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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.

Anaerobic digestion is an established technology to simultaneously produce biogas and treat different kinds of wastes. This work deals with water buffalo manure digested under mesophilic (37°C) and thermophilic (55°C) conditions with initial pH varying from 6.0 to 8.7. The digestion is investigated following the evolution of the biogas composition in time, in terms of the volume fraction of CH4, CO2 and their ratio. The growths of the biogas products are interpolated with a Gompertz equation and in all the investigated cases the methane productivity is above 63% with a CH4/CO2 ratio rather high and equal to about 2. In mesophilic conditions, an initial pH of 7.0 must be preferred to optimize the methane yield and to minimize the time required to attain it. The thermophilic conditions resulted very promising since they almost halved the time required to reach the final yield. The speed up of the process at 55°C, in our case, resulted to be due to the increase of the digestion kinetic more than to the selection of a new metabolic pathway.

Heavy crude oil samples extracted from the same well showed some rheological differences mainly in terms of viscosity and response to the addition of a small amount of dodecyl benzen sulfonate. Also slight differences in the activation energy and in the viscosity dependence on a solvent concentration were observed. The crude oil samples, also separated in maltenic and asphaltenic fractions, were fully characterized by elemental and proximate analysis, solvent extraction, thermogravimetry, mass spectrometric and spectroscopic analyses. No significant differences were found showing that the samples have the same composition and molecular structure and demonstrating that the different rheological behavior has to be related only to a different microstructural organization that is not sensed by the chemical–physical tests. This result helps to complete the picture of the complex correlation between rheological and chemical–physical properties of heavy crude oils. While it is accepted that chemical-physically different samples may, or may not, have a different rheology, we show for the first time that unperturbed samples with the same chemical–physical properties may exhibit differences in the rheological behavior.

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).

The apparent complex viscosity of a non-Brownian Newtonian concentrated suspension is known to be a non- monotonic function of the applied strain, attaining a minimum at a relative strain of about 100%. This behaviour can be nicely described in the framework of the Stokesian dynamics, which also predicts the independence of the complex viscosity on the applied frequency. Despite this, recently it was experimentally shown that the apparent viscosity of a concentrated non-Brownian suspension is function of the applied frequency in experiments run imposing a constant stress (Carotenuto et al. AIP Conference Proceedings 1599, 258, 2014). This behaviour is quite unexpected and we here confirm it in more canonical experiments run imposing a constant strain.The apparent complex viscosity of a non-Brownian Newtonian concentrated suspension is known to be a non- monotonic function of the applied strain, attaining a minimum at a relative strain of about 100%. This behaviour can be nicely described in the framework of the Stokesian dynamics, which also predicts the independence of the complex viscosity on the applied frequency. Despite this, recently it was experimentally shown that the apparent viscosity of a concentrated non-Brownian suspension is function of the applied frequency in experiments run imposing a constant stress (Carotenuto et al. AIP Conference Proceedings 1599, 258, 2014). This behaviour is quite unexpected and we here confirm it in more canonical experiments run imposing a constant strain.

In rheometry rough geometries are often used to prevent wall-slip typically encountered with heterogeneous fluids. However, the fluid does not stand still within the geometry roughness and a residual wall-slip can be often measured. The problem can be treated as the flow through a porous medium that is here investigated when the fluid is non-Newtonian. We use a Boger fluid that is a good model for the Second Order Fluids and a commercial cross-hatched plate as rough geometry. The results obtained are in good qualitative agreement with predictions available in the literature and are promising for the development of a simple procedure to use rough geometries with viscoelastic fluids.

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 study reports experimental results on the primary jet breakup parameters of three hollow cone hydraulic spray nozzles electrified by induction. While former evidence indicated that the properties of sprayed droplets are scarcely affected by induction charging, we found that an increase in charging potential from 0 kV to −10 kV led to a reduction of breakup length and an increase of spray angle. For charging potential from −10 kV and −12 kV both the parameters reached asymptotic levels. As for electrosprays, we argue that jet breakup reduction modifications depend on the establishment of electrical stresses over the water sheet, while spray angle enlargements depend on the repulsion forces caused by induced charges. In most of the cases, these modifications are not sufficient to change the secondary atomization regime, but they severely affect the charging level of sprayed droplets.

