CN212316161U - Direct reduction system for directly reducing iron ore - Google Patents

Direct reduction system for directly reducing iron ore Download PDF

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Publication number
CN212316161U
CN212316161U CN202020164809.9U CN202020164809U CN212316161U CN 212316161 U CN212316161 U CN 212316161U CN 202020164809 U CN202020164809 U CN 202020164809U CN 212316161 U CN212316161 U CN 212316161U
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gas
treatment
direct reduction
reduction system
recovery
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达里奥·保卢齐
芭芭拉·弗兰考
豪尔赫·欧亨尼奥·马丁内斯米拉门特斯
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Danieli and C Officine Meccaniche SpA
HYL Technologies de SA de CV
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Danieli and C Officine Meccaniche SpA
HYL Technologies de SA de CV
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/02—Making spongy iron or liquid steel, by direct processes in shaft furnaces
    • C21B13/023—Making spongy iron or liquid steel, by direct processes in shaft furnaces wherein iron or steel is obtained in a molten state
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B13/00—Making spongy iron or liquid steel, by direct processes
    • C21B13/02—Making spongy iron or liquid steel, by direct processes in shaft furnaces
    • 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
    • C21B13/0073—Selection or treatment of the reducing gases
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
    • C01B3/12—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents by reaction of water vapour with carbon monoxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/22—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of gaseous or liquid organic compounds
    • C01B3/24—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of gaseous or liquid organic compounds of hydrocarbons
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/32—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air
    • C01B3/34—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents
    • C01B3/36—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using oxygen or mixtures containing oxygen as gasifying agents
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
    • 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
    • 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
    • C21B2100/66—Heat exchange
    • 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

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Iron (AREA)
  • Saccharide Compounds (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)

Abstract

The utility model relates to a direct reduction system for direct reduction iron ore, this direct reduction system include the return circuit, and this return circuit is provided with: a reactor having a reduction zone adapted to be loaded with the iron ore from above; an external source of make-up reducing gas; a recovery and treatment line placed downstream of the reactor for recovering and treating the effluent gas leaving the reactor; a treatment and feed line placed upstream of the reactor for treating a process gas obtained by mixing a make-up reducing gas from an external source with the exhaust gas treated in the recovery and treatment line and for feeding the process gas to the reduction zone; characterized in that said external source of make-up reducing gas is a source of pure hydrogen or a gas having a hydrogen content equal to at least 80% by volume.

Description

Direct reduction system for directly reducing iron ore
Technical Field
The present invention relates to a direct reduction system, which is particularly suitable for producing metallic iron by directly reducing iron ore using a reducing gas.
Background
A system for producing reduced iron ore (DRI-direct reduced iron) of known type comprises a reactor, into which iron oxide is loaded in the form of pellets (pellet) and/or lumps (lump), and a line (line) for processing and supplying reducing gas, which line is adapted to reduce said iron oxide in the reactor. The reducing gas is injected into the reaction chamber or reactor at a high temperature. The reducing gas is introduced into the central portion of the reactor so as to be counter-currently returned through the iron oxide, and then extracted, reprocessed, and recycled. The exhaust gas (exhaust gas) leaving the reactor is dedusted and the reaction products (H) are removed2O and CO2) And is compressed; it is then mixed with make-up Gas (make-up Gas) (natural Gas, COG, Gas obtained in the reformer, Corex Gas (Corex Gas), synthesis Gas (Syn Gas), etc.). The gas stream, defined by the mixture of fresh make-up gas and exhaust gas recycled after appropriate treatment, is sent to a heating unit which brings it to the temperature required for the reduction process, typically above 850 ℃.
The heated reducing gas stream, into which oxygen is injected with the aim of increasing its temperature even further, is finally conveyed to the reactor, into which the oxidized pellets to be reduced are introduced from above, while DRI (reduction product) is extracted at the opposite end and conveyed by a pneumatic conveying system or by gravity or by belts to a blast furnace or an electric arc furnace or to an oxygen converter.
