AT507713A1 - METHOD AND DEVICE FOR PRODUCING RAW STEEL OR LIQUID STEEL PREPARATIONS - Google Patents

Description

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Process and apparatus for the production of pig iron or liquid steel precursors

The invention relates to a method and an apparatus for the production of pig iron or liquid steel precursors in a molten zone, wherein iron-ore-containing starting materials and optionally additives in a reduction zone by means of a reducing gas at least partially reduced, subsequently introduced into the melting zone and feeding carbon supports, especially coke and / or coal, and oxygen-containing gas and are melted to form the reducing gas, wherein the reducing gas formed is fed to the reduction zone and reacted there and optionally withdrawn after purification as export gas.

It is known in the art that reducing gases can be modified in composition. From US 3,909,244 it can be seen that reducing gas from a natural gas reformer is treated such that the hydrogen content is increased. The use of the reducing gas will not be explained in detail.

It is therefore an object of the invention to provide a method and an apparatus which enables a more efficient smelting reduction process, in particular the use of the reducing gas is improved.

This object is achieved by the method according to the invention according to claim 1 and by the device according to claim 10.

By the method according to the invention at least a portion of the export gas in a conversion reactor with the addition of water vapor and / or water of a carbon monoxide conversion (CO conversion) is subjected. In this case, in the export gas, a defined quantity ratio H2 is set to CO and at least part of it is reentered into the reduction zone and / or the melt zone as a modified reduction gas.

200822820AT •·········································································································································································· As a result of this measure, the used reducing gas, which has already been used for reduction in the reduction zone, can be withdrawn from the reduction zone.

The withdrawn reducing gas from a blast furnace or a reduction shaft is referred to as top gas and from a fluidized bed reactor as offgas. The terms were summarized under the collective term export gas. In addition, due to the pressure regulation in the melting zone, a so-called surplus gas can be generated, which is also withdrawn and can be used together with export gas. Likewise, reducing gas from the smelting unit can be used together with export gas.

In a subsequent treatment in a conversion reactor, a conversion is carried out, wherein the ratio of carbon monoxide (CO) to hydrogen (H2) in a so-called CO conversion is adjusted with the addition of water vapor and / or water and by means of catalysts. In this case, the reducing gas can be modified in such a way that it can again be introduced into the reduction zone and / or into the melting zone and used again for reduction or as energy carrier. It is advantageous that the use of the reducing gas can be improved in the reduction process, so that the necessary amount of carbon carriers can be reduced to produce reducing gas in the melting zone. On the one hand, a lower hydraulic load in the reduction zone and / or the melt zone is possible due to the lower density of hydrogen-rich gas. As a result, greater productivity can either be achieved with a given plant size, or a smaller plant may be required for a given production capacity. On the other hand, there are advantages due to the reduction kinetics, since the chemical reactions of iron oxide components (Fe203, Fe304, FeO, etc.) with H2 are much faster than with CO. , , ······ .. • ;; ; j j ···. «· 200822820AT ί ίί ί:: · * · '· * ...............: .. -3-

In the recycling of the modified reducing gas, a mixture with reducing gas from the melting zone, so that the composition of the reducing gas can be better adjusted. The direct recycling of the modified reducing gas is advantageous. The recycling of the hydrogen-rich reducing gas into the reduction zone and / or the melting zone has the advantage over entry into another reduction unit that the better reduction kinetics of hydrogen-rich gas can already be used in the melting zone or the reduction zone to increase productivity. Furthermore, it is not absolutely necessary to operate a separate reduction unit for generating directly reduced iron, whereby investment costs for the elimination of the parallel reduction shaft including edge components (scrubber, water system, etc.) can be saved.

According to an advantageous embodiment of the method according to the invention, the export gas is cooled and purified, in particular dedusted, and / or compressed and / or reheated prior to CO conversion, in particular using the waste heat of the modified reducing gas to adjust the process temperature for the CO conversion. For the CO conversion, it is advantageous to use only purified export gas, since this contains considerable amounts of solids, such as e.g. Has dusts. For some cleaning procedures, such as in wet cleaning process, it is necessary to cool the hot export gas first. The purified export gas is then, if necessary, reheated to the temperatures required for CO conversion. This rewarming can be carried out particularly advantageously by means of the waste heat from the modified reducing gas, since heat is released during the CO conversion.

