Swiss precision engineering: fine crushing at the Zingel quarry

The Zingel quarry, situated on Lake Lauerz near the town of Schwyz, has been operated by KIBAG Kies Seewen AG for 40 years. However, hard rock has been quarried there for more than a century. With an annual production volume of just under 300,000 t, the site covers one-tenth of the national demand for high-quality hard rock. Consequently, it assumes an important supply role for the regional construction industry and the Swiss Federal Railways (SBB).

Today the quarry still has licensed reserves of approx. 13 years. At the site, a type of siliceous calcareous limestone is extracted and processed. The material is low-abrasive, but its hardness is rather high (crushability index of 20), which makes it highly demanding on the processing technology that is used. After Drossard Sales & Service GmbH installed a Nordberg® NP1110™ impact crusher in the quarry this year, the productivity of the fine material increased and exceeded all requirements.

Optimizing process operations and procedures at the Zingel quarry

The close cooperation between Drossard Sales & Service and the management of the Zingel gravel and concrete plant in Seewen started no less than seven years ago. Since then, the common goal of the operators as well as Metso’s distributor Drossard has been to optimize the site’s process operations and procedures.

The primary crusher, which Drossard installed five years ago as part of the development of the new quarrying site, was the result of a previous two-year evaluation period. At that time, the new Nordberg® C120™ jaw crusher from Metso had just come on the market. It was installed at the Zingel quarry. The decision on the new stationary jaw crusher was made based on convincing machine performance, and the addition has proven to be worthwhile for the quarry.

In early 2017, KIBAG again invested in a Metso plant. This time, the Nordberg® NP1110™ impact crusher was installed as a secondary crusher for the ultra-fine particle fractions (feed material 0/16 mm). The finely adjustable, automated control of the machine ensures consistent product quality. Depending on the throughput, crushing bed positions, and machine speed, an optimum grain shape can be achieved in the continuous preparation process.

The Swiss Metso distributor Josef Drossard knew the plant and the associated technical requirements very well and had already proven the worth of the stationary primary crusher. This led to him being awarded with the contract for the new Nordberg® NP1110™ as well.

One of KIBAG's main demands was to significantly increase and optimize the sand production content via the new crusher. The potentials for flexible control provided by the Nordberg® NP1110™ were thus a feature welcomed by the operator. Before the acquisition, rock analyses were carried out and the values were inserted in Metso’s crushing simulation software Bruno. The predicted results were not only highly promising, they were also confirmed in practice after the final installation of the machine.

After commissioning, it turned out that the results corresponded 99% with the predicted results from the Bruno simulation software. "With this system, we were able to produce high-quality products right away. In addition to the accustomed service culture of our local Metso distributor Josef Drossard, we were also convinced by the high service lives of the chrome-ceramic impact bars in the new Metso crusher. The maintenance intervals are pleasingly far apart," says Workshop Manager Kaspar Herger.

Due to the long crushing beds and the longer residence time of the material inside the machine, the inter-particle comminution in the Metso crusher is much higher than its predecessor. Both crushing beds and the crusher gap can be calibrated automatically, which usually happens only once a day via the control system. Using the new Nordberg® NP1110™, the Zingel quarry additionally benefits from the higher degree of comminution. The fact that the speed of the crusher can be flexibly controlled is due to the built-in frequency converter, which covers a large speed range.

Plans for new crushers

To increase secondary crushing volumes of 16/40mm feed material at Zingel quarry, KIBAG will replace an old impact crusher with a Metso Nordberg® GP220™ stationary cone crusher during the Winter revision 2017 / 2018. The new plant will improve particle geometry quality as well as efficiency and will lower production as well as maintenance cost drastically. 

Drossard has already maximized the capacity of the plant through appropriate machine technology without having to change the material handling conditions locally. At a certain point, productivity enhancements are linked to the need for also taking into account potential bottlenecks, such as materials handling equipment, silo capacity or landfill space. In the case of Zingel, the 400m-long conveyor system would have to be retrofitted, which is currently beyond the scope and not commercially planned for the foreseeable future.

With a factory as well established as Zingel, it is always a demanding task to select new machines that not only increase productivity, but also fit perfectly into the preparation process. There is no question that the specific requirements for particle size distribution and grain shape should be considered for new crushers.

With the close cooperation between the Nordberg® GP220™ cone crusher and the new Nordberg® NP1110™ impact crusher, the proportion of sand production can be increased anytime in the future, which is also in the interest of the operators. This step also paves the way for further increased flexibility of the plant.

Depending on the market and storage depot situation, part of the final product from the Nordberg® GP220™ could then be processed into sand via the Nordberg® NP1110™. "Our production got a big boost. With the new plant, we produce higher quality sands and proportionally more fractions of our choice. The screening curve is also much more consistent," says workshop master Konrad Schorno. The sand content (0/4 mm) of the feed material (0/16 mm) is initially around 28%, but after processing by the Nordberg® NP1110™ impact crusher it is 84%. The rail ballast fraction (16/63 mm) makes up more than 50% of the total production and is the main product of the Zingel quarry. That is followed by gravel and then by crushed sands as asphalt additives (in the usual fractions of 0/2, 2/4, 4/8, 8/11, 11/16 and 16/22 mm).

The primary Nordberg® C120™ crusher currently processes 350 tons of material per hour. Due to the bottleneck situation caused by the overland belt conveyor, however, only 170 tph can currently be directly processed further. The remaining amount of material is fed via the excavated cavern to a temporary storage depot, from which it is reclaimed at a later time for further processing. About 80 tons of the immediately processed quantity from the primary crusher is going directly to further processing into railway ballast. Thanks to a direct rail connection from the site, the material can be directly loaded and dispatched. This is pretty special, as access to quarries in Switzerland is generally anything but optimal. The difficulty of accessibility is recognized by the fact that the 40-tonne primary crusher, due to the steep access route, could only be delivered in pieces and assembled at its final location. In the future, the company will do everything in its power to stay up to date technologically and thus work more productively and flexibly.