Waste oils are a very promising raw material in the biodiesel industry, which is why great efforts have focused on the removal of the free fatty acids (FFAs) present in this source, mainly through the esterification reaction. Many studies have evaluated the influence of different variables on the reaction conversion, such as temperature, catalyst concentration, and alcohol/oil ratio. However, it is still necessary to verify how the esterification is affected by higher water concentration. In this study, different acid‐catalyzed esterification reaction conditions with distinct water concentrations were tested experimentally, and a new rate expression was proposed. This newly obtained reaction kinetics was then used to undertake a complete analysis of the biodiesel production process from waste oil, evaluating the influence of higher water concentrations in the esterification, and including different optimizations and an economic evaluation. Concerning some of the process modifications, it was verified that the inclusion of three energy‐saving heat exchangers reduced utility costs by 40%. In contrast, the inclusion of an ethanol‐recycling distillation column reduced raw material costs by 40%. Different settings were also tested, varying the feed composition and the esterification reaction time and conditions, resulting in a payback period of less than 3 years in any evaluated scenario. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

No abstract

Resumo -Com a crescente demanda por combustíveis de fontes renováveis, a busca por novos métodos e aperfeiçoamento dos já existentes deve ser explorada. O processo de produção de biodiesel está em ascensão no país e, com estímulos à produção e utilização do mesmo, é de grande interesse o uso de ferramentas computacionais de modo a poder prever quais as necessidades e obstáculos a serem superados no processo, além de poder-se ter uma estimativa de custos e resultados, de forma que se tenha uma fonte confiável para a tomada da melhor decisão. Neste trabalho foram feitos experimentos em escala laboratorial para a determinação das condições para a reação de esterificação, além da obtenção dos dados necessários para a simulação. Com os resultados, realizou-se o ajuste dos parâmetros para representar a cinética da reação e, em seguida, a simulação do processo de produção de biodiesel a partir de correntes oleosas ricas em ácidos graxos. Os resultados apresentados são promissores e podem contribuir para a obtenção de biodiesel de fontes residuais e não a partir de óleos comestíveis.

Biodiesel production from residual sources is gaining considerable attention nowadays. Consequently, many different studies with in-depth analysis concerning the influence of the transesterification reaction conditions are available in the literature. However, further evaluation of the esterification of fatty acids in the biodiesel industry is still needed. In this study, different parameters influencing the esterification reaction behavior using ethanol as the alcohol and lauric acid as the FFA are analyzed through factorial design and ANOVA methodologies to verify which ones are significant in the reaction. In total, four parameters were evaluated: temperature, catalyst concentration, ethanol/FFA ratio, and ethanol/water ratio. The temperature and ethanol/water ratio had a major influence on the reaction, as increasing these parameters greatly improved reaction conversion. It was also verified that using hydrous ethanol in the esterification reaction is possible in some conditions.