JP2013193044A - Sludge drying system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sludge drying system capable of effectively recovering and using steam generated in a drier, and capable of saving energy of the whole of the system.SOLUTION: A sludge drying system 10 includes a reduced-pressure drier 11 for drying dewatered sludge, a superheated steam drier 12 for drying the dewatered sludge at a drying temperature different from the reduced-pressure drier 11, and a supply pipe passage 17 for supplying the steam generated from the dewatered sludge in the superheated steam drier 12 as a heat source of the reduced-pressure drier 11. Latent heat of the steam in exhaust gas from the superheated steam drier 12 is reused for drying the sludge in the reduced-pressure drier 11, and energy fed for drying the sludge in the superheated steam drier 12 is reused.

Description

  The present invention relates to a sludge drying system for drying dehydrated sludge with a plurality of dryers.

  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, in a drier for drying dewatered sludge, the steam generated by sludge drying is difficult to reuse because of its low energy (potential), and conventionally, it has been generally recovered as hot wastewater by a scrubber.

The absolute humidity in the gas in a normal drying process is about 0.3 to 0.5 (kg-H ₂ O / kg-DA), for example, in the case of obtaining 75 ° C. warm wastewater with the above scrubber. However, since the saturation humidity at the temperature is 0.38 (kg-H ₂ O / kg-DA), the latent heat that can be recovered is only about 0 to 24% of the whole, and the latent heat of evaporation is effectively used. At present, it has not been recovered.

  Therefore, in the system of Patent Document 1, water extracted from the gasification gas of the gasification furnace is evaporated and the vapor is pressurized by a compressor and then used as a heat source for the dryer. The energy of steam cannot be used effectively, and a power source for driving the compressor for pressurizing the steam is necessary, and electric input from the outside is large.

  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 a dryer to save energy of the entire system. The purpose is to do.

  The sludge drying system according to the present invention includes a first dryer for drying dehydrated sludge, a second dryer for drying dehydrated sludge at a drying temperature different from that of the first dryer, the first dryer, and the Among the second dryers, a supply line that supplies steam generated from the dewatered sludge in one dryer having a high drying temperature as a heat source of the other dryer having a low drying temperature is provided.

  According to such a configuration, the steam generated from the dewatered sludge in one dryer having a high drying temperature can be reused as a heat source for the other dryer. Energy (latent heat of evaporation) input for drying can be effectively reused, and energy saving of the entire system can be achieved.

  The first dryer and the second dryer are continuously provided on the same dewatered sludge drying path, and the dehydrated sludge dried by the first dryer is further dried by the second dryer. (Series arrangement), or the first dryer and the second dryer may be provided on different drying paths of dewatered sludge (parallel arrangement).

  The first dryer is a vacuum dryer that operates by depressurizing the inside of the drying container, and the drying temperature is set lower than that of the second dryer. Since the vacuum dryer heats the sludge with the inside reduced in pressure, it can be sufficiently used as a heat source even when the temperature of the steam to be reused is low.

  The second dryer may be a superheated steam dryer that dries dehydrated sludge with superheated steam. For example, by providing a superheated steam dryer after the vacuum dryer, the amount of water evaporated in the vacuum dryer can be set to, for example, about half of the total amount of moisture required for drying, and the size of the vacuum dryer can be reduced. . In addition, the use of a superheated steam dryer with extremely high drying efficiency on the steam recovery side as a heat source of the vacuum dryer makes it possible to further reduce the overall apparatus cost.

In the superheated steam dryer, when the absolute humidity of the exhaust gas containing steam generated from the sludge to be dried is maintained at 2 (kg-H ₂ O / kg-DA) or more, the reduced-pressure dryer uses the steam in the dry exhaust gas. The latent heat possessed, that is, the energy spent for water evaporation of the dewatered sludge can be recovered more efficiently and effectively reused in a vacuum dryer.

  It is good to provide the granulator which granulates the sludge thrown into the said superheated steam dryer from the said vacuum dryer. Granulation of the dried sludge discharged from the vacuum dryer suppresses dust scattering from the dried sludge during drying in the superheated steam dryer, and reduces dust in the sludge dry steam generated by the superheated steam dryer. The latent heat can be efficiently recovered and reused in the subsequent equipment.

