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Crushing work causes wear of materials

Comminution of rock is an essential but energy-consuming part of mineral processing. A new laboratory-sized jaw crusher can be used to determine how much energy is spent on the actual crushing of the rock and how much is lost on the wear of the jaws.

The energy required by the crusher to operate is an important factor when examining the effectiveness of rock comminution. The function of the crusher is the size reduction of the rock, which naturally consumes energy, but the majority of that energy is spent on overcoming friction, exciting different types of vibrations, and causing wear of the jaw plates, most of that energy eventually transforming to heat. The jaw plates experience deformation and wear due to the repeated contacts with the feed, i.e., rocks. Studying the wear in a crushing environment in laboratory conditions is challenging, in particular due to the high contact forces needed in rock crushing.

There is also a practical demand for the study of the efficiency of crushing. Unless new rich ore deposits will be discovered, the mining industry has to use lower-concentration ore deposits, which means an increased amount of crushing to obtain similar amounts of ore concentrate. Increased amount of crushed ore also increases both the consumed energy and the wear of the equipment. The energy consumption of the Finnish industry has decreased in most fields, but not in the fields of mining and metal processing. The mining industry is responsible for about 1.5% of the total energy consumption of Finnish industry. The global estimation of the mining sector’s energy consumption is about 4–7% of the total annual energy consumption.

In his doctoral dissertation, MSc Juuso Terva has studied how the movement of the jaw crusher jaws affects the amounts of wear and work during a rock comminution process. The dissertation was conducted within the DIMECC Breakthrough Materials Doctoral School in the framework of the DEMAPP and BSA programs. A new jaw crusher design, the “Dual Pivoted Jaw Crusher” (DPJC), was developed, constructed, and utilized in the study. “I designed the equipment to be used in the development of jaw plate materials, as well as to determine the abrasiveness and crushability of different mineral types,” explains Juuso Terva.

The DPJC has the unique ability to change the movement of the jaws between horizontal crushing and vertical sliding, which causes changes in the amounts of abrasive wear and work. The amount of work done in a traditional jaw crusher test is measured from the power intake of the motor, whereas in the DPJC, the work is measured directly with force and displacement sensors attached to the jaws. This facilitates the examination of the individual contacts and excludes the energy losses of the motor and the axles from the measurement. Moreover, DJPC operators can examine the interdependence of the jaw plate wear, the consumed energy, and the changes in rock size after the crushing. The DPJC test is easy to use and highly controllable due to the convenient size of the equipment and modest consumption of the rock in a test. “The results of my dissertation can be directly utilized in aggregate production and mining industry,” Juuso Terva adds.

Public defence of a doctoral dissertation on Friday, 24 February

MSc Juuso Terva will publicly defend his doctoral thesis “The effect of compression and sliding movement on the wear resistance of steels and crushing work in mineral crushing” on Friday 24 February 2017 at 12:00 at Tampere University of Technology in Konetalo lecture hall K1702. Professor Staffan Jacobson (Uppsala University, Sweden), and Docent Jari Liimatainen (Picodeon Oy, Finland) will act as opponents. The Chairperson is Professor Veli-Tapani Kuokkala from the Laboratory of Materials Science.

Juuso Terva (36) comes from Tampere, Finland, and works as a researcher at the Tampere Wear Center of Tampere University of Technology.

The dissertation is available online at: http://urn.fi/URN:ISBN:978-952-15-3917-6

Further information: Juuso Terva, tel. +358 40 849 0147, firstname.lastname@tut.fi
 

News submitted by: Sanna Kähkönen
Keywords: science and research, materials science