Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C19/00—Other disintegrating devices or methods
  • B02C19/06—Jet mills
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
  • B02C23/18—Adding fluid, other than for crushing or disintegrating by fluid energy
  • B02C23/20—Adding fluid, other than for crushing or disintegrating by fluid energy after crushing or disintegrating
  • B02C23/22—Adding fluid, other than for crushing or disintegrating by fluid energy after crushing or disintegrating with recirculation of material to crushing or disintegrating zone
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
  • B02C23/18—Adding fluid, other than for crushing or disintegrating by fluid energy
  • B02C23/24—Passing gas through crushing or disintegrating zone
  • B02C23/32—Passing gas through crushing or disintegrating zone with return of oversize material to crushing or disintegrating zone

Definitions

• the invention relates to a method and an equipment for classifying a gas-solids flow coming from a counterjet pulverizer, in which the gas-solids flow accelerated by an additional gas flow is led to a first, mainly a cent ⁇ rifugal-force based classification phase, from which a coarse fraction is returned to the pulverization and a fine fraction is led, supported by the gas flow, to a second classification phase.
• the counterjet pulverizer technique developed by the in ⁇ ventors is mainly connected with a static or dynamic classifier.
• the operation of these classifier types is described e.g. in an earlier Finnish patent publication 81732 and in an international publication WO 90/06179.
• the classi ⁇ bombs may be of a static or dynamic type or their com ⁇ binations.
• a static classifier refers to a classifier, which contains no moving parts, but the classification effect is achieved only by means of a centrifugal force caused by the speed of the gas-solids flow.
• the classifier has, for intensifying the classification effect, a winged rotor rotating at a high speed and surrounding a fine-fraction outlet opening.
• the coarse fraction of a second and possibly a next clas ⁇ sifier is usually recovered as such depending on the pro ⁇ duct or returned directly to a feeding funnel of the counterjet pulverizer e.g. by means of a separate feed screw.
• the last-mentioned solution stresses the counter ⁇ jet pulverizer to an unnecessary large extent, since part of the coarse fraction of the second classifier comprises e.g. of easily decomposing fiber bundles, the decomposi ⁇ tion of which does not require an additional pulverizati ⁇ on in the jet pulverizer.
• the object of the present invention is to eliminate the above-disadvantages, which has been achieved by means of a method, which is characterized in that the coarse frac ⁇ tion produced in the second classification phase is mixed in a vigorous additional gas flow and the additional gas- solids mixture produced is led to the feed of the first classification phase such that large speed differences occur therein, and the fine fraction is led, supported by the gas flow, to the next treatment phase.
• the particle bundles possibly present in the coarse fraction of the second classifier may be rea ⁇ dily decomposed by the action of shear forces caused by the additional or accelerating gas flowing at a high speed below the removal device of the classifier.
• a simi ⁇ lar positive effect is achieved at the point of a connec- ting pipe between the counterjet pulverizer and the first classifier, where the additional or accelerating gas pipe terminates.
• Fig. 1 shows as an example a first embodiment of the in ⁇ ventive equipment seen from one side
• Fig. 2 shows a second embodiment of the invention
• Fig. 3 shows a third embodiment of the invention.
• new material to be pulverized is brought by means of a feed screw 1 to a feeding device 2 of the pulverizer, which device 2 represents a so-cal ⁇ led valve feeding type.
• the ma- terial drops to a pressurized balancing reservoir 2b, from which it is transferred as a uniform feed by means of a screw conveoyr to a fluidization chamber 3 of the equipment, in which a working gas is fed among the mate ⁇ rial for achieving a gas-solids suspension.
• the gas-so- lids suspension thus formed flows at a high speed as a uniform flow via a dividing device 4 to accelerating nozzles 5a of the counterjet pulverizer 5, which are di ⁇ rected to a common point, in which the gas-solids jets impact against each other, whereby the solid particles are pulverized into an ultrafine form.
