JP5598423B2 - Method for producing pre-reduced agglomerates - Google Patents

Description

  The present invention produces a reducing gas from a solid carbon material using a gasification furnace, and preliminarily reduces iron oxide contained in iron ores with the reducing gas to form a prereduced product. The present invention relates to a method for producing an agglomerated product. More specifically, the reduction gas can be produced stably and efficiently to improve the metallization rate of the prereduced product, and the coke ratio is greatly reduced when the resulting prereduced agglomerated product is used as a blast furnace raw material. The present invention relates to a method for producing a prereduced agglomerated product.

Unless otherwise stated, the definitions of terms in this specification are as follows.
"Solid carbon material": For example, biomass, waste, plastic waste (waste plastics), shredding dust of automobiles and home appliances, waste wood, coal (especially non-caking coal), RDF, RPF It is a substance containing at least one hydrocarbon-containing substance. However, “RDF” is an abbreviation of “Refuse Delivered Fuel”, which means fuel derived from waste, and “RPF” is an abbreviation of “Refuse Plastic and Paper Fuel”, and among wastes, waste paper It also means fuels made mainly from waste plastics.
“Iron ores”: ores with a total iron content of 50% by mass or more, manufactured from fine-grained iron ore and iron dust, and with a total iron content of 50% by mass or more Includes ores and pellets.

[Problems with the blast furnace method]
Currently, most of the iron is produced by the blast furnace method. In the blast furnace method, iron ore, which is an iron raw material and oxide, is reduced by a reducing material and melted to produce hot metal. The iron raw material and the reducing material to be introduced into the blast furnace are required to have a particle size (particle size) that can maintain a certain level of strength and ensure air permeability in the furnace. For this reason, the carbon material used as the reducing material depends on coke obtained by blending a large amount of strongly caking coal and dry-distilled, and the iron raw material largely depends on the agglomerated sintered ore.

  That is, in the hot metal production by the blast furnace method, the raw material cost is high because high quality is required for the raw material. Moreover, it is necessary to install ancillary facilities other than the blast furnace such as a coke production facility and a sintering facility, and the facility cost is high. Furthermore, in the blast furnace, a large amount of energy and carbon materials are consumed to reduce the iron ore that is an oxide, and as a result, the steel industry accounts for 15 to 20% of carbon dioxide emissions in Japan. is occupying.

  Moreover, in hot metal production by the blast furnace method, in recent years, quality deterioration and price increase of raw materials for iron making such as iron raw materials and reducing materials have become problems. It is important to effectively use solid hydrocarbon-containing substances such as biomass in order to respond to the decline in quality and price of raw steelmaking fuel while reducing carbon dioxide emissions. However, when a solid carbon material containing a hydrocarbon-containing material is heat-treated, a large amount of hydrocarbon-based gas is generated in the temperature range of 573 to 973 K, and liquefaction occurs during the cooling process and adheres to the furnace piping. Yes, not fully utilized.

  On the other hand, in hot metal production by the blast furnace method, part of iron oxide contained in iron ores is preliminarily reduced in a prereduction furnace from relatively inexpensive fine iron ore and iron ore made from ironmaking dust. Thus, it has been studied to produce a pre-reduced product by using metallic iron as a raw material for iron in a blast furnace. Since the metallic iron contained in the pre-reduced product does not need to be reduced in the blast furnace, the coke ratio can be greatly reduced, which can be expected to reduce the carbon dioxide emission and improve the productivity. The production of pre-reduced materials continues to expand against the background of the fact that the plant is inexpensive and easy to operate, and that it can be located even on a small scale. However, in the production of the pre-reduced product, a reducing gas is necessary for pre-reducing iron ores in the pre-reduction furnace.

  Conventional methods for producing a reducing gas include a method for producing from natural gas and a method for producing from a hydrocarbon-containing substance. The method for producing a reducing gas by each method and its problems will be described below.

[Method of manufacturing from natural gas]
Non-Patent Document 1 discloses a process of a method for producing a reducing gas from a typical natural gas. In this method, in order to produce reducing gas, natural gas (main component is methane) is brought into contact with water vapor or carbon dioxide gas so that the natural gas represented by the following reaction formulas (1) and (2) is obtained at about 1073 to 1173K. A reforming reaction takes place to produce CO and hydrogen.
CH ₄ + H ₂ O → CO + 3H ₂ −205 kJ / mol (1)
CH ₄ + CO ₂ → 2CO + 2H ₂ −247 kJ / mol (2)

  If the hydrogen-rich gas produced by the reforming reaction of natural gas is used as the reducing gas for iron ores, and the resulting prereduced product is used as the iron raw material for the blast furnace, the amount of coke used and the carbon dioxide emission in iron production in the blast furnace The amount can be greatly reduced. However, the reforming reaction of natural gas shown in the above reaction formulas (1) and (2) is an endothermic reaction. Therefore, external heat compensation is necessary. Further, in the method of producing a reducing gas from natural gas, an expensive nickel-based catalyst is used to promote the reforming reaction. However, nickel-based catalysts have problems that deteriorate due to poisoning by sulfur contained in natural gas, carbon deposition on the catalyst, sintering of the catalyst, and the like.

  The same kind of reducing gas produced by a natural gas reforming reaction can also be produced by coal gasification. Patent Document 1 discloses a method for producing reduced gas by gasifying coal and producing reduced iron from iron ore using the reduced gas. However, since the method for producing reducing gas shown in Patent Document 1 uses coal, even if iron ore is used as a pre-reduced product using the produced reducing gas, it leads to a reduction in carbon dioxide emission. Absent.

[Method of manufacturing from hydrocarbon-containing substances]
In Patent Document 2, biomass and waste plastics, which are hydrocarbon-containing substances, are used as raw materials for reducing gas. Patent Document 2 discloses a raw material containing one or both of biomass and waste plastic in addition to coal, or a method of producing reducing gas by gasifying coal by partial combustion and pyrolysis with oxygen in a gasification furnace. Indicates. The produced reducing gas is cooled and then fed into a shaft furnace filled with iron ore, and the iron ore is preliminarily reduced in the process in which the reducing gas rises in the shaft furnace.

  Since carbon dioxide gas generated from biomass is not counted as carbon dioxide emission, if reducing gas derived from biomass can be used when producing hot metal by the blast furnace method, carbon dioxide emission can be greatly reduced. In addition, there is an advantage that inferior raw materials that are difficult to be directly input into a blast furnace such as biomass and waste plastic can be used not only as fuel but also as a reducing material.

  However, the reducing gas production method disclosed in Patent Document 2 has the following problems. The raw material used in the manufacturing method of the reducing gas shown by patent document 2 is blown into a gasification furnace with oxygen from a gasification burner. Therefore, the coal used as a raw material is limited to pulverized pulverized coal. That is, energy and cost for grinding must be considered.

  Moreover, although the manufacturing method of the reducing gas shown by patent document 2 can include one or both of biomass and waste plastic in addition to pulverized coal, use after making biomass and waste plastic into powder form It becomes. Therefore, the biomass added to the raw material is limited to woody and agricultural biomass that can be easily pulverized and easily transported by airflow. However, the amount of reducing gas required for hot metal production by the blast furnace method is enormous. Therefore, it is considered desirable to use as many types of biomass as possible, and it is disadvantageous that the types of biomass that can be used are limited to woody and agricultural biomass that can be easily crushed and easily transported by air. is there.

In the reducing gas production method disclosed in Patent Document 2, raw materials such as coal and biomass are burned by a gasification burner. In this case, the raw material is rapidly heated at the burner point, and CO and H ₂ are produced by gasification by partial combustion and thermal decomposition. However, the time for which the raw material is held near the fire point is extremely short, and it is considered that the raw material goes out of the fire point without being partially burned or thermally decomposed and gasified. For this reason, in the manufacturing method of the reducing gas shown by patent document 2, most of carbon contained in a raw material will exist with a solid substance even after passing through a fire point, and the combustible contained in coal or biomass The yield to reducing gas (CO, H ₂ ) is reduced.

  From the viewpoint of improving the production efficiency of reducing gas, rather than combusting raw materials such as coal and biomass with a gasification burner, a packed bed is formed in the gasification furnace with the raw material, and oxygen is blown into the packed bed. It is preferable to use a gasification furnace. If it is a gasification furnace of the type that forms a packed bed, there is no need to pulverize the raw material, and there is an advantage that the types of biomass that can be used increase.

  Incombustible substances contained in raw materials such as biomass and coal should be made completely harmless and recycled. As a means for that purpose, it is desirable to melt the incombustible component to form slag. The reducing gas manufacturing method disclosed in Patent Document 2 also describes that the incombustible component contained in the raw material is melted and dropped from the lower part of the gasification furnace to be solidified slag in the water tank. However, Patent Document 2 does not describe a specific method for recovering molten slag.

  It is important that the molten slag generated in the gasification furnace is stably discharged out of the furnace. If the molten slag does not discharge stably and remains in the gasification furnace, various troubles occur. For example, when the molten steel slag level in the gasification furnace rises and rises to a level higher than the supply port for blowing oxygen, pulverized coal, etc., the supply port is blocked and oxygen or pulverized coal is blown. It becomes unstable. Furthermore, there is a possibility that the molten slag accumulated at the height of the supply port splashes to the duct connected to the upper part of the gasification furnace due to the protruding pressure of the supplied oxygen, and the duct is blocked.

