The best Solution for Raw Material Storage and Blending

Related Vendors

DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

Glatt Ingenieurtechnik GmbH

EDL Anlagenbau Gesellschaft mbH

Claudius Peters Technologies S.A.

Blending Monitoring

When a blender is linked to a continuous analyser (PGNNA type) installed on the incoming route, then it is possible to continuously adjust the proportion of each component in the blend so that the outgoing flow is on target at any given time.

SmartStack software has been developed with the goal of precisely controlling the incoming flow and preparing blends on the stack that are as close as possible to the target. To achieve this, a complete digital 3D map of the stack is constructed by a computer that controls the analyser (mound modelling). This allows for real time predictions of the future flow with regards to any quality control parameters or other requirements.

The characteristics of the input may be altered by the system either by control of the upstream route or information provided directly to the quarry management. Further developments can establish direct connections between the mound modelling software and the stacking control system to improve the optimisation of the blending operation. This may involve changing the rotation or travel speed of the stacker.

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Stacking and Reclaiming Combinations

Table 1 examines the possible combinations of stacking patterns with reclaiming modes for both linear and circular stockyards. The most common matches are marked in bold letters.

Material Characteristics

Several key characteristics of the handled material must be taken in account. As there are no strictly identical commodities and no standard definition thereof, all records and experience with the real materials have to be taken into account wherever possible.

Bulk Density and Angle of Repose

These are the most important parameters in the determination of the size versus capacity of the stockyard and the size of most of the mechanical components. Only data recorded from existing stacks can give reliable data.

The angle of repose of a given commodity shall be regarded as depending on the 'age' of the stack. A fresh pile is rather unstable and slight disturbances trigger material slides. Day after day the angle of repose of the same stack is reduced by a few degrees.

Clients may state value ranges for the angle of repose as well as for bulk densities. The safe method consists in taking the higher value of the angle of repose for determining the maximum height of the stack and the related clearances of equipment, while considering the lower value of the same for determining the storage capacity. On the other hand, higher values of density are generally observed for stacked material due to pressure within the stack while lower values of the same are used for determining the size of the handling equipment, such as buckets, blades and conveyors.

Grain Size

Most of the materials handling equipment benefits from handling smaller sized grain. Smaller grains also help the blending performance of any type of blender. Large grains put higher stress on the machine parts, amplifies the risk of segregation and sets a limit to the homogenisation level.

It is difficult to set a standard for ideal grain size independently from the other parameters of the plant. In particular, the lower the reclaim rate, the smaller the handling devices such as reclaimer buckets. If an absolute limit to grain size was to be set it would not be above 150 millimetres.

Moisture Content

For a certain number of commodities, a high content of water may cause the flow properties of the bulk material to deteriorate. Some layered clay and chalk are likely to become difficult to handle with moisture content above 12 or 15 percent. For such materials, side reclaiming with self cleaning buckets equipped with scraping arms is recommended. n

* Simon Wintz is Engineering Manager at Claudius Peters Technologies, France

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