JP5518162B2 - Sludge dewatering machine - Google Patents

Description

  The present invention relates to a sludge dewatering machine and relates to a technique for dewatering organic sludge such as sewage sludge and industrial wastewater sludge.

  Examples of conventional sludge dehydrators include those shown in FIGS. 6 to 7, in a multi-axis screw press which is a screw press type dehydrator, the outer peripheral portion of the main body casing 1 forms a screen 2, and the pair of left and right screw shafts 3 are inserted through the main body casing 1 in the axial direction. 4 are arranged in parallel, and screw blades 5 and 6 are formed on the screw shafts 3 and 4, respectively.

  Both screw blades 5 and 6 are formed in a spiral shape opposite to each other, and the screw blades 5 and 6 have a shape in which the pitch becomes narrower toward the sludge discharge side. The other screw blade 6 or 5 is located in the valley formed between the spirals of one screw blade 5 or 6, and both screw blades 5 and 6 are engaged.

  Engaging gears 7 and 8 are provided at the base ends of both screw shafts 3 and 4, and both screw shafts 3 and 4 are driven via gears 7 and 8 by driving a motor 9 connected to one screw shaft 3. Rotate in opposite directions.

  A back pressure plate 10 is disposed on the cake discharge side of the main body casing 1 so as to face the opening, and the back pressure plate 10 can be moved back and forth toward the opening by a cylinder device 11, and pressure applied to act on the opening is applied. The dehydrating force (squeezing force) is controlled by adjusting.

In this configuration, the dewatered sludge charged into the main casing 1 is conveyed to the discharge side by the rotation of the screw shafts 3 and 4 and the screw blades 5 and 6 while being filtered by the screen 2. At this time, the pitch of the screw blades 5 and 6 becomes narrower toward the sludge discharge side, and the volume of the filtration chamber in the main body casing 1 (per pitch of the screw blades 5 and 6) decreases. Therefore, the sludge is dehydrated by the compaction force due to the reduction of the filter chamber volume, the shearing force due to the engagement of the screw blades 5 and 6, and the back pressure by the back pressure plate 10, and is discharged from the opening on the discharge side to the outside of the main casing 1. The
JP 2007-245224 A JP 2003-230988 A JP-A-6-190594 JP-A-2-255296 Japanese Patent Laid-Open No. 61-95799

  By the way, in a general screw press type dehydrator, the dehydration force necessary for the zone on the sludge supply side in the screen is defined as “filtration pressure”, and “filtration pressure” = “reference head pressure” + “external pressure” It is defined as

  “Reference water head pressure” is the filtration pressure determined structurally, such as the height of the outer casing (screen diameter). “External pressure” is the filtration pressure that can be adjusted during operation, such as the water level of the sludge charging hopper. Point to.

  In the multi-axis screw press having the above-described configuration, when the cross-sectional area of the screen is the same, the screen diameter for one screw is larger than that of a normal single-screw screw press having the same throughput capacity. Get smaller.

  For this reason, in a multi-axis screw press in which the shafts are arranged in the horizontal direction, the reference head pressure, which is one factor that defines the filtration pressure, is reduced by reducing the diameter of the screen. Therefore, if the external pressure, which is another factor that defines the filtration pressure, is constant, the filtration pressure will be lower than that of a single screw press, and the desired treatment performance cannot be improved. There was a problem.

  Further, since the screw press type dehydrator forms the screen in a circular cross section along the outer periphery of the screw blade, the shape of the screen is recessed between the screw blades and has a recess in the multi-axis screw press.

  For this reason, when a plurality of screw shafts are arranged in a horizontal direction in a multi-axis screw press, the screen has a shape having a recess in the upper part of the screen. The filtrate that passes through the screen and flows into the recesses at the top of the screen overflows over the tops of the screens on both sides or drains from both ends of the screen. Tends to remain.

  The head pressure of the filtrate remaining at the top of the screen acts on the filter chamber inside the screen from the outside of the screen through the screen, and works in the direction of canceling out the "filtration pressure" acting inside the filter chamber of the dehydrator. , It becomes a factor which the filtration efficiency in the recessed part of an upper part of a screen falls.