  Further, in order to discharge the molten slag out of the furnace stably, the temperature of the molten slag before being discharged out of the furnace needs to be maintained at 1623K or more. As a type of gasification furnace for that purpose, it is preferable to form a packed bed with the raw material and blow oxygen into the raw material rather than combusting a raw material such as coal or biomass with a gasification burner as in Patent Document 2 above. The heat exchange between the high temperature gas generated by the combustion of the combustible material contained in the solid material and the solid material (non-combustible material) is highly efficient, and the heat receiving efficiency to the solid material is improved, so that high temperature molten slag is easily generated.

  Patent Documents 3 to 7 are proposals relating to a method for producing a reducing gas using a gasification furnace of a type that forms a packed bed, wherein the packed bed is made of a solid carbon material containing waste plastic or biomass. There is.

  For example, Patent Document 3 discloses a method in which combustible waste containing plastic is introduced into a vertical shaft furnace (gasification furnace) together with iron oxide to obtain pyrolysis gas mainly composed of hydrogen together with reduced iron. Has been. In this shaft furnace (gasification furnace), a packed bed made of combustible waste and iron oxide is formed, and tuyere is installed at the bottom of the furnace. In the method for producing a reducing gas shown in Patent Document 3, the upper temperature of the packed bed is maintained at about 573 K, and the combustible waste thrown into the upper portion of the packed bed gradually decreases as it falls in the packed bed. The temperature is raised and pyrolysis gasification proceeds to generate pyrolysis gases such as hydrogen, methane and ethylene. Further, tar is produced as a by-product due to thermal decomposition, and this is adhered to the iron oxide and can be used as part of the reducing material and heat source in a high-temperature atmosphere in the furnace.

  According to the method shown in Patent Document 3, tar and soot produced as a by-product due to thermal decomposition of combustible waste adhere to iron oxide and are collected. Reducing gas).

  However, when the temperature of a hydrocarbon-containing substance such as combustible waste such as plastic is slowly raised, a part of the raw material is in a semi-molten state during the raising of the temperature. Thereby, the ventilation of the gas rising from the lower part of the packed bed is obstructed, or the unloading of the raw material in the packed bed is worsened by the semi-molten raw material adhering to the furnace wall. For this reason, the operation of the shaft furnace used as a gasification furnace becomes unstable.

  In addition, tar produced as a by-product in the process of slowly raising the temperature may cause trouble by adhering to gas piping and gas processing equipment disposed at the subsequent stage of the gasification furnace. In addition, the yield of combustible waste to reducing gas is reduced by the amount of combustible waste tarized.

  In Patent Documents 4 to 7, as in Patent Document 3, the operation of the gasifier is inefficient due to the semi-molten raw material and by-product tar generated in the process of gradually raising the temperature of the solid carbon material such as biomass and shredder dust. It is expected to be stable.

  When reducing gas is produced in a gasification furnace and raw materials for the blast furnace are obtained from the prereduced product reduced in the prereduction furnace by the reducing gas, if trouble occurs in the gasification furnace, the reducing gas to the subsequent prereduction furnace The supply of is stopped. Therefore, when trouble occurs in the gasification furnace, naturally, the preliminary reduction of iron ore cannot be performed in the preliminary reduction furnace. Therefore, if trouble frequently occurs in the gasification furnace, it becomes difficult to efficiently produce a prereduced product.

  If a reducing gas storage tank for storing reducing gas is installed between the gasification furnace and the prereduction furnace, it is possible to supply the reducing gas to the prereduction furnace even if a trouble occurs in the gasification furnace. However, if troubles occur frequently in the gasification furnace, the reducing gas cannot be stored in the gas storage tank. In that case, the supply of the reducing gas to the preliminary reduction furnace must be stopped.

R & D Kobe Steel Engineering Reports, vol. 50, no. 3 (2000), Hiroshi Inada, p. 86-89 Materia, vol. 43, no. 1 (2004), Takamoto Yamamoto, Hirotaka Sato, Yoshinori Matsukura, p. 55, FIG. Journal of Fuel Association, vol. 66, no. 9 (1987), Takashi Matsuoka, p763

JP 2002-146420 A Japanese Patent No. 4250472 JP 2003-147419 A JP 2001-311084 A JP 2004-160397 A Japanese Patent Laying-Open No. 2005-330552 JP 2005-325322 A Japanese Patent No. 3558039 Patent No. 4007389 JP 2011-63835 A

  As mentioned above, in hot metal production by the blast furnace method, the use of prereduced products obtained by prereducing iron ore as raw materials for blast furnaces, and reducing the coke ratio will be studied. Has been. This preliminary reduction requires a reducing gas, and conventional methods for producing a reducing gas include a method of producing from natural gas and a method of producing from a hydrocarbon-containing substance.

  In the method of producing from natural gas shown in Non-Patent Document 1, since the reforming reaction of natural gas is an endothermic reaction, heat compensation is required, or the catalyst used for the reaction is deteriorated. Become. Further, by the method of gasifying coal shown in Patent Document 2 to produce a reducing gas, it is possible to obtain the same kind of gas as the reducing gas obtained by the reforming reaction of natural gas. It does not lead to a reduction in the amount.

  On the other hand, as a method for producing from a hydrocarbon-containing substance, there is a method for producing a reducing gas as described in Patent Document 2, and a raw material obtained by adding biomass and waste plastic to coal is blown into a gasification furnace together with oxygen with a gasification burner. The reducing gas is produced by gasification by partial combustion and thermal decomposition. In this method, since the raw material needs to be pulverized in order to blow the raw material together with oxygen from the gasification burner, the energy and cost are required for the pulverization, and the usable biomass is limited.

  Moreover, as a method for producing from a hydrocarbon-containing substance, Patent Documents 3 to 7 show a reducing gas production method for forming a packed bed made of a solid carbon substance containing a hydrocarbon-containing substance in a gasification furnace. Yes. However, if the temperature of the hydrocarbon-containing material is raised slowly, the raw material will be semi-molten and the air permeability of the packed bed will be hindered, or it will adhere to the furnace wall and worsen the unloading of the raw material. It becomes unstable. In addition, tar generated as a result of thermal decomposition in the process of increasing the temperature adheres to gas piping and other equipment arranged at the rear stage of the gasifier and may cause troubles or turn into solid carbon material reducing gas. Decrease the yield of.

  The present invention has been made in view of such a situation, and by stably and efficiently producing a reducing gas, the metallization rate of the prereduced product can be improved, and the resulting prereduced agglomerated product is obtained. Provided is a method for producing a pre-reduced agglomerate for the purpose of significantly reducing the coke ratio when used as a blast furnace raw material.

  In order to solve the above-mentioned problems, the present inventors conducted various tests and made extensive studies. As a result, a vertical gasification furnace having a lance was used, and a packed bed made of a solid carbon material was used at the bottom of the furnace. It was found that reducing gas can be produced stably and efficiently by blowing a gas containing 70% by volume or more of oxygen toward the upper end surface of the packed bed. By prereducing the iron ores using the reducing gas thus produced, the metallization rate of the prereduced prereduced product can be improved, and the prereduced agglomerate obtained from the prereduced product can be converted into a blast furnace. It was found that the coke ratio can be greatly reduced when used as a raw material.

  Further, as a solid carbon material that forms a packed bed in the lower part of the gasification furnace when producing the reducing gas, a solid carbon material having a wet base true calorific value per kg of 13.5 MJ or more and 44.1 MJ or less is used. It was clarified that the reduction potential of the produced reducing gas can be secured by using it. Furthermore, when reducing gas is produced, the reduction potential of the produced reducing gas can be increased by blowing gaseous fuel into the gasification furnace from a position higher than the upper end surface of the packed bed. It was clarified that the metallization rate can be further improved.

  Here, the reduction potential means the sum of the dry base CO gas concentration and the hydrogen gas concentration contained in the produced reducing gas, and the CO gas concentration or hydrogen gas concentration is (CO or hydrogen gas volume) / ( (Reducing gas volume).

  This invention is completed based on said knowledge, and makes the summary the manufacturing method of the prereduction agglomerate of following (1)-(4).

(1) Using a vertical gasification furnace having a lance, a packed bed made of a solid carbon material having a wet base true calorific value per kg of 13.5 MJ or more is formed in the lower part of the furnace, A step of producing a reducing gas by blowing a gas containing 70% by volume or more of oxygen toward the upper end surface of the packed bed, and supplying iron ore together with the reducing gas to the prereduction furnace, the highest in the prereduction furnace A step of preliminarily reducing the iron ore by heating to a temperature of 973 K or higher, and producing a prereduced product having a metallization rate of 0.4 to 0.8; To produce a coarse-grained prereduced product, and agglomerate is produced by agglomerating the fine-grained prereduced product of the classified fine-grained prereduced product and coarse-grained prereduced product. The agglomerated material is classified into coarse particles and fine particles, and the agglomerated material of coarse particles is used. Method for producing a prereduction agglomerates, which comprises a step of producing a pre-reduced agglomerates, the.

