WO2011054296A1

WO2011054296A1 - Sand sedimentation tank, sand separator, and method for separating mixture of solid particles

Info

Publication number: WO2011054296A1
Application number: PCT/CN2010/078399
Authority: WO
Inventors: Guojun Yue; Xiaoming Hao; Tianyang Yu; Guoqing Wu; Jinbao Du; Xiaofeng Liu; Jiajun Huang; Hailong Lin; Likang Deng; Hu LUO
Original assignee: Cofco Limited; Guangxi Cofco Bio-Energy Co, Ltd.
Priority date: 2009-11-04
Filing date: 2010-11-04
Publication date: 2011-05-12

Abstract

A sand sedimentation tank (10) is provided, the tank (10) comprises a tank body (11), an inlet (12) and an outlet (13), wherein the tank body (11) comprises side walls (14) and a bottom (15), the outlet is arranged in a side wall (11), and the bottom (15) has at least one raised part (16) and/or at least one recessed part (17). A sand separator is further provided, the separator comprises a grading unit (30), a particle collector unit (40), and the sand sedimentation tank (10) connected in series. A method for separating mixture of solid particles is further provided. The solid particles comprise first solid particles and second solid particles, wherein, the density of the first solid particles is lower than the density of the second solid particles; the method comprises: forcing the mixture of solid particles to flow with a solvent, making the second solid particles deposit in the flow process to form a layer (22) of the second solid particles, and forcing the first solid particles to continue flowing with the solvent, wherein, the density of the second solid particles is higher than the density of the solvent.

Description

Sand Sedimentation Tank, Sand Separator, and Method for Separating

Mixture of Solid Particles

Technical Field

The present invention relates to a sand sedimentation tank, a sand separator, and a method for separating mixture of solid particles.

Background of the Invention

It is of great importance to remove sand from solid materials, especially solid particles of natural foods in food service industry, to ensure purity of the solid particles. In the prior art, to attain the purpose of sand removal, usually swirling sand separators are used. Specifically, the grout mixture of solid particles and sand grains is treated by centrifugal sedimentation, so that the sand grains that have higher density in the grout mixture are thrown to the pool wall, and then discharged through the sand discharge port located in the bottom of the pool, while the solid particles that have lower density in the grout mixture are left in water, achieving separation of solid particles from sand grains.

Though most of the sand grains can be removed with such a swirling sand separator, centrifugal force is required to throw the sand grains with higher density to the pool wall, to separate solid particles from the sand grains by force. Therefore, a whirling sand sedimentation pool and complex components such as electric motor and gearbox that generate centrifugal force are required; consequently, the structure of the swirling sand separator is complex. To maintain centrifugal force and force the grout mixture to flow into the sand separator under certain pressure in the sand separation process, the swirling sand separator usually operates under enclosed condition; as a result, the swirling sand separator can't separate sand continuously, and there is no way to monitor the sand separation process in real time. Moreover, the complex structure of the swirling sand separator severely limits the volume of grout mixture that can be treated in each operation cycle.

Summary of the Invention

To overcome the drawbacks of existing swirling sand separators in the prior art, such as complex structure, enclosed operating environment, and unavailability of continuous sand separation, the present invention provides a sand sedimentation tank that is simple in structure and can operate continuously in an open environment.

The sand sedimentation tank according to the present invention comprises a tank body, an inlet, and an outlet, wherein, the tank body comprises side walls and a bottom, the outlet is arranged in a side wall, and the bottom has at least a raised part and/or at least a recessed part. The present invention further provides a sand separator, comprising a particle grading unit, a particle collector unit, and a sand sedimentation tank connected in series, wherein, the sand sedimentation tank is the sand sedimentation tank according to the present invention.

The present invention further provides a method for separating mixture of solid particles that comprises a first solid particles and a second solid particles, wherein, the density of the first solid particles is lower than the density of the second solid particles; the method comprises: forcing the mixture of solid particles to flow with a solvent, making the second solid particles deposit in the flow process to form a layer of the second solid particles, and forcing the first solid particles to continue flowing with the solvent, wherein, the density of the second solid particles is higher than the density of the solvent.

The sand sedimentation tank and sand separator provided in the present invention can separate sand by gravity stratification, and the raised part and/or recessed part can prevent the deposited sand grains from moving with the fluid and retain the sand grains on the bottom of the sand sedimentation tank, so as to attain the effect of sand removal from the solid particles. When the sand sedimentation tank is used to remove sand, a large volume of grout mixture can be treated continuously as the fluid flows in and out continuously; moreover, the sand sedimentation tank is simple in structure, and doesn't require complex apparatus to provide high pressure and high centrifugal force. Furthermore, the open working environment is favorable for monitoring sand removal.

The method for separating mixture of solid particles provided in the present invention utilizes the density difference between the first solid particles and the second solid particles, so as to make the second solid particles with higher density to deposit and force the first solid particles to flow with the solvent, and thereby separates the first solid particles from the second solid particles. The separation method provided in the present invention can be used to remove sand from solid particles of raw material, and is easy to use, without the need for complex apparatus to provide high pressure and centrifugal force; in addition, the separation method supports continuous sand removal operation.

Brief Description of the Drawings

Fig. 1 is a schematic cross section view of an embodiment of the sand sedimentation tank according to the present invention;

Fig. 2 is a schematic cross section view of another embodiment of the sand sedimentation tank according to the present invention;

Fig. 3 is a schematic cross section view of jetting tube of the sand sedimentation tank according to the present invention;

Fig. 4 is a schematic structural view of the sand separator according to the present invention. Embodiments

Fig. 1 is a schematic cross section view of an embodiment of the sand sedimentation tank according to the present invention. As shown in Fig. 1, the sand sedimentation tank 10 comprises a tank body 11, an inlet 12, and an outlet 13, wherein, the tank body 11 comprises side walls 14 and bottom 15; the outlet 13 is arranged in a side wall 14; wherein, the bottom 15 has at least a raised part 16 and/or at least a recessed part 17.

