Abstract
The invention relates to a process for producing carburized directly reduced iron sponge from iron oxide material. Firstly, direct reduction is carried out by means of a reduction gas consisting at least predominantly of H.sub.2 and the carbon content in the iron sponge is then increased by means of a carburizing gas which is fed in, after which used carburizing gas is at least partly taken off while largely avoiding mixing with the reduction gas. The plant for producing carburized directly reduced iron sponge from iron oxide material comprises a reduction zone for directly reducing introduced iron oxide material to directly reduced product by means of reduction gas consisting predominantly of H.sub.2 and a reduction gas feed conduit opening into the reduction zone. It also comprises a carburization zone having a carburizing gas feed conduit opening into the carburization zone and a carburization offgas conduit.
Claims
1. A process for producing carburized directly reduced iron sponge from iron oxide material, comprising: firstly, directly reducing the iron oxide material in a reduction zone by a reduction gas having a hydrogen content of at least 80% by volume; and taking off a used reduction gas as a topgas; wherein: a carbon content in the directly reduced iron sponge is then increased in a carburization zone by a carburizing gas fed in; and after which used carburizing gas is at least partly taken off while avoiding mixing with the reduction gas, resulting in a proportion of carbon-containing gases in the topgas being less than 20% by volume; wherein the reduction gas is heated before it comes into contact with the iron oxide material; wherein a first partial amount of the topgas is fed to utilization as fuel gas for heating at least one of the reduction gas and the carburizing gas, and a size of the first partial amount of the topgas is regulated as a function of at least one of nitrogen N.sub.2, carbon dioxide CO.sub.2, carbon monoxide CO, and methane CH.sub.4 content in the topgas; and wherein a second partial amount of the used carburizing gas is fed to utilization as fuel gas for heating the reduction gas, and a size of the second partial amount of the used carburizing gas is regulated as a function of at least one of carbon dioxide CO.sub.2, carbon monoxide CO, and methane CH.sub.4 content in the topgas.
2. The process of claim 1, wherein a first partial amount of the used carburizing gas is, after treatment, combined again with fresh carburizing gas components and used again as carburizing gas for increasing the carbon content of the iron sponge.
3. The process of claim 1, wherein heating of at least one member of the group consisting of the two members: carburizing gas, and treated used carburizing gas before or after being combined with fresh carburizing gas components, is carried out before it comes into contact with the iron sponge.
4. The process of claim 1, wherein the carburizing gas contains components which react exothermically with the directly reduced iron sponge.
5. The process of claim 1, wherein the iron sponge is heated at least one of before and during introduction of the carburizing gas.
6. The process of claim 1, wherein solid carbon C is mixed with the iron sponge at least one of before, during, and after introduction of the carburizing gas.
7. The process of claim 1, wherein a supply conduit connects the reduction zone to the carburization zone.
8. A method for producing carburized directly reduced iron from iron oxide material, comprising: directly reducing the iron oxide material in a reduction zone by a reduction gas having a hydrogen content of at least 80% by volume; taking off a used reduction gas as a topgas; increasing, after the reducing operation, a carbon content in the directly reduced iron in a carburization zone by feeding in a carburizing gas; and taking off, after the increasing of the carbon content operation, at least some of the carburizing gas, while avoiding substantial mixing of the carburizing gas with the reduction gas, resulting in a proportion of carbon-containing gases in the topgas being less than 20% by volume; wherein the reduction gas is heated before it comes into contact with the iron oxide material; wherein a first partial amount of the topgas is fed to utilization as fuel gas for heating at least one of the reduction gas and the carburizing gas, and a size of the first partial amount of the topgas is regulated as a function of at least one of nitrogen N.sub.2, carbon dioxide CO.sub.2, carbon monoxide CO, and methane CH.sub.4 content in the topgas; and wherein a second partial amount of the used carburizing gas is fed to utilization as fuel gas for heating the reduction gas, and a size of the second partial amount of the used carburizing gas is regulated as a function of at least one of carbon dioxide CO.sub.2, carbon monoxide CO, and methane CH.sub.4 content in the topgas.
