JPS6338664B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for measuring the fusibility of coke oven charges, etc., and more specifically, for coke oven charges, particularly for charges that do not have weldability such as non-caking coal, petroleum coke, etc. The present invention relates to a method for measuring fusion properties that allows for proper evaluation of fusion properties and facilitates blending management of coke oven charges based on the fusion properties. Generally, one of the important properties required of coke etc. in a blast furnace is crushing strength. Also, sufficient fusion of each charge particle is required to maintain crush strength. In order to achieve sufficient fusion of the coke oven charge, it is necessary to know in advance the fusion properties of various charges, such as coal, and to perform appropriate blending control. However, for substances that show almost no melting properties such as non-caking coal and petroleum coke, or on the contrary, substances that show excessive melting properties such as pitch, asphalt, and liquefied coal, the fusibility of materials such as coking coal is reduced. It is difficult to evaluate and is undermining formulation control. To explain in more detail, the production of strong coke requires a preliminary step in the carbonization process, namely:
In the temperature range where coal particles soften and melt, each charge particle of various types of coal etc. needs to be compatible with each other to form a strong fused surface. That is, if the cohesiveness of the coke oven charge is insufficient, coke with a weak structure and low crushing strength is produced, which impedes the stable operation of the blast furnace. For this reason, in general, in coke factories, it is necessary to appropriately mix and manage the blending ratio of various coals according to the fusibility of each coal so that the cohesiveness of the charge to the coke oven is sufficient. It is being done. In this case, various evaluation methods are applied to estimate the fusibility of ordinary coking coal, such as maximum fluidity by Gieseler fluidity test (JIS.M-8801) and Audibert-
Total inflation rate by Arnu inflation test (JIS.M-8801)
etc. will be evaluated. These characteristic values are indicators that represent the softening and melting characteristics of coal, and by measuring these values for each coal in advance, it is possible to estimate the melting characteristics of the entire charge and enable appropriate blending management. . However, although these evaluation methods are effective for coking coal, they are not effective for coke oven charges other than coking coal, and it has been extremely difficult to evaluate the fusion properties thereof. For example, when the above-mentioned fluidity test and expansion test are performed on non-caking coal with poor melting properties, slightly caking coal, petroleum coke, etc., there is no fluidity and the total expansion rate is zero, so no matter what type of coal it is, it always Only identical results are obtained and no difference in meltability can be detected between each sample. On the other hand, asphalt,
Pitch, liquefied coal, etc. have greater meltability than coking coal, and for this reason, the maximum fluidity exceeds the measurable upper limit of the equipment, making it impossible to determine the true value. Since the release is extremely large, it is impossible to clearly understand the contraction-expansion behavior even if the above-mentioned expansion test is carried out.
For this reason, various methods have been proposed to evaluate the fusion properties of materials charged to coke ovens outside the range of normal coking coal, but no suitable evaluation method has been obtained, and for this reason, it is difficult to actually When blending at a coke factory, it is necessary to carbonize the charge to the coke oven in the blended state and check in advance whether the specified crushing strength can be obtained, which may hinder smooth blending management. It was coming. The present invention aims to solve the above-mentioned drawbacks, and in particular,
