JP6672318B2 - Dehydration apparatus, dehydration system, and dehydration method - Google Patents

Description

  The present invention relates to a dehydration apparatus, a dehydration system, and a dehydration method for removing water from a dehydration target containing water such as sludge.

  In the sludge treatment, a process is performed in which the sludge is dewatered by a dehydrator, the dewatered sludge (also referred to as a dewatered cake) is dried by a dryer, and then incinerated in an incinerator. When the dewatering effect in the dewatering process is low and the water content of the dewatered sludge obtained by the dewatering process is high, a large amount of energy is required to evaporate the water in the dewatered sludge in the subsequent drying or incineration of the dewatered sludge, It is disadvantageous for energy saving and energy creation.

  Therefore, conventionally, there has been proposed a dehydrating apparatus of a screw press type, in which a heating medium is circulated through a screw shaft and dewatering is performed while heating the sludge to thereby reduce the water content of the dewatered sludge ( For example, Japanese Patent No. 12111418). Similarly, in a screw press type dehydrator, the screw blades were made hollow to increase the heat transfer area for heating, and the heat transfer surface was increased by supplying a heat medium also to the screw blades. A dehydrator is also known (for example, Japanese Patent No. 12111418).

  However, in the dewatering device of Patent Literature 1, if the heat medium used for heating is not a high-temperature heat medium such as steam, a sufficient heating effect cannot be obtained and the dewatered sludge cannot have a sufficiently low water content. was there.

  An object of the present invention is to provide a dehydrating apparatus, a dehydrating system, and a dehydrating method that can sufficiently dehydrate by heating even at a low temperature by utilizing waste heat or the like.

  The dewatering device according to one embodiment of the present invention includes an outer cylindrical screen in which small holes are formed in a peripheral wall, a screw shaft provided inside the outer cylindrical screen, and a screw provided helically around the screw shaft. By providing a blade and rotating the screw shaft together with the screw blade, the object to be dehydrated put into the outer cylindrical screen is compressed while being conveyed in the axial direction of the screw shaft, and separated from the object to be dewatered. A dewatering device for discharging water from the small holes of the outer cylinder screen, wherein the outer cylinder screen has a heating surface to be heated and a filtering surface from which the small holes are exposed. According to this configuration, the heating surface and the filtering surface are provided on the outer cylinder screen, and the object to be dehydrated is dehydrated while being heated by the outer cylinder screen. Therefore, even when the heating surface is heated at a low temperature, the heating and dehydration can be performed.

  The dehydrating apparatus further includes a heating jacket attached to a part of the outer screen and configured to allow a heat medium to flow therein, and a portion of the outer screen to which the heating jacket is attached. May be the heating surface. With this configuration, the heating surface of the outer cylindrical screen can be configured using the heating jacket.

  In the above dehydrator, the heating jacket may have a configuration in which a heat medium flows. With this configuration, the heating jacket can be heated using the heating medium.

  In the above dehydrator, the temperature of the heat medium may be lower than 100 ° C. With this configuration, hot water can be used as the heat medium, and the heat medium can be generated using waste heat or the like obtained from the heat treatment facility. Therefore, energy saving and energy creation can be further promoted by using hot water, which has a limited use destination and is sometimes discarded.

  In the above-described dewatering device, an addition unit for adding an inorganic flocculant to the concentrated sludge may be further provided. In the case of soft sludge such as excess sludge or digested sludge, coagulation is easily broken by heating.However, by adding an inorganic coagulant, the sludge coagulation power in the dewatering section can be increased again, and the moisture content of the sludge to be dewatered by heating is increased. The effect of the reduction can be increased. In addition, since the heat medium having a temperature of less than 100 ° C. is used, evaporation of water on the heating surface is less likely to occur, and scale components in the filtrate generated during dehydration are less likely to adhere to the heating surface.

  In the above dehydrator, the heating surface and the filtration surface may be alternately arranged in the axial direction of the screw shaft. With this configuration, in the process of being conveyed, the object to be dehydrated is heated on the heating surface to decrease the viscosity, and the water retention is reduced due to thermal denaturation, so that the object is easily dewatered, and in that state, the object is dewatered. Since the heating and dehydration of filtering are repeated, the dehydration effect can be improved.

  In the above dewatering device, the heating surface may be formed in a belt shape and may be arranged in parallel with the axial direction of the screw shaft, or may be formed in an annular shape surrounding the outer cylindrical screen in a circumferential direction. Good. In addition, there may be a plurality of the heating surfaces, and each of the heating surfaces is formed only on a part of the outer cylindrical screen in a circumferential direction. The heating surface may be formed in a semi-cylindrical shape that covers a part of the outer cylindrical screen in a circumferential direction.

  In the above dehydrator, the screw shaft and / or the screw blade may have a hollow shape through which a heat medium flows. With this configuration, the object to be dehydrated can be sufficiently heated, and the dewatering effect can be improved.

  The dehydrating apparatus may further include a concentrator for concentrating the dewatering target before being put into the outer cylindrical screen. With this configuration, the dewatering target is concentrated by the concentrator and then put into the outer cylindrical screen, so that the water content of the dewatered dehydration target can be reduced.

  A dewatering device according to another aspect of the present invention includes an outer cylindrical screen having a small hole formed in a peripheral wall, a screw shaft provided inside the outer cylindrical screen, and a spiral provided around the screw shaft. By providing a screw blade and rotating the screw shaft together with the screw blade, the object to be dehydrated put into the outer cylindrical screen is compressed while being conveyed in the axial direction of the screw shaft, and separated from the object to be dehydrated. A dewatering device that discharges the removed water from the small holes of the outer cylindrical screen, wherein the screw shaft and / or the screw blades have a hollow shape through which a heat medium flows. With this configuration, the object to be dehydrated can be sufficiently heated by flowing the heat medium inside the screw shaft and / or the screw blade, and the dewatering effect can be improved.

  The dewatering system according to one embodiment of the present invention includes an outer cylindrical screen in which a small hole is formed in a peripheral wall, a screw shaft provided inside the outer cylindrical screen, and a screw provided spirally around the screw shaft. By providing a blade and rotating the screw shaft together with the screw blade, the object to be dehydrated put into the outer cylindrical screen is compressed while being conveyed in the axial direction of the screw shaft, and separated from the object to be dewatered. A dehydration system for discharging water from the small holes of the outer cylindrical screen, further comprising a structure for flowing a heat medium therein, a heating jacket attached to a part of the outer cylindrical screen, And a heat medium heater for heating the heat medium using heat. With this configuration, since the heating jacket is attached to the outer cylindrical screen and the object to be dehydrated is dehydrated while being heated, the dehydration by heating can be performed even when the heat medium is at a low temperature.

  The above-described dehydration system may further include a heat treatment facility for incinerating the dewatered object from which water has been separated, drying, or carbonizing, and the heat medium heater uses waste heat of the heat treatment facility. The heat medium may be heated. With this configuration, the dewatering effect can be improved by utilizing the waste heat of the heat treatment equipment, and energy saving can be achieved.

  The dehydration system may further include a digestion tank that performs digestion processing on the dehydration target before being put into the outer cylindrical screen, and the heat medium heating device may include a digestion tank generated in the digestion tank. The heat medium may be heated using a gas. With this configuration, the heat medium is heated by using the digestion gas generated when the digestion processing of the dehydration target is performed, so that energy saving can be realized.