The sand sedimentation tank provided in the present invention can be used to separate a variety of systems in which a type of solid particles is to be separated from other types of solid particles, as long as a type of solid particles has density higher than the rest types of solid particles and is insoluble to the solvent. The sand sedimentation tank provided in the present invention is especially advantageous for separating a type of solid particles from a mixture of two types of solid particles, in which the target type of solid particles to be separated has density lower than the other type of solid particles, and in which both types of solid particles are insoluble or slightly soluble to the solvent and have density higher than the solvent respectively. Wherein, the density of the target type of solid particles is no more than 60% of the density of the other type of solid particles, preferably is no more than 10%-50%. The solid particles described here refer to solid particles in different shapes, with particle size smaller than 2.0mm. The solvent can be a sort of organic or inorganic solvent, to which the types of solid particles described here is insoluble or slightly soluble, and the density of the solvent is lower than the density of the types of solid particles insoluble or slightly soluble to the solvent; there is no specific limitation on the quantity of the solvent, as long as the solvent mixed with the solid particles can form a sort of flowing fluid. For example, the mixture of solid particles can be carried by the solvent to flow, and thereby forms a sort of flowing fluid. However, such a manner is adverse to control the proportion of mixture of solid particles vs. solvent, causing inconsistent fluid mobility. Preferably, the mixture of solid particles can be mixed with the solvent to form a sort of homogeneous grout mixture 20 (e.g., by agitation), and then the grout mixture 20 is forced to flow and the solid particles are separated. Wherein, there is no specific limitation on the quantity of the solvent and the agitation duration, as long as a sort of grout mixture 20 with good fluidity and moderate viscosity is obtained. For example, the quantity of solvent can be 20-100 times of the total weight of the two types of solid particles, and the agitation duration can be 0.5-2h. The target type of solid particles described here can be at least one of sweet potato granules, corn grains, and tapioca granules, and the other type of solid particles can be sand grains; the solvent described here is preferably water.

Hereunder the working principle of the sand sedimentation tank 10 provided in the present invention will be described in an example of removing sand grains from tapioca granules, with reference to Fig. 1.

As shown in Fig. 1, in the sand sedimentation tank 10, in the flowing process of the grout mixture 20 mixed from tapioca granules, sand grains, and water (or a fluid formed by the mixture of tapioca granules and sand grains flowing with water), the sand grains deposit first, forming a layer of sand grains 22 on the bottom 15 of the sand sedimentation tank 10, since the density of sand grains is higher than the density of tapioca granules and the density of water, respectively; in contrast, the tapioca granules suspend in water and flow with water, since the density of tapioca granules is lower than the density of water. As the tapioca granules flow out with water from the outlet 13, the tapioca granules are separated from sand grains, and thereby the purpose of sand removal is attained.

Wherein, the tank body 11 can be in any shape and structure, as long as it has appropriate capacity and the bottom has at least a raised part 16 and/or at least a recessed part 17. For example, the circumferential cross section of the tank body 11 (i.e., the cross section parallel to the bottom) can be in rectangular, circular, or elliptical shape. The circumferential cross sections of the sand sedimentation tank can be in the same size or different sizes; preferably, the circumferential cross sections are in the same size, or reduce gradually along the direction towards the bottom, forming an open trapezoid- shaped cross section which is perpendicular to the bottom (i.e., the cross section shown in Fig. 1).

In the sand sedimentation tank according to the present invention, the inlet 12 can be arranged at any appropriate position where the grout mixture 20 (or the fluid formed by the mixture of tapioca granules and sand grains flowing with water) can flows into the tank body 11; the inlet 12 can be an opening in a side wall 14 of the tank body 11 (as shown in Fig. 1) or a tube which is arranged on a side wall 14 of the tank body 11 or extends into the tank body. To prevent the deposited sand grain layer 22 from disturbed and further improve the sand deposition effect, preferably, the inlet 12 is arranged in the upper part of or on the top of tank body 11 ; more preferably, the distance from the top end of inlet 12 to the bottom 15 (in the present invention, the "distance to the bottom 15" refers to the vertical distance to the lowermost part of the bottom 15) is 80-100% of the vertical height of the side wall (where the inlet 12 is arranged) of the tank body 11. More preferably, in order to facilitate the grout mixture 20 to flow and effectively improve sand sedimentation effect of the sand sedimentation tank, the inlet 12 and outlet 13 are arranged on opposite side walls 14; especially, in the case of the cross section of the sand sedimentation tank (the cross section shown in Fig. 1) is in rectangular or trapezoid shape, more preferably, the inlet 12 and outlet 13 are arranged on opposite side walls 14 with longer distance between each other, so that longer sand sedimentation and separation duration can be achieved under the condition of the same size of sand sedimentation tank and the same flow rate of grout mixture 20, and thereby the sand removal effect can be improved. The size of inlet 12 and the size of outlet 13 can be determined according to the actual demand.

The outlet 13 can be arrange at any position where the grout mixture 20 can flow out of the tank body 11; preferably, as described above, the outlet 13 is arrange on the side wall opposite to the side wall where the inlet 12 is arranged. To retain the deposited sand grain layer 22 in the tank body 11 effectively and further improve the sand sedimentation effect, preferably, the outlet 13 is arranged in the upper part or on the top of the tank body 11; more preferably, the distance from the lowermost part of outlet 13 to the bottom 15 is 50-95% of the vertical height of the side wall (where the outlet 13 is arranged) of the tank body 11. More preferably, the distance from the uppermost part of outlet 13 to the bottom 15 is smaller than the distance from the lowermost part of inlet 12 to the bottom 15, which is to say, the outlet 13 is in a form similar to an overflow weir.

