• Energy Research

A pilot plant of a solar chimney was tested for about 7 months in a suburban area near Naples (Italy) from February to August 2020. The solar chimney is 5 m high with a square-shaped collector of 4.5 m length on each side. In this paper we report and analyse data with the aim to study the fluid dynamic performances. Correlations between air flow and ambient parameters (solar irradiance, temperature, and relative humidity) are studied. A CFD model is developed to simulate the thermal and fluid dynamic behavior of the chimney. Results are useful for a better knowledge of the performances of solar chimneys and their main operating parameters such as air velocity, flow rate, temperature, and residence time that are very useful for the correct design of solar chimneys both as electrical power plants and as atmospheric pollutant abatement plants.

The aim of this experimental activity was to evaluate the influence of ethanol fuel on the pollutant emissions measured at the exhaust of a conventional and a hybrid scooter. Both scooters are 4-stroke, 125 cm3 of engine capacity and Euro 3 compliant. They were tested on chassis dynamometer for measuring gaseous emissions of CO, HC, NOx, CO2 and some toxic micro organic pollutants, such as benzene, 1,3-butadiene, formaldehyde and acetaldehyde. The fuel consumption was estimated throughout a carbon balance on the exhaust species. Moreover, total particles number with diameter between 20 nm up to 1 ?m was measured. Worldwide and European test cycles were carried out with both scooters fuelled with gasoline and ethanol/gasoline blends (10/90, 20/80 and 30/70% vol). According to the experimental results relative to both scooter technologies, the addiction of ethanol in gasoline reduces CO and particles number emissions. The combustion of conventional scooter becomes unstable when a percentage of 30%v of bioethanol is fed; as consequence a strong increasing of hydrocarbon is monitored, including carcinogenic species. The negative effects of ethanol fuel are related to the increasing of fuel consumption due to the less carbon content for volume unit and to the increasing of formaldehyde and acetaldehyde due to the higher oxygen availability. Almost 70% of Ozone Formation Potential is covered by alkenes and aromatics.

The valorization of residual biomass plays today a decisive role in the concept of “circular economy”, according to which each waste material must be reused to its maximum extent. The collection and energy valorization at the local level of biomass from forest management practices and wildfire prevention cutting can be settled in protected areas to contribute to local decarbonization, by removing power generation from fossil fuels. Despite the evident advantages of bioenergy systems, several problems still hinder their diffusion, such as the need to assure their reliability by extending the operating range with materials of different origin. The Italian project “INNOVARE—Innovative plants for distributed poly-generation by residual biomass”, funded by the Italian Ministry of Economic Development (MISE), has the main scope of improving micro-cogeneration technologies fueled by biomass. A micro-combined heat and power (mCHP) unit was chosen as a case study to discuss pros and cons of biomass-powered cogeneration within a national park, especially due to its flexibility of use. The availability of local biomasses (woodchips, olive milling residuals) was established by studying the agro-industrial production and by identifying forest areas to be properly managed through an approach using a satellite location system based on the microwave technology. A detailed synergic numerical and experimental characterization of the selected cogeneration system was performed in order to identify its main inefficiencies. Improvements of its operation were optimized by acting on the engine control strategy and by also adding a post-treatment system on the engine exhaust gas line. Overall, the electrical output was increased by up to 6% using the correct spark timing, and pollutant emissions were reduced well below the limits allowed by legislation by working with a lean mixture and by adopting an oxidizing catalyst. Finally, the global efficiency of the system increased from 45.8% to 63.2%. The right blending of different biomasses led to an important improvement of the reliability of the entire plant despite using an agrifood residual, such as olive pomace. It was demonstrated that the use of this biomass is feasible if its maximum mass percentage in a wood matrix mixture does not exceed 25%. The project was concluded with a real operation demonstration within a national park in Southern Italy by replacing a diesel genset with the analyzed and improved biomass-powered plant and by proving a decisive improvement of air quality in the real environment during exercise.

