Screw press type dewatering device

Abstract

The present invention provides a screw-press type dewatering apparatus that can eliminate clogging of filtration holes in the area directly below the inlet and in the gravity dewatering section during the dewatering process. [Solution] The system consists of a screw shaft, screw blades attached to the screw shaft, and an outer cylinder having filtration holes surrounding the screw blades. The outer cylinder has an inlet at one end for introducing water-containing sludge and an outlet at the other end for discharging dewatered cake. The flow path in the space enclosed by the screw shaft, screw blades, and outer cylinder narrows from the inlet to the outlet. In a screw press type dewatering apparatus that rotates a screw shaft to compress water-containing sludge introduced from the inlet, discharge the filtrate from the filtration holes, and obtain a dewatered cake from the outlet, A screw press type dewatering device in which a scraper that contacts the outer cylinder is attached to a screw blade located within a range of less than one-third of the total length from one end of the screw shaft on the inlet side.

Description

TECHNICAL FIELD

[0001] The present invention relates to a screw press type dewatering device for dewatering sludge generated from aerobic microorganism treatment devices, anaerobic microorganism treatment devices and the like, as well as sludge generated from various wastewater treatment devices, to obtain dewatered cake. BACKGROUND ART

[0002] The screw press type dewatering device comprises a screw shaft rotated by a driving means, screw blades spirally attached to the outer periphery of the screw shaft, and an outer cylinder having filtration holes surrounding the screw blades. One end and the other end of the outer cylinder are respectively provided with an inlet for feeding water-containing sludge and an outlet for obtaining dewatered cake. The flow path of the space surrounded by the screw shaft, the screw blades and the outer cylinder narrows from the inlet toward the outlet. While rotating the screw shaft, the water-containing sludge fed from the inlet is squeezed, the filtrate is discharged through the filtration holes, and the dewatered cake is obtained from the outlet, which is used for dewatering treatment of various types of sludge.

[0003] Conventionally used screw press type dewatering devices will be described in more detail with reference to the drawings.

[0004] Figure 5 is an explanatory view of a conventionally used screw press type dewatering device 31. Screw blades 2 are spirally attached to the outer periphery of a screw shaft 1 that is rotatable by a driving means (not shown), and the screw shaft 1 is installed inside an outer cylinder 4 having filtration holes 3 made of punched metal or the like. One end of the outer cylinder 4 is provided with a hopper-type inlet 5 for feeding water-containing sludge, and the other end is provided with an outlet 6 for discharging dewatered cake.

[0005] In addition, the gap between the outer cylinder 4 and the tip of the screw blade 2 is made as narrow as possible to prevent the water-containing sludge in the dewatering process from leaking through the gap, whereby the squeezing force applied to the water-containing sludge can be maximized and the dewatering effect can be improved.

[0006] However, if the design is such that the outer cylinder 4 and the tip of the screw blade 2 are in contact while the screw blade 2 rotates, there is a risk of the outer cylinder 4 being damaged. To minimize the gap between the outer cylinder 4 and the tip of the screw blade 2 without causing damage, currently it is necessary to leave a gap of about 1 to 2 mm.

[0007] Furthermore, the screw press type dewatering device 31 shown in Figure 5 is configured such that the flow path in the space enclosed by the screw shaft 1, screw blades 2, and outer cylinder 4 gradually narrows by gradually narrowing the pitch of the spirally attached screw blades 2. However, there are also conventional devices in which the flow path in the space enclosed by the screw shaft 1, screw blades 2, and outer cylinder 4 gradually narrows by gradually increasing the outer diameter of the screw shaft 1 from the inlet 5 to the outlet 6.

[0008] To dewater water-containing sludge and obtain a dewatered cake using the conventional dewatering device 31, the following procedure is performed. For example, a flocculant such as an organic polymer flocculant is added to sludge such as excess sludge discharged from an aerobic microbial treatment device and subjected to flocculation treatment. The water-containing sludge consisting of the flocculated sludge obtained in this way is then introduced through the inlet 5 while the screw shaft 1 is rotated.

