HK1070395B - Method for direct metal making by microwave energy - Google Patents

Description

Direct metal production method using microwave energy

Technical Field

The present invention relates to a direct metal production method which uses microwave energy as a primary energy or a secondary energy to reduce and melt a metal-containing substance and separate molten metal from slag.

Background

The usual processes for extracting metals from their respective ores are characterized by a large energy loss and the release of environmentally undesirable by-products, including large amounts of particulates, SO₂、CO₂And NO₂。

Prior to the present invention, steel making was carried out using an indirect process according to which iron was first produced from ore or scrap metal. The iron thus produced is then converted into steel. In a typical iron making process, iron ore is ground to 500 mesh in order to liberate iron oxide from other minerals. The resulting material is then concentrated by a separation operation such as magnetic separation and/or flotation. The resulting fines are generally agglomerated with limestone and bentonite. The pellets are sintered to make them hard and charged with coke into a furnace where the feedstock is subjected to a jet of very hot air. Iron oxide is reduced and melted in the furnace. During the melting period, the iron absorbs carbon and sulfur from the coke charged into the furnace with the pellets.

The carbon content of the iron must be reduced in order to make steel. This is typically done in a basic oxidation oven (BOF). Pure oxygen was blown into the molten iron-containing melt charged in the flask furnace at a supersonic speed. The oxygen reacts with carbon in the molten iron to form CO and CO₂. Sulphides are formed by injecting a powder into the molten steel, thereby removing sulphur that is detrimental to most steels, which is collected as slag from the top of the bath.

This production method is very inefficient in terms of energy and materials and poses very serious environmental problems. Iron ore agglomeration and sintering are required to provide air permeability required for blast and strength to withstand high load in a blast furnace. The entire process is dusty and noisy, which presents health and environmental concerns to workers and other personnel in this area. Coke must be used to generate a temperature sufficient to melt the iron. However, the addition of coke to the mixture will result in the addition of carbon and sulfur to the iron. These elements must then be removed in subsequent processing. The manufacture of coke is also an environmentally hazardous operation and coke starvation is now a serious problem.

Similar problems arise with the production of other metals such as copper, nickel, lead, zinc and iron alloys. For sulfur-containing ores, SO₂Emissions are also a problem.

Electric induction heating is particularly useful because no additional impurities are added to the metal being smelted and no local emissions are produced. One disadvantage of induction heating, however, is that it relies on the introduction of eddy currents in the material being heated. If the substance is not an electrical conductor such as a metal ore, induction heating is not feasible. Typically, induction heating is only used where scrap metal can be used for primary charging.

Arc heating is a popular method of manufacturing metals from scrap metal. Similar to the disadvantage of induction heating, the substance to be heated must be an electrical conductor. The metal ore cannot be heated directly by the electric arc.

As described herein, microwave heating transfers energy to a non-conductive substance or piece of metal more efficiently than induction heating or arc heating. Thus, an alternative is provided for the combustion of the mineral fuel and the initial heating, which may later be by induction heating or arc heating, may be accomplished.

Different methods using microwave energy have been developed in the purification of metal compounds. US4321089 discloses a process for recovering molybdenum and rhenium from sulphide ores. In the process, sulphide ores are subjected to microwave energy in the presence of oxygen or chlorine to form chlorides, respectively. In both cases no metal is reduced. These oxide or chloride intermediates are then subjected to additional treatment under reducing conditions to produce the metal. These methods all differ from the direct reduction treatment disclosed herein because the microwave treatment results in only one oxidation intermediate.

US 4324582 to Kruesi et al (the' 582 patent) also discloses a process for applying microwave energy to a copper composition to convert the composition into other compositions, such as oxides and chlorides, from which copper is more easily recovered. The scope of the claims of the' 582 patent is defined as using microwave energy "to convert sulfides and oxides in ores to other compositions from which copper is more readily recovered.

The description of the' 582 patent specifically departs from the ferrous metal treatment assertions that "oxides of the transition metals iron and molybdenum do not absorb microwaves" and that "gangue does not appreciably absorb microwave radiation.

