JP4163050B2 - Upper solids reflux type screw conveyor centrifugal dehydrator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal separator in which dehydration treatment of industrial waste water including sewage sludge and solid components, and concentration, dehydration, and recovery of solid-liquid separation components of slurry-like substances are performed by centrifugal force.
[0002]
[Prior art]
Conventionally, a decanter type centrifuge is generally used for solid-liquid separation of sludge and the like. A so-called negative system, which is a type of this decanter type centrifugal separator, basically has a sedimentation bed outlet at a position equal to or higher than the liquid level in the bowl, Even if the water head pressure is used, the water head pressure of the treatment liquid in the bowl is smaller than the water head pressure of the heavy sediment layer, and it is impossible in principle to discharge only with the water head pressure, and some kind of discharge mechanism is required And Patent Document 1 presents a centrifuge for the purpose of reducing the moisture content and improving the separation efficiency by discharging sludge directly from the portion of the bowl with the lowest moisture content in the decanter type centrifugal separator. Has been. As shown in FIG. 5, this apparatus is a centrifugal separator in which a screw conveyor 10 rotated with a relative speed difference is accommodated in a bowl 1 rotated at a high speed, and a dehydrated cake is placed in a rear end wall 2 of the bowl 1. The discharge path 20 is provided, an opening 20a into the bowl 1 of the path 20 is provided in the vicinity of the inner peripheral wall of the bowl, and the discharge port 20b to the outside of the end wall of the discharge path is at a higher position, that is, the inner peripheral wall of the bowl It is provided at a radius position smaller than the radius. As a result, the discharge cake b from the discharge path 20 can only be discharged from the precipitation layer deposited on one end of the bowl 1 from the portion having the highest consolidation effect due to the hydraulic head pressure of the centrifugal force acting on the sediment. A configuration is adopted in which the product is discharged to the outside of the bowl where no centrifugal force is applied. This directly discharges only the hardest part of the sediment deposit layer in the bowl, which is subjected to the highest consolidation action, i.e., the hardest part with the lowest moisture content. The water content of the dehydrated cake b could be lowered as much as possible. The sediment layer having a low water content is usually difficult to discharge. However, in the centrifugal separator according to the present invention, the high water head generated by forming a high sediment layer by the discharge resistance of the discharge path. The pressure can be discharged without providing any special discharging means. Therefore, a high dehydration rate and a high separation efficiency can be obtained with a relatively simple apparatus and a relatively small apparatus.
[0003]
The above-mentioned straight body type dehydrator has an excellent ability in terms of dewatering efficiency, and is an apparatus that is particularly effective for difficult-to-dewater sludge with a high VTS (organic matter content) and low fiber content. In addition, since it is necessary to operate the bowl 1 at a high speed of about 2,000 to 3,000 rpm, there is a problem that a large amount of driving energy is required. Nearly 60% of the sludge treatment in Japan adopts a standard activated sludge method that activates activated sludge with bacteria, and incinerates the activated sludge that is discharged. Since this activated sludge contains a large amount of fiber and has good dewaterability, a water content suitable for incineration can be obtained relatively easily, so an energy-saving dehydrator tends to be desired. Under such circumstances, many facilities employ low-power belt press dehydrators. The above-described straight body type dehydrator according to Patent Document 1 is greatly superior in terms of dewatering performance, but requires high-speed rotation drive, so it is necessary to increase the size of electrical equipment and to provide a soundproof package. Focusing on this point, the conditions are severe compared to belt press dehydrators.
[0004]
[Patent Document 1]
[Patent Document 1] Japanese Patent Laid-Open No. 2001-219097 “Centrifuge” published on August 14, 2001 Description of paragraph numbers [0009] to [0011] and FIG.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a new type screw discharge type decanter that is operated with a low centrifugal force while maintaining performance with high dehydration efficiency.
[0006]
[Means for Solving the Problems]
The upper solids reflux type screw conveyor centrifugal dehydrator according to the present invention includes a cylindrical bowl rotating in one direction, and a screw conveyor rotating in the same direction coaxially with the bowl in the bowl and having a rotational speed difference. The heavy components are separated and settled by centrifugal force from the processing liquid supplied into the rotating bowl, and are collected on one side of the bowl by a screw conveyor, so that the heavy components and the separated liquid are separated and discharged. In the centrifugal separator, a screw conveyor rotary drum is provided with a circulating portion consisting of a group of openings or a screen, and means for bringing a soft solid flowing out into the conveyor hub through the circulating portion into contact with a new processing liquid. A circulation system is used in which the solid sediment is brought into contact with a new solid substance in the centrifugal sedimentation section and subjected to separation treatment. As a particularly effective aspect, a discharge path for the precipitated heavy component is provided in one end wall of the bowl, an opening to the bowl of the discharge path is provided in the vicinity of the inner peripheral wall of the bowl, and the precipitation layer mainly has a weight in the vicinity of the opening. This system is incorporated into a centrifuge device that is discharged out of the bowl where no centrifugal force is applied by centrifugal head pressure of the component deposition layer.