(2) The above (1), further comprising a step of producing a prereduced agglomerated product by mixing the prereduced agglomerated product composed of the coarse agglomerated product and the coarse granular prereduced product. A method for producing the pre-reduced agglomerated product according to the above.

(3) as the solid carbonaceous material, and further, according to the above (1) or (2) wet basis net calorific value per 1kg is characterized by using a solid carbon material is 4 4.1MJ less A method for producing a pre-reduced agglomerate.

(4) Gas fuel having a dry base true calorific value per 1 Nm ³ of 10 MJ or more and 45 MJ or less is blown into the gasification furnace from a position higher than the upper end surface of the packed bed. )-(3) The manufacturing method of the pre-reduction agglomerate in any one of.

  The method for producing a pre-reduced agglomerate of the present invention can improve the metallization rate of the pre-reduced product pre-reduced from iron ore by the reducing gas by stably and efficiently producing the reducing gas. When the pre-reduced agglomerate obtained from the reduced product is used as a blast furnace raw material, the coke ratio can be greatly reduced.

FIG. 3 is a schematic diagram showing a configuration example of a gasification furnace having a lance that is a vertical gasification furnace, in which a packed bed is formed in the lower part of the furnace, and a combustion-supporting gas is blown toward an upper end surface thereof. It is a figure which shows the example of a process flow of the manufacturing method of the pre-reduction agglomerate of this invention. It is a figure which shows the relationship between the true calorific value of a solid-state carbon substance, and the reduction potential of manufactured reducing gas. It is a figure which shows the relationship between the dry base true calorific value of gaseous fuel, and the reduction potential of manufactured reducing gas.

  As described above, the method for producing the pre-reduced agglomerate according to the present invention uses a vertical gasification furnace having a lance, forms a packed layer made of a solid carbon material at the lower part of the furnace, and forms a packed bed from the lance. A step of producing a reducing gas by blowing a gas containing 70% by volume or more of oxygen toward the upper end surface, supplying iron ore together with the reducing gas to the prereduction furnace, and setting the maximum temperature in the prereduction furnace to 973K The step of preliminarily reducing the iron ore by heating as described above to produce a prereduced product having a metallization rate of 0.4 or more and 0.8 or less, and classifying the prereduced product into coarse particles and fine particles A coarse-grained prereduced product, and agglomerated by agglomerating the classified fine-grained prereduced product and the fine-grained pre-reduced product of the coarse-grained prereduced product to produce the agglomerated product. Pre-reduced agglomerates consisting of coarse agglomerates are classified into coarse and fine particles. Characterized in that it comprises the steps of forming a. The production of the reducing gas, the example of the process flow, the preliminary reduction, and the agglomeration of the preliminary reduced product in the method for producing the preliminary reduced agglomerated product of the present invention will be described in detail below.

[Production of reducing gas]
When the solid carbon material is heated and slowly heated during the production of the reducing gas, the generation of the reducing gas starts at a temperature of 573 K or higher, but in the temperature range of about 573 to 973 K, the solid carbon material is half of the solid carbon material. Melting and tar generation occur, causing operational troubles. As a means for suppressing such trouble, it is effective to rapidly heat the solid carbon material to about 1273K.

  For this reason, the method for producing a pre-reduced agglomerate of the present invention has a lance as shown in Patent Document 8 and Patent Document 9 in order to rapidly heat the solid carbon material when producing the reducing gas. Using a gasification furnace of the type, a packed bed made of a solid carbon material is formed at the lower part of the furnace, and a reducing gas is produced by blowing a combustion-supporting gas toward the upper end surface of the packed bed. As the combustion-supporting gas blown from the lance toward the upper end surface of the packed bed, a high-concentration oxygen gas containing 70% by volume or more of oxygen is used. This is because a gas having a high reduction potential can be generated by blowing high-concentration oxygen gas toward the upper end surface of the packed bed.

  FIG. 1 is a schematic diagram showing a configuration example of a gasification furnace which is a vertical gasification furnace having a packed bed formed at the lower part of the furnace and having a lance for blowing inflammable gas toward the upper end surface thereof. . In the lower part of the gasification furnace 19 shown in the figure, a packed bed made of a solid carbon material is formed, and the position of the upper end surface 9 of this packed bed is indicated by a two-dot chain line. The combustion-supporting gas 5 is blown and blown from the furnace center lance 1 disposed at the furnace center 20 toward the packed bed upper end surface 9. The temperature of the packed bed upper end surface 9 is maintained at about 1273 K by partial combustion of the solid carbon material 8 by the combustion-supporting gas 5 blown from the furnace center lance 1.

The solid carbon material 8 charged from the raw material inlet 7 falls on the packed bed upper end surface 9. Therefore, the solid carbon material 8 is rapidly heated, and CO, H ₂ , and CH ₄ are generated by thermal decomposition. The product gas includes hydrocarbons such as CH ₄ , which are reformed to CO and H ₂ by the combustion-supporting gas 5 blown from the furnace center lance 1. Further, the combustion supporting gas 5 is blown from a plurality of upper tuyere 3 arranged at a position higher than the upper end surface 9 of the packed bed, and CO or H ₂ produced thereby is partially burned and provided on the upper wall of the gasifier. The reducing gas 11 discharged by the gas discharge port 10 thus made can be easily maintained at a high temperature of 1373K or higher.

  Thus, in the gasification furnace shown in the figure, the hydrocarbons are completely decomposed by rapidly heating the solid carbon material 8 and maintaining the furnace upper temperature at a high temperature. In particular, the combustion-supporting gas blown from the furnace center lance 1 blows from above the hydrocarbons rising from the bottom, so that the mixture of the combustion-supporting gas and the hydrocarbons is promoted, and the hydrocarbons are more concentrated. It can be decomposed efficiently. By using a vertical gasification furnace having a lance in this way, reducing gas can be produced efficiently.

  The temperature of the packed bed upper end surface 9 can be managed based on the value of the temperature measurement sensor 16-2 installed on the furnace wall. The temperature control of the packed bed upper end surface 9 includes the amount of the combustion-supporting gas 5 blown from the furnace center lance 1 and the height level of the furnace center lance 1 (the distance from the tip of the furnace center lance 1 to the packed bed upper end surface 9). ) Is possible. Further, the temperature of the reducing gas 11 can be measured by installing the temperature measuring sensor 16-1 in the upper part of the gasification furnace, and can be controlled by the amount of the combustion-supporting gas 5 blown from the upper tuyere 3.

  Further, below the upper end surface 9 of the packed bed, carbon (fixed carbon) contained in the residue of the solid carbon material 8 rapidly heated at the upper end surface 9 of the packed bed by the combustion-supporting gas 5 blown from the furnace center lance 1. ). Further, the combustion-supporting gas 5 is blown from the lower tuyere 2 arranged at a position lower than the packed bed upper end surface 9 toward the furnace center 20. In this way, by combining the flammable gas blowing from the lance 1 and the lower tuyere 2, the hot spots are concentrated in the furnace center which is the intersection of these hot spots. By concentrating the melting zone of incombustible components (ash and metals) contained in the residue of the solid carbon material 8 at the center of the high temperature furnace where the hot spots are concentrated, the high temperature molten slag 12 and the molten metal 13 are formed. The molten slag 12 and the molten metal 13 can be discharged more stably as compared with the case where the furnace center lance 1 is not installed.

Thus, the molten metal 13 and the molten slag 12 generated in the packed bed 9 can be discharged from the molten metal outlet 18 provided on the lower side wall of the gasifier. The basicity (CaO / SiO ₂ mass ratio) of the molten slag is preferably controlled from 0.8 to 1.2 from the viewpoint of maintaining the fluidity of the molten slag.

  Moreover, as shown in Non-Patent Document 2, the shape of the lower part of the gasification furnace may be such that the molten slag 12 and the molten metal 13 spring out from the lower part of the packed bed and are continuously discharged out of the furnace. For example, when the gasification furnace 19 shown in FIG. 1 is used, the bottom surface of the gasification furnace is inclined so that the height of the bottom surface becomes lower as it approaches the melt discharge port 18, and from the melt discharge port 18. A spray nozzle is provided on the water tank into which the molten slag 12 and molten metal 13 to be discharged are charged, and the path for supplying the molten slag 12 and molten metal 13 discharged from the molten metal discharge port 18 to the water tank.

  By making the bottom surface of the gasification furnace lower as it approaches the molten metal discharge port 18, the molten slag 12 and the molten metal 13 generated in the lower part of the packed bed are continuously discharged from the molten metal discharge port 18 to the outside of the furnace. The The discharged molten slag 12 and molten metal 13 are crushed and cooled by water sprayed from a spray nozzle, and then fall into a water tank. Accordingly, the bottom of the gasification furnace is shaped to become lower as it approaches the molten metal discharge port 18, and by providing a water tank and a spray nozzle, the molten slag 12 and the molten metal 13 generated in the gasification furnace are more stable. It can be discharged outside the furnace and recovered.

  Using the vertical gasification furnace 19 having the lance 1 as described above, a packed layer made of a solid carbon material is formed in the lower part of the furnace, and oxygen is 70 volume% or more from the lance 1 toward the packed bed upper end surface 9. By blowing the contained gas, the solid carbon material can be rapidly heated at the upper end face 9 of the packed bed. By rapidly heating the solid carbon material at the upper end surface 9 of the packed bed, tar can be prevented from being generated as a by-product in the process of raising the temperature of the solid carbon material. In addition, it is possible to prevent a decrease in yield from the solid carbon material to the reducing gas due to the by-product of tar.

