A. Del Borghi

Toluene vapour removal in a laboratory-scale biofilter

Abstract A bench-scale biofilter with a 0.5-m high filter bed, inoculated with a toluene-degrading strain of Acinetobacter sp. NCIMB 9689, was used to study toluene removal from a synthetic waste air stream. Different sets of continuous tests were conducted at influent toluene concentrations ranging over 0.1–4.0 g m−3 and at superficial gas velocities ranging over 17.8–255 m h−1. The maximum volumetric toluene removal rate for the biofilter (242 g m−3 h−1) was obtained at a superficial gas velocity of 127.5 m h−1 (corresponding to a residence time of 28 s) and a toluene inlet concentration of 4.0 g m−3. Under these operating conditions, toluene removal efficiency was only 0.238, which suggested that effective operation required higher residence times. Removal efficiencies higher than 0.9 were achieved at organic loads less than 113.7 g m−3 h−1. A macro-kinetic study, performed using concentration profiles along the bioreactor, revealed this process was limited by diffusion at organic loads less than 100 g m−3 h−1 and by biological reaction beyond this threshold.

Simplified kinetics and thermodynamics of geraniol acetylation by lyophilized cells of Aspergillus oryzae

Kinetics and thermodynamics of geranyl acetate production by direct geraniol acetylation with lyophilized cells of Aspergillus oryzae were studied in n-heptane and compared with those of ethanol acetylation. Batch tests were performed varying the starting substrates equimolar level from 25 to 150 mM, the cell concentration from 5.0 to 30 g l−1, and the temperature from 30 to 95°C. The progressive increase in the starting product formation rate observed with increasing temperature up to 80°C and the successive fall beyond this value confirmed the occurrence of reversible biocatalyst inactivation. The simplified Arrhenius model was used to estimate the apparent activation enthalpies of both the acetylation of geraniol (ΔH# = 35 kJ mol−1) and the reversible inactivation of the biocatalyst (ΔH#i = 150 kJ mol−1). The thermodynamic parameters of the irreversible enzyme denaturation were also estimated by residual activity tests performed on lyophilized cells previously exposed in the solvent at different temperatures for variable times (ΔH#d = 28 kJ mol−1; ΔS#d = −0.28 kJ mol−1 K−1). These results on the whole suggest that the reversible inactivation and the irreversible denaturation of mycelium-bound carboxylesterases are thwarted by increases either in the hydrophobicity or in the molecular weight of the alcoholic substrate.

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.

Investigation of naphtalene sulfonate compounds sorption in a soil artificially contaminated using batch and column assays

In the present work desorption tests of an artificially contaminated soil by naphatelene sulphonated compounds have been carried out by soil washing realised by water at different pH: Naphtalene-1,5-disulfonic acid (1-5 NDS), 2-naphthol-6,8 disulphonic acid (G-acid) and sodium beta-naphtalene-sulphonate (beta-salt) have been selected as more representative organic compounds present in the ex industrial site of ACNA (Cengio, SV, Italy) in which very serious contamination levels of several pollutants are present both in the soils and surface waters. Equilibrium batch tests have been carried out in order to find the best operative condition in column washing tests. The obtained results can be considered very preliminary but useful to arrange a next experimental work that will be realised on real contaminated soils.

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,