Ethane Feed Vaporizers Startup Difficulties

Changes in configuration and operating conditions of parallel ethane feed vaporizers integrated with the ethylene refrigeration system resulted in startup difficulties. While one of the exchangers was vaporizing and superheating the ethane feed stream, the other one seemed stalled. Fouling was initially speculated as the problem cause. However, this predicament was initiated by the exchangers outlet vapor to liquid transition that resulted in a hydraulic imbalance between the 2 exchangers. The condensing side of the exchanger’s outlet is characterized by vertical pipe risers, which ties into a long horizontal header. Different liquid accumulation rates between the 2 risers and/ or preferential liquid back flow from the horizontal header to one of the risers caused the vapor supplying the exchangers to follow the path of least resistance, hence stalling one of the exchangers. This paper discusses how operating data complemented with process simulations was used for identifying this problem along with the proposed solution. A review of typical project workflow is also discussed to highlight potential design pitfalls that could result in similar situations.