WO2015103945A1 - 一种新型除贝壳的方法 - Google Patents

一种新型除贝壳的方法 Download PDF

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Publication number
WO2015103945A1
WO2015103945A1 PCT/CN2015/000022 CN2015000022W WO2015103945A1 WO 2015103945 A1 WO2015103945 A1 WO 2015103945A1 CN 2015000022 W CN2015000022 W CN 2015000022W WO 2015103945 A1 WO2015103945 A1 WO 2015103945A1
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WIPO (PCT)
Prior art keywords
mixture
shells
sea sand
sand
shell
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PCT/CN2015/000022
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English (en)
French (fr)
Inventor
刘贤铨
Original Assignee
刘贤铨
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Publication date
Priority claimed from CN201410009959.1A external-priority patent/CN104772284B/zh
Application filed by 刘贤铨 filed Critical 刘贤铨
Priority to JP2016563233A priority Critical patent/JP6309110B2/ja
Priority to EP15735062.0A priority patent/EP3159319A4/en
Publication of WO2015103945A1 publication Critical patent/WO2015103945A1/zh

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/02—Treatment
    • C04B20/026—Comminuting, e.g. by grinding or breaking; Defibrillating fibres other than asbestos
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B14/02—Granular materials, e.g. microballoons
    • C04B14/04—Silica-rich materials; Silicates
    • C04B14/06—Quartz; Sand
    • C04B14/068—Specific natural sands, e.g. sea -, beach -, dune - or desert sand

Definitions

  • the invention relates to the field of sea sand treatment, in particular to a novel method for removing shells.
  • Sea sand is used for construction very early at home and abroad. At present, more than 90% of Japanese construction sand is treated sea sand.
  • the shells contained in most sea sands are harmful components that affect the performance of building materials.
  • the strength of shells is much lower than the strength of sand grains. It can be easily cut off by hand. Its damage in concrete is equivalent to mud, national construction.
  • the standard for sand use “The mud block is a particle with a primary particle size greater than 1.18 mm in the sand, which is washed by water and less than 600 ⁇ m after hand pinching”.
  • the shells in the sea sand are scattered and distributed in the sea sand from small to large.
  • a survey of the damage of buildings in the earthquake found that the houses built with sea sand first collapsed.
  • Japan has long imposed strict restrictions on the chloride ion content of sea sand used for construction, and Japan has adopted the "rebar rust remover" to prevent steel corrosion in buildings using sea sand, thus causing sea sand construction.
  • the reason for the collapse of the house is not because the excessive structural chloride corrosion of the steel bar causes the structural strength of the building to decrease.
  • the sea sand mixed with shells can be imagined for the hidden dangers caused by the building.
  • An object of the present invention is to overcome the above-mentioned drawbacks and to provide a novel method for removing shells which can reliably and efficiently separate shells from sea sand.
  • the shell and the sea sand are mixed together and belong to a heterogeneous mixture.
  • the density of the two shells is similar.
  • the apparent density of the shell is slightly larger, and the distribution is small to large. It is difficult to separate the two by ordinary methods.
  • the shells are mixed with the sand grains.
  • the size of the sea sand in the sea sand is small to large.
  • the shells in the sea sand are more complicated, not only in size, but also in the shape of shells after long-term sea movement.
  • the invention adopts the concept of multi-stage screening to form a plurality of sea sand and shell mixture in a certain particle size interval, and then separates them by using different properties.
  • the definition of the particle size interval described in the present application refers to the particle size interval of the sea sand grit in the mixture of sea sand grains and shells.
  • a novel method for removing shells comprising the steps of:
  • the sea sand grit and the shell mixture in different particle size sections obtained in the step (1) are separately sieved separately or partially, and sieved through the sieve, and the shell in the mixture falls from the sieve hole.
  • the sea sand grit is intercepted by the screen to realize the separation of the sea sand grit and the shell; the lateral wideth of the narrow mesh hole is not larger than the grain size range of the sand in the mixture of the sea sand grit and the shell which is rescreened again.
  • the upper limit value, the longitudinal length of the elongated mesh hole is greater than a lower limit of a particle size interval of the mixture of the sea sand grit and the sea shell that is re-screened.
  • the lateral full width of the elongated mesh of the step (2) is not greater than the lower limit of the particle size interval of the sand in the mixture of the sea sand and the sea shell that is re-screened.
  • the longitudinal length of the elongated mesh hole is larger than the upper limit value of the particle size interval of the mixture of the sea sand grit and the sea shell that is re-screened.
  • the elongated mesh holes in the separating step are elliptical, rectangular, parallelogram, trapezoidal or any other elongated shape.
  • the sieve of the sieve screen of the step (1) is circular or square or triangular.
  • the sieve used in the separation of the step (2) is a grid, and the interval between the adjacent grid bars is not larger than the particle size range of the sand grains in the mixture of the sea sand grit and the shell which is re-screened. Upper limit value.
  • the invention also provides another method for removing shells from sea sand, the technical scheme of which is:
  • a novel method for removing shells comprising the steps of:
  • step (3) Separation: the mixture of sea sand grit and shell in different particle size sections obtained in step (2) is separately and partially sieved again, and the sieve used for re-screening has a pore diameter not larger than that of the sieved mixture.
  • the technical solution of the method may also be:
  • the sieve used for the re-screening in the separation of the step (3) has a pore diameter not greater than a lower limit of the particle size interval of the sand particles in the re-screened mixture.
  • the sieve in the step (1) has a pore size in the range of 75 ⁇ m to 10 mm.
  • the sieve of the sieve screen of the step (1) is circular or square or triangular.
  • the invention also provides a further method for removing shells from sea sand, the technical solution of which is:
  • a novel method for removing shells comprising the steps of:
  • the shellfish-containing sea sand is screened by a screen having a slit shape and a different lateral width, and the ratio of the lateral width of the sieve holes of the adjacent width of the transverse width is not more than 20, a mixture of sea sand grains and shells in different particle size ranges;
  • step (2) Separation: the mixture of sea sand grit and shell of different particle size sections obtained in step (1) is separately sieved separately or partially, and the widest part of the sieve hole of the sieve is larger than the sand grain which is re-screened The lower limit of the particle size interval of the mixture, the shell in the mixture is intercepted by the sieve, and the sea sand grit in the mixture falls from the sieve hole to obtain sea sand grit in different particle size ranges, thereby realizing the separation of the sea sand grit and the shell.
  • the technical solution of the method may also be:
  • the screens having different lateral widths used in the screening are different lattices between the grid bars.
  • the gate, the gap between the grating strips has a gap ratio of adjacent grids of not more than 20.
  • the sieve holes of the sieve in the step (2) are circular or square or triangular.
  • the invention also provides a further method for removing shells from sea sand, the technical solution of which is:
  • a novel method for removing shells comprising the steps of:
  • the ratio of degrees is not more than 20, and a mixture of sea sand grains and shells in different particle size ranges is obtained;
  • step (1) Crushing: respectively, the mixture of sea sand grit and shell of different particle size sections obtained in step (1) is separately and partially broken, so that the shell whose strength is smaller than the sand is broken into smaller pieces;
  • the mixture of the sea sand grit and the shell of the different particle size sections obtained in the step (2) is separately sieved separately or partially, and the shell in the mixture falls from the sieve hole, and the sand of the sea sand is sieved.
  • the mesh is intercepted to achieve separation of the sea sand grit and the shell; the pore size of the sieve for re-screening is not greater than the upper limit of the particle size interval of the sand in the mixture of the sea sand grit and the shell which is re-screened.
  • the technical solution of the method may also be:
  • the screen used in the step (1) is a grid with different gaps between the grid bars, and the gap between the grid bars has a gap ratio of adjacent grids of not more than 20.
  • the sieve used in the step (3) is a sieve having a narrow opening and a different lateral width, and the transverse width of the sieve is not larger than the sand in the mixture of the sea sand and the shell which is re-screened. 1.5 times the upper limit of the particle size interval.
  • the sieve used in the separation of the step (3) is a grid, and the interval between adjacent grids is not larger than the particle size range of the sand grains in the mixture of the sea sand grains and the shell which are re-screened. 1.5 times the upper limit.
  • the invention further provides a method for removing shells from sea sand, the technical solution of which is:
  • a novel method for removing shells comprising the steps of:
  • the technical solution of the method may also be:
  • the screens with different pore diameters in the screening are screens having a narrow opening and different lateral widths.
  • the technical solution of the method may also be:
  • the screens with different apertures in the screening are grids with different gaps between the grid bars.
  • the ratio of the gaps of the adjacent gaps of the gap size is not more than 20.
  • the present invention further provides a method of removing seashells from sea sand, characterized by comprising the steps of:
  • Hydraulic classification The sea sand containing shells is washed from the bottom to the top by the rising medium flow with different speeds. The free sedimentation speed in the mixture is higher than the rising medium flow rate. The sand and shells are settled downward, and the mixture is free. The sand particles and the shells whose final velocity is lower than the rising water flow velocity are upward with the water flow, and a mixture of sea sand sand particles and shells in different particle size ranges is obtained;
  • the technical solution of the method may also be:
  • the sieve used in the sieving is a screen having a slit shape and a different lateral width.
  • the technical solution of the method may also be:
  • the screen used in the step (3) is a grid having different gaps between the grid bars, and the gap between the grid bars is less than 1.5 of the upper limit of the particle size interval of the sand in the sieved mixture. Times.