9. The method of claim 8, wherein a supply conduit connects the reduction zone to the carburization zone.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The present invention will be illustrated by way of example below with the aid of a number of schematic figures.
(2) FIG. 1 schematically shows one variant of a plant according to the invention for producing carburized directly reduced iron sponge from iron oxide material.
(3) FIG. 2 schematically shows another variant of a plant according to the invention for producing carburized directly reduced iron sponge from iron oxide material.
(4) FIGS. 3 to 8 show various variants of the plant shown in FIGS. 1 and 2.
(5) FIG. 9 schematically shows a conventional process for producing directly reduced iron sponge from iron oxide material, in which direct reduction is carried out by means of a reduction gas consisting of H.sub.2.
DETAILED DESCRIPTION
(6) FIG. 1 schematically shows one variant of a plant 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 introduced iron oxide material 2 to directly reduced product by means of reduction gas consisting predominantly of H.sub.2. It also comprises a reduction gas feed conduit 4 opening into the reduction zone 3. It also comprises a carburization zone 5 for carburizing the directly reduced product. A carburizing gas feed conduit 6 opens into the carburization zone 5. A carburization offgas conduit 7 for taking off used carburizing gas from the carburization zone 5 goes out from the carburization zone 5. The plant also comprises at least one device for avoiding mixing of reduction gas with carburizing gas and/or used carburizing gas, here a blower 8 in the carburization offgas conduit 7. By means of the blower 8, used carburizing gas is at least partly transported out from the carburization zone and mixing with the reduction gas is in this way largely avoided. To produce carburized directly reduced iron sponge from iron oxide material 2, it is firstly directly reduced by means of the reduction gas consisting at least predominantly of H.sub.2 during its passage from the top downward through the reduction zone 3 under the force of gravity. The directly reduced product iron sponge then enters, under the force of gravity, the carburization zone 5 where the carbon content in the directly reduced product iron sponge is increased by means of a carburizing gas which is fed in during its passage from the top downward under the force of gravity. Used carburizing gas is at least partly taken off and discharged by means of the blower 8 from the carburization zone 5 via the carburization offgas conduit while largely avoiding mixing with the reduction gas. Taking-off of carburized iron sponge from the carburization zone is indicated by a block arrow.
(7) FIG. 2 schematically shows another variant of a plant 1 according to the invention for producing carburized directly reduced iron sponge from iron oxide material 2. In contrast to FIG. 1, carburization zone 5 and reduction zone 3 are accommodated in different apparatuses. The directly reduced product iron sponge is taken off from a direct reduction apparatus containing the reduction zone, in the case depicted a fixed-bed reactor 9, and then introduced via the supply conduit 10 into a separate carburization apparatus 11 containing the carburization zone. An additional transport device, for example a star feeder, or a dynamic gas barrier can also be provided in the supply conduit 10. Plant components analogous to FIG. 1 are denoted by the same reference numerals. The device for avoiding mixing of reduction gas with carburizing gas and/or used carburizing gas, in the case depicted shown by way of example as the blower 8, could also be present in the supply conduit or in the end of the direct reduction apparatus nearest the supply conduit or in the end of the carburization apparatus nearest the supply conduit or at the end of the supply conduit closest to the direct reduction apparatus or at the end of the supply conduit closest to the carburization apparatus instead of, or in addition to, the depicted arrangement in the carburization offgas conduit. These variants are not shown in the interest of clarity. Taking-off of carburized iron sponge from the carburization zone is indicated by a block arrow.
(8) FIG. 3 shows, by way of example in a depiction largely analogous to a section of FIG. 2, how the carburization offgas conduit 7 of FIG. 2 opens into a recirculation device 12 for the treatment, for example purification, compression, heating, and recirculation of used carburizing gas into the carburizing gas feed conduit 6. A first partial amount of the used carburizing gas is, after treatment, for example dust removal, conveyed via the recirculate conduit 13 and combined with fresh carburizing gas components and reused as carburizing gas for increasing the carbon content of the iron sponge. The introduction of the fresh carburizing gas components is indicated by the arrow 14. Taking-off of carburized iron sponge from the carburization zone is indicated by a block arrow.