In more detail, in the iron oxide reduction process, oxygen is removed from iron ore by chemical reaction with hydrogen and carbon monoxide, so as to obtain DRI having a high metallization level (ratio between metallic iron contained in the DRI and total iron). The overall reduction reactions involved in this process are well known and they are shown below:
Fe2O3+3H2->2Fe+3H2O(1)
Fe2O3+3CO->2Fe+3CO2(2)。
according to the reactions (1) and (2), hydrogen and carbon monoxide react with oxygen of iron oxide and are converted into water and carbon dioxide. Except for H2O and CO2Unreacted H2And CO is also present in the vent gas leaving the reactor. The exhaust gases are treated as described above in order to recover these reductants.
The use of make-up gases (natural gas, coke oven gas, Corex gas, synthesis gas, etc.) in reduction circuits containing large amounts of carbon has mainly two drawbacks:
greenhouse gas emissions (CO)2)；
A relatively high content of carbon monoxide (CO) in the reducing gas stream entering the reactor, which may result in a relatively high yield of fines during the reduction reaction, and which may increase the risk of cluster formation, hindering the movement of solid matter, due to the temperature increase caused by the reduction with carbon monoxide, which is exothermic.
In the conventional process scheme, CO is selectively removed from the exhaust gas recycled from the reactor2(which can be stored and used in the food industry or for other industrial applications) to reduce CO2Emissions (emissions) and they consist mainly of carbon dioxide released through the stack of the reformer (if present) or the heating unit of the process gas.
With respect to other known direct reduction processes, described aboveThe process, which is supplied with natural gas to promote the reforming reaction inside the reduction reactor or with the reformed gas produced by the off-line reformer, still ensures good H in the composition of the reducing gas introduced into the reactor2The ratio of/CO. At present, CO2Further reduction of emissions is extremely difficult.
Disadvantageously, to guarantee the current emission levels, the direct reduction system requires a series of indispensable components, such as devices for removing carbon dioxide in the lines for recovering and treating the exhaust gases leaving the reactor. Therefore, the system is complicated from a structural point of view, and therefore expensive.
Accordingly, it is considered desirable to develop a direct reduction system that overcomes the above-mentioned disadvantages.
SUMMERY OF THE UTILITY MODEL
The object of the present invention is to develop a direct reduction system which is simpler from a structural point of view and therefore cheaper.
The present invention has achieved at least one of such and other objects by a direct reduction system for direct reduction of iron ore, which according to the present description will become evident, comprising a circuit (circuit) provided with:
a reactor having a reduction zone (reduction area) adapted to be loaded with the iron ore from above;
an external source of make-up reducing gas (make-up reducing gas);
a recovery and treatment line placed downstream of the reactor to recover and treat the effluent gas leaving the reactor;
a treatment and feed line placed upstream of the reactor for treating a process gas obtained by mixing a make-up reducing gas from an external source with the effluent gas treated in the recovery and treatment line and for supplying the process gas to the reduction zone of the reactor;
wherein the recovery and treatment line is in downstream communication with the treatment and feed line;
and wherein said external source of make-up reducing gas is a source of pure hydrogen or a gas having a hydrogen content equal to at least 80% by volume.
Preferably, preheating of the process gas is provided upstream of the heating unit in the treatment and feed line by passing the process gas through at least one heat exchanger in the recovery and treatment line.
Optionally, the injection of natural gas may be provided in the treatment and feed lines upstream of the at least one heat exchanger by at least one means for injecting natural gas. Alternatively or additionally, the injection of natural gas may be provided in a lower, preferably conical, region of the reactor located below the reduction zone by at least one further means for injecting natural gas.
The system allows the DRI to be produced using a hydrogen-rich gas stream or a pure hydrogen stream to be supplied directly to the reduction circuit. The hydrogen may come from any external source using, for example, reforming of natural gas, electrolysis, or any other process capable of generating such types of gases.
