Low temperature conversion of some Brazilian municipal and industrial sludges

Three Brazilian municipal and industrial sludges were subjected to the Low Temperature Conversion (LTC) process. They include activated, digested and lacquer sludges. The activated sludge recorded the highest yield of LTC oil (31.4%), followed by lacquer sludge (14.0%) and the digested sludge 11%. H-1-NMR studies of the oils indicated that they consisted mainly of aliphatic and olefinic compounds, while the concentration of aromatics was below 2.5%. The major hydrocarbons in the oils were pentadecane and heptadecane. The distribution pattern of hydrocarbons present in the oils was similar to what is known from the conversion of other sludges. In addition the LTC oil from activated sludge contained 26% fatty acids, while the oils from digested and lacquer sludge contained only about 3% fatty acids. Recovery studies on the fate of heavy metals in the sludges indicated that they were accumulated in the char. Partial gasification studies of the LTC chars resulted in active carbons with quite low iodine and methylene blue numbers. However, even if their use is limited the production of active carbon together with the recovery of LTC oil constitutes a complete disposal of the sludges. (C) 2000 Elsevier Science Ltd. All rights reserved.