AU2011373344B2

AU2011373344B2 - Fluidized bed drying facility

Info

Publication number: AU2011373344B2
Application number: AU2011373344A
Authority: AU
Inventors: Takeshi Amari; Kenichi Arima; Hiromi Ishii; Masaaki Kinoshita
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2011-07-15
Filing date: 2011-07-15
Publication date: 2015-06-11
Anticipated expiration: 2031-07-15
Also published as: WO2013011542A1; AU2011373344A1

Abstract

A fluidized bed drying facility is equipped with: a fluidized bed drying device (102) that dries lignite (101); a generated steam line (L

Description

1 FLUID BED DRYING EQUIPMENT Field of the Invention [0001] The present invention relates to a fluid bed 5 dryer that dries an object while fluidizing the object by fluidizing gas, and particularly to fluid bed drying equipment capable of taking measures against flow failure of the object. 10 Background of the Invention [0001a] 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. 15 [00021 For example, brown coal that has. a high water content is used as a fuel in a brown coal combustion boiler. Further, an impact mill such as a beater mill is used for drying and milling the brown coal. When milling the brown coal using a beater mill, since a part of high-temperature 20 flue gas at, for example, 1,000 0 C from the brown coal combustion boiler is used as a heat source, the boiler efficiency is reduced. However, there has been proposed a system as a measure against the reduction of the boiler efficiency. In the system, brown coal is previously dried 25 by a fluid bed dryer using a low-temperature heat source before being put into an impact mill, and latent heat is further recovered from generated steam to thereby improve the boiler efficiency. [0003] Conventionally, such a fluid bed dryer which 30 dries an object to be dried such as brown coal is provided with a drying room that includes an air-permeable dispersion plate having a large number of openings on the bottom thereof, and a chamber located under the drying room.

2 More specifically, the fluid bed dryer dries an object while fluidizing the object by supplying fluidizing gas (drying gas) from a wind box into the drying room trough the porous plate (Patent Literature 1). 5 Citation List Patent Literature [00041 Patent Literature 1: Japanese Laid-open Patent Publication No. 2008-89243 [0005] When drying a material with high water content 10 such as brown coal, steam generated from a fluid bed dryer is saturated steam. Therefore, it has been proposed for effective utilization of the steam to perform power generation by a steam turbine, or reuse the steam as a drying heat source by compressing the steam and increasing 15 the temperature thereof by a compressor. However, there are the following problems in the utilization of the steam. 1) Since fine particles and the like are contained in dried flue gas that is the generated steam, wear of blades of a steam turbine occurs. Therefore, a precipitator such 20 as an electric precipitator is used for collecting the fine particles. However, since the capacity of the precipitator is large, the reduction of cost is a problem to be solved. 2) Further, in order to prevent wear of rotary apparatuses such as a steam turbine and a compressor 25 arranged on the downstream side, it is preferred to suppress the concentration of fine particles at the exit at several mg/Nm 3 order. However, since brown coal particles have a large electric resistance, the electric charge becomes unstable. Therefore, the collectability of 30 particles may be deteriorated. 3) Further, since the dried flue gas that is the generated steam is water-saturated, it is expected that the electric resistance of brown coal particles decreases.

