Refuse Derived Fuel Feeding and Conveying System
Solids handling specialist, Ajax Equipment, has supplied a screw based, waste handling system to a waste-to-energy pyrolysis unit manufacturer. The Ajax system comprises a twin screw feeder with hopper, three inclined screw conveyors and a plug screw feeder to discharge chopped rags into the pyrolysis unit.
Pyrolysis is an advanced thermal process that converts waste and biofuels to syngas, oil and carbon char. The syngas and oil is used to generate energy, while the carbon char acts as a fuel, producing the heat required for pyrolysis.
The waste handling system is configured such that material stored in the hopper is fed at a controlled rate via the twin screw, and then transferred by a series of inclined screw conveyors to the top of the pyrolysis unit. The waste material is then dropped into a screw compactor, which forms a plug and progressively fed into the pyrolysis chamber. Creating a plug inhibits air entering the Pyrolysis Unit, and the build-up of unwanted by-products. It also protects the feed equipment and prior material from early exposure to high temperatures from the pyrolysis process.
Like any industrial process involving bulk materials, the ease with which materials are processed is dependent upon their flow characteristics. Mark Waters, director, Ajax Equipment commented, "The materials used in fuelling pyrolysis are irregular and therefore prone to jamming most standard types of solids handling equipment. Ajax understanding of flow behaviour and their engineering expertise produce extremely tolerant equipment design which ensures the pyrolysis unit receives a constant and consistent flow of material.
On the challenges of conveying waste materials to the top of the pyrolysis unit Ajax technical director Eddie McGee said "When a screw is inclined, material tends to fall back into the prior pitch space. However, by using specially selected flights and optimising the screw's rotational speed the waste handling system is able to provide a reliable flow of fuel for pyrolysis. Chopped rags are yet another irregular material which demand real care in hopper and feeder design to ensure reliable flow and avoid material snagging or hanging up".
For more information on Ajax Equipment hopper design, screw feeders and plug screw technology call +44(0)1204 386723.