EP0447742B1 - Decanter centrifuge - Google Patents
Decanter centrifuge Download PDFInfo
- Publication number
- EP0447742B1 EP0447742B1 EP91100071A EP91100071A EP0447742B1 EP 0447742 B1 EP0447742 B1 EP 0447742B1 EP 91100071 A EP91100071 A EP 91100071A EP 91100071 A EP91100071 A EP 91100071A EP 0447742 B1 EP0447742 B1 EP 0447742B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- bowl
- ring
- head
- discharge port
- shaped
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
- B04B—CENTRIFUGES
- B04B1/00—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles
- B04B1/20—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles discharging solid particles from the bowl by a conveying screw coaxial with the bowl axis and rotating relatively to the bowl
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
- B04B—CENTRIFUGES
- B04B1/00—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles
- B04B1/20—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles discharging solid particles from the bowl by a conveying screw coaxial with the bowl axis and rotating relatively to the bowl
- B04B2001/2075—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles discharging solid particles from the bowl by a conveying screw coaxial with the bowl axis and rotating relatively to the bowl with means for recovering the energy of the outflowing liquid
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
- B04B—CENTRIFUGES
- B04B1/00—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles
- B04B1/20—Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles discharging solid particles from the bowl by a conveying screw coaxial with the bowl axis and rotating relatively to the bowl
- B04B2001/2083—Configuration of liquid outlets
Definitions
- This invention relates to a decanter centrifuge used for a solid-liquid separation of a feed solution containing suspended solids.
- this type of centrifuge comprises a bowl 1 which rotates with a high rotative speed, a screw-conveyor 2 which is disposed coaxially with the rotating bowl 1 and which is pivoted by the rotating bowl 1 so as to be included in the bowl 1. Then, a screw blade 13 is helically provided around the conveyor 2 so that there is a narrow gap between the inner surface of the bowl 1 and the external circumference of the screw blade 13. The rotating bowl 1 and the screw conveyer 2 rotate in the same direction, while there is a necessary differential rotative speed between the bowl 1 and the conveyor 2.
- a feed solution is introduced, through a supply pipe 10, to the rotating bowl 1 from the supply port 10a of the supply pipe 10. Then, due to centrifugal force caused by the rotation of the bowl 1, the feed solution is sprayed to the inner surface of the rotating bowl 1. Therefore, a pool 14 is formed in the bowl 1.
- the solidified particles of the suspended solids are separated from a clarified liquid to be sedimented on the bottom of the pool 14. The solidified particles of the suspended solids are scraped together towards the right side of this figure by the screw blade 13 and discharged.
- the clarified liquid overflows from a liquid discharge port 4 formed on a bowl-head 3 of the bowl 1 and is discharged from the bowl 1.
- a ring-shaped or a board-shaped weir 30 is normally attached to the external side of the base of the bowl-head 3 adjacent to the liquid discharge port 4, in order to adjust the level of the pool 14.
- hp 7.61 x Q x (2r)2 x N2 x 10 ⁇ 7
- hp accelerating power (KW)
- Q flow rate (m3/hr)
- r radius (m)
- N number of revolution (rpm)
- the accelerating power (P) can be decreased resulting in saving the amount of required power.
- the capacity of the rotating bowl 1 for containing the feed solution can be increased. This provides an improved separating efficiency.
- a liquid discharge port 4 is formed so as to cross slantingly the base of a bowl-head 3.
- the liquid discharge port provided on the bowl-head should be formed so as to be adjacent to the axis of the bowl head (See US-A-3,423,015).
- torsional stress is increased at this axis, further, bending stress in the direction of the axis is applied there. Accordingly, the liquid discharge port placed to be adjacent to the rotating axis often causes a problem related to the structural strength of the bowl-head. Therefore, this method for raising the level of the pool always can not be carried out because of the problem related to the structural strength.
- apparatus shown in Japanese Utility Model Publication No. 60-31793 requires high energy for discharging, thus, can not save the amount of required power.
- apparatus shown in Japanese Patent Publication No. 63-31261 is not suitable for discharging solids having a low water content, additionally, this apparatus has problems related to the abrasion of the skimming-blade and other problems related to its complicated structure.
- a rotating bowl is provided with at least one solid discharge port and at least one clarified liquid discharge port.
- a screw conveyor is disposed coaxially with the rotating bowl so as to be included in the rotating bowl. The rotating bowl and the screw conveyor are rotated in the same direction with a differential rotative speed.