Preferably, the sand sedimentation tank 10 can comprise a baffle plate, with which the position and size of the outlet 13 can be adjusted. Specifically, the distance from the lowermost part of outlet 13 to the bottom 15 and the size of the outlet 13 can be adjusted by covering the lower part of outlet 13 with the baffle plate. Apparently, an opening extending from the top of the side wall 11 for outlet 13 to the bottom of said side wall 11 can be arranged, and a part of the opening can be covered with a plurality of baffle plates, to form the outlet 13, so that the position and size of the outlet 13 can be adjusted by adjusting the positions of the baffle plates. With the adjustable distance between the outlet 13 and the bottom 15, the following benefits can be achieved: on one hand, if the sand content in the mixture is high and the sand grains accumulate at the side wall where the outlet 13 is provided, it is possible to prevent overflow of the sand grains by increasing the elevation of the outlet 13; on the other hand, if the target solid particles have high density and also deposit, they stay at a specific elevation when they flow with water to the side wall where the outlet 13 is provided, depending on the flow rate of the grout mixture 20; since the sand sedimentation tank 10 only permits water and solid particles above the elevation of the lowermost part of outlet 13 to flow out, it is possible to let the solid particles to flow out with water as much as possible by decreasing the distance from the lowermost part of outlet 13 to the bottom 15.

In the present invention, in order to prevent the sand grain layer 22 formed by sand grain deposition from flowing along with water under the action of water flowing above the sand grain layer 22 and thereby accumulating at the side wall where the outlet 13 is provided or over-flowing through the outlet 13, said at least one raised part 16 and/or at least one recessed part 17 are arranged on the bottom 15 of tank body 11 of sand sedimentation tank 10 in the present invention, as shown in Fig. 1 and Fig. 2. Preferably, the bottom 15 has a plurality of raised parts 16 and/or a plurality of recessed parts 17, wherein, the raised parts 16 and/or recessed parts 17 are arranged along the direction from the inlet 12 to the outlet 13, i.e., along the flow direction of the grout mixture 20.

The sand grain layer 22 deposits on the bottom of tank body 11 ; when the sand grain layer 22 flows along the flow direction under the action of water flowing above it, the sand grains will be trapped in the recessed part 17 or blocked by the raised part 16, and therefore can't move along the flow direction further. Even if some sand grains deposit on the top of the raised part 16, these sand grains will move along with the water flowing above it, and then will be trapped in the recessed part 17. Therefore, the sand grain layer 22 will hardly move to the side wall where the outlet 13 is provided; thus, the sand grains will not pill up to the outlet 13 and flow through the outlet 13.

As shown in Fig. 1, in order to further prevent the sand grain layer 22 from disturbed by the water flowing above it, in the cross section shown in Fig. 1 (i.e., longitudinal section, which is parallel to the direction from the inlet 12 to the outlet 13 and perpendicular to horizontal plane), the raised part 16 and recessed part 17 are in trapezoid shape. Of course, the raised part 16 and recessed part 17 can be in any other shape that is helpful for preventing the sand grain layer from flowing along the flow direction, such as wave shape or triangular shape. Preferably, the raised part 16 and recessed part 17 is provided with a bevel at a degree of 30-60 from the horizontal plane, to effectively prevent the sand grains from moving along the flow direction. Alternatively, the bottom 15 of sand sedimentation tank 10 in the present invention can have one recessed part 17 (as shown in Fig. 2) or one raised part 16. In this case, the size of the raised part 16 or recessed part 17 can be increased appropriately. As shown in Fig. 2, the amount of sand grains that can be retained in the recessed part 17 is equivalent to the total amount of sand grains retained in all recessed parts 17 shown in Fig. 1.

In order to retain sand grains effectively and prevent sand grains from moving freely, preferably the raised part 16 and/or recessed part 17 is arranged on the post-median part of the bottom 15 along the flow direction. In the case of the bottom 15 has a plurality of raised parts 16 and/or recessed parts 17, the raised parts 16 and/or recessed parts 17 are arranged on the post- median part of the bottom 15 along the flow direction. Wherein, the raised part 16 and recessed part 17 account for 40-60% of the area of the bottom 15. The distance from the uppermost part of the raised part 16 to the bottom 15 is not greater than the distance from the lowermost part of the outlet 13 to the bottom 15; more preferably, the ratio of the height variation of the bottom 15 (the vertical distance between the uppermost part and the lowermost part of the bottom 15) to the height of the side wall where the outlet 13 is provided is 1 : 5-1 :3. The raised part 16 can be formed integrally with the bottom 15 of the tank body, or it can be a baffle member fixed to the bottom 15. The recessed part 17 can be formed integrally with the bottom 15 of the tank body, or it can be grooves formed between a plurality of raised parts 16. In the case of the target solid particles can float completely on water, they can flow through the outlet 15 substantially and therefore can be collected; however, some of the target solid particles may be blocked by the sand grains and deposit with the sand grains to the sand grain layer 22. Furthermore, in the case of the density of the target solid particles is high (e.g., tapioca flour), the target solid particles may deposit in water. In that case, if the flow rate is not enough, some target solid particles may deposit to the position below the outlet 13 and further deposit onto the surface of the sand grain layer 22 but can't flow through the outlet 13 when they flow with water to the outlet 13, which would be a great loss.

To solve that problem, preferably the sand sedimentation tank 10 comprises a jetting unit that can jet gas stream and/or water stream. The jetting unit is arranged above the sand grain layer 22 and can jet gas stream and/or water stream to the surface of the sand grain layer 22, so as to drive the tapioca granules that deposit on the sand grain layer 22 to float up to the water, and flow out of the outlet 13 with the water flowing above the sand grain layer 22. In that process, the jetting unit can jet gas stream and/or water stream at an appropriate jet rate, so that the tapioca granules on the surface of the sand grain layer 22 floats away from the sand grain layer 22. Though some sand grains in the sand grain layer 22 can also float with the tapioca granules, these sand grains will deposit quickly due to their high density, and therefore will hardly be carried away by the water flow.