  • the invention further provides a method for removing seashells from sea sand, characterized by comprising the following steps Step:
  • Hydraulic classification The sea sand containing shells is washed from the bottom to the top by the rising medium flow with different speeds. The free sedimentation speed in the mixture is higher than the rising medium flow rate. The sand and shells are settled downward, and the mixture is free. The sand particles and the shells whose sedimentation velocity is lower than the rising medium flow velocity are upward with the water flow, and a mixture of sea sand grains and shells in different particle size ranges is obtained;
  • the above method for removing shells in sea sand of the present invention has the advantages of utilizing the physical properties of shells and sand grains and the strength of the shells to be lower than the strength of the sand grains, and adopting a combination of mechanical screening, hydraulic classification, and crushing,
  • the process is simple, the form is diverse, the cost is low, the environment is not polluted, and the separation effect is good.
  • the physical properties of the shell and the sand in the sea sand are different, and the two are separated.
  • Shells and sea sand are mixed together and belong to a heterogeneous mixture.
  • the density of the two is similar, and it is difficult to separate the two by ordinary methods.
  • shells are mixed with sand grains.
  • the size of sea sand in sea sand is from small to large.
  • the shells in sea sand are more complicated.
  • the apparent density of shells is slightly larger, from small to large, not only in size.
  • the shells have different shapes, generally in the form of shells, which are irregularly shaped, and the sea sand is solid particles in the form of blocks or rounds.
  • the method for removing shells in sea sand in this example is as follows:
  • sieve with a sieve with a mesh size of 10 mm sieve large-sized sand grains, stones and large shells with a particle size larger than 10 mm, and then mix the obtained sea sand grains with shells according to the mesh aperture from large to small.
  • the order of the sieves is sequentially sieved to obtain a mixture of sea sand grains and shells of different size ranges; the pore size of the screen used is gradually reduced within a range of not more than 10 mm.
  • the ratio of the size of the screens used for the two adjacent screenings should be no more than 10 to ensure the screening effect.
  • the total screening is 5 times, and the screen apertures are: 4.75 mm, 2.5 mm, 1.0 mm, 0.28 mm, and 75 ⁇ m, and the obtained particle size ranges are 2.5 to 4.75 mm, 1 to 2.5 mm, and 0.28 to 1.0 mm, respectively.
  • a mixture of sea sand grit and shell of 75 ⁇ m to 0.28 mm and 0 to 75 ⁇ m Since the sea sand grit in the range of 0 to 75 ⁇ m is lower than the lower limit of the natural sand specified in the national building sand standard, it cannot be used as a building material, and the treatment thereof is not considered. The following examples are not described again.
  • the separation treatment is carried out, that is, the sea sand grit and the shell mixture of the different particle size sections obtained above are separately sieved to separate.
  • the screen of the screen used for the separation is elongated and has a lateral width at the widest point which is not greater than the upper limit of the particle size interval of the mixture of the re-screened sea sand and the shell. Preferably, it is not more than a lower limit of a particle size interval of the mixture of the sea sand grit and the shell that is re-screened.
  • the longitudinal length of the elongated mesh hole is preferably larger than the upper limit value of the particle size interval of the mixture of the sea sand grit and the sea shell that is re-screened, so that the shell in the mixture falls from the sieve hole, and the sea sand grit is screened. Interception, the separation of sea sand grains and shells. By mixing the sea sand grains of different particle size sections obtained by each separation, a mixture of sea sand grains containing different particle diameters can be obtained, and the mixture can be desalinated to obtain a building for building construction. sand.
  • the sieves having a rectangular mesh are separately used for separation, and the mixture of each particle size interval is divided into two groups.
  • the mesh size of the sieve used is as follows:
  • the shells in the mixture of each particle size range are dropped from the sieve holes, and the sea sand grains in the mixture are intercepted by the sieve to realize the sea sand grains and shells. Separation.
  • the lateral width of the mesh of the separation step is not greater than the lower limit of the particle size interval of the mixture of sea sand grains and shells which are again screened.
  • the longitudinal length of the mesh of the separation step is greater than the upper limit of the particle size interval of the mixture of sea sand grains and shells which are again screened.
  • the pore size of the screen of the sieving step is varied stepwise from 75 ⁇ m to 4.75 mm, and the ratio of the pore sizes of adjacent screens in the sieving step is not more than 4.
  • the mesh shape of the screen used in the separating step of the method of the present invention is not limited to a rectangular shape, but may be a trapezoid, a parallelogram, an irregular quadrilateral, a pentagon, a hexagon, or even other polygons, as long as the sieve is satisfied.
  • the lateral width of the hole is not greater than the upper limit of the particle size interval of the mixture of sea sand grains and shells that are again screened, preferably not greater than the mixture of the sea sand grit and the shell that is again screened.
  • the lower limit of the particle size interval is not limited to a rectangular shape, but may be a trapezoid, a parallelogram, an irregular quadrilateral, a pentagon, a hexagon, or even other polygons, as long as the sieve is satisfied.
  • the lateral width of the hole is not greater than the upper limit of the particle size interval of the mixture of sea sand grains and shells that are again screened, preferably not greater than the
  • the mesh of the screen used in the separation step of the method of the present invention may also have an elliptical shape whose length of the minor axis is not greater than the upper limit of the particle size interval of the sea sand and shell mixture that is rescreened.
  • it is not more than a lower limit of a particle size interval of the mixture of sea sand grains and shells that are again screened; the length of the major axis is greater than the lower limit of the particle size interval of the sea sand and shell mixture that is again screened.
  • it is preferably greater than the upper limit of the particle size interval of the sea sand and shell mixture that is rescreened.
  • the granular sand having a diameter larger than the lower limit of the particle size interval can be intercepted by the screen and retained on the screen, and the shell-like shell constantly changes position in the vibration of the screen, and then a void in the sieve hole that is larger than the lower limit of the particle size interval, is slid down, and is thus taken from the mixture Separate.
  • the screen used in the separation step of the process of the present invention may also be a grid, and the spacing between adjacent grids should be no greater than the lower limit of the particle size interval of the mixture of sea sand grains and shells that are again screened.
  • the granular sand having a diameter larger than the lower limit of the particle size interval can be intercepted by the screen and retained on the screen, and the shell-like shell constantly changes position in the vibration of the grid, and then The gap between adjacent grids of the grid slides down and is separated from the mixture.
  • step (1 ⁇ ) secondary screening for each mixture of sea sand grains and shells of different particle size intervals obtained in step (1'), respectively, secondary screening, the purpose of secondary screening is to ensure that the sand is not sieved In addition, only the small-sized shells after the crushing fall from the sieve holes. Therefore, the size of the mesh of the screen used for the secondary screening should be no more than the lower limit of the particle size interval of the mixture of the sieved sea sand and the shell, thereby ensuring a better separation effect.
  • the sand grains obtained by the screens are mixed to obtain the sea sand containing the sand grains of different particle size intervals.
  • the method firstly forms a plurality of sea sand and shell mixture having a certain particle size interval, and then separates them by using different physical properties.
  • the number of times of screening, the size of the mesh, and/or the mesh of the sieve used in the separation step may be appropriately adjusted according to the particle size of the sea sand and shell mixture to be separated. Shape and size to ensure that the mixed shells are removed.
  • the above method for removing shells in sea sand of the present invention has the advantages of adopting the method of mechanical screening, the process is simple, the cost is low, and the separation effect is good.
  • the sieve is divided into 5 times, and the sieve apertures are: 75 ⁇ m, 0.28 mm, 1.0 mm, 2.5 mm, and 4.75 mm, and the obtained particle diameter ranges are 0 to 75 ⁇ m, 75 ⁇ m to 0.28 mm, and 0.28 to 1.0 mm, respectively.
  • the crushing is performed, and the mixture of sea sand grains and shells in different particle size sections obtained by the above screening step is separately crushed, and the shells having a strength smaller than that of the sand grains are broken into smaller pieces.
  • the mixture of sea sand grit and shell of each different particle size interval obtained after crushing is separately sieved again, and the sieve used for re-screening has a pore diameter not larger than the particle size interval of the sieved mixture.
  • Limit the shell in the mixture falls from the sieve hole, and the sand of the sea sand in the mixture is intercepted by the sieve to realize the separation of the shell sand and the shell containing the shell.
  • the pore size of the screen at the time of the above-mentioned sieving is preferably not more than the lower limit of the particle size interval of the sieved mixture, so that the shell in the mixture can be completely filtered out to achieve an excellent separation effect.
  • the pore size of the screen of the sieving step is varied stepwise from 75 ⁇ m to 4.75 mm, and the ratio of the pore sizes of adjacent screens in the sieving step is not more than 4.
  • the screen of the screening step has a circular opening or a square or a triangle.
  • This example is the same as the first embodiment except that the physical properties of the shell and the sand in the sea sand are different, and the two are separated.
  • the specific implementation of this example is as follows:
  • the shell-containing sea sand is passed through the sieve hole in the order of the mesh aperture from the largest to the smallest.
  • the sieve has a lateral width which is gradually reduced in a range of not more than 10 mm.
  • the ratio of the lateral width of the sieve holes of the adjacent two-stage sieves is not more than 10 to ensure the effect of the screening, and the seas with different particle size ranges are obtained. a mixture of sand grit and shells.
