CA2193855C - Direct reduction process for iron oxide-containing materials - Google Patents
Direct reduction process for iron oxide-containing materials Download PDFInfo
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- CA2193855C CA2193855C CA002193855A CA2193855A CA2193855C CA 2193855 C CA2193855 C CA 2193855C CA 002193855 A CA002193855 A CA 002193855A CA 2193855 A CA2193855 A CA 2193855A CA 2193855 C CA2193855 C CA 2193855C
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- gas
- reducing
- duct
- direct reduction
- iron
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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
- 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
- C21B2100/28—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
- C21B2100/60—Process control or energy utilisation in the manufacture of iron or steel
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/122—Reduction of greenhouse gas [GHG] emissions by capturing or storing CO2
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/143—Reduction of greenhouse gas [GHG] emissions of methane [CH4]
Abstract
A direct reduction process is disclosed for iron oxide-containing materials. Synthesis gas is mixed with top gas produced during direct reduction of the iron oxide-containing materials and is used as reduction gas for directly reducing and heating the iron oxide-containing materials up to reduction temperature. In order to set the H2S content at a predetermined value by a relatively simple technique and with a relatively simple equipment, at least part of the sulphur contained in the iron oxide-containing materials as H2S produced during heating or direct reduction is added to the reduction gas together with the top gas.
Description
2193~~~
Process for the Direct Reduction of Iron-Oxide- ontaining Material The invention relates to a process for the direct reduction of iron-oxide-containing material, wherein synthesis gas, preferably reformed natural gas, is mixed with top gas forming in the direct reduction of the iron-oxide-containing material and is used as a reducing gas for direct reduction and for heating the iron-oxide-containing material to reduction temperature, as well as a plant for carrying out the process.
A process of this type is known from EP-A - 0 571 358.
Metallic plant parts that get into contact with CO-containing reducing gas are subject to a high stress due to corrosion: The result is metal decomposition, which is denoted as "metal dusting" in the technical literature. Metal dusting occurs to an increased extent at elevated temperatures, plant parts that get into contact with hot reducing gas, thus, being particularly jeopardized. With a plant for carrying out the initially mentioned process, these are primarily the reactors employed for direct reduction and the gas heaters heating the reducing gas to reduction temperature.
To avoid or reduce metal dusting, it is internally known to provide for a content of sulfur within the reducing gas, which has been accomplished by blowing in H2S
gas through tuyeres. Such an admixture of H2S gas is not only technologically complex, but also very expensive and, in addition, involves procedural difficulties, i.e., it is difficult to adjust the H2S content in the reducing gas uniformly to a predetermined value as a function of the chemical composition of the reducing gas.
The invention aims at avoiding these disadvantages and difficulties and has as its object to provide a process of the initially defined kind and a plant for carrying out the process, which enable the adjustment of the content of H2S to a predetermined value with sufficient accuracy and by avoiding great procedural and structural expenditures as well as high costs.
In accordance with the invention, this object is achieved in that at least a portion of the sulfur contained in the iron-oxide-containing material, together with the top gas, is fed to the reducing gas in the form of H2S incurring in heating and in direct reduction, respectively.
The invention is based on the idea to utilize the sulfur usually contained in the ore and which has not been used in further processing so far, taking advantage of the fact that H2S is formed when heating sulfide ores. According to the invention, this H2S, together with the reducing gas effecting heating and by which it is absorbed, is carried off as a top gas and fed to the reducing gas.
Suitably, a content of H2S ranging from 20 to 40 ppmV, preferably amounting to about 25 ppmV, is adjusted in the reducing gas by means of the top gas.
According to a preferred embodiment, the top gas is subjected to C02 scrubbing prior to being used as a reducing gas and the adjustment of the H2S content in the reducing gas is effected by directly admixing to the reducing gas at least a partial volume of the top gas while avoiding C02 scrubbing. This variant is particularly simple to realize, because the only thing to be provided is a bypass duct bypassing the C02 scrubber. Thereby, washing out of the H2S
present in that portion of the top gas is prevented, whereas the remaining portion of the top gas is subjected to C02 scrubbing, by which also H2S is washed out. By varying the amount of top gas conducted through the bypass duct, the desired H2S content of the reducing gas may be adjusted in a simple manner.
Another preferred embodiment is characterized in that reformed natural gas is employed as the synthesis gas and that both the reformed natural gas and the top gas are subjected to C02 scrubbing prior to being used as a reducing gas, wherein a partial volume of the reformed natural gas is directly admixed to the reducing gas while avoiding C02 scrubbing. Thereby, any desired C02 content may be adjusted in a simple manner and changes in the C02 content and in the CO/C02 ratio of the reducing gas caused by the direct admixture of a portion of C02-unscrubbed top gas may be balanced out under consideration of the desired H2S content.
Another preferred way of adjusting the desired H2S content in the reducing gas is characterized in that the adjustment of the H2S content in the reducing gas is effected by varying the wash-out degree of C02 scrubbing with a view to retaining a portion of the C02 and hence a portion of the H2S in the scrubbed gas. This embodiment requires the least structural expenditure possible, i.e., not even the arrangement of a bypass duct, yet it has to be taken into account that all of the gas must be conducted through the C02 scrubber, which will have to be dimensioned accordingly.
