Screw press discharge section water-stopping mechanism 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 discharge part water stop mechanism for a screw press that prevents cleaning liquid from leaking from the discharge part of a filtration chamber during cleaning of an outer cylinder screen of the screw press, and a cleaning method using the same.

Background Art

[0002] Conventionally, after the dehydration operation of a screw press ends, outer cylinder screen cleaning is performed by injecting cleaning liquid toward the outer peripheral surface of the outer cylinder screen in order to eliminate clogging of the outer cylinder screen by sludge. As shown in FIG. 2 of Patent Document 1, a pressure plate for back pressure adjustment that is slidable in the axial direction is provided at a position facing the discharge part of the filtration chamber in the screw press, and the cake discharged from the discharge part is discharged while receiving the back pressure by the pressure plate. And during the cleaning of the outer cylinder 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 cylinder screen is cleaned in a state where the discharge part is closed.

[0003] Patent Document 2 discloses a technique in which a material supply port at the end of a tapered tube communicating with a barrel containing a rotatable screw conveyor can be sealed 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 so as to face the opening end of a screen casing provided with a rotatable screw shaft, and it is described that a plug case having an inner diameter substantially 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 Document 2

Patent Document 3

[0006] Conventionally, when cleaning the outer cylinder screen of a screw press, a pressing plate that is axially slidable was moved toward the discharge port of the filtration chamber, and cleaning was performed with the discharge port closed. However, as shown in Figure 2 of Patent Document 1, conventional pressing plates are tapered cone-shaped, expanding in diameter toward the discharge port. When the discharge port of the filtration chamber is closed with the pressing plate, the tapered surface of the pressing plate makes line contact with the corner (right-angle portion shown in the figure) of the end of the outer cylinder screen, which could damage the tapered surface of the pressing plate. Because the material could not be pressed with sufficient pressure, the discharge port could not be completely stopped, and when cleaning liquid was sprayed from outside the screen during outer cylinder screen cleaning, the cleaning liquid leaked out of the discharge port. The leaked cleaning liquid then flowed into the cake chute installed below the discharge port, increasing the moisture content of the dewatered cake in the chute. Consequently, there was a problem of reduced processing efficiency in the downstream equipment of the dewatering machine.

[0007] Patent Document 2 describes a technology that allows material to be supplied into a hopper while the inside of the apparatus is completely sealed by using a conical plug to close the material supply port at the end of a tapered tube. However, the conical plug is pushed back towards the inlet chamber by the material filling the tapered tube. Therefore, if cleaning fluid is supplied into the barrel and tapered tube, the conical plug is pushed back towards the inlet chamber by the cleaning fluid, causing the cleaning fluid to flow out from the material supply port into the inlet chamber. In other words, the conical plug does not function as a watertight mechanism. Furthermore, because the tapered material supply port is sealed with a tapered (conical) plug, it is necessary to ensure that the tapered surfaces are in close contact, thus requiring high precision of the parts. There is no description or suggestion regarding the cleaning of the apparatus.

[0008] Patent Document 3 describes a method for efficiently forming a plug made of cake by providing a plug case surrounding the back pressure plate, extending from the end of the screen casing. However, the addition of the plug case increases the range of movement of the back pressure plate when opening or closing the discharge section of the filtration chamber, requiring more time to return the back pressure plate to its predetermined position, and also increases the overall length of the device. Furthermore, because the generated cake is discharged through the inner surface of the plug case, the cake adheres to the inner surface of the plug case, and the accumulation of this cake hinders the discharge of cakes that are discharged later. In addition, since the outer diameter of the back pressure plate is designed to be the same as the inner diameter of the plug case, a high level of machining precision is required to fit it into the plug case. There is no description or suggestion regarding the cleaning of the device.

