Water stop mechanism of discharge part in screw press and cleaning method using the same

Abstract

To provide a water stop mechanism of a discharge part in a screw press which can prevent leakage of a cleaning liquid from a discharge part and prevent the cleaning liquid from flowing into a dehydrated cake discharged into a cake chute, by moving along an axial direction a pressing plate disposed to face the discharge part of a filtration chamber and cleaning an outer cylinder screen in a state where the discharge part is closed.SOLUTION: A screw press comprises a pressing plate 13 which is axially movable, expanded in diameter, tapered toward a discharge direction, and disposed in a discharge part 12 of a dehydrated cake. The screw press further comprises a base part 21 having a pressing surface 24 arranged on a tapered surface of the pressing plate 13, in parallel to a discharge-side end surface 22 of an outer cylindrical screen 5, and thereby, the discharge part 12 of a filtration chamber 16 can be water-tightly closed so as to be able to prevent the cleaning liquid from leaking from the discharge part 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a water-stopping mechanism for a discharge part of a screw press that prevents a cleaning liquid from leaking from the discharge part of a filtration chamber when cleaning an outer cylindrical screen of a screw press, and a cleaning method using the same. [Background technology]

[0002] Conventionally, after the dehydration operation of the screw press is completed, cleaning of the outer cylindrical screen is performed by spraying a cleaning liquid toward the outer peripheral surface of the outer cylindrical screen in order to remove clogging of the outer cylindrical screen caused by sludge. As shown in FIG. 2 of Patent Document 1, the screw press is provided with a back pressure adjusting pressure plate that can slide in the axial direction at a position facing the discharge part of the filtration chamber, and the cake discharged from the discharge part is discharged while receiving the back pressure from the pressure plate. During cleaning of the outer cylindrical screen, the pressure plate is slid toward the discharge part so that the cleaning liquid does not flow into the cake chute provided below the discharge part, and the outer cylindrical screen is washed with the discharge part closed.

[0003] Patent Document 2 discloses a technique for sealing a material supply port at the end of a tapered tube that communicates with a barrel containing a rotatable screw conveyor, with a conical plug that can move back and forth.

[0004] Patent Document 3 discloses a screw press in which a back pressure plate is arranged to face the open end of a screen casing in which a rotatable screw shaft is installed, and describes that a plug case having an inner diameter approximately the same as the outer diameter of the back pressure plate is provided around the back pressure plate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6555478 [Patent Document 2] Publication number 07-045599 [Patent Document 3] Patent No. 5548007 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally, when washing the outer cylinder screen of a screw press, a pressing plate that can slide in the axial direction is moved toward the discharge part of the filtration chamber to perform washing while the discharge part is closed. However, as shown in FIG. 2 of Patent Document 1, the conventional pressing plate is tapered cone-shaped with a diameter expanding toward the discharge part, and when the discharge part of the filtration chamber is closed with the pressing plate, the tapered surface of the pressing plate comes into line contact with the corner part (right angle part shown in the figure) at the end of the outer cylinder screen, so there is a possibility that the tapered surface of the pressing plate will be damaged. Since the member cannot be pressed with sufficient pressing force, the discharge part cannot be completely watertight, and when the washing liquid is sprayed from the outside of the screen during washing of the outer cylinder screen, the washing liquid leaks from the discharge part. The leaked washing liquid flows into the cake chute installed below the discharge part, increasing the moisture content of the dehydrated cake in the chute. As a result, there is a problem that the processing efficiency of the equipment downstream of the dehydrator decreases.

[0007] Patent Document 2 describes a technology that can supply material to the inside of a hopper while completely sealing the inside of the device by closing the material supply port at the end of the tapered tube using a conical plug, but the conical plug is pushed back toward the inlet chamber by the material filled in the tapered tube. Therefore, if a cleaning liquid is supplied into the barrel and the tapered tube, the conical plug is pushed back toward the inlet chamber by the cleaning liquid, and the cleaning liquid flows from the material supply port to the inlet chamber. In other words, the conical plug does not function as a watertight mechanism. In addition, since the tapered material supply port is sealed with a tapered (conical) plug, it is necessary to make the tapered surfaces tightly contact each other, which requires high part precision. There is no description or suggestion regarding cleaning of the device.

