Obtenção de amônia a partir de rotas termoquímicas utilizando biomassa animal: conversão, disponibilidade e modelagem do processo

Abstract

The investigation was developed to study the conversion of nitrogen into its byproducts, particularly focusing on NH3 formation. The study involved pyrolysis and gasification experiments using nitrogen-rich animal residues as biomass, along with an assessment of integrating this process into the Brazilian scenario to evaluate the potential increase in ammonia production. Additionally, a preliminary Computational Fluid Dynamics (CFD) model was developed to analyze the inert bed's characteristics under both cold and hot conditions, comparing the resulting gas with experimental data. The experimental methodology involved segmenting the thermochemical gasification process into sequential subprocesses of pyrolysis and gasification. Pyrolysis was conducted in fixed and fluidized bed reactors using raw biomass, while gasification experiments used the char originated from the pyrolysis experiment and only the fluidized bed reactor was used with different gasification agent mixtures, including steam. The results showed distinct nitrogen-to-NH3 conversion rates in the different stages of gasification, with the pyrolysis stage contributing approximately 49.3% to the direct NH3 conversion, while gasification of nitrogenated char accounted for 4.5% of the total conversion. The study's applicability to the Brazilian context involved two analyses: the country's fertilizer consumption demand, heavily reliant on imports, and the potential use of animal carcasses (26 million tons annually) to produce meat and bone meal (MBM) for NH3 production. Utilizing approximately 2,2 million tons of nitrogen from MBM could generate around 1,5 million tons of ammonia annually, representing a substantial reduction in costs (7 to 7,5 billion reais) and meeting nearly 80% of the National Fertilizer Plan's nitrogen fertilizer production goal. The CFD model's development occurred in three stages: adapting the fluidized bed reactor's geometry, configuring the hydrodynamics model (cold bed), and implementing the reactive model (hot bed) with species transport and chemical reactions. The model demonstrated good performance in predicting NH3 production, but improvements are necessary to consider additional chemical reactions and reactive models for species transport. Experimental validation showed promising results for NH3 prediction, but discrepancies were observed for CO, mainly attributed to gasification agent dilution. Overall, the study provides valuable insights into the conversion of nitrogen-rich biomass into NH3 and the potential implications for ammonia production in the Brazilian context. The CFD model shows promise but requires further refinement for accurate prediction of gas composition.