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FILIPPO OTTANI

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Pubblicazioni

2024 - Airborne pathogens diffusion: A comparison between tracer gas and pigmented aerosols for indoor environment analysis [Articolo su rivista]
Puglia, M.; Ottani, F.; Morselli, N.; Pedrazzi, S.; Allesina, G.; Muscio, A.; Cossarizza, A.; Tartarini, P.
abstract

The evaluation of airborne pathogens diffusion is a crucial practice in preventing airborne diseases like COVID-19, especially in indoor environments. Through this transmission route, pathogens can be carried by droplets, droplet nuclei and aerosols and be conveyed over long distances. Therefore, understanding their diffusion is vital for prevention and curbing disease transmission. There are different techniques used for this purpose, and one of the most common is the utilization of tracer gas, however, it has limitations such as the difference in size between the gas molecules and the respiratory droplets, as well as its incapability to take into account evaporation. For this reason, a new method for evaluating the diffusion of respiratory droplets has been developed. This approach involves the use of an ultrasonic emitter to release and disperse pigmented aerosols, and a colorimeter for the following quantitative evaluation. A comparison with the tracer gas technique has been carried out, showing for the pigmented aerosols methodology a response that is dependent on different relative humidity conditions, while there is no clear difference in the dispersion of tracer gas at high or low humidity.

2024 - Biochar powders coating to improve evaporative cooling in Maisotsenko-cycle systems [Relazione in Atti di Convegno]
Morselli, N.; Fracasso, F. D.; Cossu, M.; Ottani, F.; Puglia, M.; Pedrazzi, S.; Allesina, G.; Muscio, A.; Tartarini, P.
abstract

This work presents an experimental study on the performance of biochar powder coatings on aluminum surfaces for use in indirect evaporative coolers based on the Maisotsenko cycle. The performance of the biochar coated samples was compared to cellulose-coated aluminum samples and uncoated ones. Results showed that biochar coatings improved the performance of uncoated aluminum, with the 150 μm particle size coating offering performance comparable to cellulose. However, wetting times were longer, which has implications for spraying strategies.

2024 - Corrigendum to “Seeking the synergistic potential of biochar integration in municipal composting plants for techno-economic and environmental leverage” [Sustain. Energy Tech. Assess., 64 (2024) 103717, 1–17] (Sustainable Energy Technologies and Assessments (2024) 64, (S2213138824001139), (10.1016/j.seta.2024.103717)) [Articolo su rivista]
Ottani, F.; Pedrazzi, Simone; Morselli, N.; Puglia, M.; Allesina, G.
abstract

2024 - Experimental investigation of moisture influence on biochar and biochar-soil blends thermophysical properties [Relazione in Atti di Convegno]
Morselli, N.; Puglia, M.; Ottani, F.; Pedrazzi, S.; Allesina, G.; Muscio, A.; Tartarini, P.
abstract

Biochar is a carbonaceous and porous material obtained through pyrolysis or gasification. It can be extremely valuable as soil amendment since it increases the organic matter content and fertility, the microbial activity, the water retention, and the crop yields. Moreover, biochar soil application has the potential for long-term carbon sequestration which makes its application to soil interesting even outside agricultural crops. In recent years, the study of the variation of the thermophysical properties of the soil induced by mixing with biochar has attracted interest. In this work, the effect of the water content on thermal conductivity of biochar was investigated by means of the guarded hot plate apparatus λ-Meter EP500e. The same procedure was applied to various mixtures of biochar and soil. Furthermore, the specific heat was measured in order to obtain the thermal diffusivity in the various conditions through a calorimeter. Solar reflectance was also measured following the ASTM C1549 using a solar spectrum reflectometer SSR-ER. The obtained thermophysical properties can be used for the evaluation of the temperature trend of soil at different depths during the seasonal variations.

2024 - Seeking the synergistic potential of biochar integration in municipal composting plants for techno-economic and environmental leverage [Articolo su rivista]
Ottani, F.; Pedrazzi, S.; Morselli, N.; Puglia, M.; Allesina, G.
abstract

