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
  • B02C23/02—Feeding devices

Definitions

• the present invention is concerned with a device for feeding the material to be ground into a pressure chamber grinder provided with an equalizing tank, in which said equalizing tank there is substan ⁇ tially the same pressure as in the pre-grinding part ' . of the grinder, with which said pre-grinding part the equalizing tank communicates via a screw conveyor.
• the device concerned is installed in the top portion of the equalizing tank.
• a so-called plug feeder is used, by means of which the material to be ground is fed into the equalizing tank as a gas-tight plug, as is described, e.g., in the International Patent Application No. PCT/FI84/00021.
• the ejector feeder devices which are commonly used in conventional jet grinder devices, are not at all suitable for being used in pressure chamber grinders, owing to the very high operating pressures in the latter.
• a plug feeder is excel ⁇ lently suitable for this purpose in the case that the properties of the material to be ground are such that the material can be compressed into a gas-tight plug.
• the object of the present invention is also to permit the grinding of materials of this type in a pressure chamber grinder, in view of the good energy economy and excellent grinding properties of the said grinder.
• the device comprises a substantially vertical, conical feeder chamber, whose volume is, at the maximum, about one quarter of the volume of the equalizing tank and at whose top end there is a feed opening and, at the bottom end, an exhaust opening larger than the feed opening; valve members arranged in the said openings and having diameters corresponding to the said openings, the said valve members being provided with elastic closing members, operating in the way of an annular muscle for closing and opening the said openings; a gas feed pipe passing into the top portion of the feeder chamber and provided with a valve, for the generation of a pressure impact in the top end of the feeder chamber, and a gas-removing pipe provided with a valve, for lowering the pressure prevailing in the feeder chamber.
• the feeder .device concerned comprises a sub ⁇ stantially vertical conical feeder chamber 4, which is installed in the top portion of the equalizing tank 1 of the pressure chamber grinder, which is provided with a feed opening 2 and an exhaust opening 3, and whose volume is at the maximum about a quarter of the volume of the equalizing tank 1.
• the diameter of the exhaust opening 3 is larger than that of the feed opening 2.
• valve members 5, 6 are mounted whose diameters correspond to the said openings 2 and 3, respectively, which said valve members are provided with elastic closing members operating in the way of an annular muscle, for the purpose of closing and opening the said openings 2, 3.
• a gas feed pipe 8 provided with a valve 7 is passed into the top portion of the feeder chamber 4 so as to generate a pressure impact.
• a gas-removing pipe 10 provided with a valve 9 is passed from the top portion of the feeder chamber 4 so as to lower the pressure in the feeder chamber 4 to the pressure of the surrounding atmosphere.
• the pressure chamber grinder is provided with an equalizing tank 1 , in which substantially the same pressure prevails as in the pre-grinding part of the grinder and in which the material to be ground is made loose, e.g., by means of a rotor before it is fed into the said pre-grihding part by means of a screw conveyor.
• the material to be ground is fed as a very uniform flow into the pre-grinding chamber.
• the feed opening 2 of the device is prefer- ably provided with a feed funnel 11 for receiving the material to be ground, e.g., from the conveyor belt (not shown) or from a storage silo.
• a feed funnel 11 for receiving the material to be ground, e.g., from the conveyor belt (not shown) or from a storage silo.
• a pushing piston 12 which operates vertically and which is placed in line with the feed opening of the device is favourably installed above the feed funnel 11 , which said piston 12 is arranged so as to push and to compact the material to be ground into the feeder chamber 4.
• the use of a pushing piston 12 is advan ⁇ tageous in particular when the material to be ground has a very low bulk density. Since the weight of the material batch fed into the feeder chamber 4 can be increased thereby, the quantity of working gas required to detach the material and the number of times of actuation of the valves are reduced considerably per ton of material.
• the filling of one batch of material into the equalizing tank 1 takes place as follows:
• the exhaust valve 6 of the device and the valves 7, 9 of both of the gas pipes 8, 10 are kept closed; only the feed valve 5 of the device is kept open.
• the material to be ground is fed into the feed funnel 11 of the device, and it is allowed to flow from the feed funnel 11 into the feeder chamber 4 of the de ⁇ vice.
