Study On Materials’ Breaking Mechanisms And Crushing Power Consumption In A Jaw Crusher

The history of a jaw crusher is more than one hundred years, and now it is still commonly used for materials’ primary crushing in the engineering practices with many advantages such as simple structure, reliable performance, convenient maintenance, high productive efficiency. But it is also one of the devices whose power consumption is particularly high.Nowadays, the study on mechanical CAD/CAM is very popular in domestic, but investigations on crushing mechanisms and advanced methods to design and manufacture jaw crushers are still insufficient compared to the other kinds of crushers. According to the related research done by our group, the main problems are as follows: 1) The understanding on materials’ breaking mechanisms and interaction features between materials and jaw plates is not clear; 2) Unreasonable structures of the crushing cavity and jaw plates can reduce device durations and raise production costs; 3) When choosing a dynamo which is one of key designing parameters, a common designing method is just to conduct an estimation formula and not to choose the real data to determine the power of dynamo, which may result in that the calculated power is inevitably higher or lower compared to the required power. Thus it either leads to waste energy or to decline the crushing capacity.In order to solve those problems mentioned above, based on the advanced mechanical CAD/CAM technique, this article conducts numerical simulations and experimental analyses on an overall crushing processing of jaw crushers mainly used for primary crushing. Based on those ideas, this particle analyzes and explores the crushing mechanisms and establishes corresponding models for the numerical analysis, and then conducts the optimal structure design on crushing cavity and jaw plates, which can serve as the basis for the overall design of a new type of block-free jaw crushers such as the rational selection for a dynamo. The main work of this paper is as follows:1) A material model of diorite was established using the discrete element software of EDEM based on the BPM model. This material model was made up of a number of small particles bonding together and the sizes of broken particles were set to be a bi-modal distribution, which could make the packing density of material model higher and the interlock performance between particles better. Microscopic parameters of the material model were calibrated to make materials’ breakage behavior consistent with real rocks’ crushing behavior.2) Two different kinds of crushing cavities were established. A traditional type of cavity with “line-line” structure was established based on the data of PE60×100 jaw crusher and a new type of cavity with “line-curve” structure was established based on materials’ flow breakage features.3) The overall crushing processes of material in the two kinds of crushing cavities were simulated in EDEM and material’s specific crushing behaviors were obtained. It was found that in different crushing stages it was the diagonal position of the cubic material that bore the maximum force in both cavities, but the force condition in this area in the new cavity was more intensive, and thus the materials were easier to be crushed compared to the materials in the traditional cavity. The material model was presented in forms of bond, cone and vector, and thus the bonding condition inside the material and the force and velocity conditions of bonding particles were displayed clearly. The evolvement rules of the force network inside the material were analyzed, and it was found that in a parallel crushing stage it was the material in new cavity that possessed more strong force chains and they were connected to breakage behaviors in the macroscopic field. The advantages of the new type of crushing cavity were verified from the standpoint of force conditions of material. In addition the study also served as the basis for enriching the theory system of the granular material mechanics.4) The power variation curves and the load conditions of two kinds of crushing cavities were compared and analyzed. It was found that it was the middle and lower parts of jaw plates that bore the biggest crushing force in both kinds of cavities. But the jaw plates of new cavity had a long service life because the force strength of new cavity decreased by 9273.1N compared to that in traditional cavity, and the wear zone in former was small. The power diagrams of both cavities were curves with vibration waveform, and both equations of linear regression were about horizontal lines. But the average power consumption of new cavity was 0.942 kW and the crushing time 2.7s, and the corresponding data of traditional cavity were 1.473 kW and 3s. The comparison showed that the energy consumption cost of new cavity was much lower and the excellent features of new cavity were verified from the prospective of force and power conditions. In addition the obtained power data can serve as the basis for selecting a rational dynamo, which can make the device achieve optimal performances and save energy effectively.