CN1871366B - Method and apparatus for reducing metal-oxygen compounds - Google Patents

Abstract

The present invention relates to a method of reducing a metal-oxygen compound wherein carbon acts as a reducing agent, comprising in a first reaction stage, passing CO gas into a reaction chamber containing said metal-oxygen compound, under conditions such that CO is converted to solid carbon and carbon dioxide thereby introducing the solid carbon so formed to said metal-oxygen compound, and in a second reaction stage, causing said carbon, which is introduced to the metal-oxygen compound in said first reaction stage, to reduce said metal-oxygen compound, wherein there is present, at least in said second reaction stage, a first promoter material effective to promote the reduction of said metal-oxygen compound, the first promoter material comprising a first promoter metal and/or a compound of a first promoter metal. The invention also relates to an apparatus for carrying out the reduction of a metaloxygen compound wherein carbon acts as a reducing agent.

Description

Method and apparatus for reducing metal-oxygen compounds

technical field

The present invention relates to a method for reducing metal-oxygen compounds using carbon as a reducing agent for reducing metal-oxygen compounds. The present invention also relates to an apparatus for reducing metal-oxygen compounds using carbon as a reducing agent for reducing metal-oxygen compounds.

Background technique

The reduction of metal-oxygen compounds, including various metal oxides such as iron oxides, has been performed in large reduction furnaces. For the reduction of iron-oxygen compounds, blast furnaces have been used as the main equipment for producing pig iron from iron ore for more than a century. The main reducing agent and source of chemical energy in the blast furnace is coke. Coke is prepared by roasting coal in an oxygen-deficient environment in order to remove volatile hydrocarbons so that the coke has the key properties required for the stable operation of the blast furnace.

Coking is problematic from an environmental standpoint because many volatile hydrocarbons are harmful. Also, not all types of coal are suitable for coking. In addition, the demand for coking by-products has decreased.

Therefore, reducing the coke ratio in the blast furnace and the total fuel ratio has become the main focus of research and development work in recent years. Furthermore, new technologies have been developed that bypass the blast furnace process, such as direct reduction of iron ore.

Direct reduction involves the production of iron by reducing iron ore with a reducing agent, which may be a solid reducing agent or a gaseous reducing agent. The solid reductant can be coal of any size other than coke. Examples of gaseous reducing agents are natural gas and carbon monoxide. The ore used for direct reduction must meet strict specifications requiring a high iron percentage and low levels of harmful elements.

Direct reduction of iron ore can produce a solid direct reduced iron product, or, at high operating temperatures or in conjunction with a smelting unit, a liquid product can be produced.

The product of the direct reduction process can be sent to a second reactor for smelting and optional further refining, or cooled and stored for later use.

Currently, dust and sludge from integrated steel mills are recycled as raw material for the ore preparation stage. These waste materials, commonly referred to as "fines," may contain iron-containing compounds, such as iron oxides. However, because of the high content of metals such as zinc in these scraps, the accumulation of these elements, and the need to limit the amount of these metals that can be fed to the blast furnace, it is often necessary to recycle or dispose of the waste in other ways, As a result, costs or environmental burdens are additionally increased.

One known method of reducing iron ore is based on the direct reaction of coal and iron ore lumps or pellets in a rotary kiln. Another known method is based on the reduction in a rotary hearth furnace of composite pellets comprising oxides of iron and carbon from, for example, coal, coke or charcoal. The exhaust gas from the reduction reaction can be post-combusted in the furnace to provide part of the heat required by the process. Yet another known method involves the direct reduction of iron ore fines in a fluidized bed reactor.

A major disadvantage of these known reduction methods is that they have to be carried out at high temperatures. For example, the operating temperature of the rotary hearth furnace process is about 1250°C. If these processes are based on the use of coal, a further disadvantage is the production of large quantities of carbon monoxide, hydrogen and complex and harmful hydrocarbons. Condensation of these hydrocarbons must be avoided which requires removal or post-combustion of the exhaust gases while metal re-oxidation must be prevented. Furthermore, the energy efficiency of direct reduction processes is generally very low due to the high operating temperatures and consequent heat loss, as well as the production of large amounts of carbon monoxide, resulting in high rates of carbon consumption. High operating temperatures also lead to the formation of large amounts of harmful nitrogen oxides (NOx gases). In addition, direct reduction techniques based on the use of coal must deal with the high sulfur content due to the presence of sulfur in coal.

