WO2008046503A1

WO2008046503A1 - Method and device for producing molten material

Info

Publication number: WO2008046503A1
Application number: PCT/EP2007/008514
Authority: WO
Inventors: Franz Hauzenberger; Robert Millner; Norbert Rein; Johannes Schenk; Martin Schmidt; Bogdan Vuletic; Kurt Wieder; Johann Wurm
Original assignee: Siemens Vai Metals Technologies Gmbh & Co
Priority date: 2006-10-13
Filing date: 2007-10-01
Publication date: 2008-04-24
Also published as: JP2010506046A; AR063265A1; RU2009117865A; TW200827452A; CN101528948A; BRPI0719172A2; DE102006048601A1; US20100024599A1; AU2007312665A1; MX2009003725A; CL2007002941A1; ZA200902093B; EP2082066A1; CA2665763A1; KR20090068351A

Abstract

The invention relates to a method for producing molten material, wherein oxygen, reducing agents and iron that has been reduced in a reduction reactor (1) are introduced into a melter gasifier (3). The reducing agent is gasified with the oxygen and the heat thereby produced melts the reduced iron. The coupling gas from the melter gasifier (3) is used at least as a portion of the reduction gas, reacted top gas is withdrawn from the reduction reactor (1). The aim of the invention is to increase energy efficiency and raw material efficiency as well as productivity while at the same time obtaining metallurgically improved properties of the product. For this purpose, at least a portion of the top gas is branched off from the line (9) for the withdrawal of the top gas from the reduction reactor (1) and is returned via at least one return line (13, 18) leading to the melter gasifier (3) and is introduced into the melter gasifier (3).

Description

Method and device for producing molten material

The invention relates to a method for producing molten metal, wherein oxygen, reducing agent and in a reduction reactor reduced iron are introduced into a melter gasifier, the reducing agent gasified with the oxygen and the resulting heat, the reduced iron is melted, the dome gas from the A melt gasifier is used as at least a portion of the reducing gas, and wherein reacted top gas is withdrawn from the reduction reactor, and a plant for carrying out the method, with a reduction reactor, a melt gasifier with oxygen supply and a supply system for reducing agent, at least one conduit for the supply of the dome gas from the melt gasifier into the reduction reactor and at least one line for the removal of the top gas from the reduction reactor.

At blast furnaces, various carbonaceous gases, such as natural gas, coke oven gas, etc., are injected via the tuyeres or in the Bosh plane with the background to save coke and increase economy, as already described in GB 883 998 A, for example. An injection of blast furnace gas is not economical due to the high CO ₂ , N ₂ and low H ₂ content.

In smelting reduction plants, such as described in DE 36 28 102 A1, oxygen is injected at a temperature of 25 ° C and a purity of ≥95% by volume via the nozzles in the melter gasifier to gasify the reducing agent (mainly coal and coal briquettes) and to provide the required heat for the melting of the reduced iron. The dome gas of the melter gasifier (ESV) is used for indirect reduction in a fixed bed reduction shaft (FBRS) or in fluidized bed reactors (ESC). Due to the lack of gas utilization in the FBRS or WSR, there is a high specific coal or coal briquette consumption and a high energy surplus in the export gas.

The coupling of the melter gasifier operation with the reduction reactor results in a fluctuating metallization of the sponge iron of 70-90%. For example, an increase in the Charbett- and dome temperature in the melter gasifier to reduced amount of oxygen required, but also to a reduction of the reducing gas. By this reduction also sinks Metallization in the fixed bed reduction shaft or fluidized bed reactor, which in turn causes a fall of the Charbett- and dome temperature in the melter gasifier. However, this leads to a higher demand for oxygen, so that the amount of reducing gas increases and the metallization increases again. Because of the long controlled system, therefore, stable operation of the melter gasifier is not possible (inter alia due to coal breakdown) and higher specific reductant consumptions are the result.

Furthermore, the adiabatic flame temperature (RAFT) resulting from the gasification of the coal with oxygen is above 3,000 ^° C. (theoretical), whereby the reduction of the SiO ₂ to Si is promoted and therefore the pig iron can have high contents of silicon. Therefore, additional post-treatment is often necessary to achieve the desired Si values of 0.4-0.5% by weight.

