JP5246564B2 - Impeller of continuous pressure dehydrator - Google Patents

Description

  This invention is a continuous pressure dehydrator that presses a raw solution such as industrial wastewater sludge, sewage sludge, etc. into an annular filtration chamber, discharges the filtrate from the filter plate while concentrating the impeller and the raw solution, and concentrates and dehydrates it. More particularly, the present invention relates to an improvement in the impeller blades.

  Conventionally, a continuous compression dehydrator that forms a filtration chamber with a pair of disk-shaped filter plates and a filter chamber outer ring and arranges an impeller in which 4 to 6 blades are moved backward in the rotation direction in the filtration chamber is patented. Document 1 proposes the present invention.

Japanese Patent No. 3548888 (page 10 of the best mode for carrying out the invention, page 11)

The conventional continuous pressure dehydrator is used to feed the stock solution injected from the center of the filtration chamber with an impeller, while generating frictional resistance between the filter plate and the stock solution, and the cake and stock solution stacked on the filtration surface. During this period, a shear friction resistance force is generated and dehydrated, and the cake is pushed out from the outlet of the outer ring of the filter while scraping the cake on the filter surface with a scraper fixed to the blade.
As shown in the specification, the continuous press dehydrator shown in FIG. 11 of Patent Document 1 proposed by the applicant has the blade 63 of the impeller 58 having a curved plate shape, and the reference curve line of the blade 63 is a logarithm. It is set in a spiral curve and has both the function of feeding the cake in the radial direction and the function of generating filtration force on the cake.
In the logarithmic spiral curve, the delay angle α and the wedge angle β are constant regardless of the positions on the curve.
The wedge angle β is an intersection angle between the normal 61 and the tangent 56 of the straight line 57, and becomes a right angle when the delay angle α and the wedge angle β are combined.
By making the delay angle α constant, the rotational wedge action force of the blades 63 in the vicinity of the annular plate 2 where the moisture content of the cake decreases and the force that moves the cake in the radial direction increase, and shear force is applied to the cake. Is described in Patent Document 1.

An impeller of the conventional continuous pressure dehydrator is shown in FIG. FIG. 8 is a logarithmic spiral curved blade with a blade angle of the impeller having a delay angle α = 55 ° × 6, and passes through the axial center O of the impeller from the start point a of the front stage of the blade to the end point b of the rear stage. The delay angle α formed by the straight line L and the tangent to the action surface ahead of the blade in the rotation direction at the intersection of the straight line L is continuously formed to be a constant angle.
Therefore, in the cake transporting action by the rotation of the impeller, the tangential force to the cake in the filtration chamber is constant from the front stage to the rear stage, and the moisture content decreases and becomes harder in the squeezing / dehydrating part after the middle stage. It is not possible to generate a large pushing force to the final cake outlet of the filter outer ring with respect to the cake.
In addition, when the cake in the filtration chamber has a low water content or when the cake in the filter chamber is pushed out at the end of operation, there is a problem that a large pushing force cannot be generated and the dewatered cake is clogged in the filtration chamber. It was.
The present invention provides an impeller of a continuous pressure dehydrator that obtains a large pushing force to the outlet of the filter outer ring even for the final cake that has become hard during the dehydration process.

