Recycling Household Waste System
Energy-from-waste (also called waste-to-energy), converts the energy contained in waste into renewable energy:
- direct thermal energy (with the production of hot water, superheated water or steam) for delivered into a district heating system or for industrial uses
- electricity, via steam produced in a turbo alternator
- combined: heat and electricity
In this technology, combustion depends solely on the calorific value of waste in a furnace consisting mainly of a grate, where combustion takes place via the introduction of “primary” air, and a combustion chamber in which the gas released by the combustion is burned by the injection of “secondary” air. Completing the system, a so-called “recovery” boiler transfers the resulting calories to the intended utilisation. Complete combustion of waste produces residues that can in turn be recycled. Once metal particles have been removed, bottom ash is used in roadbuilding, while the metals is recycled in the metals industry.
Reliable, efficient technologies for the environment
VINCI Environnement’s technologies are designed to optimise combustion while minimising production of dioxins, the aim being to achieve near-zero atmospheric emissions. Our roller furnace is equipped with parallel flow combustion chamber between the gas and the waste, thereby very significantly reducing nitrogen oxide and carbon monoxide emissions well below the regulatory limits.
By way of comparison, a night’s fireworks display emits 6.8g I-TEQ of dioxins (source: naei.org.uk), whereas a 150,000 t/y energy-from-waste installation compliant with the 20 September 2002 ministerial decision (France) emits 0.083g annually.
Continuous technological innovation
The cooling technologies used in VINCI Environnement’s furnace grates are continuously evolving in order to adapt to the changing nature of waste and prolong the life of installations. VINCI Environnement has developed its own water-cooling technology for its original SOGE’O water-cooled stepped grate. This is particularly well-suited to high NCV waste being treated in small and medium-scale installations, as are fairly common in France and some other European countries. Moreover, VINCI Environnement has redesigned its large-capacity grate system with a new water-cooled roller in response to new needs arising from the combustion of waste obtained from selective collection and its pre-treatment.
Usually, the energy released by the combustion of waste is recovered in a boiler directly integrated into the furnace in order to optimise its recovery performance. This boiler produces superheated steam while at the same time cooling flue gas prior to final treatment. The superheated steam is then converted into electricity via a turbo-alternator. The resulting electricity is used in the installation’s processes and administrative activities. Any surplus (most of the electricity produced) is fed into the public grid.