JP2006026604A - Method and apparatus for dehydrating treatment of sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which releasing property of filter cake is improved in dehydrating treatment of sludge by an effectively utilizing method for vegetable waste and a filter-press type dehydrator, formation of a thin film reducing heat conductivity inside the filter cake is suppressed and thereby efficiency of dehydrating drying treatment of the sludge by the filter-press type dehydrator is greatly improved. <P>SOLUTION: In the method for dehydrating treatment of the sludge by the filter-press type dehydrator having a filter press, an evacuating device for making the inside of the filter press in an evacuated state and a means for heating the sludge in the filter press, the sludge is modified by addition and mixing of an expansion-pulverized matter obtained by expansion pulverization treatment of vegetables, and then dehydrating treatment of the sludge by the filter-press type dehydrator is carried out. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for dewatering organic sludge generated by treatment of organic waste such as sewage, human waste, livestock manure, garbage, and various industrial wastewater with a filter press type dehydrator. According to the present invention, in such a method, it is possible to improve the peelability of the filter cake in the dehydrator and increase the drying efficiency.

  Conventionally, sludge generated from sewage treatment plants, human waste treatment plants, industrial wastewater treatment facilities, etc. is dehydrated with a dehydrator after tempering such as addition of polymer flocculants and inorganic flocculants, and landfilled Or incinerated. As a dehydrator used for this purpose, there is a filter press equipped with a filter cloth and a device for reducing the pressure in the filter press, and a device equipped with means for heating the sludge in the filter press. A sludge filter cake is formed on the top, which is peeled off and collected.

  In such a filter press type dehydrator, the peelability of the dried cake from the filter cloth is poor, and the stripping operation must be completed and the filter press must be closed with incomplete peeling. Alternatively, there is a problem in that a thin film that inhibits heat transfer to the inside of the filter cake is formed on the surface of the filter cake, and the evaporation efficiency of the water inside the filter cake is lowered.

  As an example of a method for improving the peelability of the filter cake in the filter press type dehydrator, the pressure in the filter press is set to an upper limit of 200 mbar, and the temperature of the filter plate in the filter press is controlled to a lower limit of 40 ° C. Some avoid the thermoplastic phase of the filter cake.

  However, in this method, the effect varies depending on the properties of the sludge to be treated. Especially in the case of sludge containing a large amount of biopolymer, such as excess sludge, or sludge with advanced decay, only control of pressure and temperature is required. However, the peelability of the filter cake was not improved at all, and the dehydration drying process was hindered. In particular, no solution has been proposed as a solution to the problem that heat transfer into the filter cake is hindered by the formation of a thin film on the surface of the filter cake.

  By the way, in recent years, the dewaterability (ease of dewatering) of sludge has deteriorated due to the advancement of water treatment and the change and diversification of the properties of wastewater to be treated. Therefore, various tempering methods have been examined or proposed in order to improve the dewaterability of sludge. Among them, methods have been proposed in which rice husk, large sawdust, coffee candy, etc. are added to sludge as a dehydrating aid to perform dehydration (Patent Documents 1 and 2).

  On the other hand, in order to suppress the generation of dioxins, on-site incineration of plant wastes such as pruned branches and hay has been prohibited in recent years, and the disposal method of these plant wastes has become a major problem. ing. Therefore, it is useful to use these plant wastes as a sludge dewatering aid, which also serves as disposal of plant wastes. However, in order to use these plant wastes as dehydration aids, it is necessary to pulverize or crush the plant wastes. However, in normal shear crushing and cutting crushing, the crushed materials are not easily adapted to water, and sludge is used. Mixing with was insufficient, and the effect as a dehydrating aid was not sufficient.

JP-A-60-225699 JP 60-222118 A

  Accordingly, the present invention provides an effective method of using plant waste and the formation of a thin film that improves the peelability of the filter cake in the sludge dewatering process using a filter press-type dehydrator and reduces the heat transfer into the filter cake. It is an object of the present invention to provide a method of suppressing and thereby greatly improving the processing efficiency of sludge dehydration drying treatment by a filter press type dehydrator.

  As means for solving the above problems, one aspect of the present invention is a filter press having a filter press, a pressure reducing device for reducing the pressure inside the filter press, and means for heating sludge in the filter press. In the method of dewatering sludge with a mold dehydrator, the sludge is dewatered with the filter press dehydrator after being added to the sludge and mixed with an expanded pulverized product obtained by expanding and pulverizing the plant. To provide a method.