This work comprehensively investigates the technological, economic, and environmental implications of biochar application to a municipal composting facility through various combinations of in situ gasification or biochar trading. The aim is to find the optimal solution to minimize environmental impacts and to maximize resource utilization over the year. The study hybridizes an existing composting facility using various gasification plants chosen in between the commercial SynCraft model, resulting in a pioneering study where a gasifier is integrated in a composting plant. The techno-economic feasibility of each scenario is obtained calculating the payback time, estimating the annual biomass demand, evaluating the seasonal variability of biomass, and setting as a key-point the amount of produced electrical energy and gasification biochar. The scenarios differ in the installed gasifier sizing (500 kW, 1 MW and 1.7 MW) and the supplementary amount of biochar that may be purchased, applied at a 3 % w/w rate on the treated organic mix. Economic results reveal that a purchase of all necessary biochar is infeasible; therefore, the installation of a gasifier for biochar self-production should be always considered. For the 500-kW gasifier a 25-year payback (weighted average cost of capital = 10 %) that reduces to 14 or 12 years for the 1 MW gasifier, respectively with and without purchase of supplementary biochar. The 1.7 MW gasifier is the most cost-effective option, but it requires high initial investments. Additionally, this work studies both the carbon dioxide equivalent storage, thanks to the biochar utilization, quantifying the corresponding Carbon Credits in 3652 credits for the best scenario (through VERRA method), and the reduction of methane emissions during composting that are abated by nearly half in the best scenarios. Aiding biochar into composting operations emerges as a promising way for waste management optimization, balancing economic viability and environmental sustainability. On the other hand, some operational issues are identified and discussed in this work, but the findings highlight the significance of innovative approaches in shaping the future of composting facilities and advancing the circular economy.

2024 - Using infrared imaging to measure the friction coefficient during pin-on-disk sliding wear tests [Articolo su rivista]
Ottani, F.; Lusvarghi, L.; Bolelli, G.; Amenta, F.; Pedrazzi, S.; Morselli, N.; Puglia, M.; Allesina, G.
abstract

In a standard pin on a disk tribometer, the friction coefficient under a sliding wear configuration is commonly obtained from the experimental measurement of the tangential force, which is usually achieved through either a load cell attached to the pin holder or a torque meter attached to the disk shaft. This paper presents an alternative method to measure the friction coefficient using a combination of thermal imaging and a reverse thermal model. The measurement of the temperature evolution of the pin, allow to solve the friction heat generation problem between the mating surfaces. Heat generation is influenced by the friction coefficient and the test parameters, whilst conduction is also significantly affected by the thermophysical properties of the materials. Experimental tests with PTFE pins with lamellar bronze filler and Cr2O3-coated stainless steel disks showed an average difference of the friction coefficient of about 12% between the new thermal and the standard measurement.

2023 - A preliminary evaluation of different residual biomass potential for energy conversion in a micro-scale downdraft gasifier [Articolo su rivista]
Puglia, M.; Morselli, N.; Ottani, F.; Pedrazzi, S.; Tartarini, P.; Allesina, G.
abstract

2023 - Energy Generation Potential Through Cattle Manure Solid Phase Gasification [Articolo su rivista]
Puglia, Marco; Ottani, Filippo; Cantisani, Donato; Morselli, Nicolo; Raguzzoni, Filippo; Pedrazzi, Simone; Allesina, Giulio; Muscio, Alberto; Tartarini, Paolo
abstract

A common practice for cattle manure management, especially for farms with a small number of animals, is simply the separation of the manure solid phase from the liquid one and the subsequent spreading on the land. However, this biomass has a chemical composition similar to more valuable ones like woodchips, with the downside of the high ash content. For this reason, gasification of cattle manure solid phase in a small-scale gasifier was explored. Through this solution it is possible to provide both electrical and thermal energy to the farm, constantly throughout both the day and the year as opposed to other renewable sources like solar and wind power. In addition, a byproduct of this process is biochar, whose main application is in agriculture as soil improver and therefore it could be a valuable substitute of a fraction of the manure currently used as fertilizer. The quantity of manure available was assumed considering the typical size of an Italian dairy farm while the efficiency of the CHP system was calculated through an experimental test with a gasifier prototype. The results have been utilized for a basic comparison between the energy available through gasification and through anaerobic digestion.

2023 - Experimental investigation of chestnut shells gasification [Relazione in Atti di Convegno]
Puglia, M; Giuliani, M; Morselli, N; Ottani, F; Allesina, G; Pedrazzi, S; Tartarini, P
abstract

Fossil fuels substitution with renewable energy sources is necessary for an effective decarbonization. Biomass can represent a valid alternative to fossil fuels, reducing greenhouse gas emissions. Furthermore, bioenergy generation avoids costs and problems related to biomass disposal. This study presents the energetic valorisation of chestnut shells, a byproduct of the chestnut transformation processes. Through a thermo-conversion system based on gasification, this material was considered not as a waste, but as a resource to be exploited to produce bioenergy and biochar. The fuel gas produced through the gasification process can partially replace the LPG currently used to meet the energy required for the brulage and steam peeling processes. Experimental gasification tests were carried out to evaluate this biomass by means of a laboratory scale micro-gasifier (Imbert downdraft type). Chestnut shells were pelletized with a pelletizer machine to avoid the bridging effect inside the gasifier and increase its energy density. The fuel gas obtained was sampled and analyzed to measure its composition and HHV. In addition, the gasification efficiency was calculated obtaining a value of 70%, a result in line with the ones obtained with higher quality biomasses.