Specifically, as shown in Fig.2, the jetting unit comprises at least one jetting tube 18. Each jetting tube 18 comprises a tube body and a plurality of holes P provided in the tube body; the gas stream and/or water stream is jetted through the holes P. Apparently, a pump or pumping device can be used to jet gas stream and/or water stream through the holes P.

Each jetting tube 18 can be arranged in the tank body of the sand sedimentation tank 10 and span two opposite side walls of the sand sedimentation tank 10. For example, the jetting tubes 18 can be arranged in parallel along transverse direction of the sand sedimentation tank 10, or arranged in parallel along longitudinal direction of the sand sedimentation tank 10 as shown in the embodiment in Fig. 1, or arranged in parallel at a predefined angle relative to the transverse and longitudinal direction. Apparently, the jetting tubes 18 can also be arranged in a crossed manner. Each jetting tube 18 can have a plurality of holes P; preferably, 10 holes in 3-6mm diameter each can be arranged on the tube body per m, depending on the arrangement of the jetting tubes 18.

During the continuous sand removal process, the thickness of the sand grain layer 22 deposited in the sand sedimentation tank 10 may vary. In order to keep the jetting tubes 18 being always above the sand grain layer 22, preferably the distance between the tube bodies of jetting tubes 18 and the bottom 15 is adjustable. For example, slide tracks can be arranged on at least one of the two side walls spanned by the jetting tubes 18, and at least one end of each jetting tube 18 can be arranged in the corresponding slide track and can slide in the slide track, so that the distance between the jetting tubes 18 and the bottom 15 can be adjusted along the height direction of the two side walls.

Preferably, the holes P are arranged to point to the grooves formed between the recessed parts 17 and/or the groove formed between the raised parts 16 and the side wall where the inlet 12 and/or outlet 13 is provided. That is to say, in the case of the bottom 15 has a recessed part 17 (the recessed part 17 shall be understood as including recessed part formed integrally with the bottom 15 and recessed part formed between two raised parts 16), the holes P point to the recessed part 17; in the case of the bottom has only one raised part 16, the holes P point to the grooves between the raised part 16 and the side wall where the inlet 12 and/or outlet 13 is provided .

The holes P of the jetting tube 18 are preferably set to jet towards the surface of the sand grain layer 22; therefore, the holes P are preferably set to jet towards the bottom 15. More preferably, the holes P are set to jet downwards at an angle A relative to the flow direction of grout mixture 20 or the horizontal plane. That is to say, the axis of holes P are at an angle A relative to the horizontal plane, and the angle A is preferably degree 30-60. As shown in Fig. 1 and Fig. 3, the jetting tube 18 is arranged along the transverse direction of the sand sedimentation tank 10 (the direction shown by the solid arrow in Fig. 3 is the flow direction, which is in longitudinal direction); the holes P are arranged to jet at 45° downward inclination to the horizontal direction (as shown by the hollow arrow in Fig. 3). In that way, the target solid particles trapped on the surface of a wide range of the sand grain layer 22 are driven to float, while the sand grains will not float up. As shown in Fig. 3, the jetting tube 18 is arranged along the transverse direction of the sand sedimentation tank 10 (the direction shown by the solid arrow in Fig. 3 is the flow direction, which is in longitudinal direction); the holes P are arranged to jet at 45° downward inclination to the horizontal direction (as shown by the hollow arrow in Fig. 3).

The jetting tube 18 can be arranged near the outlet 13 to facilitate the target solid particles to be driven up with the jetting gas stream or water stream and carried away by water flow quickly; however, the speed of jetting gas stream or water stream from the jetting tube 18 must be controlled within an appropriate range, to avoid blowing up the sand grains. For example, the jetting flow speed can be set to lm/s. Alternatively, the jetting tube 18 can be arranged at a position away from the outlet 13; in such a case, the jetting tube 18 can provide jetted gas stream or water stream at a higher speed, such as 3m/s.

In the embodiments of the present invention, in order to achieve continuous sand removal operation, different measures can be taken to drive the grout mixture 20 or water to flow, for example, a pump or any other pumping device can be used, or the potential energy of the grout mixture 20 can be utilized, to force the grout mixture 20 flow into the tank through the inlet 12 and carry the target solid particles and flow out of the tank through the outlet 13. Preferably, the flow rate of the grout mixture 20 can be controlled with a pump. Especially, for the target solid particles with high density, increased flow rate can further prevent the target solid particles from depositing.

Since the upper part of the sand sedimentation tank 10 is "open", it is easy to monitor the treatment process, so as to adjust appropriately to obtain optimal flow rate and optimal elevation of outlet 13.

Apparently, the sand sedimentation tank provided in the present invention is also applicable to enclosed sand removal operation. However, enclosed operation is only suitable for solid particles that have low density and can completely float in water. In enclosed sand removal operation, the grout mixture 20 can be kept still in the sand sedimentation tank 10 for a predefined time, to wait for the sand grains to deposit completely onto the bottom 15; then, the solid particles floating in water can be carried away with water flow from the sand sedimentation tank 10. Similarly, in enclosed sand removal operation, a jetting device can be arranged in the sand sedimentation tank 10, to prevent the solid particles from being blocked by the sand grains and depositing onto the sand grain layer 22.

The sand sedimentation tank provided in the present invention not only is simple in structure but also supports continuous sand removal operation or non-continuous sand removal operation as required; moreover, the treatment process is open and easy to monitor.

Hereunder the sand separator provided in the present invention will be detailed.

As shown in Fig. 4, the sand separator provided in the present invention comprises a grading unit 30, a particle collector unit 40, and a sand sedimentation tank 10, wherein, the grading unit 30 is used to separate fine solid particles with particle diameter smaller than a predefined value from the mixture of solid particles composed by a first solid particles and a second solid particles; the particle collector unit 40 is designed to collect the fine solid particles separated from the mixture; the sand sedimentation tank 10 is designed to remove the second solid particles from the separated fine solid particles.

The sand sedimentation tank provided in the present invention can be used to separate a variety of systems in which a type of solid particles is to be separated from other types of solid particles, as long as a type of solid particles (the second solid particles) has density higher than the rest solid particles (the first solid particles) and is insoluble to the solvent. The sand separator provided in the present invention is especially advantageous for separating a type of solid particles from a mixture of two types of solid particles, in which one type of solid particles has density higher than the other type of solid particles, both types of solid particles are insoluble or slightly soluble to the solvent and have density higher than the solvent respectively. The solid particles described here refer to solid particles in different shapes, with particle size smaller than 2mm. The solvent can be a sort of organic or inorganic solvent, to which at least one type of solid particles described here is insoluble or slightly soluble, and the density of the solvent is lower than the density of said at least one type of solid particles insoluble or slightly soluble to the solvent; there is no specific limitation on the quantity of the solvent, as long as the solvent mixed with the solid particles can form a sort of flowing fluid. For example, the mixture of solid particles can be carried by the solvent to flow, and thereby obtains mobility. Preferably, the mixture of solid particles can be mixed with the solvent to form a sort of homogeneous grout mixture 20 (e.g., by agitation), and then the grout mixture 20 is forced to flow and the solid particles are separated. Wherein, there is no specific limitation on the quantity of the solvent and the agitation duration, as long as a sort of grout mixture 20 with good fluidity and moderate consistency is obtained. For example, the quantity of solvent can be 20-100 times of the total weight of the two types of solid particles, and the agitation duration can be 0.5-2h. The first solid particles described here can be one or more of sweet potato granules, corn grains, and tapioca granules, and the second solid particles can be sand grains; the solvent described here is preferably water. Hereunder the working principle of the sand separator provided in the present invention will be described in an example of removing sand grains from tapioca granules.

Tapioca granules comprise coarse tapioca granules at granularity greater than the granularity of sand grains and fine tapioca granules at granularity smaller than or equal to the granularity of sand grains. The grading unit 30 can separate the coarse tapioca granules from the fine tapioca granules by granule size, and thereby separate the mixture of tapioca granules and sand grains into two parts: one part comprises coarse solid granules SI (e.g., tapioca pieces), while the other part comprises fine solid particles S2 composed of fine tapioca granules and sand grains. The grading unit 30 can be any suitable grading device, preferably a sizing screen, more preferably a vibrating sizing screen, so that two parts of tapioca granules in different granule sizes can be obtained by filtering through screens with different mesh sizes. Since the granule size of the tapioca pieces is bigger and the grain size of sand grains is smaller, a screen with mesh size equal to or smaller than 2mm can be used to obtain coarse tapioca granules in size equal to or greater than 2mm and mixture of fine particles in size smaller than 2mm. Wherein, the coarse solid particles SI comprise tapioca pieces that contain no sand grains substantially, while the fine solid particles S2 comprise sand grains and fine tapioca flour.

As shown in Fig. 4, the mixture of tapioca granules and sand grains is separated in the grading unit 30 into two parts: coarse solid particles SI and fine solid particles S2. After grading with the grading unit 30, the coarse solid particles SI can be collected into a container 50 for further treatment, while sand removal will be performed only for the fine solid particles S2. The weight percentage of the fine solid particles only accounts for 10-30% of the material fed into the grading unit 30. Therefore, by utilizing the grading unit 30, only the fine solid particles S2 have to be treated for sand removal. Thus, the amount of solid particles to be treated by sand removing is reduced, and the efficiency of the treatment is improved. Hereunder the sand removal operation for the mixture of fine particles S2 will be detailed.

The particle collector unit 40 can be any bunker that can store materials, or a screw conveyer with agitation function. The particle collector unit 40 can supply fine solid particles S2 directly to the sand sedimentation tank 10, and force the fine solid particles S2 to flow with the agitating water flow provided by another device in the sand sedimentation tank 10, to attain the purpose of sand removal. However, such a manner is adverse to control the proportion of mixture of fine solid particles vs. agitating water, causing inconsistent fluid mobility. Preferably, the fine solid particles S2 composed of solid particles and sand grains can be mixed with water and agitated intensively, so that the tapioca granules and sand grains are mixed with water into a grout mixture 20, which can subsequently flow into the sand sedimentation tank 10 for sand removal. Wherein, the mass of water is about 20-100 times of the total mass of tapioca granules and sand grains, and the mixing duration is preferably 0.5-2h, so as to obtain a grout mixture 20 with good fluidity and moderate consistency.

The particle collector unit 40 can be any device with agitation function, preferably a screw conveyer with agitation function, so as to convey the prepared grout mixture 20 to the sand sedimentation tank 10 during the mixing operation.

The sand removal operation for the grout mixture 20 in the sand sedimentation tank 10 has been described above, and will not be further detailed hereunder.

Hereunder the method for separating mixture of solid particles provided in the present invention will be detailed.

The method for separating mixture of solid particles provided in the present invention is applicable to separation of a first solid particles from a second solid particles, as long as the following three conditions are met: (1) the density of the first solid particles is lower than the density of the second solid particles; (2) the density of the second solid particles is higher than the density of the solvent; (3) both the first solid particles and the second solid particles are insoluble or slightly soluble to the solvent. For the convenience of description, hereunder the method provided in the present invention will be described in an example, in which the first solid particles are tapioca granules, the second solid particles are sand grains, and the solvent is water.

In the method for separating mixture of solid particles provided in the present invention, the mixture of solid particles can flow with water and can be separated in the flow process. However, such a manner is adverse to control the proportion of mixture of solid particles vs. water, causing inconsistent fluid mobility. Preferably, the mixture of solid particles can be mixed with water to form a sort of homogeneous grout mixture 20 (e.g., by agitation), and then the grout mixture 20 is forced to flow and the solid particles are separated. Hereunder the method for separating mixture of solid particles provided in the present invention will be described in the case of a grout mixture 20 formed by a mixture of solid particles and water. Wherein, there is no specific limitation on the quantity of water and the agitation duration, as long as a sort of grout mixture 20 with good fluidity and moderate consistency is obtained. The inventor has found: a grout mixture 20 with the best fluidity and moderate consistency can be obtained if the mass of water is about 20-100 times of the total mass of tapioca granules and sand grains and the mixing duration is 0.5-2h. Hence, that condition is preferably used in the present invention.