[0009] The present invention provides a discharge section shut-off mechanism for a screw press having an outer cylindrical screen with a rotatable screw shaft, and a cleaning method using the same, which involves moving a pressing plate opposite the discharge section of the filtration chamber toward the discharge section along the axial direction to clean the outer cylindrical screen while keeping the discharge section watertight. [Means for solving the problem]

[0010] The present invention relates to a screw press equipped with a pressing plate that is axially movable and tapered in diameter toward the discharge direction at the discharge section of a dewatered cake. By providing a base portion on the tapered surface of the pressing plate that has a pressing surface parallel to the discharge end surface of the outer cylinder screen, the pressing surface and the discharge end surface come into surface contact when the pressing plate is moved toward the discharge section of the filtration chamber, thereby enabling the discharge section to be closed in a watertight manner.

[0011] In a screw press equipped with a pressing plate that is axially movable and tapered in diameter toward the discharge direction at the discharge section for dewatered cake, the tapered surface of the pressing plate is provided with an insertion portion that can be fitted to the inner circumferential surface of the outer cylinder screen. A sealing member is provided on the contact surface between the insertion portion and the inner circumferential surface of the outer cylinder screen to close the discharge portion of the filtration chamber. As a result, when the pressure plate is moved to the discharge section of the filtration chamber, the insertion section fits into the inner circumferential surface of the outer cylinder screen, allowing the discharge section to be sealed in a watertight manner.

[0012] By providing a sealing member on the contact surface between the pressing surface and the discharge end surface of the outer cylinder screen, the discharge portion of the filtration chamber can be closed, thereby improving the watertightness of the discharge portion.

[0014] In a screw press that regenerates the filtration surface by spraying cleaning fluid from the outside of a cylindrical outer screen, the base portion of the pressing plate has a pressing surface parallel to the discharge end face of the outer screen on its tapered surface, or the pressing plate has an insertion portion that can be fitted to the inner circumferential surface of the outer screen on its tapered surface. By moving the pressing plate along the axial direction and cleaning the outer circumferential surface of the outer screen while closing the discharge part of the filtration chamber, the outer screen can be cleaned while the discharge part of the filtration chamber is watertightly closed, so that the cleaning fluid does not leak from the discharge part. [Effects of the Invention]

[0015] According to the present invention, by moving the pressing plate axially toward the discharge section of the filtration chamber and sealing the discharge section watertight, the cleaning liquid sprayed toward the outer cylinder screen during cleaning of the outer cylinder screen does not leak out of the discharge section. By preventing the leakage of the cleaning liquid, the cleaning liquid does not flow into the dewatered cake discharged into the cake chute installed below the discharge section, so the moisture content of the dewatered cake in the cake chute does not increase. Since the dewatered cake is transported to the downstream equipment of the screw press while maintaining a low moisture content, the overall processing efficiency of the equipment does not decrease. Furthermore, since the pressing plate is a modified version of the conventional pressing plate, major design changes are unnecessary, and there is no need to change the length of the screw press. Moreover, since a single pressing plate has both the function of applying back pressure to the discharged dewatered cake and the function of sealing the discharge section of the filtration chamber, there is no need to add any additional parts. Furthermore, although the base is provided on the tapered surface of the pressing plate, high precision is not required during manufacturing, as the pressing surface of the base only needs to be machined so that it makes surface contact with the discharge end face of the outer cylinder screen. [Brief explanation of the drawing]

[0016] [Figure 1] This is a partial longitudinal cross-sectional side view of the screw press according to the invention. [Figure 2] Also, it is an enlarged view of the discharge side of the screw press. [Figure 3] Also, it is an enlarged view of the discharge side of the screw press in another embodiment.

Embodiments for Carrying Out the Invention

[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 pedestal 2. This screw press 1 has a screw shaft 7 around which screw blades 6 are wound on a cylindrical outer cylinder screen 5 having a filtering surface on its periphery. The screw shaft 7 disposed inside the outer cylinder screen 5 increases its diameter in a tapered shape from the starting end side to the terminal end side, and the relative interval between the outer cylinder screen 5 and the screw shaft 7 is decreased in the extending direction.