  According to the present invention, the steam generated from the dewatered sludge in one dryer having a high drying temperature can be reused as a heat source for the other dryer. Therefore, the energy input for the purpose can be effectively reused, so that 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 graph showing the relationship between gas saturation humidity and temperature. FIG. 4 is an overall configuration diagram of a sludge drying system according to a first modification of the drying system shown in FIG. 1. FIG. 5 is an overall configuration diagram of a sludge drying system according to a second modification of the drying system shown in FIG. 1. FIG. 6 is an overall configuration diagram of a sludge drying system according to a third modification of the drying system shown in FIG. 1. FIG. 7 is an overall configuration diagram of a sludge drying system according to a fourth 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 dewatered sludge such as sewage sludge with two dryers (a vacuum dryer 11 and a superheated steam dryer 12). At the same time, the energy (latent heat) of the steam contained in the exhaust gas from the superheated steam dryer 12 is reused as a heat source for the vacuum dryer 11.

  As shown in FIG. 1, the drying system 10 includes a vacuum dryer 11 and a superheated steam dryer 12, and a drying line 10 a that mainly performs drying treatment of dehydrated sludge, and exhaust gas discharged from the superheated steam dryer 12. And a heating line 10b for heating (dry exhaust gas).

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

  The drying line 10a is a dewatering cake storage tank 14 for storing dewatered sludge dehydrated until the water content becomes 70 to 80% by a dewatering device (not shown) for sewage sludge, etc. The sludge is dried by indirect heating with water vapor, for example, until the water content reaches 65 to 70%, and the dehydrated sludge dried by the reduced pressure dryer 11 by direct heating with superheated steam, for example, has a water content. A superheated steam dryer 12 that is dried to about 20% and a dust collector 16 that collects and removes particulates contained in the exhaust gas (sludge dry steam) discharged from the superheated steam dryer 12 are provided.

  Further, the piping system of the drying line 10a includes a supply line 17 that supplies the sludge drying steam that has exited the dust collector 16 as a heat source for the vacuum dryer 11, and a sludge drying steam that has exited the dust collector 16 as a heat exchanger (heating device). 18 is provided with a circulation line 20 that is heated indirectly by 18 to form superheated steam and supplies this superheated steam as a heat source of the superheated steam dryer 12.

  The vacuum dryer 11 decompresses the inside of the cylindrical drying container 22, for example, dewatered sludge introduced into the drying container 22 from a sludge feeder 23 constituted by, for example, a Mono pump or the like, to a relatively low-temperature heat source (for example, , About 100 ° C.) and can be heated and dried. For example, a thin film dryer, a vacuum dryer, a steam dryer or the like may be used.

  The vacuum dryer 11 is provided with an external heat jacket (heating jacket) 24 into which heating steam is introduced around a drying container 22. In order to introduce the heating steam (sludge drying steam) supplied from the supply pipe 17 into the external heat jacket 24, a pipe 17 a downstream of the supply fan 25 is connected to the upper surface of the external heat jacket 24. An inlet port 28a is provided. Further, a drain port 28b is provided on the lower surface of the outer heat jacket 24 for draining the condensed water of the heating steam obtained by indirectly heating the dewatered sludge inside the drying container 22 by the latent heat of condensation.

  On the other hand, the exhaust gas (sludge dry steam) containing vapor and odor evaporated from the dehydrated sludge by the drying action by the external heat jacket 24 in the drying container 22 is circulated from the outlet port 29a provided on the upper surface to the capacitor 30, Condensed and drained by the condenser 30, the remaining gas that has not been condensed is discharged out of the system by the fan 32 and treated for odor. That is, in the present embodiment, the steam generated from the dewatered sludge in the vacuum dryer 11 has a low temperature of about 45 ° C. and is not suitable for subsequent reuse.

