From feeder to filterpress Terex is there every step of the way


When a Swiss customer needed an end-to-end excavation wash recycling system, Terex Washing Systems answered the call.

With thousands of tonnes of construction and demolition (C&D) and excavation waste stockpiled each year, a system that can recycle this waste into a saleable product and offer aggregates producers environmental and financial benefits is especially valuable.

And this is exactly the kind of solution Albin Borer AG, a Swiss group in construction, infrastructure and material treatment, was seeking when it began to investigate recycling the waste they were sending to landfill.

Terex Washing Systems, alongside Avesco, was then tasked with finding such a solution, which resulted in the design, manufacture and installation of a complete end-to-end excavation wash recycling system.

Everything from the feeder to the filterpress was included in the installation, which manages throughputs of 250 tonnes per hour of C&D and excavation waste while producing nine saleable products.


Family business

Albin Borer AG is an independent family-owned company that has been in business since 1932, providing quality products for infrastructure and roads, as well as a wide range of services in the construction industry.

Albin Borer AG wanted to process its own waste material accumulating from infrastructure work in its local region in Switzerland. Ultimately, it wanted to generate a saleable product and open up a new revenue stream for the business.

One key aspect of the plant design was based around high capacity on a small footprint, due to site space restrictions. In addition, limited water available on the site, coupled with environmental legislation around the use of that water, demanded additional design expertise.

This washing solution was achieved by the engineers at Terex Washing Systems in partnership with its dealer, Avesco, who designed a bespoke solution suited to specific needs.

This full ‘feeder to filterpress’ solution also incorporated crushing capability from Terex MPS, as well as Terex Washing Systems’ AquaClear full water treatment solution, incorporating a Terex designed and manufactured filterpress with the ability to process 250 tonnes per hour (tph) of feed material, and 25 tonnes of sludge/final waste per hour.

The project was managed by Terex Washing Systems and Avesco, including the complete delivery, installation and commissioning of the plant. And that service continued, with Terex and Avesco provide 24–7 after-sale support as and when required.

C&D and excavation waste

The plant combines the processes of material feeding, rinsing, crushing , aggregate scrubbing and sizing, and sand production with a full Terex Washing Systems water treatment offering, ensuring that 95 per cent of the water is recycled and reused within the wash plant.

This was all achieved on a relatively compact footprint, made possible with unique and innovative design choices.

The feed material is made up of excavation from Albin Borer’s other businesses.

An AggreScalp 125 receives feed material from the loading shovel and removes oversized stones (larger than 150mm) from the material, which is achieved by the 150mm gaps in the fingers bars installed. These oversized stones are stockpiled for later use.

Medium-size stones (80–150mm) are sent via a side chute into a feed hopper, feeding the Terex MPS crusher, a horizontal shaft impactor, HIS 3434. Since occasional pieces of metal were present within the feed material, an over-band magnet was been installed after each of the feed hoppers.

The crushed stones are either passed to a dedicated stockpile, a dry 0–40 mm, or onto the main conveyor sending the raw material to the washing plant.

After oversized stones and any metals are removed from the feed material, it makes its way up the main conveyor and enters into a Terex 6×1.8m three-deck rinsing screen.

This PreScreen rinser gives the material an initial wash before the various fractions are split with different apertures on the screen mats.

The sand (0–4mm) and water from the rinsing screen passes to the PreWash tank, which has a unique design feature that allows the operator to process difficult or dirty material and ensures production of sand products that confirm to strict specifications.

The four aggregate fractions pass into the new patented Terex HydroScrub log washer, which is a unique design for aggregate scrubbing, patented by Terex, which allows operators to hydraulically adjust the hull angle from 9° to 16°, depending on which raw material has to be treated. This gives the operator the ability to process a wider range of feed materials and is ideally suited for recycling applications.

If the raw material contains a lot of light-density contaminants like wood, roots and plastics, the angle is set up ‘high’, and floating elements are easily removed.

Similarly, if the raw material contains more clay conglomerates, the angle is set ‘low’, which results in a better stone-on-stone scrubbing. This gives better throughputs and a cleaner aggregate product, and eliminates the need for secondary scrubbing on high clay-bound or dirty material.

