JPS6213296A - Method and apparatus for initial filtration of belt press dehydrator - Google Patents

Abstract

PURPOSE:To form a layer to be formed on hydrous sludge to the stabler state having uniform quality by intimately mixing the hydrous sludge by using a prescribed intimate mixer in the stage of filtering, by gravity, the hydrous sludge supplied onto an endless lower filter cloth. CONSTITUTION:A sludge supply device 7 is provided above an endless upper filter cloth 6 guided by an upper roll group 5 and the hydrous sludge supplied from the device 7 onto the filter cloth 6 is initially filtered by gravity. The hydrous sludge on the filter cloth 6 is agitated from below to above and toward the central direction of the filter cloth 6 by screw vanes of the intimate mixing device 8 disposed in a gravity filtration zone A. The layer formed on the hydrous sludge is thereby madfe uniform in quality and stabler.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention involves receiving water-containing sludge generated from the treatment of sewage, waste water, etc. between two filter cloths, sandwiching the water-containing sludge, and pressurizing the water-containing sludge. The present invention relates to an initial filtration method and device for a belt press dehydrator that performs dewatering and filtration.

``Conventional technology'' In a belt press dehydrator, tempered sludge (water-containing sludge) prepared by mixing a flocculant with the material to be treated to improve dewatering performance is first received on a lower filter cloth. Initial filtration is carried out in a so-called gravity filtration zone, where water-containing sludge is naturally dehydrated by its own weight.5 Next, after this initial filtration, the upper filtration strain is applied from above the sludge layer of a stable thickness that forms on the lower filter cloth. The water-containing sludge passes through a wedge zone where pressure is gradually applied to the sludge layer, and then through a pressure zone where strong clamping pressure is applied by pressure rolls, and the water-containing sludge becomes a sludge cake. is determined.

The above-mentioned belt press dehydrator has been widely used due to its easy operability, resource saving, and low cost, and although its characteristics such as dehydration performance and efficiency have significantly improved, it is still not suitable at the current economic pace. , its dewatering performance is, for example, when dewatering mixed raw sludge from municipal sewage using a belt press dehydrator,
If the initial moisture content is 97.5%, it is difficult to reduce it to 75% after dehydration, and even if you strengthen the filter cloth, pressure roll, etc. and increase the belt press dehydrator, the final moisture content of the dehydrated cake will be It is said to be around 72%. Therefore, in order to improve the performance of a belt press dehydrator, it is important to consider dewatering factors other than pressure, such as adding a flocculant to the sludge and improving the initial dewatering rate of the sludge supplied to the dehydrator. , efforts are being focused on researching these factors. The present invention relates to a technical treatment method for initial filtration in the gravity filtration zone of a belt press dehydrator.
As disclosed in Japanese Patent No. 6096, the sludge is evenly distributed so that the tempered sludge supplied onto the lower blemish cloth has a uniform thickness and can be pressurized uniformly in the wedge zone without excess or deficiency.
Methods for uniformizing the feed and sludge layer thickness have been investigated, since their initial filtration technology is considered to be a pervasive factor in determining the moisture content of the final sludge cake. This is because I have come.

"Problems to be Solved by the Invention" However, as a result of microscopic consideration and confirmation experiments of the water-containing sludge in the gravity filtration zone, the present inventors found that
The condition of the water-containing sludge that forms on Kamefu is not necessarily stable even if a uniform sludge is supplied and the sludge thickness is made uniform, and coarse particles, fine particles, etc. are mixed in the sludge. Is the moisture content of the final sludge cake stable depending on the agglomeration state? There was nothing I could do. In other words, if a layer of high resistance (rate-limiting layer) in the water-containing sludge formed by fine particles, etc. is formed near the filter cloth, if it is formed at a position sufficiently far from the filter cloth, or if coarse particles and fine particles are formed. This is especially important in the initial filtration of a belt press dewatering machine, when the sludge does not form a specific layer but has almost homogeneous mixed particles, resulting in a sludge density state with a uniform resistance value in each part of the sludge. We came to the conclusion that this is a significant factor.

In view of the above circumstances, the present invention resides in the rate-limiting layer, etc., and
This was an attempt to solve the problems of initial filtration, and its purpose was to stabilize the state of the sludge layer without applying excessive squeezing pressure, and to stabilize the moisture content of the final sludge cake. [Means for solving the problems] In order to achieve the above object, the method of the present invention provides a method and apparatus for a belt press dewatering machine that can reliably reduce The apparatus of the present invention mixes the water-containing sludge when the water-containing sludge fed onto the endless lower filter cloth guided by the group is filtered by gravity.
A mixing device consisting of a scraping device provided around a rotating shaft is arranged between the sludge supply device and the upper 6-layer cloth while maintaining an adjustment space between it and the lower filter cloth. .

