Dihydrodicyclopentadiene – Where Does It Come from and Can It Affect the Ethylene Unit

High level of dihydrodicyclopentadiene (DHDCPD) were found in a stream used as wash oil for the pyrolysis gas compressor. The wash oil stream originates from the plant downstream aromatic hydrotreating unit. The plant was originally designed as a liquid cracker and had been reconfigured over the years to process a variety of feedstocks. In recent years, it was converted to process 100% ethane feed with limited capabilities for propane and butane cracking. The aromatic unit was kept on stream but operates at reduced rates and also processes external streams due to the significant reduction in raw pyrolysis gasoline make from the ethylene cracker. The feed conversion to ethane has significantly affected the quantity and quality of the stream used as wash oil. As such, injection of external good quality wash oil was evaluated based on the premise that it could be cycled between the olefins and aromatics unit. However, simulation work demonstrated that the external wash oil would blend with the DHDCPD, making wash oil recovery ineffective relative to quality targeted for the recycled wash oil stream. DHDCPD is a component for which little if any information; exist relative to ethylene plant operation. It is absent from the Ethylene Producer Conference Feedstock Contaminants database. This paper discusses the potential source of DHDCPD, and the expected flow path followed by the component through the ethylene unit when the rich stream is used as wash oil to the Pyrolysis Gas Compressor.