The post-screen of the HydroScrub classifies the material into two different sizes: 4–40mm and 40–80mm.

The 40–80mm material can be sent back to the crusher or to the dry classifying screen, while the 4–40mm material is also conveyed to the set of dry screens.


Fine sand cleaning

The water that has washed the aggregates up until this point, along with the sand, is collected in the Terex PreWash tank. This unique solution receives all of the process water from the upstream process, with the sand, extrafines, clay, contaminants, and light-density particles.

The PreWash tank allows the ability to produce sand products to specification from materials with a high silt content. The principal is to pump less volume out than is entering the tank. It is designed to ‘overflow’, gently separating out extrafines and the light-density contaminants, keeping only the 0–4mm sand, which will be sent by a centrifugal pump to the sand washing Hydro-cyclones module.

The Terex FM200 Sand Plant is part of the wider solution. It is fitted with separators and high-performance cyclones, which are also specially design for recycling applications.

The use of separators means the plant can handle the variability of material that is often the case with C&D material. This results in a reduction in losses of valuable sand product, and the production of an in-specification material.

The FM200 also features the Terex double-wash process to maximum recovery of sand through the removal of silt, slimes and clays below 63µm.

The sand slurry (0–4mm and water) is pumped to the primary separator for an initial wash, and the underflow discharges onto the dewatering screen where it receives a further rinse. Any fine sand that passes through the screen is collected in the sump and pumped to the secondary separator for a final wash.

It was necessary to double wash the material at the Albin Borer site due to the high percentage passing 63µm in the feed, which was identified in the initial laboratory testing.

After this double-wash process, the two grades of sand are dewatered onto the high-frequency dewatering screen, which reduces residual water content in the final product to 10–15 per cent.

The water from both separators containing the –63µm material is collected in a ground sump and pumped into the thickener tank, where the water management process begins.

Aquaclear water management

The waste water is pumped into a low-level thickener with flocculent added, from the central control room housing unit.

Within the low-level thickener, the waste particles of silt (–63µm) and clay combine with the ‘co-polymer’, or flocculent, to create a larger, heavier particle that sinks towards the base of the cone. The flocculent dramatically speeds up this process and allows the clean water to weir over the top weir of the thickener into a collection tank, where it is recycled back into the wash plant.

The sludge that has been collected at the bottom of the deep cone thickener is pumped into a buffer tank, where it is stored until enough volume is gathered, at which point it is transferred into a filterpress.

The Filterpress on the Albin Borer site is the Terex 165 plate press. The press plates are 2x2m, and the function of the press is to recover the last remaining water within the thickened sludge.

The filterpress has a working pressure of 16bar (232 psi). Each plate is covered in a nylon filter cloth which, when filled with sludge under pressure, force the remaining water to be removed from the sludge. This water is then recycled back into the wash plant to be used for washing aggregates and sand.

After the water has been removed from the sludge, bomb doors below the filterpress open and the hydraulic ram begins to decompress. The slurry cakes are rapidly discharged into the bay below the filterpress. Particularly sticky cakes are removed with a pneumatic plate shaker that ensures all the plates are ready for the next cycle. The cakes below can then be re-used for several applications.

Albin Borer opted for an automatic cloth wash system on its filterpress, so the lifespan of the filter cloths could be extended while optimum performance was ensured. This system cleans each cloth individually using a high-pressure water jet.

“This water management system recycles 95 per cent of the water used for this application,” Terex Washing Systems product and applications manager Johnston Patterson said.

“Albin Borer only needs a small tank of water to top up the system every so often. This has a hugely positive impact on the environment and also has financial benefits.”

The result for Albin Borer is the sustainable production of usable and saleable sand and aggregate product from C&D and excavation waste. This also has the environmental benefit of being diverted from landfill. Additionally, the water management products recycle dirty water from the process and returns a clean water back to the process again for use.

“The customer is very pleased to have a solution in place to recycle their C&D and excavation waste,” Patterson said.

“The working relationship between Terex Washing Systems, Avesco and Albin Borer has played a huge part in achieving a high level of performance for this plant.”

For more information, visit the Terex website here.

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