According to the invention, the export gas is hot-cleaned prior to the CO conversion, in particular dry-dedusted, and / or cooled or heated to adjust the gas temperature of the CO conversion. Hot cleaning almost eliminates the need to reheat or reduce the energy required. In the case of particularly hot export gas, it is even possible to completely dispense with rewarming or to set a temperature necessary for CO conversion only by cooling.

According to a particularly advantageous embodiment of the method according to the invention, the modified reducing gas is first cooled prior to its introduction into the reduction zone and / or the melt zone and the deposition in a deposition process, in particular an adsorption or absorption process, takes place, wherein carbon dioxide (CO 2) from the modified reducing gas at least partially separated and discharged as tail gas. By cooling before the CO 2 deposition process, the majority of water vapor is condensed or separated.

The CO 2 -rich stream from the CO 2 separation process is discharged as tail gas. The CO 2 and water vapor must be removed as the reduction potential is reduced by CO 2 and water vapor. Adsorption and absorption processes have proven to be advantageous, wherein the deposited CO 2 is removed as so-called tail gas. This can be fed to a sequestration or a further treatment but can also be released into the atmosphere in the case of adsorption processes.

Due to the low operating costs, adsorption processes, such as vacuum pressure swing systems and pressure swing systems have proven successful in pig iron production plants. In these systems, increasing the H2 / CO ratio also increases the product gas yield, because the adsorption forces of hydrogen (H2) are significantly lower than those of carbon monoxide (CO) and nitrogen (N2), thus achieving a higher product yield for hydrogen (H2) can be. The latter property allows

200822820AT • · · · < .. · · ·· < Among other things, the separation of H2 and N2 and thus a discharge of N2 from the recycle gas stream.

According to a further advantageous embodiment of the method according to the invention is at least a portion of the modified reducing gas, in particular after a

Deposition of CO 2 and H 2 O from the modified reducing gas, mixed with reducing gas from the melting zone and, in particular after dedusting, fed to the reduction zone. By mixing with the reducing gas from the melting zone on the one hand, the composition, but also the temperature of the gas mixture, which is introduced into the reduction zone, adjusted or adjusted.

According to a particular embodiment of the method according to the invention is at least a portion of the modified reducing gas, in particular after a

Deposition of C02 and H20 from the modified reducing gas, heated, optionally mixed with dedusted reducing gas from the molten zone and fed to the reduction zone. By additional heating and larger amounts of modified reducing gas can be introduced into the reduction zone, in particular, the necessary for the reduction conditions high gas temperatures can be adjusted. In addition, by increasing the H2 / CO ratio, the heating of the reducing gas can take place predominantly in an indirect heat exchanger, since the disadvantages of metal dusting corrosion due to the high H2 content, in particular in connection with the addition of H2S or other sulfur compounds before the Heat exchangers can be avoided.

According to a suitable embodiment of the method according to the invention, a part of the reducing gas generated in the melting zone, optionally after a purification, mixed with export gas and fed to the conversion reactor. The composition of the gas mixture can be adjusted as a whole and not just the 200822820AT. * Γ ί. * Ί. ·. ···························································································································································· In addition, the density of the reducing gas is reduced by the mixture with the hydrogen-rich gas, which is formed by CO conversion and by removal of H 2 O or CO 2. This creates the opportunity to send more reducing gas at the same differential pressure through the reduction unit and thus to achieve a higher production output and a higher metallization of directly reduced iron. Furthermore, by precisely adjusting the H2 / CO ratio, the temperature control in the reduction reactor can be controlled because the reduction of iron oxides over CO is predominantly exothermic, while that over H2 is predominantly endothermic.

According to an advantageous embodiment of the method according to the invention, a portion of the reducing gas generated in the melting zone, optionally after purification, and optionally after mixing with export gas and / or tail gas, discharged as a combustible gas mixture from the process. Excess gases that can no longer be supplied to the reduction zone are provided as combustible gas mixtures for other uses, in particular their energy content is used by combustion. It is advantageous to initially store such gases while compensating their composition, since in particular the tail gas has a strongly fluctuating composition.

