Dynamic simulation of disturbances triggering loss of operability in a biogas production plant

In the recent years, the biogas industry is rapidly growing, but the sector has been affected by several major accidents related to its supply chain, which pointed out the need to perform a detailed process safety analysis. Hazards and operability analysis (HazOp) is one of the most used and efficient technique for the identification of potential accidents, but its main limitation is the qualitative nature of the results. This study aims to override this limitation by supporting HazOp study using a dynamic simulator, which is able to reproduce deviations and operational failures in a typical biogas production plant, in order to help in the quantification of HazOp results and to improve safety and reliability of the process. The main result of the study is the maximum biogas production rate that can be safely handled by the system under normal conditions and then the maximum rate that can be allowed if some safety barrier (though correctly designed) should fail has been evaluated too. The most critical failure identified is a malfunctioning in the pressure relief system of the digester, because under this condition, the maximum biogas production rate that can be reached is about 2/3 of the corresponding value for a properly working system.