Roberto Nigro

Transition from slugging to turbulent flow regimes in fluidized beds detected by means of capacitance probes

Abstract A new method of analysis of the signal acquired from capacitance probes has been developed. The trace from a single probe is analyzed to obtain the probability density function of the signal. The value of this function corresponding to the gas phase density, when plotted against gas velocity, allows determination of both Uc and Uk, the velocities at which the transition from slugging to turbulent regime respectively starts and ends. The average bed voidage can also be obtained by the signals obtained from the probe, and its variation as the gas velocity changes contributes to the understanding of how the hydrodynamics of the bed evolve from the bubbling to the turbulent regime.

Spray-dry desulfurization of flue gas from heavy oil combustion.

Abstract An experimental investigation on sulfur dioxide removal in a pilot-scale spray dryer from the flue gas generated by combustion of low-sulfur (S) heavy oil is reported. A lime-water slurry was sprayed through an ultrasonic two-fluid atomizer in the spray-dry chamber, and the spent sorbent was collected downstream in a pulse-jet baghouse together with fly ash. Flue gas was sampled at different points to measure the desulfurization efficiency after both the spray-dry chamber and the baghouse. Parametric tests were performed to study the effect of the following variables: gas inlet temperature, difference between gas outlet temperature and adiabatic saturation temperature, lime-to-S ratio, and average size of lime particles in the slurry. Results indicated that spray drying is an effective technology for the desulfurization of low-S fuel oil flue gas, provided operating conditions are chosen carefully. In particular, the lowest gas inlet and outlet temperatures compatible with baghouse operation should be selected, as should a sufficiently high lime-to-S ratio. The attainment of a small lime particle size in the slurry is critical for obtaining a high desulfurization efficiency. A previously presented spray-dry flue gas desulfurization model was used to simulate the pilot-scale desulfurization tests, to check the ability of the model to predict the S capture data and its usefulness as a design tool, minimizing the need for pilot-scale experimentation. Comparison between model and experimental results was fairly good for the whole range of calcium/S ratios considered.

Lactobacillus paracasei CBA L74 interferes with gliadin peptides entrance in Caco-2 cells

Abstract Several recent reports describe a role of probiotics as a therapeutic approach for celiac disease (CD). Two undigested A-gliadin peptides, P31-43 and P57-68, are central to CD pathogenesis, inducing an innate and an adaptive immune response, respectively. They enter enterocytes and localize to vesicular compartment to induce their toxic/immunogenics effects. In this article, we tested the effect of probiotic Lactobacillus paracasei (LP) CBA L74 (International Depository Accession Number LMG P-24778), its supernatant and LP-fermented cereals on gliadin peptides, P31-43 and P57-68, entrance in Caco-2 cells. Both LP CBA L74 and its supernatant inhibit P31-43 (intensity of fluorescence; FI: 75%) and P57-68 (FI: 50%) entrance in Caco2 cells, indicating that this biological effect is due to some product included in LP CBA L74 supernatant. This effect was present also after fermentation of cereals. This study describes a novel effect of probiotics in the prevention of undigested gliadin peptides toxic effects.

Local heat transfer coefficients and superficial bed porosity of a horizontal cylinder in bubbling fluidized beds of geldart B particles

In this work, experimental values of local heat transfer coefficients around a horizontal cylinder immersed in a bubbling fluidized bed are reported for three types of bed materials classified as Geldart B particles, fluidized with air at ambient pressure and temperature. Results are interpreted in light of a model for heat transfer coefficient in order to estimate the time-average bed porosity profile close to the exchange surface. These angular profiles of bed porosity are compared with former experiments to verify the correctness of the adopted model, and are used to provide a physical interpretation of the experimental results.

In vitro dynamic model simulating the digestive tract of 6-month-old infants

Background In vivo assays cannot always be conducted because of ethical reasons, technical constraints or costs, but a better understanding of the digestive process, especially in infants, could be of great help in preventing food-related pathologies and in developing new formulas with health benefits. In this context, in vitro dynamic systems to simulate human digestion and, in particular, infant digestion could become increasingly valuable. Objective To simulate the digestive process through the use of a dynamic model of the infant gastroenteric apparatus to study the digestibility of starch-based infant foods. Design Using M.I.D.A (Model of an Infant Digestive Apparatus), the oral, gastric and intestinal digestibility of two starch-based products were measured: 1) rice starch mixed with distilled water and treated using two different sterilization methods (the classical method with a holding temperature of 121°C for 37 min and the HTST method with a holding temperature of 137°C for 70 sec) and 2) a rice cream with (premium product) or without (basic product) an aliquot of rice flour fermented by Lactobacillus paracasei CBA L74. After the digestion the foods were analyzed for the starch concentration, the amount of D-glucose released and the percentage of hydrolyzed starch. Results An in vitro dynamic system, which was referred to as M.I.D.A., was obtained. Using this system, the starch digestion occurred only during the oral and intestinal phase, as expected. The D-glucose released during the intestinal phase was different between the classical and HTST methods (0.795 grams for the HTST versus 0.512 for the classical product). The same analysis was performed for the basic and premium products. In this case, the premium product had a significant difference in terms of the starch hydrolysis percentage during the entire process. Conclusions The M.I.D.A. system was able to digest simple starches and a more complex food in the correct compartments. In this study, better digestibility of the premium product was revealed.

