Kinetics of hydrothermal carbonization of kitchen waste based on multi-component reaction mechanism

Abstract

Hydrothermal carbonization (HTC) is a suitable method to pretreat kitchen waste with high moisture content and complex composition. Developing a precise kinetic model can accurately predict the yields of products to obtain better economic benefits in subsequent utilization, such as fuel. This study aimed to propose an HTC kinetic model of kitchen waste by studying the multi-component reaction mechanism. The HTC reactions of multi-component kitchen waste could be summarized as three key reactions: carbonization of carbohydrates, the Maillard reaction, and the amidation reaction. These reactions were reflected in the kinetic model. Moreover, the calculated results indicated the fitting degree reached 0.9995, which accurately simulated the hydrothermal process of kitchen waste. This model illustrated the rate and extent of the reaction between the components. The kinetic results showed that the rate constant of carbonization of carbohydrates was 0.0012, and that of the Maillard reaction and the amidation reaction were 0.0998 and 0.1409, respectively. The amidation reaction competed with the Maillard reaction and dominated the reaction of the constant-temperature stage. This model provided preliminary guidance for regulating and utilizing HTC products from kitchen waste in different institutions and regions.