EP4337798A1

EP4337798A1 - Method for the direct reduction of iron ore

Info

Publication number: EP4337798A1
Application number: EP22726608.7A
Authority: EP
Inventors: Nils JÄGER; Daniel Schubert
Original assignee: ThyssenKrupp Steel Europe AG
Current assignee: ThyssenKrupp Steel Europe AG
Priority date: 2021-05-11
Filing date: 2022-04-28
Publication date: 2024-03-20
Also published as: WO2022238132A1; CN117280047A; DE102021112208A1

Abstract

The invention relates to a method for the direct reduction of iron ore to sponge iron, wherein: the iron ore passes through a reduction zone (11) for reducing the iron ore to sponge iron; in the reduction zone (11), a reducing gas flows through the iron ore; the reducing gas (11.1) introduced into the reduction zone (11) comprises at least one compound of carbon and hydrogen and/or at least one compound of carbon and oxygen and/or hydrogen; the process gas (11.2) discharged from the reduction zone (11) comprises hydrogen and at least one compound of carbon and oxygen and/or at least one hydrogen-containing compound and unavoidable impurities; the process gas (11.2) is fed to at least a first process step, in which at least one compound of the process gas (11.2) and/or at least portions of the unavoidable impurities are separated out and/or removed. According to the invention, after the first process step the process gas (11.2) is processed in such a way that hydrogen is obtained as a by-product, said hydrogen either a) being completely fed to the reduction zone (11), b) being partly fed to the reduction zone (11) while the remaining portion is stored or is provided for an off-site use, or c) being completely stored or completely provided for an off-site use.

Description

1

Process for the direct reduction of iron ore

The invention relates to a method for the direct reduction of iron ore to sponge iron.

In the direct reduction process, a solids reaction takes place that removes oxygen from the iron ore. For this purpose, gasified coal and/or natural gas or hydrocarbon-containing compounds and mixtures of the combinations mentioned, in particular with hydrogen and/or compounds of carbon and oxygen, are used as the reducing gas. The recent trend has been that hydrogen is also being proposed more frequently as a reducing gas. The reaction takes place below the melting point of iron ore in the solid state, so that the internal form in particular remains unchanged in the broadest sense. In the reduction of the iron ore to the metallic product, basically only the oxygen in the ore is removed. Since there is a weight reduction of about 1/4 to 1/3 when the oxygen is removed, the reaction product has a honeycombed microstructure (solid porous iron with many air-filled interstices). For this reason, direct reduced iron is often also referred to as sponge iron. In the direct reduction process, a shaft furnace is traditionally used as the reactor with a reduction zone through which the iron ore runs counter to the reducing gas. In a special variant of the process, the reduction zone is arranged above a cooling zone in the shaft furnace, with a cooling gas flowing through the cooling zone. The iron ore then passes through the shaft furnace in a vertical direction from top to bottom. Such shaft furnaces enable a good flow of cooling gas and reduction gas through the iron ore due to the underlying chimney effect. In particular, the reduction gas flows through the reduction zone counter to a direction of movement of the iron ore. Accordingly, the cooling gas also flows through the cooling zone in the opposite direction to the movement of the sponge iron produced. The countercurrent process is therefore used both in the cooling zone and in the reduction zone in order to achieve an efficient reaction between the gases and the solids.

In particular, CO or H ₂ or a mixed gas comprising CO and H ₂ can be used as the reducing gas. The reduction reactions are as follows (“( )” means solids; curly brackets {} indicate gaseous substances):

3 (Fe ₂ 0 ₃ ) + {CO} <- (Fe ₃ 0 ₄ ) + {C0 ₂ } (Fe ₃ 0 ₄ ) + {CO} 3(FeO) + {C0 ₂ } (FeO) + {CO} (Fe) + {CO ₂ }

3(Fe ₂ 0 ₃ ) + {H ₂ } <- 2(Fe ₃ 0 ₄ ) + {H ₂ 0}

(Fe ₃ 0 ₄ ) + {H ₂ } <- 3(FeO) + {H ₂ 0}

(FeO) + {H ₂ } (Fe) + {H ₂ 0}

The reducing gas is usually generated from fossil hydrocarbons (e.g. natural gas and/or coal gas). The reaction for methane (as a main component of natural gas but also biogas) as the starting gas is explained below as an example. Other hydrocarbons are also possible as starting gas. The reduction gas is generated in a gas reformer from methane, CO ₂ and water vapor (MIDREX® process).

