Have you ever wanted to know exactly how we turn your non-recyclable waste into energy?
When our tugs and barges arrive at Belvedere’s jetty the waste containers are unloaded by two goliath gantry cranes and placed on to the trailers of our dock tractors.
These vehicles deliver the waste containers into the tipping hall of the facility and then return the empty container back to the jetty to be returned to London for re-filling at the transfer stations.
In the tipping hall the waste is tipped into one of 12 tipping bays. Each bay has a hydraulically operated door designed to minimise noise and odour during tipping. Lights on each bay indicate to the drivers of the vehicles which bay is available to receive waste.
The tipping bays open into a waste bunker that is 30m deep, 61m long and 16m wide. It can hold up to around 10,000 tonnes of waste, enough to fuel the whole plant at full capacity for five days.
Overhead cranes mix the waste to ensure a consistent quality of material is maintained throughout the feedstock and to prevent hotspots developing.
with the c.525,000 MWh
energy we generate
The EfW facility runs three combustion lines and the waste cranes feed each one in turn, ensuring that the boilers have the required feedstock for continuous 24‐hour operation.
The waste travels down the chutes onto a horizontal feeder table where hydraulically operated ram feeders push the waste onto the stoker grate.
The stoker grate is made up of alternate rows of fixed and moving cast steel bars that are arranged on a slope. The forward movement of these bars tumbles the waste slowly down the burning waste bed. The resulting burnt out product is known as incinerator bottom ash (IBA) and this falls from the base of the grate into a quench bath, it is then collected in an ash bunker. Any metals are recovered for recycling. The remaining ash is sent on our fleet of tugs and barges to an IBA treatment plant at Tilbury Docks for processing and recycling into aggregate that is used by the construction industry to build and repair London’s roads and other infrastructure. In this way we create energy from, or reuse each tonne of waste, received at our facility.
To generate the maximum amount of heat and power, primary heated combustion air is drawn from above the waste bunker and fed into the waste bed through holes in each stoker grate bar. This process dries the waste and provides the correct amount of air to allow good combustion of the waste to maximise the energy generated and gain efficiencies in exhaust gases. Taking primary air from the waste bunker also means that no odour escapes as the process maintains a negative pressure within our facility.
To help clean the flue gases and reduce emissions, secondary air is introduced and swirled above the stoker grate. This thoroughly mixes the flue gas, ensuring that the gases given off by the burning waste are thoroughly mixed, resulting in a fully optimised combustion process and lower levels of clean exhaust gases leaving the combustion chamber. Any residual harmful nitrogen oxides are treated using ammonia to convert them to water and inert nitrogen. This process is important to Cory Riverside Energy in running one of the cleanest plants of its generation.
Heat from the flue gases boils the water in the boiler tubes turning the water into super heated steam. This high energy, dry steam drives the turbine that in turn drives the generator, producing electricity.
What happens to the flue gases?
Flue gases leave the boiler and pass into a reactor tower where hydrated lime, powdered activated carbon and water are injected into the swirling gas flow to neutralise acids before passing them through one of three three fabric bag filters. These incredibly efficient filters are each made from over 2,000 individual 6m long filter bags. The neutralized exhaust gases all pass through the filters to remove any residual particles which collect on the outer surface of the bags.
We even recycle this small amount of residue, recycling it into cinder blocks for use by the construction trade.
After passing through the fabric filter bags, the cleaned gases are finally used to warm the boiler feed water before the cooled, clean exhaust gas is released through the 85 metre high stack where it is discharged into the atmosphere. This warming of the boiler feed water enables us to optimise efficiency of the facility and maximise recovery of energy from each tonne of waste processed for London. To ensure that the cleanliness of the facility is maintained, emissions are continually monitored to make sure that we stay well within the limits set down in our environmental permit.