Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/0073—Selection or treatment of the reducing gases
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/004—Making spongy iron or liquid steel, by direct processes in a continuous way by reduction from ores
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/0086—Conditioning, transformation of reduced iron ores
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/14—Multi-stage processes processes carried out in different vessels or furnaces
  • C21B13/146—Multi-step reduction without melting
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
  • C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
  • C21B2100/22—Increasing the gas reduction potential of recycled exhaust gases by reforming
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
  • C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
  • C21B2100/26—Increasing the gas reduction potential of recycled exhaust gases by adding additional fuel in recirculation pipes
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
  • C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
  • C21B2100/28—Increasing the gas reduction potential of recycled exhaust gases by separation
  • C21B2100/282—Increasing the gas reduction potential of recycled exhaust gases by separation of carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
  • C21B2100/40—Gas purification of exhaust gases to be recirculated or used in other metallurgical processes
  • C21B2100/44—Removing particles, e.g. by scrubbing, dedusting

Definitions

• the invention relates to a method for the direct reduction of iron ore to sponge iron.
• a shaft furnace is traditionally used as the reactor with a reduction zone through which the iron ore passes in opposite direction to the reducing gas.
• the reduction zone is arranged above a cooling zone in the shaft furnace, with cooling gas flowing through the cooling zone.
• the iron ore then passes through the shaft furnace in a vertical direction from top to bottom.
• Such shaft furnaces allow a good flow of cooling gas and reducing gas through the iron ore due to the underlying chimney effect TES.
• the reduction gas flows through the reduction zone counter to a direction of movement of the iron ore.
• the cooling gas also flows through the cooling zone counter to a direction of movement of the sponge iron produced.
• the countercurrent process is therefore used both in the cooling zone and in the reduction zone in order to achieve an efficient reaction between the gases and the solids.
• CO or H 2 or a mixed gas comprising CO and H 2 can be used as the reducing gas.
• the reduction reactions are as follows (“( )” indicates solids; indicates gaseous substances):
• the reducing gas is usually generated from fossil hydrocarbons (e.g. natural gas and/or coal gas).
• fossil hydrocarbons e.g. natural gas and/or coal gas.
• the reaction for methane (as a main component of natural gas but also biogas) as the starting gas is explained below as an example.
• Other hydrocarbons are also possible as starting gas.
• the reduction gas is generated in a gas reformer from methane, CO 2 and water vapor (MIDREX® process).
• the result is a gas cycle in which the used methane is mixed with new methane with the cleaned process gas from the shaft furnace upstream of the gas reformer.
• the process gas of the shaft furnace contains C0 2 and water vapor as products of the reduction reaction.
• the reducing gas Pl 2 and CO is generated from methane, CO 2 and steam.
• This reducing gas mixture is fed to the shaft furnace, where it reduces the iron ore according to the above reaction equations.
• the main reaction products are C0 2 , water vapor and sponge iron.
• C0 2 and water vapor and unused reducing gas are mixed with methane and fed back to the gas reformer.
• Sponge iron production essentially involves two basic steps.
• the iron ore is reduced to sponge iron in a reduction zone with a suitable hot reducing gas.
• a reducing gas essentially comprises compounds or mixtures of carbon and hydrogen (e.g. CH 4 ), compounds or mixtures of carbon and oxygen (e.g. CO) and/or hydrogen (PI 2 ) at temperatures ranging from 700°C to 1100oC.
• the sponge iron produced is cooled down to temperatures typically below 100 °C in a cooling zone using a cooling gas.
• Corresponding methods are known from practice.
• DD 153 701 A5 describes the feeding of different gas streams at different levels into the reduction zone of a shaft furnace for iron ore reduction.
• the method reveals a simple Chemical and cost-effective utilization of a sulphur-containing gas from a gas source in the direct reduction process.
• the object of the present invention is to further develop this method in such a way that less carbon dioxide is produced.
