EP1255611B1 - Rotary mill - Google Patents
Rotary mill Download PDFInfo
- Publication number
- EP1255611B1 EP1255611B1 EP00900046A EP00900046A EP1255611B1 EP 1255611 B1 EP1255611 B1 EP 1255611B1 EP 00900046 A EP00900046 A EP 00900046A EP 00900046 A EP00900046 A EP 00900046A EP 1255611 B1 EP1255611 B1 EP 1255611B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- chamber
- particles
- impact
- rotor
- outlet
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C13/00—Disintegrating by mills having rotary beater elements ; Hammer mills
- B02C13/02—Disintegrating by mills having rotary beater elements ; Hammer mills with horizontal rotor shaft
- B02C13/06—Disintegrating by mills having rotary beater elements ; Hammer mills with horizontal rotor shaft with beaters rigidly connected to the rotor
- B02C13/09—Disintegrating by mills having rotary beater elements ; Hammer mills with horizontal rotor shaft with beaters rigidly connected to the rotor and throwing the material against an anvil or impact plate
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C13/00—Disintegrating by mills having rotary beater elements ; Hammer mills
- B02C13/26—Details
- B02C13/288—Ventilating, or influencing air circulation
Definitions
- the present invention relates to an apparatus for ore milling. More specifically, the present invention relates to a rotary mill for impact reduction of ore.
- US Patent 3,887,141 teaches a mill for the reduction of ore that uses an impact rotor for obtaining the first reduction. Initially, the material to be reduced in size is introduced into the swept area of the rotor. When the material contacts the rotor, a portion of the accumulated kinetic energy generated by the rotor is transferred to the material, forcing it to accelerate as well as change direction. The material will tend to resist this, so the energy transferred accumulates within the material. This in turn will cause any friable material to shatter along its natural fault lines and the resulting smaller particles will be accelerated away from the rotor.
- this fluidizing rotor does not compensate for other flaws in the apparatus. Specifically, there is also a tendency for fine particles to collect within the apparatus in areas of low air pressure, as the airflow generated from the rotor is insufficient to carry all of the particles to the outlet. As these particles are naturally quite abrasive, considerable wear will occur in these areas.
- weight is the only determining factor in this apparatus as to whether or not the particle passes on to the secondary reduction chamber and the fine particle outlet, the possibility exists that a particle of sufficient size could become lodged in this region of the apparatus.
- this apparatus has the disadvantages of incurring considerable wear during operation and requiring frequent maintenance and cleaning.
- An apparatus according to the preamble of claim 1 is known from AU-B-512623 .
- an apparatus for fragmenting solid materials into particles comprising:
- a rotor with greater exposed blade or hammer surface will move more air, although, as a consequence, this type of rotor is not very durable.
- generation of airflow by the rotor is not a concern in the above-described apparatus because of the supplemental airflow generated by the exhaust fan.
- the rotor is designed to impart as much accumulated kinetic energy to the incoming material as possible by having the largest mass possible within the swept area of the rotor.
- the conveyor is positioned so that material is introduced into the rotor circle in a manner that imparts the maximum amount of the kinetic energy from the revolving rotor to the material with the least amount of strain on the rotor bearings.
- the rotor serves only to bump or tip the incoming material and to direct the fractured particles into the shatter bars.
- the position of the shatter bars is such that, following impact, the particles are directed back toward the rotor swept area and, in a continuous feed situation, these returning particles are met by new particles that have been produced by the rotor striking newly introduced material, thereby causing further attrition.
- the particles are then swept around the fixed portion of the apparatus connecting the two impact chambers, following a specifically designed curve into the second impact chamber where they are thrown against the reduction means.
- the reduction means provide the final particle size control as they form a restrictive path to the fine particle outlet.
- the reduction means may take the form of staggered bars, perforated metal plates, wire screens or all of these combined.
- the exhaust fan acts as a scavenger by creating a path of steadily moving air from the material intake to the fine particle outlet so that all material follows the desired path through the apparatus.
- the supplementary airflow also reduces wear, as it prevents entrained particles from contacting the apparatus.
- the reduction means are staggered or offset so as to force the airflow to rapidly change direction so that any particles with too much mass to remain entrained are reflected back into the flow of material until they have been sufficiently reduced in size to remain in the airflow.