  The dewatering method according to one aspect of the present invention includes an outer cylindrical screen having a small hole formed in a peripheral wall, a screw shaft provided inside the outer cylindrical screen, and a screw provided spirally around the screw shaft. A dewatering method in a dewatering apparatus including a blade, wherein by rotating a screw shaft together with the screw blade, a dewatering target put in the outer cylindrical screen is compressed while being conveyed in the axial direction of the screw shaft. Then, heating the dehydration object conveyed in the outer cylinder screen on the heating surface of the outer cylinder screen, the water separated from the dehydration object from the filtration surface where the small holes of the outer cylinder screen are exposed It has a configuration to discharge. According to this configuration, since the heating surface and the filtering surface are provided on the outer cylinder screen and the object to be dehydrated is dehydrated while being heated by the outer cylinder screen, the heating and dehydration can be performed even when the heat medium is at a low temperature.

  ADVANTAGE OF THE INVENTION According to this invention, since a heating surface and a filtration surface are provided in an outer cylinder screen and a dehydration object is dehydrated while heating with an outer cylinder screen, heating dehydration can be performed even by low temperature heating.

FIG. 1 is a block diagram illustrating a configuration of a dehydration system according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the dehydrating apparatus according to the embodiment of the present invention. FIG. 3 is a diagram showing a structure of the concentrator according to the embodiment of the present invention. FIG. 4 is a diagram showing a flow path of the heat medium of the dehydrating apparatus according to the embodiment of the present invention. FIG. 5 is a diagram showing a flow path of the heat medium of the dehydrating apparatus according to the embodiment of the present invention. FIG. 6 is a diagram showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 7 is a view showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 8 is a diagram showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 9 is a diagram showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 10 is a diagram showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 11 is a diagram showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 12 is a block diagram showing a configuration of a modification of the dehydration system according to the embodiment of the present invention.

  Hereinafter, a dehydration system according to an embodiment of the present invention 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 block diagram illustrating a configuration of a dehydration system including a dehydration device according to an embodiment of the present invention. In the drawing, solid-line arrows indicate the flow of an object to be treated, which is converted into incinerated ash from sludge through a plurality of processes, and dotted-line arrows indicate flows of gas, liquid, and electricity.

  The dewatering system 100 according to the present embodiment includes organic wastewater such as human waste, sewage, and industrial wastewater, septic tank sludge, household wastewater sludge (those containing rich SS such as household wastewater pit sludge and building pit sludge), Although effective as a system for dewatering sludge such as water sludge, the sludge to be dewatered by the dewatering system of the present invention (sludge to be dewatered) is not limited to these. The dewatering system 100 is effectively used for hardly dewaterable sludge, for which sufficient dewatering is difficult only by mechanical dewatering. In the following embodiments, the dewatering system 100 is used for sludge (organic sludge) as organic waste.

  The dewatering system 100 prepares coagulated sludge by adding a chemical such as a coagulant to the digestion tank 1 for performing anaerobic digestion treatment (methane fermentation treatment) on sludge and the digested sludge obtained in the digestion tank 1. Coagulation tank 2, a dehydration device 8 for performing a concentration treatment and a dehydration treatment on the coagulation sludge obtained in the coagulation tank 2, and a heat treatment facility for burning dehydration sludge (dehydration cake) obtained by the dehydration treatment. The incinerator 5 includes a heating medium heater 6 that heats a heating medium supplied to the dehydrator 4, and a generator 7 that generates electric power using waste heat of the incinerator 5.

  The dehydrating device 8 includes a concentrator 3 that separates water from the sludge into a concentrated sludge having low fluidity before the dehydration treatment, a chemical adding unit 9 that adds a chemical to the concentrated sludge obtained by the concentrator 3, The concentrated sludge to which the chemical has been added is provided as a sludge to be dehydrated, and a dehydrator 4 for performing a dehydration treatment on the sludge to be dehydrated is provided. The heat treatment equipment includes a carbonization equipment and a drying equipment in addition to the incinerator (incineration equipment). In addition, in the example of FIG. 1, the coagulation tank 2 has two stages so that the inorganic coagulant and the polymer can be added. However, the coagulation tank 2 may have one stage or three or more stages. Alternatively, only a polymer may be added as a coagulant.

  The digestion gas containing the methane gas generated by the methane fermentation in the digestion tank 1 is supplied to the heating medium heater 6. Waste heat generated by incineration of the incinerator 5 is supplied to the heating medium heater 6 and the generator 7. The waste heat in the generator 7 is supplied to the heating medium heater 6. The heat medium heater 6 heats a heat medium such as water, for example, and supplies the heated medium to the dehydrator 4. The heating medium heater 6 may be, for example, a hot water boiler that burns digestion gas to generate hot water, or a heat exchanger of incinerator exhaust gas and water. The dehydrator 4 dehydrates the sludge while heating it using heat obtained from the heat medium. The incinerator 5 may incinerate not only the dewatered sludge discharged from the dehydrator 4 but also other on-site sludge or sludge carried in from outside.

  FIG. 2 is a cross-sectional view of the dehydrator 8 in which the concentrator 3, the dehydrator 4, and the chemical adding unit 9 are integrally formed. In addition, the concentrator 3 and the dehydrator 4 and the chemical addition unit 9 may be integrally formed as shown in FIG. 2, or the concentrator 3 and the chemical addition unit 9 may be dehydrated independently of the dehydrator 4. It may be provided on the top or side of the machine 4.

  The dehydrator 4 of the present embodiment is a so-called screw press type dehydrator. In the dehydrator 4, a cylindrical outer cylinder screen 12 is horizontally installed on a machine base 11. The outer cylinder screen 12 is supported by a support member. Inside the outer cylinder screen 12, a screw shaft 13 is provided concentrically with the outer cylinder screen 12. The screw shaft 13 has a tapered shape whose diameter gradually increases in the sludge conveyance direction (left direction in FIG. 2), has a large-diameter end on the sludge discharge side, and has a large-diameter end on the sludge supply side. It has a small diameter end. The screw shaft 13 is rotatable and movable in the axial direction with respect to the outer cylindrical screen 12.

  The outer cylindrical screen 12 is provided with a number of small holes 14 in a peripheral wall. The small hole 14 communicates between the inside and the outside of the outer cylindrical screen 12. A screw blade 15 is spirally wound around the screw shaft 13. On the machine base 11, a movable base 16 movable along the axis of the screw shaft 13 is provided. A front bearing 17 and a rear bearing 18 are provided on the movable base 16. The front bearing 17 and the rear bearing 18 bear the small diameter end of the screw shaft 13 protruding from the closed end plate of the outer cylindrical screen 12 in the radial direction and the axial direction.

  On the front bearing 17 and the rear bearing 18, a variable speed motor 19 with a reduction gear is provided. The rotating shaft of the variable speed motor 19 and the small diameter end of the screw shaft 13 are rotationally connected by a connecting belt 20. The rotation of the variable speed motor 19 is transmitted to the screw shaft 13, and thus the rotation drive device is configured on the movable base 16.

