KR101597716B1 - Method for preparation of mixing powdered coal - Google Patents

Abstract

The present invention relates to a method for manufacturing mixed powdered coal and, more specifically, to a method for manufacturing mixed powdered coal for charging an air hole of a furnace, in which low level coal is carbonized at low temperature and mixed with high level coal used for charging an air hole of a furnace. The method for manufacturing mixed powdered coal according to an embodiment of the present invention comprises the following steps: preparing each of high level coal and low level coal; producing char by carbonizing the low level coal at low temperature in an inactive condition; crushing the high level coal and the char; and mixing the high level coal and the char.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a method for producing mixed pulverized coal, and more particularly, to a method for producing pulverized pulverized coal for blowing blast furnace by mixing low grade coal with low temperature coal to high grade coal used for blowing blast furnace tuyere.

Demand for iron ore and steel coal is increasing due to the rapid increase in global crude steel production. Therefore, it is increasingly difficult for coal prices to surge and concerns over the exhaustion of high-quality coal. Under these circumstances, various technologies have been developed and applied to diversify the coal used for blast furnace blowing and to increase the use ratio of low grade coal. In addition, the quality of coal (hereinafter referred to as coal for power generation) used as a fuel for power generation is deteriorating further, and a technique for using coal having a low calorific value is being developed. Low-grade coal that is difficult to use as a fuel for power generation. It mainly contains lignite and sub-bituminous coal, and these low grade coal accounts for 50% of the total coal reserves. Accordingly, techniques for upgrading these low grade coal to utilize it as a fuel for power generation and a fuel for steel production have been developed.

As shown in Korean Patent No. 10-0784048 (2007.12.03), coal which is used as a fuel for blast furnace blast blowing (hereinafter referred to as blast furnace blast furnace coal) is made of semi-anthracite coal having a low sulfur content and high calorific value , And can be classified into semi-anthracite (less than 14% volatile) and high-volatile (less than 14% volatile) depending on the content of volatile matter. High-quality semi-anthracite, which is mainly used, have. The process of blowing coal for blast furnace blowing into the blast furnace is as follows. The coal buried in the yard is crushed in crusher by crushing machine and stored in the hopper. If necessary, when the coal stored in the hopper is discharged by a certain amount, And the coal blown into the tuyeres is burned by the hot air (1,200 ° C) of high temperature supplied from the blast furnace.

Generally, the calorific value of coal used for power generation is about 5,000 ~ 6,000 ㎉ / ㎏, and the quality of coal for power generation is also lowered due to the increase in demand for coal for power generation worldwide and shortage of supply and reserves. Low grade coal (calorific value 4,000 ㎉ / ㎏ or less) has a wealth of reserves, low content of building materials, and low cost, but it contains 60% of water, which makes it difficult to use directly as a fuel for power generation , The volatile matter content is more than 45%, and the possibility of spontaneous combustion is high when the yard is loaded.

Low-grade coal should be used as coal for blowing in blast furnace in order to reduce the cost and supply of high-grade coal. However, since low-grade coal has low calorific value due to high moisture content and high volatile content and porosity, It can not be used directly as fuel for burning blast furnace tuyere at low temperature.

Therefore, it is necessary to use low grade coal as coal for blowing in blast furnace for the purpose of diversification of coal type for blast furnace tuyeres and reduction of charcoal cost.

Korean Patent Registration No. 10-0784048

The present invention relates to a low-grade coal having a high volatile content and a low calorific value and low-temperature carbonized to produce a char having a high calorific value and a low volatile content. By mixing such a char with high grade coal, To the mixed pulverized coal.

The method of manufacturing mixed pulverized coal according to embodiments of the present invention includes preparing high grade coal and low grade coal respectively; Low temperature carbonization of the low grade coal in an inert atmosphere to produce char; Crushing said high grade coal and said char; And mixing the high grade coal with char.

The high grade coal and the char can be crushed in the crushing step, and the high grade coal or the char can be crushed while providing a high temperature gas so that the water content of the high grade coal or the char is less than 1 wt% And the high-grade coal and the char can be crushed to a size of 74 μm or less in average particle size.

