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
  • B02C25/00—Control arrangements specially adapted for crushing or disintegrating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
• • 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
  • B02C19/065—Jet mills of the opposed-jet type
• • 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
  • B02C23/08—Separating or sorting of material, associated with crushing or disintegrating

Definitions

• This invention refers to an equipment and a method for producing 5 ultra fine dry powders by means of an energetic power gas.
• the equipment comprises an opposed jet mill with a feeding device and a classifier in direct pipe contact with the outlet of the mill, in which classifier the ground product will be classified into a coarse fraction and a fine fraction by means of centrifugal forces, said 10 classifier being provided with a separate outlet for each fraction, whereby the outlet of the fine fraction is in direct contact with a device for separating gas and solid material through a discharge channel.
• the solid substance to be ground is fluidized in a high pressurized power gas and the formed gas/solid suspension is accelerated through at least two substantially opposedly directed acceleration nozzles into a small grinding chamber, in which the solid products collide with one another and are ground, the ground
• gas/solid suspension is classified substantially by means of centrifugal forces into a coarse fraction and a fine fraction and the gas/solid suspension of the fine fraction formed is led to a device for separating gas and solid material in order to recover the final product.
• micronizmg devices In flne-grindmg/micronizing an energetic power gas, most oftenly pressurized air, is used as grinding energy.
• the micronizmg devices will need industrial compressor effects ranging from 100 kW to 1000 kW depending upon application. Due to the large separate electrical effect the energy consumption m compressing the power gas and in grinding is generally regulated only by regulating the pressure of the gas. Other regulations have not previously been carried out.
• the classification is based on centrifugal forces arising as a result of the flow rate of the power gas/solids and of the rate of rotation of the rotor.
• the controlling of the classification process has been carried out by regulating the rate of rotation of the rotor as well as of the flow rate of the power gas/solids through the classifier during an initial stage of the classification procedure, - but no continuous regulation has been carried out.
• the object of the present invention is to eliminate the above mentioned problems.
• an equipment which is characterized in that the device for separating gas and solids from each other comprises at least one ion jet tube with a concentrically extending high voltage electrode provided with a large number of radial ion jet tips, whereby the solid particles of the gas solid suspension led at a low speed through the ion jet tube are attached to the inner walls of the tube at the influence of ion jets developed by the ion jet tips, from which walls the particles are easily recoverable in exactly limited fractions, and the purified power gas is arranged to discharge from the opposite end of the ion et tube, and that in order to control the operation of the equipment an online operating measuring and analysing device, coupled to a control unit of the equipment, is mounted into the discharge channel for the fine fraction m order to determine the particle size and the fineness of the solid particles of the gas-solid suspension flowing through the discharge chanel.
• the method according to the invention is characterized in that separation of the solid material from the gas/solid suspension of the fine fraction is carried out by means of a high voltage current in one or more ion jet tubes, to which the gas/solid suspension is led at a low speed, whereby the solid particles at the influence of ion jets are forced against the inner walls of the tube, to which they are attached, and wherefrom they are easily recovered m exactly limited fractions, and the thus purified power gas, free of solids leaves the tube at the other end, and m order to control each operation of the method the particle size and the fineness of the solid particles of the gas/solid suspension of the fine fraction are continuously determined by an on-line operating measuring and analysing device, the measuring results of which are led to a control unit in order to develope control signals.
• the energy economy and the efficiency of the fine-grinding can be considerably improved, the environmental load can be decreased, and special products with a higher fineness than earlier can be produced, e.g. a product having a fineness of even a nano level.
• the energy consumption of a fine-grinding and a micronizing process can, depending upon the application, be decreased to about 30 to 50 % from the values of earlier applications.
• FIGS. 1 to 3 disclose shematically three embodiments of an equipment of the invention, provided with partially enlarged sections of the opposed jet mill, of the measuring and analysing device and of the ion jet tube.
