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Energy-from-Waste

Why?

Waste which cannot be recycled or composted can often be used to generate energy, heat and to collect residual materials for recycling.  This is carried out through the Energy-from-waste (EfW) process. This is the recovery of renewable energy in the form of electricity and/or heat from the controlled incineration of residual waste.

Fact:

23% of renewable energy comes from energy from waste facilities - the equivalent to 726,000 tonnes of oil.

Collection

Collection

Waste collection vehicles discharge their waste into bunkers where the waste is mixed to ensure an even burn in the furnace.

Control

Control

Water sprays and induction fans are used in the reception hall to reduce levels of dust and smell.

Preparation

Preparation

The waste is loaded by crane into a feed hopper, then travels down the feed chute into the furnace.

Furnace

Furnace

Inside the furnace, a series of grate bars move the waste through the furnace where it is dried and burned at temperatures of around 1000°C. Burning waste in the furnace creates 2 different materials:

  • Hot flue gas - which is then used to create energy.  This is known as renewable energy.
  • Incinerator Bottom Ash - which can be used in construction.

 

Incinerator Bottom Ash

Incinerator Bottom Ash

The burned waste produces Incinerator Bottom Ash or IBA. The IBA drops into a quench tank then along a conveyor to a storage pit. Magnets above the conveyor extract ferrous metals from the ash for recycling. Remaining IBA is sent to an Ash Recycling Plant and is subsequently used as a construction material.

Gas

Gas

The hot flue gases travel through a boiler transferring the heat to water which is runs through the boiler pipes. The hot water creates steam and the steam drives turbines which then generate electricity.

The gases from the burned waste are thoroughly cleaned by a cleaning system of adding 1) Lime to neutralize acid gases and 2) Carbon to remove dioxins and heavy metal. The gas then passes through a fine fabric filter to capture any remaining particles before being released through a chimney. Collected particles from the fabric filter are stored in a silo before going to a special waste disposal.

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