JP5697355B2 - Method for producing reduced iron - Google Patents

Description

The present invention relates to an iron ore mainly composed of iron oxide by producing a synthesis gas composed of hydrogen and carbon monoxide having high reducibility by a reforming reaction using a catalyst from an iron by-product gas containing a carbon compound. The present invention relates to a method for producing reduced iron by using it for reduction of stone.

  The iron and steel industry is an energy-intensive industry that accounts for about 10% of Japan's total energy consumption, but most of the blast furnace gas, converter gas, and coke oven gas generated in the blast furnace integrated steelmaking process is within the steelworks. It is used as a fuel gas.

Other than the iron and steel industry, coke oven gas produced as a by-product when producing coke by carbonizing coal has been used as a fuel for city gas or the like and as a raw material for chemical synthesis. In that case, generally, the unrefined coke oven gas contains impurities (H ₂ S, COS, aromatic hydrocarbons, tar, dust, etc.), and thus has been purified by a conventional method (for example, Patent Document 1). After being used. In addition, when constructing a methanol synthesis plant using coke oven gas, the refined gas produced by conventional methods has low concentrations of lower hydrocarbons and aromatic hydrocarbons, but remains, which is the catalyst coverage of the reformer. Since there is a possibility of causing poisoning, it is disclosed that these hydrocarbon components are completely removed to avoid the poisoning (for example, Patent Document 2).

On the other hand, unlike the integrated blast furnace ironmaking process, multiple types of processes for directly reducing iron oxide raw materials using natural gas or synthetic gas obtained by modifying natural gas as a reducing gas have been put into practical use. Although this process has the advantage of reducing the amount of CO ₂ generated compared to the integrated blast furnace ironmaking process, the construction of the plant of the above process is almost limited to natural gas production sites that can stably supply natural gas. In addition, there is a problem that it is not always an economical process due to the increase in natural gas prices accompanying the recent rise in crude oil (for example, Non-Patent Document 1).

JP 2000-248286 A JP 2008-239443 A

Metal, Vol. 79, no. 2, p. 145-149 (2009)

  The present invention has location restrictions and does not produce synthesis gas from expensive natural gas, but a gas containing a carbon compound by-produced in the iron making process in the presence of a catalyst at low cost and high efficiency. Another object of the present invention is to stably produce a highly reducing synthesis gas mainly composed of hydrogen and carbon monoxide.

Another object of the present invention is to significantly reduce the amount of CO ₂ generated from the iron making process by using the produced syngas as an alternative to coke for iron making reduction.

For the gas containing the carbon compound by-produced in the iron making process, the present inventors removed impurities and heavy hydrocarbons in the gas by a conventional method, and then brought into contact with the catalyst together with the modifier, We have intensively studied how to reform the carbon compounds in the gas into a highly reducing synthesis gas mainly composed of hydrogen and carbon monoxide. As a result, coke oven gas, blast furnace, by-produced in converter, coke oven gas, blast furnace gas, converter gas discharged in large quantities, along with at least one of steam, carbon dioxide as a modifier, It has been found that by bringing the catalyst into contact with a solid catalyst, a highly reducible synthesis gas mainly composed of hydrogen and carbon monoxide can be produced at a low cost and with high efficiency, compared with an ordinary method of producing from expensive natural gas. In addition, if necessary, it is found that a synthesis gas having an arbitrary hydrogen / carbon monoxide ratio can be produced in a large amount and stably by mixing a converter gas mainly composed of carbon monoxide with the synthesis gas. It came to make this invention. In addition, it has been found that by adding oxygen to the above modifier, it is possible to compensate for the amount of heat of a large endothermic reaction that occurs with water vapor or carbon dioxide, and it is possible to produce synthesis gas with high energy efficiency. Invented the invention. Furthermore, by reducing this highly reducible synthesis gas by bringing it into contact with iron ore mainly composed of iron oxide, reduced iron can be produced with high efficiency and the amount of CO ₂ generated from the iron making process can be greatly reduced. The inventors have found that this is possible and have come to make the present invention.