CH ₄ + CO _{2 <} -> 2CO + 2H ₂ CH ₄ + H ₂ 0 ^CO + 3H ₂

The result is a gas cycle in which the used methane is mixed with new methane with the cleaned process gas from the shaft furnace upstream of the gas reformer. The process gas of the shaft furnace contains C0 ₂ and water vapor as products of the reduction reaction. With the help of a catalytic reaction in the gas reformer, the reducing gas Pl ₂ and CO is generated from methane, CO ₂ and steam. This reducing gas mixture is fed to the shaft furnace, where it reduces the iron ore according to the above reaction equations. The main reaction products are C0 ₂ , water vapor and sponge iron. C0 ₂ and water vapor and unused reducing gas are mixed with methane and fed back to the gas reformer.

Sponge iron production essentially involves two basic steps. As a first step, the iron ore is reduced to sponge iron in a reduction zone with a suitable hot reducing gas. Typically, a reducing gas essentially comprises compounds of carbon and hydrogen (e.g. CH ₄ ), compounds of carbon and oxygen (e.g. CO) and/or hydrogen (PI ₂ ) at temperatures ranging from 700°C to 1100°C. In a second step, the sponge iron produced is cooled down to temperatures typically below 100 °C in a cooling zone using a cooling gas.

Corresponding methods are known from practice and are described, for example, in DD 153 701 A5 and EP 2 459 755 B1. DD 153 701 A5 discloses that the above 3 ren end of a reactor in the form of a shaft furnace withdrawn process gas cooled and ge washed (freed from dust) and heated in the presence of a catalyst to form a hot reformed reducing gas, then with a hot sulfur-containing process gas, such. B mixed coal gas or natural gas and the resulting reduction mixture is fed back into the reactor. EP 2 459 755 B1 describes that the process gas drawn off at the upper end of the reactor comprises hydrogen, carbon monoxide, carbon dioxide, methane and water. The extracted process gas is cleaned and cooled in a gas cooling unit, whereby water is condensed and removed from the process gas. Furthermore, the cleaned and cooled process gas is treated in a selective carbon dioxide removal unit to produce a stream of nearly pure carbon dioxide that can be controllably removed, thereby producing an enriched reducing gas mainly comprising hydrogen, carbon monoxide and methane . A first portion of the enriched reducing gas is returned to the reactor after it has been heated in a reducing gas heater. A second part of the enriched reducing gas is treated in a gas separation unit in such a way that a first gas stream, which has a higher concentration of hydrogen, and a second gas stream, which has a higher concentration of carbon monoxide and methane, are produced. wherein the first gas stream is used as fuel in the reduction gas heater and the second gas stream is returned to the reactor. By burning the hydrogen-containing first gas stream in the reduction gas heater instead of carbon-containing fuels, the carbon dioxide emissions into the atmosphere are reduced.

It is the object of the present invention to further develop these processes in such a way that by-products can be produced which, e.g. can be used in other fields of application.

This object is achieved by a method for the direct reduction of iron ore to sponge iron, the iron ore passing through a reduction zone for reducing the iron ore to sponge iron, a reducing gas flowing through the iron ore in the reduction zone, the reducing gas introduced into the reduction zone having at least one compound of carbon and hydrogen and/or at least one compound of carbon and oxygen and/or hydrogen, the process gas discharged from the reduction zone comprising hydrogen and at least one compound of carbon and oxygen and/or at least one hydrogen-containing compound and unavoidable impurities, wherein the process gas to at least a first process step 4, in which at least one compound of the process gas and/or at least parts of the unavoidable impurities is separated and/or separated, whereby according to the invention the process gas is (further) processed after the first process step in such a way that hydrogen is obtained as a by-product, which either a) is fed completely to the reduction zone, b) is partly stored in the reduction zone and the remaining part or made available for ex situ use or c) completely stored or made available for ex situ use.