In mountainous areas after long or intense rains, landslides may evolve into debris- or mud-flows. Their impact against obstacles may produce huge damages, sometimes with loss of lives. Prediction of the impact forces is required for a proper design of the flow barriers protecting risk prone areas. To this aim, both the effective characterization of the mud rheology and a suitable mathematical model of the flow propagation are needed. The present paper proposes a modeling framework in which the mudflow is idealized as the flow of a power-law fluid over an incline with a rigid impervious wall at the downhill end. The flow model employs the von Karman depth-integration of the one-dimensional mass and momentum conservation equations, in the long-wave approximation. The governing equations have been solved through a space/time second-order accurate numerical method. This modeling framework is applied to a test-case, based on the soil collected from Cervinara site (Avellino, South Italy), affected by a catastrophic landslide in 1999. The investigated soil is both the raw one and a washed one, the latter introduced to mimic the effect of an intense rain in terms of removal of the dissolved soil organic carbon. The rheology of both the shear-thinning mixtures has been deeply characterized in the form of a power-law function, and the dynamics of a dam-break wave ad its impact on an obstacle, has been numerically analyzed. It is shown that the removal of the soil organic carbon affects the propagation of the mudflow and at a minor extent the maximum forces and torques acting on the downstream wall. Remarkably, in the investigated conditions, the mudflow action consists of a strong impact occurring few seconds after the landslide triggering, and a subsequent cyclic loading of about three minutes.

Multiphase fluids, like suspensions, often show wall slip. This is induced by depletion of particle concentration in proximity of wall surfaces. The rheometrical data can be corrected for wall slip in a post processing analysis. Alternatively, it is typically tried to suppress wall slip using modified devices, like rough geometries. We here investigate whether rough geometries themselves affect the rheological measurements. To this end, we glue sandpaper on the smooth surfaces of a plate–plate device. We use two commercial sandpapers and we measure five different Newtonian fluids proving that the fluids actually flow within the sandpaper roughness. This shows up as an apparent wall slip that we characterise. We, then, observe that the same happens also with a model suspension made of hollow glass beads in a Newtonian fluid. Finally, we propose two experimental procedures to correctly infer the rheological properties of a fluid when rough geometries are used. The first is more time consuming and accurate, the second is fast, only requires a single measurement and, in any case, is quite robust.

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.

New regulations regarding the PM1 emission by power plants and transport vehicles require novel technical solutions for the abatement of particulate matter emission in submicron size range. Particles of this size are difficult to remove by conventional methods, and therefore various variants of wet electrostatic scrubbers have been developed. In such devices, the electrostatic forces between charged particles and collectors (water droplets) are used to permanently remove them from the gas. The paper focuses on the state-of-the-art of wet electrostatic scrubbing technique used for the removal of submicron particulate matter from exhaust gases with particular emphasis upon marine Diesel engines.

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.

In the present work rheological and mechanical properties of PEEK-PEI blends were investigated. Besides the pure components, blends with PEI concentration ranging from 10% to 90% in mass were considered. Oscillatory experiments in controlled atmosphere were conducted at different frequencies and temperatures. The frequency responses at different temperatures allowed using the TTS principle to reconstruct the master curves. All systems showed a shear thinning behavior and a flux index increasing with the percentage of PEI. The zero-shear viscosity was computed with the implementation of the Cross model and showed a decreasing behavior with the percentage of PEI. The relaxation time estimated from the crossover value of storage and loss moduli didn't change significantly with blend composition, suggesting the non-sensibility of the elasticity of the system. Lastly, tensile tests were executed to investigate the dependence of Young modulus in the different blends.

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...

Marine diesel engines emit particles that have a complex nature, being composed by carbonaceous particles, with size spanning from few nanometres to less than one micron, and inorganic particles of micron size mainly made by ashes and sulphates. On a global scale, international shipping is responsible for few percentages of the particulate matter emissions, which also affect climate, but the regional distribution of naval traffic suggests the insurgence of significant exposure risk for population living along the coastal areas, due to chronic exposure effects. Specific strategies should be implemented to reduce the emissions of all the components of particulate matter. This paper aims to present a survey on the current and innovative strategies to remove particles from marine diesel engine exhausts, along with a critical review of the most recent findings on ships emitted particles. Evidences on physical-chemical properties, toxicology and emission factors of the particles were reported. This survey indicates that several strategies can provide a significant reduction of particulate matter emissions from ships and integration between innovative after-treatment systems, ships design and operation procedures can potentially lead to overall reduction of more than 99% even with parallel fuel savings. © 2015 Elsevier Ltd.

