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Dipartimento di Ingegneria "Enzo Ferrari"

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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.

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.

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.

Ottani, F.; Pedrazzi, S.; Paris, R.; Montanari, M.; Allesina, G.

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.

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.

Ottani, F.; Parenti, M.; Moscatelli, G.; Pignagnoli, A.; Valli, L.; Morselli, N.; Pedrazzi, S.; Allesina, G.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.