  As a plant used for preparing the expanded pulverized product used as an additive to sludge in the present invention, any plant can be used as long as it has a fiber. From the viewpoint of effective use of plant waste that is currently difficult to dispose of, pruned branches, hay and the like can be preferably used, and straw, bagasse, coffee straw, bamboo, straw, etc. can also be used. Furthermore, thinned wood, construction waste, agricultural waste, rice husk, wheat straw, teacup, etc. can also be used.

  In the method of the present invention, these plants are crushed by an expansion pulverization method. In the present invention, the expansion pulverization treatment refers to a method in which an object to be crushed is brought into a high-temperature and high-pressure state in a state where an appropriate amount of moisture is present, and then released to atmospheric pressure at once. Such a method and the apparatus itself used for it are well-known techniques. Thereby, since the water | moisture content in a crushing target object evaporates at a stretch, a target object is crushed by the volume expansion. The expanded pulverized product obtained in this way is very hydrophilic because the cells themselves are destroyed, has excellent dispersibility, and is extremely easy to mix with sludge.

  In the present invention, a screw-type expansion pulverizer capable of continuous processing can be used for the expansion pulverization treatment. The concept of an example of a screw-type expansion pulverizer that can be used in the present invention is shown in FIG.

  In the screw-type expansion pulverizer shown in FIG. 1, an extrusion screw 102 is inserted and disposed inside a main body (barrel) 101, and a rotating machine (motor) 103 is connected to the screw 2. There may be one screw shaft or a plurality of screw shafts (for example, a biaxial extrusion type as shown in FIG. 1). In a state where the extrusion screw 102 is rotated, a raw material plant, for example, a thinned wood chip, is fed from the feeding hopper 104. The raw material is conveyed (extruded) forward (left side in FIG. 1) while being pulverized by the extrusion screw 102. The staying part (inside the barrel) generates a certain amount of heat due to the compression heat, but it is preferable to adjust the internal temperature by providing a heating device (not shown) as necessary. The barrel outlet (discharge port) 105 has a narrowed diameter (for example, the barrel diameter is 15 cm and the outlet diameter is about 30 mm), and the cover 106 for adjusting the outlet diameter is movable up and down. It is attached. The pulverized plant conveyed toward the outlet 105 while being pulverized remains in the vicinity of the outlet because the outlet 105 is in a squeezed state. At this time, the plant pulverized product is maintained at the “high temperature and high pressure in the presence of moisture” described above by the water vapor generated from the plant. At this stage, the temperature is preferably set to 120 to 150 ° C. Further, the pressure usually reaches 0.3 to 0.7 MPa.

Thereafter, the plant pulverized material is discharged outside from the outlet having a narrowed diameter, and simultaneously released to atmospheric pressure. Thereby, the plant is expanded and pulverized.
In the above description, the water content of the system is supplied by the water vapor generated from the plant itself. However, if the generated water alone is insufficient for the water required for the expansion and pulverization, the main body of the expansion and pulverizer is used. A water vapor (or water) supply device (not shown) can be provided to supply necessary water.

  In the present invention, the plant expanded pulverized product obtained by the above-described expanded pulverization treatment is added to and mixed with sludge. The amount of the expanded pulverized product added to the sludge varies depending on the moisture content of the sludge, that is, the solid content, the sludge properties (for example, whether or not it contains a biopolymer, the degree of spoilage, etc.). It is preferable to add and mix 10 to 100% by weight, and more preferably 10 to 40% by weight.

  Further, in the present invention, in addition to adding the expanded pulverized product of the plant to the sludge, an organic polymer flocculant and / or an inorganic flocculant known in the art is further added to obtain sludge solids. After agglomeration, it can also be dehydrated with a filter press type dehydrator. Examples of organic polymer flocculants that can be used for this purpose include cationic polymers, anionic polymers, and amphoteric polymers. Moreover, as an inorganic flocculant, poly ferric sulfate, ferric chloride, PAC, a sulfuric acid band etc. can be used, for example. In the case of an organic polymer flocculant, the amount of these flocculants added is 0.5 wt% to 5 wt%, preferably 0.5 wt% to 2 wt%, based on the solid content of the sludge. In this case, it is preferable that the content is 5 to 50% by weight, preferably 10 to 20% by weight, based on the solid content of the sludge. Either the organic polymer flocculant or the inorganic flocculant may be added to the sludge, and both the organic polymer flocculant and the inorganic flocculant may be added to the sludge. In addition, the order of the addition of the expanded pulverized product and the addition of the flocculant may be first, even if the flocculant is added to the sludge and then the flocculant is added, or the flocculant is added to the sludge. After the flocculation treatment is added, the expanded pulverized product may be added, or the expanded pulverized product and the flocculant may be added to the sludge.

