WO2017043232A1

WO2017043232A1 - Dehydration device, dehydration system, and dehydration method

Info

Publication number: WO2017043232A1
Application number: PCT/JP2016/073133
Authority: WO
Inventors: 築井　良治; 昌次郎渡邊; 榮一大久保; 入山　守生; 倫也板山; 典男有城; 賢小宮山; 喜義渋江; 石田　健一; 萩野　隆生
Original assignee: 水ｉｎｇ株式会社
Priority date: 2015-09-07
Filing date: 2016-08-05
Publication date: 2017-03-16
Also published as: JP7048654B2; JP6892943B2; JP2020093256A; JP2020099906A; JPWO2017043232A1; JP6672318B2

Abstract

Provided is a dehydration device with which it is possible to sufficiently perform heating and dehydration even with low-temperature heating through use of waste heat or the like. A screw-press-scheme dehydration device (8) is provided with an outer cylinder screen (12) having a small hole (14) provided in the peripheral wall thereof, a screw shaft (13) provided inside the outer cylinder screen (12), and a screw blade (15) provided in a helical shape to the periphery of the screw shaft (13), wherein a heating jacket (51) is provided to part of the outer cylinder screen (12), the heating jacket (51) being configured such that a heat medium generated using waste heat is allowed to flow through the interior thereof.

Description

Dehydration apparatus, dehydration system, and dehydration method

The present invention relates to a dehydration apparatus, a dehydration system, and a dehydration method for removing moisture from an object to be dehydrated containing moisture such as sludge.

In sludge treatment, sludge is dehydrated with a dehydrator, dehydrated sludge (also called dehydrated cake) is dried with a dryer, and further incinerated with an incinerator. If 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 process, It is disadvantageous for energy saving and creation energy.

In view of this, a screw press type dewatering device has been proposed, in which a heat medium is passed through the screw shaft and the sludge is dehydrated while being heated to reduce the water content of the dewatered sludge ( For example, Japanese Patent No. 12111418). Similarly, in the 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 to the screw blades as well. A dehydrator is also known (for example, Japanese Patent No. 12111418).

However, in the dehydration apparatus of Patent Document 1, if the heating medium used for heating is not a high-temperature heating medium such as steam, a sufficient heating effect cannot be obtained, and the dehydrated sludge cannot be sufficiently reduced in water content. was there.

An object of the present invention is to provide a dehydrating apparatus, a dehydrating system, and a dehydrating method capable of sufficiently heating and dehydrating even by low-temperature heating using waste heat or the like.

A dehydrating apparatus according to an aspect of the present invention includes an outer cylinder screen having a small hole formed in a peripheral wall, a screw shaft provided inside the outer cylinder screen, and a screw provided spirally around the screw shaft. The dehydration object thrown into the outer cylinder screen is compressed while being conveyed in the axial direction of the screw shaft and separated from the dehydration object by rotating the screw shaft together with the screw blade. A dehydrator for discharging moisture from the small holes of the outer cylinder screen, wherein the outer cylinder screen has a heating surface to be heated and a filtration surface from which the small holes are exposed. With this configuration, the outer cylinder screen is provided with a heating surface and a filtering surface, 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, heat dehydration can be performed.

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

In the above dehydrating apparatus, the heating jacket may have a configuration in which a heat medium is circulated therein. With this configuration, the heating jacket can be heated using the heat medium.

In the above dehydrator, the temperature of the heat medium may be less 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 heat treatment equipment. Therefore, energy saving and energy creation can be further promoted by using hot water that is limited in use and may be discarded.

The dehydrator may further include an addition unit for adding an inorganic flocculant to the concentrated sludge. Soft sludge such as excess sludge and digested sludge is prone to agglomeration by heating, but by adding an inorganic flocculant, the sludge cohesion in the dewatering section can be increased again, and the moisture content of the sludge to be dewatered by heating The effect of lowering can be increased. In addition, since a heat medium having a temperature of less than 100 ° C. is used, moisture evaporation on the heating surface hardly occurs, and scale adhesion due to scale components in the filtrate generated during dehydration hardly occurs.

In the dehydrating apparatus, the heating surface and the filtration surface may be alternately and repeatedly arranged in the axial direction of the screw shaft. With this configuration, the object to be dehydrated is heated on the heating surface in the process of being transported, the viscosity is lowered, and the water holding power is lowered due to thermal denaturation, so that it is easily dehydrated. Since the heat dehydration of being filtered is repeated, the dehydration effect can be improved.

In the dehydrating apparatus, the heating surface may be formed in a belt shape and may be arranged in parallel to the axial direction of the screw shaft, or may be formed in an annular shape surrounding the outer cylinder screen in the circumferential direction. Good. Moreover, there may be a plurality of the heating surfaces, and each heating surface may be formed only on a part of the circumferential direction of the outer cylinder screen. The heating surface may be formed in a semi-cylindrical shape that covers a part of the outer cylinder screen in the circumferential direction.

In the above dehydrating apparatus, the screw shaft and / or the screw blade may have a hollow shape in which a heat medium is circulated. With this configuration, the object to be dehydrated can be sufficiently heated, and the dehydration effect can be improved.

The dehydration apparatus may further include a concentrator that concentrates the dehydration object before being put into the outer cylinder screen. With this configuration, the object to be dehydrated is concentrated by the concentrator and then charged into the outer cylinder screen, so that the moisture content of the object to be dehydrated can be reduced.

