JPS629170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintering method using a Dwight Lloyd sintering machine, and more specifically, the temperature distribution in the sintering bed is estimated from the measured flow rate of exhaust gas in each wind box, and the temperature distribution is The present invention relates to a method for controlling and sintering.

As is well known, the quality of sintered ore is determined by the components of sintered ore and the thermal history during the sintering process.

By the way, the components of sintered ore can be adequately controlled by chemical analysis of the raw materials and adjustment of the combination of raw materials, but the following methods are known for managing the thermal history during the sintering process. There is. One method is to wait for the quality analysis results of the produced sintered ore, and then adjust the coke blending ratio and ignition intensity to determine the total calorific value, but it takes time to make the adjustments. There are too many drawbacks. The other method is to detect the coke combustion completion point (Burn Through Point) and adjust the pallet speed, layer thickness of blended raw materials, main blower suction damper opening, etc. so that coke combustion is completed within the desired range. However, since it is not based on the thermal history that shows the sintering process from ignition to the completion point of coke combustion, which is originally important, there is a time lag and it is difficult to perform sufficient control. It is.

As a means of detecting the thermal history of the sintered bed,
There is a method of directly detecting temperature changes by inserting a thermometer into the sintering bed, which is used during test operations. This method is not suitable as a method for grasping continuous temperature information within the temperature range.

In addition, as a method for estimating the temperature distribution within the sintered bed, we use a sintering mathematical model (reaction engineering model) that uses a computer to solve simultaneous partial differential equations based on heat transfer.
There have been many reports on this, but the calculation requires a huge amount of storage capacity, and the calculation time depends on the computer's ability, but it takes several tens of minutes on a normal process computer, resulting in time delay control. Therefore, the reality is that a method of controlling the sintering heat history by detecting process changes using a sintering numerical model is not generally adopted.

The present invention advantageously solves the problem of time lag control or insufficient control not based on thermal history in the prior art. Specifically, in a Dwight Lloyd type sintering machine, The exhaust gas flow rate is measured, and the relationship between the exhaust gas flow rate, the vertical advancement speed of any temperature zone in the sintered bed, and the passing gas flow rate in the sintered bed is used to calculate the flow rate of the exhaust gas in the sintered bed. The temperature distribution is estimated, and the area from the ignition position to the ore dumping position in this estimated temperature distribution is
The cross-sectional area between the 1000°C line and the 1000°C line during red tropical cooling is 5 of the total cross-sectional area of the sintered strand.
% or more and less than 15%.

The method of the present invention will be explained below based on the drawings.

FIG. 1 is a schematic explanatory diagram of a Dwight Lloyd type sintering machine showing an embodiment of the present invention.

First, a general sintering manufacturing process using a Dwight Lloyd sintering machine will be explained. A sintering raw material 8 mixed with coke is supplied onto a pallet 2 through an ore feed tank 1. The pallet 2 moves from left to right in the figure, and the ignition furnace 3 ignites the surface layer of the sintering raw material. Each of the wind boxes 4A to 4P is connected to a main blower 12, and as air is sucked in by the main blower 12, the coke combustion zone 9 advances from the upper layer to the lower layer of the sintered bed, and the coke is deposited near the ore discharge section 10. The pallet speed, layer thickness of the sintered raw material, main blower suction air volume, etc. are controlled so that the combustion completion point 11 is reached.

In the method of the present invention, each window box 4A to 4P
Exhaust gas flowmeters 5A to 5P, thermometers 6A to 6P,
Pressure gauges 7A to 7P are installed, and the temperature distribution in the sintering raw material layer above each wind box 4A to 4P is calculated using the computer 1 from the information obtained from these detection ends.
Calculate and estimate in step 3.

In order to estimate the temperature distribution inside the sintered bed using this calculator 13, first, we focus on the fact that the vertical progression speed of any temperature inside the sintered bed is proportional to the gas flow rate passing through the sintered bed. For example, the speed of movement of a given temperature in the vertical direction within the sintered bed is determined using the following formula.

FIG. 2 is an example of a graph showing the relationship between the gas flow rate x and the speed of progression of a given temperature y in the sintered bed.

In the figure, the line graphs of ~ were determined by the following formulas.

500℃ (dry zone) y = 1.09x + 2.87 1000℃ (burning zone) y = 1.02x + 3.20 1200℃ (red tropics) y = 0.95x + 3.61 1000℃ ( ) y = 0.70x + 4.90 700℃ ( Cooling zone) y = 0.65x + 5.00 (Applicable range, gas flow rate 10.0 to 25.0 m/mm) As a result, the progress speed y of any temperature in the bed can be determined from the gas flow rate x measured by the exhaust gas flowmeters 5A to 5P. Then, by integrating this from the ignition position, it is possible to estimate the temperature distribution within the sintered bed until the completion of sintering.

The calculation formula for estimating the temperature distribution described above is shown below in the form of a general formula.

