KR20110098445A

KR20110098445A - Apparatus for drying coal and system for upgrading coal quality including the same

Info

Publication number: KR20110098445A
Application number: KR1020100018080A
Authority: KR
Inventors: 김재관; 이현동
Original assignee: 한국전력공사
Priority date: 2010-02-26
Filing date: 2010-02-26
Publication date: 2011-09-01
Also published as: KR101144274B1

Abstract

The present invention relates to a coal drying apparatus and a coal high-grade system including the coal drying apparatus. According to the present invention, there is provided a coal drying apparatus for drying coal, comprising: a chamber in which a coal inlet for charging coal at the upper portion and a coal outlet for discharging dried coal at the lower portion are formed; At least one microwave irradiating unit for supplying microwaves to the second region adjacent to the coal discharging port to re-dry the coal dried in the hot air supplying unit, And a coal high-quality system including the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a coal drying apparatus and a coal high-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coal drying apparatus and a coal high-grade system including the same.

Conventional low grade coal drying and stabilization techniques are based on heat drying methods or oil

In the case of low grade coal, there is external free moisture and surface adhesion water that is dried in the range of 100 to 110 degrees. However, if it is dried for more than 1 hour at a temperature of 400 degrees or higher, chemically bonded pore water, The water is decomposed and dried. Conventionally, in the case of drying a low grade coal in a high temperature and high pressure environment of 400 ° C or higher, devolatilization of volatile matter and spontaneous ignition occur in the drying process, the fuel value is lowered, unnecessary heat consumption is large in the drying process, , There is a problem such as the deterioration of the dust collecting characteristic of the electrostatic precipitator and the inability to recycle the fly ash due to the presence of heavy oil residues in the high-grade coal.

The present invention provides a coal drying apparatus for converting low grade coal to high quality coal used in a thermal power plant by reusing the exhaust gas discharged from a combustion boiler, and a coal high quality system including the same.

The present invention provides a coal drying apparatus and a coal high-grade system capable of drying low-grade coal at a low temperature in a short time.

The present invention is to provide a coal drying apparatus and a coal high-grade system which do not spontaneously ignite after drying or drying of low grade coal.

According to an aspect of the present invention, there is provided a coal drying apparatus for drying coal, comprising: a chamber having a coal inlet through which coal is charged at an upper portion and a coal outlet through which coal dried at a lower portion is discharged; A coal transfer unit for transferring the coal charged into the coal inlet to the coal outlet; A hot air supply unit for supplying hot air to a first region adjacent to the coal inlet to dry the coal; And at least one microwave irradiating unit for supplying microwaves to the second region adjacent to the coal discharging port to re-dry the dried coal in the hot air supplying unit.

The coal drying apparatus may further include a rotating shaft rotatably disposed at the center of the chamber, and the coal transferring unit may further include a blade coupled to the rotating shaft and rotating in accordance with rotation of the rotating shaft.

The coal transferring portion includes a first blade formed in the first region; And a second blade connected to the first helical blade and formed in the second region.

The second helical blade may be formed of a Teflon material on the surface.

The hot air supply unit is formed in a pipe shape to supply hot air to the inside, and a plurality of through holes may be provided to supply hot air into the chamber.

The surface of the rotating shaft formed in the second region may be coated with Teflon.

The plurality of microwave irradiation units may be formed so that the plurality of microwave irradiation units face each other and output microwaves in mutually staggered directions.

The chamber may further include at least one inert gas inlet for supplying an inert gas.

The chamber may have a plurality of inactive gas inlet openings.

The chamber may further include a steam outlet through which steam is discharged.

The coal drying apparatus may further include at least one temperature sensor for measuring the temperature in the chamber.

The temperature sensor turns off the microwave irradiating unit when the temperature in the chamber is higher than the upper limit setting value, and turns on the microwave irradiating unit when the temperature is lower than the lower limit setting value.

The upper limit set value may be 300 ° C, and the lower limit set value may be 150 ° C.

The chamber is coated with Teflon to prevent damages to the inner wall by the microwave .