(9) It is also indicated in FIG. 3 that a gas heating device 15 is present in the carburizing gas feed conduit 6. It could instead or in addition also be present in the recirculate conduit 13. The carburizing gas is heated before it comes into contact with the iron sponge.
(10) FIG. 4 shows, by way of example in a depiction which is largely analogous to FIG. 1, how a reduction gas heating device, in the case depicted an indirect heat exchanger 16 for single-stage heating of the reduction gas before it comes into contact with the iron oxide material 2, is present in the reduction gas feed conduit. A second partial amount of the used carburizing gas is, after treatment, passed to use as fuel gas for heating the reduction gas. For this purpose, a fuel gas conduit 17 which opens into the reduction gas heating device 16 goes out from the recirculation device 12.
(11) FIG. 5 shows, in a modification of the depiction in FIG. 4, how a fuel gas feed conduit 18 opening into the gas heating device 15 goes out from the recirculation device 12. A further partial amount of the used carburizing gas is passed to utilization as fuel gas for heating the carburizing gas.
(12) FIG. 6 shows, in a depiction largely analogous to FIG. 1, how a topgas conduit 19 goes out from the reduction zone for taking off used reduction gas. A fuel conduit 20 goes out from it and can, in the interests of clarity not shown separately, open into a gas heating device 15 or a reduction gas heating device as shown by way of example in FIGS. 3 and 4 in order to feed a first partial amount of the topgas to utilization as fuel gas for heating the reduction gas and/or the carburizing gas.
(13) FIG. 7 schematically shows, in a modification of FIG. 2, how iron sponge can be heated by means of a heating unit 21 present in the supply conduit 10 before entry into the carburization zone.
(14) FIG. 8 schematically shows, in a modification of FIG. 2, how carbon can be introduced into the carburization zone 5 by means of a carbon addition device 22.
(15) FIG. 9 schematically shows a conventional process for producing directly reduced iron sponge from iron oxide material, in which direct reduction is carried out by means of a reduction gas consisting of H.sub.2. The H.sub.2 reduction gas is introduced via the reduction gas feed conduit 23 into the reduction reactor 24. Iron sponge 25 is taken off from the bottom of the reduction reactor 24. Used reduction gas after the reduction is taken off as topgas at the top of the reduction reactor 24 via the topgas conduit 26. The major part of the topgas is, after condensation of water and purification, recirculated into a scrubber 27, while a partial amount is fed as fuel to a reduction gas furnace 28. Fresh hydrogen 29 is mixed into the recirculated topgas. After preheating by means of offgas from the reduction gas furnace 28, the gas stream is heated in the reduction gas furnace 28 and then introduced into the reduction apparatus. Removal of CO.sub.2 from the recirculation circuit is not necessary.
(16) Although the invention has been illustrated and described in detail by means of the preferred working examples, the invention is not restricted by the examples disclosed and other variants can be derived therefrom by a person skilled in the art without going outside the scope of protection of the invention.
LIST OF REFERENCE NUMERALS
(17) 1 Plant for producing carburized directly reduced iron sponge from iron oxide material 2 Iron oxide material 3 Reduction zone 4 Reduction gas feed conduit 5 Carburization zone 6 Carburizing gas feed conduit 7 Carburization offgas conduit 8 Blower 9 Fixed-bed reactor 10 Supply conduit 11 Carburization apparatus 12 Recirculation device 13 Recirculate conduit 14 Addition 15 Gas heating device 16 Indirect heat exchanger 17 Fuel gas conduit 18 Fuel gas feed conduit 19 Topgas conduit 20 Fuel conduit 21 Heating unit 22 Carbon addition device 23 Reduction gas feed conduit 24 Reduction reactor 25 Iron sponge 26 Topgas conduit 27 Scrubber 28 Reduction gas furnace