  Further, by combining the flammable gas blowing from the lance 1 and the lower tuyere 2, the hot spot is concentrated at the center of the furnace that is the intersection of these hot spots. By concentrating the melting zone of incombustible components (ash and metals) contained in the residue of the solid carbon material 8 at the center of the high temperature furnace where the hot spots are concentrated, the high temperature molten slag 12 and the molten metal 13 are formed. The molten slag 12 and the molten metal 13 can be discharged more stably compared with the case where the furnace center lance 1 is not generated and troubles caused by the molten slag remaining in the gasification furnace can be prevented. By using the vertical gasification furnace having the lance 1 as described above, the reducing gas can be stably produced.

  In order to use the gas produced in the gasification furnace as the reducing gas, it is necessary to increase the reducing gas's reduction potential (the sum of the CO gas concentration and the hydrogen gas concentration), and efficient reduction of iron ore is effective. In order to proceed smoothly, the reduction potential needs to be 0.8 or more. Therefore, in the method for producing a pre-reduced agglomerated product of the present invention, it is preferable that the net calorific value per kg of the solid carbon material 8 put into the gasification furnace is 13.5 MJ or more.

By making the net calorific value per kg of the solid carbon material 8 13.5 MJ or more, the production of CO and H ₂ by thermal decomposition is promoted, so the reduction potential of the produced reducing gas Can be secured to 0.8 or more. As shown in the examples described later, the higher the true calorific value of the solid carbon material 8 on the wet base, the higher the reduction potential of the produced reducing gas.

The reason for this is that carbon and hydrogen, which are raw materials for CO gas and hydrogen gas, are contained at a higher concentration as the true calorific value of the solid carbon material is higher. When carbon and hydrogen are contained at a high concentration in the solid carbon material, the amount of generated CO gas and hydrogen gas naturally increases. In the gasifier, a part of the generated CO gas and hydrogen gas is subjected to secondary combustion (reaction formula: CO + 1 / 2O ₂ → CO ₂ , or reaction formula: H ₂ + 1 / 2O ₂ → H ₂ O). This keeps the upper part of the furnace at a high temperature and suppresses the generation of tar and the like. However, when a solid carbon material having a high true calorific value is used, a high temperature can be maintained even at a low secondary combustion rate. It becomes possible.

  From the viewpoint of increasing the true calorific value of the solid carbon material 8 on the wet basis, it is preferable to reduce the moisture content in the solid carbon material 8, and for this purpose, the solid carbon material 8 is charged into the gasifier. It is effective to dry it before. As the drying process, a method of drying the solid carbon material 8 while blowing hot air into a dryer, sun drying, or natural drying in a yard with a roof can be employed.

  From the viewpoint of utilizing a hydrocarbon-containing substance having a low true calorific value, a solid fuel such as coke can be supplementarily added to the solid carbon substance 8. By mixing solid fuel and hydrocarbon-containing material to form solid carbon material 8, if the solid calorific value of solid carbon material 8 can be maintained on a wet basis, hydrocarbon-containing material with low true calorific value can also be used. it can.

  On the other hand, if the solid calorific value 8 on the wet basis of the solid carbon material 8 exceeds 44.1 MJ, there is a risk of ignition and fire when the solid carbon material is subjected to drying treatment, and care should be taken in handling the solid carbon material. Cost. For this reason, in the method for producing a pre-reduced agglomerate of the present invention, it is preferable that the net calorific value of the solid carbon material 8 on a wet basis is 44.1 MJ or less.

  Here, the reason for prescribing the solid carbon material to be introduced into the gasification furnace with the wet base true calorific value is as follows. Generally, the amount of heat measured when a unit amount of fuel with a predetermined temperature is completely burned with necessary and sufficient dry air and the combustion gas is cooled to a predetermined temperature is called a calorific value. In a calorimeter that measures the calorific value, water vapor in the combustion gas is condensed into water, and the measured calorific value includes the latent heat of condensation of water vapor. The calorific value including the latent heat of condensation of water vapor is called the total calorific value, and the calorific value obtained by subtracting the latent heat of condensation of water vapor from this total calorific value is called the true calorific value. Inside the gasification furnace, the water vapor generated by the combustion of the solid carbon material is discharged outside the furnace without condensing. Therefore, the solid carbon material to be charged into the gasification furnace should be discussed in terms of the true calorific value that does not consider the condensation latent heat of the generated water vapor.

The true calorific value (kJ) is expressed by the following formula (3), and is a calorific value obtained by subtracting the condensation latent heat of steam (= 2500 × (9 × h + w)) from the total calorific value (kJ) measured based on JIS M8814. is there. The coefficient of 2500 means the condensation latent heat per kg of water vapor (kJ / kg). h represents the mass (kg) of hydrogen contained in 1 kg of the solid carbon material, and w represents the mass (kg) of water contained in 1 kg of the solid carbon material.
True calorific value = total calorific value−2500 × (9 × h + w) (3)

Moreover, even if it is a solid carbon material with a high true calorific value on a dry basis, a reducing gas having a high reduction potential cannot be obtained with a raw material having a high moisture content. This is because it is necessary to consider the endotherm due to the evaporation of moisture. When the endothermic reaction due to the evaporation of moisture becomes large, it is necessary to increase the input heat amount in order to maintain the temperature in the gasification furnace. For this purpose, a part of the CO gas generated by the partial combustion is subjected to secondary combustion (reaction formula: CO + 1 / 2O ₂ → CO ₂ ), or a part of the hydrogen gas is combusted (reaction formula: H ₂ + 1 / 2O ₂ → H ₂ O), and as a result, the reduction potential of the generated gas is lowered. Therefore, what is important in the solid carbon material to be introduced into the gasifier is not the true calorific value on the dry basis, but the true calorific value per unit weight of the solid carbon material containing moisture, that is, the wet basis. It is the true calorific value at.

In the method for producing a pre-reduced agglomerate of the present invention, gaseous fuel having a dry base true calorific value per 1 Nm ³ of 10 MJ or more and 45 MJ or less is blown into a gasification furnace from a position higher than the upper end surface of the packed bed. Is preferred. Thereby, the reduction potential of the produced reducing gas can be increased. LNG, coke oven gas, etc. are raised as gaseous fuel blown from a position higher than the upper end surface of the packed bed.

When the dry base true calorific value per 1 Nm ^{3 of the} gaseous fuel is less than 10 MJ, the reduction potential of the reducing gas is lowered. By increasing the true calorific value of the gaseous fuel, the reduction potential of the reducing gas can be increased. However, if it exceeds 45 MJ, the amount by which the reduction potential increases by increasing the true calorific value becomes small. Here, in consideration of the fact that the amount of the gas fuel becomes expensive due to the high amount of true heat generation, the amount of true heat generation of the gas fuel is preferably set to 45 MJ or less.

  When blowing gaseous fuel, gaseous fuel is blown into the position higher than the packed bed upper end surface 9 formed in the lower part of a gasification furnace. When blown from a position lower than the upper end surface 9 of the packed bed, the flow rate of the gas rising in the packed bed is increased, the solid carbon material forming the packed bed is fluidized and further scattered, and as a dust together with the reducing gas. It will be discharged from the gasifier. In this case, the yield of carbon and hydrogen contained in the solid carbon material to the reducing gas is reduced, and the reduction potential of the produced reducing gas is also reduced.

  In the gasification furnace shown in FIG. 1, the incombustible component contained in the solid carbon material 8 is more stable as the molten slag 12 or the molten metal 13 from the lower tuyere 2 installed at a position lower than the upper end surface 9 of the packed bed. It is possible to blow gaseous fuel such as LNG or LPG for the purpose of exhausting automatically. However, blowing more than necessary destabilizes the operation. For example, LNG and LPG are hydrocarbons, but the endothermic reaction due to thermal decomposition may cause a temperature drop in the lower part of the gasification furnace, which may hinder stable discharge of molten slag and molten metal.

  When gaseous fuel is blown from a position higher than the packed bed upper end surface 9, it is rapidly heated by heat exchange with the atmosphere in the gasification furnace, and the gaseous fuel becomes high temperature. The reforming reaction of hydrocarbons such as methane gas shown in the above reaction formulas (1) and (2) occurs by the hydrocarbons contained in the gaseous fuel and the carbon dioxide gas or water vapor contained in the atmosphere of the gasifier. CO and hydrogen are produced. Alternatively, hydrocarbons contained in the gaseous fuel are partially burned by oxygen contained in the combustion-supporting gas to be blown to produce CO and hydrogen. Thus, by blowing gaseous fuel from a position higher than the packed bed upper end surface 9, the reduction potential of the produced reducing gas can be increased.

  When gaseous fuel is blown from a position higher than the packed bed upper end surface 9, the flow velocity at the nozzle (feather) outlet is set to 1 Nm / second or more and 150 Nm / second or less. When the flow velocity at the nozzle outlet is less than 1 Nm / sec, the injected gaseous fuel rises in the vicinity of the furnace wall of the gasification furnace and is discharged without contributing to reducing gas production. On the other hand, when the flow rate exceeds 150 Nm / sec, the pressure loss in the nozzle increases, so that stable blowing becomes difficult.