Ci, j=αi×Gj+βi...(2) Gj=(Qj×273/273+tj×1033+Pj/
1033)/Sj...(3) However, Yi, j: High position of the sintered bed inner layer in the jth window box at the i temperature (mm) h: Sintered bed layer thickness (mm) Ci, j: The jth window at the i temperature Average vertical movement speed in box (mm/mm) lj: Length of wind box J (m) PS: Pallet speed (m/mm) Gj: Average gas speed at wind box J (Nm/mm) Qj : No. J wind box exhaust gas flow rate (m ³ /mm) tj: No. J wind box exhaust gas temperature (℃) Pj: No. J wind box exhaust gas pressure (g/cm ² ) Sj: No. J wind box suction area (m ² ) αi, βi: Constants related to the speed of progress of i temperature. In other words, in the above equations (1) to (3),
Information from the exhaust gas flowmeters 5A to 5P, thermometers 6A to 6P, and pressure gauges 7A to 7P installed at 4P is used to calculate the passage of any temperature within the sintered bed, which is obtained in advance at that time. The temperature distribution within the sintering bed from ignition to completion of sintering can be estimated by using the above-mentioned relational expression for calculating the progress speed with respect to the gas flow velocity. FIG. 3A is a diagram showing an example of the temperature distribution within the sintered bed estimated using the above equation. Figure 3 (b) shows the suction air volume distribution at this time, and Figure 4 shows the layer height estimated from Figure 3.
The thermal history at the 200mm position is shown.

The horizontal axis in Figure 3 A is the wind box number,
The vertical axis represents the layer height, and in the method of the present invention,
After the above calculation, the line of 1000℃ at the time of temperature rise in the Red Tropics is calculated by taking the total length of the strand from the ignition position to the ore discharge position using the wind box number on the horizontal axis, and taking the total cross-sectional area of the rectangle bounded by the vertical and horizontal axes. 5% of the area surrounded by the 1000℃ line during red tropical temperature drop.
Use a calculator to check whether the above values are within the range of less than 15%.

When the ratio of the area falls within the above range, the yield of sintered ore is kept constant, the cold strength (TI) is stabilized, and FeO and reduced It is also possible to improve the ratio (RI). In other words, it is clear that if FeO is lowered, the reducibility ratio (RI) of sinter improves and the blast furnace fuel ratio decreases as a result, but if the operation is carried out within the above range, FeO
can be stabilized at less than 5%, and the return ratio (RI) can be maintained at a high level. Fig. 5 shows the results of actual operation. If the ratio is less than 5%, there is an advantage of lowering FeO, but the yield and cold strength are significantly reduced, making sintering operation impossible. On the other hand, if it exceeds 15%, there is the advantage of improving the yield, but the disadvantage is that FeO, which is important, increases and the reduction rate (RI) decreases, which adversely affects blast furnace operation and worsens the blast furnace fuel ratio. There is. That is, by controlling the area ratio within the range of 5% or more and less than 15%, the reducibility ratio (RI) of the sintered ore can be stabilized at a high level, and the yield and cold strength can be kept constant. be able to. In order to control the temperature within this range, adjusting the pallet speed, increasing the ignition intensity, adjusting the coke blending ratio, etc., which are well-known means of action, may be carried out as appropriate while looking at the temperature distribution situation.

According to the method of the present invention, there is a method in which action is taken after checking the analysis results of sintered ore quality (TI, RI, FeO, etc.) and the situation of yield decline due to increased generation of return ore, which is one of the conventional methods, and Compared to the time-delayed control method of computer-based methods using mathematical models, it is possible to predict the quality and yield of sintered ore during the sintering reaction in the sintering machine, significantly shortening the time until action. There are advantages.

Further, according to the method of the present invention, it is possible to know the temperature distribution within the sintered bed, so there is an advantage that more accurate adjustment can be made.

Note that in order to estimate the temperature distribution according to the present invention,
It is necessary to find a relational expression between the gas speed passing through the sintering bed and the rate of progression of a given temperature within the sintering bed, but it may be determined in advance by a pot test using the same sintering raw material. It would be more practical to create a formula for calculating the speed of progress at any temperature within the sintering bed, taking into account the influence of the raw material conditions such as particle size, density, and coke blending ratio.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of a Dwight Lloyd sintering machine showing an embodiment of the present invention, Fig. 2 is a diagram showing the relationship between the gas flow rate and the speed of progress of a given temperature in the sintered bed, and Fig. 3 is an illustration of the Dwight Lloyd sintering machine. Figure 3 shows one row in the sintered bed estimated by the method according to the present invention, Figure 3B shows the suction air volume distribution at this time, and Figure 4 shows an example of estimating the temperature distribution in the sintered bed. Figure 5 shows the influence of the ratio of the red tropical area surrounded by the 1000°C line to the total cross-sectional area (total layer height x total strand length) on sintered ore quality and yield. 1...Ore feed tank, 2...Pallet, 3...Ignition furnace, 4A~4P...Wind box, 5A~5
P...Exhaust gas flow meter, 6A~6P...Thermometer, 7
A~7P...Pressure gauge, 8...Sintering raw material, 9...Coke combustion zone, 10...Ore discharge section, 11...Coke combustion completion point, 12...Main blower, 1
3...Calculator.

Claims (1)

[Claims] 1. In a Dwight Lloyd type sintering machine, measure the exhaust gas flow rate in each wind box, and compare this exhaust gas flow rate with the vertical advancing speed of any temperature zone in the sintered bed obtained in advance and the flow rate in the sintered bed. The temperature distribution inside the sintered bed is estimated from the relational expression with the passing gas flow velocity, and within this estimated temperature distribution, between the ignition position and the ore discharge position, there is a line of 1000℃ when the temperature rises in the red tropics, and a line of 1000℃ when the temperature drops in the red tropics. of
A sintering method using a Dwight Lloyd sintering machine, characterized in that sintering is performed while controlling the cross-sectional area between the lines at 1000°C to be 5% or more and less than 15% of the total cross-sectional area of the sintered strand.