Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/02—Making spongy iron or liquid steel, by direct processes in shaft furnaces
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace

Definitions

• This application discloses a method for producing reduced iron and a shaft furnace.
• a technology for producing reduced iron by reducing iron oxide using a direct reduction method using a shaft furnace. Specifically, raw materials containing iron oxide are supplied from the top of the shaft furnace to the interior, and reducing gas is supplied from the side wall of the shaft furnace to the interior. The iron oxide is reduced inside the shaft furnace, and reduced iron is obtained from the bottom of the shaft furnace.
• the reducing gas contains, for example, hydrogen gas.
• reducing gas containing hydrogen gas is supplied from the side wall of the shaft furnace to the interior, much of the hydrogen gas rises along the vicinity of the furnace wall, which can easily result in an insufficient supply of hydrogen gas to the center (central part) inside the shaft furnace. As a result, the average reduction rate of the raw materials is likely to decrease.
• Patent Document 1 discloses a technology for improving the uniformity of gas within a shaft furnace by dividing the furnace body. However, dividing the furnace body increases equipment costs and reduces the space utilization rate of the furnace.
• Patent Document 2 discloses technology for dividing the gas exhaust system at the top of a shaft furnace. However, simply dividing the gas exhaust system makes it difficult to improve the uniformity of the gas inside the furnace. Furthermore, dividing the gas exhaust system complicates the structure of the furnace top.
• Patent Document 3 discloses a technique for installing a pipe for introducing reducing gas in the center of a shaft furnace.
• the shaft furnace structure becomes complex, increasing equipment costs, and the pipe in the center of the shaft furnace is prone to damage, such as excessive pressure being generated in the pipe during operation.
• Patent Document 4 discloses a technology for controlling the feed position of raw materials into a shaft furnace in the radial direction of the furnace, depending on the temperature of the exhaust gas at the top of the shaft furnace. However, even if the feed position of raw materials is controlled, it is difficult to improve the uniformity of the gas inside the furnace.
• Patent Document 5 discloses a technology in which hollow tubes are arranged in a staggered pattern inside a shaft furnace, disrupting the vertical downward flow of powder and granular material inside the furnace and circulating high-temperature gas through the hollow tubes.
• placing hollow tubes inside the furnace increases equipment costs and reduces the space utilization rate within the furnace.
• the hollow tubes are prone to damage, such as excessive pressure being generated in them during operation.
• the present application discloses the following aspects as one of means for solving the above problems.
• ⁇ Aspect 1> Feed raw materials containing iron oxide into the shaft furnace from the top, supplying a reducing gas containing hydrogen gas into the shaft furnace from a side wall thereof; reducing the iron oxide to obtain reduced iron from a lower part of the shaft furnace;
• a method for producing reduced iron comprising: taking an action to change the flow of the reducing gas inside the shaft furnace from a side wall side of the shaft furnace to a center side of the shaft furnace;
• a method for producing reduced iron comprising: ⁇ Aspect 2> A method for producing reduced iron according to aspect 1, The action is at least one of the following actions 1 to 4: Method for producing reduced iron: Action 1: cooling at least an inner wall of the shaft furnace at least between a supply position of the raw material and a supply position of the reducing gas; Action 2: mixing the reducing gas with an inert gas; Action 3: Dividing the reducing gas supplied into the shaft furnace into a first gas having a relatively low reducing
• a method for producing reduced iron according to aspect 2 The action 1 is the following action 1A: Method for producing reduced iron: Action 1A: Cooling at least the inner wall of the shaft furnace by water cooling at least between the raw material supply position and the reducing gas supply position.
• Action 4 The method for producing reduced iron according to aspect 2 or 3
• the action 4 is the following action 4A: Method for producing reduced iron: Action 4A: Supplying the raw material to the side wall of the shaft furnace so that the average particle diameter of the raw material supplied to the center of the shaft furnace is larger than the average particle diameter of the raw material supplied to the side wall of the shaft furnace.
• Aspect 5 The method for producing reduced iron according to any one of Aspects 2 to 4,
• the first gas and the second gas in the action 3 satisfy one or both of the following conditions A and B: Method for producing reduced iron: Condition A: the temperature of the first gas is lower than the temperature of the second gas; Condition B: The hydrogen gas concentration of the first gas is lower than the hydrogen gas concentration of the second gas.
• ⁇ Aspect 6> The method for producing reduced iron according to any one of Aspects 2 to 5, estimating information about the reduction rate of the feedstock inside the shaft furnace; performing the action based on the estimated information;
• a method for producing reduced iron comprising:
• a method for producing reduced iron comprising:
• the information is a reduction rate of the raw material on the side wall side inside the shaft furnace or an index representing the reduction rate, The action is taken when the estimated payout rate or an indicator representative of the payout rate is greater than a first threshold.
• a method for producing reduced iron comprising: The information is a reduction rate of the raw material on the side wall side inside the shaft furnace or an index representing the reduction rate, The action is taken when the estimated payout rate or an indicator representative of the payout rate is greater than a first threshold.
• a method for producing reduced iron comprising: The information is a deviation in the furnace radial direction of the reduction degree of the raw materials inside the shaft furnace or an index representing the reduction degree, If the estimated deviation is greater than a second threshold, the action is taken.
• a shaft furnace including a raw material supply port, a gas supply port, a reduced iron discharge port, a gas discharge port, and an action execution device; the raw material supply port is provided at an upper portion of the shaft furnace, the gas supply port is provided in a side wall of the shaft furnace below the raw material supply port, the reduced iron discharge port is provided below the gas supply port, the gas exhaust port is provided above the gas supply port, the action execution device is configured to perform an action to change the flow of reducing gas inside the shaft furnace from a side wall side of the shaft furnace to a center side of the shaft furnace.
• Shaft furnace ⁇ Aspect 10> 10.