The gist of the impeller of the continuous pressure dehydrator of the present invention is that a pair of disc-shaped filter plates and an annular filter chamber outer ring form a filtration chamber, and the impeller is attached to a drive shaft that is inserted into the center of the filtration chamber. In a pressure dehydrator that disposes the impeller blades in the filtration chamber, forms a liquid supply path on the drive shaft, and opens a discharge port in the outer ring of the filter chamber, the blades are squeezed from the starting point. It is formed continuously from the intermediate point of the dewatering part to the end point, and retracts backward in the rotation direction as it approaches the end point, and the delay angle increases as it approaches the end point from the intermediate point, and the force to push out toward the blade tip is large. As a result, it is possible to improve the conveying efficiency of the supplied sludge and the extrusion effect of the cake. In the flow path, the resistance of movement of the impeller blades on the front and back surfaces is reduced, and partial retention can be improved to increase the pushing force to the outlet.
Since the middle point is located between 1/3 and 2/3 of the radius of the impeller from the center, the lag angle of the blade increases in proportion to the decrease in the moisture content of the cake in the squeezing / dehydrating part, and the blade tip direction easily Can be pushed out.
By setting the delay angle of the end point to 60 ° to 90 °, the rate of change of the delay angle from the intermediate point can be set freely, and a large pushing force toward the discharge port can be obtained.
If the blades of the impeller to be moved backward in the rotation direction are formed in one arc, the blades can be easily manufactured and processed, and the cost can be reduced.
In order to secure a wide sludge passage width in the concentrating portion and reduce unnecessary resistance, blades from the starting point to the intermediate point may be formed in a substantially straight line.

  The impeller of the continuous pressure dehydrator according to the present invention is configured as described above, and in the squeezing / dehydrating unit, the delay angle formed by the straight line passing through the axial center of the impeller and the tangent to the operating surface of the blade is the tip of the blade. The delay angle increases in proportion to the decrease in the moisture content of the cake in the filtration chamber, and the impeller can be easily pushed out toward the tip of the blade to increase the conveyance efficiency and the dewatering capacity. Continuous operation with a dehydrated cake having a uniform moisture content is possible, making it easy to manufacture and process the impeller and reducing costs.

It is a front view of the impeller of the continuous pressure dehydrator which concerns on this invention. Similarly, it is a longitudinal cross-sectional view of a continuous pressure dehydrator. Similarly, it is a front view of the filtration chamber which provided the impeller. Similarly, it is a front view of the filter plate used for a continuous pressure dehydrator. Similarly, it is a front view of a sheet metal filter used in a continuous pressure dehydrator. It is a comparison conceptual diagram of the impeller of the continuous pressure dehydrator which concerns on this invention, and the conventional impeller. It is a front view of the impeller of the continuous pressure dehydrator which concerns on another Example. It is a conceptual diagram of a 6-blade impeller having a delay angle α = 55 ° using a conventional logarithmic spiral curve.

An impeller of a continuous pressure dehydrator according to the present invention is shown in FIG. The blade 14 of the present invention passes through an arbitrary intermediate point c between 1/3 and 2/3 of the radius R of the impeller 6 from the start point a of the front stage portion fixed to the boss 15, and the rear stage of the other end. It is formed with a smooth curve up to the end point b of the part. The middle point c is located on a virtual circle where the compression / dehydration of the filtration chamber 4 starts, and it is desirable that the intermediate point c is located slightly on the concentration unit side from the boundary between the concentration unit and the compression / dehydration unit.
Assuming that the delay angles at the start point a, the intermediate point c, and the end point b are αa, αc, and αb, respectively, αc <αb, and the delay angle α is increased toward the end point b.
The blades 14 of the present embodiment may be formed so as to have smooth continuity, and may be a straight line continuously bent into a polygonal shape, a curved line formed in an arc shape, or a combination thereof.
Moreover, although the present Example forms the impeller with six blades, the number of blades can be appropriately selected depending on the size, width, stock solution properties, etc. of the filtration chamber.

FIG. 2 is a longitudinal sectional view of a continuous pressure dehydrator, in which a pair of disc-shaped filter plates 1 and 1 are provided with an annular filter chamber outer ring 2 at the outer peripheral end and a pair of inner ring support cylinders 3 at the inner peripheral end. Are connected, and an annular filtration chamber 4 is formed between the filtration plates 1 and 1, and a liquid supply chamber 5 is formed inside the inner ring support tube 3.
An impeller 6 is disposed in the filtration chamber 4, and a drive shaft 8 fitted to a boss 15 of the impeller 6 is pivotally supported on a bearing 10 provided on a frame 9, and one inner ring support cylinder 3 is supported. The filter plate spacer 11 is connected to the frame 9. A drive machine (not shown) supported on the frame 9 is linked to a drive shaft 8 on which the impeller 6 is fitted.
The leading end of the stock solution supply path 12 formed in the drive shaft 8 is open to the supply chamber 5, and a liquid supply hole 13 is also provided near the tip of the drive shaft 8. The stock solution is pressed into the front end portion of the liquid supply path 12 of the drive shaft 8 and the front and rear of the liquid supply chamber 5 from the liquid supply hole 13, and the stock solution is caused to flow into the filtration chamber 4 from the left and right of the base end portion of the impeller 6.