GB-A-1471544 describes a method for the direct reduction of iron ore, in which iron oxides such as magnetite are mixed with ferric chloride nucleating agents, and coal is also mixed with ferric chloride in the same form Activator mix. Mix the two mixtures together well to form balls. The pellets were purged with cold nitrogen, then heated slowly to 1050° C. with heated nitrogen, held for 30 minutes and cooled in cold nitrogen. _CO2 is initially formed from the reaction of carbon with oxides. The activator facilitates the _reduction of CO by carbon to form CO. The nucleating agent (iron from ferric chloride) facilitates the adsorption of CO on the surface of the oxide, thereby accelerating the reduction of the oxide by CO.

US-A-3979206 describes the reduction of MgO with carbon in the presence of iron, cobalt, nickel, chromium or manganese at 1000-2000°C. The Fe powder, MgO powder and C powder were heated in a vacuum furnace. Mg vapor is recovered. Fe is said to act as a catalyst, capable of lowering the reaction temperature.

Contents of the invention

It is an object of the present invention to provide a method and apparatus for the reduction of metal-oxygen compounds capable of operating at lower temperatures.

Another object of the present invention is to provide a method and apparatus for reducing metal-oxygen compounds that produce less harmful off-gas such as hydrocarbons and/or NOx gases.

Still another object of the present invention is to provide a method and apparatus for reducing metal-oxygen compounds capable of increasing carbon efficiency per unit weight of reduced metal.

Yet another object of the present invention is to provide a method and an apparatus for reducing metal-oxygen compounds with improved energy efficiency and low sulfur content in the obtained product.

Yet another object of the present invention is to provide a method and an apparatus which can be used for the reduction of mixtures of different metal-oxygen compounds to obtain metal alloys.

In order to achieve one or more of the stated objects, there is provided a method for reducing metal-oxygen compounds using carbon as a reducing agent, which comprises: in the first reaction stage, CO gas is fed into the reaction of metal-oxygen-containing compounds chamber, the conditions of the reaction chamber are such that CO is converted into solid carbon and carbon dioxide, thereby introducing the solid carbon formed into the metal-oxygen compound, and, in the second reaction stage, allowing the introduction into the metal-oxygen compound in the first reaction stage Carbon reduction of metal-oxygen compounds in wherein, at least in the second reaction stage, there is a first promoter (promoter) material effective to promote the reduction of metal-oxygen compounds, the first promoter material comprising a first promoter compound of the promoter metal and/or the first promoter metal.

A feature of the invention is the use of a first promoter material in the second reaction stage. It has surprisingly been found that the addition of a first promoter material greatly increases the rate of reduction of metal-oxygen compounds when carbon is used as the reducing agent for the metal-oxygen compounds. It has also been found that this reduction can be carried out at significantly lower temperatures compared to known direct reduction methods. For example, known methods of reducing iron-oxygen compounds employ operating temperatures above 950°C. Since the method of the present invention can be implemented at a lower temperature, it can also reduce the production of harmful nitrogen-oxygen compounds and reduce the heat loss of equipment.

It has been noted that in known reduction processes, such as in iron-oxygen compounds in iron-making blast furnaces, the metal formed during the reduction does not contribute to the reduction reaction because it does not act as a catalyst. This is believed to be related to the fact that in known processes of this type and in blast furnaces of this type, the process conditions required for the metal formed to catalyze the reduction reaction to reduce the iron-oxygen compound are not met.

In one embodiment of the invention, at least part of the first promoter metal is formed from an intermediate compound (first promoter material) selected from the group consisting of metal carbides, metal hydrides and metal nitrides, wherein, The metal in the compound is the first promoter metal, and the compound optionally contains oxygen. Such intermediate compounds can be added to metal-oxygen compounds. Intermediate compounds such as metal carbides are capable of forming the first metal, thereby facilitating the reduction of the metal-oxygen compound. Further intermediate compounds are, for example, metal hydrides, metal nitrides or mixtures comprising metal carbides and/or metal hydrides and/or metal nitrides. Another example of an intermediate compound is a metal carbonyl, which can be broken down into metal and carbon monoxide. Metal carbonyls are quite expensive and are not usually used in the production of large quantities of metals.

The advantage of using an intermediate compound is that the first promoter metal formed when the intermediate compound decomposes is finely dispersed, thus enabling it to effectively promote the reduction reaction. The first metal may (just) be formed from the intermediate compound prior to the reduction reaction that reduces the metal-oxygen compound. If the intermediate compound is a metal carbide in which the metal is the first promoter metal, when the intermediate compound decomposes, both the first promoter metal and the carbon are in a finely dispersed state, allowing the first promoter metal to be effectively The reduction reaction is promoted, and carbon effectively functions as a reducing agent in the reduction reaction.

The first promoter metal for the reduction of the metal-oxygen compound may be added to the metal-oxygen compound at any stage of the process as long as the first promoter metal is present at least when the reduction of the metal-oxygen compound should occur middle.