The characteristics are shown below.
(1) After coke oven gas generated in the iron making process is reformed using steam and catalyst or steam and oxygen and catalyst to obtain a synthesis gas with a total of 92% or more of hydrogen and carbon monoxide, This is further mixed with gas generated from the converter to produce a synthesis gas having an arbitrary hydrogen / carbon monoxide ratio of 1.5 or more and less than 3.3, and iron ore is reduced with the produced synthesis gas. A method for producing reduced iron, characterized in that:
(2) The method for producing reduced iron according to (1), wherein the reforming is performed after removing impurities and heavy hydrocarbons in the coke oven gas.
(3) steam discharged by the method for producing reduced iron according to (1) or (2), the wherein the recycled as part or all of the modifier (1) or (2) The manufacturing method of reduced iron of description.

  According to the present invention, a gas containing a carbon compound by-produced in the iron-making process is synthesized in a highly reducible manner mainly consisting of hydrogen and carbon monoxide in the presence of a catalyst at low cost and high efficiency. Gas can be produced. Further, by mixing a converter gas mainly composed of carbon monoxide with the synthesis gas, a large amount of synthesis gas having an arbitrary hydrogen / carbon monoxide ratio can be produced stably.

Furthermore, by reducing the above-mentioned synthesis gas having high reducibility by bringing it into contact with iron ore mainly composed of iron oxide, reduced iron can be produced with high efficiency, and the amount of CO ₂ generated from the iron making process can be greatly increased. Can be reduced.

  Hereinafter, the present invention will be described in more detail with reference to specific examples.

  The by-product gas generated in the iron making process used in the method for producing synthesis gas of the present invention is mainly considered to be a gas containing a large amount of carbon compounds such as coke oven gas, blast furnace gas, converter gas, and sintering furnace gas. It is done. Generally, coke oven gas is composed of about 55% hydrogen, about 30% methane, and less than about 10% of other hydrocarbon components. The blast furnace gas has a composition of about 4% hydrogen, about 22% carbon monoxide, about 22% carbon dioxide, and the rest nitrogen. Next, the converter gas is about 65% carbon monoxide, about 17% carbon dioxide, about 1% hydrogen, and the other is nitrogen. Further, the sintering furnace gas is about 1% carbon monoxide, about 6% carbon dioxide, about 10% oxygen, about 10% steam, and the rest is nitrogen. Among these, a coke oven gas containing a large amount of hydrocarbon components such as methane is particularly desirable. The hydrocarbon component contained in a large amount in the coke oven gas can be converted to hydrogen, carbon monoxide, or the like in the presence of a catalyst by a modifier such as water vapor or carbon dioxide.

However, coke oven gas (refined COG) refined by conventional methods does not remove hydrogen sulfide of about several tens of ppm, light oil of about several g / Nm ³ , and tar mist of about several mg / Nm ^3. included. Therefore, it is preferable to reduce these impurities by further desulfurization, a light oil scrubber, and a cooler before the contact with the catalyst in order to keep the catalyst life long. If it is hydrogen sulfide, it can be desulfurized to a lower concentration by using a known desulfurization catalyst such as iron oxide or zinc oxide, and it is preferable to remove the hydrogen sulfide component to less than 1 ppm, and to remove to less than 100 ppb. Is more preferable, and removal to less than 10 ppb is even more preferable.

  As the catalyst used when producing the synthesis gas from the by-product gas, a Ni-based catalyst, a noble metal-based catalyst, or the like used for a reforming catalyst such as a methane-based natural gas can be preferably used. It is not limited. The catalyst used here may be a powder or a molded body. In the case of powder, the particle size and surface area are preferably adjusted, and in the case of a molded body, the pore volume, pore diameter, shape, etc. are suitably adjusted in consideration of the surface area and strength. The shape of the molded body may be any of a spherical shape, a cylindrical shape, a ring shape, a wheel shape, a granular shape, and the like, and may be any of a metal or ceramic honeycomb substrate coated with a catalyst component.

