A Survey of Compressor Wash Oils

Dave Smith, Senior Marketing Manager, Nalco Water, Sugar Land, TX

The Process Gas Compressor (also known as the Cracked Gas or Charge Gas Compressor) is a key unit operation in the production of ethylene via the steam cracking process. It is a complex and expensive piece of equipment, and its operation often determines the run length of the unit – a compressor malfunction can result in the entire unit being shut down. Declining performance of the compressor can negatively impact energy consumption and carbon emissions, product yield, and throughput, can cause damage to the machine, or unplanned unit outage. To prevent these costs, ethylene producers have implemented a number of mitigation measures. One such measure is the use of a wash oil on the compressor.

Wash oil is a liquid hydrocarbon used to remove polymer that is formed in the compressor. It acts as a scouring agent and a solvent for polymer that is formed. There are several qualities that comprise a high-quality wash oil – that is, one likely to perform efficiently at keeping the compressor clean and functioning efficiently.

The purpose of this paper is to discuss some of the qualities of a high-quality wash oil, the tests that can be used to determine those qualities, and a survey of various wash oils used by ethylene manufacturers. In addition, the paper will explore some of the changes in wash oil quantity and quality that have occurred over the past decade, particularly in North America, as manufacturers have moved towards cracking lighter feedstock slates.