Exploring the Impact of Steam Explosion Pretreatment on the Binding Characteristics of Coal-Biomass Briquettes: A Study on Lignocellulose Type and Fibre Morphology

Abstract

AbstractThe urgency to shift from coal to renewable energy sources drives the need for innovative solutions. Steam exploded lignocellulose acting as both binder and fuel in coal-briquetting presents a pathway for this transition whilst utilizing waste coal-fines. However, the applicability of different industrially relevant feedstocks and their specific binding mechanism is unknown. In this study we assess the impact of treatment severity and explosion pressure on fibre properties and briquette tensile compressive strength (TCS) across four feedstocks (sugarcane bagasse (SCB), corn stover (CS), black wattle (BW), and pine). Lignocellulose was steam exploded at severities ranging from 3.53 to 4.71 and physical modifications due to explosion pressure was isolated by conducting explosive decompressions at pressures ranging from 3 to 22.5 bar. Briquettes, prepared using 18% by mass steam exploded lignocellulose as a binder, were quantified for TCS and results showed that as particle aspect ratio increased, so did TCS, regardless of lignocellulose type. For SCB, CS, and BW, high explosion pressure and low to moderate severity (3.5–3.8) produced the highest aspect ratios and, consequently, highest TCS (1288, 1181, 905 kPa respectively). However, at high severity and pressure, a reduction in aspect ratio was observed and, subsequently, TCS. Pine required high severity and pressure to produce barely acceptable briquette TCS (364 kPa), due to its low aspect ratio. Physical modification of fibre aspect ratio during steam explosion therefore played a crucial role in its binding performance in coal-briquettes and the relative success of SCB, CS and BW indicate that there are significant resources of lignocellulose available for this technology and allow for widespread industrial application. Graphical Abstract