A liquid treatment apparatus includes a liquid storing vessel, a first electrode, a second electrode at least partly arranged inside the vessel, a tubular first insulator surrounding a first-electrode lateral surface with a first space interposed therebetween, and including a first opening in an end surface in contact with the liquid, a tubular second insulator surrounding the first-electrode lateral surface inside the first insulator, a gas supply device supplying gas into the first space and ejecting the gas into the liquid through the first opening, and a power supply applying a voltage between the first and second electrodes and producing plasma. The second insulator is arranged with a second space interposed between the first and second insulators. Portions of the first and second insulators, those portions being positioned inside the vessel, are covered with the gas when the gas is supplied into the first space by the gas supply device.

A liquid treatment apparatus includes a liquid storing vessel, a first electrode, a second electrode at least partly arranged inside the vessel, a tubular first insulator surrounding a first-electrode lateral surface with a first space interposed therebetween, and including a first opening in an end surface in contact with the liquid, a tubular second insulator surrounding the first-electrode lateral surface inside the first insulator, a gas supply device supplying gas into the first space and ejecting the gas into the liquid through the first opening, and a power supply applying a voltage between the first and second electrodes and producing plasma. The second insulator is arranged with a second space interposed between the first and second insulators. Portions of the first and second insulators, those portions being positioned inside the vessel, are covered with the gas when the gas is supplied into the first space by the gas supply device.

A plasma cutting system includes a power supply that outputs first and second plasma cutting currents. A torch is connected to the power supply and includes a first cathode that receives the first plasma cutting current, a first electrode and swirl ring, a second cathode that receives the second plasma cutting current, and a second electrode and swirl ring. The torch simultaneously generates a first and second plasma arcs from the electrodes. A gas controller is configured to separately control a flow of a first plasma gas to the first swirl ring and a flow of a second plasma gas flow to the second swirl ring. A torch actuator moves the torch during cutting, and includes a motor having a hollow shaft rotor for rotating the torch during cutting. A motion controller is operatively connected to the torch actuator to control movements of the torch during cutting.

A plasma cutting system includes a power supply that outputs first and second plasma cutting currents. A torch is connected to the power supply and includes a first cathode that receives the first plasma cutting current, a first electrode and swirl ring, a second cathode that receives the second plasma cutting current, and a second electrode and swirl ring. The torch simultaneously generates a first and second plasma arcs from the electrodes. A gas controller is configured to separately control a flow of a first plasma gas to the first swirl ring and a flow of a second plasma gas flow to the second swirl ring. A torch actuator moves the torch during cutting, and includes a motor having a hollow shaft rotor for rotating the torch during cutting. A motion controller is operatively connected to the torch actuator to control movements of the torch during cutting.

In the present pelletizing apparatus, the induration of iron ore concentrate pellets is achieved in a tunnel furnace heated by plasma torches, wherein the generation of CO2 by the conventional iron ore pelletizing processes is reduced by using electricity powered plasma torches instead of burning natural gas, heavy oil or pulverized coal in burners, thereby reducing considerably industrial pollution of the atmosphere.

In the present invention the torch movement period is 20-40 seconds, with the torch movement period being the time required to move plasma torches (which heat the surface of molten metal in the casting mold) one time. The average heat input amount at multiple sites, which are obtained by dividing the initial solidification portion (which is where the molten metal makes contact with the casting mold and first solidifies) into multiple sites in the circumferential direction of the casting mold, is 1.0-2.0 MW/m.sup.2. The molten metal advection time, which is the time required for electromagnetically stirred molten metal to travel the length of the torch heating region of the surface of the molten metal in the lengthwise direction of the casting mold, is 3.5 seconds or less.

In the present invention the torch movement period is 20-40 seconds, with the torch movement period being the time required to move plasma torches (which heat the surface of molten metal in the casting mold) one time. The average heat input amount at multiple sites, which are obtained by dividing the initial solidification portion (which is where the molten metal makes contact with the casting mold and first solidifies) into multiple sites in the circumferential direction of the casting mold, is 1.0-2.0 MW/m.sup.2. The molten metal advection time, which is the time required for electromagnetically stirred molten metal to travel the length of the torch heating region of the surface of the molten metal in the lengthwise direction of the casting mold, is 3.5 seconds or less.

Disclosed is a plasma torch with a structure capable of performing reversed polarity/straight polarity operation, wherein the plasma torch is coupled to a melter and melts a waste material such as radioactive waste or industrial waste by generating and sustaining a plasma arc between electrodes, the plasma torch including: a rear electrode provided inside a torch pipe and electrically connected to become one of an anode and a cathode; and a front electrode provided at a front end of the torch pipe at a position adjacent to a front end of the rear electrode and electrically connected to become a remaining one of the anode and the cathode, wherein electrical connections of the rear and front electrodes are switchable with each other so that the plasma torch operates as a reversed polarity plasma torch or a straight polarity plasma torch.

Disclosed is a plasma torch with a structure capable of performing reversed polarity/straight polarity operation, wherein the plasma torch is coupled to a melter and melts a waste material such as radioactive waste or industrial waste by generating and sustaining a plasma arc between electrodes, the plasma torch including: a rear electrode provided inside a torch pipe and electrically connected to become one of an anode and a cathode; and a front electrode provided at a front end of the torch pipe at a position adjacent to a front end of the rear electrode and electrically connected to become a remaining one of the anode and the cathode, wherein electrical connections of the rear and front electrodes are switchable with each other so that the plasma torch operates as a reversed polarity plasma torch or a straight polarity plasma torch.

In the present invention the torch movement period is 20-40 seconds, with the torch movement period being the time required to move plasma torches (which heat the surface of molten metal in the casting mold) one time. The average heat input amount at multiple sites, which are obtained by dividing the initial solidification portion (which is where the molten metal makes contact with the casting mold and first solidifies) into multiple sites in the circumferential direction of the casting mold, is 1.0-2.0 MW/m.sup.2. The molten metal advection time, which is the time required for electromagnetically stirred molten metal to travel the length of the torch heating region of the surface of the molten metal in the lengthwise direction of the casting mold, is 3.5 seconds or less.