Requirements and challenges
They approached R&B Industrial for a solution to remove / separate light plastic waste material from their composting / processing site in Bournemouth, Dorset, for which we proposed an energy efficient, turnkey solution.
Solutions
Design a series of separator / extract hoods across conveyor / grading screens, providing very specific capture velocities to separate the light plastic waste from other compost material. It was crucial to maintain a constant capture velocity across the 2.0m wide separator screen; this was achieved by creating a ‘plenum-effect’ within the ‘pick-up’ hoods.
Design of Duct conveying system ensuring correct transport velocities, and minimal system resistance / pressure drops
Design, manufacture and installation of cyclone separator with drop-out chamber and rotary valve, discharging waste plastic material into skip underside. Modelling of the cyclone air-flow characteristics was carried out to ensure an efficient cyclone (cut-off frequency approx 40micron) with medium pressure drop, ensuring all the light plastic product was discharged through the drop-out chamber and rotary valve.
Design manufacture and installation of fan loading box / chamber,22 Kw fan, fitted to clean air, exhaust side of cyclone, and complete control panel, including energy efficient variable speed drive, and all associated controls.
![](https://www.rbindustrial.co.uk/wp-content/uploads/2021/02/Cyclone_Ducting_green.jpg)
Outcome
The inverter drive enables fine tuning of the air-flow / capture velocities to pick up more / less product with different grades / types of compost.
Similar cyclone separation systems previously installed onsite have a number of disadvantages compared to the R&B Industrial ‘new style design’:
They are energy inefficient as the fan is fitted on the air inlet of the cyclone, with the product passing through the fan. A comparable system being fitted with a 45 Kw fan / motor.
The fans can be prone to damaged impellers, running out-of-balance, and greater noise.
Shorter fan life-span, as the compost has high ammonia / nitrous oxide concentrations which rot the internals of ducting / fans etc. very quickly.
With a run time of approximately 8 hours / 5 day week the energy savings equate to approx £4,000 pa. Providing a system payback of less than 2 years, compared to the previous style of separator system design.
![](https://www.rbindustrial.co.uk/wp-content/uploads/2021/02/Ducting_Extraction_System.jpg)