"Operation" In the initial filtration method and apparatus of the present invention, when the water-containing sludge is placed on the lower filter cloth, the initial gravity filtration is performed with a rate-limiting layer formed at an arbitrary position of the water-containing sludge. The process never ends (by mixing the water-containing sludge, the water-containing sludge becomes flocculated (
The cambium layer is destroyed while preserving the aggregated particles),
It becomes less water-containing over time and forms a homogeneous and stable layer on the filter cloth.

"Embodiment" An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Reference numeral 1 in FIG. 1 is an upper frame, and an endless upper roll group 2 is wound around an upper roll group 2 consisting of a large number of rows whose shafts are supported by the upper frame 1. Then, below the upper frame 1, the upper frame 1
A lower frame 4 is installed opposite to the upper frame 1 and protruding to the left (upstream side) from the upper frame 1, and a lower roll group 5 consisting of a large number of rolls whose shafts are supported by the lower frame 4. An endless lower filter cloth 6 is wrapped around it. Further, above the rear end side (left end side in FIG. 1) of the lower filter 7F56, a sludge supply device 7 is installed to uniformly place the water-containing sludge on the lower filter cloth 6. There is. Between this sludge supply device 7 and the rear end (left end in FIG. 1) of the upper filter cloth 3,
A mixing device 8 for mixing the water-containing sludge on the lower filter cloth 6 is arranged above the lower filter cloth 6.

As shown in FIG. 2, the mixing device 8 includes a rotary shaft 8a rotatably provided parallel to the width direction of the lower filter cloth 6, and a pair of left and right helical shafts attached to the rotary shaft 8a. and screw blades (raking tool) 8b, and the spiral directions of the screw blades 8b are opposite to each other. A drive device 9 such as a motor is connected to the rotating shaft 8a, and this drive device rft9 allows
The rotating shaft 8a rotates, and the screw blades 8b stir the water-containing sludge while maintaining an appropriate gap (adjustment space) between the screw blades 8b and the lower filter cloth 6. It is designed to be sent towards the center.

In the paid breath dewatering machine according to the present invention, a gravity filtration sheet/A where initial filtration of water-containing sludge is performed by gravity on the lower filter cloth 6 guided by a plurality of guide rolls 10, and Multiple dewatering rolls arranged 1
1, a wedge zone B that gradually pinches the sludge layer and applies pressure, and a pressure zone C that applies strong clamping pressure by a plurality of pressure rolls 12 arranged in a zigzag pattern are sequentially arranged. It is set up.

Note that a plurality of sets of the mixing devices 8 may be installed depending on the length to the gravity filtration zone or the difference in the components of the water-containing sludge. In addition, this mixing device 8 is configured as described above, in which it is necessary to appropriately set the rotation speed of the rotating shaft 8a, etc., in order to apply an operating force within a range that does not destroy the aggregated particles (flocs) of the water-containing sludge. In the belt press dehydrator, when the water-containing sludge is placed on the lower filter cloth 6 by the sludge supply device 7, the water-containing sludge is transferred to the lower filter cloth 6 guided by the guide roll 10. However, it is initially filtered by its own weight. At this time, in this water-containing sludge, a rate-limiting layer is formed at an appropriate position due to its natural settling action, and even if movement occurs that inhibits the filtration action by gravity, the mixing device 8 disposed in the gravity filtration zone A The screw blade 8b moves the water-containing sludge on the lower filter cloth 6 from below to the upper side and the lower filter cloth 6.
Since the agitation is carried out toward the center of the lower filter cloth 6, the formation layer of the water-containing sludge is destroyed while preserving the flocs, and becomes less water-containing over time. Since the sludge is stirred up, the movement of water-containing sludge leaking from the left and right outer edges of the lower filter cloth 6 can be suppressed.

In this way, the water-containing sludge that has undergone initial filtration in the gravity filtration zone A is then transferred to the wedge zone B.
, the filter cloths 6, 6 are sandwiched between the two filter cloths 6, 6 by the dewatering roll 11, pressure is gradually applied to dewater the cloths, and then the filter cloths are passed through the pressure roll 12 in the pressure zone C to create a stronger clamping force. is fed, dehydrated and discharged as a sludge cake 13.

Next, Table 1 shows the results obtained using an example of the present invention. The apparatus conveniently used in the method of the present invention is shown in FIG. 2, and the outer diameter of the scraping tool 8b of this apparatus is 500 mm, and the rotating shaft 8a is set in order to provide an outer circumferential rotation of 50,771/min. It rotates at 32rpa. In addition, the test sludge was 0.2 to 0.2 to
The sludge is tempered sludge to which 1.0 g of polymer flocculant has been added.As can be seen from Table 1, according to the method of the present invention, the final sludge This had the effect of lowering the moisture content of the cake. In order to obtain this effect by strengthening the clamping force in the conventional method, the tension of the filter cloth used was increased from 10 kg/cMt to 15) cy/7, and the strength of other structural parts was increased to approximately 1.5 As a result, the weight of the dehydrator is approximately 1.5
ff1, resulting in a cost increase of 15 cm. That is, according to the method of the present invention, the water content can be reduced without causing an excessive increase in the weight or cost of the structural component.

