JP5714750B1 - Directly reduced iron manufacturing facility and direct reduced iron manufacturing method - Google Patents

Abstract

Provided is a production facility for directly reduced iron that can reduce the amount of coke oven gas used for producing directly reduced iron by effectively using fuel gas having a higher nitrogen concentration than coke oven gas. To do. A direct reduced iron manufacturing facility 100 that directly reduces iron oxide by bringing a raw material 32 containing iron oxide into contact with a reducing gas containing carbon monoxide and hydrogen in a direct reduction furnace 30, and directly reducing the iron oxide. The recirculation part 20 which introduce | transduces the reducing gas containing the circulation gas obtained by processing the exhaust gas from the furnace 30 directly to the reduction furnace 30, carbon monoxide, carbon dioxide, and nitrogen are contained, and nitrogen concentration is 10 A gas supply unit that supplies a supply gas having a lower nitrogen concentration and a higher carbon monoxide concentration than the fuel gas, which is obtained by refining the fuel gas that is equal to or greater than volume%, to the circulation unit 20; [Selection] Figure 1

Description

  The present invention relates to a production facility for directly reduced iron and a method for producing directly reduced iron.

  There is known a method of directly reducing iron by reducing iron oxide contained in iron ore by bringing it into contact with a reducing gas such as carbon monoxide or hydrogen in a direct reduction furnace. A coke oven gas (COG) generated at an ironworks is used as a reducing gas material used in such a method.

  By the way, of the fuel gas obtained at the steelworks, the coke oven gas has a high calorific value, so that it is effectively used as a heat source for heating steel slabs in the steelworks other than directly producing reduced iron. Usually the amount is small. On the other hand, as a fuel gas obtained at an ironworks, there is a converter gas (BOFG) in addition to a coke oven gas. Since this converter gas has a higher concentration of carbon dioxide and nitrogen and a lower amount of heat than the coke oven gas, its use is limited to that of the coke oven gas. As shown in Patent Document 1, the carbon dioxide concentration and nitrogen concentration of coke oven gas are 1-2% and 3-7%, respectively, whereas the carbon dioxide concentration and nitrogen concentration of converter gas are , 13 to 18% and 11 to 20%, respectively.

  Under such circumstances, Patent Document 1 proposes to use converter gas as a raw material for reducing gas supplied directly to the reducing furnace. In this patent document 1, it is proposed that the mixing ratio of the coke oven gas to the converter gas is 0.95 to 1.25 to directly produce reduced iron without releasing the fuel gas component to the outside of the facility. ing.

U.S. Pat. No. 8,496,730

  As described above, coke oven gas (COG) has a higher calorific value than other fuel gases obtained at steelworks. For this reason, in the production of direct reduced iron, if the coke oven gas used as the supply gas can be replaced with another fuel gas having a lower calorific value than the coke oven gas, the coke oven gas is effective for other applications. Can be used. Other fuel gases include converter gas (BOFG) and blast furnace gas (BFG). However, since these are high in nitrogen concentration, when the supply amount is increased, the nitrogen concentration in the circulation part of the direct reduction furnace rises, making it difficult to circulate and use the exhaust gas of the direct reduction furnace. It is necessary to discharge the exhaust gas to the outside.

  For example, when the nitrogen concentration of the supply gas exceeds 10% by volume, the nitrogen concentration in the exhaust gas exceeds 20% by volume, and as a result, the nitrogen concentration in the gas flowing through the circulation section increases and the iron oxide is sufficiently consumed. It becomes difficult to reduce. On the other hand, when the nitrogen concentration of the supply gas is, for example, less than 6% by volume, the nitrogen concentration in the exhaust gas can be less than 12% by volume.

  This invention is made | formed in view of the said situation, and reduces the usage-amount of the coke oven gas used for manufacture of direct reduced iron by utilizing effectively the fuel gas whose nitrogen concentration is higher than coke oven gas. An object is to provide a production facility for directly reduced iron that can be used. Also provided is a method for producing directly reduced iron capable of reducing the amount of coke oven gas used for producing directly reduced iron by effectively using fuel gas having a higher nitrogen concentration than coke oven gas. For the purpose.

  The present invention is a direct reduction iron production facility for directly reducing iron oxide by bringing a raw material containing iron oxide into contact with a reducing gas containing carbon monoxide and hydrogen in a direct reduction furnace. A reductive gas containing a recirculation gas obtained by treating the exhaust gas of the recycle gas directly into the reduction furnace, containing carbon monoxide, carbon dioxide and nitrogen, and a nitrogen concentration of 10% by volume or more Provided is a production facility for directly reduced iron, comprising: a gas supply unit that supplies, to a circulation unit, a supply gas having a lower nitrogen concentration and a higher carbon monoxide concentration than the fuel gas obtained by refining the fuel gas.

  According to the present invention, the gas supply unit purifies the fuel gas having a high nitrogen concentration, prepares the supply gas having a lower nitrogen concentration and a higher carbon monoxide concentration than the fuel gas, and circulates the supply gas. Supply to the department. For this reason, even if it uses fuel gas which has nitrogen concentration higher than coke oven gas as fuel gas, the increase in the nitrogen concentration in exhaust gas and circulating gas can be suppressed. Therefore, it becomes possible to sufficiently reduce the emission amount of the exhaust gas to the outside of the directly reduced iron production facility. Thus, according to the directly reduced iron production facility of the present invention, the amount of coke oven gas used can be reduced by effectively using the fuel gas having a high nitrogen concentration.

  In some embodiments, the nitrogen concentration of the feed gas may be 10% by volume or less, preferably 6% by volume or less. With such a nitrogen concentration, the nitrogen concentration in the exhaust gas and the reducing gas can be further reduced. Therefore, the emission of exhaust gas from the direct reduction furnace can be stopped, and the fuel gas can be used more effectively.

  In some embodiments, the circulation unit includes a heating device that heats the reducing gas, and heats a gas containing nitrogen and hydrogen and / or carbon monoxide discharged from the gas supply unit. It may be burned with. Thereby, the fuel gas whose nitrogen concentration is 10 volume% or more can be used efficiently.

In some embodiments, the gas supply unit includes a gas purification device that adsorbs and desorbs both carbon monoxide and carbon dioxide contained in the fuel gas, and the supply includes carbon monoxide and carbon dioxide as main components. You may be comprised so that gas may be supplied to a circulation part. Thus, by having a purification unit that adsorbs and desorbs both carbon monoxide and carbon dioxide contained in the fuel gas, the equipment can be made compact. Circulating unit includes a de-CO ₂ device, by supplying the de-CO ₂ device is combined with the feed gas and the exhaust gas upstream of the de CO ₂ device, to reduce the CO ₂ concentration in the reducing gas May be.

  In some embodiments, the gas supply unit adsorbs and desorbs the first gas purification device that adsorbs or absorbs carbon dioxide contained in the fuel gas, and the carbon monoxide contained in the gas from the first gas purification device. A second gas purification device, and a supply gas containing carbon monoxide as a main component may be supplied to the circulation unit. By having such a gas purifier, the concentration of carbon monoxide and carbon dioxide in the supply gas can be adjusted flexibly.

  In some embodiments, the circulation unit includes a shift reactor, and the supply gas and the exhaust gas are merged and supplied to the shift reactor on the upstream side of the shift reactor, and the supply gas and the exhaust gas are supplied by the water gas shift reaction. A circulating gas having a higher hydrogen concentration may be prepared. By providing the shift reactor in this way, the hydrogen concentration in the reducing gas can be increased. Since hydrogen has a smaller molecular size than carbon monoxide, it can easily penetrate into the iron ore. Therefore, increasing the hydrogen concentration in the reducing gas is effective for improving the reaction rate of the reduction reaction in the direct reduction furnace. In addition, the supply gas and the exhaust gas are merged upstream of the shift reactor, and both the exhaust gas and the supply gas are supplied to the shift reactor to prepare the reducing gas, thereby reducing the hydrogen of the reducing gas. The concentration can be further increased.