According to another aspect of the present invention, there is provided a combustion boiler; A pulverizer for pulverizing and supplying coal supplied to the combustion boiler; A burning portion for recovering the heat of the exhaust gas generated after the combustion from the combustion boiler; A preheating unit for preheating the air using the heat of the exhaust gas supplied from the cut-away portion; A first dust collecting part for collecting fly ash from the exhaust gas; A purifier configured to purge residual pollutants contained in the exhaust gas supplied from the dust collecting unit and to supply the generated purge gas to the preheater; And a coal drying apparatus for drying coal charged by using the clean gas preheated by the preheating unit, re-drying the dried coal by irradiating microwaves, and supplying the dried coal to the differentiator, .

The coal high-definition system may further include a first condenser for removing moisture of the clean gas from which contaminants have been removed from the cleaner and supplying the purified gas to the preheater.

The coal high-quality system may further include a waste heat absorbing unit for absorbing residual heat from the first dust collector and supplying the exhaust gas at an ambient temperature to the clean unit.

Wherein the preheater includes an air preheater for preheating atmospheric air and supplying the preheated air to the combustion boiler; And a drying gas preheating unit for preheating the clean gas and supplying the drying gas to the coal drying apparatus.

The coal drying apparatus includes a chamber having a coal inlet through which coal is introduced into the upper portion and a coal outlet through which the coal dried in the lower portion is discharged to the separator; A coal transfer unit for transferring the coal charged into the coal inlet to the coal outlet; A hot air supply unit for supplying a preheated clean gas from the drying gas preheating unit to a first region adjacent to the coal inlet to dry the coal; And at least one microwave irradiation unit for supplying the microwave to a second area adjacent to the coal outlet.

The coal high-definition system may further include a second dust collection unit for removing the coal powder contained in the steam discharged from the steam outlet and supplying the coal dust to the differentiator.

The coal high-definition system may further include a second condenser formed between the second dust collection unit and the differentiator to remove moisture of the steam from which the coal powder is removed, and to supply the steam to the differentiator.

According to the embodiment of the present invention, the air is preheated by using the exhaust gas discharged from the combustion boiler, and the inert gas from which the pollutants contained in the exhaust gas are removed is used for drying the coal to dry the low grade coal at low cost with high efficiency .

According to the embodiment of the present invention, low grade coal can be quickly dried at a low temperature and converted into high grade coal.

According to the embodiment of the present invention, spontaneous ignition can be prevented during drying of coal or after drying of coal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a coal high-definition system in accordance with an embodiment of the present invention. FIG.
2 is a cross-sectional view illustrating a coal drying apparatus according to an embodiment of the present invention.
3 is a cross-sectional view illustrating the position of the inert gas heat source supply unit shown in FIG. 2;
FIG. 4 is a cross-sectional view showing the hot air supply unit shown in FIG. 2. FIG.
5 is a sectional view for explaining the position of the microwave irradiation unit shown in FIG. 2;
6 is a cross-sectional view for explaining the hot air vent shown in FIG. 2;

While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and similarities. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In addition, numerals (e.g., first, second, etc.) used in the description of the present invention are merely an identifier for distinguishing one component from another.

Also, in this specification, when an element is referred to as being "connected" or "connected" with another element, the element may be directly connected or directly connected to the other element, It should be understood that, unless an opposite description is present, it may be connected or connected via another element in the middle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a coal drying apparatus and a coal high-grade system including the same according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a coal upgrading system according to an embodiment of the present invention.

Referring to FIG. 1, a coal high-grade system according to an embodiment of the present invention includes a combustion boiler 10, a differentiator 120, a cutting unit 20, a preheating unit 30, a first dust collecting unit 40, (60), a cleaner (70), a first condenser (90), and a coal dryer (200).

Specifically, the combustion boiler 10 is a facility for burning coal to convert it into electric energy.

The differentiator 120 crushes and supplies the coal supplied to the combustion boiler. At this time, the differentiator 120 can crush dried coal from the coal drying apparatus 200 with pulverized coal.

