Patent ID: 12241133

DETAILED DESCRIPTION OF THE INVENTION

With reference to the accompanying drawing, in which like numerals refer to like features, a process for the smelting of a metalliferous feedstock material according to the invention is generally designated by reference number10.

The process for the smelting of a metalliferous feedstock material10includes the steps of:(i) feeding an agglomerate (not shown) comprising of a fine metalliferous feedstock material (not shown) and a fine reductant (not shown) to a reactor12, the agglomerate forming a packed bed14within the reactor12;(ii) smelting the agglomerate (not shown) by passing a hot reducing gas counter current through the packed bed to form a molten material (not shown) comprising a partially reduced metalliferous constituent (not shown), an intermediate slag constituent (not shown) and entrained unreacted reductant constituent (not shown); and(iii) channeling the molten material to flow into a vessel26to form a liquid metal product16and a final slag product18.

Typically, the metalliferous feedstock material is a mined metal oxide. However, the metalliferous feedstock material may be any material containing a metal oxide.

The agglomerate is fed gravitationally to the reactor12to form a fluid permeable packed bed14of agglomerates. The packed bed14of agglomerates is stacked between 2 and 3 metres high in the reactor12. Ideally, the agglomerate has a diameter of between 10 mm and 20 mm, but the process10can accommodate agglomerates with a diameter of anything between 2 mm and 80 mm and even more. It is an advantage of the process10, owing to, amongst other things, the low height of the packed bed14in the reactor12, that agglomerates with limited strength and therefore limited, or no binder content can be utilised. The metalliferous feedstock material is dispersed within the agglomerate and is preferably a fine material having a particle size of less than 75 μm. It will be appreciated that the agglomerates may include a binder or binding agent, and the use or disuse of binder or binding agent would depend on the size of the agglomerate used in the process10and/or the height at which the packed bed14of agglomerates is stacked in the reactor12. Furthermore, the agglomerate may include a flux or fluxing agent.

In this example, the agglomerates in the packed bed14are smelted by passing a hot reducing gas (not shown) therethrough in a counter current fashion. The hot reducing gas is fed to the reactor12at an operatively downstream position20of the packed bed14of agglomerates and counter current to the direction in which agglomerates are fed to the reactor12. The hot reducing gas is fed to the reactor12at a velocity of between 3 and 4 m/s so that the hot reducing gas permeates through the packed bed14of agglomerates. The temperature of the hot reducing gas is controlled to be above 1300° C. and up to 1700° C., depending on the type of metalliferous feedstock material in the agglomerate and the extent of the reduction of the metalliferous feedstock material desired in the packed bed14of agglomerates.

By way of example, the hot reducing gas will be fed to the reactor12at a lower temperature when the metalliferous feedstock material is an iron-oxide than in an instance where the metalliferous feedstock material is a chrome-oxide. Importantly, the temperature of the hot reducing gas for smelting of iron-oxides can be set lower than the temperature at which silica-oxides and sulphides would be reduced, which will ensure a high purity pig iron being produced. The hot reducing gas is typically synthesis gas and preferably has a carbon monoxide to carbon dioxide (CO/CO2) ratio greater than 10, preferably 15. As the hot reducing gas pervades through the packed bed14of agglomerates, the metalliferous feedstock material is partially reduced towards its metallic form. Here, the CO/CO2ratio of the synthesis gas is controlled to prevent re-oxidation of the reduced metalliferous feedstock material in the packed bed14of agglomerates and reactor12.

In addition to partially reducing the metalliferous feedstock material in the agglomerates, the hot reducing gas melts the agglomerate, thereby forming a molten material comprising of a partially reduced metalliferous constituent, an intermediate slag constituent and entrained unreacted reductant constituent; the entrained unreacted reductant constituent emanates from the agglomerate. An advantage of the process of the invention is that the melting temperature of the agglomerate can be controlled. Control over the melting temperature of the agglomerate results in control over the residence time of the metalliferous feedstock material in the reactor12; i.e. the rate at which the formed molten material flows out of the packed bed14is controlled. In turn, control over the residence time of the metalliferous feedstock material in the reactor12results in control over the degree of reduction of the metalliferous feedstock material taking place in the reactor.

