Carlos Roberto Altafini

Prediction of the working parameters of a wood waste gasifier through an equilibrium model

Abstract This paper deals with the computational simulation of a wood waste (sawdust) gasifier using an equilibrium model based on minimization of the Gibbs free energy. The gasifier has been tested with Pinus Elliotis sawdust, an exotic specie largely cultivated in the South of Brazil. The biomass used in the tests presented a moisture of nearly 10% (wt% on wet basis), and the average composition results of the gas produced (without tar) are compared with the equilibrium models used. Sensitivity studies to verify the influence of the moisture sawdust content on the fuel gas composition and on its heating value were made. More complex models to reproduce with better accuracy the gasifier studied were elaborated. Although the equilibrium models do not represent the reactions that occur at relatively high temperatures (≈800 °C) very well, these models can be useful to show some tendencies on the working parameter variations of a gasifier.

Influence of mould material on ceramic disc dimensions in low-pressure injection moulding

This work presents a study regarding the influence of the cooling process, as a result of different mould insert materials, on ceramic parts dimensions obtained by low-pressure injection moulding process. Discs of ceramic with Ø80 × 2 mm, composed by 86 wt.% alumina (Al2O3) and 14 wt.% organic vehicle, were produced. An experimental injection mould was designed and manufactured with built-in heating and cooling systems, controlled by a DAQ (Measurement Computing – USB-TC) and thermocouples K type. Four types of insert materials were used: aluminium alloy (AA7075-T6), electrolytic copper, brass alloy (C36000) and SAE1045 steel. Tests were carried out considering injection moulding parameters constant, i.e. initial mould temperature, injection pressure and time and extraction temperature. All the post-process (debinding by wicking; final debinding and sintering) parameters were also kept constant. Parts were analysed considering dimensions, mass, geometry, visual aspects and defects. The results showed that the cooling rate resulting from the thermal conductivity of each material has influenced more significantly the dimensional shrinkage and mass reduction of the samples during the intermediate post-processes phases. The geometric deviations were different for each condition throughout the process and they increased in the final parts. The parts produced with higher cooling rate had higher geometric deviations.