JPS61204344A - Predicting method for reducibility of sintered ore - Google Patents

Abstract

PURPOSE:To predict quickly the reducibility of sintered ore with good accuracy by determining the content of FeO in the sintered ore and the quantity of the pores and ruggedness existing respectively in and on the sintered ore particles as the factors to affect the reducibility. CONSTITUTION:The sintered ore is sized and the average weight M per piece of the particles is calculated from the number N of the sized sintered ore and the total weight thereof or the weight W per piece of the sintered particles. On the other hand, the content of FeO and the total iron content (T.Fe) of the sintered ore are determined by the chemical analysis. The true density P is estimated from the prescribed equation between the total iron content and the true density of the particles. The average volume V of particles are then determined from the weight W and the true density P. On the other hand, the volume V0 of, for example, a circumscribed sphere 1 is calculated from the particle size 5 and the gap quantity epsilon indicating whether the total of the quantity of the internal pores 3 and the quantity 4 of the ruggedness on the surface of the particles is large or not is calculated by V--V. The predicted value RI<0> of the reducibility RI of the sintered ore is calculated by the prescribed equation using the above-mentioned content of Fe and the gap quantity epsilon.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the sintered ore reducible pipe JIS method (JISM871
3) Regarding the method of predicting quickly and at low cost without relying on K, this method is intended to be used to adjust operating conditions based on this predicted value and control so that the reducibility approaches the target value. be.

[Conventional technology]

Sinter reducibility (hereinafter referred to as RI) has an important relationship with reducing the fuel ratio in blast furnaces and reducing Si in hot metal, and has been particularly emphasized in recent years among sinter quality. be.

Therefore, if other qualities such as RDI, TI, etc. are within the specifications required by the blast furnace, it is preferable that RI be as high as possible. However, to control RI, RI
The basic measurement is This measurement method is generally JI
It is based on the S method.

[Problem that the invention seeks to solve]

However, conventional RI measurement takes a long time compared to RDI, TI measurements, etc., so it takes time to measure the RIO value and take necessary response actions, and even after taking the action. It also takes a long time to confirm the RI.

For example, to measure RI using the procedure specified in JIS M871:j, it takes at least 90 minutes to preheat the sample and 1 hour for reduction.
It is necessary to spend 80 minutes, and it takes at least close to 3 hours. No action can be taken during this time until the RI is determined, and the manufacturing process must continue to wastefully mix raw materials during this time. Therefore, even if you set a target value for sinter RI and try to achieve it, the R
I has the disadvantage that there is large variation over time and that it takes a long time to achieve the target value. Therefore, from the past, R
I is not determined by the reduction test specified by the JIS method,
A method of predicting RI from quantitative values of sintered ore structure using image processing, or a method of measuring RI for each lump iron ore in advance as in Japanese Patent Application Laid-open No. 59-38307, and calculating the blending ratio of the
Methods for predicting the RI of finished sintered ore have been developed. However, when using image processing, for example, it requires labor-intensive work such as polishing the sample, and the equipment is expensive, and the RI of the finished sintered ore can be predicted from the RI and porosity of the raw material lump ore. In this case, the accuracy is not sufficient because the RI of the sintered ore is predicted from the raw material after the properties have changed significantly through the sintering process. In view of this situation, the present invention has been developed to improve the RI of sintered ore.
This was done with the aim of quickly and accurately predicting RI at low cost, implementing corresponding actions based on the measured values, and quickly achieving the target RI while minimizing variation.

[Means for solving problems]

As a result of a detailed study on the influence of various properties of sintered ore on reducibility, the present inventors found that FeO7, the amount of pores existing inside the sintered ore particles, and the unevenness existing on the particle surface are important. Based on this knowledge, we have devised the present invention, which predicts the reducibility of sintered ore accurately, quickly, and at low cost using a mathematical formula. , the sintered ore is sized, and the average weight per particle is calculated from the number of sized sintered ore and the total weight or the weight of each sintered ore particle, and this average The average volume per sized sintered ore particle is calculated from the weight and true density, and the reducibility of the sintered ore is predicted using this average volume and the amount of FeO in the sintered ore. 0 [Operation] Factors that determine the magnitude of RI, which represents the reducibility of sintered ore, include the amount of porosity minerals, the crystalline form of minerals, and the distribution of pores and minerals. . Therefore, by formulating the influence of each of these factors on RI, it is possible to obtain a predicted value of RI without conducting a reduction test. It was discovered that there is another factor that affects fCo, and this factor will be explained below.