According to the invention, a portion of the export gas is fed to an expansion turbine for utilizing the pressure energy of the export gas. By the expansion turbine, the energy balance of the process can be improved overall.

The device according to the invention provides that at least part of the export gas from a reduction unit can be fed by means of an export gas line into a conversion reactor for CO conversion. In CO conversion, the export gas is treated with the addition of water vapor and / or water, with a

-7- 200822820AT • · • · · * ···· ·· »defined ratio H2 to CO in the export gas can be set. This can be introduced via a feed line as a modified reducing gas in the reduction zone and / or in the molten zone. By recycling the modified reducing gas, it is possible to reduce the need for carbon carriers in the smelting plant to produce reducing gas. In addition, the plant components can be kept compact and the amount of export gas produced is reduced, so that the facilities for processing export gas discharged from the process can also be carried out more cost-effectively.

According to an alternative embodiment of the device according to the invention, a compressor, in particular a single-stage or multistage compressor, and / or an entry for injecting steam and / or for injecting water into the export gas is provided in the export gas line. By the compressor, the pressure necessary for the injection of the reducing gas into the process reactors or into the supplying process gas lines can be adjusted. About the entry of water vapor and / or water for the CO conversion can be introduced into the export gas.

A possible variant of the device according to the invention provides that in the export gas line a cooling device, in particular a heat exchanger, for cooling and / or a cleaning device, in particular a wet cleaning, for cleaning the export gas before the CO conversion is / are provided. The export gas must first be cleaned due to fine-particulate solids and dusts that are discharged with the export gas from the reduction unit. Wet cleaning has the advantage that the solids and dusts are safely separated. Optionally, cooling may take place by means of a heat exchanger upstream of the cleaning device, it being possible to use the energy dissipated in the process. 200822820AT ··· ll. *. ·, · * ·· ·· ···· ···· # *., -8-

According to an alternative embodiment of the device according to the invention, a heat exchanger for heating the export gas is optionally provided using the waste heat of the modified reducing gas and / or an entry for blowing steam and / or for injecting water into the export gas in the export gas line.

Through the heat exchanger, the necessary for the CO conversion temperature can be adjusted. Again, efficient heating is achieved by using the hot modified reducing gas for heating.

According to a further embodiment of the device according to the invention, a dry dedusting for cleaning the hot export gas before the CO conversion is provided in the Exporfgasleitung. By using dry dedusting, such as a hot gas filter, only a small or even no cooling of the export gas before dedusting is necessary. Thus, the energy content of the export gas can be used for the subsequent CO conversion, so that consuming facilities for heating can be omitted.

According to an advantageous embodiment of the device according to the invention, one or more coolers are provided in the reducing gas line for cooling the modified reducing gas, for condensing and for discharging water vapor.

In this case, the pressure of the gas already treated in the conversion reactor can be adjusted for subsequent treatment steps and water vapor can be discharged from the modified reduction gas. This also applies to its temperature, which can be reduced accordingly. This is necessary for common CO 2 deposition processes, e.g. operating according to the adsorption or absorption principle, and therefore operated only at low inlet temperatures.

According to a particular embodiment of the device according to the invention, a cooling gas line is provided, which leads from the reducing gas line to one from the melting point.

200822820AT ····· «generator gas line, so that at least a subset of modified export gas can be mixed with reducing gas from the smelting unit and fed to a dedusting device, in particular a cyclone. The modified reducing gas can be further processed together with the reducing gas from the melting unit, that is dedusted and subsequently fed to the reduction unit, so that a nearly homogeneous mixture is achieved with a largely constant composition of the reducing gas.

According to a particularly advantageous embodiment of the device according to the invention, the reduction unit is designed as a shaft of a blast furnace or as a reduction shaft or as a fluidized bed reactor. Such aggregates have proven to be advantageous in the reduction of iron ore-containing feedstocks by means of reducing gases.

According to a further advantageous embodiment of the device according to the invention, the melting unit is designed as a lower part of a blast furnace or melter gasifier. The melting unit fulfills two tasks, namely to melt prereduced iron-containing starting materials and to gasify carbon carriers to form the reducing gas.