The following are some advantages of the claimed solution over the prior art:
it is no longer necessary to provide means for removing or absorbing carbon dioxide;
there is no need to provide a humidifier to increase the water content of the process gas, thereby preventing the deposition of carbon inside the process gas heating unit;
overall, the deposition of carbon inside the heating unit is very limited, if any, without the need for a system shutdown for chemical cleaning, thus increasing the reliability and availability of the system;
since the reducing gas stream is pure or almost pure hydrogen, no additional energy is required to promote the reforming reaction inside the reactor, and therefore injection of oxygen downstream of the heating unit is unnecessary;
since the process gas produced has a relatively low CO and CO content2Content, so there is no risk of metal dusting (metal dusting) inside the process gas heating unit, nor special precautions (such as using alloys with high Ni-Cr content, or installing hydrogen sulfide injection systems);
since the process gas produced has a relatively low CO and CO content2Content, acidification of process water in contact with process gas is very limited and increased consumption of expensive materials or chemicals on the return line is not required to control water quality;
the high reduction level of iron ore with hydrogen, which determines the temperature reduction inside the reactor, allows more conventional operations with little risk of agglomeration (which is typical of the reduction of CO and its exothermic reaction, like swelling);
introducing pure hydrogen or a gas with increased hydrogen content directly into the loop increases the efficiency of current natural gas based direct reduction systems (such as ZR reactors or in-line reformers);
the swelling of the pellets at the start-up of the reactor is eliminated, which is characteristic of the use of CO as a reducing agent, which can lead to the stoppage of the flow of solids and to the clogging of the reactor.
Further features and advantages will become more apparent from the detailed description of illustrative but not exclusive embodiments.
In some embodiments, the source of pure hydrogen or the source of gas having a hydrogen content equal to at least 80% by volume is connected to the treatment and feed line or to the recovery and treatment line.
In some embodiments, the treatment and feed line comprises only at least one heating unit in addition to the first conduit through which the process gas is adapted to pass;
and wherein said recovery and treatment line comprises, in addition to a second conduit through which said exhaust gas is adapted to pass, only
At least one heat exchanger for cooling the exhaust gas exiting the reactor;
at least one condensing unit arranged downstream of said at least one heat exchanger for removing water from said exhaust gas, obtaining a dehydrated gas;
and at least one pumping device for pumping the dehydrated gas into the treatment and feed lines.
In some embodiments, in the case where an external source of make-up reducing gas is connected to the treatment and feed line, the source of pure hydrogen or the gas source having a hydrogen content equal to at least 80% by volume is connected to the section of the circuit comprised between the pumping means of the recovery and treatment line and the heating unit of the treatment and feed line.
In some embodiments, in the case where an external source of make-up reducing gas is connected to the recovery and treatment line, the source of pure hydrogen or the gas source having a hydrogen content equal to at least 80% by volume is connected to the section of the circuit comprised between the condensation unit and the pumping means.
In some embodiments, the second conduit of the recovery and disposal line comprises:
a first branch conduit connecting the recovery and treatment line to a burner of the heating unit and in which a first flow of dehydrated exhaust gas is delivered as combustible gas for the burner;
and a second branch conduit connecting the recovery and treatment line to the treatment and feed line, and along which the pumping device is arranged and in which a second stream of dehydrated exhaust gas is recirculated.
In some embodiments, the conduit of the first conduit adapted to be traversed by the process gas traverses the at least one heat exchanger for preheating of the process gas upstream of the heating unit.
In some embodiments, at least one natural gas injection device is provided, the at least one natural gas injection device being adapted to inject natural gas into the first pipeline upstream of the at least one heat exchanger.
In some embodiments, at least one natural gas injection device is provided, the at least one natural gas injection device being adapted to inject natural gas into a lower region of the reactor disposed below the reduction zone.
In some embodiments, the lower region is a tapered region.