• the shaft furnace of aspect 9, comprising: the action execution device is at least one of a cooling device, a mixing device, a gas supply device, and a raw material supply device; the cooling device is configured to cool at least an inner wall of the shaft furnace at least between the raw material supply port and the gas supply port; the mixing device is configured to mix an inert gas with the reducing gas; the gas supply device is configured to supply a first gas having a relatively low reducing power and a second gas having a relatively high reducing power from the gas supply port into the shaft furnace, and the supply position of the first gas is higher than the supply position of the second gas; the raw material supply device is configured to supply the raw material into the interior of the shaft furnace through the raw material supply port so that the average particle diameter of the raw material supplied to the center side of the shaft furnace is larger than the average particle diameter of the raw material supplied to the side wall side of the shaft furnace.
• the shaft furnace of aspect 10 comprising: The cooling device is configured to cool at least an inner wall of the shaft furnace by water cooling at least between the raw material supply port and the gas supply port. Shaft furnace. ⁇ Aspect 12> 12.
• the shaft furnace of aspect 10 or 11 The raw material supply device is configured to supply the raw material to a side wall side of the inside of the shaft furnace. Shaft furnace. ⁇ Aspect 13> The shaft furnace of any one of aspects 10 to 12,
• the gas supply device is configured so that the first gas and the second gas satisfy one or both of the following conditions A and B: Shaft furnace.
• Condition A the temperature of the first gas is lower than the temperature of the second gas
• Condition B The hydrogen gas concentration of the first gas is lower than the hydrogen gas concentration of the second gas.
• ⁇ Aspect 14> The shaft furnace of any one of aspects 9 to 13, comprising an estimation device and a control device;
• the estimation device is configured to estimate information about a reduction rate of the raw material inside the shaft furnace;
• the control device controls the action execution device so that the action is performed based on the estimated information.
• Shaft furnace. ⁇ Aspect 16> 15.
• the shaft furnace of aspect 14 comprising: The information is a deviation in the furnace radial direction of the reduction degree of the raw materials inside the shaft furnace or an index representing the reduction degree, the control device controls the action execution device to perform the action when the estimated deviation is greater than a second threshold. Shaft furnace.
• the technology disclosed herein makes it possible to increase the average reduction rate of raw materials when producing reduced iron using a shaft furnace.
• FIG. 2 is a schematic diagram illustrating an example of a state before a predetermined action is performed in a method for producing reduced iron.
• 10 is a schematic diagram illustrating an example of a state after an action 1 is performed in a method for producing reduced iron.
• 10 is a schematic diagram illustrating an example of a state after an action 2 is performed in the method for producing reduced iron.
• 10 is a schematic diagram illustrating an example of a state after an action 3 is performed in the method for producing reduced iron.
• 10A and 10B schematically illustrate an example of a state after action 4 is performed in the method for producing reduced iron.
• An example of action 4 is shown schematically.
• An example of action 4 is shown schematically.
• 1 is a schematic diagram illustrating an example of a configuration for performing a predetermined estimation in a method for producing reduced iron.
• 1 is a schematic diagram illustrating an example of a configuration for performing a predetermined estimation in a method for producing reduced iron. 1 shows a schematic diagram of the furnace body structure employed in the calculations of the examples.
• a method for producing reduced iron includes the steps of: A raw material 10 containing iron oxide is supplied from the top of the shaft furnace 100 to the inside thereof, A reducing gas containing hydrogen gas is supplied into the shaft furnace 100 from the side wall 100a thereof, reducing the iron oxide to obtain reduced iron 30 from a lower portion of the shaft furnace 100;
• the method for producing reduced iron according to one embodiment includes the steps of: Taking action to change the flow of reducing gas inside the shaft furnace 100 from the side wall side of the shaft furnace 100 to the center side of the shaft furnace 100; One of its characteristics is that it contains
• Raw material 10 includes at least iron oxide.
• Raw material 10 may be, for example, at least one selected from iron ore pellets, lump ore, and sintered ore.
• raw material 10 may also include, for example, one or both of silicon dioxide and aluminum oxide.
• Raw material 10 may have a particle size distribution or may have a uniform particle diameter. The average particle diameter of raw material 10 may be, for example, 10.0 mm or more and 15.0 mm or less.
• Raw material 10 may be formed into pellets or the like, or may be in the form of a powder, a lump, or other shapes.
• the amount of raw material 10 supplied to the shaft furnace 100 may be selected optimally depending on the size and operating conditions of the shaft furnace 100, etc.
• the raw material 10 is supplied from the top of the shaft furnace 100 to the interior.
• the supply position of the raw material 10 may be above the supply position of the reducing gas.
• the raw material 10 may be supplied, for example, through a raw material supply port 101 provided at the top of the shaft furnace 100, etc.
• the method of supplying the raw material 10 is not particularly limited, and may be supplied by a hopper, chute, etc., for example.
• the raw material 10 may also be supplied by free fall. In particular, when a rotating chute is used, action 4 described below can be more easily performed.
• a packed bed 20 is formed inside the shaft furnace 100.
• the packing rate of the packed bed 20 is not particularly limited.
• the packing rate of the packed bed 20 may be the same as that in conventional methods for producing reduced iron using a shaft furnace.
• the raw materials 10 move downward inside the shaft furnace 100. That is, the interior of the shaft furnace 100 is substantially filled with raw materials 10, and they gradually move downward by falling, etc.
• the raw material particle may move continuously downward at a constant speed, or may move intermittently by repeatedly falling and stopping.
• the average downward movement speed of the raw material particle is not particularly limited. For example, the average movement speed can be adjusted depending on the supply amount (feed speed) of the above-mentioned raw materials.
• a burden feeder or the like may be used to prevent hanging.
• the configuration of a burden feeder in a shaft furnace 100 is publicly known.
• the raw material 10 may have a particle size distribution and a temperature distribution in the packed bed 20 from the top to the bottom of the shaft furnace 100 and/or in the radial direction of the shaft furnace 100.
• the particle size distribution of the raw material 10 may be, for example, a particle size distribution achieved by Action 4 described below.
• the raw material 10 may have an irregular particle size distribution in the packed bed 20.
• the temperature distribution of the packed bed 20 is not particularly limited.
• the packed bed 20 has a temperature at which reduction by the reducing gas can proceed.
• the packed bed 20 may be cooled below the supply position of the reducing gas.
