Luigi Petarca

Treatment of olive oil industry wastes

Abstract The waste products derived from olive oil extraction are an aqueous effluent (vegetation water) and a solid residue, mainly containing the olive skin and stone (olive husk). Biological purification of the vegetation water is particularly difficult because it contains solids in suspension, and a high concentration of polluting organic compounds and mineral salts. In addition, since the recovery of oil by solvent extraction from the olive husk is no longer a profitable process, the olive husk has become a waste product that must be disposed of. In this work, samples of vegetation water (VW) from olive oil mills were separated by evaporation into an aqueous liquid (80–90% of the initial volume), that could then be purified by a traditional biological process, and a residue in which about 98% of the organic load was concentrated. The properties of the concentrated VW residue and of the olive husk suggested the possibility of using a mixture of the two as an efficient fuel to provide the heat for the evaporation stage.

Devolatilization and pyrolysis of refuse derived fuels : characterization and kinetic modelling by a thermogravimetric and calorimetric approach

Abstract A characterization of pyrolysis behaviour of different refuse derived fuels (RDFs) under heating rates typical of conventional pyrolysis processes is presented. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (d.s.c.) on different RDFs, and on some materials which have been considered ‘key components’ towards thermal degradation characteristics of RDFs, are reported. The RDF weight loss curve presents two distinct weight loss steps attributable, respectively, to cellulosic materials and plastic degradation. Samples from different plants and different municipal solid waste (MSW) feedstocks show the same qualitative behaviour. In interpretation of the experimental results, the assumption has been made that the pyrolysis rate of thermal degradation of RDF can be considered as the sum of the rates of the main RDF components: paper (cellulose), wood-like materials (cellulose, lignin and hemicellulose), plastics mainly polyethylene (PE); and that each component contributed to the formation of this sum to an extent proportional to its contribution to the composition of the RDF. On the basis of these data and by means of a simple mathematical approach a method is proposed which provides a simple tool for RDF characterization and, in particular, evaluation of plastic content. A kinetic model has been developed, based on the assumption that the RDF degradation rate is the weighed sum of the rates of primary reacting species: cellulose, lignin, hemicellulose, PE. Simplified kinetic pathways were used for the description of the degradation processes of RDF components. The model allows quantitative prediction of RDF weight loss and char yield at least at the heating rates used in present work.

Fluorescence spectra and polycyclic aromatic species in a N-heptane diffusion flame

Abstract Fluorescence spectra excited with the lines of a high-pressure Hg/Xe lamp and of an Argon ion laser have been taken from the pyrolysis region of an n -heptane diffusion flame. An experimental characterization of the pyrolysis region at a given flames front in terms of broadband fluorescence spectra is represented. An initial attempt of analyzing the fluorescence in terms of the spectral responses of the polycyclic aromatic hydrocarbons (PAH) formed in the combustion process has been performed, and the concentrations of such molecular species have been estimated at different heights over the burner by employing this method of analysis. The fluorescence cross sections and other spectroscopic data for the most fluorescing PAH in diffusion flames are reported. The fluorescence measurements as well as the estimated concentration levels agree with previous determinations in diffusion flames.

Measurement of Ignition Temperature of Coal Particles Using a Thermogravimetric Technique

Abstract In this paper we describe and test the use of a thermogravimetric technique for measuring the ignition temperatures of thin layers and beds of coal particles, and we report the results of such measurements on a South African coal, a Polish coal and two chars. The technique is to compare weight-temperature curves in air and inert (N2) atmospheres in order to evaluate the ignition temperature; the results are used to test the existing theory and to obtain kinetic constants for the reactions.

Thermal behaviour of poly(methacrylic acid)/poly(N-vinyl-2-pyrrolidone) complexes

Poly(methacrylic acid)/poly(N-vinyl-2-pyrrolidone) (PMAA/PVP) complexes were prepared by two different procedures: simple mixing of preformed PMAA and PVP and radical polymerization of methacrylic acid in aqueous solution in the presence of poly(N-vinyl-2-pyrrolidone) (template polymerization). Differential scanning calorimetry, thermogravimetric analysis and Fourier-transform infrared spectroscopy were performed to evaluate the properties of the two kinds of complexes and to establish if they showed chemico-physical differences that could be related to the preparation procedure. The results of our investigation indicated that the behaviour of these complexes is qualitatively similar, although it was observed that in the case of the complexes produced by blending, the process of PMAA anhydridization induced by a programmed thermal treatment of the samples, was less favoured. This suggests that by template polymerization it is possible to prepare PMAA/PVP complexes having a more ordered structure than that of similar complexes produced by simple mixing of the preformed components.