  Here, it is preferable to reduce the reforming catalyst. However, since the reduction proceeds during the reaction, it may not be reduced. However, particularly when the reforming catalyst requires a reduction treatment before the reaction, the reducing conditions are not particularly limited as long as the reducing conditions are set to a relatively high temperature and a reducing atmosphere. It may be in a gas atmosphere containing at least one of carbon oxide and methane, in a gas atmosphere in which water vapor is mixed with these reducing gases, or in an atmosphere in which an inert gas such as nitrogen is mixed in these gases. In addition, the reduction temperature is preferably 500 ° C. to 1000 ° C., for example, and the reduction time depends on the amount of catalyst to be charged, and is preferably 30 minutes to 8 hours, for example. It may be a necessary time, and is not particularly limited to this condition.

The catalyst reactor is preferably a fluidized bed type or moving bed type when the catalyst is a powder, or a fixed bed type or moving bed type if the catalyst is a molded body, and the outlet temperature of the catalyst layer. As, it is preferable that it is 500-1100 degreeC. When the outlet temperature of the catalyst layer is less than 500 ° C., the catalytic activity when the hydrocarbon is reformed into synthesis gas mainly composed of hydrogen and carbon monoxide is hardly exhibited, which is not preferable. On the other hand, when the outlet temperature of the catalyst layer exceeds 1100 ° C., it is economically disadvantageous because the reforming apparatus becomes expensive, for example, a heat-resistant structure of the reactor is required. The outlet temperature of the catalyst layer is more preferably 600 to 1000 ° C. The reaction pressure is preferably normal pressure to 10 MPa. If the pressure is less than normal pressure, a pump for pressure reduction is required, and the production amount may not be increased. Further, when the pressure exceeds 10 MPa, a large amount of power energy is required for the booster pump, which is not preferable from the viewpoint of CO ₂ emission from the economical viewpoint. Furthermore, the reaction pressure is more preferably normal pressure to 5 MPa.

  Next, the method for producing a synthesis gas using a catalyst from the iron production byproduct gas according to the present invention, in the presence of the above-described reforming catalyst or in the presence of the reduced catalyst, converts the carbon compound in the iron production byproduct gas to water vapor. A highly reducing synthesis gas mainly composed of hydrogen and carbon monoxide is produced by contacting with a modifying agent selected from at least one of carbon dioxide.

  Also, carbon monoxide-based converter gas is mixed with hydrogen-based synthesis gas, which is reformed with steam in the presence of a reforming catalyst or in the presence of a reduced catalyst, in the iron byproduct gas. Thus, a synthesis gas having an arbitrary hydrogen / carbon monoxide ratio is produced. Here, when the converter gas is mixed with the hydrogen-based synthesis gas, the mixing method is not particularly limited, and the mixing ratio is the ratio of hydrogen to carbon monoxide in the synthesis gas or the synthesis gas. It is desirable to adjust appropriately in consideration of components such as moisture and carbon dioxide remaining therein.

  Furthermore, the carbon compound in the iron byproduct gas is selected from at least one of water vapor and carbon dioxide as the above-described modifier in the presence of the reforming catalyst or in the presence of the catalyst after the reduction. A highly reducible synthesis gas mainly composed of hydrogen and carbon monoxide is produced by contacting with oxygen. In addition, a carbon monoxide-based converter gas is converted into a hydrogen-based synthesis gas that is reformed with water vapor and oxygen in the presence of a reforming catalyst or in the presence of a reduced catalyst. To produce a synthesis gas having an arbitrary hydrogen / carbon monoxide ratio. In this way, oxygen is added to the modifier because the reaction that takes place between the carbon compound, water vapor, and carbon dioxide is a large endothermic reaction. Compensates for the amount of heat, and it is possible to establish an energy efficient process. The ratio of hydrogen and carbon monoxide in the mixed synthesis gas and the components such as moisture and carbon dioxide remaining in the synthesis gas depend on the reduced iron production equipment and production conditions. Although it is important to adjust to the composition ratio and is not particularly limited, for example, the mixing ratio of the converter gas is preferably 3 times or less, more preferably 2 times or less, more preferably the synthesis gas. . If the mixing ratio of the converter gas exceeds three times, the ratio of hydrogen in the synthesis gas becomes too small, and the reduction rate of iron ore to reduced iron is reduced as will be described later, and reduction using the mixed gas is reduced. The final reduction rate of iron may not be high.

