JP2013180243A - Sludge drying system - Google Patents

Abstract

The present invention provides a sludge drying system capable of effectively recovering and using steam generated in a drying process and saving energy of the entire system.
A sludge drying system (10) includes a dryer (12) that heats dried dewatered sludge by heating, a circulation line (20) that heats exhaust gas from the dryer (12) and circulates the exhaust gas again to the dryer (12). And a capacitor 38 as an energy recovery device for recovering the energy of the steam contained in the exhaust gas in the circulation pipe 20, and the absolute humidity of the exhaust gas is 2 (kg-H ₂ O / kg-DA) or more Thus, the energy of the steam in the dry exhaust gas generated in the dryer 12 is recovered and reused.
[Selection] Figure 1

Description

  The present invention relates to a sludge drying system for drying dehydrated sludge.

  Since dewatered sludge such as sewage sludge contains about 80% of water, enormous energy is required for water evaporation during heat treatment of sludge such as incineration, drying and carbonization. From the viewpoint of energy saving at the time of sludge heat treatment, it is expected that the energy is effectively recovered and reused.

  With regard to such a sludge drying system, for example, in Patent Document 1, water recovered from the exhaust gas (gasification gas) of a gasification furnace provided at the subsequent stage of the dryer is evaporated and pressurized with a compressor. A configuration for reusing steam as a heat source for a dryer is disclosed.

JP 2004-75740 A

  Usually, the energy spent for water evaporation of the dewatered sludge is recovered as hot wastewater when the evaporated water is condensed in the generated exhaust gas scrubber. In a general scrubber, the temperature of the warm drainage is about 50 ° C. and is not suitable for reuse. In addition, efforts have been made to obtain hot wastewater of about 75 ° C. with a scrubber, but in principle, the heat energy of steam that can be recovered is limited to the excess of saturated humidity in the gas at the temperature of the hot wastewater. At present, it has not been possible to effectively recover the heat energy.

  The present invention has been made in consideration of the above-mentioned problems of the prior art, and provides a sludge drying system that can effectively recover and use steam generated in the drying process to save energy in the entire system. The purpose is to do.

The sludge drying system according to the present invention comprises a drying container for drying dewatered sludge that is carried in by heating, and a circulation pipe that heats the exhaust gas from the drying container and circulates it again to the drying container. The drying system includes an energy recovery device that recovers energy of steam contained in the exhaust gas in the circulation pipe, and the exhaust gas has an absolute humidity of 2 (kg-H ₂ O / kg-DA) or more. It is maintained.

According to such a configuration, since the absolute humidity of the exhaust gas is maintained at 2 (kg-H ₂ O / kg-DA) or more, the energy (thermal energy) of the vapor in the exhaust gas is converted into a capacitor, a scrubber, etc. The energy recovery device can effectively recover the energy and the recovered energy can be reused as the driving power and driving force of each part of the system, so that the energy saving of the entire system can be achieved.

In this case, exhaust gas can be produced by adopting an airtight structure for preventing the outside air from entering the drying vessel and the circulation pipe, for example, a structure for preventing the entry of outside air by applying a seal structure to the drying vessel. Can be easily maintained at 2 (kg-H ₂ O / kg-DA) or more.

  Further, when the heating device for heating the exhaust gas circulating through the circulation pipe is an indirect heating method in which the exhaust gas flowing through the circulation pipe is indirectly heated from the outside of the circulation pipe, the drying container and the circulation pipe It is possible to more reliably prevent the outside air from entering the interior.

  When an energy utilization device that uses the energy recovered by the energy recovery device is provided, the energy recovered by the energy recovery device such as a capacitor is used by the energy utilization device such as a binary generator, and the driving power and driving force of each part of the system Can be reused effectively.

  The energy recovery device is a condensing device that condenses the steam by exchanging heat with the heat transfer medium, and the energy utilization device is a heat transfer medium heated by condensation of the vapor in the energy recovery device. And a binary generator that rotates the turbine by exchanging heat with the heat medium having a boiling point lower than that of the heat transfer medium and evaporating the heat medium, or power generated by the rotation of the turbine. It may be a power generator that generates

  If a dust collector that removes the exhaust gas is provided between the drying container and the energy recovery device in the flow direction of the exhaust gas, dust in the exhaust gas adheres to the energy device, and energy recovery efficiency decreases. Can be suppressed.