The step of low-temperature carbonization to form char may be performed at a temperature of 500 to 800 ° C.

The char produced by the low-grade carbonization of the low grade coal may have a calorific value of 6,800 to 7,000 ㎉ / kg, a volatile content of 5 to 15 wt%, and a combustion at a temperature of 300 to 400 캜 And combustion can be completed at a temperature of 700 to 800 ° C.

In the mixing step, the char can be mixed with less than the high grade coal.

And further adding 5 to 15 wt% of the char to the mixture of the high grade coal and char, based on the total weight of the mixture.

The mixed pulverized coal according to the embodiments of the present invention can be manufactured by the above-mentioned mixed pulverized coal production method.

The mixed pulverized coal may have a calorific value of 7,300 ㎉ / kg or more and a volatile content of 10 to 15 wt%.

In the method for producing mixed pulverized coal according to the embodiment of the present invention, since the mixed pulverized coal is manufactured by mixing char of a low grade coal having high calorific value and low volatile content by high temperature coal, with high grade coal, And a fuel for blowing in a blast furnace having excellent combustibility can be provided.

Therefore, it is possible to reduce the amount of high-grade coal that is high in price and decrease in reserves, which may cause depletion, and low-cost low-grade coal can replace a portion of high-grade coal. In addition, since the calorific value and volatile content can be controlled by controlling the carbonization temperature and the carbonization time during the low-temperature carbonization, the coal of the coal for injecting the blast furnace can be diversified to suit the application.

In addition, as the volatile content of char decreases, the combustion start temperature and the combustion completion temperature become similar to those of high grade coal, and the burning rate becomes low enough to be blown into the blast furnace. Therefore, before the low grade coal is blown into the blast furnace, It is possible to solve the problem that it is difficult to use for blast furnace blowing in advance.

On the other hand, in order to obtain a higher calorific value, it is possible to add an additional char of low-grade coal. In this case, the difference in calorific value with high-grade coal can be overcome.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing a method for producing mixed pulverized coal according to an embodiment of the present invention; FIG.
2 is a graph showing the combustibility of high grade coal according to an embodiment of the present invention.
FIG. 3 is a graph showing the combustibility of low grade carbon and low grade coal char according to an embodiment of the present invention. FIG.
4 is a graph showing the combustibility of the mixed pulverized coal according to the embodiment of the present invention.
5 is a graph showing the combustibility of the mixed pulverized coal according to the comparative example of the present invention.
FIG. 6 is a graph showing changes in the combustibility according to mixed mixed pulverized coal according to an embodiment of the present invention. FIG.
7 is a graph showing a calorific value according to the mixing ratio of the mixed pulverized coal according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. In the description, the same components are denoted by the same reference numerals, and the drawings are partially exaggerated in size to accurately describe the embodiments of the present invention, and the same reference numerals denote the same elements in the drawings.

The low grade coal to be treated in the present invention is generally a low grade coal having a high heat content of less than 4000 ㎉ / ㎏ and a high content of water such as bituminous coal and lignite of 30 wt% or more, Less than 10 wt% and calorific value of 7,000 ㎉ / ㎏ or more, and generally means bituminous coal, anthracite coal, semi-anthracite coal and bituminous coal. On the other hand, coal can be classified on the basis of the content of components such as fixed carbon powder, volatile matter and moisture. When the content of fixed carbon powder is high and the content of volatile matter and moisture is low, it can be classified as high grade coal. On the contrary, when the fixed carbon content is about 50 ~ 60 wt% and the volatile matter and moisture content are high, it can be classified as low grade coal. Here, the volatile component means a component such as tar.

1 is a flowchart illustrating a method of manufacturing mixed pulverized coal according to an embodiment of the present invention.

Referring to FIG. 1, a method for manufacturing mixed pulverized coal according to an embodiment of the present invention includes preparing a high grade coal and a low grade coal (S100), low-carbonizing the low grade coal in an inert atmosphere, (S300) of crushing the high grade coal and the char (S400), and mixing the high grade coal and the char (S400).