  Therefore, in the vacuum dryer 11, the dewatered sludge that has been input from the sludge input device 23 into the drying container 22 is conveyed while being stirred in the drying container 22, and is input into the external heat jacket 24 from the inlet port 28a. It is heated and dried indirectly by heating steam (for example, 100 ° C., about 0.01 MPa). The dried sludge (primary dried sludge), which is a dehydrated sludge that has been dried, is discharged to the outside from the discharge port 29b, sent to the granulator 34 via the double damper 33, and then superheated steam by the sludge input device 36. The dryer 12 is charged.

  The granulator (crusher) 34 suppresses dust scattering from the primary dry sludge during drying in the superheated steam dryer 12 by granulating the primary dry sludge discharged from the vacuum dryer 11. And it is an apparatus for reducing the dust in the sludge drying steam generated in the superheated steam dryer 12.

  FIG. 2 is a configuration diagram illustrating an example of the structure of the superheated steam dryer 12. As shown in FIGS. 1 and 2, the superheated steam dryer 12 is an internal heat type rotary kiln, and a pair of bearing bases 38 a and 38 b fixed to a floor surface of a factory or the like, a pair of bearing bases 38 a and 38 b, and a pair. A cylindrical rotating shell (drying container) 40 is rotatably supported about the axial direction by bearings 39a and 39b. In the superheated steam dryer 12, the downstream end of the sludge thrower 36 that feeds the primary dewatered sludge granulated from the vacuum dryer 11 through the granulator 34 into the internal space of the rotary shell 40 is the bearing base. It connects so that it may protrude in the rotation shell 40 through 38a. The sludge feeder 36 is, for example, a Mono pump. That is, in the superheated steam dryer 12, dehydrated sludge is directly charged into the rotary shell 40 from the MONO pump (sludge feeder 36).

  In order to introduce the superheated steam supplied from the circulation pipe 20 into the rotary shell 40, a pipe 20 a downstream of the heat exchanger 18 is provided on the upper surface of the bearing base 38 a to which the sludge thrower 36 is connected. An inlet port 42a to be connected is provided. On the other hand, the exhaust gas (sludge dry steam) containing steam and odor evaporated from the dehydrated sludge by the drying action by the superheated steam in the rotary shell 40 is sent from the outlet port 42b provided on the upper surface of the other bearing base 38b to the pipe 20b. After being circulated and passing through the dust collector 16, it is circulated to the pipe 20c. The sludge dry steam flowing through the pipe 20c is introduced into the heat exchanger 18 under the driving action of the circulation fan 44 and circulated again to the pipe 20a, and a part thereof is to the pipe 17a branched from the pipe 20c. And is introduced from the inlet port 28a of the vacuum dryer 11 to the external heat jacket 24 via the supply pipe line 17.

  In addition, like the piping 17b shown with a broken line in FIG. 1, the branch of the sludge dry steam from the circulation line 20 to the supply line 17 is not only heated by the heat exchanger 18 but also the heat exchanger 18. You may comprise so that the superheated steam after heated by may be distribute | circulated from the piping 20a to the piping 17a via the piping 17b.

  Therefore, in the superheated steam dryer 12, the dehydrated sludge thrown into the rotary shell 40 from the sludge thrower 36 is transported through the rotary shell 40 and superheated steam thrown into the rotary shell 40 from the inlet port 42a. (For example, about 550 ° C.). Exhaust gas (dry exhaust gas, for example, about 100 ° C.) containing sludge drying vapor that is vapor evaporated from dehydrated sludge flows from the outlet port 42 b to the circulation line 20, and partly flows to the supply line 17. On the other hand, the dried sludge which is the dried dewatered sludge is discharged to the outside from the discharge port 42c. At this time, since the primary drying sludge charged into the superheated steam dryer 12 has undergone pre-granulation by the granulator 34, it is necessary to provide a stirring blade inside the rotary shell 40 of the superheated steam dryer 12. In addition, the dried sludge can be prevented from being pulverized and scattered inside the rotating shell 40. The granulator 34 may be omitted. In this case, a stirring blade may be provided inside the rotary shell 40.