  As with the gaseous fuel, it is also effective from the viewpoint of increasing the reduction potential of the reducing gas to blow liquid fuel (liquid hydrocarbons) from a position higher than the upper end surface 9 of the packed bed.

[Example of process flow]
FIG. 2 is a diagram showing a process flow example of the method for producing a pre-reduced agglomerate according to the present invention. The process flow shown in the figure shows a solid carbon material 31 that is a raw material for the reducing gas, a drying facility 32 that dries the solid carbon material, and a gasifier 33 that produces the reducing gas. Further, in order to process the produced reducing gas, a gas cooling device 37 that cools the reducing gas, a dust removal equipment 38 that removes the cooled reducing gas, a desulfurization device 40 that desulfurizes the dust-reducing reducing gas, and a desulfurized product. 2 shows a moisture removing device 41 that removes moisture from the reducing gas and a reducing gas storage tank 43 that stores the reducing gas from which moisture has been removed. Further, a prereduction furnace 44 using iron ore 45 as a prereduced product with a reducing gas, a sieve classifying device 48 for classifying the prereduced product 46 and the agglomerated product 51 into coarse particles and fine particles, and a fine particle prereduced product 49 shows a briquetting apparatus 50 that agglomerates 49, and a blast furnace 53 that obtains hot metal 54 from a pre-reduced agglomerated material (coarse granular pre-reduced material 47, coarse granular briquette (agglomerated material 52)) or iron ore.

  In the process flow shown in the figure, a solid carbon material 31 containing biomass, waste, etc. is charged into a vertical gasification furnace 33 having a furnace center lance 34 to produce a reducing gas 36. At this time, in the gasification furnace 33, a packed bed made of a solid carbon material is formed in the lower part of the furnace, and a gas 35 containing 70% by volume or more of oxygen is blown from the furnace center lance 34 toward the upper end surface of the packed bed. As shown in the figure, the solid carbon material 31 can be put into the gasification furnace 33 after moisture is removed in advance by the drying equipment 32.

  The produced reducing gas 36 can be supplied to the preliminary reduction furnace 44 at a high temperature after being removed by the dust removing equipment 38. However, the reducing gas 36 contains moisture that inhibits the reduction reaction of iron ores. Therefore, it is preferable to supply the reducing gas 36 to the preliminary reduction furnace 44 after cooling and separating and removing moisture.

  When the reducing gas 36 is cooled by the gas cooling device 37, the solid carbon material 31 contains halogens such as chlorine, and in the course of cooling, dioxins are re-synthesized and there is a concern that they may be discharged. 8 and Patent Document 9, it is necessary to rapidly cool the high-temperature reducing gas 36 generated in the gasification furnace.

  On the other hand, when there is no concern that dioxins are re-synthesized, it is possible to utilize the sensible heat of the high-temperature reducing gas 36. For example, since the reducing gas 36 discharged from the gasification furnace 33 includes carbon dioxide gas and water vapor, these gases are brought into contact with the natural gas 58 and shown in the above-described reaction formulas (1) and (2). A reforming reaction can occur, and the concentrations of CO gas and hydrogen gas in the reducing gas can be further increased. Since the reaction formulas (1) and (2) are endothermic reactions, the reducing gas 36 is cooled as the reaction proceeds.

It is also possible to bring the hot reducing gas 36 into contact with the carbon material 57 and convert CO ₂ and H ₂ O contained in the reducing gas into CO gas and hydrogen gas according to the following reaction formulas (4) and (5). It is.
C + H ₂ O → CO + H ₂ (4)
C + CO ₂ → 2CO (5)

  After the cooling, the reducing gas 36 separates and removes the dust 39 by the dust removing equipment 38 and further removes the water 42 by the water removing device 41. If the reducing gas 36 contains sulfur such as hydrogen sulfide and there is a concern about the corrosion of the subsequent equipment, the desulfurization apparatus 40 desulfurizes. After the moisture removal, the reducing gas 36 is temporarily stored in the reducing gas storage tank 43 and then supplied to the preliminary reduction furnace 44.

  Inside the preliminary reduction furnace 44, iron ore 45 is supplied together with the reducing gas 36, and the reducing gas 36 and the iron ore 45 are brought into contact with each other, whereby the preliminary reduced product 46 is produced. The produced prereduced product 46 is classified into a coarse granular prereduced product 47 on the sieve and a fine granular prereduced product 49 under the sieve by a sieve classifier 48. The fine particulate pre-reduced product 49 under the sieve is agglomerated by the briquetting device 50 to form a briquette (agglomerated product) 51 and then classified again by the sieve classifying device 48.

  Coarse granular briquette (agglomerated product) 52 and coarse granular pre-reduced product 47 are put into a blast furnace 53. In the method for producing a pre-reduced agglomerated product of the present invention, as shown in FIG. 2, briquettes (agglomerated product) 51 can be supplied together with the pre-reduced product 46 to a single sieve classifier 48 for classification. The briquette (agglomerated product) 51 may be supplied to a sieve classification device different from the sieve classification device to which the pre-reduced product 46 is supplied for classification. In the latter case, the sieved products (coarse granular pre-reduced iron 47 and coarse granular briquette 52) classified by the respective sieve classifiers are put into the blast furnace 53. On the other hand, the fine particles under the sieve are agglomerated by the briquetting apparatus 50 as a fine granular pre-reduced product 49.

[Preliminary reduction]
As a usage destination of the reducing gas 36 manufactured in the gasification furnace, blowing into a blast furnace is also conceivable. However, even if the reducing gas 36 is blown into a blast furnace having a large furnace diameter and forming a packed bed, it is difficult to cause the reducing gas 36 to reach the center of the blast furnace. It is conceivable that most of the reducing gas 36 that has been blown passes through the wall with low ventilation resistance and is discharged without being sufficiently in contact with the iron ore. For this reason, in this invention, the method of blowing in the preliminary reduction furnaces 44, such as a shaft furnace, was adopted.

  As the preliminary reduction furnace 44, a rotary kiln furnace or a rotary hearth furnace that performs reduction with an inexpensive carbonaceous material, a reducing gas, or the like can be used. However, the preliminary reduction furnace 44 is a typical preliminary reduction furnace. It is preferred to use the shaft furnace shown. In the method described in Non-Patent Document 1, natural gas is reformed to produce CO gas and hydrogen gas, which are blown into the middle stage of a vertically elongated shaft furnace filled with iron ore, and reduced iron Manufacturing. Since this shaft furnace has a smaller furnace diameter than the blast furnace, the reducing gas 36 that has been blown in reaches the core, and can contact the iron ore 45 with high efficiency to advance the preliminary reduction. Further, since the shaft furnace blows the reducing gas into the packed bed made of iron ore, the contact efficiency between the iron ore and the reducing gas is better than that of a rotary kiln furnace or a rotary hearth furnace.

Further, a large amount of reducing gas (CO, hydrogen) remains in the exhaust gas discharged from the preliminary reduction furnace 44, and these are preferably used again as the reducing gas. However, since the exhaust gas contains CO ₂ and H ₂ O, they are separated and removed or supplied to the preliminary reduction furnace 44 after being converted to CO or hydrogen gas.

  As a means for converting to CO or hydrogen gas, a method in which the exhaust gas of the prereduction furnace 44 is brought into contact with natural gas to cause the reforming reaction shown in the above reaction formulas (1) and (2), With the method of causing the reactions shown in the reaction formulas (4) and (5) to occur, the concentration of CO gas and hydrogen gas in the exhaust gas can be increased to obtain a reducing gas. For example, in the process flow shown in FIG. 2, the exhaust gas 55 of the preliminary reduction furnace is supplied to the gas cooling device 37 and brought into contact with natural gas or carbonaceous material, so that the exhaust gas can be used again as the reducing gas.

  In the method for producing a pre-reduction agglomerated product of the present invention, the metallization rate of the pre-reduction product 46 discharged from the pre-reduction furnace 44 is set to 0.4 or more and 0.8 or less. When the metallization rate of the prereduced product 46 exceeds 0.8, it is necessary to ensure a very long residence time in the prereduction furnace 44, and the production efficiency is lowered. As the reduction rate (metallization rate) of the pre-reduced product 46 increases, the required average residence time dramatically increases. In theory, an infinite time is required to make the metallization rate 1.0. However, if the prereduced product 46 is used as a prereduced agglomerated material for the blast furnace raw material, the iron oxide contained in the prereduced product does not need to be completely metallized. This is because the blast furnace is a device for reducing iron oxide.

  On the other hand, when the metallization rate of the prereduced product 46 produced in the prereduction furnace 44 is less than 0.4, the effect of reducing the coke ratio when the prereduced agglomerate obtained is used as an iron raw material in a blast furnace. Becomes smaller. Therefore, it becomes difficult to reduce the total energy for producing the hot metal 54 as compared with the conventional method in which iron ore is reduced only with a blast furnace. Further, from the viewpoint of agglomerating the fine particulate prereduced product 49 to obtain an agglomerated product having high strength, the metalization rate of the prereduced product 46 should be 0.4 or more. Since metallic iron has ductility, when it is agglomerated by pressure molding, the irregularities on the surface of the metallic iron particles are engaged by mutual friction and pressing, forming a strong bonded state between the particles, and agglomerating with high strength. It becomes a monster. Thus, the presence of metallic iron contributes to the agglomeration. Therefore, it becomes difficult to produce an agglomerated product having a high strength when the metallization rate contained in the pre-reduced product 46 is lowered.

