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High Pressure Grinding with Roller Presses |
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The process of high-pressure grinding (comminution) by means of a roller press involves material being crushed between two counter rotating rollers under increased pressure conditions either to achieve incipient crack formation or complete particle disintegration. Successful grinding is accomplished by all equipment in the system working in unison from the time material enters the press until the final product is ultimately discharged. |
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Partial List of Materials Processed by Grinding
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- Cement Clinker
- Coal
- Kieserite
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Machine Parameters for High Pressure Grinding
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Parameters
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Range
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Roller Diameter (mm)
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800
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2800
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Roller Width (mm)
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200
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1600
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Circumferential Speed of Rollers (m/s)
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0.9
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1.9
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Specific Pressing Force (kN/m²)
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2000
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8500
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Weight of Press including Gear Reducer (mt)
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32
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450
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Motor Power (kW)
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150
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4000
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Throughput (mt/h)
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35
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2000
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Units
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Typical roller press parameters for high pressure grinding (comminution).
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HEXADUR® - The Ultimate Wear Protection
Equipment availability and the overall cost of grinding facilities utilizing roller presses are significantly influenced by the service life of wear parts, in particular the durability of the grinding rollers. This fact especially relates to the grinding of ore or cement clinker and granulated blast-furnace slag used as aggregates in cement production. To produce satisfactory grinding of such feedstock with roller presses and ensure improved availability, Maschinenfabrik Köppern GmbH & Co KG has developed HEXADUR®, a highly abrasion resistant material for wear protection for grinding rollers. The name HEXADUR® for the new armoring material has been derived from the shape and arrangement of hexagonal tiles.
A special powder-metallurgical process is used to produce HEXADUR®. The outstanding high wear resistance results from an unique combination of material and utilization of a particular geometric pattern on the grinding surface. The materials contain so-called "hard phases" which enhance the wear resistance. Increasing the amount of this hard phase is, however, limited by the metallurgical manufacturing process. With a wear-resistant welded hardfacing, the carbide content for a crackfree surface cannot exceed 20%, and for cast alloys, hard phases of up to 35% can be realized. With HEXADUR® as developed and patented by Köppern on the basis of powder metallurgy, a basic matrix having a hard phase of more than 50% can be produced.
The wear-resistant HEXADUR® surface can be designed to the specific applications with respect to the feed material characteristics. The wear surface can be up to 50 mm thick compared with welded surfaces that cannot exceed 15 mm in thickness. Another significant advantage is the HEXADUR® combination with the base material is capable of having a static strength of above 145,000 psi (1,000 MPa) (correspondent carbon content > 0.3%). This base material will not suffer damages, like peeling or large cracks, under the typical load conditions, in contrast to a weldable base material (correspondent carbon content < 0.22%) with a maximum static strength of 116,000 psi (800 MPa).
Experience gained with highly abrasive cement clinker has demonstrated the increased wear life when compared to existing hard-facing alternatives. There is no doubt that grinding rolls equipped with HEXADUR® will provide a substantial overall cost saving in operation.
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