Turning ash into cash01 February 2007

1. Building on its vast experience, Clyde Bergemann has developed a new dry bottom ash system, known as DRYCON
2. Adjustable air inlets are located along the casing
3. Air inlets are also to be found at the system's discharge end
4. Integrated is a recirculation system, which collects fine ash particles that have fallen through the plates
5. Impact tables, located on the underside of the conveyor, accommodate abnormally large lumps of ash

Power plants are increasingly operating in a more competitive climate. In a world short of mineral resources, coal continues to be the raw material of choice and correspondingly by-products from coal combustion are increasing.

Stricter regulations and a heavier legislative burden, coupled with increasing environmental awareness, have made the operation of power plants more complicated and expensive. The resultant higher transport and disposal costs associated with waste and combustion by-products mean that the power industry must look for solutions to minimise the environmental impact of operation.

Already we have seen promising results from the reutilisation of bottom ash from coal combustion, with its use in structural embankments and drainage systems. Instead of dumping bottom ash in landfill systems, when mixed with fly ash it may also be successfully redeployed in the cement industry.

A new dry bottom ash handling system continues burning of the ash during the extraction and cooling phase - passing ambient air, instead of water, over the ash. Known as DRYCON, the system not only minimises emissions and non-recyclable waste products, but also delivers increased boiler efficiency, due to the improved burning of the ash. Industry estimates these benefits to amount to savings of up to 1.4 million Euro/year.

Air is induced into DRYCON at the top end and along the length of the conveyor by the negative pressure in to the boiler. Air travels along the surface of the ash, which is carried on a steel plate conveyor. This air travels in counter-flow direction along the ash. The ash continues to burn as it travels along the conveyer. This reduces the unburned carbon level and frees up additional thermal energy.

Before entering the combustion chamber, the air is heated and adds additional thermal energy to the steam-generating process within the boiler.

DRYCON - designed by Clyde Bergemann Materials Handling - works by extracting bottom ash from coal-fired boilers, using a dry mechanical solution, eliminating the need for water treatment. As a result, it also reduces water treatment requirements and reducing corrosion, which the more commonly used 'wet' bottom ash systems can cause.

The lack of corrosion also means the DRYCON system will extend the life of the boilers, whilst also reducing maintenance and operational costs.

In today's highly competitive power industry, there is a maximum focus on improving operational efficiency and minimising costs, whilst limiting the environmental impact of production. DRYCON has the potential to provide all three.

SOE

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