  In some embodiments, the circulation unit may include an adjustment unit that adjusts the temperature and humidity of at least one of the exhaust gas and the supply gas between the direct reduction furnace and the shift reactor. Thereby, the shift reaction in the shift reactor can proceed with high reaction efficiency.

  In some embodiments, the adjustment unit may include a wet dust collector and a self-heat exchange heat exchanger that exchanges heat between the gas on the inlet side and the gas on the outlet side of the wet dust collector. This makes it possible to adjust the temperature and humidity of these gases to conditions suitable for the shift reaction while collecting the exhaust gas and the supply gas. Therefore, the shift reactor can be operated stably with high efficiency.

  In some embodiments, the adjustment unit may include a sprinkling cooling tower that cools and humidifies the exhaust gas and a dry dust collector from the upstream side. Thereby, the exhaust gas temperature and humidity can be adjusted to conditions suitable for the shift reaction. In addition, the exhaust gas can be collected with simple equipment. Therefore, the shift reactor can be operated stably with high efficiency.

  The present invention is also a method for producing directly reduced iron by directly reducing iron oxide by bringing a raw material containing iron oxide into contact with a reducing gas containing carbon monoxide and hydrogen in a direct reducing furnace. A reductive gas containing a recirculating gas obtained by treating the exhaust gas of the gas directly into the reducing furnace, carbon monoxide, carbon dioxide and nitrogen are contained, and the nitrogen concentration is 10% by volume or more. There is provided a method for producing directly reduced iron, comprising: purifying a fuel gas, and supplying a supply gas having a lower nitrogen concentration and a higher carbon monoxide concentration than the fuel gas into a circulating gas.

  According to the present invention, a fuel gas having a nitrogen concentration of 10% by volume or more is purified to prepare a supply gas having a lower nitrogen concentration and a higher carbon monoxide concentration than the fuel gas, and the supply gas is used as a circulating gas. To join. For this reason, even if it uses fuel gas which has nitrogen concentration higher than coke oven gas as fuel gas, the increase in the nitrogen concentration in exhaust gas and reducing gas can be suppressed. Therefore, it is possible to sufficiently reduce the amount of exhaust gas released to the outside of the directly reduced iron production facility. Thus, according to the method for producing directly reduced iron of the present invention, the amount of coke oven gas used can be reduced by effectively using the fuel gas having a high nitrogen concentration.

  In some embodiments, the nitrogen concentration of the feed gas may be 6% by volume or less. Thereby, the increase in the nitrogen concentration in the exhaust gas and the reducing gas can be sufficiently suppressed. Therefore, the emission of exhaust gas from the direct reduction furnace can be stopped, and the fuel gas can be used more effectively.

  In some embodiments, a gas having a higher nitrogen concentration than the fuel gas and containing hydrogen and / or carbon monoxide obtained by refining the fuel gas in the supplying step is heated with a heating device that heats the reducing gas. It may be burned. Thereby, the fuel gas whose nitrogen concentration is 10 volume% or more can be used efficiently.

  In some embodiments, the supplying step may adsorb and desorb both carbon monoxide and carbon dioxide contained in the fuel gas to obtain a supply gas containing carbon monoxide and carbon dioxide as main components. . Thus, by having a purification unit that adsorbs and desorbs both carbon monoxide and carbon dioxide contained in the fuel gas, the equipment can be made compact.

  In some embodiments, in the supplying step, carbon dioxide contained in the fuel gas is adsorbed or absorbed and removed, and then carbon monoxide contained in the gas from which the carbon dioxide has been removed is adsorbed and desorbed as a main component. A feed gas containing carbon monoxide may be obtained. By such a method, the concentration of carbon monoxide and carbon dioxide can be adjusted flexibly.

  In some embodiments, in the supply step, after the supply gas is merged with the circulation gas, a reducing gas having a higher hydrogen concentration than the supply gas and the exhaust gas may be obtained by a water gas shift reaction. Thereby, the hydrogen concentration of the reducing gas can be further increased. In some embodiments, the temperature and humidity of at least one of the exhaust gas and the feed gas may be adjusted prior to the water gas shift reaction. Thereby, the shift reaction in the shift reactor can proceed with high reaction efficiency.

  According to the present invention, the production of directly reduced iron capable of reducing the amount of coke oven gas used for the production of directly reduced iron by effectively using a fuel gas having a higher nitrogen concentration than the coke oven gas. Facilities can be provided. Also provided is a method for producing directly reduced iron capable of reducing the amount of coke oven gas used for producing directly reduced iron by effectively using fuel gas having a higher nitrogen concentration than coke oven gas. be able to.

It is the schematic which shows one Embodiment of the manufacturing equipment of the direct reduction iron of this invention. It is the schematic which shows another embodiment of the manufacturing equipment of the direct reduction iron of this invention. It is the schematic which shows another embodiment of the manufacturing apparatus of the direct reduction iron of this invention. It is the schematic which shows another embodiment of the manufacturing apparatus of the direct reduction iron of this invention. It is the schematic which shows an example of the gas purification apparatus with which the manufacturing apparatus of the direct reduction iron of this invention is equipped. It is the schematic which shows another example of the gas purification apparatus with which the manufacturing apparatus of the direct reduction iron of this invention is equipped. It is the schematic which shows another example of the gas purification apparatus with which the manufacturing apparatus of the direct reduction iron of this invention is equipped.

  Preferred embodiments of the present invention will now be described, optionally with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic view of a directly reduced iron production facility 100 in the present embodiment. The directly reduced iron production facility 100 according to the present embodiment includes a fuel gas different from the coke oven gas, a gas supply unit 10 for supplying the coke oven gas, and a raw material containing iron oxide and a reducing gas are brought into contact with each other to oxidize. A direct reduction furnace 30 that directly reduces iron, and a circulation unit 20 that circulates a reducing gas obtained by treating exhaust gas discharged from the direct reduction furnace 30 and introduces it directly into the reduction furnace 30 are provided.

  The gas supply unit 10 includes carbon monoxide, carbon dioxide, hydrogen, and nitrogen, and is configured to be able to separately supply the fuel gas having a nitrogen concentration of 10% by volume or more and the coke oven gas to the circulation unit 20. ing. The nitrogen concentration in the fuel gas may be, for example, 10 to 60% by volume. Examples of such fuel gas include converter gas (BOFG), blast furnace gas (BFG), and a mixed gas thereof. The fuel gas may contain, for example, hydrogen, a hydrocarbon such as methane, and water in addition to the above-described components. The composition of the fuel gas is, for example, 10-60% by volume of nitrogen, 20-80% by volume of carbon monoxide, 5-30% by volume of carbon dioxide, 0-10% by volume of hydrogen, and 0-5% by volume of methane. And 0 to 5% by volume of water. Note that the gas volume% and volume ratio in this specification are all values based on standard conditions (0 ° C., 1 atm).

  The fuel gas in the gas supply unit 10 is introduced into the gas purification device 12 through the gas flow path 11 constituted by piping and the like. As the gas purification device 12, for example, carbon monoxide and / or carbon dioxide is selectively absorbed using an adsorbent, and carbon dioxide is selectively used using an alkaline aqueous solution such as amine as an absorbing solution. An absorption tower that absorbs water. The gas purification device 12 may include one or more pressure swing adsorption devices and / or one or more absorption towers. For example, a plurality of pressure swing adsorption devices may be arranged in series to refine the fuel gas sequentially. In this case, the plurality of pressure swing adsorption devices may include different adsorbents.

  Known adsorbents and absorbents can be used. Examples of the adsorbent include porous adsorbents such as activated carbon, zeolite, silica gel, and cerium oxide. Examples of the absorbent include organic alkaline absorbents such as MEA (monoethanolamine) and MDEA (methyldiethanolamine). However, it is needless to say that the adsorbent and the absorbent are not limited to those described above, and other adsorbent and absorbent may be used.

