AU2012259943B2

AU2012259943B2 - Fluidized bed drying device

Info

Publication number: AU2012259943B2
Application number: AU2012259943A
Authority: AU
Inventors: Kenichi Arima; Masaaki Kinoshita; Ryuhei Takashima
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2011-05-20
Filing date: 2012-05-18
Publication date: 2015-07-16
Anticipated expiration: 2032-05-18
Also published as: WO2012161130A1; AU2012259943A1; JP2012241999A

Abstract

Provided are: a drying furnace (5) that forms a fluidized bed (3) internally by using a fluidized gas to force lignite to flow from an upstream side to a downstream side; a cyclone dust collector (34) which is disposed inside the drying furnace (5), and which is capable of collecting lignite contained in exhaust gas discharged from the drying furnace; and an ejector (35) which is disposed inside the drying furnace (5), and which feeds the lignite collected by the dust collector (34) toward the upstream side of the fluidized bed (3).

Description

1 DESCRIPTION FLUIDIZED BED DRYING DEVICE Field [0001] The present invention relates to a fluid-bed drier that dries wetting fuel such as lignite with fluidizing the wetting fuel. Background [0002] As such a fluid-bed drier, a fluid-bed drier including a drying room of which bottom is a diffusing plate having a number of openings and capable of ventilating the air, and a blast room located at the lower part of the drying room has been known in the past (For example, Patent Literature 1). The fluid-bed drier dries the material to be dried with fluidizing the material by supplying the fluidizing gas (drying gas) from the blast room through the diffusing plate to the drying room. The fluidizing gas supplied to the drying room is emitted, with the vapor generated from the material to be dried, from an emission opening formed at the upper part of the drying room. Citation List Patent Literature [0003] Patent Literature 1: Japanese Laid-open Patent Publication No. 2008-89243 [0003a] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. Summary Technical Problem [0004] According to a fluid-bed drier in the past as described above, the gas emitted through the emission opening includes the dust-shaped material that has been dried in the drying room. Thus, the emission opening of the fluid-bed drier is generally connected to a dust collector. It is necessary to separately attach a component for the collected dried material 2 when the precipitator is provided at the outside of the fluid bed drier. This makes the structure of the fluid-bed drier complicated. [0005] Thus, it is considered that the precipitator is provided around the emission opening in the drying room. The dried material accumulates in the dust collector in that case. It is necessary to remove the accumulated material. However, when the material to be removed has not been dried, the material that has not been dried is mixed with the dried material to be discharged from the drying room. Thus, the material to be discharged is possibly not dried. [0006] In light of the foregoing, an objective of the present invention is to provide a fluid-bed drier capable of preferably drying wetting fuel even when a precipitator is provided in a drying room. [0006a] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. [0006b] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". Solution to Problem [0007] According to an aspect of the present invention, a fluid-bed drier includes: a drying furnace configured to form a fluid bed therein by fluidizing wetting fuel from an upper stream to a lower stream with fluidizing gas, a precipitator provided in the drying furnace and configured to collect the wetting fuel included in flue gas discharged from the drying furnace, and an ejector provided in the drying furnace and configured to supply the wetting fuel collected with the precipitator toward the upper stream of the fluid bed.