• the pulverized gas-solids suspension flows via a connecting pipe 6 to a first, mainly centri ⁇ fugal-force based classifier 7, into which the gas-solids suspension flows at a high speed mainly tangentially.
• additional or accelerating gas is led from an additional gas source 9 into the connecting pipe 6 via an additional gas pipe 8, which terminates at the connecting pipe 6 at a distance from the classifier 7, mainly parallel with the remaining part of the connecting pipe 6.
• an additional gas pipe 8 which terminates at the connecting pipe 6 at a distance from the classifier 7, mainly parallel with the remaining part of the connecting pipe 6.
• On the peripheral surface of the classifier 7 is located a removal pocket 7a for the coarse fraction at a distance from the inlet opening of the classifier 7.
• the bottom section of the removal pocket 7a is provided with a closing device 10, preferably a rotor closing device, by means of which the coarse fraction is removed periodi ⁇ cally from the removal pocket 7 and returned to a feeding funnel 2a of the counterjet pulverizer.
• the second classifier 12 may possibly be of the same type as the first classifier 7 or possibly a classifier of a cyclone type.
• the solution according to this invention is characterized in that a removal device 13 for the coarse fraction of the classifier 12 terminates at the addi- tional or accelerating gas pipe 8, in which the coarse fraction is mixed at a high speed with the flowing addi ⁇ tional or accelerating gas, and the additional gas-solids mixture thus formed is led into the connecting pipe 6 such that large speed differences occur locally therein, by means of which shear forces are achieved, which break the particle bundles possible contained in the feed flow of the connecting pipe 6.
• the fine fraction of the second classifier 12 is led, supported by the gas flow, via a removal pipe 14 to the next treatment phase.
• new material to be pulverized may be led by means of the screw conveyor 1 and a gate feeder 15 to the gas flowing in the additional or accelerating gas pipe 8, whereby the material to be pulverized is once classified already before the pulverization, so the ult- rafine fraction present in the feed is removed therefrom before it enters into the counterjet pulverizer.
• the fine fraction of the third classifier 15 is led via a fine-fraction removal pipe 17 e.g. into a storage silo or to a next treatment phase.
• a fine-fraction removal pipe 17 e.g. into a storage silo or to a next treatment phase.
• pure additional gas may be led into it as a flushing gas from the flushing air nozzle located at the removal pocket 7a of the classifier 7. Additional gas into this flushing air nozzle is led from the addi ⁇ tional or accelerating gas source 9 via a branch pipe 18.
• a dyna ⁇ mic classifier is used in at least one classification phase, i.e. a classifier, which is provided with a rotor preventing the removal of overcoarse particles at the inlet opening of the fine-fraction removal pipe 11 of the classifier 7.

Landscapes

• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Combined Means For Separation Of Solids (AREA)
• Separation By Low-Temperature Treatments (AREA)
• Catalysts (AREA)
• Breeding Of Plants And Reproduction By Means Of Culturing (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Separating Particles In Gases By Inertia (AREA)
• Disintegrating Or Milling (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=8531806

Family Applications (1)

Country Status (7)

Families Citing this family (11)

Family Cites Families (2)

• 1991
  • 1991-01-29 FI FI910418A patent/FI910418A/fi not_active Application Discontinuation
• 1992
  • 1992-01-29 AT AT92903563T patent/ATE144165T1/de not_active IP Right Cessation
  • 1992-01-29 WO PCT/FI1992/000023 patent/WO1992012795A1/en active IP Right Grant
  • 1992-01-29 AU AU11833/92A patent/AU1183392A/en not_active Abandoned
  • 1992-01-29 DE DE69214629T patent/DE69214629D1/de not_active Expired - Lifetime
  • 1992-01-29 EP EP92903563A patent/EP0569420B1/de not_active Expired - Lifetime
  • 1992-01-29 JP JP4503534A patent/JPH06507111A/ja active Pending

Non-Patent Citations (1)

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