• This object is achieved by a method for the direct reduction of iron ore to sponge iron, the iron ore passing through a reduction zone for reducing the iron ore to sponge iron, the reduction zone being divided into a pre-reduction zone, which is fed with a first reducing gas, and a final reduction zone, which is fed with a second reducing gas, is divided, wherein the first reducing gas has a different gas composition compared to the second reducing gas, wherein a first reducing gas is used with a higher hydrogen content than the second reducing gas, which is at least 5 vol. % is higher.
• the essential reduction work for expelling oxygen from the iron ore can be performed more effectively in the pre-reduction zone than in the prior art via the first reduction gas with a hydrogen content that is at least 5% by volume higher than that in the second reduction gas. Due to the higher proportion of hydrogen in the pre-reduction zone, which is also the (last) reduction stage before the discharged process gas is discharged, in addition to the reduction work, a reaction option can also be provided at the same time, so that the discharged process gas contains significantly lower proportions of carbon dioxide and this can reduce the emission of carbon dioxide.
• the first reducing gas has a hydrogen content of at least 55% by volume. The more hydrogen that is introduced into the pre-reduction zone, the more effectively the reduction work can be performed.
• the first reduction gas has a hydrogen content of in particular at least 65% by volume, preferably at least 75% by volume, preferably at least 85% by volume.
• the other portions of the first reducing gas can contain at least one compound or mixture of carbon and oxygen and/or water vapor and unavoidable impurities such as sulfur compounds and/or nitrogen.
• the first reduction gas particularly preferably consists of hydrogen in order to be able to carry out the highest possible and optimal reduction work.
• the use of hydrogen would mean that the carbon content of the pre-reduced iron ore would generally be particularly low, since no side reactions with carbon-containing compounds can occur in the pre-reduction zone, which would deposit carbon in the pre-reduced iron ore, so that after the pre-reduction zone there would be a carbon content less than 0.25% by weight should be present in the pre-reduced iron ore.
• the first reduction gas is heated to a temperature between 500 and 1200°C.
• the first reduction gas is heated in a gas heater to the required temperature in order to effect the pre-reduction of the iron ore.
• a gas heater to the required temperature in order to effect the pre-reduction of the iron ore.
• hydrogen When (essentially 100%) hydrogen is fed in, it can be fed in without additional exposure and thus post-combustion with oxygen, i.e. this ensures that the hydrogen is used completely for the reduction of the iron ore and the process can be operated more economically as a result .
• Very high proportions of hydrogen do not have to be heated to such high process temperatures, since the reduction of the iron ore, cf. Baur-Glvesssner diagram, can take place at low temperatures.
• a second reducing gas with a higher proportion of at least one compound or mixture of carbon and hydrogen and/or at least one compound or mixture of carbon and oxygen than the first reducing gas is used.
• the higher proportion of at least one compound or mixture of carbon and hydrogen and / or at least one compound or mixture of carbon and oxygen in the second reducing gas which is introduced into the finishing zone duction zone, with which heat by corresponding reaction in the Introduced process and to further reduce the pre-reduced iron ore coming from the pre-reduction zone and carburize it at least partially.
• the second reducing gas has at least one compound or mixture of carbon and hydrogen and/or at least one compound or mixture of carbon and oxygen with a proportion of at least 55% by volume, in particular at least 60% by volume, preferably at least 65% by volume .-%, preferably at least 70 vol .-%.
• the other portions of the second reduction gas can contain oxygen as an oxidizing agent to increase the temperature, hydrogen and/or water vapor and unavoidable impurities such as sulfur compounds and/or nitrogen.
• the second reducing gas particularly preferably comprises essentially hydrocarbon-containing compounds or mixtures, thus more compounds or mixtures with carbon and hydrogen than compounds or mixtures with carbon and oxygen.
• the second reduction gas can also comprise a mixture of a make-up gas, which is supplied from a source, and a reformed gas, which is produced from the discharged process gas and is added to the make-up gas.