This work deals with the study of the effect of the soil organic carbon (SOC) content on the rheology of a concentrated natural slurry made with soil collected from a site involved in a catastrophic rapid mudflow. We considered the soil with all the original SOC and with various fractions of it, selectively removed with specific chemical treatments. In this way, we obtained samples with different quantities of SOC having different solubilities and degrees of complexation with the soil mineral matrix. Flow curves and yield stresses of slurries, with a soil volume fraction of 40%, are experimentally determined. Flow curves show a marked shear-thinning behaviour and, at each imposed shear rate, the viscosity decreases by reducing the content of SOC. Similarly, the yield stress decreases while reducing SOC. 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 slurry rheology. In particular, the dissolved organic carbon is the fundamental organic fraction stabilizing the slurry microstructure. This work deals with the study of the effect of the soil organic carbon (SOC) content on the rheology of a concentrated natural slurry made with soil collected from a site involved in a catastrophic rapid mudflow. We considered the soil with all the original SOC and with various fractions of it, selectively removed with specific chemical treatments. In this way, we obtained samples with different quantities of SOC having different solubilities and degrees of complexation with the soil mineral matrix.Flow curves and yield stresses of slurries, with a soil volume fraction of 40%, are experimentally determined. Flow curves show a marked shear-thinning behaviour and, at each imposed shear rate, the viscosity decreases by reducing the content of SOC. Similarly, the yield stress decreases while reducing SOC. 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 slurry rheology. In particular, the dissolved organic carbon is the fundamental organic fraction stabilizing the slurry microstructure.

This paper presents experimental results obtained with a prototype of wet electrostatic scrubber suitably designed to remove fine and ultrafine particles from exhaust gases. Experiments were carried out on amodel combustion gas containing particles with diameters from 10 to 450 nm, which can be negatively charged in a specially designed corona charging unit. A full-cone spray nozzle with induction electrode was used to generate positively-charged water droplets (5% of the Rayleigh limit) with a mean diameter of about 290 μm. The particles removal efficiency was determined for different magnitudes of electric charges on particles and droplets and for two values of liquid-to-gas ratio, equal to 0.88 and 1.15. The experiments revealed that when both particles and droplets were left uncharged, the removal efficiency was very small. When only droplets were charged, the efficiency was of about 35% in number. The highest efficiency, overcoming 91%, was achieved when both particles and droplets were oppositely charged. © 2014 Elsevier Ltd. All rights reserved.

A common approach to prevent or alleviate wall slip in rotational rheometry is to utilize roughened geometries. While this is a helpful strategy, the presence of the surface roughness introduces a fundamentally different boundary condition, as the flow trough the porous structure needs to be accounted for. In the present work we investigate the use of rough surfaces in rheometry, starting with simple Newtonian fluids. Both structured and randomly structured surfaces are used, i.e. a cross-hatched plate and a sandpaper disc, respectively. We show that the fluid flows within the roughened layer and that the flow in the gap of the rheometer can be modelled as a flow over and through a porous medium. Stokes’ equation and Brinkman’s equation can be coupled at the interface through a suitable stress boundary condition recently developed in the literature that takes the momentum transfer to both the fluid and the solid substrate properly into account [Minale M., Phys Fluids 26, 123102 (2014)]. The predictions of this new model are compared with the experimental results on Newtonian reference fluids and show excellent agreement for the case of the cross-hatched geometry, and satisfactory agreement for the geometry with sandpaper. The analysis provides a way to correct the apparent viscosity by dealing with the extra dissipation in the rough layer using an extrapolation length.

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.

The rheological behavior of a non-Brownian Newtonian concentrated suspension is investigated under oscillatory shear at different strain amplitudes and at two frequencies. The data are in agreement with the literature showing that the complex viscosity varies both with the number of oscillations imposed to the material and with the strain amplitude. We here also show that the response to the oscillatory shear depends on the applied frequency. This result is unexpected for a Newtonian suspension and implies the existence of some mechanism able to introduce a characteristic time into the system. Can it be cage elasticity?

