Avaliação técnica e ambiental da gaseificação do combustível derivado de resíduos sólidos urbanos

Abstract

Considering the importance of studying the current environmental solid waste management systems (MSW) and the effects of different management strategies for the environment, this work aims to carry out a technical and environmental assessment of the electricity generation process from gasification of fuel derived from waste (RDF) in a pilot plant installed in the municipality of Itajubá, State of Minas Gerais. For the simulation of the gasification process of the reference fuel (RDF briquettes) two scenarios were considered, the first scenario using air 21% O2 - 79% N2 as a gasification agent and the second scenario considering a mixture of air enriched with oxygen 60% O2 - 40% N2. The results of RDF gasification using air and equivalence ratio (ER) which corresponds to the value of the actual fuel air ratio used during the process, divided by the stoichiometric fuel air ratio from 0.20 to 0.30 indicated a maximum value of LHV equal to 5.8 MJ / Nm³ for air obtained with an ER = 0.30. For gasification with a mixture of air enriched with oxygen, an LHV of 8MJ / Nm³ was obtained for ER = 0.30. No other ranges were considered due to the specifications required for the gas composition. In order to assess the scenario of alternative electricity generation with the produced gas, a gasifier set integrated with a Gas Microturbine (SGGM) was analyzed. Subsequently, a new analysis was carried out in a new configuration using gasifier and alternative internal combustion engine (SGAICE). SGAICE showed greater electrical power (101, 4 kW) for ER = 0.30 with air enriched with oxygen as a gasification agent. For SGGM the maximum power produced was 79.6 kW for the RE = 0.30. To assess the gasification and electricity production scenarios from the environmental point of view, the Life Cycle Assessment (LCA) methodology was used with the use of the SimaPro software to assess the environmental impacts of the energy system. For the assessment of environmental impacts, the ReCiPe impact assessment method used in the SimaPro database was used. The environmental impacts determined by the ReCiPe midpoint method indicated that the pollutant emissions resulting from the burning of fossil fuel in the transport stage by heavy cargo vehicles and the consumption of electricity to drive equipment in the MSW pretreatment stage are the major contributors of environmental impacts, mainly for the impact categories Human toxicity, marine and freshwater ecotoxicity and depletion of fossil fuels. The stage of production of electric energy considering the two drivers presented positive environmental impacts for all the impact categories analyzed. The results obtained from the LCA pointed out that for the established case study, the integrated gasification technology and Alternative Internal Combustion Engine (SGAICE scenario) presented better environmental and operational performance for the production of electricity from the use of gasification gas originating from RDF and it could be a viable option for the proper management of waste and its energy use in small Brazilian municipalities.