- a feed solution to be separated is introduced into a ring-shaped space formed between the rotating bowl and the screw conveyor. The feed solution is continuously separated into solid and liquid by centrifugal force. Then, the solid is discharged from the solid discharge port and the liquid is discharged from the clarified liquid discharge port.
- This centrifuge is characterized by the provision of clarified liquid discharging apparatus which comprises the clarified liquid discharge port, a ring-shaped weir and a plurality of reducing blades.
- Each clarified liquid discharge port is formed on a bowl-head of the rotating bowl so that the inner side of the bowl and the external side of the bowl-head can communicate with each other.
- the ring-shaped weir is mounted on the external face of the bowl-head. Then, a ring-shaped overflow cavity is provided in the ring-shaped weir so as to communicate with each clarified liquid discharge port.
- the ring-shaped weir coaxially has a peripheral opening directing the rotative axis of the bowl-head.
- the plurality of reducing blades is provided in the ring-shaped overflow cavity of the ring-shaped weir in a radial direction from the rotative axis of the bowl-head. Then, the cavity is divided into a plurality of portions while each reducing blade is fixed on at least one of the internal face of the ring-shaped weir and the external face of the bowl-head.
- At least one, or preferably a plurality of liquid discharge port 4, 4 are provided on the periphery of the bowl-head 3, with a predetermined space so that the inner side of the rotating bowl 1 and the external side of the bowl-head 3 can communicate each other through the liquid discharge port 4.
- a ring-shaped weir 5 is mounted on the external face of the base of the bowl-head 3.
- the weir 5 there is a ring-shaped overflow cavity, which commnunicate with each liquid discharge port 4 and which coaxially has a peripheral opening directing the rotative axis of this bowl-head 3.
- the level of the pool 14 is determined by the position of the overflow cavity of the weir 5 on its radius direction, the level of the pool 14 can be raised easily. However, even if the level is raised, since the clarified liquid beyond the liquid discharge port 4 reaches soon at the overflow cavity of the above mentioned ring-shaped weir 5, blade free vortex flow is produced. Then, the clarified liquid overflows the ring-shaped weir 5 with a peripheral velocity, which is the same as or larger than its peripheral velocity at the liquid discharge port 4. Accordingly, pressure drop is increased at the overflow cavity of the ring-shaped weir 5 resulting in decreasing of the amount of overflown clarified liquid.
- a plurality of blades 6 as speed reducing blades is provided in the lip portion of the ring-shaped weir 5 in a radial direction.
- Each speed reducing blade can be fixed to the internal face of the ring-shaped weir 5, to the external face of the bowl-head 3, or to the both faces so as to cross them.
- peripheral velocity and the radius at the clarified liquid discharge port 4 are indicated by V4 and r4 respectively and the peripheral velocity and the radius at the ring-shaped weir 5 are indicated by V7 and r7 respectively.
- V4r4 V7r7
- V7 V4 r4 r7 in case of the provision of the reducing blades
- V4 > V7 therefore, the amount of required power is decreased.
- V7 > V4 in case of the blade free vortex flow without the reducing blades, V7 > V4, therefore, the amount of required power is increased.
- a decanter centrifuge related to the present invention has the following structure.
- a rotating bowl 1 is a combination of a conical section and a cylindrical section.
- a bowl-head 3 is fixed at the larger radius side of the rotating bowl 1 so as to close completely the rotating bowl 1.
- the hollow axis 8 of the bowl-head 3 is extended from the bowl-head 3 so as to communicate with the hollow of the rotating bowl 1.
- the hollow axis 9 of the bowl 1 is extended from the back end of the bowl 1 so as to communicate with the hollow of the rotating bowl 1.
- the hollow axis 8 of the bowl-head 3 and the hollow axis 9 of the bowl 1 are pivoted by bearing stands 18 and 19 respectively. Accordingly, the rotating bowl 1 can be supported horizontally and rotated with a high rotative speed by a rotational force, which is transformed by rotating driving means (not shown).
- a screw conveyor 2 is provided in the hollow portion of the rotating bowl 1.
- the screw conveyor 2 is pivoted coaxially with the rotating horizontal axis of the bowl 1 by means of bearings 16 and 17.
- a hollow tube 12 of the screw conveyor 2 is provided horizontally at the center of the rotating bowl 1.
- a screw blade 13 extends helically the full length of the hollow tube 12 so as to almost reach the inner surface of the bowl 1.
- a transforming rod 20 is provided in the hollow axis 8 of the bowl-head 3. Its one end is connected to the end face of the hollow tube 12 of the screw conveyor 2 and its another end is connected to a gear unit 22.
- the rotational force from the above mentioned rotating driving means (not shown) is transformed, through the intermediary of the gear unit 22, to the transforming rod 20.