  The movable base 16 is translated (moved forward or backward) in the axial direction of the screw shaft 13 by a driving device (not shown). By the movement of the movable base 16, the front bearing 17, the rear bearing 18, the variable speed motor 19, and the connection belt 20 also move in the axial direction of the screw shaft 13, and the screw shaft 13 also moves in the axial direction. I do. By the movement of the screw shaft 13 in the axial direction, the axial position of the screw shaft 13 with respect to the outer cylindrical screen 12 is changed.

  A spiral conveying compression passage 21 is formed between the screw blades 15 of the screw shaft 13. The transport compression passage 21 is covered with the outer cylinder screen 12. The cross-sectional area of the transfer compression passage 21 is smaller on the discharge side (outlet side) than on the sludge supply side (inlet side), and in the transfer compression passage 21, the sludge passes through the inner peripheral surface of the outer cylindrical screen 12 and the screw. It is conveyed while being compressed by the blade 15.

  An inlet 22 for taking in the sludge (condensed sludge) discharged from the concentrator 3 into the outer cylinder screen 12 is provided at an upper portion of the outer cylinder screen 12. Between the outer cylindrical screen 12 and the screw blade 15 of the screw shaft 13 and the large-diameter portion, an annular or cylindrical compression chamber 23 having a square cross section for further compressing the sludge passing through the transfer compression passage 21 is formed. I have. The compression chamber 23 has an outlet of the transfer compression passage 21 as an inlet.

  Below the outer cylinder screen 12, there is provided a tray 24 for collecting liquid flowing out of the small holes 14 by being separated from sludge by squeezing in the outer cylinder screen 12. A bearing plate 25 is provided upright on the base 11. The bearing plate 25 supports the large-diameter end of the screw shaft 13 protruding from the open end of the outer cylindrical screen 12 only in the radial direction.

  A plurality of hydraulic cylinders 26 are fixed to the bearing plate 25, and the piston rod 27 of the hydraulic cylinder 26 penetrates the bearing plate 25, and the tip of the piston rod 27 is connected to the discharge taper cone 29, so that the piston rod 27 moves forward. A hydraulic circuit for controlling retraction and stopping at a desired position is provided to change the position of the discharge taper cone 29 in the axial direction of the screw shaft 13. Below the large-diameter end of the screw shaft 13 and the outlet of the compression chamber 23, a fall path 28 for the dehydrated sludge flowing out of the outlet of the compression chamber 23 is provided.

  In the dehydrator 4 configured as described above, when the screw shaft 13 and the screw blade 15 integrated by the variable speed motor 19 are rotated and sludge is injected into the outer cylindrical screen 12 from the inlet 22, the sludge is screwed. While being conveyed in the axial direction of the shaft 13, it is compressed and moisture is released from the sludge. The water separated from the sludge is discharged through the small holes 14 of the outer cylinder screen 12 to the outside of the outer cylinder screen, and is received by the tray 24. The dewatered sludge generated in this dehydration treatment is discharged from the falling path 28 to the outside of the dehydrator 4.

  In the dehydrator 4, when the length from the inlet to the outlet of the compression chamber 23 is adjusted to obtain a desired dehydration performance, the screw shaft 13 is moved in the axial direction by the axial direction position changing device of the screw shaft 13. To change the axial position of the screw shaft 13 with respect to the outer cylindrical screen 12, thereby increasing or decreasing the length of the compression chamber 23.

  When the movable base 11 is advanced by a driving device (not shown) and stopped at the advanced position, and the axial direction position of the screw shaft 13 is changed to the outlet side of the compression chamber 23, the outer cylindrical screen 12 and the screw blades of the screw shaft 13 are rotated. The fitting length of the 15 to large diameter portion decreases, and the length of the compression chamber 23 decreases. Conversely, when the movable table 11 is retracted and stopped at the retracted position, and the axial direction position of the screw shaft 13 is changed to the inlet side of the transfer compression passage 21, the length of the compression chamber 23 increases.

  FIG. 3 is a diagram illustrating the structure of the concentrator 3. The concentrator 3 of the present embodiment is a sludge pressing machine, and includes a sludge hopper 31, a sludge moving unit 32, a pressurizing unit 33 provided above the sludge moving unit 32, and a sludge moving unit 32. And a water collecting means 34 provided below.

  The sludge moving means 32 includes a belt 36 formed of a filter cloth and a belt driving device 38. When the belt driving device 38 drives the belt 36, the entire upper surface (transport surface) of the belt 36 moves horizontally, and moves the flocculated sludge to the horizontal sludge discharge port side. The flocculated sludge is filtered while traveling on the belt 36, and the filtrate falls to the water collecting means 34 below.

  The pressurizing means 33 includes a pressurizing plate 33 </ b> A, which is provided diagonally with a gap between the sludge discharging means 37 and the belt 36 in front of the sludge discharge port 37 of the sludge moving means 32. When the sludge is moved to the sludge discharge port side in the horizontal direction by the sludge moving means 32, the sludge is pressurized from above when passing through the gap between the pressing plate 33A and the belt 36.

  One or two or more pressure plates 33A may be provided, and the pressure plate 33A may be provided so that the installation angle is fixed, or may be provided so that the installation angle can be changed as needed. Further, it can be pivotally supported so as to be vertically swingable. By changing the angle of the pressure plate 33A and the size of the gap with the belt 36, the pressure applied to the coagulated sludge can be adjusted, and the concentration efficiency can be adjusted. Further, instead of the pressing plate 33A, for example, a roller can be provided.

  The water collecting means 34 is provided along and below the sludge moving means 32 so as to collect water falling from the sludge moving means 32 and drain the water from a waste water outlet.

  Next, the operation of the concentrator 3 having such a configuration will be described. When the coagulated sludge is put into the sludge input hopper 31, the coagulated sludge is moved by the sludge moving means 32 to the horizontal sludge discharge port side, and is conveyed horizontally on the upper surface of the belt 36. The coagulated sludge is dewatered in this transporting process, and is further squeezed by the pressurizing plate 33A to further separate the concentrated filtrate, to bring the concentration of the concentrated sludge closer to a predetermined concentration, and to form a plate-shaped sludge from the sludge discharge port 37. Discharged as concentrated sludge. The dewatered water falls from the sludge moving means 32, is collected by the water collecting means 34, and is drained from the wastewater outlet.

  In addition, as the concentrator 3, besides the sludge press having the above configuration, a sludge press used for conventional sludge dewatering, for example, a centrifugal concentrator, a screw concentrator, an elliptic plate concentrator, etc. It is also possible to adopt. Also, a machine configured to press sludge with a flat plate can be used. Further, the structure for separating the concentrated filtrate is not limited to the belt, and a slit bar having a gap is arranged, the concentrated filtrate is discharged from the gap, and the concentrated sludge on the slit bar is transferred by mechanical transfer means. It may be replaced by a device that performs the following. In the concentrator 3, the sludge is concentrated by mechanical concentration as described above so that the sludge concentration becomes 6% or more, preferably 8% or more.

  As described above, in the concentrator 3, a squeezing force is applied at the time of concentration in order to considerably increase the concentration of the concentrated sludge to, for example, 6% or more. In this state, if the sludge is put into the dehydrator 4 and dehydrated while heating, the soft sludge with insufficient coagulation will be dehydrated, and the water content of the sludge to be dehydrated will not easily decrease. In the case of soft sludge such as excess sludge and digested sludge, coagulation tends to be broken by heating, but by adding an inorganic coagulant, the sludge coagulation power in the dewatering section can be increased again, and the water contained in the sludge to be dewatered by heating can be used. The effect of decreasing the rate can be increased.

