M.B. Murillo

Co-pyrolysis of sewage sludge and manure.

The management and valorization of residual organic matter, such as sewage sludge and manure, is gaining interest because of the increasing volume of these residues, their localized generation and the related problems. The anaerobic digestion of mixtures of sewage sludge and manure could be performed due to the similarities between both residues. The purpose of this study is to evaluate the feasibility of the co-pyrolysis of sewage sludge (SS) and digested manure (DM) as a potential management technology for these residues. Pyrolysis of a sewage sludge/manure blend (50:50%) was performed at 525°C in a stirred batch reactor under N2 atmosphere. The product yields and some characteristics of the product were analyzed and compared to the results obtained in the pyrolysis of pure residues. Potential synergetic and antagonist effects during the co-pyrolysis process were evaluated. Although sewage sludge and manure seem similar in nature, there are differences in their pyrolysis product properties and distribution due to their distinct ash and organic matter composition. For the co-pyrolysis of SS and DM, the product yields did not show noticeable synergistic effects with the exception of the yields of organic compounds, being slightly higher than the predicted average, and the H2 yield, being lower than expected. Co-pyrolysis of SS and DM could be a feasible management alternative for these residues in locations where both residues are generated, since the benefits and the drawbacks of the co-pyrolysis are similar to those of the pyrolysis of each residue.

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.

Thermal decomposition of lignocellulosic materials: comparison of the results obtained in different experimental systems

Abstract An experimental system that allows the use of large particle sizes and the simulation of different operating conditions was built to study the thermal decomposition of lignocellulosic materials. The values of solid conversion and of temperature obtained at different points using spherical particles of pine wood 2 cm in diameter are shown. The conversion values are compared with those calculated from the equations obtained in a thermobalance for small particle sizes.

Pyrolysis of black liquors from alkaline pulping of straw. Influence of a preoxidation stage on the char characteristics

Abstract New alternative processes such as low temperature gasification are currently being developed in order to use of black liquors from pulp and paper mills with energy proposes. The development of these new processes makes necessary to study the behavior of black liquors during pyrolysis and gasification paying special attention on their thermoplastic properties, which can cause important operational problems due to its swelling when heated. Present work is focused to the study of pyrolysis of alkaline black liquors from pulping of straw. The influence of an oxidation stage at low temperature previous to pyrolysis, on specific surface area of the char and on the black liquor swelling, is studied. For that, two main variables are analyzed: time of preoxidation and final temperature of pyrolysis. Dry black liquors from alkaline pulping of straw were used as material. The resulting chars obtained showed a clear decrease in swelling level of the black liquors, as well as an increase on their specific surface area, within the pyrolysis temperature and the preoxidation time. Materials with specific surface areas varying from 2 up to nearly 500 m 2 g −1 can be produced with the correct choice of experimental conditions. From the results, further research on the influence of a preoxidation stage on black liquors may lead to a better understanding of new alternative processes, which are nowadays being developed.

Thermal decomposition of a wood particle. Temperature profiles on the solid surface

Abstract The calculation of the weight loss during the thermal decomposition of lignocellulosic materials involves the solution of the heat and mass balance equations. In order to solve these equations it is necessary to know the temperature on the solid surface, which can vary at different points and can also be very different from the gas temperature. In this work, an experimental study was carried out in a system which allows the use of large particle sizes and the simulation of different operating conditions. In this study, the temperatures on the solid surface were measured and compared with those corresponding to the empty reactor.

Heat Transfer and Weight Loss in the Thermal Decomposition of Large Wood Particles

An experimental study of the thermal decomposition of spherical pine wood particles of different sizes (2–5.6 cm in diameter) has been carried out, using several heating rates of the system. An increase in the particle size produces an appreciable decrease in the weight loss of the solid during the time of its pyrolysis, caused by significant temperature profiles both radial and angular inside the solid. The experimental results have also shown the influence of the particle size and heating rate on these profiles, so that as the particle size and heating rate increase, these profiles become steeper. An analysis of the different values and trends has been performed.

Angular and radial temperature profiles in the thermal decomposition of wood

Abstract During the thermal decomposition of wood, an increase in the particle size produces an important decrease in the weight loss of the solid caused by significant temperature profiles, both radial and angular, inside the solid. In order to determine these profiles, experiments with different particle sizes (2, 3, 4 and 5.6 cm in diameter) have been carried out. In these experiments, temperatures at different points corresponding to various values of radii and angles were measured. An analysis of the different values and trends obtained has been performed.