Preferably, a sulfurous material, such as iron pyrite, is added to the particulate iron-oxide-containing material in case it does not contain any sulfur, thus causing the formation of H2S and its absorption by the reducing gas effecting heating of the iron-oxide-containing material to reduction temperature.
A plant for carrying out the process, comprising at least one direct reduction reactor for receiving the iron-oxide-containing material, heating and reducing the same, a reducing-gas supply duct leading to said direct reduction reactor and a top-gas discharge duct carrying off the direct reduction reactor the top gas forming in direct reduction as well as in heating to reduction temperature, the top-gas discharge duct running into a C02 scrubber and the reducing gas formed of synthesis gas and of top gas getting into the direct reduction reactor through the reducing-gas supply duct and the reducing-gas supply duct leading from the C02 scrubber to the direct reduction reactor, is characterized in that the top-gas discharge duct is flow-connected with the reducing-gas supply duct by means of a bypass duct avoiding the C02 scrubber.
According to a preferred embodiment, a reformer for reforming natural gas and a reformed-gas duct departing from the reformer and joining the top-gas discharge duct are provided for the production of synthesis gas, both the reformed-gas duct and the top-gas discharge duct running into the C02 scrubber.
~~s3R~~
Preferably, the reformed-gas duct is flow-connected with the reducing-gas supply duct by means of a bypass duct avoiding the C02 scrubber.
Suitably, the bypass ducts) is (are) equipped with an adjustment valve, preferably a control valve, capable of being activated via an H2S measuring means.
In the following, the invention will be explained in more detail by way of the drawing illustrating a process diagram according to a preferred embodiment.
The plant according to the invention comprises four whirl layer reactors 1 to consecutively connected in series, wherein iron-oxide-containing material, such as fine ore, through an ore supply duct 5 is supplied to the first whirl layer reactor 1, in which heating to reduction temperature (or prereduction) takes place, and subsequently is conducted from one whirl layer reactor to another whirl layer reactor via conveying ducts 6. The completely reduced material (sponge iron) is hot-briquetted in a briquetting arrangement 7.
If required, the reduced iron is protected from reoxidation during briquetting by an inert gas system not illustrated.
Prior to introducing the fine ore into the first whirl layer reactor 1, it is subjected to ore preparation, such as drying and sieving, not illustrated in detail.
Reducing gas is conducted in counterflow to the ore flow from one whirl layer reactor 4 to another whirl layer reactor 3 to 1 and is carned off the last whirl layer reactor 1, viewed in the gas flow direction, as a top gas through a top-gas discharge duct 8 and is cooled and scrubbed in a wet scrubber 9.
The production of reducing gas is effected by reforming in a reformer 10 natural gas fed through a duct 11 and desulfurized in a desulfurization plant 12. The gas leaving the reformer 10 and formed of natural gas and vapor essentially consists of H2, CO, CH4, H20 and C02. This reformed natural gas is supplied through a reformed-gas duct 13 to several heat exchangers 14, in which it is cooled, water thus being condensed out of the gas.
The reformed-gas duct 13 runs into the top-gas discharge duct 8 after the top gas has been compressed by means of a compressor 15. The mixed gas thus forming is passed through a C02 scrubber 16 and is freed from C02 and also from H2S. It is then available as a reducing gas. This reducing gas, via a reducing-gas supply duct 17, is heated to a reducing-gas temperature of about 800°C in a gas heater 18 arranged to follow the C02 scrubber 16 and is fed to the first whirl layer reactor 4, viewed in the gas flow direction, where it reacts with the fine ores to produce directly reduced iron. The whirl layer reactors 4 to 1 are arranged in series; the reducing gas gets from one whirl layer reactor to another whirl layer reactor through connection ducts 19.
A portion of the top gas is sluiced out of the gas circulatory system 8, 17, 19 in order to avoid enrichment of inert gases, such as N2. The sluiced-out top gas is fed through a branch duct 20 to the gas heater 18 for heating the reducing gas and is burnt there.
Possible shortages of energy are supplemented by natural gas supplied through a feed duct 21.
The sensible heat of the reformed natural gas emerging from the reformer 10 as well as of the reformer smoke gases is utilized in a recuperator 22 to preheat the natural gas after passage through the desulfurization plant 12, to produce the vapor required for reformation and to preheat the combustion air supplied to the gas heater 18 through duct 23 as well as, if desired, also the reducing gas. T'he combustion air supplied to the reformer through duct 24 is preheated as well.
The top gas leaving the whirl layer reactor 1 has an H2S content ranging between 40 and 140 ppmV - depending on the sulfur content of the ore. The H2S gas forms during heating of the fine ore to reduction temperature or during the prereduction of the fine ore, respectively.
According to the invention, H2S no longer is completely washed out of the top gas by means of the C02 scrubber, but it is taken care that the percentage of H2S
desired for the reducing gas be fed to the reducing gas from the top gas. On the one hand, this can be realized by means of a bypass duct 25 bypassing the C02 scrubber 16, which bypass duct departs from the top-gas discharge duct 8 via an adjustment or control valve 26 and runs into the; reducing-gas supply duct 17. The adjustment or control valve 26 is adjustable in a manner that an H2S
content ranging between 20 and 40 ppmV, preferably amounting to about 25 ppmV, is H2S
present in the reducing gas. Preferably, the adjustment or control valve 26 is activated via an H2S measuring means 27.
