Via Cavazza 45, Modena
The waste-to-energy plant is located in Modena at Via Cavazza 45, inside a multifunctional complex in which there is also a chemical-physical plant for the treatment of liquid waste managed by Herambiente S.p.A. and a biological purification plant for residential liquid waste and wastewater, managed by Hera S.p.A.
The plant's first two lines, each with the potential to process 140 metric tonnes per day, began operating in 1980.A third line, built based on the criteria set forth in Presidential Decree 915/82, was subsequently installed, with a nominal potential of 250 metric tonnes per day. When the plant began operating at the beginning of the 1990s, the total maximum annual quantity of treatable municipal solid waste was 140,000 metric tonnes, while the maximum quantity of treatable hospital waste did not exceed 5,000 metric tonnes per year. The lines described above were decommissioned in September 2009 and permanently demolished between May and December 2011, making way for the new plant configuration. The fourth line, with an approximate disposal capacity of over 180,000 metric tonnes per year, began operating in December 2008 for functional testing and in 2009 for testing with waste. One year later, it finally became fully operational.
Page update 6 August 2015
Environmental compatibility with current regulations (Legislative Decree 152/06)
The plant as a whole is currently configured as follows:
1 - Waste receipt and storage.
The plant is equipped with a storage pit with a volume of 5,000 m3.
2 - Combustion.
The plant is equipped with a water-cooled moving grate incinerator, which is able to incinerate up to 27 metric tonnes of waste 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 above it (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 a urea solution to reduce nitrogen oxides (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 uses a condensing steam turbine to produce 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 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.
Line 4 is equipped with a completely dry fume treatment system, consisting of different devices placed in succession: a selective non-catalytic nitrogen oxide reduction system (SNCR) through the injection into the post-combustion chamber of a vaporised urea solution, an electrostatic precipitator for separating particles from the fumes, a dry reactor with a system for injecting sodium bicarbonate and active carbons and a bag filter and final section for the further reduction of NOx with a catalytic system (SCR).
5 - Cogeneration of electricity and heat.
The turbine currently has a maximum power of 24.8 MW. The electricity generated is sent to a high-voltage power plant and in the future it will connect with Heraīs Modena Nord plant through a newly installed underground power line, and will then be transferred to the national transmission grid. The plant is also equipped to transfer thermal energy.
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 plantīs 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 groupīs website, where they are automatically updated every half hour.