In contrast to the use of microwaves for the above-described intermediate mass production, the method according to the invention results in the direct production of metals purified by chemical reduction of oxides, sulfides and other ores and metal sources by applying microwave energy and a suitable reducing agent in combination with induction heating or arc heating.

US 5141941 issued to Lemelson, 7.1992 discloses a process for refining metals from ores which comprises passing a stream of small particle ore into a reaction zone.

It is therefore clear that the above examples of the prior art do not represent the new contribution of the present invention to the metal industry, namely the complete direct manufacture of the metal and the efficient use of the substance. The present invention is an innovative process for producing metals directly from ore using microwave energy as the primary heating source. The method is distinct from any current metal smelting technique. The foreseeable advantages of this new metal making process over traditional metal making processes include reduced energy consumption, reduced combustion emissions, elimination or reduction of environmentally associated coke, lower capital investment and production costs, and minimal metal product impurities.

Disclosure of Invention

The object of the invention described herein includes a method for the direct production of metal from a metalliferous material such as metal ores or scrap metals.

To achieve the present invention, the present invention provides a method for directly producing a metal from a metal-containing substance, the method comprising: providing a metalliferous material and a reducing agent, mixing the metalliferous material with the reducing agent to form a mixture, charging the mixture into a vessel by suitable means other than a stream of small particles, heating the mixture with minimal impurities by applying microwave energy to the mixture until the mixture becomes electrically conductive, further heating the mixture by an electric arc or by electric induction until molten metal is released from the metalliferous material, the molten metal accumulating under gravity at the bottom of the vessel, and discharging the metal from the vessel.

Here, the mixing takes place before or after the metalliferous material and the reducing agent are introduced into a container. The container should be constructed of a material that can be used as or in a microwave chamber and should be able to withstand high temperatures without significant degradation and to allow induction or arc heating to be applied. Once the mixture of metal-containing material and reducing agent is loaded into the container in pellets, briquettes, or other suitable form, in addition to a stream of small particles, the microwave source generates dispersed microwaves and applies them to the material contained in the container. The microwave frequency selected is preferably selected to heat the metal ore or the metal of the metal-containing substance. The microwaves are continuously applied to the metal-containing material until the reducing agent breaks bonds between the metal atoms and other atoms in the metal ore to release the metal and the metal absorbs sufficient energy to become molten metal. At the same time, additional inductive or arc energy may be fed into the apparatus to assist in heating after the metalliferous material becomes electrically conductive and to allow the molten material to accumulate at the bottom of the vessel under the influence of gravity.

In the method of the invention, it is preferred that a fluxing agent is mixed with the metalliferous material. In addition, an auxiliary fuel may be mixed with the metalliferous material. Microwave absorber substances may also be mixed into the mixture. In addition, it is desirable to preheat the metalliferous material to increase its microwave absorbing capacity. The step of heating the mixture produces a molten slag. The method of the present invention further comprises the step of controlling the ambient atmosphere of said mixture during said heating. Furthermore, sulfide vapor or SO released from the metalliferous material during the heating is collected₂. The container preferably comprises a ceramic crucible. Or the vessel comprises a tiltable metal tube lined with refractory material. The container may comprise an induction coil. The container includes an electrode. The vessel comprises a static metal furnace having a molten metal discharge opening. Furthermore, the container comprises a vacuum means. In addition to this, the present invention is,the metal-containing species comprises a metal selected from the group consisting of iron, copper, nickel, cobalt, lead, and zinc.

Drawings

The present invention will be further described with reference to the several figures, without limiting the scope of the claimed invention, wherein:

FIG. 1A shows a vacuum pump;

FIG. 1B shows a sulfide condenser;

FIG. 1C shows a crucible located in a microwave chamber, which includes a valved inlet, a valved outlet, and a waveguide;

FIG. 2 shows a high power microwave oven;

FIG. 3 shows another embodiment of a high power microwave oven including means for inputting metal-containing substances and an induction coil;

FIG. 4 shows another embodiment of a high power microwave oven including means for introducing metalliferous material and arc heating means;

figure 5 shows a furnace for continuous production which includes a raw material charging port, separate molten metal discharge ports and a tap hole.

