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Faenza biomass thermoelectric power plant

Via Convertite 6, Faenza (RA)

  • 1 / 1   Faenza biomass thermoelectric power plant

Company “ENOMONDO”

The plant is located in Faenza at Via Convertite 6 and consists of a single combustion line, called CTE, which began operating in May 2010.

The plant complex also includes a composting plant able to process 30,000 t of organic and lignocellulosic waste to be sent for the production of high-quality mixed composted soil improver.


Page updated 26 August 2015

 
    Number of combustion lines
    1
    Total thermal capacity
    Approximately 44.5 MWt
    Combustion technology
    Air-cooled moving grate incinerators
    Disposal capacity
    Approximately 450 t/d with LCV of 9,378 kJ/kg
    Annual operation
    7,800 hr
    Rated electric power
    13.7 MWe
    Type of biomass
    Pomace; wood; special waste (dry non-reusable fractions), RDF

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

    The waste-to-energy plant makes it possible to recover energy by burning a variety of biomasses. The heat generated by this process is exploited to produce heat and electricity.

    1 - Fuel receipt and storage.
    The vehicles bringing the solid fuels are weighed upon entering the facility, where there are two load cell weighing machines, one for entering vehicles and the other for exiting vehicles. The vehicles then take internal roads to the unloading area.

    To minimise the environmental impact of odours and particles, the vehicles unload directly inside the storage shed.

    • Fuel movement section: Fuels are moved using tractor loaders that load and mix the fuel used in the boiler. The mixed fuel is sent to a screw hopper; from there, it arrives directly on a conveyer belt to the hopper which feeds the boiler.
    • System for feeding fuels into the combustion chamber: The loading inlet consists of a sheet metal hopper fed directly by the conveyer belt, through a system which controls the dispensing of fuel. The hopper is connected to the incinerator via the loading duct, which conveys the fuels to the combustion chamber; the ducts are water-cooled. The duct must remain full of fuel while operating, which ensures that there is a seal between the inside of the combustion chamber and the outside, thereby preventing the entry of air. Between the base of the hopper and the entrance to the relative loading duct is a hydraulic guillotine door, which ensures that the loading channel is protected from any high flames coming from the incinerator.

    The fuels are pushed into the combustion chamber by a hydraulic piston-driven feeder, the speed of which can vary based on the characteristics of the fuel, so as to achieve a uniform distribution of the fuel on the combustion grate.

    2 - Combustion.
    The air-cooled moving grate incinerator is able to use up to 18.7 t/h of biomass with a lower calorific value of 9,375 kJ/kg.
    The alternating movement of the rungs on the moving grate ensures that the biomass is mixed as it progresses to the combustion chamber. Mixing the waste facilitates combustion and reduces the presence of unburnt materials in the final slag.
    The air needed for the combustion process enters the combustion chamber through the grate (primary air) and through the openings located on the side walls (secondary air). In addition, to increase energy efficiency, before the primary air enters the combustion chamber it is pre-heated by heat exchangers which use the steam generated by the boiler.
    The air needed for the combustion process enters the combustion chamber through the grate (primary air) and through the openings located on the side walls (secondary 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 biomass 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 50 bar and a temperature of 480°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 purification line includes:

    • A selective non-catalytic system (SNCR) to reduce nitrogen oxides in the combustion chamber;
    • quenching tower;
    • chemical cooling tower (Lime/Bicarbonate and active carbon);
    • bag filter;
    • selective catalytic system (SCR) to reduce nitrogen oxides;
    • final wet safety treatment.

    5 - Cogeneration of electricity and heat.
    The energy generation system is set up for the cogeneration of electricity and heat.
    The turbo-alternator used in the plant is nothing more than a two-stage condensing turbine, with low-pressure steam discharge at the exit of the first stage.
    The steam discharged (at a pressure of 5 bar A and a temperature of 175°C) is collected by the low-pressure manifold and then sent to the thermal degasser, to be used for the steam consumption of the power plant and of the directly connected Caviro Distillerie facility.
    The energy generated by the alternator coupled with the turbine shaft is used to satisfy plant requirements and the remaining portion, approximately 85% of the energy generated, is partially transferred to the Caviro Distillerie facility and the rest to the national grid.
    The steam discharged from the turbine´s second stage (at a pressure of 0.12 bar A and a temperature of 49.4°C) is sent through transfer tubing with a diameter of 1,200 mm to a condensing system, the size of which is suitable for receiving steam in emergency conditions from the turbine´s by-pass valve unit.
    The condenser is installed above the roof of the office and services building, and the condensate reservoir (hot well) as well as the vacuum assembly are located below it.

    The emissions point is monitored in compliance with the requirements of current regulations.

    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, oxygen, temperature, flow and pressure.


    A data acquisition system then 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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