JPS6277414A - Operating method for blast furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a blast furnace operating method.

[Conventional technology]

Air permeability inside the furnace is one of the most important issues in the operation of a blast furnace, and to ensure this air permeability, it is necessary to maintain the cohesive zone, the area where the ore is softened and fused, in an appropriate shape. Begging to be needed. For this reason, various methods have been proposed for detecting the cohesive zone during operation and utilizing it for operation analysis. For example, as shown in Japanese Unexamined Patent Publication No. 50-53203, the gas temperature and gas components in the furnace measured by inserting horizontal probes at several locations in the radial direction of the furnace are substituted into a mathematical model and solved to calculate the cohesive zone position. There is a way to detect it. Also, Special Public Service No. 53-1
As shown in Publication No. 9'216, iron ore is charged twice in succession from the top of the blast furnace, instead of the usual alternate charging, such as coke - iron ore - iron ore - coke. There is a method of detecting the top of the cohesive zone by detecting the pressure change of the internal gas and calculating the falling time from charging until the pressure change is detected. Furthermore, as disclosed in Japanese Patent Publication No. 57-52925, there is a method of measuring the furnace wall temperature at a plurality of locations in the height direction of the blast furnace wall and detecting the root of the cohesive zone by statistical processing of the average value.

[Problem that the invention attempts to solve]

Conventional technology has focused on understanding the inside of the reactor by making full use of various detection ends, and has focused on the method of understanding problems phenomenologically and considering solutions on a case-by-case basis. On the other hand, the theoretical approach of modeling the reactions inside a blast furnace, constructing a mathematical model, and performing simulations has also made considerable progress due to the development of computers in recent years.

However, inside a blast furnace, phenomena such as flow, heat transfer, and reactions are intricately intertwined, and it is necessary to solve problems by assuming many unknown variables, and there are many cases where actual furnace conditions are not simulated. In this way, in order to accurately estimate and control the inside of a blast furnace, it is necessary to organically combine the ability to grasp phenomena with high precision using the detection end and a theoretically supported estimation model, and to evaluate the advantages and disadvantages of each. There is a need for an analysis system that complements technology and can be applied to a wide range of areas with accuracy not found in conventional methods. The present invention provides a method for determining the optimum position and shape of the cohesive zone by combining information obtained by a measurement sonde and a blast furnace mathematical model.

[Means for solving problems]

The configuration of the blast furnace operating method according to the present invention uses information obtained from a measurement sonde inside the furnace to simulate the position and shape of the cohesive zone using a blast furnace mathematical model that simultaneously analyzes flow, reaction, and heat transfer inside the furnace. If there are differences in the ore reduction distribution, gas temperature distribution, pressure distribution, or cohesive zone shape, the gas diffusion coefficient, gas film heat transfer resistance, core porosity, and charge descent rate distribution should be verified. By correcting the differences in parameters and searching for the optimal position and shape of the cohesive zone in an actual furnace, an inverted V shape with a moderately developed central flow was set as the ideal shape, and the burden distribution conditions and air blowing conditions were adjusted to optimize it. This is a blast furnace operating method that is characterized by finding operating conditions and applying it to actual furnaces.

As shown in Figure 3, the blast furnace mathematical model simultaneously analyzes the charge distribution, gas flow, solid flow, reaction, and heat transfer in the blast furnace. It is characterized by repeating calculations until it converges.

The method of charging raw materials into a blast furnace is to charge ore and coke alternately in layers and to control the ore weight/coke weight and particle size distribution in the radial direction, thereby appropriately distributing the gas flow distribution. At this time, the angle of inclination of the ore and coke was made small in consideration of the gas flow velocity, and a method was adopted in which the ore and coke were piled up by the charging volume around the falling point. Next, using this charging surface shape at the top of the furnace as an initial value, the flow of the charge solid is calculated as a simple piston flow. As shown in FIG. 2, the ore was assumed to shrink in the cohesive zone 1 and finally drip as a liquid. The gas flow is in the opposite direction to the solid flow, and is blown through the tuyere 3 and discharged from the top of the furnace via the cohesive zone 1, which has poor air permeability. The gas flow in the blast furnace shaft is Erg.
The relationship between pressure drop and flow rate of a packed bed shown by UN was used.

gradP= f + G+ f 2 G I G l
・”(1) where P: pressure G gas mass velocity φ: shape factor
gc: Gravity conversion coefficient dp: Average particle diameter μ:
Gas viscosity ε: void ratio ρ8: gas density Most reduction reactions in iron ore use a one-stage overall reaction rate equation, but a multi-interfacial reaction model is based on a mechanism in which reduction proceeds in parallel in multiple steps. It was adopted.

It is thought that the position of the cohesive zone 1 is determined not only by the gas flow and the reduction reaction, but also by the heat transfer mechanism between the gas and the solid. The heat transfer coefficient between particles and fluid is Ra
Based on the equation determined by nz for the packed bed, the equation was corrected using the results of measurements made using a vertical sonde, etc.

hp: Heat transfer coefficient between particles and fluid Kg: Thermal conductivity of gas Pr Nybrantl number Rep: Particle Raynozzle number dp: Particle diameter Ce: Correction term Cohesive zone 1 is a function of the softening start temperature and dripping start temperature, and the reduction rate. The shape was estimated from the temperature distribution calculated using the heat transfer mechanism. The above calculation is repeated until the cohesive zone shape is stabilized, and finally the cohesive zone shape, temperature, reduction distribution, gas flow, solid flow, etc. are output.