- the addition of the exhaust fan represents a significant improvement over the prior art.
- the airflow generated reduces wear and prevents build-up of particles throughout the apparatus.
- the rotor construction is designed to impart the greatest force on incoming material, as creating airflow with the rotor is no longer a concern. This in turn means that the rotor can be of a more durable design.
- the reduction means are arranged such that access to the fine particle outlet by oversized particles is restricted, thereby preventing clogs.
- a balanced door is provided for automatically removing oversized particles that accumulate in the base of the apparatus.
- a rotary mill 1 comprises a housing 10, a material delivery system 12 and an exhaust fan 14.
- the housing 10 comprises a rotor 16, a primary reduction chamber 18, a secondary reduction chamber 20 and an outlet chamber 22, as shown in Figure 1.
- the primary reduction chamber 18 comprises an inlet opening 24, an intake shaft 26 and a plurality of shatter bars 28.
- the inlet opening 24 provides access to the interior of the housing 10 for incoming material and for airflow generated by the exhaust fan 14.
- the inlet opening 24 is positioned beneath the material delivery system 12.
- the intake shaft 26 is arranged to direct material from the inlet opening 24 into the swept area of the rotor 16.
- the plurality of shatter bars 28 are arranged to further reduce particles deflected by the rotor 16 and direct these particles back toward the rotor 16 as described below.
- the secondary reduction chamber 20 is connected to the primary reduction chamber 18 by a curved portion 30 as described below.
- the secondary reduction chamber 18 includes reduction means 32 positioned between the secondary reduction chamber 20 and the outlet chamber 22, arranged such that particles above a given size are prevented from entering the outlet chamber 22.
- the reduction means 32 may comprise staggered bars, perforated metal plates, wire screens or combinations thereof.
- the outlet chamber 22 comprises a fan outlet 34, a fan control means 36 and a lower material outlet 38.
- the fan outlet 34 comprises the exit from the housing 10 for fine particles and for airflow generated by the exhaust fan 14 as described below.
- the lower material outlet 38 comprises a balanced door 40 situated at the base of the outlet chamber 22 for removal of heavy particles. Specifically, once a mass of material equal to the balance weight has gathered, the balanced door 40 opens and expels the material from the housing 10.
- the fan control means 36 comprises a movable baffle 42 located within the output chamber 22 for controlling airflow through the housing 10 so that the amount and size of particles drawn off at the fan outlet 34 and the lower material outlet 38 may be varied as described below.
- the rotor 16 is arranged for rotation within the housing 10 and is driven by a motor, the details of which are not shown as these will be obvious to one skilled in the art.
- the rotor 16 includes peripheral impact means 44 and is situated below the intake shaft 26. While a rotor that exposes more blade will move more air, durable construction and suitable mass for reducing incoming material conflict with ideal air moving capabilities. However, generation of airflow by the rotor 16 is not an important consideration due to the airflow generated by the exhaust fan 14. Thus, the rotor 16 is arranged so that the impact means 44 have the largest mass possible within the swept area of the rotor 16. In this embodiment, the rotor 16 includes three impact means 44, although it is of note that the construction of the rotor 16 may vary greatly.
- the exhaust fan 14 is arranged to produce an airflow through the housing. Specifically, the exhaust fan 14 is connected to the fan outlet such that the airflow generated by the exhaust fan 14 is drawn into the housing 10 via the inlet opening 24 and is drawn out of the housing 10 via the fan outlet 34.
- the details of the exhaust fan 14 are not shown as these will be obvious to one skilled in the art.
- the material delivery system 12 transports material to the rotary mill 1.
- the material delivery system 12 comprises a conveyor 46.
- the rotary mill 1 cannot be "chokeā loaded.
- computerized control of the conveyor 46 may be used to provide a steady input volume regardless of input material size.
- rotor speed and airflow may be monitored to determine loading efficiency and this information may be used to control the power source driving the conveyor 46.
- the mass of material within the rotary mill 1 may be closely controlled so that attrition of material occurs at a steady rate.
- the material to be reduced is transported by the conveyor 46 to the inlet opening 24.
- the material passes therethrough onto the intake shaft 26 at a speed at or near free fall.
- the intake shaft 26 directs the material into the swept area of the impact means 44 of the rotor 16.