According to the present invention, the absolute humidity of the exhaust gas is maintained at 2 (kg-H ₂ O / kg-DA) or more, so that the energy of the vapor in the exhaust gas is effective in an energy recovery device such as a condenser or a scrubber. Since the recovered energy can be reused as driving power and driving force for each part of the system, energy saving of the entire system can be achieved.

FIG. 1 is an overall configuration diagram of a sludge drying system according to an embodiment of the present invention. FIG. 2 is a configuration diagram illustrating an example of the structure of the superheated steam dryer. FIG. 3 is a configuration diagram illustrating an example of the structure of the capacitor. FIG. 4 is a configuration diagram illustrating an example of the structure of the binary generator. FIG. 5 is a block diagram showing an example of the structure of a scrubber, FIG. 5 (A) is a block diagram of a spray tower type scrubber, and FIG. 5 (B) is a block diagram of a packed tower type scrubber. FIG. 5C is a configuration diagram of a plate tower type scrubber. FIG. 6 is a graph showing the relationship between gas saturation humidity and temperature. FIG. 7 is a graph showing the relationship between the vapor ratio in the air and the evaporation rate of water. FIG. 8 is an overall configuration diagram of a sludge drying system according to a first modification of the drying system shown in FIG. 1. FIG. 9 is an overall configuration diagram of a sludge drying system according to a second modification of the drying system shown in FIG. 1. FIG. 10 is an overall configuration diagram of a sludge drying system according to a third modification of the drying system shown in FIG. 1.

  Hereinafter, preferred embodiments of a sludge drying system according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram of a sludge drying system 10 according to an embodiment of the present invention. The sludge drying system 10 according to the present embodiment (hereinafter also simply referred to as “drying system 10”) dries dehydrated sludge such as sewage sludge with the dryer 12 and is contained in the exhaust gas from the dryer 12. This is an energy-saving drying system that recovers and reuses the energy of steam.

  As shown in FIG. 1, a drying system 10 includes a dryer (superheated steam dryer) 12, a drying line 10 a that mainly performs a drying treatment of dehydrated sludge, and exhaust gas (dry exhaust gas) discharged from the dryer 12. And an energy recovery line 10b that recovers and reuses the energy (latent heat and sensible heat) of the steam (sludge drying steam) contained in the exhaust gas.

  First, the configuration of the drying line 10a will be described.

  The drying line 10a includes a dewatered cake storage tank 14 for storing dewatered sludge that has been dehydrated by, for example, a water content of about 78% by a dehydrator (not shown), and a dehydrated sludge transported from the dewatered cake storage tank 14. By directly heating with a dry exhaust gas (superheated steam) that circulates and uses, for example, a dryer 12 that is dried until the amount of water reaches about 20%, and particulates contained in the exhaust gas discharged from the dryer 12 are collected. And a circulation pipe 20 that indirectly heats the dried exhaust gas discharged from the dust collector 16 by a heat exchanger (heating device) 18 and supplies the dried exhaust gas as a heat source of the dryer 12.

  FIG. 2 is a configuration diagram illustrating an example of the structure of the dryer 12. As shown in FIGS. 1 and 2, the dryer 12 has a bearing base 22a, 22b fixed on a floor surface of a factory or the like, a bearing base 22a, 22b, and a pair of bearings 23a, 23b with the axial direction as the center. And a cylindrical rotating shell (drying container) 24 that is rotatably supported. In the dryer 12, the downstream end of the sludge feeder 26 that feeds the dewatered sludge conveyed from the dewatered cake storage tank 14 into the internal space of the rotary shell 24 protrudes into the rotary shell 24 through the bearing base 22 a. It is connected. The sludge feeder 26 is, for example, a Mono pump. That is, in the dryer 12, dewatered sludge is directly charged from the MONO pump (sludge feeder 26) into the rotary shell 24.