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

[0019] The sludge supplied from the supply hole 9 flows into a filtering chamber 16 formed between the outer cylinder screen 5 and the screw shaft 7, is transferred toward the terminal end side by the screw blades 6, and is concentrated and dehydrated while separating filtrate from the outer cylinder screen 5. The dehydrated cake generated after concentration and dehydration is discharged from a discharge portion 12 located at the terminal end portion of the filtering chamber 16 and flows into a cake chute 17 installed below a pressing plate 13. On the other hand, the separated filtrate permeates through the outer cylinder screen 5, flows into a filtrate tank 18 provided below the outer cylinder screen 5, and is then discharged to the outside. The outer cylinder screen 5 may be rotatable as required.

[0020] FIG. 2 is an enlarged view of the discharge side of the screw press, and a pressing plate 13 is installed so as to face the discharge portion 12 of the filtration chamber 16. The pressing plate 13 is provided so as to be reciprocally movable in the axial direction (the left-right direction in FIG. 2) by a moving means 14. By adjusting the moving amount of the pressing plate 13 to change the opening degree of the discharge portion 12, an appropriate back pressure can be applied to the dewatered cake discharged from the discharge portion 12. In the present embodiment, a fluid pressure cylinder 15 such as an air cylinder or a hydraulic cylinder is used as the moving means 14. Note that the moving means is not particularly limited as long as it can constantly apply a back pressure to the dewatered cake discharged during the operation of the screw press 1.

[0021] The pressing plate 13 has a diameter that expands in a tapered shape toward the discharge direction of the dewatered cake, and a base portion 21 is formed on the tapered surface. The base portion 21 is a portion that expands in the vertical direction from the central axis and is located near the discharge side of the tapered surface. The base portion 21 has an outer diameter larger than the diameter of the inner peripheral surface 19 of the outer cylinder screen 5.

[0022] By configuring the base portion 21 in this way, when the pressing plate 13 is moved to the broken line portion shown in the figure, the tapered surface penetrates into the filtration chamber 16, and the pressing surface 24 formed on the vertical surface of the base portion 21 is in surface contact with the discharge side end surface 22 of the outer cylinder screen 5, applying a pressing force to the discharge side end surface 22. In the present embodiment, since the pressing surface 24 is formed parallel to the discharge side end surface 22 of the outer cylinder screen 5, the base portion 21 stops in a state where the pressing surface 24 is in surface contact with the discharge side end surface 22 when moved to the above position. Thereby, the discharge portion 12 is closed in a watertight manner, and leakage of liquid from the discharge portion 12 can be prevented.

[0023] In the present embodiment, after the dehydration operation is completed, the outer cylinder screen 5 is washed. The cleaning liquid is sprayed from the injection portion 26 of the annular cleaning device 23 provided at a predetermined interval from the outer peripheral surface of the outer cylinder screen 5 toward the outer peripheral surface of the outer cylinder screen 5 to regenerate the filtration surface. However, before the start of cleaning, the pressing plate 13 is moved toward the discharge portion 12 to close the discharge portion 12, so that the cleaning liquid flowing into the filtration chamber 16 does not leak to the outside from the discharge portion 12.

[0024] The discharge-side end face 22 of the outer cylinder screen 5 is part of the downstream frame 4 and is the surface facing the pressing plate 13. Furthermore, the discharge-side end face 22 extends vertically and is connected to the outer cylinder screen 5 via a rotating plate (not shown).

[0025] In this embodiment, a watertight sealing member 20A is provided on the discharge end face 22, and when the pressing plate 13 is moved toward the discharge section 12 (in the direction of the arrow shown in the figure), the pressing surface 24 of the base 21 presses against the sealing member 20A. When the pressing surface 24 presses against the sealing member 20A at the position of the dashed line shown in the figure, the pressing plate 13 and the discharge end face 22 are sealed in a watertight manner, so that cleaning fluid does not leak from the discharge section 12.