  Here, the reforming reaction in which the coke oven gas containing a large amount of hydrocarbon components, particularly the coke oven gas containing a large amount of hydrocarbon components, is gasified by gasification is expressed by Formula 1 and Formula 2 between the steam introduced from the outside. The hydrogen-based synthesis gas is produced by such steam reforming and water gas shift reaction. In addition, a synthesis gas containing equimolar amounts of hydrogen and carbon monoxide by dry reforming with carbon dioxide as represented by Formula 3 is produced with carbon dioxide. Furthermore, when water vapor and carbon dioxide are introduced, both reactions proceed, and a synthesis gas containing hydrogen and carbon monoxide and containing a large proportion of hydrogen is produced.

(Equation 1)
_{C m H n + mH 2 O} → (m + n / 2) H 2 + mCO ( Equation 1)
mCO + mH ₂ O → mH ₂ + mCO ₂ (Formula 2)
_{C m H n + mCO 2 →} n / 2H 2 + 2mCO ( Equation 3)

  Therefore, when producing a synthesis gas having a large hydrogen / carbon monoxide ratio, it is desirable to add water vapor from the outside. On the other hand, when producing a synthesis gas having a small hydrogen / carbon monoxide ratio, it is desirable to add carbon dioxide from the outside, and a carbon monoxide-based converter is added to the hydrogen-rich synthesis gas produced by adding water vapor. It is also possible to mix gases. In addition, oxygen can be mixed to compensate for the heat of reaction between the hydrocarbon and water vapor or carbon dioxide. However, if there are too many components such as water and carbon dioxide remaining in the synthesis gas obtained here, the reduction rate is greatly reduced when reducing iron is produced from iron ore using the synthesis gas. It is desirable that the amount be small, and it depends on the production method of reduced iron. For example, the total value of both components is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less. It will never be done.

In addition, when producing synthesis gas from ironmaking by-product gas, at least one of water vapor and carbon dioxide discharged from a reduced iron production apparatus, which will be described later, is one of the modifiers required for the reforming reaction. It can be reused as a part or as a whole. By circulating and reusing the exhaust gas in this way, the amount of the modifier to be newly introduced can be greatly reduced, which is economically preferable and from the viewpoint of suppressing the amount of CO ₂ emission in the exhaust gas. Is also preferable.

Next, the method for producing reduced iron using a synthesis gas using a catalyst from the iron-produced byproduct gas of the present invention for the reduction of iron ore, iron oxide (Fe ₂ O ₃ ), which is the main component of iron ore, By contacting with the synthesis gas obtained by catalytic reforming from the iron-produced by-product gas described above, Fe is reduced to Fe via Fe ₃ O ₄ and FeO. Here, regarding the reduction of iron oxide to iron, in the synthesis gas, the reduction rate of hydrogen is several times faster than that of carbon monoxide, and the reduction proceeds easily. However, since the reduction reaction at that time is a large endothermic reaction, it is difficult to keep the temperature of the iron oxide layer high, and the final reduction rate is difficult to reach a high level. On the other hand, although carbon monoxide has a slow reduction rate, the reduction reaction is slightly exothermic, so the temperature of the iron oxide layer can be kept high, and the final reduction rate is influenced by both effects. And do not reach high levels. Therefore, in general, by using a synthesis gas composed of hydrogen and carbon monoxide, the iron oxide layer temperature is maintained at a high level, while achieving a high reduction rate, thereby obtaining iron having a high final reduction rate. be able to. The ratio of hydrogen to carbon monoxide in the synthesis gas depends on the production apparatus and production conditions of reduced iron, and it is important to adjust the composition ratio to the optimum for each.

  The reduced iron production apparatus used in the present invention may be an apparatus capable of reducing the iron oxide raw material, and is not limited to a reduction apparatus having a specific structure. For example, a shaft furnace that has already been put into practical use is preferably used. Used.

