Influence of Acid Washing Using Cattle Manure on Thermogravimetric Characteristics and Pyrolysis Kinetics in a Micro-tubing Reactor

Ash content is known to be one of the problems in the pyrolysis of cattle manure (CM) biomass. In this study, to reduce the ash content in CM, the original material was pretreated with a nitric acid solution, and the effect of the acid-washing pretreatment of CM on the pyrolysis characteristics was investigated. The experiments were performed using a micro-tubing reactor at 375–425 °C with different reaction times. The main components of the inorganic content before and after acid-washing were Ca and K, which decreased after the treatment. As a result of calculating the activation energy at a conversion of 90% using Friedman’s method, it was calculated to be 540.80 kJ/mol for the original sample that decreased to 409.93 and 391.53 kJ/mol for the samples washed with 10 and 20 wt% diluted acid solutions, respectively. In addition, a reaction kinetic model for the CM samples was established using experimental data. It was found that as the ash content decreased by the acid-washing, the char yield decreased, while the yields of bio-oil and gas increased. Finally, the compositions of the gas and bio-oil obtained through the pyrolysis of CM were systematically characterized.