Patent Application
20130072369
The present invention relates to a centrifugal separation apparatus which applies to the separation of tiny particles in slurry based on density.
There is one type of separator containing rotary bowl in current commercial separation apparatus that are used to separate slurry particles with different density. This type of separator was first public in Canada Patent CA1111809A1, and then was improved in a series of patents, such as U.S. Pat. No. 4,608,040, U.S. Pat. No. 4,846,781, U.S. Pat. No. 5,338,284, U.S. Pat. No. 5,462,513, U.S. Pat. No. 5,586,965, U.S. Pat. No. 5,601,523, U.S. Pat. No. 6,149,572, U.S. Pat. No. 6,796,934, US2004013260, US20050026766, US20060135338. This kind of separator is called Knelson or Falcon separator. The main structure of this separator includes a high speed rotary bowl and several recesses on the outer surface of the bowl. A feed duct goes into the bottom of the bowl. Vane wheel is installed at the bottom of the bowl to accelerate the slurry feed. In some patents, liquid injection devices are set up in the ring to avoid solid leftovers. Some other patents use throttling devices to keep heavy feed discharging from the bowl. Here is how it works. Slurry material goes into the rotary bowl through the vertical feed duct. Under 50-300 G gravitational force, particles stratify along the inner surface of the bowl based on different density. Heavy particles will concentrate at the bottom of the recess or discharge through the throttling devices to heavy particle outlet. Light particles will get out at the top of the rotary bowl to light particle outlet. The particle stratification is based on density and size of the particle. From the bottom to the top, the order is heavy small particle, heavy big particle, light small particle and light big particle. Due to the high relative speed of the slurry feed to inner surface of the rotary bowl or recess during the stratification, the stratified particles tend to mix up and this trend becomes more severe for smaller particles. As a result, this type of separator is ineffective to remove ash or sulfur when the coal particles are very small. In report, the minimum effective separation size is 37 microns and particles smaller than this size are unable to be separated.
The object of the present invention is to provide a centrifugal separation apparatus based on stratification effect. This centrifugal separation apparatus is able to separate much finer particles without increasing rotary speed.
The present invention relates to a centrifugal separation apparatus which can be used to separate slurry particles based on density. It comprises a separation drum, a feed inlet, at least one heavy material outlet with a ring-shaped recess and at least one light material outlet. The separation drum is an annular chamber formed by an outer shell and an inner surface. It rotates about its drive shaft under external power. The annular chamber comprises a head and a tail. The feed inlet is located at the head of the separation drum. Light material outlet is located at the intersection of outer shell and inner surface or nearby inner surface of the tail. Heavy material outlet is located through the recess at the outer shell of the tail. A feed accelerator is installed at the feed inlet. This feed accelerator cooperates with the proper form of the separation drum and the corresponding location of the material outlet to form a material differential rotation propulsion device. The material differential rotation propulsion device is capable of rotating the feed slurry material along with the separation drum in a different rotation speed and forcing the processed materials to be discharged from separation drum via different outlets. The infeed flow rate is larger than or equal to the total sum of the outfeed flow rates of heavy and light materials so that the separation drum is full of materials during operation.
In one example, the material differential rotation propulsion device is designed in approximate hollow truncated cone shape with narrow head and wide tail, the feed accelerator comprises several radial plates mounted on the drive shaft, the radial plates are extended no wider than the inner surface of the separation drum, the distance between inner edge of light material outlet and the drive shaft is larger than the distance between outer edge of feed net and the drive shaft.
In another example, the material differential rotation propulsion device is designed in approximate hollow truncated cone shape with wide head and narrow tail. The feed accelerator is a turbine that has outlet facing the rotary direction of the bowl. Or the material differential rotation propulsion device is designed in approximate hollow truncated cone shape with narrow head and wide tail. The feed accelerator is a turbine that has an outlet facing the opposite rotary direction of the bowl. Or the material differential rotation propulsion device is designed in approximate hollow truncated cone shape with wide head and narrow tail. The feed accelerator comprises several radial plates. The distance between inner edge of light material outlet and the drive shaft is larger than the distance between outer edge of feed net and the drive shaft.
Ideally, there are several light material outlets and heavy material outlets which are symmetrically spaced along the bowl. Throttling device can be installed on the light and heavy material outlets. It can be controlled in real time by a magnetic device.
In addition, several vibrating stripes can be mounted on the outer sidewall of the separation drum and vibrating stripes project inwardly and extend longitudinally. A ring-shaped heavy material buffering chamber can be disposed between the ring shape recess and heavy material outlets. The heavy material buffering chamber is communicated with the ring shape recess via a narrow gap. Moreover, the ring shape recess is provided with a thin decelerating ring which can be fixed on the sidewall of the recess via a crossbeam. The decelerating ring can be corrugated.
One or more sets of intermediate material outlets can be installed between the heavy material outlets and the light material outlets. Light material outlets can be installed on the inner sidewall of the separation drum. Or a ring shape light material buffering chamber can be installed at the light material outlets.
The centrifugal separation apparatus described in this invention rotates the slurry material along with the separation drum, maintains a speed difference between the slurry material and the separation drum, and discharges different density materials from corresponding outlets. This apparatus utilizes stratification effect. It is able to efficiently separate finer slurry particles without increasing the rotational speed.
As shown in
In one example, the material differential rotation propulsion device is designed that the separation drum 1 is approximate hollow truncated cone shape with narrow head and wide tail, the feed accelerator 6 comprises several radial plates 61 mounted on the drive shaft, the radial plates are extended no wider than the inner surface of the separation drum 1, the distance B between inner edge of light material outlet and the drive shaft is larger than the distance A between outer edge of feed inlet and the drive shaft. The center plane of plates 61 passes the axis of drive shaft, and the plates 61 conjoint with the inner surface and the outer shell of the separation drum 1.
In another example as shown in
In another example as shown in
As shown in
As shown in
A further illustration of the invention is described below in combination of specific examples.
As shown in
During operation, the separation drum rotates along the drive shaft by external power device. Slurry with particles of different density flows into the separation drum through feed inlet. It is accelerated by radial plates. According to the law of conservation of kinetic energy, the rotation radius of the slurry enlarging, the linear velocity of the slurry retains the same, its angular velocity decreases. As a result, there is a velocity difference between the slurry and the separation drum. Adjusting the relevant parameters of the centrifugal separation apparatus, keep a slight velocity difference between the slurry and the wall of separation drum. This velocity difference and the strong centrifugal force make the slurry stratify. The high density solid particles precipitate collectively towards the outer shell. When the solid particles reach a certain concentration, the centrifugal motion of the solid particles is equal to the effect that the relative motion between the slurry and the drum disturbance the slurry and prevents the solid particles' precipitate. Lighter particles move towards the inner surface in the extrusion of high density particles. Thus, particles stratify within the separation drum according to their density. This process happens simultaneously with the movement of the slurry in the separation drum. When the stratified slurry particles move to the ring shape recess, heavy particles discharge through the heavy particle outlet and light particles move beyond the recess and discharge through the light particle outlet. Both products go to corresponding product receiver passage 8.
The particle outlets need to be small enough or inlet big enough so that the separation drum is full of slurry and particles have enough time to be fully separated. The difference radius of the narrow head and wide tail of the separation drum determines the velocity difference between the slurry and the separation drum. The bigger the difference radius between the head and the tail is, the larger the velocity difference. In addition, the feed flow rate determines the velocity difference between the slurry and the separation drum. The bigger the feed flow rate, the larger the velocity difference.
The distance between inner edge of light material outlet and the drive shaft shall be no shorter than the distance between outer edge of feed inlet and the drive shaft. In this way, the centrifugal force is able to push the movement of slurry in the separation drum. Otherwise, slurry may move very slowly or even stop.
In order to discharge light and heavy materials uniformly, several outlets are installed symmetrically along the separation drum.
In the simplified specifications, all the outlets use fixed diameters.
In this example, throttle devices are installed in heavy and light particle outlets to control discharge flow rate and proportion of heavy and light materials.
To control it in real time, throttle device such as that described in U.S. Pat. No. 6,149,572 can be used. A better option could be using throttle device controlled by magnetic device 71.
As shown in
The main structure of magnetic throttle control device 71 is described as follows. The circular track 713 is mounted on the machine cover and can be adjusted by a ball screw 714. The moving magnet 712 is installed on a cantilever 7111 connected to the throttle valve. The moving magnet has the opposite magnetic pole as the circular track 713. The moving magnet 712 tends to close the throttle valve under the centrifugal force. On the other hand, it tends to open the throttle valve under the repulsion force between magnets. As a result, the throttle valve can be controlled by adjusting the position of the circular track 713.
As compared to the Keelson or Falcon separator, the separator in this invention is able to have deeper stratification and longer duration. It is also able to avoid the disturbance which could damage the existing stratification. Thus, this separator is able to separate much smaller particles and improve the accuracy of separation.
As shown in
As shown in
Although there are several heavy particle outlets, the thickness of heavy particles is different near the outlet and away from the outlet. The discharged product could be a mixture of different density particles so that the accuracy of heavy particle is affected.
To solve this problem, a narrow gap 31 is set up at the bottom of the recess. Buffering chamber 41 is set up outside the narrow gap. The heavy particle outlet is located through the Buffering chamber 41.
Heavy particle slurry goes into the buffering chamber through the narrow gap. Then it rotates in the buffering chamber and flows out of the separation drum through the heavy particle outlets.
As shown in
Slurry tends to accelerate because the sudden enlarging of the rotation radius as it enters the recess. This acceleration will harm the stratification process. To solve this problem, several thin decelerating rings 411 are installed in the recess. The decelerating ring separates the recess into multiple spaces and increases friction force of the slurry. In this way, it will decelerate the movement of the slurry in the recess and enhance the stratification. Decelerating rings are fixed by beam 412.
To further enhance the slurry stratification, corrugated ring can be used. It can cause horizontal vibrations for the slurry so that stratification effect can be enhanced.
As shown in
In operation, heavy particles concentrate in the recess near the heavy particle outlet and discharge. Other particles cross this area and enter the recess near the intermediate particle outlet. Intermediate particles concentrate and discharge from the intermediate particle outlet. Light particles cross this area and discharge from the light particle outlet.
As shown in
Based on this configuration, a buffering chamber 51 can be installed to further purify the light material. It is ring shape ball chamber which slows down the movement of the slurry. To make the movement of the slurry in the buffering chamber more uniform, a deflector 52 can be mounted in the buffering chamber 51.
All examples above only use one of four different separation drum configurations. The separation drum is designed in conical shape with narrow head and wide tail, the feed accelerator comprises several radial plates mounted on the drive shaft. Unless specified, all these examples are suitable for other configurations. They are not detailed here but these technical solutions shall also be protected by this patent.
The thin decelerating ring described in example 4 is not suitable for approximate hollow truncated cone shape separation drum with narrow head and wide tail. This configuration makes the rotational speed of slurry is higher than that of the separation drum and the decelerating ring will decrease even stop the movement of the slurry. As a result, the decelerating ring will not be used under this circumstance.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201010123864.4 | Mar 2010 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN11/71757 | 3/14/2011 | WO | 00 | 11/27/2012 |
