(32e) A New Technology for Reduction of Sulfur Contamination in Petrochemical Feed Stocks

Sai Reddy Pinappu, Hua Mo, Jerry Weers, Waynn Moran, Roger Metzler

Contamination removal in ethylene cracker feed stock is always necessary. Sulfur species are one of the potential contaminants that need to be removed. The Sulfur compounds in petrochemical grade naphtha (PCN) and gas feeds have been linked to many downstream process issues such as corrosion, contamination of products, catalyst poisoning, etc. Managing these sulfur compounds in PCN is a challenge for most producers because most of these sulfur species in the feedstock could create Hydrogen Sulfide (H₂S), Carbonyl Sulfide (COS) and other species through the cracking furnace. Although some of the sulfur species could be removed by quench water, condensation at compressor and caustic tower, some species would be hard to remove because of high volatility and short residence time in the process. As a result, it would be preferable to remove the sulfur species before they enter the cracking furnace.

Currently, there are multiple technologies for effective management of sulfur species in PCN. The technologies include mechanical, chemical, or a combination. One such treatment is a chemical treatment program based on an extraction process. An early form of sulfur management in finished fuels was treating the process streams with inexpensive materials such as sodium hydroxide solution. The water insoluble sulfur species will convert to the water soluble material and be extracted into the sodium hydroxide solution. Although liquid-liquid extraction processes are still prevalent in today’s refining operations, there are limits to the degree of sulfur removal and separation, especially with some higher molecular weight sulfur species. This led to the development of a new technology which focuses on improving the chemical treatment of scavenger-insensitive molecules such as CS_2, C4+ Mercaptans. The technology is tuned to increase scavenger reaction products’ solubility in the aqueous phase to maximize extraction efficiency. This paper will review the capabilities of this new technology. Several case studies will also be presented to discuss the efficiency of this technology.