  In order to inject the dry exhaust gas to be circulated supplied from the circulation pipe 20 into the rotary shell 24, the upper surface of the bearing base 22 a on the side to which the sludge injector 26 is connected is arranged on the downstream side of the heat exchanger 18. An inlet port 28a to which the pipe 20a is connected is provided. On the other hand, the exhaust gas containing the vapor and odor evaporated from the dehydrated sludge by the drying action by the dry exhaust gas in the rotary shell 24 is circulated from the outlet port 28b provided on the upper surface of the other bearing base portion 22b to the pipe 20b, and the dust collector 16 Is passed through the pipe 20c, introduced into the heat exchanger 18 under the driving action of the circulation fan 30, and circulated again into the pipe 20a.

  Accordingly, in the dryer 12, the dewatered sludge that has been thrown into the rotary shell 24 from the sludge thrower 26 is conveyed while being stirred by the stirring mechanism 32 in the rotary shell 24, and thrown into the rotary shell 24 from the inlet port 28 a. The dried exhaust gas is heated and dried (for example, about 550 ° C.). The dry exhaust gas (for example, about 170 ° C.) containing the sludge drying steam that is the vapor evaporated from the dewatered sludge flows from the outlet port 28b to the circulation line 20, while the dried sludge that is the dried dewatered sludge is a bearing. It is discharged to the outside from a discharge port 28c provided on the lower surface of the base 22b. Thus, in the present embodiment, an internal heat type rotary dryer is used as the dryer 12.

  The dust collector 16 removes particulates and the like contained in the exhaust gas introduced from the outlet port 28b of the dryer 12 through the pipe 20b and discharges it as dry sludge, while circulating the exhaust gas from which dust has been removed to the pipe 20c. It is a device to let you. In the present embodiment, as will be described later, in order to recover and reuse the energy (thermal energy) of the sludge dry steam that is the steam contained in the dry exhaust gas in the energy recovery line 10b, the dust collector 16 is included in the dry exhaust gas. A device that removes fine particles such as dried sludge while maintaining the energy of the contained vapor is used. Therefore, it is preferable to use a cyclone type dust collector or a bag filter as the dust collector 16, and a conventionally known one can be used.

  The heat exchanger 18 heats the sludge dry steam that has circulated through the pipe 20c at, for example, about 170 ° C. with high-temperature combustion exhaust gas discharged from a combustion furnace 34, which will be described later, and superheats it to, for example, about 550 ° C. to the pipe 20a. It is a heating device for circulating. The dry exhaust gas flowing from the pipe 20c to the pipe 20a is indirectly heated by the combustion exhaust gas from the outside of the pipe and heated. That is, the heat exchanger 18 is an indirect heating type heating device. The heat exchanger 18 may be configured not to use the combustion exhaust gas discharged from the combustion furnace 34 but to use the heat of the exhaust gas of other equipment, a boiler, or the like.

  In such a drying line 10a, the exhaust gas circuit composed of the rotating shell 24 and the circulation pipe 20 of the dryer 12 prevents the outside air from entering the interior, and increases the absolute humidity in the exhaust gas. It is a closed circuit with an airtight structure that can be used.

  Next, the configuration of the energy recovery line 10b will be described.

  The energy recovery line 10b includes a condenser (condenser, energy recovery device) 38 that recovers the energy (latent heat and sensible heat) of the steam by condensing the steam in the dry exhaust gas that has passed through the dust collector 16 from the dryer 12. Deodorizing treatment is performed by burning a binary generator (energy utilization device) 40 that uses energy recovered by the condenser 38 and a gas (non-condensable gas) that has not been condensed by the condenser 38 together with fuel 42 such as city gas. A combustion furnace 34 and a preheater (heat exchanger) 44 that preheats the combustion air of the fuel 42 in the combustion furnace 34 using the heat of the combustion exhaust gas from the combustion furnace 34 through the heat exchanger 18 are provided.

  FIG. 3 is a configuration diagram showing an example of the structure of the capacitor 38. As shown in FIGS. 1 and 3, the capacitor 38 includes a cylindrical body 48 in which a hot water conduit 46 is provided. The condenser 38 condenses the steam in the dry exhaust gas flowing into the cylinder 48 from the inlet port 52a to which the pipe 50 branched from the pipe 20c is connected by heat exchange with the hot water flowing through the hot water pipe 46. It is a condenser and a conventionally well-known thing can be used.