In addition, as a means for bringing the soft solids flowing out into the conveyor hub through the circulating portion into contact with the new processing liquid, the rotary form of the screw conveyor is not cylindrical but has a taper shape with a shorter radius toward the dewatered cake discharge port side. Was adopted.
Further, as a further configuration, the conveyor hub is provided with cleaning liquid supply means for washing away soft solids that have flowed into the conveyor hub through the openings or screens provided in the screw conveyor rotating drum. To do.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 4, when the processing liquid is separated by a high centrifugal force type decanter, the solid A which is tightly clamped on the outside in the bowl 1 and the liquid C is separated on the inside, but in the middle, the particulate floating is suspended. A soft and slimy layer in which the solid B is mixed with the liquid. The solid A that is tightly tightened is difficult to be discharged, and the soft solid-liquid mixture B is easily discharged. If the rotation difference with the screw 12 is increased so as to discharge the solid matter A, the soft solid-liquid mixture B escapes into the liquid C and the liquid separating function is lowered. If the rotational difference with the screw 12 is made small so as to discharge the soft solid-liquid mixture B from the solid discharge port 7, the solid A that has been tightly tightened is not discharged, and clogging occurs in the machine. Therefore, in the present invention, the intermediate layer in the solid-liquid mixed state is returned to the conveyor hub 4 without escape to the liquid discharge port 8 or the solid material discharge port 7, and the solid material A in the newly loaded processing liquid and The idea is to come up with a method of merging and re-centrifuged. That is, in this method, the solid A is laminated on the refluxed solid B layer, and the solid B is easily transferred to the large diameter side of the bowl by receiving a centrifugal force. Receiving, sedimentation and compaction will proceed. Further, since the solid B is also subjected to centrifugal force during the reflux, it also undergoes precipitation during that time.
[0008]
FIG. 1 shows an overall configuration diagram of an upper layer solids circulation type screw conveyor centrifugal dehydrator according to the present invention. What is shown here is the configuration of a straight barrel type high-speed centrifugal dehydrator presented in Patent Document 1 as the configuration of the screw conveyor centrifugal dehydrator, that is, the discharge path of the dehydrated cake in the one end wall 2 of the bowl 1. 20, the opening 20a into the bowl 1 of the passage 20 is provided in the vicinity of the inner peripheral wall of the bowl, and the outlet 20b to the outside of the end wall of the discharge passage is higher than that, that is, the radius of the inner peripheral wall of the bowl A configuration provided at a small radial position is adopted. As a result, the discharge cake b from the discharge path 20 can only be discharged from the precipitation layer deposited on one end of the bowl 1 from the portion having the highest consolidation effect due to the hydraulic head pressure of the centrifugal force acting on the sediment. After that, it has a function of being discharged out of the bowl where no centrifugal force is applied. The main structure peculiar to the present invention is that the rotary drum 11 of the screw conveyor 10 is not a sealed wall but a screen or a perforated wall, and the cleaning water for cleaning the space in the rotary drum 11, that is, the conveyor hub 4 is supplied. This is a point that is adopted.
[0009]
In the apparatus having the above-described configuration, when the rotation difference of the screw conveyor 10 is increased with respect to the rotation of the bowl 1, the solid A in FIG. And pressurized. Since the opening 20a of the sedimentation layer discharge path 20 is provided in the vicinity of the maximum diameter of the bowl 1, the solid substance A that is most tightly tightened is discharged therefrom, and the solid-liquid mixed solution B forming the intermediate layer is discharged from the discharge path 20 Will never be done. The solid-liquid mixture B that is pressurized and transferred to the solid discharge port 7 side together with the solid substance A that is tightly tightened is rotated through the wall of the rotary drum 11 of the screw conveyor 10 that is a screen or a perforated wall. It flows out into the conveyor hub 4 which is a space in the cylinder 11. Since the rotating drum 11 is rotating, centrifugal force is acting on the one in the conveyor hub 4. However, since the pumping force by the screw conveyor 10 is superior to the centrifugal force, solid-liquid mixing is performed. The liquid B flows out into the conveyor hub 4. The solid-liquid mixed solution B that has flowed out into the conveyor hub 4 is washed away by the cleaning liquid, is refluxed to the centrifugal sedimentation section 5 on the left side in the figure, and is centrifuged again at the centrifugal sedimentation section 5 together with the new processing liquid. Although it is not essential that the conveyor hub 4 has a tapered surface as shown in FIG. 3, when such a configuration is adopted, the solid-liquid mixed solution B and the cleaning solution are left in the figure with a large radius due to the action of centrifugal force. It is easy to be recirculated to the centrifugal sedimentation part 5 in the area. The cleaning liquid may be supplied in a cyclone flow. At that time, the centrifugal force is further increased by the generation of the cyclone flow in the conveyor hub 4, and the precipitation of solid matter can be promoted. As described above, in the present invention, the soft and easy-to-float solid B is not discharged from the sediment layer discharge path 20, but is refluxed, merged with the solid A having a large specific gravity, stacked, and centrifuged again to form a solid. The recovery rate as a thing becomes high. The cleaning liquid used at this time may be the separation liquid processed in this system, and no special cleaning liquid is required.
