Separation and recovery of biohydrogen using a Pressure Swing Adsorption plant characterized by adsorption of CO2, CO, and CH4: Novel Geometric Control with integral action to mitigate disturbances in a complex process

Abstract

70% of carbon emissions (CO₂) are generated from the excessive use of transport and industry. In the race for decarbonizing transport, biohydrogen holds a prominent position as a potential alternative to traditional fossil fuels with zero net emissions. New technologies or processes (Cryogenic separation, Membrane permeation, Electrochemistry, among others) are used to produce biohydrogen. One of the technologies that is gaining interest in research centers and industries is the Pressure Swing Adsorption (PSA) process. However, research is still needed to develop a PSA plant that mitigates disturbances, which directly affect the purity of biohydrogen (99%) that meets the criteria for use as biofuel. This article aims to propose a PSA plant for biohydrogen production using robust controllers (PID and geometric control) to mitigate disturbances and maintain a stable purity above 99%. By using geometric control, the adsorption capacity (molar fraction) increased to 0.55 CO₂, 0.04 CO, 0.04 CH₄ compared to the results obtained without control (0.35 CO₂, 0.021 CO, 0.01 CH₄), achieving a recovery greater than 60% with an energy efficiency of 0.64%. A biohydrogen productivity of 1.55$\times 10^{-5}$ $\left(kmol{s}^{-1}\right)$ was obtained with a final purity of 0.994 in the molar fraction. On the other hand, PID control presents a low adsorption capacity compared to those obtained with geometric control; likewise, a lower recovery of 55% was obtained, and an energy efficiency of 0.71% was used to obtain a purity of biohydrogen of 0.99 in molar fraction. It is concluded that the geometric control law offers greater robustness and performance in the face of disturbances that occur in a complex process such as PSA. Furthermore, this novel geometric control law produced improved results with a faster response to disturbance rejection, achieving greater productivity and purity, and meeting international standards for use as a biofuel.