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Acerra WtE plant

Acerra WtE plant is one of the largest in Europe, being capable to dispose 600.000 tons/year of selected MSW and generates 600 million kilowatt-hours per year of electric power, a quantity enough to satisfy the needs of 200.000 families.

The plant is composed of three identical combustion and flue gas treatment lines, operating in parallel, of a power generation section and of common services, as detailed here below (see also plant block diagram):

MSW receiving section

Number of units: 1 (common to the three lines)

composed of :

Weighing station

MSW storage bunker

MSW bales breaking system

Combustion and flue gas cleaning

Number of lines: 3

Configuration of each line :

Moving grate furnace integrated with boiler

Semi−dry absorption reactor for acid gas removal (reagent used : lime milk)

Activated carbon powder injection system

Bag fabric filter no. 1 for dust removal

Lime and activated carbon (mixed reagent) injection system

Bag fabric filter no. 2 for dust removal

Flue gas reclycling facility from bag filter no. 2 to bag filter no. 1

SCR DeNOx reactor

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Extraction ID (induced draft) fan

Emissions monitoring systems

110 m high stack

Power generation section

Number of units: 1 (common to the three lines)

composed of :

Steam turbine and generator

Air−cooled condenser

Thermal cycle equipment

Auxiliary systems (demi water production plant, chemicals dosing systems)

Electric substation

Diesel emergency generators

Lime storage and milk preparation system

Number of units: 1 (common)

composed of :

CaO storage bins (no. 2 units)

CaO dissolution and lime milk preparation (No. 2 lines in parallel, one of which in stand−by)

Lime milk feeding system to absorption reactors

Activated carbon and mixed reagent storage and dosage system

Number of units: 1 (common)

composed of :

Activated carbon storage bin

Mixed reagent storage bin

Pneumatic feeding system

Ash inertization plant

Number of units: 1 (common)

composed of :

Dosing and mixing system

Ash and chemicals storage system

Auxiliary systems

Wastewater treatment plant (biological + chemical−physical)

Fly ash collection and conveying to storage bins

Bottom ash storage system

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Operation parameters

Main plant operation parameters at nominal operating conditions are summarized here below:

Furnaces:

Number no. 3

Unit capacity t/h RDF 27,07

LTV of MSW kJ/kg 15070

Unit thermal input MW 113,33

Boilers:

Number no. 3

Characteristics of produced steam (each line)

state superheated

pressure bar abs 90

temperature °C 500

flowrate t/h 126,5

Flue gas cleaning:

Number of lines no. 3

Unit flowrate per line Nmc/h 200 000 (about)

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Chemicals used :

Ca(OH)2 in aqueous suspension (lime of milk), in absorption reactor

Activated carbon powder, injected upstream bag fabric filter no. 1

“Mixed reagent” (mixture of Ca(OH)2 and activated carbon), injected upstream bag fabric filter no. 2

Ammonia solution 25% , in SCR DeNOx system

Electric power production:

Characteristics of steam fed to turbine :

state superheated

pressure bar abs 88

temperature °C 498

flowrate t/h 379,5

Electric power at generator terminals MW 106,5

Highlights of plant operation

Plant first firing: March 26th, 2009

Start of plant commercial operation: September 2009.

The guaranteed emission values of Acerra WtE plant are far below the maximum allowable by law.

The measured emission values during Acerra plant operation showed to be well lower than guaranteed values , giving evidence of the efficiency of the design and of the adopted technological solutions.

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Acerra WtE plant block diagram

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Guaranteed emission limits vs. max. permissible limits