Blast furnace reduced-scale operation method

Abstract

To provide a method for operating a blast furnace with reduced operating time that can suppress a decrease in the raw material surface temperature near the center of the furnace without extending the reduced operating time. [Solution] The blast furnace reduction operation method according to the present invention includes the step of shifting the water spray direction of half or less of the total number of water spray nozzles, among a plurality of water spray nozzles arranged circumferentially at the top of the furnace, away from the direction of the center of the blast furnace, and spraying water from the top of the furnace using a plurality of water spray nozzles, including water spray nozzles whose water spray direction is shifted away from the direction of the center of the blast furnace, during reduction operation. This makes it possible to provide a blast furnace reduction operation method that can suppress a decrease in the raw material surface temperature near the center of the furnace without extending the reduction operation time.

Description

Technical Field

[0001] The present invention relates to a method for reducing the scale of a blast furnace operation.

Background Art

[0002] Generally, when carrying out operations to lower the raw material level such as blowing down or replacing staves for renovation in a blast furnace, a scale reduction operation is carried out in which the raw material charging speed is decreased or the raw material charging operation is stopped and then the blowing operation is continued to lower the raw material level to near the tuyere. During this scale reduction operation, since the top gas temperature changes to a high level, an operation of increasing the amount of water sprayed from the furnace top and an operation of decreasing the blowing amount are combined and carried out. At this time, if the water spraying location concentrates on one location in the furnace, water lands on the raw material surface directly below the water spraying location, and an aqueous gasification reaction occurs on the raw material surface. The aqueous gasification reaction is beneficial for suppressing the rise in the top gas temperature. However, during the scale reduction operation on the premise of restarting the blast furnace such as replacing staves, the aqueous gasification reaction causes a temperature drop of the furnace filling material and the furnace melt, and thus becomes a phenomenon to be avoided that induces operation troubles during restart. Against such a background, Patent Document 1 proposes a method for suppressing a temperature drop on the raw material surface by dispersedly arranging the furnace top water spraying nozzles in the circumferential direction and switching the water spraying location and the amount of water sprayed according to the top gas temperature to control the top gas temperature.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] During blast furnace operation, changes in pressure drop at the tuyeres due to factors such as uneven distribution of raw material surfaces and the influence of slag cause variations in airflow between multiple tuyeres arranged circumferentially around the blast furnace, resulting in changes in the furnace top gas temperature circumferentially. Therefore, to control the furnace top gas temperature within a predetermined range, it is necessary to extend the water spraying time of the water spray nozzles that spray water in the direction where the furnace top gas temperature is higher than the predetermined range, resulting in a deviation in the amount of water sprayed circumferentially around the blast furnace. However, if the water spraying direction of the water spray nozzles is only towards the center of the furnace, extending the water spraying time of the water spray nozzles increases the amount of water sprayed towards the center of the furnace relatively, causing a decrease in the temperature of the raw material surface near the center of the furnace. To solve this problem, it is conceivable to reduce the airflow rate to decrease the required amount of water sprayed. However, in this case, the raw material consumption rate slows down, the reduced operating time increases, and this affects subsequent processes.

[0005] The present invention was made to solve the above problems, and its objective is to provide a method for operating a blast furnace with reduced operating time that can suppress a decrease in the raw material surface temperature near the center of the furnace without extending the reduced operating time. [Means for solving the problem]

[0006] The blast furnace reduction operation method according to the present invention includes the step of shifting the water spray direction of half or less of the total number of water spray nozzles, among a plurality of water spray nozzles arranged circumferentially at the top of the furnace, away from the direction of the center of the blast furnace, and spraying water from the top of the furnace using a plurality of water spray nozzles, including water spray nozzles whose water spray direction is shifted away from the direction of the center of the blast furnace, during reduction operation.

[0007] The water spraying capacity (t / h) of the aforementioned spraying nozzles should be 1.5 times the value obtained by dividing the expected water spraying rate (t / h) for the operation of the blast furnace by the number of spraying nozzles in operation.

[0008] H2 flow rate (Nm³) at the tuyeres of a blast furnace 3 ( / min) and H2 flow rate (Nm³) at the top of the furnace. 3The method may include a step of estimating the amount of water sprayed from the spray nozzles (kg / min) that reacts with the raw material surface through a water gasification reaction, and controlling the spray nozzles to be operated according to the estimation result. [Effects of the Invention]

[0009] According to the blast furnace reduction operation method of the present invention, it is possible to suppress a decrease in the raw material surface temperature near the center of the furnace without extending the reduction operation time. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing the configuration of a blast furnace to which a reduced-scale operation method for blast furnaces, which is one embodiment of the present invention, is applied. [Figure 2] Figure 2 is a diagram illustrating the effects of the present invention. [Modes for carrying out the invention]

[0011] A method for operating a blast furnace at reduced size according to one embodiment of the present invention will be described below with reference to the drawings.

[0012] 〔composition〕 Figure 1 is a schematic diagram showing the configuration of a blast furnace to which a reduced-size operation method for a blast furnace, according to one embodiment of the present invention, is applied. As shown in Figure 1, the blast furnace to which a reduced-size operation method for a blast furnace, according to one embodiment of the present invention, is applied includes a plurality of water spray nozzles 2 and water spray nozzles 3 arranged in the circumferential direction of the furnace body 1, and a control device 10 that controls the operation of the water spray nozzles 2 and water spray nozzles 3.