The dehydrating apparatus according to another aspect of the present invention includes an outer cylinder screen having a small hole formed in a peripheral wall, a screw shaft provided inside the outer cylinder screen, and a spiral provided around the screw shaft. A screw blade, and by rotating the screw shaft together with the screw blade, the dewatered object charged in the outer cylinder screen is compressed while being conveyed in the axial direction of the screw shaft, and separated from the dewatered object. In the dehydrating apparatus for discharging the moisture that has been discharged from the small hole of the outer cylinder screen, the screw shaft and / or the screw blade has a configuration in which a heat medium is circulated therein. With this configuration, the dehydration object can be sufficiently heated by circulating the heating medium inside the screw shaft and / or the screw blade, and the dehydration effect can be improved.

A dehydrating system according to an aspect of the present invention includes an outer cylinder screen having a small hole formed in a peripheral wall, a screw shaft provided inside the outer cylinder screen, and a screw provided spirally around the screw shaft. The dehydration object thrown into the outer cylinder screen is compressed while being conveyed in the axial direction of the screw shaft and separated from the dehydration object by rotating the screw shaft together with the screw blade. A dehydrating system for discharging moisture from the small holes of the outer cylinder screen, further comprising a structure for circulating a heat medium therein, a heating jacket attached to a part of the outer cylinder screen, and a waste And a heating medium heater that heats the heating medium using heat. With this configuration, the heating jacket is attached to the outer cylinder screen and the object to be dehydrated is dehydrated while being heated, so that the heat dehydration can be performed even when the heat medium is at a low temperature.

The dehydration system may further include a heat treatment facility for incinerating, drying, or carbonizing the object to be dehydrated, and the heating medium heater uses waste heat of the heat treatment facility. The heating medium may be heated. With this configuration, it is possible to improve the dehydration effect by utilizing the waste heat of the heat treatment equipment, and to realize energy saving.

The dehydration system may further include a digestion tank that performs a digestion process on the object to be dehydrated before being put into the outer cylinder screen, and the heating medium heater is a digester that is generated in the digestion tank. The heat medium may be heated using gas. With this configuration, the heating medium is heated using the digestion gas generated when the dehydration target is digested, so that energy saving can be realized.

The dehydration method according to an aspect of the present invention includes an outer cylinder screen having a small hole formed in a peripheral wall, a screw shaft provided inside the outer cylinder screen, and a screw provided spirally around the screw shaft. A dehydrating method in a dehydrating apparatus comprising blades, wherein a screw shaft is rotated together with the screw blades to compress an object to be dewatered put on the outer cylinder screen while being conveyed in the axial direction of the screw shaft. Then, the object to be dewatered conveyed in the outer cylinder screen is heated by the heating surface of the outer cylinder screen, and moisture separated from the object to be dehydrated is filtered from the filtration surface where the small holes of the outer cylinder screen are exposed. It has a configuration to discharge. With this configuration, the outer cylinder screen is provided with a heating surface and a filtration surface, and the object to be dehydrated is dehydrated while being heated by the outer cylinder screen, so that heat dehydration can be performed even when the heat medium is at a low temperature.

According to the present invention, 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 heat dehydration can be performed even at low temperature heating.

FIG. 1 is a block diagram showing 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 the structure of the concentrator according to the embodiment of the present invention. FIG. 4 is a diagram showing a heat medium flow path of the dehydrating apparatus according to the embodiment of the present invention. FIG. 5 is a diagram showing a heat medium flow path of the dehydrating apparatus according to the embodiment of the present invention. FIG. 6 is a view 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 view showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 9 is a view showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 10 is a view showing a modification of the heating jacket according to the embodiment of the present invention. FIG. 11 is a view 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 modified example 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 when 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 adopted as appropriate.

FIG. 1 is a block diagram showing a configuration of a dehydrating system including a dehydrating apparatus according to an embodiment of the present invention. In the figure, a solid line arrow indicates a flow of a processing object that is converted into incinerated ash from sludge through a plurality of processes, and a dotted line arrow indicates a flow of gas, liquid, and electricity.

The dehydration system 100 according to the present embodiment includes organic sewage such as human waste, sewage, and factory effluent, septic tank sludge, and domestic wastewater sludge (contains a concentrated SS such as sludge in a domestic wastewater pit and bill pit sludge), Although effective as a system for dewatering sludge such as water sludge, the sludge (the sludge to be dehydrated) that is dehydrated by the dewatering system of the present invention is not limited thereto. The dehydration system 100 is effectively used for difficult-to-dehydrate sludge that is difficult to dehydrate sufficiently only by mechanical dehydration. In the following embodiment, the dehydration system 100 is used for sludge (organic sludge) as organic waste.

The dehydration system 100 prepares agglomerated sludge by adding a chemical such as a flocculant to the digestion tank 1 that performs anaerobic digestion treatment (methane fermentation process) on the sludge, and the digested sludge obtained in the digestion tank 1. As a heat treatment facility for burning the dewatering sludge (dehydrated cake) obtained by the dehydration process An incinerator 5, a heat medium heater 6 that heats the heat medium supplied to the dehydrator 4, and a generator 7 that generates power using waste heat of the incinerator 5 are provided.

The dehydrator 8 includes a concentrator 3 that separates moisture from the sludge before the dehydration process to obtain a low-fluid concentrated sludge, a chemical addition unit 9 that adds chemicals to the concentrated sludge obtained by the concentrator 3, A dewatering machine 4 for dewatering the dewatered sludge is provided, with the concentrated sludge to which the chemicals are added as the dewatered sludge. In addition to the incinerator (incineration facility), the heat treatment facility includes a carbonization facility and a drying facility. In the example of FIG. 1, the coagulation tank 2 has two stages, and the inorganic coagulant and the polymer can be added. However, the coagulation tank 2 may be one stage or a plurality of stages of three or more stages. Further, only a polymer may be added as a flocculant.

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

FIG. 2 is a cross-sectional view of the dehydrator 8 in which the concentrator 3, the dehydrator 4, and the chemical addition unit 9 are integrated. The concentrator 3 and the dehydrator 4 may be configured integrally as shown in FIG. 2, or the concentrator 3 and the chemical adder 9 may be dehydrated independently of the dehydrator 4. You may provide in the upper part of the machine 4, a side, etc.

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 the support member. A screw shaft 13 is provided concentrically with the outer cylinder screen 12 inside 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 on the sludge supply side. Has a small diameter end. The screw shaft 13 is rotatable and movable in the axial direction relative to the outer cylinder screen 12.

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

A variable speed motor 19 with a reduction gear is provided on the front bearing 17 and the rear bearing 18. The rotating shaft of the variable speed electric 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 electric motor 19 is transmitted to the screw shaft 13, and thus a rotational drive device is configured on the movable table 16.

The movable table 16 is translated (advanced or retracted) in the axial direction of the screw shaft 13 by a driving device (not shown). By the movement of the movable table 16, the front bearing 17, the rear bearing 18, the variable speed motor 19, and the connecting belt 20 also move in the axial direction of the screw shaft 13, and the screw shaft 13 also moves in the axial direction. To 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 cylinder screen 12 is changed.

A helical conveyance compression passage 21 is formed between the screw blades 15 of the screw shaft 13. The conveyance 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). In the transport compression passage 21, the sludge is separated from the inner peripheral surface of the outer cylinder screen 12 and the screw. It is conveyed while being compressed by the blade 15.

At the upper part of the outer cylinder screen 12, an inlet 22 is provided for taking the sludge discharged from the concentrator 3 (concentrated sludge) into the outer cylinder screen 12. Between the outer cylinder 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 rectangular cross section for further compressing the sludge that has passed through the transfer compression passage 21 is formed. Yes. The compression chamber 23 has the outlet of the transfer compression passage 21 as an inlet.

Below the outer cylinder screen 12, a tray 24 is provided that collects the liquid that is separated from the sludge by squeezing the outer cylinder screen 12 and flows out from the small holes 14. A bearing plate 25 is erected on the base 11. The bearing plate 25 supports the large-diameter end portion of the screw shaft 13 protruding from the open end of the outer cylinder screen 12 only in the radial direction.

A plurality of hydraulic cylinders 26 are fixed to the bearing plate 25, the piston rod 27 of the hydraulic cylinder 26 is passed through the bearing plate 25, the tip of the piston rod 27 is connected to the discharge taper cone 29, and the piston rod 27 moves forward. Then, a hydraulic circuit that controls the backward movement and the stop at the 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 dewatered sludge dropping path 28 that flows out from 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 electric motor 19 are rotated and sludge is thrown into the outer cylinder screen 12 from the inlet 22, the sludge is screwed It is compressed while being conveyed in the axial direction of the shaft 13, and moisture is released from the sludge. The water separated from the sludge is discharged from the small hole 14 of the outer cylinder screen 12 to the outside of the outer cylinder screen and is received by the receiving tray 24. The dewatered sludge generated by this dewatering process is discharged out of the dehydrator 4 from the dropping path 28.

In this dehydrator 4, when adjusting the length from the inlet to the outlet of the compression chamber 23 in order to obtain a desired dewatering 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 direction position of the screw shaft 13 with respect to the outer cylinder screen 12, thereby increasing or decreasing the length of the compression chamber 23.

When the movable base 11 is moved forward by a drive device (not shown) and stopped at its forward position, and the axial direction position of the screw shaft 13 is changed to the outlet side of the compression chamber 23, the outer blade screen 12 and the screw blades of the screw shaft 13 The fitting length of 15 to the large diameter portion is reduced, and the length of the compression chamber 23 is reduced. Conversely, when the movable base 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 showing the structure of the concentrator 3. The concentrator 3 of the present embodiment is a sludge press, and includes a sludge charging hopper 31, a sludge moving means 32, a pressurizing means 33 provided above the sludge moving means 32, and a sludge moving means 32. And water collecting means 34 provided below.

The sludge moving means 32 is composed of a belt 36 and a belt driving device 38 formed of filter cloth. When the belt driving device 38 drives the belt 36, the entire upper surface (conveying surface) of the belt 36 is moved horizontally, and the coagulated sludge is moved to the horizontal sludge discharge port side. The agglomerated sludge is filtered while moving on the belt 36, and the filtrate falls to the lower water collecting means 34.

The pressurizing means 33 is provided with a pressurizing plate 33A that is installed obliquely with a gap between the belt 36 and the sludge discharge port 37 of the sludge moving means 32. When the sludge is moved toward the horizontal sludge discharge port by the sludge moving means 32, the sludge is pressurized from above when passing through the gap between the pressure plate 33A and the belt 36.

One or more pressure plates 33A may be provided, and the pressure plate 33A may be provided such that the installation angle is fixed, or the installation angle can be changed as needed. Further, it can be pivotally supported so as to be swingable up and down. 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 pressure plate 33A, for example, a roller can be installed.

The water collecting means 34 is provided below the sludge moving means 32 so that water falling from the sludge moving means 32 can be collected and discharged from the waste water outlet.

Next, the operation of the concentrator 3 having such a configuration will be described. When aggregated sludge is charged into the sludge charging hopper 31, the aggregated sludge is moved to the horizontal sludge discharge port side by the sludge moving means 32, and is transported horizontally on the upper surface of the belt 36. The agglomerated sludge is dehydrated during the conveyance process and is squeezed by the pressure plate 33A to further separate the concentrated filtrate, thereby bringing the concentration of the concentrated sludge closer to a predetermined concentration. It is sent out as concentrated sludge. The dehydrated water falls from the sludge moving means 32, is collected by the water collecting means 34, and is drained from the waste water outlet.

As the concentrator 3, in addition to the sludge press having the above-described configuration, a sludge press used for conventional sludge dewatering, such as a centrifugal concentrator, a screw concentrator, an elliptical plate type concentrator, etc. It is also possible to adopt. Moreover, the machine of the structure which pressurizes sludge with a flat plate can also be used. In addition, the structure for separating the concentrated filtrate is not limited to the belt, and slit bars with gaps are arranged, the concentrated filtrate is discharged from the gaps, and the concentrated sludge on the slit bars is transferred by mechanical transfer means. It is also possible to substitute with such a device. In the concentrator 3, the sludge is concentrated so that the sludge concentration becomes 6% or more, preferably 8% or more by the mechanical concentration as described above.

In this way, in the concentrator 3, for example, a squeezing force is applied at the time of concentration in order to make the concentrated sludge concentration as high as 6% or more. Therefore, the sludge coagulation force due to the chemical added in the coagulation tank in the previous stage of the concentrator 3 is In this state, when the dehydrator 4 is put into the dehydrator 4 and dehydrated while being heated, the soft sludge with insufficient aggregation is dehydrated, and the water content of the dewatered sludge is unlikely to decrease. In particular, soft sludge such as excess sludge and digested sludge is prone to agglomeration by heating, but the addition of an inorganic flocculant can re-increase the sludge cohesion in the dewatering section, and the water content of the sludge to be dewatered by heating. The effect of rate reduction can be increased.

Therefore, in the present embodiment, the chemical addition unit 9 is disposed between the concentrator 3 and the dehydrator 4. The chemical addition unit 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 chemicals to the concentrated sludge passing therethrough. The concentrated sludge discharged from the concentrator 3 is added with chemicals while passing through the chemical addition unit 9 due to its gravity, and is introduced into the outer cylinder screen 12 from the inlet 22 of the dehydrator 4.

The chemical addition unit 9 adds a polymer and an inorganic chemical (inorganic flocculant) as chemicals to the sludge concentrated by the concentrator 3. As an inorganic chemical (inorganic flocculant) for sludge treatment coagulation added to the concentrated sludge in the chemical addition section 9, metal salts such as aluminum and iron (for example, polyferric sulfate, ferric chloride, sulfate bands, PAC (polyaluminum chloride) or the like can be employed. However, PAC and ferric chloride, which are metal salts containing a large amount of chlorine, contain a large amount of chlorine ions in the dehydrated filtrate after dehydration, and the corrosion of the dehydrator 4 is likely to proceed. Decreases. In particular, when heating is performed at the time of dehydration as in the present embodiment, the dehydrated filtrate becomes high temperature, and the corrosion of the screen and the casing is rapidly advanced by chlorine ions. For this reason, durable and expensive materials must be selected for the screen and casing, and the manufacturing cost of the dehydrator 4 is increased. Therefore, a metal sulfate (for example, polyferric sulfate or a sulfate band) is preferable as the inorganic chemical used in the present embodiment.

The concentrated sludge thrown into the outer cylinder screen 12 is compressed while being conveyed toward the dropping path 28 by the screw blades 15 spirally provided around the rotating screw shaft 13, and the water separated by this compression. Is discharged to the outside through a small hole 14 provided in the peripheral wall of the outer cylinder screen 12. Further, the dewatered sludge (dehydrated sludge) is discharged from the dropping 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 hollow, and the heat medium (hot water) heated by the heat medium heater 6 is introduced into the screw shaft 13 and the screw blade 15. 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 showing an example of the 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). Toward the direction of the sludge flow. The heat medium that has reached the right end (sludge supply side end) of the screw shaft 13 flows into the screw blade 15 from there.

The heat medium that has flowed into the screw blades 15 from the screw shaft 13 flows spirally through the internal space of the screw blades 15 in the sludge transport direction. The end of the screw shaft 13 on the sludge discharge side (left side in FIG. 4) has a double tube structure, and the heat medium introduced from the heat medium inlet flows into the internal space of the screw shaft 13 through the inner tube. 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 tube.

Since the screw shaft 13 and the screw blade 15 are rotating, in order to allow 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 through a rotary joint (rotary joint), It is necessary to flow to the screw blade 15 via the screw shaft 13. As in the present embodiment, the internal space of the screw shaft 13 and the internal space of the screw blade 15 are made into a series so that the heat medium flows inside the screw shaft 13 and the screw blade in the screw shaft 13. Therefore, it is not necessary to distribute the heat to the heating medium in a fixed amount, and a complicated structure is not required.

As described above, in the present embodiment, the sludge is concentrated in the concentrator 3 before being dehydrated while being heated in the dehydrator 4. By dehydrating while heating after concentration in this way, a high dehydration effect can be obtained even if the required energy is small, and since the inorganic flocculant is added to the concentrated sludge in the chemical addition section 9, the water content is low. Although it is further reduced, there is a problem that scale is generated on the heating surface by the inorganic flocculant. That is, when a heat medium having a temperature of 100 ° C. or higher, such as steam generally used as a heat medium, the heating surface temperature becomes 100 ° C. or higher, and water is easily evaporated from the dewatered sludge. The scale adheres to the heated surface due to the scale component in the filtrate. When scale adheres to the heating surface, the heat transfer rate for heating decreases, and the heating effect does not appear, or the scale grows, changing the behavior of sludge in the dehydrator and reducing the dewaterability. Or In particular, when an inorganic flocculant is added to the concentrated sludge, the concentrated sludge becomes acidic, the scale components in the sludge are easily dissolved in the dehydrated filtrate, and the amount of scale generated increases remarkably.

And if the scale adheres to the heating surface and the heat transfer rate and dewaterability decrease, it will not be possible to continuously reduce the moisture content to the target, and in severe cases, it will be blocked by the scale and the sludge will not 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 55 ° C. or higher and lower than 100 ° C. (preferably 70 ° C. or higher and lower than 90 ° C.), and is suppressed to a temperature at which sludge does not boil. The heat medium heater 6 heats the heat medium while monitoring the temperature of the heat medium with a temperature sensor so that the heat medium has a predetermined temperature (or within the range) within the above range. Alternatively, the heating medium heater 6 may be controlled so that the temperature of the heating medium becomes 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 heat medium may be warm water or reduced pressure steam under vacuum.

In addition, by introducing a heat medium into the screw shaft 13 and the screw blades 15, the surfaces of the screw shaft 13 and the screw blades 15 become heat transfer surfaces and come into contact with the sludge. It will dehydrate while heating. Thus, by ensuring a wide heat transfer surface, the sludge is sufficiently heated even with a low-temperature heat medium (for example, hot water, that is, water of less than 100 ° C.) as described above, and the low moisture content of the dewatered sludge Can be achieved.

FIG. 5 is a diagram for explaining 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 inner space in the axial direction is provided at a position corresponding to the insertion port 22. The internal space is divided into two by the partition plate 132 in the axial direction.

An inner tube 133 parallel to the axial direction is provided on one side of the partition plate 132 (left side in FIG. 5) from the end to the front of the partition plate 132. In addition, an inner tube 134 parallel to the axial direction is provided on the other side of the partition plate 132 (on the right side in FIG. 5) from the end 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 including the

inner tubes

133 and 134 and the outer tube 131 on both sides of the partition plate 132. The outer channel 135 between the outer tube 131 and the inner tube 133 communicates with the inner channel 137 in the inner tube 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 formed in a spiral shape along the spiral shape of the screw blade 15, and the left end of the screw blade 15 serves as a turning point and is connected from the forward path to the return path. The forward path of the screw blade 15 communicates with the outer flow path 136 between the outer tube 131 and the inner tube 134 on the right side of the partition plate 132, and the return path is the inner flow in the inner tube 134 on the right side of the partition plate 132. It communicates with the path 138.

The heat medium is supplied to the inside of 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 the direction opposite to the sludge conveyance direction, is stopped by the partition plate 132, and passes through the inner channel 137. It flows in the same direction as the sludge 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 in the screw blade 15 through the forward path of the screw blade 15 toward the sludge conveyance direction, and then turns back at the end to return the return path. Returns through and is discharged through the inner channel 138. 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 heat 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 through the rotary joint.

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

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

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

The dehydration process includes a separation step of separating water from sludge (squeezing the filtrate from the sludge) and a discharge step of discharging the filtrate out of the outer cylinder screen 12, and the amount of the filtrate in each step is the same. However, the time for the filtrate to process (squeeze / discharge) differs in each process, and the separation process becomes longer. Therefore, since time can be afforded in the discharging process, even if the filtration area by the small holes 14 formed in the outer cylinder screen 12 is reduced, the dehydrating process is not affected. 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 the heating medium is supplied into 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 into the heating jacket 51 for heating. By heating the sludge from the jacket 51 through the outer cylinder screen 12, the heat transfer surface becomes wider than that of the conventional dehydrator, and it is possible to sufficiently heat the sludge even with a lower temperature heating 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 cylinder screen 12 is a filtration surface (a surface where the small holes 14 are exposed) in the conveyance direction. And heating surfaces (surfaces to which the heating jacket 51 is attached) are alternately and repeatedly disposed, and sludge is conveyed while repeating heating and filtration.

It has been confirmed by experiments that the dehydration effect is improved by repeating such heating and filtration. That is, rather than installing only one heating jacket 51 having a length L in the transport direction, 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. Is known to be expensive. This is because when sludge is heated on the heating surface, the viscosity decreases, and the water retention capacity decreases due to heat denaturation, so that it becomes easy to dehydrate, and it is sufficient if the sludge reaches the filtration surface in such a state. This is because the amount of sludge is reduced due to the separation of moisture and the amount of heat necessary for heating is reduced, so that it is easily heated on the next jacket surface for heating and further dehydrated.

The heat medium is supplied from the same heat medium heater 6 to the plurality of heating jackets 51. The plurality of heating jackets 51 are respectively connected to the heating medium heater 6 by piping, 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 so that the heat medium is supplied to the plurality of heating jackets 51 in order.

In the case where a plurality of heating jackets 51 are connected in series to the heat medium heater 6, it is possible to reduce the number of pipes compared to the case where the plurality of heating jackets 51 are connected to the heat medium heater 6 in parallel. it can. In the case where a plurality of heating jackets 51 are connected in series, it is desirable that the heating medium from the heating medium heater 6 is circulated in the heating jacket 51 from the dewatered sludge discharge side 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 increased, and a lower water content can be achieved.

A bypass plate (not shown) may be provided in the heating jacket 51 to form a heat medium flow path inside the heating jacket 51. By doing so, it is possible to prevent short-circuit flow and retention of the heat medium, achieve uniform heat conduction, and further improve heat transfer efficiency by making the heat medium inside the heating jacket 51 turbulent. .