• the material to be ground/micronized is fed from a feeding tank 1 of the equipment for instance by means of a screw feeder or a lock feeder 1.1 to a supply hopper 1.2 at the top of a double valve feeder 2.1 operating as a feeder device of an equalizing tank 2 of an opposed jet mill. From the supply hopper the material is fed by means of the double valve feeder 2.1 in portions to the equalizing tank 2, wherein a static pressure required for the gringing is maintained. By means of a screw feeder or a rotor the material is transposed from the equalizing tank 2 into a flowing, energetic power gas, developed in a compressor device 7, 7.1 and 7.2 in order to form a suspension of the gas and the solid particles.
• the suspension of the gas and the solid particles is led through a dividing device 2.2 and at least two substantially opposedly directed acceleration nozzles into a small grinding chamber 2.3, wherein the par- tides to be ground collide against one another and are crushed- /ground almost autogenically.
• a slight superpressure is maintained, said chamber being in direct pipe contact with a dynamically operetin cyclone-rotor classifier 3 of the equipment.
• the gas suspension of the ground material is fed to - the cyclone-rotor classifier 3 through a special spiral part, in order to equalize the flow of the gas-solid suspension with respect to a rotor portion 3,3 of the classifier.
• the ground material is classified by means of centrifugal forces into a fine fraction and a coarse fraction.
• the coarse fraction is removed through a double valve feeder 3.1 mounted at a lower end of a conical part of said cyclone-rotor classifier.
• the coarse fraction is recycled to the hopper 1.2 of the opposed jet mill for regrinding, but in some cases the coarse fraction can be recovered as a separate final product.
• the fine fraction discharges as a gas-solid suspension through the rotor portion 3.3 at the top of the classifier into a discharge channel 3.5.
• the fine fraction is led through the discharge channel 3.5 to a device 5, 6 for separating the power gas and the solid particles from each other, in order to recover a final product.
• the device for separating gas and solids from each other comprises at least one ion jet tube 5 having a con- centrically extending electrode 5.4 provided with a large number of radial ion jet tips 5.6, to which electrode a very high direct- current voltage is fed.
• the gas-solid suspension of the fine fraction is led at a low speed through the ion jet tube 5, 6, whereby the solid particles influenced by ion jets are forced against the inner walls of the ion jet tube 5, 6, to which walls they are attached, and the thus purified power gas, free of solid particles, discharges from the opposite end of the tube 5, 6.
• the solid particles are easily removable from the walls of the ion jet tube 5, 6 in some cases by utilizing gravitation forces only, but the tube may also be provided with a mechanical cleanser, a vibrator or washing dyes.
• the solid particles will preferably discharge through a double valve 5.1, 6.1 at the lower end of the tube into recovery tanks 5.2 and 5.3 as well as 6.2, if the tube is vertical or possibly by means of a screw conveyor or conveyors if the tube is horisontal. From the horisontal tube the separated solid material can be removed at different points and in different qualities by means of screw conveyors.
• Control signals for different control parameters of the ion jet tubes can be based on measuring signals sent by a measuring and analysing device.
• the voltage of current necessary for developing the ion jets is preferably ranging from 50 to 20O kV and the intensity of current is only a few milli- a peres . The voltage range is chosen from case to case.
• the product fractions of different finenesses separated from the equipment can be removed either as dry powders or as sludges, and some fraction can be recycled for instance to the grinding unit for a new treatment.
• the separating device 5 comprises four parallelly coupled ion jet tubes 5, in which two different kinds of products are aimed to be recovered from the fine frac- tion into a tank 5.3 and a tank 5.2, respectively.
• the purified power gas, free from solid particles is led through a common gas removing pipe 5.5 directly to a compressor or a compressor group 7, 7.1, 7.2, used to pressurize the power gas of the equipment.
• the separating device fur- ther comprises an accessory unit 6 connected m series to the ion jet tubes 5, m order to make sure that the discharged air is really pure or to further classify the fine fraction.
• the flowing rate of the gas can be decreased, wherby the power gas will become almost absolutely pure and often a very valuable solid mate- r al, having a nano level fineness, can be recovered through double valves 6.1, muonted under the accessory unit 6 into a product tank 6.2.
• an on-line operating measuring and ana- lysing device 4 is provided to determine the particle size and the fineness of the solid particles in the gas-solid suspension flowing through the discharge channel 3.5 m order to regulate different operations of the equipment.
