KR20030049336A - Method for manufacturing metallurgical coke having high strength - Google Patents

Abstract

PURPOSE: A method for manufacturing metallurgical coke having high strength by controlling LMF (logarithmic maximum fluidity) of blended coal is provided. CONSTITUTION: In a manufacture method of metallurgical coke where blended coal with a strength index of greater than 4.3 is poured into coke oven together with coal, the method is characterized in that the LMF of the blended coal is increased to the range of 2.6 and 3.0 to manufacture high strength coke with a cold strength of greater than 86 %.

Description

Method for manufacturing metallurgical coke having high strength

The present invention relates to a method for producing high-strength metallurgical coke, in particular in the manufacture of coke using a coal briquette of a predetermined value or more so as to produce a metallurgical coke with high cold strength through the flow control of the coal briquettes. A method for producing high strength metallurgical coke.

In general, the use of coke is essential in the blast furnace steelmaking process. Coke input to the blast furnace not only serves as a reducing material and heat source supply to reduce iron ore, but also because it plays an important role to maintain the breathability of hot air flowing from the bottom of the blast furnace to the top. Therefore, the stable supply of high strength coke as much as possible can be said to be a basic requirement of blast furnace operation.

On the other hand, the coke quality supplied to the blast furnace is evaluated by the measured strength size, the coke strength is put a certain amount of coke in the drum at room temperature, rotate the drum and then smash the whole amount to a certain size (for example 15 mm) or more The coke content is expressed as a percentage. This is to evaluate the differentiation characteristics of coke at room temperature, which means that the smaller the content is differentiated into fine powder, the higher the coke strength. Therefore, the coke strength expressed as Drum Index (DI) is evaluated as high strength coke as the DI index is higher.

In general, since the coke is a porous carbon material having a lot of pores, the coke strength (DI) is known to be determined by the pore characteristics and the strength of the pore wall. At this time, the coke pores are more advantageous under conditions that can maintain sufficient air permeability in the blast furnace, and the coke strength is improved as the strength of the pore wall is thicker or as the optically anisotropic structure of the carbon tissue is developed in the pore wall structure having the same thickness. .

On the other hand, in order to manufacture high strength coke, it is preferable to use coal, which is a raw coal having excellent coking properties, but since raw coal having excellent coking property is expensive, a coke production cost rise factor is generated. Raw coal such as ordinary coal is blended at an appropriate ratio to produce high strength coke while suppressing an increase in manufacturing cost.

When various raw coals are blended, the respective raw coal properties are weighted averaged to the blending ratio to calculate the physical properties of the coals, and the blended coals are included in the range of the control index suitable for the coke strength and the surrounding environment. Management indexes include indices for coke strength and sulfur and ash content in consideration of environmental and process considerations. At this time, the physical properties of each raw coal is primarily measured in the coal mining region, and when the final demand is received at the steel mill, the physical properties are again confirmed by measuring the physical properties.

The evaluation items of raw coal properties in steelworks can be classified into industrial analysis, elemental analysis, structure analysis, calorific value and softening melting characteristics. Among these, the tissue analysis is to analyze the coal structure by optical microscope observation, and the average reflectance and intensity index are derived.

On the other hand, the methods commonly used in the coking coal blending are the strength index (SI) and the composition balance index (CBI) of each coal. This is an index proposed by Schappiro of the United States, and it is possible to produce high-strength coke as the composite coal with the high strength index and the tissue equilibrium index is around 1 (Journal of The Institute of Fuel, page 234, 1964). year).

Therefore, raw coal having a high strength index and a low CBI index is sold at a high price among many coal coking coals distributed in the world.

Therefore, in order to manufacture high strength coke with a cold strength of 86% or more, it is necessary to adjust the blended coal strength index as much as possible, but there are limitations in terms of manufacturing cost.

On the other hand, the biggest characteristic of the raw coal used for metallurgical coke manufacture is that a coke is obtained by melting with lead in a temperature range of 350 to 500 ° C and then solidifying at a temperature of 500 ° C or more. As a method of evaluating the melting characteristics of such raw coal, there is a method using a Gieseler Plastometer (ASTM D2639-74).

This method measures the rotational speed of the stirrer while putting coal pulverized to 0.5 mm or less into a cylindrical container and raising the temperature at a constant speed. The log value (maximum flow rate: LMF) of the maximum rotational speed is measured. It is used to show the flow rate of raw coal. Therefore, the higher the LMF value of the raw coal is classified as the raw coal having high fluidity.