  In the present invention, the sludge that has been flocculated by adding the expanded pulverized product of the plant as described above and further adding a flocculant in some cases is dehydrated by a filter press type dehydrator. The filter press type dehydrator used in the present invention has a filter press, a pressure reducing device for reducing the pressure inside the filter press, and means for heating sludge in the filter press.

  As a filter press type dehydrator that can be used in the present invention, for example, those disclosed in JP-A-2001-232109 can be used. The configuration of the filter press type dehydrator disclosed in Patent Document 4 will be described below. The flow diagram of the dehydrator is shown in FIG. 2, the configuration of the dehydrator is shown in FIG. 3, the outline of the filter frame of the dehydrator is shown in FIG. 4, and the structure inside the dehydrator is shown in FIG.

  A filter press type dehydrator that can be used in the present invention can include a dehydration drying apparatus 1, a hot water boiler 2, and a vacuum pump 3. Sludge is supplied to the dehydrating and drying apparatus 1 by a sludge supply pump 5 provided in the sludge supply line 4. The sludge supply line 4 is provided with an on-off valve V1. The sludge supply line 4 is connected to a center blow line 6 having an on-off valve V4.

  The dehydrating and drying apparatus 1 and the hot water boiler 2 are connected to each other by a hot water circulation line 7. A hot water circulation pump 8 and a back pressure valve 9 are installed in the hot water circulation line 7. The hot water boiler 2 constitutes a heat retaining fluid supply device for supplying a heat retaining fluid as a pressurized medium. The dehydrating and drying apparatus 1 is connected to a filtrate discharge line 10 having an on-off valve V2. A vacuum exhaust line 11 is connected to the filtrate discharge line 10. The vacuum exhaust line 11 is provided with an on-off valve V3, a drain pot 12, and a vacuum pump 3. Further, a dewatering line 14 having an on-off valve V5 is connected to the dehydration drying apparatus 1.

  FIG. 3 is a schematic front view showing the configuration of the dehydration drying apparatus. As shown in FIG. 3, the dehydrating and drying apparatus 1 includes a plurality of filter frames 15 and filter frame tightening devices 16 that are installed at both ends and tighten the filter frames 15. By tightening the filter frame 15 by the filter frame tightening device 16, a filter chamber (described later) surrounded by a filter cloth for dewatering sludge is formed between adjacent filter frames 15. The dehydration drying apparatus 1 includes hot water headers 17A and 17B on the hot water supply side and the return side, respectively. The hot water header 17A is connected to the hot water circulation pump 8, and the hot water header 17B is connected to the back pressure valve 9 (see FIG. 2). Further, as described above, the dehydration drying apparatus 1 is connected to the sludge supply line 4, the center blow line 6, the hot water circulation line 7, the filtrate discharge line 10, and the vacuum exhaust line 11.

  FIG. 4 is a perspective view of a filter frame in the dehydration drying apparatus. As shown in FIG. 4, the plate 15 includes a diaphragm (elastic film) 18 stretched on the front and rear surfaces thereof. The plate 15 and the diaphragm 18 may be integrally formed, and the plate itself may have a diaphragm function. FIG. 4 shows only the diaphragm 18 stretched on the front surface of the plate 15. The diaphragm 18 is formed with a plurality of drain grooves 18a for allowing the filtrate to flow to the discharge line. The filter frame 15 includes a sludge injection hole 19 into which sludge is injected, a filtrate discharge hole 20 formed at the four corners of the plate 15, and a hot water circulation hole 21 formed at the upper and lower ends of the plate 15.