A second characteristic of the present invention is that carbon monoxide is contacted with a metal-oxygen compound and, by a Boudouard reaction, said carbon and carbon dioxide are formed from carbon monoxide, preferably by means of a second accelerator material, said second accelerator The material can be, for example, a second promoter metal. The carbon is called Brinell carbon, which typically has a graphite crystal structure. Carbon monoxide may be substantially pure carbon monoxide, but may also be a gas mixture partially comprising carbon monoxide. Whether at the beginning of the process for reducing the metal-oxygen compound or during the reduction of the metal-oxygen compound, a compound similar to Brückner's carbon and in an appropriate form, such as graphite powder, can be added to the metal-oxygen compound, for at least part of the metal-oxygen compound. The reduction of the oxygen compound acts as a reducing agent.

Therefore, carbon used as a reducing agent for reducing metal-oxygen compounds is amorphous carbon and/or crystalline carbon, preferably graphite, because the reduction rate of the reduction reaction can be significantly increased. Crystalline carbon or especially graphite is a preferred form of carbon. In the present invention, the carbon is in the form of powder, which can play the role of increasing the number of contact points between reacting substances, thereby also increasing the reaction speed.

In the first reaction stage, Brookfield carbon is generated by the Brookfield reaction to decompose carbon monoxide. The Brookfield reaction is:

In the first reaction stage, the reaction conditions shift this equilibrium to the right of reaction (1), resulting in the formation of carbon. Professionals can easily select suitable conditions.

Surprisingly, it has been found that this Brückner carbon with a graphitic structure is a reducing agent which, together with a first promoter material such as a first When the metal and the metal-oxygen compound are in contact, the metal-oxygen compound can be reduced very efficiently.

As mentioned, preferably, at least in the first reaction step, there is a second promoter material comprising a second promoter metal and/or a second promoter material that promotes the conversion of CO to carbon and carbon dioxide. A compound of two promoter metals. Preferably, the second promoter material is a second promoter metal, a carbide of a second promoter metal, a hydride of a second promoter metal, or a nitride of a second promoter metal, or a combination thereof. Preferably the second accelerator material is in powder form.

Generally, in the present invention, the first and second promoter materials, especially the first and second promoter metals, have the ability to make each of the two reaction stages catalyzed or by another reaction mechanism. The ability of a reaction to occur faster, more completely, or at a lower temperature (or a combination of these effects).

Surprisingly, it has also been found that the first promoter material, for example the first promoter metal, not only contributes to the reduction of the metal-oxygen compound, but also facilitates the formation of Brunnery carbon by the Brunner reaction. A first promoter metal may be added to the process, but some of the first promoter metal may also be formed by reduction of the metal-oxygen compound already in progress at the lower temperatures at which the Brinell reaction occurs.

In one embodiment of the present invention, in the reduction reaction to reduce the metal-oxygen compound, the oxygen in the metal-oxygen compound is mainly bound to carbon formed from carbon monoxide by the Brückner reaction. When using carbon as the primary reducing agent, the process can be performed at low temperatures. This is the case when coal is used as the main carbon source. However, if natural gas is selected as the main carbon source, the amount of hydrogen produced by the cracking of natural gas (usually containing a large amount of hydrocarbons such as methane) will have an adverse effect on the operating conditions, thereby weakening the advantages obtained by the method according to the invention, especially for fossil fuels. Efficient use of fuel and lower implementation temperature.

Small amounts of hydrogen are known to promote the formation of Brunner's carbon and carbon dioxide from carbon monoxide by the Brunner reaction. When pure carbon monoxide is used, a small amount of hydrogen can be added to the carbon monoxide. Preferably the amount of hydrogen is less than 8 vol.%, more preferably less than 6 vol.%. Due to the selected working conditions, hydrogen is not critical for the reduction of metal-oxygen compounds. The hydrogen reduction of the metal-oxygen compound takes place at significantly higher temperatures, thereby negating the advantages of the method according to the invention.

In the present invention, typically more than 50%, preferably more than 70%, more preferably more than 80%, and even more preferably more than 90% of the oxygen in the metal-oxygen compound reacts with the cloth in the reduction reaction of the metal-oxygen compound. carbon bonded. If a carbon monoxide-containing gas mixture is obtained, for example, by gasification of coal, this gas mixture also contains small amounts of hydrogen.

Compounds similar to Brückner's carbon and having a suitable form can be added in the process, or compounds which generate Brückner's carbon, such as metal carbides, can be added, for example at the beginning. If so, the Brinell's carbon in the preceding embodiments is a Brinell's carbon formed from carbon monoxide and/or similar to Brinell's carbon with appropriate forms of added carbon and/or carbon derived from metal carbides. Since the gaseous reaction product of the process according to the invention comprises a high content of carbon dioxide gas compared to the exhaust gas in conventional processes, carbon is used efficiently, thereby also reducing the amount of fossil fuels used. As a result, the amount of carbon used for reduction per weight of metal in the process according to the invention is reduced.

