JP5163247B2 - Coke production method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for producing coke for blast furnace, and more particularly, to a method for producing coke without reducing strength while blending more inexpensive coal.

Coke used in the blast furnace is required to have high strength in order to ensure the air permeability of the blast furnace and operate stably. In recent years, the blast furnace volume has been increased in size, and in order to operate at a low reducing material ratio aimed at reducing CO ₂ , higher strength coke is required. For example, when the drum strength index measured by the method described in JIS-K2151 is used as the coke strength (weight fraction on a 15 mm sieve after rotating 10 kg of lump coke in a predetermined drum for 150 times), As a target value, about 85 is required.

  When producing coke for blast furnace, raw coal (hereinafter referred to as “mixed coal”) blended with a wide variety of coals of more than a dozen brands is charged into the coke oven and dry-distilled. The coal heated in the coke oven is once softened and melted in a temperature range of 350 to 500 ° C., and coal particles are combined and then solidified again to produce strong coke. The property that coal softens and melts at this time is called “caking”.

  The blended coal usually has a configuration in which dozens of types of coal having high caking properties (caking coal) and coal having low caking properties (non-caking coal) are blended. In order to produce coke with high strength, high caking properties are required, so it is preferable to add a large amount of caking coal, but good quality caking coal is expensive and resource-saving. Therefore, it is desired to increase the blending ratio (mass ratio of each coal constituting the blended coal with respect to the blended coal) of the non-slightly caking coal that has a large reserve and is cheaper than the caking coal. .

  In general, the blending ratio of non-slightly caking coal in blended coal was once about 20% by mass at the most, but recently, blended coal exceeding 40% by mass has been used. However, increasing the blending ratio of the non-slightly caking coal reduces the caking property of the blended coal, resulting in a decrease in coke strength. Therefore, in order to increase the blending ratio of the non-slightly caking coal without reducing the coke strength, it is necessary to compensate for the low caking property of the non-slightly caking coal. As one of the methods, there is a binder addition method in which a binder (binder) is added to improve the caking property of the charged coal.

  For example, Non-Patent Document 1 discloses a pitch obtained by pyrolyzing asphalt as a caking agent for each non-minor caking coal using four types of non-caking coal having different degrees of coalification. When coal is mixed at a ratio of caking material 1 to coal (non-slightly caking coal) 2 and dry-distilled, it is shown that the coke structure becomes strong by coal and pitch being compatible. ing. However, it does not show the same effect on any non-slightly caking coal and tissue, it has good compatibility with the active ingredient tissue that is relatively rich in caking property, poor caking property, or weathering It is described that the compatibility with the prepared structure is poor.

  As an example of improving coke strength by adding caking material to coal, especially non-slightly caking coal, for example, in Non-Patent Document 2, 10-50% of asphalt pyrolysis pitch was added to three different types of coal. Based on the results, by adding 20% to 30% of the pitch to non-slightly caking coal (volatile content 29%, maximum fluidity 2 ddpm), the strength of the non-slightly caking coal simple coke was close to zero. An example in which the strength is improved to a level equivalent to that of blast furnace coke is shown. The “volatile content” is a measurement value of an anhydrous base volatile content measured by the method described in the volatile content determination method of JIS M8812.

  In this way, the technology to add caking material to non-caking coal to supplement caking properties is not only the operation of charging the conditioning coal into the carbonization chamber, but also wet coal, dry coal, preheated coal, molding It is also effective for charcoal operation and stamp charge.

  In actual operation, a technique is required that efficiently defines and uses the caking additive addition rate by some method. As a method for prescribing the addition rate of the caking additive, for example, as in Patent Document 1, the caking property index (total expansion rate and maximum fluidity) of the charged coal after adding the caking additive is within a predetermined range. There is a way to satisfy. However, since this method focuses only on the caking property index after the addition of the caking additive, there is no clear description about the suitable properties of the non-minor caking coal to which the caking additive is added. . For this reason, it cannot necessarily be used on the conditions in which a caking additive exhibits an effect more.