Separately from this mathematical model, a small number of sensors are installed in the blast furnace shaft so that they can penetrate into the contents of the furnace, and the sensors measure the gas temperature, gas components, and gas pressure in the furnace from the top of the shaft. Continuously measure up to the cohesive zone.Measurement can be carried out using a vertical sonde, which has been commonly used in the past.
It can be easily detected by using JP-A-16917. Next, the blast furnace mathematical model was used to reproduce the furnace conditions such as gas flow distribution, ore reduction rate distribution, gas temperature distribution, cohesive zone shape, etc. based on the data obtained above. Set unknown parameters.

If the gas flow distributions do not match, change the furnace core void ratio coefficient to θ
In the case of the reduction rate distribution of ore, the diffusion coefficient is similarly varied from 0 to 1, considering that gas diffusion is rate-determining. Regarding the gas temperature distribution, the gas film heat transfer resistance coefficient is changed by considering that the gas film heat transfer rate is similarly determined. The above operations are repeated until the cohesive zone shape thus obtained matches that based on the data. Figure 4 shows the comparison results.

In this way, a thought experiment is carried out using a computer to solve a problem using a blast furnace mathematical model that is in one-to-one correspondence with an actual furnace. In other words, even if operational actions are taken, the effects will only be seen after a few hours, and once the furnace condition worsens, it is difficult to recover, and the reality is that the vicious cycle repeats.

In this respect, simulations using a computer can prove their effectiveness in a short period of time, and can be freely tested even under difficult operating conditions.

The main operational actions that can be considered are charge distribution control and adjustment of air blowing conditions. Specifically, the optimum operating conditions are found by combining one or more of the radial distribution of ore/coke, the radial particle size distribution of ore/coke, the air temperature, air humidity, etc. Finally, the optimal operation action is adopted based on the simulation results, its effectiveness is confirmed by the sensor, and if it is insufficient, feedback is given and the above operation is repeated again. The above ideas are summarized in the thought flow in Figure 1.

The method of the present invention can be applied to operations that have shifted from normal operations, such as pulverized coal injection, where the amount of lump coke charged is significantly reduced,
Alternatively, it has a great effect in cases where the rate of descent increases significantly and the amount of Bosch gas decreases, such as in high iron production ratio operations.

〔Example〕

Example 1 An example in which the analysis system of the present invention was implemented during the transition period from all-coke operation to pulverized coal injection (PCI) operation is shown below.

i Pulverized coal injection is an operation in which pulverized coal is injected from the tuyere 3 at the same time as air at approximately 1300°C, and it is a blast furnace operating method that aims to reduce the amount of lump coke charged from the top of the furnace and to reduce the price difference between coking coal and steam coal. It is. As shown in Figure 5, when comparing conventional all-coke operation and PCI operation, the immediate combustion zone (raceway) 2 expands and the melting capacity increases, so the surrounding ore/coke ratio is actively adjusted. Operational actions were taken to increase and maintain the central gas flow. As a result, the cohesive zone top layer 1b rose and the root portion 1a became lowered. As a result, as shown in FIG. 6, the root portion 1a was lowered stably without any change in ventilation, and the (Si) content in the hot metal was also lowered by about 0.1% earlier than in the case of all coke. For comparison, the transition from conventional all-coke operation to PCI operation without using the present invention is shown in an overlapping manner.

Since there was no such analysis system, it was only possible to find the best product through trial and error.

Example 2 In cases where increased production is required, such as during a blast furnace renovation period, high-output ratio operation using a combination of oxygen enrichment and pulverized coal injection is effective. When the oxygen enrichment rate is increased, the heat flow ratio (solid heat capacity/gas heat capacity) increases locally, and heat transfer between the gas and solid becomes insufficient, resulting in the ore dripping in an unreduced state directly above the raceway. triggered. Then increase the humidity,
The temperature of the raceway 2 was lowered and the amount of Bosch gas was increased, while the ore/coke ratio in the peripheral area was lowered so that the reduction ratio near the cohesive zone root 1a was 0.9 or more. As a result, as shown in Figure 7, the average pig iron production ratio was 2.5t/
It was possible to stably maintain a high pig iron production ratio of Dam'.

〔Effect of the invention〕

As explained in detail above, according to the method of the present invention, stable operation can be quickly achieved even when shifting to a blast furnace operation method for which there has been no prior experience, and it is extremely effective in terms of blast furnace operation, which can contribute to low fuel ratio, low (Si) operation, etc. This is an excellent invention.

[Brief explanation of drawings]

Figure 1 shows the basic concept of the blast furnace analysis system, Figure 2 shows the situation inside the blast furnace, Figure 3 shows the flowchart of the blast furnace mathematical model, and Figure 4 shows the calculations using the mathematical model. A diagram showing an output example, Figure 5 is all coke and PC
A diagram comparing the cohesive zone shapes of I operation, FIG. 6, and FIG. 7 are diagrams showing examples, respectively. 1: Cohesive zone, 1a: Cohesive zone root, 1b: Cohesive zone top, 2
Elm sway, 3: tuyere. Applicant Nippon Steel Corporation Patent Attorney Aoyagi Aoyagi Fertility Control 7th Edition PCI Yuye Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] The position and shape of the cohesive zone simulated by a blast furnace mathematical model that simultaneously analyzes the flow, reaction, and heat transfer inside the furnace was verified using information obtained from a measurement sonde inside the furnace, and the ore reduction distribution and gas temperature distribution were verified. , when there are differences in pressure distribution and cohesive zone shape, the differences are corrected using parameters such as gas diffusion coefficient, gas film heat transfer resistance, core porosity, and charge descending velocity distribution, and the optimum value for the actual furnace is determined. We searched for the location and shape of the cohesive zone, determined that an inverted V shape with a moderately developed central flow was the ideal shape, and adjusted the burden distribution conditions and air blowing conditions to find the optimal operating conditions and apply it to the actual furnace. How to operate a blast furnace.