[0010]
The greatest advantage of the present invention is that the necessary centrifugal force may be 100G to 300G. Since the separation capability is structurally high, the conventional high centrifugal force is not required. Incidentally, the conventional high centrifugal force dehydrator requires a rotation of 2,000 to 3,000 rpm and a high power of 2 KW / m ³ , but the apparatus according to the present invention operates with a low centrifugal force, so that the power consumption is 0.4 KW / m. ^It is greatly reduced to about ³ . In addition, since this is a low-rotation drive, noise is reduced, so this type of device does not require a soundproof package that was a necessary accessory. In addition, with the low centrifugal force driving, the rotating body has lower mechanical strength conditions than conventional ones, making it possible to reduce the weight and reducing the wear of parts due to processed materials, and to provide special tiles to prevent screw conveyor flight wear. There are many advantages, such as not necessary. In the present invention, the solid-liquid mixed solution B flows out into the conveyor hub, joins with a new processing solution, and is centrifuged again. The reflux path uses a conveyor hub that has been a hollow space in the past. And since it is not necessary to install a new component member, it can implement with the form of effective utilization of cavity space, without enlarging an apparatus. Any of the items listed above can effectively reduce the cost of the system.
[0011]
In the present invention, the solid-liquid mixed solution B is filtered through the wall of the rotary drum 11 of the screw conveyor 10 having a screen or a perforated wall, and flows out into a conveyor hub which is a space in the rotary drum 11. In this respect, the configuration is similar to that of a conventional berskline type decanter type centrifugal dehydrator. In the case of a berscline type decanter, since all of the processing liquid is filtered from the outer periphery of the bowl, there is a disadvantage that clogging is likely to occur, but in the present invention, only the solid liquid mixture B in the upper layer that has been centrifuged is used. Since the outflow is filtered from the outside to the inside of the screen, the amount is about 30% of the processing liquid, and solids that cause clogging are separated into the lower lower layer of the bowl and directly discharged from the precipitation bed discharge path. , Never go through this screen. Therefore, there is no concern about clogging of the screen unlike the conventional Berskline type decanter type centrifugal dehydrator.
[0012]
【The invention's effect】
The upper solids reflux type screw conveyor centrifugal dehydrator according to the present invention includes a cylindrical bowl rotating in one direction, and a screw conveyor rotating in the same direction coaxially with the bowl in the bowl and having a rotational speed difference. The heavy components are separated and settled by centrifugal force from the processing liquid supplied into the rotating bowl, and are collected on one side of the bowl by a screw conveyor, so that the heavy components and the separated liquid are separated and discharged. In the centrifugal separator, the soft solid material forming a layer inside the hard solid material layer pressed outward by centrifugal force is caused to flow out into the conveyor hub via an opening group or a screen provided in the screw conveyor rotating drum, Since it is to be subjected to separation treatment again in the centrifugal sedimentation section, the solid matter having a large specific gravity present in the newly supplied treatment liquid is placed on the soft solid matter B layer. Laminated may perform centrifuged effectively. In addition, since the centrifugal force is also applied when the inside of the conveyor hub is refluxed, a precipitation action is also applied during that time, and the soft solid is changed to a solid solid. Further, in the present invention, the solid-liquid mixed solution B flows out into the conveyor hub, joins with a new processing solution, and is centrifuged again. The reflux path uses a conveyor hub that has been a conventional hollow space. Therefore, since it is not necessary to install a new component member, the apparatus can be implemented in the form of effective use of the hollow space without increasing the size of the apparatus.
In addition, a discharge path for the precipitated heavy component is provided in one end wall of the bowl, an opening into the bowl of the discharge path is provided in the vicinity of the inner peripheral wall of the bowl, and the precipitation layer is a heavy component deposition layer mainly in the vicinity of the opening. The present invention adopting this upper solids reflux system to the screw conveyor centrifugal dehydrator that is discharged to the outside of the bowl where centrifugal force is not applied due to the centrifugal water head pressure of the present invention discharges only the hardest solids from the sediment outlet. In addition, it is possible to effectively perform dehydration by centrifugation of the solid matter.
