Patent Application
20100263484
This invention relates to a smelting furnace.
In one aspect, the invention provides a smelting furnace, a vessel of the furnace for receiving material to be smelted having an inner surface which at least at an upper portion thereof is concave and reflective.
The furnace may have an electrode at least a portion of which is within the interior of the vessel, for heating said material by application of electric potential to the electrode.
Means may be provided for introducing inert gas into the interior of the vessel, for ionisation under influence of said electric potential, to cause the gas to form a heated plasma, for effecting said heating of the material to be smelted.
The invention also provides a smelting furnace having electrode forming means for forming a conductive electrode, for use in heating material in the furnace by passage of electric current applied via the electrode, said electrode forming means being adapted to receive fluid material for forming the electrode such that the material sets in the interior of the furnace to form the electrode, such the electrode is positioned in the furnace for application of said electric current.
The means for forming a conductive electrode may include means for deriving off-gas from the interior of the furnace during said smelting, means for deriving from the off-gas carbonaceous ash material, means for combining said ash material with a liquid carbonaceous material to from said fluid material, and means for introducing said fluid material into said electrode forming means.
The electrode forming means may be in the form of an annular structure, whereby in use to cause said electrode to be formed from said fluid material in a downwardly depending annular form.
Means may be provided for introducing inert gas into said furnace through said electrode.
The furnace may be arranged for transforming said fluid material to solid form, for forming the electrode, under action of heat in the furnace.
The invention further provides a method of smelting material by electrical heating using an electrode in a furnace, wherein the electrode is formed by casting it in the furnace.
Carbonaceous ash material derived from the off-gas may be combined with a liquid carbonaceous material to form a fluid material, the fluid material being introduced into electrode forming means, to form the electrode.
By this method, the electrode may be formed as a downwardly depending annular member. The liquid carbonaceous material may be pitch.
The extruded annular member may be set by heat in the furnace.
The invention is further described by way of example only with reference to the accompanying drawing in which:
The furnace 100 illustrated in
The lower part 114 of the vessel 102 is of dished form adapted to receive material 116 which is to be smelted. The upper part 118 of the vessel 102 is of concave domed configuration, for example, of substantially hemispherical or paraboloid configuration. To facilitate assembly and disassembly of the vessel such as in manufacture or for maintenance, the upper and lower parts 114, 118 may be separately formed and attached together by releasable means (not shown).
Broadly, material 116 to be smelted is positioned in the vessel 102 so to lie on the lower part 114 of the vessel 102. Smelting is effected by application of an electric potential between a central downwardly depending carbonaceous electrode 120 in the vessel 102, which terminates above the upper surface 117 of the material 116, and a central electrode 137 in the base of the vessel 102. The electrodes 120, 137 are electrically insulated from the vessel 102. During smelting, gas (which may be an inert gas such as argon) is introduced into the chamber 104, immediately above surface 117 via an upright duct 145 which extends vertically within a central lengthwise extending passageway 122 in the electrode 120. The passage of the electric current causes ionisation of the gas introduced into the chamber 104, to cause the gas to form a heated plasma for heating and smelting of material 116. The electric supply may be a conventional low voltage high current DC source 119 which applies potential to the electrodes such that the electrode 120 is the cathode and the electrode 137 is the anode.
The electrode 120, which in use of the furnace 100, is consumed by erosion of the lower end thereof, is formed in the vessel 102 by a continuous casting process, so that it is continuously replenished. Particularly, the furnace has an electrode forming means 70 arranged such that the electrode 120 is continuously formed in a vertically elongate space 141 of annular cross section, defined between inner and outer coaxial hollow cylindrical members 123, 125 of the electrode form means 70. The electrode 120 is correspondingly formed so as to be of annular cross-section, to define therewithin the central passageway 122.
Cylindrical member 125 extends axially of the vessel 102, from an upper end which is exteriorly positioned above the upper part 118 of the vessel, downwardly through a central opening 127 in the vessel 102, above the upper part 118, and into the chamber 104. The member 125 terminates at a lower end positioned so as to be, in use of the furnace 100, a short distance above the surface 117 of the material to be smelted. The member 125 is electrically insulated from the vessel 102 by an annular insulation element 138 surrounding the periphery of the member 125 towards its upper end and positioned in opening 127. The cathode 120 is electrically insulated from the vessel 102 by an annular insulation ring 139 positioned in a lower central opening 135 in the vessel 102 and surrounding the periphery of anode 137.
The upper end of cylindrical member 125 is closed by an upper transverse wall 143. The lower end of the cylindrical member 125 is open. The upper end of duct 123 extends through a central opening in transverse wall 143 to an upper end then leads, through a control valve 148, to a receptacle 170 for material to be smelted, in flowable, eg granular form. By operation of the valve 148, the material in receptacle 170 can be released from the receptacle to pass down the interior of the cylindrical member 123 to be deposited in the chamber 104.
The duct 145 extends coaxially within the cylindrical member 123. It opens at its lower end at a location within the member 123, and at a relatively short distance above the bottom of chamber 104. The upper end passes sealingly though an opening in member 123, and leads to a source of inert gas (not shown). In use, the gas is introduced into the duct 145 from the source to flow down the duct 145, and exit from an open lower end of the duct a short distance above the lower end of electrode 120.
The lower, open, end of member 123 is open, and is located at about the same vertical height as the lower end of cylindrical member 125.
A duct 147 extends sidewardly from cylindrical member 125, at the upper end thereof, and provides communication between the space 141 between the members 123, 125, at the upper end thereof. Duct 147 communicates with the lower part of a hopper 152 which receives a particulate material 157 formed mainly from carbon ash. By operation of a valve 149 in duct 147, the material 157 in hopper 152 is controllably released from the hopper 152, to flow through duct 147 into the space 141 at the top thereof.
