Pre-screening as key driver to an efficient overall process

Limestone is considered by the construction industry and the construction materials industry to be one of the most important raw materials. Its many different characteristics enable it to be used in a variety of ways. Quarrying limestone can prove to be very difficult when contaminated. Economically efficient quarrying and high product quality can be realized, however, through the use of Kleemann plants and their mature screening technology.

Processing “impure” limestone in mobile Kleemann plants

Processing “impure” limestone in mobile KLEEMANN plants

Spain: Crushing limestone with a high percentage of clay and earth

Limestone is quarried and crushed at Canteras Foj Quarry near the Spanish city of Barcelona. A special characteristic: The feed material is contaminated by an extremely high percentage of clay, which is particularly difficult to remove by screening. As tricky tasks require special equipment, it is no surprise that quarry owner Juan Manuel Foj decided to use a MOBIREX MR 122 RR from German plant manufacturer Kleemann. “This special plant is based on the tried and tested MR 122 Z, which has been equipped with roll screens type RRS 12.5/8 and RRS 12.5/6 mounted behind one another in a graded arrangement for this special pre-screening application. So, the plant is not operated with the well-known and highly effective doubledeck heavy-duty screen,” explains Michael Schwarz, Sales Manager Europe at Kleemann. This arrangement not only ensures successful screening of the fines but also enables the plant to achieve an impressive feed capacity of up to 350 t/h.

Screening plant ensures “fine tuning”

Such top performance obviously requires an appropriate screening plant for the highquality and highly productive final grading in the second step. Four final aggregate fractions of 0 to 4 mm, 4 to 12 mm, 12 to 22 mm and +22 mm need to be produced, serving as aggregate for asphalt and concrete production. No problem at all for the mobile triple-deck screening plant type MOBISCREEN MS 20 D. It has an impressive screening surface of 2,050 mm x 6,000 mm in “banana geometry”, enabling it to achieve a discharge capacity of up to 650 t/h. Like the MR 122 RR, the MS 20 D is equipped with a diesel-electric drive system. Operation is therefore economical in terms of fuel consumption, and enables interlocking of the control systems of both plants. As an option, both plants can be operated with on-site electric power, which can significantly reduce the operating cost even further.

Russia: Two crushing stages, two pre-screening stages and four final aggregate fractions for top quality

The LSR Group counts among the biggest companies in the Russian building industry. The company’s subsidiary OOO Zement LSR is currently building a modern cement factory near St. Petersburg. Once completed, it will produce 1.85 million tons of cement per year. The required limestone is quarried in Slanzy, a small town near the Estonian-Russian border, and is processed in an efficient combination of mobile Kleemann crushing and screening plants.

Active double-deck pre-screens in operation

Around 240 tons per hour of grain size 0 – 70 mm are produced in two crushing stages – separated into three final aggregate fractions. As the feed material contains significant amounts of fines, OOO Zement LSR decided to use plants equipped with active pre-screens in both crushing stages. “Not least for that reason, we chose two mobile plants from Kleemann,” explains Mr Putjata, the chief mechanic at OOO Zement LSR. A mobile jaw crusher type MOBICAT MC 120 Z is in operation in the first crushing stage. “This plant is of extremely robust design and pre-crushes the rock, which has a feed size of 0 –800 mm, to a size of 0 –250 mm. The feed material is cleaned very effectively even in this stage by the active double-deck pre-screen. Via a ‘bypass’, the pre-screened material is sent past the crusher and directly onto the discharge conveyor, which enhances the productive operation of the plant even more,” explains Mr Kosmatschew, the Director of OOO Zement LSR. In the second crushing stage, the material is crushed to grain size 0–70 mm. This job is taken on by a mobile impact crusher type MOBIREX MR 130 Z. It is equipped with an active double-deck pre-screen as well in order to remove any remaining contaminations of grain size 0–30 mm. Oversize material of grain size +70 mm is screened by a secondary screening unit and then stockpiled – for later reuse as basic aggregate in road construction. The MR 130 Z sends the 0–70 mm material to a MOBISCREEN MS 19 Z mobile double-deck screening plant for final grading. This plant, which is suitable for use in both recycling and natural rock applications, has a screen size of 1,520 x 6,100 mm allowing discharge capacities of up to 500 t/h. It separates the material into three final aggregate fractions of 0–20 mm, 20–45 mm and 45–70 mm grain size and then stockpiles them via its generously dimensioned discharge conveyors.

Operating site: Canteras Foj Quarry near Barcelona, Spain
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