J. Arauzo

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.

Kinetics of thermal decomposition of cellulose: Part I. Influence of experimental conditions

The kinetics of weight loss in the thermal decomposition of cellulose have been determined by means of isothermal and dynamic experiments carried out under various conditions. Values for the pyrolyzable fraction, reaction order and kinetic constant have been obtained from isothermal experiments, while the important influence of the rate of heating of the system as well as the percentages of pyrolyzed solids at T ⩽ 150°C have been observed from the dynamic experiments.

Thermal decomposition of lignocellulosic materials: influence of the chemical composition

Abstract The results obtained with different lignocellulosic materials (“Pinaster” pine and barley straw) are compared with those calculated by considering the weighted contributions of the different constituents of the materials. The results obtained in isothermal and dynamic experiments with “Pinaster” pine showed a good agreement, whereas higher divergences were found for barley straw. A different method of data analysis is proposed for barley straw, which uses results directly obtained with this material.

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.

Prediction of normalized biodiesel properties by simulation of multiple feedstock blends

A continuous process for biodiesel production has been simulated using Aspen HYSYS V7.0 software. As fresh feed, feedstocks with a mild acid content have been used. The process flowsheet follows a traditional alkaline transesterification scheme constituted by esterification, transesterification and purification stages. Kinetic models taking into account the concentration of the different species have been employed in order to simulate the behavior of the CSTR reactors and the product distribution within the process. The comparison between experimental data found in literature and the predicted normalized properties, has been discussed. Additionally, a comparison between different thermodynamic packages has been performed. NRTL activity model has been selected as the most reliable of them. The combination of these models allows the prediction of 13 out of 25 parameters included in standard EN-14214:2003, and confers simulators a great value as predictive as well as optimization tool.

Kinetics of weight loss by thermal decomposition of xylan and lignin. Influence of experimental conditions

The kinetics of weight loss in the thermal decomposition of xylan and lignin in a nitrogen environment have been studied thermogravimetrically. The data from this study are analysed in the light of previous conclusions obtained with cellulose. The results from isothermal and dynamic experiments at different heating rates are related by using the results of dynamic experiments with low heating rates (1.5 °C min−1) as a reference.

Kinetics of weight loss by thermal decomposition of different lignocellulosic materials. Relation between the results obtained from isothermal and dynamic experiments

Abstract The kinetics of weight loss in the thermal decomposition of Pinaster pine and barley straw in a nitrogen environment have been studied. The results obtained under different experimental conditions are shown and compared. These results are related by using the results of dynamic experiments with low heating rates as a reference.

Low heating value gas on spark ignition engines

Abstract The performance of a spark ignition engine using low heating value (LHV) gas generated in a fixed bed downdraft (co-current) gasifier, using agricultural and forestry residues was measured on a dynamometer test bench. The parameters measured include torque, power output, emissions measurement, exhaust gas temperature for both operation on gasoline and LHV gas. Improvements in hydrocarbon and carbon monoxide emissions were obtained and the engine suffered less thermal stress under LHV gas operation. The power loss was relatively low, though the experimental arrangement restricted the power output at high throughputs of gas.

Methanolysis and ethanolysis of animal fats: a comparative study of the influence of alcohols.

Biodiesel from animal fats with methanol and ethanol was produced in the presence of sodium methoxide and sodium ethoxide as catalysts. Two samples of pork fats and one natural beef tallow were directly transesterified with a good final product yield; 87.7%, 86.7% and 86.3% for methanolysis and 78.4%, 82.6% and 82.7% for ethanolysis, respectively. Methyl ester content was also determined, being higher than 96.5 wt. % for all the samples prepared, the presence of natural C17:0 in animal fats makes it necessary to correct the method proposed in the standard EN 14103 (2003). Biodiesel density at 15 oC of the samples was between 870 and 876 kg/m3, within the acceptance range of standard EN 14214, dynamic viscosity at 40 oC of the produced biodiesels, in the range of 4.5 to 5.16 mm2/s, also fulfills requirements of EN 14214 standard. The iodine value is much lower than the superior limit established by EN 14214 standard but oxidation stability (OSI) is lower than the required limit, 6 h, of the standard, which can be attributed to the lack of natural antioxidants in tallows.

Kinetics of thermal decomposition of cellulose: Part II. Temperature differences between gas and solid at high heating rates

Abstract The use of high heating rates when studying the thermal decomposition kinetics of cellulose gives rise to a gap between the solid temperature and the thermogravimetric system temperature. A model is proposed which accounts for this temperature gap and permits the calculation of the actual solid temperature. The results for various heating rates are fitted using the same kinetic equation.