JPH067936B2 - Sludge dewatering device in the centrifugal action area of the decanter centrifuge - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for dewatering sludge in a centrifugal action area.

[Conventional technology]

When dewatering sludge, especially finely dispersible sludge produced by settling the suspension in a decanter-type screw centrifuge, the greater the radial acceleration, the greater the inner rotor and outer rotor equipped with the conveying screw. The smaller the difference in the number of revolutions and the higher the solid loading, the lower the residual water content. A so-called squeeze rate can be obtained from these three variables in consideration of the above relationship. In the predetermined range of the squeezing rate, the residual water content continuously decreases, but when the squeezing rate exceeds the predetermined squeezing rate, the amount of the residual water content does not change even if the squeezing rate is further increased. In other words, once the squeeze rate exceeds a certain limit, it is no longer possible to reduce the residual water content any further.

Physically explaining this, in the case of the limit-residual moisture, all particles are in solid contact with each other, which results in the lowest packing density. However, the theoretical value of this marginal residual water is much lower than the value obtained with an actual precipitation centrifuge. Even large-scale equipment with high technology has not reached the above limit residual water until now.

[Problems to be Solved by the Invention]

The object of the present invention is to reduce the residual water content of sludge significantly with a relatively low technical cost and economical cost, even if the force of pressing the sludge is relatively weak, and the sludge in the centrifugal action area can be reduced. It is to provide a device for dehydrating water.

[Outline of Invention]

In the present invention for solving this problem, the inner rotor rotates at a different rotational speed from the outer rotor, and the sludge is dewatered in the centrifugal force action area of the decanter type screw centrifuge in which the stirring element is provided in the inner rotor. In the device for
In addition to the agitation elements provided on the inner rotor, other agitation elements are provided on the outer rotor, the other agitation elements extending radially inward from the outer rotor.

This additional stirrer element on the outer rotor exposes the sludge to very high mechanical stresses and very little residual moisture. This is especially due to the following reasons. That is, the strong mechanical stress on the sludge locally compresses the sludge, creating a shear gap in the sludge, through which the liquid is very easily radially inward in the centrifuge. Because it flows.

The additional stirring element is preferably designed as a stirring blade with adjustable angle of attack. By this means, the device according to the invention can be optimally adapted to the respective sludges for loosening and dewatering them in the drum part.

Furthermore, all the stirring elements in the centrifuge are provided in the region of the transition from the cylindrical part to the conical part of the drum part of the outer rotor. This will not adversely affect the solid-liquid-separation process in the cylindrical part of the drum part and will enhance the dehydration of the solid already separated from the liquid in the conical part of the drum part.

To enhance the dewatering action of the sludge, it is advantageous if stirring elements are provided between the screw blades.

Further, the above problem is that at least one centrifuge is directly connected to the solid outlet side of the decanter-type screw centrifuge, and the inner rotor of the centrifuge rotates at a different rotational speed from the outer rotor to dehydrate sludge. In the device for carrying out, a centrifuge connected to a decanter-type screw centrifuge comprises, in addition to the stirring element provided on the inner rotor, another stirring element provided on the outer rotor, The solution is also that the elements extend radially inward from the outer rotor.

In this case, the screw is subjected to a stress of completely different nature in addition to the centrifugal action in the centrifuge connected to the decanter type screw centrifuge. This is because this centrifuge is designed as a shearing centrifuge. Therefore, the sludge that has already been pre-dewatered is subjected to the centrifugal action in this centrifuge (hereinafter referred to as the shearing centrifuge) connected to the decanter type screw centrifuge, and at the same time, it is unraveled so that it becomes a liquid passage. Shear gaps, through which liquid can flow radially inward from the sludge. This causes the sludge to undergo a much better dewatering action in the connected shear centrifuge than in known screw centrifuges.

It is desirable that the inner rotor of the decanter screw centrifuge and the inner rotor of the shearing centrifuge each have their own drive. As a result, the inner rotor of the decanter screw centrifuge and the inner rotor of the shearing centrifuge can be driven at different variable rotational speeds, thus optimizing solid discharge and dewatering from the centrifuge. be able to.

Further, it is desirable that the drum portion of the outer rotor of the shear centrifuge has a larger diameter than the drum portion of the outer rotor of the decanter screw centrifuge. As a result, it receives a large centrifugal force in the shearing centrifuge,
Improved sludge re-dehydration.