This work describes the results of experimental tests aimed to study the wet electrostatic scrubbing of submicron particles produced by a combustion process. A new experimental setup was adopted in order to allow the use of an electrospray exerted in dripping mode in place of a conventional spray, whose complex electro-hydrodynamics limits the quality of the information which can be inferred from experimental work. Experiments were carried out to assess the scavenging rate obtained when droplets of different sizes which were positively charged were used to scrub negatively charged combustion particles having diameters finer than 500 nm. In the investigated conditions, the particle scavenging mechanism is mainly related to the electrostatic interactions between charged droplets and particles. A particle scavenging model adopted to describe atmospheric scavenging phenomenon, once properly fitted to the experimented conditions, was used for the interpretation of experimental results.

Buffalo dung is a low-cost substrate with plenty of carbohydrates, an optimal carbon/nitrogen ratio, and a rich microbial flora, and could become a valuable source of biogas. Therefore, in the present study we compared the type and amount of specific eubacteria to the different configurations of pH, temperature and thermal pretreatment after fermentation in batch reactors in order to understand the suitability of buffalo manure for hydrogen production. The phylogenetic structure of the microbial community in fermentation samples was studied using denaturing gradient gel electrophoresis to generate fingerprints of 16S rRNA genes. The sequences analysis revealed abundance of the phyla Bacteroidetes and Firmicutes, and in particular of the order Clostridiales. Very active hydrogen producing bacteria belonging to Clostridium cellulosi species were identified demonstrating the suitability of this substrate to produce hydrogen. Moreover, a large fraction of 16SrDNA amplicons could not be assigned to lower taxonomic ranks, demonstrating that numerous microorganisms involved in anaerobic fermentation in digesters or bioreactors are still unclassified or unknown. © 2012 Springer Science+Business Media Dordrecht.

The present study analyses the performance of a scraped surface heat exchanger (SSHE) equipped with a new arrangement of blades to achieve higher thermal efficiencies than the conventional SSHE. This new design of exchanger, named here as scraped surface heat exchanger with alternate blades, A-SSHE, may be particularly suited to treat high viscous fluids, like food pastes. Experimental and numerical tests were carried out on an industrial scale A-SSHE used to heat hazelnut paste, an intermediate product widely used in Italian confectionery industry. Experimental tests include physical, chemical and rheological characterization of the hazelnut paste and the evaluation of the overall heat transfer coefficient as a function of rotational speeds and mass flow rates. Three-dimensional axial-symmetric CFD simulations of the A-SSHE were performed by using the software Fluent 6.2. For comparison, the same numerical tests were carried out for an equivalent SSHE with a conventional blades design (C-SSHE). Our studies show that the A-SSHE gives heat transfer coefficient values almost twice that of an equivalent C-SSHE, and that the numerical results are consistent with the experimental observations. The analysis of the fluid dynamics and of the thermal profiles suggests that the higher heat transfer efficiency of A-SSHE may be attributed to the occurrence of backmixing phenomena.

This paper reports an experimental investigation of shear-driven flow above and below a porous medium. A new technique based on rheological measurements is proposed and illustrated. Two configurations are investigated: One where there is a shear driven flow above the porous layer. In this case, the velocity profile in the free fluid is directly measured together with the velocity at the interface. The other where a shear flow is induced in the free fluid below a moving porous layer. In this case, the stress transferred through the porous layer is directly measured. Our results show that the stress transferred to the free fluid is essentially the same in both configurations. We have verified this with two sandpapers with different roughness, used to mimic two slender porous layers. This result might be used to validate the different boundary conditions proposed in the literature and imposed at the interface between the two domains.

In this paper, we have experimentally investigated the velocity profile of a fluid undergoing simple shear above a porous medium. To this end, we used for the first time rheological tests performed with a constant stress rheometer equipped with parallel plate geometry with a real porous medium glued on the lower plate. The velocity at the interface between the porous layer and the free fluid was inferred by extrapolating the linear velocity profile in the free fluid to the interface. These data were nicely compared with predictions obtained integrating the Brinkman extension of Darcy law in the porous medium together with Stokes equations in the free fluid coupled at the interface by the continuity of velocity and by the momentum balance suggested by Ochoa-Tapia and Whitaker [Int. J. Heat Mass Transfer 38(14), 2635 (1995)]. In the literature, the physical origin of the stress jump imposed by Ochoa-Tapia and Whitaker at the interface has been attributed to a perturbation of the velocity profile in the vicinity of the interface, both in the porous medium and in the free fluid. For the first time, the disturbance in the free fluid has been measured and quantified resulting in a satisfactory agreement with theoretical predictions.