The fuel gas is separated in the gas purification device 12 into a first gas having a high nitrogen concentration and a second gas having a lower nitrogen concentration than the first gas and having a high carbon monoxide concentration. The Since the first gas is mainly composed of nitrogen, it may be discharged from the gas flow path 14 to the outside. On the other hand, the second gas is pressurized to about 0.4 MPa by the gas compressor 15, then flows through the gas flow path 16 and is introduced into the circulation unit 20 as a supply gas. The gas flow path 16 is connected to the upstream side of the de-CO ₂ device 28 of the circulation unit 20. Accordingly, the second gas (supply gas) joins with the circulating gas that circulates in the circulation unit 20 at the connection portion, and is then introduced into the de-CO ₂ device 28. In the de-CO ₂ device 28, at least a part of carbon dioxide contained in the circulating gas is removed. As described above, since the supply gas is introduced to the upstream side of the de-CO ₂ device 28, the supply gas may contain a considerable amount of carbon dioxide. For example, the carbon dioxide concentration of the supply gas may exceed 10% by volume, for example, 11-25% by volume.

  A gas flow path 17 is connected to the gas flow path 11 so that a part of the fuel gas can be combusted by the heating device 29. A part of the fuel gas may be circulated through the gas flow path 17 and burned as a heat source by the heating device 29.

The coke oven gas is introduced from the gas supply unit 10 to the circulation unit 20 in a separate system from the fuel gas. The coke oven gas flows through the gas flow path 40 of the gas supply unit 10 and is introduced into the gas compressor 42. The coke oven gas is pressurized to about 0.7 MPa by the gas compressor 42, then flows through the gas flow path 44 and is introduced into the circulation unit 20. The carbon dioxide concentration of the coke oven gas is usually 1 to 2% by volume, which is lower than the fuel gas. For this reason, the gas flow path 44 is connected to the downstream side of the CO ₂ removal device of the circulation unit 20. Accordingly, the coke oven gas joins with a circulating gas (reducing gas) in which carbon dioxide is sufficiently reduced.

  In this embodiment, since the gas supply unit 10 includes the gas purification device 12, the fuel gas supply ratio can be sufficiently increased. The ratio of the fuel gas to the sum of the coke oven gas and the fuel gas can be, for example, 40% or more, or 60% or more, or 80% or more on the basis of the lower heating value.

  The circulation unit 20 processes exhaust gas discharged from the top of the direct reduction furnace 30 to form a circulation gas, and introduces the reducing gas obtained by joining the supply gas to the circulation gas directly into the reduction furnace 30. The exhaust gas contains carbon dioxide, carbon monoxide, hydrogen and water, and contains carbon monoxide and hydrogen having reducibility. Therefore, the circulation unit 20 processes the exhaust gas to reduce or remove components such as carbon dioxide and water that do not contribute to the reduction, and allows the component that contributes to the reduction to be reused as the reducing gas. .

  The exhaust gas discharged from the direct reduction furnace 30 is introduced into the heat exchanger 23 via the gas flow path 22. This exhaust gas contains carbon dioxide and water produced by the reduction of iron oxide, and unreacted carbon monoxide and hydrogen derived from the reducing gas. The temperature of the exhaust gas at the outlet of the direct reduction furnace 30 is, for example, 300 to 500 ° C. This exhaust gas is cooled to, for example, 200 to 350 ° C. by the heat exchanger 23. A dry dust collector 24 is provided on the downstream side of the heat exchanger 23. As the dry dust collector 24, an electric dust collector, a ceramic filter, or the like can be used. The dry dust collector 24 removes solids contained in the exhaust gas. Note that a wet dust collector (a venturi scrubber) may be provided instead of the dry dust collector 24.

A gas cooling device 26, a gas compressor 27, and a CO ₂ removal device 28 are provided in this order on the downstream side of the dry dust collector 24. In the gas cooling device 26, the exhaust gas is cooled to remove moisture contained in the exhaust gas. The gas cooling device 26 and the gas compressor 27 adjust the pressure and temperature of the exhaust gas to a range suitable for processing in the de-CO ₂ device 28.

  A gas flow path 16 that supplies a supply gas (second gas) is connected to a gas flow path between the gas cooling device 26 and the gas compressor 27. As a result, the supply gas merges with the circulation gas and flows through the circulation unit 20. In addition, the gas flow path 18 may be connected to the upstream side from the confluence | merging position of supply gas and exhaust gas. The gas flow path 18 is connected to the fuel gas flow path 17 of the heating device 29. A part of the exhaust gas may be burned by the heating device 29 using the gas flow path 18. By discharging a part of the exhaust gas containing nitrogen to the outside of the circulation unit 20 and consuming it as fuel for the heating device 29, an increase in the nitrogen concentration of the circulation gas flowing through the circulation unit 20 can be suppressed.

As the de-CO ₂ device 28, a normal carbon dioxide removal facility that removes carbon dioxide by gas-liquid contact can be used. As an absorbent used in such equipment, for example, an organic alkaline absorbent such as MEA (monoethanolamine) and MDEA (methyldiethanolamine) can be used. In this case, the temperature of the gas at the inlet of the de-CO ₂ device 28 is about 40 ° C., for example.

A gas flow path 44 is connected to the downstream side of the de-CO ₂ device 28. The coke oven gas flows through the gas flow path 44 and is supplied to the circulation unit 20 and merges with the gas from which carbon dioxide has been removed by the de-CO ₂ device 28 (circulation gas). Coke oven gas usually has a low dioxide concentration. Therefore, as in the present embodiment, it is possible to join the downstream side of the de CO ₂ 28.

  The circulating gas is heated to, for example, 800 to 1100 ° C. by the heating device 29 after joining the coke oven gas. As the heating device 29, a heating device in which a combustor and a high-temperature heat exchanger are combined can be used. The reducing gas obtained by combining the supply gas and the coke oven gas with the circulating gas is heated by the heating device 29 and then directly introduced into the reducing furnace 30.

  The temperature of the reducing gas introduced into the direct reduction furnace 30 is preferably 800 to 1100 ° C., more preferably 850 to 1050 ° C. when supplied to the direct reduction furnace 30. By setting it as such a temperature range, the reductive reaction in the direct reduction furnace 30 can be advanced more smoothly.

  A raw material 32 (iron content: 60 to 70% by mass) such as iron ore cut out from a hopper is supplied to the direct reduction furnace 30 via a charging pipe connected to the direct reduction furnace 30. . The raw material 32 is brought into contact with the reducing gas while being heated to 750 to 1050 ° C. in the direct reduction furnace 30. Thereby, iron oxide is reduced and reduced iron is obtained directly. The direct reduced iron 34 thus obtained is discharged from the bottom of the direct reduction furnace 30. The iron content of the directly reduced iron 34 is, for example, 80 to 95% by mass.

  The direct reduced iron production facility 100 is a reductive gas introduced into the direct reduction furnace 30 or a reducing gas obtained by refining the fuel gas and having a lower nitrogen concentration and a higher carbon monoxide concentration than the fuel gas. Used as a raw material. As described above, the directly reduced iron manufacturing facility 100 can reduce the amount of coke oven gas used by effectively using the fuel gas.

FIG. 2 is a schematic view of a directly reduced iron production facility 101 according to another embodiment. The directly reduced iron manufacturing facility 101 is different from the directly reduced iron manufacturing facility 100 in the connection position of the gas flow path 16 of the supply gas (second gas) obtained by purifying the fuel gas with the gas purifier 12. . That is, in the directly reduced iron production facility 101, the gas flow path 16 is connected to the gas flow path 21 between the de-CO ₂ device 28 and the heating device 29 in the circulation unit 20. Thus, at the downstream side of the de-CO ₂ device 28, by merging the feed gas to the circulating gas, it is possible to reduce the processing amount of de CO ₂ 28.