2a [0008] According to the structure, the ejector can return the wetting fuel collected in the precipitator to the upper stream of the fluid bed. This can prevent the supply of the wetting fuel that has not been dried to the lower stream of the fluid bed. Thus, the possibility in that the wetting fuel discharged from the lower stream is Docket No. PMHA-13051-PCT 3 not dried can be reduced. Returning the wetting fuel that has not been dried to the upper stream of the fluid bed can facilitate the dry of the wetting fuel in the fluid bed. Thus, the wetting fuel can preferably be dried even when 5 the precipitator is provided in the drying room. [0009] Advantageously, in the fluid-bed drier, the precipitator includes: a suction opening configured to inhale the flue gas; a cyclone precipitator unit configured to separate the wetting fuel from the inhaled flue gas; a 10 fuel discharge opening configured to discharge the wetting fuel separated in the cyclone precipitator unit; and a gas emission opening configured to emit the flue gas from which the wetting flue has been separated in the cyclone precipitator unit, and the ejector is connected to the fuel 15 discharge opening. [0010] According to the structure, the wetting fuel separated from the flue gas in the cyclone precipitator unit can be discharged from the fuel discharge opening. The ejector can return the wetting fuel discharged from the 20 fuel discharge opening to the fluid bed. [0011] Advantageously, in the fluid-bed drier, the ejector is supplied with superheated steam and the ejector supplies the lignite discharged from the fuel discharge opening to the upper stream of the fluid bed together with 25 the superheated steam by passing the supplied superheated steam through the fuel discharge opening. [0012] According to the structure, the ejector can supply the wetting fuel collected in the precipitator to the upper stream of the fluid bed using the superheated 30 steam. This can facilitate the dry of the wetting fuel and can also facilitate the dry of the inside of the fluid bed. Advantageous Effects of Invention [0013] According to the fluid-bed drier of the present Docket No. PMHA-13051-PCT 4 invention, providing an ejector in the drying furnace can return the collected wetting fuel to the upper stream of the fluid bed even when a precipitator is provided in the drying room. This can prevent the discharge of the wetting 5 fuel that has not been dried. Thus, the wetting fuel can preferably be dried. Brief Description of Drawings [0014] FIG. 1 is a schematic structure diagram of an integrated coal gasification combined cycle applying a 10 fluid-bed drier according to the present embodiment. FIG. 2 is a schematic structure diagram schematically illustrating the fluid-bed drier according to the present embodiment. Description of Embodiments 15 [0015] Hereinafter, a fluid-bed drier according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiment to be described below. Further, the components in the embodiment include 20 components that are exchangeable and simple for persons skilled in the art, or materials substantially equivalent to the components. [Embodiment] [0016] FIG. 1 is a schematic structure diagram of an 25 integrated coal gasification combined cycle applying a fluid-bed drier according to the present embodiment. An Integrated Coal Gasification Combined Cycle (IGCC) 100 applying a fluid-bed drier 1 according to the present embodiment employs an air combustion system that generates 30 gasified coal in a gasification furnace with the air as oxidant so as to generate electric power with supplying the gasified coal purified in a gas refinery as combustion gas to a gas turbine facility. In other words, the integrated Docket No. PMHA-13051-PCT 5 coal gasification combined cycle 100 according to the present embodiment is an air combustion (air blown) power plant. Lignite is used as wetting material to be supplied to the gasification furnace in that case. 5 [0017] Note that any fuel that has a high moisture content, for example, low rank coal including subbituminous coal, peat including sludge, or high rank coal can also be used as the wetting material although lignite is used in the present embodiment. Further, not only coal including 10 lignite but also biomass used as a reusable biological organic resource can be used as the wetting material. For example, forest thinning wood, scrap wood, driftwood, grasses, waste materials, sludge, or tires, or recycle fuel (pellets or chips) made of the above-mentioned materials 15 can also be used. [0018] As illustrated in FIG. 1, the integrated