Advances in Purification of Refinery Off-Gas Streams - Including a New Lead-Free Arsine Adsorbent

Refinery off-gas streams derived primarily from fluid catalytic cracking units (FCCU’s) and Coker units have historically been sent to fuel gas systems, but these light hydrocarbon rich streams can be a cost advantaged feed stock for steam crackers (ethylene plants). Prior to being fed to the fractionation section of a steam cracker, removal of a variety of contaminants is required to meet ethylene plant product specifications or result in downstream deactivation of selective hydrogenation or polymerization catalysts.

Adsorbents are cost effective and efficient means of removing many of these problematic contaminants including arsine, mercury, chloride, oxygenates, sulfur compounds and more. The adsorption systems can be operated in either regenerative or non-regenerative mode. Honeywell UOP with its extensive adsorption technology expertise, field service capabilities, broad adsorbent product portfolio and commercial experience in refinery off-gas treatment can offer solutions to these purification demands.

Honeywell UOP has developed new materials for application in refinery-off gas streams. A lead-free arsine removal adsorbent has been patented. The new arsine removal adsorbent, free of environmentally problematic lead oxide, has been field tested at a major olefins producer in Asia and is now available for use.

In this paper we will discuss:

• Contaminants of concern in refinery off-gas streams fed to steam crackers.
• Appropriate adsorbents for each purification service with case studies and resultant attainable contaminant effluent specification.
• Optimum treater operating guidance.