the inlet.
  • a vacuum pump having a large discharge capacity and the intake of the secondary gas is controlled so that the amount of secondary gas is larger than the amount of primary gas fed into each incineration reaction tube.
  • the level of vacuum in each incineration reaction tube should be less than Torrs. Below 8 Torrs, a perfectly stabilized plasma can be obtained.
  • the flow rate of primary gas introduced thereinto is usually 1 l/min per tube at most.
  • the primary gas will ordinarily be oxygen to effect incineration of the organic materials but, where other gases are known for use for this purpose in the art, they are equally suitable in the context of this invention.
  • Air is extremely convenient for this purpose as it can be merely drawn from the atmosphere but other gas, which do not deleteriously affect the system, could be substituted if desired.
  • a plasma low-temperature incinerator constructed as shown in the drawing was used.
  • Three incineration reaction tubes 1, 1' and 1" (each 75 mm in diameter and 400 mm in length) having individual gas inlets, 2, 2' and 2" and gas discharge pipes 3, 3 and 3" were connected together through a distributing manifold 4 and a collecting manifold 5.
  • a gas feed inlet port 6 of the distributing manifold 4 was connected through a pipe 9 to an oxygen gas bomb (not shown), with a flowmeter 8 having a needle valve 7 arranged at a suitable location along pipe 9, so as to allow oxygen gas to flow into the system as a primary gas.
  • the exhaust port 10 of the collecting manifold 5 is connected to a vacuum pump preferably having a discharge capacity of about 150 l/min (now shown). Between the exhaust port 10 and the vacuum pump is provided a secondary gas inlet 11 to which a flow-meter 13 having a needle valve 12 is connected and through which a secondary gas (for example air) 14 is introduced.
  • a secondary gas for example air
  • l' and 1" are provided pairs of opposed metal plates l5, l6, l5, l6 and 15", 16" to serve as electrodes, to which a 3.000- volt, 13.56-MI-Iz high-frequency oscillator is connected.
  • each needle valve is closed and the vacuum pump is operated until the pressure in each incineration reaction tube is reduced to 0.2 Torrs in about 3 minutes.
  • a high-frequency output power of about 300 W is applied to the electrodes of each incineration reaction tube, whereupon generation of plasma is observed and the impedances at the electrical output of the oscillator and at the incineration reaction tubes are matched by adjusting a variable condenser in the oscillator, If the output is increased to the level of 1,000 W under this condition, plasma spreads out to gas inlet and outlet ports of each incineration reaction tube (as in the case of a neon tube) and, when this occurs, it is no longer possible for the variable condenser to control the plasma so as to retain it inside the reaction tubes.
  • the output power is usually reduced to the level of 500 W in operation, but this is not economical.
  • oxygen gas is introduced into each incineration reaction tube at a flow rate of 200 to 300 ml/min, the pressure in each tube slightly varies within the range of 0.2 to 0.5 Torrs, causing decrease of the output to 400 W.
  • the flow rate is increased to 500 ml/min, the pressure is increased to 1 Torr, causing a further decline in the output to 300 W.
  • the matching impedance condition could be restored by operating the variable condenser manually in accordance with the change of the flow rate to thereby obtain the approximately initial output power. In this case, the amount of control by the variable condenser is proportional to'the flow rate.
  • the gas flow rate into incineration reaction tube is the value for a single incineration reaction tube.
  • a low temperature plasma incinerator for organic materials which includes at least one ceramic incinerator reaction tube for containing the material to be incinerated and having inlet and outlet ports, means for supplying gaseous oxygen to said inlet port, conduit means for connecting said outlet port to a high vacuum source, and meansfor creating a high frequency electric field within each such tube for converting said oxygen to low temperature plasma and comprising at least one pair of electrode plates arranged on opposite exterior sides of said tube, each such pair of plates being in opposed spaced relation with said tube therebetween, and means for connecting said plates to a high he quency high voltage electrical source, the improvement of a secondary inlet port in said conduit between said reaction tube outlet port and said high vacuum source connected to a source of secondary gas, and adjustable valve means for controlling the amount of secondary gas admitted through said secondary inlet port, whereby variations in the quantity of oxygen supplied to said tube can becompensated by admission of the secondary gas to maintain the tube under substantially constant vacuum.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
  • Drying Of Semiconductors (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
  • Incineration Of Waste (AREA)
US00209879A 1970-12-21 1971-12-20 Low temperature plasma incinerator and method of stabilizing impedance therein Expired - Lifetime US3818845A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP45130677A JPS4840437B1 (el) 1970-12-21 1970-12-21

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US3818845A true US3818845A (en) 1974-06-25

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JP (1) JPS4840437B1 (el)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2541428A1 (fr) * 1983-02-17 1984-08-24 Commissariat Energie Atomique Procede de combustion du bitume
US4509434A (en) * 1981-02-27 1985-04-09 Villamosipari Kutato Intezel Procedure and equipment for destroying waste by plasma technique
US4695448A (en) * 1985-09-26 1987-09-22 Grand Junction Reality Co., Inc. Reduction and disposal of toxic waste
US4718358A (en) * 1984-12-25 1988-01-12 Ebara Corporation Method and apparatus for processing waste matter
CN104315537A (zh) * 2014-11-06 2015-01-28 合肥卓越分析仪器有限责任公司 一种煤炭试样电弧引燃方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3027445A (en) * 1959-11-05 1962-03-27 Paul J Johnson Method and means for disposing of metal cans
US3173388A (en) * 1962-10-08 1965-03-16 Joseph E Menrath Carbon arc incinerator
US3357376A (en) * 1964-02-27 1967-12-12 Westinghouse Electric Corp Waste incinerator
US3503347A (en) * 1967-05-26 1970-03-31 Electrode Incinerators Inc Method and electrical arc apparatus for incinerating trash and garbage

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3027445A (en) * 1959-11-05 1962-03-27 Paul J Johnson Method and means for disposing of metal cans
US3173388A (en) * 1962-10-08 1965-03-16 Joseph E Menrath Carbon arc incinerator
US3357376A (en) * 1964-02-27 1967-12-12 Westinghouse Electric Corp Waste incinerator
US3503347A (en) * 1967-05-26 1970-03-31 Electrode Incinerators Inc Method and electrical arc apparatus for incinerating trash and garbage

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4509434A (en) * 1981-02-27 1985-04-09 Villamosipari Kutato Intezel Procedure and equipment for destroying waste by plasma technique
FR2541428A1 (fr) * 1983-02-17 1984-08-24 Commissariat Energie Atomique Procede de combustion du bitume
EP0125933A1 (fr) * 1983-02-17 1984-11-21 Commissariat A L'energie Atomique Procédé de combustion du bitume
US4631384A (en) * 1983-02-17 1986-12-23 Commissariat A L'energie Atomique Bitumen combustion process
US4718358A (en) * 1984-12-25 1988-01-12 Ebara Corporation Method and apparatus for processing waste matter
US4695448A (en) * 1985-09-26 1987-09-22 Grand Junction Reality Co., Inc. Reduction and disposal of toxic waste
CN104315537A (zh) * 2014-11-06 2015-01-28 合肥卓越分析仪器有限责任公司 一种煤炭试样电弧引燃方法

Also Published As

Publication number Publication date
JPS4840437B1 (el) 1973-11-30

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