Screens & Feeders

An eccentric solution to the primary crushing concept

Compact but powerful, ultra-productive with excellent crushing performance, highly energy efficient and well balanced.

These are attributes featured in promotional literature describing the new eccentric roll crusher (ERC) from thyssenkrupp Industrial Solutions.

The supplier says the ERC redefines the concept of primary crushing hard rock. As such, it is suited not only for use in underground operations but also in open pit mines and quarries, where its qualities are particularly useful in semi- or fully mobile operations.

For decades, gyratory and jaw crushers have proved their worth in crushing hard rock. However, their application is limited by their high headroom, requiring capital-intensive construction of large-scale, costly caverns when used in underground operations.

Moreover, in open pit operations they are only partially suitable for mobile use because of design-related residual imbalance-induced forces.

Although low-headroom crushers such as double roll crushers and sizers have become established as primary crushers in the industry, design constraints mean they are not considered capable of efficiently and economically processing hard rock.

The new ERC, with its patented design of pre-screening and crushing features, combines a compact design and the ability to crush hard rock with high throughputs in an energy-efficient manner.

Operational benefits

The ERC offers significant operational benefits. Its installation height is between 20 and 55 per cent lower than similar-performing gyratory or jaw crusher options, in an overall lighter package.

At the same time, the ERC is highly productive and energy-efficient. Its kinematics with a constantly large stroke promote a more profound crushing intensity and higher throughput rates.

High inertia moments in the roll and flywheels enhance the ERC’s energy efficiency. Its integrated pre-screening device allows for efficient bypassing of fines to significantly reduce power consumption, compaction risk and the wear rate of crushing tools.

The steady rotation of the freely rotatable crushing roll, when exposed to feed material, results in exceptionally uniform wear and high utilisation of crushing tools.

The symmetrical arrangement of the eccentrically moved crushing roll allows for easy balancing, so foundation forces and vibrations are reduced to a minimum. As a result, the ERC is particularly suitable for use in semi- or fully mobile applications.

Smart control is another decisive advantage. Thyssenkrupp’s patented hydraulic gap setting/retraction system allows for safe and simple automatic adjustment of the gap, liner wear compensation and release of tramp metal or other non-crushable material content.

Further, the ERC is equipped for Industry 4.0, incorporating a comprehensive monitoring system that allows for local or remote control and the automation of equipment parameters from the crusher’s display. In addition, an optional thyssenkrupp data acquisition system offers reliable recording and storage of relevant operational data for trouble-shooting, condition monitoring and preventative maintenance.


Operating principle

Material is fed into the crusher by an apron feeder, push feeder or the like. Fine particles in the feed are screened out by the integrated static grizzly and bypassed through the crusher housing.

Coarse particles are transferred into the crushing chamber. A rotating eccentric shaft, axially guided by two sets of roller bearings mounted in the crusher housing, generates an oscillating movement in the freely rotatable, horizontally arranged crusher roll.

Consequently, the crushing gap between the crusher roll and the jaw in the crusher housing changes continuously, which means the feed material is crushed by compressive forces as it falls by gravity, until the product exits the crushing chamber at the bottom. The eccentric shaft is driven by a V-belt drive, with the inertia of two flywheels mounted onto the shaft accumulating crushing energy (see Figure 1).

The kinematic principle applied in the ERC ensures the stroke remains the same throughout the entire crushing chamber. This unique feature significantly increases the comminution intensity compared with commonly used crushers. The jaw itself does not move during the crushing process but is supported by a fully hydraulic gap setting/retraction system with a patented safety device.

This system allows for automatic adjustment of the gap, compensation of liner wear and release of tramp metal or otherwise uncrushable feed material content.

After the detailed design of this roll crusher, a prototype of the machine was built and extensively field-tested in a six-month campaign at a hard rock quarry in Germany.

The crusher model ERC 25-25 selected for this purpose has a crushing roll of 2500mm in diameter and width. The feed opening to the crushing chamber is 2500mm wide and 1230mm high.

Both the coarse and fine run of mine feed were processed, plus selected lumps of up to five tonnes. The equipment parameters were varied with regards to eccentric shaft speed and gap closed side setting (CSS). The corresponding operating data was collected with and without the integrated grizzly.


Pilot plant

During this pilot operation, average capacities of 2000 to 3000 tonnes per hour (tph) were recorded.

The desired product size of 0-200/x mm was achieved at various settings, with P80 at CSS of 140mm recorded with about 130mm.

The integrated grizzly effectively bypassed fines and contributed between 30 and 40 per cent of the total equipment capacity. The power consumption at nominal capacity ranged between 200kW and 500kW, depending on crusher settings. However, the high energy efficiency of the ERC was confirmed by the power consumption of 0.1 to 0.2kWh/t.

The ERC from thyssenkrupp offers new standards in the primary crushing of hard rock thanks to features not found in conventional crushers.

This opens up numerous new application areas in the processing of mineral raw materials. The ERC roll crusher series comprises four units, ranging from the ERC 18-14 entry model to the top-end ERC 25-34 model, with throughputs between 600 and 10,000 tph.

The first ERC for commercial operation – the ERC 25-25, capable of generating an output of 8000 tph – has already been sold and will be on show at the bauma 2019 trade exhibition in Munich, Germany in April.

“We are constantly seeking new solutions for our customers that improve crusher availability and efficiency and reduce installation and operating costs,” said Detlef Papajewski, the head of mineral processing at thyssenkrupp Industrial Solutions’ mining technologies business unit.

“With the new ERC we have developed a technology that is the first of its kind. Its innovative design combines the advantages of conventional primary crushers with solutions to their typical disadvantages, such as large height. As a result, the ERC can be used in underground and surface mining operations and in quarries to process ore and hard rock more effectively.”

Source: thyssenkrupp Industrial Solutions

More information & further reading

Szczelina P, Drescher F, Silberman F. Compact, robust and high performance: New ERC 25-25 eccentric roll crusher revolutionises primary crushing in underground mines. A thyssenkrupp reprint from AT Mineral Processing Europe 05; 2017. sonderdruck_thyssenkrupp_screen_300617_final.pdf

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