Modena waste-to-energy plant

The plant is equipped with a storage pit with a volume of 5,000 cubic meters.

The plant is equipped with a water-cooled moving grate furnace capable of incinerating up to 27 tons per hour of waste with a lower heating value of 2,500 kcal/kg. Thanks to the alternating movement of the steps that make up the moving grate, as they advance through the combustion chamber, the waste is mixed in a way that promotes combustion and minimizes the presence of unburned waste in the final slag. The air required for the incineration process is introduced into the combustion chamber either through the grate (primary air) or through openings above it (secondary air). Primary air is drawn in from inside the waste storage pit in order to keep the pit under vacuum, preventing the spread of odors to the outside environment. In addition, to increase energy efficiency, primary air is preheated by heat exchangers using steam produced by the boiler before being introduced into the combustion chamber. To ensure completion of combustion, the residue then passes to the post-combustion chamber, which is sized to ensure that the flue gas remains at a temperature above 850°C for at least 2 seconds. The maintenance of this temperature, even in the presence of waste with low calorific value, is ensured by two support burners operating on methane gas, which are automatically activated according to the flue gas temperature. In the post-combustion chamber, the first stage of flue gas purification is also carried out through the injection of a urea solution for the abatement of nitrogen oxides (Non-Selective Catalytic Reduction process - SNCR).The combustion slag, having reached the end of the grate, falls into a water tank to ensure its complete extinguishment, and is then transferred to the storage pit by means of extraction and transport systems.

For power generation, the flue gases generated by combustion, after passing through the post-combustion chamber, pass through a recovery boiler (steam generator) which, through a condensing steam turbine, produces superheated steam at a pressure of 50 bar and a temperature of 380°C. The water-tube boiler has the dual function of recovering the heat contained in the flue gas and its cooling for subsequent purification stages. The flue gas enters the boiler at about 950-1000 °C and exits at about 180 °C for subsequent purification.

Line 4 is equipped with a flue gas treatment system, completely dry, consisting of several devices placed in series. A system for non-catalytic reduction of nitrogen oxides (SNCR) by feeding a solution of nebulized urea into the post-combustion chamber, an electrofilter for flue gas dedusting, a dry reactor with a sodium bicarbonate and activated carbon injection system, and a bag filter and final section for further reduction of NOx with a catalytic system (SCR).

The turbine currently has an installed capacity of 24.8 MW. The electricity produced is sent to a high-voltage station and in the future, via a newly built underground power line, will connect to the Hera station in Modena Nord and will then be sold to the national transmission grid. The plant is also set up for the transfer of thermal energy.