Adsorption of heavy metals for water purification is largely based on the use of activated carbons either in fixed bed columns or agitated vessels. This paper deals with the adsorption of a model cadmium solution over an oxidised activated carbon in a liquid-solid fluidised bed. Experimental studies on the equilibrium and the kinetic characteristics of cadmium adsorption on the selected sorbent and hydrodynamic tests on a lab scale fluidised bed are presented. CFD simulations of the lab scale fluidised bed were carried out with the software Fluent 6.2 by implementing the specific equations to model cadmium adsorption. The CFD simulations provide hydrodynamic results consistent with the experimental observations and, once supported by proper kinetic and thermodynamic studies, allow to clarify the complex relations among hydrodynamics and adsorption phenomena in fluidised beds.

Water electrostatic scrubber (WES) represents an alternative technology for the abatement of that submicronic fraction of particulate – belonging to the so-called Greenfield gap – usually hardly captured with other cleaning techniques. The promising potentialities of WES are recognized by the scientific and industrial communities, but the design of this kind of reactor is far from being optimized. This work reports a mathematical model to evaluate the particle removal efficiency in wet electrostatic scrubbers. The model is used to find out optimal working condition of WES units, through the maximization of the particle collection efficiency in function of different process parameters: contact time, specific water consumption, water/gas relative velocity, size and charge of sprayed droplets. The model has been validated by comparison with different experimental data available in literature, both for charged and uncharged scrubbers. Then it is applied to a reference case study to obtain generalizable results. The model shows that the process optimization for micronic and submicronic size particles follows different criteria. For micronic particles, the collection efficiency increases for higher water/gas relative velocity, with a small effect of droplet diameter and a moderate increase with the droplet charge. On the contrary, in the Greenfield gap, the water/gas velocity plays a secondary role in the capture mechanisms, while a substantial increase of collection efficiency by improving the droplet charge level and reducing the droplet size has been observed. With reference to the actual performances of water spraying and charging devices, the model predicts that a collection efficiency as high as 99.5% can be reliably obtained in few seconds with a water consumption of 100 ml/m 3 by adopting droplet diameters around 100 μm and charge to mass ratio from 1 to 3 mC/kg, corresponding to droplet charge equal to 10–30% of Rayleigh limit.

Optimization of moulding process in order to maximize the recycled fraction in EPS products is a key industrial goal. To this end effects of quality and quantity of recycled EPS upon physical properties of products are studied. Results show, on the one hand, that the introduction of a recycled fraction brings to products with a reduced density. On the other hand, small modifications of the process parameters allow for a reduction in this density decrease. Furthermore, results show that mechanical and thermal behaviour of EPS depend only on the materials density apart from the possible presence of a recycled fraction.

Morphological characterization of polymer blends is important for tailoring final properties of plastic products based on these systems. A novel technique to estimate the characteristic dimension and size distribution of a polymer blend is proposed and tested. The procedure is based on Fourier transform rheology (FTR) and large-amplitude oscillatory shear experiments and exploits their sensitivity to microstructural properties. The inference protocol requires that the experimental data are analyzed with a model capable of describing the blend dynamics. This novel technique is applicable to immiscible polymer blends of practical industrial interest. The procedure is successfully tested on a model system (an immiscible polymer blend of PDMS in PIB) by treating the polymer blends with the Maffettone–Minale model coupled with the Batchelor theory.

The thermoreversible gelation of hydroxypropylcellulose (HPC)/water solutions is investigated by means of rheological and optical techniques. The linear viscoelasticity of solutions at different concentrations is measured during heating ramps from room temperature. The experimental results suggest that the solution microstructure changes according to two sequential steps, i.e., precipitation and gelation. Temperature, temperature rate of change, and concentration are found to be relevant parameters controlling the phase transition.

A theoretical model for the analysis of a wet electrostatic scrubber, WES, is reported. The model indicates that the WES systems allow a significant increase of the collection efficiency for submicronic particles respect to classical water scrubbers. The effect of the main process parameters on the collection efficiency is analyzed in order to define preliminary criteria for the design and operation of WES.