JPH10310807A - Operation of blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately discriminate the increase of the furnace top gas flow rate caused by channeling or the other cause. SOLUTION: The detected value of blasting flow rate Vb and the detected value of furnace top gas flow rate Vt in a blast furnace body are sampled from a blasting flow meter and a furnace top gas flow meter arranged in the blast furnace body, and the arithmetic value of furnace top gas flow rate Vt ' is obtd. by using a nitrogen balance equation Vt '=(N2 content in the furnace tops gas/N2 content in blasting gas)×Vb ×60/1000. From this result, a reference value Vs =α×Vt ' for deciding whether the furnace top gas flow rate is raisen or not, is decided and a detecting index S is obtd. from Vt , Vs and Vt ' and it is decided whether the channeling is developed or not, based on whether this detecting index S becomes a boundary value β or higher or not, where αis an adjusting parameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a blast furnace, which detects a blow-by phenomenon during the operation of the blast furnace based on a variation in the gas flow rate of the furnace top and takes necessary measures.

[0002]

2. Description of the Related Art During the operation of a blast furnace, the pressure loss in the furnace locally increases, and when the pressure loss is balanced with the load of the load, the load is locally stopped, that is, a so-called shelf hanging. Then, the furnace interior material stops descending above the shelf hanging, and the furnace interior material descends below the shelf hanging, so that a cavity is created below the shelf hanging. When the cavity becomes large to a certain extent, the load in the lateral direction of the shelf hanging slides into the cavity, and in conjunction with this, the hanging of the shelf locally collapses.

[0003] If the hanging of the shelf is large and the collapse occurs rapidly, a large amount of the charge moves locally and relatively quickly, and the pressure loss in the furnace decreases locally, and the furnace gas moves upward from there. The gas blows up and instantaneously blows up to the furnace top, and the furnace top gas greatly increases. Such a blow-up phenomenon is called a so-called blow-through, and disturbs the furnace temperature distribution, the furnace interior material distribution,
Appropriate heat exchange and reduction were not performed, and the temperature of the hot metal was disturbed. In extreme cases, the hot metal was sometimes cooled. Therefore, it is necessary to detect the occurrence of a blow-by at an early stage and to perform an operation for appropriate recovery.

[0004] Since such a blow-through phenomenon cannot generally be observed directly in the furnace, the occurrence of blow-through has been conventionally judged by detecting a rise in the gas flow rate at the furnace top or the like. However, the furnace top gas flow rate is used to increase the flow rate due to the gas cleaning equipment attached to the blast furnace main body and the piping change of the furnace top pressure recovery power generation device, and to equalize the furnace top charging device with the furnace pressure. It is difficult to accurately detect a blow-through phenomenon from a change in the gas flow rate of the furnace top because the flow of the gas is affected by an increase in the flow rate or the like.

As a countermeasure against this, conventionally, for example, in Japanese Patent Application Laid-Open No. 1-319614, a level difference at the time of embedding between two successive batches is measured, and the level difference is determined to be a predetermined value. An operating method is disclosed below, in which it is determined that blow-by has occurred when the furnace top gas temperature rises rapidly, and operating conditions are controlled.

Further, Japanese Patent Publication No. 1-20203 discloses that
The static pressure on the inner wall of the furnace wall is measured at several points in the height direction of the blast furnace, and the pressure loss from each measurement position to the furnace top is determined based on the static pressure values. A technique has been proposed in which the load on the interior is determined, the conditions for blowing in the furnace are adjusted in accordance with the ratio of the determined pressure loss to the load on the charge, and the occurrence of blow-through is prevented.

[0007] Further, Japanese Patent Publication No. 4-9843 discloses that the unloading speed, pressure loss, shaft pressure, shaft temperature, fixed sonde temperature, gas utilization rate, furnace pressure are based on data from various sensors attached to the blast furnace. Obtain various data indicating the blast furnace condition such as temperature of the mouth sonde, compare these with their respective reference values to create true / false data, and based on this true / false data and experience with the blast furnace, actual data, etc. A method for predicting the occurrence of a slip or the like is disclosed.