  • the sieve used in the sieving step is a grid, which is sieved 5 times in total, and the intervals between adjacent grids of adjacent two-stage grids are: 4.75 mm, 2.4 mm, 1.1 mm, 0.29 mm. And 75 ⁇ m, a mixture of sea sand grains and shells having a particle diameter range of 2.4 to 4.75 mm, 1.1 to 2.4 mm, 0.29 to 1.1 mm, 75 ⁇ m to 0.29 mm, and 0 to 75 ⁇ m, respectively, was obtained.
  • the mixture of sea sand grit and shell in different particle size sections obtained by the above screening step is separately separated and sieved again, since the radial length of the shell in the mixture is said to be larger than the particle size of the sea sand grit,
  • the widest point of the sieve hole when sieving again should be equal to or greater than the upper limit of the particle size interval of the sieved mixture, preferably slightly larger than the upper limit of the particle size interval of the sieved mixture, and the shell in the mixture is
  • the screen is intercepted, and the sea sand grit in the mixture falls from the sieve hole to obtain sea sand grit in different particle size ranges, thereby realizing the separation of the sea sand grit and the shell.
  • the separation of the pore size is as follows:
  • the sieve holes in the separation step are circular, and the sieve holes may also be square or triangular.
  • This example is the same as the third embodiment in that the physical properties of the shell and the sand in the sea sand are different, and the two are separated.
  • the specific implementation of this example is as follows:
  • the shell-containing sea sand is sequentially passed through a sieve having a narrow opening in the order of the mesh aperture from small to large, and the lateral width of the mesh is gradually increased within a range of not more than 10 mm.
  • the shells ensure the removal effect and prevent the shells from being missed in the sea sand.
  • the ratio of the lateral width of the sieves of the adjacent two levels is not more than 10 to ensure the effect of the screening, and the sea sand grains with different particle size ranges are obtained. a mixture of shells.
  • the mesh shape used for the screening is elliptical, and the length of the short axis, that is, the lateral width of the mesh is: 75 ⁇ m, 0.28 mm, 1.0 mm, 2.5 mm, and 4.75 mm, In the method, there is no need to limit the longitudinal length of the slit-shaped mesh holes.
  • the long-axis lengths of the elliptical mesh holes are respectively: 0.3 mm, 1.4 mm, 5 mm, 10 mm, and 20 mm
  • the obtained particle diameter ranges are respectively A mixture of sea sand grains and shells of 0 to 75 ⁇ m, 75 ⁇ m to 0.28 mm, 0.28 to 1.0 mm, 1 to 2.5 mm, and 2.5 to 4.75 mm.
  • the mixture of sea sand grains and shells in different particle size sections obtained by the above screening step is separately crushed, so that the shells having a strength smaller than that of the sand grains are broken into smaller pieces.
  • the separation step is carried out: for each mixture of sea sand grit and shell obtained in each different particle size range obtained after the crushing, respectively, the mesh is narrowed and sieved, and the narrow and long mesh holes for the screening are the widest in the transverse direction.
  • the location shall not be greater than the lower limit of the particle size interval of the mixture of sea sand grit and shell that is re-screened; since the size of the shell changes significantly after the crushing step, the particle size range does not change much, the mixture
  • the shells in the sea fall from the sieve holes, and the sand grains of the sea sand are intercepted by the screen to realize the separation of the sea sand grains and the shells.
  • the separation of the pore size is as follows:
  • the sieve used in the separation step is an elliptical sieve, and the length of the short axis is the sieve.
  • the lateral width of the hole is not greater than the lower limit of the particle size interval of the mixture of sea sand grains and shells that are again screened, and the length of the long axis, that is, the longitudinal length of the mesh hole is larger than the sea sand grit and shell separated by the sieve again.
  • the upper limit of the particle size interval of the mixture is not greater than the lower limit of the particle size interval of the mixture of sea sand grains and shells that are again screened, and the length of the long axis, that is, the longitudinal length of the mesh hole is larger than the sea sand grit and shell separated by the sieve again.
  • the upper limit of the particle size interval of the mixture is not greater than the lower limit of the particle size interval of the mixture of sea sand grains and shells that are again screened.
  • the mesh shape of the sieve used in the separation step of the method is not limited to an elliptical shape, and the shape of the mesh may be other shapes such as a rectangle, a trapezoid, a parallelogram, an irregular quadrangle, a pentagon, a hexagon, or the like.
  • the polygonal shape may be any longer than the lower limit of the particle size interval of the mixture of the sea sand grains and the shell separated by the sieve again as long as the horizontal width of the sieve hole is not exceeded. In the case of performing the sieving separation in the method, there is no need to limit the longitudinal length of the elongated mesh openings.
  • the granular sand having a diameter larger than the lower limit of the particle size interval can be intercepted by the screen and retained on the screen, and the shell-like shell constantly changes position in the vibration of the screen, and then The sieve holes are slid down and are separated from the mixture.
  • the screen used in the separation step of the process of the present invention may also be a grid, and the spacing between adjacent grids should be no greater than the lower limit of the particle size interval of the mixture of sea sand grains and shells that are again screened.
  • the granular sand having a diameter larger than the lower limit of the particle size interval can be intercepted by the screen and retained on the screen, and the shell-like shell constantly changes position in the vibration of the grid, and then The gap between adjacent grids of the grid slides down and is separated from the mixture.
  • Shells and sea sand are mixed together and belong to a heterogeneous mixture.
  • the density of the two is similar, and it is difficult to separate the two by ordinary methods.
  • shells are mixed with sand grains.
  • the size of sea sand in sea sand is from small to large.
  • the shells in sea sand are more complicated.
  • the apparent density of shells is slightly larger, from small to large, not only in size.
  • the shells have different shapes, generally in the form of shells, which are irregularly shaped, and the sea sand is solid particles in the form of blocks or rounds.
  • the strength of the shell is much smaller than the strength of the sand, and in the particles of the same size and density, the sedimentation velocity of the spherical particles is the largest, and the sedimentation velocity of the other irregularly shaped particles is correspondingly small. This is because the resistance coefficient of the irregularly shaped particles is larger than the spherical particle resistance coefficient.
  • the flaky shells are more resistant to block and rounded sand and have different final settling speeds in the Newtonian fluid field. Therefore, in this example, the above physical properties of shells and grit in sea sand are different.
  • the large order is sequentially sieved to obtain a mixture of sea sand grains and shells of different diameters; the pore size of the screen used is gradually increased within a range of not more than 10 mm.
  • the ratio of the size of the screens used for the two adjacent screenings should be no more than 20, preferably not more than 4, to ensure good screening results. .
  • the crushing step is carried out: the mixture of the sea sand and the shell in different particle size sections obtained by the above screening step is separately crushed, and the strength of the shell is much smaller than the strength of the sand, so that the shell whose strength is smaller than the sand is broken into smaller pieces.
  • the broken pieces, while the sand is not broken, can better ensure the separation effect of the shells in the subsequent separation steps.
  • the mixture of sea sand and shells in different particle size ranges obtained by the above screening step is washed by the rising medium flow respectively, and the shell of the free settling velocity in the mixture is smaller than the flow rate of the rising medium flow with the water flow upward.
  • the sea sand grit in the mixture with a free sedimentation end velocity greater than the flow velocity of the rising medium flow settles downward, thereby separating the sea sand from the shell; the velocity of the medium flow should be greater than the free sedimentation velocity of the shell, and not larger than the washed pellet
  • the free settling velocity of the sand in the diameter interval The free settling velocity of the sand in the diameter interval.
  • the free settling velocity of the sea sand grit is calculated one by one.
  • the final velocity of the shell is set, and the flow velocity of the medium flow is slightly smaller than the free sedimentation velocity of the sea sand grit in the particle size interval to be separated, and is greater than the sedimentation velocity of the shell in the particle size interval.
  • the calculation is obtained.
  • the four free-formation final velocityes are all greater than 0.001 m/s and less than 20 m/s.
  • the flow rate of the medium flow used for each separation is 1 m/s. 1.5 m / s, 2.74 m / s, 5.88 m / s.
  • the free settling velocity of the settled particles ⁇ 0 is calculated by the following Stoskes formula:
  • ⁇ The rate of sinking of the particles (cm/s).
  • r - is the radius of the particle (cm).
  • d 2 - is the specific gravity of the water medium.
  • the medium stream in this example is a water stream, and the medium stream in the method of the invention may also be a sea stream.
  • the crushing step may be added before the separating step: the sea sand grit and the shell mixture of different particle size sections obtained by the sieving step are respectively crushed, and the shell is less than the sand of the sand. It is broken into smaller pieces, and the sand is not broken, which can better ensure the separation effect of the shell in the subsequent separation step.
  • the number of times of screening, the shape and size of the mesh hole, and the speed of water flow during hydraulic separation can be appropriately adjusted according to the particle size of the sea sand and shell mixture to be separated.
  • the mixed shells are cleared.
  • the seawater containing shells is washed from bottom to top by rising media flow with different speeds.
  • the free sedimentation velocity in the mixture is higher than that of the rising medium flow velocity.
  • the sand and shells continue to settle downward, and the free sedimentation velocity in the mixture is less than the rise.
  • the velocity of the water flows with the sand and the shells as the water flows upwards.
  • the velocity of the medium flow is gradually increased in the range of 0.001 m/s to 20 m/s, and the mixture obtained by the sedimentation after each stage is washed by the next-stage medium flow, and the medium in the mixture after each stage is washed.
  • the method of the present invention may also be such that the velocity of the medium flow is gradually reduced in the range of 0.001 m/s to 20 m/s, and the mixture obtained by the rise of the medium flow after each stage is washed by the next-stage medium flow.