Thus, by supplying a heat medium into the screw shaft 13 and the screw blade 15 and also supplying a heat medium into the heating jacket 51, a heat transfer surface for heating sludge can be sufficiently secured. Even when a low-temperature heating medium such as hot water obtained using waste heat is used, the sludge can be sufficiently heated and dehydrated.

Further, when the sludge is dehydrated while being heated by the screw shaft 13, the screw blades 15 and the heating jacket 15, as described above, the viscosity of the sludge is reduced, and the water retention capacity of the sludge is reduced by thermal denaturation. The filtrate is easily separated. In this way, 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 promptly after heating, and it is possible to prevent the use of extra energy by not separating the filtrate.

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

Further, by taking a large area of the heating jacket 51, sufficient heating can be performed even if the temperature of the heating medium is low (even if it is a low-temperature heating medium). As the low-temperature heat medium, hot water can be used, and the hot water can be generated using waste heat from 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, and preferably 55 ° C. or more and less than 100 ° C., and is suppressed to a temperature at which water contained in the sludge does not boil.

In the dehydration system 100 described above, a dryer connected by a chute or the like may be provided below the dropping path 28 of the dehydrator 4. By providing the dryer in the lower part of the dropping path 28 of the dehydrator 4 as described above, a device for transferring the dehydrated sludge to the dryer can be omitted, and the dehydrated sludge having heat can be cooled. The amount of heat used in the dryer can be small.

Hereinafter, modifications of the heating jacket 51 will be described. 6 to 11 are diagrams showing modifications of the heating jacket 51. 6 to 11 schematically show the relationship between the outer cylinder screen 12 and the heating jacket 51. The example of FIG. 6 shows an example in which the heating jacket 51 is provided on the outer periphery of the outer cylinder screen 12 in a lattice shape. According to this example, the outer cylinder screen 12 can secure a filtration part and can be heated uniformly by the heating jacket 51. The support of the outer cylinder screen 12 may be used as the heating jacket 51.

In the example of FIG. 7, the heating jacket 51 is provided in the middle of the outer cylinder screen 12 in the conveying direction. The heating jacket 51 has a cylindrical shape surrounding the outer periphery of the outer cylinder screen 12. The sludge is filtered again with respect to the sludge from which moisture has been removed to some extent before reaching the heating section where the heating jacket 51 is provided, is sufficiently heated by the heating section, and the subsequent moisture is easily separated.

In the example of FIG. 8, the heating jacket 51 is divided vertically. A plurality of arc-shaped heating jackets 51 are spaced 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 on the lower side of the outer cylinder screen 12. Has been placed. Each of the heating jackets 51 has a semicircular shape that covers only a part of the outer cylinder screen 12 in the circumferential direction.

Further, the plurality of upper heating jackets 51 and the plurality of 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 position to be divided vertically does not have to be the center of the height of the outer cylinder screen 12.

In the example of FIG. 9, as in 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, as compared with the example of FIG. 2, the width of each heating jacket 51 in the transport direction is narrow, and the interval between them is also narrow, 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 in the height direction of the outer periphery of the outer cylinder screen 12 over the conveying direction of the outer cylinder screen 12. The heating jacket 51 has a strip shape and is attached to the outer cylinder screen 12 in parallel with the transport direction. The heating jacket 51 shown in FIG. 10 is also provided on the opposite surface of the outer cylinder screen 12.

In the example of FIG. 11, the heating jacket 51 is provided so as to cover the upper part of the outer cylinder screen 12 over the conveying 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 cylinder screen 12, and a filtration surface is formed on the lower side.

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, since the sludge is conveyed in the discharge direction while rotating in the outer cylinder screen 12, even the heating jacket parallel to the conveyance direction can uniformly apply heat to the sludge.

Although not shown, a heating jacket 51 as shown in any of the examples of FIGS. 2 and 6 to 11 may be provided only behind the outer cylinder screen 12 in the conveying direction. Since the effect of heating becomes significant after the screw press where dehydration has progressed to some extent, an effective heating and dehydrating effect can be obtained by concentrating the heating jacket 51 behind the conveying direction. In addition, since moisture is removed in the former stage and then heated in the latter stage, the necessary amount of heat can be reduced and energy saving can be realized.

(Example)
Using the digested sludge generated at the sewage treatment plant, a dehydration test was performed using the dehydration system 100 of the present embodiment. The amount of sludge treated is 10 kg-DS / h in terms of solids, the screw press method is used as the dewatering method, and hot water is injected into the screw shaft 13 and the heating jacket 51 as a heat medium while dewatering. The sludge was heated. The temperature of the sludge thrown into the dehydrator 4 was 20 ° C., the amount thereof was 100 kg / h, and the flow rate of hot water as a heating medium was 1.5 m ³ / h.

Before adding sludge to the dehydrator 4, polyferric sulfate and polymer were added in the coagulation tank 2 and coagulated, and then concentrated to about 10% with 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 polyferric sulfate was 10 to 15%.

The arrangement method of the heating surface of the outer cylinder screen 12 was the following conditions (1) and (2). In condition (1), as shown in FIG. 7, one heating surface (heating jacket 51) is arranged in the sludge transport direction with respect to the outer cylinder screen 12. In condition (2), as shown in FIG. 2, the filtration surface and the heating surface (heating jacket 51) were alternately arranged a plurality of times in the sludge transport direction in the outer cylinder screen 12. In addition, the total area of the heating surface was made to be the same between condition (1) and condition (2).