〔Example〕

 The present invention will be described below with reference to the drawings.

As shown in FIG. 1, the outer rotor 10 is rotatably supported by rolling bearings 20 on both sides. The outer rotor 10 is provided with a decanter type drum portion 12, which is formed in the shape of a cone having a gentle slope. On the open side of this drum part, there is a conical part 13 with a steep slope.
Are connected. This steeply conical portion 13 is called a biconic portion, and this biconic portion forms a substantially ring-shaped chamber, and most of this chamber is located radially outward of the inner chamber of the drum portion 12. is doing. The inner rotor 11 is concentrically and rotatably supported in the outer rotor 10. This inner rotor has sliding bearings 2 on both sides as shown in FIG.
It is rotatably supported by the outer rotor 10 via 1. The outer rotor 10 and the inner rotor 11 have turbine blade-shaped stirring elements 14 or 15 for stirring sludge. This stirring element 14 is screwed onto the outer rotor 10 from the outside, in particular so that its angle of attack can be adjusted. The stirring element 15 of the inner rotor 11 is welded to the inner rotor body.

The pre-concentrated sludge is supplied into the apparatus via a stationary inflow pipe 16 by a pump. This inflow pipe is fixed to a clamp 17 connected to the underframe of the apparatus. The sludge flows through the openings 18 into the intermediate chamber between the inner rotor 11 and the outer rotor 10. The two rotors rotate at different rotational speeds. The rotation at different rotational speeds is achieved by the planetary gear unit.

Stirring element 1 which can be formed as a guide plate, vane or pin
The sludge is sheared between the stirring elements, since 4, 15 are interdigitated with each other from the outside and inside. At that time, the liquid is separated from the sludge. Since this liquid has a low specific gravity, it tends to flow inward in the radial direction. The liquid separated from the sludge forms a liquid layer inside the sludge in the radial direction, and the inner diameter of the liquid layer is the ring-shaped dam 30.
Adjustable by.

The sludge is transported to the open side of the drum portion 12 by the centrifugal force and flows into the conical portion 13 having a steep slope. This sludge transfer can be accelerated or decelerated by appropriate formation and placement of the stirring elements 14,15.

The sludge thus concentrated is used as the outer rotor 10
From the rotating edge of the bicone forming the steep portion 13, discharge is carried out continuously through some nozzles 19 or discontinuously through a ring-shaped slide valve that is operated. This is basically well known.

The stirring element 15 of the inner rotor 11 can also be provided in the bicone. In that case, the stirring element is arranged to be immersed in the sludge.

Known methods of measuring sludge level can be used to prevent all of the concentrated sludge from flowing out of the nozzle 19.

The sludge flow through the device is indicated by the arrows in FIG. This arrow points to the left in the inflow pipe 16 and diagonally to the upper left to pass through the opening 18,
The upper side of the nozzle 19 faces upward.

The liquid collected on the inner side in the radial direction of the sludge flows out over the weir plate 30 along the arrow pointing to the upper right.

If the sheared sludge has sufficient viscosity, the sludge can be carried upward along the tapered wall of the drum. An example thereof is shown in FIG. FIG. 2 shows a conical countercurrent device.
In this case, the spiral part of a normal screw is provided on the side where the liquid flows out. This screw helix, or screw blade, is shown at 22 in FIG.

In FIG. 2, parts similar to those of FIG. 1 are given the same numbers as in FIG.

As with the known co-current centrifuge, in the case of the device shown in FIG. 2, the pre-concentrated sludge is fed into the device from the side opposite the solids outlet. In that case, the sludge flows in the inflow pipe 16 along the arrow pointing to the left, flows leftward in the device, and flows out downward from the discharge port 31.

The liquid separated from the sludge flows over the weir plate 30 along the arrow pointing to the lower right.

Guide vane-shaped stirring element 1 screwed into the outer rotor 10
4 has its angle of attack to the generatrix of the conical drum adjustable externally. The stirring element 15 fixed to the inner rotor 11 can be welded immovably or held rotatably so that its angle of attack can be changed. The sludge to be dewatered still more flows from the stationary inlet pipe 16 into the inner rotor 11 and through the opening of this inner rotor into the separation chamber, ie the chamber between the inner rotor 11 and the outer rotor 10. The inner rotor is rotatably supported by the outer rotor via a slide bearing 21, as in the case of the device of FIG.

