Optimizing the mechanical properties of coal-fines briquettes produced with steam-exploded sugarcane bagasse as a binder
Lodewicus van der Westhuizen, Danie Diedericks, G. Akdogan, Johann F. Görgens
Abstract
Co-briquetting of coal fines and lignocellulosic biomass is a possible path for incorporating biomass energy into the current coal-based infrastructure, although the cost and performance of conventional binders remain problematic. The use of steam-exploded sugarcane bagasse (SE SCB) as a binder for coal fines briquetting was therefore investigated. SE SCB (produced at 140–220°C for 15 min) was mixed with high-ash bituminous coal-fines at various concentrations (0–18%), and briquetted at a pressure value of 24 MPa and at various temperatures (25–180°C). Following multivariate optimization, an optimal steam explosion temperature range of 185–195°C was found. At these pretreatment temperatures, sufficient disruption of the lignocellulosic structure occurred, resulting in increased binding between coal fines and SCB, while higher temperatures resulted in detrimental destruction of fiber structure and reduction in binding performance. A synergistic interaction between briquetting temperatures and SE SCB content above 100°C and 13%, respectively, substantially improved briquette properties. At these optimum conditions, the briquettes had a compressive strength of 1205 kPa, an abrasion resistance of 97%, water absorption index of 82%, and a wet compressive strength of 501 kPa. Briquettes maintained structural integrity when pyrolyzed at 700°C and had a post-pyrolysis compressive strength of 134 kPa, indicating that SE SCB could potentially be a suitable binder for coal fines briquetting.