3 However, when the electric resistance thereof becomes extremely small, the particles re-scatter in the electrode, and the collectability thereof is disadvantageously deteriorated. 5 [0006] Therefore, a simple countermeasure capable of efficiently collect fine particles contained in steam generated from a fluid bed dryer has been desired. [0006a] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of 10 the prior art, or to provide a useful alternative. [0007] In view of the above problems, the present invention is directed to provide fluid bed drying equipment capable of efficiently collect fine particles contained in steam generated from a fluid bed dryer. 15 [0007a] 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 20 "including, but not limited to". [0007b] Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. 25 Summary of the Invention [0008] According to a first aspect of the present invention in order to dolve the above problems, there is provided a fluid bed drying equipment including: a fluid 30 bed dryer for drying an object with high water content; a generated steam line for discharging generated steam in a water-saturated state to the outside of the fluid bed dryer, the generated steam being generated when the object is 4 dried by a heat transfer member; an electric precipitator disposed on the generated steam line, for removing fine particles contained in the generated steam; a heat recovery system disposed on the generated steam line at the 5 downstream side of the electric precipitator, for recovering heat of the generated steam; a branch line for branching a part of the generated steam from the electric precipitator, fine particles being removed from the generated steam and the branched generated steam being 10 supplied into the fluid bed dryer as fluidizing steam; and a cooler for cooling the object taken out from the fluid bed dryer, wherein water at a saturation temperature or higher is supplied to the generated steam after fine particles are removed therefrom between the electric 15 precipitator and the heat recovery system in the generated steam line to remove fine particles remaining the generated steam. [00091 According to a second aspect of the present invention, there is provide the fluid drying equipment 20 according to the first aspect, wherein the supply of water at a saturation temperature or higher and the removal of fine particles are performed by a scrubber. [0010] According to a third aspect of the present invention, there is provide the fluid drying equipment 25 according to the first aspect, wherein the supply of water at a saturation temperature or higher is performed by a spray device, and the removal of fine particles are performed by a cyclone separator. [0011] According to a fourth aspect of the present 30 invention, there is provide the fluid drying equipment according to any one of the first to third aspects, further including a superheated medium supply pipe laid around the generated steam line and the electric precipitator, wherein 5 fine particles are collected while reducing the temperature of the generated steam until a part of entrainer is precipitated on a surface of an electrode of the electric precipitator. 5 [0012] According to a fifth aspect of the present invention, there is provide the fluid drying equipment according to any one of the first to fourth aspects, wherein a water injection device is provided on the generated steam line at an upstream side of the electric 10 precipitator. Advantageous Effects of Invention [0013] According to the present invention, wear of the compressor, the turbine and the like of the heat recovery 15 system arranged on the downstream side is reduced by significantly reducing the concentration of fine particles remaining in the generated steam. Brief Description of Drawings [0014] FIG. 1 is a schematic view illustrating an 20 example of fluid bed drying equipment to which a fluid bed dryer according to an embodiment of the present invention is applied. FIG. 2-1 is a schematic view illustrating an example of a brown coal combustion boiler to which the fluid bed 25 drying equipment shown in FIG. 1 is applied. FIG. 2-2 is a schematic view illustrating an example of an integrated coal gasification combined cycle system to which the fluid bed drying equipment shown in FIG. 1 is applied. 30 FIG. 3 is a schematic view illustrating a fluid bed drying equipment of a first embodiment. FIG. 4 is a schematic view illustrating a fluid bed drying equipment of a second embodiment.

