S.S. 309 Romea 2.6 km, Ravenna
Ravenna Energy Recovery Plant and Plant for the Production of RDF from municipal solid waste
The plant is located at 2.6 km on S.S. 309 Romea, in Ravenna. The plant sector includes Ravenna Energy Recovery Plant and Plant for the Production of RDF from municipal solid waste a waste-to-energy system for refuse-derived fuel (RDF), special waste which can be assimilated to municipal waste and hospital waste, and a facility that automatically selects municipal solid waste with thickened RDF production.
The two plants are functionally and technically interconnected. The RDF production section is currently broken down into two processing lines which execute successive phases of grinding, sifting and mechanical and physical separation. Line 3, dedicated to the dry/wet selection processes through successive phases of grinding and sifting, began operating in June 2011 and is used for assimilable bulky waste and assimilable waste. There is also a section used to store the product obtained or possibly the analogous product obtained from third parties. The waste-to-energy section aims to recover the energy from the RDF. Finally, a silo for the temporary storage of combustion ashes and particles produced on site is directly connected to the waste-to-energy plant.
Page updated 26 August 2015
The plant consists of a section for the production of RDF (dry combustible fraction) from municipal solid waste and assimilable non-hazardous special waste, broken down into three processing lines which execute successive phases of grinding, sifting and mechanical and physical separation, and a waste-to-energy section (fluid bed incinerator) which recovers energy from the RDF.
1 - Waste receipt and storage.
The special waste is placed on a treatment line used for the dual phase of grinding and removal of iron particles. The product of this phase and the RDF are then transferred to fuel the incinerator while the hospital waste, provided in closed packaging, is sent directly to the incinerator on its dedicated line.
2 - Combustion.
The Ravenna waste-to-energy plant incinerator uses fluid bed technology, which employs a bed of sand that is kept suspended by the primary combustive air, within which the refuse derived fuel (RDF) is released. This type of incinerator is able to incinerate approximately 6 metric tonnes of fuel per hour, with a lower calorific value of 4,000 Kcal/kg. Besides the combustion and fluidisation air, limestone and a watery ammonium solution are dispensed into the incinerator. The first has the purpose of reducing the formation of sulphur oxides and increasing the ash softening temperature, while the second reduces the formation of nitrogen oxides (selective non-catalytic reduction process - SNCR).
3 - Steam generation.
The hot fumes generated by combustion move to the energy recovery section (boiler) where, through the appropriate heat exchangers (evaporators), their thermal energy is transferred to the water, transforming it into steam. The boiler is the type with membrane-lined walls, consisting of a single cylindrical body with hanging vertical-tube exchangers, and the fumes pass through it horizontally.
4 - Fume purification.
The plant is equipped with a fume treatment system consisting of different devices placed in succession: a selective non-catalytic nitrogen oxide reduction (SNCR) section which injects a vaporised ammonia solution into the post-combustion chamber, a multi cyclone for particle abatement, a dry reactor for the injection of sorbalite, a bag filter and a wet washing tower which works by flushing with a soda solution.
5 - Cogeneration of electricity and heat.
The superheated steam generated by the boiler is transformed into electricity by a turbine with nominal electric power of 6.25 MW. The step-up transformer increases the voltage of the electricity generated by the turbo-alternator unit from 6 kV to 15 kV, and it is then directly transferred to the national grid.
The plant is equipped with a Continuous Emissions Monitoring System (CEMS) which has automatic analysers functioning 24 hours per day to continuously monitor the quality of atmospheric emissions.
A suitably heated sample probe continuously transports a sample of the gas from the plant´s chimney to the analysis booth where the instrumentation is installed. The sample is put into the Fourier transform infrared spectroscopy (FTIR) analyser, which continuously detects the absorption spectra of the compounds to be measured. A mathematical process is used to compare the spectra with the typical spectra of the substances being investigated. The comparison makes it possible to determine the quantitative values (concentrations) of the elements and compounds analysed.
Besides the FTIR system, there are other continuous analysers and meters needed to complete the fume analysis by determining other parameters such as: particles, organic compounds, mercury, oxygen, temperature, flow and pressure.
A data acquisition system (SADE) also continuously provides the values obtained by calculating the half-hourly and daily averages of the concentrations measured, which are compared with the maximum admissible limit values set by the Control Bodies. These data are also provided on the group´s website, where they are automatically updated every half hour.