Sugar Cane Bagasse Gasification Using Air-Steam for Partial Oxidation and N2 as Carrier Gas

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Several technologies have been proposed to reduce the environmental impact caused by greenhouse emissions (CO2) from fossil fuel combustion processes. One of them is the use of biomass as feedstock in gasification processes. Biomass fuels which include energy crops, agricultural and forestry residues, and municipal, industrial, and animal wastes can serve as renewable feedstock for thermal gasification to produce gaseous and liquid fuels. The inclusion of biomass as feedstock in thermal conversion processes does not increase the CO2 concentration in the atmosphere because biomass is a carbon neutral fuel. The sugarcane agriculture industry around the world produces a great amount of wastes, e.g., only in Colombia about 9 million tons of bagasse wastes are produced per year. That great amount of bagasse wastes can cause pollution of natural sources (land, water, and air) if waste handling systems and storage and treatment structures are not properly managed. If thermal gasification technology is developed for sugarcane bagasse wastes (SCBW), the negative environmental impact from both SCBW and fossil-fuels could be mitigated. The current paper deals with i) SCBW adiabatic gasification modeling using air-steam blends for partial oxidation and ii) pyrolysis kinetic model to determine, by thermogravimetric analysis (TGA), the SCBW activation energy (E). The Chemical Equilibrium with Applications program (CEA), developed by NASA, was used to estimate the effect of both the equivalence ratio (ER) and steam to fuel ratio (S:F) on adiabatic temperature, gas quality (gas composition and energy density), and energy recovery of an unlimited number of species (∼150). Thermogravimetric analysis (TGA) was carried out using N2 as carrier gas and under different heating rates (β: 5, 10, 20, and 40 °C/min). The activation energy (E) was estimated based in the results from TGA and using the isoconversional method (i.e., free-model). In general for the range of parameters studied (0.3<S:F<0.8 and 2<ER<6), the results from equilibrium adiabatic modeling (CEA) showed that increasing ER and (S:F) ratios increases the production of H2 and CO2 but decreases the production of CO. At ER <4, the equilibrium temperature decreases with increased ER, but at ER > ∼ 4.0, it remains stable. The production of CH4 is only possible at ER>4. The average value of the activation energy, estimated from the kinetics model, was 266 kJ/kmol.