• the measuring signals developed by the measuring and analysing device 4 are led to a control unit of the equipment, which unit, based on these signals is arranged to deve- lope control signals for different operations of the equipment.
• the measuring and analysing device 4 is preferably mounted into a branch tube extending parallel to the discharge channel of the fine fraction and provided with an ejector pump 4.1, which branch pipe downstreams the measuring and analysing device 4 again will join the discharge channel 3.5.
• an ejector pump 4.1 By means of a pressure difference developed by the ejector pump 4.1 a representative partial flow of the gas- solid fraction flowing through the discharge channel 3.5 is drawn into the measuring and analysing device 4.
• the gas- solid suspension can, when required, be diluted to a correct level for the measuring operation.
• the measuring and analysing device 4 comprises preferably a unit, the operation of which is based on scattering of a laser beam i.e. laser diffractiometry, for defining the amount of the coarser particles in the final product and the average particle size thereof, as well as a unit, the operation of which is based on the doppler effect of the particles, for defining the amount of the small and the ultra fine particles in the final product and the specific surface of the final product.
• the purified warm power gas is led through a channel 6.3 to other purposes, such as heating or drying.
• new or recyclable power gas is pressurized in compressor units 7, 7.1, 7.2 operating parallelly, of which at least one unit is provided with a regulation system for the rate of rotation i.e. the air yield, such as an inverter.
• the operation of the said adjustable compressor unit/units is regulated by control signals developed based on measuring signals from the measuring and analysing device 4, at the same time as the other compressors are arranged to operate at a constant rate of rotation and yield at their optimal operating point. In this way the energy amount to be used for the development of the power gas can be optimized as required by the micronizing process.
• the power gas, pressurized by the compressor group can if necessary be cooled in a cooling unit 7,4.
• the on-line operable measuring and analysing device 4 can thus be used for instance for regulating the amount of the power gas, for regulating the amount of the raw material, for regulating the amount of the washing air to be fed to the classifier, for regulating the periphery speed of the rotor in the classifier, for regulating the mass of the particles in the grinding chamber, for regulating the electrical voltage of the separating device, for regulating the flow-through rate of the gas/solid suspension in the separating device and for regulating the dosage of additives to the final product.
• the most econimical way of changing the speed of the particles to be ground in the acceleration nozzles is to regulate the amount of power gas and the solids based upon obtainable on-line analytical data of the quality of the final product .
• said protectora can be utilized during further processing of the micronized material.
• particles of minerals, having natural hydrophobic properties, which particles are used in the paper manufacturing industry will be changed to hydro- philic by the influence of ion jets.
• a micronized mineral powder of this type can be sludged to a high solid content without further energy use and the stability of the sludge will remain good without considerable use of special chemicals.
• the sludging can be carried out as a continuous purifying/washing operation of the separating device, because the amount, the quality and the flow rate of the solid material are known constant values.
• ultra fine powders can be produced considerably more effectively and economically than before from different dry and moist raw materials, when the final products have a D98 particle size of 0,3 ⁇ m to 150 ⁇ m, and an average or D50 particle size of 0,01 ⁇ m to 30 ⁇ m.
• the developed equipment and method can very well be used in separating, enriching and dry enriching of different types of e.g. mine- rals, metals and organic materials as well as in the production of crystal seed used by different industrial areas.
• the method will also make it possible to produce final products having a finer particle size than previously, i.e. at the nano level from solid raw materials.

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• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Disintegrating Or Milling (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8548258

Family Applications (1)

Country Status (3)

Cited By (5)

Citations (2)

• 1997
  • 1997-02-21 FI FI970733A patent/FI970733A/fi unknown
• 1998
  • 1998-02-23 WO PCT/FI1998/000160 patent/WO1998036840A1/en active Application Filing
  • 1998-02-23 AU AU62176/98A patent/AU6217698A/en not_active Abandoned

Patent Citations (2)

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