  • the crushing step is carried out: the mixture of the sea sand and the shell in different particle size sections obtained by the above hydraulic classification step is separately crushed, and the strength of the shell is much smaller than the strength of the sand, so that the shell whose strength is smaller than the sand is broken into smaller pieces.
  • the broken pieces, while the sand is not broken, can better ensure the separation effect of the shells in the subsequent separation steps.
  • the sieve separation is carried out: the mixture of the sea sand grit and the shell of each particle size interval obtained in the above step is sieved separately, and the pore diameter of the sieve used should be equal to or slightly larger than the upper limit of the particle size range of the sieved mixture. Value, the sand in the mixture falls from the sieve hole, and the shell is intercepted by the sieve to realize the separation of the sea sand grit and the shell.
  • the sieve used for the sieve is circular, and the sieve diameters are: 75 ⁇ m, 0.3 mm, 1.0 mm, 2.6 mm, and 5 mm, respectively.
  • the mesh holes in the method of the invention may also be of other shapes such as square or triangular.
  • the number of times of screening, the shape and size of the mesh hole, and the speed of water flow during hydraulic separation can be appropriately adjusted according to the particle size of the sea sand and shell mixture to be separated.
  • the mixed shells are cleared.
  • the method of the invention adopts a combination of mechanical sieving and hydraulic grading.
  • the separation step according to the difference between the shape of the shell and the sand, the difference in the additional resistance of the different shaped objects with similar densities in the Newtonian fluid is subject to artificial
  • the relative motion is achieved in the manufactured fluid field to separate the two.
  • This example expands the range of physical properties difference for the separation of heterogeneous systems, and introduces the Newtonian fluid field into the separation of sea sand. It is also suitable for the separation of other similar heterogeneous systems.
  • the process is simple, the cost is low, and the environment is not polluted. The separation effect is good.
  • This example is the same as the embodiment 6 in that the physical properties of the shell and the sand in the sea sand are different, and the two are separated.
  • the specific implementation of this example is as follows:
  • the hydraulic classification is carried out: the sea sand with shells is washed from the bottom to the top by the rising medium flow with different speeds.
  • the free sedimentation velocity in the mixture is higher than the rising medium flow velocity, and the sand and shell continue to fall downward, and the mixture is free.
  • the sand and shells with a settling velocity less than the rising water velocity are upward with the water flow.
  • the velocity of the medium flow is gradually increased in the range of 0.001 m/s to 20 m/s, and the mixture obtained by the sedimentation after each stage is washed by the next-stage medium flow, and the medium in the mixture after each stage is washed.
  • the method of the present invention may also be such that the velocity of the medium flow is gradually reduced in the range of 0.001 m/s to 20 m/s, and the mixture obtained by the rise of the medium flow after each stage is washed by the next-stage medium flow. A mixture of sand grains and shells of different particle size intervals obtained in the mixture after the scouring.
  • the crushing step is carried out: the mixture of the sea sand and the shell in different particle size sections obtained by the above hydraulic classification step is separately crushed, and the strength of the shell is much smaller than the strength of the sand, so that the shell whose strength is smaller than the sand is broken into smaller pieces.
  • the broken pieces, while the sand is not broken, can better ensure the separation effect of the shells in the subsequent separation steps.
  • the flow rate of the shell increases with the water flow, and the sand in the mixture with the free sedimentation end velocity is higher than the rising medium flow velocity, so that the sand and the shell are separated, and the sea sand grains with different particle size ranges are obtained respectively.
  • the flow rates of the medium flows are: 0.8 m. /s, 1.3 m/s, 2.5 m/s, 5.0 m/s.

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Abstract