It has been pointed out that among the various factors mentioned above, porosity particularly has a significant influence on reducibility. Therefore, considering the mechanism by which increased porosity improves reducibility,
Similar to general solid-gas reactions, as the porosity increases, the contact area between the sintered particles and the reducing gas increases, the reaction area becomes wider, and the diffusion distance of the gas diffusing inside the particles becomes shorter, so the reduction reaction becomes more difficult. However, this porosity is the porosity that exists inside the sintered ore particles, and in previous reports, porosity mainly refers to the porosity of the pores that exist inside the particles. . However, in addition to these pores, the present inventors believe that macroscopic irregularities existing on the particle surface have the same effect of increasing the contact area with the reducing gas and shortening the diffusion distance of the reducing gas within the particle. As a result of paying attention to it, I learned that this uneven landscape has a dominant influence on reducibility. That is, prepare particles of sintered ore collected from the same lot with the outside polished (Fig. 2 (b)),
Along with particles without polishing (Figure 2 (a)), particles with a particle size of 20±
We prepared 500g each of 1ttrx and measured the RI and various properties.Even though the chemical composition, mineral composition, JIS porosity (JISM8716), etc. were the same, the RI was about 16 different. Type (a) was better. In the figure, l is a circumscribed sphere, 2 is a gap between the circumscribed sphere and the particle, 3 is an internal pore, 4 is an unevenness on the particle surface, and 5 is a particle size.

This result shows that the porosity inside the sintered ore particles, etc.
This shows that even if other properties are the same, the reducibility varies greatly depending on the amount of macroscopic unevenness on the surface. Particles of type (A) in Figure 2 obviously have a large contact area with the reducing gas, and the distance between any position inside the particle and the particle surface that is in contact with the reducing gas is short, so they have good reducibility. It is thought that it was. In the case of internal pores that have a similar effect, there is no problem if the reducing gas enters the pores quickly and cools down, but if there is no communication with the outside or there is a narrow passageway that communicates with the outside, the diffusion rate of the reducing gas becomes a problem. Taking this into consideration, the influence of the unevenness of the particle surface on the reducibility is extremely important.

Based on this knowledge, when predicting the reducibility of sintered ore using a mathematical formula, it is necessary to quantify the unevenness of the particle surface and take this influence into the mathematical formula. Therefore, we conducted a detailed study and found that the RI prediction formula incorporates three variables: particle internal porosity (hereinafter abbreviated as internal porosity), amount of unevenness on the particle surface (hereinafter abbreviated as unevenness), and FeO. It was found that RI could be estimated with sufficient accuracy.

Among these variables, as shown in Figure 3, FeO has traditionally been R
It has been reported that there is a negative correlation with I, and this is thought to be mainly due to the correlation between the amount of magnetite in the sintered ore and the amount of FeO. A part of the slag is FeO contained in the slag, but the rest is almost entirely derived from magnetite, and it is already known that magnetite has a lower reducibility than fine minerals. Regarding hematite and calcium ferrite, there is no particularly significant difference in reducibility. Be friends,
For predicting the reducibility of sintered ore! lJ The meaning of incorporating the amount of FeO as a variable is to represent the amount of magnetite, whose reducibility is noticeably lower than others, by the amount of FeO, and to take into account the factors of the mineral phase that affect the reducibility of sintered ore. Note that the amount of FeO can be easily measured by conventional methods, such as a chemical analysis method according to the JIS method (JISM8213), a method using magnetism using a so-called magmeter, and the like.

Next, the reason why internal porosity and unevenness are included in the prediction formula is that, as mentioned above, increasing the contact area with the reducing gas and shortening the diffusion distance of the gas within the particle greatly influences the reducibility.
It has been found that the measurement of internal porosity and the quantification and measurement of the amount of unevenness can be carried out simultaneously by the following method.