The desired H2S content in the reducing gas may be adjusted also by passing the total top gas through the C02 scrubber 16, yet adjusting the latter to a wash-out level at which a portion of the C02 and hence also a portion of the H2S will remain in the gas emerging from the C02 scrubber 16. This has the advantage that no auxiliary means, such as a bypass duct 25 including a control valve 26, need be provided, yet requires the total gas amount, i.e., all of the top gas and all of the reformed natural gas, to be passed through the C02 scrubber 16, the latter, thus, having to be dimensioned for such an amount.
To adjust a desired C02 content or a desired CO/C02 ratio, respectively, which is influenced by a change in the wash-out level of the C02 scrubber 16 or by the direct feeding of a portion of the top gas through the bypass duct 25, a portion of the reformed natural gas may be supplied to the reducing-gas supply duct 17 through a bypass duct 29 bypassing the C02 scrubber l6 and likewise equipped with an adjustable valve 28; that bypass duct 29 will then depart from the reformed gas duct 13. The measures pointed out above for adjusting a desired H2S content in the reducing gas may be realized individually or also jointly.
The adjustment of H2S to 25 ppmV is going to be explained by way of the :following example:
100 t/h of dried fine ore are charged into a plant for the direct reduction of fine ore configured in accordance with the drawing and designed for a production of 70 t/h of sponge iron. The fine ore has the following analysis:
Hematite 94.2 % by weight S
Ganguc 2.2 °/> by weight Sulfur 0.02 % by weight From the top gas forming in the direct reduction, 78,000 Nm3/h are mixed with 48,000 Nm3/h of reformed natural gas and passed through the C02 scrubber 16, in which the mixed gas is freed from C02 and the major portion of sulfur.
The reformed natural gas and the top gas have the chemical compositions indicated in the Table below. (In the table below and the following tables the values are based on volume.) Reformed Natural Gas Top Gas CH4 2.80 30.60 CO 4.80 5.80 C02 14.50 5.30 H2 64.40 53.00 H20 13.50 0.70 N2 0.0 4.60 H2S 0~0 60.0 ppmV
The gas mixture emerging from the C02 scrubber 16 and formed of the scmbbed reformed natural gas and of the scrubbed top gas has the following composition:
CH4 22.80 CO 6.15 C02 0,80 H2 64.90 H2O 2.10 N2 3.25 H2S 2 ppmV
This gas mixture is mixed with 78,000 Nm3/h of top gas that has not been passed through the C02 scrubber 16. This gas mixture forms the reducing gas fed to the gas heater 18 and subsequently to the whirl layer reactors 1 to 4 and having the following composition:
Reducing Gas CH4 24.50 CO 6.0 C02 3.6 H2 60.90 H2O I .5 N2 3.5 H2S 25 ppmV
The degree of metallization of the sponge iron is 92 °/~.
According to the following example, a content of E12S of 3S ppmV is obtained:
100 t/h of dried fine ore are charged into a plant for the direct reduction of tine ore configured in accordance with the drawing and designed for a production of 70 t/h of sponge iron. The fine ore has the following analysis:
Hematite 94.2 % bY weight Gangue 2.2 % bY weight Sulfur 0.02 % by weight From the top gas forming in the direct reduc~ion, 63,000 Nm3/h are mixed 'with 54,000 Nm3/h of reformed natural gas and passed through the C02 scrubber 16, in which the mixed gas is freed from C02 and the major portion of sulfur.
The reformed natural gas and the top gas have the chemical compositions indicated in the Table below.
Reformed Natural Gas Top Gas CH4 2.80 30.75 CO 4.80 5.60 C02 14.50 5.10 H2 64.40 53.25 H20 13.50 0.70 N2 0.0 4.60 H2S 0.0 73.0 ppmV
The gas mixture emerging from the C02 scrubber 16 and formed of the scnubbed reformed natural gas and of the top gas has the following composition:
CH4 20.60 CO 6.00 C02 0,80 H2 67.50 H20 2.20 N2 2.90 H2S ~ 2 ppmV
This gas mixture is mixed with 94,000 Nm3/h of top gas that has not been passed through the C02 scrubber 16. This gas mixture forms the reducing gas fed to the gas heater 18 and subsequently to the whirl layer reactors 1 to 4 and has the following composition:
Reducing Gas CH4 24.60 CO 5.8 C02 3.4 H2 61.20 H20 1.4 N2 3.6 H2S 35 ppmV
The degree of metallization of the sponge iron is 92 %.
The invention is not limited to the above-described examples, but is applicable also to other direct reduction processes, for instance, such in which the whirl layer reactors 1 to 4 are replaced with shaft furnaces for lumpy ore. The reformed natural gas also may be replaced with other reducing gases primarily containing CO and H2, such as ~ LD offgas ~ EAF offgas ~ blast furnace gas from blast furnace plants ~ blast furnace gas from Corex plants ~ coal gas Corex* gas from Corex* gasifier ~ chemical gases.
* Trade-mark
Process for the Direct Reduction of Iron-Oxide- ontaining Material The invention relates to a process for the direct reduction of iron-oxide-containing material, wherein synthesis gas, preferably reformed natural gas, is mixed with top gas forming in the direct reduction of the iron-oxide-containing material and is used as a reducing gas for direct reduction and for heating the iron-oxide-containing material to reduction temperature, as well as a plant for carrying out the process.
A process of this type is known from EP-A - 0 571 358.
