Non-water cooled consumable electrode vacuum arc furnace for continuous process
A consumable electrode vacuum arc furnace and, more particularly, a direct current consumable electrode vacuum arc furnace is provided, wherein no water cooling is needed to cool down typically neither the electrodes, nor any other parts of the furnace, and this includes the shell, the flanges ports and the electrical connections of the furnace. The present furnace uses non-metallic electrodes, such as graphite electrode, which are suitable for melting metals, smelting of metal ores, and metal oxide to elemental metal where the use of graphite electrodes is a common practice. The present furnace and electrode assemblies render possible to perform a true continuous process of melting and smelting under controlled pressure.
1 . An electric arc furnace, comprising:
a closed vessel, the vessel having a top furnace spool and a bottom furnace crucible;
a top electrode;
a bottom electrode, the top electrode being adapted to carry electric current so as to maintain a plasma arc between the top electrode and the bottom electrode;
at least one feeding port operable to be displaced between an open position for charging of materials in the vessel and a closed sealed position;
at least one exhaust port operative to exhaust furnace gas from the vessel and to be sealed from an exhaust line;
at least one tap hole operative to be displaced between an open position for removing molten material from the bottom furnace crucible and a closed sealed position;
a top electrode assembly external to the vessel, the top electrode assembly being operative to seal the top electrode from an outside environment; and
a bottom electrode assembly having:
the bottom electrode, the bottom electrode having an electrically conductive extension lead or rod; and
a cooling device adapted to having a cooling medium comprising air to be blown thereon, the cooling device having finned tubes stacked in a housing for transferring heat from the bottom electrode assembly to the cooling medium, the finned tubes being positioned between an upper conductive plate and a lower conductive plate, the upper conductive plate and the lower conductive plate being interconnected by hanger rods, the hanger rods being electrically insulated from the lower conductive plate by grommets for maintaining the housing electrically insulated from the bottom anode assembly.
2 . The electric arc furnace of claim 1 , comprising a housing atop the furnace spool with the top electrode extending within the housing and into the vessel.
3 . The electric arc furnace of claim 2 , wherein the top electrode is sealed from the outside environment through the top electrode assembly, comprising seals between lower flanges connecting a lower end of the housing to the vessel and between upper flanges connecting an upper end of the housing to the top electrode assembly.
4 . The electric arc furnace of claim 3 , comprising a sleeve externally of the top electrode and internally of the housing, wherein the top electrode and the sleeve are operative to move up and down together.
5 . The electric arc furnace of claim 4 , wherein the sleeve is located between the top electrode and vacuum seals in the top electrode assembly so that vacuum sealing is only carried out on the sleeve.
6 . The electric arc furnace of claim 4 , wherein the sleeve and the top electrode define a gap there in between, the sleeve acting as a thermal barrier between the top electrode and the housing where seals are located.
7 . The electric arc furnace of claim 4 , comprising a cleaning device made of an electrically insulated material, the cleaning device being located substantially at a junction of the furnace spool and the housing for substantially preventing particulates entrained in the furnace gas from entering the housing.
8 . The electric arc furnace of claim 7 , wherein the cleaning device is also operative to remove deposits from the top electrode, in each displacement of the sleeve.
9 . The electric arc furnace of claim 1 , comprising a non-water-cooled vessel flange at a junction of the furnace spool and the bottom furnace crucible, the non-water-cooled vessel flange being sealed thereat by a vessel seal, each one of the furnace spool and furnace crucible having refractory linings inwardly of the vessel seal thereby limiting the temperatures at the vessel seal.
10 . The electric arc furnace of claim 1 , wherein the bottom electrode assembly is connected to the bottom furnace crucible by the electrically conductive extension lead or rod.
11 . The electric arc furnace of claim 1 , comprising an electrically conductive lining at a bottom of the bottom furnace crucible, the electrically conductive extension lead or rod being embedded or buried in the conductive lining.
12 . The electric arc furnace of claim 11 , wherein, the plasma arc is to initially formed between the top electrode and the conductive lining by passing the electrical current through the electrically conductive extension lead or rod and the bottom electrode assembly, the bottom electrode assembly being connectable to a power supply.
13 . The electric arc furnace of claim 11 , wherein the tap hole extends in the bottom furnace crucible above the conductive lining so that the molten material contained in the bottom furnace crucible can be periodically tapped out through the tap hole.
14 . The electric arc furnace of claim 4 , wherein the top electrode assembly includes a removable electrical connector for connecting the top electrode to a power supply and for allowing a new top electrode to be added for compensating for consumption of a used electrode, when the top electrode is made of consumable electrode material, thereby enabling a continuous or semi-continuous process.
15 . The electric arc furnace of claim 14 , comprising a guide for ensuring that the removable electrical connector, the top electrode and the sleeve are aligned and sealing components are well positioned and maintained during an operation of the electric arc furnace, the guide extending between the sleeve and the housing of the top electrode assembly.
16 . The electric arc furnace of claim 5 , an anode housing of the bottom electrode assembly connected to the bottom furnace crucible by a flexible bellows tube operative to allow the bottom anode assembly to move slightly without affecting the vacuum seals, wherein, as the temperature of the bottom furnace crucible increases, the electrically conductive extension lead or rod linearly expands along an axis thereof, thereby pushing the bottom anode assembly downwardly, with a resulting downward displacement being compensated by the bellows tube for maintaining a desired vacuum level in the vessel.
17 . The electric furnace of claim 1 , wherein the bottom electrode comprises an electrical connector attached to a lower end of the electrically conductive extension lead or rod, wherein the electrical connector is attached to the upper conductive plate for allowing a portion of heat transferred from the bottom furnace crucible through the electrically conductive extension lead or rod to be dissipated in the bottom electrode assembly exteriorly of the bottom furnace crucible, thereby maintaining an operating temperature of the electric arc furnace for keeping sealing components below maximum service temperatures thereof.
18 . The electric arc furnace of claim 1 , wherein the hanger rods are operative to keep the finned tubes in place and to compress the upper conductive plate towards the vacuum seals for tightness and sealing, the vacuum seals being placed over an insulation ring operative to act as an electrical disconnector between the bottom anode assembly and a furnace shell, wherein the housing being connected to a lower end of the bellows tube.
19 . The electric arc furnace of claim 1 , wherein the bottom anode assembly is attached to the bottom furnace crucible via a transition flange mounted to a furnace crucible shell, the bottom electrode including an extended electrically conductive lead attached to the lower conductive plate, the bottom anode assembly being connected to a power supply by the electrically conductive extension lead or rod.
20 . The electric arc furnace of claim 14 , wherein the top electrode and the sleeve are connected together at upper ends thereof via at least the removable electrical connector, whereby the top electrode and the sleeve are operative to move up and down together.