  As a method of controlling the addition rate of the caking additive by paying attention to the properties of the non-slightly caking coal, Patent Literature 2 discloses a button index of general coal (meaning coal having a maximum fluidity of 5 ddpm or less in the literature). Based on this, a method for adjusting the addition rate of the binder is shown. Specifically, when the button index of steaming coal is in the range of 1/2 to 1, the strength of the reference blended coke is blended by simultaneously blending steaming coal and caking coal that are 0.8 to 1.6 times the binder. An example is shown that can be maintained. The button index is a common name for the crucible expansion index of coal determined by the method described in the crucible expansion test method of JIS-M8801. Here, the reason why the button index is used is that, even in the coal brand that is evaluated only as zero in the maximum fluidity, there is a thing showing caking property to some extent in the rapid heating condition used in the crucible expansion test method, It is said that these can be distinguished by evaluating with the expansibility index. However, the rate of temperature rise in actual dry distillation is close to the rate of temperature rise in the fluidity test method, and rapid heating such as when measuring the button index may overestimate the caking property of steaming coal in actual dry distillation. Is considered large.

In addition, focusing on the causticity of coal, there are names of caking coal, slightly caking coal, and non-caking coal, and the latter two types are collectively called non-caking coal. is there. In addition, there are also names of coking coal and steaming coal from the viewpoint of use, which are almost equivalent to caking coal and non-caking coal. There are other designations, but in any case, these designations also involve trading factors, so there is no clear definition of the classification method. Therefore, it is necessary to define these terms individually as in the definition of steam coal in Patent Document 2 above. In the present invention, “non-slightly caking coal” is obtained as the maximum value when the flow rate is measured with respect to the temperature as determined by the flowability test (Gieseller Plastometer method) of JIS-M8801. Means the coal with the maximum fluidity (hereinafter also referred to as “maximum fluidity”) of 7 ddpm or less, and “caking coal” means coking coal other than the defined “non-caking coal”. means.

  In recent years, coke with higher strength has been required due to expansion of the blast furnace volume. On the other hand, from the viewpoint of manufacturing cost reduction, it is required to reduce the blending ratio of expensive caking coal and increase the blending ratio of non-slightly caking coal. However, under the blending conditions corresponding thereto, coke having a desired strength may not always be obtained even if the caking loss due to the addition of non-fine caking coal is compensated by the caking material. For this reason, in practice, in order to stably secure the desired coke strength, it has to be formulated with a strength that is higher than the target coke strength. Could not be reduced.

  Here, an object of the present invention is to provide a method for producing coke that satisfies the strength required in recent years even when a blended coal in which the blending ratio of non-slightly caking coal is equal to or higher than before is used. Is to provide.

  A more specific object of the present invention is to use a caking material in combination with a non-slightly caking coal having a property that can fully utilize its properties, and thereby to increase the cost of caking coal with a small amount of resources. It is to provide a method capable of producing coke without reducing strength while reducing use.

  As a result of conducting various studies when using the caking additive, the present inventors have used a coal having a low volatile content (high degree of coalification) and poor caking properties as part of the blended coal. It has been found that it is effective to use a binder together.

  Coal with poor caking property, that is, coal called non-slightly caking coal with a maximum fluidity of 10 ddpm or less, low volatility (low volatility non-minor caking coal) and high volatility (high volatility) Non-slightly caking coal). High volatility non-coking coal has a large shrinkage during dry distillation and causes many cracks in the coke lump, causing a decrease in strength, so it maintains high coke strength even when combined with caking additive. I can't. On the other hand, the low-volatile non-caking coal exhibits the effect of maintaining the coke strength in combination with the caking additive. That is, there is an appropriate range for the volatile content of the non-slightly caking coal that can reduce the blending ratio of caking coal in combination with the caking additive, and the range by the inventors is about 25%. It was the following.

The present invention provides a method for producing coke for a blast furnace by dry distillation of a coke oven raw material containing a blended coal composed of caking coal and non-slightly caking coal, and in the preparation of the coke oven raw material, the volatile content is 25% or less. And a step of further blending the blended coal with a low-volatile non-finely caking coal having a maximum fluidity of 1 ddpm or more and 7 ddpm or less, and a step of adding a caking agent, and the low-volatility non- caking coal Is a coke production method, wherein the mass ratio of the coke oven raw material is 3 to 7% .

Preferably, the low volatile non-fine caking mass ratio with respect to the caking of (non-fine caking / Nebayuizai) is 3 hereinafter 1 or more.

