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
  • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
  • B02C17/18—Details
  • B02C17/183—Feeding or discharging devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
  • B02C17/18—Details
  • B02C17/183—Feeding or discharging devices
  • B02C17/186—Adding fluid, other than for crushing by fluid energy
  • B02C17/1875—Adding fluid, other than for crushing by fluid energy passing gas through crushing zone

Definitions

• the invention relates to a ball mill, of the type comprising a horizontal rotary drum into which a material to be ground is introduced to be returned in pulverized form in a gas stream, after being crushed by balls loaded into the drum.
• Such grinders are used in particular for grinding solid fuels with a view to their use in pulverized form for the supply of burners for boilers.
• the balls or other equivalent grinding elements made of hard material, pulverize by crushing, crushing and / or attrition the elements of material to be ground which are introduced into the rotary drum in the form of more or less large pieces through the pins which support the drum at its ends.
• the transport of the material outside the drum, after spraying, is ensured by means of a gas.
• This gas is introduced into the mill drum along with the material to be ground through the pins and it follows a circuit allowing it to come out.
• the gas used is generally air.
• This screw ensures the progression of the pieces of material to be ground towards the inside of the drum.
• Such a screw is likely to be subjected to significant and rapid wear, because it is subjected to the shocks which it undergoes undergoing the pieces of moving material, in particular if these pieces fall on it.
• This wear can also be accelerated by the passage of the pulverized material, when it is propelled against the Archimedes screw by the gas which transports it inside a trunnion.
• the gas used to transport the pulverized material is introduced through a pin via a hollow tube carrying the Archimedes screw and arranged coaxially in this pin.
• This hollow tube rotates on its axis with the mill drum and is fixed by a system of bars inside this drum, which leads to at least some parts of this bar system being subjected to the shocks of balls in movement, when the drum turns.
• the support of the hollow tube is provided by a bearing which must be impermeable to the dust transported by the propellant gas once loaded and which must be continuously cooled to evacuate the calories which the gas provides, when it has been previously heated for drying purposes.
• the installation in a drum journal of a tube fixed in the drum and on an end bearing does not favor access to the wear parts of the mill, such as in particular balls, Archimedes screws, hollow tube support bars. It is then necessary to dismantle other parts, in order to be able to access the wearing parts considered above, which in particular has the consequence of increasing the maintenance and unavailability times of the mill.
• the invention therefore provides a ball mill comprising:
• each end pin of the mill contains a rigid helical structure, of the Archimedes screw type, fixed to it and rotating with it around the tube, during the rotation of the drum, to drive the material. to be crushed towards the inside of the drum, said tube being a rigid gas injection tube which is kept stationary.
• the gas injection tube axially disposed in the trunnion placed at each end of the drum preferably penetrates this trunnion through, from the outside, the guide element which makes it possible to direct the material to be ground to the annular duct defined by this tube and this journal.
• Such an injection tube which is axially introduced into each journal at one end of the drum, is mounted on an immobilization gantry, movable relative to this drum.
• Figure 1 shows a longitudinal sectional view of a coal grinding installation.
• Figures 2 and 3 respectively show a schematic end view and a longitudinal schematic section of an end fitting for mill according to the invention.
• the example of a grinding installation presented in FIG. 1 comprises a device 10 for supplying material to be ground and a ball mill 20 supplied by this device, the material treated being, for example, coal.
• the device 10 comprises a storage hopper 1 supplying a chain conveyor 3 with the pieces constituting the material to be ground.
• the conveyor is placed in a box 4 and driven by a motor 5, it brings the pieces to be ground up to the upper end of a vertical or substantially vertical pipe 6 into which these pieces fall.
• the crusher 20 comprises a rotary drum whose axis of rotation is horizontal or substantially horizontal. This drum has a central cylindrical part 11 of revolution extending by a conical part 12, 13 towards each of its ends at each of which is fixed a pin 14, 15 for supporting the drum.
• the two pins are each placed on a bearing 16, 17.
• the drum is rotated by a geared motor not shown, it is filled with balls 27, of hard material, for example steel, or functionally equivalent hard elements .
• the installation is preferably symmetrical, in particular as regards the arrangements described below, which include the vertical pipes 6 for supplying material to be ground, situated at the two ends of the mill.
• the pieces of material to be ground fall into each pipe, such as 6, which opens near a drum end where a journal is mounted, such as the journal 15.
• the lower end of each pipe is connected to a tip 7 of an end fitting 8 which is connected to the drum at the end of a pin, such as 15, by a tip 9 and via a rotating joint, these elements being more particularly illustrated the Figures 2 and 3.
• the pieces of material to be ground which fall into a pipe, such as 6, are directed towards the drum by means of a guide element 31 which is for example of inclined plate type.
• This element is here assumed to be a wall, removable or not, of the connector 8, which is positioned under the lower end of a pipe and opposite the opening that has a pin in the axis of the drum with an orientation oblique to the respective longitudinal axes of the piping and the drum.
• a rigid gas injection tube 41 passes through the connector right through to come to align itself along the longitudinal axis XX 'of a journal in which it comes to be positioned, when the connector is in place in the mill, as seen in Figures 1 and 3.
• this tube 41 is a rectilinear tube with a cross section of elliptical shape, the major axis of which is preferably arranged vertically, it passes through the wall which constitutes the guide element 31 to allow gas to be injected into the drum from the outside, as symbolized by the arrow A.
• This gas is intended to transport the material after spraying.
• the tube 41 is mounted on an immobilization gantry 42 which can be moved relative to the drum, which therefore makes it possible to simply introduce it and extract it from the pin 15 where it comes to thread.
• the connector 8 and the tube 41 are carried by the gantry 42 which makes it possible to move them relative to the drum so as to position the connector relative to the journal to which it is connected by a rotary joint.
• the gantry 42 is here assumed to be mounted on wheels. It allows the tube-fitting assembly to be moved before it is immobilized in the required position in the installation with respect to one of the drum journals. It also allows the axial opening of the trunnion and the drum to be completely cleared by a displacement in the opposite direction.
• the length of the portion of tube 41 which passes through a trunnion 15 is preferably chosen so that the end of this tube does not enter the zone, inside the drum, where the balls and pieces of material to be ground move during the rotation of this drum. The penetration of this tube 41 into a pin is therefore limited so that the end of this tube, through which gas is injected into the drum, is housed inside the pin, slightly behind the main body of the drum.
• the dimensions of the tube 41 are chosen so as to provide a duct 35 of annular shape between its outer wall and the inner wall of the pin where this tube is introduced axially.
• This annular conduit is used for transporting the pieces of material to be ground which are directed towards the interior of the drum by a guide element 31.
• a helical structure 32 of the Archimedes screw type, is therefore fixed so as to rotate around of the tube 41 with the pin 15, when the drum is in rotation. It is designed to drive, towards the inside of the drum, the pieces, deflected by the guide member, which thus move along the outside of the tube 41.
• this structure is preferably rigid and hard, to resist the thrust of the pieces of material to be ground and the friction.
• the annular conduit 35 is also traversed by the mixture consisting of gas and by the sprayed material. This route is carried out in the opposite direction to that followed by the pieces of material to be ground. This two-way circulation of the material to be ground and of the pulverized material is possible because the blades of the helical structure 32 are sufficiently spaced from the tube 41 as shown in FIG. 3.
• the mixture, ejected out of the drum is transmitted, via the annular conduit and through the connector 8, to an outlet pipe 36 connected to a nozzle 44 of this connector.
• This mixture consisting of gas and pulverized material is here symbolized by the arrow B, it is for example used for the fuel supply of a boiler.
• the end of the drum connector includes end fittings for connection to the vertical piping and to the outlet pipe.
• the respective axes of these nozzles are in the same plane perpendicular to the axis of the injection tube. of gas passing through the fitting, at the level of the guide element, the latter being here assumed to be formed in the form of a plane, obliquely disposed with respect to the axis of the tube and that of the vertical pipe fitting .
• An additional gas inlet is optionally provided for supplying a drying box 30, in the upper part of vertical piping 6, to promote the desiccation of the material to be ground.
• the respective gas flow rates Aa through this box and A through the tube 41 at each end of the drum are then controlled in a coordinated manner in order to obtain an optimal flow rate of mixture B at the outlet of line 36.

Landscapes

• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Crushing And Grinding (AREA)
• Dry Shavers And Clippers (AREA)
• Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
• Crushing And Pulverization Processes (AREA)
• Disintegrating Or Milling (AREA)
• Excavating Of Shafts Or Tunnels (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Surgical Instruments (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1999
  • 1999-05-07 FR FR9905832A patent/FR2793168B1/fr not_active Expired - Fee Related
• 2000
  • 2000-05-04 AT AT00925386T patent/ATE244071T1/de not_active IP Right Cessation
  • 2000-05-04 US US09/959,721 patent/US6547171B1/en not_active Expired - Fee Related
  • 2000-05-04 ES ES00925386T patent/ES2202116T3/es not_active Expired - Lifetime
  • 2000-05-04 AU AU44128/00A patent/AU756235B2/en not_active Ceased
  • 2000-05-04 CZ CZ20014014A patent/CZ20014014A3/cs unknown
  • 2000-05-04 EP EP00925386A patent/EP1181101B1/de not_active Expired - Lifetime
  • 2000-05-04 DE DE60003678T patent/DE60003678D1/de not_active Expired - Lifetime
  • 2000-05-04 WO PCT/FR2000/001202 patent/WO2000067910A1/fr not_active Application Discontinuation
  • 2000-05-04 CN CNB008072965A patent/CN1209198C/zh not_active Expired - Fee Related
  • 2000-05-04 PL PL00352405A patent/PL194742B1/pl not_active IP Right Cessation
  • 2000-05-04 JP JP2000616928A patent/JP2002543966A/ja not_active Withdrawn
  • 2000-05-04 CA CA002368066A patent/CA2368066C/fr not_active Expired - Fee Related
• 2001
  • 2001-10-24 ZA ZA200108760A patent/ZA200108760B/xx unknown

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