EP3807426A1

EP3807426A1 - Producing carburized sponge iron by means of hydrogen-based direct reduction

Info

Publication number: EP3807426A1
Application number: EP19728718.8A
Authority: EP
Inventors: Robert Millner; Christian Boehm
Original assignee: Primetals Technologies Austria GmbH
Current assignee: Primetals Technologies Austria GmbH
Priority date: 2018-06-12
Filing date: 2019-06-12
Publication date: 2021-04-21
Also published as: US20210246521A1; MX2020013294A; AU2019286552A1; EP3581663A1; CA3103187A1; WO2019238720A1

Abstract

The invention relates to a method for producing carburized direct-reduced sponge iron from iron oxide material (2). First, direct reduction is performed by means of a reducing gas consisting at least predominantly of H2, thereafter the carbon content in the sponge iron is increased by means of a supplied carburizing gas, after which carburizing gas used in this process is at least partially drawn off in order to largely avoid mixing with the reducing gas. The system (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 form direct-reduced product by means of reducing gas consisting at least predominantly of H2, and a reducing-gas supply line (4), which leads into the reduction zone (3). The system also comprises a carburizing zone (5) for carburizing the direct-reduced product, having a carburizing-gas supply line (6) leading into the carburizing zone (5) and a carburizing exhaust gas line (7) going out from the carburizing zone (5) for drawing off used carburizing gas from the carburizing zone (5), and at least one device for avoiding mixing of reducing gas with carburizing gas and/or used carburizing gas.

Description

Manufacture of carburized sponge iron using hydrogen-based direct reduction

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 for example in W09924625 and

WO2014040989. Used reducing gas - called top gas - emerging from the reduction unit after the direct reduction can be used for

Recirculate reduction purposes very easily, since to a significant extent practically only dust and water have to be separated from the reducing component hydrogen H ₂ . The top gas may be due to the calcination of the used

Iron oxide material also contain some C0 ₂ . The top gas can be used when sealing nitrogen when charging iron oxide material into the

Reduction unit and / or when iron sponge is discharged - for example designed as a cyclic material lock system or dynamic lock system - also contain some nitrogen. However, the use of strongly hydrogen-containing reducing gas means that, compared to conventional direct reduction using carbon monoxide, CO or other carbon-containing gases such as methane CH ₄ , for example in a natural gas-based direct reduction system, the carbon content in the sponge iron is very low. That can happen with the further

Processing of the sponge iron, for example in EAF, has a negative impact, since the consumption of electrical energy and electrode consumption as well as tap-to-tap time for

Low carbon sponges 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, C02, CH ₄ - and increased CO ₂ emissions in the top gas. When top gas is recirculated, this makes a considerable expenditure in terms of apparatus and energy in order to separate off C0 ₂ - and other undesirable ones that may be present

non-aqueous components of hydrogen H ₂ necessary.

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, make it possible to use a predominantly hydrogen-containing reducing gas in the direct reduction of iron oxide material

To win sponge iron, which has a favorable carbon content for further processing.

Technical solution

This task is solved by a

Process for the production of carburized direct reduced iron sponge

Iron oxide material,

first by means of an at least predominantly consisting of hydrogen H ₂

Reducing gas is directly reduced,

characterized in that

then the carbon content in the. by means of a carburizing gas supplied

Sponge iron is increased

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 e. 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 hydrogen H ₂ , 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% by volume is preferred, particularly preferably at least 90% by volume, the remainder to 100% by volume being, for example, nitrogen N ₂ , carbon monoxide CO, carbon dioxide CO ₂ , water vapor H ₂ O, methane CH ₄ . The carbon content of this

Direct reduction of sponge iron obtained is then increased, for example in a carburizing zone. A carbon-containing gas is called to increase it

Carburizing gas supplied. The carburizing gas contains carbon in

carbon-containing molecules. The carburizing gas can be, for example, natural gas, methane CH ₄ , ethane C ₂ H ₆ , propane C ₃ H ₈ , butane CH ₁₀ , carbon monoxide CO, or a mixture of several of these gases. The carbon-containing molecules react with that

Sponge iron to iron carbide Fe ₃ C, or they react with the release of carbon C.

