Sutton builds 'Super-MRF' to meet recycling targets

A new 24,000 tonnes a year MRF will play a key role in ensuring that the London Borough of Sutton hits the ambitious targets for recycling it has set, culminating in 80% by 2005. LAWE reports on the new facility.

The new Materials Recycling Facility recently opened by the London Borough of Sutton will process 24,000 tonnes of dry recyclables each year. The materials which will be put through the MRF come from the Council's Dual Wheeled Bin Recycling Scheme which is currently achieving a 36% recycling rate in the areas on the scheme.

Overall, the borough is achieving a 42.6% recycling rate. The latter includes home composting (with 27,000 units provided to householders since 1992) and seasonal green collections, which are borough-wide and bring in over 200 tonnes each week between May-November.

The MRF has been built by A&J Bull Ltd, the borough's waste disposal contractor, which is a part of United Waste Services Ltd. A variation to the existing contract will allow Sutton to meet its own challenging recycling target of 50% by December 2000. Negotiations will take place later to establish a way of reaching Sutton's next target - to recycle 80% of its waste by 2005.

The MRF project involves a profit-sharing approach between A&J Bull and Sutton. A private company, Green Recycle Ltd, which previously managed Sutton's smaller MRF used for sorting plastic bottles and cans, has been re-employed by A&J Bull Ltd to operate the new MRF.

The MRF is staffed by a mix of able bodied and people with learning difficulties. This is an arrangement which Sutton wishes to continue since it enables individuals with learning difficulties to learn new skills and be gainfully employed.

Plant operation
The MRF equipment is capable of handling up to 10 tonnes per hour of pre-separated recyclable domestic waste. O.Kay Engineering Services Ltd supplied the "Super-MRF" to waste management specialist A&J Bull Ltd.

In order to sort successfully 24,000 tonnes per year of newspapers, magazines, mixed papers, card, cardboard, aluminium and ferrous cans, plastics, textiles and contaminates waste over a 15-year period, O.Kay devised a highly automated system.

Included in the plant are a Bezner Bag Opener, a vibratory Bezner horizontal screening machine, a Bezner Inclined Sorting Machine, an O.Kay ZigZag paper/card separator, an O.Kay Bag Opener, as well as the more conventional magnetic separation and eddy current technology.

The Bezner Inclined Sorting Machine, which sorts materials by shape, incorporates some interesting new features. The machine consists of a 3,000mm wide x 5,000mm long conveyor (powered by a 4kW drive unit) set at an angle with one side (its right in this case) lower than the other. The slope created causes body-shaped materials (cans, plastic bottles etc) to roll to the lower side of the conveyor where they fall on to a specially positioned collector conveyor. In addition to the gravitational effects of the slope, two rapping devices placed under the conveyor belt and powered by 0.75kW drive units disturb the cans etc, further inducing them to roll.

The flat material (news and pams etc) remains on the inclined sorting conveyor, as it is much less prone to roll down the slope. Moreover, a moving chain curtain suspended diagonally over the conveyor and powered by a 1.1kW drive unit further restrains bulky/flat material from moving down the slope. Due to the design of the curtain, body-shaped materials can pass relatively unhindered. The Bezner Inclined Sorting Machine is stated to give a high separation quality, has a low energy requirement and takes up less space than a trommel.

The Bezner Vibratory Sieve Screen, Type BSM 50/2250, works on a horizontal rotating principle, having an eccentric radius of 50mm and a rotation of 160 min-1 which is driven by a 3.45kW drive unit. The material on the 2,250 mm wide x 4,600 mm long screen is shaken. The agitation causes the <50 mm material fraction to be screened off in two screening stages. The remaining material proceeds to the next stage. Material is assisted in the required direction of travel by the screen's 15° slope. Features of the machine include an even feed across the screen (due to the design of the inlet); delivery of material in a flat format, facilitating downstream processes and removal of most of the small glass and "sharps."

The new MRF was opened in July by The Mayor of Sutton, Councillor Lal Hussain, Councillor Paul Burstow, MP and Robert J Wheatley, Group Chief Executive, United Waste Services Ltd.



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