  In the method for producing a pre-reduction agglomerated product of the present invention, iron ore is supplied to the pre-reduction furnace together with the reducing gas, and the pre-reduction furnace is heated to a maximum temperature of 973K or higher. Although the reason which prescribes | regulates the maximum temperature in a preliminary reduction furnace as 973K or more is mentioned later, by this, it can suppress pulverizing when iron ore is preliminary reduced in a preliminary reduction furnace.

  In the method for producing a pre-reduced agglomerate according to the present invention, the gasification furnace is stably operated by blowing a gas containing 70% by volume or more of oxygen toward the upper end surface of the packed bed, and the gasification furnace is stopped. This prevents the supply of reducing gas to the preliminary reduction furnace from being stopped. As a result, iron ores can be prereduced stably and efficiently, and the metallization rate of the prereduced product can be improved.

[Agglomeration of pre-reduced product]
As for agglomeration of the fine granular prereduced product 49, a method of hot forming the fine granular prereduced product and a method of cold forming at room temperature are known. When both are compared, from the viewpoint of producing a high-strength briquette by compression molding at high density, hot molding that can utilize the thermoplasticity of metallic iron is advantageous, and there are many applications. However, in the case of hot forming, the briquetting apparatus is cooled and a large installation space is required, which contributes to an increase in cost. Therefore, in the method for producing a pre-reduced agglomerated product of the present invention, it is preferable to form the granular pre-reduced product 49 in the cold and agglomerate it.

  There is a concern that the cold molding is difficult to use in the blast furnace 53 because the strength of the briquette produced is lower than the hot molding. In the case of cold molding, as shown in Patent Document 10, it is preferable that the briquette molded in the cold is immersed in water and left standing, which can greatly increase the strength and eliminate the above concerns. can do.

  When water immersion and static treatment are used, for example, a basket is placed in a pool filled with water, and the briquettes discharged from the briquetting apparatus are dropped directly on the basket in the pool and immersed in water. It is also possible to take out the briquette from the water by pulling it up together with the basket and leave it in a state where the briquette is accommodated in the basket and dry it. Thereby, the intensity | strength of a briquette can also be raised, suppressing that an impact is provided to a briquette in the conveyance process and a briquette collapse | crumbles.

  Examples of water used for the water immersion treatment include tap water and industrial water. Moreover, strength is expressed by re-oxidizing a part of the metallic iron contained in the briquette by the water immersion / stationary treatment. For this reason, when the strength of briquettes is insufficient, industrial wastewater and seawater containing chlorine that does not cause problems such as equipment corrosion can be used, which is effective in promoting strength development.

  In this way, the finely granular prereduced product is briquetted (agglomerated) to form a briquette (agglomerated product) 51 made of the prereduced product, and the coarse particles of the briquette (agglomerated product) 51 are used as the prereduced agglomerated product. . The prereduced agglomerates and coarse granular prereduced products made of coarse agglomerates thus obtained have a particle size and strength that can be directly charged into a blast furnace and have a high metallization rate. For this reason, if a pre-reduced agglomerated product and a coarse granular pre-reduced product made of coarse agglomerated material are used as blast furnace raw materials, a large amount of coke is ensured while ensuring the reducing agent action and aeration space action of coke in the blast furnace. The reduction of the ratio can be achieved, the suppression of carbon dioxide emissions can be promoted, and an excellent blast furnace method system can be constructed.

  In the method for producing the pre-reduced agglomerated product of the present invention, when the agglomerated product or the pre-reduced product is classified into coarse particles and fine particles, air permeability can be secured when the classified coarse particles are directly put into a blast furnace. Just do it. For example, coarse particles can be classified to 5 to 40 mm and fine particles can be classified to 5 mm or less.

  In the method for producing a pre-reduction agglomerated product of the present invention, it is preferable to use a sintered ore that is easily reduced and powdered in a blast furnace as the iron ores 45 that are pre-reduced in the pre-reduction furnace 44 and become pre-reduction products. This is because the reduction powdering in the blast furnace can be suppressed by pre-reducing the sintered ore. The operation will be described below.

Sinter, expands when Fe ₂ O ₃ containing at around 823K is reduced to Fe ₃ O _4, have been known to violently powdered, sinter which has been pre-reduced is Fe ₂ Reduction powdering does not occur because it contains almost no O ₃ . For this reason, the use of a pre-reduced product in which the sintered ore is iron ore is used in a blast furnace, there is an advantage that air permeability in the blast furnace can be improved without causing deterioration of air permeability due to reduced powdering. This advantage can offset the deterioration in air permeability in the blast furnace accompanying the reduction of the coke ratio. Therefore, if the prereduced product 46 produced from sintered ore is used as a blast furnace raw material by the method for producing a prereduced agglomerate according to the present invention, the reducing material action of coke and the aeration space action are secured in the blast furnace. , Can achieve a significant reduction in coke ratio, and can suppress carbon dioxide emissions.

  Naturally, it is also conceivable that the sintered ore is reduced to powder during the reduction in the preliminary reduction furnace 44. However, reducing powdering can be suppressed by preliminarily reducing the temperature of the sintered ore in the preliminary reducing furnace 44 in a temperature range in which reducing powdering hardly occurs. As described above, it is known that sintered ore vigorously reduces and powders around 823K. By causing the preliminary reduction to proceed at a temperature higher than this temperature, reducing powdering in the preliminary reduction furnace 44 can be suppressed. For this reason, the manufacturing method of the preliminary reduction agglomerate of the present invention sets the maximum temperature in the preliminary reduction furnace to 973K or higher, which is higher than 823K. On the other hand, the maximum temperature in the prereduction furnace is preferably 1573 K or less from the viewpoint of heat resistance of the prereduction furnace and energy cost.

  Further, if the sintered ore is heated from room temperature in a pre-reduction furnace and the maximum temperature is set to 973K or more, there is a concern that reduced powder is formed in the vicinity of 823K. This concern can be eliminated by starting the reduction reaction at a high temperature from the beginning. As the means, a method of supplying the sintered ore discharged from the sintering machine to the preliminary reduction furnace 44 in a high temperature state without cooling to room temperature can be adopted.

  In order to verify the effect of the method for producing the pre-reduction agglomerated product of the present invention, “pre-reduction of iron ore”, “true calorific value of solid carbon material”, “effect of gaseous fuel injection” and “fine-grained pre-reduction” A test on “briquette of reduced product” was conducted.

1. Pre-reduction of iron ore [test method]
A reduction gas production test was performed using the gasification furnace shown in FIG. 1, and a preliminary reduction test of iron ore was performed using a mixed gas having a composition simulating the reduction gas produced in the gasification furnace. In the preliminary reduction test, 500 g of sintered ore (iron ore) having a particle size of 15 to 19 mm is filled in the reaction tube for JIS-RI test (inner diameter Φ75 mm), and the test temperature (1173 K) is reached under nitrogen gas flow. After raising the temperature, a mixed gas simulating a reducing gas was supplied at a flow rate of 900 NL / h.

  The time for supplying the mixed gas in the preliminary reduction test was 1 hour. However, when the gasifier operation is stopped due to trouble or the like, the reducing gas cannot be supplied to the preliminary reduction furnace. Therefore, when a stoppage occurred in the gasification furnace, the supply of the mixed gas to the preliminary reduction test apparatus was stopped for a time corresponding to the stoppage time. The metallization rate of the sintered ore (preliminary reduction product) after preliminary reduction was investigated.

  In the reducing gas production test, industrial waste mixed with automobile waste and plastic waste was used as the solid carbon material. The component analysis values of this solid carbon material are as shown in Table 1, and the true calorific value on a wet basis was 19.2 MJ / wet-kg. Table 2 shows component analysis values of the sintered ore used in the preliminary reduction test. Here, “T.Fe” means the total iron content, and “M.Fe” means metallic iron.

  In the reducing gas production test using the gasification furnace shown in FIG. 1, the solid carbon material 8 was introduced from the inlet 7 and dropped onto the packed bed upper end surface 9 formed at the lower part of the furnace. The temperature of the packed bed upper end surface 9 is controlled by the value indicated by the temperature measuring device 16-2, and the blowing amount of the combustion-supporting gas (high-concentration oxygen gas) 5 blown from the furnace center lance 1 and the furnace center lance 1 By adjusting the height position, it was set to about 1273K. Further, the atmosphere temperature at the upper part of the gasification furnace is adjusted so that the value of the temperature measuring device 16-1 is approximately adjusted by adjusting the blowing amount of the combustion-supporting gas (high concentration oxygen gas) 5 blown from the upper tuyere 3. Control was performed to 1453K.