- the intake shaft 26 is positioned such that a maximum amount of the kinetic energy generated by the rotor 16 is transferred to the material with minimal strain on the rotor 16, so that the rotor 16 needs only to tip or bump the incoming material.
- This transfer of kinetic energy shatters the material along natural fault planes, producing smaller particles.
- the smaller particles are accelerated away from the rotor 16 and into the shatter bars 28 where further reductions occur as a result of collisions between the shatter bars 28 and the smaller particles.
- the shatter bars 28 do not have to be of massive structure or unusual hardness because of the reduced size of the particles.
- the shatter bars 28 also direct the smaller particles back towards the swept area of the rotor 16 where, in a continuous feed situation, the smaller particles encounter new particles produced by the impact means 44 of the rotor 16 striking newly introduced material and these secondary impacts between reflected material and recently shattered material result in further reduced particles.
- the rotor 16 causes a localized increase in the pressure of the airflow generated by the exhaust fan 14. This forces entrained particles, which are naturally quite abrasive, away from the housing 10, thereby drastically reducing scrubbing and wear on the rotary mill 1.
- the reduced particles are swept by the airflow drawn through the housing by the exhaust fan 14 around the curved portion 30 into the secondary reduction chamber 20.
- the curved portion 30 is arranged such that the airflow generated by the exhaust fan 14 directs the reduced particles toward the reduction means 32 in the secondary reduction chamber 20.
- the reduction means 32 are arranged such that only particles below a given size, or fine particles, pass through the reduction means 32 and enter the outlet chamber 22 while oversized particles are directed back into the flow of reduced particles leaving the rotor path.
- the reduction means 32 provide the final particle size control, forming a restriction in the path that material follows through the housing 10.
- the close, staggered configuration of the reduction means 32 causes the airflow generated by the exhaust fan 14 to change direction rapidly several times before being drawn out of the secondary reduction chamber 20. This turbulent airflow prevents particle build-up from occurring on the reduction means 32.
- the position and orientation of the reduction means 32 is not critical as they may be placed either vertically or horizontally with little or no change in their effectiveness.
- the fine particles Upon entry into the outlet chamber 22, the fine particles remain in the airflow generated by the exhaust fan 14 and are drawn off through the fan outlet 34 while heavy particles fall to the lower material outlet 38 until a mass accumulates that equals the balance weight, which opens the balanced door 40 and releases the heavy particles.
- the balanced door 40 ensures that air is drawn into the rotary mill 1 only through the inlet opening 24, thereby keeping a negative pressure on all parts of the housing 10 and serving as a form of dust control.
- the position of the movable baffle 42 within the outlet chamber 22 may be altered to vary the intensity of the airflow, thereby varying the amount and size of the particles drawn off through the fan outlet 34.
- the flow of fine particles may, for example, be blown into a bag house or cyclone or may be turned into a slurry by the addition of a water spray.
- the heavy material which exits the lower opening can be fed into any suitable classification machinery for further processing.
- this arrangement also serves as a simple means of material classification.
- the position of the rotor 16 within the housing 10 is quite critical.
- a clearance of 0.125 inches is optimum, wherein clearance refers to the ideal spacing between the rotor 16 and the housing 10 as well as the clearance between the impact means 44 and the housing 10. If too much clearance is allowed, turbulence occurs and entrained particles build up which greatly increase the wear on the rotary mill 1.
- the importance of having a constant and steady flow of incoming material can be shown when a large particle is introduced and allowed to pass through the rotary mill 1 alone.
- the resulting pile of reduced material consists of a light scattering of larger particles on the top and bottom of a cross section with the majority in the center finely pulverized, as there are few particles to carry out the attrition process.
- there is a steady impingement between fractured particles and the particle size distribution is more even.
- time of material residency is an important factor in the successful operation of the above-described rotary mill 1.
- the tendency to return particles to the new product flow can cause a build-up of material in the system.
- This has been overcome by the addition of a supplementary airflow generated by the exhaust fan 14.
- the exhaust fan 14 creates a path of steadily moving air from the inlet opening 24 to the fan outlet 34.
- the airflow overcomes turbulence created by the rotor 16 and ensures that all material continues to follow the desired path through the rotary mill 1.