  That is, the condenser 38 condenses the vapor in the dry exhaust gas flowing into the cylinder 48 from the inlet port 52a by the hot water flowing from the hot water inlet port 54a through the hot water conduit 46 to the hot water outlet port 54b. This is an energy recovery device that recovers the energy of steam with hot water, and the generated condensed water is drained from the discharge port 56, while the remaining non-condensable gas (non-condensable gas) flows from the outlet port 52b to the pipe 58. Discharged. In this manner, the condenser 38 simultaneously recovers the sensible heat for the temperature drop until the steam is condensed and the latent heat when the steam is condensed.

  FIG. 4 is a configuration diagram illustrating an example of the structure of the binary generator 40. The binary power generator 40 is a power generator that generates power using steam of a low-boiling-point heat medium (working medium) such as chlorofluorocarbon, ammonia, or hydrocarbon, and a conventionally known one can be used.

  As shown in FIGS. 1 and 4, the binary generator 40 includes an evaporator 60 that evaporates the working medium, a turbine 62 that is rotated by the working medium evaporated by the evaporator 60, and a working medium that has expanded through the turbine 62. A condenser 70 that cools and condenses the refrigerant and a pump 66 that circulates the working medium in the closed circuit 65, and can be generated by a generator 68 that is connected to the turbine 62. A cooling medium 67 circulates in the cooling circuit 67 for condensing the working medium flowing in the closed circuit 65 by the condenser 70, and this cooling medium is sent from the condenser 70 to the cooling tower (cooling tower) 64 by the pump 69. Circulated. In this case, the electricity generated by the generator 68 is used as driving power for each device constituting the drying system 10 such as the dryer 12 and the circulation fan 30, for example. It is illustrated.

  A pipe 72b from the hot water outlet port 54b of the condenser 38 and a pipe 72a to the hot water inlet port 54a are connected to the evaporator 60. That is, the evaporator 60 heats and evaporates the working medium having a boiling point lower than that of the hot water with the hot water obtained by collecting the energy of the steam in the dry exhaust gas by the condenser 38. The temperature needs to be lower than warm water (for example, about 75 ° C. to 95 ° C.) in which energy is recovered from steam in the dry exhaust gas.

  The combustion furnace 34 secures an amount of heat necessary for drying sludge with a fuel such as city gas, and also discharges gas (non-condensable gas, dry air) from a condenser 38 circulated from a pipe 58 under the driving action of a fan 74. ) Is burned together with the fuel 42 to thermally decompose the odor in the gas and deodorize it. The combustion exhaust gas from the combustion furnace 34 flows through the heat exchanger 18 and superheats the dry exhaust gas, and then is released into the atmosphere through the preheater 44. The preheater 44 constitutes a preheating circuit 78 that preheats the combustion air in the combustion furnace 34 using the heat of the combustion exhaust gas from the combustion furnace 34 under the driving action of the fan 76. Depending on the configuration, it may be omitted.

  Here, the heat exchanger 18 is an indirect heating method in which the dried exhaust gas flowing in the circulation pipe 20 is indirectly heated from the outside of the circulation pipe 20 by the combustion exhaust gas. The airtight structure which prevents that external air approachs into the circulation pipe line 20 is comprised. That is, the combustion furnace 34 constitutes a heating device that indirectly heats the dried exhaust gas flowing through the circulation pipe 20 together with the heat exchanger 18.

  In such an energy recovery line 10b, as an energy recovery device for recovering the energy of the sludge drying steam, a device other than the capacitor 38, for example, a scrubber that sprays hot water sent from a water pump into exhaust gas is used. (See FIG. 5). The scrubber may be a conventionally known scrubber, for example, a spray tower type scrubber 80a (see FIG. 5A), a packed tower type scrubber 80b (see FIG. 5B), a plate tower type scrubber 80c (see FIG. 5B). For example, refer to FIG.

  For example, in the scrubber 80a, as shown in FIG. 5 (A), hot water is sprayed by a plurality of spray sections 84a installed in the internal space of the spray tower 84 by the water pump 82, and dry exhaust gas is sprayed from the steam inlet 84b. By introducing into the tower 84, the vapor | steam in dry waste gas is condensed with the sprayed warm water, and the energy is collect | recovered. The hot water that has recovered this energy is circulated out of the spray tower 84 by the water pump 82, and in the heat exchanger 85, the hot water that has flowed through the pipe 72 a from the evaporator 60 of the binary generator 40 under the driving action of the pump 83. After the heat exchange, the waste water is again supplied to the spray section 84a, and unnecessary waste water is discharged from the drain port.

  As shown in FIG. 5B, the scrubber 80b has a configuration in which the contact efficiency between steam and hot water is increased by filling the packed column 86 with a filler 86a. Further, as shown in FIG. 5C, the scrubber 80 c has a configuration in which contact efficiency between steam and hot water is increased by providing several stages of shelf stages 88 a in the tower column 88. Of course, these scrubbers 80b and 80c can also condense the vapor in the dry exhaust gas and recover the energy by a method substantially similar to that of the scrubber 80a.

  The drying system 10 according to the present embodiment is basically configured by the drying line 10a and the energy recovery line 10b as described above, and the dry exhaust gas from the dryer 12 circulates through the circulation line 20, New steam generated from the dewatered sludge is supplied to the energy recovery line 10b via the pipe 50 branched from the pipe 20c, and the energy is effectively recovered and reused.

  By the way, in the said drying system 10, although the structure which collect | recovers the energy which the vapor | steam which generate | occur | produces from dehydrated sludge with the dryer 12 is used with the condenser 38 and the scrubbers 80a-80c, the energy (especially latent heat) which the said vapor | steam has is used. In order to effectively recover and maintain the power generation efficiency of the binary generator 40 within a practical range, outside air is in the exhaust gas closed circuit constituted by the rotating shell 24 and the circulation pipe 20 of the dryer 12. It is configured not to enter, and it is necessary to manage the absolute humidity of the vapor in the dry exhaust gas discharged from the dryer 12 to a predetermined value or more.

  Then, next, the absolute humidity value at which the latent heat of the sludge drying steam can be effectively recovered by the energy recovery device such as the condenser 38 or the scrubbers 80a to 80c will be described with reference to the graph of FIG.

FIG. 6 is a graph showing the relationship between the saturated humidity (kg-H ₂ O / kg-DA) of gas and the temperature (° C.), that is, the absolute humidity at which the gas is higher than the upward curve at a predetermined temperature. If it has, it indicates that the steam in the range up to the curve (saturated humidity) drains, and when draining, the steam releases latent heat, indicating that the latent heat of that part can be recovered. ing. For example, if the absolute humidity of the gas is 10 (kg-H ₂ O / kg-DA), when the gas is cooled to 90 ° C., latent heat recovery is possible within the range indicated by the arrow C2a. The latent heat in the range indicated by the arrow C2b is not drained and cannot be recovered. Further, on the right side of the graph, bar graphs of reference values 0.5, _{2, and} 10 (kg-H ₂ O / kg-DA) of absolute humidity of the sludge dry steam are also shown.

First, in the conventional dryer, the absolute humidity in the gas in the drying process is about 0.3 to 0.5 (kg-H ₂ O / kg-DA). Therefore, referring to a bar graph with a reference value of 0.5 in FIG. 6, when the absolute humidity of the dry exhaust gas discharged from the dryer 12 is 0.5 (kg-H ₂ O / kg-DA). The steam cannot be condensed even if the temperature is reduced to about 80 ° C. (see the broken line A in FIG. 6), that is, the hot water for condensing the dry exhaust gas discharged from the dryer 12 is 80 ° C. or less. It can be seen that the latent heat that can be recovered is very small even at 80 ° C. or lower.