- the screw conveyor 2 can be rotated with the high rotative speed.
- the rotating bowl 1 and the screw conveyor 2 are rotated in the same direction, while there is a slightly differential speed between them, which is accomplished by means of the gear unit 22.
- a solid discharge port 11 is formed at the smaller radius side of the rotating bowl 1 on the right side of this figure so that solidified particles scraped together can be discharged from the solid discharge port 11. Then, liquid discharge ports 4, 4 are formed on the base of the bowl-head 3 at the larger radius side of the rotating bowl 1.
- the portion, where the clarified liquid is overflown from each liquid discharge port 4, corresponds to clarified liquid discharging apparatus. Since the present invention is characterized by this portion, this portion will be explained closely referring to Fig. 2.
- the above mentioned plurality of clarified liquid discharge ports 4, 4 are formed so as to be disposed on the periphery of the base of the bowl-head 3 with a predetermined space and so as to be apart from the rotative center of the bowl-head 3 with a predetermined radius. Then, the ring-shaped weir 5 is mounted oil the gear unit-side face of the base of the bowl-head 3. In the weir 5, there is a ring-shaped overflow cavity, which communicate with each liquid discharge port 4 and which coaxially has a peripheral opening directing the rotative axis of this bowl-head 3. Accordingly, as shown in Fig. 1, by connecting the overflow cavity and the liquid discharge ports 4, 4, a L-shaped cross section is formed.
- ring-shaped weir 5 In the lip portion of this ring-shaped weir 5, plural number of reducing blades 6 are provided in a radial direction so as to divide the ring-shaped overflow cavity into a plurality of portions while each reducing blade is disposed between one liquid discharge ports 4 and an adjacent discharge port 4. Additionally, a ring-shaped adjusting weir board 7 is mounted on the gear unit-side face of the weir 5 so as to be removable. This adjusting weir board 7 can be changed with another adjusting weir board 7 having a different inner diameter as desired, thus, the level of the pool 14 can be adjusted within the predetermined highest and lowest limits.
- a supply pipe 10 is inserted through the hollow tube 12 of the screw conveyor 2 so as to supply the feed solution to be separated. Then, a hole 15 for the feed solution to be separated is formed on the peripheral face of the hollow tube 12 so as to correspond to the supply port 10a of the supply pipe 10. In the bowl 1, the external side of the hollow tube 12 can communicate with its internal side through the hole 15.
- the feed solution to be separated is supplied from the supply pipe 10, while the rotating bowl 1 and the screw conveyor 2 are rotated with each high rotative speed, the feed solution is introduced to the external side of the hollow tube 12 within the rotating bowl 1 through the hole 15 formed on the hollow tube 12.
- the feed solution in the rotating bowl 1 is continuously splashed toward the peripheral face of the rotating bowl 1 by a centrifugal force caused by the rotation of the rotating bowl 1. Therefore, the pool 14 is formed along the peripheral face of the rotating bowl 1.
- the solidified particles of the feed solution are separated from the clarified liquid to be segmented on the bottom of the pool 14. These particles are scraped towards the right side of Fig. 1 by means of the screw blade 13 and discharged from the solid discharge port 11.
- the separated clarified liquid is discharged from the liquid discharge ports 4, 4 formed on the bowl-head 3 and overflown beyond the adjusting weir board 7 outwardly from the rotating bowl 1.
- a hood 21 is formed so as to encircle the rotating bowl 1. Therefore, the discharged solidified particles and the clarified liquid can be prevented from being splashed outside of the hood 21.
- the reducing blades 6 are fixed only to the internal face of the ring-shaped weir 5. However, they can be fixed to only the external face of the bowl-head 3 or to the both faces so as to cross both faces.
- Apparatus of the present invention can be utilized for concentrating separation of slurry as well as solid-liquid separation explained before.
- the meaning of the solidified particles in the present invention is not limited to the solids and includes also the concentrated solution.
- a decanter centrifuge was used in this example.
- the pool level of this decanter centrifuge could not be set higher than 130 mm due to the structural strength problem of the bowl-head 3 at its clarified liquid discharge port-side portion.
- This decanter centrifuge was modified and provided with the clarified liquid discharging apparatus described in the present invention. Then, a slurry-solution, whose supplied slurry concentration is 0.5-1.0 %, was applied with the flow rate of 20 m3/hr.
- the level of the pool 14 could be raised to be 180 mm. It is concluded that the amount of required power could be reduced by 15-25 %.
- the pool level of the conventional centrifuge could not be set higher than 130 mm.