Metallic plant parts that get into contact with CO-containing reducing gas are subject to a high stress due to corrosion: The result is metal decomposition, which is denoted as "metal dusting" in the technical literature. Metal dusting occurs to an increased extent at elevated temperatures, plant parts that get into contact with hot reducing gas, thus, being particularly jeopardized. With a plant for carrying out the initially mentioned process, these are primarily the reactors employed for direct reduction and the gas heaters heating the reducing gas to reduction temperature.
To avoid or reduce metal dusting, it is internally known to provide for a content of sulfur within the reducing gas, which has been accomplished by blowing in H2S
gas through tuyeres. Such an admixture of H2S gas is not only technologically complex, but also very expensive and, in addition, involves procedural difficulties, i.e., it is difficult to adjust the H2S content in the reducing gas uniformly to a predetermined value as a function of the chemical composition of the reducing gas.
The invention aims at avoiding these disadvantages and difficulties and has as its object to provide a process of the initially defined kind and a plant for carrying out the process, which enable the adjustment of the content of H2S to a predetermined value with sufficient accuracy and by avoiding great procedural and structural expenditures as well as high costs.
In accordance with the invention, this object is achieved in that at least a portion of the sulfur contained in the iron-oxide-containing material, together with the top gas, is fed to the reducing gas in the form of H2S incurring in heating and in direct reduction, respectively.
The invention is based on the idea to utilize the sulfur usually contained in the ore and which has not been used in further processing so far, taking advantage of the fact that H2S is formed when heating sulfide ores. According to the invention, this H2S, together with the reducing gas effecting heating and by which it is absorbed, is carried off as a top gas and fed to the reducing gas.
Suitably, a content of H2S ranging from 20 to 40 ppmV, preferably amounting to about 25 ppmV, is adjusted in the reducing gas by means of the top gas.
According to a preferred embodiment, the top gas is subjected to C02 scrubbing prior to being used as a reducing gas and the adjustment of the H2S content in the reducing gas is effected by directly admixing to the reducing gas at least a partial volume of the top gas while avoiding C02 scrubbing. This variant is particularly simple to realize, because the only thing to be provided is a bypass duct bypassing the C02 scrubber. Thereby, washing out of the H2S
present in that portion of the top gas is prevented, whereas the remaining portion of the top gas is subjected to C02 scrubbing, by which also H2S is washed out. By varying the amount of top gas conducted through the bypass duct, the desired H2S content of the reducing gas may be adjusted in a simple manner.
Another preferred embodiment is characterized in that reformed natural gas is employed as the synthesis gas and that both the reformed natural gas and the top gas are subjected to C02 scrubbing prior to being used as a reducing gas, wherein a partial volume of the reformed natural gas is directly admixed to the reducing gas while avoiding C02 scrubbing. Thereby, any desired C02 content may be adjusted in a simple manner and changes in the C02 content and in the CO/C02 ratio of the reducing gas caused by the direct admixture of a portion of C02-unscrubbed top gas may be balanced out under consideration of the desired H2S content.
Another preferred way of adjusting the desired H2S content in the reducing gas is characterized in that the adjustment of the H2S content in the reducing gas is effected by varying the wash-out degree of C02 scrubbing with a view to retaining a portion of the C02 and hence a portion of the H2S in the scrubbed gas. This embodiment requires the least structural expenditure possible, i.e., not even the arrangement of a bypass duct, yet it has to be taken into account that all of the gas must be conducted through the C02 scrubber, which will have to be dimensioned accordingly.
Preferably, a sulfurous material, such as iron pyrite, is added to the particulate iron-oxide-containing material in case it does not contain any sulfur, thus causing the formation of H2S and its absorption by the reducing gas effecting heating of the iron-oxide-containing material to reduction temperature.
A plant for carrying out the process, comprising at least one direct reduction reactor for receiving the iron-oxide-containing material, heating and reducing the same, a reducing-gas supply duct leading to said direct reduction reactor and a top-gas discharge duct carrying off the direct reduction reactor the top gas forming in direct reduction as well as in heating to reduction temperature, the top-gas discharge duct running into a C02 scrubber and the reducing gas formed of synthesis gas and of top gas getting into the direct reduction reactor through the reducing-gas supply duct and the reducing-gas supply duct leading from the C02 scrubber to the direct reduction reactor, is characterized in that the top-gas discharge duct is flow-connected with the reducing-gas supply duct by means of a bypass duct avoiding the C02 scrubber.
According to a preferred embodiment, a reformer for reforming natural gas and a reformed-gas duct departing from the reformer and joining the top-gas discharge duct are provided for the production of synthesis gas, both the reformed-gas duct and the top-gas discharge duct running into the C02 scrubber.
~~s3R~~
Preferably, the reformed-gas duct is flow-connected with the reducing-gas supply duct by means of a bypass duct avoiding the C02 scrubber.
Suitably, the bypass ducts) is (are) equipped with an adjustment valve, preferably a control valve, capable of being activated via an H2S measuring means.
In the following, the invention will be explained in more detail by way of the drawing illustrating a process diagram according to a preferred embodiment.
The plant according to the invention comprises four whirl layer reactors 1 to consecutively connected in series, wherein iron-oxide-containing material, such as fine ore, through an ore supply duct 5 is supplied to the first whirl layer reactor 1, in which heating to reduction temperature (or prereduction) takes place, and subsequently is conducted from one whirl layer reactor to another whirl layer reactor via conveying ducts 6. The completely reduced material (sponge iron) is hot-briquetted in a briquetting arrangement 7.
If required, the reduced iron is protected from reoxidation during briquetting by an inert gas system not illustrated.
Prior to introducing the fine ore into the first whirl layer reactor 1, it is subjected to ore preparation, such as drying and sieving, not illustrated in detail.
Reducing gas is conducted in counterflow to the ore flow from one whirl layer reactor 4 to another whirl layer reactor 3 to 1 and is carned off the last whirl layer reactor 1, viewed in the gas flow direction, as a top gas through a top-gas discharge duct 8 and is cooled and scrubbed in a wet scrubber 9.
The production of reducing gas is effected by reforming in a reformer 10 natural gas fed through a duct 11 and desulfurized in a desulfurization plant 12. The gas leaving the reformer 10 and formed of natural gas and vapor essentially consists of H2, CO, CH4, H20 and C02. This reformed natural gas is supplied through a reformed-gas duct 13 to several heat exchangers 14, in which it is cooled, water thus being condensed out of the gas.
The reformed-gas duct 13 runs into the top-gas discharge duct 8 after the top gas has been compressed by means of a compressor 15. The mixed gas thus forming is passed through a C02 scrubber 16 and is freed from C02 and also from H2S. It is then available as a reducing gas. This reducing gas, via a reducing-gas supply duct 17, is heated to a reducing-gas temperature of about 800°C in a gas heater 18 arranged to follow the C02 scrubber 16 and is fed to the first whirl layer reactor 4, viewed in the gas flow direction, where it reacts with the fine ores to produce directly reduced iron. The whirl layer reactors 4 to 1 are arranged in series; the reducing gas gets from one whirl layer reactor to another whirl layer reactor through connection ducts 19.
A portion of the top gas is sluiced out of the gas circulatory system 8, 17, 19 in order to avoid enrichment of inert gases, such as N2. The sluiced-out top gas is fed through a branch duct 20 to the gas heater 18 for heating the reducing gas and is burnt there.
Possible shortages of energy are supplemented by natural gas supplied through a feed duct 21.
The sensible heat of the reformed natural gas emerging from the reformer 10 as well as of the reformer smoke gases is utilized in a recuperator 22 to preheat the natural gas after passage through the desulfurization plant 12, to produce the vapor required for reformation and to preheat the combustion air supplied to the gas heater 18 through duct 23 as well as, if desired, also the reducing gas. T'he combustion air supplied to the reformer through duct 24 is preheated as well.
The top gas leaving the whirl layer reactor 1 has an H2S content ranging between 40 and 140 ppmV - depending on the sulfur content of the ore. The H2S gas forms during heating of the fine ore to reduction temperature or during the prereduction of the fine ore, respectively.
According to the invention, H2S no longer is completely washed out of the top gas by means of the C02 scrubber, but it is taken care that the percentage of H2S
desired for the reducing gas be fed to the reducing gas from the top gas. On the one hand, this can be realized by means of a bypass duct 25 bypassing the C02 scrubber 16, which bypass duct departs from the top-gas discharge duct 8 via an adjustment or control valve 26 and runs into the; reducing-gas supply duct 17. The adjustment or control valve 26 is adjustable in a manner that an H2S
content ranging between 20 and 40 ppmV, preferably amounting to about 25 ppmV, is H2S
present in the reducing gas. Preferably, the adjustment or control valve 26 is activated via an H2S measuring means 27.
The desired H2S content in the reducing gas may be adjusted also by passing the total top gas through the C02 scrubber 16, yet adjusting the latter to a wash-out level at which a portion of the C02 and hence also a portion of the H2S will remain in the gas emerging from the C02 scrubber 16. This has the advantage that no auxiliary means, such as a bypass duct 25 including a control valve 26, need be provided, yet requires the total gas amount, i.e., all of the top gas and all of the reformed natural gas, to be passed through the C02 scrubber 16, the latter, thus, having to be dimensioned for such an amount.
To adjust a desired C02 content or a desired CO/C02 ratio, respectively, which is influenced by a change in the wash-out level of the C02 scrubber 16 or by the direct feeding of a portion of the top gas through the bypass duct 25, a portion of the reformed natural gas may be supplied to the reducing-gas supply duct 17 through a bypass duct 29 bypassing the C02 scrubber l6 and likewise equipped with an adjustable valve 28; that bypass duct 29 will then depart from the reformed gas duct 13. The measures pointed out above for adjusting a desired H2S content in the reducing gas may be realized individually or also jointly.
The adjustment of H2S to 25 ppmV is going to be explained by way of the :following example:
100 t/h of dried fine ore are charged into a plant for the direct reduction of fine ore configured in accordance with the drawing and designed for a production of 70 t/h of sponge iron. The fine ore has the following analysis:
Hematite 94.2 % by weight S
Ganguc 2.2 °/> by weight Sulfur 0.02 % by weight From the top gas forming in the direct reduction, 78,000 Nm3/h are mixed with 48,000 Nm3/h of reformed natural gas and passed through the C02 scrubber 16, in which the mixed gas is freed from C02 and the major portion of sulfur.
