STEEL BELT CONVEYORS FOR SEVERE CONDITIONS since 1929

PUBLIC POWER CORP.

THE CHALLENGE

In 1994 PPC, the Public Power Corporation of Greece, received approval from the European Community to start the revamping of the existing bottom ash handling system. Therefore, in 1995 a MAC® (Magaldi Ash Cooler) system was installed under the 300 MW lignite fired boiler of Ptolemais Power Station (Greece) in order to replace the old wet SCC (a Submerged Chain Conveyor).This innovative project included the recycling of the dry bottom ash to the lignite bunkers in order to re-burn the lignite ash in the boiler and recover about 12.7 MWth.
This was a significant amount of energy, equivalent to a saving of 76,000 tons of lignite per year that was previously lost in the wet bottom ash extraction system.
Thanks to the installation of the MAC® system the operational costs were drastically reduced, together with the costs associated to the water need and the bottom ash disposal. Thanks both to the wet-to-dry conversion of the bottom ash handling system and the recycling system, the only combustion by-product was fly ash.

 

THE CUSTOMER

The Public Power Corporation (PPC) S.A. is the biggest electric power company in Greece. It is controlled by the Greek government, which owns a majority of the issued shares. PPC was founded by the Greek government in 1950. Its main purpose was to plan and apply a national energy policy which, through the exploitation of the domestic products and resources, would distribute cheap electric power to all Greek citizens.
PPC started the integration of all the small local grids into the national interconnected grid. Furthermore, the corporation resolved the purchase of all the small private and local electric power production units.
Today, the PPC Group consists of 4 subsidiary companies PPC or DEI S.A., HEDNO or DEDDIE S.A., IPTO or ADMIE S.A. and PPC RENEWABLES S.A..

 

THE SOLUTION

The MAC® system receives the hot bottom ash falling from the boiler through the bottom hopper. After a primary crushing stage, the bottom ash is discharged into the secondary cooling conveyor, the so called Postcooler, and then into a buffer bin. At the exit of that bin a steel belt conveyor extracts the bottom ash,
Then the ash can be either diverted to a secondary crushing stage, in order to be transported by a pneumatic conveying system to the fly ash storage silo, or to a bucket elevator, which is followed by a set of chain and belt conveyors aimed at distributing it into the lignite hoppers.
The latter is a recycling system which brings the bottom ash back to the boiler, where it is reburnt together with fresh lignite. Through this solution maintenance costs were strongly reduced. The MAC® system has been in operation since 1995.

 

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