The method for separating mixture of solid particles provided in the present invention can be implemented with any appropriate apparatus. In an embodiment of the present invention, as shown in Fig. 1, a sand sedimentation tank 10 is used to implement the method for separating mixture of solid particles in the present invention.

As described above, the grout mixture 20 (or a fluid formed by the mixture of tapioca granules and sand grains flowing with water) flows into the sand sedimentation tank 10 through the inlet 12; the tapioca granules and the sand grains exhibit different characteristics in the flow process in the tank body 11, due to the difference in density. Since the density of sand grains is higher, the sand grains deposit quickly and form a sand grain layer 22 on the bottom of the tank body 11 ; in contrast, the tapioca granules suspend in water and flow with water; thus, the purpose of separating tapioca granules from sand grains can be attained simply by collecting the tapioca granules that flow with water. For example, when the tapioca granules flow with water to the outlet 13, the water flowing above the elevation of the outlet 13 will carry the tapioca granules and flow through the outlet 13; in that way, the tapioca granules are separated from the sand grains.

In view that the sand grain layer 22 deposited by sand grains may move in the water flow direction under the action of the water flowing above it, and thereby the sand grains accumulates at the side wall where the outlet is provided and may over-flow through the outlet 13, the method for separating mixture of solid particles in the present invention can further comprises a measure of restraining the sand grain layer 22 from moving freely in the flow direction of grout mixture 20.

Preferably, in order to prevent the sand grain layer 22 from moving freely in the flow direction of grout mixture 20, the method for separating mixture of solid particles in the present invention includes arranging a barrier located perpendicular to the flow direction in the flow process of grout mixture 20. Preferably, the barrier is higher than the sand grain layer 22 and lower than the liquid level of grout mixture 20. Specifically, the bottom 15 of the tank body 11 can have a raised part 16 and/or a recessed part 17. Since the sand grains deposit to form a sand grain layer 22 on the bottom 15 of the tank body 11 in the flow process of grout mixture 20, when the sand grain layer 22 moves in the flow direction under the action of water flowing above it, the sand grains will be trapped in the recessed part 17 or blocked by the raised part 16, and therefore can't move further in the flow direction. Even if some sand grains deposit on the top of the raised part 16, these sand grains will move along with the water flowing above it, and then will be trapped in the recessed part 17. Therefore, the sand grain layer 22 will hardly move to the side wall where the outlet 13 is provided; thus, the sand grains will not pill up to the outlet and flow through the outlet 13. Preferably, as shown in Fig. 1, the bottom 15 has a plurality of raised parts 16 and/or a plurality of recessed parts 17, and the raised parts 16 and/or recessed parts 17 are arranged on the bottom 15 of the tank body in the direction from the inlet 12 to the outlet 13. Wherein, the height of the raised part 16 or the depth of the recessed part 17 (i.e., the vertical height variation of bottom 15) is greater than the height of the sand grain layer 22, and the level of grout mixture 20 is above the raised part 16. Preferably, the ratio of the difference between the height of barrier and the liquid level of grout mixture by the height of barrier is 3:5-1 :3 , and the flow rate is set so that the second solid particles in the grout mixture is blocked by the barrier. For example, when the grout mixture 20 flows in the sand sedimentation tank 10, the difference between the height of raised part 16 or recessed part 17 (i.e., the upper end of raised part 16 or recessed part 17) and the level of grout mixture 20 is kept at 0.1-0.5m, and the height of raised part 16 or recessed part 17 (i.e., the height of raised part 16 or the depth of recessed part 17) is set to 0.1-0.3m, and, in conjunction with flow rate control, the sand grain layer 22 can be effectively prevented from moving freely and will not hinder the flow of grout mixture 20 as far as possible.

In above process, if the first solid particles also deposit at a lower rate when compared to the second solid particles, some of the first solid particles will deposit onto the layer of the second solid particles before they can flow to the outlet 13, and therefore are trapped in the sand sedimentation tank 10, resulting in material waste. Likewise, even if the density of the first solid particles is low enough to ensure the first solid particles will not settle down in the solvent, the first solid particles may be affected by the sedimentation of the second solid particles and therefore deposit with the second solid particles and are trapped in the layer of second solid particles in the flow process of the grout mixture 20; that phenomenon will also result in material waste.

To solve that problem, the flow rate of grout mixture 20 can be controlled according to the nature of the first solid particles, so that the second solid particles substantially deposit onto the bottom 15 and form a layer of the second solid particles and the first solid particles only deposit to a level above the elevation of the outlet 13 (i.e., can flow through the outlet 13) at the time of the grout mixture 20 flows to the outlet 13.

Moreover, the method for separating mixture of solid particles in the present invention can further comprise: stirring the layer of the second solid particles, to force the first solid particles trapped in the layer of the second solid particles to float up and flow with the water flowing above the layer of the second solid particles. Preferably, additional gas stream and/or liquid stream can be supplied to the layer of the second type of solid particles. More preferably, the stirring can be performed by a downward gas stream and/or liquid stream supplied above the surface of the layer of the second solid particles. Wherein, the gas in the gas stream can be a gas that doesn't react with the first solid particles, the second solid particles, and the solvent (i.e., the grout mixture), and the liquid in the liquid stream is preferably the solvent. In the case that the first solid particles are tapioca granules, the second solid particles are sand grains, and the solvent is water, air flow and/or water flow can be utilized.

In that process, a gas stream and/or liquid stream jetted at an appropriate flow rate in an appropriate amount can be utilized, so as to force the tapioca granules trapped in the sand grain layer 22 to float away from the sand grain layer 22, or at least force the tapioca granules trapped in the sand grain layer 22 to float up to the surface of the sand grain layer 22 and then carried away by the water flowing above the sand grain layer 22. Though some sand grains in the sand grain layer 22 may also float up in that process, these sand grains will settle down quickly and will hardly be carried away by water, due to the high density of sand grains.

