JP2008307535A - Apparatus for dewatering sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for dewatering sludge which enables flocculated sludge to be formed into a dewatered cake at high efficiency without being finely grained when supplied to a filter cylinder. <P>SOLUTION: In the apparatus A for dewatering the sludge, the sludge and a flocculating agent are mixed under stirring in a flocculation reactor 5 to form the flocculated sludge. The flocculated sludge is supplied into a filter cylinder 71 of a vertical type screw press 7 through a receiving port 76 provided on the lower part of the filter cylinder 71, and is dewatered by squeezing, while being conveyed upward in the filter cylinder 71 by the rotation of a screw 72 disposed in the filter cylinder 71. The flocculation reactor 5 is disposed above the receiving port 76. A supply pipe 6 is provided for supplying the flocculated sludge from the flocculation reactor 5 to the receiving port 76. The flocculated sludge is supplied into the filter cylinder 71 under pressure, while a state, where the flocculated sludge is accumulated in the supply pipe 6, is maintained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dewatering apparatus for sludge generated mainly during dredging work for dam lakes, harbors and rivers, tunnel excavation work, and the like.

  The mixture of water, clay, silt, etc. (hereinafter referred to as “sludge”) generated during dredging work in dam lakes, harbors and rivers, tunnel excavation work, etc., is separated into water by a dehydration processing device to form dehydrated cake. The sludge and flocculant are stirred and mixed in the agglomeration reaction tank to produce agglomerated sludge (floc), which is supplied into the filter cylinder of the screw press, and the filter cylinder is rotated by rotation of the screw disposed in the filter cylinder. It is pressed and dehydrated while being transported inside to form a dehydrated cake.

  The screw press includes a horizontal type in which the filter cylinder is elongated in the horizontal direction and a vertical type in which the filter cylinder is elongated in the vertical direction. Vertical screw presses that can be installed in confined spaces are often difficult in mountainous areas where dredging works are performed on dam lakes and in urban areas where tunnel excavation works. Are preferably used.

In the vertical screw press, the coagulated sludge supplied into the filter tube from the receiving port provided at the lower part of the filter tube is squeezed and dehydrated while being conveyed upward in the filter tube by the rotation of the screw. An object to be pressed (dehydrated cake) pushed upward from the discharge port at the upper end is discharged to the outside (see, for example, Patent Document 1). The agglomerated sludge is pressurized by a pump and supplied into the filter cylinder.
JP 2005-74384 A

  However, when the coagulated sludge is pressurized with a pump and supplied into the filter cylinder, the coagulated sludge is pulverized and fine particles are produced when passing through the pump. Since the fine sludge fraction passes through (leaks) the mesh of the filter cylinder and is discharged together with the filtrate, there is a problem that the production efficiency of the dehydrated cake is lowered.

  In view of the above circumstances, the present invention provides a sludge dewatering apparatus capable of increasing the efficiency of dewatered cake generation without agglomerating sludge when supplied to a filter tube. With the goal.

  In the present invention, sludge and flocculant are stirred and mixed in a flocculation reaction tank to produce flocculated sludge, and the flocculated sludge is supplied from a receiving port provided at a lower portion of the filter cylinder in a filter cylinder of a vertical screw press. In the sludge dewatering apparatus, the aggregated sludge is compressed and dehydrated while being transported upward in the filter cylinder by the rotation of a screw disposed in the filter cylinder. A reaction tank is provided, and a supply pipe for supplying the coagulated sludge from the coagulation reaction tank to the receiving port is maintained, and the state in which the coagulated sludge stays in the supply pipe is maintained. It is characterized by supplying pressure.

  According to the present invention, flocculation is aggregated in a supply pipe for supplying flocculated sludge (floc) from a flocculation reaction tank disposed above a receiving port of the flocculated sludge to a filter tube of a vertical screw press toward the receiving port. Maintains sludge retention. Then, the coagulated sludge is pressurized and supplied into the filter cylinder by the own weight of the coagulated sludge itself staying in the supply pipe. Therefore, since it is not necessary to use a pump to press the coagulated sludge, the coagulated sludge is hardly finely divided from the coagulation reaction tank to the filter tube. Accordingly, it is possible to improve the production efficiency of the dehydrated cake.

  In the present invention, it is preferable to maintain a state where the height of the coagulated sludge staying in the supply pipe is within a predetermined range.

