Briquetagem a frio e carbonização de resíduos da agroindústria cafeeira

Abstract

This study aimed to propose an alternative fuel and to evaluate its energy potencial through the production and carbonization of briquettes made with coffee husks (Coffea Arabica L.) and mixtures using crude glycerin as a binder. The briquetting process was performed at room temperature, in a cylindrical mold produced for the study. Characterizations of moisture and ash contents, briquette apparent density, fines content, tensile strength by diametrical compression, diametrical and longitudinal expansion analysis, calorific value, and proximate and elemental analysis were performed on the briquettes. The carbonization process was performed at 450 ºC and the gravimetric yields in charcoal, bio-oil and non-condensable gases were determined. The energy balance and the production of the briquettes costs were also determined. The effects of agglutination (0%, 5%, 10%, 15%, 20% and 25% w/w) on the variables moisture, volatile matter, fixed carbon and ash contents (%), briquette apparent density (kg m -3 ), resistance to diametrical compression (KPa), diametrical and longitudinal expansions (%), fines content and carbonization yields (charcoal, bio-oil and non-condensable gases) were evaluated through a completely randomized design, with three replications in each treatment. The results indicated that the addition of small amounts of crude glycerin as a binder of coffee husk briquettes might increase the resistance to diametrical compression, reduce the material fragmentation while keeping the apparent density. However, it reduced the calorific value, increase the moisture, volatile matter content, and the material expansions. Although the addition of glycerin did not affect significantly the gravimetric yields, the charcoal from coffee husk briquettes mixed with crude glycerin presented higher resistance to fragmentation. Thus, briquettes and charcoals produced in this study showed a potential use for bioenergy generation, activated carbon applications and biochar production.