For example, carburizing with methane works as follows

Or, for example, elemental carbon is formed by cracking methane Due to the subsequent reduction reaction of the hydrogen H _{2 formed} with iron ore, water vapor (H ₂ 0) arises after the following reaction and this also reacts with the methane (CH ₄ ) present, for example, via a reforming reaction:

FeO + H ₂ ^ Fe + H ₂ 0

CH ₄ + Fl ₂ 0 -> CO + 3 H ₂

As a result, CO also creates CO ₂ and water vapor

3 Fe + 2 CO - Fe ₃ C + C0 ₂

3 Fe + CO + H ₂ ^ Fe ₃ C + H ₂ 0

CO + hl ₂ -> c + H ₂ O

CO + H ₂ O CO ₂ + H ₂

2 CO -> C + C0 ₂

The product of this carburizing step with increased carbon content compared to 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 of non-hydrogen Fl ₂ gaseous products such as C0 ₂ , CO, the reactions leading to carburization, or of unconverted portions of the carburizing gas such as N ₂ , with the reducing gas consisting predominantly of hydrogen Fl _{2 introduced} into the reduction unit makes one Recirculation of top gas may require separation effort.

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 used up

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 removal is done in such a way that

Mixing of the used carburizing gas 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, C0 ₂ , CH ₄ or higher hydrocarbons - in the top gas is below 20 vol%, preferably below 10 vol%, particularly preferably below 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% CO ₂ and 4 vol% CH _{4 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 flow from the carburizing zone to the

To have a 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 C0 ₂ reduction of the top gas intended for recirculation, for example by means of C0 ₂ washing or C0 ₂ / H ₂ 0 reformer, is dispensed with. The process is also carried out without a CO ₂ reduction in top gas intended for recirculation if the top gas also contains some CO ₂ due to the calcination of the iron oxide material used. In order to avoid an enrichment of this CO ₂ or of other gas components that may be contained in the top gas during the recirculation, a first subset of the top gas is excluded from the recirculation and discharged from the circuit. If necessary, this first subset is used,

for example 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 portion of the used carburizing gas is combined with fresh carburizing gas components after processing - such as dedusting - again as carburizing gas

Increasing the carbon content of the sponge iron used.

In this way, carburizing can save resources and be more economical

be carried out because existing unreacted components in the used carburizing gas again have the opportunity to contribute to the carburizing.

According to a preferred embodiment, the carburizing gas or the processed spent carburizing gas before or after being combined with fresh ones

Carburizing gas components are heated before contacting the sponge iron. So at least one member of the group consisting of the two members is heated

carburizing

Treated spent carburizing gas before or after being combined with fresh carburizing gas components before contacting 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. Use within the process can for example also include a steam generator or a power plant. 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 by indirect heat exchange to a temperature above 700 ° C, and then in a second stage direct heating using another type of heating - for example by partial oxidation - to set an even higher

Temperature successes.

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

Increasing the temperature increased the efficiency of carburizing. 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 e 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 - FeaC

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, the

Sponge iron are mixed - 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 dependent on carbon dioxide C0 ₂ and / or

Carbon monoxide CO and / or methane CH ₄ content in the top gas regulated.

The regulation preferably takes place as a function of the content at the outlet from the

Reduction zone.

A mixture 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 - carbon dioxide C0 ₂ and / or carbon monoxide CO and / or methane CH ₄ - warns of mixing. Enlargement of the second subset of the used Carburizing gas helps to prevent any mixing that may take place.

According to a preferred embodiment, the size of the first subset of the top gas is dependent on nitrogen N ₂ and / or carbon dioxide C0 ₂ and / or

Carbon monoxide CO and / or methane CH ₄ content in the top gas regulated.

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 the top gas

Components that indicate that the used carburizing gas and reducing gas have been mixed - carbon dioxide C0 ₂ and / or carbon monoxide CO and / or methane CH ₄ - warns against mixing. The negative effects of one

optionally mixing carburizing gas or

used carburizing gas 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.

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 the input iron oxide material to the directly reduced product by means of a mixture consisting predominantly of hydrogen H ₂

Reducing gas

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 direct reduced product, with a carburizing gas supply line opening into the carburizing zone and one of the

Carburizing zone outgoing carburizing exhaust gas line for withdrawing spent 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.

Several devices can also be used to avoid mixing

Reducing gas with carburizing gas and / or spent carburizing gas may be present.

A device for avoiding mixing of reducing gas with

Carburizing gas and / or used carburizing gas can, for example, be designed as follows:

- control element, such as a control valve, in the carburizing exhaust gas line,

- A compressor or a blower to discharge from the

Carburizing zone and thus to avoid the entry of carburizing gas in the reducing gas circuit

- Reduction zone and carburizing zone 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

Karburierungsgaszuleitung.

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, there is a in the reducing gas feed line

Reduction gas heating device available. 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 from a fuel gas line opening into the reducing gas heating device. Advantageously, from the carburizing exhaust gas line and / or the recirculation device, an outlet opens into the gas heating device

Fuel gas supply line off. It is preferably a one-stage

Gas heating apparatus. 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; that reduces the necessary

Use of resources and increases the efficiency 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 iron sponge

Iron oxide material includes a top gas line for withdrawing used

Reduction 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, process at least one dedusting device - preferably a dry dedusting device, since in it If, in comparison to a likewise possible wet dedusting device, complex cleaning of process waste water from the wet dedusting can be dispensed with - included.

Such a recycling device comprises a recirculation line, which in the

Reduction gas supply leads to the treated top gas as a subset of the

To provide 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 the production of

carburized direct reduced sponge iron made of iron oxide material also a fuel line starting from the top gas line and / or the recycle device, which leads 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; that reduces the necessary

Use of resources and increases the efficiency of the process.

If a dedusting device is present in the recycling device, it is preferred that the fuel line in the flow direction of the top gas from the

Reduction zone seen after the dedusting device goes out. This saves parts of the system that have passed through later, such as compressors.

According to a preferred embodiment is between the reduction zone and the

Carburizing zone a heating system for heating the direct 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 is between the reduction zone and the

Carburization zone a carbon addition device available. According to a preferred embodiment, a carbon addition device is present in the carburizing zone. According to a preferred embodiment, viewed from the reduction zone in the direction of flow of the directly reduced product, one behind the carburizing zone

Carbon adding device available.

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 includes mixing devices such as, for example, a mixing chamber or a mixer for thorough mixing and an increased proportion

To allow 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 plant according to the invention does not include a device for reducing the CO _{2 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 housed within an aggregate. For example, that Aggregate be a shaft, in the upper part of which is the reduction zone, and in the lower part of which is the carburizing zone. 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 housed in different units. For example, the direct reduced product can be from a product containing the reduction zone

Direct reduction unit can be removed and then in a separate, the

Carburizing zone containing carburizing unit are introduced. The

Directly reduced product is sponge iron. Direct reduction unit and

Carburizing units 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 spent carburizing gas can be present in the delivery line, for example. It can also be in the delivery line end of the

Direct reduction units are available. It can also be present in the end of the carburizing unit on the delivery line, it can also be on the

Direct reduction unit facing the end of the delivery line, or on the

Carburizing unit facing the end of the delivery line.

Brief description of the drawings

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

FIG. 1 schematically shows a variant of a plant according to the invention for producing carburized, direct-reduced sponge iron from iron oxide material. FIG. 2 schematically shows another variant of a plant according to the invention for producing carburized, direct-reduced sponge iron from iron oxide material.

Figures 3 to 8 show various variants based on Figures 1 and 2.

FIG. 9 schematically shows a conventional method for producing

Directly reduced sponge iron made of iron oxide material, with direct reduction using a reducing gas consisting of H2.