• the carbon-containing, in particular hydrocarbon-containing compound or mixture of the second reducing gas can effectively carburize the pre-reduced iron ore in the finished reduction zone.
• carbon can be deposited on the prereduced iron ore as it flows through the prereduced iron ore in the final reduction zone.
• the deposited carbon diffuses into the interior of the iron and then combines with the iron in the pre-reduced iron ore to form cementite. In this way, the carbon content of the pre-reduced iron ore can be increased.
• the carbon content of the completely reduced iron ore or iron sponge can be in the range from 0.5% by weight to 3.5% by weight.
• the second reduction gas is heated to a temperature between 700 and 1300°C.
• the second reducing gas is heated in a gas heater to the required temperature to effect final reduction of the iron ore. If it is not possible to use the sponge iron coming from the reduction zone at a temperature between 500 and 800° C., the sponge iron passes through a cooling zone according to one embodiment of the method.
• the method provides that the iron ore successively passes through a reduction zone for reducing the iron ore to sponge iron and a cooling zone for cooling the sponge iron. In the cooling zone, a cooling gas flows through the sponge iron.
• the cooling gas is used to cool the sponge iron to a temperature suitable for onward transport, for example below 100 °C, and depending on the composition of the cooling gas it can also cause (further) "carburization" of the sponge iron, especially if carbon-containing compounds are used ,
• carbon dioxide C0 2
• CCS CCS or CCU
• Carbon dioxide can be used up when the sponge iron “carburizes” under the prevailing conditions.
• the carbon content of the sponge iron after cooling or after the cooling zone can be greater than 0.5% by weight, in particular greater than 1.0% by weight. preferably greater than 2.0% by weight.
• the carbon content of the sponge iron after the cooling zone can be set to less than 4.5% by weight, in particular less than 4.0% by weight, preferably less than 3.5% by weight, which has the advantage that the Sponge iron can be fed to the known further processing without an adjustment of the further processing being required.
• the sponge iron can be further processed, for example, in the Linz-Donawitz converter (also known as the “basic oxygen furnace”).
• the melting point of sponge iron can be lowered by increasing the carbon content.
• the energy requirement for melting in the electric arc furnace also referred to as "Electric Are Furnace” can also be reduced.
• the reduction zone comprising pre-reduction and final reduction zones
• the reduction zone can be arranged above the cooling zone in a shaft furnace.
• the iron ore then passes through the shaft furnace in a vertical direction from top to bottom.
• the type shaft furnaces allow a good flow through the iron ore with first and two tem reduction gas and then the finished reduced iron ore or iron sponge with cooling gas due to the underlying chimney effect.
• the first and second reduction gas flows through the preliminary and final reduction zones counter to a direction of movement of the iron ore.
• the cooling gas also flows through the cooling zone counter to a direction of movement of the sponge iron produced.
• the countercurrent process is therefore used both in the reduction zone and in the cooling zone in order to achieve an efficient reaction between the gases and the solids.
• the reduction zone comprising a pre-reduction zone and a final reduction zone each comprise at least one or more fluidized-bed reactors and/or the cooling zone comprises one or more fluidized-bed reactors.
• a fluidized bed reactor a fine-grained solid bed is whirled up by the gas flowing in continuously from below via a gas distributor. This also enables an efficient reaction between the gases and the solids.
• FIG. 1 shows an example of a method according to the invention in a schematic representation of a shaft furnace.
• FIG. 1 The invention is explained in FIG. 1 using the example of a shaft furnace (10). Iron ore “iron ore” (io) is introduced at the upper end of the shaft furnace (10). The “sponge iron” (si) produced is removed from the lower end of the shaft furnace (10). A reduction zone (11) having a pre-reduction zone (12) and a final reduction zone (13) and optionally a cooling zone (14) is arranged in the shaft furnace (10). The reduction zone (11) is arranged above the optional cooling zone (14).
