JPH062886B2 - Blast furnace operation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a blast furnace operating method.

[Conventional technology]

Permeability inside the furnace is one of the most important issues in the operation of a blast furnace, and in order to secure this permeability, it is necessary to maintain the region where the ore softened and fused, called the cohesive zone, in an appropriate shape. is necessary. Therefore, conventionally, 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, gas temperatures and gas components in the furnace, which are measured by inserting horizontal sondes in several positions in the inner diameter direction of the furnace, are substituted into a mathematical model to determine the fusion zone position. There is a way to detect. Also, Japanese Patent Publication Sho 53-
As shown in Japanese Laid-Open Patent Publication No. 19216, as in the case of coke-iron ore-iron ore-coke from the furnace top of the blast furnace, the gas in the furnace passing through the iron ore continuously charged twice instead of the usual alternate charging. There is a method of detecting the pressure change of No. 1, and calculating the fall time from the charging to the detection of the pressure change to detect the top of the cohesive zone. Further, as shown in Japanese Patent Publication No. 57-52925, there is a method of detecting the cohesive zone root portion by measuring the furnace wall temperature at each of a plurality of locations in the furnace wall height direction and statistically processing the average value thereof.

[Problems to be solved by the invention]

The conventional technology has focused on grasping the inside of the furnace by making full use of various detection ends, and mainly focuses on the method of phenomenologically grasping the problem and thinking of a solution on a case-by-case basis. It was On the other hand, the theoretical approach of modeling the reaction in the blast furnace, assembling a mathematical model, and simulating it has also progressed considerably with the development of computers in recent years. However, in the blast furnace, phenomena such as flow, heat transfer, and reaction are intricately intertwined, and it is necessary to solve the problem by assuming many unknowns, and in many cases the actual furnace conditions are not simulated. Thus, in order to accurately estimate and control the inside of the blast furnace, it is possible to organically combine the highly accurate phenomenon grasping ability utilizing the detection end with the theoretically supported estimation model to obtain advantages and disadvantages. It is desirable to have an analysis system that complements the technology and has a precision and a wide range of applications that cannot be achieved by conventional methods. The present invention provides a method for operating by finding the optimum position and shape of the cohesive zone by combining the information obtained by the measurement probe and the mathematical model of the blast furnace.

[Means for solving problems]

The configuration of the blast furnace operating method according to the present invention is the information obtained from the measurement sonde in the furnace for the position and shape of the cohesive zone simulated by the blast furnace mathematical model in which the flow, reaction, and heat transfer in the furnace are simultaneously analyzed. After verification, if there are differences in ore reduction distribution, gas temperature distribution, pressure distribution, and cohesive zone shape, gas diffusion coefficient, gas film heat transfer resistance, core porosity, and charge descent rate distribution are parameters. As a result, the optimum position and shape of the cohesive zone in the actual furnace are sought, and the inverse V type with an appropriate central flow is idealized, and the charge distribution conditions and blast conditions are adjusted to optimize Find operating conditions,
It is a blast furnace operating method characterized by being applied to an actual furnace.

As shown in Fig. 3, the mathematical model of the blast furnace is to simultaneously analyze the charge distribution, gas flow, solid flow, reaction, and heat transfer in the blast furnace. The feature is that the calculation is repeated until is converged.

In the method of charging the raw material into the blast furnace, the ore and the coke are charged alternately in layers and the ore weight / coke weight in the radial direction and the particle size distribution are controlled to appropriately distribute the gas flow distribution. At this time, the inclination angle of ore and coke was made small considering the gas flow velocity, and a method was adopted in which only the charging volume was accumulated around the falling point. Next, using the charging surface shape at the furnace top as an initial value, the solid flow of the charge is calculated as a simple piston flow. As shown in FIG. 2, the ore contracted in the cohesive zone 1 and was finally dropped as a liquid. The gas flow is in the opposite direction to the solid flow and is blown from the tuyere 3 and discharged from the furnace top through the cohesive zone 1 having poor air permeability. The gas flow at the shaft of the blast furnace is Ergun
The relationship between packed bed pressure drop and flow velocity was used.

-GradP = f ₁ + f ₂ || ... (1) where P: Pressure G: Gas mass velocity φ: Shape factor gc: Gravity conversion factor dp: Average particle size μ: Gas viscosity ε: Porosity ρ _g : Gas density Most of the overall reaction rate equations for reducing iron ore However, a multi-interface reaction model based on the mechanism that reduction proceeds in parallel in multiple stages was adopted.
It is considered that not only the gas flow and the reduction reaction determine the position of the cohesive zone 1, but also the heat transfer mechanism between the gas and the solid has the closest relationship. The heat transfer coefficient between particle fluids is Ranz
Was corrected for the measurement results of the vertical sonde, etc. based on the formula obtained for the packed bed.

hp: Heat transfer coefficient between particle fluids Kg: Thermal conductivity of gas Pr: Prandtl number Rep: Particle Reynolds number dp: Particle diameter Ce: Correction term The cohesive zone 1 is the softening start temperature and the dropping start temperature of the reduction rate. The shape was estimated from the temperature distribution calculated by the heat transfer mechanism given as a function. The above-mentioned calculation is repeated until the shape of the cohesive zone becomes stable, and finally the shape of the cohesive zone, temperature, reduction distribution, gas flow, solid flow, etc. are output.

Separately from the mathematical model, at least one sensor is installed on the shaft part of the blast furnace so as to be able to enter inside the furnace interior, and the gas temperature, gas components and gas pressure in the furnace are fused from the upper part of the shaft by the sensor. Measure continuously up to the belt. As a measuring means, a vertical sonde which has been generally used in the past can be used.
It can be easily detected by using JP-A-16917. Next, the conditions in the furnace such as gas flow distribution, ore reduction rate distribution, gas temperature distribution, and cohesive zone shape based on the data obtained above using the blast furnace mathematical model are reproduced as follows. Set unknown parameters to.