  By the way, in the filter chamber inside the screen, the sludge in the upper filter chamber in the vicinity of the sludge supply section has a low sludge concentration (solid matter concentration) and is in a state where aggregated flocs are drifting in free water. On the other hand, the sludge in the lower filter chamber is dehydrated and has a higher sludge concentration (solids concentration) than the upper filter chamber, and there are many aggregated flocs per unit volume. There is a little free water.

  This free water is liquid and has low compressibility, and it does not denature itself even when high pressure is applied. On the other hand, the coagulation floc is a semi-solid lump formed by adding a coagulant to sludge, and has internal water. Agglomerated floc in a state where a large amount of internal water is retained is weak and has a characteristic that itself collapses (disassembling the floc) when high pressure is applied, but the internal water retained once is discharged and compressed Flock has characteristics that increase its strength and withstand high pressure.

  Inside the screen of the screw press type dehydrator, in the filtration zone that is responsible for the first half of the dehydration process, the sludge is made by efficiently applying "filtration pressure" to the free water forming the liquid phase in the sludge, permeating the screen and discharging it to the outside. It is important to increase the efficiency of dehydration, and it is not the primary purpose to give mechanical squeezing force to the flocs themselves.

  On the other hand, in the dehydration zone, which is responsible for the latter half of the dehydration process inside the screen, the discharge of contained water is promoted while gradually increasing the shearing force and compaction force generated by the rotation of the screw against the solid phase containing aggregated flocs in the sludge. It is important to squeeze mechanically.

In this way, the form of force required for the filtration zone and the dehydration zone and how to add them differ within the screen of the dehydrator.
The present invention solves the above-mentioned problems, effectively applies the filtration pressure to the sludge to be dewatered, and realizes that the force applied in the filtration zone and the dewatering zone inside the screen is applied in different forms. An object of the present invention is to provide a sludge dewatering machine capable of reducing the moisture content of a dewatered cake.

In order to solve the above-described problems, the sludge dewatering machine of the present invention has a plurality of screw shafts arranged at upper and lower relative positions, screw blades are formed around each screw shaft, and a screen is arranged around the screw blades. And a sludge dewatering machine provided with sludge supply means for supplying sludge to be dehydrated into the screen from the sludge inlet , wherein the sludge inlet is located on the side wall of the main casing facing the screw blade in the axial direction of the screw shaft. Opening around the axis of the screw shaft in the low pressure side region on one side of the straight line connecting the upper and lower screw shaft centers and in the vicinity of the intermediate position of the inter-shaft distance between the upper screw shaft and the lower screw shaft It is characterized by that.

  As described above, for example, when two screw shafts are arranged at the upper and lower relative positions, the total height of the filter chamber formed in the screen of the main body casing is when the two screw shafts are arranged in the horizontal direction. It almost doubles. For this reason, the high filtration pressure resulting from the large reference | standard water head pressure doubled compared with the past acts on a dewatering object sludge toward a lower screen surface.

  However, in the upper filter chamber in the screen, the reference head pressure is relatively smaller than the lower filter chamber, and the filtration pressure is also reduced. For this reason, the efficiency of draining free water in the upper filter chamber is poor, resulting in an unbalance of the dewatered state between the upper and lower filter chambers.

  Free water is not sufficiently discharged in the filtration zone, and sludge in the upper filter chamber in a state where the floc is weak is mechanically squeezed in the dehydration zone, resulting in the collapse of the floc, resulting in an overall efficiency of the dehydrator. The moisture content of the cake discharged becomes high.

  Further, the aggregated floc whose concentration has been increased by filtration is accumulated on the inner surface of the screen, the accumulated sludge is scraped off by the blade tip of the screw blade, and the sludge is conveyed to the discharge side in the screen. However, high-concentration sludge scraped off in the upper filter chamber settles in the lower filter chamber due to gravity, and further promotes an unbalance in the dehydration state between the upper and lower filter chambers.

  By the way, as described above, in the filter chamber inside the screen, the sludge in the upper filter chamber in the vicinity of the sludge supply section has a low sludge concentration (solids concentration) and a state in which aggregated flocs float in free water. is there. On the other hand, the sludge in the lower filter chamber is dehydrated and has a higher sludge concentration (solids concentration) than the upper filter chamber, and there are many aggregated flocs per unit volume. There is a little free water.