  FIGS. 5A and 5B are diagrams showing the internal structure of the dewatering and drying apparatus, where FIG. 5A shows a sludge filtration step and FIG. 5B shows a sludge pressure dehydration step. A plurality of filter frames 15 and the like installed adjacent to each other form a filter chamber 22 therebetween, and each filter chamber 22 is arranged as an internal space of a filter cloth 23 supported by a pair of opposing diaphragms 18 (18a). Has been. In addition, the filter cloth 23 has a hole formed at a position corresponding to the sludge injection hole 19, and the sludge can pass through the hole, and the sludge can be supplied to each filter chamber 22.

  Each diaphragm 18 has a drain groove 18a (see FIG. 4) and is in contact with the filter cloth 23. As shown in FIG. 5, the filtrate discharge holes 20 of the adjacent filter frames 15 are disposed in the drain groove 18a. The filtered water flowing down is discharged. That is, the drainage groove 18a constitutes a filtrate discharge line between each diaphragm 18 and the filter cloth 23, is connected to the filtrate discharge port 20, and is further connected to an external vacuum pump (not shown). Thereby, the filtrate filtered by the filter cloth 23 is sucked and discharged to the outside of the dehydrating and drying apparatus 1 through the filtrate discharge hole 20. Further, by operating the vacuum pump, the inside of the groove 18a of the diaphragm 18 outside the filter cloth 23 is maintained under a reduced pressure atmosphere of, for example, about -0.08 MPa.

Next, a method for dewatering and drying sludge using a filter press-type dehydrator configured as shown in FIGS. 2 to 5 will be described.
First, the filter frame 15 is adjusted to a predetermined position by the filter frame tightening device 16, and sludge is injected between the filter cloths 23 and 23 to form the filter chamber 22. The conditioned sludge stored in the sludge storage tank (not shown) is dehydrated and dried by the sludge supply pump 5 provided in the sludge supply line 4 through the on-off valve V1 at a maximum filtration pressure of about 0.5 MPa. A filtration process is performed by driving the filter chamber 22 from the center of the apparatus 1 into the filter chamber 22 for a predetermined time (for example, 60 minutes) without pouring chemicals. This state is shown in FIG. This sludge supply position may be driven from the top or the bottom, and is not particularly limited. The filtered water separated into solid and liquid by the filter cloth 23 is guided to the filtrate discharge line 10 by the groove 18a engraved in the diaphragm 18 and the filtrate discharge hole 20, and is discharged outside the system via the on-off valve V2.

  Next, after setting the squeezing pressure with the back pressure valve 9, the hot water circulating pump 8 is operated, and hot water heated to 80 ° C. with the hot water boiler 2 is placed in the room partitioned by the filter frame 15 and the diaphragm 18 for 15 minutes. The squeezing process is performed by inflating the diaphragm 18 and compressing the sludge. This squeezing step is aimed at pre-heating sludge and filtering the sludge in the center so that the sludge in each filtering chamber is not out of the system during the center blowing. Therefore, the pressing time can be changed depending on the type of sludge, and may be omitted in some cases. At this time, the hot water temperature may be 70 to 90 ° C., but in this step, water may be used instead of the hot water, and a valve is provided at the return of the hot water and the valve is closed to circulate. May be stopped.

  Next, the on-off valve V1 is closed, the on-off valves V4, V5 are opened, compressed air having a pressure of 0.5 MPa is blown into the sludge injection hole 19, a center blow process is performed, and the soft remaining in the sludge injection hole 19 in each chamber Sludge is discharged. The discharged sludge is collected in the sludge storage tank.

  After the center blow process is completed, the hot water circulation pump 8 is operated again, and the set pressure of the back pressure valve 9 is preferably set to 0.5 MPa to 1.5 MPa, and the sludge in the filter chamber is pressurized and heated. In the dehydration drying process, it is preferable to increase the pressure further than the pressure applied in the pressing process or the center blowing process. The hot water temperature at this time is also preferably 70 to 90 ° C. as described above. On the other hand, the on-off valve V2 is closed, the on-off valve V3 is opened, the evacuation line 11 is opened, the vacuum pump 3 is operated, and a dehydration drying process is performed as shown in FIG. That is, when the vacuum pump 3 is operated and the outer surface of the filter cloth (the non-contact side with the concentrated sludge) is placed in a reduced-pressure atmosphere via the filtrate discharge line 10, squeezing and dehydration proceeds in the filter chamber, and at the same time, the inner surface of the filter cloth. Drying of the sludge in contact with (sludge and contact side) proceeds by pressurization and heating. At this time, the pressure outside the filter chamber is preferably as low as possible, and is preferably −0.08 MPa or less.