In the directly reduced iron production facility 101, the supply gas is directly introduced into the reduction furnace 30 from the circulation unit 20 without being processed by the de-CO ₂ device 28. For this reason, it is preferable to reduce the carbon dioxide concentration of the fuel gas in the gas purifier 12 to reduce the carbon dioxide concentration of the supply gas. As the gas purification device 12, for example, a pressure swing adsorption device that adsorbs carbon monoxide and carbon dioxide using an adsorbent, or as an absorbing solution, for example, an organic material such as MEA (monoethanolamine) and MDEA (methyldiethanolamine). It is preferable to have an absorption tower or the like that selectively absorbs carbon dioxide using a system alkaline absorption liquid. Known adsorbents and absorbents can be used.

  The directly reduced iron production facility 101 is different from the directly reduced iron production facility 100 in the supply destination of the first gas obtained by the gas purifier 12 and having a higher nitrogen concentration than the second gas. In other words, in the directly reduced iron production facility 101, the gas flow path 14 that conveys the first gas is connected to the gas flow path 17 that supplies fuel to the heating device 29. When the concentration of carbon dioxide contained in the second gas is reduced by the gas purification device 12, the concentration of carbon monoxide contained in the first gas tends to increase. For this reason, the 1st gas containing carbon monoxide can be used effectively by setting it as the structure which can utilize 1st gas as a fuel of the heating apparatus 29. FIG. Other configurations of the directly reduced iron manufacturing facility 101 are the same as those of the directly reduced iron manufacturing facility 100.

  In the directly reduced iron production facility 101, the gas flow path 16 of the second gas is connected to the upstream side of the circulation unit 20 with respect to the gas flow path 44 of the coke oven gas, but is not limited to such a configuration. . In some other embodiments, the second gas and the coke oven gas may be merged and then merged with the circulating gas that circulates in the circulation unit 20, and the coke oven gas is the first. You may merge with circulation gas upstream from 2 gas.

  FIG. 3 is a schematic view of a directly reduced iron production facility 102 according to still another embodiment. The directly reduced iron manufacturing facility 102 includes a heat exchanger 23B that cools the exhaust gas discharged from the direct reduction furnace 30. Here, the exhaust gas is cooled to, for example, 200 to 350 ° C. by exchanging heat with the exhaust gas output from the gas compressor 27. From the viewpoint of adjusting the temperature to a temperature suitable for the shift reaction in the shift reactor 25, the heat exchanger 23B is preferably a self-heat exchange type heat exchanger as shown in FIG.

  In the directly reduced iron production facility 102, the connection position of the gas flow path 16 of the supply gas (second gas) obtained by refining the fuel gas with the gas purification device 12 is directly connected to the directly reduced iron production facilities 100 and 101. Is different. That is, in the directly reduced iron manufacturing facility 102, the gas flow path 16 is connected to a gas flow path between the gas compressor 27 and the heat exchanger 23B of the circulation unit 20.

  The directly reduced iron production facility 102 includes a wet dust collector 24B. The exhaust gas cooled by the heat exchanger 23B is introduced into the wet dust collector 24B. Connected to the wet dust collector 24B are a water supply unit 62 for supplying water to the wet dust collector 24B and a water discharge unit 64 for discharging water containing dust from the wet dust collector 24B.

  The exhaust gas from which the dust has been removed by the wet dust collector 24 </ b> B is introduced into the gas compressor 27. The exhaust gas is humidified while the dust is removed by the wet dust collector 24B. The moisture (volume%) of the exhaust gas in the gas passage 22 is less than 20%, whereas the moisture (volume%) at the outlet of the wet dust collector 24B is 20 to 30%. Thus, since the exhaust gas contains a considerable amount of moisture when introduced into the shift reactor 25, the shift reaction described later can sufficiently proceed.

The exhaust gas is increased in pressure from, for example, about 0.6 to about 0.9 MPa by the gas compressor 27, and then introduced into the heat exchanger 23 </ b> B to exchange heat with the exhaust gas directly discharged from the reduction furnace 30. The exhaust gas whose pressure has been increased by the gas compressor 27 by heat exchange is raised to 200 to 350 ° C., for example. That is, the exhaust gas is adjusted to a temperature and humidity suitable for processing in the shift reactor 25 by the heat exchanger 23B and the wet dust collector 24B. That is, the heat exchanger 23B and the wet dust collector 24B constitute an exhaust gas adjusting unit 50. Since such an adjustment unit 50 is provided, the water gas shift reaction can sufficiently proceed without injecting water vapor from the outside or supplying a heat source. Since the exhaust gas is boosted by the gas compressor 27, it is not necessary to provide a gas compressor between the gas cooling device 26 and the de-CO ₂ device 28 unlike the directly reduced iron production facility 101. .

A shift reactor 25 is provided on the downstream side of the heat exchanger 23B. The dust concentration of the gas at the inlet of the shift reactor 25 is preferably 5 mg / m ³ or less. In the shift reactor 25, the water gas shift reaction represented by the following formula (1) proceeds by the catalyst. As a result, carbon dioxide and hydrogen are generated from carbon monoxide and water contained in the exhaust gas. By this reaction, the volume ratio of hydrogen to carbon monoxide in the gas can be increased. Specifically, the reaction at the outlet of the shift reactor 25 obtained by the water gas shift reaction, while the volume ratio of hydrogen to carbon monoxide of the exhaust gas before being introduced into the shift reactor 25 is about 1. The volume ratio of hydrogen to carbon monoxide can be 1 or more, for example, 3-6.

CO + H ₂ O → CO ₂ + H ₂ (1)

The reaction gas obtained in the shift reactor 25 contains carbon dioxide generated by the reduction reaction in the direct reduction furnace 30 and the water gas shift reaction. For this reason, the carbon dioxide concentration of the reaction gas is higher than the carbon dioxide concentration of the exhaust gas. At least a part of carbon dioxide contained in the reaction gas is removed by a de-CO ₂ device 28 provided on the downstream side of the shift reactor 25. Since the de-CO ₂ device 28 for removing carbon dioxide is provided on the downstream side of the shift reactor 25 in this way, carbon dioxide can be efficiently removed.

  The directly reduced iron production facility 102 includes the gas purification unit 12 in the gas supply unit 10 and the shift reactor 25 in the circulation unit 20, so that the coke oven gas having a high hydrogen concentration is usually further reduced. The ratio of the fuel gas having a nitrogen concentration of 10% by volume or more, such as converter gas or blast furnace gas, can be sufficiently increased. It is possible to operate with only fuel gas such as converter gas or blast furnace gas without using coke oven gas at all.

  Even if the fuel gas is operated only with a fuel gas different from the coke oven gas, the reduction reaction of the raw material 32 can proceed sufficiently quickly. The hydrogen concentration of the reducing gas is preferably 40% by volume or more, more preferably 45% by volume or more from the viewpoint of allowing the reduction reaction to proceed sufficiently quickly. From the same viewpoint, the volume ratio of hydrogen to carbon monoxide in the reducing gas is preferably 1 or more.

You may provide the gas flow path 19 which connects between the wet dust collector 24B and the gas compressor 27, and the gas flow path 17 for the fuel gas of the heating apparatus 29. FIG. Thereby, a part of the exhaust gas can be extracted and burned as fuel gas by the heating device 29. Other configurations of the directly reduced iron manufacturing facility 102 are the same as those of the directly reduced iron manufacturing facility 100. Note that the gas flow path 16 of the second gas (supply gas) is connected to the gas flow path 21 between the de-CO ₂ device 28 and the heating device 29 of the circulation unit 20 in the same manner as the directly reduced iron production facility 101. You may connect.

  FIG. 4 is a schematic view of a directly reduced iron production facility 103 which is still another embodiment. The directly reduced iron production facility 103 includes a sprinkling cooling tower 23 </ b> A that cools the exhaust gas discharged from the direct reduction furnace 30. Here, the exhaust gas is cooled to, for example, a temperature of 200 to 350 ° C. and is humidified to a moisture concentration (volume%) of 20 to 30% in the sprinkling cooling tower 23A. Thus, the sprinkling cooling tower 23A is adjusted to a temperature and humidity suitable for processing in the shift reactor 25 on the downstream side. That is, the sprinkling cooling tower 23 </ b> A constitutes an exhaust gas adjusting unit 51.