  Usually, the pressure applied to the liquid is transmitted most efficiently between the same phases (liquid-liquid). For this reason, pressure is applied into the screen from the middle position of the distance between the screw shaft at the lower position and the screw shaft at the upper position, that is, from the upper position or the upper position and the lower position from the boundary between the upper filter chamber and the lower filter chamber. While supplying the sludge to be dehydrated, the applied external pressure efficiently acts on the free water in the upper filter chamber on the sludge supply part side in the screen. That is, there is less solid matter contained in the sludge to be dehydrated in the upper filter chamber and the solid matter has diffused in the free water, whereas more solid matter is contained in the sludge to be dehydrated in the lower filter chamber, Free water is in a state of being contained between solid materials, and pressure is not easily transmitted.

  By the above-mentioned action, the initial dewatering efficiency in the upper filter chamber is improved, the imbalance of the dewatering efficiency in the upper and lower filter chambers is eliminated, and the sludge in the upper and lower filter chambers that have sufficiently drained free water is sent to the dewatering zone. The dewatering efficiency of the entire machine can also be improved.

  In addition, the coagulation flocs in the lower filter chamber are in close contact with each other and there is little free water, and the propagation efficiency of external pressure is low. Therefore, when sludge is supplied only to the lower filter chamber, the free water existing in the upper filter chamber is efficiently used. If the external pressure is increased excessively, the flocs will break and the sludge will leak from the lower screen.

In the sludge dewatering machine of the present invention, the sludge inlet is characterized by being long and continuously opened along the rotation direction around the axis of the screw shaft at the upper position and the screw shaft at the lower position .

In the sludge dewatering machine of the present invention , the sludge supply means is configured such that the sludge inlet and the sludge supply pump are connected via a coagulator, and the coagulant input means is connected in the middle of the pipeline between the sludge supply pump and the coagulator. It is characterized by being.

  As described above, according to the present invention, the pressure applied to the liquid is transmitted most efficiently between the same phases (liquid-liquid), and there is little solid matter contained in the sludge to be dehydrated in the upper filter chamber, and the solid matter in the free water. Since the pressure becomes easy to be transmitted in a diffused state, by supplying the sludge to be dehydrated while applying pressure into the screen from the upper position or the upper position and the lower position than the boundary between the upper filter chamber and the lower filter chamber, The applied external pressure effectively acts on the free water in the upper filter chamber, improving the initial dewatering efficiency in the upper filter chamber, and eliminating the imbalance of the dewatering efficiency in the upper and lower filter chambers, improving the dewatering efficiency of the entire dehydrator Can be made.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 2, screw shafts 53 and 54 that form a pair of upper and lower rotating shafts by inserting a screen 52 that supports both sides of a main body casing 51 in the axial direction into a substantially parallel state (including a parallel state). The screw blades 55 and 56 are formed on the screw shafts 53 and 54, respectively.

The inside of the screen 52 disposed around the screw blades 55 and 56 forms a filter chamber, the upper region of the filter chamber space forms the upper filter chamber 521, and the lower region forms the lower filter chamber 522.
In the present embodiment, the screw shaft 53 at the upper position and the screw shaft 54 at the lower position are arranged at the upper and lower positions along the vertical direction, and all screw shaft centers are arranged on the same plane forming the vertical plane. . However, in the present invention, the upper and lower relative positions of the screw shaft 53 at the upper position and the screw shaft 54 at the lower position are not limited to the configuration shown in the present embodiment. For example, the screw shaft 53 at the upper position does not necessarily have to be arranged at a position immediately above the screw shaft 54 at the lower position, that is, a vertical plane passing through the screw shaft 54 at the lower position. It is also possible to arrange them in a predetermined width region on both sides with respect to.

The predetermined width region can also be defined by the expression described below with reference to FIG. In FIG. 4, the case of three axes will be described as an example, but the same applies to two or more axes.
In the cross section perpendicular to the screw shaft, when the angle between the straight line L1 connecting the adjacent upper and lower screw shaft centers and the straight line L2 connecting the lower screw shaft center and the outer peripheral intersection of the upper and lower screens is X, the upper position If the angle between the straight line L1 connecting the screw shaft center and the screw shaft center at the lower position and the vertical line L3 upward from the screw shaft center at the lower position is Y, the angle Y is an area where the angle X is equal to or less than the angle X.