  That is, in the dehydration drying process, the moisture in the concentrated sludge has a triple moisture removal function of dehydration by dynamic squeezing force, evaporation by heating, and dehydration by making the outside of the filter cloth a reduced pressure atmosphere. The filter chamber 22 is removed. The removed water is condensed by exchanging heat with cooling water in the drain pot 12. The pressing / drying time varies depending on the type of sludge and the target moisture content, and is determined by calculating from the amount of sludge to be driven and the amount of drainage discharged in each process.

  Next, the filter frame clamping device 16 is loosened, the frame is opened, and the cake discharging process is performed to discharge the cake. In the present invention, the exfoliation property of the cake is improved by adding the expanded pulverized product of the plant to the sludge to be treated, so there is almost no cake remaining on the filter cloth, and no cleaning process is required at all. .

  Sludge dewatering cake is obtained by performing sludge dewatering treatment by the method of the present invention. The obtained sludge dewatered cake can be subjected to incineration, carbonization, composting and the like. According to the present invention, the moisture content of the sludge dewatered cake formed by the dewatering treatment can be reduced in addition to the improvement of the peelability of the cake in the filter press type dewatering machine. This is thought to be due to the improved dewaterability and drying rate of sludge due to the improved mixing with sludge because the expanded pulverized product obtained by the expansion pulverization treatment of plants has high hydrophilicity. It is done. As a result, for example, fuel consumption when carbonizing sludge dewatered cakes can be reduced, and the amount of moisture adjusting material used when composting sludge dewatered cakes, and drying of raw materials and compost products are necessary. Energy can be reduced. Furthermore, when the sludge dewatered cake is incinerated, the amount of the auxiliary combustion agent used can be reduced.

The present invention further relates to an apparatus for carrying out the above sludge dewatering method. The conceptual diagram of the sludge dehydration processing apparatus which concerns on 1 aspect of this invention is shown in FIG.
In the apparatus shown in FIG. 6, plants such as pruned branches and hay (preferably plant waste) are supplied to a steaming expansion pulverization apparatus to perform expansion pulverization. Examples of the expansion and pulverization apparatus that can be used for this purpose include the above-described twin-screw expansion and pulverization machine. Next, the organic polymer flocculant and / or the inorganic flocculant is added to the sludge from the flocculant addition apparatus to perform the flocculant treatment. The sludge subjected to these treatments is supplied to a filter press-type dehydrator for dehydration treatment, and the obtained dewatered cake is subjected to the next treatment (compost treatment, sludge carbonization treatment, sludge incineration treatment, etc.).

  FIG. 6 shows an embodiment in which the expanded pulverized product is first added to the sludge, then the flocculant is added, and then applied to a filter press-type dehydrator. The order of addition may be reversed, or the addition may be performed simultaneously.

Various aspects of the present invention are as follows.
1. In a method of dewatering sludge with a filter press-type dehydrator having a filter press, a pressure reducing device for depressurizing the inside of the filter press, and means for heating the sludge in the filter press, the plant is expanded into the sludge. A method comprising adding and mixing an expanded pulverized product obtained by pulverization, tempering, and then dehydrating with the filter press dehydrator.

2. 2. The method according to item 1 above, wherein the plant pulverized product is added and mixed in an amount of 5 to 100% by weight based on the solid content of the sludge.
3. 3. The method according to item 1 or 2, wherein the pressure in the filter press in the dehydration apparatus is 0.02 MPa or less.

4). 4. The method according to any one of the above items 1 to 3, wherein an organic ground flocculant and / or an inorganic flocculant is added to and mixed with sludge and a plant expanded pulverized product.
5. The above items 1 to 4 using pruned branches, hay, straw, bagasse, coffee straw, bamboo, firewood, thinned wood, construction waste, agricultural waste, rice husk, wheat straw, or teacup as the plant to be expanded and ground. A method according to any of the paragraphs.

