A varied plant feed: The new recycled aggregate washing plant is processing a combination feed of recycled materials containing anything from ‘muckaway’, to utility waste, trommel fines and the quantity of sand and the ratio of the sand/silt fraction completely varies in every bucket load going into the plant. However, the plant has been designed to accept a remarkably diverse feed whilst still retaining through put. Specified to process 120tph the plant is currently achieving an average of 140tph

Commissioned in December 2020, the recycled aggregate washing plant with a full water treatment system and filter press was designed by Tyrone International to fulfil the processing criteria for the material feed. The material is based on an all-in aggregate feed, using a Tyrone International twin-screen scalper which scalps off the +50mm with the -50mm being fed up the primary feed conveyor.

Positive displacement pump to extract the sludge out of the centre of the thickener is then pumped across to a large sludge holding tank where two stirrers keep the silt insuspension. From here a twin centrifugal pump fills the press and when the filter press is full the system automatically switches from the centrifugal pump to a piston pump which uses significantly less energy than the centrifugal pump and contains no wear parts compared to the centrifugal pumphence an exceptionally low operational and maintenance cost. When the water has filtered out of the cakes in the press thenthe pumps will stop and then the press will automatically open and discharge ten cakes at a time.

“The key thing about this press is that the overhead beams sit to the side which allows full access to everything on the top; unlike traditional overhead beams where everything sits in the middle and include a chain drive mechanism and hooks on the chains to open the plates.”

“Eventually all those hooks and the chain wear out and if you get a press ‘blow out’ sludge will cover all the mechanism making it extremely hard to access and maintain everything. On the F&B press, maintenance is super easy as everything sits to the side and there is full access round all sides of the press.”

Fintan, continued, “There is a robot mounted on top of the press which has three functions – it opens ten plates at a time and then shakes them and discharges them into material bays below which other overhead beams don’t do.”

“It also operates the automatic washing system which washes from the top down. This is completely different as alternate systems wash from the bottom up. When it is washing the press, a mobile trolley moves along with the washing system and collects all the water which is returned to the thickener.”

“It’s an extremely fast automated system, we have full remote access to all the control on the plant so if there are any alarms, operator problems or issues we can remotely dial into the plant and can access all the alarms and the history and can then offer advice to the plant operator as to what he needs to action.”

“The whole design philosophy of this plant is making everything as easy as possible, easy to access, easy to maintain, easy to service which has been a total success.”

FULL ACCESS AND CONTROL
At Hartshill Quarry a dedicated press service room situated beneath the press contains all the critical components which protects everything from the weather making it easy to access and maintain.

A press control panel adjacent to the press allows the operator to control the moisture content on the cake by measuring the volume of filtrate water that is coming out of the press. As it gets to a set level the pump will stop and the plates will be discharged.

Fintan, added “Control of the moisture content is done on the initial trials to achieve the perfect product by finding the balance on what is an acceptable moisture content in context to what is an acceptable production.” Access and monitoring for the plant is done remotely. Another added feature is that CCTV has been installed within the press building allowing a 24-hour visual of the press which is accessible from a mobile phone.