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Ravenna F3 incinerator

Located at the Baiona Ecological Centre, Via Baiona Ravenna

  • 1 / 1   Ravenna F3 incinerator

The incineration plant is located at the Baiona Ecological Centre in Ravenna and is authorised to dispose of 40,000 tonnes of municipal and special (including hazardous) waste per year.

Page updated 26 August 2015

 
    Number of waste-to-energy lines
    1
    Total thermal capacity
    18,500,000 Kcal/hr
    Combustion technology
    Rotary drum incinerator and static chamber
    Waste disposal capacity
    125 tonnes/d
    Annual operation
    7,680 hr
    Rated electric power
    4.2 MW
    Disposal code
    D10
    Types of waste accepted
    Special waste, including industrial hazardous waste (loose solid waste, solid and liquid waste in skips and containers, pumpable sludge, organic and inorganic liquid waste)

    The incineration section, where the high-temperature reactions take place leading to the total incineration of the waste, comprises a rotary drum incinerator and a static chamber.

    1 - Acceptance and checking of waste.
    The waste accepted at the plant complies with the Hera Group approval procedure. The incoming waste is subject to a rigorous control programme (sampling and analysis) to verify the chemical characteristics.

    2 - Waste receipt and storage.

    Loose solid waste, dehydrated sludge and organic slime arrive on lorries or in containers and are unloaded and stored in special pits which are accessed through high-speed doors. The storage area is kept in vacuum conditions to prevent the spread of unpleasant odours. The intake air is used as combustion air.

    The total volume of the pit is approximately 1,200 m, of which 1,000 m is designated for receiving and storing waste and 200 m is devoted to the preparation of the homogenous load of solid waste to be sent to the incinerator.

    The loose solid waste is taken from the pit by means of a bucket crane, homogenised in the special pit and reduced to the appropriate dimensions for incineration, if necessary, by a rotary blade shredder. It is then taken from this area and unloaded into a hopper that feeds the incinerator. An extractor located at the bottom of the hopper then transfers the waste to the rotary drum by means of a vertical channel with a double clapper to prevent the fumes from escaping during loading.

    The solid waste in drums and boxes is transferred packaged on pallets and stored in a dedicated paved area covered by a roof, with a safety curb and collection channel. The waste is fed directly to the rotary drum incinerator through the double clappers of the vertical loading channel, by means of a lift located in the top front area of the rotary drum.

    The pumpable sludge is unloaded into a hopper which has a usable volume of 60 m equipped with a covering and aspiration system to prevent the spread of unpleasant odours to the outside air and the intake air is sent for incineration in the static chamber. The waste is delivered mainly in gully suckers or water trucks. With the help of a screw pump with bridge breaker, the sludge is transferred to a reciprocating pump at the head of the rotary drum.

    The (organic and inorganic) liquid waste is transferred by tankers to two unloading tanks and then sent to dedicated storage tanks. To prevent volatile organic products from being released into the atmosphere during unloading operations, the water trucks are fitted with a nitrogen inlet system. Acid waste is unloaded using the same methods, but is sent directly to storage tanks without going through the unloading tanks. The tanks are equipped with a nitrogen treatment system, the gas emissions from which are sent for incineration.

    The total volume of the F3 incinerator tanks is 950 m. All the tanks are made of carbon steel and those used for acid storage are internally vitrified.

    The organic liquids are then taken from the storage tanks and sent to a pair of tanks where a homogeneous load suitable for fuelling the incinerator is prepared. The liquids taken from the tanks by pumps fuel the incinerator burners via a dedicated closed-loop pipe system, in order to ensure recirculation.

    3 - Combustion.

    The plant is equipped with an incinerator consisting of a horizontal rotary drum suitably lined with a refractory material, which is used for the incineration of solid waste, drums, sludge and liquid waste and a static chamber equipped with three burners for liquids and an auxiliary methane burner, the operations of which are automatically regulated by the outgoing fume temperature controller.

    4 - Steam generation.

    Before moving on to the purification section, the fumes leaving the post-combustion chamber are cooled to 220-260 C in a heat recovery boiler, resulting in the production of superheated steam at 350C and 30 bar. The superheated steam produced in the boiler fuels a 4.2 MW turbo-alternator unit for generating electricity.

    5 - Fume purification.

    The NOx abatement system ("DENOX") is the non-catalytic type (SNCR - Selective Non Catalytic Reduction). The NOx contained in the molecular N2 fumes is reduced by means of the injection of a urea solution reagent into the first vertical radiant channel of the boiler. There is an electrostatic filter with 2 electrical fields in succession for particle abatement. After the electrostatic filter comes the fume washing column, which is divided into 3 sections:

    • in the lower section ("acid circuit") cooling (quenching) and saturation of the fumes takes place with the absorption of the halogenated acid gases (HC1, HF, HBr) in bubble cap trays;
    • in the intermediate section ("undercooling circuit") the fumes are cooled for the abatement of volatile heavy metals (especially mercury) and halogenated organic micropollutants (PCDD and PCDF); soda can also be added to increase the SO2 and SO3 absorption capacity;
    • in the upper section ("basic circuit") SO2 and SO3 are absorbed and the residual traces of halogenated acid gases are neutralised through the addition of soda.

    Each section is served by a specific recirculation circuit.

    The cold fumes leave the washing column at a temperature of 40 - 45C. They pass through a fume/fume heat exchanger in which they are post-heated to 90 - 110C by the hot fumes leaving the electrofilter at a temperature of 220-260C, which are therefore cooled to 175 - 195C before entering the washing column.

    The fumes leaving the fume/fume heat exchanger then pass through the steam/fume heat exchanger which is designed to ensure that the temperature of the fumes entering the "tertiary" treatment section is always at least 120C, to prevent the compression of particles on the outer walls of the bag filter.

    The fumes undergo a finishing treatment in the next bag filter where a reagent powder made of activated carbon and calcium hydroxide is added. The reagent is deposited on the outer wall of the filter bags, forming a thin layer where the following processes take place:

    • abatement of residual traces of particles, particularly sub-micron particles;
    • abatement of dioxins and residual traces of volatile heavy metals by the activated carbon through adsorption;
    • abatement of the residual traces of acid gases by Ca(OH)2 through neutralisation.
      The purified fumes are released into the atmosphere at 100 - 120C through a special chimney, 60 m high.

    6 - Water physicochemical treatment.
    The F3 incinerator is equipped with a physicochemical plant for the treatment of discharges from the fume washing column. The incoming current is brought to a pH of 8.5 using milk of lime, added with ferric chloride, a precipitant for metals and anionic polyelectrolyte for flocculation. The water is separated from the sludge using sedimentation tanks with lamellar packs and then filtered on beds of sand and activated carbon. The sludge extracted from the sedimentation tanks is sent to a thickener, from which it is then extracted and sent for dehydration in a centrifuge

    7 - Energy recovery.

    The superheated steam produced by the steam generator is sent to a turbine coupled with an alternator, which has planned power of 4,200 kW at the terminals. The electricity produced satisfies the requirements of the plant; the excess amount is transferred for consumption by the adjacent wastewater treatment plant (TAS) and to the national grid.

    The plant is equipped with a double continuous Emissions Monitoring System (EMS) in the chimney, which continuously analyses concentrations in atmospheric emissions.

    Regular checks are also conducted on the chimneys, according to the frequencies defined by the integrated environmental authorisation, for the parameters which cannot be continuously monitored by certified laboratories.

    The monitoring programme implemented, which was approved as part of the integrated environmental authorisation, also includes checks on pollutant deposits in the soil; the soil and laurel matrices are investigated.

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