The cut-out portion 20 recovers the heat of the exhaust gas generated after the combustion from the combustion boiler 10. The exhaust gas is supplied to the preheating unit 30 after recovering a part of the heat because it is at least several hundreds of degrees C supplied from the combustion boiler 10. At this time, the heat supplied to the preheating portion 30 from the curled portion 20 is about 400 ° C or so.

The preheating unit 30 can preheat the atmospheric air and the clean gas input from the first condenser 90. The preheating section 30 may include an atmospheric air preheating section 31 for preheating the air and a drying gas preheating section 32 for preheating the clean gas.

The atmospheric air preheating section 31 can supply the preheated atmospheric air to the combustion boiler 10. In addition, the atmospheric air preheating section 31 can be supplied at the same time when pulverized coal is supplied to the combustion boiler 10 in the differentiator 120. Here, the temperature of the atmospheric air supplied from the atmospheric air preheating section 31 is about 350 to 380 ° C.

The drying gas preheating section 32 can supply the clean exhaust gas to the hot air supply section 230 of the coal drying apparatus 200. At this time, the clean exhaust gas supplied from the drying gas preheating section 32 can be maintained at about 150 ° C.

On the other hand, the exhaust gas discharged from the preheating section 30 is supplied to the first dust collecting section 40. At this time, the temperature of the exhaust gas discharged from the preheating unit 30 is lowered to about 150 ° C.

The exhaust gas discharged after combustion in the combustion boiler 10 contains a large number of pollutants, so that various stages of pollutants are removed and released to the atmosphere or reused.

The first dust collecting part (40) collects fly ash from exhaust gas. The first dust collecting part 40 can collect the fly ash by an electric dust collecting method.

The cleaning unit 70 removes the remaining contaminants contained in the exhaust gas from which the contaminants such as fly ash have been partially removed from the first dust collecting unit 40. At this time, the cleaning unit 70 removes contaminants such as sulfur and discharges the clean gas through the stack 80.

At this time, the clean gas discharged from the cleaning unit 70 is an inert gas having CO ₂ , H ₂ O, and N ₂ of 90% or more. At this time, the clean gas to be supplied to the coal drying apparatus 200 is CO2 (25%), H2O (5%), N2 (70%) or CO2 (20) , And O 2 (5%) are supplied with 95% or more of inert gas. Therefore, it is possible to prevent spontaneous ignition even if it is used as a heat source in the drying process because the concentration of active oxygen is low.

On the other hand, the temperature of the exhaust gas supplied to the air purifier 70 may still be high. A waste heat recovery unit 60 may be further included to make the temperature of the exhaust gas supplied from the cleaning unit 70 equal to the atmospheric temperature.

The waste heat recovery unit 60 absorbs the residual heat of the exhaust gas supplied from the first dust collecting unit 40 so as to become the ambient temperature, and supplies the exhaust gas of the ambient temperature to the cleaning unit 70. At this time, the exhaust gas can be supplied to the waste heat recovery unit 60 through the induction blower 50.

The first condenser 90 removes the moisture contained in the clean gas supplied from the cleaning unit 70 and supplies the moisture to the drying gas preheating unit 32.

According to an embodiment of the present invention, a second dust collector 110 may be further included.

The second dust collecting unit 110 collects a small amount of coal powder scattered during the coal drying process to remove the steam generated during the coal drying in the coal drying apparatus 200. The gas from which the coal powder has been removed from the second dust collecting unit 110 can be supplied to the differentiator 120.

In addition, according to the embodiment of the present invention, a second condenser 130 may be further included.

The second condenser 130 removes moisture contained in the gas supplied from the second dust collector 110 and supplies it to the differentiator 120.

The coal drying apparatus 200 dries and supplies high-water low-grade raw coal to the differentiator 120. The coal drying apparatus 200 performs primary drying using a clean gas preheated to about 150 ° C when low-grade raw coal is supplied to the chamber. Subsequently, the secondarily dried coal is re-dried using a microwave. The coal drying apparatus 200 can dissolve the water in the low-grade coal at a low temperature by using microwaves, thereby improving the drying speed and preventing spontaneous ignition.

That is, since the coal drying apparatus 200 uses the friction force by the molecular rotation or rearrangement by the speed corresponding to the frequency of the microwave through microwave drying, it is possible to raise the temperature faster than the thermal conduction heating. In the case of a material such as a low-grade coal organic material, the coal drying apparatus 200 permeates the microwave while the microwave is absorbed by the coal drying apparatus 200, thereby releasing heat. Therefore, the temperature inside the coal drying apparatus can be raised quickly.

Table 1 is a table comparing high-grade coal processed in a coal drying apparatus according to an embodiment of the present invention with low grade coal.

Low grade coal High-grade coal 1 High-grade coal 2 Total moisture (wt% ar) 36.4 5 6.5 Ash (wt% db) 3.0 3.21 3.18 VM (wt% db) 50.1 47.59 47.06 FC (wt% db) 42.9 44.2 43.26 Fuel ratio (-) 0.86 0.93 0.92 Heat value (kcal / kg ar) 4,253 6,910 6,905 Heat value (kcal / kg db) 6,291 7,210 7,150 C (wt% dAF) 69.76 71.03 71.52 H (wt% daf) 4.82 4.59 4.17 N (wt% daf) 1.15 1.16 1.14 S (wt% dAF) 0.12 0.16 0.14 O (wt% daf) 24.13 23.6 23.03 Particle Size (mm) 2 to 5 - -

As shown in Table 1, it can be seen that the water content of the low-grade coal is reduced through the coal drying apparatus of the high-grade system according to the embodiment of the present invention, and the thermal rate is increased.

As described above, the coal grade upgrading system according to the embodiment of the present invention can dry a low grade coal having a moisture content of 30% or more with a high grade coal for a coal-fired power plant fuel having a moisture content of 10% or less.

At this time, the exhaust gas of the combustion boiler is reused for preheating, and the pollutants are removed and reused as drying gas to remove the surface water of the low grade coal, and at the same time, It is possible to prevent spontaneous ignition by drying the degradable water at 150 ° C or lower.

An embodiment of the above-described coal drying apparatus will be described in detail with reference to Fig.

FIG. 2 is a cross-sectional view illustrating a coal drying apparatus according to an embodiment of the present invention, FIG. 3 is a cross-sectional view illustrating the position of the inert gas heat source supply unit shown in FIG. 2, FIG. 5 is a cross-sectional view illustrating the position of the microwave irradiation unit shown in FIG. 2, and FIG. 6 is a cross-sectional view illustrating the hot air discharge port shown in FIG.

2 to 6, a coal drying apparatus according to an embodiment of the present invention includes a chamber 210, a rotary shaft 250, a coal conveyance unit 220, a hot air supply unit 230, and a microwave irradiation unit 240 .

Specifically, the chamber 210 uses the supplied hot air and the irradiated microwave to dry the coal. The outer wall 211 of the chamber 210 may be formed of aluminum oxide having high resistance to microwave to prevent leakage of the irradiated microwave. The inner wall 212 of the chamber 210 may be formed of a Teflon material to prevent a fire caused by microwave reflection resistance.

The chamber 210 may include a coal inlet 213 into which coal is introduced. The coal inlet 213 may be formed in the upper part of the chamber 210. At this time, the coal inlet 213 may be formed on the upper surface of the chamber 210, but not limited thereto, as shown in FIG.

The chamber 210 may include a coal outlet 214 through which dried coal is discharged. The coal outlet 214 may be formed at the bottom of the chamber 210. The coal outlet 214 is formed on the lower side of the chamber 210, but not limited thereto, as shown in FIG.

The chamber 210 may further include a steam outlet 215 for increasing the discharge. The steam outlet 215 may be formed on the upper portion of the chamber 210. The steam outlet 215 can drain the moisture generated as the coal is dried. For this purpose, a steam outlet 215 may be formed in the upper surface of the chamber 210.

