JPS58144432A - Operation for sintering - Google Patents

Abstract

PURPOSE:To stabilize the quality of sintered ore, by adjusting the distribution of the air-flow velocity of inhaled air or the like in a manner such that the distributions of heat-retaining and cooling indices obtained by calculating the model of a numerical formula is set in a predetermined range along the depth of a layer in a pallet. CONSTITUTION:The known model of a sintering numerical formula comprising the heat and material balances of gases and solid matter in a layer to be sintered is used. From said model of the numerical formula, the mixing ratio, particle size, density and wter content of a raw material and auxiliary material, the thickness of a layer, the speed of a pallet and the condition of an igniting oven are found as data on operation, and a plurality of heat patterns along the depth of the layer is obtained using the distribution of the wind velocity of inhaled air measured during sintering. From these heat patterns, the distributions of heat- retaining and cooling indexes along the depth of the layer are calculated. In succession, the distribution of the air-flow velocity of inhaled air or the distribution of a carbon source along the depth of the layer is adjuted in a manner such that the former distribution is set in a predetermined range.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintering operation method that can effectively control the quality of sintered ore in sintering operation, and more specifically, the present invention relates to a sintering operation method that can effectively control the quality of sintered ore. The present invention relates to a sintering operation method in which the distribution of the index and cooling index in the thickness direction of the pallet layer is determined, and the wind speed distribution of the sintering machine or the distribution of the carbon material in the layer thickness direction is adjusted so that these distributions fall within a certain range.

It is well known that the heat pattern representing the thermal history within the sintered layer is related to the quality of the physical properties of the sintered ore.

FIG. 1 is a graph showing an example of a heat pattern. The horizontal axis represents the sintering time, and the vertical axis represents the internal temperature T (° C.) of the sintered layer, and temperature history curves A and Bl are drawn at two points at different depths in the layer thickness direction.

The area QT of the shaded part of curve A is the temperature T ``C
The above-mentioned holding state is called the heat retention index, and is usually expressed as Q9oo, where T=900°C, and is determined by the following formula.

CT1too, which represents the cooling rate from the highest temperature point TP of the 8 curve to, for example, 1100°C, is called the cooling index,
It is shown by the following formula.

It is well known that there is a strong correlation between strength (shutter strength) and FeO%.

Conventionally, these indices have been calculated from heat patterns actually measured by thermocouples inserted into the sintering machine. Therefore, it is a representative value obtained from actual measurements at several points within the sintered layer, and cannot be obtained over the entire thickness of the sintered layer, and is used as an index to control the quality of the entire sintered layer. was insufficient.

For example, Table 1 shows an example of the distribution of cold strength (SI), reduction decay index (RDI), and FeO in the pallet layer thickness direction of a sintered product.

Table 1 It can be seen from Table 1 that the quality of the sintered products varies greatly in the thickness direction of the pallet layer. This quality variation in the layer thickness direction cannot be managed using conventional heat patterns measured at several points.

In order to manage the quality variations in the pallet layer thickness direction, the present invention divides the pallet layer thickness direction into a large number of layers, determines a heat retention index and a cooling index for each layer, and calculates the pallet layer thickness based on these indices. By managing the distribution of directions,
It is an object of the present invention to provide a sintering operation method that stabilizes the quality of sintered ore by keeping the variation in quality of sintered ore within a certain range.

The present invention focuses on the fact that by using a sintering mathematical model used to analyze sintering operations, it is possible to freely predict the heat pattern at any point within the sintered layer, unlike actual measurements using thermocouples. The distribution of heat retention index and cooling index in the nolet layer thickness direction is determined by mathematical model calculation from operational data given as conditions and suction wind speed distribution data actually measured during the sintering process, and this distribution is determined within a certain range. This sintering operation method is characterized by adjusting the suction wind speed distribution or the layer thickness direction distribution of carbon material so that

The mathematical model of sintering used in this invention is the gas in the sintered layer,
Commonly known mathematical models consisting of solid heat and mass balances can be used.

(3) Using this known sintering formula model, we provide operational data such as the mixing ratio, particle size, density, moisture content, layer thickness, pallet speed, and ignition furnace conditions of raw materials and auxiliary materials, and calculate the actually measured sintering suction wind speed distribution. A large number of heat patterns are obtained in the layer thickness direction. A heat retention index and a cooling index are calculated from these heat patterns.

The present invention will be explained in detail below according to specific examples.

