JP6150679B2 - Fluidized bed heat recovery device and heat transporter used therefor - Google Patents

Description

  The present invention relates to a fluidized bed heat recovery apparatus that recovers heat from a gas and a heat transporter used therefor.

High-temperature exhaust gas is discharged from various heat engines such as engines and equipment such as incineration facilities. Therefore, in these devices, heat may be recovered from the exhaust gas by the heat recovery device.
A conventional fluidized bed heat recovery apparatus includes a riser in which a heat transporter flows, a solid-gas separation unit that separates exhaust gas and a heat transporter, and a downcomer that returns the separated heat transporter to the riser. . In such a fluidized bed heat recovery apparatus, first, high-temperature exhaust gas is introduced into the riser, and the heat transporter and the exhaust gas are mixed and flow to the solid-gas separation section. At this time, the heat of the exhaust gas is absorbed by the heat transporter in the riser. At the same time, there is a fluidized bed heat recovery device that renders impurities contained in the exhaust gas harmless. Thereafter, the heat transporter and the exhaust gas that have absorbed heat flow to the solid-gas separation unit, and are separated into a gas exhaust gas and a solid heat transporter by centrifugation or the like. The separated exhaust gas is discharged to the outside at a low temperature. Further, the heat transporter is returned again to the riser by the downcomer, and the above circulation is repeated.

  Here, conventionally, particles such as activated carbon, quicklime, and iron oxide have been used as heat transporters (see, for example, Patent Document 1).

JP 2008-275290 A

  However, activated carbon, quick lime, iron oxide, and other particles used as conventional heat transporters generally do not have high thermal conductivity, and in recent fluidized bed heat recovery devices that require high efficiency heat recovery, it is sufficient. There was a problem that heat recovery could not be achieved.

  In order to solve the above problems, an object of the present invention is to improve heat recovery efficiency.

  In order to achieve the above object, a heat transport body of the present invention is a heat transport body that absorbs heat of exhaust gas, and includes a carbon nanotube and a coating layer made of an inorganic material provided on the surface of the carbon nanotube. And the inorganic substance is a simple substance of Ti, Cu, Cr, Fe, Co, Ni, Zn, Au, Ag, Si, oxide, carbide, nitride, or a compound containing two or more of these. It is characterized by that.

The coating layer may have a structure in which the inorganic amorphous material is further laminated.
The carbon nanotubes further have cleaning nanoparticles supported on the surface of the carbon nanotubes, and the cleaning nanoparticles include zeolite, activated carbon, soda ash, or Fe, Ni, Co, Ti, W, Mo, V, Ru. , Ag, Au, Pt, Ir, Zn, K, and CaBa, an oxide, a carbide, or a compound containing two or more of these is preferable.

  Furthermore, the fluidized bed heat recovery device includes a riser that introduces exhaust gas from the outside to flow a mixed gas obtained by mixing the heat transporter and the exhaust gas, and converts the mixed gas into the exhaust gas and the heat transporter. A solid-gas separation unit that separates; a discharge port that discharges the separated exhaust gas; a heat exchanger that recovers heat from the mixed gas and / or the heat transporter and leads to the outside; and the heat transporter And a downcomer circulating in the riser.

  The solid-gas separation section rotates in the order of the riser side inlet, the outlet side outlet, the downcomer side outlet, and the riser side inlet, and charging is performed between the riser side inlet and the outlet side outlet. And a rotating fin that becomes uncharged while passing through the outlet on the downcomer side, and adsorbs the heat transporter from the mixed gas to the rotating fin during charging, thereby bringing the rotating fin into an uncharged state. It is preferable that the heat transport body is released from the rotary fin while passing through the vicinity of the downcomer side outlet and the heat transporter is recovered by the downcomer.

  Moreover, it is preferable that the said heat exchanger is provided in the outer wall of the said riser or / and the outer wall of the said downcomer.

  As described above, carbon nanotubes are used as the heat transporter and a coating layer is provided on the surface of the carbon nanotubes to prevent the carbon nanotubes from being bundled and prevent a decrease in heat recovery efficiency, as well as heat resistance and environmental resistance. The heat recovery efficiency can be improved with carbon nanotubes having a high specific surface area and high thermal conductivity.

