On-target fine crushing of limestone

At the production facilities of the Trollius, a lime and ballast supplier in the Upper Palatinate region of Germany, both an efficiently operating plant control system and reliable process visualization play a key role. Machinery and equipment at the facilities are always state- of-the-art thanks to ongoing investment in replacements and extensions. Since August 2009, a Metso cone crusher of the type Nordberg HP100 modular (Fig.) has been in operation for recrushing the wet mix aggregate grades. At the company’s Lauter­hofen plant, the focus is on processing limestone, for example to wet mix aggregate and high-grade chippings. Originally, an impact mill was used to recrush material to high-grade chippings. With an increasing demand for 2/5 and 5/8 grades, the impact mill produced too much unsaleable 0/2 sand. To produce much more target-size product – the especially 5/8 grade – with far less sand, the company decided to crush a sub-stream of the wet mix aggregate fractions 8/16, 16/22, 22/32 and 32/45 in a crush-er specially suited to this purpose.

 

As integration into the existing plant facilities had to be easy and low cost, the company opted for a compact and mobile unit – without its own drive unit and running gear. One option for this was the pre-installed cone crusher unit HP100 modular on a skid-mounted frame, which Trollius had already viewed at Steinexpo 2008. This plant module could be set up and put into operation in a very short time. For connection of the crusher, existing discharge outlets on the silo chambers were activated. Metered discharge for uniform crusher feeding is ensured with frequency-controlled vibrating feeders,which discharge the material onto a collector belt travelling to the cone crusher. The crusher product is sent via a connecting belt to an elevating conveyor to the high-grade chippings screening plant.

 

For a high-performance cone crusher such as the HP100, recrushing limestone or dolomite does not really present any challenge – even if the rocks are high grade and very strong like those processed at Trollius. But, in the crushing of limestone with small gap widths, there is a danger of briquetting. Uncertain about whether the particle shape would meet future requirements, Hermann Trollius initially hired the module unit for trial operation. The HP100 was fitted with Standard Medium tools, with which the throughput rate reaches 60–80 t/h at a gap width of 11 mm. After just a short time, there were convincing results in favour of opting for a HP100 modular on a permanent basis. Requirements for the product particle size, low sand content and particle shape were all met. Thanks to the convincing combination of crusher chamber profile, eccentricity and speed, the HP100 – the smallest crusher in the HP series – is optimally equipped for this application.

 

Maintenance and operation-friendly features such as the accessibility of the crushing tools from the top of the crusher as well as crusher tool attachment without sealing compound are key assets of the HP cone crushers from Metso. Another advantage is the efficient overload protection when the crusher encounters uncrushable materials or briquetting occurs. The crushing gap in the HP cone crushers is adjusted by turning the bowl, resulting in uniform wear over the entire circumference of the crushing chamber.

 

For the HP100 installed at Trollius, the IC7000 Basic intelligent crusher control system is sufficient for monitoring the main crusher functions and calling up auxiliary functions in the event of faults. If a HP cone crusher is used for crushing highly abrasive rock, the manufacturer recommends the IC7000 Advanced system, which, besides additional functions for integration in the overall plant control system, also features an operating data report function as well as several modes for monitoring the crushing gap to ensure operation with a constantly optimum gap setting.

 

Metso Minerals (Deutschland) GmbH,

Mannheim (D), Tel.: +49 621-727 00 611,

E-Mail: karl-heinz.hessler@metso.com

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