JP2020044482A - Sludge treatment system and sludge treatment method - Google Patents

Abstract

To reduce a load for treating exhaust from a dryer, while keeping a heat energy to be low, the heating energy being consumed by an entire sludge treatment system.SOLUTION: A sludge treatment system 100 for treating organic sludge includes: a dehydrator 50 for dehydrating organic sludge while indirectly heating it with warm water to discharge dehydrated sludge; and a dryer 60 that discharges the dried sludge while indirectly heating the dehydrated sludge with steam and extrudes the evaporated water with hot air, and configured to introduce the hot air exhaust from the dryer 60 into the dehydrator 50, and bring it to contact with the organic sludge in the dehydrator 50, using the steam drain water used for indirect heating of the dryer 60 as warm water for indirect heating of the dehydrator 50.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a sludge treatment system for treating sludge and a sludge treatment method.

  2. Description of the Related Art Conventionally, a sludge treatment system mechanically dehydrates sludge containing water into a dehydrated sludge by a dehydrator, and applies heat to the dehydrated sludge to dry the sludge by a dryer. Dry sludge may also be incinerated in an incinerator. As a dehydrator, a device that dehydrates sludge while heating it is known (for example, Patent Document 1).

  In a sludge treatment system that employs a dehydrator that performs such heating and dehydration, the water content of the dehydrated sludge can be reduced by the dehydrator, so that the heat energy required for a subsequent dryer or incinerator can be reduced. However, such a sludge treatment system requires heat energy to heat sludge with a dehydrator.

  On the other hand, in the dryer, for example, the dewatered sludge is dried by directly contacting hot air with the dewatered sludge and evaporating the moisture from the dewatered sludge. Since it has a bad smell, it is necessary to perform an exhaust treatment (purification treatment) before exhausting to the atmosphere. In addition, since the hot air retains a large amount of water at a high temperature, it is necessary to cool and dehumidify the air before exhausting.

  Prior arts related to the present invention include the following prior arts.

JP-A-2006-107265 JP-A-1-24970 JP-A-3-207499 JP 2017-94267 A

  An object of the present invention is to reduce the load for treating exhaust gas from a dryer while keeping the heat energy consumed in the entire sludge treatment system low.

  A sludge treatment system according to one embodiment of the present invention is a sludge treatment system for treating organic sludge, in which the organic sludge is dewatered by indirect heating with at least one of hot water and steam to discharge dehydrated sludge. And a dryer that discharges the dried sludge while indirectly heating the dewatered sludge with steam and extrudes the evaporated water with hot air.

  With this configuration, since the dewatering is performed by heating and dewatering, the moisture content of the dewatered sludge can be reduced, so that the sludge can be dried by indirect heating using less steam in the dryer, and is consumed by the entire sludge treatment system. Thermal energy can be kept low. In addition, since the heating in the dryer is indirect heating, the air volume can be reduced as compared with the direct heating, and the load of the exhaust process on the exhaust of the hot air can be reduced.

  In the above-described sludge treatment system, the steam drain water used for the indirect heating of the dryer may be used as the hot water for the indirect heating of the dehydrator.

  With this configuration, the heat energy required for heating and dehydrating in the dehydrator can be secured by using the waste heat of the dryer, so that the thermal energy consumed in the entire sludge treatment system can be further reduced.

  In the above-described sludge treatment system, the exhaust of the hot air from the dryer may be introduced into the dehydrator, and may be brought into contact with the organic sludge by the dehydrator.

  With this configuration, the exhaust of hot air from the dryer has a reduced flow velocity in the dehydrator, so that dust is collected and cooled. Therefore, the load of the exhaust processing for the exhaust of the hot air can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, while the heat energy consumed by the whole sludge processing system can be suppressed low, the load of the exhaust processing with respect to the exhaust of hot air can be reduced.

FIG. 1 is a schematic diagram showing an entire configuration of a sludge treatment system according to an embodiment of the present invention. FIG. 2 is a diagram schematically illustrating a relationship between the dehydrator and the dryer according to the embodiment of the present invention. FIG. 3 is a diagram schematically showing a relationship between a dehydrator and a dryer according to a modification of the embodiment of the present invention.

  Hereinafter, a drying apparatus according to an embodiment of the present invention and a drying system including the same will be described with reference to the drawings. The embodiment described below shows an example in which the present invention is implemented, and the present invention is not limited to the specific configuration described below. In carrying out the present invention, a specific configuration according to the embodiment may be appropriately adopted.