[0008]

SUMMARY OF THE INVENTION Incidentally, Japanese Patent Laid-Open Publication No. 1-3
According to the technology disclosed in Japanese Patent No. 19614, from a decrease in the furnace interior charge surface level and a sharp rise in the furnace top gas temperature,
Although it is determined that blow-through occurs, water may be sprayed on the furnace top for protection of the furnace top charging device and gas cleaning equipment, and the furnace top gas temperature rarely exceeds 300 ° C to 400 ° C.
It is difficult to determine whether a sharp rise in the furnace gas temperature has occurred.In addition, when blow-through occurs, slip often occurs at the same time. No detection can be expected.

Furthermore, in the techniques disclosed in Japanese Patent Publication No. 1-20203 and Japanese Patent Publication No. 4-9843, the technique of predicting blow-through also includes fluctuations in the furnace top gas component, the surface level of the furnace interior charge, and the furnace top pressure. The load and pressure loss of the blast furnace charge are determined from the furnace wall pressure, etc., and the load of the blast furnace interior charge is determined by the properties (granularity, reduced powderability, strength) of the sinter or coke and the conditions inside the furnace, such as the blast furnace. Due to fluctuations due to wear of the furnace wall, changes in internal volume, and changes in frictional resistance, there is a problem in that the accuracy of calculating the load at each point in the furnace is low, and the accuracy of estimating the possibility of hanging a shelf is low. Was.

The present inventors analyzed various operation data at the time of blow-through in the blast furnace operation and examined the detection indices. As a result, a) an increase in the flow rate of the top gas b) an increase in the pressure of the top gas c) A decrease in the N ₂ component in the top gas d) An increase in the CO component in the top gas e) A decrease in the CO _{2 in} the top gas was observed to occur in common. What is shown is the furnace top gas flow rate.
Note that the top gas temperature is not suitable for early detection because the top gas temperature rises sharply compared to the top gas flow rate, causing a delay, and the top gas composition also has a delay in analyzing the gas composition. It turned out to be an indicator.

FIG. 4 is a graph showing the change of the gas flow rate of the furnace top before and after the occurrence of blow-through during the operation of the blast furnace. The horizontal axis represents time (hours, minutes), and the vertical axis represents the gas flow rate of the furnace top (kNm ^3).
/ Hour). As is apparent from this graph, when blow-through occurs, the furnace top gas flow rate greatly fluctuates in a time series manner.

As described above, an increase in the gas flow rate at the furnace top also occurs when the piping of the gas cleaning equipment or the furnace pressure recovery power generation device is switched, or when the equalizing gas is recovered from the furnace top charging device. FIG. 5 is a graph showing an increase in the top gas flow rate due to a cause other than the blow-by, in which the horizontal axis represents time (hour, minute), and the vertical axis represents the top gas flow rate (kNm ³ / hour). is there. As is clear from the graph, it is understood that the flow rate increase due to the switching of the pipe also causes a sudden increase in the flow rate of the furnace top gas similarly to the case when the blow-up occurs.

Therefore, in distinguishing between the case of the blow-by and the case of other factors, the time during which the flow rate of the furnace top gas is maintained at a predetermined value or more and the integrated value of the flow during this time are used to identify the occurrence of the blow-through. Was found to be extremely effective.

The present invention quantifies the blow-up amount of gas at the time of occurrence of blow-through as a furnace top gas flow rate, thereby accurately detecting the occurrence of blow-through which is an abnormal condition in the furnace.
An object of the present invention is to provide a blast furnace operating method capable of improving the stability of the blast furnace operation.

[0015]

According to a first aspect of the present invention, there is provided a method for operating a blast furnace, comprising detecting a flow rate of blast supplied to a blast furnace and a flow rate of a top gas at predetermined time intervals, and detecting the detected flow rate of blast based on a nitrogen balance equation. Calculate the top gas flow rate from this, calculate and set a reference value for determining an increase in the top gas flow rate from the calculated value of the top gas flow rate, and the detected value of the top gas flow rate continuously exceeds the reference value for a predetermined time. It is determined whether or not the sum has exceeded, and the ratio of the difference between the detected value of the top gas flow rate and the reference value to the calculated value of the top gas flow rate is integrated for the predetermined time, and the integrated value reaches or exceeds a predetermined boundary value. It is characterized in that it is determined that a blow-through has occurred and the blast furnace operating conditions are changed.

According to the first aspect, when the flow rate of the furnace top gas increases, it is possible to accurately determine whether the flow rate is due to blow-by or another cause.