The reformed natural gas and the top gas have the chemical compositions indicated in the Table below. (In the table below and the following tables the values are based on volume.) Reformed Natural Gas Top Gas CH4 2.80 30.60 CO 4.80 5.80 C02 14.50 5.30 H2 64.40 53.00 H20 13.50 0.70 N2 0.0 4.60 H2S 0~0 60.0 ppmV
The gas mixture emerging from the C02 scrubber 16 and formed of the scmbbed reformed natural gas and of the scrubbed top gas has the following composition:
CH4 22.80 CO 6.15 C02 0,80 H2 64.90 H2O 2.10 N2 3.25 H2S 2 ppmV
This gas mixture is mixed with 78,000 Nm3/h of top gas that has not been passed through the C02 scrubber 16. This gas mixture forms the reducing gas fed to the gas heater 18 and subsequently to the whirl layer reactors 1 to 4 and having the following composition:
Reducing Gas CH4 24.50 CO 6.0 C02 3.6 H2 60.90 H2O I .5 N2 3.5 H2S 25 ppmV
The degree of metallization of the sponge iron is 92 °/~.
According to the following example, a content of E12S of 3S ppmV is obtained:
100 t/h of dried fine ore are charged into a plant for the direct reduction of tine ore configured in accordance with the drawing and designed for a production of 70 t/h of sponge iron. The fine ore has the following analysis:
Hematite 94.2 % bY weight Gangue 2.2 % bY weight Sulfur 0.02 % by weight From the top gas forming in the direct reduc~ion, 63,000 Nm3/h are mixed 'with 54,000 Nm3/h of reformed natural gas and passed through the C02 scrubber 16, in which the mixed gas is freed from C02 and the major portion of sulfur.
The reformed natural gas and the top gas have the chemical compositions indicated in the Table below.
Reformed Natural Gas Top Gas CH4 2.80 30.75 CO 4.80 5.60 C02 14.50 5.10 H2 64.40 53.25 H20 13.50 0.70 N2 0.0 4.60 H2S 0.0 73.0 ppmV
The gas mixture emerging from the C02 scrubber 16 and formed of the scnubbed reformed natural gas and of the top gas has the following composition:
CH4 20.60 CO 6.00 C02 0,80 H2 67.50 H20 2.20 N2 2.90 H2S ~ 2 ppmV
This gas mixture is mixed with 94,000 Nm3/h of top gas that has not been passed through the C02 scrubber 16. This gas mixture forms the reducing gas fed to the gas heater 18 and subsequently to the whirl layer reactors 1 to 4 and has the following composition:
Reducing Gas CH4 24.60 CO 5.8 C02 3.4 H2 61.20 H20 1.4 N2 3.6 H2S 35 ppmV
The degree of metallization of the sponge iron is 92 %.
The invention is not limited to the above-described examples, but is applicable also to other direct reduction processes, for instance, such in which the whirl layer reactors 1 to 4 are replaced with shaft furnaces for lumpy ore. The reformed natural gas also may be replaced with other reducing gases primarily containing CO and H2, such as ~ LD offgas ~ EAF offgas ~ blast furnace gas from blast furnace plants ~ blast furnace gas from Corex plants ~ coal gas Corex* gas from Corex* gasifier ~ chemical gases.
* Trade-mark
Claims (14)
1. A process for the direct reduction of iron-oxide-containing material, characterized by the combination of the following characteristic features.:
synthesis gas and top gas forming in the direct reduction of the iron-oxide-containing material are used as a reducing gas for direct reduction and for heating the iron-oxide-containing material to reduction temperature, both synthesis gas and top gas are subjected to CO2 scrubbing and subsequently used as a reducing gas, at least a portion of the sufur contained in the iron-oxide-containing material in the form of H2S incurring in heating and in direct reduction, respectively, is fed to the reducing gas together with the top gas.
synthesis gas and top gas forming in the direct reduction of the iron-oxide-containing material are used as a reducing gas for direct reduction and for heating the iron-oxide-containing material to reduction temperature, both synthesis gas and top gas are subjected to CO2 scrubbing and subsequently used as a reducing gas, at least a portion of the sufur contained in the iron-oxide-containing material in the form of H2S incurring in heating and in direct reduction, respectively, is fed to the reducing gas together with the top gas.
2. A process according to claim 1, characterized in that a content of H2S
ranging from 20 to 40 ppmV is adjusted in the reducing gas by means of the top gas.
ranging from 20 to 40 ppmV is adjusted in the reducing gas by means of the top gas.
3. A process according to claim 2, characterized in that the content of H2S is 25 ppmV.
4. A process according to claim 1 or 2, characterized in that to top gas is subjected to CO2 scrubbing prior to being used as a reducing gas and the adjustment of the H2S content in the reducing gas is effected by directly admixing to the reducing gas at least a partial volume of the top gas while avoiding CO2 scrubbing.
5. A process according to one or several of claims 1 to 3, characterized in that reformed natural gas is employed as said synthesis gas wherein a partial volume of the reformed natural gas is directly admixed to the reducing gas while avoiding CO2 scrubbing.
6. A process according to claim 3 or 4, characterized in that the adjustment of the H2S content in the reducing gas is effected by varying the wash-out degree of CO2 scrubbing inasmuch as a portion of the CO2 and hence a portion of the H2S remain in the scrubbed gas.
7. A process according to one of several of claims 1 to 5, characterized in that a sulfurous material is added to the iron-oxide-containing material.
