AU2013374018B2

AU2013374018B2 - Gas-extractable pulverized coal boiler

Info

Publication number: AU2013374018B2
Application number: AU2013374018A
Authority: AU
Inventors: Lin Chen; Guangming Lu; Daping SHEN; Shengmei WANG; Daohong WU; Yulin Wu
Original assignee: Beijing Shenwu Environmental and Energy Technology Co Ltd
Current assignee: Beijing Shenwu Environmental and Energy Technology Co Ltd
Priority date: 2013-01-18
Filing date: 2013-05-16
Publication date: 2016-02-04
Anticipated expiration: 2033-05-16
Also published as: ZA201505206B; WO2014110885A1; RU2015133247A; RU2612682C2; AU2013374018A1

Abstract

A gas-extractable pulverized coal boiler (100) comprises a boiler main body (1) defining a hearth (11); a regenerative rotating commutating heater (2); a fume passage (3), wherein an inlet end of the fume passage (3) is communicated with the hearth (11) and an outlet end of the fume passage (3) is communicated with the regenerative rotating commutating heater (2), so that fume in the hearth (11) is delivered into one of at least paired accommodating portions (25) and exchanges heat with a heat carrier (23) accommodated in the accommodating portion (25), and multiple superheaters are provided in the fume passage (3); an air passage (4), used for delivering air at least into the other one of the paired accommodating portions (25), so that a heat carrier (23) accommodated in the accommodating portion (25) exchanges heat with air; a high-temperature gas-extracting passage (5), wherein one end of the high-temperature gas-extracting passage (5) is communicated with one end of the fume passage (3) facing the hearth (11), and the other end of the high-temperature gas-extracting passage (5) is communicated with the outlet end of the fume passage (3); and a gas-extracting control unit (51), used for controlling a first amount of fume supplied through the high-temperature gas-extracting passage (5). By means of the pulverized coal boiler, the air preheating temperature is raised and controllable operation is achieved, the thermal efficiency of the boiler is improved, and the problem of operation stability and reliability of a large-scale boiler which carries out power generation with a low volatile content is solved.

Description

GAS-EXTRACTABLE PULVERIZED COAL BOILER FIELD The present invention relates to the field of heat-exchange, and more particularly to a 5 gas-extractable pulverized coal boiler. BACKGROUND Currently, lignite, long-flame coal, non-caking coal, gas coal, meagre coal and a small amount of anthracite may be used in Chinese coal powder boilers, among which D the lignite, long-flame coal, non-caking coal having higher volatile matters are most commonly used. China is enriched with anthracite occupying about 19% of the total coal storage. However, the anthracite has less volatile matters which cannot be burnt completely. Thus, during usage, low efficiency and low grade as well as severe pollution are the serious problems commonly faced. W-flame boiler is the main one for burning the 5 low-volatile coal, and it substantially overcomes the problem of stability and reliability of large-scale boilers using the low-volatile coal. However, the burning effects are still inferior. The low-volatile coal needs sufficient air to satisfy the oxygen demand during combustion. Meanwhile, the low-volatile coal such as the anthracite and meager coal has a higher ignition temperature, and it is difficult to ignite as well as achieve stable coal D powder stable combustion, thus limiting the applicability of such coals. To solve the ignition and burning stability of the low-volatile coal, using air with high temperature to ignite the low-volatile coal such as the anthracite and the meager coal etc may overcome the problems, so that energy may be reasonably and sufficiently utilized. However, current coal powder boilers use a metal air preheater to recycle energy in the 5 flue gas for preheating the air for burning the coal powder, due to the structural and material limitation, the flue gas can only be decreased to 500C or less to recycle the residual heat. Thus, energy saving efficiency is inferior and the air temperature may be heated to a temperature at most 300-400C. In addition, there is a low temperature corrosion problem during the operation of a rotary air preheater using a metal corrugated D plate. And since flow channels for the gas are narrow, dust accumulation or blockage, etc may easily occur.