Another embodiment of the stirring element according to the invention is shown in FIGS. In this example, a conventional centrifuge that can operate as a countercurrent decanter screw centrifuge or a co-current decanter screw centrifuge can be modified as follows by structurally modifying it. You can
That is, in addition to the sludge transportation by the screw, the sludge can be deformed so as to exert an additional mechanical action, as shown in FIG.

Between the screw blades 25, shear blade-shaped stirring elements 23 a or 23 b are mounted on the radial pins 24, respectively. This stirring element 23a advances or retracts the sludge. On the other hand, the stirring element 23b conveys the sludge in one direction. As shown in the right part of FIG.
The tongue piece 26 attached to the screw blade 25 produces a shearing action.

The mechanical stresses of the sludge obtained by the invention, in particular the shear stresses, are also brought about by the partial fracture of the screw in its peripheral region. FIG. 4 shows the screw blade 25a on the left side thereof. This screw blade has a radial cutout or slit 29a.
Is equipped with. A blade-shaped stirring element 27 is formed between the slits, and the stirring element acts to push the sludge back through the slit 29a. This shearing action then acts mechanically on the sludge to effect the dewatering that the invention provides.

To improve the transport effect, the area between the slits 29b can be bent so that an inclined blade-like stirring element 28 is formed. As a result, the outer peripheral region of the screw blade 25b is formed into a turbine blade shape.

FIG. 5 shows a cylindrical decanter type screw centrifuge 6
1 and the shearing centrifuge 62 are shown schematically in cross section. The screw blades 56 of the decanter type screw centrifuge 61 have the same pitch. The cylindrical drum portion 55a forms an outer rotor of the decanter type screw centrifuge 61 and an inner rotor of the shearing centrifuge 62. On one side of the drum part, a suspension inflow part 58 and a separated liquid outflow part 57 are indicated by arrows.
A shearing centrifuge 62 is connected to the solid discharging portion of the decanter type screw centrifuge 61 formed as the sludge valve 72. This shearing centrifuge is provided outside the decanter type screw centrifuge 61. The sludge generated by the precipitation is conveyed by the screw blade 56 and is supplied to the outer centrifugal separator 62 for shearing through the controllable sludge valve 72. The shearing centrifuge is provided with stirring elements 52 and 53, which are located outside the drum portion 55a of the decanter type screw centrifuge 61 and the shearing centrifuge 62 and the outer rotor 6.
It is attached to the inside of 3. In this shearing centrifuge, the stirring elements 52 and 53 perform shearing, and the strongly dehydrated sludge is discharged from the sludge outlet 51.
The separated liquid is discharged from the separated liquid outlet 67.

The separated liquid may be returned to the inflow part 58. Since the sludge valve 22 is provided, only the sludge that has been concentrated in advance is discharged through the drum portion 55a of the decanter type screw centrifuge 61. Outer rotor 63 of shearing centrifuge
And the screw equipped with the blade 56 are connected to each other and driven together, and therefore have the same rotational speed difference with respect to the drum portion 55a of the decanter type screw centrifuge 61.

In most cases, increasing shear rate is important for shear. This is achieved by arranging the centrifuge radially in and out, even in the case of small speed differences as required for cleaning.

Another shearing centrifuge 62 arranged to surround the decanter type screw centrifuge 61 is shown in FIG. This shearing centrifuge includes a decanter type drum portion formed in a conical shape. An outlet 51 for the sheared solids is provided in the tapered portion of the shearing centrifuge 62. The liquid separated by shear overflows from the dam 78.

The concentrated sludge exiting the cylindrical-conical decanter screw centrifuge 61 flows downward (to the right) along the cone on the surface of the cake, and the shear-concentrated cake flows countercurrently in the conical drum. Transported upward (left side). The decanter centrifuge 61 is a countercurrent type, but a parallel flow type may be used. The liquid separated by shearing is discharged from the outlet 67 in the lower region.

In FIG. 7, a decanter type screw centrifuge 61
Solids coming out of the pipe pass through the guide passage 81 and the centrifugal separator 6 for shearing.
2 is supplied. The separated liquid generated by shearing is returned to the inlet 58 of the decanter type screw centrifuge 61 via the return pipe 60. In this case, a countercurrent or cocurrent decanter type screw centrifuge can be used.