To implement the gas stream and/or liquid stream jetting procedure, a jetting unit that can jet gas stream and/or liquid stream can be arranged in the sand sedimentation tank 10. Specifically, the jetting unit comprises at least one jetting tube 18, and each jetting tube 18 comprises a tube body and a plurality of holes formed in the tube body; the gas stream and/or liquid stream is jetted through the holes P.

Each jetting tube 18 can be arranged above the sand grain layer 22 in any suitable manner; for example, the jetting tube 18 can be arranged to span two opposite side walls of the sand sedimentation tank 10. As shown in Fig. 1, the jetting tubes 18 can be arranged in parallel with the longitudinal direction of the sand sedimentation tank 10, or arranged in parallel with the transverse direction of the sand sedimentation tank 10, or arranged in parallel at a predefined angle to the transverse or longitudinal direction. Apparently, the jetting tubes 18 can also be arranged in a crossed manner.

Preferably, as shown in Fig. 2, the jetting tube 18 is arranged above the sand grain layer 22, and the holes P are arranged to jet gas stream and/or liquid stream towards the sand grain layer 22 at a downward inclination, which is to say, the jetting direction (as shown by the hollow arrow in Fig. 2) is at a downward angle A (preferably degree 30-60) relative to the flow direction of grout mixture 20 or the horizontal plane. As shown in Fig. 1 and Fig. 2, the jetting tube 18 is arranged in the transverse direction of the sand sedimentation tank 10 (the direction shown by the solid arrow in Fig. 2 is the flow direction, which is in longitudinal direction); the holes P are arranged to jet at 45° downward inclination to the horizontal direction (as shown by the hollow arrow in Fig. 2). In that way, the tapioca granules are driven to float within a wide area of the sand grain layer 22, while the sand grains will not float up.

Apparently, a pump or pumping device can be used to jet gas stream and/or water stream through the holes P at an adjustable jet rate. In the method for separating mixture of solid particles in the present invention, the flow rate of the grout mixture 20 can be adjusted, and the jet rate of the jetting unit (i.e., the flow rate and amount of gas stream and/or liquid stream) can be adjusted according to the flow rate. In the case of the flow rate of grout mixture 20 is low, the flow rate and amount of gas stream and/or liquid stream can be increased, so that the tapioca granules deposited on the sand grain layer 22 can float up and suspend in water above far from the sand grain layer 22, and will not settle down to a position below the outlet 13 again when the tapioca granules flow with water to the outlet 13. In the case of the flow rate of grout mixture 20 is high, the tapioca granules blown up by the gas stream and/or liquid stream from the jetting unit will flow with water to the outlet 13 quickly while they only settle down a small distance; therefore, lower flow rate and less amount of gas stream and/or liquid stream can be used to attain the same effect.

Furthermore, when the grout mixture 20 flows at a specific flow rate, the flow rate and amount of the gas stream and/or liquid stream jetted along the flow direction of grout mixture 20 can be reduced appropriately. Along the flow direction of grout mixture 20, in the area away from the side wall where the outlet 13 is provided, a gas stream and/or liquid stream at higher flow rate in greater amount can be used, so that the tapioca granules deposited on the sand grain layer 22 can float up to a higher level above the sand grain layer 22, and will not settle down to a level below the outlet 13 when they flow with water to the outlet 13; in the area near the side wall where the outlet 13 is provided, a gas stream and/or liquid stream at a lower flow rate in less amount can be used, so that the tapioca granules can float up and flow out of the tank with water while ensures the sand grains are retained in the tank.

The method for separating mixture of solid particles in the present invention is especially suitable for two types of solid particles with a high density difference between each other; for example, the density of the first solid particles doesn't exceed 60% of the density of the second solid particles, preferably within the range of 10%-50%.

In addition, in actual application of the separation method in the present invention, preferably the first solid particles, the second solid particles, and the solvent are thoroughly mixed first; more preferably, the weight of the solvent is 20-100 times of the total weight of the first solid particles and the second solid particles.

In an embodiment of the present invention, the first solid particles are tapioca granules in 2mm granule size, the second solid particles are sand grains, and the solvent is water; the difference between the height of the barrier and the level of the grout mixture is 0.1 -0.5m, and the flow rate is 3-10m/s.

More specifically, in the grout mixture, the weight of water is preferably 20-100 times of the total weight of tapioca granules and sand grains. The tank body of the sand sedimentation tank is a rectangular parallelepiped, the vertical height of the sand sedimentation tank is preferably 0.5-0.9m, the depth of recessed part and the height of the raised part on the bottom is 0.1-0.3m, and the total area of the raised part and recessed part accounts for 40-60% of the total area of the bottom. The liquid level of the grout mixture (i.e., the distance from the lowermost part of the outlet to the bottom) is preferably 0.4-0.85m, so that the difference between the uppermost part of the raised part or recessed part and the level of the grout mixture is kept at 0.1-0.5m, the distance from the inlet to the bottom is 0.3-0.5m, the inlet extends to the top of the side wall where the inlet is provided; the distance between the side walls where the inlet is provided and the side wall where the outlet is provided is preferably 5-7m, so that the grout mixture flows naturally at a 3-lOm/s flow rate under the head drop between the inlet and the outlet. The flow rate of the gas stream or water stream from the jetting unit is 2-4m/s. Better sand removal result can be obtained by means of repeated treatment with the sand sedimentation tank. For example, when the sand sedimentation tank is used to separate the mixture of tapioca granules and sand grains, 95% or more sand grains can be removed, by circulating the grout mixture 20 in the sand sedimentation tank 10 for 3-5 cycles.