The chamber 210 may further include at least one inert gas inlet 260 for supplying an inert gas. The inert gas inlet 260 may be formed at the bottom of the chamber 210, as shown in FIG. 2, the inert gas inlet 260 is formed at the lower end of the microwave irradiating unit 240, but the present invention is not limited thereto. The inert gas supplied at the inert gas inlet 260 may be heated before being supplied to the chamber 210.

Two inert gas inlet ports 260 may be used, as shown in Figures 2 and 3. At this time, the inlet directions may be shifted from each other such that the inert gas discharged from the inlet of the one inert gas inlet port 260 is not directed to the other inert gas inlet port 260. Accordingly, the inert gas can be distributed evenly in the chamber 210. [

The inert gas introduced into the chamber 210 can prevent spontaneous ignition by suppressing the reaction of the dried coal with oxygen when exposed to air.

The rotary shaft 250 may be rotatably disposed at the center of the chamber 210. The rotary shaft 250 can rotate according to the driving of the motor 255.

The hot air supply unit 230 supplies heated exhaust gas into the chamber 210. At this time, the exhaust gas is an inert gas at 120 to 150 ° C where the exhaust gas of the combustion boiler is subjected to a dust collecting and desulfurizing process and moisture is removed.

The hot air supply unit 230 may be integrally formed on the rotary shaft 250 as shown in FIG. The hot air supply unit 230 may be formed in a pipe shape having a plurality of through holes 235 and an empty interior. Although the rotary shaft 250 and the hot air supply unit 230 are integrally formed in the embodiment of the present invention, the present invention is not limited thereto. The hot air supply part 230 formed in a pipe shape can be supplied with hot air from the lower part of the rotary shaft 250. The hot air supply part 230 may include a plurality of through holes 235.

The through holes 235 formed in the hot air supply part 230 may be formed at a density higher than that of the second area in the first area. Also, the through hole 235 may be formed only in the first region. The through hole 235 may be 1/5 to 1/10 times as large as the coal particles. For example, when the size of the coal particles injected into the chamber 210 is 20 to 50 mm, when the size of the through hole 235 is 1/10 or less of the coal particles, the supply amount of the exhaust gas is reduced and it is difficult to sufficiently dry the coal. If the size of the through hole 235 is 1/5 or more of the coal particles, the internal pressure of the chamber 210 may be increased due to the inflow amount of the exhaust gas and it may be difficult to control the internal temperature of the chamber 210.

In the case where the rotating shaft 250 and the hot air supply unit 230 are integrally formed, Teflon may be formed on the outer surface of the rotating shaft 250. Teflon formed on the outer surface of the rotary shaft 250 can prevent sparks due to reflected microwaves in the chamber.

The coal conveyance unit 220 conveys the coal supplied from the coal inlet 213 to the coal outlet 214 through the second region where the microwave is irradiated through the first region to which hot air is supplied.

The coal transfer part 220 may include blades 221 and 222, as shown in FIG.

The blades 221 and 222 are fixed to the rotating shaft 250 and can rotate according to the rotation of the rotating shaft 250. At this time, the blades 221 and 222 may include a first blade 221 formed in the first region and a second blade 222 formed in the second region.

The first blade 221 may be made of stainless steel or the like. In addition, the first blade 221 may be coated with Teflon having a low dielectric constant.

The second blade 222 may be made of a Teflon material having a low dielectric constant because the microwave is directly irradiated. Alternatively, the second blade 222 may be coated with Teflon on the surface of the stainless steel. In this case, the second blade 222 may be formed to a thickness of about 2 cm.

Teflon formed on the first blade 221 and the second blade 222 can prevent sparks by microwaves.

The microwave irradiation unit 240 irradiates the microwave to the second region of the chamber 210. The microwave irradiation unit 240 irradiates a microwave to re-dry the coal. The microwave irradiation unit 240 outputs a signal having a frequency of 2.45 GHz.