• the packed bed 20 can be cooled by supplying a cooling gas to the packed bed 20 below the supply position of the reducing gas.
• the cooling gas may be, for example, at least one selected from an inert gas, natural gas, hydrogen gas, etc.
• the reducing gas contains at least hydrogen gas.
• the reducing gas may contain, in addition to hydrogen gas, a gas other than hydrogen gas.
• gases other than hydrogen gas include carbon monoxide gas and inert gases.
• the inert gas may be, for example, at least one selected from rare gases such as nitrogen gas and argon gas, carbon dioxide gas, and water vapor.
• the hydrogen gas concentration of the reducing gas (when the reducing gas contains the first gas and second gas described below, the average hydrogen gas concentration) may be, for example, 80% by volume or more and 100% by volume or less.
• the supply temperature of the reducing gas (the temperature immediately before contacting the packed bed) may be any temperature at which a reduction reaction with iron oxide occurs, and may be, for example, 700°C or more and 1000°C or less, or 800°C or more and 1000°C or less.
• the reducing gas is supplied from the side wall 100a of the shaft furnace 100 into the interior of the shaft furnace 100.
• a pipe or the like can be connected to a gas supply port 102 provided in the side wall 100a of the shaft furnace 100, and the reducing gas can be supplied from the outside of the shaft furnace 100 to the interior of the shaft furnace 100 via the pipe or the like.
• the tip of the pipe or the like connected to the gas supply port 102 does not need to protrude further inward than the inner wall 100ax inside the shaft furnace 100.
• reduced iron 30 is a solid reactant containing at least metallic iron.
• the reduced iron 30 may also contain unreduced iron oxide, silicon dioxide, aluminum oxide, and the like. The reduced iron 30 containing metallic iron can be recovered from the lower part of the shaft furnace 100 (below the supply position of the reducing gas).
• an action is performed to change the flow of reducing gas inside the shaft furnace 100 from the side wall side of the shaft furnace 100 to the center side of the shaft furnace 100.
• This action is performed, for example, by the action execution device 110.
• the action in question is, for example, at least one of actions 1 to 4 below, it is possible to change the flow of reducing gas inside the shaft furnace 100 from the side wall side of the shaft furnace 100 to the center side of the shaft furnace 100 without employing a complex configuration in the shaft furnace 100.
• Action 1 Cooling at least the inner wall 100ax of the shaft furnace 100 at least between the feed position of the raw material 10 and the feed position of the reducing gas.
• Action 2 Mix an inert gas with the reducing gas.
• Action 3 Divide the reducing gas supplied to the interior of the shaft furnace 100 into a first gas with a relatively low reducing power and a second gas with a relatively high reducing power, and supply the first gas from above the second gas.
• Action 4 The average particle size of the raw material 10 supplied to the center of the shaft furnace 100 is made larger than the average particle size of the raw material 10 supplied to the side wall of the shaft furnace 100.
• the position at which the reduction reaction by the reducing gas on the side wall side of the shaft furnace 100 is completed moves downward, and the flow of reducing gas inside the shaft furnace 100 is thought to change from the side wall side of the shaft furnace 100 to the center side of the shaft furnace 100.
• the shape of the packed bed inside the shaft furnace 100 is controlled, the supply of gas to the center side of the shaft furnace 100 is promoted, and the flow of reducing gas inside the shaft furnace 100 is thought to change from the side wall side of the shaft furnace 100 to the center side of the shaft furnace 100.
• At least the inner wall 100ax of the shaft furnace 100 is cooled between the raw material 10 supply position and the reducing gas supply position (above the reducing gas supply position, between the raw material supply port 101 and the gas supply port 102; for example, the reduction zone 100ay where iron oxide is reduced).
• the position where the reduction reaction is completed can be moved closer to the reducing gas supply position.
• This increases the area occupied by a reaction gas (e.g., steam) with a viscosity and density greater than that of hydrogen gas near the furnace wall, thereby increasing the pressure loss near the furnace wall.
• a reaction gas e.g., steam
• the temperatures of the reducing gas and the raw material 10 must be at a certain high temperature (e.g., 700°C or higher).
• a certain high temperature e.g. 700°C or higher.
• the reduction reaction of iron oxide with hydrogen is an endothermic reaction, the temperature in the system drops and the reduction reaction becomes difficult to proceed unless thermal energy is supplied from the outside. Therefore, conventional common sense dictates that the inner walls of the shaft furnace are not cooled, but rather the system is heated to maintain a high temperature inside the shaft furnace.
• Action 1 by deliberately adopting an operation that is unfavorable to the reduction reaction of iron oxide (cooling the inner walls of the shaft furnace), the position at which the reduction reaction is completed is moved closer to the supply position of the reducing gas, thereby improving the uniformity of the gas inside the shaft furnace 100 and suppressing uneven reaction of iron oxide.
• the proportion of iron oxide contained in the reduced iron after the reduction reaction can be reduced and the proportion of metallic iron can be increased compared to when the inner walls of the shaft furnace 100 are not cooled. That is, the average reduction rate R ave can be improved.
• the method for cooling the inner wall of the shaft furnace 100 is not particularly limited.
• the inner wall of the shaft furnace 100 can be cooled by a known cooling device 111.
• the inner wall of the shaft furnace 100 may be water-cooled, for example, by providing a mechanism for circulating cooling water inside the furnace wall between the feed position of the raw material 10 and the feed position of the reducing gas.
• Action 1 above may be Action 1A below.
• Action 1A Cooling at least the inner wall 100ax of the shaft furnace 100 by water cooling, at least between the feed position of the raw material 10 and the feed position of the reducing gas.
• the height position at which the inner wall of the shaft furnace 100 is cooled is at least between the raw material 10 supply position and the reducing gas supply position (above the reducing gas supply position, between the raw material supply port 101 and the gas supply port 102; for example, the reduction zone 100ay where iron oxide is reduced).
• the inner wall of the shaft furnace 100 may be cooled over the entire area between the raw material 10 supply position and the reducing gas supply position, or may be cooled only in a portion of the area between the raw material 10 supply position and the reducing gas supply position.
• the entire circumference of the inner wall of the shaft furnace 100 may be cooled, or only a portion of the inner circumference may be cooled. In particular, greater effects can be expected when the entire circumference of the inner wall of the shaft furnace 100 is cooled.
• mixing an inert gas with the reducing gas allows the position where the reduction reaction near the furnace wall inside the shaft furnace 100 is completed to be closer to the supply position of the reducing gas.
• This increases the area occupied by a reaction gas (e.g., water vapor) with a viscosity and density greater than that of hydrogen gas near the furnace wall, thereby increasing the pressure loss near the furnace wall.
• This increases the amount of reducing gas supplied to the interior of the shaft furnace 100, i.e., the center of the shaft furnace 100, improves gas uniformity inside the shaft furnace 100, and suppresses uneven reaction of iron oxide inside the shaft furnace 100.
• the proportion of iron oxide contained in the solid product after the reduction reaction can be reduced and the proportion of reduced iron can be increased compared to when an inert gas is not mixed with the reducing gas.
• the average reduction rate R ave can be improved.
• an inert gas supply system may be connected to the reducing gas supply system, and the inert gas may be mixed into the reducing gas via the inert gas supply system.
• the method for mixing the reducing gas and the inert gas is not particularly limited.
• the mixing of the reducing gas and the inert gas may be performed, for example, using an appropriate mixer 112.
• the amount of inert gas mixed into the reducing gas is not particularly limited.
• the inert gas may be mixed into the reducing gas so that the concentration of the inert gas in the total of the reducing gas and the inert gas is 5% by volume or more and 15% by volume or less.
• the inert gas may be at least one type selected from rare gases such as nitrogen and argon. Nitrogen is particularly preferred.
• supplying the first gas, which has a relatively low reducing power, from above the second gas, which has a relatively high reducing power can move the position where the reduction reaction is completed closer to the supply position of the reducing gas.
• This increases the area occupied by a reaction gas (e.g., steam) with a viscosity and density greater than that of hydrogen gas near the furnace wall, thereby increasing the pressure loss near the furnace wall.
• This increases the amount of reducing gas supplied to the interior of the furnace, i.e., the center of the furnace, thereby improving the uniformity of the gas in the furnace and suppressing uneven reaction of iron oxide in the furnace.
• the proportion of iron oxide contained in reduced iron after the reduction reaction can be reduced and the proportion of metallic iron can be increased. In other words, the average reduction rate R ave can be improved.
• the reducing power of the first gas will be relatively lower than the reducing power of the second gas.
• the first gas and second gas in Action 3 above may satisfy one or both of the following conditions A and B.
• Condition A The temperature of the first gas is lower than the temperature of the second gas.
• Condition B The hydrogen gas concentration of the first gas is lower than the hydrogen gas concentration of the second gas.
• condition A lowering the temperature of the first gas not only improves the reduction rate but also reduces the energy required for heating.
• the difference between the temperature of the first gas and the temperature of the second gas is not particularly limited. The difference between the temperature of the first gas and the temperature of the second gas can be adjusted appropriately depending on the target average reduction rate, etc.
• the composition of the first gas and the composition of the second gas may be the same or different.
• the first gas may or may not contain hydrogen gas.
• the second gas must contain hydrogen gas.
• the first gas and the second gas may contain gases other than hydrogen gas in addition to hydrogen gas. Examples of gases other than hydrogen gas include carbon monoxide and inert gases. Examples of inert gases include nitrogen, argon, carbon dioxide, and water vapor.
• condition B reducing the hydrogen gas concentration of the first gas not only improves the reduction rate but also reduces the amount of hydrogen gas required.
• the difference between the hydrogen gas concentrations of the first gas and the second gas is not particularly limited. The difference between the hydrogen gas concentrations of the first gas and the second gas can be adjusted appropriately depending on the target average reduction rate, etc.
• the method for reducing the hydrogen gas concentration of the first gas to be lower than that of the second gas is not particularly limited, and examples include mixing an inert gas with the first gas.
• the first gas may or may not contain hydrogen gas.
• the second gas must contain hydrogen gas.
• the first gas and the second gas may contain gases other than hydrogen gas in addition to hydrogen gas. Examples of gases other than hydrogen gas include carbon monoxide and inert gases. Examples of inert gases include nitrogen, argon, carbon dioxide, and water vapor.
• the temperatures of the first gas and the second gas may be the same or different.
• the gas supply system in the gas supply device 113 may be divided into two systems, an upper system and an lower system, or three or more systems, including an upper, middle, and lower system, and the first gas may be supplied from at least one system on the upper side, and the second gas may be supplied from at least one system on the lower side.
• the supply position of the first gas may be directly above the supply position of the second gas or diagonally above, but a particularly high effect is likely to be obtained when the supply position is directly above.
• the supply amount or supply rate of the first gas and the supply amount or supply rate of the second gas may be the same or different.
• the proportion of the first gas in the total of the first gas and the second gas supplied inside the shaft furnace 100 may be greater than 0% by volume and 10% by volume or less.
• the exhaust gas discharged from the gas outlet 104 of the shaft furnace 100 may be reused as the first gas (gas with a relatively lower hydrogen concentration than the second gas and/or gas with a relatively lower temperature than the second gas).
• the "particle diameter" of the raw material refers to the maximum outer diameter of the raw material particles.
• the “average particle diameter” of the raw material refers to the harmonic mean of the maximum outer diameter of the raw material particles.
• a predetermined position between the center and inner wall of the shaft furnace is defined as the boundary, and the area between this boundary and the center is defined as the "center side of the shaft furnace,” and the area between this boundary and the inner wall is defined as the “side wall side of the shaft furnace.”
• the range from the center of the shaft furnace to 1/4 of the furnace inner diameter (up to 1/2 of the radius) is defined as the "center side of the shaft furnace,” and the area outside of this is defined as the "side wall side of the shaft furnace.”
• the average particle diameter of the raw materials 10 supplied to the center side of the shaft furnace 100 tends to be larger than the average particle diameter of the raw materials 10 supplied to the side wall side of the shaft furnace 100.