According to a particular embodiment of the device according to the invention, the generator gas line opens into the reducing gas line, so that modified export gas and / or reducing gas can be introduced from the melting unit in the reduction unit / can. Due to the mixture with, in particular already dedusted reducing gas from the melting unit, the composition of the reducing gas, which is introduced into the reduction unit, be influenced and thus a sufficient reduction potential of the reducing gas can be ensured. • ·

200822820AT

According to an advantageous embodiment of the device according to the invention, an excess gas line is provided which leads from the generator gas line to the export gas line, wherein in the excess gas line, a cleaning device, in particular a wet cleaning, is provided for dedusting. By wet cleaning, the reducing gas can be supplied together with the advantageous also purified export gas to the conversion reactor. The mixture of the reducing gas and the export gas, optionally together with tail gas from the CO 2 deposition device, can be derived from the process and e.g. be fed to a thermal use.

A possible variant of the device according to the invention provides that in the export gas discharge an expansion turbine for the use of the pressure energy of the export gas is provided. By means of the expansion turbine, the pressure energy of the export gas can be used and used for energy production.

The invention will be explained in more detail below by way of example with reference to FIGS. 1 to 4.

Fig. 1: Inventive embodiment with a blast furnace

Fig. 2: Inventive embodiment with a melting unit and connected in series fluidized bed reactors

3 and 4: Inventive embodiment with a melting unit and a reduction unit

FIG. 1 shows the device according to the invention. In the shaft of a blast furnace, which operates as a reduction zone 1, iron ore-containing feedstocks ES and additives ZS are at least partially reduced by means of a reducing gas and then introduced into the melting zone 2, ie into the lower part of the blast furnace and melted into pig iron or steel precursors. By the gasification of carbon carriers, a reducing gas is formed, which after the reduction has taken place in the reduction zone.

200822820AT withdrawn as export gas via an export gas line 4a and first pre-cleaned in a dry dedusting 21 and then further purified in a wet scrubber 22. The export gas is subsequently compressed by a compressor 7 and further heated in a heat exchanger 12 and set the process temperature for the conversion reactor 5. By the addition of water vapor and / or water via an entry 8, a CO conversion takes place, wherein the ratio of CO to H2 is set.

The CO 2 produced in this process and H 2 O still partially present are separated off by means of a heat exchanger or by means of a condenser and a CO 2 separation device and discharged as tail gas TG via a tail gas line 23. Optionally, the tail gas TG can also be used for heating modified reducing gas in the heating device 20, wherein the tail gas is at least partially combusted while supplying air and / or top gas. The heater 20 may also be formed as a heat exchanger (e.g., gas-gas type).

The treated in the conversion reactor 5 export gas can be cooled before the CO 2 deposition in a heat exchanger 12, wherein the waste heat can be used to heat the export gas prior to its introduction into the conversion reactor 5. After the CO conversion, the modified reducing gas is first cooled by means of a cooler 14. Following the CO 2 deposition, the modified reducing gas is reintroduced into the reduction zone. This can be done in the blast furnace shaft 25 directly or via lances which project into the nozzles for the injection of oxygen-containing gas, in particular> 80% O 2. Preferably, the modified reducing gas is to be heated by means of a heating device 20 before it is introduced into the reduction zone. The heater can be heated by combustion of tail gas with the addition of air. This is necessary in particular in the case of an entry, in particular an injection, into the blast furnace shaft 25. excess

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Export gas can also be supplied to an expansion turbine 19 using the pressure energy of the export gas. In a collecting tank 26, the excess export gas and tail gas can be cached. This also compensates the composition of the gas mixture, since the tail gas has a strongly fluctuating composition.

Fig. 2 shows the invention in a plant with a melting unit 2 and four series-connected fluidized bed reactors R1, R2, R3 and R4, in which there is an at least partial reduction of the starting materials. These reduced feedstocks can be hot compacted (HCl) and further processed in the smelting unit or partly in a further smelting unit to increase power or to reduce reductants by feeding lumped coal SK or briquetted coal BK, optionally in combination with the pulverized coal injection.