  FIG. 3 is a front view of the filtration chamber in which the impeller according to the present invention is disposed. The impeller 6 is configured by fixing a plurality of blades 14... is there. The tip end portion of the blade 14 of the impeller 6 is brought close to the filter outer ring 2, and the side edge portion of the blade 14 is brought into sliding contact with the filter plate 1 as shown in FIG. A core plate 16 is fitted on the rear surface in the rotational direction of the blade 14 of the impeller 6, and the height is gradually reduced from the proximal end portion of the blade 14 to the vicinity of the distal end portion. A cake discharge port 17 provided in the outer ring 2 of the filter is disposed horizontally downward, and a flap valve which is not shown but can be opened and closed is provided at the discharge port 17.

FIG. 4 is a front view of the filter plate, in which a thin plate metal filter medium 22 is stretched inside a reinforcing frame 21 in which an outer frame 19 and an inner frame 20 are fixed to a disk-shaped punching metal 18. The filter plate 1 is composed of 21 and a thin metal filter medium 22.
FIG. 5 is a front view of a thin plate metal filter medium. The thin plate metal filter medium 22 forms a plurality of concentric annular thin plate metal filter media 22a, 22b, and 22c, and the fine holes on the filter medium surface extend from the center toward the outer periphery. Reduced in stages. An outer ring 23 and an inner ring 24 are fixed to the thin plate metal filter medium 22, and a non-porous region 25 is provided between the divided thin plate metal filter media 22a, 22b, and 22c. The divided thin plate metal filter media 22a, 22b, and 22c are subjected to hole processing by photo-etching on a thin plate metal plate such as stainless steel to form a cross section in the penetration direction in a conical shape and expand from the filtration chamber side toward the filtrate discharge side. A large number of fine holes are opened.

The stock solution supplied to the front stage near the starting point a of the blades 14 is conveyed in the direction of the terminal end b by the rotation of the impeller while being separated into solid and liquid by the filter plates 1 and 1. A large amount of liquid is separated by the filter plates 1 and 1 in the concentration part at the front stage close to the liquid supply hole 13 and becomes a concentrated cake, and the concentrated cake is further dehydrated by the pressing / dehydration part from the middle part to the rear part. The The range of the concentrating part varies depending on specifications such as stock solution properties, supply pressure, filtration area, and the like, but is generally between 1/3 and 2/3 of the radius R of the impeller 6 from the center O. As shown in FIG. 5, a thin plate metal filter medium 22a having fine pores larger than the outer peripheral portion is used in the concentrated portion with a large water load.
The stock solution is transported by the impeller 6 having a delay angle α formed by the straight line L passing through the center of the axis and the tangent to the working surface in the rotational direction of the blade 14 at the intersection of the straight line L. In the concentrated part having high fluidity due to the water content, a large conveying action is not required. Therefore, in the concentrating part in the vicinity of the inlet, the press-fitting pressure of the stock solution is increased to obtain a desired transporting action jointly with the pushing-out action of the press-fitting pressure and the transporting action of the impeller 6. Therefore, it is not necessary to satisfy αa <αc between the starting point a and the intermediate point c, and a sufficient space is secured so as not to become resistance of the stock solution supplied from the liquid supply hole 13 and smoothly guided to the discharge port. It is desirable to form the intermediate point b continuously from the starting point a so that it can be done.

