Distillation Columns Risk Assessment: When the Regular HAZOP Evaluation Is Not Enough

The HAZOP method (Hazard operability study) was developed by ICI in the early 70s. In the 1980s risk studies gradually came into use in petrochemicals, oil, chemicals, rail transport, automobiles and other industries. This methodology has been used to assess the safety of new projects or existing units and their modifications. The purpose of this risk analysis is to identify potential accident scenarios that can occur at a facility and to lower the corresponding risks to an acceptable level. Risk analysis is performed by a multi-disciplinary group.

At Rhodia the HAZOP methodology principles were implemented in the beginning of 80's. The risk analysis is mandatory and performed at each 5 years for some facilities and at each 3 years some others.

One of the common initiating causes analyzed by a HAZOP group is the faults affecting condenser capacity of distillation systems. Usually, in the HAZOP analysis, the risk of this scenario is reduced at an acceptable level by introducing active safeguards (such as steam valve closure). Nevertheless, in some cases, the regular safety system (instrumental safety chain) is not enough to guarantee a safe unit shut down.