SUMMARY Embodiments of the present invention seek to solve at least one of the problems existing in the related art to at least some extent. Accordingly, the present invention 5 provides a gas-extractable pulverized coal boiler having preheated air with enhanced and adjustable temperature. According to an embodiment of the present invention, a gas-extractable pulverized coal boiler may be provided, comprising: a boiler body defined with a furnace hearth; a rotary-type regenerative heater comprising: a main heat exchanging body; a driving D device for driving the main heat exchanging body to rotate about a central axis thereof; a separating member arranged in the main heat exchanging body along a direction of the central axis to separate the main heat exchanging body into at least a pair of receiving portions, each pair of the receiving portions being arranged diametrically in opposite, with respect to the central axis; a heat carrier received in the receiving portions respectively 5 and made of a non-metal solid material; a flue gas passage, with an inlet thereof being communicated with the furnace hearth and an outlet thereof being communicated with the rotary-type regenerative heater so that a flue gas generated in the furnace hearth is introduced into one receiving portion of the paired receiving portions in the at least one of the pair of the receiving portions and performs heat-exchange with the heat carrier D received therein, a plurality of superheaters being provided in the flue gas passage; an air passage for introducing the air into the other receiving portion of the paired receiving portions, so that the heat carrier received therein exchanges heat with the air; a high temperature gas extraction passage, with an end thereof being communicated with an end of the flue gas passage facing toward the furnace hearth and the other end thereof 5 being communicated with the outlet of the flue gas passage; and a gas-extraction control unit for regulating a first flue gas amount supplied via the high temperature gas extraction passage. According to an embodiment of the present invention, by using the rotary-type regenerative heater, the residual heat of the flue gas with a temperature up to 1200C D may be maximally recycled, so that the combustion air entering the furnace hearth may be sufficiently preheated. Thus, the low-volatile coal such as the anthracite and the meager coal may be combusted stably and sufficiently in the boiler. In addition, the powdered solid fuel boiler according to embodiments of the present invention may further have the following additional features: According to an embodiment of the present invention, the gas-extractable pulverized 5 coal boiler may comprise: at least one low temperature gas extraction passage, with an end thereof being communicated with at least one part of the flue gas passage between a plurality of superheaters, and the other end thereof being communicated with the outlet of the flue gas passage. The gas-extraction control unit may regulate a second flue gas amount supplied via the at least one low temperature gas extraction passage. Thus, by D the low temperature gas extraction passage, the flue gas may be extracted from different parts of the pulverized coal boiler. And the extraction amount and temperature of the flue gas may be controlled based on actual requirement to satisfy different demands of the pulverized coal boiler to the preheated temperature of the air. According to an embodiment of the present invention, the heat carrier may have a small 5 ball shaped, scaly shaped, or porous structure. According to an embodiment of the present invention, the pulverized coal may be made of at least one of anthracite or meagre coal. According to an embodiment of the present invention, the gas-extraction control unit may comprise an electrically or pneumatically actuated high temperature flue gas control D valve which may be arranged at the high temperature gas extraction passage. Thus, by the high temperature flue gas control valve, the amount of the glue gas with high temperature in the high temperature gas extraction passage may be adjusted accordingly. According to an embodiment of the present invention, the gas-extraction control unit may further comprise: at least one electrically or pneumatically actuated low temperature 5 flue gas control valve provided at the corresponding low temperature gas extraction passage. Thus, by the low temperature flue gas control valve, the amount of the glue gas with low temperature in the low temperature gas extraction passage may be adjusted accordingly. According to an embodiment of the present invention, the gas-extraction control unit D may control at least one of the high temperature flue gas control valve and the low temperature flue gas control valve so that the air temperature at an outlet of the air passage may be about 400-1OOOC.

