Paolo Ghetti

Thermal analysis of biomass and corresponding pyrolysis products

Biomass samples were submitted to thermoanalytical investigation to evaluate their thermal behaviour in both oxidizing and inert atmospheres. The trend of the t.g.a. and d.t.g. curves in air or He were evaluated to obtain information on reactivity of the samples and some correlations with their analytical characteristics. In particular, evaluation of lignin content was found to be useful to predict biomass thermal behaviour and the quality of pyrolysis products obtained. As the standard determination of lignin content is complicated, an alternative method using thermogravimetry was also used. A simple laboratory apparatus was used to obtain the pyrolysis products of the biomass samples, allowing a small amount of oil to be collected for thermogravimetric evaluation of its quality. The quality of biomass-derived oil depended on the lignin content of the starting material. Comparison of the thermogravimetric curve of the bio-oil with the corresponding curve of a bio-oil sample produced in an industrial plant showed that the oils obtained in the laboratory apparatus were considerably lighter and therefore better suited for use as fuel.

An investigation of the influence of sodium chloride on the desulphurization properties of limestone

Abstract This investigation shows how sodium chloride adsorbed on particles of limestone can influence certain surface characteristics of the calcium oxide obtained by the calcination process and its capability for flue-gas desulphurization. About 2 wt% of NaCl was found to favour the formation of CaO with a porous texture and also with a better size distribution, which is related both to a higher degree of conversion to CaSO 4 of the sorbent and to a higher rate of conversion. This effect reaches a maximum activity at a temperature of about 850 °C and markedly decreases with increase in the sorbent particle size. KCl behaves in a similar way, but other metallic chlorides examined led to a decrease of the sorption activity of the CaO.

DTG combustion behaviour of coal: Correlations with proximate and ultimate analysis data

Abstract Solid fuel samples were characterized by their proximate and ultimate analyses and then subjected to heat in a thermobalance, both under air and nitrogen. Trends in weight loss were recorded by thermogravimetry (TG) and derivative thermogravimetry (DTG). By examining the data obtained, it was possible to show the existence of good correlations between the VM FC , C H and (C + H) O ratios and both rate of weight loss data and the temperatures deduced from the burning and volatile release profiles. Methods for evaluating the reactivity of coal are reported showing that these substantially agree with the results obtained.

Investigation of the combustion of particles of coal

A thermogravimetric method was used to study the behaviour of seven pulverized commercial coals during the first instants of their combustion and devolatilization and combustion of the corresponding chars. Their weight variations are related to the evolution of the surface characteristics of the carbonaceous materials. In particular, BET surface areas of the chars appear to be strictly related to the volatile matter of the parent coals and to the devolatilization conditions. A thermogravimetric reactivity parameter is suggested and related to the combustion efficiency obtained from pilot plant combustion data.

Vanadium oxide catalysts supported on laser-synthesized titania powders: Characterization and catalytic activity in the selective reduction of nitric oxide

Abstract Laser-activated pyrolysis was applied to the synthesis of ultrafine TiO2, producing a non porous monocrystalline material in anatase phase with high specific surface area and uniform particle size. This powder was used as support for the preparation of vanadia catalysts with different compositions by wet impregnation. The pure TiO2 and the vanadia catalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform IR, X-ray photoelectron spectroscopy, ammonia temperature-programmed desorption and were tested in the reaction of nitric oxide reduction by ammonia. It has been proposed that two different VOx species formed in the submonolayer region: a VIV containing species which prevails up to 6 wt.-% V2O5 and a VV containing species which develops from 6 wt.-% V2O5 up to monolayer completion. The structure of these species has been hypothesized. A reaction scheme has been proposed to interpret the catalytic activity for the selective catalytic reduction (SCR) of NOx. The selectivity of catalysts for nitrogen is related to the prevalence of the VIV containing species.

Coal combustion: Correlation between surface area and thermogravimetric analysis data

Abstract A series of coals of different rank has been characterized by surface area measurements performed by sorption of both nitrogen and carbon dioxide. While the data obtained with nitrogen do not discriminate among the different coal samples, those based on carbon dioxide sorption do give a significant distinction between the samples. This technique has also been applied to the determination of the surface area of coal samples quenched after stepwise combustion in air atmosphere. It has been possible to establish a useful correlation between the latter data and the burning profile measured by derivative thermogravimetry. The aim of the present study was to gain a better understanding of the coal combustion process on a laboratory scale which could reasonably be extended to combustion plants. The results presented are relevant to some of the multivalent aspects inherent in the coal combustion process and some valuable information has been gained in respect of characterization of solid fuels.

A rapid heating TGA method for evaluating the carbon residue of fuel oil

Abstract A new TGA method for evaluating the carbon residue of heavy fuel oil (TGCR) is proposed. Using a Netzsch STA 409 thermobalance it is possible to submit the sample to a high heating rate (> 750°Cmin−1) in nitrogen obtaining a rapid pyrolysis followed by the combustion of carbon residue in oxygen. The results obtained for eight samples of heavy fuel oil are compared with the asphaltene content and with the Conradson carbon residue (CCR). This method is easy and rapid to carry out; it is characterized by good repeatability and may be widely employed in routine laboratories for fuel oil control.

DTG combustion behaviour of charcoals

Abstract In this paper, data are reported for the behaviour of some charcoals during combustion and devolatilization in a thermal analyser.

An XPS study of SO2 on a CaO surface derived from Ca(OH)2

Abstract The adsorption of SO 2 on a CaO surface derived from Ca(OH) 2 has been studied by X-ray photoelectron Spectroscopy. It is shown that SO 2 adsorbs molecularly on the CaO surface forming SO 3 2− and SO 4 2− . The adsorbate SO 3 2− species shift the Ca2 p core levels about 2 eV toward higher binding energy. However, the formation of SO 4 2− species does not induce any further observable changes in the Ca core line spectra. These results are explained and discussed in terms of an electronic charge transfer from the substrate metal atoms to the adsorbed molecules and vice versa.