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Flame synthesis of Carbon NanoParticle (CNP) films is gaining strong interest for novel industrial applications because of the easy tuning of the operating conditions that enables accurate control of the chemical and physical properties of the produced CNPs. This work proposes a novelty in the synthesis of CNP films, namely the possibility of applying electric fields in flame to trigger electrophoretic deposition phenomena. In this way, it is possible to add another degree of freedom to the harvesting process and potentially modify the properties of the CNP films, without changing the operating flame conditions. To investigate the physical mechanisms governing the thermo-electrophoretic deposition of CNPs, a numerical model to simulate the particle dynamics close to the collecting substrate has been developed, and experiments have been carried out to provide highly controlled test conditions that can be used to support model validation. The experimental results consist of Atomic Force Microscopy (AFM) measurements to determine the number of particles deposited after a controlled harvesting condition as a function of the applied electrophoretic force, imposed on the substrate by means of a DC voltage varied from 0 to -3kV. The AFM shows that the amount of deposited material increases up to six times when passing from an uncharged to the -3kV charged case. The model predictions are highly consistent with the AFM measurements and pointed out that the electric field in flame significantly alters the CNP deposition velocities and impact angles, which are likely to affect the properties of the film.

In this work hydrogen and methane production from buffalo manure has been scrutinized, by means of the anaerobic dark fermentation process and different process conditions. Animal manure characteristics are largely variable during different periods of the year because of the unavoidable changes in animal food supply and digestion apparatus of buffalo. A very significant variability was observed for water buffaloes manure, collected from the same supplier. This implies also a large variability in biogas production by anaerobic fermentation of such substrates. To overcome this variability, we mixed fresh with digested manure. This procedure is consolidated as regard methane production. We also investigated a similar strategy to optimize and stabilize H2 yield. We were able to find optimal process conditions for hydrogen and methane production with this type of substrate. The experiments have been run in batch mode. The products of fermentation, H2, CO2 and CH4, have been measured with a micro-gas chromatograph. Moreover the potential production of H2 has been maximized by thermally pre-treating the substrate and using a process temperature of the fermenter equal to 55 °C and an initial pH value of 5.5, while very high levels of potential production of CH4 have been obtained at 37 °C and with an initial pH of 7.0. The effect of different strategies has also been analyzed to highlight the different microbial community present in the substrate using the denaturing gradient gel electrophoresis (DGGE). This investigation has been carried out with the aim at isolating and selecting of natural bacterial species to use as inoculum to improve and stabilize the fermentation process of buffalo manure. More results concerning the microbial communities present in the substrate and responsible for biogas production are presented in a companion paper. Here we only list the main types of bacteria identified in the manure. In this work hydrogen and methane production from buffalo manure has been scrutinized, by means of the anaerobic dark fermentation process and different process conditions. Animal manure characteristics are largely variable during different periods of the year because of the unavoidable changes in animal food supply and digestion apparatus of buffalo. A very significant variability was observed for water buffaloes manure, collected from the same supplier. This implies also a large variability in biogas production by anaerobic fermentation of such substrates. To overcome this variability, we mixed fresh with digested manure. This procedure is consolidated as regard methane production. We also investigated a similar strategy to optimize and stabilize H2 yield. We were able to find optimal process conditions for hydrogen and methane production with this type of substrate. The experiments have been run in batch mode. The products of fermentation, H2, CO2 and CH4, have been measured with a micro-gas chromatograph. Moreover the potential production of H2 has been maximized by thermally pre-treatimg the substrate and using a process temperature of the fermenter equal to 55 °C and an initial pH value of 5.5, while very high levels of potential production of CH4 have been obtained at 37 °C and with an initial pH of 7.0. The effect of different strategies has also been analyzed to highlight the different microbial community present in the substrate using the denaturing gradient gel electrophoresis (DGGE). This investigation has been carried out with the aim at isolating and selecting of natural bacterial species to use as inoculum to improve and stabilize the fermentation process of buffalo manure. More results concerning the microbial communities present in the substrate and responsible for biogas production are presented in a companion paper. Here we only list the main types of bacteria identified in the manure. Copyright © 2014,AIDIC Servizi S.r.l.

The absorption of SO2 in electrified water sprays, either when the polluted gas is treated as is or when the gas is exposed to a corona source to ionize the SO2 was evaluated. An electrified spray with a charge-to-mass ratio of 50 ΜC/kg enabled the absorption rate of droplets to double, regardless of their polarities. Corona charging gave rise to an increase in the SO2 depletion rate over the scrubber wall, while negligible effects appeared on the actual droplets absorption rate. These findings suggested that faster absorption rates mostly, though not uniquely, depend on the modifications on the morphological and interfacial properties of the sprayed droplets induced by the free electric charge imposed on their surface. Conversely, the absorption rates were negligibly affected by the electrical interactions between droplets (either charged or uncharged) and the SO2 ions/radicals originating from the corona source.