Detailed Description

In the practice of the invention, the ore is crushed, ground and beneficiated by a separation process. The separation method may be flotation, gravity, magnetic separation, electrostatic or other physical separation methods. The fine ore particles are mixed with a reducing agent, an internal combustion auxiliary fuel and a flux in a certain proportion. It is preferable to add the reducing agent, the internal combustion auxiliary fuel and the flux in the form of powder or pellets or lumps. However, a gas or liquid may also be used. Preferred reducing agents include those containing carbon, hydrogen, hydrocarbons, Al, Si, Mn, Mg, Ti, Cr, Na, Li, Ca,Y and Zr. Preferred internal combustion support fuels include coal, coke, carbon, wood, petroleum and hydrocarbon waste. Preferred fluxes include lime, limestone, CaF₂And Na₂And O. The preferred ratio is determined based on the composition of the beneficiated ore, the reductant, the combustion auxiliary fuel and flux, and the expected percentage of energy provided by the combustion auxiliary fuel. Typically, the reductant, combustion support fuel and flux constitute 5% to 40%, 1% to 20% and 1% to 15% of the volume of the vessel, respectively (by weight).

Byproducts or metal-containing wastes such as furnace dust, scale and plating sludge can also be used as the metal-containing substance. Thus, with the present invention, the metals in these by-products or scrap can be partially or completely recovered. The by-product or waste is preferably a powder or a powder agglomerate. Scrap metal and other recoverable metals may also be added to the beneficiated ore, by-product or waste.

In some cases, the metal-containing species cannot effectively absorb microwave radiation at useful frequencies. In this case, the microwave absorber substance may be mixed with the ore or metal-containing substance to increase the microwave absorptivity. The microwave absorber material may be selected from the group consisting of metal-containing anthracite, chalcocite, arsenopyrite, bismuth, bornite, limonite, chalcopyrite, chrysotite, cobaltite, covellite, enargite, galena, graphite, hematite, ilmenite, magnetite, manganite, marcasite, molybdenite, pale-red-silver, dense-red-silver, pyrite, pyrolusite, pyrrhotite, cobaltite, tetrahedrite, zincite and hydrocarbons. Microwave absorber substances are used in the form of powders or in the form of solutions with a concentration of 0.1% to 20%. Alternatively, the metalliferous material may be preheated to a critical temperature by a gas, oil, coal or electric furnace, above which the metalliferous material becomes a good microwave absorber. The metal-containing material is then charged into a microwave oven to continue the metal production.

After mixing, the aggregates, except for the stream of small particles, are,Feedstock 101 in the form of chunks or other suitable forms is loaded into a crucible 102. It is preferable to use a crucible made of a material that absorbs microwave energy much less than the mixed raw materials. The crucible should also have a softening temperature above the melting point of the mixed feedstock. Suitable crucible materials include chamotte, mullite, SiO₂、Al₂O₃SiC, MgO, zircon and chromite.

After charging, the crucible is moved into a very high power microwave oven 103 having a single or multiple cavity 103A. The dispersed microwaves 104 are introduced into the cavity through a waveguide 105. The high power microwave oven can emit intense microwave energy in a small space. For example, the microwave energy may exceed 10W/cm³. The microwave frequency is 0.915Ghz, 2.45Ghz or other continuously adjustable frequency. A valved inlet 106 and an outlet 107 are formed in the microwave chamber for the input of gas and the release of exhaust gas to control the atmosphere within the microwave chamber.

To make the metal, the microwave power is turned on and the mixed feedstock begins to absorb microwave energy and heat up. The ore reacts directly or indirectly with the reducing agent to become a metal. In the case of direct reaction, the reducing agent reacts with air first to produce a reducing gas. The ore is then reacted with a reducing gas to produce metal. Alternatively, the ore is first decomposed into compounds, and the resulting compounds react with the reducing agent to form the metal.

