JP2006342382A - Method for evaluating gas permeability of lower part in blast furnace, and blast furnace operating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for evaluating the gas permeability of the lower part in a blast furnace where the actual gas flow rate of the wall part in a blast furnace can be measured, thus the gas permeability of the lower part in the blast furnace can be correctly evaluated, and to provide a blast furnace operating method using the method for evaluating the gas permeability of the lower part in a blast furnace. <P>SOLUTION: A method for measuring a gas flow rate characterized in that a tracer gas blown from a blast tuyere in a blast furnace is detected at a position in the upper part of the blast tuyere, and, based on the time from the blowing of the tracer gas to its detection, the gas flow rate in the furnace is measured is used. Desirably, the detection of the tracer gas is performed at a position below the bosh of the blast furnace, the gas permeability at the lower part of the blast furnace is evaluated using the gas flow rate in the furnace measured using the method for measuring a gas flow rate, and a difference in pressure between the blast tuyere measured with a manometer installed in the body of the blast furnace and the tracer gas detection position, and operating conditions are changed using the method for evaluating the gas permeability of the lower part in a blast furnace. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for evaluating the permeability of the lower part of a blast furnace and a blast furnace operating method using the same.

  Improving productivity in the blast furnace is an important issue not only from cost reduction but also from carbon dioxide reduction. FIG. 3 shows a schematic diagram of a cross section of the blast furnace. In FIG. 3A, the upper part of the blast furnace 10 is a massive band 3 formed by alternately charging ores 1 and coke 2, and the lower part is a dripping band 5 where a melt of ore comprising a coke packed bed 4 is dripped. It is. Reference numeral 6 denotes a fusion layer. FIG. 3B is an enlarged view of the vicinity of the tuyere 7 and the raceway 8 of FIG. The blast furnace 10 is a huge counter-current packed bed reaction vessel, and a uniform reaction is desirable over the entire cross-sectional area in terms of reaction efficiency. However, when the coke packed bed 4 descends in the vessel, a large portion of the void 9 having a high porosity and easy gas flow is formed in the furnace wall due to the alignment effect by the furnace wall, and further, the blast furnace 10 is hot air that is a reactive gas. Is blown from the outer periphery of the furnace through the tuyere 7, so that the gas easily flows selectively through the furnace wall (furnace wall flow).

  The above furnace wall fluidization controls the layer thickness ratio of the ore 1 and coke 2 and the ore particle size distribution in the radial direction in the massive zone 3 before the iron ore melts down (charge distribution control). However, it is inevitable that the furnace wall be fluidized in the dripping zone 5, which is the lower region where only coke is present. Therefore, the blast gas velocity (gas velocity in front of the tuyere) is increased (usually 150 to 250 m / s in domestic blast furnaces), and the gas is pushed as far as possible toward the center of the furnace through the raceway 8 where coke does not exist. . It is theoretically possible to increase the speed of the tuyere by reducing the diameter of the tuyere 7 if there is sufficient blowing function and hot-blast furnace pressure resistance, but in this case, the coke powder turning in the raceway 8 will increase in powder. As a result, furnace wall flow and production decrease due to deterioration in ventilation of the dripping zone 5 occur. Therefore, the combined use of high strength coke and high tuyere gas velocity is essential for high productivity.

  Coke strength can be measured in advance, and operations using cold strength and post-reaction strength as an index are also performed. However, because the coke pulverization mechanism in the blast furnace is complex, it is difficult to control the lower part air permeability based only on these strengths. It is impossible to completely avoid the deterioration of the permeability of the belt 5 and the accompanying flow of the furnace wall. If the air permeability of the dripping zone 5 suddenly deteriorates, the coke and molten dripping material are blown up due to pressure loss, causing malfunction of the operation. Therefore, it is necessary to constantly monitor the air permeability of the dripping zone 5.