Therefore, in this embodiment, the absolute humidity in the gas discharged from the dryer 12 is managed in a range of 2 (kg-H ₂ O / kg-DA) or more. First, referring to the bar graph of reference value 2 in FIG. 6, when the absolute humidity of the dry exhaust gas discharged from the dryer 12 is 2 (kg-H ₂ O / kg-DA), it is about 92 ° C. When the temperature is decreased to about 90%, the steam can be condensed (see the broken line B in FIG. 6), and at 90 ° C., about 30% of the latent heat can be recovered (see the arrow B1 in FIG. 6). At 75 ° C., about 81% of the latent heat can be recovered (see arrow B2 in FIG. 6). For example, in the case of 75 ° C., 1.62 (= 2-1) obtained by subtracting the saturation humidity 0.38 (kg-H ₂ O / kg-DA) from the absolute humidity 2 (kg-H ₂ O / kg-DA). .38) Since moisture of (kg-H ₂ O / kg-DA) is condensed, 81% (= 1.62 / 2 × 100) of latent heat of moisture can be recovered.

Next, referring to the bar graph of the reference value 10 in FIG. 6, when the absolute humidity of the dry exhaust gas discharged from the dryer 12 is 10 (kg-H ₂ O / kg-DA), 96 ° C. When the temperature is reduced to the extent, it becomes possible to condense the vapor (see the broken line C in FIG. 6), and for example, at 95 ° C., about 70% of the latent heat can be recovered (arrow in FIG. 6). C1), about 90% of the latent heat can be recovered at 90 ° C. (see arrow C2a in FIG. 6), and about 96% of the total latent heat can be recovered at 75 ° C. (see FIG. 6). (See arrow C3 in FIG. 6).

In the present embodiment, the absolute humidity in the dry exhaust gas discharged from the dryer 12 is managed in the range of 2 (kg-H ₂ O / kg-DA) or more, and energy recovery devices such as the condenser 38 and the scrubbers 80a to 80c are used. For example, by performing energy recovery with warm water at 75 ° C., 81 to 96% of the energy of the entire latent heat of the steam in the dry exhaust gas can be recovered. For this reason, the latent heat which the vapor | steam which generate | occur | produces from a dewatering sludge can be collect | recovered with high efficiency, and it can be used as a heat source of the binary generator 40 with the collect | recovered sensible heat simultaneously. In addition, by setting the absolute humidity of the dry exhaust gas discharged from the dryer 12 to 2 (kg-H ₂ O / kg-DA) or more, the energy recovery device such as the condenser 38 or the scrubbers 80a to 80c is used with hot water of 90 ° C. It is also possible to perform energy recovery. In other words, in the case of the dryer 12, the absolute humidity in the exhaust gas is a high value of 2 (kg-H ₂ O / kg-DA) or higher, so that the energy recovery rate can be improved at the same temperature. . Further, if the energy recovery ratio is the same, higher temperature wastewater can be obtained, and this high temperature wastewater can be supplied to the binary generator 40, and the power generation efficiency of the binary generator 40 can be improved. .

Thus, in order to manage the absolute humidity of the dry exhaust gas discharged from the dryer 12 to 2 (kg-H ₂ O / kg-DA) or more, as described above, the heat exchanger 18 is an indirect heating method, Air mixing during heating of exhaust gas is prevented. Further, it is effective to make the exhaust gas route from the rotary shell 24 of the dryer 12 to the circulation line 20 have an airtight structure so as to reduce the leakage of outside air as much as possible. Therefore, for the dryer 12, for example, the drum seal portion of the rotary shell 24 has a carbon packing structure or a steam purge seal structure, and the dewatered sludge has a direct input structure from the sludge input device 26, which is a Mono pump, and further has a dry sludge. It is also effective to adopt a seal structure in which a double damper 90 is provided in the discharge path of the dried sludge from the discharge port 28c that is a discharge unit or the dust collector 16.

  Next, Fig. 7 shows a graph of the relationship between the proportion of steam in the air and the evaporation rate of water (Publisher: Energy Conservation Center, Energy Conservation Technology Practice Series Revision / Drying Device: Revised October 12, 1995) Issued from the first print, page 35). In general, in low-temperature air, the evaporation rate of water decreases as the mixing ratio of water vapor increases, that is, the humidity increases. However, this relationship is reversed at around 170 ° C. as shown in FIG. At higher temperatures, the evaporation rate of water increases as the mixing ratio of water vapor in the air increases.