- the decanter centrifuge related to the present invention has the pool level of 180 mm. Operations were carried out by these two kinds of centrifuges respectively, with the same concentration of the supplied slurry.
- the treating capacity for concentrating slurry (Q) was 20 m3 / hr and the SS recovery was approximately 90 %.
- the treating capacity for concentrating slurry (Q) was 25 m3 / hr and the SS recovery was approximately 93-95 %. It is concluded that the containing capacity of the rotating bowl is increased, thus, the separating efficiency is extremely improved.
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- Centrifugal Separators (AREA)
Abstract
Description
- This invention relates to a decanter centrifuge used for a solid-liquid separation of a feed solution containing suspended solids.
- As shown in Fig. 1, this type of centrifuge comprises a
bowl 1 which rotates with a high rotative speed, a screw-conveyor 2 which is disposed coaxially with the rotatingbowl 1 and which is pivoted by the rotatingbowl 1 so as to be included in thebowl 1. Then, ascrew blade 13 is helically provided around theconveyor 2 so that there is a narrow gap between the inner surface of thebowl 1 and the external circumference of thescrew blade 13. The rotatingbowl 1 and thescrew conveyer 2 rotate in the same direction, while there is a necessary differential rotative speed between thebowl 1 and theconveyor 2. - A feed solution is introduced, through a
supply pipe 10, to the rotatingbowl 1 from thesupply port 10a of thesupply pipe 10. Then, due to centrifugal force caused by the rotation of thebowl 1, the feed solution is sprayed to the inner surface of the rotatingbowl 1. Therefore, apool 14 is formed in thebowl 1. Thus, the solidified particles of the suspended solids are separated from a clarified liquid to be sedimented on the bottom of thepool 14. The solidified particles of the suspended solids are scraped together towards the right side of this figure by thescrew blade 13 and discharged. On the other hand, the clarified liquid overflows from aliquid discharge port 4 formed on a bowl-head 3 of thebowl 1 and is discharged from thebowl 1. - In prior art, as shown in Fig. 3, a ring-shaped or a board-
shaped weir 30 is normally attached to the external side of the base of the bowl-head 3 adjacent to theliquid discharge port 4, in order to adjust the level of thepool 14. -
- As shown in equation (1), as the radius (r) is decreased, that is to say, as the level of the
pool 14 is raised, the accelerating power (P) can be decreased resulting in saving the amount of required power. Additionally, depending on the type of structure of the screw conveyor or solid-liquid separating efficiency, when the level of thepool 14 is raised, the capacity of the rotatingbowl 1 for containing the feed solution can be increased. This provides an improved separating efficiency. - In view of raising the level of the
pool 14, as shown in Fig. 4, aliquid discharge port 4 is formed so as to cross slantingly the base of a bowl-head 3. - Besides, there are some conventional apparatus, each of which is characterized by each discharging method of the clarified liquid. For example, in Japanese Utility Model Publication No. 60-31793 using a skimming method, a pipe-shaped skimming-blade is immersed in the clarified liquid. Then, utilizing the rotational energy of the clarified liquid, this liquid is introduced along the skimming-blade to be discharged. Further, another apparatus is shown in Japanese Patent Publication No. 63-31261. Although the object of this conventional apparatus is different from the object of the present invention, a method for raising the level of a discharged liquid is shown. In this conventional apparatus, around the peripheral face of the screw conveyor, paths for discharging solids and paths for discharging clarified liquid are provided. They radiate from the axis of this screw conveyor. Side paths are also provided so as to communicate with the paths for discharging clarified liquid. Then, controllers for the quantity of the discharged clarified liquids are equipped on the side paths, thereby, the quantity of the discharged liquids can be adjusted. This provides apparatus by which the level of the discharged liquid can be raised.
- In order to raise the level of the pool, generally the liquid discharge port provided on the bowl-head should be formed so as to be adjacent to the axis of the bowl head (See US-A-3,423,015). However, torsional stress is increased at this axis, further, bending stress in the direction of the axis is applied there. Accordingly, the liquid discharge port placed to be adjacent to the rotating axis often causes a problem related to the structural strength of the bowl-head. Therefore, this method for raising the level of the pool always can not be carried out because of the problem related to the structural strength.
- Further, in the method explained referring to Fig. 4, since the
liquid discharge port 4 is formed so as to cross slantingly the base of the bowl-head 3. the level of the pool can be raised to some degree comparing apparatus explained referring to Fig. 3. However, also in this method, there remains the problem related to the structural strength. - On the other hand, apparatus shown in Japanese Utility Model Publication No. 60-31793 requires high energy for discharging, thus, can not save the amount of required power. Next, apparatus shown in Japanese Patent Publication No. 63-31261 is not suitable for discharging solids having a low water content, additionally, this apparatus has problems related to the abrasion of the skimming-blade and other problems related to its complicated structure.