According to an embodiment of the present invention, a platen superheater and a wrapped wall superheater may be arranged in turn from the inlet of the flue gas passage toward the outlet of the flue gas passage. According to an embodiment of the present invention, a coal economizer may be 5 provided in the flue gas passage near the outlet of the flue gas passage. Additional aspects and advantages of embodiments of present invention will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present invention. D BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects and advantages of embodiments of the present invention will become apparent and more readily appreciated from the following descriptions made with reference to the drawings, in which: Fig. 1 is a schematic view of a gas-extractable pulverized coal boiler according to an 5 embodiment of the present invention; Fig. 2 is a top view of a rotary-type regenerative heater in a gas-extractable pulverized coal boiler according to an embodiment of the present invention. DETAILED DESCRIPTION D Reference will be made in detail to embodiments of the present invention. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present invention. The embodiments shall not be construed to limit the present invention. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the 5 descriptions. In the specification, unless specified or limited otherwise, relative terms such as "central", "longitudinal", "up", "below", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", and "radial" should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These D relative terms are for convenience of description and do not require that the present invention be constructed or operated in a particular orientation. In addition, terms such as "first" and "second" are used herein for purposes of description and are not intended to indicate or imply relative importance or significance or to imply the number of indicated technical features. Thus, the feature defined with "first" and "second" may comprise one or more of this feature. In the description of the present invention, "a plurality of" means 5 two or more than two, unless specified otherwise. In the description of the present invention, it should be understood that, unless specified or limited otherwise, the terms "mounted," "connected," and "coupled" and variations thereof are used broadly and encompass such as mechanical or electrical mountings, connections and couplings, also can be inner mountings, connections and D couplings of two components, and further can be direct and indirect mountings, connections, and couplings, which can be understood by those skilled in the art according to the detail embodiment of the present invention. In the following, a gas-extractable pulverized coal boiler 100 according to an embodiment of the present invention will be described with reference to Fig. 1. 5 As shown in Fig. 1, a gas-extractable pulverized coal boiler 100 according to an embodiment of the present invention may comprise a boiler body 1, a rotary-type regenerative heater 2, a flue gas passage 3, an air passage 4, a high temperature gas extraction passage 5 and a gas-extraction control unit 51. The rotary-type regenerative heater 2 may perform heat-exchange between the flue D gas with high temperature and the air to be preheated, so that the air to be preheated may be increased to a certain level. The rotary-type regenerative heater 2 may comprise a main heat exchanging body 21, a driving device (not shown), a separating member 22 and a heat carrier 23, as shown in Figs. 1 and 2. The driving device may be used to drive the main heat exchanging body 21 to rotate about a central axis 24 of the main heat 5 exchanging body 21. The separating member 22 may be arranged in the main heat exchanging body 21 along a direction of the central axis 24, to separate the main heat exchanging body 21 into at least a pair of receiving portions 25, each pair of the receiving portions 25 being arranged diametrically in opposite with respect to the central axis 24. The heat carrier 23 is received or contained in the receiving portions 25. And the heat D carrier 23 may be made of a non-metal solid material. According to an embodiment of the present invention, the main heat exchanging body 21 may be formed into a hollowed cylindrical body, and the separating member 22 may be substantially of a plate shape. The separating member 22 may extend along the central axis of the main heat exchanging body 21, to separate the main heat exchanging body 21 into a pair of receiving portions 25, and the heat carrier may be loaded in the two 5 receiving portions 25 which may be made of a non-metal solid material. The flue gas and the air to be preheated may be supplied into the two receiving portions 25, respectively. And the main heat exchanging body 21 may be driven to rotate by the driving device (not shown). The flue gas may exchange heat with the heat carrier in the receiving portion 25 to absorb the heat in the flue gas, the air to be preheated may exchange heat with the D heat carrier in the other receiving portion 25, so that the temperature of the air to be preheated is increased accordingly. Of course, the present invention is not limited hereto. According to embodiments of the present invention, the separating member 22 may divide the main heat exchanging body 21 into two pairs, three pairs or more. 5 In the prior heat exchanging system, the exit temperature of the flue gas after passing through the gas heat-exchanger may not be lowered to 130C or less, because this may lead to sulphuric acid to be separated out, so that the gas heat-exchanger made of metal may be corroded. However, in the rotary-type regenerative heater 2 of the present invention, especially for the flue gas with high temperature containing sulfur, the D heat carrier is made of nonmetal solid material such as SiC or porcelain etc., the dew point of sulfur at 130C causing corrosion may not need to be considered, so that the exit temperature of the flue gas with high temperature may be decreased to that less than the dew point of the sulfur, thus maximal heat exchanging may be performed. According to an embodiment of the present invention, the exit temperature of the flue gas with high 5 temperature out of the gas heat-exchanger may be lower than 130C. Further, the exit temperature of the flue gas with high temperature out of the gas heat-exchanger may be lower than 70 C, which is almost impossible for a conventional heat-exchanger. In addition, when the exit temperature is lowered to a temperature less than the dew point, the water steam may be separated out into liquid water, so that latent heat may be D released, and the heat absorbed 3 times when changing from the liquid water having a temperature of 100 C to the gas water having a temperature of 100 C than that of the liquid water from 0 C to 100 C. Because the heat carrier is made of non-metal solid material, the heat carrier in the receiving portion may be cleansed for further use when the sulfur is deposited to a certain degree, so that component substitution cost may be decreased. In addition, according to the computation method commonly used in the art, in 5 the flue gas heat exchanging process of the combusting boiler, the whole boiler efficiency may be increased by 0.5% for each 10 C temperature decrease at the flue gas exit, and the released latent heat increases the boiler efficiency by approximately 1.5%. Therefore, when the temperature of the flue gas may be decreased to, for example, 70'C, the efficiency of the whole boiler may be increased by 4.5% or more (0.5%X6+1.5%), thus D saving a large amount of coal to be burnt in the boiler. In addition, the useable coal may be enlarged, i.e., the coal quality may be lowered to further reduce manufacturing cost. According to an embodiment of the present invention, the boiler body 1 may be defined with a furnace hearth 11. An inlet of the flue gas passage 3 may be communicated with the furnace hearth 11, and an outlet of the flue gas passage 3 may be 5 communicated with the rotary-type regenerative heater 2 so that the flue gas in the furnace hearth 11 may be introduced into at least one receiving portion of the paired receiving portions of the rotary-type regenerative heater 2 to perform heat-exchange with the heat carrier contained in the corresponding receiving portions, a plurality of superheaters may be provided in the flue gas passage 3. The air passage 4 may D introduce air into the other receiving portion of the paired receiving portions of the rotary-type regenerative heater 2, so that the heat carrier received therein may perform heat-exchange with the air accordingly. An end of the high temperature gas extraction passage 5 may be communicated with an end of the flue gas passage 3 facing toward the furnace hearth 11 and the other end of the high temperature gas extraction passage 5 5 may be communicated with the outlet of the flue gas passage 3. The gas-extraction control unit 51 may control a first flue gas amount supplied via the high temperature gas extraction passage 5. In the following, for exemplary illustration purpose, the main heat exchanging body 21 is rotated in an anticlockwise direction, and the flue gas is supplied into the main heat D exchanging body 21 at the right side of the central axis, and the air to be preheated is supplied into the main heat exchanging body 21 from the left side of the central axis.

