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• New asphalt recycling systems completed by BG Europa

30th November 2012 - BG Europa (UK) Ltd has recently supplied and installed asphalt recycling systems on two  Gencor and Barber Greene batch plants for a major aggregate producer in the UK.

Planings milled from the road network and asphalt plant waste are a valuable source of aggregate and bitumen. Recycled materials have a value equal to the constituents that they replace in the final mix. With escalating oil costs the financial benefits of recycling bitumen bound products are increasing year on year.

In addition the environmental benefits of recycling a finite resource such as bitumen signify a move to a lower carbon and more sustainable method of construction.

The recycled material is graded to provide a 0-10mm and 0-20mm feed stock which is fed to the plant through individual RAP feed bins.

The layout of both plants and the required positioning of the recycle bins provided challenging engineering design projects for the in-house team. Key to the successful design was the installation of a support platform for the weighing conveyor which did not compromise traffic movements and provided safe access for maintenance.

The systems are nominally designed to allow the addition of 20% recycled asphalt product (RAP) to the hot mix batch at a 45 second batching rate. However when the full capacity of the system is utilised the systems can allow the addition of 25% of RAP by weight.

The plants each comprise two 15 ton capacity recycle bins specifically designed to handle marginal aggregates. The bin features a vertical discharge end bin wall with the opposing wall at 15° from vertical. The two sloping side walls are at 60° and form a self-relieving discharge opening onto the belt feeder.

All conveyors and feeders are driven by high efficiency Nord bevel helical IE2 gear units providing energy efficient high torque operation.

An inclined conveyor feeds RAP to the weighing conveyor by starting and stopping in a fully loaded condition.

The weighing conveyor is suspended on loadcells for accurate material weighing. During the weighing phase the conveyor is driven at low speed until the target weight of RAP is achieved. When the batch calls for RAP, a pneumatically operated valve system opens the steam extraction ducting and the charging chute. The weighing conveyor is then started at high speed to rapidly discharge material to the mixer. When mixer charging is complete the feed chute and steam duct are closed to prevent dust escaping.

For shutdown the weighing conveyor can be driven in reverse to allow RAP to be cleaned out of the recycle bin and conveyor system.