1,721,061 research outputs found
Modeling of wet jet in fluidized bed
No full textA wet jet zone is established in many applications wherever feeding and dispersing a liquid, solution or slurry into fluidized bed by gases is needed. In the present study, a simple mathematical model has been developed to simulate the wet jet in fluidized bed. The different stages involved inside the jet zone have been estimated and analyzed.
The evaporation stage of traveling droplets through the jet flare has been treated. The rates of evaporation of each size at all positions along the jet flare have been estimated according to the velocities and surrounding conditions. The final droplet sizes have been determined. Moreover, the total evaporation rate from traveling droplets, before collision either with entrained sand particles or flare boundaries, has been estimated. The traveling droplets, partially evaporated, may collide and settle on entrained sand particles. The model predicts the settlement rates of liquid droplets on entrained sand particles. The total part evaporated from settled liquid has been estimated as well.
The study has been applied to the pneumatic feeding of liquid fuel into fluidized bed combustors operating at 850 oC. The model has been utilized to predict the ratio of fuel vapor that releases inside the jet flare. The remaining part is assumed to evaporate inside the emulsion phase. Three different liquid fuels have been considered: a heavy oil, diesel fuel and gasoline. The main independent variables are those related to the injection conditions including the initial velocity of dispersing air, uo, and air to liquid mass ratio, ALR.
The model results demonstrate that only very small droplets completely evaporate inside the flare. The liquid settling over the entrained sand particles plays an essential role in the fuel evaporation inside the flare. The phenomenon is dominant at conditions that result in generation of droplets of larger sizes, i.e., heavier fuel, lower uo, and greater ALR. The ratio of vapor fuel released in jet flare increases with lighter fuel, higher uo and lower ALR. At uo=200 m/s and ALR=1.0 nearly all-liquid fuel evaporates inside the flare
A further contribution to modeling the low-temperature fluidized combustion of liquid hydrocarbon fuels
No full textA Study on Meat Drying Process Using the Porous Media Approach. Part 2: analysis and Mathematical Modeling
No full textThis paper delivers a contribution aimed at improving available mathematical models of salami ripening by switching to a description of the sausage as a heterogeneous material, obviously made of fat and minced lean meat, and to the adoption of the porous medium approach for water transport from the lean meat phase to outside, which represents a novelty.
The literature data as well as mathematical correlations able of describing or approximating water diffusion in fresh lean meat have been reviewed. Two semi-empirical correlations for water diffusivity as a function of the local moisture content were selected, i.e., from Saravacos and Datta. Then, the optimal parameters were determined for them by coupling a distributed-parameter mathematical model of minced meat drying (adopting the porous media approach) and an optimization algorithm with available experimental data. A code was implemented and successfully run by invoking the “transport in porous media” and “optimization” physics in the Comsol Multiphysics®4.3 platform.
The mathematical modeling work allowed discussion and comparison of the predictions against independently available experimental results, in terms of weight loss as well as space and time profiles of moisture in a reference lean meat specimen
A Sub-model of a Reacting Gas-Liquid Jet as a Tool for Better Simulation of Liquid Fuel Combustion in Fluidized Bed
No full textRecent advances in modeling the liquid fuel combustion in a low-temperature fluidized bed
No full textDisposal of olive mill waste waters through concentration and combustion: comparison between different process options
No full textDifferent process options for concentration of olive mill waste water by evaporation are compared with the aim of minimizing the overall energy requirements. In particular, vapor mechanical and steam recompression, as well as the use of heat pumps to qualify the low temperature heat of the vapor stream are considered. Comparison is carried out in terms of overall energy end exergy balances as required from the water evaporation process and made available by the combustion process of the residue
Lycopene-containing Tablets Production from Tomato Peels by Environment-friendly Extraction: Simulation and Discussion
No full textThis work aims to model the extraction process of lycopene from tomato peels using a conventional or a "green" solvent, which could be more environment-friendly, and its subsequent encapsulation. The Aspen Plus® software is used to this end. Different cases considering alternative extracting solvents, as well as the recycling of recovered solvent streams and water are evaluated and compared. The raw materials to be considered in an inventory analysis are tomato peels from local industries, solvents, drying agents and soft capsules. Based on literature data and using MS Excel® worksheets, the process mass and energy balances are set up and, hence, the extraction yield is evaluated, while the solvent recovery stage is simulated and optimized in Aspen Plus®. The economic potential of these cases is calculated by considering the cost of utilities, product and by-product sales, wastewater treatment, and raw material costs.
Results show that tomato peels can be appealing for lycopene extraction and valorization. The productivity of lycopene-containing tablets is appreciably large: 12000 pz/h of lycopene-containing tablets after extraction with ethyl acetate and 3500 pz/h in the case of limonene were obtained. Moreover, the predicted gross profit is reasonably attractive, with 39 M€/year for the conventional process and 11 M€/year for the "green" alternative
A theoretical investigation on the effects of product inhibition in a chemostat
No full textIl presente articolo si propone di studiare le condizioni di regime di un chemostato la cui popolazione microbica si sviluppa secondo una cinetica di inibizione da prodotto. Il bioreattore è descritto mediante un modello matematico non strutturato impiegando la cinetica di Aiba & Shoda [1]. Per condurre quest’analisi, si è fatto ricorso alla teoria delle singolarità che permette di definire la relazione tra i parametri del modello e la presenza di biforcazioni statiche. A questo scopo, sono stati tracciati i diagrammi delle singolarità che permettono di ricavare in maniera semplice gli intervalli di valori dei parametri per cui è possibile rilevare una molteplicità di stati stazionari. Infine, si è dimostrato che il sistema non possiede alcun punto di biforcazione dinamica per qualunque valore fisicamente coerente dei parametri coinvolti
A 1-D Zone Model for the Axial Burning Profile of Liquid Fuels in Bubbling Fluidized Beds
No full text- …