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- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Crushing And Pulverization Processes (AREA)
- Combined Means For Separation Of Solids (AREA)
- Supercharger (AREA)
- Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
- Crushing And Grinding (AREA)
Abstract
Description
- The present invention relates to an apparatus for ore milling. More specifically, the present invention relates to a rotary mill for impact reduction of ore.
- One method of removing desirable minerals from waste materials in an ore is to reduce the raw size of the ore.
US Patent 3,887,141 teaches a mill for the reduction of ore that uses an impact rotor for obtaining the first reduction. Initially, the material to be reduced in size is introduced into the swept area of the rotor. When the material contacts the rotor, a portion of the accumulated kinetic energy generated by the rotor is transferred to the material, forcing it to accelerate as well as change direction. The material will tend to resist this, so the energy transferred accumulates within the material. This in turn will cause any friable material to shatter along its natural fault lines and the resulting smaller particles will be accelerated away from the rotor. These smaller particles are directed into a series of shatter bars mounted on the walls of the primary reduction chamber, which cause further reductions in the size of the particles upon impact. In theory, airflow from the rotor is supposed to carry sufficiently reduced particles into a secondary reduction chamber wherein they are reduced to fine particles and then collected at a fine particle outlet. However, during operation, material tends to pack in the bottom of the primary reduction chamber, clogging the apparatus.US Patent 4,037,796 teaches a modified version of the ore milling apparatus including a fluidizing rotor located in the base of the primary reduction chamber. This second rotor is supposed to slow the rate at which material settles into the base of the primary reduction chamber by improving the flow of the particles. However, this fluidizing rotor does not compensate for other flaws in the apparatus. Specifically, there is also a tendency for fine particles to collect within the apparatus in areas of low air pressure, as the airflow generated from the rotor is insufficient to carry all of the particles to the outlet. As these particles are naturally quite abrasive, considerable wear will occur in these areas. One area of low pressure, due to its proximity to the outlet, is the secondary reduction chamber. Over time, particles accumulate to such an extent so as to block access to the fine particle outlet. In addition, as weight is the only determining factor in this apparatus as to whether or not the particle passes on to the secondary reduction chamber and the fine particle outlet, the possibility exists that a particle of sufficient size could become lodged in this region of the apparatus. Clearly, this apparatus has the disadvantages of incurring considerable wear during operation and requiring frequent maintenance and cleaning. - An apparatus according to the preamble of claim 1 is known from
AU-B-512623 - It is an aim of the invention, therefore, to provide a rotary mill that overcomes the shortcomings of the prior art.
- According to the invention there is provided an apparatus for fragmenting solid materials into particles, the apparatus comprising:
- a housing;
- a first impact chamber defined within the housing and having a feed opening;
- a feed system positioned above the feed opening of the first impact chamber for feed of solid materials into the impact chamber;
- a rotor having impact hammers at its periphery located within the first impact chamber for rotation about an axis of the rotor transverse to the feed opening, the rotor being positioned relative to the feed opening such that said impact hammers impact and deflect the solid materials entering through the feed opening, thereby fragmenting the solid materials to form particles;
- a plurality of shatter bars located within the first impact chamber arranged such that the shatter bars contact the deflected solid materials, thereby further fragmenting the solid material into said particles;
- a second impact chamber defined within the housing downstream of the rotor;
- means for connecting the first impact chamber and the second impact chamber such that the particles pass from the first chamber to the second chamber under momentum from the rotor;
- the rotor being arranged such that rotation thereof generates an air flow acting to carry the materials from the first impact chamber into the second impact chamber;
- an outlet chamber connected to the second impact chamber for receiving the particles therefrom;
- a plurality of reduction means located between the second impact chamber and the outlet chamber, positioned such that only particles below a predetermined size pass through the reduction means and into the outlet chamber;
- a fine particle outlet duct connected to the outlet chamber and arranged to receive the particles therefrom;
- a bottom discharge for allowing release of heavier particles from a bottom of the outlet chamber;
- an exhaust fan connected to the fine particle outlet duct for generating an additional airflow through the feed opening into the first impact chamber and from the first impact chamber into the second impact chamber;
- and a balanced flow control door which normally closes the bottom discharge such that substantially all air exiting the outlet duct passes into the first impact chamber through the feed opening and which is arranged such that it is opened under the weight of the heavier particles to allow said release of the heavier particles through the bottom discharge.
