Application of Risk Evaluation in Increasing the Operating Pressure of Etherification Reactors

Due to process changes, the operating pressure of three double-layer reactors (DLRs) containing flammable dimethyl ether and poisonous chloromethane needs to be increased to 6.3% above the design pressure, which is not in conformity with the regulations and standards in China. To evaluate the effect of the operating pressure increase on the risk of a vessel rupture, the safety margin for the wall thickness of all DLR structural components was evaluated at the increased pressure. A safety assessment employing risk-based inspection (RBI) methodology was carried out on the DLRs to evaluate the risk in the case of failure of the DLRs. The probability of failure (PoF) and consequence of failure (CoF) were analyzed using the first-order-second moment theory and the vapor cloud explosion model, respectively. The analysis results showed that the inner shell, the inner torispherical head and all nozzles were sufficiently strong to withstand the increased operating pressure of 2.66 MPa, and the knuckle of inner torispherical head was the weakest component, with a minimum safety margin of 5.64%. The assessment data showed the PoF of the DLRs was level 4, the CoF was level C, and the risk overall risk level for the DLRs was medium high.