Influence of acid washing using cattle manure on thermogravimetric characteristics and pyrolysis kinetics in a micro-tubing reactor

Abstract

Ash content is known to be one of the problems in 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 acid-washing pretreatment of CM on pyrolysis characteristics was investigated. The experiments were performed using a microtube 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 and 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 CM samples was established using experimental data. It was found that as the ash content decreased by acid-washing, the char yield decreased, while the yields of bio-oil and gas increased. Finally, the compositions of gas and bio-oil obtained through pyrolysis of CM were systematically characterized.