  As described above, by arranging the screw shaft in the predetermined width region, the effect of increasing the reference head pressure obtained by arranging the screw shaft at the upper and lower relative positions and the effect of preventing the filtrate from remaining in the screen recess are simultaneously achieved. And efficient dehydration is possible.

  Both adjacent screw blades 55 and 56 are formed in a spiral shape opposite to each other, and the screw blades 55 and 56 have a shape in which the pitch becomes narrower toward the sludge discharge side. The spiral shape of the screw blades 55 and 56 can be arbitrarily set, and both adjacent screw blades 55 and 56 can be formed in the same spiral shape and rotated in the same direction.

  Then, in the valley formed between the spirals of one screw blade 55 or 56, the other screw blades 56 or 55 are positioned and adjacent to each other, both screw blades 55 and 56 overlap in the axial direction between the pitches. ing. A gear 57 and a motor 58 are connected to the screw shaft 53 at the upper position and the screw shaft 54 at the lower position.

  A back pressure plate 59 is disposed on the cake discharge side of the main body casing 51 so as to face the opening. The back pressure plate 59 can be moved back and forth toward the opening by the cylinder device 60, and pressure applied to act on the opening can be applied. The dehydrating force (squeezing force) is controlled by adjusting. Further, a control device (not shown) for controlling the driving of the motor 58 and the cylinder device 60 is provided.

  As shown in FIG. 2A, the screen 52 is formed in a curved shape along the outer periphery of the screw blades 55 and 56, and a portion corresponding to each other between the screw blades 55 and 56 is recessed and recessed. The upper region inside the screen 52 forms the upper filter chamber 521 and the lower region forms the lower filter chamber 522 with the recess 52a as a boundary.

  By the way, when the screw blades 55 and 56 are rotated to convey the sludge to be dehydrated in the filter chamber, the sludge in the upper filter chamber and the sludge in the lower filter chamber are rotated not only in the axial direction but also in both screw blades 55 and 56. It is also transported in the direction. Since the adjacent screw blades 55 and 56 are formed in a spiral opposite to each other, the sludge in both filter chambers collide with each other at the portion where the screw blades 55 and 56 overlap and receive a high compaction force.

  Therefore, in the cross section perpendicular to the screw shafts 53, 54, the pressure in the filter chamber on the side where both adjacent screw blades 55, 56 are fed between both shaft centers rises to become the high pressure side region Hi, and conversely, The pressure in the filter chamber on the side where both screw blades 55 and 56 are sent out from between both shaft centers is relatively lowered to become a low pressure side region Lo.

  Hereinafter, the pressure distribution in the filter chamber will be described. As shown in FIG. 2 (a), in a cross section perpendicular to the screw shafts 53 and 54, an arbitrary position (indicated by a straight line L5) in the filter chamber is defined as a screw 55, with reference to a straight line L4 connecting the upper and lower screw shaft centers. 56, the pressure in the filter chamber is as shown in FIG. 5. The pressure in the filter chamber is the lowest in the region where the angle θ is around 45 °, and 270 ° ≦ θ ≦ 360 °. The filter chamber pressure is highest in the region.

Therefore, in the present embodiment, one side from the straight line L4 connecting the upper and lower screw shaft centers will be described as the low pressure side region Lo, and the other side will be described as the high pressure side region Hi.
As shown in FIG. 2B, the side wall 61 of the main body casing 51 faces the screw blades 55 and 56 in the axial direction of both screw shafts 53 and 54, and the sludge inlet 62 provided on the side wall 61. Is communicated with the low-pressure side region Lo of the filter chamber inside the screen 52, and includes the region where the above-mentioned angle θ is around 45 °.

  The sludge inlet 62 is located around the axial center of both screw shafts 53 and 54 at an upper position and a lower position with an intermediate position of an inter-shaft distance between the screw shaft 53 at the upper position and the screw shaft 54 at the lower position. Is formed so as to correspond to the upper filter chamber and the lower filter chamber inside the screen 52, and any area of the opening can always be supplied with sludge during one rotation of the screw blades 55, 56. Under pressure. In the configuration of three or more axes, the sludge inlets 62 may be formed at an upper position and a lower position with a middle position between the lowermost screw shaft and the uppermost screw shaft as a boundary.

