Pollutant characteristics of the pyrolysis of petrochemical wastewater sludge by an electric furnace

Abstract

Organic sludge represents significant reservoirs of renewable energy. However, the pollution-control costs of incinerator flue gases are high. An alternative to treating the sludge is low temperature pyrolysis process, which produces liquid oil rather than gases. The objective of this study is to examine pyrolysis of a petrochemical industrial sludge in an electric furnace. The pyrolysis was carried out in an isothermal reactor heated by a horizontal electric furnace. The element compositions of the sludge residues were analyzed with ICP. Concentrations of Zn, Cu, and Sb in a pyrolysis residue were increased with increased temperatures. This indicates that Zn, Cu, and Sb were concentrated during pyrolysis process. Volatile organic compounds (VOCs) and volatile sulfur compounds were analyzed with GC/MS to assess the exhaust gas compositions. The VOCs were generated from 400 to 900°C, but their concentration was significantly decomposed at 900°C. The concentration of volatile sulfur compounds increased when the pyrolysis temperature was increased from 400 to 700°C. When the pyrolysis temperature reached 800°C, concentrations decreased. The rate constants, reaction orders, activation energy, and frequency factor were found by fitted nonlinear and linear regression. The average reaction order was 2.5, when pyrolysis temperatures ranged from 400 to 900°C. The slope of activation energy (Ea/R) was 3243 and the frequency factor was 0.99 sec-1.