According to the invention, hydrogen (H ₂ ) is produced as a by-product via suitable means and processes via the direct reduction process for producing sponge iron from iron ore. In contrast to what is known in the prior art, the hydrogen is not added to a starting gas (fresh gas) as a mixture with other components of the cleaned process gas, such as CO, which is then used as a reducing gas in a reduction gas heater before being introduced into the reduction zone corresponding temperature it is heated, or alternatively made available as fuel gas and/or additional gas to the fuel gas for firing the reduction gas heater.

Unavoidable impurities in the discharged process gas can, if present, contain sulfur or sulphur-containing compounds, nitrogen, nitrogen oxides, dust in the form of iron and/or iron oxides, and in particular other natural ore components. In particular, unavoidable impurities are process-related reaction products which cannot be assigned to the compound of carbon and oxygen (CO, CO ₂ ), hydrogen (H ₂ ) and water vapor (H ₂ 0).

Ex situ use means use of the hydrogen obtained from the process gas outside the area of the direct reduction process, i. H. a possible application in many other areas and no return to the direct reduction process (in situ).

In the first process step, in which at least one compound or component is separated and/or separated from the process gas, water in liquid form, for example, can be separated as a reaction product in a scrubber through which the discharged process gas flows as the first unit. Alternatively, in the first process step, at least some of the unavoidable impurities in the form of dust can be separated from the discharged process gas in a process gas cleaning unit. If the introduced reducing gas contains at least one compound of carbon and hydrogen, in particular methane, methane pyrolysis takes place in the reduction zone with the iron ore, in which hydrogen is released from the methane molecule. The carbon contained in the methane remains on the one hand in the generated sponge iron in the form of deposited carbon, in particular as cementite bound in the iron (Fe ₃ C), on the other hand it is deposited as CO ₂ from the process. A large part of the hydrogen reacts with the ore in the reactor as a reducing agent. The unreacted portion of the hydrogen is discharged as part of the process gas.

If necessary, the hydrogen can (aspect a)) be completely returned to the reduction zone, ie it is the starting gas which is at least one compound of carbon and hydrogen, for example methane (CH ₄ ), and/or at least one compound of carbon and Oxygen, for example carbon monoxide (CO) and/or hydrogen (H ₂ ), is added before this is fed to a reduction gas heater as a reduction gas, heated to the appropriate operating temperature and then introduced into the reduction zone. The hydrogen obtained is thus completely fed into the reduction process (in situ).

According to an alternative (aspect b)), part of the hydrogen obtained can, as already described above, be fed back into the reduction zone or the reduction process and the remaining part can either be stored or made available for ex situ use. It can be stored in tanks/containers, gasometers known per se and stored until it is used accordingly, in order to either be fed to the reduction process or otherwise transported to the appropriate place of use via suitable transport containers by sea, rail, road or pipeline . The ex situ use can be made available via a line either in neighboring processes or, for example, fed into a public line to which other consumers have access.

According to a further alternative (aspect c)), the hydrogen can be stored completely, as described above, or made available for ex situ use, as described above. 6

According to the invention, hydrogen (H ₂ ) is obtained as a by-product via the process for the direct reduction of iron ore to sponge iron. This is an alternative method to the already established method of producing hydrogen using electrolysis.

To increase the proportion of hydrogen in the process gas, the process gas can be passed through a unit in which hot steam is added to the process gas and carbon monoxide (CO) can be formed into carbon dioxide (C0 ₂ ) and hydrogen (H ₂ ), which known as the so-called water gas shift reaction, which is slightly exothermic (DH = -41.2 kJ/mol), with the formula:

C0 ₊ H2 ₀ C02 ₊ H2 .

The process gas is passed through at least one unit in which compounds made of carbon and oxygen such as carbon dioxide (C0 ₂ ) are separated, for example by C0 ₂ separation in the form of amine scrubbing, carbonate scrubbing, various membrane separation technologies or pressure swing absorption (PSA ). In order to further improve the climate balance, the carbon dioxide (C0 ₂ ) separated from the process gas can be stored in a suitable environment, for example, using CCS (Carbon Capture and Storage) or materially as part of a CCU (Carbon Capture and Utilization) process - be used on a regular basis. Furthermore, the carbon dioxide (C0 ₂ ) can also be used as a cooling gas or part of the cooling gas in an optional cooling zone in the direct reduction process.

Sulfur, which can be part of the reducing gas (e.g. natural gas or coke oven gas) as an impurity, settles in the sponge iron. If the already expected low sulfur content in the process gas has to be further reduced, the process gas can optionally be passed through at least one unit in which sulfur or sulfur-containing compounds (S0 ₂ , S0 ₃ , H ₂ S and H ₂ S0 ₄ ) are separated can be, for example, by known non-regenerative processes in the form of a lime wash or regenerative process in the form of the so-called Wellmann-Lord process.

The process gas is passed through at least one unit, for example through a condenser, and cooled accordingly, so that the water vapor present in the process gas is condensed and thus separated from the process gas. The process gas is "dehumidified" by condensing and discharging the condensate. The arrangement of the individual units or the order in which the process gas passes through these units and thus which compounds or components are separated and/or separated from the process gas and in which order depends on the economy and the chemical composition of the reducing gas. In particular, the order depends, among other things, on the quality of the hydrogen-rich gas. High purity of the hydrogen is often not absolutely necessary in industrial processes, for example because no catalysts are damaged or because no high pressures are required in further use.

The methods in connection with the corresponding units for separating and/or separating individual elements, compounds or components from the discharged process gas are also prior art and thus known to experts, so that each method does not have to be explicitly explained in detail.

In a first process step, the process gas preferably passes through a unit for “dedusting” and thus separating at least some of the unavoidable solid-type impurities. In a further process step, the process gas is directly shifted in a water-gas shift unit in order to achieve a high hydrogen yield. In this state, high circulation rates can occur, which can lead to low sulfur levels in the process gas, for example. Subsequently, in a further process, water vapor and carbon dioxide and, if necessary, other accompanying elements such as carbon monoxide or nitrogen are separated.

Depending on the procedure and how the hydrogen is obtained, the remaining part of the process gas, which contains little or no elemental hydrogen, can be returned to the reduction process, in particular as a fuel gas or as an additional gas to the fuel gas for firing the reduction gas heater.

According to one configuration of the method, the reduction gas is heated in a reduction gas heater to a temperature of at least 700° C. and at most 1100° C., so that, in particular after the subsequent addition of oxygen, the reduction gas temperature in the reduction zone rises to a temperature profile between 900 °C and 1400 °C. 8th

In particular, at least one compound of carbon and hydrogen as the main component is provided as the starting gas, preferably methane (CH ₄ ). The mode of operation according to aspect c) is preferably used, as a result of which the component(s) of the reduction gas essentially corresponds to the component(s) of the starting gas. The reducing gas particularly preferably comprises at least one compound of carbon and hydrogen and optionally hydrogen in a proportion of up to 30% by volume. Depending on the proportion of hydrogen, hydrocarbon compounds can be replaced by the corresponding proportion as starting gas, as a result of which the corresponding costs for preparing the starting gas can be reduced.

If hydrogen is admixed according to aspects a) or b), this can reduce the corresponding proportion in the at least one compound of carbon and hydrogen in accordance with the admixture, so that the reducing gas contains hydrogen with a proportion of up to 30 vol. % and the balance comprises at least one compound of carbon. If there is no admixture, see Aspects), the reducing gas essentially corresponds to the starting gas provided. With the carbon from the at least one compound of carbon and hydrogen in the reducing gas, the iron ore in the reduction zone can be “carburized” by the reducing gas flowing through the iron ore in the reduction zone, so that carbon is deposited on the iron ore. The deposited carbon then combines with the iron in the iron ore to form cementite (Fe ₃ C). The reaction equation for this mechanism is: 3 Fe + C -> Fe ₃ C.

The use of hydrogen, almost 100%, instead of hydrocarbons, for example, would mean that the carbon content of the sponge iron produced would generally be particularly low, since no side reactions with hydrocarbons that would deposit carbon in the sponge iron can occur in the reduction zone , so that after the reduction zone the carbon content in the sponge iron should be less than 0.25% by weight. In order to be able to set a certain carbon content in the sponge iron after the reduction, a mixture of hydrogen up to 30% by volume and at least one compound of carbon and hydrogen and/or at least one compound of carbon and oxygen in the reducing gas can also be taken into account.

If it is not possible to use the sponge iron coming from the reduction zone at a temperature between 500 and 800° C., the sponge iron passes through a cooling zone according to one embodiment of the method. Thus, the method provides that the iron 9 ore sequentially passes through a reduction zone for reducing the iron ore into sponge iron and a cooling zone for cooling the sponge iron. In the cooling zone, a cooling gas flows through the sponge iron. The cooling gas is used to cool the sponge iron to a temperature suitable for onward transport, for example below 100 °C, and depending on the composition of the cooling gas it can also cause (further) "carburization" of the sponge iron, especially if carbon-containing compounds are used , Preferably carbon dioxide (C0 ₂ ), which can preferably be separated from the discharged process gas from the reduction zone and not, for example, CCS or CCU is supplied. The so-called Bosch reaction takes place in the cooling zone using carbon dioxide and hydrogen as examples.

C02 ₊ _2H2 -> C ₊ 2H20

Carbon dioxide can be consumed during the "carburization" of the sponge iron under the prevailing conditions. In the cooling zone and through the cooling gas, which comprises at least one carbon-containing compound, the carbon content of the sponge iron after cooling or after the cooling zone can be greater than 0.5% by weight, in particular greater than 1.0% by weight, preferably greater than 2 .0% by weight can be adjusted. Furthermore, the carbon content of the sponge iron after the cooling zone can be set to less than 4.5% by weight, in particular less than 4.0% by weight, preferably less than 3.5% by weight, which has the advantage that the sponge iron can be fed to the known further processing without the need for an adjustment of the further processing. In particular, the sponge iron can be further processed, for example, in the Linz-Donawitz converter (also referred to as the “Basic Oxygen Furnace”). In addition, the melting point of sponge iron can be lowered by increasing the carbon content. As a result, the energy requirement for melting in the electric arc furnace (also referred to as “Electric Are Furnace”) can also be reduced.

Thus, according to a variant of the method, the reduction zone can be arranged above the cooling zone in a shaft furnace. The iron ore then passes through the shaft furnace in a vertical direction from top to bottom. Such shaft furnaces allow a good flow of reducing gas and cooling gas through the iron ore due to the underlying chimney effect tes. In particular, the reduction gas flows through the reduction zone counter to a direction of movement of the iron ore. Correspondingly, the cooling gas also flows through the cooling zone counter to a direction of movement of the sponge iron produced. Both in the reduction 10 zone as well as in the cooling zone, the countercurrent process is used to achieve an effi cient reaction between the gases and the solids.

According to an alternative variant of the process, the reduction zone and/or the cooling zone comprise one or more fluidized bed reactors. In a fluidized bed reactor, a fine-grained solid bed is whirled up by the gas flowing in continuously from below via a gas distributor. This also enables efficient reaction between the gases and the solids.

The invention is explained in more detail using the following exemplary embodiments in conjunction with FIG. 1. FIG. 1 shows an example of a method according to the invention in a schematic representation of a shaft furnace.

The invention is explained in FIG. 1 using the example of a shaft furnace (10). Iron ore (1) is introduced at the upper end of the shaft furnace (10). The sponge iron (2) produced is removed at the lower end of the shaft furnace (10). A reduction zone (11) and optionally a cooling zone (12) are arranged in the shaft furnace (10). The reduction zone (11) is arranged above the optional cooling zone (12). The cooling zone (12) is not absolutely necessary if diligent use of the hot iron sponge leaving the reduction zone (11) is possible or if the reducing gas (11.1) introduced into the reduction zone (11) comprises at least one carbon-containing compound which, by reaction in the reduction zone (11) not only reduces the iron ore but can also "carburize" it sufficiently at the same time. The reducing gas (11.1) flows through the iron ore in the reduction zone (11) according to the countercurrent principle, thus against the direction of movement of the iron ore. Before being introduced, the reduction gas (11.1) is passed through a reduction gas heater (20) and heated to a temperature of up to 1100 °C, but at least 700 °C. The reducing gas (11) comprises at least one compound of carbon and hydrogen and/or at least one compound of carbon and oxygen and/or hydrogen. In the event that the reducing gas (11.1) should contain elemental hydrogen (Fl ₂ ), either the starting gas that is provided contains a corresponding proportion and/or aspect a) or b) of the invention consists of the Process gas (11.2) obtained hydrogen (H ₂ ) is added in the recirculation, so that ultimately the fully obtained hydrogen (aspect a)) or only part of it (aspect b)) of the reduction zone (11) is fed. Methane (CH ₄ ), for example natural gas, is preferably provided as the main component as the starting gas. Aspect c) of the invention is further preferred 11 carried out and there is no admixture of hydrogen (H ₂ ), which is obtained from the discharged process gas (11.2).

In the reduction zone (11), the iron ore is reduced to sponge iron. Because of the at least one compound of carbon and hydrogen and/or the at least one compound of carbon and oxygen in the reducing gas (11.1), the sponge iron leaves the reduction zone (11) with a carbon content of more than 0.75% by weight.

Unused reduction gas (11.1) is discharged from the reduction zone (11) together with any gaseous reaction products as process gas (11.2). The process gas (11.2) discharged from the reduction zone (11) comprises hydrogen (H ₂ ) and at least one compound of carbon and oxygen (CO, CO ₂ ) and/or at least one compound containing hydrogen (H ₂ 0) and unavoidable impurities . The process gas (11.2) is fed to at least a first process step, in which at least one compound of the process gas (11.2) and/or at least parts of the unavoidable impurities are separated and/or separated. In FIG. 1, (30) symbolically shows a unit for process gas cleaning and dedusting, in which at least some of the unavoidable impurities are separated from the discharged process gas (11.2). In a further process step, the hydrogen yield is improved by a water-gas shift reaction in a corresponding reactor (50), in which hot steam is supplied and the carbon monoxide (CO) present in the process gas is converted into carbon dioxide (C0 ₂ ) and hydrogen ( H ₂ ) converts. In a further process, the process gas (11.2) is passed through a unit (60), for example through a condenser, and cooled accordingly, so that the water vapor (H ₂ O) in the process gas (11.2) condenses and is thus separated from the process gas (11.2 ) is separated. The process gas (11.2) is "dehumidified" by condensing and discharging the condensate. Carbon dioxide (C0 ₂ ) is then deposited in a further ren process, for example in an amine wash (70) or a PSA. Alternatively, the carbon dioxide (C0 ₂ ) can also be used as a cooling gas (12.1) or part of the cooling gas (12.1) in an optional cooling zone (12).

The hydrogen (H ₂ ) obtained according to the invention from the process gas (11.2) can be completely mixed with a starting gas to form a reduction gas (11.1) and thus fed to the reduction zone (aspect a)). As an alternative, only part of the hydrogen (H ₂ ) obtained can be mixed with a starting gas to form a reducing gas (11.1) and thus fed to the reduction zone and the remaining part of the hydrogen (H ₂ ) obtained 12 can either be stored or made available for ex situ use (aspect b). As a further and particularly preferred alternative, the hydrogen (H ₂ ) obtained can be stored completely or made available for ex situ use (aspect c)). Storage and ex situ use are not shown here.