In Fig. 2, even if the amount of internal pores increases, or if the amount of surface irregularities increases and the amount of voids between the outer surface of the particle and the circumscribed sphere increases, if the particle size is constant, the solid volume of the particle, The volume of the outer part of the gap particle, excluding the internal pores, decreases. Therefore, the value C obtained by dividing the solid volume from the circumscribed sphere of the particle (hereinafter referred to as the void volume ε) is an index representing the magnitude of the sum of the internal pore volume and the unevenness volume. Therefore, in the present invention, the sum of the amount of internal pores and the amount of unevenness is included in the formula as the amount of voids -C. The value of ε is obtained by dividing the volume vl of the particle from the volume vO of the circumscribed sphere, so if vo and vl are determined, ε is determined.

Here, Vo is calculated from the particle size Do of the particles as vo=maπ(ko)3. However, since the particle shape of sintered ore may not necessarily be spherical from a macroscopic perspective, the volume of a circumscribed rectangular parallelepiped may be used instead of the circumscribed sphere as an alternative to VO. Next, vl is the weight m of the particle and the true density ρ, so V1=M
/ρ, n1ε=V, −Vl. While M can be easily measured, ρ can be measured using, for example, the JIS method (
JIS M8717) requires man-hours, so ρ
was estimated from the total amount of iron in the sintered ore. Since the main component of the sintered ore is Fe, ρ is inevitably predominantly influenced by the total amount of iron (hereinafter referred to as T and Fe). The present inventors investigated the relationship between ρ, T, and Fe for various sintered ores, and obtained the following results: ρ=a+bT−Fe z+ (1)
a, b: It was found that there was a relationship shown in the constants 0 By integrating these results, a prediction formula for the reducibility of sinter was set as shown below.

R work 0 = C-FeO + d・(vo-vl) 〇 = CFe
0+d・('-π(DO)3-')+e3
2 a+b-T, Fe "C'Fe0-a+bko1+(e+'π(DO)3-d
)-M...(2) a, b, c, d, e: constants, where n is the reducibility RI of the sintered ore obtained according to the JIS method.
When predicting e, T, Fe, FeO, Do, M
First, explain how to determine various quantities such as T.
Regarding -Fe + FeO, chemical analysis of finished sintered ore is generally carried out as a routine work in sintering plants, and T and Fe are included in this item.

Contains FeO, so unless there is a particular need,
There is no need to particularly limit the zero-order Do using this measurement value, but when measuring RI, the particle size of the sample should be 1
Considering adjusting the range from 9 to 215 m, the RI should be set to (2
) When predicting using the formula, it is desirable to size the sample to a range of 19 to 211 m. Therefore, %Do is 19-21
Taking the middle of 1Eil, 20 Homo is appropriate. Next, after preparing at least 20 particles having a particle size of % D, M is % D, after preparing at least 20 particles, taking into account representativeness, calculate the average weight per particle from the number of particles and the total weight, or After measuring the weight of each piece, the average value may be determined. in the end,(
2) When predicting RI, the formula is T-Fe +
Although FeO+ M changes, Do is fixed at an appropriate value, so the third term shown in parentheses in equation (2) is a constant.
The first term takes into account the effect on the reducibility of FeO, and the second term
In this formula, the influence of the internal pores represented by the particle volume and the amount of surface unevenness on the reducibility is taken into account. When predicting reducibility using equation (2), use the values obtained in daily routine work for T, Fe, and FeO as described above,
In addition, since the weight and number of dozens of sintered ore particles can be measured extremely easily, there is almost no increase in additional equipment or man-hours compared to the current situation, and it is possible to predict reducibility at low cost. [Example] An example in which the above knowledge was applied to actual operation will be described below. 0 (Example 1) Figure 4 shows RI and predicted value RI' when RIft is measured once a day and at the same time, RIt is predicted according to the present invention.
This shows that the present invention can predict oRI values over a wide range with high accuracy. In addition, when predicting RI in this case, the sample was taken from the exit of the secondary screen about 150 kg of +5n finished sintered ore, and using the round part, about 3 kg of particles of 19 to 21 dragon were sorted, and the total weight and number of particles were calculated. Measured to find the average weight of the particles o T
, Fe 2 , and FeO were determined by chemical analysis after extracting approximately 1 g of this +5m sintered ore and pulverizing it. The RI was measured according to the JIS method after the remaining +511L sintered ore was sieved again. , 0 indicates a comparison with the actual measured value when RI is predicted using the values of e.