  FIG. 1 is a schematic diagram showing an entire configuration of a sludge treatment system according to an embodiment of the present invention. The sludge treatment system 100 treats sludge from the water treatment facility 10 and waste from the waste treatment facility. The sludge treatment system 100 of the present embodiment treats organic waste sludge (hereinafter referred to as “organic sludge”). The sludge treatment system 100 includes a digestion tank 20, a boiler 30, a generator 90, a concentrator 40, a dehydrator 50, a dryer 60, an incinerator 70, and an exhaust treatment device 80.

  In FIG. 1, the arrows hatched with diagonal grids indicate the flow of sludge, the arrows shown with diagonal hatching rising to the right indicate the flow of hot air, and the arrows shown with dot pattern hatching are steam. It shows the flow.

  Sludge changes its state through each process, and in the following description, sludge whose state has changed will be referred to with respective names (digested sludge, concentrated sludge, dewatered sludge, dried sludge). It is also called "sludge" or "organic sludge". Also, the name of the hot air changes when the state changes (the temperature decreases), but it may also be called “hot air” regardless of the state. Similarly, the name of steam changes as its state changes (decreases in temperature) through each process, but may be referred to as "steam" regardless of the state.

(Sludge treatment process)
The organic sludge discharged from the water treatment facility 10 is first put into the digestion tank 20. The digestion tank 20 performs digestion treatment on the organic sludge by methane fermentation. Heat is supplied to the digestion tank 20 from the boiler 30 and the generator 90. The methane gas generated in the digestion treatment of the digestion tank 20 is sent to the boiler 30. The boiler 30 and the generator 90 combust the methane gas sent from the digestion tank 20 to generate heat.

  The digested sludge that has undergone the digestion treatment in the digestion tank 20 is supplied to the concentrator 40. The concentrator 40 concentrates the digested sludge into concentrated sludge. In the concentrator 40, a polymer is added to the concentrated sludge.

  The concentrated sludge is introduced into the dehydrator 50. The dehydrator 50 is a screw press type dehydrator having a cylindrical screen 51 and a screw 52 rotating inside the screen 51. The screen 51 is provided with a heating jacket 53 that covers a part of the screen 51 on the downstream side. The screw 52 includes a cylindrical screw main body and a spiral blade (spiral blade) provided around the screw main body.

  The screw 52 and the heating jacket 53 are warmed by warm water flowing inside. With respect to the screw 52, the hot water flows from the screw body to the inside of the spiral blade, and heats the screw body and the spiral blade. The sludge is heated by coming into contact with the screw body of the screw 52 and the surface (heat transfer surface) of the spiral blade. At the position where the heating jacket 53 is provided, heat is transferred from the heating jacket 53 via the screen 51. It is heated.

  Hot air is blown into the dehydrator 50. The temperature of the hot air is about 80 ° C. The hot air comes into contact with the sludge in the dehydrator 50 and is exhausted outside the dehydrator 50. As described above, the sludge is indirectly heated by the screw 52 and the heating jacket 53 and is compressed by the screw press using the screen 51 and the screw 52 while being directly heated by the warm air. Thereby, water is easily separated from the sludge, and the water content of the sludge decreases. The water content of the dewatered sludge that has undergone the dehydration step is about 65% to 85%.

  The dewatered sludge is supplied to the dryer 60. The dryer 60 is provided with two paddle-mounted shafts 61 shifted in the axial direction such that the paddles overlap each other in the axial direction. The shaft 61 with a paddle includes a cylindrical shaft main body and a paddle provided around the shaft main body. Steam is introduced into the paddle and the shaft, and the paddle-mounted shaft 61 is heated by the steam. The sludge is heated by coming into contact with the paddle of the paddle-mounted shaft 61 and the surface (heat transfer surface) of the shaft. The temperature of the steam supplied to the dryer 60 is approximately 169 ° C. (0.7 MPa) to 151 ° C. (0.4 MPa).

  Hot air is blown into the dryer 60. The temperature of the hot air is about 100 ° C. The sludge inside the dryer 60 is heated by receiving indirect heating from the shaft 61 with the paddle, and the water is evaporated. The evaporated water is pushed out by hot air. The moisture content of the dried sludge that has undergone the drying step may be, for example, about 30%, and the temperature of the dried sludge is about 100 ° C.

  The dried sludge is put into the incinerator 70. The incinerator 70 incinerates the dried sludge.