The ultimate temperature and moisture content of the dewatered sludge were measured, and the amount of heat necessary for the dehydrator 4 was calculated from the measurement results. Specifically, the necessary heat quantity E is measured by measuring a flow rate Q of hot water as a heat medium, a temperature T1 when the hot water is injected into the dehydrator 4, and a 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).

The experimental results are shown in Table 1.

(Condition (1)) The sludge was sufficiently heated, and the water content of the dewatered sludge was 72%. The amount of heat required at that time was 6.3 MJ / h. Under condition (2), the sludge could be heated more sufficiently 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 could be kept small. Thus, in the condition (2), the heating surface and the filtration surface are arranged a plurality of times, so that the effect of dehydration while heating can be increased, and the required heat amount can be made smaller than that in the condition (1).

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

In the above 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 the usage destination is limited. However, in the dehydrating system 100 according to the present embodiment, not only the screw shaft 13 but also the screw blades in the dehydrator 4. 15 and the heating jacket 51 attached to the outer cylinder screen 12, the heating medium is also supplied, so the temperature of the heating medium may be relatively low (45 ° C. or more and less than 100 ° C.), and hot water is used. it can. Therefore, energy saving and energy creation can be further promoted by using hot water that is limited in use and may be discarded.

The dehydration method according to one aspect of the present invention includes a concentration step in which sludge is concentrated to produce concentrated sludge, and the concentrated sludge generated in the concentration step is used as dewatered sludge, and the dewatered sludge is indirectly heated. Including a dehydration step of dehydrating while heating by a method and an addition step of adding an inorganic flocculant to the concentrated sludge, and the temperature of the heat medium used for heating the dewatered sludge in the dehydration step is less than 100 ° C It has the composition which is. Here, the indirect heating method refers to a method of heating in a state where the non-heated material and the heating medium are not mixed, and the heated object is present on one side of a shield such as a plate or cloth, and the heating medium is present on the other side. Is a heating method in which heat is transferred from a heating medium to an object to be heated through a shield.

According to this configuration, since the sludge is dehydrated while being heated in the dehydration step, the viscosity of the sludge is decreased, and the water retention capacity of the sludge is decreased due to thermal denaturation, and the filtrate is easily separated. The water content of dewatered sludge) can be reduced. In addition, since most of the dehydrated filtrate can be promptly separated from the sludge at the stage where heating is not completed, it is possible to prevent the use of excess heat energy in the dehydrated filtrate. Also, since the concentration of sludge is increased in the concentration step and the amount of sludge to be heated is reduced before heating, the temperature of the sludge in the dehydration step is heated to a desired temperature when dehydrating while heating in the dehydration step. Therefore, the heat energy (heating energy) can be kept low. Furthermore, since the indirect heating method is employed to heat the sludge in the dehydration step, the sludge can be heated using a heat medium such as hot water.

In addition, soft sludge such as excess sludge and digested sludge is prone to agglomeration by heating, but by adding an inorganic flocculant to the concentrated sludge, the sludge agglomeration power in the dewatering section can be increased again, and dehydration by heating. The effect of reducing the moisture content of the target sludge can be increased. Further, by using a heat medium of less than 100 ° C., moisture evaporation on the heating surface is less likely to occur, and scale adhesion due to scale components in the filtrate generated during dehydration is less likely to occur.

(Example)
Hereinafter, examples of the dehydration system 100 of the present embodiment will be described. In this example, a dewatering test was performed with the dewatering system 100 using digested sludge generated in a sewage treatment plant. The amount of sludge treated was 8 kg-DS / h in terms of solid matter, and the dehydrator 4 employed a screw press system, and a heating medium was injected into the screw shaft 13 and heated while dehydrating. Before being put into the dehydrator 4, the sludge was concentrated to about 10% with the concentrator 3 after adding polymer to the sludge in the coagulation tank 2 and coagulating it. In the chemical addition section 9, a polymer and an inorganic flocculant (specifically, polyferric sulfate) were added to the concentrated sludge. The addition rate of the polymer was 2.0 to 2.5%, and the addition rate of polyferric sulfate was 20 to 25%.

The heat medium temperature conditions in the heat medium heater 6 are 80 ° C. (warm water), 120 ° C. (steam), and no heat medium, and each time the inorganic flocculant is added to the concentrated sludge, The water content was measured. The results are shown in Table 2.

As shown in Table 2, the moisture content of the dehydrated cake was lower when heated (heating medium temperature 80 to 120 ° C.) than when not heated, regardless of whether or not the inorganic flocculant was added. Regardless of the heat medium temperature condition, the water content of the dehydrated cake was lower in conditions 1 to 3 where the inorganic flocculant was added than in conditions 4 to 6 where the inorganic flocculant was not added. This is due to the aggregation effect of the inorganic flocculant. Furthermore, in conditions 1 to 3 to which an inorganic flocculant was added, the moisture content of the cake was higher in the case of condition 3 (76%) at 120 ° C. than in the case of condition 2 (74%) where the heating medium temperature was 80 ° C. Rose. This is because, under the condition of 120 ° C., there is much scale adhesion on the heating surface of the screw shaft, the heat transfer rate for heating is reduced, and the heating effect does not appear well.

In the above embodiment, digestion gas, incineration waste heat, and power generation waste heat are all used to heat the heat medium, but only a part of them may be used, or other heat sources are used. May be. Moreover, in said embodiment, although the polymer was added to sludge with the concentrator 3, you may add a polymer to sludge in the coagulation tank 2. FIG. Further, a dehydrating aid may be added in the aggregation tank 2.

The dehydrator 4 of the dehydration system 100 is a screw press type dehydrator provided with one screw shaft 13. However, the dehydrator used in the dehydration system 100 is a screw press type provided with two screw shafts. It may be a dehydrator.