一种新型除贝壳的方法，针对海砂中贝壳的特性，利用海砂中砂粒与贝壳的特性差异，将海砂中贝壳与海砂分离。本方法成功实现了大量处理海砂中贝壳的目标，其运行费用低，分离效果好，使用寿命长。

Description

一种新型除贝壳的方法 技术领域
本发明涉及海砂处理领域，具体涉及一种新型除贝壳的方法。
背景技术
随着我国经济的快速发展，建设规模的日益扩大，特别是东南沿海地区城市进程的快速推进，导致很多沿海城市面临河砂资源枯竭的困境。随着河砂资源的日益减少和人们对河砂开采对河床、生态破坏的认识的增强，将海
砂处理后用于城市建筑已是不可避免的未来建筑用砂趋势。
国内外很早就有海砂用于建筑，目前日本建筑用砂90％以上是经过处理的海砂。绝大多数海砂中含有的贝壳是影响建筑材料性能的有害成分，贝壳的强度远低于砂粒的强度，用手就可以轻易掰断，其在混凝土中的危害相当于泥块，国家《建筑用砂》标准规定：“泥块为砂中原粒径大于1.18mm，经水浸洗、手捏后小于600μm的颗粒”。
海砂中的贝壳从小到大尺寸不尽相同地分散分布在海砂中，日本神户大地震后，对在地震中的建筑物损毁情况进行的调查发现采用海砂建造的房屋首先垮塌。由于日本早就对用于建筑的海砂的氯离子含量做了严格的限制，并且日本在使用海砂的建筑中有采用“钢筋除锈剂”以防止钢筋锈蚀的措施，因此造成海砂建造的房屋垮塌原因并不是由于过量的氯离子腐蚀钢筋造成建筑物结构强度的降低，混有贝壳的海砂用于建筑中给建筑物带来的隐患可想而知。
我国也已认识到海砂中贝壳对建筑结构强度的危害，国家建筑用砂规范规定不允许砂中含有贝壳，为了解决目前已经出现的大量使用淡化海砂作为建筑材料所带来的问题，国家在2009年底编制了《海砂混凝土应用技术规范》，对用于建筑的海砂中贝壳的含量进行了严格限制，规定海砂中的贝壳最大尺寸不应超过4.75mm。并且贝壳含量应符合下表的规定：
海砂中贝壳含量
混凝土强度等级 ≥C40 C35～C30 C25～C15
贝壳含量(按质量计，％) ≤3 ≤5 ≤8
清除海砂中的贝壳的技术的研究势在必行。在我国沿海海砂处理实践中，一般采用筛网清除大于一定粒径的贝壳，这种办法的缺陷是：在筛除大于设定粒径的贝壳时会同时筛除大于该粒径的海砂，并且无法清除小于该粒径的贝壳，因此经过处理后的海砂中仍然含有贝壳，若直接与海砂一起用到建筑上，则会降低混凝土的强度和耐久性，形成潜在的安全隐患。
贝壳含量超过规范要求的海砂不能作为建筑用砂使用，且海砂中的贝壳难以有效排除，造成海砂难以用于高强混凝土，造成资源的浪费。
目前对于如何清除小于筛网孔径的海砂中的贝壳，进行了很多研究和尝试，如采用螺旋分级机进行处理，但处理后的海砂中仍然含有大量的贝壳，也有的采用化学法处理，这种方法不仅耗资巨大，并且会造成环境污染，处理效果都不理想。
发明内容
本发明的目的在于克服上述缺陷，提供一种能够切实、高效地实现贝壳与海砂的分离的新型除贝壳的方法。
贝壳与海砂混杂在一起，属于非均相混合物，两者密度相近，贝壳的表观密度稍微大些，从小到大分散分布，采用普通的方法难以将两者分离。
在海砂中，贝壳与砂粒混杂在一起，海砂中海砂粒径从小到大分布，海砂中的贝壳情况较为复杂，不仅大小不一，并且经过长期的海水运动，贝壳的形状各异，一般以贝壳皮的形式存在，呈不规则的片状，而海砂为呈块状或类圆状的固体颗粒。本发明通过采用多级筛分的理念，形成多个一定粒径区间的海砂与贝壳混合物，然后利用二者不同的性质将其分离。
本申请中所述的粒径区间的定义是指海砂砂粒与贝壳的混合物中的海砂砂粒的粒径区间。
首先，本发明实现上述构思的技术方案是：
一种新型除贝壳的方法，其特征在于包括以下步骤：
(1)筛分：将含贝壳的海砂用不同孔径的筛网过筛，得到不同粒径区间的海砂砂粒与贝壳的混合物；所述孔径大小相邻筛网的孔径之比不大于20；
(2)分离：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳混合物分别或部分分别进行再次过筛，使其过筛孔狭长的筛，混合物中的贝壳从筛孔落下，海砂砂粒被筛网截获，实现海砂砂粒和贝壳的分离；所述狭长状筛孔的横向最宽处不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的上限值，所述狭长筛孔的纵向长度大于所述被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的下限值。
进一步地，本发明的技术方案是：
所述步骤(2)的所述狭长筛孔的横向最宽处不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的下限值。
再进一步地，所述步骤(2)中，所述狭长筛孔的纵向长度大于所述被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的上限值。
又进一步地，在所述步骤(1)的筛分后、所述步骤(2)的分离前，还包括以下步骤：
(1′)破碎：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别进行破碎，强度小于海砂砂粒的贝壳被破碎成更小的碎块。
更进一步地，在所述步骤(1′)与所述步骤(2)的分离之间，还包括以下步骤：
(1〃)二次筛分：针对步骤(1′)得到的每个不同粒径区间的海砂砂粒与贝壳的混合物，分别二次筛分，二次筛分所用的筛网的孔径不大于被二次筛分的海砂与贝壳的混合物的粒径区间的上限值。
优选地，所述分离步骤中的所述狭长的筛孔为椭圆形、长方形、平行四边形、梯形或其他任意狭长形状。
再优选地，所述步骤(1)筛分的筛网的筛孔为圆形或方形或三角形。
更优选地，所述步骤(2)分离中用的筛为格栅，相邻栅条之间的间隔不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的上限 值。
本发明还提供了另一种清除海砂中的贝壳的方法，其技术方案是：
一种新型除贝壳的方法，其特征在于包括以下步骤：
(1)筛分：将含贝壳的海砂用不同孔径的筛网过筛，得到不同粒径区间的海砂砂粒与贝壳的混合物；所述孔径大小相邻筛网的孔径之比不大于20；
(2)破碎：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块。
(3)分离：将步骤(2)得到的不同粒径区间的海砂砂粒与贝壳的混合物，分别或部分分别再次过筛，再次过筛所用的筛网的孔径不大于被筛分混合物的粒径区间的上限值；混合物中的贝壳从筛孔落下，混合物中的海砂的砂粒被筛网截获，实现海砂砂粒和贝壳的分离。
进一步地，本方法的技术方案还可以是：
所述步骤(3)分离中的再次过筛所用的筛网的孔径不大于被再次过筛的混合物中砂粒的粒径区间的下限值。
再进一步地，所述步骤(1)筛分中的所述筛网的孔径在75μm～10mm范围内。
又进一步地，所述步骤(1)筛分的筛网的筛孔为圆形或方形或三角形。
本发明还提供了又一种清除海砂中的贝壳的方法，其技术方案是：
一种新型除贝壳的方法，其特征在于包括以下步骤：
(1)筛分：将含贝壳的海砂用筛孔呈狭长状且横向宽度不同的筛网过筛，所述横向宽度大小相邻的筛的筛孔的横向宽度之比不大于20，得到不同粒径区间的海砂砂粒与贝壳的混合物；
(2)分离：步骤(1)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别再次过筛，所述筛的筛孔的最宽处大于该被再次过筛中砂粒的混合物的粒径区间的下限值，混合物中的贝壳被筛网截获，混合物中的海砂砂粒从筛孔落下，得到不同粒径区间的海砂砂粒，实现海砂砂粒与贝壳的分离。
进一步地，本方法的技术方案还可以是：
所述步骤(1)筛分中用的横向宽度不同的筛网为栅条之间间隙不同的格 栅，所述栅条之间的间隙大小相邻的格栅的间隙之比不大于20。
再进一步地，所述步骤(2)分离中的筛的筛孔为圆形或方形或三角形。
本发明还提供了又一种清除海砂中的贝壳的方法，其技术方案是：
一种新型除贝壳的方法，其特征在于包括以下步骤：
(1)筛分：将含贝壳的海砂用筛孔呈狭长状且横向宽度不同的筛网过筛，所述横向宽度大小相邻的筛的筛孔的横向宽
Figure PCTCN2015000022-appb-000001
度之比不大于20，得到不同粒径区间的海砂砂粒与贝壳的混合物；
(2)破碎：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别进行破碎，使强度小于砂粒的贝壳被破碎成更小的碎块；
(3)分离：将步骤(2)得到的破碎后的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别再次过筛，混合物中的贝壳从筛孔落下，海砂的砂粒被筛网截获，实现海砂砂粒和贝壳的分离；所述再次过筛用的筛孔的孔径不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的上限值。
进一步地，本方法的技术方案还可以是：
所述步骤(1)筛分中用的筛网为栅条之间间隙不同的格栅，所述栅条之间的间隙大小相邻的格栅的间隙之比不大于20。
优选地，所述步骤(3)分离中用的筛为筛孔呈狭长状且横向宽度不同的筛网，筛网横向宽度不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的上限值的1.5倍。
再优选地，所述步骤(3)分离中用的筛为格栅，相邻栅条之间的间隔不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的上限值的1.5倍。
本发明再提供了一种清除海砂中的贝壳的方法，其技术方案是：
一种新型除贝壳的方法，其特征在于包括以下步骤：
(1)筛分：将含贝壳的海砂用不同孔径的筛网过筛，得到不同粒径区间的海砂砂粒与贝壳的混合物；孔径大小相邻筛网孔径之比不大于20；
(2)破碎：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳混合物分别或部分分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块。
(3)水力分离：用上升的介质流分别或部分分别冲刷步骤(2)得到的不同粒径区间的海砂与贝壳的混合物，混合物中的沉降速度小于上升介质流的流速的贝壳随着水流向上，混合物中的沉降速度大于上升介质流的流速的海砂砂粒向下沉降，从而实现海砂与贝壳的分离；所述介质流的速度应不大于所冲刷的粒径区间的砂粒的自由沉降末速，且大于被破碎贝壳的沉降末速。
进一步的，本方法的技术方案还可以是：
所述步骤(1)筛分中用不同孔径的筛网为筛孔呈狭长状且横向宽度不同的筛网。
再进一步地，本方法的技术方案还可以是：
所述步骤(1)筛分中用不同孔径的筛网为栅条之间间隙不同的格栅。，间隙大小相邻的格栅的间隙之比不大于20。
本发明再提供了一种清除海砂中的贝壳的方法，其特征在于包括以下步骤：