  A pressing force (squeezing force) acts on the dewatered sludge in front of the screw blades 55 and 56 as the screw blades 55 and 56 rotate, and the concentrated sludge accumulates on the front surface of the screw blades 55 and 56. As the accumulated sludge becomes closer to the screw blades 55 and 56, it becomes a consolidated layer and the pressure increases. For this reason, when the whole area | region of the sludge inlet 62 is obstruct | occluded with the compaction layer of the front surface of the screw blades 55 and 56, supply of sludge is inhibited. Since the back surfaces of the screw blades 55 and 56 are at a low pressure, sludge can be supplied after the screw blades 55 and 56 have passed.

  On the other hand, as the distance from the front surface of the screw blades 55 and 56 decreases, the pressing force (squeezing force) becomes weaker and the pressure becomes lower. In addition, the presence of any region of the sludge inlet 62 always enables stable sludge supply.

  For this reason, the sludge inlet 62 preferably has a shape that opens long along the rotational direction around the axis of both screw shafts 53 and 54, and the screw blades 55 and 56 are located at the start end side of the opening. A shape in which at least a region on the end side of the opening is under a predetermined pressure capable of supplying sludge is desirable. Even if the region on the terminal end side of the opening is blocked by the sludge consolidation layer by the advancement of the screw blades 55 and 56, the back side of the screw blades 55 and 56 is at a low pressure, so that either of the openings of the sludge inlet 62 is always present. This area is under a predetermined pressure.

  As described above, in the present embodiment, by providing the sludge inlet 62 on the side wall 61 of the main body casing 51, the configuration of the sludge inlet 62 is simplified, and the screw shafts 53 and 54 are formed in a hollow shape. Therefore, it is easier to manufacture than the configuration in which the path for supplying the sludge to be dehydrated is formed, and the strength of the screw shafts 53 and 54 is easily secured.

  However, in the present invention, the form of the sludge inlet 62 is not limited to the configuration shown in the present embodiment. For example, it is also possible to form a hollow portion at least in the screw shaft 53 at the upper position and to form a sludge inlet that communicates with the hollow portion on the wall surface of the screw shaft 53. In this case, the sludge inlet is opened at a position on the back side of the screw blade 55 in the traveling direction of the sludge to be dehydrated, so that the sludge inlet is under a predetermined pressure at which sludge can always be supplied while the screw blade 55 rotates once. It is in.

  A sludge supply pump 63 as a sludge supply means is connected to the sludge input port 62 via a coagulation device (sealed type) 64, and the coagulant is input in the middle of a pipe line between the sludge supply pump 63 and the coagulation device 64. Means 65 is connected. The sludge supply pump 63 pumps dewatered sludge into the screen 52 of the main casing 51. The sludge supply pump passes the sludge to be dehydrated from the upper position and the lower position to the inside of the screen 52 through the sludge inlet 62 from the upper position and the lower position at the intermediate position between the screw shaft 53 at the upper position and the screw shaft 54 at the lower position. Supply.

  In the present embodiment, the sludge inlet 62 has a shape that opens around the axial centers of both the screw shaft 53 at the upper position and the screw shaft 54 at the lower position. It is also possible to have a shape that opens only around the shaft center of the shaft 53. In this case, the upper position with the intermediate position of the inter-shaft distance between the screw shaft 53 at the upper position and the screw shaft 54 at the lower position as a boundary. The sludge to be dehydrated is supplied into the screen 52 only from the position.

  The pumping by the sludge supply pump 63 sends out the sludge to be dehydrated by the action of pressure, and the sludge to be dehydrated is passed through a generally sealed structure such as a pipe line by the mechanically applied pressure. If it supplies to, the form of the sludge supply pump 63 is not limited, Various pump apparatuses are applicable.

  The operation of the above configuration will be described below. The back pressure plate 59 is disposed at a predetermined position by the cylinder device 60, and the screw shafts 53 and 54 are synchronously rotated in opposite directions by driving the gear 57 and the motor 58.

