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Ferrara waste-to-energy plant

Via Cesare Diana 44, Ferrara

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The Ferrara waste-to-energy plant is located at Via Cesare Diana 44, inside the “geothermal energy” complex, where Ferrara´s district heating plant is also located. The plant, which has been operating with one treatment line with a daily potential of 150 metric tonnes since 1994, recovers the heat generated by burning waste and converts it into electricity and thermal energy.
The district heating plant´s operations can be adjusted based on climatic conditions and user consumption. If needed, part of the steam generated by combustion is discharged from the turbine and transfers energy to the adjacent district heating plant, the main purpose of which is to produce, accumulate and distribute thermal energy to the residential network from three sources: geothermal energy, waste-to-energy and the methane gas plant.
Of the production sources used by the district heating plant, the waste-to-energy plant is in second place in terms of quantity produced. The first generation source is the thermal energy originating from geothermal fluid, extracted from the subsoil through two wells. A third source, used to produce hot water, is the heating plant consisting of seven methane-fuelled boilers.
The waste-to-energy plant has been usingtwo new waste-to-energy lines since 2008. These were built, in accordance with the provincial waste management programme, to handle the disposal of unseparated municipal waste and special waste produced in the province of Ferrara.
The maximum authorised capacity is 130,000 metric tonnes of incoming waste per year.

Page update 26 August 2015

 
    Number of waste-to-energy lines
    2
    Total thermal capacity
    Approximately 55.8 MWt
    Combustion technology
    Water-cooled moving grate incinerators
    Waste disposal capacity
    Max. 460 tonnes/d with LCV of 10,465 kJ/kg
    Annual operation
    8,000 hours
    Rated electric power
    13.0 MWe
    Disposal and recovery codes
    D13 and R1
    Type of waste accepted
    Municipal waste; non-hazardous special waste


    Environmental compatibility with current regulations (Legislative Decree 152/06)

    The waste-to-energy plant makes enables the disposal of a variety of waste through combustion. The heat this generates is exploited to produce heat and electricity.

    1 - Waste receipt and storage.
    The plant has two pits, with a total capacity of 5,000 m3.

    2 - Combustion.

    The plant is equipped with two water-cooled moving grate incinerators able to incinerate up to 9.6 metric tonnes of waste each per hour, with a lower calorific value of 2,500 kcal/kg. The alternating movement of the rungs of the moving grate ensures that while the waste progresses to the combustion chamber, it is mixed to facilitate combustion and decrease the amount of uncombusted materials in the remaining slag. The air needed for the incineration process enters the combustion chamber through the grate (primary air) and through the openings located on the side walls (secondary air). The primary air is suctioned from within the waste storage pit in order to keep the pit in a vacuum, thereby preventing the spread of odours to the outside air. In addition, to increase energy efficiency, before the primary air enters the combustion chamber it is pre-heated through heat exchangers which use the steam generated by the boiler. To ensure that combustion is complete, the residues are then conveyed to the post-combustion chamber, the size of which ensures that fumes remain at a temperature above 850°C for at least two seconds. Two methane-fuelled support burners which turn on automatically based on the fume temperature ensure that this temperature is maintained, even if there is waste with a low calorific value. Also in the post-combustion chamber, the first fume purification phase is carried out with the injection of an ammonia solution for nitrogen oxide abatement (selective non-catalytic reduction process - SNCR). Once the slag from the combustion reaches the end of the grate, it falls into a tank of water to ensure it is no longer burning and is subsequently transferred to the storage pit by way of extraction and transport systems.

    3 - Steam generation.

    To produce electricity, after the fumes generated by combustion have passed through the post-combustion chamber, they are sent to a heat recovery boiler (steam generator) which produces superheated steam at a pressure of 47 bar and a temperature of 400°C.
    The water-tube boiler has the dual function of recovering the heat contained in the fumes and cooling them for the subsequent purification phases. The fumes enter the boiler at approximately 950-1,000°C and exit at approximately 180°C, to then be sent for purification.

    4 - Fume purification.

    The two lines are equipped with a completely dry fume treatment system, consisting of different devices placed in succession for each line: a first purification stage with the abatement of the solid particulate in the bag filter which uses hydrated lime and active carbon as reagents, and a second stage entailing the injection of reagents such as sodium bicarbonate and active carbon, with an additional passing of the fumes through the bag filter and a final section for the further reduction of NOx with a catalytic system (SCR).

    5 - Cogeneration of electricity and heat.

    The steam coming from the lines, which began operating in 2008, is sent to a single turbo-alternator with nominal electric power of 13 megawatts. The cogeneration system makes it possible to produce electricity to be sent to the national grid as well as heat for the district heating network, which serves residential and industrial users. The steam exiting the turbo generator is then sent to an air-cooled condensing system.

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    • 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.

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    Termovalorizzazione dei rifiuti: smaltimento sicuro con recupero di energia
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