Therefore, in the drying system 10 according to the present embodiment, the absolute humidity of the exhaust gas inside the rotary shell 24 and the circulation pipe 20 as a drying container is maintained at 2 (kg-H ₂ O / kg-DA) or more. In this way, the sludge is dried using, for example, a superheated steam having a high temperature of about 550 ° C., so that the evaporation rate (drying rate) of the dewatered sludge in the rotating shell 24 is greatly improved while the energy is reduced. It can be efficiently collected by the capacitor 38 or the like.

As described above, in the sludge drying system 10 according to the present embodiment, the rotary shell 24 that is a drying container for drying the dewatered sludge that is carried in by heating, the exhaust gas from the rotary shell 24 is heated, and the rotary shell is again formed. 24, and a condenser 38 (or scrubbers 80a to 80c) for recovering the energy of the steam contained in the exhaust gas in the circulation pipe 20, and the absolute humidity of the exhaust gas is 2 (kg-H ₂ O / kg-DA) or more.

In this way, by managing the absolute humidity of the dry exhaust gas at 2 (kg-H ₂ O / kg-DA) or higher, the latent heat of the steam in the dry exhaust gas, that is, it can be effectively recovered and reused in the prior art. The energy consumed for the water evaporation of the dehydrated sludge that has not been recovered can be effectively recovered by the condenser 38 (or the scrubbers 80a to 80c), and the generated power from the binary generator 40 is supplied to the system components such as the dryer 12 and the circulation fan 30. The energy saving of the whole system can be achieved by supplying to and using. For example, in the conventional drying system, the power consumption of the entire system is 180 (kW / h). In the drying system 10, the power consumption of the entire system is 160 (kW / h). The power generated by the binary generator 40 is 80 (kW / h), and as a result, the actual required power is 80 (kW / h), and a power reduction rate of 50% can be obtained compared to the conventional system. .

In addition, the closed circuit of the exhaust gas composed of the rotary shell 24 and the circulation pipe 20 has an airtight structure, and the air from the outside is prevented from being mixed, so that the absolute humidity of the dry exhaust gas is 2 (kg-H ₂ O / kg-DA). ) It can be easily maintained as described above, and the steam ratio in the rotary shell 24 can be increased. Therefore, the evaporation rate (drying rate) of the dewatered sludge is greatly improved, and the drying efficiency of the entire system is further increased. It can be increased and further energy saving is possible.

  The binary power generator 40 is configured to generate power with the power generator 68 by the rotation of the turbine 62. As an energy utilization device that uses the energy recovered by the condenser 38 (or the scrubbers 80a to 80c), a power generator may be used. Other power generators can also be used. For example, as with the binary generator 40, it is also effective to include a turbine 62 and use the rotation of the turbine 62 directly as motive power instead of power generation as a drive source for the circulation fan 30 or the like. .

  In the drying system 10, the exhaust gas from the dryer 12 is removed between the dryer 12 and the condenser 38 (or the scrubbers 80 a to 80 c) as energy recovery devices in the flow direction of the exhaust gas from the dryer 12. A dust collector 16 for processing is provided. By providing such a dust collector 16, the dried exhaust gas is dedusted in a state in which the energy is retained, so that dust adhering to the downstream condenser 38 (or scrubbers 80 a to 80 c), the heat exchanger 18, etc. Thus, efficiency reduction is suppressed, and energy can be recovered more effectively.

  By the way, in said drying system 10, although the energy recovery line 10b illustrated the structure which provided the combustion furnace 34 as a processing line of the waste gas (non-condensable gas) from the capacitor | condenser 38 (or scrubbers 80a-80c), Instead of the combustion furnace 34, various combustion facilities such as incineration facilities, carbonization facilities, gasification facilities, etc. are provided, and a combined sludge treatment system in which the drying system 10 is combined with these incineration facilities, carbonization facilities, and gasification facilities. You may comprise as.

  FIG. 8 is an overall configuration diagram of a sludge drying system 100 according to a first modification of the drying system 10. In FIG. 8, the same reference numerals as those shown in FIGS. 1 to 6 indicate the same or similar configurations, and thus the detailed description is omitted as they exhibit the same or similar functions and effects. The same applies to FIGS. 9 and 10 below.