The period was 24 hours. Figure 5 shows that according to the present invention, it is possible to predict RI even from sintered ore particles having a particle size different from that of 20±1 silk, which is the particle size of the sample when actually measuring RI. (Example 2) Figure 6 shows that the RI
The target value of is set to 66, and the coke amount is adjusted with reference to Fig. 3 while predicting the RI according to the present invention, and the coke amount is adjusted while actually measuring the RI according to the JIS method. RI change is shown. In the figure, (a) shows the actual measured RI according to the JIS method, and (b) shows the predicted value according to the present invention. Note that the white circle in (b) is the eclipse result obtained by actually measuring the RI to confirm whether the predicted value is correct or not. This example shows that according to the present invention, sintered ore having the target reducibility can be produced at an early stage because RI can be predicted and countermeasures can be taken quickly.

(Example 3) In Fig. 7, when two Dwight Lloyd type sintering machines of approximately the same scale are operated at the same time using the same raw materials, the method according to the present invention is applied to one of the sintering machines. A comparison is shown in the case where an attempt was made to improve RI by adjusting operating conditions while predicting the above (white circles in the figure). When the present invention is applied, response actions can be taken early, so it is possible to approach optimal operating conditions early by repeating predictions and response actions, which significantly improves RI without keeping RDI and TI within specifications. I was able to do it.

〔Effect of the invention〕

In summary, according to the present invention, the reducibility of sintered ore can be predicted accurately, quickly, and inexpensively, and countermeasures can be taken early during the production of sintered ore, and as a result, the target It brings about advantages such as being able to produce high-quality sintered ore without waste.

[Brief explanation of drawings]

Figure 1 is a process diagram of the RI prediction procedure, Figures 2 (a) and (b) are cross-sectional views of particles with many and few surface irregularities.
Figure 83 is a correlation diagram of coke amount, FeO, and RI, Figure 4 is a comparison diagram of RI of sintered ore sized to 20±111I and predicted value, and Figure 5 is sintered ore sized to 24±1 ms. Figures 6 (a) and 6 (b), which are comparison diagrams of the RI of ore and predicted values, show the progress of achieving the target value 66 when RI was actually measured and when corresponding action was taken while predicting RI=i according to the present invention. Graph, 7th
The figure is a comparison diagram of the time course of quality when operating while actually measuring using the RItJIS method and when operating while predicting using the present invention. 1. Circumscribing method 2. Circumscribing method and voids between particles 3. Internal pores 4. Irregularities on particle surface 5. Particle size Figure 1 Figure 2 (A) (B) Figure 3 Figure 4 Interference 14 [RI' Fig. 5 Fig. 6 K 3JILIt yi (hr,) Fig. 7 Amended form for closing procedure (method) % formula % 1. Indication of the case 1985 Patent Application No. 45853 2. Invention Name: Method for predicting the reducibility of sintered ore 3, Relationship with the case of the person making the amendment Patent applicant 4, Agent 101 7y & Flit Positive contents (ω specification, page 15, lines 17-19 : "Figures 2 (a) and (b) are cross-sectional views,"
"Figure 2 is a cross-sectional view of particles with many and few surface irregularities."
(b) Specification, page 16, lines 2 to 5: “Figure 6 (a)
``(B) is...graph,'' is replaced with ``Figure 6 is R.
A graph showing the progress of achieving the target value of 66 when the corresponding action is taken while actually measuring I and predicting 9 o'clock and RI according to the present invention.''

Claims (1)

[Claims] (1) Sort the sintered ore, calculate the average weight per particle from the number of sized sintered ore and the total weight or the weight of each sintered ore particle, and calculate the average weight per particle. The average volume per sized sintered ore particle is calculated from the average weight and true density, and the reducibility of the sintered ore is predicted using this average volume and the amount of FeO in the sintered ore. Characteristic method for predicting the reducibility of sintered ore.