Schematic showing the configuration of the fluidized bed heat recovery device of the present invention The schematic perspective view which illustrates the composition of the heat transport object of the present invention. Schematic explaining the structure of the solid-gas separation part by electrostatic separation of this invention

(Embodiment 1)
First, the fluidized bed heat recovery apparatus in Embodiment 1 and the heat transport body used therefor will be described with reference to FIGS.

  FIG. 1 is a schematic diagram showing the configuration of a fluidized bed heat recovery apparatus of the present invention, FIG. 2 is a schematic perspective view illustrating the configuration of a heat transporter of the present invention, and FIG. 3 is a solid-gas separation unit by electrostatic separation of the present invention. It is the schematic explaining the structure.

  As shown in FIG. 1, the fluidized bed heat recovery apparatus 3 of the present invention includes a riser 4 through which a heat transporter 1 flows, a solid-gas separation unit 6 that separates an exhaust gas 5 and a heat transporter 1, and a post-separation And a downcomer 7 for refluxing the heat transporter 1 to the riser 4. High-temperature exhaust gas 5 is discharged from various heat engines such as engines and devices 9 such as incineration facilities. The fluidized bed heat recovery device 3 of the present invention recovers heat from the high-temperature exhaust gas 5 discharged from the equipment 9. Details will be described below.

  The heat transporter 1 is accommodated in the riser 4 in advance, and when the exhaust gas 5 is introduced from the gas inlet 8, the exhaust gas 5 and the heat transporter 1 are mixed to form a mixed gas 10, and the riser 4 Flow. At this time, the heat transporter 1 absorbs the heat of the exhaust gas 5. That is, the heat transporter 1 recovers the temperature of the exhaust gas 5 and lowers the temperature. Thereafter, the mixed gas 10 of the exhaust gas 5 flowing through the riser 4 and the heat transporter 1 flows into the solid-gas separation unit 6 through the pipe 11. The solid-gas separation unit 6 separates the mixed gas 10 into the exhaust gas 5 and the heat transport body 1, exhausts the exhaust gas 5 from the chimney 12 as the discharge port, and discharges the heat transport body 1 to the downcomer 7. In the downcomer 7, the heat of the heat transporter 1 is absorbed by the heat exchanger 13, and the absorbed heat is recovered and used by an external device (not shown). Further, the downcomer 7 circulates the heat transporter 1, which has been cooled by absorption of heat, to the riser 4 through the pipe 15 and mixes it again with the exhaust gas 5.

  Here, in the present invention, carbon nanotubes 14 are used as the heat transporter 1. Moreover, as shown to Fig.2 (a), the coating layer 19 which consists of an inorganic substance is provided in the surface of the carbon nanotube 14 used as the heat transport body 1 of this invention, It is characterized by the above-mentioned.

  Since carbon nanotubes have higher thermal conductivity than activated carbon, quicklime, and iron oxide, which are generally used as heat transporters, and have a high specific surface area, they can efficiently absorb and transport heat.

  In addition, by coating the surface of the carbon nanotubes 14, the heat resistance of the carbon nanotubes 14 can be improved, and alteration of the carbon nanotubes 14 due to the surrounding atmosphere can be suppressed. As described above, the carbon nanotubes 14 have high thermal conductivity and can efficiently absorb and transport heat. However, since the carbon nanotubes 14 have low heat resistance and are easily altered, heat transport used for the high-temperature exhaust gas 5 is performed. It was not suitable for the body. However, by coating the surface of the carbon nanotube 14, heat resistance and environmental resistance are improved, and the heat transport body 1 that efficiently absorbs heat and transports heat even with high-temperature exhaust gas 5. Can do. At this time, the coating layer 19 having a lower thermal conductivity than that of the carbon nanotubes 14 is used. However, the heat transfer in the carbon nanotubes 14 is more efficient than the conventional heat transporter, so that the overall heat recovery efficiency is improved. Can be made. Furthermore, the carbon nanotubes 14 of the heat transporter 1 may be brought into contact with each other during flow to form a bundle. By coating the surface of the carbon nanotube 14, it is possible to prevent the heat transporter 1 from being bundled even if the heat transporter 1 comes into contact.