- There are a number of methods in which material may be provided to the above-described apparatus, but the most common and efficient would be by conveyor. In this case, some method of sensing when the apparatus is loaded most efficiently must be provided, due to the fact that the machine cannot be "choke"-loaded. Preferably, computerized control of the conveyor is used to provide a steady input volume regardless of input material size. Rotor shaft RPM and airflow are monitored to indicate loading efficiency and the resulting information is used to control the power source driving the conveyor. In this manner, the mass of material within the apparatus is closely controlled and attrition occurs at a steady rate.
- Generally, a rotor with greater exposed blade or hammer surface will move more air, although, as a consequence, this type of rotor is not very durable. However, generation of airflow by the rotor is not a concern in the above-described apparatus because of the supplemental airflow generated by the exhaust fan. As a consequence, the rotor is designed to impart as much accumulated kinetic energy to the incoming material as possible by having the largest mass possible within the swept area of the rotor.
- The conveyor is positioned so that material is introduced into the rotor circle in a manner that imparts the maximum amount of the kinetic energy from the revolving rotor to the material with the least amount of strain on the rotor bearings. The rotor serves only to bump or tip the incoming material and to direct the fractured particles into the shatter bars. The position of the shatter bars is such that, following impact, the particles are directed back toward the rotor swept area and, in a continuous feed situation, these returning particles are met by new particles that have been produced by the rotor striking newly introduced material, thereby causing further attrition. The particles are then swept around the fixed portion of the apparatus connecting the two impact chambers, following a specifically designed curve into the second impact chamber where they are thrown against the reduction means. These are positioned such that only particles of the desired size can pass through and enter the fine particle outlet, while oversized particles are deflected back into the flow of particles, thereby causing yet further attrition. As a consequence, the oversized particles are further reduced in size until they can pass between the reduction means. Thus, the reduction means provide the final particle size control as they form a restrictive path to the fine particle outlet. As stated above, the reduction means may take the form of staggered bars, perforated metal plates, wire screens or all of these combined. Once past the reduction means, the fine particles are drawn off through the outlet while particles with greater weight fall to the outlet door where they accumulate until their weight equals that of the balance weight, at which time the door opens to allow their release. This door is balanced such that several pounds must collect in order for it to open. Once this accumulation has exited, the door closes again.
- While the reflection of insufficiently reduced particles into the oncoming flow of material is necessary for further size reduction, a build-up can occur in the second impact chamber and cause clogging or undesirable restriction of material flow as noted in the description of the prior art. This has been overcome by the supplementary airflow generated by the exhaust fan. In this case, the exhaust fan acts as a scavenger by creating a path of steadily moving air from the material intake to the fine particle outlet so that all material follows the desired path through the apparatus. The supplementary airflow also reduces wear, as it prevents entrained particles from contacting the apparatus. Furthermore, the reduction means are staggered or offset so as to force the airflow to rapidly change direction so that any particles with too much mass to remain entrained are reflected back into the flow of material until they have been sufficiently reduced in size to remain in the airflow.
- Clearly, the addition of the exhaust fan represents a significant improvement over the prior art. As stated above, the airflow generated reduces wear and prevents build-up of particles throughout the apparatus. As a result, the rotor construction is designed to impart the greatest force on incoming material, as creating airflow with the rotor is no longer a concern. This in turn means that the rotor can be of a more durable design. Furthermore, the reduction means are arranged such that access to the fine particle outlet by oversized particles is restricted, thereby preventing clogs. Lastly, a balanced door is provided for automatically removing oversized particles that accumulate in the base of the apparatus.
- On embodiment of the invention will now be described in conjunction with the accompanying drawing in which:
- Figure 1 is a side view in cross-section of the rotary mill.