  As shown in FIG. 8, the drying system 100 replaces the combustion furnace 34 with an energy recovery line having a gasification furnace 102 and an incinerator 104 that incinerates exhaust gas from the gasification furnace 102 via the high-temperature cyclone 103. 10c. The gasification furnace 102 is one in which dry sludge discharged to the outside from the discharge port 28c of the dryer 12 is transported by the transport mechanism 106, and this dry sludge is burned (for example, a circulating fluidized furnace). The exhaust gas discharged from the gasification furnace 102 is incinerated in the incinerator 104 after the ash and the like are removed by the high-temperature cyclone 103, and the combustion exhaust gas is sent to the heat exchanger 18.

  FIG. 9 is an overall configuration diagram of a sludge drying system 110 according to a second modification of the drying system 10. As shown in FIG. 9, the drying system 110 includes an energy recovery line 10 d having an incinerator 112 instead of the combustion furnace 34. The incinerator 112 incinerates the dried sludge transported by the transport mechanism 106, and the combustion exhaust gas is sent to the heat exchanger 18.

  FIG. 10 is an overall configuration diagram of a sludge drying system 120 according to a third modification of the drying system 10. As shown in FIG. 10, the drying system 120 includes an energy recovery line 10 e having a hot air furnace 122, a carbonization furnace 124, and a reburning furnace 126 instead of the combustion furnace 34. The carbonization furnace 124 carbonizes the dried sludge transported by the transport mechanism 106, and its heat source is circulated and used by the hot air furnace 122, and the exhaust gas is combusted in the recombustion furnace 126, and then the heat exchanger 18. Sent to.

  It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be freely changed without departing from the gist of the present invention.

  For example, when the amount of dewatered sludge is large, when the water content of the dewatered sludge is low, or when the amount of heat generated from the sludge is high, a boiler (not shown) is placed in the rear stage of the heat exchanger 18. ), And a generator such as a steam turbine or a binary generator may be further installed to generate power.

10, 100, 110, 120 Sludge drying system 10a Drying line 10b to 10e Energy recovery line 12 Superheated steam dryer 16 Dust collector 18 Heat exchanger 20 Circulation line 30 Circulating fan 38 Condenser 40 Binary generator 62 Turbine 64 Cooling tower 68 Power generation 80a-80c scrubber

Claims (6)

A drying container for drying the dewatered sludge to be brought in by heating;
A circulation line for heating the exhaust gas from the drying container and circulating it again to the drying container;
A sludge drying system comprising:
An energy recovery device for recovering the energy of the steam contained in the exhaust gas in the circulation line;
The sludge drying system, wherein the absolute humidity of the exhaust gas is maintained at 2 (kg-H ₂ O / kg-DA) or more. In the sludge drying system according to claim 1,
A sludge drying system, wherein the drying container and the circulation pipe are provided with an airtight structure for preventing outside air from entering the inside. In the sludge drying system according to claim 2,
The sludge drying system, wherein the heating device for heating the exhaust gas circulating through the circulation pipe is an indirect heating system in which the exhaust gas flowing through the circulation pipe is indirectly heated from the outside of the circulation pipeline. In the sludge drying system according to any one of claims 1 to 3,
A sludge drying system comprising an energy utilization device that utilizes energy recovered by the energy recovery device. In the sludge drying system according to claim 4,
The energy recovery device is a condensing device that condenses by exchanging heat between the steam and a heat transfer medium,
The energy utilization device is configured to cause heat exchange between a heat transfer medium heated by the condensation of the steam by the energy recovery device and a heat transfer medium having a boiling point lower than that of the heat transfer medium to evaporate the heat transfer medium. A sludge drying system, characterized in that it is a binary generator that generates electric power by rotating the turbine and a power generator that generates power by rotating the turbine. In the sludge drying system according to claim 5,
A sludge drying system, wherein a dust collector for removing dust from the exhaust gas is provided between the drying container and the energy recovery device in the flow direction of the exhaust gas.

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