2023 - Preliminary Study of a Gravimetric Approach to the 'Solid Phase Absorption' Methodology for Tars Sampling in Biomass Gasification Processes [Relazione in Atti di Convegno]
Ottani, F.; Pedrazzi, S.; Puglia, M.; Morselli, N.; Venturelli, V.; Allesina, G.
abstract

Biomass gasification is one of the most promising and valid solutions to produce energy from renewable sources. However, today there are still problems that limit its diffusion at an industrial level. Among the main ones is the presence in the synthesis gas of condensable contaminants, the so-called tars, which accumulate in the parts of the system at low temperatures, and which can compromise normal operation, even causing the plant shutdown. Since it is not possible to eliminate tars formation, it is useful to know the quantity produced by each specific gasifier to plan maintenance and components replacement. The measurement of tars with traditional methods is complex, labor-expensive due to the long procedure and sample post-processing and provides non-real-time results. This work focuses on the “Solid Phase Adsorption” (SPA) sampling technique through adsorbent cartridges. Currently, the application of this method involves gas chromatographic analysis after dissolving the samplein a polar solvent. This study, instead, investigates the gravimetric approach and it is based on the weight of the tars captured by the cartridge. This approach maintains the advantages of SPA sampling (quick and easy sampling, compact system, low set-up time) and at the same time makes the analysis procedure more economical as no expensive equipment is used (e.g.: gas chromatographs), while ensuring accurate quantitative results.The tar content in the synthesis gas is highly variable depending on the operating conditions of the process and the used biomass. For this reason, synthesis gas was replaced by commercial cigarette smoke during this work. The aim was to use a standard fuel, containing a known and declared quantity of tars, to guarantee the total repeatability of the tests. An experimental apparatus that can hold five burning cigarettes at the same time has been created. Three repetitions of sampling were carried out with the SPA methodology and three with the standard “Tar Sampling Protocol” (TSP) methodology. The TSP is taken as the reference method as it is now the most reliable methodology. The results obtained from the "gravimetric SPA" method were compared with the values obtained from the TSP method. It can be concluded that the gravimetric SPA method represents a valid, probably even better, alternative to the current gravimetric cold trapping methods (TSP). The concentration of tars measured by SPA is on average higher than the concentration obtained by TSP: respectively 0.0019 g/l and 0.0016 g/l. This result could be motivated by the greater efficiency of the SPA method in retaining highly volatile tar compounds. In conclusion, the results obtained in this work lead to a positive evaluation of the gravimetric SPA method for the determination of tars in gasification systems and to proceed with further experiments on synthesis gas generated by real gasification processes to verify this new method.

2023 - The conductivity dilemma: How biochar grain’s chemical composition and morphology hinder the direct measurement of its electrical conductivity [Articolo su rivista]
Ottani, Filippo; Morselli, Nicolo; De Luca, Aurora; Puglia, Marco; Pedrazzi, Simone; Allesina, Giulio
abstract

Although electrical conductivity is one of biochar's fundamental properties that affects the way it interacts with microorganisms in soil applications, however its measurement is not univocal. This work starts from the results of a testing campaign on gasification biochar as the basis for a larger discussion on the parameters that affect the conductivity measurement and, therefore, the limits of the most widely used compression measuring approach. Different samples were obtained by combining sifting and grinding on a single batch of biochar. The samples were tested in a PTFE cylinder with conductive plunger and cap in a range of pressures up to 25 bar. The same biochar prepared in different ways showed different conductivity behaviors, with variation up to 85%, proving that the testing condition can strongly affect the measurement. These findings encourage the scientific community to further investigate the meaning of the results obtained with a further recommendation to properly describe the sample preparation and the testing conditions when a compression method is used. The final point of this discussion hypothesizes that neither one of the obtained conductivities truly represents the conductivity perceived by the microorganism that interacts with the char in soil applications.