- A rotary mill 1 comprises a
housing 10, amaterial delivery system 12 and anexhaust fan 14. Thehousing 10 comprises arotor 16, aprimary reduction chamber 18, asecondary reduction chamber 20 and anoutlet chamber 22, as shown in Figure 1. - The
primary reduction chamber 18 comprises aninlet opening 24, anintake shaft 26 and a plurality of shatter bars 28. Theinlet opening 24 provides access to the interior of thehousing 10 for incoming material and for airflow generated by theexhaust fan 14. In this embodiment, theinlet opening 24 is positioned beneath thematerial delivery system 12. Theintake shaft 26 is arranged to direct material from the inlet opening 24 into the swept area of therotor 16. The plurality of shatter bars 28 are arranged to further reduce particles deflected by therotor 16 and direct these particles back toward therotor 16 as described below. - The
secondary reduction chamber 20 is connected to theprimary reduction chamber 18 by acurved portion 30 as described below. Thesecondary reduction chamber 18 includes reduction means 32 positioned between thesecondary reduction chamber 20 and theoutlet chamber 22, arranged such that particles above a given size are prevented from entering theoutlet chamber 22. The reduction means 32 may comprise staggered bars, perforated metal plates, wire screens or combinations thereof. - The
outlet chamber 22 comprises afan outlet 34, a fan control means 36 and alower material outlet 38. Thefan outlet 34 comprises the exit from thehousing 10 for fine particles and for airflow generated by theexhaust fan 14 as described below. Thelower material outlet 38 comprises abalanced door 40 situated at the base of theoutlet chamber 22 for removal of heavy particles. Specifically, once a mass of material equal to the balance weight has gathered, thebalanced door 40 opens and expels the material from thehousing 10. The fan control means 36 comprises amovable baffle 42 located within theoutput chamber 22 for controlling airflow through thehousing 10 so that the amount and size of particles drawn off at thefan outlet 34 and thelower material outlet 38 may be varied as described below. - The
rotor 16 is arranged for rotation within thehousing 10 and is driven by a motor, the details of which are not shown as these will be obvious to one skilled in the art. Therotor 16 includes peripheral impact means 44 and is situated below theintake shaft 26. While a rotor that exposes more blade will move more air, durable construction and suitable mass for reducing incoming material conflict with ideal air moving capabilities. However, generation of airflow by therotor 16 is not an important consideration due to the airflow generated by theexhaust fan 14. Thus, therotor 16 is arranged so that the impact means 44 have the largest mass possible within the swept area of therotor 16. In this embodiment, therotor 16 includes three impact means 44, although it is of note that the construction of therotor 16 may vary greatly. - The
exhaust fan 14 is arranged to produce an airflow through the housing. Specifically, theexhaust fan 14 is connected to the fan outlet such that the airflow generated by theexhaust fan 14 is drawn into thehousing 10 via theinlet opening 24 and is drawn out of thehousing 10 via thefan outlet 34. The details of theexhaust fan 14 are not shown as these will be obvious to one skilled in the art. - The
material delivery system 12 transports material to the rotary mill 1. In this embodiment, thematerial delivery system 12 comprises aconveyor 46. For reasons that will become apparent, the rotary mill 1 cannot be "choke" loaded. As a result, computerized control of theconveyor 46 may be used to provide a steady input volume regardless of input material size. Specifically, rotor speed and airflow may be monitored to determine loading efficiency and this information may be used to control the power source driving theconveyor 46. In this manner, the mass of material within the rotary mill 1 may be closely controlled so that attrition of material occurs at a steady rate. - In operation, the material to be reduced is transported by the
conveyor 46 to theinlet opening 24. The material passes therethrough onto theintake shaft 26 at a speed at or near free fall. Theintake shaft 26 directs the material into the swept area of the impact means 44 of therotor 16. Of note is that theintake shaft 26 is positioned such that a maximum amount of the kinetic energy generated by therotor 16 is transferred to the material with minimal strain on therotor 16, so that therotor 16 needs only to tip or bump the incoming material. This transfer of kinetic energy shatters the material along natural fault planes, producing smaller particles. The smaller particles are accelerated away from therotor 16 and into the shatter bars 28 where further reductions occur as a result of collisions between the shatter bars 28 and the smaller particles. Of note