Blends of charcoal fines and wood improve the combustibility and quality of the solid biofuels

Abstract

The effects of the blends of charcoal fines and Schizolobium parahyba var. amazonicum (parica) wood on the briquette quality and on the combustibility of this solid biofuel is not fully understood, especially from fast-growing plantations with Amazonian tree species. In addition, this paper presents new information about the occurrence of inorganic elements that may contribute to increase the emission of toxic compounds in the combustion of parica wood, for example, Cl. Thus, this study evaluated the composition of charcoal and S. parahyba var. amazonicum wood for briquettes, investigating the occurrence of inorganic elements responsible for the toxic organochlorine contaminants. Different formulations between charcoal and S. parahyba var. amazonicum wood were analyzed and later compacted in a laboratory briquetting machine with temperature of 90 °C and pressure of 5 MPa. The chemical and elemental composition of S. parahyba var. amazonicum wood was determined using X-ray fluorescence spectrometry (μ-XRF). The briquettes produced were tested for bulk and energy densities, proximate composition, heating value, equilibrium moisture, and resistance to diametral compression. S. parahyba var. amazonicum wood had chlorine levels below the recommended by international standards for solid biofuel intended for non-industrial use (< 300 mg kg−1). S. parahyba var. amazonicum, despite being a fast-growing species, has ideal chemical characteristics for energy purposes (Cl, S, and ashes). The most suitable briquettes were those produced with 50% of charcoal and 50% of S. parahyba var. amazonicum wood. This solid biofuel showed higher heating value of 22.74 MJ kg−1 and ash content of 2.65% db.