A ring-like feed member 161 is provided, surrounding the cylindrical member 125 at the upper end thereof, above vessel 102, but below the duct 147, and sealingly attached, at the inner periphery thereof to the external cylindrical surface of the member 125. As best shown in
At inner ends, the passageways 165 communicate with the space 141 via respective side openings 171 in the member 125.
The passageways 165 are normally closed by ball valves 173 having balls 175 urged by springs 179 into contact with annular valve seats 177 formed in passageways 165.
Referring now to
The receptacle 187 has a lower outlet which communicates via a duct 195 with a side opening 205 in the cylinder 193.
A piston 197 is slidingly and sealingly retained in cylinder 193, for reciprocating movement therewithin. Piston 197 is pivotally connected to one end of a connecting rod 199, the other end of which is pivotally connected at an eccentric location to a drive disc 203, mounted to the output shaft of a motor 206. When motor 206 is operated, disc 203 is rotated to cause piston 197 to be reciprocated in cylinder 193, by action of connecting rod 199. The side opening 205 in cylinder 193 is so positioned that, as the piston is reciprocated in cylinder 193 pursuant to operation of motor 206, successive charges of pitch 191 from the receptacle 187 are delivered to the cylinder 193, as the piston 197 is withdrawn in the cylinder to the location shown in
The pitch 191 introduced into the upper part of space 141 is introduced around the periphery of the particulate material 157 introduced into the space 141 via duct 147, and becomes intermingled with that material to form a body of carbonaceous material which, under continued operation of the furnace, descends in the space 141. As it descends, the material is baked by heat from the operation of the furnace to form the electrode 120.
As mentioned, the electrode 120 is continuously consumed in operation of the furnace. However because the electrode 120 is, as above described, formed by a continuous casting process, it is possible, by matching the rate of formation of the electrode 120 with the rate of erosion thereof to ensure that the electrode 120 is maintained at a stable length, and so that the lower end of the electrode 120 is maintained at a stable height above surface 117. This can be effected by appropriate control of the speed of rotation of motor 206, to control the rate of feed of the pitch 191, and by regulation of the inflow rate of the particulate material 157, by control of the valve 149 in the duct 147.
The electric potential applied between cathode 120 and anode 137 is sufficient to enable ionisation of the gas passed into the chamber 104 through duct 145 so as to form a heated plasma in the chamber 104 which melts the material 116. The interior surface 109 of the inner wall 106, at least at the upper part of the vessel 102, is rendered to a highly reflective state, such as to exhibit a mirror finish. In consequence, and because of the concave shape of the upper part of surface 109, heat is reflected within the chamber 104, so that a relatively lesser portion thereof is lost from the vessel 102 and efficient heating and smelting of the material 116 results. Molten metal from material 116, derived by the smelting, may be withdrawn via a side passageway 130 which passes through side walls 106, 108. Slag 254, resulting from the smelting may be withdrawn via a passageway 131 which passes through side walls 106, 108, entering chamber 104 at a height somewhat above the location where passageway 130 communicates with the chamber 104. In case of smelting some materials 116, it may be desirable to recover heavier metals 256, which collect at the lower part of the chamber 104 during smelting. As shown, the walls 106, 108 are configured, at the bottom of the vessel 102, to form a small recess 225 around the location of the cathode 120 at which the heavier metals 256 accumulate. There is an outlet duct 133 leading from the lower part of the surface of recess 225, through which molten metals so recovered by smelting may be taken from chamber 104.
The cathode 120 is preferably formed with upstanding fingers 137A which are electrically insulated from each other by suitable surrounding insulating material.
Walls of pipes defining the passageways 130, 133 and 131 are provided with heating coils wound therearound, at locations adjacent the interior of the chamber 102, such as between walls 106, 108, as shown. Electric current is passed through these to inhibit solidification of molten materials therewithin.
Off gas generated during smelting is taken from chamber 104 via an upper outlet duct 132.
As mentioned, at least the upper part of the surface 109 of the interior of the vessel 102 (i.e. that formed by inner surface of the upper part of the wall 106) is rendered to a highly reflective state such as by polishing it, preferably to a mirror finish. It has been found that, by this, the heating effect within the vessel 102 is greatly enhanced and efficient smelting can be achieved.
When smelting certain metals such as magnesium, the metal tends to come off as a vapour in chamber 104, which needs to be condensed to recover the metal in liquid form. In a refractory-lined kiln, the vapour tends to adhere to the refractory and recovery is impeded. In the furnace 100, however, recovery may be effected by use of a simple splash condenser at a suitable outlet.
The smelter may be used for a smelting variety of materials such as ilmenite for recovery of titanium.
The material 157 may comprise carbon ash which has been subjected to chemical action, together with graphite powder, in a mechano fuser. The resultant material may comprise small particles of carbon ash surrounded by graphite powder. The carbon ash may be recovered from the furnace 100, particularly from the off gas at opening 132 by a process illustrated in
As shown in
Particular exemplary applications of the invention are:
A) Smelting and recovery of metal from waste materials recovered from electric arc furnaces when processing metal (arc furnace dust).
It will be apparent to the skilled addressee that many modifications and changes may be made to the invention without departing from the spirit and scope thereof.
The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005904332 | Aug 2005 | AU | national |
| 2005906707 | Nov 2005 | AU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU06/01157 | 8/11/2006 | WO | 00 | 6/7/2010 |