If the gas flow distributions do not match, the porosity coefficient of the core is set to 0.
In the case of ore reduction rate distribution, the diffusion coefficient is similarly varied from 0 to 1 on the assumption that the gas diffusion rate is controlled. Regarding the gas temperature distribution, similarly, the gas film heat transfer resistance coefficient is changed by considering the film side film heat transfer rate limiting. The above operation is repeated until the shape of the cohesive zone thus obtained matches that based on the data. The comparison results are shown in FIG.

In this way, a thought experiment is carried out using a computer to solve the problem by using the blast furnace mathematical model that is in one-to-one correspondence with the actual furnace. In other words, the actual effect is that after a few hours the effect will appear even if the operation action is actually taken, and once the reactor condition deteriorates, it does not recover easily and the vicious cycle repeats itself. In that case, the simulation using a computer can be found to be effective in a short time, and can be freely tested even under drastic operating conditions.

The operation actions mainly include distribution control of charge and adjustment of blowing conditions. Specifically, one or more combinations of the ore / coke radial distribution, the ore / coke radial particle size distribution, the blast temperature, the blast moisture, and the like are used to find the optimum operating conditions. Finally, an optimal operation action is adopted from the simulation result, the effect is confirmed by the sensor, and if insufficient, feedback is given and the above operation is repeated. The above idea is summarized in the thought flow in Fig. 1.

The method of the present invention is a transition from the normal operation, for example, the charging coke amount is greatly reduced as in the case of the injection of granular pulverized coal,
Alternatively, it has a great effect in the case where the descending speed is greatly increased and the Bosch gas amount is decreased as in the case of high iron output ratio operation.

〔Example〕

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

Pulverized coal injection is an operation in which pulverized coal is blown from the tuyere 3 at the same time as air at about 1300 ° C, and it is a blast furnace operation method aiming at reduction of agglomerated coke charged from the top of furnace and difference in price between coking coal and steam coal. Is. As shown in Fig. 5, when comparing the conventional all-coke operation and PCI operation, the combustion zone (raceway) 2 in front of the tuyere expands and the melting capacity increases, so the ore / coke ratio in the surrounding area is positive. The operation action was taken to increase and maintain the central gas flow. As a result, the cohesive zone top portion 1b was raised and the root portion 1a was lowered. As a result, as shown in FIG. 6, the root portion 1a stably decreased without fluctuation of air flow, and [Si] in the molten iron could be decreased by about 0.1% earlier than in the all coke time. For comparison, the transition from the conventional all-coke operation to the PCI operation when the present invention is not used is overlaid and displayed. Since there is no such analysis system, it was possible to finally find the optimum operation by trial and error.

Example 2 When it is necessary to increase production such as during blast furnace refurbishment, a high iron output ratio operation that combines oxygen enrichment and pulverized coal injection is effective. When the oxygen enrichment rate rises, the heat flow ratio (solid heat capacity / gas heat capacity) locally rises, heat transfer between gas and solid is not sufficiently carried out, and the phenomenon that ore drops in the unreduced state is directly above the raceway. Be triggered. Therefore, the moisture content was raised, the temperature of the raceway 2 was lowered, and the amount of Bosch gas was increased, while the ore / coke ratio in the peripheral portion was lowered so that the reduction rate in the vicinity of the cohesive zone root 1a was 0.9 or more. . As a result, as shown in Fig. 7, the average iron output ratio was 2.5t /
We were able to maintain a stable high iron output ratio of Dmm ³ .

〔The invention's effect〕

As described in detail above, according to the method of the present invention, stable operation can be achieved early even if the method is changed to a blast furnace operation method that has not been used in the past, and it is possible to contribute to low fuel ratio, low [Si] operation, etc. It is an excellent invention.

[Brief description of drawings]

Fig. 1 is a diagram showing the basic concept of the blast furnace analysis system, Fig. 2 is a diagram showing the situation inside the blast furnace, Fig. 3 is a diagram showing a flowchart of a mathematical model of the blast furnace, and Fig. 4 is calculated by the mathematical model. Figure 5 shows an example of output, Figure 5 shows all coke and PC
The figure which compares the cohesive zone shape of I operation, FIG. 6, and FIG. 7 are figures which show an Example, respectively. 1: Cohesive zone, 1a: Root of fusion zone, 1b: Top of fusion zone,
2: Raceway, 3: Tuyere.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-57-70209 (JP, A) JP-A-56-136906 (JP, A) JP-A-55-110706 (JP, A) JP-A-51- 151209 (JP, A) JP-A-51-50807 (JP, A) JP-B-52-724 (JP, B2)

Claims (1)

[Claims] 1. The position and shape of the cohesive zone simulated by a blast furnace mathematical model in which the flow, reaction, and heat transfer in the furnace are simultaneously analyzed, and the position and shape of the cohesive zone are verified by the information obtained from the measurement sonde in the furnace to reduce ore. When there is a difference in distribution, gas temperature distribution, pressure distribution, and cohesive zone shape Correct the differences using the gas diffusion coefficient, gas film heat transfer resistance, core porosity, and charge descent rate distribution as parameters. , Searching for the optimum position and shape of the cohesive zone in the actual furnace, finding the optimum operating condition by adjusting the charge distribution condition and the blast condition, assuming that the inverted V type with an appropriate central flow developed is ideal Blast furnace operating method applied to actual furnace.