When the mixture in the crucible reaches the appropriate temperature, the internal combustion auxiliary fuel is ignited to generate heat 108 and further heat up. The ore begins to melt and form metal droplets 109 and slag 110. Due to the specific density difference between the metal and the slag, the molten metal falls under gravity and forms a molten pool 111 at the bottom of the crucible, on top of which the slag 110 floats. The flux melts and reacts with the slag to reduce the slag viscosity. As a result, the molten metal is better separated from the slag.

After the molten metal is formed, the slag and crucible contents continue to absorb microwave energy and remain at an elevated temperature. After the molten metal is separated from the slag, the microwave generator is turned off and the crucible is removed from the microwave oven and cooled. This cooling results in the formation of a solid metal ingot. The solidified slag is broken up and separated from the ingot by mechanical impact. Alternatively, the slag is stripped off while still molten after the crucible is removed from the microwave oven. The molten metal may then be poured into a mold and solidified to form a metal ingot.

If the ore contains a large amount of sulfide such as Cu₂S、N₂S₃PbS and ZnS, then sulfide condenser 112 or SO₂The scrubber should be connected to the outlet 107 of the furnace in order to condense sulphide vapours and capture SO released from the mixture during heating₂。

Some ores are poor microwave absorbers at ambient temperatures, but absorb microwaves more efficiently at high temperatures. To treat these materials, a mixture of ore, reducing agent and fluxing agent may be preheated to a temperature in a conventional electric, gas or oil furnace and then transferred to a microwave oven where the reduction and melting operations continue under the influence of the applied microwave energy.

Gaseous reducing agents may be used effectively in certain circumstances. In this case, the reducing gas may be continuously supplied into the microwave oven chamber during the microwave heating. Where the reducing gas effectively reacts with the metalliferous material. Can convert CO and H₂And hydrocarbons are used as the reducing gas. If the reducing gas contains carbon, CO is preferred₂Emission, H₂Or hydrogen-based reducing agents such as ammonia.

Certain ores can be reduced at high temperatures in a vacuum without the need for reducing agents. In this case, the use of reducing agents is not required, the common result being the elimination of harmful CO₂And (5) discharging. The ore is mixed with flux and pelletized. The pellets are poured into the crucible and placed into chamber 103A as shown in FIG. 1C. A vacuum pump 113 is connected to the outlet 107 and the inlet 106 is closed. The pump evacuates chamber 103A to below about 200 μm. The microwave energy heats the pellets under vacuum, and the pellets are reduced and melted to form molten metal and slag. A quartz window 114 is installed to seal the waveguide 105, but allows for microminiaturizationThe wave 104 passes through.

In an alternative method, as shown in fig. 2, the high power microwave oven is constructed with a water-cooled metal tube 201 and a movable water-cooled metal lid 202. Both the tube and the lid are lined with refractory material 203. There may be an inlet 205 and an outlet 204 in the cover 202. Gases may be input through inlet 205 and exhaust gases may be exhausted through outlet 204 to control the furnace atmosphere. To make the metal, lid 202 is removed and the mixed feed material containing the ore and reductant in the form of pellets, briquettes, or other suitable forms other than a stream of small particles is charged into microwave chamber 206. The cap 202 is then moved back to close the tube. Microwaves are input into the chamber 206 through the waveguide port 207 and dispersed throughout the chamber. Subsequently, the mixed raw materials start to absorb microwave energy and heat up. When the temperature is high enough, any auxiliary fuel input with the mixed feedstock is ignited to generate more heat 208 and further raise the temperature within the tube. The reducing agent breaks bonds between metal atoms and other atoms within the ore by directly contacting the ore. The ore begins to melt and form metal droplets 209 and slag 210. Due to the specific density difference, the metal droplets fall to form a molten pool 211 at the bottom of the tube, and the slag 210 floats on top of the molten metal. The flux melts and reacts with the slag to form a low viscosity slag that provides for better separation of the molten metal from the slag. The slag is a refractory material which continuously absorbs microwave energy and maintains high temperature when the metal and the slag are separated. After the molten metal is separated from the slag, the microwave generator is turned off and the molten mass is allowed to cool. This cooling results in the formation of solid metal ingots and slag. The solidified slag is broken away from the ingot by mechanical impact. Alternatively, the slag may be stripped after the microwave is turned off. The cover 202 is opened. The tube is tilted so as to inject slag into a slag container through the slag outlet 212. Subsequently, the molten metal is poured into a mold to form a metal ingot or into a continuous casting machine for continuous casting. It is also possible to inject the molten metal into a tundish and send it to another refining furnace.