  In this case, the pressure when supplying the coagulated sludge under pressure into the filter cylinder is within a predetermined range. Therefore, it is possible to press and supply the coagulated sludge at an appropriate pressure in the filter cylinder.

  A sludge dewatering apparatus according to an embodiment of the present invention will be described. With reference to FIG. 1, this sludge dewatering apparatus A mainly includes a sludge storage tank (raw mud tank) 1, a line mixer 2, an anionic flocculant supply unit 3, a cationic flocculant supply unit 4, and an agglutination reaction. The tank 5 is composed of a supply pipe 6, a vertical screw press 7, and a filtrate treatment tank 8.

  The sludge storage tank 1 stores sludge whose concentration has been adjusted. Sludge is a mixture of water, clay, silt, etc., from which gravels and sand have been removed from sludge generated during dredging work in dam lakes, harbors and rivers, tunnel excavation work, etc. The sludge is appropriately diluted with water so that its moisture content is about 80% and the concentration is adjusted. Moreover, it is preferable to mix the fly ash of about 10% of sludge solid content in the sludge from the viewpoint of solidification and enhancing the coagulation effect described later. The sludge stored in the sludge storage tank 1 is stirred by a stirring blade that is rotationally driven by a motor M in order to prevent sedimentation. The sludge stored in the sludge storage tank 1 is discharged by the pump P <b> 1 and is pumped toward the agglomeration reaction tank 5 through the pipeline 11.

  The line mixer 2 is interposed in a pipeline 11 that connects between the sludge storage tank 1 and the agglomeration reaction tank 5. The line mixer 2 is a static mixer in which a spiral baffle plate is provided in a pipe, and stirs the sludge discharged from the sludge storage tank 1 by the pump P1 and pumped through the pipeline 11.

  The anionic flocculant supply unit 3 mainly includes an anionic flocculant dissolution tank 31 and two communicating anionic flocculant storage tanks 32. The anionic flocculant dissolution tank 31 mixes and stirs the anionic flocculant supplied from a feeder (not shown) and the fresh water supplied from the fresh water tank 33 with a stirring blade that is rotationally driven by a motor M, Dissolve anionic flocculants. The dissolved anionic flocculant (hereinafter referred to as an anionic flocculant) is discharged by the pump P2 and supplied to the anionic flocculant reservoir 32. The anionic flocculant storage tank 32 stores the anionic dissolution flocculant in the tank while being stirred by a stirring blade that is rotationally driven by the motor M.

  The anionic flocculating agent stored in one anionic flocculating agent storage tank 32 is discharged by the pump P3 and is provided at the inlet (first inlet) provided in the portion of the pipe line 11 upstream from the line mixer 2. ) Is introduced into the pipe line 11 from 12 and is agitated and mixed with sludge by the line mixer 2. When an anionic flocculant is mixed with sludge, the viscosity increases. For this reason, if the anionic dissolution flocculant is excessively charged from the inlet 12, the sludge cannot be pumped to the aggregation reaction tank 5. Therefore, the amount of the anionic dissolution flocculant charged from the charging port 12 is set to such an amount that the sludge can be pumped to the aggregation reaction tank 5. The anionic dissolution flocculant stored in the other anionic flocculant storage tank 32 is discharged by the pump P4 and enters the aggregation reaction tank 5 from the input port (second input port) 51 provided in the aggregation reaction tank 5. It is thrown into. The input amount of the anionic dissolution flocculant from the input port 51 was obtained by subtracting the input amount of the anionic dissolution flocculant from the input port 12 from the amount of the anionic dissolution flocculant required to increase the sludge aggregation effect. Set to quantity.

  The cationic flocculant supply unit 4 is mainly composed of a cationic flocculant dissolution tank 41 and a cationic flocculant storage tank 42. The cationic flocculant dissolution tank 41 mixes and stirs the cationic flocculant supplied from a feeder (not shown) and the fresh water supplied from the fresh water tank 33 with a stirring blade that is rotationally driven by the motor M, Dissolve the cationic flocculant. The dissolved cationic flocculant (hereinafter referred to as “cationic flocculant”) is discharged by the pump P5 and supplied to the cationic flocculant reservoir 42. The cationic flocculant storage tank 42 stores the cationic dissolved flocculant in the tank while being stirred by a stirring blade that is rotationally driven by the motor M.

  The cationic dissolution flocculant stored in the cationic flocculant storage tank 42 is discharged by the pump P6 and charged into the agglomeration reaction tank 5 from the charging port 52 provided downstream from the charging port 51 of the aggregation reaction tank 5. Is done. From the inlet 52, an amount of a cationic dissolution flocculant necessary for increasing the sludge aggregation effect is charged.