• a rotating chute is used as the raw material supply device 114, and when a mountain or slope made of particles of the raw material 10 is formed on the side wall side inside the shaft furnace 100, coarse particles gather in the center of the shaft furnace 100.
• the raw material 10 is supplied into the shaft furnace 100 so that the top 20x of the packed bed 20 is formed on the side wall side of the shaft furnace 100.
• Action 4B As shown in Figure 7, multiple hoppers are provided as raw material supply devices 114 in the radial direction of the shaft furnace 100, and raw materials with fine particle sizes are supplied through the hoppers on the side walls of the shaft furnace 100, and raw materials with coarse particle sizes are supplied through the hoppers on the central side of the shaft furnace 100.
• Action 4A as shown in Figure 6 is particularly convenient. That is, in one embodiment of the method for producing reduced iron, Action 4 may be Action 4A described below.
• Action 4A Supply raw material 10 to the side wall side (inner wall 100ax side) of the shaft furnace 100 so that the average particle diameter of raw material 10 supplied to the center side of the shaft furnace 100 is larger than the average particle diameter of raw material 10 supplied to the side wall side (inner wall 100ax side) of the shaft furnace 100.
• the average particle diameter of the raw materials 10 may decrease continuously or intermittently from the center of the shaft furnace 100 to the side wall of the shaft furnace 100.
• the overall average particle diameter of the raw materials 10 is 10.0 mm or more and 15.0 mm, it is preferable that the difference between the average particle diameter of the raw materials 10 on the side wall side and the average particle diameter of the raw materials 10 on the center side be 1.0 mm or more.
• the above-described action may be taken at any timing, may be taken periodically, or may be taken based on a predetermined criterion.
• the above actions may be taken at any timing at the discretion of the operator, based on operational experience.
• information regarding the reduction rate of the raw materials 10 inside the shaft furnace 100 may be estimated, and the above action may be performed based on the estimated information.
• This information may be, for example, the reduction rate of the raw materials 10 on the side wall inside the shaft furnace 100 or an index representing the reduction rate (first form below).
• this information may be, for example, the deviation in the furnace radial direction of the reduction rate of the raw materials 10 inside the shaft furnace 100 or an index representing the reduction rate (second form below).
• the information is the reduction rate R of the raw materials 10 on the side wall side inside the shaft furnace 100 or an index I representing the reduction rate R, and the action may be taken when the estimated reduction rate R or the index I representing the reduction rate R is greater than a first threshold value.
• the reduction rate of the raw materials on the side wall side inside the shaft furnace or an index representing the reduction rate refers to the reduction rate R or an index I representing the reduction rate R of the raw materials 10 located close to the side wall inside the shaft furnace 100. Specifically, this refers to the reduction rate R or an index I representing the reduction rate R of the raw materials 10 located at a distance from the side wall inside the shaft furnace 100 within 1 ⁇ 4 of the inner radius of the shaft furnace 100.
• the height position of the side wall inside the shaft furnace 100 at which the reduction rate R of the raw materials 10 is estimated may be, for example, a region in the range of 0.2 to 0.7, where the height of the gas supply port 102 is 0 and the raw material stock level (the upper end of the packed bed 20) is 1.0.
• the reduction rate R of the raw materials 10 or an index I representing the reduction rate R can be estimated using various estimation devices 107.
• the reduction rate R of the raw materials 10 may be estimated by sampling and analyzing the raw materials 10. It can also be estimated based on a numerical simulation of the operating conditions in the shaft furnace 100.
• the gas can be sampled and analyzed to determine the index I representing the reduction rate R.
• the index I representing the reduction rate R can be, for example, the hydrogen gas concentration.
• the action is taken when the estimated reduction rate R or the index I representing the reduction rate R is greater than a first threshold value.
• the "threshold value" can be determined, for example, by numerical simulation, operational analysis, or the like.
• the action may be taken when the reduction rate R of the raw material 10 on the side wall inside the shaft furnace 100 is estimated to be 33% or higher (when it is estimated to have been reduced to wustite or more).
• the action may be taken when the hydrogen utilization rate on the side wall inside the shaft furnace 100 is estimated to be 30 mol% or higher.
• the estimated reduction rate R or the index I representing the reduction rate R is large, this indicates that the reduction reaction by the reducing gas is completed near the furnace wall inside the shaft furnace 100 and at the top of the shaft furnace 100 (near the furnace top). At this time, the reducing gas inside the shaft furnace 100 tends to flow near the furnace wall, making it difficult for the reducing gas to be sufficiently supplied to the center of the shaft furnace 100. In other words, the proportion of hydrogen gas near the furnace wall increases, reducing pressure loss and hindering gas supply to the center.
• the amount of reducing gas supplied to the center of the shaft furnace 100 i.e., the center of the shaft furnace 100
• the amount of reducing gas supplied to the center of the shaft furnace 100 can be increased, improving gas uniformity inside the shaft furnace 100 and suppressing uneven reaction of iron oxide inside the shaft furnace 100.
• the proportion of iron oxide contained in the reduced iron after the reduction reaction can decrease and the proportion of metallic iron can increase.
• the average reduction rate R can be improved.
• the information is a deviation D in the furnace radial direction for the reduction rate R of the raw materials 10 inside the shaft furnace 100 or an index I representing the reduction rate R, and the action described above may be performed if the estimated deviation D is greater than a second threshold value.
• the second mode simultaneously uses information from the center of the shaft furnace 100 in addition to the side walls of the shaft furnace 100, allowing for more accurate determination of the timing to execute an action.
• the "radial deviation (%) of the reduction rate of the raw material or the index representing the reduction rate” refers to the variation in the reduction rate R (%) of the raw material 10 or the index I representing the reduction rate R in the radial direction inside the shaft furnace 100.
• the radial position of the furnace is preferably between the side wall and the center, as this allows for greater deviation detection.
• the radial deviation D of the reduction rate R of the raw material 10 or the radial deviation D of the index I representing the reduction rate R of the raw material 10 can be estimated based on a numerical simulation of the operating conditions of the shaft furnace 100.