First, high grade coal and low grade coal are prepared (S100). The high grade coal includes high volatile coal, anthracite coal, semi-anthracite coal and bituminous coal, and high grade coal having a high calorific value of more than 7,000 ㎉ / ㎏ and a sulfur content of less than 0.5 wt% .

The low-grade coal includes a bituminous coal, lignite and the like. Since it contains a large amount of moisture and volatile matter, it can not be used directly as a fuel for combustion because it has a low calorific value and is used by being upgraded through pretreatment such as drying. In the present invention, a method of low-grade carbonization of low-grade coal is used in the present invention. In order to achieve good carbonization, low-grade carbonization may be performed after crushing low-grade coal to 5 mm or less in the crusher.

Next, low-grade coal is carbonized at low temperature in an inert atmosphere to produce char (S200). At this time, the low grade coal can be carbonized in a rotary kiln type furnace, and the carbonization temperature may be 850 ° C or lower, preferably 500 to 800 ° C, more preferably 600 to 800 ° C have. If char is produced by low-temperature carbonization, it can remove not only moisture but also volatile matter from low-grade coal, unlike drying which physically removes moisture from low-grade coal. Also, by chemical change of low grade coal, The amount of heat can be increased and the amount of heat generated can be increased. Here, the char produced by low-temperature carbonization of low-grade coal may have a moisture content of 1 wt% or less through low-temperature carbonization.

The low-temperature carbonization apparatus may include a reaction tube for heating and charging the low-grade coal, and the reaction tube may be divided into a charging / discharging portion and a reaction region in a cylindrical shape, The motor can also be rotated at a constant speed. In addition, the charging part of the reaction tube may be connected to a hopper for charging coal, and the discharging part may be a water jacket for cooling the carbonized high temperature char, A small amount of nitrogen may be supplied to the pipe. The reaction tube may be inclined by 180 ° so that the low-grade coal is charged and carbonized at a low temperature and discharged to the charging part. In this case, the charging and discharging parts can be used in the same place. In the reaction zone of the reaction tube, a plate in the form of a screw may be installed so as to uniformly heat the low grade coal. At the rear end of the reaction tube, a water for capturing moisture generated during carbonization of the low grade coal A water trap may be installed. The heater for heating the reaction tube may be spaced apart from the outer wall of the reaction tube, and a heater capable of controlling the heating rate and heating the reaction region of the reaction tube to 1,000 ° C. may be used. In addition, it is possible to pass the generated gas through the water filled barrel to collect the tar in the gas generated by the carbonization of the low grade coal, and the gas in which moisture and tar are removed can be incinerated in the incinerator and released into the atmosphere have.

The conditions of the char produced by low-temperature carbonization of low-grade coal other than the above-mentioned contents and the detailed carbonization temperature are described below with reference to Table 2 below.

Then, the char produced by low-temperature carbonization of high-grade coal and low-grade coal is crushed (S300). Here, the high grade coal and the char may be crushed at the same time, and the high grade coal and the char may be respectively crushed. When the high-grade coal and the char are crushed at the same time, the high-grade coal and the char may be mixed and crushed, or they may be crushed at one time while mixing. It is possible to simultaneously crush the high-grade coal and char without the need to mix and crush the high-grade coal and char. However, when the high-grade coal and the char are simultaneously crushed, the high-grade coal and the char have different properties such as strength and particle size, so that it is difficult to uniformly crush the high-grade coal and the char. On the other hand, when the high-grade coal and the char are crushed separately, the same materials having the same properties can be crushed, so that the size of the granules can be more uniform and the granularity You can adjust the size differently. When crushing high grade coal and char having different properties, it is preferable to crush the high grade coal and the char to homogeneous crushing.