2023 - Vine Leaves Harvesting and Utilization for Nutraceutical Purposes - Vine Leaf for Life Project [Relazione in Atti di Convegno]
Santunione, G.; Ottani, F.; Morselli, N.; Puglia, M.; Nigro, G.; Mora, M.; Allesina, G.; Pedrazzi, S.
abstract

VineLeaffor Live is a Emilia Romagna regional project focused on the valorization of the vine leaves of two regional grapes variety with high levels of nutraceutical compounds in the leaves: -Grasparossa‖ and -Salamino‖. The project is started on 28th September 2022 and during the first 8 months of activities a complete chemical characterization of 10 leaves samples from representative vineyards has been done. Furthermore, a first raw prototype of mechanical harvester has been developed and tested. Next activities will be analyze the presence of residual active compounds in the leaves and improve the mechanical harvesting doing and testinga second version of the machine optimized in terms of harvesting efficiency and reliability.

2022 - Experimental analysis of effective energy dosage in hot air weeding [Articolo su rivista]
Morselli, N.; Ottani, F.; Puglia, M.; Pedrazzi, S.; Tartarini, P.; Allesina, G.
abstract

2022 - HEMP RESIDUES VALORIZATION THROUGH A CO-COMPOSTING BIOCHAR PROCESS: A PILOT CASE STUDY [Relazione in Atti di Convegno]
Ottani, F.; Pedrazzi, S.; Paris, R.; Montanari, M.; Allesina, G.
abstract

2022 - Impacts of gasification biochar and its particle size on the thermal behavior of organic waste co-composting process [Articolo su rivista]
Ottani, F.; Parenti, M.; Pedrazzi, S.; Moscatelli, G.; Allesina, G.
abstract

This work investigates the effects of gasification biochar on the thermal behavior of organic municipal waste composting. Two different biochar granulometries were mixed in a 3% w/w share with the organic fraction of municipal waste and tested in nine (three per thesis and three as control) reactors of 1 m3 of volume, designed to simulate full-scale aerated static piles. The temperatures of each composter were monitored for 31 days of the active composting phase and used as key parameters for air flow tuning. After the active phase was completed, the air was turned off and the temperatures were monitored for an additional 31 days during compost maturation. Results show that biochar-aided composters run 4 °C hotter and are more stable in temperature compared to the control thesis. Experimental data were used as a basis for thermal energy modeling: the addition of fine biochar to composting material increased the thermal energy production by 0.5 MJ kg−1 compared to the control thesis; coarse biochar increased the thermal energy production by 0.4 MJ kg−1. The standard composting process, without biochar, produced 2.5 MJ kg−1. Results might serve as a starting point for further considerations in terms of composting time reduction, improvement of the final product and reduction of process related issues, such as undesired anaerobic decomposition, leachate production and temperature instability.

2022 - PRELIMINARY STUDY ON GASIFICATION BIOCHAR FOR THE REDUCTION OF SWINE SLURRY NITROGEN RELATED GREENHOUSE GASES EMISSIONS [Relazione in Atti di Convegno]
Ottani, F.; Parenti, M.; Moscatelli, G.; Pignagnoli, A.; Valli, L.; Morselli, N.; Pedrazzi, S.; Allesina, G.
abstract

The objective of this study is the evaluation of the best methodology for applying biochar from gasification in the reduction of nitrogen based GHGs emissions, in swine slurry in an open slurry-lagoon. European regulations and fundings are spurring in the direction of reducing equivalent greenhouse gases emissions, especially those derived from nitrogen. Swine farms are among the main culprits of nitrogen-derived greenhouse gas emissions. In the Emilia-Romagna region, in Italy, it is customary to accumulate slurry from large swine farms in open-air tanks, favoring important nitrogen emissions. Biochar, whether from pyrolysis or gasification, has already consistently demonstrated its ability to reduce and retain nitrogen emissions. However, a simple and economical method for applying this material on a large scale has not yet been defined. In this study, with a pilot-scale approach, we want to investigate three methodologies for applying biochar. To do this, 12 reactors of 1 m3 in volume each, were used to study three theses plus the control case, out of three repetitions. The theses considered are biochar used on floating grates (Th1), biochar used inside a contact filter (Th2), biochar used inside a nitrifying-denitrifying filter (Th3). The results confirm the effectiveness of using biochar for reducing greenhouse gas emissions from swine slurry. The combination of a nitrifying-denitrifying process with a substrate such as biochar, has guaranteed the best performance in terms of reducing greenhouse gas emissions. Furthermore, this has made it possible to obtain a final slurry aided with biochar that can be used as a soil amendment.

