Ethylene Processing – Dilution Steam System

Fouling of the Dilution Steam System (DSS) Heat Exchangers can be a source of high maintenance and operating costs. Common problems are:

• increased steam usage
• reduced efficient in low, medium, and high pressure steam systems
• losses of recoverable pyrolysis gasoline
• increased wastewater treatment costs
• reduced energy efficiency due to fouling of steam generator
• high downtime and cleaning costs

Significant quantities of pyrolysis gasoline (hydrocarbons) are carried over from the Quench Water system Oil-Water separator

• Dispersion is very stable and difficult to separate.
• Poor separation efficiency of the oil/water separator

Conventional coalescer and mechanical liquid/liquid separation equipment are typically less efficient when the interfacial tension is lower than 20 – 25 dyne/cm. Much of the pyrolysis gasoline flows to the Dilution Steam Heat Exchangers causing fouling and resulting in high operating and maintenance costs

There have been numerous attempts to deal with this problem varying from chemical treatment programs, frequently scheduled off-line cleaning of the heat exchangers, and installation of additional heat exchanger capacity. While some of these attempts impact the cost of operation and maintenance, none of them address the cause of the fouling problem

The lube oil can be discharged into the process gas resulting in fouling of downstream equipment and product quality problems