  Although the details of the agglomeration reaction tank 5 are not shown, the rotating shaft on which the stirring blades are formed is driven to rotate by the motor M to stir the staying matter staying inside, and the staying matter is moved from the upstream side to the downstream side. It is a two-shaft paddle mixer that is transported to. In addition, a rotating shaft having a feeding blade formed in the agglomeration reaction tank 5 may be provided, and the staying material may be transferred by rotating the shaft by a motor M. The agglomeration reaction tank 5 is disposed at the same height as the upper part of the vertical screw press 7 by the gantry 53.

  Sludge that has been agitated and mixed with the anionic flocculant in the line mixer 2 and has agglomerated to some extent to increase the viscosity is supplied into the agglomeration reaction tank 5 from the receiving port 54. The sludge supplied into the agglomeration reaction tank 5 is agitated by the stirring blade as a stagnant substance and is transferred to the downstream side by the feed blade, and the anionic dissolution flocculant charged from the inlet 51 and the downstream side thereof. By sequentially mixing and reacting with the cationic dissolving flocculant charged from the charging port 52, the agglomeration further proceeds to become agglomerated sludge (floc).

  The side wall on the downstream side of the tank where the stirring blade and the feed blade rotate as necessary is a weir 55, and the aggregated sludge overflowing the weir 55 is provided at the discharge port 56 provided at the bottom of the aggregation reaction tank 5. Falls downward from An inclined screen 57 is disposed immediately below the discharge port 56. The inclined screen 57 is a screen for draining in which a lot of fine meshes are formed, and is inclined on a receiving box. The liquid and fine particles that have passed through the mesh of the inclined screen 57 are sent to the filtrate treatment tank 8 through a receiving box. On the other hand, the coagulated sludge that cannot pass through the mesh of the inclined screen 57 falls into the supply pipe 6.

  The supply pipe 6 is a pipe for supplying the coagulated sludge from the coagulation reaction tank 5 to the vertical screw press 7 and extends mainly in the vertical direction. The coagulation sludge discharged from the discharge port 56 of the coagulation reaction tank 5 is the upper part thereof. Accept from the inside. The supply pipe 6 or the agglomeration reaction tank 5 is provided with an opening (not shown) communicating with the outside at the upper portion thereof, and air freely passes through this opening, and the pressure in the supply pipe 6 is changed to the atmospheric pressure. It is supposed to be equal.

  The supply pipe 6 has a thin sub pipe 62 that branches from the main pipe 61 and extends in the vertical direction separately from the thick main pipe 61 that communicates the aggregation reaction tank 5 and the vertical screw press 7. The sub-pipe 62 is provided with two high and low interface sensors 63 and 64. The interface sensors 63 and 64 detect whether or not the height of the interface between the coagulated sludge and water exceeds a predetermined height. By providing the two high and low interface sensors 63 and 64 in this way, it is possible to maintain a state where the height of the coagulated sludge staying in the supply pipe 6 is within a predetermined range. Specifically, when it is detected by the interface sensor 63 at a high position that the height of the coagulated sludge staying in the supply pipe 6 exceeds the upper limit, the pump P1 is stopped and the sludge storage tank 1 Stop supplying sludge. On the other hand, when it is detected by the interface sensor 64 at a low position that the height of the coagulated sludge staying in the supply pipe 6 is lower than the lower limit, the output of the pump P1 is increased and the sludge from the sludge storage tank 1 is increased. Increase supply. The setting of the upper limit and the lower limit of the height of the coagulated sludge staying in the supply pipe 6 will be described later.

  The vertical screw press 7 includes a filter cylinder 71 whose longitudinal direction is the longitudinal direction, a screw 72 rotatably disposed in the filter cylinder 71, and a gap S in the horizontal direction so as to cover the periphery of the filter cylinder 71. The aggregated sludge supplied to the filter cylinder 71 is compressed and dehydrated while being conveyed upward by the screw 72, and the separated water is discharged from the filter cylinder 71 into the gap S.