6). An expansion pulverization device for expanding and pulverizing plant materials, an expanded pulverized material adding device for adding the expanded and pulverized plant expanded pulverized product to sludge, and receiving and dewatering the sludge to which the expanded pulverized material is added. A sludge dewatering apparatus comprising a filter press, a depressurizer for reducing the pressure inside the filter press, and means for heating the sludge in the filter press. A device that is a filter press type dehydrator.
7). The apparatus according to claim 6, further comprising a flocculant addition apparatus for adding an organic polymer flocculant and / or an inorganic flocculant to the sludge.

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following description.
Using hay as the object to be crushed, the above-mentioned biaxial screw extrusion type expansion pulverizer was used to obtain a crushed product (expanded pulverized product) having a particle size of 0.5 to 2 mm.

  To the human waste surplus sludge (solid content concentration 15.8 g / L), 0% by weight (comparative example), 10% by weight or 30% by weight of the above expanded pulverized product is added and mixed with the solid content of the sludge. Ferric sulfate was added and mixed with 1.5% asFe, and then the polymer flocculant (trade name Eva Claus B034, manufactured by Ebara Seisakusho Co., Ltd.) was added to 0.7% by weight based on the solid content of the sludge for coagulation treatment. After that, it was subjected to dehydration treatment by a filter press type dehydrator.

  The dehydration process was performed using the filter press-type dehydrator shown in FIGS. First, sludge that was tempered by adding expanded crushed material was press-fitted into the filter chamber of a filter press with a sludge supply pump (filtration step). The pump pressure in the filtration process is called filtration pressure. After completion of the filtration step, the hot water circulation pump was activated to supply hot water to the space between the filter frame and the diaphragm. At this time, the hot water pressure was adjusted to 1.5 MPa with a back pressure valve. By supplying warm water, the diaphragm is deformed and the sludge in the filter chamber is squeezed and dehydrated (squeezing step). The hot water pressure in the pressing process is called pressing pressure. Next, the non-dehydrated sludge remaining between the sludge supply was blown out of the filter press with compressed air (blow process). The hot water circulation pump was restarted and the vacuum pump was driven. Since the vacuum pump is connected to the filtrate discharge line, the groove cut in the filtrate discharge line and the diaphragm is depressurized (dehydration drying step). The pressure in the filtrate line and the groove cut in the diaphragm in the dehydration drying process is called the filter press pressure, which means the pressure of the vacuum pump. In the initial stage of this step, dehydration due to pressing force mainly occurs, but dehydration due to drying mainly occurs over time. At this time, since water evaporates at a temperature corresponding to the pressure in the filter chamber, the lower the pressure, the lower the boiling point, and the temperature difference from the hot water temperature (80 to 90 ° C.) increases, so the amount of heat transfer increases. Increases drying speed.

The filter press used was a double-sided pressure method with a filtration area of 4 m ² and the thickness of the filter chamber was 30 mm. The heat source of the filter press was warm water of 85 ° C., and was circulated and supplied to the back surface of the diaphragm with a warm water circulation pump. The vacuum generator used a vacuum pump, and the pressure in the filter press was 0.01 MPa. The filtration time was 60 minutes, the filtration pressure was 0.5 MPa, the pressing time was 30 minutes, the pressing pressure was 1.5 MPa, and the drying time was 90 minutes. The ultimate moisture content was measured and the peelability of the cake was observed. . The peelability of the cake was evaluated by the ratio of the area of the cake adhering to the filter cloth after opening the filter press frame and shaking the filter cloth (cake adhering area / filtration area × 100%). The results are summarized in Table 1.

  The apparent moisture content of the dehydrated cake is an actually measured value including the weight of the additive (in the case of this experiment, ferric sulfate and polymer and expanded pulverized product), and the true moisture content is From this measured value, the moisture content relative to the sludge weight excluding the dry weight of the additive is calculated.

  In the comparative example in which the plant expanded pulverized product was not added, the true moisture content of the cake was 56.8%, but the peelability of the cake was poor, and peeling by vibration using a shaker was attempted. Despite being about 15 mm, the cake adhered to about 90% of the filter cloth surface. The degree of adhesion was also in a state where the cake was firmly biting into the filter cloth surface, and although peeling was attempted by human power using a scraper, it could not be completely peeled off.

  On the other hand, in the method of the present invention, the peelability of the cake was good and the cake peeled 100%. In particular, when 30% by weight of the expanded pulverized product was added, cake peeling occurred simultaneously with the opening of the filter press. This is presumably because the adhering force to the filter cloth was attenuated due to the stickiness of the cake itself being reduced due to the mixing of the expanded pulverized material.

