Characterization of the products from the pyrolysis of sewage sludge in 1 kg/h rotating cylinder reactor

Abstract

The objectives of this study were to produce and characterize bio-fuels through the thermal treatment of sewage sludge in an 1kg/h rotating cylinder reactor. The experimental procedure was divided into three parts: (a) initial test using the temperatures of 450, 500, 550, 600 and 650°C while the nitrogen flow, the centrifuge rotation and biomass flow were kept constant, (b) 24–1 fractional experimental design and (c) experiments exclusively for the characterization of gaseous fraction, using the temperatures of 500, 550 and 600°C. The maximum liquid yield was 10.5% obtained at the temperature of 500°C, inert gas of 200mL/min, biomass flow of 22g/min and centrifuge rotation of 20Hz. The maximum char yield was 61.9%, obtained at 500°C, inert gas of 100mL/min, biomass flow of 4g/min and centrifuge rotation frequency of 20Hz. The highest phase gas yield was 23.3%, obtained at 600°C, inert flow rate of 200mL/min, biomass flow rate of 22g/min and rotation frequency of 30Hz. The bio-oil had the following characteristics: pH between 6.80 and 6.84, density between 1.05g/mL and 1.09g/mL, viscosity between 2.5cSt and 3.1cSt and high heating value between 16.91MJ/kg and 17.85MJ/kg. Non-oxygenated aliphatic (55%) and aliphatic oxygenated hydrocarbons (27%) were found in the bio-oil. The main components detected in the gas phase were H2, CO, CO2 and CH4. Hydrogen was the main constituent, with a yield of 46.2% at 600°C. Among the hydrocarbons formed, methane was predominant (16.6%) at 500°C. The results show that increasing the temperature from 500 to 600°C favors the increase in the gaseous phase and reduction of solid and liquid fractions.