In addition, the iron oxide raw material is not particularly limited as long as it mainly contains Fe ₂ O ₃ , but for example, the form is lump iron ore (lump ore), powder iron ore (iron) Sintered ore agglomerated (including containing dusts) and pellets agglomerated powdered iron ore (including iron-containing dusts) can be suitably used.

  Furthermore, the particle size of the iron oxide raw material is selected to have an appropriate particle size because it is necessary to increase the contact area with the synthesis gas and ensure the gas permeability in order to improve the reducibility. . However, since the optimum particle size range differs between the case where the reduced iron production apparatus is a fixed bed and the case of a fluidized bed, it is important to make the particle size uniform according to each method.

The reaction temperature of the reduced iron production apparatus is not particularly limited as long as the reduction rate of the iron ore reaches the intended target, and also varies depending on the production apparatus. A range of 1500 ° C. is preferred. If it is less than 500 degreeC, there exists a possibility that the reaction rate of reduction may become slow and sufficient reduction rate may not be obtained. When the temperature exceeds 1500 ° C., it is necessary to make a heat-resistant structure, which not only becomes expensive as an apparatus, but also a large amount of CO ₂ is discharged when the temperature is raised. It is not preferable.

The reaction pressure of the reduced iron production apparatus is not particularly limited as long as the reduction rate of the iron ore reaches the intended target, and also varies depending on the production apparatus. A range of ˜2 MPa is preferred. If the pressure is less than normal pressure, the reduction reaction rate becomes slow and a sufficient reduction rate may not be obtained. Further, under a pressure of more than 2 MPa, the pump for boosting is required, it power energy is large required, it is economically disadvantageous and is not preferable from the viewpoint of CO ₂ emissions.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
( Reference Example 1)
As the syngas production apparatus, equipment having a synthesis gas flow rate of about 400 Nm ³ / h was used in the same test plant except that the scale of a normal hydrogen production plant was reduced. The catalyst-filled reaction tube has four 80mmφ and 10m tubes installed in a reforming furnace, and there is a commercial steam reforming that is a Ni-based catalyst in which Ni is supported on an alumina carrier as a reforming catalyst. Each of the ring-shaped molded catalysts (manufactured by Zude Chemie, SC-11NK: Ni-20 mass% supported) was charged in an amount of about 25 kg, for a total of about 100 kg. A burner installed on the ceiling of the reforming furnace is ignited, the inside of the furnace is heated by a downfire method in which the flame is directed downward, and the reaction tube is heated by the radiant heat to raise the temperature to a predetermined temperature. did. The high-temperature exhaust gas was passed through a heat exchanger to heat purified COG as a raw material gas. Also, steam was used as a modifier, and pure water was heated with a boiler, and then was converted into superheated steam by heat exchange with the exhaust gas from the reforming furnace and introduced together with purified COG from the upper part of the reaction tube. Prior to the reaction, the gas is set to about 900 ° C. under normal pressure with nitrogen gas, and then mixed with water vapor from nitrogen to hydrogen to perform a reduction treatment (molar ratio of water vapor / molar ratio of hydrogen = 7). And kept at about 200 Nm ³ / h for 3 hours. The obtained reformed gas was cooled with a cooler installed at the outlet of the reaction tube, and after removing water with a water separator, the gas composition was analyzed by gas chromatography.

The raw material gas used here was subjected to the concentration of hydrogen sulfide by a desulfurization unit filled with an iron oxide (Fe ₂ O ₃ ) -based commercial catalyst (manufactured by Zude Chemie, N-IDS) after the purified COG purified by a conventional method. What was desulfurized to about 0.5 ppm was used.

The raw material gas thus desulfurized and the water vapor as the modifier are each set so that the ratio (S / C) of the number of moles of water vapor to the number of carbon moles of the hydrocarbon component in the raw material gas is 1. About 260 Nm ³ / h and about 80 Nm ³ / h (equivalent to about 60 kg / h) were introduced into the reaction tube. The reaction temperature and pressure were adjusted so that the outlet temperature and pressure of the reaction tube were about 900 ° C. and normal pressure, and the operation was performed for about 1000 hours. As a result, a synthesis gas of about 400 Nm ³ / h could be stably obtained as the reformed gas.