Furthermore, the gaseous reaction product in the process according to the invention does not contain harmful hydrocarbons associated with coal, due to the use of Brinell carbon derived from carbon monoxide instead of carbon in the form of coal as the reducing agent in the process of the invention. If the carbon monoxide-containing gas mixture contains no sulfur compounds, the sulfur content of the reaction solids is not affected. If the gas mixture containing carbon monoxide comprises hydrocarbons and/or sulfur compounds, the gaseous reaction product of the process according to the invention will contain a lower content of these hydrocarbons and/or sulfur compounds, because in the process at least Some of the heavy components of hydrocarbons are cracked and/or used. Sulfur compounds can be neutralized, for example, by a known calcium treatment process to form calcium-sulfur compounds such as CaS, which can be separated from the metal fraction, for example in a cyclone.

In yet another embodiment of the invention, the first promoter metal is the same as the second promoter metal, thereby minimizing the amount of other metals entering the reduction reaction product of the reduced metal-oxygen compound. In yet another embodiment of the invention, the first and/or second promoter metal is the same as the metal in the metal-oxygen compound. When producing a single metal material, the amount of other elements is kept as low as possible to prevent contamination by other metals. When producing an alloy, it may be advantageous to use as the first and/or second promoter metal one or more metals different from the metals in the metal-oxygen compound.

In a preferred embodiment of the present invention, the reduction reaction of the metal-oxygen compound is carried out in a continuous process, the first and second reaction stages are carried out simultaneously, and the metal-oxygen compound is transferred from the first reaction zone where the first reaction stage occurs to the second reaction zone where the second reaction stage takes place. Thus, in a preferred embodiment, carbon monoxide moves relative to the mixture consisting of the metal-oxygen compound, the reducing agent for reducing the metal-oxygen compound and the first and/or second promoter metal. In yet another preferred embodiment, the metal-oxygen compound is transported in one direction and the carbon monoxide is transported in the other direction. In yet another preferred embodiment, the metal-oxygen compound is conveyed countercurrently to the carbon monoxide. Furthermore, at least part of the gaseous reaction products can be fed back into the process, thus reducing the amount of new carbon monoxide to be added. Furthermore, at least part of the substantially solid product of the metal-oxygen compound reduction reaction can be reintroduced into the process as the first and/or second promoter metal for the reduction reaction, thereby reducing the need to add new first The amount of the first and/or second accelerator material.

In consideration of reaction kinetics, the working temperature in the first reaction zone where the Brookfield reaction occurs is preferably lower than 650°C, more preferably between 300-600°C, and even more preferably between 450-550°C. In a preferred embodiment of the invention, the metal-oxygen compound comprises an iron-oxygen compound, such as iron oxide and/or iron hydroxide and/or iron carbonate. In addition, the first and/or second promoter metal may contain iron in order to limit the amount of non-ferrous metals in the obtained iron-oxygen compound reduction reaction product. In consideration of reaction kinetics, the working temperature in the reaction zone where the reduction of metal-oxygen compounds, such as iron-oxygen compounds, is carried out is preferably 550-900°C, more preferably 650-850°C, still more preferably 700-775°C. The process according to the invention described above can be carried out substantially at atmospheric pressure. It is obvious to the skilled person that carrying out the process according to the invention at non-atmospheric pressure will shift the reaction equilibrium. The invention also includes carrying out the method at subatmospheric or superatmospheric pressures, and the invention also includes controlling the use of the method according to the invention in such a way that the pressure at which the Brückner reaction (first reaction stage) takes place is closely related to the metal-oxygen It is different when the compound is reduced (second reaction stage).

It should be noted that due to the nature of the Brunner reaction and the kinetics of the reduction of the metal-oxygen compound, there can be a heavy gap between the reaction zone where carbon is formed from carbon monoxide by the Brunner reaction and the reaction zone where the metal-oxygen compound reduction mainly takes place. because some of the Brückner's carbon may still be formed in the reaction zone where the metal-oxygen compound reduction occurs and/or because some of the metal-oxygen compound may have been at least partially reduced in the reaction zone where the Brückner reaction occurred, thereby providing at least a partial The first metal used in the reduction reaction.