[0026] The sealing member 20A is determined according to the design conditions, such as installing a single seal formed in an annular shape to match the shape of the annular pressing surface 24, or installing divided seals in an annular shape at predetermined intervals. In addition, although the sealing member 20A is installed on the discharge end face 22 of the outer cylinder screen 5, it may also be installed on the pressing surface 24 side of the base 21, as a water-stopping effect can be obtained by providing it on the contact surface between the pressing surface 24 of the base 21 and the discharge end face 22.

[0027] In this embodiment, after the dewatering operation is completed, the outer cylinder screen 5 is cleaned to remove sludge clogging of the filtrate discharge holes (not shown) formed in the outer cylinder screen 5. After the dewatering operation is completed, the pressing plate 13 is moved to the position indicated by the dashed line in Figure 2, and cleaning liquid is sprayed from the spraying part 26 formed in the cleaning device 23 toward the outer surface of the outer cylinder screen 5. The cleaning liquid sprayed from outside the outer cylinder screen 5 passes through the outer cylinder screen 5, flows into the filtrate tank 18, and is then discharged to the outside. Note that the configuration of the cleaning device 23 is not limited to this.

[0028] Before starting the cleaning of the outer cylinder screen 5, the pressing plate 13 is moved axially toward the discharge section 12 using the moving means 14, thereby closing the discharge section 12. At this time, the pressing plate 13 is fixed with the pressing surface 24 of the base 21 pressing against the sealing member 20A installed on the discharge end face 22, so that the discharge section 12 is closed in a watertight manner.

[0029] In this state, even if cleaning liquid is sprayed from the cleaning device 23 toward the screen surface of the outer cylinder screen 5, the cleaning liquid that flows into the filtration chamber 16 via the outer cylinder screen 5 does not leak from the discharge section 12. Consequently, since cleaning liquid does not flow into the cake chute 17, the cleaning liquid does not mix with the dewatered cake discharged into the cake chute 17 after the dewatering operation is completed. As a result, the generated dewatered cake can be transported to downstream equipment (not shown) while maintaining a low moisture content, thereby improving the processing efficiency of the downstream equipment. By preventing the leakage of cleaning liquid from the discharge section 12, even if a chemical solution is used as the cleaning liquid, the chemical solution does not mix with the dewatered cake, and therefore the quality of the dewatered cake does not deteriorate.

[0030] Furthermore, the tapered surface may, if necessary, form an annular stepped portion (not shown), and a stepped portion having a smaller diameter than the inner circumferential surface 19 of the outer cylindrical screen 5 may be combined with the front of the base portion 21 (sludge supply side). In this configuration, by providing sealing members 20 on the pressing surface 24 formed vertically on the base portion 21 and on the stepped portion formed between the base portion 21 and the tapered surface, when the pressing plate 13 is moved toward the discharge portion 12, the pressing surface 24 and the stepped portion each make surface contact with the corner portion (right angle portion in Figure 2) formed between the discharge side end surface 22 and the discharge side end of the outer cylindrical screen 5, thereby providing a high water-stopping effect.

[0031] Figure 3 is an enlarged view of the discharge side of a screw press in another embodiment. In this embodiment, the base portion 21 of the pressing plate 13 is omitted, and an insertion portion 25 is formed on the tapered surface. Since the outer diameter of the insertion portion 25 is approximately the same as the diameter of the inner circumferential surface 19 of the outer cylinder screen 5, by moving the pressing plate 13 toward the discharge portion 12 (towards the position of the dashed line shown in the figure), the insertion portion 25 fits into the discharge portion 12. As a result, the discharge portion 12 is closed, and water is stopped.