  A dry dust collector 24 is provided on the downstream side of the sprinkling cooling tower 23A. This makes it possible to stably operate the shift reactor 25 on the downstream side for a long period of time.

  A shift reactor 25 is provided on the downstream side of the dry dust collector 24. In the shift reactor 25, as described in the directly reduced iron production facility 102, the water gas shift reaction represented by the above formula (1) proceeds. In the directly reduced iron production facility 103, the gas flow path 16 of the supply gas (second gas) obtained by the gas purification device 12 is connected upstream of the shift reactor 25. In this way, by combining the supply gas with the exhaust gas upstream of the shift reactor 25, carbon monoxide and water contained in the supply gas can also be converted into carbon dioxide and hydrogen by the shift reaction. As a result, the hydrogen concentration in the reducing gas directly supplied to the reduction furnace 30 can be sufficiently increased.

  A gas flow path 18 </ b> A is provided on the upstream side of the joining position of the supply gas and the exhaust gas so that the exhaust gas can be used as fuel for the heating device 29. Thereby, a part of the exhaust gas can be used as the fuel for the heating device 29 according to the composition of the exhaust gas. Other configurations of the directly reduced iron production facility 103 are the same as those of the directly reduced iron production facility 100.

  Next, an example of a gas purification apparatus provided in the above-described directly reduced iron production facility will be described below. FIG. 5 is a schematic diagram illustrating an example of the gas purification device 12. The gas purification device 12 is a pressure swing adsorption device 12A that adsorbs both carbon monoxide and carbon dioxide using an adsorbent. Fuel gas containing carbon monoxide, carbon dioxide, and nitrogen and having a nitrogen concentration of 10% by volume or more is supplied from the gas flow path 11 to the pressure swing adsorption device 12A by the blower 13A. The pressure swing adsorption device 12A is configured to adsorb both carbon monoxide and carbon dioxide with one device, that is, in one stage. For this reason, it can be made compact compared with the apparatus which adsorb | sucks carbon monoxide and a carbon dioxide separately, ie, the apparatus adsorb | sucking in two steps.

The low N ₂ gas mainly composed of carbon monoxide and carbon dioxide obtained by the pressure swing adsorption device 12A is conveyed to, for example, the gas compressor 15 in FIG. 1 by the vacuum pump 13C. This gas is pressurized as a supply gas by the gas compressor 15 and then supplied to the circulation unit 20. Since this supply gas contains carbon dioxide, it is preferable to join the exhaust gas (circulation gas) on the upstream side of the de-CO ₂ device 28 as in the directly reduced iron production facilities 100 and 102. Thereby, the carbon dioxide contained in the supply gas is removed by the de-CO ₂ device 28, and the reducing gas having a reduced carbon dioxide concentration can be directly supplied to the reduction furnace 30. That is, since the circulation unit 20 includes the de-CO ₂ device 28 and the supply gas is combined with the circulation gas on the upstream side thereof, the gas purification device 12 is configured in only one stage of the pressure swing adsorption device 12A. can do. When the gas containing nitrogen as a main component obtained by the pressure swing adsorption device 12A contains carbon monoxide and / or hydrogen, the gas flow channel 14 may be circulated and burned by the heating device 29. Further, when the heat quantity of the gas is low, it may be discarded.

FIG. 6 is a schematic view showing another example of the gas purification device 12. The gas purification apparatus 12 is an apparatus that performs gas adsorption in two stages. The gas purification apparatus 12 adsorbs carbon monoxide using an adsorbent and a first pressure swing adsorption apparatus 12B that adsorbs carbon dioxide using an adsorbent. And a second pressure swing adsorption device 12C. A fuel gas containing carbon monoxide, carbon dioxide, and nitrogen and having a nitrogen concentration of 10% by volume or more is introduced from the gas flow path 11 into the first pressure swing adsorption device 12B by the blower 13A. In the first pressure swing adsorption device 12B, the adsorption and desorption of carbon dioxide by the adsorbent separates into a high CO ₂ gas having a high carbon dioxide concentration and a low CO ₂ gas having a low carbon dioxide concentration.

The low CO ₂ gas is introduced into the second pressure swing adsorption device 12C by the blower 13B. In the second pressure swing adsorption device 12C, by adsorption and desorption of carbon monoxide by the adsorbent, low N ₂ gas with high carbon monoxide concentration and low nitrogen concentration, and high N with low carbon monoxide concentration and high nitrogen concentration. Separated into _two gases. The low N ₂ gas contains carbon monoxide as a main component, and the carbon dioxide and nitrogen concentrations are sufficiently reduced. The low N ₂ gas is conveyed to, for example, the gas compressor 15 in FIG. 2 by the vacuum pump 13C.

The adsorbent used in the first pressure swing adsorption device 12B and the adsorbent used in the second pressure swing adsorption device 12C may be different. For example, activated carbon and zeolite may be used in the first pressure swing adsorption device 12B and the second pressure swing adsorption device, respectively. Thereby, it is possible to obtain a supply gas containing carbon monoxide as a main component and having sufficiently reduced carbon dioxide and nitrogen concentrations at low cost. In addition, since the performance of zeolite may decrease when it comes into contact with a large amount of CO ₂ , the CO ₂ concentration of the low CO ₂ gas supplied to the second pressure swing adsorption device 12C is preferably low, for example, 1% by volume It is preferable that it is less than.

From the viewpoint of reducing the CO ₂ concentration of the low CO ₂ gas supplied to the second pressure swing adsorption device 12C, the gas pressure at the inlet of the first pressure swing adsorption device 12B is preferably high. The lower limit of the gas pressure at the inlet of the first pressure swing adsorption device 12B may be, for example, 0.3 MPa or 0.4 MPa. The upper limit of the pressure is not particularly limited, and may be, for example, 0.8 MPa or 0.6 MPa from a practical viewpoint. The gas pressure at the inlet of the second pressure swing adsorption device 12C can be made equal to the gas pressure at the inlet of the first pressure swing adsorption device 12B.

The low N ₂ gas is boosted by the gas compressor 15 as a supply gas and then supplied to the circulation unit 20. Since the supply gas has a reduced carbon dioxide concentration, it is preferable that the supply gas is combined with the exhaust gas (circulation gas) on the downstream side of the de-CO ₂ device 28 as in the directly reduced iron production facility 101. Alternatively, it may be combined with the exhaust gas on the upstream side of the shift reactor 25 as in the directly reduced iron production facility 103. Thereby, the ratio of hydrogen to carbon monoxide of the reducing gas supplied directly to the reduction furnace 30 can be increased. On the other hand, high CO ₂ gas mainly containing carbon dioxide obtained by the first pressure swing adsorption device 12B and high N ₂ gas mainly containing nitrogen obtained by the second pressure swing adsorption device 12C are hydrogen. When carbon monoxide is included, the gas passage 14 may be circulated and burned by the heating device 29. Further, when the heat quantity of the gas is low, it may be discarded. The high CO ₂ gas and the high N ₂ gas may be used for different applications without being merged, or only one gas may be discarded.

  FIG. 7 is a schematic view showing still another example of the gas purification device 12. The gas purification device 12 in FIG. 7 adsorbs and desorbs carbon monoxide by using an adsorbent with an absorption tower 12D that absorbs carbon dioxide contained in the fuel gas by bringing the fuel gas and the absorption liquid into countercurrent contact. And a second pressure swing adsorption device 12C. A fuel gas containing carbon monoxide, carbon dioxide, and nitrogen and having a nitrogen concentration of 10% by volume or more is introduced from the gas flow path 11 into the absorption tower 12D through the blower 13A. In the absorption tower 12D, carbon dioxide is absorbed by an absorbing solution such as amine.

The low CO ₂ gas in which carbon dioxide is reduced is introduced into the pressure swing adsorption device 12C by the blower 13B. In the pressure swing adsorption apparatus 12C, the adsorption and desorption of carbon monoxide by the adsorbent, high N ₂ having a low N ₂ gas having a high concentration of carbon monoxide and low nitrogen concentration, low concentration of carbon monoxide and high nitrogen concentration Separated into gas. The low N ₂ gas contains carbon monoxide as a main component, and the carbon dioxide and nitrogen concentrations are sufficiently reduced. The low N ₂ gas is conveyed to, for example, the gas compressor 15 in FIG. 2 by the vacuum pump 13C.

