Parametric studies on the pyrolysis of poultry litter

Abstract

The safe and economical disposal of poultry litter by pyrolysis process offers many advantages over the traditional method such as land application. Fast pyrolysis technology converts poultry litter into biocrude oil, char and gas. The biocrude oil can be used as heating oil and the char as an organic fertilizer. The formation of these products is known to be influenced by pyrolysis conditions. Poultry litter is a mixture of manure, feathers, feed and wood shavings. In this work, pyrolysis of a mixture of 50wt.% layer manure and 50wt.% pine wood shavings in a 50 mm bubbling fluidized bed was studied parametrically using a Box-Behnken experimental design to investigate the effect of temperature, gas flow rate and feed rate on the pyrolytic products and pH of the biocrude. The operational variables were as follows: temperature (400-550C), nitrogen gas flow rate (12-24 L/min), and feed rate (160-480 g/h). The biocrude yield was significantly influenced by temperature, feed rate and gas flow rate. Temperature was the only significant factor that influenced the char yield. Maximum biocrude yield (51.1 wt. %) was achieved at 475C with a feed rate of 480 g/h and a gas rate of 12 L/min. The lowest char yield (22.6wt.0%) was achieved at 550oC, 320 g/h and 12 L/min and the biocrude had the highest pH (4.85) at 475oC, 160 g/h and 24 L/min. Predictive models were proposed for the yields of liquid and char and also the pH of biocrude.