6 FIG. 5-1 is a schematic view illustrating a precipitator of the fluid bed drying equipment of the second embodiment and the surroundings thereof. FIG. 5-2 is a cross-sectional view taken along line X S X of FIG. 5-1. FIG. 6 is a schematic view illustrating a fluid bed drying equipment of a third embodiment. Description of Embodiments [0015] Hereinbelow, embodiments of the present invention 10 will be described in detail with reference to the drawings. However, the present invention is not limited by the embodiments described below. Further, structural elements in the following embodiments include the other elements that can be easily replaced by those skilled in the art, or 15 elements that are substantially the same as the described ones. [0016] An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view illustrating an example of fluid bed drying 20 equipment to which a fluid bed dryer according to the present embodiment is applied. [0017] As shown in FIG. 1, fluid bed drying equipment 100 according to the present embodiment is provided with a fluid bed dryer 102 which dries brown coal 101 as an object 25 to be dried with high water content supplied from a supply hopper 120, a heat transfer member (heating means) 103 which is provided inside the fluid bed dryer 102, has a tubular body, and supplies superheated steam (steam at 150 0 C, for example) A to the inside of the tubular body to 30 remove water contained in the brown coal 101, a generated steam line Li through which generated steam 104 which is generated when the brown coal 101 is dried by the heat transfer member 103 is discharged to the outside of the 7 fluid bed dryer 102, a precipitator 105 which is disposed on the generated steam line Li and removes fine particles contained in the generated steam 104, a heat recovery system 106 which is disposed on the generated steam line L, 5 at the downstream side of the precipitator 105 and recovers heat of the generated steam 104, a branch line L 2 through which a part of the generated steam 104 from which fine particles have been removed is branched from the precipitator 105 and the branched generated steam 104 is 10 supplied into the fluid bed dryer 102 as fluidizing steam 107, and a cooler 110 which cools dried brown coal 108 taken out from the fluid bed dryer 102 to produce product coal 109. Reference numeral 116 denotes a dispersion plate that 15 regulates the flow of the fluidizing steam 107 as fluidizing gas. [0018] In the fluid bed drying equipment 100, the brown coal 101 is put into the fluid bed dryer 102 from the supply hopper 120 through a supply line LO, and fluidized 20 by the fluidizing steam 107 which is introduced into the fluid bed dryer 102 separately from the brown coal 101 to form a fluid bed 111. [0019] The heat transfer member 103 is arranged inside the fluid bed 111. The superheated steam A at 150 0 C is 25 supplied into the heat transfer member 103. The brown coal 101 is indirectly dried using the latent heat of the high temperature superheated steam A. The superheated steam A that has been used for drying the brown coal 101 is discharged to the outside of the fluid bed dryer 102 as, 30 for example, condensed water B at 150 0 C. [0020] More specifically, the superheated steam A is condensed into liquid (water) on the inner surface of the heat transfer member 103 as heating means. Therefore, the 8 condensed latent heat released at this point is effectively used in heating for drying the brown coal 101. Any heat mediums can be used instead of the high-temperature superheated steam A as long as involving a phase change. 5 Examples of the heat medium include chlorofluorocarbon, pentane, and ammonia. Further, an electric heater may be provided as the heat transfer member 103 instead of a heat medium. [0021] The generated steam 104 which is generated when 10 the brown coal 101 is dried by the heat transfer member 103 is discharged to the outside of the fluid bed dryer 102 from a freeboard section F which is formed in a space above the fluid bed 111 inside the fluid bed dryer 102 through the generated steam line LI. The generated steam 104 15 contains dried and milled (fine) particles of the brown coal 101. Therefore, the particles are collected by the precipitator 105 such as a cyclone separator and an electric precipitator so as to be separated as a solid component 115. 20 The solid component 115 passes through a separation line L 3 , is then mixed with the dried brown coal 108 which has been taken out from the fluid bed dryer 102, and is then cooled by the cooler 110 on a product line L 4 to produce the product coal 109. The product coal 109 is used, 25 for example, as a source for a boiler, a gasification furnace, or the like. [0022] On the other hand, the generated steam 104 after fine particles are removed therefrom by the precipitator 105 is, for example, steam at 105 to 110 0 C. Therefore, the 30 generated steam 104 is heat-recovered by the heat recovery system 106, then treated by a water treatment unit 112, and then discharged to the outside of the fluid bed drying equipment 100 as waste water 113. The generated steam 104 9 after fine particles are removed therefrom by the precipitator 105 may, for example, be applied to a heat exchanger or a steam turbine to effectively utilize the heat thereof. 5 [0023] A part of the generated steam 104 after fine particles are removed therefrom by the precipitator 105 is sent into the fluid bed dryer 102 by a circulation fan 114 which is disposed on the branch line L 2 , and used as the fluidizing steam 107 for fluidizing the fluid bed 111 of 10 the brown coal 101. In the present embodiment, the part of the generated steam 104 is reused as a fluidizing medium for fluidizing the fluid bed 111. However, the present invention is not limited thereto. For example, nitrogen, carbon dioxide, or air with low oxygen content that 15 contains nitrogen and carbon dioxide can be used as the fluidizing medium. [0024] Further, although the heat transfer member 103 in the fluid bed dryer 102 has a tubular shape in-the present embodiment, the present invention is not limited thereto. 20 For example, the heat transfer member may have a plate-like shape. Further, although the description has been made with regard to the configuration in which the superheated steam A is supplied to the heat transfer member 103 to indirectly 25 dry the brown coal 101, the present invention is not limited thereto. The fluidizing steam 107 which fluidizes the fluid bed 111 of the brown coal 101 may directly dry the brown coal 101, or additional fluidizing gas for heating may be supplied to dry the brown coal 101. 30 [0025] The brown coal 101 has been described as an example of an object to be dried. However, a drying target may be an object such as low grade coal including subbituminous coal, and sludge as long as having a high 10 water content. [0026] An example in which the fluid bed drying equipment 100 is applied to a brown coal combustion boiler using the product coal 109 dried by the fluid bed dryer 102 S shown in FIG. 1 will be described. FIG. 2-1 is a schematic view illustrating an example of the brown coal combustion boiler to which the fluid bed drying equipment 100 shown in FIG. 1 is applied. The brown coal combustion boiler 150 according to the 10 present embodiment is provided with a furnace 151 which is arranged in the vertical direction, a combustion apparatus 152 which is arranged on the lower part of a furnace wall of the furnace 151, a flue gas duct 153 which is connected to an exit of the furnace 151, a plurality of superheaters 15 154 which are provided in the flue gas duct 153, a economizer 155, an induced draft fan 156 which is provided on the downstream part of the flue gas duct 153, and a stack 157. [0027] The combustion apparatus 152 is provided with a 20 plurality of milled coal burners 158 which are attached to the furnace wall, an impact mill 159 which produces milled coal to be supplied to the milled coal burners 158, and air supply means 160 which supplies secondary air (air) to the milled coal burners 158 as combustion air. 25 The impact mill 159 mills the brown coal 101 supplied thereto into milled coal having a size suitable for combustion (several pm to several hundred ptm, for example). The impact mill 159 introduces thereinto a part of flue gas 161 at a low temperature flowing at the downstream side of 30 the economizer 155 to dry and mill the brown coal 101. The product coal 109 which has been previously dried by the above-described fluid bed drying equipment 100 is supplied to the impact mill 159.

11 [0028] The air supply means 160 is provided with a forced draft fan (air supply device) 162 which pressurizes and supplies air, a wind box 163 which is attached to the outer wall of the furnace 151, and an air pipe 164 which 5 connects the forced draft fan 162 with the wind box 163. A rotary regenerative heat exchanger 160a is arranged across the air pipe 164 and the flue gas duct 153 to perform heat exchange between secondary air (air) and flue gas. [0029] Steam generated in the brown coal combustion 10 boiler 150 is used in turbine equipment 165. The turbine equipment 165 is provided with a plurality of turbines (high-pressure, medium-pressure, and low-pressure turbines, for example). For example, the high-pressure turbine expands superheated steam introduced from the superheaters 15 154 so as to be converted into a rotational energy, and supplies exhausted steam to a primary reheater. The medium-pressure turbine expands superheated steam that has been re-superheated by the primary reheater and a secondary reheater and then introduced into the medium-pressure 20 turbine from the secondary reheater so as to be converted into a rotational energy. The low-pressure turbine introduces thereinto exhausted steam from the middle pressure turbine, and further expands the exhausted steam so as to be converted into a rotational energy. 25 The rotational energies converted in the high-pressure turbine, the middle-pressure turbine, and the low-pressure turbine are transmitted to a generator G which is connected to the turbines by shafts, thereby generating electric power. 30 Steam exhausted in the low-pressure turbine is sent to a steam condenser 166, and condensed by the steam condenser 166 to be returned to water. The water condensed by the steam condenser 166 is sent to the economizer 155 through a 12 feed water line 167. The feed water line 167 is provided with a condensate pump, a deaerator, a feed water pump, a feed water heater, and the like (not shown). [0030] Hereinbelow, the operation of the brown coal 5 combustion boiler 150 described above will be described. The brown coal 101 supplied from a brown coal bunker (not shown) is dried by the fluid bed drying equipment 100 to remove water therefrom, and then dried and milled by the impact mill 159 using the flue gas 161 at approximately 10 1,000 0 C into milled coal having a size suitable for combustion. Then, the milled coal is mixed with pressurized conveyance air to form milled coal mixture gas. The thus formed milled coal mixture gas is sent to the milled coal burners 158 through a coal supply pipe. 15 [0031] On the other hand, the temperature of the secondary air pressurized and supplied by the forced draft fan 162 is raised by supplying heat thereto from flue gas by the rotary regenerative heat exchanger 160a. The secondary air is then supplied to the wind box 163 via the 20 air pipe 164. Thereafter, the secondary air is sent to the milled coal burners 158 from the wind box 163. The milled coal mixture gas and the secondary air are supplied into the furnace 151 from the milled coal burners 158, and flames are generated inside the furnace 151 by firing. 25 [0032] When flames are generated in the lower part of the furnace 151 in this manner, flue gas flows upward inside the furnace 151, and is then discharged into the flue gas duct 153. At this time, water supplied from the feed water pump is preheated by the economizer 155, and 30 then supplied to a waterwall tube. The water supplied to the waterwall tube is heated into superheated steam by the flue gas while flowing upward through the waterwall tube, and sent to the superheaters 154. Further, the superheated 13 steam sent to a primary superheater is then introduced into a secondary superheater, a tertiary superheater, and a quaternary superheater in this order so that the superheated steam is further superheated by the flue gas 5 161. The superheated steam generated in the quaternary superheater is supplied to the high-pressure turbine of the turbine equipment 165. On the other hand, exhausted steam that has been expanded and exhausted in the high-pressure turbine is 10 introduced into the primary reheater, and then into the secondary reheater so that the exhaust steam is re superheated by the flue gas. The superheated steam superheated in the secondary reheater is supplied to the medium pressure turbine. The steam expanded and exhausted 15 in the medium-pressure turbine is supplied to the low pressure turbine. The rotational energies generated by the expansion of steam in the high-pressure steam, the medium pressure steam, and the low-pressure steam are transmitted to the generator G which is connected to the turbines by 20 the shafts, thereby generating electric power. [0033] Steam that has been exhausted in the low-pressure turbine is sent to the steam condenser 166, and condensed by the steam condenser 166 to be returned to water. The water condensed by the steam condenser 166 is sent to the 25 economizer 155 through the feed water line 167 by the feed water pump. On the other hand, flue gas that has passed through the economizer 155 supplies heat to the secondary air passing through the air pipe 164 in the rotary regenerative 30 heat exchanger 160a. Then, purification treatments such as desulfurization, denitrification, and particle removal are performed on the flue gas, and the flue gas is then discharged into the atmosphere through the stack 157.

14 [00341 Since the brown coal combustion boiler 150 dries the brown coal 101 using the efficient fluid bed dryer 102, even when the brown coal 101 with high water content is combusted, conventional flue gas at a high temperature 5 (1000 0 C) is not necessary as a heat source that is required in the impact mill 159. Therefore, flue gas at a lower temperature (200 to 300 0 C) is enough as the heat source. In addition, since a system for recovering the latent heat from steam generated in the fluid bed dryer 102 is employed, 10 it is possible to improve the energy efficiency. As a result, stable and efficient power generation can be performed for a long period of time. [0035] An example in which the fluid bed drying equipment 100 is applied to an integrated coal gasification 15 combined cycle (IGCC) system using the product coal 109 dried by the fluid bed dryer 102 shown in FIG. 1 will be described. FIG. 2-2 is a schematic view illustrating an example of the IGCC system to which the fluid bed drying equipment 100 shown in FIG. 1 is applied. 20 [0036] As shown in FIG. 2-2, the IGCC system 200 is provided with a coal gasification furnace 203 which converts milled coal 201a obtained by milling the product coal (dried brown coal) 109 by a mill 210 into gasified gas 202, a gas turbine (GT) 204 which is driven using the 25 gasified gas 202 as a fuel, a steam turbine (ST) 208 which is driven using steam 207 produced in a heat recovery steam generator (HRSG) 206 into which turbine flue gas 205 from the gas turbine 204 is introduced, and a generator (G) 209 which is connected to the gas turbine 204 and/or the steam 30 turbine 208. [0037] In the IGCC system 200, the milled coal 201a milled by the mill 210 is gasified in the coal gasification furnace 203 to obtain the gasified gas 202 as produced gas.

15 Particle removal and purification are respectively performed on the gasified gas 202 by a cyclone separator 211 and a gas purifier 212. Thereafter, the gasified gas 202 is supplied to a combustor 213 of the gas turbine 204 5 as power generation means. In the combustor 213, the gasified gas 202 is combusted to produce high-temperature and high-pressure combustion gas 214. Then, the gas turbine 204 is driven by the combustion gas 214. The gas turbine 204 is connected to the generator 209. Therefore, 10 by driving the gas turbine 204, the generator 209 generates electric power. The turbine flue gas 205 after driving the gas turbine 204 still has a temperature of approximately 500 to 600 0 C. Therefore, the turbine flue gas 205 is sent to the HRSG 206, and the heat energy thereof is recovered 15 in the HRSG 206. In the HRSG 206, the steam 207 is produced by the heat energy of the turbine flue gas 205, and the steam turbine 208 is driven by the steam 207. In a gas cleaner 216, NOx and SOx are removed from flue gas 215 obtained by recovering the heat energy from the turbine 20 flue gas 205 in the HRSG 206. The flue gas 215 is then released into the atmosphere through the stack 217. In FIG. 2-2, reference numeral 218 denotes a steam condenser, reference numeral 219 denotes air, reference numeral 220 denotes a compressor, reference numeral 221 denotes an air 25 separation unit (ASU) which separates air into nitrogen

(N

2 ) and oxygen (02). [0038] Since the brown coal 101 is dried by the efficient fluid bed dryer 102 in the IGCC system 200, even when the brown coal 101 with high water content is gasified, 30 the gasification efficiency is improved. As a result, it is possible to stably perform power generation for a long period of time. [00391 Conventionally, the efficiency of a coal 16 combustion power plant has been approximately 40%. However, in the IGCC system 200, it is possible to improve the efficiency of a coal combustion power plant up to approximately 46% by the combination of a gas turbine and a 5 steam turbine. By virtue of the improvement of the plant efficiency, it is possible to reduce CO 2 emissions by approximately 13% relative to a conventional coal combustion boiler. [0040] 10 [First Embodiment] Hereinbelow, a fluid bed drying equipment of the first embodiment of the present invention will be described with reference to FIG. 3. FIG. 3 is a schematic view illustrating the fluid bed drying equipment of the first 15 embodiment. As shown in these figures, fluid bed drying equipment 100A of the present embodiment is provided with a fluid bed dryer 102 which dries brown coal 101 as an object to be dried with high water content, a generated steam line Li 20 through which generated steam (water-saturated steam) 104 in a water-saturated state which is generated when the object (brown coal 101) is dried by a heat transfer member 103 is discharged to the outside of the fluid bed dryer 102, an electric precipitator 105 which is disposed on the 25 generated steam line Li and removes fine particles contained in the generated steam 104, a steam turbine 145 which is a heat recovery system disposed on the generated steam line Li at the downstream side of the electric precipitator 105 and recovers heat of the generated steam 30 104, a branch line L 2 through which a part of the generated steam 104 from which fine particles have been removed is branched from the electric precipitator 105 and the branched generated steam 104 is supplied into the fluid bed 17 dryer 102 as fluidizing steam 107, a cooler 110 which cools a dried object (dried brown coal) taken out from the fluid bed dryer 102, a hot water spray device 140 which is provided between the electric precipitator 105 and the 5 steam turbine 145 in the generated steam line L, and supplies hot water 142 at a saturation temperature or higher to the generated steam 104 after fine particles are removed therefrom, and a collector 141 which collects and removes fine particles remaining in the sprayed water. 10 [0041] In the present invention, a slight amount (20 mg/Nm 3 , for example) of fine particles remaining in the generated steam 104 that has been purified by the electric precipitator 105 is reduced to approximately 5 mg/Nm 3 or less by spraying the hot water 142 at the saturation 15 temperature or higher corresponding to the pressure inside the duct, and collecting fine particles collected by the sprayed water by the collector 141. As a result, it is possible to significantly reduce wear of turbine blades of the steam turbine 145 which is used in the heat recovery 20 system arranged on the downstream side. [0042] The hot water 142 at the saturation temperature or higher is supplied as water to be sprayed in order to heat steam inside the duct to suppress the condensation of the steam inside the duct. Further, since the saturated 25 water is flushed to generate steam inside the duct, the quantity of heat recovered on the downstream side is increased. Therefore, the hot water 142 is preferred. Further, the condensed water B at 150 0 C which is obtained by condensing the superheated steam A at 150 0 C 30 used in drying in the fluid bed dryer 102 may be used as the hot water 142. [0043] In the present embodiment, the hot water spray device 140 and the collector 141 such as a cyclone 18 separator are separately arranged, and the water at a saturation temperature or higher is supplied by the spray device and fine particles are removed by the collector 141 such as a cyclone separator. However, the present 5 invention is not limited thereto. For example, a scrubber which is an integrated unit of the spray device and the collector may be used. The scrubber is not limited to any specific type. Therefore, various types of conventional scrubbers such as 10 a louver type scrubber and a venturi type scrubber can be used. [0044] As a result, wear of the compressor, the turbine and the like of the heat recovery system arranged on the downstream side is reduced by significantly reducing the 15 concentration of fine particles remaining in the generated steam 104. [0045] [Second Embodiment] Hereinbelow, a fluid bed drying equipment of the 20 second embodiment of the present invention will be described with reference to FIG. 4. FIG. 4 is a schematic view illustrating the fluid bed drying equipment of the second embodiment. FIG. 5-1 is a schematic view illustrating a precipitator of the fluid bed drying 25 equipment of the second embodiment and the surroundings thereof. FIG. 5-2 is a cross-sectional view taken along line X-X of FIG. 5-1. As shown in these figures, fluid bed drying equipment 100B of the present embodiment further includes a 30 superheated medium supply pipe (steam trace) 130 which is laid around the generated steam line Li and the electric precipitator 105 in addition to the configuration of the fluid bed drying equipment 100A of the first embodiment.

19 In the fluid bed drying equipment 100B, fine particles are collected while reducing the temperature of the generated steam 104 until a part of entrainer is precipitated on the surface of an electrode of the electric precipitator 105. 5 [0046] By reducing the temperature of the generated steam 104, in addition to the effects obtained in the first embodiment, the generated steam 104 inside a pipe 132 of the generated steam line L, is condensed, the temperature inside the electric precipitator 105 is thereby slightly 10 reduced, and fine particles are taken into the nucleus of the generated condensed water, thereby improving the efficiency of the fine particle collection in the electric precipitator 105. [0047] If the temperature of the generated steam 104 is 15 excessively reduced, the amount of steam in the heat recovery system on the downstream side, for example, in the steam turbine 145 decreases. Therefore, the temperature reduction is regulated. In FIG. 3, reference numeral 146 denotes a condenser. 20 The regulation of the temperature reduction is performed by starting and stopping the supply of a superheated medium 131 into the superheated medium supply pipe (steam trace) 130. More specifically, when the amount of steam decreases, 25 the power generation efficiency of the steam turbine 145 is deteriorated. Therefore, the supply of the superheated medium 131 into the superheated medium supply pipe (steam trace) 130 is started to suppress the condensation of the generated steam 104. 30 In FIG. 4, the steam trace 130 is indicated by a broken line. Specifically, as shown in FIG. 5-1, the superheated medium supply pipe or the like is laid around the surface of the pipe of the generated steam line L 1

.

20 [0048] In this manner, the efficiency of the fine particle collection is improved by performing control for reducing the temperature of the generated steam 104 until entrainer is precipitated on the surface of the electrode 5 of the electric precipitator 105. In the brown coal drying process, the generated steam 104 from the fluid bed dryer 102 is saturated steam. Therefore, it becomes possible to easily cause water to be precipitated on the electrode by reducing the temperature 10 of the generated steam 104 to some degree. [0049] The temperature of the electrode is regulated by reducing the temperature of gas at an entrance of the electric precipitator 105. Since the gas temperature of the generated steam 104 15 is approximately in the range of 105 to 110 0 C, condensation easily occurs by some temperature reduction. However, excessive condensation of the steam leads to the reduction in the power generation efficiency. Therefore, in order to prevent such excessive temperature reduction, in the pipe 20 from the fluid bed dryer 102 through the electric precipitator 105, a thermal insulator 133 is provided around the pipe 132 in the generated steam line L 1 for thermal insulation as shown in FIG. 5-2. The superheated medium 131 performs superheating to compensate for the heat 25 release, and the superheating is controlled by a control device (not shown). [0050] The control device (not shown) controls the supply of the superheated medium 131 from the outside by using, as the superheated medium 131 for superheating the 30 generated steam 104, the superheated steam A at 150 0 C which is supplied to the inside of the heat transfer member 103 of the fluid bed dryer 102, and the condensed water B at 21 150'C which is obtained by condensing the superheated steam A using the latent heat thereof after the drying operation. The regulation of water condensation on the surface of the electrode can be performed by regulating the degree of 5 the superheating (the amount of steam and the like). [0051] Accordingly, the temperature of the electrode surface becomes lower than the dew point due to the reduction in the temperature of dried flue gas that is the generated steam 104 in the present invention, and a part of 10 water is thereby precipitated. As a result, fine particles are efficiently captured onto the wet electrode and the wet inner wall of the electric precipitator 105. [0052] [Third Embodiment] Hereinbelow, a fluid bed drying equipment of the third 15 embodiment of the present invention will be described with reference to FIG. 6. As shown in FIG. 6, a fluid bed drying equipment 100C of the present embodiment further includes a water injection device 135 provided on the generated steam line 20 L 1 at the upstream side of the electric precipitator 105 in addition to the configuration of the fluid bed drying equipment 100B of the second embodiment. [0053] By spraying water at a low temperature into the generated steam 104 by the water injection device 135, 25 water vapor in the generated steam 104 is condensed. As a result, water vapor is condensed around nuclei formed of fine particles floating in the generated steam 104, and fine particles are further attached thereto. As a result, the diameter of fine particles increases. 30 By spraying cold fine water droplets at this point, the condensation phenomenon is accelerated around the nuclei of fine particles due to the rapid cooling. As a result, the efficiency of the fine particle collection is 22 improved. [0054] Further, since the specific resistance of particle is small in brown coal and the like, even if fine particles are once collected onto a collector electrode, 5 the collected fine particles re-scatter (jump) due to the small specific resistance. However, since the fine particles become nuclei of the condensation of the fine water droplets, the diameter of fine particles increases. Further, the collection efficiency of fine particles is 10 improved due to the wet surfaces of the fine particles. Therefore, the re-scattering of fine particles can be prevented. Further, fine particles are efficiently captured onto the electrode and the inner wall of the precipitator wetted 15 by the supply of water sprayed by the water injection device 135. Therefore, it is possible to improve the efficiency of the fine particles collection by the water injection. [0055] On the other hand, when the specific resistance 20 of particle is large, a problem of back discharge occurs. That is, a fine particle layer formed inside the electric precipitator 105 is dielectrically broken down, and, as a result, the charge state is destabilized, and the efficiency of fine particles collection is deteriorated. 25 However, even in such a case, since the surface conduction is increased due to the wet surfaces of fine particles, the back discharge does not occur. Therefore, it is possible to perform stable particles collection. [0056] As described above, according to the present 30 invention, wear of the compressor, the turbine and the like of the heat recovery system 106 arranged on the downstream side is reduced by significantly reducing the concentration of fine particles remaining in the generated steam 104.

23 Reference Signs List [0057] 100, 100A, 100B, 100C fluid bed drying equipment 101 brown coal 102 fluid bed dryer 5 103 heat transfer member 104 generated steam 105 precipitator 106 heat recovery system 107 fluidizing steam 10 108 dried brown coal 109 product coal 110 cooler 111 fluid bed 112 water treatment unit 15 113 waste water 114 circulation fan 115 solid component 130 superheated medium supply pipe (steam trace) 131 superheated medium 20 132 pipe 133 thermal insulator 135 water injection device 140 hot water spray device 141 collector 25 142 hot water 150 brown coal combustion boiler 151 furnace 152 combustion apparatus 153 flue gas duct 30 154 superheater 159 impact mill 165 turbine equipment 200 integrated coal gasification combined cycle 24 system 201a milled coal 202 gasified gas 203 coal gasification furnace 5 204 gas turbine (GT) 205 turbine flue gas 206 heat recovery steam generator (HRSG) 207 steam 208 steam turbine (ST) 10 209 generator (G) 210 mill 211 cyclone separator 212 gas purifier 213 combustor 15 214 combustion gas 215 flue gas 217 stack 218 steam condenser 219 air 20 220 compressor 221 air separation unit (ASU) A superheated steam B condensed water F freeboard section 25

Claims

1. Fluid bed drying equipment comprising: a fluid bed dryer for drying an object with high water content; 5 a generated steam line for discharging generated steam in a water-saturated state to the outside of the fluid bed dryer, the generated steam being generated when the object is dried by a heat transfer member; an electric precipitator disposed on the generated 10 steam line, for removing fine particles contained in the generated steam; a heat recovery system disposed on the generated steam line at the downstream side of the electric precipitator, for recovering heat of the generated steam; 15 a branch line for branching a part of the generated steam from the electric precipitator, fine particles being removed from the generated steam and the branched generated steam being supplied into the fluid bed dryer as fluidizing steam; and 20 a cooler for cooling the object taken out from the fluid bed dryer, wherein water at a saturation temperature or higher is supplied to the generated steam after fine particles are removed therefrom between the electric precipitator and the 25 heat recovery system in the generated steam line to remove fine particles remaining the generated steam.

2. The fluid drying equipment according to claim 1, wherein the supply of water at a saturation temperature or 30 higher and the removal of fine particles are performed by a scrubber.

3. The fluid drying equipment according to claim 1, Docket No. PMHA-13052-AU, ID 26 wherein the supply of water at a saturation temperature or higher is performed by a spray device, and the removal of fine particles are performed by a cyclone separator. 5

4. The fluid drying equipment according to any one of claims 1 to 3, further comprising a superheated medium supply pipe laid around the generated steam line and the electric precipitator, wherein fine particles are collected while reducing 10 the temperature of the generated steam until a part of entrainer is precipitated on a surface of an electrode of the electric precipitator.

5. The fluid drying equipment according to any one of 15 claims 1 to 4, wherein a water injection device is provided on the generated steam line at an upstream side of the electric precipitator.