Estudo do balanço energético do processo de pirólise de lodo de esgoto em escala laboratorial

Abstract

Tons of sewage sludge are generated in the WWTP across Brazil, and the trend is increasing, due to the access to basic sanitation that has been growing in Brazil. One of the biggest problems related to the WWTP sludge is its disposal, as it is customary to dispose of it in landfills, which are often overcrowded. In addition to having a large amount of pathogens, which contaminates the soil, also has a high combustion content, which has caused accidents in landfills throughout Brazil. Given that alternatives are being mapped worldwide to contain this problem, new research is emerging every day looking for a solution for the WWTP sludge. Among the solutions is pyrolysis, which has advantages in the generation of by-products that add value to the sludge. Aiming at new uses of the WWTP sludge, the present work aims to analyze the economical viability and the energy balance of products obtained in the sewage sludge pyrolysis at laboratory scale. The pyrolysis process was performed under temperature conditions at (450ºC), with a heating rate of (30ºC / min) and at different times (90 min - 120 min - 150 min - 180 min) in order to evaluate the best condition. of process to obtain higher yield of bio-oil, bio-char, bio-gas and aqueous fraction, aiming at the lowest possible energy consumption. The obtained bio-oil and Biochar were characterized, determined the content of N, H, C, S and the superior calorific value. The results show a higher calorific value of 11,783 Mj / kg for biochar and 34,35 Mj / kg for bio-oil. Statistical analysis of the completely randomized design with the F regression test concluded that the time, both the aqueous fraction and the solid fraction, was not statistically significant. Energy consumption for pyrolysis at different times ranged from 6 kWh and 12 kWh to the shortest and longest respectively. The value found for Bio-Oil was $ 0.35 per kilogram, for Biochar was $ 0.013 per kilogram, considering the resale price as raw material. It was observed that the shortest pyrolysis time, 90 minutes, is the most economically advantageous because it uses less energy to produce the byproducts. The amount in reais spent on energy in the 90-minute pyrolysis was R $ 3.60, yielding a value of R $ 0.00189 of biochar, bio-oil and biogas for resale as raw material, reducing the deficit to R $ -3. , 5811. For the use of biochar, bio-oil and biogas in energy transformation, the value obtained was R $ 0.0699, generating a smaller deficit than the resale, R $ - 3.5301. It can be concluded that pyrolysis with 90 minutes time is the most advantageous, but even so the value spent is higher than the value obtained with the byproducts, however the biogas and aqueous fraction values were not considered in this research, but the The price is justified by the reduction in the cost of operating sewage sludge in landfill and the environmental savings caused by the pyrolysis process in relation to sludge deposited in inappropriate places.