Advanced pulse calibration techniques for the quantitative analysis of TG-FTIR data

Abstract Two different pulse calibration techniques to estimate the total quantities of evolved gaseous substances formed in thermogravimetric (TG)–FTIR runs were compared and assessed. A gas-pulse calibration method was based on the use of a specific device able of sending a known quantity of a gaseous compound of interest to the FTIR analyzer. A second calibration method was based on the vaporization in the TG analyzer of liquid solutions of the compound of interest. Data obtained by these techniques were compared to those from conventional concentration-based calibration. The results confirmed the reliability of pulse calibration techniques to obtain quantitative data on evolved gaseous products in TG–FTIR applications. Moreover, both the gas-pulse and the vaporization-based calibration techniques proved to have several advantages with respect to conventional techniques. Among these are the need of a more limited number of standards and no need for online gas dilution systems.

LOW-TEMPERATURE AIR OXIDATION OF COAL AND ITS PYRIDINE EXTRACTION PRODUCTS - FOURIER-TRANSFORM INFRARED STUDIES

Abstract Fourier transform infrared spectroscopy has been used to study the evolution of the structure of a bituminous coal and its pyridine extraction products during oxidation. Different methods of analysis of the spectra have been used, such as curve-resolving routines, coupled to second derivative methods and area integration. The pyridine extract has been found to maintain the characteristic absorption bands of the original coal and to present marked susceptibility towards oxidation, to a greater extent than its parent coal. The analysis of the coal, extract and residue spectra and their comparison as oxidation proceeds, give an insight into the complex phenomena occurring. Pyridine extract spectra present a better separation of contributions of the bands involved, by the low temperature oxidation of low rank coals, particularly in the zones 3500-2800 and 1800-1500 cm −1 .

Film combustion of ethyl alcohol in a parallel air stream

The structure of the diffusion flame formed on a liquid fuel surface with a parallel oxidizer flow was studied both analytically and experimentally. Only the case of ethyl alcohol burning in air has been considered in this paper. The temperature and species concentration profiles across the boundary layer were determined by means of fine, carefully calibrated thermocouples and of gas chromatography. The gas analysis yielded the concentrations for the following species: N 2 , C 2 H 5 OH, O 2 , CO 2 , H 2 O, CO, CH 4 , C 2 H 2 +C 2 H 4 , C 2 H 6 , CH 3 CHO, H 2 . The mathematical model is based on the Shvab-Zeldovic formulation of conservation equations with physical properties considered as functions of temperature and species concentration. The agreement obtained between the experimental and theoretical profiles of temperature and of normalized elemental mass fractions of the atomic species N, O, C, H is satisfactory when the fuel diffusivity in nitrogen replaces the actual species and thermal energy diffusivities in the conservation equations.

Ignition and Combustion of Single, Levitated Char Particles

The paper focuses on the experimental measurement and model prediction of burnout times and ignition temperatures of single char particles. Experimental temperature-time histories of single, submillimetric char particles are compared with the predictions of a simple model that takes into account all the experimental findings obtained on a model char with an electrodynamic balance (EDB). The particular features of the experimental technique, allow the measurement of the temperature of the surface of a single levitated particle as the high temperature reaction proceeds. The particle is heated to reaction conditions with a laser while the surrounding gases are maintained at room temperature. Particle ignition temperatures and burnout times are easily detected from experimental curves. Even with the high temperature (2500-3000 K) and low characteristic time of the reaction (30-100 ms), reproducible experimental data were obtained, confirming that the EDB is a viable tool for studying high-temperature heterogeneous gas-solid reactions. Experimental results are compared with the predictions of a simple model developed for the description of high temperature combustion of single char particles. Even if particle morphological modifications occurring at high conversion degrees are not accounted for, the model well describes the particle ignition process and predicts with sufficient accuracy ignition temperatures and burnout times.

Boundary Layer Burning of Fuel Surfaces: Thermal and Aerodynamic Structure of the Flame

Abstract The main characteristics of diffusion flames formed on a liquid fuel surface with a parallel oxidizer flow have been studied both analytically and experimentally. In the present paper fuel burning rates and temperature and velocity profiles have been determined for various liquid fuels. Experimental results arc in good agreement with the theoretical model previously developed by one of the authors, except for the velocity profiles at low air velocity, which display a pronounced overshoot close to the flame zone. Present results also indicate that main flame characteristics can be controlled by means of the temperature of the liquid fuel contained in the burner and kept constant for long times. Finally, the burner studied in this research appears to be particularly suitable for the analysis of combustion kinetics.