Behavior of Flexible Biogas Digester Made of PVC-Coated PET Polyester Fabric with Increased Durability by Nanocoating Under Northridge (1994) Earthquake Effect

The purpose of this study is to ascertain how the dynamic reactions of a flexible biogas digester composed of PVC coated on PET polyester fabric are affected by nanocoating retrofitting. In this study, the effects of seismic movements on a ZrO2-coated and uncoated PVC-PET biogas digester were investigated. A semi-sphere biogas digester that was 2.5 m high was chosen for development with nanocoating. Frequency values and mode shapes were acquired by first creating a three-dimensional finite element model of the biogas digester and then performing modal analysis in SAP2000 software. Later, the ground motion data from the 1994 Northridge earthquake were used to do linear assessments of the methane digester. Dynamic evaluations were then performed after a 0.25 mm ZrO2 nanocoating was installed onto the digester’s exterior. Finally, the dynamic behavior of the biogas digester, characterized by minimum and maximum von Mises stresses and corresponding displacements, was evaluated before and after the ZrO2 coating. By the end of the study, the maximum von Mises stress had decreased from 60.47 kPa to 15.18 kPa, while the minimum von Mises stress at the digester bottom was reduced from 11.41 kPa to 4.47 kPa. Additionally, the displacements along the digester height, particularly the maximum values, were reduced from 0.057 mm to 0.013 mm. The reduction in frequency values demonstrated that ZrO2 nanocoating improved the biogas digester’s rigidity. This study makes it clear that nanocoatings will have an impact on dynamic parameters and be highly beneficial for improving biogas digesters.