(Flow of hot air)
As described above, the dryer 60 is supplied with hot air. The hot air contacts the sludge in the dryer 60, absorbs moisture evaporated from the sludge, and is exhausted from the dryer 60 to dry the sludge. The hot air used for drying in the dryer 60 comes into direct contact with the sludge in the dryer 60, thereby giving off a bad smell and mixed with the dust of the dried sludge. Further, the hot air is cooled to some extent by contacting the sludge, but is still at about 80 ° C. in the exhaust stage, and has a high temperature.

  Therefore, normally, the exhaust gas from the dryer 60 is discharged to the atmosphere through an exhaust treatment device such as a wet scrubber having a function of deodorizing and removing dust from the exhaust gas. On the other hand, in the sludge treatment system 100 according to the present embodiment, the exhaust gas from the dryer 60 is sent to the dehydrator 50 to make it contact the sludge positively, and then to the exhaust treatment device 80.

  The exhaust treatment device 80 is a wet scrubber, and performs deodorization and dust removal processing on exhaust gas from the dehydrator 50. The exhaust gas is cooled during the process of deodorization and dust removal. The exhaust gas that has been subjected to the exhaust treatment by the exhaust treatment device 80 is released to the atmosphere.

  The hot air used for discharging the moisture in the dryer 60 is introduced into the dehydrator 50 in a state where the temperature is lowered to some extent and the air is heated. The warm air supplied to the dehydrator 50 contacts sludge inside the dehydrator 50. Thereby, the sludge in the dehydrator 50 is heated, and the hot air is cooled. Further, dust contained in the warm air is captured by the sludge.

  Thus, the dehydrator 50 removes and cools the warm air discharged from the dryer 60 and discharges the heated air to the exhaust treatment device 80. Therefore, the dehydrator 50 removes and cools the exhaust from the dryer 60 to some extent before the exhaust processor 80, so that the load for the exhaust process by the exhaust processor 80 can be reduced. In addition, since the warm air discharged from the dryer 60 is introduced into the dehydrator 50 and used for heating the sludge, energy is saved.

  In addition, since the processes of dust removal and cooling are performed in the dehydrator 50, the exhaust treatment device 80 may have only a deodorizing function.

(Steam flow)
As described above, steam is supplied to the inside of the shaft 61 with the paddle of the dryer 60. The paddle shaft 61 is heated by the steam. The sludge is heated and dried by contacting the heat transfer surface of the shaft 61 with the paddle. As described above, the steam used for indirect heating of the sludge flowing through the inside of the shaft 61 with the paddle becomes hot water and is discharged from the dryer 60 as drain water. Hereinafter, an example in which the above is discharged as warm water as drain water will be described. The temperature of the hot water discharged from the dryer 60 is approximately 169 ° C. (0.7 MPa) to 151 ° C. (0.4 MPa). The drain water may be supplied to the inside of the dehydrator as it is, or the pressure may be reduced to the atmospheric pressure (0.1 MPa or less) to 100 ° C. or less and supplied to the inside of the dehydrator 50. The temperature of the drain water may be adjusted to 100 ° C. or less by dilution.

  The steam drain water discharged from the dryer 60 is supplied into the screw 52 of the dehydrator 50. The screw 52 is heated by the drain water (warm water). The sludge is heated by contacting the heat transfer surface of the screw 52 to promote dehydration. Thus, the hot water used for indirect heating of the sludge is discharged from the dehydrator 50.

  FIG. 2 is a diagram schematically illustrating a relationship between the dehydrator 50 and the dryer 60 according to the embodiment of the present invention. The sludge is put into the dehydrator 50 and discharged through the dehydration step as dehydrated sludge. The dehydrated sludge is supplied to the dryer 60, and is discharged from the dryer 60 as dried sludge through a drying process. Steam is supplied to the paddle shaft 61 of the dryer 60 to heat the paddle shaft 61 and is discharged from the dryer 60 as drain water. The drain water (warm water) discharged from the dryer 60 is supplied to the screw 52 of the dehydrator 50, and the screw 52 is heated to be discharged from the dehydrator 50.

  Hot air is supplied to the dryer 60. The hot air used for directly heating the sludge in the dryer 60 becomes hot air, is exhausted from the dryer 60, and is supplied to the dehydrator 50. In the dehydrator 50, the warm air and the sludge are positively brought into contact with each other to directly heat the sludge. The dust contained in the hot air is captured by the sludge by coming into contact with the sludge in the dehydrator 50. The warm air discharged from the dehydrator 50 is sent to the exhaust treatment device 80. The exhaust treatment device 80 performs an exhaust treatment on the exhaust gas from the dehydrator 50 and discharges the exhaust gas to the atmosphere.

