waste and provides the correct amount of air to allow good combustion of the waste bed. In compliance with the Waste Incineration Directive, the combustion process operates at <850°C.
Secondary swirling air introduced above the grate through cylindrical nozzles ensures that the gases in the waste are thoroughly mixed. This results in a fully optimised combustion process and encourages low levels of toxicity in the gases leaving the combustion chamber. NOx levels are reduced by ammonia injection to the levels required in the Environmental Permit.
Heat from the flue gases heats the water in the boiler tubes turning the water into super heated steam. This steam drives the turbine which in turn drives the generator, producing electricity.
Gases and smoke produced during combustion are drawn through the gas passes of the boiler by an induced draught fan.
Incinerator Bottom Ash is a by-product of the combustion process and accounts for approximately 28% of the facility's waste throughput.
The Incinerator Bottom Ash which drops from the grate into a quench bath is then pushed by hydraulic rams onto vibrating conveyors and from there falls into the ash bunker.
Any oversized metal or other objects fall off the conveyor into skips to be recycled.
The Incinerator Bottom Ash is moved by overhead ash cranes from the ash bunker into elevated loading hoppers which are positioned over an internal roadway.
Incinerator Bottom Ash is discharged from the hoppers into ash containers.
These containers are transported to the jetty on dock tractors and trailers and placed on barges to be taken to the IBA processing facility at Tilbury.
Around 170,000 tonnes of ash per year is sent for processing.
1. Flue gases leave the boiler and pass into a Turbosorp\circledR reactor tower where hydrated lime, powdered activated carbon and water are injected into the swirling gas flow. These help neutralise acids and capture heavy metal particles.