  The component of the synthesis gas was a mixed gas of hydrogen and carbon monoxide, the total of which was about 95%, and a hydrogen-rich synthesis gas with a hydrogen / carbon monoxide ratio of about 3.3. Moreover, the water vapor | steam and carbon dioxide which remain | survive in that case became about 0.4% in total.

The apparatus for reducing iron ore using the synthesis gas obtained here is a tube type electric furnace that simulates a shaft furnace, and a vertical furnace is provided with a tubular furnace having a size of about 400 mmφ and a length of about 6 m. About 400 Nm ³ / h was introduced from the side at a roughly central position. This tubular furnace was filled with about 1.2 t of lump iron ore and pellets having a size of about 10 mm in half and operated at a reaction temperature and a pressure of 900 ° C. and normal pressure, respectively.

As a result, the reduction rate of the produced reduced iron was about 90%.
( Reference Example 2)
The reforming reaction was performed in the same manner as in Reference Example 1 except that carbon dioxide was used as the modifying agent. Here, the carbon dioxide as the modifier is about 170 Nm ³ / h each so that the ratio (CO ₂ / C) of the number of moles of carbon dioxide and the number of moles of hydrocarbon components in the raw material gas is 1. About 80 Nm ³ / h was introduced into the reaction tube. Further, the reaction temperature and pressure were adjusted so as to satisfy the conditions shown in Table 1 as the outlet temperature and pressure of the reaction tube. As a result, a synthesis gas of about 300 to 400 Nm ³ / h could be stably obtained as the reformed gas.

  The component of the synthesis gas is a mixed gas of hydrogen and carbon monoxide. At normal pressure, the ratio of hydrogen / carbon monoxide is about 1.5, and the total of hydrogen and carbon monoxide is low at 600 ° C. However, the synthesis gas was 95% or more at 850 ° C to 1000 ° C. Further, water vapor and carbon dioxide remaining at that time were about 20% at 600 ° C. in total, but less than 1% at 850 ° C. to 1000 ° C.

  On the other hand, even for high-pressure reactions, no. 5 and no. Under the condition No. 6, a synthesis gas mainly composed of hydrogen and carbon monoxide is obtained, and the ratio of hydrogen / carbon monoxide is about 1.2. 5 and no. Under the condition of 6, it was about 10%.

The apparatus for reducing iron ore using the synthesis gas obtained here was subjected to the iron ore reduction experiment in the same manner as in Reference Example 1. The reaction temperature and pressure were operated under the same conditions as in Reference Example 1.

As a result, the reduction rate of the produced reduced iron was about 80 to 90%.
( Reference Example 3)
The reforming reaction was performed in the same manner as in Reference Example 1 except that water vapor and carbon dioxide were used as the modifier. Here, the steam and carbon dioxide as the modifier have a ratio (S / C) of 0.5 of the number of moles of water vapor to the number of moles of carbon of the hydrocarbon component in the raw material gas, the number of moles of carbon dioxide and the raw material. The raw material gas is about 200 Nm ³ / h, the water vapor is about 40 Nm ³ / h (about 30 kg / h), so that the ratio (CO ₂ / C) of the hydrocarbon component in the gas to the number of moles of carbon is 0.5. About 30 Nm ³ / h of carbon dioxide was introduced into the reaction tube. Further, the reaction temperature and pressure were adjusted so as to satisfy the conditions shown in Table 2 as the outlet temperature of the reaction tube. As a result, a synthesis gas of about 400 Nm ³ / h could be stably obtained as the reformed gas.

  The component of the synthesis gas is a mixed gas of hydrogen and carbon monoxide, and the ratio of hydrogen / carbon monoxide is about 2.2 at any temperature, and the sum of hydrogen and carbon monoxide is the same at any temperature. The synthesis gas was 92% or more. Further, water vapor and carbon dioxide remaining at that time were less than 3% at any temperature.

The apparatus for reducing iron ore using the synthesis gas obtained here was subjected to the iron ore reduction experiment in the same manner as in Reference Example 1. The reaction temperature and pressure were operated under the same conditions as in Reference Example 1.