Drawings
In the description reference is made to the accompanying drawings, which are given as non-limiting examples, and in which:
FIG. 1 illustrates a diagram of a first embodiment of a direct reduction system;
FIG. 2 illustrates a diagram of a second embodiment of a direct reduction system;
fig. 3 illustrates a diagram of a third embodiment of a direct reduction system.
Detailed Description
Some embodiments of a direct reduction system constituting the subject of the present invention are illustrated with reference to the accompanying drawings, comprising a circuit provided with:
a reactor 1, said reactor 1 having a reduction zone 12 adapted to be loaded with iron ore from above;
an external source 20 of make-up reducing gas;
a recovery and treatment line 10, said recovery and treatment line 10 being placed downstream of said reactor 1 to recover and treat the effluent gas leaving said reactor 1;
a treatment and feed line 11, said treatment and feed line 11 being placed upstream of said reactor 1 for treating a gas mixture or process gas obtained by mixing said make-up reducing gas from said external source 20 with said exhaust gas treated in said recovery and treatment line 10, and then supplying said process gas to the reduction zone 12 of the reactor 1.
The recovery and treatment line 10 communicates downstream with the treatment and feed line 11.
Advantageously, in all the embodiments of the present invention, the external source 20 of make-up reducing gas is a pure hydrogen source (100% by volume) or a gas source having a hydrogen content equal to at least 80% by volume, preferably equal to a value at least from 85% to 98% by volume.
In the case of a gas source having a hydrogen content equal to at least 80% by volume, the remainder of the composition may comprise carbon monoxide, water, carbon dioxide, methane, nitrogen.
Purely by way of example, the make-up reducing gas composition may be as follows:
hydrogen in the range of 92% -96%;
carbon monoxide in the range of 1.5% to 2.5%;
0.2% -0.6% of water;
0.0% -0.4% carbon dioxide;
0.3% -0.9% methane;
2.0% -4.0% of nitrogen.
In addition to allowing for a reduction in emissions, the use of such an external source also allows for a reduction in the number of devices traditionally located along the circuit, significantly simplifying the direct reduction system.
Advantageously, in all embodiments, the treatment and feed line 11 may comprise the following:
a duct (duct) through which the process gas obtained by mixing the treated exhaust gas leaving the reactor with the supplementary reducing gas in the external source 20 is adapted to pass;
and at least one heating unit, such as only one heating unit 18.
The system does not have any injection means arranged downstream of the heating unit 18 and adapted to inject oxygen into the reducing gas flow, which injection means are provided in prior art systems.
Further advantages of the system are represented by the fact that: the recovery and disposal line 10 may include the following:
a conduit through which the exhaust gases leaving the reactor 1 are adapted to pass;
at least one heat exchanger 22, for example only one heat exchanger, for cooling the exhaust gas leaving the reactor 1;
at least one condensation unit 36, for example only one condensation unit, arranged downstream of said at least one heat exchanger 22, for removing water from the exhaust gases, obtaining dehydrated gases;
and at least one pumping device 42, for example only one pumping device, for pumping the dehydrated gas towards the treatment and feed line 11.
Thus, the system of the present invention does not have any removal device for removing carbon dioxide, which is instead necessary in prior art systems.
Optionally, the conduit 15 in the treatment and feed line 11, which is adapted to be crossed by the process gas, passes through at least one heat exchanger 22 in the recovery and treatment line 10 for the preheating of the process gas upstream of the heating unit 18, exploiting the heat of the exhaust gas that has just left the reactor 1.
Preferably, the conduits in the recovery and treatment line 10 comprise, downstream of the condensation unit 36:
a branch conduit 34, the branch conduit 34 connecting the recovery and treatment line 10 to the burner of the heating unit 18, and in which branch conduit 34 a first flow of dehydrated exhaust gas may be delivered as combustible gas for said burner;
and a branch conduit 40, the branch conduit 40 connecting the recovery and treatment line 10 to the treatment and feed line 11, and a pumping device 42 being arranged along the branch conduit 40, and the second stream of dehydrated exhaust gas being recirculated in the branch conduit 40.
