Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
  • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
  • B07B4/00—Separating solids from solids by subjecting their mixture to gas currents
  • B07B4/08—Separating solids from solids by subjecting their mixture to gas currents while the mixtures are supported by sieves, screens, or like mechanical elements

Definitions

• the invention relates to a screening device in which a bulk material flow is to flow through a screening area for the most part, while only foreign bodies such as metal parts or clumps of material are retained. It is based on the task of reducing the screen area required for this.
• the solution according to the invention consists in that a fluidized bed conveying surface is connected upstream of the sieve surface in the conveying path of the bulk material flow with approximately the same conveying direction.
• the bulk material flow reaches the screen surface as a fluidized bed.
• the bulk material (at least its fine-grained portion) is flowable. This facilitates the movement processes associated with the sieving process, namely on the one hand the passage of the sieve underflow through the sieve openings and on the other hand the separation within the material bed.
• This increases the sieving capacity per unit area of the sieving surface; the required expansion of the screen area is reduced. This simultaneously reduces the height requirement.
• the fluidized bed conveying surface can be a conventional pneumatic conveying trough, through the porous bottom of which gas is introduced into the material bed lying on the conveying surface, as a result of which the fluid bed is brought into a flowable state.
• the conveying movement can be caused by a corresponding gradient of the conveying surface.
• the fluidized bed state cannot be maintained in the long term above the sieve surface because the gas which is the basis of the fluidized state and separates the particles from one another can easily flow up and down. It is therefore expedient that the screen area in the conveying direction is so short in relation to the conveying speed that the fluidized bed state of the Sieve overflow remains. More precisely, the bulk material bed at the end of the sieve conveying path should be in a state in which it is still flowable so that it can flow off the sieve surface. The other operating conditions must also be taken into account, in particular a slope and any vibration of the screen surface that is provided. These influences have a favorable effect on the conveyance and the flowability of the material bed. If there is a gradient or vibration, the vortex state at the end of the sieving section need not be so pronounced that the material could still flow away solely due to this vortex state.
• the sieve section is shorter than would be necessary to screen off the entire fine fraction.
• several fluidized bed conveying surfaces and sieve surfaces can be arranged one behind the other.
• the entire sieving device then presents itself as a sequence of several sections of pneumatic conveying troughs alternating with sieve sections preferably interposed in the same plane, the sieve sections each being kept so short that further conveyance does not stop there, while the pneumatic conveying stations gutter sections are so long that the required fluidized bed state can be restored.
• a device for generating a differential pressure promoting the screen passage can be provided.
• the use of a differential pressure on a screen surface is known per se (GB-A 671 232).
• FIG. 1 shows a side view of part of a plant with the screening device according to the invention
• FIG. 2 shows a longitudinal section through the screening device
• FIG. 3 shows a top view of the screening device
• FIG. 4 shows a cross section along line IV-IV of FIG. 2.
• a pneumatic conveying trough 2 is connected to the outlet of a bulk goods container 1.
• This is a known conveying element which, as the bottom of a closed conveying channel, has an air-permeable plate which is pressurized with compressed air from an air supply channel underneath, which penetrates into the material bed lying thereon after passing through the bottom and forms it as a fluidized bed flowable state. Due to the slight gradient, it starts to move.
• the sieve device 4 Connected to the pneumatic conveying trough 2 via an elastic compensator 3 is the sieve device, generally designated 4, whose underflow is carried on by a pneumatic conveying trough 5 which is connected to the sieve device via an elastic compensator 6.
• the overflow is discharged laterally at 7.
• the sieve device 4 is arranged on supports 8 by means of oscillating bearings 9 and equipped with unbalance motors 10 which set them in vibration according to known principles.
• FIG. 2 This shows an upper sieve space 11, the bottom of which is flush with the compensator 3 and connects to the ventilation bottom of the conveyor trough 2.
• a sieve sub-space 12 which is designed as a pneumatic conveyor trough with a ventilation base 13 and a ventilation space 14 for removing the sieve underflow.
• the pneumatic conveyor trough 5 is connected to the pneumatic conveyor trough of this sub-space in alignment via the compensator 6.
• the floor 15, which - as can be seen from the top view in FIG. 3 - is composed of four sieve surfaces 16 and ventilation floors 17 arranged in-between, to which compressed air from a line 18 with suitable Actuators can be supplied via the ventilation spaces 19.
• These ventilation floors and the ventilation floor of the conveyor trough 2 were referred to above with the more general expression fluidized bed conveyor surface.
• a chute 20 adjoins the last screen surface 16, which discharges the screen overflow and is provided with flaps 21 in order to prevent the inflow and outflow of air if necessary.
• a pendulum flap 22 can be provided over the beginning of the bottom 15 of the sieve device.
• the material bed enters the screening device from the pneumatic conveyor trough 2 in the state of the fluidized bed. Due to its fluidized state, the gradient and the vibration, it largely runs over the first screen surface 16. This sieve area is dimensioned shorter than would be necessary for the sieving process to be completed.
• the fluidization state of the fluidized bed is refreshed again over the following ventilation section 16, so that it reaches and overflows the following sieve section in the fluidized state, and so on.
• the screen overflow is discharged through the chute 20 at the end of the screening device.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Combined Means For Separation Of Solids (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Excavating Of Shafts Or Tunnels (AREA)
• Automatic Analysis And Handling Materials Therefor (AREA)
• Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=6893088

Family Applications (1)

Country Status (7)

Families Citing this family (5)

Family Cites Families (3)

• 1993
  • 1993-05-10 DE DE9307072U patent/DE9307072U1/de not_active Expired - Lifetime
• 1994
  • 1994-05-10 US US08/360,794 patent/US5586660A/en not_active Expired - Fee Related
  • 1994-05-10 WO PCT/EP1994/001504 patent/WO1994026428A1/fr active IP Right Grant
  • 1994-05-10 EP EP94916946A patent/EP0649349B1/fr not_active Expired - Lifetime
  • 1994-05-10 ES ES94916946T patent/ES2117274T3/es not_active Expired - Lifetime
  • 1994-05-10 DE DE59405776T patent/DE59405776D1/de not_active Expired - Fee Related
  • 1994-05-10 JP JP6524951A patent/JPH07508932A/ja active Pending
  • 1994-05-10 AT AT94916946T patent/ATE165258T1/de not_active IP Right Cessation

Non-Patent Citations (1)

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