As another alternative, an oven with microwave heating and induction heating capabilities may be constructed as shown in fig. 3. The furnace comprises a water-cooled metal tube 301 and a movable water-cooled metal cover 302 both lined with refractory material 303. The refractory material may be selected from materials with poor microwave absorbing properties such as quartz. A portion of the metal tube 301 is a coil made of copper tube, serving as the induction coil 304. The apparatus is arranged to allow cooling water to flow within the tube to cool the coil. The distance between the turns of the coil is small to prevent leakage of microwaves. The metal tube 301, the cover 302 and the induction coil 304 form a microwave chamber 305. The lid 302 may include an inlet 306 and an outlet 307 to allow for the input of process gases and exhaust emissions. Therefore, the furnace atmosphere can be controlled.

To produce metal, the lid 302 is removed and a mixed feed of metal-bearing material in the form of pellets, small blocks or other suitable forms in addition to a stream of small particles, reducing agents, and other process-enhancing chemicals, such as chemicals suitable for a particular environment, is charged into the microwave chamber 305. The lid 302 is then moved back to close the tube. Microwave energy is input through waveguide port 308 and the raw material mixture 307A begins to absorb the microwave energy, resulting in an increase in temperature. The ore reacts with the reducing agent in the mixture or with the reducing gas input through inlet 306 to release the metal. Once the metal begins to appear and the feedstock material becomes conductive, the induction heating power supply is turned on. The input of additional heat further increases the temperature of the mixture within the tube. As the temperature increases, metal droplets 309 accumulate and slag 310 forms. Due to the specific density difference between the molten metal and the slag, the metal droplets fall to the bottom under gravity and form a molten pool 311, with the slag 310 floating above the molten metal. The flux, which melts with the remaining mixture, reduces the slag viscosity and thus better separates the molten metal from the slag. The slag continues to absorb the microwave energy and continues to heat the molten metal with the induced current. After the molten metal is rapidly separated from the slag, the microwave and induction heating power supplies are turned off. The tube is tilted to inject molten slag into a slag container through the slag outlet 312. The tube is then further tilted to inject molten metal into a mold to form a metal ingot or into a continuous casting machine for continuous casting. It is also possible to inject the molten metal into a tundish and send it to another refining furnace.

A refining instant furnace may also be used. After the slag is injectedAfter a slag container is placed, the tube is returned to the vertical position and the lid 302 is replaced. The induction heating power is turned on again. Powdered substances such as CaO and NaCO can be introduced through an opening 313 in the bottom of the tube 301 or a movable tube 314 which can be immersed in the molten metal to remove S and P₃Blown into chamber 305. Scrap metals and alloys may be added to the molten metal to adjust the composition to meet specific specifications. During this part of the operation, induction heating is used to control the temperature.

As another alternative, an oven with microwave heating and arc heating capabilities may be constructed as shown in fig. 4. The furnace comprises a water-cooled metal tube 401 and a movable water-cooled metal cover 402, both lined with refractory material 403. Three graphite electrodes, having a diameter of more than 50mm, are inserted into the furnace chamber 404 through the metal cover 402. An opening 405 is opened in the lid 402 to input microwaves 406 into the oven chamber 404 through a connecting waveguide 407.

To make the metal, the lid 402 is removed and a mixture 408 of metal-containing material in the form of pellets, small pieces, or other suitable forms in addition to a stream of small particles, a reducing agent, and other operational-enhancing chemicals, such as chemicals suitable for a particular environment, is loaded into the chamber 404. The cap 302 is then moved back to close the tube. Microwaves are input through the waveguide port 407, and the raw material mixture 408 starts absorbing the microwaves, with the result that the temperature rises. When the temperature is high enough, any auxiliary fuel input with the mixed feedstock is ignited to generate more heat 409 and further raise the temperature within the tube. The ore begins to react with the reductant in the mixture at high temperatures and produces a directly reduced metal. Once the metal begins to appear and the feedstock substance becomes conductive, the feed electrode 410 is lowered to create an arc between the electrode tip S and the metal, which further heats the metal. The input of auxiliary heat further increases the temperature of the mixture in the tube. As the temperature increases, metal droplets 411 accumulate and form slag 412. Due to the specific density difference between the molten metal and the slag, the metal droplets fall to the bottom under gravity and form a molten pool 413, with the slag 412 floating above the molten metal. The flux, which melts with the rest of the mixture, reduces the slag viscosity and thus better separates the molten metal from the slag. After the molten metal is rapidly separated from the slag, the microwave and arc heating power supplies are turned off. The tube is tilted to inject molten slag into a slag container through the slag outlet 414. The tube is then further tilted to inject molten metal into a mold to form a metal ingot or into a continuous casting machine for continuous casting. It is also possible to inject the molten metal into a tundish and send it to another refining furnace.

As an alternative to a process where the aim is continuous production, a continuous microwave/induction heating furnace may be constructed as shown in fig. 5. It mainly comprises a water-cooled housing 501, a water-cooled induction heating coil 502, a raw material charging port 503, a waveguide port 504, a tap port 505 and a molten metal discharging port 506. Both the metal shell 501 and the induction coil 502 are lined with a refractory 507 that is poorly microwave absorbing. To begin the process, a mixed feedstock 508 in the form of pellets, chunks, or other suitable forms in addition to a stream of small particles is charged into the furnace through charging port 503. The microwave power is turned on and microwaves are input into the oven chamber 510 through the waveguide port 504 and dispersed therein. The raw mixture begins to absorb microwaves and warms up. As the temperature increases, the internal combustion auxiliary fuel is ignited to generate heat 509 and further heat up. The ore reacts directly or indirectly with the reducing agent in the feed material to form a metal. After the feedstock substance becomes conductive, the induction heating power supply is turned on to heat the metal. The metal begins to melt and form metal droplets 511 and slag 512. Due to the specific density difference, the metal droplets fall to the bottom under gravity and form a molten pool 513, while the slag 512 floats on top of the molten metal. The flux also melts and reacts with the slag to form a low viscosity slag for better separation of the molten metal from the molten slag. After the molten metal forms and sinks to the bottom, the induction heating power supply continues to heat and maintain the temperature of the molten metal. The slag continues to absorb microwave energy. After sufficient slag or molten metal has accumulated, the slag and metal are discharged through discharge ports 505 and 506, respectively. The vents 505 and 506 are plugged with fire clay before being poked open with a steel rod. Molten metal may be cast or continuously cast into ingots or conveyed into a refining furnace to remove impurities, adjust composition, and control temperature to produce high quality alloys. As slag and metal are tapped, more material is charged into the furnace through the charging port 503. The cycle continues with heating, ore reduction, melting, discharging and recharging.

Example 1

A sample containing an iron ore concentrate was prepared containing 65% iron mixed with 15% carbon black as the reducing agent, 1% lime as the flux and 5% pulverized coal as the auxiliary fuel. The mixture was charged into a chamotte crucible and charged into a microwave treatment apparatus MCR200 manufactured by Wavemat Co. The apparatus includes a 2.45Ghz microwave generator with a power of 300 watts to 3000 watts. The microwave device may be used in conjunction with a tunable single-mode or controllable multi-mode microwave chamber. The chamber may be evacuated or continuously flushed with an inert gas or a reducing gas. A single mode with a power of 1kw was used and the sample was heated to 1200 ℃ over 10 minutes. The temperature of the outer surface of the crucible was measured with a pyrometer. The temperature inside the crucible was not measured, but it was known that the temperature was higher than 1200 ℃. During the heating period, the pulverized coal burns and generates a flame. The sample was incubated at about 1200 ℃ for about 2 minutes and then the power was turned off. Testing of the sample after cooling to room temperature indicated the formation of metal and slag. The metal accumulates at the bottom and the slag is at the top of the crucible. Chemical composition analysis showed that the metal contained 1.53% Si, 97.72% Fe, 0.42% Al, 0.13% S and 0.2% C, while the slag contained 53.58% SiO₂15.48 percent of FeO, 0.48 percent of CaO, 1.56 percent of MgO and 15.40 percent of Al₂O₃0.53% of K₂O₃0.39% MnO and 12.59% TiO₂。

Example 2

Preparing a Cu-containing material₂A sample of S powder mixed with stoichiometric, i.e. 7.5%, carbon black as reducing agent. The mixture was charged into a chamotte crucible and charged into a microwave treatment apparatus MCR 200. The microwave chamber continuously uses N₂The discharge of the flushing detritus chamber is connected to a scrubber. The washer consists of a glass flask with a side tube and a rubber stopper for sealing its mouth. Half of the flask was filled with 10% alkaline NaOH solution.A tube passed through the rubber stopper is immersed in an alkaline solution at one end of the tube. The other end of the tube is connected to the outlet of the microwave chamber with a hose. During the heating period, the sample developed a lot of smoke and the smoke was passed into the NaOH solution. The sample was heated to 1100 ℃ over 5 minutes using a single mode. The temperature of the outer surface of the crucible was measured with a pyrometer. The temperature was maintained at about 1100 c for about 2 minutes and then the power was turned off. It was found that copper accumulated at the bottom and slag formed at the top of the crucible. Analysis showed that the washing solution contained sulfide.

Claims (15)

1. A method of directly producing a metal from a metal-containing material, the method comprising: providing a metalliferous material and a reducing agent, mixing the metalliferous material with the reducing agent to form a mixture, charging the mixture into a vessel by suitable means other than a stream of small particles, heating the mixture with minimal impurities by applying microwave energy to the mixture until the mixture becomes electrically conductive, further heating the mixture by an electric arc or by electric induction until molten metal is released from the metalliferous material, the molten metal accumulating under gravity at the bottom of the vessel, and discharging the metal from the vessel.

2. The method of claim 1, wherein the method further comprises: a step of mixing a flux with the metal-containing substance.

3. The method of claim 1, wherein the method further comprises: a step of mixing an auxiliary fuel with the metalliferous material.

4. The method of claim 1, wherein the method further comprises: mixing microwave absorber material.

5. The method of claim 1, wherein the method further comprises: a step of preheating the metal-containing substance to increase its microwave absorbing capacity.

6. The method of claim 1, wherein the step of heating the mixture produces a molten slag.

7. The method of claim 1, wherein the method further comprises: a step of controlling the ambient atmosphere of the mixture during the heating period.

8. The method of claim 1, wherein the method further comprises: collecting sulfide vapor or SO2 liberated from the metalliferous material during the heating period.

9. The method of claim 1, wherein the container comprises a ceramic crucible.

10. The method of claim 1, wherein the vessel comprises a refractory lined, tiltable metal tube.

11. The method of claim 1, wherein the container comprises an induction coil.

12. The method of claim 1, wherein the container comprises an electrode.

13. The method of claim 1, wherein said vessel comprises a static metal furnace having a molten metal discharge outlet.

14. The method of claim 1, wherein the container comprises a vacuum.

15. The method of claim 1, wherein the metalliferous material comprises a metal selected from the group consisting of iron, copper, nickel, cobalt, lead, and zinc.