• the height position within the furnace at which the reduction rate of the raw material 10 is estimated may be, for example, a region in the range of 0.2 to 0.7, where the height of the gas supply port 102 is 0 and the raw material stock level (the upper end of the packed bed 20) is 1.0.
• various devices 120 such as a flow rate measuring device or a gas analyzer, may be used to analyze the exhaust gas components in the radial direction at the furnace top, and the hydrogen distribution in the radial direction of the exhaust gas at the furnace top may be determined. This may then determine the hydrogen utilization rates on the furnace wall side and the furnace center side, and the difference between the hydrogen utilization rates on the furnace wall side and the furnace center side may be determined.
• Information obtained from the gas information at the furnace top represents the entire height of the packed bed 20. Based on this information, the deviation D of the reduction degree R of the raw material 10 in the radial direction may be estimated.
• various devices 120 may be used to measure the gas flow rate in the radial direction of the exhaust gas at the furnace top, and the deviation D of the reduction degree R of the raw material 10 in the radial direction may be estimated from the deviation of the gas flow rate in the radial direction.
• the hydrogen distribution and gas flow rate of the exhaust gas at the furnace top measured using various devices 120 may be directly used as an index I representing the reduction degree R.
• the radial deviation D of the furnace may be estimated from this information.
• the action is taken if the estimated deviation D is greater than a second threshold.
• the second threshold can be determined, for example, by numerical simulation, operational analysis, or analysis of operational performance.
• the second threshold is the coefficient of variation (2 x (sidewall value - median value) / (sidewall value + median value)), and is preferably set, for example, between 0.1 and 0.3.
• the action may be taken if the sidewall value is greater than the median by a predetermined amount (for example, 10% or more).
• the estimated deviation D indicates a large difference between the reduction rate of the raw materials 10 near the furnace walls and the reduction rate of the raw materials 10 near the center of the shaft furnace 100.
• This reflects a state in which reducing gas easily flows near the furnace walls inside the shaft furnace 100, making it difficult for reducing gas to be sufficiently supplied to the center of the shaft furnace 100.
• the reduction reaction using reducing gas is completed near the furnace walls and at the top of the shaft furnace (near the furnace top), and the proportion of hydrogen gas near the furnace walls increases, reducing pressure loss and hindering gas supply to the center.
• the amount of reducing gas supplied to the center of the shaft furnace 100 i.e., the center of the shaft furnace 100
• the amount of reducing gas supplied to the center of the shaft furnace 100 can be increased, improving gas uniformity inside the shaft furnace 100 and suppressing uneven iron oxide reaction inside the shaft furnace 100.
• the proportion of iron oxide contained in the solid product after the reduction reaction can decrease and the proportion of reduced iron can increase. In other words, the average reduction rate can be improved.
• FIGS. 2 to 7 illustrate an embodiment in which one of Actions 1 to 4 is performed in the method for producing reduced iron according to an embodiment, only one of Actions 1 to 4 may be performed, two or more of Actions 1 to 4 may be performed, three or more of Actions 1 to 4 may be performed, or all of Actions 1 to 4 may be performed. Furthermore, in the method for producing reduced iron according to an embodiment, one action may be performed followed by another action.
• an action other than Action 1 may be performed simultaneously with or after Action 1.
• the action may be interrupted or stopped as desired.
• the average reduction rate of the raw material may be improved by performing the above-described action.
• the reduced iron produced after the action has been performed has a higher reduction rate than the reduced iron produced before the action has been performed, and can be a better product reduced iron.
• a shaft furnace 100 includes a raw material supply inlet 101, a gas supply inlet 102, a reduced iron discharge outlet 103, a gas discharge outlet 104, and an action execution device 110.
• the raw material supply inlet 101 is provided at the top of the shaft furnace 100
• the gas supply inlet 102 is provided on a side wall of the shaft furnace 100 below the raw material supply inlet 101
• the reduced iron discharge outlet 103 is provided below the gas supply inlet 102
• the gas discharge outlet 104 is provided above the gas supply inlet 102.
• the action execution device 110 is configured to perform an action to change the flow of reducing gas inside the shaft furnace 100 from the side wall side of the shaft furnace 100 to the center side of the shaft furnace 100.
• the raw material supply port 101, gas supply port 102, reduced iron discharge port 103, and gas discharge port 104 are not particularly limited in shape as long as the above-described positional relationship is satisfied.
• the raw material supply port 101 may be provided, for example, at the top of the shaft furnace 100.
• the gas supply port 102 may be provided, for example, directly below the position that will become the reduction zone 100ay of the shaft furnace 100.
• the reduced iron discharge port 103 may be provided at the bottom of the shaft furnace 100.
• the gas discharge port 104 may be provided at a different location from the raw material supply port 101 at the top of the shaft furnace 100.
• a raw material 10 containing iron oxide can be supplied from the top of the shaft furnace 100 to the inside thereof to form a packed bed 20 of the raw material 10 inside the shaft furnace 100;
• a reducing gas containing hydrogen gas can be supplied to the inside of the shaft furnace 100 from the side wall 100a thereof,
• the iron oxide can be reduced to obtain reduced iron 30 from the bottom of the shaft furnace 100.
• the shaft furnace 100 includes an action execution device 110.
• the action execution device 110 may be, for example, at least one of a cooling device 111, a mixing device 112, a gas supply device 113, and a raw material supply device 114.
• the cooling device 111 is configured to cool at least the inner wall of the shaft furnace 100 at least between the raw material supply port 101 and the gas supply port 102.
• the mixing device 112 is configured to mix an inert gas with the reducing gas.
• the gas supply device 113 is configured to supply a first gas with a relatively low reducing power and a second gas with a relatively high reducing power from the gas supply port 102 into the shaft furnace 100, and is configured so that the supply position of the first gas is higher than the supply position of the second gas.
• the raw material supply device 114 is configured to supply the raw material 10 into the shaft furnace 100 through the raw material supply port 101 so that the average particle diameter of the raw material 10 supplied to the center of the shaft furnace 100 is larger than the average particle diameter of the raw material 10 supplied to the side wall of the shaft furnace 100. Details of the action performed by the action execution device 110 are as described above.
