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ARDELT: DIFFUSE EMISSIONS - DUST PREVENTION MEASURES

Design of the dust prevention walls (shown here on a side-coupled bunker)Kangaroo crane, location Brunsbüttel


The handling of dust-producing goods has been the subject of discussion for a long time. In general, the difference between a continuous conveying device and a discontinuous conveying device (grab operation) is largely limited to the diffuse emissions that are produced. However, ARDELT takes this subject further and compares not only the dust problems but, moreover, also takes into consideration the energy balance. Modern handling equipment must satisfy all the environmental aspects. During the structural design of a crane, careful attention is given to all the necessary measures for minimising the noise and dust emissions with a view to achieving the lowest possible energy consumption. This includes detailed solutions, as well as a full evaluation of the different crane types.

For reducing the dust and noise emissions as well as for optimisation of the energy balance, the kangaroo crane has proved to be the most efficient. This design of the articulated-jib luffing crane with integrated bunker provides an ideal solution with the lowest possible energy consumption, as well as minimal maintenance and repair costs.  A further advantage is the proximity of the bunker to the ship. Any spilled material which trickles down does not soil the quay but will instead be caught by the front side of the bunker, which is constructed in the form of a spillage flap.

1. Energy balance

During the goods-handling operation the jib system remains fully counter-balanced at all times and is moved almost exclusively by the luffing gear alone. This means that the handled goods are conveyed via the shortest possible path.  Due to the almost linear movement, torsion forces which would otherwise lead to rotation of the grab are avoided. In addition, the short rope length means there is also a reduced pendular movement in comparison to single-jib cranes. The digging-in of the grab is achieved by virtue of its own weight, and therefore does not require any additional energy. Through the use of power supply/regenerative feedback units, the energy liberated in this way, e.g. when the grab is being lowered, becomes available to supply the other electrical consumers on the crane, or alternatively the surplus energy can be fed back into the supply network.

2. Noise prevention

The noise emission is reduced to a minimum by means of the controlled electrical drives and through operation of the machines in the region below the field-weakening range. The noise emission produced when discharging is also kept to a minimum through the optimal choice of discharge height and a wear-resistant rubber lining on the bunker walls. Any background squeaking noises are eliminated through the use of antifriction bearings at the jib pivot points.

3. Dust prevention

Irrespective of the type of crane design (kangaroo or side-coupled bunker), ARDELT provides a semi-automatic operating mode as standard. When handling goods in semi-automatic operation, this provides a defined automatic approach to the target point (bunker) with an optimised discharge height. This prevents any uncontrolled dust and noise emission. Generally, dust prevention walls (height approx. 3 m) are used. As regards the grab, ARDELT recommends an enclosed grab design. The control system which regulates the grab closing process is designed to prevent any trickling-out of the handled goods. A variety of possible solutions has been developed, for use in combination with each other, to keep the environmental effects as small as possible. The solutions depend on the classification of the relevant bulk goods with regard to the expected dust generation (see VDI 3790), in addition to any further requirements of the operator.

3.1 Slightly dust-producing goods

In the case of slightly dust-producing goods, such as hard coal, the high dust prevention walls are generally sufficient. These walls have a special design feature. They are not simply flat, but are constructed with a semi-tubular shape at the top. The dust generated during discharge rises up against the walls and is then guided back down into the bunker again by this special shape. A simple, but very effective measure.

3.2 Moderately dust-producing goods

Building on the bunker design already mentioned above, various additional dust prevention measures can be used after consultation and agreement with the operator.

- Wetting of the handled goods with a sprinkler system or by nebulization (FOG system)

- Suction extraction via a filter system

3.3   Heavily dust-producing goods

For these kinds of handled goods, we recommend the additional use of a Flex-Flap system, in order to contain the dust within the body of the bunker.

With all these tested solutions, ARDELT can offer what is virtually a modular system capable of minimising the emissions in an optimum cost/benefit ratio. The individual possibilities are shown again in the following diagram.

The selection criteria are established in consultation with the operators, taking into account the handling criteria and the prevailing local conditions.

 

To see the efficiencies offered by these measures, please read the following article „TUKAN KÄNGURU, AN ECO-FRIENDLY CRANE MADE BY ARDELT". Two short video sequences can be viewed there which illustrate not only the function, but also the necessity of dust prevention.


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