A method using pressure measurement results at the lower part of the furnace is known as a method for evaluating the lower part breathability. If it is thought that the lower part breathability has deteriorated, temporary production reduction (decrease in air flow) is performed. Therefore, it is possible to avoid the occurrence of malfunctions. Further, when the air permeability frequently deteriorates, it can be dealt with by raising the coke strength lower limit value, but in this case, the cost increases (see, for example, Patent Document 1).
JP 2003-306708 A

  However, the method using the pressure measurement result at the lower part of the furnace has a problem that it is difficult to accurately evaluate the air permeability at the lower part of the furnace. Just as measurement of electric resistance value requires measurement of voltage and current value, accurate measurement of ventilation resistance requires measurement values of both gas flow velocity and pressure loss (pressure difference). In the prior art, only the measured value of the furnace wall pressure loss was used, and the estimated value from the blown amount was used for the gas flow velocity in the furnace wall. However, the distribution of gas from the raceway is uneven and unstable, and the estimated gas temperature must be used, so the actual gas flow velocity in the furnace wall is different from the estimated value. Conceivable.

  Therefore, the object of the present invention is to solve such problems of the prior art and to measure the actual gas flow rate in the blast furnace wall, thereby accurately evaluating the permeability of the lower part of the blast furnace. To provide an evaluation method.

  Another object of the present invention is to provide a blast furnace operating method using the above blast furnace lower air permeability evaluation method.

The features of the present invention for solving such problems are as follows.
(1) The tracer gas blown from the blower tuyere of the blast furnace is detected at the upper position of the blower tuyere, and the gas flow rate in the furnace is measured based on the time from the blowing of the tracer gas to the detection. To measure the gas flow rate.
(2) The method for measuring a gas flow rate according to (1), wherein the tracer gas is detected at a position below the blast furnace.
(3) In-furnace gas flow rate measured using the gas flow rate measurement method described in (1) or (2), and a blower tuyere and tracer gas detection position measured by a pressure gauge installed in the furnace body of the blast furnace The blast furnace lower part breathability evaluation method characterized by evaluating the blast furnace lower part breathability using a pressure difference with the blast furnace.
(4) A blast furnace operating method characterized by changing operating conditions using the blast furnace lower part air permeability evaluation method described in (3).

  According to the present invention, it becomes possible to accurately detect the deterioration of the air permeability in the lower part of the furnace, and it is possible to almost certainly avoid the malfunction of operation due to the deterioration of the air permeability. Further, it is not necessary to use an excessively high quality coke having a high strength, and the hot metal cost can be reduced. In addition, during the production increase period, it becomes possible to increase the production volume when there is room in the furnace bottom air permeability, and the productivity of the blast furnace can be improved without any trouble.

  The present inventors thought that in order to accurately evaluate the air permeability at the bottom of the blast furnace, actual measurement of the gas flow rate in the furnace wall portion was indispensable. Then, the tracer gas is blown from the tuyere, the gas is detected above the gas blowing position, and the furnace wall gas flow velocity can be measured from the time required to detect the blown gas (collected time delay). The air permeability index indicating the air permeability in the lower part of the furnace is calculated using the measured furnace wall gas flow rate, and the quality of the raw materials charged in the blast furnace and the operating conditions of the blast furnace are controlled based on the calculation result. A blast furnace operation method was found and the present invention was completed. The present invention is characterized in that the tracer gas blown from the blower tuyere of the blast furnace is detected at the upper position of the blower tuyere and the gas flow rate in the furnace is measured based on the time from the blowing of the tracer gas to the detection. This is a method for measuring the gas flow rate. The detection of the tracer gas is preferably performed at a position below the blast furnace belly. In addition, the gas flow rate in the furnace measured using the gas flow rate measurement method described above, and the pressure difference between the blower tuyere and the tracer gas detection position measured by a pressure gauge installed in the furnace body of the blast furnace, It is a blast furnace lower part air permeability evaluation method characterized by evaluating air permeability. Furthermore, the blast furnace operating method is characterized in that the operating conditions are changed using the blast furnace lower air permeability evaluation method.