A plurality of microwave irradiation units 240 may be provided. Although two microwave irradiating units 240 are illustrated in FIG. 2, the present invention is not limited thereto, and three or more microwave irradiating units 240 may be provided. Here, as shown in FIGS. 2 and 5, the two microwave irradiation units 240 are shifted from each other in order to increase microwave irradiation efficiency and avoid microwave interference . However, in order to prevent the microwaves output from each of the microwave irradiation units 240 from flowing into the opposite microwave irradiation unit, the microwave output units are disposed in a crossed manner so that no microwave flows from the opposite microwave irradiation unit.

According to an embodiment of the present invention, a temperature sensor 270 for measuring the internal temperature of the chamber 210 may be further included.

The temperature sensor 270 can control the output of the microwave irradiation unit 240 when the temperature inside the chamber 210 is out of the set temperature range. That is, the temperature sensor 270 turns off the microwave irradiation unit 240 when the temperature in the chamber 210 is higher than the upper limit setting value, and turns on the microwave irradiation unit 240 when the temperature is lower than the lower limit setting value.

For example, the temperature sensor 270 can turn on the microwave irradiation unit 240 when the temperature inside the chamber 210 is 150 ° C or lower. The chamber 210 must be maintained at a temperature of 150 ° C or higher to be capable of internal bond water decomposition and release of coal. Accordingly, the temperature sensor 270 can control the microwave irradiation unit 240 so that the internal temperature of the chamber becomes 150 ° C or higher.

Also, the temperature sensor 270 can turn off the microwave irradiation unit 240 when the temperature inside the chamber 210 is 300 ° C or more. If the temperature inside the chamber exceeds 300 deg. C and the predetermined time has elapsed, the Teflon may be deformed, so that the microwave irradiation unit 240 is turned off when the temperature sensor 270 senses 300 deg.

According to an embodiment of the present invention, the rotary shaft 250 may further include at least one hot air outlet 280. As shown in FIG. 6, the hot air outlet 280 may be formed to prevent hot air from being discharged from the through hole 235 at a high pressure when the rotary shaft 250 is formed in a pipe shape.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the following claims And changes may be made without departing from the spirit and scope of the invention.

10: Combustion boiler
20:
30:
31: Atmospheric air preheating part
32: Drying gas preheating part
40: first dust collector
50: Manned blower
60: waste heat recovery unit
70:
80: stack
90: First condenser
110: second dust collecting part
120: differentiator
130: second condenser
200: Coal dryer
210: chamber
211: chamber outer wall
212: chamber inner wall
213: coal input
214: coal outlet
215: steam outlet
220: Coal transportation part
221: First blade
222: second blade
230: Hot air supply part
235: Through hole
240: Microwave irradiation part
250:
255: motor
260: inert gas inlet part
270: Temperature sensor
280:

Claims

A coal drying apparatus for drying coal, comprising:
A chamber having a coal inlet for charging coal at the upper portion thereof and a coal outlet for discharging coal dried at the lower portion thereof;
A coal transfer unit for transferring the coal charged into the coal inlet to the coal outlet;
A hot air supply unit for supplying hot air to a first region adjacent to the coal inlet to dry the coal; And
And at least one microwave irradiating unit for supplying microwaves to a second region adjacent to the coal discharging port to re-dry the dried coal in the hot air supplying unit.

The method according to claim 1,
Further comprising a rotation axis rotatably disposed in the center of the chamber,
Wherein the coal conveying portion further comprises a blade formed in a spiral shape, the coal conveying portion being coupled to the rotating shaft and rotating according to rotation of the rotating shaft.

3. The method of claim 2,
The coal transfer part
A first blade formed in the first region; And
And a second blade connected to the first helical blade and formed in the second region.

The method of claim 3,
Wherein the second spiral blade is formed of a Teflon material.

The method according to claim 1,
The hot air supply unit
Wherein a plurality of through holes are formed in a pipe shape to supply hot air to the inside of the chamber and a hot air is supplied into the chamber.

The method according to claim 1,
Wherein the surface of the rotating shaft formed in the second region is coated with a Teflon material.