From another point of view, the present invention provides a blended coal composed of caking coal and non-slightly caking coal with low volatility non-caking that has a volatile content of 25% or less and a maximum fluidity of 1 ddpm to 7 ddpm. A method for producing a coke oven raw material comprising a step of blending charcoal and a step of adding a caking additive, wherein the mass ratio of the low volatility non-fine caking coal to the obtained coke oven raw material is 3 to 7 %, A method for producing a coke oven raw material.

In the present invention, the “blended coal” is coal that is contained in a raw material for producing coke and usually contains dozens of brands, and is composed of caking coal and non-caking caking coal.
“Charging coal” is a material (coke oven raw material) charged into a coke oven as a raw material for producing coke, and may contain components other than “blended coal”. Specific examples include caking materials, waste plastics, powder coke, oil coke, dust, waste tires, and waste wood.
“Binder” is one of the components other than “blended coal”, and is a bituminous substance added to make up for insufficient caking of the blended coal when producing coke. Specific examples include tar pitch, petroleum pitch, and solvent refined coal.

  According to the present invention, a proper amount of low-volatility non-caking coal is combined with a caking material to produce coke without reducing strength even if a large amount of cheap non-caking coal is blended. The economic effect is great.

  The present invention is a method for effectively utilizing non-coking coal during coke production, and a specific embodiment thereof will be described. In the present specification, “%” indicating the blending ratio, addition rate, and volatile content is “% by mass” unless otherwise specified.

  A feature of the present invention is that low volatile non-mineralized coal having low volatile content (anhydrous base volatile content defined in JIS M8812) (high degree of coalification) and poor caking property is used as part of the blended coal. While using it, it is to use a caking additive together in that case.

  In the present invention, “blended coal” is composed of caking coal and non-slightly caking coal as described above, and the blending ratio (mass ratio with respect to blended coal) is not particularly limited. And caking coal: 65% and non-slightly caking coal: 35%.

Coal with poor caking properties, that is, non-minor caking coal with a maximum fluidity of 10 ddpm or less, low volatility (low volatility non-minor caking coal) and high volatility (high volatility non-minor coal) Caking coal).
High volatility non-coking coal causes large cracks in the coke mass due to large shrinkage during dry distillation, causing a reduction in strength. For this reason, high coke strength cannot be maintained even if the non-slightly caking coal in the blended coal is combined with a caking agent only with a highly volatile non-slightly caking coal.

  On the other hand, low volatility non-slightly caking coal can maintain coke strength by a combination with a caking additive. In other words, there is an appropriate range for the volatile content of non-slightly caking coal that can reduce the blending ratio of caking coal in combination with the caking material, and a new range is about 25% or less. The present invention is based on the findings.

  Thus, in the present invention, low-volatile non-slightly caking coal having a volatile content of 25% or less is used, but the lower limit of the volatile content at that time is not particularly limited. However, depending on the form of use, problems may arise due to the volatile content being too low. That is, when the volatile content of the non-slightly caking coal becomes excessively low, the shrinkage during dry distillation is extremely small, so that cracks due to the difference in shrinkage with the surrounding coal may occur, and the strength of the coke may be reduced. Such a decrease in strength tends to be noticeable when the volatile content is less than 15%. Therefore, the range of the volatile content in the preferred embodiment of the present invention is 15% or more and 25% or less.

  Moreover, the appropriate range of the maximum fluidity is 1 ddpm or more and 10 ddpm or less, and the reason is as follows. That is, most of coal having a maximum fluidity of more than 10 ddpm and a volatile content of 25% or less is caking coal, and such coal has an effect of improving coke strength by blending. There is no need to combine them. In addition, the coal having substantially no caking property, that is, the coal having the highest fluidity substantially zero, that is, the coal having less than 1 ddpm, has poor adhesion with the coking structure derived from the caking coal or the caking material derived from the caking material. For this reason, even if the caking property is supplemented by the caking material, a decrease in strength is inevitable.

  The rate of addition of this low-volatile non-caking coal (mass ratio to the charged coal) depends on the properties and blending ratio of other coals that make up the blended coal, the strength required for coke, the rate of addition of the caking additive, etc. Because it changes, the range cannot be defined deterministically. However, the effect of improving the caking property is small if added in a small amount, and conversely, if added in a large amount, the coke strength may be reduced as in the case where the volatile content is excessively low. It is preferable that 3 to 7% is particularly preferable. The economic effect (cost improvement effect) of replacing expensive caking coal corresponding to this addition rate with cheap non-caking caking coal is remarkable.