Newtonian non-Brownian concentrated suspensions show a mismatch between the steady state and the complex viscosity, whatever the strain amplitude imposed in the oscillatory flow. This result is counterintuitive in the two extreme cases of vanishing strain amplitude and very large one. In the first case, the oscillatory flow should not be able to alter the steady microstructure, as well as in the other opposite limit for which the strain amplitude is so high that the oscillatory flow resembles a steady flow reversal. If the microstructure is not altered with respect to the steady one, similarly the complex viscosity should be equal to the steady one. We here investigate experimentally and numerically the origin of the viscosities mismatch at any imposed strain amplitude. We focus on the first two or three cycles of oscillations and different particle concentrations. Experimental and numerical results agree and allow to prove that for intermediate amplitudes, the oscillatory shear induces the breakage of particle clusters and the microstructure modifies so to minimise particle collisions. For very small strain amplitudes, the oscillatory shear only induces the rotation of few couples of touching particles and the complex viscosity results slightly smaller than the steady one, while for very large strains, the oscillatory flow reshuffles the particles inducing a microstructure as clustered as the steady state one but with a different angular distribution function. We show that the vast majority of the microstructure rearrangement takes place in the first half cycle of oscillation.

The paper shows experimental findings aimed to prove the effectiveness of a concept design for fine and ultrafine particle capture called condensational growth assisted bubble column. Experiments were carried out with a gas at ambient temperature and pressure polluted with calibrated polystyrene nanoparticles (mean numeric diameter 113 nm, standard deviation 120 nm). The laboratory scale equipment included the sequence of a growth tube and a bubble column. In the growth tube, the heterogeneous condensation of water vapour took place over the particles, producing a liquid-solid aerosol of size larger than the original particles. Experiments showed that the condensational growth pre-treatment improved the bubble column removal efficiency from nearly 25 % up to 90 %. The growth tube also contributed to particle capture so that the overall system reached particle removal efficiency above 95 %. The particle removal efficiency of the entire unit was higher than the sum of the single growth tube and bubble column contributions, suggesting the occurrence of favourable synergic effect between them.

The effect of the soil organic content on the stability of a soil involved in a rapid mud flow is here experimentally investigated. The soil is collected form a site where a catastrophic landslide took place (Cervinara – AV) and it is chemically treated to selectively remove different aliquots of its original organic carbon. In particular, The Dissolved Organic Carbon ( i.e. the carbon soluble in water)results the 6% of the soil organic carbon and it is removed with a mild chemical treatment to obtain the DOC 6 sample, the 77% and 89% of the Total Organic Carbon ( i.e. the pool of oxidizable soil organic carbon)is removed with a strong chemical treatment to obtain the TOC 77 and TOC 89 sample, respectively. The stabilizing effect of the organic carbon is investigated by following the evolution of the particle size distribution of soils induced by a mild mixing of diluted slurries and we showed that the particle size distribution of the original soil sample is unaffected by the slurry mixing, while those of DOC 6,TOC 77 and TOC 89 evolve during time, revealing the breakup of soil aggregates. Our findings highlight the stabilizing effect of SOC in the investigated liquid slurries and, furthermore, they suggest that the organic carbon quality, more than its quantity, plays a crucial role in the soil stability. Indeed, it is enough to remove the Dissolved Organic Carbon to register a soil disaggregation process comparable to that observed for TOC 77 and TOC 89 samples. This suggests that Dissolved Organic Carbon is the fundamental organic fraction stabilizing the slurry microstructure.

Flue Gas Desulphurization (FGD) is a key topic for most of combustion fossil fuel plants and industrial applications. Wet processes are usually preferred when the removal efficiency required to comply with environmental regulation exceed 90 %, but their flexibility makes them useful also for lower performance requirements. Recently, seawater has been considered as a viable absorbent for FGD processes in coastal and naval applications, when SO2 concentration is below 1000 ppmv. This liquid absorbs SO2 mostly thanks to its natural alkalinity (on average 2.4 mmol/L) and, of course, is also largely available. The main costs of seawater FGD (SW-FGD) plants are related to the pumps needed to supply the required amount of liquid and the cost of wash water restoration before discharge. Corrosion related to the presence of acidic seawater is also a major issue of these units. While thermodynamic limitations cannot be overcome, process design can be optimized to improve mass transfer rates and reduce seawater requirements while keeping a suitable absorber size. In this work, we report the experimental findings achieved by our group on process design and optimization of SW-FGD units. Two different kinds of SW-FGD units were tested and compared: a spray column and a packed column with structured packing.

