Sizers in Irish waste water treatment plant

Mogensen recently supplied two specially-designed, fully dust-proofed Sizers for the screening of dried waste sludge pellets, which are marketed as Bio-Fert agricultural fertiliser. The machines are installed at the Ringsend Waste Water Treatment Plant, which was commissioned by Dublin City Council but is operated and maintained by Celtic Anglian Water. The plant was completed in 2003 as part of a multi-million Euro project to improve the environment of the Dublin Bay Area.  Major benefits achieved include much cleaner water in Dublin Bay and in the city's rivers; two of Dublin's beaches, Dollymount and Seapoint have been awarded Blue Flag status. Further benefits are the economic use of the dried waste sludge and significant energy savings compared with the previous plant.

In 2007 further extensive work was carried out to improve odour control. At that time it was recognised that, as a result of the installation of new sludge dryers, the two vibratory screens used to size the 4mm diameter fertilizer pellets needed to be modified or replaced in order to satisfy the requirements of ATEX Directive 94/9/EC, the interior of each screen having been classified as a Zone20 space because of the continuous presence of a Class ST1 combustible dust at a temperature of 70 °C. It proved to be impracticable to modify the existing screens satisfactorily. Mogensen was, therefore, asked to quote for two Sizers specially designed to fit into the space occupied by the earlier machines.

The feed inlet and product outlet positions of the two machines supplied match those of the original screens: it was possible, therefore, to install the new machines without modifying the existing plant structure. The feed inlet and product outlets are all flanged and fitted with high-pressure, flexible connectors. The Sizers, in which all product-contact components are manufactured from Grade 304 (Euronorm 1.4301) stainless steel, have been certified to ATEX 94/9/EC Zone 20 and are designed to withstand an internal pressure of 0.4bar should a dust explosion occur. Each Sizer is powered by two Invicta rotary electric vibrators type BLz30-25/4 rated at 1150 watts. 

Each machine can handle a feed of 20 tph of material at 70 °C with a minimum bulk density of 350 kg/m³, and separate it into oversize, saleable product and fines. The oversize and fines are re-circulated to the pellet presses. Celtic Anglian Water is reported to be pleased with the performance of the Sizers, which have now been in operation for approximately 14 months.

Mogensen
Harlaxton Road
Grantham
Lincolnshire
NG31 7SF
UK

T: 01476 566301
F: 01476 590145

www.mogensen.co.uk