The low N ₂ gas is boosted by the gas compressor 15 as a supply gas and then supplied to the circulation unit 20. Since the supply gas has a reduced carbon dioxide concentration, it is preferable that the supply gas is combined with the exhaust gas (circulation gas) on the downstream side of the de-CO ₂ device 28 as in the directly reduced iron production facility 101. Alternatively, it may be combined with the exhaust gas on the upstream side of the shift reactor 25 as in the directly reduced iron production facility 103. Thereby, the ratio of hydrogen to carbon monoxide of the reducing gas supplied directly to the reduction furnace 30 can be increased. On the other hand, the carbon dioxide absorbed in the absorption liquid such as amine in the absorption tower 12D is separated from the absorption liquid in the regeneration tower, and can be reused for various applications as high-concentration CO ₂ . The amine regenerated in the regeneration tower can be used again in the absorption tower. When the high N ₂ gas mainly containing nitrogen obtained by the pressure swing adsorption device 12C contains hydrogen and / or carbon monoxide, the high N ₂ gas may be circulated through the gas flow path 14 and burned by the heating device 29. Further, when the heat quantity of the gas is low, it may be discarded.

  You may perform one Embodiment of the manufacturing method of the direct reduced iron of this invention using either of the manufacturing facilities 100-103 of the above-mentioned direct reduced iron. In the method for producing directly reduced iron of the present embodiment, the reduced iron 34 is obtained by directly reducing the iron oxide by bringing the raw material 32 into contact with the reducing gas containing carbon monoxide and hydrogen in the direct reduction furnace 30. In this manufacturing method, a reductive gas including a recycle gas obtained by processing exhaust gas from the direct reduction furnace 30 is directly introduced into the reduction furnace 30, and in the gas supply unit 10, carbon monoxide, carbon dioxide Supply which refine | purifies the fuel gas which contains carbon and nitrogen and whose nitrogen concentration is 10 volume% or more, and joins supply gas which has nitrogen concentration lower than fuel gas and high carbon monoxide concentration to circulation gas And a process.

  The nitrogen concentration of the supply gas obtained by the gas purification device 12 may be, for example, less than 10% by volume or 6% by volume or less. By reducing the nitrogen concentration of the supply gas, the amount of coke oven gas used can be further reduced.

In the supply step, both the carbon monoxide and carbon dioxide contained in the fuel gas may be adsorbed and desorbed simultaneously to obtain a supply gas containing carbon monoxide and carbon dioxide as main components. The carbon monoxide concentration and the carbon dioxide concentration in the supply gas are, for example, 50 to 80% by volume and 0 to 20% by volume, respectively. The carbon dioxide concentration of the supply gas may be, for example, 11 to 25% by volume. Also include this manner the feed gas carbon dioxide, in the circulating step, after merged with the exhaust gas feed gas upstream of the de CO ₂ device, by treatment with demineralized CO ₂ device, contained in the gas The CO ₂ concentration can be reduced.

  The feed gas may additionally contain hydrogen, hydrocarbons, and nitrogen. Further, in the supply step, carbon dioxide and carbon monoxide contained in the fuel gas may be sequentially adsorbed and desorbed to obtain a supply gas containing carbon monoxide and carbon dioxide as main components. Further, carbon monoxide obtained by adsorbing or removing carbon dioxide contained in the fuel gas and adsorbing and desorbing gas whose carbon dioxide is reduced to less than 1% by volume is adsorbed and desorbed, and carbon monoxide as a main component. A feed gas containing may be obtained. In this case, the carbon monoxide concentration of the supply gas may be 80 to 100% by volume.

  The method for producing directly reduced iron according to the present embodiment can be performed by the above-described procedure using the apparatus configuration of the directly reduced iron production facilities 100 to 103.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments. For example, you may perform the manufacturing method of direct reduced iron using facilities other than the manufacturing equipment 100-103 of direct reduced iron. Moreover, the structure of the gas purification apparatus 12 is not limited to the aspect of FIGS. 5-7, The various purification methods which can reduce a nitrogen concentration can be provided.

  The contents of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
Using a converter gas as the fuel gas, a gas purification simulation was performed by the pressure swing adsorption device 12A shown in FIG. The pressure of the converter gas at the inlet of the pressure swing adsorption device 12A is 0.12 MPa, and the temperature is 40 ° C. As the adsorbent of the pressure swing adsorption device 12A, activated carbon was supported by copper (I) chloride. The composition of the converter gas, the composition of each gas obtained by separating the converter gas with the pressure swing adsorption device 12A, and the flow rate ratio were determined by simulation. The results are shown in Table 1. In addition, the code | symbol in Table 1 respond | corresponds to the code | symbol in FIG. The “flow rate ratio” is a volume ratio of each gas when the converter gas is used as a reference.

From the results in Table 1, it was confirmed that the low N ₂ gas obtained by the pressure swing adsorption device 12A is useful as a supply gas in the directly reduced iron production facility and the directly reduced iron production method. On the other hand, since the high N ₂ gas has a low calorific value, it may be a waste gas instead of being used as a fuel gas. In Table 1, “effective utilization rate” is a volume ratio of carbon monoxide (hydrogen) used as supply gas or fuel among carbon monoxide (hydrogen) contained in the converter gas. In Example 1, since the high N ₂ gas is discarded, only the low N ₂ gas used as the supply gas is effectively used. In this embodiment, carbon monoxide can be used sufficiently effectively.

(Example 2)
A simulation was performed in the case of using a converter gas as the fuel gas and performing gas purification by the first pressure swing adsorption device 12B and the second pressure swing adsorption device 12C shown in FIG. The pressure of the gas at the inlet of each pressure swing adsorption device is 0.12 MPa, and the temperature is 40 ° C. Activated carbon was used as the adsorbent for the first pressure swing adsorption device 12B, and activated carbon was supported on copper (I) as the adsorbent for the second pressure swing adsorption device 12C. The composition of the converter gas, the composition of each gas obtained by separating the converter gas with the first and second pressure swing adsorption devices 12B and 12C, and the flow rate ratio were determined by simulation. The results are shown in Table 2. In addition, the code | symbol in Table 2 respond | corresponds to the code | symbol in FIG. The “flow rate ratio” is a volume ratio of each gas when the converter gas is used as a reference.

From the results in Table 2, the low N ₂ gas obtained by the first and second pressure swing adsorption devices 12B and 12C is useful as a supply gas in the directly reduced iron production facility and the directly reduced iron production method. On the other hand, high CO ₂ gas and high N ₂ gas have a low calorific value, and may be used as waste gas instead of being used as fuel gas. In Table 2, “effective utilization rate” is a volume ratio of carbon monoxide (hydrogen) used as supply gas or fuel among carbon monoxide (hydrogen) contained in the converter gas. In Example 2, since the high CO ₂ gas and the high N ₂ gas are discarded, only the low N ₂ gas used as the supply gas is effectively used.

Example 2 is the result of the simulation in the case where the operation is performed with priority given to the recovery rate of CO contained in the converter gas. Thus, when giving priority to the CO recovery rate, the carbon dioxide concentration of the low N ₂ gas tends to increase. For this reason, when the low N ₂ gas shown in Table 2 is used as the supply gas, the supply gas is preferably combined with the exhaust gas (circulation gas) upstream of the de-CO ₂ device 28 as shown in FIG. As shown in Table 2, also in Example 2, carbon monoxide can be used sufficiently effectively.

(Example 3)
A converter gas was used as the fuel gas, and similarly to Example 2, a simulation was performed in which gas purification was performed by the first pressure swing adsorption device 12B and the second pressure swing adsorption device 12C shown in FIG. The conditions were the same as in Example 2 except that zeolite was used as the adsorbent of the second pressure swing adsorption device 12C and that the gas pressure at the inlet of each pressure swing adsorption device was 0.45 MPa.