2022 - Preliminary testing of a simplified methodology for indoor environments evaluation correlated to airborne transmission: The case of a university classroom with vertical low-velocity ventilation [Relazione in Atti di Convegno]
Puglia, M.; Ottani, F.; Muscio, A.; Cossarizza, A.; Tartarini, P.
abstract

2022 - Tribological behaviour of PTFE composites: Interplay between reinforcement type and counterface material [Articolo su rivista]
Amenta, F.; Bolelli, G.; D'Errico, F.; Ottani, F.; Pedrazzi, S.; Allesina, G.; Bertarini, A.; Puddu, P.; Lusvarghi, L.
abstract

In this paper, we studied the sliding wear behaviour of polytetrafluoroethylene (PTFE)-based composites under conditions relevant to rotary seals. We specifically aimed to investigate the interactions between different particle-based reinforcements (lamellar or spheroidal bronze particles, PEEK particles) and different counterfaces (uncoated or Cr2O3-coated stainless steel), building upon our own previous work on fibre reinforced-composites to make up for the paucity of literature papers on the role of counterfaces. Pin-on-disc tests were performed under different load and speed conditions using spherical-tipped composite pins against coated or uncoated stainless steel discs to mimic the (initially) non-conformal, unidirectional sliding contact of lip seals. Though all composites attained a steady-state regime controlled by a tribochemical wear mechanism, namely tribofilm formation, there were significant differences among the tribofilms produced by different tribo-systems. Systems that released fine, oxidized metal debris (bronze-filled PTFE and/or uncoated counterpart) developed >1 μm thick, continuous tribofilms on both mating surfaces. Thickness and continuity of the tribofilm decreased with a non-wearable Cr2O3-coated counterpart and/or PEEK as a filler. The tribofilm was conducive to lower steady-state friction, but not lower wear, against stainless steel, whereas all performances (friction coefficient, specific wear rate) were levelled out with a Cr2O3-coated counterface.

2021 - A low impact alternative to common weed control systems: the case of syngas-powered flame weeding [Relazione in Atti di Convegno]
Morselli, N.; Puglia, M.; Balboni, C.; Ottani, F.; Parenti, M.; Santunione, G.; Pedrazzi, S.; Allesina, G.; Tartarini, P.
abstract

In this work, a simple model was created to estimate the benefits of replacing the LPG, currently used in flame weeding, with the syngas generated from a biomass gasification system. Results shown that 60.1 kg ha-1 of agripellet are enough to substitute 16.4 kg ha-1 of LPG when a gasification efficiency of 70% is considered. The model shown a CO2 generation of 49.8 kg ha-1 for each treatment using the LPG device and 94.5 kg ha-1 for the biomasspowered weeder which is, however, a biogenic source of carbon with a neutral impact on the climate. Moreover, for the gasification facility, a 3.3 kg ha-1 co-production of char was considered which led to the possible stock of 9.6 kgCO2 ha-1 each treatment. Eventually, the proposed model suggests that a net saving of 58.5 kgCO2 ha-1 can be realized if LPG flame weeding treatment is replaced with a syngas-powered flame weeder.

2021 - A preliminary study on torrefaction pretreatment of hemp stem for waste-toenergy valorization of woody biomass from flower hemp cultivation [Relazione in Atti di Convegno]
Parenti, M.; Ottani, F.; Puglia, M.; Morselli, N.; Pedrazzi, S.; Allesina, G.
abstract

Hemp cultivation gained an important role in recent years. Two major production chains can be defined, one dedicated to the cultivation of hemp for the production of fiber and wood and the other relating to the production of inflorescences for the market of derivative products containing cannabidiol, better known as CBD. The problem that will be highlighted and addressed in this article is related to the enhancement of cannabis production waste for CBD. In particular, since flowers are the only useful part of crops dedicated to this purpose, to date the stems of plants are considered a difficult waste to exploit. The alternatives are few and one of the simplest and most immediate is certainly the waste-to-energy process of this material; in fact it is not possible to obtain fiber and wood of good quality from the CBD production chain, because these crops are optimized for flower production. Waste-to-energy, on the other hand, requires mechanical pre-treatments in order to use the raw material within the typical thermal conversion systems (e.g. biomass boilers, pellet stoves, gasifiers). The great obstacle to being able to efficiently transform these wastes into fuel, lies in the very nature of the hemp stems as the fibers constituting the outermost part of the plant stems are well known for their good mechanical resistance. These properties however become a problem when the material has to be treated with standard machinery for pelleting and briquetting, as they hind the mechanical components suitable for the purpose giving rise to maintenance and breakdown issues. To solve the problem, the possibility of decreasing the mechanical properties of hemp fibers has to be investigated, so as to permit the transformation of this material into an economically sustainable fuel. It was therefore decided to pre-treat the stems of the plants with a torrefaction process, to sufficiently weaken the fibers to be mechanically treated. Shear resistance was tested with a “piston device” to obtain a qualitative estimate of the mechanical behaviour of the hemp fibers only; in fact it is assumed that to solve the problem, it is sufficient to concentrate on the weakening of the fiber instead of the entire stem of the plant. In conclusion, a first estimate is defined of the minimum energy necessary for the roasting of the plant stems, sufficient to weaken the fibers to make the mechanical transformation of the stems of hemp plants into fuel, possible and economically sustainable.