- It is therefore the main object of the present invention to provide a centrifuge, whose pool level can be raised without the problem of structural strength, thereby by which the amount of required power can be saved and high separating efficiency can be attained.
- In a decanter centrifuge related to the present invention, a rotating bowl is provided with at least one solid discharge port and at least one clarified liquid discharge port. A screw conveyor is disposed coaxially with the rotating bowl so as to be included in the rotating bowl. The rotating bowl and the screw conveyor are rotated in the same direction with a differential rotative speed. A feed solution to be separated is introduced into a ring-shaped space formed between the rotating bowl and the screw conveyor. The feed solution is continuously separated into solid and liquid by centrifugal force. Then, the solid is discharged from the solid discharge port and the liquid is discharged from the clarified liquid discharge port. This centrifuge is characterized by the provision of clarified liquid discharging apparatus which comprises the clarified liquid discharge port, a ring-shaped weir and a plurality of reducing blades.
- Each clarified liquid discharge port is formed on a bowl-head of the rotating bowl so that the inner side of the bowl and the external side of the bowl-head can communicate with each other.
- The ring-shaped weir is mounted on the external face of the bowl-head. Then, a ring-shaped overflow cavity is provided in the ring-shaped weir so as to communicate with each clarified liquid discharge port. The ring-shaped weir coaxially has a peripheral opening directing the rotative axis of the bowl-head.
- The plurality of reducing blades is provided in the ring-shaped overflow cavity of the ring-shaped weir in a radial direction from the rotative axis of the bowl-head. Then, the cavity is divided into a plurality of portions while each reducing blade is fixed on at least one of the internal face of the ring-shaped weir and the external face of the bowl-head.
- The operation of the present invention is explained referring to Fig. 1.
- At least one, or preferably a plurality of
liquid discharge port head 3, with a predetermined space so that the inner side of therotating bowl 1 and the external side of the bowl-head 3 can communicate each other through theliquid discharge port 4. Then, a ring-shaped weir 5 is mounted on the external face of the base of the bowl-head 3. In theweir 5, there is a ring-shaped overflow cavity, which commnunicate with eachliquid discharge port 4 and which coaxially has a peripheral opening directing the rotative axis of this bowl-head 3. - Therefore, since the level of the
pool 14 is determined by the position of the overflow cavity of theweir 5 on its radius direction, the level of thepool 14 can be raised easily. However, even if the level is raised, since the clarified liquid beyond theliquid discharge port 4 reaches soon at the overflow cavity of the above mentioned ring-shaped weir 5, blade free vortex flow is produced. Then, the clarified liquid overflows the ring-shaped weir 5 with a peripheral velocity, which is the same as or larger than its peripheral velocity at theliquid discharge port 4. Accordingly, pressure drop is increased at the overflow cavity of the ring-shaped weir 5 resulting in decreasing of the amount of overflown clarified liquid. In the present invention, in order to prevent this situation, that is to say, in order to prevent the blade free vortex flow, a plurality ofblades 6 as speed reducing blades is provided in the lip portion of the ring-shaped weir 5 in a radial direction. Each speed reducing blade can be fixed to the internal face of the ring-shaped weir 5, to the external face of the bowl-head 3, or to the both faces so as to cross them. Due to thespeed reducing blades 6, the relation between the peripheral velocity (v) and the radius (r) is shown by the equation; v = rω, where (ω) is rate of rotation. That is to say, when the rate of rotation (ω) is fixed, since the peripheral velocity is proportional to the radius, this velocity can be reduced by reducing the radius. Therefore, the pressure drop is reduced. As a result, appropriate quantity of overflow can be attained. - On the other hand, theoretically, depending on the provision of the
speed reducing blades 6, the produced pressure drop is changed, so that the amount of required power can be decreased as explained after. - In this section, the peripheral velocity and the radius at the clarified
liquid discharge port 4 are indicated by V₄ and r₄ respectively and the peripheral velocity and the radius at the ring-shapedweir 5 are indicated by V₇ and r₇ respectively.
in case of the blade free vortex flow...
V₄r₄ = V₇r₇, therefore,
in case of the provision of the reducing blades... V₄ = r₄ω, V₇ = r₇ω, therefore, -
- Accordingly, ΔPA > ΔPB. That is to say, in case of the blade free vortex, the pressure drop is increased, and the amount of overflown liquid is decreased.
