Parnaby’s experience and confidence is clearly seen at their new full size client trial wash plant

Parnaby Cyclones recently invited the HUB-4 team to take a detailed look at their new client testing facility in County Durham. Parnaby Cyclones have designed, delivered and commissioned over 160 washing plants across the globe, and recently have designed, manufactured and built a full-size trial wash plant for the demonstration and trial running of various materials. This wash plant facility has been built specifically so that clients can process their own material through the plant, and see for themselves how effective Parnaby's technology is – a unique one of its kind in the UK, try before you buy facility.

Parnaby Cyclones have used their separation technology to improve and increase efficiency for their customers’ many diverse applications and deliver significant benefits over existing dry processing methods. As well as glass washing, sand washing, soil washing, the Parnaby trial wash plant can also be used for separation in other waste and recycling industries such as recycled aggregates, C&D waste, stone, rock, IBA, shredder light fraction, automotive shredder residue, precious metals, WEEE fines and plastics.

We caught up with Ian Parnaby to learn more about the business, plant and the technology used "We are very much a family business and very proud of that. My Grandfather, Derek Parnaby founded the business back in 1973, and now my father Adrian is Managing Director, with both myself and my brother Ben working to help drive the business forward. The initial technology was developed within the coal industry, separating the rock from the coal by the use of natural medium density separation techniques. This further developed into dense medium separation with the use of magnetite to create a suspension, allowing for much more accurate separation. Over the years’ we have perfected the technologies of separation and now within the recycling industry, we are using our vast expertise of natural medium separation to provide a highly effective ‘closed-loop’ process for our clients."

"Now we have the trial plant, clients can really have confidence with wet separation techniques knowing that they can successfully process their own material. We invite them to bring as much material as they wish to our site for trial processing, and we always ask them to bring their worst material, so that they can see for themselves what will happen – seeing is believing and today is no exception, as we have invited a potential new client to join us." We took a look at the trial wash plant with Ian, and met Graham Lambert, Managing Director of Prestige Aggregates who had brought along his worst-case scenario MRF glass material to be processed. Ian explained "Normally the biggest problem within MRF glass is the organic content, the plastic, cork, paper and fibre. As we ultimately want the glass product to go back into re-melt, it's critical to remove this type of contaminated material, and the majority of clients don't know the exact make-up of their raw material, so it's down to our expertise to make sure the separation process works effectively. With Graham's raw material today, I am confident that we can produce a good clean re-melt specification glass product through one pass of the wash plant. After that, on our clients’ own sites, it would go through an optical sorting process and then back into the foundry for re-melt."

"It's a two-fold benefit to our customers here for testing, not only can they bring their worst-case scenario material to us to run through the plant, but we can analyse it to see what's in it, weigh it, and conduct a complete LOI (loss on ignition) test for them prior to, and after processing."

Most MRF glass is 50mm down to around 15 micron, the thickness of a human hair, and the Parnaby process can recover product down to 100 micron (10th of a mm), meaning that they can reliably recover around 98% of glass above 100 microns through this process.

The ProcessThe Parnaby washing plant is best visualised as two smaller circuits working together to form the overall system. The primary system is the washing/separation section of the plant, which is running continuously. The secondary system is the water treatment section of the plant, which is also running continuously. Dirty water leaves the washing/separation circuit to be processed by the water treatment circuit. ‘Clarified’ or recycled, cleaned water then is re-introduced back to the washing/separation circuit. From first turning on the washing plant, this continuous full closed loop system is cleaning its water automatically at a rate of approx. 120m3/hr.

Washing & SeparationThe waste material is loaded into a hopper, taken up a conveyor which has an over-band magnet to take the heavier ferrous metals out, and then into the barrel where it is mixed with water. The inclined rotating barrel is designed to separate out the lighter material which floats down the barrel to a trommel screen where it is de-watered and expelled. The heavier material (in this case glass) sinks down within the barrel and is caught by the integral spiral, and is driven up to the top of the barrel where it exits. An attrition exists within the barrel and this helps scrub and liberate any paper that may be glued to the surface of the glass. The whole barrel spins and a bath of water is run at 1 inch above the height of the spiral, meaning that the lights float over and the heavies sink. The length of the barrel is for efficiency and the width of the barrel is for capacity.