(1)水力分级：分别采用速度不同的上升的介质流自下往上冲刷含贝壳的海砂，混合物中的自由沉降末速大于上升的介质流流速的砂粒与贝壳向下沉降，混合物中自由沉降末速小于上升的水流速度的砂粒与贝壳随着水流向上，得到不同粒径区间的海砂砂粒与贝壳的混合物；
(2)破碎：将步骤(1)得到的不同粒径区间的海砂与贝壳的混合物分别或部分分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块；
(3)分离：将步骤(2)得到的每个粒径区间的海砂与贝壳的混合物分别或部分分别过筛，所用的筛网的孔径小于被筛分混合物中砂粒的粒径区间的上限值，混合物中的被破碎的贝壳从筛孔落下，砂粒被筛网截获，从而实现海砂砂粒和贝壳的分离。
进一步的，本方法的技术方案还可以是：
所述步骤(3)过筛中用筛网为筛孔呈狭长状且横向宽度不同的筛网
再进一步地，本方法的技术方案还可以是：
所述步骤(3)筛分中用的筛网为栅条之间的间隙不同的格栅，所述栅条之间的间隙小于被筛分混合物中砂粒的粒径区间的上限值的1.5倍。
本发明再提供了一种清除海砂中的贝壳的方法，其特征在于包括以下步 骤：
(1)水力分级：分别采用速度不同的上升的介质流自下往上冲刷含贝壳的海砂，混合物中的自由沉降末速大于上升的介质流流速的砂粒与贝壳向下沉降，混合物中自由沉降末速小于上升的介质流流速的砂粒与贝壳随着水流向上，得到不同粒径区间的海砂砂粒与贝壳的混合物；
(2)破碎：将步骤(1)得到的不同粒径区间的海砂与贝壳的混合物分别或部分分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块；
(3)分离：分别或部分分别再次用介质流自下往上冲刷由步骤(2)得到的经过破碎的不同粒径区间的海砂砂粒与贝壳的混合物，混合物中的自由沉降末速小于上升的介质流流速的贝壳随着水流向上，混合物中自由沉降末速大于上升的介质流流速的砂粒向下沉降，从而实现海砂砂粒和贝壳的分离，分别获得不同粒径区间的海砂砂粒；所述介质流的速度应大于被破碎贝壳的沉降末速，且不大于所冲刷的粒径区间的砂粒的自由沉降末速。
本发明的上述清除海砂中的贝壳的方法的优点在于：利用贝壳和砂粒的物理特性及贝壳的强度低于砂粒的强度的特点，采用机械筛分、水力分级、破碎相结合的处理方法，工艺简单，形式多样，费用低，不污染环境，分离效果好。
具体实施方式
下面结合具体实施例对本发明作进一步详细说明。
实施例1
本例中，针对海砂中贝壳与砂粒的物理特性不同，将两者分离。贝壳与海砂混杂在一起，属于非均相混合物，两者密度相近，采用普通的方法难以将两者分离。在海砂中，贝壳与砂粒混杂在一起，海砂中海砂粒径从小到大分布，海砂中的贝壳情况较为复杂，贝壳的表观密度稍微大些，从小到大分散分布，不仅大小不一，并且经过长期的海水运动，贝壳的形状各异，一般以贝壳皮的形式存在，呈不规则的片状，而海砂为呈块状或类圆状的固体颗粒。本例中的清除海砂中的贝壳的方法，具体实施方式如下：
首先用筛网孔径为10mm的筛网过筛，筛除粒径大于10mm的大粒径砂粒、石子及大的贝壳，再将得到的海砂砂粒与贝壳的混合物按照筛网孔径从大到小的顺序依次过筛，得到不同定粒度区间的海砂砂粒与贝壳的混合物；所用筛网的孔径在不大于10mm的范围内逐步减小。为达到有效清除贝壳，确保清除效果，防止贝壳遗漏在海砂中，对于相邻两次筛分所用筛网大小孔径之比应不大于10，以保证筛分的效果。本例中，共筛分5次，筛网孔径依次为：4.75mm，2.5mm，1.0mm，0.28mm和75μm，获得粒径区间分别为2.5～4.75mm，1～2.5mm，0.28～1.0mm，75μm～0.28mm和0～75μm的海砂砂粒与贝壳的混合物。因为0～75μm范围的海砂砂粒低于国家建筑用砂标准中规定的天然砂的下限，因此不能作为建筑材料，不必考虑对其的处理。下文的实施例不再赘述。
再进行分离处理，即将上述得到的不同粒径区间的海砂砂粒与贝壳混合物分别进行再次过筛，实现分离。本次分离所用的筛网的筛孔是狭长形状的，该狭长状的筛孔的横向最宽处不大于所述被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的上限值，优选不大于所述被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的下限值。所述狭长筛孔的纵向长度优选大于所述被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的上限值，从而使混合物中的贝壳从筛孔落下，海砂砂粒被筛网截获，实现海砂砂粒和贝壳的分离。将每个分离所获得的不同粒径区间的海砂砂粒混合在一起，即可得到含有不同粒径的海砂砂粒的混合物，对该混合物进行淡化处理，即可得到可用于建筑领域的建筑用砂。
本例的分离步骤中分别使用筛孔为长方形的筛网进行分离，每个粒径区间的混合物均分为两组，具体所用的筛网的筛孔尺寸如下表：
Figure PCTCN2015000022-appb-000002
Figure PCTCN2015000022-appb-000003
通过对不同粒径区间的混合物的再次过筛分离，使每种粒径区间的混合物中的贝壳从筛孔落下，而混合物中的海砂砂粒则被筛网截获，实现海砂砂粒和贝壳的分离。
本例的第一组分离例中，分离步骤的筛孔的横向最宽处均不大于被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的下限值。
本例的第二组分离例中，分离步骤的筛孔的纵向长度均大于被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的上限值。
本例中，筛分步骤的筛网的孔径在75μm～4.75mm范围内逐级变化，且筛分步骤中的相邻大小筛网孔径之比不大于4。
本发明的方法的分离步骤中所用的筛网的筛孔形状并不局限于长方形，还可以是梯形、平行四边形、不规则的四边形、五边形、六边形甚至其他多边形，其只要满足筛孔的的横向最宽处不大于被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的上限值即可，优选不大于所述被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的下限值。
本发明的方法的分离步骤中所用的筛网的筛孔的形状还可以是椭圆形，其短轴的长度应不大于被再次过筛的海砂与贝壳混合物的粒径区间的上限值即可，优选不大于被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的下限值；其长轴的长度大于被再次过筛的海砂与贝壳混合物的粒径区间的下限值即可，优选大于被再次过筛的海砂与贝壳混合物的粒径区间的上限值。
利用上述的筛网，可以使直径大于粒径区间的下限值的颗粒状的砂粒被筛网拦截，保留在筛网上，而片状的贝壳在筛网的振动中不断地改变位置，继而从筛孔中大于粒径区间的下限值的空隙处滑动落下，从而被从混合物中 分离出去。
本发明的方法的分离步骤中所用的筛还可以是格栅，相邻栅条之间的间隔应不大于被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的下限值。
利用这样的格栅，可以使直径大于粒径区间的下限值的颗粒状的砂粒被筛网拦截，保留在筛网上，而片状的贝壳在格栅的振动中不断地改变位置，继而从格栅的相邻栅条之间的空隙处滑动落下，从而被从混合物中分离出去。
在本发明的该方法的筛分步骤后、在分离步骤前，还可以增加以下步骤：
(1′)破碎：将筛分步骤得到的不同粒径区间的海砂砂粒与贝壳的混合物分别进行破碎，使强度小于海砂砂粒的贝壳被破碎成更小的碎块。利用贝壳的强度远小于砂粒的强度的特点，将筛分步骤得到的不同粒径区间的海砂砂粒与贝壳的混合物分别进行破碎，使强度小于砂粒的贝壳被破碎成更小的碎块，而砂粒硬度较高，不易破碎且破碎不多，再进行分离，这样做的优点是可以更好地保证贝壳的分离效果，并且由于贝壳的尺寸已经减小，使得贝壳更容易从筛孔中滑落，提高分离的效率，减少分离时间。
进一步地，还可以在破碎步骤与分离步骤之间，增加以下步骤：
(1〃)二次筛分：针对步骤(1′)得到的每个不同粒径区间的海砂砂粒与贝壳的混合物，分别二次筛分，二次筛分的目的是确保砂粒不被筛除，仅使破碎后的小尺寸的贝壳从筛孔落下即可。因此，二次筛分所用的筛网的筛孔的尺寸应该是不大于被筛分的海砂与贝壳的混合物的粒径区间的下限值，从而可以保证更好的分离效果。
将历次筛网上获得的砂粒混合，即可获得去除了贝壳的含有不同粒径区间的砂粒的海砂。
本方法通过采用多级筛分的理念，首先形成多个具有一定粒径区间的海砂与贝壳混合物，然后利用二者物理性质的不同将其分离。
具体实施本发明的方法时，可根据实际要分离的海砂与贝壳混合物的粒径情况，适当地调整筛分的次数、筛孔的尺寸和/或分离步骤时所用的筛网的筛孔的形状、尺寸，以确保将混合的贝壳清除出来。
本发明的上述清除海砂中的贝壳的方法的优点在于：采用机械筛分的方法，工艺简单，费用低，分离效果好。
实施例2
本例与实施例1的区别主要在于：采用筛分与破碎相结合的方法实现海砂砂粒与贝壳的分离。具体实施方式如下：
首先用筛网孔径为10mm的筛网过筛，筛除粒径大于10mm的大粒径砂粒、石子及大的贝壳，再将得到的海砂砂粒与贝壳的混合物按照筛网孔径从小到大的顺序依次过筛，得到不同定粒径区间的海砂砂粒与贝壳的混合物；所用筛网的孔径在不大于10mm的范围内逐步增大。为达到有效清除贝壳，确保清除效果，防止贝壳遗漏在海砂中，对于相邻两次筛分所用筛网大小孔径之比应不大于10，以保证筛分的效果。本例中，共筛分5次，筛网孔径依次为：75μm，0.28mm，1.0mm，2.5mm和4.75mm，获得粒径区间分别为0～75μm，75μm～0.28mm，0.28～1.0mm，1～2.5mm和2.5～4.75mm的海砂砂粒与贝壳的混合物。
然后进行破碎，将上述筛分步骤得到的不同粒径区间的海砂砂粒与贝壳的混合物分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块。
再进行分离：针对破碎后得到的每个不同粒径区间的海砂砂粒与贝壳的混合物，分别再次过筛，再次过筛所用的筛网的孔径不大于被筛分混合物的粒径区间的上限值；混合物中的贝壳从筛孔落下，混合物中的海砂的砂粒被筛网截获，实现含贝壳海砂砂粒和贝壳的分离。
上述再次过筛时的筛网的孔径优选不大于被筛分混合物的粒径区间的下限值，从而可以彻底滤除混合物中的贝壳，达到优秀的分离效果。
本例中，筛分步骤的筛网的孔径在75μm～4.75mm范围内逐级变化，且筛分步骤中的相邻大小筛网孔径之比不大于4。
本例中，筛分步骤的筛网的筛孔为圆形，也可以是方形或三角形。
实施例3
本例与实施例1同样是针对海砂中贝壳与砂粒的物理特性不同，将两者分离。本例的具体实施方式如下：
