Simulation of fixed bed adsorption processes with simplified models. Application for CO2 adsorption in biogas purification

• Autor(a) principal: Inchauspe, María Eugenia
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10198/23528
• topic: Simulation; Bed adsorption; CO2; Biogás; Engenharia Química

Biogas production has grown remarkably in recent years and this growth is expected to continue in the coming years. This growth leads to an increase in the field of biogas purification and upgrading research. Among the variety of existing purification and upgrading techniques, one of the most used today is adsorption, specifically Pressure Swing Adsorption (PSA) as it is convenient when a cost-efficiency balance is made. To describe the dynamic behavior of an adsorption column, it is necessary to know the effluent concentration-time profile, also called the breakthrough curve. A good prediction of the breakthrough curve is essential to ensure the normal and safe operation of the process. Among the existing mathematical models to make this prediction, the Bohart-Adams model is one of the oldest and simplest in terms of mathematical application. This model considers that the operation is carried out at a constant velocity, but when the feed concentration is high, as in the case of biogas purification where we can have CO2 concentrations of up to 50%, the velocity cannot be considered constant. In this work, the different forms of the Bohart-Adams equation were studied and it was observed that this model, Tomas's and Yoon Nelson's are the same with minor modifications. The main advantage of the use of a mathematically simple model such as Bohart-Adams for the design and scale-up in an adsorption process is to shorten the times in determining the design variables and construction parameters of the equipment and this advantage is accompanied by a reduction in costs in the design and calculation stage of the process. Seeking to transfer the mathematical simplicity of this equation to cases in which high concentrations are used, tests were performed using the Bohart-Adams logistic form, studying the changes in the fit of the experimental data when a correction for variable velocity is applied in the stoichiometric time calculation. These tests were carried out with three types of adsorbents along with three different concentrations, the three adsorbents were: Activated Carbon, Pellets CuBTC and Bulk CuBTC and the concentrations used were 20%, 33% and 50% CO2. It was found that using the sigmoid or logistic form of Bohart-Adams, good adjustments were achieved even with initial concentrations of 50%. In the end, it is shown how the parameters obtained from this model are useful to make a scale-up in a simple way.