Abstract Hydrogenative pyrolysis of waste tires, using 1,2,3,4-tetrahydronaphthalene (tetralin) as a model hydrogen donor, was carried out in a stirred batch reactor under a nitrogen atmosphere. The temperature, kept constant during each run, was varied in the range 260–430°C. Either tire granules (≈ 2 mm size) or tire particles (size less than 500 μm) were used. Liquid-phase and gas-phase samples were withdrawn at regular intervals during each reaction run. The gas samples and the gas present in the reactor at the end of each run were collected in a bag and analyzed. The analysis of samples was performed by gas-chromatography, usually with flame ionization detection (FID), although a mass spectrometry detector (MSD) was used for initial identification of the reaction products. More than 150 major chemical compounds in the gas and liquid phases, produced by the tire depolymerization, were detected and their concentrations were evaluated as a function of the reaction time. Liquid samples were also analyzed with a thermogravimetric (TG) balance to ascertain the presence of compounds having such high boiling points as to be undetectable by gas-chromatography. In order to check if the compounds detected represented all the tire pyrolysis products a mass balance was performed. The results of the investigation permit the identification of the most convenient operating conditions for obtaining complete depolymerization. Correspondingly, the recovery of chemicals achievable was determined.

Data on air quality collected by the regional network of fixed stations in the most urbanized areas of the Campania region in the south of Italy are examined. Two periods are considered: before and during the adoption of the main directives limiting human activities to fight the spread of SARS-CoV-2 infection. The first period is from the 5th of February to the 5th of March, and the second is from the 13th of March to the 13th of April. Meteorological conditions in the two periods were compared and significant differences were not observed. Therefore, the comparison of air quality data is feasible. During the second period, an intercontinental transport of particulate matter occurred. Data collected during this event (4 p.m. on the 30th of March to 4 p.m. on the 31st of March) were excluded from the analysis. The main reduction of pollutant concentration is observed for NO2 (−48% of the period average). PM10 shows a lower reduction (−17%). The PM2.5 average period concentration was quite constant, while the 98° percentile was reduced by −21%. Ozone shows, on the contrary, an increase in concentration due mainly to an increase in solar irradiation during the 2nd period, but also due to the decrease of NOx concentration. The reduction or the increase of pollutant concentration depends on the category of the station: background, industrial, residential, and traffic. In addition to air quality, the reduction of anthropogenic emissions is also studied. All the information available on the reduction of emissions from transport, industry, heating, and other main emissive sectors were collected. The results give useful insights for the development of air quality management policies that could be adopted when the sanitary emergency will end to guarantee the sustainable development of the Campania region.

Abstract Liquid phase pyrolysis of scrap tyres was carried out in a lab scale autoclave (300 cc) in the presence of 1,2,3,4-tetrahydronaphtalene (tetralin) as hydrogen donor. Experimental runs were carried out at T =380 and T =400°C and at 50 bar inert gas pressure. Liquid phase samples, withdrawn during the reaction runs, were analysed by GC–FPD technique to follow the fate of sulphur compounds. Gas phase was withdrawn at the end of each run and analysed by GC–FPD and GC–TCD. During the pyrolysis process, sulphur compounds undergo formation and consumption reactions. The fate of sulphur compounds has been modelled on the basis of a two-step reaction mechanism. Kinetic constants of sulphur compound reactions were evaluated lumping all sulphur compounds in a single group. Only about 1% of sulphur present in the loaded tyre was detected in the liquid phase, the remaining being released as H 2 S in the gas phase.

Abstract A kinetic model for the hydrogenative liquid-solid pyrolysis of waste tyres is presented. The model is tested with available experimental data obtained by running the pyrolysis of tyre particles (size The results of the investigation indicate that the first step of the pyrolysis is the rupture of weak bonds which leads to the dissolution of the tyre particles as large aggregates of molecules, in a time which is of the order of 1 min. Then, much more slowly, lighter products are released from these aggregates. At T = 430°C the large aggregates are completely transformed into stable compounds, detectable by GC, in about 250 min. At lower temperatures, T = 345°C, after 250 min 40% of the loaded tyre is still present as macromolecules not detectable by GC.