2021 - Co-composted biochar (Combi) production and its effects on ocimum basilicum plants growth [Relazione in Atti di Convegno]
Ottani, F.; Parenti, M.; Santunione, G.; Pedrazzi, S.; Allesina, G.
abstract

In agriculture, in recent years, more and more attention has been given to the COMBI. COMBI is a soil improver obtained from a composting process of organic material with biochar, added at the beginning of the process itself. Biochar has been used for several years and many studies have shown the benefits it brings when applied to soils, while COMBI is still little studied. This article aims to demonstrate both the effects of COMBI on the growth of Ocimum basilicum specie plants and to quantify the best quantity to be applied within the substrate. The experimental trials were performed in a greenhouse with controlled temperature and humidity, according to the following growth tests theses: Control: Soil for gardens composed mainly of peat (CTRL); thesis 1: Soil mixed with COMBI at 10% v/v (COMBI10); thesis 2: Soil mixed with COMBI at 20% v/v (COMBI20); thesis 3: Soil mixed with COMBI at 40% v/v (COMBI40); thesis 4: Soil mixed with COMBI at 80% v/v (COMBI80); thesis 5: 100% COMBI (COMBI100). The results showed good growth of basil plants in the COMBI10 and COMBI20 cases, compared to the control. COMBI80 and COMBI100 theses, on the other hand, did not lead to positive results; in particular COMBI100 did not allow either seeds germination in most cases. To compare the quality of the basil plants, the total amount of essential oil for CTRL, COMBI10, COMBI20 and COMBI 40 theses was extracted and quantified.

2021 - Emission analysis of syngas combustion and flammability limit assessment [Relazione in Atti di Convegno]
Puglia, M.; Parenti, M.; Tartarini, P.; Ottani, F.; Allesina, G.; Pedrazzi, S.; Tioli, J.
abstract

Gasification of biomass can be a very effective technology to fight climate change due to the carbon negativity of the process. However, syngas combustion could release a variety of pollutant compounds such as carbon monoxide and nitrogen dioxide. Improving the emissions of syngas combustion is very important in order to promote the diffusion of small scale gasifiers that often have no complex flue gas treatment systems. In this work a study on syngas combustion from a small scale gasification system is presented. A combustion chamber designed after a preliminary numerical evaluation was built to test different geometrical configurations. Two metal plates were used to modify the combustion chamber geometry in order to test different flare shapes. An experimental campaign with an emission analyzer was carried out to identify the best combustion chamber shape and to evaluate the pollutant released by syngas combustion. To further explore syngas combustion, the flammability limits were evaluated through the “Le Chatelier” equation and considering the presence of various inert gases.

2021 - Experimental heat transfer evaluation in a porous media [Relazione in Atti di Convegno]
Pedrazzi, S.; Allesina, G.; Puglia, M.; Morselli, N.; Ottani, F.; Parenti, M.; Tartarini, P.
abstract

The evaluation of the heat transfer coefficient between hot gases and biomass particles is not easy to estimate because of the concomitance of exothermic and endothermic reactions. However, a proper evaluation of this coefficient is fundamental to design pyrolysis apparatus. This paper presents an experimental study regarding wood pellets heating up in a batch reactor using hot exhaust gases from an engine. Temperature and flow of hot gases entering the reactor were measured over time. A first test was carried out using hemp hurd pellets with 15% of sawdust, and a second one using the carbonized pellets obtained from the previous test. Fresh pellets have a higher thermal capacity compared to carbonized pellets that is almost inert and follow a more regular heating trend. Heat transfer was calculated considering the energy released by the exhaust passing through the biomass as the sum of the energy absorbed by the pellets and the thermal losses. Convection is the predominant heat transfer mechanism and the convective heat transfer coefficient was evaluated. Finally, the energy for the pyrolysis of 1 kg of fuel was evaluated. About 0.7 kWh/kg are necessary to pyrolyze this kind of pellets while an heat transfer coefficient of 110 W/(m2K) was estimated for the inert packed bed.

