KR20020051012A - Coal blending method for producing metallurgical coke - Google Patents

Abstract

PURPOSE: A method for blending coke for production of a metallurgical coke with low expansion pressure during carbonization is provided. CONSTITUTION: A coal with reduced moisture content of 4 to 7 wt.% is blended to have total inert content of 28 to 33% so that sudden strength drop of coke is prevented and moreover coke oven collapse can be avoided by restraining excess expansion pressure during carbonization.

Description

Coal blending method for producing metallurgical coke}

The present invention relates to a method for blending raw coal for coke production, and more particularly, in blending various types of raw coal for coke production, in order to reduce the expansion pressure generated during dry distillation while maintaining the coke strength, It relates to a method of blending coal while controlling the content to an appropriate content.

Recently, a method of drying a coal to produce a water content of 4 to 7% and then charging it into a coke oven, called a coal coal control process (CMCP), has been applied in some steel mills.

In addition, the fluidized bed is used to dry the moisture of the raw coal to about 2% (this is called the dry-cleaned and agglomerated precompaction system) process and the preheating to completely remove and preheat coal moisture at a high temperature of about 200 ° C. Research on the preheated coal charge and the like is carried out to improve the productivity of coke production by charging coal in a coke oven with controlled moisture content.

However, the introduction of a process for pretreatment of coal to reduce the water content as described above has the advantage of improving the coke productivity and quality, but has a disadvantage of adversely affecting the coke furnace body. This is because a larger amount of coal is injected into the carbonization chamber of the coke oven with a constant volume, so that more gaseous components are generated during the drying process.

Increasing the amount of gas generated means an increase in the expansion pressure of coal in dry distillation. A fatal accident in which the coke oven is collapsed due to high dry distillation expansion as a result of charging the coal-coated preheated coal into the existing coke oven. Occurred. This began to emphasize the importance of techniques to control dry distillation pressures.

Therefore, in order to maintain a low dry distillation expansion pressure that does not affect the coke oven structure, it is most desirable not to reduce the water content of the raw coal blended as much as possible, but this is in a state where the equipment for improving coke production productivity is already in operation. This is an undesirable method.

In addition, if the water content of the raw coal for producing coke is reduced, the coke strength is increased as compared with the case where the water content is high. Therefore, it is necessary to newly combine the effect of the coke strength increase and the tendency to increase the expansion pressure.

On the other hand, in the conventional technique for controlling the expansion pressure in dry distillation, when blending several types of raw coal for coke production, the maximum expansion pressure of each type of coal is measured in advance and arithmetic is performed according to the proportion of each type of coal blended into the coal. There is a method of estimating the expansion pressure of coal briquettes by averaging them and then applying them to the compounding.

However, this method is not only inconvenient to measure the inflation pressure of each type of coal in advance, but also restricts the coke quality in the process of adjusting the compounding ratio of each type of coal so that the prediction of the maximum inflation pressure of the coal is reached. There are drawbacks to this. Because, in general, coal species having a high degree of coaling and low volatile content contribute to the improvement of coke quality, but the expansion pressure of these coal species is generally very high. Therefore, when adjusting the blending ratio of each type of coal so that the prediction value of the maximum expansion pressure of the coal blended into the stable zone, there is a problem that the coal type having a high degree of coalization and low volatile content enters less and consequently deteriorates the quality of coke.

The present invention has been devised to solve the above problems, the purpose of which is to maintain the quality of metallurgical coke at a level suitable for large blast furnace, while the expansion pressure during dry distillation does not affect the coke oven furnace body The present invention provides a method of blending raw coal to have a low value.

1 is a graph showing the change of the maximum gas pressure according to the TI content of the coal blend.

2 is a graph showing the change in coke strength according to the TI content of the coal blend.

In order to achieve the object as described above, the present invention is characterized in that when blending the raw coal for coke production, the raw coal having a water content of 4 to 7% so as to have a total inert content of 28 to 33%.

Hereinafter, with reference to the accompanying drawings for the raw coal blending method for producing coke according to the present invention will be described in detail.

As mentioned above, when blending raw coal, it is necessary to reduce the mixing ratio of low volatility high petroleum charcoal with high expansion pressure in order to protect the furnace body of the coke oven, while in order to manufacture high strength coke used in large blast furnaces, It is only possible to produce high strength coke while suppressing the dry dilation pressure, while solving the opposite relationship to be increased.

The coal for metallurgical coke production is characterized by exhibiting a melting behavior in the temperature range of 350 to 500 ° C. This can be said to be an essential feature required for the conversion of powdered coal to bulk coke, and it cannot be produced from coal that is not meltable or lacks.

