CRATOS Technology for Scraper Dry De-Ashers

Dry De-Ashers in cooperation with Clyde Bergemannn Power Group.

The development of ash handling plants was widened to include dry de-ashing systems in the1990s.
The advantages of dry de-ashing are:

• No water required
• No water treatment required
• Low thermal energy losses
• Reduction of unburned fuel as a resultof the after burning effect
• Improved boiler efficiency
• Easier compliance with regulations
• Ash quality is advantageous for its further marketing

RUD has contributed to the development of "dry de-ashing" systems. It has developed an Apron Conveyor system which, in comparison to other systems, remains sealed not only on the straight but also on the curved conveyor sections. This system was developed on the basis of the tried and tested round steel chain and is designed specifically for it. In contrast to wet de-ashing, the ashes are not scraped along the floor of the trough but carried along by the plates (A)attached to the conveyor chains until they are discharged. The plates run on wheels or, if required, on rails (B). The conveyor chain is protected by baffle plates (C) projecting over the side walls of the plates. The conveyor chain is driven via externally toothed pocket wheels. These are more tolerant of longitudinal chain wear than internally toothed wheels.

Conveying capacities of between 5 and 70 tonnes per hour (t/h) are achieved, depending on the angle of the inclined part of the conveyor. Through puts of 100 t/h have already been achieved. The conveyor is 2000mm wide.

Conventional conveying speeds lie between 0.01 and 0.07 m/s. They seldom exceed 0.1m/s, and are achieved with regulated electromechanical or hydraulic drives.

This principle offers the following advantages:

Lower coefficients of friction in the upper conveying compartment, which means that, in some cases, a smaller chain size can be used for a given conveyor capacity As the conveyor chain does not run through the material being conveyed, it is subjected to less wear than in a comparable wet de-asher. Relatively insusceptible to large lumps of ash, which can sometimes fall off the boiler wall when soot blisters form. Even easier to maintain than the already low-maintenance chain equipment of the SSC de-asher. Dry de-ashers with a RUD Apron Conveyor can be built with a significantly lower profile than other designs.

CRATOS Component

form the heart ofthe Apron Conveyor: the conveyor chain, the chain connectors, the drivewheels, guide wheels and the drag chain together with its attachments.

The general advantages of the RUD components are:

Highly wear-resistant to give long service life High-strength through optimal heat treatment (see operational forces,similar to those of wet deashing) Plates remain sealed, even in the curves, thanks to a patented attachment link The reinforced plates in the chain strand are optimally adapted to the conveying task, and supported by at least four chain links Simple mounting in and dismounting from the chains, and therefore Low-maintenance