On the other hand, below the packed bed upper end surface 9, the combustion-supporting gas 5 is blown from the furnace center lance 1 and the lower tuyere 2 to burn the pyrolysis residue carbon (fixed carbon) contained in the solid carbon material 8. The incombustible component was melted by the combustion heat and discharged out of the gasification furnace as high-temperature molten metal 13 and molten slag 12. The basicity (CaO / SiO ₂ mass ratio) of the molten slag was adjusted to 0.8 or more and 1.2 or less by adding lime, and the fluidity was maintained. In addition, the lower tuyere 2 has a double pipe structure, LNG was supplementarily supplied from the inner pipe, and combustion-supporting gas was blown from the outer pipe.

  In Inventive Example 1-1, a gas containing 100% by volume of oxygen was used as the combustion-supporting gas, and in Inventive Example 1-2, a gas containing 70% by volume of oxygen was used as the supporting gas. In Comparative Example 1, the furnace center lance 1 is raised to the out-of-furnace standby position of the gasification furnace, and oxygen is supplied by 100% by volume from the upper tuyere 3 and the lower tuyere 2 without injecting combustion-supporting gas from the furnace center lance. The contained supporting gas was blown.

Table 3 shows the test conditions and test results in the present invention example and the comparative example as the solid carbon material input rate (ton / day, wet basis) during operation in a steady state, and the oxygen concentration (volume%) of the combustion-supporting gas. ), Blast amount of combustion-supporting gas from the furnace center lance, upper tuyere and lower tuyere (Nm ³ / h), LNG blowing rate from the lower tuyere (Nm ³ / h), N _{2 of} purge process Gas blowing rate (Nm ³ / h), atmosphere temperature (K) at the top of the gasifier, temperature (K) at the top surface of the packed bed, composition of the produced reducing gas (mixed gas) and reduction potential (CO gas concentration and (Sum of hydrogen gas concentration), operation time in the steady state of the gasifier (hours), time of supplying the mixed gas to the prereduction unit (minutes), prereduction test temperature (K) and prereduced metal The conversion rate (M.Fe / T.Fe) is shown. Here, the N ₂ gas blowing rate (Nm ³ / h) in the purge process is N for the purpose of cooling the furnace monitoring window installed in the gasification furnace and protecting the equipment such as the packed bed upper surface level measuring device 15. is an amount that blows ₂ gas. The composition of the reducing gas is a concentration (volume ratio) on a dry basis represented by (component gas volume) / (reducing gas volume).

[Test results]
In Comparative Example 1, the reducing gas was produced without blowing the supporting gas from the furnace center lance. The temperature of the upper surface of the packed bed was as low as about 873K. Further, in Comparative Example 1, during the operation of the gasification furnace, hydrocarbons contained in the solid carbon material are semi-molten and adhere to the furnace wall, and an abrupt gas caused by the separation and dropping (shelf dropping). There were frequent problems such as frequent occurrence, and the pressure inside the furnace rose to a value exceeding the design value of the gasifier. For this reason, it was 19 hours out of 24 hours that the gasifier could be operated in a steady state. That is, the operating rate (= time during which steady operation was performed / test execution time) was 0.8. Therefore, even if the preliminary reduction is performed for 60 minutes, it should be considered that the reduction gas can actually be supplied for 48 minutes. For this reason, in the preliminary reduction test, preliminary reduction was performed for 48 minutes, and the metallization rate of the obtained preliminary reduced product was only 0.35.

  On the other hand, in Invention Example 1-1, a combustion-supporting gas containing 100% by volume of oxygen was blown from the furnace center lance. The operation of the gasifier was extremely stable, there was no trouble stop, and a reducing gas mainly composed of CO and hydrogen could be stably produced over 24 hours. For this reason, in the preliminary reduction test, preliminary reduction was performed for 60 minutes without stopping the supply of the mixed gas, and the metallization rate of the obtained preliminary reduced product reached 0.5. In addition, when the preliminary reduction was further continued for the preliminary reduction product obtained in Inventive Example 1-1, the metallization rate after 30 minutes (after the preliminary reduction for 90 minutes in total) reached 0.79.

  In Inventive Example 1-2, a combustion-supporting gas containing 70% by volume of oxygen was blown from the furnace center lance. The operation of the gasifier was stable and the reducing gas could be produced over 24 hours. However, in Example 1-2 of the present invention, the ratio of CO and hydrogen in the produced reducing gas was low, so the reduction rate of the sintered ore was lower than that of Example 1-1 of the invention, and the calcination after one hour had elapsed. The ore metallization rate remained at 0.4.

  Here, in Example 1-2 of the present invention, the combustion-supporting gas containing 70% by volume of oxygen was blown to the furnace center lance, the upper tuyere, and the lower tuyere. If the oxygen concentration of the property gas is increased, the oxygen concentration of the combustion-supporting gas blown from the furnace center lance toward the upper end surface of the packed bed can be reduced to less than 70% by volume. However, in this case, a combustion-supporting gas having a different oxygen concentration is produced. That is, two types of oxygen production facilities must be prepared.

  On the other hand, from the viewpoint of reducing gas production, it is advantageous to use a combustion-supporting gas having a high oxygen concentration. Under these circumstances, the reason for considering the use of a combustion-supporting gas having a low oxygen concentration is to increase the production efficiency of oxygen by reducing the oxygen concentration somewhat. Here, according to Non-Patent Document 3, although there is a difference depending on the manufacturing method, it is considered that there is a condition in which the manufacturing efficiency is high in the oxygen concentration range of 70 to 93% by volume. That is, as the oxygen concentration is lower, the production efficiency is not improved. Therefore, making the oxygen concentration of the combustion-supporting gas blown from the furnace center lance less than 70% by volume deteriorates the production efficiency of the combustion-supporting gas.

  Moreover, when reducing the oxygen concentration of the combustion supporting gas blown from the furnace center lance, the oxygen concentration of the combustion supporting gas from the upper tuyere and the lower tuyere needs to be increased. In this case, if a combustion-supporting gas having an oxygen concentration close to 100% by volume is blown from the upper tuyere and the lower tuyere, the production efficiency of the combustion-supporting gas is greatly reduced. That is, it is a disadvantageous method to increase the oxygen concentration of the combustion-supporting gas blown from the upper tuyere and the lower tuyere and to reduce the purity from the furnace center lance to less than 70% by volume.

2. As shown in Table 3 above, in the reducing gas produced according to Example 1-2 of the present invention, the sum of CO gas concentration and hydrogen gas concentration (reduction potential) is 0.8. However, from the viewpoint of efficiently reducing iron ores, the reduction potential needs to be higher than this value. For that purpose, it is important to manage the true calorific value of the solid carbon material to be charged.

[Test conditions]
In this test, a test was conducted in which a reducing gas was produced using a plurality of solid carbon materials having different wet base true calorific values. The reducing gas was produced under the same conditions as Example 1-1 of the present invention in the reducing gas production test of “1. Pre-reduction of iron ore” described above, except for the wet base true calorific value of the solid carbon material. Table 4 shows the substances constituting the solid carbon substance used in this test, the wet base true calorific value (MJ / wet-kg), and the reduction potential of the produced reducing gas.

  In Inventive Example 2-1 and Inventive Example 2-2, industrial waste in which automobile waste and plastic waste are mixed is used as the solid carbon material. In the present invention example 2-1 and the present invention example 2-2, since the mixing ratio of the automobile waste material and the plastic waste is different, the true calorific value of the solid carbon material is different. In Example 2-3 of the present invention, general waste was used. This general waste includes wastes derived from animals and plants such as food, papers and plants.

[Test results]
FIG. 3 is a diagram showing the relationship between the true calorific value of the solid carbon material and the reduction potential of the produced reducing gas. The figure shows the test results of Invention Examples 2-1 to 2-3. From the figure, it was confirmed that as the true calorific value of the solid carbon material increases, the reduction potential of the reducing gas produced in the gasification furnace also increases. In addition, it has been clarified that the reduction potential of the produced reducing gas can be increased to 0.8 or more by setting the wet base true calorific value per kg of the solid carbon material to be introduced into the gasification furnace to 13.5 MJ or more. .

  Here, in order to increase the true calorific value of the solid carbon material introduced into the gasification furnace, pre-drying of the raw material is an effective means, and the wet base true calorific value per kg of the solid carbon material is reduced by drying. It is also possible to set it to 13.5 MJ or more. However, when drying the solid carbon material, attention should be paid to the following points.

  As a general drying method, there is a method in which a solid carbon material is charged into a drum of a dryer and dried by blowing hot air while stirring the solid carbon material as the drum rotates. However, since the solid carbon material contains a combustible component, there is a concern about ignition and fire during drying. As a cause of ignition and fire, over-drying of solid carbon material is raised. When the moisture is dried to less than 5% by mass, there is an increased risk of trouble such as fire. Table 5 shows the true calorific value of the main solid carbon material on a dry basis.

  Among solid carbon materials, polypropylene is an example of a material having a high true calorific value. The dry base true calorific value per 1 kg of polypropylene is 46.5 MJ / dry-kg. This is 44.1 MJ / wet-kg when converted into a wet base true calorific value at a moisture content of 5 mass%. Therefore, the true calorific value of the solid carbon material discharged from the dryer should be 44.1 MJ / wet-kg or less on a wet basis. If the true calorific value is higher than this, there is a possibility of trouble occurring in the drying equipment, so care must be taken in handling the solid carbon material.

