Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/001—Injecting additional fuel or reducing agents
  • C21B5/003—Injection of pulverulent coal
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/006—Automatically controlling the process
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B5/00—Making pig-iron in the blast furnace
  • C21B5/008—Composition or distribution of the charge
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B7/00—Blast furnaces
  • C21B7/24—Test rods or other checking devices
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B2300/00—Process aspects
  • C21B2300/04—Modeling of the process, e.g. for control purposes; CII

Definitions

• the present disclosure relates to a process control method, a blast furnace operation method, a hot metal production method, a process control device, and a program.
• Hot metal temperature is an important management index in a blast furnace process of the steel industry, and is controlled mainly by adjusting pulverized coal rate and blast moisture.
• blast furnace operations have been carried out under low coke rate and high pulverized coal rate conditions in order to rationalize raw fuel costs, which can easily lead to furnace instability. Therefore, suppressing variation in hot metal temperature is necessary.
• the present disclosure provides a process control method, a blast furnace operation method, a hot metal production method, a process control device, and a program to realize proposing a reducing agent rate that depends on an intention that also continues stable operation and suppresses variation of hot metal temperature in a blast furnace.
• in-furnace pressure drop which has a direct effect on gas channeling
• the in-furnace pressure drop is a difference between blast pressure and top gas pressure (pressure at the top of the furnace).
• various other indicators of gas permeability such as ventilation resistance and facing shaft differential pressure. Therefore, another indicator of gas permeability may be used instead of the in-furnace pressure drop as the permeability, or a combination of multiple measures of gas permeability may be used.
• FIG. 2 is a diagram illustrating processing of the process control method according to the present embodiment.
• the cascade control described in Reference Literature 1 JP 7107444 B2
• a control to calculate the target pulverized coal rate (PCR) hot metal temperature control in FIG. 2
• a control to calculate the pulverized coal injection rate required for the target PCR PCR tracking control in FIG. 2
• the hot metal temperature control the target hot metal temperature (HMT), that is, the target value of the hot metal temperature, may be obtained and the target PCR may be calculated using the physical model described below.
• the hot metal temperature control not only calculates the target PCR (not only determines the operation amount of the pulverized coal rate), but also calculates the operation amount of the blast moisture.
• the process control method also includes production rate control and permeability control.
• the production rate control the target production rate (Prod), that is, the target value of the production rate, is obtained, and the operation amount of the blast volume (BV) is calculated using the physical model described below.
• the permeability control obtains an in-furnace pressure drop ( ⁇ P) upper limit, which is an upper limit of pressure drop in the furnace, and calculates the operation amounts of the blast volume and the coke rate using the physical model described below.
• ⁇ P in-furnace pressure drop
• actual performance values (which may be observed or calculated) at the plant including the blast furnace, may be fed back to update the physical model used in each control.
• mapping between the control variables and correlated operating variables in the blast furnace process is not limited to that illustrated in FIG. 1 and FIG. 2 .
• blast volume oxygen may be manipulated instead of the blast volume.
• hot metal temperature control In construction of the multi-variable control system illustrated in FIG. 2 , separate controllers (hot metal temperature control, permeability control, and production rate control) are constructed to control the hot metal temperature (HMT), the in-furnace pressure drop ( ⁇ P), and the production rate (Prod).
• the hot metal temperature is controlled by manipulation of the blast moisture and by the cascade control that manipulates the pulverized coal rate (PCR) and the pulverized coal injection rate.
• PCR pulverized coal rate
• the permeability is controlled by manipulating the blast volume and the coke rate.
• the production rate is controlled by manipulating the blast volume.
• the blast volume is manipulated in the production rate control, changes in the blast volume have an effect on the hot metal temperature.
• the physical model of the blast furnace based on reaction kinetics is used to predict future hot metal temperature and production rate.
• the process control method according to the present embodiment determines change amounts of the pulverized coal rate and blast moisture so that the predicted value approaches the target value.
• the reducing agent rate When a low reducing agent rate is used for environmental considerations, the reducing agent rate may be decreased. Further, the reducing agent rate may be increased when external requirements require a temporary increase in blast furnace exhaust gas. External requests include, for example, requests resulting from limited electrical power supply or limited raw material inventories.
• the intention includes a first intention of prioritizing decreasing the reducing agent rate and a second intention of temporarily increasing the blast furnace exhaust gas.
• the description assumes the first intention (low reducing agent rate intention), but is not limited to this and the methods of the present disclosure can be applied to the second intention (temporary exhaust gas increase intention), for example.
• Step 1 is the response prediction step.
• the response prediction step determines the predicted value of the future hot metal temperature using the physical model, based on the predicted value of the future hot metal temperature when current operating variables are held unchanged and the predicted value of the future hot metal temperature when the current operating variables are changed.
• the predicted value of the future hot metal temperature when the current operating variables are held unchanged is the free response, which is discussed below.
• the predicted value of the hot metal temperature when the current operating variables are changed is the step response described below according to the present embodiment, but is not limited to this example.
• Step 2 manipulation of the operating variables is carried out using quadratic programming so that the predicted value of the hot metal temperature in step 1 matches the target value and the reducing agent rate is minimized.
• Step 2 is part of the operation amount determination step, in which deviation between the predicted value and the target value is determined, the operation amount is determined to eliminate the deviation, and the operating variables are adjusted.
• the operating variables are the pulverized coal rate and the blast moisture.
• the blast volume may be manipulated so that the predicted value of the production rate matches the target value, and at least the coke rate may be manipulated so that the predicted value of the blast volume becomes an upper limit or less.
• the permeability is the in-furnace pressure drop, and when the predicted value of the in-furnace pressure drop exceeds a set upper limit, the permeability state is determined to be abnormal. When the permeability state is determined to be abnormal, an operation to increase the coke rate may be carried out. When the permeability state is determined to be not abnormal, that is, the predicted value of the in-furnace pressure drop is the upper limit or less, an operation to decrease the coke rate may be carried out.
• Manipulation of the blast volume and the coke rate according to step 3 is a disturbance to the hot metal temperature control.
• step 4 when the predicted value of the hot metal temperature in step 1 approximately matches the target value, amounts that can maintain the predicted value are determined as the operation amounts, which are a set of two parameters from among the pulverized coal rate, the blast moisture, and the blast temperature, depending on the intention.
• the blast temperature is the temperature of the blast and is one of the operating variables.
• the predicted value of the hot metal temperature approximately matching the target value may be determined by the absolute value of the difference between the predicted value of the hot metal temperature and the target value being less than a defined threshold value.
• the defined threshold value may be determined in advance based on past actual performance data or the like.
• the intention includes, for example, the first intention (low reducing agent rate intention) and the second intention (temporary exhaust gas increase intention).
• the operation amounts are determined so that an operation to decrease the blast moisture is treated as a set (in combination) with the operation to decrease the pulverized coal rate.
• the operation to decrease the pulverized coal rate decreases the hot metal temperature and the permeability.
• the operation to decrease the blast moisture increases the hot metal temperature and the permeability, so the effects of the two operations cancel each other out.
• FIG. 3 is a diagram illustrating effects of the pulverized coal rate, the blast moisture, and the blast temperature on a furnace.
• An increase operation is an operation that increases the value of the operating variable.
• a decrease operation is an operation that decreases the value of the operating variable. As described above, for example, by simultaneously lowering the pulverized coal rate and the blast moisture content, the predicted hot metal temperature may be maintained and stable operation may continue.
• the operation amounts may be determined to be a combination of a pulverized coal rate decrease operation and a blast moisture decrease operation. In this case, the effects on the hot metal temperature and the permeability cancel each other out.
• the combination is not limited to this, and when the intention is the first intention, the operation amounts may be determined to be a combination of a pulverized coal rate decrease operation and a blast temperature increase operation or a blast temperature decrease operation and a blast moisture decrease operation.
• the operation amounts may be determined to be a combination of a pulverized coal rate increase operation and a blast moisture increase operation.
• the combination is not limited to this, and when the intention is the second intention, the operation amounts may be determined to be a combination of a pulverized coal rate increase operation and a blast temperature decrease operation or a blast temperature increase operation and a blast moisture increase operation.
• the intention of operation is the first intention or the second intention may be predetermined, or the controller 13, described below, may accept input to specify the intention.
• the operating variables are changed to maintain the predicted value of the hot metal temperature (to cancel out effects) when the predicted value of the hot metal temperature approximately matches the target value, but the amount of change is not unlimited.
