Overcoming a Mines Embankment

IPCC-system with new Belt Conveying Concept for steep Opencast Minewalls

Overcoming a Mines Embankment

In order to allow for a continuous high capacity conveying system out of steep walled open pit mines Thyssenkrupp together with Contitech and Siemens developped the Chevron Megapipe conveyor with an up to 900 mm outer diameter. The pipe belt features highest tensile strength as well as a ribbed carrying side to hinder the transported bulk material from rolling back.
(ed. wgeisler - 30/11/2017)
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DEM-FEM Analysis for a Chevron-Megapipe Loading Point

Due to the fact that, after primary crushing of the raw material, so-called fish-lumps (meaning particles with a length to width ration >3) with edge lengths of up to 400 mm can occur in open cast mining operations and these lumps have to be securely redirected in the loading station (which is generally right-angled) from the crusher outlet belt and onto the pipe conveyor and then embedded into the material flow of the pipe, special structural requirements apply to this task area. Among other tasks, it must be ensured that fish-lumps do not land on the open belt at right angles to the direction of flow so that they do not jam between the conveyor idler stations when the troughed belt is forming into a closed pipe belt (by specially configured finger rollers) and damage the idler stations (Fig. 8). Multiple calculation runs of a coupled DEM-FEM bulk material simulation finally resulted in the optimum design for a loading station.

 Fig. 8: DEM-FEM simulation of a bulk solid with two fish-lumps, in line with and at right angles to 
 to the conveying direction                                                                                           

The crushed material from the crusher is transferred via what is known as a rock box to the conveyor belt, which is still U-shaped at this point (Figs. 9 and 10). The transfer chute to the Megapipe [4] must be designed so that the material rebounds off a rock box and then falls directly into the U-shaped pipe belt. The width of the U-shaped transfer area already corresponds to the pipe diameter that is to be formed; this ensures there is no further constriction of the clear belt width when the pipe is then formed. The U-shaped loading area is approximately 8 m in length. In this section, the material should settle and the conveying speed should simultaneously increase. Unlike in conventional pipe conveyors with classic trough loading stations, there is hardly any material shifting within the U when the belt is reshaped into its circular cross-section as it passes along the conveying direction. 

Fig. 9: The material transfer to the Megapipe involves a rock box to redirect the       
material onto the pipe conveyor.                                                           

Fig. 10: Alignment of the lumps in the U-shaped section of the pipe belt                     

As the results of the DEM-FEM simulations (Fig. 11) show, the length is sufficient to align the lumps in the conveying direction. The material guidance itself is designed to open up in the conveying direction. The clear width of the material guidance is approximately 700 mm at this point, which is sufficient, given the wide flow of the material feed, to allow a material flow of 5000 metric t/h of copper ore (particle size distribution 600...20 mm) without overfilling or blockages.

Fig. 12: DEM-FEM simulation of material transfer into the U-shaped belt for cupper ore         
(particle size 600...20 mm)                                                                              

Direct Drive Solutions for the new Transport System

Due to the boundary conditions that must be met for a Chevron-Megapipe conveyor, the right drive solution for this new transport technology is a direct drive. The high conveying capacities and the lifting heights involved require multiple megawatt drive outputs. In addition, the entire drive output has to be transferred to the belt via a single drive pulley because the chevron profiling means that no additional belt redirection using further pulleys is possible. 

The drive solution developed jointly by Siemens and Thyssenkrupp [5] does not require elastic coupling between the motor and drive pulley and it does not require more than two roller bearings for the entire drive train. This means that very few mechanical components are involved, which increases the efficiency and availability of the drive. This drive solution is already successfully used in many belt conveyor systems with motor outputs of six megawatts. 

In normal operation, the drive is started up and stopped at defined ramps by means of a frequency converter. These ramps are determined and implemented during commissioning or in a simulation analysis carried out in advance. The drive train is completed by a mechanical brake that is designed as an emergency stop and/or holding brake, depending on the requirements. 

The direct drive, combined with tried-and-tested control algorithms for belt conveyor drives, enables reliable and lasting operation of the belt conveyor.

Fig. 12: Direct drive for a belt conveyor, 2 x 4.4 megawatts                                

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