3. Effect of gaseous fuel injection [Test conditions]
The reduction potential of the reducing gas can also be increased by blowing gaseous fuel into the gasification furnace. In order to confirm this effect, in this test, the change in reduction potential when gaseous fuel was injected was calculated based on the thermal mass balance. In the above calculation, it is assumed that gaseous fuel is blown from the upper tuyere, and the other conditions are the same as those of the invention example 1-1 in the reducing gas production test of “1. Preliminary reduction of iron ores” described above. It was. The upper tuyere has a double-pipe structure, and gaseous fuel can be blown from the inner pipe and combustion-supporting gas can be blown from the outer pipe.

  The gaseous fuels targeted in this test are LNG, LPG, coke oven gas, blast furnace gas, and converter gas, and the composition of these components is shown in Table 6. The component analysis values of the solid carbon material used in this test are as shown in Table 7, and the true calorific value on a wet basis is 13.4 MJ / wet-kg.

[Test results]
Table 8 shows the solid carbon substance input rate (ton / day, wet base), the wet base true calorific value (MJ / wet-kg) of the solid carbon substance, the type of gaseous fuel injected, and the dry base true calorific value. (MJ / dry-kg) and blast volume (Nm ³ / h) and the reduction potential of the produced reducing gas are shown.

  In Comparative Example 3-1, the reduction potential of the produced reducing gas without blowing gaseous fuel was 0.79. Moreover, in Comparative Example 3-2 or Comparative Example 3-3, blast furnace gas or converter gas having a low dry base true calorific value was blown, and the reduction potential was lowered as compared with Comparative Example 3-1. In Invention Example 3-1, LNG having a high dry base true heat generation amount was blown, and the reduction potential was increased to 0.85 as compared with Comparative Example 3-1. Further, in the present invention example 3-2, coke oven gas having a high dry base true heat generation amount was blown, and in the reference example, LPG having a high dry base true heat generation amount was blown, and both the present invention example 3-2 and the reference example were compared. Compared to Example 3-1, the reduction potential increased.

FIG. 4 is a diagram showing the relationship between the dry base true calorific value of the gaseous fuel and the reduction potential of the produced reducing gas. In the same figure, the test results of Comparative Examples 3-2 and 3-3, Invention Examples 3-1 and 3-2 and Reference Example are shown, and the reduction potential of Comparative Example 3-1 in which no gaseous fuel was blown is indicated by a broken line. . From this figure, it was confirmed that the reduction potential of the produced reducing gas can be increased by blowing gaseous fuel having a dry base true calorific value per 1 Nm ³ of 10 MJ or more. Further, when the true calorific value exceeded 45 MJ, the amount of increase in the reduction potential with respect to the increase in the true calorific value of the gaseous fuel was slight. Here, it can be confirmed that it is preferable to set the dry base true heat generation amount per 1 Nm ^{3 to} 45 MJ or less in consideration of the fact that the gaseous fuel becomes expensive as the true heat generation amount is high.

4). Briquetting of fine granular pre-reduced material [Test conditions]
Among the pre-reduction products obtained by pre-reduction of iron ore, massive coarse granular pre-reduction products can be used directly in the blast furnace, but fine granular pre-reduction products cannot be directly charged into the blast furnace. .

  The fine particulate pre-reduced product should be agglomerated into briquettes and the like and then charged into the blast furnace. Therefore, the possibility of briquetting was tested. In the briquetting test, a preliminarily reduced product obtained by preliminarily reducing the sintered ore was pulverized to obtain a fine granule prereduced material derived from the sintered ore. The component analysis values of the fine granular prereduced product are as shown in Table 9, and two kinds of fine granular prereduced products having metallization rates of 0.50 and 0.79 were used. Part of this fine particulate pre-reduced product is collected, and the particle size distribution is obtained by classifying the sieve meshes in the order of 4 mm, 2.8 mm, 2.0 mm, 1.0 mm, 0.5 mm, 0.25 mm and 0.125 mm. investigated. The results of the particle size distribution investigation are as shown in Table 10.

The fine granular pre-reduced product was supplied to a double roll briquetting apparatus. On the roll surface of the briquetting apparatus, one row of almond molds serving as briquette molds is installed in the width direction. The mold has a dimension of 28 mm long × 18 mm wide × 4 mm deep, and the volume of the briquette to be manufactured is designed to be about 3 cm ³ . When briquetting, the compression pressure applied to the roll was 55 kN / cm (= total load applied to the roll / effective roll width).

  In the test, after briquetting in the cold, the briquette was submerged in water for 1 minute (water immersion treatment), and then the briquette was allowed to stand in the atmosphere for 5 days (stationary treatment). The crushing strength of the briquettes thus obtained was measured. The crushing strength here is a load when a load is applied to the briquette from above and is broken.

  Table 11 shows the type of fine particulate pre-reduced product, briquetting conditions, briquetting processing speed, product yield, and briquette crushing strength. Here, the product yield is a preliminary that is obtained by classifying the obtained briquettes (agglomerated materials) and supplying the mass (kg) of coarse particles of the briquettes (agglomerated materials) having a particle diameter of 10 mm or more to the briquetting apparatus. It is divided by the mass (kg) of the reduced powder.

[Test results]
In Example 4-1 of the present invention, a finely granular pre-reduced product (sintered ore-derived A) having a metallization rate of 0.5 was used, and the briquette crushing strength after standing treatment reached 2076 N / lum. On the other hand, in Example 4-2 of the present invention, a particulate prereduced product (sintered ore-derived B) having a metallization rate of 0.79 was used, and the briquette crushing strength reached 3520 N / lumps. Both are strong enough to use the blast furnace. From these, it was clarified that the granular prereduced product can be agglomerated (briquette) cold, and the briquettes can be made strong enough to be directly put into the blast furnace by water immersion and standing treatment.

  The method for producing a pre-reduced agglomerate of the present invention stably and efficiently produces a reducing gas from a solid carbon material. Furthermore, a prereduced product having a high metallization rate is obtained from iron ore using the produced reducing gas. By using the pre-reduced agglomerate obtained from this pre-reduced product as a blast furnace raw material, the coke ratio in the blast furnace can be greatly reduced.

  Therefore, if the method for producing a pre-reduced agglomerate according to the present invention is applied to the production of hot metal by the blast furnace method, the carbon dioxide emission can be reduced. In particular, if biomass is used as the solid carbon material, it can greatly contribute to the reduction of carbon dioxide emission.

1: Lance, 2: Lower tuyere, 3: Upper tuyere,
5: Combustion gas (high concentration oxygen gas), 6: Auxiliary fuel, 7: Raw material inlet,
8: Solid carbon material, 9: Top surface of packed bed, 10: Gas outlet,
11: reducing gas, 12: molten slag, 13: molten metal, 14: furnace wall,
15: packed bed upper end surface level measurement device, 16-1: temperature measurement sensor (furnace upper part),
16-2: Temperature measurement sensor (upper end surface of packed bed), 18: Molten metal outlet,
19: gasification furnace, 20: furnace center,
31: Solid carbon material, 32: Drying equipment, 33: Gasification furnace,
34: Lance, 35: Combustion gas (high concentration oxygen gas), 36: Reducing gas,
37: Gas cooling device, 38: Dust removal equipment, 39: Dust, 40: Desulfurization device,
41: water removal device, 42: water, 43: reducing gas storage tank,
44: Prereduction furnace, 45: Iron ore, 46: Prereduction product,
47: Coarse granular prereduced product, 48: Sieve classifier, 49: Fine granular prereduced product,
50: Briquetting apparatus, 51: Briquette (agglomerated product),
52: Coarse granular briquette (agglomerated product) 53: Blast furnace, 54: Hot metal,
55: Pre-reduction furnace exhaust gas, 57: Carbon material, 58: Natural gas

Claims (4)

Using a vertical gasification furnace having a lance, a packed bed made of a solid carbon material having a wet base true calorific value per kg of 13.5 MJ or more is formed in the lower part of the furnace, and the packed bed is formed from the lance. A step of producing a reducing gas by blowing a gas containing 70% by volume or more of oxygen toward the upper end surface;
Iron ore is supplied to the prereduction furnace together with the reducing gas, and the maximum temperature in the prereduction furnace is heated to 973 K or more to prereduce the iron ore, and the metallization rate is 0.4 to 0.8. Producing a prereduced product that is:
Classifying the prereduced product into coarse particles and fine particles to produce a coarse prereduced product;
Of the classified fine granular pre-reduced product and coarse granular pre-reduced product, the fine granular pre-reduced product is agglomerated to produce an agglomerated product, and the agglomerated product is classified into coarse particles and fine particles. And a step of producing a pre-reduced agglomerate comprising agglomerates of grains.   2. The preliminary reduction according to claim 1, further comprising a step of producing a preliminary reduction agglomerate by mixing the preliminary reduction agglomerate composed of the coarse agglomerates and the coarse granular prereduction product. A method for producing a reduced agglomerate. As the solid carbonaceous material, and further, per 1kg humidity based net calorific value is pre-reduced agglomerate of claim 1 or 2, characterized by using a solid carbon material is 4 4.1MJ less Production method. The gaseous fuel having a dry base true heat generation amount per 1 Nm ³ of 10 MJ or more and 45 MJ or less is blown into the gasification furnace from a position higher than the upper end surface of the packed bed. The manufacturing method of the prereduction agglomerate in any one.

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