  Further, by dehydrating and drying under the same conditions, the moisture content of the cake was 56.8% in the comparative example, whereas in the present invention, the true moisture content of the cake was 8 points (compared to the expanded pulverized product 10). (Weight% addition) and 12 points (expanded pulverized product addition of 30 weight%) decreased. In addition to the cake peelability being improved by the addition of the expanded pulverized product, the dewaterability is further improved and the formation of a thin film that inhibits drying in the cake layer is suppressed. It can be considered that a void portion was formed in the cake layer by the addition of the expanded pulverized product, and a vacuum portion was generated in the cake layer, thereby promoting drying.

  From the above experimental results, according to the present invention, after adding a plant expansion pulverized product to sludge, preferably adding a flocculant and performing a flocculation treatment, the filter is subjected to a dehydration treatment by a filter press type dehydrator. It can be seen that the peelability of the cake in the press can be improved, the water content of the dehydrated cake can be reduced, and the subsequent incineration, carbonization, composting, etc. can be carried out very well.

  According to the present invention, the water content of the dehydrated cake can be reduced by adding the expanded pulverized product obtained by expanding and pulverizing the plant to the sludge, and subjecting the sludge to the dehydration treatment by the filter press type dehydrator. At the same time, the peelability of the cake in the filter press can be improved. When the dehydrated cake obtained according to the present invention is composted, it can be composted in a shorter period of time than before because the organic matter loss is large. Further, by reducing the moisture content of the dehydrated cake, it is possible to reduce the amount of moisture adjusting material used when composting the dehydrated cake and reduce the amount of energy used when drying dehydrated sludge and product compost. Also, when the dehydrated cake is carbonized or incinerated, the amount of energy used can be reduced, and the amount of carbon dioxide generated can be reduced, which helps to counter global warming. Furthermore, according to the present invention, it is possible to effectively use plant waste such as pruned branches, hay, thinned wood, and building waste that are currently difficult to dispose of.

It is a figure which shows the concept of one specific example of the expansion crusher which can be used in this invention. It is a flowchart which shows the system of the filter press type | mold dehydrator which can be used in this invention. It is a schematic front view which shows the structure of the filter press type | mold dehydrator which can be used in this invention. It is a perspective view of the filter frame in the filter press type dehydrator which can be used in the present invention. It is a figure which shows the internal structure of the filter press type | mold dehydrator which can be used in this invention. (A) shows a filtration process, (b) shows a pressure dehydration drying process. It is a conceptual diagram which shows the structure of the dewatering apparatus of the sludge which concerns on 1 aspect of this invention.

Claims (7)

  In a method of dewatering sludge with a filter press-type dehydrator having a filter press, a pressure reducing device for depressurizing the inside of the filter press, and means for heating the sludge in the filter press, the plant is expanded into the sludge. A method comprising adding and mixing an expanded pulverized product obtained by pulverization and tempering, followed by dehydrating with the filter press dehydrator.   The method according to claim 1, wherein the expanded pulverized product of the plant is added and mixed in an amount of 5 to 100% by weight based on the solid content of the sludge.   The method according to claim 1 or 2, wherein the pressure in the filter press in the dehydration apparatus is reduced to 0.02 MPa or less and dried under reduced pressure.   The method according to any one of claims 1 to 3, wherein an organic ground flocculant and / or an inorganic flocculant is added to and mixed with the sludge while the plant expansion pulverized product is added and mixed with the sludge.   The plant according to any one of claims 1 to 4, wherein pruned branches, hay, straw, bagasse, coffee straw, bamboo, straw, thinned wood, construction waste, agricultural waste, rice husk, wheat straw, or teacup are used as the plant to be expanded and ground. The method of crab.   An expansion pulverization device for expanding and pulverizing plant materials, an expanded pulverized material adding device for adding the expanded and pulverized plant expanded pulverized product to sludge, and receiving and dewatering the sludge to which the expanded pulverized material is added. A sludge dewatering apparatus comprising a filter press, a depressurizer for reducing the pressure inside the filter press, and means for heating the sludge in the filter press. A device that is a filter press type dehydrator.   The apparatus of Claim 6 which comprises the flocculent addition apparatus which adds an organic polymer flocculant and / or an inorganic flocculant to sludge.

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