-
-
- As a result, in case of the provision of the reducing blades, V₄ > V₇, therefore, the amount of required power is decreased. On the other hand, in case of the blade free vortex flow without the reducing blades, V₇ > V₄, therefore, the amount of required power is increased.
- Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein preferred embodiments of the present invention are clearly shown.
- Fig. 1 illustrates a decanter centrifuge related to the present invention;
- Fig. 2 is a cross sectional view taken on line II-II of Fig. 1;
- Figs. 3 and 4 illustrate conventional apparatus for discharging clarified liquids.
- Now, the present invention is described more particularly.
- As shown in Fig. 1, a decanter centrifuge related to the present invention has the following structure.
- A
rotating bowl 1 is a combination of a conical section and a cylindrical section. A bowl-head 3 is fixed at the larger radius side of therotating bowl 1 so as to close completely therotating bowl 1. Thehollow axis 8 of the bowl-head 3 is extended from the bowl-head 3 so as to communicate with the hollow of therotating bowl 1. On the other side, at the smaller radius side of therotating bowl 1, thehollow axis 9 of thebowl 1 is extended from the back end of thebowl 1 so as to communicate with the hollow of therotating bowl 1. Thehollow axis 8 of the bowl-head 3 and thehollow axis 9 of thebowl 1 are pivoted by bearingstands rotating bowl 1 can be supported horizontally and rotated with a high rotative speed by a rotational force, which is transformed by rotating driving means (not shown). - In the hollow portion of the
rotating bowl 1, ascrew conveyor 2 is provided. Thescrew conveyor 2 is pivoted coaxially with the rotating horizontal axis of thebowl 1 by means ofbearings hollow tube 12 of thescrew conveyor 2 is provided horizontally at the center of therotating bowl 1. Ascrew blade 13 extends helically the full length of thehollow tube 12 so as to almost reach the inner surface of thebowl 1. In thehollow axis 8 of the bowl-head 3, a transformingrod 20 is provided. Its one end is connected to the end face of thehollow tube 12 of thescrew conveyor 2 and its another end is connected to agear unit 22. The rotational force from the above mentioned rotating driving means (not shown) is transformed, through the intermediary of thegear unit 22, to the transformingrod 20. Thus, thescrew conveyor 2 can be rotated with the high rotative speed. Therotating bowl 1 and thescrew conveyor 2 are rotated in the same direction, while there is a slightly differential speed between them, which is accomplished by means of thegear unit 22. - A solid discharge port 11 is formed at the smaller radius side of the
rotating bowl 1 on the right side of this figure so that solidified particles scraped together can be discharged from the solid discharge port 11. Then,liquid discharge ports head 3 at the larger radius side of therotating bowl 1. - The portion, where the clarified liquid is overflown from each
liquid discharge port 4, corresponds to clarified liquid discharging apparatus. Since the present invention is characterized by this portion, this portion will be explained closely referring to Fig. 2. - The above mentioned plurality of clarified
liquid discharge ports head 3 with a predetermined space and so as to be apart from the rotative center of the bowl-head 3 with a predetermined radius. Then, the ring-shapedweir 5 is mounted oil the gear unit-side face of the base of the bowl-head 3. In theweir 5, there is a ring-shaped overflow cavity, which communicate with eachliquid discharge port 4 and which coaxially has a peripheral opening directing the rotative axis of this bowl-head 3. Accordingly, as shown in Fig. 1, by connecting the overflow cavity and theliquid discharge ports weir 5, plural number of reducingblades 6 are provided in a radial direction so as to divide the ring-shaped overflow cavity into a plurality of portions while each reducing blade is disposed between oneliquid discharge ports 4 and anadjacent discharge port 4. Additionally, a ring-shaped adjusting weir board 7 is mounted on the gear unit-side face of theweir 5 so as to be removable. This adjusting weir board 7 can be changed with another adjusting weir board 7 having a different inner diameter as desired, thus, the level of thepool 14 can be adjusted within the predetermined highest and lowest limits. - On the other hand, a
supply pipe 10 is inserted through thehollow tube 12 of thescrew conveyor 2 so as to supply the feed solution to be separated. Then, a hole 15 for the feed solution to be separated is formed on the peripheral face of thehollow tube 12 so as to correspond to thesupply port 10a of thesupply pipe 10. In thebowl 1, the external side of thehollow tube 12 can communicate with its internal side through the hole 15. - When the feed solution to be separated is supplied from the
supply pipe 10, while therotating bowl 1 and thescrew conveyor 2 are rotated with each high rotative speed, the feed solution is introduced to the external side of thehollow tube 12 within therotating bowl 1 through the hole 15 formed on thehollow tube 12. The feed solution in therotating bowl 1 is continuously splashed toward the peripheral face of therotating bowl 1 by a centrifugal force caused by the rotation of therotating bowl 1. Therefore, thepool 14 is formed along the peripheral face of therotating bowl 1. The solidified particles of the feed solution are separated from the clarified liquid to be segmented on the bottom of thepool 14. These particles are scraped towards the right side of Fig. 1 by means of thescrew blade 13 and discharged from the solid discharge port 11. On the other hand, the separated clarified liquid is discharged from theliquid discharge ports head 3 and overflown beyond the adjusting weir board 7 outwardly from therotating bowl 1. - A
hood 21 is formed so as to encircle therotating bowl 1. Therefore, the discharged solidified particles and the clarified liquid can be prevented from being splashed outside of thehood 21. - In this embodiment, the reducing
blades 6 are fixed only to the internal face of the ring-shapedweir 5. However, they can be fixed to only the external face of the bowl-head 3 or to the both faces so as to cross both faces. - Apparatus of the present invention can be utilized for concentrating separation of slurry as well as solid-liquid separation explained before. Hence, the meaning of the solidified particles in the present invention is not limited to the solids and includes also the concentrated solution.