The method according to claim 1,
The microwave irradiation part is formed in a plurality of,
Wherein the plurality of microwave irradiation units face each other and output microwaves in mutually staggered directions.

The method according to claim 1,
The chamber
Further comprising at least one inert gas inlet for supplying an inert gas.

9. The method of claim 8,
The chamber
Wherein a plurality of the inactive gas input ports are formed in a different direction from each other.

The method according to claim 1,
The chamber
And a steam outlet through which the steam is discharged.

The method according to claim 1,
And at least one temperature sensor for measuring the temperature in the chamber.

12. The method of claim 11,
The temperature sensor
Wherein the microwave irradiation unit is turned off when the temperature in the chamber is equal to or higher than the upper limit setting value, and the microwave irradiation unit is turned on when the temperature is lower than the lower limit setting value.

13. The method of claim 12,
Wherein the upper limit set value is 300 캜 and the lower limit set value is 150 캜.

The method according to claim 1,
The chamber
And the inner wall is coated with a Teflon material to prevent damage by the microwave.

Combustion boiler;
A pulverizer for pulverizing and supplying coal supplied to the combustion boiler;
A burning portion for recovering the heat of the exhaust gas generated after the combustion from the combustion boiler;
A preheating unit for preheating the air using the heat of the exhaust gas supplied from the cut-away portion;
A first dust collecting part for collecting fly ash from the exhaust gas;
A purifier configured to purge residual pollutants contained in the exhaust gas supplied from the dust collecting unit and to supply the generated purge gas to the preheater; And
And a coal drying device for drying the charged coal using the preheated clean gas preheated by the preheating section, irradiating microwaves, re-drying the coal dried by the clean gas, and supplying the dried coal to the differentiator.

16. The method of claim 15,
Further comprising: a first condenser for removing moisture of the clean gas from which contaminants have been removed from the cleaner and supplying the cleaned gas with moisture to the preheater.

16. The method of claim 15,
And a waste heat absorbing unit for absorbing the residual heat from the first dust collector and supplying the exhaust gas of the ambient temperature to the clean unit.

16. The method of claim 15,
The pre-
An air preheater for preheating atmospheric air and supplying the preheated air to the combustion boiler; And
And a drying gas preheating unit for preheating the clean gas and supplying the preheating gas to the coal drying apparatus.

19. The method of claim 18,
The coal drying apparatus
A chamber having a coal inlet through which the coal is injected into the upper portion and a coal outlet through which the coal dried in the lower portion is discharged into the pulverizer;
A coal transfer unit for transferring the coal charged into the coal inlet to the coal outlet;
A hot air supply unit for supplying a preheated clean gas from the drying gas preheating unit to a first region adjacent to the coal inlet to dry the coal; And
And at least one microwave irradiation unit for supplying the microwave to a second area adjacent to the coal discharge port.

20. The method of claim 19,
The coal drying apparatus
Further comprising a rotation axis rotatably disposed in the center of the chamber,
Wherein the coal conveying unit further comprises a blade which is coupled to the rotation shaft and rotates in accordance with rotation of the rotation shaft and is formed in a spiral shape,

21. The method of claim 20,
The coal transfer part
A first blade formed in the first region; And
And a second blade connected to the first helical blade and formed in the second region.

21. The method of claim 20,
The hot air supply unit
And a plurality of through holes are formed in the pipe to supply hot air to the inside of the chamber.

21. The method of claim 20,
The microwave irradiation part is formed in a plurality of,
Wherein the plurality of microwave irradiation units face each other and output microwaves in mutually staggered directions,

21. The method of claim 20,
The chamber
Further comprising a steam outlet through which steam is discharged.

25. The method of claim 24,
And a second dust collecting part for removing the coal powder contained in the steam discharged from the steam discharge port and supplying the same to the differentiator.

26. The method of claim 25,
Further comprising a second condenser formed between the second dust collecting unit and the differentiator to remove moisture of the steam from which the coal powder has been removed and to supply the steam to the differentiator.