While the present invention is described and disclosed by means of above embodiments, the present invention is not limited to these embodiments. Those skilled? ? in the part can easily make variations and modifications to the embodiments, without departing from the spirit and scope of the present invention. Therefore, the present invention is only defined by the claims.

Claims

1. A sand sedimentation, comprising a tank body, an inlet, and an outlet, wherein, the tank body comprises side walls and a bottom, the outlet is arranged in a side wall, and the bottom has at least one raised part and/or at least one recessed part.

2. The sand sedimentation tank according to claim 1, wherein, the inlet and outlet are arranged in two opposite side walls.

3. The sand sedimentation tank according to claim 2, wherein, the bottom has a plurality of raised parts and/or a plurality of recessed parts, and the raised parts and/or recessed parts are arranged on the bottom along the direction from the inlet to the outlet.

4. The sand sedimentation tank according to claim 2 or 3, wherein, the longitudinal cross-section of the recessed part and/or raised part is in triangular or trapezoid shape, and the longitudinal cross-section is parallel to the direction from the inlet to the outlet and perpendicular to the horizontal plane.

5. The sand sedimentation tank according to any of the claims 1-3, wherein, the sand sedimentation tank further comprises a baffle plate, with which the size of the outlet and/or the distance from the outlet to the bottom can be adjusted.

6. The sand sedimentation tank according to claim 1, wherein, the sand sedimentation tank further comprises a jetting unit.

7. The sand sedimentation tank according to claim 6, wherein, the jetting unit comprises at least one jetting tube, each jetting tube comprises a tube body and a plurality of holes formed in the tube body, the holes are arranged to point to the recessed part and/or point to the groove formed between the raised parts and/or the groove formed between the raised parts and the side wall where the inlet and/or the outlet is provided.

8. The sand sedimentation tank according to claim 7, wherein, the holes face to the bottom, and the axes of the holes are at an angle of degree 30-60 relative to the horizontal plane.

9. The sand sedimentation tank according to claim 7 or 8, wherein, comprising a plurality of jetting tubes, each of which is arranged in the tank body of the sand sedimentation tank and spans two opposite side walls of the sand sedimentation tank.

10. The sand sedimentation tank according to claim 7, wherein, the distance from the tube body of the jetting tube to the bottom is adjustable.

11. A sand separator, comprising a grading unit, a particle collector unit, and a sand sedimentation tank connected in series; the grading unit is designed to separate fine solid particles in particle diameter smaller than a predefined value from the mixture of solid particles composed of a first solid particles and a second solid particles;

the particle collector unit is designed to collect the separated fine solid particles;

the sand sedimentation tank is designed to remove the second solid particles from the separated fine solid particles;

wherein, the sand sedimentation tank is the sand sedimentation tank according to any of the claims 1-10.

12. The sand separator according to claim 11, wherein, the grading unit is a sizing screen, with meshes in 2mm diameter.

13. The sand separator according to claim 11 or 12, wherein, the particle collector unit is a screw conveyer with agitation function.

14. A method for separating mixture of solid particles, wherein, the mixture of solid particles is composed of a first solid particles and a second solid particles, and the density of the first solid particles is lower than the density of the second solid particles; said method comprises:

forcing the mixture of solid particles to flow with a solvent, making the second solid particles deposit to form a layer of the second solid particles, while keeping the first solid particles to flow further with the solvent in the flow process of the mixture of solid particles, wherein, the density of the second solid particles is higher than the density of the solvent.

15. The method according to claim 14, wherein, the mixture of solid particles is mixed with the solvent to form a grout mixture, and the grout mixture is forced to flow.

16. The method according to claim 15, wherein, the method further comprises a measure of limiting the layer of the second solid particles from moving freely in the flow direction.

17. The method according to claim 16, wherein, the measure of limiting the layer of the second solid particles from moving freely in the flow direction comprises: arranging a barrier located perpendicular to the flow direction in the flow process, wherein, the barrier is higher than the layer of the second solid particles but lower than the liquid level of the grout mixture.

18. The method according to claim 16, wherein, the barrier is a raised part and/or a recessed part.

19. The method according to claim 17, wherein, the ratio of the difference between the height of barrier and the liquid level of grout mixture by the height of the barrier is 3:5-1:3, and the flow rate is set such that the second solid particles in the grout mixture are blocked by the barrier.

20. The method according to any of claims 15-19, further comprises: stirring the layer of the second solid particles, so that the first solid particles trapped in the layer of the second solid particles can float up and flow with the solvent.

21. The method according to claim 20, wherein, the stirring method comprises: supplying a gas stream and/or liquid stream to the layer of the second solid particles.

22. The method according to claim 21, wherein, the flow rate and amount of the gas stream and/or liquid stream is enough to make the first solid particles trapped in the layer of the second solid particles float up to the surface of the layer of the second solid particles.

23. The method according to claim 21, further comprises: adjusting the flow rate and amount of the gas stream and/or liquid stream according to the flow rate of the grout mixture, when the flow rate of the grout mixture is increased or decreased, the flow rate and amount of the gas stream and/or liquid stream is decreased or increased.

24. The method according to claim 21, wherein, the flow direction of the gas stream and/or liquid stream is at a downward inclination of degree 30-60 relative to the flow direction of the grout mixture.

25. The method according to any of the claims 20-24, wherein, the gas in the gas stream doesn't react with the grout mixture and the liquid in the liquid stream is the solvent for the grout mixture.

26. The method according to claim 15, wherein, the density of the first solid particles is 60% of the density of the second solid particles at the most, and the density of the solvent is higher than the density of the first solid particles but lower than the density of the second solid particles.

27. The method according to claim 15, wherein, the weight of the solvent is 20-100 times of the total weight of the first solid particles and the second solid particles.

28. The method according to claim 15, 19, 26, or 27, wherein, the first solid particles are tapioca granules in 2mm granule size, the second solid particles are sand grains, and the solvent is water; the difference between the height of the barrier and the level of the grout mixture is 0.1-0.5m, and the flow rate is 3-10m/s.