In this embodiment, a pair of left and right screw blades 8b, which are continuous and have opposite helical directions, are used as the scraping tool, but the invention is not limited to this.3 For example, as shown in FIG. Alternatively, a plurality of scraping rods 8C are provided radially along the axial length of the rotating shaft 8a, or a plurality of protrusions are provided on the circumferential surface of the scraping rod 8c as shown in FIG. ! 1I8d attached in a dotted, annular, or spiral shape, or as shown in FIG. 5, a scraping rod 8e is attached to the tip of the scraping rod 8C, or a scraping board as shown in FIG. It may also be one with 8f attached.

Further, as shown in FIG. 7, a continuous spiral screw rod 8h is provided along the length direction of the rotating shaft 8a via a support rod 8g, or as shown in FIG. A plurality of scraping rods (plates) 81 held by the rotary shaft 8a may be attached parallel to the axis of the rotating shaft 8a or obliquely and superimposed on each other.Furthermore, as shown in FIG. Support rod 8g
A plurality of spiral screw rods 8j held by the screw rods 8j may be arranged so as to overlap each other and rotate in the same direction or in different directions.

"Effects of the Invention" As explained above, according to the present invention, the water-containing sludge supplied onto the edge-shaped lower filter cloth guided by the lower roll group is mixed. By homogenizing and stabilizing the layer state formed in the water-containing sludge, it is possible to reduce the water content over time. In addition, a mixing device having a scraping device installed around a rotating shaft is arranged between the sludge supply device and the upper filter cloth while maintaining an adjustment space between it and the lower filter cloth. Because of this, not only can the water-containing sludge be stirred efficiently, but also the thickness of the water-containing sludge can be made uniform, and the water-containing sludge can be smoothly sandwiched between the two wedges in the wedge zone of the post-process. be able to. Therefore, it has the excellent effect of reducing the water content of the final sludge cake and not causing a significant increase in the weight or cost of the device.

[Brief explanation of drawings]

Figures 1 and 2 show one embodiment of the present invention.
The figure is a schematic diagram of the belt press dehydrator, Figure 2 is a side view of the mixing device, Figures 6 to 9 show various scraping tools used in the present invention, and Figure 3 shows the rotating shaft. Fig. 4 is an explanatory diagram of a protrusion provided on a raking bar, Fig. 5 is an explanatory diagram of a raking bar with a raking bar attached, and Fig. 6 is an explanatory diagram of a raking bar with protrusions installed. An explanatory diagram of a scraping plate attached to a rod, Figure 7 is a side view of a spiral screw rod attached to a rotating shaft via a support rod, and Figure 8 is a side view of a scraping plate attached to a rotating shaft via a supporting rod. ) is provided, and FIG. 9 is a side view showing a rotating shaft provided with a plurality of screw rods via support rods. 2... Upper roll group, 3... Upper filter cloth, 5... Lower roll group, 6... Lower α cloth, 7... Sludge supply device, 8... Mixing device, 8a ...rotation axis, 8b...
・Screw blade (raking tool), 8c... raking rod, 8d... protrusion, 8e... raking rod, 8f... raking board, 8g-- support rod, 8h... screw rod , 81・
...Scraping rod (board), 8j...Screw rod, A...
-Gravity filtration zone.

Claims (1)

[Claims] 1) Water-containing sludge is supplied onto the endless lower filter cloth guided by the lower roll group and filtered by gravity, and then the endless filter cloth guided by the upper roll group In a belt press dewatering machine that squeezes the sludge between the upper filter cloth and the lower filter cloth, pressurizes it, and dewaters it, the water-containing sludge supplied onto the lower filter cloth is pulled by gravity. An initial filtration method for a belt press dehydrator, characterized in that the water-containing sludge is mixed during filtration. 2) A sludge supply device for supplying water-containing sludge onto the lower filter cloth is provided above the endless lower filter cloth guided by the lower roll group, and on the downstream side of the sludge supply device, In a belt press dewatering machine, in which an endless upper filter cloth is provided above the lower filter cloth and guided by a group of upper rolls, a belt press is provided between the sludge supply device and the upper filter cloth, around the rotating shaft. An initial filtration device for a belt press dehydrator, characterized in that a mixing device configured with a scraping tool is disposed with an adjustment space maintained between the lower filter cloth and the lower filter cloth.