A glance at world: Combustion of poultry derived wastes for smart energy recovery in Italy.

Landfilling has traditionally been the predominant waste management option in the developing world. Many of these landfill sites remain poorly managed which has led to serious negative impacts on human health and the local environment. Inadequate financing has been cited as one of the major barrier that makes it difficult for many landfill owners/operators to operate and manage their sites in an appropriate manner. The often low gate fees charged for the disposal of waste at such sites does not provide sufficient funds to incorporate adequate environmental mitigation processes. Consequently, many sites are operated as “open dumps” or semi-managed dumpsites which have associated environmental problems such as unabated emissions of landfill gas (LFG) and leachate discharge. Furthermore, once landfilling operations have ceased, no financial provisions are made for “after-care” of the site. This is in stark contrast to the situation in Europe and other developed regions of the world. The Clean Development Mechanism (CDM) provides an opportunity for developing countries to substantially improve landfill site operation. The implementation of landfill gas capture projects not only decreases the environmental impact of methane gas but can lead to improved site management practices. It is also an opportunity to generate additional revenue through carbon credits and when possible, through energy generation. This paper explores how CDM projects offer economic benefits to overcome financial barriers to landfill site operation in developing countries. A case study has been used to illustrate the potential benefits of implementing a landfill gas CDM project at the Chunga landfill site in Lusaka, Zambia. Baseline greenhouse gases (GHGs) emissions were estimated for the site. It was found that implementing a landfill gas CDM project would generate revenue amounting to more than 18% of the gate fees over a 7-year crediting period. This additional revenue could supplement the operator’s budget required for site management and mitigate the environmental impacts currently associated with the site.

Hybrid Catalytic Combustion of Methane/Hydrogen Mixtures

Hybrid catalytic combustion technology, which is a staged process comprising a preliminary catalytic partial oxidation (CPO) step followed by a homogeneous flame combustion with interstage heat removal, was tested for the first time with mixtures of methane and hydrogen. Short contact time CPO experiments were run to elucidate the effect of the progressive substitution of methane with H2 in the fuel feed to the structured catalytic reactor, which was operated under self-sustained conditions at high temperature. Furthermore, a prototype radiant hybrid burner was realized and safely operated at atmospheric pressure with up to 80% vol. of H2 in the fuel and a primary equivalence ratio in the range 2.4–4.0. Outstanding NOx emission levels were attained with pure methane feed, which were also confirmed with H2-rich fuels, due to the effective reduction of both thermal and prompt NOx formation.

Heat and mass transfer in fluidized bed combustion and gasification systems

Abstract: The main experimental and modelling findings on heat and mass transfer in fluidized beds are reviewed with particular attention to combustion and gasification processes. The survey is separated into two sections. The first section reports the main features of heat transfer in fluidized beds starting from the large number of studies focused on surface-bed heat transfer. These features are then used to support the understanding of the less-studied particle-bed and gas-bed heat transfer mechanisms. The second section describes in detail particle-bed and gas-bed mass transfer in fluidized beds. In both sections the effect of the main process parameters (physical properties of gas and particles, bed geometry and hydrodynamic regimes) on the heat and mass transfer coefficients are discussed in order to provide guidelines for the design, the optimization and the operation of fluidized bed combustors and gasifiers.

Progesterone diffusion through snake skin as a human model membrane

Thanks to its physical and chemical structure, shed snake skin can be used as a model membrane for human skin in invitro drug delivery experiments. The progesterone mass transfer through Bitis gabonica skin has been studied using a suitable diffusion glass cell. A lag time of 5.7 hours, representative the unsteady diffusion regime, has been observed. After this lag time, the system reaches the steady-state condition during which the diffusion coefficient and the partition coefficient of progesterone in the system have been calculated by the integration of Fick’s laws.