8. A process according to claim 7, characterized in that the sulfurous material is iron pyrite.
9. A process according to one or several of claims 1 to 6, characterized in that one or several of the following gases are used as said synthesis gas:
~ LD offgas ~ EAF offgas ~ blast furnace gas from blast furnace plants ~ blast furnace gas from Corex* plants ~ coal gas ~ Corex* gas from Corex* gasifier ~ chemical gases.
~ LD offgas ~ EAF offgas ~ blast furnace gas from blast furnace plants ~ blast furnace gas from Corex* plants ~ coal gas ~ Corex* gas from Corex* gasifier ~ chemical gases.
10. A plant for carrying out the process according to one or several of claims 1 to 7, comprising at least one direct reduction reactor for receiving the iron-oxide-containing material, heating and reducing the same, a synthesis-gas duct that is flow-connected with a reducing-gas supply duct leading to said direct reduction reactor and a top-gas discharge duct carrying off said direct reduction reactor the top gas forming in direct reduction as well as in heating to reduction temperature, the top-gas discharge duct running into a CO2 scrubber and being flow-connected with the reducing-gas supply duct by means of a bypass duct avoiding the CO2 scrubber, characterized in that the synthesis- gas duct is flow -connected with the; CO2 * Trade-mark crubber and that the reducing gas formed of synthesis gas and of top gas is passed into the direct reduction reactor through the reducing-gas supply duct leading from the CO2 scrubber to the direct reduction reactor.
11. A plant according to claim 8, characterized in that a reformer for reforming natural gas and a reformed-gas duct departing from the reformer and joining the top-gas discharge duct are provided for the production of synthesis gas, both the reformed-gas duct and the top-gas discharge; duct running into the CO2 scrubber.
12. A plant according to claim 9, characterized in that the reformed-gas duct is flow-connected with the reducing-gas supply duct by means, of a bypass duct avoiding the CO2 scrubber.
13. A plant according to one or several of claims 8 to 10, characterized in that the bypass duct(s) is(are) equipped with an adjustment valve capable of being activated via an H2S measuring means.
14. A plant according to claim 13, characterized in that the adjustment valve is a control valve (26,28).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ATA1248/94 | 1994-06-23 | ||
| AT0124894A AT402825B (en) | 1994-06-23 | 1994-06-23 | METHOD FOR DIRECTLY REDUCING IRON-OXIDATING MATERIAL |
| PCT/AT1995/000121 WO1996000302A1 (en) | 1994-06-23 | 1995-06-20 | Direct reduction process for iron oxide-containing materials |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2193855A1 CA2193855A1 (en) | 1996-01-04 |
| CA2193855C true CA2193855C (en) | 2001-09-18 |
Family
ID=3509806
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002193855A Expired - Fee Related CA2193855C (en) | 1994-06-23 | 1995-06-20 | Direct reduction process for iron oxide-containing materials |
Country Status (14)
| Country | Link |
|---|---|
| US (1) | US5871560A (en) |
| EP (1) | EP0766747A1 (en) |
| JP (1) | JP3248915B2 (en) |
| KR (1) | KR100240811B1 (en) |
| AT (1) | AT402825B (en) |
| AU (1) | AU691293B2 (en) |
| BR (1) | BR9508108A (en) |
| CA (1) | CA2193855C (en) |
| MX (1) | MX9606728A (en) |
| PE (1) | PE49695A1 (en) |
| RU (1) | RU2125098C1 (en) |
| UA (1) | UA27080C2 (en) |
| WO (1) | WO1996000302A1 (en) |
| ZA (1) | ZA955177B (en) |
Families Citing this family (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6136019A (en) * | 1996-08-19 | 2000-10-24 | Mower Family Chf Treatment Irrevocable Trust | Augmentation of electrical conduction and contractility by biphasic cardiac pacing administered via the cardiac blood pool |
| US7440800B2 (en) * | 1996-08-19 | 2008-10-21 | Mr3 Medical, Llc | System and method for managing detrimental cardiac remodeling |
| US8447399B2 (en) * | 1996-08-19 | 2013-05-21 | Mr3 Medical, Llc | System and method for managing detrimental cardiac remodeling |
| US7908003B1 (en) | 1996-08-19 | 2011-03-15 | Mr3 Medical Llc | System and method for treating ischemia by improving cardiac efficiency |
| AT406382B (en) * | 1996-11-06 | 2000-04-25 | Voest Alpine Ind Anlagen | METHOD FOR THE PRODUCTION OF IRON SPONGE BY DIRECTLY REDUCTION OF MATERIAL CONTAINING IRON OXIDE |
| AUPO426096A0 (en) | 1996-12-18 | 1997-01-23 | Technological Resources Pty Limited | Method and apparatus for producing metals and metal alloys |
| AUPO426396A0 (en) | 1996-12-18 | 1997-01-23 | Technological Resources Pty Limited | A method of producing iron |
