Thermal reactor with direct passage tube for current

Details Thermal reactor with direct passage tube for current Thermal reactor with direct passage tube for current

1996-01-18

1998-06-02

Kim, Christopher

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Including heat exchanger for reaction chamber or reactants...

422197, 422202, 219 591, 219 66, 219 67, F28D 700

Patent

active

057594996

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a thermal reactor making it possible to carry out a chemical reaction under precise and controlled temperature conditions, and in particular a thermal reactor delivering a carbon-laden atmosphere with a predetermined carbon potential for the heat treatment of metal parts (hardening, carbonitriding or carburizing) in suitable furnaces.


SUMMARY OF THE INVENTION

Such reactors, which generate a carbon-laden atmosphere in heat treatment furnaces, are known. These reactors crack, at a predetermined temperature, an incoming gas mixture obtained from a mixture of air and of methane or propane, in variable proportions, into a carbon-laden gas mixture and especially into carbon monoxide (CO) and hydrogen (H.sub.2) constituting said carbon-containing atmosphere. These reactors use a sealed chamber forming a reactor or a horn heated externally to the desired temperature and the carbon-rich outlet gas mixture of which is cooled (quenching reaction) before reaching the heat treatment furnace. These reactors require a relatively bulky installation which is difficult to control and relatively expensive in terms of energy because of the external heat losses due to the heating chamber of the reactor and also because of the need to reheat the gases produced, these being quenched on introducing them into the furnace.
A reactor is known, from EP-A-0,439,614, which consists of a sealed chamber heated by internal electrical resistance elements. However, the resistance elements corrode extensively with the passage of the gaseous reactive flux and disturb the reaction, relative to that of the catalyst. Furthermore, by reason of the large and radially non-uniform temperature gradient between the resistance elements and the catalyst, complete control of the temperature of the catalyst, and therefore of the reaction, is difficult. Finally, the connection of the resistance elements to the electrical power supply requires a complex and expensive manufacture.
The invention aims to remedy these drawbacks by providing a thermal reactor comprising a chamber in which a chemical reaction is carried out under predetermined temperature conditions, characterized in that said chamber consists of a tube made of refractory metallic material forming an electrical resistance element by direct passage of the current in the tube, whose volume and material are compatible with the application, suitably supplied via its connection terminals with (low voltage) current depending on its electrical resistance in order to produce within it said reaction temperature conditions, said tube being mounted in a sealed manner, said chamber being electrically isolated and having means for supplying reaction products and means for the outlet of the products coming from the reaction.
Of course, the tube may contain a catalyst suitable for the envisaged application and, for example, a refractory catalyst based on nickel oxide, this being conventional for the production of a carbon-laden atmosphere in heat treatment furnaces.
Said tube with passage of current is a tube made from rolled, welded or centrifugally cast sheet, made of heat-resistant (refractory) metal alloy and consequently easy to manufacture and inexpensive.
Temperature-measuring thermocouples are positioned along the length of the tube so as to determine, accurately and locally, the temperature level required for the reaction. The temperature level may be set to a variable level and easily controlled by varying the electrical supply of the current generator of the tube.
The tube is advantageously encased in an insulating jacket limiting the external heat losses, these external heat losses being minimal because of the small size of the whole reactor. Possibly, a passage for a cooling or temperature-homogenizing gas (air) flow may be formed between the wall of the tube and the insulating jacket. The flow rate of the flow may be regulated to a temperature set point, by means of a controlled fan.
Of course, the reactor may be arranged outside the furnace

REFERENCES:
patent: 2235401 (1941-03-01), Gier, Jr.
patent: 3782884 (1974-01-01), Shumaker
patent: 5024818 (1991-06-01), Tibbetts et al.
patent: 5560891 (1996-10-01), Takashima et al.
patent: 5573737 (1996-11-01), Balachandran et al.
Patent Abstracts of Japan vol. 8, No. 67, Mar. 29, 1984--JP,A,58 219 945 Dec. 21, 1983.

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