Description of the embodiments

Examples

FIG. 1 schematically shows a variant of a system 1 according to the invention for producing carburized, directly reduced iron sponge from iron oxide material 2.

It comprises a reduction zone 3 for the direct reduction of input

Iron oxide material 2 to directly reduced product by means of reducing gas consisting predominantly of H ₂ . It also includes one opening into the reduction zone 3

Reduction gas gas supply line 4. It also comprises a carburizing zone 5 for carburizing the direct reduced product. One opens into the carburizing zone 5

Carburizing gas supply line 6. One goes from the carburizing zone 5

Carburizing exhaust gas line 7 for withdrawing spent 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 iron sponge from iron oxide material 2, it is first reduced directly by means of the reducing gas, which consists at least predominantly of H ₂ , while it travels through the reduction zone 3, following gravity, from top to bottom. Thereafter, the direct reduced sponge iron product enters the carburizing zone 5 following gravity, where the carbon content in the directly reduced sponge iron product is increased by means of a supplied carburizing gas, while following gravity from top to bottom is going through. Carburizing gas consumed in the process is largely reduced

Avoidance of mixing with the reducing gas is at least partially withdrawn from the carburizing zone 5 via the carburizing exhaust gas line and conducted out by means of the blower 8. Removal of carburized sponge iron from the carburizing zone is indicated by a block arrow.

FIG. 2 schematically shows 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 FIG. 1, carburization zone 5 and reduction zone 3 are accommodated in different units. The directly reduced product sponge iron is made from a direct reduction unit containing the reduction zone - in the case shown

Fixed bed reactor 9 - removed and then introduced via the delivery line 10 into a separate carburizing unit 11 containing the carburizing zone. An additional conveying element, such as a cellular wheel sluice, or a dynamic gas barrier can also be present in the delivery line 10. Plant parts analogous to FIG. 1 are identified by the same reference numerals. The device for avoiding mixing of reducing gas with carburizing gas and / or spent carburizing gas - exemplified in the illustrated case by the blower 8 - 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

Direct reduction unit, or in the delivery line end of the

Carburizing unit be present, or at the end of the delivery line facing the direct reduction unit, or at 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.

FIG. 3 shows, by way of example in a representation largely analogous to a section of FIG. 2, how the carburizing exhaust gas line 7 from FIG

Recirculation device 12 for processing - such as cleaning, compression, heating - and recirculation of spent carburizing gas into the

Carburizing gas supply line 6 opens. A first subset of the used

Carburizing gas is recombined with fresh carburizing gas components via the recirculation line 13 after processing - such as dedusting, for example used 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 is also indicated that a gas heating device 15 in the

Carburizing gas supply line 6 is present. 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.

FIG. 4 shows, by way of example, in a representation largely analogous to FIG. 1, 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

Part of the used carburizing gas is supplied after processing for use as a fuel gas for heating the reducing gas. This goes from the

Recirculation device 12 from a fuel gas line 17 opening into the reduction gas heating device 16.

Figure 5 shows a modification of the illustration in Figure 4, as of the

Recirculation device 12 opens into the gas heating device 15

Fuel gas supply line 18 goes out. Another subset of the used up

Carburizing gas is used as a fuel gas for heating the

Carburizing gas supplied.

FIG. 6 shows in a representation largely analogous to FIG. 1 how a top gas line 19 for withdrawing used reducing gas emerges 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

Reduction gas heating device as shown for example in Figures 3 and 4 open 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. FIG. 7 shows, based on FIG. 2, schematically how sponge iron 21 present in the delivery line 10 can be used to heat sponge iron before entering the carburizing zone.

Figure 8 shows schematically based on Figure 2, as by means of a

Carbon adding device 22 carbon can be input into the carburizing zone 5.