As shown in Fig. 1, the boiler body 1 is defined with the furnace hearth 11 to receive pulverized coal, an end of the flue gas passage 3 is communicated with the furnace hearth 11, and the other end thereof is communicated with the rotary-type regenerative heater 2 to supply the flue gas generated in the furnace hearth 11 into a first receiving 5 portion 211 of the rotary-type regenerative heater 2, i.e. the right side of the rotary-type regenerative heater 2 as shown in Fig. 1. A second receiving portion 212 of the rotary-type regenerative heater 2, i.e. the left side of the rotary-type regenerative heater 2 as shown in Fig. 1, is supplied with the air to be preheated. When the main heat exchanging body 21 is not rotated, the flue gas exchanges heat with the heat carrier D received in the first receiving portion 211, to raise the temperature of the heat carrier. After the heat carrier absorbs heat, the main heat exchanging body 21 is rotated in the anticlockwise direction, the first receiving portion 211 is rotated to the left side of the central axis, the second receiving portion 212 is rotated to the right side of the central axis. The heat carrier in the first receiving portion 211 rotated to the left side performs 5 heat-exchange with the air to be preheated so that the air temperature is increased, while the flue gas performs heat-exchange with the heat carrier received in the second receiving portion 212 rotated to the right side. The main heat exchanging body 21 is further rotated in the anticlockwise direction, and the first receiving portion 211 is rotated back to the right side of the central axis, and D the second receiving portion 212 is rotated back to left side of the central axis, the heat carrier in the second receiving portion 212 rotated back to the left side performs heat-exchange with the air to be preheated, and the flue gas performs heat-exchange with the heat carrier in the first receiving portion 211 rotated back to the right side, and the process is repeated to complete the heating of the air to be preheated. 5 Because the top part of the furnace hearth 11 has a higher temperature, an end of the high temperature gas extraction passage 5 may be communicated with the top art of the furnace hearth 11, and the other end of the high temperature gas extraction passage 5 is communicated with the outlet of the flue gas passage 3 to supply the flue gas with high temperature into the rotary-type regenerative heater 2. The gas-extraction control D unit 51 may be provided at the high temperature gas extraction passage 5 to control the first flue gas amount supplied via the high temperature gas extraction passage 5.