  Therefore, in the present embodiment, the chemical addition section 9 is disposed between the concentrator 3 and the dehydrator 4. The chemical addition section 9 is configured as a passage connecting the sludge discharge port 37 of the concentrator 3 and the input port 22 of the dehydrator 4, and adds a chemical to the concentrated sludge passing therethrough. The concentrated sludge discharged from the concentrator 3 is added with a chemical while passing through the chemical adding section 9 by its gravity, and is injected into the outer cylindrical screen 12 from the inlet 22 of the dehydrator 4.

  The chemical adding section 9 adds a polymer and an inorganic chemical (inorganic flocculant) as chemicals to the sludge concentrated by the concentrator 3. The inorganic chemicals (inorganic coagulant) for sludge treatment and coagulation added to the concentrated sludge in the chemical addition section 9 include metal salts such as aluminum and iron (for example, ferric polysulfate, ferric chloride, sulfate band, PAC (polyaluminum chloride) or the like can be employed. However, in the case of PAC or ferric chloride, which is a metal salt containing a large amount of chlorine, the dehydrated filtrate after dehydration contains a large amount of chloride ions, so that the corrosion of the dehydrator 4 easily progresses and the durability of the dehydrator 4 increases. Decrease. In particular, when heating is performed at the time of dehydration as in the present embodiment, the temperature of the dehydrated filtrate becomes high, and corrosion of the screen and the casing progresses vigorously due to chlorine ions. Therefore, a durable and expensive material must be selected for the screen and the casing, and the manufacturing cost of the dehydrator 4 increases. Therefore, a metal sulfate (for example, ferric polysulfate or a sulfate band) is preferable as the inorganic chemical used in the present embodiment.

  The concentrated sludge introduced into the outer cylindrical screen 12 is compressed while being conveyed toward the falling path 28 by the screw blades 15 spirally provided around the rotating screw shaft 13, and the water separated by the compression is compressed. Is discharged outside through a small hole 14 provided in the peripheral wall of the outer cylindrical screen 12. The dewatered sludge (dewatered sludge) is discharged from the falling path 28 to the outside of the dehydrator 4.

  In the dehydrator 4 of the present embodiment, the screw shaft 13 and the screw blade 15 are formed in a hollow shape, and a heat medium (hot water) heated by the heat medium heater 6 is introduced into the inside thereof. The internal space of the screw shaft 13 and the internal space of the screw blade 15 communicate with each other at the sludge supply-side end of the screw blade 15 (the internal space of the screw shaft 13 and the internal space of the screw blade 15 form a series. ing).

  FIG. 4 is a diagram illustrating an example of a flow path of the heat medium. As shown in FIG. 4, the heat medium that has flowed into the screw shaft 13 from the heat medium inlet passes through the screw shaft 13 from the sludge discharge side (left side in FIG. 4) to the sludge supply side (right side in FIG. 4). Flows in the direction opposite to the sludge transport direction. The heat medium that has reached the right end (end on the sludge supply side) of the screw shaft 13 flows into the screw blade 15 from there.

  The heat medium that has flowed into the screw blade 15 from the screw shaft 13 flows spirally in the internal space of the screw blade 15 in the sludge conveyance direction. The end of the screw shaft 13 on the sludge discharge side (left side in FIG. 4) has a double pipe structure, and the heat medium introduced from the heat medium inlet flows into the internal space of the screw shaft 13 through the inner pipe. The heat medium flowing through the internal space of the screw blade 15 and returning from the sludge supply side to the sludge discharge side is discharged through the outer pipe.

  Since the screw shaft 13 and the screw blade 15 are rotating, in order to cause the heat medium to flow into the screw blade 15, the heat medium is injected into the screw shaft 13 at the center of rotation via a rotary joint (rotary joint). It is necessary to flow to the screw blade 15 via the screw shaft 13. By forming the internal space of the screw shaft 13 and the internal space of the screw blade 15 in series as in the present embodiment, the heat medium flowing through the screw shaft 13 inside the screw shaft 13 and the screw blade There is no need to quantitatively distribute the heat medium flowing into the heat medium 15 and a complicated structure is not required.

  As described above, in the present embodiment, the sludge is concentrated in the concentrator 3 before dehydration while heating in the dehydrator 4. By performing dehydration while heating after concentration as described above, a high dehydration effect can be obtained even if the required energy is small. In addition, since the inorganic flocculant is added to the concentrated sludge in the chemical addition section 9, the water content is reduced. Although it is lower, there is a problem that scale is generated on the heated surface by the inorganic flocculant. In other words, when a heating medium having a temperature of 100 ° C. or more, such as steam generally used as a heating medium, is used, the heating surface temperature becomes 100 ° C. or more, and the sludge to be dewatered is apt to evaporate moisture, which is generated during dehydration. The scale component in the resulting filtrate tends to cause the scale to adhere to the heated surface. When the scale adheres to the heating surface, the heat transfer rate for heating decreases, the heating effect does not appear, and the growth of the scale changes the behavior of the sludge in the dehydrator, reducing the dewatering property. Or In particular, when an inorganic flocculant is added to the concentrated sludge, the concentrated sludge becomes acidic, and the scale components in the sludge are easily dissolved in the dehydrated filtrate, and the amount of scale generation is significantly increased.

  If the scale adheres to the heating surface and the heat transfer rate or dehydration property decreases, it cannot be continuously reduced to the target moisture content, and in extreme cases, the scale is blocked and sludge cannot flow. In some cases. As a result, it is impossible to provide a dehydration system that can obtain a high dehydration effect with small energy.

  Therefore, in the present embodiment, the temperature of the heat medium is set to 55 ° C. or more and less than 100 ° C. (preferably 70 ° C. or more and less than 90 ° C.), and the temperature is controlled so that the sludge does not boil. The heating medium heater 6 heats the heating medium while monitoring the temperature of the heating medium with a temperature sensor so that the heating medium has a predetermined temperature (or within the range) within the above range. Alternatively, the heating medium heater 6 may control the temperature of the heating medium to a target temperature (or within a temperature range) by adding cold water to a heating medium (water or steam) of 100 ° C. or higher. Good. The heating medium may be hot water or reduced pressure steam under vacuum.

  In addition, by introducing a heat medium into the inside of the screw shaft 13 and the screw blade 15, the surfaces of the screw shaft 13 and the screw blade 15 serve as heat transfer surfaces and come into contact with the sludge. It will be dehydrated while heating. By ensuring a wide heat transfer surface in this manner, the sludge can be sufficiently heated even with a low-temperature heat medium (for example, hot water, that is, water having a temperature of less than 100 ° C.) as described above, and the low water content of the dewatered sludge can be reduced. Can be achieved.

  FIG. 5 is a diagram illustrating another example of the flow path of the heat medium. In this example, inside the outer tube 131 of the screw shaft 13, a partition plate 132 that partitions the internal space in the axial direction is provided at a position corresponding to the inlet 22, and the outer tube 131 of the screw shaft 13 is The inner space is bisected in the axial direction by the partition plate 132.