is that the shatter bars 28 do not have to be of massive structure or unusual hardness because of the reduced size of the particles. The shatter bars 28 also direct the smaller particles back towards the swept area of therotor 16 where, in a continuous feed situation, the smaller particles encounter new particles produced by the impact means 44 of therotor 16 striking newly introduced material and these secondary impacts between reflected material and recently shattered material result in further reduced particles. Of note is that therotor 16 causes a localized increase in the pressure of the airflow generated by theexhaust fan 14. This forces entrained particles, which are naturally quite abrasive, away from thehousing 10, thereby drastically reducing scrubbing and wear on the rotary mill 1. Furthermore, the reduced particles are swept by the airflow drawn through the housing by theexhaust fan 14 around thecurved portion 30 into thesecondary reduction chamber 20. - As noted above, the
curved portion 30 is arranged such that the airflow generated by theexhaust fan 14 directs the reduced particles toward the reduction means 32 in thesecondary reduction chamber 20. As noted above, the reduction means 32 are arranged such that only particles below a given size, or fine particles, pass through the reduction means 32 and enter theoutlet chamber 22 while oversized particles are directed back into the flow of reduced particles leaving the rotor path. Thus, the reduction means 32 provide the final particle size control, forming a restriction in the path that material follows through thehousing 10. Furthermore, the close, staggered configuration of the reduction means 32 causes the airflow generated by theexhaust fan 14 to change direction rapidly several times before being drawn out of thesecondary reduction chamber 20. This turbulent airflow prevents particle build-up from occurring on the reduction means 32. Of note is that the position and orientation of the reduction means 32 is not critical as they may be placed either vertically or horizontally with little or no change in their effectiveness. - Upon entry into the
outlet chamber 22, the fine particles remain in the airflow generated by theexhaust fan 14 and are drawn off through thefan outlet 34 while heavy particles fall to thelower material outlet 38 until a mass accumulates that equals the balance weight, which opens thebalanced door 40 and releases the heavy particles. Thebalanced door 40 ensures that air is drawn into the rotary mill 1 only through theinlet opening 24, thereby keeping a negative pressure on all parts of thehousing 10 and serving as a form of dust control. Furthermore, the position of themovable baffle 42 within theoutlet chamber 22 may be altered to vary the intensity of the airflow, thereby varying the amount and size of the particles drawn off through thefan outlet 34. In cases where this fine product has value, the flow of fine particles may, for example, be blown into a bag house or cyclone or may be turned into a slurry by the addition of a water spray. Furthermore, the heavy material which exits the lower opening can be fed into any suitable classification machinery for further processing. Thus, this arrangement also serves as a simple means of material classification. - Of note is that the position of the
rotor 16 within thehousing 10 is quite critical. In this embodiment, a clearance of 0.125 inches is optimum, wherein clearance refers to the ideal spacing between therotor 16 and thehousing 10 as well as the clearance between the impact means 44 and thehousing 10. If too much clearance is allowed, turbulence occurs and entrained particles build up which greatly increase the wear on the rotary mill 1. - The importance of having a constant and steady flow of incoming material can be shown when a large particle is introduced and allowed to pass through the rotary mill 1 alone. The resulting pile of reduced material consists of a light scattering of larger particles on the top and bottom of a cross section with the majority in the center finely pulverized, as there are few particles to carry out the attrition process. However, with a constant, regulated flow of input material, there is a steady impingement between fractured particles and the particle size distribution is more even.
- Clearly, time of material residency is an important factor in the successful operation of the above-described rotary mill 1. However, the tendency to return particles to the new product flow can cause a build-up of material in the system. This has been overcome by the addition of a supplementary airflow generated by the
exhaust fan 14. Theexhaust fan 14 creates a path of steadily moving air from the inlet opening 24 to thefan outlet 34. Furthermore, the airflow overcomes turbulence created by therotor 16 and ensures that all material continues to follow the desired path through the rotary mill 1.
