Contaminants and impurities in ethylene plants can originate from feedstocks, produced from cracking or from undesired chemical reaction within the unit. Some could be imported from external streams and/ or recycles. Beside affecting unit performance and in many instances defining turnaround frequencies, some of those impurities have implication relative to process safety. Hazards, likelihood and consequences vary based on circumstances such as shutdown, turnarounds, startups, upsets and steady state operation. This portion of the tutorial intents to identify contaminants and circumstances in which they could create a process safety risk.