  The dust collector 16 removes particulates and the like contained in the exhaust gas introduced from the outlet port 42b of the superheated steam dryer 12 through the pipe 20b and discharges it as dry sludge, while the dust-exhausted exhaust gas is discharged to the pipe 20c. It is a device that circulates. In the present embodiment, since the latent heat of the sludge dry steam that is the steam contained in the dry exhaust gas is used in the supply pipe line 17, the dust collector 16 holds the energy (latent heat) of the steam contained in the dry exhaust gas. A device that precisely removes fine particles such as dry sludge in the state 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 100 ° C. with high-temperature combustion exhaust gas discharged from a combustion furnace 48, which will be described later. It is a heating device for circulating. The pipe 20c and the pipe 20a are constituted by one pipe, and the exhaust gas flowing in the pipe indirectly from the outside of the pipe is heated by the combustion exhaust gas, and the temperature is raised. 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 48 but to use the heat of the exhaust gas or boiler of other equipment.

  In such a drying line 10a, the exhaust gas circuit composed of the rotating shell 40 and the circulation pipe 20 of the superheated steam dryer 12 is a closed circuit that has an airtight structure that prevents outside air from entering the inside thereof. It has become.

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

  The heating line 10b generates a high-temperature combustion exhaust gas (hot air) by burning a fuel 50 such as natural gas (for example, city gas), processes the combustion exhaust gas from the combustion furnace 48, and releases it to the atmosphere. An exhaust gas treatment device 52 for heating the exhaust gas, and a pipe 56 for heating the outside air taken in by the fan 54 to the combustion furnace 48 by heating it with the exhaust gas treatment device 52.

  The combustion furnace 48 is a combustion facility that generates hot air (combustion exhaust gas) by burning the air preheated by the exhaust gas treatment device 52 and introduced from the pipe 56 together with the fuel 50. The combustion exhaust gas from the combustion furnace 48 flows through the exhaust gas pipe and is introduced into the heat exchanger 18, and indirectly heats the sludge drying steam from the superheated steam dryer 12 that flows in the pipe meandering through the heat exchanger 18. Then, after making it into superheated steam, it is discharged into the atmosphere through the exhaust gas treatment device 52. The heat exchanger 18 is an indirect heating method in which dry exhaust gas flowing in the circulation pipe 20 is indirectly heated by combustion exhaust gas from the outside of the circulation pipe 20. The outside air is prevented from entering the road 20. That is, the combustion furnace 48 and the heat exchanger 18 constitute a heating device that indirectly heats the dried exhaust gas flowing through the circulation line 20.

  The drying system 10 according to the present embodiment is basically configured by the drying line 10a and the heating line 10b as described above, and the dry exhaust gas from the superheated steam dryer 12 is circulated through the circulation line 20. The new steam generated from the dewatered sludge flows to the supply pipe line 17 side via the pipe 17a branched from the pipe 20c, and the latent heat is effectively reused for drying the sludge in the vacuum dryer 11. It will be.

  For example, when the ratio of solid to liquid (solid-liquid ratio) in the dewatered sludge charged into the vacuum dryer 11 is 20:80, the water content is 80%. When the water is evaporated to a primary dry sludge until the solid-liquid ratio is 20:40, the moisture content is 66% (= 40 / (20 + 40) · 100). And when this primary dry sludge is dried with the superheated steam dryer 12 and water is evaporated until the solid-liquid ratio becomes 20: 5, the moisture content is 20% (= 5 / (20 + 5). 100), and it is possible to obtain dry sludge having a desired moisture content. At this time, in the drying system 10, the energy of the steam evaporated by the superheated steam dryer 12 (in the above, the primary dry sludge having a solid-liquid ratio of 20:40 has a solid-liquid ratio of 20: 5). Energy saving is achieved by the amount of use of the reduced energy of water) as a heat source for the vacuum dryer 11.

