Co-pyrolysis characterization of pre-oxidized lignite and corn stover

Abstract

In this paper, low-rank lignite and corn stover were pre-oxidized at 200 °C with varying oxygen concentrations (0 %, 6 %, 21 %). The study investigated the effects of pre-oxidation on the physical and chemical properties of lignite and stover, including composition, functional group structure, etc. Subsequently, co-pyrolysis experiments were conducted on the pre-oxidized lignite and stover at 700 °C. The study examined the characteristics of the co-pyrolysis of lignite and corn stover under different oxygen concentrations. The results showed that pre-oxidation could effectively increase the content of fixed carbon in the raw materials, elevate the content of carbonyl and carboxyl groups in the raw materials, and reduce the number of aliphatic hydrocarbon side chains as well as hydroxyl groups. The degree of aromatization of the co-pyrolysis char produced from pre-oxidized lignite and corn stover was enhanced. The 6 % O2 pre-oxidation promoted the pyrolysis degree of the raw materials and intensified the progression of the reaction. The CO2 content of the co-pyrolysis tar was at a minimum of 23.028 % with 0 % O2, and the gas had a maximum calorific value of 11.651 MJ∙Nm−3 at this point. Pre-oxidation had an inhibitory effect on the production of co-pyrolysis tar, and the inhibitory effect became more pronounced with higher concentrations of O2. The higher the oxygen concentration, the more pronounced the inhibition. The addition of oxygen promotes the generation of phenols and ketones in the tar, reducing the content of acids and aldehydes. This improves the quality of the tar but also results in a reduction of aromatic hydrocarbons to some extent.