As the inorganic material used for the coating layer 19, Si, SiC, SiO ₂ or the like can be used. In addition, Ti, Cu, Cr, Fe, Co, Ni, Zn, Au, Ag, Si alone, an oxide, a carbide, a nitride, or a compound containing two or more of these can be used.

  If the coating layer 19 is too thin, it cannot suppress the destruction and combustion of the carbon nanotubes 14 due to heat and the alteration of the carbon nanotubes 14 due to the surrounding atmosphere. For example, it cannot withstand use in an oxygen atmosphere at 400 ° C. or higher, and heat resistance and environmental resistance cannot be improved. At the same time, if the film thickness is too thick, the flexibility of the carbon nanotubes 14 is lowered, and the piping may be damaged by erosion or the like due to the heat transporter 1 in flow. In addition, the efficiency of heat transfer from the surface is significantly reduced, and the overall heat recovery efficiency cannot be improved. Therefore, the thickness of the coating layer 19 is preferably 5 nm or more and 50 nm or less.

  The coding layer 19 is preferably provided densely on the entire outer surface of the carbon nanotube 14. By coating from the base to the tip of the carbon nanotube 14, there is no region where the carbon nanotube 14 is exposed, and heat resistance, environmental resistance, and bundle resistance are further improved. In the figure, the inner surface of the carbon nanotube 14 is also coated. However, since there are few opportunities to come into contact with the external environment or other heat transporters 1, the inner surface is not sufficient to coat the entire surface.

In order to improve heat resistance and toughness, the inorganic material of the coating layer 19 preferably has a crystal structure.
Alternatively, the coating layer 19 may have a structure in which an amorphous material such as amorphous Si is stacked on the inorganic crystal structure. By providing an amorphous material such as amorphous Si as the outermost layer, irregularities are formed on the surface of the amorphous material such as amorphous Si, thereby further increasing the contact area with the exhaust gas 5 and further improving heat absorption. To do. If the amorphous Si layer is coated directly on the surface of the carbon nanotubes 14, the carbon nanotubes 14 are exposed from defects in the amorphous structure, and the heat resistance and environmental resistance are reduced. Coating is not preferred.

Next, a method for coating the coating layer 19 will be described.
In the case of SiC, after introducing the carbon nanotubes 14 into a heat-resistant furnace in a vacuum state, Si is introduced into the heat-resistant furnace and heated to, for example, about 1000 ° C. to 1400 ° C. to sublimate Si, and the carbon nanotube 14 C React with atoms. In this way, the SiC coating layer 19 is formed on the surface of the carbon nanotube 14 by reducing Si and C.

  In the case of Si, after introducing the carbon nanotubes 14 into a vacuum heat-resistant furnace, Si is introduced into the heat-resistant furnace, Si is sublimated in the same manner as in the case of SiC, and after the formation of SiC, Si is further introduced. Then, for example, by heating to about 1000 ° C. to 1400 ° C., only Si atoms are deposited on the surface of the SiC to form the Si coating layer 19.

In the case of SiO ₂ , the Si-coated carbon nanotubes are further heated to, for example, about 1000 ° C. in an oxygen atmosphere to cause Si and O atoms to react with each other, thereby creating SiO _2. A coating layer 19 of SiO ₂ is formed on the surface.

In the above Si, SiO ₂ of the heating temperature, the non-crystal (amorphous Si, SiO ₂₎ is a condition involving, when crystallizing these coating layers 19, for example, 1300-1400 ° C. (SiO ₂ is Further heating is performed at 1600 ° C.

  Similarly, with respect to other inorganic coating methods, the coating layer 19 can be formed by introducing the carbon nanotubes 14 into a vacuum heat-resistant furnace and then introducing the coating material into the heat-resistant furnace and sublimating or evaporating it. Further, by performing sublimation or evaporation in an oxide atmosphere or a nitride atmosphere, oxides or nitrides of the coating material can be formed. If reacted with C atoms of the carbon nanotubes 14, carbides of the coating material can be formed. .

  Here, since the carbon nanotubes 14 may break during the flow if the strength is insufficient, the carbon nanotubes 14 are carbon nanotubes having two or more layers. In the present invention, the multi-walled carbon nanotubes used are three or more layers. It is desirable that In that case, at least the diameter is preferably 5 nm or more. At the same time, it is preferable that the carbon nanotubes 14 have a high specific surface area in order to ensure flexibility and prevent breakage and damage to the apparatus, and to improve heat exchange performance. Therefore, the diameter of the carbon nanotube 14 is preferably 300 nm or less. In addition, if the carbon nanotubes 14 are long, they frequently collide with other carbon nanotubes 14 during flow, and the carbon nanotubes 14 are entangled with each other to deteriorate the heat absorption performance. It becomes easy to cause clogging with the heat recovery device. Therefore, the length of the carbon nanotube 14 is preferably 500 μm or less.

  In the fluidized bed heat recovery apparatus 3, the example in which the heat exchanger 13 is provided in the downcomer 7 has been described, but the heat exchanger 16 may be provided in the riser 4 and the pipe 11. Moreover, you may provide the heat exchangers 13 and 16 in any one of the downcomer 7, the riser 4, the pipe 11, etc., or combining these places. For example, the heat exchangers 13 and 16 are heat exchange pipes provided in a coil shape along the outer wall of the downcomer 7 or the riser 4, and a structure in which a heat medium such as a coolant flows through the heat exchange pipes. can do. When the heat medium passes through the heat exchange pipe, heat exchange is performed between the mixed gas 10 or the separated heat transporter 1 and the heat medium via the downcomer 7 or the outer wall of the riser 4 and the pipe 11. The mixed gas 10 or the separated heat transporter 1 is cooled and heat is recovered in the heat medium. The heat recovered in the heat medium is conducted to the external device, and the heat recovered in the external device is used. Further, when the mixed gas 10 inside the downcomer 7, riser 4, pipe 11, etc. and the flow area of the heat transport body 1 are sufficiently secured, the heat exchange pipe can be replaced with It may be provided inside. In this case, since the mixed gas 10 or the heat transporter 1 and the heat exchange pipe are in direct contact with each other and the contact area is increased, the heat transfer is efficiently performed and the heat exchange efficiency is further improved.

  Further, the solid-gas separation unit 6 may be performed by centrifugal separation using the specific gravity difference between the exhaust gas 5 and the heat transporter 1, but may be electrostatically separated. When electrostatic separation is performed, it is preferable because separation can be easily performed even when the heat transporter 1 is small as compared with the case of centrifugation.

As shown in FIG. 3, the electrostatic separation type solid-gas separation unit 6 includes a rotating fin 17 that can be controlled to be in a charged state or an uncharged state. When the mixed gas 10 introduced from the inlet on the riser 4 side is introduced into the solid-gas separation unit 6, it comes into contact with the rotating rotating fins 17. At this time, the rotary fin 17 is charged from the position before contacting the mixed gas 10 (position A) to the position contacting the mixed gas (position B) and rotated to a position exceeding the vicinity of the outlet on the chimney 12 side (position C). The charged state is released and the non-charged state is maintained even in the vicinity (position D) near the outlet on the downcomer 7 side. Thus, by controlling the charged state and the non-charged state according to the rotational position of the rotary fin 17, the carbon nanotube 14 has conductivity. And the charged state is maintained even at the position C, so that only the exhaust gas 5 is discharged from the chimney 12 while the heat transporter 1 is adsorbed to the rotary fin 17 and the charged state is released at the position D. The heat transport body 1 is opened from the rotating fins 17 and only the heat transport body 1 is discharged to the downcomer 7. As described above, by controlling the charging state and non-charging state of the rotating rotary fin 17, the rotary fin 17 is charged in the vicinity of the outlet on the chimney 12 side that discharges the exhaust gas 5, and only the exhaust gas 5 is discharged. However, by not charging near the outlet on the downcomer 7 side, the heat transporter 1 is discharged and discharged from the downcomer 7. In order to more reliably separate the heat transporter 1 and the exhaust gas 5 by electrostatic separation, the carbon nanotubes 14 are further provided with metal particles such as iron or ferromagnetic metal (for example, Fe, Co, Ni). It may be supported. When the heat transporter 1 and the exhaust gas 5 are separated by centrifugation, particles having a specific gravity larger than that of the carbon nanotubes 14 may be supported.
(Embodiment 2)
Next, the configuration of the heat transporter in the second embodiment will be described with reference to FIGS.

  The heat transporter in the second embodiment carries the cleaning nanoparticles 2 for cleaning the exhaust gas on the surface of the carbon nanotubes relative to the heat transporter used in the fluidized bed heat recovery apparatus in the first embodiment. It is characterized by that. The cleaning particles are not limited to a spherical shape, and may be a columnar shape, a flat shape, or the like.

  As shown in FIG. 2B, the heat transport body 18 of the present embodiment has the cleaning nanoparticles 2 on the surface of the coating layer 19 of the carbon nanotubes 14 coated with the coating layer 19 shown in the first embodiment. Carry. Thus, by carrying the cleaning nanoparticles 2 having a cleaning function on the surface of the coating layer 19 of the carbon nanotubes 14 having a high heat absorption and a high heat transport rate, the heat transporter 18 can contain NOx and SOx contained in the exhaust gas. It is possible to improve the heat recovery efficiency while purifying the harmful substances such as these. In addition, since the carbon nanotubes 14 are coated, the carrying performance of the cleaned nanoparticles 2 is improved, and the cleaned nanoparticles 2 are dropped from the carbon nanotubes 14 or the cleaned nanoparticles 2 are thermally aggregated on the carbon nanotubes 14. Can be suppressed. Further, since the cleaning nanoparticles 2 are supported on the carbon nanotubes 14, the cleaning nanoparticles 2 can be electrostatically separated simultaneously with the carbon nanotubes 14.

Some exhaust gases 5 discharged from various devices 9 contain impurities, and in the fluidized bed heat recovery device 3, there are also those that detoxify harmful substances together with heat recovery.
In the fluidized bed heat recovery apparatus 3 of the present embodiment, instead of the heat transport body 1 in the first embodiment, the heat transport body 18 carrying the cleaned nanoparticles 2 as described above is used, and the following is performed. The exhaust gas 5 is treated. That is, the heat transport body 18 is accommodated in the riser 4 in advance, and when the exhaust gas 5 is introduced from the gas inlet 8, the exhaust gas 5 and the heat transport body 18 are mixed to form the mixed gas 10. Flow in 4 At this time, the heat transporter 18 absorbs the heat of the exhaust gas 5 and detoxifies harmful substances contained in the exhaust gas 5. That is, the heat transporter 18 recovers the temperature of the exhaust gas 5 and lowers the temperature while purifying the exhaust gas 5 by desulfurization and denitration. Thereafter, the mixed gas 10 of the exhaust gas 5 flowing through the riser 4 and the heat transporter 18 flows into the solid-gas separation unit 6 through the pipe 11. The solid-gas separation unit 6 separates the mixed gas 10 into the exhaust gas 5 and the heat transport body 18, exhausts the exhaust gas 5 from the chimney 12 that is the discharge port, and discharges the heat transport body 18 to the downcomer 7. Further, the downcomer 7 circulates the heat transporter 18, which has been cooled by absorbing heat, to the riser 4 through the pipe 15 and mixes it again with the exhaust gas 5.

  Thus, by carrying the cleaning nanoparticles 2 having a cleaning function on the carbon nanotubes 14 having a high heat absorption and a high heat transport rate, the heat transport body 18 has a cleaning function and improves the heat recovery efficiency. Can do.