We propose a method for measuring fusion properties that can appropriately evaluate the fusion properties of coke oven charges, especially for each charge other than ordinary coking coal, and that can facilitate actual blending control. That is, in the method of the present invention, a part of the reference coke oven charge is replaced with at least one kind of coke oven charge whose fusion properties are to be measured, and then the coke is fired, and the tensile strength of the coke after the firing is measured. Moreover, the fusion property of the coke oven charge is determined from its tensile strength. The method of the present invention will be explained in detail below. First, the fusion property of a coke oven charge is a measure of how well its particles fuse together to form a strong coke structure. Except for this, it shows the strength of the coke base itself. For this reason, the present inventors focused on tensile strength as coke base strength, since weldability is related to coke base strength, and the softening melting property, which is usually said to represent the weldability with respect to this tensile strength, We studied the relationship between As a result, it was found that the so-called softening and melting properties are nothing but an indication of the tensile strength of calcined coke. That is, as an example, various coking coals are mixed at different blending ratios and fired in a coke oven, and the tensile strength of the fired coke in this case and the common logarithm of the maximum fluidity of each raw coal alone (hereinafter referred to as When the relationship with the weighted average value (denoted as logMF) was determined, it was as shown in FIG. To explain in detail, as shown in Figure 1, the tensile strength of calcined coke is determined by the amount of each coking coal blended.
The logMF value corresponds to the logMF weighted average value at a ratio of approximately 1:1, and when the tensile strength of the calcined coke is measured, the logMF value of each coal blend can be determined from that value. In addition, from Figure 1, we can see that in addition to coking coal, non-caking coal and slightly caking coal, whose fluidity is usually difficult to evaluate, as well as various blended coals with respect to the tensile strength of fired coke, even with caking agents, etc. Its fusibility can be expressed as logMF as the degree of contribution of , and the fusibility can be evaluated in the same way as coking coal. From this point of view, in the method of the present invention, a part of the coke oven charge such as coking coal is replaced with a substance other than coking coal, and after the whole is calcined, the tensile strength of the coke is determined. Evaluate the adhesion of materials other than coking coal from the values. That is, one or more suitable coking coals are selected as the standard coke oven charge, and their logMF weighted average value (in particular, expressed as logMF ₀ ) is determined in a single or blended state. Next, a portion of the reference coke oven charge is replaced with the substance whose adhesion properties are to be measured, the proportion of this replacement being x% by weight of the reference coke oven charge. In this case, when the logMF value of the substance whose fusion properties are to be measured is expressed as logMFs, the weighted average value of logMF of the entire replacement sample is 100−x/100logMF ₀ +x/100logMFs. Therefore, if a sample is fired and the tensile strength σ _TS of the fired coke is linearly proportional as shown in Figure 1, σ _TS = a (100-x/100logMF ₀ +x/100logMFs) + b... (1) is obtained. Here, if we calculate the relationship shown in Figure 1, x, logMF ₀ , a, and b can be calculated, so
By measuring the tensile strength σ _TS , logMFs can be determined. Note that the relationship shown in Figure 1 naturally changes depending on the carbonization conditions, that is, the a and b values change, so when applying equation (1) to calculate logMFs, it is important to keep the experimental conditions the same. It is. When determining as above, it is also possible to calcine only the standard coke oven charge, measure the tensile strength σ _TO of the calcined coke, and precisely evaluate the fusion property. That is, at this time, equation (2) holds true. σ _TS =a logMF ₀ +b …(2) By eliminating logMF ₀ from equations (1) and (2),
logMFs is given by the following formula. logMFs={100(σ _TS −b) −(100−x)(σ _TO −b)}/ax …(3) Therefore, if logMF ₀ is eliminated, logMFs is completely determined from the tensile strength only. This eliminates the inconvenience of having to find a regression line close to the actual measurement point as shown in FIG. 1 and then finding it from this regression line. In short, according to the present invention, it is possible to determine the tensile strength and fusibility of coke after firing, not only for coking coal but also for coke oven charges whose fusibility has conventionally been difficult to evaluate. Next, examples will be described. Example 1 First, the logMF value of a coal pitch was determined by the method of the present invention, particularly in accordance with equation (3).
In this case, for comparison, actual measurements were made using JIS M8801 and measurements were also made using the extrapolation method, and these values are shown in Table 1.