The purified export gas, which is composed of the top gas from the direct reduction unit and the dome gas from the melter gasifier, has the following typical analysis at 1.5 barg: CO 45% by volume, CO ₂ 30% by volume, H ₂ 19% by volume , H ₂ O 3 vol% and N ₂ 3 vol%. Due to the excess gas, it must be recycled and energy optimized.

The object of the present invention was therefore to provide a process or a plant as described above, in which under increased energy and raw material efficiency and the productivity can be increased, at the same metallurgically better properties of the product are obtained.

To achieve this object, the method according to the invention is characterized in that at least a portion of the withdrawn top gas is introduced into the melter gasifier. By this injection significant savings of coal and coal briquettes are possible as a reducing agent in the melter gasifier, which are replaced by the supply of reductants (CO, H ₂ ) from the recirculation gas. In addition, cooling of the vortex zone and the charbet is achieved by deliberate lowering of the flame temperature, which results from the endothermic reaction of the coal, coal briquettes or cokes with the gas constituents and cracking of the methane.

Advantageously, the recirculated gas is compressed. According to a further advantageous variant of the method it is provided that the recirculated gas is cooled between compression and introduction into the melt gasifier, preferably to 30 to 50 ⁰ C, and the carbon dioxide content is reduced, preferably to 2 to 3% by volume. The advantage here is a higher gas volume in the charbate for the indirect gas reduction, ie more reduction work in the melter gasifier.

According to a further variant, if at least part of the recirculated gas is only compressed, at least one further part of the recirculated gas is cooled and its carbon dioxide content reduced, and the compressed and carbon dioxide reduced gas are mixed prior to introduction into the melt gasifier, the Influencing the properties are metered even more accurately in the melter gasifier.

For this purpose, it can also be provided that the recirculated and possibly cooled and carbon dioxide-reduced gas is heated prior to introduction into the melt gasifier, preferably using a partial flow of the recirculated gas as the fuel gas. By preheating the recycle gas, the amount of traceable gas can be maximized without lowering the adiabatic flame temperature (RAFT) below an undesirably low limit with disadvantages for metallurgy. This results in an additional advantageous reduction of the use of raw materials and an additional control of the process.

According to a variant of the invention, it may be provided that at least a partial flow of the recirculated gas is reformed with higher hydrocarbons and using a further partial flow of the recirculated gas as the fuel gas.

In this case, advantageously, the reformed recirculated gas with the compressed and / or the cooled and reduced carbon dioxide gas before introduction into the melt gasifier are mixed.

According to an advantageous variant of the method, it is further provided that particles entrained in the dome gas are separated off and returned to the melt gasifier, a partial flow of the gas which has been compressed and / or cooled and carbon dioxide reduced being added for transporting the recirculated particles. According to a variant of the method according to the invention, it can be provided that the theoretical adiabatic flame temperature in the vortex zone is controlled by means of the amount and / or the temperature and / or CO ₂ content of the recirculated gas, whereby a targeted control of the metallurgical processes becomes possible.

By each of the described intervention possibilities but also by combinations thereof, an efficient control of the theoretical adiabatic flame temperature in the vortex zone is possible.

The system described above is to solve the problem according to the invention characterized by at least one of the line for the top gas branching and leading into the melt gasifier return line.

In order to minimize the risk of fire or explosion, the return line for the gas to the mouth of the oxygen supply runs parallel to this.

Advantageously, a compressor is inserted in the return line.

An advantageous embodiment of the plant according to the invention is characterized in that between the compressor and the oxygen supply, a cooling device and a carbon dioxide reduction stage are used, the latter can also reduce or completely eliminate the content of water vapor.

It can be provided that the output of the compressor and the output of the carbon dioxide reduction stage lead into a common supply line for supplying oxygen to the melter gasifier.