The high grade coal and the char can be crushed to an average particle size of 74 mu m or less (that is, to a size corresponding to 200 mesh or less). In the blast furnace blowing operation, the fuel is not burnt in place but the fuel is transported to the blast furnace by the high-pressure gas and burned by the hot gas in the blast furnace tuyere. When crushed, the coal can be easily transported to the blast furnace by the high-pressure gas, and the entire surface area can be widened, so that the coal can be burned well by the hot gas. When the particle size of coal for blast furnace blowing is larger than 200 mesh, the size of coal particle is large and its weight is heavy. Therefore, coal can not be transported to blast furnace due to high pressure gas, and coal is bulky, . On the other hand, if the particle size of the blast-furnace for blast furnace tuyere is too small, the weight is so small that it can be easily flushed by high-pressure gas, which makes it difficult to control the amount of fuel and coagulate the coal particles. have. Accordingly, the grain size of the high grade coal and the char can be limited to 100 nm to 74 탆. Meanwhile, the high-pressure gas may include nitrogen gas, and the high-temperature gas may be at a temperature of 1,200 ° C.

When the high-grade coal or the char is broken, the high-grade coal or the char may be pulverized while providing a high-temperature gas so that the moisture content of the high-grade coal or the char is less than 1 wt%. The high-temperature gas may be a flue gas (180 to 250 ° C) generated in the blast furnace during blast furnace operation, and the flue gas may be used in the high grade coal or the crushing process, It is possible to remove moisture of coal or char. When the high-grade coal and the char are crushed at one time, the high-grade coal and the char are mixed together to remove water from the mixed coal, and the high-grade coal and the char, It is possible to remove moisture of the high-grade coal and the char in the process of crushing the high-grade coal and the char, respectively. Here, the high-grade coal can lower the moisture content of 8 to 9 wt% to 1 wt% or less, and the char is removed from char by 1 wt% or less by low-temperature carbonization It is possible to omit the water removal using the flue gas generated in the blast furnace.

Thereafter, the high grade coal and char are mixed (S400). At this time, the char can be mixed less than the high grade coal. Since the calorific value of the low-grade coal is lower than that of the high-grade coal even if the low-grade coal is reformed by the low-temperature carbonization, it is preferable that the content of the high-grade coal is made larger than the content of the char so as to reduce the decrease in the calorific value Do. Meanwhile, when the high grade coal and the char are mixed together, the high grade coal and the char can be crushed simultaneously and the high grade coal and the char can be mixed and crushed at the same time, It is also possible to mix grade coal and char followed by shredding. A detailed mixing ratio of the high grade coal and char is described below with reference to FIG.

Table 1 shows industrial and elemental analysis and calorific value of high grade coal.

division Industrial analysis
(wt%) Elemental analysis
(wt%) Calorific value
(㎉ / ㎏) Volatile matter Ash Fixed carbon carbon Hydrogen nitrogen brimstone Oxygen A 10.58 9.66 79.76 83.9 3.75 1.1 0.43 1.16 7430 B 13.7 8.67 77.63 83.4 3.61 1.42 0.29 2.61 7615 C 13.71 10.87 75.42 82.8 3.89 1.29 0.26 0.81 7391 D 21.83 8.57 69.6 82.4 4.4 1.38 0.49 1.34 7605

Table 1 shows industrial analysis, elemental analysis and calorific value of commonly used blast furnace blast furnace coal (i.e., high grade coal). As shown in Table 1, the blast furnace blast coal has a calorific value of 7,300 ㎉ / ㎏ or more , And that the sulfur content is 0.5 wt% or less. As for the fixed carbon content, the content is as high as about 70 wt% or more. When the volatile matter content is examined, the content of volatile matter is as low as 15 wt% or less as a whole, but the high grade coal D has a volatile content of 21.83 wt% Compared to coal, it shows relatively high content. On the other hand, it can be seen that high grade coal D has a higher calorific value than 7,600 ㎉ / ㎏, which is relatively smaller than that of other high grade coal, and it can be seen that ash content is also an important factor for classifying high grade coal have. Here, ash refers to a component that remains ash after coal is burned, and so-called silica minerals such as clay and silicon dioxide occupy the majority. On the other hand, high-grade coal having a volatile content of 15 wt% or less is mainly used as coal for blowing blast furnace tuyere, and high grade coal having a volatile content of 15 wt% or less is guaranteed to be combustible before burning into blast furnace tuyere . However, since the volatile matter content of the high grade coal D is higher than 15 wt%, it is necessary to study in detail the graph of the combustibility of FIG. 2. Here, the volatile content is used as an index mainly for determining the combustibility of the coal for blowing in blast furnace tuyere, and the combustibility refers to the degree to which the combustion is good, including the combustion start temperature, the combustion completion temperature, and the burning rate.

In FIGS. 2 to 6 below, the weight loss was measured while raising a certain amount of the sample from room temperature to 1,000 DEG C at a rate of 10 DEG C / min in an air atmosphere using a thermogravimetric analyzer to show combustion characteristics.

2 is a graph showing the combustibility of high grade coal according to an embodiment of the present invention.

Referring to FIG. 2, it can be seen that all of the high grade coal starts to burn at 350 ° C or higher, and the combustion is completed at 750 ° C or higher. From this, it can be seen that the difference between the combustion start temperature and the burning completion temperature is about 400 ° C . In the graph, the slope represents the burning rate. When the difference between the combustion start temperature and the burning completion temperature is about 400 ° C, the slope of the graph is not steep and the burning speed is appropriate, so that combustion can be maintained for a predetermined time Therefore, it is considered that the combustion efficiency is excellent. According to the volatile matter content, the higher the volatile content, the lower the combustion start temperature and the combustion completion temperature. As a result, it can be seen that the higher the volatile content, the easier the burning occurs at a lower temperature. High grade coal D is relatively higher in burning initiation temperature and burning completion temperature than other high grade coal with volatile matter content. However, since the burning start temperature is not lower than 300 ° C and combustion characteristics such as burning completion temperature, It is similar to high grade coal and has high heat value of 7,600 ㎉ / ㎏, so high grade coal D can be used as coal for injecting blast furnace. Here, if the combustion start temperature is lower than 300 ° C, the high-temperature gas of 1,200 ° C causes the pulverized coal to be burned in advance before being blown into the blast furnace tuyere, resulting in tear damage. On the other hand, if the difference between the combustion start temperature and the combustion completion temperature is too small, the pulverized coal is burned at a high speed after the pulverized coal starts to be burned and the combustion can not be maintained for a long time. So that the cost of the charcoal is increased.

Table 2 shows the industrial and elemental analysis and calorific value of low grade coal and low grade coal at low temperature carbonized char.

division Industrial analysis
(wt%) Elemental analysis
(wt%) Calorific value
(㎉ / ㎏) Volatile matter Ash Fixed carbon carbon Hydrogen nitrogen brimstone Oxygen One 45.92 4.44 49.64 72.3 5.49 1.41 0.12 16.24 6446 Char 1 32.89 6.83 60.28 74.9 4.5 1.3 0.27 12.2 6759 Char 2 26.28 7.57 66.15 76.9 3.94 1.46 0.26 9.87 6707 Char 3 8.36 13.83 77.81 77 1.87 1.57 0.27 5.46 6935

Table 2 shows, in one embodiment, that one of the low grade coal types (30% water bituminous coal) was selected and the low grade coal raw materials and raw coal were carbonized at a temperature of 550 to 750 ° C in a rotary kiln type furnace Char 1 was prepared by carbonization at 550 ° C for 20 minutes and Char 2 was produced by heating at 550 ° C for 40 minutes Char 3 was produced by carbonization at 750 ° C for 40 minutes. As shown in Table 2, it can be seen that the volatile matter content is gradually lowered and the fixed carbon content is gradually increased according to the degree of low-temperature carbonization of the low-grade coal, so that the calorific value is increased to 6,700 ㎉ / ㎉ / ㎏, respectively. Thus, low-grade coal can be carbonized at a temperature of 500 to 800 ° C., and a low-grade coal can be obtained by lowering the volatile content and increasing the content of the fixed carbon, thereby obtaining a char having a high calorific value. As shown in Table 2, the data of the raw coal was data of dried raw coal, and the calorific value was about 6,400 ㎉ / ㎏. For the power generation, there was no problem even when low grade coal was dried and mixed with high grade coal. However, Since the fuel requires a heating value of 7,000 ㎉ / kg or more, it was difficult to use the fuel as a fuel for injecting blast furnace tuyere. On the other hand, the degree of modification according to the carbonization time can be compared through the comparison of Char 1 and Char 2. When the carbonization time is short, the removal of the volatile components is insignificant. When the carbonization time is too long, It can be seen that the increase in calorific value is insignificant or the amount of calorific value is reduced by a long time. The carbonization time may be 10 to 50 minutes.

FIG. 3 is a graph showing the combustibility of low temperature carbonized char in low grade coal and low grade coal according to an embodiment of the present invention.

Referring to FIG. 3, it can be seen that Char 3 having a volatile content of about 8 wt% starts combustion at about 300 ° C, which is the highest level compared to other char, and combustion is completed at about 770 ° C. In addition, the coal of low-grade coal is found to burn at the lowest temperature as compared with char, and the combustion is completed at the lowest temperature. As a result, the higher the degree of low-temperature carbonization (the lower the volatile content) The combustion start temperature and the combustion completion temperature increase. Char 3 was modified to high grade coal in terms of calorific value, volatile matter content and combustibility. Therefore, it is considered that coal 3 can be mixed with high grade coal and used as coal for blowing in blast furnace.

On the other hand, if the combustion start temperature of coal for blowing in blast furnace tuyeres is lower than 300 ° C, it is burned too quickly by the high temperature gas of 1,200 ° C to cause tear damage. When the burning start temperature of coal for blast furnace tuyeres becomes higher than 400 ° C The unburned probability increases. Further, when the difference between the combustion start temperature and the combustion completion temperature is higher than 500 ° C, the combustion speed is slowed to generate unburnt carbon, thereby interfering with the airflow of the tuyere, and the difference between the combustion start temperature and the combustion completion temperature is less than 300 ° C It is possible to burn coal at a high speed, so that combustion can not be continued for a long time. As a result, the combustion of char is started at a temperature of 300-400 ℃ as in Char 3, considering the mixture with high grade coal, and the difference between combustion start temperature and combustion completion temperature The combustion can be completed at a visible temperature of 700 to 800 ° C.

In the following, we will use data obtained by mixing low grade coal or low grade coal with low temperature carbonized char to high grade coal B which has relatively high calorific value and average characteristics in industrial and element analysis and combustibility. Similar results were found in grade coal.

4 is a graph showing the combustibility of the mixed pulverized coal according to the embodiment of the present invention.

4 shows combustion characteristics of mixed pulverized coal having Char 3 mixed with 0, 10, 30, 40, 50 and 100 wt% in high grade coal B. Referring to FIG. 4, the combustibility of high grade coal B and Char 3 It can be seen that Char 3 starts to burn at a temperature slightly lower than that of high grade coal B, and combustion is completed at a temperature slightly lower than that of high grade coal B. In addition, it can be seen that as the mixing ratio of Char 3 increases, the combustibility of the mixed pulverized coal gradually changes from high grade coal B to Char 3.

5 is a graph showing the combustibility of the mixed pulverized coal according to the comparative example of the present invention.

5 shows combustion characteristics of mixed pulverized coal having Char 1 mixed at 0, 10, 30, 50 and 100 wt% in a high grade coal B as a comparative example of the present invention. Referring to FIG. 5, Char 1 is a high grade coal B It can be seen that the combustion is started at a temperature of about 250 캜 which is much lower than that of the high grade coal B and the combustion is completed at a temperature of about 600 캜 which is much lower than that of the high grade coal B. Also, it can be seen that as the mixing ratio of Char 1 increases in Char 1, the combustibility of the mixed pulverized coal gradually changes from high-grade coal B to Char 1. Char 1 can not reach the combustion start temperature of 300 ° C or more, so that if the content of Char 1 is more than 10 wt% in the mixed pulverized coal, the combustibility is less than the standard of the coal for injecting tuyere. If Char 1 is less than 10 wt% It will be similar to the grade coal. However, this mixing is more troublesome than the case of using only high grade coal, and the effect of cost reduction due to the use of low grade coal is insignificant. In this way, although Char 1 can replace high grade coal for blowing in blast furnace to some extent, the substitution effect is not sufficient.

FIG. 6 is a graph showing changes in the combustion characteristics of the mixed pulverized coal according to the embodiment of the present invention.

Referring to FIG. 6, when the mixed pulverized coal having Char 3 mixed with the high grade coal B is burned at about 350 ° C, the combustion is completed at about 800 ° C, and the difference between the burning start temperature and the burning completion temperature is 450 ° C It is believed that the combustion rate will be such that combustion can be sustained for a long time without occurrence of unburned carbon. In addition, it can be seen that as the raw material of Char 2 is mixed with a material having a high volatile content, the combustion rate is increased, and the combustion start temperature and the combustion completion temperature are lowered. And, the mixed pulverized coal with Char 1 or Char 2 is not different from the mixed pulverized coal with mixed raw coal. If the volatile content of char is larger than 15 wt%, the coal with high grade and char It can be seen that the low-temperature carbonization of the low-grade coal does not have a large upgrading effect on the combustibility. Accordingly, it is preferable that the volatile content of char is 15 wt% or less, and the volatile content of char is 5 to 15 wt% in consideration of the volatile content of the mixed pulverized coal when mixed with high grade coal More preferable. In the embodiment of the present invention, low-grade coal can be low-temperature carbonized at a temperature of 600 to 800 ° C. so that the volatile content of char is 5 to 15 wt%. The low-grade coal is cooled at a temperature lower than 600 ° C. The low volatility of the low grade coal is lowered at a temperature higher than 800 ° C., the volatile matter content is less than 5 wt%, the volatile matter is removed too much and the burning property is lowered, and the probability of unburned is increased . And char having a volatile content of 5 ~ 15 wt% can have a high calorific value of 6,800 ~ 7,000 ㎉ / kg as in Char 3.

As described above, low-grade coal can be carbonized at a temperature of 600 to 800 ° C such that the volatile content of char is 5 to 15 wt%, and low-grade coal is reformed through low- A char with a high calorific value of 7,000 ㎉ / ㎏ can be obtained. These characteristics are similar for all low grade coal, but exact figures may vary depending on the coal grade of low grade coal.

7 is a graph showing calorific values according to the mixing ratio of the mixed fine coal according to the embodiment of the present invention.

Referring to FIG. 7, it can be seen that the calorific value decreases linearly as the mixing ratio of char mixed in high grade coal B increases. In addition, it can be confirmed that the volatile matter content affects the calorific value because the line indicating the calculated calorific value shows a rise in the lower volatile content of the mixed material. The mixing ratio of char mixed in high grade coal B can be 20 ~ 50 wt%. If less than 20 wt% of char is mixed, the cost reduction effect of low grade coal is insignificant If the char is mixed more than 50 wt%, the calorific value is reduced to 7,300 ㎉ / ㎏ or less, and the efficiency of the fuel for injecting the blast furnace tuyeres is lowered.

The method may further include the step of adding 5 to 15 wt% of the char to the mixture of the high grade coal and char (S500) based on the total weight of the mixture. When the high grade coal is mixed with the char, the calorific value decreases compared with the case where only the high grade coal is used. Therefore, in order to overcome the difference in calorific value, a mixture of the high grade coal and char 5 to 15 wt% of the char may be further added (S500). The mixed pulverized coal mixed with the high grade coal and char can be used as fuel for injecting the blast furnace without addition of the char, but a char of a low grade coal is added to obtain a higher calorific value So that it is possible to approximate the calorific value of only the high grade coal. In this case, when the high grade coal alone is used and the cost of the charcoal is compared, the char is additionally added in a range of 5 to 15 wt% of the total weight of the high grade coal and char mixed in terms of cost It is possible to achieve the compensation of the calorific value while reducing the charcoal cost.

The mixed pulverized coal according to another embodiment of the present invention can be manufactured by the above-mentioned mixed pulverized coal production method.

The mixed pulverized coal may have a calorific value of 7,300 ㎉ / ㎏ or more by mixing a char having a high calorific value of 6,800 ~ 7,000 ㎉ / ㎏ which is a low temperature carbonized low grade coal, and may be 7,300 ~ 7,500 ㎉ / ㎏ in detail . If the volatile matter content is more than 15 wt%, the mixed pulverized coal may be burned before burning into the blast furnace trough, and the volatile matter content may be 10 wt% If it is small, the combustion property is deteriorated and the probability of unburned becomes high. Accordingly, the mixed pulverized coal can be used as coal for injecting blast furnace tuyere, and high grade coal can be partially substituted with low temperature carbonized char, so that the cost of fuel for blast furnace tuyere injection can be reduced. In addition, the mixed pulverized coal of the present invention has combustibility comparable to that of the high grade coal used as the coal for injecting blast furnace tuyeres, so that it has better combustibility than the low grade coal mixed by drying.

As described above, when the mixed pulverized coal is manufactured by the mixed pulverized coal manufacturing method of the present invention, it is possible to provide fuel for blast furnace blast blowing having a high calorific value of 7,300 ㎉ / kg or more, which is high in price, Low-grade coal can replace low-grade coal and a portion of high-grade coal can be replaced by low-grade coal. In addition, by controlling the carbonization temperature and the carbonization time during the low-temperature carbonization, the amount of coal to be injected into the blast furnace can be diversified to suit the application, by controlling the calorific value and the volatile content. The method of producing mixed pulverized coal according to the present invention can produce mixed pulverized coal having similar combustibility to high grade coal having good burnability, which was conventionally used as coal for blowing blast furnace tuyere. According to the present invention, low-grade carbonization of low-grade coal can improve the low calorific value due to a large amount of water, and can improve the problem of burning in advance before being conveyed into the furnace tuyer due to high volatile content . The mixed pulverized coal of the present invention has a combustion start temperature lower than that of the high grade coal used in the conventional blast furnace blowing coal and the burning completion temperature is similar to that of the high grade coal, The combustion efficiency can be better than that of conventional high grade coal.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limited to the embodiments set forth herein. Those skilled in the art will appreciate that various modifications and equivalent embodiments may be possible. Accordingly, the technical scope of the present invention should be defined by the following claims.

S100: Preparation of coal S200: Creation of char
S300: crushing S400: mixing

Claims (12)

Preparing high grade coal and low grade coal, respectively;
Low temperature carbonization of the low grade coal in an inert atmosphere to produce char;
Crushing said high grade coal and said char; And
Mixing the high grade coal with char,
The low-temperature carbonization step produces carbon at a temperature of 600 to 800 ° C.,
The char produced in the step of producing char by the low-temperature carbonization has a volatile content of 5 to 15 wt%, a moisture content of 1 wt% or less, and combustion starts at a temperature of 300 to 400 ° C. The combustion is completed at a temperature of 700 to 800 DEG C,
Wherein the high-grade coal is pulverized while providing a high-temperature gas, which is an exhaust gas generated in the blast furnace, so that the water content of the high-grade coal is 1 wt% or less.
The method according to claim 1,
And crushing the high grade coal and the char in the crushing step.
delete The method according to claim 1,
Wherein the high-grade coal and the char are crushed to a size of 74 mu m or less in the crushing step.
delete The method according to claim 1,
Wherein the char produced by low temperature carbonization of the low grade coal has a calorific value of 6,800 to 7,000 ㎉ / kg.
delete delete The method according to claim 1,
Wherein the mixing step mixes the char less than the high grade coal.
The method according to claim 1,
Further comprising adding 5 to 15 wt% of the char to the mixture of the high grade coal and char in the total weight of the mixture.
The mixed pulverized coal produced by the method for producing mixed pulverized coal according to any one of claims 1, 2, 4, 6, and 9 to 10.
The method of claim 11,
The mixed pulverized coal has a calorific value of 7,300 ㎉ / kg or more and a volatile content of 10 to 15 wt%.

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