  As a result, the reduction rate of the produced reduced iron was about 85 to 90%.

Further, the carbon deposition rate is a relatively low value, and becomes lower as the temperature rises. It has also been found that the overall reforming reaction also proceeds efficiently in a high temperature region of 800 ° C. or higher, and that the decomposition rate increases as the temperature increases.
(Example 1 )
As a catalyst, similar to 2 wt% of the ring-shaped formed catalyst supporting Ru on alumina as in Reference Example 1, except for using about 100kg filled in total, it was reforming reaction in the same manner as in Reference Example 1. As a result, a synthesis gas of about 400 Nm ³ / h could be stably obtained as the reformed gas.

  The component of the synthesis gas was a mixed gas of hydrogen and carbon monoxide, the total of which was about 95%, and a hydrogen-rich synthesis gas with a hydrogen / carbon monoxide ratio of about 3.3. Further, water vapor and carbon dioxide remaining at that time were about 0.5% in total. Here, a converter gas containing about 70% of carbon monoxide was mixed with the synthesis gas 1 at a volume ratio of 0.36. As a result, a synthesis gas in which the total of hydrogen and carbon monoxide was about 89% and the ratio of hydrogen to carbon monoxide was about 1.5 was obtained. Further, water vapor and carbon dioxide remaining at that time were about 4% in total.

The synthesis gas obtained here was reduced in iron ore in the same manner as in Example 1. As a result, the reduction rate of the produced reduced iron was about 90%.
(Example 2 )
In exactly the same manner as in Reference Example 1, after obtaining a synthesis gas of about 400 Nm ³ / h, a converter gas of about 140 Nm ³ / h was mixed in the synthesis gas in a gas holder and sufficiently mixed with a stirrer. As a result, the total of hydrogen and carbon monoxide in the finally obtained synthesis gas was about 88%, and the hydrogen / carbon monoxide ratio was about 1.5. The total amount of water vapor and carbon dioxide remaining in the synthesis gas was about 4%.

The synthesis gas obtained here was reduced in iron ore in the same manner as in Example 1. As a result, the reduction rate of the produced reduced iron was about 90%.
( Reference Example 4 )
The reforming reaction was carried out in the same manner as in Reference Example 1 except that water vapor and oxygen were used as the modifier. Here, the steam as the modifier is such that the ratio (H ₂ O / C) of the number of moles of steam and the number of moles of hydrocarbon components in the raw material gas is 1, and oxygen is relative to the steam. The raw material gas and the modifier were introduced into the reaction tube so that the amount was 0.1 times. As in Reference Example 1, the reaction temperature and pressure were adjusted to 900 ° C. and normal pressure as the outlet temperature pressure of the reaction tube. As a result, a synthesis gas of about 400 Nm ³ / h could be stably obtained as the reformed gas. In this test, the fuel gas required to bring the outlet temperature of the reaction tube to 900 ° C. could be operated in a smaller amount than in Reference Example 1. This is considered to be due to the effect of supplementary heat by combustion heat by partially introducing oxygen into the modifier.

  The component of the synthesis gas is a mixed gas of hydrogen and carbon monoxide, the ratio of hydrogen / carbon monoxide is about 3.3, the total of hydrogen and carbon monoxide is about 92%, the remaining water vapor and carbon dioxide Totaled over 1%.

The apparatus for reducing iron ore using the synthesis gas obtained here was subjected to the iron ore reduction experiment in the same manner as in Reference Example 1. The reaction temperature and pressure were operated under the same conditions as in Reference Example 1.

As a result, the reduction rate of the produced reduced iron was about 90%.
( Reference Example 5 )
Exactly the same as in Reference Example 1, a synthesis gas of about 400 Nm ³ / h can be obtained, and the synthesis gas is introduced into the reduction device and the moisture and dioxide contained in the exhaust gas discharged from the upper part of the tubular furnace. among carbon, captured by water only scrubber, of water vapor of about 80 Nm 3 / ^h is used as a modifier to the synthesis gas production plant, and mixed by vaporizing about 20 Nm 3 / ^h min was introduced into the reaction tube. The reformed gas thus obtained also has a composition almost the same as that before reuse, and it has been found that components that can be a modifier in the off-gas discharged from the reducing device can be recycled and reused.