A further significant advantage of the present invention is that by controlling or manipulating the composition of the agglomerates the melting temperature of the agglomerates can be controlled or manipulated. Thus, the rate of smelting of the agglomerate and the degree of reduction of the fine metalliferous feedstock material in the reactor12can be controlled. For example, by lowering the melting temperature of the agglomerate the rate of smelting of the agglomerate is increased and the degree of reduction of the metalliferous feedstock material is decreased in the reactor12. In turn, by increasing the melting temperature of the agglomerate the rate of smelting of the agglomerate is decreased and the degree of reduction of the metalliferous feedstock material is increased in the reactor12. It will be appreciated that the afore steps will determine the residence time of the agglomerate and metalliferous feedstock material containing metal oxides in the reactor12. Therefore, the degree to which the metal oxides present in the agglomerates are reduced can be controlled, which is useful to optimise profitability.

The melting temperature of the agglomerate is controlled by a number of physical and chemical characteristics of the agglomerate and its constituents. For example, the melting temperate of the agglomerate can be increased by adding a flux or a fluxing agent thereto. The nature or type of metalliferous feedstock material would also influence the melting temperature of the agglomerate; i.e. all else being equal, an agglomerate containing iron-oxide would melt at a lower temperate than an agglomerate containing chromium-oxide.

Consequently, the residence time of the agglomerate in the reactor and thereby the degree of reduction of the metalliferous feedstock material may be controlled, depending on any one or a combination of the following:the melting temperature of the metalliferous feedstock material and/or agglomerate, which is controlled by:i. the amount and nature of the flux or fluxing agent added to the agglomerate;ii. the amount and nature of the binder or binding agent added to the agglomerate; andiii. the selection of the ore types.the temperature at which the hot reducing gas is fed to the packed bed14of agglomerates; andthe size of the agglomerates.

A fluid permeable interface is formed at an operatively lower region of the packed bed14. The fluid permeable interface allows: (i) the hot reducing gas to pass therethrough and into the packed bed14of agglomerates and (ii) the molten material to flow out of and away from the packed bed14of agglomerates. In the embodiment shown inFIG.1, the fluid permeable interface is formed adjacent to an obstruction22located in the reactor12. The obstruction22ofFIG.1takes the form of a porous bed of refractories. However, the obstruction22may also take the form of a porous bed of coke particles.

The pressure-drop of the hot reducing gas across the permeable fluid interface and packed bed14of agglomerates is minimized and typically in the order of 5 to 10 kPa. The temperature of the hot reducing gas, after having passed through the permeable bed14of agglomerates, is typically less than 300° C.

Having passed through the fluid permeable interface and from the packed bed14of agglomerates and to the vessel26, electrical energy is added to the molten material. By adding electrical energy to the molten material, the partially reduced metalliferous constituent in the molten material is metallized and an optimised liquid metal product16and a final concentrated slag product18are formed. Electrical energy is added to the molten material via an electrode or electrodes24which is/are submerged in the molten material.

The optimised liquid metal and final slag products are, in an embodiment of the invention, formed via an electrochemical reaction between the partially reduced metalliferous constituent and the entrained unreacted reductant constituent, the intermediate slag serving as an electrolyte. This allows the metallisation to proceed to much higher levels compared to conventional smelting as known in the art.

Advantageously, the vessel26is in fluid flow communication with the reactor12, thereby minimising heat loss during transfer of the molten material from the partial reduction reaction and melting to the electrochemical reaction. Furthermore, additional reductant (not shown) may be added to the molten material prior to or whilst subjecting same to the electrochemical reaction.

A major breakthrough achieved in the process10of the present invention is that it allows for the processing of the ores with hot synthesis gas while further allowing the products to melt and having a process design that can transfer the molten material to a further vessel for producing a liquid metal product and final slag product. The process10of the present invention thereby shows that, contrary to the perception of people skilled in the art that ores like chrome and manganese cannot be smelted by commercially produced hot gasses, these ores can in fact be smelted through use of such gasses using the process10of the present invention.

The process10of the present invention further provides the major advantage that the process reaction temperatures can be controlled at a required temperature, this in turn allows a metal constituent to be reduced to be targeted at a selected temperature whilst avoiding reduction of impurities which are present.

It will be appreciated by those skilled in the art that the invention is not limited to the precise details as described herein and that many variations are possible without departing from the scope of the invention. As such, the present invention extends to all functionally equivalent processing equipment, structures, methods and uses that are within its scope. In particular, the steps of the process provided for need not necessarily be executed sequentially. Furthermore, it is envisaged that the steps of the process provided for need not necessarily be executed in the order listed herein.

The description is presented by way of example only in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention and/or the equipment utilised therein in more detail than is necessary for a fundamental understanding of the invention. The words which have been used herein are words of description and illustration, rather than words of limitation.