• the cooling device 111 may be configured to cool at least the inner wall 100ax of the shaft furnace 100 by water cooling, for example, at least between the raw material supply port 101 and the gas supply port 102. That is, the cooling device 111 may be a water-cooling device. More specifically, the cooling device 111 may have a mechanism for circulating cooling water inside the furnace wall of the shaft furnace 100 and at least between the raw material supply port 101 and the gas supply port 102. The cooling device 111 may be configured to cool the entire circumference of the inner wall of the shaft furnace 100.
• the cooling device 111 may have a mechanism for circulating cooling water inside the furnace wall of the shaft furnace 100 and at least between the raw material supply port 101 and the gas supply port 102 around the entire circumference of the furnace wall of the shaft furnace 100.
• the cooling device 111 may have a configuration similar to that of a device for cooling the furnace wall of a blast furnace.
• the cooling device 111 is one of the specific means for performing the above-mentioned Action 1.
• the cooling conditions by the cooling device 111 may be the same as those in the above-mentioned Action 1.
• the mixing device 112 may be configured, for example, to connect an inert gas supply system to a reducing gas supply system as shown in FIG. 3 . More specifically, the mixing device 112 may be configured, for example, to connect a reducing gas supply system from a reducing gas source and an inert gas supply system from an inert gas source, so that the reducing gas and the inert gas are mixed in the mixing device 112.
• the mixing device 112 may include valves or the like that adjust the flow rate and pressure of the reducing gas from the reducing gas supply system to the mixing device 112, and the flow rate and pressure of the inert gas from the inert gas supply system to the mixing device 112.
• the mixing device 112 is one of the specific means for performing the above-mentioned Action 2.
• the mixing conditions and supply conditions of the reducing gas and the inert gas by the mixing device 112 may be the same as those in the above-mentioned Action 2.
• the gas supply device 113 may have, for example, two gas supply systems (upper and lower) as shown in FIG. 4 , or three or more gas supply systems (upper, middle, and lower), and may be configured to supply a first gas from at least one upper system and a second gas from at least one lower system.
• the gas supply device 113 may have, for example, two or more gas supply systems, at least one of which is a first gas supply system from a first gas source, and at least one other gas supply system is a second gas supply system from a second gas source, and the first and second gas supply systems are connected to the sidewall of the shaft furnace 100, and the connection position between the first gas supply system and the sidewall of the shaft furnace 100 is higher than the connection position between the second gas supply system and the sidewall of the shaft furnace 100.
• the type of first gas in the first gas supply system and the type of second gas in the second gas supply system are as described above.
• the gas supply device 113 may be configured so that the first gas and the second gas satisfy one or both of the following conditions A and B.
• the gas supply device 113 is one of the specific means for performing the above-mentioned Action 3.
• the gas supply conditions by the gas supply device 113 may be the same as those in the above-mentioned Action 3.
• Condition A The temperature of the first gas is lower than the temperature of the second gas.
• Condition B The hydrogen gas concentration of the first gas is lower than the hydrogen gas concentration of the second gas.
• the raw material supply device 114 may be configured to supply the raw materials 10 to the side wall side of the shaft furnace 100.
• the raw material supply device 114 may be, for example, a rotating chute as shown in FIG. 6 or multiple hoppers arranged in the furnace radial direction as shown in FIG. 7. More specifically, the raw material supply device 114 may be, for example, a rotating chute that supplies the raw materials 10 into the shaft furnace 100 so that the top 20x of the packed bed 20 is formed on the side wall side of the shaft furnace 100.
• the raw material supply device 114 may be, for example, a device including multiple first and second hoppers arranged in the furnace radial direction of the shaft furnace 100, in which fine-grained raw materials are supplied from the first hopper arranged on the side wall side of the shaft furnace 100 and coarse-grained raw materials are supplied from the second hopper arranged on the central side of the shaft furnace 100.
• the first hopper may be connected to, for example, a first raw material supply source
• the second hopper may be connected to, for example, a second raw material supply source different from the first raw material supply source, such that raw material having a fine particle size is supplied from the first raw material supply source to the first hopper, and raw material having a coarse particle size is supplied from the second raw material supply source to the second hopper.
• the raw material supply device 114 is one of the specific means for performing the above-mentioned action 4.
• the raw material supply conditions by the raw material supply device 114 may be the same as those in the above-mentioned action 4.
• the shaft furnace 100 may include estimation devices 105, 107 and control devices 106, 108.
• the estimation devices 105, 107 may be configured to estimate information related to the reduction rate of the raw materials 10 inside the shaft furnace 100, and the control devices 106, 108 may control the action execution device 110 so that the action is performed based on the estimated information.
• the information estimated by the estimation device 105 may be the reduction rate R of the raw materials 10 on the side wall side inside the shaft furnace 100 or an index I representative of the reduction rate R.
• the control device 106 may control the action execution device 110 so that the action is performed when the estimated reduction rate R or the index I representative of the reduction rate R is greater than a first threshold.
• the information estimated by the estimation device 107 may be the deviation D in the furnace radial direction for the reduction rate R of the raw material 10 inside the shaft furnace 100 or the index I representing the reduction rate R, and in this case, the control device 108 may control the action execution device 110 so that the above action is taken when the estimated deviation D is greater than a second threshold value.
• the estimation device 105 may be configured to estimate the reduction degree R of the raw material 10 at the furnace inner wall or the index I representing the reduction degree R.
• the method for estimating the reduction degree R or the index I has been described above.
• the reduction degree R or the index I can be estimated, for example, based on a numerical simulation of the operating conditions in the shaft furnace 100. That is, the estimation device 105 may be a numerical simulation device.
• the estimation device 105 may sample raw material from a predetermined position on the furnace inner wall of the shaft furnace 100 and estimate the reduction degree R of the raw material based on the analysis results of the raw material.
• the estimation device 105 may estimate the index I representing the reduction degree R of the raw material from the analysis results of the sampled gas.
• the index I representing the reduction degree R can be, for example, a hydrogen gas concentration or a hydrogen utilization rate.
