The main critical issue for the environmentally friendly operation of thermal power station fuelled by woody biomass concerns the fine powders and nitrogen oxides (NOx) emission, being responsible for about 90% of the potential environmental and health damage. However, for systems larger than 100 thermal kW, emissions can be effectively reduced.

By the bag filters adoption is possible achieved an abatement of 99% of the particulate, even very fine and with a diameter below 10 μm. Similarly, the NOx formation can be significantly reduced by the so-called “secondary denitrification interventions” such as the SCR (Selective Catalytic Reduction), already applied at a large scale, which involves the injection of ammonia into the boiler flue gases: ammonia reacts at temperatures of about 300 ÷ 400 °C with the NOx present in the combustion gases, reducing them to molecular nitrogen and water in the presence of a catalyst placed inside an appropriate reactor.

The separate application of bag filters and SCR denitrification could be not practicable in the case of medium-sized biomass plants, both for the high investment and operating costs and for the large equipment size.

Thanks to the use of a pelletized catalyst, that is highly active even at temperatures as low as 140 °C, RSE demonstrated the possibility to integrate both techniques inside the pre-existing and already installed bag filters, without the need for additional space and by quick and cost-effective modifications. Compared to the traditional solution with separate devices, this arrangement requires very short installation time and offers the advantage of the extreme compactness of the integrated abatement system, resulting in a space saving and in a reduction of the investment and maintenance costs.

During previous research, the technology developed by RSE has been successfully validated through a field experimentation carried out on a pilot-scale plant installed at the Tirano (SO) biomass-fueled thermal power plant. Later, considering the positive results achieved during the field experimentation, the operator decided to apply the RSE technology also on a full-scale plant, appropriately modifying the bag filter already installed and working at its Sondalo (SO) biomass-fueled thermal power plant.

Subsequently, the CARBOTERMO company also expressed interest in evaluating the feasibility to install the technology developed by RSE in its biomass-fueled thermal power plants.

Therefore, according to a specific collaboration agreement signed with the above mentioned company, in the reference period the RSE pilot plant for the combined and simultaneous abatement of combustion particulate matter and NOx has been installed and operated under real operating conditions at CARBOTERMO’s thermal power plant in Cesano Boscone (MI).

The objective of the field experimentation was to evaluate the energy and economic advantages of the RSE technology compared to the traditional flue gas treatment system already operating on the same plant, consisting of a bag filter and SCR-DeNOx reactor installed as separate units.

The Report is available on the Italian site