In the gas-extractable pulverized coal boiler 100 according to an embodiment of the present invention, by using the rotary-type regenerative heater 2, the residual heat of the flue gas with a temperature up to 1200'C may be maximally recycled, so that the combustion air entering the furnace hearth 11 may be sufficiently preheated. Thus, the 5 low-volatile coal such as the anthracite and the meager coal etc. may be combusted stably and sufficiently in the boiler. According to an embodiment of the present invention, the gas-extractable pulverized coal boiler 100 may further comprise: at least one low temperature gas extraction passage 6, with an end thereof being communicated with at least one part of the flue gas D passage 3 between the plurality of superheaters, and the other end thereof being communicated with the outlet of the flue gas passage 3. The gas-extraction control unit 51 may regulate a second flue gas amount supplied via the at least one low temperature gas extraction passage 6. Thus, by the low temperature gas extraction passage 6, the gas may be extracted from different parts of the pulverized coal boiler based on actual 5 requirements. And the extraction amount and temperature of the flue gas may be controlled based on actual requirement to satisfy different demands of the pulverized coal boiler to the preheated temperature of the air. It should be noted that the number of the low temperature gas extraction passages 6 may be set based on actual requirements. For example, as shown in Fig. 1, there is two low temperature gas extraction D passage 6. One low temperature gas extraction passage 6 has one end provided between a wrapped wall superheater 8 and a tail flue passage superheater 9 and the other end being communicated with the outlet of the flue gas passage 3. The other low temperature gas extraction passage 6 has one end provided between the tail flue passage superheater 9 and a coal economizer 10 and the other end being communicated 5 with the outlet of the flue gas passage 3. And there are two gas-extraction control unit 51 which are provided at the two low temperature gas extraction passages 6 respectively. According to an embodiment of the present invention, the heat carrier may have a small ball shaped, scaly shaped, or porous structure Thus, by increasing contact area, the heat-exchange of the flue gas and the air to be D preheated with the heat carrier may be enhanced accordingly. According to an embodiment of the present invention, the coal powder is made of at least one of anthracite or meagre coal. However, it should be noted that the coal powder may be lignite, long-flame coal, non-caking coal, gas coal etc. According to an embodiment of the present invention, the gas-extraction control unit 51 may comprise an electrically or pneumatically actuated high temperature flue gas control valve which may be arranged at the high temperature gas extraction passage 5. 5 That is to say, the gas-extraction control unit 51 may be an electrically actuated high temperature flue gas control valve, or a pneumatically actuated high temperature flue gas control valve. Thus, by the high temperature flue gas control valve, the amount of the glue gas with high temperature in the high temperature gas extraction passage 5 may be adjusted accordingly. D According to an embodiment of the present invention, the gas-extraction control unit 51 may further comprise at least one electrically or pneumatically actuated low temperature flue gas control valve provided at the corresponding low temperature gas extraction passage 6. That is to say, the gas-extraction control unit 51 may be an electrically actuated low temperature flue gas control valve or a pneumatically actuated 5 high temperature flue gas control valve. When the gas-extractable pulverized coal boiler 100 may comprise a plurality of the low temperature gas extraction passages 6, there may be one low temperature flue gas control valve. And the low temperature flue gas control valve may be provided at one of the low temperature gas extraction passages 6. When the number of the low temperature flue gas control valves is less than the number D of the low temperature gas extraction passages 6, the low temperature flue gas control valves may be provided at some of the low temperature gas extraction passages 6. When the number of the low temperature flue gas control valves equals the number of the low temperature gas extraction passages 6, the low temperature flue gas control valves may be provided at the low temperature gas extraction passages 6 respectively. Therefore, by 5 the low temperature flue gas control valve, the amount of the flue gas with low temperature in the low temperature gas extraction passages 6 may be adjusted accordingly. According to an embodiment of the present invention, the gas-extraction control unit 51 may control at least one of the high temperature flue gas control valve and the low D temperature flue gas control valve, so that the air temperature of the air passage 4 at the outlet may be 400-1000'C. That is to say, the gas-extraction control unit 51 may have a control device (not shown), and the gas-extraction control unit 51 may control only the high temperature flue gas control valve or the low temperature flue gas control valve, so long as the temperature of the air to be preheated may enter the furnace hearth 11 with a temperature of 400-1000 C. 5 According to an embodiment of the present invention, the platen superheater 7 and the wrapped wall superheater 8 may be arranged in turn from the inlet of the flue gas passage 3 toward the outlet of the flue gas passage 3. As shown in Fig. 1, the platen superheater 7 and the wrapped wall superheater 8 may be provided in turn at the connecting point of the furnace hearth 11 with the flue gas passage 3. D According to an embodiment of the present invention, a coal economizer 10 may be provided in the flue gas passage 3 near the outlet of the flue gas passage 3. By the rotary-type regenerative heater 2, the flue gas and air may be alternatively switched to be heat-exchanged with the heat carrier, so that the physical heat in the flue gas with high temperature may be maximally recycled, thus energy may be saved greatly 5 and the thermal efficiency of the boiler may be improved accordingly. Because the preheated air entering the furnace hearth 11 is relatedly high, the flame burning area is extended to almost the boundaries of the furnace hearth 11, so that the temperature distribution in the furnace becomes even. Due to the rotary-type regenerative heater 2, the low-volatile coal with low caloric value may be stably and continuously combusted via D the preheated air with high temperature, thus the burnout rate of the fuel is increased, thus extending the applicable range of the low-volatile fuel. Thus, the low system efficiency, high pollution etc. during the application of the low-volatile coal such as the anthracite or meagre coal is coped with thoroughly. Meanwhile, the stability and sustainability of the large-scale boilers in a power plant using the low-volatile fuel is 5 solved accordingly. Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment", "another example," "an example," "a specific example," or "some examples," means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or D example of the present invention. Thus, the appearances of the phrases such as "in some embodiments," "in one embodiment", "in an embodiment", "in another example," "in an example," "in a specific example," or "in some examples," in various places throughout this specification are not necessarily referring to the same embodiment or example of the present invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or 5 examples. Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present invention, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present D invention.