In the squeezing / dehydrating section between the intermediate point c and the end point b, the delay angle α of the blade 14 is increased as the end point b is approached. This is because the undiluted liquid separated in the filtration chamber 4 has a low water content in the squeezing / dehydrating section and cannot be conveyed by the supply pressure of the undiluted liquid, but is conveyed along the working surface of the blade 14 by the rotational action of the impeller 6. is there. By gradually increasing the delay angle α, the conveying action in the direction of the discharge port 17 (peripheral direction) can be increased, and clogging of the cake in the filtration chamber 4 is eliminated.

The impeller of the continuous pressure dehydrator according to the present invention will be described in detail with reference to FIG. 6. The curve indicated by the solid line is the blade 14 of the present embodiment, and the curve indicated by the broken line is the conventional delay angle α = 55 °. Logarithmic spiral curve T. For comparison, the start point a and the end point b are set to the same position. The number of blades is 6 blades.
The blade 14 indicated by a solid line is formed in a smooth curve from the starting point a of the front stage part to an intermediate point c between 1/3 and 2/3 of the radius R of the impeller 6 to the end point b of the rear stage part. Yes.
In this embodiment, the intermediate point c is set on a virtual circle R / 2 from the center O. The radius of the imaginary circle for setting the midpoint c is preferably located slightly on the concentration unit side from the boundary between the concentration unit and the squeezing / dehydrating unit, and is appropriately set depending on the size of the filtration chamber, the properties of the concentrate, and the like.
A curve is continuously formed from the intermediate point c to the end point b so that the delay angle α gradually increases. The delay angle αb at the end point b is preferably about 60 ° to 90 ° in consideration of the pushing force to the discharge port 17. In the present embodiment, the change is made at 49 ° (intermediate point c), 50 °, 55 °, 61 °, and 68 ° (end point b) every about 15 ° from the intermediate point c toward the end point b. As the cake in the filtration chamber 4 approaches the end point b, the moisture content decreases and the frictional resistance increases, and a large pushing force is required for conveyance. Therefore, the rate of change of the delay angle α increases as the end point b is approached. It is desirable to do. The delay angle αb at the end point b is appropriately set in consideration of the number of blades and the distance between the front and rear blades 14.
The curve from the start point a to the intermediate point c may be extended from the intermediate point c to the end point b to the boss 15, but is sufficient so that it does not become the resistance of the stock solution supplied from the liquid supply hole 13 in the concentration unit. It is necessary to give priority to securing sufficient space. In the present embodiment, a curve passing through the starting point a, the intermediate point c, and the ending point b is formed by one circular arc having a constant curvature radius. If it is formed by one arc, the manufacture and processing of the blades can be facilitated and the cost can be reduced.
The winding angle θ from the intermediate point c to the end point b can be appropriately set according to the number of blades, the size of the filtration chamber, the properties of the stock solution, etc., and the six blades of this embodiment are preferably 60 ° to 70 °.

When the shape of the blade 14 of this embodiment is compared with the conventional blade shown by a broken line, it can be seen that the blade shape swells forward in the rotational direction between the intermediate point c and the end point b. This is because the delay angle α is gradually increased between the intermediate point c and the end point b where the squeezing / dehydrating part starts, and the direction of the force exerted on the cake by the working surface of the blade 14 by the rotation of the impeller 6 is The direction of the force exerted by the blades is toward the outer periphery.
Therefore, since the cake moving along the action surface of the blade 14 is pushed out in the outer peripheral direction, the cake in the filtration chamber 4 can be smoothly transported and thickened to the outer peripheral side without requiring a large force. . Since the cake having a reduced moisture content in the filtration chamber 4 is not forced to move excessively, there is no increase in frictional resistance or rotation.

FIG. 7 shows another embodiment of the impeller of the continuous pressure dehydrator according to the present invention, in which a curve is continuously formed from the intermediate point c to the end point b so that the delay angle α gradually increases and the concentration is concentrated. In order to secure the space of the part, the curve is largely bent at the intermediate point c and is formed in a substantially straight line up to the start point a. Regarding the delay angles αa to αc of the blades 14 near the center O, the concentrated sludge is in a state of high fluidity at the initial stage of supply, and the action due to the indentation due to the indentation pressure of the sludge is dominant, and the delay angle α The impact is small.