coal gasification combined cycle 100 includes a stoker 111, the fluid-bed drier 1, a coal mill 113, a coal gasification furnace 114, a char recovery unit 115, a gas refinery 116, 20 a gas turbine unit 117, a steam turbine unit 118, a generator 119, and an Heat Recovery Steam Generator (HRSG) 120 in the present embodiment. [0019] The stoker 111 includes a raw coal banker 121, a coal supplier 122, and a crasher 123. The raw coal banker 25 121 is capable of storing lignite so as to drop a predetermined amount of lignite to the coal supplier 122. The coal supplier 122 conveys the lignite dropped from the raw coal banker 121 with a conveyer or the like and drops the lignite to the crasher 123. The crasher 123 finely 30 crashes the dropped lignite so as to grind the lignite to fine particles. [0020] The fluid-bed drier 1 supplies drying steam such as superheated steam to the lignite input from the stoker Docket No. PMHA-13051-PCT 6 111 so as to heat and dry the lignite with fluidizing the lignite so as to remove the moisture content from the lignite. The fluid-bed drier 1 is provided with a cooler 131 that cools the dried lignite (dry coal) extracted from 5 the lower part of the fluid-bed drier 1 such that the dried and cooled dry coal is stored in a dry coal banker 132. The fluid-bed drier 1 is further provided with an electronic dry coal precipitator 134 that separate particles of the dry coal from the steam extracted from the 10 upper part of the fluid-bed drier 1 such that the particles of the dry coal separated from the steam are stored in the dry coal banker 132. Note that the steam from which the dry coal has been separated in the electronic dry coal precipitator 134 is supplied to the fluid-bed drier 1 as 15 drying steam after being compressed in a steam compressor 135. [0021] The coal mill 113 is a coal grinder that crashes the lignite dried in the fluid-bed drier 1 (dry coal) to fine particles so as to produce milled coal. In other 20 words, when the dry coal stored in the dry coal banker 132 is dropped with a coal feeder 136, the coal mill 113 mills the dry coal to milled coal having a predetermined particle diameter. Then, the coal milled in the coal mill 113 is separated from conveying gas in milled coal bag filters 25 137a and 137b and is stored in milled coal feed hoppers 138a and 138b. [0022] The coal gasification furnace 114 is supplied with the milled coal processed in the coal mill 113 and the char (unburned combustible components of the coal) 30 recovered in the char recovery unit 115. [0023] The coal gasification furnace 114 is connected to a compressed air feed line 141 from the gas turbine unit 117 (a compressor 161) such that the air compressed in the Docket No. PMHA-13051-PCT 7 gas turbine unit 117 can be supplied. An air separator 142 is configured to separate and produce nitrogen and oxygen from the atmosphere. A first nitrogen feed line 143 is connected to the coal gasification furnace 114. Coal feed 5 lines 144a and 144b from the milled coal feed hoppers 138a and 138b are connected to the first nitrogen feed line 143. A second nitrogen feed line 145 is also connected to the coal gasification furnace 114. A char return line 146 from the char recovery unit 115 is connected to the second 10 nitrogen feed line 145. An oxygen feed line 147 is connected to the compressed air feed line 141. In that case, the nitrogen is used as the gas for conveying the coal and the char. The oxygen is used as oxidant. [0024] The coal gasification furnace 114 is, for example, 15 an entrained-bed gasification furnace that burns and gasifies the coal, char, and air (oxygen) or steam used as gasifying agent that have been supplied therein, and generates carbon dioxide-based combustible gas (produced gas, or gasified coal) so as to cause gasification reaction 20 using the combustible gas as gasifying agent. Note that the coal gasification furnace 114 is provided with a foreign matter removal device 148 that removes foreign matter mixed with the milled coal. In that case, the coal gasification furnace 114 is not limited to an entrained-bed 25 gasification furnace and can also be a fluid-bed gasification furnace or a fixed-bed gasification furnace. The coal gasification furnace 114 is provided with a gas production line 149 of the combustible gas directed to the char recovery unit 115 such that the combustible gas 30 including the char can be emitted. In that case, providing a gas cooler on the gas production line 149 can supply the combustible gas to the char recovery unit 115 after cooling the combustible gas to a predetermined temperature.

