M.L. Salvador

CO2 as a gasifying agent for gas production from pine sawdust at low temperatures using a Ni/Al coprecipitated catalyst

Catalytic CO2 gasification of pine sawdust has been carried out at a relatively low temperature, 700°C, and at atmospheric pressure. The Ni/Al catalyst used was prepared by coprecipitation and calcined at 750°C for 3 h. The influence of the catalyst weight/biomass flow rate (W/mb) ratio on product distribution and gas composition was analyzed. Using a CO2/biomass ratio of around 1, the increase of the W/mb ratio increases H2 and CO yields while CH4 and C2 yields decrease. Deactivation of the catalyst was also observed under the experimental conditions employed. The influence of the W/mb ratio on the initial gas yields has been also analyzed. For W/mb ratios ≥0.3 h, no significant modifications are observed on the initial yields of different gases, and it is confirmed that under these conditions the initial gas composition is close to that for thermodynamic equilibrium. The influence of the reaction atmosphere on gas yields has also been carried out, analyzing the results obtained in pyrolysis, steam gasification and CO2 gasification.

Catalytic pyrolysis of biomass: influence of the catalyst pretreatment on gas yields

Abstract This experimental study of biomass catalytic pyrolysis at low temperatures (650 and 700°C) was carried out in an installation based on the Waterloo Fast Pyrolysis Process (WFPP) technology, with a Ni/Al coprecipitated catalyst introduced into the reaction bed where the thermochemical decomposition of biomass took place. The influence of the calcination temperature (750–850°C) and the activation conditions (hydrogen flow rate) of the catalyst were analyzed. The calcination temperature significantly influences the properties and performance of the catalyst. For the two reaction temperatures, 650 and 700°C, and with the catalyst calcined at 850°C, higher H 2 and CO yields were obtained with the reduced catalyst (flow rate 3080 cm 3 (STP)/min; WHSV=0.826 h −1 ) than without reduction. However, the catalyst calcined at 750°C without reduction showed a good performance at the reaction temperature of 700°C. Considering the characterization and experimental results, it can be deduced that the catalyst calcined at 750°C is reduced by the reaction atmosphere forming a stable active phase, whereas for the catalyst calcined at 850°C more severe reduction conditions are necessary.

Shelf-life extension of fresh Tuber aestivum and Tuber melanosporum truffles by modified atmosphere packaging with microperforated films.

The aim of this study was to design a modified atmosphere packaging suitable for Tuber melanosporum and Tuber aestivum truffles that extend their shelf life and their availability as a fresh product. Their respiration rates were determined by O(2) depletion and CO(2) formation in closed systems performed at different temperatures: 4, 10, and 23 degrees C. The results were fitted by exponential equations and derivatives of these equations were used to obtain the experimental respiration rates. Our results revealed high respiration rates in both species of truffles and respiratory quotients (RQ) higher than 1 in all the cases studied. A linear dependence of respiration rate, both R(O2) and R(CO2), on O(2) concentration was revealed. A mathematical model was used to predict the evolution of the gaseous composition at 4 degrees C in the interior of polypropylene trays (250 mL) heat sealed with 4 microperforated films of different transmission rates. A microperforated film with 2 holes (90 x 50 microm) was selected to produce an internal atmosphere of 15%CO(2)/7%O(2) at 4 degrees C. The predicted atmosphere composition was confirmed by the experimental results. The quality and microbiological characteristics of fresh truffles, packaged in these conditions, revealed that the microbial counts of pseudomonads and Enterobacteriaceae were decreased, the weight loss was reduced, the typical hard texture was maintained, and the development of mycelium growth was delayed, enabling good scores for aroma and flavor, and therefore prolonging the shelf life of T. melanosporum and T. aestivum truffles to 28 and 21 d, respectively. Practical Application: This study describes the benefits of using MAP with microperforated films in the postharvest storage of Tuber melanosporum and Tuber aestivum fresh truffles. The shelf life of T. aestivum is prolonged to 21 d and of T. melanosporum to beyond 28 d increasing the possibilities for a foreign market.

Scale-up of downdraft moving bed gasifiers (25-300 kg/h) - design, experimental aspects and results

Abstract Two installations with different biomass processing capacities (25–50 and 200–300 kg/h) were designed and constructed for air gasification of lignocellulosic biomass. This paper describes both installations as well as the experimental procedure. The influence of operating conditions on the amount and quality of products was determined. The results obtained from processing forestry waste are analysed. Values above 90% for mass conversion efficiency and over 70% for cold gas efficiency were reached.