- The effect of the present invention is shown more clearly by examples.
- A decanter centrifuge was used in this example. In prior art, the pool level of this decanter centrifuge could not be set higher than 130 mm due to the structural strength problem of the bowl-
head 3 at its clarified liquid discharge port-side portion. This decanter centrifuge was modified and provided with the clarified liquid discharging apparatus described in the present invention. Then, a slurry-solution, whose supplied slurry concentration is 0.5-1.0 %, was applied with the flow rate of 20 m³/hr. - From this experiment, the level of the
pool 14 could be raised to be 180 mm. It is concluded that the amount of required power could be reduced by 15-25 %. - An additional experiment was performed. In this additional experiment, a clarified liquid discharging apparatus, without reducing blades was used.
- In the case of the apparatus having reducing
blades 6 on the ring-shapedweir 5, the concentration of the concentrated solution discharged from the solid discharge port was 4-5 %, which was the desired result. On the other hand, in case of apparatus having no reducing blade, a pressure drop was produced at the overflow cavity, thus, the quantity of overflown clarified liquid was decreased. Therefore, concentration of the concentrated solution discharged from the solid discharge port was 1.5-2.0 %, which was an extremely undesired result. - A comparison was made of the separating efficiencies of the conventional decanter centrifuge and the decanter centrifuge which was modified providing the clarified liquid discharging apparatus described in the present invention. The pool level of the conventional centrifuge could not be set higher than 130 mm. On the other hand, the decanter centrifuge related to the present invention has the pool level of 180 mm. Operations were carried out by these two kinds of centrifuges respectively, with the same concentration of the supplied slurry.
- In case of the centrifuge whose pool level was 130 mm, the treating capacity for concentrating slurry (Q) was 20 m³ / hr and the SS recovery was approximately 90 %. On the other hand, in case of the centrifuge whose pool level was 180 mm, the treating capacity for concentrating slurry (Q) was 25 m³ / hr and the SS recovery was approximately 93-95 %. It is concluded that the containing capacity of the rotating bowl is increased, thus, the separating efficiency is extremely improved.
- While preferred embodiments have been described, it is apparent that the present invention is not limited to the specific embodiments thereof.
Claims (3)
- A decanter centrifuge, in which a rotating bowl (1) provided with at least one solid discharge port (11) and at least one clarified liquid discharge port (4) and a screw conveyor (2) disposed coaxially with said rotating bowl (1) so as to be included in said rotating bowl (1) are rotated in the same direction with a differential rotative speed, with which a feed solution to be separated introduced into a ring-shaped space formed between said rotating bowl (1) and said screw conveyor (2) can be separated by centrifugal force to be solid and liquid so that said solid is discharged from said solid discharge port (11) and said liquid is discharged from said clarified liquid discharge port (4) and which has clarified liquid discharging apparatus comprising:
each clarified liquid discharge port (4) which is formed on a bowl-head (3) of said rotating bowl (1) so that the inner side of said bowl and the external side of the bowl-head can communicate with each other;
a ring-shaped weir (5), which is mounted on the external face of said bowl-head (3), in which a ring-shaped overflow cavity is provided so as to communicate with each clarified liquid discharge port (4) and which coaxially has a peripheral opening directing the rotative axis of said bowl-head; and characterised by:
a plurality of reducing blades (6) which are provided in said ring-shaped overflow cavity of said ring-shaped weir (5) in a radial direction from the rotative axis of said bowl-head so as to divide said cavity into a plurality of portions and so as to be fixed to at least one of the internal face of said ring-shaped weir (5) and the external face of said bowl-head (3). - A decanter centrifuge according to claim 1, wherein a plurality of clarified liquid discharge ports (4) is provided so as to be disposed on the periphery of said bowl-head (3) with a predetermined space and each reducing blade (6) is provided between one clarified liquid discharge port and an adjusting clarified liquid discharge port.
