Comparative study for fluidized bed pyrolysis of textile dyeing sludge and municipal sewage sludge.

A comparative research was performed to evaluate the products yields and chars properties for pyrolysis of textile dyeing sludge (TDS) and municipal sewage sludge (MSS). The high fixed carbon (19.36 wt%) and low volatile (23.66 wt%) contents of TDS resulted in higher char yields and lower condensate yields. TDS char (TC) had a higher sulfur (S) retention efficiency than MSS char (MC) and CaO exhibited a great S retention effect in MC. More alkali and alkaline earth metals (e.g. Na, K, Mg and Ca) in MSS contributed to enhanced catalytic pyrolysis. In comparison to non-catalytic pyrolysis, chars from catalytic pyrolysis had lower iodine number and higher methylene blue (MB) adsorption value. MB adsorption values of MC (212.28-414.20 mg/g) were much higher than those of TC (84.32-156.07 mg/g). In contrast, heavy metals risk degrees of MC (4.20-7.56) were lower than those of TC (7.55-12.87), and heavy metals in TC and MC showed slight risks to environment.