Example 3 is the result of the simulation when the operation is performed with priority given to lowering the concentration of carbon dioxide contained in the low N ₂ gas. When priority is given to lowering the carbon dioxide concentration of the low N ₂ gas in this way, the concentration of carbon monoxide contained in the high CO ₂ gas and the high N ₂ gas tends to increase. For this reason, the high CO ₂ gas and the high N ₂ gas shown in Table 3 can be used as fuel for the heating device 29 as shown in FIG. Since the low N ₂ gas in Table 3 has a low carbon dioxide concentration, when used as a supply gas, it is preferable to join the exhaust gas (circulation gas) on the downstream side of the de-CO ₂ device 28.

In Table 3, “effective utilization rate” is a volume ratio of carbon monoxide (hydrogen) used as a supply gas or fuel among carbon monoxide (hydrogen) contained in the converter gas. In Example 3, since the high CO ₂ gas and the high N ₂ gas are used as the fuel gas, the effective utilization rate of carbon monoxide and hydrogen can be set to 100%. The recovery rate to the supply gas is as shown in Table 3. Of the carbon monoxide contained in the converter gas, the volume ratio of carbon monoxide introduced into the circulation unit 20 as the supply gas is 70%.

Example 4
A simulation was performed in which the converter gas was used as the fuel gas and the converter gas was purified by the absorption tower 12D and the pressure swing adsorption device 12C shown in FIG. The temperature of the converter gas at the inlet of the absorption tower 12D was 40 ° C., and the pressure was atmospheric pressure. An amine was used as the absorption liquid of the absorption tower 12D. The pressure of the converter gas at the inlet of the pressure swing adsorption device 12C is 0.12 MPa, and the temperature is 40 ° C. Activated carbon was used as the adsorbent of the pressure swing adsorption device 12C. The composition of the converter gas, the composition of each gas obtained by separating the converter gas with the absorption tower 12D and the pressure swing adsorption device 12C, and the flow rate ratio were determined by simulation. The results are shown in Table 4. In addition, the code | symbol in Table 4 respond | corresponds to the code | symbol in FIG. The “flow rate ratio” is the volume ratio of each gas when the converter gas is used as a reference.

From the results of Table 4, the low N ₂ gas obtained by the absorption tower 12D and the pressure swing adsorption device 12C shown in FIG. 7 is useful as a supply gas in the directly reduced iron production facility and the directly reduced iron production method. On the other hand, since the high N ₂ gas has a low calorific value, it may be a waste gas instead of being used as a fuel gas. In Table 4, “effective utilization rate” is a volume ratio of carbon monoxide (hydrogen) used as supply gas or fuel among carbon monoxide (hydrogen) contained in the converter gas. In Example 4, since the CO ₂ gas and the high N ₂ gas are discarded, only the low N ₂ gas used as the supply gas is effectively used. In this embodiment, carbon monoxide can be used sufficiently effectively.

(Example 5)
A gas purification simulation was performed in the same manner as in Example 1 except that blast furnace gas was used instead of converter gas as fuel gas. The pressure of the blast furnace gas at the inlet of the pressure swing adsorption device 12A is 0.12 MPa, and the temperature is 40 ° C. The composition of the blast furnace gas, the composition of each gas obtained by separating the blast furnace gas with the pressure swing adsorption device 12A, and the flow rate ratio were determined by simulation. The results are shown in Table 5. The “flow rate ratio” in Table 5 is the volume ratio of each gas based on the blast furnace gas.

From the results in Table 5, it was confirmed that the low N ₂ gas obtained by the pressure swing adsorption device 12A is useful as a supply gas in the directly reduced iron production facility and the directly reduced iron production method. On the other hand, since the high N ₂ gas has a low calorific value, it may be a waste gas instead of being used as a fuel gas. In Table 5, “effective utilization rate” is a volume ratio of carbon monoxide (hydrogen) used as a supply gas or fuel among carbon monoxide (hydrogen) contained in the blast furnace gas. In Example 5, since the high N ₂ gas is discarded, only the low N ₂ gas used as the supply gas is effectively used. In this embodiment, carbon monoxide can be used sufficiently effectively.

(Example 6)
A gas purification simulation was performed in the same manner as in Example 3 except that blast furnace gas was used instead of converter gas as fuel gas. However, the high CO ₂ gas obtained by the first pressure swing adsorption device 12B and the high N ₂ gas obtained by the second pressure swing adsorption device 12C are used for different applications without being merged as shown in FIG. I was able to. The high CO ₂ gas can be used as a fuel for the heating device 29, or as a fuel for a blast furnace hot stove or coke oven, as with the blast furnace gas. On the other hand, the high N ₂ gas may be a waste gas. “Flow rate ratio” in Table 6 is a volume ratio of each gas based on blast furnace gas.

In Table 6, “effective utilization rate” is a volume ratio of carbon monoxide (hydrogen) used as supply gas or fuel among carbon monoxide (hydrogen) contained in the blast furnace gas. In Example 7, the high CO ₂ gas that is utilized as a fuel gas, the effective utilization rate of the carbon monoxide and hydrogen can be sufficiently high. The recovery rate to the supply gas is as shown in Table 6. Of the carbon monoxide contained in the blast furnace gas, the volume ratio of carbon monoxide introduced into the circulation unit 20 as the supply gas is 55%.

(Example 7)
A gas purification simulation was performed in the same manner as in Example 4 except that blast furnace gas was used instead of converter gas as fuel gas. The temperature of the blast furnace gas at the inlet of the absorption tower 12D was 40 ° C., and the pressure was atmospheric pressure. The pressure of the blast furnace gas at the inlet of the pressure swing adsorption device 12C is 0.12 MPa, and the temperature is 40 ° C. The composition of the blast furnace gas, the composition of each gas obtained by separating the blast furnace gas with the absorption tower 12D and the pressure swing adsorption device 12C, and the flow rate ratio were determined by simulation. The results are shown in Table 7. In addition, the code | symbol in Table 7 respond | corresponds to the code | symbol in FIG. The “flow rate ratio” is a volume ratio of each gas when the blast furnace gas is used as a reference.

From the results in Table 7, the low N ₂ gas obtained by the absorption tower 12D and the pressure swing adsorption device 12C shown in FIG. 7 is useful as the supply gas in the directly reduced iron production facility and the directly reduced iron production method. On the other hand, since the high N ₂ gas has a low calorific value, it may be a waste gas instead of being used as a fuel gas. In Table 7, “effective utilization rate” is a volume ratio of carbon monoxide (hydrogen) used as supply gas or fuel among carbon monoxide (hydrogen) contained in the blast furnace gas. In Example 7, since the CO ₂ gas and the high N ₂ gas are discarded, only the low N ₂ gas used as the supply gas is effectively used. In this embodiment, carbon monoxide can be used sufficiently effectively.

(Example 8)
A simulation of operation in the case of supplying coke oven gas and converter gas using a directly reduced iron production facility 100 as shown in FIG. 1 was performed. As the gas purification apparatus 12, the one shown in FIG. 5 was used. The composition of the converter gas is as shown in Table 1. The composition of the coke oven gas is as shown in Table 8. The iron content of the raw material 32 was 65% by mass, and the iron content of the directly reduced iron 34 was 89% by mass. Under such preconditions, simulation was performed to determine how much the ratio of the converter gas to the coke oven gas can be increased within a range that satisfies the following simulation conditions. The simulation results are shown in Table 9.

<Simulation conditions>
-Nitrogen concentration of exhaust gas of direct reduction furnace 30: 12% or less-H ₂ / CO (volume ratio) of reducing gas introduced into direct reduction furnace 30: 1 or more

Example 9
An operation simulation was performed under the same conditions as in Example 8 except that a directly reduced iron production facility 103 having a shift reactor 25 as shown in FIG. 4 was used. The simulation results are shown in Table 9.