The pressure control valve 30 is preferably disposed along the branch conduit 34.
The heating unit 18 is supplied by combustion of a suitable combustible from a source 21. The combustible may be dehydrated exhaust gas from branch conduit 34, or pure hydrogen or natural gas or a mixture thereof.
In a first embodiment of the system shown in fig. 1, an external source 20 of pure hydrogen or an external source 20 of gas having a hydrogen content equal to at least 80% by volume is for example directly connected to the treatment and feed line 11.
In particular, the external source 20 is connected to the section of the circuit comprised between the pumping device 42 of the recovery and treatment line 10 and the heating unit 18 of the treatment and feed line 11 (stretch).
A pressure control valve 31 is arranged along a conduit 32, which conduit 32 connects the external source 20 to the process and feed line 11.
In a second embodiment of the system shown in fig. 2, an external source 20 of pure hydrogen or an external source 20 of gas having a hydrogen content equal to at least 80% by volume is for example directly connected to the recovery and treatment line 10.
In particular, the external source 20 is connected to a section of the circuit comprised between the condensation unit 36 and the pumping device 42, for example along the branch conduit 40. In this manner, make-up reducing gas may also be dispensed from external source 20 at low pressure and subsequently compressed by subsequent pumping device 42.
Further pumping means 33 and pressure control valves 31 are preferably provided along the conduit 32, the conduit 32 connecting the external source 20 to said recovery and treatment line 10.
In a third embodiment of the system shown in fig. 3 and similar to the embodiment in fig. 1, at least one first natural gas injection device 19 may be included along the duct 15 of the treatment and feed line 11, crossed by the process gas, this first natural gas injection device 19 being adapted to inject natural gas upstream of the heating unit 18 or, if a pre-heating of the process gas is provided by at least one heat exchanger 22, upstream of said heat exchanger 22.
As an alternative, or in addition to the first natural gas injection means 19, a variant of said third embodiment comprises at least one second natural gas injection means 17, said at least one second natural gas injection means 17 being adapted to inject natural gas directly into the lower, preferably conical, region 14 of the reactor 1 placed below the reduction zone 12. All variations of this third embodiment allow for adjustment of the DRI carbon content.
Also in this third embodiment, the external source 20 may for example be connected directly to the treatment and feed line 11 (fig. 3) or to the recovery and treatment line 10, as in fig. 2.
With regard to the direct reduction process implementable by the system of the present invention, pure hydrogen or a feed of gas having a hydrogen content equal to at least 80% by volume is provided in the treatment and feed line 11 or in the recovery and treatment line 10.
In case an external source 20 is connected to the treatment and feed line 11, the feeding takes place in a section comprised between the pumping means 42 of the recovery and treatment line 10 and the heating unit 18 of the treatment and feed line 11.
In the case where the external source 20 is connected to the recovery and treatment line 10, said feeding takes place in a section comprised between the condensation unit 36 and the pumping means 42 of said recovery and treatment line 10.
Described below is an example of a process for the direct reduction of iron ore by the described system of the invention when fully operational.
The exhaust gas leaving the reactor 1, preferably at a temperature in the range from about 250 ℃ to about 450 ℃, is directed into a conduit 50 in the recovery and treatment line 10, which conduit 50 carries the exhaust gas to a heat exchanger 22 for cooling the exhaust gas.
After cooling, the exhaust gas flows through conduit 24 towards condensing unit 36 to remove water, obtaining dehydrated gas.
After cooling and dewatering, the dewatered exhaust gas is split into two branch conduits 34, 40.
A small portion of the dehydrated vent gas flows through line 34, line 34 having a pressure control valve 30, with which pressure control valve 30 a portion of the gas can be purged through the circuit to eliminate the undesirable accumulation of inert gas. However, most of the dehydrated vent gas flows through conduit 40.