首先将含贝壳的海砂按照筛网孔径从大到小的顺序依次过筛孔呈狭长状 的筛，筛孔的横向宽度在不大于10mm的范围内逐步减小。为达到有效清除贝壳，确保清除效果，防止贝壳遗漏在海砂中，相邻两级的筛的筛孔的横向宽度之比不大于10，以保证筛分的效果，得到不同粒径区间的海砂砂粒与贝壳的混合物。
本例中，筛分步骤中所用的筛是格栅，共筛分5次，相邻两级格栅的相邻栅条之间的间隔依次为：4.75mm，2.4mm，1.1mm，0.29mm和75μm，获得粒径区间分别为2.4～4.75mm，1.1～2.4mm，0.29～1.1mm，75μm～0.29mm和0～75μm的海砂砂粒与贝壳的混合物。
再将上述筛分步骤得到的不同粒径区间的海砂砂粒与贝壳的混合物分别进行分离处理，再次过筛，由于混合物中贝壳的径向长度应该说是大于海砂砂粒的粒径的，因此再次过筛时的筛孔的最宽处应等于或大于该被筛混合物的粒径区间的上限值，优选略大于该被筛混合物的粒径区间的上限值，则混合物中的贝壳被筛网截获，混合物中的海砂砂粒从筛孔落下，得到不同粒径区间的海砂砂粒，实现海砂砂粒与贝壳的分离。
本例的分离步骤中分别使用孔径尺寸如下表的筛网进行分离处理：
Figure PCTCN2015000022-appb-000004
本例中分离步骤中的筛的筛孔为圆形，筛孔也可以是方形或三角形。
实施例4
本例与实施例3同样是针对海砂中贝壳与砂粒的物理特性不同，将两者分离。本例的具体实施方式如下：
首先将含贝壳的海砂按照筛网孔径从小到大的顺序依次过筛孔呈狭长状的筛，筛孔的横向宽度在不大于10mm的范围内逐步增大。为达到有效清除 贝壳，确保清除效果，防止贝壳遗漏在海砂中，相邻两级的筛的大小筛孔的横向宽度之比不大于10，以保证筛分的效果，得到不同粒径区间的海砂砂粒与贝壳的混合物。本例中，共筛分5次，筛分使用的筛孔形状为椭圆形，其短轴的长度即筛孔的横向宽度依次为：75μm，0.28mm，1.0mm，2.5mm和4.75mm，本方法中对狭长状筛孔的纵向长度无需多做限制，本例中椭圆形筛孔的长轴长度即纵向长度分别为：0.3mm，1.4mm，5mm，10mm和20mm，获得粒径区间分别为0～75μm，75μm～0.28mm，0.28～1.0mm，1～2.5mm和2.5～4.75mm的海砂砂粒与贝壳的混合物。
再将上述筛分步骤得到的不同粒径区间的海砂砂粒与贝壳的混合物分别进行破碎，使强度小于砂粒的贝壳被破碎成更小的碎块。
然后进行分离步骤：针对破碎后得到的每个不同粒径区间的海砂砂粒与贝壳的混合物，分别再次过筛孔呈狭长状的筛，本次筛分用的狭长的筛孔的横向最宽处应不大于被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的下限值；由于经过破碎步骤后，贝壳的尺寸有明显变化，而砂粒的粒径范围并无多少变化，混合物中的贝壳从筛孔落下，海砂的砂粒被筛网截获，从而实现海砂砂粒和贝壳的分离。
本例的分离步骤中分别使用孔径尺寸如下表的筛网进行分离处理：
Figure PCTCN2015000022-appb-000005
本例中，进行分离步骤时使用的是椭圆形筛孔的筛，其短轴的长度即筛 孔的横向宽度不大于被再次过筛的海砂砂粒与贝壳的混合物的粒径区间的下限值，其长轴的长度即筛孔的纵向长度大于被再次过筛分离的海砂砂粒与贝壳的混合物的粒径区间的上限值。本方法的分离步骤所用的筛的筛孔形状并不局限于椭圆形，筛孔的形状也可以是其他形状如长方形，梯形、平行四边形、不规则的四边形、五边形、六边形甚至其他多边形，其只要满足筛孔的的横向最宽处不大于被再次过筛分离的海砂砂粒与贝壳的混合物的粒径区间的下限值即可。本方法中进行再次过筛分离时，对狭长状筛孔的纵向长度无需多做限制。
利用上述的筛网，可以使直径大于粒径区间的下限值的颗粒状的砂粒被筛网拦截，保留在筛网上，而片状的贝壳在筛网的振动中不断地改变位置，继而从筛孔中滑动落下，从而被从混合物中分离出去。
本发明的方法的分离步骤中所用的筛还可以是格栅，相邻栅条之间的间隔应不大于被再次过筛分离的海砂砂粒与贝壳的混合物的粒径区间的下限值。
利用这样的格栅，可以使直径大于粒径区间的下限值的颗粒状的砂粒被筛网拦截，保留在筛网上，而片状的贝壳在格栅的振动中不断地改变位置，继而从格栅的相邻栅条之间的空隙处滑动落下，从而被从混合物中分离出去。
实施例5
贝壳与海砂混杂在一起，属于非均相混合物，两者密度相近，采用普通的方法难以将两者分离。在海砂中，贝壳与砂粒混杂在一起，海砂中海砂粒径从小到大分布，海砂中的贝壳情况较为复杂，贝壳的表观密度稍微大些，从小到大分散分布，不仅大小不一，并且经过长期的海水运动，贝壳的形状各异，一般以贝壳皮的形式存在，呈不规则的片状，而海砂为呈块状或类圆状的固体颗粒。贝壳的强度远小于砂粒的强度，且在同大小和密度的颗粒中，以球形颗粒的沉降末速为最大，其它不规则形状颗粒的沉降末速则相应较小。这是因为不规则形状颗粒的阻力系数比球形粒阻力系数大的缘故。片状的贝壳较块状及类圆状的砂粒所受到的阻力系数大，在牛顿流体力场中有不同的最终沉降速度。因此本例中针对海砂中贝壳与砂粒的上述物理特性的不同， 提供另外一种清除海砂中的贝壳的方法，即采用多级筛分，形成多个一定粒度区间的海砂与贝壳混合物，再利用二者形状不同而形成的沉降速度的差异用水力分级的方法将二者分离。具体实施方式如下：
首先，首先用筛网孔径为10mm的筛网过筛，筛除粒径大于10mm的大粒径砂粒、石子及大的贝壳，再将得到的海砂砂粒与贝壳的混合物按照筛网孔径从小到大的顺序依次过筛，得到不同定粒径区间的海砂砂粒与贝壳的混合物；所用筛网的孔径在不大于10mm的范围内逐步增大。为达到有效清除贝壳，确保清除效果，防止贝壳遗漏在海砂中，对于相邻两次筛分所用筛网大小孔径之比应不大于20，优选不大于4，以保证良好的筛分的效果。本例中，采用圆孔筛共筛分5次，筛孔孔径依次为：75μm，0.28mm，1.0mm，2.5mm和4.75mm，获得粒径区间分别为0～75μm，75μm～0.28mm，0.28～1.0mm，1～2.5mm和2.5～4.75mm的海砂砂粒与贝壳的混合物。
然后进行破碎步骤：即上述筛分步骤得到的不同粒径区间的海砂与贝壳的混合物分别进行破碎，利用贝壳的强度远小于砂粒的强度的特点，使强度小于砂粒的贝壳被破碎成更小的碎块，而砂粒破碎不多，可以更好地保证后续的分离步骤的贝壳的分离效果。
然后进行水力分离：用上升的介质流分别冲刷上述筛分步骤得到的不同粒径区间的海砂与贝壳的混合物，混合物中的自由沉降末速小于上升介质流的流速的贝壳随着水流向上，混合物中的自由沉降末速大于上升介质流的流速的海砂砂粒向下沉降，从而实现海砂与贝壳的分离；介质流的速度应大于贝壳的自由沉降末速，而不大于所冲刷的粒径区间的砂粒的自由沉降末速。本例中，针对75μm～0.28mm，0.28～1.0mm，1～2.5mm和2.5～4.75mm这四个粒径区间的海砂砂粒与贝壳的混合物，逐一计算海砂砂粒的自由沉降末速及贝壳的沉降末速，并使介质流的流速略小于该待分离的粒径区间的海砂砂粒的自由沉降末速，而大于该粒径区间的贝壳的沉降末速，本例中，计算获得的4个自由沉降末速均为大于0.001m/s，而小于20m/s，考虑到生产效率、构造和粒径等因素影响，每次实现分离所用介质流的流速依次分别为1m/s，1.5m/s，2.74m/s，5.88m/s。
沉降颗粒的自由沉降末速υ0用下述斯托斯克斯公式计算：
Figure PCTCN2015000022-appb-000006
υ——颗粒的沉速(厘米/秒)。
g——重力加速度。
r——为颗粒的半径(厘米)。
d1——颗粒的比重。
d2——为水介质比重。
μ——水介质粘度。
κ——为形状系数，随形状而变化，对球形颗粒κ＝0.222，鳞片状颗粒κ＝0.040。
本例中的介质流为水流，本发明方法中的介质流也可以是海水流。
优选地，本发明方法中，还可以在筛分步骤后，在分离步骤前增加破碎步骤：即将筛分步骤得到的不同粒径区间的海砂砂粒与贝壳混合物分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块，而砂粒破碎不多，可以更好地保证后续的分离步骤的贝壳的分离效果。
具体实施本发明的方法时，可根据实际待分离的海砂与贝壳混合物的粒径情况，适当地调整筛分的次数、筛孔的形状、尺寸，调整水力分离时水流的速度，以确保将混合的贝壳清除出来。
实施例6
本例具体实施方式如下：
分别采用速度不同的上升的介质流自下往上冲刷含贝壳的海砂，混合物中的自由沉降末速大于上升的介质流流速的砂粒与贝壳继续向下沉降，混合物中自由沉降末速小于上升的水流速度的砂粒与贝壳随着水流向上。本例中，介质流的速度在0.001m/s～20m/s范围内逐级增大，每级冲刷后因沉降获得的混合物再被下一级介质流冲刷，每级冲刷后混合物中随介质流上升而获得的是不同粒径区间的砂粒及贝壳的混合物；本例中，计算获得的海砂砂粒的自由沉降末速均大于0.001m/s，小于20m/s，考虑到生产效率、构造和粒径等因素影响，上升介质流的流速依次分别为0.05m/s，1m/s，1.5m/s，2.74m/s， 5.88m/s，获得粒径区间分别为：0～75μm，75μm～0.28mm，0.28～1.0mm，1～2.5mm和2.5～4.75mm的海砂砂粒与贝壳的混合物。
本发明方法也可以是使介质流的速度在0.001m/s－20m/s范围内逐级减小，每级冲刷后因随介质流上升而获得的混合物再被下一级介质流冲刷，每级冲刷后混合物中因沉降而获得的是不同粒径区间的砂粒及贝壳的混合物；
然后进行破碎步骤：即上述水力分级步骤得到的不同粒径区间的海砂与贝壳的混合物分别进行破碎，利用贝壳的强度远小于砂粒的强度的特点，使强度小于砂粒的贝壳被破碎成更小的碎块，而砂粒破碎不多，可以更好地保证后续的分离步骤的贝壳的分离效果。
然后进行过筛分离：将上述步骤得到的每个粒径区间的海砂砂粒与贝壳的混合物分别过筛，所用的筛网的孔径应等于或略大于被筛分混合物的粒径区间的上限值，混合物中的砂粒从筛孔落下，贝壳被筛网截获，从而实现海砂砂粒和贝壳的分离。
本例中，筛分所用筛的筛孔为圆形，筛孔直径分别为：75μm，0.3mm，1.0mm，2.6mm和5mm。
本发明方法中的筛孔也可以是其他形状如：方形、三角形。
具体实施本发明的方法时，可根据实际待分离的海砂与贝壳混合物的粒径情况，适当地调整筛分的次数、筛孔的形状、尺寸，调整水力分离时水流的速度，以确保将混合的贝壳清除出来。
本发明方法采用机械筛分和水力分级相结合的方法，在分离步骤中，针对贝壳与砂粒形状的不同，利用密度相近的不同形状物体在牛顿流体场所受附加阻力的差异，使两者在人为制造的流体场中实现相对运动，从而将两者分离。本例拓展了非均相物系分离适用物理性质差异的范围，将牛顿流体场引入海砂的分离中，同样适用于其它类似的非均相物系分离，工艺简单，费用低，不污染环境，分离效果好.