  On one side (left side in FIG. 5) of the partition plate 132, an inner pipe 133 parallel to the axial direction is provided from an end portion to a position short of the partition plate 132. Also, on the other side (the right side in FIG. 5) of the partition plate 132, an inner pipe 134 is provided parallel to the axial direction from the end portion to the front of the partition plate 132. That is, the inside of the outer tube 131 of the screw shaft 13 has a double tube structure composed of the inner tubes 133 and 134 and the outer tube 131 on both sides of the partition plate 132. The outer flow path 135 between the outer pipe 131 and the inner pipe 133 communicates with the inner flow path 137 in the inner pipe 133 before the partition plate 132.

  The screw blade 15 has a hollow structure. The internal space of the screw blade 15 is divided into an outward path (outside) and a return path (inside). The forward path and the return path are spirally formed along the spiral shape of the screw blade 15, and the left end of the screw blade 15 is a turning point and is connected from the forward path to the return path. The outward path of the screw blade 15 is on the right side of the partition plate 132 and communicates with the outer flow path 136 between the outer pipe 131 and the inner pipe 134, and the return path is on the right side of the partition plate 132 and the inner flow path of the inner pipe 134. It communicates with the road 138.

  The heat medium is supplied into the screw shaft 13 from both sides of the screw shaft 13. On the left side of the partition plate 132, the heat medium is supplied to the outer channel 135, flows in the outer channel 135 in a direction opposite to the sludge transport direction, is stopped by the partition plate 132, and passes through the inner channel 137. Sludge flows in the same direction as the transport direction and is discharged.

  On the right side of the partition plate 132, the heat medium is supplied to the outer flow path 136, flows through the outward path of the screw blade 15 and flows inside the screw blade 15 toward the sludge conveyance direction, and turns back at the end to return. And returns through the inner channel 138 and is discharged. That is, the heat medium supplied from one side of the screw shaft 13 is discharged from one side, and the heat medium supplied from the other side of the screw shaft 13 is discharged from the other side.

  The heating medium heater 6 and the screw shaft 13 are connected via a rotary joint (rotary joint). The heat medium transferred from the heat medium heater 6 is injected into the screw shaft 13 via a rotary joint.

  Also in this example, the heat medium supplied to the screw shaft 13 on the left side of the partition plate 132 and the heat medium supplied to the screw blades 15 from the right side of the partition plate 132 are distributed in a predetermined amount inside the screw shaft 13. No need, no complicated structure.

  In the dehydrator 4 of the present embodiment, the outer jacket 12 is also provided with the heating jacket 51, and the heating medium is supplied to the inside thereof. The heating jacket 51 in the example of FIG. 2 is an annular hollow member surrounding the outer periphery of the outer cylindrical screen 12. By heating the heating jacket 51 by circulating a heat medium inside, the sludge in the outer cylindrical screen 12 is heated. The heating jacket 51 can be provided along a part of the outer peripheral surface of the outer cylinder screen 12 so as to contact the outer cylinder screen 12.

  As described above, the outer cylinder screen 12 is provided with a plurality of small holes 14 for discharging the water separated from the compressed sludge to the outside of the outer cylinder screen 12. On the outer peripheral surface of the outer cylindrical screen 12 on which the heating jacket 51 is covered, the small holes 14 are closed, and the water separated from the sludge cannot be discharged, and the filtration area is reduced. No effect on processing. The reason is as follows.

  The dehydration treatment includes a separation step of separating water from the sludge (squeezing out the filtrate from the sludge) and a discharge step of discharging the filtrate to the outside of the outer cylindrical screen 12. The amount of the filtrate in each step is the same. However, the time during which the filtrate is processed (squeezed / discharged) is different for each step, and the separation step is longer. Therefore, since time is allowed in the discharging step, even if the filtration area by the small holes 14 formed in the outer cylindrical screen 12 is reduced, it does not affect the dewatering step. In other words, in the discharge step, even if the filtration area is small, the water separated from the sludge in the separation step can be sufficiently discharged.

  On the other hand, not only is the heating medium supplied to the inside of the screw shaft 13 and the screw blade 15 to heat the sludge from the screw shaft 13 and the screw blade 15, but also the heating medium is supplied to the inside of the heating jacket 51 for heating. By heating the sludge from the jacket 51 through the outer cylindrical screen 12, the heat transfer surface becomes wider as compared with the conventional dehydrator, and it is possible to sufficiently heat the sludge even with a lower temperature heat medium. Become.

  As shown in FIG. 2, in the dehydrator 4 of the present embodiment, three heating jackets 51 are provided at intervals in the sludge transport direction (axial direction of the screw shaft 13). As described above, since the plurality of heating jackets 51 are installed at intervals in the sludge conveyance direction, the outer peripheral surface of the outer cylindrical screen 12 has a filtering surface (a surface where the small holes 14 are exposed) in the conveyance direction. And the heating surface (the surface to which the heating jacket 51 is attached) are alternately and repeatedly arranged, and the sludge is conveyed while repeating heating and filtration.

  Experiments have confirmed that the dehydration effect is improved by repeating such heating and filtration. That is, it is more effective to install n heating jackets 51 having a length L / n in the transport direction apart from each other in the transport direction than to install only one heating jacket 51 having the length L in the transport direction. Is known to be high. This is because the sludge, when heated on the heating surface, has a reduced viscosity, and also has a reduced water retention capacity due to thermal denaturation, so that it becomes easily dewatered.If the sludge reaches the filtration surface in such a state, it is sufficient. This is because the amount of sludge is reduced due to the removal of moisture and the amount of heat required for heating is reduced, so that the next heating jacket surface makes it easier to be heated and becomes more easily dewatered.

  A heating medium is supplied to the plurality of heating jackets 51 from the same heating medium heater 6. The plurality of heating jackets 51 are connected to the heating medium heater 6 by pipes, respectively, and the heating medium may be supplied from the heating medium heater 6 to the plurality of heating jackets 51 in parallel. The machine 6 and the plurality of heating jackets 51 may be connected in series (in series) by piping, and the heating medium may be supplied to the plurality of heating jackets 51 in order.

  When the plurality of heating jackets 51 are connected in series to the heating medium heater 6, the number of pipes can be reduced as compared with the case where the plurality of heating jackets 51 are connected to the heating medium heater 6 in parallel. it can. When a plurality of heating jackets 51 are connected in series, it is desirable that the heating medium from the heating medium heater 6 flow through the heating jacket 51 from the discharge side of the dehydrated sludge to the supply side. In this case, since the temperature difference between the heat medium and the sludge can be made larger on the discharge side, the temperature of the sludge can be made higher, and a lower water content can be achieved.

  A bypass plate (not shown) may be provided in the heating jacket 51 to form a flow path for the heat medium inside the heating jacket 51. By doing so, short-circuit flow or stagnation of the heat medium can be prevented, uniform heat conduction can be achieved, and the heat medium inside the heating jacket 51 can be turbulent to improve heat transfer efficiency. .

  In this manner, by supplying the heating medium to the inside of the screw shaft 13 and the screw blade 15 and also supplying the heating medium to the inside of the heating jacket 51, a sufficient heat transfer surface for heating the sludge can be secured. In addition, even when a low-temperature heat medium such as hot water obtained by utilizing waste heat is used, the sludge can be sufficiently heated to perform heat dehydration.