The performance comparison test was conducted using the curved blade impeller shown in FIG. 1 and the conventional logarithmic spiral blade impeller of delay angle α = 55 ° shown in FIG.
For comparison, the starting point a and the ending point b were set at the same position as shown in FIG. Digested sludge was used as the target stock solution, and the chemical injection rate of the flocculant, the rotation speed of the impeller, and the pressure pressure of the discharge port were made constant. Table 1 shows the results of a performance comparison test between a blade having a constant radius of curvature and a logarithmic spiral blade.

In the performance comparison test, the moisture content of the cake (%) is shown on the vertical axis, and the stock solution treatment amount (kg-ds · m ² · h) is shown on the horizontal axis.
The test results show that when the moisture content of the dehydrated cake of the blade of the present invention and the logarithmic spiral curve blade is compared, when the blade of the present invention has a stock solution treatment amount of 42 kg-ds · m ² for 1 hour, the moisture content of the cake is 1 Decreased by 5 points. In the case of a stock solution treatment amount of 75 kg-ds · m ² , the moisture content of the cake could be reduced by 0.7 points.
Moreover, also in the cake discharge | emission in the filtration chamber after completion | finish of a test, the direction of the blade | wing of this invention discharged | emitted favorably in a short time, and the filtration chamber was able to be cleaned.
The improved blade of the present invention secures the cake passage, and the squeezing / dehydrating section has a larger delay angle α as it goes in the tip direction, increasing the conveying efficiency and pushing out to the discharge port. It was confirmed that the resistance to movement at the front and back of the blades was reduced, partial retention was improved, and the dewatering efficiency was improved.

In the impeller of the continuous pressure dehydrator according to the present invention, the delay angle formed between the radius of the impeller and the tangent to the working surface of the impeller is increased toward the tip of the impeller in the squeezing / dehydrating portion. Pushing force in the tip direction can be obtained, and the impeller can be improved in terms of conveyance efficiency and dewatering capacity. Continuous operation to obtain a dehydrated cake with a uniform moisture content becomes possible, and if it is formed with one arc, the manufacture and processing of the impeller can be facilitated and the cost can be reduced.
Therefore, it becomes a continuous pressure dehydrator for concentrating and pressure-dehydrating raw solutions such as sewage sludge, food wastewater sludge and human waste sludge.

DESCRIPTION OF SYMBOLS 1 Filter plate 2 Filter ring outer ring 4 Filtration chamber 6 Impeller 8 Drive shaft 12 Supply path 14 Blade 17 Discharge port a Start point b End point c Intermediate point α, αa, αb, αc Delay angle O Center R Radius

Claims (5)

A pair of disc-shaped filter plates (1, 1) and an annular filter chamber outer ring (2) form a filter chamber (4), and a blade is attached to a drive shaft (8) inserted through the center of the filter chamber (4). In the pressure dehydrator in which the vehicle (6) is disposed, the liquid supply path (12) is formed in the drive shaft (8), and the discharge port (17) is opened in the filter outer ring (2).
The blade (14) is continuously formed from the starting point (a) to the end point (b) through the intermediate point (c) of the squeezing / dehydrating part, and retracted backward in the rotational direction as the end point (b) is approached. An impeller of a continuous pressure dehydrator, wherein the delay angle (α) is increased from c) toward the end point (b). 2. The continuous pressure dehydrator according to claim 1, wherein the intermediate point (c) is positioned between 1/3 and 2/3 of the radius (R) of the impeller (6) from the center (O). Impeller. The impeller of the continuous pressure dehydrator according to claim 1 or 2, wherein a delay angle (αb) of the end point (b) is set to 60 ° to 90 °. The impeller of the continuous pressure dehydrator according to any one of claims 1 to 3, wherein the impeller (14) of the impeller (6) is formed in one arc. The impeller of the continuous pressure dehydrator according to any one of claims 1 to 3, wherein the blade (14) from the start point (a) to the intermediate point (b) is formed in a substantially straight line.