[0013] The sprinkler nozzle 2 is installed along the circumferential direction of the furnace top such that the sprinkler direction A of the main stream of water coincides with the straight line connecting the sprinkler nozzle 2 and the center position O of the furnace body 1. The sprinkler nozzle 2 sprinkles water in the sprinkler direction A according to the control signal from the control device 10. The sprinkler nozzle 3 is installed along the circumferential direction of the furnace top such that the sprinkler direction B of the main stream of water does not coincide with the straight line connecting the sprinkler nozzle 2 and the center position O of the furnace body 1. Specifically, the sprinkler nozzle 3 is installed so that the angle of the main stream of water is between the angle toward the center position of the furnace body 1 and the angle toward the inner wall surface of the furnace body 1. In addition, the number of sprinkler nozzles 3 is set to be less than half the total number of sprinkler nozzles. Furthermore, the sprinkler capacity (t / h) of sprinkler nozzles 2 and 3 is adjusted to be 1.5 times the value obtained by dividing the amount of water sprinkled assumed in the operational design by the number of sprinkler locations (number of sprinkler nozzles in operation).

[0014] The control device 10 is composed of an information processing device such as a computer and controls the operation of the water spray nozzles 2 and 3. In this embodiment, during reduced-size operation of the blast furnace, in which the blowing operation is continued to lower the raw material level to near the tuyere, the control device 10 controls the water spray nozzles 2 and 3 so that the furnace top gas temperature is within a predetermined range, thereby performing water spraying from the furnace top. The control device 10 also controls the H2 flow rate A [Nm³] from the tuyere of the blast furnace. 3 [ / min] and H2 flow rate B[Nm] from the top of the furnace. 3 The reaction rate C [kg / min] of the water gasification reaction at the raw material surface caused by water spraying from nozzles 2 and 3 is roughly estimated from the difference (BA) in [ / min], and the water spraying locations (water spraying nozzles to be operated) are controlled according to the estimation result. When operating at reduced scale, the CO gas utilization rate is low, and consequently the hydrogen gas utilization rate is also low. For estimating the reaction rate C, accuracy is not required, and operation can proceed without problems using a rough estimate. Furthermore, the gas temperature inside the furnace can be controlled, for example, by installing thermometers in four directions at the top of the furnace and controlling the on / off of the water spraying nozzles so that the temperature measured by each thermometer does not exceed the target temperature. Note that the water gasification reaction rate increases if one water spraying nozzle is used continuously, so it is advisable to determine the continuous use time of a water spraying nozzle and switch to another water spraying nozzle.

[0015] 〔effect〕 Figure 2 is a diagram illustrating the effects of the present invention. Figure 2(a) shows the watering area when only watering nozzle 2 is used, and Figure 2(b) shows the watering area when watering nozzle 2 and watering nozzle 3 are used. As shown in Figure 2(a), when the watering direction of the watering nozzles is only towards the center of the furnace (watering locations (1) to (8)), as in the method described in Patent Document 1, when the watering time of the watering nozzles is extended during reduced-scale operation, the amount of water sprayed on the center of the furnace increases relatively. As a result, the surface temperature of the raw material near the center of the furnace decreases. In contrast, as shown in Figure 2(b), when the watering direction of some of the watering nozzles is shifted from the center of the furnace (watering locations (9) to (12)), as in the present invention, when the watering time of the watering nozzles is extended during reduced-scale operation, the relative increase in the amount of water sprayed on the center of the furnace can be suppressed. Therefore, according to the present invention, it is possible to suppress the decrease in the surface temperature of the raw material near the center of the furnace without extending the reduced-scale operation time.

[0016] Although embodiments applying the invention made by the present inventors have been described above, the present invention is not limited by the descriptions and drawings that constitute part of the disclosure of the present invention in this embodiment. That is, all other embodiments, examples, and operational techniques made by those skilled in the art based on this embodiment are included in the scope of the present invention. [Explanation of symbols]

[0017] 1 Furnace body 2,3 Watering nozzles 10 Control device

Claims

1. A method for operating a blast furnace at a reduced size, comprising the step of shifting the water spray direction of less than half of the total number of water spray nozzles, among a plurality of water spray nozzles arranged circumferentially at the top of the furnace, away from the direction of the center of the blast furnace, and then spraying water from the top of the furnace using a plurality of water spray nozzles, including those whose water spray direction is shifted away from the direction of the center of the blast furnace, during reduced-size operation.

2. The method for operating a blast furnace at a reduced size according to claim 1, wherein the water spraying capacity (t / h) of the water spraying nozzle is 1.5 times the value obtained by dividing the amount of water sprayed (t / h) expected during the operation of the blast furnace by the number of water spraying nozzles in operation.

3. H at the tuyeres of a blast furnace ２ Flow rate (Nm ３ / min) and H at the top of the furnace ２ Flow rate (Nm ３ A method for operating a blast furnace on a reduced scale according to claim 1 or 2, comprising the steps of estimating the amount of reaction (kg / min) of water sprayed from a water spray nozzle reacting with water gas on the raw material surface from the amount ( / min), and controlling the water spray nozzle to be operated according to the estimation result.

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