  In addition, there is no restriction | limiting in particular about the mixture ratio of the highly volatile non-slightly caking coal in which the volatile matter contained in the coal blend concerning this invention exceeds 25%. Considering the properties and blending ratio of other coals constituting the blended coal, the strength required for coke, etc., an appropriate amount may be blended together with caking coal as part of the blended coal.

  Examples of the caking material according to the present invention include bituminous substances such as tar pitch, petroleum pitch, solvent refined charcoal, and the like, preferably petroleum pitch. In the present invention, in the broadest sense, the addition rate of the caking additive is not limited, but preferably, the mass ratio of the low volatility non-caking coal used in the present invention to the caking additive (non-caking coal / It is preferable to set the addition rate of the binder so that the binder is in the range of 1 to 4, more preferably in the range of 1-3. Further, the addition rate of the binder is preferably in the range of 1 to 5%, more preferably 2 to 3%.

  In addition to the above blended coal and caking additive, the charging coal according to the present invention, if necessary, further added at least one substance such as waste plastics, powder coke, oil coke, dust, waste tire, waste wood May be. The addition rate is preferably 1% or less.

Charging coal prepared in this way (mixed coal and caking additive, and materials such as waste plastic as necessary) is charged into, for example, a chamber-type coke oven and heated and dry-distilled. Manufactured as coke. The heating conditions, dry distillation conditions, and the like at this time are not particularly limited, and may be processed under conventional processing conditions. General dry distillation conditions include 6-9% of charged coal moisture, a furnace temperature of 1050 to 1150 ° C., and a dry distillation time of 21 to 23 hours.
When the dry distillation is completed, the produced coke is discharged from the furnace, recovered after cooling.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
Example 1
(1) Production and evaluation of reference coke In this example, a blended coal blended at the following ratio and having the properties shown in Table 1 was used as the reference coal.
Coking coal: 65%, Non-slightly caking coal with a volatile content of over 25%: 35%

After adjusting the moisture of this reference charcoal to 6% and confirming that the adjusted bulk density was 760 kg / m ³ , 50 kg was charged into the dry distillation vessel. Subsequently, dry distillation was performed at a coal temperature of 950 ° C. in an electrically heated test coke oven. After the produced coke was dry-cooled in a nitrogen atmosphere, the drum strength index was measured according to JIS-K2151.
Table 1 shows the drum strength index of the reference coke obtained by carbonizing the reference coal. The drum strength index was 85.4, and it was confirmed that the strength was high strength coke.

(2) Preparation of test coke Non-slightly caking coal A, C to E, caking coal B having the characteristics shown in Table 3 (volatile content and maximum fluidity), and caking material having properties shown in Table 2 in some cases (Asphalt pyrolysis pitch; a kind of petroleum-based pitch) was added to the above-mentioned reference coal to obtain charging coal. In addition, these addition rates are as Table 3 showing, and "%" means the mass% with respect to the charging coal after addition. The charging coal thus obtained was subjected to dry distillation and the like in the same manner as in the case of the reference coal to obtain test coke.

(3) Evaluation method of test coke Since the reference coke has high strength as described above, the charging coal used in the test was compared by comparing the drum strength index of this coke with the drum strength index of the test coke. Was suitable as a raw material for coke.
The difference between the drum strength index (DI1) of the test coke and the drum strength index (DI2) of the reference coal coke was defined as ΔDI. That is, ΔDI = DI1-DI2.

(4) Evaluation results In both cases 1 and 2 in which A and B coals with a volatile content of more than 25% and caking additive were mixed with the reference coal, the strength of the test coke was lower than that of the reference coke. .

  In addition, the coke strength of Case 1 'and Case 2' in which only these A and B coals were added to the reference coal was lower than that of Case 1 and Case 2 in which a caking additive was further added. This result shows that when non-slightly caking coal with a volatile content of more than 25% is added, the strength is lower than that of the standard coke, and by adding the caking additive, the strength is improved, but the level is restored to the standard coke level. It shows that the effect is not obtained. Even if it is simple coal B classified into caking coal in this invention (however, the maximum fluidity is low as caking coal), since the volatile matter is high, the effect is low when added together with caking material. It shows that.