In order to maximize the recyclable gas volume by preheating the recirculation gas, without disadvantages for the metallurgy due to excessive lowering of the adiabatic flame temperature (RAFT), a heater is provided after the merger of the output of the compressor and the output of the carbon dioxide reduction stage. This results in an additional advantageous reduction of the use of raw materials and an additional control of the process. Due to the advantageous further feature of the invention that the heater works with fuel gas, wherein before the compressor branches off from the return line and leads to the fuel gas connection of the heater, the use of raw materials can be reduced and thus the efficiency of the system can be further increased.

Advantageously, a reformer can be inserted between the compressor and the oxygen supply.

Here, too, the consumption of raw materials can be reduced by, according to an advantageous embodiment, starting from the return line and leading to a fuel gas connection of the reformer.

Another embodiment of the system according to the invention is characterized in that in parallel branches of the return both a cooling device and a carbon dioxide reduction stage and a reformer are provided, which lead parallel branches in a common supply line for supplying oxygen to the melter gasifier.

Preferably, a particle separator is provided in at least one duct for the dome gas, from the particle discharge of which a particle recirculation leads to the melt gasifier, with a branching from the return duct into the particle recirculation. ,

In the following description of the invention with reference to a preferred embodiment and with reference to the accompanying drawings will be explained in more detail.

In a reduction shaft 1 is of lumpy or pellet-shaped iron ore, optionally supplied with unburned aggregates. By means of discharge devices 2, the sponge iron produced in the reduction shaft 1 is introduced into the head of a melter gasifier 3. At the bottom of the melter gasifier 3, liquid pig iron and above it liquid slag accumulate, which are preferably withdrawn discontinuously via their own taps. From a supply shaft 4, a gasification agent is supplied to the melter gasifier 3, preferably coal and / or coal briquettes, possibly mixed with screened undersize of the iron ore, which otherwise could not be used for the reduction process. Via gas lines 5, an oxygen-containing gas is supplied in the lower region of the melter gasifier 3. The reducing gas generated is led out of the head of the melter gasifier 3 via a line 6, freed of solid constituents, in particular dust and fine-grained degassed coal, in a hot gas cyclone 7 and then passes via a line 8 into the reduction shaft 1. In this the reducing gas flows through the Pillar of iron ore and additives in countercurrent, thereby reducing the iron ore to sponge iron.

The separated in the hot gas cyclone 7 degassed pulverized coal and other particulate ingredients are returned to the melter gasifier 3, preferably on entry into this by arranged in the wall of the melter gasifier 3 dust burner, which also oxygen-containing gas is fed, gasified.

The at least partially consumed reducing gas is withdrawn at the upper end of the reduction shaft 1 via a top gas line 9 and fed to a laundry in the wet scrubber 10 as export gas due to the excess gas utilization and total energy optimization. For reducing the pressure of the system used reducing gas is added after washing in the wet scrubber 11 either the export gas or recycled via line 12 as a cooling gas in the line 6 before the hot gas cyclone 7.

Particularly advantageous is the utilization of at least a portion of the withdrawn top gas, or after the washing of the export gas, by recycling in the process itself, namely by recycling and introduction into the melter gasifier 3. For this purpose, the top gas to be recycled is behind the wet scrubber 10 via a Line 13 is branched off and compressed by means of a compressor 14 with the highest possible suction pressure. Advantageously, also unused reducing gas downstream of the wet scrubber 11 can be diverted via a further line 15 before admixture with the export gas and recycled.

The recirculated top gas can according to a first variant after intercooling to 30-50 ⁰ C in the cooler 16 and reduction of the CO ₂ content to 2-3% by volume in the system 17 for CO ₂ Entfemung introduced via lances 18 in the oxygen nozzles are injected into the melter gasifier 3, wherein the return line for the top gas to the mouth of the oxygen supply is parallel to this. Part of this gas treated in this way can be branched off and admixed for transporting the particles returned from the hot gas cyclone 7. In addition to saving of coal and coal briquettes as a reducing agent in the melter gasifier by supplying reductases such as CO or H ₂ from the recirculated top gas can also be a cooling of the vortex zone and the charbett by deliberate lowering of the flame temperature due to the endothermic reaction of the coal, coal briquettes or the coke with the Gas components and cracking of methane can be achieved, with the following reactions are relevant:

C + CO ₂ → 2 CO ΔH ₂₉₈ = +173 kJ / mol

C + H ₂ O → CO + H ₂ ΔH ₂₉₈ = +132 kJ / mol

CH ₄ → 2H ₂ + C AH ₂₉₈ = +74 kJ / mol

By installing the compressor 14 and optionally the CO ₂ - removal system 17 with upstream heat exchanger 16, or a reformer / reduction gas furnace 21 also results in advantages that higher melt rates and thus an increase in productivity are possible that by reduced use of reducing agent It is also possible to achieve a reduction of the specific CO ₂ emissions per tonne of pig iron, that a reduction of the operating costs and thus the rapid amortization of the additional investment costs depending on the reducing agent costs for coal, coal briquettes, coke is possible. The use as a nitrogen substitute with dust burners would be conceivable.

At most, the top gas can also be introduced directly, using the sensible compression heat. To control the CO ₂ content, for example as a function of the charbet or coupling temperature, both gas streams can also be mixed.

The recirculated top gas can also be optionally heated by means of a reduction gas furnace 19 (convective, regenerative), electrical heating, plasma torch or heat exchanger (utilization of the sensible heat of process gas eg top gas before scrubber) after the CO ₂ removal. When using a reducing gas heating furnace 19, part of the branched top gas is used via line 20 as the fuel gas.

When heating the recirculated top gas prior to introduction into the meltdown gasifier 3 through a heat exchanger, the heat energy of the

Top gas used before the wet scrubber 10. This results in the advantage of

Increase the energy efficiency of the process by reducing, for cooling the process Topgasös required process water volumes, which also means a reduction of the energy demand of the process water pump. Furthermore, the heat dissipated by the top gas into the process water is reduced, which is lost through cooling towers or causes evaporation through water loss in the system, which must be constantly balanced.

Alternatively, the recirculated top gas may also be reformed with higher hydrocarbons (e.g., natural gas) in a reformer 21, with part of the top gas supplied as a fuel gas via a conduit 22 being used for the endothermic heat of reaction.

The increased amount of reducing gas from the melter gasifier 3 due to the gas recirculation is used to increase production in the reduction stage 1 (shaft or fluidized bed) and / or for a constant metallization. The constant metallization is achieved by the decoupling of the melter gasifier 3 and the reduction shaft 1. Any time sufficient amount of reducing gas allows a constant metallization in the reduction shaft 1. Thus, no major changes in the meltdown carburetor 3 supplied oxygen amount to adjust the heat balance necessary, resulting in a constant Charbettemperatur, lower coal decomposition and thus stable operation of the melter gasifier 3 with low specific reducing agent consumption leads. An optimization of the melter gasifier operation leads to a smaller necessary amount of reducing agents for the fixed bed reduction shaft 1 (FBRS) or in fluidized bed reactors (WSR) of the plant, which is fully compensated by the return of top gas.

In addition, this results in a rapid control possibility, lowering the silicon content in the pig iron by lower adiabatic flame temperature and stable Einschmelzvergaserbetrieb to minimize the occurring at high temperatures reduction of silicon according to the following formula:

SiO ₂ + 2 C -> Si + 2 CO ΔH ₂₉₈ = +690 kJ / mol

In addition to the silicon content, it is also possible to achieve a reduction in the sulfur content in pig iron, since the return of the top gas with only 1 to 100 ppm H ₂ S results in a significantly lower sulfur input than if coal, coal briquettes or coke were used exclusively. Finally, the adjustment of the necessary jet velocity and a sufficient penetration of the vortex zone at lower melt rates is substantially facilitated by the gas recirculation.