This paper explores the effects of electrification of water sprays on the absorption of sulphur dioxide from exhaust gases. Electrification is associated with an appreciable improvement of sulphur dioxide absorption rate with low supplementary costs and candidates to be a valuable innovation for spray tower absorbers. Similar phenomena occur during thunderstorms, when scavenging of gases and aerosol are enhanced by the electric charge of raindrops. This paper aims to describe the effects of electrification on SO2 absorption on the bases of experimental and theoretical analyses. The experiments involve absorption tests in lab-and pilot scale facilities, while theoretical modelling to assess the chemical and physical properties of charged droplets, their hydrodynamics and their mass transfer rates are presented. Water electrification is accompanied by a number of chemical-physics and morphological modifications of the sprayed droplets that modify the conventional absorption rate of soluble gases. The experimental and theoretical evidences indicate the need to analyse the electrified absorption within a new and integrated theoretical framework that we define chemi-electro-hydrodynamics (CEHD).

This paper aims to evaluate how condensational growth may be used to improve the performances of a Venturi scrubber in removing soot particles, which are among the most relevant air pollutants emitted in industrial and power plants exhaust gases. Former studies on this system, called Condensational Growth assisted Venturi scrubbers (CGVS), suggested that the most relevant step to address their efficiency is the assessment of the amount of water that condense on the soot particles, which determines the actual aerosol size distribution entering the Venturi. Unfortunately, a definite physical mathematical model to predict the actual condensational growth of an ensemble of non-spherical particles is not yet available and experimental investigation is better suited to assess this point. This study reports experimental data on the size distribution achieved by exposing model soot particles to a water supersaturated gas for different residence times. The obtained size distributions are used to estimate the efficiency of a Venturi scrubber in removing the water-soot aerosols, allowing a comparison with the removal of parent soot particles. The experiments were carried out at lab scale by using a laminar-flow growth tube, a simple device to perform a controlled condensational growth. The experiments indicated that, even for a hydrophobic material as soot, condensational growth is effective even at supersaturation levels as low as 1.02. Liquid-solid aerosols from nearly 2 to >3 times larger than the parent particles are produced with a supersaturation level lower than 1.15. Finally, the analysis of experimental data indicated that the fraction of particles subjected to condensational growth is relevant. Indeed, calling as ψ the fraction of particles that become larger than the 98% percentile of the original particle size distribution, we found that ψ can be as high as 78%. The analysis of data indicated that an appreciable linear correlation exits among ψ and the 95th percentile of the supersaturation level, S95, while not being dependent on the exposure time. The experimental evidences suggest that the adsorption of water molecules over the soot surface overcome the effects of hydrophobicity and of line tension effects, favouring condensation of water over the soot surface and leading to a higher nucleation rate even at low supersaturation. Application of the Venturi scrubber model to the water-soot aerosol leaving the growth tube indicate that the CGVS may remove particles with an efficiency far higher than that achieved by the stand alone Venturi. For a given Venturi's throat length and velocity and a given liquid-to-gas ratio, the CGVS efficiency depends almost linearly on ψ and, in turns on S95. Experimental and model results suggested that the CGVS can be a valuable and effective device to capture soot particles and that condensational growth can be used as a retrofit method for existing units. © 2018 Elsevier B.V.

This paper describes lab scale experiments that were carried out to determine the scavenging rate of submicron particles in the presence of charged droplets, which helps to study the mechanisms involved in wet electrostatic scrubbing process. The main aim of this study is the need to decouple the effects of particles–droplets interactions from the specific features of the electro-hydrodynamics of a charged spray. To this end, a novel experimental methodology was developed to carry out tests with an electrospray operating in dripping mode to produce a train of uniformly sized and charged droplets. Experiments were performed either with charged or uncharged particles in order to understand the differences between wet electrostatic scrubbing in the presence of electric forces, when both droplets and particles are charged, or in the presence of image charge forces only, when particles are uncharged. The obtained results demonstrate that the particle image charge effect does not lead to appreciable particle abatement, while Coulomb interactions become the dominant particle scavenging mechanism when particles are charged. In this case, the scavenging rate can be described by a first order equation in particles concentration and the experimental results are consistent with theoretical predictions based on the classical model of atmospheric scavenging.