• the cooling zone (14) is not absolutely necessary if it is possible to use hot sponge iron leaving the reduction zone (11) directly or if the second reducing gas (23) introduced into the final reduction zone (12) contains at least one carbon-containing compound or mixture which by reaction in the final reduction zone (13) of the reduction zone (11), not only the pre-reduced iron ore is further reduced, but at the same time can also be sufficiently "carburized” to be fed to the subsequent processes with the required carbon content.
• the first reduction gas (22) as well as the second reduction gas (23) flow through the iron ore in the reduction zone (11) in the countercurrent principle, thus against a direction of movement of the iron ore.
• the second reduction gas (23) is passed through a gas heater (33) and heated to a temperature of up to 1300 °C.
• That second reduction gas (23) comprises a fresh gas (NG) from a source with at least one compound or mixture of carbon and hydrogen and/or at least one compound or mixture of carbon and oxygen, with natural gas having a very high proportion of hydrocarbon-containing compounds or Mixtures, methane (CH 4 ), is preferably used.
• the fresh gas (NG) can be mixed with a reformed gas (RG), which is prepared from the process gas (40) discharged from the reduction zone (11) of the shaft furnace (10).
• the discharged process gas (40) can be composed of unused reduction gas from any gaseous reaction products.
• the discharged process gas (40) can include hydrogen (H 2 ), at least one compound or mixture of carbon and oxygen (CO, CO 2 ) and/or at least one hydrogen-containing compound (H 2 0) and unavoidable impurities.
• the discharged process gas (40) can be fed to a first process step, in which at least one compound or mixture of the process gas and/or at least parts of the unavoidable impurities are separated and/or separated, for example in a unit for process gas cleaning and dedusting, in which at least some of the unavoidable impurities from the discharged process gas (40) are separated.
• the process gas can be passed through a unit, for example through a condenser, and cooled accordingly, so that the water vapor (H 2 O) present in the process gas is condensed and thus separated from the process gas.
• the process gas is "dehumidified” by condensing and discharging the condensate.
• a part of the "dehumidified” process gas or the complete “dehumidified” process gas, shown in dashed lines, can be used as (partial) gas a) for firing the gas heater (32, 33). If not enough "dehumidified” process gas is available, a corresponding fuel gas is made available partially or completely to fire the gas heaters (32, 33).
• carbon dioxide (C0 2 ) can be separated from the "dehumidified” process gas in a further process step, for example in a Washer.
• the separated carbon dioxide can be used as cooling gas (24) or part of the cooling gas (24) in an optional cooling zone (14).
• the process gas freed from carbon dioxide can also be used partially or completely, shown in dashed lines, as (partial) gas b) for firing the gas heater (32, 33). If not enough (partial) gas b) are available, a corresponding fuel gas is provided in part or in full to fire the gas heaters (32, 33).
• the process gas or reformed gas (RG) freed from carbon dioxide can also additionally or alternatively be fed back to the direct reduction in a further process step by it is mixed with the fresh gas (NG), in particular before the mixture is heated to a temperature between 700 and 1300 °C in the gas heater (33).
• the hot reduction gas can also be supplied with oxygen (0 2 ) in order to increase the reactivity of the second reduction gas (23) in the finished reduction zone (13) of the reduction zone (11) and thus the heat input.
• the first reduction gas (22) introduced into the pre-reduction zone (12) of the reduction zone (11) has a hydrogen content that is at least 5% by volume higher than that of the second reduction gas (23), and has in particular a hydrogen content of at least 55% by volume.
• the first reduction gas (22) particularly preferably consists of hydrogen (Fl 2 ).
• the first reduction gas (22) can be heated to a temperature of between 500 and 1200° C. in a gas heater (32).
• the sponge iron After leaving the reduction zone (11) or the final reduction zone (13), the sponge iron enters the optional cooling zone (14).