- A decanter centrifuge according to claim 1, wherein a ring-shaped adjusting weir board (7) having a smaller inner diameter than the diameter of said peripheral opening is mounted on the external face of said ring-shaped weir (5) so as to be removable.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2069019A JP2997700B2 (en) | 1990-03-19 | 1990-03-19 | Decanter centrifuge |
JP69019/90 | 1990-03-19 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0447742A2 EP0447742A2 (en) | 1991-09-25 |
EP0447742A3 EP0447742A3 (en) | 1991-12-18 |
EP0447742B1 true EP0447742B1 (en) | 1994-05-18 |
Family
ID=13390455
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP91100071A Expired - Lifetime EP0447742B1 (en) | 1990-03-19 | 1991-01-02 | Decanter centrifuge |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0447742B1 (en) |
JP (1) | JP2997700B2 (en) |
AT (1) | ATE105739T1 (en) |
DE (1) | DE69102002T2 (en) |
DK (1) | DK0447742T3 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012161560A2 (en) * | 2011-05-24 | 2012-11-29 | Lok Kong Loh Tong Weng | Modern decanter |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH09313985A (en) * | 1996-05-27 | 1997-12-09 | Kotobuki Giken Kogyo Kk | Horizontal centrifugal concentration apparatus |
KR100398168B1 (en) * | 2000-10-10 | 2003-09-19 | 임광석 | centrifugal machine |
DE10203652B4 (en) * | 2002-01-30 | 2006-10-19 | Westfalia Separator Ag | Solid bowl centrifuge with a weir |
JP5009764B2 (en) * | 2007-12-06 | 2012-08-22 | 巴工業株式会社 | Horizontal centrifuge and dam forming member |
KR101111490B1 (en) * | 2010-03-10 | 2012-02-22 | 송윤화 | Centrifugal |
KR101152176B1 (en) * | 2010-11-01 | 2012-06-15 | 송윤화 | Centrifugal |
ES2774429T3 (en) * | 2014-03-14 | 2020-07-21 | Andritz Sas | Decanting centrifuge |
EP3398687B1 (en) * | 2017-05-04 | 2020-03-18 | Andritz S.A.S. | Decanter centrifuge |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3423015A (en) * | 1967-08-23 | 1969-01-21 | Ametek Inc | Continuous centrifugal separator with pool depth control |
DE2901607C2 (en) * | 1979-01-17 | 1981-03-12 | Westfalia Separator Ag, 4740 Oelde | Solid bowl screw centrifuge |
US4334647A (en) * | 1980-12-03 | 1982-06-15 | Bird Machine Company, Inc. | Centrifuges |
-
1990
- 1990-03-19 JP JP2069019A patent/JP2997700B2/en not_active Expired - Lifetime
-
1991
- 1991-01-02 DK DK91100071.9T patent/DK0447742T3/en active
- 1991-01-02 DE DE69102002T patent/DE69102002T2/en not_active Expired - Fee Related
- 1991-01-02 AT AT91100071T patent/ATE105739T1/en not_active IP Right Cessation
- 1991-01-02 EP EP91100071A patent/EP0447742B1/en not_active Expired - Lifetime
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012161560A2 (en) * | 2011-05-24 | 2012-11-29 | Lok Kong Loh Tong Weng | Modern decanter |
WO2012161560A3 (en) * | 2011-05-24 | 2013-03-28 | Lok Kong Loh Tong Weng | Modern decanter |
Also Published As
Publication number | Publication date |
---|---|
DK0447742T3 (en) | 1994-06-20 |
JPH03270747A (en) | 1991-12-02 |
ATE105739T1 (en) | 1994-06-15 |
DE69102002T2 (en) | 1994-09-01 |
EP0447742A3 (en) | 1991-12-18 |
JP2997700B2 (en) | 2000-01-11 |
EP0447742A2 (en) | 1991-09-25 |
DE69102002D1 (en) | 1994-06-23 |
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