EP3581663A1 - Preparation of carburised sponge iron by hydrogen-based direct reduction - Google Patents

Abstract

The invention relates to a method for producing carburized, directly reduced iron sponge from iron oxide material (2). First, a reduction gas consisting at least predominantly of H2 is used for direct reduction, then the carbon content in the sponge iron is increased by means of a carburizing gas that is fed in, after which the carburizing gas used is at least partially withdrawn while largely avoiding mixing with the reducing gas. The plant (1) for producing carburized, direct-reduced sponge iron from iron oxide material (2) comprises a reduction zone (3) for the direct reduction of input iron oxide material (2) to the directly reduced product by means of reducing gas consisting predominantly of H2, and a reducing gas feed line which opens into the reducing zone (3) (4). It also comprises a carburizing zone (5) for carburizing the direct reduced product, with a carburizing gas feed line (6) opening into the carburizing zone (5) and a carburizing exhaust gas line (7) extending from the carburizing zone (5) for withdrawing used carburizing gas from the carburizing zone (5 ), and at least one device for avoiding mixing of reducing gas with carburizing gas and / or spent carburizing gas.

Description

Technical field

The application relates to a method for producing direct-reduced sponge iron from iron oxide material, direct reduction using an at least predominantly H2 gas.

State of the art

It is known to produce sponge iron by direct reduction of iron oxide material with hydrogen. Such methods are described, for example, in WO9924625 and WO2014040989 described. Used reducing gas - called top gas - emerging from the reduction unit after direct reduction can be recirculated very easily for reduction purposes, since to a significant extent practically only dust and water have to be separated from the reducing component hydrogen H2. The top gas may also contain some CO2 due to the calcination of the iron oxide material used. When nitrogen is used for sealing purposes, the top gas can also contain some nitrogen when charging iron oxide material into the reduction unit and / or when iron sponge is discharged, for example in the form of a cyclic material lock system or dynamic lock system. However, the use of strongly hydrogen-containing reducing gas leads to the fact that the carbon content in the sponge iron is very low compared to conventional direct reduction using carbon monoxide CO or other carbon-containing gases such as methane CH4, for example in a natural gas-based direct reduction plant. This can have an adverse effect on the further processing of the sponge iron, for example in EAF, since the consumption of electrical energy and electrode consumption as well as tap-to-tap time for sponge iron with a low carbon content are increased. This results in a significantly lower productivity of the arc furnace. An increase in the proportion of carbon-containing gases in the reducing gas can increase the carbon content in the sponge iron Although increasing, it leads to an accumulation of carbon-containing gas components - such as CO, CO2, CH4 - and increased CO2 emissions in the top gas. When top gas is recirculated, this requires a considerable amount of equipment and energy to separate CO2 - and other undesirable non-aqueous components that may be present from the hydrogen H2.

Summary of the invention Technical task

It is the object of the present invention to provide a method and a device which, in a simple manner and with little effort, allow an iron sponge to be obtained with direct reduction of iron oxide material with predominantly hydrogen-containing reducing gas and which has a carbon content favorable for further processing.

Technical solution

This task is solved by a
Process for the production of carburized, directly reduced iron sponge from iron oxide material,
first reducing directly by means of a reducing gas consisting at least predominantly of H2,
characterized in that
then the carbon content in the sponge iron is increased by means of a carburizing gas supplied,
whereupon the carburizing gas consumed is at least partially withdrawn while largely avoiding mixing with the reducing gas.

Iron oxide material is to be understood as any material which contains iron oxide and is suitable as a feedstock for direct reduction in the production of sponge iron. Depending on the used Direct reduction processes can be lumpy material such as ore pellets, lump ore, oxide briquettes, or fine particulate material. Lumpy material is suitable, for example, for direct reduction in fixed bed reactors. Fine particulate material is suitable, for example, for direct reduction in fluidized bed reactors.

In carburized sponge iron, the carbon content is at least 0.5% by weight, and up to 5.0% by weight, preferably between 1.0 and 3.5% by weight, the two limits being included. The carbon can be bound as iron carbide Fe3C and / or be freely available as graphitic carbon C. Chemically bound carbon as Fe3C iron carbide is better and more effective for operating an electric arc furnace (EAF).

The iron oxide material is first directly reduced by means of a reducing gas consisting at least predominantly of H2, for example in a reduction zone. The hydrogen content of the reducing gas can be up to 100 vol%. A hydrogen content of at least 80 vol% is preferred, particularly preferably at least 90 vol%, the remainder being 100 vol%, for example nitrogen N2, carbon monoxide CO, carbon dioxide CO2, water vapor H2O, methane CH4. The carbon content of the sponge iron obtained in this direct reduction is then increased, for example in a carburizing zone. A carbon-containing gas called a carburizing gas is fed to increase it. The carburizing gas contains carbon in carbon-containing molecules. The carburizing gas can be, for example, natural gas, methane CH4, ethane C2H6, propane C3H8, butane C4H10, carbon monoxide CO. The carbon-containing molecules react with the sponge iron to form iron carbide Fe3C, or they react with the release of carbon C.

For example, carburizing with methane works as follows

3 Fe + CH4 → Fe3C + 2 H2

Or, for example, elemental carbon is formed by cracking methane

CH4 → C + 2 H2

Due to the subsequent reduction reaction of the hydrogen H2 formed with iron ore, water vapor (H2O) is produced after the following reaction and this also reacts with the methane (CH4) present, for example, via a reforming reaction:

FeO + H2 → Fe + H2O

CH4 + H2O → CO + 3 H2

As a result, CO also creates CO2 and water vapor

FeO + CO → Fe + CO2

3 Fe + 2 CO → Fe3C + CO2

3 Fe + CO + H2 → Fe3C + H2O

CO + H2 → C + H2O

CO + H2O ⇔ CO2 + H2

2 CO → C + CO2

The product of this carburizing step with a higher carbon content than the product of the first step - the direct reduction - sponge iron - is called carburized sponge iron in the context of this application. When the carbon content is increased - here called carburization or carburization - carburizing gas is partially converted. Mixing non-hydrogen H2 gaseous products such as CO2, CO, the reactions leading to carburization, or unconverted portions of the carburizing gas such as N2, with the reducing gas consisting mainly of H2 introduced into the reduction unit may make effort when recirculating top gas necessary for separation.

In order to keep this effort low or to avoid it, the carburizing gas used is at least partially withdrawn while largely avoiding mixing with the reducing gas. The so-called spent carburizing gas, which is at least partially, preferably completely, drawn off, contains both gaseous products of the carburizing reactions and unreacted portions of the carburizing gas. The withdrawal is carried out in such a way that mixing of the carburizing gas used with the reducing gas is largely, preferably completely, avoided.
There is extensive avoidance of mixing with the reducing gas, if the proportion of carbon-containing gases - such as CO, CO2, CH4 or higher hydrocarbons - in the top gas is overall less than 20 vol%, preferably less than 10 vol%, particularly preferably less than 5 vol%. These values refer to measurements after cooling the top gas and condensing water vapor from the top gas. Overall means that the proportions of the individual carbon-containing gases are added up; For example, 8 vol% CO, 7 vol% CO2 and 4 vol% CH4 would give a total of 19 vol% and thus below the required limit of 20 vol%.

The used carburizing gas is therefore at least partially, preferably completely, drawn off before it is mixed with the reducing gas. The goal is to have very little or no gas flows from the carburizing zone to the reduction zone. This can be achieved, for example, by withdrawing so much used carburizing gas from the carburizing zone and separating so much used carburizing gas from a circuit of the carburizing gas that an upward flow from the carburizing zone into the reduction zone does not take place. The spent carburizing gas is practically led out laterally, for example, from an upper area of the carburizing zone before it reaches the reduction zone above it.

Accordingly, in the method according to the invention, for example, a CO2 reduction in the top gas intended for recirculation, for example by means of CO2 scrubbing or CO2 / H2O reformer, is dispensed with. The process is also carried out without reducing the CO2 in the top gas intended for recirculation if the top gas also contains some CO2 due to the calcination of the iron oxide material used. In order to avoid an accumulation of this CO2 or of other gas components that may be undesirable in the recirculation, a first subset of the top gas is excluded from the recirculation and discharged from the circuit. If appropriate, this first subset is used, for example for use as fuel gas.
The less the carburizing waste gas mixes with the reducing gas, the less top gas has to be excluded from recirculation - and the more energy-efficient it is to produce the carburized, direct-reduced sponge iron.

Advantageous effects of the invention

By carrying out the carburization after the direct reduction according to the invention and the subsequent removal of the used carburizing gas, efforts to separate undesired components from a top gas to be recirculated can be avoided.

According to a preferred embodiment, a first subset of the used carburizing gas after processing - such as dedusting - combined with fresh carburizing gas components is used again as carburizing gas to increase the carbon content of the sponge iron.
In this way, the carburization can be carried out in a more resource-efficient and economical manner, since unreacted components present in the used carburizing gas once again have the opportunity to contribute to the carburization.

According to a preferred embodiment, the carburizing gas or the processed spent carburizing gas is heated before or after being combined with fresh carburizing gas components before it comes into contact with the sponge iron. The carburization reactions run better at higher temperatures. Accordingly, the efficiency of the carburization is increased by the temperature increase.

According to a preferred embodiment, the reducing gas is heated before it comes into contact with the iron oxide material. Advantageously, a second subset of the carburizing gas used, possibly after dedusting, is used as a fuel gas for heating the reducing gas. Components with a calorific value in the carburizing gas used are used within the process; this reduces the necessary use of resources and increases the cost-effectiveness of the process. The use within the method can also include a steam generator or a power plant, for example. The reducing gas is preferably heated to over 700 ° C. by indirect heat exchange. A one-stage heating is preferably carried out by indirect heat exchange, that is to say heating while maintaining the reduction potential of the reducing gas, or without oxidative destruction of the reducing potential of the reducing gas.
However, the reduction gas can also be heated in several stages, in which one stage is indirect heat exchange. For example, in a first stage of heating be heated to a temperature above 700 ° C by indirect heat exchange, and then in a second stage direct heating by means of another type of heating - for example by partial oxidation - to achieve an even higher temperature.

According to a preferred embodiment, a further subset of the used carburizing gas, possibly after dedusting, is used as a fuel gas for heating the carburizing gas. Components with a calorific value in the carburizing gas used are used within the process; this reduces the necessary use of resources and increases the cost-effectiveness of the process.

According to a preferred embodiment, the heating of the reducing gas and the heating of the carburizing gas are carried out in the same heating unit. This requires less equipment and makes the process easier to carry out.

According to a preferred embodiment, used reducing gas is withdrawn as top gas, and a first portion of the top gas is used for use as fuel gas for heating the reducing gas and / or the carburizing gas. Components with a calorific value in the top gas are used within the process; this reduces the necessary use of resources and increases the cost-effectiveness of the process.

According to a preferred embodiment, the carburizing gas contains components which react exothermally with the directly reduced sponge iron. The carburization reactions run better at higher temperatures. Accordingly, the efficiency of the carburization is increased by the temperature increase.

According to a preferred embodiment, the sponge iron is heated before and / or while the carburizing gas is being supplied. The carburization reactions run better at higher temperatures. Accordingly, the efficiency of the carburization is increased by the temperature increase.

According to a preferred embodiment, solid carbon C is added to the sponge iron before and / or during and / or after the carburizing gas is supplied. This complements the increase in carbon content using the carburizing gas.

This also supports the desired goal of keeping the carbon content in the sponge iron constant - for example, when using it later in an EAF, constant carbon content is desired.
For example,

3 Fe + C → Fe3C

The solid carbon can be anthracite, for example.

In order to adjust the C content in the sponge iron to be as constant as possible, elemental carbon can be added in a metered form - for example by means of a metering screw or cellular wheel. Optionally, in addition to the addition, it can also be mixed with the sponge iron - for example in a mixing chamber or a mixer in order to obtain thorough mixing and an increased proportion of iron carbide. A mixer is understood to mean an assembly with moving internals, whereas a mixing chamber has no moving internals.

According to a preferred embodiment, the size of the second subset of the carburizing gas used is regulated as a function of the CO2 and / or CO and / or CH4 content in the top gas.
The regulation preferably takes place as a function of the content at the outlet from the reduction zone.
Mixing of the used carburizing gas with the circuit of the reducing gas should largely, preferably completely, be avoided.
Monitoring the top gas for components that indicate mixing has taken place - CO2 and / or CO and / or CH4 - warns of mixing. Increasing the second subset of the carburizing gas used helps to prevent any mixing that may take place.