  The vertical screw press 7 has a quadrangular columnar frame 74 composed of columns, beams, and the like and having a vertical direction as a longitudinal direction, and a bottom plate 75 is horizontally provided below the frame 74. On the bottom plate 75, a cylindrical filter tube 71 formed of punching metal or the like is erected. The cover cylinder 73 is composed of a shield plate attached so that the lower end is in contact with the bottom plate 75 between the vertical columns constituting the frame body 74. A receiving port 76 is provided at the lower portion of the filter cylinder 71, and the coagulated sludge supplied from the supply pipe 6 is introduced into the filter cylinder 71 from the receiving port 76. A reinforcing frame is provided on the outer peripheral surface of the filter cylinder 71.

  A screw 72 is rotatably inserted into the filter cylinder 71. The screw 72 includes a tapered screw shaft that gradually increases in diameter from the lower end side to the upper end side of the filter tube 71 and a helical screw blade fixed to the outer peripheral surface of the screw shaft. The screw 72 is rotationally driven by a motor M provided above the filter cylinder 71.

  When the screw 72 is rotated, the coagulated sludge received from the receiving port 76 is conveyed upward from below the filter cylinder 71 by the feeding action by the screw blades. Since the space between the filter cylinder 71 and the screw shaft is gradually narrowed upward, the coagulated sludge is squeezed while being conveyed upward of the filter cylinder 71. The moisture of the coagulated sludge is squeezed out through the filter cylinder 71, falls in the gap S as a filtrate, and is discharged to the filtrate treatment tank 8 through an opening (not shown) formed in the bottom plate 75 and a water collecting tank 77. Is done. Further, a water spray pipe 78 for spraying water to clean the outer surface of the filter cylinder 71 is provided, and this water is similarly discharged to the filtrate treatment tank 8. A discharge port 79 a is opened on the bottom surface of the discharge chamber 79 connected to the upper end of the filter cylinder 71. The dewatered cake C, which is the dewatered agglomerated sludge, is pushed out from the discharge port 79a to the discharge chamber 79 and discharged to the outside through the discharge port chute 79b. Further, a baffle plate 79d is provided above the discharge port 79a in a state of being biased toward the discharge port 79a via an air cylinder 79c, and the dehydrated cake C is pushed up while the baffle plate 79d is pushed up. More discharged. Then, the cylinder pressure of the air cylinder 79c in this state is measured, and this is used as an indirect index representing the strength and moisture content of the dewatered cake C for the operation management of the entire sludge dewatering apparatus A.

  Here, the upper limit and the lower limit of the height of the coagulated sludge staying in the supply pipe 6 described above are those of the coagulated sludge supplied to the screw press 7 such as the fly ash addition ratio, the coagulant addition ratio, and the coagulated sludge concentration. According to the properties and the operating conditions of the vertical screw press 7 (rotational speed of the screw 72), the range is set as a range where a dehydrated cake C having a predetermined range of strength or moisture content can be obtained.

  When the agglomerated sludge moves upward in the filter cylinder 71, it gradually shifts from a liquid property that is moved upward by pressurization from below to a solid property that is moved upward by a mechanical action by a screw blade. If the height of the coagulated sludge in the supply pipe 6 is within the range having a liquid property in the filter cylinder 71, the coagulated sludge can be transferred above the height of the coagulated sludge in the supply pipe 6. It becomes difficult. For this reason, the lower limit of the height of the coagulated sludge staying in the supply pipe 6 needs to be positioned above the range of the height having liquid properties in the filter cylinder 71.

  On the other hand, the upper limit is an air cylinder that energizes the strength and moisture content of the dewatered cake C and the baffle plate 79d that indirectly represents the dewatered cake C so that the dewatered cake C is not excessively compressed and blocked in the filter cylinder 71. It is set based on indices such as the cylinder pressure of 79c and the rotational torque of the screw 72.

  The filtrate treatment tank 8 treats the wastewater comprising the filtrate discharged from the vertical screw press 7 and the liquid that has passed through the mesh of the inclined screen 57. In the drainage, a small amount of fine sludge particles that have passed through the fine holes formed in the filter cylinder 71 and the inclined screen 57 also remain.

  The filtrate treatment tank 8 includes a precipitation tank 81 and a drain tank 82. The sedimentation tank 81 receives drainage. The fine particles of sludge contained in the waste water are precipitated with the passage of time and are deposited at the bottom of the settling tank 81. A flocculant may be added to agglomerate the sludge fine particles to promote precipitation. Sludge fine particles settled on the bottom of the settling tank 81 are discharged by the pump P7 and sent back into the pipe line 11 in the portion between the line mixer 2 and the agglomeration reaction tank 5. In addition, you may send back in the pipe line 11 of the part between the sludge storage tank 1 and the line mixer 2, or in the sludge storage tank 1. FIG.