  And even if it is a case where the temperature of the said sludge dry steam is low (for example, about 100 degreeC) by using the reduced pressure dryer 11 as a dryer which uses the sludge dry steam from the superheated steam dryer 12 as a heat source. In the vacuum dryer 11, this low-temperature sludge drying vapor can be sufficiently used as a heat source. Moreover, the apparatus size of the vacuum dryer 11 can be suppressed by setting the amount of evaporated water in the vacuum dryer 11 to about half of the total amount of moisture required for drying. In addition, by using the superheated steam dryer 12 with extremely high drying efficiency on the side of collecting the steam as the heat source, the overall apparatus cost can be further suppressed.

  By the way, in the said drying system 10, although the structure which utilizes the latent heat which the sludge drying steam discharged | emitted from the superheated steam dryer 12 has as a heat source of the decompression dryer 11, the latent heat which sludge drying steam has is used effectively. In order to use and maintain the drying efficiency in the vacuum dryer 11, it is configured so that outside air does not enter the exhaust gas circuit constituted by the rotating shell 40 and the circulation pipe 20 of the superheated steam dryer 12, It is effective to manage the absolute humidity in the sludge drying steam discharged from the superheated steam dryer 12 to a predetermined value or more. This is because, if air is mixed into the sludge drying steam as a heat source, the latent heat utilization efficiency in the vacuum dryer 11 is lowered, and sufficient drying becomes difficult.

  Therefore, next, the absolute humidity value that can effectively use the latent heat of the sludge drying steam as a heat source of the vacuum dryer 11 will be described with reference to the graph of FIG.

FIG. 3 is a graph showing the relationship between the saturation 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 the bar graph having a reference value of 0.5 in FIG. 3, 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 superheated steam dryer 12 is managed in a range of 2 (kg-H ₂ O / kg-DA) or more. First, referring to the bar graph of the reference value 2 in FIG. 3, when the absolute humidity of the dry exhaust gas discharged from the superheated steam dryer 12 is 2 (kg-H ₂ O / kg-DA), it is 92. When the temperature is reduced to about 0 ° C., the vapor can be condensed (see the broken line B in FIG. 3), and at 90 ° C., about 30% of the latent heat can be recovered (arrow B1 in FIG. 3). At 75 ° C., about 81% of the latent heat can be recovered (see arrow B2 in FIG. 3). For example, in the case of 75 ° C., 1.62 (= 2−0) 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. 3, when the absolute humidity of the dry exhaust gas discharged from the superheated steam dryer 12 is 10 (kg-H ₂ O / kg-DA), When the temperature is reduced to about 96 ° C., the vapor can be condensed (see the broken line C in FIG. 3). For example, at 95 ° C., about 70% of the latent heat can be recovered (in FIG. 3). At 90 ° C., about 85% of the latent heat can be recovered (see arrow C2a in FIG. 3), and at 75 ° C., about 96% of the latent heat can be recovered. (See arrow C3 in FIG. 3).

In this embodiment, the absolute humidity in the dry exhaust gas discharged from the superheated steam dryer 12 is managed in a range of 2 (kg-H ₂ O / kg-DA) or more and introduced into the vacuum dryer 11, thereby Sludge drying in the vacuum dryer 11 can be performed by recovering and using 70% or more of the total latent heat energy of steam in the dry exhaust gas.

In this way, the superheated steam dryer 12 is maintained so that the absolute humidity in the exhaust gas in the rotary shell 40 and the circulation pipe 20 of the superheated steam dryer 12 can be maintained at 2 (kg-H ₂ O / kg-DA) or more. When an airtight structure is applied to the machine 12 and the circulation line 20, the utilization efficiency of latent heat from the sludge drying steam in the vacuum dryer 11 is improved. Therefore, in the present embodiment, as described above, the heat exchanger 18 is an indirect heating method to prevent air mixing during exhaust gas heating. Furthermore, it is effective to make the exhaust gas route from the rotary shell 40 of the superheated steam dryer 12 to the circulation line 20 have an airtight structure so as to reduce the leakage of outside air as much as possible. For example, the drum seal portion of the rotary shell 40 has a carbon packing structure or a steam purge seal structure, the dewatered sludge has a direct input structure from the sludge input device 36 that is a Mono pump, and a discharge port 42c that is a dry sludge discharge portion It is also effective to adopt a seal structure in which a double damper 60 is provided in the drying sludge discharge path from the dust collector 16.

