Investigation of synergy and inhibition effects during co-gasification of tire char and biomass in CO2 environment

Abstract

This study investigates the co-gasification of tire char (TC), as a low-quality side-product of scrap tire pyrolysis, and rambutan peel (RP). The objective of this study was to comprehend any synergistic/antagonistic effects during the co-gasification of TC/RP. For this, co-gasification of TC and RP (85:15, 70:30, 50:50, 30:70, and 15:85 wt% of TC:RP) was conducted in CO2 environment by non-isothermal thermogravimetric method. The samples were heated (15 K/min) under N2 to 923 K and then under CO2 to 1400 K. Comparison of the observed and theoretical results indicated the incidence of antagonism in blends with high proportion of TC (e.g., 85%TC–15%RP and 70%TC–30%RP), possibly attributing to the high content of acid oxides (SO3 (30.1%) and SiO2 (24.8%)) in the TC-ash which could inhibit the gasification by formation of inactive silicates in the presence of alkali/alkaline earth metal-rich biomass. In blends with higher content of biomass (e.g., 30%TC–70%RP and 15%TC–85%RP), the actual gasification rates were higher than the theoretically predicted ones showing the presence of a synergism associated with the natural catalysts (K2O (40.6%) and CaO (42.3%)) in RP-ash. Activation energy and thermodynamic studies confirmed the profound effect of biomass on enhancing the reactivity of TC in reaction with CO2. These promoting effects of biomass were associated with its considerably higher alkali index (133.4) than tire (5.6), its less graphitic structure with more structural defects, and imperfections compared with TC. According to the results, the inherently low reactivity of TC in gasification can be accelerated by co-feeding of biomass with TC.