  A weir 83 is provided between the settling tank 81 and the drainage tank 82, and the supernatant of water stored in the settling tank 81 passes through the weir 83 and is discharged to the drainage tank 82. The wastewater stored in the drainage tank 82 is discharged by the pump P8 and sent to the miscellaneous drainage tank 9.

  The drain tank 82 is provided with a float switch (not shown). This float switch is a level sensor that detects whether or not the water level of the drainage tank 82 is within a predetermined range. When the water level exceeds the upper limit of the predetermined range, the pump P1 is stopped and the sludge storage tank Stop the supply of sludge from 1. On the other hand, when the water level falls below the lower limit of the predetermined range, the pump P8 is stopped, and the transfer of drainage from the drainage tank 82 to the miscellaneous drainage tank 9 is stopped.

  By the way, in the vertical screw press 7, in order to assist the agglomerated sludge to move upward in the filter cylinder 71, it is necessary to pressurize and supply the agglomerated sludge to the filter cylinder 71. Here, when the flocculation reaction tank 5 is installed on the ground, it is necessary to pump the flocculated sludge from the flocculation reaction tank 5 to the filter tube 71. And agglomerated sludge is grind | pulverized with a pump, and a fine particle part arises. Since the fine sludge content passes through the filter cylinder 71 and is discharged to the filtrate treatment tank 8, it is necessary to send it back and perform the treatment again, resulting in poor dewatered cake production efficiency.

  In contrast, in the sludge dewatering apparatus A according to the present embodiment, the agglomeration reaction tank 5 is positioned at the same height as the upper part of the vertical screw press 7 by the gantry 53, so the bottom of the agglomeration reaction tank 5 The supply pipe 6 that communicates the discharge port 56 and the receiving port 76 provided at the lower part of the filter cylinder 71 is long in the vertical direction. By maintaining the state in which the aggregated sludge stays in the supply pipe 6, the aggregated sludge is pressurized and supplied into the filter cylinder 71 of the vertical screw press 7 by its own weight. That is, the coagulated sludge that has fallen into the supply pipe 6 from the discharge port 56 of the coagulation reaction tank 5 is sent toward the filter cylinder 71 by its own weight and the coagulated sludge that falls thereafter. Therefore, unlike the case of pumping, almost no sludge fine particles are produced, and the production efficiency of the dehydrated cake is improved.

  Further, in the sludge dewatering apparatus A, the state where the height of the coagulated sludge staying in the supply pipe 6 is within a predetermined range is maintained using the interface sensors 63 and 64, and the coagulated sludge is appropriately stored in the filter cylinder 71. It can be supplied at a reasonable pressure. The operation of the pump P1 based on the detection results of the interface sensors 63 and 64 may be automated using a control means including a CPU or the like, or may be performed by a worker who has heard a warning sound for notifying the detection results. .

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the sludge dehydration processing apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sludge storage tank, 2 ... Line mixer, 3 ... Anionic flocculant supply part, 4 ... Cationic flocculant supply part, 5 ... Coagulation reaction tank, 6 ... Supply pipe, 7 ... Vertical screw press, 8 ... Filtrate Treatment tank, 9 ... miscellaneous wastewater treatment tank, 53 ... mount, 61 ... main pipe, 62 ... sub pipe, 63, 64 ... interface sensor, 71 ... filter tube, 72 ... screw, 73 ... cover tube, 76 ... receiving port, A ... Sludge dewatering equipment

Claims (2)

The sludge and the flocculant are stirred and mixed in the flocculation reaction tank to produce agglomerated sludge, and the agglomerated sludge is supplied into the filter cylinder of the vertical screw press from the inlet provided at the lower part of the filter cylinder. In the sludge dewatering apparatus, the sludge is squeezed and dewatered while being transported upward in the filter cylinder by the rotation of the screw disposed in the cylinder.
The flocculation reaction tank is disposed above the receiving port, and includes a supply pipe that supplies the flocculated sludge from the flocculation reaction tank to the receiving port, maintaining a state in which the flocculated sludge stays in the supply pipe, An apparatus for dewatering sludge, wherein the coagulated sludge is pressurized and supplied into the filter cylinder.   2. The sludge dewatering apparatus according to claim 1, wherein a state in which the height of the coagulated sludge staying in the supply pipe is within a predetermined range is maintained.