  Therefore, even when iron ore was reduced using the synthesis gas obtained here, it was confirmed that the reduction rate of the finally obtained reduced iron could be produced with the same numerical value.

Similarly, carbon dioxide contained in the off-gas discharged from the reduction device is also confirmed to be reusable as a modifier, and when iron ore is reduced using the synthesis gas obtained there, It was confirmed that the reduction rate of the finally obtained reduced iron can be produced with similar numerical values.
(Comparative Example 1)
The synthesis gas production apparatus was operated in the same manner as in Reference Example 1 except that natural gas was used as the raw material gas. In this case, since the S content in the natural gas was 0.1 ppm or less, it was introduced into the reaction tube without desulfurization. Incidentally, this natural gas had a composition of 89% methane, 7% ethane, 3% propane, and 1% butane. The natural gas and steam as a modifier are each about 100 Nm ³ / h so that the ratio (S / C) of the number of moles of steam to the number of moles of hydrocarbon components in the natural gas is 1. About 120 Nm ³ / h (equivalent to about 90 kg / h) was introduced into the reaction tube. As a result, a synthesis gas of about 440 Nm ³ / h could be stably obtained as the reformed gas.

  The component of the synthesis gas was a mixed gas of hydrogen and carbon monoxide, the total of which was about 98%, and a hydrogen-rich synthesis gas having a hydrogen / carbon monoxide ratio of about 2.9. Further, water vapor and carbon dioxide remaining at that time were about 1% in total.

The synthesis gas obtained here was reduced in iron ore in the same manner as in Reference Example 1. As a result, the reduction rate of the produced reduced iron was about 90%.

Thus, as shown in Reference Examples 1 to 5 and Examples 1 and 2 , even when purified COG was used as a starting material, hydrocarbons were in no way in comparison with the case where natural gas was used as a starting material. The reforming reaction proceeded and a high concentration of synthesis gas was obtained. Also, by using the synthesis gas, iron ore mainly composed of iron oxide could be reduced at a high reduction rate comparable to that of synthesis gas from natural gas. Therefore, by using a gas containing a carbon compound produced as a by-product in the ironmaking process, it is cheaper and more efficient than natural gas, and stably has a highly reducible synthesis mainly composed of hydrogen and carbon monoxide. It has been found to produce gas. In addition, by using the produced syngas as an alternative to coke for ironmaking reduction, the amount of CO ₂ generated from the ironmaking process can be greatly reduced, and an ironmaking process with less environmental impact can be established. it is conceivable that.

According to the present invention, a gas containing a carbon compound by-produced in the iron-making process is synthesized in a highly reducible manner mainly consisting of hydrogen and carbon monoxide in the presence of a catalyst at low cost and high efficiency. Gas can be produced. Further, by mixing a converter gas mainly composed of carbon monoxide with the synthesis gas, a large amount of synthesis gas having an arbitrary hydrogen / carbon monoxide ratio can be produced stably. Furthermore, by reducing the above-mentioned synthesis gas having high reducibility by bringing it into contact with iron ore mainly composed of iron oxide, reduced iron can be produced with high efficiency, and the amount of CO ₂ generated from the iron making process can be greatly increased. The industrial applicability is high.

Claims (3)

  The coke oven gas generated in the iron making process is reformed using steam and catalyst or steam and oxygen and catalyst to obtain a synthesis gas with a total of 92% or more of hydrogen and carbon monoxide. Mixing the gas generated from the converter to produce a synthesis gas having an arbitrary hydrogen / carbon monoxide ratio of 1.5 or more and less than 3.3, and reducing iron ore with the produced synthesis gas A method for producing reduced iron.   The method for producing reduced iron according to claim 1, wherein the reforming is performed after removing impurities and heavy hydrocarbons in the coke oven gas. The method of producing reduced iron according to claim 1 or 2 steam discharged by the method for producing reduced iron according to claim 1 or 2, characterized in that recycled as part or all of the modifying agent .