In FIG. 8, a cylindrical decanter type screw centrifuge equipped with a nozzle opening and a conical shear centrifuge provided so as to surround it are combined. In this case, the large diameter portion is located near the sludge overflow portion, that is, near the sludge valve 72. The liquid separated by shearing is discharged from the shearing centrifugal separator as shown by an arrow 67 through the opening of the back plate. The inner rotor of the decanter type screw centrifuge and the outer rotor of the shearing centrifuge 62 are provided and connected on the same shaft.

The embodiment of FIG. 9 is similar to the embodiment of FIG. 6 except that the outer rotor 79 of the shearing centrifuge 62 is cylindrical. In the region of this centrifuge, the outer rotor of the decanter-type screw centrifuge 61 is conical. Again, the stirring element 52 is mounted on the outer rotor of the decanter screw centrifuge 61 and the stirring element 53 is mounted on the inner surface of the outer rotor 79 of the shearing centrifuge 62.

The conical shearing centrifuge 62 shown in FIG. 10 is connected to a cylindrical decanter-type screw centrifuge 61. Both inner rotors are in a common decanter drum section, but can be operated at different speeds. The screw with increasing pitch is rotated by an outer rotary drive, while the drive 65 for the inner rotor of the shearing centrifuge is internal. Thereby, the difference in the number of rotations can be adjusted individually.

The device of FIG. 11 is in principle the same as the device of FIG. The difference is that the decanter type screw centrifuge 61 and the shearing centrifuge 62 are cylindrical. As a result, the outer rotor 82 of the shearing centrifugal separator 62 is also formed in a cylindrical shape.

Decanter type screw centrifuge 61 shown in FIG.
The drum section does not have a metal cone. In this case, a cylindrical drum part is used, in which a cylindrical-conical inner rotor is provided. The conical portion is formed by the sludge itself and solidifies over time.
As a result, no gap is created between the screw and the conical portion. Sludge slip-off is extremely low. Again, counter-current or co-current decanter type screw centrifuges can be used. In this example, a shearing centrifugal separator 62 is provided so as to surround the decanter type screw centrifugal separator 61.

In the case of the embodiment of FIG. 13, a cylindrical-conical decanter screw centrifuge 61 is axially fixedly connected to a shear centrifuge 62. Both drum parts of the decanter type screw centrifuge 61 and the shearing centrifuge 62 form a rigid unit. Since the inner rotor of the decanter type screw centrifuge 61 and the inner rotor of the shearing centrifuge are driven separately, they can rotate at different rotation speeds. The shafts of the inner rotors extend to one side, here to the left. Each of these axes is equipped with its own rotary drive. The sheared separation liquid is again returned to the inlet 57 via the return pipe 60.

FIG. 14 shows a cylindrical countercurrent decanter screw centrifuge and a conical shearing centrifuge combined axially. In this case, both of them can rotate at various rotational speed differences. Due to the provision of the dipping disk 71, only the bottom concentrated sludge overflows from the decanter screw centrifuge into the shear centrifuge. The sheared liquid is returned directly from the shearing centrifuge to the clarification section of the decanter screw centrifuge.

In FIG. 15, a cylindrical decanter screw centrifuge 61 is combined with a cylindrical shear centrifuge 62. At that time, the sludge flows from the cylindrical drum portion 55 into the shearing centrifugal separator 62 surrounding it. Cuff 70
With the provision of, only the concentrated outer sludge can reach the shear centrifuge.

In FIG. 16, a cylindrical decanter type screw centrifuge 61 is provided in a common drum part together with a cylindrical-conical shearing centrifuge 62. even here,
Both inner rotors can rotate at different speeds. The sludge is conveyed by the siphon tube 54 from the bottom of the decanter type screw centrifuge to the shearing centrifuge. Here, a countercurrent type decanter type screw centrifuge is shown.

In FIG. 17, a cylindrical decanter type screw centrifuge 61 is provided with two shearing centrifuges 62a and 62b. The shearing centrifuge 62a is separated from the decanter type screw centrifuge by a dipping disk 71. The water separated by this shearing centrifuge is returned to the decanter type screw centrifuge through the co-rotating overflow pipe 66. The pre-sheared solids reach the outer shearing centrifuge 62b. This structure allows
A very strong separating action is achieved.