Docket No. PMHA-13051-PCT 8 [0025] The char recovery unit 115 includes a precipitator 151 and a feed hopper 152. In that case, the precipitator 151 includes one or a plurality of bag filters or cyclones so as to separate the char from the combustible 5 gas generated in the coal gasification furnace 114. Then, the combustible gas from which the char has been separated is sent to the gas refinery 116 through a gas emission line 153. The feed hopper 152 is configured to store the char separated from the combustible gas in the precipitator 151. 10 Note that a bin can be provided between the precipitator 151 and the feed hopper 152 such that a plurality of feed hoppers 152 can be connected to the bin. The char return line 146 from the feed hopper 152 is connected to the second nitrogen feed line 145. 15 [0026] The gas refinery 116 is configured to purify the combustible gas from which the char has been separated in the char recovery unit 115 by removing impurities such as sulfur compound or nitrogen compound from the combustible gas. The gas refinery 116 produces fuel gas by purifying 20 the combustible gas so as to supply the gas to the gas turbine unit 117. Note that sulfur content (H 2 S) is still included in the combustible gas from which the char has been separated in the gas refinery 116. The sulfur content is removed by amine absorbent and is finally recovered as 25 gypsum for efficient use. [0027] The gas turbine unit 117 includes the compressor 161, a combustor 162, and a turbine 163. The compressor 161 is communicated with the turbine 163 through a rotary shaft 164. The combustor 162 is connected to a compressed 30 air feed line 165 from the compressor 161 and is connected to a fuel gas feed line 166 from the gas refinery 116. A combustion gas feed line 167 is connected to the turbine 163. The gas turbine unit 117 is provided with the Docket No. PMHA-13051-PCT 9 compressed air feed line 141 extending from the compressor 161 to the coal gasification furnace 114. A booster 168 is provided on the compressed air feed line 141. Thus, the compressed air supplied from the compressor 161 and the 5 fuel gas supplied from the gas refinery 116 are mixed with each other and burnt in the combustor 162. Rotating the rotary shaft 164 with the generated combustion gas in the turbine 163 can drive the generator 119. [0028] The steam turbine unit 118 includes a turbine 169 10 communicated with the rotary shaft 164 in the gas turbine unit 117. The generator 119 is communicated with the base end of the rotary shaft 164. The heat recovery steam generator 120 is provided on a flue gas line 170 from the gas turbine unit 117 (the turbine 163) so as to produce 15 steam by exchanging the heat between the air and the hot flue gas. Thus, a steam feed line 171 and a steam recovery line 172 including a steam condenser 173 are provided between the heat recovery steam generator 120 and the turbine 169 of the steam turbine unit 118. Thus, the 20 turbine 169 driven by the steam supplied from the heat recovery steam generator 120 rotates the rotary shaft 164 in the steam turbine unit 118 so that the rotary shaft 164 can drive the generator 119. [0029] A gas purification device 174 removes toxic 25 substance from the flue gas of which heat has been recovered in the heat recovery steam generator 120. The purified flue gas is emitted from a stack 175 into the air. [0030] Hereinafter, the operation of the integrated coal gasification combined cycle 100 in the present embodiment 30 will be described. [0031] The integrated coal gasification combined cycle 100 in the present embodiment stores raw coal (lignite) in the raw coal banker 121 of the stoker 111. The coal Docket No. PMHA-13051-PCT 10 supplier 122 drops the lignite in the raw coal banker 121 to the crasher 123 such that the lignite is crushed into a predetermined size. The crushed lignite is heated and dried in the fluid-bed drier 1 and is cooled with the 5 cooler 131. Then, the lignite is stored in the dry coal banker 132. The steam extracted from the upper part of the fluid-bed drier 1 is compressed in the steam compressor 135 after the particles of dry coal are removed from the steam in the electronic dry coal precipitator 134. After that, 10 the steam returns to the fluid-bed drier 1 as drying steam. On the other hand, the particles of dry coal separated from the steam are stored in the dry coal banker 132. [0032] The dry coal stored in the dry coal banker 132 is input to the coal mill 113 from the coal feeder 136 such 15 that the dry coal is milled into fine particles and milled coal is produced therein. The milled coal is stored in the milled coal feed hoppers 138a and 138b through the milled coal bag filters 137a and 137b. The milled coal stored in the milled coal feed hoppers 138a and 138b is supplied to 20 the coal gasification furnace 114 through the first nitrogen feed line 143 with the nitrogen supplied from the air separator 142. The char recovered in the char recovery unit 115 to be described below is supplied to the coal gasification furnace 114 through the second nitrogen feed 25 line 145 with the nitrogen supplied from the air separator 142. Further, after being boosted in the booster 168, the compressed air extracted from the gas turbine unit 117 to be described below is supplied to the coal gasification furnace 114 through the compressed air feed line 141 with 30 the oxygen supplied from the air separator 142. [0033] The coal gasification furnace 114 can generate carbon dioxide-based combustible gas (gasified coal) by burning the milled coal and char supplied thereto with the Docket No. PMHA-13051-PCT 11 compressed air (oxygen) and gasifying the milled coal and the char. Then, the combustible gas is emitted from the coal gasification furnace 114 through the gas production line 149 and is sent to the char recovery unit 115. 5 [0034] The combustible gas is first supplied to the precipitator 151 such that the precipitator 151 separates the char from the combustible gas in the char recovery unit 115. Then, the combustible gas from which the char has been separated is sent to the gas refinery 116 through the 10 gas emission line 153. On the other hand, the fine char separated from the combustible gas accumulates in the feed hopper 152 and returns to the coal gasification furnace 114 through the char return line 146 for recycling. [0035] The combustible gas from which the char has been 15 separated in the char recovery unit 115 is purified by a removal of impurities such as sulfur compound or nitrogen compound from the combustion gas in the gas refinery 116 so as to produce fuel gas. The compressor 161 generates the compressed air and supplies the compressed air to the 20 combustor 162 in the gas turbine unit 117. The combustor 162 mixes the compressed air supplied from the compressor 161 with the fuel gas supplied from the gas refinery 116 and burns the mixed gas so as to generate combustion gas. The combustion gas drives the turbine 163 so as to drive 25 the generator 119 through the rotary shaft 164. This can generate electric power. [0036] The flue gas emitted from the turbine 163 in the gas turbine unit 117 generates steam by exchanging the heat with the air in the heat recovery steam generator 120. The 30 generated steam is supplied to the steam turbine unit 118. The steam supplied from the heat recovery steam generator 120 drives the turbine 169 so as to drive the generator 119 through the rotary shaft 164 in the steam turbine unit 118.

Docket No. PMHA-13051-PCT 12 This can generate electric power. [0037] After that, the toxic substance is removed from the flue gas emitted from the heat recovery steam generator 120 in the gas purification device 174 and the purified 5 flue gas is emitted from the stack 175 into the air. [0038] Hereinafter, the fluid-bed drier 1 in the above mentioned integrated coal gasification combined cycle 100 will be described in detail. FIG. 2 is a schematic structure diagram schematically illustrating the fluid-bed 10 drier according to the present embodiment. The fluid-bed drier 1 in the present embodiment heats and dries lignite that is coal having a high moisture content with fluidizing the lignite with fluidizing gas. [0039] As illustrated in FIG. 2, the fluid-bed drier 1 15 includes a drying furnace 5 to which lignite is supplied, and a gas diffusing plate 6 provided in the drying furnace 5. The drying furnace 5 is formed into a rectangular box shape. The gas diffusing plate 6 separates the internal space of the drying furnace 5 into a chamber room 11 20 located on the vertically lower side (the lower side in the drawing) and a drying room 12 located on the vertically upper side (the upper side in the drawing). A number of through holes are formed on the gas diffusing plate 6 so as to introduce the fluidizing gas such as steam into the 25 chamber room 11. [0040] The drying room 12 of the drying furnace 5 is provided with a lignite input opening 31 from which the lignite is input, a dry coal discharge opening 41 that discharges the heated and dried lignite as dry coal, a heat 30 exchanger tube 33 that heats the lignite, a precipitator 34 that separates the lignite from the flue gas, and an ejector 35 that returns the separated lignite to a fluid bed 3.