Claims

1. A gas-extractable pulverized coal boiler, comprising: a boiler body defined with a furnace hearth; 5 a rotary-type regenerative heater comprising: a main heat exchanging body; a driving device for driving the main heat exchanging body to rotate about a central axis thereof; a separating member arranged in the main heat exchanging body along a D direction of the central axis, to separate the main heat exchanging body into at least a pair of receiving portions, each pair of the receiving portions being arranged diametrically in opposite with respect to the central axis; a heat carrier received in the receiving portions respectively and made of a non-metal solid material; 5 a flue gas passage, with an inlet thereof being communicated with the furnace hearth and an outlet thereof being communicated with the rotary-type regenerative heater, so that a flue gas generated in the furnace hearth is introduced into at least one receiving portion of the paired receiving portions and performs heat-exchange with the heat carrier received therein, a plurality of superheaters being provided in the flue gas passage; D an air passage for introducing air into the other receiving portion of the paired receiving portions so that the heat carrier received therein exchanges heat with the air; a high temperature gas extraction passage, with an end thereof being communicated with an end of the flue gas passage facing toward the furnace hearth and the other end thereof being communicated with the outlet of the flue gas passage; and 5 a gas-extraction control unit for regulating a first flue gas amount supplied via the high temperature gas extraction passage.

2. The gas-extractable pulverized coal boiler according to claim 1, further comprising: at least one low temperature gas extraction passage, with an end thereof being communicated with at least one part of the flue gas passage between a plurality of D superheaters, and the other end thereof being communicated with the outlet of the flue gas passage, wherein the gas-extraction control unit regulates a second flue gas amount supplied via the at least one low temperature gas extraction passage.

3. The gas-extractable pulverized coal boiler according to claim 1, wherein the heat carrier has a small ball shaped, scaly shaped, or porous structure.. 5

4. The gas-extractable pulverized coal boiler according to claim 1, wherein the pulverized coal is made of at least one of anthracite or meagre coal.

5. The gas-extractable pulverized coal boiler according to claim 2, wherein the gas-extraction control unit comprises an electrically or pneumatically actuated high temperature flue gas control valve which is arranged at the high temperature gas D extraction passage.

6. The gas-extractable pulverized coal boiler according to claim 5, wherein the gas-extraction control unit further comprises: at least one electrically or pneumatically actuated low temperature flue gas control valve provided at the corresponding low temperature gas extraction passage. 5

7. The gas-extractable pulverized coal boiler according to claim 6, wherein the gas-extraction control unit controls at least one of the high temperature flue gas control valve and the low temperature flue gas control valve so that the air temperature at an outlet of the air passage is about 400-1OOOC.

8. The gas-extractable pulverized coal boiler according to claim 1, wherein a platen D superheater and a wrapped wall superheater are arranged in turn from the inlet of the flue gas passage toward the outlet of the flue gas passage.

9. The gas-extractable pulverized coal boiler according to claim 1, wherein a coal economizer is provided in the flue gas passage near the outlet of the flue gas passage.