FIG. 2 is a flowchart of thermal calculation using a mathematical model. The calculation conditions are (1) blending ratio of coke, limestone, ore, initial average particle size, density, (2) mixed raw material bulk density,
(3) Layer thickness (Zmax), (4) Pallet length L) and speed (PS), (51 Ignition furnace conditions (temperature pattern)
, (6) Temperature of suction air, wind speed distribution, (7) Moisture content of mixed raw material (W), equilibrium moisture value of mixed raw material (We ), (8)
Load the coke segregation coefficient and combustion rate coefficient. Next, set the initial value of the raw material layer, advance time 0 every 0.01 minutes,
Divide the raw material layer into 4 mm thick sections, advance the position, dry zone,
Until the heat calculations for the combustion zone and the cooling zone are converged (4) A heat pattern is drawn based on the above calculation results, and the heat retention index Q is calculated from the drawing. . , cooling index CT, 1°. Calculate and output this on a graph.

FIG. 3 is the obtained graph. The horizontal axis of the figure is the layer thickness of the sintered layer, and the vertical axis is the heat retention index Q*oo ('C·m1n) and the cooling index CT11oo (''C/min).

The distribution of heat retention index and cooling index shown in FIG. 3 corresponds to the variations in cold strength (S, 1.) and FeO% shown in Table 1.

The heat retention index indicates the state of high temperature retention, and if this heat retention is insufficient, the cold strength (S, 1.) will be insufficient. It is necessary to maintain it.

The cooling index indicates the cooling rate, and since reoxidation of hematite tends to proceed if the cooling rate is slow, it is necessary to set a lower limit and maintain it within a predetermined range.

For example, if the lower limit of the heat retention index in Fig. 3 is set at 200°C/min, the range from 30 to 140 m from the surface layer is insufficient in heat, so this must be improved (6).

Furthermore, if the lower limit of the cooling index in Fig. 3 is set to 40°C/min or more from the viewpoint of preventing reoxidation of hematite, it can be seen that the lower layer 230 inches from the surface layer must be improved.

The suction wind speed distribution corresponding to FIG. 3 is shown in FIG. 4 by a solid line.

The horizontal axis in FIG. 4 represents the sintering time.

30 to 140 from the surface layer, which is the area where the heat retention index is insufficient in Figure 3.
The range of m corresponds to the time period in which there is a sintering zone in this part, that is, the sintering time period of 5 to 10 minutes in FIG. To increase the heat retention index, the wind speed in this area can be decreased.

Additionally, the cooling index is increased by increasing the wind speed in the area corresponding to the layer below 230 m in Figure 3.

This improvement is shown by the broken line in Figure 4. As a result of changing the wind speed distribution as shown in this broken line, Figure 3 is improved as shown in Figure 6, and the quality within the sintered layer is improved as shown in Table 2. Improved.

Another measure for improving the heat retention index distribution and cooling index distribution shown in Table 2 and Figure 3 is shown in Figure 5. FIG. 5 shows a method of changing the distribution of the coke blending ratio in the layer thickness direction of the sintered layer, and changing the uniform distribution shown by the solid line in the figure to the broken line to increase the heat retention index in the upper layer of the sintered layer. The aim is to reduce the heat retention index and increase the cooling index of the lower layer of the sintered layer.

The coke mixing ratio can be adjusted by a known method applying the principle of grain size segregation in the ore feed section.

The results of this improvement are shown in FIG. 7 and Table 3.

(7) As explained in detail in Table 3 and above based on specific examples, the present invention calculates the heat retention index and cooling index distribution in the layer thickness direction of the sintered ore product, and based on these results, determines the appropriate It is possible to select the sintering operating conditions, improve the quality variation in the layer thickness direction of the sintered ore, stabilize the quality of the sintered ore product, and obtain a good quality sintered ore.

[Brief explanation of the drawing]

Figure 1 is a graph illustrating the heat pattern of sintering;
The figure is a calculation flowchart of the mathematical model for sintering, Figure 3 is a graph of an example of the distribution of heat retention index and cooling index in the layer thickness direction, Figure 4 is a graph of an example of improved suction air velocity distribution, and Figure 5 is a graph of coke blending ratio. (9) (8) Figures 6 and 7 are graphs of examples of improved distribution of heat retention index and cooling index in the layer thickness direction obtained by the improvements in Figures 4 and 5, respectively. It is. A, B...Heat pattern, TP...Maximum temperature, Q
90G...Heat retention index, CT, 1°. ...Cooling index, θ...Time, Z...Layer thickness, W...Moisture, We.
...Equilibrium moisture value, C...Convergence judgment value, L...Pallet length, PS...Pallet speed

Claims (1)

[Claims] 1 The distribution of the heat retention index and the cooling index in the pallet layer thickness direction is determined by mathematical model calculation, and the suction wind speed distribution or the carbon material layer thickness direction distribution is adjusted so that the distribution falls within a certain range. Sintering operation method.