[0032] In this configuration, a sealing member 20B is provided around the outer circumferential surface of the insertion portion 25 to enhance the watertightness of the discharge portion 12. By forming the sealing member 20B with an O-ring or the like, when the insertion portion 25 is fitted into the discharge portion 12, it elastically deforms and comes into close contact with the inner circumferential surface of the outer cylinder screen 5, thereby increasing watertightness. In this configuration as well, it is sufficient to provide the sealing member 20 at the contact surface between the insertion portion 25 and the outer cylinder screen 5, so the sealing member 20 may also be provided on the inner circumferential surface 19 side of the outer cylinder screen 5. It is desirable to install the sealing members 20A and 20B to enhance the watertightness of the discharge portion 12, but they may be omitted depending on the conditions.

[0033] Alternatively, the insertion portion 25 shown in Figure 3 and the base portion 21 shown in Figure 2 may be combined to create a configuration in which, when the pressing plate 13 is moved toward the discharge portion 12 during cleaning of the outer cylinder screen 5, both the space between the inner circumferential surface 19 of the outer cylinder screen 5 and the insertion portion 25, and the space between the pressing surface 24 of the base portion 21 and the discharge end surface 22, are watertight.

[0034] In addition, the screw press can be modified as appropriate depending on the configuration of the screw press, such as applying it to a screw press in which the screw shaft 7 is slidable in the axial direction, and closing the discharge section 12 by moving the screw shaft 7 to the sludge supply side using an axial moving mechanism of the screw shaft 7 (not shown) instead of the moving mechanism 14, or by installing a sealing 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 in an annular shape or in other shapes, and is not limited to this embodiment as long as it can close the discharge section 12.

[0035] The present invention is not limited to the embodiments described in detail above. Modifications can be made as appropriate without departing from the spirit of the invention. [Industrial applicability]

[0036] The screw press discharge section water-stopping mechanism of the present invention can be implemented by modifying a part of the pressing plate installed in conventional screw presses, and is therefore easily applicable to existing screw presses. Furthermore, since the generated dewatered cake can be transported to downstream equipment while maintaining a low moisture content, the overall operating time of the equipment can be reduced, resulting in energy savings. [Explanation of Symbols]

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

Claims

1. In a screw press equipped with a dewatered cake discharge section (12) and a pressing plate (13) that is axially movable and tapered in diameter toward the discharge direction, The tapered surface of the pressing plate (13) is provided with a base portion (21) having a pressing surface (24) parallel to the discharge end face (22) of the outer cylinder screen (5). A screw press discharge section water-stopping mechanism characterized by the following features.

2. In a screw press equipped with a dewatered cake discharge section (12) and a pressing plate (13) that is axially movable and tapered in diameter toward the discharge direction, The tapered surface of the pressing plate (13) is provided with an insertion portion (25) that can be fitted onto the inner circumferential surface (19) of the outer cylinder screen (5). A sealing member (20B) is provided on the contact surface between the insertion portion (25) and the inner circumferential surface (19) of the outer cylinder screen (5) to close the discharge portion (12) of the filtration chamber (16). A screw press discharge section water-stopping mechanism characterized by the following features.

3. A sealing member (20A) is provided on the contact surface between the pressing surface (24) and the discharge end surface (22) of the outer cylinder screen (5) to close the discharge section (12) of the filtration chamber (16). The discharge section water-stopping mechanism for a screw press according to feature 1.

4. In a screw press that regenerates the filtration surface by spraying a cleaning solution from the outside of a cylindrical outer screen (5), The base portion (21) has a tapered surface of the pressing plate (13) with a pressing surface (24) parallel to the discharge end surface (22) of the outer cylinder screen (5), or the tapered surface of the pressing plate (13) has an insertion portion (25) that can be fitted onto the inner circumferential surface (19) of the outer cylinder screen (5), The outer surface of the outer cylinder screen (5) is cleaned while the pressure plate (13) is moved along the axial direction to close the discharge port (12) of the filtration chamber (16). A cleaning method using a water-stopping mechanism for the discharge section of a screw press, characterized by the above.

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