(138c) Mitigating Ethylene Plant Flaring Risk during Equipment Switching Transitions By Dynamic Simulation

Equipment switching operations involving complicated operator procedures can increase the risk of flaring which can lead to environmental incidents and economic losses. Although flaring plays an important safety role in that it protects the operators and plant during process upsets, mitigating the risk of flaring is vitally important to improving process safety and sustainability. One example of equipment switching transition in ethylene plants is switching between solid desiccant dryers, commonly an operator procedure accomplished manually. The simulation was used to determine the conditions that would lead to a faulty dryer switching transition and identify the steps that when performed incorrectly increase the risk of flaring.

In this work, the dryer switching process was analyzed and simulated using the dynamic process simulation tool Honeywell UniSim Design. The transition of important process variables from the beginning of a dryer switch to the end were modeled by dynamic simulation. A general operating procedure was developed for the standard dryer switch procedure and various operator induced fault cases were developed to describe dryer switch transition faults based on potential procedural errors. The monitored variables were selected based on their sensitivity to faults during the dryers switching. Simulation results showed that some of the operator induced fault cases could result in natural gas header pressure spikes leading to flaring.