  The sludge to be dewatered pumped into the screen 52 of the main casing 51 through the sludge inlet 62 by the sludge supply pump 63 is filtered to the discharge side by the rotation of the screw shafts 53 and 54 and the screw blades 55 and 56 while being filtered by the screen 52. Be transported.

  In the present embodiment, the two screw shafts 53, 54 and the screw blades 55, 56 are arranged in the vertical position, and the total height of the filter chamber formed inside the screen 52 of the main body casing 51 is two screw shafts 53. , 54 are almost doubled as compared with the case of arranging them in the horizontal direction. For this reason, since the high filtration pressure resulting from the large reference head pressure that doubles as compared with the prior art acts on the sludge to be dewatered toward the lower screen surface of the screen 52, the external pressure equivalent to the conventional, that is, the sludge supply pressure is reduced. Dehydration efficiency is improved below.

  When the sludge dewatering machine of the present invention is operated at a filtration pressure equivalent to the case where the two screw shafts 53 and 54 are arranged in the horizontal direction, it can be operated at an external pressure lower than that in the past, thereby saving energy. be able to.

  Moreover, since the part of the recessed part 52a which arises in the screen 52 is located in the both sides of the main body casing 51, since the filtrate which permeate | transmitted the screen 52 leaves | separates smoothly from the screen surface, without remaining in the part of the recessed part 52a, There is no external factor for reducing the filtration pressure in the internal filtration chamber, and efficient filtration can be performed by effectively using the filtration pressure.

  Next, as described above, again, in the filter chamber inside the screen 52, the sludge in the upper filter chamber near the sludge supply section near the sludge inlet 62 has a sludge concentration (solid matter concentration). As shown in FIG. 3A, the flocs F are floating in the free water W. On the other hand, the sludge in the lower filter chamber is dehydrated and has a higher sludge concentration (solids concentration) than the upper filter chamber, and a large amount of coagulated flocs per unit volume is present in the state shown in FIG. As shown in (), there is a slight free water W between the aggregated flocs F.

  This free water W is a liquid and has a low compressibility, and it does not denature itself even when a high pressure is applied. On the other hand, the floc Flock F is a semi-solid lump formed by adding a flocculant to sludge, and has internal water W1. Agglomerated floc F with a large amount of contained water W1 is weak and has a characteristic that itself collapses (disassembling the floc) when high pressure is applied, but the contained water W1 once held inside is discharged and compressed. The agglomerated floc F has characteristics that increase its strength and withstand high pressure.

  For this reason, in the filtration zone responsible for the first half of the dehydration process inside the screen of the screw press type dehydrator, the free water forming the liquid phase in the sludge is efficiently applied to the filtration pressure, permeated through the screen and discharged to the outside. In addition, it is important to filter the sludge to increase the efficiency of dehydration.

  Further, by arranging the two screw shafts 53 and 54 at the upper and lower relative positions, the reference head pressure in the lower filter chamber is almost doubled compared to the conventional case, but the upper filter chamber of the screen 52 is more than the lower filter chamber. However, the reference head pressure becomes relatively small, and the filtration pressure becomes low. For this reason, the efficiency of draining free water in the upper filter chamber is poor, resulting in an unbalance of the dewatered state between the upper and lower filter chambers. The sludge in the upper filter chamber, in which free water is not sufficiently discharged in the filtration zone and the floc is soft, is mechanically squeezed in the dehydration zone, causing the floc to collapse. The efficiency is also reduced and the moisture content of the discharged cake is increased.

  Further, the flocs flocs whose concentration has been increased by filtration are accumulated on the inner surface of the screen 52. The accumulated sludge is scraped off by the blade tips of the screw blades 55 and 56, and the high-concentration sludge scraped off in the upper filter chamber is gravity. By sinking into the lower filter chamber, the unbalance of the dehydrated state between the upper and lower filter chambers is further promoted.

  Based on the above knowledge, in the present embodiment, the sludge supply pump 63 passes the sludge inlet 62 and the upper position with the middle position of the inter-shaft distance between the screw shaft 53 at the upper position and the screw shaft 54 at the lower position as a boundary. The dewatered sludge is pumped from the lower position into the screen 52, but it may be supplied only from the upper position.