  Further, the cleaning nanoparticles 2 may be mixed separately without being supported on the carbon nanotubes 14. However, if the cleaning nanoparticles 2 exist alone, the cleaning nanoparticles 2 are cleaned when mixed with the exhaust gas 5 and flow. Nanoparticles 2 collide with each other, and the detoxification effect of harmful substances may be reduced. That is, the cleaning nanoparticles 2 may be aggregated and coarsened, the entire surface area may be reduced, and the harmful effect of harmful substances may be reduced. Furthermore, if the fine cleaning nanoparticles 2 are present alone, the cleaning nanoparticles 2 may clog the pipe 11 or the connection portion between the pipe 11 and the riser 4 or the solid-gas separation unit 6 during flow. May occur. Therefore, in the present invention, the cleaning nanoparticle 2 is supported on the surface of the carbon nanotube 14 and the cleaning nanoparticle 2 is prevented from flowing alone, thereby maintaining and flowing the cleaning function of the cleaning nanoparticle 2. The effectiveness of the layer heat recovery device can be maintained.

  Moreover, the material of the cleaning nanoparticle 2 should just have a catalyst function with respect to harmful substances, such as desulfurization and denitration, For example, a zeolite, activated carbon, and soda ash can be used. Alternatively, Fe, Ni, Co, Ti, W, Mo, V, Ru, Ag, Au, Pt, Ir, Zn, K, and CaBa may be used alone. Furthermore, these oxides and carbides may be used, or a compound containing two or more of these may be used. In addition, the particle diameter of the cleaning nanoparticle 2 is preferably 3 nm or more and 100 nm or less in consideration of being supported on the carbon nanotubes 14 and the cleaning efficiency.

DESCRIPTION OF SYMBOLS 1 Heat transport body 2 Cleaning nanoparticle 3 Fluidized bed heat recovery device 4 Riser 5 Exhaust gas 6 Solid-gas separation part 7 Downcomer 8 Gas inlet 9 Equipment 10 Mixed gas 11 Pipe 12 Chimney 13 Heat exchanger 14 Carbon nanotube 15 Pipe 16 Heat exchanger 17 Rotating fin 18 Heat transporter 19 Coating layer

Claims (6)

A heat transporter that absorbs heat of exhaust gas,
Carbon nanotubes,
A coating layer made of an inorganic material provided on the surface of the carbon nanotube, wherein the inorganic material is a simple substance of Ti, Cu, Cr, Fe, Co, Ni, Zn, Au, Ag, Si, oxide, carbide, A heat transporter characterized by being a nitride or a compound containing two or more of these.   The heat transport body according to claim 1, wherein the coating layer has a structure in which the inorganic amorphous material is further laminated. Further comprising cleaned nanoparticles supported on the surface of the carbon nanotubes;
The cleaning nanoparticles may be zeolite, activated carbon, soda ash, or Fe, Ni, Co, Ti, W, Mo, V, Ru, Ag, Au, Pt, Ir, Zn, K, CaBa, simple substance, oxide, The heat transporter according to claim 1, wherein the heat transporter is a carbide or a compound containing two or more of these. A riser that introduces exhaust gas from the outside to flow a mixed gas obtained by mixing the heat transport body according to any one of claims 1 to 3 and the exhaust gas;
A solid-gas separation unit that separates the mixed gas into the exhaust gas and the heat transporter;
An exhaust port for discharging the separated exhaust gas;
A heat exchanger for recovering heat from the mixed gas or / and the heat transporter and leading it to the outside;
A fluidized bed heat recovery apparatus comprising a downcomer that circulates the heat transporter to the riser. The solid-gas separation part rotates in order of the outlet side outlet from the riser side inlet, the downcomer side outlet, the riser side inlet, and is charged between the riser side inlet and the outlet side outlet, A rotary fin that is uncharged while passing through the downcomer side outlet,
The heat transport body is released from the rotary fin while passing through the vicinity of the downcomer side outlet by adsorbing the heat transport body from the mixed gas to the rotary fin during charging and making the rotary fin uncharged. The fluidized bed heat recovery apparatus according to claim 4, wherein the heat transporter is recovered by the downcomer.   6. The fluidized bed heat recovery apparatus according to claim 4, wherein the heat exchanger is provided on an outer wall of the riser and / or an outer wall of the downcomer.

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