2021 - Modelling of tar and water vapors condensation in a commercial micro-scale gasification power plant [Relazione in Atti di Convegno]
Morselli, N.; Barbolini, F.; Ottani, F.; Parenti, M.; Pedrazzi, S.; Allesina, G.; Tartarini, P.
abstract

In this work a psychrometric model was developed in order to estimate the water and tar vapors that can condense in the syngas filtration stage of a commercial micro-scale gasifier: The Power Pallet 30 from All Power Labs. Starting from the gravimetric tar concentration analysis performed on the PP30 in previous works, the model was able to estimate that in the first 1.5 hrs of operation, more than 5 g of class 4 and 5 of tars condensate in the pipeline. The model applied to a real temperature profile of the gasification facility suggested a minimum operating temperature of the gas line of 42°C to avoid the water condensation. Instead, to significantly reduce the condensation of light tars, the minimum working temperature resulted in 70°C.

2021 - Numerical and experimental evaluation of flue gas recirculation for syngas combustion [Relazione in Atti di Convegno]
Allesina, G.; Puglia, M.; Morselli, N.; Pedrazzi, S.; Parenti, M.; Ottani, F.; Tartarini, P.
abstract

Biomass gasification can be an interesting solution for the energy production to fight global warming and the environment pollution. The flare apparatus is an essential component of gasification systems, but considering small scale ones, it is often quite simple and not very optimized. A way to minimize the NOx production during the combustion is recirculating the flue gas into the flames, making the combustion zone cold and inhibiting the nitrogen oxides formation. In this work different flare designs were numerically evaluated through OpenFOAM software to find the best flare shape that can guarantee the flue gas recirculation. Simulations results were verified building and testing a flare with an optimized geometry for a small-scale gasification system. Numerical simulation and experimental tests shown that it can be possible to design a simple flare for syngas combustion that guarantee low combustion temperature through flue gas recirculation.

2020 - Enhanced heat transfer in tubes-in-shell heat exchanger for syngas cooling: A comparison between conventional and perforated twisted tape inserts [Relazione in Atti di Convegno]
Morselli, N.; Ottani, F.; Parenti, M.; Tartarini, P.
abstract

In this work, twisted tape inserts were applied to a tube-in-shell heat exchanger for syngas cooling. A comparison between plain tube, standard full twisted tape and perforated twisted tape was carried out by measuring the thermal-hydraulic performance and the heat dissipated. Results shown a considerable increase of heat transfer using twisted tapes for syngas cooling and perforated twisted tapes performed better than full twisted tapes, reaching a thermal-hydraulic efficiency of 1.24 and increasing the Nu number up to 47% respect of the plain tube. Perforated twisted tapes confirmed the literature results even applied to syngas cooling and are of great interest as heat transfer enhancers to reduce the heat exchanger dimensions, key parameter for micro-scale gasification power plants.

2020 - Equilibrium modeling of hemp hurd gasification [Relazione in Atti di Convegno]
Pedrazzi, S.; Morselli, N.; Puglia, M.; Ottani, F.; Parenti, M.
abstract

The aim of this work is modeling a gasification process where a non-conventional biomass is used as fuel: Hemp hurd residues. An equilibrium model of the gasification reaction was implemented in the PhytonTM software environment. Syngas composition, syngas higher heating value, tar production and gasification cold gas efficiency were evaluated at different value of biomass moisture starting from biomass ultimate analysis and reaction equivalence ratio (ER) value. The model is able to predict char and tar production as function of biomass composition, moisture and ER. A comparison with experimental data obtained from hemp hurd gasification was done to validate equilibrium model results. Gasification tests were performed using a low capacity lab-scale gasification reactor designed to use about 1 kg per hour of dry biomass fuel. Results show small errors between model results and experimental result. Several simulations were performed to assess the gasification dependency on selected boundary conditions like biomass moisture and ER of the gasifier.

2020 - Experimental and modelling evaluation of possible solutions for compact design of producer-gas heat exchangers [Relazione in Atti di Convegno]
Morselli, N.; Puglia, M.; Mason, J.; Parenti, M.; Ottani, F.; Tartarini, P.
abstract

An experimental and numerical campaign was carried out to investigate the performances of tubes in shell heat exchanger applied to cool down the producer gas of a small-scale commercial wood biomass gasifier built by All Power Labs. Producer gas is contaminated with soot and tars that condensate under 300 °C, for this reason the heat exchanger was designed in order to have an in-situ cleaning mechanism. The heat exchanger was tested both with standard plain tubes and with a set of metal twisted tapes (TT) with the aim of enhancing the heat transfer between producer gas and water. Temperatures and mass flows analyses shown a maximum increase of thermal power output and overall heat transfer coefficient respectively of 19% and 76% when TT are applied to the standard plain tubes in shell heat exchanger. Numerical simulations shown a consistency in the trends giving an average discrepancy with experimental results of the 12%.