  Thus, by supplying the sludge to be dehydrated while applying pressure to the upper and lower filter chambers, the applied external pressure is efficiently applied to the free water in the upper filter chamber on the sludge supply side inside the screen 52. Works.

  That is, normally, the pressure applied to the liquid is transmitted most efficiently between the same phase (liquid-liquid), so that there is little solid contained in the sludge to be dehydrated and in the upper filter chamber where the solid is diffused in free water. While the pressure acts efficiently on the free water, the solid matter contained in the sludge to be dehydrated increases in the lower filter chamber, and the free water is contained in the solid matter and the pressure is not easily transmitted. By the above-mentioned action, the initial dewatering efficiency in the upper filter chamber is improved, the imbalance of the dewatering efficiency in the upper and lower filter chambers is eliminated, and the sludge in the upper and lower filter chambers that have sufficiently drained free water is sent to the dewatering zone. The dewatering efficiency of the entire machine can also be improved.

  Here, the external pressure applied by pumping the sludge supply pump is a pressure obtained by removing the actual head and the pipe pressure loss from the discharge pressure of the sludge supply pump. The filtration pressure resulting from the external pressure by the sludge supply pump acts on the dewatered sludge. Since the external pressure applied by this pumping can be adjusted by the number of rotations of the pump, the valve, etc., it becomes easy to change the setting of the filtration pressure to the optimum value according to the properties of the sludge to be dehydrated.

  In addition, pumping eliminates the need for a hopper height when using a conventional charging hopper, so that the machine height can be significantly reduced, manufacturing costs are reduced, and space is limited. You can install the equipment without

  Furthermore, the pitch of the screw blades 55 and 56 that rotate synchronously becomes narrower toward the sludge discharge side, and the volume of the filtration chamber in the main body casing 51 (per pitch of the screw blades 55 and 56) decreases, so that the dewatered sludge is , While moving inside the main body casing 51, it receives a compaction force due to a decrease in the volume of the filter chamber due to a decrease in the pitch of both screw blades 55, 56, and further a shearing force due to the engagement of both screw blades 55, 56, And it is dehydrated by the back pressure by the back pressure plate 59 and discharged from the opening on the discharge side to the outside of the main body casing 51.

The schematic diagram which shows the sludge dehydrator in embodiment of this invention Schematic diagram showing the rotation direction of the screw shaft and screw blades in the same embodiment Schematic diagram showing properties of sludge to be dehydrated Explanatory drawing showing the upper and lower relative positions of the screw shaft Chart showing pressure distribution in the filter chamber Schematic diagram showing a conventional sludge dehydrator Schematic diagram showing the rotation direction of the screw shaft and screw blades in a conventional sludge dehydrator

Hi High-pressure side area Lo Low-pressure side area 51 Main body casing 52 Screen 52a Recess 53, 54 Screw shaft 55, 56 Screw blade 57 Gear 58 Motor 59 Back pressure plate 60 Cylinder device 61 Side wall
62 Sludge inlet 63 Sludge supply pump 64 Coagulator 65 Coagulant input means

Claims (3)

Sludge supply that arranges multiple screw shafts in the upper and lower relative positions, forms screw blades around each screw shaft, arranges a screen around the screw blades, and supplies the sludge to be dehydrated from the sludge inlet into the screen A sludge dewatering machine with means,
The sludge inlet is located on the side wall of the main casing facing the screw blades in the axial direction of the screw shaft, on the low pressure side region on one side of the straight line connecting the upper and lower screw shaft centers, and between the upper screw shaft and the lower position. A sludge dewatering machine that opens around the axis of a screw shaft in the vicinity of an intermediate position of the distance between the shaft and the screw shaft .   The sludge dewatering machine according to claim 1, wherein the sludge inlet is continuously opened along the rotational direction around the axis of the screw shaft at the upper position and the screw shaft at the lower position.   The sludge supply means is characterized in that the sludge inlet and the sludge supply pump are connected via a coagulation device, and the coagulant supply means is connected in the middle of the pipeline between the sludge supply pump and the coagulation device. The sludge dewatering machine according to 1 or 2.

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