Since the number of contact points between the reducing agent, the first promoter metal and the metal-oxygen compound determines the kinetics of the process of reducing the metal-oxygen compound according to the method of the present invention, it is preferred that the metal-oxygen compound or the metal-oxygen compound be combined with the second A promoter material, such as the first promoter metal, is in powder form. The particle size of the powder should preferably be less than 1 mm, but more preferably 100 μm or less. The powder or mixture thereof may be pretreated into agglomerates, such as pellets or sinters, which are sufficiently porous to allow carbon monoxide to reach the metal-oxygen compound or first metal and metal in the agglomerate. - Oxygen compounds. Although the process according to the invention is already effective when the first promoter metal is present in small amounts, it has been found that the amount of the first promoter metal should preferably be higher than 1% by weight of the metal-oxygen compound, more preferably higher than 5% by weight %, and preferably about 10% by weight at the beginning of the process where metal-oxygen compound reduction occurs.

The invention also relates to a method for carrying out the reduction in a shaft furnace, such as a blast furnace. Also included in the present invention is a method wherein the metal-oxygen compound includes an iron-oxygen compound and the reduction of the iron-oxygen compound is carried out in a shaft furnace such as a blast furnace to produce iron. It has been found that the application of the process according to the invention comprising the addition of iron as the first promoter metal for the iron ore reduction reaction in a conventional blast furnace process results in a disproportionate increase in molten iron. For example, the addition of iron, e.g. Iron mixture. During the blast furnace process, pellets are dropped into the furnace and Brinell's carbon is initially produced at an appropriate temperature from carbon monoxide gas originating from burning coke in the lower region of the blast furnace. Carbon monoxide gas is reduced to carbon dioxide gas and Brinell carbon.

It should be noted that due to the high temperatures in the production of pig iron from iron oxides in the conventional blast furnace process, the Brinell equilibrium (equation (1)) is shifted towards the formation of carbon monoxide from carbon and carbon dioxide produced from coke and blown Oxygen is formed into the bottom of the blast furnace. Therefore, no Brinell carbons are formed in the conventional blast furnace process where reduction of the iron-oxygen compound is taking place in the blast furnace.

In the method according to the invention, it is believed that the Brinell carbon is deposited on a mixture of iron-oxygen compound and iron as the first promoter metal, and that this combined material is further descended into the blast furnace. At the right temperature, the iron-oxygen compound will begin to reduce, reducing the iron-oxygen compound to iron. Eventually, after descending even further into the blast furnace, the iron will be molten and ready to be tapped from the blast furnace using known methods. Obviously, when the iron ore and the first promoter metal (which may be iron) are added as a sinter product or any other agglomerate with a large contact area between the iron ore, the first metal and carbon monoxide to the method, the method also works. As a result of the present invention, the carbon monoxide production of the blast furnace process is reduced due to the more efficient use of carbon derived from coke and the disproportionate increase in the production of molten iron per unit time of the blast furnace relative to the added iron catalyst . In other words, after adding x% iron as the first promoter metal to the iron ore per unit time, the amount of molten iron that can be withdrawn from the furnace per unit time will be greater than the amount of molten iron that can be withdrawn per unit time 100+x% of , thus making the blast furnace more efficient by increasing the amount of newly formed iron from iron ore per unit time. Obviously, the amount of iron ore used per unit time increases accordingly.

In any conventional direct reduction plant dealing with metal ores, which may be in the form of sintered bodies or pellets, for example, comparable application results to the described method can be achieved, with a comparable increase in productivity. Said plant generally comprises at least one furnace in which the reduction of the metal-oxide compound takes place, wherein said furnace is selected, for example, from the group consisting of rotary hearth furnaces, rotary kilns, shaft furnaces, cyclone furnaces or discontinuous furnaces. stove. Therefore, also included in the present invention is a process in which the reduction of metal-oxygen compounds is carried out in a fluidized bed, rotary hearth furnace, rotary kiln, vortex furnace or discontinuous furnace to obtain directly reduced metal . The present invention also includes a method in which the metal-oxygen compound is an iron-oxygen compound, and the reduction process of the iron-oxygen compound is carried out in a fluidized bed, a rotary hearth furnace, a rotary kiln, a vortex furnace or a discontinuous in the furnace.

Also included in the present invention is a method of reducing a metal-oxygen compound to a substantially solid material comprising a metallic portion and a non-metallic portion, wherein the substantially solid material is treated to separate the metallic portion from the non-metallic portion such as vein Stone or slag separation. This separation step can be carried out, for example, in a cyclone.

Also included in the invention is a method in which the metal portion is compressed to reduce its porosity. Metal parts can also be rolled into slabs, billets, blooms, bars, rolled products or strip. The method can save a step in the production process starting from the ore and ending with the slab, so that the cost and energy consumption can be significantly reduced. Metal parts can also be extruded into profiles, rolled stock or rods, or formed into near net shape products. These products require no, or only limited, final processing.

The metal part can also be used as raw material in smelting operations, for example using electric arc furnaces, or when the metal part is iron, as a steelmaking process, at least partly in, for example, the basic oxygen furnace steelmaking process or the Siemens-Martin steelmaking process Raw materials for alternatives to waste.

It should be noted that it is preferred that the metal in the metal-oxygen compound is iron, copper, cobalt, nickel, ruthenium, rhodium, palladium, platinum or iridium. It should be noted that for some metals there is more than one metal-oxygen compound, such as copper oxides and copper hydroxides. The present invention also relates to a method for a metal-oxygen compound comprising a mixture of at least two metal-oxygen compounds, wherein the metals in each metal-oxygen compound are different and each metal comprises iron, copper, cobalt, Nickel, ruthenium, rhodium, palladium, platinum or iridium, whereby reduction products comprising at least two different metals are prepared. The advantage of this embodiment is that the alloy can be prepared directly. One or said first promoter metal may also be different from the metal in the metal-oxygen compound.

The gaseous mixture containing carbon monoxide which will form carbon by the Brookfield reaction can be prepared by treating in a standard gasifier according to known methods at least one carbon-containing compound selected from the group consisting of coke, coal, A group of carbonaceous compounds including charcoal, oil, plastic, natural gas, paper, biomass, tar sands, highly polluted carbonaceous energy sources. Undesirable elements such as sulfur can be removed from the gas mixture by suitable pretreatment and/or aftertreatment. Standard gasifiers may be equipped with means to control the production of harmful or undesirable by-products from the gasification of carbonaceous compounds.

The present invention also relates to a device for reducing metal-oxygen compounds using carbon as a reducing agent. The device includes: a first-stage reaction chamber suitable for holding metal-oxygen compound solid materials; The entrance to the first stage reaction chamber, the second stage reaction chamber, the conveying device for transporting the solid material from the first stage reaction chamber to the second stage reaction chamber after the reaction in the first stage reaction chamber, for transferring CO gas means for transport from the second-stage reaction chamber to the first-stage reaction chamber, and a discharge outlet for discharging the substantially solid reaction product from the second-stage reaction chamber.

Thus, for example, the reactor used comprises a first reaction zone and a second reaction zone. In the first reaction zone, close to the inlet of the metal-oxygen compound, carbon is formed from carbon monoxide by means of the Bruchner reaction by selecting operating parameters such as temperature and pressure, and in the second reaction zone, close to the outlet of the substantially solid material originating from the reduction of the metal-oxygen compound , to reduce metal-oxide compounds by selecting operating parameters such as temperature and pressure. Preferably, the temperature of the first reaction zone is lower than that of the second reaction zone at a similar operating pressure.

It should be noted that the first and/or second accelerator material is preferably added at the beginning of the process. It is evident from the foregoing that optionally the first and/or second metal can also be added at a later or earlier stage in the process, thus requiring an optional additional inlet. In addition, not only during the start of the process, but also during the process, it is possible to add to the metal-oxygen compound a compound similar to Brückner's carbon and having a suitable form, such as graphite powder, in the metal-oxygen compound acts as a reducing agent in the reduction reaction of , and therefore, optionally requires one or more additional carbon inlets.

Preferably the apparatus includes means for generating hot CO gas to be fed to the reaction chamber of the second stage.

In another embodiment according to the invention, the plant further comprises means for refeeding at least part of the gaseous reaction product into the process. Furthermore, the apparatus may also include means for reintroducing the substantially solid material at least in part from the reduction of the metal-oxygen compound into the process.

In yet another embodiment, the various reaction zones may be physically separated to occur in separate reactors, allowing more independent selection of operating parameters such as temperature and pressure.

In yet another embodiment, said apparatus comprises a fluidized bed providing at least one of said first and second stage reaction chambers. In yet another embodiment, the apparatus comprises a furnace selected from a rotary hearth furnace, a rotary kiln, a shaft furnace, a vortex furnace, a continuous or a discontinuous furnace.

In a preferred embodiment, the device is substantially tubular, more preferably substantially axisymmetric in shape.

Description of drawings

Specific embodiments of the invention are now explained by the following non-limiting examples with reference to the schematic drawings in which:

Figure 1 schematically shows an apparatus for implementing the invention.

Figure 2 schematically shows another embodiment of a device for implementing the invention.

Figure 3 schematically shows yet another embodiment of an apparatus for practicing the invention with separate reaction zones.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In Fig. 1, the practice of the present invention is carried out in the plant of reduction metal-oxygen compound, wherein, said plant comprises reactor 1, inlet 2 of metal-oxygen compound, first and/or second kind of accelerator material ( Inlets here in the form of the first and/or second metal) (not shown, unless the first and/or second metal is added together with the metal-oxygen compound, in which case the first The inlet for the first and/or second metal is also the inlet 2), the inlet 3 for the gas mixture containing carbon monoxide, the heating means (not shown) for heating different parts of the reactor, the outlet 4 for the gaseous reaction products and the outlet 4 from the metal- Outlet 5 for the reduced substantially solid material of the oxygen compound.

Illustrated in FIG. 2 is another embodiment of the invention, wherein the apparatus comprises a reactor 1, an inlet 2 for a metal-oxygen compound, a first and/or a second promoter material (here the first form of one and/or second metal) (not shown, unless the first and/or second metal is added together with the metal-oxygen compound, in which case the first and/or The inlet for the second metal is also the inlet 2), the inlet 3 for the gas mixture comprising carbon monoxide, the heating or cooling means (not shown) for heating or cooling different parts of the reactor, the outlet 4 for the gaseous reaction products and the outlet 4 from the metal- an outlet 5 for the substantially solid material of oxygen compound reduction, delivery means 6 for transporting the solid reactant, means 7 for reintroducing at least part of the gaseous reaction product from outlet 4 into the process, and at least part of the gaseous reaction product derived from the metal-oxygen compound The reduced substantially solid material is reintroduced into means 8 .

Illustrated in Figure 3 is yet another embodiment of the present invention, wherein the reactor comprises a first reactor part 9 in which carbon production mainly occurs by the Brinell reaction, a second reactor section 9 in which reduction of metal-oxygen compounds mainly occurs Section 10, conveying means for conveying solid reactants from the first reactor part 9 to the second reactor part 10, for conveying the gas mixture comprising carbon monoxide from the second reactor part 10 to the first reactor The conveyor 11 of the section 9, the inlet 2 of the metal-oxygen compound, the inlet of the first and/or second accelerator material (here in the form of the first and/or second metal) (not shown , unless the first and/or second metal is added together with the metal-oxygen compound, in which case the inlet for the first and/or second metal is also the inlet 2), the inlet for the gas mixture containing carbon monoxide 3. Heating or cooling means (not shown) for heating or cooling the different parts of the reactor, outlet 4 for gaseous reaction products and outlet 5 for substantially solid material originating from the reduction of the metal-oxygen compound. This embodiment may also be equipped with means to reintroduce at least part of the gaseous reaction product from outlet 4 into the process, and at least part of the substantially solid material originating from the reduction of the metal-oxygen compound as the first and/or second Metals are reintroduced into the process means through the catalyst inlet, however, these are not shown in FIG. 3 .

In all three embodiments described above there may be one or more optional inlets for the introduction of a compound similar to Brookfield's carbon and of suitable form, for example graphite powder, at the beginning and/or during the process.

Examples are now given to explain and illustrate the invention. Examples 1 and 2 illustrate the effect achieved only in the second reaction stage of the invention.

Example 1

In a thermogravimetric analyzer, a homogeneous mixture of iron oxide as the metal-oxygen compound, carbon as the reducing agent for reducing the metal-oxygen compound, and iron as the first and second metals is heated. The amount of carbon is selected to be sufficient to completely reduce the iron oxide to metallic iron. The reduction in the mass of the mixture is a direct indication of the reduction of the metal-oxygen compound. When fully reduced, the expected mass loss is about 12-15%. These measurements show that complete reduction of iron oxides is achieved at 650-850°C when using crystalline carbon powders such as crystalline graphite, synthetic graphite, elektrographite or Brinell carbon. Pulverized coal, activated carbon or pulverized coke have proven to be less effective since iron oxides are not or only partially reduced to iron below 900°C. It has been demonstrated that amorphous carbon is less active in reducing iron oxide than crystalline carbon such as graphite, but more active than powdered coal, activated carbon or powdered coke.

Example 2

In a reactor comprising stainless steel tubes and a furnace, an extruder-type screw is installed as the conveying means for the solid reactants. A mixture of iron oxide, carbon similar to Brinell's carbon in a suitable form and iron powder as the first metal is fed into the tube and heated to 650-850°C. Iron oxides are quickly reduced to iron.

Embodiment 3 (embodiment of the present invention)

In the reactor according to FIG. 2 , stainless steel tubes constitute the reactor, and extruder-type screws are installed as conveying means 6 for the solid reactants. Arrows indicate the direction of transport of the solid reactants. A mixture of iron oxide as the metal-oxygen compound and iron powder as the first metal is fed through an inlet 2 at one end of the tube and conveyed by an extruder screw 6 to the other end of the steel tube. A hot gas mixture comprising carbon monoxide is introduced into the reactor through inlet 3 in countercurrent, which also provides heat for the reduction reaction in the reactor. The temperature of the reactants at the gas mixture inlet is about 900°C and the temperature of the solid reactants at the gas mixture outlet is about 550°C. At the cold end of the reactor, in the first reaction zone, the Brinell carbon is formed from carbon monoxide by the Brinell reaction with the help of metallic iron acting as a catalyst. The carbon dioxide produced leaves the process via outlet 4 as part of the gaseous reaction product. The Brinell carbon is deposited on the solid reactants and is conveyed with the solid reactants by extruder type screws to the second reaction zone. In the second reaction zone, iron oxides are reduced by Brinell's carbon to obtain metallic iron and a mixture of carbon monoxide and carbon dioxide. Part of the substantially solid iron as the first metal can be reintroduced into the process by means of means 8 via eg inlet 2 and part of the gaseous reaction products can be reintroduced by means of means 7 via eg inlet 3 .

It is to be understood, of course, that the present invention is not limited to the embodiments and examples described above, but is intended to include any and all embodiments within the scope of the claims and description and within the spirit of the invention disclosed herein.

Claims (22)

1. A method for reducing metal-oxygen compounds, wherein carbon is used as a reducing agent, the method comprising: in the first reaction stage, CO gas is sent into a reaction chamber containing the metal-oxygen compound, the reaction chamber Conditions convert CO into solid carbon and carbon dioxide, thereby introducing the formed solid carbon into the metal-oxygen compound, and, in the second reaction stage, using all said carbon reduction of said metal-oxygen compound, wherein, at least in said second reaction stage, there is a first promoter material effective to promote the reduction of said metal-oxygen compound, said first promoter material comprising a first A promoter metal and/or a compound of a first promoter metal. 2. The method according to claim 1, wherein said method is carried out continuously, said first and said second reaction stages are carried out simultaneously, said metal-oxygen compound is formed from a first reaction zone in which said first reaction stage takes place is transferred to the second reaction zone where the second reaction stage takes place. 3. The method according to claim 2, wherein the CO gas formed in the second reaction stage is used in the first reaction stage. 4. The method according to any one of the preceding claims, wherein the second reaction stage is carried out at a higher temperature than the first reaction stage. 5. The method according to any one of the preceding claims, wherein said first promoter material is said first promoter metal, or first promoter metal carbide, first promoter metal Hydride or first promoter metal nitride or a combination thereof. 6. A method according to any one of the preceding claims, wherein the first accelerator material is in powder form. 7. A method according to any one of the preceding claims, wherein said first promoter metal is the same as the metal in said metal-oxygen compound. 8. A method according to any one of the preceding claims, wherein, at least in said first reaction stage, there is a second promoter material comprising a first catalyst for the conversion of CO into carbon and carbon dioxide. Compounds of two promoter metals and/or a second promoter metal. 9. The method according to the preceding claim 8, wherein said second promoter material is said second promoter metal, or a carbide of a second promoter metal, a hydride of a second promoter metal or a nitride of a second promoter metal or a combination thereof. 10. A method according to claim 9, wherein said second accelerator material is in powder form. 11. The method according to any one of the preceding claims 1-10, wherein the metal-oxygen compound is an agglomerate formed from a powder. 12. A method according to any one of the preceding claims 1-11, wherein said metal-oxygen compound and said first promoter material and, if present, said second promoter material are formed from Powder forms agglomerates. 13. A method according to any one of the preceding claims, wherein the metal in the metal-oxygen compound is Fe, Cu, Co, Ni, Ru, Rh, Pd, Pt or Ir. 14. The method according to any one of the preceding claims, wherein the first reaction stage is carried out at below 650°C. 15. A method according to any one of the preceding claims, wherein the metal-oxygen compound comprises an iron-oxygen compound. 16. The method according to claim 15, wherein the iron-oxygen compound is iron oxide and/or iron hydroxide and/or iron carbonate. 17. A method according to any one of the preceding claims, wherein said first promoter metal and, if present, said second promoter metal is iron. 18. The method according to the preceding claim 16 or 17, wherein the second reaction stage is carried out at 550-900°C. 19. The method according to any one of the preceding claims, wherein the metal-oxygen compound comprises a mixture of at least two metal-oxygen compounds, wherein the metals in the metal-oxygen compounds are different, and, Each of the metals includes Fe, Cu, Co, Ni, Ru, Rh, Pd, Pt or Ir. 20. The method according to any one of the preceding claims, carried out in a shaft furnace, blast furnace, fluidized bed, rotary hearth furnace, rotary kiln, vortex furnace or discontinuous furnace. 21. A method according to any one of the preceding claims, wherein a substantially solid reaction product is produced in the second reaction stage, and wherein part of the reaction product produced by the second reaction stage is sent to the first reaction stage. 22. A method according to any one of the preceding claims, wherein gaseous reaction products are withdrawn and reintroduced into the process.