  In addition, when the sludge is dewatered while being heated by the screw shaft 13, the screw blade 15, and the heating jacket 15, as described above, the viscosity of the sludge decreases, and the water retention of the sludge decreases due to thermal denaturation. The filtrate is easily separated. Thus, the water content of the dewatered sludge can be reduced, and the energy required for incineration of the sludge in the incinerator 5 can be suppressed. The filtrate that can be separated is separated immediately after heating, and by not separating it, it is possible to prevent unnecessary energy from being used.

  Furthermore, in the dehydrator 8 of the present embodiment, the concentration of the sludge is sufficiently increased by the concentrator 3 and the amount of the sludge to be heated is reduced before heating by the dehydrator 4. The energy required for the heating (heating energy) can be suppressed, and the filtration area can be reduced in the dehydrator 4, and the area of the heating jacket 51 can be increased accordingly.

  Further, by increasing the area of the heating jacket 51, sufficient heating can be performed even if the temperature of the heating medium is low (even if the heating medium is a low-temperature heating medium). Hot water can be used as the low-temperature heat medium, and hot water can be generated using waste heat of the incinerator 5 and the generator 7 as shown in FIG. In the dehydrator 4, the temperature of the sludge is 45 ° C. or more and less than 100 ° C. on average, preferably 55 ° C. or more and less than 100 ° C., and the temperature is controlled so that the moisture contained in the sludge does not boil.

  In the dehydration system 100, a dryer connected by a chute or the like may be provided below the falling path 28 of the dehydrator 4. By providing the dryer in the lower part of the falling path 28 of the dehydrator 4, it is possible to omit equipment for transferring the dehydrated sludge to the dryer, and to cool the dehydrated sludge having heat. Drying can be performed without any heat, so that the amount of heat used in the dryer can be small.

  Hereinafter, a modification of the heating jacket 51 will be described. 6 to 11 are views showing modified examples of the heating jacket 51. FIG. 6 to 11 schematically show the relationship between the outer cylindrical screen 12 and the heating jacket 51. FIG. FIG. 6 shows an example in which the heating jackets 51 are provided on the outer periphery of the outer cylindrical screen 12 in a lattice shape. According to this example, in the outer cylindrical screen 12, it is possible to secure a filtration unit and to perform uniform heating by the heating jacket 51. The support of the outer cylinder screen 12 may be a heating jacket 51.

  In the example of FIG. 7, the heating jacket 51 is provided at the middle stage in the transport direction of the outer cylindrical screen 12. The heating jacket 51 has a cylindrical shape surrounding the outer periphery of the outer cylindrical screen 12. Before the sludge reaches the heating section provided with the heating jacket 51, water is removed to some extent, the heating section sufficiently heats the sludge, and the sludge from which the moisture is easily released is filtered again.

  In the example of FIG. 8, the heating jacket 51 is divided vertically. A plurality of arc-shaped heating jackets 51 are arranged apart from each other on the upper side of the outer cylinder screen 12, and a plurality of arc-shaped heating jackets 51 are also spaced apart from each other below the outer cylinder screen 12. Are located. Each heating jacket 51 has a semicircular shape that covers only a part of the outer cylindrical screen 12 in the circumferential direction.

  Further, the upper heating jackets 51 and the lower heating jackets 51 are shifted from each other in the transport direction, and the upper heating jacket 51 and the lower heating jacket 51 alternate in the transport direction. Placed in It should be noted that the vertically divided position does not have to be at the center of the height of the outer cylindrical screen 12.

  In the example of FIG. 9, similarly to the example of FIG. 2, a plurality of annular heating jackets 51 are arranged apart from each other in the transport direction. In the example of FIG. 9, compared to the example of FIG. 2, the widths of the respective heating jackets 51 in the transport direction are narrower, the intervals between them are narrower, and more heating jackets 51 are arranged.

  In the example of FIG. 10, the heating jacket 51 is provided so as to cover only a part of the middle part in the height direction of the outer periphery of the outer cylinder screen 12 over the transport direction of the outer cylinder screen 12. The heating jacket 51 has a band shape and is attached to the outer cylindrical screen 12 in parallel with the transport direction. The heating jacket 51 shown in FIG. 10 is also provided on the surface on the opposite side of the outer cylindrical screen 12.

  In the example of FIG. 11, the heating jacket 51 is provided so as to cover an upper portion of the outer cylinder screen 12 over the transport direction of the outer cylinder screen 12. The heating jacket 51 has a semi-cylindrical shape. In this example, a heating surface is formed on the upper side of the outer cylindrical screen 12, and a filtration surface is formed on the lower side.

  In the examples of FIGS. 10 and 11, the number of divisions of the jacket can be reduced, the control of the heat medium is easy, and the manufacturing cost can be reduced. In the screw press method, the sludge is conveyed in the discharge direction while rotating inside the outer cylindrical screen 12, so that even with a heating jacket parallel to the conveyance direction, heat can be uniformly applied to the sludge.

  Although not shown, a heating jacket 51 as shown in any of the examples in FIGS. 2 and 6 to 11 may be provided only on the rear side in the transport direction of the outer cylindrical screen 12. Since the heating effect becomes remarkable after the screw press to which dewatering has progressed to some extent, an effective heat dewatering effect can be obtained by concentrating the heating jacket 51 behind the transport direction. Further, since water is heated in the first stage and then heated in the second stage, the required amount of heat can be reduced and energy saving can be realized.

(Example)
A dehydration test was performed using the digested sludge generated in the sewage treatment plant, using the dehydration system 100 of the present embodiment. The sludge treatment amount is 10 kg-DS / h in terms of solid matter, and the dewatering method employs a screw press method. The sludge was heated. The temperature of the sludge introduced into the dehydrator 4 was 20 ° C., the amount was 100 kg / h, and the flow rate of hot water as a heat medium was 1.5 m ³ / h.

  Before pouring sludge into the dehydrator 4, ferric polysulfate and a polymer were added in the flocculation tank 2 to coagulate, and then concentrated to about 10% by the concentrator 3. The polymer was added again to the concentrated sludge. The polymer addition rate was 1.2 to 1.5%, and the addition rate of ferric polysulfate was 10 to 15%.

  The method of arranging the heating surface of the outer cylindrical screen 12 was based on the following conditions (1) and (2). In the condition (1), as shown in FIG. 7, one heating surface (heating jacket 51) was arranged in the sludge conveyance direction with respect to the outer cylindrical screen 12. In the condition (2), as shown in FIG. 2, the filtration surface and the heating surface (the heating jacket 51) were alternately arranged a plurality of times in the sludge conveyance direction in the outer cylindrical screen 12. Note that the total area of the heating surface was the same under the condition (1) and the condition (2).

  The ultimate temperature and water content of the dewatered sludge were measured, and the calorie required in the dehydrator 4 was calculated from the measurement results. Specifically, the required heat amount E is obtained by measuring the flow rate Q of hot water as a heat medium, the temperature T1 when the hot water is injected into the dehydrator 4, and the temperature T2 when the hot water comes out of the dehydrator 4. Then, E = α × Q × (T1−T2) was obtained (α is a coefficient for unit conversion).

Table 1 shows the experimental results.

  Under the condition (1), the sludge was sufficiently heated, and the water content of the dewatered sludge was also 72%. The amount of heat required at that time was 6.3 MJ / h. Under the condition (2), the sludge could be more sufficiently heated, and the water content of the dewatered sludge could be reduced to 70%. The amount of heat required at that time was 5.0 MJ / h, which was small. As described above, under the condition (2), by arranging the heating surface and the filtration surface a plurality of times, the effect of dehydrating while heating can be increased, and the required heat amount can be made smaller than the condition (1).