实施例7
本例与实施例6同样是针对海砂中贝壳与砂粒的物理特性不同，将两者分离。本例的具体实施方式如下：
首先进行水力分级：分别采用速度不同的上升的介质流自下往上冲刷含贝壳的海砂，混合物中的自由沉降末速大于上升的介质流流速的砂粒与贝壳继续向下沉降，混合物中自由沉降末速小于上升的水流速度的砂粒与贝壳随着水流向上。本例中，介质流的速度在0.001m/s～20m/s范围内逐级增大，每级冲刷后因沉降获得的混合物再被下一级介质流冲刷，每级冲刷后混合物中随介质流上升而获得的是不同粒径区间的砂粒及贝壳的混合物；本例中，计算获得的海砂砂粒的自由沉降末速均大于0.001m/s，小于20m/s，考虑到生产效率、构造和粒径等因素影响，上升介质流的流速依次分别为0.05m/s，1m/s，1.5m/s，2.74m/s，5.88m/s，获得粒径区间分别为：0～75μm，75μm～0.28mm，0.28～1.0mm，1～2.5mm和2.5～4.75mm的海砂砂粒与贝壳的混合物。
本发明方法也可以是使介质流的速度在0.001m/s－20m/s范围内逐级减小，每级冲刷后因随介质流上升而获得的混合物再被下一级介质流冲刷，每级冲刷后混合物中因沉降而获得的是不同粒径区间的砂粒及贝壳的混合物。
然后进行破碎步骤：即上述水力分级步骤得到的不同粒径区间的海砂与贝壳的混合物分别进行破碎，利用贝壳的强度远小于砂粒的强度的特点，使强度小于砂粒的贝壳被破碎成更小的碎块，而砂粒破碎不多，可以更好地保证后续的分离步骤的贝壳的分离效果。
再进行分离：分别再次用介质流自下往上冲刷由破碎步骤得到的经过破碎的不同粒径区间的海砂砂粒与贝壳的混合物，由于贝壳的尺寸有了明显的减小，其沉降末速也明显变小，针对每个粒径区间的混合物，只要使介质流的流速略小于所冲刷的粒径区间的砂粒的自由沉降末速，则混合物中的自由沉降末速远小于上升的介质流流速的贝壳随着水流向上，混合物中自由沉降末速大于上升的介质流流速的砂粒向下沉降，从而实现海砂砂粒和贝壳的分离，分别获得不同粒径区间的海砂砂粒。本例中针对75μm～0.28mm，0.28～1.0mm，1～2.5mm和2.5～4.75mm这五个粒径区间的海砂砂粒与贝壳的混合物，所采用的介质流的流速分别为：0.8m/s，1.3m/s，2.5m/s，5.0m/s。上述仅对本发明中的具体实施例加以说明，但并不是对本发明的保护范围作任何形式上的限定，凡是依据本发明中的设计精神所作出的等效变化或修饰，均应认为落入本发明的保护范围。

Claims (9)

  1. 一种新型除贝壳的方法，其特征在于包括以下步骤：
    (1)筛分：将含贝壳的海砂用不同孔径的筛网过筛，得到不同粒径区间的海砂砂粒与贝壳的混合物；
    (2)分离：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳混合物分别或部分分别进行再次过筛，使其过筛孔狭长的筛，混合物中的贝壳从筛孔落下，海砂砂粒被筛网截获，实现海砂砂粒和贝壳的分离；所述狭长状筛孔的横向最宽处不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的上限值。
  2. 根据权利要求1所述的方法，其特征在于：所述步骤(2)的所述狭长筛孔的横向最宽处不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的下限值。
  3. 根据权利要求1所述的方法，其特征在于：在所述步骤(1)的筛分后、所述步骤(2)的分离前，还包括以下步骤：
    (1′)破碎：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别进行破碎，强度小于海砂砂粒的贝壳被破碎成更小的碎块。
  4. 一种新型除贝壳的方法，其特征在于包括以下步骤：
    (1)筛分：将含贝壳的海砂用不同孔径的筛网过筛，得到不同粒径区间的海砂砂粒与贝壳的混合物；
    (2)破碎：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块；
    (3)分离：将步骤(2)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别再次过筛，再次过筛所用的筛网的孔径不大于被筛分混合物的粒径区间的上限值；混合物中的贝壳从筛孔落下，混合物中的海砂的砂粒被筛网截获，实现含贝壳海砂砂粒和贝壳的分离。
  5. 一种新型除贝壳的方法，其特征在于包括以下步骤：
    (1)筛分：将含贝壳的海砂用筛孔呈狭长状且横向宽度不同的筛网过筛， 得到不同粒径区间的海砂砂粒与贝壳的混合物；
    (2)分离：步骤(1)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别再次过筛，所述筛的筛孔的最宽处大于该被筛混合物中砂粒的粒径区间的下限值，混合物中的贝壳被筛网截获，混合物中的海砂砂粒从筛孔落下，得到不同粒径区间的海砂砂粒，实现海砂砂粒与贝壳的分离。
  6. 一种新型除贝壳的方法，其特征在于包括以下步骤：
    (1)筛分：将含贝壳的海砂用筛孔呈狭长状且横向宽度不同的筛网过筛，得到不同粒径区间的海砂砂粒与贝壳的混合物；
    (2)破碎：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别进行破碎，使强度小于砂粒的贝壳被破碎成更小的碎块；
    (3)分离：将步骤(2)得到的破碎后的不同粒径区间的海砂砂粒与贝壳的混合物分别或部分分别再次过筛，混合物中的贝壳从筛孔落下，海砂的砂粒被筛网截获，实现海砂砂粒和贝壳的分离；所述再次过筛用的筛孔的孔径不大于所述被再次过筛的海砂砂粒与贝壳的混合物中砂粒的粒径区间的上限值。
  7. 一种新型除贝壳的方法，其特征在于包括以下步骤：
    (1)筛分：将含贝壳的海砂用不同孔径的筛网过筛，得到不同粒径区间的海砂砂粒与贝壳的混合物；
    (2)破碎：将步骤(1)得到的不同粒径区间的海砂砂粒与贝壳混合物分别或部分分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块；
    (3)水力分离：用上升的介质流分别或部分分别冲刷步骤(2)得到的不同粒径区间的海砂与贝壳的混合物，混合物中的沉降速度小于上升介质流的流速的贝壳随着水流向上，混合物中的沉降速度大于上升介质流的流速的海砂砂粒向下沉降，从而实现海砂与贝壳的分离；所述介质流的速度应不大于所冲刷的粒径区间的砂粒的自由沉降末速，且大于被破碎贝壳的沉降末速。
  8. 清除海砂中的贝壳的方法，其特征在于包括以下步骤：
    (1)水力分级：分别采用速度不同的上升的介质流自下往上冲刷含贝壳的海砂，混合物中的自由沉降末速大于上升的介质流流速的砂粒与贝壳向下沉降，混合物中自由沉降末速小于上升的水流速度的砂粒与贝壳随着水流向 上，得到不同粒径区间的海砂砂粒与贝壳的混合物；
    (2)破碎：将步骤(1)得到的不同粒径区间的海砂与贝壳的混合物分别或部分分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块；
    (3)分离：将步骤(2)得到的每个粒径区间的海砂与贝壳的混合物分别或部分分别过筛，所用的筛网的孔径小于被筛分混合物中砂粒的粒径区间的上限值，混合物中的被破碎的贝壳从筛孔落下，砂粒被筛网截获，从而实现海砂砂粒和贝壳的分离。
  9. 清除海砂中的贝壳的方法，其特征在于包括以下步骤：
    (1)水力分级：分别采用速度不同的上升的介质流自下往上冲刷含贝壳的海砂，混合物中的自由沉降末速大于上升的介质流流速的砂粒与贝壳向下沉降，混合物中自由沉降末速小于上升的介质流流速的砂粒与贝壳随着水流向上，得到不同粒径区间的海砂砂粒与贝壳的混合物；
    (2)破碎：将步骤(1)得到的不同粒径区间的海砂与贝壳的混合物分别或部分分别进行破碎，强度小于砂粒的贝壳被破碎成更小的碎块；
    (3)分离：分别或部分分别再次用介质流自下往上冲刷由步骤(2)得到的经过破碎的不同粒径区间的海砂砂粒与贝壳的混合物，混合物中的自由沉降末速小于上升的介质流流速的贝壳随着水流向上，混合物中自由沉降末速大于上升的介质流流速的砂粒向下沉降，从而实现海砂砂粒和贝壳的分离，分别获得不同粒径区间的海砂砂粒；所述介质流的速度应大于被破碎贝壳的沉降末速，且不大于所冲刷的粒径区间的砂粒的自由沉降末速。
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