Claims

claims

A process for the production of molten metal, wherein oxygen, reducing agent and in a reduction reactor (1) reduced iron in a melt gasifier (3) are introduced, the reducing agent with the

Oxygen gasified and the resultant heat, the reduced iron is melted, wherein the coupling gas from the melt gasifier (3) is used as at least a portion of the reducing gas, and wherein reacted top gas is withdrawn from the reduction reactor (1), and at least a portion of withdrawn top gas is introduced into the melt gasifier (3) and the recirculated gas is compressed, characterized in that the recirculated gas between compression and introduction into the melt gasifier (3) is cooled and the carbon dioxide content is reduced, and / or that at least one Partial flow of the recirculated gas is reformed with higher hydrocarbons and using a further partial stream of the recirculated gas as fuel gas.

2. The method according to claim 1, characterized in that at least a portion of the recirculated gas is only compressed, at least a further portion of the recirculated gas cooled only and its carbon dioxide content is reduced, and that the compressed and the carbon dioxide-reduced gas before introduction be mixed in the melt gasifier (3).

3. The method according to any one of claims 1 and 2, characterized in that the recycled and possibly cooled and reduced carbon dioxide gas is heated prior to introduction into the melt gasifier (3), preferably below

Use of a partial flow of the recirculated gas as fuel gas.

4. The method according to any one of claims 1 to 3, characterized in that the reformed recycled gas with the compressed and / or the cooled and carbon dioxide-reduced gas before introduction into the melt gasifier (3) is mixed.

5. The method according to any one of claims 1 to 4, characterized in that entrained in the coupling gas entrained particles and in the melt gasifier (3) are recycled, wherein a partial flow of the only compressed and / or cooled and carbon dioxide-reduced gas to transport the recirculated Particles is mixed.

6. The method according to any one of claims 1 to 5, characterized in that the theoretical adiabatic flame temperature is controlled in the vortex zone by means of the amount and / or the temperature and / or the CO ₂ content of the recirculated gas.

7. The method according to any one of claims 1 to 6, characterized in that the recirculated gas between compression and introduction into the melt gasifier (3) to 30 to 50 ⁰ C is cooled.

8. The method according to any one of claims 1 to 7, characterized in that the carbon dioxide content is reduced to 2 to 3% by volume.

9. Plant for the production of molten metal, with a

Reduction reactor (1), a melt gasifier (3) with oxygen supply (5) and a supply system (4) for reducing agent, at least one line (6, 8) for the supply of the dome gas from the melt gasifier (3) in the reduction reactor (1) and at least one line (9) for removing the top gas from the reduction reactor (1), with at least one return line (13, 18) branching from the line for the top gas and leading into the melt gasifier (3), wherein the return line (13, 18) a compressor (14) is used, characterized in that between the compressor (14) and the oxygen supply (5) a cooling device (16) and a carbon dioxide reduction stage (17) are used, and / or that between the compressor ( 14) and the oxygen supply (5) a reformer (21) is used.

10. Plant according to claim 9, characterized in that the return line (13, 18) for the gas to the mouth of the oxygen supply (5) runs parallel to this.

11. Installation according to one of claims 9 and 10, characterized in that the output of the compressor (14) and the output of the carbon dioxide reduction stage (17) in a common supply line (18) for supplying oxygen (5) lead to the melter gasifier.

12. Plant according to claim 11, characterized in that after the

Merging the output of the compressor (14) and the output of the carbon dioxide reduction stage (17) is provided a heater (19).

13. Plant according to claim 12, characterized in that the heating device (19) operates with fuel gas, wherein before or after the compressor (14) a

Branch (20) from the return line (13) starts and leads to the fuel gas connection of the heater (19).

14. Plant according to claim 9, characterized in that from the return line (13), a branch (22) goes out and leads to a fuel gas connection of the reformer (21).

15. Plant according to claim 9 or 10, characterized in that in parallel branches of the return line (13, 18) both a cooling device (16) and a carbon dioxide reduction stage (17) and a reformer (21) are provided, which parallel branches into a common supply line (18) for supplying oxygen (5) to the melter gasifier (3).

16. Plant according to one of claims 9 to 15, characterized in that in at least one conduit (6) for the coupling gas, a particle separator (7) is provided, from the particle discharge a particle recycling leads to the melt gasifier (3), wherein a branch of the Return line (18) opens into the particle recirculation.