FIG. 9 schematically shows a conventional method for the production of

Directly reduced sponge iron made of iron oxide material, with direct reduction using a reducing gas consisting of Fi ₂ . The Fi ₂ 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. Most of the top gas is recirculated in a scrubber 27 after condensation of water and cleaning, while a portion is fed as fuel to a reducing gas furnace 28. 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. C0 ₂ removal is not necessary in the recirculation circuit.

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 numerals 1 Plant for the production of carburized, direct reduced iron sponge from iron oxide material

2 iron oxide material

3 reduction zone

4 Reduction gas supply

5 carburizing zone

6 carburizing gas supply line

7 carburizing exhaust pipe

8 blowers

9 fixed bed reactor

10 delivery management

1 1 carburizing unit

12 recirculation device

13 Recirculation line

14 feed

15 gas heating device

16 Indirect heat exchanger

17 Fuel gas line

18 fuel gas supply

19 Top gas line

20 fuel line

21 heating system

22 carbon adding device

23 Reduction gas supply reduction reactor

sponge iron

top gas

washer

Reducing gas oven

List of quotes

patent literature

W09924625

WO2014040989

Claims

Expectations

1 . Process for the production of carburized, directly reduced iron sponge from iron oxide material (2),

first being directly reduced by means of a reducing gas consisting at least predominantly of hydrogen H ₂ ,

characterized in that

then the carbon content in the. by means of a carburizing gas supplied

Sponge iron is increased

2. The method according to claim 1, characterized in that a first portion of the spent carburizing gas after processing with fresh

Carburizing gas components combined again as carburizing gas is used to increase the carbon content of the sponge iron.

3. The method according to claim 1 or 2, characterized in that heating at least one member of the group consisting of the two members

carburizing

processed spent carburizing gas takes place before or after combining with fresh carburizing gas components,

before it comes into contact with the sponge iron ..

4. The method according to any one of claims 1 to 3, characterized in that the carburizing gas contains components reacting exothermically with the directly reduced sponge iron.

5. The method according to any one of claims 1 to 4, characterized in that the

Sponge iron is heated before and / or while the carburizing gas is supplied.

6. The method according to any one of claims 1 to 5, characterized in that the

Solid carbon C is added to the sponge iron before and / or during and / or after the carburizing gas is supplied.

7. The method according to any 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 for use as a fuel gas for heating of the reducing gas is supplied,

preferably the size of the second subset of the consumed

Carburizing gas depending on carbon dioxide C0 ₂ and / or carbon monoxide CO and / or methane CH ₄ content in the top gas is regulated.

8. The method according to any one of claims 1 to 7, wherein used reducing gas is withdrawn as a top gas, and the reducing gas is heated before it comes into contact with the iron oxide material, characterized in that a first portion of the top gas is used as a fuel gas for heating the Reducing gas and / or

Carburizing gas is supplied;

the size of the first portion of the top gas is preferably regulated as a function of nitrogen N ₂ and / or carbon dioxide C0 ₂ and / or carbon monoxide CO and / or methane CH ₄ content in the top gas.

9. Plant (1) for producing carburized, direct-reduced sponge iron from iron oxide material (2),

comprising a reduction zone (3) for the direct reduction of input

Iron oxide material (2) to a direct reduced product using a reducing gas consisting mainly of hydrogen H ₂ , 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 directly reduced product, with a carburizing gas feed line (6) opening into the carburizing zone (5) and a carburizing exhaust gas line (7) starting 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.

10. Plant 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).

1 1. Installation according to claim 9 or 10, characterized in that in the

Carburizing gas supply line (6) a gas heating device (15) is present.

12. Plant according to one of claims 9 to 1 1, characterized in that between the reduction zone (3) and the carburizing zone (5) a heating system for heating the direct reduced product before entering the carburizing zone (5) is present and / or in the Carburization zone (5) there is a heating system (21) for heating the directly reduced product.

13. 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).

14. Plant according to one of claims 9 to 13, characterized in that the

Reduction zone (3) and the carburizing zone (5) are housed within one unit.

15. Plant according to one of claims 9 to 13, characterized in that the

Reduction zone (3) and the carburizing zone (5) are housed in different units.