Claims (1)
- An apparatus for fragmenting solid materials into particles, the apparatus comprising:a housing (10);a first impact chamber (18) defined within the housing and having a feed opening (24);a feed system (12) positioned above the feed opening of the first impact chamber for feed of solid materials into the impact chamber;a rotor (16) having impact hammers (44) at its periphery located within the first impact chamber for rotation about an axis of the rotor transverse to the feed opening, the rotor being positioned relative to the feed opening such that the impact hammers impact and deflect the solid materials entering through the feed opening, thereby fragmenting the solid materials to form particles;a plurality of shatter bars (28) located within the first impact chamber arranged such that the shatter bars contact the deflected solid materials, thereby further fragmenting the solid material into said particles;a second impact chamber (20) defined within the housing downstream of the rotor;means (30) for connecting the first impact chamber and the second impact chamber such that the particles pass from the first chamber to the second chamber under momentum from the rotor;the rotor being arranged such that rotation thereof generates an air flow acting to carry the materials from the first impact chamber into the second impact chamber;an outlet chamber (22) connected to the second impact chamber for receiving particles therefrom;a plurality of reduction means (32) located between the second impact chamber and the outlet chamber, positioned such that only particles below a predetermined size pass through the reduction means and into the outlet chamber; anda fine particle outlet duct (34) connected to the outlet chamber and arranged to receive the particles therefrom; characterised bya bottom discharge (38) for allowing release of heavier particles from a bottom of the outlet chamber;an exhaust fan (14) connected to the fine particle outlet duct for generating an additional airflow through the feed opening into the first impact chamber and from the first impact chamber into the second impact chamber; anda balanced flow control door (40) which normally closes the bottom discharge such that substantially all air exiting the outlet duct passes into the first impact chamber through the feed opening and which is arranged such that it is opened under the weight of the heavier particles to allow said release of the heavier particles through the bottom discharge.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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PCT/CA2000/000002 WO2001049417A1 (en) | 2000-01-06 | 2000-01-06 | Rotary mill |
Publications (2)
Publication Number | Publication Date |
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EP1255611A1 EP1255611A1 (en) | 2002-11-13 |
EP1255611B1 true EP1255611B1 (en) | 2007-10-31 |
Family
ID=4143030
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP00900046A Expired - Lifetime EP1255611B1 (en) | 2000-01-06 | 2000-01-06 | Rotary mill |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP1255611B1 (en) |
AT (1) | ATE376883T1 (en) |
AU (1) | AU777743B2 (en) |
CA (1) | CA2396580C (en) |
DE (1) | DE60036964T2 (en) |
ES (1) | ES2295003T3 (en) |
WO (1) | WO2001049417A1 (en) |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1737931A (en) * | 1928-01-05 | 1929-12-03 | Frank G Lugrin | Coal pulverizer |
CH269259A (en) * | 1943-08-03 | 1950-06-30 | Tortorelli Fratelli | Hammer mill. |
BE726597A (en) * | 1968-02-27 | 1969-06-16 | ||
AU512623B2 (en) * | 1973-05-30 | 1980-10-23 | Verdun Barker Arnold | Hammer mills |
US3887141A (en) | 1973-09-17 | 1975-06-03 | Ind Mining Machinery Corp | Impact-attrition mill utilizing air flow |
US4361290A (en) * | 1980-06-23 | 1982-11-30 | Francis Peter M | Adjustable rotary crusher |
EP0341260A4 (en) * | 1987-01-15 | 1990-12-19 | Graziano Sirol | A mill |
US4848677A (en) * | 1987-10-30 | 1989-07-18 | Illabo Mining Equipment Company | Comminution/recovery ore mill |
-
2000
- 2000-01-06 EP EP00900046A patent/EP1255611B1/en not_active Expired - Lifetime
- 2000-01-06 ES ES00900046T patent/ES2295003T3/en not_active Expired - Lifetime
- 2000-01-06 DE DE60036964T patent/DE60036964T2/en not_active Expired - Lifetime
- 2000-01-06 CA CA002396580A patent/CA2396580C/en not_active Expired - Lifetime
- 2000-01-06 WO PCT/CA2000/000002 patent/WO2001049417A1/en active Search and Examination
- 2000-01-06 AT AT00900046T patent/ATE376883T1/en not_active IP Right Cessation
- 2000-01-06 AU AU18533/00A patent/AU777743B2/en not_active Ceased
Also Published As
Publication number | Publication date |
---|---|
ES2295003T3 (en) | 2008-04-16 |
DE60036964D1 (en) | 2007-12-13 |
DE60036964T2 (en) | 2008-05-21 |
WO2001049417A1 (en) | 2001-07-12 |
AU1853300A (en) | 2001-07-16 |
CA2396580A1 (en) | 2001-07-12 |
EP1255611A1 (en) | 2002-11-13 |
AU777743B2 (en) | 2004-10-28 |
ATE376883T1 (en) | 2007-11-15 |
CA2396580C (en) | 2008-01-22 |
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