After leaving the reduction zone (11), the sponge iron enters the optional cooling zone (12). The sponge iron has a temperature in the range of 500 to 800 °C. Cooling gas (12.1) also flows through the sponge iron in the cooling zone (12) counter to the direction of movement of the sponge iron. Unused cooling gas exits again as process gas (12.2) together with any gaseous reaction products. Of course, a certain proportion of the cooling gas (12.1) can also enter the reduction zone (11). Likewise, a certain proportion of the reducing gas (11.1) can enter the cooling zone (12). Mixtures of cooling gas (12.1) and reducing gas (11.1) can therefore occur at the transition between reduction zone (11) and cooling zone (12). The cooling gas (12.1) comprises in particular a carbon-containing compound, preferably carbon dioxide (C0 ₂ ). If required, hydrogen (H ₂ ) can be added to the cooling gas (12.1), which causes the cooling gas (12.1) to pass through the Bosch reaction in the cooling zone (12) in the presence of hot sponge iron as a catalyst. Hydrogen (H ₂ ) and carbon dioxide (C0 ₂ ) in the cooling gas thus react according to the Bosch reaction

C0 ₂ +2 H ₂ -> C +2 H ₂ 0 to water vapor (H ₂ 0) and carbon (C), with the carbon being deposited on the sponge iron serving as a catalyst. The water vapor with other gaseous reaction products is discharged as process gas (12.2) from the cooling zone (12) of the shaft furnace (10). The deposited carbon then diffuses into the interior of the sponge iron and forms cementite (Fe ₃ C). This effect increases the carbon content of the sponge iron to between 0.5% and 4.5% by weight. The sponge iron carburized and cooled in this way can be removed in the lower area of the shaft furnace (10) and fed in a known manner to steel production for further processing.

Alternatively and not shown here, the invention can also be carried out in a cascade of fluidized bed reactors. At least one, in particular two, fluidized bed reactors form a reduction zone and, depending on the circumstances and if hot application is not possible, at least one further fluidized bed reactor in the cascade can be used as a cooling zone. 13 are turned. The iron ore would then pass through the first or at least two eddy current reactors successively and be gradually converted into sponge iron. In the last fluidized bed reactor, if necessary, the sponge iron can be cooled using cooling gas. The principle essentially corresponds to that of a shaft furnace, but distributed over several fluidized bed reactors instead of one shaft. The number of fluidized bed reactors can be interconnected as required.

Claims

14 patent claims

1. A method for the direct reduction of iron ore to sponge iron, the iron ore passing through a reduction zone (11) to reduce the iron ore to sponge iron, where the iron ore in the reduction zone (11) is flowed through by a reducing gas (11.1), the in the reduction zone (11) introduced reducing gas (11.1) comprises at least one compound of carbon and hydrogen and/or at least one compound of carbon and oxygen and/or hydrogen, with the process gas (11.2) discharged from the reduction zone (11) containing hydrogen and at least one A compound of carbon and oxygen and/or at least one hydrogen-containing compound and unavoidable impurities, the process gas (11.2) being fed to at least a first process step, in which at least one compound of the process gas (11.2) and/or at least parts of the unavoidable impurities are separated and/or is severed, characterized thereby It is possible that the process gas (11.2) is processed after the first process step in such a way that hydrogen is obtained as a by-product, which is either a) completely fed to the reduction zone (11), b) partly to the reduction zone (11) and the remaining part stored or provided for ex situ use, or c) stored in its entirety or provided for ex situ use.

2. The method according to claim 1, wherein the reducing gas (11.1) is heated to a temperature of at least 700 to 1100 °C.

3. The method according to claim 1 or 2, wherein the reducing gas (11.1) comprises at least one compound of carbon and hydrogen and optionally hydrogen in a proportion of up to 30% by volume.

4. The method according to any one of claims 1 to 3, wherein the sponge iron passes through a cooling zone (12) downstream of the reduction zone (11), in which cooling gas (12.1) flows through the sponge iron. 15 The method according to claim 4, wherein the cooling gas (12.1) comprises at least one carbon-containing compound which causes carburization of the sponge iron. A method according to claim 5, wherein the carbon content of the cooled sponge iron is in the range of 0.5% to 4.5% by weight. Process according to one of Claims 1 to 6, in which the reduction zone (11) is arranged above the cooling zone (12) in a shaft furnace (10) and the iron ore passes through the shaft furnace (10) in a vertical direction. Process according to any one of claims 1 to 6, wherein the reduction zone comprises one or more fluidized bed reactors and/or the cooling zone comprises one or more fluidized bed reactors.