The treatment of the export gas withdrawn from the fluidized-bed reactor R4 optionally comprises cooling in a heat exchanger 10 and binding dedusting, in particular wet cleaning, in a cleaning device 11. After compression by means of a compressor 7 and heating by means of a heat exchanger 12 with the addition of water vapor and / or water via an entry 8, the CO conversion in the conversion reactor 5. A portion of the modified reducing gas can be mixed after reduction of CO 2 and H 2 O, in particular for cooling purposes with reducing gas from the melter 2 and after dedusting the fluidized bed R1 or a feed tank 27 are supplied. By means of a refrigerant gas line 15, which may have a cleaning device and a compressor, the temperature of the modified reducing gas and the reducing gas may also be influenced. Furthermore, if necessary, the modified reducing gas can also be heated by means of a heating device 20. The gas mixture of export gas and reducing gas from the smelting unit 2 can in the

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Exported gas line 4b and thus also supplied to the conversion reactor.

Tail gas TG from the CO 2 deposition device or top gas or offgas and / or excess gas can be supplied to the heating device 20 by means of connecting lines 13a, 13b and at least partially burned therein and thus used to heat the modified reducing gas. Excess export gas can be fed via a line 4c to an expansion turbine 19 and homogenized in a collecting tank 26.

Figures 3 and 4 show the invention in a plant comprising a melting unit 2 and a reduction unit 1, which is designed as a reduction shaft. In the reduction unit 1, lumpy ores or pellets are reduced at least partially to directly reduced iron (HDRI). The HDRI can, if appropriate with the addition of compacted directly reduced iron (CDRI), be melted in the smelting unit 2 with the addition of coal K and fine-particle ore FE to form pig iron RE. The inventive features are implemented here analogously to the embodiments shown in Figures 1 and 2. -14-

200822820AT

REFERENCE SIGNS LIST 1 reduction unit 2 melting unit 3a, 3b reduction gas line 4 export gas line 5 conversion reactor 6a, 6b supply line 7 compressor 8 entry of water vapor and / or water 9 CO 2 separation device 10 cooling device 11 cleaning device 12 heat exchanger 13a, 13b connecting lines 14 cooler 15 cooling gas line 16 cyclone 17 excess gas line 18 Cleaning device 19 Expansion turbine 20 Heating device 21 T rock dust removal 22 Wet cleaner 23 Tail gas line 24 Ring gas line 25 Blast furnace shaft 26 Collecting tank 27 Feeding tank

Claims (22)