[0013]
In the upper solids reflux type screw conveyor centrifugal dehydrator of the present invention, when the tapered shape of the rotating drum of the screw conveyor is not cylindrical but the radius is shortened on the side of the dewatered cake outlet, The inner peripheral surface of the rotating drum is caused to flow toward the separation liquid discharge side, and is effectively centrifuged again with a new processing liquid. Further, the upper solid material of the present invention is provided with cleaning liquid supply means for washing away the soft solid material that has flowed into the conveyor hub through the opening group or screen provided in the screw conveyor rotating drum in the conveyor hub. The reflux-type screw conveyor centrifugal dehydrator can stably perform reflux of the upper layer solids without causing the clogging of the opening group or the screen provided in the rotary drum.
[0014]
The greatest merit of the upper solids reflux type screw conveyor centrifugal dehydrator of the present invention is that the necessary centrifugal force may be 100G to 300G because of its structurally high separation ability. As a result, in the device of the present invention, the power consumption is greatly reduced, the operating cost is reduced, the power receiving facility does not need to be enlarged, and the initial investment cost is also reduced. In addition, this type of equipment does not require a soundproof package, which is a necessary accessory, because of low noise. In addition, due to the low centrifugal force driving, the rotating body has lower mechanical strength conditions than before, making it possible to reduce the weight and reducing the wear of parts due to the processed material, eliminating the need for special tiles, etc. Arise. In addition, since all of the items listed above work effectively to reduce the cost of the system, they are also used as an alternative facility in sewage treatment plants that have conventionally employed low-power belt press dehydrators as energy-saving dehydrators. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an upper solids reflux type screw conveyor centrifugal dehydrator according to the present invention.
FIG. 2 is a view for explaining the mechanism of the present invention for allowing a soft solid intermediate layer to flow into a conveyor hub.
FIG. 3 is a diagram illustrating an embodiment of the present invention in which a refluxed soft solid and a new treatment liquid are joined and centrifuged.
FIG. 4 is a diagram for explaining problems of solid-liquid separation in a conventional screw conveyor centrifugal dehydrator.
FIG. 5 is a diagram illustrating a straight barrel screw conveyor centrifugal dehydrator according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bowl 12 Screw 2 Rear end wall 20 Precipitation layer discharge path 3 Front end wall 20a Opening 4 Conveyor hub 20b Discharge port 5 Centrifugal sedimentation part A Solid solid layer 7 Solid discharge port B Soft intermediate solid layer 8 Separate liquid discharge Exit C Separated liquid layer 10 Screw conveyor 11 Rotating drum

Claims (5)

A cylindrical bowl that rotates in one direction and a screw conveyor that rotates in the same direction coaxially with the bowl in the bowl and rotates in the same direction, and is fed into the rotating bowl the heavy component is separated sedimented by centrifugal force from a liquid, which was integrated on one side of the bowl by a screw conveyor, in a centrifuge device for separating discharging heavy component and separated liquid, or screen openings groups screw conveyor rotating drum And a means for bringing the soft solids flowing out into the conveyor hub through the circulation part into contact with the new processing liquid, and again contacting the new solids with the centrifugal sedimentation part for separation processing. The upper solids reflux type screw conveyor centrifugal dehydrator to be applied.   The screw conveyor centrifugal dehydrator is provided with a discharge path for precipitated heavy components in the one end wall of the bowl, an opening to the bowl of the discharge path is provided in the vicinity of the inner peripheral wall of the bowl, and the precipitation layer is mainly formed in the weight near the opening. 2. The upper solids reflux screw conveyor centrifugal dehydrator according to claim 1, wherein the upper layer solids reflux screw conveyor centrifugal dehydrator is of a type in which it is discharged out of the bowl where no centrifugal force is applied by centrifugal head pressure of the component deposition layer. The means for bringing the soft solids flowing out into the conveyor hub through the circulating section into contact with the new processing liquid is not a cylindrical shape but a taper shape with a shorter radius toward the dewatered cake discharge port. upper solid reflux type screw conveyor centrifugal dehydrator according to claim 1 or 2 as hereinbefore.   4. The cleaning device according to claim 1, further comprising cleaning liquid supply means for washing soft solids that have flowed into the conveyor hub through a group of openings or a screen provided in the rotary drum of the screw conveyor. The upper solids reflux type screw conveyor centrifugal dehydrator according to claim 1.   The upper solids reflux type screw conveyor centrifugal dehydrator according to any one of claims 1 to 4, wherein the centrifugal force during driving is a low centrifugal force of 100 to 300G.

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