[0008] In Patent Document 3, a plug case surrounding a back pressure plate is provided so as to extend from the end of the screen casing, so that a plug made of cake can be efficiently formed. However, when the discharge part of the filtration chamber is opened or closed, the back pressure plate moves a large amount, so it takes time to return the back pressure plate to a predetermined position and the overall length of the device becomes long. In addition, since the plug case is provided, the generated cake is discharged through the inner surface of the plug case, so the cake adheres to the inner surface of the plug case and accumulates, preventing the discharge of cake that is discharged later. Furthermore, since the outer diameter of the back pressure plate is designed to be the same as the inner diameter of the plug case, machining precision is also required to fit it into the plug case. There is no description or suggestion regarding cleaning of the device.

[0009] The present invention provides a water-stopping mechanism for the discharge section of a screw press having an external cylindrical screen with a rotatable screw shaft installed inside, in which a pressure plate opposed to the discharge section of a filtration chamber is moved axially toward the discharge section to wash the external cylindrical screen while keeping the discharge section watertightly closed, and a cleaning method using the same. [Means for solving the problem]

[0010] The present invention relates to a screw press having a pressure plate that is axially movable at the discharge section of the dehydrated cake and has a tapered diameter expanding in the discharge direction.The tapered surface of the pressure plate is provided with a base having a pressing surface parallel to the discharge end face of the outer cylindrical screen.When the pressure plate is moved toward the discharge section of the filtration chamber, the pressing surface and the discharge end face come into surface contact, making it possible to close the discharge section watertightly.

[0011] In a screw press provided with a pressure plate that is axially movable at the discharge section of the dehydrated cake and that tapers in diameter in the discharge direction, the tapered surface of the pressure plate is provided with an insertion portion that can fit into the inner surface of the outer cylindrical screen, so that when the pressure plate is moved to the discharge section of the filtration chamber, the insertion portion fits into the inner surface of the outer cylindrical screen, and the discharge section can be closed watertightly.

[0012] By providing a seal member on the contact surface between the pressing surface and the discharge end surface of the outer cylindrical screen to close the discharge portion of the filtration chamber, the watertightness of the discharge portion can be improved.

[0013] By providing a seal member on the contact surface between the insertion portion and the inner peripheral surface of the outer cylindrical screen to close the discharge portion of the filtration chamber, the watertightness of the discharge portion can be improved.

[0014] In a screw press in which a cleaning liquid is sprayed from the outside of a cylindrical outer tube screen to regenerate the filtration surface, the tapered surface of the pressure plate has a base having a pressing surface parallel to the discharge end face of the outer tube screen, or the tapered surface of the pressure plate has an insertion portion that can fit into the inner surface of the outer tube screen, and the pressure plate is moved along the axial direction to clean the outer surface of the outer tube screen with the discharge portion of the filtration chamber closed, so that the outer tube screen can be cleaned with the discharge portion of the filtration chamber closed watertightly, and therefore the cleaning liquid does not leak from the discharge portion. Effect of the Invention

[0015] According to the present invention, the pressure plate is moved along the axial direction toward the discharge part of the filtration chamber to close the discharge part watertightly, so that the cleaning liquid sprayed toward the external cylindrical screen does not leak out from the discharge part to the outside when the external cylindrical screen is washed. By preventing the leakage of the cleaning liquid, the cleaning liquid does not flow into the dehydrated cake discharged into the cake chute installed below the discharge part, so that the moisture content of the dehydrated cake in the cake chute does not increase. Since the dehydrated cake is transported to the downstream equipment of the screw press while maintaining a low moisture content, the processing efficiency of the entire equipment does not decrease. In addition, since the pressure plate is a partly modified shape of the conventional pressure plate, no major design change is required, and there is no need to change the length of the screw press. In addition, since one pressure plate has both the effect of applying back pressure to the discharged dehydrated cake and the effect of water blocking the discharge part of the filtration chamber, there is no need to add any additional parts. Furthermore, a base is provided on the tapered surface of the pressure plate, but during production, the part can be processed so that the pressing surface of the base can come into surface contact with the discharge side end face of the outer cylindrical screen, so high part precision is not required. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a partial vertical sectional side view of a screw press according to the present invention. [Diagram 2] FIG. 2 is an enlarged view of the discharge side of the screw press. [Diagram 3] FIG. 11 is an enlarged view of the discharge side of a screw press according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] FIG. 1 is a cross-sectional view of a screw press according to the present invention. Reference numeral 1 denotes a screw press, which is supported by a front-stage frame 3 and a rear-stage frame 4 erected on a stand 2. This screw press 1 has a screw shaft 7 with a screw blade 6 wound around a cylindrical outer tube screen 5 having a filtering surface on its periphery. The diameter of the screw shaft 7 disposed inside the outer tube screen 5 increases in a tapered manner from the starting end to the terminal end, and the relative distance between the outer tube screen 5 and the screw shaft 7 decreases in the extension direction.

[0018] A sludge supply pipe 8 is connected to the front end of the screw shaft 7, and the supply pipe 8 communicates with a supply hole 9 of the screw shaft 7 that is opened at the starting end side of the outer cylindrical screen 5. A screw drive shaft 10 is connected to the rear end of the screw shaft 7, and a drive sprocket 11 is fitted onto the screw drive shaft 10. This sprocket 11 is driven by a screw driver (not shown) to rotate the screw shaft 7.

[0019] Sludge supplied from the supply hole 9 flows into the filtration chamber 16 formed between the external cylindrical screen 5 and the screw shaft 7, is transported toward the terminal end by the screw blades 6, and is concentrated and dehydrated while the filtrate is separated from the external cylindrical screen 5. The dehydrated cake produced after concentration and dehydration is discharged from the discharge section 12 located at the terminal end of the filtration chamber 16 and flows into the cake chute 17 installed below the pressure plate 13. Meanwhile, the separated filtrate passes through the external cylindrical screen 5 and flows into the filtrate tank 18 installed below the external cylindrical screen 5, and is then discharged to the outside. The external cylindrical screen 5 may be rotatable as necessary.

[0020] 2 is an enlarged view of the discharge side of the screw press, in which a pressure plate 13 is installed so as to face the discharge section 12 of the filtration chamber 16. The pressure plate 13 is provided so as to be freely reciprocable in the axial direction (left and right direction in FIG. 2) by a moving means 14, and by adjusting the amount of movement of the pressure plate 13 to change the opening degree of the discharge section 12, an appropriate back pressure can be applied to the dehydrated cake discharged from the discharge section 12. In this embodiment, a fluid pressure cylinder 15 such as an air cylinder or a hydraulic cylinder is used as the moving means 14. Note that there is no particular limitation on the moving means as long as it can constantly apply back pressure to the dehydrated cake discharged during operation of the screw press 1.

[0021] The pressure plate 13 tapers in the direction in which the dehydrated cake is discharged, and the tapered surface forms a base 21. The base 21 is a portion whose diameter increases vertically from the central axis, and is located near the discharge side of the tapered surface. The base 21 has an outer diameter larger than the diameter of the inner peripheral surface 19 of the outer cylindrical screen 5.

[0022] By configuring the base 21 in this manner, when the pressure plate 13 is moved to the dashed line portion shown in the figure, the tapered surface is inserted into the filtration chamber 16, and the pressing surface 24 formed on the vertical surface of the base 21 comes into surface contact with the discharge side end face 22 of the external cylindrical screen 5, applying a pressing force to the discharge side end face 22. In this embodiment, the pressing surface 24 is formed parallel to the discharge side end face 22 of the external cylindrical screen 5, so that when the base 21 is moved to the above position, it comes to rest with the pressing surface 24 in surface contact with the discharge side end face 22. This causes the discharge section 12 to be closed watertightly, and leakage of liquid from the discharge section 12 can be prevented.

[0023] In this embodiment, after the spin-drying operation is completed, the outer tube screen 5 is cleaned by spraying a cleaning liquid onto the outer peripheral surface of the outer tube screen 5 from the spray section 26 of the annular cleaning device 23, which is provided at a predetermined distance from the outer peripheral surface of the outer tube screen 5, to regenerate the filtration surface. However, by moving the pressure plate 13 toward the discharge section 12 before cleaning begins to close the discharge section 12, the cleaning liquid that has flowed into the filtration chamber 16 does not leak out from the discharge section 12 to the outside.

[0024] The discharge side end surface 22 of the outer cylindrical screen 5 is a part of the rear frame 4 and faces the pressing plate 13. The discharge side end surface 22 extends vertically and is connected to the outer cylindrical screen 5 via a rotating plate (not shown).

[0025] In this embodiment, a seal member 20A having water-stopping properties is provided on the discharge side end face 22, and when the pressure plate 13 is moved toward the discharge section 12 (in the direction of the illustrated arrow), the pressing surface 24 of the base 21 presses the seal member 20A. When the pressing surface 24 presses the seal member 20A at the position of the dashed line shown in the figure, the pressure plate 13 and the discharge side end face 22 are closed watertightly, so that the cleaning liquid does not leak from the discharge section 12.

[0026] The seal member 20A is determined appropriately according to design conditions, for example, by installing a single seal formed in a circular shape to match the shape of the circular pressing surface 24, or by installing divided seals in a circular shape at predetermined intervals. Also, although the seal member 20A is installed on the discharge side end surface 22 of the outer cylindrical screen 5, it may be installed on the side of the pressing surface 24 of the base 21 because a water-stopping effect can be obtained by providing the seal member 20A on the contact surface between the pressing surface 24 of the base 21 and the discharge side end surface 22.

[0027] In this embodiment, after the spin-drying operation is completed, the outer cylindrical screen 5 is washed to remove clogging of filtrate discharge holes (not shown) formed in the outer cylindrical screen 5 due to sludge. After the spin-drying operation is completed, the pressing plate 13 is moved to the position indicated by the dashed line in FIG. 2, and a washing liquid is sprayed from a spraying portion 26 formed in the washing device 23 toward the outer peripheral surface of the outer cylindrical screen 5. The washing liquid sprayed from the outside of the outer cylindrical screen 5 passes through the outer cylindrical screen 5, flows into the filtrate tank 18, and is discharged directly to the outside. Note that the form of the washing device 23 is not limited to this.

[0028] Before starting cleaning of the outer cylindrical screen 5, the pressing plate 13 is moved axially toward the discharge part 12 using the moving means 14 to close the discharge part 12. At this time, the pressing plate 13 is fixed in a state in which the pressing surface 24 of the base 21 presses the seal member 20A installed on the discharge side end face 22, so that the discharge part 12 is closed watertightly.

[0029] In this state, even if the washing liquid is sprayed from the washing device 23 toward the screen surface of the outer cylindrical screen 5, the washing liquid that has flowed into the filtration chamber 16 through the outer cylindrical screen 5 does not leak from the discharge section 12. Accordingly, the washing liquid does not flow into the cake chute 17, so the washing liquid does not mix with the dehydrated cake discharged into the cake chute 17 after the dehydration operation is completed. This allows the generated dehydrated cake to be transported to a downstream equipment (not shown) while maintaining a low moisture content, thereby improving the processing efficiency of the downstream equipment. By preventing the washing liquid from leaking from the discharge section 12, even if a chemical solution is used as the washing liquid, the chemical solution does not mix with the dehydrated cake, so the quality of the dehydrated cake does not deteriorate.

[0030] If necessary, the tapered surface may be formed with an annular step (not shown) and combined with a step having a smaller diameter than the inner peripheral surface 19 of the external cylindrical screen 5 in front of the base 21 (sludge supply side). In this embodiment, by providing the seal members 20 on the pressing surface 24 formed in the vertical direction of the base 21 and on the step formed between the base 21 and the tapered surface, when the pressure plate 13 is moved toward the discharge section 12, the pressing surface 24 and the step come into surface contact with the corner (right angle in FIG. 2) formed by the discharge side end face 22 and the discharge side end of the external cylindrical screen 5, thereby achieving a high water-stopping effect.

[0031] FIG. 3 is an enlarged view of the discharge side of a screw press in another embodiment. The pressing plate 13 does not have the base portion 21 in this embodiment, and has an insertion portion 25 formed on the tapered surface. Since the outer diameter of the insertion portion 25 is substantially the same as the diameter of the inner peripheral surface 19 of the outer cylindrical screen 5, the insertion portion 25 fits into the discharge portion 12 by moving the pressing plate 13 toward the discharge portion 12 (toward the position of the dashed line shown in the figure). This closes the discharge portion 12 and stops water flow.