2020 - Hemp by-product valorization [Relazione in Atti di Convegno]
Pedrazzi, S.; Morselli, N.; Puglia, M.; Santunione, G.; Parenti, M.; Ottani, F.
abstract

This paper investigates possible circular economy pathways which can be applied in different hemp agriculture regimes using hemp by-products. Not only open field hemp cultivation but also the case of hemp growing in indoor greenhouses is presented. Several valorization technologies has been applied to achieve economic and environmental advantages for the farmer: Composting of green and wet residues, combustion and gasification of hemp stalks and hurds, co-composting of hemp green residues (leafs and branches) and biochar obtained from hemp ligneous residues (stalk and hurd). Every pathways is discussed from the practical point of view and also considering the entire framework including all the stakeholder involved in the process.

2020 - Implementation of a portable petrol - powered generator fueled through a tabletop biomass gasifier [Relazione in Atti di Convegno]
Puglia, M.; Morsell, N.; Ottani, F.; Tartarini, P.
abstract

Portable petrol powered generator are very popular around the world. They are used mostly when electrical power from the grid is not available, for example in blackout scenarios, remote areas or for temporary use and they are basically irreplaceable in many cases. The idea behind this work is to substitute the fossil fuel as the energy source of these systems with the syngas produced through biomass gasification, that is a carbon negative energy process in order to achieve a complete decarbonisation as soon as possible. Coupling gasifiers and reciprocating internal combustion engine is a very old technology, however there are no small and cheap systems available that can be successfully connected to this kind of generator. The laboratory scale gasifier presented in Lisbon at the 27th EUBCE in the paper titled: “Design and first tests of a micro lab scale (2kg/h) gasifier” after a series of test has been improved enhancing its efficiency, gas quality and power output. A GeoTech GGP 4000 ES petrol powered has been selected to operate with the syngas from the gasification system and its intake manifold has been modified. The gasifier is able to operate with different kinds of biomasses like wood fir pellets, wood chips, vine prunings pellets, hemp hurd etc. The fuel chosen for the test was the standard A1 ENPlus wood pellet. An Iveco air filter was used to preserve the engine from the tars and particulate present in the gas. The energetic consumption was calculated and the thermal power output from the engine exhaust was estimated measuring gas composition and the air flow and entering in the gasifier. The results from the test show that it is possible renew the way the portable petrol generator are used, making them efficient and eco-friendly without increasing dramatically the complexity of the system or the costs.

2020 - Implementation of engine exhaust gas recirculation in a fixed bed gasification reactor [Relazione in Atti di Convegno]
Allesina, G.; Ottani, F.; Parenti, M.; Pedrazzi, S.; Tartarini, P.
abstract

This study aims to increase the energy efficiency of a micro combined heat and power (micro-CHP) system able to produce electrical energy and thermal energy from wood biomass through the gasification process and an internal combustion engine. Since nowadays the engine exhaust gas is released in the atmosphere, without being exploited, the goal is to recover this gas. A fraction of gas is taken from the engine exhaust pipe and is reinserted in the gasification reactor head to provide thermal energy and a series of new reagents: A sort of exhaust gas recirculation (EGR) is created. Some tests were carried out at different fractions of EGR, 10% and 20%, on a Power Pallet 30 system (PP30) built by All Power Labs, to obtain information about syngas quality and gasification efficiency. The gas high heating value (HHV) is indirectly determined by gas chromatography that gives the syngas composition and the concentration of single compounds. The results show an increment of the nitrogen content and a reduction of hydrogen in the syngas when the EGR percentage rising. The concentration of the other gases does not change. This variation causes an HHV drop, compared to the case without EGR, which is reflected in the PP30 efficiency. Tests have revealed an increment of efficiency from 70% to 71% only in the case with EGR sets at 20%, thanks to the higher temperature at which the exhaust gas was reintroduced in the gasifier head, compared to the reactor temperature itself, that leads to an increase of syngas flow rate. Therefore, an higher gasifier efficiency has been obtained although the drop of heating value, thanks to the larger production of syngas. This higher volume of produced syngas not only can compensate the HHV drop but also bring benefit to the PP30, compared to the case without EGR. Consequently, the temperature is more important than the flow rate value or the composition of the exhaust gas reintroduced in the head of the gasifier. Taking into account the low cost of the recirculation circuit components, the EGR is a good improvement for the fixed bed gasification reactors.