In this study, we investigated the induction charging of water sprays and the effect of electric field on the breakup mechanism of liquid sprays. Two different kind of hollow cone hydraulic spray nozzles were used. Our investigation aimed to estimate the Droplet Charge to Mass Ratio (D-CMR) and the dependence of breakup length on electric potential. The experiments revealed that the D-CMR increased with the potential until to a maximum, then started to decrease. At the same time, the breakup length decreased more than 0.5 cm compared to the uncharged value, suggesting that the electric field actually influenced the jet break-up dynamics. For V

The paper presents experimetnal findings on an innovative system aimed to remove ultrafine particles from gases. The system is based on coupling a particle enlargement process with a three-phase bubble column. Calibrated polystyrene nanoparticles of about 200 nm were tested and were enlarged in a growth-tube operated at different temepartures to obtain different super-saturation levels. The experimental results showed that the aerosol cumulative distribution functions shifted towards larger diameters with the increasing of supersaturation; the total particle removal efficiency in the three-phase bubble column increased with the supersaturation reaching values of 99 %.

This paper reports preliminary results on the absorption of SO2 from water charged droplets, produced by an electrospray operated in dripping mode. Our results show that the water charging allows a ˜50% increase of the SO2 absorption rate. Since the SO2 mass transfer coefficient depends mainly on the liquid-side mass transfer coefficient, we envisage that the increase of SO2 absorption rate is ascribable to the occurrence of droplet deformation and oscillation, driven by the reduction of surface tension caused by the presence of excess charge on the droplet surface. Experiments were successfully interpreted in light of an absorption model that specifically address the droplet formation and fall and considered the model of Matteson and Giardina (1974) to account the droplet charge effect.

Anaerobic digestion is an established technology to treat different kinds of wastes and to simultaneously produce biogas, a mixture of methane and carbon dioxide, which is a useful and renewable energy source. In this work, the anaerobic digestion of buffalo manure is studied. The latter is a low cost substrate rich in carbohydrates, especially suitable to produce biogas in anaerobic digesters. The process is performed both under mesophilic (37 °C) and thermophilic (55 °C) conditions with pH spanning from 6.0 to 8.7. Many different samples, deriving both from lactating and non-lactating buffaloes, are used. Under mesophilic conditions, our results are essentially in line with literature, and the highest methane concentration in the biogas (even above 65 %) is obtained with pH = 7.0. Conversely, under thermophilic conditions, we observed that also with pH > 8.0, the anaerobic process runs efficiently. In particular, methane concentration in the biogas reaches values around 70 %, with production rates almost twice those obtained at 37 °C. This experimental observation is particularly interesting for those wastes showing a natural basic pH, as the buffalo manure at hand; in these cases, in fact, the digestion process can start without any manipulation of the pH.

Energy generation by fossil fuels produces significant amount of pollutants. Among the most toxic of them, there are SO2 and particulate matter. The first is a toxic gas that is subjected to severe regulations, the second is only partially regulated since the most toxic fractions of particles, i.e. The ultrafine particles, are nor easily measured neither properly captured by conventional technologies available at commercial level. Electrification of water sprays provide a reliable way to improve both the SO2 mass transfer rates and the particle capture efficiency, thanks to the multiple effects of electric charges imposed on the sprayed droplets. In this paper, we report experimental findings on the use of electrified sprays of water to reduce SO2 and particulate matter form a model flue gas. Tests were performed both laboratory and pilot scale. The experiments are compared with the performances of the same spray operated without electrification. In the pilot scale unit, particle removal efficiency is negligible and SO2 removal is up to 97% with the uncharged spray, The use of induction charging and exposure to corona pre-charging allow achieving >93% reduction of particulate matter and to >99% SO2 reductions. Experiments at laboratory scale shed light on the mechanisms of particle and SO2 capture. In particular, the experimental results revealed that a stochastic scavenging model presented in our former works (data not shown) well described the particle capture and that for charged droplets, the absorption rate for SO2 improved by about 60% respect to uncharged droplets.

This work reports experimental results on the effects of temperature (25, 45, and 65°C at different relative humidity) on the scrubbing of charged submicron particles by means of cold (25°C) droplets charged with opposite polarity. The aim of the study is to experiment how the capture of particles is influenced by the simultaneous presence of electrostatic and phoretic forces related to the occurrence of thermal and water vapor gradients close to the droplet surface. This information plays an important role in the development of wet electrostatic scrubbing (WES), an emerging technology for submicron and ultrafine particle capture. Tests were performed in a lab-scale system in which the particle laden-gas was scrubbed by a train of identic droplets. Particles were charged by a corona source while droplets are generated by electrospraying. Experiments revealed that for particles larger than about 250–300 nm, there were higher removal efficiencies in nonisothermal conditions, with limited differences...