Docket No. PMHA-13051-PCT 13 [0041] The lignite input opening 31 is formed on a first end (the left side of the drawing) of the drying room 12. The crasher 123 is connected to the lignite input opening 31 such that the finely grained lignite is supplied to the 5 drying room 12. [0042] The dry coal discharge opening 41 is formed on the bottom on a second end side (the right side) of the drying room 12. The lignite dried in the drying room 12 is discharged as dry coal from the dry coal discharge opening 10 41. The discharged dry coal is supplied toward the cooler 131. [0043] The lignite supplied to the drying room 12 forms the fluid bed 3 in the drying room 12 by fluidizing with the fluidizing gas supplied through the gas diffusing plate 15 6. A freeboard unit F is formed above the formed fluid bed 3. The fluid bed 3 formed in the drying room 12 fluidizes in the longitudinal direction of the drying room 12 (horizontal direction in FIG. 2). The fluidizing gas supplied to the drying room 12 is directed to the 20 precipitator 34 together with the steam generated when the lignite has been dried. [0044] The heat exchanger tube 33 is provided in the fluid bed 3. Drying steam is supplied to the inside of the heat exchanger tube 33 so as to remove the moisture content 25 from the lignite in the fluid bed 3. Thus, when the drying steam is supplied to the heat exchanger tube 33, the heat exchanger tube 33 dries the lignite in the drying room 12 using the latent heat of the drying steam. After that, the drying steam used for drying the lignite is emitted to the 30 outside of the drying room 12. [0045] The precipitator 34 is a cyclone precipitator and includes a suction port 45, a cyclone precipitator unit 46 connected to the suction port 45, a fuel discharge port 47 Docket No. PMHA-13051-PCT 14 connected to the lower side of the cyclone precipitator unit 46, and a gas emission port 48 connected to the upper side of the cyclone precipitator unit 46. [0046] The cyclone precipitator unit 46 is formed into a 5 taper shape that vertically tapers off from the upper side to the lower side. The axial direction of the cyclone precipitator unit 46 having the structure describe above is vertical. The cyclone precipitator unit 46 separates the lignite from the flue gas that has flowed into the cyclone 10 precipitator unit 46. In other words, the flowing flue gas becomes a cyclone flow in the cyclone precipitator unit 46. Thus, the lignite in the flue gas is led to the fuel discharge port 47 on the lower side whereas the flue gas from which the lignite has been separated is led to the gas 15 emission port 48 on the upper side. [0047] The suction port 45 extends in the tangential direction of the upper outer periphery of the cyclone precipitator unit 46. A first end of the suction port 45 is connected to the cyclone precipitator unit 46 and a 20 second end is a suction opening 51 that inhales the flue gas. Thus, the suction port 45 supplies the flue gas inhaled from the suction opening 51 toward the cyclone precipitator unit 46. [0048] The fuel discharge port 47 extends in the axial 25 direction of the lower side of the cyclone precipitator unit 46. The upper end of the fuel discharge port 47 is connected to the cyclone precipitator unit 46 and the lower end is a fuel discharge opening 52 that discharges the lignite. The fuel discharge opening 52 is connected to the 30 ejector 35. The fuel discharge port 47 discharges the lignite that has been separated in the cyclone precipitator unit 46 toward the ejector 35. [0049] The gas emission port 48 extends in the axial Docket No. PMHA-13051-PCT 15 direction of the upper side of the cyclone precipitator unit 46. The upper end of the gas emission port 48 is connected to the electronic dry coal precipitator 134 placed at the outside of the drying furnace 5. The lower 5 end is a gas emission opening 53 that discharges the flue gas from which the lignite has been separated. At that time, the lower end of the gas emission port 48 is positioned at the inside of the cyclone precipitator unit 46. The gas emission port 48 discharges the flue gas from 10 which the lignite has been separated in the cyclone precipitator unit 46 from the gas emission opening 53 toward the electronic dry coal precipitator 134. [0050] The ejector 35 is formed into a pipe shape that has a steam passage R1 through which the superheated steam 15 circulates. The fuel discharge opening 52 is connected to the middle of the steam passage R1. A first end (the right side in the drawing) of the ejector 35 is positioned at the outside of the drying furnace 5. The superheated steam flows into the ejector 35 from the first end. On the other 20 hand, a second end (the left side in the drawing) of the ejector 35 is positioned above the upper stream of the fluid bed 3 formed in the drying furnace 5. The lignite is discharged from the second end together with the superheated steam. 