In the blast furnace operating method according to a second aspect of the present invention, the flow rate of the blown air supplied to the blast furnace and the flow rate of the top gas are detected at predetermined time intervals. Calculate and set a reference value for judging an increase in the top gas flow rate from the calculated value of the top gas flow rate, and determine whether the detected value of the top gas flow rate continuously exceeds the reference value for a predetermined time. Judgment, the detection index is obtained by integrating the ratio of the difference between the detected value of the top gas flow rate with the calculated value of the top gas flow rate and the reference value for the predetermined time, and the detection index reaches or exceeds a predetermined boundary value. It is characterized in that it is determined that blow-by has occurred, and an operation for reducing the flow rate of air blown into the blast furnace is performed on the detection index.

According to the second aspect of the present invention, when blow-by occurs, the blast furnace flow rate to the blast furnace main body is reduced in accordance with the detection index, whereby stable blast-furnace operation can be continued immediately after blow-by occurs.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing the configuration of an apparatus for carrying out a blast furnace operating method according to the present invention, in which 1 is a blast furnace main body, M is a raw material charged in the furnace, and SE ₁ is a blast furnace. An air flow meter for detecting the air flow supplied from the lower portion of the main body 1 into the furnace, and SE ₂ is a furnace gas flow meter for detecting the gas flow at the top of the blast furnace main body 1. One or a plurality of these are provided, and when there are a plurality of them, an average value thereof is used as a detected air flow rate and a detected furnace top gas flow rate.

The air flow meter SE ₁ and the furnace gas flow meter SE ₂
Each detection value is determined at a predetermined timing _TP ( _TP
(≦ 2 seconds), the air flow rate detection value G ₁ and the furnace top gas flow rate detection value G ₂ are obtained and output to the arithmetic processing unit 3. The arithmetic processing unit 3 performs predetermined arithmetic processing based on the detected air flow rate G ₁ and the detected flow rate G ₂ of the furnace top gas input from the data detector 2 to determine whether or not blow-by has occurred. When the determination is made, a detection index S described later is output to the blast furnace operation control unit 4 and an operation command signal is output to the warning output unit 5.

The blast furnace operation control section 4 performs control so as to reduce the flow rate of air blown to the blast furnace main body 1 in accordance with the detection index S. The warning output unit 5 emits a warning sound or calls for the occurrence state of the blow-by by an artificial voice and the operation amount of the operating condition associated therewith, and also displays the fact of the blow-by detection, the value of the detection index S, the blast furnace operating condition on the display screen. The amount of operation, for example, how much the air flow into the furnace is reduced, can be displayed. Hereinafter, the processing contents of the arithmetic processing unit 3 will be described with reference to the flowchart shown in FIG.

First, a predetermined time interval T
_P(T_P≤ 2 seconds) Ventilation flow detection value V _b, Furnace top gas flow rate detection
Outgoing price V_t(Step S1). First nitrogen balun
The flow rate detection value V is calculated according to the following equation (1):_bFrom
Furnace top gas flow rate calculation value (kNm ^Three/ Hour) V_t′
(Step S2).

[0023]

(Equation 1)

A reference value V _S (kNm ³ / hour) for determining whether or not the furnace gas flow rate has increased according to the following equation (2) is calculated based on the calculated furnace gas flow rate value V _t '. And set (step S3). V _S = α × V _t ′ (2) where α is an adjustment parameter [1.1 to 1.3]

The top gas flow rate detection value V _t for a predetermined time reference value V _S is T (from time t ₁ to time t _2, the example, 10 seconds)
It is determined whether or not the number is continuously exceeded (step S
4), when exceeded, the ratio of the difference between the top gas flow rate detection value V _t and the reference value V _S for the top gas flow rate calculation value V _t ', over the excess period (t ₁ ~t ₂₎ The detection index S shown in the following equation (3) is obtained by integrating (Step S
5).