Gas formation in the thermal decomposition of large spherical wood particles

Gas formation, weight loss and temperature profiles in the thermal decomposition of relatively large particles of pine wood have been studied. Experiments with spherical particles of different sizes (2, 3 and 4 cm in diameter) have been carried out at two heating rates of the system (5 and 12°C min−1). The existence of significant radial and angular profiles in the particles causes differences in the conversion and in the formation of gases. The experimental yields obtained for the majority gas, CO2, have been compared with the calculated yields using a model without adjustable parameters. An acceptable agreement has been achieved between the experimental and calculated results.

Influence of cooking conditions on organoleptic and health-related properties of artichokes, green beans, broccoli and carrots.

Colour, pigments, total phenolic content and antioxidant activity were investigated in artichokes, green beans, broccoli and carrots cooked under different conditions. Domestic induction hobs with temperature control were used to evaluate the effect of boiling, sous-vide cooking and water immersion cooking at temperatures below 100°C on the properties of each vegetable. Sous-vide cooking preserved chlorophyll, carotenoids, phenolic content and antioxidant activity to a greater extent than boiling for all of the vegetables tested and retained colour better, as determined by a(∗). A reduction of only 10-15°C in the cooking temperature was enough to improve the properties of the samples cooked by water immersion, except for green beans. Artichokes and carrots suffered pronounced losses of antioxidant activity during boiling (17.0 and 9.2% retention, respectively), but the stability of this parameter significantly increased with sous-vide cooking (84.9 and 55.3% retention, respectively).

Influence of the heating rate on the temperature profiles and on the conversion rate of powdery cellulose and pine sawdust

Abstract An experimental study of the thermal decomposition of powdered cellulose and pine sawdust has been performed. The influence of the heating rate on the temperature profiles in the sample and on the solid conversion rate has been studied. A mathematical model without adjustable parameters has been used to calculate the temperature at different points in the solid bed and the average total solid conversion. The experimental results have been compared with those calculated by the model. A good agreement has been obtained for sawdust. Some differences are observed for cellulose at high heating rates, and the influence of the thermal conductivity and the reaction heat on the results has been analysed.

Solid weight loss in the thermal decomposition of cellulose and pine sawdust

An experimental study of the thermal decomposition of powdered lignocellulosic biomass was performed in a macrobalance system. Weight loss and temperature profiles in the bed for different heating rates were determined using mainly cellulose and pine sawdust. Some experiments with xylan and lignin were also carried out. A simple model was used to calculate weight loss and temperature at different points. An average temperature allows comparison of the results obtained.

Modeling of Changes in Atmosphere Composition in Fresh-cut Peach Packages due to Temperature Fluctuations

Storage temperature is not always constant in the distribution chain of modified atmosphere fresh food packages. A change in temperature means an alteration in the respiration rate of the product and in the gas transmission rates through the film. Because of their high metabolic activity, minimally processed products are particularly sensitive to temperature variation, and hence this study has been carried out with five cultivars of fresh-cut peaches (Prunus persica). Their respiratory activity has been determined by a closed system at 4, 15, and 25 °C. The peach segments are wrapped in microperforated films whose transmission rate is determined according to the size of the microperforations (between 100 × 130 μm and 215 × 190 μm). To quantify the effect of temperature fluctuations (5 h at 25 °C) on the O2 and CO2 concentrations of the packaging atmosphere of the product, a mathematical model has been applied. Using experimental data, it has been established that the rate of O2 consumption is a potential function of the O2 concentration, while the production of CO2 is linear. Although, all cultivars are of nonmelting fresh with no big differences in respiratory activity; these differences are accentuated with O2 concentrations greater than 10% and raising the temperature. The solution of the model provides knowledge of the behavior of the product during its nonstationary period and equilibrium once reached. The results show in all cases that the CO 2 concentration is more sensitive (increase of 5 units) to a break in the cold chain than that of O2 (reduction of 2 units).

Composición del consejo rector y género en las cooperativas turolenses

En los ultimos anos se esta observando un crecimiento en el numero de trabajos que analizan la situacion de las mujeres en los organos de gobierno de las organizaciones tanto lucrativas como de las entidades enmarcadas en el ambito de la economia social. Si bien la literatura economica es incipiente y mas abundante fuera de nuestras fronteras cada vez es mayor el numero de publicaciones que estudian la situacion en Espana. Diversos estudios muestran que un mayor numero de mujeres en los consejos representativos de las cooperativas puede ayudar a que las condiciones de trabajo mejoren y se consiga un equilibrio economico, social y cultural en este tipo de organizaciones. En este estudio se analiza la presencia femenina en los organos de gobierno de estas entidades en la provincia de Teruel y se compara con los tipos de cooperativas gestionadas por mujeres con el proposito de examinar si existen asociaciones entre ellas. Al mismo tiempo, se relaciona el periodo de creacion de la entidad con la participacion femenina, con el fin de observar la evolucion de la responsabilidad de las mujeres en distintos intervalos de tiempo.