  The present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a cross section of a blast furnace. As shown in FIG. 1, a tracer gas 13 is collected while a furnace gas is collected by a gas sampling pipe 11 and monitored by a gas analyzer 12 connected to the gas sampling pipe 11. Is blown from the tuyere 7 and the time (time delay) until the blown gas is collected by the gas sampling tube 11 is measured. Then, the gas flow rate in the furnace is calculated from the distance from the tuyere to the gas sampling tube 11 and the time delay. It is desirable to install the gas sampling tube 11 at the blast furnace or morning glory position corresponding to the dripping zone 5 of the blast furnace. In addition, the pressure difference between the tuyere 7 and the gas sampling tube 11 position is greatly affected by pressure loss at the tuyere 7 and coke combustion in the raceway 8, so a pressure gauge 14 is installed in the furnace body instead of the blowing pressure. It is desirable to use the measured value. As the tracer gas 13, it is preferable to use an inert gas, and it is preferable to use helium gas, argon gas, or the like. Moreover, it is preferable to inject tracer gas intermittently.

  The air permeability index indicating the air permeability in the furnace is calculated from the gas flow rate and the pressure loss. Although the calculation method of the air permeability index is arbitrary, the calculation method is preferably as simple as possible. For example, ΔP is a pressure difference (differential pressure), v is a gas flow rate, and the conventionally used K value is improved. (A) can be used.

K ′ = ΔP / v ^1.7 (kg / cm ² ) / (m / s) ^1.7 (A)
The air permeability at the bottom of the blast furnace is evaluated using the air permeability index. By using the air permeability index calculated using the gas flow rate measuring method of the present invention, the air permeability in the lower part of the blast furnace can be accurately evaluated.

  By using the blast furnace lower air permeability evaluation method of the present invention, it is possible to accurately evaluate the air permeability of the lower blast furnace, so by changing the operating conditions based on the obtained air permeability index, It is possible to almost certainly avoid malfunctions due to deterioration in air permeability.

In a blast furnace having an internal volume of 4000 m ^3, the same equipment as that shown in FIG. 1 was installed and air permeability was evaluated.

  The blast furnace is normally operated with a coke ratio of 360 kg / t, a pulverized coal injection rate of 140 kg / t, and a reducing material ratio of 500 kg / t, and the coke cold strength index is controlled with 84 as the lower limit. The air permeability at the bottom of the furnace is monitored using the K value calculated by measuring only the furnace wall pressure loss. If the K value rises, the production is reduced and the production target is maintained at 8700 t / d. (Conventional K value judgment).

  The operation by the conventional K value determination was performed for 6 months, and after the 6th month, the gas flow rate in the furnace was measured and switched to the determination of the lower part of the furnace by K ′ using the above formula (A). Fig. 2 shows the strength index of cold coke used for blast furnace operation and changes in production volume. By determining the remaining capacity of air permeability from the value of K ′ and actively increasing the production volume while maintaining the air permeability, it was possible to increase production by about 300 t / d.

The schematic of the section of the blast furnace explaining one embodiment of the present invention. A graph showing the strength index of cold coke used for blast furnace operation and changes in production volume. Schematic of the cross section of a blast furnace.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ore 2 coke 3 lump band 4 coke packed bed 5 drip zone 6 fusion layer 7 tuyere 8 raceway 9 most of voids 10 blast furnace 11 gas sampling pipe 12 gas analyzer 13 tracer gas 14 pressure gauge

Claims (4)

  Tracer gas blown from the blast furnace tuyere is detected at the upper position of the blower tuyere, and the gas flow rate in the furnace is measured based on the time from the introduction of the tracer gas to the detection. Measuring method.   2. The method for measuring a gas flow rate according to claim 1, wherein the tracer gas is detected at a position below the blast furnace.   The pressure difference between the gas flow velocity in the furnace measured using the gas flow velocity measuring method according to claim 1 or 2, and the pressure between the blower tuyere and the tracer gas detection position measured by a pressure gauge installed in the furnace body of the blast furnace. A method for evaluating the permeability of the lower part of a blast furnace, wherein the permeability of the lower part of the blast furnace is evaluated using   A blast furnace operating method, wherein operating conditions are changed using the blast furnace lower air permeability evaluation method according to claim 3.

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