25 [0051] In other words, after entering from the first end of the ejector 35, the superheated steam flows along the steam passage R1. After passing through the fuel discharge opening 52, the superheated steam flowing along the steam passage R1 pulls the lignite discharged from the fuel 30 discharge opening 52 into the steam passage R1. The superheated steam that has passed through the fuel discharge opening 52 flows out of the second end of the ejector 35 together with the lignite pulled from the fuel Docket No. PMHA-13051-PCT 16 discharge opening 52. [0052] When the lignite is supplied from the lignite input opening 31 to the drying room 12 in the fluid-bed drier 1 having the structure described above, the supplied 5 lignite forms the fluid bed 3 by fluidizing with the fluidizing gas supplied through the gas diffusing plate 6. The lignite formed into the fluid bed 3 is heated and dried using the fluidizing gas and the heat exchanger tube 33. After that, the fluidizing gas becomes flue gas together 10 with the steam generated from the lignite and is directed to the precipitator 34. The flue gas directed to the precipitator 34 is inhaled from the suction opening 51 of the precipitator 34 and is supplied to a cyclone precipitator unit 36 through the suction port 45. 15 [0053] When the flue gas is supplied to the cyclone precipitator unit 36, the cyclone precipitator unit 36 separates the lignite from the flue gas. While the separated lignite is directed to the fuel discharge port 47, the flue gas from which the lignite has been separated is 20 directed to the gas emission port 48 and then supplied to the electronic dry coal precipitator 134. The lignite directed to the fuel discharge port 47 is pulled into the ejector 35 and then discharged, together with the superheated steam supplied to the ejector 35, onto the 25 upper stream of the fluid bed 3 formed in the drying room 12. After that, the lignite dried in the drying room 12 is discharged from the dry coal discharge opening 41. [0054] According to the structure in the present embodiment as described above, the ejector 35 can return 30 the lignite collected in the precipitator 34 to the upper stream of the fluid bed 3. Thus, the lignite that has not been dried is not supplied to the lower stream of the fluid bed 3. This can prevent the discharge of the lignite that Docket No. PMHA-13051-PCT 17 has not been dried from the dry coal discharge opening 41. Further, the lignite that has not been dried can be returned to the upper stream of the fluid bed 3 so that the dry of the lignite in the fluid bed 3 can be facilitated. 5 [0055] Further, according to the structure in the present embodiment, separating the lignite from the flue gas with the cyclone precipitator 34 can discharge, from the drying furnace 5, the flue gas from which the lignite has been separated and can discharge the separated lignite 10 from the fuel discharge opening. This can discharge, toward the fluid bed 3 using the ejector 35, the lignite discharged from the fuel discharge opening 52. [0056] Further, according to the structure in the present embodiment, the flowing superheated steam can pull 15 the lignite discharged from the fuel discharge opening 52 into the steam passage R1 of the ejector 35. Thus, the ejector 35 can preferably dry the lignite circulating together with the superheated steam therein. [0057] Note that, although the second end of the ejector 20 35 is positioned above the upper stream of the fluid bed 3 in the present embodiment, the position is not limited to the embodiment. The second end of the ejector 35 can be positioned at the inside of the upper stream of the fluid bed 3. 25 [0058] Note that, although a cyclone precipitator is applied as the precipitator 34 in the present embodiment, the type is not limited to the embodiment. For example, a filter precipitator can be applied. Reference Signs List 30 [0059] 1 Fluid-bed drier 3 Fluid bed 5 Drying furnace 6 Gas diffusing plate Docket No. PMHA-13051-PCT 18 11 Chamber room 12 Drying room 31 Lignite feed opening 33 Heat exchanger tube 5 34 Precipitator 35 Ejector 41 Dry coal discharge opening 45 Suction port 46 Cyclone precipitator unit 10 47 Fuel discharge port 48 Gas emission port 51 Suction opening 52 Fuel discharge opening 53 Gas emission opening 15 Ri Steam passage

Claims

1. A fluid-bed drier comprising: a drying furnace configured to form a fluid bed therein by fluidizing wetting fuel from an upper stream to 5 a lower stream with fluidizing gas, a precipitator provided in the drying furnace and configured to collect the wetting fuel included in flue gas discharged from the drying furnace, and an ejector provided in the drying furnace and 10 configured to supply the wetting fuel collected with the precipitator toward the upper stream of the fluid bed.

2. The fluid-bed drier according to claim 1, wherein the precipitator includes: 15 a suction opening configured to inhale the flue gas; a cyclone precipitator unit configured to separate the wetting fuel from the inhaled flue gas; a fuel discharge opening configured to discharge the wetting fuel separated in the cyclone precipitator unit; 20 and a gas emission opening configured to emit the flue gas from which the wetting flue has been separated in the cyclone precipitator unit, and the ejector is connected to the fuel discharge opening. 25

3. The fluid-bed drier according to claim 2, wherein the ejector is supplied with superheated steam and the ejector supplies the lignite discharged from the fuel discharge opening to the upper stream of the fluid bed 30 together with the superheated steam by passing the supplied superheated steam through the fuel discharge opening.