Animal manure can be profitably used to produce energy in anaerobic fermenters increasing energy independence and reducing disposal costs and pollution. Animal manure is a low cost substrate rich in carbohydrates, especially suitable for biofuels production, such as hydrogen and methane. We preliminary studied the effect of mechanical manure pre-treatments on the fermentation process focusing on the biogas yield and composition. In particular, we investigated both the H2 and CH4 oriented fermentation. Our batch reactors consist in 280 ml serum glass bottles hermetically sealed with pierceable rubber cups. The products of fermentation were measured with a micro gas chromatograph, equipped with two capillary columns. To individuate the most suitable conditions for H2 production, a manure thermal pre-treatment, used to isolate the H2-producing bacteria, was investigated. Preliminary results show that the mechanical pre-treatments do not systematically alter the fermentation process. Concerning the thermal pre-treatment, we found that the CH4 production is inhibited when the manure is heated at the 90 °C for several hours. Moreover, we identified the most favorable conditions to optimize the production of H2: i) thermal pre-treatment on the substrate; ii) initial pH ~ 5.0; iii) process temperature of 55 °C. The favorable conditions to optimize the production of CH4 are: i) initial pH ~ 7.0;ii) process temperature of 37 °C.

Animal manure is a low cost substrate suitable for biofuels production, such as hydrogen and methane, via anaerobic fermentation (Kyazze et al., 2007). Previous studies attributed the higher biogas yield from certain types of manure to the presence of a native microflora (Yeole and Ranande, 1992) and/or a higher or better carbon-nitrogen (C/N) ratio (Fulford, 1988). Probably the main difference between the different types of dung is related to the specific food the animal eat, which changes the overall C content and C/N ratio. We measured the C/N ratio and the native microflora of dung collected during one year. We related it to the biogas yield during anaerobic fermentation both for lactating and non-lactating buffaloes manure. The results showed that the buffalo manure was in both cases plenty of carbohydrates with a C percentage content based on the dry sample weight of 36.2 ± 2.0 % and 31.4 ± 1.5 %, respectively. The C/N ratio was 18.6 ± 1.5 % and 20.6 ± 2.9 %, respectively, and it changed during the different seasons because of the fluctuating N content. Indeed we found an acceptable correlation (R = 0.75) between the average environmental temperature and the C/N ratio of lactating buffalo manure. Neither the C or N content nor the C/N ratio appeared to be strongly correlated to the biogas production. The manure was fermented in batch reactors at 37 °C and pH = 6.0 after different pretreatments of the collected manure. The analysis of the microbial community was carried out using denaturing gradient gel electrophoresis (DGGE) to generate fingerprints of 16S rRNA genes (Carillo et al., 2012). The sequences analysis revealed that the Eubacterial community during fermentation in batch reactors was much more taxon rich and diversified than the Archeal community. The study of Archeal community instead showed the presence of only three main methanogen strains very active in methane production and largely predominant. Animal manure is a low cost substrate suitable for biofuels production, such as hydrogen and methane, via anaerobic fermentation (Kyazze et al., 2007). Previous studies attributed the higher biogas yield from certain types of manure to the presence of a native microflora (Yeole and Ranande, 1992) and/or a higher or better carbon-nitrogen (C/N) ratio (Fulford, 1988). Probably the main difference between the different types of dung is related to the specific food the animal eat, which changes the overall C content and C/N ratio. We measured the C/N ratio and the native microflora of dung collected during one year. We related it to the biogas yield during anaerobic fermentation both for lactating and non-lactating buffaloes manure. The results showed that the buffalo manure was in both cases plenty of carbohydrates with a C percentage content based on the dry sample weight of 36.2 +/- 2.0 % and 31.4 +/- 1.5 %, respectively. The C/N ratio was 18.6 +/- 1.5 % and 20.6 +/- 2.9 %, respectively, and it changed during the different seasons because of the fluctuating N content. Indeed we found an acceptable correlation (R = 0.75) between the average environmental temperature and the C/N ratio of lactating buffalo manure. Neither the C or N content nor the C/N ratio appeared to be strongly correlated to the biogas production. The manure was fermented in batch reactors at 37 degrees C and pH = 6.0 after different pretreatments of the collected manure. The analysis of the microbial community was carried out using denaturing gradient gel electrophoresis (DGGE) to generate fingerprints of 16S rRNA genes (Carillo et al., 2012). The sequences analysis revealed that the Eubacterial community during fermentation in batch reactors was much more taxon rich and diversified than the Archeal community. The study of Archeal community instead showed the presence of only three main methanogen strains very active in methane production and largely predominant.