[0026]

(Equation 2)

With this detection index S, it is possible to quantify the increase amount of the furnace top gas flow rate at the time of occurrence of blow-through, and whether the detection index S has reached a predetermined boundary value β or more as shown in the following equation (4). It is determined whether or not blow-by has occurred (step S6). If it is equal to or greater than β, the warning output unit 5 and the blast furnace operation control unit 4 are operated (step S7). S ≧ β (4) β: Boundary value for blow-by detection (β = 4.0 to 5.0)

FIG. 3 is an explanatory diagram showing a relationship between the boundary value β for identifying the increase in the furnace gas flow rate due to blow-through and the increase in the furnace gas flow rate due to factors other than blow-through, and the detection index S. The adjustment parameter α was 1.2. In the figure, a white bar indicates the degree of increase in the furnace gas flow rate (case) due to the blow-through, and a black bar indicates the degree of increase in the furnace gas flow rate (case) due to factors other than the blow-through. As is clear from this,
It can be understood that, by properly setting the boundary value β, it is possible to clearly distinguish an increase in the top gas boundary due to the blow-by phenomenon and an increase in the top gas flow rate due to other factors.

In the ordinary blast furnace operation, the raw material in the furnace is melt-reduced by exchanging heat with the gas blown from the lower portion of the blast furnace main body 1. However, when blow-through occurs, the gas instantaneously passes to the furnace top. Therefore, the blown gas escapes to the furnace top without performing heat exchange. The blast furnace operation control unit 4 automatically reduces the flow rate of air blown to the blast furnace main body in proportion to the detection index S, thereby enabling stable blast furnace operation.

Next, the test results of the method of the present invention are shown in Table 1.
It will be described based on. Using a device such as shown in FIG. 1 detects blowing flow rate detection value V _b, the top gas flow rate detection value V _t at a predetermined timing T _P, obtains a reference value V _S according to Equation (2), and (3 ), The detection index S was calculated, and the occurrence of blow-by was detected using these. Table 1 illustrates the detection accuracy under the above-described conditions. The number of detections was thirteen, but was 0 when no detection was possible, and when it was determined that a blow-through was not detected.

[0031]

[Table 1]

[0032]

According to the first aspect of the present invention, the occurrence of blow-through can be accurately detected in distinction from an increase in the flow rate of the furnace top gas due to other factors.

According to the second invention, in addition to the effects of the first invention, the blast furnace can be stably operated even after blow-by by reducing the air flow rate corresponding to the detection index.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus for implementing a method of the present invention.

FIG. 2 is a flowchart illustrating a processing procedure of an arithmetic processing unit.

FIG. 3 is an explanatory diagram showing a relationship between a boundary value and a detection index for discriminating between an increase in a top gas flow rate due to blow-through and an increase in a top gas flow rate due to factors other than blow-through.

FIG. 4 is a graph showing a temporal transition of a furnace gas flow rate before and after occurrence of blow-through during blast furnace operation.

FIG. 5 is a graph showing an increase in a furnace gas flow rate due to a cause other than blow-through.

[Explanation of symbols]

 1 Blast furnace body 2 Data detector 3 Arithmetic processing unit 4 Blast furnace operation control unit 5 Alarm output unit

Claims (2)

[Claims] 1. A flow rate of a blown gas and a flow rate of a top gas supplied to a blast furnace are detected at predetermined time intervals, and a flow rate of a top gas is calculated from the detected flow rate of the blown gas based on a nitrogen balance formula. A reference value for determining an increase in the top gas flow rate is calculated and set based on the value, and it is determined whether the detected value of the top gas flow rate has continuously exceeded the reference value for a predetermined period of time. The ratio of the difference between the detected value of the furnace top gas flow rate and the reference value is integrated for the predetermined time, and when the integrated value reaches or exceeds a predetermined boundary value, it is determined that blow-by has occurred, and the operating conditions of the blast furnace are changed. Characteristic blast furnace operating method. 2. A flow rate of a blown gas and a flow rate of a top gas supplied to a blast furnace are detected at predetermined time intervals, and a flow rate of a top gas is calculated from the detected flow rate of the blown gas based on a nitrogen balance formula. A reference value for determining an increase in the top gas flow rate is calculated and set based on the value, and it is determined whether the detected value of the top gas flow rate has continuously exceeded the reference value for a predetermined period of time. The detection index is obtained by integrating the ratio of the difference between the detected value of the furnace top gas flow rate and the reference value to the predetermined time, and when the detection index has reached a predetermined boundary value or more, it is determined that blow-by has occurred and the detection is performed. A method for operating a blast furnace, characterized by performing an operation for reducing an air flow rate into the blast furnace as an index.