• the estimation device 105 has a configuration necessary for making such an estimation.
• the estimation device 105 may include a known calculation device or the like.
• the estimation device 107 may be configured to estimate the deviation D in the furnace radial direction of the reduction degree R of the raw materials 10 or the index I representing the reduction degree R.
• the method for estimating the deviation D is as described above.
• the deviation D can be estimated, for example, based on a numerical simulation of the operating conditions of the shaft furnace 100. That is, the estimation device 107 may be a numerical simulation device.
• the estimation device 107 may obtain the hydrogen utilization rates on the furnace wall side and the furnace center side by determining the hydrogen distribution in the furnace radial direction of the exhaust gas at the furnace top from the analysis results of the exhaust gas components in the furnace radial direction at the furnace top, and estimate the deviation D in the furnace radial direction of the reduction degree R of the raw materials 10 based on, for example, the difference between the hydrogen utilization rates on the furnace wall side and the furnace center side.
• the estimation device 107 may estimate the deviation D in the furnace radial direction of the reduction degree R of the raw materials 10 based on, for example, the deviation of the gas flow rate in the furnace radial direction from the measurement results of the gas flow rate in the furnace radial direction of the exhaust gas at the furnace top.
• the estimation device 107 may estimate the deviation D of the reduction degree R of the raw materials 10 in the furnace radial direction based on the reduction degrees of the reduced material on the furnace wall and the reduced material in the furnace center.
• the estimation device 107 has a configuration necessary for making such an estimation.
• the estimation device 107 may include a known calculation device or the like.
• the control device 106 may control the action execution device 110 so that the action is performed when the return rate R or the index I representing the return rate R estimated by the estimation device 105 is greater than a first threshold.
• the control device 106 has a configuration necessary to control the execution of an action based on the estimation result by the estimation device 105.
• the control device 108 may include a CPU, RAM, ROM, etc.
• the control device 108 may control the action execution device 110 so that the action is performed when the deviation D estimated by the estimating device 107 is greater than a second threshold.
• the control device 108 has a configuration necessary to control the execution of an action based on the estimation result of the deviation D by the estimating device 107.
• the control device 108 may include a CPU, RAM, ROM, etc.
• the shape of the shaft furnace 100 may be similar to that of known shaft furnaces.
• the shaft furnace 100 may have a furnace top, a furnace bottom, and a cylindrical portion (cylindrical portion) forming a sidewall between the furnace top and the furnace bottom.
• the cylindrical portion may have a barrel portion and a tapered portion located below the barrel portion, and the inner diameter of the furnace may decrease from top to bottom at the tapered portion.
• the shaft furnace 100 may also be equipped with a burden feeder or the like to prevent the packed bed 20 from hanging when moving downward inside the shaft furnace 100.
• the shaft furnace 100 may also be equipped with a cooling gas supply port for supplying cooling gas and a cooling gas outlet for discharging cooling gas below the gas supply port 102.
• the cooling gas supply port may be located inside the sidewall of the furnace, and the cooling gas outlet may be located on the sidewall of the furnace below the gas supply port 102.
• the burden feeder, the cooling gas supply port, and the cooling gas discharge port provided in the shaft furnace 100 are known.
• the shaft furnace 100 may have both the configuration according to the first embodiment and the configuration according to the second embodiment.
• the estimation device 105 and the estimation device 107 may be the same device or different devices.
• one estimation device provided in the shaft furnace 100 may function as both the estimation device 105 and the estimation device 107.
• the control device 106 and the control device 108 may be the same device or different devices.
• one control device provided in the shaft furnace 100 may function as both the control device 106 and the control device 108.
• the estimation devices 105 and 107 and the control devices 106 and 108 may be the same device or different devices.
• one device provided in the shaft furnace may function as both the estimation devices 105 and 107 and the control devices 106 and 108.
• the estimation device may be configured to estimate at least one of the reduction rate R of the raw materials 10 on the furnace inner wall or an index I representative of the reduction rate R, and a deviation D of the reduction rate R of the raw materials 10 or the index I representative of the reduction rate R in the furnace radial direction, and the control device may control the action execution device 110 to perform the action when the estimated reduction rate R, the index I, and/or the deviation D are greater than a threshold value.
• the control device may also control the action execution device 110 to suspend or stop the action.
• Furnace structure and boundary conditions When raw materials containing iron oxide are reduced with reducing gas (hydrogen gas) in a shaft furnace to obtain reduced iron, the behavior of the reducing gas inside the furnace (hydrogen concentration distribution, pressure distribution, flow velocity distribution), the reduction rate distribution of iron oxide inside the furnace, and the average reduction rate were analyzed by numerical simulation using the following furnace structure and boundary conditions.
• reducing gas hydrogen gas
• the furnace body structure used was as shown in Figure 10.
• the structure shown in Figure 10 is the left half of the furnace internal structure in a cross section passing through and along the central axis of the furnace, when the furnace internal structure is divided into right and left halves with the central axis as the boundary.
• the reducing gas flow rate was set to 6300 ( Nm3 /min), pure hydrogen was used as the reducing gas, and the temperature was 950°C.
• cooling gas was supplied below the reducing gas supply position, and CH4 was used as the cooling gas.
• the cooling gas flow rate was set to 1400 ( Nm3 /min) so that the average product temperature was approximately 80°C.
• the cooling gas withdrawal flow rate was set to 1260 ( Nm3 /min) so that it was 90% of the input amount.
• a method for producing reduced iron comprising: taking an action to change the flow of the reducing gas inside the shaft furnace from a side wall side of the shaft furnace to a center side of the shaft furnace;
• a method for producing reduced iron comprising: (2) The action is at least one of the following actions 1 to 4: Method for producing reduced iron: Action 1: cooling at least an inner wall of the shaft furnace at least between a supply position of the raw material and a supply position of the reducing gas; Action 2: mixing the reducing gas with an inert gas; Action 3: Dividing the reducing gas supplied into the shaft furnace into a first gas having a relatively low reducing power and a second gas having a relatively high reducing power, and supplying the first gas from a position higher than the second gas; Action 4: The average particle size of the raw material supplied

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