In general, if the flow rate of coal blend is too low (e.g. 2.3 or less), high strength coke cannot be produced due to lack of bonding force between coal particles, and if the fluidity is too high (e.g. 3.0 or more) Porosity and weakening of the pore walls are not suitable for the manufacture of coke for metallurgy.

In the coke oven operation, raw coal blended coal type or blending ratio is changed depending on supply and demand of various raw coals. It is said that this is indispensable in the condition which dozens of raw coals are supplied, and dozens of raw coals are mix | blended in an appropriate ratio among these. In addition, if the phenomenon that the coke quality falls below the management standard appears under the precondition that the high quality coke is constantly supplied to the blast furnace, the coke quality can be improved by increasing the mixing ratio of the raw coal having a high strength index. .

However, in this case, an increase in the mixing cost of expensive raw coal having a high strength index has a disadvantage of leading to an increase in manufacturing cost. In addition, when the raw material coal blending ratio having a high strength index is greatly increased, if the quality improvement effect does not appear, the temperature of the coke oven is increased.

The present invention was devised to solve the above-mentioned problems of the prior art, and in the case where the strength index of the coal briquettes for metallurgical coke production is 4.3 or more, the flow rate (LMF) of the coal briquettes is raised to a level of 2.6 to 3.0. It is an object of the present invention to provide a method for producing high-strength metallurgical coke capable of achieving quality stability of metallurgical coke and producing high strength coke with a cold strength of 86% or more.

1 is a graph showing the correlation between raw coal strength index and degree of coalification.

2 is a graph showing the correlation between raw coal strength index and flow rate;

Method for producing a high-strength metallurgical coke according to the present invention for realizing the above object is a method of producing a metallurgical coke by injecting a coal mixture of strength index (SI) 4.3 or more into the coke oven with coal, wherein It is characterized by producing a high strength coke with a cold strength of 86% or more by increasing the flow rate (LMF) to 2.6 ~ 3.0 level.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a graph showing the correlation between the raw coal strength index and the degree of coalization, and FIG. 2 is a graph showing the correlation between the raw coal strength index and the flow rate. In general, the strength index of the raw coal is highly correlated with the coalification degree. Have Coalization degree refers to the extent to which plants composed of organic elements such as C, H, N, and O are buried in the ground and coalified, and the carbon content increases as the coal is advanced, and the elemental content such as hydrogen and oxygen is increased. Means release and reduction to low molecular gaseous substances such as methane (CH ₄ ), carbon dioxide (CO ₂ ) water (H ₂ O).

Therefore, when the hydrogen and carbon contents of the raw coal are measured and their atomic ratios are expressed as [H / C], the raw coal having a higher degree of coalification tends to decrease in [H / C]. As shown in FIG. 1, [H / C], which is an index indicating the degree of coalification of raw coal for producing coke, and a strength index (SI) have a high correlation, and as the index of index (H / C) decreases, the strength index (SI) decreases. From the increase, the raw coal having a high strength index can be explained as raw coal having a high degree of coalification.

On the other hand, since raw coal having a high degree of coalization has a considerable size of the benzene ring, the coke structure produced therefrom has the characteristic of developing an optically anisotropic structure. The coke strength, which is a porous material, is determined by the distribution of pores and the development of the structure of the carbon body constituting the pore wall. As the anisotropic structure develops, the cold and hot strength of the coke increases. Therefore, high-strength coke is easy to manufacture from raw coal with a high degree of coalification.

The higher the degree of coalification of raw coal, the broader and larger the aromatic ring constituting the raw coal can be interpreted as having a very high average molecular weight. In general, considering that the higher the molecular weight of the carbon compound, the lower the fluidity, the larger the benzene ring, the lower the fluidity. Therefore, as shown in FIG. 2, it can be seen that, in the case of coking raw coal, the flow rate decreases as the strength index (coalization degree) is higher.

Due to this phenomenon, when the coking coal strength index is lowered to 86% or lower, which is the lower limit of management in the state where the coal briquette strength index is higher than 4.3, in order to compensate for this, the coalescing degree of coal coal is further increased. Only increase the effect, and since the flow rate is relatively lowered, there is no effect of increasing the strength, resulting in only the unit cost increases. In addition, in this case, the increase in the coke temperature gives the effect of improving the flow rate, thereby improving the coke strength slightly, but at the expense of energy input.

In the present invention, in order to solve such a problem, when the strength index of coal blended coal is higher than 4.3, by providing a sufficient fluidity in the melt zone of coal blended coal appearing in the temperature range of 350 ~ 500 ℃ of the coking oven It was intended to improve the coke strength.