  As described above, in the sludge drying system 10 according to the present embodiment, the reduced pressure dryer 11 for drying the dehydrated sludge, the superheated steam dryer 12 for drying the dehydrated sludge at a drying temperature different from the reduced pressure dryer 11, And a supply pipe 17 for supplying the sludge drying steam from the superheated steam dryer 12 as a heat source of the vacuum dryer 11.

  Accordingly, since the latent heat of the dry exhaust gas from the superheated steam dryer 12 can be effectively reused for drying sludge in the vacuum dryer 11, the energy input for sludge drying by the superheated steam dryer 12 is used. Since (evaporation latent heat) can be effectively reused, energy saving of the entire system can be achieved.

  In addition, by granulating the primary dry sludge discharged from the vacuum dryer 11 with the granulator 34, dust scattering from the primary dry sludge during drying with the superheated steam dryer 12 is suppressed, and overheating is performed. The dust in the sludge drying steam generated in the steam dryer 12 can be reduced, and the dust adheres to the external heat jacket 24 of the decompression dryer 11 that is the use destination, and the latent heat utilization efficiency is reduced due to this adhesion. Can be prevented.

  Furthermore, in the flow direction of the exhaust gas from the superheated steam dryer 12, by providing a dust collector 16 that removes the exhaust gas between the superheated steam dryer 12 and the vacuum dryer 11, the sludge dry steam is Since the dust is removed while the latent heat is retained, dust adhesion on the outer heat jacket 24 and the like and efficiency reduction are suppressed, and the latent heat can be efficiently recovered and reused.

  In addition, although the structure which has arrange | positioned the superheated steam dryer 12 in the back | latter stage of the vacuum dryer 11 was illustrated above, you may change arrangement | positioning of both. In other words, in the drying system 10, one of the two dryers (the first dryer and the second dryer) that dry the dewatered sludge at different drying temperatures (the first dryer and the second dryer) has a higher drying temperature (in the above case, overheating). If the steam dryer 12) is configured to be used as a heat source for the other dryer having a low drying temperature (in the above, the vacuum dryer 11), the energy generated by the steam can be effectively collected and recovered. It can be reused and energy saving of the entire system can be achieved.

  Further, in FIG. 1, the reduced pressure dryer 11 and the superheated steam dryer 12 are continuously provided on the same dewatered sludge drying route, and the dehydrated sludge dried by the reduced pressure dryer 11 is placed in the superheated steam dryer 12. Further, the sludge drying system 10 configured to further dry (series arrangement) is illustrated, but as shown in FIG. 4, the reduced-pressure dryer 11 and the superheated steam dryer 12 are arranged in parallel on different dewatered sludge drying paths. The sludge drying system 101 may be configured to have a configuration (parallel arrangement).

  As shown in FIG. 4, the drying system 101 includes a drying line 10 c in which a vacuum dryer 11 and a superheated steam dryer 12 are arranged in parallel. In the drying line 10c, the dewatered sludge from the dewatered cake storage tank 14 is charged into the vacuum dryer 11 and the superheated steam dryer 12, respectively. The dried sludge from the vacuum dryer 11 is discharged through the double damper 33, and the dried sludge from the superheated steam dryer 12 is discharged through the double damper 60.

  In this case, in the drying system 101, as in the drying system 10 shown in FIG. 1, the latent heat of the dry exhaust gas from the superheated steam dryer 12 can be effectively reused for drying sludge in the vacuum dryer 11. Therefore, energy (evaporation latent heat) input for sludge drying by the superheated steam dryer 12 can be effectively reused, and energy saving of the entire system can be achieved. In addition, since the dewatered sludge can be dried by parallel processing in the vacuum dryer 11 and the superheated steam dryer 12, the amount of sludge drying processing increases.

  By the way, in the said drying system 10, although the structure which provided the combustion furnace 48 using the fuel 50 was illustrated in the heating line 10b, it replaced with this combustion furnace 48, and various combustion equipment, for example, incineration equipment and carbonization equipment. Alternatively, a gasification facility or the like may be provided, and the drying system 10 (101) may be configured as a combined sludge treatment system in combination with these incineration facilities, carbonization facilities, and gasification facilities.