On the other hand, coal is a mixture of various hydrocarbon compounds in a higher order structure and exist in a mixture state containing impurities such as ash, and components exhibiting meltability and meltability in a temperature range of 350 to 500 ° C. It can be distinguished by the missing component. At this time, the component exhibiting meltability in the temperature range of 350 to 500 ° C is called the active component, and a part of the vitrinite, excitite and semi resting nitrile components constituting the coal.

On the other hand, components that do not exhibit meltability are called inert components and are composed of tissue knits, minerals, and parts of semi-tissue knits, and the total amount of inert components in a certain type of carbon is called total inert (TI). .

In blending multiple coal species, the TI content of the coal briquettes can be obtained by arithmetically averaging the TI content of individual raw coals. Because the inert components are not meltable, coke quality tends to decrease with increasing TI content of coal blends. Therefore, when manufacturing high-strength coke used in large-scale blast furnaces, a coal blend having a TI content of about 25% is used. This is based on the results of Schappiro's research that the strength of coke decreases as the raw material TI content increases. Is based. This result is a technique used before the process of reducing the raw coal moisture, and it is necessary to reconsider it with the introduction of a coal humidification facility that varies the type of coal and reduces the raw coal moisture to about 6%.

As such, the coke strength decreases as the TI content of the raw coal increases, which is mostly a result of experimenting with US coal (Journal of The Institute of Fuel, p234, 1964). However, in recent years, the number and types of coal mined in China, Russia, etc. have increased, and thus, the type of raw coal for coke has been diversified.

Accordingly, the present inventors have found that, in a raw coal moistened with low moisture of about 4 to 7%, coaling degree (eg, volatilization) and fluidity (eg: LMF), which are the key factors of the mixing, are maintained under certain conditions. As a result of repeating the experiment of preparing coke after preparing mixed coals having different TI contents while maintaining, it was found that the maximum gas pressure was significantly decreased with increasing TI content of the mixed coals.

The maximum gas pressure in the molten layer decreases with increasing TI content of coal blends, whereas the physicochemical changes such as volume expansion during melting are remarkable. It is presumably because it maintains a stable state which hardly appears.

In addition, as a result of measuring the strength of the prepared coke, the coke strength reduction phenomenon was insignificant until the TI content of about 33%, the coke strength reduction showed a significant behavior when the TI content is higher than this. The coke quality is maintained even when the TI content of coal blends is as high as 33%. In other words, part of the semi-half knit (about one third) is classified as an active ingredient with melting property, and the remainder is classified as an inert ingredient, but this means that it is difficult to apply such classification criteria in recently developed coal. can do.

Hereinafter, an embodiment of the present invention will be described.

Example 1

As shown in Example 1 while maintaining the same level of volatile matter content and the flow rate for the mixed coal A (Comparative Example 1) having a water content of about 6%, a volatile matter of 25%, a flow rate of 2.4, and a TI content of 25%. As shown in Table 1, the blended coals having a TI content of 29% (mixed carbon B), 33% (mixed carbon C) and 36% (mixed carbon D) were dried under the same conditions using a laboratory test oven. Indicated. At this time, the maximum gas pressure was measured by inserting a pressure sensor into the coal bed in the dry distillation, and the manufactured coke measured the drum strength after two drop tests.

TI content and maximum gas pressure measurement results for low flow formulations sample Mixed coal characteristics Gas pressure (mmH ₂ O) Coke Strength (DI ¹⁵⁰ ) Remarks moisture(%) Volatile fraction (%) Flow rate (LMF) TI (%) A 6.8 24.6 2.42 25.3 301 78.7 Comparative Example 1 B 6.8 24.5 2.41 29.1 187 78.2 Example 1 C 6.3 25.1 2.43 32.7 101 78.1 Example 1 D 6.6 25.2 2.42 35.4 78 76.4 Example 1

As shown in Table 1, the maximum gas pressure was higher than 300 mmH ₂ O when the TI content of the blended coal was controlled at 25%, which is a normal blending level. It can be seen.

As described above, the decrease in the generated gas pressure during dry distillation due to the increase in the blended coal TI content may be interpreted as decreasing the expansion pressure of the coal melted layer depending on the magnitude of the gas pressure.

On the other hand, the drum strength (DI ¹⁵⁰ ) indicating the quality of the manufactured coke is reduced with increasing the coal blended TI, especially when the TI content is high to 35.4% (mixed coal D), the coke strength is drastically reduced. From these results, it can be seen that the increase in the TI content of the coal blend is effective in reducing the dry distillation expansion pressure, but in order to maintain the coke strength, there is a characteristic to be controlled to be included in an appropriate range.

Example 2

As shown in Example 2 while maintaining the same level of volatile matter content and flow rate for the coal blend E (Comparative Example 2) having a water content of about 6%, a volatile matter of 25%, a flow rate of 2.6, and a TI content of 25%. Similarly, the results of preparing coke from the coal blend having a TI content of 29% (blended coal F), 33% (blended coal G) and 36% (blended coal H) are shown in Table 2.

