Vincenzo G. Dovì

Biodiesel production via transesterification: Process safety insights from kinetic modeling

Biodiesel is an alternative non-petroleum based fuel, consisting of alkyl esters obtained either by esterification of free fatty acids with low molecular weight alcohols, or by transesterification of triglycerides. The realization of a biodiesel unit can pose several safety issues and inherent safety application opportunities as the production involves the transport, use and storage of hazardous materials, either flammable or toxic. In the experimental phase, we studied, at laboratory scale, different alkali catalysts and the relevant reaction parameters, considering inherent safety opportunities. An accurate kinetic model of the transesterification process was developed and validated, allowing to provide possible minimization and simplification plant options.

A Maximum Likelihood-based Method for the Nonlinear Estimation of Equilibrium Adsorption Parameters

Adsorption technologies are widely employed in many important separation processes, especially in fine chemistry and environmental control. Thus, the increasing pressure for cost reduction in the operation of industrial plants, which calls for the use of efficient design techniques based on scientifically advanced methods, has led to the development of sophisticated physical chemical models for the description of adsorption equilibrium parameters. To account for the complex phenomena that take place at the microscopic level in the adsorption process, the most recently developed models require the estimation of a number of parameters higher than the ones present in the traditional Langmuir and Freundlich models. On the other hand, the presence of an increased number of strongly correlated parameters requires the use of suitable statistical methods for the information contained in the experimental results to be utilized efficiently. In this article we present a method that generalizes previous identification procedures to complex models containing an arbitrary number of parameters. The sensitivity of the resulting estimates on error distributions assumed and theoretical models chosen is examined using both simulated and experimental data.

Monte Carlo modelling of wet-chemical lithography with masks

We propose Monte Carlo simulation of the etching process in two dimensions for the manufacture of microchannels and microcavities on a solid substrate. The method combines the effect of two different regimes based on diffusion-limited disaggregation and reaction-limited erosion, respectively. Besides, the role of the selectivity in site extraction is taken into account to foresee the effects of the temperature of the eroding bath. This technique proves to be a valid alternative to more complex analytical methods to describe surface decay processes in the presence of overhangs. The relevant geometries of the etched surfaces are analyzed, and other statistical properties of the cavities are discussed and compared to the ones predicted by continuum models.

An Advanced Lagrangian Puff Model, With Emphasis On Low Wind Speed Conditions

Two main approaches can be outlined when dealing with the solution of transport and dispersion problems, namely Eulerian and Lagrangian one. The latter approach is becoming more and more widespread due to the availability of cheap computational power, which is a strict requirement of the relevant algorithms involved in the modelling. Lagrangian algorithms make it possible to give a much more detailed description of atmospheric diffusion phenomena, provided that the corresponding amount of information (air and soil properties) are available, Nowadays, a considerable number of well tested models is available and the state-of-the-art of the corresponding modelling is presently well developed [1]. However, there are apparently minor problems that might cause large discrepancies between predicted and measured values especially in conditions of low wind speed. In fact, under these conditions, the meandering of the flow can be quite significant, leading to enhanced horizontal dispersion, An advanced Lagrangian approach is developed in this paper, modelling in particular plume rise and very low wind speed conditions, We developed a rigorous model including mass, energy and momentum conservation equations, coupled with constitutive equations related to physical and atmospheric properties, Special procedures were developed for source extinction (estimation of the final plume rise) and source merging before reaching the final plume rise. The numerical solution of the resulting system of algebraic equations has been carried out using Powell’s dogleg strategy, Comparison with a standard widely used Lagrangian code, as well as with experimental data-set, were carried out and showed good performance of the proposed approach,