[0009] The water content of the above-mentioned water-containing sludge is usually around 99%, but approximately 90% of the water is removed as the water-containing sludge moves through the gravity dewatering section A, located on the inlet side of the screw shaft 1, which extends from the inlet 5 to the outlet 6, due to the rotation of the screw blades 2.

[0010] Next, the material is compressed and dewatered by moving sequentially through the medium-pressure dewatering section B and then the high-pressure dewatering section C, and a dewatered cake with a moisture content of approximately 75% is obtained from the outlet section 6.

[0011] The rotation of the screw blades 2 in the gravity dewatering section A is for pushing the water-containing sludge toward the medium-pressure dewatering section B. The pressure from the rotation of the screw blades 2 does not push water out of the filtration holes 3; rather, water is removed solely by gravity through the filtration action of the filtration holes 3 located in the outer cylinder 4.

[0012] As this operation continues, as mentioned above, there is a small gap between the outer cylinder 4 and the screw blades 2. As shown in Figure 6, the fine sludge F present in the water-containing sludge forms bridges that block the filtration holes 3 of the outer cylinder 4, reducing the water removal effect of the gravity dewatering section A.

[0013] Furthermore, as mentioned above, the outer cylinder 4 and the tip of the screw blade 2 are not in contact, so the sludge bridges F cannot be scraped off by the rotation of the screw blade 2, as shown in Figure 6. As a result of the formation of these bridges, the water removal capacity of the gravity dewatering section A decreases.

[0014] When this condition occurs, the moisture content of the dewatered cake obtained from the outlet 6 increases, resulting in a problem where it cannot perform at its predetermined capacity. Furthermore, if one attempts to obtain a dewatered cake with a predetermined moisture content, the processing volume must ultimately be reduced, which presents another problem.

[0015] To solve this problem, conventional methods involve spraying water from a spray nozzle installed on the outside of the outer cylinder 4 while the device is running or when it is stopped, in order to clear the blockage of the filtration holes 3.

[0016] However, since the cleaning is done from the outside of the outer cylinder 4, the bridge cannot be directly washed away, which is insufficient in terms of clearing blockages, and furthermore, it has the problem of consuming a large amount of cleaning water.

[0017] Patent Document 1 describes a method of clearing clogging by carving a groove into the tip of a screw blade 2, fitting a string-shaped scraper made of an elastic material such as urethane into the groove, and rotating the screw blade while keeping the scraper in close contact with the outer cylinder.

[0018] However, even if the aforementioned scraper can remove the fine sludge bridges blocking the filter holes, the rotation speed of the screw blades is only about 3 to 10 times per hour, so the scraping frequency is low, resulting in insufficient removal of blockages in the filter holes and failing to achieve the intended objective.

[0019] Furthermore, carving grooves into the tips of the screw blades is time-consuming in terms of machining, and since the string-like scraper is simply fitted into the groove, there is a drawback that the string-like scraper may come off due to the rotation of the screw blades. As a result, no dewatering device with a scraper attached to the tip of the screw blades has appeared. Patent Document 2 describes a vertical filtration and concentration device in which a scraping member is attached to the outer circumference of the screw, biased to make sliding contact with the inner surface of the filtration screen. However, the screw in Patent Document 2 moves the liquid to be treated downward by rotation, and its operation is different from a screw that pushes and compresses water-containing sludge into a space with a flow path that gradually narrows from the inlet to the outlet, as in a screw press type dewatering device. [Prior art documents] [Patent Documents]

[0020] [Patent Document 1] Japanese Patent Application Publication No. 8-1389 [Patent Document 2] Japanese Patent Publication No. 2017-910 [Overview of the Initiative] [Problems that the invention aims to solve]

[0021] The present invention aims to provide a screw-press type dewatering apparatus that can eliminate the problems of conventional screw-press type dewatering apparatuses, namely, the clogging of filtration holes in the gravity dewatering section A, which occurs directly below or near the inlet, during the dewatering process.

[0022] Another object of the present invention is to provide a screw press type dewatering apparatus that can continuously obtain dewatered cake with a low moisture content at a predetermined processing throughput by eliminating the clogging without reducing the moisture removal capacity of the gravity dewatering section at all. Means for Solving the Problems

[0023] In order to solve the above problems, the present invention has the following configurations. (1) Consisting of a screw shaft rotated by a driving means, screw blades spirally attached to the outer periphery of the screw shaft, and an outer cylinder having filter holes surrounding the screw blades, the apparatus has an inlet portion provided at one end of the outer cylinder for charging water-containing sludge and an outlet portion provided at the other end of the outer cylinder for discharging dewatered cake, and the flow path of the space enclosed by the screw shaft, the screw blades and the outer cylinder narrows from the inlet portion toward the outlet portion, A screw press type dewatering apparatus that squeezes the water-containing sludge charged from the inlet portion while rotating the screw shaft, discharges filtrate through the filter holes, and obtains dewatered cake from the outlet portion, A screw press type dewatering apparatus, characterized in that a scraper in contact with the outer cylinder is attached to the screw blades disposed within a range of 1 / 3 or less of the total length from the end of the screw shaft on the inlet portion side. (2) The screw press type dewatering apparatus according to (1), wherein the side surfaces near the tips of one pair or a plurality of pairs of mutually facing screw blades are joined by bridging members, and the scraper made of an elastic body is attached to the bridging members. (3) The screw press type dewatering apparatus according to (2), wherein the side surfaces near the tips of one pair or a plurality of pairs of mutually facing screw blades are joined by a plurality of bridging members arranged at equal intervals, and the scraper is attached to each of the plurality of bridging members. (4) The side surfaces near the tips of a pair of mutually facing screw blades are joined by four bridging members arranged at equal intervals, the side surfaces near the tips of another pair of mutually facing screw blades adjacent to the aforementioned pair of screw blades are joined by four bridging members arranged at equal intervals, and the scraper is attached to each of the total of eight bridging members, the screw press type dewatering apparatus as described in (3). Effects of the Invention

[0024] In the screw press type dewatering apparatus of the present invention, the scraper rotates in accordance with the rotation of the screw blades, so even if a bridge made of fine sludge blocks the filtration holes of the outer cylinder present in the gravity dewatering section, the bridge can be scraped off immediately, and clogging of the filtration holes can be prevented.

[0025] In addition, by joining a plurality of bridging members between the screw blades and attaching a scraper to each bridging member, the frequency of scraping the filtration holes is increased, so clogging of the filtration holes can be effectively prevented.

[0026] Further, by preventing the clogging of the filtration holes, it becomes possible to continuously and stably obtain dewatered cake with a low moisture content at a predetermined throughput without reducing the water removal capability of the gravity dewatering section at all. Brief Description of the Drawings

[0027] [Figure 1] It is a schematic cross-sectional view of the screw press type dewatering apparatus showing an example of the embodiment of the present invention. [Figure 2] It is an enlarged schematic cross-sectional view of the vicinity of the inlet portion of Figure 1. [Figure 3] It is a schematic cross-sectional view of the main part of the screw press type dewatering apparatus viewed from the A-A line in Figure 2. [Figure 4] It is a schematic cross-sectional view of the screw press type dewatering apparatus viewed from the B-B line in Figure 2. [Figure 5] It is a schematic cross-sectional view of a conventional screw press type dewatering apparatus. [Figure 6] This is a schematic cross-sectional view showing how fine sludge present in water-containing sludge forms bridges that block the filtration pores. [Modes for carrying out the invention]

[0028] The present invention will be described in detail below with reference to the drawings. Figure 1 is a schematic cross-sectional view of a screw press type dewatering apparatus 21 showing an example of an embodiment of the present invention; Figure 2 is an enlarged schematic cross-sectional view of the vicinity of the inlet in Figure 1; Figure 3 is a schematic cross-sectional view of the main part as seen from line AA in Figure 2; and Figure 4 is a schematic cross-sectional view as seen from line BB in Figure 2.

[0029] As shown in Figure 2, the sides near the tips of a pair of opposing screw blades 2a and 2b located directly below the inlet 5 are joined by bridging members 7, which are arranged at four equal intervals. Preferably, the bridging members 7 are joined so as to be parallel to the inner circumferential surface of the outer cylinder 4.

[0030] While welding is preferred as the method of joining the predetermined parts of the screw blades 2a and 2b to both ends of the bridging member 7, it is also acceptable to drill holes for threads in both screw blades and join the ends of the bridging member 7 to the predetermined parts of the screw blades 2a and 2b with screws.

[0031] Each of the four bridging members 7 joined between the screw blades 2a and 2b is fitted with a scraper 8 made of an elastic material such as natural rubber, synthetic rubber, or a resilient plastic.

[0032] The preferred method for attaching the scraper 8 to the bridging member 7 is to use bolts 9 and nuts 10, as shown in Figure 3.

[0033] As shown in Figure 3, it is important that the tip 11 of the scraper 8 is attached so as to be in close contact with the filtration hole 3 provided in the outer cylinder 4. When the tip 11 of the scraper 8 is in close contact with the filtration hole 3, the tip 11 of the scraper 8, which is made of an elastic material, will bend slightly. The arrow R in Figure 3 indicates the direction of rotation of the screw blade 2.

[0034] By attaching scrapers 8 to each of the four bridging members 7, the scrapers 8 are positioned at equal intervals, i.e., at a 90-degree angle, with respect to the circumference of the circle onto which the screw blades 2 rotate around the screw shaft 1. Note that the outer cylinder 4 is not shown in Figure 4.

[0035] On the other hand, as shown in Figure 2, four bridging members 7 are similarly joined between adjacent pairs of screw blades 2b and 2c, and a scraper 8 is attached to each of the bridging members 7.

[0036] Therefore, a total of eight bridging members 7 are joined to the screw blades 2a, 2b, and 2c that face each other, and a scraper 8 is attached to each of the eight bridging members 7.

[0037] Next, the operation of the screw press type dewatering apparatus 21 of the present invention will be explained using Figure 1. While the screw shaft 1 is slowly rotated by a regular drive device (not shown), water-containing sludge consisting of flocculated sludge with a water content of about 99%, which has been flocculated in a regular flocculation tank (not shown) using a flocculant such as a polymer flocculant, is continuously fed in from the hopper-type inlet 5.

[0038] In addition to the hopper type, the inlet section 5 is not limited to the hopper type; there are also screw press type dewatering devices in which an introduction pipe is connected near the screw blades 2a, and water-containing sludge is supplied from the introduction pipe.

[0039] The water-containing sludge that is introduced moves towards the outlet section 6, sliding slightly between the screw blades 2, the screw shaft 1, and the outer cylinder 4, as it is driven by the rotating screw blades 2.

[0040] In the gravity dewatering section A, which is located directly below or near the inlet section 5, the water in the water-containing sludge is mainly discharged through the filtration holes 3 by gravity.

[0041] Subsequently, the flow path in the space enclosed by the screw shaft 1, screw blades 2, and outer cylinder 4 gradually narrows along the flow direction, so the water-containing sludge present in that space is gradually compressed, and the filtrate squeezed out by the compression is discharged from the filtration holes 3 of the medium-pressure dewatering section B and the high-pressure dewatering section C.

[0042] As this operation continues, fine sludge bridges F, as shown in Figure 6, begin to form on the inner surface of the outer cylinder 4 of the gravity dewatering section A, and the filtration holes 3 in this section begin to become blocked.

[0043] However, in the present invention, eight scrapers 8 are attached to the screw blades 2a, 2b, and 2c located in the gravity dewatering section A via bridging members 7 so as to be in close contact with the filter holes 3. As the screw blades 2 rotate, the scrapers 8 also rotate, and the bridge that is about to be formed is immediately scraped away, preventing blockage of the filter holes 3, and maintaining the moisture removal effect of the gravity dewatering section A.

[0044] Therefore, the moisture content of the dewatered cake discharged from the outlet 6 is not increased, and the desired dewatering capacity can be stably achieved.

[0045] Next, the method for attaching the bridging member 7 and the scraper 8 in the present invention will be described in detail.

[0046] The bridging members 7 shown in Figure 2 are joined to the sides near the tips of two adjacent pairs of screw blades 2a, 2b and 2b, 2c, which are located directly below the entrance 5. A total of eight bridging members 7 are used to make the connection.

[0047] However, the arrangement is not limited to this; the sides near the tips of a pair of screw blades 2a and 2b may be joined together with one to four bridging members. Alternatively, the upper and lower sides near the tips of two pairs of screw blades 2a, 2b and 2b, 2c may be joined together with two bridging members 7, for a total of four bridging members 7. Or, three bridging members 7 may be joined at equal intervals to the sides near the tips of two pairs of screw blades 2a, 2b and 2b, 2c, for a total of six bridging members 7.

[0048] Alternatively, the screw blade 2 adjacent to the outlet portion 6 side of screw blade 2c and the side surfaces near the tip of screw blade 2c may be joined by adding another bridging member 7. By using four screw blades in this way and joining a bridging member 7 to each of the three pairs of screw blades, there will be three times as many bridging members as there are bridging members 7 joined to a pair of screw blades 2a and 2b. By attaching a scraper 8 to each bridging member 7, the scraping frequency of the filtration holes 3 will increase, further preventing the filtration holes 3 from becoming blocked.

[0049] In the present invention, the joining position of the bridging member 7 is preferably symmetrical to the side surfaces near the tips of the opposing screw blades 2 located at the position of the gravity dewatering section A.

[0050] This is because, in the dewatering process in the medium-pressure dewatering section B or the high-pressure dewatering section C, the water content of the water-containing sludge decreases considerably, and the resistance to the rotation of the screw blades becomes considerably larger. If any structure other than the screw blades is present in such a position, it will create significant resistance when moving the water-containing sludge toward the outlet section 6, and in some cases, the rotation of the screw shaft 1 itself may be hindered. Therefore, it is preferable to attach the bridging member 7 to the screw blades 2 located at the gravity dewatering section A rather than at the medium-pressure dewatering section B or the high-pressure dewatering section C. [Industrial applicability]

[0051] This invention can be widely used to dewater sludge generated from various devices and obtain dewatered cake. [Explanation of Symbols]

[0052] 1. Screw shaft 2, 2a, 2b, 2c Screw blades 3 Filtration holes 4. Outer cylinder 5 Entrance 6 Exit section 7. Bridging member 8. Scraper 9 volts 10 nuts 11. Tip of the scraper 21, 31 Dehydration equipment A Gravity dewatering section B Medium-pressure dewatering section C High-pressure dewatering section F Bridge R rotation direction

Claims

1. It consists of a screw shaft that rotates by a driving means, screw blades attached spirally to the outer circumference of the screw shaft, and an outer cylinder having filtration holes surrounding the screw blades, and has an inlet at one end of the outer cylinder for introducing water-containing sludge and an outlet at the other end of the outer cylinder for discharging dewatered cake, and the flow path in the space enclosed by the screw shaft, the screw blades and the outer cylinder narrows from the inlet to the outlet. In a screw press type dewatering apparatus that rotates the screw shaft while compressing the water-containing sludge introduced from the inlet and discharging the filtrate from the filtration holes, and obtaining a dewatered cake from the outlet, A screw press type dewatering apparatus characterized in that a scraper that contacts the outer cylinder is attached to the screw blades, which are attached within a range of one-third or less of the total length from one end of the screw shaft on the inlet side.

2. The screw press type dewatering apparatus according to claim 1, wherein the sides near the tips of one or more pairs of opposing screw blades are joined by a bridging member, and the scraper made of an elastic material is attached to the bridging member.

3. The screw press type dewatering apparatus according to claim 2, wherein the sides near the tips of one or more pairs of screw blades facing each other are joined by a plurality of bridging members arranged at equal intervals, and the scraper is attached to each of the plurality of bridging members.

4. The screw press type dewatering apparatus according to claim 3, wherein the sides near the tips of a pair of opposing screw blades are joined by four bridging members arranged at equal intervals, and the sides near the tips of another pair of opposing screw blades adjacent to the aforementioned pair of screw blades are joined by four bridging members arranged at equal intervals, and the scraper is attached to each of the eight bridging members in total.

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