In order to compensate for the lowering of fluidity (maintaining high viscosity) in the melting zone as the coaling degree is higher, the coal blend flow rate (LMF) is adjusted to 2.6 to 3.0, and the higher the strength index of the coal blend is, the higher the flow rate is. By controlling it high, the effect of making coke quality stable or making high strength coke of 86% or more of cold strength will appear.

Accordingly, the present invention is a method for producing a metallurgical coke by putting a coal briquette of strength 4.3 or more together with coal in a coke oven, by raising the flow rate (LMF) of the coal briquettes to 2.6 ~ 3.0 level It was intended to produce high strength coke with a cold strength of 86% or more.

In this case, the flow rate (LMF) of the coal briquettes is limited to 2.6 to 3.0, when the flow rate (LMF) of the coal briquettes is less than 2.6, the strength of coke becomes weak, and the flow rate (LMF) of the coal briquettes is 3.0 or more. This is because a bubble phenomenon having a sponge shape appears and the required coke strength cannot be obtained.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on an Example.

(Example 1)

Coal oven A with a strength index (SI) of 4.30, highest flow rate (GISler flow rate: 2.43), volatility of 25.1%, tissue equilibrium index of 1.68 and ash content of 7.37% was tested at 1100 ° C. Coke was prepared using the resultant, and the strength value of 78.1% was obtained as a result of measuring the drum strength of the prepared coke (Comparative Example 1).

However, as shown in Inventive Example 1, it was found that the coke strength was greatly improved to 80.2% when coke was manufactured by increasing the flow rate to 2.61 under the same conditions, such as the strength index and the volatilized fraction of the coal briquettes. Can be.

Sample name Mixed coal characteristics Coke strength Remarks SI Flow rate (LMF) Volatility CBI Ash DI ¹⁵⁰ Mixed coal A 4.30 2.43 25.1% 1.68 7.37% 78.1% Comparative Example 1 Mixed coal B 4.30 2.61 25.1% 1.69 7.53% 80.2% Inventive Example 1

* SI: Strength Index, * LMF: Logarithmic Maximum Fluidity,

* CBI: Composition Balance Index, DI ¹⁵⁰ : Drum Index (Coke Strength at 150 Rotation of Drum)

(Example 2)

Mixed coal C with a strength index (SI) of 4.51, maximum flow rate (Gisler flow rate: 2.LF), 2.42, volatile matter 24.6%, tissue equilibrium index 1.20, and ash content of 7.57% was tested in a coke oven at 1100 ° C. The prepared coke strength was 78.7% (Comparative Example 2).

However, as shown in Inventive Example 2, it was found that when coke was manufactured by increasing the flow rate of the coal blend to 2.82, the coke strength was greatly improved to 80.0%.

Sample name Mixed coal characteristics Coke strength Remarks SI Flow rate (LMF) Volatility CBI Ash DI ¹⁵⁰ Mixed coal C 4.51 2.42 24.6% 1.20 7.57% 78.7 Comparative Example 2 Mixed coal D 4.53 2.82 24.7% 1.26 7.31% 80.0 Inventive Example 2

(Example 3)

Mixed coal E with strength index (SI) of 4.36, highest flow rate (Gisler flow rate: LMF) of 2.41, volatile matter of 24.5%, tissue equilibrium index of 1.20, and ash content of 8.65% was tested in a coke oven at 1100 ° C. The prepared coke strength was 77.8% (Comparative Example 3).

However, as shown in Inventive Example 3, it was found that when coke was manufactured by increasing the flow rate of the coal blend to 2.98, the coke strength was greatly improved to 80.8%.

Sample name Mixed coal characteristics Coke strength Remarks SI Flow rate (LMF) Volatility CBI Ash DI ¹⁵⁰ Mixed coal E 4.36 2.41 24.5% 1.41 8.65% 77.8 Comparative Example 3 Mixed coal F 4.34 2.98 25.2% 1.51 8.49% 80.8 Inventive Example 3

As described above, according to the present invention, when the strength index of the coal briquettes for metallurgical coke production is 4.3 or more, the quality stability of the metallurgical coke manufactured by controlling the flow rate (LMF) of the coal briquettes to a certain range level is achieved. In addition, there is an effect capable of producing coke having a high strength or more than the management value.

Claims (1)

In the method for producing metallurgical coke by mixing coal with a strength index (SI) of 4.3 or more in a coke oven with coal, A method of producing high strength metallurgical coke, characterized in that to produce a high strength coke with a cold strength of 86% or more by raising the flow rate (LMF) of the blended coal to a level of 2.6 ~ 3.0.