(Comparative Example 1)
An operation simulation was performed under the same conditions as in Example 8 except that a conventional directly reduced iron production facility without the gas purifier 12 was used. This directly reduced iron production facility has the same apparatus configuration as the directly reduced iron production facility 100 of FIG. 1 except that the gas refiner 12 is not provided. The simulation results are shown in Table 9.

  As shown in Table 9, with the directly reduced iron production facility 100 of Example 8 equipped with the gas purifier 12, it was confirmed that the converter gas usage ratio could be 40% on a calorie basis. Further, it was confirmed that the direct reduced iron production facility of Example 9 provided with the gas purifier 12 and the shift reactor 25 can be operated only with the converter gas. On the other hand, in the directly reduced iron production facility of Comparative Example 1 that does not include the gas purifier 12 and the shift reactor 25, the maximum usage ratio of the converter gas was 23% (on a calorie basis).

(Examples 10 and 11, Comparative Example 2)
Simulations of Examples 10 and 11 and Comparative Example 2 were performed in the same manner as Examples 8 and 9 and Comparative Example 1 except that blast furnace gas was used instead of the converter gas. Table 5 shows the composition of the blast furnace gas used in the simulation. The simulation results are shown in Table 10.

  As shown in Table 10, it was confirmed that the direct reduction iron production facility 100 of Example 10 provided with the gas purifier 12 can make the use ratio of blast furnace gas 37% on a calorie basis. Further, it was confirmed that the direct reduced iron production facility of Example 11 provided with the gas purifier 12 and the shift reactor 25 can be operated only with blast furnace gas. On the other hand, in the directly reduced iron production facility of Comparative Example 2 that does not include the gas purifier 12 and the shift reactor 25, the maximum use ratio of blast furnace gas was 18% (on a calorie basis).

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing apparatus of direct reduction iron which can reduce the usage-amount of coke oven gas in manufacture of direct reduction iron by utilizing effectively fuel gas whose nitrogen concentration is higher than coke oven gas. And the manufacturing method of direct reduced iron can be provided.

DESCRIPTION OF SYMBOLS 10 ... Gas supply part, 11, 14, 16, 17, 18, 18A, 21, 22, 40, 44 ... Gas flow path, 12 ... Gas purification apparatus, 12A ... Pressure swing adsorption apparatus, 12B, 12C ... Pressure swing adsorption Apparatus, 12D ... Absorption tower, 13A, 13B ... Blower, 13C ... Vacuum pump, 15, 27, 42 ... Gas compressor, 20 ... Circulation part, 23 ... Heat exchanger, 23A ... Sprinkling cooling tower, 23B ... Heat exchanger 24: a dry dust collector, 24B ... wet dust collector, 25 ... shift reactor, 26 ... gas cooler, 28 ... de-CO ₂ device, 29 ... heater, 30 ... direct reduction furnace, 32 ... raw material, 34 ... DRI 50, 51 ... adjustment unit, 62 ... water supply unit, 64 ... water discharge unit, 100, 101, 102, 103 ... directly reduced iron production equipment.

Claims (14)

A direct reduced iron manufacturing facility for directly reducing iron oxide by bringing a raw material containing iron oxide into contact with a reducing gas containing carbon monoxide and hydrogen in a direct reduction furnace,
A recirculation unit for introducing the reductive gas containing a recirculation gas obtained by processing exhaust gas from the direct reductive furnace into the direct reductive furnace;
A supply gas containing carbon monoxide, carbon dioxide, and nitrogen, obtained by refining a fuel gas having a nitrogen concentration of 10% by volume or more and having a lower nitrogen concentration and a higher carbon monoxide concentration than the fuel gas. A gas supply unit for supplying to the circulation unit,
The nitrogen concentration of the supply gas is 10% by volume or less,
The gas supply unit is a system different from the fuel gas, and introduces a coke oven gas different from the fuel gas into the circulation unit,
The supply ratio of the fuel gas, Ru 18% ultra der in lower heating value, manufacturing facilities direct reduced iron to the total of the coke oven gas with the fuel gas. The said circulation part is equipped with the heating apparatus which heats the said reducing gas, and burns the gas containing nitrogen, hydrogen, and / or carbon monoxide discharged | emitted from the said gas supply part with the said heating apparatus. Item 2. A facility for producing directly reduced iron according to Item 1 . The gas supply unit has a gas purification device that adsorbs and desorbs both carbon monoxide and carbon dioxide contained in the fuel gas, and circulates the supply gas containing carbon monoxide and carbon dioxide as main components. and it supplies the parts, manufacturing equipment of direct reduced iron according to claim 1 or 2. The gas supply unit includes a first gas purification device that adsorbs or absorbs carbon dioxide contained in the fuel gas, and a second gas purification that adsorbs and desorbs carbon monoxide contained in the gas from the first gas purification device. The apparatus for producing directly reduced iron according to claim 1 or 2 , wherein the supply gas containing carbon monoxide as a main component is supplied to the circulation section. The circulation unit includes a shift reactor, and the supply gas and the exhaust gas are combined on the upstream side of the shift reactor and supplied to the shift reactor, and the supply gas and the exhaust gas are generated by a water gas shift reaction. The facility for producing directly reduced iron according to any one of claims 1 to 4 , wherein the circulating gas having a higher hydrogen concentration is prepared.   The said circulation part is equipped with the adjustment part which adjusts the temperature and humidity of at least one of the said exhaust gas and the said supply gas between the said direct reduction furnace and the said shift reactor, The direct reduction iron of Claim 5 production equipment. The said adjustment part is a manufacture of direct reduction iron of Claim 6 provided with a wet dust collector and the self-heat exchange type heat exchanger which heat-exchanges the gas of the inlet side of the said wet dust collector, and the gas of an exit side. Facility. The said adjustment part is a manufacturing equipment of direct reduced iron of Claim 6 provided with the sprinkling cooling tower which cools and humidifies exhaust gas from an upstream, and a dry-type dust collector. A method for producing directly reduced iron by directly reducing the iron oxide by bringing a raw material containing iron oxide into contact with a reducing gas containing carbon monoxide and hydrogen in a direct reduction furnace,
A circulation step of introducing the reducing gas containing the circulating gas obtained by processing the exhaust gas from the direct reduction furnace into the direct reduction furnace;
A fuel gas containing carbon monoxide, carbon dioxide, and nitrogen and having a nitrogen concentration of 10% by volume or more is purified to have a lower nitrogen concentration and a higher carbon monoxide concentration than the fuel gas, and a nitrogen concentration A supply step of merging the supply gas having a volume of 10% by volume or less with the circulation gas,
In the supplying step, a coke oven gas different from the fuel gas in a system different from the fuel gas is merged with the circulation gas, and a supply ratio of the fuel gas with respect to a total of the fuel gas and the coke oven gas is: Ru 18% ultra der in lower heating value, method for producing direct reduced iron. Combusting a gas having a higher nitrogen concentration than the fuel gas and containing hydrogen and / or carbon monoxide obtained by refining the fuel gas in the supplying step with a heating device that heats the reducing gas; The method for producing directly reduced iron according to claim 9 . Wherein the feed step, and adsorption and desorption of both carbon monoxide and carbon dioxide contained in the fuel gas, to obtain the feed gas containing carbon monoxide and carbon dioxide as the main component, to claim 9 or 10 The manufacturing method of direct reduction iron of description. In the supplying step, after carbon dioxide contained in the fuel gas is removed by adsorption or absorption, carbon monoxide contained in the gas from which the carbon dioxide has been removed is adsorbed and desorbed to contain carbon monoxide as a main component. The method for producing directly reduced iron according to claim 9 or 10 , wherein the supply gas is obtained. After merging the feed gas to the circulating gas in the supplying step, to obtain the reducing gas having a higher hydrogen concentration than the feed gas and the exhaust gas by the water gas shift reaction, any one of claims 9-12 The method for producing directly reduced iron according to one item. The method for producing directly reduced iron according to any one of claims 9 to 13 , wherein the temperature and humidity of at least one of the exhaust gas and the supply gas are adjusted before the water gas shift reaction.

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