As the floating material exits the barrel's trommel screen, it goes onto further de-watering via an inclined vibratory screen. This screen is inclined to increase residency time for aided de-watering. Again Parnaby use stainless steel wedge wire panels of 1mm aperture. The liquid collection tank below or ‘balance tank’, recirculates this liquid back up to the barrel feed launder as a continuous process to receive and flush in new material. The effluent bleed point is also located on this tank, constantly with a controlled overflow to send the dirty wash water to the effluent treatment section of the plant.

At the top end of the barrel, all heavy, dense material such as the glass and ceramics have sunk and been scrolled up by the internal welded scroll within the barrel. This material is then discharged onto the glass washing and rinsing screen. The material is rinsed with a series of spray bars to wet screen through the various product size fractions required. This rinsing also helps liberate any final organics or contamination, this fine glass is then pumped into the horizontal cyclone tangentially and swirls around creating a vortex in which the lighter particles are drawn to the middle and out through the vortex tube to a dewatering screen. The heavier particles are thrown by centrifugal force to the wall of the cyclone and are discharged at the opposite pointed end. More cyclones can be used in the process to create the desired combination to produce the required quality of final product.

The dynamic effect of the Parnaby Barrel Separator, plus the natural difference in density, efficiently cleans and removes the contamination. Any paper and plastic recovered by the cyclones is consolidated with the paper and plastic initially removed by the barrel separator to produce a common discharge point of these materials from the plant. The different final fractions are then fed to a conveyor and stock-piled, all this in just one pass of the plant.

Water TreatmentThe first part of the water treatment section of the system is the Parnaby Water Cleaning Cyclones. As the diagram shows the coarse paper particles <100um – 1mm are recovered and extracted prior to further treatment of the cyclone overflow in the DAF (Dissolved air floatation) system. The Parnaby Water Cleaning Cyclones again use dynamic effect to separate material this time on size not density. The solids are removed from the water to help take solids loading away from the rest of the water treatment equipment. The Parnaby DAF system is a combination of both mechanical and chemical processes, where the chemical (flocculent) is used to pull together solids (+ charge) to the chemical which is negatively charged. This means very small particles of paper fibre are consolidated into larger solids. As the solids collect they float to the surface for removal. To aid in the floating of organics, the vessel is introduced with a curtain of micro-bubbles. These solids are then removed with a mechanical skimmer located on the top of the DAF, sending the solids to the buffer tank before final pressing through the Parnaby Belt Press.

Solids from both the top and bottom of the Thickener/DAF system are delivered to the buffer tank. Here the buffer tank stirrer is used to ensure a homogenised state of the sludge before filter pressing. As with all processes a more consistent feed material ensures more consistent operation and de-watering capability of the filter belt press. The sludge is pumped from the buffer tank to the reception hopper positioned over top of the filter belt press. Here a paddle within the reception hopper distributes the sludge evenly over the width of the belt. Additional flocculent chemical can be added at this stage to aid in the de-watering of the sludge. As the material initially travels over the top of the filter belt press a lot of the moisture is drained through the belt membrane. The remaining solids are then squeezed between the two belts over and under a series of compression rollers to push out the remaining moisture.

The filter cake is removed at the opposite end of the machine, with a scraper to clean the belt's Additional cleaning of both top and bottom belts is facilitated with two self-cleaning spray bar systems, one dedicated to top belt cleaning, the second dedicated to the cleaning of the bottom belt. Belt cleaning is a continuous process when the machine is running, so the belt is always cleaned before receiving the next load of sludge. Moisture from the belt press is collected in a steel collection tank and is pumped back to the thickener DAF system, and therefore kept in circuit, cleaned and re-used as spray water back on the washing plant section of the process, and for the belt membrane cleaning.

Trommel FinesIan Parnaby added an important point "The process that we have developed is also a great way to deal with Trommel fines within the MRF glass recycling industry. This heavily contaminated Trommel fines material can be fed through our system in one pass, and we can produce a very clean glass based aggregate. This saves money for our clients who don't have to then pay for any unnecessary landfill. Also, as the industry standards and requirements change we have the added expertise with enhanced dense medium technology to reach the desired product specification."

What did the client think?We asked Graham Lambert, Managing Director of Prestige Aggregates what he thought of the process "The material is wonderfully clean, its going through at a good rate which is important to us for getting volume through, and we now know that the optical separators can easily take care of the final stage of separation. I’ve seen the material at the start and the comparison with the end product is unbelievable. Just getting it to this stage gives me a lot of faith that we can reclaim even more glass for re-melt."

To learn more about Parnaby please visit www.parnaby.co.uk or call +44 (0)1388 720849