TI content and maximum gas pressure measurement results in heavy fluid formulation sample Mixed coal characteristics Gas pressure (mmH ₂ O) Coke Strength (DI ¹⁵⁰ ) Remarks moisture(%) Volatile fraction (%) Flow rate (LMF) TI (%) E 5.9 26.1 2.62 25.4 367 81.0 Comparative Example 2 F 6.2 24.5 2.61 29.6 192 80.2 Example 2 G 6.3 25.1 2.63 33.0 186 79.5 Example 2 H 6.4 25.2 2.62 36.1 106 77.2 Example 2

As shown in Table 2, even when the flow rate of the coal briquettes was increased to about 2.6, it exhibited a similar behavior to that of Example 1 with low fluidity, and the TI content of the coal briquettes was controlled to about 25%, which is a general blending level. In this case, the maximum gas pressure was 367 mmH ₂ O (Comparative Example 2), but the blended coal TI content was 29.6% (blended coal F), 33%% (blended coal G), and 36.1% (blended coal H). It can be seen that as the increase, the maximum gas pressure is reduced to less than half the level.

In addition, the drum strength (DI ¹⁵⁰ ), which represents the quality of the manufactured coke, is decreased with increasing the blended coal TI, and particularly, when the TI content is high to 36.1% (blended coal H), the coke strength is rapidly decreased. From these results, it can be seen that the increase in the TI content of the coal blend is effective in reducing the dry distillation expansion pressure, but in order to maintain the coke strength, there is a characteristic to be controlled to be included in an appropriate range.

Example 3

As shown in Example 3 while maintaining the same level of volatile matter content and flow rate for the mixed coal I (Comparative Example 3) having a water content of about 6%, a volatile matter of 25%, a flow rate of 2.8, and a TI content of 25%. Similarly, the results of preparing coke from the coal blend having a TI content of 29% (blended coal J), 33% (blended coal K) and 36% (blended coal L) are shown in Table 3.

TI content and maximum gas pressure measurement results in high flow formulation sample Mixed coal characteristics Gas pressure (mmH ₂ O) Coke Strength (DI ¹⁵⁰ ) Remarks moisture(%) Volatile fraction (%) Flow rate (LMF) TI (%) I 6.3 26.7 2.82 25.6 198 81.0 Comparative Example 3 J 5.3 26.1 2.81 29.9 154 80.2 Example 3 K 5.7 25.9 2.80 32.6 139 79.5 Example 3 L 6.1 26.2 2.82 35.7 122 77.2 Example 3

As shown in Table 3, even when the flow rate of the coal briquettes was increased to about 2.8, the behavior was similar to that of Example 1 with low fluidity, and the TI content of the coal briquettes was controlled to about 25%, which is a typical compounding level. In this case, the maximum gas pressure showed a high value of 198 mmH ₂ O (Comparative Example 3), but the blended coal TI content increased to 29.9% (blended coal J), 32.6% (blended coal K), and 35.7% (blended coal L). As can be seen that there is an effect that the maximum gas pressure is reduced.

The drum strength (DI ¹⁵⁰ ), which represents the quality of the manufactured coke, is decreasing with the increase in the blended coal TI, and especially when the TI content is high to 36.1% (mixture coal H), the coke strength is rapidly decreased. From these results, it can be seen that the increase in the TI content of the coal blend is effective in reducing the dry distillation expansion pressure, but in order to maintain the coke strength, there is a characteristic to be controlled to be included in an appropriate range.

The results of Examples 1 to 3 as described above are summarized in FIG. 1. That is, FIG. 1 is a graph showing the change of the maximum gas pressure according to the TI content of the coal briquettes. As shown in FIG. 1, when the TI content is controlled to be 28% or more regardless of the flow rate of the coal briquettes, It can be seen that since the gas pressure is maintained at a lower value of 200 mmH ₂ O or lower, there is an effect of reducing the expansion pressure of the molten layer during dry distillation.

Fig. 2 summarizes the coke strength change according to the TI content of the blended coal from the results of Examples 1 to 3. As shown in FIG. 2, the coke strength decreases with increasing TI content of the coal blend, but the strength of the coal coal decreases to about 33% while the strength of the coal blend decreases to 33%. It was.

Therefore, it can be seen that managing the TI content of the coal blend within the range of 28 to 33% is effective in reducing the dry distillation pressure for protecting the body of the coke oven while maintaining the coke strength at a constant level.

As described above, the present invention has an effect of preventing sudden coke strength decrease by controlling the TI content of the coal blend having a water content of about 4% to 7% within the range of 28 to 33%. It is effective to prevent the collapse of the oven body.

Claims (1)

In blending raw coal to produce coke, A raw coal blending method for producing coke, wherein the raw coal having a water content of 4 to 7% is blended so as to have a total inert content of 28 to 33%.