200822820AT ♦ ··········································································· ::: 1. Claims 1. A process for the production of pig iron or liquid steel precursors, wherein iron-containing starting materials and optionally additives in a reduction zone are at least partially reduced by means of a reducing gas, subsequently introduced into a melting zone and fed with carbon carriers, in particular coke and / or coal, and oxygen-containing gas and are melted to form the reducing gas, wherein the reducing gas formed is fed to the reduction zone and reacted there and optionally withdrawn as an export gas after purification, characterized in that at least a portion of the export gas in a conversion reactor with the addition of water vapor and / or Water is subjected to a CO conversion, wherein in the export gas a defined ratio of H2 to CO adjusted, C02 zumi Partially deposited and that at least part of it is introduced as a modified reducing gas in the reduction zone and / or in the molten zone. 2. The method according to claim 1, characterized in that the export gas cooled and cleaned before the CO conversion, in particular dedusted, and / or compressed and / or, in particular using the waste heat of the modified reducing gas to adjust the process temperature for the CO Conversion is reheated. 3. The method according to claim 1, characterized in that the export gas before the CO conversion hot cleaned, in particular dedusted dry, and / or cooled to adjust the gas temperature of the CO conversion or heated. 4. The method according to any one of claims 1 to 3, characterized in that the modified reducing gas is first cooled prior to its introduction into the reduction zone and / or the molten zone and drive the deposition in a deposition, • in particular an adsorption or absorption process, wherein CO 2 is at least partially separated from the modified reducing gas and removed as tail gas. 5. The method according to any one of claims 1 to 4, characterized in that at least a portion of the modified reducing gas, in particular after a deposition of CO 2 and H 2 O from the modified reducing gas, mixed with reducing gas from the molten zone and, in particular after dedusting, the reduction zone is supplied. 6. The method according to any one of claims 1 to 5, characterized in that at least a portion of the modified reducing gas, in particular after deposition of CO 2 and H 2 O from the modified reducing gas, heated, optionally mixed with dedusted reducing gas from the molten zone and fed to the reduction zone , 7. The method according to any one of claims 1 to 6, characterized in that a part of the reducing gas generated in the molten zone, optionally after a purification, mixed with export gas and fed to the conversion reactor. 8. The method according to any one of claims 1 to 7, characterized in that a portion of the reducing gas generated in the melting zone, optionally after purification, and optionally after mixing with export gas and / or tail gas, is discharged as a combustible gas mixture from the process. 9. The method according to any one of claims 1 to 8, characterized in that a portion of the export gas is fed to a expansion turbine to use the pressure energy of the export gas. 10. Apparatus for producing pig iron or liquid steel precursors with at least one reduction unit (1) for at least partial reduction and optionally additives by means of a reducing gas, and a melting unit (2) for melting the at least partially reduced iron-ore-containing starting materials and optionally the aggregates, with supply of carbon carriers, in particular coke or coal, and oxygen-containing gas and forming the reducing gas by means of a reducing gas line (3a, 3b) introduced into the reduction unit (1) and can be withdrawn after passing through this and optionally after purification via an export gas line (4) as export gas, characterized in that the export gas line (4a, 4b) in a conversion reactor (5 ) for CO conversion of at least a portion of the drawn export gas with the addition of water vapor and / or water, wherein a defined ratio H2 to CO can be set in the export gas, and this via a supply line (6a, 6b) as a modified reducing gas in the reduction zone (1) and / or in the Melting zone can be introduced, and that in the supply line (6a) is arranged a CO 2 deposition device (9) for the deposition of CO 2 from the modified reducing gas. 11. The device according to claim 10, characterized in that in the export gas line (4b) a compressor (7), in particular a single or multi-stage compressor, and / or an entry (8) for blowing in steam and / or for injecting water is / are provided for in the export gas. 12. The apparatus of claim 10 or 11, characterized in that in the export gas line (4a) a cooling device (10), in particular a heat exchanger, for cooling and / or a cleaning device (11), in particular a wet cleaning, for cleaning the export gas before CO conversion is / are provided. 13. Device according to one of claims 10 to 12, characterized in that in the export gas line (4b), a heat exchanger (12) for heating the export gas -18-18- • · • · 200822820AT optionally using the waste heat of the modified reducing gas and / or an entry (8) is provided for injecting steam and / or for injecting water into the export gas / are. 14. The apparatus of claim 10 or 11, characterized in that in the export gas line (4a) a dry dedusting for cleaning the hot export gas is provided before the CO conversion. 15. Device according to one of claims 10 to 14, characterized in that in the reducing gas line (6a) one or more radiators (14) are provided for cooling the modified reducing gas, for condensation and for discharge of water vapor / is. 16. Device according to one of claims 10 to 15, characterized in that a cooling gas line (15) is provided, which leads from the reduction gas line (6a) to a generator (3) opening out of the melting unit (2), so that at least one subset modified export gas mixed with reducing gas from the melting unit (2) and a dedusting, in particular a cyclone (16), can be supplied. 17. Device according to one of claims 10 to 16, characterized in that the reduction unit (1) is designed as a shaft of a blast furnace or as a reduction shaft or as a fluidized bed reactor. 18. Device according to one of claims 10 to 17, characterized in that the melting unit (2) is designed as a lower part of a blast furnace or as a melter gasifier. 19. Device according to one of claims 10 to 18, characterized in that the generator gas line (3a) opens into the reducing gas line (6b), so that ···· 99 200822820AT • ♦ ♦ • ♦ • ♦ • • # • • · 9 9 9 9 99 ·· ·· ·· ·· ·· 99 • · · Modified export gas and / or reducing gas from the smelting unit (2) can / can be introduced into the reduction unit (1). 20. Device according to one of claims 10 to 19, characterized in that an excess gas line (17) is provided which leads from the generator gas line (3b) to the export gas line (4a), wherein in the excess gas line, a cleaning device (18), in particular a wet cleaning , intended for fine dedusting. 21. Device according to one of claims 10 to 20, characterized in that in the export gas discharge (4c) is provided an expansion turbine (19) for using the pressure energy of the export gas. 22. Device according to one of claims 10 to 21, characterized in that in the reducing gas line (6b) is provided a heating device (20) for heating the modified reducing gas.