Referring to the embodiment in fig. 1 and in fig. 3, the dehydrated exhaust gas flowing in line 40 is pushed by a pumping device 42, which may be a compressor or blower, to recycle and re-bring the portion of dehydrated exhaust gas into reactor 1. Downstream of the pumping device 42, the dehydrated exhaust gas flows through a conduit 44 and is then mixed with make-up reducing gas from the external source 20 in the processing and feed line 11.
In contrast, referring to the second embodiment in fig. 2, the dehydrated exhaust gas flowing in the conduit 40 is mixed there with the supplemental reducing gas from the external source 20. The gas mixture thus obtained, defining the process gas, is pushed by pumping means 42, which may be a compressor or a blower, so as to bring it to duct 15 in the treatment and feed line 11.
In all embodiments, the gas mixture continues to flow along the conduit 15, in which conduit 15 it is preferably preheated, conduit 15 being able to pass with its section through the heat exchanger 22 in the recovery and disposal line 10.
In any case, with or without this preheating, the gas mixture passes through the entire duct 15 until it reaches the heating unit 18, where it reaches a temperature of about 900-960 ℃.
Downstream of the heating unit 18, the reducing gas thus obtained flows through the duct 16 until it reaches the interior of the reactor 1.
Iron oxide ore in the form of lumps or pellets is supplied into the reduction zone 12 of the reactor 1 from above, which iron oxide ore reacts with hot reducing gas flowing counter-currently with respect to the iron oxide ore and is finally discharged as hot DRI.
Optionally, the iron oxide ore has a size of about 2.5mm to 19 mm; preferably about 3.5mm to 15mm in size.

Claims (18)

1. A direct reduction system for direct reduction of iron ore, characterized in that the direct reduction system comprises a circuit provided with:
a reactor (1), said reactor (1) having a reduction zone (12) adapted to be loaded with said iron ore from above;
an external source (20) of make-up reducing gas;
a recovery and treatment line (10), said recovery and treatment line (10) being placed downstream of said reactor (1) for recovering and treating the effluent gas leaving said reactor (1),
a treatment and feeding line (11), said treatment and feeding line (11) being placed upstream of said reactor (1), for treating a process gas obtained by mixing said make-up reducing gas from said external source (20) with said exhaust gas treated in said recovery and treatment line (10), and for feeding said process gas to said reduction zone (12) of said reactor (1);
wherein the recovery and treatment line (10) is in downstream communication with the treatment and feed line (11);
and wherein said external source (20) of make-up reducing gas is a pure hydrogen source or a gas source having a hydrogen content equal to at least 80% by volume.
2. Direct reduction system according to claim 1, wherein the source of pure hydrogen or the gas source having a hydrogen content equal to at least 80% by volume is connected to the treatment and feed line (11) or to the recovery and treatment line (10).
3. Direct reduction system according to claim 1, wherein the treatment and feed line (11) comprises, in addition to the first conduit through which the process gas is adapted to pass, only at least one heating unit (18);
and wherein said recovery and treatment line (10) comprises, in addition to a second conduit through which said exhaust gases are suitable to pass, only
At least one heat exchanger (22) for cooling the exhaust gas leaving the reactor (1);
at least one condensation unit (36) arranged downstream of said at least one heat exchanger (22) for removing water from said exhaust gas, obtaining a dehydrated gas;
and at least one pumping device (42) for pumping the dehydrated gas into the treatment and feed line (11).
4. Direct reduction system according to claim 2, wherein the treatment and feed line (11) comprises, in addition to the first conduit through which the process gas is adapted to pass, only at least one heating unit (18);
and wherein said recovery and treatment line (10) comprises, in addition to a second conduit through which said exhaust gases are suitable to pass, only
At least one heat exchanger (22) for cooling the exhaust gas leaving the reactor (1);
at least one condensation unit (36) arranged downstream of said at least one heat exchanger (22) for removing water from said exhaust gas, obtaining a dehydrated gas;
and at least one pumping device (42) for pumping the dehydrated gas into the treatment and feed line (11).