• the sponge iron has a temperature in the range of 500 to 800 °C.
• Cooling gas (24) also flows through the sponge iron in the cooling zone (14) counter to the direction of movement of the sponge iron. Unver consumed cooling gas occurs together with any gaseous reaction products as process gas (25) again.
• a certain proportion of the cooling gas (24) can enter the final reduction zone (13).
• a certain proportion of the second reducing gas (23) can also enter the cooling zone (14). Mixtures of cooling gas (24) and reducing gas (23) can therefore occur at the transition between the final reduction zone (13) and the cooling zone (14).
• the cooling gas (24) comprises in particular a carbonaceous compound or mixture, preferably carbon dioxide (C0 2 ) or methane. If necessary, hydrogen (H 2 ) can be added to the cooling gas (24), whereby the cooling gas (24) passes through the Bosch reaction in the cooling zone (14) in the presence of hot sponge iron as a catalyst. Hydrogen (H 2 ) and carbon dioxide (C0 2 ) in the cooling gas thus react after the reaction
• the particularly preferred procedure for the direct reduction of iron ore (io) to sponge iron (si) provides hydrogen (Fl 2 ) as the first reduction gas (22), which after heating to a temperature between 500 and 1200 ° C in the pre-reduction zone (12) of Reduction zone (11) is introduced into a shaft furnace (10).
• the reaction is essentially based on the use of hydrogen (Fl 2 ) as the first reduction gas (22) of the iron ore to form pre-reduced iron ore
• the second reduction gas (23) of the particularly preferred mode of operation is natural gas as fresh gas (NG), which, after heating to an operating temperature of between 700 and 1300 °C, is mixed with oxygen (0 2 ) as required and fed into the finished reduction zone (13) of the reduction zone (11) of the shaft furnace (10) is introduced.
• NG natural gas as fresh gas
• the reaction when using a fresh gas from natural gas (NG) without supplying additional oxygen of the pre-reduced iron ore is essentially based on sponge iron
• a cooling gas (24) composed of carbon dioxide (C0 2 ) and hydrogen (Fl 2 ) can be introduced into the cooling zone (14) and the sponge iron (si) can be cooled to a temperature below 100°C.
• the process gas (40) discharged from the shaft furnace (10) above the reduction zone (11) is, as shown in Figure 1, after its "dehumidification” fed completely as fuel gas or as part of it to the gas heater (33), shown in dashed lines, and is not added to the fresh gas (NG) and mixed with it.
• the particularly preferred configuration makes it possible to use a variable direct reduction process with hydrogen (22) and natural gas (23) in a variable mixing ratio of 0 to 100% optimally set in terms of C0 2 emissions, efficiency and the availability of the reducing gases.
• the invention can also be carried out in a cascade of fluidized bed reactors.
• At least one fluidized bed reactor in each case forms a preliminary and final reduction zone of a reduction zone and depending on the circumstances and if no hot application should be possible, at least one further fluidized bed reactor in the cascade can be used as a cooling zone.
• the iron ore would then pass through the first and second eddy current reactors in the reduction zone and optionally a third fluidized bed reactor in the cooling zone, gradually converting it into sponge iron.
• the sponge iron can be cooled using cooling gas.
• the principle essentially corresponds to that of a shaft furnace, but distributed over several fluidized bed reactors instead of one shaft.
• the number of fluidized bed reactors can be interconnected as required.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Geology (AREA)
• Manufacture Of Iron (AREA)

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• 2021
  • 2021-06-02 DE DE102021112922.2A patent/DE102021112922A1/de active Pending
• 2022
  • 2022-05-25 CN CN202280039878.9A patent/CN117413075A/zh active Pending
  • 2022-05-25 WO PCT/EP2022/064280 patent/WO2022253683A1/de active Application Filing
  • 2022-05-25 EP EP22731529.8A patent/EP4347901A1/de active Pending

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