Outer rotor 55 of the decanter type screw centrifuge 61
Is connected to the outer rotor of the shearing centrifuge and the inner rotor of the decanter screw centrifuge 61 is connected to the inner rotor of the outer shearing centrifuge.

In the case of the embodiment shown in FIG. 18, the inner rotor of the decanter type screw centrifuge and the inner rotor of the shearing centrifuge can be rotated at different rotational speeds with respect to the outer rotor. Here, the concentrated solids are separated and discharged by the peeling device 6
9 is discharged from the outer rotor. This stripping ejector is preferably provided at the end of the inner rotor of the shearing centrifuge. Decanter type screw centrifuge 61
May be a co-current type or a counter-current type. The screw blades have an increasing pitch here. The cylindrical inner rotor of the decanter type screw centrifuge and the cylindrical inner rotor of the shearing centrifuge are assembled so as to be aligned in the axial direction.

The apparatus shown in FIG. 19 also includes a peeling and discharging device 69. In this case, the diameter of the shearing centrifugal separator 62 is larger than the diameter of the cylindrical-conical decanter type screw centrifugal separator 61.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a sludge dewatering device, FIG. 2 is a vertical sectional view of another embodiment of the sludge dewatering device, and FIG. 3 is an implementation of a stirring element provided between screw blades of a conveying screw. The figure which shows an example, FIG. 4 is a figure which shows the deformation | transformation conveying screw which equips the outer peripheral area of a screw blade, and FIGS. 5, 6, 8, 9, 12, 15, and 17 are decanter type screw centrifuges. Longitudinal cross-sectional view of the sludge dewatering device having a shearing centrifugal separator on the outside in the radial direction of Fig. 7, Fig. 7, 11, 13, and 19 show a decanter-type screw centrifuge and a shearing centrifuge arranged axially. Figures 10, 14, 16 and 18 are longitudinal cross-sections of a decanter screw centrifuge and a shear centrifuge arranged axially in a common outer rotor. Reference numeral 10 ... Inner rotor 11 ... Outer rotor 14, 15, 23a, 23b ... Stirring element 25 ... Screw blade 52, 53 ... Stirring element 61 ... Decanter type screw centrifuge 63 ... For shearing centrifuge

Continuation of the front page (56) Reference JP-A-58-81454 (JP, A) Actually open 53-44373 (JP, U) Actually open 53-48277 (JP, U) JP-B 56-3784 (JP , B2)

Claims (7)

[Claims] 1. An apparatus for dewatering sludge in a centrifugal force action area of a decanter type screw centrifuge, wherein an inner rotor rotates at a different rotational speed from an outer rotor and an inner rotor is provided with a stirring element. In addition to the stirring elements (15, 23a, 23b) provided on the rotor (11), another stirring element (14) is provided on the outer rotor (10), and the other stirring element (14) is provided on the outer rotor. (10)
A device extending radially inward from the device. 2. Device according to claim 1, characterized in that the further stirring element (14) is formed as a stirring blade with adjustable angle of attack. 3. All stirring elements (14,
15. Device according to claim 1 or 2, characterized in that 15, 23a, 23b) are provided in the region of the transition from the cylindrical part to the conical part of the drum part of the outer rotor. 4. Stirring element (23a, 23b) is provided between screw blades (25) according to any one of claims 1 to 3. apparatus. 5. At least one centrifuge is directly connected to the solid outlet side of the decanter type screw centrifuge,
In a device for dewatering sludge, in which the inner rotor of this centrifuge rotates at a different rotational speed than the outer rotor, the centrifuge (62) connected to the decanter type screw centrifuge (61) is In addition to the stirring element (52) provided on the outer rotor, the other stirring element (53) provided on the outer rotor, the other stirring element (53) extending radially inward from the outer rotor. A device characterized by. 6. A decanter type screw centrifuge (61)
6. The inner rotor of claim 1 and the inner rotor of the centrifuge (62) connected to this decanter type screw centrifuge are each provided with its own drive device. apparatus. 7. The diameter of the outer rotor drum of the centrifuge (62) connected to the decanter screw centrifuge is larger than the diameter of the outer rotor drum (55) of the decanter screw centrifuge (61). An apparatus according to claim 5 or 6, characterized in that: