The main challenge for the eco-friendly operation of biomass-fired plants is the emission of fine particulates and nitrogen oxides (NOx) [1]. A reduction of 99% in particulate matter, including very fine particles with diameters below 10 μm, has been achieved through the use of baghouse filters. Similarly, NOx formation can be significantly reduced using so-called “secondary denitrification interventions,” such as Selective Catalytic Reduction (SCR). SCR, which is widely applied, involves injecting ammonia into the flue gases from the boiler. Ammonia reacts with NOx present in the combustion gases at temperatures around 300-400°C, converting them to nitrogen and water in the presence of a catalyst located in a dedicated reactor.

The separate application of baghouse filters and SCR might be impractical for medium-sized plants due to high investment and operating costs, as well as the bulkiness of the equipment. However, RSE has demonstrated that it is possible to integrate both techniques into existing baghouse filters using efficient granular catalysts that work at temperatures as low as 140°C. This approach avoids additional space requirements and involves modifications that are quick to implement and cost-effective. This integrated solution, compared to the traditional approach with separate equipment, has a much shorter installation time and offers the benefits of compactness, saving space and reducing investment and maintenance costs. It is noteworthy that this solution allows NOx reduction at 140°C and significantly improves energy efficiency compared to current practices, as conventional processes require flue gas temperatures between 320 and 350°C, leading to more than double the heat losses through the chimney.

In the first year of the PTR 2019-2021, the developed technology was tested under real operating conditions using a pilot plant for the combined and simultaneous removal of combustion particulates and NOx. This plant was installed at a biomass-fired thermal power plant operated by Teleriscaldamento Coogenerazione Valtellina – Valchiavenna – Valcamonica S.p.A. (TCVVV). The results showed that, operating at a temperature of 140°C and with a biomass combustion flue gas flow rate of 25 Nm³/h, the technology can achieve NOx removal efficiency of up to 93% and particulate removal efficiency of over 99% for PM2.5. Following the positive results from the field trial, TCVVV has fully scaled up the RSE technology, adapting the existing baghouse filter downstream of the boiler at its Sondalo plant.

This report describes the results of the experimental campaign conducted during the reference period to support the commissioning of this flue gas treatment plant and provides some economic data related to the construction and operational costs of the plant.