  FIG. 5 is an overall configuration diagram of a sludge drying system 100 according to a second modification of the drying system 10. In FIG. 5, the same reference numerals as those shown in FIGS. 1 to 4 indicate the same or similar configurations, and thus the detailed description thereof is omitted as providing the same or similar functions and effects. The same applies to FIGS. 6 and 7 below.

  As shown in FIG. 5, the drying system 100 includes a gasification furnace 102 instead of the combustion furnace 48, and a heating line 10 d having an incinerator 104 that incinerates exhaust gas from the gasification furnace 102 via the high-temperature cyclone 103. Is provided. The gasification furnace 102 is one in which dry sludge discharged to the outside from the discharge port 42c of the superheated steam dryer 12 is transported by the transport mechanism 106, and the dry sludge is gasified (for example, a circulating fluidized furnace). The exhaust gas discharged from the gasification furnace 102 is incinerated in the incinerator 104 after dust and the like are removed by the high-temperature cyclone 103, and the combustion exhaust gas is sent to the heat exchanger 18 and the exhaust gas treatment device 52. Of course, as with the drying system 101 shown in FIG. 4, the drying system 100 may be changed to a configuration including a drying line 10 c in which the vacuum dryer 11 and the superheated steam dryer 12 are arranged in parallel. The same applies to the drying systems 110 and 120.

  FIG. 6 is an overall configuration diagram of a sludge drying system 110 according to a third modification of the drying system 10. As shown in FIG. 6, the drying system 110 includes a heating line 10 e having an incinerator 112 instead of the combustion furnace 48. The incinerator 112 incinerates the dried sludge conveyed by the conveyance mechanism 106, and the combustion exhaust gas is sent to the heat exchanger 18 and the exhaust gas treatment device 52.

  FIG. 7 is an overall configuration diagram of a sludge drying system 120 according to a fourth modification of the drying system 10. As shown in FIG. 7, the drying system 120 includes a heating line 10 f having a hot air furnace 122, a carbonization furnace 124, and a reburning furnace 126 instead of the combustion furnace 48. 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. Or sent to the exhaust gas treatment device 52.

  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.

10, 100, 101, 110, 120 Sludge drying system 10a, 10c Drying line 10b, 10d to 10f Heating line 11 Depressurizing dryer 12 Superheated steam dryer 16 Dust collector 17 Supply line 18 Heat exchanger 20 Circulation line 34 Construction Grain machine

Claims (7)

A first dryer for drying the dewatered sludge;
A second dryer for drying dehydrated sludge at a drying temperature different from that of the first dryer;
A supply line for supplying steam generated from dehydrated sludge in one dryer having a high drying temperature among the first dryer and the second dryer as a heat source for the other dryer having a low drying temperature;
A sludge drying system characterized by comprising: In the sludge drying system according to claim 1,
The first dryer and the second dryer are continuously provided on the same dewatered sludge drying path, and the dehydrated sludge dried by the first dryer is further dried by the second dryer. Sludge drying system characterized by In the sludge drying system according to claim 1,
The sludge drying system, wherein the first dryer and the second dryer are provided on different drying routes of dewatered sludge. In the sludge drying system according to any one of claims 1 to 3,
The first dryer is a reduced-pressure dryer that operates by depressurizing the inside of a drying container, and the drying temperature is set lower than that of the second dryer. In the sludge drying system according to claim 4,
The said 2nd dryer is a superheated steam dryer which dries dehydrated sludge with superheated steam, The sludge drying system characterized by the above-mentioned. In the sludge drying system according to claim 5,
In the superheated steam dryer, the sludge drying system is characterized in that the absolute humidity of the exhaust gas containing steam generated from the sludge to be dried is maintained at 2 (kg-H ₂ O / kg-DA) or more. In the sludge drying system according to claim 5 or 6,
A sludge drying system comprising a granulator for granulating sludge to be fed from the vacuum dryer to the superheated steam dryer.

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