Facts and figures

The technical solution

The Energy from Waste plant at North Yard uses the energy stored in non-recyclable waste to produce heat and electricity. This called "combined heat and power"; the technology makes optimum use of the energy stored in the waste.

The plant consists of four unique processes that operate together.

Storing the waste the best way

The Waste bunker

Refuse delivery vehicles drive into the fully enclosed tipping hall and deposit the waste inside a concrete bunker. Each tipping bay is equipped with a roller shutter door which is closed once the waste has been tipped into the bunker. The area is operated under negative pressure so that no odours or litter can escape the building. Once tipped, the waste is then moved by mechanical grabs to the combustion chamber where it is burned at high temperatures.

Managing the hot side of the process

Boiler and bottom ash

The waste automatically burns on the combustion grate at temperatures of up to 1,300 °C. The residue arising from the combustion of the waste, called the incinerator bottom ash (IBA), is collected for further recycling. The recycled ash is then used as an aggregate substitute, for example in road-building. Alternatively, it can be used for quarry reclamation. The IBA amounts to about 23 per cent by weight of the waste delivered to the plant (about 57,000 tonnes per year).

Cleaning the flue gas to stringent limits

The APC System

The Air Pollution Control (APC for short) system is the process that removes potentially harmful substances from the flue gas. For the plant at North Yard, MVV utilises a process called SNCR (selective non-catalytic reduction) together with the injection of dry sodium bicarbonate (also used as baking powder) and activated carbon, together with a fabric filter.

The residue of the APC, including the fly ash, is transported off-site in special sealed containers to the north of England under contract with a specialist contractor. APC residues are classified as hazardous because they are alkaline (like cement).

The emissions are reduced to below very stringent regulatory standards before being released to the atmosphere. MVV continuously monitors the majority of emissions from the facility. Other trace emissions must be monitored by sampling; this is carried out at regular intervals as required by the Environment Agency and with its agreement. The emissions data are logged and stored and reported to the Environment Agency. They are also available on a weekly basis on MVV’s website. [Link to emissions data archive]

The Environment Agency acts as an independent monitor of the plant’s outputs. If limits were breached, it has the power to shut down the plant and impose fines accordingly.

Highly efficient processes for maximum energy generation

Using the energy

In the boiler, water is heated by the heat from the furnace to up to 420°C at a pressure of 60 bar. The steam is sent to a high efficiency steam turbine which generates up to 22.5 MW electricity and 23.3 MW heat. The steam is used to heat the Dockyard and Naval Base, plus potentially in the future houses and offices in Plymouth. The majority of the electricity is consumed by the dockyard and naval base. The balance of electricity is exported to the national grid through an existing connection point.

The net efficiency of the plant averages 39 per cent, reaching a maximum of 49 per cent – compared with around 23 per cent for a standard EfW plant without Combined Heat and Power (CHP). This efficiency is significantly higher than other processes like gasification or anaerobic digestion.

Our Office

Devonport EfW CHP Facility

Creek Road
Plymouth
PL5 1FL

+ 44 1752 393 150

 

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Waste Delivery Enquiries
Martyn Stapleton

+44 7866 190 497

General Enquiries
Karen Purdy

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Jane Ford

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