[0032] In this embodiment, a seal member 20B is provided around the outer peripheral surface of the insertion portion 25 to improve the watertightness of the discharge portion 12. By forming the seal member 20B with an O-ring or the like, when the insertion portion 25 is fitted into the discharge portion 12, it is elastically deformed and comes into close contact with the inner peripheral surface of the outer cylindrical screen 5, thereby improving watertightness. Even in this embodiment, it is only necessary to provide the seal member 20 on the contact surface between the insertion portion 25 and the outer cylindrical screen 5, so the seal member 20 may be provided on the inner peripheral surface 19 side of the outer cylindrical screen 5. Note that it is preferable to provide the seal members 20A and 20B to improve the watertightness of the discharge portion 12, but they may be omitted depending on the conditions.

[0033] In addition, by combining the insertion portion 25 shown in Figure 3 with the base 21 shown in Figure 2, when the pressure plate 13 is moved toward the discharge portion 12 during cleaning of the outer tube screen 5, both the area between the inner surface 19 of the outer tube screen 5 and the insertion portion 25, and the area between the pressing surface 24 of the base 21 and the discharge side end face 22 may be made watertight.

[0034] In addition, the present invention can be applied to a screw press in which the screw shaft 7 is slidable in the axial direction, and the discharge section 12 can be closed by moving the screw shaft 7 to the sludge supply side by an axial moving means for the screw shaft 7 (not shown) instead of the moving means 14, or by installing a seal member 20 at the end of the screw shaft 7 and moving the screw shaft 7 toward the sludge supply side to close the discharge section 12. The pressing plate 13 can also be formed such that the outer peripheral surfaces of the base 21 and the insertion portion 25 are annular or of another shape, and is not limited to this embodiment as long as it is a shape that can close the discharge section 12.

[0035] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention. [Industrial Applicability]

[0036] The water-stop mechanism for the discharge section of the screw press of the present invention can be implemented by modifying a part of the pressure plate installed in a conventional screw press, and therefore can be easily applied to existing screw presses. In addition, the generated dehydrated cake can be transported to the downstream equipment while maintaining a low moisture content, which reduces the operating time of the entire equipment and contributes to energy saving. [Explanation of symbols]

[0037] 1. Screw press 5. Outer cylinder screen 12 Discharge section 13 Pressure plate 16 Filtration Room 19 Inner surface 20A, 20B Seal material 21 Base 22 Discharge side end face 24 Pressure surface 25 Insertion part

Claims

1. In a screw press, a pressing plate (13) is provided at a discharge section (12) of a dewatered cake, the pressing plate (13) being movable in an axial direction and tapering in diameter toward the discharge direction, The pressing plate (13) has a base (21) having a pressing surface (24) parallel to the discharge side end surface (22) of the outer cylindrical screen (5) on the tapered surface. A water-stopping mechanism for the discharge section of a screw press.

2. In a screw press, a pressing plate (13) is provided at a discharge section (12) of a dewatered cake, the pressing plate (13) being movable in an axial direction and tapering in diameter toward the discharge direction, The tapered surface of the pressure plate (13) is provided with an insertion portion (25) that can be fitted into the inner peripheral surface (19) of the outer cylindrical screen (5). A water-stopping mechanism for the discharge section of a screw press.

3. A seal member (20A) is provided on the contact surface between the pressing surface (24) and the discharge end surface (22) of the outer cylindrical screen (5) to close the discharge portion (12) of the filtration chamber (16).

2. The water blocking mechanism for a discharge section of a screw press according to claim 1.

4. A seal member (20B) is provided on the contact surface between the insertion portion (25) and the inner peripheral surface (19) of the outer cylindrical screen (5) to close the discharge portion (12) of the filtration chamber (16).

3. The water blocking mechanism for a discharge section of a screw press according to claim 2.

5. In a screw press in which a cleaning liquid is sprayed from the outside of a cylindrical outer screen (5) to regenerate the filtering surface, a base (21) having a pressing surface (24) parallel to the discharge end surface (22) of the outer cylindrical screen (5) on the tapered surface of the pressing plate (13), or a through-hole (25) that can be fitted into the inner peripheral surface (19) of the outer cylindrical screen (5) on the tapered surface of the pressing plate (13); The pressure plate (13) is moved along the axial direction to close the discharge portion (12) of the filtration chamber (16) and wash the outer peripheral surface of the outer cylindrical screen (5).

2. A cleaning method using a water blocking mechanism for the discharge section of a screw press.

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