5. Direct reduction system according to claim 3, wherein, in the case of connection of an external source of make-up reducing gas to the treatment and feed line (11), the source of pure hydrogen or the source of gas having a hydrogen content equal to at least 80% by volume is connected to a section of the circuit comprised between the pumping means (42) of the recovery and treatment line (10) and the heating unit (18) of the treatment and feed line (11).
6. Direct reduction system according to claim 4, wherein, in the case of connection of an external source of make-up reducing gas to the treatment and feed line (11), the source of pure hydrogen or the source of gas having a hydrogen content equal to at least 80% by volume is connected to a section of the circuit comprised between the pumping means (42) of the recovery and treatment line (10) and the heating unit (18) of the treatment and feed line (11).
7. Direct reduction system according to claim 3, wherein, in the case of connection of an external source of make-up reducing gas to the recovery and treatment line (10), the source of pure hydrogen or the source of gas having a hydrogen content equal to at least 80% by volume is connected to the section of the circuit comprised between the condensation unit (36) and the pumping means (42).
8. Direct reduction system according to claim 4, wherein, in the case of connection of an external source of make-up reducing gas to the recovery and treatment line (10), the source of pure hydrogen or the source of gas having a hydrogen content equal to at least 80% by volume is connected to the section of the circuit comprised between the condensation unit (36) and the pumping means (42).
9. Direct reduction system according to any of claims 3 to 8, wherein the second conduit of the recovery and treatment line (10) comprises:
a first branch conduit (34), the first branch conduit (34) connecting the recovery and treatment line (10) to a burner of the heating unit (18) and in which first branch conduit (34) a first flow of dehydrated exhaust gas is conveyed as combustible gas for the burner;
and a second branch conduit (40), said second branch conduit (40) connecting said recovery and treatment line (10) to said treatment and feed line (11), and said pumping means (42) being arranged along said second branch conduit (40), and a second flow of dehydrated exhaust gas being recirculated in said second branch conduit (40).
10. Direct reduction system according to any of claims 3 to 8, wherein a conduit (15) of the first conduits adapted to be traversed by the process gas traverses the at least one heat exchanger (22) for preheating of the process gas upstream of the heating unit (18).
11. Direct reduction system according to claim 9, wherein a duct (15) of the first ducts adapted to be traversed by the process gas traverses the at least one heat exchanger (22) for preheating of the process gas upstream of the heating unit (18).
12. Direct reduction system according to claim 10, wherein at least one first natural gas injection device (19) is provided, the at least one first natural gas injection device (19) being adapted to inject natural gas into the first pipeline upstream of the at least one heat exchanger (22).
13. Direct reduction system according to claim 11, wherein at least one first natural gas injection device (19) is provided, the at least one first natural gas injection device (19) being adapted to inject natural gas into the first pipeline upstream of the at least one heat exchanger (22).
14. Direct reduction system according to any of claims 1-8 and 11-13, wherein at least one second natural gas injection device (17) is provided, the at least one second natural gas injection device (17) being adapted to inject natural gas into a lower region (14) of the reactor (1) placed below the reduction zone (12).
15. Direct reduction system according to claim 9, wherein at least one second natural gas injection device (17) is provided, the at least one second natural gas injection device (17) being adapted to inject natural gas into a lower region (14) of the reactor (1) placed below the reduction zone (12).
16. Direct reduction system according to claim 10, wherein at least one second natural gas injection device (17) is provided, the at least one second natural gas injection device (17) being adapted to inject natural gas into a lower region (14) of the reactor (1) placed below the reduction zone (12).
17. Direct reduction system according to claim 14, wherein the lower zone (14) is a conical zone.
18. Direct reduction system according to any of claims 15-16, wherein the lower zone (14) is a conical zone.
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AT410324B (en) * 2001-07-13 2003-03-25 Voest Alpine Industrianlagenba METAL PRODUCTION METHOD AND INSTALLATION, PREFERABLY FOR STEEL PRODUCTION, OF FINE-CARBON METAL OXIDE
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