Gloria Gea

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.

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.