• the pulverized coal rate and the blast moisture cannot be decreased without limit.
• the pulverized coal rate and the blast moisture cannot be increased without limit.
• the theoretical combustion temperature (calculated combustion temperature) at the point where the pulverized coal and the blast moisture are blown in needs to be within a predetermined defined range (control value).
• the main output variables of the dynamic model are gas utilization rate, solution loss carbon amount, the reducing agent rate, the production rate, the hot metal temperature, and the in-furnace pressure drop.
• the dynamic model may be used to calculate the hot metal temperature, the production rate, and the in-furnace pressure drop, which are ever-changing.
• the time interval for this calculation is not particularly limited, but is 30 minutes according to the present embodiment.
• the time difference between "t+1" and "t" in the dynamic model expressions described below is 30 minutes according to the present embodiment.
• the dynamic model may be expressed by the following expressions (1) and (2).
• the deviation of the free response, y f (t), from the target value, y pre (t), is denoted as ⁇ y.
• the square of the deviation between the predicted value of the hot metal temperature and the target value y pre (t) is indicated in expression (8) below.
• a and R are coefficients. Comparing the responsiveness of the hot metal temperature to changes in the pulverized coal rate (PCR) and the blast moisture (BM), respectively, it is known that the blast moisture has a more immediate response. However, increasing an average value of the blast moisture to ensure operable ranges in the increasing and decreasing directions is necessary so that the blast moisture can be increased or decreased. Increasing the average value of the blast moisture causes heat absorption due to the water vapor decomposition reaction of the blast moisture, and therefore more reducing agent needs to be added to compensate for the decreased heat due to the heat absorption. Therefore, a third term is introduced to limit the operation amount of the blast moisture, and the weighting of ⁇ PCR and ⁇ BM in the vector ⁇ can be changed according to the size of the elements of the coefficient vector a to adjust the distribution of the two operations.
• ⁇ is determined using expression (9) under the constraints of expressions (10) through (13) below.
• PCR max and PCR min are upper and lower limits of the target range of the pulverized coal rate (PCR), respectively.
• ⁇ PCR max is an upper limit of the magnitude of allowable change in the pulverized coal rate (PCR).
• BM max and BM min are upper and lower limits of the target range of the blast moisture (BM), respectively.
• ⁇ BM max is an upper limit of the magnitude of allowable change in the blast moisture (BM).
• the unknown variable ⁇ is determined using quadratic programming so that the evaluation function J, which is a quadratic function regarding the unknown variable ⁇ , is minimized under the constraints of the linear equations for the unknown variable ⁇ indicated in expressions (10) through (13).
• the control to determine the unknown variable ⁇ using expression (9) corresponds to the hot metal temperature control in FIG. 2 .
• the evaluation function J was designed to decrease the blast moisture to decrease the reducing agent rate, but the same effect is obtainable by using the evaluation function J that directly decreases the reducing agent rate, for example, by penalizing an increase in the pulverized coal rate.
• the evaluation function J may be designed so that the minimization of the deviation of the predicted value of the hot metal temperature from the target value and the reducing agent rate (or the blast moisture) corresponds to the maximization of the evaluation function J. That is, the operation amounts of the pulverized coal rate and the blast moisture may be determined so that the evaluation function J is minimized or maximized.
• the operating variables are also manipulated for control variables other than the hot metal temperature (the production rate and the in-furnace pressure drop) using the following method.
• the following expression (14) is used to determine ⁇ BV, the operation amount of the blast volume (BV) [Nm 3 /min], so that the deviation between the target value and the predicted value is eliminated for the production rate.
• the PCR tracking control unit 17 acquires the target value of the pulverized coal rate (target PCR) determined by the hot metal temperature control unit 14 and calculates the operation amount of the pulverized coal injection (PCI) rate to follow the target PCR by PCR tracking control.
• the PCR tracking control unit 17 is a functional unit that executes the "PCR tracking control" illustrated in FIG. 2 .

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• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture Of Iron (AREA)
• Feedback Control In General (AREA)
• Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
• Manufacture And Refinement Of Metals (AREA)

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• 2023
  • 2023-11-21 KR KR1020257021593A patent/KR20250116093A/ko active Pending
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  • 2023-11-21 EP EP23924188.8A patent/EP4628599A4/de active Pending
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