By using two screw shafts, the contact area between the shaft and sludge increases, so that sludge can be sufficiently heated even with a low-temperature heating medium. Further, the stirring and mixing of the sludge proceeds at the portion where the biaxial blades overlap each other, the sludge can be heated evenly, and the moisture content of the dewatered sludge can be stably reduced. Note that the two screw shafts may be arranged vertically or horizontally. Moreover, 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, but the heating jacket 51 has an inner periphery of the outer cylinder screen 12. It may be provided on the 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 cylinder screen 12. This is because if the sludge stays in the outer cylinder screen 12 by the heating jacket 51, the staying sludge hinders heat transfer and lowers the heating efficiency. In addition, if the jacket 51 for heating is installed in the outer peripheral surface of the outer cylinder screen 12 like said embodiment, such a concern is unnecessary.

Further, the outer cylinder screen 12 itself may be made hollow and a heat medium may be circulated there. In this case, the heating jacket 51 attached to the outer cylinder screen 12 is unnecessary, and the portion heated in the outer cylinder screen 12 Becomes both a heating surface and a filtration surface. In this case, a part of the outer cylinder screen 12 may be a heating surface, or the entire surface may be a heating surface.

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

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

FIG. 12 shows a dehydration system 101 in which the digestion gas utilization method and 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 description thereof will be omitted as appropriate.

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

The present invention provides an effect that heat dehydration can be performed even when the heat medium is at a low temperature because the outer cylinder screen is provided with a heating surface and a filtration surface and the object to be dehydrated is dehydrated while being heated by the outer cylinder screen. In addition, it is useful as a dehydrator for removing moisture from a dehydration target containing moisture 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 base, 12: outer cylinder 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: inlet, 23: compression chamber, 24: tray, 25: bearing plate, 26: hydraulic cylinder, 27: piston rod, 28: drop path, 29: taper cone, 31: sludge injection Hopper, 32: sludge moving means, 33: pressurizing means, 33A: pressurizing plate, 34: water collecting means, 36: belt, 37: sludge discharge port, 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

An outer cylinder screen with a small hole formed in the peripheral wall;
A screw shaft provided inside the outer cylinder screen;
Screw blades provided spirally around the screw shaft;
With
By rotating the screw shaft together with the screw blades, the dehydration target charged in the outer cylinder screen is compressed while being conveyed in the axial direction of the screw shaft, and moisture separated from the dehydration target is separated from the outer cylinder. A dehydrator for discharging from the small hole of the screen,
The dehydrating apparatus, wherein 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 cylinder screen and having a configuration for circulating a heat medium therein, further comprises:
The dehydrating apparatus according to claim 1, wherein a portion of the outer cylinder screen to which the heating jacket is attached is used as the heating surface.
The dehydrating apparatus according to claim 2, wherein the temperature of the heat medium is less than 100 ° C.
4. The dehydrator according to claim 3, further comprising an addition unit for adding an inorganic flocculant to the concentrated sludge.
The dehydrator according to any one of claims 1 to 4, wherein the heating surface and the filtration surface are alternately and repeatedly arranged in the axial direction of the screw shaft.
5. The heating surface according to claim 1, wherein the heating surface is formed in an annular shape that surrounds the outer cylinder screen in a circumferential direction, or in a semi-cylindrical shape that covers a part of the outer cylinder screen in the circumferential direction. The dehydration apparatus according to 1.
The dehydrating apparatus according to any one of claims 1 to 4, wherein there are a plurality of heating surfaces, and each heating surface is formed only on a part of the outer cylinder screen in the circumferential direction.
The dehydrating apparatus according to any one of claims 1 to 7, wherein the screw shaft and / or the screw blade has a hollow shape in which a heat medium is circulated.
The dehydrator according to any one of claims 1 to 8, further comprising a concentrator for concentrating the object to be dehydrated before being put into the outer cylinder screen.
An outer cylinder screen with a small hole formed in the peripheral wall;
A screw shaft provided inside the outer cylinder screen;
Screw blades provided spirally around the screw shaft;
With
By rotating the screw shaft together with the screw blades, the dehydration target charged in the outer cylinder screen is compressed while being conveyed in the axial direction of the screw shaft, and moisture separated from the dehydration target is separated from the outer cylinder. A dewatering system for discharging from the small holes of the screen,
A heating jacket attached to a part of the outer cylinder screen, having a configuration in which a heat medium is circulated inside;
A heating medium heater that heats the heating medium using waste heat;
A dehydration system comprising:
It further comprises a heat treatment facility that incinerates, dries, or carbonizes the dehydrated object from which moisture has been released,
The dehydration system according to claim 10, wherein the heat medium heater heats the heat medium using waste heat of the heat treatment facility.
Further comprising a digestion tank for performing a digestion process on the dehydrated object before being put into the outer cylinder screen;
The dehydration system according to claim 10 or 11, wherein the heating medium heater heats the heating medium using digestion gas generated in the digestion tank.
A dehydrating method in a dehydrating apparatus comprising: an outer cylinder screen having a small hole formed in a peripheral wall; a screw shaft provided inside the outer cylinder screen; and a screw blade spirally provided around the screw shaft Because
By rotating the screw shaft together with the screw blades, the dehydration target charged in the outer cylinder screen is compressed while being conveyed in the axial direction of the screw shaft,
The dehydration object conveyed in the outer cylinder screen is heated by the heating surface of the outer cylinder screen, and water separated from the dehydration object is discharged from the filtration surface where the small holes of the outer cylinder screen are exposed. A dehydration method characterized by the above.