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.

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.