  On the other hand, in cases 3, 4 and 5, in which C, D and E charcoal and caking agent having a volatile content of 25% or less and a maximum fluidity in the range of 1 to 10 ddpm were mixed with reference charcoal, The strength of coke was almost equal to that of standard coke.

However, even when the same C, D and E charcoal were used as in cases 3 ′, 4 ′ and 5 ′, the result was lower than the strength of the reference coke when no caking additive was added.
Furthermore, in cases 6 and 7 in which F and G charcoal having a maximum fluidity of zero and a binder were mixed, the strength of the obtained test coke was lower than that of the reference coke. This is because the F and G charcoal has no caking property, so the adhesion with the coking structure derived from the caking coal around or from the caking material is poor, and as a result, only caking property is obtained by the addition of caking material. This is considered to be because the high-strength standard was not reached even when supplemented.

  The results of Table 3 are plotted with the volatile content of the non-coking coal added to the reference coal as the horizontal axis and the difference (ΔDI) of the drum strength index of the obtained test coke with respect to the drum strength of the reference coke as the vertical axis. The results are shown in FIG.

  As described above, when only non-slightly caking coal is added without adding a caking agent, or combined with non-slightly caking coal whose maximum fluidity (MF) is zero even when caking material is added. In some cases, the drum strength of the test coke obtained was less than the drum strength of the reference coke. That is, ΔDI was negative.

  In other cases, that is, when a non-slightly caking coal having a maximum fluidity of 1 ddpm or more and a caking property is added in combination, the volatile content of the added non-slightly caking coal is about 15 to The result was that ΔDI was stably positive in combination with 25% coal. However, as in case 7, even when volatile matter is in the range of 15 to 25%, when adding plain charcoal that has no caking property (the maximum fluidity is 0 ddpm), ΔDI is negative. became.

(Example 2)
With respect to the reference coal of Example 1, the caking material is 3%, and the C charcoal shown in Table 3 is 0.5, 1, 3, 4 times the caking material, that is, 1.5%, 3%. 9% and 12% were added, dry distillation was performed under the same conditions as in Example 1, and the drum index of the obtained test coke was measured.

  As a result, as shown in FIG. 2, the ratio of C charcoal addition ratio to caking additive addition ratio (C charcoal / caking binder) was 3 or less, and a strength higher than the standard coke was obtained. Moreover, the result that the intensity | strength was saturated when C charcoal / caking additive was 1 or less was also obtained. This result shows that even if an excessive amount of binder is added so as to satisfy C charcoal / caking binder <1, it is disadvantageous from an economical viewpoint.

  From this, it was revealed that a particularly appropriate range of the ratio of low-volatile non-caking coal to caking material (C charcoal / caking material) is about 1 or more and 3 or less. That is, if the ratio of non-slightly caking coal to caking material (C charcoal / caking material) is within the above range, the problem of reduced coke strength is less likely to occur. However, when the addition rate of non-slightly caking coal is too small, the effect of reducing the blending ratio of caking coal that is the object of the present invention cannot be fully enjoyed.

  Needless to say, in the present invention, as long as a low volatility non-slightly caking coal such as C charcoal is used as a part of the blended coal, a highly volatile non-slightly caking coal such as A coal, for example. Can also be used as part of the blended coal. Highly volatile non-caking coal has a lower ability to reduce the amount of caking coal used in combination with caking materials than low-volatile non-caking coal.

It is a graph which shows the relationship between volatile matter amount of non-slightly caking coal, and (DELTA) DI. It is a graph which shows the relationship between the ratio of low volatile matter lignite / caking binder and coke drum index.

Claims (2)

In a method for producing coke for blast furnace by dry distillation of a coke oven raw material containing a coal mixture and a caking additive composed of caking coal and non-slightly caking coal,
The non-slightly caking coal includes a low-volatile non-slightly caking coal having a volatile content of 25% or less and a maximum fluidity of 1 ddpm or more and 7 ddpm or less; A method for producing coke, wherein the mass ratio to the coke oven raw material is 3 to 7% .   The coke manufacturing method of Claim 1 whose mass ratio (non-slightly caking coal / caking material) with respect to the said caking material of the said low-volatile non-caking coal is 1 or more and 3 or less.

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