According to a preferred embodiment, the size of the first portion of the top gas is regulated as a function of N2 and / or CO2 and / or CO and / or CH4 content in the top gas.
An enrichment of these components in the recirculated top gas would be disadvantageous for the efficiency of the direct reduction. Such components should therefore at least partially be removed from the recirculation cycle. Monitoring of the top gas for components that are due to a mixing of used carburizing gas and Indicating reducing gas - CO2 and / or CO and / or CH4 - warns of mixing. The negative effects of any mixing of carburizing gas or carburizing gas used with the reducing gas can be reduced by increasing the first portion of the top gas.
The use of the discharged gas as the first subset allows it to be used for heating purposes. Components with a calorific value in the top gas are used within the process; this reduces the necessary use of resources and increases the cost-effectiveness of the process.

• Regelorgan, wie beispielsweise ein Regelventil, in der Karburierungsabgasleitung,
• ein Kompressor beziehungsweise ein Gebläse, zur Ausschleusung aus der Karburierungszone und damit zur Vermeidung des Eintrags von Karburierungsgas in den Reduktionsgaskreislauf
• Reduktionszone und Karburierungszone getrennt durch eine mit Eisenschwamm gefüllte Leitung - beispielsweise mit oder ohne Gasschleuse , mit oder ohne Materialflussaggregat wie ein Lock-hopper-System z, einen Hot Rotary Feeder, oder eine Schwerkraftförderung.

Nach einer bevorzugten Ausführungsform mündet die Karburierungsabgasleitung in eine Rezirkulierungsvorrichtung zur Aufbereitung - wie beispielsweise Reinigung, Verdichtung, Aufheizung - und Rezirkulierung von verbrauchtem Karburierungsgas in die Karburierungsgaszuleitung.
Eine derartige Rezirkulierungsvorrichtung kann zur Aufbereitung beispielsweise zumindest eine Entstaubungsvorrichtung enthalten.
Eine derartige Rezirkulierungsvorrichtung umfasst eine Rezirkulatleitung, die in die Karburierungsgaszuleitung mündet, um aufbereitetes verbrauchtes Karburierungsgas als Teilmenge des Karburierungsgases zur Verfügung zu stellen.
Auf diese Weise kann die Karburierung resourcenschonender und wirtschaftlicher durchgeführt werden, da im verbrauchten Karburierungsgas vorhandene nicht umgesetzte Komponenten erneut die Möglichkeit bekommen, zur Karburierung beizutragen.Another object of the present application is a plant for producing carburized, direct-reduced sponge iron from iron oxide material,
comprising a reduction zone for the direct reduction of input iron oxide material to the directly reduced product by means of reducing gas consisting predominantly of H2, and comprising a reducing gas feed line opening into the reduction zone,
characterized in that
the facility also includes
a carburizing zone for carburizing the directly reduced product, with a carburizing gas supply line opening into the carburizing zone and a carburizing exhaust gas line extending from the carburizing zone for withdrawing used carburizing gas from the carburizing zone,
and at least one device for avoiding mixing of reducing gas with carburizing gas and / or spent carburizing gas.
There may also be several devices for avoiding mixing of reducing gas with carburizing gas and / or spent carburizing gas.
A device for avoiding mixing of reducing gas with carburizing gas and / or spent carburizing gas can be designed, for example:

• Control element, such as a control valve, in the carburizing exhaust gas line,
• a compressor or a blower for discharging from the carburizing zone and thus to prevent carburizing gas from entering the reducing gas circuit
• The reduction zone and carburization zone are separated by a line filled with sponge iron - for example with or without a gas lock, with or without a material flow unit such as a lock-hopper system z, a hot rotary feeder, or gravity feed.

According to a preferred embodiment, the carburizing exhaust gas line opens into a recirculation device for processing - such as cleaning, compression, heating - and recirculation of used carburizing gas into the carburizing gas supply line.
Such a recirculation device can contain, for example, at least one dedusting device for processing.
Such a recirculation device comprises a recirculation line which opens into the carburizing gas feed line in order to provide processed, used carburizing gas as a subset of the carburizing gas.
In this way, the carburization can be carried out in a more resource-efficient and economical manner, since unreacted components present in the used carburizing gas once again have the opportunity to contribute to the carburization.

According to a preferred embodiment, a gas heating device is present in the carburizing gas supply line and / or in the recirculation line. The carburization reactions run better at higher temperatures. Accordingly, the efficiency of the carburization is increased by the temperature increase.

According to a preferred embodiment, a reducing gas heating device is present in the reducing gas feed line. It is preferably a one-stage reduction gas heating device. It is preferably an indirect heat exchanger. However, it can also be a multi-stage heating device in which one stage is an indirect heat exchanger.

Advantageously, the carburizing exhaust gas line and / or the recirculation device starts with a fuel gas line opening into the reducing gas heating device. Advantageously, the carburizing exhaust gas line and / or the recirculation device starts with a fuel gas supply line which opens into the gas heating device. It is preferably a single-stage gas heating device. It is preferably an indirect heat exchanger. Components with a calorific value present in the used carburizing gas can then be used within the process; this reduces the necessary use of resources and increases the cost-effectiveness of the process. According to a preferred embodiment, the reducing gas heating device and the gas heating device are both integrated in a heating device, and the fuel gas line and / or the fuel gas supply line and / or open into the heating device. This requires less equipment.

The plant for the production of carburized, direct-reduced sponge iron from iron oxide material comprises a top gas line for withdrawing used reducing gas from the reduction zone. According to a preferred embodiment, the top gas line opens into a recycling device for processing and recycling top gas into the reducing gas feed line.
Such a recycling device can, for example, contain at least one dedusting device for processing - preferably a dry dedusting device, since in this case, in comparison to a likewise possible wet dedusting device, there is no need for complex cleaning of process waste water from the wet dedusting.
Such a recycle device comprises a recirculation line which opens into the reducing gas supply line in order to make processed top gas available as a subset of the reducing gas.
In this way, the direct reduction can be carried out in a more resource-efficient and economical manner, since unconverted components in the top gas again have the opportunity to contribute to the direct reduction.
According to a preferred embodiment, the plant for producing carburized, direct-reduced sponge iron from iron oxide material also comprises one of the Topgasleitung and / or the recycle device outgoing fuel line, which opens into the reducing gas heating device and / or into the gas heating device and / or the heating device. Components with a calorific value in the top gas can then be used within the process; this reduces the necessary use of resources and increases the cost-effectiveness of the process.
If a dedusting device is present in the recycling device, it is preferred that the fuel line, viewed in the flow direction of the top gas, extends from the reduction zone after the dedusting device. This saves parts of the system that have passed through later, such as compressors.

According to a preferred embodiment, between the reduction zone and the carburizing zone there is a heating system for heating the directly reduced product before entering the carburizing zone. According to a preferred embodiment, a heating system for heating the directly reduced product is present in the carburizing zone.

According to a preferred embodiment, a carbon addition device is present between the reduction zone and the carburization zone. According to a preferred embodiment, a carbon addition device is present in the carburizing zone. According to a preferred embodiment, a carbon addition device is present behind the carburizing zone, viewed from the reduction zone in the direction of flow of the directly reduced product.
The carbon addition device is suitable for adding solid carbon. It can include metering devices such as a metering screw or cellular wheel. According to a preferred embodiment, it also comprises mixing devices such as, for example, a mixing chamber or mixer, in order to enable thorough mixing and an increased proportion of iron carbide.

According to a preferred embodiment, the system according to the invention also comprises a regulating device for regulating the gas flow in the fuel gas line and / or the fuel gas feed line as a function of measured values obtained from the top gas. Such a control device can be one of the devices for avoiding mixing of reducing gas with carburizing gas and / or used carburizing gas.

According to a preferred embodiment, the system according to the invention also includes a regulating device for regulating the gas flow in the fuel line as a function of measured values obtained from the top gas.

According to a preferred embodiment, the system according to the invention does not include a device for reducing the CO2 of the top gas intended for recycling.

According to a preferred embodiment, the system according to the invention comprises a discharge line for discharging top gas from the recycling.

According to a preferred embodiment, the reduction zone and the carburization zone are accommodated within one unit. For example, the aggregate can be a shaft in the upper part of which the reduction zone is located and in the lower part of which the carburizing zone is located. Iron oxide material is fed into the shaft at the top and travels downward due to gravity. It is reduced directly. After passing through the reduction zone, the directly reduced product enters the carburizing zone. After passing through the carburizing zone, it emerges from the shaft.

According to a preferred embodiment, the reduction zone and the carburization zone are accommodated in different units. For example, the direct reduced product can be from a product containing the reduction zone Direct reduction unit are removed and then introduced into a separate carburizing unit containing the carburizing zone. The directly reduced product is sponge iron. Direct reduction unit and carburizing unit are connected via a delivery line for the delivery of sponge iron into the carburizing unit.
The at least one device for avoiding mixing of reducing gas with carburizing gas and / or used carburizing gas can be present in the delivery line, for example. It can also be present in the end of the direct reduction unit on the delivery line side. It can also be present in the end of the carburizing unit on the delivery line side, it can also be present on the end of the delivery line facing the direct reduction unit, or on the end of the delivery line facing the carburizing unit.

Brief description of the drawings

• Figur 1 zeigt schematisch eine Variante einer erfindungsgemäßen Anlage zur Herstellung von karburiertem direktreduzierten Eisenschwamm aus Eisenoxidmaterial .
• Figur 2 zeigt schematisch eine andere Variante einer erfindungsgemäßen Anlage zur Herstellung von karburiertem direktreduzierten Eisenschwamm aus Eisenoxidmaterial.
• Figuren 3 bis 8 zeigen in Anlehnung an die Figuren 1 und 2 diverse Varianten.
• Figur 9 zeigt schematisch ein herkömmliches Verfahren zur Herstellung von direktreduzierten Eisenschwamm aus Eisenoxidmaterial, wobei mittels eines aus H2 bestehenden Reduktionsgases direktreduziert wird.

The present invention is described by way of example below with reference to several schematic figures.

• Figure 1 shows schematically a variant of a plant according to the invention for the production of carburized direct reduced iron sponge from iron oxide material.
• Figure 2 shows schematically another variant of a plant according to the invention for the production of carburized direct reduced iron sponge from iron oxide material.
• Figures 3 to 8 show following the Figures 1 and 2 various variants.
• Figure 9 shows schematically a conventional method for producing direct-reduced sponge iron from iron oxide material, wherein direct reduction is carried out by means of a reducing gas consisting of H2.

Description of the embodiments Examples

Figure 1 schematically shows a variant of a system 1 according to the invention for producing carburized, direct-reduced sponge iron from iron oxide material 2.
It comprises a reduction zone 3 for the direct reduction of input iron oxide material 2 to the directly reduced product by means of reducing gas consisting predominantly of H2. It also includes a reduction gas gas feed line 4 opening into the reduction zone 3. It also comprises a carburizing zone 5 for carburizing the directly reduced product. A carburizing gas supply line 6 opens into the carburizing zone 5. A carburizing exhaust gas line 7 extends from the carburizing zone 5 for withdrawing used carburizing gas from the carburizing zone 5. The system also includes at least one device for avoiding mixing of reducing gas with carburizing gas and / or spent carburizing gas, here a blower 8 in the carburizing exhaust gas line 7. The blower 8 transports used carburizing gas at least partially out of the carburizing zone and thereby mixing it with the reducing gas largely avoided. To produce carburized, direct-reduced sponge iron from iron oxide material 2, it is first reduced directly by means of the reducing gas, which consists at least predominantly of H2, while it travels through the reduction zone 3, following gravity, from top to bottom. Thereafter, the direct reduced product sponge iron enters the carburizing zone 5 following the force of gravity, where the carbon content in the direct reduced product sponge iron is increased by means of a supplied carburizing gas, while it is passed from top to bottom following the force of gravity. Carburizing gas consumed in the process is withdrawn from the carburizing zone 5 via the carburizing exhaust gas line and conducted out, at least partially, by mixing with the reducing gas. Removal of carburized sponge iron from the carburizing zone is indicated by a block arrow.

Figure 2 shows schematically another variant of a system 1 according to the invention for producing carburized, direct-reduced sponge iron from iron oxide material 2. In contrast to Figure 1 carburization zone 5 and reduction zone 3 are accommodated in different units. The direct reduced product sponge iron is removed from a direct reduction unit containing the reduction zone - in the case shown a fixed bed reactor 9 - and then introduced via the delivery line 10 into a separate carburizing unit 11 containing the carburizing zone. In the delivery line 10, there may also be an additional conveying element, such as a cellular wheel sluice, or a dynamic gas barrier. To Figure 1 Analog system parts are identified with the same reference symbols. The device for avoiding mixing of reducing gas with carburizing gas and / or spent carburizing gas - represented by the blower 8 in the illustrated case - could be present in the delivery line instead of or in addition to the arrangement shown in the carburizing exhaust gas line, or in the delivery line end of the direct reduction unit, or be present in the end of the carburizing unit on the delivery line side, or on the end of the delivery line facing the direct reduction unit, or on the end of the delivery line facing the carburizing unit. For better clarity, these variants are not shown. Removal of carburized sponge iron from the carburizing zone is indicated by a block arrow.

Figure 3 shows an example of a section of the Figure 2 largely analogous representation, such as the carburizing exhaust gas line 7 Figure 2 in a recirculation device 12 for processing - such as cleaning, compression, heating - and recirculation of used carburizing gas opens into the carburizing gas supply line 6. A first subset of the used carburizing gas is used again after processing - such as for example dedusting - combined with fresh carburizing gas components via the recirculation line 13 as carburizing gas to increase the carbon content of the sponge iron. The feed of the fresh carburizing gas components is indicated by the arrow 14. Removal of carburized sponge iron from the carburizing zone is indicated by a block arrow.

In Figure 3 it is also indicated that a gas heating device 15 is present in the carburizing gas feed line 6. Instead, or in addition, it could also be present in the recirculation line 13. The carburizing gas is heated before it comes into contact with the sponge iron.

Figure 4 shows one example Figure 1 largely analogous representation of how a reducing gas heating device is present in the reducing gas feed line, in the illustrated case an indirect heat exchanger 16 for the one-stage heating of the Reduction gas before it comes into contact with the iron oxide material 2. A second subset of the used carburizing gas is supplied after processing for use as fuel gas for heating the reducing gas. To this end, the recirculation device 12 starts with a fuel gas line 17 opening into the reducing gas heating device 16.

Figure 5 shows in a modification of the representation in Figure 4 how a recirculation device 12 emanates a fuel gas supply line 18 opening into the gas heating device 15. A further subset of the carburizing gas used is supplied for use as fuel gas for heating the carburizing gas.

Figure 6 points to one Figure 1 largely analogous representation of how a top gas line 19 proceeds for withdrawing used reducing gas from the reduction zone. A fuel line 20 starts from it and can - for better clarity not shown separately - in a gas heating device 15 or a reducing gas heating device such as in the Figures 3 and 4 shown lead to supply a first portion of the top gas for use as a fuel gas for heating the reducing gas and / or the carburizing gas.

Figure 7 indicates based on Figure 2 schematically, how can be heated by means of a heating system 21 in the delivery line 21 sponge iron before entering the carburizing zone.

Figure 8 indicates based on Figure 2 schematically how carbon can be entered into the carburizing zone 5 by means of a carbon addition device 22.

Figure 9 shows schematically a conventional method for producing direct-reduced sponge iron from iron oxide material, wherein direct reduction is carried out by means of a reducing gas consisting of H2. The H2 reduction gas is introduced into the reduction reactor 24 via the reduction gas feed line 23. Sponge iron 25 is removed from the reduction reactor 24 below. Reducing gas consumed after the reduction is removed as top gas via the top gas line 26 from the top of the reduction reactor 24. The top gas is largely recirculated in a scrubber 27 after condensation of water and cleaning, while a subset is used as fuel Reduction gas furnace 28 is fed. Fresh hydrogen 29 is mixed into the recirculated top gas. After preheating with exhaust gas from the reduction gas furnace 28, heating is carried out in the reduction gas furnace 28 and then introduced into the reduction unit. CO2 removal is not necessary in the recirculation cycle.

Although the invention has been illustrated and described in detail by the preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention.

List of reference numbers

1

Plant for the production of carburized, direct reduced iron sponge from iron oxide material

2

iron oxide material

3

reduction zone

4

Reducing gas supply line

5

carburizing

6

Karburierungsgaszuleitung

7

Karburierungsabgasleitung

8th

fan

9

Fixed Bed Reactor

10

delivery line

11

Karburierungsaggregat

12

Rezirkulierungsvorrichtung

13

Rezirkulatleitung

14

feeding in

15

Gas heating apparatus

16

Indirect heat exchanger

17

Fuel gas line

18

Fuel gas supply line

19

top gas

20

fuel line

21

heating system

22

Carbon addition equipment

23

Reducing gas supply line

24

reduction reactor

25

sponge iron

26

top gas

27

washer

28

Reducing gas oven

List of quotes patent literature

WO9924625

WO2014040989

Claims (15)

Process for the production of carburized, directly reduced iron sponge from iron oxide material (2),
first reducing directly by means of a reducing gas consisting at least predominantly of H2,
characterized in that
then the carbon content in the sponge iron is increased by means of a carburizing gas supplied,
whereupon the carburizing gas consumed is at least partially withdrawn while largely avoiding mixing with the reducing gas. A method according to claim 1, characterized in that a first portion of the spent carburizing gas after reprocessing with fresh carburizing gas components is used again as carburizing gas to increase the carbon content of the sponge iron. A method according to claim 1 or 2, characterized in that the carburizing gas or the processed spent carburizing gas is heated before or after being combined with fresh carburizing gas components before it comes into contact with the sponge iron. Method according to one of claims 1 to 3, characterized in that the carburizing gas contains components reacting exothermically with the directly reduced sponge iron. Method according to one of claims 1 to 4, characterized in that the sponge iron is heated before and / or while the carburizing gas is supplied. Method according to one of claims 1 to 5, characterized in that solid carbon C is added to the sponge iron before and / or during and / or after the carburizing gas is supplied. Method according to one of claims 1 to 6, wherein used reducing gas is withdrawn as top gas, and the reducing gas is heated before it comes into contact with the iron oxide material, characterized in that a second subset of the spent carburizing gas is used as fuel gas for heating the reducing gas is fed
wherein preferably the size of the second subset of the carburizing gas used is regulated as a function of CO2 and / or CO and / or CH4 content in the top gas. Method according to one of claims 1 to 7, wherein used reducing gas is withdrawn as top gas, and the reducing gas is heated before it comes into contact with the iron oxide material, characterized in that a first subset of the top gas is used as fuel gas for heating the reducing gas and / or the carburizing gas is supplied;
wherein the size of the first subset of the top gas is preferably regulated as a function of N2 and / or CO2 and / or CO and / or CH4 content in the top gas. Plant (1) for the production of carburized, direct reduced iron sponge from iron oxide material (2),
comprising a reduction zone (3) for direct reduction of input iron oxide material (2) to direct reduced product by means of reducing gas consisting predominantly of H2,
and comprising a reducing gas feed line (4) opening into the reduction zone (3), characterized in that
the system (1) also includes
a carburizing zone (5) for carburizing the direct reduced product, with an in the carburizing gas feed line (6) opening into the carburizing zone (5) and a carburizing exhaust gas line (7) extending from the carburizing zone (5) for withdrawing spent carburizing gas from the carburizing zone (5),
and at least one device for avoiding mixing of reducing gas with carburizing gas and / or spent carburizing gas. Installation according to claim 9, characterized in that the carburizing exhaust gas line (7) opens into a recirculation device (12) for the preparation and recirculation of used carburizing gas into the carburizing gas supply line (6). Installation according to claim 9 or 10, characterized in that a gas heating device (15) is present in the carburizing gas feed line (6). Plant according to one of claims 9 to 11, characterized in that between the reduction zone (3) and the carburizing zone (5) there is a heating system for heating the directly reduced product before entering the carburizing zone (5) and / or in the carburizing zone (5 ) a heating system (21) for heating the direct reduced product is present. Plant according to one of Claims 9 to 12, characterized in that a carbon addition device (22) is present between the reduction zone (3) and the carburizing zone (5),
and or
a carbon addition device (22) is present in the carburizing zone (5), and / or
From the reduction zone (3), as seen in the direction of flow of the directly reduced product, a carbon addition device (22) is present behind the carburizing zone (5). Plant according to one of claims 9 to 13, characterized in that the reduction zone (3) and the carburizing zone (5) are accommodated within one unit. Plant according to one of claims 9 to 13, characterized in that the reduction zone (3) and the carburizing zone (5) are accommodated in different units.

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