  As described above, the dehydration system 100 is a system for dehydrating while heating organic sludge such as sewage, night soil, and garbage digested sludge. As a heat source for this heating, digestion gas, incineration waste heat ( (Including carbonization and drying) and waste heat from power generation, so no new energy source is required, reducing the water content of sludge and reducing auxiliary fuel (oil and gas) for incineration or Since it can be eliminated, energy saving and energy creation can be realized.

  In the dehydration system 100, hot water heated using digestion gas, incineration waste heat, and power generation waste heat is used as a heat medium. Generally, hot water has a low heat exchange rate due to its low temperature, and its use is limited. However, in the dewatering system 100 of the present embodiment, not only the inside of the screw shaft 13 but also the screw Since the heating medium is also supplied to the inside of the heating jacket 51 and the inside of the heating jacket 51 attached to the outer cylindrical screen 12, the temperature of the heating medium may be relatively low (45 ° C. or more and less than 100 ° C.), and hot water may be used. it can. Therefore, energy saving and energy creation can be further promoted by using hot water, which has a limited use destination and is sometimes discarded.

  Further, the dehydration method of one embodiment of the present invention includes a concentration step of concentrating the sludge to generate a concentrated sludge, and using the concentrated sludge generated in the concentration step as a sludge to be dehydrated, indirectly heating the sludge to be dehydrated. The method includes a dehydration step of dehydrating while heating in a manner and an addition step of adding an inorganic flocculant to the concentrated sludge, wherein the temperature of the heat medium used for heating the sludge to be dehydrated in the dehydration step is less than 100 ° C. It has the following configuration. Here, the indirect heating method refers to a method in which heating is performed in a state where the unheated material and the heat medium are not mixed, and there is an object to be heated on one side of a shield such as a plate or cloth, and the heat medium is on the other side. Is a heating method in which heat is transferred from a heat medium to an object to be heated via a shield.

  According to this configuration, the sludge is dewatered while being heated in the dewatering step, so that the viscosity of the sludge is reduced, and the water retention capacity of the sludge is reduced due to thermal denaturation, so that the filtrate is easily separated, and the dewatered sludge ( The water content of the dewatered sludge can be reduced. In addition, since most of the dehydrated filtrate can be quickly separated from the sludge at a stage where heating is not completed, it is possible to prevent unnecessary heat energy from being used for the dehydrated filtrate. In addition, since the concentration of the sludge is increased in the concentration step and the amount of sludge to be heated is reduced and then heated, when performing dehydration while heating in the dehydration step, the temperature of the sludge in the dehydration step is heated to a desired temperature. Energy (heating energy) can be kept low. Furthermore, since the indirect heating method is used to heat the sludge in the dehydration step, the sludge can be heated using a heating medium such as hot water.

  In addition, in the case of soft sludge such as excess sludge or digested sludge, coagulation tends to be broken by heating, but by adding an inorganic coagulant to concentrated sludge, the sludge coagulation power in the dewatering section can be increased again, and dehydration by heating can be performed. The effect of reducing the water content of the target sludge can be increased. Further, by using a heat medium having a temperature of less than 100 ° C., evaporation of water on the heating surface is less likely to occur, and scale components in the filtrate generated during dehydration are less likely to adhere to the heating surface.

(Example)
Hereinafter, an example of the dehydration system 100 of the present embodiment will be described. In the present embodiment, a dehydration test was performed in the dehydration system 100 using digested sludge generated in a sewage treatment plant. The sludge treatment amount was 8 kg-DS / h in terms of solid matter, and the dehydrator 4 employed a screw press method, in which a heating medium was injected into the screw shaft 13 to perform heating while dehydrating. Before being put into the dehydrator 4, the sludge was concentrated by adding a polymer to the sludge in the flocculation tank 2 to about 10%. In the chemical addition section 9, a polymer and an inorganic coagulant (specifically, ferric polysulfate) were added to the concentrated sludge. The addition rate of the polymer was 2.0 to 2.5%, and the addition rate of the ferric polysulfate was 20 to 25%.

The heating medium temperature condition in the heating medium heater 6 was set to three conditions of 80 ° C. (warm water), 120 ° C. (steam), and no heating medium. The water content was measured. Table 2 shows the results.

  As shown in Table 2, regardless of the presence or absence of the addition of the inorganic coagulant, the water content of the dehydrated cake was lower when heating (heating medium temperature: 80 to 120 ° C) than when not heating. In addition, regardless of the heating medium temperature conditions, the water content of the dehydrated cake was lower in the conditions 1 to 3 in which the inorganic coagulant was added than in the conditions 4 to 6 in which the inorganic coagulant was not added. This is due to the coagulation effect of the inorganic coagulant. Further, under the conditions 1 to 3 in which the inorganic coagulant was added, the cake moisture content was higher in the condition 3 (76%) at 120 ° C. than in the condition 2 (74%) at a heating medium temperature of 80 ° C. Rose. This is because, under the condition of 120 ° C., a large amount of scale adhered to the heating surface of the screw shaft, the heat transfer rate for heating was reduced, and the heating effect was not sufficiently exhibited.

  In the above embodiment, the digestion gas, incineration waste heat, and power generation waste heat are all used to heat the heat medium. However, only a part of them may be used, or other heat sources may be used. May be. Further, in the above embodiment, the polymer is added to the sludge by the concentrator 3, but the polymer may be added to the sludge in the coagulation tank 2. Further, a dehydration aid may be added in the coagulation tank 2.

  The dehydrator 4 of the above dehydration system 100 is a screw press type dehydrator having one screw shaft 13, but the dehydrator used in the dehydration system 100 is a screw press type having two screw shafts. Dehydrator may be used.

  By using two screw shafts, the contact area between the shaft and the sludge increases, so that the sludge can be sufficiently heated even with a low-temperature heat medium. Further, the agitation and mixing of the sludge proceed in the portion where the two-shaft blades overlap, the sludge can be heated uniformly, and the water content of the dewatered sludge can be stably reduced. Note that the two screw shafts may be arranged vertically or horizontally. Further, the dehydrator may include three or more screw shafts.

  In the above-described embodiment, the heating jacket 51 is attached to the outer cylinder screen 12 and the sludge is heated via the outer cylinder screen 12. It may be provided on a surface. In this case, it is desirable to set the heating jacket 51 so as not to hinder the flow of sludge inside the outer cylindrical screen 12. This is because if the sludge stays in the outer cylindrical screen 12 due to the heating jacket 51, the staying sludge hinders the heat transfer and lowers the heating efficiency. If the heating jacket 51 is installed on the outer peripheral surface of the outer cylindrical screen 12 as in the above embodiment, such a concern is unnecessary.

  Further, the outer cylinder screen 12 itself may be hollow to allow the heat medium to flow therethrough. In this case, the heating jacket 51 attached to the outer cylinder screen 12 is unnecessary, and a portion of the outer cylinder screen 12 to be heated is heated. Can be both a heating surface and a filtration surface. In this case, a part of the outer cylindrical screen 12 may be a heating surface, or the entire surface may be a heating surface.

  Further, in the above-described embodiment, the heating jacket 51 is hollow and the heat medium is circulated therein. However, in addition to or instead of this, the heating jacket 51 is used as an electric heater, and the heating jacket 51 is used as an electric heater. The 51 itself may generate heat.

  Further, a heat insulating material or a heat insulating plate may be provided on the outer side of the heating jacket 51, that is, on the surface opposite to the surface in contact with the outer cylindrical screen. Thereby, the amount of heat released from the heating jacket 51 to the outside can be reduced, and energy saving can be realized.

  FIG. 12 shows a dehydration system 101 in which the digestion gas utilization method and the incineration waste heat utilization method of the above dehydration system 100 are different. 12, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description will be appropriately omitted.

  In the dehydration system 101, the digestion gas generated in the digestion tank 1 is used in the digestion gas generator 71, and the electricity is effectively used in the site. The power generation waste heat in the digestion gas generator 71 is used for heating the digestion tank 1 and is also used as a heating heat source during dehydration. The waste heat from the incinerator 5 is used to raise the temperature of hot water by heat exchange with white smoke prevention air in the heating medium heater 6. The hot water generated by the heating medium heater 6 is supplied not only to the dehydrator 4 but also to the digester 1 and used for heating the digester 1.

  The present invention provides a heating surface and a filtration surface on an outer cylinder screen to dehydrate while heating an object to be dehydrated with the outer cylinder screen. In addition, the present invention is useful as a dehydrator or the like for removing water from a dewatering target containing water such as sludge.

  1: digestion tank, 2: coagulation tank, 3: concentrator, 4: dehydrator, 5: incinerator, 6: heating medium heater, 7: generator, 8: dehydrator, 9: chemical addition section, 11: Machine stand, 12: outer cylindrical screen, 13: screw shaft, 14: small hole, 15: screw blade, 16: movable base, 17: front bearing, 18: rear bearing, 19: variable speed motor, 20: connecting belt , 21: Transfer compression passage, 22: Input port, 23: Compression chamber, 24: Receiving tray, 25: Bearing plate, 26: Hydraulic cylinder, 27: Piston rod, 28: Falling path, 29: Taper cone, 31: Sludge input Hopper, 32: sludge moving means, 33: pressurizing means, 33A: pressurizing plate, 34: water collecting means, 36: belt, 37: sludge outlet, 38: belt driving device, 51: heating jacket, 71 : Digestion gas generator, 100, 101: Dehydration system 131: outer tube, 132: partition plate 133: inner tube, 135 and 136: outer channel, 137, 138: inner channel

Claims (8)

An outer cylindrical screen with small holes formed in the peripheral wall,
A screw shaft provided inside the outer cylindrical screen,
Screw blades provided spirally around the screw shaft,
With
By rotating the screw shaft together with the screw blade, the object to be dewatered put into the outer cylindrical screen is compressed while being conveyed in the axial direction of the screw shaft, and the water separated from the object to be dewatered is discharged to the outside. A dehydrator for discharging from the small holes of the cylindrical screen,
Further provided is a concentrator for concentrating the dehydration target before being introduced into the outer cylindrical screen so that the concentration becomes 6% or more,
The outer cylinder screen has a heating surface to be heated, and a filtration surface from which the small holes are exposed,
A heating jacket attached to a part of the outer cylindrical screen and having a configuration in which a heat medium flows therethrough,
The portion of the outer cylindrical screen to which the heating jacket is attached is the heating surface,
The temperature of the heating medium is less than 100 ° C.,
The three or more heating jackets are arranged at intervals over the entire axial direction of the screw shaft, whereby the heating surface and the filtering surface are arranged over the entire axial direction of the screw shaft. It is arranged alternately at least three times,
For the object to be dehydrated, heating and dehydrating by filtering on the filtration surface in a state where the viscosity is reduced by heating on the heating surface and the water retention capacity is reduced by thermal denaturation in the transporting process is repeated three or more times. Dewatering equipment.   The dehydration apparatus according to claim 1, further comprising an addition unit that adds an inorganic coagulant to the dewatering target concentrated by the concentrator. Dehydrating apparatus according to claim 1 or 2, characterized in that said heating surface and the filter surface are arranged alternately and repeatedly in the axial direction of the screw shaft. An outer cylindrical screen with small holes formed in the peripheral wall,
A screw shaft provided inside the outer cylindrical screen,
Screw blades provided spirally around the screw shaft,
With
By rotating the screw shaft together with the screw blade, the object to be dewatered put into the outer cylindrical screen is compressed while being conveyed in the axial direction of the screw shaft, and the water separated from the object to be dewatered is discharged to the outside. A dehydration system discharging from the small hole of the cylindrical screen,
Further provided is a concentrator for concentrating the dehydration target before being introduced into the outer cylindrical screen so that the concentration becomes 6% or more,
The outer cylinder screen has a heating surface to be heated, and a filtration surface from which the small holes are exposed,
Having a configuration for flowing a heat medium inside, further comprising a heating jacket attached to a part of the outer cylindrical screen,
The portion of the outer cylindrical screen to which the heating jacket is attached is the heating surface,
Further comprising a heating medium heater that heats the heating medium using waste heat,
The temperature of the heating medium is less than 100 ° C.,
The three or more heating jackets are arranged at intervals throughout the axial direction of the screw shaft, so that the heating surface and the filtration surface extend over the entire axial direction of the screw shaft. It is arranged alternately at least three times,
For the object to be dehydrated, heating and dehydrating by heating on the heating surface in the transporting process to reduce the viscosity and reducing the water holding power by thermal denaturation and filtering on the filtration surface in a state where the water retention ability is reduced are repeated three or more times. Dehydration system. Incineration of the dewatering target water has been desorbed, dried, or further comprising a heat treatment equipment to carbonize,
The dehydration system according to claim 4 , wherein the heat medium heating device heats the heat medium using waste heat of the heat treatment facility. Further provided with a digestion tank that performs a digestion treatment on the dehydration target before being put into the outer cylindrical screen,
The heating medium heating machine, dewatering system of claim 4 or 5, characterized in that to heat the heating medium by using a digestion gas generated in said digester. Dewatering in a dewatering device including an outer cylindrical screen having a small hole formed in a peripheral wall, a screw shaft provided inside the outer cylindrical screen, and a screw blade spirally provided around the screw shaft. The method
The dehydration target before being introduced into the outer cylindrical screen is concentrated so that the concentration becomes 6% or more,
By rotating the screw shaft together with the screw blade, the dewatering target put into the outer cylindrical screen is compressed while being conveyed in the axial direction of the screw shaft,
A heating medium having a temperature of less than 100 ° C. is circulated inside three or more heating jackets attached to the outer cylinder screen at intervals along the entire axial direction of the screw shaft, and a part of the outer cylinder screen is formed. Is the heating surface,
Heating and dehydrating the object to be dehydrated three or more times by heating on the heating surface during the transportation process to reduce the viscosity and filtering on the filtration surface where the pores are exposed in a state where the water retention capacity is reduced due to thermal denaturation. A dehydration method characterized by repeating.   A plurality of heating jackets are provided in the axial direction of the screw shaft, the plurality of heating jackets are connected in series, and the heat medium is directed from a discharge side of the dewatering target to a supply side. The dehydrating apparatus according to claim 1, wherein the dehydrating apparatus is sequentially circulated through the plurality of heating jackets.

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