| US6149859A (en) † | 1997-11-03 | 2000-11-21 | Texaco Inc. | Gasification plant for direct reduction reactors |
| AUPP554098A0 (en) | 1998-08-28 | 1998-09-17 | Technological Resources Pty Limited | A process and an apparatus for producing metals and metal alloys |
| AUPQ152299A0 (en) | 1999-07-09 | 1999-08-05 | Technological Resources Pty Limited | Start-up procedure for direct smelting process |
| AUPQ205799A0 (en) | 1999-08-05 | 1999-08-26 | Technological Resources Pty Limited | A direct smelting process |
| AUPQ213099A0 (en) | 1999-08-10 | 1999-09-02 | Technological Resources Pty Limited | Pressure control |
| AUPQ308799A0 (en) | 1999-09-27 | 1999-10-21 | Technological Resources Pty Limited | A direct smelting process |
| AUPQ346399A0 (en) | 1999-10-15 | 1999-11-11 | Technological Resources Pty Limited | Stable idle procedure |
| AUPQ365799A0 (en) | 1999-10-26 | 1999-11-18 | Technological Resources Pty Limited | A direct smelting apparatus and process |
| US6602321B2 (en) | 2000-09-26 | 2003-08-05 | Technological Resources Pty. Ltd. | Direct smelting process |
| KR100445835B1 (en) * | 2001-05-25 | 2004-08-25 | 한국타이어 주식회사 | Tire tread composition |
| KR20030037530A (en) * | 2001-11-06 | 2003-05-14 | 박재석 | Disposable Starched Utensils and the Manufacturing Process |
| CN101755056B (en) * | 2007-05-25 | 2013-03-27 | 伊尔技术有限公司 | Method and apparatus for the direct reduction of iron ores utilizing syngas |
| WO2009065843A2 (en) * | 2007-11-20 | 2009-05-28 | Shell Internationale Research Maatschappij B.V. | Process for production of elemental iron |
| CN109868335B (en) * | 2019-03-19 | 2021-01-26 | 重庆大学 | System and method for closed-loop utilization of tail gas in iron ore reduction process |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB799551A (en) * | 1956-02-06 | 1958-08-13 | Texaco Development Corp | Reduction of a metal oxide with carbon monoxide and hydrogen |
| US3377156A (en) * | 1965-07-30 | 1968-04-09 | Exxon Research Engineering Co | Process of reducing iron oxide ores with gases containing carbon monoxide |
| US3936296A (en) * | 1970-02-25 | 1976-02-03 | Campbell Donald L | Integrated fluidized reduction and melting of iron ores |
| DE2907022A1 (en) * | 1979-02-23 | 1980-08-28 | Maschf Augsburg Nuernberg Ag | Coal gasification plant gas for iron ore reduction - is divided into partial reducing, heating and sulphur-generating streams |
| US4333761A (en) * | 1979-10-22 | 1982-06-08 | Midrex Corporation | Method for direct reduction of iron using high sulfur gas |
| JPS5811484B2 (en) * | 1980-12-04 | 1983-03-03 | 三菱重工業株式会社 | Method for manufacturing reduced iron |
| AT402937B (en) * | 1992-05-22 | 1997-09-25 | Voest Alpine Ind Anlagen | METHOD AND SYSTEM FOR DIRECTLY REDUCING PARTICULATE IRON OXIDE MATERIAL |
| US5531424A (en) * | 1993-04-19 | 1996-07-02 | Fior De Venezuela | Fluidized bed direct reduction plant |
-
1994
- 1994-06-23 AT AT0124894A patent/AT402825B/en not_active IP Right Cessation
-
1995
- 1995-06-15 PE PE1995271376A patent/PE49695A1/en not_active Application Discontinuation
- 1995-06-20 JP JP50263096A patent/JP3248915B2/en not_active Expired - Fee Related
- 1995-06-20 US US08/765,342 patent/US5871560A/en not_active Expired - Fee Related
- 1995-06-20 WO PCT/AT1995/000121 patent/WO1996000302A1/en not_active Application Discontinuation
- 1995-06-20 BR BR9508108A patent/BR9508108A/en not_active Application Discontinuation
- 1995-06-20 UA UA96124793A patent/UA27080C2/en unknown
- 1995-06-20 CA CA002193855A patent/CA2193855C/en not_active Expired - Fee Related
- 1995-06-20 KR KR1019960707371A patent/KR100240811B1/en not_active IP Right Cessation
- 1995-06-20 RU RU97101124A patent/RU2125098C1/en active
- 1995-06-20 EP EP95919926A patent/EP0766747A1/en not_active Ceased
- 1995-06-20 AU AU25568/95A patent/AU691293B2/en not_active Ceased
- 1995-06-20 MX MX9606728A patent/MX9606728A/en unknown
- 1995-06-22 ZA ZA955177A patent/ZA955177B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| UA27080C2 (en) | 2000-02-28 |
| MX9606728A (en) | 1997-04-30 |
| EP0766747A1 (en) | 1997-04-09 |
| AU691293B2 (en) | 1998-05-14 |
| BR9508108A (en) | 1997-08-12 |
| JP3248915B2 (en) | 2002-01-21 |
| PE49695A1 (en) | 1996-01-22 |
| AT402825B (en) | 1997-09-25 |
| JPH10505634A (en) | 1998-06-02 |
| RU2125098C1 (en) | 1999-01-20 |
| ATA124894A (en) | 1997-01-15 |
| US5871560A (en) | 1999-02-16 |
| CA2193855A1 (en) | 1996-01-04 |
| KR100240811B1 (en) | 2000-01-15 |
| AU2556895A (en) | 1996-01-19 |
| WO1996000302A1 (en) | 1996-01-04 |
| ZA955177B (en) | 1996-01-31 |
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| EEER | Examination request | ||
| MKLA | Lapsed |