• the pushing piston 12 of the device is preferably arranged so as to perform a few pushing strokes each time when a new batch of material has been transferred into the feed funnel 11.
• the batch of material present in the feeder chamber is detached and falls down into the equalizing tank 1.
• the transfer of the material into the equalizing tank 1 takes place immediately, because there are no choking portions between the feeder chamber 4 and the equalizing tank 1, but the flow channel formed by the feeder chamber 4 and by the exhaust valve 6 becomes substantially all the time wider when moving towards the equalizing tank 1. If the diameter of the exhaust valve 6 were equal to that of the feed valve 5, a choking portion similar to a bottle-neck would be formed in the bottom portion of the feeder chamber, which would hamper and, in the worst case, completely block the transfer of material into the equalizing tank 1 , in particular if the material to be ground is readily clodding.
• the exhaust valve 6 and the valve 7 of the gas-feed pipe 8 are closed and the valve 9 of the gas-removing pipe 10 is opened in order to lower the pressure prevailing in the feeder chamber 4 to the level of the pressure of the surrounding atmosphere, whereupon the valve 9 is closed and the feed valve 5 is opened in view of receiving a new batch of material.
• it is a prere ⁇ quisite for the obtainment of a good grinding result that the feed of material by means of a screw conveyor into the pre-grinding chamber must be kept as uniform as possible.
• a relatively constant ! gas pres- sure must be maintained in the pre-grinding chamber and also in the equalizing tank.
• the size of the feeder chamber 4 such that its volume is no more than about one quarter of the volume of the equalizing tank 1, it is made sure that the pressure impacts pro- prised in the feeder chamber 4 do not have a significant effect on the pressure prevailing in the equalizing chamber.
• both the feed valve (5) and the exhaust valve (6) of the device must be of a type that has an elastic closing member operating in the way of an annular muscle.
• a valve which is usually called a premaflex valve
• no major wear occurs.
• a closing valve of an ordinary type would be worn out and become un ⁇ usable in a few hours in a feeder device of this type.
• the gas-feed pipe 8 is preferably connected to a gas source which has a gas colder than the working gas and whose pressure is about 0.5 bar higher than the pressure prevailing in the equalizing tank.
• the gas-removing pipe 10 can be connected advantageously to the bottom part of the silo, whereby the gas discharge taking place from the feeder chamber 4 at the end of each feeding step is utilized for loosening the material in the silo.
• All the operations of the feeder device are preferably controlled by means of a programmed logic unit, which receives impulses from a sensor placed in the feeder chamber 4 and arranged so as to detect when the feeder chamber 4 is empty, from a sensor placed in the equalizing tank 1 at a predetermined height and arranged so as to detect the upper level of the material quantity present in the equalizing tank 1 , which said level must not be higher than -the said height, as well as from a sensor placed in the working-gas line of the pressure chamber grinder and arranged so as to detect when working gas is being passed into the pressure chamber grinder.
• the exhaust valve (6) and the feed valve (5) operate hydraulically or pneumatically.
• a new filling step starts when the feeder chamber 4 is empty, the quantity of material in the equalizing tank does not exceed the predetermined level, and working gas is being passed into the pressure-chamber grinder, i.e. the pressure chamber grinder is in operation.
• the said wall face may be coated, e.g., with a special paint or with teflon, or be lined, e.g., with a noble-metal layer.

Landscapes

• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Filling Or Emptying Of Bunkers, Hoppers, And Tanks (AREA)
• Weight Measurement For Supplying Or Discharging Of Specified Amounts Of Material (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Air Transport Of Granular Materials (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8519735

Family Applications (1)

Country Status (8)

Families Citing this family (5)

Citations (4)

Family Cites Families (2)

• 1984
  • 1984-10-12 FI FI844028A patent/FI69255C/fi not_active IP Right Cessation
• 1985
  • 1985-10-11 DE DE8585904976T patent/DE3575876D1/de not_active Expired - Fee Related
  • 1985-10-11 WO PCT/FI1985/000082 patent/WO1986002287A1/en active IP Right Grant
  • 1985-10-11 US US06/876,868 patent/US4720049A/en not_active Expired - Fee Related
  • 1985-10-11 JP JP60504488A patent/JPS62500504A/ja active Granted
  • 1985-10-11 EP EP85904976A patent/EP0197095B1/en not_active Expired
• 1986
  • 1986-06-11 NO NO86862341A patent/NO163216C/no unknown
  • 1986-06-11 DK DK275186A patent/DK155871C/da not_active IP Right Cessation

Patent Citations (4)

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