  Thus, in the sludge treatment system 100 of the present embodiment, the steam drainage used for indirect heating in the dryer 60 is also used for indirect heating in the dehydrator 50 and used for direct heating in the dryer 60. The heated hot air is also used for direct heating by the dehydrator 50. Therefore, the thermal dehydration in the dehydrator 50 can be performed by effectively utilizing the heat energy discharged from the dryer 60. Further, since the hot air containing the dust of the sludge used for the direct heating in the dryer 60 is brought into contact with the sludge in the dehydrator 50, it is possible to remove and cool the hot air in the dehydrator 50, The load of the exhaust processing of the processor 80 can be reduced.

  The hot air used in the dryer 60 is reused in the dehydrator 50, and the steam used in the dryer 60 is reused in the dehydrator 50 (that is, the waste heat of the dryer 60 is reused in the dehydrator 50). Is not essential, and in this case, steam may be used for indirect heating of the dehydrator 50 (instead of hot water).

  FIG. 3 is a diagram schematically showing the relationship between the dehydrator 50 and the dryer 60 in the sludge treatment system 100 of such a modification. In this example, the hot air supplied to the dryer 60 is discharged from the dryer 60 and sent to the exhaust processing device 80 as it is. In the exhaust treatment device 80, the exhaust gas is deodorized, dust-removed, and cooled, and released into the atmosphere.

  Steam is supplied to the shaft 61 with paddles of the dryer 60. Steam is also supplied to the screw 52 and the heating jacket 53 of the dehydrator 50. In this example, the drain water of the dryer 60 is not used for heating the sludge in the dehydrator 50. This modification is different from the above-described embodiment in that the temperature and the amount of steam supplied to the dehydrator 50 can be arbitrarily adjusted, and the degree of heating of the sludge in the dehydrator 50 can be arbitrarily adjusted. It is advantageous.

  As described above, in the sludge treatment system 100 of the present embodiment and its modified example, the sludge is indirectly heated or heated in both the dehydrator 50 and the dryer 60. In the dryer 60, if drying is to be performed only by direct heating with hot air, the amount of hot air needs to be increased. As mentioned above, the hot air used for drying contains dust from the dried sludge and also emits a bad smell, so it is necessary to purify this with an exhaust treatment device before releasing it to the atmosphere. The load of this exhaust treatment increases. Therefore, by using indirect heating in the dryer 60, an increase in the amount of hot air can be suppressed.

  Further, digested sludge of organic waste has a high viscosity and poor cohesiveness, so that a large amount of polymer tends to be added. If the water content of the sludge (dewatered sludge) supplied to the dryer 60 is high, the sludge tends to adhere to the heat transfer surface of a shaft or paddle that performs indirect heating of the dryer 60. In the present embodiment and its modified example, the dewatering device 50 performs heating dehydration to lower the water content of the dewatered sludge, so that adhesion to the heat transfer surface of the drying device 60 can be reduced.

  INDUSTRIAL APPLICABILITY The present invention has an effect that the heat energy consumed in the entire sludge treatment system can be suppressed to a low level, and the load of the exhaust treatment on the exhaust of the hot air can be reduced, and is useful as a sludge treatment system for treating sludge. .

  100: Sludge treatment system, 10: Water treatment equipment, 20: Digestion tank, 30: Boiler, 40: Concentrator, 50: Dehydrator, 51: Screen, 52: Screw, 53: Heating jacket, 60: Dryer, 61: shaft with paddle, 70: incinerator, 80: exhaust treatment machine, 90: generator

Claims (4)

A sludge treatment system for treating organic sludge,
A dehydrator that discharges the dewatered sludge by dewatering the organic sludge while indirectly heating with at least one of hot water and steam,
A dryer that discharges the dried sludge while indirectly heating the dewatered sludge with steam, and extrudes the evaporated water with hot air,
Sludge treatment system with   The sludge treatment system according to claim 1, wherein drain water of the steam used for the indirect heating of the dryer is used as the hot water for the indirect heating of the dehydrator.   3. The sludge treatment system according to claim 1, wherein the exhaust of the hot air from the dryer is introduced into the dehydrator, and brought into contact with the organic sludge by the dehydrator. 4. A sludge treatment method for treating organic sludge,
The organic sludge is dewatered while indirectly heating with at least one of hot water and steam, and the dewatered sludge is discharged,
Discharging the dried sludge while indirectly heating the dehydrated sludge with steam, and extruding the evaporated water with hot air;
And a sludge treatment method.

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