[Table] Note that the extrapolation method here is based on Australian weakly coking coal (logMF = 1.45), which has low fluidity, because the fluidity of coal pits is extremely high and its true value is difficult to obtain. For example, 1% of that is replaced with coal pitch, and the fluidity is actually measured and the logMF value is determined. Then, the replacement ratio of coal pitch is increased in the order of 2%, 3%, etc., and the fluidity is measured for each. However, when 100% of coal pitch is extrapolated to the relationship between this coal pitch substitution rate and logMF value,
It is logMF. Next, based on the above results, in order to clarify the superiority of the logMF values of coal pits determined by the method of the present invention and the extrapolation method, we conducted the following in a 1/4 ton test furnace. A can-firing test (JIS, M-8801) was carried out. That is, first, as shown in Table 2, coals were blended according to the blending and blending, and a can-firing test was conducted in advance.

[Table] In this can firing test, the blend had a smaller logMF weighted average value and inferior fusion properties than the blend, and the strength of the fired coke was lower than that of the blend. Based on the results in Table 2, the above-mentioned coal pitch was added to the blend, and the mixture was blended as shown in Table 3 so that the logMF weighted average value became the value of the blend.
In this case, the value of logMF was calculated using the extrapolation method of the comparative example and the method of the present invention, and the blending ratio was 0.9% in the case of the extrapolation method and 3.8% in the case of the method of the present invention.
The formulation and canning test results are shown in Table 3.

[Table] As a result, when using the values obtained by the extrapolation method, it is sufficient to mix 0.9% coal pitch (mixture); It can be seen that this does not indicate the true value of the coal pitch fusion property. On the other hand, it was found that according to the method of the present invention, the fusion properties of the coal pitch were appropriately determined. Example 2 First, the logMF value of Australian non-caking coal was determined using the method of the present invention using equation (3). At this time, as in Example 1, actual measurement values and extrapolation values were also determined, and these are also shown in Table 4.

[Table] The extrapolated values here are based on US high volatile content coal (logMF=4.30), as the fluidity of this non-caking coal is extremely low and its true value is difficult to obtain. A portion of the coal was sequentially replaced with the non-caking coal to measure the fluidity, and as in Example 1, the logMF value of the non-caking coal was determined from the relationship between the logMF value and the substitution rate.
Using the logMF value of each non-caking coal determined in this way, non-caking coal was added to the blended coals in Table 2 so that the logMF weighted average value of the blends in Table 2 was achieved. Therefore, the logMF value of non-caking coal is -5.35 by the extrapolation method and -1.75 by the method of the present invention, so as shown in Table 5, the logMF value of non-caking coal is
2.6% and 4.9% were mixed, and the results of the test were as shown in Table 5: the crushing strength of fired coke was obtained.

[Table] From this Table 5, when blended according to the extrapolated values, the crushing strength is higher than the crushing strength of the blend in Table 2, and the fusion strength of Australian non-caking coal is evaluated to be lower than the actual value. I understand that. On the other hand, according to the method of the present invention
When blended according to the logMF value, almost the same crushing strength as the blend is obtained, indicating that the fusion properties of Australian non-caking coal are close to the true value. As described above in Examples 1 and 2, according to the method of the present invention, the fusion properties of the binder and non-slightly caking coal can be directly determined from the tensile strength of the calcined coke.
Fusion properties can be evaluated as appropriate. That is, coking coal with good fusion properties is unevenly distributed regionally, and its reserves are smaller than that of non-slightly caking coal. For this reason, the Japanese steel industry has adopted a coke production method that uses a binder to ensure fusion properties and also uses non-slightly caking coal, etc., from the viewpoint of effective resource utilization and stable supply of raw materials. It is requested. However, the most important issue at this time is the evaluation of the fusion properties of the caking agent and non-slightly caking coal. In this regard, according to the method of the present invention, it is possible to properly evaluate the fusion properties of coke oven charges such as caking agents and non-slightly caking coal, which have been difficult to evaluate in the past, allowing for effective use of resources and stable supply. It will help. Moreover, in reality, it has made it possible to stabilize blast furnace operations by facilitating blending control and maintaining the strength of produced coke, thereby greatly contributing to the progress of Japan's steel industry.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the logMF weighted average value of coal blends and the tensile strength of their calcined cokes.

Claims (1)

[Claims] 1. Replace a part of the reference coke oven charge with at least one kind of coke oven charge whose fusion properties are to be measured, and then fire the coke, measure the tensile strength of the coke after firing, and calculate the tensile strength from the tensile strength. A method for measuring the fusion properties of coke oven charges, etc., characterized by determining the fusion properties of the coke oven charges.